Hierarchical Routing Protocols for Mobile Wireless Sensor Networks

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1 Hierarchical Routing Protocols for Mobile Wireless Sensor Networks Simranjeet kaur 1, Dr.Trilok Chand Aseri 2 ME Research Scholar 1, Associate Professor 2 Department of Computer Science and Engineering PEC University of Technology, Chandigarh INDIA (s): simran.6262@gmail.com 1, a_trilok_chand@yahoo.com 2 ABSTRACT Mobility of sensor nodes impersonates new challenges regarding energy consumption and packet loss. Routing protocols are responsible for finding out and sustaining the routes in the network. Although, the appropriateness of a specific routing protocol mostly depends on the capabilities of the nodes and on the application requirements. The routing provided by a routing protocol is a key indicator towards the effectiveness of the sensor network architecture. In this paper we carry out a review of hierarchical routing protocols suggested for mobile wireless sensor networks. Keywords - Base station, Cluster head, LEACH, Routing Protocols, Wireless Sensor network I. INTRODUCTION In a mobile sensor network either the nodes can move under their own control or under the influence of the environment. Mobile WSN plays a vital role in some applications such as: If we require movable sensor nodes for gathering the data from inaccessible areas. But when a node moves around, it requires more energy as compared to a static node. The advantages of mobile WSN are its better targeting and data fidelity. Now, we present the architecture of a mobile wireless sensor network in section II; routing protocols in section III and then concludes the paper in section IV. II. ARCHITECTURE OF MOBILE- WIRELESS SENSOR NETWORKS Mobile wireless sensor network consists of a large number of autonomous sensor nodes that are densely deployed either inside the phenomenon or very close to it. These assemblies of sensor nodes are connected by wireless media in order to carry out the distributed sensing tasks. Sensor nodes in a wireless sensor network are able to perform two jobs simultaneously namely sensing and communicating with the close by sensor nodes. Each sensor node has the capability of performing multiple functions such as information collection, data processing, data transmission and mutual communication [1]. Wireless Sensor Network performance is based on the cooperative effort of sensor nodes. Sensor nodes are small in size, quite cheap, fitted with an on-board processor, have very low power consumption and also support short-distance communication with other nodes and sink (base station). In MWSN, the major components of a typical sensor network are sensor field, sensor nodes, base station and end user as shown in Fig. 1. Sensor Node: the sensor node is used to sense a particular event that occurs in an area in which they are deployed and then used to compute the whole information gathered. After processing that information, nodes send their data to the base station or sink nodes as per the requirement. Sensor nodes may be static or mobile depends upon the application [3]. Base Station: The base station is at the upper level of the hierarchical WSN. It is used to connect the sensor network to the end-user [3]. End User: The data in a sensor network gathered by the sensor nodes is used by the end user. This gathered data can further be used for a wide-range of applications: In military, a key application is a detection of enemy intrusion on a battle field. Environmental applications involve sensing and

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3 III.II M-LEACH LEACH-MOBILE routing protocol. In LEACH-ME Lan Tien Nguyen proposed M-LEACH routing protocol [6]. It has some features that LEACH does not support such as mobility of cluster head and member nodes during set-up phase. All the sensor nodes in M-LEACH are assumed to be homogeneous and have their location information through GPS. In M-LEACH the base station is stationary and the mobility is considered only for cluster-heads and cluster-member nodes. In the setup phase of M-LEACH, each node sends its information that involves locations, energy level etc. to the base station. After processing this information the base station groups the sensor nodes into clusters, with one node acting as the cluster head and sends the schedule to all nodes. This way each node sets up its cluster-head and schedule. In the transmission phase, each node sends its data within the stipulated time slot. Due to a fixed duration of the time slot, a node can schedule its next allocated time slot based on the number of nodes in that particular cluster. After receiving the data, cluster head aggregates the data and forwards the aggregated data to the base station. In the Invitation phase, the cluster head nodes broadcast advertisement messages using