Abstract:
A single centralized video controller is employed to convert and distribute video channels to one or more analog TVs (i.e., viewing devices or the like). This is realized without the need for changes to either the TVs or the interconnecting COAX. Specifically, the centralized controller includes one or more MPEG2 decoders, the number of which depends on a desired number of active TVs to be used in viewing different programs, and one or more wireless (e.g., radio frequency (RF)) communications links to television controllers (i.e., remote control units) associated on a one-to-one basis with the desired number of TVs. In operation, channel selection for each of the one or more TVs is communicated up-stream from the centralized controller to a remote video server and, therein, to a video services controller. The video services controller causes the video server to transmit only the selected program channels to the local centralized video controller. However, when the video channel is already being supplied from the video server to an optical line terminal and, specifically, to an optical line card to which the requesting centralized controller is connected to, there is no need to communicate the channel request to the video server. The optical line terminal simply supplies the requested channel via an optical line card to the additional requesting centralized controller and, in turn, to the requesting TV.

Description:
RELATED APPLICATIONS 
     U.S. patent application Ser. Nos. 09/356,979 and 09/356,980 were filed concurrently herewith. 
    
    
     TECHNICAL FIELD 
     This invention relates to the distribution of video signals and, more particularly, to controlling the distribution of the video signals. 
     BACKGROUND OF THE INVENTION 
     Distribution of video signals to one or more outlets at a location is now typically realized by the use of coaxial cable (COAX). In addition, video terminals connected to the one or more outlets are for the most part analog television sets (TVs). Recently, digital broadband access systems have been proposed, e.g., cable modem, fiber-to-the-home, or the like, which would deliver MPEG2 (Motion Picture Experts Group 2) standard digital video signals. These digital signals must be converted to analog video signals consistent with available TVs, and with COAX signals expected by cable ready TVs. A known approach is the use of an individual set-top-box for each TV, which includes a MPEG2 decoder, a digital-to-analog (D/A) converter, a NTSC (National Television Systems Committee) encoder and a frequency up-converter to deliver the video at the frequency of a selected channel. Typically, the use of an individual set-top-box per TV assumes the availability of all desired video channels at an input of each of the set-top-boxes. The need to deliver all channels to each set-top-box is an inefficient use of the broadband access system. Furthermore, the use of such individual set-top-boxes is inefficient, cumbersome and costly. The inefficiency results because typically only a few of the TVs and associated set-top-boxes are active at any given time. 
     SUMMARY OF THE INVENTION 
     Limitations and problems of prior known video signal distribution systems are overcome by employing a single centralized video controller to convert and distribute video channels to one or more analog TVs, i.e., viewing devices or the like. This is realized without the need for changes to either the TVs or the interconnecting COAX, and without the use of a set top box per TV. Indeed, only a remote control unit is needed for each TV. Specifically, the centralized controller includes one or more MPEG2 decoders, the number of which depends on a desired number of active TVs to be used in viewing different video programs on different channels, and one or more wireless, e.g., radio frequency (RF) or infra red, communications links to television controllers, i.e., remote control units, associated on a one-to-one basis with the desired number of TVs. 
     In operation, channel selection for each of the one or more TVs is typically communicated up-stream from the centralized controller to a video server and a video services controller, therein. The video server only transmits the selected channels to the local centralized video controller. However, when the video channel is already being supplied from the video server to an optical line terminal and, specifically, to an optical line card to which the requesting centralized controller is connected to, there is no need to communicate the channel request to the video server. The optical line terminal simply supplies the requested channel via an optical line card to the additional requesting centralized controller and, in turn, to the requesting TV. 
     In one embodiment of the invention, each of the one or more active TVs, is assigned one of a plurality of program units included in the centralized controller, and is switched to a video channel that is supplied an analog video signal by the program unit. In this embodiment, each program unit includes a broadband asynchronous transfer mode (ATM) virtual channel (VC) filter, a MPEG2 decoder, a NTSC encoder and a frequency up-converter. The MPEG2 decoder decodes a video signal supplied via the VC and supplies the analog version of the decoded video signal as its output. The analog video signal is NTSC encoded and up-converted to a fixed video channel. The video channel designation corresponds to the assigned MPEG2 decoder and is specified by the centralized video controller. The video channel number is transmitted to the TV remote control unit via a first wireless link and, then, supplied to the TV tuner via an infra red (IR) wireless link. Additionally, the remote control unit communicates channel selections via the first wireless link to the centralized video controller that, in this example, passes the channel selections to a video services controller in a video server using an up-stream communications link. In this example, the up-stream communications link is a broadband ATM VC. In response to the communicated channel selections, the video server transmits the selected channel to the centralized video controller using a down-stream communications link. In this example, the down-stream link is a constant bit rate (CBR) ATM VC. Consequently, the digital video signal is supplied to the centralized video controller as a continuous stream of ATM cells, while the up-stream communications is transmitted as bursts. In this example, a specific VC is statically assigned to each conventional broadcast video channel and other VCs are dynamically assigned for other video services, for example, video-on-demand, or the like. If the program units are all in use supplying video channels to active TVs, additional TVs can tune to any of the supplied video channels but they do not have any “program” selection capability. 
