Performance Analysis of Random Access Channel with Retransmission Gain

This paper analyzes the maximum steady throughput, optimum media access control (MAC) and stability region of a random access channel over channels with retransmission gain. The channels are defined by the packet detection probability determined by the number of packet transmissions and the number of packet collisions. For a two-user channel, the stability region and the maximum steady throughput are obtained in closed form. The conditions that the maximum throughput is reached with no MAC control are obtained for symmetrical and asymmetrical channels, respectively. The well-known results of the orthogonal and the ALOHA channels are shown to be special instances of our results. The throughputs of multiuser symmetric channels and the general multiuser asymmetric channel are further obtained. A practical random access CDMA channel exploiting retransmission diversity is analyzed based on the model. Numerical result confirms with the analytical results. As a general conclusion, retransmission gain can improve significantly channel performance.