KR100535888B1 - A Two Dimensional Forward Error Correction Method And Data Communication Method Using The Method - Google Patents

Abstract

The present invention relates to a two-dimensional forward error correction method applied to data communication, and a data communication method using the same, and provides a multimedia service having real-time transmission characteristics in a wireless communication network environment in which many packet errors such as a wireless mobile communication system occur. In order to improve the quality of service by overcoming errors on the wireless communication network. In particular, the two-dimensional forward error correction method of the present invention, in the forward error correction method, at the time of transmission, data to be transmitted variably in accordance with 'packet loss rate information provided by the receiver for data packets transmitted from the transmitter' Arrange packets in a predetermined two-dimensional block unit, and generate horizontal and vertical parity packets for each row and column of the aligned packet block -that is, vertical / horizontal parity according to packet loss rate in consideration of variable radio channel characteristics. Adjust the generation rate of the packet, and when receiving, it determines whether the data packet is lost by checking the sequence number of the received data packet, and when the loss of the data packet, together with the data packets Recovered lost data packets carrying at least one frame by using the transmitted horizontal and vertical parity packets.

Description

Two-dimensional forward error correction method and data communication method using the method

The present invention relates to a two-dimensional forward error correction method applied to data communication, and a data communication method using the same, in particular in a multimedia service having a real-time transmission characteristics in a wireless communication network environment where many packet errors such as a wireless mobile communication system occurs As an efficient and flexible packet loss recovery scheme, the present invention relates to a method for increasing a recovery rate at a receiver for packets continuously lost on a wireless communication network.

Conventionally, Korean Patent Application No. 1999-0049160, "Lost Packet Recovery on the Internet Using Interleaving," uses a voice coding method having a high sound quality and high bit rate to recover packet loss that is continuously generated by a voice recovery method using redundant audio information. A method of recovering lost packets using redundant audio information when packet loss occurs by packetizing audio information coded at different times into one packet while simultaneously performing low coding and low bit rate speech coding has been proposed. However, for this purpose, since two or more codecs must be supported to perform voice coding at different bit rates, there is a problem that processing delay occurs during packetization.

In addition, four forward error correction (FEC) techniques proposed by "RFC 2733-An Real-time Transport Protocol (RTP) Payload Format for Generic Forward Error Correction (J. Rosenberg and H. Schulzrinne)" are proposed. Is a static lost packet recovery method based on the Internet, which is a wired network. That is, the data packet is a parity packet generated as a result of performing an exclusive OR (XOR: eXclusive-OR) operation on two or more Real-time Transport Protocol (RTP) packets (hereinafter, referred to as "data packets") to be transmitted. The present invention proposes a method for recovering lost packets by using additionally transmitted parity packets when packet loss occurs. The XOR operation lists two data packets as bit streams and then pads short packets to fit the longest packet size. A bit stream formed as a result of performing an XOR operation on bit streams having the same length constitutes one parity packet.

This method is suitable for the transmission of real-time data, such as multimedia data, because it does not require retransmission of packets. On the other hand, since the parity packet needs to be additionally transmitted in addition to the data packet required for information transmission, the bandwidth use of the network is increased.

1 is a structural diagram of a parity packet generated by an XOR operation of a data packet, and FIG. 2 illustrates a structure of an FEC header among three parts constituting a parity packet.

The fields are as follows. The "SN base" field contains minimum sequence number information among data packets used to make a parity packet. Here, each data packet includes a sequence number (SN), and the sequence number having the smallest value among the sequence numbers included in the data packets used to generate the parity packet enters the "SN base" field. . The "Length recovery" field is filled with a value obtained by performing an XOR operation on the sequence number of the data packet used to make the parity packet, and the "E (Extension)" field is currently defined as '0'. In the "PT (Payload Type) recovery" field, the result of performing the XOR operation on the payload information of the data packet used to generate the parity packet, and in the "Mask" field, the data packet used to generate the parity packet. Information is filled in. Finally, the "Time Stamp (TS) recovery" field is filled with the result of performing the XOR operation on the TS of the data packet used to generate the parity packet.

In FIG. 3, the RTP header structure of the parity packet shown in FIG. 1 is illustrated. This format has the same structure as the RTP header of the original RTP packet (data packet).

