METHOD AND SYSTEM FOR EXPLICIT AP-TO-AP SOUNDING IN AN 802.11 NETWORK
A method of one AP accessing a channel occupied by a neighboring AP within CCA range, by acquiring channel knowledge via performing cooperative sounding and setting a null towards the neighboring AP, under certain conditions verifications, is provided herein. The method may include: transmitting and receive signals via a plurality of radio circuitries connected to plurality of antennas; monitoring signals received by the radio circuitries and generating a list of neighboring co-channel access points that each has plurality of antennas and are further located within a clear channel assessment (CCA) range of the access point; and instructing the radio circuitries to transmit a sounding sequence to the list of neighboring access points, and receive Channel State Information (CSI).
This application is a continuation application of U.S. patent application Ser. No. 14/449,431 filed on Aug. 1, 2014, which claims benefit from U.S. Provisional Patent Application Ser. No. 61/955,433 filed on Mar. 19, 2014, all of which are incorporated herein by reference in their entirety.
FIELD OF THE INVENTIONThe present invention relates generally to wireless communication, and more specifically to high efficiency Wi-Fi.
BACKGROUND OF THE INVENTIONPrior to setting forth the background of the invention, it may be helpful to set forth definitions of certain terms that will be used hereinafter.
The term “Wi-Fi” as used herein is defined as any wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards.
The term “Access Point” or “AP” as used herein is defined as a device that allows wireless devices (also known as User Equipment or “UE”) to connect to a wired network using Wi-Fi, or related standards. The AP usually connects to a router (via a wired network) as a standalone device, but it can also be an integral component of the router itself.
The term “client” as used herein is defined as any device that has wireless communication capabilities, specifically, the IEEE 802.11 standards. A client may be for example a smart telephone, a laptop, a tablet or a personal computer (PC).
The notation “STA” as used herein is defined in as an IEEE 802.11 client.
The term “BSS” is an acronym for Basic Service Set, which is typically a cluster of stations supported by an AP.
The term “node” as used herein is defined as general name for both IEEE 802.11 AP and IEEE 802.11 STA.
The term “serving AP” as used herein is defined in relation to one AP and one STA, wherein the STA is registered to the AP, and the AP and STA are sending and receiving data to and from each other.
The term “neighboring APs” or “neighboring nodes” relate to two co-frequency (or co-channel) APs or nodes that are within each other's sensitivity range, e.g. at least one of them can receive the other in such an signal-to-noise ratio to allows decoding of signals.
The term “CCA range” as used herein is a range between two IEEE 802.11 nodes, wherein at least one node can receive the other's transmission at a power level equal or larger than “CCA Level” e.g. −82 dBm.
The term “CSMA/CA” stands for Carrier-Sense-Multiple-Access/Collision-Avoidance, representing a requirement to listen before transmitting in a multi-node wireless system that shares a common channel on the basis of first-come-first-served.
The term “preamble” as used herein describes a certain 802.11 transmitted signal modulation appearing at the beginning of each packet, that when received by other 802.11 nodes, will force them to yield channel access.
The notation “SINR” stands for Signal to Interference and Noise.
The term “ACK” as used herein, stands for acknowledgement, and is defined as the signal transmitted from an IEEE 802.11 receiving node to the IEEE 802.11 node that has transmitted a packet to it, provided the packet was successfully received.
The term “time division duplex” (TDD) as used herein refers to systems using the same frequency spectrum for methods of communications in a time division manner such as Wi-Fi systems.
The term “channel sounding” as used herein refers to the process defined in 802.11 specifications that enables the full dimensionality of the radio channel to be determined. One sounding technique described in the 802.11 specifications is for an AP to transmit a Null Data Packet (NDP), a packet without a MAC frame.
The term “implicit feedback” or “implicit sounding” as used herein refers to a process used for TDD protocols such as Wi-Fi, where both down and up links share the same spectrum. In the aforementioned process, the uplink channel estimated by the AP, is assumed to be identical to the downlink one—based on reciprocity principle—and is therefore is considered by the AP to represent the channel towards the client/STA.
