Telephonic communications – Telephone line or system combined with diverse electrical... – Having transmission of a digital message signal over a...
Reexamination Certificate
2000-05-12
2003-06-03
Isen, Forester W. (Department: 2644)
Telephonic communications
Telephone line or system combined with diverse electrical...
Having transmission of a digital message signal over a...
C379S093060, C370S216000
Reexamination Certificate
active
06574313
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a Voice over DSL (VoDSL) architecture for supporting a “lifeline” service. More particularly, the present invention is directed to a system and method for providing a telephone service to a VoDSL customer despite an electrical power outage or integrated access device failure at the customer premise.
BACKGROUND OF THE INVENTION
Due to recent changes in the telecommunications industry (i.e., deregulation of local markets) and recent advancements in technologies that better utilize the existing copper loop infrastructure, digital subscriber line (DSL) is one of the most promising technologies for delivering viable low-cost, high-speed data to many business and residential customers. As is well known, DSL uses the existing copper loop that is traditionally used for conventional telephony to deliver voice and data at high bandwidth. DSL carries both voice and data signals simultaneously, in both directions, allowing a customer to log onto the Internet and make a telephone call at the same time. In other words, since DSL uses packet switching technology that operates independently of the voice telephone system, this allows telephone companies to provide Internet service and not lock up circuits for telephone calls. Thus, it is easy to understand why DSL technology is becoming the preferred method for sending/receiving both voice and digital data/signals in the telecommunications industry.
As is well known, there are different competing forms of digital subscriber line technologies collectively designated as xDSL technologies with the “x” representing various one or more letter combinations, which are used in front of the “DSL” acronym to designate the type of technology being used. Some of the more prevalent xDSL technologies include HDSL, ADSL, SDSL, RADSL, VADSL, and VDSL.
One particular technology known as Voice over DSL (VoDSL) provides multiple phone channels to be delivered over a DSL line, which itself is delivered over a single copper pair. Using VoDSL, multiple services—voice, data, fax, video conferencing, etc.—can be delivered over the single copper pair. In other words, by enabling up to, for example, 24 telephone channels (can be more or less than 24) and high-speed Internet access (typically at speeds up to 1.5 megabits per second) to be delivered over a single DSL connection, VoDSL systems allow service providers to apply DSL broadband access networks to small to mid-size business markets and residential homes. VoDSL essentially turns one copper pair into multiple telephone channels and one high-speed data channel. This substantially lowers the infrastructure cost for delivering such services when compared to T1 lines or multiple copper pairs.
FIG. 1
illustrates a simplified diagram of a conventional VoDSL architecture. In the conventional architecture, a regional switching center is connected to a customer premise (residential, business, small office/home office—SOHO, etc.) via a central office (CO) and a copper loop
10
(pair of copper wires). In the customer premise, an integrated access device (IAD)
12
(perhaps in a wiring closet) is connected to a data terminal such as the PC and multiple voice terminals such as telephones PH-
1
, . . . , PH-m, where m is some arbitrary number of channels/telephones. As known, the IAD
12
delivers both voice and data services to the customer and is described in greater detailer later herein.
The IAD
12
is connected to a DSL access multiplexer (DSLAM)
8
at the CO via the copper loop
10
. As known, the DSLAM
8
generally receives incoming DSL signals and aggregates the traffic onto high-speed uplink trunks such as DS
3
or SONET optical link.
In the regional switching center, an ATM (asynchronous transfer mode) switch
6
is connected to the DSLAM
8
via the high speed trunk such as DS
3
or SONET optical link. ATM is a high-speed networking standard used in WANs and often used to route DSL traffic to the Internet backbone. One ATM switch
6
can be connected to many DSLAMs (hundreds, thousands)
8
, which in turn, can support many IADs
12
. The ATM switch
6
is further connected to a data network (e.g., Internet) and a public switched telephone network (PSTN) via a voice gateway
4
and a Class 5 voice switch (C5)
2
.
The C5 switch
2
, gateway
4
, ATM switch
6
, and DSLAM
8
are well known in the industry and thus will not be discussed in great detail. Communication interface between the gateway
4
and the C5 switch
2
is through an interface standard such as TR-303 or TR-008. The TR-303 and TR-008are standard interfaces developed for the North America PSTN for inter-working of voice switches and digital loop carrier (DLC) systems.
The C5 switch
2
, gateway
4
, ATM switch
6
, DSLAM
8
, and IAD
12
are conventionally known as network elements in the reference model for the conventional architecture. The IAD
12
is not an independent network element per se, but rather a subtending subsystem to the gateway
4
. Thus, the gateway
4
and the subtending IAD
12
form an independent network element. Each gateway
4
and C5 switch
2
can support multiple IADs
12
, depending on their capacities.
Associated with each network element is a software program generically known as an element management system (EMS), which manages the operation of each network element. The operation, administration, and maintenance (OAM) functions of the VoDSL network is performed by an operation support system (OSS) which supports the C5 switch
2
, and works in conjunction with the EMSs for managing the gateway
4
and DSLAM
8
. The OSS controls and coordinates all the network elements.
During operation, the IAD
12
receives, digitizes, packetizes, compresses the voice and data signals and formats them for transmission from the customer. The IAD
12
then sends the voice and data signals out in separate virtual circuits, with the voice circuit getting priority. Virtual circuits are connected to the DSLAM
8
, which combines virtual circuits from multiple customers and/or IADs
12
and send them to the ATM switch
6
in the regional switching center. The ATM switch
6
then sends the data signals to the data network such as the Internet and the voice signals to the voice gateway
4
. The gateway
4
decompresses and depacketizes the signals and sends them to the C5 switch
2
, which signals are then sent to the PSTN.
Conversely, when the signals are sent from the regional switching center to the customer premise, the gateway
4
receives digital voice signals and formats them into packets for transmission to the ATM switch
6
. The ATM switch
6
also receives data signals from the data network. These signals are then sent to the IAD
12
through the DSLAM
8
and copper loop
10
. The IAD
12
receives the signals and distributes them to the proper terminals.
FIG. 2
illustrates a more detailed diagram of a DSLAM and IAD in the conventional VoDSL architecture of FIG.
1
. In greater detail, the DSLAM
8
consists of an ATM interface block (AIB)
20
connected to n-number of ADSL (xDSL) termination unit-CO (ATU-C)
22
a
,
22
i
,
22
n
. Each ATU-C
22
a
,
22
i
,
22
n
is further connected to a loop pair (pair-
1
, pair-i, pair-n), which terminates at a corresponding IAD-
1
12
a
, IAD-i
12
i
, IAD-n
12
n
. As can be appreciated, there will be n-number of IADs corresponding to n-number of ATU-Cs and loop pairs.
Using IAD-i
12
i
as an example, it consists of an ADSL (xDSL) termination unit-remote (ATU-R)
30
or similar unit that is further connected to a service interface block (SIB)
32
. The SIB
32
, which distributes signals to different terminals, is further connected to a data module (DM)
34
for high speed data service to the data terminal (PC) and to m-number of phone modules PM
1
36
-
1
, PMm
36
-
m
, which are connected to multiple telephones PM-
1
, PM-m, respectively. Currently, m can be any arbitrary number such as 14, 16, 24, so long as the system components can support the m number of telephone lines. Accordingly, the IAD-i
12
i
typically supports one
Chea, Jr. Ramon C. W.
Duffie P. Kingston
Isen Forester W.
Pillsbury & Winthrop LLP
Singh Ramnandan
Turnstone Systems, Inc.
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