Page 1 of 17
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`VERIZON EXHIBIT 1004
`
`

`
`5,940,387
`Page 2
`
`OTHER PUBLICATIONS
`
`Endo, K., et al., “A Home Bus System Based on Main Bus
`and Power Line Spread-Spectrum Bus”, IEEE 1988 Inter-
`national Conference On Consumer Electronics, Rosemont,
`Jun. 8-10, 1988, No. 1988, Jun. 8, 1988, IEEE, pp. 106/107.
`Quinnell, R. (editor), “Emerging 100—Mbit Ethernet Stan-
`dards Ease System Bottlenecks”, EDN Electrical Design
`News, VL. 39, No. 1, Jan. 6, 1994, pp. 35/36, 40, 42.
`Olshansky, R., et al., “Residential LAN Architecture”, Pro-
`ceedings of the 2”“ International Workshop on Community
`Networking Integrated Multimedia Services in the Home,
`Jun. 20-22, 1995, New York (US), pp. 55-60.
`
`Singh, R.P., et al., “Jitter and Clock Recovery for Periodic
`Traffic in Broadband Packet Networks”, IEEE Transactions
`on Communications, vol. 42, No. 5, May 1, 1994, pp.
`2189-2196.
`
`Droitcourt, J.L., “Understanding How Interactive Television
`Set Top Box Works .
`.
`. And What it Will Mean to the
`Customer”,
`International Broadcasting Convention, Vol.
`413, Sep. 14, 1995.
`
`Lau, Richard C., Synchronous Techniques for Timing
`Recovery in BISDN, IEEE, Feb./Apr., 1995, pp. 1810-1819.
`
`Page 2 of 17
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`Page 2 of 17
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`

`
`U.S. Patent
`
`Aug. 17,1999
`
`Sheet 1 of8
`
`5,940,387
`
`FIG. 1
`
`
`
`INTERNAL
`NETWORK
`
`
`
`1 2
`
`_
`TV 2
`anabg
`
`20
`
`HAN to Automation /Appliances
`
`1 7
`
`26
`
`
`
`I
`HFC/Cab|e/
`:
`Broadcast
`(digital or mixed‘
`analog/digital)
`I 32I
`I
`
`I®
`
`l
`I
`: 32
`I
`
`I
`
`III
`
`. _
`
`ISDN
`
`B"°ad°aSVDSS/
`F_|_|'C/FTTH/
`ADSL
`
`
`30')
`
`
`
`
`
`(analog only)
`
`Page 3 of 17
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`Page 3 of 17
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`

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`U.S. Patent
`
`Aug. 17,1999
`
`Sheet 2 of8
`
`5,940,387
`
`
`
`Printer/audio/videoetc
`
`FIG.2
`
` Network1
`Network1
`
`Page 4 of 17
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`Page 4 of 17
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`

`
`U.S. Patent
`
`Aug. 17,1999
`
`Sheet 3 of8
`
`5,940,387
`
`Q
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`Page 5 of 17
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`

`
`U.S. Patent
`
`Aug. 17,1999
`
`Sheet 4 of8
`
`5,940,387
`
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`Page 8 of 17
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`

`
`U.S. Patent
`
`Aug. 17,1999
`
`Sheet 7 of8
`
`5,940,387
`
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`Page 9 of 17
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`Page 9 of 17
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`

`
`U.S. Patent
`
`Aug. 17,1999
`
`Sheet 8 of8
`
`5,940,387
`
`FIG. 8
`
`MENU SERVICES
`
`Internet
`VODMovie
`VODBroadcast
`Game
`
`Shopping
`
`INTERNET Service
`
`VOD Movie
`
`VOD Bcast
`
`WWW
`WWW (site)
`email
`other
`
`Movie (name)
`Movie (actor)
`Latest
`Search 0
`
`Ch.9
`Ch.11
`News
`Last viewed
`
`
`
`COMMS VODMovie
`
`TELCO_FTTC
`CABLE_HFC
`Auto select low cost
`
`Auto select best quality
`
`
`
`Auto select best quality
`
`COMMS VODBrdcast
`
`DSS
`Cab|e_HFC
`Auto select low cost
`
`Auto select best quality
`
`
`
`
`
`
`
`ISDN
`
`COMMS lnternet
`
`ISDN
`CABLE_HFC
`Auto select low cost
`
`Page 10 of 17
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`Page 10 of 17
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`

`
`5,940,387
`
`1
`HOME MULTIMEDIA NETWORK
`ARCHITECTURE
`
`This application is a continuation of application Ser. No.
