U.S. patent application number 10/096612 was filed with the patent office on 2003-02-20 for two-way information transmission system, two-way information transmission method, and subscriber terminal.
This patent application is currently assigned to Sony Corporation. Invention is credited to Suzuki, Mitsuhiro.
Application Number | 20030037338 10/096612 |
Document ID | / |
Family ID | 14830456 |
Filed Date | 2003-02-20 |
United States Patent
Application |
20030037338 |
Kind Code |
A1 |
Suzuki, Mitsuhiro |
February 20, 2003 |
Two-way information transmission system, two-way information
transmission method, and subscriber terminal
Abstract
A subscriber terminal ms sends the demand including at least
information for identifying the demand subscriber terminal and
information for identifying the requested information to the
information distribution transmission center HE through the
going-up line. The information distribution transmission center HE
makes a transmission plan of the information based on this demand,
and sends the information transmission plan to the subscriber
terminal ms prior to the actual information transmission. The
subscriber terminal ms sends an information transmission request
including a share information transmission request of the
transmission information when desired transmission information is
listed in the obtained transmission schedule. The information
transmission center HE transmits the information requested
according to the information transmission schedule to the
subscriber terminal which made the information transmission request
and, during a share information transmission request, transmits the
information also to the subscriber terminal which made the share
information transmission request. A video on-demand system can be
realized with a relatively small investment, and the centralization
of traffic is mitigated, the network resource is used efficiently,
and rational charging for information transmission is enabled.
Inventors: |
Suzuki, Mitsuhiro; (Chiba,
JP) |
Correspondence
Address: |
Jay H. Maioli
Cooper & Dunham
1185 Avenue of the Americas
New York
NY
10036
US
|
Assignee: |
Sony Corporation
|
Family ID: |
14830456 |
Appl. No.: |
10/096612 |
Filed: |
March 13, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10096612 |
Mar 13, 2002 |
|
|
|
08843256 |
Apr 14, 1997 |
|
|
|
Current U.S.
Class: |
725/98 ;
348/E7.073; 725/86 |
Current CPC
Class: |
H04N 21/266 20130101;
H04H 60/97 20130101; H04N 21/2541 20130101; H04N 21/2625 20130101;
H04H 20/69 20130101; H04H 20/79 20130101; H04H 20/33 20130101; H04H
20/76 20130101; H04N 21/6581 20130101; H04N 21/25435 20130101; H04N
21/26241 20130101; H04N 7/17336 20130101; H04N 21/47202
20130101 |
Class at
Publication: |
725/98 ;
725/86 |
International
Class: |
H04N 007/173 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 19, 1996 |
JP |
P08-122217 |
Claims
What is claimed is:
1. A two-way information transmission system comprising an
information distribution transmission center and a plurality of
subscriber terminals connected to an information distribution
transmission center through going-up lines and going-down lines,
said subscriber terminal requesting an information to said
information distribution transmission center through said going-up
line, and said information distribution transmission center
transmitting the requested information in response to the request
for the transmission; said information distribution transmission
center having: transmission planning means for planning a
transmission plan to transmit the information based on an
information distribution transmission request from said subscriber
terminal, transmission implementation means for implementing the
transmission of said requested information based on the
transmission plan planned by said transmission planning means, and
going-down control data sending means for sending a going-down
control data including an information involving the transmission
implementation plan planned by said transmission implementation
means to the subscriber terminal before said transmission
implementation means implements the transmission; and said
subscriber terminal having: transmission plan receiving analysis
means for being informed of said transmission plan based on said
going-down control data sent from said information distribution
transmission center, distribution transmission request sending
means for sending said information distribution transmission
request including at least information for identifying the demand
subscriber terminal and information for identifying said requested
information, and also including a request for information
transmission shared with the information when said received
information transmission plan contains own desired information.
2. A two-way information transmission system as claimed in claim 1,
wherein said information transmission center charges a more
inexpensive fee for said share information transmission request
than that for usual information transmission.
3. A method of two-way information transmission, wherein a
subscriber terminal sends an information distribution transmission
request including at least information for identifying the demand
subscriber terminal and information for identifying said requested
information to information distribution transmission center through
a going-up line, said information distribution transmission center
makes the transmission plan of the information to be transmitted
based on said information distribution transmission request from
said subscriber terminal, and transmits the distribution
transmission plan information including the plan information in the
going-down control data to the subscriber terminal prior to the
transmission of the main information, said subscriber terminal is
informed of said transmission plan by receiving and analyzing said
going-down control data from said information distribution
transmission center and sends said information transmission request
including a request for information transmission shared with the
information when the transmission plan contains own demand
information, and said information transmission center transmits
said requested information according to said transmission plan to
the subscriber terminal which makes said transmission request
through the going-down line, and, during said share information
transmission request, the center sends the requested information
also to the subscriber terminal which makes the share transmission
request.
4. A subscriber terminal in the two-way information transmission
system which comprises an information distribution transmission
center and a plurality of subscriber terminals connected to an
information distribution transmission center through going-up lines
and going-down lines, wherein said subscriber terminal requests an
information to said information distribution transmission center
through said going-up line, and said information distribution
transmission center transmits the requested information in response
to the request for the transmission; each subscriber terminal of
said plurality of subscriber terminals having: transmission plan
receiving analysis means for being informed of the transmission
plan of information to be transmitted planned by said information
distribution transmission center based on said information
distribution transmission request from said subscriber referring to
the control data sent from said information distribution
transmission center, and distribution transmission request sending
means for sending said information distribution transmission
request including at least information for identifying the demand
subscriber terminal and information for identifying said requested
information, and also including a request for information
transmission shared with the information when said received
information transmission plan contains own desired information.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a two-way information transmission
system such as video on-demand system and information on-demand
system using a communication network such as cable television
network.
[0003] 2. Description of Related Art
[0004] Not only usual analog broadcasting service but also video
on-demand, home shopping, and television game service utilizing a
two-way cable television network have been recently planned.
[0005] One method for realizing such services is a method in which
a digital information transmission band is provided, for example,
in the transmission band of the television network separately from
the band for analog broadcasting service. In detail, for example in
the case of video on-demand system, a user transmits a demand
signal (transmission request signal) of the video on-demand to a
cable television station where a video program storing sending
system called video server is installed using a portion of the
digital information transmission band. Upon receiving the demand
signal from the user, the cable television station takes out the
program requested by the user from the video server, and provides
it to the requesting user in real-time using a band other than that
for the above-mentioned demand signal in the above-mentioned
digital information transmission band.
[0006] One of such video on-demand systems is introduced in a
journal "Nikkei Electronics" issued May 23, 1994 on pages 82 to
89.
[0007] This example involves a hybrid network system comprising
combined optical fiber and coaxial cable, the optical fiber
connects from the cable television station to an optical fiber
node, the optical fiber node performs photoelectric conversion, and
the coaxial cable connects from the optical fiber node to a
subscriber terminal called as set top box installed in the user
home. Assuming that 16 optical fiber nodes are provided and the
maximum number of subscribers connectable to a coaxial cable is
500, then one cable television station can supply to 8000
subscribers.
[0008] In assignment of transmission band of the cable television,
this video on-demand system assigns the band range from 50 MHz to
723 MHz to a transmission band for going-down from the cable
television station to a subscriber terminal of a subscriber, and
the band range from 900 MHz to 1 GHz to a transmission band for
going-up from a subscriber terminal to the cable television
station, further, a transmission band between 50 MHz to 450 MHz out
of the going-down transmission band is used for the existing analog
broadcasting service and a transmission band between 500 MHz to 708
MHz is used for digital transmission band and the residual
transmission band ranging from 450 MHz to 500 MHz is spare as shown
in FIG. 1.
[0009] At most 15 digital transmission channels with a band width
of 12 MHz can be provided in the digital information transmission
band ranging from 500 MHz to 708 MHz. Assuming that the
transmission speed per one channel is 45 M bits/sec and, for
example, the coding speed of video data is 4 M bits/sec, video data
can be supplied to about 10 subscribers by way of a channel with
the transmission speed of 45 M bits/sec in real-time.
[0010] Assuming that the proportion of requesting subscribers for
demand to 500 subscribers is 25% in the busy time called as prime
time, it is required to supply to 125 subscribers, and one channel
can supply to 10 subscribers, therefore 15 channels can supply to
150 subscribers and thus the requirement is satisfied.
[0011] In the case of this example, the control channel is assigned
near the frequency of 500 MHz, and the going-down channel to be
used for supplying a video program data desired by a user through
demand is informed to the set top box using this control channel.
The set top box fetches only a desired going-down data in the cable
television station based on the data of the control channel, and
functions to display it on a television. The transmission speed of
the control channel is 1.5 Mbits/sec, and 45 channels and 1 channel
are for going-up and for going-down respectively.
[0012] FIG. 2 shows how the transmission capacity of going-down
line is allocated to respective subscribers, the left half of the
figure shows so-called prime time and the right half shows the
midnight time zone.
[0013] In FIG. 2, the top half shows the transmission channels for
analog television broadcasting service, each long rectangle
represents one analog television program PGa. In this case, 50
channels of analog television broadcasting service are possible to
be transmitted if one channel has a band width of 6 MHz. Each
subscriber can select and view a desired program from programs
being broadcasted by way of analog channels any time.
[0014] The bottom half of FIG. 2 shows the digital information
channels for video on-demand, an arrow Tdm represents a demand
generating time point from a user, and a long rectangle represents
a one digital video program PGd. In response to a demand from a
user, one channel is occupied by the user for a time of the
service.
[0015] Since charging always for real-time transmission is
generally performed in case of video on-demand, the charged rate
does not vary according to time zones, but is often constant. As
shown in FIG. 2, therefore in prime time, the audience rating of
analog broadcast programs is high and also many demands for digital
video programs are generated. On the other hand, late at night, the
audience rating of analog TV broadcast programs is low and few
demands for digital video programs are generated.
[0016] As described hereinbefore, in the conventional video
on-demand system, video programs are supplied in real-time to all
the demands. Therefore, in the time zone like so-called prime time
when many demands are requested from subscribers, many programs
should be transmitted at a time as shown in the left side of FIG.
2.
[0017] For construction of a video on-demand system, the network
capacity and transmission system are deployed so that programs are
supplied to subscriber homes as soon as possible in real-time in
the busiest time zone when many demands are requested.
[0018] To cope with such situation, the conventional system is
involved in a problem that {circle over (1)} the network capacity
should be large, and {circle over (2)} the scale of video server
should be large in order to supply many programs simultaneously
(for example, assuming the number of subscribers is 8000 and 25% of
these subscribers request their demand in prime time, the
simultaneous transmission stream are 2000 streams). The capacity
investment for enlargement of an existing facility is required, and
an expensive large scale video server should be introduced. Unless
a program transmission fee is specified to be high, these
expenditure can render the business substantially unprofitable.
[0019] As described herein above, many demands are generated very
frequently in prime time, on the other hand, a few demand is
generated sporadically in the time zone of early morning and
midnight, the problem is inefficient use of the network facility
having a large capacity deployed so as to match with busy demand in
prime time, the capacity utilization ratio is low.
