Reducing location-dependent destructive interference in distributed antenna systems (DASS) operating in multiple-input, multiple-output (MIMO) configuration, and related components, systems, and methods

Information

  • Patent Grant
  • 10256879
  • Patent Number
    10,256,879
  • Date Filed
    Wednesday, March 7, 2018
    6 years ago
  • Date Issued
    Tuesday, April 9, 2019
    5 years ago
Abstract
Components, systems, and methods for reducing location-dependent destructive interference in distributed antenna systems operating in multiple-input, multiple-output (MIMO) configuration are disclosed. Interference is defined as issues with received MIMO communications signals that can cause a MIMO algorithm to not be able to solve a channel matrix for MIMO communications signals received by MIMO receivers in client devices. These issues may be caused by lack of separation (i.e., phase, amplitude) in the received MIMO communications signals. Thus, to provide amplitude separation of received MIMO communications signals, multiple MIMO transmitters are each configured to employ multiple transmitter antennas, which are each configured to transmit in different polarization states. In certain embodiments, one of the MIMO communications signals is amplitude adjusted in one of the polarization states to provide amplitude separation between received MIMO communications signals. In other embodiments, multiple transmitter antennas in a MIMO transmitter can be offset to provide amplitude separation.
Description
BACKGROUND

The disclosure relates generally to distribution of data (e.g., digital data services and radio-frequency communications services) in a distributed antenna system (DAS) and more particularly to multiple-input, multiple-output MIMO technology, which may be used in the DAS.


Wireless customers are demanding digital data services, such as streaming video signals. Concurrently, some wireless customers use their wireless devices in areas that are poorly served by conventional cellular networks, such as inside certain buildings or areas where there is little cellular coverage. One response to the intersection of these two concerns has been the use of distributed antenna systems. Distributed antenna systems can be particularly useful to be deployed inside buildings or other indoor environments where client devices may not otherwise be able to effectively receive radio-frequency (RF) signals from a source. Distributed antenna systems include remote units (also referred to as “remote antenna units”) configured to receive and wirelessly transmit wireless communications signals to client devices in antenna range of the remote units. Such distributed antenna systems may use Wireless Fidelity (WiFi) or wireless local area networks (WLANs), as examples, to provide digital data services.


Distributed antenna systems may employ optical fiber to support distribution of high bandwidth data (e.g., video data) with low loss. Even so, WiFi and WLAN-based technology may not be able to provide sufficient bandwidth for expected demand, especially as HD video becomes more prevalent. WiFi was initially limited in data rate transfer to 12.24 Mb/s and is provided at data transfer rates of up to 54 Mb/s using WLAN frequencies of 2.4 GHz and 5.8 GHz. While interesting for many applications, WiFi bandwidth may be too small to support real time downloading of uncompressed HD television signals to wireless client devices.


MIMO technology can be employed in distributed antenna systems to increase the bandwidth up to twice the nominal bandwidth, as a non-limiting example. MIMO is the use of multiple antennas at both a transmitter and receiver to increase data throughput and link range without additional bandwidth or increased transmit power. However, even doubling bandwidth alone may not be enough to support high bandwidth data to wireless client devices, such as the example of real time downloading of uncompressed high definition (HD) television signals.


The frequency of wireless communications signals could also be increased in a MIMO distributed antenna system to provide larger channel bandwidth as a non-limiting example. For example, an extremely high frequency (EHF) in the range of approximately 30 GHz to approximately 300 GHz could be employed. For example, the sixty GHz (60 GHz) spectrum is an EHF that is an unlicensed spectrum by the Federal Communications Commission (FCC). EHFs could be employed to provide for larger channel bandwidths. However, higher frequency wireless signals are more easily attenuated and/or blocked from traveling through walls, building structures, or other obstacles where distributed antenna systems are commonly installed. Higher frequency wireless signals also provide narrow radiation patterns. Thus, remote units in distributed antenna systems may be arranged for line-of-sight (LOS) communications to allow for higher frequencies for higher bandwidth. However, if remote units are provided in a LOS configuration and the remote units are also configured to support MIMO, multiple spatial streams received by multiple receiver antennas in the remote units may be locked into a relative phase and/or amplitude pattern. This can lead to multiple received spatial streams periodically offsetting each other when the spatial streams are combined at MIMO receivers, leading to performance degradation and reduced wireless coverage.


No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.


SUMMARY

Components, systems, and methods for reducing location-dependent destructive interference in distributed antenna systems (DASs) operating in multiple-input, multiple-output (MIMO) configuration are disclosed. The DASs include remote units employing MIMO transmitters configured to transmit multiple data streams in MIMO configuration to MIMO receivers in wireless client devices. Destructive interference in a MIMO system can occur when two or more spatial streams transmitted from multiple MIMO antennas are locked into a relative phase and/or amplitude pattern, causing periodic destructive interferences when the two or more spatial streams are combined at MIMO receivers in client devices. These issues can occur due to lack of separation (i.e., phase, amplitude) in the received MIMO communications signals, especially with closely located MIMO transmitters configured for line-of-sight (LOS) communications. Thus, to provide spatial separation of MIMO communications signals received by MIMO receivers in client devices, multiple MIMO transmitters in a remote unit in a DAS are each configured to employ multiple transmitter antennas, which are each configured to transmit in different polarization states. In certain embodiments, the amplitude of one of the MIMO communications signals is modified in one of the polarization states to further provide amplitude separation between the MIMO communications signals received by the MIMO receivers.


The components, systems, and methods for reducing location-dependent periodic destructive interference in distributed antenna systems operating in MIMO configuration may significantly improve high-data rate wireless coverage without significant dependence on transmitter and/or receive placement. This may allow for LOS communications to be more easily achieved between MIMO transmitters and MIMO receivers, especially for higher frequency communications where LOS communications may be required to reduce destructions to higher frequency signals by obstacles on the transmission path. High antenna isolation is not required in the MIMO receivers. No additional hardware component is required in the MIMO transmitters or receivers as well. The improved MIMO performance and increased coverage area can also allow higher frequency bands (e.g., 60 GHz) to be used efficiently to provide multi-gigabit per second (Gbps) data access to client devices in indoor and outdoor environments.


One embodiment of the disclosure relates to a MIMO remote unit configured to wirelessly distribute MIMO communications signals to wireless client devices in a distributed antenna system. The MIMO remote unit comprises a first MIMO transmitter comprising a first MIMO transmitter antenna configured to transmit MIMO communications signals in a first polarization and a second MIMO transmitter antenna configured to transmit MIMO communications signals in a second polarization different from the first polarization. The MIMO remote unit also comprises a second MIMO transmitter comprising a third MIMO transmitter antenna configured to transmit MIMO communications signals in the first polarization and a fourth MIMO transmitter antenna configured to transmit MIMO communications signals in the second polarization. The first MIMO transmitter is configured to receive a first downlink MIMO communications signal at a first amplitude over a first downlink communications medium, and transmit the first downlink MIMO communications signal wirelessly as a first electrical downlink MIMO communications signal over the first MIMO transmitter antenna in the first polarization. The first MIMO transmitter is also configured to receive a second downlink MIMO communications signal at the first amplitude over a second downlink communications medium, and transmit the second downlink MIMO communications signal wirelessly as a second electrical downlink MIMO communications signal over the second MIMO transmitter antenna in the second polarization. The second MIMO transmitter is configured to receive a third downlink MIMO communications signal at the first amplitude over a third downlink communications medium, and transmit the third downlink MIMO communications signal wirelessly as a third electrical downlink MIMO communications signal over the third MIMO transmitter antenna in the first polarization. The second MIMO transmitter is also configured to receive a fourth downlink MIMO communications signal over a fourth downlink communications medium, and transmit the fourth downlink MIMO communications signal at a second amplitude modified from the first amplitude, wirelessly as a fourth electrical downlink MIMO communications signal over the fourth MIMO transmitter antenna in the second polarization.


An additional embodiment of the disclosure relates to a method of transmitting MIMO communications signals to wireless client devices in a distributed antenna system is provided. The method includes receiving a first downlink MIMO communications signal at a first amplitude over a first downlink communications medium. The method also includes transmitting the first downlink MIMO communications signal wirelessly as a first electrical downlink MIMO communications signal over a first MIMO transmitter antenna in a first polarization. The method also includes receiving a second downlink MIMO communications signal at the first amplitude over a second downlink communications medium. The method also includes transmitting the second downlink MIMO communications signal wirelessly as a second electrical downlink MIMO communications signal over a second MIMO transmitter antenna in a second polarization. The method also includes receiving a third downlink MIMO communications signal at the first amplitude over a third downlink communications medium. The method also includes transmitting the third downlink MIMO communications signal wirelessly as a third electrical downlink MIMO communications signal over a third MIMO transmitter antenna in the first polarization. The method also includes receiving a fourth downlink MIMO communications signal over a fourth downlink communications medium. The method also includes transmitting the fourth downlink MIMO communications signal at a second amplitude modified from the first amplitude, wirelessly as a fourth electrical downlink MIMO communications signal over a fourth MIMO transmitter antenna in the second polarization.


An additional embodiment of the disclosure relates to a distributed antenna system for distributing MIMO communications signals to wireless client devices. The distributed antenna system comprises a central unit. The central unit comprises a central unit transmitter configured to receive a downlink communications signal. The central unit transmitter is also configured to transmit the received downlink communications signal as a first downlink MIMO communications signal over a first downlink communications medium, a second downlink MIMO communications signal over a second downlink communications medium, a third MIMO downlink communications signal over a third downlink communications medium, and a fourth downlink MIMO communications signal over a fourth downlink communications medium.


This distributed antenna system also comprises a remote unit. The remote unit comprises a first MIMO transmitter comprising a first MIMO transmitter antenna configured to transmit MIMO communications signals in a first polarization and a second MIMO transmitter antenna configured to transmit MIMO communications signals in a second polarization different from the first polarization. The remote unit also comprises a second MIMO transmitter comprising a third MIMO transmitter antenna configured to transmit MIMO communications signals in the first polarization and a fourth MIMO transmitter antenna configured to transmit MIMO communications signals in the second polarization. The first MIMO transmitter is configured to receive a first downlink MIMO communications signal at a first amplitude over a first downlink communications medium, and transmit the first downlink MIMO communications signal wirelessly as a first electrical downlink MIMO communications signal over the first MIMO transmitter antenna in the first polarization. The first MIMO transmitter is also configured to receive a second downlink MIMO communications signal at the first amplitude over a second downlink communications medium, and transmit the second downlink MIMO communications signal wirelessly as a second electrical downlink MIMO communications signal over the second MIMO transmitter antenna in the second polarization. The second MIMO transmitter is configured to receive a third downlink MIMO communications signal at the first amplitude over a third downlink communications medium, and transmit the third downlink MIMO communications signal wirelessly as a third electrical downlink MIMO communications signal over the third MIMO transmitter antenna in the first polarization. The second MIMO transmitter is also configured to receive a fourth downlink MIMO communications signal over a fourth downlink communications medium, and transmit the fourth downlink MIMO communications signal at a second amplitude modified from the first amplitude, wirelessly as a fourth electrical downlink MIMO communications signal over the fourth MIMO transmitter antenna in the second polarization. The remote unit also comprises at least one amplitude adjustment circuit configured to amplitude adjust the fourth downlink MIMO communications signal to the second amplitude.


The distributed antenna systems disclosed herein can be configured to support one or more radio-frequency (RF)-based services and/or distribution of one or more digital data services. The remote units in the distributed antenna systems may be configured to transmit and receive wireless communications signals at one or more frequencies, including but not limited to extremely high frequencies (EHF) (i.e., approximately 30 GHz—approximately 300 GHz). The distributed antenna systems may include, without limitation, wireless local area networks (WLANs). Further, as a non-limiting example, the distributed antenna systems may be an optical fiber-based distributed antenna system, but such is not required. An optical fiber-based distributed antenna system may employ Radio-over-Fiber (RoF) communications. The embodiments disclosed herein are also applicable to other remote antenna clusters and distributed antenna systems, including those that include other forms of communications media for distribution of communications signals, including electrical conductors and wireless transmission. For example, the distributed antenna systems may include electrical and/or wireless communications mediums between a central unit and remote units in addition or in lieu of optical fiber communications medium. The embodiments disclosed herein may also be applicable to remote antenna clusters and distributed antenna systems and may also include more than one communications media for distribution of communications signals (e.g., digital data services, RF communications services). The communications signals in the distributed antenna system may or may not be frequency shifted.


Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and the claims hereof, as well as the appended drawings.


It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understand the nature and character of the claims. The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the description serve to explain principles and operation of the various embodiments.





BRIEF DESCRIPTION OF THE DRAWINGS


FIG. 1 is a schematic of an exemplary distributed antenna system;



FIG. 2 is a schematic diagram of an exemplary multiple-input, multiple-output (MIMO) optical fiber-based distributed antenna system;



FIG. 3A is a top view diagram of a room having an exemplary MIMO antenna system comprising two (2) MIMO transmitter antennas in line-of-sight (LOS) with two (2) MIMO receiver antennas to illustrate periodic destructive interference in MIMO communications signals received in the same frequency channel by the MIMO receiver antennas;



FIG. 3B is a graph illustrating exemplary measured periodic performance degradations for a given placement distance between the MIMO transmitter antennas in the MIMO antenna system in FIG. 3A;



FIG. 3C is a graph illustrating an exemplary effective antenna coverage area in proximity to the MIMO transmitter antennas in FIG. 3A;



FIG. 4 is a schematic diagram of an exemplary amplitude adjustment circuit for amplitude adjusting a downlink (DL) MIMO communications signal transmitted by a MIMO transmitter antenna in FIG. 2;



FIG. 5 is a flowchart illustrating an exemplary amplitude adjustment process performed by the exemplary amplitude adjustment circuit in FIG. 4 for amplitude adjusting a downlink (DL) MIMO communications signal transmitted by a MIMO transmitter antenna in FIG. 2;



FIG. 6A is a schematic diagram of an exemplary MIMO optical fiber-based distributed antenna system employing a central unit employing a MIMO transmitter configured to electrically amplitude adjust at least one transmitted MIMO electrical downlink communications signal received and transmitted by a remote unit employing multiple MIMO transmitters each configured with multiple MIMO transmitter antennas configured to transmit in different polarization states;



FIG. 6B is a schematic diagram of an exemplary MIMO optical fiber-based distributed antenna system employing an amplitude adjustment circuit of FIG. 4 in an optical downlink communications medium configured to provide amplitude adjustment to at least one transmitted MIMO electrical downlink communications signal received and transmitted by a remote unit employing multiple MIMO transmitters each configured with multiple MIMO transmitter antennas configured to transmit in different polarization states;



FIG. 6C is a schematic diagram of an exemplary MIMO optical fiber-based distributed antenna system employing remote units employing multiple MIMO transmitters each employing multiple MIMO transmitter antennas configured to transmit in different polarization states, wherein one of the MIMO electrical downlink communications signals transmitted by one of the MIMO transmitters in a polarization state is electrically amplitude adjusted;



FIG. 7 is a schematic diagram illustrating exemplary implementation options of an amplitude adjustment circuit in FIG. 4 in a central unit in FIGS. 6A-6C;



FIG. 8A is a graph illustrating exemplary MIMO communications signal waveforms transmitted by a first MIMO transmitter antenna and a second MIMO transmitter antenna of a MIMO transmitter in a remote unit in FIGS. 6A-6C without amplitude adjustment;



FIG. 8B is a graph illustrating exemplary MIMO communications signal waveforms transmitted by a first MIMO transmitter antenna and a second MIMO transmitter antenna of a MIMO transmitter in a remote unit in FIGS. 6A-6C with amplitude adjustment;



FIG. 8C is a graph illustrating exemplary measured periodic performance degradation for a given placement distance between MIMO transmitter antennas in a MIMO transmitter in a remote unit in the distributed antenna system in FIGS. 6A-6C, when employing and not employing amplitude adjustment of at least one transmitted downlink communications signals;



FIG. 8D is a graph illustrating an exemplary effective antenna coverage versus placement distance between MIMO transmitter antennas in a MIMO transmitter in a remote unit in the distributed antenna system in FIGS. 6A-6C, for a given placement distance between MIMO receiver antennas, when employing and not employing amplitude adjustment of at least one transmitted downlink communications signal; and



FIG. 9 is a schematic diagram of a generalized representation of an exemplary controller that can be included in any central unit, remote units, wireless client devices, and/or any other components of distributed antenna systems to reduce or eliminate issues of periodic destructive interference in transmitted MIMO electrical downlink communications signals, wherein the exemplary computer system is adapted to execute instructions from an exemplary computer readable medium.