     In another embodiment of the invention, the up-converter included in each program unit is frequency agile. A video channel selected via the remote control unit is communicated to the centralized video control unit via the first wireless link and is transmitted up-stream to the video server and the video services controller, therein. The selected video program channel is also supplied to the TV tuner via the IR wireless link. Additionally, the MPEG2 decoded video signal is transmitted on the selected program channel. This is realized by dynamically controlling the channel that the video signal is up-converted to by the agile up-converter. Indeed, as the channel selections are made, the associated remote control unit transmits the channel designation to both the TV tuner and the centralized video controller using the IR wireless link and the first wireless link, respectively. 
     In still another embodiment of the invention, the up-converter has a fixed frequency, i.e., video channel, which is assigned to an associated MPEG2 decoder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows, in simplified block diagram form, a video distribution system employing an embodiment of the invention; 
     FIG. 2 shows, in simplified block diagram form, details of a video server employed in the embodiment of FIG. 1; 
     FIG. 3 shows, in simplified block diagram form, details of a centralized video controller employing an embodiment of the invention that may be employed in the system of FIG. 1; 
     FIG. 4 shows, in simplified block diagram form, details of a remote control unit, including an embodiment of the invention, that may be employed with the video controller of FIG. 3; 
     FIG. 5 is a flow chart illustrating steps in the operational process of the centralized video controller of FIG. 3 in the system of FIG. 1; 
     FIG. 6 shows, in simplified block diagram form, details of another centralized video controller employing an embodiment of the invention that may be employed in the system of FIG. 1; 
     FIG. 7 shows, in simplified block diagram form, details of a remote control unit, including an embodiment of the invention, that may be employed with the video controller of FIG. 6; and 
     FIG. 8 is a flow chart illustrating steps in the operational process of the centralized video controller of FIG. 6 in the system of FIG.  1 ; 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows, in simplified block diagram form, a video distribution system employing an embodiment of the invention. Specifically, shown is network  100  including video server  101  which supplies down-stream video signals to broadband network  102 , in response to an up-stream communication including a selection message. Broadband network  102  supplies the communications signals to and from optical line terminal  103 . At optical line terminal (OLT)  103 , optical line circuit (OLC)  104  interfaces to an optical fiber line, The optical fiber line is, for example, a power splitting passive optical network (PSPON) fiber including optical fibers  110  and  111  on which optical signals are transmitted using coarse wavelength division multiplexing. Transmission on the fiber lines  110  and  111  is achieved using two wavelengths, 1550 nano meters (nm) down-streams for example, to a home and 1310 nm up-stream, for example, from the home. The PSPON fibers  110  may be split via passive splitter  105  into a prescribed number of optical fibers  111 , for example, 32 fibers  111 , thereby interfacing via associated ONUs  106  with 32 locations. Note that OLT  103  serves one or more OLCs  104 , namely,  104 - 1  through  104 -Z, coupled to a corresponding number of fiber lines, namely,  110 - 1  through  110 -Z, respectively, and that an OLC  104  serves one or more ONUs  106  via optical fibers  111 - 1  through  111 -W. In this example, the down-stream transmission of video signals is in asynchronous transfer mode (ATM) cells via time division multiplex (TDM), while up-stream transmission of communication is via time division multiple access (TDMA), and both down-stream and up-stream communications is at 155.52 Mb/sec. Efficient TDMA communications in the up-stream direction requires all optical network units (ONUs)  106  to have equal loop delay in relationship to their associated OLC  104 . This is realized by employing a ranging procedure that is executed when each ONU  106  associated with a particular OLC  104  is installed, moved, returned to service, or the like. This is realized by employed a ranging procedure that is executed when each ONU  106  is installed. The ranging procedure defines an artificial delay that when added to the transmission loop delay of an ONU  106  yields the required common loop delay. Such ranging arrangements are known in the art. However, a preferred ranging arrangement is described in copending U.S. patent application Ser. No. 09/356,980 filed concurrently herewith and assigned to the assignee of this application. 
