JP2003333640A - Radio communication device and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a control part of a radio communication device to judge whether the device is indoors or outdoors and then appropriately select a communication frequency band in the radio communication device adaptive to a plurality of frequency bands such as a 5.2 GHz band and a 2.4 GHz band. <P>SOLUTION: A display terminal 50 constituting a radio communication system together with a base device is provided with a detection antenna 62 having a high directional sensitivity in one direction so that the direction of a high directional sensitivity may be turned to a direction opposite to the direction of gravity. A transmission signal for detection is radiated from the detection antenna 62, and a reflected wave from a reflecting material of the radio wave is received by the detection antenna 62 and is processed in a processing circuit. In accordance with a processing result, a control part (CPU) judges whether the display terminal is indoors or outdoors to select a communication frequency band. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication device and a wireless communication method for performing wireless communication using a frequency band selected from a plurality of frequency bands as a communication frequency band.

[0002]

2. Description of the Related Art As a kind of wireless LAN system constructed in a limited area such as a house or an office, a tuner 21 connected to an antenna 1 for receiving a television broadcast as shown in FIG. The base device 10 that functions as an information source or an access point, such as being built-in or connected and being connected to the telephone line 3 via the modem 23.
And a command is issued to the base device 10 by wireless communication with the base device 10, a television image is received from the base device 10, information on the Internet is received, and an LCD (liquid crystal display) is received. ) A system including a display terminal 50 that displays images and information on 51 and executes functions such as sending and receiving electronic mail via the base device 10 is considered.

In this system, the user fixedly arranges the base device 10 at an appropriate place indoors, and the display terminal 5
0 can be carried to any place indoors or outdoors within the communicable area, and the display terminal 50 at any place can receive a television broadcast, access the Internet, perform an e-mail transmission / reception function, etc. can do.

As a radio frequency band that can be used in such a radio communication system, IEEE 802.11a
The standard defines the 5.2 GHz band (in the United States, it is 5.8 GHz band, which is generically referred to as 5 GHz band).
The EE802.11b standard defines the 2.4 GHz band.

However, when a plurality of wireless channels are simultaneously set in the same area, the signals of the respective wireless channels are shown in FIG. 11 in the 5.2 GHz band so as not to interfere with each other. As described above, it is necessary to set the frequency interval between adjacent wireless channels to 20 MHz or more, and in the 2.4 GHz band, as shown in FIG. 12, the frequency interval between adjacent wireless channels is 25 MHz.
It is necessary to do the above.

Therefore, the number of wireless channels that can be simultaneously set within the same area is limited to a maximum of 4 channels in the 5.2 GHz band, as shown by channels C1, C2, C3 and C4 in FIG. In the 4 GHz band, as shown by channels C5, C6 and C7 in FIG.
Limited to channels.

The data transmission rate is 5.2 GH
In the z band, the maximum speed can be 54 Mbps (megabits / second), and in the 2.4 GHz band, the maximum speed can be 11 Mbps.

As the primary modulation (multilevel digital modulation) of data, BPSK (Binary) is used in the 5.2 GHz band.
Phase Shift Keying), QPSK
(Quadrature Phase Shift K
eyeing) or QAM (Quadrature A)
In the 2.4 GHz band, BPSK, QPSK or C is used.
CK (Complementary Code Key)
ing) is used.

As the secondary modulation, in the 5.2 GHz band,
OFDM (Orthogonal Frequency)
(Division Multiplex) is used,
In the 2.4 GHz band, OFDM or DSSS (Dir
ect SequenceSpread Spectr
am) is used.

Therefore, the radio communication system is set to 5.2 GHz.
If it corresponds to both the band and the 2.4 GHz band,
Communication can be performed using a properly selected wireless channel within a frequency band appropriately selected from the 5.2 GHz band and the 2.4 GHz band as a communication channel.

[0011]

However, 5.2 is a problem to be solved by the invention.
Regarding the GHz band, domestic regulations (ARIB STD-
According to T71), indoor use is prohibited, and outdoor use is prohibited.

