With the continuous development of wireless communication technology and vehicle industry VANET as of recent is one of the most research niches. VANET is a technology that makes use of motion vehicles as a node in a network for the creation of a mobile network. Although there is a close characteristic between VANET and MANET (Mobile Ad-Hoc Networks), VANET has special features that differentiate it from MANET. VANET offers a vehicle to vehicle and vehicle to infrastructure communication. VANET also make sure there is no break of routing path before the transmission end. VANET is a challenging domain that has created a platform for many applications to find their place. Enough time is still needed for the implementation of large-scale practical though this field has been under rigorous study for over two decades. The possibility of having vehicular connectivity has been triggered by the ever-increasing wireless connectivity and computational ability of recent vehicles. Many potential vehicular network applications have been proposed in different niches like information, safety, entertainment and traffic infrastructure management. These applications in these aforementioned applications require available wireless medium utilization of both new and existing wireless technologies. VANET comprises of two technologies known as WiMAX and Wi-Fi. The goal of this survey was to ascertain the best technology among the two technologies. In other to achieve this goal, a thorough investigation was carried out together with an evaluation on V2V2I VANET where Wi-Fi was used for amid vehicle (V2V) interaction and WiMAX used for vehicle to infrastructure (V2I) interaction. This survey begins with the VANET architecture, then discusses the characteristics and challenges of VANET, applications, before ending with a comparison of the two technologies that made of VANET, the experimental approach used, future perspectives, result and conclusion.

The long-distance high data rate transmission is accompanied by many transmission defects, which reduce the performance of optical communication systems. Therefore, due to the need to increase data capacity for the end user, signal regeneration techniques were used to mitigate these non-linear defects in the electric or optical field. Several techniques used to modify the optical signal, which is the possible solution to reduce the limit of non-linear transmission defects, especially before converting the signal from the optical field to the electric field. Since most of the techniques used to reduce the attenuation in the optical signal do not have the ability to reduce the error rate to reach a bit error rate (BER) less than 10-10 with a transmission capacity less than -10dBm. In this paper, the performance evaluation of DPSK has been validated for its adequate use in transmission systems. Nevertheless, the performance of the DPSK optical system was assessed to rely on a different coding format such as: Return to Zero (RZ) & Non-Return to Zero (NRZ-DPSK). The system is designed to withstand high data rate on long-distance optical transmission systems. The system investigated was simulated with OptiSystemTM 13.0 commercial software. The investigated system demonstrated the ability to mitigate nonlinear impairments from the noisy optical DPSK system with high bit-error rate (BER) improvement at low power transmission. Optical DPSK demonstrates the ability to send high-rate data transmission systems for use in the next generation of optical networks.