Combining calibration schemes on a real-time multiuser MIMO-OFDM system with implicit feedback

Online Calibration for LTE-Based Antenna Array System

“…As shown in Figure 4, the impulse responses involve multitaps. Note that most conventional calibration methods [5][6][7][8] assumed that the impulse responses of all the RF modules consist of a single tap. As shown in Figure 4, however, the actual impulse responses of RF modules involve multitap; thus, the given signal environment should be considered as being wideband.…”

“…All the RF modules should exhibit the same transfer characteristics for every subcarrier in a given wide bandwidth. Researches on calibrations for beamforming and Time Division Duplex (TDD) Long-Term Evolution (LTE) implementation have been performed in [ [7,8], respectively. However, most conventional calibration methods including the ones shown in [5][6][7][8] considered a narrow bandwidth signal environment only, meaning that the impulse response of each RF module consists of a single tap such that the difference in the phase delays among distinct RF modules can be compensated only for a single subcarrier.…”

“…Researches on calibrations for beamforming and Time Division Duplex (TDD) Long-Term Evolution (LTE) implementation have been performed in [ [7,8], respectively. However, most conventional calibration methods including the ones shown in [5][6][7][8] considered a narrow bandwidth signal environment only, meaning that the impulse response of each RF module consists of a single tap such that the difference in the phase delays among distinct RF modules can be compensated only for a single subcarrier. In order to apply the methods in [5][6][7][8] to wide bandwidth, each of the subcarriers should be considered separately and exhaustively, which would be extremely inefficient.…”

“…However, most conventional calibration methods including the ones shown in [5][6][7][8] considered a narrow bandwidth signal environment only, meaning that the impulse response of each RF module consists of a single tap such that the difference in the phase delays among distinct RF modules can be compensated only for a single subcarrier. In order to apply the methods in [5][6][7][8] to wide bandwidth, each of the subcarriers should be considered separately and exhaustively, which would be extremely inefficient. Particularly for mmWave application that is one of the key technologies in 5th Generation (5G) mobile communications, since the bandwidth could be up to a few GHz [9], it is practically impossible to adopt the calibration techniques given in [5][6][7][8].…”

“…In order to apply the methods in [5][6][7][8] to wide bandwidth, each of the subcarriers should be considered separately and exhaustively, which would be extremely inefficient. Particularly for mmWave application that is one of the key technologies in 5th Generation (5G) mobile communications, since the bandwidth could be up to a few GHz [9], it is practically impossible to adopt the calibration techniques given in [5][6][7][8].…”