JP5525643B2 - Wireless communication system - Google Patents

Description

  The present invention relates to a radio communication system that performs frequency hopping communication between a base station and a mobile station.

  The present invention also relates to a technique for providing a high-quality communication line by maintaining or updating a high-quality communication line over a long period of time in a wireless train control method and train control system. Maintenance of high-quality communication lines over a long period of several decades can also be expected.

  In train control methods and train control systems, there is a movement to reduce the cost of railway communication systems, and the introduction of train control systems using 2.4G-band radio frequencies that do not require licenses worldwide is being considered. Yes.

  However, there are many standards such as IEEE802.11b / g and Bluetooth (registered trademark) using 2.4G band radio frequency. These standards are used by various devices such as wireless LANs and mobile devices, and are frequency bands where interference problems cannot be avoided.

  In addition, in the train control method and the train control system, introduction of a wireless communication system using a general-purpose wireless LAN is being studied. In order to introduce a general-purpose wireless LAN to a train control system, since a mobile station moves at high speed, it is required that there is no delay in handover in which the mobile station switches base stations.

  Patent Document 1 (Japanese Patent Laid-Open No. 2009-171078) discloses an invention in which it is desired to select a frequency channel that is less affected by interference signals and noise power in a radio communication system using a frequency hopping method. According to the present invention, in a radio communication system comprising a base station installed along a predetermined route and a mobile station moving along the predetermined route, each base station has first and second hopping tables and has interference. Select the hopping table to be used according to the signal status. In the hopping table, frequency channels are set in advance so that interference with an adjacent base station does not occur regardless of which one is selected. As a result, it is possible to select an optimum frequency channel without interference without transmitting / receiving prior information such as the usage status of the frequency channel between base stations.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2008-99233), in a train control system, train control information is transmitted and received between a plurality of wireless base stations along a track along which a train moves and wireless mobile stations mounted on the train. An invention for smoothly switching between radio frequencies is disclosed. In the present invention, in a train control system that performs wireless communication between a plurality of mobile stations moving on a predetermined route and a plurality of base stations installed along a predetermined route, a different communication frequency is set for each base station. The mobile station searches for communication frequencies of a plurality of base stations installed along a predetermined route, and between the mobile station and the base station corresponding to the specific radio frequency by the searched specific radio frequency Send and receive control information.

  As a method for providing a high-quality communication line, for example, there is a method disclosed in Patent Document 1. This method describes a technique of having two frequency hopping patterns in advance and switching the frequency hopping pattern according to the state of the interference signal.

  As a method for providing a handover without delay, for example, there is a method disclosed in Patent Document 2. In this method, the mobile station searches for a communication frequency for each base station and communicates with the found frequency. This eliminates the need for negotiation before handover.

JP 2009-171078 A JP 2008-99233 A

  A common method for the frequency interference problem is frequency hopping. Frequency hopping is a method of performing communication while changing the frequency according to a predetermined frequency hopping pattern table. In Patent Documents 1 and 2, communication quality is improved by a frequency hopping pattern method.

  However, since the techniques of Patent Document 1 and Patent Document 2 do not have prior negotiation for performing handover, even if communication is performed by changing a channel according to a predetermined frequency hopping pattern, interference occurs at the changed frequency. Communication is not always successful without receiving it. Further, in the method of switching the frequency hopping pattern according to the communication status disclosed in Patent Document 2, an error due to interference is determined even when there is no mobile station.

  With respect to such a problem, an object of the present invention is to accurately grasp channel interference obtained from an actual use environment in a train control method and a train control system in which handover without delay is required. An object of the present invention is to obtain a channel interference situation without degrading the original communication reliability of the system. By accurately grasping channel interference, it becomes possible to update the table of frequency hopping patterns in a timely manner, and provide high-quality communication.

  The present invention performs wireless communication using a plurality of channels between a base station and a mobile station, performs wireless communication a plurality of times in one cycle of wireless communication, and the wireless communication channel is based on a frequency hopping pattern table. A wireless communication system to be changed, comprising: communication result determining means for determining whether or not the communication result in each channel is normal; and storage means for storing the communication result of each channel, the frequency hopping pattern When the first wireless communication within one cycle according to the table is determined to be abnormal by the communication result determination means, the channel used for the second wireless communication within one cycle is set according to the frequency hopping pattern table When the first wireless communication within one cycle according to the frequency hopping pattern table is determined to be normal by the communication result determining means, 1 As a channel to be used for the second wireless communications within the period, and sets a channel that does not conform to the frequency hopping pattern table.

