• **Radio Energy Model**

This section presents a simple concept of Energy radio model, used by the hierarchal routing protocol such as LEACH, PEGASIS, etc. [16, 17].

The following are the assumptions for Radio Energy Model (REM)


**Figure 4** displays the first order radio model that considers most of the energy is consumed in the communication operation performed by the sensor nodes. Therefore, it demonstrates that the energy needed to forward kbits-packets is computed by Eq. (3) and energy utilized in packet reception can be computed by Eq. (4).

The LEACH protocol uses radio energy model for power dissipation in the communication process. The numerical Eqs. (3) and (4) is demonstrated below to compute energy utilization in transmission and energy utilized in the receiving process.

$$\mathbf{E}\_{T}(\kappa,\partial) = \begin{cases} \kappa \mathbf{E}\_{power} + \kappa \varepsilon\_{fs} \partial^{2}, \partial < \partial\_{0} \\ \kappa \mathbf{E}\_{power} + \kappa \varepsilon\_{amp} \partial^{4}, \partial < \partial\_{0} \end{cases} \tag{3}$$

$$\mathbf{E}\_{\mathbb{R}}(\kappa) = \kappa \mathbf{E}\_{power} \tag{4}$$

The above Eqs. (3) and (4) illustrates the energy dissipation rate in the communication process of sensor nodes. The ETx(k,∂) is the transmission energy needed for (kbits-packets) over ∂ distance and Epower is the electric power utilized per bit to run the communication module such as transmission circuit and receiver circuit based on modulation and digital coding. fx∂2 and amp∂4 is the amplification power which is based on the significant rate of bit-error. The ∂0 is the square root of dividing power utilization in data aggregation by fx∂2 and amp∂4.

#### *3.2.2 PEGASIS – (power-efficient gathering in sensor information systems)*

PEGASIS is introduced as an enhanced version of the hierarchical routing protocol over the LEACH. The PEGASIS protocol follows a chain-based approach where all sensor nodes formulate a chain system, and one leader node is selected randomly to execute data transmission process to sink node. In this, the collected

**Figure 4.** *Energy radio model.*

data transfers via a node to node and if any node fails between the chain process, then the node rearranges themselves to bypass the deadly node and reconstruct chain to continue their process. The primary goal of PEGASIS is to receive and transmit data from the nearest neighbor and forward it to sink node with the support of leader node. The PEGASIS protocol involves two phases to achieve chain process which is mentioned as follows [18, 19]:

• Advantages of PEGASIS

*Energy Saving Hierarchical Routing Protocol in WSN DOI: http://dx.doi.org/10.5772/intechopen.93595*

sink node.

• Disadvantages of PEGASIS

of energy.

nodes.

nodes [20, 21].

**163**

associated CH.

current cluster round.

threshold value.

overhead communication process.

prolongs the network lifecycle.

i. It uses a greedy mechanism to build chain of nodes that result in a low

ii. In this, communication process is not disturbed because when any node fails, the protocol reconstructs the chain and is allowed to

iv. It decreases energy consumption in communication operation and

i. PEGASIS considers that each sensor nodes in chain carry an equal level

ii. This protocol sometimes results in delay because it takes more time to

iii. In this, the single leader-node can also act as a bottleneck for the other

iv. Each node in this protocol needs to be aware of network information.

TEEN is a hierarchical clustering protocol that binds sensor nodes and forms a

• Hard threshold: In this threshold value is broadcasted for the sensed attribute where the role of sensor nodes is to sense and report back its data to their

• Soft threshold: In this, a small modification is made in the sensed attributes

• Later, the sensed attribute value is stored in the internal node memory. Then based on the following condition the sensor node forwards its data in the

i. The value of the current sensed attribute must be higher than the hard

*Scurrent* > *Hcuttoff* ð*Condition 1*Þ

where it triggers the node to switch transmitter to on mode.

cluster of nodes where each node of the cluster is operated by CH. In this CH collects data from their member node and then forwards it to their higher CH node, the CH aggregates the data and delivers to the sink node. In this scenario, at each cluster varies with the time where the CH broadcast threshold value to its member

collect data from the distance node in the chain.

*3.2.3 TEEN – (threshold sensitive energy efficient sensor network protocol)*

continue the data collection and transmission process.

iii. Only leader node has permission to send data directly to the

	- i. **Chain Formulation:** The chain structure proceeds in a greedy manner, i.e. from starting nodes to the last node at the sink node and nearest node of the just previous node is selected as a next node, and in the same way all nodes will continue to arrange themselves in this pattern until a suitable chain is formed. Furthermore, the node in the chain is only able to place itself at one location. In each round, a leader node is selected randomly. In the construction phase, the protocol uses a greedy algorithm with considering that all sensor nodes are globally aware of the network condition and sensor location. When the sensor node fails due to power loss, the chain is rebuilt by utilizing the greedy method and by omitting the failure sensor nodes.
	- ii. **Data Gathering:** The concept of PEGASIS protocol avoids the formation of clusters and CH. It considers that, only a single node as a leader-node instead of multiple nodes in the chain to transmit collected data to the sink node. In this, raw data is collected and carried from one node to another node, then it is aggregated and finally leader node forwards to the sink node.

The above **Figure 5** demonstrates the chain formation and data collection and transmission process. The nodes N1, N2, N3, N4, and N5 have arranged themselves in a chain structure where N3 is randomly chosen as leader node and remaining are the normal participating nodes. The N1 forward its data to N2 then after N2 aggregates the collected data and transmits it to N3. Now, N3 broadcasts token message to N5. The node N5 sends its data to N4 then N4 aggregates collected data and transmits it to N3. The node N3 as leader node collects data from its both neighbor and then it fuses, and aggregates collected data itself and transmits to sink node (SN).

**Figure 5.** *Chain formation and data processing.*

	- i. It uses a greedy mechanism to build chain of nodes that result in a low overhead communication process.
	- ii. In this, communication process is not disturbed because when any node fails, the protocol reconstructs the chain and is allowed to continue the data collection and transmission process.
	- iii. Only leader node has permission to send data directly to the sink node.
	- iv. It decreases energy consumption in communication operation and prolongs the network lifecycle.
	- i. PEGASIS considers that each sensor nodes in chain carry an equal level of energy.
	- ii. This protocol sometimes results in delay because it takes more time to collect data from the distance node in the chain.
	- iii. In this, the single leader-node can also act as a bottleneck for the other nodes.
	- iv. Each node in this protocol needs to be aware of network information.
