JP2001044946A - Communication terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a transmitting side to make a receiving side hear more natural noise being close to background noise when the transmitting side is silent in the case the transmitting side performs transmitting voice silence operation. SOLUTION: When a frame rate detecting part 501 detects that the encoding rate of encoded data outputted from an encoder 141 is 1/8 during speech communication, the part 501 switches a changeover switch 502 to the opposite side from the shown diagram and stores the encoded data, i.e., encoded data corresponding to background noise in a RAM 503. Subsequently, when an inputting part 60 performs transmitting voice silence operation, a controlling part 510 detects the operation, transmits a transmitting voice silence signal S1 to a changeover switch 504 to switch the switch 504 to the opposite side from the shown diagram. In such a case, the encoded data corresponding to background noise is read from the RAM 503 and transmitted to the opposite party.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication terminal device used as a mobile station or the like in a mobile communication system of a code division multiple access (CDMA) system. The present invention relates to an improvement of a transmission sound muffling circuit for muffling a voice.

[0002]

2. Description of the Related Art Today, with the rapid spread of mobile communication systems, effective use of user channels is becoming increasingly important.
Attention has been focused on DMA mobile communication systems. As is well known, in a CDMA mobile communication system, a mobile station and a base station communicate using a spread spectrum technique, and a plurality of users can share the same frequency band. This has the advantage that the number of user channels can be increased.

A communication terminal device represented by a CDMA mobile station or the like has a function to mute a transmission voice so as to prevent the voice of the transmission side from being heard by the other party (the reception side) during a call. Is provided.

[0004] In this type of conventional apparatus, when the transmission voice is muted, for example, in a variable rate encoding circuit,
A signal corresponding to white noise is encoded at the lowest encoding rate used for encoding background noise, and this encoded audio signal is transmitted to a receiving device.

[0005] According to this conventional apparatus, when the transmitting side apparatus performs the mute operation of the transmitting voice, the receiving side apparatus hears noise completely different from the background noise when the transmitting side apparatus is silent. Became.

For example, in the above conventional apparatus, when the transmitting side is unvoiced, a signal corresponding to background noise near the transmitting mouth is encoded at the lowest encoding rate by the variable rate encoding circuit and transmitted to the receiving side apparatus. However, since this background noise usually differs from place to place, when the transmitting apparatus is unvoiced, the receiving apparatus transmits the coded speech corresponding to the background noise transmitted from the transmitting apparatus. Based on the signal, different background noises will be heard at each location where the transmitting apparatus is located.

[0007] On the other hand, when the transmitting side device performs a transmitting voice mute operation, the variable rate coding circuit normally uses the lowest coding rate used for coding background noise at the lowest coding rate. The signal corresponding to the noise is encoded and transmitted to the receiving device. Since the level of the white noise is fixed unlike the background noise described above, the receiving device uses the transmitting device. When the transmitting voice mute operation is performed in step (1), the user always hears the noise of the same level and the same timbre based on the coded voice signal corresponding to the white noise transmitted from the transmitting side device.

[0008]

As described above, in the above-described conventional apparatus, the signal corresponding to white noise is encoded and transmitted to the receiving apparatus by performing the transmission sound muffling operation. In the device, when the transmitting device performs the transmitting voice muffling operation, noise of a constant level and timbre is always reproduced and output based on the coded voice signal corresponding to the white noise. There is a problem that an unnatural noise remarkably different from the background noise reproduced in a silent state is heard.

[0009] The present invention solves the above-mentioned problems, and when a transmitting voice mute operation is performed on the transmitting side device, the receiving side device is
It is an object of the present invention to provide a communication terminal device capable of hearing more natural noise close to background noise when a transmitting device is silent.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, a transmission voice signal is converted into a coded voice signal by voice coding means and transmitted to a receiving side device. In a communication terminal device for performing a call by converting a coded voice signal received from a receiving side device into a received voice signal and reproducing and outputting the coded voice signal, a coded voice of a transmitted voice signal corresponding to background noise by the voice coding means is provided. A storage unit for storing a signal, based on a predetermined transmission voice mute operation during a call, in place of the output signal of the voice encoding unit,
A transmission voice mute control unit that controls the other device to transmit the encoded voice signal read from the storage unit.

