JPH07193578A - Communication system - Google Patents

Abstract

PURPOSE:To secure compatibility with a conventional existed system and to improve the deterioration of performance owing to the lack of information in the middle of transmission by providing an idle area detection means detecting an idle area in a data string and a redundancy transmission means which redundantly transmits a part of the data string through the use of the detected idle area. CONSTITUTION:Protocol processing parts 1a and 1b, redundancy work parts 2a and 2b which detect the idle area from a frame which the processing parts 1a and 1b generate and redundantly encode/decode partial information of the frame and transmission/reception parts 3a and 3b controlling an interface between a transmission medium 4 and the redundant work parts 2a and 2b and transmitting/receiving data in accordance with the transmission medium 4 are provided. The protocol processing parts 1a and 1b can use hardware used in the existed devices such as IEEE 802.2. Compatibility with the existed protocol is secured by the redundancy work parts 2a and 2b and a part of the frame is redundantly transmitted so that the deterioration of performance owing to a data error during transmission is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system for transmitting and receiving data between devices such as computers and terminals represented by LAN.

[0002]

2. Description of the Related Art In recent years, with the progress of computerization, introduction of communication systems for transmitting and receiving data between devices such as computers and terminals has become popular in offices and factories. Further, with the widespread use of small computers, mobile phones, and the like, there is an increasing demand for introducing a wireless LAN in which terminals are wireless because of various needs such as application to portable use of terminals. On the other hand, when introducing new communication equipment, there is a strong demand for smooth introduction while making effective use of existing equipment. In wireless LAN, compatibility with existing wired LAN is ensured and throughput equivalent to existing LAN is achieved. Realization of characteristics is desired. However, in a wireless LAN that finally emits data as radio waves, transmission errors may occur frequently due to factors such as reflection of walls, floors, and ceilings in the room and interruptions due to movement of people and objects. Therefore, in the realization of a wireless LAN, how to efficiently and correctly transmit data in a section with poor transmission quality is a major technical issue.

Conventionally, when data is transmitted and received between devices such as computers and terminals, transmission control information for performing transmission control such as delivery confirmation and error control is exchanged between the devices so that the transmitted data can be accurately transmitted. Is commonly done.

Hereinafter, regarding transmission / reception of transmission control information in a conventional LAN, the IEEE 802 standard CSMA / C will be described.
A D-type LAN will be described as an example.

FIG. 8 shows the IEEE 802 standard CSMA /.
This is a CD-type wired LAN protocol.
As shown in the figure, IEEE 802 standard CSMA / C
The D-type wired LAN corresponds to the lower two layers (data link layer and physical layer) of the OSI model. In this standard, the data link layer is divided into an LLC sublayer and a MAC sublayer, the LLC sublayer performs logical data link control, and the MAC sublayer controls access to a transmission medium.

Hereinafter, a process of transmitting the transmission control information from the source LLC sublayer to the destination LLC sublayer will be briefly described.

FIG. 9 shows the structure of a protocol data unit (LLC, PDU) created in the LAN sublayer. As shown in the figure, the destination service access point address (D
SAP) and the source service access point address (SS
AP), control section (CTRL), and information section. The source LLC sublayer performs DSAP, SSAP, and CT when various transmission controls such as reception confirmation, temporary stop of information transfer, and error recovery are performed.
A 32-bit size LLC PDU (having no information section) is created by setting the destination service access point and the source service access point and transmission control information (command / response) in the three fields of the RL, and Hand over to MAC sublayer.

Upon receipt of the LLC PDU from the source LLC sublayer, the source MAC sublayer receives a preamble (PRE) 56 bits and a frame start delimiter (S) as shown in FIG.
FD) 8bit, target station address (DA) 16bit or 48
bit, transmitter station address (SA) 16bit or 48bit, data length (LEN) 8bit, LLC PDU, pad (P
AD), and frame check sequence 8bit
The MAC frame composed of the eight fields is created and transmitted to the partner MAC sublayer via the physical layer.

In the MAC sublayer on the other side, the MAC frame is disassembled, the LLC PDU is taken out, and then the LLC
Pass LLC PDU in sublayer.

