Asymptotic Mutual Information Statistics of Separately-Correlated Rician Fading MIMO Channels

Precise characterization of the mutual information of MIMO systems is required to assess the throughput of wireless communication channels in the presence of Rician fading and spatial correlation. Here, we present an asymptotic approach allowing to approximate the distribution of the mutual information as a Gaussian distribution in order to provide both the average achievable rate and the outage probability. More precisely, the mean and variance of the mutual information of the separatelycorrelated Rician fading MIMO channel are derived when the number of transmit and receive antennas grows asymptotically large and their ratio approaches a finite constant. The derivation is based on the replica method, an asymptotic technique widely used in theoretical physics and, more recently, in the performance analysis of communication (CDMA and MIMO) systems. The replica method allows to analyze very difficult system cases in a comparatively simple way though some authors pointed out that its assumptions are not always rigorous. Being aware of this, we underline the key assumptions made in this setting, quite similar to the assumptions made in the technical literature using the replica method in their asymptotic analyses. As far as concerns the convergence of the mutual information to the Gaussian distribution, it is shown that it holds under some mild technical conditions, which are tantamount to assuming that the spatial correlation structure has no asymptotically dominant eigenmodes. The accuracy of the asymptotic approach is assessed by providing a sizeable number of numerical results. It is shown that the approximation is very accurate in a wide variety of system settings even when the number of transmit and receive antennas is as small as a few units.Comment: - submitted to the IEEE Transactions on Information Theory on Nov. 19, 2006 - revised and submitted to the IEEE Transactions on Information Theory on Dec. 19, 200

Information Rate Optimization for Joint Relay and Link in Non-Regenerative MIMO Channels

The optimization of the Relay Transform Matrix (RTM) in a two-hop relay network with an average relay power constraint and perfect channel state information at the relay is addressed in this paper. The study considers the most general case in terms of number of transmit and receive antennas at the source, relay, and destination, with arbitrary correlation of the received noise at all terminals. The optimization problem is reduced to a manageable convex form, which is solved by linear algebra transformation and the KKT equations. A parametric solution is given, which yields the power constraint and the capacity achieved with uncorrelated transmitted data. The solution is shown to be amenable to a \emph{water-filling-like} algorithmic implementation, which extends earlier literature results addressing the case without the direct link. Simulation results are reported concerning a Rayleigh relay network where, in particular, the role of the direct link SNR is precisely assessed.Comment: 17 pages, 4 figures, submitted to IEEE ISIT 202

A Lower Bound to the Receiver Operating Characteristic of a Cognitive Radio Network

Cooperative cognitive radio networks are investigated by using an information-theoretic approach. This approach consists of interpreting the decision process carried out at the fusion center as a binary (asymmetric) channel, whose input is the presence of a primary signal and output is the fusion center decision itself. The error probabilities of this channel are the false-alarm and missed-detection probabilities. After calculating the mutual information between the binary random variable representing the primary signal presence and the set of sensor (or secondary user) output samples, we apply the data-processing inequality to derive a lower bound to the receiver operating characteristic. This basic idea is developed through the paper in order to consider the cases of full channel and signal knowledge and of knowledge in probability distribution. The advantage of this approach is that the ROC lower bound derived is independent of the particular type of spectrum detection algorithm and fusion rule considered. Then, it can be used as a benchmark for existing practical systems.Comment: submitted to IEEE Transactions on Information Theory, July 201

On the Convergence of Multipath Fading Channel Gains to the Rayleigh Distribution

The gain of a multipath propagation scenario is addressed by this work and it is shown that the convergence to the Rayleigh distribution depends on some conditions on the path gains, which are not always satisfied. These conditions confirm the convergence to the Rayleigh distribution for some well known scenarios. However, counter-examples are also exhibited where this convergence does not hold. Furthermore, the role of the Central Limit Theorem (often advocated in the literature to prove convergence to the Rayleigh distribution) is critically discussed by showing that the Lindeberg condition may not hold. Finally, it is shown that the amplitude and phase of the asymptotic gain are independent and the phase is uniformly distributed over [0, 2π)

Fair Power Allocation Policies for Power-Domain Non-Orthogonal Multiple Access Transmission With Complete or Limited Successive Interference Cancellation