According to a second aspect of the present invention, in the first aspect of the present invention, it is determined whether or not a transmission voice signal corresponding to background noise is coded by the voice coding means during a call. And when the transmitted speech signal corresponding to background noise is encoded by the speech encoding unit, the encoded speech signal is stored in the storage unit.

According to a third aspect of the present invention, in the second aspect of the present invention, the voice coding means converts the transmission voice signal at a different coding rate depending on whether the signal is a signal corresponding to background noise. The variable rate encoding means for encoding, wherein the determining means detects an encoding rate of an encoded audio signal output from the variable rate encoding means, and performs the determination based on the detection result. Features.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing one embodiment of a communication terminal device 100 according to the present invention. In the present embodiment, the communication terminal apparatus 100 communicates with a CDMA base station (not shown).
A CDMA mobile station that performs communication by the DMA method is assumed.

In communication terminal apparatus 100, a radio carrier signal arriving from a base station is received by antenna 40, and then input to receiving section 26 via antenna duplexer 30. In the receiving section 26, the received radio frequency signal is mixed with the local oscillation signal and down-converted into a received intermediate frequency signal.

The received intermediate frequency signal output from the receiving section 26 is input to the demodulating section 25. The demodulation section 25 performs digital demodulation of the received intermediate frequency signal, thereby reproducing the digital demodulated signal. The digital demodulated signal is input to the decoder 142 of the audio codec 14 via the CPU (central processing unit) 50.

The decoder 142 decodes the digital demodulated signal into audio data [PCM (Pulse Code Modulation) encoded data], and inputs it to the D / A converter 23.

The D / A converter 23 converts the decoded signal from a digital signal to an analog signal. The decoded signal, which has been converted into an analog signal, is amplified by the receiving amplifier 22 and then output from the speaker 21 as loudspeaker.

On the other hand, the audio signal input from the microphone 11 is amplified by the transmission amplifier 12 and then converted from an analog signal to a digital signal by the A / D converter 13 and sent to the encoder 141 in the audio codec 14. Is entered.
In the encoder 141, the input signal is voice-encoded,
Transfer to CPU50.

The CPU 50 assembles frame data based on the encoded voice signal input from the encoder 141, and sends the frame data to the modulator 15. The modulation unit 15 has a CP
Digital signal (frame data) output from U50
, And digitally modulates the transmission intermediate frequency signal, and inputs the modulated transmission intermediate frequency signal to the transmission unit 16.

The transmission section 16 mixes the modulated transmission intermediate frequency signal with a local oscillation signal, upconverts the mixed signal into a radio carrier frequency, and further amplifies the signal to a predetermined transmission power level. The wireless carrier signal output from the transmitting unit 16 is transmitted from the antenna 40 to the base station via the antenna duplexer 30.

The CPU 50 is composed of, for example, a microcomputer, and has at least control means for performing functions such as a wireless channel access control means, a transmission / reception control means, and a call control means.

Among the components connected to the CPU 50, the input unit 60 has a plurality of keys and inputs various information necessary for operation control and the like (including an input during a transmission voice muting operation described later). is there. The display 70 is a liquid crystal display (LC).
D) for displaying input information from the input unit 60 and various information related to the operation control and the like. The sounder 70 is used as a means for reproducing and outputting a melody in addition to notifying a ringtone.

In the communication terminal device 100, the CPU
The control unit 50 also controls the mute of the transmitted voice when the input unit 60 performs an operation of muting the transmitted voice during the call, in addition to the basic operation control related to the above-described telephone call.

