Patent Publication Number: US-2009232226-A1

Title: Local Digital Video Distribution System for Cable

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to communications systems and, more particularly, to cable television systems. 
     Current cable television (TV) systems offer a number of services to customers such as TV programming (both network and local), pay-per-view programming and Internet access. One example of a cable TV system is a hybrid fiber/coax based network that has a bandwidth capacity of 750 MHz (millions of hertz), or more, for delivering these services to their subscribers. This bandwidth capacity is typically divided between a down stream channel and an upstream channel. The downstream channel conveys not only the TV programming but also the downstream Internet data communications to each subscriber; while the upstream channel conveys the upstream Internet data communications from each subscriber. 
     SUMMARY OF THE INVENTION 
     The above described distribution of cable TV bandwidth into a downstream channel and an upstream channel does not efficiently support local service offerings since any data communicated between endpoints must pass through the cable head-end. Therefore, and in accordance with the principles of the invention, an apparatus for use in a network comprises a port for receiving a downstream network transmission; a demodulator for receiving an upstream signal for providing a demodulated signal; and a modulator for modulating the demodulated signal for providing a downstream signal for addition to the received downstream network transmission. 
     In an illustrative embodiment in accordance with the principles of the invention, the apparatus is a video server coupled to a cable system for receiving an upstream transmission conveying video content and for retransmitting the received upstream transmission downstream to at least one cable endpoint of the cable system; wherein the server is located downstream from a head-end of the cable system. 
     In another illustrative embodiment in accordance with the principles of the invention, the apparatus is a video server coupled to a cable system for receiving an upstream transmission conveying video content and for retransmitting the received upstream transmission downstream to at least one cable endpoint of the cable system by using at least one video channel of the cable system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an illustrative cable system in accordance with the principles of the invention; 
         FIG. 2  shows an illustrative frequency spectrum in accordance with the principles of the invention; 
         FIG. 3  shows an illustrative embodiment of a server in accordance with the principles of the invention; 
         FIG. 4  shows another illustrative cable system in accordance with the principles of the invention; 
         FIGS. 5-9  show other illustrative embodiments of a server in accordance with the principles of the invention; 
         FIG. 10  shows another illustrative cable system in accordance with the principles of the invention; 
         FIG. 11  shows another illustrative embodiment of a server in accordance with the principles of the invention; 
         FIGS. 12-14  illustrate bandwidth management in accordance with the principles of the invention; 
         FIGS. 15-18  show illustrative embodiments of a programmable bandwidth device in accordance with the principles of the invention; and 
         FIGS. 19 and 20  show illustrative embodiments of endpoints in accordance with the principles of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Other than the inventive concept, the elements shown in the figures are well known and will not be described in detail. Also, familiarity with television broadcasting and receivers in the context of terrestrial, satellite and cable is assumed and is not described in detail herein. For example, other than the inventive concept, familiarity with current and proposed recommendations for TV standards such as NTSC (National Television Systems Committee), PAL (Phase Alternation Lines), SECAM (SEquential Couleur Avec Memoire) ATSC (Advanced Television Systems Committee) (ATSC) and ITU-T J.83 “Digital multi-programme systems for television, sound and data services for cable distribution” is assumed. Likewise, other than the inventive concept, familiarity with satellite transponders, cable head-ends, set-top boxes, downlink signals and transmission concepts such as eight-level vestigial sideband (8-VSB), Quadrature Amplitude Modulation (QAM), out-of-band control channels and receiver components such as a radio-frequency (RF) front-end, or receiver section, such as a low noise block, tuners, and demodulators is assumed. Similarly, formatting and encoding methods (such as Moving Picture Expert Group (MPEG)-2 Systems Standard (ISO/IEC 13818-1)) for generating transport bit streams are well-known and not described herein. It should also be noted that the inventive concept may be implemented using conventional programming techniques, which, as such, will not be described herein. Finally, like-numbers on the figures represent similar elements. Also, as used herein, the term “endpoint” includes, but is not limited to, stations, personal computers, servers, set-top boxes, cable modems, etc. 
