Optimum element arrangement of adaptive arrays for SDMA considering angular spread and Doppler effect

Frequency reuse is one of the most important issues facing future mobile communication systems because many users will utilize mobile communication services that have limited frequency resources. Space division multiple access (SDMA), which applies adaptive arrays to base stations, is a promising technique to increase the channel capacity. To actualize SDMA, the optimum element arrangement of adaptive arrays must be clarified as well as other design parameters in RF and digital signal processing blocks. We reported that the average squared spatial correlation (ASSC) is useful in designing the element arrangement of the adaptive arrays for SDMA when incoming waves are plane waves. In this paper, we derive the conditions that minimize the ASSC by extending the formula presented by Takatori, Nishimori and Hori (see Proceeding of 2000 VTC-Fall, Boston, vol.1, p.150-156, 2000). Moreover, the influences of the angular spread and Doppler effect are investigated by computer simulation and a design chart of the element arrangement for a three-element circular array is presented.