In this paper we derive a generic signalprocessing model for oversampled linear antenna arrays based on network theory and Nyquist sampling theory. the theoretical model is verified with experimental data collected o...
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ISBN:
(纸本)9781467310710
In this paper we derive a generic signalprocessing model for oversampled linear antenna arrays based on network theory and Nyquist sampling theory. the theoretical model is verified with experimental data collected on an HF OthR receive array.
Cooperative communication in energy-constrained networks is a topic of emerging interest in recent years especially for sensor network applications. We consider cooperative transmission from a cluster of nodes to a re...
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ISBN:
(纸本)1424403081
Cooperative communication in energy-constrained networks is a topic of emerging interest in recent years especially for sensor network applications. We consider cooperative transmission from a cluster of nodes to a remote receiver. the transmission protocol used is randomized orthogonal space-time block coding, which allows each node to randomly transmit one column of a given orthogonal space-time code matrix. Previous work on the topic has shown that the scheme can achieve maximum possible diversity order for a given SNR as the number of cooperating nodes increases. In this paper we examine the range extension achievable under realistic conditions accounting for time synchronization errors and use of pulse shaping filters. We show that the scaling of range as the number of nodes increase with timing error is not linear. It reaches a limit beyond which range improvement is not significant.
In this paper, we study the problem of MIMO channel tracking for communication systems that use orthogonal space-time block codes as the underlying space-time coding scheme. For such systems, we develop a two-step cha...
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ISBN:
(纸本)1424403081
In this paper, we study the problem of MIMO channel tracking for communication systems that use orthogonal space-time block codes as the underlying space-time coding scheme. For such systems, we develop a two-step channel tracking algorithm. As the first step, our proposed method uses Kalman filtering to obtain an initial channel estimate, for each block, based on the channel estimate obtained for the previous block. In the second step, we use an iterative decision-directed method to refine the initial channel estimate obtained in the first step. We show that due to specific structure of OSTBC, both steps can be significantly simplified. Simulation results show that, for a training repetition period of 10 blocks, this algorithm can have a performance within 1 dB, in terms of SNR, from the coherent ML receiver which has the perfect knowledge of the channel.
the optimal array for detecting the signal from a desired direction but contaminated by receiver noise and strong interference from different sources with unknown arriving-angles is re-examined. the well-known optimal...
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ISBN:
(纸本)1424403081
the optimal array for detecting the signal from a desired direction but contaminated by receiver noise and strong interference from different sources with unknown arriving-angles is re-examined. the well-known optimal array is obtained by inverting the covariance matrix of interference and noise to maximize the signal to interference and noise ratio (SINR). In practice, the covariance matrix is unknown and has to be estimated by a sample covariance matrix. the optimal array is thus estimated by inverting the sample covariance matrix. this procedure has been employed in optimal array research without challenge. However, it is shown in this paper that the estimated optimal array fails to yield the highest SINR in the case of unknown arriving-angles. Instead the highest SINR can be achieved by optimally estimating the arriving-angles of interference followed by a constrained matched filter, which maximizes the signal to noise ratio subject to canceling the interference from the estimated arriving-angles. In order to reduce the computational burden, an angle-tracking system for multiple targets is adopted to achieve the optimal estimation of arriving-angles. the resulting system of angle-tracking adaptive array offers the highest SINR at a computational burden only on the order of N . M-2 multiplications within a radar range-cell Delta tau, rather than N-3 multiplications in the well-known but questionable estimated optimal array. Here N is the number of sensors in the array and M the number of interference sources. Typically, N = 1,000 in a planar radar array, M = 2 similar to 10 and Delta tau = 1 mu S. Numerical simulations confirm the theoretical results.
A signalprocessing algorithm for estimating the direction of arrival of a harmonic signal using only a single sensor is proposed. the method is based on the recently invented architecture called CAROUSEL, which makes...
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ISBN:
(纸本)9781479914814
A signalprocessing algorithm for estimating the direction of arrival of a harmonic signal using only a single sensor is proposed. the method is based on the recently invented architecture called CAROUSEL, which makes use of the Doppler effect caused by observing signals using the sensor in a circular motion. the proposed method estimates the direction of arrival from the amount of phase shift of a harmonic component caused by the Doppler effect. Simulation using various harmonic signals including synthesised speech phonemes prove the proposed algorithm is able to accurately estimate the direction of arrival of the harmonic signals.
