Electrical Engineering
      and Computer Sciences

Electrical Engineering and Computer Sciences

COLLEGE OF ENGINEERING

UC Berkeley

   

2008 Research Summary

Open Dynamic Spectrum Sharing with Minimal Energy (ODYSSEY)

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Ahmad Bahai, Maryam Vareth, Sofie Pollin and Ali Motamedi

Thanks to the recent advances in wireless technology, a broad range of standards is currently emerging. Interoperability and coexistence between these heterogeneous networks are becoming key issues, which require intelligent spectrum sharing approaches that adapt to possibly changing spectrum use.

An optimal dynamic channel selection algorithm has been proposed for the case where networks try to find a channel where the probability of being affected by a more powerful network is minimal [1]. The channel selection problem is formulated as a multi-armed bandit problem that enables us to derive optimal selection rules. The model assumptions about the interfering traffic that motivate this formulation are also validated through 802.11 traffic measurements. A packet loss improvement of more than 50% is achieved, compared to no agility or a simple heuristic channel selection algorithm. The scheme does not rely on the availability of a spectrum scanning radio that guides the channel selection by collecting extra information. As illustrated also in [2] for this coexistence scenario, convergence of the channel selection algorithm might be improved when such extra scanning is available.

As a result, we are also investigating how we can obtain information about spectrum use at minimal cost. Since the cost of listening to the spectrum is to a large extent caused by the analog-to-digital converter (ADC), we look at approaches to detect or amplify spectrum use features before the signals are digitized.

Finally, we investigated how to obtain information about the spatial coverage of existing networks. Motivated by measurements of the spatial coverage of the UC Berkeley AirbearsBeyond Access Point's, we proposed a scheme to propagate coverage information efficiently and achieve an improved spatial reuse through iterative power control based on propagated spatial coverage information.

[1]
A. Motamedi and A. Bahai, "MAC Protocol Design for Spectrum-agile Wireless Networks: Stochastic Control Approach," DySPAN, 2007.
[2]
S. Pollin, M. Ergen, A. Dejonghe, L. Van der Perre, F. Catthoor, I. Moerman, and A. Bahai, "Distributed Cognitive Coexistence of 802.15.4 with 802.11," Crowncom, 2006.