JP6074905B2 - Wireless terminal and channel scanning method - Google Patents

Description

  The present case relates to a wireless terminal that performs wireless communication with a base station and a channel scanning method.

  In a wireless communication system represented by a wireless local area network (LAN), for example, a mobile station performs an operation called channel scan when switching a base station for wireless communication.

  For example, it is assumed that the mobile station is communicating with a base station operated on a certain communication channel (frequency / modulation method). Then, it is assumed that the mobile station moves to another location and enters the area of the base station operated by another communication channel.

  In this case, the mobile station searches for a base station channel by searching for a signal from the base station or another mobile station while changing the channel of the receiver, and searches for the base station. When the mobile station can find the channel, the mobile station can perform wireless communication with the new base station using the channel.

  Conventionally, a method has been proposed in which a suitable and efficient handoff can be realized even in a system in which many different frequency base stations exist (see, for example, Patent Document 1).

  Conventionally, an apparatus that continuously secures comfortable viewing for the user while suppressing unnecessary channel switching has been proposed (see, for example, Patent Document 2).

JP 2009-260448 A JP 2010-200093 A

However, the conventional channel scan has a problem that it takes time when the number of channels to be scanned is large.
For example, when a plurality of base stations perform wireless communication using 10 different channels, the mobile station will perform channel scanning of 10 channels at the maximum, and the time required for channel scanning becomes longer. End up.

  The present invention has been made in view of such a point, and an object thereof is to provide a radio terminal and a channel scan method capable of shortening a channel scan time.

  In order to solve the above problems, a wireless terminal that performs wireless communication with a base station is provided. The wireless terminal includes a storage unit that stores base station position information and channel information, a positioning unit that measures the position of the wireless terminal, and base station position information and the positioning unit that are stored in the storage unit. Based on the measured position of the wireless terminal, a calculation unit that calculates the distance between the wireless terminal and the base station, and the order of scanning the channel of the base station according to the distance calculated by the calculation unit A scanning unit that calculates and scans the channel of the base station within a predetermined distance.

  According to the disclosed apparatus and method, the channel scanning time can be shortened.

It is a figure explaining the radio | wireless terminal which concerns on 1st Embodiment. It is the figure which showed the radio | wireless communications system which concerns on 2nd Embodiment. It is a functional block diagram of a wireless terminal. It is the figure which showed the example of base station information. It is the figure which showed the example of the channel list. It is the flowchart which showed the operation | movement of a channel scan. It is a figure explaining operation | movement during communication of MS. It is the figure which showed the example of the base station information of MS. It is the figure which showed the example of the channel list of MS. It is a figure explaining operation | movement when MS moves to the other base station of the same channel. It is the figure which showed the example of the base station information of MS. It is the figure which showed the example of the channel list of MS. It is a figure explaining operation | movement when MS moves to the base station of another channel. It is the figure which showed the example of the base station information of MS. It is the figure which showed the example of the channel list of MS. It is a figure explaining operation | movement when MS moves out of an area. It is the figure which showed the example of the base station information of MS. It is the figure which showed the example of the channel list of MS. It is a figure explaining operation | movement when MS moves into the area of a base station. It is the figure which showed the example of the base station information of MS. It is the figure which showed the example of the channel list of MS. It is a figure explaining operation | movement of MS when communication is interrupted. It is the figure which showed the example of the base station information of MS. It is the figure which showed the example of the channel list of MS. It is the figure which showed the hardware block of MS. It is a figure explaining the case where BS has a plurality of channel candidates.

Hereinafter, embodiments will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 is a diagram illustrating a radio terminal according to the first embodiment. As illustrated in FIG. 1, the wireless terminal includes a storage unit 1, a positioning unit 2, a calculation unit 3, and a scanning unit 4.

The storage unit 1 stores position information and channel information of a base station with which a wireless terminal performs wireless communication.
For example, the storage unit 1 has columns of base station ID (ID: Identifier), position information, channel information, and distance as shown in FIG.

  The base station ID column stores the ID of the base station with which the wireless terminal performs wireless communication. For example, when a wireless terminal performs wireless communication with a base station having IDs of BS1 to BS5, BS1 to BS5 are stored in the column of base station ID as shown in the storage unit 1 of FIG.

  In the position information column, position information where the base station is installed is stored. For example, it is assumed that the base stations BS1 to BS5 are installed at positions a to e. In this case, a to e are stored in the position information column as shown in the storage unit 1 of FIG.

  The channel information column stores information on the channel through which the base station performs wireless communication. For example, it is assumed that the base stations of BS1 and BS2 perform wireless communication on channel 1. Assume that the base station of BS3 performs wireless communication on channel 2. Assume that the base stations of BS4 and BS5 perform wireless communication on channel 3. In this case, 1, 2, 2, 3, and 3 are stored in the channel information column as shown in the storage unit 1 of FIG.

The information stored in the storage unit 1 may be stored in the storage unit 1 in advance, for example. Further, the wireless terminal may receive from the base station. The distance column will be described later.
The positioning unit 2 measures the position of the wireless terminal.

