doc.: IEEE /0439r1 Submission Author(s)/Supporter(s): NameCompanyAddressPhone Taghavi, Hossain Takahashi, Kazuaki Trachewsky, Jason Trainin, Solomon Usuki, Naoshi Varshney, Prabodh Vertenten, Bart Vlantis, George Wang, Chao-Chun Wang, Wang, James Wong, David Tung Chong Yee, James Yucek, Tevfik Yong, Su Khiong Zhang, Hongyuan Slide 5 May 2010 Hongyuan Zhang, Marvell, et. al.
doc.: IEEE /0439r1 Submission Proposal overview This presentation is part and is in support of the complete proposal described in /432r0 (slides) and /433r0 (text) that: –Supports data transmission rates up to 7 Gbps –Supplements and extends the MAC and is backward compatible with the IEEE standard –Enables both the low power and the high performance devices, guaranteeing interoperability and communication at gigabit rates –Supports beamforming, enabling robust communication at distances beyond 10 meters –Supports GCMP security and advanced power management –Supports coexistence with other 60GHz systems –Supports fast session transfer among 2.4GHz, 5GHz and 60GHz May 2010 Hongyuan Zhang, Marvell, et. al.Slide 6
doc.: IEEE /0439r1 Submission Overview 1: SC and OFDM Single Carrier (SC) vs. OFDM –In favor of OFDM Robustness in higher delay spread environments. Scalability—higher achievable throughput. –In favor of single carrier Low PAPR, efficient PA, lower power consumption (at low delay spread) Lower complexity. Dual-Mode PHY would be the best solution for TGad: –SC mainly targeted on low power applications with lower achievable throughput. –OFDM mainly targeted on high throughput applications. –SC and OFDM rates are defined in different MCSs in the same MCS table (starting from MCS1). A low rate common mode is necessary for any device to build up the beamformed links before transmitting regular higher rate SC/OFDM MCSs (refer to ). –Named as “Control MCS”, which is MCS0 (see next slide) SC and OFDM modulation details refer to . Slide 7 May 2010 Hongyuan Zhang, Marvell, et. al.
doc.: IEEE /0439r1 Submission Overview 2: Control MCS Beamforming is necessary in 60GHz systems , and Control MCS (MCS 0) is required for SC/OFDM/Dual-Mode devices to communicate with each other before setting up beamforming connections. Main usage of Control MCS: –Beacons –Beamforming training. Control MCS Design Aspects: –SNR sensitivity (or effective rate) targeted for ~15 dB lower than the sensitivity point of 1Gbps data rate (i.e. the beamforming gain). –Use single carrier with much lower rate. –Refer to . Slide 8 May 2010 Hongyuan Zhang, Marvell et. al.
doc.: IEEE /0439r1 Submission Common Preamble Introduction Preamble is the beginning part of a PPDU—used for packet detection, AGC, frequency/timing synchronizations, channel estimation, and signaling of PSDU modulation (SC/OFDM/CtrlMCS). Regular SC and OFDM MCSs share a common preamble: –Better support of the coexistence between various types of devices –Each device (especially Dual-Mode device) need implement only one packet detection/synchronization/channel estimation mechanism. –Appropriate auto-detection and re-sampling mechanism are required. Given that OFDM and SC Data portion uses different sampling rates. PPDU with Control MCS uses a longer preamble with similar design as SC/OFDM MCSs: –Target on lower SNR sensitivity. –Appropriate auto-detection between Control MCS and regular SC/OFDM preambles is needed. Slide 9 May 2010 Hongyuan Zhang, Marvell, et. al.
doc.: IEEE /0439r1 Submission I. Common Preamble for SC and OFDM PPDU and Common Preamble general frame formats: May 2010 Hongyuan Zhang, Marvell, et. al.Slide 10 PreambleHeaderPayload SC or OFDM Mod Short Training Field (STF)Channel Estimation Field (CEF) Preamble is composed by STF and CEF: –STF used for packet detection, AGC, frequency/timing synchronizations. –CEF used for channel estimation and SC/OFDM mode auto-detection. –Details see subsequent slides.
