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In this paper, the distribution of the ratio of extreme eigenvalues of a complex Wishart matrix is studied in order to calculate the exact decision threshold as a function of the desired probability of false alarm for the maximum-minimum eigenvalue (MME) detector. In contrast to the asymptotic analysis reported in the literature, we consider a finite number(More)
In this paper, we study the tradeoff between sensing time and achievable throughput of the secondary user that employs robust eigenvalue-based spectrum sensing techniques in the presence of noise uncertainty. First, we study exact distributions of the test statistics for two types of robust eigenvalue-based sensing techniques, namely, the blind generalized(More)
This correspondence investigates the statistical properties of the ratio <i>T</i> = &#x03BB;<sub>1</sub>/&#x03A3;<sub>i=1</sub><sup>m</sup>&#x03BB;<i>i</i> , where are &#x03BB;<sub>1</sub> &#x2265; &#x03BB;<sub>2</sub> &#x2265; &#x00B7;&#x00B7;&#x00B7; &#x2265; &#x03BB;<sub>m</sub> the <i>m</i> eigenvalues of an <i>m</i> &#x00D7; <i>m</i> complex central(More)
In this paper, we study the eigenvalue-based spectrum sensing techniques for multiple-antenna cognitive radio networks. First, we study the extreme eigenvalue distributions of a complex Wishart matrix and then, in contrast to the asymptotic analysis reported in the literature, we derive the exact distribution of the test statistics of (i) maximum eigenvalue(More)
The essential tradeoff between sensing capability and achievable throughput of the secondary network is one of the active research topics for researchers working on cognitive radio. In this paper, noise uncertainty which has a great impact on sensing methods is taken into account in the maximization of throughput using eigenvalue based spectrum sensing(More)
In direct-sequence code-division multiple-access systems, impulsive noise leads to increased bit error rates and hence limits the performance. The main novel contribution of this paper is the improvement achieved on the decorrelating detector by the addition of a nonlinear clipper in order to eliminate impulsive components. The system is studied under(More)
This study deals with the main characteristics of the Maximal Length, Gold, Kasami, Walsh and variable-length orthogonal codes and their functions in code-division multiple access(CDMA) networks. The important properties of the sequences are examined. A method of multiple spreading for channelization and scrambling in CDMA is described. Auto and cross(More)
In DS-CDMA systems, fading and impulsive noise lead to increased bit error rates, and hence limit performance. Multiple access interference (MAI) is another factor which adversely affects performance. Received signal power differences (near-far problem) and asynchronism arise, especially when users are mobile. Flat fading and a Gaussian mixture for(More)