The term “explicit AP-STA feedback” or “explicit sounding” as used herein refers to a procedure where AP transmissions are channel estimated by the STA, and then fed back to the AP, providing it with the magnitude of phase and amplitude differences between the signals as transmitted by the AP vis-à-vis as received by the client/STA, allowing it to gauge possible distortions and correct them.
The term “associated STA” as used herein refers to a STA that is served by a certain AP with a certain Service Set Identifier (SSID).
The term “non-associated STA” as used herein refers to a STA within the range of the non-serving AP.
The acronym “NAV” stands for Network-Allocation-Vector and represents virtual carrier sense mechanism, used by a Wi-Fi transmitting message to broadcast the predicted duration of its transmission, signaling to other nodes how long the channel will be occupied.
The acronym “RTS” stands for Request-To-Send, and represents a message transmitted by one Wi-Fi node to another, probing it for information about its availability to receive data, per the Wi-Fi Alliance protocol.
The acronym “CTS” stands for Clear-To-Send, and represents a positive response from the other node to the node originating the RTS, indicating to the requesting node that the channel is clear from its point of view as well.
The notation “DURATION” is a message embedded in both RTS and CTS, representing a prediction of the future traffic about to be transmitted between two nodes that have captured the channel; other nodes that receive it, must clear the channel as long as the DURATION has not expired; other nodes that have received the RTS but received the CTS (hidden nodes) will avoid accessing the channel, allowing the receiving node to successfully complete the reception.
The acronym “FLA” stands for Fast Link Adaptation, and represents processes that reduce transmitting side learning time of the receiver's SINR.
The acronym “MCS” stands for Modulation Coding Scheme, mapping SINR to modulation order and code rate.
The term “beamformer” as used herein relates to a node that generates a spatial pattern, created by two or more antennas, formed in such a way that significantly in the power level received by a given receiver being a “beamformee”.
The term “null” as used herein, is a spatial pattern, created by two or more antennas, formed in such a way that significantly reduces the power level received by a given receiver (e.g., a local minimum). An “Rx Null” is a null formed by a receiver's antennas weight in order to decrease undesired signal level. A “Tx Null” is formed by transmitter's antennas weights in order to decrease its undesired transmitted signal at remote receiver's input.
The term “actual null depth” as used herein, is the estimated value of the null after a certain time period has elapse since the last explicit sounding in which the amplitude and the phase have drifted so as to yield null degradation. The actual null depth is the original null taking account the estimated null degradation.
APSS is an acronym for AP Sounding Set. This is a cluster of APs that work together with mutual sounding process to reduce interference according to this invention.
The term “AP Beacon” is a management signal that is transmitted at regular intervals (typically about 10 times per second) that indicates capability of the AP. The Beacon frame contains both mandatory information (such as SSID) and optional data that may include vendor specific information. This vendor specific data field is used to indicate the AP as an APSS capable.
AP* indicates an AP which is compatible with APSS, meaning it is equipped with special software so that it can participate in APSS, either as a sounder or as a responder.
AP*_1 indicated an AP that initiates the APSS process. If multiple AP* are present, then multiple APSS's exist.
APSS_ID indicated an N bit random code selected by AP*_1 to identify the APSS that it has created (e.g. N=12).
AP*_i indicates an AP member in a group of APs that is a recipient of an AP*_1's initiation of an APSS process, where I {2 . . . n} is the designator for the different AP* that are members of the APSS_ID. Also labeled as “Compatible Access Point”.
According to current IEEE 802.11 air protocols, two neighboring APs can download traffic (e.g. radio signals including data) over the same frequency channel to their respective STAs at the same time as long as these APs are not within CCA range of each other. When an RTS/CTS procedure is used, an additional condition is introduced. Namely, a legacy STA receiving the download traffic from its serving AP, must not be within CCA range of other neighboring APs or the STA they are supporting, if the AP is occupying the channel.
In many deployments APs on the same radio channel are within CCA range of each other; thus, an AP may be blocked from transmitting to its client STA due to activity of a neighboring nearby AP.
SUMMARY OF THE INVENTIONEmbodiments of the present invention disclose a protocol modification that allows a group of 802.11 nodes that are MIMO capable, to access an occupied channel, using novel procedure that enables acquiring knowledge of the channel between APs, based on setting up an explicit beamformer-beamformee handshake.
