Design of Adaptive Bit Interleaved TCM for Rayleigh Fading Channels

fixed rate coding in terms of SNR and average throughput was obtained. In fact, the concept of variable rate adaptive In this paper, we propose a bandwidth efficient error corcoding and modulation has been widely applied in 3rd genrection scheme, namely the variable rate adaptive biteration TDMA systems like Enhanced Data rate for GSM interleaved trellis coded modulation (ABICM), for wireless Evolution (EDGE) and UWC136. mobile channel. The code rate and modulation level are It is therefore a natural extension to combine the above varied according to the current channel state to exploit the two concepts, namely the BICM and the variable rate a d a p timevarying nature of the wireless channel. Design chaltive channel coding, together to achieve a synergy. One very lenges to achieve symbol-by-symbol adaptation, component simple way to combine the two concepts is to adopt a multicodes design, puncturing and interleaving design, adaptaframe adaptation technology similar to the EDGE system tion thresholds determination are addressed. A multi-level where the coding mode for a number of frames are fixed. TO puncturing scheme is proposed to tackle the problem of further enhance the performance gains, we have to adopt a symbol-by-symbol adaptive puncturing and interleaving. We symbol-by-symbol adaptation design. However, this is not a introduced the concept of equivalent distance spectrum for trival extension. Challenges yet to be solved include puncdesigning component codes of the ABICM system. Two turing and interleaving design, component codes design and operation modes, namely the constant throughput and the determination of optimal adaptation thresholds. In this paconstant BER controls, are introduced. The design is illusper, we address the above challenges. In section 2, we outtrated with an example and it is found that there are signifline the system design of the proposed ABICM and propme icant gains relative to the fixed rate coding in terms of SNR a new multi-level puncturing and interleaving scheme that and throughput. I t is also found that the ABICM scheme is could solve the dilemma between interleaving and symbolessentially not degraded in small interleaving depths. This by-symbol puncturing. Optimal adaptation thresholds are makes the ABICM very suitable for real time applications. determined. In section 3, we discuss the code design issues. In section 4, we illustrate the design with an example and study the performance gains for two operation modes,