JP6936279B2 - Wireless terminal and intercom system - Google Patents

Description

The present invention relates to an intercom system and a wireless terminal that allow a plurality of wireless terminals to wirelessly transmit and receive data such as voice.

The intercom system has a plurality of master units arranged as antennas. The wireless terminal wirelessly connects one of the master units as a partner station and transmits / receives data such as voice to / from the partner station. The voice input to one wireless terminal is received by the partner station. The partner station sends voice to the main device of the intercom system, and the main device delivers the received voice to each master unit. Then, each master unit wirelessly transmits the distributed voice to another wireless terminal, and the other wireless terminal outputs the voice from the speaker.

Wireless terminals are often carried and used by users, and when users move around, they often deviate from the communication range of the partner station. Therefore, as a method of wirelessly connecting the master unit and the wireless terminal, a method called handover is known (see, for example, Patent Document 1). The handover is to switch the master unit to which the wireless terminal is wirelessly connected according to the movement of the user. The wireless terminal investigates the handover destination in advance, and investigates when the reception strength of the channel used for communication with the current partner station becomes less than a predetermined value, that is, when the extension of the communicable range is reached. The candidate station obtained as a result of the above is used as a new partner station to request a wireless connection.

WO2008 / 102504

The number of wireless terminals that can be wirelessly connected to one master unit is finite. For example, when a master unit and a wireless terminal are wirelessly connected by the TDMA-TDD method, the number of time slots is the upper limit of the wireless terminals that can be wirelessly connected. Therefore, when the wireless connection of the handover destination reaches the allowable upper limit, the handover fails and the communication of the wireless terminal is disconnected. Then, the wireless terminal that cannot communicate must wait with the communication interrupted until there is a vacancy in the master unit that is trying to connect wirelessly.

The present invention has been proposed to solve the above problems, and an object of the present invention is to provide an intercom system and a wireless terminal in which communication is not interrupted even if the wireless terminal moves.

In order to achieve the above object, the present invention is a wireless terminal in which at least two master units having partially overlapping communicable ranges are set as a partner station and wirelessly connected to the partner station. A transmission / reception unit for transmitting / receiving data to / from the partner station, a measurement unit for measuring the reception intensity of each channel, and a channel having a reception intensity stronger than the channel assigned to the partner station based on the measurement results of the measurement unit. A hand that requests a wireless connection with the candidate station by searching and, if there is a channel with the strong reception strength, using the master unit to which the channel with the strong reception strength is assigned as a new candidate station to be the partner station. The transmission / reception unit includes an over control unit, and the transmission / reception unit receives data from both the current partner station and the candidate station at the request of the handover control unit, and the measurement unit receives data from both the current partner station and the current partner station. Each reception intensity of the channel assigned to both of the candidate stations is measured, and the handover control unit newly assigns one station to which the channel having a strong reception intensity is assigned based on the measurement result of the measurement unit. It is the partner station and requests the cancellation of the wireless connection with the other station .

The transmission / reception unit may transmit / receive data in the assigned time slot, and the measurement unit may measure the reception intensity of each channel during a period other than the time slot.

The reception intensity measured by the measuring unit may be a reception voltage.

Further, in order to achieve the above object, an intercom system according to the present invention, a main device for controlling transmission / reception of data in the system, and at least two master units having partially overlapped communicable ranges are used. One of the master units is used as a partner station, and a wireless terminal that wirelessly connects to the partner station is provided. The wireless terminal has a transmission / reception unit that transmits / receives data to / from the partner station, and reception strength of each channel. Based on the measuring unit to be measured and the measurement result of the measuring unit, a channel with a stronger reception intensity than the channel assigned to the partner station is searched, and if there is a channel with the strong reception intensity, the channel with the strong reception intensity is found. The assigned master unit is used as a new candidate station to be the partner station, and has a handover control unit that requests a wireless connection with the candidate station, and the main device is the handover control unit. Upon receiving the request, have a communication setting unit for setting a radio connection with the candidate station, the transceiver unit, the setting by the communication setting unit, receives data from both of the candidate station with the current of the other station Then, the measuring unit measures each reception intensity of the channel assigned to both the current partner station and the candidate station, and the handover control unit measures a strong reception intensity based on the measurement result of the measuring unit. One station to which the channel is assigned is set as the new partner station, and the wireless connection with the other station is requested to be canceled, and the communication setting unit responds to the request for cancellation by the handover control unit. The wireless connection with the other station is canceled .

