REMB-0109
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`SYSTEM AND METHOD OF COMMUNICATION VIA EMBEDDED MODULATION
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`CROSS REFERENCE TO RELATED APPLICATION
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`[0001] This application is a continuation of U.S. Application No. 11/774,803, filed on
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`July 9, 2007, which is a continuation ofU.S. Application No. 10/412,878, filed April 14, 2003,
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`which is a continuation-in-part ofU.S. Application No. 09/205,205, filed December 4, 1998, and
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`which claims priority to and the benefit of the filing date ofU. S. Provisional Application No.
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`60/067,562, filed December 5, 1997, each of which is incorporated by reference herein.
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`TECHNICAL FIELD
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`[0002] The present invention relates generally to the fields of data communications and
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`modulator/demodulators (modems), and, more particularly, to a data communications system in
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`which a plurality of modulation methods are used to facilitate communication among a plurality
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`of modem types.
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`BACKGROUND
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`[0003]
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`In existing data communications systems, a transmitter and receiver modem pair
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`can successfully communicate only when the modems are compatible at the physical layer. That
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`is, the modems must use compatible modulation methods. This requirement is generally true
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`regardless of the network topology. For example, point- to-point, dial-up modems operate in
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`either the industry standard V.34 mode or the industry standard V.22 mode. Similarly, in a
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`multipoint architecture, all modems operate, for example, in the industry standard V.27bis mode.
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`- 1 -
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`Exhibit 1207 01/22
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`

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`REMB-0109
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`While the modems may be capable of using several different modulation methods, a single
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`common modulation is negotiated at the beginning of a data session to be used throughout the
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`duration of the session. Should it become necessary to change modulation methods, the existing
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`data session is tom down, and a new session is negotiated using the new modulation method.
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`Clearly, tearing down an existing data session causes a significant disruption in communication
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`between the two modems.
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`[0004] As discussed in the foregoing, communication between modems is generally
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`unsuccessful unless a common modulation method is used. In a point-to-point network
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`architecture, if a modem attempts to establish a communication session with an incompatible
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`modem, one or both of the modems will make several attempts to establish the communication
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`link until giving up after a timeout period has expired or the maximum number of retry attempts
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`has been reached. Essentially, communication on the link is impossible without replacing one of
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`the modems such that the resulting modem pair uses a common modulation method.
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`[0005]
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`In a multipoint architecture, a single central, or "master," modem communicates
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`with two or more tributary or "trib" modems using a single modulation method. If one or more
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`of the trib modems are not compatible with the modulation method used by the master, those
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`tribs will be unable to receive communications from the master. Moreover, repeated attempts by
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`the master to communicate with the incompatible trib(s) will disturb communications with
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`compatible trib(s) due to time wasted in making the futile communication attempts.
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`[0006] Thus, communication systems comprised of both high performance and low or
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`moderate performance applications can be very cost inefficient to construct. For example, some
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`applications (e.g., internet access) require high performance modulation, such as quadrature
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`amplitude modulation (QAM), carrier amplitude and phase (CAP) modulation, or discrete
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`multitone (DMT) modulation, while other applications (e.g., power monitoring and control)
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`require only modest data rates and therefore a low performance modulation method. All users in
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`the system will generally have to be equipped with a high performance modem to ensure
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`modulation compatibility. These state of the art modems are then run at their lowest data rates
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`for those applications that require relatively low data throughput performance. The replacement
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`of inexpensive modems with much more expensive state of the art devices due to modulation
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`compatibility imposes a substantial cost that is unnecessary in terms of the service and
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`performance to be delivered to the end user.
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`[0007] Accordingly, what is sought, and what is not believed to be provided by the
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`prior art, is a system and method of communication in which multiple modulation methods are
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`-2-
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`Exhibit 1207 02/22
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`

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`REMB-0109
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`used to facilitate communication among a plurality of modems in a network, which have
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`heretofore been incompatible.
