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Optimized MIMO

Optimized MIMO. Aryan Saed, Jung Yee, Jim Wight ICEFYRE Semiconductor Inc. 11-04-0882-00-000n-optimized-mimo.ppt. Proposal for Optimized MIMO. MIMO using channel diagonalization

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Optimized MIMO

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  1. Optimized MIMO Aryan Saed, Jung Yee, Jim Wight ICEFYRE Semiconductor Inc. 11-04-0882-00-000n-optimized-mimo.ppt Aryan Saed, ICEFYRE Semiconductor Inc.

  2. Proposal for Optimized MIMO • MIMO using channel diagonalization • Allow vendor discretionary optimization for maximum rate and/or maximum reach without adding complexity and options • Allow vendor discretionary optimization of hardware and overhead through mutual signaling of MIMO complexity without adding options Aryan Saed, ICEFYRE Semiconductor Inc.

  3. Diagonalization (Beam forming) Aryan Saed, ICEFYRE Semiconductor Inc.

  4. Diagonalization by SVD Singular Value Decomposition (SVD): S is diagonal (contains singular values of H) Aryan Saed, ICEFYRE Semiconductor Inc.

  5. Diagonalization by QR-Eig Step 1: QR-Triangularization of H Step 2: Eigenvector decomposition of Q Aryan Saed, ICEFYRE Semiconductor Inc.

  6. Diagonalization by QR-Eig and Set: Then: Aryan Saed, ICEFYRE Semiconductor Inc.

  7. Implications of SVD • SVD maximizes theoretical (Shannon) capacity • SNR per stream is ranked according to singular values of channel matrix H • In practical TGn channels the SNR per sub-carrier can differ by 10dB..20dB as a result of singular value spread Aryan Saed, ICEFYRE Semiconductor Inc.

  8. Implications of SVD • To maximize practical capacity, rate depends on SNR • Usually only the strongest mode can support maximum rate (e.g. 256-QAM) • rates in all other modes are then backed-off, some only support a fraction (half, quarter, eighth) of the maximum (e.g. 16-QAM) Aryan Saed, ICEFYRE Semiconductor Inc.

  9. Implications of SVD • Rate across multiple streams not equal. Example: one stream at 54Mbps, another at 24Mbps. Data-bit multiplexing becomes a PHY function, keeping both streams equal duration (e.g. 0.25 ms) • Large portion of bits on the strongest mode. Remainder of bits on remaining weaker modes. Aryan Saed, ICEFYRE Semiconductor Inc.

  10. Implications of QR-Eig • QR-Eig has equal SNR across streams • Same rate and length per stream • Same interleaver and FEC • Same latency, and same PER • Data-bit multiplexing can be a MAC function: one MSDU per stream. Aryan Saed, ICEFYRE Semiconductor Inc.

  11. Which to choose? • Depends on application: maximum rate or maximum reach • Depends on MAC preference:- individual control over each MIMO stream (separate PER at 10%, separate ACK) or - view all streams as one packet (joint PER at 10%, joint ACK and larger data buffer) Aryan Saed, ICEFYRE Semiconductor Inc.

  12. Simulation details • TGn Comparison Criteria IEEE 802.11-03/814r31 • IM1 RAPP PA model at 14dBm output • IM4 Phase Noise • IM5 Noise Figure • IM6 half-wavelength • 2x2 MIMO Aryan Saed, ICEFYRE Semiconductor Inc.

  13. Comparison Aryan Saed, ICEFYRE Semiconductor Inc.

  14. Rate-pair Selection Aryan Saed, ICEFYRE Semiconductor Inc.

  15. Objective • To allow vendor choice of algorithm : SVD, QR-Eig or other vendor algorithm • optimized for particular usage scenario (reach, rate, latency) Aryan Saed, ICEFYRE Semiconductor Inc.

  16. Objective • Ensure mechanisms are in place in TGn to allow calculation of T and R matrix at one side of the link, and • to communicate matrix from STA to AP or from AP to STA so that matrix can be operated at both sides (Tx and Rx side) of link Aryan Saed, ICEFYRE Semiconductor Inc.

  17. Per-sub-carrier Diagonalization • 52 n-by-n (e.g. 2x2) complex matrix coefficients. Overhead in feedback. Aryan Saed, ICEFYRE Semiconductor Inc.

  18. Grouped Diagonalization • Grouping: fewer n-by-n (egg 2x2) complex matrix coefficients. Lower overhead. Aryan Saed, ICEFYRE Semiconductor Inc.

  19. Objective • To ensure mechanisms are in place in standard to allow reduced overhead from coefficient exchange • Example: AP requires grouping of 4 sub-carriers due to its reduced hardware complexity. Aryan Saed, ICEFYRE Semiconductor Inc.

  20. Objective • Groups of 4 or 8 sub-carriers reduces T and R matrix calculation and update overhead by a factor of 4 and 8 respectively. • STA and AP must communicate their capabilities Aryan Saed, ICEFYRE Semiconductor Inc.

  21. Overview Some further implications of MIMO with diagonalization: • Stream splitting: FEC, interleaving • MIMO Header Aryan Saed, ICEFYRE Semiconductor Inc.

  22. MIMO Stream splitting Aryan Saed, ICEFYRE Semiconductor Inc.

  23. Diagonalization in an 11n packet Aryan Saed, ICEFYRE Semiconductor Inc.

  24. MIMO Headers Service Field signifies • During Link Set-up, sub-carrier grouping: no grouping (52 matrices), groups of four (16 matrices), groups of eight (8 matrices). • During Link Set-up, supported rates, equal rate across all streams or stream dependent rate Aryan Saed, ICEFYRE Semiconductor Inc.

  25. MIMO Headers Service Field (STA side calculation) • During Link operation: regular feedback of channel estimation from AP to STA for matrix calculations • During Link operation: regular update of Tx side diagonalization coefficients from STA to AP Aryan Saed, ICEFYRE Semiconductor Inc.

  26. MIMO Link Set-up • AP to STA: Transmit intent for 11n Link • STA to AP: Acknowledge with 11n enabled packet. Includes 11n header for channel estimation and multiple branch utilization • AP to STA: send back AP-side estimated channel matrix and AP-side diagonalization capability (sub-carrier grouping) Aryan Saed, ICEFYRE Semiconductor Inc.

  27. MIMO Link Set-up • STA to AP: AP-side diagonalization coefficients using STA-side discretionary algorithm • AP to STA: AP-side (Tx) and STA-side (Rx) diagonalization applied • STA to AP: AP-side (Rx) and STA-side (Tx) diagonalization applied Aryan Saed, ICEFYRE Semiconductor Inc.

  28. MIMO Link Maintenance • Continual feedback per packet • Regular rejuvenation of AP channel estimate that is mirrored at STA side • Regular recalculation of AP diagonalization matrix at STA side. Aryan Saed, ICEFYRE Semiconductor Inc.

  29. Proposal Summary • Frequency domain diagonalization • Vendor discretionary algorithm (e.g. SVD, QR with Eigenvector, other) • Orthogonal LTS for MIMO Channel Estimation • Vendor discretionary grouping of sub carriers (no grouping, grouping with 4, or 8 adjacent sub carriers) Aryan Saed, ICEFYRE Semiconductor Inc.

  30. Thank you. Aryan Saed, ICEFYRE Semiconductor Inc.

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