The communication setting unit receives a request by the handover control unit may be set a wireless connection with both the candidate station the current phase hand station.

According to the present invention, even if a wireless terminal located at a position where the communicable range overlaps does not reach the extension of the wireless range with the partner station, the wireless terminal is wirelessly connected to another candidate station by handover. It becomes easier to make a free connection, and even if another wireless terminal moves to the side of this partner station, the possibility of wireless connection increases.

It is a block diagram which shows the whole structure of the intercom system which concerns on this embodiment. It is a block diagram which shows the structure of a main apparatus. It is a block diagram which shows the structure of a master unit. It is a block diagram which shows the structure of a wireless terminal. It is a sequence diagram which shows the operation of the intercom system including the handover. It is a flowchart which shows the operation of the handover request processing. It is a flowchart which shows the operation of the connection disconnection processing. It is a schematic diagram which shows the handover of the intercom system which concerns on this embodiment.

Hereinafter, the intercom system according to the embodiment of the present invention will be described in detail with reference to the drawings.

(composition)
FIG. 1 is a block diagram showing an overall configuration of an intercom system. As shown in FIG. 1, the intercom system 1 includes a main device 2, a plurality of master units 3, and a plurality of wireless terminals 4. Each wireless terminal 4 is carried by each user. In this intercom system 1, the sound input to one wireless terminal 4 is sent to the main device 2 via the master unit 3, and the sound is distributed from the main device 2 to each wireless terminal 4, so that the sound is distributed between the wireless terminals 4. Realize simultaneous communication. The voice transmission source is the wireless terminal 4, the main device 2 to which the voice input device is connected, or another main device 2 connected to the main device 2. The intercom system 1 is used in, for example, broadcasting stations, cable television stations, theaters, concert halls, stadiums, construction sites, and railways.

The plurality of master units 3 are wiredly connected to the main unit 2 by using a cable 5 capable of bidirectional data communication and power supply. The master unit 3 receives power from the main unit 2 and transmits / receives data to / from the main unit 2. Typically, one master unit 3 is connected to the main unit 2, and another master unit 3 is connected to the master unit 3 connected to the main unit 2 in a daisy chain system. Other connection methods include a star type method in which each master unit 3 is directly connected to the main device 2, and a mixed wiring of a daisy chain method and a star type method.

The plurality of wireless terminals 4 are wirelessly connected to the master unit 3. The wireless terminal 4 and the master unit 3 communicate with each other by, for example, a DECT (Digital Enhanced Cordless Telecommunications) compliant method. That is, the master unit 3 wirelessly connects to a finite number of wireless terminals 4, serves as an access point for the wirelessly connected wireless terminals 4, and relays voice transmission / reception to and from the main device 2. When the communication system between the wireless terminal 4 and the master unit 3 is the TDMA-TDD (Time Division Multiple Access --Time Division Duplex) system, the finite number is the number of time slots.

The main device 2 is a controller for the entire system, a transmission destination for receiving data from the wireless terminal 4, and a distribution source for distributing data to the wireless terminal 4. The main device 2 receives data transmitted by the wireless terminal 4 via the master unit 3, and if the received data is voice data, transmits the data to another wireless terminal 4 via the master unit 3. The data transmitted and received in the intercom system 1 includes, in addition to voice data, control data including synchronization, channel designation, time slot designation, and handover request and cancellation request.

FIG. 2 is a block diagram showing the configuration of the main device 2 in such an intercom system 1. As shown in FIG. 2, the main device 2 includes a communication setting unit 21, a communication control unit 22, a wired communication processing unit 23, a power supply unit 24, and an external interface 25.

