Recent studies have forecasted major growth in mobile broadband traffic. Due to the predicted high growth rate of mobile broadband traffic over the coming years (demand), there is a need for more wireless network capacity (supply). One of the major approaches to expand mobile wireless capacity is to add more spectrum to the market by enabling “spectrum sharing”. The FCC has issued many reports ...

Transmit power control is a central technique for resource allocation and interference management in spread-spectrum wireless networks. With increasing popularity of spread-spectrum as a multiple access technique, there has been signiicant research in the area in recent years. While power control has been considered traditionally as a means to counteract the harmful eeect of channel fading, the...

Markets for spectrum were first proposed by Ronald Coase [1] as a way to efficiently allocate this resource. It took another forty years for primary markets to be developed (in the form of spectrum auctions) as the mechanism for assigning spectrum licenses to users. It is not a secret that secondary markets would be necessary to fully realize the benefits of economic allocation of spectrum. But...

This paper investigates the capacity of multiple relay channels in different fading and shadowing environments under spectrum-sharing constraints. We consider that a secondary user (SU) is allowed to share the spectrum band with a primary user (PU) provided that the SU’s transmit power remains below an interference power threshold set by the PU. Considering a scenario where the SU’s transmitter...

In this paper, we present a general formula for the capacity region of a general interference channel with two pairs of users. The formula shows that the capacity region is the union of a family of rectangles, where each rectangle is determined by a pair of spectral inf-mutual information rates. Although the presented formula is usually difficult to compute, it provides us useful insights into ...

Cognitive radio is a new concept of reusing licensed spectrum in an unlicensed manner. The motivation for cognitive radio is various measurements of spectrum utilization, that generally show unused resources in frequency, time and space. These ”spectrum holes” could be exploited by cognitive radios. Some studies suggest that the spectrum is extremely underutilized, and that these spectrum holes...

Cognitive radio (CR) with spectrum-sharing feature is a promising technique to address the spectrum under-utilization problem in dynamically changing environments. In this paper, the achievable capacity gain of spectrum-sharing systems over dynamic fading environments is studied. To perform a general analysis, a theoretical fading model called hyper-fading model that is suitable to the dynamic ...

This paper presents a new spread-spectrum watermarking algorithm for digital images in discrete wavelet transform (DWT) domain. The algorithm is applied for embedding watermarks like patient identification /source identification or doctors signature in binary image format into host digital radiological image for potential telemedicine applications. Performance of the algorithm is analysed by va...

Recently, substantial attention has been paid to improve the spectral efficiency of communication setups using different spectrum sharing techniques. This paper aims to study the capacity of Rayleigh-fading spectrum sharing channels in the case where there is correlation between the fading channels. Assuming perfect channel state information, the channel capacity is obtained under both adaptive...

An improved capacity-demand-diagram method that uses the well-known constantductility design spectrum for the demand diagram is developed and illustrated by examples. This method estimates the deformation of inelastic SDF systems consistent with the selected inelastic design spectrum, while retaining the attraction of graphical implementation of the ATC-40 Nonlinear Static Procedure.