Design And Implementation Of TDMA MAC Protocol For Multi-hop Wireless Mesh Network

Wireless mesh network(WMN)is a novel wireless network structure.It has been proposed as a promising technology in wireless communication networks in terms of broad application prospects because of its several features such as self-organization,self-configuration and self-healing.Medium Access Control(MAC)protocol is the strategy to control the access of multiple nodes to shared channel and thus it is of great importance in WMNs.Until now,most MAC protocols in WMNs were designed according to contention based IEEE 802.11 s.Adopting this standard renders the protocol design process simple and feasible.However,with the increasing number of the nodes and the increasing hops of routing,both the delay and the throughput degrade dramatically,resulting in a decline in the efficiency of the entire network.To solve the problem presented above,this paper designs a scheduling based Time Division Multiple Access(TDMA)MAC protocol for WMNs.We analyze and solve the key technologies in the protocol design.And we also conduct simulations to validate the performance of our proposal.The main contributions of this research are two-fold.First,a centralized TDMA MAC is proposed to enable multi-hop communication.Two categories of nodes,termed master node and slave node,are defined.By overhearing the information broadcasted by slave nodes,the master node can obtain the information of its adjacent nodes within two-hop area and then compute the global network topology.Our proposal uses dynamic slots allocation strategy,according to which the master node assigns slot to each node based on the global network topology and interference model within two-hop area.To coordinate the slots reuse beyond two-hop area and improve the efficiency of slots allocation,slots allocation is performed twice after each node joins the network and after the topology becomes stable respectively.As for the implementation of the protocol,we analyze detailed mechanisms,i.e.,node's join/departure,clock synchronization,information verification and feedback and channel quality instruction,and design the format of frames as well as the interfaces with upper layer and lower layer respectively.Second,we conduct simulations to validate the performance of the proposed centralized TDMA MAC in multi-hop WMNs.By analyzing the implementation of the proposed protocol,we build a network simulation model using OPNET to fully reflect the process of the protocol.We run simulations and compare the performance of the proposed TDAM MAC against 802.11 based distributed coordination function(DCF)and conventional TDMA using fixed slots allocation strategy.The comparison validates the outperformance of our proposal in terms of both throughput and delay performance.