JP2004080188A - Receiver, reception processing method for received data and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver, a receiving process method for received data, and a computer program which reduces the communication time. <P>SOLUTION: In transmitting data from a server communication apparatus 10 to a client communication apparatus 20, a gateway 22 does not request the retransmission of packets so far as the number of missing packets is below an allowable missing packet number, if there are unreceived packets. If the number of missing packets exceeds the allowable missing packet number, the gateway 22 requests a gateway 12 to re-transmit at least a number of packets equal to the number of missing packets minus the allowable number of mission packets. By the re-transmit request, the gateway 12 re-transmits a designated number of packets. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reception device, a reception data reception processing method, and a program.
[0002]
[Prior art]
In the air or underwater communication environment, phenomena such as fading, burst noise, and antenna trial characteristics occur. Such a phenomenon has a great effect on the radio propagation characteristics and communication quality.
[0003]
Even in such a communication environment, in order to ensure that information can be transmitted from the transmitting device to the receiving device, the receiving device performs an error detection process on the transmission information, and when an error is detected, sends a retransmission request to the transmitting device. Send. Conventionally, when a retransmission of data is requested from a reception device, a transmission device retransmits all data in response to the retransmission request.
[0004]
[Problems to be solved by the invention]
However, even if there is unreceived data, or if an error is detected in only some of the data, retransmitting all the data requires time for communication. In particular, when transmitting all data in the air or underwater communication environment where the communication quality deteriorates, errors may occur each time, and the data must be retransmitted many times between the transmitting device and the receiving device. No.
[0005]
The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a receiving device, a receiving data receiving method, and a computer program that can reduce communication time.
[0006]
[Means for Solving the Problems]
In order to achieve this object, the receiving device according to the first aspect of the present invention includes:
In a receiving device that receives a plurality of packets obtained by dividing a series of data strings,
A packet loss allowable number that allows a packet loss upon restoration of the series of data strings is set in advance,
When there is an unreceived packet, the packet transmission source is provided with retransmission request means for requesting to retransmit at least the number of packets obtained by subtracting the permissible packet loss number from the number of the unreceived packets.
[0007]
According to this configuration, when there is an unreceived packet, if the number obtained by subtracting the allowable packet dropout number from the number of unreceived packets is equal to or less than zero, the retransmission request unit does not need to make a retransmission request. Unless the means makes a retransmission request to the packet transmission source, retransmission of unreceived packets is not performed. Further, even when the number obtained by subtracting the allowable packet loss number from the number of unreceived packets exceeds zero, only the number of packets exceeding zero need to be retransmitted. Therefore, the communication time is shortened at least by the time for transmitting the packet of the allowable number of missing packets.
[0008]
The series of data strings is an encoded data string encoded by an encoding method capable of error correction,
The permissible number of missing packets may be set in advance based on the number of error corrections of a decoding method capable of performing error correction corresponding to the coding method.
[0009]
It is preferable that the decoding method is one of a Viterbi decoding method, a BCH decoding method, and a turbo decoding method.
[0010]
A reception processing method for reception data according to a second aspect of the present invention includes:
Receiving a plurality of packets obtained by dividing a series of data streams;
If there is an unreceived packet, the packet transmission source subtracts the number of packets obtained by subtracting the allowable number of missing packets that is set in advance as the number that allows for missing packets when restoring the series of data strings from the number of unreceived packets. Requesting at least retransmission.
[0011]
A program according to a third aspect of the present invention includes:
On the computer,
A procedure for receiving a plurality of packets obtained by dividing a series of data streams,
If there is an unreceived packet, the packet transmission source subtracts the number of packets obtained by subtracting the allowable number of packet omissions set in advance as the number that allows packet omission when restoring the series of data strings from the number of the unreceived packets. A procedure to request at least resend,
Is to be executed.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a receiving device according to an embodiment of the present invention will be described with reference to the drawings.
