Title page for ETD etd-01262009-160431


Document Type Master's Dissertation
Author Salmon, Brian Paxton
Email brain.salmon@gmail.com
URN etd-01262009-160431
Document Title Optimizing LDPC codes for a mobile WiMAX system with a saturated transmission amplifier
Degree MEng
Department Electrical, Electronic and Computer Engineering
Supervisor
Advisor Name Title
Prof J C Olivier Supervisor
Keywords
  • low-density parity-check codes
  • density evolution
  • peak-average power-ratio
  • WiMAX
Date 2008-09-02
Availability unrestricted
Abstract

In mobile communication, the userís information is transmitted through a wireless communication link that is subjected to a range of deteriorating effects. The quality of the transmission can be presented by the rate of transfer and the reliability of the received stream. The capacity of the communication link can be reached through the use of channel coding. Channel coding is the method of adding redundant information to the userís information to mitigate the deteriorating effects of the communication link. Mobile WiMAX is a technology that makes use of orthogonal frequency division multiplexing (OFDM) modulation to transmit information over a wireless communication channel. The OFDM physical layer has a high peak average to power ratio (PAPR) characteristic that saturates the transmitterís amplifier quite easily when proper backoff is not made in the transmission power. In this dissertation an optimized graph code was used as an alternative solution to improve the systemís performance in the presence of a saturated transmissionís amplifier. The graph code was derived from a degree distribution given by the density evolution algorithm and provided no extra network overhead to implement. The performance analysis resulted in a factor of 10 improvement in the error floor and a coding gain of 1.5 dB. This was all accomplished with impairments provided by the mobile WiMAX standard in the construction of the graph code.

©University of Pretoria 2008

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