RATE OPTIMIZATION SCHEME FOR NODE LEVEL CONGESTION IN WIRELESS SENSOR NETWORKS Prabakaran.N 1 , Shanmuga Raja.B 1 Pervasive Computing Technologies, Anna University of Technology, Tiruchirappalli, India {dhoni.praba, bsraja.inba}@gmail.com Prabakaran.R 2 Asst. Professor, Dept of EEE, Anna University of Technology, Tiruchirappalli, India hiprabakaran@gmail.com V.R.Sarma Dhulipala 3 Asst. Professor, Dept of Physics, Anna University of Technology Tiruchirappalli, India dvrsarma@gmail.com Abstract-The Application specific wireless sensor network differs basically from the general data network. It focuses on tight communication but restricted in storage, lifetime, power and energy. The WSNs consists of unbelievable network load and it leads to energy wastage and packet loss. Many of the existing concepts are developed for link level congestion control. The Rate optimization technique for node level congestion will assist to control the traffic at node level. Except source and sink node the remaining nodes may participate in forwarding the packets towards the communication direction. The rate based adjustment technique is applied to avoid packet dropping in order to save the network resources. We are proposing this scheme to avoid the buffer overflow and it is not taking too much energy consumption in the communication. This scheme will assist to improve the throughput, efficiency and resource saving. Node level congestion control is effectively needed for WSN, because the node deployment can be anywhere. We are Introducing this scheme using the network simulators extended tool called mannasim. Keywords- Buffer Overflow; Congestion Control; Node deployment; sink. I. INTRODUCTION ireless sensor Networks have been used tremendously in target monitoring, location tracking and battlefield etc. Generally the sensor nodes are restricted in storage, lifetime, power, computation capability and in energy too. It can be deployed anywhere, where it might not be possible to use traditional networks. The formation of the network is done without human intervention. Similarly addition and removal of nodes is done without human help. We can operate these nodes in uninterrupted environment in order to accomplish the task. The sensor nodes are very small in nature, they consists of small processing unit, which is having the capability of limited computational power [9]. Generally they are battery powered and energy constrained. The sink node i.e. target node is most powerful which is used as gateway to the wired network and it is doing data collecting and processing. The nodes deployed area is called sensing field, where each node has its own range. The lifetime of the sensor node is normally limited, before its energy exhausted, it should be used effectively. In many of the applications, less cost sensors are used and placed in the vast region [1]. The routing technique used is challengeable one. The ad-hoc routing protocols are not applicable [4], because here nodes are numerous and power constrained. The topology also random topology since it is changing its structure frequently. During the communication flow, traffic is unavoidable one. The traffic in WSNs causes the congestion in the network. In previous research fairness bandwidth allocation is not well addressed. But it is very difficult to allocate the rate for each flow in communication. Congestion in WSNs has negative impacts on network performance and application objective, i.e., packet loss, increased packet delay, wasted node energy and severe reliability degradation. Figure 1. Simple Wireless Sensor Network However, some characteristics of WSNs, such as constrained resources, interference of paths and the lack of centralized coordination, make the congestion problem in WSNs more than traditional networks. In addition, to let the sink successfully receive the data from different sensors, we need to consider the fairness issue among the source nodes [6]. The main source for network congestion in WSNs can be Channel Contention and Interference. Another one cause can be a Packet Collisions. Increasing network contention causes an increase in packet collisions in the wireless medium. After Several unsuccessful retransmissions, these packets are dropped at the sender node. In order to control the congestion initially congestion detection is essential. In WSNs, W 978-1-4244-9190-2/11/$26.00 ©2011 IEEE