CA2106834C - Initializing terminals in a signal distribution system - Google Patents
Initializing terminals in a signal distribution systemInfo
- Publication number
- CA2106834C CA2106834C CA002106834A CA2106834A CA2106834C CA 2106834 C CA2106834 C CA 2106834C CA 002106834 A CA002106834 A CA 002106834A CA 2106834 A CA2106834 A CA 2106834A CA 2106834 C CA2106834 C CA 2106834C
- Authority
- CA
- Canada
- Prior art keywords
- address
- server
- newly
- uplink
- message
- 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 - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
- H04N21/81—Monomedia components thereof
- H04N21/8166—Monomedia components thereof involving executable data, e.g. software
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
- H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
- H04N21/235—Processing of additional data, e.g. scrambling of additional data or processing content descriptors
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
- H04N21/435—Processing of additional data, e.g. decrypting of additional data, reconstructing software from modules extracted from the transport stream
-
- 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
- H04N7/17309—Transmission or handling of upstream communications
- H04N7/17327—Transmission or handling of upstream communications with deferred transmission or handling of upstream communications
-
- 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
- H04N7/17363—Control of the passage of the selected programme at or near the user terminal
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- General Engineering & Computer Science (AREA)
- Software Systems (AREA)
- Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
- Small-Scale Networks (AREA)
- Data Exchanges In Wide-Area Networks (AREA)
Abstract
The invention relates to signal distribution systems, such as interactive cable television systems, wherein a central server communicates with remote terminals wherein the server assigns a specific address to each newly-connected terminal for control messages and polls. In the case of an interactive cable television system, such terminal is the set-top box or converter connected between the cable system and the television receiver. Periodically, the server broadcasts a control message containing a tentative address, and polls the tentative address. Upon receiving such a message, a newly-connected converter stores the tentative address and responds to the poll with an uplink message. After receiving the uplink message, the server inserts the tentative address in its polling list in accordance with the transmission delay measured from sending the poll to receiving the uplink message and selects a new tentative address to use in subsequent broadcast control messages. Uplink messages are echoed by the server and verified by the converter.
If the converter cannot verify an echoed uplink message, which can occur if morethan one newly-connected converter responds to the same broadcast control message, the converter repeats its initialization procedure to acquire a new address.
After the initialization is complete, system software can be downloaded from theserver to the converter and the converter placed in service.
If the converter cannot verify an echoed uplink message, which can occur if morethan one newly-connected converter responds to the same broadcast control message, the converter repeats its initialization procedure to acquire a new address.
After the initialization is complete, system software can be downloaded from theserver to the converter and the converter placed in service.
Description
21~8~
INITIALIZING TERMINALS IN A
SlGNAL DISTRIBUTION SYSTEM
T~-' ' ' Field This invention relates to signal distribution systems, such as inlela~livc;
5 cable television systems, and more particularly to methods and appara~us by which a terrninal connecled to such a system can be initi~li7Pd remotely to assign a specific address for control mescs~pls and polls and to download computer programs.
P~ . ' of the Invention Cable television systems have made possible the tn~n.cmi.c~ion of many 10 ch~m-Pl~ of television programs tO the homes of ~.,bs~ Instead of being limited to the number of VHF and UHF ch~ ~npl~ that can be l, r~ d and received in a given area, the number of c' ~ -Is in cable systems is limited only by the nWon chara~tPrictics of the cable itself and the ability to compress the info-m~ ior in television programs into r.al.ù~ bandwidth ~ -ls. The advent of 15 fiber-optic lli r~ j s:o~ systems for use in cable television nelwc,ll~ has also vastly h~ G&sed the number of ch~rnPl~ available.
Such increase in ch ~nnel~ has also given rise to proposals for interactive t~,lu~;;,ioll systems wherein a 5"b~ ~ .r can transmit infon~ ~ion or requests back into the system, which info~ or reguests may ~bse.~ tly affect programs or 20 lllr ~ o~ directed to such svbs ~iber. There are a wide variety of ~pp~ irJn~ for a -~ lel~,vis;oll systems, such as video games, video catalog shopping, ' ~ teaching systems, movies on demand and audio plu,gr~l~s. Each appl - -- can be tailored for an individual ~l,s~ - ;~., for example, a s~b~ ~ ;he~ may be able to select the l~ngl~agD~ of the ~ulldlra~ in a movie. However, such systems typically require -~ ~; 25 the ability (i) to control specific programs or hl[O~ ion sent to each ,,ubs~ and (ii) to receive input ~--P sC~ges or reguests from the suhsr-riher.
In many cable television systems, a special co~ ter is used at the .,bs~ location to allow the ~bsçrib~D,r to select among the various available channels, and possibly to "unscramble" premium ~ for which extra fees are 30 payable. Such converters usually provide an output on one of the .' - ---'- that a ~ -standard ~h,l,i;,ioll receiver can receive, such as Channel 3. More recently, t~ and video l-,colde.~ have been made available that are ''cable ready," that is, with the ability to receive and select among all the c transmitted ûver the cable system, but without the ability to un~rrpnlble p ~ .
, . . .
., ,,. ' ~ ~ ,,. ,, :".
~o~
channels. A converter is still needed for the premium channels.
In order to implement many of the features of hlteld.,~ television systems, it is necessa.~ for mess~g~s col-t~ g information or requests from subscribers to be transmitted to a central control location. It is desirable for these S "uplink" mec~qgçs to be Llarsl~ ed from subscribers over the same facility used to distribute programs. Conventional cable systems use frequencies above 50 MHz, ~11oc?ted in 6 MHz distribution chqnn~1s, for programs and frequencies in the 5 - 30 MHz band for such uplink m~.ss~es, However, because many subscribers will be sending m~s~oges over the same uplink r~ c-~cies, some means is needed to 10 coordinate such 1~r55~es tO prevent inte.relence and to identify the source of each mP.S~
When a subscriber is first conne~d to a cable television system with cGn.e.~,~ at subscriher locations, it is typically necessa.y for a service 1ecl.nician to install and initiqli7P a convel le~ for such subscriber in the field. Also, a visit by a 15 techni~ may be needed to re-ini~iqli7-p a converter after a service il.l~ lion or a power failure. Such visits can be costly. Accol.lingly, it is desirable to provide a col~ellel that can be ini~iq1i7Pd remotely over the cable system so that such a co~ t~ can be f~ l.ed to a ;,-~l,s~ ~ iber for self-in.ct-q~ tion and for remoteinit;~li7. ~ion or re-in~ 7-q-tion.
- 20 Summary of the l ~
One or more ~ '- in a multi-channel cable television distribution system are used for the l~ c-:on of interactive television (ITV) signals in the form of pe -~- ~; d digital inrol.nation from a server at the cable system headend to c- ~ at ~.Jbsc~ OC?tion~ Each CO.. Vt;lt~,r contains a receiver for ITV ~ -25 signals and is e~ tPd between the cable system and the subsçribçr's television receiver. Packets in the ITV signals are iderltifi-P,d as belonging to virtual ch ~- ne1c At least one virtual channel is used for control n~P~ gP~s~ which are read by each con.e.t~,l, and Con~e.lt~l~ are enabled by control l--fsC~ges to receive one or more a~d;~;r ~ virtual ~h~ ~n~ in one of the lTV cl'~r'nP-l~. Each packet trarl~llli1t~,d also 30 includes a polling address that causes an uplink message to be l~ s-..ill~d back into ~ -the cable system by the polled con.~ . The po11ing addresses are polled in an order determined by the distance from the cable- system head end to ~l~b~ ~ ;be~s, as l.e&s~,d by 1~ s:on delay, so that the nearest snbscril~Pr is polled first.
~ ,"
~; ~ ,, .
,.. ... . .. . . . .. . . . . .
The specific address of a converter is set remotely during an initialization sequence that occurs, for example, when the converter is first installed or when power is restored after an outage. Periodically, the server at the cable head end broadcasts a control message cont~ining a tentative address and then polls that address, followed by at least one 5 poll to a null address. On receipt of such a control message, a newly-connected converter stores the tentative address as its specific address and responds to such poll with an uplink message. On receipt of the uplink message, the server inserts the tentative address in its polling list in accordance with the tr~n~mi~ion delay measured from sending the poll to receiving the uplink message and selects a new tentative address to use in subsequent 10 broadcast control messages. Uplink messages from the converter are echoed by the server and verified by the converter. If the converter cannot verify an echoed uplink message, which can occur if more than one newly-connected converter responds to the same broadcast control message, the converter restarts its initialization sequence after receiving a randomly-chosen number of broadcast control messages, thus increasing the likelihood that 15 only one converter will respond to the same broadcast control message. The initialization software is loaded in ROM in the converter. After a successful initialization, system soft~,vare can be downloaded from the server into RAM in the converter and the converter is placed in service.
