Multi-User Pre-Processing in Multi-Antenna OFDM TDD Systems with Non-Reciprocal Transceivers

Authors: M. Petermann, M. Stefer, F. Ludwig, D. Wübben, M. Schneider, S. Paul, K.-D. Kammeyer
Abstract: The combination of OFDM with joint pre-processing in adaptive multi-antenna systems offers both an ease of equalization in frequency-selective channels and keepingthe signal processing at the mobile stations simple. In addition, the spatial dimension can be efficiently exploited to ensure high system throughput. With the utilization of higher-order modulation the performance of the system is highly sensitive to multiple access interference and nonorthogonal subchannels due to hardware impairments or insufficient adaptation to the current channel conditions. A further source of error in TDD systems are the non-reciprocal transceivers inhibiting the baseband-to-baseband channel reciprocity required for accurate channel state acquisition based on the uplink channel estimate. In this paper, measurement results of a low-cost hardware-based calibration are presented and the drawbacks are discussed leading to the utilization of a recently introduced relative calibration. The latter is applied to an OFDM system and achieves or at leastapproximates the baseband-to-baseband reciprocity. Thus, it enables the link adaptation using the uplink channel state in-formation. Furthermore, preliminary hardware implementations of the relative calibration running on a real-time system show accurate results.
Document type: Journal Paper
Publication: September 2013
Journal: IEEE Transactions on Communications
Pages: 3781-3793
Volume: 61
Number: 9
TCOM_2013_Petermann.pdf486 KB
Last change on 30.07.2021 by D. Wübben
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