(12) United States Patent
`Us 6,920,150 B1
`Pauls et al.
`(45) Date of Patent:
`Jul. 19, 2005
`
`(10) Patent N0.:
`
`US006920150B1
`
`(54) ADAPTIVE COMMUNICATIONS
`TRANSCODING AND ERROR CONTROL
`
`(75)
`
`Inventors: Richard Joseph Pauls, Newton, NJ
`(US); Michael Charles Recchione,
`Nutley, NJ (US)
`
`(73) Assignee: Lucent Technologies Inc., Murray Hill,
`NJ (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 823 days.
`
`(21) Appl. N0.: 08/940,760
`
`(22) Filed:
`
`Sep. 30, 1997
`
`(51)
`
` (52)
`
`(58)
`
`Int. Cl.7 ................................................... H04J 3/16
`370/465, 714/752
`..... 370/465, 466,
`370/467; 714/746, 752, 758, 759, 761,
`762
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`5,490,168 A
`5,513,181 A *
`5,533,004 A
`5,657,420 A
`5,940,772 A
`6,202,188 B1 *
`
`2/1996 Phillips et a1.
`4/1996 Bresalier et a1.
`7/1996 Jasper et 211.
`8/1997 Jacobs et 211.
`8/1999 Kameda
`3/2001 Suzuki et al.
`
`............ 370/465
`
`............... 714/758
`
`FOREIGN PATENT DOCUMENTS
`
`JP
`JP
`JP
`JP
`WO
`
`05316082 A
`06113298 A
`07245600 A
`09214507 A
`WO95/15655
`
`11/1993
`4/1994
`9/1995
`8/1997
`6/1995
`
`............ H04N/7/16
`
`OTHER PUBLICATIONS
`
`Fox et al.: “Adapting To Network And Client Variability Via
`On—Demand Dynamic Distillation.” Sep. 1, 1996; vol. 31; p.
`160—170 ACM Sigplan Notices, US Association For Com-
`puting Machinery.
`
`Hui Zao et al.: “New Go—Back—N Arq Protocols For
`Point—To Multipoint Communications.” Aug. 1, 1994; vol.
`E77B ; p. 1013—1022; IEICE Transactions On Communi-
`cations.
`
`Han R. et al.: “Dynamic Adaptation InAn Image Transcod-
`ing Proxy For Mobile Web Browsing.” Dec.1, 1998; vol. 5
`p. 8—17; IEEE Personal Communications.
`Kentarou Fukuda et al., “The relationship bdetween QoS
`parameters and requierd bandwidth in MPEG—2 video”,
`1997, Department of Informatics and Matematical Science.
`Hui Zhao, Toru Sato, and lwane Kimura, “New Go—Back—N
`ARQ Protocols for Point—to—Multipoint Communications,”
`IEICE Transactions on Communications, vol. E77—B, No. 8,
`Tokyo, JP, Aug. 1994, pp. 1013—1022.
`Richard Han, Pravin Bhagwat, Richard LaMaire, Todd
`Mumert, Veronique Perret, and Jim Rubas, IBM T. J. Watson
`Research Center, “Dynamic Adaptation in an Image
`Transcoding Proxy for Mobile Web Browsing,” IEEE Per-
`sonal Communications, Dec. 1998, pp. 8—17.
`
`* cited by examiner
`
`Primary Examiner—Bob Phunkulh
`(74) Attorney, Agent, or Firm—Jimmy G00
`
`(57)
`
`ABSTRACT
`
`invention is a method for improving data
`The present
`transfer performance over communications networks con-
`necting data networks and users using adaptive communi-
`cations formatting. Adaptive communications formatting
`includes encoding (or compressing) the data and applying
`error control schemes to reduce the amount of data being
`transmitted and to correct and/or conceal errors occurring
`during data transmission. In one embodiment, the present
`invention uses a set of transcoding techniques to encode (or
`compress) the data and a set of error control schemes to
`correct and/or conceal errors occurring during data trans-
`mission. The particular sets of transcoding techniques and
`error control schemes selected to format the data are adap-
`tive to factors, such as the nature of the communications
`network connecting a user to an access server on the data
`network, the preferences of the user, and the data type of the
`data being transmitted to the user (or the access server).