FIG. 2 is a block diagram showing a configuration of CPU 50 in communication terminal apparatus 100. As shown in the figure, the CPU 50 includes a frame rate detection unit 50.
1. Changeover switch 502, RAM (Random Access Memo)
ry) 503, changeover switch 504, frame generation unit 50
5. A control unit 510 is provided.

In the CPU 50, a frame rate detection unit 501, a changeover switch 502, a RAM 503, a changeover switch 504, and a frame generation unit 505 are interposed between the encoder 141 and the modulation unit 15 in FIG.

That is, the frame rate detector 5
01, the changeover switch 502, the RAM 503, the changeover switch 504, and the frame generation unit 505 are components of the transmission system in FIG. 1, and during a normal call operation, the changeover switch 504 is switched to the illustrated side.
The encoded audio signal from the encoder 141 is passed to the modulation unit 15 via the frame generation unit 505.

Note that, during a call, the encoder 141 controls A /
The digital audio signal input from the D conversion unit 13 is encoded by the following method and output to the CPU 50. That is,
In the communication terminal device 100, the audio codec 14
Is composed of an encoder 141 realized by a variable rate encoding circuit and a decoder 142 realized by a variable rate decoding circuit. The encoder 141 performs a variable rate encoding process on the audio signal input from the A / D converter 13 during a call.

FIG. 3 is a diagram for explaining the variable rate encoding process in the encoder 141. FIG.
Indicates an audio signal input from the A / D converter 13 during a call. This voice signal includes both a signal corresponding to background noise when the speaker on the transmitting side is unvoiced and a signal corresponding to voice emitted by the speaker on the transmitting side.

In the encoder 141, as shown in FIG. 4A, an input audio signal as shown in FIG.
9600 for the signal corresponding to the voice of the speaker on the transmitting side
Encode at the coding rate of pbs (full rate). On the other hand, the signal corresponding to the background noise is coded at the lowest coding rate of 1200 bps (１ ／ rate), and the signal corresponding to the background noise and the voice of the speaker on the transmitting side are encoded. Is encoded at a coding rate of 4800 bps (1/2 rate).

The encoder 141 performs the above-described variable rate encoding processing every 20 ms for one frame, and at that time, adds the encoding rate of the frame to the encoded data and outputs it.

FIG. 4 is a table showing information elements of encoded data (encoded audio signal) for each rate output from the encoder 141. For example, in the case of an encoding rate (full rate) of 9600 bps, , The audio data to which the rate identification bit “1” is added is output. Also, 48
In the case of a coding rate of 00 bps (音 声 rate), audio data to which a rate identification bit “2” is added is output. In the case of a coding rate of 1200 bps (１ ／ rate), a rate identification bit is output. The audio data to which "8" is added is output.

The CPU 50 interposed between the encoder 141 and the modulating unit 15 responds to the encoded data output from the encoder 141 by the variable rate encoding process,
The following processing is performed.

That is, during a normal telephone call operation (when a transmission voice operation is not performed), the changeover switch 504 of the CPU 50 is switched to the side shown in FIG. 2 and the encoded data output from the encoder 141 is transmitted. The data is passed to the modulation unit 15 via the frame generation unit 505. At this time,
The frame generation unit 505 assembles packet data using the encoded data output from the encoder 141 and sends the packet data to the modulation unit 15.

At the same time as the call operation, the CPU 50
The frame rate detection unit 501 captures encoded data output from the encoder 141, and detects the encoding rate of the encoded data based on the rate identification bits therein.

Here, the frame rate detecting section 501
When detecting that the coding rate is 1/8 rate based on the rate identification bit "8", the changeover switch 502 is switched to the side opposite to that shown in the figure, and the 1/8 rate coded data, that is, the background noise is added. The corresponding encoded data is RA
It is stored in M503. Thus, the encoded data (RAM5) corresponding to the latest background noise is stored in the RAM 503.
03 (a data amount corresponding to the storage capacity of No. 03).