In the present embodiment, a description will be given assuming that the receiving apparatus is used in a client-server communication system.
FIG. 1 shows the configuration of the client-server communication system according to the present embodiment.
The client-server communication system is, for example, a system used for communication of HF / UHF data, and includes a server communication device 10 and a client communication device 20. In the present embodiment, the server communication device 10 and the client communication device 20 will be described as a transmitting side and a receiving side, respectively.
[0013]
The server communication device 10 includes a server 11, a gateway (referred to as “GW” in the figure) 12, a modem 13, and an antenna 14.
[0014]
The server 11 is a computer that outputs transmission data, and includes an MPU (Micro Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.
The gateway 12 is a computer including an MPU, a ROM, a RAM, and the like, and performs coding of transmission data generated by the server 11, block division, and the like to generate packet data.
[0015]
The modem 13 includes a modulator (not shown), and generates a modulated signal based on the packet data converted by the gateway 12.
The antenna 14 transmits the modulated signal generated by the modem 13 as, for example, HF / UHF radio waves.
[0016]
The client communication device 20 includes a client 21, a gateway 22, a modem 23, and an antenna 24.
The antenna 24 receives the HF / UHF radio wave transmitted by the antenna 14.
[0017]
The modem 23 includes a demodulator (not shown), and extracts packet data from a radio wave received by the antenna 24.
The gateway 22 is a computer including an MPU, a ROM, a RAM, and the like. The gateway 22 assembles and decodes packet data demodulated by the modem 23, and converts the packet data into original data.
[0018]
The client 21 is a computer that performs information processing based on the original data converted by the gateway 22.
[0019]
Next, the configuration of the gateways 12 and 22 will be described.
As shown in FIG. 2, the gateway 12 of the server communication device 10 includes a receiving unit 31, a checksum information adding unit 32, a Turbo encoding unit 33, a combining unit 34, a frame dividing unit 35, A storage device 36 and a control unit 37 are provided.
[0020]
The receiving unit 31 receives transmission data from the server 11. The receiving unit 31 includes a buffer (not shown) for adjusting the data processing speed, temporarily stores received data in the buffer, and then outputs a data string.
[0021]
The checksum information adding unit 32 adds checksum information for detecting a data error to the data string output by the receiving unit 31.
[0022]
The turbo encoding unit 33 encodes the data sequence to which the checksum information is added according to a turbo encoding method. This turbo coding method is a coding method that enables error correction. The turbo encoder 33 includes an interleaver 38, encoders 39 and 40, and a multiplexer 41.
[0023]
The interleaver 38 rearranges the interleaver order of the information sequence of the data sequence to which the checksum information adding unit 32 has added the checksum information.
[0024]
The encoder 39 encodes the data string to which the checksum information is added by the checksum information adding unit 32 to generate the parity bit string 1.
[0025]
The encoder 40 encodes the information sequence in which the interleaver 38 rearranges the interleaver order, and generates the parity bit string 2 thereof. Note that the configurations of the two encoders 39 and 40 may be the same or different.
[0026]
The multiplexer 41 multiplexes the parity bit strings 1 and 2 generated by the encoders 39 and 40 simply or by puncturing.
[0027]
The synthesizing unit 34 synthesizes the data sequence to which the checksum information adding unit 32 has added the checksum information and the information sequence encoded by the turbo encoding unit 33 to generate a frame including the data sequence. .
[0028]
The frame dividing unit 35 includes an interleaver (not shown), rearranges the data sequence of the frame generated by the combining unit 34 in consideration of the bit error pattern, and converts the data sequence of the frame into a plurality of packets. It is to be divided into blocks. Further, the frame dividing unit 35 adds a header and a footer for indicating a data break to each of the divided packets.
[0029]
Note that the interleaver included in the frame division unit 35 rearranges in consideration of the bit error pattern as described above, and has a different function from the interleaver 38 of the turbo encoding unit 33. Also, the size of the divided packets is determined based on experiments and the like so that even if an error occurs during retransmission, the effect is minimized.
