Power control for wireless lan stations

Abstract

Techniques and apparatus for controlling the transmit power of an uplink (UL) signal from a user terminal in a wireless communications system in an effort to achieve some target characteristic, such as a target carrier-to-interference (C/I) ratio, at an access point (AP) are provided. In this manner, such a user terminal may help avoid or compensate for imbalances in received radio frequency (RF) power between UL signals received from multiple user terminals by the AP. For example, the transmit power at each user terminal may be controlled in an effort to achieve a target post-processing C/I ratio of 28 dB per spatial stream in an effort to reduce large power imbalances and optimize throughput per user terminal. The user terminal and the AP may compose part of a multiple-input multiple-output (MIMO) communication system utilizing spatial-division multiple access (SDMA) techniques.

1 . A method for power control of an uplink (UL) signal in a wireless local area network (WLAN), comprising:
 calculating, by a user terminal, a desired transmit power of the user terminal for transmitting the UL signal to an access point (AP) of the WLAN based at least on a target signal-to-noise ratio at the AP and a processing gain at the AP, wherein the processing gain at the AP is a function of at least one of: a number of frequencies used for transmission or a number of spatial streams;   adjusting, by the user terminal, a transmit power of the UL signal to an adjusted transmit power based on the desired transmit power; and   transmitting, by the user terminal, the UL signal, at the adjusted transmit power, to the AP.   
     
     
         2 . The method of  claim 1 , further comprising:
 determining whether the desired transmit power exceeds a capability of one or more transmitter circuit components of the user terminal; and if not   setting the adjusted transmit power to the desired transmit power.   
     
     
         3 . The method of  claim 1 , wherein the processing gain is an orthogonal frequency-division multiple access (OFDMA) processing gain at the AP. 
     
     
         4 . The method of  claim 1 , wherein the processing gain is a spatial-division multiple access (SDMA) processing gain at the AP. 
     
     
         5 . The method of  claim 1 , wherein the processing gain is a code-division multiple access (CDMA) processing gain at the AP. 
     
     
         6 . The method of  claim 1 , wherein calculating the desired transmit power of the user terminal for transmitting the UL signal is based at least on the target signal-to-noise ratio at the AP, the processing gain at the AP, a received signal strength of a downlink (DL) signal, and a thermal noise floor parameter. 
     
     
         7 . The method of  claim 1 , wherein calculating the desired transmit power of the user terminal for transmitting the UL signal is based at least on the target signal-to-noise ratio at the AP, the processing gain at the AP, a received signal strength of a downlink (DL) signal, and a parameter indicating a transmit power of the AP, wherein the parameter indicating the transmit power of the AP is advertised by the AP. 
     
     
         8 . The method of  claim 1 , wherein calculating the desired transmit power of the user terminal for transmitting the UL signal is based at least on the target signal-to-noise ratio at the AP, the processing gain at the AP, a received signal strength of a downlink (DL) signal, and one or more additional parameters calibrated during an association of the user terminal with the AP. 
     
     
         9 . The method of  claim 1 , further comprising:
 encoding an indication of a value of the adjusted transmit power in a header of an UL packet, wherein the UL signal includes the UL packet.   
     
     
         10 . The method of  claim 9 , wherein encoding the indication of the value of the adjusted transmit power comprises encoding the indication of the value in a Media Access Control (MAC) header of the UL packet. 
     
     
         11 . The method of  claim 9 , further comprising:
 communicating a peak transmit power of the user terminal to the AP during an association of the user terminal with the AP, wherein the indication of the value of the adjusted transmit power represents an amount that the adjusted transmit power is below the peak transmit power of the user terminal.   
     
     
         12 . The method of  claim 1 , further comprising:
 receiving adjustment information from the AP in response to transmitting the UL signal to the AP; and   adjusting the transmit power of a subsequent UL signal to an updated adjusted transmit power based on the adjustment information.   
     
     
         13 . The method of  claim 12 , wherein the adjustment information indicates at least one of a new target signal-to-noise ratio at the AP or an adjustment to the target signal-to-noise ratio at the AP. 
     
     
         14 . The method of  claim 12 , further comprising:
 communicating a peak transmit power of the user terminal to the AP during an association of the user terminal with the AP, wherein the adjustment information represents back-off value from the peak transmit power.   
     