In accordance with one aspect of the present invention there is provided in a 20 signal distribution system having a server and a plurality of termin~ls, each said terminal having a specified address for responding to polls and receiving control messages and wherein each said terminal responds to each poll with an uplink message to said server, a method of remotely ~signing said specified addresses to newly-connected termin~ls, characterized by in said server: storing said specified addresses in a polling list and 25 repeatedly polling said terminals in accordance with said polling list; and periodically broa~lc:l~ting a control message co.~ g a tentative address to all said terminals followed by polling said tentative address; in a newly-connected terminal: receiving one of said broadcast control messages, storing the tentative address contained in said broadcast control message as the specified address for said tçrmin~l and, in response to a poll to said 30 tentative address, sending an initial uplink message to said server; in said server: in response to said initial uplink message, inserting said tentative address in said polling list as the specified address for said newly-connected terminal, selecting a new tentative address for use in subsequent broadcast control messages, periodically polling said specified address, receiving additional uplink messages from said newly-connected terminal - 3a-and echoing at least one of said uplink messages in at least one additional control message addressed to said specified address, in said newly-connected terminal: comparing at least one character from said echoed uplink messages in said additional control messages with the corresponding at least one character in the uplink messages sent and, if said comparison reveals a difference, repeating said receiving step to acquire a different tentative address for use as the specified address of said terminal.
In accordance with another aspect of the present invention there is provided in a signal distribution system having a server and a plurality of termin~ , each said terminal having a specified address for responding to polls and receiving control messages from said server and wherein each said terminal responds to each poll with an uplink message to said server, a method of remotely assigning said specified addresses to newly-connected termin~lc, characterized by repeatedly polling said specified addresses, periodically sending a tentative address from said server to all said terminals and polling said tentative address, in a newly-connected termin~l, receiving and storing said tentative address as the specified address for said terminal and sending an initial uplink message in response to said tentative-address poll, in said server, on receipt of said uplink message, including said tentative address as a specified address, choosing a new tentative address and echoing at least one uplink message to said newly-connected terminal, in said newly-connected t~rmin~l, colllpalillg at least one echoed uplink message with the uplink message as sent, and if such messages are different, repeating said receiving and storing step to acquire a different specified address.
Brief De~ lion of the Drawings FIG. 1 is a schem~tic block diagram of a cable television system adapted for use by an interactive television system.
FIG. 2 is a block diagram of a converter in accordance with the invention for use at subscriber locations of an interactive television system.
FIG. 3 is a flow chart showing the operation of controller 214 in FIG. 2 upon receipt of a packet of information from the cable system.
FIG. 4 is a flow chart showing the operation of server 120 in FIG. 1 during initialization of a converter.
FIG. 5 is a flow chart showing the operation of a converter 200 in FIG. 2 during initialization.
INITIALIZING TERMINALS IN A
SlGNAL DISTRIBUTION SYSTEM
T~-' ' ' Field This invention relates to signal distribution systems, such as inlela~livc;
5 cable television systems, and more particularly to methods and appara~us by which a terrninal connecled to such a system can be initi~li7Pd remotely to assign a specific address for control mescs~pls and polls and to download computer programs.
P~ . ' of the Invention Cable television systems have made possible the tn~n.cmi.c~ion of many 10 ch~m-Pl~ of television programs tO the homes of ~.,bs~ Instead of being limited to the number of VHF and UHF ch~ ~npl~ that can be l, r~ d and received in a given area, the number of c' ~ -Is in cable systems is limited only by the nWon chara~tPrictics of the cable itself and the ability to compress the info-m~ ior in television programs into r.al.ù~ bandwidth ~ -ls. The advent of 15 fiber-optic lli r~ j s:o~ systems for use in cable television nelwc,ll~ has also vastly h~ G&sed the number of ch~rnPl~ available.
Such increase in ch ~nnel~ has also given rise to proposals for interactive t~,lu~;;,ioll systems wherein a 5"b~ ~ .r can transmit infon~ ~ion or requests back into the system, which info~ or reguests may ~bse.~ tly affect programs or 20 lllr ~ o~ directed to such svbs ~iber. There are a wide variety of ~pp~ irJn~ for a -~ lel~,vis;oll systems, such as video games, video catalog shopping, ' ~ teaching systems, movies on demand and audio plu,gr~l~s. Each appl - -- can be tailored for an individual ~l,s~ - ;~., for example, a s~b~ ~ ;he~ may be able to select the l~ngl~agD~ of the ~ulldlra~ in a movie. However, such systems typically require -~ ~; 25 the ability (i) to control specific programs or hl[O~ ion sent to each ,,ubs~ and (ii) to receive input ~--P sC~ges or reguests from the suhsr-riher.
In many cable television systems, a special co~ ter is used at the .,bs~ location to allow the ~bsçrib~D,r to select among the various available channels, and possibly to "unscramble" premium ~ for which extra fees are 30 payable. Such converters usually provide an output on one of the .' - ---'- that a ~ -standard ~h,l,i;,ioll receiver can receive, such as Channel 3. More recently, t~ and video l-,colde.~ have been made available that are ''cable ready," that is, with the ability to receive and select among all the c transmitted ûver the cable system, but without the ability to un~rrpnlble p ~ .
, . . .
., ,,. ' ~ ~ ,,. ,, :".
~o~
channels. A converter is still needed for the premium channels.
In order to implement many of the features of hlteld.,~ television systems, it is necessa.~ for mess~g~s col-t~ g information or requests from subscribers to be transmitted to a central control location. It is desirable for these S "uplink" mec~qgçs to be Llarsl~ ed from subscribers over the same facility used to distribute programs. Conventional cable systems use frequencies above 50 MHz, ~11oc?ted in 6 MHz distribution chqnn~1s, for programs and frequencies in the 5 - 30 MHz band for such uplink m~.ss~es, However, because many subscribers will be sending m~s~oges over the same uplink r~ c-~cies, some means is needed to 10 coordinate such 1~r55~es tO prevent inte.relence and to identify the source of each mP.S~
When a subscriber is first conne~d to a cable television system with cGn.e.~,~ at subscriher locations, it is typically necessa.y for a service 1ecl.nician to install and initiqli7P a convel le~ for such subscriber in the field. Also, a visit by a 15 techni~ may be needed to re-ini~iqli7-p a converter after a service il.l~ lion or a power failure. Such visits can be costly. Accol.lingly, it is desirable to provide a col~ellel that can be ini~iq1i7Pd remotely over the cable system so that such a co~ t~ can be f~ l.ed to a ;,-~l,s~ ~ iber for self-in.ct-q~ tion and for remoteinit;~li7. ~ion or re-in~ 7-q-tion.
- 20 Summary of the l ~
One or more ~ '- in a multi-channel cable television distribution system are used for the l~ c-:on of interactive television (ITV) signals in the form of pe -~- ~; d digital inrol.nation from a server at the cable system headend to c- ~ at ~.Jbsc~ OC?tion~ Each CO.. Vt;lt~,r contains a receiver for ITV ~ -25 signals and is e~ tPd between the cable system and the subsçribçr's television receiver. Packets in the ITV signals are iderltifi-P,d as belonging to virtual ch ~- ne1c At least one virtual channel is used for control n~P~ gP~s~ which are read by each con.e.t~,l, and Con~e.lt~l~ are enabled by control l--fsC~ges to receive one or more a~d;~;r ~ virtual ~h~ ~n~ in one of the lTV cl'~r'nP-l~. Each packet trarl~llli1t~,d also 30 includes a polling address that causes an uplink message to be l~ s-..ill~d back into ~ -the cable system by the polled con.~ . The po11ing addresses are polled in an order determined by the distance from the cable- system head end to ~l~b~ ~ ;be~s, as l.e&s~,d by 1~ s:on delay, so that the nearest snbscril~Pr is polled first.
~ ,"
~; ~ ,, .
,.. ... . .. . . . .. . . . . .
The specific address of a converter is set remotely during an initialization sequence that occurs, for example, when the converter is first installed or when power is restored after an outage. Periodically, the server at the cable head end broadcasts a control message cont~ining a tentative address and then polls that address, followed by at least one 5 poll to a null address. On receipt of such a control message, a newly-connected converter stores the tentative address as its specific address and responds to such poll with an uplink message. On receipt of the uplink message, the server inserts the tentative address in its polling list in accordance with the tr~n~mi~ion delay measured from sending the poll to receiving the uplink message and selects a new tentative address to use in subsequent 10 broadcast control messages. Uplink messages from the converter are echoed by the server and verified by the converter. If the converter cannot verify an echoed uplink message, which can occur if more than one newly-connected converter responds to the same broadcast control message, the converter restarts its initialization sequence after receiving a randomly-chosen number of broadcast control messages, thus increasing the likelihood that 15 only one converter will respond to the same broadcast control message. The initialization software is loaded in ROM in the converter. After a successful initialization, system soft~,vare can be downloaded from the server into RAM in the converter and the converter is placed in service.
In accordance with one aspect of the present invention there is provided in a 20 signal distribution system having a server and a plurality of termin~ls, each said terminal having a specified address for responding to polls and receiving control messages and wherein each said terminal responds to each poll with an uplink message to said server, a method of remotely ~signing said specified addresses to newly-connected termin~ls, characterized by in said server: storing said specified addresses in a polling list and 25 repeatedly polling said terminals in accordance with said polling list; and periodically broa~lc:l~ting a control message co.~ g a tentative address to all said terminals followed by polling said tentative address; in a newly-connected terminal: receiving one of said broadcast control messages, storing the tentative address contained in said broadcast control message as the specified address for said tçrmin~l and, in response to a poll to said 30 tentative address, sending an initial uplink message to said server; in said server: in response to said initial uplink message, inserting said tentative address in said polling list as the specified address for said newly-connected terminal, selecting a new tentative address for use in subsequent broadcast control messages, periodically polling said specified address, receiving additional uplink messages from said newly-connected terminal - 3a-and echoing at least one of said uplink messages in at least one additional control message addressed to said specified address, in said newly-connected terminal: comparing at least one character from said echoed uplink messages in said additional control messages with the corresponding at least one character in the uplink messages sent and, if said comparison reveals a difference, repeating said receiving step to acquire a different tentative address for use as the specified address of said terminal.
