U.S. patent application number 11/057196 was filed with the patent office on 2005-09-15 for activation of multiple xdsl modems with half duplex and full duplex procedures.
This patent application is currently assigned to Panasonic Communications Co., Ltd.. Invention is credited to Palm, Stephen.
Application Number | 20050201294 11/057196 |
Document ID | / |
Family ID | 31497905 |
Filed Date | 2005-09-15 |
United States Patent
Application |
20050201294 |
Kind Code |
A1 |
Palm, Stephen |
September 15, 2005 |
Activation of multiple xDSL modems with half duplex and full duplex
procedures
Abstract
A method for a remote communication system to perform a startup
session to establish a communication between the remote
communication system and a central communication system. The remote
communication system initiates a startup procedure by transmitting
a R-TONES-REQ signal to the central communication system. Upon
detecting a C-TONES signal, which is issued by the central
communication system in response to the transmitted R-TONES-REQ
signal, the remote communication system transmits a R-TONE1 signal
to the central communication system. Upon detecting a C-GALF1
signal, which is issued by the central communication system in
response to the transmitted R-TONE1 signal, the remote
communication system transmits a R-FLAG1 signal to the central
communication system. Thereafter, the remote communication system
establishes a communication session in response to detecting a
C-FLAG1 signal issued by the central communication system in
response to the R-FLAG1 signal.
Inventors: |
Palm, Stephen; (Tokyo,
JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
Panasonic Communications Co.,
Ltd.
Fukuoka
JP
|
Family ID: |
31497905 |
Appl. No.: |
11/057196 |
Filed: |
February 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11057196 |
Feb 15, 2005 |
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10740767 |
Dec 22, 2003 |
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10740767 |
Dec 22, 2003 |
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09473683 |
Dec 29, 1999 |
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60115294 |
Jan 8, 1999 |
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Current U.S.
Class: |
370/241 |
Current CPC
Class: |
H04M 11/062 20130101;
H04L 5/1438 20130101 |
Class at
Publication: |
370/241 |
International
Class: |
H04L 001/00 |
Claims
I claim:
1. A method for a remote communication system to perform a startup
session to establish a communication between the remote
communication system and a central communication system,
comprising: initiating a startup procedure by transmitting a
R-TONES-REQ signal to the central communication system;
transmitting a R-TONE1 signal to the central communication system
in response to detecting a C-TONES signal issued by the central
communication system in response to the R-TONES-REQ signal;
transmitting a R-FLAG1 signal to the central communication system
in response to detecting a C-GALF1 signal issued by the central
communication system in response to the R-TONE1 signal; and
establishing a communication session in response to detecting a
C-FLAG1 signal issued by the central communication system in
response to the R-FLAG1 signal.
2. The method of claim 1, further comprising establishing a
low-speed communication session when the communication session
cannot be established.
3. The method of claim 1, wherein the R-TONES-REQ signal is
transmitted from at least one signal family with a phase reversal
occurring every predetermined time period.
4. The method of claim 1, wherein the remote communication system
stops transmitting the R-TONES-REQ signal for a predetermined
period of time prior to transmitting the R-TONE1 signal.
5. The method of claim 1, wherein the C-GALF 1 signal issued by the
central communication system comprises issuing a hex character "81"
on a modulated carrier.
6. The method of claim 1, wherein transmitting the R-FLAG1 Flag
signal comprises transmitting a hex character "7E" on a modulated
carrier.
7. A method for a remote communication system to perform a startup
session to establish a communication between the remote
communication system and a central communication system,
comprising: initiating a startup procedure by transmitting a first
predetermined signal to the central communication system from at
least one signal family with a phase reversal every predetermined
time period; transmitting a second predetermined signal to the
central communication system in response to detecting a first
signal issued by the central communication system in response to
the second predetermined signal, the transmission of the first
predetermined signal being stopped for a certain time period prior
to transmitting the second predetermined signal; transmitting a
third predetermined signal to the central communication system in
response to detecting a second signal issued by the central
communication system in response to the third predetermined signal;
and establishing a communication session in response to detecting a
third signal issued by the central communication system in response
to the third predetermined signal.
8. The method of claim 7, further comprising establishing a
low-speed communication session when the communication session
cannot be established.
9. The method of claim 7, wherein the first signal issued by the
central communication system comprises issuing a hex character "81"
on a modulated carrier.
10. The method of claim 7, wherein transmitting the third
predetermined signal comprises transmitting a hex character "7E" on
a modulated carrier.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation application of U.S. Patent
Application of 10/740,767, filed on Dec. 22, 2003, which is a
continuation application of U.S. patent application Ser. No.
09/473,683, filed on Dec. 29, 1999, which claims the benefit under
35 U.S.C. .sctn. 119 of U.S. Provisional Application No.
60/115,294, filed on Jan. 8, 1999, the disclosures of which are
expressly incorporated by reference herein in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is directed to a communications
device, such as, for example, a modem and a method for enabling
data communication, and in particular, to an apparatus and method
that detects various communication configurations and selects an
appropriate communication configuration to establish a
communication link.
[0004] 2. Discussion of Background And Other Information
[0005] Traditionally, data communication devices, such as, for
example, modems (both analog and digital), have been employed over
public switched telephone networks (PSTN) to transmit data between
a first location and a second location. Such modems operate within
a conventional voice band (e.g., approximately 0 through 4 kHz
bandwidth) of the PSTN. Early modems transmitted data over the PSTN
at a speed of approximately 300 bits per second (bps), or less.
Over time, and with the increased popularity of the Internet,
faster communication schemes (e.g., modems) were demanded and
developed. Currently, the fastest analog modem available (referred
to as an ITU-T V.34 modem, as defined by the International
Telecommunication Union (ITU)), transmits data at a rate of
approximately 33,600 bps under ideal conditions. These modems
continue to exchange data within the approximate 4 kHz bandwidth of
the PSTN.
[0006] It is not uncommon to transfer data files that are several
megabytes (MB) in size. A modem that operates utilizing the V.34
modulation requires a long time to transfer such a file. As a
result, a need has developed for even faster modems.
[0007] Accordingly, many new communication methods are being
proposed and/or developed to transmit data on the local twisted
wire pair that uses the spectrum above the traditional 4 kHz band.
For example, various "flavors" (variations) of digital subscriber
line (DSL) modems have been/are being developed, such as, but not
limited to, for example, DSL, ADSL, VDSL, HDSL, SHDSL and SDSL (the
collection of which is generally referred to as xDSL). Several of
the various xDSL schemes permit simultaneous communication on a
single twisted pair in the voice band and the band above the voice
band.
[0008] Each xDSL variation employs a different communication
scheme, resulting in different upstream and/or downstream transfer
speeds, and utilize differing frequency bands of the twisted pair
communication channel. A wide range of physical and environmental
limitations of the various configurations of the twisted pair wires
leads to widely varying expectations of a feasible communication
capability bandwidth. Depending on, for example, the quality of the
twisted wire pair (e.g., CAT3 wire vs. CAT5 wire), a given xDSL
scheme may not be able to transmit data at its maximum advertised
data transfer rate.
[0009] While xDSL technologies exist and offer the promise of
solving the high speed data transfer problem, several obstacles
exist to the rapid deployment and activation of xDSL equipment.
[0010] Many different xDSL and high speed access technologies
solutions have been described in public, proprietary, and/or de
facto standards. Equipment at each end of a connection may
implement one standard (or several standards) that may (or may not)
be mutually compatible. In general, startup and initialization
methods of the various standards have been heretofore
incompatible.
