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

Autoren:

M. Petermann, M. Stefer, F. Ludwig, D. Wübben, M. Schneider, S. Paul, K.-D. Kammeyer

Kurzfassung:

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.

Dokumenttyp:

Journal Paper

Veröffentlichung:

September 2013

Journal:

IEEE Transactions on Communications

Seiten:

3781-3793

Volume:

Number:

Dateien:

TCOM_2013