doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

Packet Encoding Solution for 45GHz

Date: 2014-11-02

Authors:

Name Affiliations Address Phone Email

Liguang Li ZTE Corporation Shenzhen China li.liguang@zte.com.cn

Jun Xu ZTE Corporation Shenzhen China xu.jun@zte.com.cn

Zhifeng Yuan ZTE Corporation Shenzhen China yuan.zhifeng@zte.com.cn

Bo Sun ZTE Corporation Xi’anChina sun.bo1@zte.com.cn

Ke Yao ZTE Corporation Xi’anChina yao.ke5@zte.com.cn

Kaibo Tian ZTE Corporation Xi’anChina tian,kaibo@zte.com.cn

Shiwen He Southeast University (SEU)

Nanjing China hesw01@seu.edu.cn

Haiming Wang

Southeast University (SEU)

Nanjing China hmwang@seu.edu.cn

Slide 1 Liguang Li(ZTE Corp.)

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• Traditional data packet processing:– Code Block Segmentation -> FEC Encoding -> Data Y (transmit).

Slide 2 Liguang Li(ZTE Corp.)

Background: Traditional Packet

Source Data

FEC Parity Bits

0 1 a-2 a-1

0 1 a-1a-2

C0 C1 Ca-2 Ca-1

Code Block Segmentation

FEC

Data Y

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• The longer a data packet is, the worse PER it will get– The PER(Packet Error Rate) of traditional data packet: PER=1-(1-BCER)^a ≈ a ×

BCER, where a is the number of FEC code blocks, BCER denotes Block Code Error Rate of FEC

• A simple and effective solution is necessary to improve reliability of data packet in 802.11aj.– 802.11aj is used for ultra high speed data and video transmission. Therefore, wide

range of data octets of the PSDU will cause quite a lot of FEC code blocks.

Slide 3 Liguang Li(ZTE Corp.)

Background: Traditional Packet

4.8 5 5.2 5.4 5.610

-4

10-3

10-2

10-1

100 PER~=a * BCER, a=20

SNRdB(Es/N0)

PE

R/B

CE

R

PER

BCER

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• Procedure: Code block segmentation -> Adding CRC -> LDPC Encoding -> Packet Encoding -> Bits Selection -> Data Y (transmit).

Slide 4 Liguang Li(ZTE Corp.)

Proposed: Packet Encoding Solution

Source Data

Parity bits of LDPCCRC

Packet Encoding

0 1 a-2 a-1

0 1 a-2 a-1

0 1 a-1a-2

C0 C1 Ca-2 Ca-1

The number of bits are the

same.

Ca

No selecting bitsParity packet

Code Block Segmentation

Adding CRC

LDPC Encoding

Packet Encoding

Bits Selection

Data Y

Ca-1Ca-2C1C0

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• Encoding Process: – Adding CRC: Divide the source data into a groups of k bits, where k=328 for

code rate 1/2, k=412 for code rate 5/8, k=496 for code rate 3/4, k=538 for code rate 13/16. Adding 8 bits CRC sequence to each group. Then all groups are encoded to create LDPC code blocks (C0,C1,C2,…, Ca-1) with length of 672 bits.

– Packet Encoding: parity packet is created by: , where the symbol is XOR. The length of parity packet is 672 bits.

0 1 1a a C C C CaC

aC

Slide 5 Liguang Li(ZTE Corp.)

Details of the Proposed Solution

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• Encoding Process: – Bits Selection: the punctured bits number (ei, i=0 、 1 、…、 a-1) of a LDPC

code blocks are set by:

1 、 if 1<a<=15:2 、 if a>15:

Where, 3 、 if a==1: e0=0 ； • The punctured bits number (ei,i=a) of parity packet is set by:

Where, n is the size of LDPC code and n=672.

42 0,1, , 1ei i a

/ ( 1) 1 0,1, , 1ei n a i g / ( 1) , 1, , 1ei n a i g g a

/ ( 1) ( 1)g n n a a

1

0

a

iea n ei

Slide 6 Liguang Li(ZTE Corp.)

Details of the Proposed Solution

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• Encoding Process: – Data Y is generated by:

1

0

, ,

, ,

0,1, ,

0,1, , ( 1)

( ))

( )

( )

i

k

i m i m

i m i m ei

for i a

for m n ei

if m ek

else

end if

end for m

end for i

Y C

Y C

Slide 7 Liguang Li(ZTE Corp.)

Details of the Proposed Solution

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

2. 100 LDPC code blocks

1. 10 LDPC code blocks

• Examples:

Slide 8 Liguang Li(ZTE Corp.)

