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When the desired signal is present in the training snapshots, the performance of conventional orthogonal projection (OP) adaptive beamforming degrades severely due to the desired signal cancellation effect. To overcome this deficiency, the improved orthogonal projection (IOP) adaptive beamforming by using reconstructed interference covariance matrix is proposed. In the proposed algorithm, the interference...
We consider physical-layer security in a novel MISO cooperative overlay cognitive radio network (CRN) with a single eavesdropper. We aim to design an artificial noise (AN) aided secondary transmit strategy to maximize the joint achievable secrecy rate of both primary and secondary links, subject to a global secondary transmit power constraint and guaranteeing any transmission of secondary should at...
We consider a radio cell composed of one single Base Station (BS) and possibly several users. We are particularly interested in analyzing the behavior of two special users. On one hand, the first user (called the sender) has access to multiple channels and has to choose a channel to transmit its data. Obviously, the sender seeks to transmit using the best channel among the L available channels in...
Malicious interference injection or jamming is one of the simplest ways to disrupt wireless communications. Prior approaches can alleviate jamming interference to a limited extent; they are especially vulnerable to a reactive jammer i.e., a jammer that injects noise upon sensing a legitimate transmission or wideband jamming. In this paper, we leverage the inherent features of OFDM (Orthogonal Frequency...
This paper proposes an extension of the NOncircularity Rate Maximization (NORM) beamformer that takes into account noncircular interferences. The main idea of the new approach is to utilize the spatial diversity and noncircularity dissimilarity between the desired signal and interferences plus noise simultaneously. For this purpose, the weight vector is designed by maximizing the non-circularity rate...
We present a technique that merges Compressive Sensing and Wiener filtering (denoted as CS-Wiener) and compares it to standard Wiener filtering (denoted as Std-Wiener) in radar detection and estimation in a Space-Time Adaptive Processing application. The method leverages an inherent similarity in the Generalized Sidelobe Canceller transformation to that of the Compressive Sensing sampling function,...
In the present paper, the synthesis of optimized radar waveforms ensuring spectral compatibility with the overlayed electromagnetic radiators is addressed. Cognition provided by a Radio Environmental Map (REM) is exploited so as to induces dynamic spectral constraints on the radar waveform. A waveform optimization aiming at improving some radar performances is proposed, whose feasibility is extensively...
We consider the problem of secret communication through cognitive relay assisted interference channels in which secondary user (SU) is allowed to transmit simultaneously with the primary user (PU) over the same channel instead of waiting for an idle channel which is traditional for a cognitive radio. We propose two cooperative jamming (CJ) schemes to improve the secrecy rate of cognitive interference...
The correlated jamming channel is one in which the encoder uses a Gaussian codebook and the interference in the channel is generated by a jammer who can input noise which is correlated with the transmitted codeword. In this paper we look at this problem from the perspective of arbitrarily varying channels (AVCs), in which additive interference is controlled by a jammer. The jammer in our Gaussian...
GTRI is developing an 8-channel X-band experimental radar for a small unmanned aircraft system (SUAS) for adaptive multi-channel, MIMO, and waveform diversity test bed studies. New adaptive algorithms, one of which is covered in this paper, are also part of the test bed. Estimation of the statistical covariance matrix forms a central role in radar detection and adaptive beamforming algorithm. For...
In this paper we deal with the problem of estimating the disturbance covariance matrix for radar signal processing applications, when a limited number of training data is present. We determine the Maximum Likelihood (ML) estimator of the covariance matrix starting from a set of secondary data, assuming a special covariance structure (i.e. the sum of a positive semi-definite matrix plus a term proportional...
The purpose of this paper is to estimate the interference subspace quickly. We show that the solution of the proposed constrained optimization problem results the signal subspace. Then a novel subspace tracking algorithm is propounded. Theoretical analysis and simulation results show that the interference subspace could be tracked quickly by utilized this algorithm.
For target tracking in Interference Environments of cognitive radar problem, Extended Karman, Particle filter algorithms etc. are generally used to be regarded as usual solutions to state estimation. Many techniques have been developed to improve performance of target tracking. In this paper, we set the structure and key features of target's tracking design for cognitive radar, and newly propose cognitive...
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