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`SUMMARY
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`[0008] The present invention is generally directed to a system and method of
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`communication between a master transceiver and a plurality of tributary transceivers in a
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`multipoint communication system in which the tributary transceivers use different types of
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`modulation methods. Broadly stated, the communication system includes a master transceiver in
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`communication with a first tributary transceiver and a second tributary transceiver over a
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`communication medium. The first tributary transceiver uses a primary modulation method for
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`communication while the second tributary transceiver uses a secondary or embedded modulation
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`method for communication. The master transceiver and tributary transceivers each include a
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`processor, memory, and control logic for controlling their operation. While the primary
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`modulation method is normally used for transmissions on the communication medium, the
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`master transceiver can communicate with the second tributary transceiver by notifying the first
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`tributary transceiver that the primary modulation method is being temporarily replaced by the
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`secondary or embedded modulation method. The master transceiver can then exchange
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`information with the second tributary transceiver while the first tributary transceiver ignores any
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`secondary modulation transmissions. In the meantime, the first tributary transceiver conditions
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`itself to look for a trailing sequence from the master transceiver indicating that communication
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`with the second tributary transceiver is complete. When the master transceiver transmits the
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`trailing sequence using the primary modulation method, the first tributary transceiver conditions
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`itself to look for primary modulation transmissions while the second tributary transceiver
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`conditions itself to ignore primary modulation transmissions.
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`[0009] The present invention has many advantages, a few of which are delineated
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`hereafter as merely examples.
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`[0010] One advantage of the present invention is that it provides to the use of a
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`plurality of modem modulation methods on the same communication medium.
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`[0011] Another advantage of the present invention is that a master transceiver can
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`communicate seamlessly with tributary transceivers or modems using incompatible modulation
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`methods.
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`[0012] Another advantage of the present invention is that a master and tributary
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`transceiver can calculate a channel parameter using a test signal sent using embedded
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`modulation.
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`-3-
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`Exhibit 1207 03/22
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`

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`REMB-0109
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`[0013] Other features and advantages of the present invention will become apparent to
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`one with skill in the art upon examination of the following drawings and detailed description. It
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`is intended that all such additional features and advantages be included herein within the scope
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`of the present invention.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`[0014] The present invention can be better understood with reference to the following
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`drawings. The components and representations in the drawings are not necessarily to scale,
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`emphasis instead being placed upon clearly illustrating the principles of the present invention.
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`Moreover, in the drawings, like reference numerals designate corresponding parts throughout the
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`several views.
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`[0015] FIG. 1 is a block diagram of a prior art multipoint communication system
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`including a master transceiver and a plurality of tributary transceivers;
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`[0016] FIG. 2 is a ladder diagram illustrating the operation of the multipoint
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`communication system ofFIG. 1;
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`[0017] FIG. 3 is a block diagram of a master transceiver and tributary transceiver for
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`use in the multipoint communication system of FIG. 1 in accordance with the principles of the
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`present invention;
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`[0018] FIG. 4 is a block diagram of a multipoint communication system including the
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`master transceiver and a plurality of tributary transceivers of the type illustrated in FIG. 3;
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`[0019] FIG. 5 is a ladder diagram illustrating the operation ofthe multipoint
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`communication system ofFIG. 4;
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`[0020] FIG. 6 is a state diagram for a tributary transceiver of FIGS. 3-5 using a
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`secondary modulation method in accordance with the principles of the present invention;
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`[0021] FIG. 7 is a state diagram for a tributary transceiver of FIGS. 3-5 using a primary
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`modulation method in accordance with the principles of the present invention; and
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`[0022] FIG. 8 is a ladder diagram illustrating the operation of an alternative
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`embodiment of the multipoint communication system ofFIG. 4.
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`DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
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`[0023] While the invention is susceptible to various modifications and alternative
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`forms, a specific embodiment thereof is shown by way of example in the drawings and will
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`herein be described in detail. It should be understood, however, that there is no intent to limit the
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`-4-
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`Exhibit 1207 04/22
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`REMB-0109
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`invention to the particular form disclosed, but on the contrary, the invention is to cover all
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`modifications, equivalents, and alternatives falling within the spirit and scope of the invention as
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`defined by the claims.
