883 research outputs found
Adaptive Radar Detection of a Subspace Signal Embedded in Subspace Structured plus Gaussian Interference Via Invariance
This paper deals with adaptive radar detection of a subspace signal competing
with two sources of interference. The former is Gaussian with unknown
covariance matrix and accounts for the joint presence of clutter plus thermal
noise. The latter is structured as a subspace signal and models coherent pulsed
jammers impinging on the radar antenna. The problem is solved via the Principle
of Invariance which is based on the identification of a suitable group of
transformations leaving the considered hypothesis testing problem invariant. A
maximal invariant statistic, which completely characterizes the class of
invariant decision rules and significantly compresses the original data domain,
as well as its statistical characterization are determined. Thus, the existence
of the optimum invariant detector is addressed together with the design of
practically implementable invariant decision rules. At the analysis stage, the
performance of some receivers belonging to the new invariant class is
established through the use of analytic expressions
A Unifying Framework for Adaptive Radar Detection in Homogeneous plus Structured Interference-Part II: Detectors Design
This paper deals with the problem of adaptive multidimensional/multichannel
signal detection in homogeneous Gaussian disturbance with unknown covariance
matrix and structured (unknown) deterministic interference. The aforementioned
problem extends the well-known Generalized Multivariate Analysis of Variance
(GMANOVA) tackled in the open literature. In a companion paper, we have
obtained the Maximal Invariant Statistic (MIS) for the problem under
consideration, as an enabling tool for the design of suitable detectors which
possess the Constant False-Alarm Rate (CFAR) property. Herein, we focus on the
development of several theoretically-founded detectors for the problem under
consideration. First, all the considered detectors are shown to be function of
the MIS, thus proving their CFARness property. Secondly, coincidence or
statistical equivalence among some of them in such a general signal model is
proved. Thirdly, strong connections to well-known simpler scenarios found in
adaptive detection literature are established. Finally, simulation results are
provided for a comparison of the proposed receivers.Comment: Submitted for journal publicatio
A Geometric Approach to Covariance Matrix Estimation and its Applications to Radar Problems
A new class of disturbance covariance matrix estimators for radar signal
processing applications is introduced following a geometric paradigm. Each
estimator is associated with a given unitary invariant norm and performs the
sample covariance matrix projection into a specific set of structured
covariance matrices. Regardless of the considered norm, an efficient solution
technique to handle the resulting constrained optimization problem is
developed. Specifically, it is shown that the new family of distribution-free
estimators shares a shrinkagetype form; besides, the eigenvalues estimate just
requires the solution of a one-dimensional convex problem whose objective
function depends on the considered unitary norm. For the two most common norm
instances, i.e., Frobenius and spectral, very efficient algorithms are
developed to solve the aforementioned one-dimensional optimization leading to
almost closed form covariance estimates. At the analysis stage, the performance
of the new estimators is assessed in terms of achievable Signal to Interference
plus Noise Ratio (SINR) both for a spatial and a Doppler processing assuming
different data statistical characterizations. The results show that interesting
SINR improvements with respect to some counterparts available in the open
literature can be achieved especially in training starved regimes.Comment: submitted for journal publicatio
Blind user detection in doubly-dispersive DS/CDMA channels
In this work, we consider the problem of detecting the presence of a new user
in a direct-sequence/code-division-multiple-access (DS/CDMA) system with a
doubly-dispersive fading channel, and we propose a novel blind detection
strategy which only requires knowledge of the spreading code of the user to be
detected, but no prior information as to the time-varying channel impulse
response and the structure of the multiaccess interference. The proposed
detector has a bounded constant false alarm rate (CFAR) under the design
assumptions, while providing satisfactory detection performance even in the
presence of strong cochannel interference and high user mobility.Comment: Accepted for publication on IEEE Transactions on Signal Processin
Power-Aperture Resource Allocation for a MPAR with Communications Capabilities
