Note: Descriptions are shown in the official language in which they were submitted.
CA 02569723 2009-10-21
ASYMMETRIC DATA COMMUNICATIONS SYSTEM PERMITTING
SUBSCRIBER INTERACTION
Field of the Invention
The present invention relates in general to the field of data
communications, and in particular, to the fields of television and
telecommunications.
Background of the Invention
Originally, television programming was provided solely by
over-the-air broadcast. The most widely received over-the-air transmissions
were and continue'to be in the very high frequency (VHF) band and only to a
much more limited extent in the ultra high frequency (UHF) band of the RF
spectrum. In recent decades, however, the delivery of television
programming into the home increasingly has been delivered via CATV
(cable) service. CATV transmission offered considerably higher bandwidth
than was available over-the-air, while the quality of its transmission -- for
those equipped with the necessary coaxial cable for receiving the analog
signal, and the hardware required for descrambling it -- has been generally
better than analog airwave transmission, which is subject to a variety of
forms of signal interference.
The high bandwidth and transmitted signal quality of CATV
transmission relative to over-the-air broadcasting has led to CATV being a
dominant force in the market for multiple channel programming. That
CATV coaxial delivery systems in principle provide sufficient bandwidth to
permit two way communication with subscribers has fueled speculation that
CATV may provide an early venue for the provision of interactive television
services. CATV service, however, is inherently limited by the extent of its
geographic penetration. CATV service is simply unavailable in locations
that cable providers have chosen not to serve. Even where CATV service is
available. installation of the coaxial cable is disruptive as well as
expensive.
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The provision of interactive programming content has become
a major goal of the converging television, entertainment, programming.
telecommunications, on line and computing industries. Telecommunications
companies, for example. have invested significant resources in developing
"video dialtone," in which programming services would be provided by way
of the telephone system. Although this approach shows enormous potential
and the ability to revolutionize both the telecommunications and television
industries, it presents certain non-trivial technological and economic
problems. The provision of video dialtone services to the home may turn on
the installation of optical fiber and/or coaxial cable in place of existing
twisted pair telephone connections, which presents a highly expensive and
time consuming proposition that is not expected to be implemented for some
time.
Aside from efforts to move to what has become known as
high-definition television (HDTV), and to provide such HDTV services over
the air. comparatively little attention has been paid recently to enhancing
television programming services that are delivered over the airwaves. A
possible reason for the comparative lack of effort may be that the perceived
need to support interactivity would seem to militate against a video delivery
system that uses as its transport medium one that apparently lacks a return
path. The available choices for delivery of television programming.
meanwhile, have continued to grow into such areas as "wireless cable" and
direct broadcast satellite, tending to draw attention even further away from
over-the-air broadcasting.
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Still another obstacle to the provision of an alternative means
for providing programming services on a large scale, such as by over-the-air
broadcast, has to do with equipping intended recipients of the programming
services with the means to receive and view the programming. Aside from
the direct expense associated with providing a new device, viewers may
harbor concerns about the compatibility of a new in-home device with any
existing premises equipment, in which a viewer may have made a sizable
investment. Even if a device were to be provided gratis by a service
provider, for example, subscribers may be somewhat reluctant to commit to a
particular system if it were not compatible with existing delivery systems
purely for reasons having to do with such things as clutter and the
consumption of available space. Nevertheless, the apparent demand not only
for traditional television programming, but also for such services as home
shopping, video games, data services such as electronic catalogs, stock
market quotations, sports scores, and electronic newspapers, and interactive
services. as well as video on demand (Vol)), near video on demand (NVoD)
continues to grow. This consumer demand, coupled with an increased
demand by marketing organizations for demographic and consumer
preference information for use in their characterizing and targeting the
increasingly segmented consumer populace faced with a growing number of
viewing alternatives makes clear that any alternative means for delivering
programming must have a return path for enabling viewer interaction.
Summary of the Invention
The system, method and device according to the present
invention solves the problems described above by providing an asymmetric
data communications system (ADCS) capable of furnishing an alternative to
3 0 conventional over-the-air and CATV television transmission. and that is
also
capable of providing functionality not furnished by either of those delivery
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systems. The system according to the present invention provides an
alternative means for the delivery of video and audio entertainment
programming. as well as a variety of data services, such as electronic
catalogs, stock market quotations, sports scores, electronic newspapers. and
will be able to carry services that have not yet been conceptualized. The
ADCS system of the present invention at the same time provides a return
path capable of supporting viewer interactivity, enabling the viewer to
request transactions and orders for services that require authorization, to
engage in interactive participation in programming distributed on a
programming channel and other forms of interaction, as well as providing a
data path and a mechanism for gathering demographic information from
subscribers.
A first aspect of the system according to the present invention
makes available previously unusable over-the-air broadcasting spectrum.
Briefly, and as described at length below, the system according to the present
invention digitizes, compresses and modulates signals for transmission in the
UHF spectrum band that is currently assigned to television broadcasters, the
signal compression using presently available techniques to achieve eight or
more times the capacity using conventional techniques as can now be carried
in that band. The ADCS system according to the present invention thereby
provides point-to-multipoint multichannel broadcast services over-the-air on
a scale previously available only using cable, and does so with high quality
transmission and reception, and without interfering with existing channels
broadcasting under the NTSC (National Television System Committee), PAL
(Phase Alternation Line), SECAM (Sequential Couleur A Memoire), or other
color television transmission standard. In addition. a program subsystem of
the present invention aggregates heterogenous programming from a number
of content providers for digital UHF transmission, as well as Vol) and
NVoD. both services being provided only upon completion of an
3 0 authorization function.
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The system according to the present invention provides an
alternative to CATV for those who wish to subscribe to services that have
previously been considered the exclusive province of CATV. Notably,
subscribers dissatisfied with CATV services or who simply are not served by
CATV will be able to gain access to a large number of channels and at a
considerably lesser expense, since the below-described system will enable
program providers to offer the point-to-multipoint broadcasting at a cost
lower than that associated with that of the installed cable system base.
Subscribers will be able to receive and participate in interactive television
without the need for a cable connection. Such subscribers will simply need a
suitable device, referred to herein as an intelligent control box (ICB) and
described in detail below.
According to the present invention, the ICB is adapted not
only to receive, decompress, decode and transmit for display the received
digitized UHF signals, but to provide a terminal capable of establishing a
return path to the broadcaster via the public switched telephone network
(PSTN) (e.g., POTS, ISDN, ADSL. B-ISDN) or a suitable wireless
alternative. The ICB serves as an electronic gatekeeper, providing matrix
switch functionality to interface between the ADCS and a consumer
television, computer or any suitable monitor or terminal device. As further
described below, the ICB can include transmission decoding functionality,
data storage, switching and authorization functions. The ICB can also
include a capability for switching between a variety of non-ADCS inbound
or downstream sources, including conventional "over-the-air" television.
