A novel spectrum allocation scheme in femtocell networks using improved graph theory

In  this  paper,  we  propose  a  novel  spectrum  allocation  scheme  by  using  graph  coloring  and  taking  QoS  thresholds  into  account. The goal of our proposed method is to reduce interference among femtocells deployed densely and improve spectral  efficiency  after  reaching  user’s  QoS  threshold.  We  design  an  interference-based  graph  model  by  detecting  terminals’ transmit power between femtocell stations and classifying the interference levels according to the coloring algorithm. Spectrum resource is allocated based on the QoS requirement of each user in a centralized way. Unlike other spectrum allocation  method  using  graph theory,  we  take  many  significant factors into account in this  paper in  order  to  attain a more practical spectrum optimization solution. The simulation results show that when the scheme is deployed in femtocells  with  high  density,  it  can  effectively  reduce  the  interference  within  same  layer  and  improve  system  capacity  along with spectrum efficiency.