Looking at each field one by one: First, the "V (Version)" field is '2' and indicates the version of the RTP. The "P (Padding)", "X (eXtension)", and "M (Marker)" fields are filled with the result of performing the XOR operation on the P, X, and M fields of the data packet used to generate the parity packet. The "PT (Payload Type)" field contains payload type information of the parity packet. In RFC 2733, the payload type of the parity packet is defined as '127'. The "SN (Sequence Number)" field is filled with the sequence number of the parity packet incremented by one, in addition to the sequence number of the data packet. The "TS (Time Stamp)" field is time information at the moment a parity packet is generated, and the "SSRC" field contains identification (ID) information of a source that generated the parity packet. That is, information such as the "SSRC" field of the data packet header is entered. Here, the contents of the "SSRC" field of the data packet generated by the same sender all have the same value.

Next, the basic FEC techniques proposed by RFC 2733 to guarantee the quality of service of real-time traffic are as follows.

FEC technique 1: P1, P2, f (P1, P2), P3, P4, f (P3, P4),...

The first FEC technique is shown in RFC 2733 as an example. After transmitting two data packets of P1 and P2, XOR operation is performed on these data packets P1 and P2 to generate one parity packet f (P1, P2). To send. FEC scheme 1 can recover lost P2 packets using P1 and f (P1, P2) received without error when P2 packets are lost. This technique basically has 50% overhead (rate of parity packets).

FEC technique 2: P1, f (P1, P2), P2, f (P2, P3), P3, f (P3, P4), P4, f (P4, P5),...

The second FEC technique is similar to the first method, and adds parity packet f (P1, P2) by performing an XOR operation on these data packets P1 and P2 between two data packets P1 and P2. Has a head.

FEC technique 3: f (P1, P2), f (P1, P3), f (P1, P2, P3), f (P3, P4), f (P3, P5), f (P3, P4, P5), …

The third proposed FEC scheme is to transmit only parity packets F1, F2, F3, F4, F5, F6, ... without transmitting data packets P1, P2, P3, P4, .... Because this method only transmits parity packets, loss of these packets can result in irreparable data packets. In order to make up for this drawback, when a parity packet is created at the transmitting side, the data packet is duplicated so that a data packet that has not been recovered immediately can be recovered when a few parity packets are received. Therefore, FEC scheme 3 can recover the case of single packet loss and two consecutive packet losses with less overhead than FEC scheme 2. However, since only the parity packet is transmitted, the processing time of the transmitter and the receiver is longer than that of other FEC schemes.

FEC technique 4: P1, P2, f (P1, P2, P3), P3, f (P1, P3, P4), f (P1, P2, P4), P4,...

Finally, the proposed FEC scheme is designed to recover lost packets even when three or more consecutive packet losses occur. As shown in FIG. 4, a parity packet for data packets is generated to generate a parity packet. It is a method of transmitting a parity packet. FEC scheme 4 shows high efficiency in recovering continuous packet loss, but has a disadvantage of 200% overhead.

As described above, the four FEC schemes proposed by the existing RFC 2733 do not consider packet loss due to burst error, which is a channel characteristic of a wireless network, and thus it is difficult to recover packets that are continuously lost. It is not suitable for wireless environments with error characteristics. Even if it is possible to overcome the aggregation error, by having a high overhead of 200%, there is a disadvantage of wasting the bandwidth of the limited network.

In order to overcome this problem, it is necessary to overcome packet loss due to aggregation error on the wireless network. Since the FEC techniques described above do not consider the radio channel characteristics, it is not suitable to apply to the wireless network.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is possible to overcome packet loss due to a continuous error occurring during data communication with little overhead, but in particular, the characteristics of a variable communication channel By applying forward error correction method according to the change of transmission error rate in consideration of the above, it provides a 2D forward error correction method and data communication method that can improve the transmission efficiency compared with the existing static forward error correction method. Has a different purpose. Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

