JP7381993B2 - Wireless communication system and handover method in wireless communication system - Google Patents

Description

The present invention relates to a wireless communication system suitable for application to a digital cordless telephone and a handover method in the wireless communication system.

Wireless communication systems are becoming widespread in which multiple cordless communication devices each consisting of a base unit and one or more slave units are connected to a main unit connected to one or more telephone lines (for example, patented (See Document 1 (Japanese Patent Laid-Open No. 2013-85154) and Patent Document 2 (Japanese Patent Laid-Open No. 2015-177239)). This wireless communication system is used in various facilities such as companies, factories, hospitals, and offices.

In this type of wireless communication system, the range in which the base unit and handset of a cordless communication device can communicate while maintaining call quality is limited. In order to prevent calls from being interrupted even when you move with your device, the system is equipped with a handover function, and the base devices are placed far apart from each other so that the entire range of the facility is covered. constructed in such a way that it can cover

Here, the handover function is a function that causes a base unit with good communication quality to be switched as the slave unit moves and changes its location.

Japanese Patent Application Publication No. 2013-85154 Japanese Patent Application Publication No. 2015-177239

By the way, in this type of wireless communication system, in consideration of the environment where echoes occur, such as when the other party's telephone terminal is connected to an analog line, each base unit has an echo for the voice received from the other party. A canceller is provided. As this echo canceller, an adaptive echo canceller is used, which performs echo cancellation by dynamically changing filter coefficients using an adaptive algorithm.

Even when the base unit to which the slave unit in call is connected is switched due to handover as described above, echo cancellation is performed by the echo canceller of the switched base unit.

However, at the time of handover, the adaptive filter coefficients of the echo canceller of the switched base unit are not necessarily in the optimal state, and the adaptive filter coefficients are optimized using an adaptive algorithm. It has been found that, for example, it takes about 1 second to do this, and during that time, the voice received during a call may feel strange.

An object of the present invention is to provide a wireless communication system that can solve the above problems.

In order to solve the above problem, the invention of claim 1:
A plurality of cordless communication devices each consisting of a base unit and one or more handsets are connected to the main device, and the handset during a call can perform handover to switch the wirelessly connected base unit. In communication systems,
The base unit includes an echo canceller that performs echo cancellation by dynamically changing coefficients of an adaptive filter using an adaptive algorithm, with respect to received audio sent to the wirelessly connected slave unit during a call,
At the time of handover, the coefficients of the adaptive filter of the echo canceller of the base unit that was wirelessly connected to the slave unit during the call before handover are applied to the base unit that is wirelessly connected to the slave unit after handover. Provided is a wireless communication system characterized in that the transmission is transmitted and set in an adaptive filter of an echo canceller of the base unit that is wirelessly connected after the handover.

In the wireless communication system according to the invention of claim 1 configured as described above, at the time of handover, the coefficients of the adaptive filter of the echo canceller of the base unit that was wirelessly connected to the slave unit during the call before the handover are changed after the handover. The information is transmitted to the base unit that is wirelessly connected to the slave unit, and set in the adaptive filter of the echo canceller of the base unit that is wirelessly connected to the slave unit after handover.

Therefore, the adaptive filter coefficients of the echo canceller of the base unit that is wirelessly connected to the slave unit after handover are set to the adaptive filter coefficients of the echo canceller of the base unit that was wirelessly connected to the slave unit before handover. Therefore, the time it takes for the coefficients of the adaptive filter to be optimized by the adaptive algorithm is shortened, and the occurrence of unnatural sounds in the received voice during handover is reduced.

According to this invention, the coefficients of the adaptive filter of the echo canceller of the base unit that is wirelessly connected to the slave unit after handover are the coefficients of the adaptive filter of the echo canceller of the base unit that was wirelessly connected to the slave unit before handover. Since the setting is set to , even if a call is being made to a caller in an environment where echoes occur, it is possible to reduce the occurrence of an unnatural feeling in the voice received during a handover.

FIG. 1 is a block diagram for explaining an overall outline of an embodiment of a wireless communication system according to the present invention. FIG. 2 is a diagram for explaining handover in an embodiment of a wireless communication system according to the present invention. 1 is a block diagram showing a detailed configuration example of a main device forming a part of an embodiment of a wireless communication system according to the present invention; FIG. 1 is a block diagram showing an example of a detailed configuration of a parent device that forms part of an embodiment of a wireless communication system according to the present invention; FIG. FIG. 5 is a block diagram illustrating a configuration example of an audio signal processing section of the base device in the example of FIG. 4. FIG. 5 is a diagram illustrating a configuration example of an adaptive filter circuit of an echo canceller used in the audio signal processing section of the base unit in the example of FIG. 4. FIG. 1 is a block diagram showing an example of a detailed configuration of a handset forming a part of an embodiment of a wireless communication system according to the present invention; FIG. FIG. 2 is a diagram showing a first example of a sequence during handover in an embodiment of a wireless communication system according to the present invention. FIG. 6 is a diagram showing a second example of a sequence during handover in the embodiment of the wireless communication system according to the present invention. FIG. 7 is a diagram showing a third example of a sequence during handover in the embodiment of the wireless communication system according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wireless communication system according to the present invention will be described below with reference to the drawings, taking as an example a case in which it is applied to a telephone system called a business phone.

FIG. 1 is a block diagram showing an example of the overall configuration of a telephone system 10 as an embodiment of a wireless communication system according to the present invention. In the telephone system 10 of this example, for a main device 1 as an example of a host device, a plurality of cordless telephone devices 21, 22, ..., 2n (n is an integer of 2 or more. same) are connected. Each of the cordless telephone devices 21 to 2n is an example of a cordless communication device, and is connected to each of base units CS1, CS2, ..., CSn, and handset units PS1, PS2, ..., PSm (m is 2 or more). (an integer; the same applies hereinafter), and each of the base units CS1 to CSn and each of the slave units PS1 to PSm are wirelessly connected.

