Due to a drastic increase in data traffic, a Beyond-Fourth-Generation (B4G) mobile communication system requires 10 times an increase in frequency efficiency or more compared to a 4G system such as Third Generation Partnership Project (3GPP) Long Term Evolution (LTE). As physical layer techniques necessary to increase frequency efficiency 10 times or more as stated above, network MIMO, interference alignment, relay network, heterogeneous network, a large-scale MIMO technique, etc. are currently being mentioned.
The present invention relates to a massive MIMO (or large-scale antenna) system capable of obtaining a very strong effect as a technique for improving frequency efficiency. Existing large-scale antenna systems have been limited to a time-division duplex (TDD) scheme. This is because a frequency-division duplex (FDD) scheme has a problem that a large-scale antenna transmitter requires as many reference signals (RSs) and radio resources for CSI feedback as substantially impossible to obtain CSI.
In addition, since the number of users that can be simultaneously accommodated by a large-scale transmitting antenna remarkably increases, there occurs a practical problem in that the complexity of scheduling and precoding calculation becomes very higher than that of an existing system.