(12) Ulllted States Patent
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`Donohue et al.
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`(10) Patent No.:
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`(45) Date of Patent:
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`US 7,031,335 B1
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`*Apr. 18, 2006
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`US00703 l335Bl
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`(54) DIGITAL NODE FOR HYBRID FIBER/COAX
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`NETWORK
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`(75)
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`Inventors: John E. Donohue, Ridgefield, CT
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`(US); Aravanan Gurusami,
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`Wallingford, CT (US); Clarke V-
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`Greene, Middletown, CT (US)
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`(73) Assigneez fI]i)nC1e"tl:Il1(1:cao111\1/I11I:Iu$cSa)t1ons, Inc.,
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`(*) Notice:
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`Subject- to any ((11iS(C11aime£’- the germdofthis
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`01 a “me 1111 er 35
`patent 15 em“ 3
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`U.S.C. 154(b) by 0 days.
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`pnatent is subject to a terminal dis-
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`(21) APP1~ N0-3 09/432558
`.
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`Filed:
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`(22)
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`Nov. 3, 1999
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`8/1992 Radice
`5,138,440 A
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`3/1993 Petrofi"
`5,198,989 A
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`5,272,700 A * 12/1993 Hansen et al.
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`.
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`(commued)
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`FOREIGN PATENT DOCUMENTS
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`0 664 621
`7/1994
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`EP
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`(Continued)
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`OTHER PUBLICATIONS
`
`
`“Broadband Medium Attachment Unit and Broadband
`
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`T
`s
`10BROAD36”ANS/IEEE Std
`M d’
`'fi
`t'
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`80: ;““1177P:(°)15 “(*1
`YPG
`~
`(Continued)
`Primary Examiner—Huy D. Vu
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`Assistant Examiner—Daniel Ryman
`(74) Attorney, Agent, or Firm—Fogg and Associates LLC;
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`David N. Fogg
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`(51)
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`Int Cl-
`H04L 12/413
`(2006.01)
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`(52) U..S. Cl.
`...... ... ................... .. 370/445; 370/481
`.......
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`(58)
`F1e1d 01 C1aSs1ficat10n Search """"""" " 714/746;
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`348/476’ 1401; 370/480’ 328’ 438’ 315’
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`370/442; 359/167; 340/31006; 333/103
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`See app11Ca11O11 111e for 001111316316 Search 111510137‘
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`
`References Cited
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`
`
`
`ABSTRACT
`
`
`
`An Optical distribution node is provided. The Optical diSU_i_
`
`
`
`
`
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`
`
`bution node includes a laser transceiver that is coupleable to
`
`
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`
`
`
`at least one fiber optic link The optical distribution node
`
`
`
`
`
`
`
`
`
`
`communicates upstream and downstream digital data with
`
`
`
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`the head end over the at least one fiber optic link. The optical
`
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`
`
`
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`distribution node further
`includes a data concentrator
`coupled to the laser transceiver. Further, for each of at least
`
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`
`
`
`
`
`
`one coaxial cable link, the optical distribution node includes
`
`
`
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`
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`a frequency translator and a node modem. The frequency
`
`
`
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`
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`translator receives and translates the upstream digital data
`
`
`
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`
`
`
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`from modems on the at least one coaxial cable link to a
`
`
`
`
`
`
`
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`different carrier to provide a signal to the modems on the at
`
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`
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`
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`least one coaxial cable link for collision detection. The node
`
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`modem is coupled between the coaxial cable link and the
`
`
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`data concentrator. The node modem demodulates upstream
`
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`digital data for the data concentrator and modulates down-
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`stream digital data for transmission over the coaxial cable
`
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`link.
