1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Techniques for MB-OFDM improvement Date Submitted: 5 September 2003 Source: Mitsuhiro Suzuki, Chihiro Fujita, Michio Yotsuya, Kazuhisa Takamura, Takashi Usui Bob Huang Company: Sony Corporation Sony Electronics of America Address: 6-7-35 Kitashinagawa Shinagawa-ku,Tokyo. Japan 141-0001One Sony Drive TA-1 Voice: +81-3-6409-3201, FAX: +81-3-6409-3203 Park Ridge, NJ 07656 E-Mail: suzuki@wcs.sony.co.jp, chihiro@ wcs.sony.co.jp, V: 201-358-4409 yotuya@ wcs.sony.co.jp, takamura@wcs.sony.co.jp, F: 201-930-6397 usui@ wcs.sony.co.jp EMail: robert.huang@am.sony.com Re: none Abstract:This presentation introduces the unique techniques for MB-OFDM, ranging, null prefix, preamble waveform, coding, tracking Purpose:Technical contribution to MB-OFDM proposal. Notice:This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release:The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Sept 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 1

2. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 2 Ubiquitous Technology Labs Sony Corporation Sept 2003 Techniques for MB-OFDM improvement

3. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 3 Contents 1. Ranging Techniques -Clocking burst transmission -Coherent sub-banding -Frequency domain smoothing 2. Modified Tx preamble waveform 3. Null prefix for OFDM 4. Coding scheme 5. Tracking method without pilot

4. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 4 Clocking Burst Transmission (How to measure the turn around time)

5. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 5 Clocking Transmission Mechanism Define clocking period T which is longer than 2x(Max propagation delay) Device A start to clock. Device A transmit signal to Device B at the clocking timing. Device B detect the signal arrival time from A. Device B start to clock from the arrival time. Device B transmit to Device A at the clocking timing. Device A detect the signal arrival time from B. Time lag between the arrival time and the last clocking timing is 2x(Propagation delay)

6. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 6 In MB-OFDM case, T which is same as time slot length ( 312.5[ns] ) is convenient. Physical layer system closed (with no MAC help ) No negotiation is necessary.

7. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 7 Coherent sub-banding (How to improve measuring precision)

8. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 8 Current problem for ranging Frequency characteristics of each band can be obtained. However, no phase coherency between each band. Ranging resolution is determined by each bandwidth (528[MHz]).

9. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 9 1. Define reference time of t0 during the burst. ( It is the best that t0 is set to head of the channel estimation part.) 2. Define phase of each carrier set to 0[deg].  Phase coherency between each band is achieved. (even if the difference between t0 of Tx and t’0 of Rx exists.) Solution for increase measured bandwidth

10. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 10 Setting phase of each carrier Fortunately, every frequency can be synthesized from one oscillator (4224[MHz]). All carrier’s phase is set to 0[deg] at the time of 264[MHz] phase 0[deg]

11. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 11 Frequency domain smoothing (How to reduce complexity to calculate time response from frequency response )

12. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 12 Current problem of calculate time response Large size FFT is needed ( In 3 band case, 128x3=384 )

13. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 13 Frequency domain smoothing and decimation For the purpose of ranging, time response around time 0 is important. Therefore, smoothing and decimation in frequency domain is allowed. FFT size can be reduced.

14. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 14 Conclusion for ranging techniques. Turn around time can be measured only by physical layer implementation by clocking burst transmission. 1.5[GHz] bandwidth channel response measuring is possible by coherent sub-banding (3 band case) Calculation complexity can be reduced by frequency domain smoothing.

15. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 15 Tx preamble waveform improvement

16. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 16 Current preamble (time domain) Auto-correlation A little bit bad auto-correlation Preamble No.1 Hierarchical code is convenient to reduce complexity

17. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 17 Power spectrum Shape is different from OFDM part. Power spectrum shape is not flat. (Tx power have to be reduced 5[dB]!!! in FCC rule point of view) OFDM part power spectrum Preamble part power spectrum Current preamble (frequency domain) How to shape the spectrum into 500[MHz] with 528 Mchip/s chip rate ?

18. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 18 Modification of Tx Preamble Modified power spectrum ( original preamble ) Preamble at Tx side is regarded as OFDM signal which symbols are in frequency domain. Power Spectrum shape is (of course) same as OFDM. Power spectrum is (of course) flat. force to set amplitude = 1 keeping phase information force to set amplitude = 0

19. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 19 In Rx side, original preamble is used Original binary preamble is used at the receiver not to increase correlation complexity Cross-correlation Correlation characteristics improves. ( approx. 3[dB] ) Preamble for Tx(red) and Rx(blue) Tx preamble is no longer binary… ( still real number)

20. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 20 Conclusion for Tx preamble improvement Preamble at Tx: amplitude modification in frequency domain. same power spectrum as OFDM no-necessity to care about extra spectrum shaping flat power spectrum and allowed max Tx power. Preamble at Rx: same as original preamble not increase correlation complexity better correlation performance.

21. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 21 OFDM with null prefix

22. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 22 Conventional cyclic prefix GI Cyclic prefix is to avoid ICI ( Inter-subCarrier-Interference)

23. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 23 Proposed null prefix Null prefix (or postfix) OFDM can also avoid ICI by cyclic adding at the receiver.

24. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 24 Necessary processing for null prefix Need detecting multi-path time dispersion ( T MP ) ( This may be done during CCA? ) Need ADC during T MP longer period. Need cyclic adding during T MP period.

25. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 25 Picked up noise Null prefix case, the receiver will pick up same noise or (T EM +T MP )/T EM larger noise. (Depend on multi-path time dispersion: 0 < T MP < T GI ) However,,,

26. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 26 Tx power can be increased (prefix energy consumption aspect ) UWB Tx power is specified by power density. Null prefix OFDM can have (T EM +T GI )/T EM higher Tx power because it does not spend the energy for “prefix”. T GI >T MP (typical): S/N at receiver improves. T GI =T MP (worst) : S/N is same as cyclic prefix.

27. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 27 Tx spectrum shape will be flat Cyclic prefix generates ripple in spectrum. Null prefix generates no ripple in spectrum.

28. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 28 Null prefix OFDM is allowed (T EM +T GI )/T EM higher Tx power keeping FCC spectrum regulatory. Tx power can be increased (power density in MHz aspect) Null prefix has higher allowable Tx power when sub-carrier spacing is not less than 1[MHz] UWB Tx power is specified by power density in MHz

29. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 29 Conclusion for null prefix Null prefix improves from 2[dB] to 1[dB] link performance. Null prefix can be applied to modified Tx preamble

30. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 30 Coding scheme

31. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 31 Coding scheme K = 7 convolutional coding (current ) low latency, but high power consumption not so good BER/PER Decoder power consumption can not be neglected. K = 4 CC + RS(255,239) concatenation (proposed) K = 4 gate count is 1/8 smaller than K=7 K = 4 power consumption is 1/8 smaller than K=7 RS(255,239) gate count is comparable to K=7 RS(255,239) power consumption is 1/8 smaller than K=7 Decoding latency is not so critical in payload part.

32. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 32 Performance comparison To be prepared

33. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 33 Conclusion for coding scheme. a few dB better BER/PER performance than K=7 gate count is comparable to K=7 power consumption is ¼ lower than K=7 K=4 CC + RS concatenation All of considerable coding scheme should be studied. Low power consumption coding scheme is desired as mandatory.

34. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 34 Tracking method without pilot

35. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 35 Synchronization situation Fortunately, sub-carrier of OFDM and center frequency are synchronized. Modulation timing error and carrier phase error are synchronized Timing error ( carrier phase error ) is caused by reference frequency difference between Tx and Rx.

36. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 36 Rotation in frequency domain OFDM signal is described. OFDM with timing error is described. Timing error is observed rotation in symbol on each sub-carrier. The phase value of rotation is represented by center frequency, because bandwidth is small compared to center frequency.

37. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 37 Tracking method block diagram Pilot is not necessary Timing error detection part (red) is very conventional

38. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 38 Conclusion for tracking using pilot More precise timing error detection by using many (122) sub- carrier information. (current number of pilot symbol is 12) 0.5[dB] (=112/100) link performance will be improved because of no energy lost for pilot. Coding rate for high bit rate (e.g. 480[Mbps]@r=3/4 ) can be decreased and improve Eb/No performance. -More link performance will be improved. -SOP performance will be improved Pilot is not necessary ( The idea is under qualitative consideration. Quantitative value by simulation is needed. )

39. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 39 Total conclusion This document introduced 1. Ranging Techniques -Clocking burst transmission -Coherent sub-banding -Frequency domain smoothing 2. Modified Tx preamble waveform 3. Null prefix for OFDM 4. Coding scheme 5.Tracking method without pilot These achieve better performance in MB-OFDM system

40. Sept. 2003 doc.: IEEE 15-03-0337-01-003a Submission Suzuki, et al, Sony Corp., Sony Electronics Slide 40 THE END OF SLIDES Thank you!