`08/561,758 filed Nov. 22, 1995 abandoned.
`RELATED APPLICATIONS
`
`This patent application is related to U.S. application Ser.
`No. 08/561,757, filed on Nov. 22, 1995, entitled SET-TOP
`ELECTRONICS AND NETWORK INTERFACE UNIT
`
`ARRANGEMENT; U.S. application Ser. No. 08/561,535,
`filed on Nov. 22, 1995, entitled METHOD AND APPARA-
`TUS FOR RECOVERING DATA STREAM CLOCK; U.S.
`application Ser. No. 08/561,534, filed on Nov. 22, 1995, U.S.
`Pat. No. 5,579,308, entitled CROSSBAR/HUB ARRANGE-
`MENT MULTIMEDIA NETWORK.
`1. Field of the Invention
`
`The present invention relates to digital networks, and
`more particularly, to digital networks for home use which
`provide interconnectivity of products within the home and to
`external networks outside the home.
`
`2. Background of the Invention
`The rapid gains in digital technology and telecommuni-
`cations have increased the desirability of having a network
`in the home to interconnect a multitude of products in the
`home with each other and to the outside world. The range of
`available outside services includes interactive services,
`cable video and audio services, satellite networks, telephone
`company services, video on demand, and other types of
`information services. However, penetration of the personal
`computer into homes in the United States is approximately
`33% and only growing slowly, although governments desire
`more extensive penetration to encourage “telecommuting”
`and reduce road traffic and pollution. Further penetration of
`computers in the home will originate from the purchase of
`consumer entertainment and informational products contain-
`ing an embedded computer and operating system hidden by
`an opaque user interface. Such a product is a conventional
`set-top box.
`Set-top boxes are multi-media computers that augment
`the use of televisions. A conventional set-top box has an
`external network interface module that connects the set-top
`box to the external network and data provider. The network
`interface module has to perform a number of sophisticated
`functions, such as interfacing to a specific external network,
`tuning, demodulation, error correcting, video descrambling,
`recovery of MPEG clock, and encryption and decryption
`specific to the external network. Consequently, the network
`interface module is a relatively expensive component of
`set-top boxes. This expense would be necessary when even
`a single television is present in the house. However, most
`homes contain multiple televisions, and providing each with
`its own set-top box and associated network interface module
`is a duplication of expensive components.
`Another concern for homeowners is the issue of the
`
`service providers. Limitation to one service provider for all
`services introduced into the home through a set-top box,
`such as by a telephone provider, restricts the choices of a
`homeowner and possibly prevents the homeowner from
`obtaining services at the lowest competitive price. Attempt-
`ing to overcome this problem with multiple service provid-
`ers using a stack of multiple set-top boxes on every televi-
`sion in a home is not a viable solution.
`
`SUMMARY OF THE INVENTION
`
`There is a need for a home network that provides inter-
`connectivity to products in a home and to external networks
`
`10
`
`15
`
`20
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`2
`in a relatively inexpensive manner and which also provides
`the homeowner with the opportunity to select from a variety
`of different services.
`
`These and other needs are met by the present invention
`which provides a home network that has multiple set-top
`boxes and separate network interface units coupled together
`by a relatively inexpensive digital network installed in the
`home, such as Ethernet.
`The separation of the network interface unit functions
`from the set-top electronics allows a single network inter-
`face unit to be used to interface with an external network and
`
`to provide programming selectively to a multitude of set-top
`electronics and televisions within the home. This reduces the
`
`need for duplication of the network interface functions at
`each television or other end product and thereby reduces the
`costs of the home network. Further, having separate network
`interface units on the network allows the consumer to pick
`and choose among available services, and not to be con-
`strained to a single service provider. Changing a service may
`be performed simply by exchanging or adding a different
`network interface unit configured to interface with the new
`external network.
`
`The use of Ethernet in certain preferred embodiments also
`makes the network relatively low cost, as twisted pair wiring
`may be installed at low cost in a home.