     Actually, OLT  103  is a special ATM switch including a traditional ATM fabric and input/output (I/O) ports. In this example, two types of I/O boards are required, namely, standard SONET (synchronous optical network) boards, e.g., OC-12 units, and OLC units  104 . Video signals received from OLT  103  as ATM cells from one or more SONET boards are distributed to the OLC units  104 . Because of this, up-stream channel select messages being sent to video services controller  202  in video server  101  are intercepted within the OLT  103 , which accumulates the number of viewers of each video program that is OLT  103  wide. Only channel (program) selections that are not available within presently received SONET VCs are passed on to the video services controller  202  in video server  101 . Additionally, messages are sent by OLT  103  to video server  101  and, therein, to video services controller  202  whenever a transmitted video program is no longer being viewed by any OLT  103  supported TV  107 . It is noted that each of OLC units  104  includes, in this example, a CPU and memory (not shown) that may be a microprocessor with memory. 
     Optical network unit (ONU)  106  terminates the PSPON fiber  110  via an associated PSPON optical fiber  111 , and provides appropriate interfaces, in this example, to one or more television sets (TVs)  107 - 1  through  107 -N. Each of TVs  107 - 1  through  107 -N has an associated one of remote control (RC) units  108 - 1  through  108 -N, respectively. 
     Network  100  supplies, for example, via one or more video services controller  202  in video server  101  in response to specific program requests, conventional broadcast TV programs, programs similar to those supplied via cable TV providers, satellite TV providers, video on demand and the like. Procedures for requesting and transmitting video programs are described in greater detail below. 
     As shown in FIG. 1, a residential video subsystem includes an ONU  106  and one or more TVs  107  and associated RC units  108 . In this example, ONU  106  and TVs  107  are interconnected via coaxial (COAX) cable. 
     FIG. 2 is a simplified block diagram of video server  101  employed in the system of FIG.  1 . Specifically, shown are video storage server  201 , video services controller  202  and a block of MPEG2 video encoders  203 - 1  through  203 -Y. Broadcast video signals are received via inputs  204 - 1  through  204 -Y and supplied on a one-to-one basis to MPEG2 video encoders  203 - 1  through  203 -Y, respectively, where they are digitally encoded and compressed in now well known fashion. Thereafter, the digitally encoded MPEG2 video signals are supplied to video storage server  201 . As described below in relationship to FIG. 3, video storage server  201  stores the digitally encoded MPEG2 video signals, to be transmitted to subscribers. Other video signals may be prestored in video storage server  201  to support, for example, video-on-demand, or directed advertisement insertion. The transmission of the digitally encoded MPEG2 video signals is in response to control signals from a subscriber and supplied, in this example, via TDMA in ATM cells over transmission link  109  to video server  101  and, therein, via  207  to video services controller  202 . In turn, video services controller  202  supplies/and or receives control signals to and/or from video storage server  201 . In response to subscriber requests video storage server  201  supplies appropriate video signals including advertisements during commercial intervals or in accordance with the service being provided to one or more subscribers. The video signals are included in ATM cells and formatted as an ATM signal for transmission. Thereafter, the ATM formatted signal is supplied as an output from video server  201  via  206  to bi-directional transmission link  109 . 
     In operation, video server  101  delivers all video signals as MPEG2 encoded video signals. As described above, FIG. 2 shows a block diagram of the video server  101  consisting of a bank of MPEG2 video encoders  203 , a video storage server  201 , and a video services controller  202 . In order to deliver customized advertisement insertion services, all encoded broadcast video signals are delivered through the video storage server  201 . Therefore, each digital video signal stream is written to the video storage server  201  in real time, as well as, read from that server  201  in near real time. A read memory pointer in video services controller  202  just simply follows the write pointer, also in controller  202 , by some non-zero amount. It is worth noting that the delay between the writing and the reading of a video signal stream is not important. In fact, one possible advanced video service that immediately follows is a “delayed broadcast on demand”. 
     The video service controller  202  manages the writing and reading of all video signal streams, providing independent address information for each digital video signal stream that is written and/or read, as well as ATM virtual circuit (VC) information. In addition, control operations, e.g., “pause”, are also provided. In this example, data are written in blocks that are divisible by  48 . As data are read, ATM cells are formatted as part of the server&#39;s I/O operations and an ATM formatted signal is supplied as an output via  206 . 
