Coordinated multipoint is a mode in LTE-Advanced in which the concept is to increase the cell edge throughput and reliability. When a mobile user moves to the cell edge, it gets a very strong interference from the neighboring base station.
In order to increase the cell edge reliability and throughput, base stations actually coordinate with each other and multiple base stations from different cells transfer the signal to the mobile user to increase the cell edge throughput and reliability. The challenge in coordinated multipoint is that a mobile user has to synchronize with multiple base stations at the same time.
Last year, a research team at Georgia Tech has designed training signals for carrier off set estimation and timing off set estimation on the mobile user side, by utilizing the NI-based hardware, which the researcher claims have a pretty good PXI-based lead user platform which allows real-time implementation on FPGA and uses front-end adaptive modules which can be used either as a base station or a mobile user. The real aims for the research is to design training signals to facilitate synchronization with multiple base stations while they are transmitting at the same time and carrier frequency.
According to the researcher, the PXI chassis contains two FAMs and they act like two base stations. The FAM along with the RF hardware acts like a mobile user. Then, bothbase stations transmit the signal to the mobile user and it can synchronize with both of them and decode the signal in comp mode. When waving a hand through it, the signal fades and the mobile user is still able to synchronize both in time and frequency with multiple base stations at the same time.