SPECTRAL EFFICIENCY IMPROVEMENT BY BASE STATION ANTENNA PATTERN CONTROL FOR LAND MOBILE CELLULAR-SYSTEMS

This paper proposes using an adaptive array in a base station for sign al reception and transmission in order to increase the spectral effici ency without decreasing the cell radius. The adaptive array controls t he directivity pattern of the base station to reduce co-channel interf erence during reception; the same array pattern is applied during tran smission to prevent unnecessary illumination. Computer simulation resu lts show that the cluster size can be reduced to one with time divisio n duplexing (TDD), indicating that we can reuse the same frequency gro up at all cells, Thus, the improvement in spectral efficiency is as mu ch as 16 fold that of an omni-antenna. Moreover, load sharing, which i s expected to improve the channel utilization for unbalanced load situ ations, is available by cell overlapping. Frequency division duplexing (FDD) requires a weight adjust function to be applied for transmissio n since the difference in frequency between signal reception and trans mission causes null positioning error. However, simple LMS-adjusting c an provide a cluster size of one as well as cell overlapping when the frequency deference is 5%.