1. WWiSE IEEE 802.11n Proposal Authors: Date: 2005-01-06
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Sean Coffey, Texas Instruments, et al.

2. Authors, contd:
Sean Coffey, Texas Instruments, et al.

3. Abstract The presentation summarizes the WWiSE complete proposal:
Recap of proposal features
Updates since last meeting
Performance and comparisons with other proposals
New technical supporting data on several aspects of the WWiSE design
Sean Coffey, Texas Instruments, et al.

4. The WWiSE approach WWiSE = World Wide Spectrum Efficiency
The partnership was formed to develop a specification for next generation WLAN technology suitable for worldwide deployment
Mandatory modes of the WWiSE proposal comply with current requirements in all major regulatory domains: Europe, Asia, Americas
Proposal design emphasizes compatibility with existing installed base, building on experience with interoperability in g and previous amendments
All modes are compatible with QoS and e
Maximal spectral efficiency translates to highest performance and throughput in all modes
Sean Coffey, Texas Instruments, et al.

5. Summary of proposal features
WWiSE proposes 2 transmitters in 20 MHz mandatory
Rates 54, 81, 108, 121.5, 135 Mbps
Optional 40 MHz counterparts of all 20 MHz modes
Optional extensions to 3 and 4 transmit antennas
Optional space-time block codes for longer range
Optional LDPC code
MAC: HTP burst, aggregation, extended Block Ack
See r3 & r4 for a full description
Sean Coffey, Texas Instruments, et al.

6. Unified format 1/2 800 BCC, LDPC 16-QAM 3/4 2/3 64-QAM 5/6 Code rate
Cyclic prefix, ns
Code
Constellation
1/2
800
BCC, LDPC
16-QAM
3/4
2/3
64-QAM
5/6
All combinations of 2, 3, 4 transmit antennas and 20/40 MHz offer exactly these 5 modes
All 20 MHz modes have 54 data subcarriers, 2 pilots. All 40 MHz modes have 108 data subcarriers, 4 pilots
Sean Coffey, Texas Instruments, et al.

7. 2 transmitter SDM, 20 MHz (mandatory)
PHY rate
Data carriers
Pilots
Code rate
Cyclic prefix, ns
Code
Constellation
54 Mbps 54 2
1/2
800
BCC
16-QAM
81 Mbps
3/4
108 Mbps
2/3
64-QAM
121.5 Mbps
135 Mbps
5/6
Sean Coffey, Texas Instruments, et al.

8. Optional data modes 20 MHz: 3 Tx space-division multiplexing
40 MHz: (all 40 MHz modes optional)
1 Tx antenna
2 Tx space division multiplexing
3 Tx space division multiplexing
Space-time block codes: (all STBCs optional)
2x1, 3x2, 4x2, 4x3 in 20 MHz and 40 MHz
LDPC code option
Optional in all MIMO configurations and channel bandwidths
Sean Coffey, Texas Instruments, et al.

9. Optional mode data rates, multiple spatial streams
20 MHz:
Configuration
Rate ½, 16-QAM
Rate ¾, 16-QAM
Rate 2/3, 64-QAM
Rate ¾, 64-QAM
Rate 5/6, 64-QAM
3 Tx, 20 MHz 81
121.5
162
182.25
202.5
4 Tx, 20 MHz
108
216
243
270
40 MHz:
Configuration
Rate ½, 16-QAM
Rate ¾, 16-QAM
Rate 2/3, 64-QAM
Rate ¾, 64-QAM
Rate 5/6, 64-QAM
2 Tx, 40 MHz
108
162
216
243
270
3 Tx, 40 MHz
324
364.5
405
4 Tx, 40 MHz
364
432
486
540
Sean Coffey, Texas Instruments, et al.

10. Optional mode data rates, single spatial stream
2x1, 20 MHz:
1x1, 40 MHz; 2x1, 40 MHz
PHY rate, Mbps
Code rate
Constellation
6.75
1/2
BPSK
10.125
3/4
13.5
QPSK
20.25 27
16-QAM
40.5 54
2/3
64-QAM
60.75
67.5
5/6
PHY rate, Mbps
Code rate
Constellation
13.5
1/2
BPSK
20.25
3/4 27
QPSK 41 54
16-QAM 81
108
2/3
64-QAM
121.5
135
5/6
Sean Coffey, Texas Instruments, et al.

