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A method for transmitting variable length packets based on FEC coding. Data packets are successively and contiguously stored in a two-dimensional storage device. FEC coding is performed to generate parity packets. The parity packets are stored in the two-dimensional storage device. The data packets

A method for transmitting variable length packets based on FEC coding. Data packets are successively and contiguously stored in a two-dimensional storage device. FEC coding is performed to generate parity packets. The parity packets are stored in the two-dimensional storage device. The data packets, offsets representing positions of the data packets in the two-dimensional storage device, types of packets, and the parity packets are then transmitted.

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We claim: 1. A method for transmitting variable length packets on the basis of FEC (forward error correction) coding, comprising: (a) receiving input data packets to be transmitted, the input data packets having variable lengths; and (b) successively storing and arranging the input data packets in

We claim: 1. A method for transmitting variable length packets on the basis of FEC (forward error correction) coding, comprising: (a) receiving input data packets to be transmitted, the input data packets having variable lengths; and (b) successively storing and arranging the input data packets in a two-dimensional data array which has a predetermined length, performing the FEC coding to generate corresponding parity packets, arranging the generated parity packets in the two-dimensional data array, and transmitting the data packets, offsets that represent positions of the data packets in the two-dimensional data array, information about types of packets, and the parity packets. 2. The method of claim 1, wherein successively storing and arranging the data packets in the two-dimensional data array represents respectively concatenating the data packets and storing them in the two-dimensional storage device. 3. The method of claim 1, wherein the method further comprises before (a): (c) determining whether predetermined parameters for the FEC coding are to be used; and (d) determining parameters for the FEC coding and transmitting them when the predetermined parameters are not to be used. 4. The method of claim 3, wherein the predetermined parameters include a length of the two-dimensional data array, the number of the parity packets, and a factor for determining an associated packet group. 5. The method of claim 4, wherein the associated packet group is a set of the data packets and corresponding parity packets. 6. The method of claim 1, wherein (b) comprises: (i) accumulating values of factors for determining whether to transmit the parity packets; (ii) successively storing and arranging the input data packets in the two-dimensional data array; (iii) updating parity packets according to the input data packets; (iv) transmitting extension data packets including the input data packets and information for data packet restoration; (v) determining whether it is time to transmit the parity packets; (vi) transmitting the parity packets when it is the time to transmit the parity packets in (v); and (vii) resetting the factors for determining whether to transmit the parity packets in (i). 7. The method of claim 6, wherein the factors for determining whether to transmit the parity packets in (i) include at least one of a size of the input data packets, the number of the input data packets, and time information. 8. The method of claim 6, wherein the time to transmit the parity packets in (v) is at least one of: a time when an accumulated size of the data packets is at least equal to a predetermined size of a predetermined associated packet group, a time when an accumulated number of the input data packets is at least equal to a predetermined number of data packets of the predetermined associated packet group, and a time when an accumulated lapsed time of the predetermined associated packet group is at least equal to a predetermined time. 9. The method of claim 6, wherein a header of the extension packet includes information for data packet restoration. 10. The method of claim 6, wherein the parity packets are updated by calculating the data arranged in the two-dimensional storage device per a predetermined length. 11. The method of claim 6, wherein (vi) comprises: determining the number of the parity packets to be transmitted; determining whether the number of transmitted parity packets is equal to or greater than the number of the parity packets to be transmitted; transmitting an extension parity packet including one of the parity packets to be transmitted and the information for data packet restoration when the number of the transmitted parity packets is less than the number of the parity packets to be transmitted; accumulating the number of the transmitted parity packets; and resetting the parity packets and the number of the transmitted parity packets when the determined number of the transmitted parity packets is equal to or greater than the determined number of the parity packets to be transmitted. 12. The method of claim 11, wherein the number of the parity packets to be transmitted is determined according to a state of a channel on which the packets will be transmitted. 13. The method of claim 6, wherein the information for data packet restoration includes the packets' types and the packets' offsets in the case of the data packets, and it includes the packets' types and a total size of the data packets in the associated packet group in the case of the parity packets. 