Imran Shafique Ansari

A New Formula for the BER of Binary Modulations with Dual-Branch Selection over Generalized-K

Error performance is one of the main performance measures and the derivation of its closed-form expression has proved to be quite involved for certain communication systems operating over composite fading channels. In this letter, a unified closed-form expression, applicable to different binary modulation schemes, for the bit error rate of dual-branch selection diversity based systems undergoing independent but not necessarily identically distributed generalized-K fading is derived in terms of the extended generalized bivariate Meijer G-function.

Impact of Pointing Errors on the Performance of Mixed RF/FSO Dual-Hop Transmission Systems

In this work, the performance analysis of a dual-hop relay transmission system composed of asymmetric radio-frequency (RF)/free-space optical (FSO) links with pointing errors is presented. More specifically, we build on the system model presented in to derive new exact closed-form expressions for the cumulative distribution function, probability density function, moment generating function, and moments of the end-to-end signal-to-noise ratio in terms of the Meijers G function. We then capitalize on these results to offer new exact closed-form expressions for the higher-order amount of fading, average error rate for binary and M-ary modulation schemes, and the ergodic capacity, all in terms of Meijers G functions. Our new analytical results were also verified via computer-based Monte-Carlo simulation results.

On the Performance of Mixed RF/FSO Variable Gain Dual-Hop Transmission Systems with Pointing Errors

In this work, the performance analysis of a dual-hop relay transmission system composed of asymmetric radio-frequency (RF) and unified free-space optical (FSO) links subject to pointing errors is presented. These unified FSO links account for both types of detection techniques (i.e. indirect modulation/direct detection (IM/DD) as well as heterodyne detection). More specifically, we derive new exact closed-form expressions for the cumulative distribution function, probability density function, moment generating function, and moments of the end- to-end signal-to-noise ratio of these systems in terms of the Meijers G function. We then capitalize on these results to offer new exact closed-form expressions for the outage probability, higher-order amount of fading, average error rate for binary and M-ary modulation schemes, and ergodic capacity, all in terms of Meijers G functions. All our new analytical results are verified via computer-based Monte-Carlo simulations.

On the performance of hybrid RF and RF/FSO fixed gain dual-hop transmission systems

In this work, we present the performance analysis of a dual-branch transmission system composed of a direct radio frequency (RF) link and a dual-hop relay composed of asymmetric RF and free-space optical (FSO) links and compare it without having a direct RF path to see the effects of diversity on our system. The FSO link accounts for pointing errors and both types of detection techniques (i.e. indirect modulation/direct detection (IM/DD) as well as heterodyne detection). The performance is evaluated under the assumption of selection combining diversity scheme. RF links are modeled by Rayleigh fading distribution whereas the FSO link is modeled by a unified Gamma-Gamma fading distribution. Specifically, we derive new exact closed-form expressions for the cumulative distribution function, probability density function, moment generating function, and moments of the end-to-end signal-to-noise ratio of these systems in terms of the Meijers G function. We then capitalize on these results to offer new exact closed-form expressions for the outage probability, higher-order amount of fading, average error rate for binary and M-ary modulation schemes, and ergodic capacity, all in terms of Meijers G functions. All our new analytical results are also verified via computer-based Monte-Carlo simulations.

Ergodic Capacity Analysis of Free-Space Optical Links With Nonzero Boresight Pointing Errors

A unified capacity analysis of a free-space optical (FSO) link that accounts for nonzero boresight pointing errors and both types of detection techniques (i.e. intensity modulation/direct detection as well as heterodyne detection) is addressed in this work. More specifically, an exact closed-form expression for the moments of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission system is presented in terms of well-known elementary functions. Capitalizing on these new moments expressions, we present approximate and simple closed-form results for the ergodic capacity at high and low SNR regimes. All the presented results are verified via computer-based Monte-Carlo simulations.

Secrecy Outage Performance for SIMO Underlay Cognitive Radio Systems With Generalized Selection Combining Over Nakagami-m Channels

This paper considers a single-input-multiple-output underlay cognitive wiretap system over Nakagami-m channels with generalized selection combining, where confidential messages transmitted from a single-antenna transmitter to a multiple-antenna legitimate receiver are overheard by a multiple-antenna eavesdropper. Passive eavesdropping scenario is considered in this work, while the channel state information of the eavesdropping channel is not available at the secondary transmitter. We derived the closed-form expression for the exact secrecy outage probability. Simulations are conducted to validate the accuracy of our proposed analytical models.

On the Performance of Free-Space Optical Communication Systems Over Double Generalized Gamma Channel

Starting with the double generalized Gamma (GG) model to describe turbulence-induced fading in free-space optical (FSO) systems, we propose a new unified model that accounts for the impact of pointing errors and type of receiver detector. More specifically, we present unified closed-form expressions for the cumulative distribution function, the probability density function, the moment generating function, and the moments of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission system in terms of the Meijers G-function. We then use these unified expressions to evaluate performance measures such as the bit error rate, the outage probability, and the ergodic capacity of: 1) a single FSO link operating over double GG fading model; and 2) asymmetric RF-FSO dual-hop relay transmission system with fixed gain relay. Using an asymptotic expansion of the Meijers G-function at high SNR, we express all the expressions, derived earlier, in terms of elementary functions. All our analytical results are verified using computer based-Monte Carlo simulations.

On the sum of gamma random variates with application to the performance of maximal ratio combining over Nakagami-m fading channels

The probability distribution function (PDF) and cumulative density function of the sum of L independent but not necessarily identically distributed gamma variates, applicable to maximal ratio combining receiver outputs or in other words applicable to the performance analysis of diversity combining receivers operating over Nakagami-m fading channels, is presented in closed form in terms of Meijer G-function and Fox H̅-function for integer valued fading parameters and non-integer valued fading parameters, respectively. Further analysis, particularly on bit error rate via PDF-based approach, too is represented in closed form in terms of Meijer G-function and Fox H̅-function for integer-order fading parameters, and extended Fox H̅--function (Ĥ) for non-integer-order fading parameters. The proposed results complement previous results that are either evolved in closed-form, or expressed in terms of infinite sums or higher order derivatives of the fading parameter m.

New results on the sum of Gamma random variates with application to the performance of wireless communication systems over Nakagami-m fading channels†

The probability density function (PDF) and cumulative distribution function of the sum of L independent but not necessarily identically distributed Gamma variates, applicable to the output statistics of maximal ratio combining (MRC) receiver operating over Nakagami-m fading channels or in other words to the statistical analysis of the scenario where the sum of squared Nakagami-m distributions are user-of-interest, is presented in closed-form in terms of well-known Meijers G function and easily computable Foxs H-bar function for integer valued and non-integer valued m fading parameters. Further analysis, particularly on bit error rate via a PDF-based approach is also offered in closed form in terms of Meijers G function and Foxs H-bar function for integer valued fading parameters, and extended Foxs H-bar function (H-hat) for non-integer valued fading parameters. Our proposed results complement previous known results that are either expressed in terms of infinite sums, nested sums, or higher order derivatives of the fading parameter m.

Performance Analysis of Physical Layer Security Over Generalized-K Fading Channels Using a Mixture Gamma Distribution

In this letter, the secrecy performance of the classic Wyners wiretap model over generalized-K fading channels is studied. The closed-form expressions for the average secrecy capacity, secure outage probability, and the probability of strictly positive secrecy capacity are derived. The new expressions provide a unified form, which can handle several of the well-known composite fading environments as special or limiting cases. Monte-Carlo simulations are performed to verify the proposed analysis models.