     It is assumed that all video VCs are routed to the OLTs  103  (FIG. 1, and associated OLCs  104 ). Within the OLC  104 , only video streams corresponding to VCs being decoded by one or more ONUs  106  on the PSPON fiber line  110  and its associated optical fiber lines  111  are transmitted on the optical fiber. Therefore, remote channel selection is performed within the OLC  104 . 
     FIG. 3 shows, in simplified block diagram form, details of a centralized video controller, namely, one implementation of ONU  106 , employing an embodiment of the invention that may be employed in the system  100  of FIG.  1 . In this example, ONU  106  includes at least one radio frequency (RF) receiver  301 , CPU  302 , one or more program units  303 - 1  through  303 -M and RF combiner  309 . It is noted that there must be at least “M” RF receivers  301  corresponding to the number “M” of program units  303 . The number of program units  303 , i.e., M, defines the number of video programs that can be viewed simultaneously by multiple TVs  107  within a location, e.g., a home. By way of a simple example, if there are four (4) program units then only four programs can be simultaneously viewed. Thus, if there were only four TVs  107  at the location, there would not be any program “blocking”. However, if more than four (4) TVs are at the location, then only four (4) different channels may be viewed. The TVs in excess of the first four to have initiated receiving a channel would be restricted to viewing one of the four active channels, and would not have the ability to change a channel being viewed from the four active channels. 
     RF receiver  301  receives RF signals including control messages from a remote control unit associated with a TV  107  (FIG.  1 ). This may be realized by employing a RF transmitter in the TV remote control unit, described below in conjunction with FIG. 4, and a RF receiver, both of a type used in a wireless, i.e., cordless, telephone, now well known in the art. Note that there may be a plurality of TVs and a corresponding plurality of remote control units. ONU  106  would include as many RF receivers as there are remote control units. RF control messages include, for example, the associated remote control unit identity (ID) and a selected channel number. Other control messages include, in addition to the remote control ID, for example, an indication that an associated TV has been either powered ON or powered OFF. The information received in the RF control message is supplied to CPU  302 . CPU  302  is, for example, a microprocessor including memory. When CPU  302  receives a RF transmission from a previously inactive remote control unit  108 , it assigns one of program units  303  to the TV  107  associated with the remote control unit  108 , it writes the VC corresponding to the received channel number into register  304  and determines that VC through use of a look-up table. It maintains a count of how many active TVs  107  are tuned to the selected program and it stores the selected channel for this TV  107  in a lookup table. If no other served TV  107  is already tuned to the selected program, CPU  302  transmits a message up-stream to video server  101  and video services controller  202 , therein, requesting the transmission of the selected video program. The selected program is transmitted down-stream in ATM cells on the virtual circuit (VC) identified by the selected program channel number and received at the selected program unit  303 , in this example, program unit  303 - 1 . The selected channel number&#39;s VC and channel number are supplied to virtual circuit (VC) filter  305  and to agile up-converter  308 , respectfully, to tune them to the selected program channel. 
     The selected video program is received at ONU  106  and supplied to VC filter  305  as a sequence of ATM cells. VC filter  305  filters the received signal to obtain the selected program channel signal as a MPEG2 digital video signal, i.e., a compressed digital video signal, that is supplied to MPEG2 decoder  306 . In turn, MPEG2 digital decoder  306  yields an analog version of the selected video channel, which is supplied to NTSC encoder  307  where it is encoded. The NTSC encoded signal is then supplied to up-converter  308 , where the video signal is frequency converted to the selected standard video channel frequency, i.e., 6 MHz channel. Again, note that up-converter  308  is a so-called agile up-converter that adjusts its frequency to the frequency of the supplied program channel number. The resulting channel signal is supplied to RF combiner  309  where it is combined with channel signals from others of program units  303 , if any, and transmitting via COAX to one or more TVs  107 , i.e., all the TVs, at the location, e.g., a home. 
     FIG. 4 shows, in simplified block diagram form, details of a remote control unit  108  (FIG.  1 ), including an embodiment of the invention, that may be employed with the video controller of FIG.  3 . Shown is button pad  401  for keying a desired channel number that is supplied to RF transmitter  402  and infra red (IR) transmitter  403 . RF transmitter  402  transmits to ONU  106  a RF signal, for example, a packet containing a message including the remote unit ID and the selected channel number. IR transmitter  403  transmits an infra red signal in well known fashion to an associated TV  107 - 1 . 
