| Mobile Ad Hoc Networks is a wireless mobile dynamic autonomy networks, which is composed of hosts/nodes. Mobile Ad Hoc Networks does not require fixed base-station facilities. Because of the characteristics of the networks, it is easy to make up. This networks technology has very broad prospects for the application in military and emergency rescue and other special circumstances.Ad Hoc networks compared with traditional wireless networks also has the following characteristics: (1) the limited communication bandwidth. Nodes in Mobile Ad Hoc networks communicate with others through radio, compared with cable media, wireless cable has obviously smaller bandwidth. (2) the limited energy of the nodes. Each node in Mobile Ad Hoc Networks needs battery-powered, once a node exhausted its energy, it can not effectively commucate with the others; At the same time, all the nodes communicating with other nodes through this node must be using a new routing, the entire networks may be divided. (3) the mobility of nodes. Nodes in Mobile Ad Hoc networks can be mobile at any time, resulting in the networks topology may be changed.The applications of Ad Hoc networks in these special circumstances are often one-to-many or many-to-many data transmission. Since the communication bandwidth limited in Ad Hoc networks, it needs for a technology to meet the requirement of multi-point communication and will not occupy high bandwidth. Multicast is the technology for multi-point- to-multipoints or one-point-to-multipoints data transmission traffic. Multicast allows one or many senders to transmit data packets to multiple recipients (once, at the same time). The senders transmit the data packets to a specific multicast group, and only the nodes whose address belongs to the multicast group can receive data packets, multicast can be a greatly degree of saving networks bandwidth, because no matter how many goals address, any link in the networks only transmits a single data packet. This makes the investigation of multicast technology in Ad Hoc networks has great significance. Since Ad Hoc networks energy is limited, it is necessary to investigate the energy-saving technology in Ad Hoc networks.Firstly this thesis introduced the national and overseas recent researches on Ad Hoc networks multicast technology and energy problem;Secondly this thesis detailedly analyzed the basic principles of Ad Hoc networks and multicast technology, which included IP multicast principle and implementation, and also analyzed multicast characteristics in Mobile Ad Hoc Networks compared to IP Networks, then detailedly analyzed MAODV(Multicast Ad Hoc On-Demand Vector) multicast protocol in Ad Hoc networks; and then discussed two energy-saving technology of Ad Hoc Networks: wireless NIC dynamic closure mechanism and power control mechanism;Based on the above research and analysis,this thesis improved multicast tree generation algorithm of MAODV multicast protocol from the perspective of the balance of energy consumption, and designed the power control algorithm for controlling the power of multicast data transmission based on communication distance.The investigation on energy problem of Ad Hoc networks in this paper had been divided into two parts. First, the paper optimized Ad Hoc networks MAODV multicast routing protocol and improved its multicast tree generation algorithm. It optimized MAODV protocols based on the maximizing local networks lifetime multicast tree generation algorithm. Second, It investigated Ad Hoc Networks power control algorithm under the multicast environment.For improving multicast tree generation algorithm, this thesis firstly carried out a detailed analysis of the principle and implementation of multicast technology as well as IGMP protocol, then investigated MAODV multicast routing protocol of Ad Hoc networks. MAODV is a multicast tree routing protocol based on the on-demand routing technology. The so-called on-demand routing protocol refers that the routing protocol has not always been maintained the routing to all purposes, but according to the needs of source routing established the corresponding routing. This on-demand routing technology effectively reduces the control packet load of protocol in the networks channel and increased channel utilization. Multicast routing protocol on demand is very suitable for Multi-hop Wireless Ad Hoc Networks.The multicast tree generation algorithm of MAODV multicast protocol in the process of routing selection just focuses on the performance parameter of hop-count and lacks of considering balance of the nodes residual energy consumption in the routing, which had led to rapid deterioration the networks lifetime, this thesis presented that the improvement of MAODV protocol multicast tree generation algorithm based on the maximizing local networks lifetime. In the process of MAODV protocol multicast routing selection, the residual energy of the nodes would be an important parameter to balance energy consumption in the networks and extend the networks lifetime. This thesis designed and implemented the improvement of MAODV multicast tree generation algorithm on NS simulation platform, by analyzing the simulation data, the MAODV protocol which improved multicast tree generation algorithm compared with the original MAODV protocol had better improved both in energy consumption and networks lifetime, and played a good role in balancing energy consumption.For power control, this thesis focused on power control theory under multicast mechanism in Ad Hoc networks, according to the characteristics of multicast mechanism, power control algorithm under multicast communication mechanism had some difference between under unicast communication mechanism, and this thesis design a new power control algorithm besed on the above. Unlike unicast data transmission, before nodes transmitting multicast data, they do not send RTS/CTS to reserved interactive channel on the MAC layer, so traditional power control algorithm based on RTS/CTS interactive mechanism is not suitable for multicast networks. Power control algorithm in this thesis was based on the networks topology and using GPS to obtain the location information of next hop nodes, then control the multicast data transmission power according to the communication distance, and compare with the traditional one with the greatest power to transmit data, had a good improvement on saving energy. This thesis implemented the power control algorithm on NS simulation platform, by analyzing the simulation data, the power control algorithm for the multicast networks in networks lifetime and energy efficiency had a good improvement than the original multicast networks without power control.In conclusion, the primary work of this thesis is researching energy problem in Ad Hoc networks based on MAODV multicast. It is divided into two aspects, which are multicast tree generation algorithm and power control algorithm, separately from balanceing networks nodes energy consumption and improving energy efficiency, and had some improvements in networks lifetime and energy efficiency. Due to limited time, there are still many imperfections in the system at present, the author will improve it during afterward works. |
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