JP4143547B2 - Data communication system - Google Patents

Description

  The present invention relates to a data communication system for providing a high-speed data communication service to a user using an existing telephone line.

  ADSL (Asymmetric Digital Subscriber Line) is widely known as a technique for realizing a megabit-class data transmission rate using an existing telephone line metallic cable. For example, by constructing an ADSL system as shown in FIG. 6, a high-speed data communication service can be provided to the user.

  FIG. 6 is a block diagram showing an example of the configuration of the ADSL system. Note that the ADSL system shown in FIG. 6 shows a configuration example in which an Internet service (packet size: 64 bytes to 1518 bytes) is provided to two personal computers 4a and 4b used by a user.

  As shown in FIG. 6, the ADSL system includes an ATU-R (ADSL Transceiver Unit, Remote terminal end) 3 connected to personal computers (PCs) 4a and 4b which are terminal devices used by users, an ATU-R 3 and DSLAM (Digital Subscriber Line Access Multiplexer) connected via a trunk line with a broadband access server device (BAS) 1 etc. that is connected via a telephone line (ADSL line) and provides Internet services Device) 2.

  The ATU-R 3 is an ADSL modem installed on the subscriber side, and is connected to a user terminal device by various interfaces such as Ethernet (Ethernet) and USB (Universal Serial Bus). The DSLAM 2 is a line concentrator that accommodates a plurality of ADSL lines and is bridged to a high-speed, large-capacity trunk line that is arranged on the station side. 3 (SONET) / STM-1 (SDH) or the like. The general configuration of ATU-R3 and DSLAM2 is described in Non-Patent Document 1, for example.

In recent ADSL systems, the physical speed of the ADSL line connecting the ATU-R and the DSLAM has been increased. For example, the physical speed in the downlink direction (DSLAM to ATU-R) is from 1.5 Mbps immediately after the start of the ADSL service. The speed reaches 20 Mbps through 8 Mbps and 12 Mbps, and further speeding up is also being studied.
Hideyuki Motoyama, 4 others, “ADSL System”, FUJITSU ACCESS REVIEW Vol.1 No.1, [Search January 14, 2004], Internet, <URL: http://www.access.fujitsu.com /review/img_18/r2.pdf>

  The existing telephone line (ADSL line) connecting the ATU-R and the DSLAM shown in FIG. 6 is usually a part of an ATM (Asynchronous Transfer Mode) network, and therefore the ATM cell format is used between these devices. Data is sent and received. Therefore, ATU-R and DSLAM require frame conversion processing for converting user data in IP (Internet Protocol) format exchanged between the broadband access server device and the user terminal device into the ATM cell format. Thus, a header portion for ATM is added to the user data.

  Therefore, there is a problem that the transmission efficiency of the user data alone is lowered and the actual user data throughput is less than the physical speed of the telephone line even if the physical speed of the telephone line is increased.

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a data communication system capable of realizing a throughput higher than the physical speed of a telephone line.

In order to achieve the above object, a data communication system according to the present invention includes a first compression / decompression unit for compressing upstream data having an ATM cell format and decompressing the compressed downstream data to restore the ATM cell format data. ATU-R which is a modem installed on the subscriber side,
A second compression / decompression unit that decompresses the compressed uplink data and decompresses the compressed uplink data and restores the ATM cell format data, the compressed uplink data and the compressed downlink data; DSLAM, which is a concentrator disposed on the station side, for transmitting and receiving data to and from the ATU-R;
I have a,
The first compression / decompression unit includes
Encapsulation to be transmitted to the DSLAM by adding frame bits for establishing frame synchronization on the receiving side and FCS bits for detecting transmission data errors on the receiving side to the compressed upstream data Generated data,
The second compression / decompression unit includes
The compressed downlink data is transmitted to the ATU-R by adding a frame bit for establishing frame synchronization on the receiving side and an FCS bit for detecting transmission data errors on the receiving side. This is a configuration for generating encapsulated data.

