A New Joint Source-Channel Coding Scheme with Overlay Spread Spectrum Transmission

In this paper, we propose a new joint source-channel coding (JSCC) scheme, especially in conjunction with overlay spread spectrum transmission. At the transmitter, a source sequence is redescribed by classified enumerative (CE) coding, resulting in a two-stage description consisting of the index of its type-class and its rank in the associated type-class. The variable-length rank is encoded by a multiple-rate random code, while the fixed-length index of the type-class is encoded into a Walsh-Hadamard sequence, which is then overlaid (in the real field) on the coded signal corresponding to the index for transmission. In particular, to improve energy efficiency, the lower-rate component code is allocated with lower energy. At the receiver, the source can be decoded by searching for type-classes. To predict the performance of the proposed JSCC scheme, we present the estimated bound based on the performance of each type-class. Simulation results show that the performance matches well with the estimate, validating our analysis. Simulation results also show that the proposed JSCC scheme (without source statistics) can approach the JSCC bounds and outperform the double polar JSCC scheme (with perfect source statistics).