U.S. patent application number 09/005504 was filed with the patent office on 2001-11-22 for communication server apparatus and method.
Invention is credited to LOCKLEAR, ROBERT H. JR., MCHALE, JOHN F., SISK, JAMES R..
Application Number | 20010043568 09/005504 |
Document ID | / |
Family ID | 46255881 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010043568 |
Kind Code |
A1 |
MCHALE, JOHN F. ; et
al. |
November 22, 2001 |
COMMUNICATION SERVER APPARATUS AND METHOD
Abstract
A communication server maintains profile information on twisted
pair lines in a profile table. This profile information may be
generated in a training session and then retrieved to train a modem
or transceiver unit to communicate data over the associated twisted
pair line using XDSL communication techniques.
Inventors: |
MCHALE, JOHN F.; (AUSTIN,
TX) ; LOCKLEAR, ROBERT H. JR.; (AUSTIN, TX) ;
SISK, JAMES R.; (CEDAR PARK, TX) |
Correspondence
Address: |
BARTON E. SHOWALTER
BAKER & BOTTS
2001 ROSS AVENUE
DALLAS
TX
852012980
|
Family ID: |
46255881 |
Appl. No.: |
09/005504 |
Filed: |
January 8, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09005504 |
Jan 8, 1998 |
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08828421 |
Mar 28, 1997 |
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5905781 |
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08828421 |
Mar 28, 1997 |
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08625769 |
Mar 29, 1996 |
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5668857 |
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08828421 |
Mar 28, 1997 |
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08781441 |
Jan 10, 1997 |
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5852655 |
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Current U.S.
Class: |
370/254 ;
370/401 |
Current CPC
Class: |
H04Q 2213/13213
20130101; H04Q 2213/13204 20130101; H04L 12/2856 20130101; H04L
12/2874 20130101; H04M 11/062 20130101; H04L 12/2889 20130101; H04Q
2213/1329 20130101; H04Q 2213/13322 20130101; H04Q 11/0421
20130101; H04Q 2213/13003 20130101; H04Q 2213/13349 20130101; H04L
12/5692 20130101; H04Q 2213/13036 20130101; H04Q 2213/13292
20130101; H04Q 2213/1304 20130101; H04Q 2213/13203 20130101; H04Q
2213/13103 20130101; H04L 27/0008 20130101; H04M 11/06 20130101;
H04Q 2213/13106 20130101; H04Q 2213/1334 20130101; H04Q 2213/13093
20130101; H04Q 2213/13196 20130101; H04L 12/2859 20130101; H04L
12/4612 20130101; H04Q 2213/13302 20130101; H04Q 2213/1302
20130101; H04Q 2213/13199 20130101; H04Q 2213/13299 20130101; H04Q
2213/1332 20130101; H04Q 2213/13039 20130101; H04Q 2213/13109
20130101; H04Q 2213/1319 20130101; H04Q 2213/13389 20130101 |
Class at
Publication: |
370/254 ;
370/401 |
International
Class: |
H04L 012/28; H04L
012/56 |
Claims
What is claimed is:
1. A communication server coupled to a plurality of twisted pair
lines, the communication server comprising: a plurality of XDSL
transceiver units; a line profile table having profile information
for a plurality of twisted pair lines; and a system controller
operable to retrieve profile information for a twisted pair line
from the line profile table, the system controller further operable
to provide the retrieved profile information to an XDSL transceiver
unit coupled to the twisted pair line.
2. The communication server of claim 1, further comprising a
plurality of line interface modules coupled to the twisted pair
lines and the XDSL transceiver units, wherein the system controller
directs a line interface module to couple the twisted pair line to
the XDSL transceiver unit.
3. The communication server of claim 1, further comprising a
network interface coupled to the XDSL transceiver unit.
4. The communication server of claim 1, wherein the system
controller communicates with the XDSL transceiver units using a
serial management bus.
5. The communication server of claim 1, wherein each XDSL
transceiver unit includes at least one digital signal processor
having a plurality of registers, wherein the system controller
loads profile information into the registers of the digital signal
processor of the XDSL transceiver unit.
6. The communication server of claim 1, wherein the line profile
table stores profile information in non-volatile memory.
7. The communication server of claim 1, wherein the line profile
table resides on the system controller.
8. The communication server of claim 1, wherein profile information
comprises a plurality of filter coefficients that reflect physical
parameters of the twisted pair line.
9. The communication server of claim 1, wherein profile information
comprises: a plurality of filter coefficients that reflect physical
parameters of the twisted pair line; and an associated data rate
for the twisted pair line.
10. The communication server of claim 1, wherein profile
information comprises: a plurality of filter coefficients that
reflect physical parameters of the twisted pair line; an associated
data rate for the twisted pair line; and a margin for the twisted
pair line representing the difference between a current or expected
signal strength and a minimum signal strength to maintain
communication.
11. The communication server of claim 1, wherein profile
information comprises: a plurality of upstream filter coefficients
for the twisted pair line; and a plurality of downstream filter
coefficients for the twisted pair line.
12. The communication server of claim 1, wherein the line profile
table comprises profile information indexed by subscriber
information for each twisted pair line.
13. The communication server of claim 1, wherein each twisted pair
line forms a local loop to a subscriber.
14. The communication server of claim 1, wherein the XDSL
transceiver unit uses profile information to perform carrier-less
amplitude phase modulation to communicate information.
15. An XDSL transceiver unit, comprising: an XDSL chipset operable
to couple to a twisted pair line; a plurality of registers
associated with the XDSL chipset; and a microcontroller coupled to
the XDSL chipset and the registers, the microcontroller operable to
receive profile information for the twisted pair line from an
external device, the microcontroller further operable to store the
profile information in the registers in preparation for XDSL
communication using the twisted pair line.
16. The XDSL transceiver unit of claim 15, wherein the
microcontroller is further operable to direct the XDSL chipset to
perform a test on the twisted pair line after storing the profile
information in the registers.
17. The XDSL transceiver unit of claim 15, wherein the external
device comprises non-volatile memory.
18. The XDSL transceiver unit of claim 15, wherein the external
device comprises a system controller.
19. The XDSL transceiver unit of claim 15, wherein the
microcontroller communicates with the external device using a
serial management bus.
20. The XDSL transceiver unit of claim 15, wherein the registers
are associated with at least one digital signal processor in the
XDSL chipset.
21. The XDSL transceiver unit of claim 15, wherein profile
information comprises a plurality of filter coefficients that
reflect physical parameters of the twisted pair line.
22. The XDSL transceiver unit of claim 15, wherein profile
information comprises: a plurality of filter coefficients that
reflect physical parameters of the twisted pair line; and an
associated data rate for the twisted pair line.
23. The XDSL transceiver unit of claim 15, wherein profile
information comprises: a plurality of filter coefficients that
reflect physical parameters of the twisted pair line; an associated
data rate for the twisted pair line; and a margin for the twisted
pair line representing the difference between a current or expected
signal strength and a minimum signal strength to maintain
communication.
24. The XDSL transceiver unit of claim 15, wherein profile
information comprises: a plurality of upstream filter coefficients
for the twisted pair line; and a plurality of downstream filter
coefficients for the twisted pair line.
25. The XDSL transceiver unit of claim 15, wherein the twisted pair
line forms a local loop to a subscriber.
26. The XDSL transceiver unit of claim 15, wherein the XDSL chipset
uses profile information to perform carrier-less amplitude phase
modulation to communicate information.
27. A method for communicating using a plurality of XDSL
transceiver units and a plurality of twisted pair lines, the method
comprising: storing profile information for a plurality of twisted
pair lines; coupling an XDSL transceiver unit to a twisted pair
line; retrieving profile information for the twisted pair line; and
providing the retrieved profile information to the XDSL transceiver
unit coupled to the twisted pair line in preparation for XDSL
communication.
28. The method of claim 27, further comprising: receiving a request
for service on the twisted pair line; and directing a line
interface module to couple the twisted pair line to the XDSL
transceiver unit.
29. The method of claim 27, wherein providing the retrieved profile
information comprises communicating the retrieved profile
information from a system controller to the XDSL transceiver unit
using a serial management bus.
30. The method of claim 27, wherein providing the retrieved profile
information comprises loading the retrieved profile information
into a plurality of registers associated with at least one digital
signal processor in the XDSL transceiver unit.
31. The method of claim 27, wherein storing profile information
comprises storing profile information in non-volatile memory.
32. The method of claim 27, wherein storing profile information
comprises storing profile information at a system controller.
33. The method of claim 27, wherein profile information comprises a
plurality of filter coefficients that reflect physical parameters
of the twisted pair line.
34. The method of claim 27, wherein profile information comprises:
a plurality of filter coefficients that reflect physical parameters
of the twisted pair line; and an associated data rate for the
twisted pair line.
35. The method of claim 27, wherein profile information comprises:
a plurality of filter coefficients that reflect physical parameters
of the twisted pair line; an associated data rate for the twisted
pair line; and a margin for the twisted pair line representing the
difference between a current or expected signal strength and a
minimum signal strength to maintain communication.
36. The method of claim 27, wherein profile information comprises:
a plurality of upstream filter coefficients for the twisted pair
line; and a plurality of downstream filter coefficients for the
twisted pair line.
37. The method of claim 27, wherein each twisted pair line forms a
local loop to a subscriber.
38. The method of claim 27, further comprising the step of
performing carrier-less amplitude phase modulation using the
retrieved profile information.
39. A method for communicating performed on an XDSL transceiver
unit, comprising: coupling an XDSL transceiver unit to a twisted
pair line; receiving profile information for the twisted pair line
from an external device; and storing the received profile
information in the XDSL transceiver unit in preparation for XDSL
communication using the twisted pair line.
40. The method of claim 39, wherein coupling the XDSL transceiver
unit to the twisted pair line comprises coupling the XDSL
transceiver unit to the twisted pair line using a line interface
module.
41. The method of claim 39, further comprising the step of
performing a test on the twisted pair line after storing the
received profile information in the XDSL transceiver unit.
42. The method of claim 39, wherein the external device comprises a
system controller.
43. The method of claim 39, wherein receiving profile information
comprises receiving profile information from the external device
using a serial management bus.
44. The method of claim 39, wherein storing the received profile
information in the XDSL transceiver unit comprises storing the
received profile information in a plurality of registers associated
with at least one digital signal processor in the XDSL transceiver
unit.
45. The method of claim 39, wherein profile information comprises a
plurality of filter coefficients that reflect physical parameters
of the twisted pair line.
46. The method of claim 39, wherein profile information comprises:
a plurality of filter coefficients that reflect physical parameters
of the twisted pair line; and an associated data rate for the
twisted pair line.
47. The method of claim 39, wherein profile information comprises:
a plurality of filter coefficients that reflect physical parameters
of the twisted pair line; an associated data rate for the twisted
pair line; and a margin for the twisted pair line representing the
difference between a current or expected signal strength and a
minimum signal strength to maintain communication.
48. The method of claim 39, wherein profile information comprises:
a plurality of upstream filter coefficients for the twisted pair
line; and a plurality of downstream filter coefficients for the
twisted pair line.
49. The method of claim 39, wherein the twisted pair line forms a
local loop to a subscriber.
50. The method of claim 39, further comprising the step of
performing carrier-less amplitude phase modulation using the
retrieved profile information.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 08/828,421, filed Mar. 28, 1997, and entitled
"Communication Server Apparatus and Method," pending, which is a
continuation-in-part of U.S. patent application Ser. No.
08/625,769, filed Mar. 29, 1996, and entitled "Communication Server
Apparatus and Method," now U.S. Pat. No. 5,668,857, and a
continuation-in-part of U.S. patent application Ser. No.
08/781,441, filed Jan. 10, 1997, and entitled "Communication Server
Apparatus Having Distributed Switching and Method," pending.
TECHNICAL FIELD OF THE INVENTION
[0002] This invention relates in general to data communication, and
more particularly to a communication server apparatus and
method.
BACKGROUND OF THE INVENTION
[0003] A communication server provides access to communication
facilities. For example, a communication server having a bank of
modems may provide subscriber access to the modems for data
communication. A communication server may be associated with its
own dedicated communication network, or with an existing
communication network, such as the public switched telephone
network (PSTN).
[0004] As communication networks provide greater connectivity and
access to information, there is an increasing demand for data
communication at higher rates. One solution to provide increased
data rates replaces existing twisted pair wiring with high
bandwidth media, such as coaxial cables or fiber optic links. Other
solutions adopt improved communication techniques using the
existing hardware infrastructure. For example, digital subscriber
line (XDSL) technology provides higher bandwidth data service over
existing twisted pair wiring.
[0005] To deliver data service to the subscriber, a communication
server may provide a dedicated or permanent connection to its
communication facilities. For example, an existing communication
server at a central office provides enough communication facilities
to simultaneously service all PSTN subscribers. However, all
telephone subscribers may not desire data service. Furthermore, the
subscribers that desire data service may not simultaneously access
the communication server.
SUMMARY OF THE INVENTION
[0006] In accordance with the present invention, the disadvantages
and problems associated with communication servers have been
substantially reduced or eliminated. In particular, a communication
server apparatus and method are disclosed that provide data service
using profile information for twisted pair lines in an XDSL
environment.
[0007] According to one aspect of the present invention, a
communication server coupled to a number of twisted pair lines
includes a number of XDSL transceiver units. A line profile table
has profile information for the twisted pair lines. A system
controller receives profile information for a twisted pair line
from the line profile table and provides the retrieved profile
information to an XDSL transceiver unit coupled to the twisted pair
line in preparation for XDSL communication.