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The present invention for achieving the above object, in the forward error correction method, at the time of transmission, the predetermined number of data packets to be transmitted in accordance with the packet loss rate information provided by the receiver for the data packet transmitted from the transmitter side; Arrange by two-dimensional blocks of and generate horizontal and vertical parity packets for each row and column of the aligned packet block -ie, create vertical / horizontal parity packets according to packet loss rate in consideration of variable radio channel characteristics. Adjust the rate, and when receiving, examines the sequence number of the received data packet to determine whether the data packet is lost, and when the loss of the data packet occurs, the horizontal level that has been transmitted with the data packets And recovering the lost data packet carrying at least one frame using vertical parity packets. do. On the other hand, the present invention provides a data communication method comprising: an FEC determination step of determining whether to perform forward error correction (FEC) processing by using 'packet loss rate information provided by a receiver for a data packet transmitted from a transmitter'; And parity packets for arranging data packets to be transmitted in units of predetermined two-dimensional blocks, and generating horizontal and vertical parity packets for each row and column of the aligned packet blocks as the forward error correction process is determined. Including the step of generating, characterized in that the receiving rate varies the generation rate of the horizontal / vertical parity packet according to the packet loss rate information contained in the RTCP (RTP Control Protocol) packet periodically transmitted to the transmitting side. In addition, the present invention, the receiving side receiving the data packet and the parity packet determines the loss of the data packet by checking the sequence number of the received data packet, and if the data packet is lost, the lost data packet is recovered If possible, the method further includes immediately recovering the received horizontal parity packet and the vertical parity without waiting for the data packet to be received by the playout unit. According to the present invention, a data packet for generating a parity packet needs to be stored in a queue at the transmitting side, and a receiving side requires a delay until receiving a parity packet necessary for recovering a lost packet. This is necessary. The delay at the transmitting side can reduce the processing delay required for parity packet generation by copying the packet at the same time as the data packet is generated and immediately transmitting the original packet and storing the copied packet in the queue. In addition, it is possible to overcome the radio aggregation error characteristics by applying a block interleaving technique (different packet transmission order). In the present invention, the RTCP (RTP Control Protocol) that is feedback information of the transmitted RTP packet (data packet) ), It is necessary to apply different 2D FEC techniques according to the packet loss rate. In this case, in the application of the FEC technique, a method of increasing or decreasing a recovery rate according to overhead by changing (i, j) values of a matrix for a two-dimensional block of a data packet, and a process of filling a matrix to make a parity packet There is a method of generating a parity packet for a data packet within a sliding window by moving a sliding window having a size (i, j) by one column by applying the sliding window concept. The process of generating a parity packet is the same as described above. In addition, the RTP header of the parity packet described in FIG. 3 may be used to apply an adaptive two-dimensional FEC scheme according to a network situation by using the information of the received RTCP packet. have. If the FEC scheme type information is applied to the PT (Payload Type) field containing the payload type information of the parity packet by defining the applicable two-dimensional FEC scheme type, the receiver is currently applied without the need for a separate signaling or negotiation process. If the SIP (Session Initiation Protocol) is used for signaling, it is possible to identify the type of 2D FEC scheme being used. In addition, in the present invention, in order to recover a lost data packet by using the received parity packet, an additional processing delay occurs, and a method for reducing a recovery delay time at the receiving side is required. The receiving side, which receives the data packet and the parity packet, checks whether the data packet is lost by checking the sequence number of the received data packet, and if the data packet is lost, if the lost data packet is recoverable, the data is played by the playout unit. Instead of waiting for a packet to be received, the received horizontal parity packet and the vertical parity may be immediately recovered. The above-described objects, features, and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Accordingly, those skilled in the art to which the present invention pertains may easily implement the technical idea of the present invention. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a diagram conceptually illustrating a two-dimensional forward error correction method and a transmission data encoder of a transmitting side implementing the data communication method using the same.

As shown in FIG. 4, the RTP packet generator 12 packetizes an input data stream into an RTP packet (data packet) under the control of the controller 10. The data packet thus generated is copied and temporarily stored in a queue 14 to generate a parity packet by the two-dimensional forward error correction method according to the present invention. Thereafter, the data packet stored in the queue 14 is used by the parity packet generator 16 to generate the parity packet. Here, the control unit 10 performs control by adjusting the error recovery rate of the receiving side by using the RTCP packet transmitted from the receiving side.

The parity packet generated by the RTP packet generation unit 12 and the parity packet generated by the parity packet generation unit 16 are sequentially arranged in the transmission order according to the present invention by the packet order arrangement unit 18, and then output buffers sequentially. Is sent via 20.

