Coding in a Discrete Multitone Modulation System

Discrete Multitone (DMT) modulation is a multicarrier technique which makes efficient use of the channel, maximizing the throughput by sending different numbers of bits on different subchannels. The number of bits on each subchannel depends on the Signal-to-Noise Ratio of the subchannel. The performance of a DMT system can be further increased by using powerful coding techniques. This thesis investigates an implementation of coding for a DMT system. The coding techniques considered are Reed-Solomon coding combined with interleaving, and Trellis Coded Modulation. Wei’s 4-dimensional 16-state coder combined with trellis shaping is the suggested trellis code. A single encoder is used which codes across the tones of each DMT-symbol. At a bit error probability of 10-7 the suggested codes gain 3-6 dB over uncoded transmission. Hardware complexity and algorithmic aspects of coding are covered, as well as simulations to verify it. 3 (28) Coding in a Discrete Multitone Modulation System Preface This Master’s thesis has been presented in partial fulfilment of the requirements for the degree of Master of Science. The work presented in this thesis has been conducted during the autumn of 1995, and has been done as a part of developing an experimental system called MUSIC at Telia Research AB, Luleå. We would like to warmly thank the other project members, especially Mikael Isaksson2, the project leader, for their continuous support and inspiration. We would also like to give a special thank to our examiner Dr. Per Ödling1 for his help and guidance, and to Dr. Lennart Olsson2 and Dr. Tomas Nordström3 for their never ending patience with our questions. Luleå, February 21, 1996. 1. Division of Signal Processing at Luleå University of Technology, Sweden. 2. Division of Communications System at Telia Research AB, Luleå, Sweden. 3. Division of Computer Engineering at Luleå University of Technology, Sweden. Daniel Bengtsson Daniel Landström 4 (28) Coding in a Discrete Multitone Modulation System