In the wireless communication system of this embodiment, the base units constituting the cordless telephone devices 21, 22, . . . , 2n are fixed as base units CS1, CS2, . Considering the above, all of the handsets PS1, PS2, . . . , PSm can constitute cordless telephone devices 21, 22, . . . , 2n.

In this embodiment, the wireless connection between each of the base units CS1 to CSn of the cordless telephone devices 21 to 2n and each of the slave units PS1 to PSm is based on the DECT (Digital Enhanced Cordless Telecommunication) standard for digital cordless telephones. This is done using the TDMA/TDD method using .

Note that the wireless connection between each of the base units CS1 to CSn of the cordless telephone devices 21 to 2n and each of the slave units PS1 to PSm is not limited to the TDMA/TDD method using the DECT standard; , a wireless LAN (Local Area Network) system in which the master device is configured with an access point device, the slave device is configured with a station device that wirelessly connects to the access point device, and furthermore, a plurality of access point devices are connected to the main device, etc. It goes without saying that configurations of wireless communication systems with various wireless connections are possible.

The main device 1 can accommodate one or more telephone lines L1 to Li (i is an integer of 1 or more). The main units CS1 to CSn of the cordless telephone devices 21 to 2n are connected to the main unit 1 by, for example, a LAN. In the example of FIG. 1, the base stations CS1 to CSn and the main device 1 are connected by wire, but they may be connected wirelessly.

The main device 1 performs call control, circuit switching control, and other business telephone controls for the plurality of cordless telephone devices 21 to 2n, and supplies a reference synchronization signal SYNC to each of the plurality of cordless telephone devices 21 to 2n. It has functions. In this example, the reference synchronization signal SYNC is a signal with a period of 130 milliseconds (ms).

Each of the base units CS1 to CSn of the cordless telephone devices 21 to 2n synchronizes with the reference synchronization signal SYNC from the main unit 1 and transmits one frame (10 milliseconds (ms)), which is a unit communication period of a digital cordless telephone according to the DECT standard. ))), and based on the generated frame synchronization signal, TDMA/TDD wireless communication using the DECT standard is performed with slave units PS1 to PSm. . Therefore, all of the plurality of cordless telephone devices 21 to 2n operate in synchronization with the reference synchronization signal SYNC from the main device 1.

The main device 1, each of the base units CS1 to CSn, and each of the slave units PS1 to PSm of the telephone system 10 in this example has a function of performing a handover sequence as described later.

FIG. 2 is a diagram showing a state in which handover occurs. As shown in FIG. 2, the base unit CS1 and the base unit CS2 are capable of wireless communication with each of the slave units PS1 to PSm, for example, within a circular communication range of radius D, and are within the communication range of each other. They are each installed so that some of them overlap.

In this state, the handset PS1, which was wirelessly connected to the base unit CS1 and was talking to the other party, moves and, as shown in FIG. 2, wireless communication with both the base unit CS1 and the base unit CS2 is interrupted. is possible, and if the position is closer to the base unit CS2, the received field strength of the radio waves from the base unit CS2 will be higher in the slave unit PS1 than the received field strength of the radio waves from the base unit CS1. Detects that it has grown larger.

Then, based on the detected received field strength, the slave PS1 determines that communication quality can be improved by wirelessly connecting to the base CS2, and sends a handover request to the base CS2. Upon receiving this handover request, the base unit CS2 receives the information necessary for establishing a wireless connection with the slave unit PS1 from the base unit PS1 via the main unit 1, and after completing the reception, it hands over the information to the slave unit PS1. Send permission notice for over. Based on this handover sequence, the main device switches the call of the slave device PS1 from the base device PS1 to the base device PS2 and manages it. As described above, the handset PS1 can switch the wirelessly connected base unit from the base unit PS1 to the base unit PS2 by handover and continue the call.

Next, detailed configuration examples of each of the main device 1, parent devices CS1 to CSn, and slave devices PS1 to PSn in FIG. 1 will be described.

[Example of configuration of main device 1; Figure 3]
FIG. 3 is a block diagram showing an example of the configuration of the main device 1. As shown in FIG. As shown in FIG. 3, the main device 1 includes a line interface 11 to which telephone lines L1 to Lm are connected, a control circuit 12 equipped with a computer to control the entire main device 1, and a line LSI (Large Scale Integrated Circuit) section 13 and a reference oscillator 14.

Under the control of the control circuit 12, the line interface 11 supplies voice signals (received voice signals) from the lines L1 to Ln to the line LSI section 13, and supplies control signals such as call control signals from the lines to the control circuit 12. Supply to 12. Also, under the control of the control circuit 12, the line interface 11 transmits voice signals (transmission voice signals) from the line LSI unit 13 to the other party through lines L1 to Ln, and transmits call control signals from the control circuit 12, etc. The control signals are also transmitted to the other party through the lines L1 to Ln.

The line LSI unit 13 includes n extension processing circuits 131, 132, . . . , 13n and a timing signal generation unit 130 corresponding to the n extension telephone devices.

The timing signal generation unit 130 generates a transmission clock signal CK and a multiplexing/division timing signal TM from a reference clock signal from a high-precision reference oscillator 14 using a crystal oscillator, and processes n extension lines. It is supplied to circuits 131 to 13n.

The n extension processing circuits 131 to 13n have exactly the same configuration, and each includes an audio signal processing section 31, a control signal processing section 32, a synchronization signal processing section 33, and a multiplexing/division processing section. It consists of 34.