[0011] Line environments surrounding the xDSL data communication
schemes, such as, for example, their ability to co-exist with a
conventional analog modem that communicates within the conventional
voice band (e.g., 0-4 kHz bandwidth), differences in central office
equipment, the quality of the line, etc., are numerous, differ
significantly, and are complicated. Accordingly, it is essential to
be able to determine the capabilities of the communication channel,
in addition to being able to determine the capabilities of the
communication equipment, in order to establish an optimum and
non-interfering communication link.
[0012] User applications can have a wide range of data bandwidth
requirements. Although a user could always use the highest capacity
xDSL standard contained in a multiple xDSL box, in general, that
will be the most expensive service, since communication costs are
generally related to the available bandwidth. When a low bandwidth
application is used, the user may desire the ability to indicate a
preference for a low bandwidth xDSL (and hence, a less expensive
communication service), as opposed to using a high bandwidth xDSL
service. As a result, it is desirable to have a system that
automatically indicates user service and application requirements
to the other end of the link (e.g., central office).
[0013] In addition to the physical composition of the communication
equipment and communication channel, high speed data access
complexity is also influenced by regulatory issues. The result has
been that possible configuration combinations at each end of a
communication channel have grown exponentially.
[0014] The US Telecommunication Act of 1996 has opened the vast
infrastructure of metallic twisted wire pairs to both competitive
(CLEC) usage, and the incumbent telephone provider (ILEC) that
originally installed the wires. Thus, multiple providers may have
differing responsibilities and equipment deployed for a single wire
pair.
[0015] In a given central office termination, a given communication
channel (line) may be solely provisioned for voiceband-only, ISDN,
or one of the many new xDSL (ADSL, VDSL, HDSL, SHDSL, SDSL, etc.)
services. Since the Carterphone court decision, telephone service
users (customers) have a wide range of freedom for placing (i.e.,
installing and utilizing) communication customer premise equipment
(e.g., telephones, answering machines, modems, etc.) on voiceband
channels. However, customer premise equipment (CPE) associated with
leased data circuits has typically been furnished by the service
provider. As the high speed communication market continues to
evolve, customers will also expect and demand freedom in selecting
and providing their own CPE for high speed circuits using the band
above the traditional voice band. This will place increased
pressure on the service providers to be prepared for a wide range
of equipment to be unexpectedly connected to a given line.
[0016] The customer premise wiring condition/configuration inside
of the customer premise (e.g. home, office, etc.) and the range of
devices already attached to nodes in the wiring are varied and
unspecifiable. For a service provider to dispatch a technician
and/or craftsman to analyze the premise wiring and/or make an
installation represents a large cost. Accordingly, an efficient and
inexpensive (i.e., non-human intervention) method is needed to
provide for the initialization of circuits in the situation where a
plethora of communication methods and configuration methods
exist.
[0017] Still further, switching equipment may exist between the
communication channel termination and the actual communication
device. That switching equipment may function to direct a given
line to a given type of communication device.
[0018] Thus, a high speed data access start-up technique (apparatus
and method) that solves the various equipment, communication
channel, and regulatory environment problems is urgently
needed.
[0019] In the past, the ITU-T has published recommended methods for
initiating data communication over voice band channels.
Specifically, two Recommendations were produced:
[0020] 1) Recommendation V.8 (September 1994)--"Procedures for
Starting Sessions of Data Transmission over the General Switched
Telephone Network"; and
[0021] 2) Recommendation V.8bis (August 1996)--"Procedures for the
Identification and Selection of Common Modes of Operation Between
Data Circuit-terminating Equipments (DCEs) and Between Data
Terminal Equipments (DTEs) over the General Switched Telephone
Network".
[0022] Both Recommendations use a sequence of bits transmitted from
each modem to identify and negotiate mutually common (shared)
operating modes, such as the modulation scheme employed, protocol,
etc. However, both startup sequence Recommendations are applicable
only to conventional voice band communication methods. These
conventional startup sequences are only designed to work if both
ends of the communication are full duplex capable (V.8) or half
duplex capable (V.8bis). Since xDSL startup mechanisms may be full
duplex or half duplex, alternative procedures are needed to
initiate the startup mechanism without knowing whether the devices
are full duplex or half duplex capable. Further, it is desirable to
include a backward compatibility feature to connect with prior art
full duplex systems.
DEFINITIONS
[0023] During the following discussion, the following definitions
are employed:
[0024] activating station (calling station)--the DTE, DCE and other
associated terminal equipment which originates an activation of an
xDSL service;
[0025] answering station--the DTE, DCE and other associated
terminal equipment which answers a call placed on the PSTN
(GSTN);
[0026] carrier set--a set of one or more frequencies associated
with a PSD mask of a particular xDSL Recommendation;
[0027] CAT3--cabling and cabling components designed and tested to
transmit cleanly to 16 MHZ of communications. Used for voice and
data/LAN traffic to 10 megabits per second;
[0028] CAT5--cabling and cabling components designed and tested to
transmit cleanly to 100 MHZ of communications;
[0029] communication method--form of communication sometimes
referred to as moderns, modulations, line codes, etc.;
[0030] downstream--direction of transmission from the xTU-C to the
xTU-R;
[0031] Galf--an octet having the value 81.sub.16; i.e., the ones
complement of an HDLC flag;
[0032] initiating signal--signal which initiates a startup
procedure;
[0033] initiating station--DTE, DCE and other associated terminal
equipment which initiates a startup procedure;
[0034] invalid frame--frame that has fewer than four octets between
flags, excluding transparency octets;
[0035] message--framed information conveyed via modulated
transmission;
[0036] metallic local loop--communication channel 5, the metallic
wires that form the local loop to the customer premise;
[0037] responding signal--signal sent in response to an initiating
signal;
[0038] responding station--station that responds to initiation of a
communication transaction from the remote station;
[0039] session--active communications connection, measured from
beginning to end, between computers or applications over a
network;
[0040] signal--information conveyed via tone based
transmission;
[0041] signaling family--group of carrier sets which are integral
multiples of a given carrier spacing frequency;
[0042] slitter--combination of a high pass filter and a low pass
filter designed to split a metallic local loop into two bands of
operation;
[0043] telephony mode--operational mode in which voice or other
audio (rather than modulated information-bearing messages) is
selected as the method of communication;
[0044] transaction--sequence of messages, ending with either a
positive acknowledgment [ACT(1)], a negative acknowledgment (NA),
or a time-out;
[0045] terminal--station; and
[0046] upstream: The direction of transmission from the xTU-R to
the xTU-C.
ABBREVIATIONS
[0047] The following abbreviations are used throughout the detailed
discussion:
[0048] ACK--Acknowledge Message;
[0049] ADSL--Asymmetric Digital Subscriber Line;
[0050] CCITT--International Telegraph and Telephone Consultative
Committee;
[0051] CDSL--Consumer Digital Subscriber Line;
[0052] DSL--Digital Subscriber Line;
[0053] FSK--Frequency Shift Keying;
[0054] GSTN--General Switched Telephone Network (same as PSTN);
[0055] HDSL--High bit rate Digital Subscriber Line;
[0056] HSTU-C--handshaking portion of the xDSL central terminal
unit (xTU-C);
[0057] HSTU-R--handshaking portion of the xDSL remote terminal unit
(xTU-R).
[0058] ISO--International Organization for Standardization;
[0059] ITU-T--International Telecommunication
Union--Telecommunication Standardization Sector;
[0060] NAK--Negative Acknowledge Message;
[0061] NTU--Network Termination Unit (Customer premise end);
[0062] POTS--Plain Old Telephone Service PSD--Power Spectral
Density;
[0063] PSTN--Public Switched Telephone Network;
[0064] RADSL--Rate Adaptive DSL;
[0065] VDSL--Very high speed Digital Subscriber Line;
[0066] xDSL--any of the various types of Digital Subscriber Lines
(DSL);
[0067] xTU-C--central terminal unit of an xDSL; and
[0068] xTU-R--remote terminal unit of an xDSL.
