(19)
`
`"Df
`
`(12)
`
`Europdisches Patentamt
`
`European Patent Office
`
`Office européen des brevets
`
`(11)
`
`EP 0 827 336 A3
`
`EUROPEAN PATENT APPLICATION
`
`(88) Date of publication A3:
`06.10.1999 Bulletin 1999/40
`
`(43) Date of publication A2:
`04.03.1998 Bulletin 1998/10
`
`(21) Application number: 97306679.8
`
`(22) Date offiling: 29.08.1997
`
`(84) Designated Contracting States:
`AT BE CH DE DK ES FIFR GB GRIEITLILU MC
`NL PT SE
`
`(30) Priority: 30.08.1996 JP 23001596
`11.03.1997 JP 5668797
`
`(71) Applicant: MATSUSHITA ELECTRIC INDUSTRIAL
`co., LTD.
`Kadoma-shi, Osaka-fu, 571 (JP)
`
`(72) Inventors:
`¢ Shimoji, Tatsuya
`Neyagawaz-shi, Osaka-fu 572 (JP)
`¢ Okamura, Kazuo
`Hirakata-shi, Osaka-fu 573 (JP)
`¢ Hirai, Junichi
`Suita-shi, Osada-fu, 564 (JP)
`¢ Oashi, Masahiro
`Hirakata-shi, Osaka-fu 573-01 (JP)
`¢ Kakiuchi, Takashi
`Toyonaka-shi, Osaka-fu 561 (JP)
`
`
`
`(51) Int cl.@: HO4N 5/44, HO4N 7/16,
`HO4N 7/24
`
`¢ Kusumi, Yuki
`Kashiba-shi, Nara-ken 639-02 (JP)
`e Miyabe, Yoshiyuki
`Osaka-shi, Osaka-fu 532 (JP)
`* Minakata, Ikuo
`Souraku-gun, Kyoto-fu 619-02 (JP)
`¢ Kozuka, Masayuki
`Neyagawa-shi, Osaka-fu 572 (JP)
`¢ Mimura, Yoshihiro
`Hirakata-shi, Osaka-fu 573 (JP)
`¢ Inoue, Shinji
`Neyagawa-shi, Osaka-fu 572 (JP)
`¢ Mori, Toshiya
`Settsu-shi, Osaka-fu 566 (JP)
`* Takao, Naoya
`Kadoma-shi, Osaka-fu 571 (JP)
`
`(74) Representative: Crawford, Andrew Birkbyet al
`A.A. THORNTON & CO.
`Northumberland House
`
`303-306 High Holborn
`London WC1V 7LE (GB)
`
`(54)
`
`Digital broadcasting system, digital broadcasting apparatus, and associated receiver
`therefor
`
`(57)|Abroadcasting system which includes a broad-
`sets of video data and control information. The reception
`apparatus includes an extracting unit for extracting a set
`casting apparatus and a reception apparatus and which
`of video data and a set of control information in a same
`achievesinteractiveness using a broadcast wave. The
`broadcasting apparatus includes a content storing unit
`for storing the plurality of contents, each content includ-
`ing a set of video data and a set of control information
`that indicates another contentthat is a link destination
`
`content as the set of video data, a storing unit for storing
`the extracted set of control information, a reproducing
`unit for reproducing the extracted set of video data and
`outputting an image signal, an operation unit for receiv-
`ing a user operation that indicates a content switching,
`and a control unit for controlling the extracting unit to
`extract another content indicated by the set of control
`information storedin the storing unit, in accordance with
`the user operation.
