U.S. patent application number 10/047529 was filed with the patent office on 2002-05-16 for loop integrity test device and method for digital subscriber line (xdsl) communication.
This patent application is currently assigned to Netspeed, Inc., a Texas corporation. Invention is credited to McHale, John F., Sisk, James R..
Application Number | 20020057763 10/047529 |
Document ID | / |
Family ID | 25458441 |
Filed Date | 2002-05-16 |
United States Patent
Application |
20020057763 |
Kind Code |
A1 |
Sisk, James R. ; et
al. |
May 16, 2002 |
Loop integrity test device and method for digital subscriber line
(xDSL) communication
Abstract
A digital subscriber line (xDSL) communication system (10) is
disclosed that allows xDSL communication across a local loop. The
system (10) includes a local loop termination point (14) and
customer premises equipment (12) connected to a twisted pair
telephone line (16). Loop integrity test devices (22, 24) for xDSL
communication are located at the local loop termination point (14)
and the customer premises equipment (12) and are coupled to the
telephone line (16). The loop integrity test devices (22, 24) are
respectively operable to transmit test signatures across the
telephone line (16), to receive and evaluate test signatures from
the telephone line (16), and to indicate whether the telephone line
(16) can support xDSL communication based upon evaluation of test
signatures.
Inventors: |
Sisk, James R.; (Cedar Park,
TX) ; McHale, John F.; (Austin, TX) |
Correspondence
Address: |
Barton E. Showalter, Esq.
Baker Botts L.L.P.
Suite 600
2001 Ross Avenue
Dallas
TX
75201-2980
US
|
Assignee: |
Netspeed, Inc., a Texas
corporation
|
Family ID: |
25458441 |
Appl. No.: |
10/047529 |
Filed: |
January 14, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10047529 |
Jan 14, 2002 |
|
|
|
08929778 |
Sep 15, 1997 |
|
|
|
Current U.S.
Class: |
379/1.04 ;
379/27.01 |
Current CPC
Class: |
H04M 3/306 20130101;
H04M 11/062 20130101; H04Q 1/028 20130101; H04L 43/50 20130101;
H04M 3/301 20130101 |
Class at
Publication: |
379/1.04 ;
379/27.01 |
International
Class: |
H04M 001/24; H04M
003/08 |
Claims
What is claimed is:
1. A loop integrity test device for digital subscriber line (xDSL)
communication systems, the test device comprising: a line interface
unit operable to connect to and interface with a first point on a
twisted pair telephone line, the telephone line forming a
continuous electrically conductive path without intermediate
components between the first point and a second point; an output
device operable to indicate a pass state and a fail state; and a
control unit comprising: a generation unit operable to transmit a
first test signature across the telephone line for reception and
evaluation at the second point, the transmission of the first test
signature initiating a first loop integrity test; and an evaluation
unit operable to receive a second test signature transmitted across
the telephone line, the second test signature originally generated
independent of the first test signature by a second loop integrity
test device to initiate a second loop integrity test, the
evaluation unit further operable to evaluate the second test
signature to determine whether the telephone line can support xDSL
communication; the control unit operable to direct the output
device to indicate a pass state if the telephone line can support
DSL communication and to indicate a fail state if the telephone
line can not support xDSL communication.
2. The loop integrity test device of claim 1, wherein the second
loop integrity test device couples to the telephone line at the
second point and is operable to complete the first loop integrity
test by receiving and evaluating the first test signature and
indicating whether the telephone line can support xDSL
communication based upon evaluation of the first test signature and
to independently initiate the second loop integrity test by
transmitting the second test signature across the telephone
line.
3. The loop integrity test device of claim 1, wherein the
evaluation unit is further operable to evaluate the second test
signature to determine physical characteristics of the telephone
line.
4. The loop integrity test device of claim 3, wherein physical
characteristics of the telephone line comprise impedance of the
telephone line.
5. The loop integrity test device of claim 3, wherein physical
characteristics of the telephone line comprise length of the
telephone line.
6. The loop integrity test device of claim 1, wherein the
evaluation unit is further operable to evaluate the second test
signature to determine a loss of energy across the telephone
line.
7. The test device of claim 1, wherein the generation unit is
further operable to generate the first test signature using an
algorithm.
8. The test device of claim 1, wherein the output device indicates
the pass state and the fail state using at least one of a light
emitting diode (LED) device, an audible alarm, an electronic
register that can be accessed by software, and an electronic signal
provided to another component.
9. The test device of claim 1, wherein the line interface is
further operable to draw power from the telephone line sufficient
to operate the test device.