In addition, the first compression / decompression unit includes:
Of the upstream data composed of the ATM cell format, only the header data is compressed, and the compressed data and payload are frame bits for establishing frame synchronization on the receiving side and transmission data errors on the receiving side. By adding an FCS bit for detecting each, encapsulated data to be transmitted to the DSLAM may be generated,
The second compression / decompression unit
Of the downlink data in the ATM cell format, only the header data is compressed, and the frame data for establishing frame synchronization on the receiving side and the transmission data error on the receiving side in the compressed data and payload Encapsulated data to be transmitted to the ATU-R may be generated by adding an FCS bit for detecting.

  In the data communication system configured as described above, the downlink data in the ATM cell format is compressed by the second compression / decompression unit of DSLAM, and the downlink data compressed by the first compression / decompression unit of the ATU-R is compressed. Decompressing and restoring ATM cell format data improves the transmission efficiency of user data transmitted from DSLAM to ATU-R, and downlink data communication exceeding the physical speed of the telephone line connecting DSLAM and ATU-R Service can be realized.

  Similarly, the ATU-R first compression / decompression unit compresses the upstream data in the ATM cell format, and the DSLAM second compression / decompression unit decompresses the upstream data to obtain the ATM cell format data. As a result of the restoration, the transmission efficiency of user data transmitted from the ATU-R to the DSLAM is improved, and an upstream data communication service that is higher than the physical speed of the telephone line connecting the ATU-R and the DSLAM can be realized.

  In addition, the first compression / decompression unit and the second compression / decompression unit encapsulate the compressed data and transmit them to each other, thereby providing a highly reliable data communication service.

  Furthermore, by compressing only the data in the header part of the ATM cell by the first compression / decompression unit of ATU-R and the second compression / decompression unit of DSLAM, data that exceeds the physical speed of the telephone line as described above. A communication service can be realized, and the first compression / decompression unit of ATU-R and the second compression / decompression unit of DSLAM can be configured easily and inexpensively.

  Next, the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration example of a data communication system according to the present invention. Note that the DSLAM and ATU-R included in the data communication system shown in FIG. 1 have a configuration corresponding to the DSLAM and ATU-R of the ADSL system shown in FIG. .

  As shown in FIG. 1, the DSLAM 2 included in the data communication system of the present invention is an O / E conversion unit that is a communication interface with a broadband access server device that converts an optical signal into an electrical signal or an electrical signal into an optical signal. 21, an ATM processing unit 22 that executes well-known ATM processing (ATM cell generation, retransmission control, etc.), a compressing / decompressing unit 23 that compresses downstream data and decompresses / restores upstream data, and an ADSL line This is a configuration having an ADSL transceiver 24 for transmitting / receiving to / from the ATU-R3.

  The ATU-R3 included in the data communication system of the present invention includes an ADSL transmission / reception unit 31 for transmitting / receiving to / from the DSLAM 2 through an ADSL line, a compression / decompression unit 32 for decompressing / decompressing downlink data, and compressing upstream data. The configuration includes a routing processing unit 33 that performs routing processing of restored data, and a terminal-side transmission / reception unit 34 that is a communication interface with a user terminal device (PC). Downlink data indicates data transmitted in the downlink direction (DSLAM2 to ATU-R3 direction), and uplink data indicates data transmitted in the uplink direction (ATU-R3 to DSLAM2 direction).

  The data communication system according to the present embodiment compresses data on the transmission side, and decompresses and restores the compressed data on the reception side, thereby improving the transmission efficiency of user data and connecting between ATU-R3 and DSLAM2. Realizes data transmission that exceeds the physical speed of the ADSL line.

  For the data compression method, decompression method, and ATM cell data routing method implemented by the compression / decompression units 23 and 32, a known technique may be used, and any method is used to limit the characteristics of the present invention. Since it is not a thing, the detailed description is abbreviate | omitted here.

  In FIG. 1, for ease of explanation, a configuration assuming a case in which downlink data is transmitted from a broadband server device to a user terminal device is shown. However, ATU-R3 and DSLAM2 are broadband server devices. Except for the processing corresponding to the terminal device of the user, the same processing is executed for the ATM cell. That is, when transmitting uplink data from a user terminal device to a broadband server device or the like, the ATU-R 3 generates an ATM cell by an ATM processing unit (not shown), and the DSLAM 2 is restored by a routing processing unit (not shown). The ATM cell data is routed to the destination communication device.

