Supervision of faults in a receiver chain based on noise floor monitoring

Abstract

A method for supervision of faults in a receiving signal chain of a wireless communication comprises providing ( 210 ) data representing measured received powers in the receiving signal chain at a number of time instances. The method further comprises determining ( 220 ) a noise floor value at a number of time instances based on the data representing measured received powers. A time evolution of the determined noise floor values is registered ( 230 ) and any occurrence of a fault in the receiving signal chain is detected ( 240 ) based on the registered time evolution. An arrangement for performing supervision of faults in a receiving signal chain is also presented.

What is claimed is: 
     
         1 . A method for supervision of faults in a receiving signal chain of a wireless communication system, comprising:
 obtaining data representing measured received powers in said receiving signal chain at a number of time instances;   determining a noise floor value at a number of time instances based on said provided data;   registering a time evolution of said determined noise floor values; and   detecting any occurrence of a fault in said receiving signal chain based on said registered time evolution.   
     
     
         2 . The method of  claim 1 , wherein obtaining data representing measured received powers in said receiving signal chain comprises measuring received power in said receiving signal chain at a number of time instances. 
     
     
         3 . The method of  claim 1 , wherein obtaining data representing measured received powers in said receiving signal chain comprises receiving data representing measured received power in said receiving signal chain at a number of time instances. 
     
     
         4 . The method of  claim 1 , wherein said obtained data represents measured received powers at two or more positions in a receiving signal chain, and wherein:
 determining a noise floor value comprises determining separate noise floor values for each of said at least two positions; and   detecting any occurrence of a fault in said receiving signal chain is based on a comparison between said registered time evolutions of said determined noise floor values corresponding to said at least two positions.   
     
     
         5 . The method of  claim 1 , wherein determining a noise floor value further comprises:
 obtaining power related quantities at a number of time instances based on said obtained data representing measured received powers in said receiving signal chain; and   determining a noise floor value is based on said obtained power related quantities.   
     
     
         6 . The method of  claim 5 , wherein said power related quantities are obtained based on data representing at least two different types of received powers. 
     
     
         7 . The method of  claim 6 , wherein one type of received powers is received total wideband power. 
     
     
         8 . The method of  claim 6 , wherein determining a noise floor value comprises determining a minimum value of said power related quantities within a time period. 
     
     
         9 . The method of  claim 1 , wherein determining a noise floor value comprises:
 estimating probability distributions for a power quantity based on said obtained received powers, and   computing a conditional probability distribution of a noise floor measure based on at least a number of said estimated probability distributions for said power quantity.   
     
     
         10 . The method of  claim 1 , wherein detecting any occurrence of a fault in the receiving signal chain based on the registered time evolution includes:
 detecting the occurrence of the fault in a signal handling unit of the receiving signal chain responsive to the registered time evolution being at least a predetermined threshold.   
     
     
         11 . The method of  claim 1 , wherein detecting any occurrence of a fault in said receiving signal chain comprises:
 comparing said registered time evolution with a model time evolution; and   indicating a fault if a measure representing a difference between said registered time evolution and said model time evolution exceeds a threshold value.   
     
     
         12 . The method of  claim 11 , wherein said model time evolution is based on a statistical treatment of previous registered time evolutions for similar conditions. 
     
     
         13 . The method of  claim 1 , wherein:
 said wireless communication system is provided with receiver diversity and said receiving signal chain comprises at least two receiver branches;   determining a noise floor value comprises determining separate noise floor values for each of said at least two receiver branches; and   detecting any occurrence of a fault in said receiving signal chain is based on a comparison between said time evolutions of said determined noise floor values of said at least two receiver branches.   
     
     
         14 . The method of  claim 13 , wherein
 obtaining data representing measured received powers comprises obtaining measurements of received total wideband power for at least a first receiver branch and a second receiver branch at a plurality of times;   determining a noise floor value comprises:
 estimating, a plurality of times, a probability distribution for a first power quantity and a second power quantity, both being related to selected state variables of an estimation algorithm, based on said measurements of received total wideband power using selected measurement functions of said selected state variables of said estimation algorithm; 
 said selected state variables corresponding to cell power quantities; and 
 said selected measurement functions corresponding to said quantities representing said measured received total wideband power of said first and second receiver branches; and 
   determining a noise floor value further comprises:
 computing a conditional probability distribution of a first noise floor measure based on at least a number of said estimated probability distributions for said first power quantity, and a conditional probability distribution of a second noise floor measure based on at least a number of said estimated probability distributions for said second power quantity; and 
 providing said noise floor value based on said computed conditional probability distributions of said first and second noise floor measures. 
   