  The calculation unit 3 calculates the distance between the wireless terminal and the base station based on the position information of the base station stored in the storage unit 1 and the position of the wireless terminal measured by the positioning unit 2. That is, the calculation unit 3 calculates the distance between the wireless terminal and the base station stored in the storage unit 1.

  The calculation unit 3 stores the calculated distance in the storage unit 1, for example. For example, it is assumed that the distance between the wireless terminal and BS1 is 4. Assume that the distance between the wireless terminal and BS2 is 1. Assume that the distance between the wireless terminal and BS3 is 3. It is assumed that the distance between the wireless terminal and BS 4 is 15. It is assumed that the distance between the wireless terminal and BS 5 is 14. In this case, 4, 1, 3, 15, and 14 are stored in the distance column of the storage unit 1 as shown in the storage unit 1 of FIG. In the above example, the distance information is stored in the storage unit 1, but may be stored in another storage unit.

The scanning unit 4 calculates the order of scanning the channels of the base station according to the distance calculated by the calculation unit 3, and scans the channels of the base station within a predetermined distance.
For example, the scanning unit 4 calculates the order in which the channels of the base station are scanned in order of increasing distance between the wireless terminal and the base station. In the example of the storage unit 1 illustrated in FIG. 1, the distance between the wireless terminal and the base station is short in the order of BS2, BS3, BS1, BS5, BS4. Therefore, the scanning unit 4 calculates the order of BS2, BS3, BS1, BS5, BS4.

  Further, the scanning unit 4 scans a channel of a base station that is within a predetermined distance “5”, for example. For example, in the case of the above example, the base stations within a predetermined distance “5” are BS2, BS3, BS1. Therefore, the scanning unit 4 performs channel scanning of the base station using channels 1 and 2.

  Thus, the calculation unit 3 of the wireless terminal calculates the distance between the base station and the wireless terminal. The scanning unit 4 calculates the order of scanning the channels of the base station according to the distance calculated by the calculation unit 3, and scans the channels of the base station within a predetermined distance. As a result, the wireless terminal can narrow down the channel scanning time to the channel of the base station that is close to itself, thereby shortening the channel scanning time.

[Second Embodiment]
Next, a second embodiment will be described in detail with reference to the drawings.
FIG. 2 is a diagram illustrating a wireless communication system according to the second embodiment. As illustrated in FIG. 2, the wireless communication system includes wireless terminals 11 to 16 and base stations 21 to 25 and 31. The wireless terminals 11 to 16 perform wireless communication with the base stations 21 to 25. The base stations 21 to 25 perform wireless communication with the base station 31.

  The wireless communication system shown in FIG. 2 is installed in, for example, a field. The wireless terminals 11 to 16 are carried by workers who work in the field. A road 41 exists between the base stations 21 to 23 and the base stations 24 and 25.

  The wireless terminals 11 to 16 include, for example, a temperature sensor, a humidity sensor, an acceleration sensor, an angular velocity sensor, a magnetic sensor, a sensor that measures soil moisture, a sensor that measures soil conductivity, a sensor that measures soil pH, and It has a sensor that measures the radiation dose. The wireless terminals 11 to 16 are equipped with, for example, a GPS (Global Positioning System), and can acquire the positions of the wireless terminals 11 to 16.

  Information acquired by the wireless terminals 11 to 16 is transmitted to the base stations 21 to 25. The base stations 21 to 25 transmit information received from the wireless terminals 11 to 16 to the base station 31. Thereby, for example, the manager who manages the field can know the temperature of the field, the state of the soil, or the position of the worker from the information received by the base station 31.

  Note that the base stations 21 to 25 do not have to immediately transmit the information received from the wireless terminals 11 to 16 to the base station 31. For example, the base stations 21 to 25 may store a certain number of pieces of information like a DTN (Delay Tolerant Network) and then transmit the information to the base station 31 at an appropriate time.

  The base station 31 transmits predetermined information to the base stations 21 to 25. The base stations 21 to 25 transmit information received from the base station 31 to the wireless terminals 11 to 16. Thereby, for example, the manager who manages the field can give a predetermined instruction to the worker who possesses the wireless terminals 11 to 16.

  In the example of FIG. 2, the wireless terminals 11 to 16 can wirelessly communicate with the base station 21 through the channel 1. The wireless terminals 11 to 16 can wirelessly communicate with the base station 22 through the channel 2. The wireless terminals 11 to 16 can wirelessly communicate with the base station 23 through the channel 2. The wireless terminals 11 to 16 can wirelessly communicate with the base station 24 through the channel 3. The wireless terminals 11 to 16 can wirelessly communicate with the base station 25 through the channel 4.

  FIG. 3 is a functional block diagram of the wireless terminal. As illustrated in FIG. 3, the wireless terminal 11 includes an antenna 51, a transmission / reception unit 52, a control unit 53, a positioning unit 54, a sensor unit 55, and a storage unit 56.

