JPH10173668A - LAN system - Google Patents

Abstract

(57) [Summary] [Problem] To realize high-quality communication even when an acknowledgment is not performed between a transmission side and a reception side. Prior to transmission of a frame, a terminal on the transmission side checks whether the transmission requires an acknowledgment with the reception side (630). Then, for example, in the case of the individual communication, it is recognized that the confirmation response is required, and in the case of the broadcast or the multicast, the confirmation response is unnecessary. If you need an acknowledgment,
The ACK frame is transmitted, the ACK frame is returned from the receiving side, and it is confirmed whether the ACK frame is normally received. If the ACK frame is not normally received, a retransmission operation is performed (640, 650,
660). On the other hand, if no acknowledgment is required, the frame is transmitted a plurality of times, and then the transmission operation is terminated (670). As a result, even when the retransmission operation is not performed, the probability of normal reception on the receiving side increases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless or wired LAN system, and more particularly, to high-quality communication even when an acknowledgment is not performed between a transmitting side and a receiving side in a MAC layer of a data link layer. The present invention relates to a LAN system that realizes effective use of received data.

[0002]

2. Description of the Related Art Generally, in a LAN system, when communication is one-to-one individual communication, a transmitting terminal transmits a data frame to a receiving terminal and receives an ACK frame for acknowledgment from the receiving terminal. The procedure (protocol) for retransmitting the data frame if necessary is determined so that the MAC (Media Access Control) layer of the data link layer can be realized. On the other hand, when communication is performed with a plurality of communication partners such as broadcast for all terminals or multicast for a specific group, even if ACK frames are used, ACK frames of a plurality of terminals are mixed on a transmission path, and Cannot be identified. For this reason, conventionally, in the case of broadcast or multicast, in the MAC layer, the transmitting terminal only transmits a frame to the partner terminal, and does not care whether the frame is normally received by the receiving terminal. And The receiving terminal accepts the frame from the transmitting terminal if received normally, and simply discards the frame when detecting an error, and does not return an ACK frame for acknowledgment to the transmitting terminal.

[0003] A conventional LAN system of this type is a draft standard IEE80.
2.11 (Draft Standard IEEE 802.1
1) and those described in P802.11D2.0. This is because CSM is used for data communication control in the MAC layer.
A / CA (Carrier Sense Multiple Access with C
radio L that adopts ollision avoidance) and retransmits the MAC layer using an ACK frame for acknowledgment.
An AN system.

[0004]

As described above, in a conventional LAN system, when there are a plurality of communication partners such as broadcast and multicast, retransmission control using an ACK frame in the MAC layer is practically impossible. Therefore, a situation in which the receiving terminal cannot normally capture the frame has frequently occurred. In order to avoid such a situation, it is necessary for the transmitting terminal to perform individual communication with each receiving terminal in turn and perform retransmission control using an ACK frame even in broadcast or multicast. There is a problem that communication time is proportional to the number of the other parties.

[0005] On the other hand, the receiving terminal generally uses a CRC (C
Error detection of data is performed using yclic redundancy check) or the like, and if there is a bit error in the data, the frame is discarded. In this case, ACK in the MAC layer
Even in broadcast or multicast communication in which retransmission control using a frame cannot be performed, even if there is only one bit error in a received frame, the information is discarded.
For this reason, there has been a problem that information on data that does not have a practical problem even with a small bit error, such as image data used in a TV conference, is not effectively utilized.

A first object of the present invention is to provide a wireless or wired LAN.
In a system, even when acknowledgment control using an ACK frame in the MAC layer is not performed, such as broadcast or multicast, a receiving terminal can normally receive a frame without performing individual communication for each terminal in order. Is to increase the probability.

A second object of the present invention is to provide a wireless or wired LAN.
It is an object of the present invention to effectively use data that does not pose a practical problem even if there is some bit error, such as image data used in a TV conference.

[0008]

In order to achieve the first object, according to the present invention, when an acknowledgment is not performed between a transmitting side and a receiving side as in a broadcast or a multicast, a terminal on a transmitting side is used. Is characterized in that the same frame is repeatedly transmitted to the receiving terminal a plurality of times.

