Patent Application
20130196673
The present invention relates to the field of communications, and, more particularly, to wireless communications and related methods.
Cellular communication systems continue to grow in popularity and have become an integral part of both personal and business communications. Cellular telephones allow users to place and receive phone calls almost anywhere they travel. Moreover, as cellular telephone technology is advanced, so too has the functionality of cellular devices. For example, many cellular devices now incorporate Personal Digital Assistant (PDA) features such as calendars, address books, task lists, calculators, memo and writing programs, etc. These multi-function devices usually allow users to wirelessly send and receive electronic mail (email) messages and access the internet via a cellular network and/or a wireless local area network (WLAN), for example.
Cellular devices have radio frequency (RF) processing circuits and receive or transmit radio communications signals typically using modulation schemes. The typical cellular device may have multiple transmit and receive pathways from the antenna to a digital signal processor (DSP). In particular, each signal pathway may comprise a filter to help isolate the desired frequency band from extraneous electromagnetic signals, for example, noise and interference.
Nevertheless, as frequency bands change because of regulatory reasons, expansion, etc. and as more transceivers are added to the cellular device, the likelihood of self-interference may increase. For example, the cellular transceiver may desensitize the wireless local area network (WLAN) transceiver during transmission periods, i.e. potentially rendering the WLAN transceiver inoperative.
The present description is made with reference to the accompanying drawings, in which embodiments are shown. However, many different embodiments may be used, and thus the description should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. Like numbers refer to like elements throughout.
Generally speaking, a mobile wireless communications device may comprise a housing, a cellular transceiver carried by the housing and configured to operate based upon a plurality of power levels, and a WLAN transceiver carried by the housing. The cellular transceiver may be configured to send timing information, and the WLAN transceiver may be configured to schedule WLAN communications based upon the timing information and the selected power level of said cellular transceiver.
In some embodiments, the timing information may comprise a transmission time duration value and a transmission start time for the cellular transceiver. The cellular transceiver may be configured to generate the transmission start time for the cellular transceiver. The cellular transceiver may be configured to generate a logic signal for indicating the transmission start time for the cellular transceiver.
In some embodiments, the mobile wireless communications device may further comprise a clock signal generator configured to generate a common clock signal. The cellular transceiver and the WLAN transceiver may be configured to schedule communications based upon the common clock signal.
Additionally, the mobile wireless communications device may further comprise a plurality of cellular antennas. The cellular transceiver may include a controller configured to select at least one cellular antenna for cellular communications. The WLAN transceiver may be configured to schedule the WLAN communications based upon the selected at least one cellular antenna.
Each cellular antenna may have a respective cellular to WLAN antenna isolation value, and the WLAN transceiver may be configured to schedule the WLAN communications based upon the respective cellular to WLAN antenna isolation value of the selected at least one cellular antenna. The WLAN transceiver may be configured to broadcast a serial clear to send to self (CTS2SELF) message, and to selectively change a broadcast power and transmission rate for the CTS2SELF message. The WLAN transceiver may be configured to selectively change the broadcast power and the transmission rate for the CTS2SELF message based upon a WLAN base station range value. For example, the WLAN transceiver may comprise an IEEE 802.11 transceiver, and the cellular transceiver may comprise at least one of a long term evolution (LTE) transceiver and a WiMAX IEEE 802.16 transceiver.
Another aspect is directed to a mobile wireless communications device that may comprise a housing, a cellular transceiver carried by the housing, and a WLAN transceiver carried by the housing. At least one of the WLAN transceiver and the cellular transceiver may be configured to determine a cellular self-interference level and schedule WLAN communications based upon the cellular self-interference level.
Another aspect is directed to a method of operating a mobile wireless communications device comprising a cellular transceiver, and a WLAN transceiver. The method may comprise sending timing information to the WLAN transceiver from the cellular transceiver, and scheduling WLAN communications of the WLAN transceiver based upon the timing information for the cellular transceiver and a selected power level of the cellular transceiver.
