Remote keyless entry system with two-way long range communication

Abstract

Vehicle information (e.g., status information, calibratable parameters, or diagnostic data) is transmitted from a base station mounted in a vehicle to a portable RKE fob via a radio-frequency signal within a specified average field strength limit. A multi-byte vehicle message is formed and then coded into a multi-bit coded message. The multi-bit coded message is framed into a plurality of packets. The radio-frequency signal is wirelessly transmitted from the base station with a plurality of spaced packet windows having a predetermined duty cycle, each packet window including a respective one of the plurality of packets. The radio-frequency signal within each of the packet windows has a predetermined field strength greater than the average field strength limit and a substantially zero field strength between the packet windows. The predetermined duty cycle results in an actual average field strength for transmitting all of the packets not exceeding the average field strength limit.

What is claimed is: 
     
       1. A method of transmitting vehicle information from a base station mounted in a vehicle to a portable RKE fob via a radio-frequency signal within a specified average field strength limit, said method comprising the steps of:
 forming a multi-byte vehicle message; 
 coding said vehicle message into a multi-bit coded message; 
 framing said multi-bit coded message into a plurality of packets, wherein each packet corresponds to a respective portion of said vehicle message; 
 wirelessly transmitting said radio-frequency signal from said base station with a plurality of spaced packet windows having a predetermined duty cycle, each packet window including a respective one of said plurality of packets, wherein said radio-frequency signal within each of said packet windows has a predetermined field strength greater than said average field strength limit and a substantially zero field strength between said packet windows, and wherein said predetermined duty cycle results in an actual average field strength for transmitting all of said packets not exceeding said average field strength limit; 
 receiving said plurality of packets within said portable RKE fob; and 
 recovering said vehicle message in response to said received plurality of packets 
 wherein said radio-frequency signal is transmitted within a specified peak field strength limit which is a predetermined decibel level above said average field strength limit, and wherein said predetermined duty cycle corresponds to said predetermined decibel level; and 
 wherein said predetermined duty cycle has a ratio of one-half of a packet window width to a packet period which is substantially equal to a reciprocal of a ratio of said peak field strength limit to said average field strength limit. 
 
     
     
       2. The method of  claim 1  wherein a ratio of said packet window width to said packet period is about one tenth. 
     
     
       3. The method of  claim 1  wherein said vehicle message includes data indicative of a security alarm status. 
     
     
       4. The method of  claim 1  wherein said vehicle message includes data indicative of a vehicle lock status. 
     
     
       5. The method of  claim 1  wherein said vehicle message includes data indicative of a vehicle temperature status. 
     
     
       6. The method of  claim 1  wherein said vehicle message includes data identifying said portable RKE fob for which said vehicle message is intended. 
     
     
       7. The method of  claim 1  wherein said vehicle message is transmitted by said base station in response to a request message transmitted by said portable RKE fob. 
     
     
       8. The method of  claim 7  wherein said vehicle message includes data identifying said portable RKE fob for which said vehicle message is intended, and wherein said data identifying said portable RKE fob is comprised of an identifying number previously transmitted from said portable RKE fob to said vehicle transmitter in said request message. 
     
     
       9. The method of  claim 8  wherein said identifying number is generated as a random number by said portable RKE fob. 
     
     
       10. The method of  claim 1  wherein a fob message is transmitted from said portable RKE fob to said base station according to the steps of:
 coding said fob message into a multi-bit coded fob message; 
 framing said multi-bit coded fob message into a plurality of packets, wherein each packet corresponds to a respective portion of said vehicle message; 
 wirelessly transmitting a radio-frequency fob signal from said portable RKE fob with a plurality of spaced packet windows having said predetermined duty cycle, each packet window including a respective one of said plurality of packets, wherein said radio-frequency fob signal within each of said packet windows has said predetermined field strength greater than said average field strength limit and a substantially zero field strength between said packet windows, and wherein said predetermined duty cycle results in an actual average field strength for transmitting all of said packets not exceeding said average field strength limit. 
 
