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Adaptive Intelligent Cooperative Spectrum Sensing In Cognitive Radio  [PDF]
Dilip S Aldar
Computer Science , 2013,
Abstract: Radio Spectrum is most precious and scarce resource and must be utilized efficiently and effectively. Cognitive radio is the promising solutions for the optimum utilization of the scared natural resource. The spectrum owned by the primary user should be shared among the secondary user, but primary user should not be interfered by the secondary user. In order to utilize the primary user spectrum, secondary user must detect accurately, the existence of primary in the band of interest. In cooperative spectrum sensing, the channel between the secondary users and the cognitive radio base station is non stationary and causes interference in the decision in decision fusion and in information in information due to multipath fading. In this paper neural network based cooperative spectrum sensing method is proposed, the performance of proposed method is evaluated and observed that, the neural network based scheme performance improve significantly over the AND,OR and Majority rule
Channel-Adaptive Sensing Strategy for Cognitive Radio Ad Hoc Networks  [PDF]
Yuan Lu,Alexandra Duel-Hallen
Computer Science , 2012,
Abstract: In Cognitive Radio (CR) ad hoc networks, secondary users (SU) attempt to utilize valuable spectral resources without causing significant interference to licensed primary users (PU). While there is a large body of research on spectrum opportunity detection, exploitation, and adaptive transmission in CR, most existing approaches focus only on avoiding PU activity when making sensing decisions. Since the myopic sensing strategy results in congestion and poor throughput, several collision-avoidance sensing approaches were investigated in the literature. However, they provide limited improvement. A channel-aware myopic sensing strategy that adapts the reward to the fading channel state information (CSI) of the SU link is proposed. This CSI varies over the CR spectrum and from one SU pair to another due to multipath and shadow fading, thus randomizing sensing decisions and increasing the network throughput. The proposed joint CSI adaptation at the medium access control (MAC) and physical layers provides large throughput gain over randomized sensing strategies and/or conventional adaptive transmission methods. The performance of the proposed CSI-aided sensing strategy is validated for practical network scenarios and demonstrated to be robust to CSI mismatch, sensing errors, and spatial channel correlation.
SVM and Dimensionality Reduction in Cognitive Radio with Experimental Validation  [PDF]
Shujie Hou,Robert C. Qiu,Zhe Chen,Zhen Hu
Computer Science , 2011,
Abstract: There is a trend of applying machine learning algorithms to cognitive radio. One fundamental open problem is to determine how and where these algorithms are useful in a cognitive radio network. In radar and sensing signal processing, the control of degrees of freedom (DOF)---or dimensionality---is the first step, called pre-processing. In this paper, the combination of dimensionality reduction with SVM is proposed apart from only applying SVM for classification in cognitive radio. Measured Wi-Fi signals with high signal to noise ratio (SNR) are employed to the experiments. The DOF of Wi-Fi signals is extracted by dimensionality reduction techniques. Experimental results show that with dimensionality reduction, the performance of classification is much better with fewer features than that of without dimensionality reduction. The error rates of classification with only one feature of the proposed algorithm can match the error rates of 13 features of the original data. The proposed method will be further tested in our cognitive radio network testbed.
Adaptive Sensing and Transmission Durations for Cognitive Radios  [PDF]
Wessam Afifi,Ahmed Sultan,Mohammed Nafie
Mathematics , 2010,
Abstract: In a cognitive radio setting, secondary users opportunistically access the spectrum allocated to primary users. Finding the optimal sensing and transmission durations for the secondary users becomes crucial in order to maximize the secondary throughput while protecting the primary users from interference and service disruption. In this paper an adaptive sensing and transmission scheme for cognitive radios is proposed. We consider a channel allocated to a primary user which operates in an unslotted manner switching activity at random times. A secondary transmitter adapts its sensing and transmission durations according to its belief regarding the primary user state of activity. The objective is to maximize a secondary utility function. This function has a penalty term for collisions with primary transmission. It accounts for the reliability-throughput tradeoff by explicitly incorporating the impact of sensing duration on secondary throughput and primary activity detection reliability. It also accounts for throughput reduction that results from data overhead. Numerical simulations of the system performance demonstrate the effectiveness of adaptive sensing and transmission scheme over non-adaptive approach in increasing the secondary user utility.
