Cell Spectral Efficiency optimization in relay enhanced cells

The broad acceptance of smart phones results in increasing capacity demands for mobile radio networks. Decode-and-Forward (DF)-Relay Stations (RSs) are promising to improve Cell Spectral Efficiency (CSE) and to better meet the capacity demands. In our work we investigate the potential of DF-RSs combined with a pico Base Station (BS) co-located to the BS. Our system model comprises three parts, an IMT-A compliant channel model, a Physical Layer (PHY) model based on the Shannon bound and a Medium Access Control (MAC) layer model. We apply simulated-annealing to find nearly optimal positions for DF-RSs as well as nearly optimal heights for DF-RSs and pico BSs in a cellular network. The results show that nearly optimally placed DF-RSs almost double CSE and that an additional pico BS further increases CSE by about 10% thereby doubling CSE compared to conventional cells.