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Claims  |
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What is claimed is:
1. A system for providing portable computer network access comprising:
a satellite direct radio broadcast system having a first satellite and a broadcast station for transmitting broadcast programs to said first satellite;
a user terminal comprising a direct radio broadcast receiver for receiving said broadcast programs transmitted from said first satellite;
a gateway for providing computer network service; and
a communication link between said user terminal and said gateway, said user terminal being operable to generate backhaul signals comprising computer network access requests and responses of a user and to transmit said backhaul signals to said
gateway via said communication link, said broadcast station being operable to transmit data provided by said gateway in response to said backhaul signals via said first satellite.
2. A system as claimed in claim 1, wherein said communication link comprises a second satellite and said user terminal comprises a transceiver for transmitting said backhaul signals to said second satellite.
3. A system as claimed in claim 2 and comprising a plurality of user terminals, said broadcast station being operable to transmit a control word with said data from said gateway to said first satellite, said control word corresponding to a
selected one of said plurality of user terminals, each of said plurality of user terminals being operable to receive said data via said receiver but not use said data unless said control word corresponds to said user terminal.
4. A system as claimed in claim 1, wherein said communication link comprises at least one low earth orbit satellite and said user terminal comprises a transceiver configured for transmitting said backhaul signals to said at least one low earth
orbit satellite.
5. A system as claimed in claim 1, wherein said user terminal is portable.
6. A system as claimed in claim 1 and comprising a plurality of user terminals, said broadcast station being operable to provide a control word with said data from said gateway in said broadcast programs for transmission to said first satellite,
said control word corresponding to a selected one of said plurality of user terminals, each of said plurality of user terminals being operable to receive said data via said receiver but not to use said data unless said control word corresponds to said
user terminal.
7. A system as claimed in claim 1, wherein said communication link is a second satellite link.
8. A system as claimed in claim 1 and comprising a plurality of user terminals, said broadcast station being operable to transmit a control word with said data from said gateway to said first satellite, said control word corresponding to a
selected one of said plurality of user terminals, each of said plurality of user terminals being operable to receive said data via said receiver but not use said data unless said control word corresponds to said user terminal.
9. A system as claimed in claim 1, wherein said user terminal comprises a processing device, a display device, a speaker and a user input device, said processing device being programmable to play audio signals provided in one of said broadcast
programs to said speaker while processing said data received in one of said broadcast programs and generating at least one screen on said display device to provide said user with options for using the computer network, said options being selectable using
said user input device.
10. A satellite direct broadcast system for providing portable computer network access comprising:
at least one satellite for transmitting signals comprising broadcast programs to a plurality of user terminals, said plurality of user terminals each comprising a receiver for receiving said signals transmitted by said satellite;
at least one broadcast station for transmitting broadcast programs to said satellite;
at least one gateway for providing computer network service, said at least one gateway being configured to provide computer network data to said satellite for transmission to said plurality of user terminals; and
a communication link between said at least one gateway and each of said plurality of user terminals, each of said plurality of user terminals being configured to transmit output signals to said gateway via said communication link to perform at
least one of a plurality of functions selected from the group consisting of initiating an computer network session, requesting a web page, browsing, requesting downloading of
selected said computer network data, transmitting a user input in response to a screen prompt generated by said user terminal and terminating an computer network session.
11. A satellite direct radio broadcast system as claimed in claim 10, wherein said communication link comprises a low earth orbit satellite and said user terminal comprises a low earth orbit satellite transceiver for transmitting said output
signals to said gateway.
12. A satellite direct radio broadcast system as claimed in claim 10, wherein said communication link comprises a satellite, and said user terminal comprises a communication interface to said communication link for transmitting said output
signals to said gateway.
13. A user terminal for receiving satellite direct radio broadcasts comprising:
a receiver for receiving direct radio broadcasts from a first satellite;
a communication device for communicating with a digital communication network;
a display device;
an input device; and
a processor connected to said receiver, said communication device, said display device and said input device, said processor being programmable to initiate access to a digital communication network by generating and transmitting an outgoing
signal thereto via said communication device, said digital communications network being configured to download data therefrom to said user terminal via said first satellite, said processor being programmable to generate and transmit another said outgoing
signal via said communications device to communicate with said digital communication network in response to user inputs via said input device and to receive incoming signals generated by said digital communication network in response to said user inputs
via said receiver.
