US Patent 7912474 Radio channel control method in a cellular system

When a cell load becomes higher than a call setup threshold value for a first channel (CS channel), a second channel (PS channel) is changed into a channel having a low transmission rate. Consequently, the cell load is reduced and no cell loss occurs in the first channel. Therefore, the call loss rate of a first communication service is lowered. Simultaneously, a handover threshold value is higher than the call setup threshold value for the first channel so that a failure rate of handover is lowered.