Therefore, the above-mentioned radio communication system is used in 5.
When both the 2 GHz band and the 2.4 GHz band are supported, it is assumed that the base device 10 is placed indoors, and when the display terminal 50 is used indoors, either the 5.2 GHz band or the 2.4 GHz band is used. However, when the display terminal 50 is used outdoors, 2.4 is required.
Communication must be performed using the GHz band, and the user sets the communication channel within the 2.4 GHz band when using the display terminal 50 outdoors from the start of communication, and communicates indoors with the 5.2 GHz band. When the display terminal 50 is taken out to the outside such as a garden, the communication channel is set to 5.2G.
It is necessary to switch from the Hz band to the 2.4 GHz band.

However, the user is often not familiar with the regulations, and even if he / she knows it, it is troublesome for the user to select the frequency band to be used each time.

Therefore, according to the present invention, in a device that performs wireless communication using a frequency band selected from a plurality of frequency bands as a communication frequency band, the wireless communication device determines whether it is indoors or outdoors. Then, the communication frequency band can be selected according to the result of the determination.

[0015]

A wireless communication device of the present invention is a device for performing wireless communication using a frequency band selected from a plurality of frequency bands as a communication frequency band, and radiates a detection transmission signal, The detection antenna which receives the reflected wave from the reflecting object due to this and has high directional sensitivity in one direction, the reception processing means for processing the reflected wave reception signal, and the processing result, the wireless communication device is outdoors. And a control unit that determines whether or not the communication frequency band is selected according to the determination result.

In the wireless communication device having the above-described structure, the detecting antenna is attached to the wireless communication device so that the direction with high directional sensitivity of the detecting antenna faces the direction opposite to the direction of gravity, or the detecting antenna. By providing the wireless communication device with means for directing the direction with high directional sensitivity to the direction opposite to the direction of gravity, when the wireless communication device is indoors, the radio waves radiated from the detection antenna are reflected on the ceiling. As a result, the level of the reflected wave received by the detection antenna increases, and the delay time of the reflected wave received signal with respect to the detection transmission signal decreases, whereas when the wireless communication device is outdoors, it is transmitted from the ceiling. Since there is no reflected wave, the level of the reflected wave received by the detection antenna becomes zero or minute, and even when it is not zero,
The delay time of the reflected wave reception signal with respect to the detection transmission signal becomes long.

Therefore, from the processing result of the reception processing means, the control means accurately determines whether the wireless communication device is indoors or outdoors, and the communication frequency band is legally selected according to the determination result. It

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In the following, when the present invention is applied to a wireless communication system composed of a base device and a display terminal described above, a communication frequency band of 5.2 GH is obtained.
An embodiment of the present invention will be described by taking an example of using a frequency band selected from the z band and the 2.4 GHz band.

[Schematic Configuration of System: FIGS. 1 to 5] FIG.
FIG. 3 shows an external configuration of an example of a display terminal. As shown in the figure, an LCD 51 is provided on the front surface of the display terminal 50, a touch panel 52 is provided on the display screen, speakers 53 are provided on the upper and right sides of the LCD 51, and a lower portion is described below. A planar antenna 55 for wireless communication with the base device 10 is provided.

The antenna 55 has a frequency band Ba (5.2 G).
For the frequency band Bb (2.4 GHz band), one on the left side is supposed to form a hemispherical radiation pattern on the front side of the display terminal 50, and the other on the right side is Conversely, it is assumed that a hemispherical radiation pattern is formed on the rear side of the display terminal 50, and an antenna that actually performs transmission and reception is selected based on the reception level information of one of the left side and the other of the right side. As a result, an antenna having an all-spherical radiation pattern is formed as a combination of the left and right sides, and regardless of the positional relationship between the display terminal 50 and the base device 10, the display terminal 50 and the base device 10 are separated from each other. It is configured so that the wireless communication between them is performed well.

On the right side of the front surface of the display terminal 50, below the speaker 53, there are an index button 54a, a jump button 54b, and channel buttons 54c and 54d.
Is provided.

When the index button 54a is pressed, the index screen as shown in the figure is displayed on the LCD 51, and the user touches one of the menus with the touch pen or finger to display the index screen on the television. It is possible to select a channel, operate an external device connected to the base device 10, access the Internet, create / send a mail, create / display an album, and the like.

By pressing the jump button 54b, the television channel which has been received immediately before can be received. The channel button 54c
Means that the operation screen displayed on the LCD 51 can be switched in the order of TV-> external device->Internet->mail->album-> TV by pressing this, and the channel button 54d can be pressed by pressing this The operation screen displayed above can be switched in the reverse order to the above order.

An album is an image taken by a digital camera and recorded on the memory card 57, which is displayed on the LCD 51, processed on the LCD 51, attached to a mail created on the LCD 51, or a television image. A still image, an image received by mail, an image acquired on the Internet, or the like is stored in the display terminal 50 or the memory card 57.

A slot 58 into which a memory card 57 is mounted is provided on the right side surface of the display terminal 50, and a bottom surface is provided on the bottom surface.
A pair of charging terminals 56 is provided.

On the back surface of the display terminal 50, a U-shaped stand 59 for allowing the display terminal 50 to stand on its own is attached so as to be openable and closable. Although not shown in the drawing, a battery storage portion is provided in a portion surrounded by the stand 59. The battery is stored in this.

Further, in this embodiment, the display terminal 50
A groove portion 69 is formed on the upper surface of the detection device portion 60, and the detection device portion 60 including the detection antenna 62 is provided in the groove portion 69.

As shown in FIG. 2, the detection device section 60 includes a circuit board 61, a small planar detection antenna 62,
And a detection circuit portion 63 are formed on the circuit board 61.
Is attached to the weight plate 67, and the pair of shafts 68 is attached to the circuit board 61 or the weight plate 67.
Is rotatably supported in the shaft hole formed in the groove 69 shown in FIG.

Therefore, when the display terminal 50 is used while being held by hand, or when the stand 59 is opened and the display terminal 50 is made to stand on a suitable surface at a suitable inclination angle as shown in FIG. 3, or As will be described later, the weight plate 67 is used regardless of which mode the display terminal 50 is used, such as when the display terminal 50 is leaned against the base device 10.
Becomes horizontal, and the surface of the detection antenna 62 that radiates radio waves faces the sky direction (the direction opposite to the direction of gravity).

Moreover, the detection antenna 62 is an antenna having a high directional sensitivity in the direction perpendicular to the surface thereof.

Therefore, the display terminal 50 can be used in any manner.
Even when using, the radio signal is radiated from the detection antenna 62 in the sky direction when the detection transmission signal is supplied to the detection antenna 62, and when the display terminal 50 is used indoors. The reflected wave is reflected on the ceiling, the reflected wave is received by the detection antenna 62, and the reflected wave reception signal Sr is converted to the detection transmission signal St as shown on the left side of FIG.
Is obtained with a short delay time τ and a large level Lr.

On the other hand, when the display terminal 50 is used outdoors, since the reflected wave from the ceiling does not exist, the level Lr of the reflected wave reception signal Sr becomes zero or very small, and even when it is not zero, As shown on the right side of 4, the delay time τ of the reflected wave reception signal Sr with respect to the detection transmission signal St becomes long.

FIG. 5 shows an external structure of an example of the base device. As shown in the figure, the base device 10 has a structure in which the front portion 12 and the rear portion 14 are joined and integrated, and the left and right positions of the front portion 12 are used for wireless communication with the display terminal 50. A planar antenna 22 is provided.

Like the antenna 55 of the display terminal 50, the antenna 22 is shared for the frequency band Ba (5.2 GHz band) and the frequency band Bb (2.4 GHz band), and the one on the left side is the base. It is assumed that a hemispherical radiation pattern is formed on the front side of the device 10, and the other on the right side is conversely formed to form a hemispherical radiation pattern on the rear side of the base device 10, and one on the left side is formed. By selecting an antenna that actually performs transmission and reception on the basis of the other reception level information on the right side and the right side, an antenna having an all-spherical radiation pattern is formed as a combination of the left and right sides, and the base device 10 The wireless communication between the base device 10 and the display terminal 50 is performed well regardless of the positional relationship between the display device 50 and the display terminal 50.

