Date: 2013-09-17

1. Consideration of PHY design for 1.08GHz channel Date: 2013-09-17 Presenter: Changming Zhang

2. Author List Changming Zhang

3. This document is to propose a PHY design to support low power 1.08GHz PHY • It considers the PHY design with distortion compensation for I/Q imbalance for high order modulation and PA nonlinearity Abstract Xiaoming Peng

4. Background 1.08GHz modulation and coding schemes Frame structure IQ imbalance estimation and compensation PA nonlinearity treatment Conclusion Roadmap Changming Zhang

5. Channelization Consideration for 802.11aj It is necessary to define 1.08GHz PHY Changming Zhang

6. Background 1.08GHz modulation and coding schemes Frame structure IQ imbalance estimation and compensation PA nonlinearity treatment Conclusion Roadmap Changming Zhang

7. Ctrl PHY CMCS Changming Zhang

8. OFDM PHY CMCS Changming Zhang

9. MR SC PHY CMCS Changming Zhang

10. HR SC PHY CMCS Changming Zhang

11. Low power PHY CMCS Changming Zhang

12. Background 1.08GHz modulation and coding schemes Frame structure IQ imbalance estimation and compensation PA nonlinearity treatment Conclusion Roadmap Changming Zhang

13. Frame structure Ctrl PHY (The same as 11ad) OFDM PHY Changming Zhang

14. Frame structure MR SC PHY (The same as 11ad) HR SC PHY Changming Zhang

15. Frame structure Low power PHY (The same as 11ad) Changming Zhang

16. Background 1.08GHz modulation and coding schemes Frame structure IQ imbalance estimation and compensation PA nonlinearity treatment Conclusion Roadmap Changming Zhang

17. SFS-IQ imbalance estimation • SFS (Single-Frequency Sequence) • Received baseband signal model: • The phase difference between adjacent symbols is fixed at π/2, but it does not mean SFS is single-frequency signal, it is also constructed by symbols with the same time duration as the preamble and payload. • The transmit MASK mainly depends on the time duration of symbols, so the MASK is maintained after SFS is added. • SFS is in front of the original STF, thus synchronization and channel estimation are not impacted by IQ imbalance . • The length of SFS is 512, but only 128 symbols is enough for IQ imbalance estimation, others are used for initial capture before IQ imbalance estimation. Changming Zhang

18. SFS-IQ imbalance estimation By calculating the second-order expectations of every two adjacent: symbols: Furthermore, let Then Thus, we can obtain: • The reason for “≈’’ is due to the neglect of Δθ, which is reasonable as Δθ is quite small. Changming Zhang

19. SFS-IQ imbalance compensation With IQ imbalance, the received baseband signal can be expressed as: Without the presence of IQ imbalance, the baseband signals can be expressed as IQ compensation can be performed as: Changming Zhang

20. Explanations • The proposed method for IQ imbalance treatment is almost independent of CFO. • As IQ imbalance is compensated at the front of synchronization, then CFO estimation and compensation is not impacted by IQ imbalance. However, before IQ compensation, CFO estimation and compensation is quite hard. • Consider the complexity, we only address RX frequency-independent IQ imbalance. However, as for frequency-dependent IQ imbalance, the proposed method can also achieve some effects, even though the compensation is not perfect in this case. • Due to the limit of transmit EVM, TX IQ imbalance is not so significant as RX IQ imbalance, so the proposed method that only considers RX IQ imbalance is reasonable. Changming Zhang

21. L=128, r=0.05，∆r=5； • t=0.005，∆t=0.5 Changming Zhang

22. L=128, r=0.05，∆r=5； • t=0.005，∆t=0.5 Changming Zhang

23. L=128, r=0.05，∆r=5； • t=0.005，∆t=0.5 Changming Zhang

24. L=128, r=0.05，∆r=5； • t=0.005，∆t=0.5 Changming Zhang

25. Background 1.08GHz modulation and coding schemes Frame structure IQ imbalance estimation and compensation PA nonlinearity treatment Conclusion Roadmap Changming Zhang

26. Constellation diagram Standard constellation Distorted constellation • PA nonlinearity distorts the constellation. We estimate the distorted constellation (DC) with TBLK in the Header for QAM signals, and demodulate signal according to DC. Changming Zhang

27. DC estimation analysis Changming Zhang

28. Frame design • TBLK and payload BLK are with the same modulation; • Every constellation point appears with the same probability in the TBLK. Changming Zhang

29. Parameters to be estimated: Tdistorted amplitudes, T additional phases: . (T＝3 for 16QAM) • Likelihood function (LF) for the k-th symbol: • Joint LF: • Let, then • By equaling the above first-order derivatives to zero, we can obtain the estimation results: DC estimation Changming Zhang

30. Hard decision demodulation: For every received symbol, the demodulation output is the DC point with the least distance to it. • Soft decision demodulation: The DC soft demodulation style is similar to the SC soft demodulation, where the SC points should be replaced by the DC points. For example, if we require the LLR output demodulation, it can be depicted as: DC demodulation Changming Zhang

31. 11ad’s PA model • OBO=6 dB Changming Zhang

32. 11ad’s PA model • OBO=6 dB Changming Zhang

33. 11ad’s PA model • OBO=6 dB Changming Zhang

34. 11ad’s PA model • OBO=6 dB Changming Zhang

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39. Explanations • The preamble, CES and original Header are BPSK signals, and the impact of PA nonlinearity is neglectable. • Distorted constellation estimation is performed after equalization, thus the proposed method is decoupled of ISI. • If the transmit EVM is not controlled well, the impact of PA nonlinearity is serious especially for 64-QAM, and the proposed method can overcome the impact well at receiver. • If the transmit EVM meets the requirements, PA nonlinearity is relatively weak, and impact is weaker, but the proposed method still achieves some performance improvement. Changming Zhang

40. r=0.05，∆r=5； • t=0.005，∆t=0.5 Changming Zhang

41. r=0.05，∆r=5； • t=0.005，∆t=0.5 Changming Zhang

42. r=0.05，∆r=5； • t=0.005，∆t=0.5 Changming Zhang

43. r=0.05，∆r=5； • t=0.005，∆t=0.5 Changming Zhang

44. Background 1.08GHz modulation and coding schemes Frame structure IQ imbalance estimation and compensation PA nonlinearity treatment Conclusion Roadmap Changming Zhang

45. CMCSs of 1.08 GHz PHY • For Ctrl PHY, OFDM PHY, and Low power PHY, the CMCSs are the same as that of 11ad. • SC PHY is divided into MR SC PHY and HR SC PHY, MR SC PHY corresponds to PSK modulation, and HR SC PHY corresponds to QAM modulation. Here 13/16-16QAM, and 64QAM are new compared with 11ad. • Frame structure of 1.08 GHz PHY • Including Ctrl PHY, OFDM PHY, MR SC PHY, HR SC PHY, and Low power PHY. • The frame structure of Ctrl PHY, MR SC PHY, and Low power PHY are consistent with that of Ctrl PHY, SC PHY, and Low power PHY of IEEE 802.11ad, respectively. • Compared with 11ad, SFS is added at the beginning for OFDM PHY, which is used to estimate and compensate IQ imbalance. • Compared with the SC PHY of 11ad, also SFS is added at the beginning for HR SC PHY that used to estimate and compensate IQ imbalance. In addition, TBLK is added before payloads, which is used to estimate distorted constellation to react PA nonlinearity. • The proposed methods that compensate IQ imbalance and PA nonlinearity work well, which can be observed from the performance evaluation. Conclusion Changming Zhang

46. Thanks！ Changming Zhang