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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an interactive multimedia system for
supplying information to users in their homes and, more particularly, to
an interactive multimedia system with distributed information processing
and storage which is hardwired to the user through existing cable
television systems.
2. Description of the Related Art
Distributed processing find storage are relatively new concepts in data
management and--because of the various technological hurdles--have not
been considered until now for application to the field of videotex. The
Prodigy.RTM. information service, which is now being marketed nationwide
by Sears and IBM, claims to use a distributed database architecture.
However, that system only distributes the database to regional mainframe
computers. Their underlying technology--as with all other current videotex
technology--still relies completely on the maintenance of continuous,
real-time, two-way communication of a personal computer (or other
terminal) in the home with a mainframe computer at some remote location.
Nearly all videotex services use phone lines and modems to link the two,
though some experiments with two-way cable TV and other media have been
attempted. These existing systems have numerous limitations.
Since each user of a traditional videotex system is directly connected to a
central mainframe when on-line, this central computer must be capable of
simultaneously handling the many subscribers it gets during prime usage
periods, while it may sit almost idle the rest of the time. As the number
of users increases, additional large computers must be added to the system
at great expense. Any problem with the central computer or the
communications net linking it to the users can cause the entire system to
cease functioning.
The speed with which information may be retrieved from such systems is
limited to the speed with which the central computer can recognize the
users' requests and locate the information in its central data storage
media. Even the largest and fastest of central computers cannot overcome
the severe limitations of how quickly information may be carried by the
phone lines or other media that connect it to the user. Phone lines have a
narrow bandwidth and can carry only a limited amount of information at any
one time. For example, it takes 8 to 10 seconds for a central computer to
send a screen full of just text information to a user terminal over a
telephone line, assuming a typical communications speed of 2400 baud. A
complex graphic or photographic quality image could take at least 1/2 hour
per image.
The newer Integrated Services Digital Network (ISDN) and fiber optic cable
technologies will provide greater information transmission capability for
businesses, but these technologies will not be wired into a large number
of individual homes for at least another ten years. Moreover, even using
high speed fiber optics connecting a central computer to a home terminal,
the largest of computers cannot keep up with an entire city of users
especially during prime time. As an example, the largest airline
reservation system can only process 8000 transactions per second.
This bandwidth problem has never been adequately addressed by those working
in the field because--until very recently--all computer interfaces were
just character-based or used very low resolution alphamosaic style
displays utilizing protocols such as NAPLPS or Teletel. While simple
character-based information may be transmitted over phone lines relatively
easily, the resulting display is difficult to interpret and use. Even
simple alphamosaic displays take long enough--about 8 seconds--to transmit
over a phone line that the level of interactively declines and, with the
low quality of the display, the systems tend to become uninteresting and
awkward to use. After the novelty wears off, the typical consumer finds
that the difficulty of using such systems to obtain useful information,
coupled with their slow speed and uninteresting graphics, makes other more
traditional ways of obtaining information, i.e., printed information, more
attractive.
Graphic user interfaces, particularly those using the high resolution,
"photorealistic" displays are far more interesting and easier to use, but
require vastly greater amounts of data to be transmitted in order to
generate interesting screen images that will respond to the user's
requests quickly. What has not been addressed by workers in the videotex
field is that, while wide bandwidth transmission media remain very limited
and/or expensive, the relative costs of memory media such as magnetic disk
drives, dynamic random access chips (DRAMS) and other ways of storing data
have been dropping quickly, as has the cost of fast microprocessors that
can efficiently access and display data stored in the media. This suggests
that a highly distributed architecture would overcome the bandwidth
limitations and provide a cost effective and very fast information
delivery system. The system of the present invention exploits these
ongoing technological changes and thus overcomes the above-noted problems
in the videotex field.
SUMMARY OF THE INVENTION
The present invention, unlike prior art systems, provides
easy-to-understand photographic quality images and full-motion video,
accompanied by sound (speech and music), as well as traditional text and
graphical information. This combination is commonly referred to in the art
as a "multimedia" system. This is possible only because the data needed
by the user of the present invention is stored locally in the memory of
the processing module or node that is serving the individual home or small
group of homes over the existing broadband media of the coaxial TV cable
drop that goes into each household and directly to the television set.
