Media access control for MIMO wireless network

• US 7,301,924 B1
• Filed: 07/15/2002
• Issued: 11/27/2007
• Est. Priority Date: 07/15/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Stephenson, David, Pignatelli, David, Douglas, Bretton, Gurbuz, Ozgur, Ayanoglu, Ender, Perahia, Eldad
• Primary Examiner(s): Nguyen; Chau
• Assistant Examiner(s): SMITH, MARCUS
• Application Number:
  US10/197,300
• Time in Patent Office: 1,961 Days
• Field of Search: 370/336, 370/345, 370/346, 370/335, 370/338, 370/342
• US Class Current: 370/335
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0628 Diversity capabilities
• CPC Class Codes: H04B 7/0689 using different transmission schemes, at least one of them being a diversity transmission scheme
• CPC Class Codes: H04B 7/0871 using different reception schemes, at least one of them being a diversity reception scheme
• CPC Class Codes: H04W 28/22 Negotiating communication rate
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

The MAC layer of a wireless communication standard is modified to facilitate MIMO (multiple input multiple output) processing and thereby increase capacity and/or spectral efficiency. In one implementation, the IEEE 802.11a standard is modified in this way. A contention free period (CFP) is divided between MIMO communications and non-MIMO communications. An access point may maintain a list of nodes operating in MIMO mode and nodes operating in non-MIMO mode.

Claims

1. In a wireless communication system having nodes operating in a Multiple Input Multiple Output (MIMO) mode and nodes operating in a non-MIMO mode, a method for operating an access node, the method comprising:

maintaining a list of nodes operating in a MIMO mode and nodes operating in a non-MIMO mode;

dividing a contention free period into non-overlapping subperiods; and

within a designated contention free period, polling MIMO-mode nodes and non-MIMO-mode nodes for transmissions in said corresponding non-overlapping subperiods of said contention free period;

wherein said access node communicates with nodes operating in said MIMO mode during one of said non-overlapping subperiods and communicates with nodes operating in said non-MIMO mode during another of said non-overlapping subperiods.

2. The method of claim 1 further comprising:

during a contention period, receiving a request from a selected node desiring to switch between MIMO mode and non-MIMO mode.

3. The method of claim 2 wherein said request comprises an 802.11 reassociation request having a supplemental MIMO status information element.

4. The method of claim 1 further comprising:

transmitting a MIMO beacon to allow nodes to evaluate MIMO transmission conditions.

22. The method of claim 1 further comprising transmitting in said non-MIMO mode to all of said nodes during a contention period.

23. The method of claim 2 further comprising transmitting a confirmation to said selected node to switch between said MIMO mode and said non-MIMO mode.

5. In a wireless communication network, a method of operating a Multiple Input Multiple Output (MIMO)-capable subscriber node, said method comprising:

receiving a MIMO beacon;

measuring MIMO transmission conditions based on said MIMO beacon;

during a contention period, requesting an access point for permission to switch between a MIMO mode and a non-MIMO mode; and

upon receiving permission, switch between said MIMO mode and said non-MIMO mode;

wherein requesting said access point for permission to switch between said MIMO mode and said non-MIMO mode occurs in response to said measured MIMO transmission conditions.

6. The method of claim 5 wherein requesting comprises transmitting an 802.11 reassociation request having a supplemental MIMO status information element.

7. The method of claim 5 further comprising:

during a non-contention period;

communicating data with said access point in a MIMO subperiod if said subscriber node is in MIMO mode;

communicating data with said access point in a non-MIMO subperiod if said subscriber node is in non-MIMO mode.

8. In a wireless communication system having nodes operating in a Multiple Input Multiple Output (MIMO) mode and nodes operating in a non-MIMO mode, a computer program product for operating an access node, the computer program product comprising:

code that maintains a list of nodes operating in a MIMO mode and nodes operating in a non-MIMO mode;

code that divides a contention free period into non-overlapping subperiods;

code that, within a designated contention free period, polls MIMO-mode nodes and non-MIMO-mode nodes for transmissions in said corresponding non-overlapping subperiods of said contention free period, wherein said access node communicates with nodes operating in said MIMO mode during one of said non-overlapping subperiods and communicates with nodes operating in said non-MIMO mode during another of said non-overlapping subperiods; and

a computer-readable storage medium that stores the codes.

