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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a pay television system of using unidirectional
television signals as in television broadcasting using a broadcasting
satellite, and more particularly to a charging system of its receiving
charge.
2. Description of the Prior Art
In a unidirectional signal transmisstion and receiving system as in a
satellite television broadcasting, to collect a receiving charge at a
terminal receiver as in the case of receiving a charged program of CATV,
it is necessary to have the receiving charge paid by the subscribers on a
"pay later" basis, and to disable the terminal receiver of the subscriber
who does not pay.
This is practiced in a pay television of bidirettional CATV system.
In the case of CATV system, however, subscribers must apply for viewing a
specivied pay television program to the transmission center by the up line
of the bidirectional communication lines or by telephone, and such method
cannot be employed in the unidirectional system such as satellite
broadcasting. And in this method, when many subscribers apply for a same
program at the same time to the center, an overflow of the capacity of the
telephone line or overflow of the processing capacity at the receiving
side occurred.
An example of such conventioanl composition is shown in FIG. 1, in which
numeral 1 is a computer center of a CATV station for controlling the
record of payment of receiving charge by the subscribers, selection of
programs to be transmitted according to the request of the subscribers,
compilation of control codes, and others while a CATV center 2 transmits
the video signals prepared by VTR, film or at the studio according to its
computer commands, together with said control codes. Reference number 3A
is a head-end for signal transmission, and sends out plural television
signals from the CATV center 2 in a form of, for example, mid-band
television signals of VHF. Reference number 3B is a buffer circuit for
receiving up signals from each receiving terminal, and the head-end 3A and
tuner/converter 4 at the receiving terminal side of CATV and buffer
circuit 3B are connected by a same cable or different cables. Or a
telephone line may be used instead of the cable for up signal from the
tuner/converter 4 to the buffer circuit 3B.
Numeral 4 is a terminal side tuner or converter for frequency conversion of
mid-band signals into a first-channel (or second-channel) signals of VHF,
and one channel is CATV signals of the mid-band is converted into one
channel of VHF by the command from a key pad 5. Incidentally, when the
CATV signal is scrambled, it is once converted into a base band signal,
and descrambled, then converted into an RF signal again to be delivered as
signal of one channel of VHF.
Numeral 6 is a television receiver for VHF band reception. The viewer
applies for a desired program (charged) to the computer center 1 by
operating the key pad 5 or through telephone set 7. At the center 1, the
charge is set at every terminal. Or when sending out signals by
scrambling, the descrambling key code is transmitted in the sequence of
center computer 1, CATV center 2, head-end 3, and converter/tuner 4. At
the tuner/converter 4, the received signals are descrambled by using this
key code, and NTSC video signals of normal picture are reproduced, and are
converted into one channel of VHF to be supplied into the television
receiver 6. There are multiple tuners/converters 4 to telephone sets 7
which are terminal stations, and a central intervenes between the
telephone set 7 and telephone interface 8. At the telephone interface 8,
generally, an operator hears the request from each terminal, and it is
converted into the format of input to the center computer 1. This is an
example of the prior art.
OBJECT OF THE INVENTION
This invention is to present a system to realize a pay television system in
a unidirectional television signal transmission such as satellite
television broadcasting system. More particularly, it is intended to
present a pay television system capable of effectively preventing illegal
access to the program having hard-to-read key codes.
BRIEF OF THE INVENTION
This invention, relating to a unidirectional television system such as
satellite television broadcasting system, is intended to transmit and
receive the chargig information corresponding to the content of the
program being transmitted in the digital form at certain time intervals,
and account the amount by a charging amount accounting means built in the
receiver from said information and the time of receiving the television
program, write the charge data proportional to the amount in a memory,
read out the charge data in the memory when necessary, and display it on a
display means.
Also in this invention, when the charge information of each terminal is
sent from the television program transmission side at every terminal, this
charge information is transmitted to a memory, and is compared with the
charge information preliminarily stored in the memory, and only when the
both amounts agree or the charge sent from the transmission side is larger
than the charge in the memory, a new key code sent from the transmission
side is stored so that the television program may be received.
