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`US007245874B2
`
`c12) United States Patent
`Rest et al.
`
`(IO) Patent No.:
`(45) Date of Patent:
`
`US 7,245,874 B2
`Jul. 17, 2007
`
`(54)
`
`INFRASTRUCTURE FOR TELEPHONY
`NETWORK
`
`(75)
`
`Inventors: Yehuda Rest, Lev Hashomron (IL);
`Salit Drobiner Gros, Kiryat Ono (IL);
`Avraham Barda, Hod-Hasharon (IL)
`
`(73)
`
`Assignee: Shiron Satellite Communications
`(1996) Ltd., Petach Tikva (IL)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 1078 days.
`
`(21) Appl. No.: 09/918,443
`
`(22) Filed:
`
`Aug. 1, 2001
`
`(65)
`
`Prior Publication Data
`
`US 2003/0027567 Al
`
`Feb. 6, 2003
`
`(51)
`
`Int. Cl.
`(2006.01)
`H04B 71185
`(52) U.S. Cl. ...................................... 455/12.1; 455/502
`(58) Field of Classification Search ................ 455/427,
`455/12.1, 433, 417, 426, 3.01, 3.02, 13.2,
`455/98, 506, 502, 445; 370/389, 310, 316
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`. ........... 340/825.52
`9/1988 Blair et al.
`12/1996 Burgess et al .............. 710/110
`9/1999 Bjorkman et al.
`.......... 370/389
`8/2001 Wiedeman ............... 455/426.l
`512004 Davidson et al ............ 370/316
`212005 Sigler et al ................. 370/310
`.......... 455/517
`3/2002 McKenna et al.
`
`4,773,001 A *
`5,590,369 A *
`5,959,988 A *
`6,272,339 Bl *
`6,735,184 Bl*
`6,850,497 Bl *
`2002/0037733 Al *
`* cited by examiner
`Primary Examiner-Edward F. Urban
`Assistant Examiner-Tu X. Nguyen
`
`(57)
`
`ABSTRACT
`
`A cellular telephone network comprises peripheral branches
`and a central high-capacity data trunking region or network
`backbone. The invention concerns effective utilization of
`trunking capacity to provide backbone facilities for such a
`network. The network backbone comprises a satellite inter(cid:173)
`face for a satellite connection and alternatively or addition(cid:173)
`ally a backup backbone route. For example an Internet
`backbone route and a satellite backbone route may be used,
`one backing up the other.
`
`12 Claims, 12 Drawing Sheets
`
`32
`
`Abis lntetiace
`
`38
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`Air lntetiace
`
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`
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`
`16
`
`Pet., Exh. 1001, p. 1
`
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`U.S. Patent
`
`Jul. 17, 2007
`
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`U.S. Patent
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`Jul. 17, 2007
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`Jul. 17, 2007
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`

`
`U.S. Patent
`
`Jul. 17, 2007
`
`Sheet 11 of 12
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`US 7 ,245,87 4 B2
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`

`
`US 7,245,874 B2
`
`1
`INFRASTRUCTURE FOR TELEPHONY
`NETWORK
`
`FIELD OF THE INVENTION
`
`The present invention relates to infrastructure for a tele(cid:173)
`phony network and more particularly but not exclusively to
`infrastructure including backbone and peripheral infrastruc(cid:173)
`ture for a cellular telephony network.
`
`BACKGROUND OF THE INVENTION
`
`Cellular networks generally comprise a series of base
`stations arranged to allow mobile stations within range of
`the network to contact other mobile stations and be able to
`access the public switched telephone network (PSTN). The
`base stations maintain wireless communication links with
`nearby mobile stations, but generally require hard infrastruc(cid:173)
`ture in the form of wiring to link the base stations to other
`parts of the cellular network and to outside networks and 20
`backbone networks. The laying of cable to provide such
`infrastructure is expensive and becomes more expensive if
`the infrastructure is to include any kind of backup provision.
`The cost of wired infrastructure is one of the limiting factors
`in extending a cellular network to remote areas.