DETAILED DESCRIPTION

Components, systems, and methods for reducing location-dependent destructive interference in distributed antenna systems (DASs) operating in multiple-input, multiple-output (MIMO) configuration are disclosed. The DASs include remote units employing MIMO transmitters configured to transmit multiple data streams in MIMO configuration to MIMO receivers in wireless client devices. Destructive interference in a MIMO system can occur when two or more spatial streams transmitted from multiple MIMO antennas are locked into a relative phase and/or amplitude pattern, causing periodic destructive interferences when the two or more spatial streams are combined at MIMO receivers in client devices. These issues can occur due to lack of separation (i.e., phase, amplitude) in the received MIMO communications signals, especially with closely located MIMO transmitters configured for line-of-sight (LOS) communications. Thus, to provide spatial separation of MIMO communications signals received by MIMO receivers in client devices, multiple MIMO transmitters in a remote unit in a DAS are each configured to employ multiple transmitter antennas, which are each configured to transmit in different polarization states. In certain embodiments, the amplitude of one of the MIMO communications signals is modified in one of the polarization states to further provide amplitude separation between the MIMO communications signals received by the MIMO receivers. Various embodiments will be explained by the following examples.


Before discussing examples of components, systems, and methods for reducing location-dependent destructive interference in distributed antenna systems operating in MIMO configuration starting at FIG. 4, an exemplary distributed antenna system is described in regard to FIGS. 1-3C. In this regard, FIG. 1 is a schematic diagram of a conventional distributed antenna system 10. The distributed antenna system 10 is an optical fiber-based distributed antenna system. The distributed antenna system 10 is configured to create one or more antenna coverage areas for establishing communications with wireless client devices located in the radio frequency (RF) range of the antenna coverage areas. In an exemplary embodiment, the distributed antenna system 10 may provide RF communication services (e.g., cellular services). As illustrated, the distributed antenna system 10 includes a central unit 12, one or more remote units 14, and an optical fiber 16 that optically couples the central unit 12 to the remote unit 14. The central unit 12 may also be referred to as a head-end unit. The remote unit 14 is a type of remote communications unit, and may also be referred to as a “remote antenna unit.” In general, a remote communications unit can support wireless communications or wired communications, or both. The central unit 12 is configured to receive communications over downlink electrical RF signals 18D from a source or sources, such as a network or carrier as examples, and provide such communications to the remote unit 14. The central unit 12 is also configured to return communications received from the remote unit 14, via uplink electrical RF signals 18U, back to the source or sources. In this regard, in this embodiment, the optical fiber 16 includes at least one downlink optical fiber 16D to carry signals communicated from the central unit 12 to the remote unit 14 and at least one uplink optical fiber 16U to carry signals communicated from the remote unit 14 back to the central unit 12.


One downlink optical fiber 16D and one uplink optical fiber 16U could be provided to support multiple full-duplex channels each using wave-division multiplexing (WDM), as discussed in U.S. patent application Ser. No. 12/892,424, entitled “Providing Digital Data Services in Optical Fiber-based Distributed Radio Frequency (RF) Communications Systems, And Related Components and Methods,” incorporated herein by reference in its entirety. Other options for WDM and frequency-division multiplexing (FDM) are also disclosed in U.S. patent application Ser. No. 12/892,424, any of which can be employed in any of the embodiments disclosed herein. Further, U.S. patent application Ser. No. 12/892,424 also discloses distributed digital data communications signals in a distributed antenna system which may also be distributed in the distributed antenna system 10 either in conjunction with the RF communications signals or not.


The distributed antenna system 10 has an antenna coverage area 20 that can be disposed around the remote unit 14. The antenna coverage area 20 of the remote unit 14 forms an RF coverage area 21. The central unit 12 is adapted to perform or to facilitate any one of a number of Radio-over-Fiber (RoF) applications, such as RF identification (RFID), wireless local-area network (WLAN) communication, or cellular phone service. Shown within the antenna coverage area 20 is a client device 24 in the form of a mobile device, which may be a cellular telephone as an example. The client device 24 can be any device that is capable of receiving RF communications signals. The client device 24 includes an antenna 26 (e.g., a wireless card) adapted to receive and/or send electromagnetic RF signals.


With continuing reference to FIG. 1, to communicate the electrical RF signals over the downlink optical fiber 16D to the remote unit 14, to in turn be communicated to the client device 24 in the antenna coverage area 20 formed by the remote unit 14, the central unit 12 includes a radio interface in the form of an electrical-to-optical (E/O) converter 28. The E/O converter 28 converts the downlink electrical RF signals 18D to downlink optical RF signals 22D to be communicated over the downlink optical fiber 16D. The remote unit 14 includes an optical-to-electrical (O/E) converter 30 to convert the received downlink optical RF signals 22D back to electrical RF signals to be communicated wirelessly through an antenna 32 of the remote unit 14 to the client device 24 located in the antenna coverage area 20.


Similarly, the antenna 32 is also configured to receive wireless RF communications from the client device 24 in the antenna coverage area 20. In this regard, the antenna 32 receives wireless RF communications from the client device 24 and communicates electrical RF signals representing the wireless RF communications to an E/O converter 34 in the remote unit 14. The E/O converter 34 converts the electrical RF signals into uplink optical RF signals 22U to be communicated over the uplink optical fiber 16U. An 0/E converter 36 provided in the central unit 12 converts the uplink optical RF signals 22U into uplink electrical RF signals, which can then be communicated as uplink electrical RF signals 18U back to a network or other source.


As noted, one or more of the network or other sources can be a cellular system, which may include a base station or base transceiver station (BTS). The BTS may be provided by a second party such as a cellular service provider, and can be co-located or located remotely from the central unit 12.


In a typical cellular system, for example, a plurality of BTSs is deployed at a plurality of remote locations to provide wireless telephone coverage. Each BTS serves a corresponding cell and when a mobile client device enters the cell, the BTS communicates with the mobile client device. Each BTS can include at least one radio transceiver for enabling communication with one or more subscriber units operating within the associated cell. As another example, wireless repeaters or bi-directional amplifiers could also be used to serve a corresponding cell in lieu of a BTS. Alternatively, radio input could be provided by a repeater, picocell, or femtocell, as other examples. In a particular exemplary embodiment, cellular signal distribution in the frequency range from 400 MHz to 2.7 GHz is supported by the distributed antenna system 10.


Although the distributed antenna system 10 in FIG. 1 allows for distribution of radio frequency (RF) communications signals; the distributed antenna system 10 is not limited to distribution of RF communications signals. Data communications signals, including digital data signals, for distributing data services could also be distributed in the distributed antenna system 10 in lieu of or in addition to RF communications signals. Also note that while the distributed antenna system 10 in FIG. 1 discussed below includes distribution of communications signals over optical fiber, the distributed antenna system 10 is not limited to distribution of communications signals over optical fiber. Distribution media could also include, but are not limited to, coaxial cable, twisted-pair conductors, wireless transmission and reception, and any combination thereof. Also, any combination can be employed that also involves optical fiber for portions of the distributed system.


A distributed antenna system, including the distributed antenna system 10 in FIG. 1, can be configured in MIMO configuration for MIMO operation. In this regard, FIG. 2 illustrates a schematic diagram of an exemplary MIMO optical fiber-based distributed antenna system 40 (hereinafter referred to as “MIMO distributed antenna system 40”). The MIMO distributed antenna system 40 is configured to operate in MIMO configuration. MIMO technology involves the use of multiple antennas at both a transmitter and receiver to improve communication performance. In this regard, a central unit 42 is provided that is configured to distribute downlink communications signals to one or more remote units 44. FIG. 2 only illustrates one remote unit 44, but note that a plurality of remote units 44 is typically provided. The remote units 44 are configured to wirelessly communicate the downlink communication signals to one or more client devices 46 that are in communication range of the remote unit 44. The remote units 44 may also be referred to as “remote antenna units 44” because of their wireless transmission over antenna functionality. The remote unit 44 is also configured to receive uplink communication signals from the client devices 46 to be distributed to the central unit 42. In this embodiment, an optical fiber communications medium 47 comprising at least one downlink optical fiber 48D and at least one uplink optical fiber 48U is provided to commutatively couple the central unit 42 to the remote units 44. The central unit 42 is also configured to receive uplink communication signals from the remote units 44 via the optical fiber communications medium 47, although more specifically over the at least one uplink optical fiber 48U. The client device 46 in communication with the remote unit 44 can provide uplink communication signals to the remote unit 44 which are then distributed over the optical fiber communications medium 47 to the remote unit 44 to be provided to a network or other source, such as a base station for example.


With continuing reference to FIG. 2, more detail will be discussed regarding the components of the central unit 42, the remote unit 44, and the client device 46 and the distribution of downlink communications signals. The central unit 42 is configured to receive electrical downlink MIMO communication signals 50D from outside the MIMO distributed antenna system 40 in a signal processor 52 and provide electrical uplink communications signals 50U received from client devices 46, to other systems. The signal processor 52 is configured to provide the electrical downlink communication signals 50D to a mixer 60, which may be an IQ signal mixer in this example. The mixer 60 in this embodiment is configured to convert the electrical downlink MIMO communication signals 50D to IQ signals. The mixer 60 is driven by a frequency signal 56 that is provided by a local oscillator 58. Frequency conversion is optional. In this embodiment, it is desired to up-convert the frequency of the electrical downlink MIMO communication signals 50D to a higher frequency to provide electrical downlink MIMO communication signals 66D to provide for a greater bandwidth capability before distributing the electrical downlink MIMO communications signals 66D to the remote units 44. For example, the up-conversion carrier frequency may be provided as an extremely high frequency (e.g. approximately 30 GHz to 300 GHz).


With continuing reference to FIG. 2, because the communication medium between the central unit 42 and the remote unit 44 is the optical fiber communications medium 47, the electrical downlink MIMO communication signals 66D are converted to optical signals by an electro-optical converter 67. The electro-optical converter 67 includes components to receive a light wave 68 from a light source 70, such as a laser. The light wave 68 is modulated by the frequency oscillations in the electrical downlink MIMO communication signals 66D to provide optical downlink MIMO communication signals 72D to be communicated over the downlink optical fiber 48D to the remote unit 44. The electro-optical converter 67 may be provided so that the electrical downlink MIMO communication signals 66D are provided as radio-over-fiber (RoF) communications signals over the downlink optical fiber 48D.


With continuing reference to FIG. 2, the optical downlink MIMO communication signals 72D are received by an optical bi-directional amplifier 74, which is then provided to a MIMO splitter 76 in the remote unit 44. The MIMO splitter 76 is provided so that the optical downlink MIMO communication signals 72D can be split among two separate communication paths 77(1), 77(2) to be radiated over two separate MIMO transmitter antennas 78(1), 78(2) provided in two separate MIMO transmitters 79(1), 79(2) configured in MIMO configuration. The MIMO splitter 76 in the remote unit 44 is an optical splitter since the received optical downlink MIMO communication signals 72D are optical signals. In each communication path 77(1), 77(2), optical-to-electrical converters 80(1), 80(2) are provided to convert the optical downlink MIMO communication signals 72D to electrical downlink MIMO communication signals 82D(1), 82D(2). In this embodiment, as will be discussed in more detail below, an amplitude adjustment circuit 84 is provided in one of the transmission paths 77(1), 77(2) to provide amplitude adjustment in one of the optical downlink MIMO communication signals 72D(1), 72D(2) transmitted over one of the MIMO transmitter antennas 78(1), 78(2) to help reduce or eliminate periodic destructive interferences when received electrical downlink MIMO communication signals 82D are combined at the client device 46.


A destructive interference occurs when the electrical downlink MIMO communication signals 82D(1), 82D(2) are locked into a relative phase and/or amplitude pattern, causing them to cancel each other when combined at MIMO receivers 85(1), 85(2). Because the electrical downlink MIMO communication signals 82D(1), 82D(2) are periodic radio frequency waves, the destructive interference also becomes periodic as result. When physical obstacles (e.g., buildings, walls, trees, vehicles, etc.) standing in radio transmission paths between the MIMO transmitter antennas 78(1), 78(2) and the MIMO receiver antennas 86(1), 86(2), the electrical downlink MIMO communication signals 82D(1), 82D(2) transmitted by the MIMO transmitter antennas 78(1), 78(2) typically arrive at the MIMO receiver antennas 86(1), 86(2) from different directions and/or angles (also known as “multipath”) due to reflections from the physical obstacles. Due to multipath effect, the electrical downlink MIMO communication signals 82D(1), 82D(2) transmitted by the MIMO transmitter antennas 78(1), 78(2) may arrive at the MIMO receiver antennas 86(1), 86(2) with slight delays among each other, resulting in natural phase shifts between the electrical downlink MIMO communication signals 82D(1), 82D(2). Further, the amplitudes of the electrical downlink MIMO communication signals 82D(1), 82D(2) may also be modified due to different reflection angles caused by different obstacles along different transmission paths. In this regard, multipath acts to break up the locked-in phase and/or amplitude pattern among the electrical downlink MIMO communication signals 82D(1), 82D(2) transmitted by the MIMO transmitter antennas 78(1), 78(2) and, thus, helps mitigate periodic destructive interferences at MIMO receivers 85(1), 85(2). However, when a millimeter wave radio frequency band (e.g., 60 GHz) is employed as the carrier frequency between the MIMO transmitter antennas 78(1), 78(2) and the MIMO receiver antennas 86(1), 86(2), there cannot be any physical obstacle stand in the radio transmission path. This is because higher frequency signals like a 60 GHz signal are inherently incapable of penetrating or bouncing off physical obstacles. To prevent millimeter wave radio frequency signals from being blocked by physical obstacles, the MIMO transmitter antennas 78(1), 78(2) and the MIMO receiver antennas 86(1), 86(2) must be configured in a line-of-sight (LOS) arrangement, which is further elaborated in FIGS. 3A-3C. With the LOS arrangement, multipath becomes non-existent between the MIMO transmitter antennas 78(1), 78(2) and the MIMO receiver antennas 86(1), 86(2). Therefore, periodic destructive interferences often occur when the electrical downlink MIMO communication signals 82D(1), 82D(2) are combined at the MIMO receivers 85(1), 85(2).


With continuing reference to FIG. 2, the client device 46 includes two MIMO receivers 85(1), 85(2) that include MIMO receiver antennas 86(1), 86(2) also configured in MIMO configuration. The MIMO receiver antennas 86(1), 86(2) are configured to receive the electrical downlink MIMO communication signals 82D(1), 82D(2) wirelessly from the remote unit 44. Mixers 88(1), 88(2) are provided and coupled to the MIMO receiver antennas 86(1), 86(2) in the client device 46 to provide frequency conversion of the electrical downlink MIMO communication signals 82D(1), 82D(2). In this regard, a local oscillator 90 is provided that is configured to provide oscillation signals 92(1), 92(2) to the mixers 88(1), 88(2), respectively, for frequency conversion. In this embodiment, the electrical downlink MIMO communications signals 82D(1), 82D(2) are down converted back to their native frequency as received by the central unit 42. The down converted electrical downlink MIMO communication signals 82D(1), 82D(2) are then provided to a signal analyzer 94 in the client device 46 for any processing desired.



FIG. 3A illustrates a top view of a room 100 employing the exemplary MIMO distributed antenna system 40 in FIG. 2 to discuss performance of MIMO communications as affected by antenna placement. As illustrated in FIG. 3A, the two MIMO transmitter antennas 78(1), 78(2) of the remote unit 44 are shown as being located in the room 100. Similarly, a client device 46 is shown with its two MIMO receiver antennas 86(1), 86(2) configured to receive the electrical downlink MIMO communication signals 82D(1), 82D(2) from the two MIMO transmitters 81(1), 81(2) (shown in FIG. 2) in MIMO configuration. The two MIMO transmitter antennas 78(1), 78(2) and two MIMO receiver antennas 86(1), 86(2) are placed according to the LOS arrangement. The LOS arrangement ensures that the electrical downlink MIMO communication signals 82D(1), 82D(2) from the two MIMO transmitters 81(1), 81(2) are directed towards the two MIMO receiver antennas 86(1), 86(2), even if the electrical downlink MIMO communication signals 82D(1), 82D(2) are reflected on the downlink propagation path. In other words, the LOS arrangement does not stop the two MIMO receiver antennas 86(1), 86(2) from receiving reflected signals. The MIMO transmitter antennas 78(1), 78(2) in the MIMO transmitters 81(1), 81(2) in the remote unit 44 are separated by a distance D1. The MIMO receiver antennas 86(1), 86(2) in the client device 46 are separated by a distance D2. In absence of multipath due to the LOS arrangement, issues can arise, due to destructive interference, with MIMO algorithm being able to solve the channel matrix for received electrical downlink MIMO communication signals 82D(1), 82D(2) at the client device 46 as a function of the distance D1 between the MIMO transmitter antennas 78(1), 78(2) in the remote unit 44, the distance D2 between MIMO receiver antennas 86(1), 86(2) in the client device 46, and the distance D3 between remote unit 44 and the client device 46. These issues are also referred to herein as location-dependent destructive interference issues.


