U.S. patent application number 12/536520 was filed with the patent office on 2010-02-11 for signaling in a medical implant based system.
This patent application is currently assigned to Texas Instruments Incorporated. Invention is credited to Jaiganesh BALAKRISHNAN, Sriram MURALI, Sthanunathan RAMAKRISHNAN, Kumar Divyesh SHAH, Ganesan THIAGARAJAN.
Application Number | 20100036459 12/536520 |
Document ID | / |
Family ID | 41653655 |
Filed Date | 2010-02-11 |
United States Patent
Application |
20100036459 |
Kind Code |
A1 |
RAMAKRISHNAN; Sthanunathan ;
et al. |
February 11, 2010 |
SIGNALING IN A MEDICAL IMPLANT BASED SYSTEM
Abstract
Signaling in a medical implant based system. A method includes
transmitting bits modulated with a predefined sequence in a band of
channels by a first medical transceiver. The method includes
detecting the predefined sequence by a second medical transceiver.
The method also includes performing predetermined action if the
predefined sequence is detected. In one example, the predetermined
action includes determining presence of a signal.
Inventors: |
RAMAKRISHNAN; Sthanunathan;
(Bangalore, IN) ; THIAGARAJAN; Ganesan;
(Bangalore, IN) ; SHAH; Kumar Divyesh; (Bangalore,
IN) ; BALAKRISHNAN; Jaiganesh; (Bangalore, IN)
; MURALI; Sriram; (Bangalore, IN) |
Correspondence
Address: |
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS
TX
75265
US
|
Assignee: |
Texas Instruments
Incorporated
Dallas
TX
|
Family ID: |
41653655 |
Appl. No.: |
12/536520 |
Filed: |
August 6, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61086663 |
Aug 6, 2008 |
|
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|
Current U.S.
Class: |
607/60 |
Current CPC
Class: |
A61N 1/3727
20130101 |
Class at
Publication: |
607/60 |
International
Class: |
A61N 1/08 20060101
A61N001/08 |
Claims
1. A method comprising: transmitting bits modulated with a
predefined sequence in a band of channels by a first medical
transceiver; detecting the predefined sequence by a second medical
transceiver; and determining presence of a signal if the predefined
sequence is detected.
2. The method as claimed in claim 1, wherein the first medical
transceiver is one of a medical implant transceiver and a medical
controller transceiver; and the second medical transceiver is one
of the medical implant transceiver and the medical controller
transceiver.
3. The method as claimed in claim 1, wherein the transmitting
comprises one of: transmitting the bits modulated with a
pseudorandom sequence; transmitting the bits modulated with a gold
code sequence; transmitting the bits modulated with a barker
sequence; and transmitting the bits modulated with a walsh code
sequence.
4. The method as claimed in claim 1, wherein the transmitting
comprises: spreading the bits with the predefined sequence.
5. The method as claimed in claim 1, wherein the detecting
comprises: correlating the signal with the predefined sequence.
6. The method as claimed in claim 5, wherein the detecting further
comprises: determining a peak value of a sample in a band of
channels; and checking the peak value against a threshold.
7. The method as claimed in claim 5, wherein the detecting further
comprises: determining a ratio of a peak value of a sample in an
output obtained from the correlating to an average value of
off-peak samples in the output; and checking the ratio against a
threshold.
8. The method as claimed in claim 1 and further comprising:
entering into an inactive state if the predefined sequence is not
detected.
9. A method comprising: transmitting bits modulated with a first
predefined sequence of a plurality of predefined sequences by a
first medical transceiver; detecting the first predefined sequence
by a second medical transceiver when the second medical transceiver
enters into an active state; and performing a predetermined action
if the first predefined sequence is detected.
10. The method as claimed in claim 9 and further comprising:
determining the plurality of predefined sequences based on
autocorrelation and cross-correlation properties.
11. The method as claimed in claim 9 and further comprising:
dividing a location comprising multiple first medical transceivers
into cells; assigning a predefined sequence of the plurality of
predefined sequences for modulating the bits for association to the
cells; and assigning other predefined sequences of the plurality of
predefined sequences to the cells for modulating bits for a
predefined function, wherein no two adjacent cells have a similar
predefined sequence for modulating the bits for the predefined
function.
