CA1218144A - Two-way cable-television system - Google Patents
Two-way cable-television systemInfo
- Publication number
- CA1218144A CA1218144A CA000469853A CA469853A CA1218144A CA 1218144 A CA1218144 A CA 1218144A CA 000469853 A CA000469853 A CA 000469853A CA 469853 A CA469853 A CA 469853A CA 1218144 A CA1218144 A CA 1218144A
- Authority
- CA
- Canada
- Prior art keywords
- signals
- subsystem
- head
- cable
- command
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/173—Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
- H04N7/17345—Control of the passage of the selected programme
- H04N7/17354—Control of the passage of the selected programme in an intermediate station common to a plurality of user terminals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/173—Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
- H04N2007/17381—Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal the upstream transmission being initiated by the user terminal
Abstract
ABSTRACT OF THE DISCLOSURE
A tree-type two-way data communications system for use in a cable television system having a single head-end subsystem, data sources and a cable television distribution network. Each data source is a source of digital commands to the head-end subsystem. The two-way system has a number of interface subsystems intermediate of the head-end subsystem and each one of the data sources.
The interface subsystems are coupled in a tree structure to the head-end subsystem and each one of the data sources is coupled to one of the interface subsystems. Each one of the interface subsystems is coupled to at least one other of the interface subsystems. The interface sub-systems receive without acknowledgment through the cable distribution network from at least one of the data sources the digital command signals. Each interface subsystem verifies data format and regenerates and forwards at least some of the digital commands as command packet signals in a packet signal format on an unlinked carrier towards the head-end subsystem. The head-end subsystems receive the digital command signals as command packet signals and develop response signals. The cable-distribution sub-system couples response signals in a tree-structure without loops from the head-end subsystems to each one of the data sources through a common signal path. That path is independent of the unlink for acknowledging receipt of the command packet signals.
A tree-type two-way data communications system for use in a cable television system having a single head-end subsystem, data sources and a cable television distribution network. Each data source is a source of digital commands to the head-end subsystem. The two-way system has a number of interface subsystems intermediate of the head-end subsystem and each one of the data sources.
The interface subsystems are coupled in a tree structure to the head-end subsystem and each one of the data sources is coupled to one of the interface subsystems. Each one of the interface subsystems is coupled to at least one other of the interface subsystems. The interface sub-systems receive without acknowledgment through the cable distribution network from at least one of the data sources the digital command signals. Each interface subsystem verifies data format and regenerates and forwards at least some of the digital commands as command packet signals in a packet signal format on an unlinked carrier towards the head-end subsystem. The head-end subsystems receive the digital command signals as command packet signals and develop response signals. The cable-distribution sub-system couples response signals in a tree-structure without loops from the head-end subsystems to each one of the data sources through a common signal path. That path is independent of the unlink for acknowledging receipt of the command packet signals.
Description
BACKGROUND OF THE INVENTION
Jo The present invention relates to cable television generally and more particularly to a two-way intricate) cable-television system having distributed processing and means for regulating the upstream signal flow ¦ Cable television, also referred to as community i antenna television (CAT), has come a long way from its ,10 humble beginning as a means of providing rural television ¦ reception. Presently, cable television is an important means ¦
of providing reception of local, non-local and premium tote- ¦
vision programs and promises to become an important means of ¦
providing many new, Tao (interactive) services in the future. Heretofore, cable television also promised a number of problems.
One such problem, even for one-way cable-televisionl systems, is that of signal security. Many prior-art one-way !
cable-television systems transmit signals conveying premium television programs only to those who have made arrangements ¦
in advance (paid for such programs. To restrict the recipe lion of such programs the signals conveying the programs are , scrambled and those who have made arrangements to receive the programs are provided suitable descramblers. Unfortunately, j such descramblcrs are relatively expensive. Further, it is l difficult to securely scramble television signals, the rerun- !
I dent information in the signals maying the signals relatively¦
easy to dcscramble. oven for those who lack the requisite ; skills to build descramblers, such devices can often by pun-chased. or many Tao services, such as electronic mail, I
Lo the signal security problem is even more acute Another problem for two-way cable-teleYision soys- !
terms is that of noise. Noise, which typically enter at the 'drop cable level, must be prevented from propagating up the System (upstream) to disable the entire system.
A very serious problem is that of system loading.
It is difficult to provide highly interactive services to a relatively large number of subscribers without so loading down prior-art~type two-way cable-television systems that the ¦
response time Doyle during peak hours becomes intolerable.
An interactive Tao) cable-television system is disclosed in the United States patent 3, 9g7, 718 which issued to Rickets et at Disclosed is an interactive l cable-television system employing a head-end subsystem a ! 15 plurality of subscriber units and a coaxial cable subsystem I Which interconnects the head-end subsystem with the various I subscriber unit. The system is operative to distribute telex vision signals to the various subscriber units and to pro- ¦
, vise two-way digital data communications between the head-end !
subsystem and the various subscriber units. An encoder is employed in the head-end subsystem; and, a decoder is ' employed in each of the subscriber units, the combination for !
j scrambling/descrambling premium television signals to no-strict the use thereof. Alto employed is a mini-computer 25 in the head-end subsystem and the combination of an alpha-numeric keyboard with alpha-numeric electronics in each of the subscriber units to operate with a subscriber's tote-1 vision as a data terminal for Tao digital data commune- ¦
i cations with the mini-computer. Two-way digital data comma-I 30 nication is carried on synchronously with each s~bscr.ibex unit being allocated a time slot in which to respond.
Another system employing many of the same elements is disk I¦ closed in the United States patent 4,245,245 issued to Matsumoto et at.
I!
Al 5 A two-way cable-television system is disclosed in United States patent 3,750,022 which issued to Curry et at.
Employed therein is a tree-type distribution subsystem having modally disposed filters. Each of the filters responds to respective head-end subsystem generated commands to isolate noise developed on a respective coaxial cable (drop cable leading to a corresponding subscriber units).
Another two-way cable-television system employing a tree-type distribution network is disclosed in the United States patent 3,840,912 which issued to T. Takeuchi. The , 15 system employs a number of modally disposed modulation units Jo each for modulation by an alarm signal generated by one of ¦¦ a number of associated subscriber alarm transmitters. Not !¦ only does each of the modulation units operates upon a I distinct carrier frequency; but each of the alarm trays-,20 millers associated therewith also operates upon a aistinctaudio frequency. This permits a head-end subsy~kem to identify the origin Jo on alarm signal. rho modally dip-If posed modulation units operate upon the alarm signals so as Jo to permit a such larger number of subscriber transmitters to share the distribution network than would otherwise be pox-Sibley Finally, twig c~ble-television system is disk i close by I. Bernhard in the United Slates patent 3,g34,079 in which it Is indicated that two-way digital communication is by means of synchronously generated data packets.
_ !
A data communication (time share) network is disk ¦ closed in the United States patent ~,156,79~ issued to l M. Dallas. The network employs number of host processing I
-systems each coupled by a communications network to a number of terminal devices. Each of the processing systems is interconnected with the other processing systems to share data. The communications network includes a plurality of ~wo-part buffer storage memories, fan-out node device, line-master exchange unit devices, line exchange unit devices, l 10 and terminal exchange unit devices, all convected in a complex I tree-ring configuration. Communication between the host pro- ?
Suzanne system and a terminal device is by means of data I blocks 9 erroneous blocks being discarded by the respective I terminal exchange unit.
! 15 Television type infrared remote control units , are disclosed in the United States patents 4,231,~31 and l 4,156,810, which issued to Brother eta and S. I~arashi, ! respectively. Both units employ infrared radiation.
, Brother et at disclose the use of infrared pulse spacing to ¦
represent each bit of digital data. In the So I~arashi 1, disclosure, the infrared pulse spacing represents a i! digital quantity (word), in this case the desired channel ! number .
,25 It is therefore a material object of the present Al invention to provide a novel two-way cable-television system I which is sufficiently versatile so as to provide a relatively wide range ox services to a relatively large number of sub-scribers without significant overload delays ~30 another object of the present invention is to pro-vise a two-way cable-television system having relatively if high signal security ¦¦ Still another object of the present invention is I to provide a two-way cable-television system which is rota- i ¦ 5 lively immune to noise.
, I Briefly, the preferred embodiment of the present / ¦ invention employs a head-end computer and a head-end sub-system including a source of television program signals for distribution by the system, a cable-distribution subsystem ! lo including a plurality of corrective regenerators, a plurality of control processors and a plurality of subscriber i subsystems each including a selection of standard and optic eel units chosen to provide a mixture of services as is I¦ appropriate to provide the desired services. Each of the ¦~15 corrective regenerators buffers and retransmits signals no-presenting commands sentries) encoded in a packet format ! which are propagating upstream) from a subscriber subbases-them to the head-end subsystem. Signals representing impure- !
it pertly formatted packets art ignored by each of the cornea- !
jl20 live regenerators which also discards certain packet signals !
when overloaded. Each of the control processors, which interfaces a number of subscriber subsystems to thy cable- ¦
distribution subsystem, includes a number of receivers each ¦ for conditioning a television program signal on a selected channel before coupling the signal to a respective sub-scriber-subsystem unit, A material advantage of the present invention is l I
i its versatility. I L
Another advantage of the present invention is thy ¦
¦ 30 ability it affords to provide a relatively wide range of services to a relatively large number of subscriber ¦
without significant overload problems.
These and thwacks objects and advantages of the pro-sent invention will no doubt become apparent to those skilled¦
¦ 5 in the art after having read the following detailed descrip- i ¦ lion of the preferred embodiment which it illustrated in the ¦
I figure of the drawing.
Al In the drawing Figure 1 is a combined block diagram and perspective view showing a two-way cable-. television system in accordance with the present ¦ invention-If The preferred embodiment of a two-way (interactive) ! cable-televisivn system in accordance with the present invent-!
. 15 lion is shown in Figure 1 generally designated by the number j ! lo. Employed therein are a head-end subsystem 12, a cable-distribution subsystem 14, a plurality of control pro-censors, collectively designated by the number 16 including a typical processor 18, and a plurality of subscriber sub systems, collectively designated by thy number 2Q including ¦' an illustrative subsystem 22. For clarity, the above ¦' mentioned subsystems are described in order from the bottom Jo up.