Another aspect is directed to a method of operating a mobile wireless communications device comprising a cellular transceiver, and a WLAN transceiver. The method may include determining a cellular self-interference level via at least one of the WLAN and cellular transceivers, and scheduling WLAN communications based upon the cellular self-interference level.
Example mobile wireless communications devices may include portable or personal media players (e.g., music or MP3 players, video players, etc.), remote controls (e.g., television or stereo remotes, etc.), portable gaming devices, portable or mobile telephones, smartphones, tablet computers, etc.
Referring now to
The WLAN transceiver 14 illustratively includes a controller 15, a receiver 18 coupled to the controller, a transmitter 17 coupled to the controller, and an antenna 19 coupled to the receiver and transmitter. For example, the WLAN transceiver 14 may comprise one or more of an IEEE 802.11 transceiver (operating at 2.4 GHz), and a Bluetooth transceiver. The mobile wireless communications device 10 illustratively includes a clock signal generator 13 configured to generate a common clock signal for the cellular transceiver 11 and the WLAN transceiver 14. In particular, the common clock signal provides a common time reference for the operations of the transceivers 11, 14.
During operation, the mobile wireless communications device 10 generates data for exchange with another device (e.g. base station) via either the cellular transceiver 11 or the WLAN transceiver 14. If the mobile wireless communications device 10 has only WLAN communications to send out and no cellular communications, the WLAN transceiver 14 proceeds to perform those communications (Blocks 33, 35) without regard to the silent/absent cellular radio. On the other hand, if the mobile wireless communications device 10 also has some cellular communications to perform, the device performs selective scheduling of the WLAN communications because of potential desensitization of the WLAN receiver 18 during cellular transmit periods. This desensitization may be the result of the WLAN transceiver 14 and cellular transceiver 11 operating on adjacent frequency bands. Of course, the teachings herein may be applied to non-adjacent frequency bands that cause interference. In some embodiments, the mobile wireless communications device 10 may selectively schedule cellular communications to avoid desensitization.
When the mobile wireless communications device 10 commences a cellular transmission, the cellular transceiver 11 is configured to send one or more transmission activity indicators, such as timing information related to the cellular transmission activity, to the WLAN transceiver 14 (Block 33). The transmission activity indicators comprise, for example, a transmission time duration value and a transmission start time for the cellular transceiver. The mobile wireless communications device 10 may include a digital interface between the cellular transceiver 11 and the WLAN transceiver 14. For example, the digital interface may comprise a data communications bus or a single wire connection.
In some embodiments, the cellular transceiver 11 may generate a digital message including transmission activity indicators, such as the transmission time duration value and the transmission start time for the cellular transceiver (Block 37). In other embodiments, the cellular transceiver 11 may be configured to generate a logic signal for indicating the transmission start time for the cellular transceiver. In other words, the cellular transceiver 11 would include an output pin for indicating when the cellular transmission is occurring. In some embodiments, the transmission start time for the cellular transceiver is provided near instantaneously. In some embodiments, the cellular transceiver 11 also provides an indication of near instantaneous cellular transmission. For example, this signal may comprise a hardware logic signal being activated during all cellular transmission periods and deactivated otherwise, and the logical signal may further be based on at least one of the cellular transmission power, antenna, cellular to WLAN antenna isolation, frequency/band.
The WLAN transceiver 14 is configured to schedule WLAN communications based upon the transmission time duration value and the transmission start time for the cellular transceiver 11. For example, the WLAN transceiver 14 may stagger WLAN communications to avoid the desensitizing effect. In other embodiments, the WLAN transceiver 14 may cooperate with the cellular transceiver 11 to pause or delay cellular transmissions to permit receipt of WLAN signals. In embodiments including the clock signal generator 13, including the illustrated embodiment, the cellular transceiver 11 and the WLAN transceiver 14 may be configured to schedule communications based upon the common clock signal.
