Field Experiment of Network Control Architecture for CoMP JT in LTE-Advanced over Asynchronous X2 Interface

CoMP (Coordinated Multiple Point transmission and reception) is a key technology in 3GPP LTE-A (3rd generation partnership project long term evolution advanced) which is expected to greatly improve the cell-edge throughput performance by the cooperation of multiple eNBs (evolved NodeBs). We developed a prototype system to realize CoMP JT (joint transmission) using a novel network control architecture. The developed CoMP JT system is designed to work over an asynchronous IP-based X2 interface. Therefore we need a simultaneous transmission scheme from multiple eNBs to a UE (user equipment) using the asynchronous X2 interface. We developed a GPS-based (global positioning system based) scheme for the simultaneous transmission. In addition, we developed several new functions to achieve CoMP JT over an asynchronous X2 interface. As a result, a UE can automatically start or stop CoMP JT and the HARQ retransmission is possible during CoMP JT. We conducted a field trial using the developed CoMP JT system. It is demonstrated that the network control architecture implemented in the CoMP JT system works properly over a real asynchronous IP backhaul network.