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MU-MIMO Explicit Feedback Dimension Reduction Procedures

This submission discusses procedures for controlling dimension reduction in MU-MIMO to optimize channel feedback and beamforming operations. It presents methods for efficient dimension management, impact of resolvable vs. non-resolvable LTFs, and user-AP interaction for optimal results. Suggestions are made for enhancing the NDPA frame to handle dimension allocations flexibly, empowering beamformers to tailor feedback for individual users.

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MU-MIMO Explicit Feedback Dimension Reduction Procedures

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  1. MU-MIMO Explicit Feedback Dimension Reduction Procedures Authors: Date: 2010-11-09 Nir Shapira et al, Celeno Communications

  2. 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. 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 Dimension Reduction with Resolvable and non-Resolvable LTFs Nir Shapira et al, Celeno Communications

  4. 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. 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 Communicating Dimension Reduction Information Nir Shapira et al, Celeno Communications

  6. 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? Pre Motion #1 Nir Shapira et al, Celeno Communications

  7. 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? Pre Motion #2 Nir Shapira et al, Celeno Communications

  8. [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 References Nir Shapira et al, Celeno Communications

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