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Time Domain Simulation of Optical MIMO Channels

Köhnke H., Bartmann P., Ahrens A., Lochmann S.

Przegląd Elektrotechniczny

2015

R. 91, nr 4

56--59

In recent years the interest in optical multiple-input multiple-output (MIMO) transmission has increased significantly. Focus of this work is the development of a time domain model of optical MIMO channels using modal diversity. Next to modal and chromatic dispersion, modal crosstalk caused by mode combiner, splitter, splices and also modal coupling within the transmitting fiber can be taken into account. The simulated MIMO impulse responses are validated by practical measurements. The channel measurements confirm the accuracy of the proposed time domain model.

W artykule omawia się optyczny system transmisji typu MIMO (multiple input – multiple output). Zaproponowano model czasowy optycznego kanału MIMO. Wzięto pod uwagę modalną i chromatyczną dyspersję , modalny crosstalk (przesłuch) oraz modalne sprzężenie włókna optycznego.

Modulation-Mode Assignment in SVD-Aided Downlink Multiuser MIMO-OFDM Systems

Aust S., Ahrens A., Benavente-Peces C. C.

International Journal of Electronics and Telecommunications

2011

Vol. 57, No. 4

459-464

Multicarrier transmission such as OFDM (orthogonal frequency division multiplexing) is an established technique for radio transmission systems and it can be considered as a promising approach for next generation wireless systems. However, in order to comply with the demand on increasing available data rates in particular in wireless technologies, systems with multiple transmit and receive antennas, also called MIMO (multiple-input multiple-output) systems, have become indispensable for future generations of wireless systems. Due to the strongly increasing demand in high-data rate transmission systems, frequency non-selective MIMO links have reached a state of maturity and frequency selective MIMO links are in the focus of interest. In this field, the combination of MIMO transmission and OFDM can be considered as an essential part of fulfilling the requirements of future generations of wireless systems. However, single-user scenarios have reached a state of maturity. By contrast multiple users' scenarios require substantial further research, where in comparison to ZF (zero-forcing) multiuser transmission techniques, the individual user's channel characteristics are taken into consideration in this contribution. The performed joint optimization of the number of activated MIMO layers and the number of transmitted bits per subcarrier shows that not necessarily all user-specific MIMO layers per subcarrier have to be activated in order to minimize the overall BER under the constraint of a given fixed data throughput.

Modulation-Mode Assignment for SVD-assisted Downlink Multiuser MIMO Transmission Schemes with Iterative Detection

Ahrens A., Benavente-Peces C.

International Journal of Electronics and Telecommunications

2011

Vol. 57, No. 1

127-134

Since the capacity of multiple-input multiple-output (MIMO) systems increases linearly with the minimum number of antennas at both, the transmitter as well as the receiver side, MIMO systems have attracted a lot of attention for both frequency and non-frequency selective channels and reached a state of maturity. By contrast, MIMO-aided multiple-user systems require substantial further research. In comparison to zero-forcing (ZF) multiuser transmission techniques, where all users are treated jointly, the investigated singular value decomposition (SVD) assisted DL multiuser MIMO solution takes the individual user's channel characteristics into account. In analogy to bit-interleaved coded irregular modulation, we introduce a MIMO-BICM scheme, where different user-specific signal constellations and mapping arrangement were used within a single codeword. Extrinsic information transfer (EXIT) charts are used for analyzing and optimizing the convergence behaviour of the iterative demapping and decoding. Our results show that in order to achieve the best bit-error rate, not necessarily all user-specific MIMO layers have to be activated.