Recently a spectral scarcity has arisen as a serious problem, because current static frequency allocation schemes cannot further accommodate an increasing number of devices requesting higher data rate. Therefore, CR (cognitive radio) technique has been considered as a potential solution to improve spectrum utilization by sharing the spectrum. In this chapter, the main concept of CR was introduced.

This study presents a genetic algorithm for spectrum allocation and power control, both with constraints, in cognitive radio networks. The models for spectrum allocation and power control with constraints are formulated in a partially distributed manner, then the scheme based on genetic algorithms is presented. Simulation results demonstrate that the proposed genetic algorithm-based scheme is e...

Cognitive radio (CR) is the enabling technology for supporting dynamic spectrum access: the policy that addresses the spectrum scarcity problem that is encountered in many countries. The spectrum sensing problem has gained new aspects with cognitive radio networks. Radio spectrum is the most valuable resource in wireless communication. The cognitive radio and cognitive based networking are tran...

The Radio spectrum has always been a scarce resource right from its initial deployment in 1920s. The television spectrum band is poorly utilized in Indian scenario. Also more efficient spectrum usage is possible with the migration from analogue to digital broadcasting. The use of Cognitive Radios allows an efficient use of the available resources so as to solve the problem of spectrum scarcity....

Dynamic spectrum auction is an effective solution to manage spectrum across many small networks. As the number of participants grows, collusion poses a serious threat to auction performance. Small groups of colluding bidders can make use of the interference constraints to manipulate auction outcomes, leading to unfair spectrum distribution and significant loss in auction revenue. Prior designs,...

The opening up of the unlicensed bands for commercial use has been a tremendous success. Wireless communications in computing, mobile, medical and consumer electronics market segments have grown rapidly in the past few years. Due to this success, radio resources in the unlicensed bands are progressively becoming scarce. Recently, the Spectrum Policy Task Force (SPTF) within the FCC has recommen...

With today’s increase in the usage of wireless devices and the consequent spectrum allocation, radio spectrum is becoming scarce. However studies have shown that most of the allotted spectrum is not used for large periods of time. Cognitive radio has been proposed to exploit the presence of these spectrum holes. Spectrum sensing which is one of the most important operations of cognitive radio, ...

Frequency Allocation Problem in wireless cellular networks is a major area of research in telecommunication industries. Since users of mobile phones are increasing exponentially, the existing limited frequency spectrum is unable to provide services efficiently. To enhance the performance of the networks, some measures must be taken to reduce drop call probabilities due to non availability of fr...

V Because of th nation's increasing demand for sore *<>lecommunication capacity, there is a continuing r.e^-i for nor* efficient ways of sharing ehe radio spectrum. Th-3 ccr.ver.tior.ai ways o* allocating the soeC-rum are by frequency, space ar.d time division. However, for systems using new technology this is inefficient. Hence, it is desirable to re-examine alternative procedures that might b...

Optimal sex allocation is frequency-dependent, but senescence may cause behaviour at old age to be suboptimal. We investigated whether sex allocation changes with parental age, using 16 years of data comprising more than 2500 molecularly sexed offspring of more than 600 known-age parents in common terns (Sterna hirundo), slightly sexually size-dimorphic seabirds. We decomposed parental age effe...