IMPLANTABLE MEDICAL DEVICE TELEMETRY WITH PERIODIC FREQUENCY HOPPING

• US 20080015656A1
• Filed: 07/12/2006
• Published: 01/17/2008
• Est. Priority Date: 07/12/2006
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Bange, Joseph E., Vallapureddy, Vineel
• Granted Patent: US 7,623,922 B2
• Time in Patent Office: Days
• US Class Current: 607/32
• CPC Class Codes: A61N 1/37223 Circuits for electromagnetic coupling
• CPC Class Codes: A61N 1/37252 Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data
• CPC Class Codes: A61N 1/37254 Pacemaker or defibrillator security, e.g. to prevent or inhibit programming alterations by hackers or unauthorised individuals
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

A far-field radio-frequency (RF) telemetry system for data transmission between an implantable medical device and an external system includes a plurality of channels each representing a frequency band within a predetermined frequency range. The data transmission is performed using at least one active channel at any instant. Channel hopping is performed on a periodic basis throughout a telemetry session such that the active channel keeps scanning through an array of channels selected from the plurality of channels. If a data frame is not successfully transmitted, it is repeatedly re-transmitted using the current and/or the next active channels until its transmission becomes successful.

Claims

1. A cardiac rhythm management (CRM) system, comprising:

an implantable medical device including;

a CRM module; and

an implant telemetry module; and

an external system;

a programming module; and

an external telemetry module,

wherein the implant telemetry module and the external telemetry module each include a telemetry circuit including;

an antenna;

a transceiver coupled to the antenna, the transceiver including a plurality of channels each representing a predetermined frequency band for data transmission between the implantable medical device and the external system; and

a telemetry controller coupled to the transceiver, the telemetry controller adapted to control a channel hopping including selecting an active channel from the plurality of channels on an approximately periodic basis, to control the data transmission using the active channel during a synchronous scan mode during which the channel hopping in the external system and the channel hopping in the implantable medical device are synchronous, to start an asynchronous scan mode after the channel hopping in the external system and the channel hopping in the implantable medical device become asynchronous, and to restore the synchronization of the channel hopping in the external system and the channel hopping in the implantable medical device during the asynchronous scan mode.

2. The system of claim 1, wherein the CRM module comprises a sensing circuit adapted to sense one or more physiological signals.

3. The system of claim 2, wherein the CRM module comprises a therapy circuit adapted to deliver cardiac electrical stimulation pulses.

4. The system of claim 1, wherein the telemetry controller comprises:

a selection controller adapted to produce channel selection commands each specifying a channel in a scan channel list on the approximately periodic basis when a scan timer escape interval expires; and

a hop controller adapted to control the channel hopping in response to each of the channel selection commands, the channel hopping making the channel specified in the each of the channel selection commands the active channel.

5. The system of claim 4, wherein the selection controller is adapted to produce channel selection commands each specifying a channel in a synchronous scan channel list on the approximately periodic basis when a synchronous scan timer escape interval expires during the synchronous scan mode, and wherein the telemetry controller further comprises:

a synchronous scan timer adapted to time the synchronous scan timer escape interval during the synchronous scan mode; and

a synchronous scan hop counter adapted to count a synchronous scan hop count during the synchronous scan mode and to start the asynchronous scan mode when the synchronous scan hop count reaches a predetermined maximum hop count, the synchronous scan hop counter being incremented when the synchronous scan timer escape interval expires and reset by a signal indicative of successful data exchange between the implantable medical device and the external system.

6. The system of claim 5, further comprising an asynchronous scan timer adapted to time an asynchronous scan timer escape interval during the asynchronous scan mode, and wherein the selection controller is adapted to produce channel selection commands each specifying a channel in an asynchronous scan channel list on the approximately periodic basis when the asynchronous scan timer escape interval expires during the asynchronous scan mode.

7. The system of claim 6, wherein the synchronous scan timer escape interval is in a range of approximately 10 to 250 milliseconds.

8. The system of claim 7, wherein the asynchronous scan timer escape interval has a length allowing the external system to hop through all channels of its asynchronous scan channel list while the implantable medical device stays with one channel of its asynchronous scan channel list.

