Quality of Service in Wireless Network Diversity Multiple Access Protocols Based on a Virtual Time-Slot Allocation

In this paper, we propose a new resource allocation mechanism which is designed to improve the multiuser detection of wireless network diversity multiple access (NDMA) protocols. The mechanism consists of allocating an average number of time- slots to the active user population according to a prescribed quality of service requirement. It is dubbed virtual because it does not rely on user scheduling over different time-slots, but instead it is controlled by adjusting the probability of false alarm of each user. The allocation mechanism improves the throughput of conventional NDMA protocols at the expense of both an access delay degradation and an increased system complexity. The system requires to recover the signals from a mixing system with more outputs (the collected network transmissions) than inputs (the collided packets). By setting the average allocated time-slots to remain constant over different traffic loads, both the optimum transmission probabilities and the stability region of the protocol are approximated by relevant closed-form expressions. Also, the proposed analytical formulation extends the expressions of conventional NDMA systems to the asymmetrical user case (i.e. users with different data rates and detection statistics). Finally, it is shown that under extreme traffic loads, multiuser detection conditions and quality of service requirements, the proposed system degrades into the equivalent of the traditional networking protocols TDMA (time division multiple access) and Slotted- ALOHA (S-ALOHA).