  Further, the present invention is used for the second wireless communication within one cycle when the first wireless communication within one cycle according to the frequency hopping pattern table is determined to be normal by the communication result determining means. Regardless of the frequency hopping pattern table, a channel in which it is stored in the storage means that the communication result is abnormal is set as the channel to be performed.

  In the wireless communication system of the present invention, when the first wireless communication in one cycle according to the frequency hopping pattern table is determined to be normal by the communication result determining means, the second wireless communication in one cycle Regardless of the frequency hopping pattern table, a channel stored in the storage means that the communication result is abnormal is set as a channel to be used.

  Furthermore, the wireless communication system of the present invention is characterized in that the storage means stores the number of times that the communication result determination means has determined a reception error as the communication result of each channel.

  According to the present invention, channel interference situations can be collected without reducing communication reliability. In addition, since communication for interference state collection is performed immediately after successful communication, communication errors due to physical shielding and absence of trains can be excluded, and only pure interference can be collected. Further, it can be determined whether interference has occurred in downlink communication data or uplink communication data.

The block diagram of the radio | wireless communications system of the Example of this invention. The basic sequence figure of the radio | wireless communications system of the Example of this invention. The functional block diagram of AP of the Example of this invention. 2 is a channel interference collection table configuration according to the first embodiment of the present invention. The reception result storage table structure of Example 1 of this invention. The interference channel collection sequence figure of the radio | wireless communications system of Example 1 of this invention. FIG. 3 is a flowchart of an intra-AP channel selection process according to the first embodiment of this invention. FIG. 3 is an in-AP RF reception process flowchart according to the first embodiment of the present invention. The received electric field strength transmission sequence diagram of Embodiment 2 of the present invention. A part of response data frame of Example 2 of the present invention.

  Hereinafter, a wireless communication system to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a wireless communication system according to a first embodiment of the present invention. In the illustrated wireless communication system, a plurality of base stations 13 a to 13 c arranged about every 350 m on a predetermined route 11 are installed. The mobile station 12 changes the base stations 13a, 13b, 13c... That communicate with each other while moving on the predetermined route 11.

  FIG. 2 is a diagram illustrating a basic sequence of a wireless communication system performed between the base stations 13a, 13b, 13c... Described in FIG.

  The illustrated basic sequence will be described in order. An access point master (Access Point Master, hereinafter referred to as AP) that supervises an access point (hereinafter referred to as AP) 22 of each of the plurality of base stations 13a, 13b, 13c,. APM (described as APM) 21 transmits communication data to the AP 22 at regular intervals. There are 13 conventional radio channels, and 3 channels with non-overlapping frequencies are divided into 16 channels with no frequency overlapping in the present invention. Communication is performed at intervals of about 500 msec.

  As shown in FIG. 2, the AP 22 acquires a transmission channel (one of 16 channels from 0 to 15) from the frequency hopping pattern table 24 stored therein, and transmits communication data to a mobile station station (Station or lower). , Simply described as STA). Further, after a certain time, the next channel is taken out from the frequency hopping pattern table 24, and the communication data is transmitted to the mobile station 23 again after changing the channel. After completing the transmission twice, the response data from the mobile station 23 is transmitted to the APM 21. In the AP 22 of this embodiment, frequency hopping (time diversity) is performed twice in one cycle to improve the establishment of successful communication data with the mobile station 23. FIG. 2 shows a state in which channel 0 is taken out at the first transmission frequency, channel 8 is taken out at the second time, channel 4 is taken out at the second cycle, and channel 4 is taken out at the third time. FIG. 2 shows a case where communication on all channels is normal.

  FIG. 3 is a diagram illustrating functional blocks of the AP 22. The Ethernet (registered trademark) unit 31 manages a function of transmitting / receiving communication data to / from the APM 21. The wireless unit 32 manages the function of transmitting and receiving communication data with the STA 23 wirelessly. In the ETH transmission / reception process 33, communication data received from the APM 21 is transferred to the channel selection process 34, and communication data received from the RF reception process 35 is transferred to the Ethernet unit 31.

  In the channel selection process 34, when activated from the ETH transmission / reception process 33, a channel is determined from the frequency hopping pattern table 24 based on the serial number included in the communication data, and a transmission request is made to the RF transmission process 36. Also, after a certain time, the channel is changed based on the frequency hopping pattern, and a second transmission request is made. In the second transmission request, the transmission channel is determined with reference to the reception result storage table 38 that stores the reception result from the STA 23 and the channel interference collection table 37 that stores the channel collection mode and the like.

