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Real Time Communication in Sensor Networks

Sarat Chandra Vaibhav Gupta R. Vamshi Krishna

Sensor Networks „ „ „ „ „

Sensor Nodes Sensor Field Sink Base Station Event Node

Internet and Satellite

Sink

E

C D

B

Task Manager Node User

Sensor field Sensor nodes

A

Communication Issues „

Data Centric Paradigm {

{ {

Multiple nodes generate data for same event. This data must be aggregated This is unlike traditional networks which are address-centric.

Communication Issues „

Location Based { { { {

Nodes deal with physical locations IDs are not permanenent. Queries refer to location rather than IDs. Result of queries is aggregated and sent.

Communication Issues „

Real-Time { { {

Deployed in Real world situations. Time guarantees are a must. Eg. A Sensor node detects radiation leak. „ „

Must alert the security in time. Or a catastrophe might result.

Communication Issues „

Scalability { { {

{

Large number of nodes in sensor network Node density might also be high. Protocols must maintain minimum global information Must be stateless.

Communication Issues „

Fault Tolerance {

High failure rate of sensor nodes. „

{ {

Physical, Environmental, Power depletion

Data being sent is critical data. Minimum affect on network due to node failures.

Communication Issues „

Resource Constraints {

{

Radio Transmission uses most of the power. Energy efficient routes must be found based on „ „

available power. Energy required for transmission.

Protocol Stack

Data Link Layer Physical Layer

Task management plane

Network Layer

Mobility management plane

Transport Layer

Power management plane

Application Layer

SPEED Protocol „ „ „

Provides soft Real-Time guarantee. Stateless and localized. Three types of Real-time services { { {

Real-Time unicast Real-Time area-multicast Real-Time area-anycast

SPEED „ „

„ „

Only immediate neighbor information. Uses the concept of ‘speed’ to achieve the soft Real-Time guarantee. Can co-exist with existing BE MAC. Uses feedback control and nondeterministic geographic forwarding.

SPEED Protocol „

Neighbor Beacon Exchange { {

„ „

„

Delay beacon, backpressure beacon NeighbourID, Position, Delay, Expiry

Delay Estimation Stateless Non-deterministic Geographic forwarding Back-Pressure Rerouting

Conclusion „

The issues that concern Real-time communication between sensor networks has been presented.

„

A protocol called SPEED has been presented.

References „

Tian He, John A. Stankovic, Chenyang Lu. SPEED : A Stateless protocol for Real-Time Communication in Sensor Networks. International Conference of Distributed Computing Systems, May 2003.

References „

John A. Stankovic, Chenyang Lu, Lui Sha, Tarek F. Abdelzaher and Jennifer Hou. Real-time Communication and Co-ordination in Sensor Networks. In Proceedings of IEEE, July 2003.

References „

Ian F. Akyildiz, Weilian Su, Yogesh Sankarasubramaniam and Erdal Cayirci. A Survey on Sensor Networks. IEEE Communication Magazine, 40(8):102-114, August 2002.