     In operation, a user turns ON the TV  107 - 1  by pressing an “ON” button on button pad  401  of remote control  108 - 1 . This results in two communications events. First, a wireless IR signal transmission is made via IR transmitter  403  to the TV  107 - 1 , which turns its power ON in usual fashion. Second, a wireless RF transmission is made via RF transmitter  402  of a control packet containing the identification (ID) of the remote control unit  108 - 1  and a power ON command. ONU  106  (FIG. 3) via CPU  302  retains knowledge of the channel that each TV  107  at the location was tuned to when the particular TV was last turned OFF, which is the channel that the TV should be initially tuned to when it is turned ON. This is so the TV  107  closely mimics current conventional analog video delivery techniques. ONU  106  utilizes this retained information to perform two operations. First, if the previously viewed channel is not being viewed currently by another TV  107 , ONU  106  employs the information to insure that a MPEG2 decoder  306 , if one is available, and associated circuitry is assigned to the retained channel, i.e., to the corresponding ATM VC. Second, ONU  106  sends a control packet up-stream to video server  101  (FIG. 1) and, therein, to video services controller  202 , requesting that a program on the desired previously viewed channel be transmitted to the ONU  106 . Assuming that a MPEG2 decoder  306  is available, the associated TV now displays the program on the channel that the TV was last tuned to prior to being turned OFF. 
     As a user changes TV channels, using the remote control  108 - 1 , as is done with conventional remote controls, the TV&#39;s channel is changed through the IR link. In addition, however, “wireless” RF control messages are transmitted via RF transmitter  402  to the ONU  106  and, therein, to RF receiver  301 . ONU  106  appropriately formulates and passes up-stream messages via CPU  302  to the video server  101  and, therein, to a remote video services controller  202  requesting that the transmitted digital video program for that PSPON  110  and  111  be appropriately changed. Also, if not already assigned, a MPEG2 decoder  306  and associated circuitry are assigned. If a digital video program is selected that is already being decoded by a MPEG2 decoder  306 , the previously assigned MPEG2 decoder is released. CPU  302  retains information regarding the number of TVs  107  that are viewing each requested video program. When a requested video program is no longer being viewed by any of TVs  107 , CPU  302  transmits an up-stream message to video server  101  and, therein, to video services controller  202  indicating that the video program is no longer being viewed. 
     If the selected program is not a conventional broadcast program, the system operation might be different. For example, if video-on-demand (VOD) is selected, the user is assigned an otherwise unused channel for point-to-point delivery of the interactive video preview/select program. The MPEG2 decoder  306 , for this example, is dedicated to that TV  107 , remote control  108  pair. Other TVs can also view that video, but its interactive control is disabled, as long as, the TV  107  associated with the initiating remote control  108  is still viewing the program. If the initiating remote control  108  is employed to select a different program, control of the VOD is relinquished and the next remote control  108  that attempts an interactive control function, e.g., pause, is assumed to be the initiating remote control  108 . Similarly, other interactive TV applications can be accessed. For some interactive applications, such as games, multiple controlling remote controls  108  are appropriate. In such a situation, however, the application would typically distinguish between the active remote controls  108 . 
     In summary, when CPU  302  (FIG. 3) receives a RF transmission from a previously inactive remote control unit  108 , it responds as follows: 
     if no other active TV  107  is presently viewing the selected program channel number, it assigns a program unit  303 ; 
     it writes the selected channel number&#39;s VC contained in a look-up table in CPU  302  to register  304 ; 
     it maintains a count of how many active TVs  107  are receiving the selected program channel number and stores the selected channel number in the look-up table; 
     it transmits a message up-stream to video server  101  and, therein, to video services controller  202 , requesting the transmission of the selected program channel number on the VC corresponding to the selected program channel number; 
     if the selected program channel number is presently being viewed by another active TV  107 , only the count of how many of TVs  107  are receiving the selected program channel number is updated. 
     Advantages of the embodiments of FIGS. 3 and 4 are: 
     the COAX frequency allocation is identical to that used for conventional analog CATV configurations; 
     recording on a VCR does not require any special VCR procedures due to the conventional COAX frequency allocation, however, a procedure must be defined to reserve a MPEG2 decoder and to insure that the program to be recorded is transmitted on the PSPON fiber  110  and the associated fiber  111  at the appropriate time; 
     TV features such as the LED display that shows the selected channel number, are still correct; 
     only a one way “wireless” RF control link is required. 
