Routing Strategies in Hierarchical Cluster Based Mobile Wireless Sensor Networks

Muhammad Arshad, Naufal M. Saad, Nidal Kamel and Nasrullah Armi

Department of Electrical and Electronics Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar 31750 Tronoh, Perak, MALAYSIA

muarshad74@gmail.com

Abstract—Ubiquitous communication networks is a keystone for New Generation Network (NWGN). Mobile Wireless Communication Networks (MWSN) is a viable solution to accomplish the requirements of NWGN. Due to mobility of sensor nodes, the data reliability and end-to-end delay with energy efficiency in the network is an enormous concern. Various real-time and delay sensitive applications enforced to use both environments mobile and fixed sensor nodes, whereas the others claims an entire mobile sensors environments in network. Packet loss ratio and end-to-end delay happened because of the nodes mobility which is directly impact to degrade the quality of service, network lifetime and energy consumption. This paper enlightens a comprehensive comparison between single and multi hop inter-cluster routing strategy from cluster head to base station. Moreover, the performance of multi hop routing is calculated and compared with single hop LEACH routing strategy. The simulation results reveal that multi hop routing strategy is to increase the sensor nodes throughput and network lifetime but not efficient approach for delay sensitive and data reliable applications. Keywords—Mobile Sensor Networks, WSN, Network

Protocol and Reliable transport protocol.

I. INTRODUCTION

IRELESS Sensor Network (WSN) is a latest emerging technology during the last decades, lot of

researchers doing effort to find a low cost and energy efficient wireless sensor network. WSN can connect information world with physical world together and using in different applications such as battlefield surveillance, remote healthcare, land monitoring for smart farming and environmental monitoring [1, 2, 3]. While designing algorithms and protocols of WSNs, several challenges occurs like maintaining connectivity and maximizing network lifetime are severe considerations.

Mobile devices are the best approach to resolve the WSNs

problems in an efficient way. Number of the existing WSN scenarios using mobile platforms, such as animal monitoring, traffic monitoring and battlefield surveillance applications. MWSN is a specified category of WSN where mobility acting a primary part in the application execution. In recent years, researchers and vendors are entirely focused to retain mobility in WSN [4]. Major MWSN parameters over WSN are Nodes Location, Utilization of Energy, Sink/Gateway and Topology of the network [5, 6].

A. Mobile WSN Architecture

MWSNs can be classified into a flat, 2-tier or 3-tier hierarchical architecture: Flat or level-like, the network architecture contains a number of heterogeneous devices to

communicate in ad-hoc mode. Two-tier architecture consist number of nodes in network and locates mobile nodes. Moving nodes form an overlay network or the role of data mules to transfer data across the network. In the three-tier architecture, a set of fixed sensor nodes transmit data at a set of mobile devices, which then transmits data to one set of access points. The heterogeneous network is designed to cover large areas and be compatible with several applications simultaneously [7, 8].

B. Clustering Techniques

Hierarchical based routing and in particular the clustering techniques make an immense enhancement in the field of WSNs. These approaches to reduce the utilization of energy and enhance the performance of the network, when the entire sensor nodes sending a data to base station or central collection center. Fig. 1 explains the general architecture of cluster based WSN, and to investigate how the phenomenon of clustering is an integral part of organizational structure [9, 10].

Figure 1. Cluster Based Wireless Sensor Network The core components of the cluster based WSN are sensor

nodes, clusters, cluster heads, base station and end user. Sensors nodes are an essential part of the WSN. Organizational unit of WSN are clusters. Cluster heads are the organizer of the cluster. In hierarchical WSN the upper levels is base station and establish a communication link between end user and sensor network. Sensor marks which is generated by end user, where data are collected from a query sent by the network [1]. The energy aware routing protocol for sensor networks can be classified into four categories: Data centric, Hierarchical cluster based, Location based and Network flow and QoS-aware protocols. Much of the research and potential models for sensor networks are formed but do not support end-to-end data reliability, reduce packet loss and latency time control.

This paper explains a comprehensive comparison of

inter-cluster routing strategy, in terms of single and multi-hop communication for mobile WSN environmental

W

Sensor Node Cluster head

Internet Link PDA Terminal User Equipment

Cluster

International Conference on Electrical, Control and Computer Engineering Pahang, Malaysia, June 21-22, 2011

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applications. This guides throughput, network lifetime, packet loss ratio and end-to-end delay among the sensor nodes to base station. The basic parameters of networks are: Fixed base station which is far away from the sensors nodes, Homogenous and energy controlled sensor nodes and no high-energy nodes during the communication. Data fusion is best approach to avoid information overload which is used in different hierarchical cluster based routing protocols.