In accordance with another aspect of the present invention there is provided in a signal distribution system having a server and a plurality of termin~ , each said terminal having a specified address for responding to polls and receiving control messages from said server and wherein each said terminal responds to each poll with an uplink message to said server, a method of remotely assigning said specified addresses to newly-connected termin~lc, characterized by repeatedly polling said specified addresses, periodically sending a tentative address from said server to all said terminals and polling said tentative address, in a newly-connected termin~l, receiving and storing said tentative address as the specified address for said terminal and sending an initial uplink message in response to said tentative-address poll, in said server, on receipt of said uplink message, including said tentative address as a specified address, choosing a new tentative address and echoing at least one uplink message to said newly-connected terminal, in said newly-connected t~rmin~l, colllpalillg at least one echoed uplink message with the uplink message as sent, and if such messages are different, repeating said receiving and storing step to acquire a different specified address.
Brief De~ lion of the Drawings FIG. 1 is a schem~tic block diagram of a cable television system adapted for use by an interactive television system.
FIG. 2 is a block diagram of a converter in accordance with the invention for use at subscriber locations of an interactive television system.
FIG. 3 is a flow chart showing the operation of controller 214 in FIG. 2 upon receipt of a packet of information from the cable system.
FIG. 4 is a flow chart showing the operation of server 120 in FIG. 1 during initialization of a converter.
FIG. 5 is a flow chart showing the operation of a converter 200 in FIG. 2 during initialization.
2.1Q~3~
Detailed Description The invention will be described in the context of an hlle-~.clive cable television system in which a central server at the cable headend communicates with converters at subscriber locations. However, it will be clear to those skilled in the art 5 that the invention can be used in other signal distribution systems in which a central server communicates with remote terminals.
FIG. 1 is a schen~tic block diagram of a cable television system adapted for use as an h.t~ .clive television system in accordance with the invention. A
typical cable television system co~ ,.ises headend equipment 101 at a central 10 location, a distribution network consisting of various feeders 102 and branches 103 and connections to subscriber locations such as 104, where conveIlel~ and television e-~ieivels (or cable-ready television receivers alone) receive the signals from the distribution network. Feeders 102 and b-~;cl-cs 103 can be coaxial cable, optical Sber cable, combinations of the two or other e~lui~..lent means. In a typical cable 15 tcle~ision system, various television programs are fed into the different ch~nnP1Q of the system by headend e~lu.F - 101. Such programs may be received from local ~adc~ts by broadc&~l Iticeive-~ 110, from co- ... ~ tions satellites by satellite ceiv~,~ 111 or directly from local sources 112.
Intc.u~li.c television (ITV) subscribers are served via dçdicated 20 ~ of the cable t,l~ ision system &om lTV server 120. Server 120 obtains its p.o~ g material from such sources as progI~ uing center 121 or program - --library 122. Program library 122 contains stored versions of movies, musical SP~ l;o-~&, texts, pictorial information and other materials that may be acc~Ps~d by lTV svbsrr1h-Prs F'~o~,. ..~--;n~ center 121 may be a direct source of program 25 material for server 120 or may prepare such material for library 122.
ITV server 120, pl~ lling center 121 and program library 122 may be at the sa ne or different loc~ ~jon~ and may themselves be connPctPd in nel~.oIh.
There can be multiple servers 120 for different cable systems. Program library 122 may consist of a number of libraries at different loc~ n~ However, there will 30 typically be a server 120 ded;r~Pd to a particu1ar cable system to interact with the on that system's di;~tli~ulion network.
There are a wide variety of possible confi~llration~ for server 120, all of which will typically include at least one central pI~cessor to control programs and - other information trar. -.. il~d to subscribP,rs 104 over the ~Pdi~ ~ ITV ~c~ '~ in 35 the cable system and to receive and respond to uplink mpssD~ps from s.~bs~
104. ,, ~ . - . ... .. .. , . - ... . .. .- ... , . , .. .. ,.. ..... , . .. ... ~ , . . . . . . . . .
2~,n~J~
Using well-known compression tPchni-lues, a number of full-motion television signals can be tran~mit~Pd in panlfeti7~d form over a cable channel in a cable television system. For example, a full-motion NTSC television signal can be compressed and digitized for transmission at 1.5 Mbits/second. By p -rl~Pli7ing such 5 digital information and interleaving such packets, it is possible that as many as 16 such television signals (24 Mbits/second) can be sent via virtual ch~nn~ over a standard 6MHz cable channel. If a lower bandwidth signal (such as an audio signal) is to be sent over a virtual channel, fewer packets need be L~nc,.~ d for such channel per unit of time.
A typical packet consists of two bytes for a polling address, two bytes ide.ltify;ng the virtual channel of which the packet is a part and 48 data bytes. The data bytes contain the colllp~ sed video, audio or other infonnation being transmitted in the virtual channel. At least one virtua1 channel (for e~mrlP, channel 00) is reserved for control l,,Pss~g~s The data bytes in a typical control message 15 include a field cG~ l-g the address of the converter for which the message isd a field idenlify;ng the virtual channel to which the message relates, a field spccirying the kind of data to be ~ lPd on such virtual channel (i.e. still pictures, full motion television, stereo audio, text) and other control inform~tion Control n~ a~s are also used to ini~igli7~ con~ as will be desnribed in more 20 detail below.
FIG. 2 is a block diagram of a converter 200 for cor~nPction between a cable system and a bcl~is;oll receiver at a subscriher~s PlGIIIiSeS. Input cable 202 is typically a coaxial cable or an optical- fiber cable cc ~ i to the cable ~i~tribution system. Cable 202 is connf~t~ d to inputs of band-stop filter 204, selPct~lc channel 25 receiver 206 and lTV channel receiver 208 and to the output of uplink modulator 210. Cable 202 is part of an input circuit that also contajns any amrlification and f.,. i ~ circuits (not shown) needed to connect the cable system to filter 204, 206 and 208 and modulator 210. Such amplificntion and l,.~ g circuits are well known to those skilled in the art.
lTV channel receiver 208 is tuned to receive the cable channel over which the p~ n ~; ~d digital .nfo..,~at;o~ for the h.~ , television features is being t ~~ni~od The actual cable channel or ch~~n~l$ used for such purpose are ~ign~d by the ,-~ t~ldlOl~ of the cable system. If more than one such channel isprovided, one of the c~- ~~'s is usually considered the "default" channel, which is 35 the channel used to jn;tjsli~ co.l~en~ such as co--~,vn~,- 200. Upon initialization, a con~_~. can be transferred to a different lTV channel by means of a control , - ,' .
Detailed Description The invention will be described in the context of an hlle-~.clive cable television system in which a central server at the cable headend communicates with converters at subscriber locations. However, it will be clear to those skilled in the art 5 that the invention can be used in other signal distribution systems in which a central server communicates with remote terminals.
FIG. 1 is a schen~tic block diagram of a cable television system adapted for use as an h.t~ .clive television system in accordance with the invention. A
typical cable television system co~ ,.ises headend equipment 101 at a central 10 location, a distribution network consisting of various feeders 102 and branches 103 and connections to subscriber locations such as 104, where conveIlel~ and television e-~ieivels (or cable-ready television receivers alone) receive the signals from the distribution network. Feeders 102 and b-~;cl-cs 103 can be coaxial cable, optical Sber cable, combinations of the two or other e~lui~..lent means. In a typical cable 15 tcle~ision system, various television programs are fed into the different ch~nnP1Q of the system by headend e~lu.F - 101. Such programs may be received from local ~adc~ts by broadc&~l Iticeive-~ 110, from co- ... ~ tions satellites by satellite ceiv~,~ 111 or directly from local sources 112.
Intc.u~li.c television (ITV) subscribers are served via dçdicated 20 ~ of the cable t,l~ ision system &om lTV server 120. Server 120 obtains its p.o~ g material from such sources as progI~ uing center 121 or program - --library 122. Program library 122 contains stored versions of movies, musical SP~ l;o-~&, texts, pictorial information and other materials that may be acc~Ps~d by lTV svbsrr1h-Prs F'~o~,. ..~--;n~ center 121 may be a direct source of program 25 material for server 120 or may prepare such material for library 122.
ITV server 120, pl~ lling center 121 and program library 122 may be at the sa ne or different loc~ ~jon~ and may themselves be connPctPd in nel~.oIh.
There can be multiple servers 120 for different cable systems. Program library 122 may consist of a number of libraries at different loc~ n~ However, there will 30 typically be a server 120 ded;r~Pd to a particu1ar cable system to interact with the on that system's di;~tli~ulion network.
