A study on RAT selection algorithms in combined UMTS/GSM networks

The future mobile network will be a heterogeneous system, which integrates different Radio Access Technologies (RATs). A major challenge arising in this heterogeneous network architecture is the radio resource management (RRM) strategy. Common RRM (CRRM) was proposed to jointly manage radio resources among different RATs in an optimized way rather than deal with them separately in each of the RATs. This paper studies RAT selection algorithms in co-located UMTS/GSM networks. A three-complex algorithm, IN*VG*Load, is proposed based on the improvement from the IN*VG algorithm introduced by J. Perez-Romero et al.(2005). The simulation results show that the IN*VG*Load algorithm can optimize system performance in highly loaded combined UMTS/GSM networks. A new algorithm that best suites for low to medium loaded combined UMTS/GSM networks is also proposed and simulated in this paper.