Pilot Value Definitions March 2012 Pilot Value Definitions Date: 2012-03-12 Authors: Seunghee Han, LG Electronics

March 2012 Seunghee Han, LG Electronics

March 2012 Seunghee Han, LG Electronics

March 2012 Motivation Pilot tones in data OFDM symbols can be used for the purpose of phase tracking and for compensation of residual frequency offset error after initial compensation. For >= 2MHz mode, it is straightforward to adopt pilot values and tone indices as in 11ac spec [2] applying down-clocking by a factor of 10. Since the Pilot tone indices and values for 1MHz mode cannot be obtained by down-clocking from 11ac, the specification is needed. We have pilot tone indices based on [3] stating “Define 1MHz tone allocation as: 24 Data tones, 2 Pilot tones at tone indices +/-7, 3 Guard tones on left and 2 guard tones on right, and 1 DC tone [11/1484r6]”. However, the pilot values need to be defined. Seunghee Han, LG Electronics

March 2012 Background (1/2) Design principle on pilot sequence in 11ac [1] For fast phase tracking, identical pilot sequence values are used for all space-time streams in data symbols in 11ac so that the receiver can track phase without MIMO channel estimation on pilot tones. For 20 and 40 MHz, the pilot sequence shall be the single spatial stream pilot sequence of 11n copied to the NSTS streams before the per-stream CSDs are applied. For 80 MHz, the pilot sequence shall be the following sequence (which is the 40 MHz pilot sequence for NSTS = 1 extended with a [1, 1] on the right, resulting in the lowest PAPR on the pilot tones after applying [1 -1 -1 -1] rotation on the 20 MHz subbands), copied to the NSTS streams before the per-stream CSDs are applied: Seunghee Han, LG Electronics

Background (2/2) Further design principles on pilot sequence in 11ac March 2012 Background (2/2) Further design principles on pilot sequence in 11ac BPSK based (+1 or -1) pilot sequence values to avoid complex multiplication by using sign converter. Both time and frequency domain varying pilot sequence values by means of Modulo operation as a function of symbol index n in both time and frequency domains Pseudo random sequence (ie. pn as defined in [5]) to prevent the generation of spectral line [4] The worst case would be that all elements have the same signs (eg. All ‘1’ or all ‘-1’). Seunghee Han, LG Electronics

Proposed Design Criteria for Pilot Values March 2012 Proposed Design Criteria for Pilot Values For >= 2MHz mode, Reuse the definitions as in 11ac For 1 MHz mode, Succeed the design philosophy of 11ac with; Minimum impact on specification works Single table for pilot values with nested property for all bandwidths BPSK based sequence value for low complexity Provision of both time and frequency domain varying sign properties with modular operation It is noted that pseudo random sequence pn is further applied to avoid spectral line [5].  Not part of our proposal Seunghee Han, LG Electronics

Proposal on Pilot Values for 1 MHz Mode March 2012 Proposal on Pilot Values for 1 MHz Mode Based on slide 7, For a 1MHz transmission, two pilot tones shall be inserted in . The pilot mapping for subcarrier for symbol shall be as specified in the following equation. where is given in the right table and where n is the DATA symbol index Table 22-20 in 11ac D2.0 Seunghee Han, LG Electronics

Proposal on Pilot Values for >=2 MHz Modes March 2012 Proposal on Pilot Values for >=2 MHz Modes Based on slide 7, The pilot mapping and values for 2/4/8/16 MHz transmissions, respectively, refer those for 20/40/80/160 MHz transmissions in section 22.3.10.10 (Pilot subcarriers) of IEEE P802.11ac™/D2.0 with the same pilot positions and values. Seunghee Han, LG Electronics

March 2012 Straw Poll 1 Do you support to insert slide 8 at R.3.2.3.2.A of the spec framework as pilot mapping and values for 1MHz mode? Seunghee Han, LG Electronics

March 2012 Straw Poll 2 Do you support to insert slide 9 at the spec framework as pilot mapping and values for 2/4/8/16 MHz modes? Seunghee Han, LG Electronics

March 2012 References [1] Richard van Nee et al, “Pilot Sequence for VHT-DATA”, IEEE 802.11-10/0811r1 [2] Draft P802.11ac_D2.0 [3] Minyoung Park, “Proposed Specification Framework for TGah”, IEEE 802.11-11/1137r5 [4] Matthew S. Gast, “802.11 Wireless Networks – The Definitive Guide”, O’REILLY [5] Draft P802.11REVmb_D12.0 Seunghee Han, LG Electronics