An Energy Balancing LEACH Algorithm for Wireless Sensor Network

Abstract

As a typical hierarchical routing algorithm in wireless sensor network, LEACH protocol can reduce the routing overhead greatly. And it makes the network load balance relatively and have a good scalability. But there are still many deficiencies, such as the uneven clustering, unreasonable cluster head-selection, the single hop communication inter clusters and unsuitable for the large-scale network. Therefore, this paper proposes a new energy balancing routing algorithm, which determines the optimal number of cluster head based on the energy consumption of the network and selects the optimal cluster head based on network load balancing. The simulation results show that the algorithm can balance network load, prolong the network lifetime effectively. Introduction WSN (wireless sensor network) is a self organizing system. This system consists of sensor nodes, sink nodes and management nodes. And it is widely used in military, medical, environmental monitoring and so on. However, sensor nodes have the shortcomings such as energy limited storage capacity, low computing power and weak communication capabilities[1,2]; The network lifetime depends on the energy consumption of sensor nodes largely. Therefore, we can improve the efficiency of routing greatly in the network, reduce the routing overhead and the energy consumption of the nodes properly to reach the balance between energy consumption and communication[3,4]. It will greatly promote the development and application of wireless sensor networks. The rest of the paper is organized as follows: section 2 introduced several famous papers about reducing energy consumption in LEACH protocol proposed before; section 3 described the network energy consumption model and the radio model in this paper; the fourth section analyzed the deficiency of the LEACH algorithm. In the fifth section we carefully described the proposed algorithm and discussed the performance of the improved algorithm by simulating the network lifetime. In the end, we gave the conclusion and our future work. Related work In order to make the WSN energy minimization, researchers have proposed many efficient routing protocols recently. Heinzelman first proposes the LEACH protocol [5]. It selects cluster head randomly which balances the network load and energy consumption. But it does not consider the residual energy of nodes; Then Heinzelman proposes LEACH-C routing algorithm, which is a centralized cluster head election algorithm. The base station selects the cluster head node according to the location and the residual energy information of nodes [6]. But it causes the instability of the network easily; Gao and Yoo propose PLEACH algorithm based on LEACH-C, which calculates the optimal number of cluster head nodes. It recognizes the sink node as the center of the network and divides region into equal size, and selects the cluster head according to the residual energy in various regions [7].Though it can make the cluster distribution more uniform, but it did not consider the influence of the number of clusters and cluster size[8,9] on the network balancing. Based on the above discussion, this paper proposed an improved algorithm for LEACH routing based on optimal cluster head. The algorithm gets the relationship between the total energy consumption of nodes and the cluster head number through the analysis of the influence factors on 2nd International Conference on Electrical, Computer Engineering and Electronics (ICECEE 2015) © 2015. The authors Published by Atlantis Press 752 the optimal number of clusters, and deduces the optimal cluster head ratio formula. And it gives an energy balancing clustering routing algorithm in wireless sensor network, which considers node residual energy and the distance between the member node and sink node in the cluster head election process to balance the node energy consumption and prolong the network lifetime. Network energy consumption model At the stage of selecting the cluster head in LEACH protocol, every node generate a random number between [0, 1]. If the number is less than the threshold TT(nn) (which is determined by the formula (1) ), the node will become a cluster head. pp is the percentage of cluster heads in all nodes. rr is the number of selection round. G is a collection of unselected nodes. Since then,the number can act as cluster heads is less. So the probability of other nodes becoming cluster heads will increase to ensure the number of cluster heads of each round. After 1 pp � − 1 rounds, the probability of the node which is not selected as cluster node will be 1. After 1 pp � rounds, all nodes begin the random decision to act as cluster head or not. However, the cluster head selection methods did not consider the node residual energy and distance information. TT(nn) = � pp 1−pp∗�rrrrrrrr pp� iiii nn ∈ GG 0 ooooheerreeiieeee (1) In this paper, we use the transmission system model which is proposed by reference[5] to calculate the energy consumption of the network. In the LEACH algorithm, the model have three conditions: all nodes are same and have limited energy in the network; The radio signals have same energy consumption in each direction; The position of base station is fixed. The model includes: the energy consumption of transceiver circuit, amplifier circuit and receiver circuit. The node energy consumption of sending ll bits packet is: EETT(ll,dd) = EETT eeeeeeee(ll) + EETT aarrpp(ll,dd) = � EE eeeeeeee ∗ ll + EE eeeeeeee ∗ eeffff ∗ dd2 dd ≤ dd0 EE eeeeeeee ∗ ll + EE eeeeeeee ∗ eerrpp ∗ dd4 dd > dd0 (2) Here EE eeeeeeee is energy consumption of transceiver or receiver processing 1 bit. And dd is transmission distance, eeffff and eerrpp is energy consumption of transceiver of amplification circuit. dd0 is the transmission distance threshold value, and dd0 = �eeffff/eerrpp. If the transmission distance is less than the threshold value dd0, power loss model is to use free space model; And if the transmission distance is greater than or equal to the threshold value dd0, power loss model is to use multipath attenuation model. Energy consumption of the sensor node receiveing ll bits message can be calculated as: EERR(ll) = EERR eeeeeeee(ll) = EE eeeeeeee ∗ ll (3) Therefore, the energy consumption of ll bits data from the node nnii transfered to nnjj can be expressed as: EEii,jj(ll) = EERR(ll) + EETT(ll,dd) (4) Deficiency of the LEACH algorithm Although the LEACH algorithm has a better performance, but there are still many shortcomings: (a) The selection of cluster heads is determined by the time only, and it do not have a relationship with the residual energy of nodes; cluster head selection frequently will lead to large amount of broadcast messages and the node energy cost. (b) In the formation of cluster, all the non-cluster head nodes are involved, and the percentage of cluster heads in all nodes is the same all the way. So it will increase the complexity of the formation of cluster.