There are a wide variety of possible confi~llration~ for server 120, all of which will typically include at least one central pI~cessor to control programs and - other information trar. -.. il~d to subscribP,rs 104 over the ~Pdi~ ~ ITV ~c~ '~ in 35 the cable system and to receive and respond to uplink mpssD~ps from s.~bs~
104. ,, ~ . - . ... .. .. , . - ... . .. .- ... , . , .. .. ,.. ..... , . .. ... ~ , . . . . . . . . .
2~,n~J~
Using well-known compression tPchni-lues, a number of full-motion television signals can be tran~mit~Pd in panlfeti7~d form over a cable channel in a cable television system. For example, a full-motion NTSC television signal can be compressed and digitized for transmission at 1.5 Mbits/second. By p -rl~Pli7ing such 5 digital information and interleaving such packets, it is possible that as many as 16 such television signals (24 Mbits/second) can be sent via virtual ch~nn~ over a standard 6MHz cable channel. If a lower bandwidth signal (such as an audio signal) is to be sent over a virtual channel, fewer packets need be L~nc,.~ d for such channel per unit of time.
A typical packet consists of two bytes for a polling address, two bytes ide.ltify;ng the virtual channel of which the packet is a part and 48 data bytes. The data bytes contain the colllp~ sed video, audio or other infonnation being transmitted in the virtual channel. At least one virtua1 channel (for e~mrlP, channel 00) is reserved for control l,,Pss~g~s The data bytes in a typical control message 15 include a field cG~ l-g the address of the converter for which the message isd a field idenlify;ng the virtual channel to which the message relates, a field spccirying the kind of data to be ~ lPd on such virtual channel (i.e. still pictures, full motion television, stereo audio, text) and other control inform~tion Control n~ a~s are also used to ini~igli7~ con~ as will be desnribed in more 20 detail below.
FIG. 2 is a block diagram of a converter 200 for cor~nPction between a cable system and a bcl~is;oll receiver at a subscriher~s PlGIIIiSeS. Input cable 202 is typically a coaxial cable or an optical- fiber cable cc ~ i to the cable ~i~tribution system. Cable 202 is connf~t~ d to inputs of band-stop filter 204, selPct~lc channel 25 receiver 206 and lTV channel receiver 208 and to the output of uplink modulator 210. Cable 202 is part of an input circuit that also contajns any amrlification and f.,. i ~ circuits (not shown) needed to connect the cable system to filter 204, 206 and 208 and modulator 210. Such amplificntion and l,.~ g circuits are well known to those skilled in the art.
lTV channel receiver 208 is tuned to receive the cable channel over which the p~ n ~; ~d digital .nfo..,~at;o~ for the h.~ , television features is being t ~~ni~od The actual cable channel or ch~~n~l$ used for such purpose are ~ign~d by the ,-~ t~ldlOl~ of the cable system. If more than one such channel isprovided, one of the c~- ~~'s is usually considered the "default" channel, which is 35 the channel used to jn;tjsli~ co.l~en~ such as co--~,vn~,- 200. Upon initialization, a con~_~. can be transferred to a different lTV channel by means of a control , - ,' .
message. The output of tuner 208 is a digital bit stream comprising the p~l'Pti~Pd digital information, which is forwarded to controller 214.
Controller 214 performs many functions and is typically a n~ic~opl(,cessor with both random-access memory (RAM) and read-only memory 5 (ROM). Controller 214 sends control and video information to combiner 216, sends eontrol mes~g~ps to receivers 206 and 208 specifying the identity of ch~lnPl~ to be received, receives manual inputs from manual input devices 218, sends video packets to decoder 21S and audio packets to decoder 216, and l.~ns.lliLs information to the cable headend via uplink modulator 210. Controller 214 ean also be a source 10 of audio and/or video inforrn~tion Such information can be retrieved from memory in controller 214 or generated by computer programs in controller 214 under the control of m~ssqg~ps from receiver 208 or input devices 218. Examples of such inforn~tion are symbols or text to be superimposed on video signals or ~ d sounds to be combined with audio signals.
ln a typical cable system, uplink ".~ cc~,v s are sent in the 5 - 30 MHz band. If desired, uplink .~- c~ v s can also be sent over more than one uplink channel in this range, with the particular channel to be used by a particular CC)..
200 being ~speçifiPd to uplink modu1ator 210 by controller 214 in response to a eontrol message from server 120. Uplink ch~~nP~ will typically have a bandwidth 20 in the range from 100,000KHz to lMHz.
l~ecodPr~ 215 and 216 can also be Illicroplocessol~, such as digital signal processo,~, SpPCifi~ y pl'Og~ d to decode compressed video or audio - in~.. ~ ~;on, as the case may be, in acco~ e with the appl~,pliate decoding~lgQrithm~ as is well known in the art. Other output devices 220 capable of leceiving 25 digital inrO. " ~tjon sueh as a printer, can be co~nr~,ted to eontroller 214 as desired.
The output of selc.,lol/co--lbiner 217 is a tclevisioll signal, the eomponents of whieh ean be either (i) selected from one of a number of sourees, sueh as reeeiver 206, eontroller 214, deeoder 215 or deeoder 216 or (ii) comhin~d from sueh sourees. In its simplest form, ~Icclol/col.lbiner 217 forwards to ~: 30 mod ~ ~ 222 either the television signal reeeived by receiver 206 or the telev s - -signal obtained by eombining video deeoded by deeoder 215 with audio decoded by decoder 216. Other versions of sclc~ eo..,biner 217 ean inelude app~tus eontrolled by eontroller 214 to eombine various video and audio sourees into thet~,h,~,i;,ion signal to be trans...ilted to mo~ - - 222. Many tec~ es are known in 35 the art for COm~inill~ video sources, sueh as overlays, windows and split sereens.
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210~3~
Selector/combiner 217 operates on digital lep-esel~ldtions of video signals in which each pixel of a scene is ~eplcse~,~d by a.number of bits and ondigital l~p~en~ on~ of audio signals in which sounds are ~epr"sellt~d by digitized samples. The outputs of decoder 215, decoder 216 and any audio and video outputs5 from controller 214 are in digital form; also, the video portion of the television signal from receiver 206 is converted to digital form in convel ling apparatus (not shown). Such collvelling apparatus is well known in the art. These digidzed video and audio elPment~ are combined in selector/combiner 217 to produce a se~lucnce of digital frames and digital audio samples (possibly for more than one audio channel).
10 These samples are then converted to a conventional television signal, such as an NSTC signal, by appald~us (not shown) also well known in the art.
Band stop filter 204 deletes at least one of the ITV channels, p,~felably the default channel, from the signal received from cable 202, passing the rPm~ining c~ to output cable 230. Modulator 222 modulates the television signal 15 received from selcclo./co,l,biner 217 into one of the blocked lTV çh~nnPl~ on output cable 230. Thus, conv~l~. 200 replaces the pac~t;,~d digital signal received from the cable system in such ITV channel with the video signal from sele.;lor/colllbiner 217. Such ITV channel can then be selected and viewed in the conventional way ona cable-ready television receiver col-nec~ed to output cable 230. As descnbed above, 20 the television signal n~ocl~ into such ITV channel can be produced from ITV
packets received over any of the lTV ~' --'-FIG. 3 is a flow chart showing the overall ope.dtion of controller 214 onreceipt of packets from receiver 208. If the "virtual channel" bytes indicate that suchpacket is a control message, (block 302) and the address field in the control message 25 indicate that the message is intended for con~ 200 (block 304), then controller 214 pf" r,..--~ the control function specified by the .~ g contents of the message (block 306). If the "virtual channel" bytes indicate that such packet is part of a program channel, such as a channel carrying an encoded and digitized video signal, - -and controller 214 is ~ tly enabled to receive from such channel (block 308), 30 then controller 214 plucei~s the packet contents in accor~ - e with the type of ; program in such virtual channel (block 310), sending data from the packet to the input buffer in the app~pliate output device, such as decoder 215 or decoder 216.
Each packet in which the "polling address" bytes indicate that c~ tel 200 is being polled (block 312) causes such co~ ,.tel to transmit an uplink message 35 to the cable headend (block 314). (The address in the "polling address" bytes is not necessarily the same as in the address field in a control message that may be included . ~ ' .
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.. : , . . . .. . . . . . ..
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in the same packet). This uplink mf~s~g~ typically no more than a few bytes, cancontain control information or information entered manually by the subscriber in one of manual input devices 218. Because this message is initiated by a downlink message (from the headend to the subscriber) having an address known at the S headencl this address can be associated with the uplink message when received, and there is no need to identify the source of uplink mes~ges.
As mentioned above, controller 214 can contain both RAM and ROM.
The ROM includes co~ ul~ programs that can be pÇnn~lently loaded, such as programs con~ining initi~li7~tion routines; whereas the RAM can be downloaded 10 from the headend by the use of control messages. Such downloading will typically occur when a converter is first connPc~ed to the cable system or when programs must be updated. Also, different progMms for different pul~oses can be downloaded in controller 214 at different times. Such downloading capability ~1;,.,in t s the need for program-loading capabilities at converter 200, although such capability cou1d be 15 provided if desired by means of devices such as a disk drive.
FIG. 4 is a flow chart showing the polling seque-nce followed by server 120 in FIG. 1. As desç~ihed above, each packet sent by server 120 to conv~ 200at ;,.~ r loca~ion~ 104 contains a polling address, and server 120 receives uplink messages from co~ t~rs polled. If more than one disllibulion channel is used as an 20 ITV channel, such polling ~u~,nce is used for the "default" ITV channel.