The communication setting unit 21 sets the connection relationship between the wireless terminal 4 and the master unit 3. For example, the communication setting unit 21 sets the communication of the multi-channel access system and the TDMA-TDD system. The communication setting unit 21 assigns a channel to each master unit 3 and also assigns a channel and a time slot to each wireless terminal 4. In response to the handover request, the communication setting unit 21 determines whether the time slot is free, and if there is a free time slot, assigns a channel and a time slot to the wireless terminal 4 according to the request. Further, in response to the request for canceling the handover, the communication setting unit 21 deletes the settings of the channel and the time slot assigned to the wireless terminal 4. Then, the communication setting unit 21 transmits the control data including the assigned contents to the wireless terminal 4 via the master unit 3.

The communication setting unit 21 stores a voice matrix in which the allocation status is recorded, and the allocation is set by rewriting the voice matrix.

The communication control unit 22 determines the delivery destination of the received voice data. When the master units 3 are grouped, the communication control unit 22 attaches a local address indicating each master unit 3 in the group to a data frame including voice data. If there is no grouping of the master unit 3, the multicast method may be used. When the wireless terminals 4 are grouped, a slave unit ID that identifies the wireless terminal 4 to which the voice data is distributed is attached, and the local of the master unit 3 having a channel assigned to the wireless terminals 4 in the group. Give an address. A data frame matched to the TDMA frame may be generated, and the audio data may be stored in the data area matched to the time slot.

The wired communication processing unit 23 transmits / receives data according to a communication protocol. The communication protocol conforms to IEEE802.3, such as Ethernet (registered trademark). The wired communication processing unit 23 encodes and serializes the data to be transmitted, converts it into a signal waveform, and sends it to the cable 5. Further, the wired communication processing unit 23 digitally identifies from the received signal waveform, parallelizes it, and decodes it. The power supply unit 24 converts the electric power received from the commercial power source into the electric power for the master unit 3 and supplies the electric power to the master unit 3 through the cable 5. That is, the power supply unit 24 has a PSE (Power sourcing equipment) function. A microphone and another main device 2 can be connected to the external interface 25. The voice data input through the external interface 25 is distributed to the same group in the same manner as the voice data input to the wireless terminal 4.

FIG. 3 is a block diagram showing the configuration of the master unit 3. The master unit 3 includes a wired communication processing unit 31, a baseband processing unit 32, an RF processing unit 33, and an antenna 34.

The baseband processing unit 32 digitally modulates and analog-converts the audio data received from the main device 2. Examples of the digital modulation method include π / 4 shift QPSK (Quadrate phase shift keying) and GMSK (Gaussian Minimum Shift Keying). The RF processing unit 33 waveform-shapes the analog signal output by the baseband processing unit 32 using a low-pass filter, frequency-modulates the analog signal according to the channel assigned by the main device 2 using an orthogonal converter, and amplifies the signal. After that, it outputs to the antenna 34 at the timing of the set time slot. The antenna 34 transmits the signal input from the RF processing unit 33 as an electromagnetic wave in the air.

On the other hand, at the timing when the wirelessly connected wireless terminals 4 transmit data, the antenna 34 receives the audio data of each wireless terminal 4 in a time-division manner. The RF processing unit 33 converts the RF signal of each time slot received by the antenna 34 into an intermediate frequency in two steps using a local oscillator and a mixer, and demodulates it into a baseband signal using an orthogonal converter. The baseband processing unit 32 converts the baseband signal into a digital signal, digitally demodulates the baseband signal, and generates data in which the slave unit ID is attached to the audio data. A data frame matched to the TDMA frame may be generated, and the audio data may be stored in the data area matched to the time slot.