[0030]
The storage device 36 is configured by an HDD (Hard Disk Drive) or the like, and stores transmitted packet data and the like.
[0031]
The control unit 37 controls each unit of the gateway 12. Further, the control unit 37 writes the transmitted packet data and the like to the storage device 36 and, when there is a request for retransmission of the packet data, reads out the packet data from the storage device 36 in response to the request.
[0032]
As illustrated in FIG. 3, the gateway 22 of the client communication device 20 includes a receiving unit 51, a frame assembling unit 52, a turbo decoding unit 53, a checksum checking unit 54, and a control unit 55.
[0033]
The receiving unit 51 receives a packet extracted by the modem 23, and recognizes a header and a footer of each received packet. The receiving unit 51 includes a buffer (not shown) for adjusting a data processing speed, and temporarily stores a received packet in the buffer.
[0034]
The frame assembling unit 52 assembles a plurality of divided packets to generate a frame including encoded data.
[0035]
The turbo decoding unit 53 decodes encoded data forming a frame according to a turbo decoding method, and includes a decoder 56, an interleaver 57, a decoder 58, and a deinterleaver 59.
[0036]
The decoder 56 receives the encoded data as a reception sequence, performs a decoding process, and outputs a decoding result of each information symbol and its reliability information.
[0037]
The interleaver 57 rearranges the data output from the decoder 56.
The decoder 58 performs a decoding process on the data sequence rearranged by the interleaver 57, and calculates reliability information using the reliability information decoded by the decoder 56 and the received sequence.
[0038]
The deinterleaver 59 rearranges the data sequence decoded by the decoder 58 into the original data sequence, and sends the rearranged data sequence to the decoder 56.
[0039]
The checksum checker 54 receives the decoded data string from the turbo decoder 53 and performs error detection based on the checksum information included in the data string.
The control unit 55 controls each unit in the gateway 22. In addition, the control unit 55 includes a memory for storing a preset guaranteed number and a permissible number of missing packets.
[0040]
The guaranteed number is the number of packets required to guarantee the restoration of a series of data. Further, the allowable number of missing packets is a number that allows the missing of packets when restoring a series of data. That is, assuming that the guaranteed number is pa, the allowable number of missing packets is pb, and the number of packets of a plurality of packets obtained by dividing a series of data strings is ptotal, (pa + pb) becomes ptotal. The guaranteed number and the permissible packet loss number are determined based on the error correction capability of the turbo decoding system, and are set in advance based on experiments and the like.
[0041]
Next, operations of server communication device 10 and client communication device 20 according to the present embodiment will be described.
In the server communication device 10, the server 11 sends transmission data as shown in FIG.
[0042]
The reception unit 31 of the gateway 12 receives the transmission data transmitted by the server 11 and temporarily stores the transmission data in a buffer, and outputs the data sequence to the checksum information addition unit 32 while adjusting the data processing speed.
The checksum information adding unit 32 adds checksum information to the data string, as shown in FIG.
[0043]
The turbo encoding unit 33 encodes the data sequence to which the checksum information is added according to a turbo encoding method.
First, the encoder 39 generates the parity bit sequence 1 based on the information sequence of the data sequence to which the checksum information has been added.
[0044]
The interleaver 38 rearranges the interleaver order of the information sequence of the data sequence to which the checksum information is added, and generates the parity bit sequence 2. The multiplexer 41 multiplexes the two parity bit strings simply or by thinning them out. Then, the multiplexer 41 sends the multiplexed data sequence to the combining unit 34.
[0045]
The combining unit 34 combines the data sequence to which the checksum information is added by the checksum information adding unit 32 and the information sequence encoded by the turbo encoding unit 33.
Thus, a frame as shown in FIG. 4C is formed.
[0046]
The frame dividing unit 35 rearranges the data sequence of the frame generated by the combining unit 34 in consideration of the bit pattern, and divides the data sequence into a plurality of packets as shown in FIG. Further, the frame dividing unit 35 adds a header and a footer to each divided packet as shown in FIG.
[0047]
The control unit 37 stores the packet thus generated in the storage device 36 so that the packet can be retransmitted in response to a retransmission request.
[0048]
The modem 13 generates a modulated signal based on the packet converted by the gateway 12. The antenna 14 transmits the modulated signal generated by the modem 13 as HF / UHF radio waves.
[0049]
In the client communication device 20, the antenna 24 receives the radio wave transmitted from the antenna 14.
The modem 23 extracts each packet from the radio wave received by the antenna 24, as shown in FIG. In the extracted packet, data error may occur due to burst noise or the like. However, since the interleaver order is rearranged by the interleaver 38 of the turbo encoder 33, the data error is corrected when the turbo decoder 53 decodes this packet, and the influence of burst noise and the like is suppressed. You.
[0050]
The receiving unit 51 of the gateway 22 receives the packets extracted by the modem 23 and recognizes a header and a footer of each packet. Further, the receiving unit 51 temporarily stores the received packet in a buffer, and then outputs the packet to the frame assembling unit 52.
[0051]
If there are no unreceived packets as shown in FIG. 4 (g), the frame assembling unit 52 assembles the plurality of received packets to form a frame composed of a series of data strings as shown in FIG. 4 (h). I do.
[0052]
The turbo decoding unit 53 decodes the data sequence of the frame formed by the frame assembling unit 52. First, the decoder 56 receives a data sequence from the frame assembling unit 52 as a reception sequence, performs a decoding process, and outputs a decoding result of each information symbol and its reliability information.
[0053]
The interleaver 57 rearranges the decoding result of each information symbol output from the decoder 56 and the data of its reliability information.
The decoder 58 performs a decoding process using the reliability information from the decoder 56 and the received sequence, and calculates the reliability information.
[0054]
The deinterleaver 59 rearranges the data sequence decoded by the decoder 58 into the original data sequence, and outputs the rearranged data sequence to the decoder 56.
[0055]
The decoder 56 executes the decoding process of the reliability information and the received sequence from the decoder 58 again.
[0056]
The decoder 56, the interleaver 57, the decoder 58, and the deinterleaver 59 repeat such processing several times to several tens of times. By repeating the process, the error is corrected and the reliability is increased. Thereafter, the decoder 58 makes a final determination of the reliability and, when determining that the reliability is equal to or higher than a preset level, outputs the data string to the checksum inspection unit 54.
[0057]
As shown in FIG. 4 (i), the checksum checking unit 54 checks the data for errors based on the checksum information added to the decoded data string. The data string as shown is sent to the client 21.
[0058]
Next, when there is a missing packet in the received packet, the control unit 55 of the client communication device 20 requests the server communication device 10 that is the source of the packet to retransmit the packet.
[0059]
This operation is shown in the flowchart of FIG.
The control unit 55 acquires the number of missing packets based on the header and footer information recognized by the receiving unit 51 (step S11).
The control unit 55 determines whether or not the number of missing packets is equal to or less than the allowable number of missing packets pb (step S12).
[0060]
When it is determined that the number of missing packets is equal to or smaller than the permissible number of missing packets pb (Yes in step S12), the control unit 55 ends this processing because the data string can be restored by error correction.
[0061]
If it is determined that the number of missing packets is greater than the permissible number of missing packets pb (No in step S12), the data sequence cannot be restored even if error correction is performed. A request is made to retransmit the number of packets obtained by subtracting the permissible dropout number pb (step S13). Then, the control unit 55 ends this processing.
[0062]
The control unit 37 of the server communication device 10 receives a retransmission request for retransmitting the packet. When the control unit 37 receives this retransmission request, the control unit 37 performs a packet retransmission process.
