IEEE 802.11n PHY Motorola HT Partial Proposal Month 2002 doc.: IEEE 802.11-02/xxxr0 September 2004 IEEE 802.11n PHY Motorola HT Partial Proposal Alexandre Ribeiro Dias, Stéphanie Rouquette-Léveil, Markus Muck, Marc de Courville, Jean-Noël Patillon, Sébastien Simoens, Karine Gosse, Keith Blankenship, Brian Classon Motorola Labs

Overview Overall goal and key features of proposal September 2004 Overview Overall goal and key features of proposal Multiple-Antenna schemes OFDM modulator and data rates Preamble definitions Simulation results Hardware complexity estimation

Overall goal of the proposed PHY design Month 2002 doc.: IEEE 802.11-02/xxxr0 September 2004 Overall goal of the proposed PHY design Modification of IEEE 802.11a-1999 PHY in order to provide new OFDM PHY modes meeting the IEEE802.11n PAR with: High spectrum efficiency for achieving target performance with increased data rates Data streams transmitted in parallel using multi-antenna transceivers Optimized multi-carrier modulation with lower overhead Enhanced forward error correction schemes Improved link budget for lower to medium data rates Providing the IEEE802.11a PHY data rates with increased range/link quality Adapted to the support of services requiring small packet size such as VoIP Exploit multi-antenna capabilities for robust transmission modes Turn gains in spectral efficiency into link budget advantages Favored short term implementation and deployment with robust, low complexity techniques Open-loop multi-antenna solutions: simple, robust and without protocol overhead (feedback signalization) Improve operation in limited Outdoor environments with support of long channel impulse responses

Key features (1/2) Multi-antenna extension: September 2004 Key features (1/2) Multi-antenna extension: MIMO with at least 2Tx/2Rx antennas scaling up to 4Tx Support for asymmetric antenna configurations to accomodate various classes of devices Open-loop modulation technique Second OFDM modulator (optional): 2 bandwidths supported: 20MHz and 40MHz Optionally 128 carriers in 20/40MHz with 104 data carriers, and guard interval of 32 samples 8% PHY rate increase for 20MHz mode 117% PHY rate increase for 40MHz mode vs 20MHz/64-carriers Turbo Codes: Increase roubustness

September 2004 Key features (2/2) New nPLCP preambles for MIMO support (same for 64- and 128-point IFFT/FFT) High order modulation (optional): 256-QAM Space/frequency interleaver Compatibility to legacy systems: IEEE 802.11a convolutional code with code rates 1/2, 2/3, 3/4 and 5/6

Turbo Codes: Motivation September 2004 Turbo Codes: Motivation Stable, well-understood technology Good performance Block size and code rate flexibility Padding can be used to reduce number of interleavers Puncturing patterns simple to describe and implement Incremental redundancy procedures easily defined Highly parallelizable “parallel window” decoder architecture Easily scaled to meet latency requirements Motorola 2048-bit information block implementation benchmark of 10ms per iteration on 2001-era FPGA scales to 1.25ms per iteration on current technology ASIC with clock rate increase and window size decrease Interleavers can be parallelized to avoid memory contentions without performance penalty Known intellectual property landscape

Coding Functional Description September 2004 Scrambling before padding insertion Before decoding, receiver may insert large LLRs at known locations Padding Inserts minimum number of zeros to make block size multiple of 512 bits Zeros are inserted uniformly across the SERVICE+PSDU at the ends of 256-bit sub-blocks Turbo interleaver maps padding to odd-numbered positions in second encoder Segmentation Breaks padded sequence into 2048-bit segments plus at most one segment of length 512, 1024, or 1536 bits

Turbo Encoder Rate-1/3 3G turbo code polynomials September 2004 Turbo Encoder Rate-1/3 3G turbo code polynomials Code rates 2/3, 2/3, 3/4, and 5/6 can be achieved exactly through puncturing Contention-free turbo interleavers Performance nearly identical to WCDMA down to 10-4 frame error rates Constituent encoders left unterminated Helps preserve exact code rate Negligible performance degradation

Contention-Free Interleavers September 2004 Contention-Free Interleavers Inter-window shuffle (IWS) interleaver i = output position p(i) = input position r() = bit reversal intra-window permutation (same for all windows) j(j) = {j0(j),j1(j),,jM-1(j)} = j-th permutation of {0,1,,M-1} (periodic) M = number of windows (2,4,6,8 for block size 512,1024,1536,2048, resp.)

