Patent Application
20150003436
The present invention relates generally to wireless communication, and particularly to methods and systems for Wireless Local Area Network (WLAN) communication.
A Wireless Local-Area Network (WLAN) typically comprises one or more Access Points (APs) that communicate with stations (STAs). WLAN communication protocols are specified, for example, in the IEEE 802.11 family of standards, such as in the 802.11n-2009 standard entitled “IEEE Standard for Information technology—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 5: Enhancements for Higher Throughput,” 2009; in the 802.11ac-2013 standard entitled “IEEE Standard for Information technology—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 4: Enhancements for Very High Throughput for Operation in Bands below 6 GHz,” 2013; and in the IEEE 802.11k-2008 standard entitled “IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements; Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications; Amendment 1: Radio Resource Measurement of Wireless LANs,” 2008, which are incorporated herein by reference. WLANs are also commonly referred to as Wi-Fi networks.
An embodiment of the present invention that is described herein provides a method including communicating in a Wireless Local Area Network (WLAN) device on a first communication channel using one or more primary transmission/reception (TX/RX) chains. Concurrently with communicating on the first communication channel using the primary TX/RX chains, WLAN communication is received on one or more second communication channels using an auxiliary reception (RX) chain whose input signal is provided from an output of a receive amplifier in one of the primary TX/RX chains.
In some embodiments, receiving the WLAN communication includes receiving WLAN frames, and transferring the received WLAN frames to a host. The method may include selecting only a subset of the WLAN frames received on the second communication channels, and transferring only the selected subset of the WLAN frames to the host. In an embodiment, selecting the subset includes selecting the WLAN frames of one or more selected types, or the WLAN frames having one or more selected addresses. In a disclosed embodiment, the method includes removing, at least partially, payloads of the WLAN frames received on the auxiliary channel, before transferring the WLAN frames to the host.
In some embodiments, receiving the WLAN communication includes detecting WLAN frames, and transferring one or more attributes of the detected WLAN frames to a host. In an embodiment, the method includes selecting a channel for subsequently serving as the first communication channel by the primary TX/RX chains, by analyzing the WLAN communication received on the second communication channels. Additionally or alternatively, the method may include selecting a channel for performing double-bandwidth communication, by analyzing the WLAN communication received on the second communication channels.
In another embodiment, the method includes, in response to detecting a signal in only one of the auxiliary RX chain and the primary TX/RX chain, setting a gain of the receive amplifier based on the detected signal. In yet another embodiment, the method includes setting a gain of the receive amplifier based on a signal received in the primary TX/RX chain. The method may include modifying a gain of the receive amplifier based on a signal received in the primary TX/RX chain, and compensating for the modified gain by adjusting a variable-gain element in the auxiliary RX chain.
In some embodiments, the method includes assigning circuitry alternately between the auxiliary RX chain and a primary TX/RX chain, designated from among the primary TX/RX chains. The circuitry may include baseband processing circuitry and/or gain control circuitry. In an embodiment, assigning the circuitry includes assigning the circuitry to the auxiliary RX chain only when no signal is to be processed by the primary TX/RX chain.
In another embodiment, assigning the circuitry includes initially assigning the circuitry to the auxiliary RX chain, and, upon detecting a signal in the primary TX/RX chain, re-assigning the circuitry to the primary TX/RX chain regardless of whether the auxiliary RX chain is processing signals. In still another embodiment, assigning the circuitry includes initially assigning the circuitry to the auxiliary RX chain, and, upon detecting a signal in the primary TX/RX chain, processing the detected signal received in one or more other primary TX/RX chains.
In some embodiments, receiving the WLAN communication includes identifying periodic patterns of sequences of beacon frames transmitted on multiple second communication channels, and receiving the beacon frames by tuning the auxiliary RX chain alternately among the second communication channels in accordance with the identified periodic patterns. In an embodiment, the method includes deactivating the auxiliary RX chain while one or more of the primary TX/RX chains are in a transmission mode. In another embodiment, when one or more of the primary TX/RX chains are in a transmission mode, the method includes continuing to receive WLAN communication using the auxiliary RX chain while limiting a permitted gain of the auxiliary RX chain.