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`[0024] With reference to FIG. 1, a prior art multipoint communication system 22 is
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`shown to comprise a master modem or transceiver 24, which communicates with a plurality of
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`tributary modems (tribs) or transceivers 26-26 over communication medium 28. Note that all
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`tribs 26-26 are identical in that they share a common modulation method with the master
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`transceiver 24. Thus, before any communication can begin in multipoint system 22, the master
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`transceiver and the tribs 26-26 must agree on a common modulation method. If a common
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`modulation method is found, the master transceiver 24 and a single trib 26 will then exchange
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`sequences of signals that are particular subsets of all signals that can be communicated via the
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`agreed upon common modulation method. These sequences are commonly referred to as
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`training signals and can be used for the following purposes: 1) to confirm that the common
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`modulation method is available, 2) to establish received signal level compensation, 3) to
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`establish time recovery and/or carrier recovery, 4) to permit channel equalization and/or echo
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`cancellation, 5) to exchange parameters for optimizing performance and/or to select optional
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`features, and 6) to confirm agreement with regard to the foregoing purposes prior to entering into
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`data communication mode between the users. In a multipoint system, the address of the trib with
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`which the master is establishing communication is also transmitted during the training interval.
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`At the end of a data session a communicating pair of modems will typically exchange a sequence
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`of signals known as trailing signals for the purpose of reliably stopping the session and
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`confirming that the session has been stopped. In a multipoint system, failure to detect the end of
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`a session will delay or disrupt a subsequent session.
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`[0025] Referring now to FIG. 2, an exemplary multipoint communication session is
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`illustrated through use of a ladder diagram. This system uses polled multipoint communication
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`protocol. That is, a master controls the initiation of its own transmission to the tribs and permits
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`transmission from a trib only when that trib has been selected. At the beginning of the session,
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`the master transceiver 24 establishes a common modulation as indicated by sequence 32 that is
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`used by both the master 24 and the tribs 26a, 26b for communication. Once the modulation
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`scheme is established among the modems in the multipoint system, The master transceiver 24
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`transmits a training sequence 34 that includes the address of the trib that the master seeks to
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`communicate with. In this case, the training sequence 34 includes the address of trib 26a. As a
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`result, trib 26b ignores training sequence 34. After completion of the training sequence 34,
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`master transceiver 24 transmits data 36 to trib 26a followed by trailing sequence 38, which
`- 5-
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`Exhibit 1207 05/22
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`

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`REMB-0109
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`signifies the end of the communication session. Note that trib 26b ignores data 36 and trailing
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`sequence 38 as it was not requested for communication during training sequence 34.
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`[0026] At the end of trailing sequence 38, trib 26a transmits training sequence 42 to
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`initiate a communication session with master transceiver 24. Because master transceiver 24
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`selected trib 26a for communication as part of training sequence 34, trib 26a is the only modern
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`that will return a transmission. Thus, trib 26a transmits data 44 destined for master transceiver
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`24 followed by trailing sequence 46 to terminate the communication session.
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`[0027] The foregoing procedure is repeated except master transceiver identifies trib 26b
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`in training sequence 48. In this case, trib 26a ignores the training sequence 48 and the subsequent
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`transmission of data 52 and trailing sequence 54 because it does not recognize its address in
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`training sequence 48. Master transceiver 24 transmits data 52 to trib 26b followed by trailing
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`sequence 54 to terminate the communication session. To send information back to master
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`transceiver 24, trib 26b transmits training sequence 56 to establish a communication session.
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`Master transceiver 24 is conditioned to expect data only from trib 26b because trib 26b was
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`selected as part of training sequence 48. Trib 26b transmits data 58 to master transceiver 24
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`terminated by trailing sequence 62.
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`[0028] The foregoing discussion is based on a two-wire, half-duplex multipoint system.
