U.S. patent application number 12/536562 was filed with the patent office on 2010-02-11 for parallel search circuit for a medical implant receiver.
This patent application is currently assigned to Texas Instruments Incorporated. Invention is credited to Visvesvaraya Pentakota, Sthanunathan Ramakrishnan, Jawaharlal Tangudu.
Application Number | 20100036460 12/536562 |
Document ID | / |
Family ID | 41653655 |
Filed Date | 2010-02-11 |
United States Patent
Application |
20100036460 |
Kind Code |
A1 |
Ramakrishnan; Sthanunathan ;
et al. |
February 11, 2010 |
PARALLEL SEARCH CIRCUIT FOR A MEDICAL IMPLANT RECEIVER
Abstract
Parallel search circuit for a medical implant receiver. The
circuit includes a radio frequency receiver that receives a first
set of contents of a band of channels. The circuit also includes a
processing circuit coupled to the radio frequency receiver to
process in parallel a second set of contents of a plurality of
channels of the band of channels and to detect a signal in the band
of channels.
Inventors: |
Ramakrishnan; Sthanunathan;
(Bangalore, IN) ; Tangudu; Jawaharlal; (Bangalore,
IN) ; Pentakota; Visvesvaraya; (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.: |
12/536562 |
Filed: |
August 6, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61086663 |
Aug 6, 2008 |
|
|
|
Current U.S.
Class: |
607/60 ;
455/334 |
Current CPC
Class: |
A61N 1/3727
20130101 |
Class at
Publication: |
607/60 ;
455/334 |
International
Class: |
A61N 1/08 20060101
A61N001/08; H04B 1/16 20060101 H04B001/16 |
Claims
1. A method for signaling in a medical implant based system, the
method comprising: receiving a first set of contents of a band of
channels by a receiver; processing in parallel a second set of
contents of a plurality of channels from the band of channels; and
detecting a signal in the band of channels based on the
processing.
2. The method as claimed in claim 1, wherein the receiver is a
medical implant receiver.
3. The method as claimed in claim 1, wherein the processing
comprises: converting the first set of contents into digital
samples.
4. The method as claimed in claim 3, wherein the second set of
contents comprises: the digital samples of the first set of
contents.
5. The method as claimed in claim 3, wherein the processing further
comprises: storing the digital samples of the first set of contents
in a storage device; and selecting the second set of contents from
the digital samples.
6. The method as claimed in claim 1, wherein processing content of
each channel comprises: correcting a frequency offset to obtain a
filtered content; and correlating the filtered content with a
predefined sequence.
7. The method as claimed in claim 1, wherein processing content of
each channel comprises: hypothesizing on one or more frequency
offsets; and correlating filtered content obtained from each
hypothesis with a predefined sequence.
8. The method as claimed in claim 7, wherein the predefined
sequence is one of: a pseudorandom sequence; a gold coded sequence;
a barker sequence; and a walsh code sequence.
9. The method as claimed in claim 1, wherein processing content of
each channel comprises: determining a peak value of a sample in an
output of the processing; and checking the peak value against a
threshold.
10. The method as claimed in claim 1, wherein processing content of
each channel comprises: determining a ratio of a peak value of a
sample in an output of the processing to an average value of
off-peak samples in the output of the processing; and checking the
ratio against a threshold.
11. The method as claimed in claim 1 and further comprising:
identifying a channel that carries the signal.
12. A method for signaling in a medical implant based system, the
method comprising: receiving a first set of contents of a band of
channels by a receiver; converting the first set of contents into
digital samples; storing the digital samples of the first set of
contents; selecting a subset of the digital samples, the subset
comprising contents of a plurality of channels from the band of
channels; correcting one or more frequency offsets in the subset in
parallel to obtain a filtered content for each channel; correlating
the filtered content with a predefined sequence; and detecting a
signal in the band of channels based on an output of the
correlating.
13. A receiver circuit comprising: a radio frequency receiver that
receives a first set of contents of a band of channels; a
processing circuit coupled to the radio frequency receiver to
process in parallel a second set of contents of a plurality of
channels of the band of channels, and detect a signal in the band
of channels.
14. The receiver circuit as claimed in claim 13 and further
comprising: an analog-to-digital converter, coupled to the radio
frequency receiver, that converts the first set of contents into
digital samples.
15. The receiver circuit as claimed in claim 14 and further
comprising: a storage device, coupled to the analog-to-digital
converter, that stores the digital samples.