`The telephony system including cellular networks and the
`PSTN, is generally based on the El, or possibly Tl, protocol
`for multiplexing transmissions into time slots. The protocol
`is strongly synchronous in that the individual transmission to
`which a time slot is assumed to belong to is determined from 30
`its temporal position amongst the other time slots. Thus an
`individual transmission which does not have current data
`creates blank slots to reserve its current position.
`Much available data carrying capacity is based on the
`TCP/IP protocol, which involves individual data packets
`being sent out over a network in accordance with destination
`information contained in a packet header. A single transmis(cid:173)
`sion is thus broken down into numerous packets which are
`each sent out independently over the network. The packets
`may be sent along different routes depending on availability
`and may not arrive in the order in which they have been sent.
`However the packet headers may be used by the receiving
`application to rebuild an original sequence from the packets.
`The El (and Tl) protocol thus depends on the preserva(cid:173)
`tion of a temporal relationship between time slots whereas
`the TCP/IP protocol does not preserve timing information.
`Thus TCP/IP based capacity cannot be used to transport El
`data since synchronization is not preserved, rendering the El
`datastream irrecoverable.
`
`2
`comprises a satellite interface for a satellite connection using
`a non-synchronous data communication protocol.
`Preferably, the high capacity trunking region comprises a
`terrestrial high capacity trunking connection in parallel with
`the satellite connection such that the satellite connection is
`usable to back up the terrestrial connection.
`Preferably, the synchronous data communication protocol
`is the El data protocol and the asynchronous data commu(cid:173)
`nication protocol is the TCP/IP data communication proto-
`10 col, and wherein the satellite interface comprises an
`El-TCP/IP converter.
`Preferably, the high capacity trunking region comprises a
`terrestrial high capacity trunking connection in parallel with
`the satellite connection such that the terrestrial high capacity
`15 trunking connection is usable to back up the satellite con-
`nection.
`Preferably, the synchronous data communication protocol
`is the El protocol and the asynchronous data communication
`protocol is the TCP/IP protocol and wherein the interface
`comprises El-TCP/IP converters.
`Preferably, the El-TCP/IP converter comprises a multi(cid:173)
`plexer for converting between the El signal and the TCP/IP
`signal.
`Preferably, the satellite link is via geostationary orbit
`25 satellite.
`Preferably, the El-TCP/IP converter comprises a multi(cid:173)
`plexer for converting between the El signal and the TCP/IP
`signal.
`Preferably, the converter is operable to receive El sig(cid:173)
`naling containing SS7 control signaling distributed therein
`at a predetermined data rate, the converter comprising
`an extractor for extracting the SS7 signaling, and
`a TCP/IP packet former for arranging the extracted sig-
`35 naling into TCP/IP packets.
`Preferably, the converter comprises an encoder for encod(cid:173)
`ing synchronization control data describing the El signal
`into headers of TCP/IP packets, thereby to enable subse(cid:173)
`quent synchronous reconstruction of the El signal.
`Preferably, at least one of the peripheral branches com-
`prises a satellite link and an El-TCP/IP interface.
`According to a second aspect of the present invention
`there is provided a branch of a cellular telephone network
`based on a first synchronous data communication protocol,
`45 comprising interfaces to a satellite link using a second,
`asynchronous, data communication protocol, wherein the
`interfaces comprise converters for converting data between
`the first data communication protocol and the second data
`communication protocol.
`Preferably, the interfaces are arranged to provide the
`satellite link as a parallel path to a terrestrial data link.
`Preferably, the interfaces comprise encoders for encoding
`synchronization control information of the first protocol
`when encoding data of the first protocol into the second
`55 protocol, thereby to enable reconstruction of a signal in the
`first protocol from data in the second protocol, which
`reconstructed data retains the synchronization.
`Preferably, the system comprises at least one base station
`connected to at least one mobile switching center, the at least
`60 one mobile switching center being associated with at least
`one location register, and wherein the satellite link is
`arranged to connect the at least one mobile switching center
`with the at least one location register.
`Preferably, the interfaces comprise decoders operable to
`65 decode synchronization control information from data arriv(cid:173)
`ing from the link, to reconstruct a synchronized telephony
`protocol data stream.