     FIG. 5 is a flow chart illustrating steps in the operational process of the centralized video controller of FIG. 3, namely, ONU  106  including agile up-converter  308 , in the system of FIG.  1 . Note that parameters for each of program units (PUNs)  303  in ONU  106  include number of viewers, PUN status and the program channel (CH). Now referring to FIG. 5, ONU  106  waits to receive a RF message from a remote control unit  108 . Thus, step  501  tests to determine if a message is being received. If the test result in step  501  is NO, step  501  just repeats until the test result is YES and a message has been received that yields a YES result. Then, step  502  causes the program channel (CH) to be set to the last selected channel CH (N), where “N” corresponds to the remote control unit  108 . Thereafter, step  503  tests to determine if the message is to turn “power ON”. If the test result is YES, control is transferred to step  509 . If the test result in step  503  is NO, step  504  tests to determine if the message is to change the program channel, i.e., change CH=NEWCH, or “power OFF”. If the tests result in step  504  is NO, control is returned to step  501 . If the tests result in step  504  is YES, step  505  tests to determine if a program unit (PUN)  303  (FIG. 3) is assigned. If the test result is NO, control is transferred to step  507 . If the test result in step  505  is YES, step  506  causes parameters for the assigned PUN to be retrieved; sets VIEWERS=VIEWERS−1; if VIEWERS=0 send message to OLC  104  to discontinue transmission of CH; sets PUN STATUS=IDLE; and restores parameters for the PUN. Then, step  507  tests to determine if the message was power OFF. If the test result is YES, control is returned to step  501 . If the test result in step  507  is NO, step  508  causes the program channel to be set to CH=NEWCH and sets LAST SELECTED CH(N)=CH for the associated remote control unit  108 . Thereafter, control is transferred to step  509 , which tests to determine if a PUN is assigned to the program channel (CH). If the tests result is YES step  510  causes parameters for the assigned PUN to be retrieved; sets VIEWERS=VIEWERS+1; and restores the parameters for the assigned PUN. If the tests result in step  509  is NO there is no assigned PUN and step  511  tests to determine if an idle PUN is available. If the test result is NO, the selected CH cannot be viewed and control is returned to step  501 . If the test result in step  511  is YES, an idle PUN is available and step  512  causes it to be assigned to CH. Thereafter, step  513  causes for the assigned PUN the following: set VIEWERS=1; send message to OLC requesting transmission of CH; set PUN STATUS=ASSIGNED; restore parameters for PUN; and set PUN(M)=PUN. Then, control is returned to step  501  and ONU  106  waits for a received message. 
     FIG. 6 shows, in simplified block diagram form, details of another centralized video controller employing an embodiment of the invention that may be employed in the system of FIG.  1 . In this example, ONU  106  includes at least one radio frequency (RF) receiver  301  and at least one associated RF transmitter  603 , CPU  302 , one or more program units  601 - 1  through  601 -M and RF combiner  309 . It is noted that there are as many RF transceivers including a receiver  301  and transmitter  603 , as there are remote units  108 . The number of program units  601 , i.e., M, defines the number of video programs that can be simultaneously viewed by multiple TVs within a location, e.g., a home. By way of a simple example, if there are four (4) program units than only four programs can be simultaneously viewed. Thus, if there were only four TVs at the location, there would not be any program “blocking”. However, if more than four (4) TVs are at the location, then only four (4) different channels may be viewed. The TVs in excess of the first four to have initiated receiving a channel would be restricted to viewing one of the four active channels, and would not have the ability to change a channel being viewed from the four active channels. 
     As in the embodiment of FIG. 3, RF receiver  301  receives RF signals including control messages from a remote control unit associated with a TV  107  (FIG.  1 ). This may be realized by employing a RF transmitter  402  in the TV  107  remote control unit  108 , described below in conjunction with FIG. 7, and a RF receiver  301 , both of the type used in a wireless telephone, which are well known in the art. In this example, each RF receiver  301  has an associated RF transmitter  603  for transmitting a “wireless” RF signal to an associated remote control unit  108  including the fixed channel number that up-converter  602  is tuned to, as described below. Note that there may be a plurality of TVs  107  and a corresponding plurality of remote control units  108 . Again, note that ONU  106  would include as many RF receivers and associated RF transmitters, as there are remote control units  108 . The received RF control message includes, for example, the associated remote control unit identity (ID) and a selected channel number. Other control messages include, in addition to the remote control ID, an indication of an associated TV being either powered ON or Powered OFF. The information received in the RF control message is supplied to CPU  302 . CPU  302  is, for example, a microprocessor including memory. CPU  302  retains a look-up table containing information indicating the last selected program channel number for each of TVs  107 , including those of TVs  107  that are currently inactive. When CPU  302  receives a RF transmission from a previously inactive remote control unit  108 , it assigns one of program units  601  to the TV associated with the remote control unit, it writes the last selected program channel number into register  304 , it writes the RF video program channel number being used by the assigned program unit  601  to RF transmitter  603  which, in turn, transmits the RF signal to the RF receiver in an associated remote control unit  108 , it maintains a count of how many active TVs are tuned to the selected channel number and it stores the selected channel number for this TV  107  in a lookup table. If no other served TV  107  is already tuned to the selected channel number, CPU  302  transmits a message up-stream to video server  101  and a video services controller  202 , therein, requesting the transmission of the selected channel. The selected channel is transmitted down-stream in ATM cells on the virtual circuit (VC) identified by the selected program channel number and received at the selected program unit  601 , in this example, program unit  601 - 1 . The selected channel number&#39;s VC is supplied to virtual circuit (VC) filter  305  to tune it to the selected program channel. 