14. A user terminal as claimed in claim 13, wherein said digital communication network comprises a second satellite and said communication device comprises a transceiver for transmitting said outgoing signal to said second satellite.
15. A user terminal as claimed in claim 13, wherein said digital communication network comprises a radio frequency network and said user terminal comprises a transceiver configured for transmitting said output signals and said user inputs to
said radio frequency network, said gateway being operable to transmit said data to said first satellite in response to said output signals to provide global computer network access.
16. A user terminal as claimed in claim 15, wherein a control word is transmitted with said data from said gateway to said first satellite and said user terminal is one of a plurality of user terminals, said control word corresponding to a
selected one of said plurality of user terminals, each of said plurality of user terminals being operable to receive said data via said receiver but not use said data unless said control word corresponds to said user terminal.
17. A method of providing portable user terminals with global computer network access comprising the steps of:
generating a request to access the computer network from one of said user terminals;
transmitting said request from said user terminal via a communication link to a gateway for providing access to the computer network;
generating a broadcast program using data provided by said gateway;
transmitting said broadcast program to all of said user terminals using a satellite in a direct radio broadcast system;
receiving said broadcast program at each of said user terminals comprising a satellite direct radio broadcast receiver;
generating a backhaul signal using at least one of said user terminals; and
transmitting said backhaul signal from said user terminal to said gateway via said communication link.
18. A method as claimed in claim 17, wherein said step of generating a broadcast program further comprises the step of providing a control word in said broadcast program for addressing a selected one of said user terminals.
19. A method as claimed in claim 18, wherein said receiving step comprises the step of each of said user terminals receiving said data via said direct radio broadcast receiver but not using said data unless said control word corresponds to said
user terminal.
20. A method as claimed in claim 17, wherein said backhaul signal is selected from the group consisting of initiating an computer network session, requesting a web page, browsing, requesting downloading of selected said computer network data,
transmitting a user input in response to a screen prompt generated by said user terminal and terminating an computer network session. |
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Claims |
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Description |
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FIELD OF THE INVENTION
The present invention relates generally to a system and method for providing remote user terminals with global portable Internet access using a satellite direct radio broadcast system in combination with another communication system.
BACKGROUND OF THE INVENTION
Due to the expanding, worldwide use of personal computing devices, telecommunications devices and the Internet, the global economy is currently undergoing an information revolution that is expected to be as significant as the industrial
revolution of the nineteenth century. A significantly large population of people, however, are generally underserved and dissatisfied with their telecommunications options and are therefore presently limited in their ability to participate in this
information revolution. This population of people is primarily located in Africa, Central America, South America and Asia, where communication services have, to date, been characterized by the poor sound quality of short-wave radio broadcasts, or the
coverage limitations of amplitude modulation (AM) band and frequency modulation (FM) band terrestrial radio broadcast systems.
A satellite-based direct radio broadcast system to transmit audio and data signals, including images, to low-cost consumer receivers in essentially any part of the world has been proposed. The satellite-based direct radio broadcast system
provides a number of advantages over existing satellite systems, such as the ability to provide portable services. Many existing satellite systems fail to provide portable services because they require large satellite antennas to access such systems.
Low earth orbit (LEO) satellite systems are currently used to serve mobile and portable users. In addition, a number of geostationary satellite systems can provide portable or mobile communication services. However, existing LEO and
geostationary satellite systems do not provide adequate channel capacity to provide the high outbound data rates required for transmission of information from the Internet and the World Wide Web (WWW) to many different users.
Systems have been proposed to use satellites to provide worldwide Internet/WWW access capability to fixed-site users. For example, systems which use geostationary satellites and multiple spot beams (e.g., Hughes Spaceway and Loral Cyberstar)
have been proposed, as well as systems comprising hundreds of satellites in a geodesic dome-like arrangement around Earth or in multiple orbits (e.g., Teledesic). These systems, however, fail to provide global, portable Internet/WWW access capability.