[0008] In accordance with another aspect of the present invention,
an XDSL transceiver unit includes an XDSL chipset that couples to a
twisted pair line and a number of registers associated with the
XDSL chipset. A microcontroller coupled to the XDSL chipset and the
registers receives profile information for the twisted pair line
from an external device and stores the profile information in the
registers in preparation for XDSL communication using the twisted
pair line.
[0009] Important technical advantages of the present invention
include a communication server that provides data service to a
number of subscribers using a reduced number of XDSL communication
facilities. Over-subscription of data service is accomplished by
selectively coupling a number of twisted pair data lines to a
reduced number of XDSL modems. A controller polls the data lines
simultaneously or in succession, in groups or individually, to
determine which subscribers of the communication system need data
service. Upon detecting a need for data service on a selected data
line, the controller directs a switch to couple the selected data
line to an available modem. The communication server may then
provide data service suitable for high bandwidth applications, such
as video-on-demand, multimedia, or Internet access.
[0010] Another important technical advantage of the present
invention includes a communication server that provides
over-subscribed XDSL data service using the existing infrastructure
of the public switched telephone network (PSTN). Asymmetric digital
subscriber line (ADSL), symmetric digital subscriber line (SDSL),
high-speed digital subscriber line (HDSL), very high-speed digital
subscriber line (VDSL), or other suitable XDSL technology can
provide higher bandwidth data service over existing twisted pair
wiring. These technologies may support data service simultaneously
with traditional telephone service using a separation technique,
such as frequency division multiplexing. In one embodiment, a
splitter divides each incoming twisted pair subscriber line into a
twisted pair phone line and a twisted pair data line. The phone
line is coupled to a telephone switch to provide telephone service
and the data line is coupled to the communication server to provide
over-subscribed XDSL data service. The communication server and
splitter may be located at a central office, remote terminal, or
other point of presence of the data service provider.
[0011] Another important technical advantage of the present
invention includes the management and monitoring of XDSL data
service provided to subscribers. To accomplish this, the
communication server maintains an activity table to determine
status information on twisted pair data lines and XDSL modems. In
addition, the communication server can track subscriber usage,
monitor subscriber information and generate billing and demographic
information. In a particular embodiment, an activity detector
disconnects a subscriber after a predetermined period of inactivity
to release a modem for use by another subscriber.
[0012] An important technical advantage of the present invention is
the distribution of the switching function to allow scalability of
the number of supported data lines and over-subscription of XDSL
modems.
[0013] A further important technical advantage of the present
invention includes isolating the switch from the data lines and
subscriber lines. The switch can thereby operate without
constraints imposed by technical requirements for interaction with
the data lines and subscriber lines. For example, isolation of the
switching matrix can allow CMOS switches to be used rather than
more expensive solid state relays or mechanical relays.
[0014] Yet another important technical advantage of the present
invention includes the ability to provide a two-wire isolated
interface that can use a single switch to couple a data line to a
specific modem. The present invention thus allows one switch per
modem per data line configuration. The isolation system of the
present invention can transform the data line impedance to an
intermediate impedance in order to increase system performance.
[0015] A further important technical advantage of the present
invention includes the maintenance of profile information for one
or more twisted pair lines coupled to an XDSL transceiver unit.
This profile information may specify filter coefficients, equalizer
tap values, sub-band weighting, data rates, margins, and other
information that reflects electrical and/or physical parameters of
the twisted pair lines. In a particular embodiment, the XDSL
transceiver unit performs a training session on the twisted pair
line at a variety of bands and rates to generate profile
information. The profile information is stored in an appropriate
non-volatile memory, such as a memory maintained by the system
controller or other device external to the XDSL transceiver unit.
The XDSL transceiver unit receives the stored profile information
to engage in XDSL communication without a protracted training
period. The XDSL transceiver unit may also perform a full or
partial retraining of the line as needed.
[0016] The profile information may include, for example, digital
filter coefficients used in carrier-less amplitude phase (CAP)
modulation, discrete multi-tone (DMT) modulation, or other suitable
modulation. In a particular embodiment, a communication server
includes a number of XDSL transceiver units arranged on cards that
communicate with one or more system controller cards to receive
profile information of associated twisted pair lines serviced by
the communication server. Line interface modules (LIMs) couple the
twisted pair lines to selected XDSL transceiver units under the
control of the system controller. In this embodiment, the system
controller maintains profile information associated with each
twisted pair line serviced by the communication server. Other
important technical advantages are readily apparent to one skilled
in the art from the following figures, descriptions, and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] 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:
[0018] FIG. 1 illustrates a communication system that provides data
service;
[0019] FIG. 2 illustrates a communication server in the
communication system;
[0020] FIG. 3 illustrates in more detail the controller of the
communication server;
[0021] FIG. 4 illustrates in more detail the switch and modem pool
of the communication server;
[0022] FIG. 5 illustrates in more detail the transceiver in the
controller of the communication server;
[0023] FIG. 6 illustrates in more detail the detector in the
controller of the communication server;
[0024] FIG. 7 illustrates an activity table used by the controller
of the communication server;
[0025] FIG. 8 is a flow chart of a method for coupling a data line
to a modem in the communication server;
[0026] FIG. 9 is a flow chart of a method to decouple a data line
from a modem in the communication server;
[0027] FIG. 10A illustrates another implementation of the
communication server;
[0028] FIG. 10B illustrates in more detail a line interface device
of the communication server of FIG. 10A;
[0029] FIG. 10C illustrates in more detail the controller of the
communication server of FIG. 10A;
[0030] FIG. 10D illustrates in more detail a detector of the
communication server of FIG. 10A;
[0031] FIG. 10E illustrates in more detail a modem in the modem
pool of the communication server of FIG. 10A;
[0032] FIG. 11A illustrates in more detail an analog filter
implementation of a detector of the communication server;
[0033] FIG. 11B illustrates in more detail a tone decoder
implementation of a detector of the communication server;
[0034] FIG. 11C illustrates in more detail a digital signal
processor implementation of a detector of the communication
server;
[0035] FIG. 12 illustrates in more detail a digital switching
matrix implementation of the switch of the communication
server;
[0036] FIG. 13A illustrates in more detail a frequency multiplexing
implementation of the switch of the communication server;
[0037] FIG. 13B is a diagram of frequencies used in the switch of
FIG. 13A;
[0038] FIG. 14A illustrates line interface modules and the modem
pool of a distributed switching implementation of the communication
server;
[0039] FIG. 14B illustrates in more detail the line interface
modules and the modem pool of the communication server of FIG.
14A;
[0040] FIG. 15 illustrates a functional block diagram of one
embodiment of a distributed switching implementation of the
communication server;
[0041] FIG. 16 illustrates a block diagram of one embodiment of a
line interface module of FIG. 15;
[0042] FIG. 17 illustrates one embodiment of ATM based transport
communication protocols supported on the local loop and the network
interface of the communication server;
[0043] FIGS. 18A and 18B illustrate a system block diagram for one
embodiment of the communication server;
[0044] FIG. 19 illustrates an exemplary line profile table that
stores profile information;
[0045] FIG. 20 is a flowchart of a method for training a line;
and
[0046] FIG. 21 is a flowchart of a method for retrieving profile
information in preparation for XDSL communication.
DETAILED DESCRIPTION OF THE INVENTION
[0047] FIG. 1 illustrates a communication system 10 that provides
both telephone and data service to a subscriber 12. A station 14 is
coupled to subscriber 12 using subscriber line 16. In operation,
station 14 provides telephone service, data service, or both
telephone and data service to subscriber 12 using subscriber line
16. Subscriber line 16 may support simultaneous telephone and data
service using twisted pair wiring.
[0048] Subscriber 12 includes a telephone 20 and a computer 22,
both coupled to an interface 24. A splitter 25 is coupled to
subscriber line 16 and operates to split subscriber line 16 into a
twisted pair phone line 26 and a twisted pair data line 28. Phone
line 26 is coupled to telephone 20 using interface 24. Similarly,
data line 28 is coupled to computer 22 using interface 24.
Subscriber 12 refers to one or more components at the subscriber
premises shown in FIG. 1, as well as the user of these
components.
[0049] Telephone 20 is a traditional telephone transceiver, a
cordless telephone transceiver, or any other device suitable for
allowing communication over telephone line 26. Computer 22
comprises a mainframe device, mini-frame device, server, desktop
personal computer, notebook personal computer, or other suitable
computing device having an XDSL modem 30 that communicates data
using data line 28. Modem 30 couples to other components of
computer 22 using a Peripheral Component Interconnect (PCI) bus, an
Industrial Standard Architecture (ISA) bus, a Personal Computer
Memory Card International Association (PCMCIA) interface, or any
other suitable technology that provides input/output capability to
computer 22. The selection and design of modem 30 for computer 22
may depend on the type or functionality of computer 22, as well as
the data service rate supported by data line 28.
[0050] Modem 30 transmits and receives data in communication system
10 using any suitable digital subscriber line technology, referred
to generally as XDSL. Modem 30 also supports Ethernet, Fast
Ethernet, V.35 data protocol, frame relay, asynchronous transfer
mode (ATM), switched multi-megabit data service (SMDS), high-level
data link control (HDLC), serial line Internet protocol (SLIP),
point-to-point protocol (PPP), transmission control
protocol/Internet protocol (TCP/IP), or any other appropriate
protocol, collectively referred to as digital protocol. For
example, computer 22 may include a network interface 31 to receive
data from station 14 or to further communicate data to a local area
network (LAN), wide area network (WAN), or other suitable network
coupled to computer 22 using link 18. In general, modem 30
translates information between the communication protocol supported
by communication system 10 and the digital protocol supported by
computer 22.
[0051] Communication system 10 includes numerous other twisted pair
subscriber lines 16 coupled to other subscribers 12. In an
exemplary embodiment, station 14 comprises a central office or
other device in the public switched telephone network (PSTN) that
provides phone and data service to a number of subscribers, with
each subscriber 12 including one or more components described above
at its premises. The subscribers and subscriber lines in
communication system 10 are referred to collectively in the plural
as subscribers 12 and subscriber lines 16.
[0052] Interface 24 couples phone line 26 to telephone 20, and data
line 28 to computer 22. In one embodiment, interface 24 provides
additional couplings to additional telephones 20 and computers 22
at subscriber 12. Splitter 25 is a passive or active splitter that
divides subscriber line 16 into phone line 26 and data line 28 of
the same type. Throughout this description, phone line 26 and data
line 28 may be referred to specifically, or collectively as part of
subscriber line 16.
[0053] Subscriber line 16 couples subscriber 12 to station 14.
Subscriber line 16 comprises twisted pair wiring that is commonly
installed at subscriber premises and as the local loop in many
public switched telephone networks (PSTNs). Subscriber line 16 may
be unshielded twisted pair (UTP), shielded twisted pair (STP), or
other suitable type or category of twisted pair wiring made of
copper or other suitable material. Phone line 26 and data line 28
associated with subscriber line 16 may be the same or different
type or category of twisted pair wiring.
[0054] Station 14 includes an optional splitter 50 coupled to
subscriber line 16. Like splitter 25 at subscriber 12, splitter 50
at station 14 is a passive or active splitter that divides
subscriber line 16 into a twisted pair phone line 52 and a twisted
pair data line 54. Phone line 52 and data line 54 associated with
subscriber line 16 may be the same or different type or category of
twisted pair wiring. In a particular embodiment, a telephone switch
56 at station 14 is coupled to phone line 52 to provide plain old
telephone system (POTS) service to subscriber 12. Telephone switch
56 also represents other components in the PSTN or other suitable
voice communication network, such as switches, wireline or wireless
links, satellites, microwave uplinks, and other communication
facilities to deliver telephone service to subscriber 12.
[0055] A communication server 58 is coupled to splitter 50 using
data line 54. As described in detail below, communication server 58
manages the provisioning of data service to subscriber 12.
Communication server 58 performs off-hook detection on the local
loops formed by subscriber lines 16 to determine if subscriber 12
desires data service. Specifically, communication server 58 couples
a modem to subscriber line 16 upon detecting a need for data
service from computer 22. Communication server 58 tracks subscriber
usage, monitors subscriber information, and generates billing and
demographic information, as described below.
[0056] The data off-hook detector in communication server 58 can
use one of several methods to determine whether subscriber 12
should be connected to an XDSL modem. The off-hook detector may
monitor direct current voltages, electrical tones, data link
frames, or any other protocol or data sequencing to determine
whether subscriber 12 needs data access. The off-hook detector in
communication server 58 may monitor electrical tones generated by
modem 30 while in the process of training, notching, equalizing, or
performing any other task that puts electrical tones onto
subscriber line 16 and its associated data line 54. Communication
server 58 may also detect frames or packets. These frames or
packets could be Ethernet, ATM, HDLC, or any suitable data
communications frame format. The off-hook detector in communication
server 58 could also examine various protocols such as TCP/IP, PPP,
or any other suitable network protocol or data stream.
[0057] Communication server 58 multiplexes modem digital outputs
into a multiplexed digital line 62 for delivery to a router or
other network device 60. In one embodiment, multiplexed digital
line 62 carries a single bidirectional and multiplexed signal for
all subscribers 12 in communication system 10. Signals on
multiplexed digital line 62 may support any appropriate digital
protocol used by network device 60. A communication network 64,
such as a global communication network like the Internet, is
coupled to network device 60. Communication network 64 may also
include a synchronous optical network (SONET), a frame relay
network, an asynchronous transfer mode (ATM) network, a T1, T3, E1,
or E3 network, or any other suitable communication network.