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`46 Claims, 3 Drawing Sheets
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`
`105
`
`Netflix, Inc. Exhibit 1025
`
`
`HEADEND
`NETWORK
`SWITCH OR
`TERMINATION
`BACKBONE
`TRANSPORT
`
`CABLE MODEM
`ADAPTOR
`
`
`
`COMEINER
`
`
`M119
`1_|_|"l_l—1'
`DISIRIBUTION
`HUB on HEADEND
`
`
`
`
`
`
`
`
`
`
`
`
`Netflix, Inc. Exhibit 1025
`
`

`
`
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`
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`
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`Page 2
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`12/2002 Nazarathy et al.
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`5,153,537 A
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`6,181,687 B1*
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`
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`
`
`6,377,782 B1
`
`
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`
`
`
`
`
`
`
`
`
`for
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`
`
`
`
`
`
`
`
`
`
`
`
`OTHER PUBLICATIONS
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`
`
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`
`
`
`“Scienfific-Atlanta Armounces New Technology To Enable
`P th F
`t.
`H. h_C
`.t D.
`.t 1 R
`I t
`S _
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`
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`.‘g,, apacly
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`Or neraclw’
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`
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`
`
`
`Netflix, Inc. Exhibit 1025
`
`Netflix, Inc. Exhibit 1025
`
`

`
`U.S. Patent
`
`Apr. 18,2006
`
`Sheet 1 of3
`
`US 7,031,335 B1
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`Netflix, Inc. Exhibit 1025
`
`Netflix, Inc. Exhibit 1025
`
`
`
`

`
`
`U.S. Patent
`
`
`
`
`
`
`Apr. 18,2006
`
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`
`Sheet 2 of 3
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`Netflix, Inc. Exhibit 1025
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`Netflix, Inc. Exhibit 1025
`
`
`

`
`
`
`U.S. Patent
`
`
`
`
`Apr. 18,2006
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`Sheet 3 of 3
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`US 7,031,335 B1
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`Network
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`Netflix, Inc. Exhibit 1025
`
`Netflix, Inc. Exhibit 1025
`
`

`
`
`
`US 7,031,335 B1
`
`
`
`1
`
`DIGITAL NODE FOR HYBRID FIBER/COAX
`
`
`
`
`
`NETWORK
`
`
`CROSS REFERENCE TO RELATED
`
`
`
`APPLICATIONS
`
`
`This application is related to the following commonly
`
`
`
`
`
`
`
`
`
`assigned, co-pending applications:
`U.S. application Ser. No. 09/273,197, entitled “DIGITAL
`
`
`
`
`
`
`
`RETURN PATH FOR HYBRID FIBER/COAX NET-
`
`
`
`
`
`
`WORK” and filed on Mar. 19, 1999 and
`
`
`
`
`
`
`U.S. application Ser. No. 09/433,332, filed on the same
`
`
`
`
`
`
`
`
`date as the present application and entitled “DIGITAL
`
`
`
`
`
`
`
`NODE FOR HYBRID FIBER/COAX NETWORK”.
`
`
`
`
`
`
`
`
`10
`
`15
`
`TECHNICAL FIELD OF THE INVENTION
`
`
`
`
`
`The present invention relates generally to the field of
`
`
`
`
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`
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`
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`telecommunications and, in particular, to a digital node for
`
`
`
`
`
`
`
`a hybrid fiber/coax network.
`
`
`
`
`
`20
`
`
`
`BACKGROUND
`
`
`Cable networks originally carried programming from a
`
`
`
`
`
`
`head end to subscribers over a network of coaxial cable.
`
`
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`
`
`Over time, these networks have changed. Some cable net-
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`
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`
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`works now include fiber optic links as part of the network.
`
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`
`
`This variety of cable network is colloquially referred to as a
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`
`
`
`
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`“hybrid fiber/coax” (HFC) network.
`
`
`
`
`A hybrid fiber/coax network typically includes a head end
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`
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`that broadcasts programming over the network to subscrib-
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`ers in a downstream direction. The network includes two
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`main portions. The first portion of the network is optical
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`links that connect the head end with a number of geographi-
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`
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`cally dispersed distribution nodes. These nodes are referred
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`
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`to as “optical distribution nodes” or “ODNs.” At the ODNs,
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`
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`signals from the head end that carry the programming are
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`
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`
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`converted from optical signals to electrical signals. The
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`second portion of the network is coaxial links that connect
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`the ODNs with subscriber equipment. The electrical signals
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`are transmitted to the subscriber equipment over the coaxial
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`cable links.
