Location-based Mobile Relay Selection and Impact of Inaccurate Path Loss Model Parameters

In this paper we propose a relay selection scheme which uses collected location information together with a path loss model for relay selection, and analyze the performance impact of mobility and different error causes on this scheme. Performance is evaluated in terms of bit error rate by simulations. The SNR measurement based relay selection scheme proposed previously is unsuitable for use with fast moving users in e.g. vehicular scenarios due to a large signaling overhead. The proposed location based scheme is shown to work well with fast moving users due to a lower signaling overhead.
The required location accuracy was found to be comparable to the accuracy of standard GPS. As the scheme was found to be highly sensitive to NLOS situations with unknown attenuation, knowledge of obstacle locations obtained either by sensing online or from a map of obstacles, was identified as a prerequisite in these situations. As the location-based scheme relies on a path loss model to estimate link qualities and select relays, the sensitivity with respect to inaccurate estimates of the unknown path loss model parameters is investigated. The parameter ranges that result in useful performance were found to be wide enough to allow them to be estimated in practical systems.