According to the present invention, a method for generating a parity packet includes a first method of adjusting a recovery rate by changing (i, j) values of a matrix, and a second sliding window concept in filling a matrix to generate a parity packet. There is a method of generating a parity packet for a data packet within a sliding window while moving a sliding window having a size (i, j) by one column by applying.

A first method for generating a parity packet (a method of adjusting a recovery rate by changing a value of (i, j) of a matrix) may be, for example, a parity packet generation method as illustrated in FIGS. 6 and 7. In the same figures, when the matrix (i, j) value is (3, 3), when the values of i and j are different, the packet generation order is also different.

The method shown in FIGS. 6 and 7 uses the exclusive OR (XOR) calculation method used for parity packet generation in the FEC method proposed in RFC 2733.

In order to increase the recovery rate of the lost RTP packet (data packet) at the receiving side, the transmitting side first selects the matrix (i, j) of the adaptive data packets according to the transmission error rate of the wireless network. Here, a method of adjusting the recovery rate of lost packets at the receiving side will be described. According to the matrix (i, j) value of the selected data packet, the number of additionally transmitted parity packets varies, and as the number of transmitted parity packets increases, the recovery rate increases. When the number of transmitted parity packets decreases, the recovery rate also decreases. You lose. For example, if the matrix of data packets is (3,3), the overhead (rate of parity packets) is 66%; if the matrix of data packets is (2,2), the overhead is 100%. The recovery rate is higher than that at (3, 3). Therefore, if the packet loss rate on the receiving side is low, apply the matrix of data packets to (4,4) or (3,4) .If the packet loss rate on the receiving side is high, then the matrix of data packets is (3,3) or (2, 3) or (2,2).

Second, if the generated RTP packets (data packets) are arranged in a two-dimensional (i, j) matrix, and the first row is filled with j columns according to the value of (i, j), j data packets are filled. Generates one horizontal parity packet through an XOR operation. The same process is repeated to the i th row to generate i parity packets. When the i-th row of the first column is filled with i, the parity packet is generated. Thus, one vertical parity packet is generated through the XOR operation on the i data packets. The same process is repeated to the jth column to generate j parity packets. This generates i * j data packets and (i + j) parity packets. The data packet and the parity packet generated in this way have a sequence number incremented by one, and a start number is randomly selected. Third, the receiving side finds the lost data packet using the sequence number of the received data packet and then recovers the lost packet using the received data packet and the parity packet. Fourth, the last received data packet and the recovered data packet are ordered based on the sequence number and then played out in a playout unit.

As described above, according to the present invention, a two-dimensional FEC technique (that is, generating and transmitting FEC parity packets in the horizontal and vertical directions) having different overheads may be applied.

Meanwhile, the second parity packet generation method according to the present invention is a method of generating a parity packet while determining a sliding window size and moving the column size by one column.

8 shows another example of generating a parity packet in the 2D FEC scheme according to the present invention when the sliding window size is (2,2). If the window size is changed, the size of the matrix for generating the parity packet is also changed accordingly.

That is, the generated data packets P1, P2, ..., P20, ... are arranged as shown in Fig. 8 corresponding to the matrix (2, 2) which is the window size. First, a horizontal parity packet F1 is generated through an XOR operation of the data packets P1 and P3 on the data packets P1, P2, P3, and P4 corresponding to the matrix (2, 2), which is the window size, and the data packet P1. Vertical parity packet F2 is generated through XOR operations of P2 and P2. Horizontal parity packet F3 is generated through XOR operations of data packets P2 and P4, and vertical parity is performed through XOR operations of data, packets P3 and P4. Generate packet F4. Then, horizontal parity packets and vertical parity packets are moved as described above with respect to (2,2) size data packets corresponding to the sliding windows, respectively, moving the (2,2) size window by one column. Create

In the present invention, an interleaving technique may or may not be applied in transmitting the data packet and the parity packet generated as described above. In this case, the interleaving technique may be classified into a block interleaving technique and a random interleaving technique.

If the interleaving scheme is not applied, the packets are transmitted in the order in which the data packets and the parity packets are generated in transmitting the data packets and the parity packets generated at the transmitter. That is, an example in which the interleaving technique is not applied is as shown in FIG. 7.

