PERFORMANCE COMPARISON OF ACKNOWLEDGEMENT PROTOCOLS FOR MULTIHOP CODE DIVISION MULTIPLE ACCESS NETWORKS.

Abstract

Three acknowledgement protocols are proposed for multihop code-division multiple-access (CDMA) networks. Time is divided into fixed length slots. Under protocol 1, the length of each time slot is equal to the transmission time of a data packet and an acknowledgment (ACK) packet. The ACK will be sent immediately following a successful data packet transmission. Under protocol 2, the length of each time slot is equal to the length of a data packet transmission. The time slot immediately following a transmission will be reserved for the ACK packet. Thus each transmission will use up two time slots. The length of a time slot in protocol 3 is the same as that in protocol 1, however, the ACK packet is used to acknowledge the data packet transmission in the previous slot, and the starting time of the ACK within the slot is randomized. The throughput/delay performance of these three protocols in multihop CDMA packet radio networks with buffered nodes are analyzed. It is shown that acknowledgement protocol 3 is the best choices for a wide range of network operation scenarios. However, it requires global knowledge of the ACK transmission time in each slot. Loss of this synchronization will degrade the performance dramatically.