Downlink power control method and CDMA communication system incorporating the control method

• US 20020001292A1
• Filed: 02/06/2001
• Published: 01/03/2002
• Est. Priority Date: 02/07/2000
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Miyamoto, Yukie
• Granted Patent: US 6,940,839 B2
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04W 52/143 Downlink power control
• CPC Class Codes: H04W 52/367 Power values between minimum and maximum limits, e.g. dynamic range

Abstract

The transmit power of a CDMA downlink channel is controlled from a base station by receiving a command signal from a mobile station requesting it to decrease the transmit power of the downlink channel. In response, the base station decreases the transmit power if a hypothetically decremented value of the transmit power is higher than a nominal lower limit of its power control range, and further decreases the transmit power if the downlink channel still has a quality higher than a specified value at the mobile station even when the hypothetically decremented value is lower than the nominal lower limit. The base station sets the transmit power equal to the nominal lower limit if the hypothetically decremented value is lower than the nominal lower limit and the downlink channel still has a quality higher than the specified value at the mobile station.

Claims

1. A method of controlling the transmit power of a plurality of CDMA downlink channels from a base station within a control range between a nominal lower limit and a nominal upper limit, comprising the steps of:

receiving, at said base station, a command signal from a mobile station requesting the base station to decrease the transmit power of a downlink channel; and

decreasing, at said base station, said transmit power of said downlink channel if said downlink channel has a quality higher than a specified threshold value at said mobile station.

2. The method of claim 1, further comprising the steps of:

receiving, at said base station, a command signal from said mobile station requesting the base station to increase the transmit power of said downlink channel; and

increasing said transmit power if total transmit power of said downlink channels is lower than a specified threshold value.

3. A method of controlling the transmit power of a plurality of CDMA downlink channels from a base station within a control range between a nominal lower limit and a nominal upper limit, comprising the steps of:

receiving, at said base station, a command signal from said mobile station requesting the base station to increase the transmit power of said downlink channel; and

increasing said transmit power if total transmit power of said downlink channels is lower than a specified threshold value.

4. A method of controlling the transmit power of a plurality of CDMA downlink channels from a base station within a control range between a nominal lower limit and a nominal upper limit, comprising the steps of:

a) receiving, at said base station, a command signal from a mobile station requesting the base station to decrease the transmit power of a downlink channel;

b) decreasing the transmit power of said downlink channel if a hypothetically decremented value of said transmit power is higher than said nominal lower limit;

c) decreasing said transmit power of said downlink channel if said downlink channel has a quality lower than a specified threshold value at said mobile station even when said hypothetically decremented value is lower than said nominal lower limit; and

d) setting said transmit power of said downlink channel equal to said nominal lower limit if said hypothetically decremented value is lower than said nominal lower limit and the quality of said downlink channel is lower than said specified threshold value.

5. The method of claim 4, further comprising the steps of:

receiving, at said base station, a command signal from said mobile station requesting the base station to increase the transmit power of said downlink channel;

increasing said transmit power of said downlink channel if a hypothetically incremented value of the transmit power is lower than said nominal upper limit;

increasing said transmit power if total transmit power of said downlink channels is lower than a specified threshold value even when said hypothetically incremented value is greater than said nominal upper limit; and

setting said transmit power equal to said nominal upper limit if said hypothetically incremented value is greater than said nominal upper limit and said total transmit power is equal to or higher than said specified threshold value.

6. The method of claim 4, wherein the step (c) comprises the steps of:

c₁) receiving, at said base station, a quality indicating signal from said mobile station indicating a quality of said downlink channel at said mobile station;

c₂) determining whether the quality of said downlink channel indicated by said quality indicating signal is higher than said specified threshold value; and

c₃) decreasing said transmit power if said quality is higher than said specified threshold value even when said hypothetically decremented value is lower than said nominal lower limit.

7. The method of claim 6, wherein said quality indicating signal represents a signal to interference ratio of said downlink channel at said mobile station.

