EXPERIMENTAL EVALUATION OF SPACE FREQUENCY POLARIZATION DIVERSITY IN THE INDOOR WIRELESS CHANNEL

A series of experiments that were conducted to evaluate the relative merits of three types of diversities in the indoor portable radio channels at 900 MHz is described. Unmodulated tones were used to probe the channel in a typical university work environment. The statistics of the signal envelopes were analyzed to determine the correlation of the field strengths when the signals are separated in space, frequency or polarization. According to the results presented here, the performance of a narrow-band system (< 200 kHz) at 900 MHz could greatly benefit from a frequency diversity scheme provided that the separation between the two frequencies is greater than approximately 5 MHz. Similarly, the advantage of space diversity is found significant when the two antennas are spaced by 3/4 wavelength or more. It is also reported that co-polarized and cross-polarized signals are nearly uncorrelated and their relative field strengths differ by less than 2 dB in most locations.