Research On Energy-optimized Routing Protocols In Wireless Ad Hoc Networks

Compared with traditional networks, wireless ad hoc networks (hereinafter termedas ad hoc networks) are energy-constrained in many applications, because the nodes arepowered by batteries and batteries recharging is infeasible. Energy limitation is one ofthe most critical bottlenecks that restrict their potential applications and developments.How to design energy-optimized routing protocols in the increasingly complex networkenvironment has become a premier research topic. In recent years, numerous domesticand foreign researchers have proposed many energy-optimized routing protocols toaddress a series of practical issues based on some assumptions in specific environment.However, with the ad hoc networks moving toward the direction of intellectualization,complexity and multifunction, more and more simulation results and applications showthat the existing energy-optimized routing protocols can not fully solve practicalproblems and meet various application requirements for energy conservation. Forcertain specific circumstances, energy-optimized routing is still needed to further studyprotocols.In this thesis, the related work on energy-optimized ad hoc routing is analyzed, andsome critical issues involved in the energy optimization for ad hoc networks in thecurrent network environment are pointed out. By incorporating the characteristic ofenergy consumption with network delay, communication interference, and geographicinformation and so on, some pracatical issues in energy-optimized routing for ad hocnetworks are addressed. The main research results and innovations are summarized asfollows:1. Research on Cross-layer power-optimized routingA cross-layer power-optimized routing protocol is proposed. Without the nodelocation information, the proposed scheme adaptively establish a number of routes atdifferent power levels, and select the route to destination node with the minimum powerlevel for data delivery. In order to further reduce energy consumption, each nodeholding the data packets adjusts its transmission power level to the same as the powerlevel of the selected routing entry for delivery data packet, and the control packets of network layer and MAC layer.2. Research on delay-oriented power-optimized routingA delay-oriented power-optimized routing protocol is proposed, which aims atreducing the total energy consumption while meeting the desired delay requirement.The proposed scheme adaptively builds different delay-oriented routing entries overseveral fixed discrete power levels, and selects the route with the minimum power levelfor data delivery. To further reduce energy consumption, the proposed scheme utilizescross-layer power control strategy to transmit data packets, and the control packets ofnetwork layer and MAC layer.3. Research on energy-optimized single-path geographic routingFor existing geographic routing, too much energy will be wasted in sensornetworks and the path from the source to the destination becomes long when itencouters routing void. To adrress this issue, an energy-optimized single-pathgeographic routing is proposed. In our shcheme, the anchor nodes are introduced toguide data delivery. Each node holding the message utilizes geographic information, thecharacteristics of energy consumption and the metric of advance energy cost to makeforwarding decisions. This way, each data packet is routed to destination node along anenergy-optimized route, thereby both improving the routing efficiency and optimizingnetwork performance.4. Research on energy-optimized multi-path geographic routingNoting that the range of transmission has a significant effect on the powerconsumption of the listeners, a more realistic energy model is used to calculate theactual energy consumption. This model is an abstraction of real energy overhead for thenetwork. It statistics the energy consumption of both communication nodes and thenodes within their transmission ranges. This model contributes great benefit to us tocalculate the actual energy consumption, and provides a reference for geographicrouting to select energy-optimized path. Based on this cognition, an energy-optimizedmulti-path geographic routing is proposed. The existing geographic routing tends toutilize one fixed routing path to delivery the data packets, this may rapidly deplete theenergy of the nodes on the path and thus shorten the network lifetime. To solve thischallenge, our scheme uses a dynamic anchor list to shift routing path for load balance,and utilizes geographic information, the characteristics of energy consumption and the metric of advanced energy cost to select the next forwarding node for energyconservation. The optimal anchor node is different with different data packets, thusdifferent data packets may be routed to destination along different routes as far aspossible. The proposed approaches contribute great benefit to energy conservation andprolonging network lifetime, and also enhance network performance in terms ofend-to-end delay and packet delivery ratio.5. Research on interference-sensitive energy-optimized geographic routingThe interference is an inherent characteristic of wireless communications and mayresult in data collisions and consequently data retransmissions, thereby reducing therouting efficiency and shortening the network lifetime. However, most existingenergy-aware geographic routing protocols rarely or at most simply take into accountthe interference reduction as the optimization objective. To address this issue, aninterference-sensitive energy-optimized geographic routing protocol is proposed, whichfocuses on minimizing the total network energy consumption and reducing interference.In order to avoid detouring mode, our scheme adaptively obtains an anchor list to guidepacket delivery. For energy conservation and interference reduction between twoconsecutive anchor nodes, each forwarding node selects the neighbor with the minimuminterference as the next relay node in energy-optimal relay area, and dynamicallyadjusts its transmission power so as just to reach the selected neighbor. The scheme isfirst introduced by us, and has a profound effect on energy conservation andinterference reduction simultaneously, thereby maintaining good network performance.