In other words, the WLAN transceiver 14 is configured to determine a cellular self-interference level and schedule WLAN communications based upon the cellular self-interference level. The determination of the cellular self-interference is based upon at least one of the transmission time duration value, the transmission start time for said cellular transceiver, the selected power level of the cellular transceiver, the cellular-to-WLAN isolation value for the selected antenna, and an interference power value detected at the WLAN transceiver 14.
In some embodiments, the cellular transceiver 11 may be configured to operate based upon a plurality of power levels. For example, the plurality of power levels may comprise at least one of a cellular transmit power level, and a WLAN antenna received power coupled from the cellular transmitter. For example, the cellular base station may provide control information for the cellular transmit power level. In these embodiments, the WLAN transceiver 14 may be configured to schedule the WLAN communications based upon the selected power level of the cellular transceiver 11 (Block 41). For example, if the cellular transmit power level is low enough, the WLAN receiver 18 may not be substantially desensitized.
In the illustrated embodiment, Blocks 37, 39, & 41 are shown with dashed lines to indicate that one or more of these steps is optional. In particular, the controller 15 of the WLAN transceiver 14 may schedule communications based upon one or more of the transmission activity indicators.
In some embodiments, the cellular transmit power level is provided in the digital message, but in other embodiments, the cellular transmit power level may be detected by a power sensor/WLAN interference sensor. In yet other embodiments, the cellular transceiver 11 may communicate the selected cellular transmit power level via a corresponding plurality of signals, such as hardware logic signals.
In embodiments of the mobile wireless communications device 10 that have cellular antenna diversity, such as the illustrated example embodiment. More specifically, the mobile wireless communications device 10 illustratively includes a plurality of cellular antennas 23-24 (second antenna shown with dashed lines) coupled to the cellular transmitter and receiver 21-22. In these embodiments, depending on the received signal characteristics, the controller 12 is configured to select at least one cellular antenna 23-24 for cellular transmission. The WLAN transceiver 14 may be configured to schedule the WLAN communications based upon the selected at least one cellular antenna (Block 39). In some embodiments, the selected at least one cellular antenna is also provided in the digital message or an indicator.
In particular, one of the cellular antennas may have greater respective isolation values than other with the WLAN antenna, the WLAN transceiver 14 may be configured to schedule the WLAN communications based upon a respective cellular to WLAN antenna isolation value of the selected at least one cellular antenna with the WLAN antenna. For example, if the respective cellular to WLAN antenna isolation value is great enough to avoid substantial interference with WLAN receiver 18 operations, the WLAN communications may not need to be selectively scheduled at all. Once the WLAN transceiver 14 has the cellular transceiver 11 operation indicators noted above, the WLAN transceiver can then commence WLAN communication activities effectively by, for example, scheduling the reception of WLAN communications during periods no cellular transmission (Blocks 43, 45) or only cellular reception. In other embodiments, the WLAN transceiver 14 can coordinate with the cellular transceiver 11 and schedule WLAN and cellular communications periodically in time slots and/or block cellular transmit operations temporarily.
In some embodiments, the controller 15 of the WLAN transceiver 14 may schedule WLAN communications being received at the mobile wireless communications device 10, i.e. scheduling transmission at the companion device. The WLAN transceiver 14 is configured to broadcast a CTS2SELF message, and to selectively change a broadcast power and transmission rate for the CTS2SELF message. As will be appreciated by those skilled in the art, the CTS2SELF message causes the companion devices, and any WLAN device within range to cease WLAN transmissions. The WLAN transceiver 14 may be configured to selectively change the broadcast power and the transmission rate for the CTS2SELF message based upon a WLAN base station range value.
Another aspect is directed to a method of operating a mobile wireless communications device 10 comprising a cellular transceiver 11, and a WLAN transceiver 14. The method may comprise sending a transmission time duration value to the WLAN transceiver 14 from the cellular transceiver 11, and scheduling WLAN communications of the WLAN transceiver based upon the transmission time duration value and a transmission start time for the cellular transceiver.