     Turning now to  FIG. 1 , an illustrative cable system  100  in accordance with the principles of the invention is shown. Illustratively, cable system  100  is a hybrid-fiber coax (HFC) system. For simplicity, the fiber portion is not described herein. It should be noted that although the inventive concept is described in the context of coaxial cable (coax), the inventive concept is not so limited and can be extended to the processing of fiber optic signals. A plurality of stations, as represented by stations  120 - 1  to  120 - 6 , are connected to a common head-end  105  by a tree and branch cable network. In the context of the inventive concept, a head-end is an example of a controller for a network. Each station is associated with a cable subscriber. Each station includes, e.g., a set top box for receiving video programming and a cable modem for bi-directional data communications to a two-way network, e.g., the Internet. Head-end  105  is a stored-program-processor based system and includes at least one processor (e.g., a microprocessor) with associated memory, along with a transmitter and receiver coupled to the cable network (for simplicity, theses elements are not shown). Ignoring for the moment element  200 , the cable network comprises a main coaxial cable  106  having a plurality of taps  110 - 1 ,  110 - 2  to  110 -N. Each of these taps serves a corresponding feeder cable. For example, tap  110 - 1  serves feeder cable  111 - 1 . Each feeder cable in turn serves one, or more, stations via a tap and a drop. For example, feeder cable  111 - 1  serves station  120 - 1  via tap  115 - 1  and drop  116 - 1 . For the purposes of this description, it is assumed that the devices of cable network  100 , e.g., taps, drops, etc., are addressable and controllable by head-end  105  via an out-of-band signaling channel (not shown in  FIG. 1 ). Other than the inventive concept, the use of an out-of-band signaling channel to address and control devices in particular portions of the cable network is known. For example, an out-of-band control channel that is a frequency shift keying (FSK) based can be used for both addressing and control of devices in a cable network. One such system is the Addressable Multi-Tap Control System available from Blonder Tongue Laboratories, Inc. 
     In cable system  100 , communications between head-end  105  and the various stations occurs in both an upstream direction and a downstream direction. The upstream direction is towards head-end  105  as represented by the direction of arrow  101  and the downstream direction is towards the stations as represented by the direction of arrow  102 . In accordance with the principles of the invention, cable system  100  includes a device that provides a local service offering to at least one portion of the cable network without having to pass through the head-end  105 . As described herein, the local service offering provides video content. This is further illustrated in  FIG. 1  by server  200 , which is illustratively located at the beginning of feeder cable  111 - 1 . However, the inventive concept is not so limited and a device including the server function can be located in any portion of the cable network. Similarly, the inventive concept is not limited to video and other services can be provided, e.g., audio content (streaming) can be provided to one, or more, endpoints of the cable system. 
     Turning for the moment to  FIG. 2 , and in accordance with one embodiment of the inventive concept, a number of communication bands are added to the existing cable frequency spectrum. Typically, a cable system provides services via an upstream band  11  and a downstream band  12 . These services include Internet communications and television programming. However, in order to enable peer-to-peer communications, additional pairs of upstream and downstream bands are now added. These pairs of peer-to-peer frequency bands are different from those used by the cable system for Internet communications. Illustratively,  FIG. 2  illustrates three pairs of peer-to-peer bands located between upstream band  11  and downstream band  12 . However, the inventive concept is not so limited and more, or less, bands may be used and their placement in the spectrum may vary. It should also be noted that  FIG. 2  is not to scale and that transition regions between bands may be required. As shown in  FIG. 2 , the three pairs of peer-to-peer bands are: B 0 , B 1  and B 2 . The pair B 0  comprises an upstream band, B 0   u  ( 51 ) and a downstream band, B 0   d  ( 54 ); the pair B 1  comprises an upstream band, B 1   u  ( 52 ) and a downstream band, B 1   d  ( 55 ); and the pair B 2  comprises an upstream band, B 2   u  ( 53 ) and a downstream band, B 2   d  ( 56 ). 
     Returning to  FIG. 1 , server  200  receives a communication from an endpoint located off of feeder cable  111 - 1  (e.g., station  120 - 1 ) via an upstream peer-to-peer band as represented by dashed arrow  31  (e.g., B 0   u  of  FIG. 2 ). Server  200  translates the frequency of this received signal and changes its direction to transmit that communication downstream to other users located off of feeder cable  111 - 1  via a downstream peer-to-peer band as represented by dashed arrow  32  (e.g., B 0   d  of  FIG. 2 ). 
