An efficient hybrid ARQ protocol for point-to-multipoint communication and its throughput performance

This paper presents a new point-to-multipoint communication protocol, the nonselective repeat (NSR) protocol, for error control over broadcast channels. It is a hybrid forward-error-correction (FEC)/automatic-repeat-request (ARQ) scheme, based on the adaptive coding technique using incremental redundancy of Mandelbaum (1974). The FEC code is a rate-compatible punctured and shortened Reed-Solomon (RS) code, used for error correction only. The scheme is most attractive in situations where error occurrences are almost independent between the recipients of the messages. The throughput performance of the NSR protocol is analyzed in terms of all the parameters involved. Analysis shows that NSR significantly outperforms all the existing pure ARQ broadcast schemes. It is also shown that, even with a large number of recipients, NSR achieves performance which stays close to the capacity of the broadcast q-ary erasure channel, where q=2^m and m is the size in bits of a transmitted packet. Furthermore, on slow Rayleigh fading channels, this protocol is expected to provide better throughput performance than other hybrid ARQ protocols