8. The method of claim 4, wherein the step (b) comprises decrementing said power level by a stepsize value which varies depending on the length of time during which said power level is lower than a predetermined level.

9. The method of claim 4, wherein the step (c) comprises decrementing said power level by a stepsize value which varies depending on the length of time during which said power level is lower than a predetermined level.

10. The method of claim 8, wherein the step (b) comprises the steps of incrementing a count value if said power level is lower than said predetermined level and increasing said stepsize value when the count value reaches a predetermined value.

11. The method of claim 9, wherein the step (c) comprises the steps of incrementing a count value if said power level is lower than said predetermined level and increasing said stepsize value when the count value reaches a predetermined value.

12. A method of controlling the transmit power of a plurality of CDMA downlink channels from a base station within a control range between a nominal lower limit and a nominal upper limit, comprising the steps of:

receiving, at said base station, a command signal from a mobile station requesting the base station to decrease the transmit power of a downlink channel;

decreasing the transmit power of said downlink channel if a hypothetically decremented value of said transmit power is higher than said nominal lower limit;

incrementing a count value as long as said hypothetically decremented value is lower than said nominal lower limit;

setting the transmit power of said downlink channel to said nominal lower limit if said count value is smaller than a predetermined count value; and

decreasing the transmit power of said downlink channel if said count value reaches said predetermined count value.

13. The method of claim 12, further comprising the steps of:

receiving, at said base station, a command signal from said mobile station requesting the base station to increase the transmit power of said downlink channel;

increasing said transmit power of said downlink channel if a hypothetically incremented value of the transmit power is lower than said nominal upper limit;

increasing said transmit power if total transmit power of said downlink channels is lower than a specified threshold value even when said hypothetically incremented value is greater than said nominal upper limit; and

setting said transmit power equal to said nominal upper limit if said hypothetically incremented value is greater than said nominal upper limit and said total transmit power is equal to or higher than said specified threshold value.

14. A method of controlling the transmit power of a plurality of CDMA downlink channels from a base station within a control range between a nominal lower limit and a nominal upper limit, comprising the steps of:

receiving, at said base station, a command signal from said mobile station requesting the base station to increase the transmit power of said downlink channel;

increasing said transmit power of said downlink channel if a hypothetically incremented value of the transmit power is lower than said nominal upper limit;

increasing said transmit power if total transmit power of said downlink channels is lower than a specified threshold value even when said hypothetically incremented value is greater than said nominal upper limit value; and

setting said transmit power equal to said nominal upper limit value if said hypothetically incremented value is greater than said nominal upper limit value and said total transmit power is equal to or higher than said specified threshold value.

15. A CDMA communication system comprising:

a plurality of mobile stations; and

a base station for establishing a plurality of downlink channels to said mobile stations, receiving a power command signal from a mobile station requesting the base station to decrease the transmit power of a downlink channel, and decreasing said transmit power regardless of a nominal lower limit of a power control range if the downlink channel has a quality higher than a specified threshold value at said mobile station.

16. The CDMA communication system of claim 15, wherein the base station is further arranged to:

receive a command signal from a mobile station requesting the base station to increase the transmit power of a downlink channel, and

increase said transmit power of the downlink channel if total transmit power of said downlink channels is lower than a specified threshold value.

17. A CDMA communication system comprising:

a plurality of mobile stations; and

a base station for establishing a plurality of downlink channels to said mobile stations, receiving a command signal from a mobile station requesting the base station to increase the transmit power of a downlink channel, and increasing said transmit power of the downlink channel if total transmit power of said downlink channels is lower than a specified threshold value.

18. A CDMA communication system comprising:

a plurality of mobile stations; and

a base station for establishing a plurality of downlink channels to said mobile stations, receiving a command signal from a mobile station requesting the base station to decrease the transmit power of a downlink channel, decreasing the transmit power of said downlink channel if a hypothetically decremented value of said transmit power is higher than a nominal lower limit of a power control range, decreasing said transmit power of said downlink channel if said downlink channel has a quality lower than a specified threshold value at said mobile station even when said hypothetically decremented value is lower than said nominal lower limit, and setting said transmit power of said downlink channel equal to said nominal lower limit if said hypothetically decremented value is lower than said nominal lower limit and the quality of said downlink channel at said mobile station is lower than said specified threshold value.

