JPH10340322A - Communication system and communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce collisions and to shorten the entire processing time by maximizing the number of times of re-transmission for the transmission of a response to a main equipment at the reception of command from the main equipment and repeating it until the transmission succeeds. SOLUTION: A card reader-writer 4 transmits an optional command into a communication area 2 through an antenna 1. In performing first command transmission, the card reader-writer 4 adds the number of times of the re- transmission of the response from respective cards to the command. The number of times of the re-transmission is the maximum number of times capable of re-transmitting the response before receiving the next command when the respective cards fail in response transmission to the card reader-writer 4. The respective cards 3 transmit the response to the card reader-writer 4. At this point, since the probability that the cards 3a and 3b of excellent communication conditions succeed in returning the response to the card reader-writer 4 is high, the card reader-writer 4 attaches acknowledgment(ACK) to the ID and performs the transmission.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a communication system in which a main device and a plurality of communication devices perform non-contact communication and a communication device used in the communication system. For example, the present invention relates to a communication system and a communication device that enable efficient communication between a plurality of cards (communication devices) at the same time when a large number of cards (communication devices) enter the communication area of one card reader / writer (main device).

[0002]

2. Description of the Related Art In a case where one main unit and a large number of communication units perform communication almost simultaneously and without contact, a collision problem occurs as long as the communication is asynchronous. Therefore, when the communication device fails to transmit a response to the command transmission from the main device, the response transmission is usually retransmitted to the main device. In this case, if the response transmission is not successful even after retransmitting the predetermined number of times, an error is terminated.

[0003] Such a phenomenon occurs, for example, in a system using a card reader / writer and a card that communicates with the card reader / writer in a non-contact manner. It is easy to happen when it becomes.

[0004]

However, when a large number of cards (communication devices) enter the communication area of the card reader / writer (main device) at one time, the card reader / writer (main device) and each card (communication device). Since the communication between them is asynchronous and the priority of communication is not predetermined for each card (communication device), a lot of collisions occur as shown in FIG. In FIG. 1, reference numeral 1 denotes an antenna of a card reader / writer (main device), and reference numeral 2 denotes a communication area covered by the antenna 1. Also, 3 (3
a, 3b,... 3d) indicate cards (communication devices) that have entered the communication area 2 at one time. A command is transmitted from the antenna 1 to each card (communication device) 3 in the communication area 2 at a time, but in the situation shown in FIG. Transmission fails, and the number of retransmissions of a response from the card to the card reader / writer (main device) increases. For example, the cards (communication devices) 3c, 3d, etc., located far from the antenna 1 have relatively poor communication conditions, and thus often retransmit responses. As described above, when a large number of cards (communication devices) simultaneously enter the communication area 2, the retransmission of the response increases as the communication condition becomes worse, so that a card having a relatively good communication condition (for example, the antenna 1). (Such as cards 3a, 3b, etc.) that are too close to each other, the probability of failure increases, and as a result, the communication efficiency becomes very poor. Such a problem is not only in systems in which a large number of communication devices enter the communication area at once, but also in a warehouse management system or the like that communicates with each communication device at a time when a main device power switch is turned on. The same occurs.

An object of the present invention is to provide a communication system and a transmission / reception apparatus capable of reducing collision and shortening the entire processing time when it becomes necessary to communicate with many communication apparatuses at once. is there.

[0006]

A communication system according to claim 1 of the present application adds the number of retransmissions of a response from a communication device to an arbitrary command transmitted from a main device to a communication device in a contactless manner. A command transmitting means for transmitting the command to the communication device while increasing the number of retransmissions, the command transmission means being provided in the main device, and transmitting a response to the main device when a command is received from the main device by maximizing the number of retransmissions; The communication device is provided with a response transmitting unit that performs until the communication succeeds.