Server 120 ~ polling addresses in successivti packets, preferably in accold -: with an ordered list, the order being d~ t~ ed by the relative res of the con~ from the cable- system headend (block 401). The first address on the list is that of the closest ccn~ t~,~ to the headend as measured by 25 ~ n time; the last address on the list is that of the farthest collv~rt~,r. This p.~e~lu.t; avoids possible inte.l~ among uplink .~ s~ge s sent in ~sponse to polls. The position of an address in the ordered list is delel-nined during ;o-~ as will be deserihed below. Server 120 I..~inl~;nc such an ordered list for the default ITV channel and each other lTV channel that may be in service in the 30 system.
After all the add~s~s in the ordered list have been polled, plefe.dbly at least one packet is sent with a null (I~O~ g) polling addresses (b1Ock 402), thereby insc.lin& enough delay in the polling se~.,enf,e for the ~esponse to the last ~ ~ poll in the ordered list to be received from the farthest ccll~elt~,. before the ordered - ~ ~ 35 list is polled again (block 402). The co~ are programmed to respond to every poll with an uplink mP.QQagP. If such a l~sponse is missing (block 403), server 120 ': ' ' .:
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21 0~3~
determines whether or not to continue polling the unresponsive converter (block 404), as will be explained in more detail below.
Each converter 200 interprets at least the address portion of all control meSS~geS to identify me.~.c~geS intended for such converter. However, some special 5 control mess~gç~s are not addressed to specific converters. For example, periodically (such as once per minute) a special control message is broadcast over the virtual channel used for control signals in the default channel. This special control message is not addressed to a specific converter, but contains a tentative address for use by any newly-connected converter. If such a message ha~s been sent during the last 10 polling se.luence (block 405) such tentative address is polled (block 406), again followed by enough polls to a null address to permit a response from the farthest con~ el (block 407). Because the position of a new converter is not known initially, these null polls insure that a response from a new converter will be received before those from the next iteration of the ordered list.
As will be expl~ined in more detail below in conjunction with the description of FIG. 5, a newly-connP.ctPd converter operates under an initi~li7~tion program stored in ROM in the converter. Such init;~li7.:~tion program stores thetentative address from such a broadcast control message as its specified address for responding to polls and for receiving control m~ ges and responds to a subsequent 20 poll of such specifi~d address with an uplink m~scage If an uplink message is received in response to a poll of the tentative address (block 408), in(iin~ling that there is a newly- conn~ct~d converter, thetentative address is stored in the ordered list (block 409) and a new tentative address is selected for ;,.,bse.l-,e~ tentative-address mes~ag~s, To dPle~ ."in.5 the place of 25 such address in the ordered list, server 120 measures the elapsed L~ ;on time from polling the tentative address in block 406 to receiving the resulting uplink n~QqBe Finally, a dialogue is conduc~ed with the newly-connPctPd convt;lt~l (block 410) con~:sl ;~g of control m~ s sent by server 120 to the con~c~ ~1 using the tentative address stored in the ordered list and uplink mPcs~ges evoked by polls 30 to such address pu~ to block 401. If no l,,.,ponse is received to the poll of the tentative address, in~linating that no new converter has been co~ e.le~l then server 120 returns to block 401 and repeats the endre polling sequence - During the dialogue in~ ted by block 410, a newly-colllu(l~ d CO-.~ l typically will send information to identify itself in uplink mess~ges 35 responding to such tentative-address polls. Such inforrn~ion can be stored in ROM
in the con~el~., such as a unique serial number assigned to the converter, or be .. . : .
-; . , . . . ......................... ~
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entered manually by the person in.ct;~lling ~he converter. Some examples of suchmanually entered information are subscribers' personal identification numbers, types of service desired and billing addresses. In case of manually-entered information, control mçcQsgPs sent by server 120 can cause an appropriate request for such 5 information to appear on the screen of a television receiver connected to the co-~ve. ler.
If desired, server 120 can conduct the initi~li7~tion dialogue over a different virtual channel than the virtual channel in the default ITV channel over which the tentative address is broadcast. Such different virtual channel can also be in 10 the default ITV channel or, if there is more than one ITV channel in use in the system, in a different ITV channel. The server initiates such a channel change by tranC~nitting applupliatc contro1 mPc~Ps to the newly-conmPc~Pd collv~llel 200 to enable such con~e~ to respond to control mpcsag~ps in the new channel. Similarly, if more than one uplink channel is provided, one uplink channel can be used as a15 "default" uplink channel for ~~,~pons~s to polls in the "default" ITV channel, and con-c.le. 200 can be caused to transmit over a different uplink channel by an applvpliate control message from server 120.
Preferably, a con~c.t~,l always responds with an uplink message to a poll to its srAcifiPd address, even though it may have no information to send. A dummy 20 uplink message can be used in such cases. For eY~~rle, in sitv~ion~ where i.,rO.. ~;0~ is being entered manuaily for l.~ - by a CO..~,lt~,., there may be a number of polls occ~ g before and during such transmission when there is no inr~" ~ r to send. Such dummy uplink .~es~ges can be sent in response to polls , ' in such cases.
It is dcs;l ~!e to confirm at least some uplink me~qges from a newly-c c ~ ~ ~ ~ ,~r to insure that co.,l~ ionc are clearly established and that only a single new con~rt, l has been con~rct~l Therefore server 120 echoes at least some uplink ~neC~qges to the new converter during dialogue 410. It may be p.~re~l~,d to echo only uplink messages c~u~ g actual i..rol -~'on and not dummy uplink 30 . P5~gP5~ As will be seen, the con~e.~c~ cn -~pl ~S the echoed mesC~gPs with the onB;~o1c~ to confirm correct trans~ni~;on and, if the echoed message is incoll~
- ~ ~ restarts its initialization plOCe(lul~i. In the case of such a restart, the COll~ no longer l.,SpC- ~ to polls or ~-~C~C~,es to its current polling address. Since an uplink message from a co..~. 100 to server 120 typically contains fewer bytes than a 35 control message from server 120 to such con~c-h-s, it may be preferred to combine ~; ~ a number of echoed uplink ~Acr~s into one conlrol mPCc~ge~
~1 Q ~ .' 4 Failure of a newly-connected converter to respond to a poll after an echoed uplink message probably indicates that the echoed message did not match the original when compared by the converter and that the convelle- restarted its initi~liY~tion plUce-lult;. Such missing response can be prùcessed (block 404) by 5 simply deleting the address of such converter from the ordered list. Other missing re~,pollses may indicate that a converter has been ~li~ollnP.led or that a power failure has occurred. In the case of a converter that has been fully initiali_ed and placed in service, it may be preferable to wait for several non-l~,sponses to polls beforedeledng the address of such a converter.
At the end of the initi~1i7:~tion dialogue, co.,lputer programs can be downloaded by server 120 to RAM in controller 214 of cG~Iv~lte- 200. It may be desirable to continue to echo uplink me~Ps to co.,v~,ler 100 so that the co"~ tion~ Iink between con~e~ler 200 and server 120 operates in full-duplex mode.
FIG. 5 shows the operation of a converter 200 during initi~li7~tion. The proce.l~e shown can be stored in ROM in controller 214 and arranged to start when CO~ . t~r 200 is co~ P. t~ d to a source of power or when a manual "bootstrap" or ~initi~liYPI~ control is operated. Counter "n" is used in resolving contPntions with other newly-co~ t~ d Conv~ , and is initially set to " 1 " to permit collv~lt~,l 200 20 to respond to the first tentative address message received (block 501). As will be seen, "n" is set to a random number if an echoed l~sponse is incoll~,~,l.
Initially, controller 214 in con~_.t~- 200 moni~ors the default ITV
channel for control tnP~QqgP-s (block 502). When a broadcast control message that contains a tentadve address is received on the default channel (block 503), counter 25 "n" is decremented (block 504) and, if n = O (block 505), the tentative address is - - stored by controller 214 as the speçifiP~d address of con~c.t~r 200 for polls and control me~qg~ps (block 506). When the tentative address is first polled, controller . 214 l~spOnrl~ by sending an uplink message to server 120 (block 507). Such message can be chosen to specific~lly identify this particular l~;spûnse as an inidal 30 ùplink n~es~ag~
Converter 214 then ploceeds with the i'~ i7.~1iûn dialogue with server ~- - 120 (block 508), l~;ving control .~ e~gPs addressed to the stored spcçifi~d address and sending uplink rnPs~agPs in Ic~ponse to polls to such address. As des~ih~Pd above, the uplink message sent when the cp~PcifiPd address is po11ed can contain35 ."r~ - ~r stored in ROM in controller 214 or information from manual input, or can be a dummy up1ink message if no information is available.
