| In recent years, mobile communication networks have more demand for high-speed data services, while the study revealed that the majority of wireless data services occur in the indoor environment. How to improve spectrum efficiency and indoor coverage to provide high-speed data services have gotten more attention. Although the femtocell can be a good solution to the indoor coverage and the demand for high-speed data services, but it also brings interference problems to the legacy macrocell network, which affects the overall network performance.To solve the interference problems between femtocell and macrocell, 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) and Femto Forum proposed interference coordination techniques based on femtcell heterogeneous network. Existing interference coordination technologies are power domain control, frequency domain allocation and time domain control, this paper focuses on the frequency domain interference coordination. Current frequency domain solutions are orthogonal frequency allocation (OFA) and partial orthogonal. These schemes can solve the cross-tier interference problems between femtocell and macrocell, but they ignore the ownership change of femtocell base stations, resulting in network topology unpredictable and changeable. Thus, it will cause the low system spectrum efficiency.After the summary of existing frequency domain interference coordination schemes, this paper proposed the downlink interference coordination scheme based on hybrid resource allocation (HRA). Through interference information measurements of macrocell users, the interference source and interference information of around femtocell can be detected by femtocell base stations. Combined with system characteristic of OFDM (Orthogonal Frequency Division Multiplexing), the femtocells make reasonable adjustments of available resources in unit of sub-channel. The hybrid resource allocation scheme can mitigate downlink cross-tier interference from randomly deployed femtocells, also achieve the goal of system spectrum efficiency.This system also designed the simulation platform of LTE femtocell interference coordination technique, compared existing frequency-domain coordination schemes with the proposed scheme. Simulation results show that the HRA scheme can improve the channel quality of macrocell user, and increase the spectrum efficiency of heterogeneous network. |
