The throughput of hybrid-ARQ protocols for the Gaussian collision channel

In next-generation wireless communication systems, packet-oriented data tra nsmission will be implemented in addition to standard mobile telephony. We take an information-theoretic view of some simple protocols for reliable pa cket communication based on "Hybrid-ARQ," over a slotted multiple-access Ga ussian channel with fading and study their throughput (total bit per second per hertz) and average delay under idealized but fairly general assumption s, As an application of the renewal-reward theorem, we obtain closed-form t hroughput formulas. Then, we consider asymptotic behaviors with respect to various system parameters. The throughput of automatic retransmission reque st (ARQ) protocols is compared to that of code division multiple access (CD MA) with conventional decoding. Interestingly, the ARQ systems are not inte rference-limited even if no multiuser detection or joint decoding is used, as opposed to conventional CDMA.