I The components of subscriber subsystem 22 which are generally standard with all subscriber subsystems include a power-inserting unit 26, a set-top unit 29 for use with the respective sub~cri~er'~l conventional television set 30 and a wireless remote control unit 32. The remaining come pennants of subscriber subsystem 22 each ox which is optional with other subscriber subsystem include another set-top unit with an associated remote-control unit, collectively l designated by the number 34, a keyboard unit 36 and a term-! net unit 38. The above-mentioned units, as opposed to the associated control processor, are disposed at subscriber convenient locations within the respective subscriber's home (inside units Power-inserting unit 26 is connected to control processor 18 by means of a drop cable represented by a cable 50. Additionally, unit 26 is either directly connected to set-top unit 28 by means of a cable (not shown or, in order to accommodate additional units, couple thereto by means of one or more conventional signal splitters, represented by a splitter 52 which is connected to unit I by a cable 54 and to unit 28 by a cable 56. An infrared beam (link) 58 couples remote-control unit 32 to set-top unit 2B which has provision for connection to television set 30 by means of a cable, represented by a cable 60. As illustrated, set-top unit 34 is connected to signal splitter 52 by a cable 64;
,¦ and, keyboard unit 36 is coupled to the splitter by a cable 66. Finally, terminal unit 38 is shown coupled to signal splitter 52 by a cable 68, another signal splitter 70 and another cable 72.
From the bottom end up, remote control unit 32 j has a keypad 76 for command entry, a microprocessor snot .,25 shown) for scanning the various keys of the keypad to detect each key closure, and an infrared transmitter (also not l shown) driven by the microprocessor so as to selectively ¦ develop beam 58 as necessary to transmit to set-top unit 32 ¦ the identity of each key upon the closure thereof. us used herein, the term "command is intended to include all entries including requests for a particular service, data, etc. Keypad 76 includes keys for panic use.
Each of the set-top units, including unit 28, pro-vises a means for limited command entry and a means for 1 5 controlling an associated television set, such as set 30.
¦ Set-top unit 28 has a microprocessor with associated memory (not shown), a keypad 78, which is similar to keypad 76, an infrared detector (also not shown), provision for con-section to a home bus, represented by a line By provision for connection to a number of burglar alarm and smoke-detector switches by a number of lines represented by a line 1! 82, power-controllinq and monitoring circuitry (not shown I and a pair of 7-segment display devices 84 and 86. The ¦ microprocessor scans the various keys of keypad I and monitors the infrared detector to detect key closures . from which the microprocessor assembles commands. Those commands which the microprocessor cannot execute directly are transmitted to control. processor 18. Further, the microprocessor interfaces home bus 80 to the system and monitors the lines represented by line 82 to ascertain the status of each of the switches, notifying control processor 18 of changes therein. The microprocessor controls the AC
or on of coupled to television set 30 and monitors the power being consumed thereby, notifying control processor 18 of changes therein (set on~Qff~. From information trays-milted to set-top unit 28 ho control processor 18, the unit microprocessor refreshes display devices 84 and I so as to display a number representing an associated television channel when the television set is in use or the time of day. ¦
i30 Sct-top unit I executes command transmitted there-I
to by control processor lo. The commands are transmitted to i unit 28 encoded in a packet signal format. The individual binary bits of each packet are conveyed as amplitude module-lion levels of individual cycles ox a 8.056 Megahertz .
carrier signal which control processor 18 develops on cable 50~.
Packet signals are also employed as a means for transmitting commands from set-top unit 28 to command pro-j censor 18. Individual bits of each packet are conveyed as lo amplitude modulation levels of respective cycles of a carrier signal which unit 28 develops on cable 56 by divide in in half the frequency of the 8.056 egrets carrier signal developed by control processor 18. Prior to transmitting a . packet signal, unit 28 develops on cable 56 a request-to-l15 send signal in the form of a constant-level signal at the half-8.056 Megahertz frequency. Upon receipt of a clear-to-send packet signal transmitted by control processor 18, l set-top unit 28 transmits the packet signal and awaits an ! acknowledgement packet signal. Normally, a generally ¦20 addressing clear-to-send packet signal is transmitted by it control processor lo. when more than one unit of subscriber I! subsystem 22 attempts to transmit simultaneously, control it ¦ processor 18 simply transmits a mute packet signal and then individually polls the units.
Additionally, situp unit 28 has volume control-lying circuitry (not shown) which receives a conventional television signal on a preset one of two special channels employed or transmitting television signals from the come mend processor to the associated unit. the circuitry de-¦30 modulates the signal to develop a husband video signal .!
Al and a base-band audio signal. Next, as directed by the micro processor, the circuitry attenuates the base-band audio signal to a subscriber selected level. Finally, top circuit- !
rye employs the base-band video signal and the attenuated if 5 audio signal to modulate suitable carrier signals so as to develop a conventional television signal on a preset one of the three channels two, three or four for driving television set 30.
Power-inserting unit 26 has a transformer (not shown for connection to a conventional AC power line, the transformer for developing a 24 volt AC potential for powering control processor 18. In addition to coupling the i AC potential to cable 50, power-insertiny unit 76 couples between cables 50 and 52 the signals developed thereon including the packet signets and the special channel tote- !
l vision signals.
I Keyboard unit 36, which is similar to set-top unit ¦
28, has a remote-control unit with a full keyboard 90, as opposed to the limited.keypa~ of unit 32. The full keyboard is better suited for use in text processing and electronic i¦ mail handling. I
I Terminal unit 38 has a suitable connector 92 and a ¦ microprocessor with associated memory (not shown) for inter- ¦
it facing 110 through 19200, RS-232-type units to the system j,25 including a modem and a computer terminal, the latter hying represented by a computer terminal 94. In interfacing Tom- !
! puterterminalg4tothe5ystem;terminalunit38convert5 I various escape-sequence coxes as might be ¦ employed by the particular type of terminal to the respective;
codes employed by the system.
I
I
Among other units which may be included with j subscriber subsystem are an alarm unit for interfacing additional burglar-alarm and smoke-detector switches to the system, a frame grabber unit for receiving and displaying on a subscriber's television set individual frames of a video picture, a video pickup unit having a frame grabber, the combination for transmitting individual video frames and a if game unit for downloading games to a subscriber convene-i chenille video game.
Each of the control processors, including processor , 18 is employed to interface up to eleven subscriber subsystems I to cable distribution subsystem 14. Included in each pro-Jo censor are eleven frequency-agile digitally-tuned receivers (not shown each for driving a respective set-top unit. I
'15 Two receivers of control processor 18 are dedicated to sub-scriber subsystem 22, one for driving situp unit I and ! the other for driving unit 34. Each receiver receives a signal on a selected one of a number of channels employed to ¦
transmit conventional television program signals on cable !29 distribution subsystem 14 and converts the frequency of the signal to the special channel frequency appropriate for drive i in the respective set-top unit. Among the signals which may ¦
i! be selected are 50 plus channels of signals in thy 55-400 megahertz conventional cable television band transmitted on ! us each of two cable subsystems including an ray cable subsystem to which control processor 18 is coupled by a signal splitter !
I (tap) lQ2 and a distribution cable 104 and a By cable sub- ¦
! system, to which processor I is coupled by another signal j splitter tap) 103 and another distribution cable 108. the ~30 "A" and "I" cable subsystems are discussed below in kinks 1218~L~4 1'1 with ~able-distribu~ion subsystem 143 In addition to the abovc-mention~d wrecker, etch control processor, including processor 18, includes Another receiver (not shown or receiving commands huh are transmitted by head-end subsystem 12 over cable distribution subsystem 14 on a one of four channels which are dedicated to this purpose.
Each of the control processors, including processor lo, transmits and receives commands encoded in packet format 10 Individual bits of each of the packet which are transmitted over ~able-dis~ribution subsystem î 4 are muddied frequency modulation ~MFM1 encoded and conveyed as amplitude modulation .
levels of a tarrier signal suitable for the respective channel employed therefore. The packets which are received by the 15 various processors on a channel in the 55-400 egret band dedicated to this purpose, are transmitted a 2~014 Megabit I rate: and, the packets, which are transmitted my the various processors on a channel of five channels which are slow 35 Megahertz, are transmitted at 1.007 Megabit rate. The pack t f 20 are transmitted over the cable-distri~ution subsystem by a control processor beginning coincident with the beginning of z n interval assigned to the respective processor, the interval being defined by on assigned three-line lnterv~l during each field of a conventional television signal. I previously 25 indicated the individual bits of packets which are transmitter d between a control processor and one of the associated subscri~
subsystems, such as between processor I and subsystem I are conveyed as amplitllde modulation levels of a tarrier ~ignalD
The carrier signal employed by Mach professor for transmittance 30 packets his a 8.056 Megahertz frequency and, the carrier sign at employed by each subsceiber-s~system units for transmitting ¦
packets to the respective command processor has a frequency h 1 f the 8.055 Megahertz Eeequerlcy.
Also included in each of the control processors, including processor 18, are a phase-locked GUPPY, timing and display circuitry and microprocessor with associated memory (all not shown). From the MUM encoded signal, the 5 phase-locked loop develops the 8.056 Megahertz carrier signal, four signals including a 32.2 Megahertz signal, a 16.1 Megahertz signal, a 10.7 Megahertz s;qnal and a 8.05 Megahertz signal, one of which is employed as the carrier signal to transmit jackets to head-end subsystem 12l and a 10 32.2 Megahertz signal. Driven by the 32.2 Megahertz signal, the timing and display circuitry develops three conventional television signals each of which maps the contents of memory locations into corresponding elements of a television picture. The memory mapped signals are selectively coupled to various ones of the associated subscriber subsystems so as to display, on television set 30 for example, subscriber prompts and messages, electronic mail, requested view data and teletexed frames, billing information, bulletin board, shopping and banking text and the like Further each control processor microprocessor, encodes/decodes sensitive packets in accordance with the National Bureau of Standards DES algorithm.