  The antenna 51 wirelessly transmits a signal output from the control unit 53 to the base stations 21 to 25. The antenna 51 receives signals wirelessly transmitted from the base stations 21 to 25 and outputs the signals to the transmission / reception unit 52.

  The transmission / reception unit 52 converts the signal output from the transmission / reception unit 52 into a radio frequency signal and outputs the signal to the antenna 51. In addition, the transmission / reception unit 52 converts the frequency of the signal received by the antenna 51 into the frequency of the baseband signal and outputs it to the control unit 53.

  The control unit 53 performs overall control of the wireless terminal 11. For example, the control unit 53 calculates the distance between the wireless terminal 11 and the base stations 21 to 25 or calculates a channel for channel scanning of the base stations 21 to 25.

The positioning unit 54 measures the position of the wireless terminal 11. The positioning unit 54 is, for example, a GPS.
The sensor unit 55 measures temperature and soil state. The sensor unit 55 is formed by, for example, the various sensors described above.

  The storage unit 56 stores data. The storage unit 56 stores, for example, position information of the base stations 21 to 25 and channel information used by the base stations 21 to 25 for wireless communication. In addition, the storage unit 56 stores, for example, information on channels that the wireless terminal 11 performs channel scanning.

  Note that the storage unit 56 in FIG. 3 corresponds to the storage unit 1 in FIG. 1, for example. The positioning unit 54 corresponds to, for example, the positioning unit 2. The control unit 53 corresponds to the calculation unit 3 and the scan unit 4, for example.

Although the wireless terminal 11 has been described above, the wireless terminals 12 to 16 also have the same functional blocks as in FIG.
Hereinafter, the wireless terminals 11 to 16 may be referred to as MS (Mobile Station) 1 to MS6. The base stations 21 to 25 may be referred to as BS (Base Station) 1 to BS5. In addition, IDs for identifying the base stations 21 to 25 may be BS1 to B5. The base station 31 may be called CS (Control Station).

  FIG. 4 is a diagram illustrating an example of base station information. The base station information 61 illustrated in FIG. 4 indicates base station information included in the wireless terminal 11 (MS1). The base station information 61 is stored in the storage unit 56 shown in FIG. The base station information 61 includes a base station ID column, a latitude column, a longitude column, an altitude column, a channel column, and a distance column.

In the base station ID column, IDs for identifying BS1 to BS5 are stored.
The latitude column, longitude column, and altitude column store the latitude, longitude, and altitude where BS1 to BS5 are installed. That is, the position information of BS1 to BS5 is stored in the latitude column, the longitude column, and the altitude column. For example, assuming that the latitude, longitude, and altitude of BS1 are x1, y1, and h1, the latitude, longitude, and altitude fields of BS1 are x1, y1 as shown in the base station information 61. , And h1 are stored.

  The channel column stores the channels through which BS1 to BS5 communicate wirelessly with MS1 to MS6. For example, it is assumed that BS1 performs wireless communication with MS1 to MS6 through channel 1. In this case, “1” is stored in the channel field of BS 1 as shown in the base station information 61.

  Information stored in the base station ID column, the latitude column, the longitude column, the altitude column, and the channel column is stored in the storage unit 56 in advance. Or you may make it receive such information from CS via BS1-BS5. The information in the distance column described below is calculated by the control unit 53 of the MS 1 and stored.

  The distance column stores the distance between MS1 and BS1 to BS5. The control unit 53 of the MS 1 determines between the MS 1 and BS 1 to BS 5 based on the position of the MS 1 measured by the positioning unit 54 and the information stored in the latitude column, the longitude column, and the altitude column. The distance is calculated.

  For example, the control unit 53 includes the latitude, longitude, and altitude stored in the latitude column, longitude column, and altitude column of BS1, and the latitude, longitude, and altitude of MS1 measured by the positioning unit 54. From the above, the distance between MS1 and BS1 is calculated. Then, the control unit 53 stores the calculated distance in the BS1 distance column. The control unit 53 similarly calculates the distance to the MS1 for the BS2 to BS5 and stores it in the column for the distance of the BS2 to BS5.

In the above description, the distance information is stored in the distance column of the base station information 61, but may be managed separately from the base station information 61.
Although the base station information of MS1 has been described above, MS2 to MS6 also have the same base station information as in FIG.

  FIG. 5 is a diagram illustrating an example of a channel list. A channel list 62 shown in FIG. 5 is a channel list that the MS 1 has. The channel list 62 is stored in the storage unit 56 shown in FIG.

  The channel list 62 is a list indicating the channels that the control unit 53 of the MS 1 performs channel scanning. For example, in the case of the example of FIG. 5, the control unit 53 performs channel scanning with two channels “2” and “1”. In addition, the control unit 53 performs a channel scan from channels higher in the channel list. In the case of the example in FIG. 5, the priority of the channel “2” is the highest, and the next is the channel “1”.

