7,429 research outputs found
MU-MIMO Communications with MIMO Radar: From Co-existence to Joint Transmission
Beamforming techniques are proposed for a joint multi-input-multi-output
(MIMO) radar-communication (RadCom) system, where a single device acts both as
a radar and a communication base station (BS) by simultaneously communicating
with downlink users and detecting radar targets. Two operational options are
considered, where we first split the antennas into two groups, one for radar
and the other for communication. Under this deployment, the radar signal is
designed to fall into the null-space of the downlink channel. The communication
beamformer is optimized such that the beampattern obtained matches the radar's
beampattern while satisfying the communication performance requirements. To
reduce the optimizations' constraints, we consider a second operational option,
where all the antennas transmit a joint waveform that is shared by both radar
and communications. In this case, we formulate an appropriate probing
beampattern, while guaranteeing the performance of the downlink communications.
By incorporating the SINR constraints into objective functions as penalty
terms, we further simplify the original beamforming designs to weighted
optimizations, and solve them by efficient manifold algorithms. Numerical
results show that the shared deployment outperforms the separated case
significantly, and the proposed weighted optimizations achieve a similar
performance to the original optimizations, despite their significantly lower
computational complexity.Comment: 15 pages, 15 figures. This work has been submitted to the IEEE for
possible publication. Copyright may be transferred without notice, after
which this version may no longer be accessibl
Orbital Angular Momentum Waves: Generation, Detection and Emerging Applications
Orbital angular momentum (OAM) has aroused a widespread interest in many
fields, especially in telecommunications due to its potential for unleashing
new capacity in the severely congested spectrum of commercial communication
systems. Beams carrying OAM have a helical phase front and a field strength
with a singularity along the axial center, which can be used for information
transmission, imaging and particle manipulation. The number of orthogonal OAM
modes in a single beam is theoretically infinite and each mode is an element of
a complete orthogonal basis that can be employed for multiplexing different
signals, thus greatly improving the spectrum efficiency. In this paper, we
comprehensively summarize and compare the methods for generation and detection
of optical OAM, radio OAM and acoustic OAM. Then, we represent the applications
and technical challenges of OAM in communications, including free-space optical
communications, optical fiber communications, radio communications and acoustic
communications. To complete our survey, we also discuss the state of art of
particle manipulation and target imaging with OAM beams
Joint Range and Doppler Adaptive Processing for CBM based DFRC systems
Recently, dual-function radar communication (DFRC) systems have been proposed
to integrate radar and communication into one platform for spectrum sharing.
Various signalling strategies have been proposed to embed communication
information into the radar transmitted waveforms. Among these, complex
beampattern modulation (CBM) embeds communication information into the complex
transmit beampattens via changing the amplitude and phase of the beampatterns
towards the communication receiver. The embedding of random communication
information causes the clutter modulation and high range-Doppler sidelobe.
What's more, transmitting different waveforms on a pulse to pulse basis
degrades the radar target detection capacity when traditional sequential pulse
compression (SPC) and moving-target detection (MTD) is utilized. In this paper,
a minimum mean square error (MMSE) based filter, denoted as joint range and
Doppler adaptive processing (JRDAP) is proposed. The proposed method estimates
the targets' impulse response coefficients at each range-Doppler cell
adaptively to suppress high range-Doppler sidelobe and clutter modulation. The
performance of proposed method is very close to the full-dimension adaptive
multiple pulses compression (AMPC) while reducing computational complexity
greatly.Comment: 11 pages, 5 figure
Application of advanced technology to space automation
Automated operations in space provide the key to optimized mission design and data acquisition at minimum cost for the future. The results of this study strongly accentuate this statement and should provide further incentive for immediate development of specific automtion technology as defined herein. Essential automation technology requirements were identified for future programs. The study was undertaken to address the future role of automation in the space program, the potential benefits to be derived, and the technology efforts that should be directed toward obtaining these benefits
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