The fast user growth in wireless communications has created significant demands for new wireless services in both the licensed and unlicensed frequency spectra1. Recent studies show that a fixed spectrum assignment policy cannot achieve good spectrum utilization (FCC, 2005) . To address this problem, cognitive radio (CR) has been developed as a technology to facilitate the utilization of tempor...

In order to satisfy the spectrum requirements of the future international mobile telecommunication (IMT) systems, to realize scientific allocation and usage of spectrum resources and to avoid spectrum waste brought by allocation in advanced, there is a need to make a reasonable estimation for the spectrum demands of future IMT systems. The estimation results can also provide guidelines for the ...

Richard E. Frye*, John Slattery, Derrick F. MacFabe, Emma Allen-Vercoe, William Parker, John Rodakis, James B. Adams, Rosa Krajmalnik-Brown, Ellen Bolte, Stephen Kahler, Jana Jennings, Jill James, Carl E. Cerniglia and Tore Midtvedt Division of Neurology, Arkansas Children’s Hospital Research Institute, Little Rock, AR, USA; Department of Pediatrics, University of Arkansas for Medical Sciences,...

The radio spectrum used by wireless communication systems is becoming increasingly crowded. One approach to overcome this problem is to perform real-time dynamic spectrum assignment. To this end, it is necessary to collect information about the radio spectrum, also called spectrum sensing. In this paper a framework is presented which can be used for collecting information about radio spectrum u...

This paper presents a novel approach to solve channel assignment problems by using clustering technique with Fuzzy Hopfield neural network (FHNN). Channels are regarded as data sample and cells are taken as clusters. Channels are adequately distributed to the dedicated cells while satisfying the interference constraints. The goal is to avoid the interference and serve the expected traffic with ...

Cognitive Radio is one of the most promising paradigms for wireless communication, as it enables a flexible use of the radio spectrum. For this, several new techniques were developed that provide a good overview about the current spectrum usage and facilitate dynamic adaptation to it. Moreover, it was investigated how to integrate those techniques into the current static spectrum assignment. Th...

We propose optical path routing and frequency slot assignment algorithms that can make the best use of elastic optical paths and the capabilities of distance adaptive modulation. Due to the computational difficulty of the assignment problem, we develop algorithms for 1+1 dedicated/1:1 shared protected ring networks and unprotected mesh networks to that fully utilize the characteristics of the t...

intentional assignment of entitlements (as opposed to debts) is a legal institution which is based on the possibility of separation of entitlements from the personality of creditor and of its assignment to a third party. in the voluntary assignment of entitlements, the creditors may assign their rights to a third party. after long discussions, voluntary assignment of rights has been accepted in...

The Huggins band of ozone is investigated by means of exact dynamics calculations using a new (diabatic) potential energy surface for the (1)B(2) state. The remarkable agreement with the measured spectrum strongly suggests that the Huggins band is due to the two C(s) potential wells of the (1)B(2) state. The vibrational assignment, based on the nodal structure of wave functions, supports the mo...

Today’s wireless networks are characterized by a fixed spectrum assignment policy. On the other hand, a huge portion of the assigned spectrum is underutilized. But in contrast, rapid development of wireless communication technologies is seriously challenged by spectrum scarcity problem and lower spectrum utilization. Cognitive radio network (CRN), a revolutionary technology in wireless communic...