Each of the control processors, including processor 18, maintains a subscriber authorization profile for each 25 associated subscriber subsystem. Prior to providing a requested service, the respective control processor tests the request command ) against the respective subscribe author-ration profile to ensure that the service it authorized for the particular subsystem. Thus, the subscriber authorization 30 profiles provide a means of limiting Sirius to certain classes of subscriber subsystems. For example, access to certain premium channels may require advance arrangements.
i21814~
¦ Also, certain programs may be limited to certain profess I signals such as doctors. Additionally, a modesty code to be j entered at a subscriber-subsystem unit before access to a particular channel may be included to permit parents to restrict the programs their children watch. -Upon initialization, and as is appropriate there-after, each control processor, including processor 18, receives from headwind subsystem 12 by means of packet signals transmitted over cable-distribution subsystem 14 a series of instructions (software) for execution by the i processor microprocessor, an assignment of the three-line interval coincident with ye inning of which the professor may begin i , transmission ox a packet signal to ye head-end system the respective i subscriber authorization profiles. Responsive to status ¦
15 requests transmitted my head-end subsystem 12 once each Jo minute, each control processor, including processor 18, ¦' polls its respective subscriber subsystem units, including ¦ unit 28, to obtain a status report which the processor trays-¦
if mitt to the head-end subsystem. Each status report includes . 20 the operational status of the control processor and also-elated subscriber-subsystem units and thy services being , provided there through.
I Cable-distribution subsystem 12 includes a pair of I main trunk cables 120 and 122, number of branch cable, a ! 25 large number of distribution cables, including cables 104 and 1 108, a number of amplifiers reprint by a pair of amply-liens 126 and 12~ and a number of nested Crockett regenerate ions represented by three regenerators 132, 134 and 1}6. us ¦
strutted, corrective regenerator 132 is connected between Jo a pair ox branch cables 138 and 140 and the two distribution ¦ cables 104 and 108. The above-mentioned cables, amplifier and corrective regenerators are connected in a pair of tree- ¦
type structures referred Jo as the "A" cable subsystem and two By cable subsystem. Each of the above-mentioned subsystems 5 conducts signals in a S5-400 Megahertz band from head-end subsystem 12 (downstream) to each ox the control processors, including processor 18, and forwards certain signals in the below 35 Megahertz band, signals which represent most ! properly formatted packets, from each of the command ¦10 processors (upstream) to the head-end subsystem as will be- ¦
If come apparent shortly.
! The amplifiers, including amplifiers 126 and 128, are employed so as to compensate for cable losses. Typical- ¦
lye one amplifier is employed for each half mile of cable.
1115 Each of the amplifiers amplifies signals in the SS-400 Al megahertz band which are propagating from head-end subsystem If 12 (downstream) to the various control processors including If processor lo, and amplifies signals in the below 35 I Megahertz band which are propagating from the various control ¦120 processors (upstream to the head-end subsystem.
The principal difference between cable-distribution subsystem 14 and those of prior art design is that subsystem 1 14 includes corrective regenerators Each corrective ¦ regenerator, including regenerator 132, has filters and a US microprocessor with associated memory (all not shown). The ¦¦ filters pass signals in the 55-400 Megahertz band and trap interest signals in the below 35 I Mcgahert2 band. The microprocessor and memory, buffer and retransmit ;ntcrcepte~ signals which rc~rcsent curtain properly formatted pockets propagating from each of the individual control processors, including processor 18, (upstream to head-end subsystem 12. The principal kirk-texistics of the corrective regenerators is that each i regenerator ignores signals which do not represent properly formatted packets and, when overloaded, discards (ignores) certain signals which represent properly formatted packets . so as to favor older commands, as will become apparent l shortly.
! Properly formatted packets propagating from a lo control processor (upstream) to the headwind subsystem have a header t Betty byte, a repeat flag bit, three carbon copy bits, a packet length bit and 35 address bits. Short packets ¦
I'; t having a 16 octet format) also have a packet type byte, 7 ¦, data bytes and 2 CRC bytes. Long packets having a 64 octet format) also have 2 place mark bits, 6 packet type bits, 55 data bytes and 2 C~C bytes.
Proper protocol requires that when a packet signal has successfully propagated upstream) from a control pro-. censor, such as processor 18, through the various layers of ¦120 corrective regenerators, in this case through regenerators 132 j¦ and 134, to head-end subsystem 12, that subsystem 12 'j acknowledge receipt ox the packet signal. Upon failure if to receive such an acknowledgement, because the packet signal has been destroyed due to collision with another packet signal or the packet signal has been discarded by a corrective regenerator the respective control processor waits a ran period of to within a deterministic to interval and retransmit the packet signal. The repeat slag bit and carbon copy number bits provide etch o~rre~ive r~ne~ator a meats of ascertaining go of thy respective command and, thus, a means of L81~
I¦ prioritizing packet signals for discarding purposes.
I The number of subscriber subsistence which may be 'i accommodated in one system and, to accommodate the subbases-¦, terms, the required number of control processors and cornea-¦ 5 live regenerators and nesting thereof, is a function of the peak loading generated by the service demand, the peak delay ¦
which will be tolerated in providing the services and the data rate.
It should be noted that by limiting the number of lo control processors which are connected to each corrective I regenerator to 87 processors, each processor may be assigned i a unique three-line interval for transmitting packet signals to the regenerator to avoid any probability of collision. Of curse, some probability of collision is acceptable. A
15 preferred embodiment employs 18,000 set-top units 9 including i unit 22, 3,000 control processors, including processor 18, I 40 corrective regenerators, including regenerator 132, and I one head-cnd subsystem, subsystem 12. The preferred data I rates are 1.007 Megabit per second per channel upstream i 20 and megabytes per second per channel downstream. Where a !
i substantially larger number of subscriber subsystems are to be accommodated, the preferred embodiment employs several 1, systems, the head-end subsystems of which being intercom-, netted as will become apparent shortly.
Head-end subsystem 12 includes a source of eye vision program signals each for transmission on a respective i I channel of cable-distribution subsystem 14, the source being I represented by a satellite earth station 150.
Preferably, base-band television pram signals are developed each of which is employed to directly drive a respective one of an array of transmitters to develop signals suitable for transmission over the cable-distribution subsystem. Alternatively, the base-band television program signals are coupled to the transmitter array by a signal switcher. The signal switcher interposes the channels upon which the television program signals are transmitted by interchanging signals when the synchronization portions Jo thereof are in time coincidence.
More specifically, the signal switcher has 112 synchronization strippers each driven a respective one of the base-band program television signals to develop a Saigon which identifies the start of each frame thereof and 112 lo monostable multi vibrators each driven by a respective one of the synchronization strippers to develop a series ox constant-width pulses. Additionally, the signal switcher has an oscillator driven counter, eight 16-line-to-4-line multiplexes and a microprocessor The counters and multi-plexers are configured so as to couple in turn each of the multi vibrators to an interrupt input of the microprocessor, each multi vibrator being coupled to the microprocessor during a respective sub interval of each of a series of interval delineated by the counter US A carry output of the counter is connected to another input of the microprocessor to delineate the counter interval Finally, the signal switcher has a microprocessor driven crossbar wow tech for interconnecting the various base-band television program signals and the various receivers of the receiver array. When the microprocessor is interrupted by two multi vibrator generated pulses during any one counter delineated interval, the microprocessor causes the crossbar switch to interchange the corresponding base-band television signals, unless such an interchange has previously occurred within a predetermined interval.
lo included in head-end subsystem 12 is a heckle-end computer 160, whir, for clarity, it shown divided into -lo-functional modules including a cable-interface module 162, :
a data- bay module 164, a gate way module 166, components of the various modules are configured to prevent system failure due to the failure of any single computer component as will become apparent shortly.
Cable-interface module 162 has four combined transmitter-receivers, two (cable-interface module) local ¦ buses, two processors each controlling a respective one of i the ( cable-interface module) local buses and three Quadram port memory modules ( all not shown). Two of the trays-mitter-receivers are connected to main-trunk cable 120 of cable "A", the other two of thy transmitter-receivers being i connected to main-trunk cable 12~ of cable on, Each of the transmitter-receivers transmits packet signals on a recipe-, 15 live channel in the 55-400 megahertz band and receives packet ! signals on a respective channel in the under 35 Lockhart ! band. Further, each of the transmitter-receivers is connect-¦
If Ed to each ox the (cable-interface module) local buses ! whereby each of the processors may provide packet signals ¦ 20 for transmission over cable-distribution subsystem 14 and obtain packet signals transmitted over the cable-distrihution 1 subsystem. Each of the quadra-port memory modules is con I nectcd so as to be available to each of the processors on respective ones of the two (cable-interface module local buses and to be available to each of a pair of processors Gun a rcs~ective one of a pair of buses local to sys~em-control module lG2.
Data-base module 164 has two (Dobbs module) local busts, two processors each controlling a respective one of that ~a~a-base-modulc) local uses and Tracy quadr~-~ort I
L81~ , ., ¦ memory modules each connected to be available to each of the processors on respective ones of the (data-base-module) local buses and to each of the two processors on respective ones of - the system-control-module local buses. Additionally, data-base nodule 164 has three 60-Megabyte disc drives with associated disks, each drive being coupled by a respective disc interface module to each of the (data-~ase-module) local ¦ buses, two 65-Megabyte tape units each coupled by a respect l live tape interface module to each of the (data-base-module) 1l10 local buses an two high-speed printers each coupled by an RS-232 interface module to each of the two (data-base-module) !! local buses.
j, Gateway module 166 has two gateway module) local Al buses, two processors each controlling a respective one of ¦~15 the gateway module) local buses and three quadra-port memory modules each connected to be available to each of the processors on a respective one of the (gateway-module) local buses and to each of the two processors on respective ones I¦ of the system-module-control local buses. Further, gate-1! 20 way module 166 has four RS~232-interface modules each connect-I Ed to each of the gateway module local buses, a 9600 baud i modem and a 1200 baud mammal the two modems being driven by . respective ones of two of the R5-232-interfaces. The l modems and the other two RS-232 interface modules permit the ¦
'25 system to be connected to external data bases and/or other cable-television systems to share data, the connection being ¦
represented by line 174.
j As previously indicated, system-control module 168 1 has two(i~ystcm-control-module) local buses, two processors 1.
each controlling a rcsp~ctlvc one of the (systcm-control-!!
I
module) local buses, three quadra-port memory modules which I are shared with cable-interface module 160, three quadra-port j, memory modules which are shared with data-base module 164 i; and three quadra-port memory modules which are shared with gateway module 166.
j Only one of the two processors of each of the modules operates at a time. Control is transferred between the two processors of each module on a periodic basis respond ! size to a processor-resetting signal having period of one ! 10 quarter of a second.