There is additionally provided, in accordance with an embodiment of the present invention, a Wireless Local Area Network (WLAN) device including one or more primary transmission/reception (TX/RX) chains and an auxiliary reception (RX) chain. The primary TX/RX chains are configured to communicate on a first communication channel. The auxiliary RX chain is configured to accept an input signal from an output of a receive amplifier in one of the primary TX/RX chains, and to receive in the input signal WLAN communication on one or more second communication channels concurrently with communication of the primary TX/RX chains on the first communication channel.
The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which:
Embodiments of the present invention that are described herein provide improved methods and systems for WLAN communication. In the disclosed embodiments, a WLAN device (which may serve as an AP or STA) comprises one or more primary transmission/reception (TX/RX) chains for conducting WLAN communication with a remote WLAN device on a primary communication channel. In addition, the WLAN device comprises an auxiliary reception (RX) chain that is configured to receive WLAN communication on one or more other communication channels, referred to as auxiliary channels, in parallel with the normal communication conducted on the primary channel by the primary TX/RX chains.
In some embodiments, reception on the auxiliary RX chain is used for various activity mapping, sniffing and monitoring purposes. As such, in these embodiments the WLAN device applies only physical-layer (PHY) processing, and not Medium Access Control (MAC) processing, to WLAN frames received on the auxiliary channels. The WLAN device may use the output of the auxiliary RX chain, for example, as part of a channel selection process and/or for selective switching to a double-bandwidth communication mode. By using the auxiliary chain, the WLAN device is able to perform such tasks without disrupting normal communication on the primary channel.
Several example implementations of the auxiliary RX chain are described herein. Automatic Gain Control (AGC) design considerations and hardware commonality aspects are also addressed.
In the present example, device 20 transmits and receives WLAN signals using four transmission/reception (TX/RX) chains, also referred to as primary chains. The four TX/RX chains comprise four respective front-ends 24A . . . 24D and four respective Radio Frequency (RF) chains 36A . . . 36D. RF chains 36A . . . 36D are comprised in an RF Integrated Circuit (RFIC) 28. Baseband processing of the transmitted and received signals is performed in a Baseband Integrated Circuit (BBIC) 32. BBIC 32 also comprises a control unit 124, which controls and manages the operation of device 20. WLAN device 20 further comprises a host processor 34 (also referred to simply as host).
In each TX/RX chain, the transmit path begins in BBIC 32, which generates a digital baseband signal for transmission. A pair of Digital to Analog Converters (DACs) convert the digital baseband signal into an analog signal. In the corresponding RF chain, a pair of Band-Pass Filters (BPFs) 48 filter the analog signal, a pair of mixers 52 up-convert the signal to RF, and amplifiers 56 and 60 amplify the RF signal. In the respective front-end, a Power Amplifier (PA) 64 amplifies the RF signal. The signal is then filtered with a Low-Pass Filter (LPF) 68, and provided via a TX/RX switch 72 to an antenna 76.
In the receive path of each TX/RX chain, antenna 76 receives an RF signal, and the signal passes through switch 72 and is filtered by a filter 80. A Low-Noise Amplifier (LNA) 84, referred to as an external LNA, amplifiers the signal before providing it to the corresponding RF chain in RFIC 28. In the RFIC, the signal is amplified by an additional LNA 88, referred to as an internal LNA. A pair of mixers 92 down-convert the RF signal to baseband, a pair of baseband filters 96 filter the down-converted signal, and the signal is then amplified by a pair of Variable-Gain Amplifiers (VGAs) 100. The baseband signal is then provided to BBIC 32, where it is converted into a digital signal by a pair of Analog-to-Digital Converters (ADCs) 104. The BBIC then proceeds to demodulate the digital signal. In a WLAN, the signal may comprise, for example, an Orthogonal Frequency Division Multiplexing (OFDM) signal.
The four TX/RX chains of device 20 are typically tuned to the same communication channel, so as to support various diversity or Multiple-Input Multiple-Output (MIMO) schemes. Thus, mixers 92 in the four RF chains 36A . . . 36D are typically driven with the same Local Oscillator (LO) frequency. The channel frequency on which the four TX/RX chains communicate is denoted frequency A, and the corresponding LO signal is typically generated in a single synthesizer (or other frequency source, not shown in the figure).
