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BACKGROUND OF THE INVENTION
This invention pertains to a broadcasting cable system, and more
particularly to a programming-on-demand cable system wherein any one of a
plurality of stored video programs can be broadcast in a non-real-time
basis to a user.
Generally and to the best of applicant's knowledge, existing video
broadcast services provide a user any one of a plurality of programs to be
viewed on a real-time basis. The user may select any one of the video
programs, however, he is restricted in his enjoyment of the program in
that the user has no control over when in time the program is broadcast to
his video or television set. For example, video programs are routinely
announced in video or television guides listing the programs available to
the user for his choice in viewing at a specific time of day.
Consequently, the user does not have the choice of viewing the program
when he so desires, but rather is restricted to that particular time
listed in the video or television guide.
Moreover, it would be much too impractical and costly to provide the
necessary equipment to process numerous concurrent requests for real-time
transmission of video programs at any time desired by the users.
Present broadcasting systems transmit the data by one of many methods, for
example, "over-the-air", electrical lines or cables, fiber optic lines or
cables, and the like. Presently, transmission by means of fiber optics is
becoming more practical, however, the user is still restricted to viewing
his program at a broadcasting time not of his choosing.
SUMMARY OF THE INVENTION
The present invention overcomes the problems and disadvantages of present
broadcasting systems by providing an improved programing-on-demand cable
system.
The programming-on-demand cable system of the present invention overcomes
the inability of a user to select any one of a number of video programs
for viewing at a time of his choice by providing a non-real-time
transmission of the desired program. Any number of various programs are
stored in memory devices at a central location or library and are viewable
by a user at any time by means of the cable system of the present
invention. A host computer at the library is electrically connected to the
memory devices, and upon receiving an address signal from a keyboard
located at the user's location, the host computer selects the memory
device identified by the address signal, and causes the program stored
therein to be transmitted by a fiber optic line to a data receiving
station at the user's location. A central data station, of which the host
computer is a part, causes the program identified by the address signal to
be converted from electrical data to optical data and transmitted over the
fiber optic line to the data receiving station, which then reconverts the
optical data back to the original electrical data. Thereafter, the
reconverted electrical data is transmitted to the user's television set
for virtually immediate viewing; or the reconverted electrical data is
stored in a memory module in the data receiving station for subsequent
viewing by the user at the time of his choice. If necessary, the
electrical data received by the data receiving station is reconstructed,
which may be necessary if the electrical data is received in a form not
acceptable by the television for viewing, and is transmitted at a normal
rate to the user's television.
Further, the data transmitted from the central data station to the data
receiving station is transmitted in multiplexed fashion so that the
equipment at the central data station is dedicated for only a short period
of time, for example, on the order of 20 to 30 seconds, thereby minimizing
any delay between transmission of an address signal by the user and the
receipt of the desired program at the user's location.
To facilitate the storage and manipulation of the video programs, and to
allow the method to be placed under automatic computer control, the
electrical data representing each video program is converted to compressed
digital form and stored in suitable high density memory devices.
In one form of the invention, there is provided an improvement in a
broadcasting system including a central data station having means for
converting electrical data to optical data, a data receiving station
having means for reconverting the optical data back to the electrical
data, a fiber optic line means connecting the central data station and
data receiving station for transmitting the optical data therethrough, and
a broadcasting device electrically connected to the receiving station for
receiving and broadcasting the reconverted electrical data to the user.
The improvement comprises a plurality of memory devices electrically
connected to the central data station, wherein each memory device is
identifiable by a respective address signal and has preprogrammed therein
respective electrical data representing a video program. Each memory
device is responsive to its received address signal to thereby transmit
its electrical data to the converting means. A user-operable generator
device at the user's location is operatively connected to the central data
station for selectively generating any one of the address signals and
transmitting a selected address signal to the central data station,
whereby the central data station transmits that address signal to the
identified memory device which then transmits its electrical data to the
converting means for subsequent transmission to and broadcasting by the
broadcasting device at the user's location.
