U.S. patent application number 13/027539 was filed with the patent office on 2011-06-09 for method and apparatus for automatic selection and operation of a subscriber line spectrum class technology.
Invention is credited to Gordon Bremer, Philip J. Kyees.
Application Number | 20110134977 13/027539 |
Document ID | / |
Family ID | 34713322 |
Filed Date | 2011-06-09 |
United States Patent
Application |
20110134977 |
Kind Code |
A1 |
Bremer; Gordon ; et
al. |
June 9, 2011 |
Method and Apparatus for Automatic Selection and Operation of a
Subscriber Line Spectrum Class Technology
Abstract
Systems and methods for selecting an operating mode for a
communication device are disclosed. The operating mode is
compatible with one or more spectrum management classes. One such
method includes measuring subscriber loop characteristics and
identifying a first allowable class corresponding to the measured
subscriber loop characteristics. The allowable class is chosen from
a group of spectrum management classes. The method further includes
selecting an operating mode from a group of possible operating
modes. The selected operating mode is compatible with the first
allowable class.
Inventors: |
Bremer; Gordon; (Clearwater,
FL) ; Kyees; Philip J.; (Largo, FL) |
Family ID: |
34713322 |
Appl. No.: |
13/027539 |
Filed: |
February 15, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11074029 |
Mar 7, 2005 |
7894472 |
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13027539 |
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09573518 |
May 17, 2000 |
6970501 |
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11074029 |
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60134590 |
May 17, 1999 |
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Current U.S.
Class: |
375/222 |
Current CPC
Class: |
H04L 5/1438 20130101;
H04M 11/062 20130101 |
Class at
Publication: |
375/222 |
International
Class: |
H04B 1/38 20060101
H04B001/38 |
Claims
1. A method for selecting an operating mode for a communication
device capable of operating in a mode that is compatible with one
or more spectrum management classes, the method comprising the
steps of: measuring subscriber loop characteristics; identifying a
first allowable class corresponding to the measured subscriber loop
characteristics, where the allowable class is chosen from a group
of spectrum management classes; and selecting an operating mode
from a group of possible operating modes, where the selected
operating mode is compatible with the first allowable class.
2. The method of claim 1, wherein each spectrum management class
defines transmit power requirements.
3. The method of claim 1, wherein each spectrum management class
defines transmit power spectral density (PSD) requirements.
4. The method of claim 1, wherein the spectrum management classes
are defined by a standard.
5. The method of claim 1, further comprising the steps of:
determining that the selected operating mode is not currently
compatible with the first allowable class; and ceasing line
signaling upon such determination.
6. The method of claim 1, further comprising the steps of:
determining that the selected operating mode is not currently
compatible with the first allowable class; identifying a second
allowable class corresponding to the measured subscriber loop
characteristics; and selecting one of the operating modes that is
compatible with the second allowable class.
7. The method of claim 1, further comprising the steps of:
determining which one of the operating modes optimizes performance;
and selecting the one operating mode that optimizes
performance.
8. A computer-readable medium containing a program for determining
whether a communication device is capable of operating in a mode
that is compatible with one or more spectrum management classes,
the program designed to perform the steps of: performing a test on
a subscriber loop coupled to the communication device; and
determining, responsive to the test, whether at least one of a
plurality of operating modes is currently compatible with at least
one of a plurality of spectrum management classes.
9. The computer-readable medium of claim 8, wherein each spectrum
management class defines transmit power requirements for the
modem.
10. The computer-readable medium of claim 8, wherein the spectrum
management classes are defined by a standard.
11. The computer-readable medium of claim 8, the program further
designed to perform the step of determining that none of the modes
is currently compatible with any of the spectrum management
classes, and to refrain from data transmission and reception upon
such determination.
12. The computer-readable medium of claim 8, the program further
designed to perform the step of measuring characteristics of the
subscriber loop.
13. The computer-readable medium of claim 12, the program further
designed to perform the step of automatically selecting, based on
the measured characteristics, one of the modes that is compatible
with at least one of the spectrum management classes.
14. The computer-readable medium of claim 12, wherein the measured
characteristic is loop length.
15. A modem coupled to a subscriber loop, the modem capable of
operating in a plurality of modes that are each compatible with one
or more spectrum management classes, each spectrum management class
defining transmit power requirements to which the modem must adhere
in order to be compatible with the class, the modem configured to
determine whether at least one of the modes is currently compatible
with at least one of the spectrum management classes.
16. The modem of claim 15, wherein each spectrum management class
defines transmit power spectral density (PSD) requirements.