Because each local node can handle all of the households attached to it,
and since it is independent of any central computer except for daily
updates, the system is also very reliable and economically scalable.
Whether two households or two hundred thousand households use the system
simultaneously will not impact performance, and the system will continue
to work and provide information to end users even if the source of
updates, usually from the central processing computer, is shut down for
quite some time.
Briefly, the system of the present invention includes:
a regional processing center for assembling and processing the information
to be transmitted over the television cable distribution system; and
at least one node coupled to the cable television distribution system for
capturing and storing the processed and assembled information, the node
being associated with at least one of the home televisions.
Preferably, many cable television subscribers share the information stored
in a node. A subscriber can display and interact with the information
stored in the associated node by communicating commands to the node. Since
each of the nodes in the cable television distribution system contains a
substantially identical copy of the information transmitted by the
regional processing center, the subscriber interacts directly with the
information stored in the node, and not with the information stored in the
regional processing center.
Each of the nodes in the system is coupled to a feeder cable of the cable
television distribution system at a location immediately after the cable
line extender amplifier (approximately every quarter mile). Typically,
there are from one to ten taps of four or more outputs each between any
two line extender amplifiers on a feeder cable, all of which are served by
one node in the present invention. The nodes transmit the information to
the home televisions at television channel frequencies unused by the cable
distribution system for transmitting ordinary cable television
programming. These frequencies are typically above the last used cable TV
channel.
Feeder inserters are used to connect the nodes to the feeder cable. The
feeder inserters include a low pass filter for blocking information from
any upstream nodes, while permitting the video frequencies used by the
cable system for ordinary cable television programming to pass through
downstream unattenuated.
The nodes output information to their associated home televisions over a
plurality of frequency channels. A home interface controller coupled to
each home television receives and descrambles a channel from the node,
preferably on the next available frequency channel (on a contention
basis). The home interface controller communicates back to the node on a
low band frequency on a polled basis. In this contention embodiment, each
of the home interface controllers contains electronics which unscrambles
only the channel assigned to it for viewing by the user. In other
embodiments of the invention, the controllers communicate with their
associated node on a non-contention basis.
As mentioned above, the user retrieves selected multimedia information by
sending commands back to the node. These commands travel to the node over
a return path using the existing cable television wire, just as the
multimedia information itself sent from the node to the home televisions
travel over the existing cable TV wire.
Preferably, users of the system are provided with a remote control touch
pad device, available with or without a full typewriter style keyboard,
for inputting user commands into the home interface controller coupled to
their television. Alternately, or in addition, the home interface
controllers are adapted to receive user commands from a conventional PC
keyboard, via an infrared interface attached to the keyboard.
Yet another option is to provide users with printers for printing hard
copies of information received from the node, including tickets to
entertainment events or coupons for merchandise discounts, etc.
Preferably, the system is configured to allow user responses to be
transmitted from the subscriber terminals to a selected merchant. The user
responses return to the selected merchants after passing up the subscriber
cable to the node, then via a telephone line attached to the node (or the
upstream nodes send user responses downstream to an end node, which has
the telephone line). Optionally, as an added convenience, an autodialer
device may be provided to dial the telephone of the user to allow the user
to speak directly to a system advertiser, for example the seller of an
item described in a classified ad on the system.
Advantageously, the nodes of the present invention can also be used for
decompressing compressed television programming and distributing the
decompressed programming to users connected to the system.
The importance of the present invention to the electronic information
distribution and multimedia industries is that it can deliver photographic
quality images, as well as full-motion video with sound, to millions of
homes simultaneously. The system can meet peek demand periods, and most
importantly, can deliver information with a look and feel equivalent to
what the home viewer has come to expect from network television, i.e.,
interesting colorful 3-D graphics, photographic quality images and
smoothly rendered text. This contrasts to existing systems with limited
graphics that look like video games and have jagged, poorly rendered text.