The wired communication processing unit 31 receives the data transmitted from the main device 2 according to the communication protocol and outputs the data to the baseband processing unit 32. Further, the wired communication processing unit 31 transmits the data output from the baseband processing unit 32 to the main device 2 according to the communication protocol. The communication protocol conforms to IEEE802.3, for example, Ethernet. The wired communication processing unit 23 has a PD (Powered device) function.

FIG. 4 is a block diagram showing the configuration of the wireless terminal 4. The wireless terminal 4 includes an antenna 48, a transmission / reception unit 44, a communication control unit 41, a headset interface 45, a measurement unit 46, and a handover control unit 47. The transmission / reception unit 44 includes a baseband processing unit 42 and an RF processing unit 43.

A headset including a microphone and a speaker is connected to the headset interface 45 by wire. For example, when the talk switch of the wireless terminal 4 is turned on, the microphone of the headset collects the sound, and the audio data is input to the wireless terminal 4 through the headset interface 45.

The transmission / reception unit 44 transmits / receives data to / from the master unit 3 using the antenna 48. When the voice data is wirelessly transmitted in the transmission / reception unit 44, the baseband processing unit 42 has an AD converter and a transcoder, digitally converts the voice data input through the headset interface 45, and compresses the voice data. do. Further, the baseband processing unit 42 performs digital modulation and analog conversion. The RF processing unit 43 waveform-shapes the analog signal output by the baseband processing unit 42 using a low-pass filter, and frequency-modulates the analog signal using an orthogonal converter according to the channel assigned to the wirelessly connected master unit 3. Then, after the signal is amplified, it is output to the antenna 48. The antenna 48 transmits the signal input from the RF processing unit 43 as an electromagnetic wave in the air. The wireless transmission of this voice data is performed within the period of the assigned time slot.

Examples of the audio data compression method include ADPCM (Adaptive Differential Pulse Code Modulation), but the method is not limited to this, and a known method can be used. Examples of the digital modulation method include π / 4 shift QPSK (Quadrate phase shift keying) and GMSK (Gaussian Minimum Shift Keying), but the digital modulation method is not limited to these, and known methods can be used.

On the other hand, at the reception timing, the antenna 48 receives the RF signal of the assigned time slot. The RF processing unit 43 converts the RF signal received by the antenna 48 into an intermediate frequency in two steps using a local oscillator and a mixer, and demodulates it into a baseband signal using an orthogonal converter. The baseband processing unit 42 converts the baseband signal into a digital signal, digitally demodulates the baseband signal, and decompresses the compressed audio data. Then, the baseband processing unit 42 performs analog conversion and outputs it to the headset interface 45. The headset interface 45 outputs an input signal to the headset.

The communication control unit 41 controls transmission / reception of the wireless terminal 4 based on the channels and time slots assigned by the main device 2. That is, the RF processing unit 43 specifies the frequency of the carrier wave, manages the arrival of the assigned time slot, and executes the transmission / reception processing.

The measuring unit 46 detects the received voltage of each channel. The measuring unit 46 has, for example, a diode, and detects the envelope of the received signal by the diode. The received signal input to the measuring unit 46 may be an intermediate frequency signal processed by the RF processing unit 43 or a baseband signal. The received voltage to be detected may be an RSSI value substantially proportional to the logarithmic value of the received voltage.

The handover control unit 47 controls the measurement unit 46 and the RF processing unit 43, and requests the main unit 2 to wirelessly connect to the master unit 3 to which a channel having a stronger radio wave than the channel currently wirelessly connected is assigned. .. That is, the handover control unit 47 controls the RF processing unit 43 to receive radio waves of each channel including the assigned channel. When the RF processing unit 43 receives the radio waves of each channel, each received radio wave is input to the measuring unit 46, and the measuring unit 46 detects the reception voltage of each channel. The handover control unit 47 compares the reception voltage of each channel detected by the measurement unit 46, generates control data requesting connection with the channel having the highest reception voltage, and transmits the control data to the main device 2.

It is desirable that the reception timing of the radio waves of each channel is a period other than the assigned time slot. The received signal is preferably a beacon output by the master unit 3. Further, the probe request may be sent and the probe response may be received.

