November 2012 doc IEEE 802 11 12 1331

November 2012 doc. : IEEE 802. 11 -12 -1331 -01 -00 ah DFT spreading OFDM optional specification proposal for 11 ah low rate PHY Authors: Submission Date: 2012 -11 -12 Slide 1 Masahiro Umehira et. al

November 2012 doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Background • TGah PHY supports 2/4/8/16 MHz signals based on the down clocked versions of 11 ac 20/40/80/160 MHz, and an 1 MHz signals based on 32 FFT. – Both 2 MHz and 1 MHz receptions are mandatory in TGah PHY. • DFT spreading OFDM (DFTs-OFDM) is adopted for the uplink in IMT-2000 LTE for battery operated mobile terminal. • DFTs-OFDM application to 11 ah PHY was suggested in IEEE 802. 11 -11/0753 r 0, and IEEE 802. 11 -12/0349 r 2 in 2012/3. • The proposal of IEEE 802. 11 -0349 r 2 was well-supported for its advantage of lower PAPR and lower ACPL (adjacent channel power leakage) in non-linear HPA operation. – Y 16 Submission N 1 A 23 Slide 2 Masahiro Umehira et. al

November 2012 doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Abstract • This contribution is a follow-up of IEEE 802. 11 -0349 r 2. • We propose DFT-spreading OFDM based optional specification for 11 ah low rate PHY, especially for 1 MHz and 2 MHz modes, aiming at sensor network applications which need high power efficiency. Submission Slide 3 Masahiro Umehira et. al

doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Review of advantages of DFTs-OFDM • Battery driven wireless terminals are used for sensor network applications • Basic requirements for the use cases of 1 a/1 f and 2 d/2 e/2 f – Low transmission speed: 2 MHz mode and 1 MHz mode – Long battery life time – Low power consumption at wireless sensor terminals • Basic Requirements for the use cases – Lower PAPR and lower ACPL (adjacent channel power leakage) with higher energy efficiency, i. e. low output power back-off operation at HPA. – Less BER performance degradation in non-linear HPA operation. Submission Slide 4 Masahiro Umehira et. al

November 2011 doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Null DC sub-carrier DFTs-OFDM • 57 DFT/IDFT is the simplest approach for DFTs-OFDM, however FFT algorithm can not be applied for DFT/IDFT implementation since 57 is neither “power of two” nor “even”. – It needs large amount of signal processing for DFT/IDFT. • 56 DFT/IDFT is another simple approach for DFTs-OFDM. – 56 DFT/IDFT needs less amount of signal processing than 57 DFT/IDFT. – DC tone is replaced with one data tone. • DC offset error at modulator and demodulator can degrade BER performance in the conventional DFTs-OFDM. . • No BER performance degradation in OFDM since DC sub-carrier is not used. • DFTs-OFDM with null DC sub-carrier is proposed for 11 ah low rate PHY optional specification, especially for sensor network applications where high power efficiency is required. – No BER performance degradation due to DC offset error in the proposed DFTs-OFDM since DC sub-carrier is made null. Submission Slide 5 Masahiro et. al Hongyuan. Umehira Zhang, et. Al.

January 2012 doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Block diagram of NDCS-DFTs-OFDM : Additional blocks required for NDCS-DFTs-OFDM Scrambler FEC Interleaver BPSK/QPSK mapper DFT IFFT GI & Window Analog & RF (a) Transmitter side of NDCS-DFTs-OFDM De. Scrambler FEC decoder Deinterleaver BPSK/QPSK De-mapper IDFT Frequency Domain Equalization FFT Remove GI Analog & RF (b) Receiver side of NDCS-DFTs-OFDM • DFT on the transmission side – 26 points DFT for 1 MHz, 56 points DFT for 2 MHz • IDFT and FDE on the reception side – 26 points IDFT for 1 MHz, 56 points IDFT for 2 MHz – FDE is performed using CSI. Submission Slide 6 Masahiro Umehira et. al

doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Details of DFT/IDFT in NDCS-DFTs-OFDM • M=56 and N=64 for 2 MHz signals (52 Data tones, 4 Pilot tones, 7 Guard tones, and 1 DC tone) • M=26 and N=32 for 1 MHz signals (24 Data tones, 2 Pilot tones, 5 Guard tones, and 1 DC tone) Spectrum splitting M M/2 M+1 N N GI windowing . . . MOD . . . S/P DFT 0 IFFT . . . Data P/S Output D/A . . . M/2 (1) Transmitter side X FDE FFT … IDFT … … DEM … P/S S/P GI N Remove N … Data M/2 M+1 … M A/D Input M/2 (2) Receiver side Submission Masahiro Umehira et. al

doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Preamble and signal design for NDCS-DFTs-OFDM • DFTs-OMDF optional specification for 1 MH/2 MHz BPSK/QPSK signals. • No change in the preamble and basic signal design of OFDM signals. – 1 MHz (32 FFT) • 24 Data tones, 2 Pilot tones, 5 Guard tones, and 1 DC tone – 2 MHz(64 FFT) • 52 Data tones, 4 Pilot tones, 7 Guard tones, and 1 DC tone AH-STF AH-LTF AH-SIG AHLTF 1 DFTSOFDM 2 … DFTSOFDM n DFT Spreading is applied in the data field only. Submission Slide 8 Masahiro Umehira et. al

doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Comparison of PAPR Null DC subcarrier DFTs-OFDM (NDCS-DFTs-OFDM) achieves 2. 0 d. B lower PAPR than OFDM, but 0. 5 d. B higher than conventional DFTs. OFDM at CCDF=0. 1%. 2. 0 d. B M=56 N=64 Modulated by random data. Submission Masahiro Umehira et. al

doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Comparison of adjacent channel power leakage NDCS-DFTs-OFDM has almost the same adjacent channel power leakage as the conventional DFTs-OFDM, which is 3 -4 d. B lower than that of OFDM when OBO=3 d. B. Rapp model Submission Masahiro Umehira et. al

doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Estimated PAE improvement DFTs-Spreading approach can reduce OBO from 6 d. B to 4. 5 d. B to maintain ACLP. 5 56 sub-carriers / 2 MHz mode / QPSK 0 1. 5 d. B OBO reduction improves 20% in PAE (power-added-efficiency) from 15% to 18%. Power Density [d. B] 6 d. B (OFDM) -5 6 d. B 5 d. B -10 4 d. B -15 -20 -25 -30 0 1 2 3 Frequency (MHz) Jeonghu Han et al, “A Fully-Integrated 900 -MHz CMOS Power Amplifier for Mobile RFID Reader Applications, ” IEEE RFIC Symposium, 2006. Submission Masahiro Umehira et. al

doc. : IEEE 802. 11 -12 -1331 -01 -00 ah EVM according to DC offset error in NDCS -DFTs-OFDM No EVM (Error Vector Magnitude) degradation is observed in NDCS-DFTs-OFDM. M=56 N=64 QPSK Submission Masahiro Umehira et. al

doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Signal processing complexity Estimation of required complex multiplications per OFDM symbol. (1) 1 MHz mode DFT spreading(26 point) IFFT(32 point) Total OFDM 0 80 80 DFTs-OFDM 338 80 418 NDCS-DFTs-OFDM 338 80 418 Note: 26 point DFT is decomposed to 2 X 13 point DFT. (2) 2 MHz mode OFDM DFTs-OFDM NDCS-DFTs-OFDM DFT spreading(56 point) 0 476 IFFT(64 point) 192 192 Total 192 668 Note: PFA (Prime Factor FFT algorithm) can be applied for 56 (8 X 7) points DFT. Submission Masahiro Umehira et. al

November 2011 doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Summary • NDCS-DFTs-OFDM optional specification for 11 ah low rate PHT is proposed. – 26 point DFT and 32 point FFT for 1 MHz mode QPSK/BPSK. – 56 point DFT and 64 point FFT for 2 MHz mode QPSK/BPSK. – DC sub-carrier is made null • Features of the proposed specification – No change in the preamble and basic signal design of OFDM signals. – Lower PAPR and lower ACPL than OFDM – No EVM degradation due to DC offset error – Less signal processing complexity by spectrum splitting Submission Slide 14 Masahiro Umehira et. al

November 2011 doc. : IEEE 802. 11 -12 -1331 -01 -00 ah References [1] 011 -11 -0753 -00 -00 ah-dft-spread-ofdm-optimized-for 802 -11 ah [2] 11 -11 -1482 -00 -00 ah-preamble-format-for-1 -MHz [3] 11 -11 -1483 -00 -00 ah-11 ah-preamble-for-2 MHz-andbeyond [4] 11 -11 -1484 -06 -00 ah-11 ah-phy-transmission-flow [5] 11 -12 -0349 -02 -00 ah-dft-spreading-OFDM-options-for 11 ah-phy-enhancement Submission Slide 15 Masahiro Umehira Hongyuan Zhang, et. al Al.

November 2011 doc. : IEEE 802. 11 -12 -1331 -01 -00 ah Straw Poll • Do you support NDCS-DFTs-OFDM based optional specification for 11 ah low rate PHY ? – Mainly for 1 MHz/2 MHz signals with BPSK/QPSK mode. • Y • N • A Submission Slide 16 Masahiro Umehira et. al Hongyuan Zhang, et. Al.