     Again, the selected video program channel is received at ONU  106  and supplied to VC filter  305  as a sequence of ATM cells. VC filter  305  obtains the selected program channel signal as a MPEG2 digital video signal that is supplied to MPEG2 decoder  306 . In turn, MPEG2 digital decoder  306  yields an analog version of the selected video channel that is supplied to NTSC encoder  307  where it is encoded. The NTSC encoded signal is then supplied to up-converter  602  where the video signal is frequency converted to a predetermined standard video channel frequency, i.e., 6 MHz channel. The resulting channel signal is supplied to RF combiner  309  where it is combined with channel signals from others of program units  601 , if any, and transmitted via COAX to one or more TVs  107  at the location, e.g., a home. 
     FIG. 7 shows, in simplified block diagram form, details of a remote control unit  108  (FIG.  1 ), including an embodiment of the invention, that may be employed with the video controller  106  of FIG.  6 . Shown is button pad  401  for keying a desired channel number that is supplied to RF transmitter  402 . RF transmitter  402  transmits a RF packet signal including the remote units ID and the selected channel number to ONU  106 . RF receiver  701  receives the RF signal including the RF video program channel number of up-converter  602  of the assigned program unit  601  from RF transmitter  603  (FIG. 5) and supplies the channel number to IR transmitter  702 . In turn, IR transmitter  702  transmits an infra red signal in well known fashion to an associated TV  107 . 
     ONU  106  of FIG. 6 has a fixed channel, i.e., RF frequency, assigned to each MPEG2 decoder  306 , actually its up-converter  602 . Therefore, the video signal from each MPEG2 decoder  306  of FIG. 6 is always transmitted on the same channel. A TV  107  would be assigned a MPEG2 decoder  306  when it is turned ON. The VC is changed as channels are changed, but the TV  107  stays tuned to the channel number of the MPEG2 decoder  306  it was assigned. 
     As in ONU  106  of FIG. 3, the user turns on the TV  107  by pressing the “power ON” button of the associated remote control  108 . This directly results in only one communications event. A “wireless” RF control packet containing the identification of the remote control, and the “power ON” command is sent to the ONU  106 . The ONU  106  retains knowledge of the channel each TV  107  was tuned to when it was last turned OFF and, therefore, the channel that should be initially delivered to that TV  107  to closely mimic conventional analog video delivery techniques. As described above, the ONU  106  uses that information to perform three operations. First, it insures that a MPEG2 decoder  306 , if one is available, and associated circuitry is assigned to that video channel (i.e. that ATM VC). In addition, if the selected program channel is not being viewed by another of TVs  107 , ONU  106  sends a control packet up-stream to video server  101  and, therein, to video services controller  202 , requesting that the selected program channel, i.e., VC, be transmitted on that access PSPON fiber  110  and fiber  111  associated with the ONU  106 . Finally, the ONU  106  transmits a return “wireless” control message back to the associated remote control  108  containing the channel number used by the assigned MPEG2 decoder  306 . In response, the remote control  108  sends an IR transmission to the associated TV  107 , turning its power ON, and tuning it to the designated channel. Assuming that a MPEG2 decoder  306  was available, that TV  107  now displays the program of the channel that TV was displaying when last turned OFF. 
     As a user changes TV channels using the remote control  108  as is done with conventional remote controls, the “wireless” RF control messages are transmitted to the ONU  106  indicating those channel changes. The ONU  106  appropriately changes the MPEG2 decoder&#39;s VC, and passes up-stream messages requesting that the transmitted digital video channels for that PSPON  110  and the associated fiber  11  be appropriately changed. 
