Performance analysis and design of CQBT algorithm for a ring network with spatial reuse

A full-duplex ring network combined with destination removal can achieve a network throughput level much higher than the channel transmission rate. However, such a network exhibits fairness problems, particularly under asymmetric-loading conditions. Messages generated by nodes which are located as downstream neighbors of a heavily loaded node, can experience very long time delays. In this paper, we propose and study a new simple protocol, the check-quota-before-transmission (CQBT) algorithm, to effectively reduce the unfairness features associated with such a network. Under this algorithm, considering for example a slotted ring operation, each heavily loaded node monitors the ring traffic to determine the access opportunities provided to its downstream neighboring nodes. The monitoring nodes then release empty slots those downstream nodes which have been prevented from accessing the ring for unacceptable periods. Illustrative performance examples are presented to demonstrate the effectiveness of this algorithm. In addition, analytical performance results are shown to be very close to those obtained by simulations, for a wide range of offered load levels