SUMMARY OF THE INVENTION
[0069] Based on the foregoing, the overall purpose of the present
invention is to develop a communication method, modem device and a
data communication system that detects and notifies the opposite
terminal of which type of duplexing (e.g., full duplex or half
duplex) is used.
[0070] An object of the present invention is to provide a method
for performing a startup session to establish a communication
session between a first communication system (such as, for example,
a central office system) and a second communication system (such
as, for example, a remote system). A start-up procedure is
initiated by one of the first communication system and the second
communication system transmitting a signal from at least one signal
family, with the first communication system acknowledging one of a
full-duplex operating mode and a half-duplex operating mode in
response to a request by the second communication system. The first
communication system then establishes one of the full duplex
operating mode and the half duplex operating mode for further
communication that is compatible with a mode requested by the
second communication system.
[0071] Further, a phase of the transmitted signal is reversed at
predetermined time intervals.
[0072] According to a feature of the invention the first
communication system and the second communication system each
support an xDSL communication session for initiating a high speed
xDSL communication session.
[0073] According to another feature of the invention, a low-speed
(e.g., analog) communication session can be established if a
high-speed communication can not be established.
[0074] Another object of the instant invention pertains to a method
for performing a startup session to establish one of a full duplex
communication and a half duplex communication between a first
communication system (such as, for example, a central office
system) and a second communication system (such as, for example, a
remote system). A communication session (such as, for example, an
xDSL communication session) is initiated by one of the first
communication system and the second communication system in one of
a full duplex operating mode and a half duplex operating mode. A
request is issued for the communication session to be established
in one of the full duplex operating mode and the half duplex
operating mode, the request being issued by the second
communication system. The initialization of the communication
session is then completed by having the first communication system
use one of the full duplex operating mode and the half duplex
operating mode that complements a mode requested by the second
communication system.
[0075] An advantage of the instant invention is that a low-speed
communication session may be established if a high-speed
communication can not be established. The low-speed communication
session comprises a communication session occupying an approximate
4 KHz bandwidth.
[0076] According to a still further object of the invention, a
method is disclosed for performing a startup session to establish a
high speed communication session. A first communication (such as,
for example, a remote) system transmits a predetermined signal to a
second communication (such as, for example, a central office)
system, in which the first communication system and the second
communication system both support a half duplex operating mode. The
predetermined signal is detected at the second communication
system, and the second communication system responds by
transmitting a selected signal. The transmission of the
predetermined signal is halted for a predetermined time period by
the first communication system when the selected signal is detected
by the first communication system. A second predetermined signal,
indicating a half duplex operating mode, is transmitted by the
first communication system upon an expiration of the predetermined
time period, and the second communication system stops transmitting
upon detection of the second predetermined signal. The half-duplex
mode is acknowledged by the second communication system by the
turning OFF of the selected signal, so that a high speed
half-duplex mode communication session is established.
[0077] In a feature of this invention, the first communication
system and the second communication system each support a high
speed xDSL communication session.
[0078] Another feature of the invention resides in the first
communication system transmitting the predetermined signal from at
least one predetermined set of signal families.
[0079] According to an advantage of the invention, the first
communication system re-transmits the second predetermined signal
when the half-duplex mode is not acknowledged by the second
communication system, so as to re-try establishing the high-speed
half-duplex mode communication session. Further, the first
communication system may transmit a third predetermined signal when
the half-duplex mode is not acknowledged by the second
communication system, so as to try establishing a full-duplex mode
communication session.
[0080] According to another advantage of the invention, a low-speed
communication session is established if a high-speed half-duplex
mode communication session can not be established. Such a
communication session comprises a communication session occupying
an approximate 4 KHz bandwidth.
[0081] Another object of the invention pertains to disclosing a
method for performing a startup session of a high speed
communication session, in which a first communication (such as, for
example, a remote) system transmits a predetermined signal to a
second communication (such as, for example, a central office)
system, with the first communication system supporting only a half
duplex operating mode while the second communication system
supports only a full duplex operating mode. The predetermined
signal is detected at the second communication system, which
responds by transmitting a selected signal. The transmission of the
predetermined signal is halted for a predetermined time period when
the selected signal is detected by the first communication system.
A second predetermined signal, indicating a half duplex operating
mode, is then transmitted by the first communication system upon an
expiration of the predetermined time period. The first
communication system detects that the second communication system
continues to transmit the selected signal during the time when the
second predetermined signal should have been detected, and thus,
concludes that a high speed half duplex operating mode can not be
established.
[0082] The first communication system and the second communication
system may each support an xDSL (e.g., high speed xDSL)
communication session.
[0083] According to an advantage of the invention, a low-speed
communication session (occupying an approximate 4 KHz bandwidth)
can be established if the high-speed half duplex operating mode can
not be established.
[0084] A still further advantage of the invention is that a
termination signal can be transmitted by the first communication
system to terminate the startup session when the high speed half
duplex operating mode can not be established.
[0085] In an other object of the invention, a startup session of a
high speed communication is performed by having a first
communication system transmit a first predetermined signal to a
second communication system, in which the first communication
supports only a full duplex operating mode while the second
communication system supports only a half duplex operating mode.
The predetermined signal is detected at the second communication
system, which responds by transmitting a selected signal. When the
selected signal is detected by the first communication system the
transmission of the predetermined signal is halted for a
predetermined time. A second predetermined signal, indicating a
full duplex operating mode, is then transmitted by the first
communication system upon an expiration of the predetermined time
period. If the first communication system determines that the
second communication system has stopped transmitting the selected
signal after the second predetermined signal is transmitted, the
first communication system concludes that a high speed full duplex
operating mode can not be established between the first
communication system and the second communication system.
[0086] According to a feature of this invention, the first
communication system and the second communication system may each
support an xDSL (e.g., high speed xDSL) communication session.
[0087] Another feature of the invention resides in the invention
establishing a low-speed (e.g., analog) communication session if
the high speed full duplex operating mode can not be established.
The low-speed communication session preferably occupies an
approximate 4 KHz bandwidth.
[0088] A still further feature of the invention is that a
termination signal is transmitted (by, for example, the first
communication system) to complete the startup session when the high
speed full duplex operating mode can not be established.
[0089] In another object of the invention, a method is disclosed
for performing a startup session of a high speed communication, by
having a central system transmit a predetermined signal to a first
communication office system, the first communication system and the
second communication system both supporting a half duplex operating
mode; detecting the predetermined signal at the first communication
system, the first communication system responding to the second
communication system by transmitting a selected signal, indicating
a half duplex mode, to the second communication system; halting,
for a predetermined time period, the transmission of the
predetermined signal when the selected signal is detected by the
second communication system, a second predetermined signal,
indicating a half duplex operating mode, being transmitted by the
first communication system to the second communication system; and
acknowledging the half-duplex mode by the second communication
system, so that a high speed half-duplex mode communication session
is established.
[0090] Another object of the invention pertains to a method for
performing a startup session of a high speed communication, by
having a central system transmit a predetermined signal to a first
communication system, the first communication system supporting
only a half duplex operating mode while the second communication
system supports only a full duplex operating mode; detecting the
predetermined signal at the first communication system, the first
communication system responding to the second communication system
by transmitting a selected signal indicating a half duplex
operating mode; and detecting, by the first communication office
system, that the second communication system continues to transmit
the predetermined signal after the selected signal is transmitted,
the first communication system concluding that a high speed half
duplex operating mode can not be established between the first
communication system and the second communication system.
