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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...
Downlink closed loop transmission schemes for multi user MIMO systems are usually sensitive to delays in the feedback of channel state information (CSI). We present a novel and simple transmit precoding scheme which exploits the delayed interference state information (INTSI) and the concept of interference alignment (IA). We design the precoding such that the inter-cell interference subspace from...
Adaptive beamformers such as LSMI provide an excellent robustness against various types of mismatches. These beamformers are sometimes too conservative because they are worst-case optimization based beamformers. A rank-one beamformer based on probability-constrained optimization has been proved to have better performance. In this paper, a probability-constrained beamformer for general-rank signal...
This paper studies the multi-cell cooperative transmission based on interference alignment (IA). A new macro-diversity approach is presented in which each BS not only transmits data to its serving users but also transmits data to the users belonging to the cooperative BSs. By coherently designing the precoding and detection matrices, desired signals from multi-BSs are detected to achieve macro-diversity...
Adaptive beamformers attempt to eliminate loud interferers in order to facilitate the detection of quiet sources. The Dominant Mode Rejection (DMR) beamformer does this by placing notches in its beampattern corresponding to signals contained in the interference subspace. This subspace is defined by the eigenvectors associated with the largest eigenvalues of the sample covariance matrix. A companion...
In this paper, we consider the detection of a deterministic signal with an unknown scaling amplitude in the presence of a colored noise, when there is a covariance mismatch between the null and alternative hypotheses. Specifically, we consider a scenario where the target incurs an additional subspace interference that is orthogonal to the target steering vector and only present under the alternative...
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 existing oblique projection (OP) technique usually pays attention to white background noise, but a colored noise assumption is more practical. To solve this problem, a minimized interference constrained generalized oblique projection (MIGOP) operator is proposed under colored noise scenario for interference suppression. It is proven that the OP filter is a special case of the MIGOP filter whereas...
Two techniques for channel estimation and co-channel interference rejection are presented for the multiple-input, multiple-output (MIMO) uplink in the Long Term Evolution-Advanced (LTE-Advanced) system. The first technique consists of estimating the desired users' channels in the frequency domain (FD) before estimating interference covariance matrices for interference rejection. In the second technique,...
We consider the problem of joint routing, scheduling and power control in a multihop wireless network when the nodes have multiple antennas. We focus on exploiting the multiple degrees-of-freedom available at each transmitter and receiver due to multiple antennas. Specifically we use multiple antennas at each node to form multiple access and broadcast links in the network rather than just point to...
Because of its simplicity, amplify-and-forward (AF) is one of the most popular cooperative relaying technique. Relays are used in cooperative communication to improve reliability, coverage or spectral efficiency of cell-edge users. However, relays tend to increase the interferences seen by users of adjacent cells, particularly by the cell-edge users, when used in multi-cell systems. In this paper,...
Under real conditions, severe signal cancellation often occurs in adaptive beamformers because of reverberation, microphone transfer function mismatch or steering vector error. Therefore, usually voice activity information is necessary to pause the beamformer update during the speech activity. However, this information is not available or not sufficiently accurate in most applications. Here we propose...
The degrees of freedom of cellular networks with constant channels are characterized. Conditions for the feasibility of interference alignment in symmetric cellular networks are found. Based on the analytic results a user selection scheme for alternating interference alignment algorithms is proposed. The user selection ensures the feasibility of interference alignment. The analytic results are sustained...
The traditional signal-subspace projection (SSP) method combats the problem of array manifold uncertainty to gain the robustness by means of projecting the nominal manifold vector onto the signal subspace so as to eliminate the errors lying in the noise subspace. The main contribution of this paper is to extent the SSP approach from one dimension to multi-dimension. We assume that the actual manifold...
In this paper, the manifold vector of the desired signal is assumed to lie in a known subspace, but the associated coordinates are random variables. This model is suitable for the fast varying environment. The so-called matched subspace beamforming is referred to as the beamformer resolving the signal that are drawn from this multi-dimension subspace. By jointly using such subspace and the signal...
We carried out the overview and comparative analysis of efficiency in “energy speed - computational complexity” criterion of various methods for Hermitian Toeplitz covariance matrix estimation in regular systems of space-time adaptive signal processing (STAP).
We carried out the overview and comparative analysis of efficiency in “energy speed — computational complexity” criterion of various methods for Hermitian Toeplitz covariance matrix estimation in regular systems of space-time adaptive signal processing (STAP).
A new widely linear (WL) adaptive beamforming algorithm for non-circular sources based on the conjugate gradient (CG) method is proposed, which we refer to as the widely linear conjugate gradient (WL-CG) algorithm. It is designed according to the widely linearly constrained minimum variance (WL-CMV) criterion and takes full advantage of the second-order statistics of the non-circular data. Since only...
In this paper, we consider the problem of assessment the target's radiated noise in the presence of target motion using the sensor array. Suppressing the strong interference signal and remaining the characteristics of the target's radiated noise must be both concerned. We use the gneralised sidelobe canceller (GSC) structure, combining frequency invariant beamformer (FIB) and null broadening technique...
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