Study on multiple stream transmission by using multiple polarizations

In this paper, we propose a new method for achieving multiple stream transmission by using multiple polarizations. Using polarization switching sequences corresponding to streams enables interferences to be canceled and multiple streams to be made because the polarizations are symmetrical regardless of antenna spacing. Therefore, the method is effective when antenna spacing is small. To achieve high data rates, a number of antennas should be placed in a limited space by using higher frequency bands and multiple-input multiple-output (MIMO) technology, thus small antenna spacing is necessary for future wireless communication systems. In the conventional MIMO method, however, the channel capacity is degraded due to spatial correlation and a number of antennas cannot be placed in a limited space because large antenna spacing is needed to decrease the spatial correlation. To solve the problem, we propose a multiple stream transmission method in which multiple polarizations can be used with any antenna spacing. Numerical analysis revealed that the channel capacity per unit area achieved with our method increases in proportion to the number of streams.