FIG. 5 is a sequence showing the handover process using the handover control unit 47. FIG. 6 is a flowchart showing the processing of the handover request. It is assumed that the intercom system 1 includes two master units 3 of a master unit 3A and a master unit 3B, and a wireless terminal 4 called a slave unit 4A performs a handover in the system. Further, it is assumed that the slave unit 4A is assigned a channel Cha that wirelessly connects to the master unit 3A from the main unit 2. It is assumed that the master unit 3B has room for wireless connection with the wireless terminal 4, that is, there is a vacancy in the time slot.

First, as shown in FIG. 5, the slave unit 4A transmits / receives voice data during the assigned time slot period (step S110).

For example, when audio is input to the slave unit 4A, the slave unit 4A wirelessly transmits audio data using the channel Cha during the assigned time slot period. The radio signal carrying the voice data is received by the master unit 3A, and the voice data is passed to the main device 2. Further, when the voice input to the other wireless terminal 4 is sent to the main device 2, the main device 2 transmits the voice data to the master unit 3A to which the slave unit 4A is wirelessly connected. The master unit 3A wirelessly transmits the audio data received from the main unit 2 in the time slot assigned to the slave unit 4A. The slave unit 4A performs reception processing in the assigned time slot, receives the voice data input to the slave unit 4A, converts it into sound waves, and outputs it.

If there is a channel with a stronger reception strength in a period other than the assigned time slot, the slave unit 4A processes a handover request requesting a wireless connection to that channel (step S120). Hereinafter, the master unit 3A currently wirelessly connected is also referred to as a partner station, and the master unit 3 to which a channel having a stronger reception strength is assigned is also referred to as a candidate station.

As shown in FIG. 6, in step S120, the handover control unit 47 switches channels so that the transmission / reception unit 44 receives radio waves (step S121). The measuring unit 46 detects the received voltage of the switched channel (step S122). The detection result of the received voltage is output to the handover control unit 47. Steps S121 and S122 are repeated while switching channels until the reception voltage of all channels is detected (step S123).

The handover control unit 47 compares the reception voltages of all channels (step S124) and searches for the highest reception voltage (step S125). The handover control unit 47 determines whether the partner station is assigned the channel with the highest reception voltage (step S126). When the channel with the highest reception voltage is not assigned to the partner station (step S126, No), the handover control unit 47 switches the wireless connection to the candidate station to which the channel with the highest reception voltage is assigned. Is generated (step S127), and the transmission / reception unit 44 is made to wirelessly transmit (step S128).

Returning to FIG. 5, the handover request is received by the master unit 3A, and the master unit 3A transmits the handover request to the master unit 2 (step S130). Then, the main device 2 performs a handover process for changing the channel in response to the handover request (step S140).

In step S140, the main device 2 determines whether or not there is a vacancy in the time slot of the requested channel in response to the handover request. That is, the communication setting unit 21 refers to the time slot set in the candidate station. Here, the communication setting unit 21 stores, for example, a voice matrix in which information for identifying the wireless terminal 4 is registered for each combination of channels and time slots. The communication setting unit 21 may refer to the voice matrix and determine whether or not there is a time slot in which the information for identifying the wireless terminal 4 is not registered for the channel included in the handover request. When there is a vacant time slot, the communication setting unit 21 registers the information for identifying the slave unit 4A for the requested channel and the vacant time slot.

In response to the handover request, the main device 2 responds by transmitting control data including information on the newly registered channel and time slot to the slave unit 4A (step S150).

At this time, the slave unit 4A is in a state of being wirelessly connected to both the master unit 3A, which is the partner station, and the master unit 3B, which is the candidate station. Therefore, the voice data is transmitted / received using the two systems of the partner station and the candidate station (step S160). For example, the voice data transmitted to the slave unit 4A is transmitted from the main unit 2 to both the master unit 3A and the master unit 3B, and the slave unit 4A transmits the voice data wirelessly transmitted by both the master unit 3A and the master unit 3B. receive. In the slave unit 4A, the measurement unit 46 detects the reception voltage of both audio data, and the communication control unit 41 outputs the audio data of the high reception voltage to the headset interface 45.