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`In recent years, the cable industry has experimented with
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`systems
`that
`allow for bi-directional
`communication
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`between subscriber equipment and the head end. This allows
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`for services such as video-on-demand, telephony and Inter-
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`net traffic to be offered over a cable network. Typically the
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`5 to 42 MHZ frequency range is reserved for upstream
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`transmission from customers to the head end. Frequencies
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`between 50 MHZ and an upper limit, e.g., 750 MHZ or 850
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`MHZ, typically carry downstream transmissions.
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`The design of the reverse path for transporting data over
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`a hybrid fiber/coax network is laced with difficult technical
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`issues. First, many customers must communicate over a
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`common coaxial cable. Interference between customers and
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`noise ingress onto the cable can cause disruptions and errors
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`in this communication. Ingress and other interference is
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`especially a problem at the low frequencies typically pre-
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`scribed for upstream communications. Transporting simul-
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`taneous data transmissions from many customers also intro-
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`duces complexity into the system design.
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`In most current systems, the reverse path is implemented
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`with one of a number of different analog modulation
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`schemes, e.g., MCNS, Data Over Cable Service Interface
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`Specification (DOCSIS). These schemes are complicated to
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`implement due to strict timing requirements and complex
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`2
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`modulation schemes. Other systems, such as AT&T’s mini
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`fiber node (mFNs), introduce other complexities into the
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`return path.
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`For the reasons stated above, and for other reasons stated
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`below which will become apparent to those skilled in the art
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`upon reading and understanding the present specification,
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`there is a need in the art for an improved digital data path for
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`a hybrid fiber/coax network.
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`SUMMARY
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`The above mentioned problems with telecommunications
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`systems and other problems are addressed by the present
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`invention and will be understood by reading and studying
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`the following specification. A hybrid fiber/coax network is
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`described which includes an optical distribution node that
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`combines CSMA/CD error detection through frequency
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`translation (“frequency tum-around”) with modem function-
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`ality and data concentration.
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`In one embodiment, an optical distribution node is pro-
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`vided. The optical distribution node includes a laser trans-
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`ceiver that is coupleable to at least one fiber optic link. The
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`optical distribution node communicates upstream and down-
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`stream digital data with the head end over the at least one
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`fiber optic link. The optical distribution node further
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`includes a data concentrator coupled to the laser transceiver.
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`Further, for the at least one coaxial cable link, the optical
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`distribution node includes a node modem. The node modem
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`is coupled between the coaxial cable link and the data
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`concentrator. The node modem demodulates upstream digi-
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`tal data for the data concentrator and modulates downstream
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`digital data for transmission over the coaxial cable link. In
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`another embodiment,
`the optical distribution node also
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`includes a frequency translator coupled to the at least one
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`coaxial cable link. The frequency translator receives and
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`translates the upstream digital data from modems on the at
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`least one coaxial cable link to a different carrier to provide
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`a signal to the modems on the at least one coaxial cable link
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`for collision detection.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 1 is a block diagram of an embodiment of a hybrid
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`fiber/coax network constructed according to the teachings of
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`the present invention.
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`FIG. 2 is a block diagram of another embodiment of an
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`optical distribution node for a hybrid fiber/coax network
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`according to the teachings of the present invention.
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`FIG. 3 is a dataflow diagram that illustrates an embodi-
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`ment of a layered implementation of communication proto-
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`col stacks for an optical distribution node according to the
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`teachings of the present invention.
