Multiplex communications – Channel assignment techniques – Messages addressed to multiple destinations
Reexamination Certificate
1998-03-27
2002-02-26
Chin, Wellington (Department: 2664)
Multiplex communications
Channel assignment techniques
Messages addressed to multiple destinations
C709S219000, C709S227000
Reexamination Certificate
active
06351467
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the distribution of multimedia content in a multicast network environment, and more particularly to a multicast network system having a high-speed multicast communication channel to multicast information to one or more receivers, and also having a return channel, which may operate at a lower speed, for permitting the receivers to interact with the network.
2. Description of Related Art
The most popular method for distributing multimedia information is the Internet's world wide web (WWW). Referring to
FIG. 1
, the WWW can be considered as a set of network accessible information resources, wherein many web servers
10
and web browsers
12
are connected to the Internet
14
via the TCP/IP protocols. (These protocols are described in the book “Internetworking with TCP/IP, Vol. I” by Douglas Comer, published by Prentice-Hall in 1991, which is incorporated by reference herein.) The web browsers
12
typically reside in personal computers (PCs)
16
which are connected to the Internet. The connection between the PCs
16
and the Internet
14
is often a low speed connection, such as a dial-up modem telephone line connection. The web servers
10
are also connected to the Internet, typically by high-speed dedicated circuits such as a 1.5 Mbps T1 connection. A PC user uses the browser
12
to access web sites
18
(which contain web pages, graphics and other multimedia content) from the servers
10
via the Internet
14
using Hypertext Transfer Protocol (HTTP). This “conventional” method for retrieving information from the world wide web requires a separate TCP connection each time a user accesses a web site, even if the user repeatedly access the same web site.
The world wide web is founded on three basic ideas:
(1) a global naming scheme for resources—Uniform Resource Locators (URLs);
(2) protocols for accessing named resources—the most common is the HTTP; and
(3) hypertext—the ability to embed links to other resources which is typically done according to the Hypertext Markup Language (HTML).
Each web site
18
contains a collection of web pages operated by a single enterprise which appears to a user of a web browser
12
as a single set of related content. Web pages within a web site
18
are formatted according to the Hypertext Markup Language (HTML) standard. The HTML standard provides for the display of high-quality text, including control over the location, size and font for the text and the display of graphics within the web page. The HTML standard also provides for the “linking” from one web page to another, including linking between web pages stored on different web servers and even different web sites. Each HTML document, graphic image, video clip or other individual piece of content is identified by an Internet address, referred to as a Uniform Resource Locator (URL). As used herein, “URL” refers to an address of an individual piece of web content (HTML document, image, sound-clip, video-clip, etc. ), and “URL data item” refers to the individual piece of content addressed by the URL.
While very popular, the above-described conventional dial-up method of accessing multimedia information is limited in at least two very important ways. First, most PC users access the Internet using dialup modems through an ordinary telephone line. These lines operate at a relatively low speed (e.g. 28.8 or 56 kbps) so that the display of an ordinary web page (e.g. 150 kbytes) takes a long time (e.g. 50 seconds) and the display of even short video clips (such as a 6 MB movie trailer in low-resolution “Quicktime” format) takes much longer (e.g. half an hour). Also, a user's telephone line is unavailable for normal voice calls the entire time that the Internet is being accessed.
Second, the conventional method uses point-to-point transfer, wherein each web site
18
must individually deliver its content to each web browser
12
. Thus, a single 150 kbyte web page must be individually carried from the web server across the Internet to each browser that displays that page. If a popular web server delivers ten reasonably large pages (for a total of 1.5 MB) to each of 10,000 users during a busy hour, the web server would require at least a 33 Mbps bandwidth link to the Internet. The link to the Internet and a web server fast enough to fill the link is presently prohibitively expensive and complicated. Support for a million or more users during the busy hour would be completely impossible with current Internet technology.
The world wide web presently supports two methods (advertisements and subscriptions) for a web site operator to obtain revenue for its site's content. Advertisements are embedded into a web site's web pages, typically in the form of images, wherein a user can “link” to the advertiser's web site for more information by clicking on the image. Web-based advertising is superior to normal multicast advertising (e.g. TV, radio and newspaper advertising) in that the web server
10
is able to track exactly how many users have seen a given advertisement and, for repeat users, track by user which advertisements and how many such advertisements the user has seen.
If a web site generates revenue through subscriptions a user is only able to access that web site's content if they have “subscribed” to the site, i.e., agreed to pay to access the site. By requiring the user to provide an account name and password each time the user wishes to access the site, a web site controls access so that only paying subscribers can access the site.
Multicast systems are able to accommodate large numbers of users much more easily than the Internet when the users are accessing common content, because a given data item is multicast (i.e., sent only once) regardless of the number of receivers. Multicast networks distributing multimedia content have been in use in recent years over wide-area networks, such as a geosynchronous satellite multicast or FM-radio side-band transmission.
Some multimedia multicast systems have been proposed in academia which involve individually multicasting frequently accessed URLs which have been tagged to allow the receiver to filter and store only those web pages which, based on past history, may be of interest to the receiver. These systems have failed to be commercially deployed because they copy and multicast content without permission, thereby creating possibly conflict with copyright laws. Further, they do not guarantee the user a consistent set of content which can be accessed “offline” (i.e. not while connected to the Internet) and they do not provide a mechanism for preserving a web site's subscription and advertising revenue.
A commercially deployed multimedia multicast system is AirMedia, Inc.'s Internet Antenna system which uses an FM-radio side-band multicast to distribute news and information (with limited graphics). A computer terminal receives the multicast information and stores it on the computer's hard disk. The information is multicast in a proprietary format and is made available to the user via a special purpose application. The AirMedia system suffers from a lack of compelling content, partly due to its very low speed (e.g. 19 kbps) FM side-band multicast transmission system.
Another such system is Intel's Intercast system, which uses the vertical blanking interval within an NTSC multicast to multicast information in order to “data enhance” the TV channel it is carried on. The vertical blanking interval, which is normally used to carry closed caption information, is also a low-speed multicast (e.g. 30 kbps). Unlike the Air Media system, Intercast multicasts its data in a standard HTML format. Intercast provides a viewer application similar to a web browser which, together with special hardware, allows the user to watch the TV program on a computer monitor while simultaneously accessing the supplementary HTML multimedia data.
The primary problem with such multicast systems is the availability of good content for multi
Chin Wellington
Harper Kevin C.
Hughes Electronics Corporation
Sales Michael W.
Whelan John T.
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