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We consider cooperative spectrum sensing for cognitive radios. We develop an energy efficient detector with low detection delay using sequential hypothesis testing. Sequential Probability Ratio Test (SPRT) is used at both the local nodes and the fusion center. We also analyse the performance of this algorithm and compare with the simulations. Modelling uncertainties in the distribution parameters...
In this paper, we provide exact expressions for the bit error rate (BER) for single relay maximal ratio combining (MRC) based decode and forward (DF) cooperative systems in Nakagami-m fading. This is done by expressing the decision variable as a sum of gamma conditionally Gaussian (CG) random variables. The characteristic function (CF) of gamma CG variables is then derived and used to obtain the BER...
The statistics of gamma conditionally Gaussian (CG) random variables are derived in closed form. These variables can be loosely defined to be normally distributed with mean and variance proportional to a gamma random variable. In this paper, we provide exact expressions for the bit error rate (BER) for single relay maximum likelihood (ML) decode and forward (DF) cooperative systems in Nakagami-m fading...
This paper considers the problem of spectrum sensing in cognitive radio networks when the primary user employs Orthogonal Frequency Division Multiplexing (OFDM). We specifically consider the scenario when the channel between the primary and a secondary user is frequency selective. We develop cooperative sequential detection algorithms based on energy detectors. We modify the detectors to mitigate...
This paper considers the problem of spectrum sensing in cognitive radio networks when the primary user is using Orthogonal Frequency Division Multiplexing (OFDM). For this we develop cooperative sequential detection algorithms that use the autocorrelation property of cyclic prefix (CP) used in OFDM systems. We study the effect of timing and frequency offset, IQ-imbalance and uncertainty in noise and...
We consider the problem of spectrum sensing in cognitive radio networks. In our previous work we have developed DualCUSUM, a distributed algorithm for change detection and used it for cooperative spectrum sensing. The algorithm is based on sequential change detection techniques which optimally use the past observations. But DualCUSUM requires the knowledge of the channel gains for each of the secondary...
We address the problem of estimating a random field via a wireless sensor network. We use a Multiple Access Channel (MAC) as the basic building block for such a network. For Gaussian sources over Gaussian MACs, we show that Amplify and Forward scheme (AF) performs well in such sensor network scenarios where the battery power is at a premium. We then extend this result to the hierarchical network scenario...
Cognitive radio networks have the ability to efficiently utilize the scarce radio spectrum by allowing unlicensed users to access the licensed frequency bands in the absence of licensed users. Transmit beamformers can be designed by setting constraints on the interference temperature of the licensed users and signal to interference and noise ratios (SINRs) of the cognitive users. This design is however...
We propose a robust solution to the problem of multiuser downlink beamforming with constraints on per antenna power and quality of services (QoS). We assume only the erroneous channel state information (CSI) is available at the transmitter, which may arise due to quantization, feedback delay, feedback error, etc., and solve this problem within the framework of worst-case performance optimization....
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