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Switching the operation mode of a zigbee node in an embedded device Disclosure Number: IPCOM000146061D
Original Publication Date: 2007-Feb-01
Included in the Prior Art Database: 2007-Feb-01
Document File: 2 page(s) / 44K

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A very low power radio (VLPR) transceiver is used to send a signal to a ZigBee module indicating it should switch from acting as a coordinator node to being a leaf node on a specific PAN.

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Switching the operation mode of a zigbee node in an embedded device

ZigBee is a RF technology that was developed in particular for enabling wirelessly networked monitoring and control applications involving sensors and actuators. A ZigBee node in a Personal Area Network (PAN) can either act as a coordinator or as a leaf node: a coordinator controls a PAN and leaf nodes join PANs. Current ZigBee implementations do not allow a ZigBee node to act as both a coordinator of a PAN and be a leaf node participating in another PAN. However this feature would be extremely advantageous for certain ZigBee based applications.

A prime example of such an application is an embedded controller which collects sensor information from its environment via ZigBee and then needs to forward that information to a back-end whenever it is in reach of a second network. The embedded controller in this case acts as a ZigBee coordinator and establishes a specific PAN defined by its PAN ID and channel number; the ZigBee enabled sensors act as leaf nodes attaching
to the PAN spanned by the coordinator. To retrieve the collected information from the embedded controller, e.g., using a handheld device, it would be desirable to utilize the existing ZigBee infrastructure. The obvious solution would be to have the handheld device participate in the PAN as a leaf node but it has the drawback that it would work only as long as there is only one such PAN in any given environment of a certain size. As soon as it is necessary to have several PANs in the same environment (e.g., different apartments in an apartment block with ZigBee enabled sensors for temperature, electricity usage, door closed status, etc.) it is necessary to use different PAN IDs as ZigBee does not allow two PANs with the same PAN ID and channel to coexist in close proximity. This in turn requires to know which PAN ID and channel configuration is to be used for a certain area. Managing this information is a complex task. Furthermore mobile collection devices (e.g., a handhelds) bring the complication of intermittent connectivity between the collecting device and the embedded controller.

Current solutions either use a second ZigBee controller or every so often reset the ZigBee device attached to the embedded controller and have it change roles from coordinator to leaf node and back. The drawback of the first solution is costs and power consumption. The second solution has the drawback that the ZigBee device in the embedded controller might not be in leaf node mode at the right point in time and thus might not detect the collecting device.

A solution is proposed in which the collecting device utilizes a very low power radio (VLPR) transceiver to signal to the embedded controller that it should switch from coordinator to leaf node mode and join a specific PAN. Low cost VLPR transceivers are used for example in car keys.

The advantage of the proposed solution is that it d...