PACKET COMBINING SYSTEMS BASED ON THE VITERBI DECODER

Type-I hybrid-ARQ protocols can be used to construct powerful adaptive rate algorithms through the use of packet combining techniques. In th is paper several packet combining schemes are presented for use in con junction with the Viterbi decoder over stationary and time-varying cha nnels. The first technique presented is an averaged diversity combiner , which is shown to be identical in performance to an interleaved code combiner over an AWGN channel. The averaged diversity combiner is the n generalized to make use of packet weights based on either ideal chan nel state information or weights derived from side information generat ed by the Viterbi decoder. It is shown that the weighted diversity com biner using decoder side information performs almost as well as the sy stem using ideal channel state information. All of the packet combinin g schemes discussed in this paper provide improved throughput and reli ability performance relative to that provided by the standard type-I h ybrid-ARQ or FEC systems. This performance improvement is obtained at the expense of negligible to moderate modifications to the transmitter and receiver. Performance bounds are derived for each of the combinin g schemes and their tightness verified through simulation results.