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`DETAILED DESCRIPTION
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`The following detailed description refers to the accom-
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`panying drawings which form a part of the specification. The
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`drawings show, and the detailed description describes, by
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`way of illustration specific illustrative embodiments in
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`which the invention may be practiced. These embodiments
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`are described in sufficient detail to enable those skilled in the
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`art to practice the invention. Other embodiments may be
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`used and logical, mechanical and electrical changes may be
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`made without departing from the scope of the present
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`invention. The following detailed description is, therefore,
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`not to be taken in a limiting sense.
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`Netflix, Inc. Exhibit 1025
`
`Netflix, Inc. Exhibit 1025
`
`

`
`4
`
`
`
`US 7,031,335 B1
`
`
`
`3
`
`I. EMBODIMENT OF A HYBRID FIBER/COAX
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`NETWORK
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`FIG. 1 is a block diagram of an embodiment of a hybrid
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`fiber/coax (HFC) network, indicated generally at 100, and
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`constructed according to the teachings of the present inven-
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`tion. Network 100 is a bi-directional network that carries
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`signals between head end or hub 102 and a number of
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`modems 103-1-1, .
`, 103-M-N. Advantageously, network
`.
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`100 includes a bi-directional data path that carries data in
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`digital format, e.g., as Ethernet or other packets of digital
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`data using Internet Protocol
`(IP), between modems
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`103-1-1, .
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`, 103-M-N and head end 102.
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`Head end 102 is coupled to modems 103-1-1,
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`103-M-N over a combination of fiber optics and coaxial
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`cable. Namely, head end 102 is coupled via fiber optic link
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`105 with optical distribution node 106. Fiber optic link 105
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`is used to carry digital data between head end 102 and
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`modems 103-1-1, .
`, 103-M-N. In one embodiment, fiber
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`optic link 105 includes two fiber optic cables: a first cable to
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`carry upstream digital data from modems 103-1-1,
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`103-M-N to head end 102 and a second cable to carry
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`downstream digital data from head end 102 to modems
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`, 103-M-N. In another embodiment, fiber optic
`.
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`103-1-1, .
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`link 105 comprises a single fiber optic cable that uses
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`wavelength division multiplexing or frequency division
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`multiplexing to separate upstream and downstream digital
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`data on fiber optic link 105.
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`Optical distribution node 106 is also coupled to coaxial
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`cable links or branches 108-1,
`.
`, 108-M. Modems,
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`represented by modems 103-1-1,
`, 103-M-N, are
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`selectively coupled to coaxial links 108-1, .
`, 108-M via
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`directional couplers 110.
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`In one embodiment, the network 100 includes a transport
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`path for digital data (bi-directional) and a transport path for
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`other broadband services. For the other broadband services,
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`network 100 combines signals from one or more sources at
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`combiner 112 of head end 102. In one embodiment, com-
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`biner 112 receives analog and digital video signals. In
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`another embodiment, combiner 112 also receives other data
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`appropriate for transmission over network 100. Combiner
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`112 is coupled to optical transmitter 114. Optical transmitter
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`114 provides optical signals to optical distribution node 106
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`over fiber optic link 115. These optical signals are received
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`by optical receiver 116 and coupled to coaxial cable links
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`108-1,
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`, 108-M through couplers 118-1,
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`respectively.
`The bi-directional data path includes cable modem ter-
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`mination system 111 at head end 102. Termination system
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`111 includes network termination 113. Network termination
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`113 is coupled to public switched telephone network (PSTN)
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`or backbone network 121 through headend switch or back-
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`bone transport adaptor 119. Termination system 111 is also
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`coupled to optical transceiver 123. Optical transceiver 123 is
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`coupled to optical transceiver 142 at optical distribution
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`node 106 over fiber optic link 105.
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`In one embodiment, data on fiber optic links 105 and 115
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`is carried as base-band digital data using on-olf keying. In
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`another embodiment, data on fiber optic links 105 and 115
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`is carried using modulated carriers. Further, data on fiber
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`optic links 105 and 115 is transmitted using the l00BaseT
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`Ethernet protocol or any other standard or custom protocol.
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`Optical distribution node 106 includes data concentrator
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`or switch 140 that is coupled to optical transceiver 142 and
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`to at least one node modem 138-1,
`.