10. A method for local loop integrity testing of digital subscriber
line (xDSL) communications, the method comprising: initiating a
test of a local loop telephone line by transmitting a test
signature from a first point on the local loop telephone line, the
local loop telephone line forming a continuous electrically
conductive path without intermediate components between the first
point and a second point; receiving the test signature at the
second point on the local loop telephone line; evaluating the
received test signature at the second point to determine whether
the local loop telephone line can support xDSL communication; and
indicating whether the telephone line can support xDSL
communication.
11. The method of claim 10, wherein the test signature indicates
initiation of the test to a device at the second point and provides
sufficient information for the device to complete the test by
indicating whether the telephone line can support xDSL
communication.
12. The method of claim 10, wherein evaluating is accomplished
based upon changes to the test signature caused by transmission
across the local loop telephone line.
13. The method of claim 10, wherein evaluating the received test
signature further comprises determining physical characteristics of
the telephone line.
14. The method of claim 13, wherein determining physical
characteristics of the telephone line further comprises determining
impedance of the telephone line.
15. The method of claim 13, wherein determining physical
characteristics of the telephone line further comprises determining
length of the telephone line.
16. The method of claim 10, wherein evaluating the received test
signature further comprises determining a loss of energy across the
telephone line.
17. The method of claim 10, wherein indicating includes is at least
one of providing a visual display of a pass state or a fail state,
providing an electronic signal, and storing data in an electronic
register.
18. A loop integrity test device for digital subscriber line (xDSL)
communication systems, the test device comprising: means for
initiating a test of a local loop telephone line by transmitting a
test signature from a first point on the local loop telephone line,
the local loop telephone line forming a continuous electrically
conductive path without intermediate components between the first
point and a second point; means for receiving the test signature at
the second point on the local loop telephone line; means for
evaluating the received test signature at the second point to
determine whether the local loop telephone line can support xDSL
communication; and means for indicating whether the telephone line
can support xDSL communication.
19. The test device of claim 18, wherein the test signature
indicates initiation of the test to a device at the second point
and provides sufficient information for completing the test by
indicating whether the telephone line can support xDSL
communication.
20. The test device of claim 18, wherein the means for evaluating
is operable to determine at least one of impedance of the telephone
line, length of the telephone line, and a loss of energy across the
telephone line.
21. A loop integrity test device for digital subscriber line (XDSL)
communication systems, the test device comprising: a line interface
unit operable to connect to and interface with a first point on a
twisted pair telephone line, the telephone line forming a
continuous electrically conductive path without intermediate
components between the first point and a second point; an output
device operable to indicate a pass state and a fail state; and a
control unit comprising: a generation unit operable to transmit a
first test signature across the telephone line for reception and
evaluation at the second point by a second loop integrity test
device, the transmission of the first test signature initiating a
first loop integrity test, wherein the second loop integrity test
device couples to the telephone line at the second point and is
operable to complete the first loop integrity test by receiving and
evaluating the first test signature and indicating whether the
telephone line can support xDSL communication based upon evaluation
of the first test signature; and an evaluation unit operable to
receive a second test signature transmitted across the telephone
line, the second test signature originally generated independent of
the first test signature by the second loop integrity test device
to initiate a second loop integrity test independent of the first
loop integrity test, the evaluation unit further operable to
evaluate the second test signature to determine whether the
telephone line can support xDSL communication; the control unit
operable to direct the output device to indicate a pass state if
the telephone line can support DSL communication and to indicate a
fail state if the telephone line can not support xDSL
communication.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 08/929,778, filed Sep. 15, 1997, by James R. Sisk and John F.
McHale, entitled "Loop Integrity Test Device and Method for Digital
Subscriber Line (xDSL) Communication".
TECHNICAL FIELD OF THE INVENTION
[0002] This invention relates in general to data communication, and
more particularly to a loop integrity test device and method for
digital subscriber line (xDSL) communication.
BACKGROUND OF THE INVENTION
[0003] Digital subscriber line (xDSL) communication can provide a
high bandwidth data path supported by the twisted pair wiring
infrastructure of the public switched telephone network (PSTN).
xDSL technologies support data service simultaneously with
traditional telephone service using a separation technique.
Suitable xDSL technologies include asymmetric digital subscriber
line (ADSL), rate adaptable digital subscriber line (RADSL),
symmetric digital subscriber line (SDSL), high-speed digital
subscriber line (HDSL) and very high-speed digital subscriber line
(VDSL).
[0004] In general, an xDSL communication link is established across
the local loop between customer premises equipment (CPE) and the
local loop termination point (e.g., central office or remote
terminal). The local loop termination point typically has a xDSL
access multiplexer (DSLAM) that handles the XDSL link on the
network side, and the CPE typically includes one or more xDSL
termination units (XTU) that handle the xDSL link on the customer
premises side. One architecture for xDSL communication is disclosed
in U.S. Pat. No. 5,668,857 (Ser. No. 08/625,769), filed Mar. 29,
1996, by John F. McHale, and entitled "Communication Server
Apparatus and Method."