`The foregoing and other features, aspects and advantages
`of the present invention will become more apparent from the
`following detailed description of the present invention when
`taken in conjunction with the accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a schematic block diagram of a home network
`constructed in accordance with an exemplary embodiment
`of the present invention.
`FIG. 2 is a depiction of an exemplary installation of the
`home network of the present invention within a home.
`FIG. 3 is a logical diagram of the home network of FIG.
`
`1.
`
`FIG. 4 is a schematic depiction of a network interface unit
`and a set-top electronics unit constructed in accordance with
`preferred embodiments of the present invention.
`FIG. 5 is a block diagram of a network interface of the
`set-top electronics constructed in accordance with an exem-
`plary embodiment of the present invention.
`FIG. 6 is a block diagram of the network interface of the
`network interface unit constructed in accordance with an
`
`embodiment of the present invention.
`FIG. 7 is a block diagram of a hub and direct circuit
`crossbar, constructed in accordance with an embodiment of
`the present invention, coupled to a network interface unit
`and a set-top electronics unit.
`FIG. 8 is a logical diagram of an exemplary user interface
`for the home network of the present invention.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`FIG. 1 is a schematic depiction of a home multimedia
`network 10 constructed in accordance with an embodiment
`
`of the present invention. This embodiment is exemplary
`only, however, as the network 10 may be configured in any
`of a number of different ways within the scope of the
`invention, and may include different devices coupled to the
`network 10. Additionally,
`the invention is not limited to
`networks located in homes, but is applicable to networks
`
`Page 11 of 17
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`5,940,387
`
`3
`installed in other types of structures, such as offices, apart-
`ment buildings, etc. For purposes of illustration, however,
`the exemplary embodiment will be described in the context
`of a home installation.
`
`The network 10 is a digital network that provides con-
`nectivity of different types of equipment to the world outside
`the home. This equipment can be, for example, analog
`television 12, digital television 14, digital VCR 16, digital
`camcorder 18, personal computers 20, audio equipment 22,
`printers 24, facsimile machines 26, and telephones 28,
`among others. In addition to connecting this equipment to
`the outside world, the network 10 also connects the digital
`video, digital audio, computer and telephone equipment
`together internally in the home. This unifies communication
`and control within the home, making the full power of the
`external network connections or internal data sources avail-
`
`able to any terminal on the network 10.
`Communication with the outside world is performed
`through a number of separate network interface units
`(NIU’s) 32 and may be combined physically in an entrance
`unit 30, with each network interface unit 32 permitting a
`connection between a different external network and the
`
`home network 10. The different external networks may carry
`different
`types of signals. These may be, for example,
`broadcast signals (digital or mixed analog/digital) carried on
`hybrid fiber coax or cable. Other types of signals are ISDN,
`broadcast/digital satellite service, FTTC, FTTH, ADSL, and
`others. At least the following data types may be carried:
`compressed video, compressed audio, compressed internet
`WWW graphics and data, internet e-mail and other data,
`computer file data and control message data.
`Logically all terminals in the home network 10 receive
`equal access to the network interface units 32 and a user
`would be unaware of the physical sitting of them. The
`number of network interface units 32 that are required is
`determined by the number of streams required per home, e.g.
`the number of different program channels (i.e., video, audio,
`and other) required simultaneously, not by the number of
`terminal units in a home.
`
`In certain preferred embodiments, cable or antenna tele-
`vision is retained unmodified with distribution by regular
`in-home coax (plain old television, or POTV). POTS (plain
`old telephone service) is also carried on the in-home digital
`network 10.
`
`The digital signals are distributed throughout the home
`over an internal network 34.
`In certain preferred
`embodiments, the internal network 34 is essentially Ethernet
`of type 10 base-T or 100 base-T twisted pair but a special
`switch hub is employed to make the network scalable to any
`number of terminal units each able to receive high bit-rate
`video.
