MU-MIMO Explicit Feedback Dimension Reduction Procedures November 2010 doc.: IEEE 802.11-10/1265r0 November 2010 MU-MIMO Explicit Feedback Dimension Reduction Procedures Date: 2010-11-09 Authors: Nir Shapira et al, Celeno Communications

November 2010 doc.: IEEE 802.11-10/1265r0 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

Dimension Reduction with Resolvable and non-Resolvable LTFs November 2010 doc.: IEEE 802.11-10/1265r0 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

Beamformer Control of Returned Dimension November 2010 doc.: IEEE 802.11-10/1265r0 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

Communicating Dimension Reduction Information November 2010 doc.: IEEE 802.11-10/1265r0 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

November 2010 doc.: IEEE 802.11-10/1265r0 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

November 2010 doc.: IEEE 802.11-10/1265r0 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

November 2010 doc.: IEEE 802.11-10/1265r0 November 2010 References [1] Nir Shapira, et. al., Dimension Reduction Proposal, TGac, IEEE 802.11-10/1114r1 [2] Simone Merlin, et. al., Protocol for SU and MU Sounding Feedback, TGac, IEEE 802.11-10/1091 Nir Shapira et al, Celeno Communications