A paradigm change in mobile communications enables the transition to cooperative systems. Research here focuses on cooperative communication strategies for distributed antennas, also referred as 'Coordinated Multi Point' (CoMP) techniques. Permitting cooperation between several distributed antennas offers advantages from the spatial structure of the wireless propagation medium. Significantly increased spectral efficiency is expecetd by the use of spatial diversity and reduced co-channel interference. We have hence developed a theory for modelling and optimising interference-coupled radio networks. To determine achievable gains in practice, we use multi-cell MIMO simulations as well as channel measurements.
Cooperative strategies are of primary importance for users at the cell boundaries which experience poor channel conditions due to propagation loss and strong inter-cell interference.
We develop protocols and algorithms for adaptive CoMP systems in conjunction with multi-antenna techniques and resource allocation.
One promising way of dealing with this problem is the use of distributed relays which relay information via several hops. This not only increases the range and reduces the - usually high - infrastructure costs, but additionally leads to an extraordinary reduction in interferences between cells.
- Live demonstration of "Collaborative MIMO" was at IEEE ICC 2009, June 14-18, Dresden, Germany
- L. Thiele, T. Wirth, M. Schellmann, Y. Hadisusanto, and V. Jungnickel, "MU-MIMO with Localized Downlink Base Station Cooperation and Downtilted Antennas", IEEE International Workshop on LTE Evolution, Dresden, Germany, June 2009.
- L. Thiele, T. Wirth, T. Haustein, V. Jungnickel, E. Schulz, and W. Zirwas,"A Unified Feedback Scheme for Distributed Interference Management in Cellular Systems: Benefits and Challenges for Real-Time Implementation", 17th Euopean Signal Processing Conference (EUSIPCO2009), Glasgow, Scotland, Aug. 2009, invited.
- Y. Hadisusanto, L. Thiele, and V. Jungnickel, "Distributed Base Station Cooperation via Block-Diagonalization and Dual-Decomposition", Proc. of IEEE Global Telecommunications Conference (GLOBECOM), New Orleans, USA, Nov. 30 - Dec. 4, 2008.
- V. Jungnickel, L. Thiele, M. Schellmann, T. Wirth, W. Zirwas, T. Haustein, and E. Schulz, "Implementation Concepts for Distributed Cooperative Transmission", 42nd Asilomar Conference on Signals, Systems and Computers, Monterey, USA, Oct. 2008.
- L. Thiele, M. Schellmann, T. Wirth, and V. Jungnickel, "Cooperative Multi-User MIMO based on Reduced Feedback in Downlink OFDM Systems", 42nd Asilomar Conference on Signals, Systems and Computers, Monterey, USA, Oct. 2008.