17. The modem of claim 15, wherein the spectrum management classes
are defined by a standard.
18. The modem of claim 15, the modem further configured to
automatically select one of the modes that is compatible with at
least one of the spectrum management classes.
19. The modem of claim 15, wherein the modem is further configured
to determine that none of the modes is currently compatible with
any of the spectrum management classes, and to refrain from data
transmission and reception upon such determination.
20. The modem of claim 15, wherein the modem is further configured
to measure subscriber loop length.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
11/074,029, filed Mar. 7, 2005, which is a continuation of
application Ser. No. 09/573,518, filed May 17, 2000, which claims
the benefit of U.S. Provisional Application No. 60/134,590, filed
May 17, 1999. These applications are entirely incorporated herein
by reference.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates generally to a method and
apparatus for automatically selecting a subscriber line Spectrum
Management Class technology mode of operation for communication
over metallic subscriber loop cables. More particularly, the
present invention relates to a communication device that
automatically detects which of a plurality of Spectrum Management
Classes the communication device is capable of operating in and
selects a mode of operation that is compatible with one or more of
the Spectrum Management Classes.
BACKGROUND OF THE INVENTION
[0003] The American National Standard for Telecommunications is
developing a standard that sets forth spectrum management
requirements and recommendations for the administration of services
and technologies that use metallic subscriber loop wire pairs,
commonly referred to as subscriber loops. The goal of the standard
is to administer the loop plant in a way that provides spectral
compatibility for services and technologies that use pairs in the
same cable binder. The standard is particularly directed to
minimizing the potential for cross-talk interference in twisted
pair subscriber loop cables that are shared by multiple service
providers (carriers). In situations where multiple service
providers utilize twisted pairs in the same loop binders, services
and technologies may interfere with each other if they are deployed
in an uncontrolled manner. The standard provides spectrum
management requirements and deployment recommendations for the
administration of services and technologies in such an environment
in a way that prevents or minimizes such deleterious effects.
[0004] The Spectrum Management Classes address (1) transmit signal
power spectral density (PSD) requirements, (2) transmit signal
average power requirements, (3) transverse balance requirements,
(4) deployment restrictions based upon the subscriber loop
characteristics, and (5) loop assignment guidelines. A
communication device or system that meets all of the applicable
requirements for one of the spectrum management classes is deemed
to be in conformance with the standard. If a communication device
or system does not meet all of the requirements associated with at
least one of the spectrum management classes, the communication
device or system is deemed to be non-compliant with the
standard.
[0005] It would be desirable to provide a communication device,
such as a digital subscriber line (DSL) modem, for example, that is
capable of operating in a manner that is compatible with one or
more of the spectrum management classes. It would also be desirable
to provide a communication device that is capable of automatically
detecting which of the spectrum management classes it is capable of
operating in and of automatically selecting a mode of operation
that is compatible with one of the spectrum management classes.
Furthermore, it would be desirable to provide such a communication
device that could detect when it is capable of operating in a mode
that is compatible with more than one of these classes and that
would automatically select a mode of operation that is compatible
with the class that optimizes performance of the communication
device. It would also be desirable to provide such a communication
device that could detect when it is no longer capable of operating
in a mode that is compatible with at least one of the spectrum
management classes and which would prevent operation of the
communication device when such a determination is made.
[0006] Although it is generally known for certain DSL modems and
subscriber line technologies to have automatic and adaptive
algorithms that seek to optimize performance, it is not known to
provide a modem that detects compatibility with one or more
spectrum management classes of the aforementioned standard and that
selects the appropriate or best mode of operation based on that
determination. For example, algorithms that automatically select
transmit spectrum bandwidths and/or bandwidth locations are known.
These algorithms are utilized to optimize performance in accordance
with the ITU V.34 standard. The ITU V.34 standard also provides for
adaptive equalizers and echo-cancelers.
[0007] Another type of automatic algorithm provided for by the ITU
V.34 standard, which is often referred to as an auto-rating
algorithm, provides for modifying a data transmission rate of a
modem to allow the highest data rate possible to be utilized in the
presence of certain line impairments. However, this algorithm is
not truly "adaptive" because it is necessary to temporarily disrupt
communication while the rate change is being accomplished. An
auto-rate algorithm that is utilized with Multiple Virtual Lines
(MVL) technology is known, which was developed by the assignee of
the present application. The MVL auto-rating algorithm enables the
rate change to be accomplished without disrupting communication.
Therefore, the MVL auto-rating algorithm is adaptive.
