1. MU-MIMO Explicit Feedback Dimension Reduction Procedures
November 2010
doc.: IEEE /1265r0
November 2010
MU-MIMO Explicit Feedback Dimension Reduction Procedures
Date:
Authors:
Nir Shapira et al, Celeno Communications

2. November 2010
doc.: IEEE /1265r0
November 2010
Abstract
Last meeting ([1]) motion passed to support explicit feedback dimension reduction (DR): “A sounding responder shall have the ability to reduce the receive side feedback dimension of its MIMO channel with explicit MU-MIMO feedback. The extent of the reduction is TBD”
In this submission we present procedures for dimension reduction control
Nir Shapira et al, Celeno Communications

3. Dimension Reduction with Resolvable and non-Resolvable LTFs
November 2010
doc.: IEEE /1265r0
November 2010
Dimension Reduction with Resolvable and non-Resolvable LTFs
With resolvable LTFs DR operation mainly effects sounding operation
AP is free to make any further DR decision on top of Users’. User can detect additional DR operation from LTFs in each DL-MU frame
In the non-resolvable case the AP must use entire reduced channel as returned by user
Further reduction by AP will corrupt signal on user side
User must store DR information (DR receive matrix) for proper MU packet decoding
Nir Shapira et al, Celeno Communications

4. Beamformer Control of Returned Dimension
November 2010
doc.: IEEE /1265r0
November 2010
Beamformer Control of Returned Dimension
Two main options for control
Control exact (or maximum) dimension
Enables overhead control and prediction for grouping analysis and decisions
Recommend a dimension
Each user sees narrow picture of AP-to-client channel => users will tend to improve their local condition and return full channel. Only AP can make globally optimal trade-offs
In non-resolvable LTF case: if user ignores AP recommendation, beamformer might not be able to use MU mode, since in this case AP cannot reduce dimension by itself (e.g. the case of 4,3,3,3,3).
Conclusion: controlling the exact (or maximum) dimension is the only way to ensure capping of overhead
Nir Shapira et al, Celeno Communications

5. Communicating Dimension Reduction Information
November 2010
doc.: IEEE /1265r0
November 2010
Communicating Dimension Reduction Information
NDPA frame ([2]) is the natural candidate frame to carry dimension reduction information
We suggest to add to NDPA a list of dimension allocations, one for each participating user
Gives AP maximum flexibility in dimension allocation
AP can occasionally sound individual users for full channel rank to update dimension allocation decision
Nir Shapira et al, Celeno Communications

6. November 2010
doc.: IEEE /1265r0
November 2010
Pre Motion #1
Do you support enabling the beamformer to control the explicit feedback dimension for each user in MU-MIMO operation, and to update the specification framework document accordingly?
Nir Shapira et al, Celeno Communications

7. November 2010
doc.: IEEE /1265r0
November 2010
Pre Motion #2
Do you support adding TBD dimension reduction information per user in MU-MIMO operation to the NDPA frame, and update the Specifications Framework document accordingly?
Nir Shapira et al, Celeno Communications

8. November 2010
doc.: IEEE /1265r0
November 2010
References
[1] Nir Shapira, et. al., Dimension Reduction Proposal, TGac, IEEE /1114r1 [2] Simone Merlin, et. al., Protocol for SU and MU Sounding Feedback, TGac, IEEE /1091
Nir Shapira et al, Celeno Communications