A satellite-based direct radio broadcast system, however, is limited in that the receivers are one-way and do not permit a user to transmit voice or other information. Users of these receivers, therefore, cannot communicate bi-directionally via
the satellite-based direct radio broadcast system and, accordingly, do not have access to the Internet. Thus, a need exists for a low-cost user terminal which provides users with the advantages of a satellite-based direct radio broadcast system (e.g.,
large geographic coverage, good sound quality, high outbound data rates and low cost), as well as bi-directional communication for global, portable Internet/WWW access capability.
SUMMARY OF THE INVENTION
In view of the foregoing disadvantages and limitations, it is an object of the present invention to provide a system and method for allowing global Internet access using low-cost, portable user terminals.
A further object of Se present invention is to make it possible for a user to obtain satellite direct radio broadcasts of audio programs, along with satellite direct radio broadcasts of data, including images, downloaded from the Internet or WWW.
A further object of the present invention is to use at least one identification code in a control word in a broadcast program to address a satellite direct radio broadcast channel to a selected user terminal.
It is a still further object of the present invention to allow a user terminal to communicate backhaul signals on a communication link connecting the user terminal to an Internet service provider's gateway, and to receive information from the
Internet service provider, such as menu screens and web pages, via a satellite direct radio broadcast.
These and other objects of the present invention are achieved, in part, by providing remote users with user terminals which incorporate both broadcast receivers for receiving satellite direct radio broadcasts, and a communication device for
communicating with an Internet service provider via a communication link separate from the satellite direct radio broadcast system.
In one aspect, therefore, the Internet service provider is configured to receive requests from a user terminal for Internet access via the communication link. The Internet service provider has a gateway configured to route multimedia data to be
provided to the user from Internet/WWW to a broadcast station. The broadcast station formats the data into a broadcast program and transmits the broadcast program to a satellite in the satellite direct radio broadcast system. The user terminal can
receive audio signals in the broadcast program and provide them to a speaker, as well as display image data and continue to interact with the Internet service provider via the communication device and an input device (e.g., a keyboard or mouse).
In another aspect, the communication link comprises a low earth orbit satellite and the communication device comprises a low earth orbit satellite transceiver.
In a still further aspect, the present invention is directed to a method for providing low-cost, global, portable user devices with Internet access. The method comprises the steps of generating a request for Internet access from a portable user
terminal and transmitting the request to an Internet service provider using a first communication link. The Internet service provider subsequently determines if the user terminal is authorized to access the Internet and then provides subsequent screens
and multimedia data requested by the user terminal to a broadcast station. The broadcast station downloads the screens and data to the user terminal via a satellite direct radio broadcast. The user terminal reproduces or processes the downloaded
multimedia data as desired. The user terminal continues to enter responses and requests to the Internet service provider via the communication link and to receive broadcast screens and multimedia data from the satellite until the Internet access session
is terminated.
BRIEF DESCRIPTION OF THE DRAWINGS
The various objects, advantages and novel features of the present invention will be more readily apprehended from the following detailed description when read in conjunction with the appended drawings, in which:
FIG. 1 is a diagrammatic illustration of the manner in which global, portable Internet access can be provided to users through a satellite direct radio broadcast system in accordance with a preferred embodiment of the present invention;
FIG. 2 illustrates the reallocation of information from uplink frequency division multiple access channels into a downlink time division multiplexed channel in a satellite direct radio broadcast system of the type shown in FIG. 1;
FIG. 3 illustrates the manner in which on-board satellite signal processing may be carried out in a satellite direct radio broadcast system of the type shown in FIG. 1;
FIG. 4 is a block diagram illustrating the manner in which data and images from the Internet may be combined with audio at a broadcast station and uplinked to the digital broadcast satellite of FIGS. 1-3;
FIG. 5 is a block diagram illustrating the construction of a user terminal which incorporates both a digital broadcast receiver and a LEO satellite transceiver in accordance with a preferred embodiment of the present invention;
FIGS. 6-8 illustrate three different ways in which images and data from the Internet can be downlinked from the digital broadcast satellite of FIGS. 1-3; and
FIGS. 9A and 9B are flow charts which summarize the series of operations carried out by the user terminal of FIG. 5 when Internet image or data transmission operations are desired.
