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Winter 2003
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Special Report:
What's Next for ECEs?
April 2003
For more information, please see the following:

MPRG website

Michael Buehrer

Cross-Layer Optimization

ECE researchers are studying a new, holistic wireless communications design approach in order to develop techniques and tools so that large increases in throughput can be realized.

For the past few years, significant work has been done to find efficient wireless techniques, but most of the work has concentrated on optimizing a single layer in the protocol stack. Recent results indicate that local optimization of all layers may not lead to global optimization. “We are looking at optimizing across layers, not merely within single layers,” explained Mike Buehrer, who is leading an investigation.

He provided an example, using CDMA voice systems. “Recently, it was shown that 2-way transmit diversity (transmitting from two antennas) provides nice gains for CDMA voice systems. This has lead researchers to push for higher order diversity (e.g., 4-way) for CDMA voice and data systems. However, much work has ignored upper layers (e.g., data link, and medium access). When we include the effect of these layers, we find that 4-way transmit diversity provides little to no improvement at a doubling of the RF cost,” he said.

The team is working to develop a simulation tool that can examine link and system-level protocols and evaluate total system efficiency. The simulation is expected to be able to model network, MAC, and physical layers while maintaining reasonable simulation runtimes. Traditionally, network and physical layer functions have been simulated separately due to the large difference in system granularity needed. The challenge is to combine the two simulation approaches while maintaining both reasonable runtime and fidelity.

 
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Last updated: Tue, Sep 9, 2003