Non-Termination Performance September 2004 Non-Termination Performance 8-th iteration static binary channel FER with IWS interleavers (no tail compared with full 12-bit tail) Non-termination helps preserve exact code rate with negligible performance impact 512-bit block 2048-bit block

September 2004 Padding Removal To preserve code rate, all padding bits and associated parity bits (i.e., on same trellis step) are removed prior to puncturing removed padding

Multi-antenna aspects of the proposal September 2004 Multi-antenna aspects of the proposal Transmission of 1, 2 or 3 parallel streams using: Space-Time Block Coding (STBC), Spatial Division Multiplexing (SDM) or robust hybrid solutions (STBC/SDM) optimize the rate vs link budget trade-off 2, 3 or 4 transmit antennas The number of receive antennas determines the maximum number of spatial streams that can be transmitted. The capability of decoding 2 parallel data streams is mandatory all the devices have to be able to decode all the modes where the number of spatial streams is lower or equal than the number of receive antennas in the device. It is required for a device to exploit all its antennas in transmission even for optional modes. 2 or more receive antennas With STBC or STBC/SDM, asymmetric antenna configurations can be supported Importance of configurations in which NTx ≠ NRx NTx > NRx e.g. between AP and mobile handset (in DL) NTx < NRx e.g. between MT and AP (UL), or if MT have upgraded multi-antenna capabilities compared to AP (infrastructure upgrade cost)

2 transmit antenna schemes proposed September 2004 2 transmit antenna schemes proposed 3 transmit antenna schemes proposed 4 transmit antenna schemes proposed

OFDM modulation 1st OFDM modulation based on IEEE802.11a parameters: September 2004 OFDM modulation 1st OFDM modulation based on IEEE802.11a parameters: 48 data subcarriers, 64-point IFFT/FFT, 20MHz Bandwidth 180Mbps maximum PHY rate (120Mbps mandatory) 2nd OFDM modulation (optional extension): 104 data subcarriers, 128-point IFFT/FFT, 8 pilots, 20MHz Bandwidth  195Mbps maximum PHY rate 3rd OFDM modulation (optional extension): 128-point IFFT/FFT, 40MHz Bandwidth 104 data subcarriers, 8 pilots Guard interval duration: 0.8s 234Mbps maximum PHY rate

Mode: 2-TX 48 carriers 20MHz Mode: 2-TX 104 carriers 20MHz Month 2002 doc.: IEEE 802.11-02/xxxr0 September 2004 288 384 8 3/4 256QAM 2 144Mbps 240 6 5/6 64QAM 120Mbps 216 108Mbps 192 2/3 96Mbps 144 4 16QAM 72Mbps 1 60Mbps 48Mbps 36Mbps 96 1/2 24Mbps 72 QPSK 18Mbps 48 12Mbps 24 BPSK 6Mbps Data bits/ symbol (NDBPS) Coded bits/ symbol (NCBPS) Coded bits per subcarrier per stream (NBPSC) Coding rate (R) Modulation Number of spatial streams (NS) Data rate (Mbits/s) Mode: 2-TX 48 carriers 20MHz 624 832 8 3/4 256QAM 2 156Mbps 520 6 5/6 64QAM 130Mbps 468 117Mbps 416 2/3 104Mbps 312 4 16QAM 78Mbps 1 65Mbps 52Mbps 39Mbps 208 1/2 26Mbps 156 QPSK 19.5Mbps 104 13Mbps 52 BPSK 6.5Mbps Data bits/ symbol (NDBPS) Coded bits/ symbol (NCBPS) Coded bits per subcarrier per stream (NBPSC) Coding rate (R) Modulation Number of spatial streams (NS) Data rate (Mbits/s) Mode: 2-TX 104 carriers 20MHz