The operation of head-end subsystem 12, and the system generally, is illustrated by means of a typical transaction. It is assumed that a view data frame has been requested by means of a command (request) entered through 'l remote-control unit 32. it the closure of each key of keypad 76, beam 58 is generated so as to transmit the ides !
!¦ nitty of the respective key to set-top unit OWE Responsive ¦ thereto, set-top unit 28 assembles the requisite command and i ¦. notifies control processor I that a command has been entered ,29 by developing on cable 56 a constant level (request-to~send~
¦ signal at the half~B.056 Megahertz rockiness Upon receiving a clear to-send packet signal from trot processor 18, I set-top unit 28 transmits the command in pocket signal format¦
'l and awaits an acknowledgement packet signal ¦
us At ye inn of ye appropriate three-line innately, trot I¦ processor 18 transmits the packet signal to corrective regenerator 132 which forwards the packet signal through the ¦
j various layers of corrective regenerators to cable-interf~ce ¦
'1, module 162~ Cable-interface module 162 transmits a soft ,!30 acknowledge packet signal to temporarily inhibit troll I
1~18144 processor 18 from sending duplicate packet signals.
In turn, the command request) is forwarded from cable-interface module 162 to system-control module 16~ which forwards the request for the frame and a billing notation for the requested frame to data-base module 164. Data-base module 164 retrieves from the disc the requested frame which is forwarded to system-control module 168. Additionally, data-base module 168 stores the billing notation on the disc and, when the billing notation has been properly verified, so 10 notifies system-control module 168. System-control module 1! 168 transfers the requested frame to cable-interface module ! 162 for transmission to control processor 18 and instructs tune module to transmit a herd acknowledge of the command (request)¦
I to the control processor. Finally, control processor 18 develops a conventional television signal to display on set 1 30 the requested frame and, re~pon5ive to the hard acknowledge if packet signal, purges from its memory the command request lo for the f fame).
! I t is important to note aye the system is rota-it lively immune to noise. Noise entering at say the Levi 1, of drop cable 50, does not propagate upstream. The next higher level component, in this case command processor 18, I ignores the noise since it does not represent a properly i formatted packet. Also, when polled once each minute by hcad-end computer 60, command processor 18 indicates to the computer that there is a problem with subscriber subsystem ! I
! odd i t tone 1 lye i t should be noted sons i t it packet . signals tr~vclling over c~blc-clistribution subsystem 14 ore ! 30 encoded. issue, only r~qucst~d end authorized channel signals ¦! are available at the drop cable level, such as on cable 50 for subscriber subsystem 20. Further, to reduce the accessibility of premium television signals being transmitted ¦
'over cable-distribution subsystem 14, the channel assignments of these signals may be periodically randomly) changed with ! each of the eomman~ processors being notified of the changes (supplied mappings so that the associated receivers may 5 track the signals.
It is contemplated that after having read the l~10 preceding disclosure certain alterations and modifications Al of the present invention will no doubt become apparent to Al those skilled in the art. It is therefore intended that the ¦
! following claims be interpreted to cover all such alter- !
lions and modifications as fall within the true spirit and lo scope of the invention.
if l I ' i !
Jo The present invention relates to cable television generally and more particularly to a two-way intricate) cable-television system having distributed processing and means for regulating the upstream signal flow ¦ Cable television, also referred to as community i antenna television (CAT), has come a long way from its ,10 humble beginning as a means of providing rural television ¦ reception. Presently, cable television is an important means ¦
of providing reception of local, non-local and premium tote- ¦
vision programs and promises to become an important means of ¦
providing many new, Tao (interactive) services in the future. Heretofore, cable television also promised a number of problems.
One such problem, even for one-way cable-televisionl systems, is that of signal security. Many prior-art one-way !
cable-television systems transmit signals conveying premium television programs only to those who have made arrangements ¦
in advance (paid for such programs. To restrict the recipe lion of such programs the signals conveying the programs are , scrambled and those who have made arrangements to receive the programs are provided suitable descramblers. Unfortunately, j such descramblcrs are relatively expensive. Further, it is l difficult to securely scramble television signals, the rerun- !
I dent information in the signals maying the signals relatively¦
easy to dcscramble. oven for those who lack the requisite ; skills to build descramblers, such devices can often by pun-chased. or many Tao services, such as electronic mail, I
Lo the signal security problem is even more acute Another problem for two-way cable-teleYision soys- !
terms is that of noise. Noise, which typically enter at the 'drop cable level, must be prevented from propagating up the System (upstream) to disable the entire system.
A very serious problem is that of system loading.
It is difficult to provide highly interactive services to a relatively large number of subscribers without so loading down prior-art~type two-way cable-television systems that the ¦
response time Doyle during peak hours becomes intolerable.
An interactive Tao) cable-television system is disclosed in the United States patent 3, 9g7, 718 which issued to Rickets et at Disclosed is an interactive l cable-television system employing a head-end subsystem a ! 15 plurality of subscriber units and a coaxial cable subsystem I Which interconnects the head-end subsystem with the various I subscriber unit. The system is operative to distribute telex vision signals to the various subscriber units and to pro- ¦
, vise two-way digital data communications between the head-end !
subsystem and the various subscriber units. An encoder is employed in the head-end subsystem; and, a decoder is ' employed in each of the subscriber units, the combination for !
j scrambling/descrambling premium television signals to no-strict the use thereof. Alto employed is a mini-computer 25 in the head-end subsystem and the combination of an alpha-numeric keyboard with alpha-numeric electronics in each of the subscriber units to operate with a subscriber's tote-1 vision as a data terminal for Tao digital data commune- ¦
i cations with the mini-computer. Two-way digital data comma-I 30 nication is carried on synchronously with each s~bscr.ibex unit being allocated a time slot in which to respond.
Another system employing many of the same elements is disk I¦ closed in the United States patent 4,245,245 issued to Matsumoto et at.
I!
Al 5 A two-way cable-television system is disclosed in United States patent 3,750,022 which issued to Curry et at.
Employed therein is a tree-type distribution subsystem having modally disposed filters. Each of the filters responds to respective head-end subsystem generated commands to isolate noise developed on a respective coaxial cable (drop cable leading to a corresponding subscriber units).
Another two-way cable-television system employing a tree-type distribution network is disclosed in the United States patent 3,840,912 which issued to T. Takeuchi. The , 15 system employs a number of modally disposed modulation units Jo each for modulation by an alarm signal generated by one of ¦¦ a number of associated subscriber alarm transmitters. Not !¦ only does each of the modulation units operates upon a I distinct carrier frequency; but each of the alarm trays-,20 millers associated therewith also operates upon a aistinctaudio frequency. This permits a head-end subsy~kem to identify the origin Jo on alarm signal. rho modally dip-If posed modulation units operate upon the alarm signals so as Jo to permit a such larger number of subscriber transmitters to share the distribution network than would otherwise be pox-Sibley Finally, twig c~ble-television system is disk i close by I. Bernhard in the United Slates patent 3,g34,079 in which it Is indicated that two-way digital communication is by means of synchronously generated data packets.
_ !
A data communication (time share) network is disk ¦ closed in the United States patent ~,156,79~ issued to l M. Dallas. The network employs number of host processing I
-systems each coupled by a communications network to a number of terminal devices. Each of the processing systems is interconnected with the other processing systems to share data. The communications network includes a plurality of ~wo-part buffer storage memories, fan-out node device, line-master exchange unit devices, line exchange unit devices, l 10 and terminal exchange unit devices, all convected in a complex I tree-ring configuration. Communication between the host pro- ?
Suzanne system and a terminal device is by means of data I blocks 9 erroneous blocks being discarded by the respective I terminal exchange unit.
! 15 Television type infrared remote control units , are disclosed in the United States patents 4,231,~31 and l 4,156,810, which issued to Brother eta and S. I~arashi, ! respectively. Both units employ infrared radiation.
, Brother et at disclose the use of infrared pulse spacing to ¦
represent each bit of digital data. In the So I~arashi 1, disclosure, the infrared pulse spacing represents a i! digital quantity (word), in this case the desired channel ! number .
,25 It is therefore a material object of the present Al invention to provide a novel two-way cable-television system I which is sufficiently versatile so as to provide a relatively wide range ox services to a relatively large number of sub-scribers without significant overload delays ~30 another object of the present invention is to pro-vise a two-way cable-television system having relatively if high signal security ¦¦ Still another object of the present invention is I to provide a two-way cable-television system which is rota- i ¦ 5 lively immune to noise.
, I Briefly, the preferred embodiment of the present / ¦ invention employs a head-end computer and a head-end sub-system including a source of television program signals for distribution by the system, a cable-distribution subsystem ! lo including a plurality of corrective regenerators, a plurality of control processors and a plurality of subscriber i subsystems each including a selection of standard and optic eel units chosen to provide a mixture of services as is I¦ appropriate to provide the desired services. Each of the ¦~15 corrective regenerators buffers and retransmits signals no-presenting commands sentries) encoded in a packet format ! which are propagating upstream) from a subscriber subbases-them to the head-end subsystem. Signals representing impure- !
it pertly formatted packets art ignored by each of the cornea- !
jl20 live regenerators which also discards certain packet signals !
when overloaded. Each of the control processors, which interfaces a number of subscriber subsystems to thy cable- ¦
distribution subsystem, includes a number of receivers each ¦ for conditioning a television program signal on a selected channel before coupling the signal to a respective sub-scriber-subsystem unit, A material advantage of the present invention is l I
i its versatility. I L
Another advantage of the present invention is thy ¦
¦ 30 ability it affords to provide a relatively wide range of services to a relatively large number of subscriber ¦
without significant overload problems.
These and thwacks objects and advantages of the pro-sent invention will no doubt become apparent to those skilled¦
¦ 5 in the art after having read the following detailed descrip- i ¦ lion of the preferred embodiment which it illustrated in the ¦
I figure of the drawing.
Al In the drawing Figure 1 is a combined block diagram and perspective view showing a two-way cable-. television system in accordance with the present ¦ invention-If The preferred embodiment of a two-way (interactive) ! cable-televisivn system in accordance with the present invent-!