9. The computer program product of claim 8 further comprising:

code that, during a contention period, receives a request from a selected node desiring to switch between MIMO mode and non-MIMO mode.

10. The computer program product of claim 9 wherein said request comprises an 802.11 reassociation request having a supplemental MIMO status information element.

11. The computer program product of claim 8 further comprising:

code that transmits a MIMO beacon to allow nodes to evaluate MIMO transmission conditions.

12. In a wireless communication network, a computer program product operating a Multiple Input Multiple Output (MIMO)-capable subscriber node, said computer program product comprising:

code that receives a MIMO beacon;

code that measures MIMO transmission conditions based on said MIMO beacon;

code that, during a contention period, requests an access point for permission to switch between a MIMO mode and a non-MIMO mode;

code that, upon receiving permission, switches between said MIMO mode and said non-MIMO mode; and

a computer-readable storage medium that stores the codes;

wherein requesting said access point for permission to switch between said MIMO mode and said non-MIMO mode occurs in response to said measured MIMO transmission conditions.

13. The computer program product of claim 12 wherein requesting comprises transmitting an 802.11 reassociation request having a supplemental MIMO status information element.

14. The computer program product of claim 12 further comprising:

code that, during a non-contention period;

communicates data with said access point in a MIMO subperiod if said subscriber node is in MIMO mode and communicates data with said access point in a non-MIMO subperiod if said subscriber node is in non-MIMO mode.

15. In a wireless communication system having nodes operating in a Multiple Input Multiple Output (MIMO) mode and nodes operating in a non-MIMO mode, apparatus for operating an access node, said apparatus comprising:

a MIMO-capable physical layer transceiver; and

a Medium Access Control (MAC) layer block that maintains a list of nodes operating in a MIMO mode and nodes operating in a non-MIMO mode, and within a designated contention free period, polls MIMO-mode nodes and non-MIMO-mode nodes for transmissions in corresponding non-overlapping subperiods of said contention free period;

wherein said access node communicates with nodes operating in said MIMO mode during one of said non-overlapping subperiods and communicates with nodes operating in said non-MIMO mode during another of said non-overlapping subperiods.

16. The apparatus of claim 15 wherein said MAC layer block, during a contention period, receives a request from a selected node desiring to switch between MIMO mode and non-MIMO mode.

17. The apparatus of claim 16 wherein said request comprises an 802.11 reassociation request having a supplemental MIMO status information element.

18. The apparatus of claim 16 wherein said MAC layer block transmits a MIMO beacon to allow nodes to evaluate MIMO transmission conditions.

19. In a wireless communication network, apparatus for operating a Multiple Input Multiple Output (MIMO)-capable subscriber node, said method comprising:

a MIMO-capable physical layer transceiver; and

a Medium Access Control (MAC) layer block that, during a contention period, requests an access point for permission to switch between a MIMO mode and a non-MIMO mode upon receiving permission, switches between said MIMO mode and said non-MIMO mode;

wherein said MAC layer block receives a MIMO beacon;

measures MIMO transmission conditions based on said MIMO beacon, and requests said access point for permission to switch between said MIMO mode and said non-MIMO mode occurs in response to said measured MIMO transmission conditions.

20. The apparatus of claim 19 wherein said MAC layer block requests by transmitting an 802.11 reassociation request having a supplemental MIMO status information element.

21. The apparatus of claim 19 wherein said MAC layer block:

during a non-contention period;

communicates data with said access point in a MIMO subperiod if said subscriber node is in MIMO mode and communicates data with said access point in a non-MIMO subperiod if said subscriber node is in non-MIMO mode.