Since the advent of radio communications, radio spectrum has been increasingly getting crowded with different kinds of applications. Different radio communications systems have been developed for various purposes and multiple actors became interested in using these systems at the same time and space. Such situation inevitably led to the point when practically entire usable radio spectrum became occupied by different actors. To alleviate this problem, Dynamic Spectrum (Re)Allocation (DSA) has been proposed, which is a branch of frequency spectrum management that aims to improve spectrum usage efficiency and end-user experience by introducing more flexibility to spectrum usage. This thesis aims to provide additional insight into DSA applicability and effectiveness in a typical realistic cellular network, in intra-operator scenario, taking into account 2G and 4G radio technologies, with the aim of improving 4G performance without adverse impact to 2G. We use realistic dynamic system level simulations to assess DSA performance in the selected cellular network areas that can be classified as urban, suburban and rural. Our simulation results show that DSA is capable of improving 4G throughput without adverse impact to 2G performance in all simulated areas. Among the simulated areas, urban area benefits from DSA most, as significant throughput gains for 4G are achieved without adverse impact to 2G performance, while simulations show that spectrum refarming is clearly not an option for this type of area. However, throughput gains for 4G in urban area are limited during the busy-hours. Suburban and rural areas indicate benefits from DSA too, however the difference between DSA and spectrum refarming in these areas is diminishing. Hence, with reasonable half-rate timeslot tolerance for 2G voice calls, spectrum refarming could be an option in the simulated suburban and rural areas.