Research On Energy Efficient Routing Technologies In Mobile Ad Hoc Networks

A Mobile Ad hoc NETwork (MANET) is a wireless communication system with special structure. It is composed of a group of mobile, wireless nodes which cooperate in forwarding packets in a multi-hop fashion. It can be distributedly and dynamicly self-orgnized without any centralized administration and can be deployed in many complicated environments to support data communication. As a new branch of the wireless communication technologies, MANET has been developed rapidly and widely used in both military and civil applications. However, the wireless nodes in MANET are usually powered by batteries with limited energy, while the capability of the batteries cannot be greatly improved in a short term. Thus, energy efficiency has been the key problem in MANET's practical application. This thesis researches on the energy efficient algorithms in both MAC layer and network layer in MANET. Through deep analysing in theory and mathematical modeling, a series of energy efficient algorithms are proposed in this thesis to reduce the energy consumption and improve the cooperating time of all the nodes in the network. The main contributions of this thesis are listed as follows:In Chapter 3,a Signal Attenuation Rate based Power Control Algorithm (SAR-PCA)is proposed. SAR-PCA ultilizes the signal attenuation rate (SAR) to perform power control in MAC layer. Through in-depth analysis on the two common-used wireless signal propagation models (the free-space model and the ground reflection model), the author concluded that although the signal attenuation rate still numerically depends on the propagation model and the distance between two communicating nodes, it can be calculated only by the signal transmission power at the sender side and the received signal power at the receiver side. Thus SAR-PCA does not need the support of GPS (Global Position System) equipments and the localization algorithms. Since SAR-PCA works in a cross-layer fashion, it can be easily cooperate with energy efficient routing protocols. The simulation results show that SAR-PCA can efficiently improve the packet delivery number and prolong the lifetime of the nodes, thus improve the economic efficiency of MANET.Chapter 4 analyses the energy deficiency of route selection criteria in the Dynamic Source Routing (DSR) protocol of the MANET. By cooperating with SAR-PCA, a Minimum Energy Consumption routing Protocol based on DSR (MECP-DSR) is proposed. Through in-depth analysis in theory, MECP-DSR concludes that the reciprocal SAR is equivalent to the signal transmission power, thus can be used in the route discovery procedure to find a path with minimum power in DSR. However, MECP-DSR still lacks the mechanisms of balancing the energy consumption between nodes, a Power Aware Routing protocol based DSR (PAR-DSR) is also proposed in this chapter. By defining a new cost function, the nodes that have little battery energy possess large cost and consequently avoid being selected as the forwarding nodes in the route. The simulation results show that both MECP-DSR and PAR-DSR can significantly prolong the lifetime of MANET. MECP-DSR outperforms PAR-DSR in decreasing the energy consumption of the whole network, while PAR-DSR ourperforms MECP-DSR in reducing the differences of the nodes' lifetimes. Chapter 5 addresses the problem that the existence of retransmission in MANET does harm to the energy efficiency of the traditional energy efficient routing protocols which do not consider the packet error rate. The in-depth theoretical analysis shows that the routes found by traditional minimum consumption routing protocols tend not to be optimal in both End-to-End Retransmission (EER) model and Hop-by-Hop Restransmission (HHR) model. A more General Retransmission (GR) model is studied in this chapter. In this model, a node implements a limited number of retransmissions if the packet delivery fails. If all these retransmissions fail, the end-to-end reliability is guaranteed by the upper layers. This chapter analyses GR model in probability theory and proposes a mathematical model to calculate the accumulated path cost under this model. Also, the mathematical analysis shows that both EER model and HHR model are two special cases of GR model, thus the GR model is of excellent practicability. To satisfy the energy efficiency in the presence of GR model, an Energy-Efficient Routing protocol for Reliable Communication (ERRC) is proposed. The simulation results show that ERRC outperforms and is more accurate than the energy efficient routing protocols which do not considerate the packet error rate.Chapter 6 proposes a MultiPoint-Relaying-based Energy efficient Broadcasting protocol (MPREB) to overcome the drawback of the flooding broadcast mechanism that it cannot provide instructions for energy efficient routing protocols. MPREB provides 3 MPR selection strategies. In MPREB, each node uses some MPR selection strategy to select a part of its neighbors to establish a MPR set. When a node receives a broadcasting packet from one neighbor, it simply drops the packet to reduce the broadcast overhead if it determines that it is not among the MPR set of the sender. Simulation result shows that MPREB is energy efficient and significantly reduces the amount of necessary routing packets for energy efficient routing protocols.