1. IEEE 802.11n PHY Motorola HT Partial Proposal
Month 2002
doc.: IEEE /xxxr0
September 2004
IEEE n 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

2. 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

3. Overall goal of the proposed PHY design
Month 2002
doc.: IEEE /xxxr0
September 2004
Overall goal of the proposed PHY design
Modification of IEEE a-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

4. 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

5. 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 a convolutional code with code rates 1/2, 2/3, 3/4 and 5/6

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

7. 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

8. 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

9. 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.)

10. 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

11. 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

12. 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)

13. 2 transmit antenna schemes proposed
September 2004
2 transmit antenna schemes proposed
3 transmit antenna schemes proposed
4 transmit antenna schemes proposed

14. 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

15. Mode: 2-TX 48 carriers 20MHz Mode: 2-TX 104 carriers 20MHz Month 2002
doc.: IEEE /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

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

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

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

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

20. 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

21. nPLCP preamble (I/2)
September 2004

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

23. 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

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

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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)

36. 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

37. 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

38. 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

39. Implementation complexity
September 2004
Implementation complexity

40. 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

41. September 2004
Thank you !