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In adaptive Time Division Duplex (TDD) broadcast multi-antenna Orthogonal Frequency Division Multiplexing (OFDM) systems, non-reciprocal transceiver chains at the Base Station (BS) cause multi-user interference. This is due to the inappropriate spatial filter design at the BS based on the reverse link estimate. Hence, BS transceiver calibration is required. Provided that an estimate of the forward link channel is available at the BS, e.g., in a calibration phase, the transceiver parameters can be estimated by solving a Total Least Squares (TLS) problem. In addition, if mutual coupling between the antennas exists the number of unknown front-end parameters to be estimated increases. Consequently, large matrices need to be decomposed via Singular Value Decomposition (SVD) to attain a calibrated system.
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