Downlink CoMP (Co-ordinated Multi-Point) in LTE Advanced
The Coordinated Multipoint (CoMP) feature is available for the DL and the UL. In the DL, CoMP transmission occurs, while CoMP reception is allowed in the UL. At a high level, CoMP transmission resembles soft handover and fast cell switching.
CoMP transmission supports two cases, namely, Joint Processing (JP) and Coordinated Scheduling and Beamforming (CS/CB).
Joint Processing (JP) has two use cases. The first case is where more than one cell transmits the same information at the same time. The UE then combines these two signals similar to 3G soft handover. The benefit of joint transmission is increased throughout in the handover region due to increased SIR.
Another possible JP implementation method is dynamic point selection. In this method, one cell among a set of cells is dynamically chosen for the DL transmission to the UE. Fast switching of cells can yield the benefits of link adaptation and spatial/ macro diversity.
CoMP also supports the ability to perform CS/CB where the cells use the same radio resources to transmit data to the users and use beamforming to avoid overlapping and interference of various transmissions with one another.