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Research Group Communications Engineering - Project Description

Quality of Service-Aware Cross-Layer Optimization in Heterogeneous Multiuser MIMO-OFDM Systems

Wireless local area networks are facing various challenges by modern applications. While the average data rate is the key criterion for file transfers, a maximum delay may not be exceeded for other services like, e.g., video telephony or streaming. In order to guarantee certain quality of service parameters, a strong coupling between layers in the OSI reference model is required.

The multicarrier technique OFDM has proven to be well suited for broadband communications. By using multiple transmit and receive antennas, the quality of transmission can be significantly improved. To this end, many different approaches have been proposed during the last few years. Another interesting aspect is the impact of channel knowledge at the transmitter. It can not only be used to adapt the transmit power and data rate, but also to reduce the signal processing complexity at the mobile devices by suitable precoding. Furthermore, subcarriers can be allocated to different user (OFDMA), or user can be even separated in space (SDMA) instead of using the conventional time division multiple access (TDMA). When selecting the active users, the channel and queue states as well as the application specific requirements must be taken into account.

In this project, the combination of channel and application aware scheduling with different transmission and multiple access schemes is analyzed. Especially the influence of imperfect channel state information at the transmitter is investigated.


German National Science Foundation (DFG), 2008 - 2009


Kühn, V.; Böhnke, R.; Kammeyer, K.-D.:
Adaptive MIMO-OFDM for Future Mobile Radio Communications. Sixth IEE International Conference on 3G & Beyond, London, UK, 2005
Böhnke, R.; Kühn, V.; Kammeyer, K.-D.:
Diversity vs. Adaptivity in Multiple Antenna Systems. IEEE International Workshop on Signal Processing Advances in Wireless Communications, New York, USA, 2005
Böhnke, R.; Kühn, V.; Kammeyer, K.-D.:
Fast Sum Rate Maximization for the Downlink of MIMO-OFDM Systems. IEEE Canadian Workshop on Information Theory, Montreal, Canada, 2005
Böhnke, R.; Kühn, V.; Kammeyer, K.-D.:
Efficient Near Maximum-Likelihood Decoding of Multistratum Space-Time Codes. IEEE Semiannual Vehicular Technology Conference (VTC2004-Fall), Los Angeles, USA, 2004