Abstract-Unlike terrestrial wireless communication which uses radio waves, underwater communication relies on acoustic waves. The long latency and limited bandwidth pose great challenges in underwater Media Access Control (MAC) protocol design. As a result, terrestrial MAC protocols perform inefficiently when deployed directly in an underwater environment. In this paper, we examine how an existing asynchronous handshaking based protocol called Multiple Access Collision Avoidance (MACA) can be adapted for use in multi-hop underwater networks. Three areas of improvement are investigated, namely, the state transition rules, the packet forwarding strategy, and the backoff algorithm. Throughput performance is also evaluated through extensive simulation in multi-hop underwater networks. Due to its simplicity and throughput stability, our proposed MAC protocol can be adopted as a reference MAC protocol for underwater networks, with which a more sophisticated underwater MAC may benchmark its performance.

No abstract

No abstract

In most existing sender-initiated handshaking based underwater Media Access Control (MAC) protocols, only the initiating sender is allowed to transmit data packets to its intended receiver after the channel has been reserved; none of the potentially backlogged neighbors of the sender can transmit in the duration after the current handshake. Therefore, each of those neighbors must initiate their own handshakes, which incur additional overheads and potentially result in poor channel utilization. In this paper, we present a novel approach to increase the channel utilization by allowing a sender to invite its one-hop neighbors (appenders) to opportunistically transmit (append) their data packets. After the sender finishes transmitting its packets to its own receiver, it can immediately switch its role to receive the incoming appended data packets, which arrive in a packet train manner. This greatly reduces the relative proportion of time spent on control signaling. We refer to this MAC protocol as ROPA-Reverse Opportunistic Packet Appending. From our extensive simulations and comparisons with existing protocols, we show that ROPA significantly increases the channel utilization and offers performance gains in terms of throughput and delay.

No abstract

Unlike most existing underwater Medium Access Control (MAC) protocols that use unidirectional data exchange, the recently proposed BiC-MAC protocol allows each senderreceiver pair to exchange multiple rounds of bidirectionalconcurrent data transmissions. Via simulations, it was shown that BiC-MAC greatly improves channel utilization. In this paper, we propose a novel analytical framework based on an absorbing Markov chain to analyze the single-hop saturation throughput for slotted BiC-MAC, under error-prone channel conditions. Motivated by the insight that time-slotting loses its effects when inter-nodal delay is longer than packet transmission time, the presented results can serve as a close approximation for the original, unslotted BiC-MAC protocol. We model the protocol behavior for a sender-receiver pair that attempts to bidirectionally exchange their backlogged batch of packets. To compute saturation throughput from batch service time, we systematically derive both the state transition probabilities and the expected time spent in each Markov chain. Via comparison against the simulation results of unslotted and slotted BiC-MAC in both small and large topologies with channel errors, we show that the model approximates unslotted BiC-MAC reasonably well. We also present another approach that uses the actual inter-nodal delay information and offers even closer approximation to the throughput of unslotted BiC-MAC. Index Terms-Underwater acoustic networks, MAC protocols, BiC-MAC, performance analysis.1536-1276 (c)

No abstract

No abstract