Moreover, in this invention, the memory is divided into three sections, and
the charge information proportional to the receiving time of every program
is stored in the first memory, the content of the first memory is added to
the content of the second memory at every termination of reception of a
pay program, such as when the program ends, the power is cut off, or the
channel is changed, and the content of the second memory is transferred
and store.d in the third memory when receiving the charge display
indication code sent out from the transmission side at every time
interval.
When receiving the data corresponding to the paid charge individually sent
from each receiver from the transmission side, the data is compared with
the content of the first or second memory, when the two are equal or the
content of the second or third memory is smaller than the received data,
the contents of the second and third memories are cleared, and when the
received data is smaller than the content of the second or third memory,
the balance is stored in the second and third memories, and the amount of
this balance is displayed.
Furthermore, in this invention, the memory for storing the charge
information, and the memory for storing the key code signal for
descrambling the scrambled video signal and sound signal are separately
provided. As the key code signal memory, the first memory for storing the
presently effective key code and the second memory for storing the key
code signal which becomes effective in the future are provided, and by
storing the key code signals into them, the key code signals continuously
sent from the transmission side are written once into the memory. Besides,
there is another memory for storing flags indicating the rewriting data
and the type of charge information at that time according to the charge
information of individual terminals as the content of the charge
information memory is sent from the transmission side, and by the key code
changeover signal from the second memory, the transfer of the content of
the second memory into the first memory is stored in this third memory.
Still more, in this invention, while the individual addresses assigned to
every terminal are scrambled by a first scrambling method to be stored in
the memory, the information by descrambling the terminal key code
scrambled a second scrambling method is scrambled by the first scrambling
method and stored in the memory, and the program for descrambling this
first scrambling method is stored in the memory, such as ROM, on the chip
of a microprocessor for main control.
Eventually, key codes may be transmitted in different scrambling method to
different terminals, so that illegal access to pay program may be
effective prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a pay television system in one example of the
prior art;
FIG. 2 is a block diagram of a satellite television broadcasting system for
realizing the pay television system of this invention;
FIG. 3 is a waveform diagram of video signal in the same system;
FIG. 4 is a block diagram of a receiver used in a pay television
system in one of the embodiments of this invention;
FIGS. 5 and 6 are waveform diagrams of signals used in the same receiver;
FIG. 7 is a block diagram of an amount memory used in the same receiver;
FIG. 8 is a block diagram of a receiver used in a pay television system in
a different embodiment;
FIG. 9 is a block diagram of key code processing circuit used in the same
receiver; and
FIG. 10 is a chart of signals used in the same receiver.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments of the present invention are further described below in
conjunction of the accompanying drawings.
One of the embodiments of the present invention is shown in FIG. 2, in
which numeral 11 denotes a transmission center of satellite broadcast,
being generally called a DBS center. Numeral 12 is a large-sized parabolic
antenna for sending out signals to a geostationary satellite 13 which is a
repeater for retransmitting the signal sent from the earth back to the
earth. Numeral 14 is a receiving antenna installed at a receiver terminal
on the ground. Numeral 15 is a low noise converter, and it converts, for
example, the television broadcast signal of 12 GHz ban received by the
antenna 14 into one of 1 GHz band, and transmits it to a receiver 16 as a
first IF signal.
Numeral 19 in the receiver 16 is called an IF demodulator unit (IDU), and
it converts, for example, the first IF input of 1 GHz band into a second
IF signal of 400 MHz, and amplifies and detects it, and delivers a base
band signal. Numeral 20 is a data processing circuit for picking up
digital signals from the output, processing and feeding to a descrambler
21.