In the illustrated embodiment, the controllers 12, 15 of the cellular and WLAN transceivers 11, 14 cooperate to schedule of WLAN communications. Nevertheless, in other embodiments, it should be understood that the mobile wireless communications device 10 may include a processor unit coupled to the cellular and WLAN transceivers 11, 14 and configured to perform the operations of the controllers 12, 15. The processor unit may be separate from the cellular and WLAN transceivers 11, 14, in some embodiments, on a separate integrated circuit chipset. For example, the processor would determine the timing information, such as the transmission time value and transmission start time, of the cellular transmission activity and would schedule WLAN communications based upon the timing information. Also, these values would be delivered not from the cellular transceiver 11 to the WLAN transceiver 14, but rather directly from the cellular transceiver 11 to the processor.
For illustrative purposes, the following discussion of an exemplary embodiment of the mobile wireless communications device 10 is provided.
Devices with co-located radios operating concurrently in adjacent or nearby/harmonic bands may suffer from coexistence issues. An example of this is coexistence of the LTE B40 (2.3-2.4 GHz) or WiMAX (2.5-2.7 GHz) with WLAN operating in the 2.4 GHz ISM band. More specifically, no concurrent transmit (TX)/receive (RX) operation may occur due to the de-sensing and receiver saturation caused in one band by a transmission in the other band. With typical antenna isolation (e.g. 15 to 25 dB) and while operating at the maximum transmission power (e.g. 23 dBm for both radios), it may be difficult for the filtering option to solve this issue in the frequency domain with acceptable size components for handset applications.
In IEEE 802.11 compliant WLANs, a CTS2Self frame may be used to silence all WLAN stations that receive the CTS2Self on the medium for a specified duration to prevent WLAN reception during co-located cellular TX operation. This frame type was defined to allow coexistence between orthogonal frequency-division multiplexing (OFDM) and legacy physical layers in IEEE 802.11 WLANs and has an impact on throughput performance of all stations receiving it on the WLAN operating frequency. To mitigate the impact of blocking all stations on the medium, a WiFi Direct (P2P) standard (Wi-Fi Direct—P2P Communication standard draft) defines a Notice of Absence (NoA) frame type that is used exclusively by a group owner (i.e. a WLAN access point in a mobile hotspot scenario) to advertise/schedule periods of unavailability only to its associated clients. One application of the NoA frame is to prevent overlapping WLAN RX and cellular TX operations. However, albeit not to the same extent as a CTS2Self frame, a NoA frame may cause the mobile hotspot to suffer a performance hit. Using these frame types may be undesirable and should be used as sparingly as possible.
Approach One: It has been observed that cellular technology has been designed with aggressive RF power control techniques, whereby the maximum TX output power is rarely used. In some applications, the two interfering radios are co-located on the same device, an interface between the two radios to communicate one of 1 through 3 as well as 4:
A potential advantage of the option 2 over 1 and 3 is that no software message is required between the two radios. The potential disadvantage is the duration may be determined wrongly at the very first TX operation, and at the first TX slot whenever the configuration of TX duration changes. The potential advantage of options 1 and 2 over 3 is that the two radios (WLAN and cellular) do not require a common time reference.
If the TX power is in a range that WLAN-to-cellular antenna isolation and the attenuation offered by coexistence filters are sufficient to overcome the interference introduced by the cellular TX at the WLAN receiver given the WLAN RSSI, then no WLAN blocking mechanism is employed. Otherwise, if a WLAN Rx is expected (e.g. in response to a PS-POLL or a QoS Null frames, or a periodic beacon reception) during the upcoming cellular UL transmission, then a WLAN blocking mechanism is employed to prevent overlapping the WLAN RX (i.e. the other party's WLAN TX) and cellular TX operation. In devices with cellular transmit antenna selective diversity, there may be multiple characterized cellular-to-WLAN antenna isolation values. For example, in devices with two cellular antennas, there are two cellular-to-WLAN antenna isolation values. In one embodiment, the smallest antenna isolation is used in determining whether a WLAN blocking mechanism shall be used. This conservative approach shall be used if the choice of the cellular antenna is unknown or possibly changing during the expected overlapping WLAN RX operation.