12. The method as claimed in claim 9, wherein the detecting
comprises: detecting the first predefined sequence at a physical
layer of the second medical transceiver.
13. The method as claimed in claim 9, wherein performing the
predetermined action comprises: determining presence of a signal
for association if the first predefined sequence is detected.
14. The method as claimed in claim 13 and further comprising:
processing the signal for association; and sending an
acknowledgment based on the processing.
15. The method as claimed in claim 14 and further comprising:
transmitting information identifying a predefined sequence of the
plurality of predefined sequences that the first medical
transceiver will use to transmit data.
16. The method as claimed in claim 9, wherein performing the
predetermined action comprises one of: determining presence of a
poll signal if the first predefined sequence is detected; and
determining presence of a signal for data transfer if the first
predefined sequence is detected.
17. A system comprising: a medical implant transceiver comprising a
radio frequency receiver that receives a signal; a demodulator that
demodulates bits of the signal modulated with a predefined
sequence; a correlator that correlates the signal with the
predefined sequence to detect the predefined sequence, that
determines presence of the signal in the channel.
18. The system as claimed in claim 17 and further comprising: a
medical controller transceiver comprising a predefined sequence
spreader that spreads the bits with the predefined sequence; a
modulator that modulates the bits with the predefined sequence; and
a radio frequency transmitter that transmits the bits.
19. The system as claimed in claim 17, wherein the medical implant
transceiver further comprises: a peak-to-off-peak signal to noise
ratio detector that detects the predefined sequence.
Description
REFERENCE TO PRIORITY APPLICATION
[0001] This application claims priority from U.S. Provisional
Application Ser. No. 61/086,663 filed Aug. 6, 2008, entitled
"Wake-up signaling in MICS implants", which is incorporated herein
by reference in its entirety.
TECHNICAL FIELD
[0002] Embodiments of the disclosure relate to signaling in a
medical implant based system.
BACKGROUND
[0003] A medical implant based system includes a medical controller
and a medical implant. The medical implant is present inside body
of a living organism and the medical controller is external. Power
consumption of the medical implant is one of the major determinants
of lifetime of the medical implant. The power consumption in a
medical implant transceiver forms a significant portion of the
overall power consumption in the medical implant. Hence, it is
desired to maximize efficiency of the medical implant transceiver
to increase lifetime of the medical implant.
[0004] The power of the medical implant transceiver is utilized for
performing various functions. In one example, power consumption in
the medical implant transceiver is dominated by a listen mode of
the medical implant transceiver. In the listen mode (when the
implant transceiver listens for the signal), the medical implant
transceiver wakes up periodically and searches for presence of a
signal in a band of channels. It is desired to minimize time spent
by the medical implant transceiver, in the listen mode, for
detecting the signal to save power.
[0005] A medical controller transceiver selects a channel based on
certain parameters and transmits the signal in that channel. The
channel, in which the signal is transmitted, is unknown to the
medical implant transceiver. Hence, the medical implant transceiver
has to scan all channels to detect the signal. Currently, a power
measurement technique is used to scan the channels. However, the
power measurement technique may not be effective for the signals
having low signal strength than the threshold. Further, the power
measurement technique is sensitive to filter attenuation and noise.
Also, the power measurement technique is prone to false alarms with
interference and spurs.
[0006] The signal once detected is decoded to determine whether the
signal is intended for the medical implant transceiver. It is
possible that the medical implant transceiver detects a signal
which is not intended for the medical implant transceiver. For
example, a signal for associating with a medical controller
transceiver is not intended for the medical implant transceiver
which is already associated. However, such determination is made at
medium access control (MAC) layer at the medical implant
transceiver leading to wastage of power. The situation worsens if
several controllers are present in an area as the probability of
detecting unwanted signals from different medical controllers
increases.
SUMMARY
[0007] An example of a method includes transmitting bits modulated
with a predefined sequence in a band of channels by a first medical
transceiver. The method includes detecting the predefined sequence
by a second medical transceiver. The method also includes
determining presence of a signal if the predefined sequence is
detected.