`
`40
`
`50
`
`SUMMARY OF THE INVENTION
`
`It is an aim of the present embodiments to solve the above
`mentioned problems and to provide a system in which the
`incompatibility between TCP/IP and El is overcome.
`It is a further aim of the present embodiments to provide
`IP based infrastructure and infrastructure backup for cellular
`telephony networks.
`It is a further aim of the present embodiments to provide
`IP based backbone infrastructure and infrastructure backup
`for cellular telephony based networks.
`According to a first aspect of the present invention there
`is thus provided a cellular telephone network comprising
`peripheral branches and a central high-capacity data trunk(cid:173)
`ing region and using a synchronous data communication
`protocol and wherein the high-capacity data trunking region
`
`Pet., Exh. 1001, p. 14
`
`

`
`US 7,245,874 B2
`
`4
`independent packets and an encoder operable to insert
`within each one of the independent packets, header infor(cid:173)
`mation indicating synchronization information of the packet
`as part of the El data.
`Preferably, the packager comprises a filter for identifying
`and discarding empty El time slots.
`Preferably, the filter further comprises a filter encoder for
`encoding positions of the discarded slots.
`Preferably, the filter is operable to discard predetermined
`time slots.
`According to a further aspect of the present invention
`there is provided a TCP/IP-El data reconverter comprising
`an input buffer for receiving TCP/IP packaged El data as a
`series of unsynchronized TCP/IP packets,
`a header reader for reading El synchronization data from
`the packets,
`and a reconstructor for using the El synchronization data
`to provide a reconstruction of an original El data stream
`from the TCP/IP data packets.
`Preferably, the El synchronization data comprises infor(cid:173)
`mation of discarded timeslots and wherein the reconstructor
`is operable to regenerate the discarded timeslots for insertion
`into the reconstructed El data stream.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`3
`Preferably, the interface further comprises a buffer con(cid:173)
`trollable according to the decoded synchronization informa(cid:173)
`tion to recreate time delay relationships of the telephony
`protocol data stream.
`Preferably, the telephony protocol allows non-data carry(cid:173)
`ing time slots, and the interfaces comprising a non-data
`carrying time slot remover for removing the non-data car(cid:173)
`rying time slots during conversion into the asynchronous
`protocol and a time slot regenerator for regenerating non(cid:173)
`data carrying time slots during reconstruction of the tele- 10
`phony protocol datastream.
`According to a third aspect of the present invention there
`is provided a hub for connecting to a satellite link, the hub
`being associated with an interface for interfacing between a
`synchronous telephone data protocol and an asynchronous 15
`satellite data protocol, thereby to allow telephone data to be
`sent via the satellite link.
`Preferably, the interface comprises a multiplexer for con(cid:173)
`verting between the telephone data protocol and the satellite
`data protocol, and an encoder for encoding timing informa- 20
`tion of the telephone data protocol.
`The hub is preferably operable to send the data via
`geostationary satellites.
`According to a further aspect of the present invention,
`there is provided an interface for interfacing between an El 25
`data network and a TCP/IP data network, the interface
`comprising a multiplexer for converting between El and
`TCP/IP data formats and comprising an encoder for encod(cid:173)
`ing timing information of the El format when encoding El
`data into TCP/IP data and a buffer for recreating El syn- 30
`chronization when converting the data back into El data.
`According to a yet further aspect of the present invention
`there is provided a method of managing an El-based tele(cid:173)
`phone network using a combination of El and TCP/IP high
`speed data links each having a given capacity, the method 35
`comprising:
`routing data directly via the El data links until their
`capacity is filled,
`converting excess data to TCP/IP format and routing via
`TCP/IP high speed data links, and
`reconverting the excess data to El format at a destination
`end of the TCP/IP high speed data links.
`Preferably, converting and reconverting are carried out by
`multiplexing the excess data.
`Preferably, the TCP/IP high speed data links comprise
`satellite data links.
`Preferably, the satellite data links utilize satellites in
`geostationary orbit.
