Tag communication device, control device, and tag communication method

• US 20070205868A1
• Filed: 06/29/2006
• Published: 09/06/2007
• Est. Priority Date: 03/06/2006
• Status: Abandoned Application

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Tanaka, Yoshinori
• Application Number:
  US11/476,719
• Publication Number:
  US 20070205868A1
• Time in Patent Office: Days
• US Class Current: 340/10.200
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas

Abstract

The present invention includes a no-response detecting unit, an interference channel detecting unit, a post-transmission stop time setting unit, and a transmission control unit. The no-response detecting unit performs carrier sense. Then, after communication from an open channel is started, the no-response detecting unit detects the communication state with the tag. The interference channel detecting unit performs carrier sense on all channels, detects a channel with a high interference level, and outputs the detected channel to an external control device, when the no-response detecting unit detects that the communication state is degraded. The post-transmission stop time setting unit updates and sets the stop time after transmission (T_sleep) when an interferer notification, notifying that the tag communication device is an interferer, is given by the control device. The transmission control unit notifies the control device of the channel used at the start of the transmission to the tag. In addition, following the transmission to the tag, the transmission control unit starts the carrier sense after transmission is stopped for the post-transmission stop time (T_sleep).

Claims

1. A tag communication device for which maximum continuous transmission time for one transmission to a tag is determined, the tag communication device comprising:

a state detecting unit configured to detect an open channel by carrier sense, and to detect a communication state between the tag communication device and the tag, the communication state after transmission using the open channel is started;

a channel detecting unit configured to perform carrier sense on all channels used for communication with the tag to detect a channel having a high interference level, and to output interference channel information indicative of detected channel, to an external control device, when the state detecting unit detects that the communication state is degraded;

a time setting unit configured to re-set a post-transmission stop time, when an interferer notification is received from the control device, the interferer notification indicating that the tag communication device is an interferer that causes interference in another device; and

a control unit configured to notify the control device of a channel used at a time of starting the transmission, to stop transmission to the tag for time equivalent to the post-transmission stop time, and to start the carrier sense after stopping transmission for the time.

2. The tag communication device according to claim 1, wherein the state detecting unit is configured to detect that the communication is degraded when there is no response from the tag for a predetermined time, and to detect that the communication is degraded when transmission errors continue for a predetermined period.

3. The tag communication device according to claim 1, wherein the state detecting unit is configured to detect that the communication state is degraded when a timeout continuously occurs a predetermined number of times, the timeout in a state in which communication with the tag is impossible to be started, and/or to detect that the communication state is degraded when an open channel is not detected for a predetermined duration.

4. The tag communication device according to claim 1, wherein the channel detecting unit is configured to perform the carrier sense on all channels and to output the interference channel information, when number of occurrence of a timeout exceeds a threshold, the timeout in a state in which communication with the tag is impossible to be started due to degradation of the communication state.

5. The tag communication device according to claim 1, wherein

the control unit is configured to stop transmission to the tag for a time equivalent to the post-transmission stop time, upon completion of transmission to the tag, the transmission having duration shorter than a maximum continuous transmission time, and

the post-transmission stop time has a time length equal to or more than a minimum transmission stop time.

6. The tag communication device according to claim 5, wherein the time setting unit is configured to re-set the post-transmission stop time to a time equal to or more than the maximum continuous transmission time when the interferer notification is received.

7. The tag communication device according to claim 1, further comprising a judging unit configured to judge, when the detecting unit detects that the communication state is degraded, whether a timeout has occurred by determining whether a predetermined timeout time has elapsed while the communication state is degraded, wherein

the control unit is configured to start, when the judging unit judges that the timeout has occurred, the carrier sense after transmission to the tag is stopped for a timeout stop time.

8. The tag communication unit according to claim 7, wherein the control unit is configured to start the carrier sense after the transmission is stopped for the timeout stop time, not for the post-transmission stop time, when the judging unit judges that the timeout has occurred.

9. The tag communication device according to claim 7, wherein the judging unit is configured to set the timeout time based on the communication state and a transmission priority level.

10. The tag communication device according to claim 9, wherein the judging unit is configured to set the timeout time and the transmission priority level, such that the timeout time is longer and the transmission priority level is higher as frequency of the timeout increases.

11. The tag communication device according to claim 7, wherein the control unit is configured to set a random value to the timeout stop time, the random number being smaller than a predetermined maximum value.

12. The tag communication device according to claim 11, wherein the control unit is configured to set the maximum value according to recent frequency of the timeout.

13. The tag communication device according to claim 1, wherein the tag communication device is connected to a plurality of other tag communication devices via a network, the tag communication device further comprising:

a channel usage table configured to store latest information on a channel notified by each of the other tag communication devices, in an associated manner with each of the other tag communication devices;

a determining unit configured to search the channel usage table to determine a tag communication device using a channel causing interference, when the interference channel information is input; and

a notifying unit configured to output the interferer notification to determined tag communication device to notify that the determined tag communication device is an interferer.

14. A control device connected to a plurality of other tag communication devices via a network, comprising:

a channel usage table configured to store latest information on a channel notified by each of the tag communication devices, in an association manner with each of the tag communication devices;

a determining unit configured to search the channel usage table to determine a tag communication device using a channel causing interference, when interference channel information indicative of a channel having a high interference level is input; and

a notifying unit configured to output the interferer notification to determined tag communication device to notify that the determined tag communication device is an interferer.

15. A method of tag communication for which maximum continuous transmission time for one transmission to a tag is determined, the method comprising:

detecting an open channel by carrier sense;

detecting a communication state between a tag communication device and the tag, the communication state after transmission using the open channel is started;

performing carrier sense on all channels used for communication between the tag communication device and the tag to detect a channel having a high interference level;

outputting interference channel information indicative of detected channel, to an external control device;

re-setting a post-transmission stop time, when the tag communication device receives an interferer notification from the control device, the interferer notification indicating that the tag communication device is an interferer that causes interference in another device;

notifying the control device of a channel used at a time of starting the transmission;

stopping transmission to the tag from the tag communication device for time equivalent to the post-transmission stop time; and

starting the carrier sense after stopping transmission for the time.