[0091] According to a feature of the invention, the first
communication system and the second communication system each
support a high speed xDSL communication session. Furthermore, a
low-speed communication session may be established if the high
speed half duplex operating mode can not be established.
[0092] A still further feature of the invention is that the first
communication system transmits a termination signal to complete the
startup session when the high speed half duplex operating mode can
not be established.
[0093] In another object of the invention, a startup session of a
high speed communication is performed by having a central system
transmit a predetermined signal to a first communication system,
the first communication system supporting only a full duplex
operating mode while the second communication system supports only
a half duplex operating mode; detecting the predetermined signal at
the first communication system, the first communication system
responding to the second communication system by transmitting a
selected signal, indicating a full duplex mode, to the second
communication system; halting the transmission of the predetermined
signal when the second communication system detects the selected
signal transmitted by the first communication system; and
determining, by the first communication system, that the second
communication system stopped transmitting the predetermined signal
after the selected predetermined signal was transmitted, the first
communication system concluding that a high speed full duplex
operating mode can not be established between the first
communication system and the second communication system.
[0094] It is noted that the first communication system and the
second communication system may each support a high speed (e.g.,
xDSL) communication session. Additionally, a low-speed
communication session may be established if the high speed full
duplex operating mode can not be established. Before establishing
the low-speed communication session, the first communication system
transmits a termination signal to complete the startup session.
[0095] The present disclosure refers to the following documents,
the subject matter of which is expressly incorporated herein by
reference in their entireties:
[0096] Recommendation V.8 (Sepetember 1994), entitled "Procedures
For Starting Sessions Of Data Transmission Over The General
Switched Telephone Network", published by Telecommunication
Standardization Sector of the ITU;
[0097] Recommendation V.8 bis (August 1996), entitled "Procedures
For The Identification And Selection Of Common Modes Of Operation
Between Data Circuit-Terminating Equipments (DCEs) and Between Data
Terminal Equipments (DTEs) Over The General Switched Telephone
Network", published by Telecommunication Standardization Sector of
the ITU;
[0098] Recommendation T.35, entitled "Procedure For The Allocation
Of CCITT Defined Codes For Non-standard Facilities", published by
Telecommunication Standardization Sector of the ITU; and
[0099] Recommendation V.34 (October 1996), entitled "A Modem
Operating At Data Signaling Rates Of Up To 33,600 bit/s For Use On
The General Switched Telephone Network And On Leased Point-To-Point
2-Wire Telephone-Type Circuits", published by Telecommunication
Standardization Sector of the ITU.
[0100] The present disclosure relates to subject matter contained
in U.S. Provisional Application No. 60/115,294, filed on Jan. 8,
1999, the subject matter of which is expressly incorporated herein
by reference in its entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0101] The foregoing and other objects, features and advantages of
the invention will be apparent from the following more particular
description of preferred embodiments, as illustrated in the
accompanying drawings which are presented as a non-limiting
example, in which reference characters refer to the same parts
throughout the various views, and wherein:
[0102] FIG. 1 illustrates a block diagram of a data communication
system using a modem device according to a first embodiment of the
present invention;
[0103] FIG. 2 illustrates a detailed block diagram of a data
communication system of FIG. 1;
[0104] FIG. 3 illustrates a startup initiated by the xTU-R, with
both the xTU-R and the xTU-C supporting the full duplex mode;
[0105] FIG. 4 illustrates a startup initiated by the xTU-C, with
both the xTU-R and the xTU-C supporting the full duplex mode;
[0106] FIG. 5 illustrates a timing sequence for deactivating a
session by either the xTU-R or the xTU-C, using full duplex
procedures;
[0107] FIG. 6 illustrates the timing sequence for deactivating a
session by either the xTU-R or the xTU-C, using half duplex
procedures;
[0108] FIG. 7 illustrates a startup initiated by the xTU-R, with
both the xTU-R and the xTU-C supporting the half duplex mode;
[0109] FIG. 8 illustrates a startup initiated by the xTU-R, with
the xTU-R supporting the half duplex mode and the xTU-C supporting
the full duplex mode;
[0110] FIG. 9 illustrates a startup initiated by the xTU-R, with
the xTU-R supporting the full duplex mode and the xTU-C supporting
the half duplex mode;
[0111] FIG. 10 illustrates a startup initiated by the xTU-C, with
both the xTU-R and the xTU-C supporting the half duplex mode;
[0112] FIG. 11 illustrates a startup initiated by the xTU-C, with
the xTU-R supporting the half duplex mode and the xTU-C supporting
the full duplex mode; and
[0113] FIG. 12 illustrates a startup initiated by the xTU-C, with
the xTU-R supporting the full duplex mode and the xTU-C supporting
the half duplex mode.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0114] The particulars shown herein are by way of example and for
purposes of illustrative discussion of embodiments of the present
invention only and are presented in the cause of providing what is
believed to be the most useful and readily understood description
of the principles and conceptual aspects of the present invention.
In this regard, no attempt is made to show structural details of
the present invention in more detail than is necessary for the
fundamental understanding of the present invention, the description
taken with the drawings making apparent to those skilled in the art
how the present invention may be embodied in practice.
[0115] According to a first embodiment of the present invention, a
data communication system comprises a central office system 2 and a
remote system 4, which are interfaced together via a communication
channel 5, as shown in FIG. 1.
[0116] The central office system 2 includes a main distribution
frame (MDF) 1 that functions to interface the central office system
2 to the communication channel 5. The main distribution frame (MDF)
1 operates to connect, for example, telephone lines (e.g.,
communication channel 5) coming from the outside, on one side, and
internal lines (e.g., internal central office lines) on the other
side.
[0117] The remote system 4 includes a network interface device
(NID) 3 that functions to interface the remote system 4 to the
communication channel 5. The network interface device (NID) 3
interfaces the customer's equipment to the communications network
(e.g., communication channel 5).
[0118] It is understood that the present invention may be applied
to other communications devices without departing from the spirit
and/or scope of the invention. Further, while the present invention
is described with reference to a telephone communication system
employing twisted pair wires, it is understood that the invention
is applicable to other transmission environments, such as, but not
limited to, cable communication systems (e.g., cable modems),
optical communication systems, wireless systems, infrared
communication Systems, etc., without departing from the spirit
and/or scope of the invention.
[0119] Basic Hardware Description
[0120] FIG. 2 illustrates a detailed block diagram of the first
embodiment of the data communication system of FIG. 1. This
embodiment represents a typical installation, in which both the
central office system 2 and the remote system 4 implement the
instant invention.
[0121] As shown in FIG. 2, the central office system 2 comprises a
low pass filter 34 and a high pass filter 38, a test negotiation
block 46, a high speed data receiving section 68, a high speed data
transmitting section 70, and a computer 82: Computer 82 is
understood to be a generic interface to network equipment located
at the central office. Test negotiation block 46 performs all of
the negotiation and examination procedures which takes place prior
to the initiation of an actual high speed data communication.
[0122] The low pass filter 34 and high pass filter 38 function to
filter communication signals transferred over the communication
channel 5. The test negotiation block 46 tests and negotiates
conditions, capacities, etc. of the central office system 2, the
remote system 4, and the communication channel 5. The procedures of
the test negotiation block 46 are completed prior to, and initiate
the selection of the high speed modem receiving and transmitting
sections (e.g., modems) 68 and 70. The high speed receiving section
68 functions to receive high speed data transmitted from the remote
system 4, while the high speed data transmitting section 70
transmits high speed data to the remote system 4. The high speed
sections 68 and 70 may comprise, but not be limited to, for
example, ADSL, HDSL, SHDSL, VDSL, CDSL modems. High speed sections
68 and 70 can be a plurality of high speed transmission devices
which "share" the common block 46 during the initial negotiation
procedure. The negotiation data receiving section 52 and the high
speed data receiving section 68 transmit signals to computer 82.