Prior art videotex systems could not do more, or look better, without
adopting the approach outlined in this summary, and set forth in greater
detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages of the present invention will
become apparent when the following text is read in conjunction with the
accompanying drawings in which:
FIG. 1 illustrates the regional network architecture of the invention,
where a regional facility receives and preprocesses data for all the
cities in the region and distributes the preprocessed data to respective
cable TV systems, and where the data is in turn broadcast to nodes for
access by individual home interface controllers;
FIG. 2 illustrates the hardware of the present invention coupled to a
typical cable TV system. FIGS. 2A-2C illustrate various alternative
configurations for coupling nodes to a cable TV system;
FIG. 3 illustrates a diagram showing the node of the present invention
connected to a typical cable TV feeder and showing the connection of a
node to a cable TV subscriber home;
FIG. 4 is a diagram showing the bandwidth usage of the system on a typical
TV system;
FIG. 5 is a schematic of a feeder inserter which is used to couple each
node into the cable feeder;
FIGS. 6A and 6B, collectively, represent a schematic diagram of a node;
FIG. 7 is a schematic diagram of an extender module which is used to add
more channels to a node;
FIG. 8 is a schematic diagram of a home interface controller which
interfaces between a node and a user's TV set; FIG. 8A is a block diagram
of the frame grabber circuitry of the home interface controller;
FIG. 9 is a diagram of a second embodiment of the invention in which a tap
interface is used to reduce the amount of electronics in each home
interface controller;
FIG. 10 is a schematic diagram of a node in a second embodiment of the
invention;
FIGS. 11A and 11B, collectively, represent a schematic diagram of the tap
interface used in the second embodiment of the invention in a contention
configuration;
FIG. 12 is a schematic diagram of the tap interface used in the second
embodiment of the invention in a non-contention configuration;
FIG. 13 is a schematic diagram of the simplified home interface controller
used in the second embodiment of the invention;
FIG. 14 is a schematic diagram of a still further embodiment of the
invention in which all the node electronics are in the home interface
controller of each user;
FIG. 15 is a schematic of the touch pad remote control device preferably
used in the system of the present invention;
FIGS. 16-18 illustrate, respectively, an optional PC keyboard interface, a
home interface controller telephone interface, and video input electronics
for inputting user-created video to create classified ads;
FIG. 19 shows the operation of the invention to remotely control electronic
products in a subscriber's home;
FIG. 20A shows an embodiment of the invention in which information is sent
to the nodes from an external source;
FIGS. 21-25 illustrate various bandwidth utilization schemes for
distributing decompressed television programming using the nodes of the
present invention;
FIG. 26 illustrates an embodiment in which the nodes of the invention are
disposed in remote stations of a telephone company fiber optic system;
FIG. 27 illustrates an embodiment in which RF distribution nodes are
utilized and the bulk of the nodes electronics and storage is centralized
in a node at the headend;
FIG. 28A illustrates the simplified electronics of a distribution node;
FIG. 28B illustrates the electronics for video compression/decompression
in a node; and FIG. 28C illustrates the feeder inserter electronics for a
distribution node.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
I. System Overview
The present invention is a distributed computer system that offers a
variety of consumer-oriented information and advertisement sources. The
user interacts with the system using a remote control device and views the
system output on an unmodified home television set as just another TV
channel.
A small home interface controller containing a remote control receiver sits
atop the TV set and is connected to the cable TV wiring in series with the
user's television. This unit transmits user remote control actions back up
the subscriber cable TV drop to a local computer--called a node--which is
wired to the cable line outside the home.
The node computer directly interacts with the user and has stored, on an
internal storage medium such as a hard disk, a complete copy of all data
of the entire system. This node computer is complete in all respects and
does not have to refer back to a central computer to complete user
information requests. The node computers are placed throughout the cable
system on poles, underground, or in apartment building basements and each
serves about 40 homes apiece.
II. Data Flow through the System
Referring now to the drawings, where like reference numbers indicate like
elements, and specifically referring first to FIG. 1, data for the system
originates from various contracted information providers or service
providers. Data from these providers is received via computer modem over
telephone lines 2 by regional processing center 4. Advertisements and
information listings, such as classified ads and TV listings, come into
the regional center 4 throughout the day. This information is processed
and customized into data "magazines" for each cable system. A processed
data magazine is ready to go by the next morning and is transmitted via
computer modem over telephone lines 6 to a computer 8 placed in the
headend 10 of the target cable system.
The headend computer 8 acts as a store and forward device to receive this
data and rebroadcast it to all of the nodes 12 throughout the cable system
14. The headend computer 8 transmits the data updates at a preferred data
rate of 9600 bps or greater. The entire set of updates is transmitted
repeatedly until the next day. This ensures that random noise induced data
errors not corrected by the block error correction codes are corrected on
the next pass of the data set.