As the modern electro-magnetic environment in urban and battlefield scenarios becomes increasingly denser, system designers tend to gravitate toward wide bandwidth solutions. Not only do spread spectrum designs permit...
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ISBN:
(纸本)1424403081
As the modern electro-magnetic environment in urban and battlefield scenarios becomes increasingly denser, system designers tend to gravitate toward wide bandwidth solutions. Not only do spread spectrum designs permit increased co-channel utilization, they also tend to be inherently more secure, decreasing the probability of intercept by non-cooperative receivers. this is in part due to the code that must be applied in order to modulate the information bandwidth into a much wider transmitted bandwidth. In addition the non-cooperative receiver must contend with issues of increased noise, decreased sensitivity, and increased signalprocessing resource requirements among others. the problem is further exacerbated for receivers that must perform emitter geo-location or other forms of spatial processing, since the conventional high-resolution techniques rely on phase measurements based on the monochromatic assumption. this paper will discuss some of the existing methods suggested to contend with wide bandwidth spatial processing for noncooperative receivers and their limitations. It will introduce a new method based on the bilinear transformation that overcomes some of these limitations. It will present simulation results that demonstrate the advantage of this technique.
We consider a non-regenerative MIMO relay system where the source, relay and destination are all equipped with multiple antennas. the relay does not decode the packets but performs a multidimensional amplify-and-forwa...
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ISBN:
(纸本)1424403081
We consider a non-regenerative MIMO relay system where the source, relay and destination are all equipped with multiple antennas. the relay does not decode the packets but performs a multidimensional amplify-and-forward function (a relay matrix) on the baseband signals. Under the condition that the source is white, the relay matrix that maximizes the capacity between the source and the destination has been previously found. In this paper, we show a new result on how the source covariance matrix and the relay matrix can be jointly optimized to maximize the source-destination capacity. It is shown that the optimal coordinate system governed by the previously discovered relay matrix is still valid under the joint optimization, and the joint optimization yields a further capacity gain when the SNR at the relay is low.
A technique is presented for incorporating pulse-to-pulse (inter-pulse) motion effects into side-looking array radar data models yielding a motion-sensitive space-time snapshot. Low flying, highly-maneuverable Unmanne...
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ISBN:
(纸本)1424403081
A technique is presented for incorporating pulse-to-pulse (inter-pulse) motion effects into side-looking array radar data models yielding a motion-sensitive space-time snapshot. Low flying, highly-maneuverable Unmanned Aerial Vehicles (UAV) represent a potential worst case application scenario given their roll, yaw, and pitch rates are primarily limited by structural integrity. High degrees of maneuverability during the Coherent processing Interval (CPI) allow clutter and target returns to change significantly. the technique presented uses M coordinate transformations to describe platform attitude variations throughout the CPI. Ward's model then is extended to incorporate maneuver-induced changes in spatial frequency and Doppler. the new motion-sensitive space-time snapshot is used to characterize Space Time Adaptive processing (STAP) performance without motion-compensation applied. Results clearly show motion-induced clutter-null broadening with measurable degradation of STAP algorithm minimal discernable velocity.
the estimation of directions of arrival is formulated as the decomposition of a 3-way array into a sum of rank-one terms. However, a low-rank tensor approximation does not always exist. We propose an optimization tech...
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ISBN:
(纸本)9781479914814
the estimation of directions of arrival is formulated as the decomposition of a 3-way array into a sum of rank-one terms. However, a low-rank tensor approximation does not always exist. We propose an optimization technique based on differentiable angular constraints on the factors, ensuring the existence of the low-rank tensor decomposition. the efficiency of the proposed algorithm is demonstrated via numerical simulations, and compared to Cramer-Rao bounds.
In this paper, we discuss high-resolution target sensing through the exploitation of multi-frequency sparse arrayprocessing. By using simple design examples of a three-element sensorarray coupled withthe sensing si...
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ISBN:
(纸本)9781728119465
In this paper, we discuss high-resolution target sensing through the exploitation of multi-frequency sparse arrayprocessing. By using simple design examples of a three-element sensorarray coupled withthe sensing signals consisting of three well-designed frequencies, we provide insights to achieve a high number of consecutive lags, unique lags, and array aperture. Such multi-frequency sensorarrays with reduced number of sensors can be attractive in many applications to achieve effective sensing with a low cost.
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