SUMMARY OF THE INVENTION
[0020] It is an object of the present invention to provide a
two-way information transmission system capable of solving the
above-mentioned problem especially in consideration of a charging
method.
[0021] A two-way information transmission system comprising an
information distribution transmission center and a plurality of
subscriber terminals connected to an information distribution
transmission center through going-up lines and going-down lines,
the subscriber terminal requesting an information to the
information distribution transmission center through the going-up
line, and the information distribution transmission center
transmitting the requested information in response to the request
for the transmission;
[0022] the information distribution transmission center having:
[0023] transmission planning means for planning a transmission plan
to transmit the information based on an information distribution
transmission request from the subscriber terminal,
[0024] transmission implementation means for implementing the
transmission of the requested information based on the transmission
plan planned by the transmission planning means, and
[0025] going-down control data sending means for sending a
going-down control data including an information involving the
transmission implementation plan planned by the transmission
implementation means to the subscriber terminal before the
transmission implementation means implements the transmission;
and
[0026] the subscriber terminal having:
[0027] transmission plan receiving analysis means for being
informed of the transmission plan based on the going-down control
data sent from the information distribution transmission
center,
[0028] distribution transmission request sending means for sending
the information distribution transmission request including at
least information for identifying the demand subscriber terminal
and information for identifying the requested information, and also
including a request for information transmission shared with the
information when the received information transmission plan
contains own desired information.
[0029] Further, the information distribution transmission center
charges the lower fee for the share transmission request than the
fee for usual transmission.
[0030] In the two-way information transmission system of the
present invention with the above configuration, the information
distribution transmission center makes the transmission plan based
on the transmission request made by the subscriber terminal and
sends the information specified as the going-down control data to
the subscriber terminal. The subscriber terminal can issue a share
transmission request included in the transmission information when
there is a desired program to be transmitted in the obtained
transmission plan.
[0031] The information distribution transmission center transmits
information to the subscriber terminals according to the
transmission plan behind the time when the subscribers terminal
make the transmission requests. In this case, the center implements
information transmission to all the subscriber terminals who made
the share transmission requests when the subscriber terminals make
share transmission requests of information to be transmitted. The
center can therefore implement information transmission at a time
in response to a plurality of information transmission requests,
thus enabling traffic reduction. Since the lower fee is charged for
a subscriber terminal which makes a share transmission request than
the fee for usual transmission, more share transmission requests
are expected, and transmission capacity can be used
effectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a diagram for describing an example of
transmission frequency band assignment in a two-way information
transmission system.
[0033] FIG. 2 is a diagram for illustrating the use of going-down
information transmission channels in the conventional video
on-demand system.
[0034] FIG. 3 is a diagram for illustrating an example of a network
structure of one embodiment of the two-way information transmission
system in accordance with the present invention.
[0035] FIG. 4 is a diagram for illustrating an example of a cable
television station structure as an information transmission center
in one embodiment of the two-way information transmission system in
accordance with the present invention.
[0036] FIG. 5 is a block diagram for illustrating a partial
structure of the cable television station facility shown in FIG.
4.
[0037] FIG. 6 is a block diagram for illustrating an interchanging
equipment in one embodiment of the two-way information transmission
system in accordance with the present invention.
[0038] FIG. 7 is a block diagram for illustrating an interchanging
equipment in one embodiment of the two-way information transmission
system in accordance with the present invention.
[0039] FIG. 8 is a block diagram for illustrating a structural
example of a subscriber terminal in one embodiment of the two-way
information transmission system in accordance with the present
invention.
[0040] FIG. 9 is a block diagram for illustrating a partial
structure of the subscriber terminal shown in FIG. 8.
[0041] FIG. 10 is a functional block diagram of a selected portion
for illustrating one embodiment of the two-way information
transmission system in accordance with the present invention.
[0042] FIG. 11 shows an example of the list of programs to be
transmitted.
[0043] FIG. 12 shows an example of the table of charges for
transmission in one embodiment of the two-way information
transmission system of the present invention.
[0044] FIG. 13 is a diagram for illustrating the use of the
going-down transmission channels in one embodiment of the two-way
information transmission system in accordance with the present
invention.
[0045] FIG. 14 is a flowchart for describing an example of demand
transmission processing from a subscriber terminal in one
embodiment of the two-way information transmission system in
accordance with the present invention.
[0046] FIG. 15 shows an example of part of the input screen on
demand in one embodiment of the present invention.
[0047] FIG. 16 is a flowchart for describing an example of demand
receiving processing in a cable television station in one
embodiment of the two-way information transmission system in
accordance with the present invention.
[0048] FIG. 17 is a flowchart for describing an example of
receiving processing of going-down digital transmission data at a
subscriber terminal in one embodiment of the two-way information
transmission system in accordance with the present invention.
[0049] FIG. 18 is a flowchart for describing an example of
information reading (reproduction) processing at a subscriber
terminal in one embodiment of the two-way information transmission
system in accordance with the present invention.
[0050] FIG. 19 is a flowchart for describing an example of
reproduction request receiving processing in a cable television
station in one embodiment of the two-way information transmission
system in accordance with the present invention.
[0051] FIG. 20 is a diagram for describing an example of the
network structure in another embodiment of the two-way information
transmission system in accordance with the present invention.
[0052] FIG. 21 is a diagram for describing an example of
transmission frequency band assignment in another embodiment of the
two-way information transmission system in accordance with the
present invention.
[0053] FIG. 22 is a block diagram for illustrating a structural
example of a cable television station in another embodiment of the
two-way information transmission system in accordance with the
present invention.
[0054] FIG. 23 is a block diagram for illustrating structural
example of a subscriber terminal in another embodiment of the
two-way information transmission system in accordance with the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0055] Embodiments of the two-way information transmission system
in accordance with the present invention will be described in
detail referring to the drawings for the example of video on-demand
system. The direction from a subscriber to a cable television
station is referred to as going-up, and the inverse direction is
referred to as going-down in the description hereinafter.
[0056] FIG. 3 shows the outline of a network structure used for
realizing a video on-demand of an embodiment of the two-way
information transmission system. This example has the same
structure as that of the two-way cable television system described
in the chapter of related art.
[0057] The cable television station HE called head end provides
analog television broadcast programs always during the broadcasting
time zone and also video programs in response to the demand from
subscribers and other programs.
[0058] The cable television station HE can cover, for example, 8000
subscribers as described herein above, 8000 subscribers are divided
into 16 sections and each section covers 500 subscribers MS. One
interchange equipment IM called as optical fiber node (referred to
as optical fiber node IM hereinafter) is installed for each
section. An optical fiber node IM performs mutual conversion
between optical signal and electric signal.
[0059] In the case of this embodiment, an optical fiber cable FB
connects between each section and the television station HE in
order to transmit a signal without degrading in quality across a
long distance. In each section, one coaxial cable CB is connected
to an optical fiber node IM, and each subscriber MS is connected to
the coaxial cable through a coaxial confluent distributor MPX. At
most 500 subscribers MS are connectable to one coaxial cable CB as
described hereinbefore.
[0060] The cable television station HE has information sources
including video server, and is connected to an optical fiber trunk
SHW in order to fetch digital information from the optical fiber
trunk SHW and provide it to the subscribers in addition to digital
data from the digital information source of the cable television
station HE itself. Further, a parabola antenna AT is provided for
receiving satellite broadcast, and received television broadcast is
supplied to respective subscribers as analog television
broadcast.
[0061] FIG. 4 shows an example of facility components of the cable
television station HE, and in this example, the facility comprises
the above-mentioned analog television broadcasting facility not
shown in FIG. 4, for example video server 21 and tape information
library system 22 as a digital information source equipment, high
speed ATM (non-synchronous transfer mode) exchanger 23, HE
controller 24 for controlling the whole system of the cable
television station HE, and 16 node controllers 25a to 25p provided
between 16 respective optical fiber cables FB and ATM
exchangers.
[0062] In this example, the video server 21 obtains, for example,
400 streams as a bit stream of simultaneous transmission video
signal. The coding rate of each bit stream data is, for example, 4
Mbits/sec, and, for example, MPEG is used as a data compression
system. In this case, two video servers may be provided as the
video server 21 if, for example, simultaneous transmission stream
quantity is 200 streams. Data VA of each video stream from the
video server 21 is supplied to ATM exchanger 23.
[0063] The tape information library system 22 is provided with a
multi-shelf container rack 22L in which many video tapes are placed
on respectively specified positions, a plurality of video tape
players VTR1 to VTRn, and a retrieving transferring mechanism (not
shown in the figure) which is successively operated for retrieving
in the horizontal and vertical direction to find out the position
of a requested video tape in the container rack 22L, for fetching
the video tape, setting the video tape into any one of video tape
players VTR1 to VTRn to playback the video tape, such tape
information library system 22 is so-called as cart machine. In this
example, 160 video tape players are deployed. Therefore, the number
of bit streams of the simultaneous transmission video signal is
160.
[0064] Data VB of the digital video data stream of respective video
tape players VTR1 to VTRn has a transmission rate of, for example,
45 M bits/sec. The data VB is supplied to the ATM exchanger 23.
[0065] The tape information library system 22 provides programs
more and easier than the video server 21.
[0066] The HE controller 24 controls the whole cable television
station HE including the control of the video server 21, control of
the tape information library system 22, and control of the ATM
exchanger 23, generates a going-down control data DM to be
transmitted to a subscriber and supplies it to the ATM exchanger 23
in response to an operation input from an operator to the HE
controller 24 and a going-up control data UM (data such as a demand
signal of the video on-demand) from a subscriber terminal supplied
through the ATM exchanger 23.
[0067] Also digital data VC obtained from the optical fiber trunk
SHW is supplied to the ATM exchanger 23.
[0068] The ATM exchanger 23 exchanges the above-mentioned digital
data VA, VB, and VC, and going-down control data DM and divides or
gathers them to generate information necessary for respective
transmission sections. The ATM exchanger 23 also transfers a
going-up control data UM from a subscriber terminal to the HE
controller 24.
[0069] Respective 16 node controllers 25a to 25p receive the analog
television broadcast signal AV and going-down information from the
ATM exchanger 23, and converts them to a signal having the
frequency band previously assigned and converts an electric signal
to light signal, and send it to the optical fiber FB as described
in FIG. 1. The respective 16 node controllers 25a to 25p convert a
going-up control data UM from a light signal to electric signal,
and transfer it to the ATM exchanger 23.
[0070] Every node controllers 25a to 25p have the same structure.
FIG. 5 is a block diagram for illustrating the structure of one
node controller out of the node controllers 25a to 25p. The optical
fiber FB comprises three optical fibers fb1, fb2, and fb3.
[0071] The analog television information AV is supplied to a band
pass filter 102 through an input terminal 101, and converted to
information having a frequency band of 50 MHz to 450 MHz, and
supplied to the electric-to-light converter 103.
[0072] The analog television information Av is supplied to the band
pass filter 102, converted to an information having a frequency of
50 MHz to 450 MHz, and supplied to the electric-to-light converter
103. The electric-to-light converter 103 converts it to a light
signal and sends it to the optical fiber fb1.