According to some embodiments, an AP equipped with Tx/RX MIMO capability may serve several STAs while simultaneously null its transmitted signal toward the interfering AP, based on acquiring channel knowledge via a sounding process targeted at neighboring APs, similar to explicit sounding process defined for 802.11ac beamforming and MU-MIMO targeted at served STAs.
Embodiments of a MU-MIMO procedure are described herein, enabling a neighboring AP to access a channel already occupied by another downloading AP; the procedure may be initiated by establishing a subgroup of neighboring APs which agree to adhere to a mutual sounding protocol, e.g. subscribe to an AP Sounding Set (APSS), exchanging invites and accepts to the set, and performing mutual sounding handshakes that enable acquisition of each other's channel information, consequently used for null setting towards each other—also labeled as beamformer-beamformee nulling process.
Each of the aforementioned member AP may perform an APSS initialization by surveying the neighboring co-channel APs periodically, listing those who are within its CCA range, and eliminating from the list ones that are not APSS capable, and ones that are too strong to be nulled, e.g., ones that cannot be pushed below CCA Level via nulling, either due to limited nulling capability, or due to a very close proximity, or both.
The aforementioned beamformer's nulling capability is defined as the power level difference between its trained null towards the Beamformee, and its Omni directional antenna pattern, as received by the Beamformee's receiver.
Such nulling capability is estimated by a beamformer AP via periodical sounding of the APs that are within its CAA range, and by then interpolating the acquired phase and amplitude accuracy deterioration over time, which has elapsed from last sounding.
Successful nulling capability verification may allow a beamformer AP to access (for downloading purposes) a channel occupied by the downloading beamformee AP, provided certain additional conditions are met.
The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be more fully understood by reference to the following detailed description when read with the accompanying drawings in which:
In the following description, various aspects of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details presented herein. Furthermore, well-known features may be omitted or simplified in order not to obscure the present invention.
Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining,” or the like, refer to the action and/or processes of a computer or computing system, or similar electronic computing device, that manipulates and/or transforms data represented as physical, such as electronic, quantities within the computing system's registers and/or memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices.
The reason for the protocol's requirement that prohibits AP_1 from transmitting is to avoid harmful interference to the AP_2's session, as well as in consideration of a possible harmful interference of AP_2 transmission to AP_1's contemplated package delivery.
It is noted that in cases depicted in
Baseband processor 30 may be configured to monitor signals received by the radio circuitries 20-1 to 20-N and generate a set or list of neighboring co-channel access points that each has plurality of antennas and are further located within a clear channel assessment (CCA) range of the access point. Baseband processor 30 may be further configured to instruct radio circuitries 20-1 to 20-N to transmit a sounding sequence to the list of neighboring access points, and receive Channel State Information (CSI) therefrom. The sounding sequence being a sequence of control frames sent to beamformees and data frames indicative of the channel from the beamformee.
According to some embodiments, an explicit sounding process invoked between the access point and each of the listed neighboring access points.
In a case that AP*_1 receives any ACK-to-APSS response 304, AP*_1 updates its APSS table 305. In a case AP*_1 does not receive any ACK-to-APSS response, the next AP*_i from the list is being picked and the method goes on to the AP*_1 sending Request-to-Join-APSS to the picked AP*_i 303 and so forth. When a Request-to-Join is not being responded with ACK-to-APSS, AP*_i may re-send the Request-to-Join several times, (e.g. resending the Request-to-Join three times, each request being sent a few milliseconds after the previous request) before proceeding to next neighboring AP*_i 306, and revisit the non-responding AP*_i after an extended time period, e.g. 1 minute.
One embodiment of the invention has APSS compatible AP indicate their capability by a flag set in a vendor specific information element (for example Element Identifier (ID) 122) in the beacon management frame (See e.g.
Once the list of APSS is established, each AP*_i can try to access an occupied channel following the APSS procedure which is based on expanding the 802.11ac multi-user-MIMO (MU_MIMO) explicit sounding.
In essence, the APSS process in one embodiment differs from the existing MU-MIMO by replacing one of the simultaneously served STAs with a neighboring AP; specifically, an AP that is capable of serving L simultaneous STAs, is configured to serve only L−1 STAs while nulling a neighboring AP which is currently occupying the channel.
