Femtocell Resource Allocation Based On Interference Management

In celluar networks, almost 2/3 of voice calls and more than 90% of data traffic are expected to originated from indoor users, that is why it is important for cellular networks to provide high-quality indoor coverage. With the increasing demand for data rate and energy efficiency, studies focusing on femtocell system are becoming more and more popular. Kinds of interference management have been raised to deal with the co-channel interference from large-scale femtocell deployment, which improve both spectrum efficiency and energy efficiency.This thesis researches the background, development and privilege of femtocell system, describes the deloyment and access modes of femtocell networks, concludes the newest femtocell technologies, and analyzes the existing femtocell interference managing strategies.Moreover, the co-tier interference and cross-tier interference is studied in femtocell and cellular network. The graph-based femtocell spectrum reusing schemes are also studied, and based on classic dynamic channel allocation algorithms, a joint channel allocation scheme between femtocell and cellular network with macrocell QoS requirment is introduced. It is proven by simulation results that with macrocell QoS guarantee, the macro user outage is reduced drastically without causing more femtocells suffering severe interference.This thesis also proposes a joint resource allocation scheme. Firstly, a joint spectrum allocation of macrocell and femtocells is introduced based on a dynamic heuristic clustering algorithm, which effectively mitigates cross-tier interference. An optimization problem is then formed to minimize the total power consumption of FAPs under the QoS constraint both at each femto user and each macro user, A close form of optimized power solution of FAPs is derived to solve the optimization problem with subgradient method. Simulation results show that the system interference and the outage of femtocells are drastically decreased with the proposed algorithm, therefore, the energy efficiency of femtocells is enhaunced by the proposed algorithm.This thesis models the co-channel interference based on stochastic geometry theory in the network system while femtocell and macrocell sharing the whole spectrum, and derives the outage probability for both femtocell and macrocell given certain target SINRs. To guarantee the femtocell outage and minimize the transmitting power of femto BS, a receiving-signal-based power control scheme is introduced for femtocells. By applying this power control scheme, both the co-tier interference among femtocells and the cross-tier interference between femtocells and macrocell are well-controlled. Under the power control scheme, the highest femtocell density is calculated assuring the QoS for femtocells in the Macro Base Station’s coverage without causing severe interference to macro users.