     If a MPEG2 decoder  306  is not available, which is only possible if there are more TVs  107  than decoders  306 , the TV  107  will display noise unless the selected channel is one already being decoded for another TV  107 . In that situation, a “wireless” RF control message is sent to the remote control  108 , and passed to the associated TV  107  using the IR link, appropriately changing TV channels. Only the remote control  108  that selected the program can change it. However, if that TV  107  is turned OFF, the next remote control  108  to attempt to change the channel will be given control of that MPEG2 decoder  306 . 
     In summary, when CPU  302  (FIG. 6) receives a RF transmission from a previously inactive remote control unit  108 , it responds as follows: 
     if no other active TV  107  is presently viewing the selected program channel number, it assigns a program unit  303 ; 
     it writes the selected channel number&#39;s VC contained in a look-up table in CPU  302  to register  304 ; 
     it maintains a count of how many active TVs  107  are receiving the selected program channel number and stores the selected channel number in the lookup table; 
     it transmits a message up-stream to video server  101  and, therein, to video services controller  202 , requesting the transmission of the selected program channel number on the VC=selected program channel number; 
     if the selected program channel number is presently being viewed by another active TV  107 , only the count of how many of TVs  107  are receiving the selected program channel number is updated; 
     it transmits a RF message to the corresponding remote control unit  108  containing the last selected channel number. 
     Advantages of the embodiments of FIGS. 6 and 7 are: 
     the up-converter  608  need not be frequency agile. 
     FIG. 8 is a flow chart illustrating steps in the operational process of the centralized video controller of FIG. 6 in the system of FIG.  1 . namely, ONU  106  including fixed frequency up-converter  608 , in the system of FIG.  1 . Note that parameters for each of program units (PUNs)  601  in ONU  106  include PUN status and the program channel (CH). Now referring to FIG. 8, ONU  106  waits to receive a RF message from a remote control unit  108 . Thus, step  801  tests to determine if a message is being received. If the test result in step  801  is NO, step  801  just repeats until the test result is YES, and a message has been received that yields a YES result. Thereafter, step  803  tests to determine if the message is to turn “power ON”. If the test result is YES, control is transferred to step  812 . If the test result in step  803  is NO, step  804  tests to determine if the message is to change the program channel, i.e., change CH=NEWCH, or “power OFF”. If the tests result in step  804  is NO, control is returned to step  801 . If the tests result in step  804  is YES, step  805  causes the setting of PUN=PUN(M). Thereafter, step  806  tests to determine if PUN=NONE. If the test result is YES, control is transferred to step  815 . If the test result instep  806  is NO, step  807  causes parameters to be retrieved for the PUN: setting of VIEWERS(CH)=VIEWERS(CH)−1; and if VIEWERS=0 a message is sent to OLC to discontinue transmission of CH. Then step  809  tests to determine if the message is power OFF. If the test result is YES, step  810  causes setting PUN STATUS=IDLE; setting last selected CH(N)=CH where “N” is a corresponding one of remote control units  108 - 1  through  108 -N; and restoration of the parameters for PUN. Thereafter, control is returned to step  801 . If the test result in step  809  is NO, step  811  causes the setting of CH=NEWCH; setting of last selected CH(N)=CH; if VIEWERS(CH)=0 sending a message to OLC requesting transmission of CH; setting VIEWERS(CH)=VIEWERS(CH)+1; and restoration of parameters for PUN. Then, control is transferred to step  801 . Returning to step  815 , which tests to determine if the message is power OFF, if the test result is YES, control is returned to step  801 . If the test result in step  815  is NO, control is transferred to step  813 . Returning to step  812 , it causes the setting of CH=LAST SELECTED CH(N) and control is transferred to step  813 . Step  813  tests to determine if an idle PUN is available. If the test result is NO, control is returned to step  813  and the CH cannot presently be viewed. If the tests result in step  813  is YES, a PUN is available. Then, step  814  causes the following: if VIEWERS(CH)=0, send message to OLC requesting transmission of CH; setting of VIEWERS(CH)=VIEWERS(CH)+1; setting PUN STATUS=ASSIGNED; setting PUN(M)=PUN; and restoring parameters for PUN. Thereafter, control is returned to step  801  where ONU  106  waits for a message. 
     It should be noted that in the above embodiments a location, e.g., a house, may have more active TVs than there are Program Units, however, only a number of different video channels may be viewed at the location equal to the number of program units in an associated ONU. 
     The above-described embodiments are, of course, merely illustrative of the principles of the invention. Indeed, numerous other methods or apparatus may be devised by those skilled in the art without departing from the spirit and scope of the invention.