Ray tracing is an efficient method for analyzing transmission characteristic of indoor wireless systems. However for simulating the transmission characteristic, using a path profile obtained by ray tracing, calculation times become enormous and there is no good theoretical model which can link a path analysis result with digital transmission characteristics evaluation. To overcome such problems, in this paper, a simple calculation method on spatial distribution of error occurrence due to intersymbol interference (ISI) based on "the equivalent transmission-path (ETP) model" is proposed. The ETP model is a technique that can simply estimate statistics of errors due to ISI that arise in Rayleigh and Nakagami-Rice fading environments. If a simple calculation method proposed in this paper is used, calculation time of digital transmission characteristics evaluation become tremendously shorter and results of this method agree with those of exact simulations with sufficient accuracy.

In order to assess the effect of multipath fading on Orthogonal Frequency Division Multiplex (OFDM) signal transmission when the delay profile exceeds the guard interval, a simple prediction model is developed based on the Equivalent Transmission-Path (ETP) model. This model, which is described in this paper, is referred to as the ETP-OFDM-statistical model. The validity of the model is demonstrated by comparing the calculated digital transmission characteristics to results obtained by computer simulation. Using the newly developed ETP-OFDM-statistical model, digital transmission characteristics of the OFDM signal in a multipath environment when the delay profile exceeds the guard interval are shown as a function of delay spread, guard interval and OFDM symbol period.