  The channel list 62 is generated by the control unit 53. The control unit 53 calculates the channel scanning order according to the distances from the BS1 to BS5. Then, the control unit 53 generates BS channels within a predetermined distance as the channel list 62.

  For example, the control unit 53 increases the priority of the channel scanning order as the distance from the BS1 to BS5 is shorter. For example, in the example of FIG. 4, it is assumed that the distance between MS1 and BS2 is the shortest. Next, it is assumed that the distance between MS1 and BS1 is short. Assume that the distance between MS1 and BS5 is the longest. In this case, the channel scanning order is BS2, BS1,..., BS5.

  For example, the control unit 53 generates a channel of a BS within a distance “5” as the channel list 62. For example, in the example of FIG. 4, it is assumed that BS1 and BS2 are within a distance "5". In this case, the control unit 53 generates, as the channel list 62, the channels “2” and “1” of BS2 and BS1 within the distance “5” among the calculated BS2, BS1,. To do.

  Note that if the same channel exists in the calculated channel scan order, the control unit 53 generates only the first calculated channel as the channel list 62. For example, assume that the channel order for channel scanning is 1, 2, 1, 3, and 4. The BS channels within a predetermined distance are the upper four channels, 1, 2, 1, 3. In this case, the third channel 1 is omitted, and the channel list 62 is 1, 2, and 3. That is, since it is not necessary to scan the same channel ‘1’ twice, the control unit 53 registers only the first calculated channel in the channel list 62 when calculating the same channel.

FIG. 6 is a flowchart showing the channel scan operation.
[Step S1] The positioning unit 54 measures the position of the MS1.
[Step S2] The control unit 53 determines the distance between the MS1 and the BS1 to BS5 based on the position of the MS1 calculated by the positioning unit 54 and the positions of the BS1 to BS5 stored in the base station information 61. calculate.

  [Step S3] The control unit 53 generates a channel list 62. The control unit 53 calculates the order of scanning the channels BS1 to BS5 according to the distance calculated in step S2. And the control part 53 produces | generates the channel of BS1-BS5 within the predetermined distance as the channel list 62. FIG.

[Step S <b> 4] The control unit 53 stores “1” in the variable N.
[Step S5] The controller 53 determines whether or not a channel is stored in the Nth channel list 62. When the channel is stored in the Nth channel list 62, the control unit 53 proceeds to step S6. When the channel is not stored in the Nth channel list 62, the control unit 53 proceeds to step S11.

[Step S <b> 6] The control unit 53 sets the channel to be communicated to the Nth channel in the channel list 62.
[Step S7] The control unit 53 performs a channel scan on the channel set in step S6. That is, the control unit 53 scans BS1 to BS5 capable of wireless communication.

  [Step S8] The controller 53 determines whether BS1 to BS5 capable of wireless communication have been scanned. When the control unit 53 has scanned BS1 to BS5 capable of wireless communication, the process proceeds to step S10. When the control unit 53 cannot scan BS1 to BS5 capable of wireless communication, the control unit 53 proceeds to step S9.

[Step S9] The controller 53 adds 1 to the variable N.
[Step S10] The control unit 53 starts wireless communication on the scanned channels BS1 to BS5.

[Step S11] The control unit 53 determines that the MS 1 exists outside the service area of BS1 to BS5.
The above operation is performed periodically, for example. Or the positioning part 54 and the control part 53 may perform the operation | movement of the said flowchart, when the communication disconnection with BS1-BS5 which is performing radio | wireless communication is detected. That is, the positioning unit 54 and the control unit 53 may execute the operation of the above flowchart when the MS 1 moves to another area and the channel for wireless communication changes.

  Note that the control unit 53 does not perform a channel scan when a channel is not stored in the channel list 62. For example, if N = 1 and it is determined in step S5 that no channel is stored in the channel list 62, the control unit 53 proceeds to step S11 and ends the process.

Hereinafter, an operation example of the MS 1 will be described.
FIG. 7 is a diagram for explaining the operation during communication of the MS. FIG. 7 shows a wireless communication system. BS1 can wirelessly communicate with MS1 through channel (CH in the figure) 1. BS2 can wirelessly communicate with MS1 on channel 1. BS 3 can communicate wirelessly with MS 1 over channel 2. BS 4 can wirelessly communicate with MS 1 on channel 3. BS 5 can communicate wirelessly with MS 1 over channel 3. In FIG. 7, MS 1 is communicating wirelessly with BS 1 via channel 1.

  FIG. 8 is a diagram illustrating an example of MS base station information. If the example of FIG. 7 is followed, the base station information which MS1 has will become like the base station information 71 shown in FIG. That is, 1, 1, 2, 3, and 3 are stored in the channel column of BS1 to BS5.

  Further, the distance between MS1 and BS1 to BS5 is close to BS1, BS2, BS3, BS5, BS4 in this order. Accordingly, for example, 1, 2, 3, 15, and 14 are stored in the distance column of the base station information 71.

