Error recovery properties of quasi-arithmetic codes and soft decoding with length constraint

In this paper, we propose a method to analyse the error recovery properties of quasi-arithmetic codes. This method is adapted from the one proposed in J. Maxted and J. Robinson (1985) for variable length codes. The expected number of symbols affected by a single bit error and the probability mass function of the gain/loss (P.F. Swaszek and P. DiCicco, 1995) of symbols following a single bit error can be computed with this method. A method to estimate this probability mass function when a bitstream is sent over a binary symmetrical channel is then proposed. The aggregated state model for soft decoding of variable length codes proposed in H. Jegou et al. (2005) is then extended to quasi-arithmetic codes, as the synchronisation recovery properties of both kind of codes are similar. The soft decoding results of this scheme reveal high performance with a reasonable computing cost