11. Update Information exchange mechanism added Rate & mode recommendation
Channel state information
10 MHz channelization supported
All 20 MHz modes have a ½-data rate 10 MHz counterpart
ZIFS (zero interframe space) mode deleted
HTP Burst already allows this in effect
Sean Coffey, Texas Instruments, et al.

12. Performance & comparisons
Sean Coffey, Texas Instruments, et al.

13. The context within the task group
Common points across the complete proposals:
2 transmitter space-division multiplexing MIMO-OFDM
20 MHz
Open loop
Varying evolutions to the ag OFDM format
Data rates significantly in excess of 2x54 Mbps
Aggregation of varying kinds
Block acknowledgements
Sean Coffey, Texas Instruments, et al.

14. “Scalable Architecture across several dimensions” (adapted from 11-04-0888r3/slide 5 [TGnSync])
Market segments
“The same HT technology able to function in all markets and environments”
- Wi-Fi Alliance MRD, Nov.’03 PC
Enterprise
Consumer Electronics
Public Access
Handset
WWiSE rates; applicable in all listed market segments
135Mbps
270Mbps
540Mbps
Perf.
over
time
140Mbps
315Mbps
630Mbps
10MHz (.11j/p)
20MHz
In WWiSE; unified format means exact match of offerings across bandwidths
Regulatory Domains
40MHz
Sean Coffey, Texas Instruments, et al.

15. “… And a well-defined Core” (adapted from 11-04-0888r3/slide 6 [TGnSync])
Market segments
Mandatory WWiSE features:
Two antennas
20 MHz
135 Mbps
Mandatory Features:
Two antennas
20MHz
140 Mbps
(TGnSync)
Perf .
over
time
Regulatory Domains
Sean Coffey, Texas Instruments, et al.

16. Comparisons & contrasts
Robustness:
Although the data rates are similar, WWiSE and TGnSync use quite different ag modifications
Different MIMO interleavers (in all channel bandwidths)
Different FEC code rate (5/6 in WWiSE, 7/8 in TGnSync)
Cyclic prefix: TGnSync uses a short cyclic prefix to reach the highest rates; WWiSE uses the regular cyclic prefix in all modes
Tone usage (20 MHz only): WWiSE uses 56 tones (54 data, 2 pilots); TGnSync uses 52 tones (48 data, 4 pilots)
Sean Coffey, Texas Instruments, et al.

17. Comparisons & contrasts, contd.
Different MIMO interleavers:
The WWiSE MIMO interleaver design appears to outperform the TGnSync design by 1 dB or more
The complexities are virtually identical
This gives better WWiSE performance in all channel bandwidths at no cost
Different FEC code rate:
No significant ASIC implementation complexity difference
Significant robustness difference: rate 5/6 to rate 7/8 costs approx. 2 dB
Sean Coffey, Texas Instruments, et al.

18. Comparison & contrasts, contd.
Cyclic prefix:
Shortening the cyclic prefix reduces resistance to multipath.
It is not clear that this mode works at all in an enterprise environment
Per TGnSync specification,
Tone usage:
56 tone OFDM symbols fit existing ag spectral mask
See r3 and r4 for experimental results
Adjacent Channel Interference: there is no significant difference between 52-tone and 56-tone OFDM symbols
See new information in r0
Pilot tones: 2 pilots with 2 receive antennas provides the same or better tracking performance as legacy ag
See r4
Sean Coffey, Texas Instruments, et al.

19. Comparisons & contrasts, contd.
Simplicity & scalability:
The sets of modes are substantially different in the two proposals
WWiSE has a single unified format in all multi-antenna configurations and channel bandwidths
Does not require new technology in new applications
Eases development, testing, interoperability, rate selection
E.g., the top rate 540 Mbps mode = 135 Mbps x 2 x 2
Space-time block codes fit in a modular way on top of existing modes
Offers longer range and/or support for lower cost clients; supports asymmetric configurations with more antennas at AP, fewer at STA
Modular design means this capability fits seamlessly with the entire proposal
Sean Coffey, Texas Instruments, et al.

20. Comparisons & contrasts, contd.
Simplicity & scalability, contd:
FEC design:
The WWiSE proposal parallelizes the BCC format in the most demanding configurations (3 or 4 spatial streams in 40 MHz)
This eases constraints on receiver design substantially
Otherwise very high system clock speeds are required, or else a substantial redesign of the decoder
The optional LDPC code has block size that is matched to the OFDM structure in all bandwidths
Minimizes efficiency loss due to pad bits
Sean Coffey, Texas Instruments, et al.

