Spectrum sharing cognitive radio with transmit antenna selection and maximal ratio combining is analyzed, under the peak interference constraint at the primary user receiver. The ergodic capacity of the secondary link with an arbitrary number of transmit and receive antennas is derived, for the case of Rayleigh fading and transmit power constraint. For the case of unlimited transmit power, the closed-form expression for the capacity is derived. The correctness of analytical results is verified by using an independent simulation model.

Spectrum sharing cognitive radio with multiple antennas at the primary user receiver and maximal ratio combining applied at the secondary user receiver is analyzed. The closed-form expression is derived for the ergodic capacity of the secondary link with an arbitrary number of receive antennas and Nakagami fading distribution. Analytical expressions are derived for both cases of peak and average interference constraint at the primary user receiver. The correctness of analytical results is verified by using an independent simulation model.

A hybrid satellite–terrestrial relay network is a simple and flexible solution that can be used to improve the performance of land mobile satellite systems, where the communication links between satellite and mobile terrestrial users can be unstable due to the multipath effect, obstacles, as well as the additional atmospheric losses. Motivated by these facts, in this paper, we analyze a system where the satellite–terrestrial links undergo shadowed Rice fading, and, following this, terrestrial relay applies the selection relaying protocol and forwards the information to the final destination using the communication link subjected to Nakagami-m fading. For the considered relaying protocol, we derive the exact closed-form expressions for the outage probability, outage capacity, and ergodic capacity, presented in polynomial–exponential form for the integer-valued fading parameters. The presented numerical results illustrate the usefulness of the selection relaying for various propagation scenarios and system geometry parameters. The obtained analytical results are corroborated by an independent simulation method, based on the originally developed fading simulator.

In this paper, the exact closed-form expressions for the level crossing rate (LCR) and the temporal autocorrelation function (ACF) of the signal-to-noise ratio (SNR), at the output of the spatially correlated multiple-input-multiple-output (MIMO) systems with orthogonal space-time block codes (OSTBCs), are derived. The expressions are derived for the case of an arbitrary number of Rayleigh distributed branches and any form of the covariance matrix. The derived identities can be applied to isotropic and nonisotropic scattering environments, and they are validated by Monte Carlo simulations.

The performance analysis of an energy constrained Internet of Things (IoT) system with unmanned aerial vehicle (UAV) is provided in this paper. In the considered system, a power beacon is used for the energy supply of a sensor node that has no other power sources, while the UAV is used for the collection of sensor data. The outage and capacity performances are analyzed under the assumption of a Nakagami-m fading environment, for the case when the power and information transfer are performed based on the time-switching protocol and the UAV is randomly positioned at a certain height. Based on the provided analysis we derive the exact closed-form expressions for the outage probability, the outage capacity and the ergodic capacity of the power beacon assisted IoT system. The analytical results are confirmed using an independent simulation method. The performed analysis demonstrates the impact of various system and channel parameters on system performances.