The audio signal processing section 31 is connected to the line interface 11 and also to the multiplexing/division processing section 34, and processes the received audio signal from the line interface 11 and the transmission from the multiplexing/division processing section 34. This is a speech signal processing circuit. The audio signal processing section 31 is supplied with a transmission clock signal CK from the timing signal generation section 130.

The control signal processing section 32 is connected to the control signal input/output terminal of the control circuit 12, and is also connected to the multiplexing/division processing section 34, and handles calls at the time of origination, reception, and termination of a call. This is a processing circuit for control signals such as control signals and control signals during handover sequences (both control signals from the main device 1 to the cordless telephone device and control signals from the cordless telephone device to the main device 1). This control signal processing section 32 is also supplied with the transmission clock signal CK from the timing signal generation section 130.

The synchronization signal processing section 33 is connected to the synchronization signal output terminal of the control circuit 12 and also to the multiplexing/division processing section 34, and receives a reference synchronization signal having a predetermined synchronization signal pattern from the control circuit 12. This is a SYNC processing circuit. Similarly, the synchronization signal processing section 33 is also supplied with the transmission clock signal CK from the timing signal generation section 130.

The multiplexing/division processing unit 34 is connected to the audio signal processing unit 31, the control signal processing unit 32, and the synchronization signal processing unit 33, and is also connected to each of the base units CS1 to CSn of the cordless telephone devices 21 to 2n. Ru. The multiplexing/division processing unit 34 then outputs the audio signal (received audio signal) from the audio signal processing unit 31 and the control signal from the control signal processing unit 32 based on the timing signal TM from the timing signal generation unit 130. The signal and the reference synchronization signal SYNC from the synchronization signal processing section 33 are multiplexed (time division multiplexed) to generate a multiplexed signal, and the generated multiplexed signal is supplied to each of the main units CS1 to CSn. Furthermore, the multiplexing/division processing unit 34 divides the multiplexed signal from each of the base units CS1 to CSn into an audio signal and a control signal based on the timing signal TM from the timing signal generation unit 130. The audio signal (transmission audio signal) is supplied to the audio signal processing section 31, and the control signal is supplied to the control signal processing section 32, respectively.

[Example of configuration of cordless telephone device]
Each of the plurality of base devices CS1 to CSn and the plurality of slave devices PS1 to PSn all have the same configuration. Therefore, in the following description, an example of the configuration of the base unit and the handset will be explained by taking the case of the base unit CS1 and the slave unit PS1 of the cordless telephone device 21 as an example.

<Example of configuration of base unit; Figure 4>
FIG. 4 is a block diagram illustrating a configuration example of base unit CS1. As shown in FIG. 4, the base unit CS1 includes a control circuit 41 for controlling the entire base unit CS1, a line LSI section 42, a synchronization signal generation circuit 43, a wireless communication circuit 44, an oscillator 45, and a 46.

The control circuit 41 includes a computer. The control circuit 41 has a function of controlling the base unit CS1, such as call control and handover control.

The line LSI section 42 is a circuit for exchanging audio signals, control signals, and synchronization signals with the main device 1, and includes a division/multiplexing processing section 421, a control signal processing section 422, and an audio signal processing section 421. It consists of a processing section 423, a synchronization signal processing section 424, and a PLL (Phase locked Loop) section 425.

The PLL section 425 is supplied with an oscillation signal of a reference frequency from the oscillator 45 and also supplied with a multiplexed signal from the main device 1 . In this example, the frequency of the oscillation signal from the oscillator 45 is, for example, 2048 MHz (0.488 nanoseconds (ns)).

The PLL section 425 extracts the component of the clock signal CK from the timing signal generation section 130 of the main device 1 from the multiplexed signal from the main device 1 by so-called self-clocking, and combines the extracted clock signal CK component with the oscillator. Based on the comparison result, a system clock signal SCK of the main unit CS1 synchronized with the clock signal CK component is generated from the oscillation signal of the oscillator 45.

The PLL unit 425 then sends the generated system clock signal SCK to each of the division/multiplexing processing unit 421, control signal processing unit 422, audio signal processing unit 423, and synchronization signal processing unit 424 as a clock signal for signal processing. At the same time, it is also supplied to the synchronization signal generation circuit 43.

The division/multiplexing processing section 421 is connected to the extension processing circuit 131 of the main device 1, and is also connected to the control signal processing section 422, the audio signal processing section 423, and the synchronization signal processing section 424. Then, the division/multiplexing processing unit 421 divides the control signal, the audio signal, and the reference synchronization signal SYNC from the multiplexed signal from the main device 1, and sends the control signal to the control signal processing unit 422, and sends the audio signal to the audio signal. The reference synchronization signal SYNC is supplied to the signal processing section 423 and the synchronization signal processing section 424, respectively.

Furthermore, the division/multiplexing processing unit 421 multiplexes the control signal from the control signal processing unit 422 and the audio signal from the audio signal processing unit 423 to generate a multiplexed signal, and the generated multiplexed signal is supplied to the main device 1.

The control signal processing unit 422 is connected to the control signal input/output terminal of the control circuit 41 and is also connected to the division/multiplexing processing unit 421, and is used to control signal processing at the time of outgoing call, incoming call, handover, and end of call. This is a processing circuit for control signals such as call control signals (both the control signal from the main device 1 to the cordless telephone device 21 and the control signal from the cordless telephone device 21 to the main device 1).

The audio signal processing section 423 is connected to the wireless communication circuit 44 and also to the division/multiplexing processing section 421, and as shown in FIG. It includes a transmitted audio signal processing circuit 4231 that processes a transmitted audio signal, and a received audio signal processing circuit 4232 that processes a received audio signal received from the other party's device from the division/multiplexing processing section 421.

