Performance analysis of variable rate: symbol-by-symbol adaptivebit interleaved coded modulation for Rayleigh fading channels

摘要

A challenging problem for a high-speed data service over wirelessnis to protect data over the error-prone fading channel in an effectivenway (high-bandwidth efficiency). We propose a bandwidth-efficient errorncorrection scheme, namely variable rate adaptive bit interleaved codednmodulation (ABICM), for the wireless mobile channel. The code rate andnmodulation level are varied according to the current channel state tonexploit the time-varying nature of the wireless channel. Designnchallenges to achieve symbol-by-symbol adaptation are addressed. Innparticular, we address the criteria for choosing the family of componentncodes for the ABICM system. We propose a multilevel puncturing schementhat solves the problem of symbol-by-symbol adaptive puncturing andninterleaving. The equivalent distance spectrum for variable ratensymbol-by-symbol adaptive codes is introduced and analytical bounds onnadaptive codes are derived that enable us to determine the optimalnadaptation thresholds. Two operation modes, namely constant throughputnand constant bit error rate (BER) controls, are proposed. It is foundnthat there are significant gains relative to fixed-rate coding in termsnof signal-to-noise ratio (SNR) and throughput. It is also found that thenABICM scheme is essentially not degraded when used with smallninterleaving depths. This makes the ABICM very suitable for real-timenapplications