`
`The home network 10 connects those computers, or
`products with embedded computers, that can support the
`networking bandwidth, protocols, routing, buffering and
`addressing. Other high bandwidth products that do not
`support this complex functionality must attach to such a host
`unit either directly or via a local peripheral network to
`achieve interoperability. Examples of computers or products
`with embedded computers located on the home network 10,
`functioning as end user devices, include: the network inter-
`face units I/O computers performing external network to
`home network conversion and conditioning; computers,
`such as the set-top electronics (STE); PC’s; workstations;
`high end printers; and special computers providing gateway/
`control functions. Other end user devices that can be coupled
`to the network 10 include video products: digital com-
`
`10
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`
`pressed (MPEG) and uncompressed video equipment; digi-
`tal video camcorder products; digital video tape recording
`products and digital
`tv display products and analog tv
`display and recording products. Audio products that can be
`coupled to the network 10 include: digital compressed
`(MPEG) and uncompressed audio equipment; HIFI stereo;
`digital audio tape recording products. Other types of prod-
`ucts that can connect to the network 10 are data products,
`such as printers and other peripherals. Still further products
`that can be controlled through the network 10 include home
`automation and appliances: central heating/AC, security
`controller, microwave oven and other kitchen equipment,
`lighting, sprinkler and other power control.
`Certain embodiments of the home network 10 include one
`
`or more local peripheral networks 15 that provide local
`connection for future very high bit rate, motion-JPEG or
`I-frame-only-MPEG video devices, audio devices, printers
`and such peripherals. These devices need continuous local
`digital connection at a high bandwidth, where the data
`transfer is continuous from, for example, digital camera to
`digital VCR. Accommodating such devices directly on the
`internal network 34 would require greater network band-
`width over the entire network 34 than normally needed.
`Instead, the local peripheral network 15 is normally con-
`nected by gateway to the internal network 34 for interoper-
`ability. However,
`in certain other embodiments of the
`invention, the home network 10 is provided with hardware
`and software that accommodates the high speed devices so
`that a local peripheral network 15 is not necessary.
`A home automation network 17 is provided for home
`automation. This home automation network 17 may run on
`the power line or other low bit rate network for controlling
`appliances, home security systems, lighting, etc. This spur
`originates from a control computer 20 located within the
`home.
`
`An exemplary model of the installation of the home
`network 10 of the present invention within a house 36 is
`depicted in FIG. 2. The home network 10 is a long range
`backbone capable of up to100 m cable runs, for example,
`from a switched hub 38 that forms part of the internal
`network 34. In the exemplary installation depicted in FIG. 2,
`the entrance unit 30 with its multiple network interface units
`32 are located in a utility area of the house, along with the
`switched hub 38.
`
`Twisted pair cable is run to each room of the house 36 and
`terminates at a wall socket. Cat-5 twisted pair (for 100
`Mbits/s),
`for example, may be used when doing an
`installation, as the majority of the cost is labor. For tempo-
`rary retro-installation, twisted pair cable is small enough that
`it may be customer fitted under a carpet edge. A user in the
`home will connect a computer product in a room by plug-
`ging the Ethernet port of the computer product
`to the
`Ethernet wall socket.
`
`In the embodiment of FIG. 2, the hub 38 is depicted as a
`separate device, but in other embodiments the hub 38 is
`integrated into one or more of the network interface units 32.
`The hub 38 provides the connectivity to all areas of the
`house and the one or more network interface units 32.
`
`Upgrading, expanding both the aggregate bandwidth and
`connectivity of the internal network 34, is accomplished by
`additional plugging or changing to a larger hub. The hub will
`be discussed in more detail later.
`
`invention, as shown in FIGS. 1 and 2,
`The present
`separates the functionality of the network interface units 32
`from the set-top electronics 40. Conventionally, a set-top
`box contains a network interface unit whose components are
`
`Page 12 of 17
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`

`
`5,940,387
`
`5
`internally connected by a bus to the set-top electronics
`components. By contrast, however,
`the present invention
`provides a separation of the network interface units 32 and
`the set-top electronics 40, with the internal network 34
`interposed therebetween. This arrangement permits multiple
`set-top electronics to be distributed throughout the home 36
`less expensively, since the electronics of a network interface
`unit do not have to be duplicated for each set-top electronics.
`Additionally, having separate network interface units 32
`coupled to different external networks and to a common
`internal network 34 frees the homeowner from being forced
`to receive all programming from a single source, such as the
`telephone or cable company. The separation also allows the
`homeowner to add, drop or change services simply by
`changing one of the network interface units 32, without the
`need for replacing all of the set-top electronics 40 through-
`out the home 36.