`
`for a present content, and a transmitting unit for multi-
`plexing a set of video data and a plurality of sets of the
`same control information included in a same content as
`
`the set of video data, and for transmitting the multiplexed
`
`EP0827336A3
`
`Printed by Jouve, 75001 PARIS (FR)
`
`IPR2022-01227
`IPR2022-01227
`EXHIBIT 1003 - PAGE 00701
`EXHIBIT 1003 - PAGE 00701
`
`

`

`EP 0 827 336 A3
`
`O)) EuropeanPatent
`
`Office
`
`EUROPEANSEARCH REPORT
`
`ApplicationNumber
`
`EP 97 30 6679
`
`DOCUMENTS CONSIDERED TO BE RELEVANT
`Relevant
`CLASSIFICATION OF THE
`Citation of document with indication, where appropriate,
`to claim APPLICATION (Int.Ct.6)
`
`of relevant passages
`
`Category
`
`1,29,43,| HO4N5/44
`EP 0 680 216 A (THOMSON CONSUMER
`48
`HO4N7/16
`ELECTRONICS) 2 November 1995 (1995-11-02)
`14,28,|HO4N7/24
`47,49
`
`
`
`1,29,43,
`48
`14,28,
`47,49
`
`1,14, 28,
`29,43,
`47-49
`
`
`
`TECHNICALFIELDS
`SEARCHED
`{int.Ci.6)
`
`HO4N
`
`Examiner
`
`* page 3,
`* page 4,
`* page 4,
`
`line 14 - line 35 *
`line 19 - line 30 *
`line 53 - page 5,
`line 8 *
`
`US 5 422 674 A (HOOPER DONALD F_
`6 June 1995 (1995-06-06)
`
`ET AL)
`
`* column 5,
`* column 7,
`* column 9,
`* figure 7 *
`
`line 59 —- line 68 x
`line 39 — column 8,
`line 45 - line 65 *
`
`line 2 *
`
`US 5 541 662 A (ADAMS ROBERT
`30 July 1996 (1996-07-30)
`
`ET AL)
`
`line 45 - line 65 *
`column 4,
`line 39 - line 47 *
`column 5,
`line 43 — column 8,
`column 7,
`column 8, Tine 64 - column 9,
`—_-
`
`line 23 *
`line 10 *
`_
`
`* * a *
`
`The present search report has been drawnup forall claims
`Placeof search
`Date of completion of the search
`
`
`
`
`
`EPOFORM150303.82(P04C01)
`
`THE HAGUE
`CATEGORYOF CITED DOCUMENTS
`X : particularly ralevantif taken alone
`Y : particularly relevantIf combined with another
`documentof the same category
`A: technological background
`©: non-writtan disclosure
`P : intermediate document
`
`17 August 1999
`Sindic, G
`T : theory or principle underlying the invention
`E : earlier patent document, but published on, or
`after the filing date
`D : documentcited in the application
`L: document cited for other reasons
`dese eteaeceeceeeteeeeeseenreee Uitepeseecsesamen ts iyeeaenanansssaeeeenee seeeenesenesrseeee tees
`& : memberof the same patent family, corresponding
`document
`
`IPR2022-01227
`IPR2022-01227
`EXHIBIT 1003 - PAGE 00702
`EXHIBIT 1003 - PAGE 00702
`
`

`

`EP 0 827 336 A3
`
`O) EuropeanPatent
`
`Office
`
`EUROPEANSEARCH REPORT
`
`ApplicationNumber
`
`EP 97 30 6679
`
`
`
`Category
`
`X
`
`A
`
`* * page 33,
`
`DOCUMENTS CONSIDERED TO BE RELEVANT
`Citation of documentwith indication, where appropriate,
`of relevant passages
`
`"LA NORME MHEG, VIDEO A LA
`COLAITIS F:
`DEMANDE ET TELEVISION INTERACTIVE. THE
`MHEG STANDARD FOR VIDEO ON DEMAND AND
`DIGITAL TELEVISION SERVICES”
`REE: REVUE GENERALE DE L ELECTRICITE ET DE
`L ELECTRONIQUE,
`no. 4,
`1 October 1995 (1995-10-01), pages
`33-39, XP000533328
`ISSN: 1265-6534
`
`left-hand column, paragraph 1 -
`* page 36,
`paragraph 3 *
`* page 38, right-hand column, paragraph 3
`*
`
`“MHEG EXPLAINED"
`
`MEYER-BOUDNIK T ET AL:
`IEEE MULTIMEDIA,
`vol. 2, no. 1, 21 March 1995 (1995-03-21),
`pages 26-38, XP000500084
`ISSN: 1070-986X
`* page 28,
`left-hand column, paragraph 4 -
`right-hand column, paragraph 4 *
`* page 32, right-hand column, paragraph 4
`
`left-hand column, paragraph 5 -