Multifunction phased array radars (MPARs) exploit the intrinsic flexibility of their active electronically steered array (ESA) to perform, at the same time, a multitude of operations, such as search, tracking, fire control, classification, and communications. This paper aims at addressing the MPAR resource allocation so as to satisfy the quality of service (QoS) demanded by both line of sight (LOS) and reflective intelligent surfaces (RIS)-aided non line of sight (NLOS) search operations along with communications tasks. To this end, the ranges at which the cumulative detection probability and the channel capacity per bandwidth reach a desired value are introduced as task quality metrics for the search and communication functions, respectively. Then, to quantify the satisfaction level of each task, for each of them a bespoke utility function is defined to map the associated quality metric into the corresponding perceived utility. Hence, assigning different priority weights to each task, the resource allocation problem, in terms of radar power aperture (PAP) specification, is formulated as a constrained optimization problem whose solution optimizes the global radar QoS. Several simulations are conducted in scenarios of practical interest to prove the effectiveness of the approach
Diversity-Integration Trade-offs in MIMO Detection
In this work, a MIMO detection problem is considered. At first, we derive the
Generalized Likelihood Ratio Test (GLRT) for arbitrary transmitted signals and
arbitrary time-correlation of the disturbance. Then, we investigate design
criteria for the transmitted waveforms in both power-unlimited and
power-limited systems and we study the interplay among the rank of the
optimized code matrix, the number of transmit diversity paths and the amount of
energy integrated along each path. The results show that increasing the rank of
the code matrix allows generating a larger number of diversity paths at the
price of reducing the average signal-to-clutter level along each path
Power-Aperture Resource Allocation for a MPAR with Communications Capabilities
Multifunction phased array radars (MPARs) exploit the intrinsic flexibility
of their active electronically steered array (ESA) to perform, at the same
time, a multitude of operations, such as search, tracking, fire control,
classification, and communications. This paper aims at addressing the MPAR
resource allocation so as to satisfy the quality of service (QoS) demanded by
both line of sight (LOS) and non line of sight (NLOS) search operations along
with communications tasks. To this end, the ranges at which the cumulative
detection probability and the channel capacity per bandwidth reach a desired
value are introduced as task quality metrics for the search and communication
functions, respectively. Then, to quantify the satisfaction level of each task,
for each of them a bespoke utility function is defined to map the associated
quality metric into the corresponding perceived utility. Hence, assigning
different priority weights to each task, the resource allocation problem, in
terms of radar power aperture (PAP) specification, is formulated as a
constrained optimization problem whose solution optimizes the global radar QoS.
Several simulations are conducted in scenarios of practical interest to prove
the effectiveness of the approach.Comment: 12 pages, 14 figure
Power-Aperture Product Resource Allocation for Radar ISAC
This article deals with the problem of power aperture product (PAP) management in a multifunction phased array radar (MPAR) performing sensing in both line of sight (LOS) and non line of sight (NLOS), and communications. To this end, two different quality metrics are introduced, namely the range where the cumulative detection probability (for sensing) and the channel capacity per bandwidth (for communications) attain a specified value. Then, suitable utility functions are defined to map the quality index relative to the corresponding perceived utility for each task. The resource allocation is hence formulated as a constrained optimization problem whose solution optimizes the global radar quality of service (QoS). The method is finally validated by means of numerical simulations
A Priority-Based Scheduling Scheme for Search, Track, and Communications in MPARS
The modern battlefield scenario is strongly influenced by the innovative capabilities of the multifunction phased array radars (MPARs) which can perform sequentially or in parallel a plethora of sensing and communication activities. As a matter of fact, the MPAR can functionally cluster its phased array into bespoke sub-apertures implementing different tasks. Accordingly, a portion of the other available resources, e.g., bandwidth, power-aperture product (PAP), and time, is also assigned to each sub-aperture and the grand challenge is the definition of strategies for an optimal scheduling of the tasks to be executed. In this respect, a rule-based algorithm for task scheduling is proposed in this paper. In a nutshell, in each time window, the procedure first allocates the radar tasks (viz. volume search, cued search, update and confirmation tracking) and then utilize the communication (COM) looks so as to fill the empty intra-slot time left by the radar tasks. When there are two concurrent looks, the allocation is performed according to their priorities. Moreover, if the bandwidth and PAP are sufficient, some of them can be also scheduled in parallel. Interesting results in term of bandwidth and time occupancy efficiency are observed from simulations conducted in challenging scenarios comprising also multiple maneuvering targets
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