Abstract:
A method and apparatus for coupling a system propagating home networking communications signals over telephone lines to a system propagating television signals over a coaxial cable system to a television device. A three port adapter has a phone line port, a first coaxial cable port and a second coaxial cable port. The first coaxial cable port is coupled to the phone line port through a low pass filter and wideband balun adapted to pass home networking communications signals while being adapted to reject television signals. The first coaxial cable port is also coupled to the second coaxial port through a high pass filter while being adapted to reject home networking communications signals. The phone line port is coupled to the system propagating home networking communications signals. The first coaxial cable port is coupled to the system propagating television signals over coaxial cable. The second coaxial cable port to the television device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application claims priority to and the benefit of the filing date of U.S. Provisional Patent Application No. 60/291,770 filed May 17, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to the field of communications, and, in particular, to a frame-based communications network utilized by consumers on customer premises. 
     As computers become more and more cost effective for the everyday consumer and for small businesses, such computers become more plentiful for use within local area environments such as homes, office buildings and the like. For example, within a home a person with a computer in the bedroom, and another in the living room, may want to share common files, utilize a common digital subscriber line (DSL), or otherwise transfer information between the computers. Accordingly, various technologies are being developed for computer interconnection of multiple computers located within such environments. One example of such technologies are the Home Phoneline Network Alliance (HPNA) specifications for local area network (LAN) computer interconnection which utilize existing telephone lines within the local environment for the transmission of data packets between the computers, as described in detail in copending U.S. patent application Ser. No. 09/826,239 filed on Apr. 4, 2001, entitled “Transceiver Method and Signal Therefor Embodied in a Carrier Wave for a Frame-Based Communications Network”, and as implemented in Broadcom Corporations&#39; ILINE ™ family of products. 
       FIG. 1  shows in block diagram form a general home networking environment within which the present invention can be implemented. Home network  10  includes existing (installed) plain old telephone service (POTS) wiring  12 , network clients  14 , the computer port side of modem  16  and fax  18 . POTS wiring  12  provides wiring infrastructure used to network multiple clients at a customer premises (e.g., home or office)  20 . POTS wiring  12  can be conventional unshielded twisted pair (UTP) wiring that is generally routed internally in the walls of the customer premises  20  to various locations (e.g., rooms) within the customer premises. POTS telephones  26  are typically connected to POTS wiring  12 . Subscriber loop  22 (also called a local loop) is a physical wiring link that directly connects an individual customer premises  20  to the Central Office through telephone network interface  24 , a demarcation point between the inside and outside of customer premises  20 . Of particular importance for residential networks are systems that provide communication between computers as reliably and with as high a data rate as possible. Communication over residential telephone wiring is provided through frame-oriented link, media access and physical layer protocols. 
     Further, in most cases today, a home&#39;s entertainment center (e.g., televisions)is not networked in any way. Typically, a phone jack is not present at or near most home entertainment centers. It is normally too expensive or undesirable to add new wiring to provide a new phone jack. Likewise, an Ethernet LAN network connection is too costly and troublesome to provision for such home entertainment centers as opposed to its use in computer networking. Some cable television installers have used inexpensive HF band FM wireless modems to provide a simple, low bandwidth analog modem connection to the home entertainment system. This enables low-speed Internet access and pay-per-view services. These low speed wireless modem links are not suitable for high bandwidth, high quality video or Voice over IP (VoIP) services. 
     Other, higher bandwidth, wireless networking products such as those implementing the IEEE 802.11b specification and more recently the IEEE 802.1a specification are available, but these products suffer from poor link reliability over even fairly short transmission distances and cannot offer the low bit error rates necessary to carry digital video without significant interruption to the viewer. Additionally, high bandwidth wireless nodes are relatively expensive when compared to using HPNA 2.0 over existing coaxial cable. However, at or very near almost every home entertainment center there is pre-wired coaxial cable (e.g., RG-6 or RG-59 coax) that feeds the cable television or TV antenna signal to other rooms in the house. Typically, coax is installed to all the other likely entertainment locations in the house—the bedrooms, the study, the family room or lounge—making coax ideal for the delivery of high-speed digital content to exactly where it is desired. 
     In addition to physical installation considerations, when designing home networks another important consideration is spectral management. The coaxial cabling within a typical home is subject to several sources of ingress. In addition to the expected terrestrial broadcast and cable broadcast television signals, other intentional signals such as cable modems or set top box conditional access signals may be present. Examples of the several signals of services and frequencies that may be present on household coaxial cable and may interfere with each other are shown in  FIG. 2 . Additionally, there are some unintentional noise sources on the household coaxial cable. Older built-in TV tuners can generate significant amounts of intermediate frequency (IF) egress out of their antenna/cable TV F-connectors. Televisions that are directly connected to the coaxial cable may cause some interference to the HPNA signals on the coaxial cable. 
