System and method for simultaneous co-channel access of neighboring access points

• US 8,995,416 B2
• Filed: 06/06/2014
• Issued: 03/31/2015
• Est. Priority Date: 07/10/2013
• Status: Active Grant

• Current Assignee: Magnolia Broadband Incorporated
• Original Assignee: Magnolia Broadband Incorporated
• Inventors: Kludt, Kenneth, Wang, Sherwin J., Chen, Phil F., Jeffery, Stuart S., Harel, Haim
• Primary Examiner(s): Lai, Andrew
• Assistant Examiner(s): LEE, ANDREW CHUNG CHEUNG
• Application Number:
  US14/297,898
• Publication Number:
  US 20150016438A1
• Time in Patent Office: 298 Days
• Field of Search: 370/208, 370/252, 370/295, 370/310, 370/328, 370/334, 370/338, 375/264, 375/267, 375/299
• US Class Current: 370/338
• CPC Class Codes: H04L 5/0055 Physical resource allocation for ACK/NACK for physical mapping arrangements in ARQ protocols H04L1/1861
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 74/0816 with collision avoidance
• CPC Class Codes: H04W 76/10 Connection setup
• CPC Class Codes: H04W 8/005 Discovery of network devices, e.g. terminals
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A system and method for overriding Carrier-Sense-Multiple-Access/Collision-Avoidance (CSMA/CA) and virtual carrier sense, without harming the traffic that occupies the channel is described herein. Further provided herein are measurements and qualifying criteria for performing the aforementioned channel sharing. The system and method may be based, for example, on opportunistic spatial isolation of nodes from each other and selectively implementing ultra-fast link adaptation.

Claims

1. A communication node comprising:

a plurality of antennas;

a plurality of radio circuits configured to transmit and receive in compliance with IEEE 802.11 standard; and

a baseband processor,

wherein said plurality of radio circuits and antennas are located within a clear channel assessment (CCA) range of a number N neighboring nodes sharing a co-channel with the communication node,

wherein the baseband processor is configured to set weights on the radio circuits such that spatial signatures are generated in both downlink and uplink transmissions, for allowing said communication node to access said co-channel, known by said communication node_to be currently used by at least one of the N neighboring nodes, by reducing a power level of signals transmitted by said antennas, as received by said N neighboring nodes, below a CCA range power level,

wherein the nulling created by said nulling AP, are in both downlink and uplink toward to the nulled APs,

wherein said communication node is a nulling Access point (AP) and the neighboring nodes are nulled APs, and wherein the APs communicate in compliance with the 802.11 standard, wherein the nulling created by said nulling AP, are in both downlink and uplink toward to the nulled APs, and

wherein the nulling AP performs channel estimation of the nulled AP'"'"'s preamble Legacy-Long Training Field (L-LTF) field, calculates Rx null weights and uses reciprocity to create the downlink Tx null.

2. The communication node according to claim 1, wherein a downlink Tx null of the nulling AP is performed in order to protect an ACK reception of the nulled AP from being jammed by the nulling AP'"'"'s transmission.

3. The communication node according to claim 1, wherein an uplink Rx null of the nulling AP is performed in order to protect the nulling AP ACK reception from being jammed by the nulled AP'"'"'s transmission.

4. The communication node according to claim 1, wherein the downlink transmit null is executed while transmitting request to send (RTS) to a station prior to serving by the nulling AP, and the clear to send (CTS) is received while the uplink receive nulls are executed.

5. The communication node according to claim 1, wherein the nulling AP sends a request to send (RTS) to a station prior to serving by the nulling AP, and conditions the nulling with reception of clear to send (CTS).

6. The communication node according to claim 1, wherein the nulling AP receives a preamble of the nulled AP and identifies a destination address of the station (STA) served by the nulled AP, and validates that said STA is not within CCA range of the nulling AP.

7. The communication node according to claim 1, where the nulling is conditioned on the nulling AP'"'"'s reception of the Modulation Coding Scheme (MCS) transmitted by a nulled AP and identified as high order MCS.

8. The communication node in claim 7, wherein the high order MCS indicates SNR greater than 10*log(K) dB above an SNR associated with an MCS of order zero, where K is the number of receiving antennas of said nulled AP.

9. The communication node according to claim 8, wherein if said K is unknown, then the nulling AP'"'"'s transmit power is reduced by 6 dB.