The present invention also provides a method for broadcasting on a
non-real-time basis any one of a plurality of electrical data representing
different video programs comprising the steps of providing a central data
station including an electro-optical transducer for converting electrical
data to optical data, a data receiving station including an
opticoelectrical transducer for reconverting the optical data back to the
electrical data, a fiber optic line means connecting the transducers, and
a broadcasting device electrically connected to the data receiving station
for receiving and broadcasting the electrical data transmitted. The method
further comprises the steps of providing a plurality of memory devices
electrically connected to the central data station, wherein each of the
memory devices is identifiable by a respective address signal, and
preprogramming each memory device with respective electrical data
representing a video or broadcast program, each memory device being
responsive to its received address signal to thereby transmit its
electrical data to the electro-optical transducer. Further provided is a
user-operable generator device at the location of the broadcasting device
and which is operatively connected to the central data station and
responsive to input applied by the user for generating any one of the
address signals. Further steps are applying an input to the generator
device to generate a selected one of the address signals, and transmitting
the generated address signal to the central data station for
identification of the memory device identifiable by the generated address
signal. Thereafter, transmitting the generated address signal to the
identified memory device, whereby the memory device transmits its
electrical data to the electro-optical transducer for converting the
electrical data to optical data and transmitting the optical data through
the fiber optic line to the opticoelectrical transducer for reconverting
the optical data back to the electrical data, and then transmitting the
electrical data to the broadcasting device for the broadcast thereof.
It is an object of the present invention to provide a programming-on-demand
cable system which permits a user to selectively control which program he
desires to view at a particular time, subject only to the contents of the
library of video programs maintained at the central data station.
Another object of the present invention is to provide a method for allowing
a user to selectively control when and what program he desires to view,
subject only to the contents of the library of video programs available.
Further objects of the present invention will appear as the description
proceeds.
BRIEF DESCRIPTION OF THE DRAWINGS
The above mentioned and other features and objects of this invention, and
the manner of attaining them, will become more apparent and the invention
itself will be better understood by reference to the following description
of an embodiment of the invention taken in conjunction with the
accompanying drawings, wherein:
FIG. 1 is a schematic of a preferred embodiment of the present invention;
FIG. 2 is a schematic of a portion of the central data station and a
multi-fiber data bus of the embodiment in FIG. 1;
FIG. 3 is a schematic illustrating how data is divided among a memory
device of the embodiment in FIG. 1; and
FIG. 4 is a schematic illustrating a portion of the multifiber data bus and
the data receiving station of the embodiment of FIG. 1
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to FIG. 1, programming-on-demand cable system 10 is schematically
illustrated generally comprising central data station 12, data receiving
station 14, a multi-fiber data bus 16, and keyboard 18.
Central data station 12 includes host computer 20 electrically connected to
electronic switching system 22. The electronic switching system 22 is
electrically connected to a library of memory modules 24, 26, 28, 30, 32,
34, as indicated by digital data flow arrows 36, 38, 40, 42, 44, 46,
respectively. Electronic switching system 22 selectively connects any one
of the memory modules 24-34 to multi-fiber data bus 16, as will be
described in detail hereinafter. Although only one data bus 16 is
illustrated in FIG. 1, the present invention contemplates numerous such
data buses 16 wherein electronic switching system 22 is capable of
selectively electrically connecting any memory module 24-34 to any one or
plurality of other such data buses 16.
Although only six memory modules 24-34 are illustrated in FIG. 1 as
representing a library of video programs, it should be understood that
more or fewer such memory modules may be included in the library and
connected to electronic switching system 22. In this particular
embodiment, only six such memory modules 24-34 are illustrated, and each
one contains a specific video program for broadcasting. The video programs
are preprogrammed into respective memory modules 24-34 in digital format
for rapid and inexpensive transmission, as will be described in greater
detail below. It should be realized however, that the video programs may
be stored in other formats, such as an analog format.
Central data station 12 further includes four laser diode modules 48, 50,
52, 54, each of which includes four pulse code modulators respectively
connected in series with four laser diodes for converting digital data to
optical data and one holographic plate, a description of which will be
made in greater detail below with reference to FIG. 2. Continuing with
FIG. 1, laser diode modules 48-54 are optically connected to fiber optic
lines 56, 58, 60, 62, respectively, of multi-fiber data bus 16.
Host computer 20 is also electrically connected to communications
controller 64 by line 66, which is further electrically connected to
respective laser diode modules 48-54 by lines 68, 70, 72, 74. Following a
command from host computer 20, communications controller 64 assumes
control of fiber optic lines 56-62 of data bus 16.