By the way, the above-mentioned CSMA / CD type L
In the AN, the size of the frame is checked by the MAC sublayer on the receiving side, and if it is smaller than 512 bits, a method is adopted in which some data in the frame is lost due to a collision or the like during transmission. Therefore, the size of the frame depends on the physical layer, and in the case of 10BASE5 with a physical transmission rate of 10 Mb / s and a cable length of 500 m, the frame length is specified as n octet length and the minimum frame length is specified as 512 bits ( This is a limitation determined by the processing operation of CSMA / CD, propagation delay, etc.). Therefore, if the data size is less than 512 bits or if the data length cannot be divided by 8 bits when expressed as a bead, dummy data called a pad is inserted. Therefore, when exchanging transmission control information such as a positive acknowledgment of user data, a retransmission request, and a primary interruption of transmission, as described above, since it is a 32-bit LLC PDU, DA and S are included in the frame.
Dummy data will be inserted into the remaining 412 bits except A, LEN, DSSP, SSAP, and CTRL. Thus, in the CSMA / CD system protocol,
When transmitting data such as transmission control information shorter than 512 bits, dummy information was added to the frame in order to purposely match the minimum frame length.

[0011]

As described above,
When data communication is performed in a section with poor transmission quality such as a wireless section, transmission of transmission control information greatly affects the performance of communication equipment. On the other hand, compatibility with existing protocols is strongly desired from the viewpoint of effective utilization of existing equipment.
However, due to the restrictions of the existing protocol, dummy information is often added simply to match the frame lengths, but in particular, a vacant area may occur in a frame containing transmission control information.

Therefore, an object of the present invention is to provide a communication system capable of improving performance deterioration due to loss of information during transmission while ensuring compatibility with existing conventional systems.

[0013]

According to the present invention, in a communication system for transmitting and receiving data, a free area detecting means for detecting a free area in a data series and a part of the data series by utilizing the detected free area. It is characterized by comprising redundant transmission means for redundant transmission.

[0014]

According to the present invention, in a communication system for transmitting and receiving data, an empty area detecting means for detecting an empty area in a data series, and redundant transmission for redundantly transmitting a part of the data series by utilizing the detected empty area. By including the means, it is possible to redundantly transmit information that greatly affects the performance of the communication system when performing data communication in a section with poor transmission quality. Therefore, it is possible to improve performance deterioration due to loss of information being transmitted, and further, it is possible to ensure compatibility with conventional existing systems.

[0015]

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

FIG. 1 is a conceptual diagram of the configuration of a communication system to which the present invention is applied.

As shown in FIG. 1, the communication system of the present invention includes a protocol processing unit 1a, 1b which creates and delivers a fixed unit of information (hereinafter referred to as a frame) based on a communication protocol (protocol) and a protocol. Processing units 1a and 1b
A redundant processing section 2a, 2b for detecting an empty area in the frame created by the above and redundantly encoding and decoding a part of the information of the frame, the transmission medium 4, and the redundant processing section 2a,
It is composed of transmission / reception units 3a and 3b which control the interface with 2b and transmit / receive data according to the transmission medium.

The protocol processing units 1a and 1b described above are
Software or hardware for protocol processing used in existing devices such as IEEE802.2 and IEEE802.3 may be used, and redundant processing units 2a and 2b may be used.
The feature of this method is that a part of the frame is redundantly transmitted so as to improve the performance deterioration due to the data error during the transmission while ensuring the consistency with the existing protocol.