The negotiation data transmitting section 54 and the high speed
data transmitting section 70 receive signals issued from the
computer 82.
[0123] In the disclosed embodiment, test negotiation block 46
comprises a negotiation data receiving section 52 and a negotiation
data transmitting section 54. The negotiation data receiving
section 52 receives negotiation data, while the negotiation data
transmitting section 54 transmits negotiation data. The operation
of the various sections of the central office system 2 will be
described, in detail, below.
[0124] Remote system 4 comprises a low pass filter 36, a high pass
filter 40, a test negotiation block 48, a high speed data receiving
section 72, a high speed data transmitting section 66, and a
computer 84. Computer 84 is understood to be a generic interface to
network equipment located at the remote system. Test negotiation
block 48 performs all of the negotiation and examination procedures
that take place prior to the actual high speed data
communication.
[0125] The low pass filter 36 and high pass filter 40 operate to
filter communication signals transferred over the communication
channel 5. The test negotiation block 48 tests and negotiates
conditions, capacities, etc. of the central office system 2, the
remote system 4, and the communication channel 5. The high speed
receiving section 72 functions to receive high speed data
transmitted from the central office system 2, while the high speed
data transmitting section 66 transmits high speed data to the
central office system 2. The negotiation data receiving section 56
and the high speed data receiving section 72 transmit signals to
the computer 84. The negotiation data transmitting section 50 and
the high speed data transmitting section 66 receive signals issued
from the computer 84.
[0126] In the disclosed embodiment, the test negotiation block 48
comprises a negotiation data receiving section 56 and a negotiation
data transmitting section 50. The negotiation data receiving
section 56 receives negotiation data, while the negotiation data
transmitting section 50 transmits negotiation data. The operation
of the various sections of the remote system 4 will be described,
in detail, below.
[0127] The negotiation data transmitting section 50 of the remote
system 4 transmits the upstream negotiation data to the negotiation
data receiving section 52 of the central system 2. The negotiating
data transmitting section 54 of the central system 2 transmits the
downstream negotiating data to the negotiation data receiving
section 56 of the remote system 4.
[0128] The central office system 2 includes a plurality of channels
6, 10, 14, 16 and 18 that are used to communicate with a plurality
of channels 22, 26, 28, 30 and 32 of the remote system 4. In this
regard, it is noted that in the disclosed embodiment, channel 6
comprises a central voice channel that is used to directly
communicate with a corresponding remote voice channel 32 in a
conventional voice band (e.g., 0 Hz to approximately 4 kHz), which
has been filtered by low pass filters 34 and 36. Further, a remote
voice channel 33 is provided in the remote system 4 that is not
under the control of the central office system 2. Remote voice
channel 33 is connected in parallel with the communication channel
5 (but prior to the low pass filter 36), and thus, provides the
same service as the remote voice channel 32. However, since this
channel is connected prior to the low pass filter 36, the remote
voice channel 33 contains both the high speed data signal and a
voice signal.
[0129] It is noted that the filters may be arranged to have
different frequency characteristics, so that a communication may
take place using other, low band communication methods, such as,
for example, ISDN, between voice channels 6 and 32. The high pass
filters 38 and 40 are selected to ensure a frequency spectrum above
4 kHz. It is noted that some systems do not require, nor implement,
some (or all) of the filters 34, 36, 38, and 40.
[0130] Bit streams 10, 14, 16 and 18 (in the central office system
2) and bit streams 22, 26, 28 and 30 (in the remote system 4)
comprise digital bit streams that are used to communicate between
the central computer 82 and the remote computer 84, respectively.
It is understood that it is within the scope of the present
invention that bit streams 10, 14, 16, and 18 could be implemented
as discrete signals (as shown), or bundled into an interface, or
cable, or multiplexed into a single stream, without changing the
scope and/or function of the instant invention. For example, bit
streams 10, 14, 16 and 18 may be configured as (but are not limited
to) an interface conforming to a RS-232, parallel, FireWire
(IEEE-1394), Universal Serial Bus (USB), wireless, or infrared
(IrDA) standard.
[0131] Likewise, it is understood that bit streams 22, 26, 28 and
30 can be implemented as discrete signals (as shown in the
drawings), or bundled into an interface, or cable, or multiplexed
into a single stream, as described above.
[0132] Negotiation data (e.g., control information) corresponding
to the condition of the communication line (e.g., frequency
characteristics, noise characteristics, presence or absence of a
splitter, etc.), capabilities of the equipment, and user and
application service requirements is exchanged between the
negotiation data receiving section 52 and negotiation data
transmitting section 54 of the central office system 2, and the
negotiation data receiving section 56 and negotiation data
transmitting section 50 of the remote system 4.
[0133] The essential features of the hardware portion of the
invention is the functionality contained in the test negotiation
blocks 46 and 48, which test and negotiate the conditions,
capabilities, etc. of the central office system 2, the remote
system 4, and the communication channel 5. In practice, the
configuration of the central office system 2 and the remote system
4 is subject to wide variations. For example, the configuration of
the external voice channel 33 is not under the control of the same
entities that control the central office system 2. Likewise, the
capabilities and configuration of the communication channel 5 are
also subject to wide variation. In the disclosed embodiment, test
negotiation blocks 46 and 48 are embedded within modems 42 and 44.
However, the functionality of test negotiation blocks 46 and 48
may, alternatively, be implemented separate and distinct from the
modems 42 and 44. Signals transmitted and received between the test
negotiation blocks 46 and 48 are used for testing the environment
itself as well as communicating the results of the tests between
the central office system 2 and the remote system 4.
[0134] The purpose of each signal path in FIG. 2 will be explained
followed by an explanation of the devices used to create the
signals. Examples of specific values for the various frequencies
will be discussed in detail, below.
[0135] In the disclosed embodiment, frequency division multiplexing
(FDM) is utilized for various communication paths to exchange
information between the central office system 2 and the remote
system 4. However, it is understood that other techniques (such as,
but not limited to, for example, CDMA, TDMA, spread spectrum, etc.)
may be used without departing from the spirit and/or scope of the
present invention.
[0136] The range from frequency 0 Hz until frequency 4 kHz is
typically referred to as the PSTN voice band. Some of the newer
communication methods typically attempt to use the frequency
spectrum above 4 kHz for data communication. Typically, the first
frequency where transmission power is allowed occurs at
approximately 25 kHz. However, any frequency may be used. In this
regard, it is noted that tone bursts at a frequency of 34.5 kHz are
used to initiate T1E1 T1.413 ADSL moderns. As a result, if
possible, that frequency should be avoided in the spectrum used by
precursor negotiation methods.
[0137] The communication paths are defined in pairs, one path for
an upstream communication from the remote system 4 to the central
office system 2, and another path for a downstream communication
from the central office system 2 to the remote system 4 The
negotiation upstream bits are transmitted by the negotiation data
transmitting section 50 of the remote system 4, and received by the
negotiation data receiving section 52 of the central office system
2. The negotiation downstream bits are transmitted by the
negotiation data transmitting section 54 of the central office
system 2, and received by the negotiation data receiving section 56
of the remote system 4. Once the negotiation and high speed
training has been completed, the central office system 2 and the
remote system 4 use high speed data transmitting sections 66 and
70, and high speed data receiving sections 72 and 68 to perform a
duplex communication.