[0073] In this example, as shown in the above-mentioned FIG. 1, 15
channels are allocated for the going-down digital transmission data
of 45 M bits/sec per one channel. Therefore, the node controller
has 15 digital transmission data input terminals 104.sub.1 to
104.sub.15. The ATM exchanger 23 switches directly the digital data
such as video stream from the tape information library system 22 to
any one of 15 input terminals 104.sub.1 to 104.sub.15 of a node
controller corresponding to the section of the addressee
subscriber.
[0074] The ATM exchanger 23 switches a digital data of 4 M bits/sec
bit stream from the video server 21 in a manner that at most 10
streams are multiplexed and allocated to one channel.
[0075] Respective 45 M bits/sec digital data transmitted through
the input terminals 1041 to 10415 are supplied to hexternal QAM
(Quadrature Amplitude Modulation) modulation circuits 105.sub.1 to
105.sub.15 respectively and modulated. The output data from the
hexternal QAM modulation circuits 105.sub.1 to 105.sub.15 are
converted by the frequency conversion circuits 106.sub.1 to
106.sub.15 respectively to signals of 15 channels which are signals
of 15 frequency bands with no superposing each other in the
frequency band ranging from 500 MHz to 708 MHz as shown in FIG. 1.
The output data from the frequency conversion circuits 106.sub.1 to
106.sub.15 are supplied to the adding circuit 107 and the frequency
of the data is converted.
[0076] A node controller has an input terminal 110 for receiving
1.5 M bits/sec going-down control data DM of one channel. The
control data DM which passed through the input terminal 110 is
supplied to QPSK (Quardature Phase Shift Keying) modulation circuit
112 through the multiplexing circuit 111, and subjected to QPSK
modulation, and then supplied to a frequency conversion circuit 113
and converted to a signal of the going-down control channel near
500 MHz shown in FIG. 1. Subsequently, the signal is supplied to
the adding circuit 107 and subjected to frequency multiplexing.
[0077] The frequency multiplexed data from the adding circuit 107
is supplied to the band pass filter 108 and subjected to band
restriction to a signal in a frequency band ranging from 500 MHz to
708 MHz, and supplied to the electric-to-light converter 109. The
electric-to-light converter 109 converts it to a light signal, and
sends it to the optical fiber fb2 as a digital transmission
data.
[0078] The optical fiber fb3 is used for the going-up control
channel, a going-up control signal such as a demand of a subscriber
which is QPSK modulated and includes 45 channels by frequency
multiplexing is supplied to a light-to-electric converter 121
through the optical fiber fb3, and the signal is converted from a
light signal to an electric signal. The output signal from the
light-to-electric converter 121 is supplied to a band pass filter
122 and subjected to the band restriction, and then only the
going-up control data having a frequency band ranging from 900 MHz
to 972 MHz is fetched.
[0079] The control data from the band pass filter is supplied to 45
frequency conversion circuits 123.sub.1 to 123.sub.45 corresponding
to frequency bands of 45 channels and subjected to frequency
conversion, the frequency converted data are processed as
modulation data for respective channels. The modulation data for
each channel from the frequency conversion circuits 123.sub.1 to
123.sub.45 is demodulated in a QPSK demodulation circuit 124.sub.1
to 124.sub.45 to a control data of 1.5 M bits/sec. The control data
is subjected to time slicing multiplexing in the multiplexing
circuit 111, and it is sent to the ATM exchanger 23 through an
output terminal 125 as a going-up control data UM.
[0080] Next, the structure of the optical fiber node IM is
described. FIG. 6 is a block diagram of an example of an optical
fiber node.
[0081] A light-to-electric converter 201 receives an analog
television signal through the optical fiber fb1 for the analog
television broadcast line and converts it to an electric signal,
thereafter supplies it to a band pass filter 202. The band pass
filter 202 fetches only an analog television signal in a frequency
band ranging from 50 MHz to 450 MHz from the input signal, and
supplies it to an adding circuit 203.
[0082] A light-to-electric converter 204 receives a going-down
digital transmission data of 15 channels through the optical fiber
fb2 and converts it to an electric signal, and supplies it to a
band pass filter 205. The band pass filter 205 fetches only a
digital transmission data in a frequency band ranging from 500 MHz
to 708 MHz from the input data, and supplies it to the adding
circuit 203.
[0083] The adding circuit 203 adds the analog television broadcast
signal and digital transmission data for frequency multiplexing,
and supplies the frequency multiplexed signal to a band pass filter
207 through an amplifier 206. The band pass filter 207 performs
band restriction within 50 MHz to 708 MHz frequency band on the
input signal, and thereafter sends the frequency multiplexed signal
to the coaxial cable CB.
[0084] A data sent from a subscriber terminal through the coaxial
cable CB is supplied to a band pass filter 208. The band pass
filter 208 performs band restriction within 900 MHz to 972 MHz on
the input data and fetches a going-up control data, and supplies it
to an electric-to-light converter 210 through an amplifier 209. The
electric-to-light converter 210 converts the going-up control data
to an light signal and sends it to the optical fiber fb3.
[0085] Next, a structural example of a coaxial confluent
distributor MPX is described referring to FIG. 7. In detail, a
going-down line data from the coaxial cable CB of the optical fiber
node IM side is supplied to a band pass filter 211. The band pass
filter 211 performs band restriction on the input signal within a
band ranging from 50 MHz to 708 MHz, and supplies it to a
distributor 212.
[0086] The distributor 212 supplies the going-down line data to a
subscriber terminal connected to the coaxial confluent distributor
MPX. Also, the distributor 212 supplies the going-down line data to
a band pass filter 214 through an amplifier 213. The band pass
filter 214 performs band restriction on the going-down line data
for down-stream subscribers within a frequency band ranging from 50
MHz to 708 MHz, and sends it to the down-stream side coaxial cable
CB.
[0087] A data from the down-stream side coaxial cable CB is
supplied to a band pass filter 215. The band pass filter 215
performs band restriction on the input data within a frequency band
ranging from 900 MHz to 972 MHz to allow the going-up control data
to pass, and supplies it to a synthesis circuit 216. The synthesis
circuit 216 adds the going-up control data from down-stream
subscribers and the going-up control data from the subscriber
connected to the coaxial confluent distributor MPX, and supplies
the synthesized data to a band pass filter 218 through an amplifier
217. The band pass filter 218 performs band restriction on the
input data within a frequency band ranging from 900 MHz to 972 MHz
and sends it to the up-stream coaxial cable CB.
[0088] The frequency band for control data of respective
subscribers is previously assigned so as not to overlap each other
in one section.
[0089] Next, a structural example of a subscriber terminal ms
provided in a subscriber's house MS is described referring to FIG.
8 and FIG. 9.
[0090] In detail, a going-down channel data from the coaxial
confluent distributor MPX is fed to an input terminal 301. A
going-up control data is sent from an output terminal 302 to the
coaxial confluent distributor MPX. The coaxial input terminal 301
and coaxial output terminal 302 are connected to a
demodulation/modulation unit.
[0091] The demodulation/modulation unit 303 has the structure shown
in FIG. 9. In detail, a going-down line data from the coaxial input
terminal is supplied to a band pass filter 304. The band pass
filter 304 extracts an analog television broadcast signal in a
frequency band ranging from 50 MHz to 450 MHz and supplies it to a
frequency conversion circuit 305.
[0092] The frequency conversion circuit 305, which corresponds to a
mixer circuit of a tuner, converts a signal of the broadcast
program (broadcast channel) selected by a user out of received
analog television broadcast signals to a signal having a frequency
which can be demodulated by a subsequent analog television
demodulation circuit 306 in response to a channel select control
signal corresponding to a channel select operation of the user
supplied from a terminal controller 320 described hereinafter, and
supplies it to an analog television demodulation circuit 306. The
demodulation circuit 306 supplies the demodulated television signal
to a television through a switch circuit 315 and video output
terminal 316 shown in FIG. 8.
[0093] Further, a going-down line data from the coaxial input
terminal 301 is supplied to a band pass filter 307. The band pass
filter 307 extracts a going-down digital data having a frequency in
the band ranging from 500 MHz to 708 MHz and supplies it to a
frequency conversion circuit 308 and frequency conversion circuit
309.
[0094] The frequency conversion circuit 308 converts only the
signal of the channel to which a video program delivered in
response to the demand from the demand subscriber terminal based on
a channel select control signal from the terminal controller 320 to
a prescribed frequency which can be demodulated. A digital
transmission data such as a video program data addressed to the
demand subscriber terminal from the frequency conversion circuit
308 is supplied to a hexternal QAM demodulation circuit 310 and
demodulated. The 45 M bits/sec digital data from the demodulation
circuit 310 is supplied to the de-multiplexing circuit 317.
[0095] The frequency conversion circuit 309 frequency-converts the
frequency of a control channel data assigned previously to the
demand subscriber terminal to a frequency which can be demodulated
based on a channel select control signal from the terminal
controller 320. The going-down control data from the frequency
conversion circuit 309 is supplied to a QPSK demodulation circuit
311 and demodulated. The 1.5 M bits/sec control data from the
demodulation circuit 311 is supplied to the de-multiplexing circuit
317.
[0096] A QPSK modulation circuit 312 of the demodulation/modulation
unit 303 receives a going-up control data, which will be described
hereinafter, through the de-multiplexing circuit 317, and modulates
it, and supplies it to a frequency conversion circuit 313. The
frequency conversion circuit 313 frequency-converts the frequency
of the input signal to a frequency of the control channel assigned
to the demand subscriber terminal in a frequency band ranging from
900 MHz to 972 MHz. The going-up control data from the frequency
conversion circuit 313 is sent to the coaxial cable CB through a
band pass filter 314 for band restriction in 900 MHz to 972 MHz and
through the output terminal 302.
[0097] The de-multiplexing circuit 317 extracts a 4 M bits/sec
digital transmission data addressed to the demand subscriber
terminal from a 45 M bits/sec output data supplied from the
hexternal QAM demodulation circuit 310 based on the control signal
from the terminal controller 320 if the digital transmission data
is a 4 M bits/sec immediate real-time transmission data, and
supplies it to a digital television signal decoding circuit 319
through a switch circuit 318.
[0098] The switch circuit 318 receives a switching control signal
from the terminal controller 320, selects digital data from the
de-multiplexing circuit 317 during real-time transmission, and
selects the read data as an output and supplies the data to the
digital television signal decoding circuit 319 when data is read
from the temporary memory means 330 in response to a reading
request inputted by the user.
[0099] The digital television signal decoding circuit 319 decodes
the digital data and converts it to an analog television signal,
and supplies the analog television signal to a television through
the switch circuit 315 and video output terminal 316.
[0100] In the embodiment, the digital television signal decoding
circuit 319 is provided with the circuit section for removing
copying prohibiting processing of the information to be transmitted
for which copying prohibiting processing is specified to enable the
copying of the information transmitted in real time or the
information stored in the temporary memory means 330, as described
later, when the user makes a request for removing copying
prohibiting processing of the information.
[0101] The control signal for removing the copying prohibiting
processing is sent from the cable television station through the
going-down control line. Then, the terminal controller 320 receives
the control signal for removing the copying prohibiting processing
and transfers the control signal to the digital television signal
decoding circuit 319 to make the circuit 319 remove the copying
prohibition processing. In this case, processing applied to
recording information of a currently available video cassette tape
is used as the copying prohibiting processing.
