1. Ben Miller

2.   A distributed algorithm is a type of parallel algorithm  They are designed to run on multiple interconnected processors  Separate parts of the algorithm are run simultaneously on independent processors What is a Distributed Algorithm?

3.   Each of the processors has its own memory  The processors send messages to each other What is a Distributed Algorithm?

4.   Wireless Sensor Networks are made up of a series of distributed sensors  The sensors collect data and pass it through the network  The sensors are designed to consume very little power Wireless Sensor Networks

5.   Each sensor node typically consists of a microcontroller, radio, and battery Wireless Sensor Networks

6.   Self-Spreading  Transmission Power Control  Distributed Fault Tolerant Routing Distributed Algorithms for Sensor Networks

7.   One of the challenges in the field of sensor networks is the deployment of the sensors  The sensors must be properly spaced.  If the sensors are too far apart the coverage regions won’t overlap and the network could become partitioned  If the sensors are too close to each other they won’t cover the entire area of interest Distributed Self-Spreading Algorithm

8.   A node’s movement is based on the combined forces acting on it due to its neighboring nodes. Distributed Self-Spreading Algorithm

9.  The algorithm has 4 parts:  1: Initialization  2: Partial Force Calculation  3: Oscillation Check  4: Stability Check  Parts 2,3, and 4 repeat until the node stops moving Distributed Self-Spreading Algorithm

10.  The Problem: Sensor networks use wireless communication to transmit their observations Sensors have a limited energy supply, so they have to work as efficiently as possible Radio communication uses a lot of energy Transmission Power Control

11. Solution: Sensor networks can use distributed algorithms to dynamically adjust transmission power Each sensor node should use the lowest possible transmission power while remaining connected to the network Transmission Power Control

12.  Local Mean Algorithm  All nodes start with the same Transmission Power  Each node periodically broadcasts a message containing its identity  All the other nodes that receive the message send an acknowledgment message back to the sender  If the number of acknowledgments received is under a minimum threshold, the node increases transmission power before broadcasting again Distributed Transmission Power Control Algorithm

13.   The node increases its transmission power by a certain factor for every neighbor that is missing towards the minimum threshold  The node decreases its transmission power by a certain factor for every neighbor exceeding its maximum threshold  The node stops adjusting its transmission power once it is within the neighbor threshold Local Mean Algorithm

14. Advantages:  Increased network lifetime compared to fixed-transmission power assignments  Easy to implement  Highly scalable due to its dynamic nature Local Mean Algorithm

15.  In large-scale Wireless Sensor Networks, sensor nodes are grouped into clusters. Each cluster has a leader called a Cluster Head, or Gateway, which collects data from the cluster and sends it to a basestation Distributed Fault Tolerant Routing

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17.  The Problem:  Gateways consume a lot of power, and they are often deployed in harsh environments  This makes them prone to failure  The failure of a Gateway can leave entire clusters of sensor nodes unable to send data to the basestation Distributed Fault Tolerant Routing

18. Solution  If a gateway fails, the gateways behind the failed gateway should send their data to a different nearby gateway instead Distributed Fault Tolerant Routing

19.  The Algorithm:  Each gateway broadcasts a Hello message  If a gateway receives a Hello message from a neighbor that is closer to the basestation, the neighbor is added to the Forward set.  If the neighbor is not closer, it is put in a Backup set Distributed Fault Tolerant Routing

20.  The Algorithm:  If a gateway is within range of the basestation, it sends its data directly to the basestation  If the basestation is not within range, the gateway sends data to a neighbor in the Forward set  If the Forward set is empty, send to a gateway in the Backup set Distributed Fault Tolerant Routing

21.  Case 1: Failure of a Forward Gateway  If a gateway in the Forward set is found to be faulty, choose another gateway in the Forward set Distributed Fault Tolerant Routing

22.  Case 2: Gateway with no Forward Gateways  If a gateway’s Forward set is empty, select a gateway from the backup set (G3 reroutes to G2 when G7 and G8 die) Distributed Fault Tolerant Routing

23.   Lenzen, Christoph. "Distributed Algorithms for Sensor Networks." Hebrew University of Jerusalem .  Heo, and Varshney. “Energy-Efficient Deployment of Intelligent Mobile Sensor Networks”  http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.307.4273&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.307.4273&rep=rep1&type=pdf  Kubish, Karl, Wolisz, Zhong, Rabaey, “Distributed Algorithms for Transmission Power Control in Wireless Sensor Networks”  http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1200410 http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1200410  Md. Azharuddin, Prasanta K. Jana “A distributed algorithm for energy efficient and fault tolerant  routing in wireless sensor networks” August 2014  http://link.springer.com/article/10.1007%2Fs11276-014-0782-2#/page-1 Sources