The front part 12 is inclined rearward, and a support 16 for leaning the display terminal 50 against the base device 10 is provided in the lower center of the front part 12, and a pair of charging members are provided inside the support 16. A terminal 18 is provided. Further, various terminals such as an antenna terminal and a line terminal, which will be described later, are provided on the lower rear surface of the rear portion 14.

The display terminal 50 is attached to the front portion 1 of the base device 10.
When leaning against 2, the charging terminal 56 of the display terminal 50
However, the battery attached to the display terminal 50 can be charged by the base device 10 by contacting and connecting to the charging terminal 18 of the base device 10.

[Functional Configuration of System: FIG. 6 to FIG. 9] FIG.
Shows an example of a functional block configuration of the base device 10.
The control unit 30 includes a CPU 31, and a bus 33 is provided with a C
A ROM in which a program to be executed by the PU 31 and fixed data are written, and a memory 35 including a RAM functioning as a work area of the CPU 31 are connected.

An antenna 1 for receiving television broadcasting is connected to the antenna terminal 11, and the television broadcasting signal received by the antenna 1 is demodulated and tuned by a tuner 21 and further converted into video data and audio data. Bus 3
3 is sent.

The telephone line 3 is connected to the line terminal 13, and the line terminal 13 is connected to the bus 33 via the modem 23.
Connected to.

Further, an Ethernet (registered trademark) terminal 15 for connection such as an ADSL modem or a CATV modem is connected to the bus 33 via the interface 25.

A DVD player, a hard disk recorder, or an external device 7 is connected to the external device connecting terminal 17 as an external device 7.
Alternatively, a digital CS tuner or the like is connected, and the image data and audio data from now on are transferred to the interface 27.
Is sent to the bus 33 via.

Further, the AV mouse 9 is connected to the terminal 19, the terminal 19 is connected to the bus 33 via the interface 29, and infrared rays transmitted from the light emitting portion of the AV mouse 9 in response to a command signal from the control unit 30. When the remote control signal is received by the light receiving section provided in the external device 7, the external device 7 is operated.

On the other hand, on the bus 33, a MAC (Media Access Cont) constituting a packet assembling / disassembling unit
41) is connected to the MAC 41 and the OFD
BBP (Base Band P) configuring the M modulation / demodulation unit
43) and a BBP 44 constituting a DSSS modulation / demodulation unit are connected, and a front end 46 of a frequency band Ba (5.2 GHz band) that can be used only indoors is connected to the BBP 43, and BBPs 43 and 44 can also be used outdoors. The front end 47 in the frequency band Bb (2.4 GHz band) is connected, and the antenna 22 is connected to the front ends 46 and 47.

The data transmitted from the base device 10 to the display terminal 50 is packetized by the MAC 41, the packetized data is OFDM-modulated by the BBP 43, the DSSS-modulated by the BBP 44, and the OFDM-modulated signal is Frequency band Ba at the front end 46 or 47
Alternatively, the signal after being converted into the high frequency signal of Bb and DSSS modulated is converted into the high frequency signal of the frequency band Bb at the front end 47, and the converted high frequency signal is transmitted from the antenna 22 to the display terminal 50.

The high frequency signal transmitted from the display terminal 50 to the base device 10 is received by the antenna 22, the high frequency signal in the frequency band Ba is orthogonally demodulated by the front end 46 and converted into a base band signal, and the BBP 43 is used. OF
The DM demodulated high frequency signal in the frequency band Bb is orthogonally demodulated by the front end 47 and converted into a baseband signal, OFDM demodulated by the BBP 43 and D by the BBP 44.
SSS demodulation is performed. The packet structure data after demodulation from the BBP 43 or 44 is unpacked by the MAC 41, and the received data is taken into the bus 33.

FIG. 7 shows an example of a functional block configuration of the display terminal 50. The control unit 70 includes a CPU 71, and a bus 73 is connected to a ROM 75 in which programs to be executed by the CPU 71 and fixed data are written, and a memory 75 including a RAM functioning as a work area of the CPU 71.

