U.S. patent application number 12/145343 was filed with the patent office on 2008-10-23 for dynamic telemetry link selection for an implantable device.
This patent application is currently assigned to Cardiac Pacemakers, Inc.. Invention is credited to Raymond P. Kinnamon, Hui Li, Sylvia Quiles, Michael Seeberger.
Application Number | 20080262573 12/145343 |
Document ID | / |
Family ID | 35287039 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080262573 |
Kind Code |
A1 |
Seeberger; Michael ; et
al. |
October 23, 2008 |
DYNAMIC TELEMETRY LINK SELECTION FOR AN IMPLANTABLE DEVICE
Abstract
Communications with an implantable device are conducted using a
physical telemetry link dynamically selected from multiple physical
telemetry links based on selected criteria including, for example,
bandwidth, security, data throughput, channel availability and
reliability.
Inventors: |
Seeberger; Michael;
(Bayport, MN) ; Li; Hui; (Maple Grove, MN)
; Quiles; Sylvia; (Edina, MN) ; Kinnamon; Raymond
P.; (St. Michael, MN) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG & WOESSNER/BSC-CRM
PO BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Cardiac Pacemakers, Inc.
|
Family ID: |
35287039 |
Appl. No.: |
12/145343 |
Filed: |
June 24, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10914638 |
Aug 9, 2004 |
7406349 |
|
|
12145343 |
|
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Current U.S.
Class: |
607/60 |
Current CPC
Class: |
Y10S 128/903 20130101;
A61N 1/37223 20130101 |
Class at
Publication: |
607/60 |
International
Class: |
A61N 1/00 20060101
A61N001/00 |
Claims
1. A system comprising: an implantable device comprising: a first
telemetry circuit configured to establish a near field wireless
link with an external device and a second telemetry circuit
configured to establish a far field wireless link with the external
device; and an external device comprising: a communication circuit
configured to communicate with the implantable device using the
near field and far field wireless links; and a processor
communicatively coupled to the communication circuit, wherein the
processor is configured to dynamically switch a priority link
between the near field link and the far field link for
communication with the implantable device, wherein a communication
session is first attempted using the priority link.
2. The system of claim 1, wherein the processor selects the
priority link according to a type of data to be communicated from
the implantable device.
3. The system of claim 2, wherein the processor selects the near
field link as the priority link when the type of data to be
communicated requires a higher level of security.
4. The system of claim 2, wherein the processor selects the far
field link as the priority link when the type data to be
communicated requires increased bandwidth.
5. The system of claim 1, wherein the processor is configured to:
determine a measure of data throughput between the implantable
device and the external device, and select the priority link
according to the measure of data throughput.
6. The system of claim 1, wherein the processor is configured to:
determine a number of errors in a wireless link; and select the
priority link according to the determined number of errors.
7. The system of claim 1, wherein the implantable device includes a
battery to provide energy to the device, and wherein the processor
of the external device is configured to select the priority link
based on a capacity of the battery.
8. The system of claim 1, wherein the processor is configured to
select the priority link according to the most recently used
wireless link.
9. The system of claim 1, wherein the processor is configured to:
determine an availability of the near field link and the far field
link; and select the priority link according to a detected
availability of the near field and far field telemetry link.
10. The system of claim 1, wherein the processor is configured to
cease attempts to switch the priority link when a number of
attempts to switch links exceeds an attempt limit number.
11. The system of claim 1, wherein the processor is configured to
dynamically switch the priority link in order to complete a current
communication session.
12. A method comprising: establishing a near field wireless link
and a far field wireless link between an implantable device and an
external device; and dynamically switching between the near field
link and the far field link as a priority link for communication
between the implantable device and the external device, wherein a
communication session is first attempted using the priority
link.
13. The method of claim 12, wherein dynamically switching between
the near field link and the far field link includes selecting the
priority link according to a type of data to be communicated from
the implantable device.
14. The method of claim 13, wherein selecting the priority link
according to a type of data includes selecting the far field link
as the priority link when a volume of data to be communicated
exceeds a threshold data amount.
15. The method of claim 13, wherein selecting the priority link
according to a type of data includes selecting the near field link
as the priority link according to a level of security required for
the data.
16. The method of claim 12, including: determining a measure of
data throughput between the implantable device and the external
device, and wherein dynamically switching between the near field
link and the far field link includes selecting the priority link
according to the measure of data throughput.
17. The method of claim 12, including: determining a number of
errors in a wireless link, and wherein dynamically switching
between the near field link and the far field link includes
selecting the priority link according to the determined number of
errors.
18. The method of claim 12, wherein dynamically switching between
the near field link and the far field link includes selecting the
priority link based on a remaining battery capacity of the
implantable device.
19. The method of claim 12, including ceasing attempts to switch
the priority link when a number of attempts to switch links exceeds
an attempt limit number.
20. The method of claim 12, including dynamically switching the
priority link in order to complete a current communication session.
Description
CROSS-REFERENCE TO RELATED DOCUMENTS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/914,638, filed Aug. 9, 2004, which is
incorporated herein by reference in its entirety.
[0002] This document is related to U.S. patent application Ser. No.
10/914,499, entitled "TELEMETRY SWITCHOVER STATE MACHINE WITH
FIRMWARE PRIORITY CONTROL," filed Aug. 9, 2004 by Quiles et al.
(Attorney Docket 00279.772US1) and is incorporated herein by
reference.
[0003] This document is related to U.S. patent application Ser. No.
