System and method for sharing a common communication channel between multiple systems of implantable medical devices

• US 20050197680A1
• Filed: 06/10/2004
• Published: 09/08/2005
• Est. Priority Date: 03/03/2004
• Status: Active Grant

• Current Assignee: Alfred E. Mann Foundation For Scientific Research
• Original Assignee: Alfred E. Mann Foundation For Scientific Research
• Inventors: Karr, Lawrence J., DelMain, Gregory J., Folkman, Dan, DeRocco, Paul
• Granted Patent: US 7,406,105 B2
• Time in Patent Office: Days
• US Class Current: 607/60
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 2560/063 Devices specially adapted for delivering implantable medical measuring apparatus
• CPC Class Codes: A61B 2562/08 Sensors provided with means for identification, e.g. barcodes or memory chips
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: A61B 5/0024 for multiple sensor units attached to the patient, e.g. using a body or personal area network
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/07 Endoradiosondes
• CPC Class Codes: A61B 5/145 Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissuemeasuring of blood pressure or blood flow A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61N 1/3727 characterised by the modulation technique
• CPC Class Codes: A61N 1/37288 Communication to several implantable medical devices within one patient
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: H04W 92/02 Inter-networking arrangements

Abstract

A system and method that facilitates multiple systems of communicating devices, i.e., a master device and one or more implantable slave devices, to coexist on a common, e.g., RF, communication channel having a limited temporal bandwidth while maintaining the required update rate between each master device and its associated slave devices. In embodiments of the present invention, master devices periodically transmit one or more beacon messages that are suitable for identification by other such master devices at a communication range greater than the communication range that may cause interference between systems and thus enabling one or more systems to cause the position of its frame periods to be interleaved with the frame periods of other such systems in anticipation of systems moving in closer proximity and actually interfering with each other.

Claims

1. A method of enabling a plurality of systems to cooperatively coexist on a common communication channel wherein each system is comprised of a master device having a unique identification code and one or more associated slave devices that communicate with said master device during periodic and essentially temporally contiguous frame periods determined by each said master device and having occupied temporal portions of each said frame period comprised of transmission communication periods dedicated to each master device and to each slave device and wherein each said frame period has a start and an end that essentially spans the entire temporal bandwidth of said common communication channel, said method comprising the steps of:

transmitting a plurality of beacon message types during each frame period from each said master device wherein each said beacon message type has a unique beacon marker code portion and at least one beacon message type has a moveable temporal offset from the start of its respective frame period;

receiving beacon messages by said master devices from other said master devices that are within communication range;

calculating the relative temporal displacement of the frame periods of other master devices according to the relative temporal offsets of one or more of said beacon messages to the start of the frame periods of said master devices;

determining whether at least one of said systems may interfere with communications of another one of said systems and accordingly calculating a new temporal placement for the frame period of a selected one of said systems according to said received beacon messages and said unique identification codes; and

causing said selected one of said systems comprised of a master device and one or more associated slave devices to temporally displace the start of its frame period to allow said occupied temporal portions of said selected one of said systems to be temporally interleaved with other occupied temporal portions of said systems on said common communication channel when said determining step has determined the potential for communication interference between two or more of said systems.

2. The method of claim 1 wherein said step of transmitting a plurality of beacon message types comprises the steps of:

transmitting a first fixed beacon message type having a predetermined temporal offset from said start of said frame period; and

transmitting a second wandering beacon message type having a predetermined but variable temporal offset selected from a predetermined set of temporal offset values.

3. The method of claim 2 wherein said step of transmitting a second wandering beacon message type step comprises selecting different temporal offset values from said predetermined set of temporal offset values for temporally contiguous frame periods and wherein said step of calculating the temporal displacement of the frame period comprises the step of processing the difference between received temporal offset values from at least two different frame periods relative to the start of said frame period of a receiving master device.

4. The method of claim 3 wherein said step of processing the difference between received temporal offset values additionally comprises comparing said difference to potential differences corresponding to said predetermined set of temporal offset values and thereby determining which received beacons correspond to other master devices.

5. The method of claim 1 wherein said step of receiving beacon messages comprises the step of determining the correlation of received data to one or more predefined beacon marker codes.

