Error correction of messages by passive radar system

Abstract

Receiving a message including bits corresponding to an identifier, the identifier including a unique address for a aircraft transponder, extracting the unique address from the identifier, comparing the unique address to a set of predetermined addresses, changing selected ones of the identifier bits when the unique address is not one of the set of predetermined addresses, wherein the changing of the identifier bits changes a value of the unique address in the identifier, re-comparing the updated unique address to the set of predetermined addresses and processing the message when the unique address matches one of the set of predetermined addresses.

1 - 19 . (cancelled)  
     
     
         20 . A method, comprising the steps of: 
 receiving a message;    extracting information from the message;    comparing the information extracted from the message to previously stored information;    altering the information when the information differs from the previously stored information;    re-comparing the updated information to the previously stored information; and    processing the message when the updated information matches the previously stored information.    
     
     
         21 . The method of  claim 20 , wherein the extracted information is a unique address.  
     
     
         22 . The method of  claim 21 , wherein the unique address is a Mode S transponder address.  
     
     
         23 . The method of  claim 20 , further comprising the step of: 
 determining a format of the message.    
     
     
         24 . The method of  claim 20 , wherein the message is one of an interrogation from a Mode S ground radar and a reply from a Mode s aircraft transponder.  
     
     
         25 . The method of  claim 20 , wherein the previously stored information includes a set of unique addresses for aircraft in a predetermined area.  
     
     
         26 . The method of  claim 20 , wherein the altering step includes changing a bit value in the message.  
     
     
         27 . The method of  claim 26 , wherein the bit value corresponds to a unique address.  
     
     
         28 . A method, comprising the steps of: 
 receiving a message including an address;    determining a format of the message;    determining the address when the format matches an expected format; and    storing the address based on a criteria.    
     
     
         29 . The method of  claim 28 , wherein the message is one of an interrogation from a Mode S ground radar and a reply from a Mode s aircraft transponder.  
     
     
         30 . The method of  claim 28 , wherein the address is a unique identifier for an aircraft transponder.  
     
     
         31 . The method of  claim 30 , wherein the aircraft transponder is a Mode S transponder.  
     
     
         32 . The method of  claim 28 , wherein the format is an in-the-clear format.  
     
     
         33 . The method of  claim 32 , wherein the in-the-clear format includes one of an all-call message and an extended squitter message.  
     
     
         34 . The method of  claim 28 , wherein the step of determining the address includes the sub-steps of: 
 extracting the address using a CRC calculation; and    verifying the result of the CRC calculation includes an acceptable value check sum value.    
     
     
         35 . The method of  claim 34 , wherein the acceptable check sum value is an interrogation identifier.  
     
     
         36 . The method of  claim 28 , further comprising the step of: 
 verifying the stored address for further use.    
     
     
         37 . The method of  claim 36 , wherein the verifying step includes one of storing the address a predetermined number of times and storing the address at least twice within a predetermined time period.  
     
     
         38 . A system, comprising: 
 a database including a set of predetermined addresses; and    a processor receiving a message including bits corresponding to an identifier, the identifier including a unique address, and comparing the unique address to the set of predetermined addresses, wherein the processor changes at least one identifier bit in the message when the unique address is not in the set of predetermined addresses.    
     
     
         39 . The system of  claim 38 , wherein the processor re-compares the updated unique address to the set of predetermined addresses and processes the message when there is a match.