14. The method of claim 13, wherein the information for data packet restoration further includes the data packets' offsets in the case of the parity packets. 15. A method for receiving variable length packets on the basis of FEC (forward error correction) coding, comprising: (a) receiving extension packets, each of the extension packets including one of the variable length data packets and parity packets, successively storing and arranging the variable length packets in a first dimension of a two-dimensional data array which has a predetermined storage length; and (b) performing FEC decoding on code words aligned in a second dimension of the two-dimensional data array to restore data packets from the variable length data packets and parity packets, and delivering the data packets to an upper layer; wherein the extension packets include offsets, the offsets representing positions of the variable length packets in a two-dimensional transmission data array of a transmission apparatus that transmits the extension packets, when the transmission apparatus successively stores and arranges the variable length packets in the two-dimensional transmission data array, and the successively storing and arranging in the step (b) is performing based on the offsets; and wherein the FEC decoding corresponds to the FEC encoding used in the transmission apparatus. 16. The method of claim 15, wherein the method further comprises before (a): (c) determining whether predetermined parameters for the FEC decoding are to be used; and (d) receiving parameters from a transmitter if the predetermined parameters are not to be used. 17. The method of claim 15, wherein (a) comprises: (i) receiving one of the extension packets; (ii) determining whether the received extension packet is an extension data packet or an extension parity packet; (iii) separating the data packet from information for data packet restoration when the received extension packet in (ii) is an extension data packet including the data packet; (iv) separating the parity packet from information for data packet restoration when the received extension packet in (ii) is an extension parity packet including the parity packet; and (v) sequentially arranging the separated data packet and the parity packet in (iii) or (iv) in the two-dimensional data array. 18. The method of claim 15, wherein successively storing and arranging the packets in the two-dimensional data array represents concatenating the data packets and storing them in the two-dimensional data array so that the corresponding storage length may be a storage length of the two-dimensional data array. 19. The method of claim 15, wherein (b) comprises: (i) determining whether it is time to deliver the associated packet group to the upper layer; and (ii) delivering the separated data packets to the upper layer when it is determined to be the time to deliver the associated packet group to the upper layer. 20. The method of claim 19, wherein the time to deliver the associated packet group to the upper layer may be a time when the last packet in the associated packet group or a packet in a subsequent associated packet group arrives, or a time when a predetermined time has lapsed. 21. The method of claim 19, wherein (ii) comprises: (ii-i) determining whether the separated data packets have a lost portion; (ii-ii) determining whether the data packet has a restorable portion when the data packets have a lost portion; (ii-iii) restoring the lost data packets when the lost portion is restorable in (ii-ii); (ii-iv) determining whether all lost portion can not be restored in (ii-iii); (ii-v) delivering lost positions to the upper layer when it is determined that no restorable portion remains in (ii-ii) or when a portion is not restored in (ii-iv); and (ii-vi) delivering the received data packets to the upper layer when no data packet is lost in (ii-i), or delivering the received data packets including the restored data packets to the upper layer when data are restored in (ii-iii). 22. A method for transmitting variable length packets using FEC (forward error correction) coding, comprising: (a) receiving data packets to be transmitted, the data packets having variable lengths; (b) successively storing the data packets contiguously in a two-dimensional data array, (c) performing the FEC coding to generate corresponding parity packets, (d) successively storing the generated parity packets contiguously in the two-dimensional data array; and (e) transmitting the data packets, offsets that represent positions of the data packets in the two-dimensional data array, information about types of packets, and the parity packets. 23. A method for receiving variable length packets using FEC (forward error correction) coding, comprising: (a) receiving extension packets, each of the extension packets including one of the variable length data packets and parity packets, successively and contiguously storing the variable length packets in a first dimension of a two-dimensional data array; and (b) performing FEC decoding on code words aligned in a second dimension of the two-dimensional data array to restore data packets from the received variable length data packets and parity packets, and delivering the data packets to an upper layer; wherein the extension packets include offsets, the offsets representing positions of the variable length packets in a two-dimensional transmission data array of a transmission apparatus that transmits the extension packets, when the transmission apparatus successively stores and arranges the variable length packets in the two-dimensional transmission data array, and the successively storing and arranging in the step (b) is performing based on the offsets; and wherein the FEC decoding corresponds to the FEC encoding used in the transmission apparatus.