Throughout the drawing figures, like reference numerals
will be understood to refer to like parts and components.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A global, portable Internet service system 10 for providing a remotely located user with the ability to receive high quality sound, data and images and to transmit information in accordance with the present invention is preferably implemented
using a satellite direct radio broadcast system. The direct radio broadcast system preferably consists of three geostationary satellites (one of which is indicated at 20 in FIG. 1), low cost radio receivers or user terminals, and associated ground
networks. For illustrative purposes, a single user terminal 22 is shown which comprises a hand-held radio receiver 21 connected to a computer 29. One or more low earth orbit (LEO) satellites 24 are preferably used in accordance with the present
invention to receive signals transmitted via the user terminals 22 and to forward the signals to at least one system gateway 23, for example. Thus, users can communicate with a system gateway 23 to access the Internet and World Wide Web (WWW), which are
generally depicted at 25. The system gateway 23 can operate as an Internet service provider, as well as perform operations common to two or more Internet service providers, which are indicated generally at 31. As described in further detail below, the
system gateway 23 provides a broadcast station 26 in the direct radio broadcast system with multimedia information from the Internet such as web pages, sound bites and other data for transmission to the user terminals 22 via the satellites 20. The
global, portable Internet service system 10 therefore is advantageous because it can download relatively large amounts of data from an Internet service provider, for example, to a user terminal 22 efficiently and cost effectively using the satellite
direct radio broadcast system, as well as transmit relatively small amounts of data such as backhaul data (e.g., menu selections) from a user terminal 22 to the Internet service provider via the LEO satellite link.
The preferred satellites 20 of the direct radio broadcast system cover the African-Arabian region, the Asian region and the Caribbean and Latin American regions from the following geostationary orbits:
21.degree. E orbital location, providing service to Africa and the Middle East.
95.degree. W orbital location, providing service to Central and South America.
105.degree. W orbital location, providing service to Southeast Asia and the Pacific rim.
Coverage for other areas, such as North America and Europe, can be provided with additional satellites.
The direct radio broadcast system preferably uses the frequency band of 1467 to 1492 MHz, which has been allocated for Broadcasting Satellite Service (BSS) Direct Audio Broadcast (DAB) at WARC 92, that is, in accordance with resolutions 33 and
528 of the ITU. The broadcasters 26 use feeder uplinks in X band, from 7050 to 7075 MHz.
The direct radio broadcast system uses digital audio coding techniques. Each satellite delivers direct radio audio signals having qualities equivalent to AM monaural, FM monaural, FM stereo and CD stereo throughout its respective coverage area,
together with ancillary data such as paging, video and text transmissions directly to the radios. The system can also deliver multimedia services such as large database downloads to PCs for business applications, map and printed text information for
travelers, and color images to augment audio programs for advertising and entertainment.
The digital information assembled by a broadcast service provider (e.g., the system gateway 23) at a broadcast station 26 is preferably formatted in 16 kbps prime rate increments (PRIs) wherein n is the number of PRIs purchased by the service
provider (e.g., n.times.16 kbps). The digital information is then formatted into a broadcast channel frame having a service control header (SCH). The SCH is useful to send data to each user terminal 22 tuned to receive the broadcast channel in order to
control reception modes for various multimedia services, to display data and images, to send key information for decryption, and to address a specific user terminal, among other functions. The number of prime rate increments per program channel can
range from 1 to 8, thus yielding a program channel bit rate of 16 to 128 kbps in 16 kbps increments. Each frame is preferably assigned n.times.224 bits for the SCH such that the bit rate becomes approximately n.times.16.519 kbps. Each frame is also
preferably scrambled by the addition of a pseudo random bit stream to the SCH. Accordingly, information control of the scrambling pattern by a key permits encryption.
