Adaptive resource management in femtocell coexisted mobile communication systems

Abstract

Mobile communication system has been evolving in order to achieve improvement in 3C; $\It{Capacity}$, $\It{Coverage}$, and $\It{Cost }$. In this circumstance, many recent researches focus on integrating femtocell concept into mobile communication system, because a femtocell system can surely bring significant improvement on 3C. Femto BSs can be cheaply manufactured like WiFi Access Points (APs) and keep connectivity to a core network with no deployment cost. In addition, the femto BSs generally serve the users who are very close to them and path loss of transmitters` signal in the femtocell system is much smaller compared to that in the mobile communication system, which implies that link capacity is likely to be very higher in case of the femtocell system. However, there are many issues which should be solved in order to utilize femtocell system in mobile communication system. Especially, it is important to solve an issue of capacity improvement, on which we mainly focus in this thesis. In order to improve system capacity, we firstly propose a simple resource allocation scheme when femto cells are in a macro cell and are sufficiently far each other so that interference effect from femto cells can be ignored. We compare a single codeword transmission scheme with a multiple codeword transmission scheme and figure out that the single codeword transmission scheme is suitable for the femtocell system. And then, we propose a heuristic scheme for allocating resources when single codeword transmission is performed in multi-user environment. Throughout the derivation, we use a new concept called $\It{mutual information}$, which makes it easy to analyze packet error rate(PER). Secondly, we derive Media Access Control(MAC) overhead due to transmission of scheduling information which causes to degrade system performance. MAC overhead due to transmission of scheduling information is inverse-proportional to size of a traffic packet and data rate of scheduling informati...