The parity packet generation process when the interleaving technique is applied is the same as when the interleaving technique is not applied, and there is a difference in the transmission order of the generated data packet and the parity packet. That is, in the case of the block interleaving scheme, as shown in FIG. 9, for example, the two-dimensional FEC of (3, 3) is performed, and then the packets constituting the block are transmitted in the vertical order. In the case of a random interleaving scheme, packets constituting a block are randomly transmitted without a certain rule.

In the case of delay-sensitive traffic, it is important to reduce processing delays at the transmitting and receiving sides, so it is necessary to carefully select the interleaving technique.

Next, packet generation at the transmitting side will be described with reference to the flowchart of FIG. 10 and the encoder block diagram of FIG. 5.

First, when a data stream to be transmitted to the encoder on the transmitting side is input, the RTP packet generation unit 12 generates an RTP packet (data packet) (steps S1 and S3).

At this time, the encoder control unit 10 can know the quality (packet loss rate) of the packet being transmitted by receiving the RTCP packet containing the feedback information from the receiving side. That is, the receiving side feeds back the number of packets lost from the total received RTP packets (data packets), inter-packet transmission delay (ie, delay jitter) information, etc. in the RTCP packet to the transmitting side. The RTCP packet is divided into a Sender (SR) packet, a RR (Receiver Report) packet, a SDES (Source Description) packet, a BYE (Bye) packet, and an APP (Application Specific) packet. Here, the RTCP packet includes feedback information. Means RR packet.

The encoder control unit 10 determines, for example, whether or not FEC processing is performed by checking a "fraction lost" field containing packet loss ratio information in a field of the received RTCP packet (i.e., RR packet) (step S5). .

Here, if the packet loss rate is 0%, it is preferable to decide not to perform FEC processing, and to determine not to perform FEC processing.

If it is determined in step S5 not to perform the FEC process, the RTP packet (data packet) generated by the RTP packet generation unit 12 is controlled by the packet order arrangement unit 18 under the control of the control unit 10. Arranged as described above and transmitted through the output buffer 20 (step S7). In this case, the data packet is generated in a size of a predetermined packet size, the header and payload are filled, and then transmitted. At this time, the sender does not need to store the generated data packet in a queue.

On the other hand, if it is determined in the step S5 to perform the FEC process, the controller 10 checks the "fraction lost" field containing the packet loss rate information in the field of the received RTCP packet (ie, RR packet), and applies it. Determine the FEC type to be made (step S9). For example, if the packet loss rate is 10% or more, the FEC in units of the FEC type 1 (2, 2) unit. If the packet loss rate is 5% to 10%, the matrix (2, 3) is the FEC type 2. ) FEC in units of 3,5% of packet loss rate, FEC of type 3 (3,3) if packet loss rate is 3%, and matrix of FEC type 4 if packet loss rate is less than 3% (4 And 3) determine the FEC of the unit.

Thereafter, an FEC parity packet is generated according to the FEC type determined in step S9 (step S11). That is, under the control of the controller 10, the RTP packets (data packets) generated by the RTP packet generator 12 are copied and temporarily stored in the queue 14, and the parity packet generator 16 is stored in the queue. The two-dimensional FEC parity packet is generated according to the determined FEC type with reference to the RTP packets (data packets) (step S11).

In this case, as shown in FIG. 3, when the FEC scheme type information applied to the PT (Payload Type) field containing the payload type information of the parity packet is included, the receiver is currently applied without any separate signaling or negotiation process. Identify types of two-dimensional FEC techniques.

Subsequently, the FEC parity packets generated in step S11 are aligned with the RTP packets (data packets) generated by the RTP packet generation unit 12 in the packet order alignment unit 18 in the transmission order and then output buffer ( 20) (step S13).

That is, in the case of applying the FEC, the parity packet is generated through the XOR operation of the data packet for generating the parity packet when the parity packet transmission turn is performed according to the applied two-dimensional FEC scheme. In this process, data packets needed to generate parity packets are copied and stored in a queue before being transmitted. The copied data packet stored in the queue to generate the parity packet in the 2D FEC block is deleted from the queue when the last parity packet is generated. Since the sequence number information of the data packets used to generate the parity packet is recorded in the mask field in the header part of the parity packet by RFC 2733, which parity packet should be used to recover the lost data packet at the receiving side. I can see.