Location-dependent destructive interference for the received electrical downlink MIMO communication signals 82D(1), 82D(2) can negatively affect MIMO communications performance. These issues with electrical downlink MIMO communication signals 82D(1), 82D(2) received by the MIMO receiver antennas 86(1), 86(2) can occur due to lack of separation (e.g., phase, amplitude) in the received electrical downlink MIMO communication signals 82D(1), 82D(2), especially in LOS communications. To illustrate the effect of these issues, FIG. 3B illustrates a graph 102 illustrating the exemplary measured performance degradation for a given placement distance between the MIMO transmitter antennas 78(1), 78(2) in FIG. 3A. The graph 102 in FIG. 3B illustrates the capacity on the y-axis in Gigabits per second (Gbps) versus the MIMO transmitter antennas 78(1), 78(2) separation distance D1 in centimeters. As illustrated in the graph 102, at separation distances D1 of approximately 42 centimeters (cm) and 85 cm, the communications capacity illustrated by a capacity curve 104 is periodically degraded due to periodic destructive interferences between the received electrical downlink MIMO communication signals 82D(1), 82D(2). Similarly, a MIMO condition number curve 106 in FIG. 3B also illustrates the effect periodic destructive interferences between the received electrical downlink MIMO communication signals 82D(1), 82D(2), which is complementary to the capacity curve 104.



FIG. 3C illustrates a graph 108 representing an exemplary effective communication coverage area provided by the MIMO distributed antenna system 40 in FIG. 2 according to the MIMO transmitter antennas 78(1), 78(2), separation distance D1, the MIMO receiver antennas 86(1), 86(2), separation distance D2 in FIG. 3A, and distance D3 therebetween. As illustrated in FIG. 3C, a desired antenna coverage area 109 is shown as being provided by the area formed inside a boundary line 110. However, an actual communication coverage area 113 for the remote unit 44 is provided inside the boundary line 112, illustrating the effect in reduction communication range of the remote unit 44.


To address these issues, FIGS. 4-8D are provided to illustrate exemplary distributed antenna systems configured to reduce location-dependent destructive interference in distributed antenna systems operating in MIMO configuration. In these embodiments, to provide spatial separation of MIMO communication signals received by MIMO receivers in client devices, multiple MIMO transmitters in a remote unit are each configured to employ multiple transmitter antennas. The multiple transmitter antennas are each configured to transmit communications signals in different polarization states. In certain embodiments, one of the MIMO communications signals is amplitude adjusted in one of the polarization states to provide amplitude separation between MIMO communication signals received by the MIMO receivers.


In this regard, FIG. 4 illustrates an exemplary amplitude adjustment circuit for amplitude adjusting a DL MIMO communication signal transmitted by a MIMO transmitter antenna 78 in FIG. 2. The exemplary amplitude adjustment circuit 120 comprises a signal controller 122 and an amplitude adjustment logic 124. As a non-limiting example, the amplitude adjustment logic 124 may be implemented by a hardware component, a software function, or a combination of both. In another non-limiting example, the signal controller 122 may be a digital baseband processor, a digital signal processor, a MIMO controller, or a general-purpose processor (e.g., central processing unit (CPU)). The signal controller 122 receives a MIMO performance measurement 126 on an uplink reception path (not shown). The signal controller 122 is configured to compare the MIMO performance measurement 126 with a pre-determined MIMO performance threshold. If the MIMO performance measurement 126 indicates a MIMO performance level is below the pre-determined MIMO performance threshold, the signal controller 122 is further configured to provide an amplitude adjustment signal 128 to the amplitude adjustment logic 124 to perform amplitude adjustment on a downlink MIMO communication signal 130. The amplitude adjustment logic 124 in turn performs amplitude adjustment on the downlink communication signal 130 received from a downlink transmission path (not shown). The amplitude adjustment circuit thus produces an amplitude-adjusted downlink communication signal 134 that is sent to a MIMO transmitter antenna on the downlink transmission path (not shown). In a non-limiting example, if the DL MIMO communication signal 130 has an original amplitude x, the amplitude adjustment logic 124 may produce a modified amplitude y that is different from the original amplitude x for the amplitude-adjusted downlink communication signal 134.


With continuing reference to FIG. 4, FIG. 5 illustrates an exemplary amplitude adjustment process performed by the exemplary amplitude adjustment circuit in FIG. 4. FIGS. 2 and 4 are referenced in connection with FIG. 5 and will not be re-described herein. The amplitude adjustment process 140 is invoked when wireless communication starts (block 142). The signal controller 122 receives and processes a MIMO performance measurement (block 144) and compares the MIMO performance measurement with a pre-determined threshold (block 146). If the MIMO performance measurement is above the pre-determined threshold, it indicates that the MIMO transmitter antennas 78 are performing as expected. In this case, the signal controller 122 will not take any action and awaits a next MIMO performance measurement. If, however, the MIMO performance measurement is below the pre-determined threshold, it is an indication that the MIMO transmitter antennas 78 are not performing as expected. Under such circumstance, the signal controller 122 will instruct the amplitude adjustment logic 124 to modify the amplitude of the downlink MIMO communication signal 130 (block 148). The amplitude adjustment process 140 repeats the step of comparing MIMO performance measurement against the pre-determined threshold (block 146) and the step of amplitude adjustment (block 148) until the next MIMO performance measurement is above the pre-determined threshold.


In this regard, FIGS. 6A-6C illustrate alternative MIMO distributed antenna systems 40(1)-40(3) similar to the MIMO distributed antenna system 40 in FIG. 2. FIGS. 6A-6C respectively illustrate three (3) different downlink signal processing stages in the MIMO distributed antenna systems 40(1)-40(3) wherein the amplitude adjustment circuit 120 may be provided. The MIMO distributed antenna systems 40(1)-40(3) in FIGS. 6A-6C are configured to reduce or eliminate periodic destructive interferences between received downlink communication signals at a MIMO receiver in a client device so as to reduce or eliminate performance degradation such as shown in FIGS. 3B and 3C above. The MIMO distributed antenna systems 40(1)-40(3) may include the same components in the MIMO distributed antenna system 40 in FIG. 2 unless otherwise noted in FIGS. 6A-6C. Elements of FIG. 4 are referenced in connection with FIGS. 6A-6C and will not be re-described herein.


With reference to FIG. 6A, a central unit 42(1) is configured to receive the electrical downlink MIMO communications signals 50D as discussed in regard to FIG. 2. However, a signal processor 52(1) is configured to split the electrical downlink MIMO communications signals 50D into four (4) electrical downlink MIMO communications signals 50D(1)-50D(4) over four separate channels. As a first option, an amplitude adjustment circuit 120(1) is provided in the central unit 42(1) to amplitude adjust at least one of the electrical downlink MIMO communications signals 50D. Note that although the electrical downlink MIMO communications signal 50D(4) is amplitude adjusted in this example, any other(s) downlink MIMO communications signal(s) 50D(1)-50D(3) could be amplitude adjusted as well. The amplitude adjustment circuit 120(1) may be programmed or controlled by the signal controller 122 to provide a pre-determined level of amplitude adjustment, if desired. Turning back to the central unit 42(1), electro-optical converters 67(1)-67(4) are provided to convert the electrical downlink MIMO communications signals 50D(1)-50D(4) into optical downlink MIMO communications signals 72D(1)-72D(4) provided over optical fiber communications medium 47(1).


With continuing reference to FIG. 6A, the remote unit 44(1) includes two MIMO transmitters 154(1), 154(2) in MIMO configuration. However, the MIMO transmitters 154(1), 154(2) each include two MIMO transmitter antennas 156(1)(1), 156(1)(2), and 156(2)(1), 156(2)(2). The first MIMO transmitter 154(1) includes the first MIMO transmitter antenna 156(1)(1) configured to radiate the first electrical downlink MIMO communications signals 82D(1) (after conversion from optical to electrical signals) in a first polarization 158(1). The first MIMO transmitter 154(1) also includes the second MIMO transmitter antenna 156(1)(2) configured to radiate the second electrical downlink MIMO communications signal 82D(2) in a second polarization 158(2) different from the first polarization 158(1). In this manner, the first and second electrical downlink MIMO communications signals 82D(1), 82D(2) can be received by two different MIMO receiver antennas 160(1), 160(2) in MIMO receivers 162(1), 162(2), respectively, each configured to receive signals in different polarizations 158(1), 158(2) among the first and second polarizations 158(1), 158(2) without experiencing periodic destructive interferences. Thus, the MIMO receivers 162(1), 162(2) can receive the first and second electrical downlink MIMO communications signal 82D(1), 82D(2) in different polarizations 158(1), 158(2), respectively, from the first MIMO transmitter 154(1) so that a MIMO algorithm can solve the channel matrix for the first and second electrical downlink MIMO communications signal 82D(1), 82D(2). In this embodiment, the first polarization 158(1) is configured to be orthogonal to the second polarization 158(2) to maximize spectral efficiency and minimize cross talk between the electrical downlink MIMO communications signals 82D(1), 82D(2) at the MIMO receivers 162(1), 162(2), but this configuration is not required.


With continuing reference to FIG. 6A, the second MIMO transmitter 154(2) in the remote unit 44(1) includes a third MIMO transmitter antenna 156(2)(1) configured to radiate the third electrical downlink MIMO communications signals 82D(3) (after conversion from optical to electrical signals) in the first polarization 158(1). The second MIMO transmitter 154(2) also includes the fourth MIMO transmitter antenna 156(2)(2) configured to radiate the fourth electrical downlink MIMO communications signal 82D(4) in the second polarization 158(2) different from the first polarization 158(1). In this manner, the third and fourth electrical downlink MIMO communications signals 82D(3), 82D(4) can also be received by the two different MIMO receiver antennas 160(1), 160(2) in MIMO receivers 162(1), 162(2), respectively, each configured to receive signals in different polarizations 158(1), 158(2) among the first and second polarizations 158(1), 158(2). Thus, the MIMO receivers 162(1), 162(2) can receive the third and fourth electrical downlink MIMO communications signal 82D(3), 82D(4) in different polarizations, respectively, from the second MIMO transmitter 154(2) between the third and fourth electrical downlink MIMO communications signal 82D(3), 82D(4). The electrical downlink MIMO communications signals 82D(1)-82D(4) are received by the MIMO receivers 162(1), 162(2) and provided to a signal processor 164 and a MIMO processor 166 for processing.


As previously discussed above, the amplitude adjustment circuit 120(1) is provided in the central unit 42(1) to amplitude adjust the electrical downlink MIMO communications signal 50D(4) The amplitude adjustment in the above example in turn causes the second and fourth electrical downlink MIMO communications signals 82D(2), 82D(4) to be received by the second MIMO receiver antennas 160(2) to have a small but sufficient amplitude difference. Further, the second and fourth electrical downlink MIMO communications signals 82D(2), 82D(4) are also received by the second MIMO receiver antenna 160(2) in the second polarization 158(2), which is different from the first and third electrical downlink MIMO communications signals 82D(1), 82D(3) received by the first MIMO receiver 162(1) in the first polarization 158(1). This combination of amplitude adjustment and MIMO transmitter antenna polarization can reduce or eliminate periodic destructive interferences between the first and the third electrical downlink MIMO communications signals 82D(1), 82D(3) being received by the first MIMO receiver 162(1) and between the second and the fourth electrical downlink MIMO communications signals 82D(2), 82D(4) being received by the second MIMO receiver 162(2).


As previously stated above, the amplitude adjustment circuit 120 can be provided in other downlink signal processing stages of the MIMO distributed antenna system 40 other than in the central unit, as provided in the MIMO distributed antenna system 40(1) in FIG. 6A. In this regard, FIG. 6B is a schematic diagram of another MIMO optical fiber-based distributed antenna system 40(2) (“MIMO distributed antenna system 40(2)”) employing an amplitude adjustment circuit 120(2) in the optical fiber communications medium 47(1). The amplitude adjustment circuit 120(2) can be tunable to allow for the amplitude adjustment to be controlled and tuned. The amplitude adjustment circuit 120(2) may be an optical attenuator or amplifier that makes the amplitude of the optical downlink MIMO communications signal 72D(1) smaller or larger, respectively, than the other downlink optical fibers of the optical fiber communications medium 47(1). Common elements between the MIMO distributed antenna system 40(1) in FIG. 6A and the MIMO distributed antenna system 40(2) in FIG. 6B are noted with common element numbers and will not be re-described. In this embodiment, the amplitude adjustment circuit 120(2) is configured to optically amplitude adjust the optical downlink MIMO communications signal 72D(4) received and transmitted by the second MIMO transmitter 154(2) to the client device 46(1). The central unit 42(2) in FIG. 6B does not include the amplitude adjustment circuit 120(1) to amplitude shift downlink electrical communications signals like provided in the central unit 42(1) in FIG. 6A.


As previously discussed above with regard to FIGS. 6A and 6B, the amplitude adjustment circuit 120 can be provided in the central unit 42(1) and/or the optical fiber communications medium 47(1) to amplitude adjust the electrical downlink MIMO communications signal 50D(4). In this regard, FIG. 6C is a schematic diagram of another MIMO optical fiber-based distributed antenna system 40(3) (“MIMO distributed antenna system 40(3)”) employing an amplitude adjustment circuit 120(3) in the form of an antenna power attenuator or amplifier in the remote unit 44(2). Common elements between the MIMO distributed antenna system 40(3) in FIG. 6C and the MIMO distributed antenna systems 40(1), 40(2) in FIGS. 6A and 6B are noted with common element numbers and will not be re-described. In this embodiment, a signal processor 174 in the remote unit 44(2) receives the optical downlink MIMO communications signals 72D(1)-72D(4) and converts these signals into electrical downlink MIMO communications signals 82D(1)-82D(4) in an optical-to-electrical converter. The amplitude adjustment circuit 120(3) is configured to electrically amplitude adjust the electrical downlink MIMO communications signal 82D(4) received and transmitted by the second MIMO transmitter 154(2) in the remote unit 44(2) to the client device 46(1) so that periodic destructive interferences resulting from LOS arrangement can be reduced or eliminated at the MIMO receivers 162(1), 162(2).


With reference back to FIG. 4, the amplitude adjustment circuit 120 includes the amplitude adjustment logic 124 configured to make amplitude adjustment on the DL MIMO communication signal 130 based on the amplitude adjustment signal 128 received from the signal controller 122. Also with reference back to FIG. 6A, the amplitude adjustment circuit 120(1) is provided in the central unit 42(1) of the MIMO distributed antenna system 40(1) to electronically amplitude adjust at least one of the electrical downlink MIMO communications signals 50D(4). The amplitude adjustment circuit 120(1) may be configured to provide amplitude adjustment in a plurality of ways depending on how the amplitude adjustment logic 124 is implemented. In this regard, FIG. 7 illustrates exemplary implementation options of the amplitude adjustment circuit 120(1) in the central unit 42(1). Elements of FIGS. 4 and 6A are referenced in connection with FIG. 7 and will not be re-described herein. Common elements between the central unit 42(1) in FIG. 6A and the central unit 42(3) in FIG. 7 are noted with common element numbers and will not be re-described.


With reference to FIG. 7, an amplitude adjustment circuit 120(4) in the central unit 42(3) may be implemented in three different options 120(4)(1), 120(4)(2), and 120(4)(3). An amplitude adjustment option 120(4)(1) comprises a signal controller 122(1) configured to receive a control signal 170(1) from a baseband signal processing module (not shown) and provide an amplitude adjustment signal 128(1) to an amplitude adjustment logic 124(1). In response to receiving the amplitude adjustment signal 128(1), the amplitude adjustment logic 124(1) performs amplitude adjustment on a downlink MIMO communications signal 50D(4) received from a signal processor 52(1). The amplitude adjustment logic 124(1), in this non-limiting example, is a tunable attenuator or a variable gain amplifier (VGA) that may be electronically controlled by the signal controller 122(1) to reduce or increase amplitude of the downlink MIMO communications signal 50D(4). An amplitude adjusted downlink MIMO communications signal 172 is received by an electrical/optical converter 67(4) and converted into an optical downlink MIMO communications signal 72D(4) (not shown) for transmission over the fiber communication medium 47(1) (not shown). Note that although the electrical downlink MIMO communications signal 50D(4) is amplitude adjusted in this example, any other(s) downlink MIMO communications signal(s) 50D(1)-50D(3) could be amplitude adjusted in the same way as the downlink MIMO communications signal 50D(4). Alternatively, an amplitude adjustment option 120(4)(2) comprises an amplitude adjustment logic 124(2) configured to provide amplitude adjustment on the downlink MIMO communications signal 50D(4) received from the signal processor 52(1) by adjusting bias signal of a laser diode. Common elements between the amplitude adjustment option 120(4)(1) and the amplitude adjustment option 120(4)(2) are noted with common element numbers and will not be re-described.


With continuing reference to FIG. 7, a third amplitude adjustment option 120(4)(3) comprises an amplitude adjustment logic 124(3) that is an optical modulator. In a non-limiting example, the amplitude adjustment logic 124(3) may be a Mach-Zehnder modulator (MZM) or an electro-absorption modulator (EAM). A bias voltage signal 175 is provided to the amplitude adjustment logic 124(3) from a laser diode 176. Biasing in electronic circuits is a method of establishing various pre-determined voltage or current pointes to provide proper operating conditions in the amplitude adjustment logic 124(3). In a typical EAM, for example, a 0.3 volt (V) variation in bias signal results in approximately three (3) decibel (dB) amplitude variation in an output signal. Thus, by providing the bias voltage signal 175 to the amplitude adjustment logic 124(3), the amplitude of the downlink MIMO communications signal 50D(4) received from the signal processor 52(1) may be adjusted. Other common elements among the amplitude adjustment circuit 120(4)(1), 120(4)(2), 120(4)(3) are noted with common element numbers and will not be re-described.


