The Energy Efficiency In Ad Hoc Networks

Ad hoc networks are multi-hop wireless networks without fixed infrastructure.Because node's strong dependency on batteries, the Ad hoc networks areenergy-constrained. How to improve energy efficiency is an important design issuedue to the limited battery life.This paper presents a summary of recent work on energy efficiency among alllayers of Ad hoc networks, defines a model of Ad hoc network using random graphtheorem, and gives an energy consumption model by realistic test. Our researchesfocus on energy efficiency of the MAC layer and the network layer.In the MAC layer, we develop a new energy efficiency MAC protocol calledPEMAC. This protocol reduces the energy consumption of node. Using PEMAC, anode with packet to transmit sends an RTS message, and the destination node returnsa CTS. The node should switch into the sleep state when:(1) if there is no packet totransmit after an idle period, or (2) it receives an RTS/CTS message destined to othernode. A Markov chain model for PEMAC is presented to obtain the optimal sleepingtime of the node. Simulation results show that, compared with traditional IEEE802.11 Ad hoc networks, PEMAC outperforms in terms of network lifetime andnetwork throughput.TBER is a new energy-efficiency metric for determining routes in Ad hocnetworks. With TBER, the node's residual energy (remaining battery capacity) andMAC load are taken into account. As a result, an established route avoids usingnodes with minimum energy or heavy load. A comparison of MPTR routing andTBER routing metric is conducted. The analysis and simulation results show thatTBER routing metric can prolong the network lifetime and increase networkthroughput when there are enough routes to be selected. Results also show that theimprovement is limited due to overhearing.We also combined the PEMAC with TBER and get the conclusion thatincorporation of energy efficiency methods appropriately can further improvenetwork lifetime and throughput.