Date of Final Oral Examination (Defense)

5-2011

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Computer Science

Department

Computer Science

Major Advisor

Dr. Sirisha Medidi

Abstract

Wireless Sensor Networks (WSNs) are used to achieve either continuous monitoring or event-detection in the area of interest. In continuous monitoring applications, each sensor node transmits its sensed data to the sink node (base station) periodically; while in event-detection driven applications, nodes report to the sink node once an event occurs. Continuous monitoring applications require periodic refreshed data at the sink node. Data reaching the sink node after a certain threshold is not useful for processing or analysis because it is stale. Data freshness along with reliable data delivery is critical in such applications. Current protocols in this area measure freshness only in terms of latency or delay of packets received at the sink node. However, improving overall delay alone does not necessarily improve data freshness. To address the needs of continuous monitoring applications, we adapt an existing protocol that provides packet-level reliability and augment it with prioritization and rate control mechanisms to improve data freshness. We implemented our protocol using the ns-2 simulator for evaluating its performance and identified metrics for measuring data freshness. Results show that prioritization and rate control improves data freshness significantly.

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