  Next, the operation of the data communication system of the present invention shown in FIG. 1 will be described with reference to FIGS. In the following, the operation of ATU-R3 and DSLAM2 will be described by taking as an example a case in which downlink data is transmitted from the broadband server device to the user terminal device.

  FIG. 2 is a schematic diagram showing a format of compressed data used in the data communication system of the present invention, and FIG. 3 is a schematic diagram showing a configuration example of data after encapsulation generated by the compression / decompression unit shown in FIG. It is.

  When the DSLAM 2 receives user data from the broadband server device, the ATM processing unit 22 executes well-known ATM processing and sends data in the ATM cell format to the compression / decompression unit 23.

  As shown in FIG. 2, the compression / decompression unit 23 compresses ATM cell format data including a header (5 bytes) and a payload (data portion: 48 bytes) at a predetermined compression rate, and compresses the data to 53 bytes or less. Generate data. Furthermore, as shown in FIG. 3, the compressed data is encapsulated by adding frame bits F and FCS (Frame Check Sequence) bits, respectively, and the encapsulated data is sent to the ADSL transceiver 24. The ADSL transmission / reception unit 24 transmits the data received from the compression / decompression unit 23 to the ATU-R 3 via the ADSL line. Note that the frame bit F is for establishing synchronization of each frame (cell) on the receiving side, and is a fixed pattern having a preset number of forward protection stages and backward protection stages. The FCS bit is for detecting an error in transmission data on the receiving side, and an operation result by a preset CRC (Cyclic Redundancy Check) generator polynomial is inserted.

When the ATU-R3 receives the downlink data from the DSLAM2 by the ADSL transmission / reception unit 31, the ATU-R3 establishes synchronization of the frame data (downlink data) received using the frame bit F by the compression / decompression unit 32 , and uses the FCS bit. Error detection of received downlink data is performed.

If there is no error in the received downlink data, the compression / decompression unit 32 extracts the compressed data from the downlink data, decompresses the compressed data, restores the data in the ATM cell format, and then sends it to the routine processing unit 33. . The routing processing unit 33 performs a routing process so that the downlink data is transferred to the specified terminal device according to the information in the header part of the restored ATM cell data.

  Even when uplink data is transmitted from a user terminal device to a broadband server device or the like, the same processing as the above DSLAM2 is performed by the ATU-R3 on the transmitting side, and the same processing as the above ATU-R3 is performed by the DSLAM2 on the receiving side. Then, the encapsulated uplink data including the compressed data is transmitted from the ATU-R3 to the DSLAM2.

  According to the data communication system of the present invention, the downlink data in the ATM cell format is compressed by the compression / decompression unit 23 of the DSLAM2, and the downlink data compressed by the compression / decompression unit 32 of the ATU-R3 is decompressed to obtain the ATM cell format. Since the transmission efficiency of user data transmitted from DSLAM2 to ATU-R3 is improved by restoring the data of, the downlink data communication service at or above the physical speed of the telephone line connecting DSLAM2 and ATU-R3 can be realized. .

  Similarly, the compression / decompression unit 32 of the ATU-R3 compresses the upstream data in the ATM cell format, decompresses the upstream data compressed by the compression / decompression unit 23 of the DSLAM2, and restores the data in the ATM cell format. Since the transmission efficiency of user data transmitted from the ATU-R 3 to the DSLAM 2 is improved, it is possible to realize an upstream data communication service that is higher than the physical speed of the telephone line connecting the ATU-R and the DSLAM.

  Further, the compressed / decompressing units 23 and 32 encapsulate the compressed data and transmit them to each other, thereby providing a highly reliable data communication service.

