Pulse or digital communications – Transceivers – Modems
Reexamination Certificate
1999-08-03
2002-07-23
Pham, Chi (Department: 2631)
Pulse or digital communications
Transceivers
Modems
C455S557000
Reexamination Certificate
active
06424675
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to data and voice communications, and more particularly, to a system and method for implementing V.90 central site mode functionality at a customer premises.
BACKGROUND OF THE INVENTION
Modern data and voice communications have progressed to a point at which it is now possible to implement communication systems that are capable of delivering very large amounts of information to individual customer premises locations. For example, it is possible to implement digital subscriber line (DSL) technology at a residential location over the existing copper wire pair that has served in the past to support only a plain old telephone service (POTS) communication system. Other digital technology, similar in the service provided but differing in the approach in which implemented, is also available in addition to the above mentioned DSL technology. Examples of this technology include multiple virtual lines (MVL), asymmetric digital subscriber lines (ADSL), etc., whereby the result is the establishment of a digital communication interface at a customer premises, the digital connection provided over a single copper wire pair.
One of the benefits of this digital technology is the ability to provide a high speed data connection (on the order of 128 kilobits per second (Kb/s) and higher), while simultaneously providing an embedded channel over which conventional voice traffic may be communicated.
Unfortunately, there remain many customer premises locations to which the latest digital technology is unavailable, or at which the customer has chosen an existing analog communications technology, such as an analog modem, with which to send and receive information. The latest and fastest analog modems are ones that comply with the V.90 communication standard and connect a customer premises, also referred to as an “end-point” to a telephone company central office via a conventional copper wire pair. Typically, the central office to which the end-point V.90 modem is connected is connected to another central office via a four wire digital connection, such as a T1/E1, synchronous optical fiber network (SONET) or some other high speed, high capacity digital connection. This network can be a public switched telephone network (PSTN), a public data network (PDN), or the like.
The above-mentioned two wire connection is one in which signals traveling in both directions are combined over the single wire pair, while the four wire connection maintains the signals traveling in each direction on a separate wire pair.
This central office typically connects via a four wire digital connection to another modem compatible with the V.90 specification. This modem is typically referred to as a “central site” modem, and typically resides at a service provider location, such as an Internet service provider (ISP). So, in this communication scheme, one of the V.90 modems must connect to a central office via a digital four wire interface in order to provide communication services to a customer premises, or end-point. In the above-described V.90 communication environment, the data transfer rate between the end-point and the central site is asymmetrical. For example, it is possible to achieve a data rate approaching approximately 56 Kb/s in the downstream direction (from central site to end-point), but the data rate in the upstream direction (end-point to central site) is limited to approximately 33.6 Kb/s because of the analog two wire connection between the end-point V.90 modem and the central office serving the end-point.
While there are some situations in which this asymmetrical data transfer may be acceptable, there are other instances in which it would be desirable to have the ability to transfer data from an end-point to a central site at a faster rate.
FIG. 1
is a block diagram illustrating an existing point-to-point analog communication environment
11
. Communication environment
11
is said to be point-to-point because it typically involves communication between two individual subscribers, commonly referred to as “endpoint” locations. For example, modem
12
connects to central office
16
via two wire analog connection
14
, and modem
24
connects to central office
21
via two wire analog connection
22
. Modem
12
may be located at a customer premises and modem
24
may be located at a remote customer premises. The two wire analog connections
14
and
22
are the copper wire pair that extends between a telephone company central office and an individual subscriber location, and are sometimes referred to as the “subscriber loop”.
Central office
16
typically connects to central office
21
via four wire digital connection
18
. The four wire digital connection
18
is typically a high speed trunk comprised of, for example but not limited to, T1/E1, or a synchronous optical network (SONET). This four wire digital connection
18
is typically the high speed backbone that interconnects a plurality of telephone company central offices.
In the above-described point-to-point communication environment
11
, the maximum bi-directional data transfer speed is typically on the order to 33.6 kilobits per second (Kb/s). The data rate is typically limited by two wire analog connections
14
and
22
because, in order to maintain bidirectional communication over two wires, it is necessary to filter the transmit and receive signals in order to eliminate interference. This filtering typically limits the data rate over the two wire analog connection to a maximum of approximately 33.6 Kb/s.
While modems
12
and
24
may be capable of higher speed communications, they are typically limited by the two wire analog connection
14
and
22
. For example, it is possible to install a modem complying with the V.90 standard, however, because of the two wire analog connection that exists between each modem and its respective central office, the maximum achievable speed over the two wire analog connection is limited to approximately 33.6 Kb/s by the V.34 standard. It would be desirable to have the ability to implement a higher data rate from modem
12
to modem
24
, or to another endpoint modem (not shown).
FIG. 2
is a block diagram illustrating an existing V.90 communication environment
31
The communication environment
31
shown in
FIG. 2
is similar to point-to-point communication environment
11
with the exception that a four wire digital connection
42
exists between central office
41
and modem
44
. Modem
32
, which is compatible with the V.90 standard, is considered an end-point modem and is located at an individual subscriber location. Modem
32
connects to central office
36
via the above-mentioned two wire analog connection
34
. Central office
36
connects to central office
41
via a four wire digital connection
38
, that is similar to four wire digital connection
18
described above with respect to FIG.
1
.
Typically, modem
44
, which also complies with the V.90 communication standard, is considered a central site modem and is generally located at a service provider location. An example of a service provider location would be an Internet service provider (ISP). Because modem
44
is located at a service provider location that typically has access to a four wire digital connection to central office
41
, it is possible to implement a higher data rate in the direction of central site modem
44
towards end-point modem
32
. This direction is typically referred to as the “downstream” direction. When central site modem
44
and end-point modem
32
are operating in compliance with the V.90 standard, the data rate between central site modem
44
and end-point modem
32
approaches 56 Kb/s.
The data rate in the “upstream” direction, which is the direction from end-point modem
32
to central site modem
44
, is still limited to a maximum data rate of approximately 33.6 Kb/s because of the two wire analog connection
34
between end-point modem
32
and central office
36
.
This scheme works well in the situation where it is desirable to have a faster data rate from
Macdonald Alistair Malcolm
Nauman Keith R.
Bayard Emmanuel
Paradyne Corporation
Pham Chi
Thomas Kayden Horstemeyer & Risley, L.L.P.
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