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`Nevertheless, it should be understood that the concept is equally applicable to four-wire systems.
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`[0029] Consider the circumstance in which master transceiver 24 and trib 26b share a
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`common modulation type A while trib 26a uses a second modulation type B. When master
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`transceiver attempts to establish A as a common modulation during sequence 32, trib 26a will
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`not be able to understand that communication. Moreover, trib 26a will not recognize its own
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`address during training interval34 and will therefore ignore data 36 and trailing sequence 38.
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`Master transceiver 24 may time out waiting for a response from trib 26a because trib 26a will
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`never transmit training sequence 42, data 44, and trailing sequence 46 due to the failure of trib
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`26a to recognize the communication request (training sequence 34) from master transceiver 24.
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`Thus, if the tribs in a multipoint communication system use a plurality of modulation methods,
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`the overall communication efficiency will be disrupted as specific tribs will be unable to
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`decipher certain transmissions from the master transceiver and any unilateral transmission by a
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`trib that has not been addressed by the master transceiver will violate the multipoint protocol.
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`[0030] As discussed hereinbefore, however, it is desirable to design a multipoint
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`communication system comprising tribs that use a plurality of modulation methods. For example,
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`one moderately priced trib may be used to communicate at a relatively high data rate for some
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`applications, such as Internet access, while another, lower priced, trib is used to communicate at
`-6-
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`Exhibit 1207 06/22
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`

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`REMB-0109
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`a lower data rate for other applications, such as power monitoring and control. The needs of
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`these different applications cannot be efficiently met by a single modulation. While it is possible
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`to use high performance tribs running state of the art modulation methods such as QAM, CAP, or
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`DMT to implement both the high and low data rate applications, significant cost savings can be
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`achieved if lower cost tribs using low performance modulation methods are used to implement
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`the lower data rate applications.
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`[0031] A block diagram of a master transceiver 64 in communication with a trib 66 in
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`accordance with the principles of the present invention is shown in FIG. 3. Master transceiver 64
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`comprises a central processing unit (CPU) 68 in communication with modulator 72, demodulator
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`74, and memory 76. Memory 76 holds software control program 78 and any data necessary for
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`the operation of master transceiver 64. Control program 78 includes logic for implementing a
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`plurality of modulation methods. For purposes of illustration, control program 78 can implement
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`both a type A and a type B modulation through modulator 72 and demodulator 74.
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`[0032] Trib 66 comprises CPU 82 in communication with modulator 84, demodulator
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`86, and memory 88. Memory 88, likewise holds software control program 92 and any data
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`necessary for the operation oftrib 66. Control programs 78 and 92, are executed by CPUs 68 and
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`82 and provide the control logic for the processes to be discussed herein. Control program 92
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`includes logic for implementing a particular modulation method, which, for purposes of
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`illustration, is called type X Inasmuch as master transceiver 64 is capable of running either a
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`type A or a type B modulation method, type X refers to one of those two modulation methods.
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`The master transceiver 64 communicates with trib 66 over communication medium 94.
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`[0033] Referring now to FIG. 4, a multipoint communication system 100 is shown
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`comprising a master transceiver 64 along with a plurality of tribs 66-66. In this example, two
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`tribs 66a-66a run a type A modulation method while one trib 66b runs a type B modulation
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`method. The present invention permits a secondary or embedded modulation method (e.g., type
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`B) to replace the standard modulation method (e.g., type A) after an initial training sequence.
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`This allows the master transceiver 64 to communicate seamlessly with tribs of varying types.
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`[0034] The operation of multipoint communication system 100 will be described
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`hereafter with reference to the ladder diagram of FIG. 5 and the state diagrams of FIGS. 6 and 7.
