Reverse-link capacity and transmit power in a power-controlled cellular DS-CDMA system
K. Ohno, Fumiyuki Adachi · Electronics and Communications in Japan (Part I Communications) · 1997
This paper considers the DS-CDMA with an imperfect transmit power control and analyzes the relationship between the reverse-link capacity and the average transmit power, considering the space/path (RAKE) diversity. A simple formula for calculation is derived. Using the space diversity, an instantaneous large transmit power can be avoided when the transmit power is controlled. It is shown that, at that time, the interference from other cells can be reduced and the reverse-link capacity can be increased. Especially, when the spreading bandwidth is narrow and the single-path reception is used, the space diversity is shown to be necessary. It is known in CDMA that the link capacity can be increased by sectorizing the cell. In the practical antenna, however, where the directivity of the antenna overlaps with other sectors, there can be interference from adjacent sectors. A calculation formula is derived considering the antenna directivity. Using that formula, the reverselink capacity and the average transmit power are examined precisely for the case where the pilot symbol interpolation QPSK coherent detection is used in the data modulation/demodulation. Finally, the effect of the shadowing correlation is investigated. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80 (4): 72–82, 1996