In this communication system, when a large number of communication devices enter the communication area of the main device at once, the main device transmits a command to all the communication devices that have entered the communication area to transmit each communication device. Wait for a response from the device. At this time, a communication device close to the antenna of the main device or a communication device with good power conditions generally has good communication conditions, and a communication device away from the antenna or a communication device with poor power conditions generally has bad communication conditions. Since the degree of communication status differs for each communication device, a communication device with good communication status can return a response to the main device, but a communication device with poor communication status may not be able to return a response. . Normally, a communication device that fails to return a response attempts to return a response again. However, the number of retransmissions of the response from the communication device is added to the command transmitted from the main device to each communication device. Therefore, the communication device can transmit a response to the main device only up to the number of retransmissions of the response.

[0008] For example, when the number of retransmissions is zero, if the communication device once fails to transmit a response, the communication device cannot retransmit the response and must wait for the next command. On the other hand, the number of retransmissions of the response added to the command from the main device is controlled to gradually increase. For this reason,
Immediately after the first command transmission, there is no retransmission of the response from the communication device with poor communication status, but since the response is gradually retransmitted after that, the occurrence of collisions is reduced and the frequency of communication errors is low. It becomes possible to process sequentially from a good card.

The invention according to claim 2 of the present application is characterized in that the number of retransmissions is increased each time the number of communication devices that have successfully received a response reaches a certain number. The invention according to claim 3 is characterized in that the number of retransmissions is increased each time a predetermined time elapses from the first command transmission to which the new number of retransmissions is added. In addition, it is also conceivable to increase the number of retransmissions every time the ratio of the number of successful communication devices to the total number of communication devices existing in the communication area reaches a predetermined value.

The invention according to claim 4 of the present application is characterized in that the main device is constituted by a card reader / writer, and the communication device is constituted by a non-contact card which can communicate with the card reader / writer in a non-contact manner. I do. A non-contact card has a function of communicating with a card reader / writer as a main device using electromagnetic waves, infrared rays, and the like, and includes a card that uses an electromagnetic wave transmitted from a battery or a card reader / writer as a power source.

The invention according to claim 5 of the present application is characterized by a configuration of a main device side of the communication system,
The invention according to claim 6 is characterized by a configuration on the communication device side of the communication system.

[0012]

FIG. 1 is a diagram conceptually showing an operation of a communication system according to an embodiment of the present invention. In this embodiment, a card reader / writer (R / W) is used as a main device.
4 are used. The communication device includes a card 3 (3a, 3b) that communicates with the card reader / writer 4 in a non-contact manner.
...) are used. The antenna 1 that covers a communication area 2 in a certain range is connected to the card reader / writer 4, and each card that has entered the communication area 2 and the card reader / writer 4 can communicate with each other. In this embodiment, as described later, each card 3 does not include a battery, and uses an electromagnetic wave radiated from the antenna 1 as a power source. As an application of this communication system, for example, a moving object identification device in which a card 3 is attached as a tag to a moving object conveyed on a belt conveyor, and this is recognized at a predetermined position on the conveyor, A shopping checkout system in a supermarket, which is attached to a product as a tag so that a consumer collectively brings the product to a checkout corner or the like, can be considered.

In FIG. 1, a card reader / writer 4 transmits an arbitrary command to a communication area 2 via an antenna 1. The command in this case is for the entire card, not for the individual card. Therefore, the ID is not added. As this type of command, for example, there is an unconditional polling command without ID designation. The command transmission timing may be at regular intervals, may be a timing at which one or more cards 3 have reached the communication area 2, or may be a command transmitted by the operator. It may be timing. When transmitting the first command, the card reader / writer 4 adds the number of retransmissions of the response from each card to the command. The number of retransmissions is the maximum number of times that a response can be retransmitted before receiving the next command when each card fails to transmit a response to the card reader / writer 4. Each card 3
Sends a response to the card reader / writer 4 upon receiving the command. At this time, the card 3 having a good communication condition, for example, the cards 3a and 3b located very close to the antenna 1 has a high probability of succeeding in returning a response to the card reader / writer 4, and the card 3 having a bad communication condition For example, the cards 3c and 3d farthest from the antenna 1 have a relatively high probability of failing to return a response to the card reader / writer 4. Since the card reader / writer 4 can know the ID of the card that has correctly received the response, an ACK
(Acknowledgement) and send. The card that has received the ACK knows that the response transmission has succeeded, and does not perform processing to return a response even if the card receives the command thereafter.
The command is the card 3 that has entered the communication area 2
Is a command for acquiring an ID (such as an unconditional polling command) transmitted first. On the other hand, a card having a poor communication condition has a low probability of receiving an ACK from the card reader / writer 4, and if this ACK is not received, it is considered that a response transmission has failed. At this time, the number of retransmissions added to the command transmitted from the card reader / writer 4 is checked to determine whether the response can be retransmitted. If retransmission is possible, the response is transmitted again. Hereinafter, similarly, the card that has successfully transmitted the response does not perform the response transmission processing even if the command is received thereafter.