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Some of the control messages from server 120 to converter 200 during such dialogue will contain one or more echoed uplink messages. On receiving such a control me~scit~e controller 214 compares at least some characters from the echoed uplink messqgP$ with the corresponding cl.~h~le,s in the uplink mçcs~Ps as sent to S detect any mi~ ~t~hPs If a given converter receives a control message containing an echoed uplink message that was not sent by such converter or that does not match an uplink message sent by such converter, which can occur if more than one newly-conl-~P~ led c~nv~. lel responds to polls to the same tentative address, then the given COIl~,~,.lt;l ignores further polls and messA~gPs to its current specified address and 10 restarts its initiql - on routine to acquire another address. However, in such a case, counter "n" is first set equal to a random number (block 509) and the default channel is again monitored for tentative address mPs~ Ps (blocks 502 and 503). ~.~Sl~min~
that muldple newly-connc~;led converters do not select the same random number, such con~crte~ will respond at separate times because of the different countdowns 15 of counter "n." The probability of contendon among uplink mP~Q~rs from more than one newly-co~ fc~ed conver~er is thereby reduced.
An alternate method of dealing with an echo mi~m~-~5h in accol.lance with the in~. ~r is to count a random number of such micrnA-~ch~ps before ~ ~ling the ini~iqli7.~~ion routine. In such a method, the p vcedu-~s in~ir~t~d in blocks 504 20 and 505 would be performed in block 508. If the micn~~n~sh is caused by more than one newly-~ d cO..~/GItGl responding to the same polling address, then such co..~,.t~ will restart ini~iqli7,~-~ion at random. After the next-to-last such C(JII~
Minitiqli7ps~ leaving a single con-~r with such polling address, mi.~m~~l~Ps will d- -~I'P ~ ~ ~ and such single con~c. t~,r will not need to r~Pinitiqli7P
When the initi~li7,~-~ion dialogue is comrlPtP~ software can be downloaded, in the form of control .~csc~,Ps~ from server 120 and stored in RAM in controller 114 (block 510) and converter 200 is then ready for service.
- The in.c,.llio. has been shown and df s~ ;hed with reference to p&lL-,uld en~bod;~-P-~s However, it will be understood by those skilled in the art that various 30 change may be made therein without dep~ling from the spirit and scope of the invention.
What is claimed is:
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Controller 214 performs many functions and is typically a n~ic~opl(,cessor with both random-access memory (RAM) and read-only memory 5 (ROM). Controller 214 sends control and video information to combiner 216, sends eontrol mes~g~ps to receivers 206 and 208 specifying the identity of ch~lnPl~ to be received, receives manual inputs from manual input devices 218, sends video packets to decoder 21S and audio packets to decoder 216, and l.~ns.lliLs information to the cable headend via uplink modulator 210. Controller 214 ean also be a source 10 of audio and/or video inforrn~tion Such information can be retrieved from memory in controller 214 or generated by computer programs in controller 214 under the control of m~ssqg~ps from receiver 208 or input devices 218. Examples of such inforn~tion are symbols or text to be superimposed on video signals or ~ d sounds to be combined with audio signals.
ln a typical cable system, uplink ".~ cc~,v s are sent in the 5 - 30 MHz band. If desired, uplink .~- c~ v s can also be sent over more than one uplink channel in this range, with the particular channel to be used by a particular CC)..
200 being ~speçifiPd to uplink modu1ator 210 by controller 214 in response to a eontrol message from server 120. Uplink ch~~nP~ will typically have a bandwidth 20 in the range from 100,000KHz to lMHz.
l~ecodPr~ 215 and 216 can also be Illicroplocessol~, such as digital signal processo,~, SpPCifi~ y pl'Og~ d to decode compressed video or audio - in~.. ~ ~;on, as the case may be, in acco~ e with the appl~,pliate decoding~lgQrithm~ as is well known in the art. Other output devices 220 capable of leceiving 25 digital inrO. " ~tjon sueh as a printer, can be co~nr~,ted to eontroller 214 as desired.
The output of selc.,lol/co--lbiner 217 is a tclevisioll signal, the eomponents of whieh ean be either (i) selected from one of a number of sourees, sueh as reeeiver 206, eontroller 214, deeoder 215 or deeoder 216 or (ii) comhin~d from sueh sourees. In its simplest form, ~Icclol/col.lbiner 217 forwards to ~: 30 mod ~ ~ 222 either the television signal reeeived by receiver 206 or the telev s - -signal obtained by eombining video deeoded by deeoder 215 with audio decoded by decoder 216. Other versions of sclc~ eo..,biner 217 ean inelude app~tus eontrolled by eontroller 214 to eombine various video and audio sourees into thet~,h,~,i;,ion signal to be trans...ilted to mo~ - - 222. Many tec~ es are known in 35 the art for COm~inill~ video sources, sueh as overlays, windows and split sereens.
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210~3~
Selector/combiner 217 operates on digital lep-esel~ldtions of video signals in which each pixel of a scene is ~eplcse~,~d by a.number of bits and ondigital l~p~en~ on~ of audio signals in which sounds are ~epr"sellt~d by digitized samples. The outputs of decoder 215, decoder 216 and any audio and video outputs5 from controller 214 are in digital form; also, the video portion of the television signal from receiver 206 is converted to digital form in convel ling apparatus (not shown). Such collvelling apparatus is well known in the art. These digidzed video and audio elPment~ are combined in selector/combiner 217 to produce a se~lucnce of digital frames and digital audio samples (possibly for more than one audio channel).
10 These samples are then converted to a conventional television signal, such as an NSTC signal, by appald~us (not shown) also well known in the art.
Band stop filter 204 deletes at least one of the ITV channels, p,~felably the default channel, from the signal received from cable 202, passing the rPm~ining c~ to output cable 230. Modulator 222 modulates the television signal 15 received from selcclo./co,l,biner 217 into one of the blocked lTV çh~nnPl~ on output cable 230. Thus, conv~l~. 200 replaces the pac~t;,~d digital signal received from the cable system in such ITV channel with the video signal from sele.;lor/colllbiner 217. Such ITV channel can then be selected and viewed in the conventional way ona cable-ready television receiver col-nec~ed to output cable 230. As descnbed above, 20 the television signal n~ocl~ into such ITV channel can be produced from ITV
packets received over any of the lTV ~' --'-FIG. 3 is a flow chart showing the overall ope.dtion of controller 214 onreceipt of packets from receiver 208. If the "virtual channel" bytes indicate that suchpacket is a control message, (block 302) and the address field in the control message 25 indicate that the message is intended for con~ 200 (block 304), then controller 214 pf" r,..--~ the control function specified by the .~ g contents of the message (block 306). If the "virtual channel" bytes indicate that such packet is part of a program channel, such as a channel carrying an encoded and digitized video signal, - -and controller 214 is ~ tly enabled to receive from such channel (block 308), 30 then controller 214 plucei~s the packet contents in accor~ - e with the type of ; program in such virtual channel (block 310), sending data from the packet to the input buffer in the app~pliate output device, such as decoder 215 or decoder 216.
Each packet in which the "polling address" bytes indicate that c~ tel 200 is being polled (block 312) causes such co~ ,.tel to transmit an uplink message 35 to the cable headend (block 314). (The address in the "polling address" bytes is not necessarily the same as in the address field in a control message that may be included . ~ ' .
. .
.; - - . . .. . . , . ,, . . ~ , . ; , - . .. .
.. : , . . . .. . . . . . ..
. .
. : ~ , , . :, . : . , ~lQ~
.
in the same packet). This uplink mf~s~g~ typically no more than a few bytes, cancontain control information or information entered manually by the subscriber in one of manual input devices 218. Because this message is initiated by a downlink message (from the headend to the subscriber) having an address known at the S headencl this address can be associated with the uplink message when received, and there is no need to identify the source of uplink mes~ges.
As mentioned above, controller 214 can contain both RAM and ROM.
The ROM includes co~ ul~ programs that can be pÇnn~lently loaded, such as programs con~ining initi~li7~tion routines; whereas the RAM can be downloaded 10 from the headend by the use of control messages. Such downloading will typically occur when a converter is first connPc~ed to the cable system or when programs must be updated. Also, different progMms for different pul~oses can be downloaded in controller 214 at different times. Such downloading capability ~1;,.,in t s the need for program-loading capabilities at converter 200, although such capability cou1d be 15 provided if desired by means of devices such as a disk drive.
FIG. 4 is a flow chart showing the polling seque-nce followed by server 120 in FIG. 1. As desç~ihed above, each packet sent by server 120 to conv~ 200at ;,.~ r loca~ion~ 104 contains a polling address, and server 120 receives uplink messages from co~ t~rs polled. If more than one disllibulion channel is used as an 20 ITV channel, such polling ~u~,nce is used for the "default" ITV channel.
Server 120 ~ polling addresses in successivti packets, preferably in accold -: with an ordered list, the order being d~ t~ ed by the relative res of the con~ from the cable- system headend (block 401). The first address on the list is that of the closest ccn~ t~,~ to the headend as measured by 25 ~ n time; the last address on the list is that of the farthest collv~rt~,r. This p.~e~lu.t; avoids possible inte.l~ among uplink .~ s~ge s sent in ~sponse to polls. The position of an address in the ordered list is delel-nined during ;o-~ as will be deserihed below. Server 120 I..~inl~;nc such an ordered list for the default ITV channel and each other lTV channel that may be in service in the 30 system.
After all the add~s~s in the ordered list have been polled, plefe.dbly at least one packet is sent with a null (I~O~ g) polling addresses (b1Ock 402), thereby insc.lin& enough delay in the polling se~.,enf,e for the ~esponse to the last ~ ~ poll in the ordered list to be received from the farthest ccll~elt~,. before the ordered - ~ ~ 35 list is polled again (block 402). The co~ are programmed to respond to every poll with an uplink mP.QQagP. If such a l~sponse is missing (block 403), server 120 ': ' ' .:
' - .;
,~ ' .
