Studies On Energy-efficient Nodes Lacement In Wireless Sensor Networks

In recent few years, with the booming growth of Internet,System-on-a-Chip (SoC), wireless communication and softwaretechnology, Wireless Sensor Networks (WSNs) have been used in a lot ofindustries more and more. WSNs consist of a lot of tiny sensor nodes (SN)which are placed in the Region of Interest (ROI), and these nodes form acommunication network by wireless communication. The nodes sense thelocation where they are, gather information, process information andtransmit the information to the observer (sink) who will make decisions.WSNs enable people to detect the ROI without accessing to theenvironment, which not only conserves time and purse, but also canprovide data for people more accurately, more effectively and more timely.Due to that the nodes in WSNs are usually driven by batteries, theinitial energy of the nodes is generally relatively low, which makes thelifetime and the network energy efficiency be two main concerned issueswhen designing the networks. To improve the network energy efficiency,this paper focuses on the issues of sensor nodes placement and relay nodesplacement. The main contents of this paper are mainly as follows:1. Assuming the gap between the transmitter and the receiver to befixed, based on the different fading models of the wireless transmissionchannel and environment noise models, calculate the re-transmissionprobability and the expected value of the total energy consumption whenthe transmitter sends data with different power, respectively. Then theoptimal transmission power is obtained. Theoretical analysis prove thatwhen the transmitter sends data by the optimal transmission power, theexpected energy consumption when the data has been processedsuccessfully by the receiver is minimized. Besides, the simulation resultscertify the theoretical derivation.2. When the source node is far from the destination and it sends thedata to the destination directly, the optimal transmission power will be verylarge and may be larger than the maximum transmission power of the node,which will decrease the energy efficiency. On the other hand, the energy efficiency will be also low even though the maximum transmission powerof the node is large enough due to the nonlinear fading characteristic in thewireless transmission environment. To improve the network energyefficiency, the data can be transmitted by multi-hop communication. In thispaper, the optimal one-hop transmission range is carried out and is alsochecked by simulation.3. A novel sensor node placement algorithm is proposed based on theoptimal one-hop transmission range and the coverage requirement of thenetwork, and this algorithm can balance the energy consumption and avoidthe energy hole. Simulation results indicate that the network energyefficiency is raised by the proposed algorithm compared to the schemeproposed in [17].4. WSNs are usually used for monitoring the harsh environment, sothe sensor nodes are prone to a variety of unexpected factors and losingfunction, which makes the network to be some disconnected segments.Depended on the connection requirement and the lifetime requirement, aconnection algorithm is raised by placing relay nodes. The proposedalgorithm needs the least relay nodes compared to the algorithms proposedin [24] and [47].