Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1999-12-07
2003-08-05
Nguyen, Steven (Department: 2665)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S392000, C370S400000
Reexamination Certificate
active
06603760
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the provision of local telephone services.
BACKGROUND
The telecommunications industry is currently undergoing a transformation from a traditional circuit switched based PSTN network, which was originally designed and optimized for carrying voice telephony traffic, to packet based networks which will be capable of efficiently supporting both voice and data communications. A next generation network (NGN) is a packet-based network that employs new control, management, and signaling techniques to provide both narrow-band voice telephony services and broadband, multimedia services. NGNs are able to satisfy a user's need for higher bandwidth while allowing service providers to offer innovative services, enabling new services and revenue streams, and reducing management costs and time to market.
A generalized local service provider NGN architecture is shown in FIG.
1
. It consists of two subnetworks, a public switched telephone network (PSTN) and an integrated voice and data packet network, which comprises access network
104
and a backbone network
106
. The access packet network
104
physically connects subscribers
120
to the local service provider network. In the case of residential customers, the access network
104
will typically be based on digital subscriber loop (xDSL) technology deployed in the local loop or MSCNS DOCSIS technology deployed over coax cable. On the customer side, the access network terminates on the customer premises device, which is called here the access gateway
108
. The particular implementation of an access gateway depends on the technology utilized in the access network. For access networks utilizing xDSL technology, the access network
108
may include an xDSL modem. For a hybrid fiber-coax based access, the access gateway
108
may be merged with set top boxes traditionally utilized for receiving TV signals broadcasted from cable-based distribution plants. Traditional telephone sets are either directly connected to the access gateway
108
or they are connected via a more elaborate home area network.
The packet based backbone network
106
is optimized for efficiently transmitting large amounts of data and typically utilizes IP, ATM and/or SONET technologies. For example, in the initial network deployment stages, the access and backbone networks could utilize ATM technology. However, since ATM switched virtual circuit (SVC) technology is not mature and ubiquitous enough to deploy end-to-end in the packet network, private virtual circuits (PVCs) are used in the access network and, frequently, in the backbone network.
The access network
104
is connected to the backbone network
106
via backbone gateways
110
, which bridge transport technologies utilized in the two networks. For example, in the case of a xDSL based access network the backbone gateway
110
includes digital subscriber loop access multiplexer (DSLAM) functionality. Calls spanning the packet network and PSTN network, such as calls originating from access gateways
108
and terminating on the PSTN or vice versa, are routed through trunking gateways
112
. A signaling gateway
114
is responsible for receiving signaling information from the PSTN (e.g., signaling system
7
packets) and routing that information to the appropriate network elements in the NGN. The signaling gateway can be a separate component or can be integrated into a service manager (SM)
116
.
The NGN has its own control infrastructure. Typically, network elements are designated to support service, session and connection signaling. In this document, these elements are called service managers (SMs) but depending on the protocols involved, these elements are also called media gateway controllers, call agents, gatekeepers, and signaling agents.
Local service providers have started the transition of their networks from the traditional PSTN infrastructure to an NGN architecture to offer both local and long distance services. The challenge for the NGN network equipment vendors will be to support graceful transition of the current local service subscribers to the new infrastructure.
A serious limitation of the NGN architecture of
FIG. 1
is that it does not support graceful migration of local services from the existing circuit switched infrastructure to the NGN network. In this architecture, the NGN network must provide all local services for phones utilizing packetized voice in the local loop. In addition, once a particular line is provisioned to receive local services from NGN, there is no easy and inexpensive way of re-provisioning the line to utilize PSTN local services.
Furthermore implementing within the NGN network all of the local services that are currently available in the PSTN is not a trivial task. Class 5 switches providing local PSTN services have been evolving for decades and by some estimates currently support over 500 different local service features. It is not reasonable to expect that all these features will be totally replicated in the new NGN infrastructure within a short timeframe. However, if NGN supports only a small subset of the local features then the deployment of the NGN may be limited to a small number of very specific target customers. Success of the NGN deployment will then depend on the reliability of the prognosis that can be made for defining a limited set of features to satisfy the needs of targeted customers until the NGN network matures. These deployment limitations could hamper the growth of the NGN network.
Prior techniques to address the migration of PSTN to NGN have certain limitations.
FIG. 2
illustrates a specific implementation of the general NGN architecture depicted in FIG.
1
. In this xDSL-based architecture, local service features for some telephones
222
are implemented by a class 5 end office switch
218
. For other telephones
220
, local service features are implemented based on the NGN service control infrastructure (i.e. based on the SM
216
network component).
For each set of telephone lines multiplexed over a single xDSL equipped local loop, the phone
222
utilizing analog transmission uses the bottom 4 kHz of the frequency spectrum of the access loop. The media stream for this line is separated in the DSLAM
209
and connected to the line side of the class 5 switch
218
which is connected to a tandem switch
224
in the PSTN
200
. For the remaining phones
220
, voice communication is implemented by transmitting packetized voice stream over the upper portion of the frequency spectrum. The packetized voice stream is routed via the DSLAM
209
and the network gateways
211
which are connected to the backbone packet network
206
. The SM
216
controls local service features for telephones utilizing packetized voice.
While a limited number of lines are able to access local services provided by a class 5 switch in this architecture, these lines are unable to access any innovative features provided by the NGN. In addition, no easy or cost effective way exists to re-provision a line for a packetized voice customer who wishes to utilize services offered only on a class 5 switch.
FIG. 3
a
illustrates a network architecture that provides users access to class 5 switch features and an NGN architecture for transport. Phones
322
use traditional local loop facilities to connect to a class 5 switch
318
. In this architecture, the class 5 switch
318
connects to an NGN network
303
via a packet data interface
319
located at the switch
318
. While this architecture provides a service provider with access to some of the bandwidth and cost reduction benefits of the NGN, customers are not able to access innovative features offered by the NGN.
This architecture is sometimes modified to include packetized local loops as illustrated
FIG. 3
b
. Virtual phones
320
use packetized local loop facilities (e.g., DSL) to connect to a local loop gateway
309
. The packetized local loop network communicates with a class 5 switch
318
using traditional local loop signaling (e.g., channel associated signaling) through a
Giordano Joseph
Molinari Michael J
Nguyen Steven
Telcordia Technologies Inc.
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