Host computer 20 is electrically connected to electronic switching system
22 by line 76, and electronic switching system 22 is electrically
connected to laser diode modules 48-54 as illustrated by digital data flow
arrows 78, 80, 82, 84, respectively.
Continuing to refer to FIG. 1, data receiving station 14 includes four
photo-diode modules 86, 88, 90, 92 optically connected to fiber optic
lines 62, 60, 58, 56, by fiber optic lines 94, 96, 98, 100, respectively.
It is emphasized that fiber optic lines 56-62, which make up four of the
five lines in multi-fiber data bus 16, continue on as illustrated in FIG.
1 by arrows to additional users. Each photodiode module 86-92 includes
four filters, four photodiodes, and four demodulators connected in series
as illustrated in FIG. 4, a more detailed description of which will
continue below.
Photodiode modules 86-92 are connected to memory module 102 as illustrated
by digital data flow arrows 104, 106, 108, 110, respectively. Data
receiving station 14 further includes control computer 112 electrically
connected to memory module 102 by line 114, to DA (digital-to-analog)
converter 116 by line 118, and to RF modulator 120 by line 122. Control
computer 112 is electrically connected to each of the photodiode modules
86, 88, 90, 92 by lines 117, 119, 121, 123, respectively, which branch off
from line 115; this allows control computer 112 to transmit clock signals
for data that requires synchronization to modules 86-92.
Host computer 20 is connected to control computer 112 by line 124, laser
diode module 126, fiber optic line 128, fiber optic line 129 coupled to
line 128, photodiode module 130, and digital data flow arrow 132. Laser
diode module 126 includes only two pulse code modulators, two laser
diodes, and one holographic plate; and photodiode module 130 includes two
interference filters, two photodiodes, and two demodulators, which will be
described in greater detail below with reference to FIG. 2. Fiber optic
line 128 is the fifth of the five fiber optic lines in data bus 16 and
continues on as illustrated in FIG. 1 to additional users. Communications
controller 64 is connected to control computer 112 by line 131, laser
diode module 126, fiber optic lines 128, 129, photodiode module 130, and
digital data flow arrow 132.
Data receiving station 14 further includes automatic modem 134 electrically
connected to control computer 112 by line 136. Automatic modem 134
communicates with host computer 20 by means of line 138, which is
connected to the user's telephone line 140, telephone line 142, modem 143,
and line 145.
Keyboard 18 is electrically connected to control computer 112 by line 144,
and television 146 is connected to RF modulator 120 by analog data flow
arrow 148.
Referring now to FIG. 2, a more detailed description of the interface
between central data station 12 and multi-fiber data bus 16 will be made.
FIG. 2 illustrates in an exploded manner the method in which laser diode
modules 48-54 are operatively connected to fiber optic lines 56-62,
respectively, and since the connection between each of the four laser
diode modules to its respective fiber optic line is identical only one
such description will be made and will suffice for all four.
Briefly, each program in each digital memory module 24-34 is logically
divided into 16 data cells in that particular memory module so as to
reduce the transmission time of the program. Each laser diode module 48-54
is designed to transmit four of the sixteen cells of data representing the
program and are illustrated in FIG. 2 by digital, data flow arrows 150,
152, 154, 156, which are included in, by example only in FIG. 1, digital
data flow arrow 46 and make up the digital data flow arrow 84 when memory
module 34 is selected.
It should be understood that, while four groups of data streams 150-156 are
shown in FIG. 2, the data included in these groups of data streams is not
identical. Each of the sixteen illustrated data streams 150-156 transfers
data from respective ones of the sixteen unique data cells of one of the
memory modules 24-34, each data stream comprising a portion of a single
program. Continuing to refer to FIG. 2, four of the sixteen cells of data
representing a single program of memory module 34 are separately
transmitted to pulse code modulators 158, 160, 162, 164 for subsequent
transmission to laser diodes 166, 168, 170, 172, respectively. Pulse code
modulators 158-164 are electrically connected to laser diodes 166-172 by
lines 174, 176, 178, 180, respectively. Digital data transmitted to pulse
code modulators 158-164 are individually modulated and transmitted to
laser diodes 166-172 by lines 174-180, and laser diodes 166-172 then
transmit the digital data as optical data having different light
wavelengths to holographic plate 182. As illustrated laser diodes 166-172
are oriented such that the four different light wavelengths L1, L2, L3,
L4, converge at holographic plate 182, which redirects the four
wavelengths in a parallel manner to fiber optic line 62. As described, the
digital data transmitted to laser diode module 54 is now spectrally
multiplexed in fiber optic line 62. Various methods for deflecting light
beams, for example, by holographic plates, are disclosed in U.S. Pat. No.