Power-Domain Non-Orthogonal Multiple Access (NOMA) transmission has been addressed in this paper with a proportional fairness optimization criterion (which includes MAX-MIN fairness as a special case) and an arbitrary number of users. The optimization of the power allocation coefficients required to achieve the optimum proportional fairness objective leads to a nonconvex optimization problem, which is generally hard to solve and may lead to multiple local optima. However, a simple optimality condition is characterized in the paper, leading to the solution of a nonlinear equation in a single variable. This equation reduces to polynomial form in the case of MAX-MIN fairness. Departing from the complete Successive Interference Cancellation (SIC) paradigm, typical of NOMA systems, a limited SIC technique is discussed and the relevant power allocation coefficients are obtained with the same optimization criterion. This approach eases the implementation of downlink NOMA when a large number of low-complexity hand-held terminals cannot sustain the computationally intensive task of complete SIC, at the cost of reduced their achievable rates. Numerical results are presented to illustrate the impact of complete and limited SIC, with power allocation optimization and two proportional fairness criteria. Among these results, the sum-rate loss due to proportional fairness and the impact of limited SIC on the system performance are illustrated

Diversity-Multiplexing Tradeoff of Multi-Layer Scattering MIMO Channels

Multi-layer (or multi-cluster) scattering Multiple-Input Multiple-Output (MIMO) channels are considered in the framework of the diversity-multiplexing tradeoff (DMT). This MIMO channel model finds application in indoor networks, typical of 5G architectures, in which the signal propagates from the transmitter to the receiver through the walls and floors of a building (represented by scattering layers). These results extend the seminal work by Zheng and Tse from the independent identically distributed (iid) Rayleigh fading MIMO channel to a channel matrix which is the product of iid Rayleigh fading matrix components. It is worth noting that the resulting product channel matrix elements are not independent. It is shown that the presence of multiple scattering layers eventually degrades the DMT performance of a MIMO channel by an amount depending only on the least three dimensions of the matrices characterizing the product channel matrix

On the Outage Capacity of Orthogonal Space-time Block Codes Over Multi-cluster Scattering MIMO Channels

Multiple cluster scattering MIMO channel is a useful model for pico-cellular MIMO networks. In this paper, orthogonal space-time block coded transmission over such a channel is considered, where the effective channel equals the product of n complex Gaussian matrices. A simple and accurate closed-form approximation to the channel outage capacity has been derived in this setting. The result is valid for an arbitrary number of clusters n-1 of scatterers and an arbitrary antenna configuration. Numerical results are provided to study the relative outage performance between the multi-cluster and the Rayleigh-fading MIMO channels for which n=1.Comment: Added references; changes made in Section 3-

On jamming detection methods for satellite Internet of Things networks

Despite the fast growth of machine-type communications via satellite, the vulnerability of such networks to intentional interference and malicious jamming attacks is a raising concern. Specifically, in this paper, we address a class of jamming attacks in which the adversary uses the underlying knowledge of the satellite physical and access protocol to increase the jamming impact. In particular, we focused on a type of camouflage jamming attack (using publicly known preamble) to deceive the receiver, which rapidly leads to poor performance. Compared to conventional constant jamming attacks, these jamming strategies are known to be more effective and potentially more harmful to the targeted communication network. We analyze methods to detect such jamming attacks and provide examples of jamming detection techniques for the satellite Internet of Things (IoT) networks. Results indicate the effective performance of the jamming detection techniques for a variety of representative system parameters. More specifically, we introduce a simple (counting) jamming detection method along with numerical results for realistic system parameters, which confirms system design vulnerability as well as how the jammer may improve her strategy

Random Matrix Products in Wireless (Multiantenna) Sytems

Modeling a multiantenna wireless channel via a product of independent random matrices captures the main geometrical and electromagnetic features of the communication link. Upon a proper tuning of the various parameters (e.g. marginal distribution of each matrix entry, size of each matrix factor, etc.) the product model, early introduced by Mu ̈ller [1], is suitable to model different scenarios, across several generations of wireless systems. Among the various applications of random matrix theory in the performance analysis of wireless systems represented by product models, we focus hereinafter on a finite-blocklength setting. Specifically, we evaluate the so-called channel dispersion, a metric useful to determine the impact of channel dynamics and antenna selection rules on the communication rate, for an isotropic (i.e. unitarily invariant in law) channel. Then, we provide the statistics of the mutual information corresponding to non-isotropic product channels, paving the way to the characterization of the dispersion in more realistic scenarios