6. The method of claim 5 wherein said step of determining the correlation of received data to one or more predefined beacon marker codes additionally comprises the step of integrating received data from within said beacon messages that are received during at least two different frame periods to thereby increase the receive sensitivity of said determining step and thereby increasing the effective communication range.

7. The method of claim 1 wherein said step of calculating a new temporal placement for the frame period of a selected one of said systems comprises the step of comparing the relative magnitudes of said unique identification codes to determine higher and lower priority systems wherein according to said comparison said lower priority one of said systems is selected to be the one to change its temporal placement within said common communication channel.

8. The method of claim 7 additionally comprising the step of altering at least one of the beacon messages of the master device of said lower priority one of said systems prior to altering its temporal placement to acknowledge that it is selected to be the one to change its temporal placement within said common communication channel.

9. The method of claim 8 additionally comprising the step of changing the temporal placement within said common communication channel of said higher priority one of said systems if a predetermined period of time has elapsed without receiving a beacon message from said lower priority one of said systems that acknowledges that said lower priority one of said systems will be altering its temporal placement within said common communication channel.

10. The method of claim 1 wherein said step of causing said selected one of said systems comprised of a master device and one or more associated slave devices to temporally displace the start of its frame period comprises the steps of:

notifying each of said associated slave devices by said master device of said selected one of said systems of a determined new temporal placement; and

moving the temporal placement of said master device with said associated slave devices that comprise said selected one of said systems.

11. The method of claim 10 wherein said notifying step additionally comprises the step of instructing two or more of said associated slave devices to alternately share a temporal portion of said frame period and thereby increasing the effective temporal bandwidth of said frame period to allow more systems to cooperatively coexist on said common communication channel.

12. The method of claim 1 wherein said step of determining a new temporal placement for the frame period of a selected one of said systems additionally comprises the step of adjusting the duration of the frame period of said selected one of said systems to essentially match the duration of the frame period of said other system as determined from relative temporal offsets between said received beacon messages.

13. The method of claim 1 wherein said determining step additionally comprises the step of notifying one or more of said systems if it is determined that said systems cannot coexist on the common communication channel and thereby facilitate avoiding interference between said systems.

14. The method of claim 1 wherein said determining step additionally comprises the step of notifying each of said systems to extend their frame periods to thereby increase the temporal bandwidth of the common communication channel if it is determined that said systems cannot coexist on the common communication channel at the current frame period duration.

15. The method of claim 1 wherein said determining step additionally comprises the step of notifying at least one of said systems to alter its communication channel to another communication channel if it is determined that said systems cannot coexist on the common communication channel.

16. The method of claim 15 where said notifying step comprises notifying at least one of said systems to alter its communication frequency to thereby assign said system to another communication channel.

17. For a system comprised of a master device having a unique identification code and one or more associated slave devices that communicate with said master device during periodic and essentially temporally contiguous frame periods determined by each said master device and having occupied temporal portions of said frame period comprised of transmission communication periods dedicated to each master device and to each slave device and wherein each said frame period has a start and an end that essentially spans the entire temporal bandwidth of a common communication channel, an enhanced communication processing system to enable a plurality of said systems to cooperatively coexist on said common communication channel, said enhanced communication processing system comprising:

at least one fixed beacon message generator having a unique beacon marker code portion for adding a fixed beacon message portion offset a fixed amount from said start of said frame period to communications from said master device during each frame period;

at least one wandering beacon generator having a unique beacon marker code portion for adding a wandering beacon message portion offset a predetermined but variable amount from said start of said frame period to communications from said master device during each frame period;

a plurality of correlators for identifying said beacon message portions according to said unique beacon marker codes;

a remote frame location processor coupled to said correlators for determining the relative temporal displacement of the frame period of each other detected master device according to the relative temporal offsets of one or more of said beacon messages to each said master device;

a new temporal placement processor for determining whether at least one of said systems may interfere with communications of another one of said systems and accordingly calculating a new temporal placement for the frame period of a selected one of said systems according to said received beacon messages and said unique identification codes; and

a relocation processor for causing said selected one of said systems comprised of a master device and one or more associated slave devices to temporally displace the start of its frame period to allow said occupied temporal portions of said selected one of said systems to be temporally interleaved with other occupied temporal portions of said systems on said common communication channel when said new temporal placement processor determines the potential for communication interference between two or more of said systems.

