CHAPTER 4 THRESHOLD BASIS CLUSTER HEAD SELECTION TECHNIQUES

Transcription

1 173 CHAPTER 4 THRESHOLD BASIS CLUSTER HEAD SELECTION TECHNIQUES 4.1 ORGANIZATION CHART OF ROUTING PROTOCOLS IN WIRELESS SENSOR NETWORKS Issues and challenges, Estrin et al (1999), considered as a result of major constrained energy supply and bandwidth in WSN when managing the network necessitates the need for development of energy awareness protocol at all levels of networking protocol stack. To propose efficient power management protocol in WSN, researches, Gang et al (2007), focuses on areas such as system-level power awareness like radio communication hardware, low duty cycle issues and energy-aware MAC (Medium Access Protocol) protocols and algorithms, Yan et al (2013). In addition, it is observed that the network layer offers a better means through which reliable relaying of data and energy-efficient route setup within a network can help to enhance the network life span, Khanna et al (2006). It should be prominent that routing in WSN has much distinguishable features compare to contemporary communication and ad-hoc networks. The classification routing protocol for WSN is stated clearly as shown in Figure 4.1 as follows: WSN cannot be built with global addressing (internet protocol address) scheme due to the huge number of sensor nodes There is noteworthy redundancy in generated data because several sensor nodes may gather the same data within a

2 174 particular field. These redundancy needs to be removed to increase the bandwidth utilization and also reduce energy consumption in the network Transmission power, processing capacity and storage are constraint factors to be considered when managing a WSN By seeing these differences, new routing protocols are being researched and created to eliminate the problem faced in WSN. These routing protocols have been fashioned on sensor nodes characteristics alongside it application and architectural constraint. The various routing protocols can be classified as location-based, data-centric or hierarchical. The details of those routing protocols are as follows. Location base protocol Most of the routing protocol technique for WSN depends on location information of sensor nodes for estimation of distance between two specific sensor nodes to deduce energy consumption. For instance, to sense a known area, through the use of location sensor, a specified query can be sent to that known area and this will significantly decrease transmitted data compare to a broadcast request being sent to the entire network. In other way, the location-based protocol utilizes the position information to communicate the data to the desired regions rather than the whole network. An example of a routing protocol that uses this technology is MECN (minimum energy communication network). MECN sets up and maintains a low energy in a WSN by using low power global power positioning system (GPS).

3 175 Data-centric protocol As assigning global identifiers to every sensor nodes in a WSN may come into view not visible in some randomly deployed application, Maraiya et al (2011), data transmitted by every sensor node within a particular area has noteworthy redundancy with it. To decrease this redundancy, data centric protocols are developed to select a set of sensor nodes and also utilize data aggregation during relaying of data. On of the example of data centric is a Sensor Protocol for Information via N named using metal-data that highly explain the characteristics of the data which is the important feature of SPIN. Flooding is one more type of routing protocol in which each sensor node receives data and then sends them to the neighbors by broadcasting, unless a maximum number of hops for the packet are reached or the destination of packet is achieved, Perrig et al (2002). The pro of SPIN is that the topological changes are localized since each of the sensor nodes needs to know only its single-hop neighbors. Though, it has a drawback of scalability and the sensor nodes around the base station (BS) could run down their energy if the BS is interested in too many event. In delivery of data. For example, if the sensor nodes which are interested in the data are far away from the source node and the sensor nodes between source node and destination node are not interested in that data, such a data will not be transmitted to the destination at all. Hierarchical routing In WSN hierarchical routing involves the arrangement of clusters in form of hierarchy when sending information from the sensor nodes to the base station. Hierarchical routing competently reduces energy consumption by

4 176 employing multi-hop communication for a specific cluster and thus performing aggregation of data and fusion in a way that reduces the number of data carried across the network to the sink. The cluster formation is based on residual energy in the sensor nodes and election of a cluster head (CH). An excellent example of a hierarchical routing protocol is Low-Energy Adaptive Clustering Hierarchy (LEACH). The approach involves formation of clusters of sensor nodes centered on the received signal quality and the use of a local CH as a router to the BS. In LEACH energy consumption in data transmission is achieved as the CH is involved in transmission to the BS rather than individual sensor nodes. The inconvenience in LEACH is its inabilities to be deployed in large network. Figure 4.1 Classification of routing protocol in WSNs Table 4.1 Comparison of routing technique Issues Data centric Hierarchical Location-based Technique Technique Technique Scalability Limited Good No Lifetime Long Long Long Data diffusion No Yes No Power required Limited High Limited

5 177 The Table 4.1 shows the comparison of the different routing protocols in terms of scalability, lifetime, data diffusion and power required in WSN. From Table 4.1, we understand that hierarchical technique offers an approach to energy minimization and scalability features in a WSN. The classification of routing protocol in wireless sensor network is shown in Figure BASIC RADIO ENERGY MODEL FOR WIRELESS COMMUNICATION In this research work, the first order radio model is used in this communication system. Here some of very essential and required assumptions are desired for our new implementation of routing protocol. The assumptions are as follows. (a) Sensor nodes in the field network are within the wireless communication, (Goldsmith, A 2005), range to communicate with each other sensor node or to the base station (BS). (b) All the available sensors nodes are homogeneous in behavior of sensing, computing, communication and other capabilities. (c) The random deployment scheme is applied to create the WSN topology. (d) In our system the position of the base station (BS) is located in the center of the sensor networks and BS has infinity energy resource. (e) All the available sensor nodes in the network have the same initial energy resource and dissipate their energy resource at the same rate at the time of iteration. (f) The total network lifetime is the main factor defined as the time span from the deployment to the instant when the first sensor node dies or when the entire sensor nodes die. At the time of iteration, all the sensor nodes would drain out their energy resource at the same time.

6 178 Figure 4.2 Radio energy model (g) The energy dissipation of sensing data and the energy dissipation for clustering are having negligible value and it is neglected. (h) The one iteration round is defined as the time span that BS collects the information from all the sensor nodes and the cluster head communicating the once. Each iteration sensor node has only one sensed data with same packet size which is defined in the network. (i) The sensor nodes in the field network that receive the data combine one or more packets to produce a same-size resultant packet, and the number of data that need to send by radio is reduced, because it is having much correlation among the data sensed by the different sensor nodes. (j) The sensor node energy dissipation of fusing one bit data is a constant having value. The Equation (4.1) is used to calculate transmission costs and receiving costs for a k-bit message and a distance d are respectively shown in Figure 4.2. Radio energy dissipation model adopted wireless channel models in the reference. Thus, to transmit a 1-bit message a distance d, the radio energy model expends the following. The electronics energy, Eelec, fs, d 2, amp, d 4 depends on the distance to the receiver and the acceptable bit error rate and d o is a distance constant. To receive this message, the radio energy model expends the following in (4.2)