L is connected to the bus 73 via the display control unit 91.
The CD 51 is connected, and the speaker 5 is connected via a DAC (D / A converter) 93 and an audio amplifier circuit 95.
3 are connected. Further, the touch panel 52 is connected to the bus 73 via the coordinate detection unit 92, and the key operation unit 54 including the index buttons 54a shown in FIG. 1 is connected to the bus 73 via the interface 94.

On the other hand, a MAC 81 constituting a packet assembling / disassembling unit is connected to the bus 73, and the OFD is connected to the MAC 81.
The BBP83 forming the M modulation / demodulation unit and the BBP84 forming the DSSS modulation / demodulation unit are connected to the BBP83,
Frequency band Ba (5.2 GHz band) that can be used only indoors
Front end 86 is connected to BBPs 83 and 8
4, the frequency band Bb (2.4 GHz that can be used outdoors)
The front end 87 of the band) is connected, and the antenna 55 is connected to the front ends 86 and 87.

The data transmitted from the display terminal 50 to the base device 10 is packetized by the MAC 81, the data of the packet configuration is OFDM-modulated by the BBP 83, the DSSS-modulated by the BBP 84, and the OFDM-modulated signal is Frequency band Ba at the front end 86 or 87
Alternatively, the signal after being converted into the high frequency signal of Bb and subjected to the DSSS modulation is converted into the high frequency signal of the frequency band Bb at the front end 87, and the converted high frequency signal is transmitted from the antenna 55 to the base device 10.

The high frequency signal transmitted from the base device 10 to the display terminal 50 is received by the antenna 55, the high frequency signal in the frequency band Ba is orthogonally demodulated by the front end 86 and converted into a base band signal, and the BBP 83 is used. OF
The DM demodulated, high-frequency signal in the frequency band Bb is orthogonally demodulated by the front end 87 and converted into a baseband signal, OFDM demodulated by the BBP83, and D by the BBP84.
SSS demodulation is performed. The packet structure data after demodulation from the BBP 83 or 84 is unpacked by the MAC 81, and the received data is taken into the bus 73.

Further, a detection circuit section 63 including a transmission circuit 64, a directional coupler 65 and a reception processing circuit 66 is connected between the bus 73 and the detection antenna 62.

In the detection circuit unit 63, the transmission circuit 64 generates a detection transmission signal under the control of the control unit 70, and the detection transmission signal is supplied to the detection antenna 62 through the directional coupler 65. And the detection antenna 62
Is emitted from the ceiling as a radio wave as described above, and the reflected wave from the ceiling due to the radio wave is received by the detection antenna 62, supplied to the reception processing circuit 66 through the directional coupler 65, and received. It is processed by the processing circuit 66.

The detection transmission signal generated by the transmission circuit 64, the processing by the reception processing circuit 66, and the determination by the control unit 70 can be configured as in the following (1) to (5).

(1) A millimeter wave that has been pulse-modulated is used as the detection transmission signal, and the reception processing circuit 66 determines the delay time of the reflected wave reception signal with respect to the detection transmission signal, from the display terminal 50 (detection antenna 62). To the reflector, the control unit 70 compares the measured distance with a threshold value, and when the measured distance is less than the threshold value, it is determined that the display terminal 50 is indoors, and the measurement is performed. When the determined distance is equal to or greater than the threshold, it is determined that the display terminal 50 is outdoors.

(2) The reception processing circuit 66 detects the reflected wave reception signal to detect the level Lr thereof, and the control section 70.
Then, the level Lt is compared with a threshold, and when the level Lt is equal to or higher than the threshold, it is determined that the display terminal 50 is indoors, and when the level Lt is less than the threshold, it is determined that the display terminal 50 is outdoors. To do.

(3) The reception processing circuit 66 detects the detection transmission signal and the reflected wave reception signal, and outputs the level L of both signals.
The difference (Lt-Lr) or the ratio (Lt / Lr) between t and Lr is detected, and the control unit 70 compares the difference (Lt-Lr) or the ratio (Lt / Lr) with a threshold value, and the difference (Lt -Lr) or the ratio (Lt / Lr) is equal to or more than the threshold value, it is determined that the display terminal 50 is indoors, and when the difference (Lt-Lr) or the ratio (Lt / Lr) is less than the threshold value, the display terminal 50 is displayed. It is determined that 50 is outdoors.