As shown in FIG. 5, the received voice signal processing circuit 4232 includes an echo canceller 60. The echo canceller 60 is composed of an adaptive digital filter (ADF) 61 and a subtraction circuit 62.The received voice signal d(k) received from the other party's device is input to one of the inputs of the subtraction circuit 62. Furthermore, the transmitted audio signal u(k) received from the handset PS1 is supplied to the other input terminal of the subtraction circuit 62 through the adaptive filter circuit 61.Then, the output of the subtraction circuit 62 Signal e(k) is fed back to adaptive filter circuit 61.

In this case, if the other party's telephone terminal is connected to an analog line, the incoming voice signal d(k) is The transmitted audio signal from PS1 may include a component that is delayed and returned to handset PS1, and this may appear as an echo in the received audio emitted from the handset of handset PS1. The quality of the received voice will deteriorate.

The adaptive filter circuit 61 converts the transmitted audio signal u(k) from the handset PS1 into an output signal by converting a component that approximates the component that the transmitted audio signal from the handset PS1 is delayed and returns to the handset PS1 into an output signal. y(k). Then, the output signal y(k) of the adaptive filter circuit 61 is subtracted from the received audio signal d(k) by the subtraction circuit 62, so that the output signal y(k), which is included in the received audio signal d(k), is subtracted from the received audio signal d(k). The subtraction circuit 62 outputs an output signal e(k) from which the return component of the transmitted audio signal u(k) has been removed.

Note that the adaptive filter circuit 61 is configured to reduce the transmission audio signal from the handset PS1 due to not only the echo component generated due to the presence of the hybrid circuit when the other party's telephone terminal is connected to an analog line, but also other factors. It is also possible to perform echo cancellation at the same time for echo components that are delayed and return to the slave PS1.

In this example, the adaptive filter circuit 61 of the echo canceller 60 includes an FIR (Finite Impulse Response) filter 611 and an adaptive algorithm calculation unit 612, as shown in FIG. In the example of FIG. 6, the FIR filter 611 includes q delay circuits 611D (q is an integer of 1 or more) and (q+1) delay circuits 611D that delay the transmitted audio signal u(k) from the handset PS1 by one sample. It consists of a coefficient multiplication circuit 611M and a sum calculation circuit 611S.

The q delay circuits 611D are sequentially connected in cascade, and the received audio signal d(k) is supplied to the input side of the q cascade-connected delay circuits 611D. Then, the received voice signal d(k) is supplied to the sum calculation circuit 611S via one of the coefficient multiplication circuits 611M, and the output signals of each of the q delay circuits 611D are supplied to a separate coefficient multiplication circuit 611M. The output signal y(k) of the adaptive filter circuit 61 is supplied from the summation calculation circuit 611S through the summation calculation circuit 611S.

Then, the adaptive algorithm calculation unit 612 calculates coefficients h0(k), h1(k), h2(k), . is generated and supplied to each of the (q+1) coefficient multiplication circuits 611M. In this case, the adaptive algorithm calculation unit 612 performs an adaptive algorithm calculation to minimize the return component of the transmitted audio signal u(k) from the slave unit PS1, which is included in the output signal e(k) of the subtraction circuit 62. The coefficients h0(k), h1(k), h2(k), . . . hq(k) are dynamically generated so that

In this embodiment, coefficients h0(k), h1(k), h2(k), . The information (k) is also configured to be supplied to the control circuit 41.

As will be described later, when the control circuit 41 receives a handover request from a wirelessly connected handset, the control circuit 41 inputs the coefficient h0(k ), h1(k), h2(k), .

Further, at the time of handover, the control circuit 41 of the master device after the handover uses the coefficient h0(k) sent from the master device before the handover and supplied to each of the (q+1) coefficient multiplication circuits 611M. , h1(k), h2(k), . (k) should be set as the initial value.

As a result, the adaptive filter circuit 61 of the echo canceller 60 of the audio signal processing unit 423 of the base unit after handover is set to (k), h1(k), h2(k)... hq(k) information can be taken over and echo cancellation operation can be started, so echo cancellation will work effectively even during handover. It is possible to reduce the feeling of discomfort in the received voice.

The synchronization signal processing section 424 receives the reference synchronization signal SYNC from the division/multiplexing processing section 421, and detects a predetermined synchronization signal pattern included in the reference synchronization signal SYNC, thereby generating a signal at the time of the detection. A reference synchronization pulse PS that is synchronized with the reference synchronization signal SYNC and has the same period (130 ms) as the reference synchronization signal SYNC is generated. Then, the synchronization signal processing section 424 supplies the generated reference synchronization pulse PS to the synchronization signal generation circuit 43.

The synchronization signal generation circuit 43 includes a counter 431 and a synchronization signal generation section 432. The counter 431 is supplied with a reference synchronization pulse PS having a period of 130 ms from the synchronization signal processing section 424 of the line LSI section 42 to a preset terminal, and is also supplied with the system clock SCK from the PLL section 425 as a count input. Then, the output count value CNT of this counter 431 is supplied to the synchronization signal generation section 432.

The synchronization signal generation unit 432 generates a frame synchronization signal having a DECT standard frame period (10 ms) from the output count value CNT of the counter 431. The synchronization signal generation circuit 43 supplies the frame synchronization signal generated by the synchronization signal generation section 432 to the wireless communication circuit 44.

Next, in this embodiment, the wireless communication circuit 44 uses a general-purpose base unit wireless communication LSI for performing DECT wireless communication. This wireless communication circuit 44 includes a control section 441, a TDMA modem section 442, and a wireless communication section 443. The wireless communication unit 443 is a circuit unit for performing wireless communication with the slave device PS1.