`
`35 Claims, 4 Drawing Sheets
`
`
`
`
`
`Eflmfl cannot
`VlflED/IPASE l
`
`VIDEO/ME 1
`TWSCODBI
`
`\ VIDEO/IMAGE 2
`mmsccnen
`
`
`
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`US. Patent
`
`Jul. 19, 2005
`
`Sheet 1 OH
`
`US 6,920,150 B1
`
`DATA NETMURK
`
`FIG.
`1
`35 \
`
`
`
`
`
`HIRED/MIHELESS
`COMMUNICATION
`
`SYSTEM
`
`
`
`COMMUNICATIONS
`NETWORK
`
`MIREU/NIHELESS
`COMMUNICATION
`SYSTEM
`
`
`
`
`
`COMMUNICATION
`DEVICE
`
` REMOTE
`
`COMPUTER
`
`FIG. 2
`
`
`
`USER ID
`comm INFO
`
`
`
`‘
`
`“UNITED
`
`ERROR
`
`0m TYPE
`
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`901%“ .000010m
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`
`
`COMBINER
`
`
`ERROR CONTROL
`
`SPEECH/VOICE 2
`
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`FIG. 4
`
`
`
`DATA TYPES
`
`USER #
`
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`spew/vows
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`
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`
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`SPEECH/VOICE 1
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`DATA TYPE
`
`SUB-TYPES [BIT HATE)
`
`TRANSCOOER ENCODING ALGORITHMS
`(BIT RATE)
`
`ADAPTATION LAYERS
`
`
`
`BKbps;
`VCELP
`BKbgs;
`VSEDP
`(4-3 K ps]
`EDRU
`
`
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`
`SPEECH/VOICE
`
`
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`AUDIO
`54 Kbp8)
`HAVE
`SPEECH [32 Kbpps)
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`
`(MUTING)
`
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`
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`HYBRID REG
`TIFF
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`GIFF
`ERROR CONCEALHENT
`VIDEO/ IMAGE
`H.263
`[8—24 Kbps)
`
`
`(1; 5Mbp s!
`MPEG
`TINTERPOLATION)
`(a.0 Mbps)
`HPE62
`
`
`
`
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`US 6,920,150 B1
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`1
`ADAPTIVE COMMUNICATIONS
`TRANSCODING AND ERROR CONTROL
`
`BACKGROUND OF THE INVENTION
`
`Subscribers of wireless communications systems are
`increasing to phenomenal numbers with more than forty-five
`million subscribers in the United States and one-hundred
`
`and twenty million subscribers worldwide. As new service
`providers enter the wireless communication market,
`the
`level of competition for old service providers increases to
`retain existing customer base while attracting new subscrib-
`ers. To maintain continued growth of subscriber numbers
`and revenue levels, service providers are offering value-
`added services to their subscribers.
`
`The Internet explosion has provided service providers of
`wired and wireless communications systems with a direction
`for developing value-added services. Currently, there are
`more than fifty million users of the Internet. Access to the
`Internet is typically via a wired communication network.
`However, wired Internet access requires some type of physi-
`cal connection between the users and the wired communi-
`
`cations network. Thus, the mobility of users accessing the
`Internet via a wired connection is severely limited. By
`contrast, access to the Internet via a wireless communica-
`tions system offers a great deal of mobility to users/
`subscribers. However, wireless Internet access can be pro-
`hibitively expensive to most users/subscribers. Specifically,
`wireless communications systems, such as those based on
`the GSM and 18-95 CDMA standards, are limited in air
`interface access speeds (i.e., narrow bandwidth) and are
`subjected to an error prone transmission environment. For
`example, data transmitted over an 18-95 CDMA based
`wireless communication systems may be subject to a 3% or
`more bit error rate. Such limitations increase the amount of
`
`time required for successful data transfers between the
`Internet and the user/subscriber which, in turn, increases the
`cost of a wireless telephone call
`to the user/subscriber.
`Accordingly, there exists a need to improve data transfer
`performance (i.e., reduce transmission time) over commu-
`nication networks connecting the Internet or other data
`networks to the user/subscriber.