According to some embodiments of the present invention, beamformer AP*_1 may send an NDP announcement to the listed neighboring beamformees APs, followed by an NDP, and a compressed matrix V representing the channel response (herein: compressed V response) from a first neighboring AP*_i and a series of poll requests to a next beamformee neighboring AP*_i and a corresponding V compressed response, until all listed neighboring beamformees neighboring APs are polled and all V compressed responses are consummated.
More specifically, the two byte STA field 506 of the MU-MIMO protocol is retrofitted into a APSS ID field 501, rather than a STA field, containing similar structure, i.e. a subfield APSS ID (e.g. 12 bits), a subfield indicating the FB feedback type being used (e.g. 1 bit), and a subfield NC the Number of Columns in the feedback matrix (e.g. 3 bits).
According to some embodiments of the present invention, the APSS NDP announcement and NDP may include an APSS ID field replacing in the MU MIMO protocol the STA ID field.
There is a set of topologic conditions and qualifications that are verified before an AP*_1 may perform an APSS process and access the busy channel: the beamformer AP is outside the CCA range of the STA currently served by the beamformee AP; the beamformee AP is outside the CCA range of the STA to be served by the Beamformer AP; both served STAs are verified to be located closer than the edge of their serving cells, since their corresponding AP*'s' sensitivity is slightly reduced by minor residual interference caused by the APSS process conditions are outlined as follows:
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- Beamformer AP identifies the Beamformee served station by decoding the destination field, and either does not identify such a STA MAC address in its neighborhood, or receives it at RSSI<CCA level;
- Beamformer AP identifies the MCS transmitted by the Beamformee AP to its served STA, and uses it in order to calculate the proximity of said STA to the Beamformee's cell edge, e.g. low MCS may indicate large range, and if so, will refrain from accessing the channel;
- The beamformer AP will use RTS/CTS for serving the STA it is intending to download data to, in order to make sure said STA will not be jammed by the beamformee AP; and
- The beamformer AP will gauge the RSSI of the CTS coming from the STA it is intending to serve, calculates the proximity of the STA to the beamformer AP's cell edge, in which case it will refrain from accessing the channel.
Additionally, in order to guarantee the AP*_i session is not harmed by the AP*_1 access, a null depth verification and validation is required.
As a non-zero time has elapsed between such last APSS channel estimation and the usage of the acquired weights for nulling, a null deterioration estimation is performed as described below, and then a nulling capability is calculated as described further, yielding actual null depth figure of merit Null—depth.
Therefore, proceeding to AP*_1 access of the occupied channel, is conditioned by measuring RSSIAP*
According to some embodiments of the present invention, a decision to access a channel occupied by a listed compatible neighboring AP within CCA range, may be subject to verification and validation of the access point null's capability to reduce the interference caused by the access point to the neighboring AP below CCA Level, for at least one of the neighboring AP antennas.
According to some embodiments of the present invention, the access point may be configured to keep or store records (e.g. on a memory) of fading rates of each listed compatible neighboring APs within CCA range, in terms of amplitude and phase variation over time, and further calculates for each of the listed neighboring APs the standard deviation 1σ, 2σ, 3σ of the amplitude and phase variations, and further estimates a corresponding amplitude and phase drift rate.
According to some embodiments of the present invention, the access point may be further configured to keep or store records of fading rates of each listed compatible neighboring APs within CCA range, in terms of amplitude and phase variation over time, and further calculates for each of the listed compatible neighboring AP within CCA range the standard deviation 1σ, 2σ, 3σ of the amplitude and phase variations, and further estimates a corresponding amplitude and phase drift rate.
According to some embodiments of the present invention, the access point may be further configured to estimate the nulling capability by calculating the time elapsed between the last sounding of the compatible neighboring AP within CCA range and the time the condition is being examined, apply the amplitude and phase drift rate, and further estimates the null depth degradation, caused by the accumulated drift, yielding actual null depth.
According to some embodiments of the present invention, the access point may be further configured to null compatible neighboring AP within CCA range while downloading a packet to served STA, in a case where the neighboring AP RSSI—Actual Null Depth<CCA Level, provided several predefined topologic conditions are met.