[0005] In order to support xDSL communication, the twisted pair
line on the local loop between the customer premises and the loop
termination point must meet certain physical characteristics. If it
does not, an xDSL communication link can not be successfully
established. Consequently, it can be desirable to allow the xDSL
capability of the local loop to be quickly verified at the same
time that xDSL service is installed at the customer premises.
Further, it can be desirable to monitor the xDSL capability of the
local loop on an ongoing and continuous basis.
SUMMARY OF THE INVENTION
[0006] In accordance with the present invention, a loop integrity
test device and method for digital subscriber line communication
are disclosed that provide advantages over conventional xDSL
communication devices and systems.
[0007] According to one aspect of the present invention, a digital
subscriber line (xDSL) communication system allows xDSL
communication across a local loop. The system includes a local loop
termination point and customer premises equipment connected to a
twisted pair telephone line. Loop integrity test devices for xDSL
communication are located at the local loop termination point and
the customer premises equipment and are coupled to the telephone
line. The loop integrity test devices are respectively operable to
transmit test signatures across the telephone line, to receive and
evaluate test signatures from the telephone line, and to indicate
whether the telephone line can support xDSL communication based
upon evaluation of test signatures.
[0008] According to another aspect of the present invention, a loop
integrity test device is disclosed that includes a line interface
unit operable to connect to and interface with a twisted pair
telephone line. The test device also includes an output device
operable to indicate a pass state and a fail state. Further, the
test device includes a control unit having a generation unit and an
evaluation unit. The generation unit is operable to transmit a test
signature across the telephone line. The evaluation unit is
operable to receive and evaluate a test signature to determine
whether the telephone line can support xDSL communication. The
control unit is then operable to direct the output device to
indicate a pass state if the telephone line can support DSL
communication and to indicate a fail state if the telephone line
can not support xDSL communication.
[0009] A technical advantage of the present invention is that the
integrity of the local loop can be verified at the time of
installation of high speed xDSL data service at a customer
premises. In particular, the present loop integrity test device
provides an immediate indication of whether the loop can support
xDSL communication when it is installed.
[0010] Another technical advantage of the present invention is an
improvement in the reliability and monitoring of the xDSL
communication system. The test devices implement a continuous
integrity check of the local loop that allows the telephone company
or other service provider to be alerted to a problem on the local
loop. This notification may allow the service provider to correct
the problem before a degradation of service is noticed by the
customer.
[0011] Other technical advantages should be readily apparent to one
skilled in the art from the following figures, description, and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a more complete understanding of the present invention,
and for further features and advantages, reference is now made to
the following description taken in conjunction with the
accompanying drawings, in which:
[0013] FIG. 1 is a block diagram of one embodiment of an xDSL
communication system having loop integrity test devices for xDSL
communication according to the present invention;
[0014] FIG. 2 is a block diagram of one embodiment of a loop
integrity test device for xDSL communication according to the
present invention; and
[0015] FIG. 3 is a flow chart of a method for local loop integrity
testing for xDSL communication according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] FIG. 1 is a block diagram of one embodiment of an xDSL
communication system, indicated generally at 10, having loop
integrity test devices for xDSL communication according to the
present invention. System 10 includes customer premises equipment
12 that can be located at any one of a number of customer premises.
System 10 also includes a local loop termination point 14 which is
connected to customer premises equipment 12 via a twisted pair
telephone line 16. Customer premises equipment 12 typically
includes a network interface device (NID) 18 which forms a physical
interface between the customer premises and the telephone network
as well as any other equipment located at the customer premises or
other remote loop termination point. Local loop termination point
14 can be a central office, remote terminal or other appropriate
termination of the local loop and can include an xDSL access
multiplexer (DSLAM) 20 that provides xDSL high bandwidth data
service. Telephone line 16 supports conventional voice traffic and
is intended to support xDSL communications. However, depending upon
physical characteristics of telephone line 16, it may not support
xDSL communication or may only support limited xDSL communication.
For example, the distance of the local loop, any splices in
telephone line 16, loading on telephone line 16 and other physical
characteristics affect the integrity of telephone line 16 for xDSL
communication.
[0017] According to the present invention, a loop integrity test
device 22 is located at customer premises equipment 12, and a loop
integrity test device 24 is located at local loop termination point
14. Both loop integrity test devices 22 and 24 are coupled to
telephone line 16. Loop integrity test devices 22 and 24
respectively operate to transmit test signatures across telephone
line 16 and to receive and evaluate a test signature from telephone
line 16. The test signature can be a signal with implanted high
frequency tones, DC voltages or other distinctive characteristics
and can be transmitted periodically at some time interval. For
example, the test signature can be pulses, tones, modulated tones,
xDSL symbols (e.g., Quadrature Amplitude Modulated (QAM) symbols or
Discrete Multitone (DMT) symbols), or other xDSL physical layer
symbols chosen to allow determination of the line characteristics
and the ability of the line to support xDSL communication. Based
upon evaluations of the test signature, loop integrity test devices
22 and 24 indicate whether telephone line 16 can support DSL
communication. In this manner, loop integrity test devices 22 and
24 both provide an initial indication of the line integrity upon
installation as well as provide an ongoing monitoring of the line
integrity.
