Radiated power control for a multi-antenna transmission

Abstract

To meet a radiated power limit, a transmitting station determines a synthesized antenna pattern based on steering vectors used for spatial processing and estimates an array gain based on the synthesized antenna pattern. Different spatial processing modes (e.g., eigensteering and spatial spreading) result in different synthesized antenna patterns. The array gain may be estimated based on the spatial processing mode used for the data transmission and applicable parameters (e.g., eigenvalues) for that mode. An element gain for each antenna used for data transmission may also be estimated. The transmitting station then limits the transmit power for the data transmission based on the array gain, the element gain, and the radiated power limit, which may be an effective isotropic radiated power (EIRP) limit imposed by a regulatory agency.

1 . A method of controlling radiated power for a data transmission, comprising:
 estimating an array gain based on a synthesized antenna pattern for the data transmission; and   limiting the transmit power for the data transmission based on the array gain and a radiated power limit.   
   
   
       2 . The method of  claim 1 , further comprising:
 determining the synthesized antenna pattern based on at least one steering vector used for spatial processing for the data transmission.   
   
   
       3 . The method of  claim 1 , wherein the estimating the array gain based on the synthesized antenna pattern comprises:
 determining an eigenvalue for a spatial channel used for the data transmission; and   deriving the array gain based on the eigenvalue.   
   
   
       4 . The method of  claim 1 , wherein the estimating the array gain based on the synthesized antenna pattern comprises:
 determining a plurality of eigenvalues for a plurality of spatial channels used for the data transmission; and   deriving the array gain based on the plurality of eigenvalues.   
   
   
       5 . The method of  claim 1 , wherein the estimating the array gain based on the synthesized antenna pattern comprises:
 determining a plurality of eigenvalues for a plurality of frequency subbands of at least one wideband spatial channel used for the data transmission; and   deriving the array gain based on the plurality of eigenvalues.   
   
   
       6 . The method of  claim 1 , wherein the estimating the array gain based on the synthesized antenna pattern comprises:
 determining a plurality of eigenvalues for a plurality of frequency subbands of a wideband spatial channel used for the data transmission; and   deriving the array gain based on a largest eigenvalue among the plurality of eigenvalues.   
   
   
       7 . The method of  claim 1 , wherein the estimating the array gain based on the synthesized antenna pattern comprises:
 determining a plurality of eigenvalues for a plurality of frequency subbands of a wideband spatial channel used for the data transmission; and   deriving the array gain based on an average of the plurality of eigenvalues.   
   
   
       8 . The method of  claim 1 , wherein the estimating the array gain based on the synthesized antenna pattern comprises:
 setting the array gain to a predetermined value if the synthesized antenna pattern is a spatially spread synthesized antenna pattern.   
   
   
       9 . The method of  claim 1 , wherein the estimating the array gain based on the synthesized antenna pattern comprises:
 determining a spatial processing mode used for the data transmission; and   setting the array gain to a predetermined value for the spatial processing mode used for the data transmission.   
   
   
       10 . The method of  claim 1 , further comprising:
 estimating an element gain for each of a plurality of antennas used for the data transmission, and wherein the transmit power for the data transmission is limited further based on the element gain.   
   
   
       11 . The method of  claim 1 , wherein the radiated power limit is an effective isotropic radiated power (EIRP) limit. 
   
   
       12 . An apparatus in a wireless communication network, comprising:
 a controller to estimate an array gain based on a synthesized antenna pattern for a data transmission; and   a control unit to limit transmit power for the data transmission based on the array gain and a radiated power limit.   
   
   
       13 . The apparatus of  claim 12 , wherein the controller determines the synthesized antenna pattern based on at least one steering vector used for spatial processing for the data transmission. 
   
   
       14 . The apparatus of  claim 12 , wherein the controller determines at least one eigenvalue for at least one spatial channel used for the data transmission and derives the array gain based on the at least one eigenvalue. 
   
   
       15 . The apparatus of  claim 12 , wherein the controller determines a plurality of eigenvalues for a plurality of frequency subbands of at least one wideband spatial channel used for the data transmission and derives the array gain based on the plurality of eigenvalues. 
   
   
       16 . The apparatus of  claim 12 , wherein the controller sets the array gain to a predetermined value if the synthesized antenna pattern is a spatially spread synthesized antenna pattern. 
   
   
       17 . The apparatus of  claim 12 , wherein the controller estimates an element gain for each of a plurality of antennas used for data transmission, and wherein the processor limits the transmit power for the data transmission further based on the element gain. 
   
   
       18 . An apparatus in a wireless communication network, comprising:
 means for estimating an array gain based on a synthesized antenna pattern for a data transmission; and   means for limiting transmit power for the data transmission based on the array gain and a radiated power limit.   
   
   
       19 . The apparatus of  claim 18 , further comprising:
 means for determining the synthesized antenna pattern based on at least one steering vector used for spatial processing for the data transmission.   
   
   
       20 . The apparatus of  claim 18 , wherein the means for estimating the array gain based on the synthesized antenna pattern comprises:
 means for determining at least one eigenvalue for at least one spatial channel used for the data transmission; and   means for deriving the array gain based on the at least one eigenvalue.   
   
   
       21 . The apparatus of  claim 18 , wherein the means for estimating the array gain based on the synthesized antenna pattern comprises:
 means for determining a plurality of eigenvalues for a plurality of frequency subbands of at least one wideband spatial channel used for the data transmission; and   means for deriving the array gain based on the plurality of eigenvalues.   
   
   
       22 . The apparatus of  claim 18 , wherein the means for estimating the array gain based on the synthesized antenna pattern comprises:
 means for setting the array gain to a predetermined value if the synthesized antenna pattern is a spatially spread synthesized antenna pattern.   
   
   
       23 . The apparatus of  claim 18 , further comprising:
 means for estimating an element gain for each of a plurality of antennas used for data transmission, and wherein the transmit power for the data transmission is limited further based on the element gain.   
   
   
       24 . A computer-program storage apparatus for controlling radiated power for a data transmission comprising a memory having one or more software modules stored thereon, the one or more software modules being executable by one or more processors and the one or more software modules comprising:
 code for estimating an array gain based on a synthesized antenna pattern for a data transmission; and   code for limiting transmit power for the data transmission based on the array gain and a radiated power limit.   
   
   
       25 . The computer-program storage apparatus of  claim 24 , further comprising:
 code for determining the synthesized antenna pattern based on at least one steering vector used for spatial processing for the data transmission.   
   
   
       26 . The computer-program storage apparatus of  claim 24 , wherein the code for estimating the array gain based on the synthesized antenna pattern comprises:
 code for determining at least one eigenvalue for at least one spatial channel used for the data transmission; and   code for deriving the array gain based on the at least one eigenvalue.   
   
   
       27 . The computer-program storage apparatus of  claim 24 , wherein the code for estimating the array gain based on the synthesized antenna pattern comprises:
 code for determining a plurality of eigenvalues for a plurality of frequency subbands of at least one wideband spatial channel used for the data transmission; and   code for deriving the array gain based on the plurality of eigenvalues.   
   
   
       28 . The computer-program storage apparatus of  claim 24 , wherein the code for estimating the array gain based on the synthesized antenna pattern comprises:
 code for setting the array gain to a predetermined value if the synthesized antenna pattern is a spatially spread synthesized antenna pattern.   
   
   
       29 . The computer-program storage apparatus of  claim 24 , further comprising:
 code for estimating an element gain for each of a plurality of antennas used for data transmission, and wherein the transmit power for the data transmission is limited further based on the element gain.