水声网络全双工定向碰撞避免媒体接入控制协议

近年来水声网络(UAN)技术飞速发展，但仍然面临诸多严峻挑战，能量效率成为水声网络的首要考虑因素。此外，水声信道传播时延大且可用带宽受限，严重制约了水声通信技术的可靠性和有效性，进而限制了水声网络的整体性能。定向通信技术可以有效改善上述情况，通过波束聚焦能力将声波能量聚集在一定角度范围内，获得比全向通信更高的通信范围和信噪比，提升整个网络的能耗效率和空间复用率。但该技术需要对目的节点的位置具备先验知识，且会面临“聋节点”问题，因此该文提出一个水声网络全双工定向碰撞避免(FDDCA)媒体接入控制(MAC)协议，通过装备两个分别处于不同工作频带的全向换能器和定向换能器解决“聋节点”问题，并通过降低节点的冲突域解决了“暴露终端”问题。仿真结果表明，与水下Aloha(UW-Aloha)和时隙地面多址接入(S-FAMA)协议相比，FDDCA在多汇聚节点的网络拓扑下吞吐量分别提升了140%和400%，网络能效上节省了90%和94%。

Full-Duplex Directional Collision Avoidance Medium Access Control Protocol for Underwater Acoustic Networks

A great improvement in Underwater Acoustic Network (UAN) has been witnessed in past few years, but severe challenges still remain, and energy efficiency becomes the primary consideration of UAN. In addition, the reliability and effectiveness of underwater acoustic communication technology are seriously restricted by the large propagation delay of the underwater acoustic channel and the limitation of available bandwidth, and the performance of UAN is limited. Through the ability to focus a beam, the above challenges can be effectively addressed by directional communication technology, resulting in a higher communication range and signal-to-noise ratio than omnidirectional communication, as well as energy consumption efficiency and spatial reuse ratio of the whole network are improved. However, a priori knowledge of the location of the destination node is required and the problem of deafness occurs. Therefore, the Full-Duplex Directional Collision Avoidance (FDDCA) Medium Access Control (MAC) protocol is proposed in this paper, with which the problem of deafness is resolved by using two transducers that work in omnidirectional and directional modes, respectively, as well as the exposed terminal problem. Results supporting the conclusions are shown in the simulations, where 90% and 94% energy savings, 140% and 400% throughput improvements are acquired in different network topologies by FDDCA, compared with UnderWater Aloha (UW-Aloha) and Slotted FAMA (S-FAMA) protocol.