To help visualize the concept of amplitude adjustment, FIGS. 8A-8B are provided. Elements of FIGS. 6A-6C are referenced in connection with FIGS. 8A-8B and will be re-described herein. FIG. 8A is a graph illustrating exemplary MIMO communication signal waveforms transmitted by MIMO transmitter antennas 156(2)(1), 156(2)(2) in a remote unit 44(1) without amplitude adjustment. As shown in FIG. 8A, when amplitude adjustment is not provided to the MIMO transmitter antennas 156(2)(1), 156(2)(2) in FIG. 6A, the downlink MIMO communications signals 82D(3), 82D(4) both have the same first amplitudes x. FIG. 8B is a graph illustrating exemplary MIMO communication signal waveforms transmitted by MIMO transmitter antennas 156(2)(1), 156(2)(2) in a remote unit 44(1) when amplitude adjustment is provided to the MIMO transmitter antenna 156(2)(2). As can be seen in FIG. 8B, a second amplitude y of the downlink MIMO communications signal 82D(4) is smaller than the first amplitude x of the downlink MIMO communications signal 82D(3). An amplitude adjustment factor α is computed as the ratio between y and x (α=y/x). For example, the amplitude adjustment factor α=0.7 indicates that the second amplitude y is 70% of the first amplitude x. As previously described in FIGS. 6A-6C, such amplitude difference, in conjunction with different polarization states 158(1), 158(2), can help reduce or eliminate periodic destructive interferences between the downlink MIMO communications signals 82D(3), 82D(4) at the MIMO receivers 162. Note that although in FIG. 8B, the amplitude y of the downlink MIMO communications signal 82D(4) is shown to be smaller than the amplitude x of the downlink MIMO communications signal 83D(3), it is possible to amplify the amplitude y of the downlink MIMO communications signal 82D(4) to be larger than the amplitude x of the downlink MIMO communications signal 82D(3). Further, although the downlink MIMO communications signals 82D(4) in FIGS. 8A and 8B are shown to have the same phase, it is also possible to simultaneously phase shift and amplitude adjust the downlink MIMO communications signal 82D(4).


To illustrate the performance improvements provided by the amplitude adjustment circuits 120(1)-120(3) in the MIMO distributed antenna systems 40(1)-40(3) in FIGS. 6A-6C, FIG. 8C illustrates a graph 180 illustrating exemplary performance degradation curves for a given placement distance between the MIMO transmitters 154(1), 154(2). Similar to graph 102 in FIG. 3B, FIG. 8C illustrates MIMO distributed antenna systems 40(1)-40(3) capacity on the y-axis in units of Gigabits per second (Gbps) versus MIMO transmitter antennas 78(1), 78(2) separation distance on the x-axis in units of centimeters (cm). The capacity degradation curve 182 in FIG. 8C, which is equivalent to the capacity curve 104 in FIG. 3B, illustrates severe periodic capacity dips resulting from periodic destructive interference when amplitude adjustment techniques described above for MIMO distributed antenna systems 40(1)-40(3) are not employed. As shown in the graph 180, for a given transmitter antenna separation distance and a given wireless distance (e.g., a distance between a wireless transmitter and a wireless receiver), a capacity degradation curve 184 and a capacity degradation curve 186 illustrate different degrees of capacity degradations when amplitude adjustment techniques described above for MIMO distributed antenna systems 40(1)-40(3) are employed. In this non-limiting example, the capacity degradation curves 184 and 186 are associated with amplitude adjustment factors α=0.7 and α=0.9, respectively. As can be seen in the capacity degradation curves 184, 186, periodic capacity dips, although not completely eliminated, do become more moderate as result of reduced periodic destructive interference provided by amplitude adjustment techniques described above for MIMO distributed antenna systems 40(1)-40(3).



FIG. 8D is a graph 190 illustrating an exemplary effective antenna coverage versus placement distance between MIMO transmitters 154(1), 154(2) in the distributed antenna systems 40(1)-40(3) in FIGS. 6A-6C, for a two (2) cm placement distance between the MIMO receivers 162(1), 162(2). When the amplitude adjustment techniques described above for the MIMO distributed antenna systems 40(1)-40(3) are employed, coverage curve 192 illustrates consistent 100% antenna coverage regardless of placement distance between MIMO transmitters 154(1), 154(2) in the distributed antenna systems 40(1)-40(3) in FIGS. 6A-6C. When the amplitude adjustment techniques described above for the MIMO distributed antenna systems 40(1)-40(3) are not employed, coverage curve 194 illustrates inconsistent antenna coverage dependent upon placement distance between MIMO transmitters 154(1), 154(2) in the distributed antenna systems 40(1)-40(3) in FIGS. 6A-6C.


It may also be desired to provide high-speed wireless digital data service connectivity with remote units in the MIMO distributed antenna systems disclosed herein. One example would be WiFi. WiFi was initially limited in data rate transfer to 12.24 Mb/s and is now provided at data transfer rates of up to 54 Mb/s using WLAN frequencies of 2.4 GHz and 5.8 GHz. While interesting for many applications, WiFi has proven to have too small a bandwidth to support real time downloading of uncompressed high definition (HD) television signals to wireless client devices. To increase data transfer rates, the frequency of wireless signals could be increased to provide larger channel bandwidth. For example, an extremely high frequency in the range of 30 GHz to 300 GHz could be employed. For example, the sixty (60) GHz spectrum is an EHF that is an unlicensed spectrum by the Federal Communications Commission (FCC) and that could be employed to provide for larger channel bandwidths. However, high frequency wireless signals are more easily attenuated or blocked from traveling through walls or other building structures where distributed antenna systems are installed.


Thus, the embodiments disclosed herein can include distribution of extremely high frequency (EHF) (i.e., approximately 30—approximately 300 GHz), as a non-limiting example. The MIMO distributed antenna systems disclosed herein can also support provision of digital data services to wireless clients. The use of the EHF band allows for the use of channels having a higher bandwidth, which in turn allows more data intensive signals, such as uncompressed HD video to be communicated without substantial degradation to the quality of the video. As a non-limiting example, the distributed antenna systems disclosed herein may operate at approximately sixty (60) GHz with approximately seven (7) GHz bandwidth channels to provide greater bandwidth to digital data services. The distributed antenna systems disclosed herein may be well suited to be deployed in an indoor building or other facility for delivering of digital data services.


It may be desirable to provide MIMO distributed antenna systems, according to the embodiments disclosed herein, that provide digital data services for client devices. For example, it may be desirable to provide digital data services to client devices located within a distributed antenna system. Wired and wireless devices may be located in the building infrastructures that are configured to access digital data services. Examples of digital data services include, but are not limited to, Ethernet, WLAN, WiMax, WiFi, DSL, and LTE, etc. Ethernet standards could be supported, including but not limited to, 100 Mb/s (i.e., fast Ethernet) or Gigabit (Gb) Ethernet, or ten Gigabit (10G) Ethernet. Examples of digital data services include, but are not limited to, wired and wireless servers, wireless access points (WAPs), gateways, desktop computers, hubs, switches, remote radio heads (RRHs), baseband units (BBUs), and femtocells. A separate digital data services network can be provided to provide digital data services to digital data devices.



FIG. 9 is a schematic diagram representation of additional detail illustrating components that could be employed in any of the components or devices disclosed herein, but only if adapted to execute instructions from an exemplary computer-readable medium to perform any of the functions or processing described herein. In this regard, such component or device may include a computer system 220 within which a set of instructions for performing any one or more of the location services discussed herein may be executed. The computer system 220 may be connected (e.g., networked) to other machines in a LAN, an intranet, an extranet, or the Internet. While only a single device is illustrated, the term “device” shall also be taken to include any collection of devices that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein. The computer system 220 may be a circuit or circuits included in an electronic board card, such as, a printed circuit board (PCB), a server, a personal computer, a desktop computer, a laptop computer, a personal digital assistant (PDA), a computing pad, a mobile device, or any other device, and may represent, for example, a server or a user's computer.


The exemplary computer system 220 in this embodiment includes a processing device or processor 222, a main memory 224 (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM), such as synchronous DRAM (SDRAM), etc.), and a static memory 226 (e.g., flash memory, static random access memory (SRAM), etc.), which may communicate with each other via a data bus 228. Alternatively, the processing device 222 may be connected to the main memory 224 and/or static memory 226 directly or via some other connectivity means. The processing device 222 may be a controller, and the main memory 224 or static memory 226 may be any type of memory.


The processing device 222 represents one or more general-purpose processing devices, such as a microprocessor, central processing unit, or the like. More particularly, the processing device 222 may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing other instruction sets, or other processors implementing a combination of instruction sets. The processing device 222 is configured to execute processing logic in instructions 230 for performing the operations and steps discussed herein.


The computer system 220 may further include a network interface device 232. The computer system 220 also may or may not include an input 234, configured to receive input and selections to be communicated to the computer system 220 when executing instructions. The computer system 220 also may or may not include an output 236, including but not limited to a display, a video display unit (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), an alphanumeric input device (e.g., a keyboard), and/or a cursor control device (e.g., a mouse).


The computer system 220 may or may not include a data storage device that includes instructions 238 stored in a computer-readable medium 240. The instructions 238 may also reside, completely or at least partially, within the main memory 224 and/or within the processing device 222 during execution thereof by the computer system 220, the main memory 224 and the processing device 222 also constituting computer-readable medium. The instructions 238 may further be transmitted or received over a network 242 via the network interface device 232.


While the computer-readable medium 240 is shown in an exemplary embodiment to be a single medium, the term “computer-readable medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions. The term “computer-readable medium” shall also be taken to include any medium that is capable of storing, encoding, or carrying a set of instructions for execution by the processing device and that cause the processing device to perform any one or more of the methodologies of the embodiments disclosed herein. The term “computer-readable medium” shall accordingly be taken to include, but not be limited to, solid-state memories, optical and magnetic medium, and carrier wave signals.


The embodiments disclosed herein include various steps. The steps of the embodiments disclosed herein may be formed by hardware components or may be embodied in machine-executable instructions, which may be used to cause a general-purpose or special-purpose processor programmed with the instructions to perform the steps. Alternatively, the steps may be performed by a combination of hardware and software.


The embodiments disclosed herein may be provided as a computer program product, or software, that may include a machine-readable medium (or computer-readable medium) having stored thereon instructions, which may be used to program a computer system (or other electronic devices) to perform a process according to the embodiments disclosed herein. A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium includes: a machine-readable storage medium (e.g., ROM, random access memory (“RAM”), a magnetic disk storage medium, an optical storage medium, flash memory devices, etc.); a machine-readable transmission medium (electrical, optical, acoustical, or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.)); and the like.


Unless specifically stated otherwise and as apparent from the previous discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing,” “computing,” “determining,” “displaying,” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data and memories represented as physical (electronic) quantities within the computer system's registers into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission, or display devices.


The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatuses to perform the required method steps. The required structure for a variety of these systems will appear from the description above. In addition, the embodiments described herein are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the embodiments as described herein.


Those of skill in the art will further appreciate that the various illustrative logical blocks, modules, circuits, and algorithms described in connection with the embodiments disclosed herein may be implemented as electronic hardware, instructions stored in memory or in another computer-readable medium and executed by a processor or other processing device, or combinations of both. The components of the distributed antenna systems described herein may be employed in any circuit, hardware component, integrated circuit (IC), or IC chip, as examples. Memory disclosed herein may be any type and size of memory and may be configured to store any type of information desired. To clearly illustrate this interchangeability, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. How such functionality is implemented depends on the particular application, design choices, and/or design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present embodiments.


The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. Furthermore, a controller may be a processor. A processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).


The embodiments disclosed herein may be embodied in hardware and in instructions that are stored in hardware, and may reside, for example, in RAM, flash memory, ROM, Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, a hard disk, a removable disk, a CD-ROM, or any other form of computer-readable medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a remote station. In the alternative, the processor and the storage medium may reside as discrete components in a remote station, base station, or server.


It is also noted that the operational steps described in any of the exemplary embodiments herein are described to provide examples and discussion. The operations described may be performed in numerous different sequences other than the illustrated sequences. Furthermore, operations described in a single operational step may actually be performed in a number of different steps. Additionally, one or more operational steps discussed in the exemplary embodiments may be combined. Those of skill in the art will also understand that information and signals may be represented using any of a variety of technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips, that may be references throughout the above description, may be represented by voltages, currents, electromagnetic waves, magnetic fields, or particles, optical fields or particles, or any combination thereof.


Further and as used herein, it is intended that terms “fiber optic cables” and/or “optical fibers” include all types of single mode and multi-mode light waveguides, including one or more optical fibers that may be upcoated, colored, buffered, ribbonized, and/or have other organizing or protective structure in a cable such as one or more tubes, strength members, jackets, or the like. The optical fibers disclosed herein can be single mode or multi-mode fibers. Likewise, other types of suitable optical fibers include bend-insensitive optical fibers, or any other expedient of a medium for transmitting light signals. An example of a bend-insensitive, or bend resistant, optical fiber is ClearCurve® Multimode fiber, commercially available from Corning Incorporated. Suitable fibers of this type are disclosed, for example, in U.S. Patent Application Publication Nos. 2008/0166094 and 2009/0169163, the disclosures of which are incorporated herein by reference in their entireties.


Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that any particular order be inferred.


It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the invention. Since modifications combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and their equivalents.

Claims
  • 1. A method of transmitting multiple-input, multiple-output (MIMO) communications signals, the method comprising: receiving a first optical downlink MIMO communications signal at a first amplitude over a first downlink communications medium;converting the first optical downlink MIMO communications signal to a first electrical downlink MIMO communications signal;transmitting the first electrical downlink MIMO communications signal over a first MIMO transmitter antenna in a first polarization;receiving a second optical downlink MIMO communications signal at the first amplitude;converting the second optical downlink MIMO communications signal to a second electrical downlink MIMO communications signal;transmitting the second electrical downlink MIMO communications signal over a second MIMO transmitter antenna in a second polarization;receiving a third optical downlink MIMO communications signal at the first amplitude;converting the third optical downlink MIMO communications signal to a third electrical downlink MIMO communications signal;transmitting the third electrical downlink MIMO communications signal over a third MIMO transmitter antenna in the first polarization;receiving a fourth optical downlink MIMO communications signal;converting the fourth optical downlink MIMO communications signal to a fourth electrical downlink MIMO communications signal; andtransmitting the fourth electrical downlink MIMO communications signal at a second amplitude, over a fourth MIMO transmitter antenna in the second polarization.
  • 2. The method of claim 1, wherein: transmitting the first electrical downlink MIMO communications signal comprises transmitting to a line-of-sight (LOS) wireless client; andtransmitting the second electrical downlink MIMO communications signal comprises transmitting to a LOS wireless client.
  • 3. The method of claim 2, wherein: transmitting the third electrical downlink MIMO communications signal comprises transmitting to a LOS wireless client; andtransmitting the fourth electrical downlink MIMO communications signal comprises transmitting to a LOS wireless client.
  • 4. The method of claim 3, further comprising amplitude adjusting the fourth optical downlink MIMO communications signal.
  • 5. The method of claim 4, further comprising receiving the fourth optical downlink MIMO communications signal at the second amplitude modified from the first amplitude in a central unit.
  • 6. The method of claim 4, further comprising receiving the fourth optical downlink MIMO communications signal at the second amplitude modified from the first amplitude in the fourth downlink communications medium.
  • 7. The method of claim 1, further comprising amplitude adjusting the fourth optical downlink MIMO communications signal.
  • 8. The method of claim 7, further comprising receiving the fourth optical downlink MIMO communications signal at the second amplitude modified from the first amplitude in a central unit.
  • 9. The method of claim 7, further comprising receiving the fourth optical downlink MIMO communications signal at the second amplitude modified from the first amplitude in the fourth downlink communications medium.
  • 10. The method of claim 1, further comprising receiving the fourth optical downlink MIMO communications signal at the second amplitude modified from the first amplitude in a central unit.
  • 11. The method of claim 1, further comprising receiving the fourth optical downlink MIMO communications signal at the second amplitude modified from the first amplitude in the fourth downlink communications medium.
PRIORITY APPLICATIONS

This application is a continuation of U.S. application Ser. No. 15/372,490, filed Dec. 8, 2016, which is a continuation of U.S. application Ser. No. 14/447,014, filed on Jul. 30, 2014, the contents of which are incorporated herein by reference in their entireties.