[0138] All messages in the present invention are sent with one or
more carriers using, for example, a Differential (Binary) Phase
Shift Keying (DPSK) modulation. The transmit point is rotated 180
degrees from the previous point if the transmit bit is a 1, and the
transmit point is rotated 0 degrees from the previous point if the
transmit bit is a 0. Each message is preceded by a point at an
arbitrary carrier phase. The frequencies of the carriers, and the
procedures for starting the modulation of carriers and messages,
will be described below.
[0139] The present invention goes to great lengths, both before the
handshake procedure is performed and during the handshake
procedure, to be spectrally polite or as non-obtrusive as possible.
Carriers are typically selected so as to be different for the
upstream and downstream paths, avoid existing system activation
tones, be reasonably robust against inter-modulation products, have
sufficient spacing, etc. Some suitable sets of carrier tones using
4.3125 kHz and 4.0 kHz base frequencies, are shown below:
1 Upstream Downstream Signal Frequency Indices Frequency Indices
Designation (N) (N) A43 9 17 25 40 56 64 B43 37 45 53 72 88 96 C43
7 9 12 14 64 A4 3 5 B4 4 28 34 66 67 76
[0140] After the remote system 4 analyzes the equipment
capabilities, the application desires, and the channel limitations,
it makes a final decision on the communication method to use.
[0141] After the central office system 2 has received the final
decision, the transmission of the negotiation downstream data is
stopped. When the remote system 4 detects the loss of energy
(carrier) from the central office system 2, the remote system 4
stops transmitting the negotiation upstream data. After a short
delay, the negotiated communication method begins it's
initialization procedures.
[0142] Startup Protocol
[0143] Either the central office (xTU-C) system 2 or the remote
(xTU-R) system 4 may initiate modulation channels. Once the
negotiation modulation channels have been established, the remote
station is always considered the initiating modem (in terms of the
transaction messages), and the central office terminal is
considered the responding station.
[0144] In the following description, characteristics of the
transmitted signals are distinguished and identified by the way the
signals are named. Various prefixes and suffixes are added to
distinguish between a location on a time sequence and which unit is
sending the signal.
[0145] TONE (singular)--unmodulated carriers from one carrier
family.
[0146] TONES (plural)--unmodulated carriers from one or more
carrier families.
[0147] TONES-REQ (plural)--unmodulated carriers with periodic phase
reversals from one or more carrier families.
[0148] FLAGS--hex character "7E" sent with modulated carriers
[0149] GALF--hex character "81" sent with modulated carriers.
(inverse of "7E").
[0150] Further, FIGS. 3-12 show two time periods; .tau..sub.1 and
.tau..sub.2. In the disclosed invention, .tau..sub.1 is less than
approximately 500 ms, and may be, for example, approximately 100
ms. Similarly, in the disclosed invention, .tau..sub.2 is greater
than approximately 50 ms but less than approximately 500 ms.
However, it is understood that different time periods can be
employed for .tau..sub.1 and .tau..sub.2 without departing from the
spirit and/or scope of the invention.
[0151] xTU-R Initiates Startup--xTU-R And xTU-C Both Support Full
Duplex Mode
[0152] In the prior art, both the central office and the remote
system communicate with each other in a full duplex mode. FIG. 3
illustrates a timing sequence for an example in which the xTU-R
initiates a startup procedure, in which both devices operating in a
full duplex mode. As shown in FIG. 3, the xTU-R initiates the
startup procedure by transmitting signals from one (or both) of its
signal families (R-TONES-REQ), with a phase reversal occurring
approximately every 16 ms. When the R-TONES-REQ signal is detected
by the xTU-C, the xTU-C responds by transmitting signals from one
(or both) of its signal families (C-TONES). When the C-TONES signal
is detected by the xTU-R, the xTU-R stops transmitting (e.g.,
transmits silence) for a predetermined time period .tau..sub.2,
such as, for example, between approximately 50 ms to approximately
500 ms, and then transmits signals from only one signal family
(R-TONE1). When the xTU-C detects the R-TONE1 signal, it responds
by transmitting C-GALF1 (hex character "81") on the modulated
carriers. The xTU-R receives the C-GALF1 characters, and responds
by transmitting R-FLAG1 flags (hex character "7E") on modulated
carriers. After R-FLAG1 flags are received by the xTU-C, the xTU-C
responds by transmitting C-FLAG1 Flags. When the xTU-R has received
the C-FLAG I Flags transmitted from the xTU-C, the xTU-R can begin
a first transaction.
[0153] xTU-C Initiates Startup--xTU-R And xTU-C Both Support Full
Duplex Mode
[0154] FIG. 4 illustrates a timing sequence for a prior art example
in which the xTU-C and the xTU-R communicate with each other in the
full duplex mode, and the xTU-C initiates the startup procedure. In
this example, the xTU-C starts by transmitting signals from one (or
both) of its signal families (C-TONES). When the C-TONES signal is
detected by the xTU-R, the xTU-R responds by transmitting signals
from only one signal family (R-TONE1). When the xTU-C detects the
R-TONE1 signal, the xTU-C responds by transmitting C-GALF1 GALFs
(hex character 81) on the modulated carriers. When the C-GALF1
GALFs characters are received by the xTU-R, the xTU-R responds by
transmitting R-FLAG1 Flags (hex character 7E) on the modulated
carriers. Once the R-FLAG1 Flags are received by the xTU-C, the
xTU-C responds by transmitting C-FLAG1 Flags. The xTU-R receives
the C-FLAG1 Flags, and can begin the first transaction.
[0155] Prior art systems have been unable to establish a
communication session when the operating mode of the central office
system and the remote system differ. The present invention
discloses a scheme for addressing this problem. The specific
procedure depends on which device (e.g., the xTU-C or the xTU-R)
initiates the activation sequence, and the full duplex/half duplex
capabilities of each device. The initialization signals and process
of the instant invention is fully backward compatible with the
existing prior art equipment, and will be described below. This
backward compatibility between the equipment of the present
invention and the prior art handshake equipment (that only support
the full duplex mode), is an important feature of the instant
invention.
[0156] The various initiation startup sessions addressed by the
current invention, to be described below, include:
[0157] (a) Startup initiated by xTU-R, where both the xTU-R and the
xTU-C support the half duplex mode, as illustrated in FIG. 7;
[0158] (b) Startup initiated by xTU-R, where the xTU-R only
supports the half duplex mode and the xTU-C supports only the full
duplex mode, as illustrated in FIG. 8;
[0159] (c) Startup initiated by xTU-R, where the xTU-R only
supports the full duplex mode and the xTU-C only supports the half
duplex mode, as illustrated in FIG. 9;
[0160] (d) Startup initiated by xTU-C, where both the xTU-R and the
xTU-C support the half duplex mode, as illustrated in FIG. 10;
[0161] (e) Startup initiated by xTU-C, where the xTU-R only
supports the half duplex mode and the xTU-C only supports the full
duplex mode, as illustrated in FIG. 1; and
[0162] (f) Startup initiated by xTU-C, where the xTU-R only
supports the full duplex mode and the xTU-C only supports the half
duplex mode, as illustrated in FIG. 12.
[0163] An xTU-R indicates it desires to conduct a transaction in
full duplex mode by responding to C-TONES with R-TONE1 instead of
R-FLAG1. An xTU-R indicates it desires to conduct a transaction in
half duplex mode by responding to C-TONES with R-FLAG1 instead of
R-TONE1.