In each TX/RX chain, LNA 88 and VGAs 100 have variable gains, which are typically controlled by control unit 124 as part of an Automatic Gain Control (AGC) mechanism. In an example implementation, the AGC mechanism may set the gains of LNA 88 and VGAs 100 such that LNA 84, LNA 88 and ADCs 104 do not saturate.
In addition to the four primary TX/RX chains, device 20 further comprises an auxiliary reception (RX) chain 40. Auxiliary chain 40 is typically used for receiving WLAN frames on an auxiliary channel, different from the primary channel used by the primary TX/RX chains. (Throughout the present patent application, the terms “channels,” “frequency channels” and “communication channels” are used interchangeably.) The use of auxiliary chain 40 is addressed in greater detail below.
In the example of
Providing the input to the auxiliary chain from the output of a receive amplifier (e.g., LNA) of a primary chain is advantageous for several reasons. For example, since most of the RF hardware is shared between the primary and auxiliary chains, the added cost, size and power consumption incurred by the auxiliary chain is small. Moreover, the LNA output typically has a high impedance, which simplifies splitting of the signal. After the split, the signal is typically converted to current before down-conversion in the mixers. Furthermore, since the splitting is performed after the LNA, the impact of the split on the sensitivity or noise figure of the primary chain is minimal, typically less than 1 dB. When the primary chain in question is one of several (e.g., four) primary chains, the impact of the split on the overall reception performance is typically negligible.
The frequency on which the primary TX/RX chains communicate is referred to as frequency A. The frequency on which the auxiliary chain receives at a given time is denoted frequency B. The corresponding LO signal, for driving mixers 108, is typically generated by an additional synthesizer (or other frequency source, different from the frequency source that drives mixers 92).
In some embodiments, the additional synthesizer used for the auxiliary chain may be designed for lower performance (and thus lower cost) than that of the synthesizer of the primary chains. Other components of the auxiliary chain, such as mixer 108 or analog front-end components, may also be designed with relaxed performance relative to the corresponding components in the primary chains.
In some embodiments, device 20 already comprises a second synthesizer for some other operating mode or purpose. In such an embodiment, the existing second synthesizer can be re-used for driving the auxiliary chain, further minimizing the added cost, size and power consumption.
The configuration of WLAN device 20 shown in
The division of functions among the front-ends, RFIC, BBIC and host may differ from the division shown in
The different elements of device 20 may be implemented using suitable hardware, such as in one or more RFICs, Application-Specific Integrated Circuits (ASICs) or Field-Programmable Gate Arrays (FPGAs). In some embodiments, some elements of device 20, e.g., control unit 124 and/or host 34, can be implemented using software, or using a combination of hardware and software elements. Elements of device 20 that are not mandatory for understanding of the disclosed techniques have been omitted from the figure for the sake of clarity.
In some embodiments, control unit 124 and/or host 34 is implemented using a general-purpose processor, which is programmed in software to carry out the functions described herein. The software may be downloaded to the computer in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory.
In some embodiments, WLAN device 20 receives WLAN frames on the auxiliary channel using auxiliary RX chain 40, concurrently with the normal WLAN communication conducted by the primary TX/RX chains on the primary channel. Parallel reception of WLAN frames on the auxiliary channel can be used for various purposes, such as for mapping WLAN activity on various channels as part of a channel selection process. Such tasks can be carried out without disrupting communication on the primary channel.
Typically, the WLAN device applies only physical-layer (PHY) reception processing to the signals received by the auxiliary chain on the secondary channel. Medium Access Control (MAC) processing is typically performed only on the outputs of the primary TX/RX chains on the primary channel. Thus, in some embodiments, BBIC 32 transfers the WLAN frames received on the auxiliary channel, and/or information relating to these received frames, to host 34 or to any other processing circuitry.
In some embodiments, BBIC 32 filters the WLAN frames (i.e., selects only a subset of the WLAN frames) before transferring them to host 34. Additionally or alternatively, the BBIC may extract selected information from the received frames and pass the extracted information to the host. Such tasks may be performed, for example, by control unit 124. This technique is useful, for example, when the data throughput on the interface between BBIC 32 and host 34 is limited, and also helps to reduce computational load in the host.