[0008] Although the aforementioned algorithms seek to optimize
performance, they do not take into account restrictions on transmit
bandwidth and/or transmit power level or other types of
restrictions that are in effect on a particular subscriber line on
which they operate. These are examples of the types of restrictions
that must be met in order to comply with the spectrum management
classes defined in the standard. Therefore, these algorithms are
not suitable for automatically selecting an appropriate mode of
operation that is in compliance with one of the spectrum management
classes.
[0009] A feature known as Spectrum Manager is used with Etherloop
modems, which are marketed by a company known as Elastic Networks.
Etherloop modems base the use of transmit spectrum on the presence
or absence of other devices in the binder, i.e., on the presence or
absence of other devices communicating on the same copper pair.
Etherloop modems correlate an allowable use of spectrum to the
length of the loop to which the modem is connected. The Etherloop
modem adjusts its usage of transmit spectrum based on a detection
of cross-talk caused by other DSL systems in the binder.
[0010] However, the Etherloop modem does not adjust its use of
spectrum based on loop parameters required for spectrum management
class compliance. Furthermore, when an Etherloop modem is operating
properly, it will, under many circumstances, select modes of
operation that are not in compliance with the aforementioned
spectrum management classes. Also, Etherloop modem adjustments are
based on a measurement of transient conditions and other conditions
that are difficult to measure. It is not based on measurement
parameters that are directly related to the deployment rules
associated with the spectrum management classes.
[0011] Accordingly, a need exists for a communication device, such
as a modem, that is capable of detecting whether it is capable of
operating in a mode that is compatible with one or more of the
spectrum management classes and which automatically selects a mode
of operation that is compliant with one of the spectrum management
classes. A need also exists for such a communication device that is
capable of determining whether it is capable of operating in
multiple modes that are compliant with multiple spectrum management
classes and which is capable of selecting the mode of operation
that optimizes the performance of the communication device. A need
also exists for such a communication device that is capable of
determining when it is not capable of operating in a mode that is
compliant with at least one of the spectrum management classes and
which prevents operation of itself upon determining that it is not
capable of operating in a mode that is compliant with at least one
of the spectrum management classes.
SUMMARY OF THE INVENTION
[0012] The present invention provides a communication device, such
as a modem, that is capable of detecting whether it is capable of
operating in a mode that is compatible with one or more of the
spectrum management classes and which automatically selects a mode
of operation that is compliant with one of the spectrum management
classes. The communication device determines whether it is capable
of operating in multiple modes that are compliant with multiple
spectrum management classes and which is capable of selecting the
mode of operation that optimizes the performance of the
communication device. The communication device is also capable of
determining when it is not capable of operating in a mode that is
compliant with at least one of the spectrum management classes and
which prevents operation of itself upon determining that it is not
capable of operating in a mode that is compliant with at least one
of the spectrum management classes.
[0013] These and other aspects and advantages of the present
invention will become apparent from the following discussion,
drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a block diagram illustrating a portion of the
system in which the method and apparatus of the present invention
may be implemented.
[0015] FIG. 2 is a block diagram illustrating the apparatus of the
present invention in accordance with one exemplary embodiment.
[0016] FIG. 3 is a flow chart representing an example of the manner
in which the present invention can be used to determine whether one
or more Spectrum Management Classes are available for communicating
over the loop 3 and subscriber line 5 shown in FIG. 1.
[0017] FIG. 4 is a flow chart demonstrating the method of the
present invention in accordance with one exemplary embodiment,
wherein the parameter being measured to determine the best mode of
modulation is loop length.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The present invention provides a Network Access Provider
(NAP) Test Feature that enables one or more tests to be performed
to determine which of multiple transceivers of a data communication
equipment (DCE) device should be operating over a subscriber loop.
The test(s) of the NAP test feature are utilized in accordance with
the preferred embodiment of the present invention to determine
which spectrum management class or classes a DCE device may operate
in over the subscriber loop. It should be noted that the tests of
the NAP Test Feature of the present invention are not limited to
being used to determine which spectrum management class or classes
a communication device may operate in on a subscriber loop. The
present invention is capable of being utilized to determine the
appropriate spectrum management class or classes defined in the
aforementioned American National Standard for Telecommunications,
although the present invention is not limited to being utilized for
this purpose.
[0019] FIG. 1 is a block diagram illustrating the loop plant 3 that
connects a central office (CO) 2 to several different subscriber
premises, each of which comprises a DCE device 7 (e.g., an xDSL
modem) and data terminal equipment (DTE) 8 (e.g., one or more
computers). The CO 2 comprises at least one DCE 4 that is
compatible with the DCEs 7 located at the subscriber premises. The
loop plant represented by the line 3 is comprised of one or more
twisted copper pairs, as is well known in the industry. The
subscriber lines 5 are also twisted copper pairs that connect the
subscriber premises to the loop plant 3. The subscriber lines 5 are
normally viewed as being part of the loop plant 3. In accordance
with the present invention, one or more tests are performed to
determine the operating capability of the DCEs 4 and/or 7 located,
respectively, at the CO 2 and at the subscriber premises. The DCE 4
located at the CO 2 preferably is an xDSL modem having similar or
identical functional capabilities as those of the DCEs 7 located at
the subscriber premises, which, as stated above, preferably are
also xDSL modems.
[0020] By performing these test(s), one or more Spectrum Management
Classes that the DCEs 4 and/or 7 are capable of operating in can be
determined. FIG. 2 is a block diagram illustrating the apparatus of
the present invention in accordance with one exemplary embodiment.
The apparatus preferably is comprised in an xDSL modem, which is
represented by each of the DCEs 4 and 7 shown in FIG. 1. Each of
the DCEs 4 and 7 comprises four transceivers 11, 12, 13 and 14,
which are available for connection, one at a time, to the
subscriber line 5 via a selector 10 and the subscriber line
interface 16.
[0021] Instead of one of the transceivers being connected to the
subscriber line 5 at a particular time, the selector 10 can instead
connect the Automatic Class Measurement device 15 to the subscriber
loop 5 via the subscriber line interface 16. The Automatic Class
Measurement device 15 is capable of performing certain tests to
determine which of the transceivers 11, 12, 13 or 14 should be
connected to the subscriber line 5. Once this determination has
been made, the Automatic Class Measurement device 15 notifies the
selector 10 as to which transceiver is to be connected. The manner
in which this determination is made will be discussed below in
detail with respect to the NAP tests of the present invention.
[0022] Connection of the appropriate transceiver to the subscriber
line 5 enables the modem 7 to communicate with the DCE 4 located at
the CO 2 within the determined Spectrum Management Class dictated
by the physical characteristics of the subscriber line 5 (e.g.,
loop length, gauge, etc). Once the appropriate transceiver has been
connected, the Adaptive Class Measurement device 19 monitors the
subscriber line 5 and determines whether the connected transceiver
of the modem 7 is currently capable of communicating with the CO 2
within the particular Spectrum Management Class. If not, the
transceiver is then taken out of service and the transceiver that
is most appropriate for communicating within the current Spectrum
Management Class with the DCE 4 of the central office 2 is
connected to the subscriber loop 5 via the selector 10 and
subscriber line interface 16. The manner in which the Adaptive
Class Measurement device 19 performs these tasks will be discussed
below with reference to the NAP tests of the present invention.
[0023] In the exemplary embodiment shown in FIG. 2, a transceiver
is provided for four Spectrum Management Classes, namely, very low
band symmetric (VLB) Class, the low band symmetric (LB) Class, the
mid band symmetric (MB) Class and the high band symmetric (HB)
Class. Upon measurement by the Automatic Class Measurement device
15 of the loop length and/or other loop parameters defined by the
Spectrum Management Class deployment rules, the Spectrum Management
Class or Classes that correspond to the measured parameters are
identified as Allowable Classes. This measurement by the Automatic
Class Measurement device 15 will occur automatically whenever a
modem incorporating the invention is placed into service and
powered on.
[0024] As stated above, at other times the Adaptive Class
Measurement device 19 will measure parameters in an adaptive
background manner to determine whether or not the Allowable Classes
have changed. Both of the devices 15 and 19 are configured to be
capable of controlling the selector 10 to connect the appropriate
transceiver of the DCE 7 to the subscriber line 5. Furthermore, the
Adaptive Class Measurement device 19 is capable of removing the
currently connected transceiver from service and causing the most
appropriate transceiver to be connected. The Adaptive Class
Measurement device 19 preferably is configured to perform some or
all of the loop qualification NAP testing capabilities described
below in detail. Preferably, the communication device 1 at the CO 2
and the DCE 7 at the subscriber premises are configured to
cooperate with each other in performing these tests. However, as
discussed below, at least some of the tests may be performed by the
DCE 4 at the CO 2 without a DCE 7 being located at the subscriber
premises, and vice versa.