Proposed: Packet Encoding Solution

42 bits

C0

C1

C9

C10

42 bits

Punctured bits Selected bits

C2

42 bits

42 bits

42 bitsC8

252Packet Encoding

7 bits

C0

C1

C66

C99

C100

C65

7 bits

7 bits

6 bits

6 bits

Punctured bits Selected bits

6 bitsPacket Encoding

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• Simulation parameters:– Channel: AWGN. – Modulation Mode: QPSK, 16QAM, 64QAM. – Code Rate: 1/2, 5/8, 3/4, 13/16. – The number of LDPC code blocks in a data packet: 10, 20, 50,100.

• Performance Comparison:– Compensation of 8 CRC bits for traditional packet: , where

k is the information bits length of LDPC code. The value of k is 328 for code rate 1/2, 412 for 5/8, 496 for 3/4 and 538 for 13/16.

Slide 9 Liguang Li(ZTE Corp.)

Simulation

1010 log (( 8) )k k

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• Performance(QPSK, AWGN):

– Rate of 13/16, gain(PER=0.1):

10 LDPC: 0.2dB ；50 LDPC: 0.6dB ；100 LDPC: 0.8dB 。

1.4 1.6 1.8 2 2.2 2.4

10-2

10-1

100

Packet Encoding, Rate=1/2

SNRdB(Es/N0)

PE

R

New,Num=10New,Num=50New,Num=100Trad,Num=10Trad,Num=50Trad,Num=100

0.1dB 0.3dB

0.3dB

5.5 6 6.5

10-2

10-1

100

Packet Encoding, Rate=13/16

SNRdB(Es/N0)

PE

R

New,Num=10New,Num=50New,Num=100Trad,Num=10Trad,Num=50Trad,Num=100

0.2dB

0.6dB

0.8dB

– Rate of 1/2, gain (PER=0.1):

10 LDPC: 0.1dB ；50 LDPC: 0.3dB ；100 LDPC: 0.3dB 。

Slide 10 Liguang Li(ZTE Corp.)

Simulation

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• Performance(16QAM, 64QAM, AWGN):

– 20 LDPC ， 64QAM ， gain(PER=0.1): Rate of 5/8: 0.3dB ；Rate of 3/4: 0.3dB ；Rate of 13/16: 0.6dB.

7 8 9 10 11 1210

-2

10-1

100 Packet Encoding, 16QAM, NUM=20

SNRdB(Es/N0)

PE

R

New,R=1/2

New,R=3/4Trad,R=1/2

Trad,R=3/4

0.2dB0.3dB

13 14 15 16 17 18 1910

-3

10-2

10-1

100

Packet Encoding, 64QAM, NUM=20

SNRdB(Es/N0)

PE

R

New,R=5/8New,R=3/4

New,R=13/16

Trad,R=5/8

Trad,R=3/4Trad,R=13/16

0.6dB0.3dB 0.3dB

– 20 LDPC, 16QAM ， gain(PER=0.1):

Rate of 1/2: 0.3dB;

Rate of 3/4: 0.2dB.

Slide 11 Liguang Li(ZTE Corp.)

Simulation

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• Transmitter – 1. cumulative XOR module (parallel or serial) for packet encoding. 2. buffer (size

of 672 bits) for results of XOR.

• Receiver– 1. Buffers for LLR of LDPCs decoded failure and result of cumulative XOR of

LDPCs decoded correctly. 2. Decoder of XOR(min-sum, parallel or serial) .

• Conclusion: Low complexity

Demodulation LDPC Decoding

LLR Buffer

Packet Decoding

LDPC Decoding

Decoding Data

Slide 12 Liguang Li(ZTE Corp.)

Complexity Analysis

LDPC Encoding

Packet Encoding Buffer

Bits Selection

Adding CRC ModulationCode Block

Segmentation

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• Why does it work?– According to Information Theory, for any single FEC (Forward Error Correction)

code, the longer it is, the better performance it will get. – LDPC can not support any code length and the length can not be very long due to

complexity.– Usually, the large traditional data packet is divided into small FEC code blocks,

the PER of the whole data packet can be proximately equal to BCER*a. Where a is the number of FEC code blocks. BCER is a relatively constant value for a certain setting. So the longer of the large data packet is, the worse PER it will get using traditional processing.

– The proposed solution builds relationship among all the code blocks, so that we will get a gain similar to that of a large data packet using LDPC encoding.

– Of course the operation we introduced is XOR instead of the complex LDPC, so the gain will not be so large as LDPC. And in order to reach the same rate as traditional data packet processing we puncture some bits which will affect the gain. These effects can hardly be derived algebraically, therefore simulation is an effective way to measure it.

Slide 13 Liguang Li(ZTE Corp.)

Effectiveness Analysis

doc.: IEEE 802.11-14/1387 r0

Submission

November 2014

• We proposed a packet encoding solution for group discussion.

• The simulation results show that the packet encoding solution brings a good gain compared to the traditional method with adding low complexity for both transmitter and receiver.

Slide 14 Liguang Li(ZTE Corp.)

Summary