[0058] One important technical advantage of the present invention
is the ability to over-subscribe the XDSL communication facilities
of communication server 58 to service an increasing number of
subscribers 12 in communication system 10. Communication server 58
may couple to the same number and type of data lines 54 as
represented by subscriber lines 16 in communication system 10. For
example, if station 14 services one thousand subscribers 12 using
twisted pair subscriber lines 16, then data lines 54 coupled to
communication server 58 may represent as many as one thousand
twisted pair lines.
[0059] In one embodiment, not all subscribers 12 in communication
system 10 desire access to data service provided by communication
server 58. Splitter 50 need not provide a separate data line 54 for
those subscribers 12 that only desire phone service from telephone
switch 56. As more subscribers 12 desire access to data service,
the XDSL communication capabilities of splitter 50 and
communication server 58 may be supplemented in a modular and cost
effective manner to meet the demand.
[0060] Communication system 10 supports data service over
subscriber lines 16 using asymmetric digital subscriber line
(ADSL), symmetric digital subscriber line (SDSL), high-speed
digital subscriber line (HDSL), very high-speed digital subscriber
line (VDSL), or any other suitable technology that allows high rate
data service over twisted pair wiring that forms the local loops to
subscribers 12. All of these technologies are referred to
collectively as XDSL or communication protocol. In one embodiment,
subscriber line 16 and components of subscriber 12 and station 14
support communication using ADSL techniques that comply with ANSI
standard T1.413. In another embodiment, ADSL communication over
subscriber line 16 may be performed using the carrier-less
amplitude phase modulation (CAP) technique developed by AT&T
Corporation.
[0061] In an ADSL communication system, the downlink data rate 32
from station 14 to subscriber 12 is greater than the uplink data
rate 34 from subscriber 12 to station 14. This allows high
bandwidth communication to subscriber 12, while still providing
lower bandwidth communication to station 14. ADSL communication is
well-adapted for applications, such as video-on-demand, multimedia,
and Internet access, that transfer large volumes of information to
subscriber 12 in response to shorter requests for information. In
one specific embodiment, downlink data rate 32 is approximately 1.5
Mbps, whereas uplink data rate 34 is approximately 750 kbps. In
other embodiments, downlink data rate 32 may be six Mbps or more
depending on the specific XDSL technology employed, the quality and
length of subscriber line 16, and the contribution of noise and
distortion from other components in communication system 10.
[0062] To support high bandwidth data service, local loops formed
by subscriber lines 16 may have a maximum length imposed by the
XDSL modulation technique or hardware. For example, an existing
ADSL implementation operates over local loops of 12,000 feet or
less. However, the present invention contemplates, expects, and
specifically includes additional communication technologies that
extend the maximum length, bandwidth, and quality of communication
between subscribers 12 and station 14.
[0063] XDSL technology provides data service using existing
subscriber lines 16 without interrupting normal telephone service.
This is accomplished by a separation technique, such as frequency
division multiplexing (FDM), to separate frequencies that provide
telephone service from those frequencies that provide data service.
Dynamic noise cancellation techniques and a guard band between the
data and phone service frequencies ensure reliable and simultaneous
access to data and phone service over subscriber line 16. For
example, subscriber 12 may simultaneously engage in both a data
communication session using computer 22 and a voice conversation
using telephone 20.
[0064] In operation, communication system 10 provides phone and
data service to subscriber 12. Subscriber 12 accesses phone service
by using telephone 20 to initiate a call. Upon going off-hook,
communication system 10 establishes a circuit between telephone 20
and telephone switch 56 using interface 24, phone line 26, splitter
25, subscriber line 16, splitter 50, and one of phone lines 52.
Upon establishing this telephone circuit, subscriber 12 using
telephone 20 receives POTS service from telephone switch 56.
[0065] To access data service, subscriber 12 turns on computer 22,
executes a program, such as an Internet browser, or performs some
other affirmative or passive activity that generates a request,
command, data packet, electrical tone, or other suitable
information or signal that indicates a need for data service. In
one embodiment, modem 30 repetitively transmits the need for data
service in a request interval, where the request interval comprises
the time length of the request and the silent interval until the
next request. Alternatively, the need for data service indicated at
subscriber 12 may be based on the establishment of a closed circuit
between subscriber 12 and station 14 or on one or more analog or
digital signal transitions. Modem 30 communicates the need to
communication server 58 at station 14 using interface 24, data line
28, splitter 25, subscriber line 16, splitter 50, and one of data
lines 54.
[0066] As described in detail below, communication server 58
detects the need for data service and selects an XDSL modem at
communication server 58 to communicate with XDSL modem 30 in
computer 22. Upon establishing a modem connection between modem 30
in computer 22 and a selected modem in communication server 58,
subscriber 12 engages in a data communication session with
communication network 64 using network device 60. In addition,
computer 22 may function as a gateway into communication network 10
for other devices coupled to network interface 31 using link
18.
[0067] XDSL technology allows simultaneous use of subscriber line
16 for both phone and data service using the existing twisted pair
wiring in communication system 10. In one embodiment, splitter 50,
communication server 58, and network device 60 are located at a
central office of the PSTN to provide an efficient and modular
provisioning of XDSL data service and voice service to subscribers
12. In a data-only embodiment, communication server 58 and network
device 60 may be located at a central office, end office, remote
terminal, private premises, or any other location that provides a
point of presence of network 64. Splitter 50, communication server
58, and network device 60 may be located at any site or sites
remote from subscribers 12 without departing from the scope of the
present invention.
[0068] FIG. 2 illustrates in more detail communication server 58.
Data lines 54 associated with subscriber lines 16 are coupled to a
switch 70. In one embodiment, each data line 54 corresponds to an
associated subscriber line 16 and its related subscriber 12. Switch
70 couples selected data lines 54 to output lines 72 that in turn
couple to modem pool 74. The format of signals on data lines 54 and
output lines 72 is the same as the format of signals on subscriber
lines 16. For example, if communication system 10 adopts XDSL
technology, signals on data lines 54 and output lines 72 are
modulated using XDSL techniques.
[0069] Modems in modem pool 74 convert signals in an appropriate
XDSL communication protocol into digital data in an appropriate
digital protocol on digital lines 76. A multiplexer 78 is coupled
to digital lines 76 and combines the signals on digital lines 76
into a fewer number of multiplexed digital lines 62. In one
embodiment, multiplexer 78 combines information for delivery to
network device 60 using a single multiplexed digital line 62.
[0070] A controller 80 is coupled to data lines 54 using a link 82.
Controller 80 is also coupled to switch 70 and modem pool 74 using
links 84 and 86, respectively. Controller 80 detects a need for
data service generated by subscribers 12 and communicated over
subscriber lines 16 to data lines 54. In response, controller 80
using link 84 directs switch 70 to couple a selected subset of data
lines 54 to selected output lines 72 that couple to modems in modem
pool 74. For example, controller 80 may monitor one thousand data
lines 54 to provide XDSL data services using one hundred modems in
modem pool 74.
[0071] Controller 80 also receives information from modem pool 74
using link 86 to determine status information of modems in modem
pool 74. As digital lines 76 become inactive for a predetermined
period of time, modem pool 74 detects this inactivity and generates
a timeout indication for communication to controller 80. Upon
receiving the timeout indication, controller 80 releases the
inactive modem in modem pool 74 for later use.
[0072] In operation, communication server 58 detects a need for
data service on a selected data line 54. This need may be indicated
by current voltages, electrical tones, data link frames, packets,
or any other suitable analog or digital protocol or data
sequencing. Controller 80 detects the need using link 82 and
configures switch 70 to provide a coupling between the selected
data line 54 and one of the output lines 72 coupled to a selected
modem pool 74. The selected modem translates bidirectional
communication between a communication protocol on output line 72
and a digital protocol on digital line 76. Multiplexer 78
translates information between digital lines 76 and one or more
multiplexed digital lines 62.
[0073] FIG. 3 illustrates in more detail controller 80. Data lines
54 through link 82 are coupled to polling circuitry 100. In one
embodiment, polling circuitry 100 includes a number of terminals
102 corresponding to each data line 54. A switch 104 having a
conductive probe 106 contacts terminals 102 to sample the signal on
the associated data line 54. Polling circuitry 100 may comprise
electromagnetic components, such as a relay or switch, solid state
circuitry, or both. It should be understood that the present
invention embodies any polling circuitry 100 that allows sampling,
in succession or simultaneously, one or more data lines 54.
[0074] Transceiver 108 receives a selected signal 110 from polling
circuitry 100. A detector 112 is coupled to transceiver 108, which
in turn is coupled to processor 116. Detector 112 may include a
media access controller (MAC) and associated memory to detect and
store frames or packets of an appropriate digital protocol.
Detector 112 may also include less complicated circuitry to detect
current voltages, electrical tones, data bit transmissions, or
other analog or digital information generated by transceiver
108.
[0075] Transceiver 108 and detector 112 may collectively be
represented as modem 115, as indicated by the dashed line. Modem
115 provides an interface between the XDSL communication protocol
of communication system 10 and processor 116. Modem 115 also
includes similar components and performs similar functions as modem
30 in computer 22 to enable modem 30 and modem 115 to exchange
information using XDSL technology. Throughout this discussion, the
term detector may refer to detector 112 or collectively modem
115.
[0076] A processor 116 is coupled to detector 112 and controls the
overall operation of controller 80. A timer 117 is coupled to
processor 116. Processor 116 is coupled to input/output circuitry
118, which in turn is coupled to switch 70 and modem pool 74 using
links 84 and 86, respectively. Processor 116 is also coupled to
switch 104 of polling circuitry 100 using input/output circuitry
118. In one embodiment, processor 116 controls the data line
selection, dwell time, and other suitable parameters of polling
circuitry 100.
[0077] Processor 116 is also coupled to database 120 that includes
a program 121, an activity table 122, a line profile table 124, and
a subscriber table 126. Database 120 stores information as one or
more tables, files, or other data structure in volatile or
non-volatile memory. All or a portion of database 120 may reside at
controller 80, within communication server 58, within station 14,
or at another location in communication system 10. For example,
several communication servers 58 in one or more central offices or
other devices of communication system 10 can access database 120
stored in a central location to provide more intelligent management
and provisioning of XDSL data service in communication system 10.
One or more stations 14 may be coupled together and the resources
of their associated communication servers 58 shared using simple
network management protocol (SNMP) techniques.
[0078] Program 121 contains instructions to be executed by
processor 116 to perform the functions of controller 80. Program
121 may reside in database 120 as shown or may be integral to
memory components in transceiver 108, detector 112, and/or
processor 116. Program 121 may be written in machine code,
pseudocode, or other appropriate programming language. Program 121
may include modifiable source code and other version control
features that allow modification, debugging, and enhancement of the
functionality of program 121.
[0079] Activity table 122, described in more detail below with
reference to FIG. 7, maintains status information on data lines 54,
switch 70, and output lines 72. In particular, activity table 122
contains information on inactive and active data lines 54, data
lines 54 corresponding to current valid subscribers 16 of XDSL data
service, and the mapping performed by switch 70 between data lines
54 and output lines 72. Moreover, activity table 122 includes
information that specifies the inactivity of a modem in modem pool
74, the status of a data line 54 as dedicated, and any other
suitable information that enables processor 116 to monitor and
control the operation of switch 70 and modem pool 74.
[0080] Profile table 124 stores profile information on data lines
54. This profile information reflects electrical or physical
characteristics of data line 54, its associated subscriber line 16
and data line 28, intervening components such as interface 24,
splitter 25, splitter 50, and polling circuitry 100, as well as any
other component or factor that effects the performance or
electrical characteristics of signals received on data lines 54.
Processor 116 may access profile table 124 and provide profile
information to transceiver 108 using link 125. Alternatively,
transceiver 108 may be a more robust and broadband device that does
not need profile information from profile table 124. Processor 116
may also provide profile information to program XDSL modems in
modem pool 74 once a coupling is made to a selected data line 54.
The existence and complexity of profile information in profile
table 124 depends on the requirements of transceiver 108 and XDSL
modems in modem pool 74, as well as the complexity of signals that
indicate a need for data service from subscriber 12.
[0081] Subscriber table 126 stores subscriber information indexed
by one or more identifiers of subscriber 12, computer 22, modem 30,
subscriber line 16, or other information that associates data line
54 with a particular subscriber 12. Subscriber table 126 includes
subscriber connect times, session duration, session activity,
session logs, billing data, subscriber account information, and any
other suitable subscriber information. This information may be
summarized and additional information included to generate billing
and demographic data on subscribers 12 in communication system
10.
[0082] For example, subscriber table 126 may maintain summary
statistics on the number of subscribers 12 served by communication
server 58, the average connect time, load factors, time-of-day
connection profiles, and other statistics to assess the
communication facilities to be deployed at communication server 58,
the over-subscription ratio that can be supported by communication
system 10, and other provisioning and management issues.
Furthermore, subscriber table 126 may combine subscriber
information from one or more communication servers 58 in one or
more stations 14 in communication system 10.