7 179 Wireless Sensor Networks Topology X-Coordinate in metres Figure 4.3 Basic LEACH and wireless sensor network initialization The wireless sensor network includes some of the initial setting of energy parameters used in our system of work and the topology initialization of the sensor nodes shown in Figure 4.3. The random generation and deployment of wireless sensor nodes are in the M M m 2 of the region. Here sensor nodes are randomly deployed for a m 2 area for our simulation work. The sink node is located at (50m, 50m). Figure 4.3 describes basic LEACH and wireless sensor network topology initialization. 4.3 ENERGY SAVING SCHEMES IN CLUSTERING TECHNOLOGY OF WSNS Clustering concept is a method by which sensor nodes are hierarchically organized on the basis of their comparative proximity to each other, Tyagi et al (2011). Hierarchical (sensor nodes arranged in clustering) energy consumption creates an effectual and reliable means of routing collected data from the physical surroundings, through the sensor nodes to the BS, Ergin

8 180 et al (2013). It is done more easily the clustering, Katiyar et al (2011), concept of sensor nodes helps to compress the routing table that the discovery mode between sensor nodes, Jawhar et al (2012). Clustering can also preserve communication bandwidth because it limits the scope of inter-cluster interactions to CHs and avoids redundant exchange of messages among sensor nodes. Each sensor node in the network performs a route table look up for the CH in its area and then routes its collected data to the CH. The CH performs a route discovery estimation based on shortest distance to a beneficiary CH closer to the BS or directly to the BS, Barnawi & Hafez (2009). So as to maintain the routing table, link information is exchanged from time to time between sensor nodes to adapt to the change in energy requirement for data transmission by all nodes. Cluster formation and rotation In recent evolving trend in application and management of WSN, Younis et al (2006), clustering provides an efficient means of organization sensor nodes in order to prolong its life span. A number of clustering formation technique had been developing in the past for instance random competition based clustering (RCC). The RCC algorithm uses random timer and node identification for cluster formation is based on First Declaration Wins Rule. This rule assigns governorship position to any node which declares itself first as being a CH to other nodes in its radio network by broadcast. In addition, there are other approaches to cluster formation and an example is the broadcasting technique. Broadcasting can simply be explained as when one sensor node is sending a packet to all other sensor node in WSN. It is noted that not all broadcast messages are useful and also some of the messages sent by the sensor node are dropped because a sensor nodes status has already been assigned and cannot be changed. In direct broadcasting method, cluster advertisement message is sent to all sensors within a selected

9 181 region. For instance, two clusters formation requires two random nodes selected for broadcasting. This randomly selected node is known as an initiator. All the selected initiators broadcast a cluster advertisement message to all sensor nodes in the network. If any node in the network that is not an initiator receives an advertisement message within the cluster, it sends a message to the initiator from which the message is received. It will not only send a reply but also refrain from accepting any other cluster advertisement message for that simulation round. This sensor node will however become a The method of direct broadcasting is very simple when it comes to its implementation but it is not cost effective in terms of energy consumption. This is due to the fact that all sensor nodes receive a broadcast from the CH. The sensor nodes that are very far to the cluster head will still need to receive broadcast but it does not mean that the sensor will respond to the message. In a situation where a sensor node receives a broadcast from an initiator node, the subsequent broadcast message will be dropped, and energy which is used in transmission will be under utilized. Multi-hop broadcasting on the other side uses specific transmission range to transmit a cluster advertisement message to the sensor nodes. It is the responsibility of the receiving sensor node to proceed in sending the cluster advertised message to all the sensor nodes in its transmission range. This method works very closely to direct broadcasting technique for the fact that it also selects an initiator node that sends cluster advertisement messages at the start of cluster formation. These methods use a concept which is known as minimum communication energy which means that the sensor node that is easiest to reach will form part of the initiator cluster. Moreover, when cluster are formed dynamically, the restructuring is done on a periodic basis. The initiator node is selected at the starting of every period and broadcasted messages are sent out using one of the above-mentioned methods for cluster organization. The multi-hop

10 182 broadcasting decreases the problem of energy usage. This is due to that there is a limit for transmission because the highest amount of energy that can be wasted is the minimum transmission energy of neighboring sensor nodes. So, no need for the sensor nodes which are far away from each other to transmit directly. It has a drawback in the sense that it has more delay when compared to the former method of broadcasting. This is because of multi-hop broadcasting, where the data are required to be processed by each sensor node along the multi-hop path, which makes delay in the formation of cluster. Though, the multi-hop is much better than the direct broadcast if the problem of delay is taken care of. 4.4 CLUSTER HEAD ELECTION AND ROTATION After the formation of cluster, CHs are elected which act as a head in each cluster. The elected cluster heads are saddled with the task for data aggregation and the base station and the clusters that consist of many sensor nodes have a higher saddle than clusters with fewer nodes as the CHs for those large-sized clusters have to receive, cumulate and transmit more data. A CH can be elected randomly or pre-assigned by the developer of the network. A CH can also be elected by taking into consideration the residual energy of nodes in the cluster. The CHs are known to have higher saddles than member nodes. So the role of CH is rotated to share the burden and thus improving the useful life span of those clusters. In random selection of CH based on the probability, that it has never being selected during the entire lifetime of the network. This decreases the traffic burden on a CH since the role of CH is spread throughout the sensor nodes. The rotation is done at a periodic interval. But, in the residual energy selection, the sensor node that has the highest amount of energy in the cluster is selected as the cluster head. It will continue to remain the CH until the energy drops below the average energy of the entire cluster.

11 183 As a result, rotation of CH is done at every instance when its energy level drops below the average cluster energy. This rotation of CHs will lead to the overall energy of the sensor network being evenly distributed. This method eventually improves the life span of the network. Alternate approach to cluster head selection, Handy et al (2002), is based on minimizing the distance to cluster nodes as this offers diminution in energy usage during data transmission to the BS. In this method of minimising sum of distances to CH, the cluster formation is better enhance to reduce energy usage as transmission takes place. It helps in reducing the unnecessary energy which the sensor node uses in communicating with the CH by minimizing the transmission distances from sensor node to any CH. Even though the communication energy is an important concept to consider in wireless transmission the energy greatly depends on distance. So, it is very good idea to reduce the distance in transmitting data from sensor nodes to base station via the CH, as this helps to reduce the communication energy in WSN. The obtainable routing protocol is classified into two major groups, one is network structure, Cheng et al (2011) and based and other one is protocol based. In network structure based routing protocol can be divided into flat networks, hierarchal networks and location based, Kumar & Chand (2011), routing protocol. From hierarchical networks type of routing protocol, the LEACH (Low Energy Adaptive Clustering Hierarchy) routing is the base protocol for the research work, Heinzelman et al (2000),(2000 a) (2002 b), The LEACH, which is presented by Heinemann in the paper, it is a lowenergy adaptive clustering hierarchy for Wireless sensor networks, Limin et al (2005). The important operation of LEACH can be divided into number of rounds. Each round, it has two phases, one is setup phase and other one is steady state phase. Each round begins with a set-up phase when the clusters are formed, followed by a steady state phase where several frames of data are transferred form the nodes to the cluster head and on to the base station. At

