Performing power control in a mobile communications system

Abstract

A mobile communications system includes base stations and mobile units. A power control scheme is provided in which a mobile unit can enter into a discontinuous transmission (DTX) mode. During DTX mode, the mobile unit is not transmitting traffic channels that can be monitored to determine frame errors so that the target ratio of energy per bit to noise spectral density (target Eb/No) can be adjusted. Instead, the base station monitors bit errors of bits in a pilot channel communicated by the mobile unit during DTX mode. Using this technique, the target Eb/No can be adjusted even when the mobile unit is not transmitting traffic channels, so that outer-loop power control can be performed. A number of mechanisms can also be used to detect when a mobile unit has entered DTX mode.

1 . A method of performing power control in a mobile communications system having a base station and a mobile unit, comprising: 
 detecting an error in control signaling transmitted over a reverse link between the base station and the mobile unit when traffic channels are not being communicated in the reverse link; and    adjusting a power control element based on the detected error,    wherein adjusting the power control element comprises adjusting a target ratio of energy per bit to noise spectral density based on the detected error in the control signaling.    
   
   
       2 . The method of  claim 1 , further comprising receiving a pilot channel from the mobile unit over the link, the control signaling comprising the pilot channel, wherein detecting the error in control signaling comprises detecting the error in the pilot channel from the mobile unit.  
   
   
       3 . The method of  claim 1 , wherein detecting the error comprises detecting an error in the control signaling over a given period of time.  
   
   
       4 . The method of  claim 1 , wherein detecting the error comprises detecting an error in a given number of samples of the control signaling.  
   
   
       5 . The method of  claim 4 , wherein detecting the error comprises detecting an error in a given number of bits of the control signaling.  
   
   
       6 . The method of  claim 1 , further comprising communicating a power control command based on the power control element to affect transmission power of the mobile unit.  
   
   
       7 . The method of  claim 1 , wherein detecting the error comprises detecting a bit error rate in the control signaling of the reverse link.  
   
   
       8 . The method of  claim 1 , further comprising receiving the control signaling over a reverse link according to a code-division multiple access protocol.  
   
   
       9 . The method of  claim 1 , further comprising detecting that the mobile unit is in a discontinuous transmission mode, wherein detecting the error and adjusting the power control element are performed while the mobile unit is in the discontinuous transmission mode.  
   
   
       10 . The method of  claim 9 , wherein detecting that the mobile unit is in discontinuous transmission mode comprises detecting a power level of a traffic channel transmitted by the mobile unit.  
   
   
       11 . The method of  claim 9 , wherein detecting that the mobile unit is in discontinuous transmission mode comprises detecting a state of a predetermined information field.  
   
   
       12 . The method of  claim 11 , wherein the information field comprises one or more power control bits of a data frame transmitted by the mobile unit.  
   
   
       13 . The method of  claim 9 , wherein adjusting the power control element is based on the detected error if the mobile unit is detected to be in the discontinuous transmission mode, the method further comprising adjusting the power control element based on a frame error rate of traffic channels when the mobile unit is detected to be not in discontinuous transmission mode.  
   
   
       14 . An article comprising at least one storage medium containing instructions that when executed cause a system to: 
 detect an error in control signaling transmitted over a reverse link from a mobile unit when traffic is not being communicated in the reverse link; and    adjust a target ratio of energy per bit to noise spectral density based on the detected error in the control signaling.    
   
   
       15 . The article of  claim 14 , wherein detecting the error in the control signaling comprises detecting the error in a pilot channel.  
   
   
       16 . The article of  claim 14 , wherein the instructions when executed cause a system to further communicate a power control command based on the adjusted target ratio of energy per bit to noise spectral density to affect transmission power of the mobile unit.  
   
   
       17 . The article of  claim 14 , wherein the instructions when executed cause the system to further detect that the mobile unit is in a discontinuous transmission mode, wherein detecting the error and adjusting the target ratio of energy per bit to noise spectral density are performed while the mobile unit is in the discontinuous transmission mode.  
   
   
       18 . A system for use in a communications system, comprising: 
 a receiver to receive control signaling from a mobile unit; and    a controller to: 
 detect an error in the control signaling received from the mobile unit in the reverse link when traffic is not being communicated from the mobile unit; and  
 adjust a target ratio of energy per bit to noise spectral density based on the detected error in the control signaling.  
   
   
   
       19 . The system of  claim 18 , wherein the controller detects the error in the control signaling when the mobile unit is in discontinuous transmission mode.