19. The CDMA communication system of claim 18, wherein said base station is arranged to:

receive a command signal from said mobile station requesting the base station to increase the transmit power of said downlink channel;

increase said transmit power of said downlink channel if a hypothetically incremented value of the transmit power is lower than said nominal upper limit;

increase said transmit power if total transmit power of said downlink channels is lower than a specified threshold value even when said hypothetically incremented value is greater than said nominal upper limit; and

set the transmit power equal to said nominal upper limit if said hypothetically incremented value is greater than said nominal upper limit and said total transmit power is equal to or higher than said specified threshold value.

20. The CDMA communication system of claim 18, wherein the base station is arranged to:

receiving a quality indicating signal from said mobile station indicating a quality of said downlink channel at said mobile station;

determine whether the quality of said downlink channel indicated by said quality indicating signal is higher than said specified threshold value; and

decrease said transmit power if said quality is higher than said specified threshold value even when said hypothetically decremented value is lower than said nominal lower limit.

21. The CDMA communication system of claim 18, wherein said quality indicating signal represents a signal to interference ratio of said downlink channel at said mobile station.

22. The CDMA communication system of claim 18, wherein the base station is arranged to decrement said power level by a stepsize value which varies depending on the length of time during which said power level is lower than a predetermined level.

23. The CDMA communication system of claim 18, wherein the base station is arranged to decrement said power level by a stepsize value which varies depending on the length of time during which said power level is lower than a predetermined level.

24. The CDMA communication system of claim 22, wherein the base station is arranged to increment a count value if said power level is lower than said predetermined level and increase said stepsize value when the count value reaches a predetermined value.

25. The CDMA communication system of claim 24, wherein the base station is arranged to increment a count value if said power level is lower than said predetermined level and increase said stepsize value when the count value reaches a predetermined value.

26. A CDMA communication system comprising:

a plurality of mobile stations; and

a base station for establishing a plurality of downlink channels to said mobile stations, receiving a command signal from a mobile station requesting the base station to decrease the transmit power of a downlink channel, decreasing the transmit power of said downlink channel if a hypothetically decremented value of said transmit power is higher than said nominal lower limit incrementing a count value as long as said hypothetically decremented value is lower than said nominal lower limit, setting the transmit power of said downlink channel to said nominal lower limit if said count value is smaller than a predetermined count value, and decreasing the transmit power of said downlink channel if said count value reaches said predetermined count value.

27. The CDMA communication system of claim 26, wherein the base station is arranged to:

receive a command signal from said mobile station requesting the base station to increase the transmit power of said downlink channel;

increase said transmit power of said downlink channel if a hypothetically incremented value of the transmit power is lower than said nominal upper limit;

increase said transmit power if total transmit power of said downlink channels is lower than a specified threshold value even when said hypothetically incremented value is greater than said nominal upper limit; and

set the transmit power equal to said nominal upper limit if said hypothetically incremented value is greater than said nominal upper limit and said total transmit power is equal to or higher than said specified threshold value.

28. A CDMA communication system comprising:

a plurality of mobile stations; and

a base station for establishing a plurality of downlink channels to said mobile stations, receiving, at said base station, a command signal from said mobile station requesting the base station to increase the transmit power of said downlink channel, increasing said transmit power of said downlink channel if a hypothetically incremented value of the transmit power is lower than a nominal upper limit of a power control range, increasing said transmit power if total transmit power of said downlink channels is lower than a specified threshold value even when said hypothetically incremented value is greater than said nominal upper limit, and setting said transmit power equal to said nominal upper limit if said hypothetically incremented value is greater than said nominal upper limit and said total transmit power is equal to or higher than said specified threshold value.