ROUTING PROTOCALS FOR WSNs: LEACH, DIRECT Diffusion and PEGASIS.

Distinctive routing protocols are designed where energy awareness is considered as essential design issue. The main objective of routing is to enhance the lifetime of the network by selecting appropriate route. Wireless Sensor Networks (WSNs) consist of numerous spatially distributed autonomous sensors that collect and transmit data over a network. These sensors typically monitor environmental conditions such as temperature, sound, and motion. Due to the energy-constrained nature of sensor nodes, efficient routing protocols are crucial for optimizing network lifetime and overall performance. Three widely researched and applied routing protocols for WSNs are LEACH (Low-Energy Adaptive Clustering Hierarchy), Direct Diffusion, and PEGASIS (Power-Efficient GAthering in Sensor Information Systems). Each of these protocols has its unique approach to addressing energy efficiency, communication overhead, and data aggregation in WSNs.

LEACH (Low-Energy Adaptive Clustering Hierarchy)

Leach protocol is hierarchical protocol in which cluster heads are used for the assembling of data from nodes and forward that data to the sink. Cluster head is responsible for the creation of TDMA (Time Division Multiple Access) schedule all the other nodes of a cluster are member nodes of that cluster. LEACH is a hierarchical routing protocol designed to reduce energy consumption in WSNs through clustering. It was among the first energy-efficient routing protocols, utilizing a dynamic clustering mechanism where nodes are organized into clusters with one node acting as the cluster head . The primary functions of LEACH are data aggregation, energy distribution, and reduced communication overhead.

➢ Cluster Formation and Cluster Head Selection: In LEACH, the network is divided into clusters, and each node has a chance to become a cluster head. The selection of the CH is probabilistic, with each node independently deciding whether to become a CH in a given round. This rotation of CHs ensures energy load balancing among the nodes.

➢ Data Aggregation and Transmission: The CH aggregates data from the cluster members, processes it (e.g., removing redundancies), and transmits it directly to the base station or sink node. This minimizes the number of transmissions, which conserves energy.

➢ Advantages and Limitations: LEACH is highly efficient in reducing communication overhead within a cluster, and the periodic rotation of CHs prevents energy depletion in individual nodes. However, LEACH has limitations, such as unequal cluster sizes and single-hop communication between CHs and the base station, which may not scale well in large networks.

Direct Diffusion

Direct Diffusion is a data-centric routing protocol designed to save energy by avoiding unnecessary data transmissions. The protocol revolves around querying the network for specific data, and only nodes that detect relevant events communicate with the sink. The main idea is to establish paths that are reinforced based on the quality of the data being transmitted.

➢ Data-Centric Communication: Unlike traditional address-centric communication models, Direct Diffusion focuses on named data rather than specific nodes. The sink node broadcasts an interest message specifying the required data. Nodes that sense relevant data send back the response along a gradient, establishing a path between the sink and the event source.

➢ Path Reinforcement: Once the sink starts receiving data, it reinforces the path by sending reinforcement messages to the source nodes. The reinforced path becomes the optimal route for data transmission. Nodes along this path continue to forward data until the sink no longer requires it or the data becomes irrelevant.

➢ Advantages and Limitations: Direct Diffusion is energy-efficient, as it focuses only on nodes that detect relevant data, thus reducing the number of transmissions. Additionally, data aggregation further reduces redundancy. However, the protocol may not be ideal for highly mobile networks or scenarios where real-time communication is crucial since the query-based approach introduces delays.

PEGASIS (Power-Efficient GAthering in Sensor Information Systems)

PEGASIS is an extension of the LEACH protocol but seeks to further reduce energy consumption by forming chains of sensor nodes rather than clusters. The primary focus of PEGASIS is on minimizing energy usage by allowing each node to communicate only with its closest neighbor and rotating the responsibility of communicating with the base station.

➢ Chain Formation: In PEGASIS, nodes form a chain by communicating with their nearest neighbor's. Each node receives data from one neighbor, aggregates it, and passes it along the chain until the data reaches the designated leader node, which transmits the aggregated data to the base station.

➢ Rotation of the Leader Node: Similar to the cluster head in LEACH, PEGASIS rotates the responsibility of leader nodes across rounds to evenly distribute the energy burden among nodes. This mechanism helps avoid energy depletion in specific nodes, extending the overall network lifetime.

➢ Advantages and Limitations: PEGASIS achieves significant energy savings by reducing the number of transmissions to the base station. However, the chain-based structure can introduce delays, especially in large networks where nodes must relay data across several hops before it reaches the sink. Additionally, the chain formation process can be complex, particularly in dynamic networks with node failures.

Comparison and Conclusion

In summary, LEACH, Direct Diffusion, and PEGASIS each provide distinct strategies to optimize energy efficiency in wireless sensor networks, but their suitability depends on the specific requirements of a given network. LEACH utilizes clusters to manage communication effectively but struggles with scalability, especially in larger networks. Direct Diffusion’s query-based approach minimizes redundant transmissions, though it may introduce latency. PEGASIS excels in energy savings through a chain-based structure but can experience delays as data is passed along multiple hops. The choice of the most appropriate routing protocol depends on factors such as network size, real-time data needs, and energy constraints. 

As WSNs continue to advance and grow more complex, the need for more sophisticated and adaptive routing protocols will increase. LEACH, Direct Diffusion, and PEGASIS offer valuable insights into how energy-efficient routing can significantly extend network lifetime and optimize performance, laying the groundwork for future innovations in sensor network design.