Aloha-Based MAC Protocols with Collision Avoidance for Underwater Acoustic Networks

Abstract

Unlike terrestrial networks that mainly rely on radio waves for communications, underwater networks utilize acoustic waves, which have comparatively lower loss and longer range in underwater environments. However, the use of acoustic waves pose a new research challenge in the networking area. While existing network schemes for terrestrial sensor networks are mainly designed for negligible propagation delay and high data rate, underwater acoustic communications are characterized by high propagation delay and low data rate. These terrestrial schemes, when directly applied to the underwater channel, will under-utilize its already limited capacity. We investigate how the underwater channel's throughput may be enhanced via medium access control (MAC) techniques that consider its unique characteristics. Specifically, we study the performance of Aloha-based protocols in underwater networks, and propose two enhanced schemes, namely, Aloha with collision avoidance (Aloha-CA), and Aloha with advance notification (Aloha-AN), which are capable of using the long propagation delays to their advantage. Simulation results have shown that both schemes can boost the throughput by reducing the number of collisions, and, for the case of Aloha-AN, also by significantly reducing the number of unproductive transmissions.

The Feasibility of Exploiting IEEE 802.11n for Addressing MAC Layer Overheads in UASNs

“…There have been many trials to use them for acoustic communications in UASNs [2,7,8]. CSMA requires a node to sense medium for the potential ongoing communication before it attempts to access the medium.…”

Media Access Control Protocol based on Dynamic Time Slot Assignment in Underwater Mobile Ad-hoc Network

“…이들 중에서 가장 기본적인 통 신 방법으로는 Pure ALOHA [6] Clustering Hierarchy(LEACH) [8] 는 센서망의 에너지 효 율성에 중점을 두고 고안된 프로토콜이다. 그러나 LEACH 에서는 확률적인 방법으로 클러스터 헤드를 선출하므로 모든 노드들이 항상 에너지를 효율적으로 사용하도록 클러스터 형태가 만들어지지 못한다.…”

RIPT: A Receiver-Initiated Reservation-Based Protocol for Underwater Acoustic Networks

“…The throughput analysis of Aloha in underwater is recently presented in [14] and [15]. In [16], we proposed two Alohabased MAC protocols, namely, Aloha with collision avoidance (Aloha-CA) and Aloha with advance notification (Aloha-AN). Both protocols are capable of exploiting the acoustic channel's long propagation delay, leading to superior throughput performance and lower collision rates when compared with other Aloha-based variants.…”

“…The buffer size for both new packets and relayed packets are set to 100 each, and the parameter M train is initialized to 1. We choose to benchmark our protocol with two previously proposed schemes, namely, Aloha-AN [16] and MACA [4]. For both of these protocols, we set the control packet length (i.e., NTF packet for Aloha-AN, and RTS/CTS packets for MACA) to 64 bits, while keeping all other parameters the same.…”