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`A communication session between the master transceiver 64 and a type B trib 66b will be
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`discussed first. A state diagram for a type B trib 66b is shown in FIG. 6. Type B trib 66b is
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`initialized in state 102 in which type A modulation transmissions are ignored. In the present
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`example, the primary modulation method is type A, thus, as shown in FIG. 5, master transceiver
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`64 establishes type A as the primary modulation in sequence 104. Note that because trib 66b
`-7-
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`Exhibit 1207 07/22
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`

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`REMB-0109
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`responds only to type B modulation transmissions, only the type A tribs 66a-66a are receptive to
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`transmission sequence 1 04.
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`[0035] To switch from type A modulation to type B modulation, master transceiver 64
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`transmits a training sequence 106 to type A tribs 66a in which these tribs are notified of an
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`impending change to type B modulation. The switch to type B modulation could be limited
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`according to a specific time interval or for the communication of a particular quantity of data.
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`After notifying the type A tribs 66a of the change to type B modulation, master transceiver 64,
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`using type B modulation, transmits data along with an address in sequence 108, which is
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`destined for a particular type B trib 66b. The type B trib 66b targeted by the master transceiver
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`64 will transition to state 112 as shown in FIG. 6 upon detecting its own address where it
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`processes the data transmitted in sequence 108.
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`[0036] After completing transmission sequence 108, master transceiver 64 transmits a
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`trailing sequence 114 using type A modulation thus notifying all type A tribs 66a that type B
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`modulation transmission is complete. If master transceiver 64 has not transmitted a poll request
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`to the type B trib 66b in sequence 108, then the type B trib 66b that was in communication with
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`the master transceiver 64 will return to state 102 after timing out based on the particular time
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`interval defined for the type B modulation transmission or transfer of the particular quantity of
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`data. Note that the trailing sequence 114 is ineffective in establishing the termination of a
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`communication session between master transceiver 64 and a type B trib 66b because the trailing
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`sequence is transmitted using type A modulation.
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`[0037]
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`If, however, master transceiver 64 transmitted a poll request in sequence 108,
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`then the type B trib 66b transitions to state 116 where it will transmit data, using type B
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`modulation, to master transceiver 64 in sequence 118. After completion of this transmission, the
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`type B trib 66b returns to state 1 02 where type A transmissions are ignored.
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`[0038] With reference to FIG. 5 and FIG. 7, a communication session between the
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`master transceiver 64 and a type A trib 66a will now be discussed. A state diagram for a type A
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`trib 66a is shown in FIG. 7. A type A trib 66a is initialized in state 122 in which it awaits a type
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`A modulation training sequence. If, however, master transceiver transmits a training sequence in
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`which the type A tribs 66a-66a are notified of a change to type B modulation as indicated by
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`sequence 106, then a transition is made to state 124 where all type B transmissions are ignored
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`until a type A modulation trailing sequence (e.g., sequence 114) is detected. Upon detecting the
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`type A trailing sequence, a type A trib 66a returns to state 122 where it awaits a training
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`sequence.
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`- 8 -
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`Exhibit 1207 08/22
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`

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`REMB-0109
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`[0039] To initiate a communication session with a type A trib 66a, master transceiver
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`64 transmits a training sequence 126 in which an address of a particular type A trib 66a is
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`identified. The identified type A trib 66a recognizes its own address and transitions to state 128
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`to receive data from master transceiver 64 as part of sequence 132.
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`[0040] After completing transmission sequence 132, master transceiver 64 transmits a
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`trailing sequence 134 using type A modulation signifYing the end of the current communication
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`session. If master transceiver 64 has not transmitted a poll request to the type A trib 66a in
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`sequence 132, then the type A trib 66a that was in communication with the master transceiver 64
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`will return to state 122 after receiving trailing sequence 134.
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`[0041]
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`If, however, master transceiver 64 transmitted a poll request in sequence 132,
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`then the type A trib 66a transitions to state 136 after receiving trailing sequence 134 where it will
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`transmit training sequence 138, followed by data sequence 142, and terminated by trailing
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`sequence 144 all using type A modulation. After completion of these transmissions, the type A
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`trib 66a returns to state 122 to await the next type A modulation training sequence by master
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`transceiver 64.
