Measurement-based delay spread analysis of indoor distributed antenna systems

Delay spread characteristics of distributed antenna system (DAS) at 3.52 GHz are analyzed by using the measurement data. The measurement is conducted in a typical office, and signals are transmitted from seven distributed antennas to a mobile receiver. It is verified that the mean value and the standard deviation of root mean square (RMS) delay spread are smaller in DAS than the ones in centralized antenna systems (CASs). The results show that with the existences of line of sight (LOS) paths, the RMS delay spread relies on the nearest transmitter antenna in different measured locations. It is indicated that there is a relationship between the RMS delay spread and the distance from distributed transmitters to the receiver. Then a new metric, harmonic access (HA) distance, is defined. The measurement results show that in DAS the RMS delay spread and the HA distance have the same changing tendency.