[0008] Another example of a method includes transmitting bits
modulated with a first predefined sequence of a plurality of
predefined sequences by a first medical transceiver. The method
includes detecting the first predefined sequence by a second
medical transceiver when the second medical transceiver enters into
an active state. The method also includes performing a
predetermined action if the first predefined sequence is
detected.
[0009] An example of a system includes a medical implant
transceiver. The medical implant transceiver includes a radio
frequency receiver that receives a signal. Further, the medical
implant transceiver includes a demodulator that demodulates bits of
the signal modulated with a predefined sequence. The medical
implant transceiver also includes a correlator that correlates the
signal with the predefined sequence to detect the predefined
sequence and to determine presence of the signal in the
channel.
BRIEF DESCRIPTION OF THE VIEWS OF DRAWINGS
[0010] In the accompanying figures, similar reference numerals may
refer to identical or functionally similar elements. These
reference numerals are used in the detailed description to
illustrate various embodiments and to explain various aspects and
advantages of the disclosure.
[0011] FIG. 1 illustrates an environment, in accordance with one
embodiment;
[0012] FIG. 2 is a flow diagram illustrating a method for
determining presence of a signal, in accordance with one
embodiment;
[0013] FIG. 3 is a flow diagram illustrating a method for
signaling, in accordance with one embodiment;
[0014] FIG. 4 is an exemplary illustration of a correlation graph,
in accordance with one embodiment;
[0015] FIG. 5 illustrates a block diagram of a portion of a medical
controller transceiver, in accordance with one embodiment; and
[0016] FIG. 6 illustrates a block diagram of a portion of a medical
implant transceiver, in accordance with one embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0017] FIG. 1 illustrates an environment 100 including a medical
implant based system. Examples of the environment 100 include, but
are not limited to, intensive cares units (ICUs), hospital wards,
and home environment. The environment 100 includes one or more
medical implant transceivers, for example a medical implant
transceiver 105a (hereinafter referred to as implant transceiver
105a) and a medical implant transceiver 105b (hereinafter referred
to as implant transceiver 105b), and one or more medical controller
transceivers, for example a medical controller transceiver 110a
(hereinafter referred to as controller transceiver 110a) and a
medical controller transceiver 110b (hereinafter referred to as
controller transceiver 110b). The implant transceivers (105a and
105b) are present inside living organisms to monitor health and to
transmit health details to the controller transceivers (110a and
110b). The implant transceivers (105a and 105b) are in different
medical implants. The controller transceivers (110a and 110b) are
in different medical controllers.
[0018] The implant transceiver 105a includes or is connected to an
antenna 115a, and the implant transceiver 105b includes or is
connected to an antenna 115b to transmit and receive signals. The
implant transceiver 105a can also include or be connected to
sensors, for example a sensor 120a and the implant transceiver 105b
can also include or be connected to sensors, for example a sensor
120b. Each sensor monitors and senses various health details.
Examples of the sensors include, but are not limited to, pacemakers
and brain sensors. Similarly, the controller transceiver 110a also
includes or is connected to an antenna 115c, and the controller
transceiver 110a also includes or is connected to an antenna 115d
to transmit and receive signals.
[0019] An implant transceiver, for example the implant transceiver
105a, and a controller transceiver, for example the controller
transceiver 110a, can communicate with each other in a medical
implant communication service (MICS) frequency band. The MICS
frequency band ranges from 402 megahertz (MHz) to 405 MHz. The
implant transceiver 105a and the controller transceiver 110a can
also communicate with each other in a medical data services (MEDS)
frequency band. The MEDS frequency band ranges from 401 MHz to 402
MHz, and from 405 MHz to 406 MHz. The frequency band can be
referred to as a band of channels.
[0020] Each implant transceiver can have two states, an associated
state and an unassociated state (listen mode). The associated state
can be defined as a state in which an implant transceiver is
associated with a controller transceiver. The unassociated state
can be defined as a state in which an implant transceiver is not
associated with a controller transceiver. The implant transceivers
(105a and 105b) transition between an active state and an inactive
state (a sleep state) irrespective of being in the associated state
or the unassociated state. The implant transceivers (105a and 105b)
spend bulk of the time in the inactive state. In the active state,
the implant transceivers (105a and 105b) receive, transmit and
process signals which lead to power consumption.