In the base station information 71 in FIG. 8, the latitude column, the longitude column, and the height column are collectively used as the position column with respect to the base station information 61 described in FIG.
FIG. 9 is a diagram showing an example of an MS channel list. The control unit 53 calculates the order of scanning the channels BS1 to BS5 based on the distance column of the base station information 71. In the case of the example of the base station information 71 shown in FIG. 8, the order of channels to be scanned is 1, 1, 2, 3, 3.

  It is assumed that the control unit 53 generates BS channels within a distance “5” as a channel list. In the example of the base station information 71 shown in FIG. 8, the distance between BS4 and BS5 is greater than '5'. Accordingly, channel 3 of BS4 and BS5 is excluded from the channel scan, and the scanning order is 1, 1 and 2.

In addition, the control unit 53 excludes overlapping channels. Accordingly, the channel list generated by the control unit 53 is 1 and 2, as shown in the channel list 72 of FIG.
FIG. 10 is a diagram for explaining the operation when the MS moves to another base station on the same channel. In FIG. 10, compared with FIG. 7, MS1 moves to the area of BS2 and performs wireless communication with BS2.

  FIG. 11 is a diagram illustrating an example of MS base station information. In the example of FIG. 10, the distance between MS1 and BS1 to BS5 is close to BS2, BS3, BS1, BS4, BS5 in this order. Therefore, according to the example of FIG. 10, the base station information possessed by the MS 1 becomes the base station information 73 shown in FIG. For example, 3, 1, 2, 14, and 15 are stored in the distance column of the base station information 73.

  FIG. 12 is a diagram illustrating an example of a channel list of the MS. The control unit 53 calculates the order of channel scanning of the BS1 to BS5 based on the distance column of the base station information 73. In the case of the example of the base station information 73 shown in FIG. 11, the order of channels to be scanned is 1, 2, 1, 3, 3.

  It is assumed that the control unit 53 generates BS channels within a distance “5” as a channel list. In the case of the example of the base station information 73 shown in FIG. 11, the distance between BS4 and BS5 is larger than '5'. Therefore, channel 3 of BS4 and BS5 is excluded from the channel scan, and the scanning order is 1, 2, 1.

In addition, the control unit 53 excludes overlapping channels. Accordingly, the channel lists generated by the control unit 53 are 1, 2 as shown in the channel list 74 of FIG.
FIG. 13 is a diagram for explaining the operation when the MS moves to a base station of another channel. In FIG. 13, compared with FIG. 10, MS1 moves to the area of BS3 and performs wireless communication with BS3.

  FIG. 14 is a diagram illustrating an example of MS base station information. In the example of FIG. 13, the distance between MS1 and BS1 to BS5 is close to BS3, BS2, BS1, BS4, BS5 in this order. Therefore, according to the example of FIG. 13, the base station information possessed by the MS 1 becomes the base station information 75 shown in FIG. For example, 5, 3, 2, 14, and 15 are stored in the distance column of the base station information 75.

  FIG. 15 is a diagram illustrating an example of a channel list of the MS. The control unit 53 calculates the channel scan order of the BS1 to BS5 based on the distance column of the base station information 75. In the example of the base station information 75 shown in FIG. 14, the order of channels to be scanned is 2, 1, 1, 3, 3.

  It is assumed that the control unit 53 generates BS channels within a distance “5” as a channel list. In the example of the base station information 75 shown in FIG. 14, the distance between BS4 and BS5 is greater than '5'. Therefore, channel 3 of BS4 and BS5 is excluded from the channel scan, and the scanning order is 2, 1, 1.

In addition, the control unit 53 excludes overlapping channels. Accordingly, the channel list generated by the control unit 53 is 2, 1 as shown in the channel list 76 of FIG.
FIG. 16 is a diagram for explaining the operation when the MS moves out of the area. In FIG. 16, with respect to FIG. 13, MS1 has moved out of the area of BS1 to BS5.

  FIG. 17 is a diagram illustrating an example of MS base station information. In the example of FIG. 16, the distance between MS1 and BS1 to BS5 is close to the order of BS1, BS2 = BS5, BS4, BS3 (BS2 and BS5 are the same distance). Therefore, according to the example of FIG. 16, the base station information possessed by the MS 1 is as shown in the base station information 77 shown in FIG. For example, 11, 12, 15, 14, 12 are stored in the distance column of the base station information 77.

  FIG. 18 is a diagram illustrating an example of a channel list of the MS. The control unit 53 calculates the channel scan order of the BS1 to BS5 based on the distance column of the base station information 77. In the example of the base station information 77 shown in FIG. 17, the order of channels to be scanned is 1, 1, 3, 3, 2 or 1, 3, 1, 3, 2.

  It is assumed that the control unit 53 generates BS channels within a distance “5” as a channel list. In the example of the base station information 77 shown in FIG. 17, the distance between BS1 to BS5 is larger than '5'. Therefore, the channel list generated by the control unit 53 is empty as shown in the channel list 78 of FIG.