     Turning now to  FIG. 3 , an illustrative embodiment of server  200  is shown. Server  200  comprises directional coupler  205 , upstream demodulator  225  and downstream demodulator  245 . Server  200  is coupled to a cable network via path  201 . An upstream signal from drop  201  is received via directional coupler  205 , which is provided to upstream demodulator  225  via signal path  214 . Demodulator  225  is tuned to the appropriate peer-to-peer band. This can be accomplished via the earlier mentioned out-of-band control channel (not shown in  FIG. 3 ) or can be preconfigured in server  200 . Upstream demodulator  225  demodulates the received upstream signal in the designated peer-to-peer band (e.g., B 0   u ) and provides a demodulated signal to downstream modulator  245 . The demodulated signal represents video which can be in a compressed format (e.g., MPEG2, H.263, H.264, VC1, or other formats). Downstream modulator  245  modulates the demodulated signal to provide downstream signal  246  in the corresponding peer-to-peer band (e.g., B 0   d ). Downstream signal  246  is coupled back to drop  201 , via directional coupler  205 , for transmission back downstream for receipt by, e.g., station  120 - 2 . It should be noted that, if necessary, separate decoder and coder functions may be included in the demodulator and modulator, respectively. Alternatively, a separate decoder and coder may be added to the embodiment shown in  FIG. 3  for further processing of the demodulated signal. For example, server  200  may provide a transcoding function, where the upstream video is coded in one video format; while the resulting downstream video is coded in another video format. 
     As noted above, a cable system may have one, or more, devices supporting a server function located in one, or more, portions of the cable network. Illustratively,  FIG. 1  shows a server coupled to a feeder cable. Another illustrative location and type of server is shown in  FIG. 4 . The elements in  FIG. 4  are similar to those found in  FIG. 1  except for server  300 , which serves feeder cable  111 - 1 . As can be observed, all upstream and downstream communications pass through server  300 . An illustrative embodiment of server  300  is shown in  FIG. 5 . 
     Server  300  comprises upstream/downstream filters  210 , upstream demodulator  225 , downstream modulator  245 , controller  250  and directional coupler  205 . Controller  250  controls the various elements of server  300  and is, e.g., a microprocessor with associated memory. For simplicity, the various control signals from controller  250  to different ones of the elements of server  300  are not shown. The operation of server  300  is similar to the description above with respect to server  200  except for the inclusion of upstream/downstream filters  210 . In this example, it is assumed that a particular one of the peer-to-peer bands shown in  FIG. 2  is designated for use by server  300 . Upstream/downstream filters  210  have a stop band that corresponds to the designated peer-to-peer band (e.g., B 0  of  FIG. 2 ). As a result, all downstream signals received, via path  316 , are first filtered by upstream/downstream filter  210  to provide a filtered signal, which is passed, via path  211  and directional coupler  205 , to path  331  for further transmission downstream. Likewise, all upstream signals received, via path  331 , are also filtered by upstream/downstream filter  210  before being passed, via path  316 , for transmission further upstream. For example, if server  300  is configured to only use peer-to-peer band B 0  of  FIG. 2 , upstream/downstream filters  210  have stop bands corresponding to peer-to-peer band B 0   u  and B 0   d  to prevent any interference with the peer-to-peer transmission using band B 0  on feeder cable  111 - 1 . 
