Throughput evaluation for ARQ protocols in finite-interleaved slow-frequency hopping mobile radio systems

The errors distribution for packet transmission over mobile radio systems employing slow-frequency hopping (SFH) with nonideal interleaving is analytically studied. A new analytical methodology is then presented to evaluate automatic repeat request (ARQ) techniques, taking into account forward error correction (FEC) and nonideally interleaved SFH over Rayleigh fading channels. The selective-repeat (SR) ARQ and the type I hybrid ARQ/FEC techniques are compared when varying the number of bits per hop, thus gradually passing from the noninterleaved non-SFH case to the perfect interleaved case. It is found that the use of SFH and/or interleaving deteriorates the efficiency of the transmission: in other words, when ARQ is applied to slow fading channels the best performance is obtained without SFH and interleaving. The ARQ/FEC technique analyzed here gives marginal improvements with respect to pure SR only when perfect interleaving and SFH are applied