`page 34, right-hand column, paragraph 1 *
`
`Relevant
`to claim
`
`CLASSIFICATION OF THE
`APPLICATION (Int.Ci.6)
`
`TECHNICAL FIELDS
`SEARCHED
`_(int.Cl.6)
`
`
`
`
`A
`
`WO 96 05699 A (ACTV INC)
`22 February 1996 (1996-02-22)
`
`* page 12,
`* page 14,
`* page 18,
`
`line 22 - line 33 *
`line 25 - page 15,
`-—-
`line 25 — page 19,
`
`line 4 *
`line 7 *
`
`The present search report has been drawn upfor all claims
`Place of search
`Date of completion of the search
`Examiner
`
`THE HAGUE
`
`17 August 1999
`
`Sindic, G
`
`CATEGORY CF CITED DOCUMENTS
`X: particularly relevantif taken alone
`Y : particularty relevantif combined with another
`document of the same category
`4: technological background
`QO: non-written disclosure
`P : intermediate document
`
`T : theory or principle underlying the invention
`E : earlier patent document, but published on, or
`after thefiling date
`D: document cited in the application
`L : documentcited for other reasons
`seaeesesiacceeossneensaeapesseanaaeanenees cepsesenesessesssevepnnsaseeessenensiereeneneseaseeneane
`& | memberof the same patent family, corresponding
`decument
`
`IPR2022-01227
`IPR2022-01227
`EXHIBIT 1003 - PAGE 00703
`EXHIBIT 1003 - PAGE 00703
`
`
`
`&9
`
`&2
`
`os
`8
`8
`=
`=
`2
`wi
`2
`
`

`

`EP 0 827 336 A3
`
`European Patent
`Office
`
`EUROPEAN SEARCH REPORT
`
`DOCUMENTS CONSIDERED TO BE RELEVANT
`Citation of documentwith indication, where appropriate,
`of relevant passages
`
`“TRANSMISSION OF
`ATZORI L ET AL:
`HYPERTEXTUAL INFORMATION USING MPEG-2
`PRIVATE DATA”
`PROCEEDINGS OF THE SPIE,
`vol. 2952, 7 October 1996 (1996-10-07),
`pages 582-590, XP000675526
`
`* page 582, paragraph 4 - page 583,
`paragraph 1 *
`* page 585, paragraph 5 - paragraph 6 *
`
`WO 96 42144 A (NOKIA OY AB ;SALOMAEKI ARI
`(FI)) 27 December 1996 (1996-12-27)
`
`» C
`
`ategory
`
`PX
`
`PA PX
`
`P,A
`
`* page 4,
`* page 7,
`
`line 24 - line 32 *
`line 1 - line 8 *
`
`Relevant
`to claim
`
`1,29,43,
`48
`
`14,28,
`47,49
`
`|1,29,43,
`48
`14,28,
`47,49
`
`
`
`Application Number
`EP 97 30 6679
`
`CLASSIFICATION OF THE
`APPLICATION (Int.Cl.6)
`
`
`
`TECHNICAL FIELDS
`SEARCHED
`{Int.C1.6)
`
`Examiner
`
`
`
`
`
`The present search report has been drawnup forall claims
`Place of search
`Date of completion of the search
`
`
`
`
`
`EPOFORM150303.82(P04C01)
`
`CATEGORY OF CITED DOCUMENTS
`
`X : particularly relevant if taken atone
`Y : particularly relevant if combined with another
`document of tha same catagory
`A: technological background
`O : non-written disclosure
`P : intermediate document
`
`: theory or principle underlying the invention
`: earlier patent document, but published on, or
`after thetiling date
`: documentcited in the application
`: documentcited for other reasons
`
`
`
`~e:-~Omo "memberofthe samepatentfamily, corresponding
`
`document
`
`4
`
`IPR2022-01227
`IPR2022-01227
`EXHIBIT 1003 - PAGE 00704
`EXHIBIT 1003 - PAGE 00704
`
`

`

`EP 0 827 336 A3
`
`ANNEXTO THE EUROPEAN SEARCHREPORT
`ON EUROPEANPATENTAPPLICATION NO.
`
`EP 97 30 6679
`
`This annexlists the patent family membersrelating to the patent documents cited in the above-mentioned European search report.
`The members are as contained in the European Patent Office EDPfile on
`The European Patent Office is in no way liable for these particulars which are merely given for the purpose of information.
