Prediction-based transmission power control in a mobile communications system

• US 6,088,324 A
• Filed: 05/29/1997
• Issued: 07/11/2000
• Est. Priority Date: 05/30/1996
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Sato, Toshifumi
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): Harper, Kevin C.
• Application Number:
  US08/865,316
• Time in Patent Office: 1,139 Days
• Field of Search: 370/203, 370/206, 370/207, 370/320, 370/335, 370/342, 370/441, 370/479, 370/252, 375/200, 375/206, 375/207
• US Class Current: 370/203
• CPC Class Codes: H04W 52/221 using past power control commands
• CPC Class Codes: H04W 52/223 predicting future states of the transmission

Abstract

A mobile communication system is arranged to have a code divisional multi access system as in the North America standard system and to control a transmission power for reducing an influence of interference of one channel to the other ones by lowering a control error of the electric power transmitted on an up line. In the base station, a receiving section 106 of a tranceiving unit 100 provides a pilot symbol in-phase adding circuit 113 for detecting a carrier signal point represented by an in-phase component and an quadrature component at regular intervals. The amplitude of the detected carrier signal point is corrected by an amplitude correcting circuit 114 by using the previous control values for transmission power 116 read from a memory 115. Then, a predicting circuit 117 predicts a carrier signal point at a time when the next control for transmission power is executed by using the corrected carrier signal point. The predicted carrier signal point is compared with a reference signal through a comparing circuit 119. Next, a transmission power control circuit 121 generates a control value for transmission power at a time when the next control for transmission power is executed, transmits the control value to the mobile devices, and store the control value in the memory 115. The mobile devices control the transmission power based on the control value.

Claims

1. A mobile communication system comprising:

a base station; and

a plurality of mobile devices;

wherein said base station comprises;

means for detecting a carrier signal point represented by an in-phase component and a quadrature component at regular intervals;

means for correcting an amplitude of said carrier signal point detected by said detecting means according to previous transmission power control values;

means for predicting a carrier signal point at a time point when next control for transmission power is executed by using said carrier signal point whose amplitude is corrected by said correcting means;

means for comparing an electric power of said carrier signal point predicted by said predicting means with a predecided reference value;

means for generating a control value for said transmission power at said time point when said next control for transmission power is executed, based on said compared result given by said comparing means;

a memory for storing said control value for transmission power generated by said generating means and supplying said previous control values for transmission power to said correcting means;

means for transmitted said control value for transmission power; and

wherein said plurality of mobile devices are connected to said base station through a radio wave of one frequency so that said mobile devices are controlled to keep signal electric powers received by said base station identical with each other according to said control value for transmission power transmitted from said base station.

2. The mobile communication system as claimed in claim 1, wherein said means for detecting said carrier signal point comprises means for detecting said carrier signal point by detecting pilot symbols inserted at regular periods.

3. The mobile communication system as claimed in claim 1, wherein said means for detecting said carrier signal point comprises means for detecting said carrier signal point by detecting an M-valued quadraturely modulated data signal point.

4. The mobile communication system as claimed in claim 1, wherein said predicting means comprises means for deriving said predicted value by interpolating amplitude corrected values of the latest received two carrier signal points.

5. The mobile communication system as claimed in claim 1, wherein said predicting means comprises means for deriving said predicted value by performing a linear prediction of least squares with respect to amplitude corrected values of the latest received carrier signal points.

6. The mobile communication system as claimed in claim 1, wherein said predicting means comprises means for deriving said predicted value by performing a linear prediction of least squares with respect to amplitude corrected values of the latest received plural carrier signal points.

7. A mobile communication system for doing communications in a direct diffuse code divisional multi access system, comprising:

a base station; and

a plurality of mobile devices;

wherein said base station comprises;

means for detecting a carrier signal point composed of an in-phase component and a quadrature component of a path at regular intervals, said detecting means being prepared for each of plural paths of radio signals;

means for correcting an amplitude of said carrier signal point detected by said detecting means according to previous control values for a transmission power, said correcting means being prepared for each of said paths and in correspondence to said detecting means;

means for predicting a carrier signal point at a time when next control for said transmission power is executed by using said carrier signal point whose amplitude is corrected by said correcting means, said predicting means being provided in correspondence to each of said correcting means;