     
         15 . A user terminal, comprising:
 at least one processor; and   memory coupled to the at least one processor, wherein the at least one processor and the memory are configured to direct the user terminal to:
 calculate a desired transmit power of the user terminal for transmitting an uplink (UL) signal to an access point (AP) of the WLAN based at least on a target signal-to-noise ratio at the AP and a processing gain at the AP, wherein the processing gain at the AP is a function of at least one of: a number of frequencies used for transmission or a number of spatial streams; 
 adjust a transmit power of the UL signal to an adjusted transmit power based on the desired transmit power; and 
 transmit the UL signal, at the adjusted transmit power, to the AP. 
   
     
     
         16 . The user terminal of  claim 15 , wherein the at least one processor and the memory are further configured to direct the user terminal to:
 receive adjustment information from the AP in response to transmitting the UL signal to the AP; and   adjust the transmit power of a subsequent UL signal to an updated adjusted transmit power based on the adjustment information.   
     
     
         17 . The user terminal of  claim 16 , wherein the adjustment information indicates at least one of a new target signal-to-noise ratio at the AP or an adjustment to the target signal-to-noise ratio at the AP. 
     
     
         18 . The user terminal of  claim 16 , wherein the at least one processor and the memory are further configured to direct the user terminal to:
 communicate a peak transmit power of the user terminal to the AP during an association of the user terminal with the AP, wherein the adjustment information represents back-off value from the peak transmit power.   
     
     
         19 . A user terminal, comprising:
 means for calculating a desired transmit power of the user terminal for transmitting the UL signal to an access point (AP) of the WLAN based at least on a target signal-to-noise ratio at the AP and a processing gain at the AP, wherein the processing gain at the AP is a function of at least one of: a number of frequencies used for transmission or a number of spatial streams;   mean for adjusting a transmit power of the UL signal to an adjusted transmit power based on the desired transmit power; and   transmitting the UL signal, at the adjusted transmit power, to the AP.   
     
     
         20 . The user terminal of  claim 19 , further comprising:
 means for receiving adjustment information from the AP in response to transmitting the UL signal to the AP; and   means for adjusting the transmit power of a subsequent UL signal to an updated adjusted transmit power based on the adjustment information.   
     
     
         21 . The user terminal of  claim 20 , wherein the adjustment information indicates at least one of a new target signal-to-noise ratio at the AP or an adjustment to the target signal-to-noise ratio at the AP. 
     
     
         22 . The user terminal of  claim 20 , further comprising:
 means for communicating a peak transmit power of the user terminal to the AP during an association of the user terminal with the AP, wherein the adjustment information represents back-off value from the peak transmit power.   
     
     
         23 . A computer-program product for power control of an uplink (UL) signal in a wireless local area network (WLAN), comprising a non-transitory computer-readable medium having instructions stored thereon, the instructions being executable by one or more processors of a user terminal to direct the user terminal to:
 calculate a desired transmit power of the user terminal for transmitting an uplink (UL) signal to an access point (AP) of the WLAN based at least on a target signal-to-noise ratio at the AP and a processing gain at the AP, wherein the processing gain at the AP is a function of at least one of: a number of frequencies used for transmission or a number of spatial streams;   adjust a transmit power of the UL signal to an adjusted transmit power based on the desired transmit power; and   transmit the UL signal, at the adjusted transmit power, to the AP.   
     
     
         24 . The computer-program product of  claim 23 , further comprising instructions to direct the user terminal to:
 receive adjustment information from the AP in response to transmitting the UL signal to the AP; and   adjust the transmit power of a subsequent UL signal to an updated adjusted transmit power based on the adjustment information.   
     
     
         25 . The computer-program product of  claim 24 , wherein the adjustment information indicates at least one of a new target signal-to-noise ratio at the AP or an adjustment to the target signal-to-noise ratio at the AP. 
     
     
         26 . The computer-program product of  claim 24 , further comprising instructions to direct the user terminal to:
 communicate a peak transmit power of the user terminal to the AP during an association of the user terminal with the AP, wherein the adjustment information represents back-off value from the peak transmit power.