[0021] A communication session is initiated by the controller
transceiver 110a. The controller transceiver 110a selects a channel
for transmission based on certain parameters. In one example, the
controller transceiver 110a selects either a least interfered
channel or a channel which has interference power below a
threshold. The selection process can be referred to as "Listen
Before Talk" (LBT). The controller transceiver 110a then transmits
a signal in the channel. The signal can be of various types, for
example a signal for association, a poll signal and a signal for
data transfer.
[0022] When in the unassociated state, the implant transceiver 105a
searches for the signal for association from the controller
transceiver 110a. The channel in which the signal for association
is present is unknown to the implant transceiver 105a and hence,
the implant transceiver 105a needs to scan various channels to
determine presence of the signal for association. The implant
transceiver 105a needs to detect the signal for association in a
time efficient manner. The controller transceiver 110a may transmit
different types of signals for different implant transceivers. For
example, in a hospital ward the controller transceiver 110a may be
associated with different implant transceivers of various living
organisms, and may be transmitting various poll signals and signals
for data transfer. Hence, the implant transceiver 105a also needs
to discard the poll signals and the signals for data transfer.
[0023] When in the associated state, the implant transceiver 105a
searches for the poll signal or the signal for data transfer from
the controller transceiver 110a. The implant transceiver 105a needs
to detect the poll signal or the signal for data transfer in a time
efficient manner. The controller transceiver 110a may transmit
different types of signals for different implant transceivers.
Hence, the implant transceiver 105a also needs to discard unwanted
signals, for example the signal for association.
[0024] The controller transceivers (110a and 110b) transmit signals
for respective implant transceivers (105a and 105b), and it is
desired that the implant transceiver 105a detects the signal
transmitted by the controller transceiver 110a and not from the
controller transceiver 110b. For example, a living organism having
the implant transceiver 105a and residing in an apartment having
the controller transceiver 110a does not want the implant
transceiver 105a to detect signals from the controller transceiver
110b present in a neighboring apartment. In another example, in an
ICU, a living organism having the implant transceiver 105a
concerned with brain details does not want the implant transceiver
105a to detect signals from the controller transceiver 110b used
for monitoring heart. Detection of the signal from the controller
transceiver 110b by the implant transceiver 105a may lead to
malfunctioning of the implant transceiver 105a and can cause damage
to the living organism. Further, such detection also leads to
unnecessary power consumption.
[0025] A method for determining the signal in the band of channels
in a power efficient manner is explained in detail in conjunction
with FIG. 2.
[0026] FIG. 2 is a flow diagram illustrating a method for
determining presence of a signal.
[0027] At step 205, bits of the signal modulated with a predefined
sequence are transmitted. The bits can be transmitted by a first
medical transceiver. The first medical transceiver can be a medical
controller transceiver, hereinafter referred to as the controller
transceiver or a medical implant transceiver, hereinafter referred
to as the implant transceiver.
[0028] The predefined sequence is selected based on desired
autocorrelation properties. Autocorrelation can be defined as a
measure of correlation of a signal with itself. Examples of the
predefined sequence include, but are not limited to, a pseudorandom
sequence, a gold code sequence, a barker sequence, and a walsh code
sequence. The length of the predefined sequence may be selected
based on requirement, for example to achieve a desired processing
gain.
[0029] In one embodiment, the bits are spread using the predefined
sequence. For example, if the predefined sequence is of length 7
then a bit is spread using the predefined sequence and for every
bit 7 chips are transmitted. A binary sequence that does not carry
information but is used only for spreading is referred to as a
chip. The processing gain that can be achieved in the implant
transceiver is equal to 10*log.sub.10(Length)=10*log.sub.10(7) dB.
After the bits are spread using the predefined sequence, the bits
are modulated and transmitted. Various techniques can be used for
modulation. Examples of the modulation techniques include, but are
not limited to, binary phase shift keying, quadrature phase shift
keying, and differential phase shift keying.