On the other hand, when determining the presence or absence of FEC processing in step S5, since the RTCP packet is not received at the time of the first transmission, to apply a specific FEC type (for example, FEC of the matrix (4,3) unit of FEC type 4), When the RTCP packet is received at the receiving end with respect to the transmitted packets by applying the FEC type, it is preferable to determine whether the FEC is processed and the FEC type according to the reception result.

Next, a packet receiving procedure at the receiving side will be described with reference to the flowchart of FIG. 11 and the decoder block diagram of FIG.

First, when the packets encoded by the encoder at the transmitting side are received by the decoder at the receiving side as described above (step S21), it is determined whether the packets received at the decoder type determining unit 30 are FEC processed packets (step S23). ). Here, it may be determined whether the packet is an RTP packet or a parity packet from information written in the "PT (Payload Type)" field in the header of the received packet.

If it is determined in step S23 that no FEC processing has been performed, the received packet is decomposed by the depacketizer 36, restored to the original data stream, and input into the playout buffer 37. At this time, the data stream bits input to the buffer 37 are played out in predetermined units (steps S25 to S31).

On the other hand, if it is determined in step S23 that the FEC processing has been performed, the processed FEC type is checked for the received packets (step S33). Here, if the FEC type is recorded in the PT (Payload Type) field of the parity packet in the transmitting encoder, the type discriminator 30 of the receiving decoder may refer to the PT (Payload Type) field of the parity packet to easily determine the FEC type. Able to know.

Thereafter, the received packets are separated into an RTP packet (data packet) and an FEC parity packet so that the RTP packet (data packet) is temporarily stored in the RTP buffer 32, and the FEC parity packet is temporarily stored in the FEC buffer 33. (Steps S35, S37).

Subsequently, the packet loss discrimination unit 34 sequentially reads the RTP packets (data packets) stored in the RTP buffer 32 and checks the sequence numbers of the RTP packets (data packets) to determine whether the packets are lost. (Steps S39, S41).

If it is determined in step S41 that there is no packet loss, the RTP packet (data packet) read into the RTP buffer 32 is transferred to the depacketizer 36, and the process of steps S25 to S31 described above. Is processed.

On the other hand, if it is determined in step S41 that there is a packet loss, the packet loss discrimination unit 34 determines whether the lost packet is recoverable based on the FEC type determined by the type discrimination unit 30. (Step S43).

If it is determined in step S43 that the recovery is possible, the packet recovery unit 35 recovers the lost RTP packet (data packet) using the parity packets stored in the FEC buffer 33 (step S45). Here, the parity packet and the data packets necessary for the recovery are recovered through the XOR operation as in the case of generating the parity packet, and the recovered data packet is transmitted to the depacketizer 36 according to the sequence number. The process is performed by the above steps S25 to S31.

On the other hand, if it is determined in step S43 that it is not recoverable, the packet recovery unit 35 pads the lost data with "0" or "1" for the lost RTP packet (data packet) ( Step S47), the padded data packet is transferred to the depacketizer 36 and processed by the above-described steps S25 to S31.

In the case of the 2D FEC scheme according to the present invention, since it is possible to check whether packet recovery is possible twice for one data packet with a horizontal parity packet and a vertical parity packet, there is less overhead than the techniques proposed in the conventional RFC 2733. The recovery rate can be increased. The present invention described above can be variously substituted, modified, and changed without departing from the technical spirit of the present invention for those skilled in the art. It is not limited by the embodiment and the accompanying drawings.

The present invention as described above, by applying a two-dimensional FEC technique for transmitting a horizontal parity packet and a vertical parity packet at the same time when the packet loss occurs over the air to overcome the error characteristics of the radio channel by providing a real-time multimedia service Can be improved.

In particular, the present invention can improve the transmission efficiency by changing the overhead according to the packet loss rate in consideration of the variable radio channel characteristics, and can also be applied to various interleaving techniques to overcome the aggregation error when the wireless network conditions are not good It can work.

