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HPWREN News

January 25, 2006

HPWREN-supported UCSD Master's student Daeseob Lim graduated with his "Distributed Proxy-Layer Scheduling in Heterogeneous Wireless sensor Networks" thesis

Heterogeneous wireless sensor networks, such as HPWREN, have significant challenges with competing QoS needs from different applications, excessive contention between wireless nodes, insufficient network throughput capacity, and battery lifetime. A graduate student researcher supported by HPWREN, Daeseob Lim, recently finished his UCSD Master's degree thesis on a distributed hybrid multi-cell scheduling algorithm for heterogeneous wireless sensor networks that addresses these issues. Tajana Simunic Rosing, UCSD professor in the Department of Electrical & Computer Engineering was his thesis advisor and committee chair.

Some of the research results.

PDF versions are available of the thesis and a slide presentation.

Daeseob Lim thesis

The scheduling algorithm consists of two parts; cell-level scheduling and node-level scheduling. The cell-level scheduling algorithm decides which cells are active so that the interference between active cells is reduced drastically. Node-level scheduling algorithm decreases the contention among wireless nodes by limiting the number of active nodes accessing a wireless channel. By combining these two scheduling algorithms, we measure a throughput improvement of up to 10.31% and maximum power savings of 85.54%.

Full Abstract of the Master's Thesis:

In this thesis, we present a distributed hybrid multi-cell scheduling algorithm for heterogeneous wireless sensor networks. The proposed scheduling algorithm addresses the issues of limited power on mobile nodes and throughput degradation due to contention in multi-cell wireless networks. Our scheduling algorithm consists of two parts; cell-level scheduling and node-level scheduling.

The cell-level scheduling algorithm decides which cells are active so that the interference between active cells is reduced drastically. Node-level scheduling algorithm decreases the contention among wireless nodes by limiting the number of active nodes accessing a wireless channel. By combining these two scheduling algorithms, we reduce energy consumption of communication devices on mobile nodes and improve aggregate throughput in multi-cell wireless networks.

The proposed scheduling algorithm is designed to run in a distributed manner. To show the efficiency of our node-level algorithm, we first give, for comparison, an optimal node-level scheduling algorithm and show that the problem is NP-complete. Finally, we present a heuristic scheduling algorithm and convert it into our distributed node-level scheduling algorithm.

We also evaluate the performance of our algorithm. Simulation results from the ns-2 network simulator show that our scheduling is effective in saving communication power while improving throughput of multi-cell wireless networks. Our scheduling achieves a throughput improvement of up to 10.31% and maximum power saving of 85.54%.

Tajana Simunic Rosing
Professor
Department of Electrical & Computer Engineering
University of California San Diego


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