`17-08-1999
`
`
` Publication
`Patent document
`Publication
`
`
`Patent family
`date
`date
`
`cited in search report member(s)
`
`
`EP 0680216
`02-11-1995
`5548532 A
`20-08-1996
`US
`5448568 A
`05-09-1995
`CN
`1114814 A
`10-01-1996
`JP
`8046950 A
`16-02-1996
`SG
`30364 A
`01-06-1996
`
`
`
`
`
`
`
`
`
`21-10-1998
`
`
`
`
`
`
`
`
`
`
`
`
`US 5422674
`
`US 5541662
`
`A
`
`A
`
`06-06-1995
`
`30-07-1996
`
`WO 9605699
`
`A
`
`22-02-1996
`
`WO 9642144
`
`A
`
`27-12-1996
`
`DE
`EP
`US
`
`AU
`EP
`WO
`US
`
`US
`AU
`AU
`BR
`CA
`EP
`uP
`
`FI
`AU
`
`69418580 D
`0660609 A
`5493638 A
`
`3411595 A
`0783818 A
`9610888 A
`5760838 A
`
`5585858 A
`688496 B
`2290895 A
`9506316 A
`2173996 A
`0723729 A
`9504156 T
`
`98175 B
`6127696 A
`0872053 A
`
`24-06-1999
`28-06-1995
`20-02-1996
`
`26-04-1996
`16-07-1997
`11-04-1996
`02-06-1998
`
`17-12-1996
`12-03-1998
`07-03-1996
`05-08-1997
`22-02-1996
`31-07-1996
`22-04-1997
`
`15-01-1997
`09-01-1997
`
`EPOFORMP0459 For more details aboutthis annex : see Official Journal of the European Patent Office, No. 12/82
`
`5
`
`IPR2022-01227
`IPR2022-01227
`EXHIBIT 1003 - PAGE 00705
`EXHIBIT 1003 - PAGE 00705
`
`

`

`(19)
`
`0)
`
`Europdisches Patentamt
`
`EuropeanPatentOffice
`
`Office européen des brevets
`
`(11)
`
`EP 0 859 535 A2
`
`(12)
`
`EUROPEAN PATENT APPLICATION
`
`(43) Date of publication:
`19.08.1998 Bulletin 1998/34
`
`(21) Application number: 98102634.7
`
`(22) Date offiling: 16.02.1998
`
`(84) Designated Contracting States:
`AT BE CH DE DK ES FI FR GB GRIEIT LI LU MC
`NL PT SE
`Designated Extension States:
`AL LT LV MK RO SI
`
`(80) Priority: 17.02.1997 JP 31610/97
`
`(71) Applicant:
`Matsushita Electric Industrial Co., Ltd.
`Kadoma-shi, Osaka 571-0050 (JP)
`
`(51) Int. cl8: HO4Q 11/04
`
`
`
`(72) Inventors:
`- Ohyama,Satoshi
`Ashiya-shi, Hyogo 659-0033 (JP)
`* Higashida, Masaaki
`Moriguchi-shi, Osaka 570-0011 (JP)
`* Morioka, Yoshihiro
`Kashiba-shi, Nara 639-0261 (JP)
`
`(74) Representative:
`Grtnecker, Kinkeldey,
`Stockmair & Schwanhdusser
`Anwaltssozietat
`Maximilianstrasse 58
`
`80538 Munchen (DE)
`
`(54)
`
`Communications system
`
`(57)©Acommunications system hasa real time sig-
`storing the real time signal for a prescribed number, N,
`nal generating part for generating the real time signal of
`of frames in the real time signal receive buffer part, the
`data rate R with one frame as one unit; a transmission
`real time signal outputting part is activated, thereby per-
`part, having a transmission rate C (C > R), over which
`forming control so that all generated portions of the real
`the real time signal is transmitted; and a real time signal
`time signal can be output at the receiving end without
`outputting part for outputting the real time signal stored
`interruption.
`in a real time signal receive buffer part, wherein after
`
`Fig. 1
`
`MEMORY
`CONTROLLER]
`
`111 Pcr BUS
`
`
`
`
`102
`
`
`
`AIM-NIC
`
`ATM-NIC
`
`Printed by Xerox (UK) Business Services
`2.16.3/3.4
`
`IPR2022-01227
`IPR2022-01227
`EXHIBIT 1003 - PAGE 00706
`EXHIBIT 1003 - PAGE 00706
`
`EP0859535A2
`
`

`

`1
`
`EP 0 859 535 A2
`
`2
`
`Description
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates to an apparatus for
`transmitting and receiving image data, voice data, and
`other supplementary data over a network, and more
`particularly to a communications system capable of
`maintaining the real time requirement of such data.
`
`2. Description of the Related Art
`
`In recent years, with increasing performance of
`microcomputers and the advent of OSs equipped with
`networking capabilities, coupled with increasing speeds
`of peripheral interfaces and increasing performance of
`computers, dramatic changes have been occurring in
`the field of computers, particularly personal computers
`and workstations, these changesentailing changesin
`information that computers handle. Earlier, information
`handled by computers was character code, such as
`ASCII and JIS, but gradually expandedto include graph-
`ics and the like in the field of CAD, and nowadays, han-
`dling of multimedia information such as moving images
`and voiceis increasing in importance. The most notable
`feature of multimedia information is that information
`
`occurs continuously in real time (hereinafter referred to
`as the real time requirement). On the other hand, with
`the spread of high-speed wide area networks, networks
`are being commercially implemented that store and
`manage such multimedia data and that have fast data
`transfer rates that enable such data to be launched into
`the networks. What characterizes such networksis that
`
`whentransmitting signals having the real time require-
`ment over the network, the transmitting end must send
`out data notlater than the time expectedat the receiving
`end.