4,062,043 issued Dec. 6, 1977 to Zeidler et al. The methods disclosed in
Zeidler are used to deflect multiple light wavelengths onto a single
fiber.
In a similar manner the other twelve cells of digital data are likewise
spectrally multiplexed and transmitted through fiber optic lines 56-60.
FIG. 2 further illustrates the interface between fiber optic line 128 with
central data station 12 and multi-fiber data bus 16 by means of laser
diode module 126 comprising pulse code modulator 184 electrically
connected in series with laser diode 186 and pulse code modulator 188
electrically connected in series with laser diode 190. Digital data flow
arrow 193 represents line 124 connecting host computer 20 to laser diode
module 126 in FIG. 1. Digital data flow arrow 193 transmits certain
control data from host computer 20 to data receiving station 14 for
display on the user's television 146. Digital data flow arrows 192, 194
represent line 131 (FIG. 1) connecting communications controller 64 to
laser diode module 126. Flow arrow 192 transmits other control data to
control computer 112, and flow arrow 194 illustrates transmission of
synchronization data from communications controller 64 to control computer
112. The control and synchronization data are spectrally multiplexed in
fiber optic line 128 in an identical manner as described above for line
62.
As explained above, optical data transmitted from laser diodes 166-172 is
oriented to converge on holographic plate 182, however, it is recognized
that the optical data could be transmitted from laser diodes 166-172 in a
parallel fashion to a convex lens to be deflected to holographic plate
182.
Referring now to FIG. 3, an exemplary description will be made of how
digital data is stored in one of the memory modules 24-34. FIG. 3
illustrates a memory module 196 containing only three cells 198, 200, 202
in this example. Memory module 196 is of the recirculating shift register
type, and is logically divided into the three cells 198-202 and is
illustrated as storing a nine bit program. Storing is by the bit rotation
logic method wherein bit one is stored in cell 202, bit 2 stored in 200,
bit 3 stored in cell 198, bit 4 stored in cell 202, etc. The data are
retrieved from memory module 196 in a parallel fashion and are
subsequently transmitted to the fiber optic lines of the data bus, which
also operate in parallel. The purpose for the use of bit rotation is to
permit memory module 102 in FIG. 1 in data receiving station 14 to operate
at a lower data rate during playback.
Referring now to FIG. 4, there is schematically illustrated the interface
between fiber optic lines 94-100 and 129 at data receiving station 14.
Since the interface between fiber optic lines 94-100 are identical, and
129 similar, only one such interface will be described using fiber optic
line 94. Fiber optic line 94 is connected to photodiode module 86
comprising diverging optical element 204, interference filters 206, 208,
210, 212, photodiodes 214, 216, 218, 220, and demodulators 222, 224, 226,
228. Photodiodes 214-220 are connected to respective demodulators 222-228
by respective lines 230, 232, 234, 236. The spectrally multiplexed light
beam is transmitted from fiber optic line 94 to diverging optical element
204 which divergingly transmits the light beam to interference filters
206-212, each of which permits only a discrete wavelength to pass
therethrough to thereby demultiplex the light beam. As illustrated in FIG.
4, filter 206 permits only wavelength L1 to pass through, filter 208
permits only wavelength L2, filter 210 permits only wavelength L3, and
filter 212 permits only wavelength L4 to pass through. The operation of
diverging optical element 204 is known and disclosed in U.S. Pat. No
4,062,043 issued Dec. 6, 1977 to Zeidler et al., which is incorporated by
reference herein.
The light wavelengths are then transmitted to photo-diodes 214-220 and
demodulators 222-228 for converting the optical data back to the original
digital data The data is then transmitted to memory module 102 as
illustrated by digital data flow arrow 104 in FIG. 1. Memory module 102 is
arranged identically to memory modules 24-34 with sixteen parallel cells
for containing the data.
Thereafter the digital data is retrieved and fed to the DA converter 116 on
command from control computer 112 for converting the digital data to
analog data, and is then transmitted to RF modulator 120 for subsequent
transmission and broadcasting by television 146.