Carrier- Sense-Multiple Access (CSMA) MAC protocol to other sensors in the network. Then each node has the information that to which cluster it belongs and compares it with the current cluster. If they are different, the node will send DISJOIN message to the current cluster head node and JOIN message to the new cluster head node. A cluster head is able to add or remove the nodes from its schedule according to the messages it receives that is JOIN or DIS-JOIN. Then the updated cluster schedule is broadcasted by the cluster head node to all the other nodes in the same cluster and accordingly the nodes reschedule their transmission accordingly. After the Invitation phase then there is a Transmission phase. initial cluster is created based upon some random selection. Then cluster head sends ACTIVE message to all its cluster members to wake up simultaneously. After receiving the ACTIVE message, all cluster members broadcast their IDs and time-stamp. All cluster member nodes set time-out to receive broadcast of their entire neighboring node IDs that helps a individual node to know its neighbors. Once the broadcast ID timer expires, each node calculates the remoteness based on the IDs received and the time at which they are received. The calculated remoteness information is broadcasted by every single node that helps the neighbors to know the remoteness of each other. Once all the remoteness values of neighbors are received, nodes are able to go for the cluster head selection. Principally, the node with minimal mobility factor and energy level above the threshold value is selected as the cluster head. The decision of adding ACTIVE slot in the next TDMA schedule is taken based on the average transition count calculated for the last few schedules. Selected cluster head sends the data request to the respective nodes in their TDMA time slot. Data request is sent with the active flag as zero if there is no ACTIVE slot in the TDMA slot. After receiving the data request from cluster head, a member node sends its data along with transition count for the last few cycles to the cluster head. After receiving the data from all the member nodes, cluster-head calculates the average transition count for the last few cycles and compares it to the threshold decided earlier to know if it is above the threshold. If the value is above the threshold, then in the next TDMA cycle ACTIVE slot is added by setting a active flag in the data request message. After receiving the data request with active flag set, the cluster members need to reschedule the TDMA time slot accordingly to ACTIVE frame. Data received by the cluster head is further aggregated and forwarded to the base station. If a III.III LEACH-MOBILE ENHANCED(LEACHnode doesn t receive any data request message from the cluster head when it is awake, it marks itself as suspect ME) of being a non-member of that cluster. If the same thing repeats during the next frame slot allotted then it Kumar et al. proposed LEACH-Mobile-Enhanced assumes that it is no more a member of the cluster. After routing protocol [7] which is the enhancement of becoming the non-member of a particular cluster it

4 broadcasts JOIN request message. The cluster-head on getting the JOIN request message allots a time slot in its TDMA schedule and broadcasts it to all the member nodes including the new member node. As soon as it receives the new TDMA schedule the mobile node becomes a member of the cluster. III.IV LFCP-MWSN(Location aware fault tolerant clustering protocol for mobile WSN) L. Karim proposed LFCP-MWSN routing protocol [9] for mobile WSN in which sensors localize themselves using range free localization technique during cluster formation and every time a sensor moves into another cluster. Initially, base station groups sensor nodes into clusters based on the locations of sensors and then assigns ID to the clusters as well as sensors. Then sensors are localised using the range free localization technique [10]. Base station selects the cluster heads based on the initial node energy and positioning of the sensors. Initially all the nodes have same energy, so initially cluster-head is selected based on random number amongst 0 and 1. After that cluster-heads broadcast their position and IDs. A sensor node is assigned to a cluster whose cluster-head is at the minimum distance from that node. Then that node sends a registration message to that cluster-head mentioning its ID and location. Whole information of that cluster is then sent to the base station for centralized operation. Cluster-head is assumed to be static until new cluster-head is selected in the next round based upon the mobility factor. In the steady state phase, cluster-head assigns time slots to the member nodes using TDMA schedule. Member nodes of a cluster transmit data in their time slots and receive acknowledgement from the cluster head. Member nodes also count their movement inside and outside of the cluster at their allocated timeslot. During each time slot, a frame is kept aside so that the moving nodes can notify the cluster-head of a new cluster. If a node moves into a new cluster it sends a JOIN REQUEST message to the cluster-head of new cluster at the free timeslot. Clusterhead of this new cluster accepts the JOIN REQUEST of that node only when a timeslot becomes free. After that the Cluster-head of this cluster sends the ID of that inducted node to the base station. Thus, if the base station receives ID of the same node from two different cluster-heads as a leaving node from a cluster at frame y and as a entering node into a cluster at frame y + t, then that node is considered to have moved. Otherwise, that node is considered to be a failed node. Also a special packet is sent by a member node if it does not have any sensed data to send to the cluster head at its allocated timeslot. However if the cluster-head does not receive any data or special packet from that particular node within the allocated timeslot then cluster-head assumes that either (i) data or special packet tr ansmission has failed (ii) node A moves out of the cluster or (iii) node A dies. If cluster-head does not receive any frame then cluster-head waits until the next timeslot so that the transmission failure for that node is confirmed. If cluster-head does not receive data or special packet from that node in the next timeslot as well then cluster-head deletes that node from its member list, discards the timeslot of node A and also notifies base station about the ID of that node. LFCP-MWSN protocol is more efficient in terms of energy consumption, network lifetime and data transmission as compared to the existing LEACH-M and LEACH-ME protocols. III.V CBR Mobile-WSN Awwad proposed cluster based routing protocol for mobile nodes in WSN (CBR Mobile-WSN) [11]. Setup phase consists of selection of cluster heads and determination of TDMA schedule. Each sensor node in the cluster randomly selects a cluster-head. At the end of the round, one more cluster head gets selected for the next round. It resembles LEACH-Mobile in a way that the cluster heads are assumed to be stationary and static throughout the rounds. Cluster-head broadcasts an advertisement message to the sensor nodes in the network using a Carrier Sense Multiple Access with Collision Avoidance Medium Access Control (CSMA/CA MAC) protocol. All cluster-heads use the same amount of transmitting energy for transmitting advertisement messages. All the sensor nodes are required to keep their receivers ON to receive the advertisement message from their cluster-head. On reception of the advertisement messages from one or more cluster-heads, sensor nodes compare the received signal strength of the received advertisement messages. They then decide such a cluster head for which the minimum amount of transmitted energy is needed for

5 communication. If there seems to be a tie then the cluster head is chosen randomly. After deciding the cluster, each node sends a registration message to inform the cluster head. Then the cluster-head creates a TDMA schedule based on the number of nodes and assigns each node a time slot. The schedule is broadcasted to all the sensor nodes within the cluster. After the clusters are created and the TDMA schedule is determined, steady state phase takes place. In this the data transmission from sensor nodes to their cluster-head will be executed according to their TDMA scheduled time slot. On reception of data request from the cluster-head, a sensor node turns on its radio and sends its data. As soon as the transmission gets over, the sensor node turns off its radio. The cluster-head is required to keep its radio ON so as to send data request messages, receive data from the sensor nodes and also to send and receive other critical messages that flow in the network. Each cluster-head keeps some free timeslots so that it can enable other incoming mobile nodes to join its cluster. When a cluster-head sends data request message to the member nodes if in return the cluster-head does not receive data from a member, the packet is considered to be lost and the cluster-head discards the membership of the node at the end of the frame. Similarly if a sensor node does not receive data request message from its respective cluster-head then node tries to go for a new cluster so that it s packets do not get lost. There can also be a case that the sensor node receives data request message from cluster-head but does not possess any data to return to it, then that node will not be able to hold onto any time slot and instead this timeslot will then be IV. assigned to another member node that has data for communication. If a sensor node moves out of the cluster and is not able to receive the data request message from its cluster-head at its allocated timeslot then that node will now send its data to the new free cluster-head so that the loss of data is avoided. In addition to this, it also sends a registration message to join this cluster. After receiving the data cluster-head checks whether it has received the data messages from all of its members and then removes those sensor nodes from which it did not receive any data or response. Each sensor node wakes up one timeslot ahead of its scheduled timeslot to check whether it has actually been assigned that timeslot. If node finds out that it has not been assigned any timeslot it again goes back to the sleep mode and its timeslot might be used by a mobile sensor node that enters the cluster. III.VI MECA(Mobile-Sink Based Energy Efficient Clustering Algorithm) Wang Yin proposed MECA [12]. In MECA, network is grouped into several equal clusters. Clusterhead is selected based on the residual energy that collects data and sends it to the mobile sink. Except the sink all the other nodes are assumed to be static. Sink either moves clockwise or counter clockwise. Using multi-hop scheme an intra-cluster routing algorithm is also proposed in such a algorithm. Initially mobile sink is deployed at the edge of the sensing field that moves along a fixed track and is predictable. Sink only needs to broadcast its current location at the beginning and that too just for once. As sensor nodes keep record of the original location of the sink they can reduce the changed angle after a time interval t and helps determining new location of sink. After the broadcasting, the mobile sink starts to collect data. For a network to complete a round of data collection the mobile sink stays at a particular location for a long period of time. After collecting data, clusterhead aggregates that data and sends it to the sink. CONCLUSION Routing is a key performance metric for various applications in WSNs. This paper reviewed the hierarchical routing protocols for a Mobile-WSN. The flat protocols are considered to be an ideal solution for a small network but due to processing overhead they become infeasible in a large network. The hierarchical protocols solve this problem and produce scalable and efficient solutions. They divide the whole network into clusters, efficiently maintain the energy consumption of sensor nodes, and perform data aggregation and fusion in order to decrease the number of transmitted messages to the sink.

6 Thus, hierarchical protocols are best suited for sensor networks with heavy load and wide coverage area. They not only improve the routing process but also improve network lifetime, data report timeliness and reliability at the same time. REFERENCES [1] Ian F. Akyildiz, Weilian Su, Yogesh Sankarasubramaniam, and Erdal Cayirci, A Survey on Sensor Network, IEEE Communications Magazine, pp , Aug [2] S.Prasanna, Srinivasa Rao, An Overview of Wireless Sensor Networks Applications and Security, International Journal of Soft Computing and Engineering (IJSCE) ISSN: , Volume-2, Issue-2, May [3] Ankita Joshi and Lakshmi Priya.M, A Survey of Hierarchical Routing Protocols in Wireless Sensor Network, pp [4] Wendi B. Heinzelman, Anantha P. Chandrakasan, and Hari Balakrishnan, Energy-Efficient Communication Protocol for Wireless Micro sensor Networks, Proceedings of the 33rd Hawaii International Conference on System Sciences [5] Do-Seong Kim and Yeong-Jee Chung, Self- Organization Routing Protocol Supporting Mobile Nodes for Wireless Sensor Network, Proceedings of the First International Multi-Symposiums on Computer and Computational Sciences (IMSCCS'06), IEEE [6] Lan Tien Nguyen, Xavier Defago, Razvan Beuran and Yoichi Shinoda, An Energy Efficient Routing Scheme for Mobile Wireless Sensor Networks, IEEE, ISWCS [7] G. Santhosh Kumar, Vinu Paul M V and K. Poulose Jacob, Mobility Metric based LEACH-Mobile Protocol, IEEE,ADCOM [8] Karim, L., Nasser, N.: Energy efficient and fault tolerant clustering protocol for mobile sensor network. IEEE Int. Communications Conf. (ICC 11), Kyoto, Japan, 5 9 June [9] Karim, L., Nasser, N.: Reliable location-aware routing protocol for mobile wireless sensor network. IET Commun., 2012, Vol. 6, Iss. 14, pp [10] Karim, L., Nasser, N., Salti, T.E.: RELMA: a range free localization approach using mobile anchor node for wireless sensor networks. IEEE Globecom 2010, Miami, Fl, 6 10 December [11] Samer A. B. Awwad, Chee K.Ng, Nor K. Noordin, and Mohd. Fadlee A. Rasid, cluster based routing protocol for mobile nodes in WSN, proceeding of IEEE conference on Computer Network, pp , may [12] Jin Wang, Yue Yin, Jeong-Uk Kim, Sungyoung Lee and Chin-Feng Lai, An Mobile-sink Based Energy-efficient Clustering Algorithm for Wireless Sensor Networks, IEEE 12th International Conference on Computer and Information Technology