9. The system of claim 6, wherein the telemetry circuit further comprises a memory circuit configured to store the synchronous scan channel list and the asynchronous scan channel list, the synchronous scan channel list including a first array of channels listed in a synchronous hopping sequence, the asynchronous scan channel list including a second array of channels listed in an asynchronous hopping sequence, the second array of channels being a subset of the first array of channels.

10. The system of claim 4, wherein the telemetry controller further comprises a synchronization controller adapted to maintain synchronization of the channel hopping in the external system and the implantable medical device during the synchronous scan mode and to enter the synchronous scan mode by restoring the synchronization of the channel hopping in the external system and the implantable medical device during the asynchronous scan mode.

11. The system of claim 10, wherein the synchronization controller of the external system is adapted to transmit commands selected from the channel selection commands according to a predetermined synchronization schedule to the implantable medical device during the synchronous scan mode.

12. The system of claim 11, wherein the synchronization controller of the external system is adapted to transmit information specifying one or more of the synchronous scan channel list and the asynchronous scan channel list.

13. The system of claim 11, wherein the synchronization controller of the external system is adapted to transmit a scan command to the implantable medical device during the asynchronous scan mode, and to resynchronize the channel hopping in the external system and the implantable medical device when the response to the scan command is received, indicating a match between the active channels of the external system and the implantable medical device.

14. A method for data transmission between an implantable medical device and an external system, the method comprising:

producing channel selection commands each specifying a channel in a scan channel list when a scan timer escape interval expires, the scan channel list including channels selected from a plurality of channels each representing a predetermined frequency band;

performing a channel hopping in response to each of the channel selection commands, the channel hopping making the channel specified in the each of the channel selection commands an active channel;

performing data transmission between the implantable medical device and the external system using the active channel during a synchronous scan mode during which the channel hopping in the external system and the channel hopping in the implantable medical device are synchronous;

starting an asynchronous scan mode after making a predetermined number of attempts to transmit data using different channels in the scan channel list without success; and

restoring the synchronization of the channel hopping in the external system and the channel hopping in the implantable medical device during the asynchronous scan mode.

15. The method of claim 14, wherein producing the channel selection commands comprises producing each of the channel selection commands when a synchronous scan timer escape interval expires during the synchronous scan mode, the channel selection commands each specifying a channel in a synchronous scan channel list of the scan channel list.

16. The method of claim 15, wherein starting the asynchronous scan mode comprises:

counting a synchronous scan hop count during the synchronous scan mode;

starting the asynchronous scan mode when the synchronous scan hop count reaches a predetermined maximum hop count;

incrementing the synchronous scan hop count when the synchronous scan timer escape interval expires; and

resetting the synchronous scan hop count in response to a signal indicative of successful data transmission.

17. The method of claim 16, wherein producing the channel selection commands comprises producing each of the channel selection commands when an asynchronous scan timer escape interval expires during the asynchronous scan mode, the channel selection commands each specifying a channel in an asynchronous scan channel list of the scan channel list.

18. The method of claim 17, further comprising:

generating the synchronous scan channel list including a first array of channels listed as a synchronous hopping sequence, the first array of channels selected from the plurality of channels; and

generating the asynchronous scan channel list including a second array of channels listed as an asynchronous hopping sequence, the second array of channels selected from the plurality of channels,

wherein the second array of channels is a subset of the first array of channels.

19. The method of claim 18, wherein the asynchronous scan timer escape interval has a length allowing the external system to hop through all channels of its asynchronous scan channel list while the implantable medical device stays with one channel of its asynchronous scan channel list.

20. The method of claim 14, further comprising transmitting commands selected from the channel selection commands from the external system to the implantable medical device according to a predetermined synchronization-maintenance schedule.

21. The method of claim 20, further comprising transmitting information specifying the scan channel list from the external system to the implantable medical device.

22. The method of claim 14, wherein restoring the synchronization of the channel hopping in the external system and the channel hopping in the implantable medical device comprises:

transmitting a scan command from the external system to the implantable medical device;

receiving a response signal to the scan command transmitted from the implantable medical device to the external system; and

resynchronizing the channel hopping in the external system and the channel hopping in the implantable medical device when the response to the scan command is received, the response to the scan command indicating a match between the active channels of the external system and the implantable medical device.