Interference Coordination In Heterogeneous Cellular Networks

In the era of mobile internet, wireless data trafc from various mobile terminalshas skyrocketed in the recent years. It has been difcult for traditional cellular networkand physical technologies to cater for this huge demand for capacity. This motivatedthe development of heterogeneous network which combines macro base station andfemto base station. Such a new network topology has brought much transformation forthe traditional cellular network, along with which many challenges also surfaces. Theinterference management in Het-Net is one of the headaches.Firstly, for the co-layer interference problem in Het-Net, a hypergraph-based fre-quency reuse method is proposed. In the frst step, the interference scenario in densefemtocell network is modelled by a hypergraph by taking into account the cumula-tive interference from multiple base station to the users in a base station. Then witha heuristic coloring of the interference hypergraph and proportional frequency sub-bands allocation, spectrum is reused efciently in the whole network. It is shown inour simulation results that the Signal-to-Interference-plus-Noise-Ratio(SINR) of usersis improved and the throughput per femtocell is enhanced signifcantly by using theproposed scheme compared with fxed spectrum assignment method and conventionalfrequency reuse methods.Secondly, for the problem of femtocell downlink interference to macro-cell users,we propose a fexible outage-threshold based interference coordination algorithm. Inthe frst step, all the base stations take a proportional fair schedule for the resource al-location among their served users. Secondly, the macro-user that has unsatisfed SINRshould be protected from interference coordination. This is implemented by letting thefemto BSs in the adjacent femtocell list of the user be silent on the corresponding sub-channel according their interference power until the SINR of the user is well satisfed. Oursimulationresultshowsthat, withtheproposedmethodthemacro-celluserscanbeprevented from the serious cross-tier interference and can have low outage probabilitywithout much impairment of the throughput on the femtocell side.