Coordinated MultiPoint (CoMP) Systems
6.1 Overview of CoMP
Future cellular networks will need to provide high data rate services for a large number of User Equipments (UEs), which requires a high spectral efficiency over the entire cell area. Hence it is important that the radio interface is robust to interference. In particular Inter-Cell Interference (ICI) appears when the same radio resource is reused in different cells in an uncoordinated way. Naturally, ICI particularly degrades the performance of UEs located in the cell-edge areas, which creates a performance discrepancy between cell-edge and inner-cell UEs.
Over the years, several different methods have been studied in order to mitigate ICI. Interference averaging techniques (WINNER-II 2007a) aim at averaging the interference over all UEs, thereby reducing the interference experienced by some UEs. Frequency hopping (Carneheim 1994), which is used in GSM, is a well-known example of an interference averaging technique. Interference avoidance techniques (WINNER-II 2007b), on the other hand, aim at explicitly coordinating and avoiding interference, for example, by setting restrictions on how the radio resources are used. An example of this is Inter-Cell Interference Coordination (ICIC), which is available in the 3GPP Long Term Evolution (LTE) standard (see e.g. Dahlman et al. 2008).