     
     
         15 . A circuit for supervision of faults in a receiving signal chain of a wireless communication system, comprising a processing circuit configured to:
 determine a noise floor value at a number of time instances based on power measurement data representing measured received power in said receiving signal chain at a number of time instances;   evaluate a time evolution of said noise floor values; and   detect any occurrence of a fault in said receiving signal chain based on said time evolution.   
     
     
         16 . The fault supervision circuit of  claim 15 , further comprising a power measurement circuit operative to measure received power in said receiving signal chain at a number of time instances and to generate said power measurement data. 
     
     
         17 . The fault supervision circuit of  claim 15 , further comprising a data receiving circuit operative to receive said power measurement data. 
     
     
         18 . The fault supervision circuit of  claim 15 , wherein said power measurement data represents received powers at two or more positions in said receiving signal chain; and wherein said processing circuit is further configured to:
 determine separate noise floor values for two or more positions in said receiving signal chain; and   detect any occurrence of a fault in said receiving signal chain based on a comparison between said time evolution of said determined noise floor values at said two or more positions.   
     
     
         19 . The fault supervision circuit of  claim 15 , wherein said processing circuit is configured to obtain power related quantities based on said power measurement data, and wherein said noise floor value is based on said obtained power related quantities. 
     
     
         20 . The fault supervision circuit of  claim 19 , wherein said power related quantities are obtained based on power measurement data representing at least two different types of received powers. 
     
     
         21 . The fault supervision circuit of  claim 20 , wherein one of said at least two different types of received powers is received total wideband power. 
     
     
         22 . The fault supervision circuit of  claim 20 , wherein said processing circuit is further configured to determine a minimum value of said power related quantities within a time period. 
     
     
         23 . The fault supervision circuit of  claim 15 , wherein the processing circuit is further configured to detect the occurrence of the fault in a signal handling unit of the receiving signal chain responsive to the registered time evolution being at least a predetermined threshold. 
     
     
         24 . The fault supervision circuit of  claim 15 , wherein said processing circuit is further configured to compare said time evolution with a model evolution and to indicate a fault if a measure representing a difference between said time evolution and said model evolution exceeds a threshold value. 
     
     
         25 . The fault supervision circuit of  claim 24 , wherein said model evolution is based on a statistical treatment of previous time evolutions for corresponding conditions. 
     
     
         26 . The fault supervision circuit of  claim 15 , wherein said processing circuit is further configured to:
 estimate probability distributions for a power quantity based on said measured received powers; and   compute a conditional probability distribution of a noise floor measure based on at least a number of said estimated probability distributions for said power quantity.   
     
     
         27 . The fault supervision circuit of  claim 15 , wherein said wireless communication system is provided with receiver diversity and said receiving signal chain comprises at least two receiver branches and said obtained power related quantities are related to received powers at said at least two receiver branches; and wherein said processing circuit is configured to:
 determine separate noise floor values for each of said at least two receiver branches; and   detect any occurrence of a fault in said receiving signal chain based on a comparison between said time evolutions of said determined noise floor values of at least two receiver branches.   
     
     
         28 . The fault supervision circuit of  claim 27 , wherein said power measurement data comprises measurements of received total wideband power for at least a first receiver branch and a second receiver branch at a plurality of times, and wherein said processing circuit is further configured to:
 estimate, at a plurality of times, a probability distribution for a first power quantity and a second power quantity, both being related to selected state variables of an estimation algorithm, from said received total wideband power measurements using selected measurement functions of said selected state variables of said estimation algorithm; said selected state variables corresponding to cell power quantities; said selected measurement functions corresponding to said quantities representing said measured received total wideband power of said first and second receiver branches;   determine a noise floor value at a number of time instances by:
 computing a conditional probability distribution of a first noise floor measure based on at least a number of said estimated probability distributions for said first power quantity, and a conditional probability distribution of a second noise floor measure based on at least a number of said estimated probability distributions for said second power quantity; and 
 providing said noise floor value based on said computed conditional probability distributions of said first and second noise floor measures. 
   
     
     
         29 . A network node for use in a wireless communication system comprising a fault supervision circuit according to  claim 15 . 
     
     
         30 . A network node according to  claim 29 , wherein said network node is a base station. 
     
     
         31 . A wireless communication system comprising at least one node according to  claim 29 .