1,577 research outputs found
Joint Design of Overlaid Communication Systems and Pulsed Radars
The focus of this paper is on co-existence between a communication system and
a pulsed radar sharing the same bandwidth. Based on the fact that the
interference generated by the radar onto the communication receiver is
intermittent and depends on the density of scattering objects (such as, e.g.,
targets), we first show that the communication system is equivalent to a set of
independent parallel channels, whereby pre-coding on each channel can be
introduced as a new degree of freedom. We introduce a new figure of merit,
named the {\em compound rate}, which is a convex combination of rates with and
without interference, to be optimized under constraints concerning the
signal-to-interference-plus-noise ratio (including {\em signal-dependent}
interference due to clutter) experienced by the radar and obviously the powers
emitted by the two systems: the degrees of freedom are the radar waveform and
the afore-mentioned encoding matrix for the communication symbols. We provide
closed-form solutions for the optimum transmit policies for both systems under
two basic models for the scattering produced by the radar onto the
communication receiver, and account for possible correlation of the
signal-independent fraction of the interference impinging on the radar. We also
discuss the region of the achievable communication rates with and without
interference. A thorough performance assessment shows the potentials and the
limitations of the proposed co-existing architecture
Overlapped-MIMO Radar Waveform Design for Coexistence With Communication Systems
This paper explores an overlapped-multiple-input multiple-output (MIMO)
antenna architecture and a spectrum sharing algorithm via null space projection
(NSP) for radar-communications coexistence. In the overlapped-MIMO
architecture, the transmit array of a collocated MIMO radar is partitioned into
a number of subarrays that are allowed to overlap. Each of the antenna elements
in these subarrays have signals orthogonal to each other and to the elements of
the other subarrays. The proposed architecture not only improves sidelobe
suppression to reduce interference to communications system, but also enjoys
the advantages of MIMO radar without sacrificing the main desirable
characteristics. The radar-centric spectrum sharing algorithm then projects the
radar signal onto the null space of the communications system's interference
channel, which helps to avoid interference from the radar. Numerical results
are presented which show the performance of the proposed waveform design
algorithm in terms of overall beampattern and sidelobe levels of the radar
waveform and finally shows a comparison of the proposed system with existing
collocated MIMO radar architectures.Comment: accepted at IEEE WCN
Joint Design of surveillance radar and MIMO communication in cluttered environments
In this study, we consider a spectrum sharing architecture, wherein a
multiple-input multiple-output communication system cooperatively coexists with
a surveillance radar. The degrees of freedom for system design are the transmit
powers of both systems, the receive linear filters used for pulse compression
and interference mitigation at the radar receiver, and the space-time
communication codebook. The design criterion is the maximization of the mutual
information between the input and output symbols of the communication system,
subject to constraints aimed at safeguarding the radar performance. Unlike
previous studies, we do not require any time-synchronization between the two
systems, and we guarantee the radar performance on all of the range-azimuth
cells of the patrolled region under signal-dependent (endogenous) and
signal-independent (exogenous) interference. This leads to a non-convex
problem, and an approximate solution is thus introduced using a block
coordinate ascent method. A thorough analysis is provided to show the merits of
the proposed approach and emphasize the inherent tradeoff among the achievable
mutual information, the density of scatterers in the environment, and the
number of protected radar cells.Comment: Submitted to IEEE Transaction on Signal Processing on June 24, 201
Adaptive Interference Removal for Un-coordinated Radar/Communication Co-existence
Most existing approaches to co-existing communication/radar systems assume
that the radar and communication systems are coordinated, i.e., they share
information, such as relative position, transmitted waveforms and channel
state. In this paper, we consider an un-coordinated scenario where a
communication receiver is to operate in the presence of a number of radars, of
which only a sub-set may be active, which poses the problem of estimating the
active waveforms and the relevant parameters thereof, so as to cancel them
prior to demodulation. Two algorithms are proposed for such a joint waveform
estimation/data demodulation problem, both exploiting sparsity of a proper
representation of the interference and of the vector containing the errors of
the data block, so as to implement an iterative joint interference removal/data
demodulation process. The former algorithm is based on classical on-grid
compressed sensing (CS), while the latter forces an atomic norm (AN)
constraint: in both cases the radar parameters and the communication
demodulation errors can be estimated by solving a convex problem. We also
propose a way to improve the efficiency of the AN-based algorithm. The
performance of these algorithms are demonstrated through extensive simulations,
taking into account a variety of conditions concerning both the interferers and
the respective channel states
Fundamental Limits on Performance for Cooperative Radar-Communications Coexistence
abstract: Spectral congestion is quickly becoming a problem for the telecommunications sector. In order to alleviate spectral congestion and achieve electromagnetic radio frequency (RF) convergence, communications and radar systems are increasingly encouraged to share bandwidth. In direct opposition to the traditional spectrum sharing approach between radar and communications systems of complete isolation (temporal, spectral or spatial), both systems can be jointly co-designed from the ground up to maximize their joint performance for mutual benefit. In order to properly characterize and understand cooperative spectrum sharing between radar and communications systems, the fundamental limits on performance of a cooperative radar-communications system are investigated. To facilitate this investigation, performance metrics are chosen in this dissertation that allow radar and communications to be compared on the same scale. To that effect, information is chosen as the performance metric and an information theoretic radar performance metric compatible with the communications data rate, the radar estimation rate, is developed. The estimation rate measures the amount of information learned by illuminating a target. With the development of the estimation rate, standard multi-user communications performance bounds are extended with joint radar-communications users to produce bounds on the performance of a joint radar-communications system. System performance for variations of the standard spectrum sharing problem defined in this dissertation are investigated, and inner bounds on performance are extended to account for the effect of continuous radar waveform optimization, multiple radar targets, clutter, phase noise, and radar detection. A detailed interpretation of the estimation rate and a brief discussion on how to use these performance bounds to select an optimal operating point and achieve RF convergence are provided.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201
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