Alternative Cell Configurations for Digital Mobile Radio Systems

Alternative Cell Configurations for Digital Mobile Radio Systems By C.-E. S U N D B E R G * (Manuscript received January 19, 1982) This paper introduces a novel class of antenna configurations and applies it to cellular digital mobile radio systems with frequency reuse. Directional antennas are used extensively. Cooperation between more base stations than are in the conventional three-corner directional antenna scheme is required for the alternative cells. The paper studies the relationship between signal-tocochannel interference and trunking efficiency (availability of channels) and compares conventional systems with the same base-station locations. We concluded that the new antenna configurations can significantly improve trunking efficiency. Time-division retransmission systems with space diversity are considered for some cases. Furthermore, we show how transmitter power weighting (i.e., certain transmitters have higher output power than others) can improve the signal-to-cochannel-interference ratio for the novel cellular systems. I. INTRODUCTION Good spectral efficiency in digital mobile radio systems is obtained through frequency reuse. That is, each cell in the cellular system is assigned a number of channels in a frequency-division system, and each channel (frequency) is reused at a cell further away. The closer this second cell is, the higher the system capacity. On the other hand, cochannel interference increases when the interfering cells are too close. Omnidirectional and directional antenna arrangements have * Bell Laboratories.