Cognitive radio has been an active research area in wireless communications over the past 10 years. TV Digital Switch Over resulted in new regulatory regimes, which offer the first large-scale opportunity for cognitive radio and networks. This article considers the most recent regulatory rules for TV White Space opportunistic usage, and proposes technologies to operate in these bands. It addres...

Cognitive radio is a technology that is of growing interest internationally. Currently, there is a highly active worldwide community of academic and industrial researchers working in this field. Efforts focus on the many technical questions as well as the economic and political challenges of moving this new technology from research concept to reality [1, 2]. Cognitive radio holds much promise n...

This paper describes the concepts, architecture and implementation of the Celadon framework for zone-based services: informational and transactional services offered by businesses to mobile users in public spaces. Celadon is designed to foster an overall ecosystem that addresses the requirements of both the mobile user and the business owner. This is accomplished through an extensible architect...

This note provides historical perspectives and background on the motivations which led to the invention of the modulation spaces by the author almost 25 years ago, as well as comments about their role for ongoing research efforts within time-frequency analysis. We will also describe the role of modulation spaces within the more general coorbit theory developed jointly with Karlheinz Gröchenig, ...

For the iteration of spherical average (A1)N and Laplace operator Δ, we consider boundedness Δ(A1)N on α-modulation spaces \(M_{p,q}^{s,\alpha }\). The authors obtain some sufficient necessary conditions to ensure spaces. main theorems significantly improve known results.

We study the action on modulation spaces of Fourier multipliers with symbols e, for real-valued functions μ having unbounded second derivatives. We show that if μ satisfies the usual symbol estimates of order α ≥ 2, or if μ is a positively homogeneous function of degree α, the corresponding Fourier multiplier is bounded as an operator between the weighted modulation spaces M δ and M, for every ...

In this paper we give a sharp estimate on the norm of the scaling operator Uλf(x) = f(λx) acting on the weighted modulation spaces M s,t (R). In particular, we recover and extend recent results by Sugimoto and Tomita in the unweighted case [15]. As an application of our results, we estimate the growth in time of solutions of the wave and vibrating plate equations, which is of interest when cons...

We introduce a family of coarse quantization algorithms for heavily oversampled Gabor expansions of certain classes of functions in L2(R). These algorithms, which we call the TF quantization algorithms, are inspired by sigma–delta modulation, a widely implemented coarse quantization scheme for oversampled bandlimited functions. We show that the TF algorithms produce weak type approximations whe...

We consider the channel capacity of an optical intensity-modulated direct-detection (IM/DD) system using multiple-subcarrier modulation (MSM) with fixed bias. The channel is modeled as an additive white Gaussian noise (AWGN) channel with nonnegative input waveform. The mean of the nonnegative input waveform is the average transmitted optical power. The mean of the waveform during a symbol perio...

This paper reports "work in progress" on a project which I've titled, "The Spaces of Transnational Cultures". The aim of the project is to build on, but be methodologically different from, my earlier research on the architecture and urbanism of colonial and postcolonial cities in which the principal objective had been to demonstrate the inherently constitutive relationship between the political...