10/914,641, entitled "SECURE REMOTE ACCESS FOR AN IMPLANTABLE
MEDICAL DEVICE," filed Aug. 9, 2004 by Quiles (Attorney Docket
00279.771US1) and is incorporated herein by reference.
TECHNICAL FIELD
[0004] This document pertains generally to implantable devices, and
more particularly, but not by way of limitation, to telemetry link
selection for an implantable device.
BACKGROUND
[0005] Implantable devices typically communicate using an inductive
telemetry link. Inductive telemetry refers to communications
involving a loop antenna of an external device inductively coupled
with a loop antenna of the implantable device.
[0006] Communication inefficiencies associated with inductive
telemetry impair the delivery of medical care. Inefficiencies
include low bandwidth and limitations associated with the
requirement for close physical proximity. Improved telemetry
systems are needed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] In the drawings, which are not necessarily drawn to scale,
like numerals describe substantially similar components throughout
the several views. Like numerals having different letter suffixes
represent different instances of substantially similar components.
The drawings illustrate generally, by way of example, but not by
way of limitation, various embodiments discussed herein.
[0008] FIG. 1 includes an illustration of an implantable device in
communication with an external device.
[0009] FIGS. 2, 3, 4 and 5 include illustrations of flow charts for
selecting a physical link.
DETAILED DESCRIPTION
[0010] The following detailed description includes references to
the accompanying drawings, which form a part of the detailed
description. The drawings show, by way of illustration, specific
embodiments in which the invention may be practiced. These
embodiments, which are also referred to herein as "examples," are
described in enough detail to enable those skilled in the art to
practice the invention. The examples may be combined, other
examples may be utilized, or structural, logical and electrical
changes may be made without departing from the scope of the present
invention. The following detailed description is, therefore, not to
be taken in a limiting sense, and the scope of the present
invention is defined by the appended claims and their
equivalents.
[0011] In this document, the terms "a" or "an" are used, as is
common in patent documents, to include one or more than one. In
this document, the term "or" is used to refer to a nonexclusive or,
unless otherwise indicated. Furthermore, all publications, patents,
and patent documents referred to in this document are incorporated
by reference herein in their entirety, as though individually
incorporated by reference. In the event of inconsistent usages
between this document and those documents so incorporated by
reference, the usage in the incorporated reference(s) should be
considered supplementary to that of this document; for
irreconcilable inconsistencies, the usage in this document
controls.
Introduction
[0012] An implantable device allows exchange of data with an
external device using multiple telemetry circuits to communicate
using different physical links having different characteristics. In
one example, the implantable device includes a near field telemetry
circuit which communicates using a near field physical link and a
far field telemetry circuit which communicates using a far field
physical link. The near field physical link and the far field
physical link differ in terms of bandwidth, communication range,
power consumption, security and other factors.
[0013] One example of an implantable device includes both a far
field radio frequency telemetry system, which provides broadband
and long range communication, and a near field inductive telemetry
system, which provides short range communication while drawing a
relatively low current consumption. The far field radio frequency
telemetry link and the near field inductive telemetry link are
examples of physical links.
[0014] The selection of the physical link is determined by external
device based on predetermined selection criteria. In one example,
as between a radio frequency telemetry link and an inductive
telemetry link, the radio frequency telemetry link is faster and
therefore preferred over the inductive telemetry link. In one
example, the data to be communicated may be sensitive or
confidential and thus, security is of greater concern than speed.
As another example, a user selection may include a preference for
one telemetry link or a hierarchy of telemetry links. Other
factors, including data throughput rate, are also contemplated for
selecting one physical link rather than another.
[0015] In one example, the physical link is selected by a procedure
of alternately attempting to establish communications using one
physical link followed by attempting to establish communications
using a second physical link. In one example, external device
includes programming, circuitry or logic to select the physical
link and the implantable device functions as a slave and adjusts
accordingly.
[0016] A controller coupled to the telemetry circuits of the
implantable device selects one of the multiple telemetry circuits
for communicating with an external device based on an instruction
or command received from the external device. In various examples,
the selection of the telemetry circuit, and therefore, the physical
link, is determined by at least one parameter or other data
provided by the implantable device, the external device or by a
combination of the implantable and external device. For example, a
parameter corresponding to a battery condition of the implantable
device can affect the physical link selection.
[0017] Data is communicated between the external device and the
implantable device in a unit of data referred to as a data frame
(also referred to as a frame). A frame exchange refers to the
conveyance of the frame. In one example, a frame exchange must
start and finish on the same physical link. A frame can include,
for example, a frame such as an instruction to change a value
stored in implantable device 110, deliver a particular therapy,
begin a test, write a parameter, take an action or read a storage
register.
[0018] In one example, two modes are available for communicating
between the implantable device and the external device. In one
mode, referred to as real time telemetry, data is continuously
streamed from the implantable device to the external device. In
real time telemetry, the data can include, for example,
electrocardiogram data and physical link switching can occur right
before the start of a new frame exchange (including programmer
re-tries) or if the current link becomes unavailable (after the
loss of a signal for a period of time). In another mode, referred
to as command telemetry, data from the external device is sent to
the implantable device. The data can include an instruction or
other command and the external device always expects responses to
commands on the same telemetry link in which they were
transmitted.
Structure
[0019] FIG. 1 illustrates system 100 including implantable device
110 and external device 160, each having dual telemetry
circuits.
[0020] Implantable device 110 includes processor 115 coupled to
device 120. Device 120, in various examples, includes a monitor
circuit and a therapy circuit. Exemplary therapy circuits include a
pulse generator (such as a pacemaker, a cardiac rhythm therapy
device, a heart failure or cardiac resynchronization device, a
cardioverter/defibrillator, a pacer/defibrillator) and a drug
delivery device (such as an implantable drug pump). An exemplary
monitor circuit includes electrodes or other sensors coupled to a
heart to monitor cardiac function or other physiological stimulus.