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`[0042]
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`In an alternative embodiment ofthe present invention, embedded modulations
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`can be used as a way to measure transmission line characteristics between a master transceiver
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`and tributary transceiver, as shown in FIG. 8. In this embodiment, both a master transceiver 64
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`and a tributary transceiver 66a would have the ability to transmit using at least two modulation
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`methods, type A and type B. In the present example, the primary transmission type is type A.
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`Thus, as shown in FIG. 8, the master transceiver 64 establishes type A as the primary modulation
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`in sequence 150.
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`[0043] To switch from type A to type B modulation, master transceiver 64 transmits a
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`notification sequence 152 to the tributary 66a. Thus, the tributary 66a is notified of an impending
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`change to modulation type B. The switch to type B modulation could be limited according to a
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`specific time interval or for the communication of a particular quantity of data, such as a test
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`signal. After notifYing the tributary 66a of the change to type B modulation, the master
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`transceiver 64, transmits a test signal sequence 154 using type B modulation.
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`[0044]
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`In this embodiment, the tributary transceiver can contain logic which enables the
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`tributary 66a to calculate at least one channel parameter from the test signal sequence 154.
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`Channel parameters typically include transmission line characteristics, such as, for example, loss
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`versus frequency, non-linear distortion, listener echoes, talker echoes, bridge tap locations,
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`impedance mismatches, noise profile, signal-to- noise ratio, group delay versus frequency, cross-
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`-9-
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`Exhibit 1207 09/22
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`

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`REMB-0109
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`talk presence, cross-talk type, etc. Moreover, the tributary transceiver 66a could be configured to
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`communicate a channel parameter back to the master transceiver 64.
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`[0045] After transmitting the test signal sequence 154 to the tributary transceiver 66a,
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`the master transceiver 64 can transmit a trailing sequence 156 to the tributary transceiver 66a
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`using type A modulation to indicate the end of the transmission using type B modulation. The
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`master transceiver 64 can then send information to the tributary transceiver 66a using primary
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`modulation type A, as shown by training, data and trailing sequences 158, 160 and 162.
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`Likewise, the tributary transceiver 66a can send information to the master transceiver 64 using
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`primary modulation type A, as shown by training, data and trailing sequences 164, 166 and 168.
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`[0046]
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`In a further alternative embodiment, the master transceiver 64 or tributary
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`transceiver 66a may identify a time period within which test signal sequences may be
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`transmitted. This would eliminate the training and trailing sequences which alert the tributary
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`transceiver 66a to the beginning of a new modulation method. The identification of the time
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`period could be initiated by the master transceiver 64 or tributary transceiver 66a and could
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`include a time period noted in the header of a transmission between the tributary transceiver 66a
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`and master transceiver 64.
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`[0047] The control programs 78 and 92 of the present invention can be implemented in
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`hardware, software, firmware, or a combination thereof. In the preferred embodiment(s ), the
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`control programs 78 and 92 are implemented in software or firmware that is stored in a memory
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`and that is executed by a suitable instruction execution system.
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`[0048] The control programs 78 and 92, which comprise an ordered listing of
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`executable instructions for implementing logical functions, can be embodied in any computer(cid:173)
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`readable medium for use by or in connection with an instruction execution system, apparatus, or
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`device, such as a computer-based system, processor-containing system, or other system that can
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`fetch the instructions from the instruction execution system, apparatus, or device and execute the
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`instructions. In the context of this document, a "computer-readable medium" can be any means
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`that can contain, store, communicate, propagate, or transport the program for use by or in
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`connection with the instruction execution system, apparatus, or device. The computer readable
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`medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic,
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`infrared, or semiconductor system, apparatus, device, or propagation medium. More specific
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`examples (a nonexhaustive list) of the computer-readable medium would include the following:
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`an electrical connection (electronic) having one or more wires, a portable computer diskette
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`(magnetic), a random access memory (RAM) (magnetic), a read-only memory (ROM)
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`(magnetic), an erasable programmable read-only memory (EPROM or Flash memory)
`- 10-
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`Exhibit 1207 10/22
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`REMB-0109
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`(magnetic), an optical fiber (optical), and a portable compact disc read-only memory (CDROM)
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`(optical). Note that the computer-readable medium could even be paper or another suitable
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`medium upon which the program is printed, as the program can be electronically captured, via
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`for instance optical scanning of the paper or other medium, then compiled, interpreted or
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`otherwise processed in a suitable manner if necessary, and then stored in a computer memory.