18. The enhanced communication processing system of claim 17 wherein said at least one wandering beacon generator additionally comprises:

a predetermined set of potential wandering beacon locations;

a random number generator; and

wherein

said random number generator is used at least in part to select a wandering beacon location different from the location selected for the prior frame period for the next sequential frame period.

19. The enhanced communication processing system of claim 17 wherein said remote location frame processor additionally comprises:

a displacement table for determining in part the start of the frame period of a remote master device relative to the start location of a local master device; and

a database table for accumulating the locations of the temporal portions of said communication channel currently occupied by a remote system comprised of a remote master device and its associated slave devices.

20. The enhanced communication processing system of claim 19 wherein said remote location frame processor additionally comprises:

a predetermined set of potential wandering beacon locations;

a list of available wandering beacon locations wherein available locations are removed from said list if their temporal locations conflict with known occupied temporal locations as determined from said database table;

a random number generator; and

wherein

said random number generator is used at least in part to select from said list of wandering beacon locations different from the location selected for the prior frame period for the next sequential frame period.

21. The enhanced communication processing system of claim 19 wherein said new temporal placement processor is coupled to said database table, the local unique identification code from a local master device, and a received unique identification code from a remote master device and whereby said new temporal placement processor determines a new temporal placement from the frame period of a selected one of said systems according to the relative magnitude of said unique identification codes and thereby one of said systems is selected to be the one to change its temporal placement on said common communication channel.

22. The enhanced communication processing system of claim 17 wherein said relocation processor causes said master device of said selected one of said systems to notify each of said one or more associated slave devices of a determined new temporal placement and to move the temporal placement of said master device with said associated slave devices that comprise said selected one of said systems.

23. The enhanced communication processing system of claim 17 wherein said relocation processor instructs two or more of said associated slave devices to alternately share a temporal portion of said frame period to thereby increase the effective temporal bandwidth of said frame period to allow more systems to cooperatively coexist on said common communication channel.

24. The enhanced communication processing system of claim 17 wherein each of said master devices additionally comprises a clock generator that can be adjusted in frequency and wherein said communication processor additionally calculates the difference in frame period durations between said master devices and alters the frequency of at least one of said master devices according to the unique identification codes of said master devices and thereby match the frame period durations between systems.

25. The enhanced communication processing system of claim 17 additionally comprising an annunciator, wherein said annunciator is activated if said new temporal placement processor determines that the detected systems cannot coexist in proximity to each other without interference.

26. The enhanced communication processing system of claim 17 wherein one or more of said slave devices is implantable.

27. The enhanced communication processing system of claim 17 wherein one or more of said master devices is implantable.

28. The enhanced communication processing system of claim 17 wherein said system additionally determines whether another one of said systems is interfering with communications between said master device and one or more of its associated slave devices and wherein in response to said determination said relocation processor is additionally configured for causing said system of a master device and one or more associated slave devices to temporally displace the start of its frame period.

29. A communication protocol configured for enabling a plurality of systems to cooperatively coexist on a common communication channel wherein each system is comprised of a master device having a unique identification code and one or more associated slave devices that communicate with said master device during periodic and essentially temporally contiguous frame periods determined by each said master device and having occupied temporal portions of each said frame period comprised of transmission communication periods dedicated to each master device and to each slave device and wherein each said frame period has a start and an end that essentially spans the entire temporal bandwidth of said common communication channel, said communication protocol comprising:

a system control message transmitted from each said master device for defining addressable data to be directed to each of a plurality of associated slave devices;

a response time period temporally displaced from said system control message for each said slave device to transmit data to its associated master device;

at least one fixed beacon message transmitted from each said master device wherein said fixed beacon message has a unique beacon marker code portion and a fixed predetermined offset from the start of said frame period;

at least one wandering beacon message transmitted from each said master device wherein said wandering beacon message has a unique beacon marker code portion and a moveable offset from the start of said frame period selected from a predetermined set of offsets; and

