Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1998-08-24
2002-11-12
Marcelo, Melvin (Department: 2663)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S494000
Reexamination Certificate
active
06480487
ABSTRACT:
BACKGROUND OF THE INVENTION
TECHNICAL FIELD
The present invention relates to remote terminals for use in digital loop carrier transmission systems, more specifically to terminals configured for providing broadband services such as video and high speed data to subscribers in the digital loop carrier serving area.
DESCRIPTION OF RELATED ART
Public switched telephone networks have served subscribers by transporting telephone signals between a central office and customer premises equipment using a subscriber loop, also referred to as the local loop. The local loop is composed of wires, poles, terminals, conduits, and other outside plant that connect customer premises equipment to the central office of the local exchange carrier. The distance that a copper subscriber loop can be extended from a given central office can be many thousands of feet.
Loop carrier systems have been developed to improve the economics of loop deployment for services such as POTS and ISDN in a given central office. In subscriber loop carrier (SLC) systems, such as digital loop carrier (DLC) systems, bidirectional communication usually occurs between a central office (e.g., a local digital switch), a central office terminal (COT) and a remote terminal (RT), located in the vicinity of a customer's premises. Information is transferred between the central office and the COT according to Bellcore TR-008, TR-57, and TR-303 interface standards. Information between the COT and RT is carried as 64 kb/s encoded digital channels multiplexed on an optical transport, for example an OC-3 SONET transport. The remote terminal includes optical to electrical interfaces for converting the OC-3 signal from the incoming optical fiber into an electrical signal, and a demultiplexer for demultiplexing the 64 kb/s digital telephone channels, which are directed to telephone line cards. Each telephone line card is usually configured to serve several customers, according to either POTS or ISDN protocol via respective copper pairs supplying two-way telephone signals to respective subscriber premises equipment.
Proposals have been suggested for utilizing the digital loop carrier infrastructure to provide transmission of broadband data, for example high speed data, multimedia or video services. One proposal suggests reserving a portion of the OC-3 transport capacity of the optical fibers between the COT and the remote terminal for broadband data, where a second broadband facility is output from the remote terminal to an adjacent remote terminal. Alternatively, a fiber may be run from the central office to the second remote terminal direct from the central office. In either case, the second terminal has asymmetrical digital subscriber line (ADSL) modem or other broadband line cards. The broadband data is passed via the second broadband facility, e.g. from the first remote terminal (having telephone line cards), to the second remote terminal (having broadband line cards) to modulate the broadband data onto the subscriber loops.
Such an arrangement, however, suffers from the disadvantage that an additional remote terminal must be installed adjacent to the existing remote terminal providing telephone service. This arrangement involves substantially increased costs associated with the expense of an additional remote terminal, plus legal issues involving the necessity of additional right-of-way for the additional remote terminals. Moreover, the ADSL modem cards cannot be connected to the corresponding subscriber loops without providing a tap between each of the twisted wire pair connections between the first remote terminal and the second remote terminal. This further increases costs due to manual rewiring and decreased stability due to substantially complex twisted pair connections.
U.S. Pat. Nos. 5,534,912 to Kostreski and 5,608,447 to Farry et al., the disclosures of which are incorporated in their entirety by reference, illustrate video networks that use ADSL modems for supplying broadband video data to a subscriber. For example,
FIG. 4
of U.S. Pat. No. 5,534,912 to Kostreski discloses ADSL “muldems” that modulate video signals onto different frequencies and a frequency combiner
320
that outputs the modulated video signals as a combined spectrum to an intermediate distribution point
330
via a fiber plant. The intermediate distribution point
330
includes a plurality of ADSL filter/combiners
355
. Each ADSL filter/combiner unit
355
receives a copper twisted wire pair for a selected subscriber from the standard telephone facilities
365
, frequency multiplexes the telephone signals with the ADSL-modulated signals, and supplies the frequency multiplexed signals to the subscriber premises
360
via a copper twisted wire pair. The remote ADSL unit
305
′ at the subscriber location
360
receives and demultiplexes the various telephone, video, and embedded operations channel (EOC) and control signals for use as required.
U.S. Pat. No. 5,608,447 to Farry et al. discloses in
FIG. 11
an intelligent access peripheral (IAP) having an ADSL unit that frequency multiplexes broadband data onto subscriber loops. In particular, the IAP has a first port that receives broadcast video in ATM cell format from a broadcast headend, a second port that receives a second ATM cell stream carrying non-broadcast (point-to-point) data, and a third port that receives a copper pair (POTS) connection from a POTS switch. The IAP extracts the ATM cell streams from the first and second ports, and outputs digital video information and the telephone signals (POTS or ISDN) to the subscriber premises.
As is apparent from the foregoing, both U.S. Pat. Nos. 5,534,912 to Kostreski and 5,608,447 to Farry et al. require a separate distribution component (e.g., intermediate distribution point
330
or IAP) that requires a twisted pair connection from a POTS switch in order to multiplex digital video data with the corresponding telephone signals for transmission as a combined spectrum signal to a subscriber. As described above, these broadband distribution points, if implemented in a digital loop carrier serving area, would still require installation of the broadband distribution unit in addition to the existing remote terminal. Moreover, the broadband distribution units would still require a tap between each of the twisted wire pair connections from the remote terminal to the broadband distribution units in order to provide telephone service. Hence, the Kostreski and Farry et al. patents still suffer from the disadvantage of requiring a second distribution unit in addition to an existing remote terminal, plus the necessity of a tap between each of the twisted pair connections between the original remote terminal and the broadband distribution units.
SUMMARY OF THE INVENTION
There is a need for an arrangement for adding broadband services in an existing digital loop carrier system having a remote terminal configured for transporting information between a central office and the subscriber premises by respective subscriber loops, in a manner that avoids installation of additional remote terminals within the digital loop carrier system.
There is also a need for an arrangement that enables transport of broadband data in a digital loop carrier system, without requiring labor-intensive taps to be installed between POTS line interface cards and separate xDSL equipment.
There is also a need for providing broadband data services to subscribers in a digital loop carrier serving area, without the necessity of installing a separate distribution infrastructure to the subscriber premises equipment for the broadband data services.
These and other needs are attained by the present invention, where a remote terminal configured for providing communication between a central office and subscriber premises equipment within a digital loop carrier serving area includes integrated subscriber line circuits. The integrated subscriber line circuits are configured for providing either a downstream broadband data connection or both telephone-based connections and a downstream broadband data
Brooks Kenneth R.
Wegleitner Mark A.
Forbis Glenn E.
Marcelo Melvin
Suchyta Leonard D.
Swingle Loren C.
Verizon Services Group
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