Effect of Inter-Cell Inter-Radio Access Technology (RAT) interference on the performance of multi-RAT cellular systems

Containing interference within cellular communication systems requires the use of dedicated frequency bands to mitigate interference from other wireless systems. Based on this design principle, the Radio Frequency (RF) resources of a multi-Radio Access Technology (RAT) cellular system are apportioned between co-deployed RATs. However, traffic variations within multi-RAT systems result in the suboptimal utilization of RF resources under fixed, system-level spectrum allocation policies. On the other hand, flexible spectrum allocation policies that permit using the same frequency band to deploy different RATs at different locations introduce Inter-cell inter-RAT Interference (IRI). The potential impact of IRI prevents the use of flexible spectrum management techniques that disrupt system-level spectrum allocation in multi-RAT systems. This paper studies the effect of IRI on the performance of multi-RAT cellular systems employing Global System for Mobile Communications (GSM), High Speed Packet Access (HSPA) and Long Term Evolution (LTE). Detailed system level simulations are performed to measure the impact of deploying different RATs at different locations using the same frequency band.