[0083] Management interface 128 is coupled to processor 116 and
database 120 and allows external access to the functionality of
processor 116. Management interface 128 is also coupled to database
120, which allows modification of program 121, as well as remote
access and modification of information in activity table 122,
profile table 124, and subscriber table 126. In one embodiment, the
telephone service provider or other entity that operates station 14
or communication system 10 accesses management interface 128 to
provide management and control over the operations of controller 80
and communication server 58. For example, the telephone service
provider uses management interface 128 to access activity table 122
and/or subscriber table 126 to update the valid subscribers 12 that
have access to communication server 58. A local or remote computer
130 is coupled to program interface 128 using an appropriate data
link 132, such as a serial RS-232 link, to provide this management
feature.
[0084] In operation, modem 30 in computer 22 indicates a need for
data service, and communicates this need to an associated data line
54 using interface 24, data line 28, splitter 25, subscriber line
16, and splitter 50. In one embodiment, modem 30 transmits
successive requests at a predetermined request interval. Processor
116 accesses activity table 122 to determine which data lines 54 to
poll, depending on the active or inactive status of the data line
54, whether subscriber 12 corresponding to data line 54 is a
current and valid subscriber, and other appropriate considerations.
For example, activity table 122 may indicate valid and
non-dedicated subscribers 12 to poll.
[0085] Polling circuitry 100 successively or simultaneously polls
one or more selected data lines 54, as directed by processor 116,
using link 82 to detect a need for data service. For each data line
54 polled, processor 116 may access profile table 124 in database
120 and provide associated profile information to transceiver 108
using link 125. Polling circuitry 100 dwells on each data line 54
for a predetermined polling interval to detect a need. In one
embodiment, the polling interval is at least two times a request
interval of modem 30.
[0086] Upon detecting the need for data service associated with a
selected data line 54 from polling circuitry 100, transceiver 108
may translate the information from the selected XDSL communication
protocol employed on subscriber line 16 into digital or analog data
for detection by detector 112. A media access controller (MAC) in
detector 112 may transform serial digital data from transceiver 108
into a parallel digital format. Detector 112 receives the
information translated by transceiver 108, and stores this
information in a suitable memory location for access by processor
116. Processor 116 periodically accesses detector 112 to determine
if a need for data service has been detected.
[0087] Upon detecting a need for data service, processor 116
accesses database 120 to determine the availability and status of
modems in modem pool 74. Processor 116 selects an available modem
from modem pool 74. Processor 116 then directs switch 70 to make
the appropriate coupling between selected data line 54 and output
line 72 coupled to the selected modem. Upon establishing coupling
between modem 30 in computer 22 at subscriber 12 and a selected
modem in modem pool 74, controller 80 continues to monitor the
remaining data lines 54 using polling circuitry 100.
[0088] Processor 116 can transmit status or connection information
to modem 30 in computer 22 using transceiver 108. This may be
performed before, during, or after coupling the selected modem in
modem pool 74 to data line 54. For example, processor 116 may send
acknowledgment information to modem 30 that includes an indication
that a modem is or is not available, an identification of the
available modem, a time interval before modem 30 should attempt
communication with the selected modem in modem pool 74, or any
other suitable information. Furthermore, processor 116 may access
information from subscriber table 126, such as billing and account
information, historical connection information, or other suitable
subscriber information, and transmit this information separate to
or as part of the acknowledgment information described above.
[0089] Processor 116 may also transmit connection information and
updated billing and subscriber information to modem 30 at computer
22 using link 86 and the associated XDSL modem in modem pool 74.
This information may include the length of the current session, the
current balance in the account of subscriber 12, as well as any
other suitable information that relates to the account or activity
of subscriber 12 with communication server 54. Generally, processor
116 may communicate any suitable information stored at or made
available to controller 80 to subscribers 12 using transceiver 108
or the associated modem in modem pool 74.
[0090] FIG. 4 illustrates in more detail switch 70 and modem pool
74 of communication server 58. Data lines 54 are coupled to switch
70, now shown in more detail as a cross-bar or cross-point matrix
switch. In this particular embodiment, data lines 54 correspond to
lines 150, and output lines 72 correspond to lines 152 in switch
70. The number of lines 150 (n) is greater than the number of lines
152 (m). This allows switch 70 to couple selected data lines 54 to
a reduced number of output lines 72 to provide an over-subscription
of XDSL data service in communication system 10. For example,
switch 70 couples the second of lines 150 to the last of lines 152
by establishing connection 154. Similarly, switch 70 couples the
last of lines 150 and the first of lines 152 by establishing
connection 156.
[0091] Although switch 70 is shown in FIG. 4 to be a cross-bar or
cross-point matrix switch, it should be understood that any device
that can couple a number of data lines 54 to a reduced number of
output lines 72 may be used. Switch 70 may incorporate
electromagnetic components, such as relays and contacts, or may be
implemented in whole or in part using one or more solid state
devices.
[0092] Modem pool 74 includes XDSL modems 160 associated with
output lines 72 from switch 70. Modems 160 translate information
between an appropriate XDSL communication protocol on output lines
72 and an appropriate digital protocol on digital lines 76. In one
embodiment, modems 160 may be similar in construction and operation
to modem 30 at subscriber 12. A detector 162 coupled to modems 160
detects the activity of modems 160 to determine if the line has
become inactive for a predetermined interval of time. For example,
if one of the modems 160 does not display activity over a
five-minute interval, detector 162 generates a timeout indication
to notify processor 116 of the inactive modem. Processor 116
releases or decouples the inactive modem for later subscriber
sessions. In one embodiment, detectors 162 may include one-shot
timers or other retriggerable timers set for a predetermined time
interval to detect the inactive status of modems 160.
[0093] Detector 162 is a monitoring circuit that passes through the
digital output of modems 160 to digital lines 76 for presentation
to multiplexer 78. Multiplexer 78 may combine signals from digital
lines 76 into a single multiplexed digital line 62. Alternatively,
multiplexer 78 may employ any suitable reduction ratio that places
signals on digital lines 76 on a fewer number of multiplexed
digital lines 62.
[0094] Processor 116 may directly communicate with modems 160 using
link 164. For example, link 164 allows processor 116 to program
modems 160 with profile information retrieved from profile table
124. Link 164 also supports communication between processor 116 and
selected subscribers 12 during an active subscriber session using
modems 160. Moreover, link 164 allows processor 116 to monitor the
information received from and transmitted to subscribers 12 during
a communication session.
[0095] In operation, switch 70 couples a selected subset of data
lines 54 to output lines 72 in response to signals received from
controller 80 using link 84. Each of the output lines 72 is coupled
to an associated modem 160 which translates the information
formatted in an analog communication protocol, such as XDSL, into
an appropriate digital signal. The digital information output from
modems 160 passes through detector 162, which monitors the activity
on the output line of modems 160. If detector 162 senses inactivity
over a predetermined interval, a timeout indication is provided to
processor 116 using link 86. Signals on digital lines 76 may be
reduced to fewer multiplexed digital lines 62 using multiplexer
78.
[0096] FIG. 5 illustrates in more detail transceiver 108 in
controller 80. To receive information, transceiver 108 includes
filters and magnetics 170 to condition the signal from selected
data line 54. The conditioned signal is provided over differential
lines 172 to analog bit pump 174. Bit pump 174 performs the
specific demodulation technique for the chosen XDSL communication
protocol. For example, bit pump 174 may execute a discrete
multi-tone demodulation (DMT) or carrier less amplitude phase
demodulation (CAP) to demodulate an XDSL signal on differential
lines 172 into a digital stream on line 176. Logic and timing
circuitry 178 contains decode logic, timing and synchronization
circuitry, steering logic, and other appropriate digital processing
circuitry to produce a data signal on receive data line 180 and a
corresponding clock signal on clock line 182 for delivery to
detector 112 or processor 116. Detector 112 may include a MAC to
support any digital protocol or signal detection that indicates a
need for XDSL data service. The data may be in non-return-to-zero
format or any other suitable format.
[0097] To transmit information, transceiver 108 receives a data
signal on transmit data line 184 from detector 112 or processor
116. Using the clock line 182, logic and timing circuitry 178
digitally processes signals received on transmit data line 184 for
delivery to analog bit pump 174. Using an appropriate modulation
technique, such as DMT or CAP, analog bit pump 174 produces an
analog signal for delivery over differential lines 172 to filters
and magnetics 170 for transmission over selected data line 54.
[0098] FIG. 6 illustrates in more detail a specific embodiment of
detector 112 that includes a MAC 113 and a memory 114. MAC 113 is
coupled to receive data line 180 and clock line 182, and translates
received data from a serial data format, such as a
non-return-to-zero format, into an appropriate parallel digital
format. MAC 113 translates the data from the chosen digital
protocol and provides the data to memory 114 using data bus 190.
MAC 113 also provides an address to memory 114 using address bus
192 to specify the location in memory 114 to store data provided on
data bus 190. In addition, MAC 113 provides a write signal to
memory 114 using control line 194.
[0099] To transmit data, MAC 113 provides a read signal to memory
114 using control line 194, and an associated address of the data
to be read using address bus 192. In response, memory 114 provides
the requested data on data bus 190. MAC 113 translates the data
into the selected digital protocol for placement on transmit data
line 184.
[0100] FIG. 7 illustrates one embodiment of activity table 122
stored in database 120 of controller 80. Processor 116 accesses and
modifies entries in activity table 122 to direct the operation of
controller 80. In addition, management interface 128 provides
external access to activity table 122. For example, a telephone
service provider using management interface 128 can add, delete, or
otherwise modify entries in activity table 122 to maintain a
listing of valid subscribers 12. Database 120 stores some or all of
the status information shown in this exemplary activity table 122,
as well as other information that may be used by processor 116 to
direct the activities of controller 80.
[0101] Activity table 122 includes a data line column 200 that
contains an address or other appropriate identifier of data lines
54 associated with subscriber lines 16 and their related
subscribers 12. Status column 202 indicates the status of data line
54 identified in data line column 200. For example, status column
202 may contain one or more indications that the associated data
line 54 is inactive (I), active (A), or dedicated (D). A timeout
column 204 indicates whether detector 162 in modem pool 74 has
detected a timeout associated with a particular data line 54. A
modem column 206 includes an identifier of the modem 160 associated
with the corresponding data line 54.
[0102] An entry in activity table 122 corresponds to a row that
designates a selected data line 54 in data line column 200, the
status of the selected data line 54 in status column 202, a timeout
indication of the selected data line 54 in timeout column 204, and
the modem associated with the selected data line 54 in modem column
206. For example, entry 208 relates to data line "D1" which is
inactive. Entry 210 represents data line "D2" which is inactive but
dedicated to modem "M1." Entry 212 indicates that data line "D4" is
active, coupled to modem "M3," but a timeout indication has been
detected.
[0103] Subscribers 12 indicated in status column 202 as dedicated
may be serviced by communication server 58 in a specific way.
Switch 70 in communication server 58 maintains a coupling between
data line 54 corresponding to dedicated subscriber 12 and its
associated and dedicated modem 160. In this manner, controller 80
need not detect a need for data service or reconfigure the
couplings for data line 54 corresponding to dedicated subscriber
12. In this manner, communication server 58 provides the option of
a different class of service for a dedicated subscriber 12 that
desires uninterrupted access to XDSL communication facilities.
[0104] FIG. 8 is a flow chart of a method performed at controller
80 to couple data lines 54 to modems 160 in modem pool 74. The
method begins at step 300 where processor 116 of controller 80
loads activity table 122 from database 120 which contains an entry
for each valid subscriber 12 served by communication server 58.
Using management interface 128, a telephone service provider may
ensure that activity table 122 reflects valid subscribers 12 by
monitoring past due accounts, the overuse of data service,
successive invalid attempts to access communication server 54, or
other factors that may cause subscribers 12 to be invalid.
Processor 116 selects the first inactive and non-dedicated data
line 54 indicated by the designation "I" in status column 202 of
activity table 122. Since switch 70 is configured to continuously
couple dedicated subscribers 12 to their dedicated modems 160,
processor 116 need not select an inactive data line 54 that is also
dedicated, as indicated by the designation "I/D" in status column
202.
[0105] Using input/output circuitry 118, processor 116 directs
switch 104 of polling circuitry 100 to couple transceiver 108 to
the selected inactive and non-dedicated data line 54 at step 304.
If appropriate, processor 116 accesses profile table 124 in
database 120 and provides profile information for the selected data
line 54 to transceiver 108 using link 125 at step 306. Processor
116 initializes timer 117 with a predetermined polling interval at
step 308.
[0106] If a need for data service has not been detected by
transceiver 108 at step 312, then processor 116 checks timer 117 at
step 314. If the polling interval monitored by timer 117 has not
expired at step 314, then processor 116 again determines if a need
has been detected at step 312. However, if the polling interval
monitored by timer 117 has expired at step 314, processor 116
selects the next inactive and non-dedicated data line 54 as
indicated in status column 202 of activity table 122 at step 316,
and returns to step 304.
[0107] If a need for data service is detected at step 312, the
associated information may be further processed by detector 112 and
placed in memory for access by processor 116 at step 318. Before,
during, or after step 318, transceiver 108, detector 112, and/or
processor 116 may validate the need for data service. Validation
may be performed at a low level, such as a verification of the
checksum or detection of an incomplete transmission, or at a higher
level, such as a verification of an identifier, password, or other
security information that provides access to communication server
58. Validation contemplates any level of validation or security
handshake that confirms that the received need is valid and
accepted by controller 80.