`
`SUMMARY OF THE INVENTION
`
`
`
`The present invention is a method for improving data
`ransfer performance over communications networks con-
`iecting data networks and users using adaptive communi-
`cations formatting. Adaptive communications formatting
`'ncludes encoding (or compressing) the data and applying
`error control schemes to reduce the amount of data being
`ransmitted and to correct and/or conceal errors occurring
`during data transmission. In one embodiment, the present
`'nvention uses a set of transcoding techniques to encode (or
`compress) the data and a set of error control schemes to
`correct and/or conceal errors occurring during data trans-
`nission. The particular sets of transcoding techniques and
`error control schemes selected to format the data are adap-
`ive to factors, such as the nature of the communications
`letwork connecting a user to an access server on the data
`aetwork, the preferences of the user, and the data type of the
`data being transmitted to the user (or the access server).
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The features, aspects, and advantages of the present
`invention will become better understood with regard to the
`following description, appended claims, and accompanying
`drawings where:
`FIG. 1 depicts an architecture for a system for accessing
`a data network in accordance with the present invention;
`
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`2
`
`FIG. 2 depicts a bitstream entering and exiting the access
`server;
`
`FIG. 3 depicts a functional block diagram of the access
`server in accordance with one embodiment of the present
`invention;
`
`FIG. 4 depicts a table for selecting transcoding techniques
`and error control schemes to use to format data; and
`FIG. 5 depicts a chart illustrating examples transcoding
`techniques and error control schemes which might be used
`for transmission of particular data types over wireless con-
`nections.
`
`DETAILED DESCRIPTION
`
`FIG. 1 illustrates an architecture for a system 10 for
`accessing a data network in accordance with the present
`invention. The system 10 comprises a data network 12 (e.g.,
`the Internet), a user 14, and a communications network 16.
`The communications network 16 comprises a plurality of
`wired and/or wireless communications systems for provid-
`ing a wired and/or wireless connection between the data
`network 12 and the user 14. Wired communications systems
`include Public Switching Telephone Networks (PSTN), and
`networks based on Integrated Services Digital Network
`(ISDN), T1 lines and E1 lines. Wireless communications
`systems include those based on Frequency Division Mul-
`tiple Access (FDMA), Time Division Multiple Access
`(TDMA) and Code Division Multiple Access (CDMA). The
`data network 12 comprises a plurality of interconnected
`computers including at least one access server 20 and at least
`one host 22. The access server 20 is a computer associated
`with a service provider to which the user 14 subscribes for
`accessing the data network 12. The host 22 is a computer
`havir g data sought by the user 14. The access server 20 and
`the host 22 may also be the same computer.
`The user 14 comprises a communication device 24 (e.g.,
`telep lone, mobile-telephone and/or modem) for receiving
`and t ansmitting data from and to the access server 20 via the
`communications network 16, and a remote computer 26
`havirg software for processing data for transmission to the
`access server 20 or for display on an output device associ-
`ated with the remote computer 26, such as a video display,
`an at dio display, a printer, memory, etc. The user 14 gains
`access to the data network 12 through the access server 20.
`Spec'fically, the user 14 dials a number associated with the
`access server 20. The communication network 16 connects
`
`the user 14 to the access server 20 using the dialed number.
`Upor connecting to the access server 20, the user 14 can
`retrieve data from the host 22.
`
`
`
`In general, data (being retrieved by the user) may be in the
`form of a file or an output of a real time recording device,
`such as a video camera, microphone, scanner, fax, transduc-
`ers or measuring devices. In all cases, the data will have
`associated information indicating a data type for the data.
`For purposes of discussion, the present invention will be
`described herein as retrieving data in the form of a file from
`the host 22. It should not be construed, however, to limit the
`present invention to retrieving data in the form of a file.
`The data (or file) is retrieved via a bitstream from the host
`22 to the access server 20 to the user 14. The bitstream
`includes the data and control
`information. The data has
`associated a filename with a file extension indicative of a
`
`information
`data type (and/or sub-type). The control
`includes a user indicator for identifying the user to whom the
`data is intended, error control information for correcting
`and/or concealing errors occurring during data transmission,
`and/or a data type indicator to identify the data type of the
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`associated data. Data types include, but are not limited to,
`speech/voice, video/image and text. Each data type has one
`or more sub-types. Examples of speech/voice sub-types (and
`file extensions) include audio (.au), wave (.wav) and speech
`(.sp). Examples of video/image sub-types include tagged
`image format files (.tif), graphic image format files (.gif),
`Moving Picture Experts Group files (.mpg and .mp2).