In addition, the present invention uses only the XOR operation in the process of generating the parity packet and recovering the lost packet, thereby improving overall performance by reducing complexity and processing delay.

By applying the adaptive two-dimensional FEC scheme for packet loss over the air, the present invention can guarantee the data transmission quality over the air by using the FEC scheme suitable for the environment against continuous errors, and facilitates high-speed multimedia service. There is an effect that can provide.

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1 is a structural diagram of a parity packet by general forward error correction (FEC).

2 is an FEC header structure diagram of the parity packet of FIG.

3 is a real-time transport protocol (RTP) header structure diagram of the parity packet of FIG.

4 is a conceptual diagram of an encoder implementing a two-dimensional forward error correction method according to the present invention.

5 is a conceptual diagram of a decoder implementing a two-dimensional forward error correction method according to the present invention.

6 and 7 are diagrams for explaining an embodiment of the FEC parity packet generation and packet transmission procedure in the two-dimensional forward error correction method according to the present invention.

8 is a view for explaining another embodiment of the FEC parity packet generation process in the two-dimensional forward error correction method according to the present invention.

9 is a view for explaining another embodiment of the FEC parity packet generation and packet transmission procedure in the two-dimensional forward error correction method according to the present invention.

10 is a flowchart illustrating a flow of processing a packet at a transmitting side using a two-dimensional forward error correction method according to the present invention.

11 is a flowchart illustrating a flow of receiving and processing a packet transmitted using a two-dimensional forward error correction method according to the present invention.

Claims (10)

In the forward error correction method, At the time of transmission, the data packets to be transmitted are variably arranged in predetermined two-dimensional block units according to the packet loss rate information provided by the receiver for the data packets transmitted from the transmitter, and each row of the aligned packet blocks Generates parity packets in the horizontal and vertical directions with respect to the column -that is, adjusts the generation rate of the vertical and horizontal parity packets according to the packet loss rate in consideration of the variable radio channel characteristics . Upon reception, the sequence number of the received data packet is examined to determine whether the data packet is lost, and when a loss of the data packet occurs, horizontal and vertical parity packets transmitted together with the data packets are determined. And recovering the lost data packet carrying at least one frame using the two-dimensional forward error correction method. In the data communication method, An FEC determination step of determining whether to perform forward error correction (FEC) by using 'packet loss rate information provided by a receiver for a data packet transmitted from a transmitter'; And As the forward error correction process is determined, parity packet generation is performed, in which data packets to be transmitted are arranged in predetermined two-dimensional blocks, and horizontal and vertical parity packets are generated and transmitted for each row and column of the aligned packet blocks. Including steps, And a generation rate of a horizontal / vertical parity packet according to packet loss rate information included in an RTCP packet periodically transmitted to the transmitting side by the receiving side. The method of claim 2, In the FEC determination step, the predetermined block unit is determined, In the parity generation step, the data packet to be transmitted in units of the determined block is arranged. The method of claim 3, wherein The data packet is a Real-time Transport Protocol (RTP) packet, The packet loss rate information is contained in the RTCP (RTP Control Protocol) packet. The method of claim 4, wherein In the Payload Type field of the RTP header portion of the generated parity packet, And the block unit information is included. The method of claim 3, wherein In the FEC determination step, And determining a block unit having a high number of data packets when the packet loss rate is low, and determining a block unit having a low number of data packets when the packet loss rate is high. The method of claim 2, In the parity packet generation step, After copying the data packet necessary to generate the horizontal and vertical parity packet, the original data packet is immediately transmitted, and the copied data packet is stored in a queue before the generation of the horizontal and vertical parity packet. Data communication method, characterized in that used for. The method according to any one of claims 2 to 7, In the parity packet generation step, the transmission order of data packets and parity packets is A data communication method comprising applying an interleaving technique or a non-interleaving technique. The method of claim 8, The interleaving technique, A data communication method comprising applying a block interleaving technique or a random interleaving technique. The method according to any one of claims 2 to 7, Receiving side receiving the data packet and the parity packet determines whether the data packet is lost by checking the sequence number of the received data packet, and if the lost data packet is recoverable by the playout unit if the data packet is lost. Immediately recovering using the received horizontal parity packet and the vertical parity without waiting for a data packet to be received; Data communication method further comprising.