Proactive and reactive hierarchical routing protocols. A Survey

Abstract

The application of wireless sensor networks a increasing day by day. As the demand for this network increase so is the need to evaluate the characteristics of the existing networks so as to maximize the performance of these networks. Once implemented, the network is in- accessible to the user hence the design of the network should be in an energy efficient manner. Wireless sensor networks are formed by a number of sensor nodes which are battery powered with limited energy available per node. Wireless sensors are not only used for monitoring but also for gathering data from the network. Extracting data should be performed with minimized energy as sensor networks are battery powered and wastage of which will result in the inefficient functioning of the network. The Low Energy Adaptive Clustering Hierarchy (LEACH) is the most popular protocol in this category which is based on adaptive clustering technique. This paper presents a study on the various cluster-based routing protocols and their performance in simple wireless network in terms of routing and energy issues related to it.

Keywords: Wireless Sensor Networks(WSN), Routing Protocols, energy efficiency, cluster head .

I.INTRODUCTION

Wireless sensor networks consists of sensor nodes that are interconnected and they are controlled by a base station(BS).Routing protocol for wireless sensor networks is designed for two reasons: to increase the performance and efficiency of the network. Routing can be broadly classified into three categories based on the underlying network structure: flat, hierarchical, and location routing. In case of flat routing, all nodes are typically assigned equal roles or functionality. In hierarchical routing, nodes play different roles in the network. In case of location routing, sensor nodes' positions are exploited to route data in the network.

In case of adaptive routing, certain system parameters can be controlled in order to adapt to the current network conditions and available energy levels. These protocols can be further classified into multipath, query, negotiation, QoS, and coherent depending on the operation of protocol.

In addition to the above, routing protocols can be subdivided into three categories, namely, proactive, reactive. And hybrid protocols depending on how the source node finds a route to the destination node. In case of proactive protocols, all the routes are calculated before they are really needed, while in reactive protocols, routes are calculated based on demand. Hybrid protocols use a combination of these two protocols. When sensor nodes are static, it is better to have table driven routing protocols rather than reactive protocols. A huge amount of energy is used in discovery of routes and setup of reactive protocols. Next class of routing protocols is called the cooperative routing protocols. In case cooperative routing, nodes send data to a central node where the data can be aggregated and can be subject to further processing if needed, hence reducing route cost in terms of energy use. Many other protocols rely on timing and position information.

II.GENERAL CLASSIFICATION OF WIRELESS SENSOR NETWORKS -ROUTING CHALLENGES

Based on the mode of operation and the type of target application sensor networks can be classified [11] into two major types. They are:

A. Proactive Networks

The nodes perform sensors-switching and transmitters sense the environment periodically and transmit the sensed data to a BS through the predetermined route. At regular intervals they provide a snapshot of the cluster and its sensed data. This type is suitable for applications that require periodic monitoring of data in network.

B. Reactive Networks

The nodes in this network react immediately to sudden changes in the value of the sensed attribute beyond some pre-determined threshold value. They are therefore suited for time critical applications like military surveillance or temperature sensing.