In another embodiment, the instantaneous choice of the cellular antenna—if available—shall be used to reflect the most accurate antenna isolation value allowing for reduced application of WLAN blocking mechanisms in scenarios where large cellular-to-WLAN antenna isolation is available. In one embodiment, the cellular radio not only indicates to the WLAN the TX power used, it also indicates the antenna used, so that WLAN blocking decision is based on both. In another embodiment, instead of indicating the TX power of cellular radio to the WLAN, the interference level (referenced at the WLAN antenna) from the cellular radio is indicated to the WLAN so that the blocking decision is based on the received interference levels. Such an indication can be implemented, for example, by a power sensor, and can also be implemented by accounting for the characterized antenna isolation values, the TX power level and the antenna used to TX.
Approach Two: (Applicable to WLAN client stations utilizing CTS2Self) In situations where Approach 1 above uses a CTS2Self frame, the method further includes another refinement by reducing WLAN TX power level used to transmit the CTS2Self frame and/or choosing the appropriate data rate used for the CTS2self frame, so as to prevent unnecessary blocking of other WLAN stations listening on the medium but not of interest to the sending WLAN station of CTS2self in question.
To determine the TX power of CTS2Self, the client device can determine the path loss through a beacon signal and the received signal strength indicator (RSSI) of the beacon signal observed by the client, and calculate the needed TX power and/or data rate so as to be just enough to reach the access point that client is trying to communicate with. To limit the range of the CTS2Self frame, it should be transmitted at the minimum power level that will be just enough to guarantee correct reception by the WLAN access point (i.e. without amble link budget, this power level denoted as Pmin (dBm)). To accomplish this, the co-located WLAN radio may use the transmitted power level of the WLAN beacon and beacon RSSI value to determine the path loss, PL (dB), to the WLAN access point. Then based on the data rate used to transmit the CTS2Self, determine the required RSSI, X (dBm), at the WLAN access point to correctly decode the frame. For example, if 1 Mbps is used, then an RSSI value of −93 dBm is acceptable. Pmin should be set to −93+PL.
Example components of a mobile wireless communications device 1000 that may be used in accordance with the above-described embodiments are further described below with reference to
The housing 1200 may be elongated vertically, or may take on other sizes and shapes (including clamshell housing structures). The keypad may include a mode selection key, or other hardware or software for switching between text entry and telephony entry.
In addition to the processing device 1800, other parts of the mobile device 1000 are shown schematically in
Operating system software executed by the processing device 1800 is stored in a persistent store, such as the flash memory 1160, but may be stored in other types of memory devices, such as a read only memory (ROM) or similar storage element. In addition, system software, specific device applications, or parts thereof, may be temporarily loaded into a volatile store, such as the random access memory (RAM) 1180. Communications signals received by the mobile device may also be stored in the RAM 1180.
The processing device 1800, in addition to its operating system functions, enables execution of software applications 1300A-1300N on the device 1000. A predetermined set of applications that control basic device operations, such as data and voice communications 1300A and 1300B, may be installed on the device 1000 during manufacture. In addition, a personal information manager (PIM) application may be installed during manufacture. The PIM may be capable of organizing and managing data items, such as e-mail, calendar events, voice mails, appointments, and task items. The PIM application may also be capable of sending and receiving data items via a wireless network 1401. The PIM data items may be seamlessly integrated, synchronized and updated via the wireless network 1401 with corresponding data items stored or associated with a host computer system.