(4) As the detection transmission signal, a signal frequency-modulated with a triangular wave or a waveform close to it is used, and the reception processing circuit 66 mixes the detection transmission signal and the reflected wave reception signal to obtain the beats of both signals. A frequency signal is obtained, and from the beat frequency, the display terminal 50 (detection antenna 6
The distance from 2) to the reflector is measured, the control unit 70 compares the measured distance with a threshold value, and when the measured distance is less than the threshold value, it is determined that the display terminal 50 is indoors. When the measured distance is equal to or greater than the threshold value, it is determined that the display terminal 50 is outdoors.

(5) As a transmission signal for detection, UWB (U
The signal of the intra wide band) is used. UW
B transmits and receives signals by using an ultra wide band of 3.1 GHz to 10.6 GHz, and recently, FCC (Fede)
ral Communications Commis
sion: US Federal Communications Commission) has approved its use. In UWB, distance can be measured on the order of cm. Using this UWB distance measurement function, the reception processing circuit 66 measures the distance from the display terminal 50 (detection antenna 62) to the reflector, and the control unit 70 compares the measured distance with a threshold value. Then, when the measured distance is less than the threshold, it is determined that the display terminal 50 is indoors, and when the measured distance is equal to or greater than the threshold, it is determined that the display terminal 50 is outdoors.

FIG. 8 shows the control unit 70 (CPU 7) of the display terminal 50 in the wireless communication system of the above embodiment.
An example of a communication frequency band selection processing routine executed by 1) will be shown.

This communication frequency band selection processing routine 100
Then, when transmitting the connection request and command to the base device 10 for receiving the television broadcast and accessing the Internet, the control unit 70 of the display terminal 50 first detects from the detection antenna 62 in step 101. Emits a transmission signal for.

Next, the control unit 70, in step 102,
The result of the processing of (1) to (5) of the reception processing circuit 66 is fetched, and the process proceeds to step 103. From the processing result, the display terminal is processed by the method of (1) to (5). Determine if 50 is outdoors.

When it is determined that the display terminal 50 is indoors, the control section 70 proceeds from step 103 to step 104 to set the frequency band Ba as the communication frequency band.
(5.2 GHz band) or frequency band Bb (2.4 GHz)
Band), and further proceeds to step 105 to establish a communication link with the base device 10,
Communication with 0 is started.

When the frequency band Ba and the frequency band Bb are compared, as described above, the frequency band Ba (5.2 GHz band) can have a higher transmission rate than the frequency band Bb (2.4 GHz band).

Therefore, in this case, for example, the frequency band Ba
Priority is given to a non-wireless communication device such as an interfering wave (communication radio wave from another wireless communication system or a microwave oven) on an idle channel (a wireless channel not used as a communication channel in the system) in the frequency band Ba. Radio wave) from which there is no interfering wave in the frequency band Ba, and when there is no free channel in the frequency band Ba in which no interfering wave exists, a wireless channel in which no interfering wave exists is searched from among the free channels in the frequency band Bb. And configure the system to set the communication channel.

On the other hand, in the frequency band Bb, radio waves are more likely to pass through walls than in the frequency band Ba. Therefore, contrary to the above, the system is configured so that the frequency band Bb is prioritized and the communication channel is set. You can also do it.

When the communication channel is set in the frequency band Ba, OFDM modulation / demodulation is selected as the secondary modulation / demodulation method, and when the communication channel is set in the frequency band Bb, the secondary modulation / demodulation method is selected. Is selected as OFDM modulation / demodulation. However, since there are many multipaths indoors and OFDM modulation / demodulation is stronger than DSSS modulation / demodulation, the system is configured so that OFDM modulation / demodulation is selected when a communication channel is set in the frequency band Bb. You can also do it.

On the other hand, when it is determined in step 103 that the display terminal 50 is outdoors, the control unit 70 proceeds from step 103 to step 106, and the frequency band Bb permitted to be used outdoors as a communication frequency band. (2.4
(GHz band), and proceed to step 107,
A communication link is established with the base device 10 and communication with the base device 10 is started.

