Utilise Multipath Propagation to Improve the performance of BCH and RS Codes
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Transcript of Utilise Multipath Propagation to Improve the performance of BCH and RS Codes
Utilise Multipath Propagation to Improve the performance of BCH and RS Codes
Presenter: Alyaa Al-Barrak, Co-authors: Ali Al-Sherbaz, Triantafyllos Kanakis, Robin Crockett
The University of Northampton, The School of Science and Technology,
Department of Computing and Immersive Technologies
8th Computer Science & Electronic Engineering Conference
Outlines• Forward Error Correction (FEC);• FEC Codes Types;• FEC Codes Error Correction Capability;• Multipath propagation phenomenon;• The aim of paper• Utilise the multipath propagation phenomenon;• Hamming weight combiner;• How signals are chosen; and,• Simulation and Results.
What is FEC?Forward Error Correction (FEC).
It is a control errors technique used to enhance communication reliability over unreliable communication channel.
How dose it works?
m
(k symbols)
x
(n symbols)Channel
Error free
Error detected
Error correction
Encoder
x + noise
(n symbols)
DecoderEstimated m
(k symbols)
Types? Block Codes:
BlockEncoder
m = 10011…11
(k symbols)x= 10011…11110…1
(n symbols)
Bit Rate= k/n
ConvolutionalEncoder
m = 10011…11
(k symbols)
x= 101011…111
(n symbols)
Bit Rate = k/n
Convolutional Codes:
3
Error correction capability
10
BCH Codes (invented in 1959)
Reed-Solmono Codes (invented in 1960)
n k Error correction capability (t)
31 26 1
31 21 2
31 16 3
31 11 5
31 6 7
n k Error correction capability (t)
31 29 1
31 27 2
31 25 3
31 23 4
31 21 5 4
Multipath propagation
NLoS
Multipath is a propagation phenomenon in wireless communication. According to it, the receiver antenna will receive two or more copies of the same signal from different routes.
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The aim of paper Improve the the performance of forward error correction (FEC) codes without extra
redundancy, in order to improve data transmission reliability and increase the bit rate over wireless communication channels.
RELATED WORK
Most research focuses on:1. Increase redundancy to improve the error correction capability (Turbo code 1993).
2. Analysing the performance of various FEC techniques rather than how to improve it without extra redundancy.
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Utilise the multipath propagation phenomenonThe paper has been considered the received signals (Line-of-sight (LoS) and Non-line-of-sight (NLoS)) as redundant copies of the transmitted signal. All signals differ in their transmission length and propagation delay.
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Direct pathτD1
Reflected path
Transmitter Receiver τR2
τR1
Reflected path
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Useful copies
Uti
lise
mul
tipa
th p
ropa
gati
on t
o …
(3)
Source
BCH/RS Encoder
Modulation
Distention
BCH/RS Decoder
Demodulation
Combiner
NLoS
NLoS
LoS
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Hamming weight combiner
LoS C1 = [0 1 0 1 0 1 1 0 0 0],
Useful NLoS C2 = [1 1 1 1 0 1 1 0 0 0],
Useful NLoS C3 = [0 0 0 0 0 1 1 0 0 0],
Useful NLoS C4 = [1 1 1 1 1 1 1 1 1 1],
Useful NLoS C5 = [0 0 0 0 0 0 0 0 0 0].
𝐿𝑐 =ۏ����������ێ�����ێ�����ێ�����0ۍ����������������� 11 1 0 11 1 0 1 1 0 0 00 1 1 0 0 00 010 10
0 010 100 1 1 0 0 010 10 10 10 1 10 ۑ��������������ے������������������0
ۑ��������������ۑ��������������ې�����
Note: L should be odd number Y= [0 1 0 1 0 1 1 0 0 0]
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How signals are chosen?
There are variations methods to select multipath signals to be combined such as:
First N signals: Only the first N signals received are combined;
Best N signals: Only the N signals with highest SNR are combined; and,
Threshold: Combines only the signals that above a threshold
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Simulation and Results
BCH and RS codes with different error correction capability;
Number of paths 3, 5, 7, and 9 paths;
Additive white Gaussian noise channel; and
The threshold value was set as 40%..75% from SNR of LoS signal to choose NLoS signals.
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Simulation and Results Multipath and Hamming weight combiner
Hamming weight combiner with different threshold values.
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The combined packets (useful NLoS+LoS) improved the signals, where the improvement is increased when the number of combined paths are increased. Also, the performance improvement depends on the threshold value.
Simulation and ResultsBCH codes, Multipath, and Hamming weight combiner BCH (15, 11), BCH (127, 120) and BCH (255, 247) codes have error correction capability t1=1. BCH
(15, 7), BCH (127, 113) and BCH (255, 239) codes have error correction capability t1=2.
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The combining of three paths improved the performance of BCH codes which have error correction capability t1=1. Furthermore, their performance is better than the performance of BCH codes which have error correction capability t2=2.
Simulation and Results
RS (15, 13), RS (127, 125) and RS (255, 253) codes have error correction capability t1=1. RS (15, 11), RS (127, 123) and RS (255, 251) codes have error correction capability t1=2.
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The combining of three paths improved the performance of RS codes which have error correction capability t1=1. Furthermore, their performance is better than the performance of RS codes which have error correction capability t2=2.
RS codes, Multipath, and Hamming weight combiner
Conclusions
My proposed improved the performance of FEC with low
redundancy and low error correction capability to perform
better than the one with higher redundancy and higher error
correction capability. This is achieved through utilising an
existing phenomenon in the wireless communication called
multipath propagation and proposing a combiner known as
Hamming weight combiner with low complexity.
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Future work
This research could be extended by analysing
and evaluating the performance of FEC
techniques with high modulation schemes,
multiple-input multiple-output (MIMO) systems
and over different wireless channel models
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Thank You