Performance evaluation of packet reservation multiple access with an adaptive array

For local wireless communications, the packet reservation multiple access (PRMA) protocol, which combines random access with time division access, is known as an efficient access method to use silence periods of voice traffic. However, the performance of PRMA at the base station is degraded under heavy load conditions where many mobile stations transmit packets at the same time, because of the contention mechanism of random access. Also, for integrated transmission of voice and data, the performance of the voice terminal is degraded due to the data traffic. In this paper, we propose the use of the adaptive array antenna with PRMA protocol to improve the performance. In the proposed model, the adaptive array can acquire a packet by pointing the peak antenna pattern toward that packet even when a collision occurs. First, we evaluate the throughput and the packet dropping probability for voice-only traffic by theoretical Markov analysis and computer simulation, and show that the proposed model attains higher throughput and lower packet dropping probability than the conventional PRMA when the traffic load is high. Next, we evaluate the throughput and the packet dropping probability for integration of voice and data traffic by computer simulation, and show that the proposed model reduces the performance degradation of the voice terminal due to the addition of data traffic, compared to the conventional PRMA.