. 15 lion is shown in Figure 1 generally designated by the number j ! lo. Employed therein are a head-end subsystem 12, a cable-distribution subsystem 14, a plurality of control pro-censors, collectively designated by the number 16 including a typical processor 18, and a plurality of subscriber sub systems, collectively designated by thy number 2Q including ¦' an illustrative subsystem 22. For clarity, the above ¦' mentioned subsystems are described in order from the bottom Jo up.
I The components of subscriber subsystem 22 which are generally standard with all subscriber subsystems include a power-inserting unit 26, a set-top unit 29 for use with the respective sub~cri~er'~l conventional television set 30 and a wireless remote control unit 32. The remaining come pennants of subscriber subsystem 22 each ox which is optional with other subscriber subsystem include another set-top unit with an associated remote-control unit, collectively l designated by the number 34, a keyboard unit 36 and a term-! net unit 38. The above-mentioned units, as opposed to the associated control processor, are disposed at subscriber convenient locations within the respective subscriber's home (inside units Power-inserting unit 26 is connected to control processor 18 by means of a drop cable represented by a cable 50. Additionally, unit 26 is either directly connected to set-top unit 28 by means of a cable (not shown or, in order to accommodate additional units, couple thereto by means of one or more conventional signal splitters, represented by a splitter 52 which is connected to unit I by a cable 54 and to unit 28 by a cable 56. An infrared beam (link) 58 couples remote-control unit 32 to set-top unit 2B which has provision for connection to television set 30 by means of a cable, represented by a cable 60. As illustrated, set-top unit 34 is connected to signal splitter 52 by a cable 64;
,¦ and, keyboard unit 36 is coupled to the splitter by a cable 66. Finally, terminal unit 38 is shown coupled to signal splitter 52 by a cable 68, another signal splitter 70 and another cable 72.
From the bottom end up, remote control unit 32 j has a keypad 76 for command entry, a microprocessor snot .,25 shown) for scanning the various keys of the keypad to detect each key closure, and an infrared transmitter (also not l shown) driven by the microprocessor so as to selectively ¦ develop beam 58 as necessary to transmit to set-top unit 32 ¦ the identity of each key upon the closure thereof. us used herein, the term "command is intended to include all entries including requests for a particular service, data, etc. Keypad 76 includes keys for panic use.
Each of the set-top units, including unit 28, pro-vises a means for limited command entry and a means for 1 5 controlling an associated television set, such as set 30.
¦ Set-top unit 28 has a microprocessor with associated memory (not shown), a keypad 78, which is similar to keypad 76, an infrared detector (also not shown), provision for con-section to a home bus, represented by a line By provision for connection to a number of burglar alarm and smoke-detector switches by a number of lines represented by a line 1! 82, power-controllinq and monitoring circuitry (not shown I and a pair of 7-segment display devices 84 and 86. The ¦ microprocessor scans the various keys of keypad I and monitors the infrared detector to detect key closures . from which the microprocessor assembles commands. Those commands which the microprocessor cannot execute directly are transmitted to control. processor 18. Further, the microprocessor interfaces home bus 80 to the system and monitors the lines represented by line 82 to ascertain the status of each of the switches, notifying control processor 18 of changes therein. The microprocessor controls the AC
or on of coupled to television set 30 and monitors the power being consumed thereby, notifying control processor 18 of changes therein (set on~Qff~. From information trays-milted to set-top unit 28 ho control processor 18, the unit microprocessor refreshes display devices 84 and I so as to display a number representing an associated television channel when the television set is in use or the time of day. ¦
i30 Sct-top unit I executes command transmitted there-I
to by control processor lo. The commands are transmitted to i unit 28 encoded in a packet signal format. The individual binary bits of each packet are conveyed as amplitude module-lion levels of individual cycles ox a 8.056 Megahertz .
carrier signal which control processor 18 develops on cable 50~.
Packet signals are also employed as a means for transmitting commands from set-top unit 28 to command pro-j censor 18. Individual bits of each packet are conveyed as lo amplitude modulation levels of respective cycles of a carrier signal which unit 28 develops on cable 56 by divide in in half the frequency of the 8.056 egrets carrier signal developed by control processor 18. Prior to transmitting a . packet signal, unit 28 develops on cable 56 a request-to-l15 send signal in the form of a constant-level signal at the half-8.056 Megahertz frequency. Upon receipt of a clear-to-send packet signal transmitted by control processor 18, l set-top unit 28 transmits the packet signal and awaits an ! acknowledgement packet signal. Normally, a generally ¦20 addressing clear-to-send packet signal is transmitted by it control processor lo. when more than one unit of subscriber I! subsystem 22 attempts to transmit simultaneously, control it ¦ processor 18 simply transmits a mute packet signal and then individually polls the units.
Additionally, situp unit 28 has volume control-lying circuitry (not shown) which receives a conventional television signal on a preset one of two special channels employed or transmitting television signals from the come mend processor to the associated unit. the circuitry de-¦30 modulates the signal to develop a husband video signal .!
Al and a base-band audio signal. Next, as directed by the micro processor, the circuitry attenuates the base-band audio signal to a subscriber selected level. Finally, top circuit- !
rye employs the base-band video signal and the attenuated if 5 audio signal to modulate suitable carrier signals so as to develop a conventional television signal on a preset one of the three channels two, three or four for driving television set 30.
Power-inserting unit 26 has a transformer (not shown for connection to a conventional AC power line, the transformer for developing a 24 volt AC potential for powering control processor 18. In addition to coupling the i AC potential to cable 50, power-insertiny unit 76 couples between cables 50 and 52 the signals developed thereon including the packet signets and the special channel tote- !
l vision signals.
I Keyboard unit 36, which is similar to set-top unit ¦
28, has a remote-control unit with a full keyboard 90, as opposed to the limited.keypa~ of unit 32. The full keyboard is better suited for use in text processing and electronic i¦ mail handling. I
I Terminal unit 38 has a suitable connector 92 and a ¦ microprocessor with associated memory (not shown) for inter- ¦
it facing 110 through 19200, RS-232-type units to the system j,25 including a modem and a computer terminal, the latter hying represented by a computer terminal 94. In interfacing Tom- !
! puterterminalg4tothe5ystem;terminalunit38convert5 I various escape-sequence coxes as might be ¦ employed by the particular type of terminal to the respective;
codes employed by the system.
I
I
Among other units which may be included with j subscriber subsystem are an alarm unit for interfacing additional burglar-alarm and smoke-detector switches to the system, a frame grabber unit for receiving and displaying on a subscriber's television set individual frames of a video picture, a video pickup unit having a frame grabber, the combination for transmitting individual video frames and a if game unit for downloading games to a subscriber convene-i chenille video game.
Each of the control processors, including processor , 18 is employed to interface up to eleven subscriber subsystems I to cable distribution subsystem 14. Included in each pro-Jo censor are eleven frequency-agile digitally-tuned receivers (not shown each for driving a respective set-top unit. I
'15 Two receivers of control processor 18 are dedicated to sub-scriber subsystem 22, one for driving situp unit I and ! the other for driving unit 34. Each receiver receives a signal on a selected one of a number of channels employed to ¦
transmit conventional television program signals on cable !29 distribution subsystem 14 and converts the frequency of the signal to the special channel frequency appropriate for drive i in the respective set-top unit. Among the signals which may ¦
i! be selected are 50 plus channels of signals in thy 55-400 megahertz conventional cable television band transmitted on ! us each of two cable subsystems including an ray cable subsystem to which control processor 18 is coupled by a signal splitter !
I (tap) lQ2 and a distribution cable 104 and a By cable sub- ¦
! system, to which processor I is coupled by another signal j splitter tap) 103 and another distribution cable 108. the ~30 "A" and "I" cable subsystems are discussed below in kinks 1218~L~4 1'1 with ~able-distribu~ion subsystem 143 In addition to the abovc-mention~d wrecker, etch control processor, including processor 18, includes Another receiver (not shown or receiving commands huh are transmitted by head-end subsystem 12 over cable distribution subsystem 14 on a one of four channels which are dedicated to this purpose.
Each of the control processors, including processor lo, transmits and receives commands encoded in packet format 10 Individual bits of each of the packet which are transmitted over ~able-dis~ribution subsystem î 4 are muddied frequency modulation ~MFM1 encoded and conveyed as amplitude modulation .
levels of a tarrier signal suitable for the respective channel employed therefore. The packets which are received by the 15 various processors on a channel in the 55-400 egret band dedicated to this purpose, are transmitted a 2~014 Megabit I rate: and, the packets, which are transmitted my the various processors on a channel of five channels which are slow 35 Megahertz, are transmitted at 1.007 Megabit rate. The pack t f 20 are transmitted over the cable-distri~ution subsystem by a control processor beginning coincident with the beginning of z n interval assigned to the respective processor, the interval being defined by on assigned three-line lnterv~l during each field of a conventional television signal. I previously 25 indicated the individual bits of packets which are transmitter d between a control processor and one of the associated subscri~
subsystems, such as between processor I and subsystem I are conveyed as amplitllde modulation levels of a tarrier ~ignalD
The carrier signal employed by Mach professor for transmittance 30 packets his a 8.056 Megahertz frequency and, the carrier sign at employed by each subsceiber-s~system units for transmitting ¦
packets to the respective command processor has a frequency h 1 f the 8.055 Megahertz Eeequerlcy.
Also included in each of the control processors, including processor 18, are a phase-locked GUPPY, timing and display circuitry and microprocessor with associated memory (all not shown). From the MUM encoded signal, the 5 phase-locked loop develops the 8.056 Megahertz carrier signal, four signals including a 32.2 Megahertz signal, a 16.1 Megahertz signal, a 10.7 Megahertz s;qnal and a 8.05 Megahertz signal, one of which is employed as the carrier signal to transmit jackets to head-end subsystem 12l and a 10 32.2 Megahertz signal. Driven by the 32.2 Megahertz signal, the timing and display circuitry develops three conventional television signals each of which maps the contents of memory locations into corresponding elements of a television picture. The memory mapped signals are selectively coupled to various ones of the associated subscriber subsystems so as to display, on television set 30 for example, subscriber prompts and messages, electronic mail, requested view data and teletexed frames, billing information, bulletin board, shopping and banking text and the like Further each control processor microprocessor, encodes/decodes sensitive packets in accordance with the National Bureau of Standards DES algorithm.