CATV, MMDS (multipoint microwave distribution system, or "wireless
cable"). DBS ("direct broadcast satellite"), LMDS ("local multipoint
distribution system," provided, e.g., by CellularVision), VCRs,
computer/video games, and mass storage devices.
A final part of an ADCS system according to the present
invention is a return path facility which, along with ICBs to which it is
linked
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by the PSTN or wireless alternative, constitutes the return path subsystem of
the ADCS system according to the present invention.
Accordingly. it is an object of the present invention to provide
an alternative to conventional wired cable television (CATV).
It is another object of the present invention to provide this
alternative to conventional wired cable television in the form of an over-the-
air radio frequency (RF) point-to-multipoint broadcast and receiving system.
It is a further object of the present invention to provide an
alternative to conventional wired cable television that includes a return path
by way of which user transactions, orders, demographics and other
information may be sent or collected from a subscriber premises device.
It is yet another object of the present invention to provide the
return path in the form of a wired point-to-point configuration, such as a
configuration using switched (analog or digital) telephone technology, that in
the context of a digital UHF point-to-multipoint broadcast system provides
an asymmetrical data communications system.
It is another object of the present invention to provide an
ADCS having a program subsystem capable of aggregating a variety of
heterogeneous programming, digitizing and compressing these signals for
UHF broadcast.
Another object of the present invention is to provide an
ADCS having a return path facility accessed by subscribers over a public
telecommunications network for capturing and fulfilling program requests
and other transactions and also for collecting subscriber demographics
information.
It is still a further object of the present invention to provide an
intelligent control box to act as an electronic gate keeper at the
subscriber's
presence in the form of a matrix switch capable of providing an interface,
capable of receiving and decoding a digital RF transmission in the UHF
3o band. and communicating subscriber messages to the ADCS.
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Brief Description of the Drawings
Figure 1 is a schematic view of an embodiment of an
asymmetrical data communications system according to the present
invention.
Figure 2 is a component block diagram of the components of
an embodiment of an asymmetrical data communications system according
to the present invention, showing data paths between the components.
Figure 3 is a block diagram showing the architecture and
functions of the major components of an embodiment of an asymmetrical
data communications system according to the present invention.
Figure 4 is a component block diagram of a program
subsystem of an embodiment of an asymmetrical data communications
system according to the present invention.
Figure 5 is a block diagram showing the signal processing
steps of multiple video sources performed in the program subsystem and/or
transmission subsystem of an embodiment of an asymmetrical data
communications system according to the present invention, and indicating
alternative suitable techniques for performing each step.
Figure 6 is a block and partially schematic diagram showing
the transmission subsystem of an embodiment of an asymmetrical data
communications system according to the present invention.
Figure 7 is a component block diagram of an ICB of an
embodiment of an asymmetrical data communications system according to
the present invention.
Figure 8 is a component block diagram of a return path
facility of an embodiment of an asymmetrical data communications system
according to the present invention.
Figure 9 is a logic flow diagram for a representative operation
of the ICB and return path facility of an asymmetrical data communications
3 0 system according to the present invention.
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Detailed Description of the Invention
The system and components of the system according to the
present invention will be described with reference to the accompanying
figures. and in an order that reflects the delivery of services to consumers.
A
high-level view of an embodiment of the system according to the present
invention is provided in Figure 1. As shown, a program subsystem 10 is
equipped to receive content from various sources, including: non-local
content providers 12 via satellite or any other suitable means or transmission
path (including optical fiber, for example); from local TV programming
entities 14 via microwave, optical fiber, cable, or other suitable
transmission
paths; or over any suitable path from any other source (not shown). The
received content may include conventional channel television broadcasts,
home shopping, data services, electronic catalogs stock market quotations,
sports scores, electronic newspapers and other content, whether or not
presently available. Video-on-demand (VOD) or near video-on-demand
(NVoD) may also be received by any known means and provided by
conventional video servers, as described at greater length below.
Program subsystem 10 collects and processes the signals from
these various sources and, after processing the signals, provides the
programming, data and any other received content in an appropriate form and
over a suitable data link 18 to a transmitter subsystem or site 20.
Transmitter subsystem 20 includes transmission equipment,
described in detail below, for generating a signal having sufficient effective
radiated power (ERP) and signal-to-noise ratio (SNR) to reach a set of
intended subscribers 30 with acceptably high quality reception. In the
preferred embodiment of the present invention, program subsystem 10 and
transmitter subsystem 20 transmit this combined content in digital form and
in the ultra high frequency (UHF) band of the RF spectrum (407-806 MHz).
Subscribers 30 each are equipped at their premises with
3 0 appropriate receiving and processing equipment (not shown in this view,
but
described in detail below). Using this equipment, subscribers 30 can select
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from among the variety of content carried by the signal(s) transmitted by the
equipment at transmission site 20. as well as from among the full array of
other programming sources as to which the premises equipment acts as an
electronic gateway. Communications from subscribers 30 can include
requests for VoD, NVoD, or other interactive or non-interactive program
service, and can also include marketing information regarding subscriber 30.
Messages from (or about) subscriber 30 are transmitted via switched
telephone technology, i.e., the public switched telephone network (PSTN)
lines 40 (or a suitable wireless alternative, not shown) and via switching and
other service sites maintained and operated by a local telephone service
provider 45, to a return path facility 50 (which may also be operated by a
telephone service provider. BellSouth Corp., for example).
Return path facility 50 may also undertake transactions with
other service providers (collectively identified by reference numeral 48).
Return path facility 50 also receives communications from other subscribers
(via lines 49A, 49B.....49N), and performs a variety of functions including
the control of sessions with subscribers 30 and conducting administrative
functions, both of which will be discussed in detail below. Finally, return
path facility 50 communicates authorization requests to program subsystem
10 via a high capacity data link 52, such as a broadband circuit or other high
capacity link.
The overall architecture of the ADCS according to the present
invention is shown in somewhat greater detail and in block diagram form in
Figure 2. At premises 32 of subscriber 30, for example, an antenna 131 is
installed for receiving a broadcast signal from transmission subsystem 20.