`Examples of text sub-types include MS Word (.doc) and
`ASCII (.txt).
`Adaptive Communications Formatting
`At the access server 20,
`the data is formatted using a
`mixture of transcoding techniques and error control schemes
`to facilitate data transmission within acceptable quality
`levels, as will be described herein. FIG. 2 illustrates a
`bitstream 23 entering and a bitstream 25 exiting the access
`server 20. When the bitstream 23 arrives at the access server,
`the bitstream 23 includes the data and user indicator-control
`
`information for identifying the user to whom the data is
`intended. The data is formatted by the access server 20 and
`transmitted to the user 14 via the bitstream 25, which
`includes encoded data, error control information for con-
`trolling and/or concealing errors resulting from data
`transmission, and data type indicator-control information for
`identifying the data type of the associated (encoded) data, as
`will be described herein.
`
`Transcoding techniques include encoding algorithms for
`encoding (or compressing)
`the data. Encoding (or
`compressing) the data facilitates data transmission by reduc-
`ing the amount of data to be transmitted which, in turn,
`decreases the time required to transmit the data (i.e., trans-
`mission time) from the access server to the user over a
`transmission channel of limited bandwidth (i.e., slower
`access speeds). Some encoding algorithms, however, have
`associated loss that may adversely affect data quality. Alge-
`braic Code Excited Linear Prediction (ACELP), Vector Sum
`Excited Linear Prediction (VSELP), Enhanced Variable
`Rate Coder (EVRC), h.263 (which is a set of guidelines
`being considered by the International Telecommunications
`Union for
`implementation into standards), pkzip (by
`PKWare,
`Inc.), MPEG and MPEG2 (Moving Pictures
`Experts Group), and JPEG (Joint Pictures Experts Group)
`are some examples of encoding algorithms which are well-
`known in the art. Each of the aforementioned encoding
`algorithms have associated different levels or percentages of
`compression.
`Error control schemes include techniques for correcting
`and/or concealing errors occurring during the transmission
`of data from the access server 20 to the user 14. Error control
`
`schemes provide means for assuring data integrity has not be
`compromised beyond acceptable levels. Some error control
`schemes, however, increase data transmission time by add-
`ing control information to the data and/or requiring retrans-
`missions of the data when data error is detected. Forward
`
`Error Correction (FEC), Cyclical Redundancy Check
`(CRC), Automatic Retransmission Query (ARQ), hybrid
`ARQ (i.e., combination of ARQ and FEC) and error con-
`cealment (e.g., muting, extrapolation from previous good
`frames, and interpolation from previous and succeeding
`good frames) are some examples of error control schemes
`which are well-known in the art. Each of the aforementioned
`error control schemes have associated different levels of
`error correction and/or concealment.
`
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`The particular transcoding techniques and error control
`schemes used to format
`the data should be adaptive to
`factors such as the nature of the communications network 16
`
`65
`
`connecting the user 14 to the access server 20, the prefer-
`
`ences of the user 14, and the data type of the data, as will be
`discuss herein. Note that the present invention should not be
`limited to being adaptive to only the aforementioned factors.
`Other factors, such as interactivity, bit rate and transmission
`delay, may also be applicable.
`First Factor
`The first factor involves the nature of the communications
`
`network 16 connecting the user 14 to the access server 20.
`The nature of communications systems,
`in general
`(regardless of whether the communication system is wired
`or wireless), varies from one to another. The nature of
`communications system depends on sub-factors such as
`whether the communications system is wired or wireless,
`whether the communications system is analog or digital, the
`available bandwidth, the bit rate, the signal-to-noise ratio,
`the bit error rate and the transmission delay, as will be
`described herein.
`
`the communications network 16
`As mentioned earlier,
`comprises a plurality of wired and/or wireless communica-
`tion systems for providing the user 14 with either a wired or
`a wireless connection to the access server 20. For purposes
`of discussion, a wireless connection involves using at least
`one wireless communication system to connect the user 14
`to the access server 20. By contrast, a wired connection
`involves using no wireless communication system to con-
`nect the user 14 to the access server 20. Wireless connec-
`
`tions have several distinct disadvantages over wired con-
`nections. First, the transmission times for data over wireless
`connections are typically greater than the transmission times
`for the same data over wired connections. The reasons for
`
`this are because wireless connections generally have less
`available bandwidth, lower bit rates and longer transmission
`delays than wired connections. Therefore, it may be desir-
`able to use a transcoding technique that will encode (or
`compress) the data as much as possible to reduce the
`transmission time over wireless connections (and perhaps
`some wired connections). The benefits realized in facilitat-
`ing data transmission should, however, be balanced against
`losses associated with compression (or encoding).
