Thesis - Analysis of Coded OFDM System over Frequency Selective Fading Channe

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【文件名】:0652@52RD_Thesis - Analysis of Coded OFDM System over Frequency Selective Fading Channels.pdf
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This thesis considers the analysis of system performance and resource allocation for a
coded OFDM system over frequency selective fading channels. Due to the inseparable
role taken by channel coding in a coded OFDM system, an information theoretical
analysis is carried out and taken as the basis for the system performance and through-
put.
Based on the results of the information theoretical analysis, the optimal sys-
tem BER performance of a coded OFDM system is rst shown to converge to the
outage probability for large OFDM block lengths. Instead of evaluating the out-
age probability numerically, we provide in this thesis a simple analytical closed form
approximation of the outage probability for a coded OFDM system over frequency
selective quasi-static fading channels. Simulation results of the turbo-coded OFDM
systems further conrm the approximation of the outage probability.
By taking the instantaneous channel capacity as the analytical building block,
system throughput of a coded OFDM system is then provided. With the aim to
compare the performance dierence between adaptive and uniform resource alloca-
tion strategies, the system throughput of dierent allocation schemes under various
channel conditions is analyzed. First, it is demonstrated that adaptive power alloca-
tion over OFDM sub-carriers at the transmitter achieves very little gain in terms of
throughput over a uniform power distribution scheme. Theoretical analysis is then
iv
provided of the throughput increase of adaptive-rate schemes compared with xed-
rate schemes under various situations. Two practical OFDM systems implement-
ing rate-compatible-punctured-turbo-code-based (RCPT-based) hybrid automatic-
repeat-request (Hybrid-ARQ) and redundancy incremental Hybrid-ARQ protocols
are also provided to verify the analytical results.