Further, in order to achieve the second object,
In the present invention, when an acknowledgment is not performed between the transmitting side and the receiving side such as broadcast or multicast, the receiving side terminal receives the frame as valid without discarding the received frame even if there is a bit error in the received frame. It is characterized by:

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. In this embodiment, a wireless LAN system is targeted, but a wired LAN system is used.
The same applies to the system. Further, in the embodiment, the acknowledgment is not uniformly performed in the transmission of the control frame, the acknowledgment is performed only in the individual communication in the case of the transmission of the user frame, and the acknowledgment is performed in the other communication such as broadcast and multicast. No.

FIG. 1 is an overall configuration diagram showing an embodiment of a wireless LAN system targeted by the present invention. This wireless LA
The N system includes a plurality of wireless terminal devices 2a, 2b, which exist in a cell (local area) 1 indicating the same frequency region,
2c and 2d.

Here, each wireless terminal device 2 in the cell 1
Suppose that mutual communication is performed using a low-speed frequency hopping spread spectrum system in which a carrier frequency is changed at a constant period longer than a symbol period. That is,
In this wireless LAN system, each wireless terminal 2 in the cell 1
, The carrier frequency used changes periodically (hopping). In this embodiment, the hopping cycle is set to 1
The description will be made assuming that 00 ms and the number of hopping is 13.

FIG. 2 shows assignment of carrier frequencies used in the present wireless LAN system. In this system, 2471-splits assigned for the spread spectrum system
The ISM band 3 having a bandwidth of 2497 MHz and a bandwidth of 26 MHz is used. This ISM band 3 is 13 MHz each having a 2 MHz width.
Is divided into sub-channels 4a to 4m. Therefore,
The center frequency of each carrier frequency is fi = 2472 + 2i
(I = 0,..., 12) MHz. Each wireless terminal device 2 has a hopping pattern specified by a hopping master that exists only in the cell 1 described later, for example, f
0, f6, f12, f5, f11, f4, f10, f
Each sub-channel is hopped according to a repetition pattern of 3, f9, f2, f8, f1, and f7.

FIG. 3 shows the contents of one hopping cycle 5 in a wireless section of the wireless LAN system. One hopping cycle 5 is 100 ms, and the user frame area RU51, the non-transmission area RN52, and the control frame area R
C53 and a dummy area RD54. In the user frame area RU51, user data is transmitted and received using a user frame. The non-transmission area RN52 is
This is an area provided to avoid collision between the user frame transmitted in the user frame area RU51 and the control frame transmitted in the next control frame area RC53, and no new user frame can be transmitted between the non-transmission areas RN52. To do. The control frame region RC53 is a region for transmitting a control frame, and is a region for transmitting a control frame in which information necessary for hopping control such as a hopping pattern is placed. The hopping control is performed by a wireless terminal device 2 called a hopping master that exists only in the cell 1, and the hopping master is set for any one wireless terminal device 2 before the system operation. The hopping master sends a control frame to each wireless terminal device 2 in the cell 1 to notify hopping information as needed. The dummy area RD54 is an area for securing time required for synthesizer switching. During this area, each wireless terminal device 2 in the cell 1 performs a carrier frequency switching operation.

FIG. 4 shows an example of a frame format transmitted and received between wireless terminal devices in the cell 1. Here, the area P61 of the frame format 6 is a dummy area for giving time to the physical layer for establishing and maintaining synchronization in the physical layer. The area F62 is an area P61
And indicates the effective head of the valid information in the present frame. An area FC63 is a frame control area in which identification information of a user frame and a control frame, a sequence number described later, and the like are set. For example, when the wireless terminal device 2 that has become the hopping master notifies the other wireless terminal devices 2 in the cell 1 of the hopping information, the communication is performed by validating the bit indicating the control frame in the area FC63. The same applies to a case where an arbitrary wireless terminal device 2 other than the hopping master transmits a control frame to another wireless terminal device 2. The area DA64 indicates a destination address, and the area SA65 indicates a source address. The area I66 is an information section. For example, the hopping master
Here, hopping information is set. The area FCS67 is a frame check sequence, and detects an error in the entire frame excluding the area P61 using a CRC code or the like which is an error detection code.

FIG. 5 shows one radio terminal 2 in the cell 1.
FIG. 3 is a diagram showing an example of the configuration. The wireless terminal device 2 includes an antenna 201, a modulation / demodulation unit 202, a transmission / reception control unit 203, a sequence management table 204, a reception buffer 205, and a transmission buffer 206, and is connected to a personal computer 208 via a system bus 207.