FIG. 2 shows an example of the structure of a wireless LAN terminal to which the present invention is applied. Reference numeral 10 denotes a data terminal such as a personal computer, which is IEEE802.2 or IEEE802.
A LAN cable 11 for performing communication protocol processing such as 3 is provided as an expansion board.
2 is connected to the external wireless LAN adapter 13. The wireless LAN adapter 13 includes an AUI cable transmission / reception interface 20, a redundancy processing unit 21 that redundantly encodes and restores part of information of a frame, and a modulation unit 22 that modulates data to create a radio signal. , A demodulation unit 23 for demodulating data from the received radio wave signal, the transmission / reception interface 20, the redundancy processing unit 21, and the modulation unit 22 described above.
In addition, the demodulation unit 23 and the control unit 25 that controls the entire wireless adapter device 13, and the antenna 24 that transmits and receives radio signals to and from the wireless section. With this configuration, it becomes possible to replace the existing LAN with a wireless LAN device by simply connecting the wireless LAN adapter to the terminal. FIG. 3 is a frame configuration example of an embodiment of the present invention.
a, 2b, IEEE802.2 LLC (Logical Li
nk Control) and IEEE802.3 are applied. FIG. 10A is a diagram showing a frame structure transmitted / received between the protocol processing unit and the redundancy processing unit. The frame 30 is composed of 8 fields (preample 3156 bits, which are created by the IEEE802.3 MAC). Stop frame delimiter 328bit, destination address 3348bit
, Source address 3448bit, data length 3516bit,
Frame check sequence 408bit) is IEEE80
2.2 LLC PDU created by LLC (DSAP
368 bit, SSAP 378 bit, CTRL 3816 bit, information section 0 bit). If the data length 35 (bit length from the beginning of the DA to the end of the frame) is less than 512 bits or if the data length cannot be divided by 8 bits when expressed in bits, dummy data called a pad is inserted. For example, when sending a 32-bit LLCPDU for confirmation of reception, the pad 39 is being inserted (vacant area) for 412 bits from the 33rd bit from the end of the data length field. FIG. 2B shows a frame 50 transmitted / received between the redundancy processing unit and the transmission / reception unit. The figure shows the LLC PDU
Redundantly process the part of, and increase data 1 by redundant processing 1
Reference numeral 5 is a frame that has been redundantly processed using an empty area (the pad information portion this time). As described above, the frame structure according to the embodiment of the present invention is characterized in that a part of the frame is redundantly processed by utilizing the area of the information added for matching the protocols.

The structure of the redundancy processing section, the transmission operation and the reception operation of the redundancy processing section will be described below in order. FIG. 5 is a functional block configuration diagram of the redundant processing unit in the embodiment of the present invention, and the free area detection unit 1 for detecting a free area in a frame.
01, a redundant encoding unit 102 that redundantly encodes a part of the frame, a redundant restoration unit 103 that restores the original frame from the redundantly encoded frame, the empty area detection unit 101, and redundant encoding. The control unit 104 controls the unit 102 and the redundancy restoration unit 103.

FIG. 6 shows the operation of the redundant processing section during transmission according to an embodiment of the present invention.

That is, first, an empty area is detected from the received frame (step 1). If it is determined in step 1 that there is no free area, the frame is transmitted as it is (step 2). If it is determined in step 1 that there is an empty area, the frame is passed to the redundant encoding unit to create a frame (redundant frame) in which a part of the information of the frame is redundantly encoded, and then the redundant frame Is transmitted (step 3). The detection of the empty area in the frame in step 1 described above can be easily performed by referring to the data length field of the third field from the received frame in the case of the frame configuration as shown in FIG. 3A, for example. Can be found. That is, when only the transmission control information is transmitted, the data lengths are DSAP, SSAP, and CT.
If the total length of RL is 32 bits and it is 32 bits by referring to the data field length, 412 bits from the 33rd bit from the end of the data length field may be regarded as pad insertion (vacant area).

Further, the redundancy processing in step 3 is performed by adding a Hamming code having a coding rate of 0.5 for error correction to the information of the 32-bit LLC PDU, and the 32-bit information increased by the coding is the 32-bit pad area. If used, it can be transmitted sufficiently. As described above, the redundancy processing in step 3 can use an error correction code or an error detection code as used in the conventional redundant bit addition method.

FIG. 7 shows the operation of the redundant decoding section in one embodiment of the present invention. As shown in the figure, the received data is referred to, and it is determined whether or not redundant data exists (step 21). If it is determined that there is no redundant data, the frame is passed to the upper layer as it is (step 22). ), If it is determined that there is redundant data, the redundant frame is restored to the original frame, and then the frame is passed to the upper layer (step 23). In step 21 described above, for example, in FIG.
In the case of the frame structure as shown in (b), the data length field of the third field from the received frame may be referred to, and if it is 32 bits, it may be determined that it has been redundantly processed. Further, in step 23, the operation opposite to the redundant processing of the transmission source may be performed. When processing is performed by the transmission source with the Hamming code, the decoding operation of the Hamming code is also performed to correct the error in the frame. be able to.

