JP3008893B2 - Packet multiplexing apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable length packet having a header including packet length information, which is used for packet communication, and having a predetermined data length and determining the position of the first data of the variable length packet. An apparatus and method for multiplexing into a fixed length frame having a header including a first header pointer as shown.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram showing an example of a conventional packet multiplexer. In this figure, a variable length packet 907 is temporarily stored in a storage buffer 901 and is read out by a fixed amount by a data input control unit 902. From the data input control unit 902, the storage buffer 9
Each time a variable-length packet is read from 01, a count-up pulse 9 indicating the read amount, that is, the number of bytes.
08 is input to the up counter 903 and counted up.

When the variable-length packet has been read up to the beginning of the header of the next variable-length packet 907, that is, when all the variable-length packets 907 have been read, the count value 909 of the up counter 903 is changed to the header generation unit 904.
Is output to Using the count value 909, the header generation unit 904 uses the fixed length including the first data of the first data of the variable length packet, that is, the first header pointer indicating the position of the head of the variable length packet in the fixed length frame. Generate the frame header.

On the other hand, the read variable-length packet data is temporarily stored in another storage buffer 905, and after data having a length satisfying the data zone of the fixed-length frame is stored in the storage buffer 905, The fixed-length frame header 911 is first output from the data output control unit 906, and then the fixed-length frame 912 is output by outputting the data 910.

[0005]

However, the prior art has the following problems.

A first problem is that in the conventional technique shown in FIG. 9, a buffer 90 for storing input variable-length packets is used.
In addition to (1), another storage buffer 905 for storing data read from the storage buffer 901 at the time of generation of the fixed-length frame header is required, resulting in an increase in circuit size. The reason is that the first header pointer is directly calculated from the read amount of the variable-length packet, so that the data of the variable-length packet is still being read when the fixed-length frame header is created.

A second problem is that in the conventional technique shown in FIG. 9, the delay time from the input of a variable-length packet to the output of a fixed-length frame increases. The reason is that after reading data from the packet accumulation buffer 901,
This is because data is stored in another storage buffer 905 in order to generate a fixed-length frame header.

The present invention has been made in view of the above problems, and has as its object to reduce the number of storage buffers to reduce the size and weight, reduce the power consumption, and simplify the circuit / device configuration. It is another object of the present invention to provide a packet multiplexing apparatus and method capable of improving transmission efficiency by reducing the delay time of generating a fixed-length frame.

[0009]

According to the gist of the present invention, a variable length packet having a header including packet length information is input, and the variable length packet is replaced with a first header indicating the position of the first data of the variable length packet. In a packet multiplexing apparatus for multiplexing into a fixed-length frame having a header including a pointer, a buffer memory for temporarily storing variable-length packets, packet reading means for reading variable-length packets from the buffer memory, and packet reading means Reading amount detecting means for detecting the variable length packet reading amount; packet length extracting means for extracting packet length information from the header of the variable length packet; fixed length including a first header pointer from the variable length packet reading amount and the packet length information A header generating means for generating a header of the frame; It consists in packet multiplexing apparatus characterized by comprising a fixed-length frame generating means for generating a fixed-length frame by a header generated by the length packet and the header generation unit. Further, the gist of the present invention is a packet multiplexing method for multiplexing a variable length packet having a header including packet length information into a fixed length frame having a header including a first header pointer indicating the position of the first data of the variable length packet. In the conversion method, a variable length packet read amount of a variable length packet is detected, packet length information is extracted from a variable length packet header, and a fixed length frame including a first header pointer is extracted from the variable length packet read amount and the packet length information. A packet multiplexing method is characterized in that a header is generated and a fixed-length frame is created from the variable-length packet and the header.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First Embodiment FIG. 1 is a block diagram showing a packet multiplexing apparatus according to a first embodiment of the present invention, and FIG. 2 is a principle diagram of multiplexing from variable-length packets to fixed-length frames. is there.

As shown in FIG. 1, the variable length packet 106
Is input to the accumulation buffer 101, and the accumulation buffer 1
01 is temporarily stored. The output of the storage buffer 101 is connected to a data input / output control unit 102, and the variable length packets stored in the storage buffer 101 are read by the data input control unit 102 in units of a predetermined read amount. The read unit differs depending on the protocol. In CCCDS described later, the minimum unit is octet (= 8 bi).
t), 4 octets (= 32 bits) in TCP / IP
It is.