  In the RF reception process 35, the rationality of the communication data received from the radio unit 32 is checked, the result is stored in the reception result storage table 38 and the channel interference collection table 37, and normal communication data is received by the ETH transmission / reception process 33. hand over. In the RF transmission process 36, the channel selection process 34 is started, and a request is made to transmit to the RF unit using the channel determined in the channel selection process 34.

  FIG. 4 is a diagram showing the structure of the channel interference collection table. The channel collection range 41 sets a channel that the AP 32 can set as a transmission channel for a channel with a poor communication result. The purpose is to prevent the channel for collecting channel interference from being duplicated between adjacent APs when a plurality of APs 32 are installed, so that the channels are not duplicated between neighboring APs.

  The transmission channel 42 sets a channel being transmitted. The channel collection mode 43 sets whether to perform channel interference collection. The fixed channel 44 collects designated channel interference by setting an arbitrary channel. Further, the number of normal receptions and the number of abnormal receptions are stored as statistical data.

  FIG. 5 shows the structure of the reception result storage table. In the reception NG channels 0 to 15 (51), when the communication data from the STA 23 is determined to be reception NG, a reception NG channel for the corresponding channel is set.

  FIG. 6 is a sequence for collecting channel interference conditions. When receiving communication data from the APM 61, the AP 62 acquires the transmission channel 0 from the frequency hopping pattern table 24 and transmits it to the STA 63. After receiving the response communication data from the STA 63, the transmission channel is changed and the second transmission is performed.

  In the second time, it is checked whether or not there is a reception NG channel in the reception result confirmation table. If there is no reception NG channel, the channel 8 according to the frequency hopping pattern table 24 is transmitted as it is. If the communication result is abnormal, the communication data of the response from the STA 63 with respect to the communication data transmitted on the channel 8 has not been received, so the presence of reception NG is recorded in the corresponding channel of the reception result storage table.

  In the next cycle, the transmission channel 4 is acquired from the frequency hopping pattern table 24 and communication data is transmitted to the STA 63. It is assumed that the communication result is normal. Next, since communication data transmission / reception on channel 4 was successful, as a process of collecting channel characteristics, it is checked whether there is a reception NG channel in the reception result confirmation table, and channel 8 that was NG is within the channel collection range. Check and re-use as characteristic collection channel. However, FIG. 6 shows a case where communication data for response is received again. If not received, the channel 8 records the presence of reception NG in the channel 8 of the reception result storage table 38, and records the number of abnormal receptions as the statistical data 45.

  In the embodiment of the present invention, the second transmission for interference check is performed after the normal communication for the first time while transmitting twice from AP 62 to STA 63 in one cycle. Channel interference can be checked without degrading communication reliability. In addition, since the check communication data is transmitted after the first normal communication, the possibility of a reception abnormality due to physical shielding is low, and only accurate channel interference can be measured.

  FIG. 7 is a flowchart of channel selection processing in the first embodiment. After power-on (step 70), the system waits for activation from the ETH transmission / reception process (step 71). After the activation request, a channel is selected from the frequency hopping pattern table 24 based on the serial number included in the communication data (step 72). After selecting the channel, the RF transmission processing is requested to transmit (step 73). Thereafter, the response result of the STA 12 with respect to communication data transmission is determined (step 74), and if it is confirmation NG, the channel is selected from the frequency hopping pattern table 24 for the second transmission (step 78). If the response result determination is OK (normal), it is further determined whether there is a reception result NG channel and within the channel collection range (step 75). If there is a corresponding channel, a second transmission is requested as a channel interference collection channel (step 75). 76). Here (step 75), if the response result determination is NG, the channel is selected from the frequency hopping pattern table 24 for the second transmission (step 78). The RF transmission process (step 77) returns to the waiting for activation from the ETH transmission / reception process (step 71) after the transmission request.

  In this embodiment, the reception NG channel is configured to be extracted from the reception result storage table in step 76. However, the frequency selection to be communicated in the next cycle is set to the next channel with a predetermined channel regardless of the frequency hopping pattern table. It is also possible to configure to perform wireless communication.

  FIG. 8 is a flowchart of the RF reception process in the first embodiment. After the power is turned on (step 80), the reception data from RF is waited (step 81). When receiving from RF, a serial number error, CRC error, etc. are determined in the received data (step 82). The number of normal receptions is set for the corresponding channel in the collection table 37 (step 83). If the determination is NG, the reception NG channel is set in the reception result storage table 38 (step 85), and the corresponding channel result NG is stored in the reception result storage table 38. (Step 86), the number of times of abnormal channel reception in the channel interference collection table 37 is set in the statistical data 45 (step 87), and the content of abnormal reception (serial number error, CRC error) is set in the corresponding channel in the channel interference collection table ( Step 88). The activation of the ETH transmission / reception process (step 84) returns to waiting for reception data from the RF (step 81).

