Abstract—Nowadays, the spectrum is becoming more and more scarce because of not only the demand increase for wireless services and applications but also inflexible and rigid spectrum allocation policies. A promising solution to overcome this challenge is to exploit spectrum holes for secondary users in cognitive radio. Taking advantage of cognitive radio and dynamic spectrum access improves the...

The great increase of the number of users requires efficient management of the spectrum. In hierarchical cellular systems based on CDMA, FBRA algorithm is proposed to allocate frequency spectrum more efficiently. This algorithm lends frequency spectrum of macrocell to microcells when mass hot spot occurred. We analyze the interference to signal ratio and reverse link capacity in case of using t...

in this paper in order to determine performance point (pp) in a simply way, a program has been introduced using excel software. actually, to determine the pp point, using capacity spectrum, a lot of and error and efforts to be done. unfortunately this method does not give an accurate value. most of engineers use simple methods such as, method of ratio as given in codes of practice, but the resu...

AbstractIn cognitive radio network, through efficient spectrum utilization the secondary user (SU) capacity maximization is an important work, here we optimize the secondary user capacity through threshold in the dual threshold scheme of cooperative spectrum sensing by taking the primary user( PU ) on priority as well as SU on priority in AWGN and Rician channel with the evolutionary optimizati...

We propose a joint optimal power allocation and sensing threshold selection for capacity maximization at the secondary user (SU) in spectrum sharing (SS) cognitive radio networks (CRNs). Hence, both optimal power allocation (OPA) and spectrum sensing (SpSe) is considered in the SS CRNs model. The obtained results show that such a joint optimal selection improves the performance of the SU by max...

The spectral efficiency of a hybrid cellular direct-sequence/frequency hopping code-division multiple-access (DS/FH-CDMA) system operating in a Rayleigh-fading environment is examined. In this work, spectral efficiency is evaluated in terms of the theoretically achievable channel capacity (in the Shannon sense) per user, on the condition that this is estimated in an average sense. The analysis ...

Adaptive modulation exploits the time-variant channel capacity uctuation of fading channels using a range of di erent modem modes according to Equation 1 and Table1. This is achieved at the cost of some latency penalty, which is quanti ed in this treatise and mitigated by frequency hopping.

there are many different ways to subdivide the spectrum of a bounded linear operator; some of them aremotivated by applications to physics (in particular, quantum mechanics). in this study, the relationship betweenthe subdivisions of spectrum which are not required to be disjoint and goldberg's classification are given.moreover, these subdivisions for some summability methods are studied.

Parallel rendezvous multi-channel MAC mechanisms are regarded as an efficient method for media access control in cognitive radio networks since they do not need a control channel and use only one transceiver. However, existing parallel rendezvous MAC mechanisms assume that all channels have the same maximum capacity and channel availability for secondary users. In this paper, we propose a dynam...

Using the enhanced data rates for GSM evolution (EDGE) system with cyclic frequency hopping as an example, we apply a Kalman-filter power control method based on interference tracking to packet voice service in wireless networks. Our results show that the power-control method significantly improves the spectral efficiency by enabling the 1/3 frequency reuse while maintaining a stringent require...