On the Throughput Performance of Some Continuous ARQ Strategies with Repeated Transmissions

The paper considers a class of continuous ARQ strategies, whereby multiple copies of each data block are sent contiguously (instead of one single copy), and whereby the data blocks are delivered at the receiver side in their order of arrival at the transmitter. In order to achieve the best possible throughput efficiency-within this class-an optimum value for the number of copies to be sent is determined, in terms of the block error probability and the propagation delay. It turns out that, depending on these parameters, the optimum scheme is one of the two following alternatives: 1) sending each data block repeatedly until a positive acknowledgment is received for it; 2) sending each block a constant (optimum) number of times. A throughput comparison of the optimum scheme with other related ARQ strategies is given.