Code Design for Frame-Headers in Adaptive Coding and Modulation systems

In this paper we address the coding problem for the adaptive coding and modulation indicator (ACMI) in systems where users are divided into several classes according to their channel quality. A novel method is presented for constructing codebooks for ACMI with variable length codewords. The proposed construction, based on a greedy approach, shows considerable gains in both the maximal and average length of codebook with respect to the current state of the art. Our method provides a systematic way for constructing codebooks where codewords are not uniformly distributed, and thus some codewords are more protected than the others. The proposed construction can be easily modified, by zero padding, to obtain a fixed length codebook, with length equal to the maximal length of the designed variable length code.