Each of the control processors, including processor 18, maintains a subscriber authorization profile for each 25 associated subscriber subsystem. Prior to providing a requested service, the respective control processor tests the request command ) against the respective subscribe author-ration profile to ensure that the service it authorized for the particular subsystem. Thus, the subscriber authorization 30 profiles provide a means of limiting Sirius to certain classes of subscriber subsystems. For example, access to certain premium channels may require advance arrangements.
i21814~
¦ Also, certain programs may be limited to certain profess I signals such as doctors. Additionally, a modesty code to be j entered at a subscriber-subsystem unit before access to a particular channel may be included to permit parents to restrict the programs their children watch. -Upon initialization, and as is appropriate there-after, each control processor, including processor 18, receives from headwind subsystem 12 by means of packet signals transmitted over cable-distribution subsystem 14 a series of instructions (software) for execution by the i processor microprocessor, an assignment of the three-line interval coincident with ye inning of which the professor may begin i , transmission ox a packet signal to ye head-end system the respective i subscriber authorization profiles. Responsive to status ¦
15 requests transmitted my head-end subsystem 12 once each Jo minute, each control processor, including processor 18, ¦' polls its respective subscriber subsystem units, including ¦ unit 28, to obtain a status report which the processor trays-¦
if mitt to the head-end subsystem. Each status report includes . 20 the operational status of the control processor and also-elated subscriber-subsystem units and thy services being , provided there through.
I Cable-distribution subsystem 12 includes a pair of I main trunk cables 120 and 122, number of branch cable, a ! 25 large number of distribution cables, including cables 104 and 1 108, a number of amplifiers reprint by a pair of amply-liens 126 and 12~ and a number of nested Crockett regenerate ions represented by three regenerators 132, 134 and 1}6. us ¦
strutted, corrective regenerator 132 is connected between Jo a pair ox branch cables 138 and 140 and the two distribution ¦ cables 104 and 108. The above-mentioned cables, amplifier and corrective regenerators are connected in a pair of tree- ¦
type structures referred Jo as the "A" cable subsystem and two By cable subsystem. Each of the above-mentioned subsystems 5 conducts signals in a S5-400 Megahertz band from head-end subsystem 12 (downstream) to each ox the control processors, including processor 18, and forwards certain signals in the below 35 Megahertz band, signals which represent most ! properly formatted packets, from each of the command ¦10 processors (upstream) to the head-end subsystem as will be- ¦
If come apparent shortly.
! The amplifiers, including amplifiers 126 and 128, are employed so as to compensate for cable losses. Typical- ¦
lye one amplifier is employed for each half mile of cable.
1115 Each of the amplifiers amplifies signals in the SS-400 Al megahertz band which are propagating from head-end subsystem If 12 (downstream) to the various control processors including If processor lo, and amplifies signals in the below 35 I Megahertz band which are propagating from the various control ¦120 processors (upstream to the head-end subsystem.
The principal difference between cable-distribution subsystem 14 and those of prior art design is that subsystem 1 14 includes corrective regenerators Each corrective ¦ regenerator, including regenerator 132, has filters and a US microprocessor with associated memory (all not shown). The ¦¦ filters pass signals in the 55-400 Megahertz band and trap interest signals in the below 35 I Mcgahert2 band. The microprocessor and memory, buffer and retransmit ;ntcrcepte~ signals which rc~rcsent curtain properly formatted pockets propagating from each of the individual control processors, including processor 18, (upstream to head-end subsystem 12. The principal kirk-texistics of the corrective regenerators is that each i regenerator ignores signals which do not represent properly formatted packets and, when overloaded, discards (ignores) certain signals which represent properly formatted packets . so as to favor older commands, as will become apparent l shortly.
! Properly formatted packets propagating from a lo control processor (upstream) to the headwind subsystem have a header t Betty byte, a repeat flag bit, three carbon copy bits, a packet length bit and 35 address bits. Short packets ¦
I'; t having a 16 octet format) also have a packet type byte, 7 ¦, data bytes and 2 CRC bytes. Long packets having a 64 octet format) also have 2 place mark bits, 6 packet type bits, 55 data bytes and 2 C~C bytes.
Proper protocol requires that when a packet signal has successfully propagated upstream) from a control pro-. censor, such as processor 18, through the various layers of ¦120 corrective regenerators, in this case through regenerators 132 j¦ and 134, to head-end subsystem 12, that subsystem 12 'j acknowledge receipt ox the packet signal. Upon failure if to receive such an acknowledgement, because the packet signal has been destroyed due to collision with another packet signal or the packet signal has been discarded by a corrective regenerator the respective control processor waits a ran period of to within a deterministic to interval and retransmit the packet signal. The repeat slag bit and carbon copy number bits provide etch o~rre~ive r~ne~ator a meats of ascertaining go of thy respective command and, thus, a means of L81~
I¦ prioritizing packet signals for discarding purposes.
I The number of subscriber subsistence which may be 'i accommodated in one system and, to accommodate the subbases-¦, terms, the required number of control processors and cornea-¦ 5 live regenerators and nesting thereof, is a function of the peak loading generated by the service demand, the peak delay ¦
which will be tolerated in providing the services and the data rate.
It should be noted that by limiting the number of lo control processors which are connected to each corrective I regenerator to 87 processors, each processor may be assigned i a unique three-line interval for transmitting packet signals to the regenerator to avoid any probability of collision. Of curse, some probability of collision is acceptable. A
15 preferred embodiment employs 18,000 set-top units 9 including i unit 22, 3,000 control processors, including processor 18, I 40 corrective regenerators, including regenerator 132, and I one head-cnd subsystem, subsystem 12. The preferred data I rates are 1.007 Megabit per second per channel upstream i 20 and megabytes per second per channel downstream. Where a !
i substantially larger number of subscriber subsystems are to be accommodated, the preferred embodiment employs several 1, systems, the head-end subsystems of which being intercom-, netted as will become apparent shortly.
Head-end subsystem 12 includes a source of eye vision program signals each for transmission on a respective i I channel of cable-distribution subsystem 14, the source being I represented by a satellite earth station 150.
Preferably, base-band television pram signals are developed each of which is employed to directly drive a respective one of an array of transmitters to develop signals suitable for transmission over the cable-distribution subsystem. Alternatively, the base-band television program signals are coupled to the transmitter array by a signal switcher. The signal switcher interposes the channels upon which the television program signals are transmitted by interchanging signals when the synchronization portions Jo thereof are in time coincidence.
More specifically, the signal switcher has 112 synchronization strippers each driven a respective one of the base-band program television signals to develop a Saigon which identifies the start of each frame thereof and 112 lo monostable multi vibrators each driven by a respective one of the synchronization strippers to develop a series ox constant-width pulses. Additionally, the signal switcher has an oscillator driven counter, eight 16-line-to-4-line multiplexes and a microprocessor The counters and multi-plexers are configured so as to couple in turn each of the multi vibrators to an interrupt input of the microprocessor, each multi vibrator being coupled to the microprocessor during a respective sub interval of each of a series of interval delineated by the counter US A carry output of the counter is connected to another input of the microprocessor to delineate the counter interval Finally, the signal switcher has a microprocessor driven crossbar wow tech for interconnecting the various base-band television program signals and the various receivers of the receiver array. When the microprocessor is interrupted by two multi vibrator generated pulses during any one counter delineated interval, the microprocessor causes the crossbar switch to interchange the corresponding base-band television signals, unless such an interchange has previously occurred within a predetermined interval.
lo included in head-end subsystem 12 is a heckle-end computer 160, whir, for clarity, it shown divided into -lo-functional modules including a cable-interface module 162, :
a data- bay module 164, a gate way module 166, components of the various modules are configured to prevent system failure due to the failure of any single computer component as will become apparent shortly.
Cable-interface module 162 has four combined transmitter-receivers, two (cable-interface module) local ¦ buses, two processors each controlling a respective one of i the ( cable-interface module) local buses and three Quadram port memory modules ( all not shown). Two of the trays-mitter-receivers are connected to main-trunk cable 120 of cable "A", the other two of thy transmitter-receivers being i connected to main-trunk cable 12~ of cable on, Each of the transmitter-receivers transmits packet signals on a recipe-, 15 live channel in the 55-400 megahertz band and receives packet ! signals on a respective channel in the under 35 Lockhart ! band. Further, each of the transmitter-receivers is connect-¦
If Ed to each ox the (cable-interface module) local buses ! whereby each of the processors may provide packet signals ¦ 20 for transmission over cable-distribution subsystem 14 and obtain packet signals transmitted over the cable-distrihution 1 subsystem. Each of the quadra-port memory modules is con I nectcd so as to be available to each of the processors on respective ones of the two (cable-interface module local buses and to be available to each of a pair of processors Gun a rcs~ective one of a pair of buses local to sys~em-control module lG2.
Data-base module 164 has two (Dobbs module) local busts, two processors each controlling a respective one of that ~a~a-base-modulc) local uses and Tracy quadr~-~ort I
L81~ , ., ¦ memory modules each connected to be available to each of the processors on respective ones of the (data-base-module) local buses and to each of the two processors on respective ones of - the system-control-module local buses. Additionally, data-base nodule 164 has three 60-Megabyte disc drives with associated disks, each drive being coupled by a respective disc interface module to each of the (data-~ase-module) local ¦ buses, two 65-Megabyte tape units each coupled by a respect l live tape interface module to each of the (data-base-module) 1l10 local buses an two high-speed printers each coupled by an RS-232 interface module to each of the two (data-base-module) !! local buses.
j, Gateway module 166 has two gateway module) local Al buses, two processors each controlling a respective one of ¦~15 the gateway module) local buses and three quadra-port memory modules each connected to be available to each of the processors on a respective one of the (gateway-module) local buses and to each of the two processors on respective ones I¦ of the system-module-control local buses. Further, gate-1! 20 way module 166 has four RS~232-interface modules each connect-I Ed to each of the gateway module local buses, a 9600 baud i modem and a 1200 baud mammal the two modems being driven by . respective ones of two of the R5-232-interfaces. The l modems and the other two RS-232 interface modules permit the ¦
'25 system to be connected to external data bases and/or other cable-television systems to share data, the connection being ¦
represented by line 174.
j As previously indicated, system-control module 168 1 has two(i~ystcm-control-module) local buses, two processors 1.
each controlling a rcsp~ctlvc one of the (systcm-control-!!
