There were some talks on dynamic spectrum access as well as waterfilling and other resource allocation problems.
- Resource consumption in dynamic spectrum access networks: Applications and Shannon limits (Michael B. Pursley and Thomas C. Royster IV, Clemson University)
This talk tried to address how to choose a modulation scheme to maximize throughput in dynamic spectrum access networks. The scheme could be power or bandwidth efficient, and trading off these efficiencies is important. One way of capturing the impact is to look at how the transmission of one radio affects other radios across bandwidth and time. So a radio preventing 3 radios talking over a 2 Hz for 1 second is using 6 units of “resource.” The limits on communication can be rephrased in terms of the familiar Eb/N0.
- Spectrum sharing on a wideband fading channel with limited feedback (Manish Agarwal and Michael Honig, Northwestern University)
Suppose that K users over N channels wish to share the spectrum effectively in a multiple-access setting. They can probe the channels to see which ones are available — if more than K’ probe a given channel, the destination can assign it for transmission. The goal is to choose a the number of channels to probe so that there is little overhead but users still get a fair allocation. At least that’s how I understood the problem. They show a scheme that probes N/(log N)^2 but the rate for each user grows like log(log N).
- Asynchronous iterative water-filling for Gaussian frequency-selective interference channels: A unified framework (Gesualdo Scutari, Univ. of Rome “La Sapienza”, Daniel P. Palomar, Hong Kong Univ. of Science and Technology, and Sergio Barbarossa, Univ. of Rome “La Sapienza”)
This work looked at a new geometric intuition for the waterfilling algorithm for Gaussian channels, where the waterfilling allocation is a kind of projection onto a simplex. This projection view allows them to get convergence results for asynchronous waterfilling algorithms for the interference channels. The conditions for convergence match those for the multiple-access and broadcast channels.
- Spectrum sharing: fundamental limits and self-enforcing protocols. (Raul Etkin, U.C. Berkeley and HP-Labs)
This talk focused on how to do interference management and generate self-enforcing protocols for spectrum-sharing systems. In the first part, he showed that a kind of Han-Kobayashi scheme gets to within 1 bit of the capacity region for the interference channel. The key is to show a tighter converse and comes from looking at certain genie-aided channels that are not too loose. The second part of the talk was a game-theoretic approach to guaranteeing good behavior in a spectrum-sharing system. The approach is to use punishments — if any user deviates from the protocol then the other users spread their power, punishing him. This game has an equilibrium and greatly improves on the static game, which has an unbounded price of anarchy. I just like writing that — “price of anarchy.”