`
`One example of a network suitable for multimedia
`communications is the ATM (Asynchronous Transfer
`Mode) network. With ATM, transmission systems capa-
`ble of 156 Mbit/s, for example, have been commercially
`implemented. ATM specifications are being discussed
`and standardized by the ITU-T (International Telecom-
`munications Union-Telecommunication Standardization
`Sector), the ATM Forum, etc., and manyrelated books
`have been published. Besides ATM,
`there are other
`techniques, such as 100-Mbps Ethernet (100BASE-T)
`and Fiber Distributed Data interface (FDDI), that can
`provide fast transmission capabilities of 100 Mbit/s or
`higher and can achieve multimedia information commu-
`nications. With slower versions of Ethernet (IEEE 802.2,
`IEEE 802.3) also, since switching hubs are now readily
`available, each terminal connected to the switching hub
`is capable of a transmission rate of about 10 Mbit/s and
`is therefore able to transmit real time signals that do not
`require data rates higher than that. In the Internet also,
`
`signals having real time requirements, such as video-
`conferencing and Internet telephone signals, are being
`transmitted.
`
`Prior art examples of communications systemsfor
`real time signals are disclosed, for example,
`in Japa-
`nese Patent Unexamined Publication Nos. 7-170502, 7-
`170503, 7-170290, 7-170291, 7-170504, and 7-170292.
`Japanese Patent Unexamined Publication No. 7-
`170502 discloses a system in which, when the amount
`of video or voice data in a buffer memoryat the receiv-
`ing end exceeds an upperlimit value or drops below a
`lowerlimit value, the buffer memoryis controlled in such
`a manner as to discard portions of the video or voice
`data other thancritical portions thereof.
`Japanese Patent Unexamined Publication No. 7-
`170503 concerns a system in which, when the amount
`of videoor voice data in the buffer memoryat the receiv-
`ing end exceeds an upperlimit value or drops below a
`lower
`limit value,
`the clock rate for buffer
`read is
`adjusted.
`Japanese Patent Unexamined Publication No. 7-
`170290 describes a system in which, when the amount
`of voice data in the buffer memoryat the receiving end
`exceeds an upperlimit value or drops below a lower
`limit value, a control signal is sent to alert the transmit-
`ting end, and at the transmitting end the clock rate for
`memoryreadis adjusted.
`Japanese Patent Unexamined Publication No. 7-
`170291 proposes a system in which, when the amount
`of voice data in a buffer memoryat the transmitting end
`exceeds an upperlimit value or drops below a lower
`limit value, video and voice data in the buffer memory
`are discarded.
`
`Japanese Patent Unexamined Publication No. 7-
`170504 provides a system in which a frame buffer is
`placed in front of the buffer memoryat the transmitting
`end and, when the amouniof data in the buffer memory
`exceeds an upper limit value or drops below a lower
`limit value, the amount of data is adjusted by adjusting
`the clock rate of the frame buffer memory.
`Japanese Patent Unexamined Publication No. 7-
`170292 discloses a system in which, when the amount
`of voice data in the buffer memory at the transmitting
`end exceeds an upperlimit value or drops below a lower
`limit value, the clock rate for memory read is adjusted,
`and when the amountof voice data in the buffer mem-
`
`ory at the transmitting end exceeds an upperlimit value
`or drops below a lowerlimit value, the amount of com-
`munication is controlled by changing the compression
`ratio.
`
`However, the prior art systems disclosed in Japa-
`nese Patent Unexamined Publication Nos. 7-170502, 7-
`170503, 7-170290, 7-170291, 7-170504, and 7-170292
`have had the problem that the system size increases
`becauseof the provision of extra circuitry such as a cir-
`cuit for measuring the amount of buffer contents, a cir-
`cuit for manipulating the discarding of buffer contents, a
`circuit for judging mathematical operations, and a circuit
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`IPR2022-01227
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`EXHIBIT 1003 - PAGE 00707
`
`

`

`3
`
`EP 0 859 535 A2
`
`4
`
`for specifying compression parameters necessary for
`obtaining the desired image compressionratio.
