1. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Pilot Design for OFDM PHY for 802.11aj(45 GHz) Authors/contributors: Date: 2015-1-21 Presenter: Shiwen HE Slide 1

2. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 2 Background The multiplication of the pilot tones allow receivers to track phase and frequency offset. The 802.11ad spec mandates that –2.16 GHz packets have pilot tones at {±10, ±30, ±50, ±70, ±90, ±110, ±130, ±150} in 512 subcarriers [1]. Possible tone location has been discussed in [2]. There are some differences between 11n\ac\ad protocols, in how to define the values of pilot subcarriers [1,3,4]. This presentation focuses on a near optimal data and pilot tone mapping for 802.11aj (45 GHz).

3. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 3 Input and Output Relation Let,which denotes the transmitted pilot sequence.,which denotes the received pilot sequence. denotes the pilot of the subcarrier, is the corresponding frequency domain channel, is the corresponding noise. The relation between them is where, denotes the sampling clock offset, is the number of pilot tones, denotes the remained phase offset.

4. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 4 Number of pilot subcarriers With more pilot tones to track phase and frequency offset, the better performance can be gotten. Simulation results show that the performance gap between 8 and 12 pilot tones is small. See Annex. It is proposed that 11aj packets use 8 pilot tones for 540 MHz, and use 16 pilot tones for 1080 MHz.

5. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 5 Location of pilot subcarriers(1/2) Then total phase offset in frequency domain can be obtained as Let, and, denotes a vector size of, then is obtained, based on the principle of least squares criterion, the estimation of the sampling clock offset and the estimation of the remained phase offset can be expressed as Let denotes the distance between adjacent pilot, and pilot distribution is symmetrical, then and.

6. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 6 Location of pilot subcarriers(2/2) Then and can be expressed as is not related to, so only NMSE of needs to be optimized. According to simulation results, is optimal. See Annex. It is proposed that 11aj packets use 8 pilot tones for 540 MHz, the location is {±11, ±33, ±55, ±77}; use 16 pilot tones for 1080 MHz, the location is {±11, ±33, ±55, ±77, ±99, ±121, ±143, ±165}.

7. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 7 Values of pilot subcarriers Pilot polarity table is combined with to determine the values of pilot subcarriers in same space-time stream. At OFDM symbol the pilot sequence is multiplied by the value, where is a periodic sequence of length 127 generated by the polynomial.

8. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 8 Conclusion(1/4) For 540 MHz, FFT point = 256, (39 + 38) guard tones, 3 DC tones, 8 pilot tones.

9. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 9 Conclusion(2/4) Pilot tones at {±11, ±33, ±55, ±77}. is defined as 111 111

10. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 10 Conclusion(3/4) For 1080 MHz, FFT point = 512, (79 + 78) guard tones, 3 DC tones, 16 pilot tones.

11. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 11 Conclusion(4/4) Pilot tones at {±11, ±33, ±55, ±77, ±99, ±121, ±143, ±165}. is defined in Table below. The above pilot mapping shall be copied to all space-time streams before the space-time stream cyclic shifts are applied. 1 11 111 11

12. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 12 Simulation Parameter Pilot polarity table is used. Values of pilot subcarriers in all space-time streams is same. NOTE: denote Gaussian distribution with the mean of, variance of. Scheme1Scheme2Scheme3 Num. of pilot tones8812 Location of pilot tones {±10, ±30, ±50, ±70}{±11, ±33, ±55, ±77}{±8, ±23, ±38, ±53, ±68, ±83} MIMO1×1, 4×4 for 1,4 streams, respectively Bandwidth540 MHz Multipath delay spread50~60 ns Num. of distinguishable paths 18 Sampling clock offset Remained phase offset Channel realization5000

13. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 13 References 1.IEEE Draft P802.11ad_D9.0 2.IEEE 802.11-10/0370r1, S. Srinivasa et al, 80 MHz Tone Allocation. 3.IEEE Std 802.11n-2009. 4.IEEE Draft-802.11ac_D5.1 5.Sourour E., El-Ghoroury H., McNeill D, “Frequency offset estimation and correction in the IEEE 802.11a WLAN”, Vehicular Technology Conference, 2004.

14. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 14 Annex ： Number and Location of Pilot tones

15. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 15 As shown in left, no matter what the scope and variance of sampling clock offset are, d=22 is optimal.

16. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 16 As shown in left, no matter SISO or MIMO, d=22 is optimal.

17. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 17 As shown in left As the number of symbols increased, RMSE performance got an improvement [5].

18. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 18 As shown in left Scheme2 is 0.2dB worse than ideal and better than Scheme1, PER=0.1; The performance gap between 8 and 12 pilot tones is small, 8 is enough.

19. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 19 As shown in left Scheme2 is 0.4 dB worse than ideal and better than Scheme1, PER=0.1; The performance gap between 8 and 12 pilot tones is small, 8 is enough.

20. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 20 As shown in left Scheme2 is 0.45dB worse than ideal and better than Scheme1, PER=0.1; The performance gap between 8 and 12 pilot tones is small, 8 is enough.

21. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 21 As shown in left Scheme2 is 0.6 dB worse than ideal and better than Scheme1, PER=0.1; The performance gap between 8 and 12 pilot tones is small, 8 is enough.

22. doc.:IEEE 802.11-15/0206r0 Submission January 2015 Shiwen He, Haiming Wang Slide 22 Thanks for Your Attention.