Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via frequency channels
Reexamination Certificate
1998-09-02
2002-07-30
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via frequency channels
C370S465000, C370S480000
Reexamination Certificate
active
06426961
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to telecommunications, and particularly relates to the use of voice service and data service in an asymmetrical digital subscriber line (ADSL) system in the local loop between a central office of a telecommunications network and a customer's premises.
BACKGROUND
New technologies are being developed to increase the capacity and bandwidth of telecommunications networks. One of these new technologies provides for the use of an asymmetric digital subscriber line (ADSL) system in the local loop between a central office of a telecommunications network and a customer's premises served by that central office. An ADSL system makes use of the existing twisted pair wiring provided to the customer's premises to deliver the voice service including plain old telephone service (POTS) and to deliver data service including data signals such as may be used to communicate over the Internet. Advantageously, the ADSL system allows a customer to engage in a telephone call while also engaging in digital communications such as by interacting with the Internet. Additional information regarding ADSL systems may be obtained from American National Standards Institute Standard ANSI-Ti.413-1995, which is incorporated herein by reference.
FIG. 1
illustrates an ADSL system
10
such as may be used in a local loop between a customer's premises
12
and a central office
14
of a telecommunications network that serves the customer's premises
12
. In the central office
14
, voice signals from a switch
16
are combined with data signals from an ADSL modem
18
. This combination of voice signals and data signals typically takes place in a splitter
20
, which then transmits the combined signals over the twisted pair wiring
22
serving the customer's premises. The splitter
20
in the central office
14
earns its name when combined signals are received in the central office
14
from the customer's premises over the twisted pair wiring
22
. The splitter
20
splits the combined signals into voice signals which are transmitted to the switch
16
, and into data signals which are transmitted to the ADSL modem
18
.
Referring again to the case where the splitter
20
in the central office
14
transmits the combined signals over the twisted pair wiring
22
serving the customer's premises
12
, these combined signals are received at a splitter
24
in the customer's premises
12
. This splitter
24
also earns its name by splitting the combined signals into voice signals and data signals. The voice signals are transmitted to the telecommunications devices
26
in the customer's premises
12
, thereby providing voice service. The data signals are transmitted to the data devices in the customer's premises, thereby providing data services. For example, the splitter
24
provides data signals to an ADSL modem
28
which performs the appropriate demodulation and provides the demodulated data signals to a computer
30
. The splitter
24
in the customer's premises also transmits combined signals from the customer's premises
12
to the central office
14
. In particular, the splitter
24
receives voice signals from a telecommunications device
26
and combines these voice signals with data signals received from the computer
30
via the ADSL modem
28
. The splitter
24
transmits the combined signals over the twisted pair wiring
22
to the central office
14
. By this described configuration, the ADSL system
10
simultaneously provides a customer with voice service and data service so that a customer may use his or her computer
30
while he or she (or another individual) makes use of the telephone
26
.
In the ADSL system
10
of
FIG. 1
, as noted, the splitter
24
in the customer's premises
12
is used substantially in two ways. First, the splitter
24
is used to split the combined voice and data signals transmitted from the central office
14
over the twisted pair wiring
22
. Second, the splitter
24
is used to combine the voice signals from the customer's telecommunications device
26
with the data signals of the customer's computer
30
and to transmit the combined voice and data signals over the twisted pair wiring
22
to the central office
14
. Based on both of these uses, the splitter
24
must be installed on the customer's premises, which typically requires appropriate access and special wiring to make the proper connections. These requirements present problems to the telecommunications service provider and are viewed as complications by the customer. To the service provider, these requirements are costly and inconvenient. To the customer, these requirements of an ADSL system seem complex in comparison to the familiar use of an analog modem. Typically, a customer simply plugs the analog modem into a telecommunications outlet and programs the computer appropriately. To install an analog modem, generally special wiring and connections are unnecessary. Of course, an analog modem does not provide the advantage of an ADSL system whereby the customer may simultaneously use voice services and data services. Yet, the problems presented by the splitter
24
in the customer's premises
12
are obstacles to the further deployment of ADSL systems.
As illustrated in
FIG. 2
, to overcome the problems presented by the splitter
24
in the customer's premises
12
, an ADSL system
32
without a splitter in the customer's premises
12
is currently being developed. Generally, such an ADSL system
32
includes ADSL modems that operate at lower power than the ADSL modems in an ADSL system
10
with a splitter in the customer's premises. Additional information regarding an ADSL system without a splitter in the customer's premises may be obtained from Universal ADSL Working Group, an industry consortium formed to develop Universal ADSL standards. Further information may be obtained also from the following documents which are incorporated herein by reference: U-ADSL Framework Document—Terms of Reference, Implementation Guide, Rev. 1.2 (Jun. 15, 1998), Universal ADSL Working Group; and U-ADSL Framework Document—Loop Plants, Impairments and Testing. In-Line Low-Pass Filter Requirements and Design Guide, Rev. 1.2 (Jun. 15, 1998).
A comparison of
FIG. 2
to
FIG. 1
reveals that in the central office
14
the configuration of the ADSL system
32
without a splitter is the same as the configuration of the ADSL system
10
with a splitter. The principal differences between the ADSL systems
10
,
32
are in the customer's premises.
In the ADSL system
32
without a splitter, the combined voice and data signals transmitted over the twisted pair wiring
22
from the central office
14
are received in the customer's premises
12
and are provided to both the customer's telecommunications devices and to the customer's data devices. In particular, in providing the combined voice and data signals to the telecommunications devices, the combined signals are received in the customer's premises
12
and provided over connection
34
to an optional low pass filter (LPF)
36
which is connected in series to the customer's telecommunications device
26
. The low pass filter
36
passes the voice signals (0-4 KHz) to the telecommunications device
26
, but significantly blocks the other signals. In providing the combined voice and data signals to the data devices, the combined signals are received in the customer's premises
12
and provided over connection
38
to a high pass filter (HPF)
38
which is connected in series to the ADSL modem
28
. The high pass filter
38
passes the data signals (above 20 KHz) to the ADSL modem
28
, but blocks the other signals. The ADSL modem
28
, in turn, then transmits the data signals to the computer
30
.
The ADSL system
32
illustrated in
FIG. 2
has done away with the problems of a splitter
24
in the customer's premises. But the ADSL system
32
without a splitter in the customer&ap
Bellsouth Intellectual Property Corporation
Hsu Alpus H.
Kilpatrick & Stockton LLP
Tran T
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