[0164] xTU-R Initiates Startup--xTU-R And xTU-C Both Support Half
Duplex Mode
[0165] FIG. 7 illustrates the situation in which the xTU-R
initiates the startup sequence, and both the xTU-R and the xTU-C
support the half duplex mode. The xTU-R begins transmitting signals
from one (or both) of its signal families (R-TONES-REQ), with phase
reversals occurring at predetermined time intervals, such as, for
example, approximately every 16 ms. When the R-TONES-REQ signal is
detected by the xTU-C, the xTU-C responds by transmitting signals
from one (or both) of its signal families (C-TONES). When the
C-TONES signal is detected by the XTU-R, the xTU-R stops
transmitting (e.g., transmits silence) for a predetermined period
of time .tau..sub.1, such as, for example, approximately 50 ms to
approximately 500 ms. Then, the xTU-R transmits signals from one
signal family (R-FLAG1) for a selected period of time .tau..sub.1,
such as, for example, at least 100 ms, until the xTU-C turns off
the C-TONES signal. After the last R-FLAG1 flag is transmitted, the
xTU-R continues sending the message, followed by at least two flags
(R-FLAG-HD2). When the xTU-C detects R-FLAG-HD2, it responds by
transmitting flags (C-FLAG-HD) for a certain time period, such as,
for example, approximately 100 ms. After the last flag has been
transmitted, the xTU-C continues sending the message, followed by
at least two flags (C-FLAG-HD2). If the xTU-C message was an ACK,
the xTU-R begins the selected mode initialization sequence. On the
other hand, if the ATU-C message was not an ACK, the xTU-R resumes
transmitting R-FLAG I (above), and continues as described above.
Likewise, the xTU-C prepares to receive R-FLAG1, and continues as
described above.
[0166] xTU-R Initiates Startup--xTU-R Only Supports Half Duplex
Mode and xTU-C Only Supports Full Duplex Mode
[0167] FIG. 8 illustrates the situation in which the xTU-R
initiates the startup sequence, with the xTU-R supporting only the
half duplex mode and the xTU-C supporting only the full duplex
mode. The xTU-R begins transmitting signals from one (or both) of
its signal families (R-TONES-REQ), with phase reversals occurring
every predetermined time interval, such as, for example,
approximately every 16 ms. When the R-TONES-REQ signal is detected
by the xTU-C, the xTU-C responds by transmitting signals from one
(or both) of its signal families (C-TONES). When the C-TONES signal
is detected by the xTU-R, the xTU-R stops transmitting (e.g.,
transmits silence) for a predetermined period of time r, such as,
for example, approximately 50 ms to approximately 500 ms. Then, the
xTU-R transmits signals from a signal family (R-FLAG1) for a
selected period of time .tau..sub.1, such as, for example, at least
100 ms.
[0168] Since the xTU-C operates only in the full duplex mode, the
xTU-C does not transmit a C-GALF signal, nor does it turn off the
C-TONES signal it has been transmitting. Instead, the xTU-C
continues to transmit the C-TONES signal. Because the xTU-R does
not see the end of the C-TONES signal, the xTU-R concludes that the
xTU-C cannot support the half duplex mode. Accordingly, the xTU-R
transmits at least 2 octets of the R-GALF Galfs signal to terminate
the session, and then stops transmitting. Since the xTU-C sees the
R-GALF Galfs signal, the xTU-C stops transmitting the C-TONES
signal, and the startup session is over.
[0169] XTU-R Initiates Startup--xTU-R Only Supports Full Duplex
Mode And xTU-C Only Supports Half Duplex Mode
[0170] FIG. 9 illustrates the situation in which the startup
session is initiated by the xTU-R, in which the xTU-R supports only
a full duplex mode and the xTU-C supports only a half duplex mode.
The xTU-R begins the session by transmitting signals from one (or
both) of its signal families (R-TONES-REQ), with phase reversals
occurring every predetermined time interval, such as, for example,
approximately every 16 ms. When the R-TONES-REQ signal is detected
by the xTU-C, the xTU-C responds by transmitting signals from one
(or both) of its signal families (C-TONES). When the C-TONES signal
is detected by the xTU-R, the xTU-R stops transmitting (e.g.,
transmits silence) for a predetermined period of time .tau..sub.2,
such as, for example, approximately 50 ms to approximately 500 ms.
After the predetermined period of time elapses, the xTU-R transmits
signals from a signal family (R-TONE1) for a selected period of
time .tau..sub.1, such as, for example, at least 100 ms.
[0171] Since the xTU-C operates only in the half duplex mode, the
xTU-C turns off the C-TONES signal it has been transmitting. Since
the xTU-R does not see a C-GALF signal within a suitable time
period, but can detect a transmission energy drop (e.g., that the
transmission of data has stopped), the xTU-R concludes that the
xTU-C cannot support the full duplex mode. Accordingly, the xTU-R
transmits at least 2 octets of the R-GALF signal, and stops
transmitting. At this point, the startup session is completed.
[0172] xTU-C Initiates Startup--xTU-R And xTU-C Only Support Half
Duplex Mode
[0173] FIG. 10 illustrates the situation where the startup is
initiated by xTU-C, with the xTU-R only supporting the half duplex
mode and the xTU-C only supporting the half duplex mode. The xTU-C
beings transmitting signals from one (or both) of its signal
families (C-TONES). When the C-TONES signal is detected by the
xTU-R for a predetermined period of time .tau..sub.2, such as, for
example, approximately 50 ms to approximately 500 ms, the xTU-R
transmits signals from one signal family (R-FLAG1) for a selected
period of time .tau..sub.1, such as, for example, at least
approximately 100 ms, until the xTU-C turns off the C-TONES signal.
After the last flag has been transmitted, the xTU-R continues
sending the message, followed by at least two flags (R-FLAG-HD2).
When the xTU-C detects the R-FLAG-HD2 signal, the xTU-C begins
transmitting flags (C-FLAG-HD) for a period of, for example,
approximately 100 ms. After the last flag is transmitted, the xTU-C
continues sending the message, followed by at least two flags
(C-FLAG-HD2).
[0174] If the xTU-C message was an ACK, the xTU-R begins the
selected mode initialization sequence. On the other hand if the
xTU-C message was not an ACK, the xTU-R continues to transmit the
R-FLAG I (described above), and continues as described above. In a
similar fashion, the xTU-C prepares to receive the R-FLAG1 signal,
and continues as above. The xTU-R terminates the session with the
ACK signal.
[0175] xTU-C Initiates Startup--xTU-R Only Supports Half Duplex
Mode and xTU-C Only Supports Full Dupex Mode
[0176] FIG. 11 illustrates the situation where the startup is
initiated by xTU-C, with the xTU-R only supporting the half duplex
mode and the xTU-C only supporting the full duplex mode. The xTU-C
begins transmitting signals from one (or both) of its signal
families (C-Tones). When the C-Tones signal is detected by the
xTU-R for a predetermined period of time .tau..sub.2, such as, for
example, from approximately 50 to approximately 500 ms, the xTU-R
transmits flag signals from a signal family (R-FLAG1) for a
selected period of time .tau..sub.1, such as, for example, at least
100 ms. Since the xTU-C only supports the full duplex mode, the
xTU-C does not transmit a C-GALF signal, nor does the xTU-C turn
off the C-TONES signal. Instead, the xTU-C continues transmitting
the C-TONES signal. As a result, the xTU-R does not detect (see)
the end of the C-TONES signal, and concludes that the xTU-C cannot
support the half duplex mode. Accordingly, the xTU-R transmits at
least 2 octets of R-GALF, and then stops transmitting. The xTU-C
detects the R-GALF, stops transmitting the C-TONES signal, and the
session is completed.