     Given the HPNA home networking system depicted in  FIG. 1 , and the desirability that the HPNA home networking system be interconnected to pre-existing coaxial cable system(s) within the home, such as one connecting cable TV, and the desirability of appropriately managing the spectrum on the coaxial cable network, a need therefore exists for a system, method and apparatus for transporting home networking frame-based communications signals over coaxial cables. The present invention provides a solution to meet such need. 
     SUMMARY OF THE INVENTION 
     In one embodiment of the present invention a method and apparatus is provided for coupling a system propagating home networking communications signals over telephone lines to a system propagating television signals over a coaxial cable system to a television device. A three port adapter has a phone line port, a first coaxial cable port and a second coaxial cable port. The first coaxial cable port is coupled to the phone line port through a low pass filter and wideband balun adapted to pass home networking communications signals while being adapted to reject television signals. The first coaxial cable port is also coupled to the second coaxial port through a high pass filter while being adapted to reject home networking communications signals. The phone line port is coupled to the system propagating home networking communications signals. The first coaxial cable port is coupled to the system propagating television signals over coaxial cable. The second coaxial cable port is coupled to the television device. The three port adapter includes a DC bypass path between the first coaxial port and the second coaxial cable port. The low pass filter passes signals in the 4 to 30 MHz band and the high pass filter passes signals greater than 30 MHz. The wideband balun includes a transformer for matching 75 ohm coaxial cable to an approximately 100 ohm to 135 ohm twisted, untwisted, shielded or unshielded wire pair. The wire pair can be a phone line. 
     In another embodiment of the present invention a method and apparatus for splitting television signals propagating over a coaxial cable system is provided. A three port adapter has a first coaxial cable port, a second coaxial cable port and a third coaxial cable port. The first coaxial cable port splits power between the second coaxial port and the third coaxial port through a ferrite bead splitter. The first coaxial cable port, the second coaxial cable port and the third coaxial cable port are coupled to each other through an inductor/capacitor circuit adapted to provide a low loss path there between at frequencies propagating home networking communication signals. 
     As will become readily apparent in view of the detailed description set forth below, network communication utilizing HPNA 2.0 16/32 Mbps home networking communication signal technology sharing a home&#39;s existing coaxial cable provides high-speed networking for delivery of high quality digital video, voice over IP (VoIP) and shared broadband Internet access throughout the house without adding any new wires. HPNA 2.0 can be added to the existing coaxial cable and be totally compatible with the existing cable TV or off-air TV signals. Additionally, HPNA 2.0 nodes are relatively inexpensive. Further, as more bandwidth is required, future HPNA standards that provide up to 100 Mbps could be employed over exactly the same network infrastructure, offering a simple upgrade path for future services such as high definition television. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows in block diagram form a general home networking environment within which the present invention can be implemented. 
         FIG. 2  shows in table format examples of several signals of services and frequencies that may be present on household coaxial cable and which may interfere with each other. 
         FIG. 3  is one embodiment implementing the present invention. 
         FIG. 4  shows in block diagram form a three port adapter in accordance with the present invention. 
         FIG. 5  shows the three port adapter of  FIG. 4  in schematic form. 
         FIGS. 6   a  and  6   b  show the coax port to HPNA port frequency response of the three port adapter depicted in  FIGS. 4 and 5 . 
         FIG. 7  shows the coax port to TV port frequency response of the three port adapter depicted in  FIGS. 4 and 5 . 
         FIGS. 8   a  and  8   b  show the TV port to HPNA port frequency response of the three port adapter depicted in  FIGS. 4 and 5 . 
         FIG. 9  is a schematic diagram of a bypass splitting adapter in accordance with the present invention. 
         FIGS. 10   a  and  10   b  show typical customer premises coaxial cable environments. 
         FIG. 11  shows an embodiment in accordance with the present invention. 
         FIG. 12  shows a further embodiment in accordance with the present invention. 
         FIG. 13  shows still another embodiment in accordance with the present invention. 
         FIG. 14  shows a still further embodiment in accordance with the present invention. 
         FIG. 15  is still another embodiment in accordance with the present invention. 