`Furthermore, since the degree of network conges-
`tion varies overtime, there can occur cases where data
`cannot be handled at one or more exchange points, etc.
`resulting in overflow. Generally, when a networkfalls
`into such a condition, the amount of transmission is
`reduced to alleviate the condition. The above prior art
`systems have had the problem that, when the transmis-
`sion capacity is restricted,
`it becomes impossible to
`maintain the real time requirement of real time signals
`or image quality degrades more than necessary.
`The present invention has been devised to over-
`comethe above-outlined problems,and it is an object of
`the invention to provide a communications system that
`is simple in configuration and that, when transmitting
`digital data having a real time requirement such as a
`moving image (video) signal or voice signal, ensures
`transmission of all frames without compromising the
`real time requirement of the data.
`
`SUMMARYOF THE INVENTION
`
`To resolve the above problems, the present inven-
`tion provides a communications system for communica-
`tion of a real time signal having a real time requirement,
`comprising:
`
`real time signal generating means for generating
`the real time signal of data rate R;
`real time signal transmit buffer means for temporar-
`ily storing the real time signal;
`real time signal transmitting means for transmitting
`the real time signal;
`transmission means, having a transmission rate C
`(C > R), over whichthe real time signalis transmit-
`ted;
`real time signal receiving means for receiving the
`real time signal transmitted from the real time signal
`transmitting meansover the transmission means;
`real time signal receive buffer means for temporarily
`storing the real time signal received bythe real time
`signal receiving means; and
`real time signal outputting means for outputting the
`real time signal stored in the real time signal receive
`buffer means.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Figure 1 is a diagram showing the configuration of a
`communications system accordingto a first embod-
`iment of the present invention;
`Figure2 is a flow chartillustrating a control program
`in a transmitting terminal 102 according to the first
`embodiment of the invention;
`Figure 3 is a flow chartillustrating a control program
`in a receiving terminal 103 according to the first
`embodimentof the invention;
`
`Figure 4 is a conceptual diagram showing a frame
`data buffer used in the first embodiment of the
`invention;
`
`Figure 5 is a timing chart showing the operation ina
`normal condition according to the first embodiment
`of the invention;
`Figure6 is a timing chart showing the operation ina
`congested condition according to the first embodi-
`ment of the invention;
`Figure 7 is a diagram showing a TCP segmentfor-
`mat;
`Figure 8 is a diagram showing the configuration of a
`communications system according to a second
`embodiment of the present invention;
`Figure 9 is a diagram showing the configuration of a
`communications
`system according to a_
`third
`embodimentof the present invention;
`Figure 10 is a flow chartillustrating a control pro-
`gram in a transmitting terminal 102 according to the
`third embodiment of the invention;
`Figure 11 is a flow chartillustrating a control pro-
`gram in a receiving terminal 103 according to the
`third embodimentof the invention; and
`Figure 12 is a diagram showing the configuration of
`a communications system according to a fourth
`embodiment of the present invention.
`
`DESCRIPTION OF THE PREFERRED EMBODI-
`MENTS
`
`The preferred embodiments of the present inven-
`tion will be described below with reference to the
`
`accompanying drawings.
`The real time signal contemplated by the present
`invention can be applied to any signal having a real time
`requirement, such as a moving image signal or a voice
`signal, but in the embodiments of the present invention,
`a digitized moving image signalis taken as an example
`of the real time signal, unless otherwise stated.
`Further, the present invention is applicable regard-
`less of the quality of the transmitted moving image
`which is determined by the number of samples in the
`horizontal and vertical directions relating to the resolu-
`tion of the moving image or by whether compression is
`applied or not and,
`if compression is applied, then by
`the type of compression applied. That is, the present
`invention is applicable regardless of the bit rate of the
`transmitted real time signal.
`In the embodiments of the present invention, an
`image signal employing the sampling method and com-
`pression method used in VTRs manufactured to the
`DVC standard is taken as an example.
`DVCis an acronym for Digital Video Cassette, and
`the DVC standard was agreed upon by the HD Digital
`VCR Consortium. This standard is described, for exam-
`ple, in a magazine "National Technical Report", Vol. 41,
`No. 2, April 1995, pp. 152-159.
`In the embodiments of
`the present invention, the NTSC signal compliant with
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`the DVC standard is taken as an example. According to
`the method defined by the DVC standard (NTSCsig-
`nal),
`the data bit
`rate is 28.8 Mbit/s
`(hereinafter
`described as 28.8 Mbps).
