Interactive video distribution systems – User-requested video program system – Video-on-demand
Reexamination Certificate
1997-11-28
2004-05-18
Srivastava, Vivek (Department: 2611)
Interactive video distribution systems
User-requested video program system
Video-on-demand
C725S118000, C725S082000, C725S099000, C709S217000, C370S395500, C370S466000
Reexamination Certificate
active
06738981
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to telecommunication networks, data communication networks and broadcasting networks in general, and to access networks in particular.
An access network may in broad terms be defined as the means by which services of a network are made available to a terminal which is connected to the access network. The access system in its turn is connected to service provided network. In PSTN, for example, the access system comprises the network formed by the subscriber lines and equipment connected at each end of the individual subscriber lines; such as telephones at the subscriber side and terminal units at the local office side.
In this document an access system is defined as the means by which the services of an entity are made available to another entity at a certain point, the service access point (SAP) and enabling users to exploit the services. In this paper, an access system is an arrangement, separate from the accessed entities, which makes the services of one or several communication networks, and/or of one or several broadcasting networks, exploitable to a set of users. Thus, an access system provides a set of service access points to a number of different service providing networks.
Access systems are used to distribute the service access points of a set of service providing networks to locations, which are suitable for the users of the services of the networks.
STATE OF THE ART
Dedicated Accesses
Traditionally, telecommunication services have been provided by vertically integrated networks. The designers of the network and its components and protocols have used the knowledge of which services it would provide, and of the contexts, in which these services were to be provided. E.g., a PSTN is designed to provide point to point two-way connections, aimed to support 3.1 kHz speech. The networks were not designed for other services and contexts. This results in network components that fit together like pieces of a jigsaw puzzle. Such pieces are hard to reuse for other purposes, or for a new contexts.
Also the access arrangements are integrated in the same way. E.g., the access network of PSTN is simply seen as an extension of the PSTN. It is assumed that each terminal is connected over a dedicated pair of copper wires, and at least some of the control signaling is performed by opening and/or closing the loop. There is no need to have a separate address domain in the access network, since each service access point has its own dedicated copper line.
The integration of access arrangement and network goes so far that it is possible to classify vertically integrated networks by their access type; that is access protocoll, kind of terminal used for the access and services provided by the service providing network. Sometimes the terminal itself makes it possible to identify the service network. A telex apparatus for example is dedicated to the telex service of the telex network. Likewise a telephone set is dedicated to a telephony network; it cannot be used in any other type of network. An mobile telephone set gives access to the mobile telephony service, it cannot be used in the PSTN because its access protocol is different from the PSTN access protocols.
Besides the analogue access to PSTN, there are e.g. X.25 and X.21, which are dedicated access protocols interfacing specialized networks.
The recent development of access networks to PSTN and ISDN, e.g. the V5 standards, follows the same line. The access arrangement is dedicated for the services of PSTN and ISDN. It is also assumed that the owner of the access network is the same as the owner of the accessed network. The possibility to access more than one network of the same kind, but with different ownership, seems not to be covered.
If we look at mobile telephone networks, there are a number of different analogue and digital access types. Dedicated terminals are required for each type of network and are incompatible with other networks. The different networks provides basically the same type of service. From the above it is obvious, that an access is dedicated to a combination of network and service, not to a service only.
Integrated Services Networks
For a long time, new techniques have been developed in order to increase the transmission capabilities of traditional access infrastructure. An example of this is DSL (Digital Subscriber Line), which is the transmission protocol for ISDN access, which provides a 144 kb/s transmission link over a traditional copper subscriber line. Other modulation techniques, xDSL, are already specified, or are under specification, which gives symmetrical or asymmetrical rates up to several Mb/s over a copper wire.
During the last couple of decades, a number of network concepts have been proposed like ISDN and B-ISDN. They aim to provide a number of services, which traditionally have been provided by different networks, by a single network with its own address domain.
Also in these cases, a dedicated access approach is taken. E.g., for ISDN (Integrated Services Digital Network), services like telephony, which were accessed in one way when they were provided by the legacy networks, are accessed in a quite different way over the integrated ISDN access. The way a user accesses the services of these networks is still dedicated, but the range of services is wider, and it is easier to add new services. We call this type of access to an integrated service network an integrated access. In ISDN Network Terminals (NT) are used, which connects to a number of terminals. Simple NTs just conveys the access protocols to the terminals, but more complicated NTs exists, e.g. with a functionality like a traditional Private Branch Exchange (PABX).
The integrated networks were defined as a single, homogeneous network with its own, specific interfaces, even towards the terminals. When new services are required, new capabilities have to be integrated in the integrated networks. New services are traditionally added following the three step method. In the first step the new service is described in an implementation independent manner. In the second step the units required to support the new service and to be added to the nework are defined. The units are sorted in functional groups which then are distributed to physical units. The third step is to design protocols in the integrated network. This latter step means that the integrated network is essentially service specific. Possibly, but not necessarily, new capabilities need to be integrated also in the terminals when new services are added to an integrated network.
When the integrated service networks were defined, migration issues were not focused. There are at least two aspects of migration. The first one is the relation between legacy networks (i.e. the existing networks, which do not confirm to the new one) and new networks. The other is the relation between users (and the equipment of users) and the services, which used to be provided in one way by a legacy network, but which now can be provided in another way over an integrated access of an integrated services network.
The second relation is basically that the user has to change terminals and other communications equipment, and in most cases also their address (such as telephone number), if they decide to connect to a network of this kind. There is sometimes a possibility to reuse the terminals by adding an adapter, which adapts to the interfaces of the integrated access.
The first type of migration is handled in the following way. The legacy networks are seen as something, which breaks the homogeneity of the integrated network, and is dealt with by Interworking Functions, which map the services of the legacy networks on the services of the integrated network as good as possible. In this way, the connectivity (i.e. the addressable destinations and the information transfer services, which can operate between them) of the new network can be extended to the legacy networks. This may include address conversions between different address domains (e.g. between IP addresses
Hansson Allan
Tönnby Ingmar
Brown Reuben M.
Srivastava Vivek
Telefonaktlebolaget LM Ericsson (publ)
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