10. The communication node according to claim 1, wherein the nulling AP performs channel estimation of each data stream transmitted by the nulled AP, during the transmission of a Very High Throughput-Long Training Field (VHT-LTF) field, and grade a power level of the data streams, labeling the power level of the data streams as strongest, second strongest, until N−

1.

11. The communication node according to claim 10, wherein the nulling AP creates K−

1 uplink Rx nulls towards the K−

1 respective strongest data streams, wherein K is the number of receiving antennas of the nulling AP.

12. The system according to claim 10, wherein the nulling AP has at least 3 antennas, and calculates a family of an integer number Q downlink nulls towards the said preamble of the nulled AP, and selects one of the Q downlink nulls.

13. The communication node according to claim 12, wherein the served STA is located close to a Cell Edge, the power projected by the nulling AP towards the STA intended to be served by the nulling AP P_STA, is maximized via selection of optimum solution out of said Q calculated nulls.

14. The communication node according to claim 13, wherein cell edge indication is derived at the nulling AP via estimating the said STA'"'"'s previously received SINR_ACK<

5 dB.

15. The communication node according to claim 14, wherein the said maximization is performed as follows:

the nulling AP transmits RTS to the STA it is about to serve, using first Nulling solution out of the Q nulls solution, and if CTS is received, the Nulling AP stores the said solution for the next time it serves the said STA; and

If CTS is not received, the nulling AP selects two other solutions one by one out of the Q null solutions, and repeats the RTS transmission, and if both do not result in CTS, no nulling is attempted.

16. The communication node according to claim 1, wherein the nulling AP monitors co-channel neighboring APs, registering the APs whose −

62 dBm>

RSSI>

−

82 dBm, labeling the APs whose −

62 dBm>

RSSI>

−

82 dBm as close-neighbors, and grading the APs whose −

62 dBm>

RSSI>

−

82 dBm by a corresponding RSSI level.

17. The communication node according to claim 16, wherein the nulling AP identifies within the close-neighbors list subgroups of APs that are within CCA range of each other, labeling the subgroups of APs that are within CCA range of each other as channel-sharing subgroups.

18. The communication node according to claim 17, wherein said identification is done by registering preamble time and NAV periods from different close-neighbors which never overlap each other during a last hour.

19. The communication node according to claim 18, wherein the nulling AP estimates the SINR of the previous ACK, and compares it with the highest RSSI amongst each of said sharing groups, and conditions the application of a nulling procedure by the following:

ACK RSSI>

Highest RSSI+Margin, wherein Margin=minimum required SINR for ACK reception.

20. The communication node according to claim 1, wherein a depth of the receive null is estimated by the nulling AP and, wherein the receive null is applied to said beacon transmitted by a nulled AP based on the estimated depth, and wherein a measured resultant RSSI after applying said null, is residual RSSI.

21. The communication node according to claim 20, wherein before uplink null is attempted, the residual RSSI is compared to a previous STA ACK signal level received by the nulling AP and conditions the nulling by meeting the following:

ACK Signal level−

residual RSSI>

Margin, where Margin is the minimum SINR required for reception of ACK.

22. A method comprising:

transmitting and receiving signals via a plurality of antennas and radio circuits in compliance with IEEE 802.11 standard, located within a clear channel assessment (CCA) range of a number N neighboring nodes sharing a co-channel with the radio circuits; and

setting weights on the radio circuits such that spatial signatures are generated in both downlink and uplink transmissions for allowing an access to said co-channel, known by said radio circuits to be currently used by at least one of the N neighboring nodes, by reducing a power level of the signals transmitted by said antennas, as received by said N neighboring nodes, below a CCA range power level,

wherein said weights setting results in nulling the neighboring nodes being nulled APs, wherein the nulling is in both downlink and uplink toward the nulled APs, and

wherein the nulling AP performs channel estimation of the nulled AP'"'"'s preamble L-LTF field, calculates Rx null weights and uses reciprocity to create the downlink Tx null.

23. The method according to claim 22, wherein the nulling on the transmit downlink is performed in order to protect an ACK reception of the nulled APs from being jammed by the transmitting of the signals by the radio circuits.

24. The method according to claim 22, wherein the wherein the nulling on the transmit downlink is performed in order to protect an ACK reception by the radio circuits from being jammed by the nulled AP'"'"'s transmission.

25. The method according to claim 22, wherein the downlink transmit null is executed while transmitting a request to send (RTS) signal to a station about to be served by the radio circuits, and a clear to send (CTS) signal is received while the uplink receive nulls are executed.