Suppose, for instance, that the video signal is scrambled by synchronism
shifting and video component random inversion while the sound is scrambled
by digital sound with the bit arrangement changed at random. When the
output of the IDU 19 is directly projected on the CRT of the color
television receiver 17, the luminance is inverted on the screen, and the
horizontal and vertical deflections cannot be synchronized, so that the
picture is destroyed and unintelligible. Or when the sound is directly
delivered from the speaker, it is a mere noise. Accordingly, the
descrambler 21 changes over inversion or noninversion of the picture
depending on the output from the data processing circuit 20, and the bits
of the digital signal of sound are rearranged to descramble to normal
picture and sound. At an A/V reproducing circuit 22, only the horizontal
blanking period of the output from the IDU 19, that is, only the portion
t.sub.1 to t.sub.2 in FIG. 3 B is varied in the DC level, and is
synthesized with the portion t.sub.2 to t.sub.11 of the output of
descrambler 21 (FIG. 3 C), and the original video signal (FIG. 3 A) is
reproduced, and the digital sound signal of the output of descrambler 21
is converted to an analog sound signal.
The output of this A/V reproducing circuit 22 is converted into a signal of
a proper channel of VHF band in an RF modulator 23, and when its output is
fed to the antenna input of an ordinary color television receiver 17, the
scrambled picture and sound are received in a normal descrambled state.
Such program to be received by returning scrambled picture and sound to
normal picture and sound is often a charged program. If charged, the mount
of charge is indicated by the digital signal for control superposed in the
vertical blanking period (VBL) of the video signal of the program, and the
charge is recorded in the memory of the receiver. Generally, when a
certain program is received for 2 to 10 minutes or more, the charge for
the entire program will be billed.
As a method of payment of the charge, for example, a card reader is
attached to the data processing circuit 20 in FIG. 2, and a purchased card
(such as a season ticket) is inserted into it, and the control signal for
descrambling to the descrambler 21 is sent out from the data processing
circuit 20 only for the time corresponding to the paid amount. Or, in
other method, the charge is prepaid to a bank 18, and according to this
prepaid charge data, a code expressing the paid-in charge is sent from the
DBS center 11 to each terminal (where an address is provided individually)
through the geostationary satellite 13, and its charge code is written in
the memory at the terminal and the charge code in the memory is changed
(decreased) every time charge program is received at the terminal, and
when the remainder becomes zero, the charge is paid again to the bank 18
and the same procedure is repeated.
More specifically, the content of the data processing circuit 20 in FIG. 2
is composed as indicated by numerals 31 to 50 in FIG. 4, and when a
charged program is received, the charge corresponding to the receiving
time is calculated at the terminal side according to the charge data
superposed in the VBL period of the video signal and is written into the
nonvolatile memory, and the subscriber pays the viewing charge equal to or
more than the amount received within the month to the bank every month. At
the center, the signal indicating the paid-in amount is sent to each
terminal (at every address) from the DBS center 11 by polling, and at the
individual terminal the content of the memory 47 is decreased by the
portion of the amount indicated by that amount signal, and the receiver is
controlled so that charged programs may not be received from the next
month unless the content of the memory 47 is canceled to zero.
In FIG. 4, numeral 31 is a waveform forming circuit which shapes the
waveform of data signal, such as FIG. 5 A signal, superposed in the VBL
period in the output of the IDU 19, and composes a pulse waveform signal
as shown in FIG. 5 B. Numeral 32 is a clock detecting circuit which, using
iterative clock run signals CR of "1" and "0" signals of 2 bytes in the
head portion of FIG. 5 B, reproduces clock pulses synchronized with them,
detects a framing code at the 8th bit of framing code signal FC within the
reception signal to establish frame synchronizing, and synchronizes the
sampling clock-generated in a sampling clock generating circuit 33 to the
reception signal. Numeral 33 is a circuit to form a sampling clock of thus
controlled appropriate phase. Its output is divided by a main clock
forming circuit 34 to compose a main clock to drive the work RAM 37, work
ROM 38, center processing unit (CPU) 39, etc.
