Berlin LTE-Advanced Testbed

The Berlin LTE-Advanced Testbed has been set up in a typical European metropolitan deployment in the center of Berlin. It serves for the early evaluation of LTE-advanced concepts in a realistic cellular environment and for the demonstration of key technology features to increase spectral efficiency, range, throughput and quality-of-service (QoS).

The testbed is operated from three sites located at Fraunhofer HHI, Deutsche Telekom Laboratories and Technische Universität Berlin.

LTE transmission is based on a combination of OFDM and multi-antenna techniques which are also referred to as MIMO (Multiple-Input Multiple-Output). The base system with Orthogonal Frequency-Division Multiple Access (OFDMA) in the downlink and Single-Carrier (SC) FDMA in the uplink was successfully presented to the general public by Nokia Siemens Networks at ITU Telecom World 2006. The system was extended by link adaptation algorithms and presented at the 3GSM World Congress 2007 in Barcelona. With this system, a real outdoor urban field trial with multiple users has been made, where the base station was located at the top of the HHI building and cars with LTE terminals demonstrating a coverage of several km from a single base station.

Challenges

• Reducing inter-cell interference is the next challenge for further performance enhancements in mobile networks
• Cooperation between adjacent base stations promises a higher performance in the cellular network
• Distributed cooperative signal processing is required to make these so called 'Coordinated Multi Point' (CoMP) techniques less complex and scalable

Technology features

• Inter-cell interference coordination
• Synchronized base stations
• Multi-cell channel estimation
• Interference-aware scheduling
• Interference cancellation
• High-speed low-latency backbone network
• Distributed cooperation between base stations
• Exchange of data and channel knowledge

The testbed has been used for several single-cell measurements. The algorithms are evaluated under real conditions in a multi-cell testbed set up in cooperation together with Deutsche Telekom AG.

Acknowledgments

This work was supported in part by the Federal Ministry of Educational and Research (BMBF) in the project EASY-C.