1. Symbol Interleaving for Single Carrier PHY in 802.11aj (45 GHz)
Date:
Presenter: Shiwen HE
Authors/contributors:

2. Abstract
This presentation describes symbol interleaving for SC PHY in aj (45 GHz).
With the proposed symbol interleaving mechanism, the performance can be improved up to 2 dB.

3. Introduction In 802.11n/ac , bit interleaving is combined with BCC to
protect against consecutive bits burst errors, especially caused by frequency selective fading.
In ac, symbol interleaving is combined with LDPC, since
without symbol interleaving, the full frequency diversity cannot be achieved if the length of one LDPC codeword is less than the number of code bits per OFDM symbol ( i.e. LCW < NCBPS ).
Symbol interleaving would be used for SC PHY in aj (45 GHz), since
LDPC has a stronger ability to correct discrete errors than BCC, so that bit interleaving is not necessary.
symbol interleaving can protect against burst errors by discretizing these errors at the transmitter and correcting them at the receiver.

4. Symbol Interleaving Mechanism(1/2)
Block interleaving is proposed to use for SC PHY in aj (45 GHz).
where
Parameters：
NROW
NCBPB
NBLKS
NSS
NDSPB
number of rows of interleaving matrix
number of coded bits per block
number of blocks
number of spatial streams
number of data symbols per block

5. Symbol Interleaving Mechanism(2/2)
Block interleaving would be implemented with a matrix of size
for each block of each stream, by writing row-wise and reading
back column-wise.
Example: BW = 540 MHz, NDSPB = 256, NROW = 8, NSS = 1
Write
Read 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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6. Interleaving Depth NROW （1/2）
For each bandwidth, it would be desirable to have a NROW which is
at least as large as , so that one LDPC codeword covers the whole block.
an integer divisor of the number of symbols per block.
Potential parameters
For BW = 540MHz, Modulation = 64 QAM, NSS = 4, NCBPB = 256*6 = 1536, NCBPB/LCW = 1536*4/672 = 9.14, so the potential values for NROW are: 16, 32, 64, 128.
For BW = 1080 MHz, Modulation = 64 QAM, NSS = 4, NCBPB = 512*6 = 3072, NCBPB/LCW = 3072*4/672 = 18.29, so the potential values for NROW are: 32, 64, 128, 256.

7. Interleaving Depth NROW （2/2）
For each simulation, the best two NROW values are found and selected into optional parameter set, and the first/second element in the optional parameter set corresponds to the best/second best parameter.
For each bandwidth, the intersection set of the optional parameter sets will be achieved.
For each bandwidth, the element in the intersection which leads to the best performance for most simulation situations is proposed to be the optimal NROW .

8. Simulation Setup Packet length: 4096 bytes
Number of distinguishable paths: 18
Simulation antennas: 1x1, 2x2, 4x4 for 1, 2, 4ss, respectively
Modulation and code rate: {QPSK ½},{16 QAM ½}, {64 QAM ½}
5000 channel realizations for each PER curve

9. Simulation Results
Simulation results show that using symbol interleaving for SC PHY can
achieve up to 2 dB gain.
Proposed optional parameter set for 540 MHz
Using the same method, optional parameter set for 1080 MHz can be
obtained.
Appendix-A gives simulation results for 540 MHz bandwidth.
Parameters
NSS = 1
NSS = 2
NSS = 4
{QPSK ½}
{16,32}
{16,64}
{16 QAM ½}
{64 QAM ½}
Notes: Since the performances of all NROW for low-order modulations are very close, their optional parameters sets could be ignored which are marked as “\” in the table.

10. Conclusions
Symbol interleaving should be used for SC PHY in aj (45 GHz).
Interleaving depth NROW for SC PHY in aj (45 GHz) BW
540 MHz
1080 MHz
NROW 16 32

11. Reference
[1] “ ac-interleaver-for-nss-greater-than-4”, Yonghong Qi et al.
[2] “ af-interleaver-parameters”, Ron Porat et al.
[3]“Required Interleaving Depth in Rayleigh Fading Channels”, King Ip Chan et al.
[4]“ Draft P802.11ac_D5.1”

12. Simulation Results for 540 MHz Bandwidth
APPENDIX A:
Simulation Results for 540 MHz Bandwidth

13. Optional parameter set is {16,32}
0.3 dB gain

14. Optional parameter set is {16,32}
0.3 dB gain

15. Optional parameter set is {16,32}
0.2 dB gain

16. Optional parameter set is {16,32}
0.5 dB gain

17. Optional parameter set is {16,32}
1.5 dB gain
Optional parameter set is {16,32}

18. Optional parameter set is {16,64}
0.2 dB gain

19. Optional parameter set is {16,32}
0.9 dB gain
Optional parameter set is {16,32}

20. Optional parameter set is {16,32}
2 dB gain
Optional parameter set is {16,32}

21. Thanks for Your Attention.