As described above, according to this embodiment, the empty area detecting means for detecting an empty area in the data series and the redundant transmission means for redundantly transmitting a part of the data series by utilizing the detected empty area are provided. With the provision, it becomes possible to redundantly transmit information that greatly affects the performance of the communication system when performing data communication in a section with poor transmission quality. Further, in the case of adding an error correction code or an error correction code to the transmission control information to make it redundant, conventionally it was necessary to change the hardware and software of the LLC sub-encapsulation that creates the transmission control information. According to the method, the LLC sublayer and the MAC sublayer can be used as they are.

The present invention is not limited to the above embodiment.

For example, in the above-described embodiment, the case where the Hamming code with the coding rate of 0.5 is used for the coding and decoding of the redundancy processing section is shown, but the coding rate may be changed depending on the state of the transmission medium. Of course, the same can be realized when another code is used.

Further, as shown in FIG. 4, when creating a redundant frame, information other than the empty area is left as it is.
If only the free area is converted into additional information associated with redundancy such as error correction code, a terminal that communicates in the frame format before conversion and a terminal that communicates in the redundant frame format according to the present invention Even if they are mixed, they can communicate with each other. Further, in the above-described embodiment, the case where IEEE802.2 and IEEE802.3 are used for the protocol processing unit has been described. However, it is assumed that the LLC PDU is 32 bits when transmitting the transmission control information, but other T
The same can be realized when a protocol such as CP / IP or HDLC is used.

[0029]

As described above, according to the present invention,
In a communication system for transmitting and receiving data in an environment with poor transmission quality, a free area detecting means for detecting a free area in a data series, and redundant transmission for redundantly transmitting a part of the data series using the detected free area By including means, by redundantly transmitting information that greatly affects the performance of the communication system when performing data communication in a section with poor transmission quality, it is possible to improve performance deterioration due to loss of information during transmission, Furthermore, it is possible to ensure compatibility with conventional existing systems.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a communication system according to an embodiment of the present invention.

FIG. 2 is a configuration example of a wireless LAN device to which the present invention is applied.

FIG. 3 is a structural example of a redundant frame according to an embodiment of the present invention.

FIG. 4 is a structural example of a redundant processing frame according to an embodiment of the present invention.

FIG. 5 is a block configuration example of a redundant processing unit.

FIG. 6 is a flowchart showing an operation at the time of transmission of the redundancy processing unit in the embodiment of the present invention.

FIG. 7 is a flowchart showing an operation at the time of reception of the redundant processing unit in the embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between IEEE802.3 and an OSI reference model.

FIG. 9 is a diagram showing the structure of an LLC PDU.

FIG. 10 is a diagram showing the structure of a MAC frame.

[Explanation of symbols]

1a, 1b ... Protocol processing unit, 2a, 2b ... Redundancy processing unit, 3a, 3b ... Transceiver unit, 4 ... Transmission medium.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04L 29/10 9371-5K H04L 13/00 309A

Claims (7)

[Claims] 1. In a communication system for transmitting and receiving data, an empty area detecting means for detecting an empty area in a data series, and a redundant transmission means for redundantly transmitting a part of information in the data series by using the empty area. And a communication system. 2. The communication system according to claim 1, wherein the empty area is additional information added to user data transmitted and received between terminals so as to have consistency between protocols. 3. The communication system according to claim 1, wherein said redundant transmission means is means for processing a part of information in the data sequence so as to detect that there is an error during transmission. 4. The communication according to claim 1, wherein the redundant transmission means is means for processing a part of information in the data sequence so as to correct the error when there is an error during transmission. system. 5. The communication system according to claim 1, wherein a part of the data sequence includes transmission control information transmitted and received between terminals. 6. The part of the data series includes address information added to the data.
The communication system described. 7. The communication system according to claim 1, wherein the means for processing a part of the information in the data series converts only the information in the empty area.