US Referenced Citations (872)
Number Name Date Kind
4365865 Stiles Dec 1982 A
4449246 Seiler et al. May 1984 A
4573212 Lipsky Feb 1986 A
4665560 Lange May 1987 A
4867527 Dotti et al. Sep 1989 A
4889977 Hayden Dec 1989 A
4896939 O'Brien Jan 1990 A
4916460 Powell Apr 1990 A
4939852 Brenner Jul 1990 A
4943136 Popoff Jul 1990 A
4972346 Kawano et al. Nov 1990 A
5039195 Jenkins et al. Aug 1991 A
5042086 Cole et al. Aug 1991 A
5056109 Gilhousen et al. Oct 1991 A
5059927 Cohen Oct 1991 A
5125060 Edmundson Jun 1992 A
5159479 Takagi Oct 1992 A
5187803 Sohner et al. Feb 1993 A
5189718 Barrett et al. Feb 1993 A
5189719 Coleman et al. Feb 1993 A
5206655 Caille et al. Apr 1993 A
5208812 Dudek et al. May 1993 A
5210812 Nilsson et al. May 1993 A
5260957 Hakimi Nov 1993 A
5263108 Kurokawa et al. Nov 1993 A
5267122 Glover et al. Nov 1993 A
5268971 Nilsson et al. Dec 1993 A
5278690 Vella-Coleiro Jan 1994 A
5278989 Burke et al. Jan 1994 A
5280472 Gilhousen et al. Jan 1994 A
5299947 Barnard Apr 1994 A
5301056 O'Neill Apr 1994 A
5325223 Bears Jun 1994 A
5339058 Lique Aug 1994 A
5339184 Tang Aug 1994 A
5343320 Anderson Aug 1994 A
5377035 Wang et al. Dec 1994 A
5379455 Koschek Jan 1995 A
5381459 Lappington Jan 1995 A
5396224 Dukes et al. Mar 1995 A
5400391 Emura et al. Mar 1995 A
5420863 Taketsugu et al. May 1995 A
5424864 Emura Jun 1995 A
5444564 Newberg Aug 1995 A
5455592 Huddle Oct 1995 A
5457557 Zarem et al. Oct 1995 A
5459727 Vannucci Oct 1995 A
5469523 Blew et al. Nov 1995 A
5500763 Ota Mar 1996 A
5502446 Denninger Mar 1996 A
5513176 Dean et al. Apr 1996 A
5519830 Opoczynski May 1996 A
5543000 Lique Aug 1996 A
5546443 Raith Aug 1996 A
5557698 Gareis et al. Sep 1996 A
5574815 Kneeland Nov 1996 A
5583517 Yokev et al. Dec 1996 A
5598288 Collar Jan 1997 A
5606725 Hart Feb 1997 A
5615034 Hori Mar 1997 A
5627879 Russell et al. May 1997 A
5640678 Ishikawa et al. Jun 1997 A
5644622 Russell et al. Jul 1997 A
5648961 Ebihara Jul 1997 A
5651081 Blew et al. Jul 1997 A
5661582 Kintis et al. Aug 1997 A
5668562 Cutrer et al. Sep 1997 A
5677974 Elms et al. Oct 1997 A
5682256 Motley et al. Oct 1997 A
5694232 Parsay et al. Dec 1997 A
5703602 Casebolt Dec 1997 A
5708681 Malkemes et al. Jan 1998 A
5726984 Kubler et al. Mar 1998 A
5765099 Georges et al. Jun 1998 A
5774789 van der Kaay et al. Jun 1998 A
5790536 Mahany et al. Aug 1998 A
5790606 Dent Aug 1998 A
5793772 Burke et al. Aug 1998 A
5802173 Hamilton-Piercy et al. Sep 1998 A
5802473 Rutledge et al. Sep 1998 A
5805975 Green, Sr. et al. Sep 1998 A
5805983 Naidu et al. Sep 1998 A
5809395 Hamilton-Piercy et al. Sep 1998 A
5809422 Raleigh et al. Sep 1998 A
5809431 Bustamante et al. Sep 1998 A
5812296 Tarusawa et al. Sep 1998 A
5818619 Medved et al. Oct 1998 A
5818883 Smith et al. Oct 1998 A
5821510 Cohen et al. Oct 1998 A
5825651 Gupta et al. Oct 1998 A
5828658 Ottersten et al. Oct 1998 A
5832379 Mallinckrodt Nov 1998 A
5835857 Otten Nov 1998 A
5838474 Stilling Nov 1998 A
5839052 Dean et al. Nov 1998 A
5852651 Fischer et al. Dec 1998 A
5854986 Dorren et al. Dec 1998 A
5859719 Dentai et al. Jan 1999 A
5862460 Rich Jan 1999 A
5867485 Chambers et al. Feb 1999 A
5867763 Dean et al. Feb 1999 A
5881200 Burt Mar 1999 A
5883882 Schwartz Mar 1999 A
5896568 Tseng et al. Apr 1999 A
5903834 Wallstedt et al. May 1999 A
5910776 Black Jun 1999 A
5913003 Arroyo et al. Jun 1999 A
5917636 Wake et al. Jun 1999 A
5930682 Schwartz et al. Jul 1999 A
5936754 Ariyavisitakul et al. Aug 1999 A
5943372 Gans et al. Aug 1999 A
5946622 Bojeryd Aug 1999 A
5949564 Wake Sep 1999 A
5953670 Newson Sep 1999 A
5959531 Gallagher, III et al. Sep 1999 A
5960344 Mahany Sep 1999 A
5969837 Farber et al. Oct 1999 A
5983070 Georges et al. Nov 1999 A
5987303 Dutta et al. Nov 1999 A
5995832 Mallinckrodt Nov 1999 A
6005884 Cook et al. Dec 1999 A
6006069 Langston et al. Dec 1999 A
6006105 Rostoker et al. Dec 1999 A
6011980 Nagano et al. Jan 2000 A
6014546 Georges et al. Jan 2000 A
6016426 Bodell Jan 2000 A
6023625 Myers, Jr. Feb 2000 A
6031645 Ichikawa Feb 2000 A
6037898 Parish et al. Mar 2000 A
6049705 Xue Apr 2000 A
6061161 Yang et al. May 2000 A
6069721 Oh et al. May 2000 A
6088381 Myers, Jr. Jul 2000 A
6112086 Wala Aug 2000 A
6118767 Shen et al. Sep 2000 A
6122529 Sabat, Jr. et al. Sep 2000 A
6127917 Tuttle Oct 2000 A
6128470 Naidu et al. Oct 2000 A
6128477 Freed Oct 2000 A
6148041 Dent Nov 2000 A
6150921 Werb et al. Nov 2000 A
6157810 Georges et al. Dec 2000 A
6192216 Sabat, Jr. et al. Feb 2001 B1
6194968 Winslow Feb 2001 B1
6198432 Janky Mar 2001 B1
6211978 Wojtunik Apr 2001 B1
6212397 Langston et al. Apr 2001 B1
6222503 Gietema Apr 2001 B1
6223201 Reznak Apr 2001 B1
6232870 Garber et al. May 2001 B1
6236784 Ido May 2001 B1
6236789 Fitz May 2001 B1
6236863 Waldroup et al. May 2001 B1
6240274 Izadpanah May 2001 B1
6268946 Larkin et al. Jul 2001 B1
6275990 Dapper et al. Aug 2001 B1
6279158 Geile et al. Aug 2001 B1
6286163 Trimble Sep 2001 B1
6292673 Maeda et al. Sep 2001 B1
6295451 Mimura Sep 2001 B1
6301240 Slabinski et al. Oct 2001 B1
6307869 Pawelski Oct 2001 B1
6308085 Shoki Oct 2001 B1
6314163 Acampora Nov 2001 B1
6317599 Rappaport et al. Nov 2001 B1
6323980 Bloom Nov 2001 B1
6324391 Bodell Nov 2001 B1
6330241 Fort Dec 2001 B1
6330244 Swartz et al. Dec 2001 B1
6334219 Hill et al. Dec 2001 B1
6336021 Nukada Jan 2002 B1
6336042 Dawson et al. Jan 2002 B1
6337754 Imajo Jan 2002 B1
6340932 Rodgers et al. Jan 2002 B1
6353406 Lanzl et al. Mar 2002 B1
6353600 Schwartz et al. Mar 2002 B1
6359714 Imajo Mar 2002 B1
6370203 Boesch et al. Apr 2002 B1
6374078 Williams et al. Apr 2002 B1
6374124 Slabinski Apr 2002 B1
6389010 Kubler et al. May 2002 B1
6400318 Kasami et al. Jun 2002 B1
6400418 Wakabayashi Jun 2002 B1
6404775 Leslie et al. Jun 2002 B1
6405018 Reudink et al. Jun 2002 B1
6405058 Bobier Jun 2002 B2
6405308 Gupta et al. Jun 2002 B1
6414624 Endo et al. Jul 2002 B2
6415132 Sabat, Jr. Jul 2002 B1
6421327 Lundby et al. Jul 2002 B1
6438301 Johnson et al. Aug 2002 B1
6438371 Fujise et al. Aug 2002 B1
6448558 Greene Sep 2002 B1
6452915 Jorgensen Sep 2002 B1
6459519 Sasai et al. Oct 2002 B1
6459989 Kirkpatrick et al. Oct 2002 B1
6477154 Cheong et al. Nov 2002 B1
6480702 Sabat, Jr. Nov 2002 B1
6486907 Farber et al. Nov 2002 B1
6496290 Lee Dec 2002 B1
6501965 Lucidarme Dec 2002 B1
6504636 Seto et al. Jan 2003 B1
6504831 Greenwood et al. Jan 2003 B1
6512478 Chien Jan 2003 B1
6519395 Bevan et al. Feb 2003 B1
6519449 Zhang et al. Feb 2003 B1
6525855 Westbrook et al. Feb 2003 B1
6535330 Lelic et al. Mar 2003 B1
6535720 Kintis et al. Mar 2003 B1
6553239 Langston Apr 2003 B1
6556551 Schwartz Apr 2003 B1
6577794 Currie et al. Jun 2003 B1
6577801 Broderick et al. Jun 2003 B2
6580393 Holt Jun 2003 B2
6580402 Navarro et al. Jun 2003 B2
6580905 Naidu et al. Jun 2003 B1
6580918 Leickel et al. Jun 2003 B1
6583763 Judd Jun 2003 B2
6587514 Wright et al. Jul 2003 B1
6594496 Schwartz Jul 2003 B2
6597325 Judd et al. Jul 2003 B2
6598009 Yang Jul 2003 B2
6606430 Bartur et al. Aug 2003 B2
6615074 Mickle et al. Sep 2003 B2
6628732 Takaki Sep 2003 B1
6634811 Gertel et al. Oct 2003 B1
6636747 Harada et al. Oct 2003 B2
6640103 Inman et al. Oct 2003 B1
6643437 Park Nov 2003 B1
6652158 Bartur et al. Nov 2003 B2
6654590 Boros et al. Nov 2003 B2
6654616 Pope, Jr. et al. Nov 2003 B1
6657535 Magbie et al. Dec 2003 B1
6658269 Golemon et al. Dec 2003 B1
6665308 Rakib et al. Dec 2003 B1
6670930 Navarro Dec 2003 B2
6675294 Gupta et al. Jan 2004 B1
6678509 Skarman et al. Jan 2004 B2
6687437 Starnes et al. Feb 2004 B1
6690328 Judd Feb 2004 B2
6696917 Heitner et al. Feb 2004 B1
6697603 Lovinggood et al. Feb 2004 B1
6704298 Matsumiya et al. Mar 2004 B1
6704545 Wala Mar 2004 B1
6710366 Lee et al. Mar 2004 B1
6714800 Johnson et al. Mar 2004 B2
6731880 Westbrook et al. May 2004 B2
6745013 Porter et al. Jun 2004 B1
6758913 Tunney et al. Jul 2004 B1
6763226 McZeal, Jr. Jul 2004 B1
6771862 Karnik et al. Aug 2004 B2
6771933 Eng et al. Aug 2004 B1
6784802 Stanescu Aug 2004 B1
6785558 Stratford et al. Aug 2004 B1
6788666 Linebarger et al. Sep 2004 B1
6801767 Schwartz et al. Oct 2004 B1
6807374 Imajo et al. Oct 2004 B1
6812824 Goldinger et al. Nov 2004 B1
6812905 Thomas et al. Nov 2004 B2
6823174 Masenten et al. Nov 2004 B1
6826163 Mani et al. Nov 2004 B2
6826337 Linnell Nov 2004 B2
6836660 Wala Dec 2004 B1
6836673 Trott Dec 2004 B1
6842433 West et al. Jan 2005 B2
6842459 Binder Jan 2005 B1
6847856 Bohannon Jan 2005 B1
6850510 Kubler Feb 2005 B2
6865390 Goss et al. Mar 2005 B2
6873823 Hasarchi Mar 2005 B2
6876056 Tilmans et al. Apr 2005 B2
6879290 Toutain et al. Apr 2005 B1
6882311 Walker et al. Apr 2005 B2
6883710 Chung Apr 2005 B2
6885344 Mohamadi Apr 2005 B2
6885846 Panasik et al. Apr 2005 B1
6889060 Fernando et al. May 2005 B2
6895249 Gaal May 2005 B2
6909399 Zegelin et al. Jun 2005 B1
6914539 Hoctor et al. Jul 2005 B2
6915058 Pons Jul 2005 B2
6915529 Suematsu et al. Jul 2005 B1
6919858 Rofougaran Jul 2005 B2
6920330 Caronni et al. Jul 2005 B2
6924997 Chen et al. Aug 2005 B2
6930987 Fukuda et al. Aug 2005 B1
6931183 Panak et al. Aug 2005 B2
6931659 Kinemura Aug 2005 B1
6933849 Sawyer Aug 2005 B2
6934511 Lovinggood et al. Aug 2005 B1
6934541 Miyatani Aug 2005 B2
6941112 Hasegawa Sep 2005 B2
6946989 Vavik Sep 2005 B2
6961312 Kubler et al. Nov 2005 B2
6963289 Aljadeff et al. Nov 2005 B2
6963552 Sabat, Jr. et al. Nov 2005 B2
6965718 Koertel Nov 2005 B2
6967347 Estes et al. Nov 2005 B2
6968107 Belardi et al. Nov 2005 B2
6970652 Zhang et al. Nov 2005 B2
6973243 Koyasu et al. Dec 2005 B2
6974262 Rickenbach Dec 2005 B1
6977502 Hertz Dec 2005 B1
7002511 Ammar et al. Feb 2006 B1
7006039 Miyamoto et al. Feb 2006 B2
7006465 Toshimitsu et al. Feb 2006 B2
7013087 Suzuki et al. Mar 2006 B2
7015826 Chan et al. Mar 2006 B1
7020473 Splett Mar 2006 B2
7020488 Bleile et al. Mar 2006 B1
7023382 Akano Apr 2006 B1
7024166 Wallace Apr 2006 B2
7035512 Van Bijsterveld Apr 2006 B2
7035671 Solum Apr 2006 B2
7039399 Fischer May 2006 B2
7043271 Seto et al. May 2006 B1
7047028 Cagenius et al. May 2006 B2
7050017 King et al. May 2006 B2
7053838 Judd May 2006 B2
7054513 Herz et al. May 2006 B2
7069577 Geile et al. Jun 2006 B2
7072586 Aburakawa et al. Jul 2006 B2
7082320 Kattukaran et al. Jul 2006 B2
7084769 Bauer et al. Aug 2006 B2
7092726 Shi et al. Aug 2006 B2
7093985 Lord et al. Aug 2006 B2
7103119 Matsuoka et al. Sep 2006 B2
7103377 Bauman et al. Sep 2006 B2
7106931 Sutehall et al. Sep 2006 B2
7110795 Doi Sep 2006 B2
7114859 Tuohimaa et al. Oct 2006 B1
7123939 Bird et al. Oct 2006 B1
7127176 Sasaki Oct 2006 B2
7142503 Grant et al. Nov 2006 B1
7142535 Kubler et al. Nov 2006 B2
7142619 Sommer et al. Nov 2006 B2
7160032 Nagashima et al. Jan 2007 B2
7171244 Bauman Jan 2007 B2
7184728 Solum Feb 2007 B2
7190748 Kim et al. Mar 2007 B2
7194023 Norrell et al. Mar 2007 B2
7199443 Elsharawy Apr 2007 B2
7200305 Dion et al. Apr 2007 B2
7200391 Chung et al. Apr 2007 B2
7228072 Mickelsson et al. Jun 2007 B2
7250907 Krumm et al. Jul 2007 B2
7263293 Ommodt et al. Aug 2007 B2
7269311 Kim et al. Sep 2007 B2
7280011 Bayar et al. Oct 2007 B2
7286843 Scheck Oct 2007 B2
7286854 Ferrato et al. Oct 2007 B2
7295119 Rappaport et al. Nov 2007 B2
7310430 Mallya et al. Dec 2007 B1
7313415 Wake et al. Dec 2007 B2
7315735 Graham Jan 2008 B2
7324730 Varkey et al. Jan 2008 B2
7343164 Kallstenius Mar 2008 B2
7348843 Qiu et al. Mar 2008 B1
7349633 Lee et al. Mar 2008 B2
7359408 Kim Apr 2008 B2
7359674 Markki et al. Apr 2008 B2
7366150 Lee et al. Apr 2008 B2
7366151 Kubler et al. Apr 2008 B2
7369526 Lechleider et al. May 2008 B2
7379669 Kim May 2008 B2
7388892 Nishiyama et al. Jun 2008 B2
7392025 Rooyen et al. Jun 2008 B2
7392029 Pronkine Jun 2008 B2
7394883 Funakubo et al. Jul 2008 B2
7403156 Coppi et al. Jul 2008 B2
7409159 Izadpanah Aug 2008 B2
7417724 Kotola et al. Aug 2008 B1
7424228 Williams et al. Sep 2008 B1
7429951 Kennedy, Jr. et al. Sep 2008 B2
7442679 Stolte et al. Oct 2008 B2
7444051 Tatat et al. Oct 2008 B2
7450853 Kim et al. Nov 2008 B2
7450854 Lee et al. Nov 2008 B2
7451365 Wang et al. Nov 2008 B2
7453363 Reynolds Nov 2008 B2
7454222 Huang et al. Nov 2008 B2
7460507 Kubler et al. Dec 2008 B2
7460829 Utsumi et al. Dec 2008 B2
7460831 Hasarchi Dec 2008 B2
7466925 Iannelli Dec 2008 B2
7469105 Wake et al. Dec 2008 B2
7477597 Segel Jan 2009 B2
7483504 Shapira et al. Jan 2009 B2
7483711 Burchfiel Jan 2009 B2
7496070 Vesuna Feb 2009 B2
7496384 Seto et al. Feb 2009 B2
7505747 Solum Mar 2009 B2
7512419 Solum Mar 2009 B2