`, 138-M for each
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`coaxial cable link 108-1, .
`.
`, 108-M, respectively. Due to
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`the similarity between the circuitry for each coaxial cable
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`5
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`, 108-M, only the path in optical distribution
`link 108-1, .
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`node 106 for coaxial cable link 108-1 is described here.
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`However, it is understood that the remaining coaxial cable
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`links include similar circuitry in optical distribution node
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`106. Data concentrator or switch 140 also includes enter-
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`prise network drop 141.
`In one embodiment, drop 141
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`comprises a 10/ l00BaseT interface for a local area network.
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`As fiber optical
`links 105 and 115 allow nodes 106 to
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`penetrate deeper into network 100, drop 141 provides the
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`advantage of allowing direct access to node 106 for an
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`enterprise network.
`.
`.
`, 103-1-N
`.
`In one embodiment, modems 103-1-1,
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`launch upstream, digital data on coaxial cable link 108-1 by
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`on-off-keying of one of a selected number of radio frequency
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`carriers, e.g., fl in FIG. 1, with digital data in the form of
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`Ethernet packets. In other embodiments other modulation
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`techniques are used, e.g., quadrature phase shift keying
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`(QPSK), quadrature amplitude modulation (QAM), and
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`other appropriate modulation techniques. Each modem 103-
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`1-1, .
`.
`, 103-1-N uses one ofthe select number of carriers.
`.
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`It is understood that any appropriate number of carriers can
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`be used. In one embodiment, each of the select number of
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`carriers falls in the frequency range below 42 MHZ. In other
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`embodiments, at least a portion of the select number of
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`carriers fall in a frequency range below the lower cutolf
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`frequency for the downstream data path.
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`The bi-directional path of optical distribution node 106
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`includes frequency translator 124 that is coupled to coaxial
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`cable link 108-1 through couplers 126 and 128. In one
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`embodiment, coupler 126 comprises a directional coupler.
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`Coupler 128 comprises a diplexer, a conventional 3 dB or
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`other ratio coupler, or a directional coupler. The output of
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`frequency translator 124 is coupled to coupler 128. Node
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`modem 138-1 is also coupled to frequency translator 124
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`through coupler 126.
`Frequency translator 124 provides a loopback mechanism
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`to implement a collision detection protocol for the bi-
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`directional path of network 100 on coaxial cable link 108-1.
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`Frequency translator 124 translates modulated carriers, e.g.,
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`to other frequencies, e.g.,
`f2. Essentially,
`frequency
`fl,
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`translator 124 provides aggregate data received from all
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`modems 103-1-1, .
`, 103-1-N on coaxial cable link 108-1
`.
`.
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`and node modem 138-1 back to modems 103-1-1,
`.
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`,
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`103-1-N. Each modem 103-1-1, .
`.
`, 103-1-N compares its
`.
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`transmitted data with the aggregate data to determine
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`whether its data was received at optical distribution node
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`106 without collision with other data or without corruption
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`from ingress noise.
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`When a modem detects a collision, the modem provides
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`a collision detection signal on another carrier. Modems
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`103-1-1, .
`.
`, 103-M-N and node modem 138-1 further wait
`.
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`a randomly selected period of time to attempt retransmission
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`of any corrupted data. Advantageously, this process allows
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`network 100 to transmit upstream signals in the band below
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`the downstream band despite ingress and other interference
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`since interference looks like a collision to network 100 and
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`data affected by the interference is automatically retransmit-
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`ted. This also provides for bi-directional transport of data
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`with symmetrical data rates between upstream and down-
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`stream data paths since the same frequency is used by
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`modem 138-1 and modems 103-1-1,
`, 103-M-N. The
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`downstream signals from modem 138-1 are frequency trans-
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`lated by translator 124 such that the downstream transmis-
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`sions are transported on, e.g., frequency f2.