[0102] The de-multiplexing circuit 317 sends the digital
transmission data which is to be transmitted to the demand
subscriber terminal to the temporary memory means 330 and stores it
temporarily in the case that the digital transmission data is a
delaying transmission data referring to a control data from the
terminal controller 320. In this case, the delaying transmission
data may be 4 M bits/sec rate or 45 M bits/sec rate as described
hereinafter.
[0103] A semiconductor memory 331 which is a data memory device
having a large capacity (about 1 G bits) and high speed
transmission rate, hard disk device 332 (about 10 G bits), or data
streamer 333 (about 200 G bits) is used as the temporary memory
means 330. The temporary memory means 330 has such a mechanism that
that the memory medium such as a semiconductor memory, disk, or
tape cannot directly be removed from the outside, that is, from the
inside of the body of the subscriber terminal. In other words, for
example, the whole of the temporary memory means 330 is contained
in a shielded cabinet. Or, devices 331, 332, and 333 are contained
respectively in different cabinets and so structured that each
memory medium cannot be removed.
[0104] In the embodiment, the user cannot issue a write (record)
instruction and a read (reproduce) instruction to respective
devices 331 to 333 of the temporary memory means 330 directly via
the interface 321, but such instructions can be issued under the
control from the cable television station.
[0105] According to a storing instruction issued from the cable
television station through the terminal controller 320, the digital
transmission data from the de-multiplexing circuit 317 is therefore
stored in the temporary memory means 330, while, according to a
reading instruction issued from the cable television station
through the terminal controller 320, the stored data is read, and
the read data is supplied to the digital television signal decoding
circuit 319 through the switch circuit 318.
[0106] In this case, as described hereinafter, the terminal
controller 320 determines which memory means is to be selected
among the plurality of memory means of the temporary memory means
330 as the memory for storing the going-down digital data
dependently on the random access potential and transmission format
(such as data transmission rate) of the digital data to be stored
which are specified by the going-down control data or determined by
the demand sent by the demand subscriber terminal.
[0107] For example, if the data transmission rate is 4 M bits/sec
and the data has a low random access potential such as usual video
program, then the data is stored in the data streamer device 333
which uses tapes as the recording medium, on the other hand, if the
data has high random access potential such as stock market
information, then the data is stored in the hard disk device 332,
and if the data is a transmission data with a data transmission
rate of 45 M bits/sec, then the data is written in the
semiconductor memory 331 capable of high speed writing, as
described herein, the memory means in which a data is to be stored
is controlled and selected.
[0108] The de-multiplexing circuit 317 supplies a going-down
control data from the QPSK demodulation circuit 311 to the terminal
controller 320 by controlling the terminal controller 320.
[0109] The terminal controller 320 analyzes the going-down control
data fed to the terminal controller 320 through the de-multiplexing
circuit 317, and if the control data is addressed to the demand
subscriber terminal, the terminal controller 320 generates various
control signals as described herein above based on the control
data. For example, the terminal controller 320 acquires various
information that when the video data demanded by the demand
subscriber terminal will be transmitted by way of what channel out
of 15 going-down channels in what transmission format, from the
received going-down control data, and prepares for receiving. The
channel select control signal to the frequency conversion circuit
308, the control signal for multiplexing to the multiplexing
circuit 317, and the select control signal for selecting a memory
device in the temporary memory device 330 which are described
herein above are generated from this going-down control data.
[0110] Further, the terminal controller 320 receives an operational
input by a user through a user interface 321 comprising a remote
control device and key operation board, generates a going-up
control data, namely demand signal of video on-demand, and supplies
it to the de-multiplexing circuit 317. The terminal controller 320
controls the whole subscriber terminal ms.
[0111] A going-up control data such as video program demand sent
from the terminal controller 320 to the de-multiplexing circuit 317
is supplied successively to the QPSK modulation circuit 312 of the
demodulation/modulation unit 303, frequency conversion circuit 313,
and band pass filter 314, modulated as described hereinbefore,
frequency-converted to a signal of the control channel assigned to
the demand subscriber terminal, and sent to the cable television
station HE.
[0112] The de-multiplexing circuit 317 is connected to CATV
telephone terminal (not shown in the figure) through the terminal
341 and 342, subscribers can communicate with operators of the
cable television station HE.
[0113] The information transmission mechanism and transmission of a
signal in the two-way CATV system having the system structure as
described above are described hereinafter.
[0114] <Analog Television Broadcast>
[0115] Analog television broadcast is transmitted from the cable
television station HE to subscriber terminals ms by way of one-way
transmission as usual without demand from subscribers.
[0116] When a user wants to view an analog television broadcast
from the cable television station HE, the user operates channel
select operation for selecting an analog television broadcast of
the cable television station HE through the user interface 321 of
the subscriber terminal ms. Then, the terminal controller 320 of
the subscriber terminal ms supplies a channel select signal
corresponding to the channel select operation of the user to the
frequency conversion circuit 305 of the demodulation/modulation
unit 303, and the switch circuit 315 is switched to the mode for
selecting an analog television signal from the analog television
demodulation circuit 306 of the demodulation/modulation unit 303,
and thereby an analog television signal is supplied from the video
output terminal 316 to a television. Thus the subscriber can view
an analog television broadcast program selected by the user from
the cable television station.
[0117] <Digital Information Transmission>
[0118] FIG. 10 is a block diagram for describing mainly functions
which are performed at the HE controller 24 of the cable television
station HE and the terminal controller 320 of a subscriber terminal
ms to transmit digital information in the system of the
above-mentioned embodiment in which the cable television station HE
and subscriber terminals ms are connected through the going-up and
going-down lines comprising optical fiber and coaxial cable.
[0119] As shown in FIG. 10, the cable television station HE
provided as an information distribution transmission center is
connected to a plurality of subscriber terminals ms through the
going-up line Cu which is the line for transmission toward the
cable television station and the going-down line Cd. As described
above, the going-down line contains a line for program information
to be transmitted and a line for the going-down control data.
[0120] The cable television station HE functionally comprises
digital information source 1, going-down information signal
generator 2, information transmission control means 3, transmission
planning means 4, demand receiving analysis means 5, control
information generating means 6, charging means 7, and
authentication information and charging information database 8.
[0121] The digital information source 1 includes video server 21,
tape information library device 22, and so on. The going-down
information signal generator 2 comprises an ATM exchanger 23 and
node controllers 25a to 25p.
[0122] The demand receiving analysis means 5 receives and analyzes
the contents of the demand from a subscriber terminal ms and passes
the analyzed contents to the information transmission control means
3 and the transmission planning means 4. The transmission planning
means 4 make a transmission plan according to the results of the
demand analysis. Such a plan is made that for a A-class demand, a
fee channel is found from among the going-down lines prepared for
real-time transmission, and information is transmitted through the
channel, and that for a B- and C-class demands, at the time behind
the demands, fee channels are found from among the going-down lines
prepared for respective demands, and the fee channels are allocated
one by one. The transmission planning means 4 passes the
transmission plan to the control information generating means 6 and
the information transmission control means 3.
[0123] The information transmission control means 3 controls the
transmission of going-down digital information and the sending of
going-down control data by controlling the digital information
source 1, the going-down information signal generator 2, and the
control information generating means 6.
[0124] The control information generating means 6 generates
going-down data based on the control information and necessary
information from the information transmission control means 3 and
the transmission planning means 4 and information from the data
base 8. The time of the transmission plan for each demand, the
authentication information for copying permission, a reproduction
start control signal in response to the reading request
(reproduction request) from the subscriber terminal described
later, deletion instruction signal, and the list of programs to be
transmitted included in the transmission plan information are
referred to as an example of the going-down data.
[0125] The list of programs to be transmitted is, for example, as
shown in FIG. 11, indicates the information transmission plan in
response to the demands all the subscriber terminals are going to
send behind at the time after delay. The list of programs to be
transmitted is created, for example, at a preferable time
intervals, and the created list is sent to the subscriber terminal
when the subscriber terminal makes a request for the list of
programs to be transmitted. Such a broadcast format may be used
that the list of programs to be transmitted is sent to all the
subscriber terminals for use as going-down control data.
[0126] The subscribers can receive programs by specifying the
programs in the program list, in such a way that information
transmission for the already issued demands is shared with the
current information transmission. If the results of the analysis by
the demand analysis means 5 are that the demands from the
subscriber terminals are share demands, the information
transmission control means 3 specifies a plurality of information
transmission destinations so that simultaneous information
transmission is performed also for the subscriber terminals who
made share demands during the transmission of information for which
share information transmission is specified.
[0127] The charging means 7 performs charging based on the results
of the demand analysis received from the transmission planning
means 4 and the information on charging from the database 8. A
charge for share information transmission is specified as lower
than a charge for usual transmission.
[0128] The data base 8 holds the authentication information for the
permission of the copying of transmission information and the table
of charges to be used when the charging means 7 performs
charging.
[0129] The information transmission control means 3, transmission
planning means 4, analysis section of the demand receiving analysis
means 5, and charging means 6 are realized as functions of the HE
controller 24 (realized by software).
[0130] Respective subscriber terminals ms receive the going-down
control data of their own destinations from the demand sending
means 11 for sending a demand (transmission request) to the
going-down Cu, the temporary memory means 12 with a large capacity,
and the going-down line Cd, and each subscriber terminal is
provided with a transmission plan receiving analysis means 13 for
analyzing the transmission plan information included in the
going-down control data, a transmission information receiving
control means 14, and a copying enabled conversion means 15.
[0131] The transmission information receiving control means 14
receives the digital transmission data of own destination from the
going-down line Cd, demodulates the data, supplies the demodulated
output to a monitor/television set, not shown, through the copying
enabled conversion means 15 when real-time reproduction is
required, or stores received transmission information of own
destination in the temporary memory means 12 when no real-time
reproduction is required.
[0132] The copying enabled conversion means 15 is a circuit section
included in the above-mentioned digital television decoding circuit
319 and, as described above, removes copying prohibition
processing, what is called, a copy guard applied to the video
program information to be transmitted.
[0133] The demand transmission means 11 receives a demand of a user
through the user interface such as a remote controller or key
board, generates a distribution transmission request signal (demand
signal), and sends it to the going-up line Cu.
[0134] A demand signal includes a user ID which is an
identification code of each subscriber, transmission program
specifying information (program identifying data) for specifying a
video program requested for distribution, request time information
which is a information relating to the urgency of the requested
information transmission such as the time when the program is
desired to be transmitted or the time when the subscriber wants to
view, and transmission format specifying information for specifying
which format of 4 M bits/sec digital information or 45 M bits/sec
digital information is desired.
[0135] In this case, the information of the time may be used as it
is as the request time information, however in this embodiment,
several classes are defined depending on the urgency of a request,
and the request time information specifies a class. In detail,
{circle over (1)} if a user wants to view the program immediately,
then the program is demanded as A-class urgency, {circle over (2)}
if a user wants to view later, then the program is demanded as
B-class urgency, and {circle over (3)} if a user wants to view
within a half or one day, then the program is demanded as C-class
urgency.