According to some embodiments of the present invention, the topologic conditions may be defined as, for example: (i) the access point is not within CCA range of the STA served by compatible neighboring AP within CCA range (ii); the neighboring AP is not within CCA range of the STA or STAs about to be served by the access point (iii); and/or the served STAs are not on their servicing cell's edges.
AP*_1 may perform periodical APSS sounding process with a given AP*_i, when the AP*_i is not transmitting; such period are preferably done at intervals larger than the maximum packet duration (e.g. 7 ms or more).
According to some embodiments of the present invention, the access point may perform the sounding of the listed neighbors that have agreed to join the APSS, on a periodic basis, whenever a given compatible neighboring AP within CCA range is not transmitting. Such periods are preferably carried out at intervals longer than the maximum packet duration (e.g. 7 ms or more).
According to some embodiments of the present invention, the access point may be configured to limit a number of responses produced by it so as to allocate up to approximately 10% of a transmitting time to respond to sounding requests from the listed neighboring access points.
According to some embodiments of the present invention, the sounding of the listed neighboring access points may be performed based on IEEE 802.11ac MU MIMO sounding procedure, wherein the access point may respond to a limited number of compatible neighboring APs including up to eight strongest RSSIs.
According to some embodiments of the present invention, the access point may carry out an actual download of a packet to a STA, or a group of STAs, while the channel may be occupied by a compatible neighboring AP within CCA range, may be carried out with such antenna pattern that may minimize the power received by at least one of the neighboring AP antennas.
Following fading fluctuation over time, and average time interval between consecutive APSS sounding, a phase and amplitude gradients are calculated (e.g. standard deviation 1σ, 2σ, 3σ), and applied to a null deterioration chart (See
According to some embodiments of the present invention, the access point may include: a plurality of antennas; a plurality of radio circuitries configured to transmit and receive signals via the plurality of antennas; and a baseband processor configured to monitor signals received by the radio circuitries and generate a list of neighboring co-channel access points that each has plurality of antennas and are further located within a clear channel assessment (CCA) range of the access point.
The baseband processor may further be configured to instruct the radio circuitries to transmit a sounding sequence to the list of compatible neighboring access points, and receive Channel State Information (CSI) from the compatible neighboring access points, wherein the compatible neighboring access points indicate having a capability of responding to sounding sequences by transmitting identification of the capability in a beacon management frame. The baseband configuration capabilities may be broadcasted to the compatible neighboring access points via unused bits within the beacon management frame.
As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or an apparatus. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” For example, a baseband processor or other processor may be configured to carry out methods of the present invention by for example executing code or software.
The aforementioned flowcharts and block diagrams illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
In the above description, an embodiment is an example or implementation of the inventions. The various appearances of “one embodiment,” “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments.
Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment.
Reference in the specification to “some embodiments”, “an embodiment”, “one embodiment” or “other embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments, of the inventions. It will further be recognized that the aspects of the invention described hereinabove may be combined or otherwise coexist in embodiments of the invention.
The principles and uses of the teachings of the present invention may be better understood with reference to the accompanying description, figures and examples.
It is to be understood that the details set forth herein do not construe a limitation to an application of the invention.
Furthermore, it is to be understood that the invention can be carried out or practiced in various ways and that the invention can be implemented in embodiments other than the ones outlined in the description above.
It is to be understood that the terms “including”, “comprising”, “consisting” and grammatical variants thereof do not preclude the addition of one or more components, features, steps, or integers or groups thereof and that the terms are to be construed as specifying components, features, steps or integers.
If the specification or claims refer to “an additional” element, that does not preclude there being more than one of the additional element. It is to be understood that where the specification states that a component, feature, structure, or characteristic “may”, “might”, “can” or “could” be included, that particular component, feature, structure, or characteristic is not required to be included.
Where applicable, although state diagrams, flow diagrams or both may be used to describe embodiments, the invention is not limited to those diagrams or to the corresponding descriptions. For example, flow need not move through each illustrated box or state, or in exactly the same order as illustrated and described. The descriptions, examples, methods and materials presented in the claims and the specification are not to be construed as limiting but rather as illustrative only.
