The Research Of Multi-Rate In Wireless Ad Hoc Networks

A wireless ad hoc network is a set of nodes that can communicate with others in a multi-hop fashion without any assistance of fixed infrastructures. Its main advantage is that it can be rapidly deployed without base station. A wireless ad hoc network can be applied where pre-deployment of network infrastructure is difficult or impossible, for example, mobile meeting, disaster areas, armies on the march.IEEE 802.11 protocol has been accepted as a standard protocol of Medium Access Control (MAC) layer and Physical layer (PHY). The original IEEE 802.11 protocol provides only a single rate. By employing different modulation and channel coding schemes, the IEEE 802.11 PHY provides multiple transmission rates. Since IEEE 802.11 protocol does not specify any schemes to efficiently utilize the multiple transmission rates. Moreover multi-rate is also important for increasing throughput and energy efficiency. This thesis studies four multi-rate issues on the network layer and MAC layer for wireless ad hoc networks, including energy efficiency and network lifetime maximization in IEEE 802.11-base multi-rate wireless ad hoc networks, multi-rate unicast routing and multi-rate multicast routing.The main results of the thesis are as follows:(1)Energy Efficiency Rate Selection in IEEE 802.11-Base Wireless Ad Hoc Networks: This thesis studies the transmission rate selection on a path. The objective is to minimize the total energy consumption over the entire path subject to delay constraint. This thesis formulates it as a multiple-choice knapsack problem and presents an adaptive greedy rate selection algorithm named AGRSA. The simulation results show that AGRSA can reduce much energy consumption than the classic technique that all nodes transmit packets with the highest rate.(2) Rate Adaptation for Network Lifetime Maximization in Wireless Ad Hoc Networks: This thesis formulates it as a mixed integer nonlinear programming, which can be solved using branch and bound methods. Further, a greedy distributed maximizing network lifetime rate adaptation algorithm called MNLRAA is present. MNLRAA tries to selects the lower transmission rates for each link based on the traffic and the remaining energy at nodes so as to reduce energy consumption. The simulation results show that the network lifetime of MNLRAA performs better than that of the classic technique.(3) Multi-Rate Aware Unicast routing: According to the inherent limitation of on-demand routing protocol, this thesis presents a based on delaying RREQ multi-rate aware routing protocol named BDRMAR. After an intermediate node receives a RREQ, it forwards the packet suffer a time delay. The time delay is relation with the transmission rate of the link between this node and the sender of the RREQ. As a consequence, the route may contain a lot of high rate links. Simulation results show that, the throughput in BDRMAR is better than that in the common protocols.(4) Multi-Rate Aware Multicast routing: According to the fact that on-demand multicast routing protocol select routes between a source and a destination independently, this thesis makes an analysis of it and draws a conclusion it may decrease throughput with PHY providing multiple rates. This thesis proposes a cooperation-based multi-rate aware multicast algorithm named CMAM. CMAM replaces one low rate transmission with multiple high rate with the assistance of relay nodes where the sender of the low link with multiple receiver. CMAM can improve throughput and decrease delay.