Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04Q—SELECTING
  • H04Q11/00—Selecting arrangements for multiplex systems
  • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
  • H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
  • H04Q11/0435—Details
  • H04Q11/0457—Connection protocols
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04Q—SELECTING
  • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
  • H04Q2213/13204—Protocols
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04Q—SELECTING
  • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
  • H04Q2213/13209—ISDN
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04Q—SELECTING
  • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
  • H04Q2213/13296—Packet switching, X.25, frame relay
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04Q—SELECTING
  • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
  • H04Q2213/13389—LAN, internet

Definitions

• the present invention relates to a method for transmitting multimedia information such as images, voice, and data in multimedia communications, and in particular, to a technology for transmitting broadband multimedia data over an integrated service digital network (ISDN).
• ISDN integrated service digital network
• a general method for transmitting broadband multimedia data on an ISDN line is to bind and align n (I> 1) B channels before performing data transmission.
• the so-called broadband multimedia data refers to multimedia information such as images, voice, and data with a bandwidth exceeding 64 Kbits.
• a device that performs B channel bonding and alignment functions is called a channel aggregation unit (CAU).
• Figure 1 is a schematic diagram of a system that uses the traditional method to transmit multimedia data with a maximum bandwidth of n X 64 bit / s.
• Two multimedia data terminal equipment (DTE) are connected to the ISDN network through CAU. When communication starts, the two parties first establish a link connection.
• DTE multimedia data terminal equipment
• CAU performs binding and alignment on the n B channels, and finally transmits multimedia data on the bound n B channels.
• This method has the following disadvantages: CAU equipment and its corresponding implementation software are required; if the binding or alignment is lost due to sliding code or other reasons during the communication, you need to rebind or disconnect the connection, which will affect the communication The effect caused adverse effects; although some methods stipulate that simple error detection processing can be performed on the received data, forward error correction processing cannot be performed, so low bit error rate or even error-free transmission of real-time data cannot be performed, especially in some bit errors multimedia communication impossible SUMMARY normal on 10 "3 ISDN line - rate as high as 10.4
• the technical problem to be solved by the present invention is to overcome the shortcomings of the existing broadband multimedia data transmission technology in the background technology, and propose a method for transmitting broadband multimedia data with low bit error rate or even error free, that is, using packet transmission and error correction coding technology in Broadband multimedia data is transmitted on ISDN lines.
• the method for transmitting broadband multimedia data on an ISDN line according to the present invention includes two processes of B channel establishment and multimedia data transmission;
• the establishment of the B channel includes:
• Establishing an initial B-channel connection that is, establishing a first B-channel connection between two terminals through an ISDN network
• the calling end and the called end use information packets that have undergone RS (Reod-Solomon) error correction coding to negotiate information such as capability parameters;
• RS Reod-Solomon
• the called end After the capability negotiation is passed, the called end also uses the RS error-coded information packet to return the calling numbers of the remaining B channels;
• the calling end uses the returned call number to establish the connection of the remaining B channels;
• the multimedia data transmission includes:
• the sender performs RS. Error correction coding on the multimedia data
• the sender encapsulates the multimedia data encoded with RS error correction into a packet; the sender sends the data packets in sequence on all B channels;
• the receiving end locates the data packet position and sorts the data packets according to the packet sequence number
• the receiver unpacks and performs RS error correction decoding on the data. Data packets are lost due to excessive line error codes or slipping codes, that is, data packets cannot be located. In the process of multimedia communication by using the method of the present invention, the characteristics of the packet structure and error correction coding can be quickly re-used. Locate data packets without having a significant impact on communication quality.
• the error packets will be discarded for code streams such as images and voice with strict real-time requirements but low accuracy requirements; for real-time
• code streams such as images and voice with strict real-time requirements but low accuracy requirements; for real-time
• the data stream with low sexual requirements but strict accuracy requirements can retransmit erroneous data packets to ensure the accuracy of the data.
• the packet transmission technology is used, the dedicated CAU equipment and its software can be eliminated, and the adverse consequences caused by the loss of binding and alignment that may occur during the communication process are avoided; through RS error correction coding technology It also greatly reduces the bit error rate of transmitted data, and can even achieve error-free transmission, which is very suitable for transmitting broadband multimedia data with high quality on ISDN lines with low transmission quality.
• FIG. 1 is a schematic diagram of a traditional ISDN-based broadband multimedia data transmission system.
• FIG. 2 is a flowchart of B channel establishment according to the present invention.
• FIG. 3 is a flowchart of multimedia data transmission according to the present invention.