     Another illustrative embodiment of a server  300  in accordance with the principles of the invention is shown in  FIG. 6 . This device is labeled as  300 ′. Server  300 ′ is similar to server  300  except that upstream/downstream filters  210  has been replaced with a programmable upstream/downstream filters  210 ′ and controller  250  allows a system control processor (not shown) in the cable network (e.g., located in head-end  105 ) the ability to configure server  300 ′ by setting filter parameters of upstream/downstream filters  210 ′. In particular, controller  250  is responsive to the above-mentioned out-of-band signaling channel (represented by signal  254 ) for setting the filter stop bands via control signal  251  (shown in dotted line form). In this regard, the out-of-band signaling channel is modified to include predefined commands that are associated with the different filter settings. Another illustrative embodiment of a server  300  in accordance with the principles of the invention is shown in  FIG. 7 . This device is labeled as  300 ″. Server  300 ″ is similar to server  300 ′ except for the addition of elements  220 ,  265  and  270 . This illustrative embodiment provides a server for inserting the local video into an existing channel of the downstream video transport stream as opposed to using the above-described peer-to-peer bands. Illustratively, this use of an existing channel can be determined beforehand, e.g., channel  81  is designated for local video. As such, directional coupler  215  provides the downstream signal to element  220 , which demodulates the downstream video transport portion thereof to provide a digital transport signal to multiplexer (mux)  265 . As known in the art, the digital transport signal represents a number of video channels. Mux  265  replaces the video content on the designated channel with the video content conveyed by the demodulated signal from upstream demodulator  225  to provide a new video transport signal to element  270 . Element  270  modulates this signal to provide a new downstream video transport signal for reception by one, or more, of the downstream stations on this portion of the cable network. Thus, these downstream stations merely have to tune their TVs or set top boxes to the designated video channel for viewing the local video thereon. In this embodiment, upstream/downstream filters  210  pass other downstream channels (e.g., those bands designated for providing Internet service) further along downstream via directional coupler  205 . 
     Another illustrative embodiment of a server  300  in accordance with the principles of the invention is shown in  FIG. 8 . This device is labeled as  300 ′″. Server  300 ′″ is similar to server  300 ″ except for the addition of elements  230  and  235 . These elements provide a transcoding function. In other words, local video content may be received in any one of a number of compressed formats (other than MPEG2). Video decoder  230  suitably decompresses the demodulated signal provided by upstream demodulator  225  and provides the uncoded signal to MPEG2 coder  235 , which encodes the video into an MPEG2 format for retransmission back downstream. It should be noted that although shown as separate elements, the decoding and coding functions may be a part of the demodulator and modulator, respectively. 
     Another illustrative embodiment of a server in accordance with the principles of the invention is shown in  FIG. 9 . This device is labeled as  500  in  FIG. 9 . Server  500  comprises switches  315 ,  320  and  325 , up/down band stop (BS) filter  310 , controller  305 , splitter  330  and server  200 . The latter is identical to server  200  of  FIG. 3 , except that directional coupler  205  of  FIG. 3  is coupled to path  204  as shown in  FIG. 9 . Controller  305  allows a system control processor (not shown) in the cable network (e.g., located in head-end  105 ) the ability to configure the server, e.g., whether it is on or off, establish frequency (e.g., which peer-to-peer bands to use) and/or gain settings. Illustratively, in this embodiment, controller  305  controls whether or not the server function is enabled for feeder cable  111 - 1 . In particular, controller  305  is responsive to the above-mentioned out-of-band signaling channel (represented by signal  304 ) for enabling or disabling the server function in server  500  via switches  315 ,  320  and  325 , which are controlled by controller  305  via control signal  306  (shown in dotted-line form). In this regard, the out-of-band signaling channel is modified to include predefined commands that are associated with enabling or disabling the server function in a particular device. When the server function is disabled, switches  315  and  310  are configured such that all upstream signals received, via path  331 , from feeder cable  111 - 1  are passed, via splitter  330 , to main coaxial cable  106 . Likewise, all downstream signals received, via path  316 , from the main coaxial cable  106  are passed, via splitter  330 , to feeder cable  111 - 1 . In addition, switch  315  disconnects server  200  from the network. However, when the server function is enabled, all upstream signals received, via path  331 , from feeder cable  111 - 1  are also provided to server  200 , via switch  325 . Server  200  functions as described above to provide a local video signal back downstream. Further, when the server is enabled, up/down BS filter  310  is now switched in to further filter both upstream and downstream communications. BS filter  310  has stop bands that correspond to the peer-to-peer bands used by server  200 . For example, if server  200  is configured to only use peer-to-peer band B 0  of  FIG. 2 , up/down BS filter  310  has a stop band corresponding to peer-to-peer band B 0  to prevent any interference with the peer-to-peer transmission using band B 0  on feeder cable  111 - 1 . 
