6May 2010Proposal overviewThis 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 GbpsSupplements and extends the MAC and is backward compatible with the IEEE standardEnables both the low power and the high performance devices, guaranteeing interoperability and communication at gigabit ratesSupports beamforming, enabling robust communication at distances beyond 10 metersSupports GCMP security and advanced power managementSupports coexistence with other 60GHz systemsSupports fast session transfer among 2.4GHz, 5GHz and 60GHzHongyuan Zhang, Marvell, et. al.
7Overview 1: SC and OFDM May 2010 Single Carrier (SC) vs. OFDM In favor of OFDMRobustness in higher delay spread environments.Scalability—higher achievable throughput.In favor of single carrierLow 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 7Hongyuan Zhang, Marvell, et. al.
8May 2010Overview 2: Control MCSBeamforming 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:BeaconsBeamforming 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 8Hongyuan Zhang, Marvell et. al.
9Common Preamble Introduction May 2010Common Preamble IntroductionPreamble 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 devicesEach 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 9Hongyuan Zhang, Marvell, et. al.
10I. Common Preamble for SC and OFDM May 2010I. Common Preamble for SC and OFDMPPDU and Common Preamble general frame formats:PreambleHeaderPayloadSC or OFDM ModShort 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.Slide 10Hongyuan Zhang, Marvell, et. al.
11Preamble Composed by Golay Complementary Sequences Ga128Ga128Ga128…Ga128Ga128-Ga128GU512GV512GV128STF, 15 periods (1920 chips)CEF, 1152 chipsPreamble is composed by repeated 128-chip complimentary Golay sequences, denoted as Ga128/Gb128.GU512/GV512//GV128 are composed by Ga128/Gb128.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.Slide 11Hongyuan Zhang, Marvell, et. al.
12STFGa128Ga128Ga128…Ga128Ga128-Ga128GU512GV512GV128STF, 15 periods (1920 chips)CEF, 1152 chipsPacket 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 Ga128 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.Slide 12Hongyuan Zhang, Marvell, et. al.
13CEF -Gb128 Gv128 GU512 GV512 -Gb128 Gv128 GU512 GV512 SC: Ga128 -Gb128 STFCEF…Ga128-Ga128-Gb128-Ga128Gb128-Ga128-Gb128Ga128-Gb128-Ga128-Gb128Gv128Postfix of GV512GU512Prefix of GU512GV512Prefix of GV512Postfix of GU512OFDM:STFCEF…Ga128-Ga128-Gb128Ga128-Gb128-Ga128-Gb128Ga128Gb128Ga128-Gb128Gv128Postfix of GV512GU512Prefix of GU512GV512Prefix of GV512Postfix of GU512Slide 13Hongyuan Zhang, Marvell, et. al.
14CEF—Discussions Zero side lobe of length 256 around the main tap. Frame Delimiter can be realized by either detecting the sign flip at the end of STF, or detecting GU512 in CEF.GU512/GV512 are a pair of Golay complementary sequences, and are composed by Ga128/Gb128.GU512/GV512 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 GU512/GV512 sequences in SC and OFDM PPDUs.Slide 14Hongyuan Zhang, Marvell, et. al.
15Preamble SamplingThe 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 hfilt 2x downsamplingThe TGad spec needs to define hfilt, so that receiver may recover the appropriate channel estimations.hfilt with a frequency response satisfying the OFDM transmit mask.Slide 15Hongyuan Zhang, Marvell, et. al.
16II. Preamble for Control MCS May 2010II. Preamble for Control MCSGb128Gb128Gb128…Gb128-Gb128-Ga128GU512GV512GV128STF, 40 periods (5120 chips)CEF, 1152 chipsRepeated Gb128 in STF (v.s. Ga128 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.Slide 16Hongyuan Zhang, Marvell, et. al.
17III. 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 Ga128 with zero-DC after chip level π/2 rotation (i.e. the STF in regular SC/OFDM MCSs).Prefer to choose GCP Ga128/Gb128 with large zero correlation zone (e.g. 64 taps) around the main tap.Delay units Dn are chosen to minimize the memory size.The GCP :D7 = [ ], W7 = [ ].Slide 17Hongyuan Zhang, Marvell, et. al.
18Shorter GCS ChoicesA Ga64 code is needed for the GI insertions in SC MCSs ; and a Ga32 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 Ga64, D6 = [ ], W6 = [ ].To get Ga32, D5 = [ ], W5 = [ ].Guarantees good correlation properties between preamble and shorter GCS codes in SC data portion.Slide 18Hongyuan Zhang, Marvell, et. al.
19STF Cross-Correlations (AWGN) Regular SC/OFDM STF Xcorr with Ga128:Ctrl MCS STF Xcorr with Gb128:Hongyuan Zhang, Marvell, et. al.
20CEF Cross-Correlations (SC@AWGN) SC CEF Xcorr with Gu512:Example CE Output (256 taps)SC CEF Xcorr with Gv512:Hongyuan Zhang, Marvell, et. al.
21Conclusions A Common preamble proposed for different PHY modes. May 2010ConclusionsA 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.Slide 21Hongyuan Zhang, Marvell, et. al.