`According to a further aspect of the present invention
`there is provided a communication backbone comprising
`high capacity El links and high capacity TCP/IP links and
`El-TCP/IP converters therebetween.
`Preferably, the high capacity TCP/IP data links comprise
`satellite links.
`According to a yet further aspect of the present invention, 55
`there is provided the use of synchronization preserving
`El-TCP/IP protocol conversion to allow interconnection of
`geostationary satellite links and Internet backbone links with
`mobile telephone networks to form a unified network.
`According to a yet further aspect of the present invention 60
`there is provided a series of TCP/IP data packets each having
`a packet header comprising timing information to allow
`reconstruction of the series as an El stream, the packets each
`carrying SS#7 data payload.
`According to yet another aspect of the present invention 65
`there is provided an El-TCP/IP data converter comprising a
`packager operable to package the El data as a series of
`
`45
`
`For a better understanding of the invention and to show
`how the same may be carried into effect, reference will now
`be made, purely by way of example, to the accompanying
`drawings.
`With specific reference now to the drawings in detail, it is
`stressed that the particulars shown are by way of example
`and for purposes of illustrative discussion of the preferred
`embodiments of the present invention only, and are pre(cid:173)
`sented in the cause of providing what is believed to be the
`most useful and readily understood description of the prin-
`ciples and conceptual aspects of the invention. In this regard,
`no attempt is made to show structural details of the invention
`40 ~~a:~~~ ~e;a;~:~:~~t~e~,e~~:ryd:~~r~t~~~::~ta~i~:~~~
`drawings making apparent to those skilled in the art how the
`several forms of the invention may be embodied in practice.
`In the accompanying drawings:
`FIG. 1 is a generalized block diagram showing part of a
`standard GSM-based mobile telephony system including a
`base station subsystem and a network subsystem,
`FIG. 2 is a simplified block diagram of a converter or an
`IP multiplexer (IPMux), which is able to convert between
`synchronous and asynchronous protocols, in particular
`50 between El/Tl and TCP/IP.
`FIG. 3 is a simplified block diagram showing a satellite
`connection in use as part of the infrastructure of a cellular
`network,
`FIG. 4 is a simplified block diagram of a star connected
`satellite-based network linking parts of a cellular network.
`FIG. 5 is a simplified block diagram of a star connected
`satellite based network as in FIG. 4 but with additional mesh
`connections between remote gateways,
`FIG. 6 is a simplified block diagram of a satellite link
`comprising a hub and the remote gateway of FIG. 5 pro(cid:173)
`viding an infrastructure link within a cellular network, in
`accordance with one embodiment of the present invention,
`FIG. 7 is a simplified block diagram of the remote
`gateway of FIG. 6 in greater detail, the remote gateway
`being operable to connect El/Tl networks to a TCP/IP based
`satellite link,
`
`Pet., Exh. 1001, p. 15
`
`

`
`US 7,245,874 B2
`
`5
`FIG. 8 is a simplified block diagram showing the hub
`station of FIG. 6 in greater detail,
`FIG. 9 is a simplified block diagram showing the use of
`satellite TCP/IP, terrestrial TCP/IP and El/Tl backbone in
`parallel to link parts of a cellular network,
`FIG. 10 is a simplified block diagram showing a commu(cid:173)
`nication channel bridging mobile and satellite components,
`and illustrating another preferred embodiment of the present
`invention,
`FIG. 11 is a simplified block diagram showing a remote
`gateway of a satellite link for use with the embodiment of
`FIG. 10, and
`FIG. 12 is a simplified block diagram showing in greater
`detail the satellite hub of FIG. 10.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Before explaining at least one embodiment of the inven(cid:173)
`tion in detail, it is to be understood that the invention is not
`limited in its application to the details of construction and
`the arrangement of the components set forth in the following
`description or illustrated in the drawings. The invention is
`applicable to other embodiments or of being practiced or
`carried out in various ways. Also, it is to be understood that 25
`the phraseology and terminology employed herein is for the
`purpose of description and should not be regarded as lim(cid:173)
`iting.