The data input / output control unit 102 has a counter (not shown) for managing the capacity of the variable-length packets 106 stored in the storage buffer 101.
The count value is incremented each time the variable length packet 106 is written to 01, and the count value is decremented each time the variable length packet 106 is read from the accumulation buffer 101. This data input / output control unit 102
Variable length packet 10 read from accumulation buffer 101
6, the packet length information 108 is extracted from the header of the down counter 1 as the initial value of the down counter 103.
03 is output. Generally, the packet length refers to the length of the packet including the header, but as described later, the CCS
In the DS, the packet length is set to the length of the data zone (the unit is equal to the read unit described above) -1. Also, the data input / output control unit 102 generates a countdown pulse 109 indicating the read amount every time data is read from the accumulation buffer 101, and the countdown pulse 109 is input to the down counter 103 and the count value is decremented. Is done.

Further, the data input / output control unit 102 is connected to the output selector 105 for switching the fixed-length frame output 114 between a header portion and a data portion, and converts the data 107 read from the accumulation buffer 101 into fixed-length data 112. To the output selector 105. The switching signal 111 for the header / data output of the fixed-length frame is generated by the data input control unit 102 and the output selector 1
05 and the header generation unit 104.

The down counter 103 is connected to the fixed-length frame header generation unit 104 and has a counter value 110
Is input to the header generation unit 104. Header generation unit 104
Is connected to the output selector 105, and inputs the generated fixed-length frame header 113 to the output selector 105.

FIG. 2 shows the principle of multiplexing a variable length packet 201 into a fixed length frame 202. The variable length packet 201 has packet length information (Packet Length) 203 indicating the length of the data portion in the packet header. A plurality of variable length packets 201
When multiplexing to 02, if the length of the data portion of the variable length packet 201 is longer than the length of the data portion of the fixed length frame 202, the variable length packet 201 is divided into a plurality of fixed length frames 202. A first header pointer (First Header Pointer) 204 indicating the first header position of the variable length packet 201 is provided in the header portion of the fixed length frame 202.
There is. In the example of FIG. 2, the head position of “PACKET # k + 1” 205 corresponds to the first header pointer 204.

Next, the operation of the packet multiplexing apparatus according to the present embodiment will be described in detail with reference to FIGS. 1 and 3. In particular, a fixed-length frame header generating method using a down counter which is a feature of the present apparatus will be described. This will be described in detail with reference to the flowchart of FIG.

The packet multiplexer shown in FIG. 1 multiplexes and divides the input variable-length packet 106 into fixed-length packets 112, adds a fixed-length frame header 113, and outputs a fixed-length frame 114. Device.

First, the variable length packet 106 input from the outside is temporarily stored in the storage buffer 101.
When the storage amount exceeds the data zone length of one fixed-length frame, the data input / output control unit 102 controls the storage buffer 1
The data reading from 01 is started.

When the apparatus is started, the down counter 10
The value of 3 is initialized to 0 (step 301). Thus, at the time of the first data read, the first header pointer can be set to 0 (step 302).

The data input / output control unit 102 outputs a fixed-length frame header 113 to the header generation unit 104 and the output selector 105 by a header / data switching signal 111 before reading data from the storage buffer 101. The fixed-length frame header 113 is generated by the header generation unit 104, and its first header pointer is the down counter 1 at the end of the previous fixed-length frame output.
03 (Step 302).

After outputting the header 113, the data input / output control unit 102 switches the header / data switching signal 111 to data, and starts reading data from the accumulation buffer 101. At this time, if the value of the down counter 103 is 0 (step 303), the data read from the accumulation buffer 101 is read as a variable length packet header (step 304), and the packet length information 108 is extracted and set in the down counter 103. (Step 30
5). At the same time, the variable length packet header is output selector 1
05, and the output selector 105 outputs the fixed-length frame output 114 (step 306).

After the output of the variable-length packet header and when the value of the down counter 103 is not 0, the data read from the accumulation buffer 101 is read as the data portion of the variable-length packet and output to the output selector 105. The data is output as the fixed-length frame output 114 (step 307). At the same time, a countdown pulse 109 is output to the down counter 103, and the value of the down counter 103 is decremented (step 308).