Next, the slave unit 4A processes a cancellation request for canceling the wireless connection of the master unit 3A and the master unit 3B, whichever has the weaker reception voltage, during a period other than the assigned time slot (step S170). ).

As shown in FIG. 7, in step S170, the measuring unit 46 detects the reception voltage of the voice data wirelessly transmitted by both the partner station and the candidate station (step S171). Both detection results are input to the handover control unit 47. The handover control unit 47 compares the reception voltage of the voice data wirelessly transmitted by both the partner station and the candidate station (step S172). As a result of comparison, the handover control unit 47 generates control data including a request for canceling the wireless connection with the master unit 3 to which the channel having the weak reception voltage is assigned (step S173), and wirelessly transmits the control data (step S174). ..

For example, when the high reception voltage is the master unit 3B, that is, the candidate station that is separately wirelessly connected after the handover request, the handover control unit 47 is connected to the master unit 3A, that is, the partner station having a relatively weak reception voltage. The control data includes a request to disconnect the wireless connection of the device, and the device is transmitted wirelessly.

Returning to FIG. 5, the release request is transmitted to the main device 2 (step S180). The transmission path may be a master unit 3A which is a partner station, a master unit 3B which is a candidate station, both, or a master unit 3 to which a channel having a relatively high reception voltage is assigned. Then, the main device 2 cancels the wireless connection in response to the request for canceling the wireless connection (step S190). That is, the voice matrix is changed according to the control data. After that, the voice data to be transmitted to the slave unit 4A is transmitted from the main unit 2 only to the master unit 3B which is the new partner station, and the slave unit 4A receives the voice data from the master unit 3B which is the new partner station. become.

(Action)
FIG. 8 is a schematic view showing the arrangement of the master unit 3 and the wireless terminal 4. Here, it is assumed that two master units 3 of the master unit 3A and the master unit 3B are arranged. Further, it is assumed that the maximum number of wireless terminals 4 that can be connected to each master unit 3 is 5, that is, the TDMA frames are separated by 5 time slots. The master unit 3A is already connected to five wireless terminals 4, which are the maximum number of slave units 4A to 4E that can be connected, and the master unit 3B is provided with one room for connection to the slave units 4F to 4I. It is assumed that the remaining four wireless terminals 4 are already connected. Further, it is assumed that the slave units 4A to 4I belong to the same group, and the master unit 3A and the master unit 3B also belong to the same group. That is, it is assumed that the slave units 4A to 4I can be wirelessly connected to both the master unit 3A and the master unit 3B.

As shown in FIG. 8, the master unit 3A and the master unit 3B are arranged so that the communicable ranges Ea and Eb partially overlap. The communicable ranges Ea and Eb are ranges in which error correction is possible even if a bit error occurs and audio reproduction is guaranteed. As shown in FIG. 8, the slave unit 4B wirelessly connected to the master unit 3A is located within both the communicable range Ea of the master unit 3A and the communicable range Eb of the master unit 3B.

The slave unit 4B detects and compares the reception voltage of the radio waves received from both the master unit 3A and the master unit 3B. It is assumed that the slave unit 4B is within the communication range of both Ea and Eb, but has moved to a position closer to the master unit 3B than the master unit 3A (in the figure, the same distance on the dotted line). At this time, the reception voltage of the radio wave received from the master unit 3B is higher than the reception voltage of the radio wave received from the master unit 3A. In this example, it is assumed that there is no obstacle and the reception voltage is determined only by the distance. Therefore, the slave unit 4B requests the main unit 2 to perform a handover with the master unit 3B.

