Two-layer retransmission reliability for CDMA2000 1×-EV

We study the reliability as offered jointly by the medium access control (MAC) and the radio link protocol (RLP) for CDMA systems, particularly for the cdma2000 evolution standard cdma2000 1-EV. The retransmission mechanism in the RLP has a considerable amount of delay associated with it which might not be able to sustain real-time communications with strict delay requirements. Retransmissions done at a lower layer, such as the MAC, enhances the performance of the system. We show how the performance varies with respect to delay and throughput as observed from the RLP, for finite number of retransmissions at the MAC. We also consider that soft packet combining at the receiver is supported, which effectively lowers the frame error rate (FER). Simulation experiments have been conducted where synthetically generated HTTP traffic was used as the application, the objects of which were fragmented into equal sized RLP frames before being transmitted over the wireless channel. We observe that the the delay and the RLP retransmissions are low enough to sustain real-time communications with the incorporation of fast retransmissions at the MAC layer.