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In orthogonal frequency division multiple access(OFDMA) based femtocell networks,the co-tier interference among femto base stations(FBS) becomes important in multiuser and densely deployed environment.In order to mitigate the co-tier interference and enhance the system total throughput,this paper proposed a best effort spectrum allocation scheme based on the extension of graph theory.In the scheme,a controller was proposed to collect the channel state information(CSI)of all femtocell user equipments(FUEs) in a certain range.Then,the controller evaluated the signal-to-interference Ratio(SIR) of each FUE and determined the set of its interference neighbors.By calculating the received power matrix(RPM) among FUEs and building interference graph matrix(IGM),different spectrum resource blocks(RBs) were assigned to the users with interference relation,while users without interference relation shared the same RBs,which could increase the spectrum efficiency.Simulation results show that the proposed algorithm can significantly improve the RB usage efficiency compared with the basic graph coloring theory,and more than 80% improvement can be acquired in dense deployment scenario.Besides,the throughput of both cell edge macro user equipments(MUEs) and cell edge FUEs is guaranteed on the premise of low interference.
In orthogonal frequency division multiple access (OFDMA) based femtocell networks, the co-tier interference among femto base stations (FBS) becomes important in multiuser and densely deployed environment. In order to mitigate the co-tier interference and enhance the system total throughput, this paper proposed a best effort spectrum allocation scheme based on the extension of graph theory. The scheme, a controller was proposed to collect the channel state information (CSI) of all femtocell user equipments (FUEs) in a certain range. The controller evaluated the signal-to-interference ratio (SIR) of each FUE and determined the set of its interference neighbors.By calculating the received power matrix (RPM) among FUEs and building interference graph matrix (IGM), different spectrum resource blocks ) were assigned to the users with interference relation, while users without interference relation shared the same RBs, which could increase the spectrum efficiency. Simulation results show that the pr oposed algorithm can significantly improve the RB usage efficiency compared to the basic graph coloring theory, and more than 80% improvement can be acquired in dense deployment scenario. Besides, the throughput of both cell edge macro user equipments (MUEs) and cell edge FUEs is guaranteed on the premise of low interference.