The rest of the paper organized as follows: section II

summarizes the related works of Hierarchical cluster based routing protocols; section III presents a multi hop LEACH routing strategy; section IV describes the results and discussions and finally conclusion and future works presented in section V.

II. RELATED WORKS

The major objective of hierarchical routing is to preserve efficient energy utilization by multi-hop communication, the data aggregation and merger is to decrease the number of messages sent to the sink. Clustering technique is usually the energy maintain of sensors which is near the cluster head. This section provides a brief introduction about different hierarchical cluster based routing protocol. A. LEACH: Construction of Low Energy Adaptive Clustering Hierarchy (or LEACH) is the initial significant developments to conventional clustering approaches in WSN. Traditional approaches to algorithms such as MTE (Minimum Transmission Energy) or a direct transfer does not lead to dissipation of energy through the network. LEACH to provide balancing energy consumption in a random rotation of cluster heads. The algorithm is self organized, employs single hop approach and the data combination technique can decrease the rate of data transfer as illustrated in Fig. 2 [11].

Figure 2. Single Hop LEACH Routing Strategy

B. TL-LEACH: Two levels of the hierarchy LEACH (or TL-LEACH) is a proposed extension of the algorithm of LEACH which support parent child combination and then transmits data to base station by single hop fashion. It uses two levels of cluster heads (primary and secondary), and other simple detection nodes. In this algorithm, the primary cluster head in each group communicates with the secondary and the contact with corresponding nodes in their sub-cluster. The structure of two levels of TL-LEACH as shown in Fig. 3 reduces the number of nodes when data is transmitted from source to the base station and reducing total energy consumption [12].

CHi & CHij – First & Second Level Cluster Head

Figure 3. Topology of Two-Tier Hierarchy In assessing the data reliability of both LEACH and

TL-LEACH protocols some of the important aspects that are included in the protocol. To avoid collision by CSMA method and CDMA techniques used to eliminate interference between clusters. Random selection of cluster heads to extend the network lifetime, providing full connectivity. TL-LEACH two-level hierarchy does not provide direct improvements in the reliability of the standard LEACH.

C. TEEN: Threshold sensitive Energy Efficient sensor Network protocol (TEEN) is another type of cluster based hierarchical and reactive protocol based on single hop, which is planned to be sensitive to unexpected modification in the perceived elements such as habitat monitoring and measuring the temperature. The simulation results of TEEN shows better than LEACH because TEEN’s offers the best performance since number of the transmissions is reduce, but TEEN is not appropriate for high-quality applications which involve cyclic reports [13]. D. EECS: An Energy Efficiency Clustering Scheme (EECS) is a single hop clustering algorithm, where the cluster head candidates competing for the ability to raise the cluster head for a specified cycle. This responsibility includes broadcasting candidates’ and remaining energy of neighboring candidates. If a node fails to find the node with more remaining energy then it becomes a cluster head. This algorithm extends the size of the dynamic clusters based on cluster distance of the base station.

EECS offers the same reliability as LEACH, but the

energy consumption of EECS is better overall the network, connectivity can be fully achieved for a longer period [14].

III. MULTI HOP LEACH ROUTING STRATEGY

Multi hop LEACH routing strategy is based on single hop LEACH routing protocol, usually LEACH protocol transmits compressed data from cluster heads to base station directly. In large environmental setup sensor nodes are distributed pervasively, begin at same energy storage and create clusters. Some of the clusters utilize more energy dissipation due to the far away from the base station and rest of the clusters operates at less energy consumption. Therefore, after the some successful rounds there will be a

Cluster

Base Station

Sensor Node Cluster head

BS – Base Station SN – Sensor Node

SN

BS

CH1

CH11

CH2 CH3 CH4

CH31 CH21

SN SN SN SN

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significant variation in nodes energy consumption. Finally, the network performance will be turn down because the distribution of the live and dead nodes within the network. Furthermore, during the setup phase, nodes short messages are collide to each other due to the nodes communication ranges are to each other and uses same frequency band. The network performance will be degrading partially; some of the nodes have not maintained the cluster membership and lost the network connectivity [15].

