Method and apparatus for two-way communications amongst a plurality of communications devices
In a security system, a method and apparatus for two-way frequency hopping communications between the control panel and each peripheral device which maintains channel synchronization through the assignment of fixed beacon frequencies for the transmission of synchronizing data. The use of frequency hopping provides high immunity to jamming and interference, reduced occurrence of multi-path phenomena, and allows for transmissions at a much higher output power than conventional fixed-frequency communications, to thus increase the effective range of the peripheral devices while providing effective and reliable two-way communications between the control panel and the peripheral devices. The invention also provides a large number of channels, which allows for actuators such as sirens, strobes and line seizing devices to be wireless in addition to sensors. The invention provides a high immunity to signal jamming, interference from other wireless systems and miss-detection due to multi-path phenomena; reduces opportunities for collision between peripheral transmissions; and eliminates the redundant emission of peripheral transmissions to reduce RF traffic in the vicinity of the system and extend the life of batteries used in the peripheral devices.
1. A security system, comprising
a control panel for communicating with a plurality of peripheral devices, and
a plurality of peripheral devices, each comprising a transceiver for transmitting and receiving synchronization data packets on at least one fixed frequency, and transmitting and receiving operating data packets on a plurality of variable frequencies varied according to a frequency hopping sequence assigned by the control panel,
the control panel comprising a transceiver for transmitting to and receiving from the peripheral devices synchronization data packets on a plurality of fixed frequencies, and transmitting to and receiving from the peripheral devices operating data packets on a plurality of variable frequencies varied according to the frequency hopping sequence,
wherein when a peripheral device is unable to detect a synchronization signal from the control panel during a selected interval, the peripheral device transmits a signal to the control panel at a fixed frequency to notify the control panel that the peripheral device has lost synchronization with the frequency hopping sequence.
2. The security system of claim 1 wherein the plurality of variable outgoing frequencies and the plurality of fixed outgoing frequencies comprise a first group of frequencies in a transmission frequency band, and the plurality of variable incoming frequencies and the at least one fixed incoming frequency comprise a second group of frequencies in the transmission frequency band, such that the first and second groups of frequencies are divided by sufficient bandwidth to avoid transmission collision and receiver desensitization.
3. The security system of claim 2 wherein each transceiver of the plurality of peripheral devices and the control panel transceiver operate in the 900 MHz range.
4. The security system of claim 1 wherein when the control panel receives the signal at a fixed frequency notifying the control panel that the peripheral device has lost synchronization with the frequency hopping sequence, the control panel transmits a synchronization signal at the same fixed frequency for receipt by the peripheral device that has lost synchronization.
5. The security system of claim 1 wherein the synchronization data packets and the operating data packets comprise a header address unique to one of the plurality of peripheral devices.
6. The security system of claim 1 wherein the plurality of peripheral devices comprises at least one perimeter monitor.
7. The security system of claim 1 wherein the plurality of peripheral devices comprises at least one transceiver for monitoring the status of an article located within the range of the control panel transceiver.
8. The security system of claim 1 wherein the peripheral devices transmit on a first set of fixed frequencies, the control panel transmits on a second different set of fixed frequencies, the peripheral devices transmit on a first set of variable frequencies and the control panel transmits on a second different set of variable frequencies.
9. A method of two-way communication in a security system between a control panel and a plurality of peripheral devices, comprising the steps of:
a) the control panel assigning a frequency hopping sequence for the communication of operating data packets over a plurality of hopping frequencies,
b) communicating all or part of the frequency hopping sequence to the peripheral devices on a fixed frequency,
c) communicating operating data over the plurality of hopping frequencies according to the frequency hopping sequence,
d) where any peripheral device loses synchronization with the frequency hopping sequence,
A. detecting loss of synchronization with the frequency hopping sequence,
B. communicating notification of the loss of synchronization to the control panel over a fixed frequency, and
C. communicating synchronizing data packets to the peripheral device to reestablish synchronization with the frequency hopping sequence.
10. The method of claim 9 , further comprising the steps of, where any peripheral device loses synchronization with die frequency hopping sequence,
D. communicating verification data to the control panel to verify that the synchronization has been reestablished, and
B. communicating acknowledgement to the peripheral device that the verification data has been received.
11. A method for synchronizing two-way communication between a control panel and a plurality of peripheral devices in a security system, the method comprising the steps of:
a) assigning a frequency hopping sequence for the communication of operating data packets over a plurality of hopping frequencies,
b) communicating all or part of the frequency hopping sequence to the peripheral devices on a fixed frequency,
c) upon a detection of loss of synchronization of any peripheral device with the frequency hopping sequence,
A. communicating notification of the loss of synchronization to the control panel over a fixed frequency, and
B. communicating synchronizing data packets over the fixed frequency to the peripheral device to reestablish synchronization with the frequency hopping sequence.
12. The method of claim 11 further comprising the steps of assigning a further frequency hopping sequence for the communication of operating data packets over a plurality of hopping frequencies and communicating all or part of the further frequency hopping sequence to the peripheral devices on a hopping frequency in accordance with the frequency hopping sequence.