[0063]
This process is shown in the flowchart of FIG.
The control unit 37 reads out the requested number of retransmission packets from the storage device 36 (step S21).
[0064]
The control unit 37 sends the read packet to the modem 13 (Step S22). Then, the control section 37 ends this processing. The packet transmitted to the modem 13 is transmitted to the client communication device 20.
[0065]
Next, this operation will be specifically described.
As shown in FIG. 7A, packets obtained by dividing a series of data strings are referred to as P1 to P8. The total number of packets ptotal is eight. In addition, the guaranteed number pa is set to seven, and the allowable packet missing number pb is set to one. That is, if 7 packets out of the total number of 8 packets are received, a series of data strings can be restored.
[0066]
As shown in FIG. 7B, assuming that the packets P1 and P4 have not been received, the control unit 55 subtracts at least the packet loss allowable number pb = 1 from the number 2 of unreceived packets. What is necessary is just to request that the packet of Formula 1 be retransmitted. In this case, a retransmission request can be made by designating the missing packet.
When one packet is retransmitted as shown in FIG. 7C in response to the retransmission request, the number of received packets becomes seven as shown in FIG. Can be restored.
[0067]
Next, FIG. 8 shows the relationship between the data size and the data transmission time when the retransmission processing is executed.
In the drawing, a straight line A indicates the relationship between the data size and the data transmission time when no error correction is performed, and a straight line B indicates the relationship between the data size and the data transmission time when the error correction is performed. S1 indicates the data size. Each retransmission is performed only once.
[0068]
First, the total data transmission time when error correction is not performed even if there is an error is obtained. The data transmission time for transmitting a packet without error correction is defined as ta1, and the data transmission time for transmitting all packets having an error is defined as ta2. The total data transmission time in this case is (ta1 + ta2). This is the total data transmission time according to the conventional method.
[0069]
On the other hand, assuming that the guaranteed number is not considered when a packet is missing, the total data transmission time for correcting an error is obtained. It is assumed that the data transmission time (including the error correction time) of the data to be corrected is tb1, and the time required for retransmitting the erroneous packet is tb3. The total data transmission time in this case is (tb1 + tb3). The total data transmission time (tb1 + tb3) is shorter than the time (ta1 + ta2).
[0070]
Next, assuming that only the number of packets exceeding the guaranteed number is retransmitted when a packet is missing, the total data transmission time for correcting an error is obtained. The time required to retransmit the number of packets exceeding the guaranteed number is defined as tb2. The total data transmission time in this case is (tb1 + tb2). The total data transmission time (tb1 + tb2) is shorter than the time (tb1 + tb3) by considering the guaranteed number. That is, considering the guaranteed number, the data to be retransmitted is reduced, and the data transmission time is the shortest.
[0071]
As described above, according to the present embodiment, if there are unreceived packets, if the number of missing packets is equal to or smaller than the allowable packet loss pb, no packet is retransmitted, and the number of missing packets is When the number of packets dropped exceeds the allowable number pb, at least the number of packets obtained by subtracting the packet drop allowable number pb from the number of packets lost is retransmitted. Therefore, in the present embodiment, the data transmission time can be reduced as compared with the conventional method of retransmitting all packets when there is a packet loss.
[0072]
In carrying out the present invention, various modes are conceivable, and the present invention is not limited to the above embodiments.
For example, when there is an unreceived packet, the number of packets obtained by subtracting the allowable number of missing packets from the number of missing packets may be retransmitted.
[0073]
To explain with reference to the example of FIG. 7, retransmission of a packet with a guaranteed number of 7 may be requested on the premise of the content shown in FIG. In this way, even if some of the retransmitted packets do not arrive, it is not necessary to make a retransmission request again.
