Gulzaib Rafiq

On the Statistical Properties of the Capacity of Spatially Correlated Nakagami-M MIMO Channels

This paper studies the statistical properties of the channel capacity of spatially correlated Nakagami-m multiple- input multiple-output (MIMO) channels. We have derived closed- form expressions for the probability density function (PDF), the cumulative distribution function (CDF), the level-crossing rate (LCR), and the average duration of fades (ADF) of the lower bound on the channel capacity. In order to study the impact of the spatial correlation on the channel capacity, the analysis of the statistical properties of the channel capacity is carried out for different receiver antenna spacings. It is observed that the antenna spacing has a significant influence on the spread and maximum value of the PDF and LCR. The proposed method can be employed to study the statistical properties of the capacity of MIMO channels in different fading environments. The correctness of the analytical expressions is confirmed by simulations.

What?s New in Intelligent Transportation Systems?: An Overview of European Projects and Initiatives

This article is a taxonomy of recent intelligent transportation systems (ITS) initiatives/projects in Europe, and it covers nearly all of the main segments of the transportation sector. The purpose is to appraise the milestones that have been reached so far in the area of ITS. Furthermore, this article will help in identifying directions for future research. By highlighting the potential advantages users get through deployed ITS solutions, this article stimulates the interest of users and relevant stakeholders in the uptake of this technology. Finally, it will also serve as a useful resource for those agents of the scientific community who are interested in taking part in the European Commissions (ECs) funded projects related to ITS.

The Influence of Spatial Correlation and Severity of Fading on the Statistical Properties of the Capacity of OSTBC Nakagami-m MIMO Channels

This paper deals with the analysis of statistical prop- erties of the capacity of spatially uncorrelated orthogonal space- time block coded (OSTBC) Nakagami-m multiple-input multiple- output (MIMO) channels. We have derived exact closed-form expressions for the probability density function (PDF), cumula- tive distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the channel capacity. We have also investigated the statistical properties of the approximated capacity of spatially correlated OSTBC Nakagami-m MIMO channels. The results are studied for different values of the fading parameter m, corresponding to different fading conditions. It is observed that an increase in the MIMO dimension 1 or a decrease in the severity of fading increases the mean channel capacity. While, a significant decrease in the mean channel capacity is observed with an increase in the spatial correlation. The correctness of theoretical results is confirmed by simulations.

Sparse multipath channels: Modelling, analysis, and simulation

A sparse multipath channel is characterized by a small number of randomly distributed scatterers. This study proposes a methodology for the modelling of sparse multipath channels. The new methodology is then used to develop a sparse narrowband multipath channel model by applying the sum-of-cisoids (SOC) principle. The statistical properties of the presented sparse SOC multipath channel model are studied. Analytical expressions are derived for the mean value, variance, autocorrelation function (ACF) and cross-correlation function (CCF) of the complex channel gain, as well as for the probability density function (PDF) of the envelope. Our study shows that mobile radio channels behave in sparse scattering environments completely different from what is known from innumerable studies assuming rich scattering. The derived analytical expressions unfold their full significance if the number of multipath components is small and the path gains are unbalanced, which prevents invoking the central limit theorem.

A Study of the Influence of Shadowing on the Statistical Properties of the Capacity of Mobile Radio Channels

This paper studies the influence of shadowing on the statistical properties of the channel capacity. The problem is addressed by using a Suzuki process as an appropriate statistical channel model for land mobile terrestrial channels. Using this model, exact solutions for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the channel capacity are derived. The results are studied for different levels of shadowing, corresponding to different terrestrial environments. It is observed that the shadowing effect has a significant influence on the variance and the maximum value of the PDF and LCR of the channel capacity, but it has almost no impact on the mean capacity of the channel. The correctness of the theoretical results is confirmed by simulation using a stochastic channel simulator based on the sum-of-sinusoids principle.