[0108] Upon selecting an unused modem at step 332, processor 116
generates a command that directs switch 70 to couple the selected
data line 54 to the selected modem 160 at step 333. Processor 116
may communicate status or connection information to subscriber 12
using transceiver 108 or the selected modem 160 at step 334.
Processor 116 updates activity table 122 at step 336 to indicate
that the selected data line 54 is now active and that the selected
modem 160 is now being used. Processor 116 directs activity
detector 162 to initialize the inactivity interval for the selected
modem 160 at step 338. Processor 116 then selects the next inactive
and non-dedicated data line 54 in activity table 122 at step 316,
and returns to step 304.
[0109] FIG. 9 is a flow chart of a method for monitoring and
decoupling modems 160 due to inactivity. It should be understood
that the methods described with reference to FIGS. 8 and 9 may be
performed simultaneously or in alternative succession by processor
116 to couple and decouple data lines 54 with modems 160. The
method begins at step 400 where processor 116 loads activity table
122 which contains an entry for each valid subscriber 12 served by
communication server 58. Processor 116 selects a first active and
non-dedicated data line 54 as indicated by the designation "A" in
status column 202 of activity table 122 at step 402. Since switch
70 is configured to maintain a coupling between dedicated
subscribers 12 and their dedicated modems 160, processor 116 need
not select an active data line 54 that is also dedicated, as
indicated by the designation "A/D" in status column 202.
[0110] Processor 116 retrieves timeout status for modem 160
associated with the selected active data line 54 from detector 162
using link 86 and input/output circuitry 118 at step 404. Processor
116 determines if a timeout has occurred for the selected active
data line 54 at step 408. If a timeout has not occurred, processor
116 selects the next active and non-dedicated data line 54 as
indicated in status column 202 of activity table 122 at step 410,
and returns to step 404.
[0111] If a timeout has occurred at step 408, processor 116 may
communicate status or connection information to subscriber 12
associated with the selected active data line 54 using transceiver
108 or the associated modem 160 at step 412. Processor 116
generates a command to direct switch 70 to decouple the active data
line 54 from its associated modem 160 at step 414. Processor 116
updates activity table 122 at step 416 to indicate that data line
54 is now inactive and that the associated modem 160 is available
for another subscriber session.
[0112] FIG. 10A illustrates another implementation of communication
server 58 in communication system 10. Communication server 58 of
FIG. 10A provides switching at an isolated four-wire interface. As
shown in FIG. 10A, data lines 54 are coupled to and received by a
plurality of line interface units 500. Each line interface 500
provides an analog interface, line driver and transformer for
processing signals on data lines 54. Each line interface unit 500
is coupled to a switching matrix 502 and communicates with
switching matrix 502 across a transmit data pair 504 and a receive
data pair 506. Each line interface unit 500 operates to interface
between transmit data pair 504 and receive data pair 505 and
twisted pair data line 54.
[0113] In the implementation of FIG. 10A, a detector 508 is coupled
to each receive data pair 506. Each detector 508 operates to detect
a request for service on the associated receive data pair 506 and,
upon detection, provides a signal to controller 80 indicating a
request for service. Detector 508 is shown in more detail in FIG.
10D, and implementations of detectors are shown in more detail in
FIGS. 11A, 11B and 11C. It should be understood that other
implementations can combine polling with multiple detectors to
reduce the number of inputs to controller 80 and to reduce the
number of detectors. For example, FIG. 3 shows an implementation
using polling circuitry 100 that can be used with the detector in
the communication server embodiment of FIG. 10A.
[0114] As shown, switching matrix 502 is coupled to a modem pool
510 and communicates with modem pool 510 across transmit data pairs
512 and receive data pairs 514. Transmit data pairs 512 and receive
data pairs 514 contain a number of pairs equal to the number of
modems in modem pool 510. As described above, modems in modem pool
510 convert signals in an appropriate XDSL communication protocol
into digital data in an appropriate digital protocol on digital
lines 76. Multiplexer 78 is then coupled to digital line 76 and
provides a multiplexed digital line output 62. Also as described
above, controller 80 provides switch control signals 84 to
switching matrix 502 and communicates modem selection and control
information 86 with modem pool 510.
[0115] In operation, each detector 508 detects a request for
service on the associated receive data pair 506 and informs
controller 80 that a request for service has occurred. Controller
80 then checks which modems in model pool 510 are assigned and
which data lines 54 are valid. Controller 80 assigns a modem from
modem pool 510 to the requesting data line 54 using switching
matrix 502 to connect the associated receive data pair 506 and
transmit data pair 504 to the appropriate receive data pair 514 and
transmit data pair 512.
[0116] A technical advantage of providing switching at a four-wire
interface within communication server 58 is that switching matrix
502 is isolated from data lines 54 and subscriber lines 16 by
transformers in line interface units 500. Because of this
isolation, switching matrix 502 can operate without constraints
imposed by technical requirements for interaction with data lines
54 and subscriber lines 16. For example, the isolation of switching
matrix 502 allows CMOS switches to be used rather than more
expensive solid state relays or mechanical relays.
[0117] FIG. 10B illustrates in more detail line interface device
500 of communication server 58 of FIG. 10A. Line interface device
500 includes a line protection circuit 520 that is coupled to and
receives data line 54. Line protection circuit 54 operates to
ensure that activity down stream in communication server 58 does
not affect the integrity of data line 54. Line protection circuit
520 is coupled to a magnetics/hybrid unit 522. Magnetics/hybrid
unit 522 can comprise a transformer and operates to interface
between the data line and an internal transmit data pair 524 and
receive data pair 526. Magnetics/hybrid unit 522 also isolates the
four-wire interface provided by internal receive data pair 526 and
transmit data pair 524 from data line 54.
[0118] A line receiver 528 receives receive data pair 526 and
drives signals to a receive filter 530. The output of receive
filter 530 is receive data pair 506 which is coupled to switching
matrix 502 as shown in FIG. 10A. Similarly, transmit data pair 504
is coupled to a transmit filter 532 which provides signals to a
cable driver 534. Cable driver 534 then drives signals on transmit
data pair 524 to magnetics/hybrid unit 522.
[0119] FIG. 10C illustrates in more detail controller 80 of
communication server 58 where a plurality of detectors provide
indications of a request for service. Controller 80 of FIG. 10C
includes processor 116 and input/output circuitry 118 as discussed
above with respect to FIG. 3. Controller 80 also includes a scanner
or processor interrupt circuit 540 which receives the request for
service indications from detectors 508 and provides a scanner
output or processor interrupt to processor 116. This allows the
outputs of a number of detectors 508 to be sampled to provide an
appropriate signal to processor 116 when a request for service has
been detected. As mentioned above, it should be understood that
selection of the number of detectors and the amount of polling can
be made as appropriate for the desired application. In one
implementation, scanner or processor interrupt circuit 540
comprises a gate array having logic circuitry for generating
appropriate interrupt signals to processor 116.
[0120] FIG. 10D illustrates in more detail a detector 508 of
communication server 58. As shown, detector 508 includes a receiver
circuit 550 and a service request detector 552. Receiver circuit
550 is coupled to a receive data pair 506 and provides an output to
service request detector 552. Service request detector 552 then
operates to identify a request for service. Upon detection, service
request detector 552 provides a signal indicating a request for
service to controller 80. For ADSL systems (e.g., CAP and DMT), the
request for service can be an initial tone that is a pure sinusoid
or a modulated sinusoid. Three implementations of a detector 508
are illustrated in more detail in FIGS. 11A, 11B and 11C and
described below.
[0121] FIG. 10E illustrates in more detail a modem 560 in modem
pool 510 of communication server 58. Modem 560 is analogous to
modem 108 of FIG. 5 with filters and magnetics 170 removed. Modem
560 includes a bit pump 174 which communicates with switching
matrix 502 across receive data pair 526 and transmit data pair 524.
Modem 560 does not need to include filters and magnetics 170
because of the functions provided by line interface units 500 to
create the four-wire interface described above. Bit pump 174 and
logic and timing circuitry 178 otherwise operate as discussed with
respect to FIG. 5. Conceptually, the implementation of FIG. 10A
moves the function of filters and magnetics 170 of modem 108 to
line interface units 500 to isolate switching matrix 502 from data
lines 54.
[0122] FIG. 11A illustrates in more detail an analog filter
implementation of a detector 508 of communication server 58.
Detector 508 of FIG. 11A detects the tone or modulated tone using
an analog filter circuit tuned to the distinct frequency used to
transmit a subscriber request for service. Detector 508 comprises a
differential receiver 570 that is coupled to an associated receive
data pair 506. Differential receiver 570 is coupled to and provides
a signal to a band pass filter 572. Band pass filter 572 is coupled
to a gain device 574 which is coupled to a signal processing
circuit 576. The output of signal processing circuit 576 is coupled
to a rectifier circuit 578 which is coupled to a low pass filter
580. The output of low pass filter 580 is then provided as one
input to a voltage comparator 582. The other input to voltage
comparator 582 is connected to a reference voltage 584.
[0123] In operation, detector 508 operates to detect a tone or
modulated tone that indicates a request for service on receive data
pair 506. Differential receiver 570 produces a voltage output which
is filtered by band pass filter 572 and provided to gain device
574. Gain device 574 then amplifies the signal and provides it to
signal processing circuit 576. The signal processing circuit 576
processes or demodulates the XDSL signals generated at the customer
location that indicate a request for data service. Signal
processing circuit 476 provides the signal to rectifier circuit 578
that outputs the signal to low pass filter 580. Low pass filter 580
filters low frequency noise to provide a DC voltage as an input to
voltage comparator 582. Voltage comparator 582 compares that DC
voltage with reference voltage 584 and outputs a logic high when
the DC voltage is greater than reference voltage 584. Reference
voltage 584 is set so that voltage comparator 582 signals a request
for service only when the appropriate tone or modulated tone is
present on receiver data pair 506.
[0124] It should be understood that detector 508 of FIG. 11A, as
well as those of FIGS. 11B and 11C, can be connected to polling
circuit 100 of FIG. 3 or other polling circuits to reduce the
number of detectors required or to scan the outputs of the
detectors. The number of lines that can be polled by a single
polling circuit is generally limited by the amount of time that is
required by the detector to reliably detect the subscriber request
for service.
[0125] FIG. 11B illustrates in more detail a tone decoder
implementation of detector 508 of communication server 58. Detector
508 comprises a differential receiver 590 that is coupled to
receive data pair 506 and provides an output to a band pass filter
592. Band pass filter 592 is coupled to a gain device 594 which
provides an output to a signal processing circuit 596. The signal
processing circuit 576 processes or demodulates the XDSL signals
generated at the customer location that indicate a request for data
service. The output of signal processing device 596 is then coupled
to a tone decoder circuit 598. Tone decoder integrated circuit 598
provides an output to controller 80 indicating a request for
service upon detection.
[0126] In one implementation, tone decoder circuit 598 comprises an
integrated circuit, and specifically is an LMC567 tone decoder
available from NATIONAL SEMICONDUCTOR. In this implementation, tone
decoder circuit 598 includes a phase locked loop detector for
identifying the tone or modulated tone that indicates a request for
service. The phased locked loop detects when the received tone or
modulated tone matches the signaling frequency, and the tone
detector circuit responds by signaling a request for service.
[0127] FIG. 11C illustrates in more detail a digital signal
processor implementation of detector 508 of the communication
server 58. Detector 508 of FIG. 11C comprises a polling circuit 600
that is coupled to a plurality of receive data pairs 506. Polling
circuit selects each receive data pair 506 and connects it to a
line receiver 602. Line receiver 602 is coupled to a filter 604
which is coupled to an analog/digital converter 606. Analog/digital
converter converts the signal to a digital signal and provides an
output to a digital signal processor 608. Upon detection, digital
signal processor provides a request for service indication to
controller 80.
[0128] In the implementation of FIG. 11C, polling circuitry 600
connects line receiver 602, filter 604, analog/digital converter
606 and digital signal processor 608 to each line in succession.
Digital signal processor 608 reads the data from the analog/digital
converter 606 and demodulates or detects the request for service.
The dwell time for polling circuitry 600 can be set, for example,
such that detector 508 can poll the lines in less than half the
duration of the subscriber request for service tone or modulated
tone. The number of lines that can be polled by a single digital
signal processor 608 is then determined by the amount of time
required for digital signal processor 608 to reliably perform the
detection algorithm and the duration of the tone described
above.
[0129] Digital signal processor 608 is programmable to detect the
subscriber request for service tone or modulated tone using an
appropriate tone detection algorithm or demodulation algorithm. One
advantage provided by the detector implementation of FIG. 11C is
this programmability of the algorithm within digital signal
processor 608.
[0130] It should be understood that the tones used to indicate
service in the above description of FIGS. 11A, 11B, and 11C, may be
the tone used in standard non-switched applications of XDSL modems,
or may be additional tones added specifically to facilitate
detection in switching.
[0131] FIG. 12 illustrates in more detail a digital switching
matrix implementation of communication server 58. The
implementation of FIG. 12 is appropriate for both a two-wire and
four-wire interface to provide digital switching of the modem
connections. Communication server 58 of FIG. 12 includes line
interface components and data off-hook detection units 610 that
interface with subscriber lines 54 and detect subscriber requests
for service. Request for service indications are then provided to
controller 612 for controlling the modem connections.
[0132] Each line interface and detection unit 610 is coupled to an
associated analog/digital and digital/analog converter 614.