Thereafter, when there is a transmission voice mute operation at the input unit 60, the control unit 510 detects this and detects a
04, a transmission mute signal S1 is transmitted. By the transmission mute signal S1, the changeover switch 504 switches to the side opposite to that shown in the figure.

As a result, the coded data (corresponding to background noise) stored up to that point is read from the RAM 503 and output to the frame generator 505. The frame generation unit 505 assembles the packet data using the encoded data read from the RAM 503 and sends the packet data to the modulation unit 15.

When the transmitting side performs the operation of muting the transmitting voice by the transmitting voice muting control in the CPU 50 described above, it corresponds to the latest background noise stored in the RAM 503 in the call up to that time. The coded voice signal is transmitted to the receiving side, and the receiving side receives and reproduces the coded voice signal. Therefore, on the receiving side, when the transmitting side performs the transmitting voice mute operation, the same noise as the ambient noise in the previous call can be heard, and it is clear that the transmitting side has performed the transmitting voice mute operation. You do not have to hear unnatural noises that you can understand.

Although the above embodiment has been described by taking a CDMA mobile station as an example, the present invention is not limited to this, and can be applied to all communication terminal apparatuses having a function of silencing transmission voice. You can do it.

[0040]

As described above, according to the present invention,
The coded voice signal corresponding to the ambient noise is stored, and when a transmission voice mute operation is performed during a call, the coded voice signal is output instead of the coded voice signal output from the voice coding means, and stored. Since the coded voice signal corresponding to the ambient noise is read and transmitted to the receiving device, the receiving device can hear the ambient noise when the transmitting device silences the transmitting voice and when the transmitting device is silent. You will hear the same noise as, and added a natural voice transmission silencing function that does not have an extreme difference between the noise when the transmitting side device is silent and the noise when the transmitting voice muting operation is performed. can do.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a communication terminal device according to the present invention.

FIG. 2 is a block diagram showing a configuration of a CPU of the communication terminal device.

FIG. 3 is a diagram illustrating a variable rate encoding process performed by an encoder of the communication terminal device.

FIG. 4 is a table showing information elements of encoded data for each rate output from an encoder.

[Explanation of symbols]

 Reference Signs List 100 communication terminal device 11 microphone 12 transmission amplification unit 13 A / D conversion unit 14 audio codec 141 encoder 142 decoder 15 modulation unit 16 transmission unit 21 speaker 22 reception amplification unit 23 D / A conversion unit 25 demodulation unit 26 reception unit 30 antenna Duplexer 40 Antenna 50 CPU (Central Processing Unit) 501 Frame Rate Detector 502, 504 Changeover Switch 503 RAM (Random Access Memory) 505 Frame Generator 510 Controller

Claims (3)

[Claims] 1. A transmission voice signal is converted into a coded voice signal by voice coding means and transmitted to a receiving device, and the coded voice signal received from the receiving device is converted into a received voice signal and reproduced. In a communication terminal device that performs a call by outputting, a storage unit that stores an encoded voice signal of a transmitted voice signal corresponding to background noise by the voice encoding unit, and a predetermined transmitted voice mute operation during the telephone call. And a transmission voice mute control unit that controls the other device to transmit the coded voice signal read from the storage unit instead of the output signal of the voice coding unit. Terminal device. 2. A communication system comprising: a decision unit for judging whether or not a transmission speech signal corresponding to background noise is encoded by the speech encoding unit during a call, wherein the speech encoding unit corresponds to background noise. 2. The communication terminal device according to claim 1, wherein when the transmitted voice signal to be transmitted is coded, the coded voice signal is stored in the storage unit. 3. The voice coding means is constituted by variable rate coding means for coding a transmission voice signal at a different coding rate according to whether the signal is a signal corresponding to background noise, and 3. The communication terminal device according to claim 2, wherein the means detects a coding rate of a coded voice signal output from the variable rate coding means, and makes the determination based on the detection result.