After a certain period of time has elapsed after such operations are continuously performed, the card reader / writer 4 adds the command to the command to be transmitted when the number of communication devices that have successfully received the response reaches a certain number. The number of retransmissions is increased by a predetermined number. Further, after a certain period of time, the same processing is repeated by further increasing the number of retransmissions. In the example shown in FIG. 1, a command with the number of retransmissions of 0 is transmitted first, and a response is received from the card 3 b having the best communication condition and cards around the card 3 b. A response is received from a certain card 3e and its peripheral cards and the like, and thereafter, a command in which the number of retransmissions is increased to one is transmitted. An example is shown in which a response is received from a peripheral card or the like. In a series of these processes, the card that has successfully transmitted the response does not transmit a response again to the subsequent command transmission.

Therefore, the card reader / writer 4 executes communication with a card having a good communication condition first by reducing retransmission of a card having a bad communication condition at the beginning of communication.
It is possible to gradually communicate with a card having a poor communication condition. As a result, the processing time required for the entire communication can be reduced. After a successful response transmission to the command, a command to which an ID is added (a write command, a read command, etc.) is transmitted from the card reader / writer 4. At this time, it is confirmed that the IDs match. After that, processing according to the command content is performed.

FIG. 2 shows a card reader / writer 4 and a card 3
2 shows a schematic configuration of the first embodiment. The card reader / writer 4
A control circuit 40 for exchanging data with a host computer such as a personal computer, a transmission circuit 41 for converting transmission data from the control circuit 40 into a transmission analog signal, and converting an analog reception signal into reception data and passing the reception data to the control circuit 40 And a receiving circuit 42. The antenna 1 includes an antenna coil L1 and a resonance circuit 10 that resonates with the antenna coil L1. The card 3 includes a control circuit 30 including a nonvolatile memory, a transmission amplifier 31, a reception amplifier 32, a resonance circuit 33, and a coil L2. The resonance circuit 33 includes a capacitor that obtains drive power for the control circuit 30 and the like by charging the voltage induced in the coil L2. Each card 3 has a unique ID.
, And this ID is stored in a memory in the control circuit 30 in advance. This ID is added when transmitting a response in response to a command from the card reader / writer 4.

FIG. 3 shows a protocol for performing communication between the card reader / writer 4 and each card 3.
A, B, and C indicate communication protocols when the number of retransmissions is 0, 1, and 2, respectively. Hereinafter, the operation will be described in detail for each of A, B, and C.

A: Communication with Card 3a with 0 Retransmissions (1) A command is transmitted from the card reader / writer 4 to all cards in the communication area. At this time, the number of retransmissions added to the command is zero. Note that the command at this time does not include an ID but is a command for all cards.

(2) The card 3a that has received the command transmits a response to the card reader / writer 4. The card 3a is sent from the card reader / writer 4
It is in a K reception waiting state. The ACK includes an ID for identifying the card.

(2 ') The card 3b performs the same operation as the card 3a. That is, a response transmission operation to the card reader / writer 4 is performed.

