Measurements of base station two-branch space and polarization diversity reception and a comparison of the diversity gain based on the CDF of signal level and simulations of BER in a GSM system

Abstract

This paper summarizes the results of a measurement campaign to evaluate the performance of different diversity schemes. The measurements have been carried out using the Siemens proprietary wideband channel sounder, the SIMOCS-2000. The key objective of the measurement campaign has been to evaluate the performance of polarization diversity as compared to space diversity. In addition, we contrasted the results for diversity gain based on signal statistics with results from link level simulations. The measurements have been carried out at 1815 MHz and GSM has been assumed for the standard dependent evaluations by means of link level simulations. Evaluating the measurements based on the well known and widely used CDF method according to Turkmani, Arowojolu, Jefford and Kellett (see IEEE Trans. Vehic. Technol., vol.44, no.2, p.318-26, 1995), space diversity provides a maximum value of 6 dB diversity gain for a horizontal separation of 10 /spl lambda/ between two vertically polarized antennas. Using a /spl plusmn/45/spl deg/ dual polarized antenna polarization diversity results in a diversity gain of 5.5 dB and performs as well as space diversity. The use of a horizontal/vertical polarized antenna provides a diversity gain of 3-4 dB. Comparing the figures for the diversity gain computed according to Turkmani et al. with those obtained by GSM link level simulations we show that the CDF method results in diversity gain figures which are 2-3 dB too optimistic. However, a modification of the method according to Turkmani et al. which takes into account the effects of an interleaver in the transmission chain of the real communication system results in an almost perfect match.