Figure 4. Multi Hop LEACH Routing Strategy In Fig. 4, Multi hop routing strategy is vital solution to enhance the energy transmission dissipation and network lifetime with same single hop LEACH routing strategy. The recent trend is multi hop routing strategy, which uses in many sensor and Ad-hoc networks. In this strategy the data sent from source to destination node relayed by the assistance of middle nodes to take multiple hops. The most important benefit of this strategy is to decrease the nodes energy consumption but increase end-to-end delay. Most of the sensor applications are delay sensitive that cannot afford end-to-end delay, but some applications require energy efficient and enhance network lifetime approaches. Within the cluster the data is directly transmitted from sensor nodes to cluster head and then cluster head responsible to forward the data to base station using by multi hops with another cluster heads. Cluster heads operate as a backbone of the network, multi hop routing strategy implies to reduce the energy consumption between the sensor nodes. As we discussed earlier multi hop routing strategy follows a single hop LEACH network model, all sensor nodes are homogenous and utilizes same infrastructure. Sensor nodes have limited power and the transmission range is enough to communicate straight with another node and base station as well as. Each sensor node is able to support multiple protocols and signal processing tasks because of sufficient processing power. Moreover, the neighboring nodes whose are nearby to each other have redundant data for base station. During cluster formation all nodes are autonomous; self organized and arranged into clusters through short messages same as single hop LEACH strategy. Every node has to make a choice to be converted into a cluster head or not with the probability of Pi, Pi is calculated same as LEACH cluster head selection. The next is steady-state phase that contain many frames, each frame send the data to cluster head within the given time period. Time Division Multiple Access scheduling to avoid collisions and reduce energy consumption between data messages in the cluster and

enables each member of the radio equipment off when not in its time slot. During the time of each frame all member sensor nodes forward the data to cluster head, then cluster head combined and discard the unnecessary data and finally send the compact data to base station. When the compressed data successfully arrives at cluster head then cluster head discover a best possible path to deliver the data to base station indirectly by multi hops. The strategy of route selection is same like MTE routing strategy not like LEACH protocol. Consequently, the selection on multi hop routing strategy uses one or more central nodes to deliver the data towards the base station which reduce the squared distance.

IV. RESULTS AND DISCUSSION The simulated network has 40 sensor nodes dispersed in 1000*1000 meters area. The following performance metrics has been measured by computer simulation. A. Throughput of Sensor Nodes and Network Lifetime:

Figure 5. Nearest Distance Node Throughput

Figure 6. Average Distance Node Throughput

Cluster

Sensor Node Cluster head

Base Station

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Figure 7. Farthest Distance Node Throughput

In Fig. 5, 6 and 7 that are nearest, average and farthest distance node throughput of the sensor nodes after the multiple simulations runs over single and multi hop LEACH routing strategy. In these graphs there is no significant difference in throughput of the nearest, average and farthest nodes of the network that evidence the energy consumption of the nodes is gradually reduces. The energy utilization of sensor nodes is directly impact on the network performance or network lifetime.

Figure 8. Network Lifetime The simulated result of Fig. 8 is exposed the considerable variation in network lifetime. Therefore, multi-hop LEACH routing strategy is better than single hop LEACH routing strategy in terms of network lifetime because it stays active as a whole longer, and falling slightly faster.

B. Packet Loss Ratio, End-to-End Delay and Throughput of Base Station:

Figure 9. Packet Loss Ratio (BS)

Figure 10. End-to-End Delay (BS)

Figure 11. Throughput (BS) As illustrated in Fig. 9 the packet loss ratio of single hop routing strategy is slightly difference than multi hop, but the

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significant difference in end-to-end delay towards the base station as shows in Fig. 10 End-to-end delay is the most important metric which is directly impact on the network throughput. Fig. 11 demonstrates the throughput over time of single and multi hop LEACH routing strategy.

V. CONCLUSION AND FUTURE WORK This paper addresses the considerable comparison in single and multi hop routing strategy for cluster based LEACH protocol. According to aforementioned simulated results are the evidence for multi hop routing strategy is better than single hop routing strategy in terms of sensor nodes throughput, decrease energy consumption and extensively improve the network lifetime for cluster based LEACH protocol. But multi hop routing strategy is not an efficient solution for delay sensitive and data reliable applications where end-to-end delay and packet loss ratio are essential. For the achievement of end-to-end delay and reduce the packet loss ratio within the network, multi hop routing strategy for all nodes is a most viable solution for cluster based LEACH protocol, where compressed data is collected at cluster head and finds a best possible route from all nodes of the network to deliver the data to base station. On other hand rendezvous-based solution is another technique to get the compressed data from cluster heads and directly send the data to base station, cluster heads randomly listen the mobile data collectors.