Steps 303 to 308 are repeated until data of the data length of the fixed-length frame 114 has been read. After reading the data of the data length (step 309), the process returns to step 302, where the next fixed-length frame header is generated from the value of the down counter 103, and the process is repeated.

In the packet multiplexing apparatus according to the present embodiment, when the variable length packet 106 is read from the storage buffer 101, information on the packet length is read from the variable length packet header and multiplexed into a fixed length frame. 101 to variable-length packet data 112
By reading out the counter value, by decrementing the counter value by the read capacity, the remaining packet data length at that time can be ascertained. Therefore, fixed-length frame 1
At the time of generation of 14, the remaining packet data length indicates the position of the next packet data, which can be used as the first header pointer of the next fixed-length frame header.

As described above, the remaining packet data length is determined before the data of the fixed-length frame to be generated is read from the storage buffer. The header of the long frame 114 can be generated, and it is not necessary to have a storage buffer for generating a fixed-length frame header as in the related art. As a result, the size and weight of the device can be reduced, the power consumption can be reduced, and the circuit / device configuration can be simplified. This effect is a great advantage particularly when the packet multiplexing device of the present embodiment is used as a space-borne device. Further, since the fixed-length frame can be output without being stored in the storage buffer, the delay time from the input of the variable-length packet to the output of the fixed-length frame can be reduced. -2nd Embodiment-

FIG. 4 shows a second embodiment of the present invention, in which a CCSDS packet, which is a variable-length packet, is converted into a fixed-length frame, M_PDU (Multiplexing Protocol Data Uniform).
FIG. 5 is a block diagram showing an M_PDU generation device multiplexed in t), and FIG. 5 is a principle diagram of multiplexing the CCSDS packet format 501 and the M_PDU format 502 according to the CCSDS recommendation (CCSDS 701.0-B-2).

As shown in FIG. 4, M_PD according to the present embodiment
In the U generation device, the CCSDS packet 406 is input to the accumulation buffer 401 and is temporarily accumulated in the accumulation buffer 401. The output of the accumulation buffer 401 is connected to the data input / output control unit 402,
Is read by the data input control unit 402.

The data input / output control unit 402 is connected to the down counter 403 in order to set the packet length information (Packet Lentgh) 408 extracted from the CCSDS packet header read from the accumulation buffer 401 into the down counter 403. Each time data is read from the accumulation buffer 401, a countdown pulse 409 is read.
The countdown pulse 409 is input to the down counter 403, and the value of the down counter 403 is decremented.

Further, the data input / output control unit 402
_PDU output is connected to an output selector 405 for switching between an M_PDU header portion and an M_PDU data portion, and data 407 read from the accumulation buffer 401.
Output selector 405 as M_PDU data 412
To enter. The switching signal 411 for the header / data output of the M_PDU is generated by the data input control unit 402,
It is input to the output selector 405 and the M_PDU header generation unit 404 described above.

The down counter 403 is connected to the M_PDU header generation unit 404, and converts the counter value 410 to M
_PDU header generation unit 404. The M_PDU header generation unit 404 is connected to the output selector 405 described above, and inputs the generated M_PDU header 413 to the output selector 405.

FIG. 5 shows that the CCSDS packet 501 is
An example of multiplexing to a PDU 502 is shown. CCSD
The S packet 501 is a variable length packet, and has a Packet Length 503 indicating the length of the data portion in the packet header. A plurality of CCSDS packets are fixed-length M_PDU
When multiplexing to CSDDS packet 501, the length is M
If the data length is longer than the _PDU data length, the CCSDS packet 501 is divided into a plurality of M_PDUs 502. M_P
The DU header has a first header pointer 504 indicating the position of the first packet header. In the example of FIG. 2, the first position of “CCSDS PACKET # k + 1” 505 corresponds to the First Header Pointer 504.

Next, the operation of the M_PDU generation device of the present embodiment will be described in detail with reference to FIGS. 4 and 6, and in particular, the M_PD using a down counter which is a feature of the present device.
The U header generation method will be described in detail with reference to the flowchart in FIG.

The M_PDU generation device multiplexes and divides the input variable-length CCSDS packet 406 into fixed-length M_PDU data 412,
3 is a device that adds 3 and outputs it as M_PDU 414.