In addition, processor 115 is coupled to radio frequency telemetry
circuit 140 and inductive telemetry circuit 150. Radio frequency
telemetry circuit 140 includes a transceiver coupled to radio
frequency antenna 145. Antenna 145 is configured to generate and
receive far field signals. In one example, power delivered to radio
frequency telemetry circuit 140 is controlled or managed based on
instructions received from processor 115.
[0021] Inductive telemetry circuit 150 is coupled to inductive
antenna 155. In one example, inductive telemetry circuit 150
includes a continuously powered transceiver. Antenna 155 is
configured for near field transmission and reception, and, in one
example, includes a loop antenna.
[0022] Implantable device 110 includes clock 125 coupled to
processor 115. Clock 125 provides a timing signal for the benefit
of processor 115. Memory 122, also coupled to processor 115,
provides storage for data, parameters or instructions. In various
examples, memory 122 includes read-only memory, random access
memory or other storage and in one example, is remotely
programmable.
[0023] External device 160 includes processor 165 coupled to
interface 195. Interface 195, in various examples, includes a
display monitor, a printer, a keyboard, a touch-sensitive screen, a
cursor control, a speaker, a microphone, a storage device and a
network interface device. External device 160, in one example,
includes a programmer for use by a physician or other medical
personnel at the time of implantation as well as during follow-up
visits. As a programmer, external device 160 allows interrogation
as well as programming of implantable device 110, and accordingly,
includes a user-accessible interface. External device 160, in one
example, includes a remote interrogation device (sometimes referred
to as a repeater) which allows connecting with a bi-directional
communication network such as a local area network (Ethernet), a
wide area network (such as the Internet) or telephone lines in a
home (plain old telephone service via the public switched telephone
network). In addition, processor 165 is coupled to radio frequency
telemetry circuit 170 and inductive telemetry circuit 180. Radio
frequency telemetry circuit 170 includes a transmitter and receiver
(also referred to as a transceiver) coupled to radio frequency
antenna 175. Antenna 175, like antenna 145, is configured to
generate and receive far field signals.
[0024] Inductive telemetry circuit 180 includes a transceiver
coupled to inductive antenna 185. Antenna 185, in one example, is
part of a hand-operable device sometimes referred to as a wand. The
wand enables inductive communications over a short range of
approximately 6 inches. Antenna 185, like antenna 155, is
configured to generate and receive near field signals and, in one
example, includes a loop antenna.
[0025] External device 160 includes clock 190 coupled to processor
165. Clock 190 provides a timing signal for the benefit of
processor 165. Memory 192, also coupled to processor 165, provides
storage for data, parameters or instructions. In various examples,
memory 192 includes read-only memory, random access memory,
removable or non-removable media or other storage and in one
example, is programmable.
[0026] In various examples, electrical power for external device
160 is provided by a portable power supply, such as a battery, or
by a metered line service. When powered by a battery, external
device 160 can be configured for handheld use. External device 160
can communicate using a wired or wireless communication
channel.
Method
[0027] In one example, system 100 operates according to flow chart
200 as shown in FIG. 2. At 205, external device 160 receives a
parameter that is used in determining the physical link for the
communication session. In various examples, the parameter is
received by interface 195 coupled to external device 160. For
example, a user accessible data entry device, such as a mouse,
keyboard, touch sensitive screen, memory device, audio transducer
or other component can receive a user input. In one example,
external device 160 is coupled to a communication network, such as
an Ethernet, local area network or the Internet and configured to
receive data corresponding to the parameter.
[0028] The parameter received at 205 is used to select the physical
link. In various examples, the physical link is determined based on
considerations including, but not limited to security, bandwidth,
reliability and noise. In one example, the physical link selection
parameter changes over time. In one example, the parameter used to
select the physical link can change such that, at one time, the
physical link is determined based on a security measure and at
another time, the physical link is determined based on a
reliability measure. In one example, a combination of two or more
criteria is used in generating a parameter used to select a
physical link.
[0029] The selection of the physical link can be based on various
criteria. In one example, communication system 100 is configured
with a preference for one particular link rather than another. For
example, a radio frequency physical link may exhibit a larger
bandwidth and therefore, is favored over an inductive physical
link. Accordingly, the physical link can be selected based on a
system-dependent parameter.
[0030] In one example, the parameter relates to a user specified
preference or priority among a number of physical links. For
example, the user may indicate that a radio frequency physical link
is given first priority and an optical physical link is given a
second priority.
[0031] In one example, the parameter relates to a measure of
reliability for a particular physical link. For example, an
inductive physical link may exhibit greater reliability than a
radio frequency physical link.
[0032] In one example, the parameter relates to a measure of
security. The measure of security, in various examples, corresponds
to different levels of, or to the use of different passwords. For
example, when transmitting the patient's name or other patient
health information, a physical link offering a particular level of
security may be selected. Accordingly, for patient health
information, one example provides that an inductive physical link
is more secure than a radio frequency physical link. As another
example, sensitive or important data is communicated using a secure
physical link without regard for communication speed or other
performance criteria. In one example, data stored in implantable
device 110 is read using an inductive physical link. In one
example, the data is encrypted by a processor implementing an
encryption algorithm and the encrypted data is communicated using a
radio frequency physical link.