     Another illustrative embodiment of a cable system in accordance with the principles of the invention is shown in  FIG. 10 . This figure is similar to  FIG. 4  except for tap  400 , which includes the server function. Tap  400  is shown in more detail in  FIG. 11 . As can be observed from  FIG. 11 , tap  400  comprises server  300  (described above) of  FIG. 3  (or the servers of  FIGS. 6 ,  7 ,  8  and  9 ). Thus, and in accordance with the principles of the invention, tap  400  is used to provide a server function in the cable system. 
     As described above, peer-to-peer channels may be used to convey the local services as illustrated in  FIG. 2 . These peer-to-peer channels are different from the existing upstream and downstream channels used to convey programming and Internet communications in the cable system. Alternatively, an existing channel used to convey downstream programming may also be used in accordance with the principles of the invention. This was illustrated in  FIGS. 7 and 8  in the context of using a preexisting video channel. In addition, since it is difficult to reuse just any downstream channel, a band select amplifier may be used that allows a boundary between upstream and downstream communications to be moved over different portions of the cable network. In accordance with the principles of the invention, the bandwidth of cable system  100  is divided into a number of bands as illustrated in  FIG. 12 . There is a fixed upstream band B 0  ( 11 ) for upstream communications, a fixed downstream band B 3  ( 12 ) for downstream communications and a number of programmable bands, as represented by B 1  ( 71 ) and B 2  ( 72 ). Illustratively, the programmable bands are arranged between upstream band B 0  and downstream band B 3 , but the inventive concept is not so limited as to either the location of these bands or their number. As a result, in a particular portion of the cable network the boundary between upstream and downstream communications can be moved. This is illustrated by  FIGS. 13 and 14 . In  FIG. 13 , the upstream communications initially include bands B 1  and B 2 . In  FIG. 14 , it can be observed that one of the upstream bands, B 2  ( 72 ) has now been allocated to downstream communications. In the context of these figures, the suffix “u” or “d” is attached to the band B 1  or B 2  as appropriate to further indicate whether B 1  or B 2  is allocated to the upstream or downstream directions, respectively. 
     Turning now to  FIGS. 15 and 16 , an illustrative block diagram of filter  210  for use in the above-described server embodiments is shown.  FIG. 15  illustrates the downstream filter portion of filter  210 , this comprises a bank of filters  520 ,  525  and  530 , along with multiplexers (switches)  515  and  535 , which are controlled via the above-described control signal  251 . As shown in  FIG. 15 , the multiplexers are used to route the signal through one of the filters as determined by control signal  251 . Each filter has a pass band that corresponds to one of the downstream bands shown in  FIG. 12  (again, the suffix d denotes the filter is in the downstream path). For example, if only filter  520  is selected then any downstream communications using bands B 1  and B 2  from the head-end are blocked, freeing those bands for use by server  300 . In this regard, the out-of-band signaling channel is modified to include predefined commands that are associated with particular bandwidth configurations. 
     Similar comments apply to  FIG. 16 , which illustrate the upstream filter portion of filter  210 . This portion comprises a bank of filters  570 ,  575  and  580 , along with multiplexers (switches)  565  and  585 , which are controlled via control signal  251 . As shown in  FIG. 16 , the multiplexers are used to route the signal through one of the filters as determined by control signal  251 . Each filter has a pass band that corresponds to one of the upstream bands shown in  FIG. 12  (again, the suffix u denotes the filter is in the upstream path). 
     Other illustrative embodiments of a filter  210  in accordance with the principles of the invention are shown in  FIGS. 17 and 18 , which show alternative embodiments for the downstream and upstream portions of filter  210 . In  FIG. 17 , the downstream filter portion comprises a splitter  805 , a set of filters  810 ,  815  and  820 , multiplexers (switches)  825  and  830  and a combiner  835 . The downstream signal  316  is applied to splitter  805 , which splits the signal for application to each filter. As shown in  FIG. 17 , filter  810  has a pass band B 3 ; filter  815  has a pass band B 2  (again, the suffix d denoting the filter is in the downstream path) and filter  820  has a pass band B 1 . Multiplexers  825  and  830  are controlled via control signal  251  to either pass or block signals from their respective filters for application to combiner  835 . The latter combines any applied signals and forms the downstream signal  211 . 
     Likewise, in  FIG. 18 , the upstream portion comprises a splitter  855 , a set of filters  860 ,  865  and  870 , multiplexers (switches)  875  and  880  and a combiner  885 . The upstream signal  211  is applied to splitter  855 , which splits the signal for application to each filter. As shown in  FIG. 18 , filter  860  has a pass band B 0 ; filter  865  has a pass band B 1  (again, the suffix u denoting the filter is in the upstream path) and filter  870  has a pass band B 2 . Multiplexers  875  and  880  are controlled via control signal  251  to either pass or block signals from their respective filters for application to combiner  885 . The latter combines any applied signals and forms the upstream signal  311 . 
     As described above, the inventive concept provides an alternative approach for providing local service offerings to customers in a cable network. Thus, it is possible to provide location-specific information to different portions of the cable network, such as video from a guard house of an apartment complex, or news and information of interest to a local group on a portion of the cable network. 
     Turning now to  FIG. 19 , an illustrative embodiment of an apparatus for use in one, or more, of the stations of the cable system of, e.g.,  FIG. 1 , is shown. Apparatus  600  comprises camera  605 , video encoder  610  and upstream modulator  620 . The physical location of the various components can vary, i.e., camera  605  does not have to be co-located with upstream modulator  620 . Alternatively, two or more of the elements shown in  FIG. 19  can be arranged in a single unit (e.g., a video camera that includes upstream modulator  620 ). Camera  605  provide a video signal to video encoder  610 . The latter compress the video signal into a compressed video format (e.g., MPEG2, H.263, H.264, VC1, or other formats). The compressed video is provided to upstream modulator  620  for modulation in the appropriate upstream channel for communication to, e.g., server  200  (or server  300 , etc.). 
     Another illustrative embodiment of a cable modem in accordance with the principles of the invention is shown in  FIG. 20 . Cable modem  700  comprises a peer-to-peer (P2P) modulator  705 , a P2P demodulator  710 , a downstream demodulator  715  and an upstream demodulator  720 . Cable modem  700  is coupled to a cable network via a drop  701 , a splitter  85  and path  704 . The splitter  85  also provides a cable signal  702  to other equipment located at the station, e.g., a set top box (not shown). Upstream modulator  720  and downstream modulator  715  function as known in the art and enable a user to have Internet service and run Internet applications (e.g., a browser located on a personal computer (PC) (not shown). P2P modulator  705  and P2P demodulator  710  provide the above-mentioned peer-to-peer connectivity and are configurable to one, or more, of the peer-to-peer bands (e.g., as illustrated in  FIG. 2 ). These settings may be determined via software as options set by the user via the PC coupled to cable modem  700 . In addition, the PC may store address information for particular members of the peer-to-peer network, where each address is associated with a particular peer-to-peer band. Upstream peer-to-peer communications is provided via signal  706  to P2P modulator  705 , which provides an upstream signal in the designated peer-to-peer band. Downstream peer-to-peer communications is provided via signal  711  from P2P demodulator  710 , which demodulates received signal in the designated peer-to-peer band. As described herein, peer-to-peer communications includes not only messaging, but also, e.g., broadcast messages, multi-casting, etc. For example, a user can stream content from one endpoint to one or more other endpoints of the cable system in accordance with the principles of the invention. This content can be video, audio, etc. Further, although the inventive concept was described in the context of application to a traditional cable system, the inventive concept is not so limited and is applicable to any form of network, even, e.g., a home network, campus network, etc. 
     As such, the foregoing merely illustrates the principles of the invention and it will thus be appreciated that those skilled in the art will be able to devise numerous alternative arrangements which, although not explicitly described herein, embody the principles of the invention and are within its spirit and scope. For example, although illustrated in the context of separate functional elements, these functional elements may be embodied in one or more integrated circuits (ICs). Similarly, although shown as separate elements, any or all of the elements may be implemented in a stored-program-controlled processor, e.g., a digital signal processor (DSP) or microprocessor that executes associated software. For example, the separate modulator and demodulator functions shown in  FIG. 3  may be located in one, or more, DSPs. Further, although shown in particular configurations, the elements therein may be distributed in different units in any combination thereof. For example, a cable modem may be a part of a personal computer, etc. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.