Multiplex communications – Channel assignment techniques – Details of circuit or interface for connecting user to the...
Reexamination Certificate
1999-01-28
2004-09-14
Rao, Seema S. (Department: 2666)
Multiplex communications
Channel assignment techniques
Details of circuit or interface for connecting user to the...
C370S434000, C370S359000, C370S360000, C370S386000, C370S420000
Reexamination Certificate
active
06791999
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to switching technology in a digital access network and more particularly to techniques for providing dynamic bandwidth switching functionality in an access network which supports only static or nailed up bandwidth switching.
The increasing demand for terminal user services has spurred rapid advances in the field of data communications. Initially, telecommunication services were provided to subscribers via individual copper wire lines connected between subscribers and the telephone exchanges. However, with the rapid increase in the number of subscribers, this approach soon became costly and unmanageable.
Driven by a desire to lower communication costs and to improve the quality of both transmission services and network management services, communication networks are increasingly using digital technology to transport voice, data, audio, video and other types of information to subscribers. Access networks and digital loop carrier (DLC) systems have been developed which further facilitate provision of services to subscribers.
FIG. 1A
depicts a conventional communication network
10
including an access network
14
coupled with a local digital switch (LDS)
12
. LDS
12
may also be referred to as a central office (CO) switch and is usually a Class 4 or a Class 5 switch. LDS
12
typically performs bandwidth management and switching functions in order to provide services to subscribers
20
. LDS
12
integrates access network
14
into a wider telecommunication network (not shown). Examples of LDS
12
include the 5ESS switch manufactured by Lucent, and the DMS 100 switch manufactured by Nortel.
Access network
14
is coupled with LDS
12
using communication links
16
-
1
and
16
-
2
. In a specific embodiment, communication links
16
-
1
and
16
-
2
are T-1communication links which transport data using the DS-1 digital format. Several other types of communication links known in the art may also be used for communication links
16
-
1
and
16
-
2
. The DS-1 format is the basic transmission format for digital communications. The DS-1 data format supports a bandwidth of 1.544 Mb/s and may be used to transport services of various types including voice, data, audio, video, and the other types of services known to those of ordinary skill in the art. Each DS-1 signal consists of 24 DS-0 channels each of which supports a bandwidth of 64 kb/s and represents a communication channel. Each DS-0 channel terminates in a network termination.
Access network
14
facilitates provision of services to subscribers
20
. As shown, access network
14
comprises one or more remote terminals (RTs)
18
-
1
,
18
-
2
coupled to LDS
12
via communication links
16
-
1
and
16
-
2
, and coupled to subscribers
20
via subscriber links
28
. The DS-0 channels of communication links
16
-
1
and
16
-
2
end at RTs
18
-
1
and
18
-
2
to form network terminations
22
, while subscriber links
28
end in the RTs to form subscriber terminations
24
. Each RT is responsible for establishing a communication path between LDS
12
and subscribers
20
. Functions performed by each RT include demultiplexing the DS-0 channels received via the communication links, demodulating the digital signals received via communication links
16
-
1
and
16
-
2
, providing connections between network terminations and subscriber terminations, and delivering services to and from subscribers
20
. RTs may be placed at customer premises or in central offices.
In conventional systems like the one shown in
FIG. 1A
, the communication interface between LDS
12
and RTs
18
-
1
and
18
-
2
is generally based on a static bandwidth switching standard such as Bellcore's well known TR-TSY-000008 (TR-8) standard. In order to support a static switching standard such as the TR-8 standard, LDS
12
must be TR-8 compliant and RTs
18
-
1
and
18
-
2
must be equipped with interface modules which support the TR-8 interface. According to the TR-8 standard each DS-0 channel within a DS-1 is dedicated to a particular subscriber. Accordingly, in order to provide a communication path between LDS
12
and a subscriber
20
, according to the TR-8 standard a DS-0 network termination
22
of a DS-0 channel is “nailed up” or dedicated to a particular subscriber termination connected to the subscriber. In effect, a dedicated one-to-one relationship or a static relationship exists between a DS-0 channel from communication links
16
-
1
and
16
-
2
and a subscriber. TR-8 compliant RTs thus provide static bandwidth allocation.
As shown in
FIG. 1A
, nailed up connections
26
exist between network terminations
22
and subscriber termination
24
in the RTs. The provisioning of DS-0s for each of the subscribers and the nailing up of DS-0 network terminations with subscriber terminations is performed when access network
14
is configured, usually when the network is setup for providing services to subscribers
20
. Typically, a network management station (not shown) is coupled to RTs
18
-
1
and
18
-
2
to facilitate provisioning of access network
14
.
Due to the static nature of the connection between a DS-0 channel network termination and a subscriber termination, the number of subscribers which can be serviced by the RTs is dependent on the number of DS-0 channels between LDs
12
and the RTs. Thus, according to the TR-8 standard, a single DS-1 signal comprising 24 DS-0s can support a maximum of 24 subscribers. In order to support additional subscribers, additional DS-1 communication lines must be leased from the communications exchange provider managing LDS
12
. Thus, as shown in
FIG. 1A
, each RT which is connected to a DS-1 channel supports up to 24 subscribers. In order to support additional subscribers, for example subscribers
25
through
48
, a second DS-1 communication link
16
-
2
is required. Leasing additional communication links is usually expensive and thus presents a financial obstacle for increasing the number of subscribers serviced by access network
14
.
The use of static switching standards, such as the TR-8 standard, also result in under-utilization of communication links' bandwidth capacity. For example, a DS-0 which has been dedicated to a particular subscriber termination cannot be used to communicate data to another subscriber even when the subscriber to which the DS-0 channel is dedicated is not utilizing the DS-0 channel. This results in wastage of valuable bandwidth resources.
Due to the limitations inherent in static switching techniques, several new standards, for example Bellcore's TR-TSY-000303 (TR-303) standard, are being developed which allow dynamic switching between communication channels and subscribers. Dynamic switching mechanisms such as the TR-303 standard eliminate the concept of “nailed up” or dedicated connections between network terminations and subscriber terminations. In order to support a dynamic switching standard such as the TR-303 standard, LDS
12
must be TR-303 compliant and all RTs connected to the LDS must be equipped with an interface module which supports the dynamic switching or TR-303 interface.
FIG. 1B
depicts a communication network
30
comprising an access network
34
coupled with LDS
32
which supports a dynamic switching standard, such as the TR-303 standard. Access network
34
includes one or more RTs
36
(only one of which is shown) which support a TR-303 standard. RT
36
is connected to TR-303 compliant LDS
32
via communication link
16
-
1
, and to subscribers
20
via subscriber links
28
. RT
36
thus provides network terminations
22
for the DS-0 channels of communication link
16
-
1
and subscriber terminations
24
for subscriber links
28
. As in
FIG. 1A
, communication link
16
-
1
is typically a T-1 link and supports the DS-1 digital format. However, unlike
FIG. 1A
, there are no nailed up connections between network terminations
22
and subscriber terminations
24
. According to the TR-303 standard, a connection between a DS-0 network termination and a subscriber termin
Budhraja Virendra K.
Nair Vinod K.
Abelson Ronald
Baker & Botts L.L.P.
Cisco Technology Inc.
Rao Seema S.
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