A note on lattice quantized coded modulation method

Abstract

AbstractThere is the expectation that lattice quantizers that use lattice basis vectors will be capable of source coding at high rates and low distortion. the application of lattice theory in coded‐modulation, on the other hand, is now at a practical stage (as can be seen in such applications as general telephone networks and mobile communication modems). Research into source coding schemes that use this type of lattice quantization has up to date been considered independently from research into lattice coded‐modulation. In this paper, a unified coding approach is considered. A new method is proposed that realizes in an integrated fashion coded‐modulation schemes that have recently received a great deal of attention as well as source coding methods suitable for data with frequency distributions typical of those of images. Then, as a specific example, a combined coding method is considered in detail that is realized by using the structure of the lattice to bridge lattice quantization and QAM modulation steps. As a result, it is shown that (i) it is possible to reduce the average modulation power of the entire system by performing a simple mapping that depends on the frequency of use of the lattice points; (ii) that maximum likelihood decoding can be more easily implemented since combined coding is accomplished in a way that preserves the structure of the lattices; and (iii) a simple, nearly optimum technique is proposed and it is shown that this system's average modulation power can also be reduced. Furthermore, simulation experiments are performed that clearly demonstrate the effectiveness of a system that combines E8 and A16 lattices with 256‐QAM modulation.