Interactive video distribution systems – Video distribution system with upstream communication – Transmission network
Reexamination Certificate
1997-04-17
2004-05-18
Srivastava, Vivek (Department: 2611)
Interactive video distribution systems
Video distribution system with upstream communication
Transmission network
C725S087000, C455S003020
Reexamination Certificate
active
06738983
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to delivery of digital information to subscriber premises and more particularly to providing this access without substantial new wiring expense.
The delivery of digital video services to the home represents one important aspect of the much publicized “information highway.” These services include HDTV, video-on-demand (VOD), near-video-on-demand (NVOD) providing staggered program starting times, interactive video services (IVS), and other digital variants of conventional broadcast services.
One of the main obstacles to the introduction of these services is development of the necessary infrastructure for delivering digital video information to the subscriber' premises. Video services, even with the use of modern compression standards such as MPEG-1 and MPEG-2, intrinsically require large bandwidths. Somehow an infrastructure must be constructed to distribute the necessary signals to individual subscriber premises. At a minimum, each subscriber should be able to select from among numerous digital video programs as can be done now with analog broadcast television.
Various solutions have been proposed. In one scheme, the digital data are distributed via an asynchronous transfer mode (ATM) network to each subscriber's premises. The physical medium of the ATM network may be implemented in more than one way. One way is to lay optical fiber to each home. Alternatively, fiber may be laid up to the curb, from which point a coaxial cable can relay the ATM cells. The advantages of this technique are the low latency and flexibility of the ATM technology and a large bidirectional bandwidth sufficient to distribute numerous interactive digital video programs. Nonetheless, this approach is practically infeasible today since the cost of laying fiber or coaxial cable to each home is prohibitive. Additionally, the time required to deploy such an infrastructure over a large geographic area makes the scheme even more unattractive.
An alternative scheme is the so-called hybrid fiber coax (HFC) scheme. The HFC scheme provides a two-level network. At the higher level, optical fibers are used to distribute digital information to a plurality of Cable Headends or Host Digital Terminals (HDT). Each Headend or HDT in turn distributes information to multiple hybrid fiber coaxial cables, each of which serves several hundred subscriber units in a bus/loop architecture. The return channel over the coaxial cable is also shared by multiple subscriber units by employing Time Division Multiplexing (TDM). Again, for those network providers that do not already have such an infrastructure installed, costs are prohibitive because coaxial cable must be brought to each home. Furthermore, the use of TDM coupled with highly limited bandwidth gives rise to a large latency in the return channel. Network security is another drawback of the HFC architecture as several users share a single coaxial cable, a particular concern for interactive services that may require transmission of a subscriber's private information.
Other schemes take advantage of the existing telephone network by using ADSL technology to transfer high data rate information, such as video, over existing telephone company twisted pair lines to subscriber premises. Optical fiber may be used to transfer digital information to the telephone company central office or to a curbside interface where the twisted pair lines begin. The latter architecture is commonly referred to as Fiber-To-The-Curb (FTTC). Alternatively, fiber may be deployed till the basement of a large building, from which point existing twisted pair lines can establish connection with each subscriber. Such an architecture is commonly referred to as Fiber-To-The-Building (FTTB). The disadvantage of this approach is that ADSL provides insufficient bandwidth. Most current ADSL trials carry only 1.5 or 2 Mb/s over twisted pair. Laboratory demonstrations have shown that in the next few years cost effective solutions that provide up to 25 Mb/s may be possible, but even this would be insufficient to provide a broadcast or NVOD service with an acceptable number of service selections. Approaches which bring fiber to the curb carry the added cost of laying the fiber.
Prior art digital data delivery schemes that use relatively narrow bandwidth connections to the subscriber premises require point-to-point sessions between the ultimate server and subscriber unit. This is because the narrow bandwidth link that is closest to the subscriber permits only a point-to-point connection if the desired service quality is expected to be reasonable. These point-to-point sessions waste bandwidth since the server must separately transmit to multiple subscriber units requesting the same program. If the user wishes to switch channels, there is significant extra latency resulting from the need to end the previous point-to-point session before beginning a new one. Furthermore, the network and server hardware needed to accommodate point-to-point sessions is particularly complex and expensive.
SUMMARY OF THE INVENTION
The invention provides a network architecture for distributing digital data to subscriber units wherein selection from among multiple digital services is accomplished by transmitting a tuning command from a subscriber unit to one or more intermediate interfaces in a series of links interconnecting the subscriber unit and a server. An example of such digital data is digital video and the services could be multiple digital video programs. The network architecture of the present invention is capable of providing public broadband access without the use of very high bandwidth access lines to subscriber premises.
Using the information received from the subscriber unit, the intermediate interface selects the desired digital service from a multitude of services available in a broadband link coupled to the interface's input and transmits it to the subscriber unit over a bandwidth-constrained link. The bandwidth-constrained link may be implemented with existing infrastructure, yet the subscriber unit may readily access a wide variety of digital services available on the broadband network. The present invention thus combines universal broadband access with low cost.
In accordance with the invention, a service provider may offer broadcast services over the network in addition to point-to-point interactive services. The broadcast services may be offered without requiring multiple point-to-point sessions from the server to each requesting subscriber unit. Instead, a single copy of a digital stream provided via the broadband link is sufficient to service multiple subscriber units which request it via their intermediate interfaces, thus conserving bandwidth. By contrast, in the prior art point-to-point schemes, the broadband network would be forced to carry a separate point-to-point connection for each requesting subscriber unit.
Note that the present invention provides the advantages of forgoing point-to-point connections for broadcast purposes without requiring the construction of the very high bandwidth links necessary to continuously transmit each available program to each subscriber unit. Thus digital broadcast and NVOD services may be provided effectively and at low cost.
In accordance with one aspect of the present invention, a conventional telephone network is enhanced to provide universal high bandwidth digital service. Typically, telephone service is provided to subscriber premises via individual access lines extending from the subscriber premises to a neighborhood hub or pedestal. The access lines are private and secure twisted pair lines. The pedestal is fed by a high data-rate trunk line, typically implemented as a fiber optic connection.
High bandwidth digital service, including video programming, is transmitted over a twisted pair connection by implementing Asymmetric Digital Subscriber Link (ADSL) modulation and demodulation over the connection which allows for transmission of high speed digital data in a manner that is transparen
Elsbach Martin D.
Lévesque Gilbert
Rao R. Padmanabha
Siccardo Paolo L.
Irdeto Access, Inc.
Srivastava Vivek
Tran Hai V.
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