**2. Related works**

The main aim of hierarchical routing is to efficiently maintain the energy consumption of sensor nodes by involving them in multi-hop communication within a particular cluster and by performing data aggregation and fusion in order to decrease the number of transmitted messages to the sink.

LEACH (W. Heinzelman et al., 2000) is one of the rst hierarchical routing approaches for sensors networks. The idea proposed in LEACH has been an inspiration for many hierarchical routing protocols. We explore recent works in this section.

### **2.1. Low-energy adaptive clustering hierarchy (LEACH)**

Low-energy adaptive clustering hierarchy (LEACH) (W. Heinzelman et al., 2000) is one of the most popular hierarchical routing algorithms for sensor networks. The idea is to form clusters of the sensor nodes based on the received signal strength and use local cluster heads as routers to the sink. This will save energy since the transmissions will only be done by such cluster heads rather than all sensor nodes.

All the data processing such as data fusion and aggregation are local to the cluster. Cluster heads change randomly over time in order to balance the energy dissipation of nodes. This decision is made by the node S choosing a random number x between 0 and 1. The node becomes a cluster head for the current round if the number x is less than the following threshold:

$$\text{T(S)} = \begin{cases} \frac{\text{P}}{\text{1} - \text{P} \ast \text{(r \, mod \, \frac{\text{I}}{\text{P}})}} & \text{if } \text{S} \in \text{G} \\\ 0 & \text{otherwise} \end{cases} \tag{1}$$

Where ܲ is desired percentage of cluster head nodes in the sensor network, ݎ is current round number, and ܩ is the set of nodes that have not been cluster heads in the last ͳȀ rounds.

**Figure 1.** Network model with clustering

314 Energy Efficiency – The Innovative Ways for Smart Energy, the Future Towards Modern Utilities

stability period in section 6. Finally, in section 7, we conclude the chapter.

hierarchical routing protocols. We explore recent works in this section.

**2.1. Low-energy adaptive clustering hierarchy (LEACH)** 

T(S) � �

such cluster heads rather than all sensor nodes.

performance in the presence of energy heterogeneity.

**2. Related works** 

messages to the sink.

threshold:

impact of heterogeneity of nodes, in terms of their energy, in wireless sensor networks that are hierarchically clustered. In these networks some high-energy nodes called NCG nodes (Normal node|Cluster Head| Gateway) are elected "cluster heads" to aggregate the data of their cluster members and transmit it to the chosen "Gateways" that requires the minimum communication energy to reduce the energy consumption of cluster head and decrease probability of failure nodes and properly balance energy dissipation. Simulation result shows an improvement in effective network lifetime and increased robustness of

The organization of this chapter is as followings: We briefly review related work in section 2. Section 3 describes heterogeneous sensor network. Sensor network models is analysed in section 4. In section 5, we present our HABRP protocol. Simulation results of the proposed protocol are discussed in terms of energy consumption, Length of stable region for different values of heterogeneity, number of alive nodes per round, variation of the Base Station location, sensitivity to degree of heterogeneity in large scale networks, improvement of

The main aim of hierarchical routing is to efficiently maintain the energy consumption of sensor nodes by involving them in multi-hop communication within a particular cluster and by performing data aggregation and fusion in order to decrease the number of transmitted

LEACH (W. Heinzelman et al., 2000) is one of the rst hierarchical routing approaches for sensors networks. The idea proposed in LEACH has been an inspiration for many

Low-energy adaptive clustering hierarchy (LEACH) (W. Heinzelman et al., 2000) is one of the most popular hierarchical routing algorithms for sensor networks. The idea is to form clusters of the sensor nodes based on the received signal strength and use local cluster heads as routers to the sink. This will save energy since the transmissions will only be done by

All the data processing such as data fusion and aggregation are local to the cluster. Cluster heads change randomly over time in order to balance the energy dissipation of nodes. This decision is made by the node S choosing a random number x between 0 and 1. The node becomes a cluster head for the current round if the number x is less than the following

> P 1 − P ∗ (r mod <sup>1</sup>

P)

0 otherwise

if S ϵ G

(1)

LEACH achieves over a factor of 7 reduction in energy dissipation compared to direct communication and a factor of 4–8 compared to the minimum transmission energy routing protocol (Akkaya & Younis, 2005). The nodes die randomly and dynamic clustering increases lifetime of the system. LEACH is completely distributed and requires no global knowledge of network. However, LEACH uses single-hop routing where each node can transmit directly to the cluster-head and the sink. Therefore, it is not applicable to networks deployed in large regions. Furthermore, the idea of dynamic clustering brings extra overhead, e.g. Head changes, advertisements etc., which may diminish the gain in energy consumption.