(3) The card reader / writer 4 which has normally received the response from the card 3a transmits an ACK to the card 3a. By receiving this ACK, the card 3a does not send a response even after receiving the same command.

(3 ') The card reader / writer 4 is the card 3
ACK is not transmitted to the card 3b because the response from the client 3b cannot be correctly received. Therefore, the card 3b which has timed out the ACK reception determines whether or not the response can be retransmitted based on the command content (the number of retransmissions) of (1). Here, the response cannot be retransmitted because the number of retransmissions is zero. Therefore, the card 3b stops communication. In addition, card 3
a and the card 3b transmit responses almost simultaneously in the above (2) and (2 '). However, since the communication condition of the card 3b is not good, the response transmitted from the card 3b is extremely weak and collides with the response of the card 3a. There is not enough power to do it. Therefore, the response (2) transmitted from the card 3a is correctly received by the card reader / writer 4.

B: Communication with Cards 3b and 3c with One Retransmission Number (1) A command is transmitted from the card reader / writer 4 to all cards in the communication area 2. The number of retransmissions added to the command at this time is one.

(2) The card 3b receiving the command transmits a response to the card reader / writer 4,
It is in a K reception waiting state.

(2 ') The card 3c performs the same operation as the card 3b. However, the communication status of the card 3c is relatively poor.

(3) The card reader / writer 4 that has correctly received the response from the card 3b transmits an ACK to the card 3b. When the card 3b receives this ACK, it knows that the transmission of the response was successful, and does not perform the operation of transmitting the response even if the same command is received thereafter.

(3 ') Since the card reader / writer 4 did not normally receive the response from the card 3c,
ACK is not transmitted to the card 3c.

(4 ') The card 3c that has timed out the ACK reception checks the number of retransmissions added to the command (1). Here, the response is transmitted to the card reader / writer 4 again because the number of retransmissions is one. Then, an ACK reception wait state is set.

(5 ') The card reader / writer 4 which has normally received the retransmission response from the card 3c
ACK is transmitted. The card 3c that has received the ACK recognizes that the response has been correctly transmitted, and does not perform an operation of transmitting a response to the same command thereafter.

C: Communication with Cards 3d and 3f with 2 Retransmissions (1) A command is transmitted from the card reader / writer 4 to all cards in the communication area 2. The number of retransmissions added to the command in this case is two.

(2) The card 3d receiving the command,
A response is sent to the card reader / writer 4 and A
The CK reception wait state is set.

(2 ') The card 3f performs the same operation as the card 3d.

(3) The card reader / writer 4 that has failed to correctly receive the response of the card 3d does not transmit ACK to the card 3d.

(3 ') The card reader / writer 4 is the card 3
Since the response of f cannot be received, ACK is not transmitted to the card 3f as in (3).

(4) When the ACK reception time-out occurs, the card 3d checks the number of retransmissions added to the command, and when recognizing that the number of retransmissions is two, retransmits the response (first retransmission).

(4 ') The card 3f similarly retransmits the response (first retransmission). (5) The card reader / writer 4 which has correctly received the first retransmission response from the card 3d sends an ACK to the card 3d. Send. As a result, the card 3d determines that the response has been correctly transmitted, and thereafter stops transmitting the response to the same command.

(5 ') The card reader / writer 4 is the card 3
ACK is not transmitted to the card 3f because the response relating to the first retransmission from f cannot be correctly received.

(6 ') Since the number of retransmissions added to the command is two, the card 3f transmits a response again.

(7 ') The card reader / writer 4 correctly receives the response (second retransmission) from the card 3f,
An ACK is transmitted to the card 3f. The card 3f is
When this ACK is received, it is determined that the response (the second retransmission) has been correctly transmitted, and thereafter, transmission of the response to the same command is stopped.

The above operation is shown in a flowchart as shown in FIGS.

FIG. 4 is a block diagram of the card reader / writer
9 is a flowchart illustrating an operation when a command transmission without a D designation is performed. When one or more cards 3 enter the communication area 2, this state is detected in ST1. Note that the detection method includes a method using a separately provided intrusion sensor, a method for detecting a button operation by an operator, and the like.