[0033] In one example, data generated by implantable device 110 is
used to select a physical link. For example, the data generated by
implantable device 110 may indicate that the battery is approaching
the end of its useful life. Accordingly, a measure of the battery
capacity is used in one example to generate a parameter that is
used in selecting the physical link for communicating. A low
current consumption transceiver is given preference over a
transceiver that draws greater current consumption. In one example,
an inductive telemetry circuit draws less current than that of a
radio frequency transceiver. In one example, the data generated by
implantable device 110 is used in conjunction with other criteria
in generating a parameter for selecting a physical link. In one
example, a measure of power consumption is used in generating the
parameter.
[0034] In one example, the physical link selection parameter is
generated based on a measure of data throughput or based on a
measure of communication channel performance. For example, a speed
or bandwidth measurement is used in selecting a communication
channel.
[0035] In one example, the physical link exhibiting a greater
bandwidth, data throughput, security or reliability enjoys priority
over another telemetry link. In one example, the radio frequency
telemetry link is faster than an inductive telemetry link, and
therefore the radio frequency telemetry link enjoys priority. In
other examples, a different telemetry link may have priority over
the radio frequency telemetry link.
[0036] In one example, an externality (measured or detected) is
used in selecting a physical link. For example, an externality,
such as an excessively noisy environment, may compel the use of
inductive physical link rather than radio frequency physical link.
The externality may affect the error rate, reliability, security,
data throughput, channel availability or other parameter associated
with a telemetry link.
[0037] The physical link describes the channel or band by which
implantable device 110 and external device 160 conduct
communications. Exemplary physical links include inductive
telemetry, radio frequency telemetry, infrared, optical, acoustical
and magnetic.
[0038] For a particular physical link, any of a variety of
encoding/decoding or communication protocols may be used. For
example, modulation techniques such as frequency shift keying or
quadrature phase shift keying can be applied using an inductive
physical link as well as a radio frequency physical link.
[0039] At 210, external 160 device executes one or more
instructions, using processor 165, to determine a physical link for
communicating with implantable device 110. In one example, the
instructions implement an algorithm that includes a comparison of
two physical links. In one example, the instructions implement an
algorithm that calculates a factor, such as signal quality, signal
to noise ratio, bandwidth or other parameter which is used in
selecting a physical link.
[0040] At 215, processor 165 generates an instruction for delivery
to implantable device 110 which specifies the physical link. In one
example, the instruction is encoded in the form of a signal or a
missing signal in a series of signals. In one example, a series of
synchronization (or sync) signals are transmitted by external
device 160 and implantable device 110 replies with an alignment
signal to indicate that the devices are synchronized. In one
example, external device 160 signals implantable device 110 of a
change in the physical link by dropping a predetermined number of
sync signals in a series of sync signals.
[0041] FIG. 3 illustrates method 300 including an example of an
algorithm for switching physical links. At 305, external device
160, which can include a remote interrogation device, a programmer
or other device, is receiving real time data through the radio
frequency physical link. In one example, the radio frequency
physical link remains available as long as the frame error count is
less than 12 consecutive frame errors, as shown at 310. At 315, if
the frame error count exceeds a predetermined value, then real time
communications are no longer available on this link. In the example
illustrated, a query is presented to determine if the user entered
command is received, at 320, which triggers the transition from
real time mode to command mode. The user entered command, in
various examples, includes a command to perform an action such as
reading or writing data to a register. While synchronized, external
device 160 continues to periodically send a synchronization
signal.
[0042] If, at 320, the user entered command is not received, then
processing returns to 305 where the radio frequency telemetry link
is used.
[0043] Following receipt of the user entered command, external
device 160 drops three consecutive sync signals, as shown at 325.
Implantable device 110 recognizes the absence of the three
consecutive sync signals as a signal to suspend transmission of
real time data and await a command from external device 160. In
addition, upon dropping the three consecutive sync signals, the
frame error count value is reset when real time telemetry is
terminated.
[0044] At 330, external device 160 transmits a command to
implantable device 110. In one example, external device 160
monitors for a response to the transmitted command and a counter is
used to limit the number of attempted re-transmissions. At 335, a
counter of external device 160 is initiated. At 340, a query is
presented to determine if a response was received from implantable
device 110. In one example, a valid response will arrive prior to a
predetermined response timeout value. At 340, if a response is not
received prior to expiration of the response timeout value, then,
processing continues to 345 where the counter is incremented. At
355, a query is presented to determine if the counter has reached a
predetermined limit value. If the limit value has not been met,
then, as shown at 350, the command is re-sent by external device
160 and the query at 340 is repeated. If the counter limit is
reached and no response was received from implantable device 110,
as shown at 360, then external device 160 switches the physical
link from the radio frequency link to an inductive link. If, on the
other hand, a response is received from implantable device 110,
then, as shown at 365, processing and communications continue using
the radio frequency link.
[0045] In one example, if no reply is received from implantable
device 110 after seven attempts, then external device 160 will
attempt to switch telemetry links. In the example illustrated by
method 300, the physical link transition is triggered after having
attempted and failed using the same exchange for seven times. In
one example, the waiting time to switch is approximately one
second.
[0046] FIG. 4 illustrates method 400 including an example of an
algorithm for switching physical links. At 405, a wand coupled to
external device 160 is placed near implantable device 110 during a
time when real time transmissions are being continuously received
through the inductive link. If the distance between the wand and
implantable device 110 is increased to exceed the communication
range, as shown at 410, then external device 160 will detect this
by noting the absence of alignment signals in four consecutive sync
intervals and signaling the out of range condition, as shown at
415. Upon detecting the out of range condition, external device 160
will drop the inductive synchronization signals, as shown at 420,
and allow implantable device 110 to disengage from the inductive
sync state. In one example, external device 160 will disengage from
the inductive link and resume real time telemetry by sending radio
frequency sync signals, as shown at 425, after approximately 100
milliseconds.
[0047] Establishing radio frequency telemetry entails sending
periodic syncs from external device 160 using the radio frequency
physical link. In one example, external device 160 will maintain
the radio frequency physical link for as long as the frame error
count is less than 12. In one example, the real time transmission
is not a frame exchange. In one example, the loss of the inductive
physical link serves to trigger the telemetry link switching.
[0048] FIG. 5 illustrates method 500 including an example of an
algorithm for switching physical links. At 505, a wand coupled to
external device 160 is placed near implantable device 110 during a
time when real time transmissions are being continuously received
through the inductive link. At 510, external device 160 receives an
input which forms the basis of a command for implantable device
110. The input can be received by a user input device or by a
connection to a communication network. In one example, the user
selects an action for communicating to implantable device 110. Upon
receiving the input for transmission to implantable device 110,
external device 160 will switch from the inductive physical link to
the radio frequency physical link since external device 160 favors
the radio frequency physical link. In one example, external device
160 will indicate that the communication channel, or band, is in
use if the channel is unavailable.
[0049] At 515, external device 160 drops inductive sync signals and
begins sending radio frequency sync signals. In addition, at 520,
external device 160 sends the first element of the command in the
telemetry sequence using the radio frequency physical link.
[0050] At 525, a response counter is initialized to monitor the
number of communication attempts. In one example, a timer is
provided to monitor the duration of attempted communications. At
530, a query is presented to determine if a response is received
from implantable device 110. If a response is received, then, at
550, processing continues with the transmission and reception of
additional elements of the command.
[0051] As shown at 535, if a response is not received, then the
response counter is incremented followed by a query to determine if
the maximum number of attempts has been reached. If the count
remains below the counter limit, then the element of the command is
re-sent at 540, followed by the query at 530 to determine if
implantable device 110 has responded. In one example, external
device 160 attempts to send the command up to seven times using the
radio frequency physical link.
[0052] After having reached the counter limit at 545, processing
continues at 560 where external device 160 then switches the
physical link and returns to the inductive physical link. The
counter limit may have been reached, for example, by a failure of a
cyclic redundancy check code in the response. If the inductive
telemetry wand remains in range of implantable device 110, then
external device 160 completes the command by using the inductive
physical link, as shown at 565.
[0053] In one example, a particular telemetry link is preferred for
use with those commands involving the transmission of a large
volume of data and the most recently used, or current, telemetry
link is used for transmissions involving a small volume of data.
The overhead involved in attempting to select a telemetry link is
not warranted for transmissions involving a small volume of
data.
[0054] At 570 a query is presented to determine if the next element
in the command calls for transmitting a large volume of data. If
the next element in the command does not call for transmitting a
large volume of data, then external device 160 remains in the
inductive telemetry link, as shown at 595. If the next element in
the command calls for transmitting a large volume of data, then
external device 160 attempts to transmit the command using the
radio frequency telemetry link, as shown at 575. The switch to the
radio frequency physical link shown at 575 is the second selective
link switch attempt.
[0055] If external device 160 unsuccessfully attempts a
predetermined number of inductive physical link to radio frequency
physical link switches, then external device 160 will continue with
the inductive physical link and complete the telemetry transaction
without any further attempts to switch physical links. In one
example, the predetermined number of unsuccessful attempts is five,
however more or less than five are also contemplated.
[0056] A counter monitors the number of telemetry switches and
prevents excessive attempted switching. At 580, the counter is
incremented after the switch noted at 575. At 585, a query is
presented to determine if the counter has reached a limit. If the
limit is met, then at 590, transmission of the command is completed
using the inductive physical link. If the limit is not met, then
processing continues at 515 where transmission of the next element
of the command is attempted using the radio frequency physical
link.
[0057] If the inductive physical link is unavailable (for example,
the distance between implantable device 110 and external device 160
is beyond the supported communication range) at any time prior to
completing the transmission of the full user request (for example,
a full interrogation of implantable device 110), then external
device 160 will switch repeatedly between the inductive and radio
frequency physical link until one becomes available or until the
user request is cancelled or aborted.
[0058] In one example, external device 160 can be forced to switch
to the radio frequency physical link by, for instance, moving the
inductive wand out of range of implantable device 110. In one
example, external device 160 can be forced to switch to the
inductive physical link by moving the inductive wand into range of
implantable device 110. The act of positioning a wand near the
implantable device, in one example, indicates a user preference to
select a particular telemetry link. In one example, the user can
terminate the radio frequency telemetry session by initiating a new
interrogation using a telemetry wand of another external
device.
[0059] An inductive physical link override occurs if a series of
inductive syncs are started within 100 milliseconds of the last
radio frequency sync. In one example, implantable device 110 will
wait for at least three inductive syncs before processing a frame
received using the inductive physical link.
[0060] In one example, to switch from an inductive physical link to
a radio frequency physical link, implantable device 110 will look
for a period of at least 100 milliseconds during which no inductive
syncs are received before processing a frame received using the
radio frequency physical link.
[0061] In one example, external device 160 transmits an express
instruction to select a particular telemetry link and implantable
device 110 responds by selecting the specified telemetry link.
Exemplary Alternatives
[0062] In one example, the telemetry links available include an
inductive physical link and a radio frequency physical link. In one
example, more than two telemetry links are available. In one
example, the present system selects a particular physical link from
the available links including two radio frequency physical links
(each operating using different protocols or different frequencies)
and an inductive physical link.
