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This paper investigates the resource allocation problem in heterogeneous cognitive radio networks (HCRNs). In this paper, two types of users, i.e., multi-homing and single-network cognitive radio users (CRUs), are considered to coexist in HCRNs. Multi-homing CRUs can access multiple networks simultaneously, while single-network CRUs can be served by only one network at a time. With the aim of maximizing...
Increasing demand has led to wireless spectrum shortages, with many parts of the existing spectrum being heavily used. Dynamic spectrum access (DSA) has been proposed to allow cognitive radio networks to use existing spectrum more efficiently. It will allow secondary users to transmit on already allocated spectrum on a non-interference basis. Cognitive radios are able to change bandwidth and other...
VANET and cognitive radio network (CRN) are both new emerging technologies in wireless networking. The application of CR concept in wireless communication systems for intelligent vehicles has been envisioned as a promising idea towards solving the problem of scarce spectrum. This paper discusses CR technologies for VANETs aimed at opportunistic spectrum access (OSA) for improved vehicular communication...
The cognitive radio (CR) have been proposed to improve spectral efficiency and to meet growing demands for higher data rates in mobile communications and satellite communications. In this paper, we propose a blind estimation algorithm for a secondary user to estimate transmission parameters of the primary signal in an OFDM overlay system, using only the available fast Fourier transform (FFT) component...
Channel assignment is a key problem in Cognitive Radio Networks. The channels are leased to the secondary users when the licensed or primary users are OFF, provided that the secondary users will leave those channels as soon as the primary users are reactivated. Therefore, to achieve a high performance of the network, we should lease a channel to a secondary user while both of them achieve the best...
The paper presents an exhaustive visualization of different problems encountered in efficient utilization of spectrum for advanced wireless communication. It is a well known fact that there is a crisis for available radio spectrum due to incredible expansion and advancement of the communication systems and technologies. But in reality, there is no shortage of available spectrum but only lack of advance...
Primary User Emulation (PUE) attack is one of the major concerns and problems in cognitive radio networks. Essentially, an intruder who tries to interfere and occupy the vacant spectrum of the primary user (PU) can emulate or impersonate the primary user by mimicking certain characteristics and features of the primary user signal. As a direct result, it may seem to secondary users (SUs) as though...
An almost square patch, a square patch and a stacked square patch with corner truncation for circular polarization (CP) are researched and developed at X-band for cognitive radios. Experimental results indicate, first, that the impedance bandwidth of a CP almost square patch fed from the edge by a 50 ohm line is 1.70% and second, that of a CP square patch fed from the ground plane side by a surface...
In this paper, we use a Spectrum Sharing/allocation algorithm to implement a Cognitive Radio network without spectral awareness. This allows radio resources to be allocated to primary users and to secondary users in such a way that primary system and secondary system are aware of each other. By doing this, sensing of spectrum holes is avoided but the primary users will be protected and will always...
Usually energy-detection based spectrum sensing techniques for Cognitive Radios need, as preliminary operation, the spectrum segmentation in smaller sub-bands, in order to apply test statistic over each sub-band rather than over the entire span, resulting in a sensitivity and selectivity improvement of the output. Despite uniform subdivision is the easiest way, the problem resides on the optimal sub-band...
In this paper, we study a spectrum allocation mechanism of Cognitive Radio Networks based on multi-backpack problem, and then propose a discrete hybrid leapfrog algorithm and a spectrum allocation method based on this algorithm. This algorithm uses the integer coding method and designs the corresponding algorithm search strategy, using the crossover and mutation operator to improve the algorithm performance...
Cognitive radio is an emerging technology that has been under heavy research in the recent years, as it is considered to be a promising solution for the spectrum scarcity problem. In the European Defense Agency's project Cognitive Radio for Dynamic Spectrum Management (CORASMA) a high precision cognitive radio simulation environment was developed based on an artificial UHF waveform. Target of that...
Priority queue-based techniques improve spectrum efficiency by allocating the underutilized spectral bands (holes) of primary users to secondary users in Cognitive Radio Networks (CRN). This article proposes a Distributed Precedence Queuing scheme for Efficient Spectrum Management (DPQESM) in CRNs. The proposed method classifies the available channels into periodic and aperiodic based on the state...
Cognitive Radio requires both efficient and reliable spectrum sensing of wideband signals. In order to cope with the sampling rate bottleneck when dealing with such signals, sub-Nyquist methods have been proposed. However, these techniques decrease the signal to noise ratio (SNR) due to aliasing effects. Cyclostationary detection, which exploits the periodic property of communication signal statistics,...
Multiple point-to-point (p2p) communication links that share noncontiguously available spectrum via noncontiguous orthogonal frequency division multiple access (NC-OFDMA) are considered in this paper. NC-OFDMA divides the spectrum into orthogonal subcarriers and assigns nonoverlapping subsets of these subcarriers to each of the links. Such a setup is motivated by the need for dynamic and opportunistic...
The rapid advancement in the era of wireless applications and services has made huge demand of spectrum resources. The cognitive radio is a new concept that can utilize radio spectrum resources efficiently and sufficiently. The spectrum sensing is a function of cognitive radio. This paper develops an energy detection algorithm based on wavelet packet transform for spectrum sensing. The performance...
Recent years have shown an increase demand for wireless communication which creates new challenges in the field where intelligent spectrum utilization is necessary to maintain high network performance. The emergence of Cognitive Radios which provide opportunistic access to the spectrum, introduce an improvement in the spectrum utilization and the communication quality. Through dynamic spectrum access...
Frequency reconfiguration is a requirement in most of the communication related activities involving multiband communication. A novel frequency reconfigurable Vivaldi antenna that can be used for cognitive radio is explored. In a Cognitive Radio system, the antenna should be capable of sensing the entire bandwidth and should be able to select a specific frequency. In this work, spectrum sensing is...
Dynamic spectrum allocation techniques are usually based on the assumption of a homogeneous cognitive radio network. In this work we describe a Continuous time Markov chain model that allows different types of bandwidth requirements and priority traffic. We have improved the lowest priority user's performance using channel aggregation and fragmentation, which are mechanisms envisioned for the LTE-A/4G...
In recent years, the deployment of wireless short-range devices has increased dramatically, especially in urban settings with high density buildings. This is causing high levels of interference at the ISM bands, thus deteriorating performance. However, there is spectrum being unused and if the devices could make opportunistic use of available channels in other bands (OSA) it will improve their performance...
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