Next, the card 3 existing in the communication area 2
(ST2). At this time, the number of retransmissions is added to the command as shown in FIG. The number of retransmissions is initially zero. Subsequently, in ST3 and ST4, a response from the card is waited. When a response from any of the cards is received, it is determined whether or not the response is a normal response (ST5). Send FIG. 5B shows a response format, and FIG. 5C shows an ACK format. In each case, an ID for specifying the card is added. If the response is received but the content is not normal (ST5), the card with the ID is stored in the memory as the error card corresponding to the ID (ST8). Return to ST2.

On the other hand, in ST9, it is determined whether or not a predetermined time T2 has elapsed since the command with the new number of retransmissions was transmitted (the first time a command with the number of retransmissions of 0 was transmitted). For example, in ST11, it is determined whether or not the time that seems to have processed the approximate card has elapsed. This time is defined as the processing end time. If the processing has not been completed yet, the process returns to ST2 to reissue the command. In ST9, if the predetermined time T2 has elapsed, the process proceeds to ST10, and the number of retransmissions is incremented. Thus, the next time a command is transmitted in ST2, the number of retransmissions is increased by one. Further, counting of the certain time T2 in ST9 is started.

If a reception time-out occurs while waiting for a response from the card in steps ST3 and ST4,
That is, when the response from the card has failed, the process proceeds to ST12. Here, the current time corresponding to the number of retransmissions is compared with the time corresponding to the set number of retransmissions added at the time of the immediately preceding command transmission. If the current number of retransmission times is less than the set number of retransmission times, there is a response retransmission from the card thereafter, and the process returns to ST3 and waits for a response. If not, that is, if there is no possibility of resending the response from the card, go through here and return to ST.
Return to 9.

After receiving the response with the ID of each card by the above operation, a write command or a read command can be transmitted to each card by using the ID.

FIG. 6 is a flowchart showing the operation of the card 3 in response to the above-mentioned command without ID designation.

When the card enters the communication area 2 and receives the carrier signal from the card reader / writer 4, the operation starts with the stored power of the capacitor charged with the received signal (ST20). First, in ST21, a command from the card reader / writer 4 is waited. When a command without ID designation is received, the number of retransmissions added to the command is analyzed (ST22), and a response is transmitted to the card reader / writer 4 (ST22). ST23). Subsequently, it is determined whether or not ACK has been received from the card reader / writer 4,
If it has been received, it is determined whether or not all the processes in the card have been completed (ST25). If it has been completed, the process is terminated. If not, the process returns to ST21 to return to the command analysis waiting state. Become. The ACK waiting state for the response transmitted in ST23 is described in ST24 and ST2.
6, when the ACK waiting time has timed out, the process proceeds to ST27 to determine whether the current number of retransmissions is less than the number of retransmissions (set retransmission number) added to the immediately preceding command. If the current number of retransmissions is less than the set number of retransmissions, the process returns to ST23 and resends the response. Otherwise, the process proceeds to ST25.
When a command with an ID designation (a write command, a read command, or the like) is received from the card reader / writer 4, processing corresponding to the command is performed.

By the above operation, as shown in FIG.
Communication with a plurality of cards can be performed while sequentially increasing the number of retransmissions.

In the embodiment shown in FIG. 4, a predetermined time T2 from the first command transmission to which a new number of retransmissions (including the case where the number of retransmissions is 0) is added in ST9.
Although it is determined whether or not the time has elapsed, instead, it may be determined whether or not the number of cards that have successfully received a response to a command transmission of a certain number of retransmissions has reached a certain number. . In the case of such a configuration, a flowchart as shown in FIG. 7 is obtained. That is, in ST5 ', the number of cards that have been processed normally, that is, the number of cards that have undergone processing such as receiving a normal response and extracting an ID, are counted, and ACK is transmitted to the card (ST6). It is determined whether or not the counted number of cards has reached a certain number (ST
9 ').