7522552 Fein et al. Apr 2009 B2
7539509 Bauman et al. May 2009 B2
7542452 Penumetsa Jun 2009 B2
7546138 Bauman Jun 2009 B2
7548138 Kamgaing Jun 2009 B2
7548695 Wake Jun 2009 B2
7551641 Pirzada et al. Jun 2009 B2
7557758 Rofougaran Jul 2009 B2
7580384 Kubler et al. Aug 2009 B2
7586861 Kubler et al. Sep 2009 B2
7590354 Sauer et al. Sep 2009 B2
7593704 Pinel et al. Sep 2009 B2
7599420 Forenza et al. Oct 2009 B2
7599672 Shoji et al. Oct 2009 B2
7610046 Wala Oct 2009 B2
7627250 George et al. Dec 2009 B2
7630690 Kaewell, Jr. et al. Dec 2009 B2
7633934 Kubler et al. Dec 2009 B2
7639982 Wala Dec 2009 B2
7646743 Kubler et al. Jan 2010 B2
7646777 Hicks, III et al. Jan 2010 B2
7653397 Pernu et al. Jan 2010 B2
7668565 Ylänen et al. Feb 2010 B2
7675936 Mizutani et al. Mar 2010 B2
7688811 Kubler et al. Mar 2010 B2
7693486 Kasslin et al. Apr 2010 B2
7697467 Kubler et al. Apr 2010 B2
7697574 Suematsu et al. Apr 2010 B2
7715375 Kubler et al. May 2010 B2
7715722 Hoke et al. May 2010 B1
7751374 Donovan Jul 2010 B2
7751838 Ramesh et al. Jul 2010 B2
7760703 Kubler et al. Jul 2010 B2
7768951 Kubler et al. Aug 2010 B2
7773573 Chung et al. Aug 2010 B2
7778603 Palin et al. Aug 2010 B2
7787823 George et al. Aug 2010 B2
7787854 Conyers et al. Aug 2010 B2
7809012 Ruuska et al. Oct 2010 B2
7812766 Leblanc et al. Oct 2010 B2
7812775 Babakhani et al. Oct 2010 B2
7817958 Scheinert et al. Oct 2010 B2
7817969 Castaneda et al. Oct 2010 B2
7835328 Stephens et al. Nov 2010 B2
7844273 Scheinert Nov 2010 B2
7848316 Kubler et al. Dec 2010 B2
7848731 Dianda et al. Dec 2010 B1
7848770 Scheinert Dec 2010 B2
7853234 Afsahi Dec 2010 B2
7870321 Rofougaran Jan 2011 B2
7880677 Rofougaran et al. Feb 2011 B2
7881755 Mishra et al. Feb 2011 B1
7894423 Kubler et al. Feb 2011 B2
7899007 Kubler et al. Mar 2011 B2
7907972 Walton et al. Mar 2011 B2
7912043 Kubler et al. Mar 2011 B2
7912506 Lovberg et al. Mar 2011 B2
7916706 Kubler et al. Mar 2011 B2
7917177 Bauman Mar 2011 B2
7920553 Kubler et al. Apr 2011 B2
7920858 Sabat, Jr. et al. Apr 2011 B2
7924783 Mahany et al. Apr 2011 B1
7929940 Dianda et al. Apr 2011 B1
7936713 Kubler et al. May 2011 B2
7948897 Stuart et al. May 2011 B2
7949364 Kasslin et al. May 2011 B2
7957777 Vu et al. Jun 2011 B1
7962111 Solum Jun 2011 B2
7969009 Chandrasekaran Jun 2011 B2
7969911 Mahany et al. Jun 2011 B2
7990925 Tinnakomsrisuphap et al. Aug 2011 B2
7996020 Chhabra Aug 2011 B1
8018907 Kubler et al. Sep 2011 B2
8023886 Rofougaran Sep 2011 B2
8027656 Rofougaran et al. Sep 2011 B2
8031121 Rofougaran et al. Oct 2011 B2
8036308 Rofougaran Oct 2011 B2
8082353 Huber et al. Dec 2011 B2
8086192 Rofougaran et al. Dec 2011 B2
8107464 Schmidt et al. Jan 2012 B2
8174428 Wegener May 2012 B2
8274929 Schmidt et al. Sep 2012 B2
8275265 Kobyakov et al. Sep 2012 B2
8279800 Schmidt et al. Oct 2012 B2
8310963 Singh Nov 2012 B2
8346091 Kummetz et al. Jan 2013 B2
8422884 Mao Apr 2013 B2
8467823 Seki et al. Jun 2013 B2
8548330 Berlin et al. Oct 2013 B2
8548526 Schmidt et al. Oct 2013 B2
8583100 Koziy et al. Nov 2013 B2
8599794 Ahmadi Dec 2013 B2
8634766 Hobbs et al. Jan 2014 B2
8676214 Fischer et al. Mar 2014 B2
8681917 McAllister et al. Mar 2014 B2
8693342 Uyehara et al. Apr 2014 B2
8694034 Notargiacomo Apr 2014 B2
8699881 Iannone Apr 2014 B1
8699982 Singh Apr 2014 B2
8737300 Stapleton et al. May 2014 B2
8792933 Chen Jul 2014 B2
8873585 Oren et al. Oct 2014 B2
8908607 Kummetz et al. Dec 2014 B2
8913892 Berlin et al. Dec 2014 B2
8948816 Fischer et al. Feb 2015 B2
8958789 Bauman et al. Feb 2015 B2
8976067 Fischer Mar 2015 B2
9001811 Wala et al. Apr 2015 B2
9130613 Oren et al. Sep 2015 B2
9258052 George et al. Feb 2016 B2
9432095 Berlin et al. Aug 2016 B2
9525472 George Dec 2016 B2
9531452 George et al. Dec 2016 B2
9929786 George Mar 2018 B2
20020009070 Lindsay et al. Jan 2002 A1
20020075906 Cole et al. Jun 2002 A1
20020085643 Kitchener et al. Jul 2002 A1
20020092347 Niekerk et al. Jul 2002 A1
20020111149 Shoki Aug 2002 A1
20020111192 Thomas et al. Aug 2002 A1
20020114038 Amon et al. Aug 2002 A1
20020123365 Thorson et al. Sep 2002 A1
20020126967 Panak et al. Sep 2002 A1
20020128009 Boch et al. Sep 2002 A1
20020130778 Nicholson Sep 2002 A1
20020181668 Masoian et al. Dec 2002 A1
20020190845 Moore Dec 2002 A1
20030002604 Fifield et al. Jan 2003 A1
20030007214 Aburakawa et al. Jan 2003 A1
20030016418 Westbrook et al. Jan 2003 A1
20030045284 Copley et al. Mar 2003 A1
20030078074 Sesay et al. Apr 2003 A1
20030112826 Ashwood Smith et al. Jun 2003 A1
20030141962 Barink Jul 2003 A1
20030161637 Yamamoto et al. Aug 2003 A1
20030165287 Krill et al. Sep 2003 A1
20030174099 Bauer et al. Sep 2003 A1
20030209601 Chung Nov 2003 A1
20040001719 Sasaki Jan 2004 A1
20040008114 Sawyer Jan 2004 A1
20040017785 Zelst Jan 2004 A1
20040033076 Song et al. Feb 2004 A1
20040037565 Young et al. Feb 2004 A1
20040041714 Forster Mar 2004 A1
20040043764 Bigham et al. Mar 2004 A1
20040047313 Rumpf et al. Mar 2004 A1
20040068751 Basawapatna et al. Apr 2004 A1
20040078151 Aljadeff et al. Apr 2004 A1
20040095907 Agee et al. May 2004 A1
20040100930 Shapira et al. May 2004 A1
20040102196 Weckstrom et al. May 2004 A1
20040105435 Morioka Jun 2004 A1
20040126068 Van Bijsterveld Jul 2004 A1
20040126107 Jay et al. Jul 2004 A1
20040139477 Russell et al. Jul 2004 A1
20040146020 Kubler et al. Jul 2004 A1
20040149736 Clothier Aug 2004 A1
20040151164 Kubler et al. Aug 2004 A1
20040151503 Kashima et al. Aug 2004 A1
20040157623 Splett Aug 2004 A1
20040160912 Kubler et al. Aug 2004 A1
20040160913 Kubler et al. Aug 2004 A1
20040162084 Wang Aug 2004 A1
20040162115 Smith et al. Aug 2004 A1
20040162116 Han et al. Aug 2004 A1
20040164902 Karlsson et al. Aug 2004 A1
20040165568 Weinstein Aug 2004 A1
20040165573 Kubler et al. Aug 2004 A1
20040175173 Deas Sep 2004 A1
20040196404 Loheit et al. Oct 2004 A1
20040202257 Mehta et al. Oct 2004 A1
20040203703 Fischer Oct 2004 A1
20040203704 Ommodt et al. Oct 2004 A1
20040203846 Caronni et al. Oct 2004 A1
20040204109 Hoppenstein Oct 2004 A1
20040208526 Mibu Oct 2004 A1
20040208643 Roberts et al. Oct 2004 A1
20040218873 Nagashima et al. Nov 2004 A1
20040233877 Lee et al. Nov 2004 A1
20040258105 Spathas et al. Dec 2004 A1
20050041693 Priotti Feb 2005 A1
20050052287 Whitesmith et al. Mar 2005 A1
20050058451 Ross Mar 2005 A1
20050068179 Roesner Mar 2005 A1
20050076982 Metcalf et al. Apr 2005 A1
20050078006 Hutchins Apr 2005 A1
20050093679 Zai et al. May 2005 A1
20050099343 Asrani et al. May 2005 A1
20050116821 Wilsey et al. Jun 2005 A1
20050123232 Piede et al. Jun 2005 A1
20050141545 Fein et al. Jun 2005 A1
20050143077 Charbonneau Jun 2005 A1
20050147071 Karaoguz et al. Jul 2005 A1
20050148306 Hiddink Jul 2005 A1
20050159108 Fletcher Jul 2005 A1
20050174236 Brookner Aug 2005 A1
20050176458 Shklarsky et al. Aug 2005 A1
20050201761 Bartur et al. Sep 2005 A1
20050219050 Martin Oct 2005 A1
20050224585 Durrant et al. Oct 2005 A1
20050226625 Wake et al. Oct 2005 A1
20050232636 Durrant et al. Oct 2005 A1
20050242188 Vesuna Nov 2005 A1
20050252971 Howarth et al. Nov 2005 A1
20050266797 Utsumi et al. Dec 2005 A1
20050266854 Niiho et al. Dec 2005 A1
20050269930 Shimizu et al. Dec 2005 A1
20050271396 Iannelli Dec 2005 A1
20050272439 Picciriello et al. Dec 2005 A1
20060002326 Vesuna Jan 2006 A1
20060014548 Bolin Jan 2006 A1
20060017633 Pronkine Jan 2006 A1
20060025101 Li Feb 2006 A1
20060028352 McNamara et al. Feb 2006 A1
20060045054 Utsumi et al. Mar 2006 A1
20060046662 Moulsley et al. Mar 2006 A1
20060056283 Anikhindi et al. Mar 2006 A1
20060056327 Coersmeier Mar 2006 A1
20060062579 Kim et al. Mar 2006 A1
20060063494 Zhang et al. Mar 2006 A1
20060094470 Wake et al. May 2006 A1
20060104643 Lee et al. May 2006 A1
20060120395 Xing et al. Jun 2006 A1
20060128425 Rooyen Jun 2006 A1
20060159388 Kawase et al. Jul 2006 A1
20060182446 Kim et al. Aug 2006 A1
20060182449 Iannelli et al. Aug 2006 A1
20060189280 Goldberg Aug 2006 A1
20060189354 Lee et al. Aug 2006 A1
20060203836 Kim Sep 2006 A1
20060217132 Drummond-Murray et al. Sep 2006 A1
20060223439 Pinel et al. Oct 2006 A1
20060233506 Noonan et al. Oct 2006 A1
20060239630 Hase et al. Oct 2006 A1
20060262014 Shemesh et al. Nov 2006 A1
20060268738 Goerke et al. Nov 2006 A1
20060274704 Desai et al. Dec 2006 A1
20060276227 Dravida Dec 2006 A1
20070008939 Fischer Jan 2007 A1
20070009266 Bothwell Jan 2007 A1
20070040687 Reynolds Feb 2007 A1
20070054682 Fanning et al. Mar 2007 A1
20070058978 Lee et al. Mar 2007 A1
20070060045 Prautzsch Mar 2007 A1
20070060055 Desai et al. Mar 2007 A1
20070071128 Meir et al. Mar 2007 A1
20070072646 Kuwahara et al. Mar 2007 A1
20070076649 Lin et al. Apr 2007 A1
20070093273 Cai Apr 2007 A1
20070099578 Adeney May 2007 A1
20070104165 Hanaoka et al. May 2007 A1
20070135169 Sychaleun et al. Jun 2007 A1
20070149250 Crozzoli et al. Jun 2007 A1
20070155314 Mohebbi Jul 2007 A1
20070166042 Seeds et al. Jul 2007 A1
20070173288 Skarby et al. Jul 2007 A1
20070182626 Samavati et al. Aug 2007 A1
20070184841 Choi et al. Aug 2007 A1
20070224954 Gopi Sep 2007 A1
20070243899 Hermel et al. Oct 2007 A1
20070248358 Sauer Oct 2007 A1
20070253714 Seeds et al. Nov 2007 A1
20070257796 Easton et al. Nov 2007 A1
20070264009 Sabat, Jr. et al. Nov 2007 A1
20070264011 Sone et al. Nov 2007 A1
20070268846 Proctor et al. Nov 2007 A1
20070274279 Wood et al. Nov 2007 A1
20070280159 Liu et al. Dec 2007 A1
20070280370 Liu Dec 2007 A1
20070292143 Yu et al. Dec 2007 A1
20070297005 Montierth et al. Dec 2007 A1
20080002652 Gupta et al. Jan 2008 A1
20080005219 Nabar et al. Jan 2008 A1
20080007453 Vassilakis et al. Jan 2008 A1
20080008134 Satou et al. Jan 2008 A1
20080013473 Proctor, Jr. et al. Jan 2008 A1
20080013909 Kostet et al. Jan 2008 A1
20080013956 Ware et al. Jan 2008 A1
20080013957 Akers et al. Jan 2008 A1
20080014948 Scheinert Jan 2008 A1
20080026765 Charbonneau Jan 2008 A1
20080031628 Dragas et al. Feb 2008 A1
20080043714 Pernu Feb 2008 A1
20080056167 Kim et al. Mar 2008 A1
20080058018 Scheinert Mar 2008 A1
20080063397 Hu et al. Mar 2008 A1
20080070502 George et al. Mar 2008 A1
20080080863 Sauer et al. Apr 2008 A1
20080084951 Chen et al. Apr 2008 A1
20080089692 Sorin Apr 2008 A1
20080089699 Li et al. Apr 2008 A1
20080098203 Master et al. Apr 2008 A1
20080107202 Lee et al. May 2008 A1
20080118014 Reunamaki et al. May 2008 A1
20080119198 Hettstedt et al. May 2008 A1
20080124086 Matthews May 2008 A1
20080124087 Hartmann et al. May 2008 A1
20080129594 Pera et al. Jun 2008 A1
20080129634 Pera et al. Jun 2008 A1
20080134194 Liu Jun 2008 A1
20080145061 Lee et al. Jun 2008 A1
20080150514 Codreanu et al. Jun 2008 A1
20080166094 Bookbinder et al. Jul 2008 A1
20080194226 Rivas et al. Aug 2008 A1
20080207253 Jaakkola et al. Aug 2008 A1
20080212969 Fasshauer et al. Sep 2008 A1
20080219670 Kim et al. Sep 2008 A1
20080232799 Kim Sep 2008 A1
20080233967 Montojo et al. Sep 2008 A1
20080247716 Thomas Oct 2008 A1
20080253280 Tang et al. Oct 2008 A1
20080253351 Pernu et al. Oct 2008 A1
20080253773 Zheng Oct 2008 A1
20080260388 Kim et al. Oct 2008 A1
20080261656 Bella et al. Oct 2008 A1
20080268766 Narkmon et al. Oct 2008 A1
20080268833 Huang et al. Oct 2008 A1
20080273844 Kewitsch Nov 2008 A1
20080279137 Pernu et al. Nov 2008 A1
20080280569 Hazani et al. Nov 2008 A1
20080291818 Leisten Nov 2008 A1
20080291830 Pernu et al. Nov 2008 A1
20080292322 Daghighian et al. Nov 2008 A1
20080298813 Song et al. Dec 2008 A1
20080304831 Miller, II et al. Dec 2008 A1
20080310464 Schneider Dec 2008 A1
20080310848 Yasuda et al. Dec 2008 A1
20080311876 Leenaerts et al. Dec 2008 A1
20090022304 Kubler et al. Jan 2009 A1
20090028087 Nguyen et al. Jan 2009 A1
20090028317 Ling et al. Jan 2009 A1
20090041413 Hurley Feb 2009 A1
20090047023 Pescod et al. Feb 2009 A1
20090059903 Kubler et al. Mar 2009 A1
20090061796 Arkko et al. Mar 2009 A1
20090061939 Andersson et al. Mar 2009 A1
20090073916 Zhang et al. Mar 2009 A1
20090087179 Underwood et al. Apr 2009 A1
20090088071 Rofougaran Apr 2009 A1
20090092073 Doppler et al. Apr 2009 A1
20090135078 Lindmark et al. May 2009 A1
20090141780 Cruz-Albrecht et al. Jun 2009 A1
20090149221 Liu et al. Jun 2009 A1
20090154621 Shapira et al. Jun 2009 A1
20090169163 Abbott, III et al. Jul 2009 A1
20090175214 Sfar et al. Jul 2009 A1
20090180407 Sabat et al. Jul 2009 A1
20090218407 Rofougaran Sep 2009 A1
20090218657 Rofougaran Sep 2009 A1
20090237317 Rofougaran Sep 2009 A1
20090239521 Mohebbi Sep 2009 A1
20090245084 Moffatt et al. Oct 2009 A1
