Routing Protocols In Wireless Sensor Networks

Published Date: 02 Nov 2017

The significant advances in wireless sensor network technology has provided the need of green computing such as small and low cost sensor nodes have the ability of sensing, processing and communicating capabilities. By networking a large number of tiny sensor nodes, various applications in wireless sensor networks that connect the physical world to the virtual world. Nowadays, wireless sensor networks are facing various issues like power and bandwidth constraints, less transmission speed and low storage capabilities among these the power efficient is an major issue. So Green - energy technology is now playing an important role in this physical world to improve the power saving factor. There are various routing protocols achieving the contemporary methodologies such as network flow, energy efficiency, Quality of service (Qos), security in the wireless sensor networks are proposed. Yet now, these routing protocols are not achieved the maximum range of energy efficiency, storage capacity, low computing power. In this paper we give a survey of energy-efficient hierarchical routing protocols and their classification in detail.

Keywords: Wireless Sensors Networks, Hierarchical Routing Protocols & Energy Efficiency.

Introduction

The recent technological development in wireless sensor network (WSN) has become hot area nowadays in research1. The WSN typically consists of a large number of small size multifunctional wireless sensor nodes which is capable of sensing, processing, storing, routing and also various computation capabilities2.Using these sensor nodes all the wireless mobile devices will be capable to communicate with each other to form complete infrastructure. Several hundreds or even thousands of tiny sensor nodes connected form WSN as shown in Figure 1. Due to the vast potential of sensor networks to enable the applications that connect the physical world to the virtual world. Each node acts both router and host and the topology of network also vary rapidly. The characteristics of sensor networks and application requirements have a decisive impact on the network design objectives in term of network capabilities and network performance3. Many routing protocols are implemented with Green energy computing technology (low power and high energy efficiency) to form complete infrastructure in wireless sensor network as discussed in this paper. The design of routing protocols for WSN is challenging because of several network constraints like synchronization, node localization, low battery power etc. A large number of research activities have been carried out to explore and overcome the various issues and energy constraints in wireless sensor networks. In this paper we discuss and survey hierarchical routing protocols and their classification in briefly.

†Dean, Arunai College of Engineering, Thiruvannamalai - Tamilnadu, INDIA

Figure.1 wireless sensor networks

Routing Protocols in Wireless Sensor Networks

For an efficient route for an un-interrupted communication, many protocols are suggested depending upon the various applications and type of networks.

The three main categories of routing protocols are proactive, reactive and hybrid. In proactive protocols, routs are computed automatically and independently, while in reactive protocols the nodes react immediately on demand based. Hybrid protocols are the combination of proactive and reactive routing protocols.

A significant amount of energy is used in route discovery and setup of reactive protocols. Many techniques are used in routing protocols among those the three main techniques are Flat, Hierarchical and Location-based Protocols. The Hierarchical routing protocols plays an important role in efficient energy consumption in wireless sensor networks.

Green Energy Efficient Hierarchical Routing Protocols

Green - energy technology aims to reduce resource consumption and improve power - saving like energy consumption etc., Hence Green Computing is used to achieve cost-reduction and operational benefits in wireless sensor networks. Hierarchical or cluster-based routing is utilized to perform energy-efficient routing in WSNs.

The creation of clusters and assigning special tasks to cluster heads can greatly contribute to overall system for low power high energy efficiency and the data aggregation and fusion greatly reduce the energy consumption and increase the network lifetime by decreasing the number of messages sent to the base station in wireless sensor networks.

Two layers used in hierarchical routing protocol is one layer for selecting cluster head and another layer for selecting routing.To attain low power & high energy efficiency in WSNs ,our goal is mainly focuses on the five major different Hierarchical routing protocols like LEACH, PEGASIS, HEED, TEEN and APTEEN.

Figure 1- Hierarchical Routing Protocols

Low Energy Adaptive Clustering Hierarchy (LEACH) : LEACH 4,5,6 is the first and most popular energy-efficient hierarchical clustering algorithms for sensor networks. It is an proactive hierarchical routing protocol. This was proposed for reducing power consumption. Based on the duration the clustering task is rotated among the sensor nodes.

The Cluster Head (CH) uses direct communication by forwarding the data to the base station (BS).LEACH use clusters to lengthen the life of the wireless sensor network. LEACH uses the aggregation technique that combines the original data into a smaller size of data to carry out meaningful information to all sensors in the sensor field.

In LEACH, randomize rotation of high energy CH position is selected instead of static manner in order to give chance to all sensors to act as CHs and avoid battery depletion of individual sensors and avoid dieing in very short period of time. The operation of LEACH is divided into rounds having two phases namely a setup phase to organize the network into clusters, CH advertisement and transmission to the sink by minimizing the communication cost between sensors and their cluster heads to achieve green energy technology.

LEACH uses single-hop routing where each node can transmit directly to the cluster-head and the sink. So it is not applicable to wireless sensor networks deployed in large regions. Thus dynamic clustering brings overhead and reduce the gain in energy consumption.

