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.
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Document type: |
Journal Paper |
Publication: |
September 2013 |
Journal: |
IEEE Transactions on Communications |
Pages: |
3781-3793 |
Volume: |
61 |
Number: |
9 |
Files: |
BibTEX
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