12 184 the time of set-up phase, each sensor node tries to select itself as a cluster head according to probability model. Figure 4.4 describes the available phases in LEACH protocol. Set up phase Frame Steady state phase Time Round Figure 4.4 LEACH protocol phases The selection of a cluster head, each sensor node generates a random number between 0 and 1. If the number is less than the threshold value T (n), the sensor node selects itself as a cluster head for current round; the threshold value selection Equation (4.3) is presented as follows: In Equation (4.3), p is the prearranged percentage of cluster heads (e.g., p = 0.1), r is the current round of iteration and G is the set of nodes that have not been cluster heads in the last 1/ p rounds. Keeping this threshold, each node will be getting a chance of cluster head at some round within 1/ p rounds. After the 1/ p rounds, all nodes are once again eligible to become cluster heads. In normal LEACH, the optimization, Kulkarni & Venayagamoorthy (2011),(2011a) of number of cluster heads are estimated by given equation to be about 10% of the total number of available sensor nodes. Each node is getting the chance of that has elected itself a cluster head for the current round and immediately broadcasts an advertisement message to the remaining available sensor nodes in the wireless sensor network. Other remaining non cluster head nodes, after receiving this advertisement message,

13 185 decide on the cluster to which they will belong for this round. This decision is based on the received signal strength of the advertisement messages. The cluster head from each cluster receives all the messages from the nodes that would like to be included in the cluster and based on the number of nodes in the cluster, the cluster head creates a TDMA (Time Division Multiple Access) schedule and assigns each node a time slot when it can transmit, Pantazis et al (2009). At the time of the steady-state phase, the sensor nodes can begin sensing and transmitting data to cluster heads. The radio energy model of each nonallocated transmission time. The cluster heads are receiving all the data from the member node in the cluster and aggregate it before sending it to the sink node. 4.5 BASIC LEACH PROTOCOL LEACH is self-organized, adaptive clustering protocol which uses random distribution of sensor nodes in area, Kumar & Trilok (2010), to evenly distribute energy between nodes in sensor network. In LEACH, sensor nodes are organized in such a way that some of nodes become CHs which are responsible to transmit data to BS. In this process, CHs are elected on the basis of probability. Sensors nodes are elected as CHs at any given time with a certain probability which is a random number between, 0 and 1. Nodes compare this probability with a given threshold. If random number is less than threshold then sensor node becomes a CH and transmits data to BS. Otherwise, the node attaches itself to any CH for communication with BS. CHs broadcast their status to other sensor nodes in network. Each sensor node joins CH on basis of Received Signal Strength Indicator (RSSI). Once network is organized into clusters, each CH creates a TDMA schedule for nodes in its cluster. This allows radio components of each non CH node to be turned off at all times except during transmission time, thus, minimizing

14 186 energy dissipation by individual sensors. Once CH has all aggregated data from nodes in its cluster, then CH node aggregates data and transmits compressed data to BS. Since BS is faraway in scenario which we are examining, there is high transmission energy is required however; there are only a few CHs. Therefore, a small number of nodes are affected. Being CH for a long time drains out battery of sensor nodes. To avoid this unnecessary draining of energy of single node, CHs do not remain same in all rounds. Thus, clustering seems to be an energy-efficient technique in routing protocols, Javaid et al (2013). 4.6 TYPES OF LEACH PROTOCOL The wireless sensor network system can be implemented in two ways. One is static LEACH protocol and the other is mobile, LingaRaj et al (2012), LEACH protocol. In static LEACH protocol all sensor nodes in the field are fixed i.e. no movement. But in the case of mobile LEACH protocol all the sensor nodes or some of the sensor nodes in the field are in mobility. The details are as follows Static LEACH Protocol In this static LEACH protocol, the sensor nodes from the entire network is shown in Figure 4.5, are divided into number of clusters as per the requirement, cluster-head sensor nodes communicate with the local base station, then the local base station feed data to the entire network of base stations, and terminal user according to the application can access useful information. The distance between the local base stations and the cluster node is very close, consequently greatly reducing the energy consumption of these nodes send their information to local base station. Taking into consideration of static clustering protocol seems to be a more energy efficient protocol. Even if in the entire network life cycle, these clusters and cluster-head nodes

15 187 are fixed, and the local base station is assumed as a high-energy nodes situation. In most of the situation, the local base station is an energyconstrained node. The whole network may die soon because of excessive usage of local base station node. Figure 4.5 Static LEACH protocol Mobile LEACH Protocol LEACH-Mobile (Mobile Low energy adaptive clustering protocol) Mobility support is an important issue in Leach routing protocol. Leach-M is proposed to mitigate this issue. Leach-M involves the mobility of non cluster head nodes and cluster head during the setup and steady state phase. The nodes in Leach-M are assumed to be homogeneous and have their location information through GPS. The basic idea in LEACH-Mobile is to confirm whether a mobile sensor node is able to communicate with a specific cluster head, as it transmits a message which requests for data transmission back to mobile sensor node from cluster head within a time slot

16 188 allocated in TDMA schedule of a wireless sensor cluster. If the mobile sensor node does not receive the data transmission from cluster head within an allocated time slot according to TDMA procedure, it sends join-request message at next TDMA time slot allocated. Then it decides the cluster to which it will belong for this moment by receiving cluster joinacknowledgement messages back from specific cluster heads. The LEACH- Mobile protocol achieves definite improvement in data transfer success rate as mobile nodes increase compared to the non-mobility centric LEACH protocol. LEACH-Mobile could be appropriated for mobilitycentric routing protocol in wireless sensor network. The main drawback is as follows: LEACH-M handles node mobility by assuming that the CHs are stationary. Hence, LEACH-M is not effective in terms of energy consumptions and data delivery rate because a large number of packets are lost if the CH keeps moving before selecting a new CH for the next round. 4.7 TYPES OF CLUSTERING CONCEPT In wireless sensor network system of implementation, the data communication process is being done in different ways. This can be done by single hop or multi hop of data communication, Rauthan & Mishra (2012). This may classify by its energy efficient, Kumar et al (2011), process of routing protocols related wireless sensor networks. It is classified as constant and variable re-clustering, Akkaya et al (2005). The concept of direct communication all sensor nodes directly transmit sensed data to the BS. Because the BS is far away from each sensor node in the WSN, the energy dissipation of transmitting data by the sensor node in the WSN is too big when compared to LEACH protocol. It is shown in Figure 4.6.

17 189 BS Sensor Network Field Figure 4.6 Direct data communication system in WSNs Constant Clustering In constant clustering concept of wireless sensor network implementation all the available sensor nodes in the field has number of clusters. In side the each cluster constant and uniform numbers of sensor nodes are available i.e. each clusters has equal number of sensor nodes. For each cluster constant cluster head is appointed up the end of the process of implementation or iteration. All sensor nodes are static and have same characteristics. It is called homogeneous system of wireless sensor networks. It is stated in Figure 4.7. Each sensor node collects its sensed information and passed to its cluster head. Each cluster head aggregate the total data and send it to the base station for end user application process. In constant cluster system the cluster, cluster member and cluster head is permanent up to the end of rounds or iterations.

