A new method to measure parameters of frequency-selective radio channels using power measurements

Abstract

This paper describes a method of deriving channel parameters for a time-dispersive (=frequency-selective) radio channel from simple wide-band power measurements. A novel relationship is found allowing the estimation of the root-mean-square (rms) delay spread from such data. Furthermore, we describe a set of equations that can be used for fitting the (measured) channel parameters to a mathematical model, the so-called frequency-domain (FD) model. We also show a simulation procedure, which directly implements the mathematical description of the channel. The output of this procedure-realizations of frequency-selective channel transfer functions-may be used for instance in the investigation of OFDM systems. The study is restricted to the small-scale modelling; Rayleigh and Ricean fading channels are considered. The estimation of the rms delay spread is based on the frequency-domain level crossing rate (LCR f), which is derived from the FD-channel model. It is shown that the rms delay spread is proportional to the LCR f. Because of the simple hardware required for finding the LCR f, the suggested measurement method is particularly interesting for the millimeter-wave frequency band (>30 GHz). However, it can be used at other frequencies as well, where standard laboratory equipment is sufficient for conducting the measurements. The accuracy of this technique depends on the bandwidth observed and can be increased further by combining multiple measurements performed within a small local area.