Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
Due to the increasing demand of traffic, mobile networks requires flexibility to modify the area of service at any time. The use of antenna tilt is a crucial element in the design of modern networks as this element can modify the area of served cell and affects several parameters like coverage capacity or energy. The tilt of antennas automatically with remote electrical tilt (RET) is particularly relevant due to new smart networks that require the control of the system remotely. However, RET has limitations as a result of the imperfections of the design of real antennas. This is due to the fact that the whole pattern can vary for each tilt iteration.
This study proposes a system level simulation of two real antennas with similar characteristics like gain, beam width and frequency, in order to evaluate the results in terms of coverage and capacity for different degrees of tilt. The results show that remote electrical tilt improves both coverage and capacity up to 32% and 50% respectively. However the performance of both the antennas differ. For example, different sizes of networks are simulated and different degree of optimum tilt is obtained for each antenna, which is explained by the comparison of the radiation patterns. The difference between the angles of the optimum tilt for different sizes of the network also affects to the energy efficiency metrics that have been simulated. One type of antenna shows better effects when tilt is applied and the energy efficiency improves up to 13% with respect to the other antenna.
Through the comparison of the radiation pattern, it is possible to conclude which elements are the most important for different areas of coverage of the network. The high gain and the roll off of the main beam play an important role for cell edge coverage. In addition, sharp roll-off inclination and higher gain are the elements which have the strongest influence on tilt. Finally, the effect of side lobe levels on other parameters of the network is shown in this study. Lower side lobe level affects the areas closer to the base station and upper side lobe level interfere the adjacent cell. This study shows how these levels change for each tilt iteration and, thus, explains the difference in the performance of both antennas.
2015. , 70 p.