`The embodiments concern cellular and other wireless
`networks comprising branches and a heavy data trunking
`region which is required to carry large amounts of data
`rapidly and thus to serve as the backbone of the network.
`Generally, telephony based systems use the El/Tl telephony
`protocols whereas data carrying capacity that uses the TCP/
`IP Internet protocol is readily available. Such data capacity 35
`is available in the form of satellite capacity, particularly via
`geostationary satellite, and by terrestrial IP resources. The
`embodiments describe how these IP resources may be incor(cid:173)
`porated into telephony networks as cellular infrastructure, as
`high capacity backbone or as a backup to either the infra(cid:173)
`structure or the backbone of a telephony network. The
`embodiments also show and describe interface devices and
`methods.
`Reference is now made to FIG. 1, which is a generalized
`block diagram of a standard mobile telephone system. In
`FIG. 1, a user (not shown) connects to a base station
`subsystem 10 (BSS) via a mobile station (MS) 12 over an air
`interface. The mobile station 12 comprises a subscriber
`identity module (SIM) 14 that allows the mobile station 12
`to be identified to the system, both so that calls can be routed
`to it and so that it can be billed. The base station subsystem
`is connected to a network subsystem 16 which provides a
`link to the outside world of the regular telephone network 18
`(PSTN) and other parts of the mobile phone network (other
`MSC) 20.
`Referring to the base station subsystem 10 in more detail,
`it comprises a base transceiver station (BTS) 22, which
`supports two way communication with the mobile stations
`12, and base station controllers (BSC) 24 which control the
`transceivers 22 and route data between the transceivers and 60
`the network subsystem.
`Referring now to the network subsystem 16 in more
`detail, it comprises a mobile switching center 26 (MSC)
`through which data is routed and which controls tracking of
`mobile stations so that the mobile station is correctly iden(cid:173)
`tified, so that data is routed to the correct base station and so
`that handover between base stations is carried out correctly
`
`6
`during movement of the mobile station over the course of a
`call. The MSC 26 is the central component of the network
`subsystem 16, and performs the switching functions of the
`network. It also supports connections (18, 20, 38) to other
`5 networks.
`In order to carry out the above-mentioned tasks the
`mobile switching center is supported by an authentication
`center (AUC) 28 for authenticating identifications made of
`mobile stations, for example using digital signatures. A
`10 home location register 30 (HLR) and a visitor location
`register 32 (VLR) comprise lists of mobile stations so that
`identification of the mobile station can be carried out, and an
`operations and maintenance center 34 allows for overall
`supervision of the system.
`15 More particularly the HLR 30 is a dynamically defined
`database that stores information of the subscribers within the
`coverage area of an MSC. It stores the current location of the
`subscribers and the services to which they have access. The
`location of the subscriber corresponds to the SS7 address of
`20 the Visitor Location Register (VLR) 32.
`The VLR 32 is used for subscribers away from their home
`part of the cellular network. The VLR 32 contains informa(cid:173)
`tion taken from a subscriber's own local HLR in order to
`provide the subscribed services to visiting users in the
`current mobile region. When a subscriber enters the cover(cid:173)
`ing area of a new MSC, the VLR associated with the new
`MSC requests information about the new subscriber from
`his HLR. The VLR preferably obtains enough information to
`provide the subscriber with the appropriate services without
`30 needing to ask the source HLR each time a communication
`is established.
`The VLR is generally implemented together with an
`MSC; so that the area under control of the MSC is identical
`with the area under control of the VLR.
`Equipment identity register (EIR) 36 is connected to the
`MSC 26. The EIR is a register containing information about
`individual mobile units. More particularly, it contains a list
`of all valid terminals. A terminal is identified by its Inter(cid:173)
`national Mobile Equipment Identity (IMEI). The EIR uses
`40 the number and the register to forbid calls from stolen or
`unauthorized terminals, unauthorized including for example
`a terminal that does not respect the specifications concerning
`the output RF power).
