As presented in this master thesis, the LTE is unavoidable in taking measures towards the satisfaction of mobile network users. To describe its necessity and all the requirements it is supposed to comply with, a thorough layout of its architecture and functionalities has been presented through multiple sections. The first section presented an introduction to LTE principles and ideas. By doing so a standpoint has been set for a better understanding of further descriptions and elaborations. It also paves the path towards the second section, which is the LTE architecture. The second section, which includes both the LTE architecture and its behavioral patterns, serves the purpose of setting a technical background for the lower levels of LTE services. This way the main point of this theses is brought closer to the scope and is made more understandable. The third section describes the IMS, which is the environment in which the practical part of this master thesis is tested. It consists of three main entities: the CSCFs, the ASs and the HSS. The latter is the main focus of this thesis and is as such described in more detail. The fourth section describes the Diameter protocol, which enables the communication between the AS and the HSS, which is the main point of this thesis. It provides all necessary services for user profile handling, such as updates, subscriptions and retrievals. It is also used in the testing part of the thesis. The final section describes the testing result of the Diameter traffic load analysis. Here the results are displayed along with the expected outcomes. There were two testing environments in which the testing was done: the ideal simulator and the industrial real-life network. Both of them provided different results based on the test scenarios. Those included different test parameters in combination with different traffic distributions. In the end a conclusion is presented to provide the final outcome of the thesis. In this case there were little unexpected measurements and most of the results matched up to the expectations.