Pulse or digital communications – Transceivers – Transmission interface between two stations or terminals
Reexamination Certificate
2000-06-07
2004-08-31
Chin, Stephen (Department: 2634)
Pulse or digital communications
Transceivers
Transmission interface between two stations or terminals
C379S029010, C379S027060
Reexamination Certificate
active
06785325
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to telephony systems, methods and devices, and more particularly to a DSL splitter and method that provide access to an interconnected subscriber loop.
BACKGROUND OF THE INVENTION
In recent years, the demand for high bandwidth data services to customer premises has increased dramatically. Recent telephony advances have allowed the use of the existing copper wire subscriber loop to carry traffic at increased bandwidths. Now, through the use of digital subscriber line (DSL) technology, the existing subscriber loop, typically terminated at a central office (CO), may be used to carry broad band data. In fact, several DSL variants have been developed. These include HDSL, IDSL, SDSL, RADSL, and ADSL (collectively often referred to as xDSL).
To allow DSL services to co-exist with conventional telephone services on the same loop, some of the developed technologies use frequency division multiplexing to permit the copper wire to carry conventional voice signals at relatively low frequencies, and data at higher frequencies. Notably, asymmetric DSL (ADSL) allows the plain old telephone service (POTS) to coexist with DSL services on the same subscriber loop. POTS services are transmitted over the POTS frequency band of the loop. This band operates from about 100 Hz to 4 kHz. Upstream and downstream bands at higher frequencies carry data from and to the subscriber, and are isolated in frequency from each other and from the POTS band.
Accordingly, ADSL services are typically provided at a CO through use of a splitter that includes a high pass filter (HPF) and a low pass filter (LPF). The HPF is used to pass DSL signals from and to the loop, while the low pass filter is used to pass POTS signals from and to the loop. International Telephony Union Recommendation G.992.1, and ANSI Standard T1E1.4/98007R4, the content of which are both hereby incorporated by reference, for example, includes detailed specifications for a CO ADSL splitter.
In view of the ability to provide two distinct services over a single loop, it has now become possible for two separate service providers to provide POTS and DSL services independently. In fact, recent regulatory changes in some jurisdictions have mandated existing owners of the subscriber loops provide access to competitive service providers. As a result Incumbent local exchange carriers (“ILEC”s) typically lease space to competitive service providers (known as competitive local exchange carrier (“CLEC”)) within a CO, and provide access to DSL or POTS ports of installed CO splitters.
As a result of multiple provider access to the subscriber loop, each of the providers also needs the facility to test the physical loop. Conventional POTS testing may be performed through the LPF of the splitter. However, this is often unsatisfactory as the test may be affected by the characteristics of the LPF as well as by the presence of the HPF and DSL equipment on the loop. Similarly, testing of the loop by a DSL provider is impeded by the presence of the HPF, the LPF and POTS equipment. DSL testing, in particular, typically requires wide band testing often performed using time-domain reflectometry. In fact, empirical evidence reveals that presence of the LPF impacts the magnitude of the wide band noise measurement resulting being 15 to 20 dB lower than it should be.
Thus, as will be appreciated, independent direct test access to the loop by the two providers is highly desirable.
Accordingly, an improved device allowing both POTS and DSL providers the ability to test an interconnected subscriber loop are desirable.
SUMMARY OF THE INVENTION
In accordance with an aspect of the present invention, a DSL splitter in a first test mode, allows testing of an interconnected subscriber loop by way of a DSL input. A disconnect in series with an associated LPF disconnects the POTS input. Such a splitter may similarly provide access to allow testing of the subscriber loop by way of the POTS input in a second test mode. In this second test mode, a by-pass by-passes the LPF, and a disconnect may disconnect an associated HPF and DSL input. Preferably, the splitter only assumes its test modes after receipt of authorization from the other provider. The splitter may be controllable by way of a control circuit having an access port used to receive commands to have the splitter assume its normal, or first or second test mode.
In accordance with another aspect of the invention, a splitter facilitating modulation of digital subscriber line (DSL) signals and conventional telephony signals onto a telephone subscriber loop includes first and second inputs, for receiving the DSL signals and conventional telephony signals, respectively; and an output in communication with the first input. The output may interconnect the splitter to the telephone subscriber loop. An LPF is in communication with the second input and the output. A first controllable disconnect is in series with the LPF, and is controllable to disconnect the second input in a first test mode, only in response to receiving commands from both a conventional telephone service provider providing the conventional telephone signals and from a DSL service provider providing the DSL signals at the splitter.
In accordance with a further aspect of the invention, a splitter facilitating the modulation digital subscriber line (DSL) and conventional telephony signals onto a telephone subscriber loop includes, a first and second inputs, for receiving the DSL signals and conventional telephony signals, respectively; and an output, in communication with the first input. This output is for interconnecting the splitter to the telephone subscriber loop. An LPF is in communication with the second input and the output. A first controllable disconnect is in series with the LPF, and is controllable to disconnect the second input from the output in a first test mode. A control circuit in communication with the first disconnect controls the disconnect so as to disconnect the second input from the output in a first test mode. This control circuit includes an access port to receive control commands to control operation of the first disconnect.
In accordance with yet a further aspect of the invention, a method of providing test access to a subscriber loop, interconnected with a first digital subscriber line (DSL) provider and a second conventional telephone service provider by way of a splitter, includes providing test access through the splitter, after receiving instructions from one of the providers and authorization from the other provider.
In accordance with another aspect of the invention, a method of operating a splitter interconnecting a first digital subscriber line (DSL) provider and a second conventional telephone service provider, with a subscriber loop includes causing the splitter to assume a test mode that provides one of the providers test access to the subscriber loop through the splitter. After a timeout period the splitter assumes a normal operating mode, allowing the providers to again provide conventional telephone and DSL signals by way of the subscriber loop.
Use of an access port to control the operating modes of the splitter conveniently allows changing modes of the splitter using out-of-band signalling. Such a splitter may be used with conventional test equipment.
Advantageously, the control circuit may prevent one service provider from initiating loop testing without authorization of the other provider.
Advantageously, the control circuit may also prevent the splitter from remaining in one of its test modes indefinitely.
REFERENCES:
patent: 5757803 (1998-05-01), Russell et al.
patent: 5889856 (1999-03-01), O'Toole et al.
patent: 5930340 (1999-07-01), Bell
patent: 6181775 (2001-01-01), Bella
patent: 6477249 (2002-11-01), Williamson et al.
ITU-T Telecommunication Standardization Sector of ITU, Recommendation G.992.1 Annex E, Pots and ISDN-BA splitters, p 1-16. (2000).
Turnstone Systems Inc., Addition of Remote Actuated Metallic Bypass Capability to CO Splitter Standard, Committee T1—T
Haw Alfred
Liu Gin
Peck Anthony
Chin Stephen
Kim Kevin
Nortel Networks Limited
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