Green Energy Efficient Hierarchical Routing Protocols

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 real-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. This paper we give a small survey on 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 wireless sensor network has large number of thousands 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 sensor mobile devices is capable of 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.The vast potential of sensor networks which enable the applications that connect the physical world to the real-world. Each node acts both router and host and the topology of network also vary rapidly. The wireless sensor network characteristics and their application requirements have a great effect on the network design objectives like 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. In WSN the design of routing protocols is challenging because of several network constraints like synchronization, node localization, low battery power etc. In future a large set of research activities have to be carried out to 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.

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 cluster creation and assigning special tasks to cluster heads in senor network can greatly contribute to overall system for low power high energy efficiency and the data aggregation and fusion greatly reduce the loss of energy 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 algorithm for clustering in 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. In LEACH, the aggregation technique which combines all the original datas into a smaller size of datas 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 wireless sensors to act as CHs and avoid battery depletion of individual sensors and avoid dieing in very short period of time. In LEACH operation is divided into rounds having two phases namely a setup phase to organize sensor 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. In single-hop each node can transmit data directly to the cluster-head and 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.

LEACH helps the sensors within the cluster disappearing 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 base station (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 complete 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 sensor 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

terminating the clustering process within a constant number of iterations

minimizing control overhead, and

producing well-distributed CHs and compact clusters.

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

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

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 . The 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). In TEEN the sensor architecture is based on a hierarchical grouping. Such as closer nodes form clusters and this process goes on the second level , third level etc., until the base station (sink) is reached.

The various applications in TEEN is based upon the energy efficiency, data accuracy, and periodical time reply. In TEEN data-centric method is used with hierarchical approach. The most important features of TEEN include its suitable for time critical sensing applications.

Thus, TEEN protocol 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 allows sensor to send their sensed data periodically and react if any sudden changes in the value of the sensed data by reporting the corresponding values to their CHs. APTEEN and TEEN have same architecture. APTEEN uses the concept hierarchical clustering for energy efficient communication between source sensors and the sink (BS).

APTEEN supports three different query types namely

(i) historical query means to analyze past data values,

(ii) one-time query means to take a snapshot view of the wireless network; and

(iii) 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. in order to activate the green energy in physical world.

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 Quality of service 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.