An apparatus in a wireless communication system, the apparatus comprising: an antenna array (605a-n, 1005, 1505, 1705) comprising a plurality of antennas; a transceiver array (610a-n) comprising a plurality of transceivers electrically connected to one or more of the antennas, respectively; a coupling network (640, 1010, 1500, 1700) electrically connected to each of the transceivers; a calibration transceiver (645, 1515) electrically connected to each of the transceivers in the transceiver array (610a-n) via the coupling network (640, 1010, 1500, 1700) at each antenna, the calibration transceiver (645, 1515) including: a calibration transmitter, Tx, configured to transmit a first calibration signal via the coupling network (640, 1010, 1500, 1700), and a calibration receiver, Rx, configured to receive a second calibration signal based on the first calibration signal, that was transmitted by the transceiver array (610a-n) in a time division duplex, TDD, pattern via the coupling network (640, 1010, 1500, 1700), wherein the calibration transceiver (645, 1515) is configured to: generate an Rx calibration measurement, R 1, based on the first calibration signal received by the transceiver array (610a-n) via the coupling network (640, 1010, 1500, 1700); and generate a Tx calibration measurement, T 1, based on receipt of the second calibration signal by the calibration receiver via the coupling network (640, 1010, 1500, 1700); and at least one processor configured to perform a joint Tx/Rx, TRx, calibration based on HR, Ri, and T 1, where H is a channel response in air interface, R is a channel response of receivers in transceiver array (610a-n), wherein to perform the joint TRx calibration, the at least one processor is configured to generate a downlink channel estimate, HT, based on an equation of HRR 1 − 1 T 1 = HT. an antenna array (605a-n, 1005, 1505, 1705) comprising a plurality of antennas; a transceiver array (610a-n) comprising a plurality of transceivers electrically connected to one or more of the antennas, respectively; a coupling network (640, 1010, 1500, 1700) electrically connected to each of the transceivers; a calibration transceiver (645, 1515) electrically connected to each of the transceivers in the transceiver array (610a-n) via the coupling network (640, 1010, 1500, 1700) at each antenna, the calibration transceiver (645, 1515) including: a calibration transmitter, Tx, configured to transmit a first calibration signal via the coupling network (640, 1010, 1500, 1700), and a calibration receiver, Rx, configured to receive a second calibration signal based on the first calibration signal, that was transmitted by the transceiver array (610a-n) in a time division duplex, TDD, pattern via the coupling network (640, 1010, 1500, 1700), wherein the calibration transceiver (645, 1515) is configured to: generate an Rx calibration measurement, R 1, based on the first calibration signal received by the transceiver array (610a-n) via the coupling network (640, 1010, 1500, 1700); and generate a Tx calibration measurement, T 1, based on receipt of the second calibration signal by the calibration receiver via the coupling network (640, 1010, 1500, 1700); and at least one processor configured to perform a joint Tx/Rx, TRx, calibration based on HR, Ri, and T 1, where H is a channel response in air interface, R is a channel response of receivers in transceiver array (610a-n), wherein to perform the joint TRx calibration, the at least one processor is configured to generate a downlink channel estimate, HT, based on an equation of HRR 1 − 1 T 1 = HT. a calibration transmitter, Tx, configured to transmit a first calibration signal via the coupling network (640, 1010, 1500, 1700), and a calibration receiver, Rx, configured to receive a second calibration signal based on the first calibration signal, that was transmitted by the transceiver array (610a-n) in a time division duplex, TDD, pattern via the coupling network (640, 1010, 1500, 1700), wherein the calibration transceiver (645, 1515) is configured to: generate an Rx calibration measurement, R 1, based on the first calibration signal received by the transceiver array (610a-n) via the coupling network (640, 1010, 1500, 1700); and generate a Tx calibration measurement, T 1, based on receipt of the second calibration signal by the calibration receiver via the coupling network (640, 1010, 1500, 1700); and at least one processor configured to perform a joint Tx/Rx, TRx, calibration based on HR, Ri, and T 1, where H is a channel response in air interface, R is a channel response of receivers in transceiver array (610a-n), wherein to perform the joint TRx calibration, the at least one processor is configured to generate a downlink channel estimate, HT, based on an equation of HRR 1 − 1 T 1 = HT. generate an Rx calibration measurement, R 1, based on the first calibration signal received by the transceiver array (610a-n) via the coupling network (640, 1010, 1500, 1700); and generate a Tx calibration measurement, T 1, based on receipt of the second calibration signal by the calibration receiver via the coupling network (640, 1010, 1500, 1700); and at least one processor configured to perform a joint Tx/Rx, TRx, calibration based on HR, Ri, and T 1, where H is a channel response in air interface, R is a channel response of receivers in transceiver array (610a-n), wherein to perform the joint TRx calibration, the at least one processor is configured to generate a downlink channel estimate, HT, based on an equation of HRR 1 − 1 T 1 = HT.