The speaker is Prof. Allen MacKenzie from the Dept. of Electrical and Computer Engineering at Virginia Tech. The abstract of his talk is as follows: Efforts to create modern wireless networks have occasionally suffered from approaches that seeks to replace static resource allocation schemes with fully dynamic schemes, failing to adequately compensate for the benefits associated with stable, predictable resource allocation, such as reduced communication overhead and computational complexity. In this talk, I describe ongoing research on channel assignment in multihop, multitransceiver wireless networks that demonstrates that many of the advantages of dynamic assignment are available via a hybrid approach that builds a static network topology and then enhances it dynamically in response to network traffic. Then, I will briefly describe future work that seeks to apply a broadly similar approach to spectrum assignment. In the first portion of the talk, I describe a proposed channel assignment scheme for cognitive radio networks that balances the need for topology adaptation to maximize flow rate and the need for a stable baseline topology to support network connectivity. We focus on networks in which nodes are equipped with multiple radios or transceivers, each of which can be assigned to a channel. First, we assign channels independently of traffic, to achieve basic network connectivity and support light loads such as control traffic, and, second, we dynamically assign channels to the remaining transceivers in response to traffic demand. We formulate the problem as a two-stage mixed integer linear program (MILP) and show that with this two-stage approach we can achieve performance comparable to a fully dynamic channel assignment scheme while preserving a static, connected topology. I describe ongoing work to implement this strategy via distributed channel assignment algorithms. In the second portion of the talk, I will describe a similar problem faced in the realm of spectrum assignment. Classical, static approaches to spectrum allocation are extremely inefficient, but provide a stable environment for wireless systems. Dynamic spectrum access (DSA) has been a popular research topic in the last five years, but deployment of DSA systems has been slowed by difficult technical challenges at multiple layers of the protocol stack and delayed adoption by spectrum regulators. I will briefly describe future research which will investigate hybrid approaches with the potential to offer both stability and improved efficiency.

Location:	2150 Torgersen Hall
Contact:	T. M. Murali murali@cs.vt.edu 5402318534
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