wherein

when one of said master devices is within communication range of an other one of said master devices and receives at least two or more of said beacon messages, the relative temporal difference between said beacon messages is suitable to determine the relative temporal placement of the frame period of said other one of said master devices relative to its frame period and according to data within said beacon messages and said unique identification codes a new temporal placement for the frame period of a selected one of said systems is determined if at least one of said systems may interfere with communications of another one of said systems wherein said new temporal placement is used to cause said selected one of said systems comprised of a master device and one or more associated slave devices to temporally displace the start of its frame period to allow said occupied temporal portions of said selected one of said systems to be temporally interleaved with other occupied temporal portions of said systems across said common communication channel.

30. A method of enabling a plurality of systems to communicate over a common communication channel wherein each system is configured to enable communication during periodic and essentially temporally contiguous frame periods determined essentially asynchronously by each said system and having occupied temporal portions of each said frame period comprised of transmission communication periods dedicated to each system and wherein each said frame period has a start and an end that essentially spans the entire temporal bandwidth of said common communication channel, said method comprising the steps of:

transmitting during each said frame period at least one type of beacon message having a unique heavily-coded beacon marker code portion;

receiving beacon messages by said systems according to said heavily-coded beacon marker code portions from other said systems that are within communication range; and

processing two or more of said received heavily-coded beacon marker code portions of said beacon messages to thereby determine the start of the frame period of another one of said systems.

31. The method of claim 30 wherein said transmitting during each said frame period at least one type of beacon message additionally comprises transmitting a data portion within said beacon message.

32. The method of claim 31 additionally comprising the step of integrating data portions from said received beacon messages that correspond to other said systems over a plurality of frame periods to thereby increase the receive sensitivity and the effective communication range and thereby facilitating extracting said data portions.

33. The method of claim 30 wherein said step of transmitting at least one type of beacon message additionally comprises the step of transmitting at least one wandering beacon message having a moveable temporal offset from the start of its respective frame period.

34. The method of claim 33 additionally comprising the step of determining which received beacon messages uniquely correspond to other said systems according to uniquely defined temporal displacements between said received wandering beacon messages.

35. The method of claim 33 wherein said step of transmitting at least one wandering beacon message having a moveable temporal offset from the start of its respective frame period comprises selecting said temporal offsets from a predetermined set of temporal offset values.

36. The method of claim 30 wherein said step of transmitting at least one beacon message additionally comprises transmitting a wandering beacon message type having temporal offset values selected from a predetermined set of temporal offset values for at least two different frame periods and wherein said method additionally comprises the step of determining in part which received beacon messages uniquely correspond to other said systems according to uniquely defined temporal displacements between received beacon messages by comparing the differences between temporal offset values of wandering beacon messages from other frame periods according to said predetermined set of temporal values.

37. The method of claim 30 wherein said step of transmitting at least one type of beacon message additionally comprises the step of periodically ceasing transmissions from said systems to facilitate said steps of receiving beacon messages and integrating data portions from said received beacon messages.

38. The method of claim 33 wherein said systems are comprised of a master device and one or more associated slave devices that communicate with said master device during said frame periods determined by each said master device, said method additionally comprising the steps of:

calculating the relative temporal displacements of the frame periods of other master devices;

determining whether at least one of said systems may interfere with communications of another one of said systems and accordingly calculating a new temporal placement for the frame period of a selected one of said systems according to said received beacon messages; and

causing said selected one of said systems comprised of a master device and one or more associated slave devices to temporally displace the start of its frame period to allow said occupied temporal portions of said selected one of said systems to be temporally interleaved with other occupied temporal portions of said systems across said common communication channel when said determining step has determined the potential for communication interference between two or more of said systems.

39. The method of claim 38 wherein each said master device has a unique identification code that is used within at least some of said beacon messages and said calculating step determines in part the new temporal placement for the frame period of a selected one of said systems according to said received beacon messages and said unique identification codes.

40. The method of claim 38 wherein said calculating step determines in part the new temporal placement for the frame period of a selected one of said systems according to relative movement of the temporal placements of two or more sequential beacon messages received from another one of said master devices.