The Third Generation Partnership Project (3GPP) has recently announced its Release 16, which introduces advanced functionalities to support the cellular vehicle to everything (C-V2X) technology. C-V2X allows direct communication between vehicles through the sidelink operation. This appears as an option to DSRC technologies; both are key wireless technologies that play a vital role in implementing and deploying advanced driving applications. This paper presents a thorough review of the available open-source frameworks intended for the performance evaluation of C-V2X protocols and V2X applications. For this, we consider validated OMNeT++-based simulation libraries and frameworks: SimuLTE, OpenCV2X, Artery-C, 5G-Sim-V2I/N, and Simu5G. We focus on the different frameworks' support regarding advanced V2X communications on 5G mobile networks.

Most of the classic fading variables can be obtained through Nakagami-m distribution and the sum of them has a pivotal role in the analytical performance evaluation of many practical wireless applications. However, the exact probability density function (PDF) of this sum of fading variables could be difficult to obtain. In this paper, we investigate the performance of the Maximum Likelihood Estimation to find a simple accurate approximation to the probability density function of the sum of Nakagami-m random variables. This approach provides expressions that can be used straightforwardly in the performance analysis of a number of wireless communication systems including multibranch receivers such as Maximal Ratio Combining and Equal Gain Combining, for which we present the application of the proposed framework. Numerical simulations show that our proposed method outperforms the well- known approach based on moment-matching method in terms of accuracy and simplicity. Moreover, the easiness of our proposal makes it suitable to be incorporated in network simulators to model and configure several wireless environments without additional computational complexity.

The use of light-emitting diodes (LEDs) for ambient illumination leads to visible light communications (VLC) as a promising technology for providing both constant lighting and high-speed wireless services in indoor environments. Since multiple LED sources can be transmitted to several users, this scenario naturally forms a multiple-user multiple-input single-output system. In this sense, transmit precoding (TPC) schemes based on channel state information at the transmitter (CSIT) originally devised for radio-frequency (RF) systems have been proposed for their implementation in VLC. However, beyond providing CSIT or the need for cooperation among transmitters, which also result challenging in RF systems, there are several constraints such as the non-negativity of the transmitted signal or providing constant illumination that hamper the performance of TPC schemes in VLC. Considering these constraints, this paper explores the use of blind interference alignment (BIA) for achieving multiplexing gain without CSIT or cooperation among LED lights. To do that, we devise the concept of reconfigurable photodetector that allows switching among distinct and linearly independent channel responses. Simulation results show that the use of BIA in VLC systems schemes based on the proposed reconfigurable photodetector results suitable for VLC systems.