• FIG. 4 is a specific structural diagram of an RS error-coded information packet according to the present invention.
• FIG. 5 is a flowchart of capability negotiation and number backhaul according to the present invention.
• FIG. 6 is a schematic diagram of the composition of a multimedia data packet subjected to RS error correction coding according to the present invention.
• Figure 7 is a detailed structure diagram of a data packet.
• FIG. 8 is a timing example diagram of sequentially transmitting data packets on a B channel according to the present invention.
• FIG. 9 is a flowchart of a positioning data packet according to the present invention.
• FIG. 10 is a flowchart of a method for relocating a data packet during a communication process according to the present invention.
• 1 is a schematic diagram of a conventional ISDN-based multimedia data transmission system with a maximum bandwidth of nX 64 Kbit / s. The specific content is described in the background art.
• FIG. 2 it is a flowchart of a B channel establishment method according to the present invention, which specifically includes the following steps:
• an initial B-channel connection is established, that is, the first B-channel connection (S1) between two terminals is established through the ISDN network.
• the calling end and the called end negotiate information such as capability parameters by using the RS error-coded information packet (S2).
• the called end In the third step, after the capability negotiation is passed, the called end also uses the RS error-coded information packet to return the calling numbers of the remaining B channels (S3).
• the caller uses the returned call number to establish the connection of the remaining B channels (S4).
• 3 is a flowchart of multimedia data transmission according to the present invention, which specifically includes the following steps: In the first step, the transmitting end performs RS error correction coding on the multimedia data (S10).
• the transmitting end encapsulates the multimedia data encoded with RS error correction into a packet (Sl l).
• the transmitting end sequentially sends data packets on all B channels (S12).
• the receiving end locates the position of the data packet, and sorts the data packet according to the packet sequence number (S 13).
• the receiving end unpacks and performs RS error correction decoding operation on the data (S14).
• FIG. 4 it is a detailed structural diagram of the RS error-coded information packets used in the second and third steps shown in FIG. 2.
• the information packet is mainly used to negotiate the processing capabilities of the two multimedia terminals after the initial B channel is established, including: the information packet identification code, the negotiation process serial number, the protocol version number, the multiple of the main bandwidth of the payload, the level of the error correction capability, and the payload. Bandwidth multiple, reserved digits, serial number of return telephone number, decimal telephone number, check code and padding code.
• the packet identification code is used to identify the start position of the packet, and is a fixed value, here is OxlffD, of course, other values can also be used;
• the negotiation process number is used to indicate the capability negotiation process, and the negotiation process number is incremented by one each time the negotiation is completed;
• the protocol version number indicates the currently used protocol version, and is used to judge the consistency of the protocol versions used by the receiving and sending ends to ensure the normal transmission of multimedia data;
• the payload sub-bandwidth is an integer multiple of 2 Kbit / s, which represents the portion of the bandwidth that is not an integer multiple of 64 Kbit / s. It is expressed as an integer multiple of the payload sub-bandwidth.
• the error correction capability level indicates the error correction capability of the communication system, and the length of the check code when RS error correction coding is performed is twice the error correction capability level. If the negotiated error correction capability level is 8, RS codec is decoded according to [255, 239, 8] for the payload of 80 bytes;
• the force level is a variable that needs to be negotiated for the data packet, which is determined by both parties according to the actual situation such as processing capacity.
• the error correction level of the information packet is fixed to a constant, such as 4, which can of course also be based on the actual situation. Make adjustments.
• the protocol version number, the multiple of the main payload bandwidth, the number of error correction capability levels, and the multiple of the sub-bandwidth of the payload need to be negotiated by both parties.
• the range of the multiples of the main bandwidth of the payload is 1 to 255
• the range of the multiples of the sub bandwidth of the payload is 0 to 31.
• a maximum of 255 B channels can be used for multimedia data communication.
• the multimedia transmission rate can be higher, but it has no practical application value.
• the number of B channels is generally controlled within 32 or 64.
• serial number of the returned telephone number is non-zero, it means that the telephone number is being returned.
• Each number starting from 1 will be incremented by 1.
• Each decimal telephone number digit is represented by 4 binary digits. For example, the decimal number 9 is represented by "1001". The least significant digit is placed on byte 10, and so on. The short bits are filled with "11 11". When there is no return number, the phone number digits are all set to '1111', and they do not participate in RS codec.
• All valid data (information codes other than padding code and check code) in the packet are RS error-correction coded according to [255, 247, 4], and the generated check code is placed in bytes 23 ⁇ 30. Because the effective data is only 22 bytes, the zero-padding operation needs to be performed on the insufficient code during encoding and decoding. The zero-padding code is not transmitted.