`
`In certain embodiments, a “master” set-top box is pro-
`vided with multiple network interface units. However, this
`embodiment is logically the same as described above, as the
`network interface units are connected in this embodiment to
`
`the internal network, and not by a bus to the set-top
`electronics.
`
`FIG. 3 is a logical view of the home network 10 of the
`present invention. As apparent from the diagram, the multi-
`port switched hub 38 forms the center of the network
`connections. In certain embodiments, in which inter-packet
`jitter is adequately controlled, a traditional, commercially
`available packet switched hub is employed. In other pre-
`ferred embodiments, such as that depicted in FIG. 3, the
`switched hub 38 is a combination of networked ports and
`ports that are direct (circuit) switched for the duration of a
`session. The direct connected ports (and systems) can be
`phase locked via the network (coded) clock. To provide this
`functionality,
`the switched hub 38 therefore comprises a
`relatively simple and inexpensive hub 42 and a direct circuit
`crossbar 44. The hub 42, in certain preferred embodiments,
`may be a commercially available device, such as Am79C981
`manufactured by Advanced Micro Devices, of Sunnyvale,
`Calif. Details of the direct circuit crossbar 44 will be
`
`described later with respect to FIG. 7.
`A star topology as defined by Ethernet 10/100 base-T is
`used in conjunction with the switching hub 38. The switch-
`ing hub 38 provides fan out to most rooms in the house 36.
`The maximum system bandwidth is a multiple of the wire bit
`rate ((bit rate><number of ports)/2), for example, 20 ports and
`100 Mbits/s bit rate=1 Gb/s aggregate maximum bandwidth.
`The switched hub 38 enables special treatment for the
`heavily asymmetric traffic, e.g., compressed digital video
`and internet data by directly routing these cases from
`transmitter to receiver. This traffic is thus separated from the
`internal network 34 and allows an overall aggregate band-
`width to be limited only by the expandability of the hub 38,
`although it will remain limited by the 10 Mbits/s per branch.
`Use of 100 base-T technology instead of 10 base-T tech-
`nology will uprate the network if required.
`The switching hub’s direct synchronous (Manchester or
`block encoded) connections are used primarily for
`the
`transmission of MPEG video where a continuous, high bit
`rate,
`long duration connection is required. High bit rate
`video in compressed form can be as high as 8 Mbits/sec and
`is needed for live video and high action movies and sports.
`Low bit-rate video is 1.5 Mbits/sec. According to the present
`invention, MPEG digital video is retained throughout the
`network 10. Conversion to real video takes place only at the
`display device (e.g., television 12) or the set-top electronics
`40.
`
`6
`Two separate direct circuits are depicted as examples in
`FIG. 3. For example, the network interface unit 32 that is
`coupled to an ISDN network is directly connected through
`the direct circuit crossbar 44 to the personal computer 20 of
`the local peripheral network 15. Another, separate direct
`circuit is provided by the direct circuit crossbar 44 between
`a different network interface unit 32 (coupled to hybrid fiber
`coax, for example) and the set-top electronics 40 coupled to
`the television 12. Those devices that are not directly con-
`nected through the direct circuit crossbar 44 remain attached
`to the hub 42 and are thus networked.
`
`With respect to the switching hub architecture, where a
`direct point-to-point path is configured, all data traversing
`this path is provided directly to the end point terminal of the
`path, even data intended for one or more other terminals.
`Thus, in certain preferred embodiments, a rule is followed
`that data multiplexed with the high rate data (typically
`messaging) must be issued to networked terminals by the
`end point of the direct path returning such packets to the hub
`38. For example, messages sent over the ISDN network that
`are not intended for a device on the local peripheral network
`15 will be returned by the local peripheral network host 20
`to the hub 38 for distribution. This rule saves the expense
`and complication of having a packet router type switched
`hub, with the demultiplexing distributed at the end point(s)
`rather than centrally, and works well for asymmetric data
`flow and local destination,
`i.e., not subject
`to layers of
`switches.
`
`An advantage of directly switched paths is that potential
`delays in obtaining access to the network 34 (and possibly
`upsetting the delicate clock reference timing carried in the
`MPEG stream) are avoided altogether.
