CDMA communication system and its transmission power control method

A transmission power control method for a spectrum spreading communication system which performs communication between a base station and a plurality of mobile terminals by using a plurality of channels, wherein:

• said plurality of channels includes first channels allocated to said mobile terminals for transmitting a data packet to said base station and a second channel used by said base station to transmit a control signal to said plurality of mobile terminals, said second channel being shared by said plurality of mobile terminals;
• said base station measures the reception level of a signal received at each of said first channels, generates a transmission control signal in accordance with the reception level, and transmits a transmission power control signal of each of said first channels to said second channel, as part of said control signal;
• and
• each of said plurality of mobile terminals receives said transmission power control signal destined thereto at said second channel, and controls the transmission power of a signal to be transmitted via a corresponding one of said first channels in accordance with said received transmission power control signal.

A transmission power control method for a spectrum spreading communication system which performs communication between a base station and a plurality of mobile terminals, wherein:

• each of said plurality of mobile stations receives a control signal transmitted from said base station, and transmits a reservation packet representative of a transmission request for a data packet, at a transmission power corresponding to the reception level of said control signal;
• said base station receives said reservation packet, generates an initial transmission power control signal in accordance with the reception level of said reservation packet, and transmits said initial transmission power control signal to a corresponding one of said plurality of mobile terminals, said initial transmission power control signal being contained in an answer packet indicating a traffic channel via which said corresponding one transmits said data packet;
• and
• said corresponding one starts transmitting said data packet at a transmission power corresponding to said initial transmission power control signal contained in said answer packet.

A base station for communicating with a plurality of mobile terminals by spectrum spreading, comprising:

• a reception circuit for receiving a data packet transmitted from each of said plurality of mobile terminal;
• a unit for measuring the reception level of said received data packet;
• a generator for generating a transmission power control signal in accordance with said measured reception level of said data packet;
• and
• a transmission circuit for transmitting a common transmission power control signal to said plurality of mobile terminals, said common transmission power control signal containing said generated transmission power control signal of each of said plurality of mobile terminals.

A base station for communicating with a plurality of mobile terminals by spectrum spreading, comprising:

• a reception circuit for receiving a data packet transmitted from each of said plurality of mobile terminal;
• a unit for measuring the reception level of said received data packet;
• a generator for generating a transmission power control signal in accordance with said measured reception level of said data packet;
• and
• a transmission circuit for transmitting said generated transmission power control signal to said plurality of mobile terminals, as part of control information.

A base station for communicating with a plurality of mobile terminals by spectrum spreading, comprising:

• a first reception circuit for receiving a reservation packet representative of a transmission request for a data packet to be transmitted from each of said plurality of mobile terminals;
• second reception circuits for receiving data packets transmitted from said plurality of mobile terminals;
• a unit for measuring the reception level of said received data packet;
• a traffic channel transmission power control signal generator for generating a transmission power control signal in accordance with said measured reception level of said data packet;
• and
• a transmission circuit for transmitting a common transmission power control signal to said plurality of mobile terminals, said common transmission power control signal containing said generated transmission power control signals to be transmitted to said plurality of mobile terminals.

A mobile terminal for communicating with a base station by spectrum spreading, comprising:

• a reception circuit for receiving a common transmission power control signal transmitted from said base station, said common transmission power control signal containing transmission power control signals of a plurality of mobile terminals;
• a calculator for calculating a gain in accordance with a transmission power control signal destined to the mobile terminal and derived from said common transmission power control signal;
• and
• a transmission circuit for transmitting a data packet at a transmission power corresponding to said calculated gain.

A mobile terminal for communicating with a base station by spectrum spreading, comprising:

• a first reception circuit for receiving a common transmission power control signal transmitted from said base station, said common transmission power control signal containing transmission power control signals of a plurality of mobile terminals, and for receiving an answer packet transmitted from said base station, said answer packet indicating a traffic channel via which the mobile terminal transmits a data packet;
• a calculator for calculating a gain in accordance with a transmission power control signal destined to the mobile terminal and derived from said common transmission power control signal;
• and
• a transmission circuit for transmitting said data packet at a transmission power corresponding to said calculated gain via said traffic channel designated by said answer packet.

A mobile terminal for communicating with a base station by spectrum spreading, comprising:

• a first reception circuit for receiving a common transmission power control signal transmitted from said base station, said common transmission power control signal containing transmission power control signals of a plurality of mobile terminals, and for receiving an answer packet transmitted from said base station, said answer packet indicating a traffic channel via which the mobile terminal transmits a data packet;
• a second reception circuit for receiving said data packet containing said transmission power control signal transmitted from said base station;
• a switch for switching a connection to a gain calculator between said first reception circuit and said second reception circuit;
• and
• a transmission circuit for transmitting said data packet at a transmission power corresponding to the gain calculated by said gain calculator via the traffic channel designated by said answer packet,
• wherein said gain calculator calculates the gain in accordance with said common transmission power control signal or said transmission power control signal derived from said data packet.