First, an externally input CCSDS packet is temporarily stored in a storage buffer 401. When the storage amount exceeds the 1M_PDU length, the data input / output control unit 402 starts reading data from the storage buffer 401.

When the apparatus is started, the down counter 40
The value of 3 is initialized to 0 (step 601). As a result, at the time of the first data read, the First Header
Pointer can be set to 0 (step 602).

Before reading data from the storage buffer 401, the data input / output control unit 402 sends an M_PDU header 4 to the M_PDU header generation unit 404 and the output selector 405 by using a header / data switching signal 411.
13 is output. The M_PDU header 413 contains M_P
The DU header generation unit 404 generates the M_P
It is generated from the value of the down counter 403 at the end of the DU output (step 602).

After outputting the M_PDU header 413, the data input / output control unit 402 switches the header / data switching signal 411 to M_PDU data, and starts reading data from the accumulation buffer 401. At this time, if the value of the down counter 403 is 0 (step 603), the data read from the accumulation buffer 401 is read as a CCSDS packet header (step 604), and the packet Len is read.
gth is extracted and set in the down counter 403 (step 605). The data read at the same time is CCS
The DS packet header is output to the output selector 405,
The output selector 405 outputs the output as the M_PDU output 414 (step 606).

After the output of the CCSDS packet header and when the value of the down counter 403 is not 0, the data read from the accumulation buffer 401 is read as the data part of the CCSDS packet and output to the output selector 405, and the output selector 405 outputs the M_PDU output. 414 (step 607). At the same time, a countdown pulse 409 is output to the down counter 403, and the value of the down counter 403 is decremented (step 60).
8).

Steps 603 to 608 are repeated until the data of the M_PDU length has been read. M_
After reading the data for the PDU length (step 60)
9), returning to step 602, generating the next M_PDU header from the value of the down counter 403, and repeating the processing.

Third Embodiment Next, a packet multiplexing apparatus according to a third embodiment of the present invention will be described with reference to FIG.

In the packet multiplexing apparatus shown in FIG. 1, an input variable-length packet is first stored in the storage buffer 101, and then the packet is read out from the storage buffer 101 when the packet is read out.
In the packet multiplexer shown in FIG. 7, the variable length packet is input to the data input control unit 702, the input data is stored in the packet storage buffer 701, and the header of the input packet is extracted. From Pa
The packet length is extracted and the packet length accumulation buffer 70 is extracted.
Store in 3.

At the time of data output, the packet length is not extracted, but the packet length accumulation buffer 703 is used instead.
And set it in the down counter 705. The data output control unit 704 includes a packet accumulation buffer 701
, And outputs a countdown pulse to the down counter 705 each time data is read. When outputting the header of the fixed-length frame, the output selector 707 selects the header by the header / data switching signal, and the header generation unit 706 outputs the fixed-length frame header generated using the value of the down counter 705. When outputting data,
The output selector 707 selects data by the header / data switching signal, and the data output control unit 701 outputs the data read from the packet accumulation buffer 701.

Fourth Embodiment Next, a packet multiplexing apparatus according to a fourth embodiment of the present invention will be described with reference to FIG.

In the packet multiplexing apparatus shown in FIG. 1, the first header pointer is calculated by setting the packet length of the variable length packet in the down counter 103 and decrementing it, as shown in FIG. In the multiplexer, the remaining output data length of the fixed-length frame data is managed by the down counter 803. Data input / output control unit 80
2 inputs the packet length of the variable-length packet to the header generation unit 804 when reading the variable-length packet header from the accumulation buffer 801. The header generation unit 804 compares the packet length with the remaining amount of the fixed-length frame data. Length ≧
In the case of the remaining fixed-length frame data, the packet length minus the fixed-length frame data remaining is calculated, and this is used as the first header pointer of the next fixed-length frame header.

In the present embodiment, the present invention is not limited to this, and can be applied to a packet multiplexing apparatus suitable for applying the present invention.

[0047]

Since the present invention is configured as described above, the following effects can be obtained.

The first effect is that the number of storage buffers that the device should have can be reduced. As a result, the size and weight of the device can be reduced, the power consumption can be reduced, and the circuit / device configuration can be simplified. The reason is that the packet multiplexing device of the present invention can generate a fixed-length frame header before starting to read variable-length packet data from the storage buffer. This is because only a buffer for storing variable-length packets can be used, and there is no need to have another buffer for storing data read from the storage buffer when generating a fixed-length frame header until header generation is completed.