Mode: 3/4-TX 48 carriers 20MHz Month 2002 doc.: IEEE 802.11-02/xxxr0 September 2004 Mode: 2-TX 104 carriers 40MHz Mode: 3/4-TX 48 carriers 20MHz

Mode: 3/4-TX 104 carriers 20MHz Month 2002 doc.: IEEE 802.11-02/xxxr0 September 2004 Mode: 3/4-TX 104 carriers 20MHz Mode: 3/4-TX 104 carriers 40MHz

OFDM Parameters Overview (I/2) September 2004 OFDM Parameters Overview (I/2) 20MHz 48 Carriers 20MHz 104 Carriers

OFDM Parameters Overview (II/2) September 2004 OFDM Parameters Overview (II/2) 40MHz 104 Carriers

Frequency and space interleaver September 2004 Frequency and space interleaver IEEE802.11a based frequency interleaver defined for both 48 and 104 data subcarriers Spatial division: NSD : number of data subcarriers

nPLCP preamble (I/2) September 2004

nPLCP preamble (II/2) Overview on different frame structures: September 2004 nPLCP preamble (II/2) Overview on different frame structures:

September 2004 Simulation results AWGN, TGnB, TGnD, TGnE channel comparisons for 20MHz Bandwidth Essential points Throughput increase with optional modes (FFT-128) at constant SNR requirements in AWGN channels Robust modes based on STBC for good coverage and support of asymetric configurations Unilateral modification of number of antennas in TX and RX can be exploited  Useful for independent evolution of AP/MT

Simulation results - AWGN September 2004  2TX/2RX to 4TX/4RX configuration and SNR ~21dB: 120Mbps  180Mbps (130Mbps  195Mbps)

Simulation results - TGnB September 2004 XXX  42dB  34dB 180 10dB  7dB  6dB 12 20dB  16dB  14dB 48 32dB  24dB  21dB 96 36dB  28dB  24.5dB 120 SNR for PER=10-1 Mode/ Mbps Diversity gain for all streams 120 Mbps lowers SNR ~ 36dB  28dB  24.5dB

Simulation results - TGnB September 2004 For new schemes: Same behaviour is observed for diversity modes as for classical schemes Clear improvements for 2 streams from 2x2  3x3 mode Clear improvements for 3 streams from 2x2/3x3  4x4 mode

Simulation results - TGnB September 2004 26.5dB 120 5dB 12 16dB 48 24dB 96 SNR for PER=10-1 Mode/Mbps 31.5dB 120 11dB 12 20dB 48 28dB 96 SNR for PER=10-1 Mode/Mbps # TX antennas < # RX antennas  e.g. Update of MT # TX antennas > # RX antennas  e.g. Update of AP

PHY Throughput Analysis – TGnB September 2004 Link adaptation is based on long term average SNR  sub-optimum  inferior bound Finer grid possible with more modes

Simulation results - TGnD September 2004 XXX  36dB  29dB 180 (effect) 180 5dB  4.5dB  3.5dB 12 18dB  14dB  11dB 48 27.5dB  21dB  19dB 96 35dB  25.5dB  23dB 120 SNR for PER=10-1 Mode/ Mbps Diversity gain for all streams 120 Mbps lowers SNR ~ 35dB  25.5dB  23dB

Simulation results - TGnD September 2004 24dB 120 2dB 12 14.5dB 48 20dB 96 SNR for PER=10-1 Mode/Mbps 30dB 120 7dB 12 17dB 48 25.5dB 96 SNR for PER=10-1 Mode/Mbps # TX antennas < # RX antennas  e.g. Update of MT # TX antennas > # RX antennas  e.g. Update of AP

PHY Throughput Analysis – TGnD September 2004 Link adaptation is based on long term average SNR  sub-optimum  inferior bound Finer grid possible with more modes

