JP3462314B2 - Packet communication device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet communication device, and more particularly to a packet communication device capable of transmitting data at high speed using a plurality of channels. 2. Description of the Related Art Conventionally, when a large amount of data such as image data is to be transmitted from outside, it is necessary to use, for example, a portable satellite ground station or a microwave relay device. However, it was expensive and large, and it was difficult to use it easily. Therefore, when image data is temporarily stored in the storage device and transmitted, for example, a MODEM
To perform data transmission by connecting. Further, when transmitting data, a transmission error occurs. Therefore, the error can be reduced by packetizing the data and retransmitting the packet in which the error is detected. [0003] In data transmission using a portable telephone as described above, the transmission speed is at most about 4800 bps due to the use of MODEM. Therefore, there is a problem in that it is impossible to transmit image data in real time, and much time is required to transmit a large amount of data. Furthermore, when data is divided and transmitted using a plurality of transmission channels, if the transmission quality of a specific channel is poor, it takes time for all data to be aligned on the receiving side, and transmission delay increases. Alternatively, there is a problem that the data transmission efficiency is reduced. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a communication device capable of transmitting a large amount of data in a short time using a communication channel of an arbitrary speed. [0004] The present invention provides a method for transmitting data.
Packet, and the resulting packet is transmitted to multiple
A communication apparatus for transmitting assigned to transmission channels, Pas
The packetizing means includes error check data and
Includes a means for assigning a number, and packets for each channel in order
Distribution means for allocating a predetermined number of packets, and transmission within a predetermined time
Least retransmitted number in error-free channel
Retransmission means for allocating a retransmission packet to a new channel . According to the present invention, with such a configuration, it is possible to prevent delay due to repeated retransmission of a retransmission packet in a channel with poor transmission quality, and reduce transmission variations among a plurality of channels. Therefore, even if the transmission quality of a specific channel is poor, the transmission delay does not increase and the transmission efficiency is improved. Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a packet communication device to which the present invention is applied. The packet transmission device 1 receives, for example, an image signal from the VTR 2, encodes the image signal, and temporarily stores the encoded image signal. Then, the packetized M
The signal is converted into an AC signal by an ODEM (modulator / demodulator) and output to the mobile phones 3 and 4. The packet receiving device 8 connected to the mobile phones 3 and 4 by the base station 5 and the communication network 6 of the mobile phone system demodulates an AC signal by a built-in MODEM, detects a packet, and extracts data. The received data is temporarily stored and output to a display device 8 such as a monitor, for example. The CPU 10 in the packet transmission device 1
The entire packet transmission device 1 is controlled based on the control program stored in the OM 11. The RAM 12 is used as a work area and a buffer. The image input circuit 13 inputs an image signal from a VTR, a camera, etc.
The D / D conversion is performed, and encoding / data compression such as MPEG is performed.
The disk 14 is a large-capacity storage device such as a magnetic disk device, and stores encoded image data and the like. The plurality of communication devices 15 and 16 are, for example, RS-23, respectively.
CPU including 2C transmission control circuit and MODEM circuit
The packet data is converted into a serial signal by the control of
The output is modulated by ODEM. Also, a response signal returned from the packet receiving device 7 is received and demodulated,
The signal is converted into a parallel signal and stored in the reception buffer. If the mobile telephones 3 and 4 have digital signal input terminals for data transmission, the MODEM is unnecessary. The CPU 20 in the packet receiving device 7
The entire packet receiving device 7 is controlled based on the control program stored in the OM 21. The RAM 22 is used as a work area and a buffer. The image output circuit 23 reads out the received and stored image signal,
Decoding and D / A conversion are performed and output. Disk 24
Is a mass storage device such as a magnetic disk device,
The received image data and the like are stored. Multiple communication devices 2
Reference numerals 5 and 26 include, for example, an RS-232C transmission control circuit and a MODEM circuit, respectively.
