802.11ac Preamble Date: 2010-01-18 Authors: Month Year Month Year doc.: IEEE 802.11-yy/xxxxr0 doc.: IEEE 802.11-yy/xxxxr0 802.11ac Preamble Date: 2010-01-18 Authors: Slide 1 Hongyuan Zhang, Vinko Erceg et al. Page 1 John Doe, Some Company John Doe, Some Company

Outlines Numerology Preamble Structure VHTSIG field considerations Conclusions Hongyuan Zhang, Vinko Erceg et al.

Proposed Basic Numerology Month Year doc.: IEEE 802.11-yy/xxxxr0 Proposed Basic Numerology Max number of transmit (Tx) antennas sounded: 8 Reasonable complexity, cost, and preamble length trade-off Max number of Nss (spatial streams) in the SU case: 8 Given that 8 Tx antennas are proposed to be sounded, then there is inherent support for up to 8 spatial streams Max number of Nss per user in the MU case: 4 Given that multiple users will share spatial streams, it is natural to make this number smaller than 8 Fits VHT-SIG size limitations, reduces number of representation bits required Maximum number of Nss summed over users in the MU case: 8 Max number of MU users: 4 Larger number significantly increases MAC/PHY complexity Hongyuan Zhang, Vinko Erceg et al. John Doe, Some Company

Preamble Design Goals Backward compatibility Robust legacy 11a deferral Robust legacy 11n deferral Reliable auto-detection among 11a, 11n (MM and GF), and VHT preambles Single preamble structure in SU and MU Signaling of VHT PHY information by VHTSIG. Training for wider channels, and detection and deferral in each sub-channel. Low PAPR Minimize overall preamble length Hongyuan Zhang, Vinko Erceg et al.

Spoofing and Auto-detection Use L-SIG spoofing for both 11a and 11n receivers: As 11n spoofing for 11a/g receivers. Rate=6Mbps, Length/Rate indicates duration. Use 90-deg rotated BPSK (QBPSK) on VHTSIG symbol for VHT auto-detection. 11n receiver will treat the packet as 11a packet (L-SIG spoofing). Hongyuan Zhang, Vinko Erceg et al.

Preamble Structure T Rate=6Mbps Length determined by T 2 symbols L-STF L-LTF L-SIG VHTSIGA VHT-STF VHT-LTFs VHTSIGB VHTData T VHT auto-detection Hongyuan Zhang, Vinko Erceg et al.

MU Packets VHT-SIG indicates PPDU duration only (number of OFDM symbols) No per user length indication in preamble Use A-MPDU structure to provide length information for individual MPDUs Require that A-MPDU always be used with VHT frame MAC provides an A-MPDU that fills the frame up to the last byte for each per-user stream, and PHY provides 0-7 bits of padding. Same padding scheme also defined in SU packets. “Aggregation” bit in VHTSIG is then not needed. Details refer to document 11-10-0064r0 (VHT frame padding). Hongyuan Zhang, Vinko Erceg et al.

Further Discussions on VHTSIG In MU, VHTSIGA contains the “common” bits for all clients. Indicates number of space-time streams (NSTS) for each user. Need prior multiuser group and user ID assignment frame exchanges before DL-MU packets (e.g. by sounding and/or management frames). Each user will be able to get its own NSTS information from VHTSIGA.. Details refer to document 11-10-0073r0 (Group ID Concept for Downlink MU-MIMO Transmission). VHTSIGB contains user-specific information (e.g. modulation and coding rate) and is spatially multiplexed for different clients. It is placed after all the VHTLTFs to enable better receiver side interference mitigation in DL-MU before decoding VHTSIGB. This requires each client getting as many LTFs as needed to train the total number of spatial streams across all users—named as “resolvable VHTLTF”. “Non-resolvable VHTLTF” may be selected if all clients do not support receiver side interference mitigation, or if interference mitigation is not required . Rx interference mitigation in DL-MU refer to document 11-09-1234r0 (Interference Cancellation for Downlink MU-MIMO). Hongyuan Zhang, Vinko Erceg et al.

VHTSIG Fields Considerations (SU) Duration Bandwidth Short GI MU/SU Indication (=SU) MCS STBC Coding Type Smoothing Sounding CRC & Tail For further investigations: Number of Extension Streams MAC ID Hongyuan Zhang, Vinko Erceg et al.

VHTSIG Fields Considerations (MU) Duration Bandwidth Short GI MU/SU Indication (=MU) Group ID Indication of Number of Space-Time Streams for each user Mod/Coding per user STBC Coding Type CRC & Tail For further investigations: Sounding Number of Extension Streams Smoothing Resolvable/Non-resolvable LTF Indication Hongyuan Zhang, Vinko Erceg et al.

Conclusions Basic PHY numerology is proposed. Tradeoff between performance and complexity. A common preamble structure for both MU and SU is proposed: Use L-SIG spoofing, and auto-detection with QBPSK in VHT-SIG. Minimum preamble length for DL-MU. Considerations for some of the subfields in VHTSIG. Hongyuan Zhang, Vinko Erceg et al.