Restricting access point transmissions

Abstract

Transmissions by a first access point (e.g., a femto cell) are restricted upon detecting an access terminal in the vicinity of the first access point in the event the access terminal is communicating with a second access point (e.g., a macro cell). Upon detection of such an access terminal, the access terminal restricts transmission (e.g., beacon transmission) on a downlink carrier frequency on which the access terminal is actively receiving information from the second access point. This restriction of transmission by the access point may involve, for example, temporarily reducing transmit power, reducing the periodicity of transmission, or ceasing transmission.

What is claimed is: 
     
         1 . A method of communication, comprising:
 detecting, by a first access point, an access terminal located near the first access point, wherein the access terminal is communicating with a second access point;   identifying, by the first access point, a downlink carrier frequency on which the access terminal is receiving information from the second access point; and   restricting, by the first access point, transmission on the identified downlink carrier frequency as a result of the detecting of the access terminal, wherein the restricting of transmission includes reducing transmit power of the first access point on the identified downlink carrier frequency to below a threshold power value.   
     
     
         2 . The method of  claim 1 , wherein the reducing of the transmit power of the first access point is based on a measurement of a received power and a measurement of a total received downlink power. 
     
     
         3 . The method of  claim 1 , wherein the reducing of the transmit power of the first access point is based on a measurement of an uplink received power. 
     
     
         4 . The method of  claim 1 , wherein the detecting of the access terminal includes one of:
 determining that the access terminal is subject to interference from beacons transmitted by the first access point on the downlink carrier frequency; or   determining that the access terminal is being or has been handed-over from the first access point.   
     
     
         5 . The method of  claim 1 , wherein the detecting of the access terminal includes:
 measuring received signal strength on an uplink carrier frequency; and   comparing the measured received signal strength with a threshold.   
     
     
         6 . The method of  claim 5 , wherein the identifying of the downlink carrier frequency includes identifying a downlink carrier frequency paired with the uplink carrier frequency when the measured received signal strength is greater than or equal to the threshold. 
     
     
         7 . The method of  claim 5 , further comprising synchronizing timing of the measurement of received signal strength with beacon transmission timing. 
     
     
         8 . The method of  claim 5 , further comprising determining the threshold based on:
 allowed path loss between the first access point and the access terminal; and   estimated transmit power used by the access terminal to communicate with the second access point.   
     
     
         9 . The method of  claim 5 , further comprising determining the threshold by:
 measuring received signal strength on the uplink carrier frequency over a period of time;   calculating a nominal received signal strength based on the measuring of the received signal strength over the period of time; and   determining the threshold based on the nominal received signal strength.   
     
     
         10 . The method of  claim 5 , further comprising determining the threshold by:
 determining that the access terminal has been handed-over from the first access point;   measuring received signal strength on the uplink carrier frequency as a result of the determining that the access terminal has been handed-over; and   determining the threshold based on the measuring of the received signal strength as a result of the determination that the access terminal has been handed-over.   
     
     
         11 . The method of  claim 1 , further comprising determining that the first access point provides service for access terminals on the identified downlink carrier frequency, wherein the detecting of the access terminal includes:
 measuring out-of-cell interference on an uplink carrier frequency associated with the downlink carrier frequency; and   comparing the out-of-cell interference with a threshold.   
     
     
         12 . The method of  claim 1 , wherein the restricting of the transmission includes one or more of:
 temporarily restricting beacon transmissions by the first access point on the identified downlink carrier frequency,   temporarily reducing transmit power used by the first access point on the identified downlink carrier frequency,   reducing a periodicity at which the first access point transmits signals on the identified downlink carrier frequency,   reducing how frequently the first access point transmits beacon signals on the identified downlink carrier frequency, or   temporarily ceasing transmissions by the first access point on the identified downlink carrier frequency.   
     
     
         13 . The method of  claim 12 , wherein the temporary reducing of the transmit power includes:
 determining a maximum transmit power value based on a measurement of received signal strength on an uplink carrier frequency; and   setting a reduced transmit power as the maximum transmit power value.   
     
     
         14 . The method of  claim 1 , further comprising:
 measuring received signal strength on an uplink carrier frequency associated with the downlink carrier frequency;   determining that the received signal strength is less than or equal to a threshold; and   terminating the restricting of the transmission as a result of the determining that the measured received signal strength is less than or equal to the threshold.   
     
     
         15 . An apparatus for communication, comprising:
 a detection controller operable to detect an access terminal located near the apparatus, wherein the access terminal is communicating with an access point, and further operable to identify a downlink carrier frequency on which the access terminal is communicating with the access point; and   a transmission controller operable to restrict transmission by the apparatus on the identified downlink carrier frequency as a result of the detection of the access terminal, wherein the restriction of transmission includes reducing transmit power of the first access point on the identified downlink carrier frequency to below a threshold power value.   
     
