In the last few years we have witnessed incredible growth in demand for mobile broadband services, the requirements for the growing mobile data speeds and providing large capacities due to swift rise in the number of mobile devices connected to the Internet. The thesis consists of a comprehensive analysis of the operation of advanced LTE systems which will help us in the future to satisfy the above listed needs. It presents in details one of the most important functionality called carrier aggregation that allows the aggregation of multiple different frequency bands, and thereby effective use of a very wide frequency spectrum. Due to the complexity the functionality of carrier aggregation is involved in the LTE release 10 onwards with a purpose to efficiently use of fragmented spectrum and it is one of the most important techniques which together with other techniques provide the evolution of mobile networks in the long term.
Expected data rates of real 4G system requires in the future speeds reaching up to 1 Gbit / s over a radio access network. These requirements can be achieved only by using large transmission bandwidth and high spectral efficiency of the system. Long Term Evolution Advanced (LTE-A) reaches and even exceeds previously mentioned requirements for factor 3 by using the techniques of carrier aggregation, which will in the future enable the aggregation of up to five carriers of common bandwidth of 100 MHz. In the LTE-A system the high spectral efficiency is achieved by using advanced MIMO techniques. The main objective of the thesis is the insight into the operation of carrier aggregation and a detailed analysis of the actual usefulness of advanced LTE systems to the end user in different environments (indoor and outdoor). Due to wide fragmentation of spectrum we see in practice combining of low and high frequency bands in different networks, and because of the nature of the frequency spectrum we see different indoor signal penetration. Advantages and disadvantages of combining carriers outside and inside of the buildings are also presented with measurements and simulations. These have shown that the use of carrier aggregation is limited in different areas; however, it still presents a great advantage compared to the use of a single carrier. In addition, we demonstrated with field measurements in a commercial network the practical peak data rates, that users can reach in case of combining two 20 MHz carriers. With the results of the measurements we have managed to prove that every user using proper terminal and if network supports this feature can reach the theoretical performance of these systems.