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PAPR Reduction Techniques for High-Efficiency HE SIG-B Data Signals

Investigating two schemes for reducing peak-to-average power ratio in HE SIG-B data signals, including the use of scramblers and phase rotation techniques.

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PAPR Reduction Techniques for High-Efficiency HE SIG-B Data Signals

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  1. PAPR Reduction for HE SIG-B Date: 2016-05-16 Authors: Bin Tian, Qualcomm

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  11. Introduction • HE SIG-B can have very large PAPR when one OFDM symbol has all (or almost all) zeros or ones • Several examples are provided in the following slides. • In this presentation we investigate two schemes for HE SIG-B PAPR reduction Bin Tian, Qualcomm

  12. Example 1: All Zero Padding Bits Non-padding SIGB symbols Zero Padding symbols Zero Padding STA specific information subfields/CRC/Tail Common bits … Zero Padding STA specific information subfields/CRC/Tail Common bits SIG-B Channel 1 SIG-B Channel 2 …

  13. Example 2: Long Sequence of Zeros in HE-SIGB Content Common bits CRC (4) Tail (6) 2 STA info (21) + CRC (4) + Tail (6) 2 STA info (21) + CRC (4) + Tail (6) Padding … SIGB symbol (26 bits) 36 zeros in a row 000000 00000000000 0000 000 0 0 0 00000000011 1000 000 1 0 1 6 11 4 3 1 1 1 11 4 3 1 1 1 4 Tail STAID Nss BF DCM Coding STAID Nss BF DCM Coding CRC MCS MCS Broadcast Frame Unicast Frame Broadcast Frame Unicast Frame Note: Cases with a lot of sequential zeros can happen even if the bit ordering of the field are shuffled. Bin Tian, Qualcomm

  14. Solutions 1: Scrambler • Reuse the 11a scrambler on HE SIG-B content • Fixed scrambling seed preferred. No additional seed signaling required • Seed may not be optimal for certain content • Implementation drawback: need to skip scrambling tail bits in each common/per user code block • Use random padding bits • Assume scrambler doesn’t cover the padding bit Bin Tian, Qualcomm

  15. Solutions 2: Phase Rotation • Phase rotation is proposed in [1] to mitigate the PAPR issue for DCM MCS0 • Same approach can be reused to solve PAPR issue for other modulations • Phase rotation on data tones after constellation mapping • In each 20MHz HE-SIGA/B, there are 52 data tones. For the kth data tone, phase rotation pattern is defined as in [1] 1 for 0=<k<26 (-1)k for 26=<k<52 • For DCM + MCS0, since the same rotation is applied in the DCM BPSK bit mapping, this step of phase rotation after constellation mapping can be skipped • Legacy gamma rotation still applies among different 20MHz channels Bin Tian, Qualcomm

  16. Simulation • High PAPR configuration identified is simulated • PAPR results of following cases are compared • Data • HE-SIGB: without PAPR mitigation • HE-SIGB +11a scrambler with random seed • HE-SIGB +11a scrambler with fixed seed (0x01) • HE-SIGB with phase rotation Bin Tian, Qualcomm

  17. Simulation Results – MCS0 • Both scrambler and phase rotation method can effectively reduce the PAPR Bin Tian, Qualcomm

  18. Simulation Results – MCS5 • Both scrambler and phase rotation method can effectively reduce the PAPR Bin Tian, Qualcomm

  19. Summary • Two schemes are proposed for PAPR reduction on HE SIG-B • 11a scrambler based approach • Phase rotation • Simulations show that both schemes are effective • Prefer the phase rotation approach due to its simplicity in implementation Bin Tian, Qualcomm

  20. Straw Poll 1 • Do you support the following PAPR reduction scheme for HE SIG-B • Phase rotation is applied to the HE SIG-B data tones after constellation mapping. For the kth data tone in the HE SIG-B, the phase rotation pattern is defined as 1 for 0=<k<26 and (-1)k for 26=<k<52 • For DCM + MCS0, since the same rotation has already been applied in the DCM BPSK bit mapping, this step of phase rotation after constellation mapping shall be skipped • Legacy gamma rotation still applies among different 20MHz channels Bin Tian, Qualcomm

  21. Reference [1] IEEE 802.11-16/0xxxr0 On Modulation of MCS0 DCM and DCM Capability Bin Tian, Qualcomm

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