18 190 Figure 4.7 Constant clustering Variable Re-clustering In variable re-clustering concept of wireless sensor network implementation all the sensor nodes are deployed randomly in the field. In this concept each round or iteration cluster heads are elected as per the residual energy comparison. Under probability base some number of sensor nodes in the field can be elected as cluster heads. The selected cluster head sensor nodes advertise the cluster message to the neighbor sensor nodes to form the cluster. The non cluster member sensor nodes are deciding themselves to join as member in the cluster by comparison of cluster head signal strength around its area and distance between the cluster head. Then the non member sensor nodes give its acknowledgement to the respective cluster head as member. In variable re-clustering, each round the cluster head selection, Kusdaryono & Lee (2011), procedure is being done based on that the clusters are formed. Here in each cluster does not have equal number of sensor nodes. Each cluster has different number of member sensor nodes i.e. variable size of cluster members. The re-clustering is nothing but in each round of simulation or iteration cluster head, cluster member and cluster size

19 191 can be changed based on the selection of cluster head selection under residual energy. This is illustrated in Figure 4.8. In Figure 4.8 hundred sensor nodes are randomly deployed and under the probability value as threshold some number of sensor nodes are elected as cluster heads. The cluster formation by the cluster head with variable size and member sensor nodes are clearly shown in the figure. Variable Re-clustering WSN Node Delpoyment Topology X Coordinate (m) Figure 4.8 Variable re-clustering 4.8 DISADVANTAGE OF LEACH PROTOCOL The prominent LEACH protocol designed for static sensor nodes and static targets joins the notions of energy efficient cluster-based routing and media access with application-specific data aggregation to achieve good performance in terms of system lifetime, latency and application-perceived quality, Polastre et al (2004). All regular sensor nodes that are not cluster head within each cluster transmit data packets to their own cluster heads

20 192 periodically. There are two energy-consumption inefficiencies in LEACH, both affecting cluster heads. First, there is the hotspot problem: due to its extra duties, a cluster head uses more energy than regular sensor nodes. Second, the regular sensor nodes with overlapping sensing areas generate redundant data, which creates unnecessary load on cluster heads receiving these data. LEACH does not propose a complete solution to either of these problems. It incorporates randomized rotation of the cluster head role among all nodes in a cluster, and ensures that all nodes serve as a cluster-head only once during WSN lifetime; in this way LEACH tries to even out in a long term energy usage by all nodes in a cluster. However, LEACH does not compensate for the loss of energy suffered by a node during its cluster head service. The randomized rotation of the cluster head role is only a partial solution for only the first (hotspot) problem. LEACH does not give solutions for reducing transmission of redundant data by nodes redundantly covering the same targets. 4.9 CLASSIFICATION IN LEACH PROTOCOL SYSTEM The classification of LEACH protocol system is divided into two categories. One is homogeneous system of wireless sensor network and another one is heterogeneous, Kavitha & Sridharan (2013), system of wireless sensor networks Homogeneous LEACH System The wireless sensor network field has same quality of sensor nodes. All sensor nodes are having same initial energy and identical behavior. This type of wireless sensor network system is called homogeneous concept. In this case the LEACH protocol concept is implemented in the WSN field. The homogeneous system of node deployment is shown in Figure 4.9. Here

21 193 sensor nodes are randomly deployed. The base station is located at centre of the field. All sensor nodes are having 0.5 Joule of initial energy. Homogeneous LEACH Protocol Topology X Coordinate (m) Figure 4.9 Homogeneous LEACH protocol topology Subsequent details are some of the salient features of a single hop homogeneous sensor network. As all the nodes are indistinguishable, the main design aim is to guarantee a certain network lifetime in terms of number of data gathering, Kalpakis et al (2003) and cycles. At the same time make sure that all the sensor nodes expire at about the same time. So that there is very little residual energy left behind when the network expires. That's why LEACH uses random and periodic rotation of the cluster heads for load balancing, Zhu et al (2010). The role rotation also makes sure that a node which is located near the periphery of a cluster is nearer to the cluster head at some other time. As each node has to be capable of acting as a cluster head, it is necessary for each node to have the hardware capable of performing long range transmissions to the remote base station, complex data computations, and co-ordination of MAC and routing within a cluster, Shi & Stromberg

22 194 (2007). While all the nodes are capable of acting as a cluster head; the failure of a few sensor nodes does not seriously affect the working of the scheme. Thus the system is robust to node failures Heterogeneous LEACH System The wireless sensor network field has different quality of sensor nodes. All sensor nodes are having different initial energy and different behavior, Lee et al (2006). This type of wireless sensor network system is called heterogeneous, Brahim et al (2010), concept. In this case the LEACH protocol concept is implemented in the WSN field. The heterogeneous system, Qing et al (2006), of node deployment is shown in Figure Here sensor nodes are randomly deployed. The base station is located at centre of the field. Some percentage of sensor nodes is having additional initial energy. The heterogeneous type of sensor nodes is having 1 Joule of initial energy, Said et al (2010). This system implementation of LEACH protocol is shown in Figure The heterogeneous sensor nodes are indicated in green color of + symbol. Heterogeneous LEACH Protocol Topology Homogeneous Node Base Station Cluster Head Node Heterogeneous Node X Coordinate(m) Figure 4.10 Heterogeneous LEACH Protocol Topology

23 195 Heterogeneous sensor nodes in the networks use two or more types of nodes with different functionalities, Smaragdakis et al (2004). For illustration, the plan with two types of sensor nodes has, type 0 nodes which act as pure sensor nodes and type 1 nodes which act as the cluster head nodes with different initial input energy. A few significant features of such networks are: Since the cluster head nodes are may be predetermined. Sensor nodes use single hop communication to reach the cluster head nodes, the sensor nodes near the periphery of the cluster have the highest energy expenditure among all the sensor nodes. It is most evil case energy expenditure that has to be taken into account in battery energy dimensioning. Hence there is a waste of energy due to the residual battery energy of the sensor nodes that are near the cluster heads. Since only the cluster head nodes stand the responsibility of transmitting to the distant base station, the remaining sensor nodes can be designed with simple hardware that enables short range communication. As a result the hardware complexity is limited to only a few nodes. A cluster head node serves as the fusion point, in addition to the command center of its cluster. As a result when a cluster head node fails, all the sensor nodes in that cluster have to be re-assigned to other neighboring clusters. In the extreme case, it is possible that all the cluster head nodes might fail, thereby bringing down the entire network. Thus the system is less robust to node failure as compared to a homogeneous sensor network SIMULATION OF HOMOGENEOUS AND HETEROGENEOUS LEACH PROTOCOL The process of proposed protocol implementation starts with basic homogeneous LEACH protocol and heterogeneous LEACH protocol and its

24 196 comparison without adaptation of node scheduling concept is shown in Figure 4.11and Figure Homogeneous LEACH Protocol(After Simulation) X-Coordinates in meters Figure 4.11 Homogeneous LEACH Protocol (After 1400 rounds) Heterogeneous LEACH protocol(after Simulation) X-Coordinates in meters Figure 4.12 Heterogeneous LEACH Protocol (After 1400 rounds)