16. The receiver circuit as claimed in claim 13, wherein the
processing circuit comprises: a plurality of mixers; and a
plurality of filters, a first one of the plurality of filters
coupled to a first one of the plurality of mixers, the first one of
the plurality of filters selecting content from the first set of
contents in conjunction with the first one of the plurality of
mixers to form a first path, the first path and the content being
corresponding to a first channel.
17. The receiver circuit as claimed in claim 16, wherein the first
path of the processing circuit comprises: at least one mixer that
hypothesizes on a frequency offset of the content; at least one
correlator responsive to hypothesizing to correlate filtered
content obtained from the hypothesizing with a predefined sequence;
and at least one accumulator that adds correlated content.
18. The receiver circuit as claimed in claim 17, wherein the first
path of the processing circuit further comprises: at least one peak
to off-peak estimator that determines a ratio of a peak value of a
sample in an output of processing to an average value of off-peak
samples in the output of the processing and compares the ratio
against a threshold.
19. The receiver circuit as claimed in claim 13 and further
comprising: a state machine circuit, coupled to the processing
circuit, that identifies a channel that carries the signal.
20. The receiver circuit as claimed in claim 13, wherein the
receiver circuit is a medical implant receiver.
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" and U.S. Non-provisional
application Ser. No. 12/536,520 filed Aug. 6, 2009, entitled
"Signaling in a medical implant based system", which are
incorporated herein by reference in their entirety.
TECHNICAL FIELD
[0002] Embodiments of the disclosure relate to a parallel search
circuit for a receiver.
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 receiver forms a significant portion of the overall
power consumption in the medical implant. Hence, it is desired to
maximize efficiency of the medical implant receiver to increase
lifetime of the medical implant.
[0004] The energy of the medical implant receiver is utilized for
performing various functions. In one example, the power consumption
in the medical implant receiver is dominated by a listen mode of
the medical implant receiver. In the listen mode, the medical
implant receiver wakes up periodically and search for presence of a
signal in a band of channels. 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 receiver. Hence, the
medical implant receiver has to scan all channels to detect the
signal.
[0005] Currently, a power measurement technique is used to detect a
channel that carries the signal. Power is estimated in the band of
channels before and after filtering noise from the band of
channels. If the power measured in both the cases differ by a
magnitude greater than a threshold then it is determined that the
band of channels does not include the signal, else presence of the
signal is detected. However, the power measurement technique may
not be effective for the signals having strength lesser than a
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] Another technique includes processing channels one by one to
detect presence of the signal in the channel. However, processing
channels one by one is time inefficient. Further, power consumption
is also high as a radio frequency receiver, an analog filter and an
analog-to-digital converter is active during the processing.
SUMMARY
[0007] An example of a method for signaling in a medical implant
based system includes receiving a first set of contents of a band
of channels by a receiver. The method further includes processing
in parallel a second set of contents of a plurality of channels
from the band of channels. The method also includes detecting a
signal in the band of channels based on the processing.
[0008] An example of a method for signaling in a medical implant
based system includes receiving a first set of contents of a band
of channels by a receiver. The method further includes converting
the first set of contents into digital samples. The method also
includes storing the digital samples of the first set of contents.
Moreover, the method includes selecting a subset of the digital
samples, the subset including contents of a plurality of channels
from the band of channels. The method also includes correcting one
or more frequency offsets in the subset in parallel to obtain a
filtered content for each channel. Further, the method includes
correlating the filtered content with a predefined sequence.
Furthermore, the method includes detecting a signal in the band of
channels based on an output of the correlating.
[0009] An example of a receiver circuit includes a radio frequency
receiver that receives a first set of contents of a band of
channels. The receiver circuit also includes a processing circuit
coupled to the radio frequency receiver to process in parallel a
second set of contents of a plurality of channels of the band of
channels, and to detect a signal in the band of channels.
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 illustrates a block diagram of a receiver, in
accordance with one embodiment;
[0013] FIG. 3 illustrates a block diagram of a processing circuit
of a receiver, in accordance with one embodiment;
[0014] FIG. 4 illustrates an exemplary correlation graph, in
accordance with one embodiment; and
[0015] FIG. 5 is a flow diagram illustrating a method for signaling
in a medical implant based system, in accordance with one
embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0016] FIG. 1 illustrates an environment 100 including, for example
a medical implant based system. Examples of the environment 100
include, but are not limited to, intensive care units (ICUs),
hospital wards, and home environment. The environment 100 includes
a receiver, for example a medical implant receiver 105, herein
referred to as the implant receiver 105, and a medical controller
transceiver 110, herein referred to as the controller transceiver
110. The implant receiver 105 is present inside living
organisms.
[0017] The implant receiver 105 includes or is connected to an
antenna 115a to receive signals. The implant receiver 105 can also
include or be connected to sensors, for example a sensor 120. 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 110 also includes or
is connected to an antenna 115b to transmit and receive
signals.
[0018] The implant receiver 105 and the controller transceiver 110
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 receiver 105 and the
controller transceiver 110 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.
[0019] A communication session is initiated by the controller
transceiver 110. The controller transceiver 110 selects a channel
for transmission based on certain parameters. In one example, the
controller transceiver 110 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 110 then transmits a
signal in the channel.
[0020] The implant receiver 105 scans the band of channels, and
detects the signal and identifies the channel that carries the
signal. A portion of the implant receiver 105 is explained in
detail in conjunction with FIG. 2.
[0021] Referring to FIG. 2, the implant receiver 105 includes a
radio frequency receiver 205 that receives a first set of contents
of a band of channels through an antenna 115a. The content in the
band of channels can be referred to as the first set of contents.
The first set of contents can be referred to as the contents
received at the radio frequency receiver 205. The implant receiver
105 includes a processing circuit 210 that is coupled to the radio
frequency receiver 205. The radio frequency receiver 205 can be
centered in middle of MICS+MEDS band to receive the band of
channels. The radio frequency receiver 205 includes a low noise
amplifier 215 for amplifying the first set of contents of the band
of channels. The radio frequency receiver 205 also includes a mixer
220 for down-converting the first set of contents. The radio
frequency receiver 205 can also include an analog filter 225 that
is capable to filter the first set of contents.
[0022] In one embodiment, the first set of contents is converted to
digital samples using an analog to digital converter. The digital
samples can then be referred to as a second set of contents which
is processed in parallel by the processing circuit 210.
[0023] In another embodiment, the digital samples can be stored and
subset of the digital samples can be processed in parallel by the
processing circuit 210.
[0024] In yet another embodiment, the first set of contents can be
processed in parallel using analog circuit.
[0025] The processing circuit 210 includes various components for
processing the second set of contents. The processing circuit 210
is explained in detail in conjunction with FIG. 3.
[0026] Referring to FIG. 3, the processing circuit 210 includes an
analog-to-digital converter (ADC) 301 that converts the first set
of contents into digital samples. Examples of the ADC 301 include,
but are not limited to, a flash type ADC, a
successive-approximation type ADC, and a sigma-delta type ADC. The
bandwidth and operating rate of ADC 301 are capable to process the
band of channels simultaneously. The digital samples are then
processed in parallel.
[0027] In some embodiments, the processing circuit 210 includes a
storage device, coupled to the ADC 301, to store the digital
samples. The stored digital samples are then processed one by one
or in parallel. The storage device helps in reducing number of
parallel paths and hence reduction in area. Further, the ADC 301
and radio frequency components of an implant receiver can be
inactivated, after the digital samples are stored, to save
power.
[0028] The processing circuit 210 includes at least one mixer, for
example, a mixer 310a and a mixer 310n, that divides the digital
samples into multiple paths, for example a first path and a second
path. Each path corresponds to a channel. In one embodiment, the
processing circuit 210 can include a single path. For example, if
the processing circuit 210 includes the storage device, then the
digital samples can be processed one by one in a single path. The
path can be programmed differently every time to search for the
signal in the different channels. For example, there can be 10
channels each of bandwidth 300 KHz in the MICS band. Each channel
of 300 KHz can be processed one by one. If we do not want to use a
memory then we need to have processing circuit that can process all
10 channels in parallel, thereby increasing the area. Once we have
the memory, then each channel may even be processed one at a time
using only area for one channel. The channel is then programmed
differently every time to search for signal in the different
channels.
[0029] In another embodiment, the processing circuit 210 can have
two paths. For example, a first path corresponds to channels Fch0
to Fch4 and a second path corresponds to channels Fch5 to Fch9. The
two paths can then further be divided to yield a path for each
channel.
[0030] In yet another embodiment, the processing circuit 210 can
have a plurality of paths. For example, the processing circuit 210
can have a first path for channel Fch0, a second path for channel
Fch1, a third path for channel Fch2 and so on. For example, there
can be 10 channels each of bandwidth 300 KHz in the MICS band. The
10 channels can be processed in parallel. In some embodiments,
various numbers of channels for example 2 or 3 or 4 channels can be
processed in parallel.
[0031] The mixer 310a can be referred to as a first one of the
plurality of mixers. The mixer 310a in conjunction with the RRC
filter 315a selects content from the first set of contents to form
a first path. The first path and the content correspond to a
channel.
[0032] A frequency band corresponding to a path can be selected
using the mixer 310a and a frequency Fch0. The frequency band
corresponding to another path can be selected using the mixer 310n
and a frequency Fch9. The processing circuit 210 further includes
at least one filter, for example a root-raised-cosine (RRC) filter
315a and a RRC filter 315n coupled to the mixer 310a and the mixer
310n respectively. The filter can also be a low-pass filter. The
RRC filter 315a, in one embodiment, is matched to a transmit pulse
shaping filter, which is used for pulse shaping the transmitted
signal in the transmitter. The RRC filter 315a also removes out of
band signals and noise from the input.
[0033] The processing circuit 210 can further include a circuit for
correcting a frequency offset. Each path includes at least one
mixer. For example, the first path includes a mixer 310a1, a mixer
310a2, and a mixer 310a3. A second path includes a mixer 310n1, a
mixer 310n2, and a mixer 310n3. Each mixer hypothesizes on the
frequency offset. Any mismatch between the transmit carrier
frequency and the receiver's channel frequency produces a frequency
offset in the digital samples. The frequency offset can be removed
by hypothesizing on the offset and correcting the hypothesized
frequency from the signal. In one example, three hypotheses are
used per path. By using three hypotheses, any radio frequency error
in the digital samples is reduced to one third of total error. For
example, for the frequency offset in the range of .+-.25 parts per
million (ppm) which is approximately equal to .+-.18 degrees per
digital symbol for a symbol rate of 200 KHz, the phase change can
be calculated as follows:
Phase change=360*delta*10 (-6)*fc*Ts.
where delta is the ppm mismatch between the transmission and
receiving frequencies, fc is the channel frequency and Ts is the
time between one digital symbol and the next. For example, consider
delta=25, fc.about.=400 MHz and Ts= 1/200 KHz=5 usecs. Therefore,
phase change=360.times.25.times.400.times.5e-6=18 degrees
[0034] By using three hypotheses, the uncertainty is reduced to
.+-.6 degrees per digital symbol. The reduction of phase change
helps in detection of certain types of signals. For example, if a
pseudo-random sequence is used to modulate the bits at the
controller transceiver, then the implant receiver depends on the
correlation pattern of the pseudo-random sequence to detect the
signal in presence of noise. The correlation pattern deviates from
a desired correlation pattern, if the frequency offset between
transmission and reception is large. In one example, the frequency
offset can be calculated as follows:
Frequency offset=.+-.25e-6.times.400e6=.+-.10 KHz
[0035] In one example, corresponding to each mixer in the first
path, three frequencies F0, F1, and F2 can be selected for
hypothesizing. The three frequencies can be F0=+6.6 KHz, F1=0 KHz,
and F2=-6.6 KHz respectively. The frequency offset of the signal to
be detected can be 7 KHz. Then the output of mixer 310a1
corresponds to +13.6 KHz, the output of mixer 310a2 corresponds to
7 KHz, and the output of mixer 310a3 corresponds to 0.4 KHz. The
lowest frequency offset is also referred to as residual frequency
offset. For example, the residual frequency offset is 0.4 KHz in
the illustrated example. Further, correlation of the digital
samples can result in a peak amplitude for the frequency
corresponding to mixer 310a3 as the residual frequency offset is
lowest in the output of mixer 310a3, thereby determining the signal
in the channel.
[0036] Each path includes at least one correlator. For example, the
first path includes a correlator 320a1, a correlator 320a2, and a
correlator 320a3. The second path includes a correlator 320n1, a
correlator 320n2, and a correlator 320n3. Each correlator
correlates the digital sample with a predefined sequence, for
example a pseudorandom sequence, a gold coded sequence, a barker
sequence, and walsh code sequence, present in the implant receiver.
Correlation is a measure of the similarity of the two signals. Each
correlator determines a peak value of a sample of the signal and
checks the peak value against a threshold.
[0037] Each path further includes at least one accumulator. For
example, the first path includes an accumulator 325a1, an
accumulator 325a2, and an accumulator 325a3. The second path
includes an accumulator 325n1, an accumulator 325n2, and an
accumulator 325n3. Each accumulator, for example the accumulator
325a1, adds an output of corresponding correlator, for example the
correlator 320a1, non-coherently across multiple periods to yield a
correlation peak. The multiple periods can be equal to storage
length of the pseudorandom sequence. For example, for the
pseudorandom sequence with length 7, the accumulator 325a1 adds
successive correlated signals every 7 samples. If y(n) is the
output of the accumulator 325a1 and x(n) is the input of the
accumulator 325a1, then y(n)=y(n-7)+x(n). In other embodiments,
block addition can also be performed, where y(n)=.SIGMA.x(n-7i),
where i=0,1, . . . ,N-1, where N is the number of blocks of length
7 that are added. If the correlation peak exceeds a correlation
threshold then the signal is detected.
[0038] In some embodiments, each path also includes at least one
peak to off-peak estimator. For example, the first path includes a
peak to off-peak estimator 330a1, a peak to off-peak estimator
330a2, and a peak to off-peak estimator 330a3. The second path
includes a peak to off-peak estimator 330n1, a peak to off-peak
estimator 330n2, and a peak to off-peak estimator 330n3. Each peak
to off-peak estimator determines a ratio of a peak value of a
sample in an output of the accumulator or the correlator to an
average value of off-peak samples in the output and compares the
ratio against a threshold.
[0039] The processing circuit 210 further includes a state machine
circuit 335 that identifies a channel carrying the signal based on
at least one of the correlation peak and peak to off-peak ratio of
each channel. Each path is connected to the state machine circuit
335. In one example, the state machine circuit 335 selects the
channel that has the highest peak-to-off-peak ratio or correlation
peak. The state machine circuit 335 indicates presence of the
signal in the path and identifies the channel corresponding to the
path as the signal carrying channel. In other embodiments, the
state machine 335 may indicate the most likely channels which may
then be searched for longer time to detect the actual channel in
which signal is present.
[0040] It is noted that any existing circuit for the state machine
circuit 335 can be used.
[0041] In some embodiments, the processing circuit 210 also
includes an automatic gain controller (AGC) 340 coupled to the ADC
301 to adjust the gain based on input power and output power of the
filter 305. The processing circuit 210 also includes a received
signal strength indicator (RSSI) circuit coupled to the AGC. The
RSSI is a power estimation circuit that estimates power in the
digital samples. The RSSI can also detect presence of the signal
having high strength. The RSSI can be used for when the implant
receiver is in low sensitivity mode.
[0042] The processing circuit 210 can be included in a physical
layer circuit of the implant receiver. The implant receiver can
have several layers, for example a radio frequency layer, a
physical layer, a medium access control layer and other layers.
[0043] 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.
[0044] 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.
[0045] FIG. 5 is a method for signaling in a medical implant based
system.
[0046] At step 505, a first set of contents of a band of channels
is received by a receiver, hereafter referred to as implant
receiver. In one embodiment, the first set of contents can be
converted into digital samples and processed.
[0047] At step 510, a second set of contents of a plurality of
channels from the band of channels is processed in parallel.
[0048] In one embodiment, the first set of contents is converted to
digital samples using an analog to digital converter. The digital
samples can then be referred to as a second set of contents which
is processed in parallel.
[0049] In another embodiment, the digital samples can be stored and
subset of the digital samples can be processed in parallel.
[0050] In yet another embodiment, the first set of contents can be
processed in parallel.
[0051] The processing includes forming a first path for contents of
a first channel, a second path for contents of a second channel and
so on. One path is formed for one channel. Several such paths can
be formed based on area requirement of the implant receiver. In
each path a frequency offset can be corrected. The correcting
includes hypothesizing on the frequency offset to yield a filtered
content which has less residual frequency offset. The removal of
frequency improves correlation. Further, the filtered content
obtained from the hypothesis is correlated with a predefined
sequence. The correlation results in a correlation peak. The
correlation peak is checked against a correlation threshold. If the
correlation peak exceeds the correlation threshold then step 515 is
performed, else the path and hence the channel is discarded.
[0052] It is noted that various methods of correcting frequency
offset can be used.
[0053] In some embodiments, a ratio of a peak value of a sample in
an output of the correlation to an average value of off-peak
samples in the output can be determined and checked against a
threshold. The output of the correlation can be referred to as the
output of the processing. If the threshold is exceeded then step
515 is performed, else the path and hence the channel is
discarded.
[0054] At step 515, a signal is detected in the band of channels.
Further, a channel that carries the signal is identified, for
example by using a state machine circuit.
[0055] In the foregoing discussion, the term "coupled or connected"
refers to either a direct electrical connection between the devices
connected or an indirect connection through intermediary devices.
The term "signal" means at least one current, voltage, charge,
data, or other signal.
[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.
* * * * *