989 research outputs found
Solutions to Integrals Involving the Marcum Q-Function and Applications
Novel analytic solutions are derived for integrals that involve the
generalized Marcum Q-function, exponential functions and arbitrary powers.
Simple closed-form expressions are also derived for the specific cases of the
generic integrals. The offered expressions are both convenient and versatile,
which is particularly useful in applications relating to natural sciences and
engineering, including wireless cpmmunications and signal processing. To this
end, they are employed in the derivation of the channel capacity for fixed rate
and channel inversion in the case of correlated multipath fading and switched
diversity.Comment: 15 Pages, 2 Figure
Study of Gaussian Relay Channels with Correlated Noises
In this paper, we consider full-duplex and half-duplex Gaussian relay
channels where the noises at the relay and destination are arbitrarily
correlated. We first derive the capacity upper bound and the achievable rates
with three existing schemes: Decode-and-Forward (DF), Compress-and-Forward
(CF), and Amplify-and-Forward (AF). We present two capacity results under
specific noise correlation coefficients, one being achieved by DF and the other
being achieved by direct link transmission (or a special case of CF). The
channel for the former capacity result is equivalent to the traditional
Gaussian degraded relay channel and the latter corresponds to the Gaussian
reversely-degraded relay channel. For CF and AF schemes, we show that their
achievable rates are strictly decreasing functions over the negative
correlation coefficient. Through numerical comparisons under different channel
settings, we observe that although DF completely disregards the noise
correlation while the other two can potentially exploit such extra information,
none of the three relay schemes always outperforms the others over different
correlation coefficients. Moreover, the exploitation of noise correlation by CF
and AF accrues more benefit when the source-relay link is weak. This paper also
considers the optimal power allocation problem under the correlated-noise
channel setting. With individual power constraints at the relay and the source,
it is shown that the relay should use all its available power to maximize the
achievable rates under any correlation coefficient. With a total power
constraint across the source and the relay, the achievable rates are proved to
be concave functions over the power allocation factor for AF and CF under
full-duplex mode, where the closed-form power allocation strategy is derived.Comment: 24 pages, 7 figures, submitted to IEEE Transactions on Communication
Frequency estimation in multipath rayleigh-sparse-fading channels
Maximum-likelihood (ML) data-aided frequency estimation in multipath Rayleigh-fading channels with sparse impulse responses is investigated. We solve this problem under the assumption that the autocorrelation matrix of the pilot signal can be approximated by a diagonal matrix, the fading of different path amplitudes are independent from each other, and the additive noise is white and Gaussian. The ML frequency estimator is shown to be based on combining nonlinearly transformed path periodograms. We have derived the nonlinear function for the two cases: known and unknown fading variances. The new frequency estimators lead, in particular cases, to known ML frequency estimators for nonsparse multipath fading channels. The use of a priori information about the mean number of paths in the channel allows a significant improvement of the accuracy performance. Exploiting the sparseness of the channel impulse response is shown to significantly reduce the threshold signal-to-noise ratio at which the frequency error departs from the Cramer-Rao lower bound. However, precise knowledge of the channel sparseness is not required in order to realize this improvement
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A closed-form approximation of correlated multiuser MIMO ergodic capacity with antenna selection and imperfect channel estimation
Abstract—Antenna selection (AS) is a promising technology to substantially reduce the complexity of massive multiple-input multiple-output (MIMO) systems. However, spatial correlation and imperfect estimation of channel state information (CSI) are well known to have a direct impact on the capacity of feasible MIMO schemes. In this paper, a tight closed-form approximation of the ergodic capacity for correlated Rayleigh fading multiuser
MIMO channels with receive AS and imperfect CSI is presented. The derived expression takes into account the spatial correlation at both link sides and channel estimation error at the receiver. It can be used for arbitrary numbers of users, antennas, and receive
RF chains. Furthermore, a concise analytical capacity formula is derived in the high signal-to-noise ratio (SNR) region. Numerical results validate the accuracy of our closed-form expressions over different channel conditions and SNRs. The new capacity approximation extends the state-of-the-art and enables efficient
performance evaluation of varied multiantenna applications including massive MIMO for 5G systems
Laboratory measurement campaign of DVB-T signal with transmit delay diversity
The requirements for future DVB-T/H networks demand that broadcasters design and deploy networks that provide ubiquitous reception in challenging indoors and other obstructed situations. It is essential that such networks are designed cost-effectively and with minimized environmental impact. The EC funded project PLUTO has since its start in 2006 explored the use of diversity to improve coverage in these difficult situations. The purpose of this paper is to investigate the performance of Transmit Delay Diversity (DD) with two antennas to improve the reception of DVB-T/H systems operating in different realistic propagation conditions through a series of tests using a SPIRENT SR5500 dual channel emulator. The relationship between correlation coefficient between channels, receiver velocity and diversity gain is nvestigated. It is shown that transmit delay diversity significantly improves the quality of reception particularly in simulated fast fading mobile broadcasting applications. This paper documents research conducted by Brunel University and Broadreach Systems
Adaptive filtering of radar images for autofocus applications
Autofocus techniques are being designed at the Jet Propulsion Laboratory to automatically choose the filter parameters (i.e., the focus) for the digital synthetic aperture radar correlator; currently, processing relies upon interaction with a human operator who uses his subjective assessment of the quality of the processed SAR data. Algorithms were devised applying image cross-correlation to aid in the choice of filter parameters, but this method also has its drawbacks in that the cross-correlation result may not be readily interpretable. Enhanced performance of the cross-correlation techniques of JPL was hypothesized given that the images to be cross-correlated were first filtered to improve the signal-to-noise ratio for the pair of scenes. The results of experiments are described and images are shown
On the Secrecy Degress of Freedom of the Multi-Antenna Block Fading Wiretap Channels
We consider the multi-antenna wiretap channel in which the transmitter wishes
to send a confidential message to its receiver while keeping it secret to the
eavesdropper. It has been known that the secrecy capacity of such a channel
does not increase with signal-to-noise ratio when the transmitter has no
channel state information (CSI) under mild conditions. Motivated by Jafar's
robust interference alignment technique, we study the so-called staggered
multi-antenna block-fading wiretap channel where the legitimate receiver and
the eavesdropper have different temporal correlation structures. Assuming no
CSI at transmitter, we characterize lower and upper bounds on the secrecy
degrees of freedom (s.d.o.f.) of the channel at hand. Our results show that a
positive s.d.o.f. can be ensured whenever two receivers experience different
fading variation. Remarkably, very simple linear precoding schemes provide the
optimal s.d.o.f. in some cases of interest.Comment: to appear in Proc. of IEEE International Symposium on Information
Theory (ISIT2010
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