The BBIC may filter the frames received on the auxiliary channel in various ways. For example, the BBIC may select and transfer to the host only frames of one or more selected types, e.g., only beacon frames, or only frames having one or more selected MAC addresses. The host may use frames filtered in this manner, for example, as part of a channel selection process: By analyzing received beacon frames, the host may count the number of APs active on the auxiliary channel. By analyzing MAC address and frame type information, the host may count the number of WLAN devices (APs and/or STAs) active on the auxiliary channel. These counts may be assessed on different auxiliary channels and used as channel selection criteria, possibly in combination with other factors.
In some embodiments, the BBIC removes at least part of the payload of each frame received on the auxiliary channel, before transferring the frames to the host. The BBIC may remove the entire payload and transfer only the frame header to the host, or limit the transferred payload size and transfer the frames with truncated payloads. In such embodiments, the outputs of the primary RX chains typically have priority over the output of the auxiliary chain on the BBIC-host interface.
In some embodiments, the BBIC does not transfer the frames themselves from the auxiliary channel to the host. Instead, the BBIC only detects the frames and transfers one or more attributes of the detected frames, e.g., the frame lengths.
As noted above, host 34 may use the output of the auxiliary RX chain (e.g., frames, parts of frames and/or frame attributes) for various monitoring, sniffing and analysis purposes. For example, the host may use the auxiliary chain output for channel selection, i.e., for selecting an alternative channel that will subsequently serve as the primary channel in case of a need for channel switch.
As another example, the host may use the auxiliary chain output for selecting a channel to serve for double-bandwidth communication together with the primary channel. In an operational mode denoted “80+80”, for example, WLAN device 20 communicates simultaneously on two 80 MHz channels. Typically, the WLAN device operates initially on only one of the channels, to support a wide variety of remote WLAN devices. In case a given remote WLAN device supports the “80+80” mode, device 20 may decide to switch to this mode. Switching to the “80+80” mode, however, is worthwhile only if the additional 80 MHz channel is sufficiently clear. Otherwise, collisions on the additional channel will degrade performance. In such an embodiment, host 34 may check whether a certain auxiliary channel is relatively free of WLAN traffic and interference to justify operation in double-bandwidth mode together with the currently-used primary channel.
Further additionally or alternatively, host 34 may use the auxiliary chain output for selecting a channel for any other suitable purpose.
As noted above, in some embodiments control unit 124 carries out an Automatic Gain Control (AGC) process that controls the gains of LNAs 88 and VGAs 100 in the various primary chains depending on the received signal. In some embodiments, control unit 124 also controls the gains of VGAs 116 in auxiliary chain 40.
As can be seen in
Typically, control unit 124 sets the gain of the common LNA based on the requirements of the primary chain, i.e., based on the signal received in primary chain 36D on frequency A. As a result, the gain of the auxiliary chain may be suboptimal. In many practical cases, however, the signal level in the auxiliary chain is still suitable for frame reception, especially since the control unit has separate control over VGAs 116.
The ability to receive frames on the auxiliary chain, notwithstanding the sub-optimal gain setting, may depend on the Modulation and Coding Scheme (MCS) used in that frame, i.e., high-order constellations may not be decodable, whereas low-order constellations (low MCSs) may be decoded successfully. Reception in the auxiliary chain may also be disrupted if the control unit changes the gain of the common LNA during frame reception, as part of the AGC process of the primary chain. Even in such a case, information relating to the beginning of the frame, e.g., the frame mode that is determined from the preamble, can still be determined and transferred to the host.
In yet another embodiment, if a signal is detected only in one of the two chains (on frequency A in chain 36D or on frequency B in chain 40), control unit 124 sets the gain of the common LNA based on that signal. This mechanism is particularly suitable for intermittent or packetized protocols such as IEEE 802.11 WLAN.
In still another embodiment, the control unit may set the gain of the common LNA while considering the requirements of both chains, e.g., set the LNA to some average of the gain requirements of the two chains. Further alternatively, control unit 124 may control the gain of the common LNA in any other suitable way.