The clock synchronized with each bit of the reception signal from the
output of the sampling clock generating circuit 33 is fed to the sampling
circuit 35, and each bit of the reception signal is sampled. The pulse
width of each bit of reception signal is about 175 ns at 5/8 fsc, and in
this cycle time it is difficult to operate the work RAM 37 to CPU 39 in
FIG. 4. When an 8-bit microprocessor is used as the CPU 39, it is
convenient to handle the reception data by 8-bit parallel signals.
Therefore, as the sampling circuit 35, a shift register of series
input-parallel output type such as SN74LS164 is suited. When its output is
stored in a latch circuit 36 at every 8 bits on the basis of the 8th bit
of the framing code, the output is an 8-bit parallel signal, and varies in
the cycle time of 8.times.5/5f.sub.sc 1.4 .mu.s. This cycle time is suited
to operation of each circuit. This output is connected to a bus line 40.
Numeral 37 is a work RAM of CPU 39, and 38 is a work ROM of CPU 39. The CPU
39 is an 8-bit microprocessor (for example, MB6809E).
Referring now to control codes C.sub.0, C.sub.1 to C.sub.7 in the reception
signal B in FIG. 5, C.sub.0 and C.sub.1 are iterative clock run signals CR
of 1 and 0, and C.sub.2 is a framing code signa; of 11100101. C.sub.3 is
composed of information of 4 bits, humming check code of 3 bits, and
parity bit of 1 bit, C.sub.4 and subsequently data are all in the same
composition in every byte. The contents of information of C.sub.3 and
C.sub.4 are compiled Table 1, in which only three kinds necessary for
explanation are shown. Actually, more than several kinds can be
considered. Similarly, the contents of information of 4 bits of C.sub.5
are give in Table 2.
TABLE 1
______________________________________
LM
SS
BB
______________________________________
00000000 Dummy packet
10000000 Teletext
01000000 DBS signal
11000000
. Spare
.
11111111
.BHorizBrace. .BHorizBrace.
C.sub.3 C.sub.4
______________________________________
TABLE 2
______________________________________
LM
SS
BB
______________________________________
0000 Dummy
1000 Program data
0100 Scrambled data
1100 Address data
0010
. Spare
.
1111
.BHorizBrace.
C.sub.5
______________________________________
In the case of satellite televison broadcasting, is used in 8 bits of
C.sub.3, C.sub.4, and any one of 1000, 0100, 1100 is used in C.sub.5.
When the data of 28 bytes in the recpetion signal as in FIG. 5 A is program
data, an example is shown in FIG. 5 C. In its beginning portion, the
number indicating the kind of program is expressed in a four-digit BCD
code in 4 bytes as the tag-code. Therefore, 9999 kinds can be specifed.
The next keyword code which is changed every month, and it is indispensable
for descrambling the signals received at the terminal side, and the
reception at the unpaid terminal is stopped by stopping the transmission
of this key code from the DBS center. For example, the payment data is set
on the 20th day every month, and the key code is changed from the first
day of each month. Since the receiver 16 in FIG. 2 is always energized and
it is operating unless the power cord is unplugged.
The next charge code contains a four-digit BCD information in 4 bytes. The
charge code varies with the passing of the time, and the charge
proportional to the program viewing time (the time being displayed on the
CRT) is recorded. Its content is described in details below.
The next PN key is a four-byte (or 16-bit as information) expression of the
initial value of the PN code for descrambling the scrambled signals.
Prevetion of illegal access by PN key is a first measure of security. The
next date code, comprising 2 digits of BCD for the month and 2 digits of
BCD for the day, uses 4 digits of BCD, that is, information bit.times.4 in
the four bytes. The time also comprises of 2 digits of BCD for the hour
and 2 digits of BCD for the minute. The content is composed as shown above
when the data is program data packet (C.sub.5 is 1).