### **2.2. Power-Efficient Gathering in Sensor Information Systems (PEGASIS)**

This is improved version from LEACH. The main idea of PEGASIS (Lindsey & Raghavendra, 2002) is that nodes are formed into a chain where each node receive from and transmit to closest neighbor only. The distance between sender and receiver is reduced as well as decreasing the amount of transmission energy. To construct a chain, PEGASIS uses a greedy algorithm that starts from the farthest node from the base station.

**Figure 2.** Chain is constructed using the greedy algorithm

In Fig.2, the algorithm starts with node 0 that connects to node 3. Then, node3 connects to node 1 and node 1 connects to node 2, which is the closest one to the base station ܤܵ. Because nodes already in the chain cannot be revisited, the neighbor distance will increase gradually. When a node dies (out of battery), the chain will be reconstructed by repeating the same procedure to bypass the dead node.

Hierarchical Adaptive Balanced Routing Protocol

for Energy Efficiency in Heterogeneous Wireless Sensor Networks 317

probability based on the ratio between residual energy of each node and the average energy of the network. The epochs of being cluster heads for nodes are different according to their

The authors have assumed that all the nodes of the sensor network are equipped with different amount of energy, which is a source of heterogeneity. DEEC is also based on LEACH protocol, it rotates the cluster head role among all nodes to expend energy

Two levels of heterogeneous nodes are considered in the algorithm and after that a general solution for multi-level heterogeneity is obtained. To avoid that each node needs to know the global knowledge of the networks, DEEC estimates the ideal value of network lifetime, which is used to compute the reference energy that each node should expend during a round. Simulation results show that DEEC achieves longer lifetime and more effective

**2.5. Improved and balanced LEACH for heterogeneous wireless sensor networks** 

(S. Ben alla et al. 2010) proposed Improved and Balanced LEACH (IB-LEACH), in which some high energy nodes elect themselves to be gateway at any given time with a certain probability. Base station confirms that whether those nodes suit to be gateway. These nodes broadcast their status to the other sensors in the network using advertisement message (ADV). The non -gateway nodes elect themselves to be cluster heads with a certain probability. These cluster head nodes broadcast their status to the other sensors in the network using advertisement message (ADV). The non-cluster head nodes wait the cluster head announcement from other nodes. Each sensor node determines to which cluster it wants to belong by choosing the cluster head that requires the minimum communication energy, and send the join -request (Join- REQ) message to the chosen cluster head, and the

Each cluster head collect and aggregate the data of their cluster members and transmit it to the chosen gateways that requires the minimum communication energy to reduce the energy consumption of cluster head and decrease probability of failure nodes. Simulation results show that this protocol performs better than LEACH and SEP in terms of network

**2.6. Cluster head relay routing protocol for heterogeneous sensor networks** 

(Du & Lin, 2005) proposed a cluster head relay (CHR) routing protocol for heterogeneous sensor networks. This protocol uses two types of sensors to form a heterogeneous network with a single sink: a large number of low-end sensors, denoted by L-sensors, and a small number of powerful high-end sensors, denoted by H-sensors. Both types of sensors are static and aware of their locations using some location service. Moreover, both L-sensor and

cluster head nodes wait for join-request message from other nodes.

H-sensors are uniformly and randomly distributed in the sensor field.

initial and residual energy.

messages than LEACH, SEP and LEACH -E.

uniformity.

lifetime.

In one round of transmission, a randomized node is appointed to be the leader to transmit data to ܤܵ. If the ܤܵ locates outside the range of this node, multi-hop transmission will be employed. The leader will be changed randomly in every round, so that overall energy dissipation is balanced out. For transmitting a packet in each round, a token is used that passing from the one end of the chain to the other end of the chain. Only node that has a token can transmit a data packet to its intermediate node in the chain. When intermediate node receives data from one neighbor along with a token, it fuses the data packet with its own data and transmits a new data packet to the next node in the chain.

**Figure 3.** Token passing approach in PEGASIS

In fig.3, C0 will pass its data and token to C1. C1 fuses a data packet with its own data and pass a new data packet to the leader C2. C2 does not transmit a data packet to BS yet, but rather it passes a token to C4. When C2 receives a data from C4 and C3, it fuses and transmits the sensed data to BS.

#### **2.3. A Stable Election Protocol (SEP)**

A Stable Election Protocol (SEP) (G. Smaragdakis et al, 2004) is improved version of LEACH protocol. Main aim of it was used heterogeneous sensor in wireless sensor networks. This protocol have operation like LEACH but with this difference that, in SEP protocol sensors have two different level of energy. SEP based on weighted election probabilities of each node to become cluster head according to their respective energy. This approach ensures that the cluster head election is randomly selected and distributed based on the fraction of energy of each node assuring a uniform use of the nodes energy.

In SEP, two types of nodes (normal and advanced) are considered. It is based on weighted election probabilities of each node to become cluster head according to the remaining energy in each node. This prolongs the stability period i.e. the time interval before the death of the first node.
