Computer Science – Performance
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995phdt.........8r&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF HAWAII, 1995.Source: Dissertation Abstracts International, Volume: 56-05, Section: B, page: 2792.
Computer Science
Performance
Trellis
Scientific paper
The mobile satellite (MSAT) channel is subject to multipath fading, shadowing, Doppler frequency shift, and adjacent channel interference (ACI). Therefore, transmitted signals face severe amplitude and phase distortions. This dissertation investigates various high performance and low decoding complexity coded modulation schemes for reliable voice and data transmissions over the shadowed mobile satellite channel and the Rayleigh fading channel. The dissertation consists of four parts. The first part presents a systematic technique for constructing MPSK trellis coded modulation (TCM) codes for voice transmission over the MSAT channel. The multilevel coding method is used for constructing TCM codes using convolutional codes with good free branch distances as the component codes or using both convolutional and block codes as the component codes. Simulation results show that these codes achieve good coding gains over the uncoded reference system and outperform existing TCM codes with the same decoding complexity. In the second part, using the multilevel coding method, multilevel block coded modulation (BCM) codes are constructed for voice transmission over the MSAT channel. Even though BCM is generally less power efficient than TCM for AWGN channels, BCM has a great potential to compete with TCM in the MSAT channel because of its shorter decoding depth and hence more effective interleaving. Binary Reed -Muller (RM) codes of length up to 32 are used as component codes. Simulation results show that these codes achieve good coding gains over the uncoded reference system and outperform TCM codes with the same decoding complexity. In the third part, a simple and systematic technique for constructing multilevel concatenated BCM schemes for data transmission over the shadowed MSAT channel and the Rayleigh fading channel is presented. These schemes are designed to achieve high-performance or large coding gain with reduced decoding complexity. Construction is based on a multilevel concatenation approach in which long powerful (binary or non-binary) codes are used as the outer codes and coset codes constructed from a linear BCM code and its subcodes are used as the inner codes. Simulation results show that these codes achieve large coding gains over the uncoded reference system and outperform single-level concatenated BCM codes with the same inner codes. Especially, some multilevel concatenated BCM codes achieve an error-floor free communication at BER of 10^{-5 }. In the final part of the dissertation, product coded modulation schemes are constructed by using multilevel concatenating approach. In product coded modulation, the product coding technique and coded modulation are combined to achieve high performance with reduced decoding complexity. Good product 8-PSK modulation codes are constructed for various shadowed MSAT channels. Simulation results show that these codes achieve large coding gains over the uncoded reference system and outperform single-level concatenated BCM codes with the same inner codes.
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