Routing in Wireless Sensor Network

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This ppt gives an overview of the two routing protocols in the wireless sensor networks namely Rumor Routing and LEACH.



2. OUTLINE Introduction Challenges and Design issues LEACH Rumor Routing Conclusion 3. Introduction Routing protocols differ in WSN based on the application and network architecture. Based on the network structure, routing protocols are classified into three: Flat Routing Same role is assigned to all the nodes Hierarchical Routing Different roles are assigned to nodes Location based Routing Position of the nodes are exploited to route the data. Further classified into multipath-based, query-based, negotiation-based, QoS-based, and coherent-based depending on the protocol operation. Trade off exists between energy consumption and communication overhead. 4. Challenges and design issues Node deployment Manual Deployment Random Deployment Data routing methods Application-specific Time-driven: Periodic monitoring Event-driven: Respond to sudden changes Query-driven: Respond to queries Hybrid 5. Challenges and design issues Node link/ heterogeneity Homogeneous sensors Heterogeneous sensors Fault tolerance Transmission media Connectivity Coverage Data aggregation Quality of Service 6. Leach - Low Energy Adaptive Clustering Hierarchy It is a hierarchical routing protocol that suggests both hierarchical and centralized schemes. Self-Organizing, adaptive clustering protocol. Minimal setup time, even distribution of energy load among the sensors thus enhancing the lifetime of the network. Dynamic cluster formation. Randomized rotation of cluster heads after each round. Cluster-heads communicate data with the base station. Application-specific data processing, such as data aggregation. 7. leach Each LEACH round consists of two phases: Set-up Phase Cluster head selection Cluster formation Steady-State Phase Cluster head maintenance Data transmission between nodes 8. Leach Set up phase At the beginning of each round, each node advertises it probability to be the Cluster Head, to all other nodes. Probability for each node i to be the Cluster-head at time t where Ci(t) = determines whether node i has been a Cluster head in the most recent rounds Higher the probability better are the chances to be chosen as the Cluster Head. 9. Leach Set up phase Cluster Head broadcasts an advertisement message (ADV) using CSMA MAC protocol. Based on the received signal strength of the ADV message, each non- cluster head node decides its Cluster Head for that round. Each node transmits a join-request message (Join-REQ) back to its chosen Cluster Head. Cluster Head node sets up the TDMA schedule for coordinating data transmission with the cluster. Using TDMA schedule has two advantages: Avoid collision of data packets from different nodes within a cluster. Conserve energy in the non-cluster head nodes. 10. Leach steady state phase Node uses the time slot assigned to it to transfer data to the cluster head. Cluster head aggregates the data received from all the nodes of the cluster. Communication is via direct-sequence spread spectrum (DSSS) and each cluster uses a unique spreading code to reduce inter-cluster interference. Intra-cluster communication uses TDMA and Inter-cluster communication uses CDMA. 11. Rumor routing It is a flat routing protocol. Ensures network longevity, robustness in handling node failures. Intended to fill the region between query flooding and event flooding. Transmits data packets through random paths rather than shortest path. Event Abstraction of a localized phenomena occurring in a fixed region of space. Query Information of interest to be retrieved. 12. Rumor routing Each node maintains a list of neighbors and its event table. When a node witnesses an event, it adds it to its event table with distance zero and generates an agent simultaneously. An agent is a long-lived packet, which travels the network, propagating information about local events to distant nodes. Any node can generate a query, then forward the query in a random direction to find the path. The query keep going until its TTL expires or it intersects with the agent path leading it to the destination event. If the node that originated the query determines the query died, it can retransmit, give up or flood the query. 13. Rumor routing Basic scheme Each node maintain A lists of neighbors An event table When a node detects an event Generate an agent Let it travel on a random path The visited node form a gradient to the event When a sink needs an event Transmit a query The query meets some node which lies on the gradient Route establishment 14. Agent Set up path by random walk. Aggregate paths. Optimize paths in the network. 15. Agent Each agent carries a list of all the events it encountered along with the number of hops to that event. Each node among the path maintains a table of events, the number of hops to that event and the next node in the path toward the event. 16. Agent A straightening algorithm is used when determining the agents next hop Agent maintains a list of recently seen nodes. When it decides the next hop, it tries the nodes not in the list. When it passes a node, the nodes neighbors are added to the list. A node that witnessed an event would generate an agent at a fixed probability in the simulation The future work can do better by generating agents according to number of events, event size and node density. For applications where events are temporal, the event table may have an expiration timestamp associated with each event 17. Query A query can be generated at any time by any node. Before reaching the path, nodes forward queries using the same straightening algorithm keep a list of recently seen nodes and avoid visiting them. Each query has a TTL to avoid looping routes. If the query dies, the node originating the query detects the failure and decide to retransmit it or flood the query. 18. References 1. Rumor Routing Algorithm for Sensor Networks 002sept-Brainsky-Etrin-Rumor.pdf 2. Energy- Efficient Communication Protocol for Wireless Microsensor Networks 3. Introduction to Wireless and Mobile Systems by Dharma Prakash Agarwal and Qing-An Zeng. 19. THANK YOU ! QUERIES ?