267 research outputs found
Massive MIMO for Wireless Sensing with a Coherent Multiple Access Channel
We consider the detection and estimation of a zero-mean Gaussian signal in a
wireless sensor network with a coherent multiple access channel, when the
fusion center (FC) is configured with a large number of antennas and the
wireless channels between the sensor nodes and FC experience Rayleigh fading.
For the detection problem, we study the Neyman-Pearson (NP) Detector and Energy
Detector (ED), and find optimal values for the sensor transmission gains. For
the NP detector which requires channel state information (CSI), we show that
detection performance remains asymptotically constant with the number of FC
antennas if the sensor transmit power decreases proportionally with the
increase in the number of antennas. Performance bounds show that the benefit of
multiple antennas at the FC disappears as the transmit power grows. The results
of the NP detector are also generalized to the linear minimum mean squared
error estimator. For the ED which does not require CSI, we derive optimal gains
that maximize the deflection coefficient of the detector, and we show that a
constant deflection can be asymptotically achieved if the sensor transmit power
scales as the inverse square root of the number of FC antennas. Unlike the NP
detector, for high sensor power the multi-antenna ED is observed to empirically
have significantly better performance than the single-antenna implementation. A
number of simulation results are included to validate the analysis.Comment: 32 pages, 6 figures, accepted by IEEE Transactions on Signal
Processing, Feb. 201
Performance Analysis and Design of Maximum Ratio Combining in Channel-Aware MIMO Decision Fusion
In this paper we present a theoretical performance analysis of the maximum
ratio combining (MRC) rule for channel-aware decision fusion over
multiple-input multiple-output (MIMO) channels for (conditionally) dependent
and independent local decisions. The system probabilities of false alarm and
detection conditioned on the channel realization are derived in closed form and
an approximated threshold choice is given. Furthermore, the channel-averaged
(CA) performances are evaluated in terms of the CA system probabilities of
false alarm and detection and the area under the receiver operating
characteristic (ROC) through the closed form of the conditional moment
generating function (MGF) of the MRC statistic, along with Gauss-Chebyshev (GC)
quadrature rules. Furthermore, we derive the deflection coefficients in closed
form, which are used for sensor threshold design. Finally, all the results are
confirmed through Monte Carlo simulations.Comment: To appear in IEEE Transactions on Wireless Communication
Virtual MIMO RADAR using OFDM-CDM Waveforms
This paper addresses a new perspective on the exploitation ofdiversity resembling recent seminal proposals with multiple antennas known as MIMO radar. Our focus pursues similar advantages as spatial MIMO systems but intending to achieve the desired resistance over fading or/and SNR increase without relying on multiple antennas. We design an OFDM-CDM waveform well inspired in modern communications systems that creates a virtual MIMO system operating on the artificial 2D domain formed by a set ofwell separated carriers (OFDM) and several OFDM symbols each one modulated by orthogonal codes (CDM). We consider the most general scenario with moving targets and large size targets originating an equivalent time variant andfrequency selective channel model. Our proposal proceeds in two steps, a first one to reorthogonalize the transmitted set of OFDMsignal by proper time andfrequency synchronization (this stage provides range and velocity estimators), and a second one based on Neyman Pearson detection improved by the diversity gain
Detection in Analog Sensor Networks with a Large Scale Antenna Fusion Center
We consider the distributed detection of a zero-mean Gaussian signal in an
analog wireless sensor network with a fusion center (FC) configured with a
large number of antennas. The transmission gains of the sensor nodes are
optimized by minimizing the ratio of the log probability of detection (PD) and
log probability of false alarm (PFA). We show that the problem is convex with
respect to the squared norm of the transmission gains, and that a closed-form
solution can be found using the Karush-Kuhn-Tucker conditions. Our results
indicate that a constant PD can be maintained with decreasing sensor transmit
gain provided that the number of antennas increases at the same rate. This is
contrasted with the case of a single-antenna FC, where PD is monotonically