In some embodiments, the primary chain notifies the auxiliary chain of each gain change applied to the common LNA. The auxiliary chain aims to maintain a target overall gain (which may be configurable, and may have different optimal settings for radar detection and for activity monitoring). Upon receiving a notification, the auxiliary chain attempts to compensate for the LNA gain change by changing the gain of VGAs 116, such that the target overall gain is maintained of the auxiliary chain.
Additionally, a “VALID” signal may be sent from the primary chain to the auxiliary chain. The VALID signal is de-asserted after the gain of the common LNA is changed, and re-asserted when the gain change settles. When the VALID signal is de-asserted, auxiliary chain operation is paused, to prevent false detection due to gain instability effects.
In some embodiments, certain circuitry, such as some of the processing circuitry in BBIC 32, is shared by the fourth primary chain and by auxiliary chain 40. The shared circuitry may comprise, for example, circuitry for frame detection or other baseband processing circuitry, and/or AGC circuitry that controls the gain of common LNA 88. In an example embodiment, the shared circuitry is connected to the fourth primary chain and to the auxiliary chain through a multiplexer, which is controlled by control unit 124. The control unit may use various criteria for deciding when to assign the shared circuitry to which chain.
Typically, priority in assignment of the shared circuitry is given to the fourth primary chain, and the control unit assigns the circuitry to the auxiliary chain only if the fourth primary chain has no signal to process. In one embodiments, if a signal appears in the fourth primary chain while the shared circuitry is processing a signal for the auxiliary chain, control unit 124 aborts the processing and immediately assigns the shared circuitry to the fourth primary chain (and accordingly controls the gain of LNA 88 according to the signal received in the fourth primary chain). In this embodiment, partial information from the auxiliary chain can still be transferred to the host.
In another embodiment, the control unit waits until processing for the auxiliary chain is completed, and only then assigns the shared circuitry to the fourth primary chain. In yet another embodiment, if signals are present in the fourth primary chain and in the auxiliary chain, control unit 124 continues to receive the frame on channel B the auxiliary chain, and in parallel continues to receive the frame on channel A using the primary chains other than the fourth primary chains.
Typically, WLAN devices transmit beacon frames in sequences having a periodic pattern. In some embodiments, control unit 124 detects beacon frames on various auxiliary channel frequencies and identifies the periodic patterns (e.g., period interval and timing) of the various beacon sequences. In some embodiments, control unit 124 uses this information to tune the auxiliary channel so as to hop among multiple auxiliary channel frequencies, according to the identified patterns. In this manner, the control unit can efficiently capture beacon frames of multiple WLAN devices on multiple different frequencies simultaneously.
In some embodiments, when the shared baseband circuitry is assigned to the auxiliary RX chain, control unit 124 deactivates at least part of the fourth primary chain in order to reduce power consumption. In one embodiment all other primary chains are deactivated, as well. In another embodiments, the remaining three primary chains remain active, and continue normal communication without the fourth chain, possibly at reduced performance.
In some embodiments, when one or more of the primary chains are transmitting, control unit 124 deactivates auxiliary chain 40, or at least stops processing the signal produced by the auxiliary chain. The rationale behind this mechanism is that transmission from the nearby primary chains is likely to saturate or otherwise distort reception in the auxiliary chain.
In some embodiments, when one or more of the primary chains are transmitting, control unit 124 retains auxiliary chain 40 active, and controls the gain of the common LNA (LNA 88) based on the signal level in the auxiliary chain. When the auxiliary chain is active in parallel with primary chain transmission, in some cases the LNA gain control is limited in range so as not to saturate the LNA, and/or to limit cross-modulation between the leakage from the transmitted signal and the received signal in the auxiliary chain. The effects of transmitted signal leakage can be calibrated per WLAN device to determine the LNA gain control limits.
It will be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art. Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in these incorporated documents in a manner that conflicts with the definitions made explicitly or implicitly in the present specification, only the definitions in the present specification should be considered.
This application is a continuation-in-part of U.S. patent application Ser. No. 14/278,117, filed May 15, 2014, which claims the benefit of U.S. Provisional Patent Application 61/829,070, filed May 30, 2013. The disclosures of these related applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61829070 | May 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14278117 | May 2014 | US |
| Child | 14485735 | US |