I
module) local buses, three quadra-port memory modules which I are shared with cable-interface module 160, three quadra-port j, memory modules which are shared with data-base module 164 i; and three quadra-port memory modules which are shared with gateway module 166.
j Only one of the two processors of each of the modules operates at a time. Control is transferred between the two processors of each module on a periodic basis respond ! size to a processor-resetting signal having period of one ! 10 quarter of a second.
The operation of head-end subsystem 12, and the system generally, is illustrated by means of a typical transaction. It is assumed that a view data frame has been requested by means of a command (request) entered through 'l remote-control unit 32. it the closure of each key of keypad 76, beam 58 is generated so as to transmit the ides !
!¦ nitty of the respective key to set-top unit OWE Responsive ¦ thereto, set-top unit 28 assembles the requisite command and i ¦. notifies control processor I that a command has been entered ,29 by developing on cable 56 a constant level (request-to~send~
¦ signal at the half~B.056 Megahertz rockiness Upon receiving a clear to-send packet signal from trot processor 18, I set-top unit 28 transmits the command in pocket signal format¦
'l and awaits an acknowledgement packet signal ¦
us At ye inn of ye appropriate three-line innately, trot I¦ processor 18 transmits the packet signal to corrective regenerator 132 which forwards the packet signal through the ¦
j various layers of corrective regenerators to cable-interf~ce ¦
'1, module 162~ Cable-interface module 162 transmits a soft ,!30 acknowledge packet signal to temporarily inhibit troll I
1~18144 processor 18 from sending duplicate packet signals.
In turn, the command request) is forwarded from cable-interface module 162 to system-control module 16~ which forwards the request for the frame and a billing notation for the requested frame to data-base module 164. Data-base module 164 retrieves from the disc the requested frame which is forwarded to system-control module 168. Additionally, data-base module 168 stores the billing notation on the disc and, when the billing notation has been properly verified, so 10 notifies system-control module 168. System-control module 1! 168 transfers the requested frame to cable-interface module ! 162 for transmission to control processor 18 and instructs tune module to transmit a herd acknowledge of the command (request)¦
I to the control processor. Finally, control processor 18 develops a conventional television signal to display on set 1 30 the requested frame and, re~pon5ive to the hard acknowledge if packet signal, purges from its memory the command request lo for the f fame).
! I t is important to note aye the system is rota-it lively immune to noise. Noise entering at say the Levi 1, of drop cable 50, does not propagate upstream. The next higher level component, in this case command processor 18, I ignores the noise since it does not represent a properly i formatted packet. Also, when polled once each minute by hcad-end computer 60, command processor 18 indicates to the computer that there is a problem with subscriber subsystem ! I
! odd i t tone 1 lye i t should be noted sons i t it packet . signals tr~vclling over c~blc-clistribution subsystem 14 ore ! 30 encoded. issue, only r~qucst~d end authorized channel signals ¦! are available at the drop cable level, such as on cable 50 for subscriber subsystem 20. Further, to reduce the accessibility of premium television signals being transmitted ¦
'over cable-distribution subsystem 14, the channel assignments of these signals may be periodically randomly) changed with ! each of the eomman~ processors being notified of the changes (supplied mappings so that the associated receivers may 5 track the signals.
It is contemplated that after having read the l~10 preceding disclosure certain alterations and modifications Al of the present invention will no doubt become apparent to Al those skilled in the art. It is therefore intended that the ¦
! following claims be interpreted to cover all such alter- !
lions and modifications as fall within the true spirit and lo scope of the invention.
if l I ' i !
Claims (4)
1. A tree-type two-way data communications system for use in a cable television system having a single head-end subsystem, a plurality of data sources and a cable television distribution network wherein each said data source is a source of digital commands to said head-end subsystem, said two-way system comprising:
a plurality of interface subsystems intermediate of said head-end subsystem and each one of said data sources, said interface subsystems being coupled in a tree structure to said head-end subsystem, each one of said data sources being coupled to one of said interface subsystems, and each one of said interface subsystems being coupled to at least one other of said interface subsystems, said interface subsystems receiving without acknowledgment through said cable distribution network from at least one of said data sources said digital command signals, each said interface subsystem verifying data format and regenerating and for-warding at least some of said digital commands as command packet signals in a packet signal format on an upland carrier towards said head-end subsystem;
said head-end subsystems receiving said digital command signals as said command packet signals and developing response signals; and said cable-distribution subsystem coupling response signals in a tree-structure without loops from said head-end subsystems to each one of said data sources through a common signal path independent of said unlink for acknowledging receipt of said command packet signals.
a plurality of interface subsystems intermediate of said head-end subsystem and each one of said data sources, said interface subsystems being coupled in a tree structure to said head-end subsystem, each one of said data sources being coupled to one of said interface subsystems, and each one of said interface subsystems being coupled to at least one other of said interface subsystems, said interface subsystems receiving without acknowledgment through said cable distribution network from at least one of said data sources said digital command signals, each said interface subsystem verifying data format and regenerating and for-warding at least some of said digital commands as command packet signals in a packet signal format on an upland carrier towards said head-end subsystem;
said head-end subsystems receiving said digital command signals as said command packet signals and developing response signals; and said cable-distribution subsystem coupling response signals in a tree-structure without loops from said head-end subsystems to each one of said data sources through a common signal path independent of said unlink for acknowledging receipt of said command packet signals.
2. In a communications system according to claim 1 wherein each said interface subsystem comprises a corrective regenerator means, said corrective regenerator means for forwarding verified command packet signals toward said head-end subsystem and further to reject selected current ones of said command packet signals in favor of prior ones of said command packet signals when said cor-rective regenerator means is overloaded with signal pro-cessing tasks.
3. In a communications system according to claim 2 further including means for developing at least one television type signal in response to a selected command signal and means for selectively coupling said television type signal to a display device associated with the said data source associated with said selected command signal in replacement of another television type signal.
4. In a two-way communications system according to claim 2, further characterized in that said data sources are a plurality of subscriber subsystems and command pro-cessor means;
that each subscriber subsystem includes means for entering a control command and for generating said digital command signals and means for coupling a television signal on a preset channel to a television set subsystem; that said head-end subsystem further includes means for receiving cable channel signals from a cable channel signal source; that a plurality of subscriber subsystems are coupled to a single command processor means; and that a plurality of command processor means are coupled to one of said corrective, regenerators, each command processor meats monitoring for acknowledgment of receipt of said command packet signals from said head-end subsystem and retransmitting unacknowledged command packet signals through a plurality of said corrective regenerators after a random period of time within a deterministic time interval indicative of failure to receive said acknowledgement.
that each subscriber subsystem includes means for entering a control command and for generating said digital command signals and means for coupling a television signal on a preset channel to a television set subsystem; that said head-end subsystem further includes means for receiving cable channel signals from a cable channel signal source; that a plurality of subscriber subsystems are coupled to a single command processor means; and that a plurality of command processor means are coupled to one of said corrective, regenerators, each command processor meats monitoring for acknowledgment of receipt of said command packet signals from said head-end subsystem and retransmitting unacknowledged command packet signals through a plurality of said corrective regenerators after a random period of time within a deterministic time interval indicative of failure to receive said acknowledgement.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/373,048 US4509073A (en) | 1982-04-29 | 1982-04-29 | Two-way cable-television system |
| EP84114912A EP0183871A1 (en) | 1982-04-29 | 1984-12-07 | Two-way cable-television system |
| JP59259436A JPS61139141A (en) | 1982-04-29 | 1984-12-10 | Bidirectional data communication system |
| CA000469853A CA1218144A (en) | 1982-04-29 | 1984-12-11 | Two-way cable-television system |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/373,048 US4509073A (en) | 1982-04-29 | 1982-04-29 | Two-way cable-television system |
| EP84114912A EP0183871A1 (en) | 1982-04-29 | 1984-12-07 | Two-way cable-television system |
| JP59259436A JPS61139141A (en) | 1982-04-29 | 1984-12-10 | Bidirectional data communication system |
| CA000469853A CA1218144A (en) | 1982-04-29 | 1984-12-11 | Two-way cable-television system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1218144A true CA1218144A (en) | 1987-02-17 |
Family
ID=49883406
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000469853A Expired CA1218144A (en) | 1982-04-29 | 1984-12-11 | Two-way cable-television system |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4509073A (en) |
| EP (1) | EP0183871A1 (en) |
| JP (1) | JPS61139141A (en) |
| CA (1) | CA1218144A (en) |