The transmission / reception control unit 203 controls the entire frame transmission / reception. In the case of the hopping master wireless terminal device 2, the transmission / reception control unit 203 issues a hopping instruction to another wireless terminal device 2. Modem 202
Performs a modulation process and a frequency conversion process to a 2.4 GHz band on the frame transmitted from the transmission / reception control unit 203, and transmits the frame from the antenna 201.
The base station performs a frequency conversion process to a baseband and a demodulation process on the frame received from No. 1 and sends the frame to the transmission / reception control unit 203. When the same frame is received a plurality of times, the sequence management table 204 registers its source address and sequence number. The reception buffer 205 temporarily stores the reception frame, and the transmission buffer 206 temporarily stores the transmission frame.

FIG. 6 is a flowchart of the frame transmission operation of the transmission / reception control unit 203 according to one embodiment of the present invention. The transmission frame is stored in the transmission buffer 206 from the personal computer 208 via the system bus 207 and the transmission / reception control unit 203, and a frame transmission request is sent to the transmission / reception control unit 203. Upon receiving the transmission request (step 610), the transmission / reception control unit 203 first determines whether the frame can be transmitted,
The presence or absence of a carrier on the wireless transmission path is checked via the modem unit 202 (step 620). No carrier,
If the transmission of the frame is possible, it is subsequently checked whether or not the frame requested to be transmitted is a target for which an acknowledgment is to be made between the transmission side and the reception side (step 63).
0). This can be done by referring to the frame control area FC63 and the destination address area DA64 of the frame format 6 shown in FIG. That is, in the present embodiment, since all control frames do not perform acknowledgment,
If the control frame indication bit is set in the area FC63 of the frame requested to be transmitted, the transmission frame is a control frame, and it is recognized that an acknowledgment is unnecessary. Also,
In the case of a user frame, confirmation of the transmission frame is performed by determining whether the unique terminal address of the individual communication partner or the broadcast address or the multicast address is set in the destination address area DA64 of the frame requested to be transmitted. Recognize the necessity / unnecessity of response. The necessity / unnecessity of the acknowledgment may be performed in advance on the personal computer 208 side, and the result may be set in the control area FC63 of the transmission request frame or may be directly notified to the transmission / reception control unit 203 together with the transmission request.

When the necessity of the acknowledgment is recognized in step 630, the transmission / reception control unit 203 transmits the transmission frame from the transmission buffer 206 to the wireless transmission path via the modulation / demodulation unit 202 and the antenna 201 (step 640). In order to check whether or not the ACK frame has been normally received, an operation of waiting for an ACK frame for acknowledgment from the wireless terminal device on the receiving side is started (step 650). And
The ACK frame is returned from the wireless terminal device on the receiving side within a predetermined time, and if it indicates normal reception, the frame transmission is terminated. However, the ACK frame is not returned or returned within the predetermined time. However, when a retransmission request is instructed, the transmission / reception control unit 203 recognizes that the transmission frame has not been normally received, and again transmits the transmission frame to the transmission buffer 206.
Then, the signal is transmitted to the wireless transmission path via the modulation / demodulation unit 202 and the antenna 201 (step 660), and it is checked whether or not it has been normally received. Steps 650 and 660
If an ACK frame indicating normal reception is returned during that time, the frame transmission is terminated there, and even if a predetermined number of times are repeated, the normal reception A
If the CK frame is not returned, the process ends abnormally.

In the operation flow of FIG. 6, steps 610, 620, 640, and 6 except for step 630 are performed.
Since the flow of steps 50 and 660 is the same as the conventional one, further detailed description is omitted.

On the other hand, if it is recognized in step 630 that no acknowledgment is required, the transmission / reception control unit 203 transmits the transmission frame from the transmission buffer 206 to the modulation / demodulation unit 202 and the antenna 20.
The operation of transmitting the data to the wireless transmission path via the communication line 1 is repeated a plurality of times (step 670). At this time, the transmission / reception control unit 203 sets a sequence number in the frame control area FC63 of the same frame to be repeatedly transmitted, and when a plurality of different frames are continuously transmitted a plurality of times, respectively, when the wireless terminal on the receiving side is Make it possible for the device to recognize up to what is in the same frame. In this way, when the same frame is repeatedly transmitted a predetermined number of times, the transmission / reception control unit 203 ends transmission of the frame. On the other hand, in the wireless terminal device on the receiving side, since the same frame is repeatedly transmitted a plurality of times, for example, even if there is a bit error in the first received frame, if there is no bit error in the second received frame, The frame can be made valid.