[0025] The Adaptive Class Measurement device 19 performs the tests
necessary to determine the Spectrum Management Class or Classes for
which the subscriber line 5 is qualified. It may then further
determine from test results which compliant transceiver will
provide best performance. In accordance with one aspect of the
present invention, Pre-qualification Test(s) are performed to
permit preliminary Class identification to be ascertained by the
communication device 1 of the CO without the necessity of a
subscriber premises test device (e.g., a DSL modem configured to
cooperate with the communication device 1 during the test(s)). The
Pre-qualification Test(s) permit more accurate Class identification
to be performed from the CO 2 when being utilized in conjunction
with a premises test device (e.g., a DSL modem 7).
[0026] FIG. 3 is a flow chart representing an example of the manner
in which the present invention can be used to determine whether one
or more Spectrum Management Classes are available for communicating
over the loop 3 and subscriber line 5. This flow chart applies to
situations where the determination is made with and without the
premises test device, which is represented by the DSL modem 7. In
this example, the loop length is measured to determine the
available Spectrum Management Class or Classes, as indicated by
block 21. The Allowable Spectrum Management Class or Classes are
then identified at the CO 2 by the communication device 1 and/or at
the subscriber premises by the modem 7. Preferably, the allowable
Spectrum Management Class or Classes are tagged, as indicated by
block 25. The most appropriate transceiver of the modem 7 is then
selected and connected to the subscriber line 5 via selector 10 and
subscriber line interface 16.
[0027] When the Automatic Class Measurement device 15 of the modem
7 is determining the allowable Spectrum Management Class or
Classes, it will cause the selector 10 to select the appropriate
transceiver for connection to the subscriber line 5. If the
communication device 1 at the CO 2 is making the determination, it
will send a command to the modem 7, once the modem 7 has been
placed in operation, to cause the appropriate transceiver to be
selected. The modem 7 will then operate in compliance with one of
the allowable Spectrum Management Classes, as indicated by block
27.
[0028] In-Service Tests of the NAP test feature of the present
invention are performed by the Adaptive Class Measurement device
19. This aspect of the present invention permits continual
monitoring to determine and select the transceiver corresponding to
the most appropriate Spectrum Management Class. If none of the
transceivers 11, 12, 13, 14 and 15 are capable of operating in
compliance with the available Spectrum Management Class or Classes,
the Adaptive Class Measurement device 19 will cause the modem 7 to
cease operating.
[0029] Loop length or reach is a prime parameter used in
establishing the allowable Spectrum Management Class. Measurement
of this parameter can be made during In-Service Tests. The
aforementioned ANSI standardized deployment rules for identifying
the available Spectrum Management Class or Classes are not yet
finalized and, even once finalized, are always subject to change.
Therefore, rather than describing the manner in which the
non-finalized rules may be applied to determine the allowable, or
available, Spectrum Management Classes, the basic NAP tests of the
present invention will be described and examples of the manner in
which they can be applied to determine allowable Spectrum
Management Classes will be provided.
[0030] The subscriber line 3/5 is comprised of a wire pair
connecting the DCE 4 located at the CO 2 to the DCE 7 located at
the subscriber premise. The pair may be comprised of, for example,
a single wire gauge, typically AWG 24 or AWG 26. Alternatively, the
pair may be of mixed gauge with some lengths of one gauge and some
lengths of another gauge. The subscriber loop may have bridged taps
attached to the wire pair at one or more points. Depending on the
detailed Spectrum Management Class deployment rule definition of
"reach", the parameters to be tested may vary. The following
example is representative of the manner in which "reach" can be
determined, but variations can be accommodated by the test methods
of the present invention, as will be understood by those skilled in
the art in view of the discussion provided herein. The following
example assumes that the "reach" test is performed by either DCE 7
or DCE 4. It should also be noted that the "reach" test could also
be determined by a device external to the DCEs 7 and 4, even a
device manufactured by a manufacturer other than the manufacturer
of the DCEs 4 and 7. The "reach" determination could then be
entered into the Adaptive Class Measurement device 19, by a service
technician, for example.
[0031] For exemplary purposes, it will be assumed that the
standardized deployment rule definition of "reach" is the
"equivalent length of an AWG 26 wire pair for the measured
end-to-end loss vs. frequency, irrespective of any bridged taps."
For this case, it is necessary to measure the end-to-end loss while
identifying and discounting any effect of any bridged taps. The
loss vs. frequency of an AWG 26 wire pair at any reach is well
known. Therefore, if a determination is made that no bridged taps
are present, a direct loss vs. frequency measurement can be
compared with known AWG 26 reach tables and the loop reach can be
determined from those tables. This method of determining reach is
suitable even if the actual wire gauge is not AWG 26, or is of
mixed gauge, because the deployment rule is only directed to
determining "equivalent" length. Unfortunately, if no priori
information on bridged taps is available, bridged taps must be
identified by the test and either compensated for by the testing
signals or compensated for in the interpretation of the loss vs.
frequency data, or both. The manner in which this determination is
made will now be described.
