Preamble design aspects for MU-MIMO support Month Year doc.: IEEE 802.11-yy/xxxxr0 Preamble design aspects for MU-MIMO support Date: 2009-11-13 Authors: Name Company Address Phone email Yujin Noh LG Electronics, Inc. LG R&D Complex 533, Hogye-1dong, Dongan-Gu, Anyang-Shi, Kyungki-Do, 431-749, Korea +82-31-450-7897 gajadoll@lge.com Daewon Lee cents@lge.com Yongho Seok +82-31-450-1947 yhseok@lge.com Bonghoe Kim +82-31-450-4131 ofdm88@lge.com John Doe, Some Company

Accelerate Contribution November 2009 Accelerate Contribution Introduction Preamble modes VHT mixed mode VHT green field mode Outstanding issues in order to support MU-MIMO General PLCP design principle for SU/MU-MIMO support Over-lapping PLCP design or Non-over-lapping PLCP design Introduction of scramble signal and steered sounding PPDU Straw poll Questions LG Electronics, Inc.

Accelerate Contribution November 2009 Accelerate Contribution Discussion Topics General PLCP design principle for SU/MU-MIMO support Over-lapping PLCP design Introduction of potential issues with over-lapping design and methods to mitigate interference issues Non-over-lapping PLCP design LG Electronics, Inc.

Preamble Modes for consideration VHT-Mixed Mode To support VHT transmission in BSS with Legacy, HT and VHT stations VHT-Green Field Mode To support VHT transmission in BSS with only VHT stations

General concept on SU/MU-MIMO SU-MIMO MU-MIMO Each STA can use all transmitted streams from its own AP More than one STA can use partial spatial streams from one AP * Note that number of spatial streams for each STA can be larger than 1

General PLCP frame format design issue Separate design for SU/MU-MIMO Optimization for SU-MIMO and MU-MIMO separately Transmission of SU or MU PLCP frame format chosen by transmitter (e.g. AP) For SU, simple extension of HT PLCP frame format (e.g. MCS, number of supported layers, etc) For MU, optimized MU PLCP frame format design Common PCLP frame format for both SU/MU-MIMO PLCP frame designed (and optimized) for MU-MIMO Consider SU-MIMO a subset of MU-MIMO operation

Accelerate Contribution November 2009 Accelerate Contribution Discussion Topics General PLCP design principle for SU/MU-MIMO support Over-lapping PLCP design Introduction of potential issues with over-lapping design and methods to mitigate interference issues Non-over-lapping PLCP design LG Electronics, Inc.

PLCP frame format design Option 1 (1/3) November 2009 Accelerate Contribution PLCP frame format design Option 1 (1/3) Overlapping PLCP format design STA specific VHT-SIG fields Pre-coding of VHT-SIG Spatial multiplexing of VHT-SIG for different STAs Insertion of VHT-STF prior to VHT-SIG due to pre-coding effects Partial spatial stream channel estimation as baseline Only estimate spatial stream of appropriate receive data streams May only allow partial MMSE (or even MRC) at receiver side Note: all STAs may estimate channel of entire transmitted spatial streams depending on VHT LTF and VHT-SIG designs and utilize full MMSE LG Electronics, Inc.

PLCP frame format design Option 1 (2/3) November 2009 Accelerate Contribution PLCP frame format design Option 1 (2/3) Conceptual example PLCP transmission for overlapping PLCP design VHT-mixed mode *Note : the example shown assumes STA1 with 3 spatial streams and STA2 with 2 spatial streams are MU-MIMO paired LG Electronics, Inc.

PLCP frame format design Option 1 (3/3) Conceptual example PLCP transmission for overlapping PLCP design VHT GF mode *Note : the example shown assumes STA1 with 3 spatial streams and STA2 with 2 spatial streams are MU-MIMO paired

Accelerate Contribution November 2009 Accelerate Contribution Discussion Topics General PLCP design principle for SU/MU-MIMO support Over-lapping PLCP design Introduction of potential issues with over-lapping design and methods to mitigate interference issues Non-over-lapping PLCP design LG Electronics, Inc.

Potential issues with overlapping design (1/2) Scatter-rich environments In scatter-rich environments, imperfect pre-coding can cause spatial streams to interfere with each other Interference can cause degradation in channel estimation, data demodulation performance loss, etc.

Potential issues with overlapping design (2/2) Null-space deficient environments STAs with large number of receive antennas increase the statistical probability of null-space deficiency between AP-STA Zero Forcing or Block Diagonal beam-forming may not be possible when null-space is not available for certain STAs Case 1-1 Case 1-2 Clear separation between Two STAs STA1 suffering from interference from paired STA2

Steered Sounding PPDU Partial channel sounding or virtualized channel sounding instead of full channel sounding AP recognizes smaller number of Rx antenna for STA restrict the subspace of STA in order to increase null-subspace between AP-STA

Stream Scrambling Scramble signals for each STA Scrambling allows the possibility to suppress interference with scrambling processing gain

Accelerate Contribution November 2009 Accelerate Contribution Discussion Topics General PLCP design principle for SU/MU-MIMO support Over-lapping PLCP design Introduction of potential issues with over-lapping design and methods to mitigate interference issues Non-over-lapping PLCP design LG Electronics, Inc.

PLCP frame format design Option 2 (1/3) November 2009 Accelerate Contribution PLCP frame format design Option 2 (1/3) Non-overlapping PLCP format design STA specific VHT-SIG fields VHT-SIG transmitted in omni-directional transmission method (cyclic delay shifting across physical antenna) No spatial multiplexing of VHT-SIG (single stream transmission) spatial stream (virtual spatial layer) indication for each STA receiving data All MU STA can estimate channel for all spatial layers allow full MMSE equalization implementation at receiver side LG Electronics, Inc.

PLCP frame format design Option 2 (2/3) November 2009 Accelerate Contribution PLCP frame format design Option 2 (2/3) Conceptual example PLCP transmission for Non-overlapping PLCP design VHT-Mixed mode 그림이 overlapping으로 바껴있음 -_-; *Note : the example shown assumes STA1 with 3 spatial streams and STA2 with 2 spatial streams are MU-MIMO paired LG Electronics, Inc.

PLCP frame format design Option 2 (3/3) Conceptual example PLCP transmission for Non-overlapping PLCP design VHT-GF mode *Note : the example shown assumes STA1 with 3 spatial streams and STA2 with 2 spatial streams are MU-MIMO paired

Straw poll Questions Q1) Single PLCP frame format for both SU/MU-MIMO ? Yes No Q2) Support of spatial multiplexing of STA specific VHT-SIG in order to reduce preamble overhead ? Single stream transmission of VHT-SIG (conceptually non over-lapped design) Multi-stream transmission of VHT-SIG (conceptually over-lapped design)