25 197 It is clearly evidenced that the number of live sensor nodes are indicated in blue color and the count of live sensor nodes after 1400 rounds attest the increased lifetime of the network. In Figure 4.11four sensor nodes are alive and in Figure 4.12 sixteen sensor nodes are alive after simulation. For normal homogeneous LEACH protocol in Figure 4.11 and heterogeneous LEACH protocol (10% Heterogeneous sensor nodes) in Figure 4.12 and their simulation with comparison is presented in Figure Heterogeneous LEACH protocol incorporated WSNs has longer lifetime by attest the number of alive sensor nodes in Figure Homogeneous LEACH protocol Heterogeneous LEACH protocol Number of Rounds Figure 4.13 Homogeneous and heterogeneous LEACH protocol comparison by simulation 4.11 DETAILS OF NODE SCHEDULING CONCEPT In this section, we describe the implementation of proposed routing protocol which incorporates the node scheduling or activation process in each cluster of the wireless sensor network. The structure of the proposed routing protocol for wireless sensor networks is shown in Figure The number of sensor nodes shown in Figure 4.14, the

26 198 formation of the clusters are followed by Equation (4.3) for the proposed protocol. The cluster head selection for each cluster is being done by comparing the residual energy of the individual sensor node in every round. From Equation (4.3), below value of threshold sensor nodes are elected as head nodes. The elected cluster head sensor nodes are forming the cluster by sending the advertisement message to its communication range. The noncluster head sensor nodes are compared to the strong signal strength of the advertisement message of the cluster heads and then the individual noncluster sensor node can decide to join in the cluster by giving acknowledgement information. At this moment the node scheduling or activation process is being implemented in the wireless sensor networks. Figure 4.14 Proposed LEACH protocol with node scheduling Node scheduling or activation technique implementation In node scheduling process, each round of iteration in each cluster, half numbers of sensor nodes are being in active mode to sense the data and remaining sensor nodes are kept in sleep mode. In this process of

27 199 implementation, two ways of node scheduling process is being adopted in the wireless sensor network. The first one is active / sleep mode node scheduling concept and the second is active then sleep mode node scheduling concept Case 1: Odd/Even (Sleep/Active) Case1: Before simulation, forming the cluster heads and its cluster, half numbers of sensor nodes are activated to active mode and the remaining sensor nodes are kept in sleep mode in each cluster. After certain number of rounds, the entire active mode sensor nodes in the network are coming to zero energy level i.e. in die condition. At this time, available sleep mode nodes are activated to active mode to continue the simulation up to zero energy level. This process is called active then sleeps node scheduling method. The important information in each round of iteration is the process of re-clustering formation; cluster head selection and its cluster are being done. The reason for forming re-clustering is due to the cluster head selection in each round is based on the threshold value followed by the equation (4.3).This process is being implemented in homogeneous and heterogeneous wireless sensor networks. The heterogeneous wireless sensor network has higher energy level sensor nodes deployed in certain percentage. Under case1, the process of proposed protocol is being adopted with active/sleep node scheduling or activation concept in homogeneous LEACH protocol and heterogeneous LEACH protocol implemented wireless sensor network and its simulation is shown in Figure It is clearly evidenced that the number of live sensor nodes are indicated in green and blue color and the count of live sensor nodes after 2500 rounds attest the increased lifetime of the wireless sensor network depicted in Figure In Figure 4.15(a,b), after simulation of 2500 rounds five sensor nodes are alive in homogeneous node scheduling LEACH protocol active/sleep type and eighteen sensor nodes are alive in heterogeneous node scheduling LEACH

28 200 protocol active/sleep type. This comparison is depicted in Figure Hence the heterogeneous node scheduling LEACH protocol active/sleep type incorporated WSNs has longer lifetime by attest the number of alive sensor nodes after 2500 rounds. Homogeneous Active/Sleep Node Scheduling LEACH Protocol X Coordinate in metres Heterogeneous Active/Sleep Node Scheduling LEACH Protocol X Coordinate in metres Figure 4.15(a,b) Homogeneous and heterogeneous active/sleep node scheduling LEACH protocol (After 2500 Rounds)

29 201 Homogeneous Active/Sleep Node Scheduling Protocol Heterogeneous Active/Sleep Node Scheduling Protocol Number of Rounds Figure 4.16 Homogeneous and heterogeneous active/sleep node scheduling LEACH protocol comparison by simulation Case 2: Odd then Even (Sleep then Active) Case2: Before simulation, forming the cluster heads and its cluster, half numbers of sensor nodes are activated to active mode and the remaining nodes are kept in sleep mode in each cluster. Second time of iteration active mode nodes are activated to sleep mode nodes and the sleep mode nodes are activated to active mode nodes. Similarly this change of mode activation of active to sleep and sleep to active is perfectly followed with forming of reclustering of clusters and head selection is being done in each round. The sensor node in sleep mode consumes much neglected negligible energy. Under case 2, the process of proposed protocol contains the adaptation of active then sleep node scheduling scheme in homogeneous LEACH protocol and heterogeneous LEACH protocol in the wireless sensor networks. The scheme implemented sensor node deployment topology is depicted in Figure 4.17(a,b).

30 202 Homogeneous Active then Sleep Node Scheduling LEACH Protocol X Coordinate in metres Heterogeneous Active then Sleep Node Scheduling LEACH Protocol X Coordinate in metres Figure 4.17(a,b) Homogeneous and heterogeneous active then sleep node scheduling LEACH protocol (After 2500 Rounds) It is clearly evidenced that the number of live sensor nodes are indicated in green and blue color and the count of live sensor nodes after 2500 rounds attest the increased lifetime of the wireless sensor network depicted in Figure In Figure 4.18, after simulation of 2500 rounds nine sensor nodes are alive in homogeneous node scheduling LEACH protocol active then sleep

31 203 type and forty sensor nodes are alive in heterogeneous node scheduling LEACH protocol active then sleep type. This comparison is depicted in Figure Hence the heterogeneous node scheduling LEACH protocol active then sleep type incorporated WSNs has longer lifetime by attest the number of alive sensor nodes after 2500 rounds. Homogeneous Active then Sleep Node Scheduling Protocol Heterogeneous Active then Sleep Node Scheduling Protocol Number of Rounds Figure 4.18 Homogeneous and heterogeneous active then sleep node scheduling LEACH protocol comparison by simulation 4.12 SIMULATION FOR HOMOGENEOUS AND HETEROGENEOUS NODE SCHEDULING CONCEPT The explained experimental simulations are giving the energy consumed and lifetime improved in rank about the wireless sensor network system from the base of LEACH protocol. The basic homogeneous LEACH protocol and heterogeneous LEACH protocol and its simulation work attest the heterogeneous LEACH protocol is giving better result of energy consumption which is in Figure 4.13.