`The visitor location register 32 is operatively associated
`45 with other visitor location registers 38, thereby to assist in
`managing handover and like procedures. In the following,
`the network subsystem and the base station subsystem and
`the connections within and therebetween are referred to as
`the cellular infrastructure. High capacity connections that
`50 link different MSCs or groupings ofMSCs are referred to as
`the cellular backbone. High capacity connections that form
`part of the PSTN 18 are referred to as the PSTN backbone.
`In general, both the cellular and PSTN systems use
`telephony protocols such as El. Additional network capacity
`55 is available in the form of communication links that use the
`TCP/IP Internet protocol, such as much of the geostationary
`satellite based links and Internet structure, but this capacity
`is not available for telephony due to incompatibility between
`the different protocols, as explained in the introduction.
`Reference is now made to FIG. 2, which is a simplified
`diagram of an interfacing device comprising an internet
`protocol multiplexer (IPMux) for use in a first embodiment
`of the present invention. The IPMux 50 comprises a first
`input port 52 for receiving an El or Tl data stream. The El
`65 or Tl data stream is generally a highly synchronized or
`ordered data stream comprising numerous communication
`channels (transmissions) multiplexed together in different
`
`Pet., Exh. 1001, p. 16
`
`

`
`US 7,245,874 B2
`
`7
`time slots within a continuous stream. The time slots com(cid:173)
`prise both data and associated control signaling. The mul(cid:173)
`tiplexer packages the data stream and associated control
`signaling into TCP/IP data packets as data payload such the
`packaging can be removed at the far end to leave the original
`El or Tl data stream in its entirety. The TCP/IP data packets
`are first stripped of blank time slots, TO slots and other user
`predetermined parts of the El signal, by a filter 51. The
`filtered data is then packaged into IP data packets of a
`predetermined size by packager 53 and then a header 10
`encoder 55 encodes synchronization or ordering information
`of the El data stream so that the original stream can be
`reconstructed at a receiving end. The newly packaged data
`is delivered to a TCP/IP data port 54 for output to a network
`based on TCP/IP.
`The multiplexer 50 also carries out the reverse operation
`on TCP/IP data packets supplied to an input port 56. The
`original order of the incoming TCP/IP packets has generally
`been lost over the TCP/IP link, since the TCP/IP protocol
`does not provide any packet order delivery feature. The
`disordered packets are entered into a buffering mechanism
`57 which is connected to a header reader 59. The header
`reader 59 reads the synchronization or ordering information
`that has been encoded in the packet headers and operates the
`buffering mechanism to reproduce the original timing infor- 25
`mation of the El signal. As the packets emerge from the
`buffering mechanism, the TCP/IP packaging is stripped off
`and the original ordered El stream is reconstructed by El
`reconstructor 61, again using the synchronization or order(cid:173)
`ing information obtained from the headers. The recon(cid:173)
`structed stream is then sent to output port 58 to be passed on
`to any telephony network.
`As mentioned above, the sequential order of the data
`packets is preferably encoded into packet headers at the
`sending end and the IPMux 50 is able to recreate the 35
`temporal order of the data when recreating the El stream.
`Buffering allows exact time difference sequences to be
`reconstructed. The IPMux 50, using data encoded into the
`packet headers, is also able to recreate blank slots, which
`have no meaning within a TCP/IP environment but are 40
`necessary in the El environment for maintaining correct
`sequence between time slots. Suitable buffering and recon(cid:173)
`struction thus allows an El stream at the output which is a
`reconstruction of the El stream at the input despite having
`used an asynchronous protocol in between. Thus the IPMux 45
`50 provides transparent bridging between Ell/Tl based
`systems and switch based packet networks including but not
`restricted to TCP/IP based networks.
`The IPMux 50 is preferably configurable to set desired
`packet sizes, and the filter 51 is preferably configurable to
`filter out El time slots that do not carry data. A definition for
`a non-data carrying time slot is preferably provided to filter
`51 by an operator prior to use. Preferably, TSO slots of the
`El protocol are also filtered out since these have no meaning
`in the TCP/IP protocol and may in any case be regenerated 55
`at the receiving end.
`Reference is now made to FIG. 3, which is a simplified