2,960 research outputs found
Asymptotically Exact Approximations for the Symmetric Difference of Generalized Marcum-Q Functions
(c) 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. DOI: 10.1109/TVT.2014.2337263In this paper, we derive two simple and asymptotically exact approximations for the function defined as ÎQm(a, b) =Î Qm(a, b) - Qm(b, a). The generalized Marcum Q-function Qm(a, b) appears in many scenarios in communications in this particular form and is referred to as the symmetric difference of generalized Marcum Q-functions or the difference of generalized Marcum Q-functions with reversed arguments. We show that the symmetric difference of Marcum Q-functions can be expressed in terms of a single Gaussian Q-function for large and even moderate values of the arguments a and b. A second approximation for ÎQm(a, b) is also given in terms of the exponential function. We illustrate the applicability of these new approximations in different scenarios: 1) statistical characterization of Hoyt fading; 2) performance analysis of communication systems; 3) level crossing statistics of a sampled Rayleigh envelope; and 4) asymptotic approximation of the Rice Ie-function.Universidad de MĂĄlaga. Campus de Excelencia Internacional. AndalucĂa Tech
An efficient approximation to the correlated Nakagami-m sums and its application in equal gain diversity receivers
There are several cases in wireless communications theory where the
statistics of the sum of independent or correlated Nakagami-m random variables
(RVs) is necessary to be known. However, a closed-form solution to the
distribution of this sum does not exist when the number of constituent RVs
exceeds two, even for the special case of Rayleigh fading. In this paper, we
present an efficient closed-form approximation for the distribution of the sum
of arbitrary correlated Nakagami-m envelopes with identical and integer fading
parameters. The distribution becomes exact for maximal correlation, while the
tightness of the proposed approximation is validated statistically by using the
Chi-square and the Kolmogorov-Smirnov goodness-of-fit tests. As an application,
the approximation is used to study the performance of equal-gain combining
(EGC) systems operating over arbitrary correlated Nakagami-m fading channels,
by utilizing the available analytical results for the error-rate performance of
an equivalent maximal-ratio combining (MRC) system
An Approximation of the First Order Marcum -Function with Application to Network Connectivity Analysis
An exponential-type approximation of the first order Marcum -function is
presented, which is robust to changes in its first argument and can easily be
integrated with respect to the second argument. Such characteristics are
particularly useful in network connectivity analysis. The proposed
approximation is exact in the limit of small first argument of the Marcum
-function, in which case the optimal parameters can be obtained
analytically. For larger values of the first argument, an optimization problem
is solved, and the parameters can be accurately represented using regression
analysis. Numerical results indicate that the proposed methods result in
approximations very close to the actual Marcum -function for small and
moderate values of the first argument. We demonstrate the accuracy of the
approximation by using it to analyze the connectivity properties of random ad
hoc networks operating in a Rician fading environment.Comment: 6 pages, 4 figures, 1 tabl
Turbo receivers for interleave-division multiple-access systems
In this paper several turbo receivers for Interleave-Division Multiple-Access (IDMA) systems will be discussed. The multiple access system model is presented first. The optimal, Maximum A Posteriori (MAP) algorithm, is then presented. It will be shown that the use of a precoding technique at the emitter side is applicable to IDMA systems. Several low complexity Multi-User Detector (MUD), based on the Gaussian approximation, will be next discussed. It will be shown that the MUD with Probabilistic Data Association (PDA) algorithm provides faster convergence of the turbo receiver. The discussed turbo receivers will be evaluated by means of Bit Error Rate (BER) simulations and EXtrinsic Information Transfer (EXIT) charts
Communications over fading channels with partial channel information : performance and design criteria
The effects of system parameters upon the performance are quantified under the assumption that some statistical information of the wireless fading channels is available. These results are useful in determining the optimal design of system parameters. Suboptimal receivers are designed for systems that are constrained in terms of implementation complexity.
The achievable rates are investigated for a wireless communication system when neither the transmitter nor the receiver has prior knowledge of the channel state information (CSI). Quantitative results are provided for independent and identically distributed (i.i.d.) Gaussian signals. A simple, low-duty-cycle signaling scheme is proposed to improve the information rates for low signal-to-noise ratio (SNR), and the optimal duty cycle is expressed as a function of the fading rate and SNR. It is demonstrated that the resource allocations and duty cycles developed for Gaussian signals can also be applied to systems using other signaling formats.
The average SNR and outage probabilities are examined for amplify-and-forward cooperative relaying schemes in Rayleigh fading channels. Simple power allocation strategies are determined by using knowledge of the mean strengths of the channels.
Suboptimal algorithms are proposed for cases that optimal receivers are difficult to implement. For systems with multiple transmit antennas, an iterative method is used to avoid the inversion of a data-dependent matrix in decision-directed channel estimation. When CSI is not available, two noncoherent detection algorithms are formulated based on the generalized likelihood ratio test (GLRT). Numerical results are presented to demonstrate the use of GLRT-based detectors in systems with cooperative diversity
Performance Evaluation of Impulse Radio UWB Systems with Pulse-Based Polarity Randomization
In this paper, the performance of a binary phase shift keyed random
time-hopping impulse radio system with pulse-based polarity randomization is
analyzed. Transmission over frequency-selective channels is considered and the
effects of inter-frame interference and multiple access interference on the
performance of a generic Rake receiver are investigated for both synchronous
and asynchronous systems. Closed form (approximate) expressions for the
probability of error that are valid for various Rake combining schemes are
derived. The asynchronous system is modelled as a chip-synchronous system with
uniformly distributed timing jitter for the transmitted pulses of interfering
users. This model allows the analytical technique developed for the synchronous
case to be extended to the asynchronous case. An approximate closed-form
expression for the probability of bit error, expressed in terms of the
autocorrelation function of the transmitted pulse, is derived for the
asynchronous case. Then, transmission over an additive white Gaussian noise
channel is studied as a special case, and the effects of multiple-access
interference is investigated for both synchronous and asynchronous systems. The
analysis shows that the chip-synchronous assumption can result in
over-estimating the error probability, and the degree of over-estimation mainly
depends on the autocorrelation function of the ultra-wideband pulse and the
signal-to-interference-plus-noise-ratio of the system. Simulations studies
support the approximate analysis.Comment: To appear in the IEEE Transactions on Signal Processin
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