32 204 Case 1 scheme adopted active/sleep node scheduling system of wireless sensor network is being implemented in homogeneous LEACH protocol and heterogeneous LEACH protocol. The comparison between these routing protocol implementation evidenced that the heterogeneous active/sleep node scheduling LEACH protocol lifetime is more by available count of live sensor nodes in the network which is depicted in Figure Case 2 scheme adopted active then sleep node scheduling system of wireless sensor network is being implemented in homogeneous LEACH protocol and heterogeneous LEACH protocol. The comparison between these routing protocol implementation evidenced that the heterogeneous active then sleep node scheduling LEACH protocol lifetime is more by available count of live sensor nodes in the network which is depicted in Figure Table 4.2 Simulation parameters Name of the parameter Parameter values Network area(variable) m *m Number of nodes(variable) Initial Energy for Homogeneous nodes(variable) 0.5Joules Initial Energy for Heterogeneous nodes(variable) 1 Joules E elec E tx =E rx 50nJ/bit 50nJ/bit fs(friss-amp) 10pJ/bits/m 2 mp (Two-ray-amp) pJ/bit/m 4 Distance d o E DA Packet size(variable) fs / mp) 5nJ/bit 4000 bits

33 205 From the above explained methods are implemented from the basic concept of LEACH protocol in both homogeneous and heterogeneous wireless sensor networks. Among all the implemented routing protocol, the heterogeneous active then Sleep type node scheduling LEACH protocol is giving the best result of energy consumption and increased lifetime of the overall wireless sensor networks, Sandeep Krishna & Rajendra (2012). These complete comparison results of the simulation work of the proposed routing protocol are depicted in Figure The simulation parameters used in the implemented routing protocol is available in Table 4.2. Homogeneous LEACH Protocol Heterogeneous LEACH Protocol Homogeneous Active/Sleep Node Scheduling LEACH Protocol 80 Heterogeneous Active/Sleep Node Scheduling LEACH Protocol 60 Homogeneous Active then Sleep Node Scheduling LEACH Protocol Heterogeneous Active then Sleep Node Scheduling LEACH Protocol Number of Rounds Figure 4.19 Overall types of homogeneous and heterogeneous node scheduling LEACH protocols with leach protocol simulation and comparison 4.13 THRESHOLD BASED CLUSTER HEAD SELECTION CONCEPT To get the best way of energy savings method to improve the lifetime of the wireless sensor network in clustering concept is by choosing

34 206 different optimum value of threshold value based cluster head selection equation, Yang, Z, et al (2009). This is giving better performance from the basic equation BASIC THRESHOLD EQUATION FOR CLUSTER HEAD SELECTION In earlier discussed how to select the cluster head nodes based on the threshold value of p in probability and showed the threshold denoted by Equation (4.3). In this way, each node in the network has the same probability to as a cluster head. Moreover, it can make the network energy efficiently, distribute to each sensor node. However, since random selection of cluster heads, they may be located in the edge of the network or in the place where the density is very low. In these cases, some nodes have to bridge long distance to reach a cluster head. Therefore, it is important to avoid the low energy level nodes to be elected as cluster heads; this thesis will present a modified algorithm in the next section Type 1: Threshold Equation for Cluster Head Selection The approach increasing the network lifetime is the inclusion of the remaining energy level available in each node. It can be achieved by modifying the threshold. In this way, each node has different threshold in comparison with a random number. Therefore, high energy level nodes have greater probability to be elected as cluster heads than low energy level ones. Case1: From Equation (4.3), the modified threshold value can be obtained by using number of sensor nodes and cluster head nodes present in the network is as follows in Equation (4.4):

35 207 where N as the total number of sensor nodes in the network, c as the number of cluster head nodes for each round, r as the number of the current round, and G is the set of nodes that have not been selected as cluster heads in the last N/c rounds. The nodes shall transmit broadcast information after being selected as cluster heads. Each non-cluster head node determines to which cluster it belongs by choosing the cluster head that requires minimum communication energy. After this, it must inform the cluster head node that it will be a member of the cluster. Each node transmits a join-request message (Join-REQ) back to the chosen cluster head using a non-persistent CSMA MAC protocol, Qiong et al (2011). During the steady-phase, the cluster head keeps its receiver on to receive all the data from the nodes in the cluster. Once the cluster head receives all the data, it can operate on the data, and then resultant data are sent from the cluster head to the base station. Through the above-mentioned ways, after a period of time, the network will enter into the next clustering process till not meeting the network requirements. In order to minimize the set-up overhead, the steady-state phase is long compared to the set-up phase Type 2: Threshold Equation for Cluster Head Selection Case 2: An additional method of finding the threshold based selection of cluster heads among the sensor nodes is formulated in the followings. In this network E o as the initial energy of each node, it is clear now that when multiple cluster heads are randomly selected within a small area, a big extra energy loss occurs. The amount of lost energy is approximately proportional to the number of cluster heads in the area. Of course, there is a precondition on this conclusion, that is, cluster heads are

36 208 very closely located and the distance between them becomes negligible. Thus the new threshold is made to have reasonable numbers of cluster heads are consuming minimum energy and the network lifetime is also ultimately increased by the Equation (4.5). Where, s is the number of nodes that are excluded from the cluster head selection due to the location reason, with an initial value of 0. When s increases, increases as well, which will ensure sufficient number of cluster heads will be generated OPTIMAL CLUSTER HEAD SELECTION CONCEPT The optimal number of cluster-heads can be achieved based on analyzing the network energy consumption. First, the total energy consumption for data communication can be reduced to minimum in each round. Second, it is necessary to make sure the network energy can be distributed to each sensor node, thus effectively extending the network lifetime. To simplify the algorithm, here are some assumptions in this paper. Each cluster has the equal number of sensor nodes, and a total of N nodes are deployed in a field of size M M. If the WSN consists of c clusters, N/c nodes can be achieved in each cluster, including one cluster-head and (N/c)-1 non-cluster head sensor nodes. The WSNs is covered by a circular area. The radius is proposed as follows in Equation (4.6): The sensor nodes in the network were uniformly distribution, so the probability density function (PDF) is shown below in Equation (4.7).

37 209 According to the first order radio model and the process of LEACH protocol, the energy consumption of each cluster head consists of receiving data from the non-cluster head nodes, data fusion, Luo et al (2006), transmitting the resultant data to base station. Additionally, the cluster heads are far away from the base station, so they use the multi-path model to calculate the transmission energy consumption. Therefore, the energy consumption of one cluster-head in a frame can be calculated using Equation (4.6) and (4.7) as follows in Equation (4.8). In Equation (4.8), where k or l is the length of data packet, d tobs is the distance from cluster-head to the base station, E DA as the energy consumption of data fusion for each signal and as the data fusion ratings. Considering the distance between the cluster-head and its clustering members is not far, so the energy consumption for transmitting data can be calculated using the free space model, which can be presented below in Equation (4.9). where, d toch as the distance from the non-cluster head nodes to their clusterhead. All the sensor nodes are deployed in the field of size M M so the area of M 2 /k can be achieved for each cluster. We assumed that (x, y) as the probability density function for arbitrary region, so the mathematical expectation of distance square from the non-cluster head nodes to their cluster- head can be calculated as follows in Equation (4.10).