The second effect is that the delay time from the input of a variable length packet to the output of a fixed length frame can be reduced. The reason is that the fixed-length frame header can be generated before the variable-length packet is read from the accumulation buffer, so that it is not necessary to accumulate the data in another buffer, and it is necessary to multiplex the data into the fixed-length frame. This is because if a variable-length packet is input, it can be output as a fixed-length frame immediately.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a packet multiplexer according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of generating a fixed-length frame by multiplexing variable-length packets.

FIG. 3 is a flowchart for explaining the operation of the packet multiplexer of the first embodiment.

FIG. 4 is a block diagram illustrating an M_PDU generation device according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of multiplexing CCSDS packets to generate M_PDU.

FIG. 6 is a flowchart illustrating an operation of the M_PDU generation device according to the second embodiment.

FIG. 7 is a block diagram illustrating a packet multiplexer according to a third embodiment of the present invention.

FIG. 8 is a block diagram illustrating a packet multiplexer according to a fourth embodiment of the present invention.

FIG. 9 is a block diagram illustrating an example of a conventional packet multiplexer.

[Explanation of symbols]

 Reference Signs List 101 accumulation buffer 102 data input / output control unit 103 down counter 104 header generation unit 105 output selector 201 variable length packet 202 fixed length frame 203 packet length 204 first header pointer 401 accumulation buffer 402 data input / output control unit 403 down counter 404 header generation Unit 405 output selector 501 variable-length packet 502 fixed-length frame 503 packet length 504 first header pointer 701 packet accumulation buffer 702 data input control unit 703 Packet Length accumulation buffer 704 data output control unit 705 down counter 706 header generation unit 707 output selector 801 Accumulation buffer 802 data input control unit 803 down counter 804 header generation unit 805 data output control unit 901 accumulation buffer 902 data input control unit 903 up-counter 904 the header generating unit 905 accumulates the buffer 906 the data output control unit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04L 12/56 H04L 12/28

Claims (6)

(57) [Claims] 1. A variable length packet having a header including packet length information is input, and the variable length packet is converted into a fixed length frame having a header including a first header pointer indicating the position of the first data of the variable length packet. In a packet multiplexing apparatus for multiplexing, a buffer memory for temporarily storing the variable-length packets, packet reading means for reading the variable-length packets from the buffer memory, and detecting a variable-length packet read amount by the packet reading means A packet length extracting unit for extracting packet length information from a header of the variable length packet, a first length based on the variable length packet reading amount and the packet length information.
Header generating means for generating a header of a fixed-length frame including a header pointer; fixed-length generating the fixed-length frame from the variable-length packet read by the packet reading means and the header generated by the header generating means A packet multiplexing device comprising a frame creating means. 2. The header generating means includes subtraction means for subtracting the packet length information extracted by the packet length extraction means according to a variable length packet read amount by the packet reading means. 2. The packet multiplexing apparatus according to claim 1, wherein the first header pointer is calculated based on a result of the subtraction. 3. A fixed length frame output amount detecting means for detecting a fixed length frame output amount by the fixed length frame generating means, wherein the header length generating means includes a packet length information extracted by the packet length extracting means. 2. The packet multiplexing apparatus according to claim 1, wherein the first header pointer is calculated based on the fixed length frame output amount detected by the fixed length frame output amount detection means. 4. A packet multiplexing method for multiplexing a variable length packet having a header including packet length information into a fixed length frame having a header including a first header pointer indicating the position of the first data of the variable length packet. Detecting a variable length packet reading amount of the variable length packet, extracting packet length information from a header of the variable length packet, and extracting a first packet length information from the variable length packet reading amount and the packet length information.
A packet multiplexing method comprising: generating a header of a fixed-length frame including a header pointer; and creating the fixed-length frame by using the variable-length packet and the header. 5. The packet according to claim 4, wherein said packet length information is subtracted according to said variable length packet readout amount, and said first header pointer is calculated based on a subtraction result of said subtraction means. Multiplexing method. 6. The packet according to claim 4, wherein the fixed-length frame output amount is detected, and the first header pointer is calculated based on the packet length information and the fixed-length frame output amount. Multiplexing method.