New Reservation Multiaccess Protocols for Underwater Wireless Ad Hoc Sensor Networks

In a wireless network, where propagation delay is high and communications are sporadic, some kind of reservation protocol is generally used. Reservation access protocols were proposed earlier in earth stations-to-satellite communication with known propagation delay. However, optimality of the number of access slots with respect to the system performance parameters, such as system utilization, blocking probability, and delay, were not thoroughly studied. Besides, the effect of propagation delay uncertainty, which predominantly happens in underwater communications, are yet to be addressed. In this paper, we first analyze the system performance in many-to-one multiaccess data transfer scenario in underwater wireless ad hoc sensor networks with a fixed number of access slots and with the assumption of perfect propagation delay information. We propose two system state aware dynamic approaches to suitably adjust the number of access slots, and investigate the optimum slotting strategy to maximize the system utilization. Next, by accounting the propagation delay uncertainty, we relook into the optimality criteria on the number of access slots, where we apply a modified receiver-synchronized slotted Aloha principle to maximize the access performance. Via mathematical analysis, supported by discrete event simulations, we show that the system utilization and blocking probability performances with our proposed dynamic reservation protocols are consistently better compared to the competitive reservation protocols with fixed as well as variable access slots. Further, we conduct NS3 simulations to study the protocol performances under more realistic channel and traffic conditions, which also demonstrate that the proposed optimized dynamic slotting offers a much better system utilization performance compared to a similar underwater reservation multiaccess protocol.