FIG. 19 is a diagram for explaining the operation when the MS moves into the area of the base station. In FIG. 19, with respect to FIG. 16, MS1 has moved into the area of BS5.
FIG. 20 is a diagram illustrating an example of MS base station information. In the example of FIG. 19, the distance between MS1 and BS1 to BS5 is close to BS5, BS4, BS2, BS1, BS3 in this order. Therefore, according to the example of FIG. 19, the base station information of the MS 1 is as shown in the base station information 79 shown in FIG. For example, 12, 11, 15, 2, 1 are stored in the distance column of the base station information 79.

  FIG. 21 is a diagram showing an example of the channel list of the MS. The control unit 53 calculates the channel scan order of the BS1 to BS5 based on the distance column of the base station information 79. In the example of the base station information 79 shown in FIG. 20, the order of channels to be scanned is 3, 3, 1, 1, 2.

  It is assumed that the control unit 53 generates BS channels within a distance “5” as a channel list. In the example of the base station information 79 shown in FIG. 20, the distance between BS1 to BS3 is larger than '5'. Therefore, channels 1 and 2 of BS1 to BS3 are excluded from the channel scan, and the channel scan order is 3, 3.

In addition, the control unit 53 excludes overlapping channels. Therefore, the channel list generated by the control unit 53 is 3, as shown in the channel list 80 of FIG.
FIG. 22 is a diagram for explaining the operation of the MS when communication is interrupted. In FIG. 22, with respect to FIG. 19, MS1 has moved to the boundary between the area of BS2 and the area of BS3.

  Assume that MS 1 is performing wireless communication with BS 3 using channel 2. Assume that BS3 has failed. In this case, the control unit 53 detects a disconnection with the BS 3 and performs a channel scan again.

  FIG. 23 is a diagram showing an example of MS base station information. In the example of FIG. 22, the distance between MS1 and BS1 to BS5 is close to BS3, BS2, BS1, BS4, BS5 in this order. Therefore, according to the example of FIG. 22, the base station information possessed by the MS 1 is as shown in the base station information 81 shown in FIG. For example, 5, 4, 3, 12, and 15 are stored in the distance column of the base station information 81.

  FIG. 24 is a diagram illustrating an example of a channel list of the MS. The control unit 53 calculates the channel scan order of BS1 to BS5 based on the distance column of the base station information 81. In the example of the base station information 81 shown in FIG. 23, the order of channels to be scanned is 2, 1, 1, 3, 3.

  It is assumed that the control unit 53 generates BS channels within a distance “5” as a channel list. In the example of the base station information 81 shown in FIG. 23, the distance between BS4 and BS5 is greater than '5'. Therefore, channel 3 of BS4 and BS5 is excluded from the channel scan, and the order of channel scan is 2, 1, 1.

In addition, the control unit 53 excludes overlapping channels. Therefore, the channel list generated by the control unit 53 is 2, 1 as shown in the channel list 82 of FIG.
The control unit 53 performs a channel scan based on the channel list 82. However, as described with reference to FIG. 22, since the BS 3 is out of order, the control unit 53 cannot scan the channel 2 of the BS 3.

  The control unit 53 performs a channel scan on the second channel 1. Since MS1 is at the boundary between BS2 and BS3, the control unit 53 can scan channel 1 of BS2. That is, the control unit 53 can perform wireless communication with the BS 2.

  22 to 24, the control unit 53 detects the disconnection with the BS 3, calculates the distance to the BS 1 to BS 5, and generates the channel list 82. On the other hand, the control unit 53 may perform the channel scan with the periodically generated channel list without generating the channel list 82 when the communication disconnection is detected.

  Next, an operation start example of the MS 1 will be described. First, the operation when there is a beacon will be described. When information related to communication (time information, ID of BS1 to BS5, etc.) is periodically transmitted (beacon), the control unit 53 of the MS1 wirelessly communicates with the highest channel in the channel list 62. Set the channel.

  The control unit 53 performs carrier sense or reception operation, receives beacons or communication packets of BS1 to BS5 and other MS2 to MS6, and confirms whether BS1 to BS5 of the set channel exist. If the control unit 53 cannot find BS1 to BS5, it sets the next channel in the channel list 62 and performs the same operation as described above.

  If the control unit 53 fails to find BS1 to BS5 even after trying all the channels, the control unit 53 enters a dormant state and performs the above-described operation at a predetermined timing (for example, after a certain time has elapsed or operation of the BS1). Perform the action.

  When the control unit 53 finds BS1 to BS5, the control unit 53 tries to communicate with the BS1 to BS5 using the time and method permitted by the BS1 to BS5. For example, the control unit 53 attempts communication with the BS1 to BS5 by the following method.

  1. A CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) based communication is attempted in the CAP (Contention Access Period) region defined in IEEE (The Institute of Electrical and Electronics Engineers) 802.15.4.

  2. A request to allocate a TDMA (Time Division Multiple Access) slot is made to BS1 to BS5 to acquire a TDMA slot. If the time slot to be communicated is known in advance for each of BS1 to BS5, that slot is used.