`Second, data transmitted over a wireless connection is
`more susceptible to data error than data transmitted over a
`wired connections. The reasons for this are because wireless
`
`connections generally have lower signal-to-noise ratios and
`higher bit error rates than wired connections. Therefore, it
`may be desirable to increase the amount of error control
`being applied to data transmissions over wireless connec-
`tions. The benefits of increased error control (i.e., increased
`quality) should, however, be balanced against increased data
`transmission time.
`Second Factor
`
`The second factor involves the preferences of the user 14.
`The preferences of the user 14 should reflect the hardware
`and software capabilities of the user 14 and the access server
`20, and a balancing between facilitating data transfer and
`acceptable data quality. The service provider and the sub-
`scribers should agree on the manner in which the data is to
`be formatted, i.e., agree on which transcoding techniques
`and error control schemes to use. Whatever manner is used
`
`by the access server 20 to format the data, the user 14 should
`be able to un-format the formatted data. In other words, the
`access server 20 should agree to use transcoding techniques
`and error control schemes compatible with transcoding
`techniques and error control schemes available at the user
`14. Failure to use compatible transcoding techniques and
`error control schemes will result in the user 14 receiving a
`bitstream that it can not un-format. This agreement may be
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`negotiated between the service provider and subscriber
`before or at the time the user connects to the access server
`
`20. Preferences of the user 14 should also reflect a balancing
`by the user between facilitating data transfer and acceptable
`data quality. For example, if the user 14 requires high quality
`data, the user 14 might have to trade-off facilitating data
`transfer for increased data quality. Thus, the user 14 might
`select a transcoding technique with less compression and
`minimal loss (e.g., pkzip) and an error control scheme with
`greater error correction (e.g., ARQ) for formatting the data
`at the access server.
`Third Factor
`
`The third factor is the data type of the data. Certain
`transcoding techniques and error control schemes are more
`effective when used to format particular data types. Thus, the
`transcoding techniques and error control schemes selected to
`format the data should be adaptive to the data type, as will
`be described herein. Transcoding techniques include encod-
`ing algorithms for encoding or compressing particular data
`types: gzip and pkzip for text data; VCELP, ASELP and
`EVRC for speech/voice data; and h.263 for Video/image
`data. Using a text transcoding technique (e.g., a transcoding
`technique with gzip) to compress speech/voice data may not
`be as effective as using a speech transcoding technique (e .g.,
`a transcoding technique with VCELP) to compress the same
`data—that is, the amount of data compression may not be
`the same.
`
`Error control schemes include techniques for different
`levels of error correction and/or concealment. The level or
`
`error correction and/or concealment applied to data should
`depend on the amount of error tolerable by the user which,
`in turn, depends on the data type. For example, errors in
`audio/speech and Video/image data types may be tolerable to
`some extent. In such cases, errors in audio/speech data types
`may best be concealed by muting, and errors in Video/image
`data types may best be concealed by interpolating from
`previous good frames. By contrast, errors in text data types
`may be intolerable. In this case, errors are corrected (not
`concealed) by requesting retransmissions of the data, i.e.,
`ARQ.
`
`FIG. 3 is a functional block diagram of the access server
`20 in accordance with one embodiment of the present
`invention. The access server 20 comprises a data selector 30,
`a plurality of text, speech/voice and video/image transcod-
`ing techniques 32-11 (i.e., transcoding techniques for text,
`speech/voice and Video/image data types), a plurality of text,
`speech/voice and video/image error control schemes 34-n
`(i.e., error control schemes for text, speech/voice and Video/
`'mage data types) and a combiner 38 for multiplexing
`ormatted data. The data selector 30 is a device, such as a
`nicroprocessor with software, for selecting a transcoding
`echnique 32-n and an error control scheme 34-n for for-
`natting the data. The transcoding technique 32-11 and error
`control scheme 34-11 is selected using the data type,
`the
`'dentity of the user, and/or a user table 40 specifying user
`areferences (i.e., transcoding techniques and error control
`schemes preferred by each user for each data type and/or
`sub-type). The data selector 30 can determine the data type
`ising the file extension, other information contained within
`he bitstream, default data types and/or a combination of the
`aforementioned. For example,
`the data selector 30 may
`determine data with .wav file extensions are speech/voice
`data types. The data selector 30 can determine the identity of
`the user using the user indicator-control information (in the
`bitstream). Note that FIG. 3 shows an one-on—one correla-
`tion between the transcoding techniques and error control
`schemes. This should not, however, be construed to limit the
`
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`present invention to embodiments with such a correlation.
