CDMA communication system and its transmission power control method

1. A base station for communicating with a plurality of mobile terminals by CDMA, comprising:

a generator for generating at least two transmission power control signals, each of which is for one of said plurality of mobile terminals; and

a transmission module for transmitting said transmission power control signals via a common CDMA channel shared by said plurality of mobile terminals;

wherein there are at least said common CDMA channel and a plurality of traffic channels formed between said base station and said plurality of mobile terminals, each of said plurality of traffic channels for communication between said base station and one of said plurality of mobile terminals.

2. A base station according to claim 1 , further comprising a reception circuit for receiving a packet from one of the plurality of mobile terminals, wherein said generator generates said transmission power control signal for said one mobile terminal which transmitted the received packet in response to the reception of said packet.

3. A base station according to claim 2 , further comprising a unit for measuring a received level of said received packet, wherein said generator generates the transmission power control signal for said mobile terminal based on said measured received level.

4. A base station according to claim 1 , wherein said transmission power control signal is transmitted to said mobile terminal together with an ID information for said mobile terminal.

5. A base station according to claim 1 , wherein said transmission power control signal is for controlling transmission power of an uplink channel for said mobile terminal, and said transmission power control signal is transmitted according to said uplink channel for said mobile terminal.

6. A transmission power control method for a CDMA communication system having a base station and a plurality of mobile terminals, wherein:

a plurality of traffic channels, each of said plurality of traffic channels for communication between said base station and one of said plurality of mobile terminals, and a common CDMA channel shared by said plurality of mobile terminals are formed between said base station and said plurality of mobile terminals, and

said base station generating at least two transmission power control signals, each of which is for one of said plurality of mobile terminals, spreading said transmission power control signals, modulating said spread transmission power control signals, and transmitting said modulated transmission power control signals via said common CDMA channel.

7. A transmission power control method according to claim 6 , wherein said base station transmits said modulated transmission power control signal to said mobile terminal via said common channel when there is not provided a downlink traffic channel for said mobile terminal.

8. A transmission power control method according to claim 6 , wherein said base station receives a packet transmitted from one of the mobile terminals and generates said transmission power control signal for said one mobile terminal in response to reception of said packet.

9. A transmission power control method according to claim 8 , wherein said base station measures the received level of the packet received from said mobile terminal and generates said transmission power control signal according to said measured received level.

10. A transmission power control method according to claim 6 , wherein said mobile terminal receives said transmission power control signal transmitted from said base station, demodulates said received transmission power control signal, despreads said demodulated transmission power control signal and controls a transmission power of a packet to be transmitted to said base station according to said despread transmission power control signal.

11. A transmission power control method according to claim 6 , wherein said modulated transmission power control signal is transmitted to said mobile terminal together with an ID information for said mobile terminal.

12. A transmission power control method according to claim 6 , wherein said transmission power control is for controlling a transmission power of an uplink channel for said mobile terminal, and said modulated transmission power control signal is transmitted according to said uplink channel.

13. A transmission power control method for a base station in a CDMA communication system having a base station and a plurality of mobile terminals, wherein a plurality of traffic channels, each of said plurality of traffic channels for communication between said base station and one of said plurality of mobile terminals, and a common CDMA channel shared by said plurality of mobile terminals are formed between said base station and said plurality of mobile terminals, having the steps of:

generating at least two transmission power control signals, each of which is for one of said plurality of mobile terminals;

spreading said transmission power control signals in a spreader;

modulating said spread transmission power control signal in a transmission radio module; and

transmitting, from an antenna, said modulated transmission power control signals to said mobile terminal via said common CDMA channel.

14. A transmission power control method according to claim 13 , wherein said modulated transmission power control signal is transmitted when a downlink traffic channel for said mobile terminal is not provided.

15. A transmission power control method according to claim 13 , further having the step of receiving a packet from said mobile terminal prior to generating said transmission power control signal, wherein the base station generates said transmission power control signal in response to the reception of said packet.

16. A transmission power control method according to claim 15 , further having the step of measuring a received level of said received packet, wherein said transmission power control signal is generated according to said measured received level.

17. A transmission power control method according to claim 13 , wherein said transmission power control signal is transmitted to said mobile terminal together with an ID information for said mobile terminal.

18. A transmission power control method according to claim 13 , wherein said transmission power is for controlling a transmission power of an uplink channel for said mobile terminal, and said transmission power control signal is transmitted according to said uplink channel for said mobile terminal.