Mobile radio delay spread prediction based on frequency correlations

It is important to clearly understand multipath propagation to develop high speed digital mobile communication system(l-$) . The r.m.s. delay spread can be directly obtained by measuring the delay profile. The problem has been that delay profi Ie measurements that are accurate must be taken for a wide frequency band. For example, with wideband measurement equipment using pseudo-noise signals, a frequency band of 10MHz is necessary for accuracy of 200n5. Jakes proposed delay spread prediction method using narrow frequency bands{$) . This narrow band method is based on coherent bandwidth, which is derived by correlating the rece ived levels of different frequencies. The delay spreads In both N. Y. and Tokyo have been measured by th i s method (I. 1). Th i s method is simple but it requires that we predict the type of delay profile, which is generally assumed to be exponential. If the actual delay profile is not exponential, the method results in prediction errors. This paper proposes a new predic t ion method that is based on the delay profi Ie with the maximum I ikel ihood of appearing. We cal I this the SPSP method which stands for spread prediction by selecting profi Ie type. The prediction errors of Jakes and SPSP methods are compared through computer simulation and measurements.