doc.: IEEE /0439r1 Submission Preamble Composed by Golay Complementary Sequences Preamble is composed by repeated 128-chip complimentary Golay sequences, denoted as G a128 /G b128. –G U512 /G V512/ /G V128 are composed by G a128 /G b128. –Golay sequence is used due to its good auto-correlation property, and simple correlator structure. Composed by adders and shifters, no complex number multipliers required. –Chip-level π/2-BPSK modulation achieve constant envelope with appropriate filter design. G a128 -G a128 STF, 15 periods (1920 chips) CEF, 1152 chips … G U512 G V128 G V512 G a128 Hongyuan Zhang, Marvell, et. al.Slide 11
doc.: IEEE /0439r1 Submission STF Packet detection, AGC convergence, frequency synchronization and timing synchronization need to be conducted through STF. –Appropriate symbol timing accuracy and frequency offset is required before entering channel estimations. 15 repetitions of G a128 is a good tradeoff between PPDU efficiency and preamble detection/synchronization sensitivity. –Preamble det/sync SNR sensitivity matches those for decoding Header, and Payload with MCS1. G a128 -G a128 STF, 15 periods (1920 chips) CEF, 1152 chips … G U512 G V128 G V512 G a128 Hongyuan Zhang, Marvell, et. al.Slide 12
doc.: IEEE /0439r1 Submission CEF G a128 -G a128 STF CEF G U512 G V512 … -G a128 G b128 -G a128 - G b128 G a128 - G b128 -G a128 - G b128 Gv 128 Postfix of G V512 Prefix of G U512 Prefix of G V512 Postfix of G U512 SC: OFDM: G a128 -G a128 STF CEF G U512 G V512 … G a128 -G b128 -G a128 - G b128 G a128 G b128 - G b128 G a128 - G b128 Gv 128 Postfix of G V512 Prefix of G U512 Prefix of G V512 Postfix of G U512 Hongyuan Zhang, Marvell, et. al.Slide 13
doc.: IEEE /0439r1 Submission CEF—Discussions Frame Delimiter can be realized by either detecting the sign flip at the end of STF, or detecting G U512 in CEF. G U512 /G V512 are a pair of Golay complementary sequences, and are composed by G a128 /G b128. G U512 /G V512 are with 128-chip cyclic prefix and postfix in an overlapping format. –Interference free time or frequency domain channel estimations can be realized. Zero side lobe of length 256 around the main tap. SC/OFDM Auto Detection. –Required for Header/Data processing. –Realized by swapping G U512 /G V512 sequences in SC and OFDM PPDUs. Hongyuan Zhang, Marvell, et. al.Slide 14
doc.: IEEE /0439r1 Submission Preamble Sampling The preamble defined above is based on SC chip rate (1760MHz ). OFDM Header and Data are sampled with clock rate 2640MHz (3/2 of SC clock) . Resampling of 3/2 is required for transmitting the common preamble in a OFDM modulated PPDU. –3x upsampling go through a resampling filter h filt 2x downsampling –The TGad spec needs to define h filt, so that receiver may recover the appropriate channel estimations. h filt with a frequency response satisfying the OFDM transmit mask. Hongyuan Zhang, Marvell, et. al.Slide 15
doc.: IEEE /0439r1 Submission II. Preamble for Control MCS Repeated G b128 in STF (v.s. G a128 in SC/OFDM preamble) for reliable auto-detection between Control MCS and regular SC/OFDM MCSs at low SNR. –Control MCS needs to conduct a sync process different from regular SC/OFDM, for lower SNR target and longer delay channels. Longer STF for lower SNR sensitivity target and longer delay channels. –40 periods is a good tradeoff between efficiency and preamble detection/synchronization sensitivity. –The preamble detection/sync SNR sensitivity matches that for decoding CP Header and Payload. CEF with the same format as in regular SC PPDU. May G b128 -G a128 STF, 40 periods (5120 chips) CEF, 1152 chips … G U512 G V128 G V512 G b128 Hongyuan Zhang, Marvell, et. al.Slide 16
doc.: IEEE /0439r1 Submission III. Golay Complementary Sequences (GCS) Length-128 GCS and length-512 GCS are chosen for STF and CEF respectively, for the best tradeoff among efficiency, correlation complexity, signal acquisition sensitivity (especially for low rate packets), and channel estimation quality (especially for high rate packets). Choosing the GCS: –Prefer to choose Golay Code G a128 with zero-DC after chip level π/2 rotation (i.e. the STF in regular SC/OFDM MCSs). –Prefer to choose GCP G a128 /G b128 with large zero correlation zone (e.g. 64 taps) around the main tap. –Delay units D n are chosen to minimize the memory size. –The GCP : D 7 = [ ], W 7 = [ ]. Hongyuan Zhang, Marvell, et. al.Slide 17
doc.: IEEE /0439r1 Submission Shorter GCS Choices A G a64 code is needed for the GI insertions in SC MCSs ; and a G a32 code is needed for data spreading in the Control MCS . Choosing the shorter GCS: –Use a subset of the delay vector D (reuse correlator hardware), with different coefficient W vectors. To get G a64, D 6 = [ ], W 6 = [ ]. To get G a32, D 5 = [ ], W 5 = [ ]. –Guarantees good correlation properties between preamble and shorter GCS codes in SC data portion. Hongyuan Zhang, Marvell, et. al.Slide 18
doc.: IEEE /0439r1 Submission STF Cross-Correlations (AWGN) Regular SC/OFDM STF Xcorr with G a128: Ctrl MCS STF Xcorr with G b128: Hongyuan Zhang, Marvell, et. al.
doc.: IEEE /0439r1 Submission CEF Cross-Correlations SC CEF Xcorr with G u512: SC CEF Xcorr with Gv 512: Example CE Output (256 taps) Hongyuan Zhang, Marvell, et. al.
doc.: IEEE /0439r1 Submission Conclusions A Common preamble proposed for different PHY modes. –SC and OFDM MCSs share the same preamble structure. –Control MCS uses a longer preamble with similar STF and CEF structures. Complementary Golay spreading codes are applied in preamble to simplify receiver processing. Appropriate auto-detection among different modes are also proposed. May 2010 Hongyuan Zhang, Marvell, et. al.Slide 21