Remote keyless entry system for a vehicle and a method of controlling a vehicle function by the same

1. A remote unit for a keyless entry system, the remote unit comprising:

a controller configured to generate a command signal for transmission during a transmission period in response to a user input, the command signal comprising a first command message and a second command message, wherein the first command message comprises first and second high power, low data rate portions having data indicative of a function corresponding to the user input and the second command message comprises a low power, high data rate portion having data indicative of the function corresponding to the user input;

wherein the first low data rate portion has a first transmission length within the transmission period, the second low data rate portion has a second transmission length within the transmission period, and the high data rate portion has a third transmission length within the transmission period;

wherein the data rate portions are arranged in the command signal such that the first low data rate portion precedes the high data rate portion and the high data rate portion precedes the second low data rate portion;

wherein the power and transmission lengths of the data rate portions are matched such that an average strength of the command signal is lower than a first threshold and such that a peak strength of the command signal is lower than the sum of the average strength of the command signal and a second threshold greater than the first threshold; and

a transmitter configured to transmit the command signal.

2. The remote unit according to claim 1 wherein the first low data rate portion has a transmission data rate in the range of approximately 500 to 2K bits/second and the high data rate portion has a transmission data rate in the range of approximately 5K and 20K bits/second.

3. The remote unit according to claim 1 wherein the user input corresponds to actuation of a manually-activated control element.

4. The remote unit according to claim 1 wherein the high data rate portion has a power transmission in the range of approximately 60 to 74 dBμV/m and the first low data rate portion has a power transmission in the range of approximately 78 to 95 dBμV/m.

5. A vehicle-mounted base unit for a keyless entry system, the vehicle-mounted base unit comprising:

a receiver configured to receive a command signal corresponding to a user input, the command signal comprising a first command message and a second command message, wherein the first command message comprises first and second high power, low data rate portions having data indicative of a vehicle function and the second command message comprises a lower power, high data rate portion having data indicative of the vehicle function;

wherein the first low data rate portion has a first transmission length within a transmission period of the command signal, the second low data rate portion has a second transmission length within the transmission period, and the high data rate portion has a third transmission length within the transmission period;

wherein the data rate portions are arranged in the command signal such that the first low data rate portion entirely precedes the high data rate portion and the high data rate portion entirely precedes the second low data rate portion;

wherein the power and transmission lengths of the data rate portions are matched such that an average strength of the command signal is lower than a first threshold and such that a peak strength of the command signal is lower than the sum of the average strength of the command signal and a second threshold greater than the first threshold; and

a controller configured to control the vehicle function in response to the command signal.

6. The vehicle-mounted base unit according to claim 5 wherein the first low data rate portion has a transmission data rate in the range of approximately 500 to 2K bits/second and the high data rate portion has a transmission data rate in the range of approximately 5K and 20K bits/second.

7. The vehicle-mounted base unit according to claim 5 wherein the user input corresponds to actuation of a manually-activated control element.

8. The vehicle-mounted base unit according to claim 5 wherein the high data rate portion has a power transmission in the range of approximately 60 to 74 dBμV/m and the first low data rate portion has a power transmission in the range of approximately 78 to 95 dBμV/m.

9. A keyless entry system for a vehicle, the keyless entry system comprising:

a remote unit configured to transmit a command signal during a transmission period in response to a user input, the command signal comprising a first command message and a second command message, wherein the first command message comprises first and second high power, low data rate portions having data indicative of a vehicle function and the second command message comprises a low power, high data rate portion having data indicative of the vehicle function;

wherein the first low data rate portion has a first transmission length within the transmission period, the second low data rate portion has a second transmission length within the transmission period, and the high data rate portion has a third transmission length within the transmission period;

wherein the data rate portions are arranged in the command signal such that the first low data rate portion precedes the high data rate portion and the high data rate portion precedes the second low data rate portion;

wherein the power and transmission lengths of the data rate portions are matched such that an average strength of the command signal is lower than a first threshold and such that a peak strength of the command signal is lower than the sum of the average strength of the command signal and a second threshold greater than the first threshold; and

a vehicle-mounted base unit configured to receive the command signal and to control the vehicle function in response to the command signal.

10. The keyless entry system according to claim 9 wherein the first low data rate portion has a transmission data rate in the range of approximately 500 to 2K bits/second and the high data rate portion has a transmission data rate in the range of approximately 5K and 20K bits/second.

11. The keyless entry system according to claim 9 wherein the user input corresponds to actuation of a manually-activated control element.

12. The keyless entry system according to claim 9 wherein the high data rate portion has a power transmission in the range of approximately 60 to 74 dBμV/m and the first low data rate portion has a power transmission in the range of approximately 78 to 95 dBμV/m.

13. The keyless entry system according to claim 9 wherein the first command message is received by the vehicle-mounted base unit when the remote unit transmits the command signal within 500 m.

14. The keyless entry system according to claim 9 wherein the first low data rate portion initiates the receiver.