Each broadcast service provider selects the number of 16 kbps prime rate increments in accordance with the broadcaster's specific application. As stated previously, typical broadcast channel increments are preferably 16, 32, 64, 80, 96, 112 and
128 kbps. The satellite direct radio broadcast system described in connection with FIG. 1 is advantageous because it provides a common base of capacity incrementation for a multiplicity of broadcast companies or service providers whereby broadcast
channels of various bit rates can be constructed with relative ease and transmitted to a user terminal 22. The size and cost of a broadcast station 26 can therefore be designed to fit the capacity requirements and financial resource limitations of a
broadcast company. In addition, the broadcast company can allow a number of service providers to share the resources of the broadcast station with efficiency and cost effectiveness. A broadcast company of meager financial means can install a small VSAT
terminal requiring a relatively small amount of power to broadcast a 16 kbps service that is sufficient to carry voice and music, for example, that has better quality than short-wave radio. On the other hand, a sophisticated broadcast company of more
substantial financial means can broadcast FM stereo quality programs and other data using a slightly larger antenna and more power at 64 kbps. With further increases in capacity, the broadcast company can broadcast near compact disc (CD) stereo quality
audio programs and larger amounts of data at 96 kbps, and full CD stereo quality audio programs and even larger amounts of data at 128 kbps.
The system gateway 23 preferably purchases a selected number of PRIs from a broadcast station 26 for transmitting multimedia information such as web pages to user terminals 22 at selected times during the day. The system gateway 23 is preferably
able to transmit information to the user terminals 22 twenty-four hours a day via a broadcast station 26. The system can take advantage of the fact the users often request similar data for downloading during similar time frames. In accordance with an
embodiment of the present invention, the system gateway 23 is operable to
store data requested by many users for downloading within a predetermined period of time in a download buffer. The system gateway 23 can provide the broadcast station 26 with the identities of the user terminals 22 requesting the information.
The broadcast station, in turn, can provide the SCH corresponding to the data stored in the download buffer with a number of identification codes for uniquely identifying each of the terminals for transmission of the requested data thereto.
To protect the broadcaster's program channel, a forward error correction (FEC) method is used. It comprises a Reed Solomon (255,223) coder concatenated with an interleaver, and a rate 1/2 Viterbi constant length 7 coder. This error correction
coding (together with the addition of a sync header) elevates the prime rate channel to 19 kbps.
The FEC-coded broadcast channel frame is subsequently demultiplexed using a channel distributor at the broadcast station 26 into n parallel prime rate channels (PRCs), each carrying 16320 bits in terms of sets of 8160 two-bit symbols. The
symbols are preferably assigned across the PRCs of a broadcast program in a round-robin fashion, as described below, such that the PRCs are spread on the basis of time and frequency, thereby reducing errors at the user terminal 22 caused by interference
in transmission. A PRC synchronization preamble containing 48 symbols is subsequently placed in front of each group of 8160 symbols to synchronize the clock of the user terminal 22 clock for recovery of the symbols from the downlink satellite
transmission. During on-board processing by a satellite 20, the PRC preamble is used to absorb timing differences between the symbol rates of uplink signals and the on-board clock used to switch signals and assemble downlink TDM streams. The n PRC
frames, each comprising the PRC and the corresponding PRC preamble, are then differentially encoded, QPSK modulated on to IF carrier frequencies assigned as the broadcast channel for the service provider and up-converted to the X-band for transmission to
the satellite 20. Thus, the transmission method employed at a broadcast station 26 incorporates a multiplicity of n Single Channel Per Carrier, Frequency Division Multiple Access (SCPC/FDMA) carriers into the uplink signal 28. These SCPC/FDMA carriers
are spaced in a grid of center frequencies which are preferably separated by 38,000 Hertz (Hz) from one another and are organized into groups of 48 contiguous center frequencies or carrier channels.
Each satellite 20 is preferably equipped with three downlink spot beams, having beamwidths of about 6.degree.. Each beam covers approximately 14 million square kilometers within power distribution contours that are 4 dB down from beam center and
28 million square kilometers within contours that are 8 dB down. The beam center margin may be 14 dB based on a receiver gain-to-temperature ratio of -13 dB/K.
Each satellite 20 carries two types of payloads. One is a "processing" payload that regenerates the uplink signals and assembles 3 TDM downlink carriers, and the other is a "transparent" payload that repeats the uplink signals on 3 TDM downlink
carriers. The TDM signals from the two payloads are each transmitted in 3 beams, with the processed and transparent signals in each beam having opposite circular polarization (LHCP and RHCP). Each TDM dowmaink signal carries 96 prime rate channels in
assigned time slots. To a user terminal 22, all of the TDM downlink signals appear the same, except for carrier frequency. The total capacity per satellite is 2.times.3.times.96=576 prime rate channels.