20090245153 Li et al. Oct 2009 A1
20090245221 Piipponen Oct 2009 A1
20090247109 Rofougaran Oct 2009 A1
20090252136 Mahany et al. Oct 2009 A1
20090252204 Shatara et al. Oct 2009 A1
20090252205 Rheinfelder et al. Oct 2009 A1
20090258652 Lambert et al. Oct 2009 A1
20090278596 Rofougaran et al. Nov 2009 A1
20090279593 Rofougaran et al. Nov 2009 A1
20090285147 Subasic et al. Nov 2009 A1
20090316609 Singh Dec 2009 A1
20100002626 Schmidt et al. Jan 2010 A1
20100027443 LoGalbo et al. Feb 2010 A1
20100056200 Tolonen Mar 2010 A1
20100080154 Noh et al. Apr 2010 A1
20100080182 Kubler et al. Apr 2010 A1
20100091475 Toms et al. Apr 2010 A1
20100118864 Kubler et al. May 2010 A1
20100127937 Chandrasekaran et al. May 2010 A1
20100134257 Puleston et al. Jun 2010 A1
20100142598 Murray et al. Jun 2010 A1
20100142955 Yu et al. Jun 2010 A1
20100144285 Behzad et al. Jun 2010 A1
20100148373 Chandrasekaran Jun 2010 A1
20100150060 Vitek Jun 2010 A1
20100156721 Alamouti et al. Jun 2010 A1
20100159859 Rofougaran Jun 2010 A1
20100188998 Pernu et al. Jul 2010 A1
20100190509 Davis Jul 2010 A1
20100202326 Rofougaran et al. Aug 2010 A1
20100225413 Rofougaran et al. Sep 2010 A1
20100225520 Mohamadi et al. Sep 2010 A1
20100225556 Rofougaran et al. Sep 2010 A1
20100225557 Rofougaran et al. Sep 2010 A1
20100232323 Kubler et al. Sep 2010 A1
20100246541 Kim Sep 2010 A9
20100246558 Harel Sep 2010 A1
20100255774 Kenington Oct 2010 A1
20100258949 Henderson et al. Oct 2010 A1
20100260063 Kubler et al. Oct 2010 A1
20100261501 Behzad et al. Oct 2010 A1
20100265874 Palanki et al. Oct 2010 A1
20100284323 Tang et al. Nov 2010 A1
20100290355 Roy et al. Nov 2010 A1
20100309049 Reunamäki et al. Dec 2010 A1
20100311472 Rofougaran et al. Dec 2010 A1
20100311480 Raines et al. Dec 2010 A1
20100329161 Ylanen et al. Dec 2010 A1
20100329166 Mahany et al. Dec 2010 A1
20110007724 Mahany et al. Jan 2011 A1
20110007733 Kubler et al. Jan 2011 A1
20110008042 Stewart Jan 2011 A1
20110013904 Khermosh et al. Jan 2011 A1
20110019999 George et al. Jan 2011 A1
20110021146 Pernu Jan 2011 A1
20110021224 Koskinen et al. Jan 2011 A1
20110026932 Yeh et al. Feb 2011 A1
20110065450 Kazmi Mar 2011 A1
20110066774 Rofougaran Mar 2011 A1
20110069668 Chion et al. Mar 2011 A1
20110071734 Van Wiemeersch et al. Mar 2011 A1
20110086614 Brisebois et al. Apr 2011 A1
20110116572 Lee et al. May 2011 A1
20110122912 Benjamin et al. May 2011 A1
20110126071 Han et al. May 2011 A1
20110135308 Tarlazzi et al. Jun 2011 A1
20110149879 Noriega et al. Jun 2011 A1
20110158298 Djadi et al. Jun 2011 A1
20110182230 Ohm et al. Jul 2011 A1
20110194475 Kim et al. Aug 2011 A1
20110200325 Kobyakov et al. Aug 2011 A1
20110201368 Faccin et al. Aug 2011 A1
20110204504 Henderson et al. Aug 2011 A1
20110206383 Chien et al. Aug 2011 A1
20110211439 Manpuria et al. Sep 2011 A1
20110215901 Van Wiemeersch et al. Sep 2011 A1
20110222415 Ramamurthi et al. Sep 2011 A1
20110222434 Chen Sep 2011 A1
20110222616 Jiang et al. Sep 2011 A1
20110222619 Ramamurthi et al. Sep 2011 A1
20110223958 Chen et al. Sep 2011 A1
20110223960 Chen et al. Sep 2011 A1
20110223961 Chen et al. Sep 2011 A1
20110227795 Lopez et al. Sep 2011 A1
20110243201 Phillips et al. Oct 2011 A1
20110244887 Dupray et al. Oct 2011 A1
20110256878 Zhu et al. Oct 2011 A1
20110268033 Boldi et al. Nov 2011 A1
20110268446 Cune et al. Nov 2011 A1
20110274021 He et al. Nov 2011 A1
20110274433 Presi et al. Nov 2011 A1
20110281536 Lee et al. Nov 2011 A1
20110305284 Mueck Dec 2011 A1
20120002750 Hooli et al. Jan 2012 A1
20120046039 Hagerman et al. Feb 2012 A1
20120087670 Han et al. Apr 2012 A1
20120140660 Kang et al. Jun 2012 A1
20120170542 Zangi Jul 2012 A1
20120177026 Uyehara et al. Jul 2012 A1
20120208581 Ishida et al. Aug 2012 A1
20120213111 Shimezawa Aug 2012 A1
20120243513 Fujishima et al. Sep 2012 A1
20120314797 Kummetz et al. Dec 2012 A1
20120327800 Kim et al. Dec 2012 A1
20130017863 Kummetz et al. Jan 2013 A1
20130095875 Reuven Apr 2013 A1
20130101005 Aryanfar Apr 2013 A1
20130150063 Berlin et al. Jun 2013 A1
20130195000 Shen Aug 2013 A1
20130235962 O'Keefe Sep 2013 A1
20130343765 Rohde et al. Dec 2013 A1
20140078920 Tandra Mar 2014 A1
20140126914 Berlin et al. May 2014 A1
20140211875 Berlin et al. Jul 2014 A1
20140226698 Negus Aug 2014 A1
20140269859 Hanson et al. Sep 2014 A1
20140314061 Trajkovic et al. Oct 2014 A1
20150003565 George Jan 2015 A1
20150023283 Liu et al. Jan 2015 A1
20150098351 Zavadsky et al. Apr 2015 A1
20150098372 Zavadksy et al. Apr 2015 A1
20150098419 Zavadsky et al. Apr 2015 A1
20150256237 George et al. Sep 2015 A1
20160036505 George et al. Feb 2016 A1
20160134348 George et al. May 2016 A1
20160173223 Rosenfelder et al. Jun 2016 A1
20170093472 George et al. Mar 2017 A1
Foreign Referenced Citations (150)
Number Date Country
645192 Oct 1992 AU
731180 Mar 1998 AU
2065090 Feb 1998 CA
2242707 Jan 1999 CA
20104862 Aug 2001 DE
10249414 May 2004 DE
0355328 Feb 1990 EP
0477952 Apr 1992 EP
0477952 Apr 1992 EP
0709974 May 1996 EP
0461583 Mar 1997 EP
851618 Jul 1998 EP
0687400 Nov 1998 EP
0938204 Aug 1999 EP
0993124 Apr 2000 EP
1037411 Sep 2000 EP
1085684 Mar 2001 EP
1179895 Feb 2002 EP
1267447 Dec 2002 EP
1347584 Sep 2003 EP
1363352 Nov 2003 EP
1391897 Feb 2004 EP
1443687 Aug 2004 EP
1455550 Sep 2004 EP
1501206 Jan 2005 EP
1503451 Feb 2005 EP
1530316 May 2005 EP
1511203 Mar 2006 EP
1267447 Aug 2006 EP
1693974 Aug 2006 EP
1742388 Jan 2007 EP
1227605 Jan 2008 EP
1954019 Aug 2008 EP
1968250 Sep 2008 EP
1056226 Apr 2009 EP
1357683 May 2009 EP
2219310 Aug 2010 EP
2313020 Nov 1997 GB
2323252 Sep 1998 GB
2399963 Sep 2004 GB
2428149 Jan 2007 GB
H4189036 Jul 1992 JP
05252559 Sep 1993 JP
05260018 Oct 1993 JP
05327569 Dec 1993 JP
05327576 Dec 1993 JP
09083450 Mar 1997 JP
09162810 Jun 1997 JP
09200840 Jul 1997 JP
11068675 Mar 1999 JP
2000152300 May 2000 JP
2000341744 Dec 2000 JP
2002264617 Sep 2002 JP
2002353813 Dec 2002 JP
2003148653 May 2003 JP
2003172827 Jun 2003 JP
2004172734 Jun 2004 JP
2004245963 Sep 2004 JP
2004247090 Sep 2004 JP
2004264901 Sep 2004 JP
2004265624 Sep 2004 JP
2004317737 Nov 2004 JP
2004349184 Dec 2004 JP
2005018175 Jan 2005 JP
2005087135 Apr 2005 JP
2005134125 May 2005 JP
2007228603 Sep 2007 JP
2008172597 Jul 2008 JP
20010055088 Jul 2001 KR
20110087949 Aug 2011 KR
9603823 Feb 1996 WO
9613102 May 1996 WO
9804054 Jan 1998 WO
9810600 Mar 1998 WO
00042721 Jul 2000 WO
0072475 Nov 2000 WO
0178434 Oct 2001 WO
0184760 Nov 2001 WO
0186755 Nov 2001 WO
0221183 Mar 2002 WO
0230141 Apr 2002 WO
02091619 Nov 2002 WO
02102102 Dec 2002 WO
03024027 Mar 2003 WO
03098175 Nov 2003 WO
2004030154 Apr 2004 WO
2004047472 Jun 2004 WO
2004056019 Jul 2004 WO
2004059934 Jul 2004 WO
2004086795 Oct 2004 WO
2004093471 Oct 2004 WO
2004107783 Dec 2004 WO
2005062505 Jul 2005 WO
2005069203 Jul 2005 WO
2005073897 Aug 2005 WO
2005079386 Sep 2005 WO
2005101701 Oct 2005 WO
2005111959 Nov 2005 WO
2006011778 Feb 2006 WO
2006018592 Feb 2006 WO
2006019392 Feb 2006 WO
2006039941 Apr 2006 WO
2006051262 May 2006 WO
2006060754 Jun 2006 WO
2006094441 Sep 2006 WO
2006105185 Oct 2006 WO
2006133609 Dec 2006 WO
2006136811 Dec 2006 WO
2007048427 May 2007 WO
2007075579 Jul 2007 WO
2007077451 Jul 2007 WO
2007088561 Aug 2007 WO
2007091026 Aug 2007 WO
2007133630 Nov 2007 WO
2008008249 Jan 2008 WO
2008027213 Mar 2008 WO
2008033298 Mar 2008 WO
2008039830 Apr 2008 WO
2008116014 Sep 2008 WO
2006046088 May 2009 WO
2009100395 Aug 2009 WO
2009100396 Aug 2009 WO
2009100397 Aug 2009 WO
2009100398 Aug 2009 WO
2010087919 Aug 2010 WO
2010090999 Aug 2010 WO
2010132739 Nov 2010 WO
2011005162 Jan 2011 WO
2011043172 Apr 2011 WO
2011100095 Aug 2011 WO
2011112373 Sep 2011 WO
2011139939 Nov 2011 WO
2011158302 Dec 2011 WO
2011160117 Dec 2011 WO
2012024345 Feb 2012 WO
2012054553 Apr 2012 WO
2012148256 Nov 2012 WO
2012148938 Nov 2012 WO
2012148940 Nov 2012 WO
2012170865 Dec 2012 WO
2013009283 Jan 2013 WO
2013009835 Jan 2013 WO
2014070236 May 2014 WO
2014082070 May 2014 WO
2014082072 May 2014 WO
2014082075 May 2014 WO
2014144314 Sep 2014 WO
2015054162 Apr 2015 WO
2015054164 Apr 2015 WO
2015054165 Apr 2015 WO
Non-Patent Literature Citations (113)
Entry
Fan et al; “Spectrally Efficient 60-GHZ XY-MIMO Data Transport Over a Radio-Over-Fiber System for Gigabit Wireless Local Area Networks”; IEEE 2010; 4 Pages.
Lee et al; “Evaluation of 60 GHZ MIMO Channel Capacity in the Conference Room STA-STA Scenario”; 2011 IEEE; 5 Pages.
Sheldon et al; “A 60GHZ Line-of-Sight 2X2 MIMO Link Operating at 1.2GBPS”; IEEE Xplore; IEEE 2008; 4 Pages.
Arredondo, Albedo et al., “Techniques for Improving In-Building Radio Coverage Using Fiber-Fed Distributed Antenna Networks,” IEEE 46th Vehicular Technology Conference, Atlanta, Georgia, Apr. 28-May 1, 1996, pp. 1540-1543, vol. 3.
Bakaul, M., et al., “Efficient Multiplexing Scheme for Wavelength-Interleaved DWDM Millimeter-Wave Fiber-Radio Systems,” IEEE Photonics Technology Letters, Dec. 2005, vol. 17, No. 12, pp. 2718-2720.
Cho, Bong Youl et al. “The Forward Link Performance of a PCS System with an AGC,” 4th CDMA International Conference and Exhibition, “The Realization of IMT-2000,” 1999, 10 pages.
Chu, Ta-Shing et al. “Fiber optic microcellular radio”, IEEE Transactions on Vehicular Technology, Aug. 1991, pp. 599-606, vol. 40, Issue 3.
Cooper, A.J., “Fiber/Radio for the Provision of Cordless/Mobile Telephony Services in the Access Network,” Electronics Letters, 1990, pp. 2054-2056, vol. 26.
Cutrer, David M. et al., “Dynamic Range Requirements for Optical Transmitters in Fiber-Fed Microcellular Networks,” IEEE Photonics Technology Letters, May 1995, pp. 564-566, vol. 7, No. 5.
Dolmans, G. et al. “Performance study of an adaptive dual antenna handset for indoor communications”, IEE Proceedings: Microwaves, Antennas and Propagation, Apr. 1999, pp. 138-144, vol. 146, Issue 2.
Ellinger, Frank et al., “A 5.2 GHz variable gain LNA MMIC for adaptive antenna combining”, IEEE MTT-S International Microwave Symposium Digest, Anaheim, California, Jun. 13-19, 1999, pp. 501-504, vol. 2.
Fan, J.C. et al., “Dynamic range requirements for microcellular personal communication systems using analog fiber-optic links”, IEEE Transactions on Microwave Theory and Techniques, Aug. 1997, pp. 1390-1397, vol. 45, Issue 8.
Gibson, B.C., et al., “Evanescent Field Analysis of Air-Silica Microstructure Waveguides,” The 14th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 1-7803-7104-4/01, Nov. 12-13, 2001, vol. 2, pp. 709-710.
Huang, C., et al., “A WLAN-Used Helical Antenna Fully Integrated with the PCMCIA Carrier,” IEEE Transactions on Antennas and Propagation, Dec. 2005, vol. 53, No. 12, pp. 4164-4168.
Kojucharow, K., et al., “Millimeter-Wave Signal Properties Resulting from Electrooptical Upconversion,” IEEE Transaction on Microwave Theory and Techniques, Oct. 2001, vol. 49, No. 10, pp. 1977-1985.
Monro, T.M., et al., “Holey Fibers with Random Cladding Distributions,” Optics Letters, Feb. 15, 2000, vol. 25, No. 4, pp. 206-208.
Moreira, J.D., et al., “Diversity Techniques for OFDM Based WLAN Systems,” The 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, Sep. 15-18, 2002, vol. 3, pp. 1008-1011.
Niiho, T., et al., “Multi-Channel Wireless LAN Distributed Antenna System based on Radio-Over-Fiber Techniques,” The 17th Annual Meeting of the IEEE Lasers and Electro-Optics Society, Nov. 2004, vol. 1, pp. 57-58.
Author Unknown, “ITU-T G.652, Telecommunication Standardization Sector of ITU, Series G: Transmission Systems and Media, Digital Systems and Networks, Transmission Media and Optical Systems Characteristics—Optical Fibre Cables, Characteristics of a Single-Mode Optical Fiber and Cable,” ITU-T Recommendation G.652, International Telecommunication Union, Jun. 2005, 22 pages.
Author Unknown, “ITU-T G.657, Telecommunication Standardization Sector of ITU, Dec. 2006, Series G: Transmission Systems and Media, Digital Systems and Networks, Transmission Media and Optical Systems Characteristics—Optical Fibre Cables, Characteristics of a Bending Loss Insensitive Single Mode Optical Fibre and Cable for the Access Network,” ITU-T Recommendation G.657, International Telecommunication Union, 20 pages.
International Search Report and Written Opinion for International patent application PCT/US2007/013802 dated May 8, 2008, 12 pages.
Opatic, D., “Radio over Fiber Technology for Wireless Access,” Ericsson, Oct. 17, 2009, 6 pages.
Paulraj, A.J., et al., “An Overview of MIMO Communications—A Key to Gigabit Wireless,” Proceedings of the IEEE, Feb. 2004, vol. 92, No. 2, 34 pages.