38 210 calculated below: According to Equation (4.6), (4.7), and (4.10) can be further Equation (4.8) using in (4.11) can be modified as follows in (4.12) So the energy consumption of each cluster can be calculated as follows in Equation (4.13): Therefore, the energy consumption of whole network can be shown below in Equation (4.14): Now, the optimal number of cluster heads can calculated according to Equation (4.14), which can be presented as follows in Equation (4.15)

39 211 According to the data presented in Table 4.2 for 300 sensor nodes the distance of d to BS is in between m < d to BS < 152m, so the optimal number of cluster heads must meet the requirement as follows in Equation (4.16) SIMULATION OF DIFFERENT THRESHOLD BASED CLUSTER HEAD SELECTION CONCEPT EQUATIONS WITH NODE SCHEDULING In earlier section 4.14 and 4.15 is clearly explained about the different levels of threshold basis number of cluster head selection algorithm and optimal number of cluster head selection procedures respectively. This proposed method can be used in the homogeneous system of wireless sensor networks, which contains the threshold basis cluster head selection system and the optimal number of cluster head selection technique. Based on the above said information, it is properly utilized in our node scheduling concept in the network and found the best level of threshold to have number of clusters and optimal number of cluster heads. In node scheduling concept in cluster half numbers of nodes are active mode and the remaining nodes are inactive mode. After certain number rounds all the active nodes are lost their energy then the inactive nodes are now in active mode. Here properly applying the threshold basis head selection and also found the optimal number of cluster heads. This system of approach is giving good saving of energy and ultimately the sensor network lifetime increased. The head node selection algorithm and optimal head node selection technique is properly defined in earlier section 4.14 and 4.15 respectively. In this thesis, the overall simulation

40 212 part of the work has been implemented through MATLAB to draw the picture of sensor nodes deployment randomly, which set sensor nodes in the field of size m m. Therefore, the energy of the total network can be calculated in the following Equation (4.17). resultant information is given in Table 4.3 and Table , after the simulation the Table 4.3 Simulation data for without Node Activation concept Equation First node die (FND) in rounds Last node die (LND) in rounds Equation (4.3) : T(n) Equation (4.4) : T(n) Equation (4.5) : T(n) Table 4.4 Simulation data for with Node Activation concept Equation First node die (FND) in rounds Last node die (LND) in rounds Equation (4.3) : T(n) Equation (4.4) : T(n) Equation (4.5) : T(n) in Table 4.3 and 4.4, and the corresponding bar chart figures, it is clearly proved that the Equations (4.3),(4.4) and (4.5) results for without and with node scheduling shows the maximum of rounds which ultimately increase the lifetime of the network for with node scheduling concept. Here in Table 4.4 the node scheduling adopted concept of system, the first node die is having lesser value than the values in Table 4.3, because of the node active and

41 213 inactive system have half numbers of the nodes are inactive and remaining nodes are active. So, the network have fifty percent of nodes are involved in all the active nodes are dead, now the inactive nodes are come to active. 80 Simulation Result - without Node Activation Protocol T(n), p=0.1 T(n)1, k=5 T(n)2, p=0.1, s= Number of Rounds Figure 4.20 Simulation results for without node activation protocol SIMULATION RESULTS for NODE ACTIVATION PROTOCOL T(n), P = 0.1 T(n)1, k = 5 T(n)2, P = 0.1, S = 8 Figure 4.21 Simulation results for node activation protocol

42 214 Finally all the nodes are dead, the number rounds is giving the clear evidence of increased lifetime of network. The simulation results are shown in Figure 4.20 and Figure 4.21 respectively ENERGY COMPETENT HIERARCHICAL ROUTING FOR WSNS method: Proposed hierarchical routing technique with node activation Various techniques can be found in hierarchical routing protocol. The basic idea of the techniques is a situation whereby nodes are clustered so that cluster heads can do some aggregation and a compression of data in order to save energy thereby prolonging the lifetime of WSN. The proposed hierarchical routing with and without node activation schemes follows. Description about the Proposed Hierarchical routing protocol is as Main points adopted in our proposed routing protocol are It is based on the principle of clustering algorithm, Abbasi & Younis (2007). Data transmission at the network layer Modified transfer LEACH protocol in terms of hierarchical data Clusters are formed by geographical area division

43 215 Cluster head selection is based on the residual energy comparison in each round Geographical formation of cluster sizes is based on equal segmentation of area space i. No segmentation of area - First hierarchical level system - one cluster (Figure 4.23) ii. Two segmentation of area - Second level hierarchical system - Two clusters (Figure 4.24) iii. Three segmentation of area - Third level hierarchical system - Three clusters (Figure 4.25) In the above hierarchical levels are adopted the node scheduling or activation algorithm. Thus, it is implemented to get the improvement in lifetime of the wireless sensor networks. Algorithm description of the routing protocol as follows. Level 1 -- One cluster with one head (Overall area) Level 2 -- Two clusters with two heads (Overall area is divided in to two groups) Level 3 -- Three clusters with three heads (Overall area is divided in to three groups) Data communication from each sensor node to cluster head and cluster head to base station is under multi hop communication by finding shortest path.

44 216 A. Hierarchical routing without node activation scheme In this scheme, level 1 has overall area of 300m x 300m with 250 sensor nodes, which is considered as one single cluster and under the principle of clustering concept one cluster head can be selected in each round of data communication by comparing the residual energy of the individual sensor node. (Refer Figure 4.23) In level 2, the overall area space is divided in to two segments and the 250 sensor nodes are randomly deployed in two groups with two heads are elected as per the residual energy basis in each round. (Refer Figure 4.24) In level 3, the overall area space is divided in to three segments and the 250 sensor nodes are randomly deployed in three groups with three heads are elected as per the residual energy basis in each round. (Refer Figure 4.25) In all the levels the available sensor nodes are active mode. B. Hierarchical routing with node activation scheme 1-active / sleep concept In all the levels, inside the cluster, half of the sensor nodes from the available sensor nodes are activated to active mode and the remaining half are activated to sleep mode. After the first round of data communication active nodes are activated to sleep mode and sleep nodes are activated to active mode. In this implementation of sensor node activation, the above said three levels of hierarchical routing is being simulated and it is proved with better results than the hierarchical routing without node activation scheme. (Refer Figure 4.31, 4.32 and 4.33)

45 217 C. Hierarchical routing with node activation scheme 2-active then sleep concept In all the levels, inside the cluster, initially half of the sensor nodes from the available sensor nodes are activated to active mode and the remaining half are activated to sleep mode. In simulation all the active sensor nodes are drain out of its energy after some rounds then the sleep nodes are become activated to active nodes. In this implementation of sensor node activation, the above said three levels of hierarchical routing is being simulated and it is proved with better results than the hierarchical routing without node activation scheme and hierarchical routing with Node activation scheme 1-Active / Sleep concept. (Refer Figure 4.37, 4.38 and 4.39) Simulation results comparison as follows Above said three category scheme of simulation work has obtained and the residual energy of the sensor nodes is also obtained for all levels. After 400 rounds of simulation in each category A. Hierarchical routing without node activation scheme, B. Hierarchical routing with node activation scheme 1-active / sleep concept. C. Hierarchical routing with node activation scheme 1-active then sleep concept The level 3 Hierarchical Routing with Node activation scheme 2- Active then Sleep concept is proving the best of lifetime improvement which is depicted in Figures from 4.27 to 4.32 one by one.

46 218 This is made in two categories, after implementation of work based on the LEACH protocol the comparisons are clearly explained in conclusion section. The scheme of categories is as follows Category 1: Hierarchical routing without node scheduling Category 2: Hierarchical routing with node scheduling Category 1 Hierarchical routing without node scheduling This work is purely based on the Hierarchical routing protocol. From hierarchical concept, one of the clustering concept key routing, so called LEACH (Low energy adaptive clustering hierarchy) protocol is the base for this thesis. Sensor nodes deployment All the sensor nodes are deployed randomly in the area of 300 meters by 300 meters. It is shown in Figure Single cluster with one cluster head (Level 1) Based on the hierarchical concept, in this work initially the sensor nodes are deployed in 300 meters by 300 meters area and also considered as a single cluster with only one cluster head. The operation procedure of LEACH protocol is being implemented, Malik & Singh (2013). Each sensor node sends the sensed data to its cluster head. Cluster head aggregate the data and send it to sink node. It is shown in Figure 4.23.

