Spatially Coupled Codes in Turbo Equalization
(2019) EITM02 20191Department of Electrical and Information Technology
- Abstract
- In this thesis we investigate the application of spatial coupling in turbo equalization. We show that with spatial coupling we can have a fresh perspective on the trade-off between performance in the waterfall and error floor region often encountered in the choice of codes for turbo equalization.
Describing turbo equalization in the perspective of message passing on factor graphs, we show various ways of introducing memory in the encoding process and compare the performance improvement through simulations. We also discuss an effective way of decoding such spatially coupled system by using window decoding in order to minimize the decoding latency and complexity.
We manged to show that with spatial coupling we can have it both ways;... (More) - In this thesis we investigate the application of spatial coupling in turbo equalization. We show that with spatial coupling we can have a fresh perspective on the trade-off between performance in the waterfall and error floor region often encountered in the choice of codes for turbo equalization.
Describing turbo equalization in the perspective of message passing on factor graphs, we show various ways of introducing memory in the encoding process and compare the performance improvement through simulations. We also discuss an effective way of decoding such spatially coupled system by using window decoding in order to minimize the decoding latency and complexity.
We manged to show that with spatial coupling we can have it both ways; that is, have a good performance in the waterfall region while having low error floors. (Less) - Popular Abstract
- It is hard to imagine modern life without digital communications. It is estimated that nearly 5 billion people use mobile phones worldwide. A mobile phone nowadays is no longer a device to just make calls and send short messages but it is increasingly becoming integrated into the internet offering a range of remote services and interactive applications. Apart from mobile phones we have computers for personal and business uses most of which are now interconnected in the internet in addition to television and radio broadcasting. In addition to aspects that every one interacts directly in daily lives we also have a wide range of other areas such as underwater communications, sensor networks, industrial automation and so on.
To transfer... (More) - It is hard to imagine modern life without digital communications. It is estimated that nearly 5 billion people use mobile phones worldwide. A mobile phone nowadays is no longer a device to just make calls and send short messages but it is increasingly becoming integrated into the internet offering a range of remote services and interactive applications. Apart from mobile phones we have computers for personal and business uses most of which are now interconnected in the internet in addition to television and radio broadcasting. In addition to aspects that every one interacts directly in daily lives we also have a wide range of other areas such as underwater communications, sensor networks, industrial automation and so on.
To transfer information from one point to another most digital communication systems has to use some medium to transmit some form of a wave. The information is represented by zeros and ones which are grouped to form symbols transmitted over a range of time and frequency. As the demand for more speed and volume of data to be transferred increases, a strain is placed on the communication system to use the smallest time for each symbol and more range of frequencies (bandwidth) to meet these demands. There however some impairments which makes it harder to reach the desired speed. If the medium is wireless, for example, the transmitted signal may take several paths to reach the receiver which may result into symbols sent at one time interval to interfere with symbols sent at later times a phenomenon called inter-symbol interference (ISI). Inter-symbol interference also happens with wired medium if there is limited bandwidth or distortions in the frequency range of the signal.
To mitigate the effect of ISI it is customary for the receiver to employ some form of equalization by which the effect of other symbols is taken care of in determining the transmitted symbols. The data is also protected by some form of error correcting codes where some controlled redundancy is added to help the receiver correct some of the errors. To get good results it is important these two tasks be performed together instead of treating them separately. One way to do this with reasonable complexity is to use an iterative receiver in which the equalizer and error control decoder exchange some information in a number of cycles. This scheme is called turbo equalization.
The design of a turbo equalization is usually done with the trade-off between having good performance at low signal-to-noise-ratio (SNR) commonly called as the waterfall or having good error floors at higher SNR. This thesis investigates how we can use spatial coupling, where blocks of codewords over time are interlinked to form a chain, can be applied to turbo equalization. It is demonstrated that with spatial coupling we can go around this trade-off and obtain good performance in the waterfall while having good error floors. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/8985337
- author
- Mashauri, Mgeni Makambi LU
- supervisor
- organization
- course
- EITM02 20191
- year
- 2019
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Turbo equalization, spatial coupling, waterfall versus error floor, codes on graphs, iterative receivers, LDPC codes in turbo equalization
- report number
- LU/LTH-EIT 2019-703
- language
- English
- id
- 8985337
- date added to LUP
- 2019-06-20 10:46:44
- date last changed
- 2019-06-20 10:46:44
@misc{8985337,
abstract = {{In this thesis we investigate the application of spatial coupling in turbo equalization. We show that with spatial coupling we can have a fresh perspective on the trade-off between performance in the waterfall and error floor region often encountered in the choice of codes for turbo equalization.
Describing turbo equalization in the perspective of message passing on factor graphs, we show various ways of introducing memory in the encoding process and compare the performance improvement through simulations. We also discuss an effective way of decoding such spatially coupled system by using window decoding in order to minimize the decoding latency and complexity.
We manged to show that with spatial coupling we can have it both ways; that is, have a good performance in the waterfall region while having low error floors.}},
author = {{Mashauri, Mgeni Makambi}},
language = {{eng}},
note = {{Student Paper}},
title = {{Spatially Coupled Codes in Turbo Equalization}},
year = {{2019}},
}