[0030] At step 210, presence of the predefined sequence is detected
by a second medical transceiver, functioning as a receiver.
Detecting presence of the predefined sequence includes detecting
the predefined sequence. The second medical transceiver can be the
implant transceiver or the controller transceiver. For example, if
the first medical transceiver is the controller transceiver then
the second medical transceiver can be the implant transceiver.
[0031] The implant transceiver alternates between an active state
and an inactive state. When the implant transceiver is in the
active state, the implant transceiver scans a band of channels. A
signal present in a channel is received and correlated with the
predefined sequence. An output of correlation is then processed to
detect the predefined sequence. In some embodiments, the output of
the correlation is averaged across multiple lengths of the
predefined sequence. For example, if the predefined sequence of
length 7 is used, then the output of the correlation may be
averaged across 7 chips to improve strength of the signal and
suppress noise. The averaging can be performed coherently or
non-coherently. Different metrics can be used to detect the
predefined sequence at the output of the correlation. For example,
a ratio of a peak value of a sample, having a maximum peak, to an
average value of peaks of off-peak samples can be used as a metric.
The samples correspond to the signal. In one example, when there is
no noise and the length of the predefined sequence is 7, the ratio
is 7. The metric can then be compared against a threshold to detect
the predefined sequence. The threshold can be selected to minimize
probability of false alarm and to minimize probability of missing
detection for a length of time allowed for detection of the
predefined sequence. If the ratio exceeds the threshold then the
predefined sequence is detected. Other metrics, for example
comparing the peak value against another threshold can also be
used. The processing gain achieved by the predefined sequence helps
in detection of the signals with low strength, thereby enabling the
implant transceiver to have high sensitivity.
[0032] The predefined sequence is embedded in the implant
transceiver. If the predefined sequence is detected then step 215
is performed.
[0033] At step 215, presence of the signal is determined.
[0034] In some embodiment, the bits are demodulated and de-spreaded
over the predefined sequence to obtain data. The signal can then be
processed further.
[0035] FIG. 3 is a flow diagram illustrating a method for
signaling.
[0036] At step 305, bits modulated on a first predefined sequence
of a plurality of predefined sequences are transmitted by a first
medical transceiver. The first medical transceiver can be a
controller transceiver or an implant transceiver.
[0037] The predefined sequences can be selected based on
autocorrelation and cross-correlation properties of the predefined
sequences. The predefined sequences that have autocorrelation
separated by a value exceeding an autocorrelation threshold and
cross-correlation by a value less than a cross-correlation
threshold can be selected. Cross-correlation can be defined as a
measure of similarity of two signals. Autocorrelation can be
defined as a measure of correlation of a signal with itself. In one
example, four pseudorandom sequences of length 7 satisfying the
autocorrelation and cross-correlation properties can be determined.
The predefined sequences can then be assigned to and used by the
controller transceiver for different functions.
[0038] In one scenario, for example an ICU, the ICU can be divided
into cells, for example hexagonal cells. The four pseudorandom
sequences (P1, P2, P3 and P4) can be assigned to the cells based on
requirement. For example, P1 can be assigned to the cells for
transmitting signal for association. P2, P3 and P4 can be assigned
for transmitting signals indicating a predefined function. Examples
of the predefined function include, but are not limited to, polling
and data transfer. P2, P3 and P4 can be assigned in a way that
controller transceivers in neighboring cells do not have same
predefined sequence for transmission of signals for same function.
Assigning of the sequences based on requirement minimizes
interference among signals from different controller transceivers
in adjacent cells. Predefined sequences with higher length,
yielding more predefined sequences satisfying the autocorrelation
and cross-correlation properties can also be used.
[0039] In another scenario, the ICU can have different controller
transceivers for different organs of a living organism. For
example, a controller transceiver for brain and another controller
transceiver for heart. Different predefined sequences can then be
assigned and used for different organs.
[0040] In some embodiments, the predefined sequences are hardcoded
into the controller transceiver. The controller transceiver can
select the predefined sequence for a specific use in response to an
input from a user. The selected predefined sequence can be referred
to as the first predefined sequence.
[0041] The bits are then spreaded and modulated with the predefined
sequence, and transmitted. The spreading and modulating can be
performed at a physical layer of the controller transceiver.
[0042] At step 310, presence of the predefined sequence is detected
by a second medical transceiver. Detecting presence of the
predefined sequence includes detecting the predefined sequence. The
second medical transceiver can be the implant transceiver or the
controller transceiver. For example, if the first medical
transceiver is the controller transceiver then the second medical
transceiver can be the implant transceiver.
[0043] The predefined sequence is detected at a physical layer of
the implant transceiver and step 315 is then performed.
[0044] At step 315, a predetermined action is performed. The
predetermined action includes at least one of determining presence
of a signal for association, determining presence of a poll signal
and determining presence of a signal for data transfer.
[0045] In some embodiments, if the signal for association is
determined then the implant transceiver can get associated with the
controller transceiver after performing further processing of the
signal. The implant transceiver can send an acknowledgement to
indicate association. The controller transceiver can then also send
information indicating the predefined sequence that will be used by
the controller transceiver for transmitting data in subsequent
signals.
[0046] FIG. 4 illustrates an exemplary correlation graph. X-axis
represents time corresponding to various signals and Y-axis
represents amplitudes of various signals. A peak value of a sample
405 having a maximum peak indicates that the predefined sequence is
detected. In some embodiments, ratio of the peak value and an
average value of off-peak samples 410 can also be calculated and
checked against a threshold. If the ratio exceeds the threshold
then the predefined sequence is detected. The ratio can be referred
to as peak-to-off-peak signal to noise ratio.
[0047] In one example, the off-peak samples can include samples
other than the sample having the maximum peak. In another example,
the off-peak samples can include samples other than the sample
having the maximum peak and other than adjacent samples of the
sample having the maximum peak.
[0048] FIG. 5 illustrates a block diagram of a portion of a
controller transceiver, for example a controller transceiver
110a.
[0049] The controller transceiver 110a includes a predefined
sequence spreader 505 that spreads bits with a predefined sequence.
The controller transceiver 110a also includes a modulator 510 that
modulates the bits with the predefined sequence. The controller
transceiver 110a includes a radio frequency transmitter 515 that
transmits signals. The radio frequency transmitter 515 transmits
the signals through an antenna 115c.
[0050] The controller transceiver 110a also includes a radio
frequency receiver that receives signals. In one embodiment, a
radio frequency transceiver can be present for performing functions
of the radio frequency transmitter 515 and the radio frequency
receiver.
[0051] The modulator 510 and the predefined sequence spreader 505
are present at a physical layer of the controller transceiver
110a.
[0052] FIG. 6 illustrates a block diagram of a medical implant
transceiver, for example an implant transceiver 105a.
[0053] The implant transceiver 105a includes a radio frequency
receiver 605 that scans a band of channels and receives signals in
the band of channels. The implant transceiver 105a includes a
demodulator 610 that demodulates the bits modulated with the
predefined sequence. The implant transceiver 105a also includes a
correlator 615 that correlates the received signal with the
predefined sequence. The correlator 615 also de-spreads the bits
modulated with the predefined sequence. The implant transceiver
105a also includes an accumulator 620 that adds signals with a
delay. In one example if the PN sequence length=7, then the
accumulator 620 adds a delay equal to 7.
[0054] In some embodiments, the implant transceiver 105a further
includes a peak-to-off-peak signal to noise ratio detector 625 that
detects the predefined sequence.
[0055] The demodulator 610, the correlator 615, the accumulator
620, and the peak-to-off-peak signal to noise ratio detector 625
are present at a physical layer of the implant transceiver
105a.
[0056] The foregoing description sets forth numerous specific
details to convey a thorough understanding of embodiments of the
disclosure. However, it will be apparent to one skilled in the art
that embodiments of the disclosure may be practiced without these
specific details. Some well-known features are not described in
detail in order to avoid obscuring the disclosure. Other variations
and embodiments are possible in light of above teachings, and it is
thus intended that the scope of disclosure not be limited by this
Detailed Description, but only by the Claims.
* * * * *