Meanwhile, when C.sub.5 is 2 (00100) and the scrambled data packet is sent
out, all of 28 bytes (of which 14 bytes are information data) are data as
shown in C', and 14 bytes of the information portion of them are written
into specified positions of the work RAM. This data differs in the content
in very program. Various contents and kinds of scrambled data may be
considered, but they are ommitted in this description.
Or when C.sub.5 is 3 (0011), the address data packet is sent in 28 bytes as
shown in C". This address data packet includes, as shown in FIG. 5 C", the
address indicating two terminals within one packet. This C' is magnified
in FIG. 6, and its first half 14 bytes are magnified in FIG. 6 D. The
information bits of the first half 7 bytes of D are 28 bits of the portion
of 7 bytes, and 2.sup.28, or about 268 million, terminal address can be
distinguished.
The latter hald 8 bytes may be divided as shown in FIG. 6 E, in which E
refers only the information bits, that is, 32 bits of the portion of 8
bytes. The first two bytes of E (the first one byte in the case of
information only) are for sending the directions from the DBS center to
the terminals in the maximum of 255 kinds, and, for example, when "1" is
specified as in FIG. 6, the total amount of the pay television viewed at
the specific terminal up to that point is indicated. When the amount is
given at increments of 25 cents each, up to 210 dollars can be specified
in the right-hand 12 bits in FIG. 6 (the information of 1.5 bytes in the
data area of 3 bytes). Therefore, when clearing the charge, the code of
amount (1024 dollars 75 cents at maximum) is sent from very terminal,
while the amount paid by the subscriber to the bank is sent from the DBS
center 11 to each terminal, so that the content in the amount memory 47 at
the terminal is updated. If the amount of viewing the programs is written
in the amount memory 47 in the unit of 25 cents, the amount sent from the
DBS center 11 is subtracted from its content, and when the content in the
amount memory 47 becomes zero, it is detected by the CPU 39, and the key
code in FIG. 6 is read in. If the content in the amount memory 47 does not
become zero, that is, if the paid-in amount is short, the key code is not
taken in, so that the scrambled information (picture, sound) cannot be
descrambled and viewed from the next month. The amount is written (that
is, subtracted from) into the memory 47 once every month, and the charge
data is sent from the DBS center 11 consecutively for about a week each at
the end and beginning of a month. Therefore, if the power source of the
receiver is cut off by mistake, when the power is connected even in a day
within this two-week period, the paid charge can.be written into the
amount memory 47 to cancel the content to zero, so that the key code may
be read in. The key code, and entry of date, time, etc. into the amount
memory 47 are written into a nonvolatile memory 53 as in the case of
writting into the amount memory 47 in FIG. 4. In the memory 53, the data
writing data (time) into the amount memory 47 is written, and if the
amount is paid twice or more by mistake, it is controlled so that the data
may be written correctly into the amount memory 47 as the first time,
second time, and so forth.
Referring then to key codes, a key code is composed of 12 bits, and
represents a formula to determine the -1 PN series signals. For example,
the key code is sent forth as 011000010001, the formula becomes x.sup.11
+x.sup.7 +x.sup.2 +x=f(x). Or this polynominal may contain 11 bits or
less, instead of 12 bits. Or the key code may contain 16 bits, and the
message in FIG. 6 E may be decreased from 1 byte to 4 bits.
The actual operation is described below. When a terminal is purchased, all
contents in the buffer circuit 46 in FIG. 4 are zero, and when the power
is supplied to this terminal (suppose X), first the key code is taken in.
If this terminal is purchased in the middle of a month, since periodic
polling to all terminals is not effected by the DBS center 11, polling of
the number of terminals installed on or around that day (for example,
10,000) is effected temporarily. As clear from FIG. 6, since two terminals
can be polled by 1H (horizontal period), when 5H in the VBL period is
assigned for polling, it results in 10 terminals/field=600/sec=36,000/min,
which means polling of newly subscribed terminals can be effected within a
minute. Therefore, a newly purchased terminal can take in the key code of
the contemporary month within about 1 minute. When a terminal is installed
at the end of a month, though the key code for the next month is
periodically sent to all subscribers periodically, if, for example, half
of 1H of 5H the VBL period is used for polling of key code of the month
for new subscribers, it becomes (36000/10).times.3=10.800 as evident from
the explanation above, and polling of about 10,000 new subscribers can be
finished in about 3 minutes. Supposing the total number of subscribers at
this point to be 10 million, all subscribers can be polled in about 61
minutes.
