Spectrum measurement studies have shown that substantial portions of the allocated wireless spectrum are highly underutilized. Frequency-agile radios (FARs) have the potential to make opportunistic use of such spectrum holes without causing harmful interference to users of the allocated spectrum. Toward this goal, we develop a framework for modeling the interference caused by FARs employing spe...

Abstract— In this paper, we propose a direct/cooperative amplify-and-forward relay (D/AR) switching using a spectrum division/adaptive subcarrier allocation (SDASA) for increasing the uplink capacity of single carrier-frequency division multiple access (SC-FDMA). In the D/AR switching, switching between direct communication and cooperative AF relay is done so that the channel capacity is maximi...

Ahstrurf -A random coding strategy for discrete-time additive Gaussian noise channels with feedback is analyzed. It has long been known that feedback may increase the capacity of such channels as long as the additive noise process is not white. We prove that a strictly positive gain is always achieved. In addition, we prove that as the signal power goes to zero the ratio of feedback capacity to...

Reinforced concrete frame buildings with Open Ground Story (OGS) are one of the most common building configurations in urban habitat. These configurations are known to be vulnerable to seismic excitations, primarily due to the sudden loss in strength in the ground story and differential stiffness distribution throughout the structure. The differential stiffness distribution is attributed primar...

This paper considers a spectrum-sharing cognitive network in which a secondary user shares spectrum with an existing primary user as long as the interference caused by the secondary user to the primary user is below permissible levels. We investigate the delay quality-of-service (QoS) guaranteed capacity gains with imperfect channel state information (CSI) between the secondary transmitter and ...

The overlay of an intelligent Frequency Diversity Spread Spectrum System (FDSS) on the Advanced Mobile Phone Service system (AMPS) is studied. The worst-case condition is considered for the downlink analysis. Moreover, the effect of sidelobes outside the FDSS principal spectrum is considered. The downlink and uplink capacity of both systems are given using a model of 25 cells. Results show that...

Cognitive Radio (CR) is promising technique for access of spectrum resources. The sensors deployed vast environmental area are in need of hundreds to thousands of sensor nodes which is mostly energy constrained and their batteries are not rechargeable in most Wireless Sensor Networks applications. A Cognitive Radio Sensor Network (CRSN) is defined as wireless sensor network equipped with cognit...

In this two-part paper, we study three capacity regions for fading broadcast channels and obtain their corresponding optimal resource allocation strategies: the ergodic (Shannon) capacity region, the zerooutage capacity region, and the capacity region with outage. In Part I, we obtained the ergodic capacity region of the fading broadcast channel under di erent spectrum-sharing techniques. In th...

The evolution of the Kolmogorov–Zakharov (K–Z) spectrum of weak turbulence is studied in the limit of strongly local interactions where the usual kinetic equation, describing the time evolution of the spectral wave-action density, can be approximated by a PDE. If the wave action is initially compactly supported in frequency space, it is then redistributed by resonant interactions producing the ...