MIMO SEARCH OVER MULTIPLE ACCESS POINTS

• US 20120115523A1
• Filed: 11/04/2010
• Published: 05/10/2012
• Est. Priority Date: 11/04/2010
• Status: Active Grant

• Current Assignee: Allied Telesis Israel Ltd.
• Original Assignee: Extricom Limited (Allied Telesis Holdings KK)
• Inventors: Shpak, Eran
• Granted Patent: US 8,588,844 B2
• Time in Patent Office: Days
• US Class Current: 455/507
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
• CPC Class Codes: H04L 5/0023 Time-frequency-space

Abstract

A method for communication includes arranging multiple access points in a wireless local area network (WLAN) to communicate over the air with a station in a multiple-input multiple-output (MIMO) configuration. Transmission quality is measured, in alternation, between two or more of the access points and the station in a plurality of different MIMO states. Each MIMO state is characterized at least by a respective number of spatial streams to be transmitted in the state. Responsively to the measured transmission quality, one of the access points and one of the MIMO states are selected to transmit data to the station.

Claims

1. A method for communication, comprising:

arranging multiple access points in a wireless local area network (WLAN) to communicate over the air with a station in a multiple-input multiple-output (MIMO) configuration;

measuring transmission quality, in alternation, between two or more of the access points and the station in a plurality of different MIMO states, each MIMO state characterized at least by a respective number of spatial streams to be transmitted in the state; and

responsively to the measured transmission quality, selecting one of the access points and one of the MIMO states to transmit data to the station.

2. The method according to claim 1, wherein the access points are configured to communicate with the station over a common frequency channel and using a common basic service set identification (BSSID) for all the access points.

3. The method according to claim 1, wherein selecting the one of the access points comprises sending and receiving messages over a communication medium linking the access points in order to report the measured transmission quality and to indicate the selected one of the access points and the selected one of the MIMO states.

4. The method according to claim 1, wherein each MIMO state is characterized by a modulation type and a forward error correction (FEC) coding rate, selected from a plurality of available modulation types and FEC coding rates, in addition to the respective number of the spatial streams.

5. The method according to claim 1, wherein measuring the transmission quality comprises collecting first transmission statistics for a first MIMO state, and then selecting, responsively to the first transmission statistics, a second, different MIMO state in which to collect second transmission statistics.

6. The method according to claim 1, wherein measuring the transmission quality comprises, after selecting a first access point and a first MIMO state in which to transmit and receive the data, intermittently measuring the transmission quality for a second access point, different from the first access point, in a second MIMO state, different from the first MIMO state.

7. The method according to claim 1, wherein measuring the transmission quality comprises measuring a respective downlink transmission throughput for each of the plurality of different MIMO states.

8. The method according to claim 1, wherein each of the access points comprises multiple antennas, and wherein the multiple antennas are used for beam forming in at least one of the MIMO states.

9. Communication apparatus, comprising:

multiple access points, which are arranged in a wireless local area network (WLAN) to communicate over the air with a station in a multiple-input multiple-output (MIMO) configuration; and

an access manager, which is coupled to control the access points so as to measure transmission quality, in alternation, between two or more of the access points and the station in a plurality of different MIMO states, each MIMO state characterized at least by a respective number of spatial streams to be transmitted in the state, and responsively to the measured transmission quality, to select one of the access points and one of the MIMO states to transmit data to the station.

10. The apparatus according to claim 9, wherein the access points are configured to communicate with the station over a common frequency channel and using a common basic service set identification (BSSID) for all the access points.

11. The apparatus according to claim 9, wherein the access points and access manager are configured to send and receive messages over a communication medium linking the access points in order to report the measured transmission quality and to indicate the selected one of the access points and the selected one of the MIMO states.

12. The apparatus according to claim 9, wherein each MIMO state is characterized by a modulation type and a forward error correction (FEC) coding rate, selected from a plurality of available modulation types and FEC coding rates, in addition to the respective number of the spatial streams.

13. The apparatus according to claim 9, wherein the access manager is configured to collect first transmission statistics for a first MIMO state, and then to select, responsively to the first transmission statistics, a second, different MIMO state in which to collect second transmission statistics.

14. The apparatus according to claim 9, wherein the access manager is configured, after selecting a first access point and a first MIMO state in which to transmit and receive the data to and from the station, to intermittently measure the transmission quality for a second access point, different from the first access point, in a second MIMO state, different from the first MIMO state.

15. The apparatus according to claim 9, wherein the transmission quality is measured in terms of a respective downlink transmission throughput for each of the plurality of different MIMO states.

16. The apparatus according to claim 9, wherein each of the access points comprises multiple antennas, and wherein the multiple antennas are used for beam forming in at least one of the MIMO states.