decreasing with transmit gain. On the other hand, we show that when the
transmit power is high, the single- and multi-antenna FC both asymptotically
achieve the same PD upper bound.Comment: 4 pages, 2 figures, accepted by the 8th IEEE Sensor Array and
Multichannel Signal Processing Workshop (SAM), Apr. 201
Initial synchronisation of wideband and UWB direct sequence systems: single- and multiple-antenna aided solutions
This survey guides the reader through the open literature on the principle of initial synchronisation in single-antenna-assisted single- and multi-carrier Code Division Multiple Access (CDMA) as well as Direct Sequence-Ultra WideBand (DS-UWB) systems, with special emphasis on the DownLink (DL). There is a paucity of up-to-date surveys and review articles on initial synchronization solutions for MIMO-aided and cooperative systems - even though there is a plethora of papers on both MIMOs and on cooperative systems, which assume perfect synchronization. Hence this paper aims to ?ll the related gap in the literature
Decision Fusion in Space-Time Spreading aided Distributed MIMO WSNs
In this letter, we propose space-time spreading (STS) of local sensor
decisions before reporting them over a wireless multiple access channel (MAC),
in order to achieve flexible balance between diversity and multiplexing gain as
well as eliminate any chance of intrinsic interference inherent in MAC
scenarios. Spreading of the sensor decisions using dispersion vectors exploits
the benefits of multi-slot decision to improve low-complexity diversity gain
and opportunistic throughput. On the other hand, at the receive side of the
reporting channel, we formulate and compare optimum and sub-optimum fusion
rules for arriving at a reliable conclusion.Simulation results demonstrate gain
in performance with STS aided transmission from a minimum of 3 times to a
maximum of 6 times over performance without STS.Comment: 5 pages, 5 figure
Reduced Complexity Optimal Hard Decision Fusion under Neyman-Pearson Criterion
Distributed detection is an important part of many of the applications like wireless sensor networks,
cooperative spectrum sensing in the cognitive radio network. Traditionally optimal non-randomized
hard decision fusion rule under Neyman Pearson(NP) criterion is exponential in complexity. But
recently [4] this was solved using dynamic programming. As mentioned in [4] that decision fusion
problem exhibits semi-monotonic property in a special case. We use this property in our simulations
and eventually apply dynamic programming to solve the problem with further reduced complexity.
Further, we study the eïżœect of using multiple antennas at FC with reduced complexity rule
Short Packets over Block-Memoryless Fading Channels: Pilot-Assisted or Noncoherent Transmission?
We present nonasymptotic upper and lower bounds on the maximum coding rate
achievable when transmitting short packets over a Rician memoryless
block-fading channel for a given requirement on the packet error probability.
We focus on the practically relevant scenario in which there is no \emph{a
priori} channel state information available at the transmitter and at the
receiver. An upper bound built upon the min-max converse is compared to two
lower bounds: the first one relies on a noncoherent transmission strategy in
which the fading channel is not estimated explicitly at the receiver; the
second one employs pilot-assisted transmission (PAT) followed by
maximum-likelihood channel estimation and scaled mismatched nearest-neighbor
decoding at the receiver. Our bounds are tight enough to unveil the optimum
number of diversity branches that a packet should span so that the energy per
bit required to achieve a target packet error probability is minimized, for a
given constraint on the code rate and the packet size. Furthermore, the bounds
reveal that noncoherent transmission is more energy efficient than PAT, even
when the number of pilot symbols and their power is optimized. For example, for
the case when a coded packet of symbols is transmitted using a channel
code of rate bits/channel use, over a block-fading channel with block
size equal to symbols, PAT requires an additional dB of energy per
information bit to achieve a packet error probability of compared to
a suitably designed noncoherent transmission scheme. Finally, we devise a PAT
scheme based on punctured tail-biting quasi-cyclic codes and ordered statistics
decoding, whose performance are close ( dB gap at packet error
probability) to the ones predicted by our PAT lower bound. This shows that the
PAT lower bound provides useful guidelines on the design of actual PAT schemes.Comment: 30 pages, 5 figures, journa
- âŠ