LTE Advanced: 3GPP Solution for IMT-Advanced

13.8 CoMP Field Trials

A variety of downlink and uplink CoMP concepts have already been successfully tested in field trials. In the research projects EASY-C and Artist4G, partially funded by the German Ministry for Education and Research (BMBF) and the European Union, respectively, a large cellular test system for LTE-Advanced has been setup in downtown Dresden, Germany.

One of the downlink CoMP schemes tested was a joint transmission of up to three cells with two antennas each to three terminals with two receive antennas each. Here, it could be shown that if the terminals are fairly static and located close to the cell edge between the three cells, joint transmission can strongly mitigate the effect of inter-cell interference and consequently boost the data rates of all three terminals. The successful trials also showed that a sufficient synchronization of base stations in frequency domain can be obtained, and that it is in principle possible to feed channel information back from the terminals to the infrastructure in sufficient quality. In fact, the downlink CoMP gains measured in field trials were larger than stated in this chapter, but this may be explained by the fact that in the downlink trials, only the subset of base stations involved in a joint transmission was turned on. Hence, there was no background interference from other base stations, as is typically assumed in system level simulations.

To evaluate uplink CoMP concepts in practice, two terminals were driven along ...