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NT-12 on Beamforming (BRP)

NT-12 on Beamforming (BRP). Date: 2010-05-01. Proposal overview. This presentation is part and in support of the complete proposal described in 802.11-10/432r0 (slides) and 802.11-10/433r0 (text) that: Supports data transmission rates up to 7 Gbps

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NT-12 on Beamforming (BRP)

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  1. NT-12 on Beamforming (BRP) Date: 2010-05-01 Carlos Cordeiro, Intel, et. al.

  2. Carlos Cordeiro, Intel, et. al.

  3. Carlos Cordeiro, Intel, et. al.

  4. Carlos Cordeiro, Intel, et. al.

  5. Proposal overview • This presentation is part and in support of the complete proposal described in 802.11-10/432r0 (slides) and 802.11-10/433r0 (text) that: • Supports data transmission rates up to 7 Gbps • Supplements and extends the 802.11 MAC and is backward compatible with the IEEE 802.11 standard • Enables both the low power and the high performance devices, guaranteeing interoperability and communication at gigabit rates • Supports beamforming, enabling robust communication at distances beyond 10 meters • Supports GCMP security and advanced power management • Supports coexistence with other 60GHz systems • Supports fast session transfer among 2.4GHz, 5GHz and 60GHz Carlos Cordeiro, Intel, et. al.

  6. Beamforming Protocols (10/0430-NT-11) • 802.11ad must define protocols, not algorithms • General framework and messaging are defined • Antenna specifications and beamforming adjustment algorithms are left to implementations • Our proposal employs • Directional TX / low gain (quasi-omni) RX for acquisition • Sector Sweep Phase (10/0430-NT-11) • Refinement stage adds RX gain and final adjustment for combined TX and RX (this presentation) • Tracking during data transmission to adjust for channel changes (this presentation) §9.25.2-9.25.5, §21.8 in 11-10/0433r0 §9.25.6 in 11-10/0433r0

  7. Why Beam Refinement? (1) Example of sector sweep • To meet 60GHz beamforming requirements in 09/1153r2, beamforming consists of two phases: • Sector sweep: Allows for signal acquisition (and low-rate PHY comm. @ 10s of Mbps) by enabling coarse selection of TX sector with quasi-omni (see 09/1153r2) RX • Beam refinement: Allows for high-rate PHY comm. (Gbps) by enabling directional RX, and finer TX and RX beamforming training (i.e. finer AWV adjustment) Quasi-omni pattern Example of beam refinement From doc #: IEEE 802.11-09/1153-r2 Carlos Cordeiro, Intel

  8. Why Beam Refinement? (2) • Allows for high-rate PHY communication by • Enabling directional RX • Finer adjustment of TX and RX AWVs (antenna weight vectors) • Example link budget • 10 dBm TX power • 64 GHz • 10 meter range • TX gain 15 dB • RX gain 15 dB • Received power is -48.6dBm • Receive sensitivity for • 4.6 Gbps (SC): -53dBm => > 3dB margin • 5.2 Gbps (OFDM): -51dBm => > 2dB margin TX Antenna with 15 dB gain TX Antenna with 12 dB gain Sector Sweep Beam refinement RX Antenna with 0 dB gain RX Antenna with 15 dB gain Received power is -66.6dBm Enables usage of Control PHY @ 27.5 Mbps, -78dBm sensitivity Carlos Cordeiro, Intel

  9. Why Beam Refinement? (3) • Allows overcoming TX, RX hardware calibration errors that reduce the effective beamforming gain. • Approach: Select initial AWV from a TX OR RX sector sweep • Conduct fine-grained beam refinement with the selected AWV as a starting point for BOTH TX and RX • Approach allows treating paths from the antenna to the receiver (i.e. phase shifters or LNAs) as part of the channel CDF of gain without beam refinement for different phase calibration errors. CDF of gain with beam refinement for different phase calibration errors. Carlos Cordeiro, Intel

  10. Forward link Initiator Responder Reverse link Beam Refinement Phase (BRP): Definition FSS RSS P1: SLS SS-FBCK SS-ACK Iterative procedure used to improve TX and/or RX antenna array configuration Optional sub-phases P2: BRP §9.25.2 in 11-10/0433r0

  11. Forward link Initiator Responder Reverse link Beam Refinement Phase (BRP): Modularity FSS RSS P1: SLS SS-FBCK SS-ACK BRP setup sub-phase 1. Additional sector level training Optional sub-phases P2: BRP §9.25.2 in 11-10/0433r0 BRP transactions 2.

