A trace-back-free Viterbi decoder using a new survival path management algorithm
The problem of survival memory management of a Viterbi decoder is classically solved either by a power-hungry register-exchange implementation, or by a trace-back scheme with large latency. In this paper, we show that by introducing a novel matrix transformation operator to the algebraic foundation originally proposed in Fettweis (1995), we obtain a new survival-path-management algorithm that sorts the survival paths in parallel with the decoding of the information bits to eliminate long recursive trace-back operations. Furthermore, it avoids power and complexity problems associated with register exchange by only tracing and recording the changes of the survival path with a set of dynamic pointers. A prototype of the Viterbi decoder for the GSM TCH/FS system has been mapped into a Xilinx Virtex xcv400HQ240-6 operating at 23.6 MHz with a decoding throughput of 3.37 Mbit/s and 80 mW power consumption, a 43% increase over the same application based on StarCore SC140 DSP in terms of throughput per MHz.