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`In one embodiment, modems 103-1-1,
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`transmit Ethernet packets over network 100. It is understood
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`Netflix, Inc. Exhibit 1025
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`Netflix, Inc. Exhibit 1025
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`US 7,031,335 B1
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`5
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`that in other embodiments, the data transmitted over net-
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`work 100 may comprise other formats.
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`In operation, digital data is transmitted between modems
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`103-1-1, .
`. .,103-M-N and head end 102 over network 100.
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`For example, digital data originating at modem 103-1-1 is
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`provided to coaxial cable 108-1 on a modulated carrier.
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`Frequency translator 124 translates the frequency of the
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`modulated carrier and retransmits the data back to modem
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`103-1-1 with aggregate data from all modems on coaxial
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`link 108-1 and downstream data from node modem 138-1.
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`Modem 103-1-1 checks for collisions and if any, transmits
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`a collision detect signal on a separate carrier and then waits
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`a random amount of time and retransmits the data.
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`In the absence of a collision, the data is passed to data
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`concentrator 140 and concentrated with data from other
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`coaxial links. This data is passed to head end 102 over
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`optical fiber link 105 by transmitter 142. At head end 102,
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`the data is routed or switched to network 121.
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`Downstream data is transmitted from head end 102 over
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`fiber optic link 115 to optical distribution node 106. At node
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`106, the downstream digital data is demodulated by node
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`modem 138-1 and provided to frequency translator 124. The
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`translated data is provided to modems 103-1-1, .
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`over coaxial cable link 108-1 with the aggregate upstream
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`downstream data from node modem 138-1. In this embodi-
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`ment, modem 138-1 and modems 103-1-1, .
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`are substantially the same thus the available bandwidth in
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`upstream and downstream directions is the same.
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`It is noted that in embodiments with more than one carrier
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`frequency used for upstream communication on coaxial
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`cable links,
`then additional node modems are coupled
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`between frequency translator 124 and concentrator 140 for
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`each coaxial cable link.
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`Node 106 of FIG. 1 advantageously combines CSMA/CD
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`error detection through frequency translation (“frequency
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`turn-around”) with modem functionality and data concen-
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`tration. This combination of functionality is shown in FIG.
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`3. Frequency tum-around is performed at the physical layer
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`as indicated next to blocks 302 and 304. Bridging or modem
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`functionality is provided at the data link layer as indicated at
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`blocks 306 and 308. Further, routing functionality, e.g.,
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`concentration and switching,
`is provided at the network
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`layer as indicated by blocks 310 and 312. In this manner, the
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`frequency tum-around scheme does not require modulation
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`or demodulation processes and is kept transparent to the
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`hardware at node 106.
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`II. ANOTHER EMBODIMENT OF AN OPTICAL
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`DISTRIBUTION NODE
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`FIG. 2 is a block diagram of another embodiment of an
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`optical distribution node,
`indicated generally at 206 and
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`constructed according to the teachings of the present inven-
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`tion. In this embodiment, optical distribution node 206
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`advantageously provides for asymmetrical transport of data
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`between a head end and modems. Node 206 includes trans-
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`ceiver 242 that coupled to the head end over a fiber optic
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`link. Transceiver 242 is coupled to data concentrator or
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`switch 240. Data concentrator 240 is coupled to a plurality
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`of node modems represented by node modem 238.
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`Node modem 238 provides upstream and downstream
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`communication for digital data in node 106. In the down-
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`stream path, node modem 238 is coupled to a coaxial cable
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`link through couplers 226 and 228, and diplexer 218. In the
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`upstream direction, data is received from the coaxial cable
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`link by node modem 238 via couplers 226 and 229, and
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`diplexer 218. Couplers 226, 228 and 229 comprise direc-
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`tional couplers or conventional 3 dB or other ratio couplers.
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`In this manner, the downstream data from node modem 238
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`is not frequency translated at frequency translator 224 and
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`thus the downstream data is provided to the modems on a
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`different carrier frequency. This allows for different data
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`rates to be used in the downstream and the upstream
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