[0063] If implantable device 110 and external device 160 are within
inductive communication range, then attempting to establish a radio
frequency link in a noisy environment can be wasteful of power
resources and time. Accordingly, and under these conditions,
external device 160 does not attempt to establish a radio frequency
telemetry link. In one example, implantable device 110 attempts to
use the radio frequency link for a predetermined amount of time and
if it fails to establish a telemetry link, then implantable device
110 reverts to the inductive link. If, in turn, the inductive
telemetry link is unavailable, then external device 160 will
sequentially switch back and forth between the inductive and radio
frequency telemetry links.
[0064] Furthermore, if a first telemetry link is unavailable, or
does not provide satisfactory performance, then communications are
attempted using a second telemetry link. In one example, a
procedure is executed for attempting to establish communications
using a plurality of telemetry links.
[0065] Unsuccessful attempts to establish communications may
negatively impact the user's experience by introducing additional
delay. The procedure for selecting a telemetry link can affect the
user's perception of system performance.
[0066] In one example, a processor of external device 160 executes
instructions to first attempt to establish communications with an
implantable device using a first physical link and, if
unsuccessful, then attempt to establish communications with
implantable device 110 using a second physical link. If the second
physical link is also unsuccessful, then, in one example, external
device 160 repeats the sequence of attempts using the first
physical link followed by the second physical link. In one example,
external device 160 attempts to establish a communication session
with an implantable device using a physical link selected based on
the physical link used most recently in a previous communication
session. For example, if the radio frequency telemetry circuit was
most recently used, then a later communication session with the
same devices will be first attempted using the radio frequency
telemetry circuit.
[0067] In one example, if external device 160 experiences an error
rate in excess of a first particular value, then external device
160 terminates further attempts to establish a radio frequency
telemetry session and attempts to establish an inductive telemetry
session. In one example, external device 160 suspends attempts to
establish a radio frequency telemetry link if a frame error count
exceeds a particular value in a period of time or after a
predetermined number of synchronization signals. In one example,
the predetermined number of synchronization signals is 12 with each
signal having a duration of approximately 8 milliseconds.
[0068] In one example, if the inductive telemetry wand is out of
range of implantable device 110, or the inductive telemetry circuit
is otherwise not available, then after a second particular value of
time, external device 160 terminates efforts to establish an
inductive communication session and attempts to establish a radio
frequency telemetry session. In one example, the second particular
value is of a shorter duration than the first particular value. In
one example, the second particular value is four synchronization
periods.
[0069] In one example, the durations corresponding to the first and
second particular values are determined by the type of
communication session to be conducted. In one example, the system
provides both a real time communication session and a command
session. In a real time communication session, data generated by
the implanted device (for example, electrocardiogram data) is
communicated to external device 160 in a continuous data stream and
rendered as a scrolling image on a display or stored for later
processing and display. In a command session, external device 160
communicates an instruction or command to implantable device 110.
In a real time communication session, the durations are shorter
than that of a command session.
[0070] In one example, external device 160 is operating in either a
command mode or a real time mode. In other words, if external
device 160 is not actively sending a command to implantable device
110 during a communication session, then real time data is being
received.
[0071] In one example, external device 160 will terminate attempts
to establish a radio frequency telemetry link and attempt to
establish an inductive telemetry link when (a) there have been 12
consecutive frames during which implantable device 110 has not
responded or (b) a cyclic redundancy code indicates an error.
[0072] In the command mode, external device 160 has data, an
element, an instruction or command to communicate to implantable
device 110. In command mode, external device 160 initially attempts
to communicate using a radio frequency telemetry link. If
implantable device 110 is non-responsive to the radio frequency
command, then external device 160 conducts a series of repeated
attempts for a particular number of times. If, for example, after
seven attempts to establish a radio frequency telemetry link, then
external device 160 terminates further attempts using radio
frequency telemetry and attempts to establish communications using
an inductive telemetry link. In one example, external device 160
completes a predetermined number of attempts to establish an
inductive telemetry link after which external device 160 terminates
further attempts using inductive telemetry and attempts to
establish a radio frequency telemetry link. In one example,
external device 160 will repeat the sequence of attempting to
establish a telemetry link using radio frequency telemetry and
inductive telemetry.
[0073] In one example, external device 160 initially attempts to
establish a radio frequency telemetry link regardless of whether a
wand coupled to external device 160 is located near implantable
device 110. Assuming noise or another interfering signal precludes
satisfactory use of radio frequency telemetry, external device 160
switches and attempts to establish an inductive telemetry link.
[0074] In one example, and when available, external device 160 will
use the radio frequency telemetry link. Accordingly, selective link
switching, from inductive telemetry to radio frequency telemetry,
will occur even when the inductive link is available. In one
example, the user specifies a preferred telemetry link which may be
different than a radio frequency telemetry link.
[0075] In one example, a frame exchange starts and ends on the same
physical link. Selective link switching will occur just before the
start of a new telemetry sequence, except when the same telemetry
sequence is repeated multiple times for a single user request
(e.g., a command to read selected memory registers). In this case,
inductive physical link to radio frequency physical link selective
switching will occur before the first sequence is issued. Selective
link switching from inductive physical link to radio frequency
physical link can also occur in the middle of a telemetry sequence.
In one example, this form of selective link switching can occur up
to a predetermined number of times (for example, five times) during
the telemetry sequence. In one example, a failed attempt at
selective switching to radio frequency physical link is counted
towards the maximum number of selective link switching attempts of
five. This limits the delay to respond to the user and makes it
predictable for long sequences (e.g. initial interrogation) when
the inductive physical link is available but the radio frequency
physical link is not.