`One-to-many correlation between transcoding techniques
`and error control schemes, or vice-versa, are also possible.
`FIG. 4 illustrates an example of a user table 40. The
`transcoding techniques and error control schemes in the
`table 40 specified for each user and data type (and/or
`sub-type) should reflect the aforementioned factors, i.e., the
`nature of the communications network connecting the user
`to the access server, the equipment and software capabilities
`and/or preferences of the user and the access server, and the
`data type of the data. For example, suppose user number
`000001 connects to the access server using a wireless
`connection. The table 40 specifies for user number 000001
`a set of transcoding techniques and error control schemes for
`each data type (and/or sub-type) that are available to both
`user number 000001 and the access server and will facilitate
`
`data transmission within acceptable quality levels over a
`wireless connection. By contrast, user number 000222 is
`connected to the access server 20 via a wired connection.
`
`For users connected Via a wired connection (e.g., user
`number 000222), the table 40 specifies no formatting (i.e.,
`no transcoding techniques or error control schemes) because
`wired connections (with broader bandwidths) are less prone
`to error than narrower bandwidth wireless connections.
`
`Note that the present invention should not be limited to
`using the table 40 depicted in FIG. 4. Other types of tables
`or collections of information, such as databases, may also be
`used to specify transcoding techniques and error control
`schemes for formatting data intended for particular users.
`Other information may also be stored in the table, such as an
`indication whether the user is connected via a wired or
`
`wireless connection, or separate sets of transcoding tech-
`niques and error control schemes for wired and wireless
`connections. Note that if the data selector needs to make a
`
`determination regarding the manner in which the user is
`connected to the access server, such a determination can be
`made using a flag indicative of the connection, a default, the
`telephone number dialed by the user to connect to the access
`server, etc.
`
`The access server 20 may create or obtain the table 40 in
`a variety of manners. The subscriber may submit a competed
`form to the service provider indicating the transcoding
`techniques and error control schemes available to the user
`and the manner in which the user will connect to the access
`
`server. The service provider will use the information in the
`completed form to select transcoding techniques and error
`control schemes available to both the user and the access
`
`server, and optimal for the manner of connection. Such
`selections are then added to or used to build the table 40.
`
`the user may provide such information elec-
`Alternately,
`tronically when accessing the access server 20 or the table
`may be constructed using default sets of transcoding tech-
`niques and error control schemes.
`After the data selector 30 selects a transcoding technique
`and an error control scheme, the selected transcoding tech-
`nique 32-11 is used to encode (or compress) the data and the
`selected error control scheme 34-11 is used to add error
`
`control information to the encoded data, as shown by the
`bitstream 25 in FIG. 2. Data type indicator-control informa-
`tion is then added to the formatted data (i.e., encoded data
`with associated error control information) when the format-
`ted data is being multiplexed by the combiner 38. The
`multiplexed data is subsequently caused to be transmitted by
`the access server 20 to the user 14 over the communications
`
`the multiplexed data is
`the user 14,
`network 16. At
`de-multiplexed and un-formatted using the appropriate sets
`of transcoding techniques and error control schemes.
`
`|PR2018—01413
`
`Sony EX1004 Page 8
`
`IPR2018-01413
`Sony EX1004 Page 8
`
`

`

`US 6,920,150 B1
`
`7
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`8
`
`Specifically, the user 14 looks at the data type indicator-
`control
`information to select
`the appropriate transcoding
`techniques and error control schemes for un-formatting (or
`reciprocating the operations of the transcoding techniques
`and error control schemes at the access server) the formatted
`data. The un-formatted data is subsequently output to a
`video display, audio display, printer and/0r computer
`memory associated with the remote computer 26.
