TRANSMIT TIME OFFSET IN UPLINK MULTI-USER MULTIPLE INPUT-MULTIPLE OUTPUT SYSTEM

• US 20150139090A1
• Filed: 06/26/2014
• Published: 05/21/2015
• Est. Priority Date: 11/19/2013
• Status: Active Grant

• Current Assignee: Ax Wireless LLC (SY Ventures)
• Original Assignee: Intel IP Corporation (Intel Corporation)
• Inventors: Stephens, Adrian P., Stacey, Robert J., Kenney, Thomas J.
• Granted Patent: US 9,462,504 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04L 5/0091 Signaling for the administration of the divided path
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 52/146 Uplink power control
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/267 taking into account the information rate
• CPC Class Codes: H04W 52/346 distributing total power among users or channels
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 74/006 in the downlink, i.e. towards the terminal
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A method for transmit time offset in a UL-MU-MIMO system monitors respective transmit powers, over a wireless channel, for a plurality of stations in the system. A respective transmit time offset is determined for each station in response to the respective transmit power of each station. A poll exchange sequence is initiated in which the transmit time offsets are transmitted to each respective station. An access point can then receive data from the stations at times adjusted by the respective transmit time offsets.

Claims

1. An apparatus including a processor and circuitry to monitor respective transmit powers for a plurality of wireless stations, determine a transmit time offset for a station having a lowest respective transmit power of the plurality of wireless stations, transmit the transmit time offset to the station, and receive data from the station at a time adjusted by the transmit time offset in accordance with a UL-MU-MIMO technique.

2. The apparatus of claim 1, wherein the apparatus is further configured to transmit a frame to the plurality of wireless stations wherein the frame comprises a respective transmit time offset for each of the plurality of wireless stations.

3. The apparatus of claim 1, wherein the apparatus is further configured to monitor a signal-to-noise ratio (SNR) of a wireless channel between the apparatus and the plurality of wireless stations.

4. The apparatus of claim 1, wherein the apparatus is further configured to identify the plurality of wireless stations as a station group.

5. The apparatus of claim 4, wherein the apparatus is further configured to transmit a poll frame including respective transmit time offsets for each of the wireless stations in the station group.

6. The apparatus of claim 1, wherein the apparatus is further configured to:

generate a non-zero transmit time offset for a wireless station having a lower transmit power than other stations of the plurality of wireless stations; and

transmit the non-zero transmit time offset to the wireless station having the lower transmit power.

7. The apparatus of claim 1, wherein the data is received from the plurality of wireless stations in accordance with the UL-MU-MIMO technique during a high efficiency WiFi (HEW) control period during which the AP, operating as a master station, has exclusive use of a channel.

8. A non-transitory computer-readable storage medium that stores instructions for execution by processing circuitry in controlling a transmit time of stations, the operations to perform the transmit time control:

monitor respective transmit powers, over a wireless channel, for a plurality of stations;

determine a respective transmit time offset for each station, of the plurality of stations, in response to the respective transmit power of each station;

transmit a frame to the plurality of stations wherein the frame includes the respective transmit time offsets for each of the stations; and

receive respective data from the plurality of stations at a time adjusted by the respective transmit time offset.

9. The non-transitory computer-readable storage medium of claim 8 wherein the operations to perform the transmit time control further:

determine a station of the plurality of stations that has a lowest respective transmit power; and

generate a non-zero transmit time offset for the station.

10. The non-transitory computer-readable storage medium of claim 8 wherein the operations to perform the transmit time control further:

determine a first station of the plurality of stations that has a lowest respective transmit power;

generate a non-zero transmit time offset for the first station; and

generate a zero transmit time offset for other stations of the plurality of stations.

11. The non-transitory computer-readable storage medium of claim 10 wherein the operations to perform the transmit time control further:

associate the plurality of stations with a group identifier; and

transmit the non-zero transmit time offset and the zero transmit time offsets in a poll frame associated with the group identifier.

12. A method for transmit time offset in a wireless system, the method comprising:

monitoring respective transmit powers, over a wireless channel, for a plurality of stations;

determining a transmit time offset for a station, of the plurality of stations, in response to the respective transmit power of the station;

transmitting the transmit time offset to the station; and

receiving data from the station at a time adjusted by the transmit time offset.

13. The method of claim 12, wherein monitoring the respective transmit powers comprises monitoring a signal-to-noise ratio (SNR) of the wireless channel between each of the plurality of stations and an access point.

14. The method of claim 12, further comprising grouping the plurality of stations of the wireless system into a station group.

15. The method of claim 14, wherein transmitting the transmit time offset to the station comprises transmitting a respective transmit time offset to each of the stations in the station group.

16. The method of claim 12, further comprising:

creating an association between the plurality of stations and a group identifier in a setup frame; and

transmitting the setup frame including the group identifier and the respective transmit time offsets to the plurality of stations.

17. The method of claim 14, wherein determining the transmit time offset for the station in response to the respective transmit power of the station comprises generating a non-zero transmit time offset for the station having a lower transmit power than other stations of the plurality of stations.

18. The method of claim 17, further comprising:

determining a station having a highest transmit power of the plurality of stations; and

assigning a zero transmit time offset to stations, in the plurality of stations, having a respective transmit power within a predetermined power difference from the highest transmit power.

19. A wireless device comprising:

a memory for storing instructions; and

a processor coupled to the memory and configured to receive a frame comprising a transmit time offset associated with a transmit power of the station;

to determine a transmit time for transmitting data in response to the frame, the transmit time substantially equal to a nominal transmit time plus the transmit time offset; and

to transmit the data at the transmit time.

20. The device of claim 19, wherein the processor is configured to control transmission of a Physical Layer Convergence Procedure (PLCP) Protocol Data Unit (PPDU) to the AP at the transmit time.

21. The device of claim 19, wherein the processor is further configured to control receipt of a non-zero transmit time offset when a respective transmit power of the station is less than a respective transmit power of other stations in the system.

22. A system comprising:

a radio configured to communicate over a channel;

a memory to store instructions for execution;

a processor, coupled to the memory and the radio, configured to receive a frame comprising a transmit time offset associated with a transmit power of the station;

to determine a transmit time for transmitting data in response to the frame, the transmit time substantially equal to a nominal transmit time plus the transmit time offset; and

to control transmission of the data at the transmit time.

23. The system of claim 22, wherein the channel is an IEEE 802.11ax standard channel.

24. The system of claim 22, further comprising at least one antenna coupled to the radio.

25. The system of claim 22, wherein the radio is configured to communicate using High-Efficiency Wireless LAN or High Efficiency Wi-Fi (HEW) protocols.