The received signal is routed to an intelligent control box ("ICB") 130. which
is also configured to receive input from all other available sources 100. ICB
130 is equipped to receive input from subscriber 30 and to transmit an
appropriate signal. such as an NTSC. PAL. SECAM or other analog standard
3 0 television signal. to television 34. ICB 130 may also be equipped to route
signals to one or more additional televisions or other terminal devices, such
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as personal computers ("PCs")(not shown). ICB 130 may be coupled to a
network interface unit ("NIU") 36 in order to communicate over a network.
Alternatively, the functionality of NIU 36 could as easily be implemented by
a device resident within ICB 130.
Also shown in Figure 2 as connecting subscriber premises 32
with return path facility 50 by way of the PSTN 40 and telephone service
provider facilities 45 is an optional path 42 via which return path facility
50
can send messages to ICB 130. Return path facility 50 receives via
telephone service provider 45 messages not only from subscriber 30, as
shown, but also from any number of subscribers (not shown in this view)
reached by transmission subsystem 20, preferably by a high capacity link of
sufficient bandwidth to simultaneously accommodate messages from a large
number of subscribers.
I. Program Subsystem
As shown schematically in Figures 1 and 2 and functionally in
Figure 3, and as shown in still greater detail in Figure 4, program subsystem
10 is equipped with conventional equipment to receive content via any
suitable communications link from all programming and data sources.
Programming and data from non-local content providers 12 can be received.
for instance, via satellite (see Figure 1) by tuner 23A. while programming
from local TV content providers 14 could be received by tuner 23B from
other transmission media, such as microwave or cable, and also by video
tape, compact disc ("CD") delivered to the program subsystem. Among the
variety of sources of content to which program subsystem 10 is preferably
linked are video and audio entertainment programming. data services such as
electronic catalogs, stock market quotations, sports scores and the like,
electronic newspapers and other services, as well as other types of content
that are as yet unavailable.
In addition to equipment for receiving the variety of content
via various transmission paths, program subsystem 10 includes conventional
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video server means 28 for providing Vol) and/or NVoD services, for
example. With Vol) and NVoD, a preselected set of films is delivered
simultaneously, but out of phase (i.e., staggered) by a predetermined amount
of time, in order to permit VCR-like functionality to subscribers 30, as
discussed in greater detail below. For example, a selection of the 10 top
films at any given time may be provided.
Program subsystem 10 tuners 23A and 23B and video server
system 28 are coupled to program subsystem bus 21, on which the received
data may be read and managed by one or more processors 24. Processor 24
can be implemented by a conventional device or set of devices having
sufficient processing power to manage the receipt and suitable signal
processing of content, as described, and also to manage the video server
system 28. In carrying out its tasks, processor 24, by way of program
subsystem bus 21, can read system software and other data from static
memory 25. and can store and retrieve data in dynamic memory 26 and mass
storage device or devices 27. all of which can be implemented with
conventional technology.
Additional input to program subsystem 10 originates at return
path facility 50 and is provided over link 52, which can be a broadband link
or other link suitable for carrying a large volume of data. The data provided
to program subsystem 10 by return path facility 50 includes, but is not
limited to, requests for authorization for requested programming, such as
pay-per-view, VoD, or NVoD. According to known techniques, the
processor or processors of program subsystem 10 includes functionality for
receiving requests for pre-stored authorization codes corresponding to the
subscribers and for incorporating one or more codes into the broadcast signal
in order to enable a requesting subscriber to receive an encrypted program, as
will be further described below. Input received over link 52. in the form of
authorization requests or messages, is demodulated or otherwise processed as
3o necessary by I/O device 22A, and is provided on program subsystem bus 21
for processing. management and storage by processor 24. Messages can be
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sent by program subsystem 10 via I/O device 22A back to return path facility
50 as necessary, such as to acknowledge an authorization request or to
provide information for use in managing the ADCS.
Referring again to Figure 2. the primary functionality of the
program subsystem 10 is shown. Incoming channel service. Vol) or NVoD
sources. and all other input content are received according to known
methods. The received programming and content are then processed to
produce a signal that can be provided via link 18 to transmitter subsystem 20
in a form suitable for physical transmission. The processing performed by
program subsystem 10 applies known methods to achieve a maximum
transmission rate and a minimal probability of transmission errors, while
keeping to a minimum the amount of transmitter power required, and the RF
bandwidth required.
The available bandwidth for transmission is likely to be
driven in part by the regulatory environment, as well as by the availability
(or
lack of availability) of suitable UHF channels in a given market. Under the
present regulatory framework, channels are defined in 6 MHz RF bands. The
UHF spectrum, defined as the 470-806 MHz band, is divided into 56 such 6
MHz channels, which are identified by convention as numbers 14 to 69. The
2 o UHF band has been used to provide television service for decades, thus
transmission equipment is available from a variety of vendors.
Propagation of signals in the UHF spectrum is generally line-
of-sight. and thus limited by obstructions in the path between the transmitter
and a receiver, such as mountains and the curvature of the earth. However.
the presence of these obstructions can lead to the diffraction of UHF signals
and thus to a certain degree of circumvention of the obstacles. Signals in the
UHF spectrum also reflect off certain obstructions, which tends to divide the
energy in the signals into fractions that propagate to a given receiver over
more than one path. Such multipath propagation can lead to fractions of a
UHF signal arriving at a receiver at slightly different times. causing a
phenomenon known as "ghosting," in which one or more phantom images
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trail a primary image on the television screen. Ghosting can be addressed
through channel equalization techniques.
Transmission of a large number of component signals in a
single-to-multipoint UHF transmission poses a number of technical and
regulatory problems. Present FCC allocation rules. for example, grant RF
spectrum rights to one use or user exclusive of others and in such a manner
as to be protected from interference. Co-channel interference is addressed by
enforcing a mileage separation of broadcast facilities to hold the desired to
undesired signal ratio (D/U) to a predetermined level.
Digital transmission is less susceptible to co-channel
interference. Nevertheless, it is expected that existing NTSC (or PAL,
SECAM or other analog television standard) channels will be protected to
the extent presently required for a number of years.
In addition to co-channel protection, UHF signals are
protected by rules designed to limit interference between adjacent channels.
These rules, known as "UHF taboos," constrain the D/U between
immediately adjacent channel signals to be -6 dB or greater, require
separation of transmitter sites by a predetermined distance to address
interference introduced by local oscillator radiation, require separation of
image frequencies associated with the visual and sound carriers. and preclude
use of the second through fifth adjacent channels to combat intermodulation
distortion. The UHF taboos are set forth in 47 C.F.R. 73.699 (Table
II)~
In order to support the delivery of the maximum number of
programming channels, as well as a desirable number of films available for
VoD or NVoD delivery. and permitting this service to be as close as possible
to "VCR functionality." it is desirable to substantially reduce the bandwidth
necessary for the delivery of adequate service. Several approaches may be
used.