[0136] In this embodiment of the present invention, down-stream
digital information transmission channels include digital
television broadcast channels, and thus the subscriber can watch
the programs in the digital television broadcast channels
immediately even if the subscriber does not issue any demand. The
digital television broadcast channel class is called a D class
hereinafter.
[0137] As described above, the demand sending means 11 also sends
such a share demand that information reception is performed being
shared with information transmission in response to the already
issued demand.
[0138] In this embodiment, a user's command via the user interface
is not directly supplied to the temporary memory means 12 in the
subscriber terminal ms, and writing (recording) and reading
(reproducing) are enabled under the control of the cable television
station HE. This prevents a free use of transmission information in
the temporary memory means 12 to protect the copyright of the
information.
[0139] When the user wants to read the video program information
stored in the temporary memory means by the user, the demand
sending means 11 receives a reading request made by the user via
the user interface and sends the reading request to the cable
television station HE through the going-up line Cu. The reading
request includes reading request identification data, a user ID,
program identification data for specifying a video program to be
read. In this embodiment, as described later, it is defined that
the user is permitted to copy a video program, but the copying
permission request is included in the above-mentioned reading
request.
[0140] The going-down control information receiving analysis means
13 receives and analyzes the going-down control data sent from the
cable television station HE to examine whether information is
transmitted in real time or behind time, the degree of random
accessibility, whether authentication information used to permit
copying is included in the control information, and suchlike. The
transmission information receiving control means 14 and the copying
enabled conversion means 15 are controlled according to the results
of the analysis.
[0141] In this case, when the authentication information for
copying permission is not detected, the copying enabled conversion
means 15 outputs the input signal (real-time transmission
information and the information read from the temporary memory
means 12) as it is, and copying prohibition processing is still
applied to the input signal. When the authentication information
for copying permission is detected, the copying enabled conversion
means 15 operates to remove the copying prohibition processing of
the input signal and outputs the signal. If the output signal is
recorded with a VTR, the signal can therefore be reproduced and
used as it is.
[0142] Next, charging for information transmission is described. In
this embodiment, different charges are specified for each demand
class. FIG. 12 is an example of the table of charges. In this
example, charges vary according to the periods of time when
information transmission is performed as well as demand classes.
Since the information must be transmitted within the prime time
when a A- or B-class demand is made in prime time, a high charge is
applied to the transmission. A low charge is applied to the
transmission during midnight and early morning. In addition, the
higher the information transmission urgency of a class demand is,
the higher charge is applied to the class demand.
[0143] In the embodiment, the share demands can be specified for B-
and C-class demands, and charges for the share demands are
specified as low in the same way.
[0144] When copyright fees are collected for information
transmission of each program, the copyright fees are included in
each charges in the above-mentioned table of charges. However, in
the same way as for broadcasting, the copyright fee is charged each
time a program is used. As described above, in this embodiment, it
is designated that the user is permitted to copy the video program
stored in the temporary memory means 12. In this case, however, an
additional fee can be collected as a copyright fee applied during
copying every time a desired video program is copied, as shown in
FIG. 12.
[0145] In this example, free channels are prepared so that
information transmission can be performed at a time other than the
prime time in response to C-class demands and real-time information
transmission can be performed in prime time in response to A-class
demands.
[0146] Charges are specified as described above to suppress the
concentration of traffic in prime time by raising the fee for
information transmission in the time zone of much traffic. Further,
an appropriate additional fee is specified for copying.
[0147] In this embodiment, in the 45 MHz.times.15 channel
transmission band for the going-down digital transmission data, the
transmission capacity is allocated dynamically to the demand
urgency classes dependently on the actual traffic condition of
respective time zones in a day in order to use efficiently the
transmission capacity.
[0148] For example, in prime time zone, when many A-class demands
are generated, the capacity is allocated as described
hereinafter.
[0149] Transmission to A-class demand: 45 M bits/sec.times.5
channels
[0150] Transmission to B-class demand: 45 M bits/sec.times.8
channels
[0151] Transmission to C-class demand: No allocation
[0152] Transmission to D-class: 45 M bits/sec.times.2 channels
[0153] In midnight time zone when a few demands are generated, the
capacity is allocated as described herein under.
[0154] Transmission to A-class demand: 45 M bits/sec.times.2
channels
[0155] Transmission to B-class demand: 45 M bits/sec.times.2
channels
[0156] Transmission to C-class demand: 45 M bits/sec.times.10
channels
[0157] Transmission to D-class: 45 M bits/sec.times.1 channel
[0158] It is considered that many demands for video programs are
requested in prime time, no program is transmitted to C-class
demands and more number of channels is allocated for transmission
to A-class and B-class demands in order to transmit programs with a
waiting time as short as possible.
[0159] Two channels are allocated to D-class transmission in order
to provide many digital broadcast programs in prime time.
[0160] On the other hand, it is considered that a few demands for
digital television broadcast programs is requested in the midnight
time zone and the number of broadcast programs may be not many, the
number of transmission channels for digital television broadcast is
reduced by one channel comparing with the number in prime time
zone. It is considered that a fewer demands for video programs is
requested in the midnight time zone than in prime time zone, then
the number of channels for transmission to A-class and B-class
demands is reduced, and more transmission capacity and more channel
are allocated to C-class demands so that C-class demands which have
been accepted previously are transmitted.
[0161] An example of the allocation of transmission capacity for
the going-down digital transmission data allocated as described
herein above is shown in FIG. 13. In FIG. 13, the abscissa
represents the time, and the axis of ordinate represents the
allocation of 15 channel capacity for the digital transmission
data.
[0162] An arrow .Arrow-up bold. represents a time point of
generation of a distribution transmission request instruction, and
a section enclosed by a rectangle represents a program. "For
broadcast" represents the transmission capacity for digital
television broadcast, "real-time V. O. D." represents the
transmission capacity for real-time transmission of A-class
demands, "little delay V. O. D" represents the transmission
capacity for digital information transmission of B-class demands,
and "much delay V. O. D" represents the transmission capacity for
digital information transmission of C-class demands like the
above-mentioned FIG. 2.
[0163] As shown in FIG. 13, no transmission capacity is allocated
for transmission of C-class demands in prime time. The allocated
channels "real-time V. O. D" transmits in real-time in response to
a demand, and the allocated channel "little delay V. O. D" transmit
with a little delay from a demand with looking for a free channel.
The transmission time of one program can be shorter than the
transmission time by way of the allocated channel to "real-time V.
O. D" because of 45 M bits/sec transmission in this case.
[0164] In the midnight time zone, more channels are allocated to
"much delay V. O. D", and many programs are transmitted to the
previously accepted C-class instructions which allows much delay.
Accordingly, the midnight time zone when usually a little demand is
generated is used efficiently, and the transmission is performed
efficiently.
[0165] [Generation and Transmission of Distribution Transmission
Request Signal]
[0166] FIG. 14 is a flowchart of routine for generation and
transmission of demand signals of video on-demand at a subscriber
terminal.
[0167] Upon receiving a command input for sending a distribution
transmission request form a user through the user interface 321 in
the subscriber terminal ms, the processing routine shown in FIG. 14
starts. In step S1, the user displays the operation menu for demand
input. In the step, when the user selects the item on charges, the
table of charges is displayed as shown in FIG. 15. The contents of
the table are the same as those of the above-mentioned table of
charges. The user can specify a class for a demand, referring to
the displayed table.
[0168] As described above, the charge for a demand varies according
to the demand input time. In the table of charges in FIG. 15, an
applied charge is for example highlighted according to the time of
the input operation of the demand. If the demand input time is in
prime time, for instance, the A- and B-class fields for the prime
time zone and a C-class field are highlighted with a double frame
in FIG. 15, and the user is notified of the highlighted charges for
the demands.
[0169] When the subscriber wants to issue a share demand, the
subscriber sends a request for the list of programs to be
transmitted to the cable television station on the menu display
screen. When the list of programs to be transmitted is reached at
the subscriber, the list of programs to be transmitted as shown in
FIG. 11 is displayed on the screen of the monitor television set.
When there is a desired program to be specified as a B- or C-class
demand in the program list, the subscriber specifies the program
and inputs a share demand.
[0170] When the input by the user is accepted in step S1, it is
determined whether the inputted demand is a share demand in the
next step S2. When it is determined that the inputted demand is not
a share demand, the process proceeds to step S3.
[0171] In the step S3, it is determined which class demand has been
specified as request time information on the urgency of
transmission. If an A-class demand is specified as request time
information, the process proceeds to step S4, in which an A-class
demand signal is generated, and the process proceeds to step S5, in
which it is determined whether a copying permission request is
inputted by the user. When a copying permission request is inputted
in advance, the process proceeds to step S6, in which the copying
permission request is included in a demand. The process proceeds to
step S9, in which the demand signal is sent to the going-up line
Cu. Unless the copying permission request is inputted in step S5, a
jump is made to step S9, in which the demand excluding the copying
permission request is sent to the going-up line Cu.
[0172] The distribution transmission request demand signal includes
a user ID for identifying the subscriber terminal and a program
identifying data for identifying a desired video program as
described hereinbefore.
[0173] If the request time information is B-class or C-class, the
process proceeds to the step S7, the specification of transmission
format is judged to be transmission rate of the transmission data
of 4 M bits/sec or 45 M bits/sec, and the specification of random
access is judged. Then, the process proceeds to the next step S8, a
demand signal including the judged format, random access, and
urgent class is generated, and the demand signal is sent to the
going-up line Cu in the step S9.
[0174] Further, in the step S2, in which when it is determined that
the demand inputted by the user is a share demand, the process
proceeds step S10, and the share demand including the own user ID,
share program identification data, and identification data which
indicates that the demand is a share demand is generated. The
process then proceeds to step S9, the subscriber terminal sends the
share demand to the cable television station HE through the
going-up line. This is the end of the processing routine of sending
a demand at the subscriber terminal.
[0175] [Receiving Processing of Distribution Transmission Request
Demand]
[0176] FIG. 16 is a flowchart of processing routine for receiving a
demand signal from a subscriber terminal in the HE controller 24 of
the cable television station HE.
[0177] Upon receiving the demand signal sent from a subscriber
terminal through the going-up line Cu, the demand receiving
analysis means 5 of the cable television station HE analyses the
contents and passes the request time information included in the
demand signal and the user ID and program identification data to
the transmission planning means 4 and the information transmission
control means 3. The demand receiving analysis means 5 also passes
the information on whether the received demand is a usual demand or
a share demand to the transmission planning means 4 (step S11).
[0178] Further, the transmission planning means 4 determines
whether the received demand is a usual demand or a share demand
(step S12), in which when the means 4 determines that the received
demand is a usual demand, the process proceeds to step S13.
[0179] In the step S13, the transmission planning means 4 analyzes
the request time information, and determines which demand class of
A-class, B-class, or C-class is included in the request time
information included in the demand signal (step S13). The
determination result is reported to the charging means 7.
[0180] If the request time information is determined as A-class
which requests real-time transmission, then the transmission
planning means 4 looks for a free going-down line transmission
channel assigned to "for real-time V. O. D" shown in FIG. 13, and
if the transmission planning means 4 finds a free channel, the free
channel is decided to be a real-time transmission channel (step
S14).