It should be noted that since the headend computer 8 acts merely as a
buffer, it is not a required element of the system; i.e., the system could
operate with the data being sent from regional processing center 4
directly to the nodes 12. However, the headend computer 8 is included in
the preferred embodiment of the invention since it provides an extra level
of backup storage in event of a failure of a regional processing center.
The home user interacts with the system using a infrared remote control
device. The remote control signal is received by a set-top unit called a
home interface controller (HIC) 16. HIC 16 sends the user commands
received from the remote control back up the cable drop to node 12 outside
the home.
Some of the information and services carried on the system offer
interactive sessions with the user, such as purchasing tickets for the
theater, music or sports events, as well as home shopping opportunities.
The user's choices are relayed from the node 12 along the feeder cable to
the last downstream node (the "end node"), and from there back to the
headend computer 8 via a telephone line 18 connected to the end node. The
headend computer 8 then relays user response packets back to the regional
center 4 over telephone lines 20. The regional processing center 4
converts user response packets into a format expected by the particular
service provider and relays the user data back to the respective provider
via computer modem over telephone line 22.
III. Information Content and System Database
Typical information carried on the system includes: TV listings for a month
in advance; classified ads; Yellow Pages type ads and listings, local
restaurant guide; local entertainment listings; and miscellaneous
information such as: current sports scores, financial news, traffic
conditions, current weather radar image and forecasts.
The various sources of information and advertisements will originate in
digitized video format for pictorial information, digitized sound for
radio, and ASCII or EBCDIC text for textual information. Listings and
advertisements will be transmitted to regional processing center 4 via
computer modem from the supplier's computer (computer to computer link).
The regional processing center 4 converts and normalizes incoming digitized
pictures, digitized sound and text into system standardized format. The
normalized data is then moved into an object-oriented database. Each
object in the database is made up of one or more of the following
components: one or more digitized photographic or computer-graphic images
(e.g. sequences of images for animation); digitized sound tracks; a
hypertext-like script language (to define, based on user input, when and
how to show images and play audio); textual information (such as body text
of a classified ad or company address and hours of business); location
coordinates of enterprise or business (used to compute distance of
business from users home); and thesaurus entries (used to store
associations between objects).
Once normalized and stored in the object database, the data are grouped by
category (TV listings, classified ads, etc.). The grouped (categorized)
data are then further processed to establish relevant associations or
meaning amongst the data objects. The associations, where relevant, are
added to the respective objects in the form of thesaurus entries so that
the associations travel with the data object.
The hypertalk-like script language, mentioned above, is used to guide the
user interface program in translating user commands from the remote
control into actions on the user's TV screen. For example, these actions
might include displaying an image and playing an audio track when the home
user, using the remote control, positions an on-screen cursor on top of a
particular icon, word, or other image and then presses the "PLAY" button
on the remote control.
The data objects of the system database are advertisements in the form of
layered of stacked information which allow a viewer to dig into the stack
(like turning pages in a catalog) to reveal levels of information that
interest the viewer. The layered advertisement is a video equivalent of a
consumer brochure or catalog where the viewer can flip through at will to
view relevant sections.
The data structure of the layered advertisement can be used for any type of
information carried by the network. The advertisements carried by the
system can be text only, such as a simple classified ad for a used car, or
could contain a picture of the used car for sale. The system can store and
display in layered fashion an entire catalog for a department store with
hundreds of images and audio tracks in one object module. Alternatively,
the system can store as an object module a list of information, such as a
month of TV listings. If desired, that month of TV listings can contain
selected images of actors of scenes from movies or TV shows that are
displayed along with audio tracks when the viewer browses through the TV
listings.
To summarize, the system utilizes a generalized storage methodology to
package diverse kinds of information from audio/visual full-motion
segments to static images to textual lists of information. The layered
data structure presents a uniform structure to the decoding and display
logic which the user interacts with.
Information and service providers, ad agencies, newspaper ad departments,
etc. are supplied with video-graphics workstations based on popular
personal computer technology. These workstations contain proprietary and
commercial software to enable third parties to create finished, broadcast
quality advertisements combining short full-motion segments, still images,
and audio as desired. These advertisements can then be transmitted via
modem to the regional processing center for preparation for inclusion on
the system database.
