Method and system for closed loop power control in wireless systems

Abstract

The present invention relates to a method and system for closed loop power control in a mobile communication system. Error is determined between a target signal-to-interference (SIR) and a received SIR. A power control scheme at a power controller of a base station determines a power change that is proportional to the error. Gain of the power controller is selected to achieve minimum error at a subsequent time instant.

1 . A transmission power control method for a mobile communication system comprising the steps of: 
 determining a target Signal-to-Interference Ratio (SIR);    estimating a received SIR of a base station;    determining error between the received SIR and the target SIR; and    determining a power control scheme at a power controller of the base station to determine a power change for the transmission power of a mobile to the base station in proportion to the error; and    selecting a gain of the power controller to achieve minimum error at a subsequent time instant.    
   
   
       2 . The method of  claim 1  wherein said gain is determined as a minimization of a square of the error.  
   
   
       3 . The method of  claim 1  further comprising the step of: 
 estimating channel variation and using said estimated channel variation in said step of selecting said gain.    
   
   
       4 . (canceled)  
   
   
       5 . (canceled)  
   
   
       6 . (canceled)  
   
   
       7 . (canceled)  
   
   
       8 . (canceled)  
   
   
       9 . The method of  claim 1  wherein said power change is transmitted from said base station to said mobile in a frame format on a downlink from said base station to said mobile.  
   
   
       10 . The method of  claim 9  wherein overhead of said power change is in the range of 3 to 5 bits per frame.  
   
   
       11 . A transmission power control system for a mobile communication system comprising: 
 means for determining a target Signal-to-Interference Ratio (SIR);    means for estimating a received SIR of a base station;    means for determining error between the received SIR and the target SIR; and    means for determining a power control scheme at a power controller of the base station to determine a power change for the transmission power of a mobile to the base station in proportion to the error; and    means for selecting a gain of the power controller to achieve minimum error at a subsequent time instant.    
   
   
       12 . The system of  claim 11  wherein said gain is determined as a minimization of a square of the error.  
   
   
       13 . The system of  claim 11  further comprising: 
 means for estimating channel variation and using said estimated channel variation in said step of selecting said gain.    
   
   
       14 . (canceled)  
   
   
       15 . (canceled)  
   
   
       16 . (canceled)  
   
   
       17 . (canceled)  
   
   
       18 . (canceled)  
   
   
       19 . The system of  claim 11  wherein said power change is transmitted from said base station to said mobile in a frame format on a downlink from said base station to said mobile.  
   
   
       20 . The system of  claim 19  wherein overhead of said power change is in the range of 3 to 5 bits per frame.