`The hub 38, in certain preferred embodiments, is required
`to be “full-duplex aware” meaning that a directly routed path
`connects only a transmitter terminal “up” path only to a
`receive terminal “down” path. By contrast, the path down to
`the transmitter and path up to the receiver are not affected by
`the direct circuit and would normally be attached to the
`network, i.e., attached to all the remaining terminal paths
`connected together.
`Specific routing occurs in response to user service
`requests. Messages are picked up by the hub control and any
`direct routing changes implemented. Devices not switched
`from the network remain connected and no routing is
`required.
`The MPEG clock recovery is performed at the network
`interface units 32, as described later. With the MPEG clock
`recovery at the network interface units 32, and the estab-
`lishment of a direct circuit to the home network destination,
`jitter in the signal received at the destination (such as the
`television 12)
`is substantially eliminated. Direct circuit
`capability works well for the heavily asymmetric point to
`point traffic expected in the entertainment (video) home
`scenario.
`
`For analog only services, e.g., transitional cable TV, this
`is not considered part of the digital network. For mixed
`digital/analog services such as hybrid fiber coax (HFC) and
`newer forms of mixed cable TV, this is considered a tran-
`sitional state and dealt with as a temporary add-on to the all
`digital system of the present invention. The signal from the
`hybrid fiber coax is provided directly to a set-top electronics
`40 or to a network interface unit 32/set-top electronics 40
`combination. Two ports are required to connect to the home
`network 10, one for the network interface unit 32 and one for
`the set-top electronics 40. A bypass is provided in certain
`preferred embodiments to link the analog signals across to
`the audio/video circuits of the set-top electronics 40.
`
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`The home network 10 is controlled via hand held com-
`
`8
`when the internal network 34 is a 10 base-T Ethernet
`
`mander or computer keyboard to software running at the
`local terminals, such as the personal computers 20, or set-top
`electronics 40. Control software local to each home terminal
`
`manages source availability, source selection, path manage-
`ment by communication with the network interface units 32
`and external gateways. The external network protocols are
`buffered in the network interface units 32 to provide a
`standard interface to the terminals on the home network 10.
`
`FIG. 8 depicts one an example of a user interface. In this
`embodiment, the home network 10 is transparent and the
`user is only aware of it
`indirectly from the number of
`connected services.
`
`FIG. 4 is a block diagram depicting a single network
`interface unit 32 coupled by the internal network 34 to a
`single set-top electronics unit 40. The remaining portions of
`the home network 10, including the switching hub 38, are
`not shown in FIG. 4 for purposes of illustration and expla-
`nation.
`The network interface unit 32 has one or more network
`interface modules 50 that interface the network interface
`
`unit 32 to a particular external network. In the example of
`FIG. 4, the network interface module 50 provides an inter-
`face to an external network that carries MPEG video data.
`
`The MPEG video data is provided to an internal network
`interface device 52 that prepares the data for transport over
`the internal network 34. In certain preferred embodiments,
`the internal network 34 is an Ethernet network, so that the
`internal network interface device 52 is an Ethernet interface
`device.
`
`The architecture of the present invention assumes that for
`some networks a first stage demultiplexing at the network
`interface unit 32 is necessary to stay within a definable
`bandwidth limit (one stream) rather than an arbitrary band-
`width set by the construction of the incoming stream
`(multiple streams). Making the assumption that MPEG-2
`video is being used,
`there is a demultiplexing from a
`multiple program transport stream into a single program
`transport, as defined in the MPEG-2 specification. This is
`performed by an MPEG transport chip 54, such as the 9110B
`chip commercially available from C-Cube. (A second stage
`demultiplexing to separate the video, audio and other data
`still occurs in the set-top electronics, while decoding is
`preferably only performed at
`the display terminal or
`computer.) With this approach, it is not necessary to send
`high bandwidth streams throughout the house and the ter-
`minals in the home 36 need see only a standardized single
`program interface. Compression is required for video gen-
`erated in the home, e.g. security front door camera or video
`conference camera.
