Effects of power control error on the performance of spread ALOHA protocols

The works that have been published on spread slotted ALOHA systems have assumed that power control errors are lognormally distributed. The analytical models that these works have produced have shown that the power control errors cause a reduction in the channel capacity (maximum throughput). On the other hand, the research done in slotted ALOHA systems has shown that differences in the received powers of packets contending for a common receiver lead to the capture effect. The capture effect is known to improve the channel capacity, packet delay and other important performance measures. This paper, motivated by these apparent uncertainties, examines the effects of power control errors in a spread-spectrum slotted ALOHA system using a single threshold in a channel-load-sensing scheme. The system assumes a finite population of data users that have variable length messages. The performance of the system with perfect and imperfect power control is examined through simulations. The capacity for systems with both perfect and imperfect power control is compared.