On the Performance of Adaptive Modulation in Cognitive Radio Networks  [PDF]
F. Foukalas,G. T. Karetsos
Computer Science , 2013,
Abstract: We study the performance of cognitive radio networks (CRNs) when incorporating adaptive modulation at the physical layer. Three types of CRNs are considered, namely opportunistic spectrum access (OSA), spectrum sharing (SS) and sensing-based SS. We obtain closed-form expressions for the average spectral efficiency achieved at the secondary network and the optimal power allocation for both continuous and discrete rate types of adaptive modulation assuming perfect channel state information. The obtained numerical results show the achievable performance gain in terms of average spectral efficiency and the impact on power allocation when adaptive modulation is implemented at the physical layer that is due to the effect of the cut-off level that is determined from the received signal-to-noise ratio for each CRN type. The performance assessment is taking place for different target bit error rate values and fading regions, thereby providing useful performance insights for various possible implementations.
The Performance Gain of Cognitive Radio in Adaptive Modulation Scheme  [PDF]
Fotis Foukalas
Wireless Engineering and Technology (WET) , 2010, DOI: 10.4236/wet.2010.11002
Abstract: Cognitive radio is considered as one of the main enablers for provisioning dynamic and flexible spectrum/channel allocation in wireless communications. The reliable data transmission over cognitive radio should employ modulation, coding etc. and thus the performance of such a new communication system should be realized. In this paper, we provide the performance analysis of adaptive modulation over a cognitive radio system in order to study the potential gain of cognitive radios in terms of spectral efficiency. The results obtained show that the performance gain of cognitive radio in adaptive modulation is remarkable.
Channel Exploration and Exploitation with Imperfect Spectrum Sensing in Cognitive Radio Networks  [PDF]
Zhou Zhang,Hai Jiang,Peng Tan,Jim Slevinsky
Mathematics , 2012,
Abstract: In this paper, the problem of opportunistic channel sensing and access in cognitive radio networks when the sensing is imperfect and a secondary user has limited traffic to send at a time is investigated. Primary users' statistical information is assumed to be unknown, and therefore, a secondary user needs to learn the information online during channel sensing and access process, which means learning loss, also referred to as regret, is inevitable. In this research, the case when all potential channels can be sensed simultaneously is investigated first. The channel access process is modeled as a multi-armed bandit problem with side observation. And channel access rules are derived and theoretically proved to have asymptotically finite regret. Then the case when the secondary user can sense only a limited number of channels at a time is investigated. The channel sensing and access process is modeled as a bi-level multi-armed bandit problem. It is shown that any adaptive rule has at least logarithmic regret. Then we derive channel sensing and access rules and theoretically prove they have logarithmic regret asymptotically and with finite time. The effectiveness of the derived rules is validated by computer simulation.
Blind Spectrum Sensing in Cognitive Radio over Fading Channels and Frequency Offsets  [PDF]
Ido Nevat,Gareth W. Peters,Jinhong Yuan
Mathematics , 2010,
Abstract: This paper deals with the challenging problem of spectrum sensing in cognitive radio. We consider a stochastic system model where the the Primary User (PU) transmits a periodic signal over fading channels. The effect of frequency offsets due to oscillator mismatch, and Doppler offset is studied. We show that for this case the Likelihood Ratio Test (LRT) cannot be evaluated poitnwise. We present a novel approach to approximate the marginilisation of the frequency offset using a single point estimate. This is obtained via a low complexity Constrained Adaptive Notch Filter (CANF) to estimate the frequency offset. Performance is evaluated via numerical simulations and it is shown that the proposed spectrum sensing scheme can achieve the same performance as the near-optimal scheme, that is based on a bank of matched filters, using only a fraction of the complexity required.
Q-Learning Based Sensing Task Management Algorithm for Cognitive Radio Systems
基于Q-Learning的认知无线电系统感知管理算法

Li Mo,Xu You-yun,Cai Yue-ming,
李默
,徐友云,蔡跃明

电子与信息学报 , 2010,
Abstract: More than an adaptive system, the cognitive radio system is an intelligent system. The Q-Learning of the intelligent control theory is adopted in the paper, to solve the sensing task allocation problem among cognitive users. And a Q-Learning based sensing management algorithm is proposed. The algorithm allocates sensing tasks to users through times of interaction with the environment and self-learning. The scheme of the paper works without any channel state information and estimation of primary traffic. From the simulation result, the algorithm could improve the sensing efficiency compared to the static allocation algorithm and attain to the convergence in a short time, which could be an attempt to the future intelligent cognitive radio systems.
Energy Detection Performance of Spectrum Sensing in Cognitive Radio  [cached]
Md. Shamim Hossain,Md. Ibrahim Abdullah,Mohammad Alamgir Hossain
International Journal of Information Technology and Computer Science , 2012,
Abstract: Spectrum sensing is a challenging task for cognitive radio. Energy detection is one of the popular spectrum sensing technique for cognitive radio. In this paper we analyze the performance of energy detection technique to detect primary user (PU). Simulation results show that the probability of detection increases significantly when signal to noise ratio increases. It is also observed that the detection probability decreases when the bandwidth factor increases.
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