• the length of the packet is fixed at 80 bytes.
• FIG. 5 is a specific flowchart of capability negotiation and number backhaul shown in FIG. 2.
• the capability negotiation process is performed after the connection is established in the initial B. It is initiated by the calling end.
• the negotiation determines the protocol version number, the main payload bandwidth multiple, the error correction capability level, and the payload sub-bandwidth multiple that the two parties can accept.
• the backhaul process is performed after the capability negotiation is passed, and the calling parties establish the remaining B-channel connections according to the returned call number.
• the specific process of capability negotiation and number return is:
• the calling end sets an initial protocol version number, a multiple of the main payload bandwidth, an error correction capability level, and a multiple of the sub-bandwidth of the payload, and encapsulates the information into a packet and sends it to the called end (S101).
• the called terminal receives the information packet, it determines whether the parameters proposed by the calling terminal are acceptable according to the preset working parameters. The acceptable parameters remain unchanged, and the unacceptable parameters are set as acceptable. Value.
• the above information is encapsulated in an information packet and sent to the calling end (S102).
• the caller determines whether the other party has accepted the above three parameters after receiving the reply packet from the called party. If the parameter value remains unchanged, the other party is considered to have accepted it; if the parameter value changes, the The working parameters judge whether the parameters proposed by the called party are acceptable. If the parameters are acceptable, the original values remain unchanged. Otherwise, these parameters are set to the values of the packets sent to the other party last time to indicate that they cannot accept and are ready to be disconnected. Connection of the initial B channel (S103).
• the number backhaul process is started; if the consensus negotiation results are not reached, the two parties that failed the negotiation are disconnected (S104).
• the called terminal In the fifth step, on the basis of successful capability negotiation, the called terminal returns the remaining B channel call numbers through the telephone number digits, and the sequence number of the returned telephone number starts from 1 until the number of all B channels decreases by 1 (S105).
• the calling terminal receives the remaining B channel calling numbers according to the serial number of the returned telephone number, and after each number is received, it returns the number to the called terminal intact to indicate that the number has been received. Go to and look forward to the next number (S 106).
• the calling end calls the remaining B-channel numbers to establish a connection with the remaining B-channels (S107).
• sequence number of the negotiation process of the information packet starts from 1 and increments by 1 each time the negotiation is completed.
• the sequence number of the return telephone number is set to 0, and the decimal telephone number bits are all set to "1111".
• the information packet occupies the entire 64 Kbit / s bandwidth, that is, the two sides repeatedly send the information packet after sending the information packet with the new content until receiving the reply packet from the other party.
• the sequence number of the negotiation process of the repeatedly sent information packets is not incremented, and the original value is maintained.
• the sequence number of the negotiation process is incremented only when the information packet with the new content is sent. Referring to FIG. 6, it is an RS error-coded multimedia data packet used in FIG. Composition diagram.
• the length of the packet header is 8 bytes, of which the packet identification code occupies 2 bytes, the packet sequence number, protocol version number, payload main bandwidth multiple, error correction capability level, payload sub-bandwidth multiple, and reserved code each occupy 1 byte.
• the packet identification code is OxlffS, which is used to indicate and identify the start position of a data packet; the packet sequence number is used to indicate the order of the received data packets, which are cyclically selected from 0 to 255 in sequence; protocol version number, payload master Bandwidth multiples, error correction capability levels, and payload sub-bandwidth multiples are exactly the same as defined in the packet.
• the reserved code is reserved for future function expansion requirements. The payload and checksum together make up the data portion of the packet. Refer to FIG.
• FIG. 7 is a detailed structural diagram of a data packet designed according to FIG. 6.
• This data packet is used to complete the transmission of multimedia data with a bandwidth of 128Kbit / s on 3 B channels.
• the multiple of the main bandwidth of the payload is 2, and the multiple of the sub bandwidth of the payload is 0, that is, the payload bandwidth is 2 X 64 Kbit / s + 0 X 2 Kbit / s, and the level of error correction capability is 8.
• the present invention does not specifically specify the discharge position and data amount of multimedia data in the data packet, but no matter what method is used to discharge the data, both communication parties must know this discharge method before communication, because these contents are not negotiated content.
• encoding is performed once for every 80 bytes of data
• the length of the check code is 16, and two sets of 80 bytes of data are interleaved.
• the letter A in Figure 7 indicates the first group of 80 bytes
• B indicates the second group of 80 bytes.
• the two sets of data are encoded according to [255, 239, 8] and then interleaved to form the figure. Show structure.