Converters 614 are in turn connected to parallel/serial and
serial/parallel converters 616. Converters 616 are coupled to a
digital multiplexer 618 which operates under control of controller
612 to connect converters 616 to assigned modems in modem pool 620.
Modems in modem pool 620 are coupled to a network
interface/multiplexer 622 and can be implemented using digital
signal processors. As shown, network interface/multiplexer 622 is
coupled to and communicates with controller 612. This allows
network interface/multiplexer 622 to know which modems and lines
are active without having to monitor the communication traffic on
the lines.
[0133] In operation, incoming communications are converted to
digital words by converters 614 and then converted to serial bit
streams by converters. The serial bit streams are connected to an
assigned modem by digital multiplexer 618. The modems in modem pool
620 then communicate with network interface/multiplexer 622. For
outgoing communications, the process is reversed. Serial bit
streams from the modems are converted to parallel words and then to
analog signals for transmission on data lines 54. This digital
switching implementation of communication server 58 can be
advantageous for switching of higher frequency XDSL
communications.
[0134] FIG. 13A illustrates in more detail a frequency multiplexing
implementation for switching modem connections in communication
server 58. This frequency multiplexing implementation could be
appropriate for being located at a cable operator as well as a
central office of a telephone network. As shown, data lines 54 are
coupled to receiver/buffers 630 and transmit/buffers 632. Data
off-hook detectors 634 are coupled to the output of
receiver/buffers 630 and provide request for service indications to
controller 636. For each data line 54, communication server 58
includes a frequency agile modulator 638 and a frequency agile
demodulator 640. Each modulator 638 operates to modulate an
incoming analog signal at a selectable frequency. In the
illustrated embodiment, the frequency is set to one of a plurality
of frequencies, f1 to fN, equal in number to the number of
available modems. Similarly, each demodulator 640 operates to
demodulate at a selectable frequency where the frequency is set to
one of the plurality of frequencies, f1 to fN. Associated
modulators 638 and demodulators 640 are set to operate at the same
frequency.
[0135] Modulators 638 provide signals to and demodulators 640
receive signals from a mixer 642. Mixer 642 mixes the signals from
modulators 638 and provides the combined signal to demodulators
644. Each demodulator 644 operates to demodulate the incoming
signal at one of the frequencies, f1 to fN, as designated by
controller 636. Each demodulator 644 is coupled to and provides the
demodulated signal to an associated modem 648 in the modem pool. By
designating the appropriate frequency, controller 636 effectively
connects an assigned a modem 648 to a data line 54.
[0136] Outgoing signals are processed in an analogous manner. Each
modem 648 provides outgoing analog signals to an associated
modulator 646 designated to operate at the same frequency as the
associated demodulator 644. Modulators 646 modulate the analog
signal and provide the modulated signal to mixer 642. Mixer 642
combines the modulated signals and provides the combined signal to
each demodulator 640. Demodulators 640 demodulate the combined
signal to recover the appropriate analog signal at their selected
frequency and provide the demodulated analog signal to
transmit/buffers 632 for transmission. In this manner, modems 648
are connected to data lines 540 by modulating and demodulating
signals at one of the frequencies, f1 to fN.
[0137] FIG. 13B is a diagram of frequencies, f1 to fN, used in the
implementation of FIG. 13A. This results in each of the modems, m1
to mN, being assigned to one of the frequencies, f1 to fN, based
upon the frequency for the connected data line 54, as shown. In
order to connect a data line 54 to a assigned modem 648, modulators
644 and demodulators 646 are designated to operate at the frequency
of the modulator 638 and demodulator 640 for that data line 54.
[0138] FIG. 14A illustrates line interface modules (LIM) 650 and
modem pool 652 of a distributed switching implementation of
communication server 58. A controller 653 is coupled to line
interface modules 650 and to modem pool 652. As shown, a plurality
of line interface modules 650 are coupled to the data lines and to
modem pool 652. Each line interface module 650 is operable to
detect a request for service on the data lines and to connect each
of the data lines it receives to each modem in modem pool 652.
Controller 653 operates to select a modem from modem pool 652 in
response to a detected request for service. Controller 653 then
directs the appropriate line interface module 650 to connect the
requesting data line to the selected modem. In the illustrated
implementation, each line interface module 650 receives N data
lines and includes switches to connect the N data lines to any of
the M modems in modem pool 652. In this manner, the switching
function is distributed across line interface modules 650 and is
scalable as support for more data lines is added. In addition,
although a two-wire interface is shown, the architecture of FIG.
14A can be used at a two-wire or four-wire interface.
[0139] Line interface modules 650 allow switching capabilities to
be scalable with the desired number of modems and
over-subscription. As an example, one implementation has four data
lines connected to each line interface module 650 and thirty-two
modems in modem pool 652. For a 10:1 over-subscription, this
implementation would use 80 line interface modules 650 for
connecting 320 data lines to the 32 modems in modem pool 652. In
order to double the number of supported data lines, another 80 line
interface modules 650 could be added along with another 32 modems.
On the other hand, if a 5:1 over-subscription for 32 modems is
desired, 40 line interface modules 650 would be used to service 160
data lines.
[0140] FIG. 14B illustrates in more detail line interface modules
650 and modems 660 in modem pool 652. As shown, each line interface
module 650 includes a plurality of line interface units 654 that
receive one of the N tip and ring data lines. Each line interface
device 654 includes magnetics 656 and a plurality of switches 658.
In the illustrated implementation, magnetics 656 includes a
transformer that receives tip and ring lines of the associated data
line. As shown in FIG. 14B, a T line is then provided to a
plurality of switches 658 for connecting the T line to one of M
outgoing lines. As shown, the M outgoing lines are equal in number
to the number of modems 660 in modem pool 652. Then outputs of each
line interface device 654 are connected together so that line
interface module 650 has one output line for each modem 660 in
modem pool 652 in addition to one output for the R lines. It should
be understood that this can be implemented differentially using a
pair of switches to switch the modem to the data line, rather than
a single switch and a common R line, to enable switching R lines as
well.
[0141] Modem pool 652 includes a plurality of modems 660 of which
only the front-end portion are shown. Each modem 660 receives two
lines from line interface modules 650 using magnetics 662. Because
of magnetics 656 and magnetics 662, the switching and connections
between line interface devices 654 and modems 660 are isolated from
the data lines and from the back-end of modems 660. In one
implementation, the connections between line interface modules 650
and modems 660 are accomplished on the back plane of a
telecommunications chassis, and the line interface modules 650 and
modems 660 are implemented as cards that plug into the back plane.
In this implementation, a controller communicates with line
interface modules 650 and modems 660 to control switching
connections to modems 660.
[0142] In general, the communication server of the present
invention detects a request for data transport service from a
subscriber's XDSL modem, XDSL transceiver unit or other customer
premises equipment as well as, for example, from a central office
multiplexer. The detected request for service is then used to
switch into connection an XDSL transceiver unit located at the
central office, remote terminal or other local loop termination
point providing, for example, a point of presence for an
information service provider (ISP) or corporate network. The
request-for-service detection mechanism allows a large pool of
subscribers to be served by a smaller pool of XDSL transceiver
units, thereby providing the basis for a cost-effective, massively
deployable XDSL service. The request for service detection also
makes fault tolerance possible since no subscriber is required to
be dependent upon any specific XDSL transceiver unit in the
pool.
[0143] FIG. 15 illustrates a functional block diagram of one
embodiment of a distributed switching implementation of the
communication server, indicated generally at 700. For clarity, one
set of line interface modules 702 and POTS filter modules 704 are
shown. Larger or smaller numbers of line interface modules and POTS
filter modules can be used. In addition, POTS filter modules 704,
which can provide the splitting function for voice and data
traffic, are optional equipment and are not typically used when the
communication server services terminated twisted pair data lines.
Communication server 700 also includes line power modules (LPMs)
706 for powering line interface modules 702 and LIM control modules
(LCs) 708 for controlling the line interface modules 702.
Communication server 700 further includes XDSL transceiver units
(xTU-C's) 710, system controllers (SCs) 712, and network interface
modules (NIs) 714. In addition, communication server 700 can
include expansion units 716.
[0144] A number of data buses within communication server 700 are
shown in FIG. 15. Communication server 700 of FIG. 15 operates
through the use of four major bus systems on a backplane of
communication server 700: an analog switching bus 718, a digital
serial bus 720, serial management buses 722, and a power bus (not
shown in FIG. 15). Each of these buses can support redundancy and
fault tolerance. In addition, an analog test bus (ATB) can be
present for optional analog path testing, a protect bus can be
present to allow 1:15 or 1:31 equipment protection for 1:1
deployments, and a busy bus can be used to distribute a busy
indication to the line interface modules 702.
[0145] In one embodiment, the communication server consists of a
multiplexer chassis, one or more optional POTS filter chassis, and
one or more optional line interface module (LIM) chassis. In this
embodiment, XDSL lines that carry a combined POTS/XDSL signal from
the customer premises, can be terminated in a POTS filter shelf,
which is a passive unit capable of accepting, for example, up to
twenty POTS filter modules 704. These POTS filter modules 704 can
contain lightning and power cross protection as well as passive
filters which split out any analog POTS connections to the Public
Switched Telephone Network (PSTN). Four lines, for example, can be
terminated by each POTS module 704, giving the POTS filter shelf a
maximum capacity, for example, of 80 subscriber terminations. As
mentioned above, where the XDSL lines do not carry both POTS and
XDSL signals, the POTS modules 704 are not used.
[0146] Wire pairs carrying XDSL service, whether originating from
the subscriber or coming from the POTS filter shelf, can then be
connected to line interface modules 702. Line interface modules 702
can reside, for example, either in a multiplexer chassis or in a
separate LIM chassis. The multiplexer chassis can be capable of
supporting up to eight LIM chassis, for a maximum capacity of 640
subscriber lines, or 10:1 oversubscription. The LIM chassis can
accept, for example, up to twenty line interface modules 702, with
each module 702 terminating four subscriber lines, giving the LIM
chassis a capacity of eighty subscribers (at 10:1
oversubscription). The line interface modules 702 can contain line
isolation circuitry, digital service request detection circuitry,
and an analog switching matrix which performs the concentration of
lines to the pool of available XDSL transceiver units 710.
[0147] The XDSL signals from the line interface modules 702 can be
connected to XDSL transceiver units via analog switching bus 718.
The multiplexer chassis can support, for example, up to thirty two
XDSL transceiver unit modules 710, with each module 710 containing
two XDSL transceiver units, for a total of sixty four XDSL
transceiver units. The XDSL transceiver units can be organized in
two pools of thirty-two terminations each. Each transceiver can be
connected to analog switching bus 718 carrying XDSL signals from
the line interface modules 702. Each XDSL port on line interface
modules 702 can be connected to one of the thirty two XDSL
transceiver units in the assigned pool using a set of analog
switches resident on the line interface modules 702.
[0148] System controller 712 maintains database 120 which stores
program 121, activity table 122, profile table 124, and subscriber
table 126. Profile table 124 is discussed in more detail below with
reference to FIG. 19. All or selected portions of database 120 may
be stored in one or more components internal or external to
communication server 700. Each XDSL transceiver unit 710 includes
registers 711 to store profile information retrieved from profile
table 124 maintained at system controller 712. Registers 711 may be
any form of registers, memory, or other storage devices or units
that allow profile information to be maintained locally at XDSL
transceiver unit 710 during an XDSL communication session. For
example, registers 711 may be associated with one or more digital
signal processors (DSPs) in XDSL transceiver unit 710. System
controller 712 reads from and writes to registers 711 in XDSL
transceiver unit 710 using serial management bus 722.
[0149] Two network interface (NI) modules 714 can be provided in
the multiplexer chassis, allowing a redundant network interface to
be installed if desired. The XDSL transceiver unit modules 710 can
be connected to the network interface modules 714 via redundant
digital serial point-to-point buses 720, carrying ATM cells on
synchronous duplex lines. The network interface modules 714 can
statistically multiplex cells to and from XDSL transceiver unit
modules 710 in a cell switch architecture. The network interface
modules 714 can also processes network signaling data.
[0150] Two slots can be provided for system controller (SC) modules
712. One system controller module 712 can be designated as the
primary module, and the other system controller module 712 can be
installed for redundancy. The System controller modules 712 can
contain a processor which manages the multiplexer chassis and LIM
chassis. Each line interface module 702 and XDSL transceiver unit
module 710 can communicate with the System controller module 712
over dual redundant serial management buses 722 for configuration
information and to report status. The System controller modules 712
also can provide, for example, both Ethernet and RS-232 management
interfaces which can run either SNMP or TL1 protocols respectively.
Further, the System controller modules 712 can contain power supply
circuitry providing bus bias voltage as well as provide alarm
contacts and alarm cut-off functions.
[0151] The multiplexer chassis can further contain two expansion
unit (EX) slots. Expansion unit units 716 in those slots can be
used for a variety of different functions. The expansion unit units
716 can have access to the network interface modules 714 through
redundant high-speed serial buses. A separate line power module
(LPM) 706 can be used to power line interface modules 702 when they
are located in the multiplexer chassis. Line power modules 706 can
be placed, for example, in any universal slot and can be
redundantly deployed. Further, all modules in communication server
700 can be "hot" insertable. A separate bias supply, generated by
the System controller modules 712 or LIM control modules 708, can
be used to bias bus logic and allow hitless insertion of all
modules in the system. Auto detection of newly inserted modules can
then be supported by the System controller modules 712.
