A Coverage Analysis of Amplify-and-Forward Relaying Schemes in Outdoor Urban Environment

The use of cellular systems enhanced by fixed relays has previously been proposed as a way to provide wide area coverage for high bit-rate at a reduced cost of the wireless access network. In this paper, three amplify-and-forward relaying schemes are analysed on the downlink, in a scenario where 95% coverage has to be provided for a predefined bit-rate in a typical urban environment. Numeric results show that combining diversity, such as SIMO has only marginal gains over selection diversity when only one relay is used. The use of transmission diversity for the MIMO relaying scheme reduces the base station density, but the relaying gain is comparable with the ones for selection and SIMO. With the random (unplanned) relay deployment considered in this study, 0.03 to 0.15 base stations are saved for each deployed relay. This means that the cost of a relay can be at most 3 to 15% the cost of a base station. The highest reduction is achieved when micro base stations are used.