[0018] In one implementation, loop integrity test devices 22 are
installed in network interface device (NID) 18 at the customer
premises. This is done for ease of installation by a service
provider and to avoid interference with other customer premises
equipment 12 located behind network interface device (NID) 18.
Also, in this implementation, loop integrity device 24 is installed
separate from DSL access multiplexer 20 at local loop termination
point 14. Similarly, this is done to avoid interference with DSL
access multiplexer 20. It should be understood that other
implementations are possible within the scope of the present
invention. For example, loop integrity device 22 can be implemented
as part of other equipment at the customer premises or loop
termination point 14 such as part of an xDSL termination unit.
[0019] FIG. 2 is a block diagram of one embodiment of a loop
integrity test device, indicated generally at 30, for xDSL
communication according to the present invention. As shown, test
device 30 can comprise a line interface unit 32 that connects to a
telephone line 34. Line interface unit is coupled to a control unit
36 which can comprise a test signature generation unit 38 and a
test signature evaluation unit 40. Control device 36 is, in turn,
coupled to an output device 42. Output device 42 can, for example,
comprise light emitting diode (LED) devices, an LCD display, a
speaker, a register, an electronic signal output or a combination
of thereof.
[0020] In operation, line interface unit 32 provides an interface
between control unit 36 and telephone line 34. Control unit 36
manages the operation of test device 30 and directs output device
42. Within control unit 36, generation unit 38 periodically
generates and transmits a test signature through line interface
unit 32 and across telephone line 34. Generation unit 38 can, for
example, generate a test signature by obtaining one from local
storage or based upon a generation algorithm. Once generated, the
test signature is transmitted to the opposite end point of the
local loop. When test device 30 is located at a local loop
termination unit, the test signature is transmitted to test devices
located at customer premises. Conversely, when test device 30 is
located at the customer premises, the test signature is transmitted
to the local loop termination equipment. The test signature is
designed such that pertinent physical characteristics of telephone
line 34 can be determined from analysis of changes to the test
signature after it has traveled across telephone line 34. In
general, xDSL communication is sensitive in that it uses higher
frequencies across the twisted pair cooper lines, thus physical
characteristics such as impedance and line length are important to
the integrity of telephone line 34.
[0021] Evaluation unit 40 receives test signatures transmitted
across telephone line 34 and evaluates the test signatures to
determine whether telephone line 34 can support some level of xDSL
communication. The evaluation can assess such things as loss of
energy, change in bit stream pattern, and other changes of the test
signature. Based upon analysis of the test signature, evaluation
unit 40 identifies whether telephone line 34 can support xDSL
communication. Evaluation unit 40 can then direct output device 42
to provide an indication based upon the results of the evaluation.
In particular, if telephone line 34 can support xDSL communication,
then a pass state can be indicated. If not, then a fail state can
be indicated. The indication can, for example, take the form of an
audible alarm, a visual display, an electronic message or an
electronic signal. In one implementation, output device 52 can
provide an electronic flag to software such that automated loop
monitoring can be established at the local loop termination
point.
[0022] FIG. 3 is a flow chart of a method for local loop integrity
testing for xDSL communication according to the present invention.
As shown, in step 50, a test signature is transmitted across the
local loop telephone line to be tested. In step 52, the test
signature is received at the opposite end of the local loop. The
received test signature is then evaluated, in step 54, to determine
whether the telephone line can support xDSL communication. This
determination is accomplished based upon changes to the test
signature caused by transmission across the telephone line. Then,
in step 56, an indication is made whether the telephone line can
support xDSL communication.
[0023] According to the present invention, instant verification of
loop integrity for xDSL communication across the local loop can be
obtained at install time. This functionality can be accomplished
using loop integrity test devices that can be loop powered. Once
installed, the test devices can also provide continuous monitoring
of the loop (i.e., twenty-four hours a day, seven days a week) and
can provide both hardware and software alarms to the customer
premises and to the service provider. The test devices are
relatively low in cost and provide important qualification of the
local loop for spectral compatibility and loop viability for xDSL
communication.
[0024] Although the present invention has been described with
several embodiments, a myriad of changes, variations, alterations,
transformations, and modifications may be suggested to one skilled
in the art, and it is intended that the present invention encompass
such changes, variations, alterations, transformations, and
modifications as fall within the spirit and scope of the appended
claims.
* * * * *