[0181] Upon receiving this decision, the information transmission
control means 3 informs the subscriber who sent the demand of the
real-time transmission channel to (step S15). It is determined
whether a demand contains a copying permission request (step S16).
When the copying permission request is contained in the demand,
authentication information for copying permission is acquired from
the data base 8, and the subscriber is informed of the acquired
information (step S17). The video program specified by program
identification data is extracted from the digital source 1, and
real-time transmission is carried out (step S18).
[0182] Further, the process proceeds to step S19, in which charging
is performed, and then demand receiving processing is terminated.
In this case, charging is performed for the A-class demand included
in a copying permission request.
[0183] As a result of determination in step S16, if no copying
permission request is included in the demand, the process proceeds
from step S16 to step S20, in which the authentication information
for copying permission is not sent, but real-time information
transmission is performed. Then, the process proceeds to step S21,
in which charging is performed for the A-class demand that does not
include a copying permission request.
[0184] At this time, the digital transmission data is fetched from
the video server 21 and transmitted by way of the channel of the
above-mentioned "for real-time V. O. D".
[0185] If the request time information judged in the step S12 is
B-class and is the transmission request which allows a little
delay, the transmission planning means 4 looks for a free channel
from the going-down channel "for little delay V. O. D" in FIG. 13
for B-class, and decides a transmission time so as to transmit by
way of the free channel (step S22).
[0186] The transmission planning means 4 informs the information
transmission control means 3 of the free channel to be used for the
transmission, transmission time, and above-mentioned analysis
result. The transmission planning means 4 also informs the charging
means 7 of information on the transmission time. Further, the
transmission planning means 4 analyzes the transmission format
information included in the demand signal and random access
information, and informs the information transmission control means
3 of the analysis result.
[0187] The information transmission control means 3 generates
going-down control data including the free channel, transmission
time (starting time and ending time), transmission format (4 M
bits/sec transmission rate or 45 M bits/sec transmission rate), and
random access information. The going-down control data has the user
ID as header information. In addition, the information transmission
control means 3 sends the going-down control data to the subscriber
who sent a demand specified by the user ID, and reports the
transmission time, transmission format, and so on to the terminal
of the subscriber who sends the demand (step S24).
[0188] When the time comes to the transmission time (step S25), the
information transmission control means 3 extracts the specified
video program based on the program identifying data included in the
transmission request demand and transmission format from the video
server 21 in the case of the transmission rate of 4 M bits/sec or
from the tape information library system 22 in the case of the
transmission rate of 45 M bits/sec, and transmits it (step S26).
After completion of the transmission, charging for the transmission
is performed (step S27).
[0189] If the request time information is determined to be C-class
in the step S12, that is, the transmission request allows much
delay of a half day to one day, the transmission planning means 4
finds out a free channel from the transmission plan of the
going-down line channels (("for much delay V. O. D) shown in FIG.
13) assigned to the midnight time zone, and decides a transmission
time so as to transmit by way of the free channel (step S22).
[0190] Then, in the same way as for B-class demands, the
transmission planning means 4 informs the information transmission
control means 3 of the free channel to be used for the
transmission, transmission time, and above-mentioned analysis
result, and notifies the charging means 7 of the information on the
transmission time. Further, the transmission planning means 4
analyzes the transmission format information included in the demand
signal and random access information, and gives the analysis result
to the information transmission control means 3.
[0191] The information transmission control means 3 transmits
previously the free channel, transmission time (starting time and
ending time), transmission format (4 M bits/sec transmission rate
or 45 M bits/sec transmission rate), and random access information
to the subscriber who sent the demand and is specified by the user
ID as the going-down control data having the user ID header
information (step S24), and when the time comes to the transmission
time (step S25), the information transmission control means 3
extracts the specified video program based on the program
identifying data included in the transmission request demand and
transmission format from the video server 21 in the case of the
transmission rate of 4 M bits/sec or from the tape information
library system 22 in the case of the transmission rate of 45 M
bits/sec, and transmits it (step S26). After completion of the
transmission, charging for the transmission is performed (step
S27).
[0192] Further, when the demand from the subscriber terminal is a
share demand in step S12, the process proceeds to step S28, in
which the transmission planning means 4 adds a user ID included in
the share demand for use as the transmission destination of the
program indicated by the program identification data included in
the share demand.
[0193] Next, the process proceeds to step S25, in which, at the
time of information transmission, the corresponding information
programs are transmitted to all of a plurality of the subscribers
whose identification data are stored for use as destinations. Then,
the process proceeds to step S27, in which share fee is applied for
the subscribers. In this case, the share fee is also applied to the
user who first sent an usual demand. However, a usual fee may be
applied to the user who first sent an usual demand. Accordingly,
the processing routine ends.
[0194] [Receiving Processing of a Control Data and Transmission
Data in a Subscriber Terminal]
[0195] FIG. 17 is a flowchart of a processing routine performed
when the terminal controller 320 of a subscriber terminal receives
a going-down control data and transmission digital data.
[0196] The subscriber terminal receives a control data of the
transmission plan addressed to the demand subscriber terminal
referring to the user ID in the going-down control data from the
going-down line Cd (step S31), analyzes it (step S32), and judges
whether it requires the immediate real-time transmission referring
to the analysis result (step S33). The judgment may be based on,
for example, no inclusion of transmission time data in the
going-down control data. Alternately, a class information or flag
which indicates whether it requires the real-time transmission or
does not is included in the going-down control data, and the
judgment may be performed based on the class information or
flag.
[0197] When the determination result based on the analysis
indicates real-time information transmission, it is determined
whether the authentication information for copying permission is
received (step S34). If the authentication information is received,
the copying enabled conversion means 15 operates to control the
digital television decoding circuit 319 in order to remove copying
prohibition processing (step S35).
[0198] According to the results of the analysis in step S32, the
terminal controller 320 detects a transmission channel, supplies a
select signal to the frequency conversion circuit 308 to convert
the going-down digital transmission data of the transmission
channel to data having a frequency band which can be demodulated,
switches the switch circuit 318 so as to select 4 M bits/sec data
from the de-multiplexing circuit 317, and switches the switch
circuit 15 so as to select the television signal from the digital
television decoding circuit 319 to supply it to a television set
through the output terminal 316 (step S36). Copying prohibition
processing is removed from the video signal of this case, and so
the signal can be copied.
[0199] When, as a result of the determination in step S34, it is
determined that the authentication information for copying
permission is not received, the process bypasses step S35 and
proceeds to step S36, in which transmission information is received
in real time to supply the information to the television set, then
the receiving processing routine ends. Copying prohibition
processing is still applied to the video signal of this case.
[0200] If the determination result in the step S33 does not show an
immediate real-time transmission, then the terminal controller 320
recognizes the transmission time, transmission channel,
transmission format, and random access information based on the
analysis result of the above-mentioned going-down control data, and
prepares for receiving (step S37). The terminal controller 320
waits for the transmission time of the transmission information
(step S38), and when the time comes to the transmission time, the
terminal controller 320 supplies a select signal for converting the
going-down digital transmission data of the transmission channel to
a data having a frequency band which can be demodulated to the
frequency conversion circuit 308, and starts to receive the digital
transmission data according to the transmission format (step
S39).
[0201] Further, any one medium to be used for storing the
transmission information is selected previously from the
semiconductor memory, hard disk, data streamer, and digital VTR in
the temporary memory device 330 according to the transmission
format included in the going-down control data and random access
information (step S40), and the received transmission information
is stored in the selected temporary memory device based on the
memory permission information which is going-down data to be sent
prior to transmission information, then the receiving processing
routine ends.
[0202] The cable television station HE stores the history of the
programs transmitted to each subscriber which, as described later,
is used for references when the subscribers send reading requests
to the cable television station HE.
[0203] In this case, if the transmission format specifies high
speed transmission and the semiconductor memory is selected as the
temporary memory means, the transmission information is transmitted
with the high speed transmission rate of 45 M bits/sec, and the
transmission data is stored in the semiconductor memory 331 which
serves as the temporary memory means as it is high speed
transmission rate.
[0204] For example, if the transmission rate of a compressed
digital data is 1.5 M bits/sec and a program is a two-hour program,
the program compressed to 45 M bits/sec rate is transmitted, then
the transmission requires only about 4 minutes, and alternately if
the transmission rate is 4 M bits/sec, the transmission of a
two-hour program requires only about 11 minutes.
[0205] In the case that the transmission date rate is 4 M bits/sec
due to the transmission format, the selection of a temporary memory
means depends on random access, and the hard disk device is
selected for high random access and the data streamer device 333 is
selected for low random access as the temporary memory means.
[0206] High fee may be applied to the request for low rate format
transmission in real-time, on the other hand, low fee may be
applied to the request for high speed rate because the transmission
time is short.
[0207] As described herein above, the receiving processing of the
transmission information is performed in a subscriber terminal. The
television signal received in real-time transmission is supplied to
a television without storing in the temporary memory device.
Therefore, a user can view the program with a slight delay from the
demanding.
[0208] On the other hand, the video data stored in the temporary
memory device 330 is reproduced at the arbitrary time and provided
to the subscriber in response to a reading request (reproduction
request) from the subscriber through the user interface 321. FIG.
18 shows a flow of an example of the reproduction processing
routine.
[0209] For the case that a plurality of video programs is
registered in the temporary memory device due to a plurality of
demands, in this example, the terminal controller 320 of a
subscriber terminal ms is provided with a function to display the
menu of accumulated video programs on the television monitor, the
user can select and view any program from the menu. The terminal
controller 320 stores program identification data of each
transmission program (called program IDs hereinafter) and memory
devices in which the transmission programs are stored, between
which a correspondence has been established.
[0210] When a subscriber specifies the program transmitted after
delay via the user interface 321 and inputs a reproduction request
including a copying permission request as the need arises, the
routine in FIG. 18 starts, and in step S51, the user's reproduction
request is accepted. Next, the process proceeds to step S52, in
which it is determined whether the copying permission request is
included in the user's reproduction request.
[0211] When it is determined that the copying permission request is
included in the user's reproduction request in step S52, the
process proceeds to step S53, the reproduction request command
including an own user ID, the program ID of a program selected by
the user from the information stored in the temporary memory device
330, and the copying permission request is sent to the cable
television station HE through the going-up line.
[0212] The process proceeds from step S53 to step S54 and waits for
the authentication information for the copying permission to be
received from the cable television station HE. When it is confirmed
that the authentication information for the copying permission is
received in step S54, the process proceeds to step S55, in which
the copying enabled conversion means of the digital television
signal decoding circuit 319 is made operable. Then, the process
proceeds to step S57 and waits for the reproduction start control
signal (including a program ID) to be received from the cable
television station HE.
[0213] When it is determined that the copying permission request is
not included in the user's reproduction request in step S52, the
process proceeds to step S56, the reproduction request command
including the own user ID and the program ID of the program
specified by the user and excluding the copying permission request
is sent to the cable television station HE through the going-up
line. After the step S56, the process proceeds to step S57 and
waits for the reproduction start control signal to be received from
the cable television station HE.