The signal is demodulated by the EM, converted into a parallel signal, and output to the reception buffer. Also, the response data indicating the reception result is converted into a serial signal, modulated by the MODEM, and output. Although FIG. 1 shows a configuration for performing one-way communication, it is also possible to perform bidirectional full-duplex communication between both disks with the same configuration. FIG. 2 is a functional block diagram showing the transmission control system of the present invention. The data 30 in the disk device of the packet transmission device 1 is converted by the packetizing unit 31 into a fixed-length packet having a format similar to, for example, an HDLC frame. The packet is added with serial number data and error detection data such as a CRC check code. The generated packet is distributed by the distribution unit 32 to a plurality of transmission channels. The distribution method is arbitrary, but a distribution method is adopted in which the receiving side can detect a missing packet in each transmission channel and does not delay only a specific packet. For example, if the number of transmission channels is 4, packets are assigned to each channel one by one in order from the serial number 0. Therefore, the first transmission channel has 0,
Packets are allocated in the order of 4, 8,... Each of the communication control units 33 and 34 of each channel has a transmission buffer, and when a buffer becomes available, the distribution unit 32 transfers the next packet allocated to the channel. [0010] The communication control units 36 and 37 of each channel in the packet receiving device 7 have a receiving buffer for storing received packets. Then, an error check is performed, and if normal, the packet is transferred to the unpacketizing unit 38, but if an error, the packet is discarded. The response unit 40 is notified of the reception result and the serial number. The unpacketizer 38 extracts data from the packets received from each channel, and arranges them in order of serial numbers to reproduce the original data. The response section 40 receives the reception result and the serial number information from each of the communication control sections 36 and 37, and if the reception is normal and there is no packet missing, an ACK (acknowledgement) signal including the serial number information Will be returned. If there is an error, a NACK (negative acknowledgment) is sent back. NACK for the dropped packet is returned. The channel that returns the response signal may be the channel that received the packet, or the same response signal may be returned on all channels. Further, the signal may be returned using the channel with the smallest error rate. Retransmission control unit 35 in packet transmitting apparatus
Analyzes a response signal received from an arbitrary channel and performs retransmission control. When the ACK is received, the transmission channel is determined from the serial number, and the corresponding packet in the transmission buffer corresponding to the channel is deleted. Also, NA
When the CK is received, a transmission channel to be retransmitted is determined by a method described later, and if the channel is different from the original channel, the packet data is moved to the buffer of the retransmission channel. At this time, the retransmission packet may be interrupted at the head of the transmission buffer so that the packet is transmitted with priority. FIG. 4A is a flowchart showing a packet transmission process. In step S1, the CPU
Reference numeral 10 packetizes data such as images stored in the disk 14. The format may be, for example, the same format as the HDLC frame. The packet is added with serial number data and error detection data such as a CRC check code. In step S2, the generated packet is allocated to each transmission channel. As an allocation method, for example, when the number of transmission channels is four
If so, packets are assigned to each channel one by one in order from the serial number 0. Therefore, packets are allocated to the first transmission channel in the order of 0, 4, 8,.... In step S3, the packets assigned to the transmission channel buffers of each transmission channel are transferred in ascending order of the serial number. In step S4, the availability of each channel buffer is monitored. The packet in the channel buffer is erased when the transmission is completed normally, and a space is left. In step S4, when there is free space in any of the channels, the process proceeds to step S5. In step S5, it is determined whether or not there is still a packet to be transmitted to the corresponding channel. If the result is affirmative, the process proceeds to step S3, but if negative, the process proceeds to step S6. In step S6, it is determined whether or not transmission has been completed in all channels. If the result is negative, the process proceeds to step S4, but if affirmative, the process ends. FIG. 3 is a flowchart showing a packet receiving process of the response unit 40 in the receiving device. The communication control units 36 and 3 of each channel in the packet receiving device 7
A reception buffer 7 stores received packets. In step S20, it is determined whether or not the result of the error check is OK. If the result is affirmative, the process proceeds to step S21, but if the result is negative, the process proceeds to step S24. In step S24, the received packet is discarded, and in step S25, a NACK response including the serial number of the packet is returned. If the packet has been received normally, an ACK is returned in step S21. Step S
At 22, the serial number is compared with a serial number sequence to be originally received in the channel, and it is determined whether or not there is any omission. The serial number sequence to be originally received is generated based on distribution rule information of the distribution unit 32 in the transmitting device, which is notified or set in advance. In the case of a retransmitted packet, there is a possibility that the channel is to be received on another channel. However, since the channel to be originally received is determined from the serial number, it is determined that the channel is missing. If a missing is detected in step S22, the process proceeds to step S23, where NACK including the missing serial number information is included.