In one embodiment of the system and method according to the
present invention, the resolution of the programming is purposely selected to
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be equivalent to that available from video home system (VHS) video tapes or
other publicly acceptable medium having resolution lower than is associated
with conventionally broadcast television signals. The resolution of VHS-
quality video is approximately 256 by 240 pixels. Since video consumers
appear comfortable with this resolution, transmission by the ADCS program
and transmission subsystems would appear to be efficient yet
unobjectionable at that degree of resolution.
In another embodiment, a data compression scheme is used,
for example, MPEG2 compression (Moving Pictures Expert Group standard
2. an international video and audio compression and transmission standard
described in ISO/IEC CD 13818-1),
or any other suitable standard, format, protocol, data
structure. sequence or organization scheme for reducing the bandwidth
required for transmission. Assuming video stream(s) encoded at 3 Mbps, the
number of such digital video streams available in a 6 MHz channel can be
computed according to the following relation:
R = B=1og2(N)= U
where R = bit rate;
B = channel bandwidth;
N.= signalling (or quantizing) level of modulation;
U = payload useability (to take into account forward error
correction);
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Quantizing Log2(N) 3/4 Payload Bandwidth Bit Rate Number of
Level N Video Streams
2 1 0.75 6 4.5 1
4 2 0.75 6 9 3
8 3 0.75 6 13.5 4
16 4 0.75 6 18 6
32 5 0.75 6 22.5 7
64 6 0.75 6 27 9
128 7 0.75 6 31.5 10
256 8 0.75 6 36 12
The foregoing relation applies to any video encoding/compression scheme
and the results in the table apply for any video streams encoded at 3 Mbps
per video stream.
The quantizing level and the efficiency with which the video
streams are encoded are functions of available technology. In general,
programming that will be provided as channel service is digitized, suitably
compressed, encoded and modulated according to known techniques, some
alternatives for which are shown in Figure 5. To begin with, the multiple
video sources received by program subsystem 10 may each be source coded
112 (or "compressed") if possible in order to reduce the bandwidth needed
for transmitting them. Suitable source coding techniques that may be used
include character coding. sampling, quantization, pulse code modulation
(PCM), differential PCM (DPCM), block coding, and synthesis/analysis
coding. Another class of source coding or compression techniques,, known
as redundancy reducing coding. reduces the volume of data required to
transmit a signal by eliminating redundancy in the signal, as well as
information that would rejected rather than processed by a viewer because of
psychobiological limitations on human perception. For example. a typical
scene in a video contains much information that does not change from frame
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to frame. Transmitting only the changes in the scene permits a significant
reduction in the volume of data transmission without any loss of information
to the viewer. Another form of source coding or compression takes
advantage of the psychobiological phenomenon that the human eye is less
capable of resolving colored images than black and white images, permitting
a commensurate reduction in the amount of data to be transmitted without a
detectable loss of resolution.
Well-known compression techniques may be used. For
example, but without limitation, the MPEG-1 (Motion Picture Experts Group
of the International Standards Organization (ISO)), or MPEG-2 standard
would offer the possibility of "scalable" resolution, and which is currently
being implemented in the form of a commercially available integrated circuit
chip. However, any other suitable compression technique could also be used.
Using MPEG-1 merely as an example, a compression ratio on the order of
] 00: 1 can be achieved. Accounting for imperfections in transmission. the
effective bandwidth required for a video stream can accordingly be reduced
to the order of 0.08 MHz, implying a theoretical upper limit of 72 VHS-
quality video streams per 6 MHz channel according to the current spectrum
allocation.
Suitable transmission efficiencies may be achieved with
currently available channel coding methods, such as 16-QAM (quadrature
amplitude modulation), 4-VSB (vestigial sideband), 1-PSK (phase-shift
keying) or OFDM (orthogonal frequency division multiplexing). The second
processing step for the incoming video streams is channel coding 114. which
can be used to reduce required bandwidth and the presence of transmission
errors. Channel coding includes waveform coding, such as M-ary signalling,
and antipodal. orthogonal. biorthogonal and transorthogonal coding.
Channel coding also can include structured sequence coding, for example
using block codes or convolutional codes. Both block codes and
3 0 convolutional codes are directed to minimizing the bit error ratio (BER)
via
forward error correction (FEC). BER is one of the most important quality
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factors observed in evaluating digital transmission systems. FEC techniques
are intended to reduce residual BER by several orders of magnitude and also
to increase system gain by encoding the bit stream prior to modulation. The
coding involves adding extra bits to the bit stream according to specific
rules:
thus, they intentionally add a certain amount of redundancy. Using the
foregoing techniques, reliability can be traded off against efficiency to
achieve suitable system performance.
After the incoming signal has been suitably source coded and
channel coded, the compressed multiple video sources may be further
processed using spreading or spread spectrum techniques 116, such as direct
sequencing (DS), frequency hopping (FH), time hopping (TH) and hybrids of
these techniques. Spread spectrum techniques improve a signal's interference
resistance and thus bandwidth efficiency characteristics by distributing the
transmitted power over a bandwidth sufficiently wide to ensure that the
power per unit bandwidth is kept very small.
Spread spectrum signals are difficult for a casual listener to
intercept, but true security requires encryption. In order to protect them
against unintended reception. the multiple video source signals are encrypted
l 18 according to known methods, such as block and data stream encryption
techniques.
The digital multiple video source signals. having been
compressed. channel coded and spread. are also synchronized 120 and
modulated 122 according to known methods, some of which methods are
listed, without limitation, in Figure 5.
Finally, the compressed, channel coded, spread, encrypted.
synchronized and modulated multiple video source signal is multiplexed 124
according to known techniques listed at reference numeral 124 of Figure 5.
including. without limitation, frequency division multiplexing, time division
multiplexing, code division multiplexing. space division multiplexing and
polarization division multiplexing. The fully processed. modulated and
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multiplexed signal is provided, as shown in Figures 1 and 2. over link 18 to
transmitting site 20.
The techniques referred to in the schematic of Figure 5 and
the accompanying description, are illustrative but not exhaustive of the
techniques that could be used to practice the present invention. Other known
techniques may also be used, and their choice, as well as chosen parameters.
may depend not only on designer preferences but on design constraints
imposed by the setting of the transmitter, the chosen equipment, and other
factors. Moreover, the processing associated with these techniques could be
performed in program subsystem 10. as described above, but could
alternatively be done, at least in part, at transmission subsystem 20 as shown
in Figure 6 and described in the text accompanying that figure.
The Vol) or NVoD functionality of the program subsystem
may also be implemented according to known methods. Vol) service is
widely understood to mean that a desired video program can be viewed
within 5 minutes after it has been selected. Preferably, a user can exercise
virtual control over the transmission by pausing, rewinding, fast forwarding
or other function as one would do with a conventional video cassette player.
In order to achieve this functionality, for example with a two-hour long film.
it would be necessary for twenty four simultaneous video streams to be
transmitted, one beginning anew every five minutes. Fast forwarding.
rewinding and pausing are thus achieved by tuning to the appropriate time-
shifted channel. The program subsystem 10 would receive a request for
authorization from a subscriber 30, as further described in connection with
2s Figure 9, and would transmit this authorization, for example in a vertical
blanking interval of a preselected channel. The authorization would be
received by the ICB 130 of the requesting subscriber 30 and thereby enable
receipt and viewing of the appropriately time-shifted channel. Providing 10
film offerings of two-hour duration with 5 minute Vol) functionality would
require 240 simultaneous video streams. Provided that 8 video streams can
be reliably transmitted in a single 6 MHz RF channel. 30 RF channels will be
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required for this VoD function, the availability of which channels will
depend on the market, as well as the state of applicable federal regulations.
To facilitate the provision of VoD, relaxing the delay from 5 to 10 minutes,
thus being closer to NVoD, would reduce by half the required total
bandwidth to 15 RF channels.
II. Transmission Subsystem
Transmission subsystem 20 is shown in detail in Figure 6.
Although the multiplexing and modulation of signals has been described
above in connection with program subsystem 10, that functionality, or some
of it. could alternatively be provided at transmission subsystem 20, as shown
in Figure 6. If the functionality were provided in the program subsystem 10,
it could accordingly be excluded from transmission subsystem 20. As shown
herein, however, transmission line, 18, which may include a plurality of
separate lines, delivers the entirety of the programming content from
program subsystem 10 to transmission subsystem 20. Subsets of the
programming content may be input to multiplexers 21 A. 21 B. 21 C..... 21 N.
where they are multiplexed according to known methods, as described in
connection with box 124 of Figure 5. The multiplexed signals output from
multiplexers 21 A, 21 B. 21 C,.... 21 N are then digitally modulated at 22A,
22B, 22C...,, 22N, respectively, according to conventional modulation
techniques. Each multiplexed, modulated signal is then upconverted to RF
frequency by a corresponding upconverter 23A. 23B1.... 23N. which may be
implemented by conventional equipment. Output from upconverters 23A-
23N is then amplified by power amplifiers 24A, 24B. 24C,.... 24N,
respectively. Each power amplifier 24A-24N. which may be conventional
equipment. should be capable of generating a peak output sufficient for
appropriate radiated RF energy to allow proper reception of equivalent
NTSC (or PAL. SECAM or other analog television standard) transmission.
Output from each power amplifier 24A-24N is filtered by one or more filters
25A. 25B. 25C..... 25N. each filter being of a conventionally available sort
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CA 02569723 2006-12-14
and sufficiently sized to accommodate the power of the output of the
corresponding amplifier 24A-24N. to reduce spurious signals to acceptable
levels. In an alternative embodiment. the number of sets of transmitting
equipment could be reduced by further multiplexing a set of signals prior to
modulation, upconversion and amplification.
The output signals from the filters 25A-25N are applied to
combiners, which may be conventionally available equipment. For example.
output from filters 25A and 25B are combined by combiner 26AB, while
output from filter 25C and perhaps other filters are fed to combiner 26C, and
output from filters including filter 25N are input into combiner 26N. The
output of each combiner 26AB, 26C,.... 26N is applied, if necessary, to
corresponding transmission lines 27AB, 27C,....27N, respectively. Since the
transmission lines may be required to transmit several high-powered signals.
conventional coaxial transmission lines may not be useable. In such cases.
transmission lines are preferably waveguides of large diameter (e.g., 18
inches in diameter). Waveguide size is driven by the lowest frequency to be
carried, while the highest frequency that can be carried by the same
waveguide is limited by the transmission efficiency, which may be about
10% above the lowest channel frequency. Since the UHF television band
straddles 470-806 Mhz, as many as five different waveguides would be
needed to support transmission across that band. although for convenient
illustration, three are shown.
Portions of waveguide transmission lines 27AB, 27C and 27N
are supported by at least one transmission tower 28 having a suitable height
2s above the ground. while taking into account the relative altitude of its
base.
For example. transmission tower 28 could be 1000 feet high or more, if
required. Each of the waveguide transmission lines 27AB, 27C and 27N is
coupled to a corresponding antenna 29AB. 29C and 29N, respectively.
These antennas are also supported by transmission tower 28. which must be
sufficiently strong to bear them along with the waveguide transmission lines
27AB. 27C and 27N. and should accordingly be fabricated with sufficient
CA 02569723 2006-12-14
strength according to known methods. Preferably. at least three antennas
should be used in order to support transmission across the entire UHF band.
As with transmission lines, antenna efficiencies are frequency-dependent.
The height of transmission tower 28 should ensure sufficient vertical aperture
of antennas 29AB, 29C and 29N. As an alternative to a large single
structure. several smaller supporting structures could be used (not shown).
The transmission subsystem 20 can be expected to generate a high level of
non-ionizing radiation, which, depending upon the height at which the
antenna(s) are actually mounted, may require that its site be located most
preferably at an appreciable physical distance from human populations.
As described above, known components can be used in
transmission subsystem 20, preferably of a type suitable at least for use with
high definition television (HDTV).
M. Return Path Subsystem
Broadcasts by the transmission subsystem 20 are received by
subscribers who are within the broadcast pattern of the transmission
subsystem 20 and who at their premises 32 have a proper receiving device.
According to the present invention, the receiving device is a component of a
piece of equipment having a number of functions. and which is referred to as
an ICB (intelligent control box) 130.
Along with the return path facility 50 to which it is linked by
a telecommunications system. such as PSTN lines 40 (or a suitable wireless
alternative, not shown) and switching and other facilities operated and
maintained by public telephone services provider 45. the ICB 130 constitutes
a portion of the return path subsystem 80 of the described embodiment of the
system according to the present invention. The use of the PSTN lines 40
between the portions of the return path subsystem 80 takes advantage of the
realization that the timing and information content of communications by
3 0 humans differ enormously from those of the broadcast path. perhaps on the
order of 109. Information sent upstream by a subscriber 30. moreover, would
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tend to be sporadic rather than continuous. The second portion of the return
path, return
path facility 50, implements two types of functionality: switching and
accounting system
60 and external transaction system 70, each of which will be described below.
A. Intelligent Control Box (ICB)
ICB 130 forms that portion of the return path subsystem 80 of the system
according to the present invention that resides at the premises of subscriber
30 and
receives the digital UHF broadcast from the transmission subsystem 20. In
addition to this
role, ICB 130 also provides subscribers 30 with a variety of additional
capabilities and
functions.
The architecture for an embodiment of ICB 130 according to the present
invention is shown in Figure 7. ICB 130 acts as a matrix switch (i.e., an
electronic
gatekeeper) to provide an interface between the ADCS, the full variety of
other
programming sources, and the viewer's television monitor, computer, or other
peripheral
devices. In addition to over-the-air UHF ADCS broadcast, ICB 130 is provided
with input
ports to receive signals from any number of available sources. ICB 130 can
accept input
from an antenna 132, which can carry NTSC signals as well as digitized UHF
signals
transmitted by transmission subsystem 20. According to the present invention,
ICB 130
can also accept input from any number of non-ADCS inbound program sources,
such as
from a VCR 133, from a DBS provider 134, from an MMDS provider 135, from an
LMDS provider 136, or from a CATV provider 137. Input from any other available
source, including a mass storage or other device, as well as any presently
existing or future
transmission type, may be received by ICB 130, as denoted by the input port
identified as
"other" 138, which may be adapted or retrofitted to receive an appropriate
connector as
necessary.
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All program inputs received by ICB 130 are transmitted to
input selector (matrix switch) 170. which can be any available hardware for
switching between a plurality of signals. most preferably under the control of
a conventional or custom processor. Input selector 170 is coupled to system
control bus 180 of ICB 130 by way of which it can receive switching signals
from CPU 184 in order to execute the selection commands of subscriber 30,
as further discussed below.
ICB 130 includes at least one dedicated tuner for each input
type. Signals switched by input selector 170 are each provided to an
appropriate tuner. A selected over-air-air NTSC signals received via
antenna 131, for example, can be tuned by analog tuner 161, as can a selected
CATV signal received at port 137. In an alternative embodiment, one or
more additional analog tuners could be provided for simultaneously
receiving two analog signals, if it is desired to route two such signals to
different televisions, computers or other devices, to provide a picture-in-
picture (PIP) display, or to support other functionality.
Signals on input 132B, such as the digital UHF signal
transmitted by transmission subsystem 20 according to the present invention
are received by ATV tuner 162, which can be a conventionally available
digital tuner and demodulator. DBS input arriving at port 134, if selected
and accordingly switched by input selector 170, can be received by tuner
163, while MMDS signals entering at port 135 and switched by input
selector 170 are received by MMDS tuner 164. Similarly. LMDS signals
arriving at 136 and switched by input selector 170 can be tuned by LMDS
tuner 165. All of the foregoing tuners may be implemented by any
commercially available devices for receiving the respective signals.
Moreover, the foregoing tuners are illustrative rather than exhaustive;
signals
requiring tuning that cannot be done byway of the foregoing tuning devices.
such as signals according to as yet unconceived schemes, can be received by
3 0 a suitable associated tuning device or devices represented by box 166 with
which ICB 130 can be retrofitted as desired. Subscriber 30 thus does not
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have to collect, operate and maintain a set of devices from various vendors
each of which provides only a single purpose solution.
The output from analog tuner 161 (and any additional analog
tuners that may optionally be included in ICB 130) may be transmitted to
secure processor subsystem 172. Secure processor subsystem 172 may be
any known system for receiving scrambled or otherwise secured signals over
a private distribution system. Typically, the secured processor subsystem
172, its components, and their functionality are compatible with encryption
techniques of the sort employed in program subsystem 10, illustrated, for
example, at block 118 of Figure 5. Secure processor subsystem 172 includes
a conventional analog descrambler 173 for descrambling signals received and
forwarded by analog tuner 161. Secure processor subsystem 172 (or other
processor means described below) is programmed to detect one or more
authorization codes included in received transmissions and only to
descramble a particular transmission on detection of such code or codes.
Secure processor subsystem 172 may include a non-volatile memory subsystem 174
for storing information necessary for decoding received
transmissions. including normal cable program transmissions, pay-per-view
program transmissions and the like.
In order to interface televisions or other viewing devices
accepting a baseband input with a decoding device (for example, a CATV
decoder, not shown), secure processor subsystem 174 is optionally coupled
to EIA-563 standard baseband interface, the baseband output of which it can
provide to baseband-equipped televisions or other devices over line 182B.
Turning to the digital signals received by ICB 130, each tuner
among the set of tuners 162-166, demodulates signals it is tuned to receive in
order to reconstruct the desired analog signal. The resulting signal from each
tuner is transmitted by a dedicated line (here shown in a bundle of such lines
denoted in Figure 7 using the notation "/5") to video decoder 176. a
conventionally available device for interpreting an input stream according to
a preselected technique compatible with the method used for compressing the
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CA 02569723 2006-12-14
video signal at the program subsystem 10. for example. Video decoder 176
thereby recovers the compressed signal to produce a video signal. An analog
channel received for example by analog tuner 161 and selected by input
selector 170 may be routed via secure subprocessor system 172 directly to
NTSC signal generation module 182. Digital signals received by tuners 162-
166 may also be provided on dedicated lines (shown in bundled form using
the notation "/5") to system control bus 180, via which it could be provided.
as one illustrative example, via computer interface 196 to a computer or other
device.
Analog descrambler 172 and video decoder 176 are both
coupled to graphics assist module 178. Graphics assist module 178 can be
any conventional graphics processor suitable for adding a desired graphics
overlay onto the video signals received from the video decoder 176 and/or
the analog descrambler 172 in response to instructions implemented by
software running on CPU 184 and provided over system control bus 180.
The functionality of graphics assist module 178 could alternatively be
implemented by CPU 184. if it were suitably programmed and capable of
sufficient throughput. As will be further described below, graphics assist
module 178 generates a video signal overlaid on the existing television signal
providing, in response to instructions received over system bus 180. For
example. a menu of viewing options, information regarding the ordering of a
VOD or Nvod video, or any other information regarding subscriber
transactions may be overlaid on the screen. Graphics assist module 178 may
generate a menu, a button image, or a logo or other pattern or symbol, and
inject the image into the video stream such that the image appears in a
designated portion of the screen. Information used in generating the screen
images. as described below. may be available in received signals or may use
information stored in the ICB 130. for example, pre-loaded in static memory
186.