[0076] During real time telemetry, link switching occurs if the
current telemetry link in use is lost (assuming there is no other
system constraint). If the current telemetry link in use is the
inductive link, the telemetry link is lost when the telemetry wand
is out of range. External device 160 then drops inductive syncs for
a predetermined number of intervals (in one example, 12 intervals)
to allow implantable device 110 to disengage from its inductive
sync state. When implantable device 110 is in the inductive sync
state, a predetermined period of time (in one example, 100
milliseconds) is introduced before transitioning to the radio
frequency physical link. If the wand has been out of range for at
least a predetermined period of time (in one example, 100
milliseconds), then the transition can occur immediately. If the
current telemetry link in use is the radio frequency physical link,
then determining when the telemetry link is lost is based on frame
error counts.
[0077] If the radio frequency physical link is not available for
telemetry transactions, then external device 160 will try to start
a frame exchange using the inductive link. When a channel is
available (whether radio frequency or inductive), a frame exchange
is tried twice on the inductive link or seven times on the radio
frequency link before attempting to switch telemetry links.
[0078] To determine channel availability, external device 160
generates a measure of quality. Examples of a measure of quality
include a frame error count and a bit error rate. A frame error is
counted when (a) a frame cyclic redundancy check code fails (as
determined by a cyclic redundancy check code error response frame
received from implantable device 110 or if the cyclic redundancy
check code of the received frame fails); (b) the frame is not
received when expected (as determined during real time if a data
frame is not received during the current sync interval, such as
during a frame exchange if a data frame is not received before the
response timeout expires); or (c) the frame received does not match
the expected values in the frame format (for example the frame is
that of another system within communication range). No frame is
declared when either a command response time out occurs or a real
time data frame is not received in the current synchronization
interval.
[0079] In one example, external device 160 evaluates a telemetry
link by using a spectrum analyzer. The spectrum analyzer provides a
measure of the quality of a channel. External device 160 executes a
method whereby the channel quality is sampled using the spectrum
analyzer and generates a measure of quality without first
attempting to communicate using that particular telemetry link.
[0080] In one example, the frame error count is not incremented
more than once per sync interval during real time or more than once
per command during frame exchanges. The frame error count is reset
anytime a valid frame is received (as determined by the above
conditions) or upon switching telemetry links.
[0081] In one example, selective link switching is limited to no
more than five failed attempts per every user initiated telemetry
transaction. In one example, external device 160 switches telemetry
links if any of the following conditions occur: [0082] 1. Radio
frequency physical link to inductive physical link: frame error
count for the radio frequency physical link indicates that 12
consecutive frame errors were detected during real time. [0083] 2.
Inductive physical link to radio frequency physical link: telemetry
wand is out of range while using the inductive link during real
time. [0084] 3. Radio frequency physical link to inductive physical
link: a frame exchange in the radio frequency physical link fails
after being tried seven times. [0085] 4. Inductive physical link to
radio frequency physical link: a frame exchange in the inductive
physical link fails after being tried twice. [0086] 5. Inductive
physical link to radio frequency physical link (selective link
switching): while using the inductive physical link, before the
start of a telemetry sequence or the first of a repeated set of the
same sequence (e.g., a command to read selected memory registers).
[0087] 6. Inductive physical link to radio frequency physical link
(selective link switching): while using the inductive physical
link, before the start of a read or write command (read
logical/physical, write logical, read history) during a telemetry
sequence or a repeated set of the same sequence (e.g., a command to
read selected memory registers).
[0088] In one example, external device 160 continues to alternate
attempts between both telemetry links until one becomes available
or the user cancels the current action request. In one example, if
real time is enabled, then telemetry link switching may continue
indefinitely.
[0089] In one example, implantable device 110 and external device
160 have a slave/master relationship where external device 160 is
always the master and implantable device 110 is always the
slave.
[0090] In one example, the system is limited to one active radio
frequency communication session in a given radio frequency channel.
The session limit ensures that a new session just starting does not
interfere with another active session. Radio frequency sync signals
and radio frequency frames include a header which allows external
device 160 to detect other sessions in progress. External device
160 is responsible for enforcing the radio frequency session
limitation of one active radio frequency communication session in a
given radio frequency channel. Once a session is initiated,
implantable device 110 retains the session access code until the
session is terminated. In one example, implantable device 110
supports multiple active sessions at a time.
[0091] In one example, external device 160 will monitor radio
frequency traffic for a period of time (200 milliseconds in one
example) before establishing a radio frequency communication link.
If external device 160 includes a programmer, and if radio
frequency traffic is noted, then external device 160 communicates
using the inductive link. If external device 160 includes a remote
interrogation device, and if traffic is noted, then external device
160 waits for a clear channel before communicating.
[0092] External device 160 can be configured to allow inductive
only, radio frequency only or automatic link selection in which the
physical link is selected based on predetermined criteria. In one
example, implantable device 110 is a slave to external device 160
implantable device 110 monitors more than one telemetry link for a
command from external device 160 while in the automatic link
selection mode.
[0093] When sending a table, chart or other large volume of data to
implantable device 110, external device 160 operates in the command
mode. In one example, each element of the table is considered a
separate exchange, and thus, for a chart having ten elements, each
element is transmitted as a separate exchange. In other words, a
separate attempt to establish a telemetry link is commenced for
each element of the table. Thus, for example, if the first element
is successfully sent using inductive, then for the second element,
the radio frequency telemetry link is initially attempted and if
noise precludes the use of radio frequency telemetry for the second
element, then an inductive telemetry link is used.
