A Hybrid-ARQ System Using Rate-Compatible Trellis Codes Designed for Rayleigh Fading
Fuja, Tom E.
MetadataShow full item record
This paper presents classes of rate-compatible trellis codes designed for channels with flat, slow Rayleigh fading. The codes thus described are ﲭultiple TCM (MTCM) codes as proposed by Divsalar and Simon - i.e., codes in which multiple symbols are associated with each transition through the trellis; by applying appropriate puncturing tables to low-rate MTCM codes, we obtain families of MTCM codes, all of which can be decoded with (essentially) the same decoder.<P>By means of computer search, several such families are designed so that each family member is at least as good as any comparable code in the literature. (ﲇood here is defined in terms of minimum time diversity and minimum squared product distance, the most important parameters for performance over Rayleigh fading channels.) A protocol to implement these rate-compatible trellis codes in a type-II hybrid ARQ format with only a low-rate feedback channel is described. Upper bounds on the resulting bit error rate are developed and the results are used to select the best adaptive code from several possibilities. Simulation results comparing the proposed scheme with fixed-rate codes of the same throughput show substantial coding gain. Finally, a protocol modification limiting the variability of the code rate over a frame is described; this modification eliminates the need for excessive buffering, with a very small effect on performance