[0214] When it is confirmed that the reproduction start control
signal is received from the cable television station HE in step
S57, the process proceeds to step S58, in which the terminal
controller 320 reproduces (reads) the program information
identified with the above-mentioned program ID from the medium of
the temporary memory device 330 in which the program information
specified with the program ID is stored.
[0215] Upon receiving the reproduction instruction, the temporary
memory device reads the corresponding digital video data of the
program, and supplies it to the digital television decoding circuit
319 through the switch circuit 318. In this case, the rate of the
read digital data is 4 M bits/sec. The video signal from the
decoding circuit 319 is supplied to a television through the output
terminal 316, and provided to the user. When information copying is
permitted, the video signal from the output terminal 316 can be
recorded in VTR or suchlike.
[0216] Then, the process proceeds to step S59 and waits for the
reproduction end instruction to be received through the user
interface 321 of the subscriber. When the reproduction end
instruction is confirmed in step S59, the process proceeds to step
S60, in which a deletion request including the own user ID and
program ID is sent to the cable television station HE through the
going-up line. When the deletion instruction control signal is
received from the cable television station HE in step S61, the
process proceeds to step S62, in which the used transmission
program is deleted from the above-mentioned temporary memory
device, then the reproduction processing routine ends.
[0217] Next, an example of receiving a production request from the
subscriber is described referencing the flowchart in FIG. 19.
[0218] The processing routine in FIG. 19 starts when the cable
television station HE receives a reproduction request from the
subscriber, and the production request is accepted in step S71.
Next, the process proceeds to step S72, in which it is determined
by a program ID whether the program has really been transmitted or
whether the program should have already been deleted. In this case,
as described above, since the cable television station HE retains
the history of the transmitted programs for each user ID, the
determination processing is performed referencing the retained
information.
[0219] When it is determined that the program has not been
transmitted yet or should already have been deleted in step S72,
the processing routine ends.
[0220] When it is determined that the program has been transmitted
and has not yet been deleted in step S72, the process proceeds to
step S73, in which it is determined whether the copying request is
made. When the copying request is already made, the process
proceeds to step S74, in which the authentication information for
the copying permission is fetched from the data base 8 and the
fetched information as going-down control data is sent to the
subscriber who made the copying request. In the next step S75, an
additional fee for the copying permission is charged for the
corresponding subscriber.
[0221] Next, the process proceeds to step S76, in which the
reproduction start control signal specifying a program to be
reproduced with a program ID is sent to the subscriber who made the
reproduction request. Thus, the reproduction request receiving
processing ends.
[0222] When the deletion request including a user ID and a program
ID is received from the subscriber, as described above, the cable
television station HE sends the deletion control signal to the
corresponding subscriber.
[0223] In the above example, the user makes a request for the
permission of copying a program to be transmitted after delay at
the same time when the user makes a request for reproducing the
program. However, the copying permission request may be included in
a program. When the user already makes the copying permission
request, transmission demand. In this case, when the user makes a
request for reproducing the transmitted program, the cable
television station determines whether the user makes a copying
permission request during the program demand. The cable television
station sends the authentication information for the copying
permission to the user before the reproduction start control
signal.
[0224] Further, in case of making a copying permission request
during such a demand, the instruction of whether the user wants to
use the same program again is included in the reproduction end
instruction. After the reproduction end instruction is confirmed,
it is determined whether the reusing request is made. When no
reusing request is made, the used transmission program is deleted
from the above-mentioned temporary memory device. When it is
determined that a reusing request is made, the used transmission
program is not deleted, and the reproduction processing routine is
terminated, thus enabling the use of the same program more times
than once. In this case, an additional fee is charged for the
copying permission whenever the program is reproduced.
[0225] Since consideration is given to copying in the above
example, the deletion instruction is issued before instructions to
be issued by the cable television station. In the system in which
copying is impossible, however, reproduction is performed at the
subscriber terminal, and it may be specified that, after a program
is used, the program can be deleted without fail only under the
control by the subscriber terminal.
[0226] In the first embodiment described herein above, a user can
demand not only the immediate real-time transmission but also the
delayed transmission, therefore, a user who wants to view the
program in prime time zone can demand for the program to be
transmitted during the midnight time zone and the program is stored
in the temporary memory device, and the user can view the demanded
program at the desired time.
[0227] The above-mentioned demand-delayed view system favors the
demand for immediate real-time transmission in prime time to
decrease.
[0228] Since demands are classified into various types according to
the classes which indicate the urgency of information transmission,
and for example, the lower fee to the demand allowable of delayed
transmission than that to the demand for immediate real-time
transmission is applied according to the delay time length, such
fee system favors the demand in prime time to decrease.
[0229] Such suppressed generation of the immediate real-time
transmission in prime time allows the cable television station to
be provided with a smaller scale facility in comparison with the
conventional cable television station which transmits programs only
in real-time.
[0230] Transmission capacity of going-down digital transmission
data is allocated to an independent plurality of transmission
channels depending on the information relating to the class which
indicates the urgency of information transmission in the demand and
many channels are allocated to the immediate real-time transmission
in prime time. On the other hand, many channels are allocated to
the delayed transmission in midnight, and such change of allocation
depending on the time zone allows the transmission capacity to be
used efficiently.
[0231] In the above-mentioned embodiment, high speed transmission
is possible for delayed transmission in comparison with real-time
transmission, and the time required for transmission of one program
is shortened in comparison with the conventional method, in this
aspect also, the transmission capacity is used efficiently.
Accordingly, charges for the subscriber can be reduced to low
rates, and it is expected that the wide use of the video on-demand
systems are promoted.
[0232] After the transmission program is used, the program stored
in the subscriber terminal is automatically deleted, thus enabling
the sure protection of the copyright of the program. In addition,
since an additional special fee is charged for program copying,
effective copyright protection can be expected.
[0233] [Example of Change]
[0234] In the above-mentioned first embodiment, allocation of the
number of transmission channels depending on the information
relating to the urgency class of the demand is changed in the time
zone in a day, but the allocation may be changed dependently on
days in a week, or may be changed in combination of time zone and
week.
[0235] In the above-mentioned first embodiment, the allocation of
transmission channels depending on the information relating to the
urgency class of the demand is changed within only the transmission
capacity of the going-down digital information data, but, because
the audience rate of analog television broadcast decreases, the
transmission band of analog television broadcast is reduced and the
reduced transmission band is used as the transmission band of
digital information data.
[0236] In this case, a program table including channel assignment
different between prime time and midnight is prepared for analog
television broadcast, and this program table is transmitted to
subscribers previously to inform the change of program channel
depending on the time zone.
[0237] A plurality of data compression systems of digital
transmission data is provided in the cable television station, for
example, depending on requested degree of resolution, and any one
of data compression systems may be selected by way of the demand
from a subscriber terminal. In this case, a plurality of decoders
are provided in a subscriber terminal depending on the
above-mentioned plurality of data compression systems, the
information including compression system information in the
going-down control data from the television station is sent to the
subscriber terminal, and the decoder is switched dependently on the
compression system information.
[0238] In this case, the compression rate is low and the amount of
data is large, but the charges for high-resolution and high-quality
video program transmission are specified as high in consideration
of the long transmission time. On the other hand, for a high
compression rate, a small data amount, and short transmission time,
the charges can be specified as low.
[0239] In the above-mentioned embodiment, B-class demand is stored
necessarily in the temporary memory means, but because it is
possible to display the transmission time sent from the station on
a display of a subscriber terminal and to inform it to a user, a
mode for specifying real-time transmission reproduction for B-class
demand without storing in the temporary memory means may be
provided.
[0240] Further in the above-mentioned embodiment, the temporary
memory means is selected based on the transmission format and
random access relating information in the going-down control data
in a subscriber terminal, but alternately a demand signal sent from
a subscriber terminal is stored in the subscriber terminal, and the
temporary memory means may be selected for the transmitted
transmission data depending on the stored demand signal. In this
case, an identification data ID for identifying the demand signal
may be added in the demand signal to judge the demand. In this
case, the information relating to transmission format and random
access is not necessarily included in the going-down control
data.
[0241] [Second Embodiment]
[0242] The second embodiment shows an example in which an existing
CATV cable network is used. In a conventional CATV cable network, a
cable television station is connected to a plurality of subscriber
terminals by way of coaxial cable, and provides mainly analog
television broadcast to each subscriber terminal by way of coaxial
cable.
[0243] In the second embodiment, a facility for transmission of
digital data such as video data is added to a cable television
station without change of the conventional transmission line
facility using coaxial cable, and a receiving unit for receiving
digital data provided with a large capacity temporary memory device
is added to a subscriber terminal. The public phone network is used
as the going-up line for transmission of digital data demand.
[0244] FIG. 20 shows the whole network structure of the embodiment.
In a cable television station 40, an analog television broadcast
signal Va from the above-mentioned analog television broadcast
facility 401 and digital data Vb such as digital video data from
the digital transmission data transmission facility 402 are
synthesized to generate a frequency multiplexed signal, and sent to
the coaxial cable CB through an amplifier 404.
[0245] A plurality of telephone lines L1 to Ln is connected to the
public phone network PSTN, and a station side controller 405 for
receiving demands from subscribers through the telephone lines L1
to Ln and for sending video programs corresponding to the demand
from the digital data transmission facility 402.
[0246] Also in this embodiment, the station side controller 405
generates a going-down control data Vc including a user ID for
specifying the addressed subscriber terminal which receives the
digital data, program ID, transmission channel, and transmission
time information in order to send the digital data to the
subscriber terminal which transmitted the demand, supplies it to a
synthesizer 403 to frequency-multiplex the information for
transmission of the going-down control data Vc, and sends it to a
subscriber terminal.
[0247] FIG. 21 shows the frequency assignment of frequency
multiplexed signal for transmitting in the coaxial cable CB, 50 MHz
to 450 MHz frequency band is used for analog television broadcast
signals as it is used conventionally. The frequency band around 500
MHz is used for the going-down control data having a transmission
rate of 1.5 M bits/sec as it is used in the above-mentioned
embodiment. Two frequency bands in higher frequency are used for
transmission of the going-down digital data having a transmission
rate of 45 M bits/sec. In other words, two channels are assigned to
digital data.
[0248] Subscriber terminals 50 are connected to the coaxial cable
CB through coaxial confluent distributors 60 as it is so connected
in the sectional network in the above-mentioned embodiment. The
coaxial confluent distributor 60 comprises an input buffer
amplifier 61 for receiving information from the coaxial cable CB
connected to the coaxial confluent distributor connected in front,
a distributor 62 for identifying the signal between a signal to be
distributed to the subscriber terminal connected to the coaxial
confluent distributor and a signal to be distributed to subscriber
terminals in the down stream, and an output buffer amplifier 63 for
supplying output signal to subscriber terminals in the down
stream.
[0249] A subscriber terminal 50 is connected to the public phone
network PSTN through a telephone line Lms as shown in FIG. 20. A
telephone 70 is connected to the telephone line Lms through the
subscriber terminal 50, and a television 80 is connected to the
subscriber terminal 50.
[0250] The cable television station 40 has in detail, for example,
a structure shown in a block diagram of FIG. 22. In detail, an
analog television broadcast signal Va is subjected to band
restriction to generate a signal of the band for the
above-mentioned analog television broadcast through a band pass
filter 411, and thereafter is sent to a synthesis circuit 403.