  12. Forward link Initiator Responder Reverse link Beam Refinement Phase (BRP): Setup FSS RSS P1: SLS SS-FBCK SS-ACK BRP setup sub-phase 1. • Used to exchange intent and capabilities. • intent: the sub-phase composition • capabilities: number of AWVs, antennas, etc. P2: BRP §9.25.2.1 in 11-10/0433r0

  13. Beam Refinement Phase (BRP): Setup §7.3a.4 in 11-10/0433r0 BRP Request field For setting up BRP transactions For additional (optional) sector-level training Feedback capabilities Intent: TX training? RX training? Capabilities: Number of AWVs for TX/RX training? Carlos Cordeiro, Intel

  14. Forward link Initiator Responder Reverse link Beam Refinement Phase (BRP): Transactions FSS RSS P1: SLS SS-FBCK SS-ACK BRP setup sub-phase 1. BRP Transaction: - A set of frames composed of requests and responses - Each frame acts as an ACK for the previous frame BRP transactions 2. P2: BRP • To enable • initial RX AWV training • fine-grained TX and RX AWV training §9.25.5.3 in 11-10/0433r0

  15. Forward link • Training (TRN) fields appended to frames • AWVs changed when sending or receiving TRN fields • Fine-grained feedback (SNR, amplitude , phase of I & Q) can be sent with TRN fields in reverse direction. Initiator Responder Reverse link Beam Refinement Phase (BRP): Training FSS RSS P1: SLS SS-FBCK SS-ACK Frame-details Optional sub-phases Fback1 P2: BRP §21.8.2.2 in 11-10/0433r0 Fback2

  16. BRP Packet (i.e. BRP-RX/TX) Details (1) • Consists of a “data” part followed by an AGC training field and the TRN-R/T training fields • Header fields: pkt-type and training-length indicate BRP-RX/TX, and length of training fields. • AGC and TRN-R/T are composed of a pre-specified number of repetitions of Golay sequences §21.8 in 11-10/0433r0

  17. Forward link Initiator Responder Reverse link Beam Refinement Phase (BRP): Additional sector training FSS RSS P1: SLS SS-FBCK SS-ACK BRP setup sub-phase 1. Additional sector level training Optional sub-phases P2: BRP §9.25.5.2 in 11-10/0433r0 BRP transactions 2.

  18. Why additional sector level training? • Gain of quasi-omni RX pattern (see 09/1153r2) varies! • See EM simulation results for three different HW approaches Roughly 5-10dB quasi-omni gain variation should be expected with planar patch antennas Leads to ~20% probability of sub-optimal TX sector selection! Carlos Cordeiro, Intel

  19. Forward link Initiator Responder Reverse link Metal (Height 2mm) Beam Refinement Phase (BRP): Additional sector training FSS 2mm Patch 4mm RSS P1: SLS SS-FBCK 10mm 4mm SS-ACK 10mm BRP setup sub-phase 1. Additional sector training P2: BRP Used to address sub-optimal sector selection due to imperfections in RX quasi-omni patterns Radiation pattern of the antenna with and without side metals

  20. Beam Refinement Phase (BRP): Additional sector training • Motivation: ~5-10dB gain variation in quasi-omni RX pattern => best TX sector not chosen after sector sweep • Idea: Select TX and RX sector after an additional phase based on the trial of multiple TX and RX sectors • Approach: • Select multiple TX sector candidates from sector sweep • Conduct joint trial of TX and RX sectors (either the full set of a partial set) TX Sector sweep STEP 1: Select the best SET of TX Sector IDs STA2 E.g. IDTX #1, IDTX #2, …, IDTX #7 STA1 Carlos Cordeiro, Intel

  21. Beam Refinement Phase (BRP): Additional sector training OPTION 1 RX AWV detection STEP 2: Select the best SET of RX Sector IDs STA1 IDRX #1, IDRX #2, …, IDRX #7 STA2 STEP 3: Joint trial of TX and RX sectors Joint trial of TX and RX sectors IDTX #1 IDRX #1 IDTX #2 IDRX #2 STA2 STA1 IDTX #7 IDRX #7 §9.25.5.2.1 in 11-10/0433r0 TX and RX sector for further refinement chosen after

