Communication system and communication method with diversity features

Abstract

A communication system and a communication method arranged to obtain a diversity effect in mobile communication, to reduce the influence of multipath interference, fading or the like, to perform comparatively simple information communication such as message communication with improved reliability, and to achieve effective utilization of frequencies. A plurality of base stations having receivers are provided around an urban area within base station zones. The base stations repeatedly transmit the same message data. Receiving repeaters are provided in the urban area and small or medium suburban zones. Each receiving repeater relays a signal from a small mobile terminal via an Internet network if the output level of the mobile terminal is so low that direct transmission to one of the base stations is impossible. A 25 kHz frequency band is divided into four narrower bands of 6.25 kHz in one of the embodiments. Of frequencies f1, f2, f3, and f4 in these bands, frequencies f1 to f3 are used for “down data transmission” from the base stations to a mobile terminal while f4 is used for “up data transmission” from the mobile station to one or more of the base stations.

What is claimed is:  
     
         1 . A communication system having a first area where communication with a mobile terminal can be performed and a second area where communication can be performed with the mobile terminal when on a periphery of the first area, said system comprising: 
 a plurality of base stations provided on the periphery of the first area, each of said base stations being configured to communicate via wireless communication in the first area, down message data being transmitted on a first frequency in a first narrow band of a channel frequency from an originating base station of said plurality of base stations, each of the other plurality of base stations configured to receive the down message data and then transmit the down message data on the first frequency; and    a mobile terminal configured to receive the down message data transmitted from the originating base station and other base stations and configured to transmit up message data to the plurality of base stations by using a second frequency in a second narrow band of the channel frequency different from the first frequency used for transmission of the down message data.