21 0~3~
determines whether or not to continue polling the unresponsive converter (block 404), as will be explained in more detail below.
Each converter 200 interprets at least the address portion of all control meSS~geS to identify me.~.c~geS intended for such converter. However, some special 5 control mess~gç~s are not addressed to specific converters. For example, periodically (such as once per minute) a special control message is broadcast over the virtual channel used for control signals in the default channel. This special control message is not addressed to a specific converter, but contains a tentative address for use by any newly-connected converter. If such a message ha~s been sent during the last 10 polling se.luence (block 405) such tentative address is polled (block 406), again followed by enough polls to a null address to permit a response from the farthest con~ el (block 407). Because the position of a new converter is not known initially, these null polls insure that a response from a new converter will be received before those from the next iteration of the ordered list.
As will be expl~ined in more detail below in conjunction with the description of FIG. 5, a newly-connP.ctPd converter operates under an initi~li7~tion program stored in ROM in the converter. Such init;~li7.:~tion program stores thetentative address from such a broadcast control message as its specified address for responding to polls and for receiving control m~ ges and responds to a subsequent 20 poll of such specifi~d address with an uplink m~scage If an uplink message is received in response to a poll of the tentative address (block 408), in(iin~ling that there is a newly- conn~ct~d converter, thetentative address is stored in the ordered list (block 409) and a new tentative address is selected for ;,.,bse.l-,e~ tentative-address mes~ag~s, To dPle~ ."in.5 the place of 25 such address in the ordered list, server 120 measures the elapsed L~ ;on time from polling the tentative address in block 406 to receiving the resulting uplink n~QqBe Finally, a dialogue is conduc~ed with the newly-connPctPd convt;lt~l (block 410) con~:sl ;~g of control m~ s sent by server 120 to the con~c~ ~1 using the tentative address stored in the ordered list and uplink mPcs~ges evoked by polls 30 to such address pu~ to block 401. If no l,,.,ponse is received to the poll of the tentative address, in~linating that no new converter has been co~ e.le~l then server 120 returns to block 401 and repeats the endre polling sequence - During the dialogue in~ ted by block 410, a newly-colllu(l~ d CO-.~ l typically will send information to identify itself in uplink mess~ges 35 responding to such tentative-address polls. Such inforrn~ion can be stored in ROM
in the con~el~., such as a unique serial number assigned to the converter, or be .. . : .
-; . , . . . ......................... ~
- , . . . . :
. . . . . . . . . .
entered manually by the person in.ct;~lling ~he converter. Some examples of suchmanually entered information are subscribers' personal identification numbers, types of service desired and billing addresses. In case of manually-entered information, control mçcQsgPs sent by server 120 can cause an appropriate request for such 5 information to appear on the screen of a television receiver connected to the co-~ve. ler.
If desired, server 120 can conduct the initi~li7~tion dialogue over a different virtual channel than the virtual channel in the default ITV channel over which the tentative address is broadcast. Such different virtual channel can also be in 10 the default ITV channel or, if there is more than one ITV channel in use in the system, in a different ITV channel. The server initiates such a channel change by tranC~nitting applupliatc contro1 mPc~Ps to the newly-conmPc~Pd collv~llel 200 to enable such con~e~ to respond to control mpcsag~ps in the new channel. Similarly, if more than one uplink channel is provided, one uplink channel can be used as a15 "default" uplink channel for ~~,~pons~s to polls in the "default" ITV channel, and con-c.le. 200 can be caused to transmit over a different uplink channel by an applvpliate control message from server 120.
Preferably, a con~c.t~,l always responds with an uplink message to a poll to its srAcifiPd address, even though it may have no information to send. A dummy 20 uplink message can be used in such cases. For eY~~rle, in sitv~ion~ where i.,rO.. ~;0~ is being entered manuaily for l.~ - by a CO..~,lt~,., there may be a number of polls occ~ g before and during such transmission when there is no inr~" ~ r to send. Such dummy uplink .~es~ges can be sent in response to polls , ' in such cases.
It is dcs;l ~!e to confirm at least some uplink me~qges from a newly-c c ~ ~ ~ ~ ,~r to insure that co.,l~ ionc are clearly established and that only a single new con~rt, l has been con~rct~l Therefore server 120 echoes at least some uplink ~neC~qges to the new converter during dialogue 410. It may be p.~re~l~,d to echo only uplink messages c~u~ g actual i..rol -~'on and not dummy uplink 30 . P5~gP5~ As will be seen, the con~e.~c~ cn -~pl ~S the echoed mesC~gPs with the onB;~o1c~ to confirm correct trans~ni~;on and, if the echoed message is incoll~
- ~ ~ restarts its initialization plOCe(lul~i. In the case of such a restart, the COll~ no longer l.,SpC- ~ to polls or ~-~C~C~,es to its current polling address. Since an uplink message from a co..~. 100 to server 120 typically contains fewer bytes than a 35 control message from server 120 to such con~c-h-s, it may be preferred to combine ~; ~ a number of echoed uplink ~Acr~s into one conlrol mPCc~ge~
~1 Q ~ .' 4 Failure of a newly-connected converter to respond to a poll after an echoed uplink message probably indicates that the echoed message did not match the original when compared by the converter and that the convelle- restarted its initi~liY~tion plUce-lult;. Such missing response can be prùcessed (block 404) by 5 simply deleting the address of such converter from the ordered list. Other missing re~,pollses may indicate that a converter has been ~li~ollnP.led or that a power failure has occurred. In the case of a converter that has been fully initiali_ed and placed in service, it may be preferable to wait for several non-l~,sponses to polls beforedeledng the address of such a converter.
At the end of the initi~1i7:~tion dialogue, co.,lputer programs can be downloaded by server 120 to RAM in controller 214 of cG~Iv~lte- 200. It may be desirable to continue to echo uplink me~Ps to co.,v~,ler 100 so that the co"~ tion~ Iink between con~e~ler 200 and server 120 operates in full-duplex mode.
FIG. 5 shows the operation of a converter 200 during initi~li7~tion. The proce.l~e shown can be stored in ROM in controller 214 and arranged to start when CO~ . t~r 200 is co~ P. t~ d to a source of power or when a manual "bootstrap" or ~initi~liYPI~ control is operated. Counter "n" is used in resolving contPntions with other newly-co~ t~ d Conv~ , and is initially set to " 1 " to permit collv~lt~,l 200 20 to respond to the first tentative address message received (block 501). As will be seen, "n" is set to a random number if an echoed l~sponse is incoll~,~,l.
Initially, controller 214 in con~_.t~- 200 moni~ors the default ITV
channel for control tnP~QqgP-s (block 502). When a broadcast control message that contains a tentadve address is received on the default channel (block 503), counter 25 "n" is decremented (block 504) and, if n = O (block 505), the tentative address is - - stored by controller 214 as the speçifiP~d address of con~c.t~r 200 for polls and control me~qg~ps (block 506). When the tentative address is first polled, controller . 214 l~spOnrl~ by sending an uplink message to server 120 (block 507). Such message can be chosen to specific~lly identify this particular l~;spûnse as an inidal 30 ùplink n~es~ag~
Converter 214 then ploceeds with the i'~ i7.~1iûn dialogue with server ~- - 120 (block 508), l~;ving control .~ e~gPs addressed to the stored spcçifi~d address and sending uplink rnPs~agPs in Ic~ponse to polls to such address. As des~ih~Pd above, the uplink message sent when the cp~PcifiPd address is po11ed can contain35 ."r~ - ~r stored in ROM in controller 214 or information from manual input, or can be a dummy up1ink message if no information is available.
:
Some of the control messages from server 120 to converter 200 during such dialogue will contain one or more echoed uplink messages. On receiving such a control me~scit~e controller 214 compares at least some characters from the echoed uplink messqgP$ with the corresponding cl.~h~le,s in the uplink mçcs~Ps as sent to S detect any mi~ ~t~hPs If a given converter receives a control message containing an echoed uplink message that was not sent by such converter or that does not match an uplink message sent by such converter, which can occur if more than one newly-conl-~P~ led c~nv~. lel responds to polls to the same tentative address, then the given COIl~,~,.lt;l ignores further polls and messA~gPs to its current specified address and 10 restarts its initiql - on routine to acquire another address. However, in such a case, counter "n" is first set equal to a random number (block 509) and the default channel is again monitored for tentative address mPs~ Ps (blocks 502 and 503). ~.~Sl~min~
that muldple newly-connc~;led converters do not select the same random number, such con~crte~ will respond at separate times because of the different countdowns 15 of counter "n." The probability of contendon among uplink mP~Q~rs from more than one newly-co~ fc~ed conver~er is thereby reduced.
