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Research Group Communications Engineering - Project Description

Cooperative Transmission for increased Reliability in Mobile Relay Networks

In recent years, peak data rates of cellular communication networks have been improved remarkable. LTE advanced aims to provide rates up to 168 Mbit/s. A key challenge still remaining is to ensure acceptable rates especially at the cell edges. One possibility to improve coverage is to decrease the cell size at the expense of high infrastructure costs (CAPEX). An attractive alternative is the deployment of relay nodes which allow for high data rates even at cell borders. Relays need not to be as powerful as conventional base stations and they do not require a connection to a backbone network. They lower the path loss between nodes and enable space diversity by cooperative strategies.

The project investigates multiple access and transmission techniques for relay networks. Besides generell relay concepts, orthogonal access techniques like TDMA and OFDMA will be compared with nonorthogonale techniques like IDMA. While orthogonal approaches allow simple receiver structures, they require an appropriate synchronization with a corresponding signaling overhead. Contrarily, nonorthogonalen techniques do not require synchronization but have to cope at the receiver with multiuser interference. Advantages and disadvantages of orthogonal and nonorthogonal approaches shall be compared under realistic conditions. As a special topic, appropriate coding techniques in relay networks have to be analyzed.


German National Science Foundation (DFG), 2007 - 2012


1. Vorköper, S.; Lenkeit, F.; Kühn, V.; Wübben, D.; Dekorsy, A.:
Distributed IDM-STC versus Cooperative OFDM for the Two-Hop Decode-and-Forward Multiple-Access Relay Channel. International ITG Workshop on Smart Antennas (WSA'13), Stuttgart, 2013
2. Vorköper, S.; Kühn, V.:
Power and Subcarrier Allocation Scheme for Uplink OFDMA. Proceedings of OFDM 2012, 17th International OFDM Workshop 2012 (InOWo'12), pp. 1-6, 2012
3. Vorköper, S.; Kühn, V.:
Performance Comparison of Distributed IDM-STC versus Cooperative OFDM for practical Decode-and-Forward Relay-Networks. International ITG Workshop on Smart Antennas (WSA'12), pp. 145-151, Dresden, 2012
4. Angierski, A.; Schedler, S.; Kühn, V.:
Investigations on Cooperative Transmission for the Multiple Access Relay Channel. Proc. of IEEE International Symposium on Wireless Communication Systems 2011 (ISWCS'11), pp. 589-593, Aachen, Germany, 2011
ISBN: 978-1-61284-403-9, ISSN: 2154-0217, DOI: 10.1109/ISWCS.2011.6125424
5. Vorköper, S.; Kühn, V.:
CFO Estimation and Compensation in LTE Compliant DF Relay Networks. Proc. of the 16th International OFDM-Workshop 2011 (InOWo'11), pp. 76-80, Hamburg, Germany, 2011
6. Vorköper, S.; Kühn, V.:
Analyzing the Performance of Error-Prone Relay Networks. Proc. IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP'11), Prague, 2011
7. Vorköper, S.; Kühn, V.:
Error-Prone Relay Networks with Soft- and Hard-Decision Re-Encoding. International ITG Workshop on Smart Antennas (WSA'11), Aachen, Germany, 2011
8. Vorköper, S.; Kühn, V.:
Noise Variance Estimation in OFDM Cyclic Delay Diversity Relay Networks. 14th International OFDM-Workshop (InOWo 2009), Hamburg, Germany, 2009
9. Weitkemper, P.; Vorköper, S.; Wübben, D.; Kammeyer, K.-D.; Kühn, V.:
Distributed IDM-STC versus OFDM-CDD in Two-Hop Relay-Networks. 14th International OFDM-Workshop (InOWo 2009), Hamburg, Germany, 2009
10. Vorköper, S.; Kühn, V.:
Reducing the Channel Estimation Error for Relay Networks with Cyclic Delay Diversity. 15th European Wireless Conference (EW 2009), pp. 53-57, Aalborg, Denmark, 2009
11. Khan, A.; Kühn, V.; Vorköper, S.:
Information Combining Based ARQ in Relay Networks. 15th European Wireless Conference (EW 2009), Aalborg, Denmark, 2009
12. Kühn, V.; Vorköper, S.:
Information Combining for Relay Networks. IEEE International Conference on Communications (ICC 2009), Dresden, Germany, 2009
13. Kühn, V.; Vorköper, S.:
Application of Information Combining to Relay Networks. IEEE Vehicular Technology Conference (VTC 2009 Spring), Barcelona, Spain, 2009
14. Vorköper, S.; Kühn, V.:
Information Combining for OFDM-based Relay Networks. 13th International OFDM-Workshop, Hamburg, Germany, 2008
15. Weitkemper, P.; Wübben, D.; Kühn, V.; Kammeyer, K.-D.:
Soft Information Relaying for Wireless Networks with Error-Prone Source-Relay-Link. 7th International ITG Conference on Source and Channel Coding, Ulm, Germany, 2008


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Prof. Dr.-Ing. habil. Volker Kühn

Phone:   0381 / 498-7330
Fax:   0381 / 498-7302
Room:   W: 8.233
E-Mail:   volker.kuehn(at)

Institut für Nachrichtentechnik
R.-Wagner-Str. 31 (Haus 8)
18119 Rostock/Warnemünde

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