IV. Overview of the Distributed Architecture of the System
The regional processing center 4 is responsible for the processing and
assembly of the complete sets of information (called magazines) for each
cable system. Once the data is assembled and processed at the regional
center 4, it is ready for viewing. The data needs only to be transferred
to nodes 12 for access by the home users.
The nodes 12 are the end point of the distributed architecture of the
system of the present invention. Each node 12 can serve up to about 60
homes on a contention basis (with an optional node extension module 124
discussed below), where up to 31 of the 60 homes can use the node
independently and simultaneously. The home user interacts with node 12
through a home interface controller 16 using an infrared remote control
device 40 (discussed later).
The node 12 receives and stores on an internal mass storage medium all of
the advertisement data broadcast by the headend computer 8. The daily
broadcasts from the regional center to the computer 8 and then from the
headend computer 8 to the nodes 12 consist only of changes to the node
database. These changes consist of additions of new data, deletion of
expired data, and changes to existing data. These updates will affect
approximately 20 percent of the total database, for a given day, although
the system is designed to accommodate 100% change every night.
The entire database that a user interacts with is local to the user. A full
bandwidth TV channel is available from the node 12 to each home. A cable
system may use a thousand or more nodes. This is in contrast with past and
present videotex systems communicating over telephone lines with 1/1000
the bandwidth of a TV channel and a singular central computer to serve an
entire city of tens of thousands or more.
V. System Interface to Cable TV System
Referring to FIGS. 1 and 2, some advertisements are created at information
suppliers and ad agencies offices on workstations. Data listings, such as
TV listings, movie listings, and classified ads are imported from
information providers via computer modem over telephone lines 2 into the
regional processing center 4 and converted into advertisement object
modules.
Once normalized, the object modules are grouped together for transmission
to their respective cable TV system. The data magazine (group of
advertisements) is transmitted over leased line 6 at a preferred data rate
of 56 kbps (although the data rate can be anywhere between 2400 band to T1
(1.544 mbs/sec). The headend computer 8 then rebroadcasts the data
magazine at an appropriate data rate (preferably 9600 baud) across the
cable system to all nodes 12 simultaneously to update the nodes'
databases.
The headend computer 8 is preferably an industrial microprocessor-based
controller computer with high capacity magnetic or optic read/wide storage
devices. The output of the headend computer 8 is an rf carrier at 74
megahertz (between TV channels four and five). This carrier is modulated
using a simple frequency shift key (FSK) technique, preferably at a data
rate of 9600 bps.
The data modulated 74 mhz carrier is connected in the cable TV headend 10
to the existing cable TV plant through the rf combiner along with the
regular cable TV channels. As in an ordinary or typical cable TV system,
the output of the RF combiner connects to the trunk coaxial cable 24. The
trunk 24 is a high quality coaxial cable that forms the backbone of the
cable system. Trunk amplifiers 26 are placed every quarter mile to
maintain signal strength. At cross streets or where needed, bridger
amplifiers 28 split some signal off of the trunk to supply the feeder
coaxial cable 30 which runs down residential streets.
Like the trunk cable 24, the feeder cable 30 has amplifiers, called line
extenders 32, placed every quarter mile--which usually equates to every
ten telephone poles. At every telephone pole, and sometimes mid-span, taps
34 are spliced onto the feeder. Each tap 34 usually has from four to eight
outputs to which subscriber drop cables 36 are attached. The subscriber
drop 36 attaches to the home and then runs inside, terminating at the
subscribers' TV sets 38. There are usually two line extender amplifiers
per feeder cable, sometimes there are three amps, but rarely any more for
signal quality reasons.
One node 12 is placed at the start of the feeder cable just after the
bridger amplifier 28. Additional nodes 12 are placed after each line
extender 32 along every feeder cable 30. As an example, for a large cable
system of 100,000 homes with typically 2000 miles of cable feeder, there
will be approximately 8000 line amplifiers. Such a system would
correspondingly employ 8000 nodes.