Therefore, when the outdoor communication is started, the use of the frequency band Ba which is prohibited to be used outdoors is automatically prevented.

Also in this case, a free channel in the frequency band Bb is searched for a radio channel in which no interfering wave exists, and
Configure the system to set the communication channel.
The secondary modulation / demodulation method is OFDM modulation / demodulation or DS.
SS modulation / demodulation is selected.

In step 105 or 107, when the communication link is established and the communication is started, after waiting for a fixed time such as 10 to 30 seconds, the process returns to step 101 and the processes of step 101 and thereafter are repeated.

Therefore, when the user goes out of the garden or the like with the display terminal 50 while communicating indoors in the frequency band Ba, it is determined in step 103 that the display terminal 50 is outdoors, and step 106. The communication frequency band is switched from the frequency band Ba to the frequency band Bb, and the use of the frequency band Ba which is prohibited to be used outdoors is automatically prevented.

In the example of FIG. 7, the transmission signal for detection radiated from the detection antenna 62 is generated by the transmission circuit 64 separately from the signals in the frequency bands Ba and Bb. The display terminal 50 is configured so that the radiated detection transmission signal is generated as a signal in the frequency band Bb by the MAC 81, the BBP 83 or 84, and the front end 87 in the frequency band Bb and supplied to the detection antenna 62. You can also do it.

FIG. 9 shows an example of this case. A switch 89 is provided between the antenna 55 for communication with the base device 10 and the front end 87 of the frequency band Bb.
Normally, the switch 89 is switched so as to connect the front end 87 to the antenna 55, but at a certain time interval such as 10 seconds to 30 seconds described above, the switch 89 temporarily changes the front end 87. To be connected to the detection circuit section 63.

At this time, MAC 81 and BBP
A detection transmission signal is generated at 83 or 84, is converted into a signal in the frequency band Bb at the front end 87, and is radiated from the detection antenna 62 through the switch 89 and the directional coupler 65. The reflected wave from the reflected object due to the radio wave is received by the detection antenna 62, supplied to the reception processing circuit 66 through the directional coupler 65, and processed by the reception processing circuit 66. Is the same.

[Other Embodiments] The display terminal 50 described above.
Is used when the user holds it in his / her hand, makes it stand by the stand 59 as shown in FIG. 3, or leans against the front portion 12 of the base device 10 for use.
In either case, it is used with a slight inclination to the vertical direction.

Therefore, the detection antenna 62 is attached to the weight plate 67 and not rotatably attached to the display terminal 50 as shown in FIG.
It may be fixedly attached to the display terminal 50 so that the direction with high directional sensitivity faces the sky direction when 0 is slightly inclined with respect to the vertical direction.

In this case, when the display terminal 50 is used while being held in the hand, if the inclination of the display terminal 50 is slightly changed, the radiation direction of the radio wave does not accurately go to the sky direction, but the ceiling is still present. Since there is a significant difference in the level of the reflected wave reception signal and the delay time between indoors and outdoors without a ceiling, the control unit 70 of the display terminal 50 causes the control unit 70 of the above (1)-
By the method of (5), it is possible to accurately determine whether the display terminal 50 is indoors or outdoors.

The frequency band currently recognized by the IEEE standard and the domestic standard as the radio frequency band is 5.2 GH.
Only the z band (5 GHz band) and the 2.4 GHz band, but other frequency bands may be used as the radio frequency band.
It is technically possible and may be approved in the future, and the frequency band that can only be used indoors (frequency band that is prohibited to use outdoors) can be changed in the future, so it can be used outdoors. The frequency band that can be used is not limited to the 2.4 GHz band, and the frequency band that can be used only indoors is 5.2 GHz.
It is not limited to the z band (5 GHz band).

Further, the present invention is applicable to the case of supporting three or more frequency bands, in which one or more frequency bands can be used outdoors and one or more frequency bands can be used only indoors. Can also be applied.

Further, each wireless communication device forming the wireless communication system is not limited to the above-mentioned base device and display terminal.