         FIG. 16  is yet another embodiment in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 3 , one embodiment implementing the present invention is shown. System  100  includes computer  14 , which can transmit and receive data in accordance with the HPNA protocol, and televisions  102  are interconnected over a coaxial cable transmission medium to Cable TV Network Feed  104 . As the home entertainment market moves towards high bandwidth broadband digital media delivery, digital distribution of that media content within the home becomes essential. With the broadband access point at the home entertainment center via cable modem/set top box  106  and with an in-home network emanating from that point, it becomes possible to provide high-quality digital streaming video, VoIP and Internet access services throughout the home. In accordance with the present invention a simple way is provided to transport digital media using HPNA 2.0 traffic over 75Ω coaxial cable, in addition to phone cable as described above and shown in  FIG. 1 , that may already exist in a home wherein HPNA 2.0 communication traffic can coexist on the house&#39;s existing coaxial cable and provide high quality service to all nodes on most coaxial cable installations. Adapters  108  splice and match the HPNA signal into the coaxial cable, e.g., RG-6/59. The HPNA signal will coexist on the coaxial cable with most existing cable TV or off-air TV transmissions. In the limited cases in which there exists spectrum conflict, dedicated coax can be run from the point of entry to the DOCSIS cable modem or conditional access set top box. In accordance with the present invention adapters  108 , described in more detail below, are simple passive three port devices which allow the HPNA 2.0 signals to coexist on the coaxial cable. In another aspect of the present invention, an inexpensive HPNA bandpass splitter device  110  is provided, also described in more detail below. To direct the Cable TV Network Feed  104  a series of RF splitters  112  are used. Video unit  114  receives and decodes a full-bandwidth MPEG2 video stream from cable modem/set top box  106 . Cable modem/set top box  106  interfaces with adapter  108  through Ethernet to HPNA bridge  116 . 
     Referring to  FIG. 4 , adapter  108  is shown in block diagram form. Adapter  108  is used, one per phone cable based HPNA node on the coaxial cable system, to splice and impedance match the HPNA signal onto the coaxial cable. Adapter  108  (also identified as an HPNA to Coax Tap, or HCT) is a simple passive three port diplexer/balun device with coax to coax DC bypass. Adapter  108  includes HPNA—RJ11 connector port  120 , Coax (to wall)—‘F’ type RF connector port  122 , and TV—‘F’ type RF connector port  124 . The electrical characteristics between the ports are as follows. There is isolation between the TV port  124  and HPNA port  120 . Between the coax port  122  and TV port  124  there is DC continuity. Between the coax port  122  and HPNA port  120  and TV port  124  there is diplexer function  126  having low-pass filter  128  and high-pass filter  130 , such that energy from the coax port  122  in the 4 to 30 MHz band is directed to the HPNA port  120  (and vice versa) and energy above about 30 MHz is directed to the TV port  124 (and vice versa). Additionally, the HPNA port includes transformer/balun  132  to match the 75 ohm of the coaxial cable to the 135 ohm of the HPNA node. 
     Adapter  108  as shown in  FIG. 4  is shown in more detail schematically in  FIG. 5 . Transformer  132  has windings of 8t:6t of 26 awg coated copper wire on an Amidon FT23-43 core (or the like). This impedance matches the 135 ohm phone line of HPNA port  120  to the 75 ohm coax port  122  while simultaneously performing a balun function. Diplexer  126  is formed by the 82 pF capacitor C 1 /0.39 uH inductor L 2  and 82 pF capacitor C 2 /0.39 uH inductor combination. A preferred diplexer cross-over frequency is 27.4 MHz, which is a convenient frequency between the top of the HPNA band and the bottom of the TV/Cable band. 0.01 uF capacitors C 3 , C 4 , C 8  and C 9  provide DC blocking. 0.39 uH 350 mA miniature inductor L 4  provides a DC bypass between coax port  122  and TV port  124 . Inductor L 4 &#39;s 350 mA minimum current rating allows up to 0.5A to pass between these ports without saturating inductor L 4 . Those skilled in the art can appreciate that the component values may be adjusted for circuit optimization. 
       FIGS. 6   a  and  6   b  show the coax port to HPNA port frequency response of HCT adapter  108 .  FIG. 6   a  is for 0-10 MHz, while  FIG. 6   b  is for 0-500 MHz. There is very low loss between the coax port and HPNA port in the HPNA band (about 1.2 dB maximum at 10 MHz) and excellent isolation between these two ports at frequencies above 30 MHz. 
       FIG. 7  shows the coax port to TV port frequency response of HCT adapter  108  for 0-500 MHz. There is very low loss (less than 1 dB) above 50 MHz between the coax port and TV port. Also it should be noted that there is good isolation between these two ports in the HPNA band. This will prevent stray IF interference from the TV from affecting the HPNA on the coaxial cable. 
       FIGS. 8   a  and  8   b  show the TV port to HPNA port frequency response of HCT adapter  108 .  FIG. 8   a  is for 0-10 MHz, while  FIG. 8   b  is for 0-500 MHz. There is excellent isolation between the TV port and HPNA port at all frequencies. The worst case (at the diplexer crossover frequency of 30 MHz) is still better than 6 dB. 
     Referring to  FIG. 9 , bypass splitting adapter  110  is shown center line  3 L of the cylindrical piston bore  3 , the distance D 1  from the base portion of the reed valve element  35  to the center while also providing a bypass for HPNA frequencies between all ports. Bypass splitting adapter  110  replaces conventional RF splitters in wiring situations where there are multiple levels of RF splitters. Conventional RF splitters, found in nearly all home coaxial cable wiring systems, have significant isolation (loss) between its output ports at frequencies above a 2 or 3 MHz. Since HPNA adapters use frequencies above 4 MHz, conventional RF splitters need to have an additional bandpass function. Essentially, bypass splitting adapter  110  is a conventional splitter with extra passive components added to provide a bypass for the HPNA frequencies between all ports on the splitter. Ferrite bead splitter provides the power split function with isolation between the two output ports  142   a ,  142   b  at VHF/UHF, while three 0.39 μH inductors  144   a ,  144   b ,  144   c  and 82 pF capacitor  146  provide a low-loss path between all three ports  142   a ,  142   b ,  142   c  for HPNA signals. Those skilled in the art can appreciate that simply by adding more 0.39 μH inductors, one per port, multi-port HBS products can easily be produced. 
     Representative typical environments within which the present invention can be most useful are shown referring to  FIGS. 10   a  and  10   b . Although there are many possible scenarios in homes, the embodiments of the present invention set forth in  FIGS. 11-16  are representative of typical scenarios including systems which may have installations of an entertainment (e.g. Direct Broadcast System (DBS), Multi Service Operator (MSO)) system that uses HPNA over coaxial cable. 
     Referring to  FIG. 10   a , typical home coaxial cable installation  200  is shown. Two levels of splitters  210   a ,  210   b  feed coaxial cables  212  to most rooms in the house, connecting cable head end  214  with televisions  216 . In  FIG. 10   b  an additional splitter tier  210   c  for connecting cable head end  214  through additional cable  212   a  and cable modem  230  to computer  232  is added to the system of  FIG. 10   a.    
     In  FIG. 11 , the existing cable broadcast services shown in  FIG. 10   a  is replaced with DBS  218 . In addition Video NIC device  219  is included, wherein a full bandwidth MPEG2 video stream is desired to be received and decoded. “X”  220  indicates where the exiting cable is cut. Arrow  222  indicates where a splitter is reoriented. Typically, a house will only use either cable TV or an off-air antenna but not both, since that would require doubling up every coaxial cable run in the house. The “top of the tree” point is a point of entry where the cable TV or antenna gets fed into the house&#39;s coaxial wiring plant. This is usually at the top of the splitter tree  210   a ,  210   b . Typically, up to two or three “levels” of splitters may be used. RF splitters can be two-, three- or four-way devices. They are simple passive devices that have about 4 dB split loss per two way split and about 10 dB of isolation between the output ports per two way split over a frequency range from below 5 MHz to above 500 MHz. Two-way splitters have the least split loss and isolation. Internally, three- and four-way splitters use multiple cascaded two-way splitters to achieve the multi-way split. A three-way splitter consists of 2 two-way splitters and a four-way splitter consists of 3 two-way splitters. In the worst case, a four-way splitter has about 8 dB loss per split and about 20 dB isolation between the extremities of the splitter tree. Path loss of 4 db per two-way split down the splitter tree from the top is acceptable for HPNA 2.0 which will work at full rate up to about 28 dB attenuation. The attenuation of the coaxial cable (RG-6 or RG-59)  212  at HPNA frequencies (4 to 10 MHz) over the typical distances found in a home is insignificant. In a typical home, if two-way splitters were used, the worst case coax path loss from the end of any one coaxial cable to another would only be 14 dB. (4 dB going up the tree from the second level splitter plus 10 dB across the top-level splitter). If the same two level system used four-way splitter devices instead of two way devices, the worst case coax path loss from the end of any one coaxial cable to another could be as much as 28 dB. (8 dB from the second level splitter plus 20 dB across the top level splitter.) HPNA would still be able to provide full performance with this level of attenuation. For streaming video, VoIP or Internet access services from the broadband access point at the top of the splitter tree down to any end node, the end-to-end path loss will be 22 dB (=8+8+3+3 dB, per our worst case with all four way splitters used scenario). As previously noted, this will not affect the performance of the HPNA system. For the initial introduction of HPNA 2.0 over coaxial cable systems it is anticipated that all streaming of high-speed video will be from the top of the splitter tree. End node to end node traffic is likely to have only low bandwidth needs and so a path loss of even 42 dB should still be considered acceptable. Services that need high bandwidth between the end nodes or coaxial cable installations with more than two levels of four-way splitters will require some level of mitigation to remove the isolation loss between output ports on the splitters in the HPNA frequency band. Similarly, more levels of splitters will require mitigation of isolation loss at more than one device. Essentially, existing splitter configurations have a few extra passive components added to them to provide a bypass for the HPNA frequencies between all ports on the splitter. Likewise, for households that wish to receive MSO services, HPNA over coaxial cable can distribute digital data over the coaxial cable used to distribute the cable content. Architectures with MSO services generally require one extra run of coaxial cable to the new main STB and possible reorientation of some of the existing splitters. This allows the existing coaxial cable to be reused with the main STB becoming the top of the distribution tree. 
     Referring now to  FIG. 12 , there is depicted a system wherein MSO content is provided with a DOCSIS cable modem. Main STB  240  does not include a DOCSIS cable modem. Content is transmitted from cable headend  214  to main STB  240  using new coaxial cable run  242  and the existing coaxial cable tree is used to distribute digital data from the main STB as well as relay the RF content through the main STB. Any DOCSIS cable modems  230  use existing coaxial cable separate from the HPNA over coaxial cable network. Alternatively, if main STB  240  does contain DOCSIS cable modem functionality, existing cable modem  230  becomes redundant. In these types of scenarios, the existing coaxial cable is used to distribute digital data from main STB  240  using HPNA. Existing cable modem  230  as seen in  FIG. 12  is replaced with an HCT and a HPNA adapter  244  as shown in  FIG. 13 . Again, content is transmitted from cable headend  214  to main STB using new coaxial cable run  246  and the existing coaxial cable tree is used to distribute digital data from the main STB as well as relay the RF content through the main STB. 
     Referring now to  FIG. 14 , the scenario shown is similar to the DBS scenario shown in  FIG. 11  except that the customer retains cable modem service in addition to DBS content. The topology is similar except that the cabling for cable modem  230  is separated from the other coaxial cabling. 
     Referring now to  FIG. 15 , there is shown a typical topology for a home that receives content via a DSL provider  250 . The DSL access line is terminated in DSL modem with a residential gateway (router) 252 . Existing telephone wiring  254  can be used to connect computer device. An HCT adapter  256  is added to bridge the telephone wiring to the coaxial cable wiring  212  in which digital video signals can be distributed to STBs/Video NICs  219 . 
     Referring to  FIG. 16 , another embodiment of the present invention is shown wherein a system having cable head  214 , cable modem  230 /computer  323 , DBS system  218 , Video NIC  219 , and televisions  216  is provided that combines the use of the HCT adapter  108  as depicted in  FIGS. 4 and 5 , HBS splitter  110  as depicted in  FIG. 9  and includes IF TV noise filter (ITF)  260 . HBS  110  replaces splitter  210   a  of  FIG. 13 . HCT adapter  308   a  interfaces between DBS  218 , television  316   a  and HBS adapter  110 . HCT adapter  308   b  interfaces between Video NIC  219 , television  316   b  and an output port of splitter  210   b . ITF  260  is coupled between an other output port of splitter  210   b  and television  316   c . ITF  260  mitigates Intermediate Frequency TV noise that may be coupled onto the coaxial cable from the input F-connector on a television. IF noise typically is centered around 6 MHz which fails directly in the 4 to 10 MHz HPNA band. ITF  260  is a 2-port device with two F-type 750 connectors on it, one for the Coax connection (wall) and the other for the TV. A third port would be internal to the device (the “HPNA” port) and be terminated with a resistor. ITF  260  would direct all energy from the TV below 30 MHz into the internal terminated port, thus, no interfering energy in the HPNA band would appear on the coax port. 
     Those skilled in the art can appreciate that there could be variations or equivalent embodiments which implement the present invention. For example, while the present embodiments depict an adapter as a physically separate unit with one of the ports being a telephone line, those skilled in the art might envision devices having an embedded adapter with just one physical coaxil port and internally the signal after the low-pass filter and balum will connect directly to the HPNA transceiver without ever transiting on a telephone line.