Space Time Block Coding for SC.PHY in 11ay

April 2017 doc.: IEEE 802.11-17/0590r0 Space Time Block Coding for SC PHY in 11ay Date: 2017-04-11 Authors: Name Affiliations Address Phone email +7 (831) 2969444 Turgeneva 30, Nizhny Novgorod, 603024, Russia artyom.lomayev@intel.com Artyom Lomayev Intel alexander.maltsev@intel.com Alexander Maltsev Intel miki.genossar@intel.com Miki Genossar Intel claudio.da.silva@intel.com Claudio da Silva Intel carlos.cordeiro@intel.com Carlos Cordeiro Intel Submission Slide 1 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 Introduction This presentation proposes a Space Time Block Code (STBC) for SC PHY, [1]. Submission Slide 2 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 SC Symbol Blocking for STBC The proposed STBC scheme applies coding to the data part of the SC symbol block and utilizes symbol blocking structure defined in [1]. It performs mapping of a single spatial stream (NSS = 1) to two space-time streams (NSTS = 2). The STBC code combining is performed in frequency domain in a similar way as for OFDM in 11n/ac, [2]. Submission Slide 3 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 SC Symbol Blocking for STBC (Cont d) STBC coding: Input two SC symbol blocks xNSPB and yNSPB, NSPB defines the number of symbols per SC block; For example, let s define NSPB = 448 as in case of normal GI type; (x448(n), y448(n)) blocks are mapped to the first space-time stream; (-y*448(-n), x*448(-n)) blocks are mapped to the second space-time stream; (g1,64(n), g2,64(n)) are two Guard Intervals (GIs) of length 64 for space-time stream 1 and 2 accordingly; Figure below illustrates the proposed structure, (-n) defines reverse of symbols in time, * defines complex conjugation; GI DATA GI DATA GI STS #1 g1,64 g1,64 g1,64 x448(n) y448(n) STS #2 g2,64 g2,64 g2,64 -y*448(-n) x*448(-n) T1 T2 Submission Slide 4 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 Signals Definition Transmit signals in frequency domain: STS#1: XT1(k) = X(k) + G1(k); YT2(k) = Y(k) + G1(k); where: X = DFT(x), Y = DFT(y), G1 = DFT(g1), G2 = DFT(g2); ( ) n ( ) n = = , 0 : 447 , 0 : 447 x n y n ( ) n ( ) n 448 448 = = x y = = , 0 448 : 511 , 0 448 : 511 n n = = , 0 n , 0 n 0 : 447 0 : 447 n n ( ) n ( ) n = = g g ( ) ( ) 1 2 = = 448 , 448 , g g 448 : 511 448 : 511 n n , 1 64 , 2 64 Submission Slide 5 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 Signals Definition (Cont d) Received signals in frequency domain: Time interval T1: RT1(k) = H1(k)*X(k) ph(k)*H2(k)*Y*(k) + H1(k)*G1(k) + H2(k)*G2(k) + ZT1(k); Time interval T2: RT2(k) = ph(k)*H2(k)*X*(k) + H1(k)*Y(k) + H1(k)*G1(k) + H2(k)*G2(k) + ZT2(k); where: ph(k) = exp(+j(2 /512)* t*k), t = 65 chips; ZT1(k) and ZT2(k) AWGN ~CN(0, 2) noise samples; TX antenna #2 RX antenna #1 H2 Combiner H1 Noise Submission Slide 6 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 Signals Definition (Cont d) Phasor explanation for STS#2: x*(-n) = ( x*(447), x*(446), , x*(0), 00, 01, , 063 ); Phasor operation applied in frequency domain makes cyclic shift in time domain as follows: x~(n) = (x*(0), 00, 01, , 063, x*(447), x*(446), , x*(1) ); Due to the property of DFT provided in Appendix, this gives complex conjugated subcarriers in frequency domain, i.e. X*(k) = DFT(x~(n)); Hence, DFT(x*(-n)) * exp(-j(2 /512)*65*k) = X*(k); and DFT(x*(-n)) = X*(k) * exp(+j(2 /512)*65*k); The same derivation is applicable for y*(-n) signal; Phasor can be treated as a part of H2 channel; Submission Slide 7 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 Demodulation Method The combining method is similar to OFDM 11n/ac, the difference is that MMSE solution is used: The estimated X^(k) and Y^(k) signals can be written as follows: 2 ( ) ( ) k ( ) ( ) k ( ) k ( ) k 65 j k ^ X k R k * 1 1 H H e 512 = 1 T * 2 ( ) * ( ) k ( ) k 2 2 2 ^ Y + + R 2 H H + ( ) k ( ) k 65 j k * 2 H e H 2 T 512 1 2 1 This provides data estimation in the frequency domain, which in turn can be transformed to the time domain applying IDFT to get x^(n) and y^(n) estimations; Submission Slide 8 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 Demodulation Method (Cont d) MMSE equalizer for GI part: The equalizer solution considered at the previous slide provides a perfect equalization of the data part only, but NOT for the GI part of the signal; After conversion to the time domain GI sequences will not be perfectly" equalized; Due to the fact that GI signals are known to receiver, they can be pre-calculated during channel estimation stage as follows: 2 ( ) ( ) k ( ) ( ) k ( ) ( ) k ( ) ( ) k ( ) ( ) k ( ) k ( ) k 65 j k + ~ 1 G k H k G k H k G k * 1 1 H H e 512 = 1 1 2 2 2 ( ) k ( ) k 2 2 2 + ~ 2 * 1 * 1 * 2 * 2 + + G H G H G 2 H H + ( ) k ( ) k 65 j k * 2 ) H e H 512 1 2 1 ( ) ( = = ~ 1 ~ 1 ~ 2 ~ 2 , g IDFT G g IDFT G The g~1 and g~2 signals can be used for phase tracking in time domain as known GIs; Submission Slide 9 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 SP/M Do you agree: to include the text from (11-17-0587-00-00ay 30 5 6 4 3 Space Time Block Coding) defining SC STBC scheme to the spec draft? Submission Slide 10 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 Appendix DFT complex conjugation property: 2 N 1 1 N N ( ) k ( ) n j nk = n DFT: = X x e 0 2 N 1 N 1 N ( ) k ( ) n j nk = n = * * Complex conjugated sample in frequency domain: X x e 0 2 2 2 1 ( ) k ( ) 0 ( ) 1 ( ) 2 ( ) 3 2 3 j k j k j k = + + + * * * * * Specific example for N = 4: X x x e x e x e 4 4 4 4 2 2 2 1 ( ) k ( ) 0 ( ) 1 ( ) 2 ( ) 3 2 3 2 2 2 j k j k j k j k j k j k Can be rewritten: = + + + * * * * * X x x e x e x e 4 4 4 4 2 2 2 1 ( ) k ( ) 0 ( ) 1 ( ) 2 ( ) 3 3 2 j k j k j k Using: = 2 je k = + + + * * * * * 1 X x x e x e x e 4 4 4 4 2 2 2 1 ( ) k ( ) 0 ( ) 3 ( ) 2 ( ) 1 2 3 j k j k j k = + + + * * * * * Reordering: X x x e x e x e 4 4 4 4 2 N 1 N 1 N ( ) k ( ) j nk = n In general case: = * * X x n e 0 Submission Slide 11 Intel Corporation

April 2017 doc.: IEEE 802.11-17/0590r0 References 1. Draft P802.11ay_D0.3 2. IEEE802.11-2016 Submission Slide 12 Intel Corporation