  22. Beam Refinement Phase (BRP): Additional sector training OPTION 2 STEP 2: Joint trial of set of TX and all RX AWVs/sectors Joint trial of TX and RX sectors IDTX #1 IDRX #1 IDTX #2 IDRX #2 STA1 STA2 IDTX #7 IDRX # NRX Total number of RX sectors = NRX §9.25.5.2.2 in 11-10/0433r0

  23. Beam Tracking • Messaging to enable periodic TX/RX beam refinement • A STA may request tracking if it feels the link quality deteriorates (not used when the link is lost) • Can be done while sending DATA • BR frames are piggy-backed onto DATA/ACK frames • A bit in the PLCP header is used to indicate intent • BR frames include training (e.g. AGC, TRN-R/T) fields and/or feedback information (e.g. SNR) §9.25.6 in 11-10/0433r0 Carlos Cordeiro, Intel

  24. Summary • Beamforming is necessary for 60 GHz systems to provide gain to compensate for additional path loss and increased system bandwidth • The 802.11ad amendment must specify interoperable protocols to enable beamforming • Beam refinement enables the fine-grained adjustment of AWVs essential to enable Gbps speeds

  25. Extra Slides Carlos Cordeiro, Intel

  26. Simulation Parameters • TX: 32 element array with a cross configuration. • RX either as TX or a single antenna. • Channel Model – conference room, NLOS • 400 channels, 10 realizations per channel. • Sequence used in BF is Golay sequence with 128 points, transmitted twice, only second one is used for estimation. • TX sector sweep – energy based, based on two 128 point sequences. Carlos Cordeiro, Intel

  27. Beam Refinement Phase (BRP): Training • Requests and responses can be combined in the same frame – see example below. §9.25.2 in 11-10/0433r0 Carlos Cordeiro, Intel

  28. Initiate BRP setup sub-phase – get STA capabilities and intent ACK + signal to end BRP setup sub-phase Transmit + Receive beam refinement request/notification PCP/AP I-TXSS SS feedback BRP frame … SS frame SS frame BRP frame BRP frame Sector sweep BRP setup BRP transactions … SS frame SS frame BRP frame BRP frame STA R-TXSS Time separation between BRP frame exchanges: > SIFS & < BRPIFS Return STA beamforming capabilities and intent Beam Refinement Phase (BRP): Setup TX training TX training + FBCK §9.25.2.1 in 11-10/0433r0 Carlos Cordeiro, Intel

  29. Grant MID. Request for SNR info from prior TX sector sweep ACK and End BRP Setup sub-phase Request MID sub-phase I-TXSS I-MID Initiator SS feedback … … BRP frame BRP frame SS frame SS frame BRP frame BRP frame Sector sweep BRP setup BRP (MID) … SS ACK SS frame SS frame BRP frame BRP frame BRP frame Responder R-TXSS Refuse MID sub-phase request. Request MID sub-phase. Return ranked list of TX sectors from MID Indicate number of TX sectors to be used during MID ACK and End BRP Setup sub-phase Time separation between BRP frame exchanges: ≥ SIFS & < BRPIFS Beam Refinement Phase (BRP): MID sub-phase only §9.25.5.2.2 in 11-10/0433r0 Carlos Cordeiro, Intel

  30. Beam refinement transactions: Examples RX training TX training §9.25.5.3.3 in 11-10/0433r0 Carlos Cordeiro, Intel

  31. Beam Refinement Phase (BRP): Transactions BRP Request field §7.3.2.93 in 11-10/0433r0 Indicating that RX/TX training fields are appended to this BRP packet Beam refinement Information Element Operation Feedback Carlos Cordeiro, Intel

  32. §21.6.3.1.1 & §21.5.3.1.1 in 11-10/0433r0 Carlos Cordeiro, Intel

  33. §21.3.3.8 in 11-10/0433r0 Carlos Cordeiro, Intel

  34. Beam Refinement Phase (BRP): Feedback Channel measurement feedback Information Element §7.3.2.99 in 11-10/0433r0 Carlos Cordeiro, Intel

  35. Beam Refinement Phase (BRP): Feedback Channel measurement Information Element §7.3.2.99 in 11-10/0433r0 Carlos Cordeiro, Intel

  36. Beam Refinement Phase (BRP): Additional sector training BRP Request field Request/grant for MID and BC sub-phases Beam refinement Information Element Operation Feedback Carlos Cordeiro, Intel

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