  When the control unit 53 becomes communicable with BS1 to BS5, it receives the base station information 61 and periodically generates the channel list 62. And the control part 53 transmits the information which the positioning part 54 and the sensor part 55 acquired regularly to CS.

  When the control unit 53 moves out of the area of BS1 to BS5 due to movement or the like, the control unit 53 performs a channel scan based on the periodically generated channel list 62. Alternatively, the control unit 53 newly generates a channel list 62 and performs a channel scan.

Next, the operation when there is no beacon will be described. If BS1 to BS5 do not transmit a beacon, MS1 switches channels and attempts to communicate with BS1 to BS5.
1. When the communication method with the BS1 to BS5 is CSMA, the control unit 53 of the MS1 performs data transmission to the BS1 to BS5 when it is found that there is no other MS2 to MS6 in communication by performing carrier sense or the like (for example, , Position information, sensor information, or control signals). And the control part 53 confirms presence of BS1-BS5 by the presence or absence of ACK (ACKnowledge) from BS1-BS5 and other data reception.

  If the controller 53 does not receive a reply even after performing data transmission a predetermined number of times, the controller 53 assumes that BS1 to BS5 operating on that channel do not exist and switches to the next channel.

  2. When the transmission / reception timing between MS1 to MS6 and BS1 to BS5 is determined in advance, the control unit 53 performs data transmission at the allocated time. In the same manner, the presence confirmation of BS1 to BS5 and data communication are simultaneously performed. When the positioning unit 54 is GPS, time synchronization between the MS1 to MS6 and the BS1 to BS5 can be accurately performed by using the GPS reference time.

  When the control unit 53 becomes communicable with BS1 to BS5, it receives the base station information 61 and periodically generates the channel list 62. And the control part 53 transmits the information which the positioning part 54 and the sensor part 55 acquired regularly to CS.

  When the control unit 53 moves out of the area of BS1 to BS5 due to movement or the like, the control unit 53 performs a channel scan based on the periodically generated channel list 62. Alternatively, the control unit 53 newly generates a channel list 62 and performs a channel scan.

  FIG. 25 is a diagram illustrating hardware blocks of the MS. As shown in FIG. 25, the MS 1 includes a processor 91, a memory 92, a wireless unit 93, a GPS 94, a sensor 95, and a bus 96.

The processor 91 is connected to a memory 92, a wireless unit 93, a GPS 94, and a sensor 95 via a bus 96, and controls the entire apparatus.
The memory 92 stores an OS (Operating System) program and application programs executed by the processor. The memory 92 stores various data necessary for processing by the processor 91. The processor 91 is, for example, a CPU (Central Processing Unit) or a DSP (Digital Signal Processor).

  The wireless unit 93 performs wireless communication with BS1 to BS5. For example, the radio unit 93 performs D / A (Digital to Analog) conversion on the digital signal processed by the processor 91, up-converts the frequency of the D / A converted signal, and transmits the converted signal to BS1 to BS5. For example, the radio unit 93 down-converts the frequency of the signal received from BS1 to BS5 and performs A / D (Analog to Digital) conversion. The A / D converted signal is subjected to predetermined processing by the processor 91.

The GPS 94 measures the current position of the MS 1. The sensor 95 detects the temperature and the state of the soil.
The function of the transmission / reception unit 52 illustrated in FIG. 3 is realized by, for example, the wireless unit 93. The function of the control unit 53 is realized by the processor 91, for example. The function of the positioning unit 54 is realized by the GPS 94, for example. The function of the sensor unit 55 is realized by the sensor 95, for example. The function of the storage unit 56 is realized by the memory 92.

  Thus, the control part 53 of MS1 calculates the distance of BS1-BS5 and MS1. The control unit 53 calculates the order of scanning the channels BS1 to BS5 in accordance with the calculated distance, and scans the channels BS1 to BS5 within a predetermined distance. As a result, the MS 1 can narrow down the channel scanning time to the channels BS1 to BS5 whose distance from the mobile station is within a predetermined range.

  Moreover, since the control part 53 performs a channel scan from the channel of BS1-BS5 with a short distance, the discovery of a channel becomes quick and it can shorten the time of a channel scan.

  In the above description, each of BS1 to BS5 wirelessly communicates with MS1 to MS6 through one channel. For example, in the example of FIG. 4, BS1 wirelessly communicates with MS1 to MS6 on channel 1, BS2 wirelessly communicates with MS1 to MS6 on channel 2, and BS5 wirelessly communicates with MS1 to MS6 on channel 4. .

  On the other hand, each of BS1 to BS5 has a plurality of channel candidates, and one channel may be selected from the candidates to perform wireless communication with MS1 to MS6. In this case, the control unit 53 calculates the channel scan order in the order of the channels with the highest priority of the BS1 to BS5 that are close to each other.

