Co-scheduling based on steering vector orthogonality

Patent metadata

Field	Value
Publication number	US-9474083-B2
Application number	US-201414286034-A
Country	US
Kind code	B2
Filing date	May 23, 2014
Priority date	Nov 9, 2009
Publication date	Oct 18, 2016
Grant date	Oct 18, 2016

Abstract

The invention relates to a method and apparatus for determining whether two user equipments (UEs) in a wireless network can be co-scheduled by an uplink scheduler of a base station. The method includes: the determination of a steering vector for each of a plurality of user equipments to be considered; and, for each pair of the user equipments, the determination of a corresponding orthogonality factor based on the steering vectors of the user equipments comprising the pair. A pair of user equipments may be selected for co-scheduling based on the orthogonality factors. For example, a pair of user equipments may be co-scheduled if its orthogonality factor is below a threshold. As another example, a pair of user equipments that has the lowest of the orthogonality factors may be co-scheduled.

First claim

What is claimed is:

1. A method of operating a receiver station in a wireless network, the wireless network including the receiver station and a plurality of user equipments, wherein the receiver station includes a plurality of antennas, wherein each of the user equipments includes at least one antenna, the method comprising:
a) for each of the user equipments, determining a corresponding steering vector based on a corresponding initial transmission from the user equipment to the receiver station;
b) for a first pair of the user equipments, computing an orthogonality factor based on the steering vector of the first user equipment of the first pair and the steering vector of the second user equipment of the first pair, wherein smaller values of the orthogonality factor represent greater orthogonality between the steering vectors of the first pair; and
c) co-scheduling the first pair of the user equipments based at least in part on a determination that the orthogonality factor is less than a threshold.

2. The method of claim 1 , wherein, prior to c), the orthogonality factor for the first pair of the user equipments is modified by multiplying the orthogonality factor by a scalar value that is a function of a signal to interference-and-noise ratio (SINR) of the first user equipment in the first pair and a signal to interference-and-noise ratio (SINR) of the second user equipment in the first pair.

3. The method of claim 2 , wherein the scalar value is the greatest of the SINR for the first user equipment of the first pair and the SINR of the second user equipment of the first pair.

4. The method of claim 2 , wherein the scalar value is a logarithm of the maximum of the SINR for the first user equipment of the first pair and the SINR of the second user equipment of the first pair.

5. The method of claim 2 , wherein the scalar value comprises a ratio of SINR MAX to SINR MIN ,
wherein SINR MAX is a maximum of the SINR for the first user equipment of the first pair and the SINR for the second user equipment of the first pair,
wherein SINR MIN is a minimum of the SINR for the first user equipment of the first pair and the SINR for the second user equipment of the first pair.

6. The method of claim 1 , wherein the orthogonality factor is calculated using a multiplication of one of the steering vectors of the first pair and a conjugate transpose of the other steering vector of the first pair.

7. The method of claim 1 , wherein one or more additional pairs of the user equipments are successively co-scheduled in successively increasing value of the orthogonality factor.

8. The method of claim 1 , further comprising:
receiving a signal in response to co-scheduled transmissions from the first pair of user equipments; and
performing successive interference cancellation (SIC) to separate the co-scheduled transmissions.

9. The method of claim 1 , wherein, for each of the user equipments, said corresponding initial transmission from the user equipment is a scheduled uplink sounding burst.

10. A receiver station in a wireless network, the wireless network including the receiver station and a plurality of user equipments, wherein each of the user equipments includes at least one antenna, the receiver station comprising:
a plurality of antennas;
an input, wherein, for each of the user equipments, the input is configured to receive a corresponding steering vector;
a comparator, wherein, for a first pair of the user equipments, the comparator is configured to compute an orthogonality factor based on the steering vector of the first user equipment of the first pair and the steering vector of the second user equipment of the first pair, wherein smaller values of the orthogonality factor represent greater orthogonality between the steering vectors of the first pair;
a processor configured to co-schedule the first pair of the user equipments based at least in part on a determination that the orthogonality factor is less than a threshold.

11. The receiver station of claim 10 , wherein the comparator is configured to modify the orthogonality factor for the first pair of the user equipments by multiplying the orthogonality factor by a scalar value that is a function of a signal to interference-and-noise ratio (SINR) of the first user equipment in the first pair and a signal to interference-and-noise ratio (SINR) of the second user equipment in the first pair.

12. The receiver station of claim 11 , wherein the scalar value is the greatest of the SINR for the first user equipment of the first pair and the SINR of the second user equipment of the first pair.

13. The receiver station of claim 11 , wherein the scalar value is a logarithm of the maximum of the SINR for the first user equipment of the first pair and the SINR of the second user equipment of the first pair.

14. The receiver station of claim 11 , wherein the scalar value comprises a ratio of SINR MAX to SINR MIN ,
wherein SINR MAX is a maximum of the SINR for the first user equipment of the first pair and the SINR for the second user equipment of the first pair,
wherein SINR MIN is a minimum of the SINR for the first user equipment of the first pair and the SINR for the second user equipment of the first pair.

15. The receiver station of claim 10 , wherein the comparator is configured to calculate the orthogonality factor using a multiplication of one of the steering vectors of the first pair and a conjugate transpose of the other steering vector of the first pair.

16. The receiver station of claim 10 , further comprising:
a channel selector configured to select a channel where the change of phase and amplitude of a transmission from each of the plurality of user equipment devices is substantially consistent, wherein said plurality of user equipments are selected from a superset of user equipments which may transmit data across the channel.

17. A non-transitory memory medium for operating a receiver station in a wireless network, the wireless network including the receiver station and a plurality of user equipments, wherein the receiver station includes a plurality of antennas, wherein each of the user equipments includes at least one antenna, wherein the memory medium stores program instructions executable by a processor to implement:
a) for each of the user equipments, determining a corresponding steering vector based on a corresponding initial transmission from the user equipment to the receiver station;
b) for a first pair of the user equipments, computing an orthogonality factor based on the steering vector of the first user equipment of the first pair and the steering vector of the second user equipment of the first pair, wherein smaller values of the orthogonality factor represent greater orthogonality between the steering vectors of the first pair; and
c) co-scheduling the first pair of the user equipments based at least in part on a determination that the orthogonality factor is less than a threshold.

18. The non-transitory memory medium of claim 17 , wherein the program instructions are executable by the processor to further implement:
prior to c), modifying the orthogonality factor for the first pair of the user equipments by multiplying the orthogonality factor by a scalar value that is a function of a signal to interference-and-noise ratio (SINK) of the first user equipment in the first pair and a signal to interference-and-noise ratio (SINR) of the second user equipment in the first pair.

19. The non-transitory memory medium of claim 18 , wherein the scalar value is a logarit

Assignees

• Apple Inc

Inventors

• Bevan David
• Gale Simon
• Robson Julius
• Deane Peter

Classifications

• H04W72/121 Primary

  for groups of terminals or users · CPC title

• H04W72/046

  the resource being in the space domain, e.g. beams · CPC title

• H04B7/0452 Primary

  Multi-user MIMO systems · CPC title