`FIG. 5 is a chart 50 illustrating examples transcoding
`techniques and error control schemes which might be used
`for transmission of particular data types over wireless con-
`nections. The chart 50 shows data sub-types and their
`associated bit rates, encoding algorithms and the bit rate of
`the data after encoding (or compression), and error control
`schemes. For example, data with an audio sub-type has a 256
`Kbps bit rate. If a transcoding technique with a VCELP
`encoding algorithm is used to encode the audio data, the bit
`rate can be reduced to 8 Kbps. Subsequently, hybrid ARQ
`and muting (a form of error concealment) is applied to the
`encoded (or compressed) data in the error control scheme
`before being transmitted over a wireless connection.
`Although the present invention has been described in
`considerable detail with reference to certain embodiments,
`other versions are possible. Therefore, the spirit and scope of
`the present invention should not be limited to the description
`of the embodiments contained herein.
`We claim:
`
`1. A method for transmitting data over a communications
`network, the method comprising the steps of:
`determining a data type for the data;
`selecting a transcoding technique and an error control
`scheme to format the data based on the data type;
`encoding the data using the selected transcoding tech-
`nique; and
`applying the selected error control scheme to the encoded
`data, the selected error control scheme adding error
`control information to the encoded data.
`
`2. The method of claim 1 comprising the additional step
`
`of:
`
`multiplexing the data for transmission over the commu-
`nications network.
`
`3. The me hod of claim 2, wherein the step of multiplex-
`ing includes adding a data type indicator to the data.
`4. The method of claim 1, wherein the data type is
`determined Lsing a file extension associated with the data.
`5. The method of claim 1, wherein the data type is
`determined Lsing a default data type.
`6. The me hod of claim 1, wherein the transcoding ech-
`1ique and error control scheme are also selected based on
`iature of the communications network.
`
`
`
`
`
`
`
`7. The me hod of claim 1, wherein the transcoding ech-
`1ique and error control scheme are also selected based on
`preferences of a user.
`8. The me hod of claim 1, wherein the transcoding ech-
`1iques and error control schemes are selected using iifor-
`nation specifying a set of transcoding techniques and error
`control schemes for each data type.
`9. The method of claim 1, wherein the transcoding ech-
`1iques and error control schemes are selected using iifor-
`nation specifying a set of transcoding techniques and error
`control schemes for each user.
`
`10. The method of claim 1, wherein the transcoding
`echniques and error control schemes are selected using
`information specifying a set of transcoding techniques and
`error control schemes for a wireless connection between an
`access SCIVCI’ and a user.
`
`
`
`11. The method of claim 1, wherein the transcoding
`techniques and error control schemes are selected using
`default transcoding techniques and error control schemes.
`12. The method of claim 1, wherein a traascoding tech-
`nique using a pkzip encoding algorithm is selected for text
`data types.
`13. The method of claim 1, wherein a traiscoding tech-
`nique using a ACELP encoding algorithm is selected for
`speech data types.
`14. The method of claim 1, wherein a traiscoding tech-
`nique using a VSELP encoding algorithm is selected for
`speech data types.
`15. The method of claim 1, wherein a traiscoding tech-
`nique using a EVRC encoding algorithm is selected for
`speech data types.
`16. The method of claim 1, wherein ar error control
`scheme using a hybrid ARQ error control scheme is selected
`for speech data types.
`17. The method of claim 1, wherein ar error control
`scheme using a hybrid ARQ error control scheme is selected
`for video data types.
`18. The method of claim 1, wherein ar error control
`scheme using an ARQ error control scheme is selected for
`speech data types.
`19. The method of claim 1, wherein an error control
`scheme using an ARQ error control scheme is selected for
`video data ty3es.
`20. The nethod of claim 1, wherein an error control
`scheme using a muting technique is selected for speech data
`types.
`21. The nethod of claim 1, wherein an error control
`scheme using interpolation techniques based on previous
`and succeediag good frames is selected for speech data
`types.
`22. The nethod of claim 1, wherein an error control
`scheme using extrapolation techniques based on previous
`good frames is selected for speech data types.
`23. The nethod of claim 1, wherein an error control
`scheme using interpolation techniques based on previous
`and succeeding good frames is selected for Video data types.
`24. The method of claim 1, wherein an error control
`scheme using extrapolation