Indoor propagation characteristics including radiation pattern and polarization of base station

For radio communication inside indoor environments, such as buildings, underground shopping centers and subway stations, it is necessary to use a micro or pico cell system to increase the traffic capacity. In such a small sized cell, the propagation environments are based on the line-of-sight (LOS) path, then diversity gain by using the space diversity technique to eliminate the fast fading is not expected because the fading structure is Rician. However, the polarization diversity technique at the base station is assumed to increase the average up-link level when the hand held terminals are always used at a tilted angle. The conventional cellular systems use vertical polarization and a few references have reported the use of horizontal polarization or circular polarization to reduce the fading effects. On the other hand, the optimum polarization for the transmitting antenna, as the base station has not been considered, expand or restrict the cell size. When the propagation environments are changed, the optimum polarization is assumed to be different for the micro or pico cell. This paper presents the radiation pattern and polarization characteristics obtained from experiments and by the ray tracing method.