基于IEEE 802.11的长距离无线Mesh网络

Long-Distance IEEE 802.11 Wireless Mesh Networks: A Survey

基于IEEE 802.11的长距离无线Mesh网络(LDmesh)的单跳链路长度在几十到上百公里,具有带宽高、成本低、覆盖广等优点,可广泛应用于偏远乡村或人口分布稀疏地区的无线宽带接入等.LDmesh网络是点到点的链路,链路的干扰特性和传输特性与传统无线Mesh网络有显著不同,原有的基于CSMA的MAC协议不再适用,进而影响到上层协议的设计.分析了LDmesh网络的研究进展,从链路性能、MAC协议、路由协议及网络管理等方面深入论述了LDmesh网络面临的挑战和进一步研究方向.

Long-distance IEEE 802.11 wireless Mesh networks （LDmesh） have been emerged in recent years for its high bandwidth, low cost and large coverage. It can be applied in rural regions or sparse-populated areas to provide high-bandwidth Internet access. In LDmesh networks, links are point-to-point and as long as tens to hundreds of kilometers. To achieve the long range, the wireless nodes are usually equipped with high-power （e. g. 400 roW） 802.11 wireless cards and high-gain （e. g. 32 dBi） directional antennas. The links in one node cannot transmit or receive data simultaneously because of the inter-link interference. The traditional CSMA/CA MAC protocol suffers poor performance in such a network for its long propagation delay, ACK timeout and inter-link interference. Therefore new TDMA-type MAC protocols have been proposed to solve the above issues, such as 2P MAC, WiLDNet and JazzyMac. The upper layer protocols such as routing and network management thus face great challenges and appeal new design diagram. In this paper, we introduce the fundamental concepts of LDmesh networks, survey the research activities in recent years, and discuss in depth the challenges in terms of link performance, MAC protocols, routing protocols and network management. The future work is also discussed.