Large Scale Characteristics and Capacity Evaluation of Outdoor Relay Channels at 2.35 GHz

In this paper we present single antenna relay channel measurements conducted in an urban environment at 2.35 GHz. Three types of links, i.e. base station to mobile station (BS-MS), relay station to mobile station (RS-MS) and base station to relay station (BS-RS), were measured at two sites. Our investigation focuses on the characteristics of large scale parameters (LSP) of the RS-MS link, which is characterized by the low antenna height at RS and short RS-MS distance. Measurement results show that the current BS-MS path loss model cannot perfectly predict the propagation loss of RS-MS link. The distance dependent property and the distribution of Ricean K-factor are analyzed. The RS-MS link is found to exhibit lower Ricean K-factor compared to the BS-MS link. We also investigate the capacity gain provided by the relay link when the MS is located in the shadowing area of BS. Furthermore, it is observed that the capacity gap between decode-and-forward (DF) and the fixed gain amplify-and-forward (AF) relay schemes vanishes, provided the large K-factor and high SNR of BS-RS link. This gap becomes larger as the K-factor of BS-RS link decreases.