[0081]

As described above, according to the present invention, in a wireless communication device adapted to a plurality of frequency bands, the control unit of the wireless communication device determines whether the device is indoors or outdoors. The communication frequency band can be legally selected.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an external configuration of a display terminal as a wireless communication device.

FIG. 2 is a diagram illustrating an example of a detection device unit including a detection antenna.

FIG. 3 is a diagram showing a state in which the display terminal is self-supporting.

FIG. 4 is a diagram for explaining a detection transmission signal and a reflected wave reception signal.

FIG. 5 is a diagram showing an example of an external configuration of a base device as a wireless communication device.

FIG. 6 is a diagram showing an example of a functional block configuration of a base device.

FIG. 7 is a diagram showing an example of a functional block configuration of a display terminal.

FIG. 8 is a diagram showing an example of a communication frequency band selection processing routine executed by a control unit of the display terminal.

FIG. 9 is a diagram showing another example of a functional block configuration of a display terminal.

FIG. 10 is a diagram showing a schematic configuration of an example of a wireless communication system.

FIG. 11 is a diagram showing a channel configuration in the 5.2 GHz band.

FIG. 12 is a diagram showing a channel configuration in the 2.4 GHz band.

[Explanation of symbols]

Since the main parts are all described in the figure, they are omitted here.

Claims (12)

[Claims] 1. An apparatus for performing wireless communication using a frequency band selected from a plurality of frequency bands as a communication frequency band, which radiates a detection transmission signal and receives a reflected wave from a reflection object thereby. A detection antenna with high directional sensitivity in one direction, reception processing means for processing the reflected wave reception signal, and whether or not the wireless communication device is outdoors is judged from the processing result, and according to the judgment result. And a control unit for selecting a communication frequency band. 2. The wireless communication device according to claim 1, further comprising means for directing a direction having high directional sensitivity of the detection antenna in a direction opposite to a direction of gravity. 3. The wireless communication device according to claim 1, wherein the control means causes the detection antenna to radiate the detection transmission signal at regular intervals to determine whether the wireless communication device is outdoors. A wireless communication device that determines whether or not. 4. The wireless communication device according to claim 1, wherein the detection transmission signal is a signal in a frequency band permitted to be used outdoors in the plurality of frequency bands. . 5. The wireless communication device according to claim 1, wherein the control unit determines whether the wireless communication device is outdoors based on a delay time of the reflected wave reception signal with respect to the detection transmission signal. A wireless communication device that determines whether or not. 6. The wireless communication device according to claim 1, wherein the reception processing unit detects a level of the reflected wave reception signal, and the control unit has an absolute value of the level, or
A wireless communication device for determining whether or not the wireless communication device is outdoors based on a difference or a ratio between the level and the level of the detection transmission signal. 7. The wireless communication device according to claim 1, wherein the reception processing unit mixes the detection transmission signal and the reflected wave reception signal, and from the beat frequencies of both,
A wireless communication device that measures a distance from the wireless communication device to a reflector, and the control unit determines whether the wireless communication device is outdoors based on the measured distance. 8. The wireless communication device according to claim 1, wherein the detection transmission signal is an ultra wide band signal, and the reception processing means uses the reflected wave reception signal,
A wireless communication device that measures a distance from the wireless communication device to a reflector, and the control unit determines whether the wireless communication device is outdoors based on the measured distance. 9. A method of performing wireless communication using a frequency band selected from a plurality of frequency bands as a communication frequency band, the method comprising: radiating a detection transmission signal from a detection antenna having high directional sensitivity in one direction; The process of receiving the reflected wave from the reflected object by the detection transmission signal and processing the reflected wave received signal, and judging from the processing result whether the wireless communication device is outdoors or not, and depending on the judgment result Selecting a communication frequency band according to the present invention. 10. The wireless communication method according to claim 9, wherein the steps are repeated at regular intervals during communication. 11. The wireless communication method according to claim 9, wherein, as the detection transmission signal, a signal in a frequency band permitted to be used outdoors in the plurality of frequency bands is used. 12. The wireless communication method according to claim 9, wherein an ultra wide band signal is used as the detection transmission signal.