There is room for one connection in the base unit 3B. Therefore, the main device 2 registers the connection between the slave unit 4B and the master unit 3B. Therefore, the slave unit 4B is temporarily wirelessly connected to both the master unit 3A and the master unit 3B. Then, the slave unit 4B requests the main unit 2 to cancel the wireless connection with the master unit 3A, and the main unit 2 cancels the registration of the wireless connection between the slave unit 4B and the master unit 3A. That is, the slave unit 4B does not have a period during which the slave unit 4B is not connected to the master unit 3 during the handover, and the wireless connection destination of the slave unit 4B is seamlessly switched. In this way, the sound for the slave unit 4B is not interrupted.

Then, due to this handover, there is room for one connection in the master unit 3A. After that, it is assumed that the slave unit 4F is separated from the communicable range Eb of the master unit 3B and reaches the communicable range Ea of the master unit 3A. Since there is room for connecting one unit to the master unit 3A, the slave unit 4F is wirelessly connected to the master unit 3A. When the movement route of the slave unit 4F passes through the overlapping area of the communicable range Ea and Eb, when the reception voltage of the radio wave received from the master unit 3A exceeds the reception voltage of the radio wave received from the master unit 3B. Seamless handover connection.

Here, consider a case where the slave unit 4B does not hand over to a channel having a strong reception voltage as in the conventional case, but continues to be wirelessly connected to the master unit 3A while in the communicable range Ea. Even if the slave unit 4B is in the overlapping area of the communicable range Ea and Eb and the reception voltage of the radio wave received from the master unit 3B is stronger than that of the master unit 3A, the slave unit 4B is still connected to the master unit 3A. Maintain a wireless connection. Therefore, the number of wirelessly connectable units to the master unit 3A remains the maximum, and there is no room for accepting another wireless terminal 4.

Then, when the slave unit 4F moves away from the communicable range Eb of the master unit 3B and reaches the communicable range Ea of the master unit 3A, the slave unit 4F is released from the wireless connection with the master unit 3B, and moreover, the slave unit 4F and the master unit 3A The wireless connection cannot be established. That is, the slave unit 4F cannot transmit and receive voice data.

However, in the intercom system 1 of the present embodiment, even if the slave unit 4B is within the communicable range Ea, the slave unit 4F is switched to the wireless connection with the master unit 3B, so that the slave unit 4F is wireless with the master unit 3A. You can connect.

(effect)
As described above, in the intercom system 1, at least two communicable ranges Ea and Eb of the master unit 3 are arranged so as to partially overlap each other. The wireless terminal 4 includes a transmission / reception unit 44 that transmits / receives data to / from the partner station, a measurement unit 46 that measures the reception strength of each channel, and a handover control unit 47 that requests a handover with the master unit 3. I did. The handover control unit 47 searches for a channel having a stronger reception strength than the channel assigned to the partner station based on the measurement result of the measurement unit 46, and if there is a channel with the strong reception strength, the channel with the strong reception strength is selected. The assigned master unit 3 is used as a new candidate station to be the partner station, and a wireless connection with the candidate station is requested.

As a result, even if the wireless terminal 4 at the position where the communicable range Ea and Eb overlap does not reach the extension of the wireless possible range Ea with the partner station, the wireless terminal 4 is wirelessly connected to another candidate station by handover. It becomes easier to make a vacancy in the wireless connection of, and the possibility of wireless connection increases even if another wireless terminal moves to the side of this partner station.

Although the wireless connection method with the master unit 3 is the TDMA-TDD system, FDMA (Frequency Division Multiple Access) that divides the frequency band of the same channel if the wireless connection with the master unit 3 has an upper limit. This embodiment can be applied to any method such as a method.

Further, in the present embodiment, a channel having a strong reception voltage is searched as an example of handover, but when the extension of the communicable range is reached in combination with this, that is, the reception voltage becomes a predetermined value or less. , The handover may be requested when an event occurs such that error correction becomes difficult and voice reproduction cannot be guaranteed.