Pickrell, G.R., et al., “Novel Techniques for the Fabrication of Holey Optical Fibers,” Proceedings of SPIE, Oct. 28-Nov. 2, 2001, vol. 4578, 2001, pp. 271-282.
Roh, W., et al., “MIMO Channel Capacity for the Distributed Antenna Systems,” Proceedings of the 56th IEEE Vehicular Technology Conference, Sep. 2002, vol. 2, pp. 706-709.
Schweber, Bill, “Maintaining cellular connectivity indoors demands sophisticated design,” EDN Network, Dec. 21, 2000, 2 pages, http://www.edn.com/design/integrated-circuit-design/4362776/Maintaining-cellular-connectivity-indoors-demands-sophisticated-design.
Seto, I., et al., “Antenna-Selective Transmit Diversity Technique for OFDM-Based WLANs with Dual-Band Printed Antennas,” 2005 IEEE Wireless Communications and Networking Conference, Mar. 13-17, 2005, vol. 1, pp. 51-56.
Shen, C., et al., “Comparison of Channel Capacity for MIMO-DAS versus MIMO-CAS,” The 9th Asia-Pacific Conference on Communications, Sep. 21-24, 2003, vol. 1, pp. 113-118.
Wake, D. et al., “Passive Picocell: A New Concept n Wireless Network Infrastructure,” Electronics Letters, Feb. 27, 1997, vol. 33, No. 5, pp. 404-406.
Windyka, John et al., “System-Level Integrated Circuit (SLIC) Technology Development for Phased Array Antenna Applications,” Contractor Report 204132, National Aeronautics and Space Administration, Jul. 1997, 94 pages.
Winters, J., et al., “The Impact of Antenna Diversity on the Capacity of Wireless Communications Systems,” IEEE Transcations on Communications, vol. 42, No. 2/3/4, Feb./Mar./Apr. 1994, pp. 1740-1751.
Yu et al., “A Novel Scheme to Generate Single-Sideband Millimeter-Wave Signals by Using Low-Frequency Local Oscillator Signal,” IEEE Photonics Technology Letters, vol. 20, No. 7, Apr. 1, 2008, pp. 478-480.
Second Office Action for Chinese patent application 20078002293.6 dated Aug. 30, 2012, 10 pages.
International Search Report for PCT/US2010/022847 dated Jul. 12, 2010, 3 pages.
International Search Report for PCT/US2010/022857 dated Jun. 18, 2010, 3 pages.
Decision on Appeal for U.S. Appl. No. 11/451,237 dated Mar. 19, 2013, 7 pages.
Decision on Rejection for Chinese patent application 200780022093.6 dated Feb. 5, 2013, 9 pages.
Non-Final Office Action for U.S. Appl. No. 15/655,228, dated May 18, 2018, 17 pages.
Notice of Allowance for U.S. Appl. No. 15/655,228, dated Sep. 14, 2018, 9 pages.
Final Office Action for U.S. Appl. No. 15/271,843, dated Feb. 7, 2018, 13 pages.
Attygalle et al., “Extending Optical Transmission Distance in Fiber Wireless Links Using Passive Filtering in Conjunction with Optimized Modulation,” Journal of Lightwave Technology, vol. 24, No. 4, Apr. 2006, 7 pages.
Bo Zhang et al., “Reconfigurable Multifunctional Operation Using Optical Injection-Locked Vertical-Cavity Surface-Emitting Lasers,” Journal of Lightwave Technology, vol. 27, No. 15, Aug. 2009, 6 pages.
Chang-Hasnain, et al., “Ultrahigh-speed laser modulation by injection locking,” Chapter 6, Optical Fiber Telecommunication V A: Components and Subsystems, Elsevier Inc., 2008, 20 pages.
Cheng Zhang et al., “60 GHz Millimeter-wave Generation by Two-mode Injection-locked Fabry-Perot Laser Using Second-Order Sideband Injection in Radio-over-Fiber System,” Conference on Lasers and Electro-Optics and Quantum Electronics, Optical Society of America, May 2008, 2 pages.
Chrostowski, “Optical Injection Locking of Vertical Cavity Surface Emitting Lasers,” Fall 2003, PhD dissertation University of California at Berkely, 122 pages.
Dang et al., “Radio-over-Fiber based architecture for seamless wireless indoor communication in the 60GHz band,” Computer Communications, Elsevier B.V., Amsterdam, NL, vol. 30, Sep. 8, 2007, pp. 3598-3613.
Hyuk-Kee Sung et al., “Optical Single Sideband Modulation Using Strong Optical Injection-Locked Semiconductor Lasers,” IEEE Photonics Technology Letters, vol. 19, No. 13, Jul. 1, 2007, 4 pages.
Lim et al., “Analysis of Optical Carrier-to-Sideband Ratio for Improving Transmission Performance in Fiber-Radio Links,” IEEE Transactions of Microwave Theory and Techniques, vol. 54, No. 5, May 2006, 7 pages.
Lu H H et al., “Improvement of radio-on-multimode fiber systems based on light injection and optoelectronic feedback techniques,” Optics Communications, vol. 266, No. 2, Elsevier B.V., Oct. 15, 2006, 4 pages.
Pleros et al., “A 60 GHz Radio-Over-Fiber Network Architecture for Seamless Communication With High Mobility,” Journal of Lightwave Technology, vol. 27, No. 12, IEEE, Jun. 15, 2009, pp. 1957-1967.
Reza et al., “Degree-of-Polarization-Based PMD Monitoring for Subcarrier-Multiplexed Signals Via Equalized Carrier/Sideband Filtering,” Journal of Lightwave Technology, vol. 22, No. 4, IEEE, Apr. 2004, 8 pages.
Zhao, “Optical Injection Locking on Vertical-Cavity Surface-Emitting Lasers (VCSELs): Physics and Applications,” Fall 2008, PhD dissertation University of California at Berkeley, pp. 1-209.
Advisory Action for U.S. Appl. No. 12/712,758 dated Sep. 16, 2013, 3 pages.
Final Office Action for U.S. Appl. No. 12/712,758 dated May 24, 2013, 17 pages.
Non-final Office Action for U.S. Appl. No. 12/712,758 dated Jan. 10, 2012, 14 pages.
Examination Report for European patent application 07835803.3 dated Aug. 13, 2013, 6 pages.
Extended European Search Report for patent application 10014262.9 dated Mar. 14, 2011, 6 pages.
International Search Report and Written Opinion for PCT/US2012/034853 dated Aug. 6, 2012, 12 pages.
International Search Report and Written Opinion for PCT/US2012/034855 dated Jul. 26, 2012, 10 pages.
Written Opinion of the International Searching Authority for European patent application 11701916.6 dated Sep. 21, 2012, 10 pages.
International Search Report for PCT/US2011/021799 dated Apr. 6, 2011, 4 pages.
Examination Report for European patent application 10702806.0 dated Sep. 12, 2013, 11 pages.
Non-final Office Action for U.S. Appl. No. 13/194,429 dated Mar. 1, 2013, 22 pages.
Notice of Allowance for U.S. Appl. No. 13/194,429 dated Jul. 9, 2013, 9 pages.
International Search Report for PCT/US2011/043405 dated Apr. 25, 2012, 4 pages.
Non-final Office Action for U.S. Appl. No. 11/958,062 dated Nov. 6, 2013, 16 pages.
Chowdhury et al., “Multi-service Multi-carrier Broadband MIMO Distributed Antenna Systems for In-building Optical Wireless Access,” Presented at the 2010 Conference on Optical Fiber Communication and National Fiber Optic Engineers Conference, Mar. 21-25, 2010, San Diego, California, IEEE, pp. 1-3.
International Search Report and Written Opinion for PCT/US2007/025855 dated Mar. 19, 2008, 14 pages.
International Preliminary Report on Patentability for PCT/US2007/025855 dated Jul. 2, 2009, 9 pages.
Bahl et al. “Enhancements to the RADAR User Location and Tracking System,” Microsoft Research Technical Report, Feb. 2000, pp. 1-13.
Frikel et al, “A Robust Mobile Positioning Algorithm,” EURASIP Proceedings, ISCCSP 2006, pp. 1-4.
Pahlavan et al, “An Overview of Wireless Indoor Geolocation Techniques and Systems,” LNCS 1818, pp. 1-13, 2000.
Wann et al, “Hybrid TDOA/AOA Indoor Positioning and Tracking Using Extended Kalman Filters,” 63rd IEEE VTC 2006, pp. 1058-1062.
Ibernon-Fernandez, R., et al., “Comparison Between Measurements and Simulations of Conventional and Distributed MIMO System,” IEEE Antennas and Wireless Propagation Letters, vol. 7, Aug. 2008, pp. 546-549.
Tarlazzi L., et al., “Characterization of an Interleaved F-DAS MIMO Indoor Propagation Channel,” Loughborough Antennas & Propagation Conference, Nov. 2010, Loughborough, United Kingdom, IEEE, pp. 505-508.
Tolli, Antti, “Resource Management in Cooperative MIMO-OFDM Cellular Systems,” Academic Dissertation—ACTA Universitatis Ouluensis, No. C Technica 296, Apr. 11, 2008, pp. 1-198.
Vitucci, E.M., et al., “Analysis of the Performance of LTE Systems in an Interleaved F-DAS MIMO Indoor Environment,” Proceedings of the 5th European Conference on Antennas and Propagation (EUCAP), Apr. 11-15, 2011, Rome, Italy, IEEE, pp. 2184-2186.
Wei, Xinning, et al., “Cooperative communication with partial channel-state information in multiuser MIMO systems,” International Journal of Electronics and Communications, vol. 65, No. 4, Apr. 2011 (available online May 15, 2010), Elsevier GmbH, pp. 349-360.
International Search Report for PCT/US2013/070489 dated Feb. 24, 2014, 4 pages.
Biton et al., “Challenge: CeTV and Ca-Fi—Cellular and Wi-Fi over CATV,” Proceedings of the Eleventh Annual International Conference on Mobile Computing and Networking, Aug. 28-Sep. 2, 2005, Cologne, Germany, Association for Computing Machinery, 8 pages.
Hansryd, Jonas et al., “Microwave capacity evolution,” Ericsson Review, Jun. 21, 2011, 6 pages.
Seto et al., “Optical Subcarrier Multiplexing Transmission for Base Station With Adaptive Array Antenna,” IEEE Transactions on Microwave Theory and Techniques, vol. 49, No. 10, Oct. 2001, pp. 2036-2041.
Examination Report for European Patent Application No. 11733965.5 dated Oct. 10, 2014, 6 pages.
International Search Report for PCT/US2013/034328 dated Jul. 3, 2013, 5 pages.
International Preliminary Report on Patentability for PCT/US2013/034328 dated Oct. 1, 2014, 8 pages.
Non-Final Office Action for U.S. Appl. No. 14/078,949 dated Sep. 10, 2015, 29 pages.
Notice of Allowance for U.S. Appl. No. 13/598,078 dated May 12, 2015, 8 pages.
Non-final Office Action for U.S. Appl. No. 14/148,908 dated May 22, 2015, 20 pages.
Notice of Allowance for U.S. Appl. No. 14/242,139 dated Oct. 22, 2014, 12 pages.
Diehm, et al., “The FUTON Prototype: Broadband Communication through Coordinated Multi-Point using a Novel Integrated Optical/Wireless Architecture,” Presented at Globecom Workshops, Dec. 6-10, 2010, Miami, Florida, IEEE, pp. 757-762.
Fan, Shu-Hao et al., “Spectrally Efficient 60-GHz xy-MIMO Data Transport over a Radio-Over-Fiber System for Gigabit Wireless Local Area Networks,” Presented at IEEE Global Telecommunications Conference, Dec. 6-10, 2010, Miami, Florida, IEEE, 4 pages.
Lee et al., “Evaluation of 60 GHz MIMO Channel Capacity in the Conference Room STA-STA Scenario,” Vehicular Technology Conference (VTC Sping), 2011 IEEE 73rd, pp. 1-5, May 15-18, 2011.
Sheldon, C. et al., “A 60GHz Line-of-Sight 2x2 MIMO Link Operating at 1.2 Gbps,” Presented at Antennas and Propogation Society International Symposium, Jul. 5-11, 2008, San Diego, California, IEEE, 4 pages.
Written Opinion for European Patent Application No. 13798863.0 dated Aug. 6, 2015, 10 pages.
Non-final Office Action for U.S. Appl. No. 14/487,232 dated Jun. 23, 2015, 15 pages.
Notice of Allowance for U.S. Appl. No. 14/227,108 dated Nov. 18, 2015, 8 pages.
Final Office Action for U.S. Appl. No. 14/487,232 dated Oct. 15, 2015, 7 pages.
Author Unknown, “Fiber Optic Distributed Antenna System,” Installation and Users Guide, ERAU Version 1.5, May 2002, Andrews Corporation, 53 pages.
Heath, Robert, et al., “Multiuser MIMO in Distributed Antenna Systems with Out-of-Cell Interference,” IEEE Transactions on Signal Processing, vol. 59, Issue 10, Oct. 2011, IEEE, 4885-4899.
Notice of Allowance for U.S. Appl. No. 14/078,949 dated Feb. 3, 2016, 9 pages.
Non-final Office Action for U.S. Appl. No. 14/079,977 dated Mar. 4, 2016, 21 pages.
Notice of Allowance for U.S. Appl. No. 14/079,977 dated Apr. 29, 2016, 8 pages.
Non-final Office Action for U.S. Appl. No. 14/447,014 dated Jan. 20, 2016, 6 pages.
Non-final Office Action for U.S. Appl. No. 14/721,357, dated Jan. 4, 2016, 10 pages.
Final Office Action for U.S. Appl. No. 14/721,357 dated Mar. 1, 2016, 12 pages.
Advisory Action for U.S. Appl. No. 14/721,357, dated Jun. 30, 2016, 3 pages.
Notice of Allowance for U.S. Appl. No. 14/721,357, dated Aug. 16, 2016, 7 pages.
Non-Final Office Action for U.S. Appl. No. 14/962,279, dated Jan. 27, 2017, 18 pages.
Non-Final Office Action for U.S. Appl. No. 14/997,694, dated Feb. 8, 2017, 16 pages.
Notice of Allowance for U.S. Appl. No. 14/962,279, dated May 12, 2017, 8 pages.
Notice of Allowance for U.S. Appl. No. 14/997,694, dated Jul. 5, 2017, 8 pages.
Non-Final Office Action for U.S. Appl. No. 15/271,843, dated Jun. 21, 2017, 21 pages.
Non-Final Office Action for U.S. Appl. No. 15/372,490, dated Aug. 21, 2017, 9 pages.
Related Publications (1)
Number Date Country
20180198498 A1 Jul 2018 US
Continuations (2)
Number Date Country
Parent 15372490 Dec 2016 US
Child 15914088 US
Parent 14447014 Jul 2014 US
Child 15372490 US