Mobile and wireless networks have recently seen a remarkable development at the global level. This applies to previous and current generations, which have seen the development of telecommunications networks mainly in GSM, 2G, UMTS and 3G networks. Evolutions are continuing everywhere of specialized networks such as sensors, smart tags, and telecom networks. They now see contend solutions which coming from various horizons: classic telecom world with HSDPA, world of wireless networks with WiMAX even in the world of satellite and terrestrial broadcasting (DVB-T, DVB-H, DVB-S). The fourth-generation (4G) wireless network is truly a turning point in the proliferation and disparity of existing solutions. The main parameters of the 4G network that have made this network the best and the most expensive are its very high bandwidth used, the much lower latency than in the 3G network, a high bandwidth, a flexible frequency band, and a interoperability with other networks so this parameter gives the choice to the user for their use within the 4G. This paper presents an analysis of the performance of 4G networks and its different Quality of Service. A simulation demonstrating the performance of 4 th generation cellular networks is presented. Good simulation and good results were obtained using the NetSim simulator.