21. Interleaver comparison with TGnSync
Both schemes have 2x2, 64-QAM, rate 3/4
WWiSE: Mbps
TGnSync: 108 Mbps
WWiSE interleaver has an advantage of 1.25 dB at 2% PER
Sean Coffey, Texas Instruments, et al.

22. 108 Mbps modes comparison, WWiSE and TGnSync
Both schemes are 108 Mbps
WWiSE: rate 2/3
TGnSync: rate 3/4
WWiSE interleaver has an advantage of 3.75 dB at 2% PER
Sean Coffey, Texas Instruments, et al.

23. Pending comparisons, modes & interleavers
WWiSE 135 Mbps vs. TGnSync 126 Mbps
2x2 rate 5/6 with WWiSE interleaver vs. 2x2 rate 7/8 with TGnSync interleaver
WWiSE 135 Mbps vs. TGnSync 144 Mbps
2x2 rate 5/6 64-QAM vs. 2x2 rate 3/4 256-QAM
WWiSE 243 Mbps vs. TGnSync MHz; WWiSE 108 Mbps vs. TGnSync MHz
Different interleavers
Sean Coffey, Texas Instruments, et al.

24. New technical information - I
Adjacent channel interference:
r0, “Adjacent channel interference and filtering for 56-carrier signals,” Dave Hedberg.
Requirements for Tx and Rx filtering for the 56 carrier WWiSE signals do not increase complexity significantly e.g. anti-aliasing filters do not need to change
With “conservative” filter examples shown, WWiSE PER simulations show several dB of ACR/AACR margin for 20 MHz HT MIMO modes relative to .11a/g 54 Mbps levels
The added dispersion due to required narrower filter transition band does not significantly impact channel performance
Sean Coffey, Texas Instruments, et al.

25. New technical information - II
Short training sequence experimental results:
r0, “Short training sequence compatibility with legacy g devices,” Tushar Moorti, Christopher Young, Chris Hansen.
Analytical results show that 400 nsec shift provides best power estimation accuracy
Laboratory results show that 400 nsec shift provides the best legacy protection
Backward compatible MIMO preambles based on a 400 nsec cyclic shift on the 2nd antenna (2 TX case) are appropriate for n
Sean Coffey, Texas Instruments, et al.

26. New technical information - III
AGC impact of preamble design:
r0, “AGC power variations with WWiSE cyclic preamble structures,” Dave Hedberg, Mark Webster, Michael Seals.
The relatively long cyclic shifts employed in the WWiSE Greenfield preambles result in well behaved AGC power statistics
The AGC power statistics for mixed mode receptions of 11n signals are the same as for Greenfield modes – since the STS portion of the two preamble types is the same
The legacy portion of mixed mode preambles employ shorter cyclic shifts for the legacy LTS/SF portion – and consequently exhibit larger variation – for MM signal-field decoding
Extensive testing of legacy device detection capability with this format is documented in IEEE /1590r0
Sean Coffey, Texas Instruments, et al.

27. New technical information - IV
MAC mechanisms performance:
r0, “TGn features vs. performance,” Matthew Fischer.
HTP Burst performance
Block Ack/No Ack comparison
MSDU Aggregation performance
Multipoll performance loss
Sean Coffey, Texas Instruments, et al.

28. Conclusion
Sean Coffey, Texas Instruments, et al.

29. High performance, simplicity of implementation
The Task Group has begun to converge on the general shape of n
The remaining questions are which specific enhancements to adopt in order to carry out the overall plan
The WWiSE enhancements provide very significant gains in robustness, compared to other possibilities
New technical information has been provided to support several aspects of the WWiSE design
The WWiSE design is modular and consistent
Maximizes ease of implementation and scaleability, minimizes testing and interoperability burdens
Sean Coffey, Texas Instruments, et al.

30. References and further information
IEEE / n, “WWiSE group PHY and MAC specification.”
IEEE / n, “WWiSE proposal response to functional requirements and comparison criteria.”
IEEE / r3-000n and –r4-000n, “WWiSE complete proposal presentation.”
See also
Or send to
Sean Coffey, Texas Instruments, et al.