Further, the transmission / reception unit 44 receives data from both the current partner station and the candidate station at the request of the handover control unit 47. Then, the measurement unit 46 measures each reception intensity of the channels assigned to both the current partner station and the candidate station, and the handover control unit 47 measures the channel with a strong reception intensity based on the measurement result of the measurement unit 46. One of the stations to which is assigned is set as the new partner station, and the wireless connection with the other station is requested to be canceled.

As a result, the master unit 3 can be seamlessly switched without interruption of communication during the handover, and the communication quality is improved. When measuring the reception strength of both the partner station and the candidate station, instead of measuring the radio wave on which the data is carried, the beacon signal is separately received and the radio wave strength of the beacon signal is measured. , The probe response may be received and the radio field intensity of the probe response may be measured. However, by measuring the radio wave on which the data is carried, it is possible to quickly switch to one master unit 3, and it is possible to reduce the period in which the connection resources are used twice by wirelessly connecting to both master units 3. ..

1 Intercom system 2 Main unit 21 Communication setting unit 22 Communication control unit 23 Wired communication processing unit 24 Power supply unit 25 External interface 3 Master unit 31 Wired communication processing unit 32 Baseband processing unit 33 RF processing unit 34 Antenna 4 Wireless terminal 41 Communication control unit 42 Baseband processing unit 43 RF processing unit 44 Transmission / reception unit 45 Headset interface 46 Measuring unit 47 handover control unit 48 Antenna 5 Cable

Claims (5)

A wireless terminal that wirelessly connects to at least two master stations whose communicable range partially overlaps with one of the other master stations as the partner station.
A transmitter / receiver that sends / receives data to / from the partner station,
A measuring unit that measures the reception strength of each channel,
Based on the measurement result of the measuring unit, a channel having a stronger reception strength than the channel assigned to the partner station is searched, and if there is a channel having the strong reception strength, the parent to which the channel having the strong reception strength is assigned. With the machine as a new candidate station to be the partner station, a handover control unit that requests a wireless connection with the candidate station, and
Equipped with a,
At the request of the handover control unit, the transmission / reception unit receives data from both the current partner station and the candidate station, and receives data from both the current partner station and the candidate station.
The measuring unit measures each reception intensity of the channels assigned to both the current partner station and the candidate station.
Based on the measurement result of the measurement unit, the handover control unit sets one station to which a channel having a strong reception strength is assigned as the new partner station, and requests the cancellation of the wireless connection with the other station.
Wireless terminal. The transmitter / receiver transmits / receives data in the assigned time slot, and transmits / receives data.
The measuring unit measures the reception intensity of each channel during a period other than the time slot.
The wireless terminal according to claim 1. The reception intensity measured by the measuring unit is the reception voltage.
The wireless terminal according to claim 1 or 2. The main device that controls the transmission and reception of data in the system,
With multiple master units that have at least two communication ranges that partially overlap,
A wireless terminal that uses one of the master units as a partner station and wirelessly connects to the partner station,
With
The wireless terminal is
A transmitter / receiver that sends / receives data to / from the partner station,
A measuring unit that measures the reception strength of each channel,
Based on the measurement result of the measuring unit, a channel having a stronger reception strength than the channel assigned to the partner station is searched, and if there is a channel having the strong reception strength, the parent to which the channel having the strong reception strength is assigned. With the machine as a new candidate station to be the partner station, a handover control unit that requests a wireless connection with the candidate station, and
Have,
The main device is
Upon receiving a request by the handover controller, have a communication setting unit for setting a radio connection with the candidate station,
The transmission / reception unit receives data from both the current partner station and the candidate station according to the setting by the communication setting unit.
The measuring unit measures each reception intensity of the channels assigned to both the current partner station and the candidate station.
Based on the measurement result of the measurement unit, the handover control unit sets one station to which a channel having a strong reception strength is assigned as the new partner station, and requests the cancellation of the wireless connection with the other station.
The communication setting unit cancels the wireless connection with the other station in response to the cancellation request by the handover control unit .
Intercom system. The communication setting unit receives a request by the handover controller sets a radio connection with both the candidate station the current phase hand station,
The intercom system according to claim 4.

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