By the way, this terminal X is given its own address in 28 bits. These 28
bits are, in order to prevent illegal access to charged programs,
scattered about, for example, in the memory comprising 256 bits, or
written in part of the work ROM 38 or in an independent chip so that a
correct address may be obtained by operating the address code of 28 bits
according to the keyword in FIG. 5 C. If, for example, operated by the
keyword, it is necessary to receiver the packet of FIG. 5 C. Considering
the data transmission efficiency, if superposing a same packet in all of
5H at a rate of once a second and sending out, the keyword is received
within a second at the receiving side, and is written into the work RAM
37. This keyword has an information capacity of 16 bits. By operating the
data after the keyword and other data according to the keyword and
descrambling the scrambled data, a second means of security (prevention of
illegal access) may be achieved.
After receiving the keyword, the packet in the form of FIG. 5 C" is
received, and 28 bits of the address of terminal X are searched. When the
address data 28 bits being transmitted and the address 28 bits in the said
work ROM 38 coincide, the eight bytes of FIG. 6 E are taken into the wor
RAM 37. Since the content of the amount memory 47 at terminal X is zero,
MSB of the message in FIG. 6 E and the bit of one position lower are seen
according to the instruction from the CPU 39. Such program is assembled in
the work ROM 38. The following explanation is given on the same principle,
that is, the CPU 39 conforms to the program of work ROM 38.
Since the MSB is "1" in the middle of a month (the code should be-assigned
so that other bits can be ignored), the 12 bits of the key code are taken
into the work RAM 37, and sent to the nonvolatile memory 53 through the
bus line and stored. Thereafter, by using this key code, the data of FIG.
5 C, C', C" are descrambled.
If a received program is a charged one, the charge per unit time is
indicated in the charge code. It is ideal for the charged program that the
charge proportional to the received duration may be directly billed. As
one of the methods, for example, suppose one 60-minute program costs 6
dollars, and 25 cents is charged for every 2.5 minutes. In this case, as
the charge code, the content of the code is varied every 2.5 minutes, one
bit (corresponding to 25 cents) is fed to the counters 43 to 45 every time
the code is changed, and the pulses corresponding to the received time are
counted. When the program end data (such as all "1" in charge code or
spare code) is detected, or the receiving channel is changed, or the power
source is cut off, the output of the counters 43 to 45 (indicating the
multiples of 25 cents) is written into the amount memory 47 composed of
nonvolatile memory through the buffer. The amount memory 47 is a
nonvolatile memory including an adder, and has, for example, 12 bits. When
the power source is cut off, the counter 43 to amount memory 47 are
supported temporarily by the battery, and the data in counters 43 to 45 is
written into the amount memory 47 through the buffer 46.
In other method, the viewing charge amount from start of a program till a
specific time is sent in codes from the DBS center 11 every 2.5 minutes,
and the balance of the first received charge code and the final one is
written into the amount memory 47 at the terminal X. In this method, every
time the charge code varies, the unit charge is calculated to detect how
many multiples of 25 cents, and pulses corresponding to the number are
supplied to the counter 43 to 45 through the up detection circuit 41 to
count them up.
In either method, at every passing of the time corresponding to 25 cents,
the counters 43 to 45 are counted up every bit through the up detection
circuit 41.
Incidentally, the amount memory 47 may be also composed as in FIG. 7. That
is, possessing two sets of memories 47A, 47B, the content of the buffer 46
is always written into the memory 47, and when one program is finished
(that is, when t | | |