The video stream emerging from analog descrambler 173 or
video decoder 176. and from graphics assist module 178. is provided to
CA 02569723 2006-12-14
NTSC signal generation module 182. As an alternative to NTSC. signal
generation module 182 could generate signals according to any available and
desired video format. NTSC signal generation module 182 includes
conventional circuitry for transforming the output of analog descrambler 172,
video decoder 176 and graphics assist module 178 into a standard form
usable by a conventional television or monitor (not shown in this view).
This functionality could, alternatively, convert input signals to any suitable
standard format. As shown in Figure 7, NTSC signal generation module 182
generates a set of coordinated signals and provides them to one or more
terminal devices (not shown) adapted to receive and display television
signals, including without limitation one or more televisions or personal
computers. Output from NTSC signal generation module 182 to the one or
more terminal devices includes an NTSC video stream 182A on channel 3
and/or 4. a composite/Svideo Out signal 182B (which may also carry
baseband signals routed through EIA-563 171), and left and right audio
signals 182C. The signal provided by ICB 130 could be any signal deriving
in whole or in part from received input and be in any desired form. Even
more generally, CPU 184 can issue instructions to manage televisions,
computers. or other terminal or peripheral devices without limitation, for
example. via computer interface 196, which can be any suitable conventional
device. coupled to system control bus 180.
In addition to the previously described components and
functionality, which have to do with the receipt and provision of television
signals. possibly with inserted graphics, ICB 130 includes a number of
additional components for implementing other functions. The processing
associated with managing and controlling the functions of the ICB 130 is
performed by CPU 184. CPU 184 may be any suitable commercially
available processor. and preferably one capable of performing in excess of 30
Mips. such as a POWER PC or PENTIUM integrated circuit (IC) chip,
programmed to process the incoming digitized UHF signal according to
known methods. as well as selecting and processing the remainder of the
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CA 02569723 2006-12-14
input provided at ports 134. 138, 140, 144 and 145. when chosen by
subscriber 30. Alternatively, CPU 184 could be a custom chip or chip set for
carrying out the same set of functions. In running system software stored in
static memory 186 (which may be an EEPROM, ROM or the like). CPU 184
has access via system control bus 180 to static memory 186 and to dynamic
memory 188, which may be conventionally available memory, preferably
with a storage capacity of at least about 4-5 MB. CPU 184 also has access
via system control bus 180 to information regarding the current channel, to
the graphics assist module 178 regarding graphical display signals, and to
video decoder 176 and input selector 170, as well as to secure processing
subsystem 172, and the tuners 161-166, in order to assert appropriate
command messages to those components.
Interaction by subscriber 30 with ICB 130 may be by any
suitable means, but is preferably by conventional infrared (IR) remote
control. as in the described embodiment. Input controller 190 receives
signals from subscriber-controlled remote control input device 158 via an IR
receiver and associated circuitry (not shown). Using input device 158 (or
any other suitable input means), subscriber 30 may issue to the ICB 130
instructions to switch between programs, to request VoD or NVoD services
via the return path facility 50, to control the delivery of such requested
services with VCR functionality, to purchase items offered for sale on
shopping channels, or to provide any desired input originating with
subscriber 30. Instructions received by input controller 190 may be asserted
via system control bus 180 as commands to input selector 170 and tuners
161-166. to secure processor subsystem 172, as well as to video decoder 176,
and graphics assist module 178. Input controller 190 can also send messages
to CPU 184 when. for example, subscriber 30 requests an interactive
program or other service.
Interaction by the ICB 130 with return path facility 50 via
PSTN lines 40 and telephone service provider 45 is conducted by CPU 184
through WAN communications processor and modem 192. WAN
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CA 02569723 2006-12-14
communications processor and modem 192 can be any conventional device
suitable for converting messages received via system control bus 1 80 into a
WAN-compatible protocol. such as IP (internet protocol). and modulating
the converted message signals received from WAN communications
processor for transmission over the PSTN lines 40 and via switching and
other facilities maintained and operated by a telephone service provider 45
(as shown in Figures 1-3).
In addition to the primary function of delivering television
programming to subscriber 30, or management instructions to one or more
terminal devices such as televisions or computing devices, CPU 184
operating according to software residing in static memory 186. for example,
and using known methods, implements an authorization function enabling
subscribers (and only subscribers) of particular services, to be able to view
programming associated with those services. CPU 184 is also programmed
to capture and send via telecommunication connection 194 to return path
facility 50 subscriber requests for transactions input via remote control
system 1 58, as well as data regarding viewership and other observable
events.
B. Return Path Facility
A second portion of the return path subsystem 80 is a return
path facility 50. Return path facility 50 is shown in Figure 2 in schematic
form, illustrating the functionality of that component of the system according
to the present invention. Referring to Figure 8, return path facility is shown
in greater detail.
In brief. return path facility 50 provides an external
transaction system for facilitating viewing requests, purchases and other
transactions by subscriber 30 executed from the premises via the ADCS
according to the present invention, system, and also for facilitating
fulfillment of the viewing, purchase. or other request. including taking an
order. processing the order. establishing delivery of the item requested or
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CA 02569723 2006-12-14
purchased. conducting billing for the transaction or purchase. and sharing of
the proceeds with the seller. In addition, return path facility 50 also may
capture viewing and purchase pattern information for subsequent compilation
by a.market analysis center to determine types of content most valuable to
each individual customer. This process facilitates the transmission of
targeted advertising messages that can trigger interactions for more
information or a transaction.
The return path subsystem 50 is ultimately adaptable from an
ADCS to a symmetrical data communications system when the PSTN or
other non-broadcast return path has sufficient available bandwidth to
accommodate full video delivery. Return path facility 50 includes
conventional processing means 54, which can be one or more commercially
available processors and which is coupled via a return path facility bus 51 to
at least one static memory device 55, at least one dynamic memory device
56, and which may also be coupled to at least one mass storage device 57.
These memory devices can all be implemented with commercially available
hardware.
Two way communications between return path facility 50 and
subscribers. such as illustrative subscriber 30. can be maintained over a
public telephone.or other transmission line or lines via I/O device 53. which
can be any conventional device suitable for modulating and demodulating
input and output in a manner consistent with the transmission line. Since the
return path subsystem 50 is responsible for receiving request messages,
demographics and other information from all of the subscribers within the
signal range of transmission subsystem 20. the transmission line or lines are
preferably of capacity sufficient to handle this traffic.
According to functionality described at greater length below.
return path subsystem 50 sends messages. such as authorization requests, to
program subsystem 10 via I/O device 58 on return path subsystem bus 51.
Optionally, messages such as demographic, billing or other transaction data
can also be sent to other service providers 48 via I/O device 59 on return
path
29
CA 02569723 2006-12-14
subsystem bus 51. I/O devices 58 and 59 can be implemented by any
conventional equipment suitable for this purpose.