[0177] xTU-C Initiates Startup--xTU-R Only Supports Full Duplex
Mode While xTU-C Only Supports Half Duplex Mode
[0178] FIG. 12 illustrates the situation when the startup sequence
is initiated by the xTU-C, with the xTU-R only supporting the full
duplex mode and the xTU-C only supporting the half duplex mode. The
xTU-C begins transmitting signals from one (or both) of its signal
families (C-TONES). When the C-TONES signal is detected by the
xTU-R for a predetermined period of time .tau..sub.2, such as, for
example, approximately 50 ms to approximately 500 ms, the xTU-R
responds by transmitting signals from a signal family (R-TONE1) for
a selected period of time .tau..sub.1, such as, for example, at
least approximately 100 ms. Since the xTU-C only supports the half
duplex mode, it stops transmitting (turns off) the C-TONES signal.
The xTU-R does not detect C-GALF prior to the occurrence of a
suitable timeout, but does detect the energy drop (e.g.,
non-transmission of the C-TONES signal). Accordingly, the xTU-R
concludes that the xTU-C cannot support the full duplex mode, and
transmits 2 octets of R-GALF, after which the xTU-R ceases its
transmission, completing the startup session.
[0179] In each of the above descriptions, the startup session is
eventually terminated. FIG. 5 displays the timing for deactivating
a session by either the xTU-R or the xTU-C using fill duplex
procedures. When the xTU-R (or the xTU-C) has completed sending an
MS (mode select) message, it begins to transmit the Flag (hex "7E")
characters. When the xTU-C (or the xTU-R) receives the MS message,
the xTU-C (or the xTU-R) stops sending the Flag characters and
sends an ACK(1) message. When the xTU-R (or the xTU-C) receives the
ACK(1) message, the xTU-R (or the xTU-C) sends a single GALF octet
(hex "81"), stops transmitting data (e.g., transmits silence) and
exits to the selected operating mode. When the xTU-C (or the xTU-R)
receives either the GALF character or detects the period of
silence, the xTU-C (or the xTU-R) stops transmitting data (e.g.,
transmits silence) and also exits to the selected operating
mode.
[0180] FIG. 6 displays the timing for deactivating a session by
either the xTU-R or the xTU-C using half duplex procedures. The
procedure is similar to that described above for the full duplex
procedure. Specifically, the xTU-R (or the xTU-C) sends an ACK(1)
message. When the xTU-R (or the xTU-C) receives the ACK(1) message,
the xTU-R (or the xTU-C) stops transmitting data (e.g., transmits
silence), sends a single GALF octet (hex "81"), and exits to the
selected operating mode. When the xTU-C (or the xTU-R) detects the
period of silence, the xTU-C (or the xTU-R) stops transmitting data
(e.g., transmits silence) and also exits to the selected operating
mode.
[0181] After the handshake session has been initiated, and before
it is terminated, one or more transactions are used to exchange
data between the xTU-C and the xTU-R. Each transaction consists of
one or more messages which contain data and/or requests, and then
concludes with an acknowledgment message (or a
negative-acknowledgment message). The data includes, but is not
limited to, for example: equipment capabilities, channel
capabilities, available modes of operation, user requests,
application requests, and service requests. Requests may include,
but are not limited to, for example: requested mode of operation,
requested data rates, and requested protocol. The unit responding
to a message indicates an acceptance (with an acknowledgment
message), a rejection (with a negative-acknowledgment message), or
a desire to initiate a different type of message with a request
message. Depending on the response, a unit may initiate another
transaction or terminate the handshake session. An acknowledgment
to a mode selection message will cause the handshake session to be
terminated, and the communication mode selected in the mode
selection message to be initiated, using known techniques.
[0182] During the message transmission, several categories of
information are transmitted. The categories include, but are not
limited to, for example: Identification of Service Parameters and
Channel Capabilities; Standard Information of Modulations and
Protocols; and Non-standard information, which is proprietary to
the implementation or manufacturer. The information is specific to
communication methods, as well as generically described
information. Analysis of the information by each terminal enables
selection of the communication mode and parameters for an optimized
communication.
[0183] Examples of Identification information include, but are not
limited to, for example: message type; vendor identification;
amount and type of bandwidth; splitter information; spectrum usable
frequencies; and number of data channels.
[0184] Examples of Standard Information include, but are not
limited to for example: types of xDSL standards supported, regional
considerations, and xDSL modulation parameters; error correction
protocol information; data compression protocol information; and
other protocol information. The methods for generating and
analyzing the information content is well known by those skilled in
the art, and thus, is not discussed herein.
[0185] The information content of the messages must be encoded in a
consistent, scalable, and extensible manner so as to promote
interoperability among equipment and compatibility with future
equipment and services. The prior art (e.g., V.8, V.8bis) provides
general examples of means to frame and format handshaking data.
Handshaking for xDSL modems also require the transmission of new
data types, such as variables and multiple resolution parameters.
Examples of encoding mechanism are given below. Specific names and
encodings of parameters are dependent on the particular high speed
communication system being used.
[0186] Table 1 illustrates how to encode a small integer
variable:
2TABLE 1 Number of segments octet Segments NPar(3)s 8 7 6 5 4 3 2 1
Unspecified by terminal x x 0 0 0 0 0 0 # segments (bits 6-1) x x x
x x x x x Reserved for allocation by the x x 1 1 1 1 1 1 ITU-T
[0187] Table 2 illustrates how to encode a variable with a range
larger than the number of bits:
3TABLE 2 Duration octet Data rate NPar(3)s 8 7 6 5 4 3 2 1 Duration
(bits 6-1 .times. 5 ms) x x x x x x x x Reserved x x 1 1 1 1 1
1
[0188] Table 3 illustrates how to encode a parameter with
multi-resolutions. Bit 6 is used to indicate the multiplying factor
for bits 1 through 5. Additionally, a special code is used to
indicate a data rate that is not a multiple of 32 nor 64
kbit/sec:
4TABLE 3 Training parameters - Octet 2 - NPar(3) coding Data rate
NPar(3)s 8 7 6 5 4 3 2 1 Unspecified by terminal x x 0 0 0 0 0 0
Data rate (bits 5-1 .times. 32 kbit/s) x x 0 x x x x x Data rate x
x 1 x x x x x (bits 5-1 .times. 64 kbit/s + 1024 kbit/s) Data rate
1544 kbit/s x x 1 1 1 1 1 0 Reserved x x 1 1 1 1 1 1
[0189] As discussed above, the handshaking procedures must be
capable of supporting a wide range of equipment types, including
equipment designed and deployed before the present invention, such
as, but not limited to, for example, equipment based on ANSI T1.413
or ITU-T V.34. In addition to interoperating with full duplex and
half duplex equipment, the instant invention also implements
procedures to recognize and function with "legacy" equipment.
Legacy equipment can be implicitedly activated by manipulating, for
example, a specific escape sequence. With implicit activation, a
device supporting the invention will monitor for legacy activation
signals, and will transmit legacy activation signals if there are
no responses to the handshaking activation signals. In addition to
legacy xDSL equipment, a terminal may communicate with voiceband
equipment by supporting voiceband standards, indicating the
availability thorough the information fields, and then escaping to
voiceband standard activation signaling methods.
[0190] It is noted that the foregoing examples have been provided
for the purpose of explanation, and are in no way to be construed
as limiting the present invention. While the present invention has
been described with reference to an exemplary embodiment, it is
understood that the words which have been used herein are words of
description and illustration, rather than words of limitation.
Changes may be made, within the purview of the appended claims, as
presently stated and as amended, without departing from the scope
and spirit of the present invention in its aspects. Although the
present invention has been described herein with reference to
particular means, materials and embodiments, the present invention
is not intended to be limited to the particulars disclosed herein;
rather, the present invention extends to all functionally
equivalent structures, methods and uses, such as are within the
scope of the appended claims.
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