47 219 Two cluster with two cluster heads (Level 2): The sensor node deployment area is divided into two equal segments and the number of sensor nodes can be deployed into two groups with two cluster heads. Same procedure of LEACH protocol is being followed. It is shown in Figure Three cluster with three cluster heads (Level 3) The sensor node deployment area is divided into three equal segments and the number of sensor nodes can be deployed in to three groups with three cluster heads. Same procedure of LEACH protocol is being followed. It is shown in Figure Hierarchical routing with out node scheduling concept The proposed hierarchical routing protocol is basically based on the principle of clustering algorithm. With data transmission at the network layer being the core area of interest, the modified LEACH protocol in terms of hierarchical data transfer with the employment of energy prediction technique for selection of cluster head via any shortest path to the base station. In the proposed model, clusters are formed geographically. Geographical formation of cluster sizes is based on equal segmentation of area space. Apart from the one cluster formation which makes use of the entire sensors area space, other formation such as two clusters formation and three clusters formation involves equal segregation of area space.

48 220 Figure 4.22 Basic wireless sensor network topology Figure 4.23 Hierarchical routing Level X Co-ordinate (m) Wireless Sensor Networks Topology X Co-ordinate (m) Wireless Sensor Networks Topology- Hierarchical Level -1

49 221 Figure 4.24 Hierarchical routing Level 2 Figure 4.25 Hierarchical routing Level X Co-ordinate(m) Wireless Sensor Networks - Hierarchical Level X Co-ordinate(m) Wireless Sensor Networks - Hierarchical Level - 3

50 222 The two and three cluster formation is known as second level and third level hierarchy respectively. The deployment of sensor nodes are randomly deployed in the field is shown in Figure The hierarchical routing sensor node topology for level 1to 3 is shown in Figure 4.23 to Figure 4.25, Salhiel et al (2001). In Figure 4.22 hundred and two fifty sensor nodes are deployed in 300 meters by 300 meters area. Each node has its ID. These nodes are randomly deployed in the field. In Figure 4.23 two hundred and fifty sensor nodes are deployed in 300m x 300m area. It is considered as hierachical level 1. In level 1, total number of sensor nodes are in one group i.e. one cluster and it has one cluster head. Based on LEACH protocol all sensed data are send to the cluster head. In each round of iteration, based on the energy level comparision of all nodes, the higher energy node will get the chance of cluster head. So, the available energy can be distributed uniformly and getting out of its energy. Figure 4.24 is hierarchical routing level 2. Here the area is segmented into two and 250 sensor nodes are randomly deployed. Here two groups of clusters and has two cluster heads each. One of the cluster sensor nodes are in green colour and another cluster sensor nodes are in blue colour as mentioned in Figure Figure 4.25 is hierarchical routing level 3. The given area of sensor field is segmented into three as shown in Figure 4.25 equally. It has three clusters with three cluster heads respectively. The third cluster is indicated in red color.

51 223 Category 2 Hierarchical routing with node scheduling Node scheduling Incorporating node scheduling process into the network, forming the cluster heads and its cluster, half numbers of sensor nodes are activated to active mode and remaining nodes are sleep mode in each cluster. After certain number of rounds, the entire active mode sensor nodes in the network are coming to zero energy level i.e. in die condition. At this time, available sleep mode nodes are activated to active mode to continue simulation up to its zero energy level. These processes are called active then sleep node scheduling method. The important information in each round of iteration, process of reclustering formation, cluster head selection and its cluster are being done. The reason for forming re-clustering in each round, cluster head selection is being done based on the threshold value followed by the equation. This work is purely based on the Hierarchical routing protocol. From hierarchical concept, one of the clustering concept key routing, so called LEACH (Low energy adaptive clustering hierarchy) protocol is the base for this paper. In each level sensor nodes are activated in two modes. One mode is active and the other is sleep mode. Sensor nodes deployment All the sensor nodes are deployed randomly in the area of 300 meters by 300 meters. Single cluster with one cluster head (Level 1) Based on the hierarchical concept, in this thesis initially the sensor nodes are deployed in meters by meters area and also considered as a single cluster with only one cluster head. The operation procedure of LEACH

52 224 protocol is being implemented. Each sensor node sends the sensed data to its cluster head. Cluster head aggregate the data and send it to sink node. Node activation or scheduling is implemented. Two cluster with two cluster heads (Level 2) The sensor node deployment area is divided into two equal segments and the number of sensor nodes can be deployed in to two groups with two cluster heads. Same procedure of LEACH protocol is being followed. Node activation or scheduling is implemented. Three cluster with three cluster heads (Level 3) The sensor node deployment area is divided into three equal segments and the number of sensor nodes can be deployed into three groups with three cluster heads. Same procedure of LEACH protocol is being followed. Node activation or scheduling is implemented. Hierarchical routing with node activation methods The basic concept of hierarchical routing is being implemented along with node activation method which is exhibited in Figure Along with hierarchical routing two methods of node activation is incorporated to get minimum consumed energy and prolonging the lifetime of entire wireless sensor networks. The idea behind method one is node active /sleep concept and method two have node active and sleep concept. Node Activation Method 1 The base hierarchical routing has three levels of hierarchy which has the concept of available total topological area can be divided to get further levels. The level one hierarchical routing has total available area within that number of cluster formation and the cluster head procedure being done. In

53 225 level two and three hierarchical routing, available topology area is equally divided into two and three. In all the levels the procedure of forming cluster and cluster head are followed by LEACH protocol. In method one in each level available sensor nodes are being activated under the active/sleep concept, which is nothing but in each cluster half number of nodes are being active and the remaining sensor nodes are being kept in sleep mode. Under this condition the simulation work being done and the obtained results show that the lifetime is absolutely increased. Each round the active sensor nodes changes its mode to sleep and sleep to active. Up to the energy level comes to zero this procedure being done. Node Activation Method 2 The base hierarchical routing has three levels of hierarchy which has the concept of available total topological area can be divided to get further levels. The level one hierarchical routing has total available area with in that number of cluster formation and the cluster head procedure being done. In level two and three hierarchical routing, available topology area is equally divided into two and three. Proposed Hierarchical Routing Technique Hierarchical Rou ng Level 1 Hierarchical Rou ng Level 2 Hierarchical Rou ng Level 3 Node Ac ve/sleep Concept Hierarchical Rou ng Level 1- Node Ac va on Method 1 Hierarchical Rou ng Level 2- Node Ac va on Method 1 Hierarchical Rou ng Level 3- Node Ac va on Method 1 Node Ac ve then Sleep Concept Hierarchical Rou ng Level 1- Node Ac va on o Method 2 Hierarchical Rou ng Level 2- Node Ac va on Method 2 Hierarchical Rou ng Level 3- Node Ac va on Method 2 Figure 4.26 Proposed hierarchical routing with node activation methods