`Any transmission means may be used aslongasit
`has a transmission capacity greater than the bit rate of
`the real time signal used, but in the embodiments of the
`present invention, an ATM network having a transmis-
`sion rate of 156 Mbit/s is used as the transmission
`
`means; further, as a network protocol, a scheme called
`IP over ATM is used that is defined in RFC 1577 and
`
`that realizes a virtual IP network, and as higher layer
`protocols, TCP/IP (Transmission Control Protocol/Inter-
`net Protocol), now the standard suite of protocols for the
`Internet, is used in the examples described herein.
`Generally, the lowest level ina communications net-
`work provides unreliable packet delivery.
`If a transmis-
`sion error occurs that affects the data, orif the network
`load becomestoo heavyto be handled properly, pack-
`ets maybelost or destroyed. In a network that dynami-
`cally routes packets, the packets may be delivered out
`of order, may be duplicated, or may evenarrive after a
`large delay. Therefore, at the highest level, program-
`mers are required to incorporate error detection and
`recovery into application programs to achieve transmis-
`sion of large volumesof data.
`TCP/IP uses the basic technique called the positive
`acknowledgementwith retransmission to provide relia-
`ble transmission. This technique requires that
`the
`receiver communicate with the sender and return an
`
`acknowledgement (ACK) message each time data is
`received. The sender maintains records of each trans-
`
`mitted packet, and sends the next packet after an
`acknowledgementarrives. The senderalso activates a
`timer when sending a packet and, if the timer has timed
`out before arrival of an acknowledgment, retransmits
`the packet.
`The transfer unit used by TCP is called a segment.
`Figure 7(a) illustrates the TCP segment format. Each
`segmentis divided into two areas, the header and the
`data area. The headeris known as the TCP header and
`
`carries expected identification and control information.
`The SOURCE PORTfield and the DESTINATION
`PORTfield contain the TCP port numbers identifying
`application programs at both ends of the connection.
`The SEQUENCE NUMBER field identifies the position
`in a byte stream of the sender's data contained in the
`segment. The ACKNOWLEDGEMENT NUMBER field
`identifies
`the beginning of
`the sequence number
`expected to be received next (the next octet to be
`received). Since the TCP headerlength varies depend-
`ing on the options selected, the HLEN field indicates the
`offset of the data area in the segment. The six-bit field
`labeled RESERVED is set aside for future use. The
`TCP segment may beused to carry a connection setup
`or connection clear request or to carry only an acknowl-
`edgementor data. The six-bit field labeled CODE BITS
`is used to determine the purpose and contents of the
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`segment. More specifically, the CODE BITSfield dic-
`tates the way howthe otherfields in the headerare to
`be interpreted in accordance with the table shown in
`Figure 7(b). The WINDOWfieldtells the amountof data
`the receiving end is willing to accept, by specifying the
`buffer size each time a segmentis sent. Data that needs
`immediate processingis called urgent data. If the urgent
`code bit is on, that means that this segment contains
`urgent data. The URGENT POINTER field carries a
`pointer that indicates the position where the urgent data
`ends. The CHECKSUM field in the TCP header con-
`tains an integer checksum usedto verify the integrity of
`the TCP header and the data. The OPTIONS field is
`
`used for expanded TCP specifications, for example, but
`it is usually used to notify the remote end of the maxi-
`mum receivable segmentsize.
`As previously described, TCP/IP uses the tech-
`nique called the positive acknowledgement; however, in
`a simple positive acknowledgement protocol, since
`transmission of the next packet hasto wait until a posi-
`tive acknowledgement
`for
`the previous packet
`is
`received,
`the available bandwidth of the network is
`wasted. To address two important problems of efficient
`transfer and flow control, TCP uses a special mecha-
`nism called a sliding window.
`In this method, a fixed-
`length window is set in the sequence, and all packets
`inside the window are transmitted at a time. For exam-
`
`in a sliding window protocol of windowsize 8, the
`ple,
`senderis allowed to transmit eight packets before an
`acknowledgementis received. After the sender receives
`an acknowledgementfor the first packet,
`the sender
`slides the window and sends another packet. The win-
`dow continues to slide as long as an acknowledgement
`is received.In this case, the numberof packets that may
`be remaining unacknowledged at any giventimeis lim-
`ited by the windowsize, andis restricted to a small pre-
`determined value. Further, when the remaining capacity
`of the receiving buffer becomes low, for example, the
`amount of data being transmitted from the remote end
`can be reducedby reducing the window size value. TCP
`performs flow control by using this value.
