The performance of rate-compatible punctured convolutional codes for future digital mobile radio

A study is reported of the unequal error protection capabilities of convolutional codes belonging to the family of rate-compatible punctured convolutional codes. The performance of these codes is analyzed and simulated for the fast-fading Rice and Rayleigh channels with differentially coherent 4-phase modulation. Interleaving performed over one or two blocks of 256 channel bits to mitigate the effect of fading. Examples are provided to show that it is possible to accommodate widely different error protection levels within short information blocks. The effect of the code and channel parameters is considered, such as the encoder memory, the code rate, interleaver depth, fading bandwidth, and the contrasting performance of hard and soft decisions on the received symbols. The authors highlight the need for soft decisions and soft channel state information to extract the maximum benefit from Viterbi decoding on a channel as harsh as the one with Rayleigh fading