| 摘要 |
<p>The invention relates to a method and an arrangement for improving the communication between a base station and a number of mobile units belonging to it in a microcell system. In greater detail, the invention has the aim of reducing the fading which is a problem when the mobile units are moving slowly or are standing still. According to the invention, the problem is solved by introducing diversity on the downlink in the system. The antenna pattern of the base station is turned so that a wave pattern varying with time is produced with spatially separated fading points. The communication preferably utilises time-division multiple access (TDMA), the turning of the antenna pattern being effected step by step between suitable time slots, preferably between TDMA frames. The turning of the antenna pattern is advantageously produced by controlling a sectoral antenna (7, 7'). In a preferred embodiment, the directional antenna (7') comprises an active element (10') in the form of a half-wave dipole surrounded by a dielectric (11) which, in turn, is enclosed in a cylinder which is made up of a number of passive elements (9') insulated from one another. The turning of the antenna pattern of the directional antenna is produced by electrically switching the passive elements. <IMAGE></p> |