• the first group of 80 bytes is subjected to RS error correction coding together with the header 8 bytes.
• the packet length is 240 bytes and the payload length is 160 bytes.
• the length of each packet can be solved using the following formula:
• the payload length, error correction code length, and header length in the above formula can be calculated as follows:
• Payload length multiple of the main bandwidth of the payload X 80
• Error correction code length multiple of payload bandwidth X error correction capability level X 2
• the payload length in each packet is no longer an integer multiple of 80, but the formula for solving the packet length is still applicable, and the calculation method of each parameter is changed. It is not specified here how to calculate these parameters when the sub-bandwidth multiple is not 0, but the basic idea is the same as before.
• the main prerequisite is to ensure that the code stream formed by the data packet is continuous while correcting the valid data.
• the present invention proposes to encode once every 80 bytes, which can make the encoding process simple and clear, and also suitable for some multimedia application environments. For example, the multiframe of H.221 frames contains 80 bytes. Interleaving encoding of multiple sets of data can improve the error correction capability of burst errors.
• the above method is the recommended content of the present invention and does not exclude other methods. Referring to FIG. 8, it is a specific example diagram of the third step in FIG. 3, that is, a timing diagram of sequentially transmitting data packets on 4 B channels.
• the receiver receives data packets simultaneously on all B channels.
• the sending end sends data packets at certain intervals to reduce the processing pressure on the receiving end.
• the time interval is 10 ms, of course, it does not exclude the time interval, and other values are used. This approach is very beneficial to some processing processes involving H.221 frames.
• Fig. 8 shows the application of transmitting data packets on 4 B channels as an example, and shows the manner in which data packets are sequentially transmitted on the B channel at a certain time interval.
• the i-th data packet is sent on the first B-channel. After an interval of 10 ms, the i + 1 data packet starts to be sent on the second B-channel, and the i-th and 2 data packets are spaced another 10 ms. Start to send on the 3rd B channel, and then send the 10th i + 3 data packet on the 4th B channel, and then send it on the 4th B channel again on the 10th interval. Send on the channel.
• the length of each packet is 40 ms, that is, the length is 320 bytes.
• the length of the data packet can be determined according to the multiples of the main payload bandwidth, the number of error correction capability levels, the multiples of the payload sub-bandwidth, and the number of multimedia data in each packet.
• the definition of the data packet length is not unique and can be defined according to the specific application. Referring to FIG. 9, it is a specific implementation method of the fourth step in FIG. 3 proposed by the present invention, that is, a simple, reliable, and fast method for locating a data packet.
• the first step is to find the packet identification code at the receiving end (S201);
• the second step is to perform RS error correction decoding on the data packet after finding the packet identification code (S202).
• the third step is to determine whether the correct decoding is performed (S203). If decoding or error correction can be performed, the data packet is considered to be located ( S204);
• the fifth step it is judged whether the error correction decoding on the data packet is correct (S207). If it is correct, then it is confirmed that the data packet is located (S204), otherwise it starts searching for the packet identification code again (S201).
• the above method can locate the data packet within one data packet as fast as possible.
• the use of secondary positioning can eliminate the problem of difficult packet positioning caused by excessive line errors, thereby speeding up the positioning of the data packet.
• FIG. 10 is a method of relocating a data packet during data transmission according to the method of FIG.
• the invention provides a method for judging whether a data packet is permanently misaligned and relocating the data packet during a communication process.
• the above step of determining whether the packet identification code loss count is greater than or equal to 3 (S215) is repeated, and if the count is not greater than or equal to 3, repeat the above steps S216 to S220.
• Step if the count is greater than or equal to 3, it is considered that the data packet must be relocated if the slip code is generated on the line, otherwise the data packet will be permanently lost (S221), SP: if it is judged that the data packet has been permanently lost after three decoding times, re-locate.
• the three judgments in the above method can also be changed to two judgments.

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• Data Exchanges In Wide-Area Networks (AREA)
• Communication Control (AREA)
• Detection And Prevention Of Errors In Transmission (AREA)

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• 2002
  • 2002-08-29 CN CNB02136754XA patent/CN1306757C/zh not_active Expired - Fee Related
  • 2002-12-19 BR BRPI0215871-0A patent/BRPI0215871B1/pt active IP Right Grant
  • 2002-12-19 MX MXPA05002326A patent/MXPA05002326A/es active IP Right Grant
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  • 2002-12-19 WO PCT/CN2002/000900 patent/WO2004021736A1/zh not_active Application Discontinuation
• 2005
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