[0094] While in the command mode, external device 160 implements
selective link switching in which attempts to send the data
elements by first checking for a satisfactory radio frequency link
and, if unsatisfactory, then using an inductive telemetry link.
After a series of failed attempts to communicate using radio
frequency telemetry followed by successful telemetry using the
inductive telemetry link, external device 160 terminates any
further attempt to use radio frequency telemetry and selects the
inductive telemetry link for additional elements in the table or
block of data. In one example, the series of failed attempts
includes five attempts, however more or less are also contemplated.
In one example, the user can force the telemetry link switch by
positioning the inductive telemetry wand near implantable device
110. If the inductive telemetry link is not available (for example,
the wand is not near implantable device 110), then, external device
160 continues to attempt to establish a telemetry link by
alternating between inductive and radio frequency telemetry.
[0095] In one example, external device 160 selects a particular
telemetry link for communicating a unit of data without alternating
between possible telemetry links. For example, in a situation where
the radio frequency telemetry link is unsatisfactory, then, while
in command mode, external device 160 selects inductive telemetry
without attempting to communicate using radio frequency
telemetry.
[0096] In one example, and when operating in real time mode,
external device 160 executes an algorithm to select the telemetry
channel at the outset of a new frame exchange. In one example, if
the current telemetry link becomes unavailable, then the physical
link selection algorithm is executed.
[0097] In one example, external device 160 executes multiple
attempts to establish a communication session. For example, if
external device 160 issues a command to implantable device 110,
external device 160 begins by transmitting a series of
synchronization signals to implantable device 110. The data
corresponding to the command is transmitted in the time between
synchronization signals. After the command has been sent, in one
example, external device 160 waits 100 milliseconds for implantable
device 110 to respond. After the 100 millisecond period during
which external device 160 fails to receive a response from
implantable device 110, external device 160 performs a re-try
procedure in which the command is sent again. The sequence of
waiting and re-trying the command, in one example, is repeated
seven times before terminating further attempts using the
particular telemetry link. Implantable device 110 can fail to
respond within the time period if the distance between devices is
too great or other failure occurs.
[0098] In one example, the response time-out period is 100
milliseconds while in command mode. Therefore, since real time
communication is suspended until the frame exchange is completed
(that is, until the response from implantable device 110 is
received), the time before changing (increasing) the frame error
count may take up to the response time. External device 160 waits
for the duration of the response time-out period before declaring
no response from implantable device 110.
[0099] In one example, external device 160 drops the
synchronization signals to assure that implantable device 110 is
operating in a known state before receiving the command. By
dropping the synchronization signal, any other procedure that may
be executing on implantable device 110 is terminated and
implantable device 110 then enters a mode conducive to receiving a
command.
[0100] After sending the command, external device 160 enters a
receive mode and awaits acknowledgment from implantable device 110
that confirms that the instruction was received.
[0101] In one example, external device 160 initially attempts to
establish a communication session using the radio frequency
telemetry link. In one example, a frame exchange is started and
ended on the same physical link and thus, switching telemetry links
will occur immediately prior to starting a new frame exchange or if
the current telemetry link is lost during a real time telemetry
session (assuming there are no other telemetry system
restraints).
[0102] If the radio frequency telemetry link is unavailable, then
external device 160 will attempt to start a frame exchange using
the inductive telemetry link. When a telemetry channel is available
(for example, radio frequency or inductive), then a frame exchange
is retried once before attempting to switch telemetry links.
[0103] In one example, external device 160 will attempt telemetry
link switching during a session when (a) the frame error count for
the current telemetry link indicates three consecutive frame
errors; (b) the frame exchange in the current telemetry link fails
after being re-tried once; or (c) while using inductive telemetry
link, the start of a frame exchange is issued and the radio
frequency link is available (no other external device is disabling
the radio frequency channel, no other radio frequency system
session is in progress and the frame error count is less than
three).
[0104] At the outset of a communication session with an implantable
device, all telemetry systems are powered up. All systems are
initially activated to allow seamless switching between different
telemetry links during the session. For example, security
considerations may dictate that an inductive telemetry link is used
rather than a far field radio frequency telemetry link. As another
example, a far field radio frequency telemetry link may be
preferred rather than using a wand associated with an inductive
telemetry link for communications conducted during a sterile
medical procedure. In addition, reliability considerations may
dictate that one telemetry system is used rather than another.
Furthermore, the availability of an open communication channel may
determine whether communications can be conducted using far field
radio frequency telemetry or inductive telemetry.
[0105] Implantable device 110 communicates with an external device
using a single telemetry link at any given time during a
communication session.
[0106] It is to be understood that the above description is
intended to be illustrative, and not restrictive. For example, the
above-described embodiments (and/or aspects thereof) may be used in
combination with each other. Many other embodiments will be
apparent to those of skill in the art upon reviewing the above
description. The scope of the invention should, therefore, be
determined with reference to the appended claims, along with the
full scope of equivalents to which such claims are entitled. In the
appended claims, the terms "including" and "in which" are used as
the plain-English equivalents of the respective terms "comprising"
and "wherein." Also, in the following claims, the terms "including"
and "comprising" are open-ended, that is, a system, device,
article, or process that includes elements in addition to those
listed after such a term in a claim are still deemed to fall within
the scope of that claim. Moreover, in the following claims, the
terms "first," "second," and "third," etc. are used merely as
labels, and are not intended to impose numerical requirements on
their objects.
* * * * *