means for combining electric powers of said carrier signal points predicted by said predicting means;

means for comparing said electric power combined by said combining means with a predecided reference value;

means for generating a control value for said transmission power at a time point when said next control for said transmission power is executed, based on said compared result given by said comparing means;

a memory for storing said control value for said transmission power generated by said generating means and supplying said control value as said previous control values for said transmission power to said correcting means; and

a control circuit for controlling said transmission power, said control circuit having means for transmitting said control value for said transmission power; and

wherein said plurality of mobile devices are connected to said base station through radio waves of one frequency so that said mobile devices are controlled to keep signal electric powers received by said base station identical with each other according to said control value for transmission power transmitted from said base station.

8. A mobile communication system for doing communications in a direct diffuse code divisional multi access system, comprising:

a base station; and

a plurality of mobile devices;

wherein said base station comprises;

radio wave receiving means for receiving a signal of a radio band and converting said signal into a complex baseband signal;

de-spreading means for extracting a signal of a subject channel by replicating diffuse codes of said complex baseband signal code-divided and multiplexed after said conversion;

de-multiplexing means for separating an output of said de-spreading means into pilot symbols and data symbols;

means for performing an in-phase addition of said adjacent pilot symbols received in time series from said de-multiplexing means, for enhancing S/N rato;

means for correcting an amplitude of said in-phase added pilot symbol according to previous control values for transmission power;

means for predicting a received signal point of said pilot symbol at a time when next control for transmission power is executed by said pilot symbol whose amplitude is corrected by said correcting means;

means for comparing a received electric power of said piolot symbol predicted by said predicting means with a predecided reference value;

means for generating a control value for transmission power at a time when said next control for transmission power is executed, based on said compared result given by said comparing means;

a memory for storing said control value for transmission power generated by said generating means and supplying said control value as said previous control values for transmission power to said correcting means; and

a circuit for controlling said transmission power, said circuit having means for transmitting said control value for transmission power; and

wherein said plurality of mobile devices are connected to said base station through a radio waves of one frequency so that said mobile devices are controlled to keep the signal electric powers received by said base station identical with each other according to said control value for transmission power.

9. A mobile communication system for doing communications in a direct diffuse code divisional multi access system and an M-valued quadrature modulate system, comprising:

a base station; and

a plurality of mobile devices;

wherein said base station comprises;

radio wave receiving means for receiving a signal of a radio band and converting said signal into a complex baseband signal;

de-spreading means for extracting a signal of a subject channel by replicating diffuse codes of said complex baseband signal code-divided and multiplexed after said conversion;

quadrature modulating means for calculating a correlation value of said complex baseband signal with each of M quadrature codes, M is a positive integer;

means for selecting one of said M correlation values so that said selected value gives rise to a maximum electric power;

means for correcting an amplitude of said correlation value selected by said selecting means according to previous control values for transmission power;

means for predicting a signal point at a time point when next control for transmission power is executed by said amplitude corrected correlation value;

means for comparing an amplitude of said predicted signal point with a predecided reference value;

means for generating a control value for transmission power at a time point when said next control for transmission power is executed, based on said compared result given by said comparing means;

a memory for storing said control value for transmission power generated by said generating means and supplying said control values as said previous control values for transmission power to said amplitude correcting means; and

a circuit for controlling said transmission power, said circuit having means for transmitting said control value for transmission power; and

wherein said plurality of mobile devices are connected to said base station through radio waves of one frequency so that said mobile devices are controlled to keep said signal electric powers received by said base station identical with each other according to said control value for transmission power transmitted by said base station.

10. A method for controlling transmission power in a mobile communication system, comprising the steps of:

detecting a carrier signal point represented by an in-phase component and a quadrature component at regular periods;

correcting an amplitude of said detected carrier signal point by referred to stored previous control values for said transmission power;

predicting a carrier signal point at a time when the next control for transmission power is executed by using said carrier signal point whose amplitude is corrected;

comparing an electric power of said predicted carrier signal point with a predecided reference value;

generating a control value for transmission power at said time when the next control for transmission power is executed, based on said compared result;

storing said generated control value for transmission power as a previous control value for transmission power; and

transmitting said control value for transmission power to plural mobile devices connected through radio waves of one frequency and controlling said transmission power in a manner to keep said transmission powers received by a base station equal to each other, based on said control value for transmission power.

