1,721,171 research outputs found
Hybrid clutter-map/L-CFAR procedure for clutter rejection in nonhomogeneous environment
No full textThe author introduces a new CFAR procedure, which relies on a hybrid clutter-map/L-CFAR strategy, aimed at improving the system robustness against possible nonhomogeneities, while preserving target detectability in a homogeneous environment. After presenting the procedure, guidelines for the design of the relevant system subblocks are given, from both quantitative and qualitative points of view. As to the performance analysis, closed-form formulas are given for the detection and false alarm probabilities in case of a single point-like target, showing that proper system design yields near-optimum performance. Moreover, approximated expressions of the detection probability are derived for the case of multiple targets entering the map cell, and possibly persisting in there for several scans: it is shown that data censoring prevents the masking effect which is typical of clutter-map systems, at the price of a very limited incremental CFAR loss
Simultaneous suppression of multiaccess and narrowband interference in asynchronous CDMA networks
No full textAutomatic suppression of narrowband interference in direct sequence spread spectrum systems
No full textPerformance of iterative data detection and channel estimation for single-antenna and multiple-antennas wireless communications
No full textIn iterative data-detection and channel-estimation algorithms, the channel estimator and the data detector recursively exchange information in order to improve the system performance. While a vast bulk of the available literature demonstrates the merits of iterative schemes through computer simulations, in this paper analytical results on the performance of an iterative detection/estimation scheme are presented. In particular, this paper focus is on uncoded systems and both the situations that the receiver and the transmitter are equipped with either a single antenna or multiple antennas are considered. With regard to the channel estimator, the analysis considers both the minimum mean square error and the maximum likelihood channel estimate, while, with regard to the data detector, linear receiver interfaces are considered. Closed-form formulas are given for the channel-estimation mean-square error and for its Crame/spl acute/r-Rao bound, as well as for the error probability of the data detector. Moreover, the problem of the optimal choice of the length of the training sequence is also addressed. Overall, results show that the considered iterative strategy achieves excellent performance and permits, at the price of some complexity increase, the use of very short training sequences without incurring any performance loss. Finally, computer simulations reveal that the experimental results are in perfect agreement with those predicted by the theoretical analysis
OS-CFAR thresholding in decentralized radar systems
No full textIn a decentralized detection scheme, several sensors perform
a binary ( hard) decision and send the resulting data to a fusion
center for the final decision If each local decision has a constant
false alarm rate (CFAR), the final decision is ensnred to be CFAR.
We consider the case that ea"h local decision is a threshold
decision, and the threshold is proportional, through a suitable
multiplier, to a linear coniJination of order statistics (OS) from a
reference set (a generalization of the concept of OS thresholding).
We address the following problem: given the fusion rule and the
relevant system parameters, select each threshold multiplier and
the coefficients of each linear combination so as to maximize
the overall probability of detection for constrained probability of
false alarm. By a Lagrangian maximization approach, we obtain
a general solution to this problem and closed-form solutions for
the AND and OR fusion logics. A performance assessment is
carried on, showing a global superiority of the OR fusion rule in
tel111S of detection probability (for operating couditions matching
the design assumptions) and of robustness (when these do not
match). We also investigate Ilhe effect of the hard quantization
performed at the local sensors, by comparing the said performance
to those achievable by the same fusion rule in the limiting case of
no quantizatio
Simultaneous suppression of multiaccess and narrowband interference in asynchronous CDMA networks
No full textLl-CFAR: a flexible and robust alternative
No full textA new family of constant false alarm rate (CFAR) processors is introduced. An Ll-CFAR forms its noise power estimate by linearly filtering ranked samples from the reference set; the weights of this combination, however, depend not only on the rank, but also on the relative proximity of the sample to the cell under test. From the class of Ll-CFARs may be chosen members which effectively censor spurious targets; members which exhibit impressive control of false alarm in the presence of a clutter edge; and members which are robust against both such inhomogeneities. While the design of such schemes is involved, their implementation is not significantly more burdensome than that of plain ordered statistic CFAR (OS-CFAR). After a discussion of the stochastic training of Ll-CFAR, the performance is thoroughly assessed under the most commonly encountered instances of environmental conditions, and compared with those of classical CFAR techniques
Automatic suppression of narrowband interference in direct sequence spread spectrum systems
No full text
MMSE RAKE reception for asynchronous DS/CDMA overlay systems and frequency-selective fading channels
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