On Optimal Slot Allocation for Reservation TDMA MAC Protocol in Shadow Fading Environment

This paper investigates the problem of providing delay guarantees to time-sensitive users sharing an uplink channel. The channel is a time slotted joint AWGN and impulsive noise channel in a shadow fading environment. Guaranteeing delay in shadow fading and noisy environment requires the MAC layer to be aware of the application delay requirements and the physical layer characteristics of the wireless channel. One of the important components of the base station MAC is the slot allocation module that allocates time slots to users. Existing slot allocation schemes use linear proportional schemes based on the queue state and priority factor. We develop an optimal slot allocation scheme that bases its allocation decision on the buffer content, the traffic class factor and the wireless channel quality. We specify the wireless channel quality in terms of the probability of connectivity between users and the base station and develop a method of estimating this quantity. Instead of absolute no transmission during bad wireless link states our optimal slot allocation module allots fewer slots in bad link states. The slot allocation module is used in a reservation TDMA base station (BS) MAC to control queuing delay and improve throughput. The performance of the slot allocation scheme is evaluated using OPNET simulation.