The control section 441 is connected to the TDMA modulation/demodulation section 442 and the wireless communication section 443, and is also connected to the control circuit 41. The control section 441 controls the overall operation of the wireless communication circuit 44 and supplies a control signal based on the control signal obtained from the control circuit 41 to the TDMA modulation/demodulation section 442 .

The TDMA modulation/demodulation section 442 is connected to the control section 441 and the audio signal processing section 423 of the line LSI section 42, and is also connected to the wireless communication section 443. Modulation is performed to transmit the audio signal to the slave unit PS1. The signal modulated by this TDMA modulation/demodulation section 442 is transmitted to the slave device PS1 through the wireless communication section 443.

Further, the TDMA modulation/demodulation section 442 demodulates the audio signal and the control signal from the received signal from the handset PS1 received by the wireless communication section 443, and supplies the demodulated audio signal to the audio signal processing section 423, where it is demodulated. The control signal is supplied to the control section 441.

The TDMA modulation/demodulation section 442 includes a PLL section 4421 for clock generation. This PLL section 4421 is supplied with an oscillation signal from the oscillator 46 and a frame synchronization signal from the synchronization signal generation circuit 43.

The PLL unit 4421 compares the phases of the frame synchronization signal from the synchronization signal generation circuit 43 and the oscillation signal from the oscillator 46, and determines the timing for synchronizing the oscillation signal of the oscillator 46 with the frame synchronization signal based on the comparison result. Generate signals and clock signals.

The TDMA modulation/demodulation unit 442 uses a timing signal and a clock signal synchronized with the frame synchronization signal to generate a transmission signal to the slave PS1 in a period corresponding to one of the downlink slots that can be allocated and used. One of the uplink slots is used to process the received signal from the slave PS1.

[Example of configuration of slave unit; Figure 7]
FIG. 7 is a block diagram showing an example of the configuration of slave device PS1. As shown in FIG. 7, the handset PS1 includes a wireless communication circuit 51, a control circuit 52, a codec circuit 53, an oscillator 54, a microphone 55, and a speaker 56. The microphone 55 constitutes a transmitter, and the speaker 56 constitutes a receiver.

The wireless communication circuit 51 uses a general-purpose slave wireless communication LSI for performing DECT wireless communication. This wireless communication circuit 51 includes a control section 511, a TDMA modem section 512, and a wireless communication section 513. The wireless communication unit 513 is a circuit unit for performing wireless communication with the main unit CS1.

The control section 511 is connected to the TDMA modulation/demodulation section 512 and the wireless communication section 513, and is also connected to the control circuit 52. The control section 511 controls the overall operation of the wireless communication circuit 51 and supplies a control signal based on the control signal obtained from the control circuit 52 to the TDMA modulation/demodulation section 512. The control unit 511 also detects the received field strength of the radio waves from the base unit that can be received through the wireless communication unit 513, and transmits information on the detected received field strength of the radio waves from the base unit that can be received to the control circuit 52. .

The TDMA modulation/demodulation section 512 is connected to the control section 511 and the wireless communication section 513 as well as to the codec circuit 53, and transmits a control signal from the control section 511 and an audio signal from the codec circuit 53 to the base unit CS1. Perform modulation to The signal modulated by this TDMA modulation/demodulation section 512 is transmitted to the main unit CS1 through the wireless communication section 513.

Furthermore, the TDMA modulation/demodulation section 512 demodulates the audio signal and the control signal from the received signal from the base unit CS1 received by the wireless communication section 513, supplies the demodulated audio signal to the codec circuit 53, and supplies the demodulated control signal to the codec circuit 53. is supplied to the control section 511.

The TDMA modulation/demodulation section 512 includes a PLL section 5121 for clock generation. This PLL section 5121 is supplied with an oscillation signal from the oscillator 54, and is also supplied with a demodulated signal of the received signal from the wireless communication section 513, and from the oscillation signal from the oscillator 54, A clock signal synchronized with the clock component of the demodulated signal of the received signal is generated. The clock signal from the PLL section 5121 is used as a processing clock signal in the TDMA modulation/demodulation section 512.

When the handset PS1 makes a call, the control circuit 52 transmits a call control signal at the time of the call to the base unit CS1 through the wireless communication circuit 51, and also receives a call control signal at the time of incoming call from the base unit CS1. When a call is received, processing such as emitting a ringtone from the speaker 56 is performed. The control circuit 52 also switches the base unit that is currently connected wirelessly for a call to another base unit based on the received field strength of the radio waves from the receivable base unit detected by the control unit of the wireless communication circuit 51. When it is determined that the communication quality will be better if the communication quality is better, the handover request is sent to another base unit that is expected to have better communication quality. The control circuit 52 then performs a sequence for handover.

The codec circuit 53 decodes the audio signal demodulated by the TDMA modulation/demodulation section 512, converts it into an analog audio signal, supplies the analog audio signal to the speaker 56, and outputs it as received audio. Further, the codec circuit 53 encodes the analog audio signal picked up by the microphone 55 and supplies it to the TDMA modulation/demodulation section 512 .

The above explanation is about the base unit CS1 and handset PS1 of the cordless telephone device 21, but as mentioned above, the base unit CS2 to CSn and the handset PS2 to PSn of the other cordless telephone devices 22 to 2n are explained. also has a similar configuration.

[Example of sequence during handover]
Next, in a wireless communication system configured as described above, in a situation where a handset during a call moves and a handover becomes necessary, the information on the coefficients of the adaptive filter of the echo canceller is updated before the handover. Several examples of sequences including transmission from the base unit to the base unit after handover will be described.

