A model for local/mobile radio communications with correct packet capture

The performance of a local/mobile radio communications system utilizing the slotted ALOHA multiple random access protocol is analyzed. The probability of correct packet capture is evaluated for a packet radio system using ideal coherent binary phase-shift-keying (BPSK) modulation. Both the near/far effect and the effect of Rayleigh fading on the probability of correct packet capture are taken into account, but the effect of thermal noise is neglected since the interference due to competing packets is dominant in practical systems. Spatial diversity, forward error-correction coding, and hard-decision Viterbi decoding are used to improve the probability of correct packet reception so that system throughput can be increased. The pseudo-Bayesian algorithm that has been developed to stabilize a packet system based on the slotted ALOHA protocol at maximum channel throughput is found to be adaptable to the local/mobile operating environment. For the system considered it is possible to obtain channel throughputs as high as 0.66, provided a spatial diversity of around ten can be implemented