[0251] The digital transmission data transmission facility 402 is
provided with a tape information library system 412. The tape
information library system 412 comprises a tape container rack
412L, a plurality of players VTRa to VTRd, a transferring mechanism
(not shown in the figure) for taking out a desired cassette tape
from the tape container rack and for charging it to any one of the
players VTRa to VTRd as it is so structured in the above-mentioned
embodiment, but in this second embodiment, two players VTR are
provided to each channel, that is, total four players VTRa, VTRb,
VTRc, and VTRd are provided, the facility is simplified in
comparison with the tape information library system of the
above-mentioned cable television station HE having the digital
facility.
[0252] The station side controller 405 controls the selection of a
channel out of the two channels and decides the selection of a
player out of the two players by switching and controlling switch
circuits 413 and 414. Like the prescribed first embodiment,
charging is performed. In details, different charges are specified
according to the urgency of transmission, transmission time, and
data compression rate, high rates are charged for urgent
transmission and transmission in time zone of much traffic such as
prime time and for low data compression rate. An additional fee is
charged for the permission of copying.
[0253] Digital data from respective switches 413 and 414 is
modulated in hexternal QAM modulation circuits 415 and 416 as it is
so modulated in the above-mentioned embodiment, subsequently
supplied to the frequency conversion circuits 417 and 418, and
frequency-converted to a signal of the band for each channel shown
in FIG. 16. The output signal of the frequency conversion circuits
417 and 418 is supplied to the synthesis circuit 403.
[0254] A going-down control data Vc from the station side
controller 405 is supplied to a QPSK modulation circuit 419 and
modulated, then frequency-converted to a signal of the band for
control data shown in FIG. 19. The output signal from the frequency
conversion circuit 420 is supplied to the synthesis circuit
403.
[0255] A going-up demand data sent from a subscriber terminal
through the telephone lines L1 to Ln is taken in the station side
controller 405 through modulators 421 to 42n. The going-down
control data Vc is generated based on the going-up demand data. The
demand data includes a user ID for identifying the subscriber
terminal, data for identifying the requested program, and request
time information described hereinafter. The demand data sometime
includes a copying permission request.
[0256] Next, a subscriber terminal has a structure, for example,
shown in detail in a block diagram of FIG. 22.
[0257] The going-down signal from the coaxial confluent distributor
60 is supplied to band pass filters 502 and 503 through a input
terminal 501. The band pass filter 502 has a pass band of the
analog television broadcast signal frequency band shown in FIG. 18,
the analog television signal obtained from the band pass filter 502
is supplied to a frequency conversion circuit 504.
[0258] The channel selection control signal corresponding to the
channel selection operation through the user interface 530 from the
terminal controller 520 is supplied to the frequency conversion
circuit 504, and the analog broadcast program channel signal
selected by a user is converted by the frequency conversion circuit
504 to a signal of a frequency which can be demodulated by the
subsequent analog television demodulation circuit 505. The output
signal from the frequency conversion circuit 504 is supplied to the
analog television demodulation circuit 505, and the television
signal of the above-mentioned selected analog television broadcast
program channel is demodulated. The demodulated television signal
is supplied to an output terminal 507 through a switch circuit
506.
[0259] A television 70 is connected to the output terminal 507. A
user interface 530 comprises a remote controller and key board
device as it so comprises in the above-mentioned embodiment.
[0260] The going-down control data and going-down digital
information data are obtained from the band pass filter 503. The
going-down control data is converted by a frequency conversion
circuit 512 to a signal of a band which can be demodulated by the
subsequent QPSK demodulation circuit 513, then supplied to a QPSK
demodulation circuit 513 and demodulated. The demodulated control
data is supplied to a de-multiplexing circuit 514, and only the
control data of the channel given to the demand subscriber terminal
by the control signal from the terminal controller 520 is taken
out, and supplied to the terminal controller 520.
[0261] The terminal controller 520 interprets the control data,
judges whether the control data is addressed to the demand
subscriber terminal based on the user ID included in the control
data, and if the control data is addressed to the demand subscriber
terminal, the terminal controller 520 analyzes the control data and
informed of the above-mentioned program ID, transmission time, and
transmission channel (which channel out of the digital data
transmission channels).
[0262] The digital information data from the band pass filter 503
is supplied to a frequency conversion circuit 508. In the frequency
conversion circuit 508, only the information data of the
transmission channel found by analyzing the above-mentioned control
data is converted to a signal of a frequency which can be
demodulated by a hexternal QAM demodulator 504 based on the control
signal from the terminal controller 520. The output signal from the
frequency conversion circuit 508 is supplied to the hexternal QAM
demodulation circuit 509 and demodulated, the demodulated signal is
supplied to a data streamer device 510 and temporarily stored.
[0263] The data streamer device 510 has such a structure that a
tape medium cannot be removed from the device. The recording of
data in and reproduction from the data streamer device 510 are
performed under the control of the cable television station.
[0264] In the same way as for the above-mentioned first embodiment,
the terminal controller 520 sends the reproduction request to the
cable television station 40 in response to the reproduction request
input including the program ID through the user interface 530 of
the user. When the terminal controller 520 receives a reproduction
start control signal from the cable television station 40, the
controller 520 issues a reproduction instruction including the
program ID to the data streamer 510. The data streamer device 510
reads and regenerates the digital information specified by the
program ID out of temporarily stored information in response to the
reproduction instruction.
[0265] The read digital information is subjected to error
correction decode processing in a digital television signal
decoding circuit 511, converted to an analog television signal, and
supplied to the switch circuit 506.
[0266] When a copying request is included in a reproduction
request, the copying enabled conversion means of the digital
television signal decoding circuit 511 is made operable, and the
digital television signal decoding circuit 511 outputs the signal
from which copying prohibition processing is removed in the same
way as for the above-mentioned first embodiment.
[0267] The switch circuit 506 is switched to the analog television
signal demodulation circuit 505 side during analog television
broadcast receiving channel selection or to the digital television
signal decoding circuit 511 side when watching the temporarily
stored program dependently on the switching signal from the
terminal controller 520 in response to the user input through the
user interface 530, the user can view the respective programs in
the television connected to the output terminal 507. When the
user's program viewing ends, that is, program reproduction ends,
the corresponding program is deleted from the data streamer 510 in
the same manner as for the above-mentioned first embodiment.
[0268] The terminal controller 520 generates a demand signal as a
going-up data in response to a demand input for a digital
information program through the user interface 530. The demand
signal includes the user ID, ID of the demanded program, and
request time information of the urgency for the demanded program as
it so includes in the above-mentioned embodiment. If the same
plurality of compression methods as used for digital transmission
of video signal transmitted from the cable television station side
is provided and a user can select the compression method
dependently on the demanded information and necessary resolution,
then the demand signal includes the transmission format such as
data compression ratio. As described above, a request for copying
may be included in the demand signal.
[0269] The demand signal from the subscriber terminal is modulated
by a modulator 521, and sent out to the telephone line Lms
connected to the public telephone network through NCU (network
control unit) 522. A telephone 70 is connected to NCU 522 through
the telephone terminal 524, and the telephone 70 is used as it is
used usually.
[0270] In the second embodiment, the cable television station 40 is
acceptable of only transmission request for delay allowable demands
corresponding to B-class and C-class demands in the above-mentioned
first embodiment. More in detail, real-time transmission and
digital television broadcast are not involved, two-way information
transmission is realized only with adding some additional facility
to the existing cable television system facility.
[0271] In this embodiment, when a user inputs a demand to the
subscriber terminal, the user selects a request time information
which is either B-class demand allowable of little delay or C-class
demand allowable of a delay of from a half day to one day.
[0272] Upon receiving the demand from the user through the public
telephone network PSTN, the cable television station 40 makes a
transmission plan so as to transmit successively requested programs
if the demand is B-class. In detail, if there is a free channel in
the going-down digital information data band, the cable television
station 40 makes the transmission plan so as to transmit the
demanded program information to the subscriber terminal by way of
the free channel.
[0273] Upon completion of the transmission plan, the cable
television station 40 transmits previously a going-down information
including the time when the requested program is to be transmitted,
the channel to be used for the transmission, and the going-down
control data including transmission format information to the
subscriber terminal which transmitted the demand through a control
data transmission channel. In the same way as for the
above-mentioned first embodiment, the list of programs to be
transmitted for a share demand is sent according to the request
made by the subscriber terminal or at constant time intervals. As
described above, charging is performed according to B- and C-class
demands and transmission time zones, and charging for share demands
and additional fee charging for copying permission requests are
performed.
[0274] The subscriber terminal 50 acquires the control data
addressed to the demand subscriber terminal, and is informed of
previously the time to be transmitted, channel to be used for the
transmission, and transmission format, and prepares for receiving.
Monitoring the time for finding the transmission time, the
subscriber terminal 50 receives the digital information data
transmitted with a address to the demand subscriber terminal 50
through the above-mentioned band pass filter 503, frequency
conversion circuit 508, and hexternal QAM demodulation circuit 509,
and stores the received digital information data in the data
streamer device 510.
[0275] When the user input at an arbitrary time a reproduction
request for the selected specified program out of temporarily
stored programs through the user interface 530, the terminal
controller 520, as described above, sends the reproduction request
to the cable television station 40 and waits for a reproduction
start control signal to be incoming. When the reproduction start
control signal is incoming, the terminal controller 520 sends a
reproduction instruction of the specified program to the data
streamer device 510. The data streamer device 510 reads and
regenerates the specified program in response to the reproduction
instruction, and supplies the television signal to the television
through the output terminal 507, and the user can view the program.
When the user's program viewing ends, the corresponding program is
automatically deleted.
[0276] In the second embodiment, processing and charging are
performed for the permission of copying a transmitted program in
the same way as for the first embodiment.
[0277] As described herein above, in the case of the second
embodiment, the real-time transmission is not necessary, the
introduction of a large scale system such as video server is not
necessary, the video on-demand system is realized with a relatively
small investment, the digital information data can be transmitted
with a delay efficiently during the time zone such as midnight when
traffic is infrequent, thus the transmission band can be used
efficiently.
[0278] A demand signal is sent to the television station through
the public telephone network, therefore it is unnecessary to
provide extra transmission line for going-up data, thus extra
investment for this purpose is not necessary.
[0279] The application of this invention to the video on-demand
system is described hereinbefore, however, the present invention
can be applied to not only video system but also other every
two-way information transmission systems which transmit various
information in response to a demand.
[0280] In the above embodiment, deleting information from the
memory is used as the means for disabling the reusing of the
information. In addition, such a method may also be used that a
specified noise is written over the corresponding information to
disable the reusing of the information.
[0281] As described hereinbefore, according to the present
invention, the video on-demand system can be realized without
introduction of large scale system such as video server and with
relatively small investment. The centralization of traffic is
mitigated, and the network resource is used efficiently.
[0282] Rational charging can be performed in response to
transmission requests. That is, the wide use of the two-way
information transmission systems is promoted by specifying low fees
for real-time transmission even for delay transmission and for a
transmission request which shares another person's transmission
request.
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