FIG. 26 is a diagram illustrating a case where a BS has a plurality of channel candidates. FIG. 26 shows base station information 101 of BS1 to BS3.
For example, it is assumed that BS1 can perform wireless communication with MS1 to MS6 through channels 1 and 2. It is assumed that channel 1 is higher in priority than channel 2. Further, it is assumed that BS 2 can perform wireless communication with MS 1 to MS 6 through channels 5 and 4. The priority is assumed to be higher for channel 5 than for channel 4. Further, it is assumed that BS 3 can perform wireless communication with MS 1 to MS 6 through channels 3 and 2. The priority is assumed to be higher for channel 3 than for channel 2. The distance between MS1 and BS1 to BS3 is 2, 3, and 4.

  In this case, the control unit 53 calculates the order of scanning the channels BS1 to BS3 as 1, 2, 5, 4, 3, 2. The first and second channels 1 and 2 are the channels of BS1 that are closest to the MS1. The third and fourth channels 5 and 4 are BS2 channels that are the second closest to the MS1. The fifth and sixth channels 3 and 2 are channels of the BS 3 that is the farthest from the MS 1.

Since the distance between BS1 to BS3 is within a predetermined distance '5' and the channel 2 overlaps, the control unit 53 scans the channels in the order of 1, 2, 5, 4 and 3.
That is, the control part 53 calculates the order which scans a channel in order of the channel with the high priority of each BS1-BS3 in order of base station BS1-BS3 with a short distance.

When the distance between BS1 to BS3 is equal to or less than a predetermined value, selection of BS1 to BS3 itself may be prioritized over channel candidates in BS1 to BS3.
For example, it is assumed that the distance between BS1 and BS2 is less than or equal to a predetermined value, and the distance between BS2 and BS3 is greater than a predetermined value. In this case, the control unit 53 gives priority to the selection of BS1 and BS2, and calculates the channel scan order as 1, 5, 2, 4, 3, 2. The first channel 1 is the channel with the highest priority of BS1. The second channel 5 is the channel with the highest priority of BS2. The third channel 2 is the second highest priority channel of BS1. The fourth channel 4 is the second highest priority channel of BS2. The fifth and sixth channels 3 and 2 are channels of the BS 3 that is the farthest from the MS 1.

DESCRIPTION OF SYMBOLS 1 Memory | storage part 2 Positioning part 3 Calculation part 4 Scan part

Claims (7)

In a wireless terminal that performs wireless communication with a base station,
A storage unit storing base station position information and channel information;
A positioning unit for positioning the position of the wireless terminal;
A calculation unit that calculates a distance between the wireless terminal and the base station based on the position information of the base station stored in the storage unit and the position of the wireless terminal measured by the positioning unit;
Wherein the order in which the calculating section based on the distance calculated to identify the base stations within a predetermined distance, scanning the 該Chi Yaneru the remaining channels excluding the channel overlapping of the channels of the identified base station calculated based on the calculated distance, and a scanning unit for scanning the channels based on number that order,
Have
The calculation unit calculates the distance between the wireless terminal and the base station at the timing when the communication disconnection with the base station currently performing wireless communication is detected,
The scanning unit includes a table that stores channels of base stations within a predetermined distance in which the scanning order is calculated, and the table is based on the distance calculated by the calculating unit at the timing when the communication disconnection is detected. And a channel scan is performed based on the channel of the table. The scanning unit includes, in order distance is near the base station, and calculates the order in which to scan the channel of the base station, the wireless terminal according to claim 1. The calculation unit periodically calculates the distance between the wireless terminal and the base station,
The scan unit, and updates the table periodically, the wireless terminal according to claim 1. The scan unit, if the channel in the table is not stored, characterized in that it does not implement the channel scan, the wireless terminal according to any one of claims 1 to 3. When the base station performs wireless communication by selecting one of a plurality of channels,
The scan unit, the order of the base stations close in distance, and calculates the order in which to scan the channels in order of higher channel priority of each base station, to any one of claims 1 to 4 The wireless terminal described. The scan unit, when the distance between base stations is smaller than a predetermined value, and wherein the priority order of the base station, the wireless terminal according to claim 5. In a channel scanning method of a wireless terminal that performs wireless communication with a base station,
Positioning the wireless terminal,
Based on the position information of the base station stored in the storage unit storing the position information and channel information of the base station and the position of the wireless terminal measured by the positioning unit, the distance between the wireless terminal and the base station To calculate
Based on the calculated distance to identify base stations within a predetermined distance, the order of scanning the 該Chi Yaneru the remaining channels excluding the channel overlapping of the channels of the specified base station to the distance the calculated based calculated, by scanning the channels based on number that order,
In the step of calculating the distance, the distance between the wireless terminal and the base station is calculated at the timing when the communication disconnection with the base station currently performing wireless communication is detected,
In the step of scanning , the distance calculated in the step of calculating the distance at the timing when the communication disconnection is detected using a table storing channels of base stations within a predetermined distance in which the order of scanning is calculated A channel scan method comprising: updating the table based on the channel and performing a channel scan based on the channel of the table.

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