Hereinafter, an operation example in the case of repeating the same frame transmission of this embodiment a plurality of times will be described in detail with reference to FIG. Here, in order to simplify the description, the wireless terminal device 2
a is a transmitting side and the wireless terminal 2b is a receiving side. Only the processing in both terminals will be described. For example, in the case of broadcast or multicast, the processing in the wireless terminal 2c and 2d is the processing in the wireless terminal 2b. Is the same as Here, it is assumed that the wireless terminal device 2a transmits the same frame twice and allocates one byte to the sequence number.

The wireless terminal device 2a first transmits a first frame to the wireless terminal device 2b. At this time,
As shown in FIG. 7A, the wireless terminal device 2a stores the sequence number “0000 00” in the area FC63 in the frame.
"01" is transmitted with the source address of the terminal 2a added to the area SA65. In the wireless terminal device 2b, this frame is transmitted from the antenna 201 shown in FIG.
The data is temporarily stored in the reception buffer 205 via the transmission / reception control unit 203. Here, if there is no bit error in the received frame, the transmission / reception control unit 203 refers to the area FC63 of the received frame to identify whether the frame is a user frame or a control frame, and determines the source address and the sequence. Check the number. In this source address and sequence number check, if the source address and the sequence number added to the frame are not in the sequence management table 204, the frame is regarded as not received twice or more, and is regarded as normal reception. To process. In the example of FIG. 7A, since nothing is registered in the sequence management table 204 in the terminal 2b, it is assumed that the signal has not been received twice or more, and the signal is normally received. Then, the sequence management table 204
, The transmission source address extracted from the frame and the sequence number “0000 0001” are added, and the sequence management table 204 is updated.

If there is no free space in the sequence management table 204, the oldest one registered in the table is deleted and used. The number to be registered in the sequence management table 204 (the combination of the source address and the sequence number is counted as one) is two or more.

Thus, when the user frame is normally received, the frame is transmitted from the reception buffer 205 to the personal computer 208 via the transmission control unit 203 and the system bus 207. When the control frame is normally received, the transmission / reception control unit 203 extracts necessary information from the control frame and then discards the information.

On the other hand, if there is a bit error in the received frame, the wireless terminal device 2b discards the frame and does not perform any of the above-described processing, and just waits for the next frame.

As shown in FIG. 7B, following the first frame transmission, the wireless terminal 2a transmits the same frame to the wireless terminal 2b. At this time, the wireless terminal device 2a has the same sequence number “0000” as the previous sequence number.
The same frame to which "0001" is added is transmitted.
If there is no bit error in the received frame, the wireless terminal device 2b performs the same processing as described above, and checks the source address and sequence number of the frame. At this time, as shown in FIG. 7B, in the sequence management table 204 of the wireless terminal device 2b, there is a sequence management table in which the source address and the sequence number match. Discard.

As shown in FIG. 7 (c), the wireless terminal 2a that has transmitted the same frame twice transmits the sequence number "0" to the wireless terminal 2b if there is a next transmission frame.
000 0010 ”is transmitted next. If there is no bit error in the received frame, the wireless terminal device 2b receiving this frame performs the same processing as described above and performs a frame sequence check. At this time, as shown in FIG. 7C, in the sequence management table 204 of the wireless terminal device 2b, since there is no one whose transmission source address matches the sequence number, it is regarded that the reception has not been performed twice or more. Receive normally. The sequence management table 204 stores the source address extracted from the frame and the sequence number “0000 00”.
10 ”is added and the sequence management table 204 is updated. Hereinafter, the same processing as described above is repeated to continue communication.

Although the transmission interval of a plurality of frames is arbitrary, when the frequency hopping spread spectrum system is used, the same frame may be transmitted a plurality of times at the same frequency, or the frequency to be transmitted may be changed. The same frame may be transmitted a plurality of times using any method. In the method of indicating the frequency, even if the communication state at a certain specific frequency is poor due to the characteristics of the wireless transmission path, there is a high possibility that the poor communication state can be avoided by changing the frequency and transmitting.

In the case where no acknowledgment is made between the transmitting side and the receiving side, a mode for transmitting the same frame a plurality of times as in the present invention and a mode for transmitting once only as in the prior art are provided (mode switch). May be able to select any mode as needed. In this case, at the time of frame transmission, for example, the transmission / reception control unit 203 of the transmission-side terminal device
By performing the mode check in, even if no acknowledgment is performed as in the case of broadcast or multicast, it is possible to execute frame transmission only once as in the past, and the compatibility with the conventional system is maintained.