  FIG. 9 is a diagram showing a basic sequence in the second embodiment of the present invention. The illustrated basic sequence will be described in order. The communication data is broadcasted from the APM 91 to each of the APs 92a and 92b (AP1 and AP2) at a constant cycle as in the first embodiment. Each of AP1 and AP2 92a and 92b acquires a transmission channel from the frequency hopping pattern table 24 (see FIG. 2) stored therein, and transmits communication data to the mobile station STA93. At this time, the frequency hopping pattern table 24 is set so that the channels transmitted from the adjacent AP1 and AP2 92a and 92b do not overlap. The first communication in the first cycle shown in FIG. The mobile station STA 93 searches for the communication channel of the base station at a fixed period, stores the received field strength of the channel found, stores the response field and the received field strength of the channel found by searching for the channel to be transmitted as response data. At the same time, it is transmitted to AP92.

  In the example of FIG. 9, channel 0 and channel 8 are found in the electric field intensity collection 94a, and the response data is transmitted to AP1 (92a) as response / field intensity data 95a using the channel 8. In the second electric field intensity collection 94b, since channel 4 was not found but only channel 8 was found, it indicates that response data was transmitted to AP2 (92b) as response / field intensity data 95b. In the APM 91, it is determined from the response data received from each AP 92 whether there is interference in downlink data or uplink interference based on the presence / absence of the electric field strength of the channel transmitted as downlink data.

  FIG. 10 is a diagram showing a part of response data received by the APM 91 from the APs 92a and 92b. The APM 91 collects the transmission / reception results of the channels of the APs 1 and 2 from the response data received from the APs 92a and 92b. In the collection method, all transmission channels are extracted from the response data 101 (response / field strength data) received from the APs 1 and 2. Next, when the channel in which the electric field strength value is set is extracted from each response data, and the transmission channel and the channel in which the electric field strength value are set match, it can be understood that there is no interference up to the downlink data. It can be seen that the transmission channel in which the field strength value corresponding to the transmission channel is not found does not reach the SAT 93 for downlink data transmission.

  11: predetermined route, 12: mobile station, 13: base station, 13a: 13b: 13c: base station, 21: APM, 22: AP (base station), 23: STA (mobile station) 24: frequency hopping pattern table 31: Ethernet part (ETH), 32: Radio part (RF), 33: ETH transmission / reception process, 34: Channel selection process, 35: RF reception process, 36: RF transmission process, 37: Channel interference collection table, 38: Reception result storage table, 41: channel collection range, 42: transmission channel, 43: channel collection mode, 44: fixed channel, 61: APM, 62: AP, 63: STA, 91: APM, 92a: AP1, 92b: AP2 93: STA, 94a: electric field intensity collection, 94b: electric field intensity collection, 95a: response / field intensity data, 95b: response / field intensity data Data, 101: AP response part of the data

Claims (4)

Wireless communication is performed between a base station and a mobile station using a plurality of channels, wireless communication is performed a plurality of times in one cycle of wireless communication, and the wireless communication channel is changed based on a frequency hopping pattern table A communication system,
Communication result determination means for determining whether or not the communication result in each channel is normal, and storage means for storing the communication result of each channel,
If the first wireless communication within one cycle according to the frequency hopping pattern table is determined to be abnormal by the communication result determining means, the channel used for the second wireless communication within the one cycle is the frequency hopping. Set according to the pattern table,
When the first wireless communication within one cycle according to the frequency hopping pattern table is determined to be normal by the communication result determining means, the frequency is used as a channel used for the second wireless communication within one cycle. A wireless communication system, wherein a channel that does not follow a hopping pattern table is set.   When the first wireless communication within one cycle according to the frequency hopping pattern table is determined to be normal by the communication result determining means, the frequency is used as a channel used for the second wireless communication within one cycle. 2. The wireless communication system according to claim 1, wherein a channel in which an abnormal communication result is stored in the storage unit is set regardless of a hopping pattern table.   When the first wireless communication within one cycle according to the frequency hopping pattern table is determined to be normal by the communication result determining means, the frequency is used as a channel used for the second wireless communication within one cycle. 2. The wireless communication system according to claim 1, wherein a channel in which an abnormal communication result is stored in the storage unit is set regardless of a hopping pattern table.   The wireless communication system according to claim 1, wherein the storage unit stores the number of times the communication result determination unit determines that the reception is abnormal as a communication result of each channel.

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