Downlink interference detection using transmission matrices

Abstract

A method of detecting downlink interference in a communications system may include selecting a set of user equipment for measuring interference and generating a downlink interference neighbor list for some or all of the user equipment in the set. Empty resource blocks that are common to base stations on each downlink interference neighbor list are identified, and signals that are received by the set of user equipment during the empty resource blocks are analyzed to detect interference. Certain aspects of the method may be practiced before or after an interference detection period. A system for detecting downlink interference is also provided.

What is claimed is: 
     
         1 . A method of detecting downlink interference in a communications system, the method comprising:
 selecting a set of user equipment for measuring interference;   generating, for user equipment of the set of user equipment, downlink interference neighbor lists;   identifying, for each downlink interference neighbor list, empty resource blocks common to base stations of the downlink interference neighbor list; and   analyzing signals received by the set of user equipment during the empty resource blocks to detect interference.   
     
     
         2 . The method of  claim 1 , wherein selecting the set of user equipment comprises:
 designating user equipment in a region of interest; and   adding the user equipment in the region of interest to the set of user equipment.   
     
     
         3 . The method of  claim 1 , wherein selecting the set of user equipment comprises:
 comparing a number of base stations on a downlink interference neighbor list for a first user equipment to a threshold value; and   adding the first user equipment to the set of user equipment when the number of base stations is less than the threshold value.   
     
     
         4 . The method of  claim 1 , wherein selecting the set of user equipment comprises:
 arranging a plurality of user equipment in ascending order according to a number of base stations on each downlink interference neighbor list of the plurality of user equipment;   adding user equipment from an upper portion of the list to the set of user equipment; and   excluding a lower portion of the list from the set of user equipment.   
     
     
         5 . The method of  claim 1 , wherein selecting the set of user equipment comprises:
 designating a first base station;   determining whether the first base station is on a downlink interference neighbor list of a user equipment; and   when the first base station is on the downlink interference neighbor list of the user equipment, adding the user equipment to the set of user equipment.   
     
     
         6 . The method of  claim 1 , wherein a downlink interference neighbor list is generated for each user equipment in the set of user equipment. 
     
     
         7 . The method of  claim 1 , wherein generating the downlink interference neighbor lists comprises:
 receiving neighboring base station signals from user equipment at a base station;   comparing the neighboring base station signals to a threshold value; and   when a base station signal exceeds the threshold value, adding a base station associated with the base station signal to a downlink interfering neighbor list of the user equipment that detected the base station signal.   
     
     
         8 . The method of  claim 1 , wherein identifying the empty resource blocks comprises:
 generating transmission matrices for base stations on the downlink interfering neighbor lists; and   collating the transmission matrices to identify the empty resource blocks.   
     
     
         9 . The method of  claim 8 , further comprising:
 comparing a number of user equipment attached to a first base station to a number of base stations on downlink interfering neighbor lists of the user equipment to generate a first value;   when the first value exceeds a threshold value, collating the transmission matrices at the first base station; and   when the first value is less than the threshold value, collating the transmission matrices at a central computing device of the system.   
     
     
         10 . The method of  claim 8 , further comprising:
 determining a frequency at which a first base station appears on downlink interfering neighbor lists of a plurality of user equipment of the set of user equipment; and   comparing the frequency to a threshold value,   wherein only base stations whose frequency exceeds the threshold value are included in the collating.   
     
     
         11 . The method of  claim 1 , further comprising:
 removing known interference from the signals received by the set of user equipment during the empty resource blocks.   
     
     
         12 . The method of  claim 1 , further comprising:
 allocating resources of a base station to change the location of empty resource blocks in a transmission schedule.   
     
     
         13 . The method of  claim 1 , wherein identifying the empty resource blocks is performed after the signals have been received by the set of user equipment during the empty resource blocks. 
     
     
         14 . A system for identifying interference in a cellular network, the system comprising:
 a plurality of base stations; and   a memory;   a processor; and   one or more non-transitory computer readable medium associated with the processor, the one or more computer readable medium having computer executable instructions stored thereon which, when executed by an associated one or more processor, perform the following steps:   selecting a set of user equipment for measuring interference;   generating, for user equipment of the set of user equipment, downlink interference neighbor lists;   identifying, for each downlink interference neighbor list, empty resource blocks common to base stations of the downlink interference neighbor list; and   analyzing signals received by the set of user equipment during the empty resource blocks to detect interference.   
     
     
         15 . The system of  claim 14 , wherein selecting the set of user equipment comprises:
 designating user equipment in a region of interest; and   adding the user equipment in the region of interest to the set of user equipment.   
     
     
         16 . The system of  claim 14 , wherein selecting the set of user equipment comprises:
 comparing a number of base stations on a downlink interference neighbor list for a first user equipment to a threshold value; and   adding the first user equipment to the set of user equipment when the number of base stations is less than the threshold value.   
     
     
         17 . The system of  claim 14 , wherein selecting the set of user equipment comprises:
 arranging a plurality of user equipment in ascending order according to a number of base stations on each downlink interference neighbor list of the plurality of user equipment;   adding user equipment from an upper portion of the list to the set of user equipment; and   excluding a lower portion of the list from the set of user equipment.   
     
     
         18 . The system of  claim 14 , wherein selecting the set of user equipment comprises:
 designating a first base station;   determining whether the first base station is on a downlink interference neighbor list of a user equipment; and   when the first base station is on the downlink interference neighbor list of the user equipment, adding the user equipment to the set of user equipment.   
     
     
         19 . The system of  claim 14 , wherein generating the downlink interference neighbor lists comprises:
 receiving neighboring base station signals from user equipment at a base station;   comparing the neighboring base station signals to a threshold value; and   when a base station signal exceeds the threshold value, adding a base station associated with the base station signal to a downlink interfering neighbor list of the user equipment that detected the base station signal.   
     
     
         20 . The system of  claim 14 , wherein identifying the empty resource blocks comprises:
 generating transmission matrices for base stations on the downlink interfering neighbor lists; and   collating the transmission matrices to identify the empty resource blocks.   
     
     
         21 . The system of  claim 20 , wherein the steps executed by the associated one or more processor further include:
 comparing a number of user equipment attached to a first base station to a number of base stations on downlink interfering neighbor lists of the user equipment to generate a first value;   when the first value exceeds a threshold value, collating the transmission matrices at the first base station; and   when the first value is less than the threshold value, collating the transmission matrices at a central computing device of the system.   
     
     
         22 . The system of  claim 20 , further comprising:
 determining a frequency at which a first base station appears on downlink interfering neighbor lists of a plurality of user equipment of the set of user equipment; and   comparing the frequency to a threshold value,   wherein only base stations whose frequency exceeds the threshold value are included in the collating.   
     
     
         23 . The system of  claim 14 , wherein the steps executed by the associated one or more processor further include:
 removing known interference from the signals received by the set of user equipment during the empty resource blocks.   
     
     
         24 . The system of  claim 14 , wherein the steps executed by the associated one or more processor further include:
 allocating resources of a base station to change the location of empty resource blocks in a transmission schedule.   
     
     
         25 . The system of  claim 14 , wherein identifying the empty resource blocks is performed after the signals have been received by the set of user equipment during the empty resource blocks. 
     
     
         26 . The system of  claim 14 , wherein the one or more computer readable medium includes a first computer readable medium disposed at the target base station and a second computer readable medium disposed at a central location of the system, and
 wherein the processor includes a first processing core disposed at the target base station and a second processing core disposed at the central location of the system.