The embodiment of the present invention has been described in which the transmitting terminal transmits the same frame a plurality of times when the acknowledgment is not performed. A description will be given of a process of another embodiment in which a terminal device receives a frame without discarding even if a bit error occurs in a received frame. Note that the frame transmission operation in the terminal device on the transmission side is the same as the conventional one.

As shown in FIG. 1, it is assumed that a user frame is broadcast from the wireless terminal 2a to the wireless terminals 2b, 2c and 2d. Wireless terminal device 2
The user frame transmitted from the wireless terminal device 2b,
2c and 2d, but the wireless terminal devices 2b, 2c and 2d refer to the destination address area DA64 of the received user frame and set a broadcast address, so that acknowledgment is unnecessary (that is, ACK is not required).
Frame return is unnecessary). In this case, even if there is a bit error in the received frame, the wireless terminal devices 2b, 2c, and 2d receive and validate the frame without discarding it. At this time, it may be combined with error correction using a Reed-Solomon code or the like.

In this embodiment, when the acknowledgment is not performed between the transmitting side and the receiving side, even if there is a bit error in the received frame, a mode in which the frame is received without discarding the frame, If there is, a mode for discarding the frame may be provided (mode switch) so that the user can select any mode as necessary. In this case, when a frame is received, a mode check is performed by, for example, the transmission / reception control unit 203 of the reception-side terminal device. Even if a confirmation response is not performed, the frame can be discarded if there is a bit error in the reception frame. And compatibility with the conventional system is maintained.

When the bit error rate of the received frame is high, the following control can be performed.
That is, even if there is a bit error in the frame addressed to itself,
If the bit error rate of the received data is below a certain threshold, the frame is received without discarding, and if the bit error rate of the received signal is above a certain threshold, the frame is discarded. I do.

Although the embodiment of the present invention has been described above, the present invention is not limited to this. For example,
In the embodiment, acknowledgment is unnecessary for all control frames, and acknowledgment is unnecessary for user frames except for individual communication. However, the present invention is not limited to this. Also, the present invention is basically a wireless LA
Not only N, but also applicable to a wired LAN.

[0036]

As described above, according to the present invention, in a wireless or wired LAN system, an acknowledgment is not performed between the transmission side and the reception side, and a retransmission request cannot be made to the transmission side upon abnormal reception. Even in such a case, the transmitting side transmits the same frame a plurality of times, thereby increasing the probability of normal reception and enabling high-quality communication.

If no acknowledgment is sent between the transmitting side and the receiving side, the receiving side terminal device receives the bit error in the received frame without discarding the frame. Even if there is some bit error, such as image data used for a TV conference using broadcast or multicast, it is possible to effectively use data that does not cause any practical problem.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a wireless LAN system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating assignment of carrier frequencies.

FIG. 3 is a diagram showing the contents of a hopping cycle.

FIG. 4 is a diagram illustrating an example of a format of a transmission frame.

FIG. 5 is a diagram illustrating a configuration example of the wireless terminal device of FIG. 1;

FIG. 6 is a flowchart illustrating a frame transmission operation according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a specific operation of frame transmission.

[Explanation of symbols]

 1 cell 2a to 2d wireless terminal device 201 antenna 202 modulation / demodulation unit 203 transmission / reception control unit 204 sequence management table 205 reception buffer 206 transmission buffer 207 system bus 208 personal computer

Continued on the front page (72) Inventor Kenichiro Oda 810 Shimo-Imaizumi, Ebina-shi, Kanagawa Prefecture Hitachi Systems, Ltd. Office Systems Division (72) Inventor Koji Aoyama 1-Horiyamashita, Hadano-shi, Kanagawa Prefecture (72) Inventor Mutsumi Hamasaki 810 Shimoimaizumi, Ebina-shi, Kanagawa Prefecture Hitachi Systems Ltd. Office Systems Division

Claims (2)

[Claims] In a LAN system in which a plurality of terminals are interconnected wirelessly or by wire, when an acknowledgment is not performed between a transmitting side and a receiving side, the transmitting side terminal is the same as the receiving side terminal. A LAN system for repeatedly transmitting a frame a plurality of times. 2. In a LAN system in which a plurality of terminals are interconnected wirelessly or by wire, when no acknowledgment is made between the transmitting side and the receiving side, the receiving side terminal has a bit error in the received frame. A LAN system for receiving the frame as valid.