**2.4. Distributed energy efficient clustering algorithm for heterogeneous wireless sensor networks**

(Qing et al, 2006) proposed a distributed energy efficient clustering scheme for heterogeneous wireless sensor networks, which is called DEEC. In DEEC, the cluster heads are elected by a 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 initial and residual energy.

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

own data and transmits a new data packet to the next node in the chain.

the same procedure to bypass the dead node.

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

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

energy of each node assuring a uniform use of the nodes energy.

transmits the sensed data to BS.

of the first node.

**sensor networks** 

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

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

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

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

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

**2.4. Distributed energy efficient clustering algorithm for heterogeneous wireless** 

(Qing et al, 2006) proposed a distributed energy efficient clustering scheme for heterogeneous wireless sensor networks, which is called DEEC. In DEEC, the cluster heads are elected by a 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 uniformity.

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 messages than LEACH, SEP and LEACH -E.

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

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 lifetime.

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

The CHR protocol partitions the heterogeneous network into clusters, each being composed of L-sensors and led by an H-sensor. Within a cluster, the L-sensors are in charge of sensing the underlying environment and forwarding data packets originated by other L-sensors toward their cluster head in a multi-hop transmission. The H-sensors, on the other hand, are responsible for data fusion within their own clusters and forwarding aggregated data packets originated from other cluster heads toward the sink in a multi-hop transmission using only cluster heads. While L-sensors use short-range data transmission to their neighboring H -sensors within the same cluster, H-sensors perform long-range data communication to other neighboring H-sensors and the sink. Simulation results demonstrate that CHR performs better than directed diffusion and SWR.

Hierarchical Adaptive Balanced Routing Protocol

for Energy Efficiency in Heterogeneous Wireless Sensor Networks 319

**Computational heterogeneity** means that the heterogeneous node has a more powerful microprocessor and more memory than the normal node. With the powerful computational resources, the heterogeneous nodes can provide complex data processing and longer-term

**Link heterogeneity** means that the heterogeneous node has high bandwidth and longdistance network transceiver than the normal node. Link heterogeneity can provide a more

**Energy heterogeneity** means that the heterogeneous node is line powered or its battery is

Among above three types of resource heterogeneity, the most important resource heterogeneity is the energy heterogeneity because both computational heterogeneity and

If there is no energy heterogeneity, computational heterogeneity and link heterogeneity will bring negative impact to the whole sensor network, i.e ., decreasing the network lifetime.

**Decreasing latency of data transportation**: Computational heterogeneity can decrease the processing latency in immediate nodes and link heterogeneity can decrease the waiting time in the transmitting queue. Fewer hops between sensor nodes and sink node also mean fewer

**Prolonging network lifetime**: The average energy consumption for forwarding a packet from the normal nodes to the sink in heterogeneous sensor networks will be much less than

**Improving reliability of data transmission**: It is well known that sensor network links tend

With heterogeneous nodes, there will be fewer hops between normal sensor nodes and the sink. So the heterogeneous sensor network can get much higher end-to-end delivery rate

Some performance measures that are used to evaluate the performance of clustering

**Network lifetime (stability period):** It is the time interval from the start of operation (of the

**Number of cluster heads per round**: Instantaneous measure reflects the number of nodes which would send directly to the base station, information aggregated from their cluster

to have low reliability and each hop significantly lowers the end-to-end delivery rate.

Placing few heterogeneous nodes in the sensor network can bring following benefits:

storage.

replaceable.

forwarding latency.

reliable data transmission.

link heterogeneity will consume more energy resource.

the energy consumed in homogeneous sensor networks.

protocols are listed below(R. Sheikhpour et al., 2011).

sensor network) until the death of the first alive node.

than the homogeneous sensor network.

**3.3. Performance measures** 

members.

**3.2. Impact of heterogeneity on wireless sensor networks** 