An alternate method of dealing with an echo mi~m~-~5h in accol.lance with the in~. ~r is to count a random number of such micrnA-~ch~ps before ~ ~ling the ini~iqli7.~~ion routine. In such a method, the p vcedu-~s in~ir~t~d in blocks 504 20 and 505 would be performed in block 508. If the micn~~n~sh is caused by more than one newly-~ d cO..~/GItGl responding to the same polling address, then such co..~,.t~ will restart ini~iqli7,~-~ion at random. After the next-to-last such C(JII~
Minitiqli7ps~ leaving a single con-~r with such polling address, mi.~m~~l~Ps will d- -~I'P ~ ~ ~ and such single con~c. t~,r will not need to r~Pinitiqli7P
When the initi~li7,~-~ion dialogue is comrlPtP~ software can be downloaded, in the form of control .~csc~,Ps~ from server 120 and stored in RAM in controller 114 (block 510) and converter 200 is then ready for service.
- The in.c,.llio. has been shown and df s~ ;hed with reference to p&lL-,uld en~bod;~-P-~s However, it will be understood by those skilled in the art that various 30 change may be made therein without dep~ling from the spirit and scope of the invention.
What is claimed is:
'' ' ' " ' " ''" ' ''' ~' ' " ' " . ' '' !
~ . . . . . . . . . .
:'' ' '' " ~ '.' . . .. ..
Claims (9)
1. In a signal distribution system having a server and a plurality of terminals, each said terminal having a specified address for responding to polls and receiving control messages and wherein each said terminal responds to each poll with an uplink message to said server, a method of remotely assigning said specified addresses to newly-connected terminals CHARACTERIZED BY:
in said server:
storing said specified addresses in a polling list and repeatedly polling said terminals in accordance with said polling list; and periodically broadcasting a control message containing a tentative address to all said terminals followed by polling said tentative address;
in a newly-connected terminal:
receiving one of said broadcast control messages, storing the tentative address contained in said broadcast control message as the specified address for said terminal and, in response to a poll to said tentative address, sending an initial uplink message to said server;
in said server:
in response to said initial uplink message, inserting said tentative address in said polling list as the specified address for said newly-connected terminal, selecting a new tentative address for use in subsequent broadcast control messages, periodically polling said specified address, receiving additional uplink messages from said newly-connected terminal and echoing at least one of said uplink messages in at least one additional control message addressed to said specified address, in said newly-connected terminal:
comparing at least one character from said echoed uplink messages in said additional control messages with the corresponding at least one character in the uplink messages sent and, if said comparison reveals a difference, repeating said receiving step to acquire a different tentative address for use as the specified address of said terminal.
in said server:
storing said specified addresses in a polling list and repeatedly polling said terminals in accordance with said polling list; and periodically broadcasting a control message containing a tentative address to all said terminals followed by polling said tentative address;
in a newly-connected terminal:
receiving one of said broadcast control messages, storing the tentative address contained in said broadcast control message as the specified address for said terminal and, in response to a poll to said tentative address, sending an initial uplink message to said server;
in said server:
in response to said initial uplink message, inserting said tentative address in said polling list as the specified address for said newly-connected terminal, selecting a new tentative address for use in subsequent broadcast control messages, periodically polling said specified address, receiving additional uplink messages from said newly-connected terminal and echoing at least one of said uplink messages in at least one additional control message addressed to said specified address, in said newly-connected terminal:
comparing at least one character from said echoed uplink messages in said additional control messages with the corresponding at least one character in the uplink messages sent and, if said comparison reveals a difference, repeating said receiving step to acquire a different tentative address for use as the specified address of said terminal.
2. The method of claim 1 FURTHER CHARACTERIZED BY:
in said newly-connected terminal:
in repeating said broadcast-message receiving step, receiving a random number of said broadcast control messages and, in said storing step, storing thetentative address contained in the last said broadcast control message received as said specified address, thereby reducing the probability of contention with uplink messages from other newly-connected terminals.
in said newly-connected terminal:
in repeating said broadcast-message receiving step, receiving a random number of said broadcast control messages and, in said storing step, storing thetentative address contained in the last said broadcast control message received as said specified address, thereby reducing the probability of contention with uplink messages from other newly-connected terminals.
3. The method of claim 1 FURTHER CHARACTERIZED BY:
in said newly-connected terminal:
in said comparing step, before repeating said broadcast-message receiving step, receiving a random number of said echoed uplink messages in which said comparison reveals a difference.
in said newly-connected terminal:
in said comparing step, before repeating said broadcast-message receiving step, receiving a random number of said echoed uplink messages in which said comparison reveals a difference.
4. The method of claim 1 FURTHER CHARACTERIZED BY:
in said server:
ordering said specified addresses in said polling list in accordance with the distances of the terminals associated with said specified addresses from said server and, in said terminal polling step, beginning said polling step by polling the closest terminal and following said polling step with at least one additional poll to a null address, thereby reducing the probability of interference among uplink messages from different terminals.
in said server:
ordering said specified addresses in said polling list in accordance with the distances of the terminals associated with said specified addresses from said server and, in said terminal polling step, beginning said polling step by polling the closest terminal and following said polling step with at least one additional poll to a null address, thereby reducing the probability of interference among uplink messages from different terminals.
5. The method of claim 1 FURTHER CHARACTERIZED BY:
in said server:
following said poll of said tentative address with at least one poll of a null address.
in said server:
following said poll of said tentative address with at least one poll of a null address.
6. The method of claim 3 FURTHER CHARACTERIZED BY:
determining said distance from said server to each newly-connected terminal by:
measuring the response time from polling said tentative address to receipt of said initial uplink message from said newly-connected terminal.
determining said distance from said server to each newly-connected terminal by:
measuring the response time from polling said tentative address to receipt of said initial uplink message from said newly-connected terminal.
7. The method of claim 1 FURTHER CHARACTERIZED BY:
in said server:
if an uplink message is not received in response to polling a given newly-connected terminal, removing the specified address of said terminal from said polling list.
in said server:
if an uplink message is not received in response to polling a given newly-connected terminal, removing the specified address of said terminal from said polling list.
8. The method of claim l FURTHER CHARACTERIZED IN THAT:
said signal distribution system is an interactive cable television system, said terminals are converters at subscriber locations for connecting said cable television system to television receivers and said control messages and polls are contained in digital packets in at least one channel of said cable television system.
said signal distribution system is an interactive cable television system, said terminals are converters at subscriber locations for connecting said cable television system to television receivers and said control messages and polls are contained in digital packets in at least one channel of said cable television system.
9. In a signal distribution system having a server and a plurality of terminals, each said terminal having a specified address for responding to polls and receiving control messages from said server and wherein each said terminal responds to each poll with an uplink message to said server, a method of remotely assigning said specified addresses to newly-connected terminals CHARACTERIZED BY
repeatedly polling said specified addresses, periodically sending a tentative address from said server to all said terminals and polling said tentative address, in a newly-connected terminal, receiving and storing said tentative address as the specified address for said terminal and sending an initial uplinkmessage in response to said tentative-address poll, in said server, on receipt of said uplink message, including said tentative address as a specified address, choosing a new tentative address and echoing at least one uplink message to said newly-connected terminal, in said newly-connected terminal, comparing at least one echoed uplink message with the uplink message as sent, and if such messages are different, repeating said receiving and storing step to acquire a different specified address.
repeatedly polling said specified addresses, periodically sending a tentative address from said server to all said terminals and polling said tentative address, in a newly-connected terminal, receiving and storing said tentative address as the specified address for said terminal and sending an initial uplinkmessage in response to said tentative-address poll, in said server, on receipt of said uplink message, including said tentative address as a specified address, choosing a new tentative address and echoing at least one uplink message to said newly-connected terminal, in said newly-connected terminal, comparing at least one echoed uplink message with the uplink message as sent, and if such messages are different, repeating said receiving and storing step to acquire a different specified address.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/965,463 US5373288A (en) | 1992-10-23 | 1992-10-23 | Initializing terminals in a signal distribution system |
| US965,463 | 1992-10-23 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2106834A1 CA2106834A1 (en) | 1994-04-24 |
| CA2106834C true CA2106834C (en) | 1998-10-13 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002106834A Expired - Fee Related CA2106834C (en) | 1992-10-23 | 1993-09-23 | Initializing terminals in a signal distribution system |
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| US (2) | US5373288A (en) |
| EP (1) | EP0594353B1 (en) |
| JP (1) | JP2834397B2 (en) |
| CA (1) | CA2106834C (en) |
| DE (1) | DE69319059T2 (en) |
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-
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- 1992-10-23 US US07/965,463 patent/US5373288A/en not_active Expired - Lifetime
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- 1993-09-23 CA CA002106834A patent/CA2106834C/en not_active Expired - Fee Related
- 1993-10-13 DE DE69319059T patent/DE69319059T2/en not_active Expired - Fee Related
- 1993-10-13 EP EP93308165A patent/EP0594353B1/en not_active Expired - Lifetime
- 1993-10-22 JP JP5286157A patent/JP2834397B2/en not_active Expired - Lifetime
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1994
- 1994-12-12 US US08/354,174 patent/US5559503A/en not_active Expired - Lifetime
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|---|---|
| CA2106834A1 (en) | 1994-04-24 |
| DE69319059T2 (en) | 1998-11-19 |
| EP0594353A1 (en) | 1994-04-27 |
| US5559503A (en) | 1996-09-24 |
| JPH06237462A (en) | 1994-08-23 |
| US5373288A (en) | 1994-12-13 |
| DE69319059D1 (en) | 1998-07-16 |
| EP0594353B1 (en) | 1998-06-10 |
| JP2834397B2 (en) | 1998-12-09 |
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| EEER | Examination request | ||
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