Optimum bit-mapping of TCH codes

Recent studies have determined the performance of TCH(n,k) (Tomlinson, Cercas, Hughes) codes in different environments, namely for mobile satellite channels for which TCH codes of small length n (e.g. 16) present some advantages when compared with TCH codes of higher length (e.g. 256). However, the correlation characteristics of TCH codes of small length present some peaks that deteriorate its performance. In this paper we present a method to properly bit-map the incoming data bits to the code words so as to minimize this effect. The improvement in performance was obtained by simulation and is compared with previous known results.