In the example of the sequence described below, as shown in FIG. 2, when the handset PS1 is talking to, for example, an external phone terminal on an analog line via the base unit CS1 and the main unit 1, due to handover, This is a case where the base unit to which the slave unit PS1 is wirelessly connected is switched from the base unit CS1 to the base unit CS2.

In the sequence described below, the operations performed by the slave device PS1, the parent devices CS1, CS2, and the main device 1 are mainly performed by the control circuit 52, the control circuit 41, and the control circuit 12 provided in each of them. be.

<First example: Transmitting adaptive filter coefficients via main device 1 (Fig. 8)>
FIG. 8 is a first example of a handover sequence in the wireless communication system of this embodiment. In this first example, the adaptive filter coefficients are transferred via the main device 1 from the base unit CS1 that was wirelessly connected to the slave unit PS1 before the handover to the base unit CS1 that will be wirelessly connected to the slave unit PS1 after the handover. It is transmitted to CS2.

In addition, in FIG. 8, for the sake of simplicity, the other party's telephone terminal that is in communication with the handset PS1 is omitted. Regarding the communication paths, in order to make the explanation easier to understand, only the communication paths between the handset PS1, the base unit CS1, and the base unit CS2 are shown. The same applies to the second example and third example described later.

That is, in the example of FIG. 8, when the handset PS1 is making an outside line call with the other party's telephone terminal via the base unit CS1 and the main device 1, as explained using FIG. When the control circuit 52 of the slave PS1 determines that a handover is necessary to perform switching, the control circuit 52 of the slave PS1 sends a "handover request" to the base CS2.

Having received the handover request, the base unit CS2 sends a "source base unit information acquisition request" to the main unit 1, which is a request to acquire communication information with the slave unit in order to wirelessly communicate with the slave unit PS1 through handover. .

The main device 1 that received this "source device information acquisition request" knows that the source device that is currently in wireless connection with the slave device PS1 is the parent device CS1, so it responds to this request. Based on this, an "information acquisition request" is sent to base unit CS1.

Upon receiving this "information acquisition request," the base unit CS1 acquires the communication information with the slave unit PS1 that is currently connected wirelessly, and also sets the coefficients h0(k) and h1(k) of the adaptive filter circuit 61 of the echo canceller 60. , h2(k) . . . hq(k) information is acquired. The base unit CS1 then performs "information acquisition" including the acquired communication information with the slave unit PS1 and information on adaptive filter coefficients h0(k), h1(k), h2(k)...hq(k). response” is returned to the main device 1.

Having received this "information acquisition response", the main device 1 sends a "move source base device information acquisition response" including the acquired communication information with the slave device PS1, and a "move source base device information acquisition request". Return it to the base unit CS2 that came.

The base unit CS2 that has received this "source base unit information acquisition response" uses the communication information with the slave unit PS1 included in this "source base unit information acquisition response" to establish a wireless connection with the slave unit PS1. A communication path is generated, a "handover response" is sent to the slave PS1, and handover of the slave PS1 to the base CS2 is permitted.

Next, in this example, the main device 1 sends the coefficients h0(k), h1(k), h2(k), . . . of the adaptive filter circuit 61 of the echo canceller 60 to the base unit CS2. An "adaptive filter coefficient setting request" including information on hq(k) is sent. Upon receiving this "adaptive filter coefficient setting request", base unit CS2 sends the coefficients h0(k), h1(k), h2(k), . . . hq(k) to the adaptive filter circuit 61 of its own echo canceller 60. Set as the initial value.

Note that the main device 1 sends information on the coefficients h0(k), h1(k), h2(k), . . . hq(k) of the adaptive filter circuit 61 of the echo canceller 60 to the "adaptive filter coefficient setting request". Instead of including it and sending it to the base station CS2 after handover, it may be included in the "information acquisition response" and sending it to the base station CS2 after handover. In that case, the base unit CS2 may set the coefficients in response to the "adaptive filter coefficient setting request" from the main device 1, and the "adaptive filter coefficient setting request" from the main device 1 is unnecessary. As a result, the coefficients may be set at the time the coefficients are obtained.

Next, in this example, after the base unit CS2 completes setting the coefficients to the adaptive filter circuit 61 of this echo canceller 60, the base unit CS2 informs the main device 1 that the base unit that wirelessly communicates with the slave unit PS1 is connected to the base unit CS1. A "slave unit movement notification" is sent from the base unit CS2 to the base unit CS2. When the main device 1 receives this "handset movement notification", the main device 1 switches the audio path for the handset PS1 from the path via the base unit CS1 to the path via the base unit CS2.

On the other hand, the slave device PS1 that has received the "handover response" from the base device CS2 switches the wireless communication path to the base device CS2, switches the audio path, and disconnects the wireless communication path with the base device CS1. Note that the slave PS1 sends a "location registration" to the master CS2 to inform it of its own location.

The handover is completed through the above sequence, and the handset PS1 is in a state where it can continue talking with the other party's terminal through the path through the base station CS2. In this case, the coefficients h0(k), h1(k), h2(k), . As initial values, the coefficients h0(k), h1(k), h2(k), . (k) is set.

Therefore, in the echo canceller 60 of the base unit CS2 after handover, the coefficients h0(k), h1(k), h2(k), . . . hq(k) of the adaptive filter circuit 61 are optimized. The time is shortened, and the occurrence of discomfort in the received voice of a call during handover is reduced.

In this first example, the base unit CS2 sends the slave unit movement notification to the main unit 1 after setting the coefficients in the adaptive filter circuit 61 of the echo canceller 60. When a communication path is generated from the PS1 to the other party's terminal through the base station CS2 and the main device 1, the adaptive filter circuit can be expected to be in an optimal state.