`
`All the external network interfacing, decryption, access
`control, demultiplexing to a single program stream, etc., is
`performed by the network interface module 50. Thus, the
`network interface module 50 buffers the home network
`
`hardware and software from the peculiarities of the attached
`external network. Multiple different programs require mul-
`tiple network interface crossbar connections whether from
`one or multiple providers. In certain embodiments, a dual
`module is provided with two connections to the crossbar,
`providing two programs received from the same external
`network.
`
`The MPEG transport chip 54 performs the MPEG clock
`recovery and provides the recovered 27 MHZ clock and the
`selected program to an internal network connection 56. The
`27 MHZ clock is received by an MPEG to network synthe-
`sizer 58 and converted to a 10 MHZ clock, for example,
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`network. The 10 MHZ clock, as well as the selected program,
`are provided to a conventional transceiver 60 (such as an
`Ethernet transceiver) connected to the internal network 34.
`The synthesiZer 58 acts to lock the Ethernet clock to the
`recovered MPEG clock. When the packet of data is trans-
`mitted from the network interface unit 32 to the set-top
`electronics 40, the set-top electronics 40 is locked to the
`recovered MPEG data at 27 MHZ. At the set-top electronics
`40, the 27 MHZ clock is regenerated from the Ethernet 10
`MHZ clock by another synthesiZer.
`The data is received in the set-top electronics 40 by a
`network interface device 62 that includes a network inter-
`
`face 64. The 10 MHZ clock recovered by the network
`interface 64 from the data stream off the network 34 is gated
`through gate 66 to a network to MPEG synthesiZer 68.
`Gating is needed so that the locking function is performed
`only when there is a packet of data present. The 10 MHZ
`clock is converted to a 27 MHZ clock provided to an MPEG
`decoder 70 and a video decoder/encoder 72. The selected
`program is provided by the network interface 64 to the
`MPEG decoder 70, which decodes the MPEG data and
`provides it to the video decoder/encoder 72. The data stream
`is converted by the video encoder 72 to a format (e.g., NTSC
`or SVideo) suitable for use by a display device, such as a
`television. The video decoder is for the case (HFC) where
`there may be an NTSC analog signal to digitiZe and merge
`with on-board graphics hardware.
`The network 34 in FIG. 4 is depicted schematically, and
`it should be understood from the previous description that
`the video data may be placed on the network 34 through the
`hub 42, but that a direct circuit of the network interface unit
`32 and the set-top electronics 40 through the direct circuit
`crossbar 44 of the network 34 is preferred to provide a jitter
`free transfer of video data.
`
`FIG. 5 is a more detailed diagram of an exemplary
`embodiment of the network interface device 62 of the
`
`set-top electronics 40 depicted in FIG. 4. The network
`interface device 62 includes the network synthesiZer 68
`coupled to a program logic device operating as the gating
`device 66. The network synthesiZer 68 may be implemented
`by a commercially available chip, such as the MC145151
`manufactured by Motorola. The program logic device 66
`may be implemented by a commercially available chip, such
`as the MC7958, also manufactured by Motorola. A voltage
`controlled crystal oscillator 80 operates at 27 MHZ and
`provides its signal to the program logic device 66, which
`gates the 10 MHZ signal to the synthesiZer 68 when there is
`a received data packet. The synthesiZer divides down the 10
`MHZ and 27 MHZ frequencies to a common frequency
`which is fed into a phase detector of the synthesiZer 68. The
`output of the phase detector of the synthesiZer 68 is provided
`as a control signal to the voltage controlled crystal oscillator
`80 to adjust the local frequency up or down to lock to the
`incoming Ethernet frequency.
`The signal informing the program logic device 66 of the
`receipt of a data packet, and the 10 MHZ clock, are provided
`by a serial interface adapter 82 serving as a receive enable.
`A commercially available product suitable for the serial
`interface adapter is Am7992B, manufactured by Advanced
`Micro Devices.
`
`The data stream is received through a transformer/filter
`84, such as one commercially available from Pulse
`Engineering,
`the PE68026. Collision information is also
`received through another transformer/filter 86, which can be
`the same type of transformer/filter as 84. The received data
`
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`5,940,387
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`is provided to a first network transceiver 88, such as a
`twisted pair Ethernet transceiver plus (Am79C100). The
`output of the first network transceiver 88 (the received data)
`is made available to the receive enable 82 an