REFERENCES [1] Akyildiz, I.F.; Weilian Su; Sankarasubramaniam, Y.;

Cayirci, E.; , "A survey on sensor networks," Communications Magazine, IEEE , vol.40, no.8, pp. 102- 114, Aug 2002

[2] Chunguo Jing; Dongmei Shu; Deying Gu; , "Design of Streetlight Monitoring and Control System Based on WSN," Industrial Electronics and Applications, 2007. ICIEA 2007. 2nd IEEE Conference on , vol., no., pp.57-62, 23-25 May 2007

[3] Muhammad Arshad, Nidal Kamel, Naufal M. Saad, Nasrullah Armi, “Performance Evaluation of Wireless Sensor Nodes for Environmental Applications,” Proceedings Third IEEE International Conference on Intelligent & Advanced Systems (ICIAS), July 2010

[4] Eylem Ekici, Yaoyao Gu, Doruk Bozdag, “Mobiltiy-Based Communication in WSN,” IEEE Communication Magazine, Vol 44, No. 7, 2006, pp. 56-62

[5] Qin Wang; Hempstead, M.; Yang, W.; "A Realistic Power Consumption Model for Wireless Sensor Network Devices," Sensor and Ad Hoc Communications and Networks, SECON '06. 3rd Annual IEEE Communications Society on , vol.1, no., pp.286-295, 28-28 Sept. 2006

[6] Gandham, S.R.; Dawande, M.; Prakash, R.; Venkatesan, S.; , "Energy efficient schemes for WSN with multiple mobile base stations," Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE , vol.1, no., pp. 377- 381

[7] Munir, S.A.; Biao Ren; Weiwei Jiao; Bin Wang; Dongliang Xie; Man Ma; , "Mobile Wireless Sensor Network: Architecture and Enabling Technologies for Ubiquitous Computing," Advanced Information

Networking and Applications Workshops, 2007, AINAW '07. 21st International Conference on , vol.2, no., pp.113-120, 21-23 May 2007

[8] Amundson, I., Koutsoukos, X., Sallai, J.: “Mobile sensor localization and navigation using RF doppler shifts,” In: 1st ACM International Workshop on Mobile Entity Localization and Tracking in GPS-less Environments, MELT (2008)

[9] Arboleda L.M., Nasser N., “Comparison of Clustering Algorithms and Protocols for WSN,” In Canadian Conference on Electrical and Computer Engineering (CCECE’06), pages 256-261. Ottawa, May 2006.

[10] Akkaya K., Younis M., “A Survey on Routing Protocols for WSN”, Elsevier Ad Hoc Network Journal, 3(3):325-349, 2005.

[11] W. R. Heinzelman, A. Chandrakasan, and H. Balakrishnan, “Energy-Efficient Communication Protocol for WSN,” Proceedings of the 33th Hawaii International Conference on System Sciences, 2000.

[12] Loscri, V.; Morabito, G.; Marano, S.; , "A two-levels hierarchy for low-energy adaptive clustering hierarchy (TL-LEACH)," Vehicular Technology Conference, 2005. VTC-2005-Fall. 2005 IEEE 62nd , vol.3, no., pp. 1809- 1813, 25-28 Sept., 2005

[13] A. Manjeshwar and D. P. Agrawal, “TEEN: A Protocol for Enhanced Efficiency in WSN," in the Proceedings of the 1st International Workshop on Parallel and Distributed Computing Issues in Wireless Networks and Mobile Computing, San Francisco, CA,

[14] Mao Ye; Chengfa Li; Guihai Chen; Wu, J.; , "EECS: an energy efficient clustering scheme in WSN," Performance, Computing, and Communications Conference, 2005. IPCCC 2005. 24th IEEE International , vol., no., pp. 535- 540, 7-9 April 2005

[15] Rahul C. Shah and Jan Rabaey, “Energy Aware Routing for Lowe Energy Ad Hoc Sensor Networks”, IEEE Wireless Communications and Networking Conf. (WCNC), March 17-21, 2002, Orlando, FL.

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