Meanings of technical and scientific terms used herein are to be commonly understood as by one of ordinary skill in the art to which the invention belongs, unless otherwise defined.
The present invention may be implemented in the testing or practice with methods and materials equivalent or similar to those described herein. While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of some of the preferred embodiments. Other possible variations, modifications, and applications are also within the scope of the invention. Accordingly, the scope of the invention should not be limited by what has thus far been described, but by the appended claims and their legal equivalents.
Claims
1. An access point (AP) comprising:
- a plurality of antennas;
- a plurality of radio circuitries configured to transmit and receive signals via the plurality of antennas; and
- a baseband processor configured to monitor the signals received by the radio circuitries and generates a list of neighboring co-channel access points (APs), each is further located within a clear channel assessment (CCA) range of said access point,
- wherein the baseband processor is further configured to establish a subgroup of neighboring co-channel APs which agree to join an access point sounding set (APSS), instruct the radio circuitries to transmit a sounding sequence to said APSS, and receive channel state information (CSI) therefrom.
2. The access point according to claim 1, wherein the baseband processor is further configured to set weights on the radio circuitries to produce a null at one or more antennas of said APSS which currently transmits on a same frequency channel and download a packet to a station (STA), or a group of STAs.
3. The access point according to claim 2, wherein the null weights are determined via explicit sounding process invoked between said access point and each of the APSS, based on APSS Null Data Packet (NDP) announcement by said AP and response by APSS.
4. The access point according to claim 3, wherein the AP sends an APSS NDP announcement to all APs in APSS, followed by an NDP, and a V compressed response from a first neighboring AP and a series of poll requests to a next neighboring AP and a corresponding V compressed response, until all APs in APSS are polled and all V compressed responses are consummated, wherein V is a compressed matrix representing the channel response.
5. The access point according to claim 3, wherein the APSS NDP announcement and NDP comprise an APSS ID field replacing in the IEEE 802.11ac MU MIMO sounding protocol the STA ID field.
6. The access point according to claim 3, wherein the Poll Request field is retrofitted to address a neighboring APs rather than STAs in the IEEE 802.11ac MU MIMO sounding protocol.
7. A method of performing an explicit sounding process to neighboring access points (APs) by a beamformer access point (AP) comprising:
- transmitting and receiving signals via a plurality of radio circuitries connected to a plurality of antennas;
- monitoring the signals received by the radio circuitries and generating a list of neighboring co-channel access points, each being located within a clear channel assessment (CCA) range of the access point;
- establishing a subgroup of neighboring co-channel APs which agree to join an access point sounding set (APSS); and
- instructing the radio circuitries to transmit a sounding sequence to the list of neighboring co-channel access points, and receive channel state information (CSI) from APs in APSS.
8. The method according to claim 7, wherein the baseband processor is further configured to set weights on the radio circuitries to produce a null at one or more antennas of said APSS which currently transmits on a same frequency channel and download a packet to a station (STA), or a group of STAs.
9. The method according to claim 8, wherein the null weights are determined via explicit sounding process invoked between said access point and each of the APSS, based on APSS Null Data Packet (NDP) announcement by said AP and response by APSS.
10. The method according to claim 9, wherein the AP sends an APSS NDP announcement to all APs in APSS, followed by an NDP, and a V compressed response from a first neighboring AP and a series of poll requests to a next neighboring AP and a corresponding V compressed response, until all APs in APSS are polled and all V compressed responses are consummated, wherein V is a compressed matrix representing the channel response.
11. The method according to claim 9, wherein the APSS NDP announcement and NDP comprise an APSS ID field replacing in the IEEE 802.11ac MU MIMO sounding protocol the STA ID field.
12. The method according to claim 9, wherein the Poll Request field is retrofitted to address a neighboring APs rather than STAs in the IEEE 802.11ac MU MIMO sounding protocol.
Type: Application
Filed: Aug 3, 2015
Publication Date: Nov 26, 2015
Inventors: Stuart S. JEFFERY (Los Altos, CA), Haim HAREL (New York, NY), Kenneth KLUDT (San Jose, CA)
Application Number: 14/816,545