     
         16 . The apparatus of  claim 15 , wherein the transmission controller is further operable to reduce the transmit power of the first access point based on a measurement of a received power and a measurement of a total received downlink power. 
     
     
         17 . The apparatus of  claim 15 , wherein the transmission controller is further operable to reduce the transmit power of the first access point is based on a measurement of an uplink received power. 
     
     
         18 . The apparatus of  claim 15 , wherein to detect the access terminal, the detection controller is further operable to:
 determine that the access terminal is subject to interference from beacons transmitted by the first access point on the downlink carrier frequency; or   determine that the access terminal is being or has been handed-over from the first access point.   
     
     
         19 . The apparatus of  claim 15 , wherein to detect the access terminal, the detection controller is further operable to:
 measure received signal strength on an uplink carrier frequency; and   compare the measured received signal strength with a threshold.   
     
     
         20 . The apparatus of  claim 19 , wherein, to identify the downlink carrier frequency, the detection controller is further operable to includes identify a downlink carrier frequency paired with the uplink carrier frequency when the measured received signal strength is greater than or equal to the threshold. 
     
     
         21 . The apparatus of  claim 19 , wherein the detection controller is further operable to synchronize timing of the measurement of received signal strength with beacon transmission timing. 
     
     
         22 . The apparatus of  claim 19 , wherein the detection controller is further operable to determine the threshold based on:
 allowed path loss between the first access point and the access terminal; and   estimated transmit power used by the access terminal to communicate with the second access point.   
     
     
         23 . The apparatus of  claim 19 , wherein the detection controller is further operable to determine the threshold by:
 measuring received signal strength on the uplink carrier frequency over a period of time;   calculating a nominal received signal strength based on the measurement of received signal strength over the period of time; and   determining the threshold based on the nominal received signal strength.   
     
     
         24 . The apparatus of  claim 19 , wherein the detection controller is further operable to determine the threshold by:
 determining that the access terminal has been handed-over from the first access point;   measuring received signal strength on the uplink carrier frequency as a result of the determination that the access terminal has been handed-over; and   determining the threshold based on the measurement of received signal strength as a result of the determination that the access terminal has been handed-over.   
     
     
         25 . The apparatus of  claim 15 , wherein:
 the detection controller is further operable to determine that the first access point provides service for access terminals on the identified downlink carrier frequency; and   wherein, to the access terminal, the detection controller is further operable to:
 measure out-of-cell interference on an uplink carrier frequency associated with the downlink carrier frequency, and 
 compare the out-of-cell interference with a threshold. 
   
     
     
         26 . The apparatus of  claim 15 , wherein to restrict the transmission, the transmission controller is further operable to:
 temporarily restrict beacon transmissions by the first access point on the identified downlink carrier frequency;   temporarily reduce transmit power used by the first access point on the identified downlink carrier frequency;   reduce a periodicity at which the first access point transmits signals on the identified downlink carrier frequency;   reduce how frequently the first access point transmits beacon signals on the identified downlink carrier frequency; or   temporarily cease transmissions by the first access point on the identified downlink carrier frequency.   
     
     
         27 . The apparatus of  claim 26 , wherein a maximum transmit power value for the reduced transmit power is specified based on a measurement of received signal strength on an uplink carrier frequency. 
     
     
         28 . The apparatus of  claim 15 , wherein:
 the detection controller is further operable to measure received signal strength on an uplink carrier frequency associated with the downlink carrier frequency;   the detection controller is further operable to determine that the measured received signal strength is less than or equal to a threshold; and   the transmission controller is further operable to terminate the restriction of transmission as a result of the determination that the measured received signal strength is less than or equal to the threshold.   
     
     
         29 . An apparatus for communication, comprising:
 means for detecting an access terminal located near the apparatus, wherein the access terminal is communicating with an access point;   means for identifying a downlink carrier frequency on which the access terminal is communicating with the access point; and   means for restricting transmission on the identified downlink carrier frequency as a result of the detection of the access terminal.   
     
     
         30 . A computer-readable medium storing computer executable code, comprising:
 code for causing a computer to detect, at a first access point, an access terminal located near the first access point, wherein the access terminal is communicating with a second access point;   code for causing the computer to identify, at the first access point, a downlink carrier frequency on which the access terminal is communicating with the second access point; and   code for causing the computer to restrict, at the first access point, transmission on the identified downlink carrier frequency as a result of the detection of the access terminal.