Sept 2003 doc IEEE 15 03 0337 01

Sept 2003 doc. : IEEE 15 -03 -0337 -01 -003 a Project: IEEE P 802. 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 Company: Sony Corporation Address: 6 -7 -35 Kitashinagawa Shinagawa-ku, Tokyo. Japan 141 -0001 Voice: +81 -3 -6409 -3201, FAX: +81 -3 -6409 -3203 E-Mail: suzuki@wcs. sony. co. jp, chihiro@ wcs. sony. co. jp, yotuya@ wcs. sony. co. jp, takamura@wcs. sony. co. jp, usui@ wcs. sony. co. jp Bob Huang Sony Electronics of America One Sony Drive TA-1 Park Ridge, NJ 07656 V: 201 -358 -4409 F: 201 -930 -6397 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 P 802. 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 P 802. 15. Submission Slide 1 Suzuki, et al, Sony Corp. , Sony Electronics

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

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a 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 Submission Slide 3 Suzuki, et al, Sony Corp. , Sony Electronics

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

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a Clocking Transmission Mechanism Define clocking period T which is longer than 2 x(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 2 x(Propagation delay) Submission Slide 5 Suzuki, et al, Sony Corp. , Sony Electronics

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a 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. Submission Slide 6 Suzuki, et al, Sony Corp. , Sony Electronics

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

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a 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]). Submission Slide 8 Suzuki, et al, Sony Corp. , Sony Electronics

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a Solution for increase measured bandwidth 1. Define reference time of t 0 during the burst. ( It is the best that t 0 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 t 0 of Tx and t’ 0 of Rx exists. ) Submission Slide 9 Suzuki, et al, Sony Corp. , Sony Electronics

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a 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] Submission Slide 10 Suzuki, et al, Sony Corp. , Sony Electronics

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

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

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a 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. Submission Slide 13 Suzuki, et al, Sony Corp. , Sony Electronics

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a 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. Submission Slide 14 Suzuki, et al, Sony Corp. , Sony Electronics

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

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

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

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a Modification of Tx Preamble ( original preamble ) force to set amplitude = 0 force to set amplitude = 1 keeping phase information 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. Modified power spectrum Submission Slide 18 Suzuki, et al, Sony Corp. , Sony Electronics

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

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a 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. Submission Slide 20 Suzuki, et al, Sony Corp. , Sony Electronics

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

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

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

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

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

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

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

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

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

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

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a Coding scheme Decoder power consumption can not be neglected. Decoding latency is not so critical in payload part. K = 7 convolutional coding (current ) low latency, but high power consumption not so good BER/PER 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 Submission Slide 31 Suzuki, et al, Sony Corp. , Sony Electronics

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

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

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

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a 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. Submission Slide 35 Suzuki, et al, Sony Corp. , Sony Electronics

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a 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. Submission Slide 36 Suzuki, et al, Sony Corp. , Sony Electronics

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

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a Conclusion for tracking using pilot More precise timing error detection by using many (122) subcarrier information. (current number of pilot symbol is 12) 0. 5[d. B] (=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. ) Submission Slide 38 Suzuki, et al, Sony Corp. , Sony Electronics

Sept. 2003 doc. : IEEE 15 -03 -0337 -01 -003 a 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 Submission Slide 39 Suzuki, et al, Sony Corp. , Sony Electronics

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