Families Citing this family (68)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4965825A (en) | 1981-11-03 | 1990-10-23 | The Personalized Mass Media Corporation | Signal processing apparatus and methods |
| US7831204B1 (en) | 1981-11-03 | 2010-11-09 | Personalized Media Communications, Llc | Signal processing apparatus and methods |
| USRE47642E1 (en) | 1981-11-03 | 2019-10-08 | Personalized Media Communications LLC | Signal processing apparatus and methods |
| US4586078A (en) * | 1983-09-12 | 1986-04-29 | Zenith Electronics Corporation | CATV upstream signal transmission at nonharmonic video frequencies |
| US4905280A (en) * | 1984-10-12 | 1990-02-27 | Wiedemer John D | High security videotext and videogame system |
| AU590236B2 (en) * | 1984-12-21 | 1989-11-02 | Sony Corporation | Communication system for video information apparatus |
| US5230073A (en) * | 1986-07-21 | 1993-07-20 | Bell Communications Research, Inc. | System and method for accessing and updating a continuously broadcasted stored database |
| US4829372A (en) * | 1987-08-20 | 1989-05-09 | Telaction Corporation | Presentation player |
| US5235619A (en) * | 1990-03-20 | 1993-08-10 | Scientific-Atlanta, Inc. | Cable television radio frequency subscriber data transmission apparatus and rf return method |
| US5155590A (en) * | 1990-03-20 | 1992-10-13 | Scientific-Atlanta, Inc. | System for data channel level control |
| CA1327238C (en) * | 1988-04-21 | 1994-02-22 | Michel Dufresne | Catv network with filters |
| US4989081A (en) * | 1988-11-14 | 1991-01-29 | Sony Corporation | Home-bus-information system |
| US4959713A (en) * | 1989-10-10 | 1990-09-25 | Matsushita Electric Industrial Co., Ltd. | Home automation system |
| US5255086A (en) * | 1990-03-20 | 1993-10-19 | Scientific-Atlanta, Inc. | Method and apparatus for RF data transfer in a CATV system |
| US5142690A (en) * | 1990-03-20 | 1992-08-25 | Scientific-Atlanta, Inc. | Cable television radio frequency data processor |
| US5220420A (en) * | 1990-09-28 | 1993-06-15 | Inteletext Systems, Inc. | Interactive home information system for distributing compressed television programming |
| US5526034A (en) * | 1990-09-28 | 1996-06-11 | Ictv, Inc. | Interactive home information system with signal assignment |
| US5557316A (en) * | 1990-09-28 | 1996-09-17 | Ictv, Inc. | System for distributing broadcast television services identically on a first bandwidth portion of a plurality of express trunks and interactive services over a second bandwidth portion of each express trunk on a subscriber demand basis |
| US20040073953A1 (en) * | 1990-09-28 | 2004-04-15 | Qi Xu | Audio/video apparatus for use with a cable television network |
| US5587734A (en) * | 1990-09-28 | 1996-12-24 | Ictv, Inc. | User interface for selecting television information services through pseudo-channel access |
| US5412720A (en) * | 1990-09-28 | 1995-05-02 | Ictv, Inc. | Interactive home information system |
| US5883661A (en) | 1990-09-28 | 1999-03-16 | Ictv, Inc. | Output switching for load levelling across multiple service areas |
| US5594507A (en) * | 1990-09-28 | 1997-01-14 | Ictv, Inc. | Compressed digital overlay controller and method for MPEG type video signal |
| JP2938611B2 (en) * | 1991-05-14 | 1999-08-23 | 富士通株式会社 | TV signal exchange system |
| GB2256115B (en) * | 1991-05-16 | 1995-05-17 | Cabletime Ltd | Cable television |
| US6034678A (en) * | 1991-09-10 | 2000-03-07 | Ictv, Inc. | Cable television system with remote interactive processor |
| US5421030A (en) * | 1991-09-17 | 1995-05-30 | Com21, Inc. | Communications system and method for bi-directional communications between an upstream control facility and downstream user terminals |
| US5590366A (en) * | 1992-05-27 | 1996-12-31 | Digital Equipment Corporation | Packet forwarding system for measuring the age of data packets flowing through a computer network |
| ATE183352T1 (en) * | 1992-12-09 | 1999-08-15 | Discovery Communicat Inc | IMPROVED TOP-UP TERMINAL FOR CABLE TELEVISION DISTRIBUTION SYSTEMS |
| US20050114906A1 (en) * | 1993-05-03 | 2005-05-26 | Ictv, Inc. | System for interactive television |
| US6193520B1 (en) * | 1993-05-10 | 2001-02-27 | Yugengaisha Adachi International | Interactive communication system for communicating video game and karaoke software |
| IL106746A (en) * | 1993-08-19 | 1997-02-18 | News Datacom Ltd | CATV systems |
| US5481542A (en) * | 1993-11-10 | 1996-01-02 | Scientific-Atlanta, Inc. | Interactive information services control system |
| DE19508394A1 (en) * | 1995-03-09 | 1996-09-12 | Sel Alcatel Ag | Broadband communication system and method therefor |
| US5574495A (en) * | 1995-10-18 | 1996-11-12 | General Instrument Corporation | Cable television data path error analyzer located at the set-top terminal |
| US5715242A (en) * | 1995-12-20 | 1998-02-03 | Ortel; William C. G. | System for integrated distribution of switched voice and television on coaxial cable with phase distortion correction |
| US5999970A (en) * | 1996-04-10 | 1999-12-07 | World Gate Communications, Llc | Access system and method for providing interactive access to an information source through a television distribution system |
| US5893024A (en) * | 1996-08-13 | 1999-04-06 | Motorola, Inc. | Data communication apparatus and method thereof |
| US6166730A (en) * | 1997-12-03 | 2000-12-26 | Diva Systems Corporation | System for interactively distributing information services |
| US7069575B1 (en) | 1997-01-13 | 2006-06-27 | Sedna Patent Services, Llc | System for interactively distributing information services |
| US6305019B1 (en) | 1997-01-13 | 2001-10-16 | Diva Systems Corporation | System for interactively distributing information services having a remote video session manager |
| US6253375B1 (en) * | 1997-01-13 | 2001-06-26 | Diva Systems Corporation | System for interactively distributing information services |
| US5870134A (en) * | 1997-03-04 | 1999-02-09 | Com21, Inc. | CATV network and cable modem system having a wireless return path |
| US5986691A (en) * | 1997-12-15 | 1999-11-16 | Rockwell Semiconductor Systems, Inc. | Cable modem optimized for high-speed data transmission from the home to the cable head |
| US6889095B1 (en) * | 1998-06-11 | 2005-05-03 | Agilent Technologies, Inc. | Computer network adapted for industrial environments |
| US6519773B1 (en) * | 2000-02-08 | 2003-02-11 | Sherjil Ahmed | Method and apparatus for a digitized CATV network for bundled services |
| EP1224779B1 (en) * | 2000-06-20 | 2005-04-06 | Koninklijke Philips Electronics N.V. | Communication bus system |
| US20070011717A1 (en) * | 2005-07-06 | 2007-01-11 | Lauder Gary M | Distribution of interactive information content within a plurality of disparate distribution networks |
| US8074248B2 (en) | 2005-07-26 | 2011-12-06 | Activevideo Networks, Inc. | System and method for providing video content associated with a source image to a television in a communication network |
| US9294728B2 (en) * | 2006-01-10 | 2016-03-22 | Imagine Communications Corp. | System and method for routing content |
| US8180920B2 (en) * | 2006-10-13 | 2012-05-15 | Rgb Networks, Inc. | System and method for processing content |
| US9042454B2 (en) | 2007-01-12 | 2015-05-26 | Activevideo Networks, Inc. | Interactive encoded content system including object models for viewing on a remote device |
| US9826197B2 (en) | 2007-01-12 | 2017-11-21 | Activevideo Networks, Inc. | Providing television broadcasts over a managed network and interactive content over an unmanaged network to a client device |
| US8627509B2 (en) | 2007-07-02 | 2014-01-07 | Rgb Networks, Inc. | System and method for monitoring content |
| US7818355B2 (en) * | 2007-11-07 | 2010-10-19 | Mills Brendon W | System and method for managing content |
| US9473812B2 (en) | 2008-09-10 | 2016-10-18 | Imagine Communications Corp. | System and method for delivering content |
| WO2010045289A1 (en) * | 2008-10-14 | 2010-04-22 | Ripcode, Inc. | System and method for progressive delivery of transcoded media content |
| CN102301679A (en) | 2009-01-20 | 2011-12-28 | Rgb网络有限公司 | System and method for splicing media files |
| US9021541B2 (en) | 2010-10-14 | 2015-04-28 | Activevideo Networks, Inc. | Streaming digital video between video devices using a cable television system |
| US9204203B2 (en) | 2011-04-07 | 2015-12-01 | Activevideo Networks, Inc. | Reduction of latency in video distribution networks using adaptive bit rates |
| WO2013106390A1 (en) | 2012-01-09 | 2013-07-18 | Activevideo Networks, Inc. | Rendering of an interactive lean-backward user interface on a television |
| US9800945B2 (en) | 2012-04-03 | 2017-10-24 | Activevideo Networks, Inc. | Class-based intelligent multiplexing over unmanaged networks |
| US9123084B2 (en) | 2012-04-12 | 2015-09-01 | Activevideo Networks, Inc. | Graphical application integration with MPEG objects |
| US10275128B2 (en) | 2013-03-15 | 2019-04-30 | Activevideo Networks, Inc. | Multiple-mode system and method for providing user selectable video content |
| EP3005712A1 (en) | 2013-06-06 | 2016-04-13 | ActiveVideo Networks, Inc. | Overlay rendering of user interface onto source video |
| US9294785B2 (en) | 2013-06-06 | 2016-03-22 | Activevideo Networks, Inc. | System and method for exploiting scene graph information in construction of an encoded video sequence |
| US9219922B2 (en) | 2013-06-06 | 2015-12-22 | Activevideo Networks, Inc. | System and method for exploiting scene graph information in construction of an encoded video sequence |
| US9788029B2 (en) | 2014-04-25 | 2017-10-10 | Activevideo Networks, Inc. | Intelligent multiplexing using class-based, multi-dimensioned decision logic for managed networks |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3934079A (en) * | 1973-10-26 | 1976-01-20 | Jerrold Electronics Corporation | Bilateral communications system for distributing commerical and premium video signaling on an accountable basis |
| US4002843A (en) * | 1973-12-17 | 1977-01-11 | Rackman Michael I | Tamper-proof two-way cable system |
| FR2386211A1 (en) * | 1977-03-31 | 1978-10-27 | Europ Teletransmission | DIGITAL COMMUNICATION SYSTEM |
| NL189062C (en) * | 1980-02-15 | 1992-12-16 | Philips Nv | METHOD AND SYSTEM FOR TRANSFER OF DATA PACKAGES. |
| CA1158738A (en) * | 1980-04-30 | 1983-12-13 | Manitoba Telephone System (The) | Video and data distribution module with subscriber terminal |
| DE3022725A1 (en) * | 1980-06-18 | 1981-12-24 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | SERVICE INTEGRATED MESSAGE TRANSMISSION AND MEDIATION SYSTEM |
| JPS59123354A (en) * | 1982-12-29 | 1984-07-17 | Fujitsu Ltd | System for detecting and processing abnormal congestion |
-
1982
- 1982-04-29 US US06/373,048 patent/US4509073A/en not_active Expired - Lifetime
-
1984
- 1984-12-07 EP EP84114912A patent/EP0183871A1/en not_active Withdrawn
- 1984-12-10 JP JP59259436A patent/JPS61139141A/en active Pending
- 1984-12-11 CA CA000469853A patent/CA1218144A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4509073A (en) | 1985-04-02 |
| EP0183871A1 (en) | 1986-06-11 |
| JPS61139141A (en) | 1986-06-26 |
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