OS Design Issues WSN operates at two levels. One is at the network level and the other is at node level. Network level interests are connectivity, routing, communication channel characteristics, protocols, etc. Node level interests are hardware, radio, CPU, sensors and limited energy. At a higher level OS for WSN can also be classified as node-level (local) and networklevel (distributed). The important issues related to node-level are limited resource management; concurrency handling, power management and memory management where as issues related to both are inter-node communication, failure handling, heterogeneity and scalability. Should be compact and small in size. Should provide ...
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Sensor Network as Database: Think of a sensor network as a distributed database that store data within the network and allow queries to be injected anywhere in the network. Research issues how is data stored and organized after sensing what’s the user interface to the sensor database How does an external query find and process the data in an efficient manner? Challenges The system is highly volatile Relational tables are not static New data is continuously sensed High communication cost In-net processing during query execution Arbitrarily long delay and rate of data arrival is variable Limited storage Older data has ...
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SINGLE HOP SCHEME Overlapping connectivity Approximate Point in Triangle MULTI HOP SCHEME
Definition The task of initiating collaborative environment for sensor network when that network is activated is called infrastructure establishment. Sensor network consists of normal nodes and anchor nodes, where the normal nodes do not know their position but the anchor nodes are able to acquire their positions via external positioning device such as GPS. All sensor nodes including the normal node and the anchor node are randomly deployed in a sensor field, and they do not move after the initial deployment. In addition, each sensor node has a unique ID and the same data transmission radius When sensor network is ...
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PEGASIS based on the assumption that all sensor nodes know the location of every other node. Any node has the required transmission range to reach the BS in one hop, when it is selected as a leader. The goal of PEGASIS are as following Minimize the distance over which each node transmit Minimize the broadcasting overhead Minimize the number of messages that need to be sent to the BS Distribute the energy consumption equally across all nodes To construct a chain of sensor nodes, starting from the node farthest from the BS. At each step, the nearest neighbor which has ...
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Time synchronization is highly critical in sensor networks for purposes such as: Data Diffusion (Merging individual sensor readings into a high level sensing result) Coordinated Actuation (all surrounding nodes made active at the same time) Object Tracking To Synchronize all the nodes in the sensor network using a method that: Eliminates error efficiently Energy conservative Provides tight synchronization Applications of Time Synchronization Secure cryptographic schemes Coordination of future action Ordering logged events during system debugging Concept of TTS- Traditional Time Synchronization The sender periodically sends a message with its current clock as a timestamp to the receiver Receiver then synchronizes ...
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Grouping of similar objects or sensors in our context Distance or proximity Logical organizing Topology control approach Load balancing, network scalability Types of clustering Static: local topology control Dynamic: changing network parameters Single hop and multi hop Homogeneous and heterogeneous Advantages of Clustering Transmit aggregated data to the data sink reducing number of nodes taking part in transmission Useful energy consumption Scalability for large number of nodes Reduces communication overhead for both single and multi hop
Aim to make communication more efficient Trade-off between routing overhead and data transmission cost Strategies incur differing levels of communication and storage overhead Hybrid approaches are possible Stateless Routing Nodes maintain no routing information Flooding –Messages rebroadcast to neighbours Gossiping –Messages rebroadcast to neighbours, probability <1 Geographic –Need to know direction to destination Epidemic –Pairwise exchange of messages between carriers –Copes with temporary network partition –No routing state, but message buffering infeasible in WSNs Proactive and Reactive Routing Proactive routing –Routes created and maintained in advance –Low latency, high resource demand –Does not scale to large networks Reactive routing –Routes ...
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The design of routing protocols in WSNs is influenced by many challenging factors. These factors must be overcome before efficient communication can be achieved in WSNs. Node deployment Energy considerations Data delivery model Node/link heterogeneity Fault tolerance Scalability Network dynamics Transmission media Connectivity Coverage Data aggregation/converge cast Quality of service Node Deployment Node deployment in WSNs is application dependent and affects the performance of the routing protocol. The deployment can be either deterministic or randomized. In deterministic deployment, the sensors are manually placed and data is routed through pre-determined paths. In random node deployment, the sensor nodes are scattered randomly ...
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Dissemination = The act of spreading something, spreading, distribution. Gathering = Assemble or collect Data Dissemination Process of Distribution of data. Information flow from one sensor node to another. The originator of data is known as Source Node and Receiver of the data is called Sink node or Gateway. The Sink registers its interest to receive the data from source. The Source reports the data information to the Sink. The information thus reported is called event. Process of Data Dissemination The node that is interested in some events, like temperature or air humidity, broadcasts its interests to its neighbors periodically. ...
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