In an alternative embodiment shown in FIG. 2A, the node connected to the
start of the feeder cable 30 can also service homes up to the first line
extender 32 on other feeder cables connected to the same bridger amplifier
28. If a return path is added, a single node 12 can also service homes on
both sides of a line extender 32, as shown in FIG. 2B. Finally, as shown
in FIG. 2C, if the line extenders 32 on a feeder line are upgraded to pass
650 MHz and if a return path is also added, one node can service all homes
on multiple feeders from a single bridger amplifier 28.
The home user interacts with the system using an infrared remote control
40. The remote control signal is received by the Home Interface Control
(HIC) 16 atop the user's TV set 38. HIC 16 is connected in series with the
subscriber cable drop 36 (and cable converter box when used) and the
user's TV 38. The user commands are relayed back up the subscriber cable
drop 36 and through the tap 34 back to the node 12 on the pole nearby the
home. This signaling, between HIC 16 and node 12, is done in the 5 to 50
MHz band, which is reserved by all cable system for return channel
signaling.
The last node 42 on each feeder 30 has a telephone line 18 attached that is
used by that node to send user responses back to the headend computer 8.
All nodes along the feeder (usually two nodes) upstream from the end node
42 send their user responses to the end node 42 via an rf carrier at 74.5
MHz (between channels 4 and 5) at a preferred data rate of 9600 bps. To
complete the loop, the headend computer 8 sends user responses back to the
regional center 4 via datalink 20.
In summary, the system moves data updates across the cable system without
using any cable TV channels by utilizing unused inter-channel space. The
return path for interactive services is up the subscriber drop to the node
at a low frequency, then downstream in inter-channel space along the
feeder cable to the end of every feeder, then telephone lines back to the
headend computer and telephone lines again to the regional computer center
and telephone from there to the respective service provider. The aggregate
delay from user back to service provider is no more than 5 seconds.
VI. Bandwidth Utilized by the System
Referring now to FIGS. 3, 4 and 5, each node 12 broadcasts on up to 32
standard TV channels. The 32 channels are broadcast as a block of adjacent
channels above the last used channel of the cable system. For instance, if
the cable system offers 50 channels of service, then the system of the
present invention will use channels 51 to 82. The frequencies of 462 to
654 MHz would be used by the present invention on a 50 to 450 MHz cable
system. If the cable system used 50 to 300 MHz bandwidth, the present
invention would use 312 to 450 MHz, etc. These frequencies pass through
the tap 34 and any splitters inside the home, but do not pass through the
line extenders 32 or bridger trunk amps 28 unattenuated. These outband
frequencies are unusable by the cable system from their headend because of
the bandwidth limitation of the series of trunk and feeder amplifiers.
The shaded areas of FIG. 4 illustrate the bandwidth usage. The vertical
grey bands passing through 28 and 32 represent areas of minimum bandwidth.
For a typical cable system, as mentioned above, this bandwidth is 300 to
450 mHz. The node 12 exploits the unused bandwidth of the feeder cable 30,
taps 34, and subscriber drop 36 to the home, which is a minimum of 600
MHz. This is represented by the horizontal hashed area 44. Each node 12
only services the taps up to the next line extender 32, which is usually
less than twenty taps total and an average of thirty homes.
Some signals in the 462 to 654 MHz range from the nodes 12 will pass
through line extenders 32, as the line extenders do not have a sharp
cut-off at their top frequency--450 MHz in our example. To deal with this,
the feeder inserter 46 contains a low pass filter 48 that sharply blocks
the band above 450 MHz, so that the next node 12 can reuse the 462 to 654
MHz frequency range for the next group of taps up to the next line
extender, and so on.
When a user presses a key on the infrared remote control 40, the HIC 16
receives the command and modulates it onto an 11 MHz carrier which is sent
up the subscribe drop 36 through the tap 34, through the feeder inserter
46 and into the node 12. The feeder inserter 46 contains a notch filter 49
to block the 11 MHz carrier from going further upstream (left in the
drawings) on two-way cable systems that have return path amplifiers (5 to
50 MHz) installed in the line extenders 32 and bridger amplifiers 28.
All HICs 16 signal back to their respective node 12 on an 11 MHz carrier.