In the above description, the compression / decompression section 32 of the compression / decompression unit 23 and the ATU-R3 of DSLAM2, although an example of compressing the entire ATM cell including a header section and a payload, the compression of DSLAM2 / decompression unit 23 The ATU-R3 compression / decompression unit 32 may compress only the data in the header portion of the ATM cell as shown in FIG. The process of compressing only the header data may be performed by either the DSLAM2 compression / decompression unit 23 or the ATU-R3 compression / decompression unit 32 , or may be performed by both.

In this case, the compression / decompression unit 23 of DSLAM2 and the compression / decompression unit 32 of ATU-R3 add frame bits F and FCS bits to the data composed of compressed data (5 bytes or less) and payload, respectively, as shown in FIG. Then, it is encapsulated and sent to the ADSL transceivers 24 and 31. Although FIG. 5 shows a configuration in which the FCS bit is added after the compressed data, the FCS bit may be added after the payload. In the configuration in which the FCS bit is added after the compressed data, error detection is performed only for the compressed data. However, since the number of bits of the FCS can be reduced, the transmission efficiency of user data is further improved. By compressing only the header part of the ATM cell in this way, a data communication service exceeding the physical speed of the telephone line can be realized as described above, and the compression / decompression parts 23 and 32 of DSLAM2 and ATU-R3 can be simplified. And can be configured at low cost.

  In the above description, a data communication system in which ATU-R3 and DSLAM2 are connected by an ADSL-compatible telephone line has been illustrated. (High data rate Digital Subscriber Line), VDSL (Very High Speed Digital Subscriber Line) and the like are also applicable to data communication systems using xDSL (x Digital Subscriber Line) technology, or other technologies.

It is a block diagram which shows the example of 1 structure of the data communication system of this invention. It is a schematic diagram which shows the format of the compression data used with the data communication system of this invention. It is a schematic diagram which shows one structural example of the data after encapsulation produced | generated by the compression / decompression part shown in FIG. It is a schematic diagram which shows the other format of the compression data used with the data communication system of this invention. It is a schematic diagram which shows the other structural example of the data after encapsulation produced | generated in the compression / decompression part shown in FIG. It is a block diagram which shows one structural example of an ADSL system.

Explanation of symbols

2 DSLAM
3 ATU-R
21 O / E conversion unit 22 ATM processing unit 23, 32 Compression / decompression unit 24, 31 ADSL transmission / reception unit 33 Routing processing unit 34 Terminal side transmission / reception unit

Claims (4)

ATU which is a modem installed on the subscriber side, comprising a first compression / decompression unit for compressing upstream data in ATM cell format and decompressing the compressed downstream data to restore ATM cell format data -R,
A second compression / decompression unit that decompresses the compressed uplink data and decompresses the compressed uplink data and restores the ATM cell format data, the compressed uplink data and the compressed downlink data; DSLAM, which is a concentrator disposed on the station side, for transmitting and receiving data to and from the ATU-R;
I have a,
The first compression / decompression unit includes
Encapsulation to be transmitted to the DSLAM by adding frame bits for establishing frame synchronization on the receiving side and FCS bits for detecting transmission data errors on the receiving side to the compressed upstream data Generated data,
The second compression / decompression unit includes
The compressed downlink data is transmitted to the ATU-R by adding a frame bit for establishing frame synchronization on the receiving side and an FCS bit for detecting transmission data errors on the receiving side. A data communication system for generating encapsulated data. The first compression / decompression unit includes
Of the upstream data composed of the ATM cell format, only the header data is compressed, and the compressed data and payload are frame bits for establishing frame synchronization on the receiving side and transmission data errors on the receiving side. The data communication system according to claim 1, wherein the encapsulated data to be transmitted to the DSLAM is generated by adding an FCS bit for detecting the data. The second compression / decompression unit
Of the downlink data in the ATM cell format, only the header data is compressed, and the frame data for establishing frame synchronization on the receiving side and the transmission data error on the receiving side in the compressed data and payload The data communication system according to claim 1, wherein the encapsulated data to be transmitted to the ATU-R is generated by adding an FCS bit for detecting each of them. The data communication system according to any one of claims 1 to 3 , wherein the ATU-R and the DSLAM are connected by an ADSL-compatible telephone line.

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