[0032] A bridged tap at or very near one end of the loop, which is
the typical case, is readily discoverable and quantifiable by test
equipment at that end. The bridged tap creates a frequency
dependent impedance that is a function of the length of the bridged
tap. For example, the impedance associated with the bridged tap is
typically lowest at a frequency of about 150 kHz/B, where B is the
length of the bridged tap in kilofeet. A typical test signal
generator with a non-zero output impedance, say 100 ohms, would be
expected to transmit a signal that has a small loss vs. frequency
variation when no bridged tap is present. However, since the
bridged tap will normally introduce a lower impedance at the
frequency identified above, the length of the bridged taps can be
deduced by measuring at a test signal generator the signal level
placed on to the wire pair.
[0033] The objective of this test is to disregard effects of
bridged taps. Two approaches may be used to achieve this. The first
approach is to set the test generator output impedance near zero so
that the low impedance caused by the bridged tap is substantially
inconsequential. The second is to equalize the transmit test
signal. In both cases, the transmit test signal loss vs. frequency
variation will be substantially negligible. By using either of
these approaches at each end of the loop, a determination can be
made as to (1) whether a bridged tap is present at either or both
ends of the loop, and (2) the length of any bridged taps that are
present. These determinations can then be used to overcome the
influence of the taps on the end-to-end loss vs. frequency
measurements.
[0034] Once the effect of bridged taps at or near the ends of the
subscriber loop has been mitigated, end-to-end loss vs. frequency
data can be obtained in each direction. However, it remains
possible that bridged taps far from either end of the loop are
present. It is probably not possible to accurately account for all
such bridged taps in this manner. However, since the large majority
of bridged taps are near one end of the loop and the large majority
are less than 1000 ft from one end of the loop, restricting the
loss vs. frequency to frequencies well below 150 kHz assures that
the desired reach calculation of this example can be achieved.
[0035] Measurement of loop reach may be accomplished by
transmitting from one end of the loop, such as from the CO 2, a
signal with a known spectral content and measuring at the other
end, such as at the DEC, the level at various frequencies across
the frequency band of interest. Such a signal can be a swept sine
wave as is used in classical spectrum analyzers or other test
signals, which are well known in the art. By knowing the spectral
content of the transmitted signal and of the received signal, the
loss vs. frequency characteristics of the of the test signal over
the channel can be determined, as will be understood by those
skilled in the art. The same test can be performed to make this
determination in both directions.
[0036] It should be noted that, if a loop is classed at, for
example, Spectrum Management Class LB, it is also useable for Class
VLB DSLs since Class VLB falls within the requirements of Class LB.
The test would then be to measure performance parameters and select
the best modulation method that is compliant with both Class VLB
and Class LB. This is demonstrated by the flow chart of FIG. 4. The
example demonstrated in the flow chart of FIG. 4 assumes that the
parameter being measured to determine the best mode of modulation
is loop length. Therefore, loop length is measured, as indicated by
block 33 to determine the allowable Spectrum Management Classes, as
indicated by block 35.
[0037] Once the allowable Spectrum Management Classes, if any, have
been identified, a determination is made as to whether any
allowable Spectrum Management Classes exists, as indicated by block
37. If not, operation in the current modulation mode and line
signals are prohibited, as indicated by block 39. If at least one
allowable Spectrum Management Class has been identified, the
allowable Spectrum Management Class(es) is tagged, as indicated by
block 41. A determination is then made as to whether more than one
allowable Class was identified, as indicated by block 43. If only
one allowable Class has been identified, then the Adaptive Class
Measurement device 19 causes the selector 10 to select the
transceiver (11, 12, 13, 14) corresponding to the mode of
operations that is compliant with the Allowable Spectrum Management
Class, as indicated by block 45. If more than one allowable Class
has been identified, then the Adaptive Class Measurement device 19
causes the selector 10 to select the transceiver (11, 12, 13, 14)
corresponding to the best mode of operations that is compliant with
each of the allowable Spectrum Management Class, as indicated by
block 47. The following table lists classes of tests that are
provided in accordance with the present invention. Each class of
tests may be performed without a prerequisite performance of any
other class of tests. That is, each class has a test set that
provides results without need to perform other. Those skilled in
the art will understand the manner in which these tests are
performed.
TABLE-US-00001 Class Test Name Pre-Qualification Tests Premises
modem not Operational Note: Tests with an "*" POTS Available
Qualification may be Loading Coils Present performed and report for
both POTS Splitter Present on/off-hook status. Loop Length
Prediction On-Off Hook Interfering POTS Activity DSL/CO Average
Noise* DSL/CO Impulse Noise* DSL/CO Noise Spectrum* DSL/CO
Crosstalk Type* DSL/CO Tonal Interferences* DCE Performance
Prediction* Qualification Tests Premises modem Operational But test
operator has no Note: each multipoint POTS Available control over
premises. premises DSL modem Loading Coils Present Note: Tests with
an "*" are may be individually POTS Splitter Present performed and
report for both tested. Loop Length on/off-hook states. Downlink
Loop Characteristic, or DLC Uplink Loop Characteristic, or ULC
On/Off Hook Phone Filter Present Interfering POTS Activity CO/DLC
Non-Linear Distortion* Premises Non-Linear Distortion* DSL/CO
Average Noise* Premises Average Noise* DSL/CO Impulse Noise*
Premises Impulse Noise* DSL/CO Noise Spectrum* Premises Noise
Spectrum* DSL/CO Crosstalk Type* Premises Crosstalk Type* DSL/CO
Tonal Interferences* Downstream Data Rate*. Upstream Data Rate*
In-Service Tests Premises modem Operation Note: Tests with an "*"
are On-Off Hook performed and reported for Downstream Data Rate*
both on/off-hook states. Upstream Data Rate* Test operator has
control over Downstream Block Test* premises. Upstream Block Test*
Downstream User Byte Count* Upstream User Byte Count* Downstream
Data Efficiency* Upstream Data Efficiency* POTS State Change Count
Retrain Count CO/DLC Receive LevelPremises Receive Level CO/DLC
Receive Ratio Premises Receive Ratio Service User Modem Service
Available Service User Tests Modem Service Available Note: Tests
with an "*" are On-Off Hook performed and reported for Downstream
Data Rate* both on/off-hook states. Upstream Data Rate* Test
operator has control over Downstream Block Test* premises. Upstream
Block Test*
[0038] The Pre-Qualification Tests involve testing from a CO
without a modem (i.e., a DSL modem) at the subscriber premises.
Alternatively, the Pre-Qualification Tests could be performed by
the modem located at the subscriber premises without the need for
cooperation by the modem located at the CO. The accuracy of some of
these tests is limited due to the absence of known termination and
DCE equipment at the premises or at the CO. For purposes of
explanation, it will be assumed that the Pre-Qualification Tests
are to be performed by the modern located at the CO. The first
objective of these tests is to estimate, prior to any premises
installation, the likelihood that a modem, if installed at the
subscriber premises, will perform according to the proposed service
offering. The second objective of these tests is to identify
impairments that may limit performance of the modem once installed
at the subscriber premises.
[0039] The Qualification Tests involve testing from a modem at a CO
in conjunction with a modem located at the subscriber premises, but
with the premises modem service being disrupted or disabled. Each
multipoint premises modem can be individually tested, if desired.
The accuracy of these tests is high due to the use of the premises
modem equipment in conjunction with the testing equipment located
at the CO (DCE 4 shown in FIG. 1). The first objective of these
tests is to establish premises modem performance compared to the
proposed service offering. The second objective is to identify
impairments that may limit the performance of the premises
modem.
[0040] The In-Service Tests involve testing from a CO modem
concurrent with and without interfering with normal service
provided by the premises modem. Each premises modem can be
individually tested, if desired. The accuracy of these tests is
high. The first objective of these tests is to measure the premises
modem performance according to the proposed service offering. A
second objective is to report impairments that may lead to either
performance improvements or the offering of higher performance
services.
[0041] The Premises User Tests provide test results at a premises
modem concurrent with normal operational service of the modem,
i.e., without interrupting service provided by the premises modem.
Each multipoint premises modem can be individually tested, if
desired. The accuracy of these tests is high. The first objective
of these tests is to provide information to the service user to
permit direct assessment of performance from the premises modem to
the CO without contacting the service provider. The second
objective is to identify performance limiting impairments or
attached POTS devices within the premises. Each multipoint premises
modem can be individually tested, if desired.
[0042] It should be noted that although the modem located at the
subscriber premises has been discussed only in terms of preferably
being an xDSL modem, this is not a requirement of the present
invention. However, the present invention preferably is directed to
providing xDSL services between subscriber premises and a CO. The
services are provided by a network service provider (NSP).
Therefore, the CO DCE 4 and the DCEs 7 preferably are xDSL modems.
The assignee of the present application has invented technology for
implementation in xDSL modems known as multiple virtual line (MVL)
technology. MVL DSL modems are capable of being utilized at a
subscriber premise to enable multiple DTE devices, such as a
facsimile machine and a personal computer, to operate
simultaneously and communicate over a single telephone line
coupling the subscriber premise to the CO. The present invention
may be implemented in various types of DCE devices, including
various xDSL modems and MVL xDSL modems.
[0043] Those skilled in the art will understand the manner in which
these tests can be performed. Therefore, no further discussion of
the manner in which any of these tests can be performed will be
provided herein in the interest of brevity. Preferably, the tests
of the present invention are implemented in software in the modem
located at the subscriber premises, as well as in the modem located
at the CO. As stated above, some tests are performed solely by the
modem 4 located at the CO whereas others are performed solely by
the modem 7 located at the subscriber premise. Others are performed
in part by the subscriber premises modem 7 and in part by the modem
4 located at the CO 2. Therefore, only the code that is needed at
those locations will need to be installed at those locations. It is
desirable, but not required, to have the test software reside
permanently in the same software codes used for operation of modems
implementing xDSL and MVL/xDSL technology. In other words, either
the test code itself, or modem operational code including the test
code, would be selected, rather than loaded, to perform the testing
routines. One reason for this is that some modem with which the
present invention could be implemented may have difficulty running
test software while simultaneously running multiple operational
modern codes.
[0044] Therefore, the manner in which the test software is
implemented may depend on the type of modem with which it is to be
implemented. With respect to MVL technology, which was developed by
the assignee of the present application, it is desirable for the
test software to reside without change in progressive releases of
MVL, even new classes of MVL technology are released. One reason
for this is to maintain permanence of test results so that data
collected in the past can be deemed to be reliable. Another reason
is to provide independence of test code releases from operational
code releases.
[0045] Preferably, test signal transmissions are generic so that
received data can be (1) immediately analyzed, and (2) stored for
later analysis, perhaps by analysis programs not yet in existence.
It is also desirable for the test signal transmission (digital to
analog writes) and test signal reception (analog to digital reads)
to have rather short, finite lengths commensurate with memory and
backhaul data capacities of the modem hardware (DSP and DSLAM
hardware, respectively). In the case where the subscriber premise
modem utilizes MVL/xDSL technology, it may be desirable for as much
signal analysis as possible to be performed outside of the MVL
operational system. That is, while the xDSL/MVL modem will generate
and receive test signals upon command, the raw data received should
be analyzed outside of this system by, for example, a personal
computer (PC) so that performance of the MVL tasks is not limited
by processing of the received test signal.
[0046] One possible architecture of the present invention will now
be described with reference to a modem incorporating xDSL/MVL
technology. It will be assumed that the tests are limited to tests
that are not run in the MVL operational mode. The tests listed
above can be categorized into either the operational mode or the
test mode. Preferably, every MVL software code set would have both
some MVL operating software and the Test Software of the present
invention. When instructed, the Test Software would be enabled and
test parameters would be loaded that would select the transmitted
test signals, the cadence of these signals, and the capture of
these signals. The Test Software would have a test signal
generation capability (i.e., a digital-to-analog (D/A) write at the
sample rate) and a test signal reception capability (i.e., an
analog-to-digital (A/D) read at the sample rate). In all cases, the
D/A writes and the A/D reads would occur simultaneously (including
null D/A generation). A single counter would identify and label the
transmit and receive sample pairs.
[0047] The test signal generations would be accomplished by one or
more algorithms capable of generating periodic waveforms, including
pseudo-random periodic waveforms. The objective here would be to
utilize very small program space and very small data memory space.
Each algorithm can have a parameters set, or the parameter set may
be loaded from an external source. Loading the parameters from an
external source provides great flexibility and use of test signals
not yet known.
[0048] It should be noted that the present invention has been
described with reference to preferred embodiments, but that the
present invention is not limited to those embodiments. It should
also be noted that, although the present invention preferably is
implemented in software, the present invention may also be
implemented solely in hardware, if so desired. If implemented in
software, the software is not limited to being stored on any
particular type of storage device. A suitable storage device for
this purpose may be, for example, a magnetic storage medium, such
as a magnetic disk, a solid state storage medium, such as random
access memory (RAM) or read only memory (ROM), or an optical
storage medium, such as an optical compact disk ROM (CD-ROM).
Therefore, the present invention is not limited with respect to the
type of computer-readable medium employed for storing the software.
Those skilled in the art will understand that various modifications
may be made to the embodiments and features discussed above without
deviating from the spirit and scope of the present invention.
* * * * *