To avoid contention, the node 12 polls the HICs 16 on 12 MHz in a
round-robin fashion. This HIC polling frequency also carries data for the
printer 50 when the user chooses a selection on screen that allows
printouts, such as store coupons or theater tickets. A third use of this
12 MHz carrier is for available channel status from the node 12 to the
HICs 16. When the user first picks up the remote control 40 and touches
any bottom, the HIC 16 reads this status word and selects the lowest
channel available, if any. The HIC 16 then signals back to the node 12 on
the 11 MHz carrier to reserve the channel.
For interactive services, such as home shopping or purchasing tickets, the
user responses need to get back to the respective service provider. As
mentioned above, the system supports two-way interactivity via a chain of
store and forward nodes. Assume a user is interacting with the left-most
node in FIG. 4. User responses are transmitted on a 11 MHz carrier from
the HIC 16 and travel up the drop 36 to the node 12. The node 12 transfers
the users response on a 74.5 MHz carrier to the last node 42 on the feeder
cable 30. The end node 42 includes a modem 67 (FIG. 6A) and transfers user
responses via telephone lines 18 to the headend computer 8, which relays
the user responses to the regional center 4, which finally transfers the
responses to the respective service provider. The total delay through the
network will be less than five seconds from user to service provider.
VII. Overview of the Node and HIC
All but one of the channels of the system are interactive. These
interactive channels are allocated on a first-come-first-served basis. All
channels are scrambled and a channel can only be viewed by the home that
it was allocated to. Once allocated, the channel is descrambled by the HIC
16 for each respective viewer. A system channel is assigned to one and
only one home upon request (the user activates the remote control 40 to
request a channel). The channel remains allocated until the user releases
it or a certain number of minutes pass without any activity from the user.
There are enough channels available for any particular node to allow for a
2 to 1 or greater contention. Audio/video rf modules (described later in
connection with FIG. 6B) are inserted (4 channels per module) to populate
a node for the desired contention level.
Once a system channel has been allocated to one of the approximately forty
homes that can contend for it, the home user interacts with the node 12 in
privacy. The channel is not viewable by other homes. To the user, the
system is a dedicated channel to their TV set. The user interacts with the
system using the remote control 40 to move an on-screen pointer over an
icon, text, or image of choice and presses a button on the remote control
40 marked "PLAY" to select choices and call-up desired information.
When the user tunes to the system channel, the channel is displaying the
latest TV listings. All subscribers on the cable TV system can see this
service by just tuning to the cable television channel assigned to the
system of the present invention. Upon tuning to this channel, the user
sees the non-interactive channel of the system. If the user picks up the
remote control 40 and touches any button, a request is sent to the node 12
for a dedicated system channel. The system then switches to one of the up
to 31 dedicated interactive channels automatically (assuming one is
available) and the user can begin to use the system, unaware of the
channel change.
The change from the non-interactive display only channel to an interactive
channel is effected by the home interface controller (HIC) 16 on top of
the user's TV set 38. The home interface controller 16 monitors a 12 MHz
FSK data stream from the node 12 modulated with a polling command to
activate HIC 16 in a round-robin fashion. (An alternate embodiment uses
the vertical blanking interval of the non-interactive channel to receive
channel assignment and channel release commands from the node).
Since the user typically spends a significant amount of time viewing menus
and other non-moving displays of information in using the system, the
virtual channel can be released for use by others during these "dead"
periods (when no new information is being received from the node) by
installing a frame grabber 39 in each HIC. Thus, the user is assigned a
virtual channel only during the short periods that data is actually being
transferred from the node to the HIC, making more efficient use of the
virtual channels and thus avoiding contention problems.
Frame grabber 39, shown in detail in FIG. 8A, consists of frame grabber
control logic 202, a video D/A converter 204, a video RAM 206, a video A/D
converter 208, and a NTSC encoder 212. In operation, the frame grabber
control logic 202, upon receiving a gating command from CPU 80, activates
video D/A 204 at the appropriate time (based upon the NTSC synch signal)
to convert a frame of video into digital data. That frame of data is
stored in video RAM 206 at an address supplied by frame grabber control
logic 202. The frame of data stored in video RAM 206 is converted back to
video by video D/A converter 208 (under control of frame grabber control
logic 202), routed to NTSC encoder 212 and then out to an A/B switch 41.
A/B switch 41, operating under control of CPU 80, gates either the video
from the virtual channel or the frame of video from frame grabber 39 to RF
modul | | |