Returns a response. As described above, the channel that returns the response signal may be the channel that received the packet,
The same response signal may be returned on all channels. Further, the signal may be returned using the channel with the smallest error rate. FIG. 4B is a flowchart showing a response reception interrupt process in the transmitting device. This process is started each time a response signal is received on an arbitrary channel. In a predetermined area of the RAM 12, an error flag and a retransmission number counter (not shown) are provided for each transmission channel. In step S10, if the received response signal is ACK, an error flag corresponding to the channel that transmitted the packet is set to 0,
Set to 1 if NACK. ACK
If so, an instruction to delete the packet in the transmission buffer is also issued. In step S11, it is determined whether or not there is a packet to be retransmitted that has not been allocated to a channel. If the result is negative, the process is terminated. Transition. In step S12, it is determined whether or not there is a channel to which a retransmission packet has not been allocated. If the result is negative, the process ends. If the result is positive, the process proceeds to step S13. In step S13, it is determined whether or not there is a channel whose error flag is 0 among channels to which no retransmission packet is assigned,
If the result is negative, the process ends. If the result is positive, the process proceeds to step S14. In step S14, step S1
Among the channels whose error flag is 0 detected in step 3, the channel with the least number of retransmissions is selected, the packet to be retransmitted is assigned to the channel, and the retransmitted packet is transferred. In step S15, 1 is added to the retransmission counter for the channel. By such processing, a retransmission packet is allocated to each channel according to a predetermined rule, so that the possibility of transmission delay for a specific channel is reduced. Although the embodiments have been disclosed above, the following modified examples are also conceivable. In a packet in which an error is detected, if the error check range includes a serial number, it cannot be determined whether the serial number is incorrect. Therefore, a different error check code may be added to the data and the serial number information, or an error check code may be added to only the serial number separately from the entire error check code. Steps S22 and S23 may be omitted, or step S25 may be further omitted and only ACK may be returned without detecting omission on the receiving side. In this case, the transmitting side detects the omission from the response and retransmits the response. This eliminates the need for the receiving side to know the packet arrival order in advance,
Packets can be freely distributed on the transmission side. For example, every time a transmission buffer of an arbitrary channel becomes available, packets can be allocated in the order of serial numbers. When the transmission channel is disconnected halfway, for example, neither ACK nor NACK may be returned. Therefore, a timer may be provided for each packet being transmitted, and packets that do not respond after a predetermined time may be retransmitted from another channel. It is not necessary to assign a unique number to the entire data, but it is sufficient to assign a serial number repeated with a finite number of digits. In this case, the number of digits is set to a number that can represent a value larger than the expected variation in the arrival time of the packet. ) To transmit the packet. In the present invention, the transmission channel is not limited to a mobile phone,
An arbitrary transmission line such as a normal telephone line, ISDN, or a dedicated line can be used. It is also possible to use transmission paths of different types in a mixed manner. If the transmission rates are different in each channel, a number of packets proportional to the transmission rates may be allocated. In the embodiment, an example in which a full-duplex line is used has been disclosed. However, the present invention can be applied to a half-duplex line or a unidirectional line. In this case, a dedicated line may be provided for returning a response. Although a method in which data input and output are once stored in a disk device or the like is disclosed, transmission can be performed in real time if the transmission speed of the entire transmission channel is faster than the input data speed. The type of data is arbitrary. As described above, according to the present invention,
Packetize the data and the resulting packet
In a communication device that transmits a packet by assigning the packet to a plurality of transmission channels,
Data and means for assigning numbers.
Distribution means for allocating a predetermined number of packets to the
Number of retransmissions in a channel in which no transmission error occurred in the interval
Since retransmission means for allocating a retransmission packet to a channel having the least number of transmissions is included, it is possible to prevent a delay due to retransmission of a retransmission packet repeatedly in a channel having poor transmission quality, and thereby to prevent transmission variation among a plurality of channels. Can be reduced. Therefore,
Even if the transmission quality of a specific channel is poor, there is an effect that transmission delay does not increase and transmission efficiency improves.
Further, when used for transmitting image data, it is possible to prevent omission of a part of data, and it is possible to smoothly execute video reproduction in the middle of data transmission.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a packet communication device to which the present invention is applied. FIG. 2 is a functional block diagram showing a transmission control method according to the present invention. FIG. 3 is a flowchart illustrating a packet reception process. FIG. 4 is a flowchart illustrating a packet transmission process and a response reception interrupt process. [Description of Signs] 1 ... Packet transmitting device, 2 ... VTR, 3/4 ... Mobile phone, 5 ... Base station, 6 ... Communication network, 7 ... Packet receiving device,
8 Display device

────────────────────────────────────────────────── (5) References JP-A-6-152600 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 29/08 H04L 1/16 H04L 12 / 56 H04Q 7/38

Claims (1)

(57) [Claim 1] In a communication device for packetizing data and allocating the generated packet to a plurality of transmission channels and transmitting the packet, the packetizing means includes error check data and Distribution means for assigning a predetermined number of packets to each channel in sequence, and retransmission means for allocating a retransmission packet to a channel having the least number of retransmissions within a channel in which a transmission error has not occurred within a predetermined time. A packet communication device comprising: