Industrial wireless network with message authentication

Abstract

A process control and monitoring method for wirelessly communicating with multiple devices is disclosed. The method includes a basestation that communicates with multiple field units via a wireless messages and in accordance with a wireless protocol and multiple field units that receive wireless messages in accordance with the wireless protocol from the basestation and respond to requests from the basestation via wireless messages in accordance with the wireless protocol. The wireless protocol includes messages containing unique identifiers for confirming the authenticity of the wireless messages.

1 . A process control and monitoring method for wirelessly communicating with multiple devices, the method comprising: 
 a. sending a wireless start-frame message from a basestation to multiple field units in a first time slot of a frame, the start-frame designating a respective time slot within the frame for each of at least one selected field units to respond;    c. sending, with the selected field units, during the respective time slot designated for that field unit, a response to a request in the basestation's wireless start-frame message, the response containing an identifier;    d. confirming, with the basestation, the authenticity of the responses received during the respective time slots from the selected field units by comparing an identifier in that response with a stored identifier associated with the field unit designated to that respective time slot, and    e. accepting data in the field unit's wireless message only if authenticity is confirmed.    
   
   
       2 . The method of  claim 1 , wherein the selected field units send the identifier to the basestation at a prearranged time within the time slot, and the step of confirming the authenticity further includes determining if the identifier was sent at the correct time.  
   
   
       3 . The method of  claim 1 , wherein the selected field units send the identifier to the basestation at a prearranged frequency, and the step of confirming the authenticity further includes determining if identifier was sent at the correct frequency.  
   
   
       4 . The method of  claim 1 , wherein the basestation alerts a field unit when a response is not accepted.  
   
   
       5 . The method of  claim 1 , wherein the start-frame message and the response are encrypted.  
   
   
       6 . The method of  claim 1 , wherein the identifier is a unique numeric code.  
   
   
       7 . The method of  claim 1 , wherein data communicated in the response is range checked and the response is not accepted if any data is not within a valid range.  
   
   
       8 . The method of  claim 1 , wherein the start-frame message from the basestation includes an identifier and the selected field units which receive the start-frame message from the basestation authenticate the messages using the identifier.  
   
   
       9 . A process control and monitoring method for wirelessly communicating with multiple devices, the method comprising: 
 a. sending a wireless start-frame message from a basestation to multiple field units in a first time slot of a frame, the wireless start-frame message designating at least one time slot in the frame for receiving wireless logon request messages from the field units;    c. confirming, with at least one field unit, the authenticity of the wireless start-frame message;    d. sending, with the at least one field unit, a wireless logon request message from the field unit to the basestation if authenticity is confirmed by that at least one field unit; and    e. confirming, with the basestation, the authenticity of the wireless logon request message sent from the at least one field unit.    
   
   
       10 . The method of  claim 9 , wherein confirming the authenticity includes comparing an identifier within the received signal with stored identifiers.  
   
   
       11 . The method of  claim 9 , wherein confirming the authenticity includes comparing the time at which a message is received with a prearranged time for sending the message.  
   
   
       12 . The method of  claim 9 , wherein confirming the authenticity includes comparing the frequency at which a message is received with a prearranged frequency.  
   
   
       13 . The method of  claim 9 , wherein confirming the authenticity includes comparing received data with the expected range for the data, and rejecting any data not within a valid range.  
   
   
       14 . The method of  claim 9 , wherein the basestation does not respond to the wireless logon request message if the logon message fails authentication.  
   
   
       15 . The method of  claim 9 , wherein the field unit does not respond to the basestation if the wireless start-frame message fails authentication.