<Second example: Transferring adaptive filter coefficients between base units (Figure 9)>
FIG. 9 is a second example of a handover sequence in the wireless communication system of this embodiment. In this second example, the adaptive filter coefficients are transferred from the main unit CS1, which was wirelessly connected to the slave unit PS1 before the handover, to the base unit CS2, which is wirelessly connected to the slave unit PS1 after the handover. Transmit information without going through the media.

In this second example, as shown in FIG. 9, after a handover request is sent from the handset PS1 during a call to the base unit CS2 through the base unit CS1, the main device 1 sends an "information acquisition request" to the parent unit CS1. The sequence up to sending to the machine CS1 is the same as the first example shown in FIG.

In this second example, base unit CS1 receives an “information acquisition request” from main device 1, acquires communication information with slave unit PS1 that is currently connected wirelessly, and performs communication with acquired slave unit PS1. An “information acquisition response” containing the information is returned to the main device 1.

Having received this "information acquisition response", the main device 1 sends a "move source base device information acquisition response" including the acquired communication information with the slave device PS1, and a "move source base device information acquisition request". Return it to the base unit CS2 from which it came. In this second example, this "source base unit information acquisition response" includes the address on the LAN of the base unit CS1, which is the base unit of the move source.

Next, in this second example, base unit CS2 uses the address of base unit CS1 on the LAN to request base unit CS1 to acquire the coefficients of adaptive filter circuit 61 of echo canceller 60. Send "adaptive filter coefficient acquisition request".

Upon receiving this "adaptive filter coefficient acquisition request", base unit CS1 acquires the coefficients h0(k), h1(k), h2(k), . . . hq(k) of the adaptive filter circuit 61 of its own echo canceller 60. The "adaptive filter coefficient acquisition response" including the information of the acquired adaptive filter coefficients h0(k), h1(k), h2(k)...hq(k) is converted into "adaptive filter coefficient acquisition response". The request is returned to the base unit CS2 that sent the request for obtaining coefficients.

Next, the base unit CS2 generates a wireless communication path with the slave unit PS1 using the communication information with the slave unit PS1 included in the “movement source base unit information acquisition response” received from the main device 1, A "handover response" is sent to the slave PS1 to permit handover of the slave PS1 to the base CS2.

Next, in this second example, the base unit CS2 receives the coefficients h0(k), h1(k), h2(k), h2(k), etc. of the adaptive filter circuit 61 of the echo canceller 60 from the base unit CS1. - Set hq(k) as an initial value in the adaptive filter circuit 61 of its own echo canceller 60.

After the base unit CS2 finishes setting the coefficients to the adaptive filter circuit 61 of the echo canceller 60, the base unit CS2 informs the main device 1 that the base unit that wirelessly communicates with the slave unit PS1 is transferred from the base unit CS1 to the base unit CS2. Sends a "child unit movement notification" to notify you of the movement. When the main device 1 receives this "handset movement notification", the main device 1 switches the audio path for the handset PS1 from the path via the base unit CS1 to the path via the base unit CS2.

On the other hand, the slave device PS1 that has received the "handover response" from the base device CS2 switches the wireless communication path to the base device CS2, switches the audio path, and disconnects the wireless communication path with the base device CS1. Note that the slave PS1 sends a "location registration" to the master CS2 to inform it of its own location.

The handover is completed according to the sequence of the second example explained above, and the handset PS1 is in a state where it can continue talking with the other party terminal through the path through the base station CS2. In the case of this second example as well, the same effects as in the above-mentioned first example can be obtained.

In the second example, after sending the "information acquisition response" to the "information acquisition request" to the main device 1, the base unit CS1 acquires information on the coefficients of the adaptive filter circuit 61 of the echo canceller 60. However, similarly to the first example, when receiving the "information acquisition request" from the main device 1, information on the coefficients of the adaptive filter circuit 61 of the echo canceller 60 is also acquired along with communication information with the slave device PS1. You may also do so.

<Third example: Transmitting adaptive filter coefficients through slave device (Figure 10)>
FIG. 10 is a third example of a handover sequence in the wireless communication system of this embodiment. In this third example, the adaptive filter coefficients are transferred from the base unit CS1, which was wirelessly connected to the slave unit PS1 before the handover, to the base unit CS2, which is wirelessly connected to the slave unit PS1 after the handover. to communicate via.

In this third example as well, as shown in FIG. 10, after a handover request is sent from the handset PS1 during a call to the base unit CS2 through the base unit CS1, the main device 1 sends an “information acquisition request” to the parent unit CS1. The sequence up to sending to the machine CS1 is the same as the first example shown in FIG.

In this third example as well, similarly to the first example, the main unit CS1 that has received the “information acquisition request” obtains communication information with the slave unit PS1 that is currently connected wirelessly, and also transmits the echo canceller 60. Information on coefficients h0(k), h1(k), h2(k), . . . hq(k) of the adaptive filter circuit 61 is acquired. However, in this third example, base unit CS1 returns to main device 1 an “information acquisition response” that includes only the acquired communication information with slave unit PS1. In this third example, the "adaptive filter" including the acquired information on the coefficients h0(k), h1(k), h2(k), . . . hq(k) of the adaptive filter circuit 61 of the echo canceller 60 is used. A filter coefficient transfer request is sent to the slave device PS1.

Receiving this "adaptive filter coefficient transfer request", the slave unit PS1 transmits the coefficients h0(k), h1(k), h2(k), . . . hq(k) of the adaptive filter circuit 61 of the echo canceller 60 of the base unit CS1. ) is transferred to the main unit CS2.