As shown in Figure 3. the functionality of return path
subsystem 50 includes two main modules: session control module 60 and
administrative module 70. Processing associated with both modules is
performed by processor 54 according to software that may be pre-stored in
static memory 55, and utilizing dynamic memory 56 and mass storage 57 as
necessary. In the illustrated embodiment, but without limitation, session
control module 60 of return path facility 50 is responsible for maintaining an
interface with each ICB 130 that has initiated a session. Requests for
programming or other transactions are managed and monitored, as are
audience observations provided by ICB 130 according to a desired,
predetermined approach. Session control module 60 also includes the
recording of desired aspects of messages and transactions in mass storage
device 57. Also, transaction requests, demographic or other marketing data,
or other received messages are forwarded for processing by administrative
module 70.
Administrative module 70 captures the occurrence of
requested transactions for purposes of billing, recording viewing patterns.
and for fulfilling the requested transaction by transmitting appropriate
requests as necessary over link 52 to program subsystem 10. Requests for
other sorts of transactions, such as purchasing offerings on home shopping
channels or any other transaction may be accounted for and then provided to
the appropriate one of a set of other service providers 48 with which the
operator of the ADCS has established a relationship. Administrative module
70 also gathers customer information regarding customer viewership,
purchasing patterns, and demographic or psychological information
important for marketing and stores this information as necessary and/or
provides it to one or more of the other service providers 48 according to a
predetermined arrangement. Such information gathering may be done. for
example. but without limitation, pursuant to agreements with subscribers
CA 02569723 2012-05-07
permitting the gathering of such information, possibly with a reduction in
subscription rate
or some other consideration to the subscriber.
Administrative module 70 of return path subsystem 50 according to a
predetermined
scheme can also keep track of viewing and transaction requests for one or more
other
service providers 48, and can use this information to conduct billing on
behalf of those
providers 48.
IV. Operation of the ADCS System
According to the Present Invention
A logic flow diagram for processing associated with a representative
transaction performed by an embodiment of an ADCS according to the present
invention
is shown in Figure 9. In particular, subscriber 30 via ICB 130 initiates a
request for a
particular program requiring authorization, and the ensuing processing or
activity by the
ICB 130, the return path subsystem 50, program subsystem 10, and transmission
subsystem 20 are described. On the top edge of each box is indicated the
subsystem of the
ADCS responsible for performing the indicated function.
Process 200 begins at step 202, at which the ICB 130 tuner (i.e., the input
selector 170) is tuned to regular programming selected by subscriber 30, which
may be a
default setting that could be either factory set or determined by subscriber
30. Using the IR
remote 158, the user may request a viewing session, at 204. CPU 184 of ICB 130
retrieves
from static memory 186 (or other storage not shown in Figure 7) pre-stored
code for a
viewing selection list and performs any necessary processing. Then, via system
control
bus 180 and, if necessary, video decoder 176 and graphics assist 178, the pre-
stored
selection list code is processed by NTSC signal generation module 182 and
provided over
line 182A to a terminal device, such as television set 34, at step 208.
If subscriber 30 expresses no interest in a transaction, process 200 simply
returns to the beginning, step 202. If subscriber 30 requests a transaction
however at 210
(using IR remote 158) and IR controller 190
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CA 02569723 2012-05-07
receives the request, at 212, the CPU 184 of ICB 130 retrieves from static
memory 186 a
pre-stored request for a personal identification number (PIN), which it then
causes to be
displayed on television set 34 as, for example, the character string "Enter
PIN." The
subscriber 30, having been prompted by the message, via IR remote 158 enters
his or her
PIN, which is received by IR controller 190 and stored by CPU 184 in dynamic
memory
188. The CPU 184 of ICB 130 according to instructions it retrieves from static
memory
186 initiates a procedure to verify the PIN, at 224.
If the PIN is not verified, CPU 184 causes to be displayed on television set
34 the legend "Wrong PIN, Cancel?", or other legend to the same effect, and
waits for a
response from subscriber 30. If subscriber 30 responds in the negative,
process 200 returns
to step 214, in which the PIN is again requested (a memory or input error
presumably
having been made by subscriber 30). If subscriber 30 responds in the
affirmative, process
200 simply returns to initial step 202.
If, on the other hand, the PIN was verified at step 224, then CPU 184
invokes WAN communications processor and modem 192, CPU 184 dials return path
subsystem 50 (which might also be referred to as "head end", as it is in
Figure 9).
Processor 54 of return path subsystem 50 establishes a session with ICB 130
and reads
subscriber 30's request, PIN, and other desired subscriber information.
Processor 54 of
return path subsystem 50, invoking the administrative module 70, generates
billing data
associated with this request.
For purposes of this logic flow, "headend" is also, for convenience,
intended to include functionality implemented by program subsystem 10. At step
230, the
processor 54 of return path subsystem 50 generates and transmits to program
subsystem 10
a message that subscriber 30 is authorized for a particular selected viewing
choice. An
authorization code, which may have been pre-stored at return path facility 50
and retrieved
for program subsystem 10, or which could alternatively have been pre-stored in
program
subsystem 10, is then included in the transmission by program
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subsystem 10 to transmission subsystem 20 and is thus broadcast, for
example in the vertical blanking interval of a particular video stream. The
authorization code is inserted into a video stream being transmitted in a
frequency band to which ICB 130 is programmed to tune to look for this
information. Accordingly, the authorization code is identified in that band
by the ICB 130 and extracted according to known, methods, at step 232, for
use in enabling the decoding of the selected transmission, or tuning to an
authorized channel, step 234.
CPU 184 of ICB 130 then ensures that the ATV tuner 162 is
tuned to the appropriate band, if necessary, that the input selector 170 is
switching the transmission from the ATV tuner 162 through to the video
decoder 176, and that the video decoder 176 has the necessary authorization
for descrambling the authorized transmission. At 238 the subscriber 30 may
end the session using IR remote 158, either at the end of the program, or for
any other reason. If subscriber 30 during the course of the transmission does
not indicate that he or she wishes to terminate the session, CPU 184
continues to cause the authorized channel to be displayed on television set
34. During this period, other functionality could be represented. including
VCR functionality or other subscriber interaction. If, on the other hand,
subscriber 30 does end the session. or if it terminates on its own, process
200
in that case returns to initial step 202.
The foregoing describes a preferred embodiment of the
present invention. Various changes and modifications to what is disclosed
may be adopted or implemented without departing from the scope or spirit of
the invention.
33