ST9 in FIG. 4 and ST9 'in FIG. 7 are steps for determining whether a certain number of cards have been processed. In addition, instead of such a method, when the total number of cards that have entered the communication area 2 is counted in advance, or when it is expected, the ratio of cards processed normally reaches a predetermined value. Or not. In this case, the value of the predetermined value increases as the number of retransmissions increases.

As described above, the number of response retransmissions is added to the command transmitted from the card reader / writer, and communication with each card is performed while the number of retransmissions is gradually increased. Is postponed, the processing of the card with good communication status is performed first, and the retransmission of the response of the card with poor communication status that is postponed is limited, so that the occurrence of collisions is reduced, thereby As a whole, the number of retransmissions of each card is reduced, and the processing time of the entire card is shortened. In addition, since a card having a good communication condition is processed first and no response is transmitted thereafter, a communication condition of a card having a bad communication condition is improved.

The communication system according to the present invention is a shopping system in which a card is attached to a product as a tag and a plurality of products selected by the customer for purchase are automatically processed at a checkout corner. A transport system that attaches tags to conveyed goods and recognizes them collectively at specific locations. A warehouse management system that attaches tags to each item stored in the warehouse and identifies them at a specific timing such as when the power is turned on. And so on. Further, the main device and the communication device are not limited to the card reader / writer and the card as described above, and any communication device having 1 to n can be applied.

[0053]

According to the present invention, the processing of a communication device having a bad communication condition is postponed, and the communication device having a good communication condition is processed first. Since the number of times is reduced and the number of collisions is reduced accordingly, the processing time required for communication as a whole can be reduced. Furthermore, since a communication device with a good communication condition is processed first, and thereafter, a response transmission from a communication device with a bad communication condition is mainly performed, the communication condition of a card with a bad communication condition is improved. Also, the processing time required for communication as a whole is reduced.

[Brief description of the drawings]

FIG. 1 is a diagram conceptually showing an operation of a communication system according to an embodiment of the present invention;

FIG. 2 is a diagram showing a configuration diagram of a card reader / writer and a card according to the embodiment of the present invention;

FIG. 3 is a view for explaining a protocol of the communication system according to the embodiment of the present invention;

FIG. 4 is a flowchart showing the operation of the card reader / writer in the communication system according to the embodiment of the present invention;

FIG. 5 (A) to (C) Command, response, and ACK
The figure which shows the transmission data format of FIG.

FIG. 6 is a flowchart showing the operation of the card in the communication system according to the embodiment of the present invention;

FIG. 7 is a flowchart showing the operation of another example of the card reader / writer.

FIG. 8 is a diagram illustrating a conventional problem of a card system.

Claims (6)

[Claims] 1. An apparatus according to claim 1, further comprising the step of adding the number of retransmissions of a response from the communication apparatus to an arbitrary command transmitted from the main apparatus to the communication apparatus in a contactless manner, and increasing the number of retransmissions to the communication apparatus. A command transmitting means for transmitting is provided in the main device, and a response transmitting means for transmitting a response to the main device when the command is received from the main device is set to the maximum number of retransmissions and the transmission is successful until the transmission is successful. A communication system characterized by the following. 2. The communication system according to claim 1, wherein said command transmission means increases the number of retransmissions each time the number of communication devices that have successfully received a response reaches a certain number. 3. The communication system according to claim 1, wherein said command transmission means increases the number of retransmissions every time a predetermined time elapses from the first command transmission to which the new number of retransmissions is added. 4. The communication system according to claim 1, wherein the main device is a card reader / writer, and the communication device is a contactless card that communicates with the card reader / writer without contact. 5. A command transmitted to a destination without contact is added with the number of retransmissions of a response from the destination, and the command is transmitted to the destination while increasing the number of retransmissions. A communication device comprising command transmission means. 6. A response transmitting means for transmitting a response to a main device when the command to which the number of times of retransmission of a response is added is received from a main device of a command transmission source until the transmission is successful. A communication device comprising: