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Practical Aspects of Reduced Complexity LDPC Decoding using Forced Convergence

Farooq, Muhammad Umar LU and Garcia Garcia, Maria LU (2016) EITM02 20161
Department of Electrical and Information Technology
Abstract
This thesis is an extension to the previous work done at Department of EIT in
investigating the complexity reduction of LDPC decoding using the stochastic
approximation method to improve the energy efficiency of energy-limited applica-
tions, such as in mobile phones.
The research carried out in this thesis investigates the complexity and conver-
gence results of adaptive performance control algorithm (PCAA) that changes the
forced convergence threshold in OMS LDPC FC decoding algorithm. The simula-
tions are performed on IEEE802.11n OFDM communication system for Additive
White Gaussian Noise (AWGN), indoor Rayleigh time varying frequency flat and
Rayleigh frequency selective fading channels. Performance results are obtained
by... (More)
This thesis is an extension to the previous work done at Department of EIT in
investigating the complexity reduction of LDPC decoding using the stochastic
approximation method to improve the energy efficiency of energy-limited applica-
tions, such as in mobile phones.
The research carried out in this thesis investigates the complexity and conver-
gence results of adaptive performance control algorithm (PCAA) that changes the
forced convergence threshold in OMS LDPC FC decoding algorithm. The simula-
tions are performed on IEEE802.11n OFDM communication system for Additive
White Gaussian Noise (AWGN), indoor Rayleigh time varying frequency flat and
Rayleigh frequency selective fading channels. Performance results are obtained
by running various combinations of LDPC decoding parameters and results are
documented for parameter profiles that meet the specified BLER target criteria.
In order to visualize the results, simulations are performed by implementing
OFDM, PCAA and relevant channel models in MATLAB c
and LDPC forced
convergence decoder in C. By doing that it was possible to shorten the simulation
time as LDPC decoder takes longer in MATLAB c
compared to C. Performance
metrics such BLER against E b /N 0 , complexity and convergence for various mod-
ulation and coding (MCSs) schemes are produced via this setup.
The aim of the thesis is accomplished and results obtained indicate signifi-
cant convergence time reduction compared to previous methodology [1]. It is also
concluded that optimum complexity and convergence trade-off is obtained when
Δθ d is set to Block Error Rate target (BLER t ) in AWGN channel set-up. By
applying this optimum configuration to both time varying frequency flat fading
and frequency selective fading channel encouraging results are observed. PCAA
tracks the channel changes in both fading cases while meeting specified BLER t
and with significant complexity savings relative to non-forced convergence LDPC
decoding. (Less)
Popular Abstract
Nowadays, people are using their mobile devices, i.e. mobile phones, more
and more. According to the Smarphone Market Research, 340 million
smartphones were shipped to the market in the first quarter of 2016. One of
the main complains is the time their batteries last. With the solution we
propose in our research project, it is possible for the battery to last longer in
such devices.
When a message, for example, an image, is transferred wirelessly from the
transmitter side to the receiver side, the wireless medium will introduce
errors to the message. When we receive the message there are methods that
can correct the errors but the correction requires more power from the
battery. However, it might not be necessary to... (More)
Nowadays, people are using their mobile devices, i.e. mobile phones, more
and more. According to the Smarphone Market Research, 340 million
smartphones were shipped to the market in the first quarter of 2016. One of
the main complains is the time their batteries last. With the solution we
propose in our research project, it is possible for the battery to last longer in
such devices.
When a message, for example, an image, is transferred wirelessly from the
transmitter side to the receiver side, the wireless medium will introduce
errors to the message. When we receive the message there are methods that
can correct the errors but the correction requires more power from the
battery. However, it might not be necessary to correct each and every error.
For example, receiving a medium quality picture instead of the full-HD
version might be good enough. Hence, an error control vs. energy efficiency
trade-off is introduced using the results presented in this research.
First of all, an impact of having an energy efficient system would lead to
longer periods between battery charging, resulting in saving energy
consumption. Secondly, the chemicals contained in batteries are classified
hazardous, by having an energy efficient device, the battery disposal rate
would decrease, creating a more environmental friendly device. The results
in this project presents a way to achieve good error control while not wasting
too much energy.
We created a computer model (for a specific Wi-Fi standard) of an everyday
life scenario of a user with a mobile station moving inside of a building.
Then we investigated how the errors get introduced into the message sent by
a transmitter in such indoor environment. Finally, we found a way to deal
with those errors while not consuming too much power.
The implementation was done using a Low-Density Parity-Check (LDPC)
decoder with Forced Convergence (FC) to shorten the amount of time the
decoder takes to receive the message. Using this technique, the image
received would be reliable enough. The image at the receiver side will not
be the best quality, however, it will have a good enough quality. Without FC
the decoder would take a longer time to decode the image to get the full-HD version of it. Having a reduced amount of time at the decoder achieves lower
energy consumption. The project was done in collaboration with the EIT
department at Lund University. (Less)
Please use this url to cite or link to this publication:
author
Farooq, Muhammad Umar LU and Garcia Garcia, Maria LU
supervisor
organization
course
EITM02 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
LDPC, Forced Convergence, Decoding, OFDM, IEEE802.11
report number
LU/LHT-EIT 2016-529
language
English
id
8885619
date added to LUP
2016-06-28 15:13:07
date last changed
2016-06-29 15:53:38
@misc{8885619,
  abstract     = {This thesis is an extension to the previous work done at Department of EIT in
investigating the complexity reduction of LDPC decoding using the stochastic
approximation method to improve the energy efficiency of energy-limited applica-
tions, such as in mobile phones.
The research carried out in this thesis investigates the complexity and conver-
gence results of adaptive performance control algorithm (PCAA) that changes the
forced convergence threshold in OMS LDPC FC decoding algorithm. The simula-
tions are performed on IEEE802.11n OFDM communication system for Additive
White Gaussian Noise (AWGN), indoor Rayleigh time varying frequency flat and
Rayleigh frequency selective fading channels. Performance results are obtained
by running various combinations of LDPC decoding parameters and results are
documented for parameter profiles that meet the specified BLER target criteria.
In order to visualize the results, simulations are performed by implementing
OFDM, PCAA and relevant channel models in MATLAB c
 and LDPC forced
convergence decoder in C. By doing that it was possible to shorten the simulation
time as LDPC decoder takes longer in MATLAB c
 compared to C. Performance
metrics such BLER against E b /N 0 , complexity and convergence for various mod-
ulation and coding (MCSs) schemes are produced via this setup.
The aim of the thesis is accomplished and results obtained indicate signifi-
cant convergence time reduction compared to previous methodology [1]. It is also
concluded that optimum complexity and convergence trade-off is obtained when
Δθ d is set to Block Error Rate target (BLER t ) in AWGN channel set-up. By
applying this optimum configuration to both time varying frequency flat fading
and frequency selective fading channel encouraging results are observed. PCAA
tracks the channel changes in both fading cases while meeting specified BLER t
and with significant complexity savings relative to non-forced convergence LDPC
decoding.},
  author       = {Farooq, Muhammad Umar and Garcia Garcia, Maria},
  keyword      = {LDPC,Forced Convergence,Decoding,OFDM,IEEE802.11},
  language     = {eng},
  note         = {Student Paper},
  title        = {Practical Aspects of Reduced Complexity LDPC Decoding using Forced Convergence},
  year         = {2016},
}