[0074]
Particularly, in a place where the communication environment is deteriorated, such as in the air or underwater, the retransmitted packet may not be delivered. In this case, if more packets are retransmitted than the total number ptotal, the frame assembling unit 52 selects either the already received packet or the retransmitted packet, assembles the selected packet, and Generate
[0075]
In the present embodiment, the number of missing packets and the allowable number of missing packets pb are compared to determine whether or not to make a retransmission request. However, the present invention is not limited to this, and the number of received packets may be compared with the guaranteed number pa, with the same result.
[0076]
In the above embodiment, the server communication device 10 has been described as the transmitting device, and the client communication device 20 has been described as the receiving device. However, the present invention is not limited to this, and the server communication device 10 and the client communication device 20 may be a receiving device and a transmitting device, respectively. In this case, the gateway 12 has the configuration shown in FIG. 3, and the gateway 22 has the configuration shown in FIG.
[0077]
The coding method is not limited to the turbo coding method. For example, a Viterbi coding scheme and a BCH (Bose-Chaudhuri-Hocquenghem code) coding scheme can be used. However, among these, the coding method having the highest error correction capability is the turbo coding method, and it is preferable to use this coding method in a communication environment where the communication quality deteriorates, such as in the air or underwater.
[0078]
In addition, a program for causing a computer to operate as a whole or a part of a playback device, or for executing the above-described processing, includes a flexible disk, a compact disk read-only memory (CD-ROM), and a digital versatile disk (DVD). Alternatively, the program may be stored and distributed on a computer-readable recording medium, such as a computer, installed on a computer, and operated as the above-described means, or the above-described steps may be executed.
[0079]
【The invention's effect】
As described above, according to the present invention, the communication time can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a client-server communication system according to a first embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a gateway provided in the server communication device of FIG. 1;
FIG. 3 is a block diagram illustrating a configuration of a gateway provided in the client communication device in FIG. 1;
FIG. 4 is an explanatory diagram showing a process of data processing.
FIG. 5 is a flowchart illustrating a retransmission request process executed by a control unit of the client communication device.
FIG. 6 is a flowchart illustrating a retransmission process performed by a control unit of the server communication device.
FIG. 7 is an explanatory diagram for specifically explaining a retransmission process.
FIG. 8 is an explanatory diagram showing a relationship between a data transmission time and a data size when compared with a conventional case.
[Explanation of symbols]
Reference Signs List 10 server communication device 11 server 20 client communication device 21 client 12, 22 gateway (GW)
33 Turbo encoding unit 37 Control unit 53 Turbo decoding unit 55 Control unit

Claims (5)

In a receiving device that receives a plurality of packets obtained by dividing a series of data strings,
A packet loss allowable number that allows a packet loss upon restoration of the series of data strings is set in advance,
In the case where there is an unreceived packet, the packet transmission source has retransmission request means for requesting to retransmit at least the number of packets obtained by subtracting the allowable packet loss number from the number of the unreceived packets,
A receiving device, characterized in that: The series of data strings is an encoded data string encoded by an encoding method capable of error correction,
The permissible number of missing packets is set in advance based on the number of error corrections of a decoding scheme capable of performing error correction corresponding to the encoding scheme,
The receiving device according to claim 1, wherein: The decoding method is one of a Viterbi decoding method, a BCH decoding method, and a turbo decoding method.
The receiving device according to claim 2, wherein: Receiving a plurality of packets obtained by dividing a series of data streams;
If there is an unreceived packet, the packet transmission source subtracts the number of packets obtained by subtracting the allowable number of missing packets that is set in advance as the number that allows for missing packets when restoring the series of data strings from the number of unreceived packets. Requesting at least retransmission.
A reception processing method for receiving data. On the computer,
A procedure for receiving a plurality of packets obtained by dividing a series of data streams,
If there is an unreceived packet, the packet transmission source subtracts the number of packets obtained by subtracting the allowable number of missing packets that is set in advance as the number that allows for missing packets when restoring the series of data strings from the number of unreceived packets. A procedure to request at least resend,
The program to execute.

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