While LEACH helps the sensors within the cluster dissipate their energy slowly, the CHs consume a large amount of energy when they are located farther away from the sink is a great draw back in LEACH.

Power-Efficient Gathering in sensor Information Systems (PEGASIS): PEGASIS 4,7,13 is an extension of the LEACH protocol it forms chains from sensor nodes. PEGASIS avoids cluster formation and use chain formation. Each sensor node transmits and receive data from the neighbors and from that chain only one node is selected to transmit data to the base station (sink). Finally all datas are gathered and moves from each node to another node, aggregated and equally sent to the base station. Thus the chain construction is performed. Among clusters, only one node from the chain transmit data to the BS(sink) instead of using multiple nodes. In data fusion phase the sensor transmits to its local neighbors instead of sending directly to its Cluster Head (CH) like LEACH. In construction phase all the sensors have global knowledge about the sensor network, particularly, the positions of the wireless sensors and their chain formation. If sensors fails due to low battery power, the chain formation is constructed in the similar approach by bypassing the failed sensors. The cost of energy expenditure is reduced in each round by randomly selecting sensor nodes in each rotation, that nodes transmit the aggregated data to the BS.

Dynamic network topology is required in PEGASIS in order to avoid the drawbacks, like energy status with neighbor nodes should be known by each node in order to route its data to the sink (BS).

Hybrid, Energy-Efficient Distributed Clustering (HEED): HEED 4,8,9,12,13 extends the basic scheme of LEACH. Power balancing is achieved in HEED by using residual energy and node degree as a metric for cluster selection. HEED operates in multi-hop networks.

Four primary goals are proposed in HEED namely

prolonging network lifetime by distributing energy consumption

(ii) terminating the clustering process within a constant number of iterations (iii) minimizing control overhead, and

(iv) producing well-distributed CHs and compact clusters.

In HEED protocol to the combination of two clustering parameters the proposed algorithm periodically selects CHs. The primary parameter is their residual energy of each sensor node and the secondary parameter is the intra-cluster communication cost as a function of cluster density or node degree (i.e., number of neighbors).The primary parameter is used to select an initial set of CHs while secondary parameter is used for breaking ties.

Thus in HEED clustering network lifetime is much longer than LEACH clustering, because LEACH protocol randomly selects CHs, which may result in faster loss (i.e., death) of some nodes. The final CHs selected in HEED are well distributed across the network and the communication cost is minimized to achieve green computing.

Threshold Sensitive Energy Efficient Sensor Network Protocol (TEEN): TEEN 4,10,13 is hierarchical clustering protocol and group sensors into cluster with each wireless sensor is led by a Cluster Head . In wireless sensors within a cluster report their sensed data to their Cluster Head. The Cluster Head sends aggregated data to higher level Cluster Head, until the data reaches the base station (sink). Thus, the wireless sensor network architecture in TEEN is based on a hierarchical grouping where closer nodes form clusters and this process goes on the second level until the BS (sink) is reached.

TEEN is useful for applications, depending upon the energy efficiency, data accuracy, and periodical time reply. In TEEN data-centric method is used with hierarchical approach. Important features of TEEN include its suitable for time critical sensing applications.

Thus, TEEN is not suitable for sensing applications where periodic reports are needed since the user may not get any data at all if the thresholds are not reached.

Adaptive Periodic Threshold Sensitive Energy Efficient Sensor Network Protocol (APTEEN) : APTEEN 4,11,13 is an improvement of TEEN to overcome its shortcomings and aims at both capturing periodic data collections (LEACH) and reacting to time-critical events (TEEN). APTEEN is a hybrid clustering-based routing protocol. APTEEN allows the sensor to send their sensed data periodically and react to any sudden change in the value of the sensed attribute by reporting the corresponding values to their CHs. The architecture of APTEEN and TEEN are same. APTEEN uses the concept hierarchical clustering for energy efficient communication between source sensors and the sink (BS).

APTEEN supports three different query types namely (a) historical query means to analyze past data values, (b) one-time query means to take a snapshot view of the wireless network; and (c) persistent queries means to monitor an event for a period of time. APTEEN guarantees lower energy loss and a larger number of sensors alive 10.

Conclusion and Future Research

The tremendous growth in wireless sensor networks gets lot of issues for developing routing protocols. Routing Protocols needs robustness, scalability and energy efficiency in wireless sensor networks. But here in hierarchical routing protocols we summarized various results such as Cluster formation and Cluster head communication among the sensor nodes is an open issue for research, as well as analyzing periodical reports to the sink without time delay and Qos is also an open issue for research.

Thus in this paper we studied and surveyed various energy efficient hierarchical routing protocols their advantages, features, limitations and drawbacks. In future a large set of research activities have to be done, to design a new effective routing protocols for green technology to enhance energy efficiency in wireless sensor networks.

Acknowledgements

I would like to thank my correspondent, principal and my guide for their valuable support. I also thank Mr.K.Padmanabhan, M.P.Singh and D.K.Singh for their valuable suggestions and letting us to use their Hierarchical Routing Protocols notes.