Adaptive Reed-Solomon Coding in Eigen-MIMO with Non-Adaptive Modulation

Abstract

An adaptive coding scheme for spectral efficiency improvement in eigen-MIMO is presented. It uses Reed-Solomon (RS) codes with non-adaptive QAM. Non-adaptive modulation is of interest since it reduces the high complexity - in both the electronics and the protocol - required for deploying the more commonly treated adaptive modulation. RS codes have practical advantages in terms of their algorithmic simplicity, memory requirements and decoder complexity. Unlike many codes, an analytical solution for the error probability is available for RS coding. This facilitates finding the jointly optimal code rate(s) and power allocation on the eigenchannels, with the criterion of maximum instantaneous practicable capacity (data throughput). The adaptation is applied to two different architectures of the encoders/decoders (CODECs) for eigen-MIMO, and their performances are compared with the uncoded case. The outer coding architecture refers to a single CODEC working on the overall serial data, and inner coding refers to separate CODECs for different eigenchannels. The adaptive RS system with optimum power allocation reveals new capacity behavior which is different to that of water-filling. For the moderate values of SNR (6-20 dB) typical of wireless systems, the improvement in the capacity over the no-coding case is greater for the inner coding architecture.