Hierarchical. Protocols.pptx

Hierarchical. Protocols.pptx

1. Agenda 1 overview and key concepts of hierarchical protocols in WSNs · Examples of Hierarchical Protocols LEACH, PEGASIS, Hierarchical PEGASIS, TEEN, APTEEN, Energy-aware routing · Detailed Look at LEACH Cluster formation, CH rotation, data transmission, communication phases · TEEN Protocol Hard and soft threshold values, data transmission · Advantages and Disadvantages of TEEN & APTEEN · Energy-aware Routing Assumptions

2. Hierarchical Protocols Hierarchical protocols, also known as cluster-based protocols, organize the sensor nodes in a WSN into clusters. Each cluster has a leader, often referred to as a cluster head (CH), which is responsible for coordinating the communication between the nodes in its cluster and the base station (BS). Key Concepts in Hierarchical Protocols: Clusters : Groups of sensor nodes that are managed by a cluster head. This division helps in reducing the communication overhead and energy consumption. Cluster Head (CH) : A special node within each cluster responsible for collecting data from its member nodes, performing data aggregation, and transmitting the aggregated data to the base station. The CH role can rotate among nodes to distribute the energy consumption. Base Station (BS) : The central node that receives data from various CHs and processes it. The BS often has more computational power and energy resources compared to the sensor nodes. Scalability : Clustering allows the network to manage large numbers of nodes efficiently. Data Aggregation : CHs can perform data fusion to reduce redundant data, further conserving energy and reducing bandwidth usage.

3. 3 Hierarchical Protocols Maintain energy consumption of sensor nodes By multi-hop communication within a particular cluster By data aggregation and fusion  decrease the number of the total transmitted packets

4. 4 Hierarchical Protocols LEACH – Low-Energy Adaptive Clustering Hierarchy Power-Efficient GAthering in Sensor Information Systems (PEGASIS) Hierarchical PEGASIS Threshold sensitive Energy Efficient sensor Network protocol (TEEN) Adaptive Threshold TEEN (APTEEN) Energy-aware routing for cluster-based sensor networks Self-organizing protocol

5. 5 Hierarchical Protocols LEACH – Low-Energy Adaptive Clustering Hierarchy One of the first hierarchical routing protocols Forms clusters of the sensor nodes based on received signal strength Local cluster heads route the information of the cluster to the sink Cluster heads change randomly over time  balance energy dissipation Data processing & aggregation done by cluster head

6. 6 Hierarchical Protocols Threshold sensitive Energy Efficient sensor Network protocol (TEEN) Good for time-critical applications Hierarchical along with a data-centric approach Hierarchical grouping: Close nodes form clusters and this process goes on the second level until sink is reached Cluster headers broadcast: Hard Threshold Soft Threshold Not good for applications that need periodic reports

7. 7 Hierarchical Protocols

8. LEACH (Low-Energy Adaptive Clustering Hierarchy LEACH is one of the most popular hierarchical protocols designed to improve energy efficiency in wireless sensor networks (WSNs). Here’s how it works in detail: Cluster Formation : Nodes organize themselves into clusters. Each node decides whether to become a cluster head (CH) based on a pre-determined probability. A node elects itself as a CH with a certain probability and broadcasts its decision. Non-CH nodes then join the nearest CH to form clusters. Randomized Rotation of CHs : To evenly distribute energy consumption, the role of the CH rotates among the nodes. This rotation is based on a probability that ensures all nodes have an equal chance to become a CH over time. Data Transmission : Nodes send their data to their respective CHs. CHs aggregate this data to reduce redundancy, minimizing the amount of data that needs to be transmitted to the base station (BS).

9. Continue…. 4. Communication Phases : Setup Phase : Clusters are formed, and CHs are selected. Steady-State Phase : Data is transmitted from nodes to CHs, aggregated, and then sent to the BS. Advantages : Significant reduction in energy consumption due to data aggregation and rotation of CH roles. Increased network lifetime. Disadvantages : The randomized CH selection can lead to uneven distribution of CHs, causing some clusters to have a higher workload

10. 10 Hierarchical Protocols Power-Efficient GAthering in Sensor Information Systems (PEGASIS) Improvement of LEACH Forms chains from sensors rather than clusters Data aggregation in the chain  one node sends the data to the base station Outperforms LEACH Excessive delay for distant nodes in the chain

11. TEEN (Threshold-sensitive Energy Efficient sensor Network protocol) Threshold Values : Hard Threshold (HT) : The minimum value of an attribute to trigger data transmission. If the sensed value exceeds this threshold, the node transmits data. Soft Threshold (ST) : A small change in the sensed attribute value that triggers further data transmission. This helps in reducing the number of transmissions by only sending data when there are significant changes. Data Transmission : Nodes continuously sense their environment but only transmit data when the hard threshold is crossed. If the hard threshold is crossed, data is transmitted. Subsequent data transmissions occur only if the change in the sensed value is greater than the soft threshold TEEN is specifically designed for time-critical applications where the sensor nodes react to sudden changes in the sensed attributes, like temperature, humidity, etc.

12. 12 Hierarchical Protocols Adaptive Threshold TEEN (APTEEN) Captures both periodic data collection and reacting to time-critical events APTEEN supports queries: Historical -Analyze past data values One-Time –Take a snapshot of the current network view Persistent monitor an event for a period of time

13. 13 Hierarchical Protocols – TEEN & APTEEN Advantages Outperform LEACH in terms of energy dissipation and total lifetime of the network Disadvantages Overhead and complexity of: Forming multiple level clusters Implementing threshold-based functions Dealing with attribute-based naming of queries

14. 14 Hierarchical Protocols Energy-aware routing for cluster-based sensor networks Assumptions: Sensors are grouped into clusters prior to network operation Cluster Heads (Gateways) less energy constrained Cluster Heads know the location of the sensors  Known Multi-Hop routing to collect data Communication node (sink) communicates only with gateways