Communication functions, including data and voice communications, are performed through the communications subsystem 1001, and possibly through the short-range communications subsystem 1020. The communications subsystem 1001 includes a receiver 1500, a transmitter 1520, and one or more antennas 1540 and 1560. In addition, the communications subsystem 1001 also includes a processing module, such as a digital signal processor (DSP) 1580, and local oscillators (LOs) 1601. The specific design and implementation of the communications subsystem 1001 is dependent upon the communications network in which the mobile device 1000 is intended to operate. For example, a mobile device 1000 may include a communications subsystem 1001 designed to operate with the Mobitex™, Data TAC™ or General Packet Radio Service (GPRS) mobile data communications networks, and also designed to operate with any of a variety of voice communications networks, such as Advanced Mobile Phone System (AMPS), time division multiple access (TDMA), CDMA, Wideband code division multiple access (W-CDMA), personal communications service (PCS), GSM, enhanced data rates for GSM evolution (EDGE), etc. Other types of data and voice networks, both separate and integrated, may also be utilized with the mobile device 1000. The mobile device 1000 may also be compliant with other communications standards such as 3GSM, 3rd Generation Partnership Project (3GPP), Universal Mobile Telecommunications System (UMTS), 4G, etc.
Network access requirements vary depending upon the type of communication system. For example, in the Mobitex and DataTAC networks, mobile devices are registered on the network using a unique personal identification number or PIN associated with each device. In GPRS networks, however, network access is associated with a subscriber or user of a device. A GPRS device therefore typically involves use of a subscriber identity module, commonly referred to as a SIM card, in order to operate on a GPRS network.
When required network registration or activation procedures have been completed, the mobile device 1000 may send and receive communications signals over the communication network 1401. Signals received from the communications network 1401 by the antenna 1540 are routed to the receiver 1500, which provides for signal amplification, frequency down conversion, filtering, channel selection, etc., and may also provide analog to digital conversion. Analog-to-digital conversion of the received signal allows the DSP 1580 to perform more complex communications functions, such as demodulation and decoding. In a similar manner, signals to be transmitted to the network 1401 are processed (e.g. modulated and encoded) by the DSP 1580 and are then provided to the transmitter 1520 for digital to analog conversion, frequency up conversion, filtering, amplification and transmission to the communication network 1401 (or networks) via the antenna 1560.
In addition to processing communications signals, the DSP 1580 provides for control of the receiver 1500 and the transmitter 1520. For example, gains applied to communications signals in the receiver 1500 and transmitter 1520 may be adaptively controlled through automatic gain control algorithms implemented in the DSP 1580.
In a data communications mode, a received signal, such as a text message or web page download, is processed by the communications subsystem 1001 and is input to the processing device 1800. The received signal is then further processed by the processing device 1800 for an output to the display 1600, or alternatively to some other auxiliary I/O device 1060. A device may also be used to compose data items, such as e-mail messages, using the keypad 1400 and/or some other auxiliary I/O device 1060, such as a touchpad, a rocker switch, a thumb-wheel, or some other type of input device. The composed data items may then be transmitted over the communications network 1401 via the communications subsystem 1001.
In a voice communications mode, overall operation of the device is substantially similar to the data communications mode, except that received signals are output to a speaker 1100, and signals for transmission are generated by a microphone 1120. Alternative voice or audio I/O subsystems, such as a voice message recording subsystem, may also be implemented on the device 1000. In addition, the display 1600 may also be utilized in voice communications mode, for example to display the identity of a calling party, the duration of a voice call, or other voice call related information.
The short-range communications subsystem enables communication between the mobile device 1000 and other proximate systems or devices, which need not necessarily be similar devices. For example, the short-range communications subsystem may include an infrared device and associated circuits and components, a Bluetooth™ communications module to provide for communication with similarly-enabled systems and devices, or a NFC sensor for communicating with a NFC device or NFC tag via NFC communications.
Many modifications and other embodiments will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that various modifications and embodiments are intended to be included within the scope of the appended claims.