[0152] Analog switching bus 718 (ASB) is a shared switching bus to
which all line interface modules 702 have access. Analog switching
bus 718 can consist of individual two-wire connections from the
line interface modules 702 to ports for the XDSL transceiver units
on modules 710. The XDSL lines from the customer premises equipment
(CPE) are connected to analog switching bus 718 using a matrix of
analog switches on respective line interface modules 702. These
switches allow each port of line interface modules 702 to be
connected to, for example, any one of thirty-two two-wire
connections to XDSL transceiver units on modules 710. Sixty four
XDSL line terminations, for example, can be supported in the
multiplexer chassis in the form of two pools of thirty-two
terminations each. Analog switching bus 718 connections can be
provided internally on the multiplexer chassis backplane for line
interface modules 702 located in the multiplexer chassis. For the
LIM chassis, analog switching bus 718 connections can be provided
via cable assemblies from the LIM chassis to the multiplexer
chassis. The analog switching bus 718 cables can be "daisy-chained"
for multiple LIM chassis, as opposed to direct connections from
each LIM chassis to the multiplexer chassis, to minimize connectors
and cabling.
[0153] Digital serial bus 720 provides a path from XDSL transceiver
units on modules 710 to network interface modules 714. Each XDSL
transceiver unit port can drive two serial data and
transmit/receive clock buses towards network interface modules 714,
one bus for each network interface module 714, for redundancy. Each
network interface module 714 can also drive two serial data buses
towards the XDSL transceiver unit ports, and each XDSL transceiver
unit can be programmed for which bus to receive by system
controller 712.
[0154] Serial management bus (SMB) 722 can consist of two buses.
Each redundant system controller 712 can drive and operate one of
buses 722. The serial management bus 722 can be used to manage all
modules on the multiplexer chassis and LIM chassis backplanes. The
bus electrical format can be TTL on the multiplexer chassis
backplane and LIM chassis backplane and can be multipoint RS485
from system controllers 712 to LIM controller modules 708 via
external cabling. The serial management bus 722 can be an
asynchronous bus and can carry a heartbeat message sent on the
serial management bus 722 by the system controller modules 712. The
other modules can be programmed to automatically switch to the
alternate serial management bus 722 if the heartbeat signal is not
received. Two control signals issued by the system controller
module 712 can be used to determine whether the primary or
secondary serial management bus 722 should be used.
[0155] XDSL transceiver unit modules 710 provide local loop
termination for XDSL service. Each module 710 can support, for
example, two XDSL connections to line interface modules 702. In
this case, each module 710 can include two XDSL transceiver
subsystems, two sets of digital serial data bus interfaces which
connect to the network interface modules 714, and a microcontroller
and serial management bus interface for configuration and control.
The digital serial buses 720 between each XDSL transceiver unit
module 710 and the redundant network interface modules 714 can
carry demodulated data to the network interface modules 714 and
digital data from the network interface modules 714 to be
modulated. Data can be, for example, in the form of ATM cells or
HDLC-framed packets, and the serial bus can consist of transmit and
receive clock and data pairs to each network interface module 714.
Each XDSL transceiver unit port on the modules 710 can be
programmed by the system controller module 712 for which network
interface bus to receive (i.e. which network interface module 714
is active). The microcontroller on the XDSL transceiver unit module
710 can be used to manage communications with the system controller
module 712 and to control the XDSL terminations. Rate adaptive
decisions, provisioning, performance monitoring, and other control
functions can be performed by the microcontroller.
[0156] In the illustrated embodiment, system control module 712 is
responsible for overall control of the communication server and for
gathering of status information. Two system controller modules 712
can be provided for redundancy. In a redundant configuration, the
two system controller modules 712 communicate with each other over
a dedicated communications bus for sharing database information,
self-checking, and online/offline control. Data requiring
persistent storage, such as provisioning, performance statistics
and billing information, can be stored on the system controller
module 712 in non-volatile memory. Performance monitoring
information can be collected for the network interface modules 714
and for each XDSL line, including information from remote customer
premises equipment units.
[0157] Network interface modules 714 provide a high-speed
connection for aggregated data traffic from the XDSL transceiver
units. The network interface modules 714 connect to the XDSL
transceiver unit modules 710 via point-to-point serial data buses
720. A high-speed serial interface to subtend host modules (SHMs)
can also be provided. In one embodiment, two types of network
interface modules 714 are supported: DS3/OC-3 ATM and DS1 ATM. A
DS1 Frame Relay interface may also be provided. An OC3/DS3 ATM
network interface can support ATM cell traffic at the XDSL
transceiver unit interface, and either a 155 Mbit single-mode
optical ATM User-Network Interface or a DS3 75 ohm coaxial
interface on the network side. A DS1 ATM network interface can
support ATM cell traffic at the XDSL transceiver unit interface,
and a 1.544 Mbps DS1 ATM user-network interface on the network
side. A DS1 Frame Relay network interface can support a 1.544 Mbit
unchannelized DS1 Frame Relay port.
[0158] The subtend host module (SHM) is an expansion unit 716 that
allows ATM data from multiple multiplexer chassis to be aggregated
before being presented to the switched data network, using a
technique called subtending. This technique provides full
utilization of the ATM switch ports in the network. The subtend
host module can contains six DS1 interfaces, and can be used to
subtend one to six remote communication servers. The subtend
interface can essentially be six DS1 UNI interfaces containing ATM
cells, from the remote communication server. DS1 is terminated by
the subtend host module and remote cells are sent to the network
interface over individual and aggregate 10 Mbit serial connection.
Each subtend host module has a serial interface to both network
interface modules 714, providing full redundancy. Cell delineation
is performed on the network interface 714, and cells are forwarded
to the switching matrix in the same manner as cells from the XDSL
transceiver unit interfaces.
[0159] Line interface module 702 can contain, for example,
intra-office line protection/termination, XDSL start tone
detection, test bus access, busy bus access, and switching for four
XDSL connections. Line interface modules 702 can be located either
in the multiplexer chassis for smaller system configurations, or in
an LIM chassis for large configurations. A pair of lines from the
POTS filter chassis can be routed to each line interface module 702
through the backplane for each interface. The shared analog
switching bus 718 between the line interface modules 702 and the
XDSL modem pool carries the switched signal from each active line
to an XDSL transceiver unit. Service request detection circuitry
detects the presence of start tones generated by the customer
premises equipment (CPE) and signals the LIM controller 708 or
system controller 712 through the serial management bus 722.
[0160] FIG. 16 illustrates a block diagram of one embodiment of
line interface module 702 of FIG. 15. As shown, line interface
module 702 includes a plurality of intra-office protection circuits
730 that receive a two-wire interface for XDSL communications.
Intra-office protection circuits 730 are coupled to an analog
switch matrix 732. Analog switch matrix 732 connects selected
intra-office protection circuits 730 to XDSL transceiver units. In
the illustrated embodiment, analog switch matrix 732 connects each
of four intra-office protection circuits 730 to one of thirty-two
XDSL transceiver units. Line interface module 702 further includes
a microcontroller 734 and a start tone detect circuit 736. In this
embodiment, analog switch matrix 732 is used to connect each
intra-office protection circuit 730 to start tone detect circuit
736 in succession to identify a request for service.
[0161] The LIM control modules (LCMs) 708 are responsible for
receiving service request detect information from the line
interface modules 702, configuring the analog switching matrix 732
under control of the system controller module 712, generating a
busy signal for all line interface modules 702 in the chassis, and
providing power for the line interface modules 702. One LIM control
module 708 can be designated as a primary and another as a
redundant back-up. For connection initiation, the LIM control
module 708 can poll the line interface modules 702 to identify any
pending service request detection events. The LIM control module
708 can then notify the system controller module 712, which in turn
selects an available XDSL transceiver unit. The system controller
module 712 then instructs the line interface module 702 to
configure the analog switching matrix 732 to connect the requesting
port to the selected XDSL transceiver unit. Connection termination
notification is provided by the XDSL transceiver unit module 710 to
the system controller module 712 upon detecting loss of carrier at
the XDSL facility. The system controller module 712 then signals
the LIM control module 708 to disconnect the line interface module
702 from the XDSL transceiver unit by clearing the switching matrix
connection. Power for the line interface modules 702 can also be
provided by the LIM control module 708.
[0162] FIG. 17 illustrates one embodiment of ATM based transport
communication protocols supported on the local loop and the network
interface of the communication server. Loop protocols refers to the
data encapsulation protocols which reside on the local loop
interface. It should be recognized that standards bodies are
currently formulating a strategy on local loop protocols and the
communication server is intended to support various protocol models
with minimal hardware impact. PPP over ATM is one implementation
for the disclosed communication server architecture. As shown in
FIG. 17, the hardware can consist of a communication server 740
that interconnects a network router 742 and computing devices 744
with an access server 746 for an Internet service provider (ISP) or
corporate network 748.
[0163] In this implementation, supported protocols are carried over
ATM cells. The communication server 740 then becomes an ATM
multiplexer switching ATM cells from the low speed XDSL ports to
the high speed network interface port. The communication server 740
network interface can perform this switching independently of the
underlying adaptation protocol. All cells can be indiscriminately
switched. Specific support for ML1, ML3/4, ML5, OAM, and raw cell
formats also can be incorporated into the network interface
switching element. RFC1577 compatible IP over ML is a protocol that
can be supported over the ATM layer of the XDSL loop. Point to
point PVC or SVC connections can be established between the router
742 or device 744 at the customer premise and the access server 746
at the home network. PPP can be used to encapsulate IP, IPX, or
Ethernet frames over ATM from the customer premises equipment
across the XDSL link to the communication server 740. PPP over ML5
can be encapsulated using RFC1483 guidelines. SNAP/LLC headers can
be used to distinguish PPP traffic from other possible traffic
types.
[0164] The use of PPP allows many protocol encapsulations,
including IP and IPX, and bridging using RFC1638. PPP can be
carried through the ATM network to the access server 746 located at
the corporate or ISP gateway. Authentication can then be performed
between the customer premises and the service network using PPP
authentication services such as the Password Authentication
Protocol (PAP) and the Challenge Handshake Authentication Protocol
(CHAP). In this scenario, PPP packets from remote users are
transported to the ISP or corporate network 748 for authentication,
thus freeing a network provider from authenticating each user to
various network destinations. PPP also has the advantage of being
relatively protocol independent and may be the wrapper for many
networking protocols. In addition, Ethernet bridging may be
supported through the use of ATM Forum LAN Emulation (LANE). LANE
allows the bridging of multiple remote users to the home LAN over
ATM.
[0165] FIGS. 18A and 18B illustrate a system block diagram for one
embodiment of the communication server. As shown, the communication
server of FIGS. 18A and 18B includes a plurality of line interface
modules (LIMs) 750 and a plurality of ADSL transceiver units 752
interconnected by dual analog buses 754. ADSL transceiver units 752
are connected to serial buses 756. Each line interface module 750
includes intra-office protection circuits 758, hybrid circuits 760,
switch 762 and detect circuit 764. Each ADSL transceiver unit 752
includes an ADSL chipset 766 (e.g., CAP, DMT) for each transceiver
channel, serial bus drivers 768 and other devices 770
(microcontroller, flash RAM). Chipset 766 is shown to include
registers 711, but registers 711 may be in any other appropriate
location within transceiver unit 752. Chipset 766 may include a
number of digital signal processors, logic devices, memory devices,
and other circuitry to perform any suitable form of XDSL
modulation. In a particular embodiment, registers 711 are
associated with at least one digital signal processor in chipset
766. These registers 711 may receive profile information (e.g.,
filter coefficients, equalizer tap coefficients, sub-band weights,
margin) to train the line and engage in XDSL communication without
a protracted training period.
[0166] Redundant OC3/DS3 ATM network interface units 772 are
connected to ADSL transceiver units 752 by serial buses 756. Each
network interface unit 772 includes a plurality of ATM cell
delineation circuits 774 connected to ATM cell switch fabric 776.
The switch fabric 776 is controlled by OAM/signaling cell access
unit 778 and processor 780. A DRAM 782 and a flash memory 784
provide memory space for processor 780. A physical interface 786
and a line interface unit 788 are connected to switch fabric 776
and provide the physical DS3 connection.
[0167] Redundant system controllers 790 each include serial drivers
792 connected to a processor 794. Relay driver circuits 796 are
connected to processor 794 and to alarm relays 798. Receiver
circuits 800 also are connected to processor 794 and are connected
to OPTO circuits 802. Memory 804 and flash memory 806 provide
memory space for processor 794. For example, memory 804 may store
database 120 which includes program 121, activity table 122,
profile table 124, and subscriber table 126. Profile table 124 is
discussed in more detail below with reference to FIG. 19. Processor
794 is further connected to Ethernet interface 808 and to serial
interface 810. System controller 790, network interface 772, ADSL
transceiver units 752, and line interface modules 750 operate
generally as described above to accomplish the functions of the
communication server.
[0168] FIG. 19 illustrates in more detail an exemplary embodiment
of profile table 124, which generally includes subscriber
information 820 and a variety of profile information 824.
Subscriber information 820 may include a subscriber line 826, a
subscriber ID 828, and a circuit ID 830 that alone or in
combination identify a particular subscriber and/or line serviced
by communication server 58. In a particular embodiment, subscriber
line 826 denotes the chassis, module, and port associated with
components in communication server 700. Subscriber ID 828 may be a
telephone number, network address, or other identifier maintained
by the telephone company or other entity to identify a subscriber.