On the other hand, the main device 1 sends to the base device CS2 a "movement source base device information acquisition response" that includes the communication information with the slave device PS1 acquired from the base device CS1. generates a wireless communication path with the slave PS1 using the communication information with the slave PS1 included in the "source base unit information acquisition response" received from the main device 1, and sends a "handover response". It is sent to the slave device PS1 to permit handover of the slave device PS1 to the master device CS2.

Next, in this third example, the base unit CS2 receives the coefficients h0(k), h1(k) of the adaptive filter circuit 61 of the echo canceller 60, which are received from the base unit CS1 via the slave unit PS1. h2(k)...hq(k) are set as initial values in the adaptive filter circuit 61 of its own echo canceller 60.

After the base unit CS2 finishes setting the coefficients to the adaptive filter circuit 61 of the echo canceller 60, the base unit CS2 informs the main device 1 that the base unit that wirelessly communicates with the slave unit PS1 is transferred from the base unit CS1 to the base unit CS2. Sends a "child unit movement notification" to notify you of the movement. When the main device 1 receives this "handset movement notification", the main device 1 switches the audio path for the handset PS1 from the path via the base unit CS1 to the path via the base unit CS2.

On the other hand, the slave device PS1 that has received the "handover response" from the base device CS2 switches the wireless communication path to the base device CS2, switches the audio path, and disconnects the wireless communication path with the base device CS1. Note that the slave PS1 sends a "location registration" to the master CS2 to inform it of its own location.

The handover is completed according to the sequence of the third example described above, and the handset PS1 is in a state where it can continue talking with the other party's terminal through the path through the base station CS2. In the case of this third example as well, the same effects as in the above-mentioned first example can be obtained.

In the third example, when receiving the "information acquisition request" from the main device 1, the main device CS1 transmits information on the coefficients of the adaptive filter circuit 61 of the echo canceller 60 along with the communication information with the child device PS1. However, as in the second example, after sending the "information acquisition response" to the "information acquisition request" to the main device 1, the information on the coefficients of the adaptive filter circuit 61 of the echo canceller 60 is acquired. It may be configured to acquire the information and perform the subsequent sequence.

1...Main device, 21 to 2n...Cordless communication device, CS1, CS2...CSn...Base unit, PS1, PS2...PSm...Slave unit, 423...Audio signal processing unit of base unit, 4232...Received voice signal Processing circuit, 60...Echo canceller, 61...Adaptive filter circuit, 62...Subtraction circuit, 611...FIR filter, 611D...Delay circuit, 611M...Coefficient multiplication circuit, 611S...Sum calculation circuit, 612...Adaptive algorithm calculation unit, h0( k), h1(k), h2(k)...hq(k)...Coefficients of adaptive filter

Claims (7)

A plurality of cordless communication devices each consisting of a base unit and one or more handsets are connected to the main device, and the handset during a call can perform handover to switch the wirelessly connected base unit. In communication systems,
The base unit includes an echo canceller that performs echo cancellation by dynamically changing coefficients of an adaptive filter using an adaptive algorithm, with respect to received audio sent to the wirelessly connected slave unit during a call,
At the time of handover, the coefficients of the adaptive filter of the echo canceller of the base unit that was wirelessly connected to the slave unit during the call before handover are applied to the base unit that is wirelessly connected to the slave unit after handover. A wireless communication system characterized in that the information is transmitted and set in an adaptive filter of an echo canceller of the base unit that is wirelessly connected after the handover. During the handover sequence, the coefficients of the adaptive filter are transmitted from the base unit that was wirelessly connected to the slave unit during the call to the base unit after the handover via the main unit. The wireless communication system according to claim 1, wherein the information is transmitted to the base unit that is wirelessly connected. The base unit that was wirelessly connected to the handset during the call before the handover acquires the coefficients of the adaptive filter from the echo canceller in response to the information acquisition request from the main unit, and included in an information acquisition response corresponding to the information acquisition request and sent to the main device;
The main device transmits coefficients of the adaptive filter received from the base unit that was wirelessly connected to the slave unit during the call and the base unit that was wirelessly connected after the handover to the base unit that is wirelessly connected after the handover. The wireless communication system according to claim 2, wherein the adaptive filter of the echo canceller is set. The coefficients of the adaptive filter are determined during the handover sequence from the base unit that was wirelessly connected to the slave unit during the call before the handover to the base unit that was wirelessly connected to the slave unit after the handover. The wireless communication system according to claim 1, wherein the wireless communication system is transmitted to the base unit. The coefficients of the adaptive filter are determined in the handover sequence from the base unit that was wirelessly connected to the handset during the call before the handover, through the handset during the call. The wireless communication system according to claim 1, wherein the information is transmitted to the base unit that is wirelessly connected to the slave unit after the handover. The base unit that is wirelessly connected to the slave unit after the handover applies the adaptive filter before sending a slave unit movement notification to the main unit indicating that the base unit that is wirelessly connected to the slave unit is changed. The wireless communication system according to any one of claims 2 to 5, wherein a coefficient of is set in an adaptive filter of the echo canceller. A plurality of cordless communication devices each consisting of a base unit and one or more slave units are connected to the main unit, and the base unit responds to received audio sent to the wirelessly connected slave unit during a call. A wireless communication system comprising an echo canceller that performs echo cancellation by dynamically changing coefficients of an adaptive filter using an adaptive algorithm, and in which the handset during a call can perform handover to switch the base unit to which it is wirelessly connected. In the handover method,
At the time of handover, the coefficients of the adaptive filter of the echo canceller of the base unit that was wirelessly connected to the slave unit during the call before handover are transferred to the base unit that will be wirelessly connected to the slave unit after handover. A handover method in a wireless communication system, characterized in that the base unit that is wirelessly connected after the handover sets the received coefficients of the adaptive filter to the adaptive filter of its own echo canceller.

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