`There are two major causesfor the loss of a TCP
`segmenttransferred over a network. One is a sporadic
`error. This, however, is not common in LANs and WANs
`whereline quality is good. The otheris the existence of
`a bottleneck such as a low-speedline or low-processing
`capacity router in the path through which the TCP seg-
`mentis carried. A condition in which a critical delay is
`caused by overload with datagrams at one or more
`exchange points such as routers is called congestion.
`Once congestion occurs, the delay increases and the
`router begins to queue datagrams until they can be
`routed out. In the worst case, the total numberof data-
`gramsarriving at the congested router reachesthe limit
`of the router's capacity and the router begins to drop
`datagrams. Usually, an end point has no detailed idea of
`where and how the congestion has occurred, and the
`congestion simply manifests itself as an increased delay
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`in turn, causes
`at the end point. The increased delay,
`the transport protocol to request retransmissions due to
`timeouts, further increasing the traffic on the network
`and exacerbating the congestion. This condition is
`called congestion collapse.
`in TCP it is recom-
`To avoid congestion collapse,
`mended to use two techniques, slow siart and multipli-
`cative decrease congestion avoidance.
`In multiplicative decrease congestion avoidance, a
`second restriction called a congestion windowis pro-
`vided to control congestion, and anytime, TCP com-
`pares the receiver's window size (buffer size) with the
`congestion window size and uses the smaller window in
`transmission. Each time a segmentlossis detected, the
`congestion windowsize is reduced by one half (the min-
`imum value is 1 segment) and the timeout interval
`is
`doubled. This strategy provides a quick and significant
`decreasein traffic and allows a sufficient time to clear
`
`the datagrams already queued at the router.
`When it
`is determined that the congestion has
`ended, TCP initializes the congestion window to 1,
`sendsthefirst segment, and waits for an acknowledge-
`ment. Thereafter, the congestion window is increased
`by one segment each time an acknowledgement
`arrives. This technique is called slow start.
`To prevent the windowsize from increasing too rap-
`idly and thereby causing congestion again, TCP pro-
`vides a still another restriction. That
`is, when the
`congestion window size reaches onehalf of its original
`size, TCP enters a congestion avoidance stage and
`reducesthe increasing speed of the congestion window
`size. During the congestion avoidanceperiod, the con-
`gestion window is increased only by 1 even if the
`acknowledgements for all the segments in the window
`are received.
`
`The above has described the process in TCP from
`the occurrence of congestion to the recovery from the
`congestion. While this processis in progress, the net-
`work can only transmit data at a lower transmission rate
`than its actual transmission capacity and imposes extra
`loads on end points. This presents a problem, espe-
`cially when transmitting real time signals. That is, the
`real time signals cannot be delivered in time and the
`real time requirementis impaired.
`In the present invention, the numberof frames of a
`real time signal accumulated in advanceatthe receiving
`end can be applied to any signals having real time
`requirements. In the embodiments of the present inven-
`tion, description will be given by taking a digitized mov-
`ing image signal as an example, unless otherwise
`stated.
`
`(Embodiment 1)
`
`Figure 1 shows a system configuration according to
`a first embodimentof the present invention. In Figure 1,
`reference numeral 101 is a camera for capturing a mov-
`ing image, 102 is a transmitting terminal, 103 is a
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`receiving terminal, 104 is an ATM switch, and 105 is a
`monitor.
`
`In the transmitting terminal 102, reference numeral
`106 is a DVC encoder for applying DVC compression,
`107 is a CPU, 108 is a transmit memory for temporarily
`storing transmit data and a conirol program for the
`transmitting terminal 102, 109 is a memory coniroller for
`controlling the transmit memory 108, 110 is an ATM net-
`workinterface card (ATM-NIC), and 111 is a PCI bus.
`In the receiving terminal 103, reference numeral
`112 is a DVC decoder, 113 is a CPU, 114 is a receive
`memory for temporarily storing received data and a con-
`trol program for the receiving terminal 103, 115 is a
`memory controller for controlling the receive memory
`114, 116 is an ATM networkinterface card (ATM-NIC),
`and 117 is a PCI bus.
`
`The operation of the thus configured communica-
`tions system will be described below.
`First,
`in the transmitting terminal 102, the moving
`image signal from the camera 101 is input into the DVC
`encoder 106 where DVC compression is applied on a
`frame by frame basis. Since the NTSC signal consists of
`30 frames per second, data for 30 frames per secondis
`obtained in the em