Interference Management In LTE Femtocell System

ABSTRACT

LTE-Advanced is the winning technology approved by International Telecommunications Union (ITU) as a 4G mobile communication system. It is an evolution of LTE and backward compatible with LTE because they both use the same air-interface technologies such as OFDMA and MIMO. To meet the challenge of growing bandwidth demand by indoor users, femtocell is the technology suggested in LTE-Advanced. Users have the capability of expanding their capacity by buying and self installing these mini base stations in their office/home. They operate in the licensed spectrum as the traditional outdoor base stations (macrocell) installed by mobile operators. This introduces great cross-layer (femtocell-macrocell) interference. Distance between femtocell and macrocell and split spectrum between femtocell and macrocell can be studied to mitigate interference. This dissertation investigates the mentioned distance with different levels of spectrum splitting on throughput so as determine if an algorithm that matches distance to level of split spectrum can be designed. The investigation was done using a simulator. LTE-Sim simulator was used to implement different scenarios which portray the environments to be tested. Contrary to the researcher’s initial expectation, it was shown that in an environment with both macrocell users and femtocell users, the network throughput is independent on distance. On the other hand, in the scenario where macrocell users were ignored, there was a clear relationship between distance, splitting of spectrum and network throughput. It was shown that when the femtocell is given 20% of the bandwidth, it has the highest throughput for all simulated distances.