11. The control method for transmission power in a mobile communication system as claimed in claim 10, wherein the step of detecting said carrier signal point comprises a step of detecting said carrier signal point by detecting each of pilot symbols inserted at regular periods.

12. The control method for transmission power in a mobile communication system as claimed in claim 10, wherein the step of detecting said carrier signal point comprises a step of detecting said carrier signal point by detecting a data signal point which is subject to the M-valued quadrature modulation.

13. The control method for transmission power in a mobile communication system as claimed in claim 10, wherein the step of detecting said carrier signal point comprises a step of deriving a predictive value by extrapolating amplitude-corrected values of the latest received two carrier signal points.

14. The control method for transmission power in a mobile communication system as claimed in claim 10, wherein the step of detecting said carrier signal point comprises a step of deriving a predictive value by performing a straight-line approximation of least square with respect to amplitude-corrected values of the latest received plural carrier signal points.

15. The control method for transmission power in a mobile communication system as claimed in claim 10, wherein the step of detecting said carrier signal point comprises a step of deriving a predictive value by performing a linear approximation of lest square based on amplitude-corrected values of the latest received plural carrier signal points.

16. A control method for transmission power in a mobile communication system, comprising the steps of:

detecting a carrier signal point represented by an in-phase component and a quadrature component on each path at regular periods;

correcting an amplitude of said carrier signal point detected on each path, based on previous control value for transmission power;

predicting a carrier signal point at a time when the next control for transmission power is executed by using said carrier signal point whose amplitude is corrected on each path;

adding and combining electric powers at said predicted carrier signal points;

comparing said combined electric power with a predecided reference value;

generating a control value for transmission power at said time when the next control for transmission power is executed, based on said compared result;

storing said generated control value for transmission power as said previous control values for transmission power; and

transmitting said control value for transmission power to plural mobile devices connected through radio waves of one frequency and controlling said transmission power in a manner to keep said transmission powers received by a base station equal to each other, based on said control value for transmission power.

17. A control method for transmission power in a mobile communication system for doing communications in a direct spreading code divisional multi access manner, comprising the steps of:

receiving a radio band signal and converting said signal into a complex baseband signal;

extracting a signal of a subject channel by replicating diffuse codes of the complex baseband signal code-divided and multiplexed after the conversion;

separating said extracting signal into a pilot symbol and a data symbol;

performing an in-phase addition of adjacent pilot symbols input in series for improving an S/N power ratio;

correcting an amplitude of said in-phase added pilot symbol according to previous control values for transmission power;

predicting a receive signal point of said pilot symbol at a time when the next control for transmission power is executed by using said corrected pilot symbol;

comparing said predicted receive electric power of said pilot symbol with a predecided reference value;

generating a control value for transmission power at said time when the next control for transmission power is executed, based on said compared result;

storing said generated control value for transmission power as a previous control value for transmission power; and

transmitting said control value for transmission power to plural mobile devices connected through radio waves of one frequency and controlling said transmission power in a manner to keep said transmission powers received by a base station equal to each other, based on said control value for transmission power.

18. A control method for transmission power in a mobile communication system for doing communications in a direct diffuse code divisional multi access manner and M-valued quadrature modulation manner, comprising the steps of:

receiving a radio band signal and converting said signal into a complex baseband signal;

extracting a signal of a subject channel by reversely spreading said complex baseband signal code-divided and multiplexed after conversion;

calculating a correlative value between said complex baseband signal and each of M quadrature codes, M being a positive integer;

selecting a value for derving a maximum electric power from M correlative values;

correcting an amplitude of said selected correlative value, based on a previous control value for transmission power;

predicting a signal point at a time when the next control for transmission power is executed by using said amplitude-corrected correlative value signal;

comparing an amplitude of said predicted signal point with a predecided reference value;

generating a control value for transmission power at said time when the control for transmission power is executed, based on said compared result;

storing said generated control value for transmission power as said previous control value for transmission power; and

transmitting said control value for transmission power to plural mobile devices connected through radio waves of one frequency and controlling said transmission power in a manner to keep said transmission powers received by a base station equal to each other, based on said control value for transmission power.