Patent ID: 7174167

Claim:
A system for mobile communication based on code division multiple access, comprising: base stations, each of which communicates with mobile stations by using a plurality of radio frequencies covering respective cells, the respective cells including a first cell covered by a first radio frequency and a second cell covered by a second radio frequency; and a base-station controller which communicates with said base stations, and controls the mobile stations to switch from the first cell of a first base station to the first cell of a second base station via a soft hand-off operation and switch between the first cell and the second cell within any base station via a hard hand-off operation, said base-station controller providing the mobile stations with no direct switch between the second cell of said first base station and the second cell of said second base station, wherein each of said base stations transmits only the first radio frequency when a number of the mobile stations belonging to the first cell thereof is smaller than a given threshold, and transmits the second radio frequency in addition to the first radio frequency when the number exceeds the given threshold, and wherein said base-station controller controls some of the mobile stations to switch from the first cell to the second cell as transmission of the second radio frequency starts.