1. LDPC Tone Mapping for IEEE 802.11aj(45GHz)
Date: September 13, 2019
Presenter: Haiming WANG
Authors/contributors:
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

2. Abstract
This presentation describes LDPC tone mapping mechanism for IEEE aj(45GHz)
Using the proposed LDPC tone mapping mechanism, the performance can be improved up to 4.2dB
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

3. Introduction In 11n, interleaving is not needed for LDPC, since
one 1944-bit LDPC codeword covers almost all streams and tones within an OFDM symbol.
LDPC has an intrinsic pseudo-randomness property that protects against burst errors.
In 11ac/ad/af, tone mapping is used for LDPC, since
multiple streams and/or high MCSs lead to large NCBPS , so the coded bits from one LDPC codeword are transmitted only through a fraction of the tones when LCW < NCBPS , and the full frequency diversity would not be achieved.
Notes: NCBPS means the number of code bits per OFDM symbols, LCW means the
length of one LDPC codeword
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

4. Introduction LDPC tone mapping distance in 11af, 11ad and 11ac
by discretizing the burst errors, tone mapping can protect against burst errors, and overcome frequency selective fading better
At the receiver, tone mapping can be implemented as part of the FFT block, with no additional delay
LDPC tone mapping distance in 11af, 11ad and 11ac
for 11ad, DTM is 2/3 for 16QAM/64QAM
for 11ac, DTM is 4/6/6/9 for 20/40/80/160MHz
for 11af, DTM is 8/9 for 2/4 segment operation
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

5. Tone Mapping Mechanism(1/2)
LDPC tone mapping could be used like ac, for each stream, map consecutive QAM symbols to data tones which are separated by at least DTM -1 other data tones
where
Notes: DTM means LDPC tone mapping distance, NSD means the total number of data subcarriers, NSS,u means the number of streams for user u, Nuser means the number of users
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

6. Tone Mapping Mechanism(2/2)
Using a block-interleaving matrix with DTM rows and NSD /DTM
columns for every OFDM symbol at each stream, tone mapping can be
implemented by writing row-wise and reading back
column-wise
Example: BW=540MHz, NSD =168, DTM =8, NSD /DTM =21, NSS =1
Write 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99
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Read
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

7. Tone Mapping Distance(1/3)
Procedure for choosing optimal DTM
For each bandwidth, it would be desirable to have a DTM which is
at least as large as , so that one LDPC codeword covers the full range of tones
an integer divisor of the number of subcarriers, NSD
constant over all rates within each bandwidth, so that the tone de-mapper
can be implemented at Rx in the FFT block with fixed tone processing
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

8. Tone Mapping Distance(2/3)
Possible parameters
For BW= 540MHz, NSD = 168, NSS= 4, Modulation= 64QAM,
NCBPS/LCW= 168*6*4/672=6, so possible values for DTM are:
6,7,8,12,14,21,24,28,42,56,84
For BW= 1080MHz, NSD = 336, NSS= 4, Modulation= 64QAM,
NCBPS/LCW= 336*6*4/672=12, so possible values for DTM are:
12,14,21,24,28,42,48,56,84,112,168
For each simulation, the best two DTM values are selected into optional parameter set, and the first/second element in the set is the best/second best parameter
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

9. Tone Mapping Distance(3/3)
For each BW, the intersection set of the optional parameter sets will be achieved
For each BW, the element in intersection which leads to best performance for most simulation situations is proposed to be the optimal DTM
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

10. Simulation Setup Channel model: Conference Room
Number of distinguishable paths : 12
Packet length: 4096 bytes
LDPC codeword length: 672bits
Number of channel realizations: 5000
Simulation antennas: 1x1, 2x2, 4x4 for 1, 2, 4ss, respectively
Modulation and code rate: {BPSK ½},{QPSK ½},{16QAM ½},
{64QAM ½}
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

11. Simulation Results(1/2)
Proposed optional parameter set
For 540MHz
For 1080MHz
Parameters
NSS=1
NSS=2
NSS=4
{QPSK ½}
{6,7}
{16QAM ½}
{64QAM ½}
{7,6}
Parameters
NSS=1
NSS=2
NSS=4
{QPSK ½}
{12,14}
{16QAM ½}
{14,12}
{64QAM ½}
Notes: Since the performances of all DTM s for low-order modulations are very close, so their optional parameters sets could be ignored which are marked as “\” in the table.
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

12. Simulation Results(2/2)
Base on the results above, we can get the intersection for 540MHz and 1080MHz
Appendix-A gives simulation results for DTM with bandwidth 540MHz
Appendix-B gives simulation results for DTM with bandwidth 1080MHz BW
540MHz
1080MHz
Intersection
{6,7}
{12,14}
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

13. Conclusions
LDPC tone mapping should be used for OFDM in IEEE aj (45GHz)
Optimal DTM for LDPC tone mapping in aj BW
540MHz
1080MHz
DTM 6 12
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

14. Reference [1] “11-10-1300-00-00ac-ldpc-for-11ac”, Jun Zheng et al.
[2] “ ac-proposed-correction-of-ldpc-tone-mapping-equation”, Hossein Taghavi et al.
[3] “ af-interleaver-parameters”, Ron Porat et al.
[4] “Draft P802.11ad_D9.0”
[5] “ Draft P802.11ac_D5.1”
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

15. Simulation Results for 540MHz
APPENDIX A:
Simulation Results for 540MHz
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

16. Optional parameter set is {6,7} 2 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

17. Optional parameter set is {6,7} 2.2 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

18. Optional parameter set is {7,6} 2 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

19. Optional parameter set is {6,7} 0.7 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

20. Optional parameter set is {6,7} 3 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

21. Optional parameter set is {7,6} 2 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

22. Simulation Results for 1080MHz
APPENDIX B:
Simulation Results for 1080MHz
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

23. Optional parameter set is {14,12} 2 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

24. Optional parameter set is {14,12} 4 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

25. Optional parameter set is {12,14} 4 .2dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

26. Optional parameter set is {14,12} 4 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

27. Optional parameter set is {12,14} 1.8 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

28. Optional parameter set is {12,14} 3.5 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

29. Optional parameter set is {12,14} 3.5 dB gain
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)

30. Thanks for Your Attention!
Shiwen He, Haiming Wang, et al. (SEU/CWPAN)