Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1999-07-20
2004-04-20
Maung, Nay (Department: 2684)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S426200, C455S445000
Reexamination Certificate
active
06725059
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to communication systems, and more particularly, to a system and method for improving communications between a digital loop carrier (DLC) and a central office (CO).
2. Discussion of the Related Art
In recent years, telephone communication systems have expanded from traditional plain old telephone system (POTS) communications to include high-speed data communications as well. As is known, POTS communications include the transmission of voice information, as well as PSTN (public switched telephone network) modem information, control signals, and other information that is transmitted in the POTS bandwidth.
Prompted largely by the growth in Internet usage, the provision of XDSL services to customer premises has proliferated over recent years. In this regard, the descriptor “x” preceding the DSL designator is used to broadly denote a variety of DSL services, including ADSL, RADSL, HDSL, etc. As is known, xDSL transmissions are sent to customer premises over the same twisted pair cabling as POTS transmission are sent. Since XDSL transmissions are communicated in a frequency band that is separate and distinct from the POTS frequency band, transmitting both types of signals over the same cabling (even at the same time), generally is not a problem. Specifically, the POTS frequency band is defined between approximately DC and approximately 4 kHz, while xDSL frequency bands (although they vary depending upon the specific service) are generally defined by a lower cutoff frequency of approximately 26 kHz, and an upper cutoff frequency that depends upon the particular xDSL service. As will be used hereinafter, the term DSL will be used interchangeably with the term xDSL, and should be construed to generically reference any of the of the various DSL services.
As is known, DSL is an additional service the customer typically purchases from its local service provider. The local service provider typically charges an additional service charge for the provision of the service. Until recently, the additional service charges have been somewhat substantial, resulting in a general limitation of the service to business enterprises. However, the services are now becoming more affordable, and therefore in higher demand. This higher demand, however, is beginning to create problems due to the existing infrastructure. Indeed, due to the existing infrastructure of the telecommunications system, DSL services are frequently unavailable to a would-be subscriber.
To better appreciate problems associated with the current infrastructure, reference is made to
FIG. 1
, which is a block diagram of an existing prior art telecommunications system. The telecommunications system includes a central office
10
in communication with a plurality of customer premises
14
,
16
,
18
, and
20
through a digital loop carrier (DLC)
12
. As is known, a DLC is a telecommunications device that connects end users to a central office. Frequently, the end users connected to a central office through a DLC are usually located more than 18,000 feet away from the central office. DLCs consist of a box containing line cards that concentrate individual lines within a given area, and then send the traffic over a high speed digital connection to the CO
10
. In this way, DLCs extend the reach of telecommunications services from a CO, beyond the reach of a typical local loop. DLCs are frequently used in office parks, housing developments, apartments, etc. to minimize the need to run local loops over several miles to the CO servicing area. This, in turn, minimizes the use of copper, as each of the copper wire pairs
30
can carry up to 24 digitized voice channels (up to 30 digitized voice channels in some countries outside the U.S.). Instead, local loops connect a cluster of homes or businesses to a remote terminal (the DLC), which in turn concentrates the traffic into a higher bandwidth for delivery to the CO.
The high speed digital connection
30
extending between the central office
10
and the DLC
12
typically includes a plurality of T
1
(in the U.S.) lines or E
1
(in Europe) lines. As is known, a T
1
line operates at speeds of 1.544 Mbps, which is capable of carrying 24 voice channels. One very common configuration includes a DLC that is configured to service 96 users. Such a configuration requires four T
1
circuits in order to allow all 96 users to simultaneously use the telephone system. In such a configuration, the high speed interface
30
between the DLC
12
and the central office
10
may comprise five T
1
circuits. The fifth T
1
circuit typically acts as a spare that may be utilized in the event of a line failure, noise, etc. The economics of utilizing five copper pairs (the T
1
lines), in place of 96 copper pairs, while delivering identical service to the end user provides significant value to the telephone companies, particularly when the distances to the remote locations are lengthy.
In recent years, many installations have replaced the T
1
circuits
30
extending between the central office
10
and the DLC
12
with fiber optic cables, which can provide tremendous bandwidth between the CO and the DLC. However, the cost of replacing these lines is quite expensive. Therefore, where possible, it is desired to avoid replacing the T
1
lines with fiber optics.
Having described the infrastructure in a large percentage of the existing telecommunications systems, it can be appreciated that the bandwidth requirements for DSL services pose a significant problem to such a (copper/T
1
) system. For example, ADSL can provide downstream rates from 1.5 Mbps to 8 Mbps, and upstream rates from 64 kbps to 1.5 Mbps, over a copper wires in existing telephone systems. However, it should be readily appreciated that the existing T
1
service interconnect
30
existing between central office
10
and DLC
12
cannot support the bandwidth demands of simultaneous use by multiple users at customer premises
14
,
16
,
18
, and
20
of such DSL services. As is more particularly illustrated in
FIG. 1
, a customer premises
14
may include multiple telephones
22
,
23
and one or more computers
21
that communicate over the same two wire pair
15
to the DLC
12
. If the computer
21
is equipped with a DSL card, the frequency spectra of the communications that occur over the local loop
15
may be like that illustrated by reference numeral
25
. Specifically, it may include a voice band
26
that extends from approximately dc to approximately 4 KHz. Likewise, it may include an upstream frequency band
27
that extends from 64 kbps to 1.5 kbps. It may further include a downstream frequency band
28
that extends from 1.5 Mbps to 4 Mbps. It is readily appreciated that the four or five T
1
lines interconnecting the central office
10
to the DLC
12
cannot support the full bandwidth capabilities of DSL, if multiple users within the various customer premises are attempting to carry on data communications over the Internet.
This problem may be manifest in either a significant data slowdown (from the stand point of the user). Alternatively, the service provider (central office) may simply inform customers that customer premises
14
,
16
,
18
, and
20
, that DSL services are not available for their customer premises. Certainly, with the growing demand for DSL services, there is a commensurately growing need for the service provider to enable the equipment to facilitate these services for the customer.
As previously mentioned, one approach is to replace the high speed communication link
30
between the DLC
12
and the central office
10
with fiber optic cabling. However, the cost of burying cable can be significant, particularly when there are significant distances separating the central office
10
from the DLC
12
. An alternative solution is to provide individual local loops extending between the central office
10
and each of the customer premises
14
,
16
,
18
, and
20
. Again, burying or otherwise extending cable between the central of
Globespanvirata, Inc.
Sobutka Philip J.
Thomas Kayden Horstemeyer & Risley
LandOfFree
System and method for improving communications between a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System and method for improving communications between a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System and method for improving communications between a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3276653