Simulation results - TGnE September 2004 XXX  43dB  31dB 180 7dB  5dB  4dB 12 19dB  15dB  12dB 48 30dB  22.5dB  20dB 96 37dB  26.5dB  24dB 120 SNR for PER=10-1 Mode/ Mbps Diversity gain for all streams 120 Mbps lowers SNR ~ 37dB  26.5dB  24dB

Simulation results - TGnE September 2004 25dB 120 4dB 12 15dB 48 21.5dB 96 SNR for PER=10-1 Mode/Mbps 31.5dB 120 9dB 12 18dB 48 26.5dB 96 SNR for PER=10-1 Mode/Mbps # TX antennas < # RX antennas  e.g. Update of MT # TX antennas > # RX antennas  e.g. Update of AP

PHY Throughput Analysis – TGnE September 2004 Link adaptation is based on long term average SNR  sub-optimum  inferior bound Finer grid possible with more modes

Simulation results – TGnD/TGnE September 2004 Similar to TGnB: 2Tx: Diversity gain for 1 stream, but not for 2 streams 120 Mbps requires SNR ~ 35dB (TGnD) 37dB (TGnE) 3Tx: Diversity gain for 2 streams, but not for 3 streams 120 Mbps lowers SNR: ~ 36dB  26dB (TGnD) ~ 37dB  26.5dB (TGnE) 4Tx: Diversity gain for all streams 120 Mbps lowers SNR ~ 36dB  26dB  23dB (TGnD) ~ 37dB  26.5dB  24dB (TGnD)

Simulation results – Offset compensation September 2004 Simulation results – Offset compensation No significant impact at 10% PER in channel E (NLOS) Figure 42 - Offset impact in 4x4 antenna configuration

Simulation results – Offset compensation September 2004 Simulation results – Offset compensation Antenna configuration Data rate (Mbits/s) PER when carrier offset = -40ppm carrier offset = 0ppm carrier offset =+40ppm 2x2 12Mbps 0.0003 0.0002 48Mbps 0.0016 0.0018 96Mbps 0.0039 0.0037 0.0042 120Mbps 0.0297 0.0183 0.0298 Impact of carrier frequency offset and symbol clock offset at SNR=50dB in channel E (LOS): Small degradation of the PER performance High data rate modes are more impacted: PER (+40ppm) = 112/100xPER (0ppm) at 48Mbps PER (+40ppm) = 163/100xPER (0ppm) at 120Mbps Figure 42 - Offset impact in 4x4 antenna configuration

Simulation results – Offset compensation September 2004 Simulation results – Offset compensation Antenna configuration Data rate (Mbits/s) PER when carrier offset = -40ppm carrier offset = 0ppm carrier offset =+40ppm 3x3 12Mbps 0.0002 0.0001 ~0 48Mbps 0.0006 0.0005 96Mbps 0.0041 0.0043 120Mbps 0.0045 0.0050 180Mbps 0.0963 0.0617 0.0974 Antenna configuration Data rate (Mbits/s) PER when carrier offset = -40ppm carrier offset = 0ppm carrier offset =+40ppm 4x4 12Mbps ~0 48Mbps 0.0001 96Mbps 0.0016 0.0019 120Mbps 0.0021 0.0022 180Mbps 0.0023 0.0024 0.0029 High data rate modes are less impacted if spatial diversity: 3x3: PER (+40ppm) = 158/100xPER (0ppm) at 180Mbps 4x4: PER (+40ppm) = 121/100xPER (0ppm) at 180Mbps Figure 42 - Offset impact in 4x4 antenna configuration

Implementation complexity September 2004 Implementation complexity

Conclusion Proposal: MIMO extension of IEEE802.11a addressing September 2004 Conclusion Proposal: MIMO extension of IEEE802.11a addressing Short term implementation needs through mandatory modes relying on a mix of STBC and SDM Take into account device size constraints allowing asymmetric TX/TX antenna configuration  independent upgrade of APs / MTs possible Enable PHY throughput covering 54Mbits/s  180 (468) Mbps

September 2004 Thank you !