The data in memory modules 24-34 is in compressed digital form, thereby
accomplishing a considerable savings in transmission costs. After host
computer 20 has signaled electronic switching system 22 to electrically
connect the selected one of the memory modules 24-34, host computer 20
then signals communications controller 64 to assume control of the
compressed digital data transmitted to laser diode modules 48-54.
Communications controller 64 also then assumes control of laser diode
module 126. The digital data is compressed in memory modules 24-34 by a
technique known as inter-frame differential pulse code modulation. The
digital data is received, as described above, at data receiving station 14
and reconstructed by control computer 112. The inter-frame differential
pulse code modulation technique just described is known in the art, and
additional circuitry may be added to avoid problems caused by rapid motion
in the picture. Further, the bit rate requirements may be reduced even
further by means of other similar but more complicated procedures.
By utilizing inter-frame differential pulse code modulation, each second of
video program playing time yields about 44 megabits. Further, according to
the present state of the art, 650 megabits per second can be transmitted
on a single wavelength, and since in the present embodiment there are 16
optical data channels in the four fiber optic lines 56, 58, 60, 62, the
total transmission rate is 10,400 megabits per second. Therefore, a two
hour movie can be transmitted in about 31 seconds (7,200 seconds.times.44
megabits per second /10,400 megabits per second).
In operation, the user determines which program he desires to watch, and
then inputs the correct address signal in keyboard 18 which transmits the
signal to computer control 112, which in turn transmits the signal to
automatic modem 134. Automatic modem 134 then transmits via lines 138,
142, modem 143, and line 145 the address signal to host computer 20 which
determines which data bus 16 serves the user and enters the address signal
in a queue for the particular data bus 16 of the user. Host computer 20
then transmits a receipt signal through line 145, modem 143, lines 142,
138, automatic modem 134, and line 136 to control computer 112, which in
turn transmits the signal through line 122 to RF modulator 120 for display
on television 146, thereby indicating to the viewer that the host computer
20 has received and entered the selected address signal. Thereafter, host
computer 20 transmits other instructions and information to the viewer via
digital data flow arrow 193 (FIG. 2) which represents line 124 in FIG. 1.
When the user's turn comes up, host computer 20 transmits the address
signal to electronic switching system 22 which selects the one identified
memory module 24-34 containing the selected video program. Following this,
host computer 20 signals communications controller 64 to assume control of
laser diode modules 48-54, 126, after which communications controller 64
causes electronic switching system 22 to transmit the selected digital
data to laser diode modules 48-54 and thereafter to data receiving station
14 as described above. Communications controller 64 communicates with
control computer 112, as described above, when each step of the
transmission sequence is begun and terminated.
After transmission, the video program is stored in memory module 102 of
data receiving station 14 as earlier described, and communications
controller 64 communicates with host computer 20 that data transmission is
complete. Host computer 20 then informs the user via digital data flow
arrow 193 (FIG. 2) that the program is ready for viewing by displaying a
ready signal on television 146. The user begins the video program by
depressing a "START" switch on keyboard 18, whereby control computer 112
signals memory module 102 to transfer the digital data to DA converter 116
as illustrated by digital data flow arrow 238 for converting the digital
data to analog data upon command from control computer 112. Thereafter
control computer 112 commands converter 116 to transmit the analog data to
modulator 120 as illustrated by digital data flow arrow 240, and then to
television 146 via the analog data flow arrow 148.
Although the above description includes converting the digital data to
analog data at the data receiving station 14 for display on television
146, it is contemplated that this step may be eliminated with television
sets capable of receiving digital data for display thereof.
Although the above description was made in terms of a fully completed
transmission of a program before viewing by the user, the present
invention fully contemplates that the user may begin viewing his program
before the complete transmission thereof. Central data station 12 may
transmit only a portion of the selected program to the user for his
viewing, and then begin transmitting a portion of another selected program
to a second user. This permits central data station 12 to simultaneously
handle several users, rather than waiting for complete transmission of one
selected program before proceeding with another user's address signal.
While this invention has been described as having a preferred embodiment,
it will be understood that it is capable of further modifications. This
application is therefore intended to cover any variations, uses, or
adaptations of the invention following the general principles thereof, and
including such departures from the present disclosure as come within known
or customary practice in the art to which this invention pertains and fall
within the limits of the appended claims.
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