     
     
       11. A vehicle base station in a vehicle for wirelessly transmitting a radio frequency signal to a portable fob, said radio-frequency signal being broadcast within a specified average field strength limit, said station comprising:
 a message controller for forming a multi-byte vehicle message, coding said vehicle message into a multi-bit coded message, and framing said multi-bit coded message into a plurality of packets, wherein each packet corresponds to a respective portion of said vehicle message; and 
 a transceiver for wirelessly transmitting said radio-frequency signal from said base station with a plurality of spaced packet windows having a predetermined duty cycle, each packet window including a respective one of said plurality of packets, wherein said radio-frequency signal within each of said packet windows has a predetermined field strength greater than said average field strength limit and a substantially zero field strength between said packet windows, and wherein said predetermined duty cycle results in an actual average field strength for transmitting all of said packets not exceeding said average field strength limit; wherein 
 said transceiver transmits said radio-frequency signal within a specified peak field strength limit which is a predetermined decibel level above said average field strength limit, and 
 said predetermined duty cycle corresponds to said predetermined decibel level; and 
 said predetermined duty cycle has a ratio of one-half of a packet window width to a packet period which is substantially equal to a reciprocal of a ratio of said peak field strength limit to said average field strength limit. 
 
     
     
       12. The vehicle base station of  claim 11  wherein said vehicle message includes data identifying said portable fob for which said vehicle message is intended. 
     
     
       13. A method of transmitting information from a portable RKE fob to a base station mounted in a vehicle via a radio-frequency signal within a specified average field strength limit, said method comprising:
 forming a multi-byte fob message;   coding said fob message into a multi-bit coded message;   framing said multi-bit coded message into a plurality of packets, wherein each packet corresponds to a respective portion of said fob message;   wirelessly transmitting said radio-frequency signal from said fob with a plurality of spaced packet windows having a predetermined duty cycle, each packet window including a respective one of said plurality of packets, wherein said radio-frequency signal has within each of said packet windows a predetermined field strength greater than said average field strength limit and has a substantially zero field strength between said packet windows, and wherein said predetermined duty cycle results in an actual average field strength for transmitting all of said packets not exceeding said average field strength limit;   receiving said plurality of packets within said base station; and   recovering said fob message in response to said received plurality of packets;   wherein said radio-frequency signal is transmitted within a specified peak field strength limit which is a predetermined decibel level above said average field strength limit, and wherein said predetermined duty cycle corresponds to said predetermined decibel level; and   wherein said predetermined duty cycle has a ratio of transmission on time of a packet window width to a packet period greater than or equal to a reciprocal of a ratio of said peak field strength limit to said average field strength limit.   
     
     
       14. A portable fob for wirelessly transmitting a radio-frequency signal to a base station in a vehicle, said radio-frequency signal being broadcast within a specified average field strength limit, said fob comprising:
 a message controller for forming a multi-byte fob message, coding said fob message into a multi-bit coded message, and framing said multi-bit coded message into a plurality of packets, wherein each packet corresponds to a respective portion of said fob message; and   a transceiver for wirelessly transmitting said radio-frequency signal from said fob with a plurality of spaced packet windows having a predetermined duty cycle, each packet window including a respective one of said plurality of packets, wherein said radio-frequency signal has within each of said packet windows a predetermined field strength greater than said average field strength limit and has a substantially zero field strength between said packet windows, and wherein said predetermined duty cycle results in an actual average field strength for transmitting all of said packets not exceeding said average field strength limit;   wherein said transceiver transmits said radio-frequency signal within a specified peak field strength limit which is a predetermined decibel level above said average field strength limit, and   said predetermined duty cycle corresponds to said predetermined decibel level; and   said predetermined duty cycle has a ratio of transmission on time of a packet window width to a packet period greater than or equal to a reciprocal of a ratio of said peak field strength limit to said average field strength limit.