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`[0049]
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`In concluding the detailed description, it should be noted that it will be obvious
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`to those skilled in the art that many variations and modifications can be made to the preferred
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`embodiment without substantially departing from the principles of the present invention. All
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`such variations and modifications are intended to be included herein within the scope of the
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`present invention, as set forth in the following claims. Further, in the claims hereafter, the
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`corresponding structures, materials, acts, and equivalents of all means or step plus function
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`elements are intended to include any structure, material, or acts for performing the functions with
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`other claimed elements as specifically claimed.
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`- 11 -
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`Exhibit 1207 11/22
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`

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`REMB-0109
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`What is Claimed:
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`1.
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`A communication system, comprising:
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`a transmitter capable of transmitting at least two modulation methods, wherein the
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`at least two modulation methods comprise a first modulation method and a second modulation,
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`wherein the second method is different than the first modulation method, and wherein the first
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`transceiver is configured to transmit
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`a first sequence, in the first modulation method, that indicates an impending change from
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`the first modulation method to the second modulation method, and
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`a second sequence, in the second modulation method, wherein the second sequence is
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`transmitted after the first data sequence.
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`2. The system of claim 1, wherein the transceiver is configured to transmit a third sequence
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`after the second sequence, wherein the third sequence is transmitted in the first modulation
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`method and indicates that communication has reverted to the first modulation method.
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`3. The system of claim 1, wherein first modulation method is a frequency shift keying
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`modulation.
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`4. The system of claim 3, wherein the second modulation method is a shift keying modulation.
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`5. The system of claim 1, wherein the second modulation method is different than the first
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`modulation method in performance.
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`6. The system of claim 5, wherein the first modulation method has a lower performance than
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`the second modulation method.
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`7. The system of claim 1, wherein the second modulation method is different than the first
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`modulation method in data rate.
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`8. The system of claim 7, wherein the first modulation method has a lower data rate than the
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`second modulation method.
`
`- 12-
`
`Exhibit 1207 12/22
`
`

`
`REMB-0109
`
`9. The system of claim 1, wherein the first transceiver is configured to transmit the second
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`sequence according to a specific time interval.
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`10. The system of claim 1, wherein the first transceiver is configured to transmit the second
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`sequence according to a particular quantity of data.
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`11. The system of claim 1, further comprising a processor and a memory, wherein the memory
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`has stored therein instructions that when executed by the processor cause the transmitter to
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`transmit the first sequence and the second sequence.
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`12. The system of claim 11, wherein the memory has stored therein program code for the first
`
`modulation method and the second modulation method.
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`13. The system of claim 11, wherein the memory comprises random access memory.
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`14. The system of claim 11, wherein the memory comprises read-only memory.
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`15. The device of claim 11, wherein the memory has stored therein program code for a
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`multipoint communications protocol.
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`16. The system of claim 1, wherein the first sequence comprises an address.
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`17. The system of claim 1, wherein the first sequence and the second sequence are contained in
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`a burst transmission.
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`18. The system of claim 17, wherein the burst transmission is a poll in accordance with a
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`multipoint communications protocol.
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`19. A communications device, comprising:
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`a processor; and
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`a memory having stored therein executable instructions for execution by the processor,
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`wherein the executable instructions direct transmission of first data with a first modulation
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`method followed by second data with a second modulation method, wherein the first modulation
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`method is different than the second modulation method, and wherein the first data comprises an
`
`- 13-
`
`Exhibit 1207 13/22
`
`

`
`REMB-0109
`
`indication of an impending