Mobile data communication system

A method for transmitting data from a base station to a mobile station in a mobile communication system, comprising the steps of:

• a) preparing a plurality of predetermined frequency channels;
• b) monitoring a received signal strength in at least one side of the base station and the mobile station;
• at the base station,
• c) concurrently transmitting a plurality of radio signals to the mobile station through the predetermined frequency channels, respectively, when the received signal strength reduces to less than a predetermined level, wherein each of the radio signals conveys the same data in data blocks;
• at the mobile station,
• d) receiving the radio signals from the base station to produce streams of received data in data blocks, the streams of received data corresponding to the radio signals, respectively;
• e) determining quality of data block for each of the streams of the received data;
• f) determining whether a block of low-quality data of quality lower than a predetermined quality level exists in the streams of the received data;
• g) transmitting a retransmission request for the block of low-quality data to the base station when the block of low-quality data exists;
• at the base station,
• h) transmitting a radio retransmission signal conveying data corresponding to the block of low-quality data to the mobile station;
• at the mobile station,
• i) a transceiver at the mobile station transmits a mobile-to-base radio signal of frequency fup to the base station and receives a base-to-mobile radio signal of frequency fD1 from the base station, a receiver at the mobile station receives a base-to-mobile radio signal of frequency fD2 from the base station and does not transmit a mobile-to-base radio signal, and
• i. in a normal receive communication mode, power is supplied to the transceiver to perform normal communications with the base station, and power is not supplied to the receiver, and
• ii. when radio communications through the transceiver are impaired, the mobile terminal changes from the normal receive mode to a receive-only mode in which power is supplied to both the receiver and the transceiver to receive the same data from the base station through two different frequency channels, such that base-to-mobile signals of frequencies fD1 and fD2 are concurrently received by the transceiver and the receiver.

A mobile communication system comprising a plurality of base stations and mobile stations, wherein a plurality of predetermined frequencies are available,

• a base station comprising:
• at least one receiver;
• a plurality of transmitters each corresponding to a different one of the predetermined frequencies;
• and
• a transmitting controller for controlling the transmitters respectively to concurrently transmit a plurality of radio signals to a mobile station communicating therewith when a received signal strength in at least one side of the base station and the mobile station reduces to less than a predetermined level;
• and
• a mobile station comprising:
• at least one transmitter;
• a plurality of receivers for receiving the radio signals from the base station;
• a processor for producing streams of received data corresponding to the receivers, respectively;
• a transceiver at the mobile station transmits a mobile-to-base radio signal of frequency fup to the base station and receives a base-to-mobile radio signal of frequency fD1 from the base station, a receiver at the mobile station receives a base-to-mobile radio signal of frequency fD2 from the base station and does not transmit a mobile-to-base radio signal, and
• i. in a normal receive communication mode, power is supplied to the transceiver to perform normal communications with the base station, and power is not supplied to the receiver, and
• ii. when radio communications through the transceiver are impaired, the mobile terminal changes from the normal receive mode to a receive-only mode in which power is supplied to both the receiver and the transceiver to receive the same data from the base station through two different frequency channels, such that base-to-mobile signals of frequencies fD1 and fD2 are concurrently received by the transceiver and the receiver.