Statistical properties of the capacity of Rice channels with MRC and EGC

In this paper, we have studied the statistical properties of the capacity of Rice channels for both maximal ratio combining (MRC) and equal gain combining (EGC) schemes. We have analyzed the effect of the number of diversity branches and the amplitude of the line-of-sight (LOS) components in the diversity branches on the statistics of the channel capacity. Specifically, we have derived analytical expressions for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the capacity of Rice channels when using MRC and EGC. It is observed that if the number of diversity branches or the amplitude of the LOS components increases, then the mean channel capacity increases, while the spread and the ADF of the channel capacity decreases. The presented results are very helpful for wireless communication system designers to optimize the receiver design for the case when spatial diversity combining is employed.

On the statistical properties of the capacity of amplify-and-forward channels under LOS conditions

Amplify-and-forward channels in cooperative networks provide a promising improvement in the network coverage and system throughput. Under line-of-sight (LOS) propagation conditions in such cooperative networks, the overall fading channel can be modeled by a double Rice process. In this article, we have studied the statistical properties of the capacity of double Rice fading channels. We have derived the analytical expressions for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the channel capacity. The obtained results are studied for different values of the amplitudes of the LOS components in the two links of double Rice fading channels. It has been observed that the statistics of the capacity of double Rice fading channels are quite different from those of double Rayleigh and classical Rice fading channels. Moreover, the presence of an LOS component in any of the two links increases the mean channel capacity and the LCR of the channel capacity. The validity of the theoretical results is confirmed by simulations. The results presented in this article can be very useful for communication system designers to optimize the performance of cooperative networks in wireless communication systems.

The Influence of the Severity of Fading and Shadowing on the Statistical Properties of the Capacity of Nakagami-Lognormal Channels

This paper deals with the study of the statistical properties of the capacity of Nakagami-lognormal (NLN) channels for various fading environments. Specifically, the impact of shadowing and the severity of fading on the channel capacity is investigated. We have derived analytical expressions for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the channel capacity. These results are analyzed for different levels of shadowing and for various fading conditions, corresponding to different terrestrial environments. It is observed that the severity of fading and shadowing has a significant influence on the spread and the maximum value of the PDF and LCR of the channel capacity. Moreover, it is also observed that if the fading gets less severe as compared to the Rayleigh fading, the mean channel capacity increases. However, the shadowing effect has no impact on the mean channel capacity. The validity of all analytical results is confirmed by simulations.

The influence of severity of fading on the statistical properties of the capacity of Nakagami-m channels with MRC and EGC

In this article, we have studied the statistical properties of the capacity of Nakagami-m channels when spatial diversity combining, such as maximal ratio combining (MRC) and equal gain combining (EGC), is employed at the receiver. The presented results provide insight into the statistical properties of the channel capacity under a wide range of fading conditions in wireless links using L-branch diversity combining techniques. We have derived closed-form analytical expressions for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the channel capacity. The statistical properties of the capacity are studied for different values of the number of diversity branches and for different severity levels of fading. The analytical results are verified with the help of simulations. It is observed that increasing the number of diversity branches increases the mean channel capacity, while the variance and ADF of the channel capacity decreases. Moreover, systems in which the fading in diversity branches is less severe (as compared to Rayleigh fading) have a higher mean channel capacity. The presented results are very helpful to optimize the design of the receiver of wireless communication systems that employ spatial diversity combining.

Statistical properties of the capacity of multipath fading channels

It is well known that a frequency-nonselective multipath fading channel can be modeled by a sum of complex sinusoids, also called sum-of-cisoids (SOC). By using the SOC, we can efficiently model the scattered component of the received signal in non-isotropic scattering environments. Such SOC-based multipath channel models provide the flexibility of having correlated in-phase and quadrature phase components of the received signal. This paper presents the derivation and analysis of the statistical properties of the capacity of multipath fading channels under LOS conditions. As an appropriate stochastic model for the multipath fading channel, we have adopted the SOC model. We have derived the exact analytical expressions for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the channel capacity. The statistical behavior of the channel capacity is studied for different values of the number of multipaths (cisoids) in the SOC model and the results are compared with the reference model which can be obtained by using an infinite number of cisoids. It is shown that the SOC model with ten cisoids produces results very close to the reference model. The validity of all the theoretical expressions is tested with the help of simulations.