University of Rostock

The deployment of relay nodes in cellular mobile radio networks is intensively discussed in the upcoming LTE-Advanced standard.

In particular, relays shall improve coverage and outage capacity at cell borders. Although the capacity of relay networks is generally unknown, upper bounds can be obtained by applying the max-flow min-cut theorem. These bounds illuminate substantial gains of non-orthogonal compared to orthogonal relay protocols and emphasize the importance of optimizing the time sharing for a 2-hop communication. Contrarily, most of the literature as well as practical implementations deal with orthogonal protocols using fixed time slot lengths. Based on the max-flow min-cut bounds, the project shall evaluate if and how the theoretical gains are achievable in a system using with discrete modulation schemes, imperfect coding and discrete rates. Appropriate transmission strategies have to be developed for non-orthogonal relay protocols and corresponding detection algorithms have to be optimized. The achievable performance has to be compared with the upper bounds as well as standard approaches. Within the project, an OFDM-based system with half-duplex relays will be considered.

German National Science Foundation (DFG), 2013 - 2015