Circuit ID 830 includes a similar address or identifier used by the
telephone company or other entity to specify the physical line
serviced by communication server 58. Subscriber information 820 may
also include a logical modem pool 832. Logical modem pool 832
specifies any arrangement or combination of XDSL modems or
transceiver units to accomplish any desirable ratio of
over-subscription or dedicated service to subscribers in
communication system 10.
[0169] Profile information 824 contemplates a variety of digital
signal processor (DSP) filter coefficients, parameters,
configuration, and line training parameters used by XDSL modems or
transceiver units to establish an XDSL communication session.
Generally, profile information 824 illustrated in FIG. 19 includes
maximum rates 834, margins 836, and a variety of
coefficients/parameters 838. Maximum rates 834 specify both
upstream and downstream maximum baud rates for the identified line.
Maximum rates 834 may be based on the tariffed rate for the
subscriber, physical limitations on the line, or other factors. For
example, the line identified by subscriber line 826 with a
chassis/module/port designation of "1.15.3" maintains a maximum
upstream rate of one megabit per second (1 Mbps) and a maximum
downstream rate of 4 Mbps based, for example, on a particular class
of service for the subscriber. Alternatively, the line identified
by subscriber ID 828 of "214-555-1212" has a maximum upstream rate
of 2 Mbps and a maximum downstream of 8 Mbps, based on, for
example, the maximum rate obtainable by the hardware and software
in communication system 10.
[0170] Margin 836 represents the difference between a current or
expected signal strength and a minimum signal strength to maintain
communication at the specified maximum rate 834 over the designated
line. In a particular embodiment, margin 836 is the difference
between the achievable or current signal-to-noise ratio and the
minimum signal-to-noise ratio to maintain communication for a given
bit error rate (BER) such as 10E-7. Margin 836 may be expressed in
dB and generally represents the quality of data communication on
the line at maximum rates 834.
[0171] Coefficients/parameters 838 comprise digital filter
coefficients, equalizer tap coefficients, sub-band weights,
quadrature amplitude modulation(QAM) constellation configuration,
bit capacity, or other coefficients and/or parameters that reflect
physical and/or electrical characteristics of the line. Profile
table 124 maintains coefficients/parameters 838 for each band
(e.g., upstream, downstream, sub-band) for each line at one or more
selected rates.
[0172] In a particular embodiment, each XDSL transceiver unit 710
includes one or more chipsets 766 that each have registers 711 for
receiving profile information 824 in preparation for XDSL
communication on a specified line. Registers 711 may be associated
with digital filters implemented by DSPs in chipset 766. Using CAP,
DMT, or other appropriate modulation technique, profile information
824 provided to registers 711 characterizes or fashions chipset 766
for communication over a particular line.
[0173] The maintenance of profile information 824 in profile table
124 provides a particular advantage in training lines and quickly
establishing XDSL sessions in communication system 10. Each line
served by communication server 58 includes a number of physical
parameters, such as length, gauge, bridge taps, or other
impairments or characteristics that govern the transmission of
electric signals along the line. In addition, adjacent wires may
contribute to interference on the line. Many of these
characteristics and parameters are static as the physical structure
of the line remains unchanged. The present invention takes
advantage of this by initially training the line to generate
profile information 824 for storage in profile table 124.
Communication server 58 then retrieves stored profile information
824 for a selected line and provides this information to XDSL
transceiver unit 710 coupled to the selected line in preparation
for XDSL communication. The use of stored profile information 824
significantly decreases the amount of time needed to establish XDSL
communication, and may substantially reduce or eliminate any need
for retraining the line. By storing and selectively loading profile
information 824 in XDSL transceiver unit 710, the present invention
eliminates or hastens convergence of various adaptive elements
(e.g., equalizers, filters) to improve access and performance.
[0174] FIG. 20 is a flowchart of a method for training a line to
generate or modify profile information 824. Although this method is
described generally with reference to the architecture illustrated
in FIG. 15, this method applies to any architecture or operation of
communication system 10. Moreover, this method applies to any XDSL
transceiver device located at a central office, remote terminal,
point of presence of a service provider, customer premises, or
other location that is coupled to a line that can be trained.
[0175] The method begins at step 850 where transceiver unit 710
establishes a physical connection with an associated line over
analog switching bus 718. This may be performed using LIMs 702 and
optionally POTS filter modules 704. Transceiver unit 710 retrieves
profile information 824 from profile table 124 associated with the
line at step 852. This may be performed by microcontroller 770 in
transceiver unit 710 receiving profile information 824 from system
controller 712 using serial management bus 722. System controller
712 accesses the proper profile information 824 using subscriber
information 820.
[0176] Transceiver unit 710 selects a band for training, which
could include the upstream, downstream, or sub-band supported by
the particular modulation technique used in communication system
10. For example, using CAP modulation, transceiver unit 710 may
select an upstream or a downstream band to train. Using DMT
modulation, transceiver unit 710 may select a discrete sub-band
used by the DMT modulation technique. Alternatively, transceiver
unit 710 may train two or more bands simultaneously. After
selecting a band at step 854, the method resets a training flag at
step 855 to indicate that the selected band of the selected line
has not been trained.
[0177] To begin a training session, transceiver unit 710 selects an
initial baud rate at step 856, which may be included in or derived
from profile information 824 retrieved at step 852 (e.g., maximum
rates 834) or generated locally by transceiver unit 710.
Transceiver unit 710 then runs a test to determine the quality or
characteristics of the line at step 858. This test may be a measure
of signal strength and/or noise to determine a line margin, a bit
error rate (BER) test, or any other measurement or method to
determine the quality or characteristics of the line. In a
particular embodiment, a BER test sends and receives known
information on the line using chipset 766. Transceiver unit 710
adjusts profile information 824 in response to the test at step 860
to improve signal quality. For example, transceiver unit 710 may
adjust filter coefficients, equalizer tap coefficients, sub-band
weights, QAM constellation configurations, bit rate, or any other
coefficient or parameter that enables chipset 766 to communicate
data more effectively over the line. If more adjustments need to be
made as determined at step 862, transceiver unit 710 continues to
run tests (step 858) and adjust profile information 824 (step 860)
until achieving satisfactory performance from chipset 766. In
particular, transceiver unit 710 may make adjustments until it
achieves a bit error rate of less than a particular threshold, such
as 10E-7.
[0178] After making adjustments, transceiver unit 710 determines if
it passed the training session at step 864. Again, this pass/fail
determination may be based on the computed bit error rate being
above or below a pre-defined threshold. Upon passing, transceiver
unit 710 computes margin 836 at step 866. Margin 836 may be
expressed in dB and represents the difference between a current or
expected signal strength and a minimum signal strength to maintain
communication at the selected baud rate (step 856) in one or more
selected bands (step 854). If transceiver unit 710 determines that
margin 836 is sufficient at step 868, then system controller 712
stores profile information 824 in profile table 124 of database 120
at step 870. The method sets the training flag at step 872 to
indicate successful training of one or more selected bands of the
line.
[0179] If transceiver unit 710 does not pass the training session
(step 864) or does not achieve sufficient margin 836 (step 868),
then transceiver unit 710 determines if it has previously trained
successfully at this band by checking the status of the training
flag at step 880. If the training flag indicates successful
training at step 880, transceiver unit 710 proceeds if necessary to
select another band for training at step 854. If the training flag
indicates no successful training at step 880, transceiver unit 710
selects a lower baud rate at step 882 and proceeds with another
training session at the lower baud rate at step 858.
[0180] Upon storing profile information 824 at step 870 and setting
the training flag at step 872, transceiver unit 710 may determine
at step 890 to attempt training at a higher rate as selected at
step 892. Training at a higher rate may depend upon maximum rate
834 or other subscriber information that limits the maximum data
rate for a particular line. Also, the selection of a higher baud
rate at step 892 may depend on margin 836 computed at step 866. In
a particular embodiment, a large margin 836 may cause transceiver
unit 710 to skip an interim baud rate and select a higher baud rate
at step 892 to further decrease training time. Upon selecting a
higher baud rate, transceiver unit 710 proceeds with a training
session at the higher baud rate at step 858.
[0181] If transceiver unit 710 cannot or does not select a higher
baud rate for training at step 890, the method determines if all
bands have been trained at step 894 and, if not, continues with
step 854 to select the next band for training. The method ends
after all bands for the line are trained and all associated profile
information 824 for each band stored.
[0182] FIG. 21 is a flow chart of a method for establishing data
communication using stored profile information 824. Although this
method is described generally with reference to the architecture
illustrated in FIG. 15, this method applies to any architecture or
operation of communication system 10. Moreover, this method applies
to any XDSL transceiver device located at a central office, remote
terminal, point of presence of a service provider, customer
premises, or other location that is coupled to a line whose
physical and/or electrical parameters can be characterized using
profile information 824 stored in profile table 124.
[0183] The method begins at step 900 where communication server 700
receives a request for service using an associated POTS filter
module 704 and/or LIM 702. LIM controller 708 notifies system
controller 712 of the request for service using serial management
bus 722. In response, system controller 712 determines subscriber
information 820 (e.g., subscriber line 826, subscriber ID 828,
circuit ID 830) at step 902 and determines the subscriber's logical
modem pool 832 at step 904 by accessing database 120 containing
profile table 124. System controller 712 selects an available
transceiver unit 710 at step 906 and causes the associated LIM 702
to couple the line to the selected transceiver unit 710 at step
908.
[0184] Steps 900-908 may implement the digital off-hook and
over-subscription capabilities of communication server 700.
However, in a CPE environment, steps 900-908 may be unnecessary,
especially if there is a one-to-one or known association between
lines and transceiver units. In the CPE environment, a request for
service received at step 900 may be a local indication that the
subscribers' communication equipment desires to establish XDSL
communication.
[0185] In either embodiment, the selected transceiver unit 710
retrieves profile information 824 from profile table 124 maintained
at database 120 in system controller 712 at step 910. In a
particular embodiment, microcontroller 770 in transceiver unit 710
communicates with system controller 712 using serial management bus
722 to receive information stored in database 120. As described
above with reference to FIG. 19, this information indexed by
subscriber information 820 may include maximum rate 834, margin
836, or any variety of coefficients/parameters 838 (e.g., filter
coefficients, equalizer tab coefficients, sub-band weights), or
other suitable information that characterizes the line and the
appropriate communication parameters for transceiver unit 710. Upon
receiving profile information 824 over serial management bus 722,
transceiver unit 710 loads this information into suitable registers
711 at step 912. In a particular embodiment, microcontroller 770
passes profile information 824 to registers 711 associated with at
least one digital signal processor in chipset 766. Upon receiving
and loading profile information 824 from profile table 124,
transceiver unit 710 prepares to communicate data using maximum
rate 834, margin 836, and coefficients/parameters 838 specific to
the line.
[0186] In a particular embodiment, transceiver unit 710 performs a
test at a selected baud rate to confirm the quality of the line and
the accuracy or effectiveness of profile information 824 retrieved
from profile table 124 at step 914. This test may be a measure of
signal strength and/or noise to determine a line margin, a bit
error rate (BER) test, or any other measurement or method to
determine the quality or characteristics of the line. If
transceiver unit 710 passes the test as determined at step 916,
then transceiver unit 710 proceeds to communicate data associated
with the session at step 918. If transceiver unit 710 does not pass
the test as determined at step 916, then the method determines
whether the baud rate and/or profile information 824 should be
adjusted at step 920. If the baud rate and/or profile information
824 are to be adjusted, transceiver unit 710 proceeds to lower the
baud rate and/or adjust profile information 824 at step 922 in
preparation for another test. For example, transceiver 710 may
simply lower the baud rate at step 922 and perform a confirming
test at step 914 without a significant sacrifice in time to train
the line. Transceiver unit 710 may also make adjustments in profile
information 824, with or without a baud rate adjustment, to retrain
the line.
[0187] If the baud rate and/or profile information should not or
cannot be adjusted at step 920, then the method determines whether
full retraining of the line is appropriate at step 922. If full
retraining is appropriate, the method proceeds to step 854 in FIG.
20 to perform retraining to update and modify profile information
824 maintained in profile table 124. Communication server 700 may
perform retraining of the line at periodic intervals or when
physical or electrical characteristics of the line indicate a need
for retraining.
[0188] After communicating data at step 918, the method determines
if transceiver unit 710 has been idle for a predetermined period of
time at step 924. If transceiver unit 710 has been idle, system
controller 712 retrieves profile information 824 from registers 711
and stores this information in profile table 124 at step 926. It is
important that system controller 712 retrieve modified or updated
profile information 824 stored in registers 711 of transceiver unit
710 to maintain the most recent information for the line in profile
table 124. System controller 712 then releases transceiver unit 710
at step 928.
[0189] If more data for the communication session is received at
step 930, the method proceeds to step 906 and selects another
available transceiver unit 710 to proceed with communication of the
additional data. If more data is not received at step 930 and a
timeout occurs at step 932, then the method ends. Therefore, as
long as the line maintains communication activity without timing
out at step 932, communication server 700 will continue to support
data communication using one or more transceiver units 710
depending on the bursty character of the session. The idle time
(step 924) and timeout (step 932) are chosen to maximize the
efficient use of transceiver units 710 in communication server
700.
[0190] 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.
* * * * *