FIG. 1 illustrates the overall operation of a global, portable Internet service system 10 in accordance with a preferred embodiment of the present invention. In the case of the satellite processing payload, uplink signals 28 issue from
broadcasters via individual frequency division multiple access (FDMA) channels from broadcast stations 26 located anywhere within the terrestrial visibility of the satellite 20 with elevation angles higher than 10.degree.. Each broadcaster has the
ability to uplink directly from its own facilities to one of the satellites 20 by placing one or more 16 kbps prime rate channels on the FDMA carriers. Alternatively, broadcasters which have no capacity for direct access to the satellite 20 may have
access through a hub station. For example, the system gateway 23 can broadcast web pages directly to one of the direct radio broadcast satellites 20 or indirectly via a hub 27. Use of FDMA for the uplink offers the highest possible flexibility between
multiple independent broadcast stations.
Conversion between uplink FDMA and downlink multiple-channel-per-carrier, time division multiplex (MCPC/TDM) in the direct radio broadcast system of FIG. 1 is achieved on board the satellite 20 by an on-board processor. At the satellite 20, each
prime rate channel transmitted by a broadcast station 26 is demultiplexed and demodulated into individual 16 kbps baseband signals. Individual channels are routed via a switch to one or more of the downlink beams 30, each of which is a single TDM
signal. This baseband processing provides a high level of channel control in terms of uplink frequency allocation and channel routing between uplink and downlink. Uplink signals are received in the satellite in X band and converted to L band by the
on-board processor. The downlinks 30 to the user terminals 22 use MCPC/TDM carriers. One such carrier is used in each of the three beams on each satellite 20. The manner in which the direct radio broadcast system formats the FDMA uplinks and performs
payload processing to generate the TDM downlinks permits reception of a significant amount of data, including high sound quality audio programs, using low cost receivers, among other advantages.
For the transparent payload, the TDM signals are assembled at a broadcast station and appear in precisely the same structure as do those assembled on board the satellite 20 by the processing payload. The TDM signal is sent to the satellite in
the X band and is repeated in the L band in one of the three downlink beams. The power level is the same for downlink TDM signals generated by the processing payload.
FIG. 2 illustrates the on-board re-allocation of prime rate channels from uplink frequency division multiple access channels into a downlink MCPC/TDM channel in the processing payload of the satellite 20 of FIG. 1. The overall uplink capacity is
preferably between two hundred eighty-eight (288) and three hundred eighty-four (384) prime rate uplink channels 32 of 16.519 kbps each. Ninety-six (96) prime rate channels 34 are selected and multiplexed for transmission in each downlink beam 30, and
time division multiplexed onto a carrier of approximately 2.5 MHz bandwidth as indicated at 36. Each uplink channel may be routed to all, some or none of the downlink beams. The order and placement of prime rate channels in a downlink beam is fully
selectable via a command link from a telemetry, range and control (TRC) facility 38, shown in FIG. 1.
Software is preferably provided at a broadcast station 26 or, if more than one broadcast station 26 exists in the system 10, in a regional broadcast control facility 39 to assign space segment channels in the uplink beam to a satellite 20. The
regional broadcast control facility 39 is preferably connected to the TRC facility 38 via a communication link. The software optimizes use of the uplink spectrum by assigning PRC carriers whenever space is available in the 48 channel groups. The
carriers associated with a particular broadcast channel need not be continuous within a group of 48 carrier channels and need not be assigned in the same group of 48 carrier channels.
The carrier frequencies in each downlink beam 30 are different to enhance beam-to-beam isolation. Each TDM downlink channel is operated in the satellite payload at saturation, giving the highest possible power efficiency in terms of link
performance. Use of single carrier per transponder operation achieves maximum efficiency in the operation of the satellite communication payload in terms of conversion of solar power into radio frequency power. This is far more efficient than
techniques requiring simultaneous amplification of a multiplicity of FDM carriers. The system produces high receive margins suitable for stationary and mobile reception indoors and outdoors.
The system 10 carries out audio source coding using MPEG 2.5, Layer 3 which achieves the cited qualities at bit rates of 16, 32, 64 and 128 kbps, respectively, and also includes the capability to perform 8 kbps coding. Image coding is carried
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