KR100684944B1 - Apparatus and method for improving the quality of a voice data in the mobile communication - Google Patents

Abstract

The present invention relates to an apparatus for improving sound quality for voice data transmitted from a mobile communication system. The present invention relates to a voice frame, in particular, in a mobile communication system for transmitting a voice data frame transmitted from a transmitting mobile terminal to a receiving mobile terminal. An error determination unit that determines whether or not an error is detected; A rate determining unit determining to generate a quarter rate frame when it is determined that the received voice frame is an error frame as a result of the determination of the error determining unit; And a frame forming unit generating a frame according to the determination of the rate determining unit.

Mobile communication, error frame, quarter rate frame, rate determining unit, frame forming unit

Description

Apparatus and method for improving sound quality for voice data transmitted from mobile communication system {APPARATUS AND METHOD FOR IMPROVING THE QUALITY OF A VOICE DATA IN THE MOBILE COMMUNICATION}

1 is a view illustrating a voice call path concept between terminals in a general mobile communication system.

2 is a view illustrating an error frame processing method for voice data in a conventional mobile communication system.

3 is a diagram illustrating an error frame processing method for voice data according to the present invention.

4 is a diagram illustrating an error frame processing apparatus for voice data according to an embodiment of the present invention.

5 is a diagram illustrating an error frame processing procedure for voice data according to an embodiment of the present invention.

6 is a graph showing sound quality of received data according to a conventional error frame processing method.

7 is a graph illustrating sound quality of received data according to an error frame processing method of the present invention.

<Explanation of symbols for the main parts of the drawings>

100, 200: transmitting mobile terminal MS1 110: transmitting SDU

120: receiving side SDU 130, 240: receiving side mobile terminal (MS2)

210: transmitting base station 220: control station

230: receiving base station 240: 1/8 rate frame

300: 1/4 rate frame 400: error determination unit

410: rate determining unit 420: frame forming unit

The present invention relates to an apparatus and method for improving sound quality for voice data transmitted in a mobile communication system, and more particularly, to an apparatus and method for improving sound quality of voice data according to an improvement in an error frame processing method.

To date, communication services have been developed into two categories: mobile communication and wired communication services. Mobile communication is a technology that provides voice and wireless data services using mobile phones. Advanced Mobile Phone Service system (AMPS), Global System for Mobile communication (GSM) and Inter-Standard-95 (CDMA) code of IS-95 series Division Multiple Access (CDMA) system, cdma2000 1x / Ev-Do (Evolution Data only), Wideband CDMA (WCDMA), and the like. Such technologies are rapidly growing despite the high usage fee due to the feature that the voice communication and wireless data service can be provided anytime, anywhere using a mobile communication terminal.

In general, digital mobile communication systems use PCM (Pulse Code Modulation) and Vocoder to convert analog voice signals into digital signals. The PCM converts a human voice signal to a data rate of 64 Kbps, which is mainly used in general fixed line telephones. 64 Kbps means converting a voice signal for 1 second into 64000 digital signals.

Therefore, when converting the voice signal to digital, it is possible to improve the frequency usage efficiency by converting to low data rate if possible. To this end, the vocoder extracts only the voice feature from the 64Kbps data generated by the PCM to 8.6Kbps. 4.0 Kbps. 2.0 Kbps. Four data rates such as 0.8 Kbps are selectively converted. For example, when the speech is fast, the data rate is 8.6Kbps, and when the speech is slow, the data rate is 4.0Kbps. In addition, if a person speaks little, it converts to either 2.0Kbps or 0.8Kbps. In this way, when a person slows down, the vocoder converts the data to a low data rate so that the frequency can be used efficiently.

In the digital communication such as the CDMA communication system, in order to use the frequency efficiently as described above, the human voice is compressed and transmitted without being transmitted as it is. Normal human voice has a band up to 4Khz, and after sampling process, it is converted into 8khz signal, and it is 8bit coded to convert it into PCM (Pulse Code Modulation) signal and finally 64Kbps signal. Becomes In the CDMA method, the 64Kbps signal is compressed without being transmitted as it is and made into 8Kbps or 13Kbps signal.

1 is a diagram illustrating a concept of a voice call path between terminals in a general mobile communication system. Referring to FIG. 1, when voice data is transmitted from the transmitting terminal 100 to the receiving terminal 130, the voice data transmitted from the transmitting terminal 100 is transmitted by the vocoder stored in the terminal. Encoded. The data transmitted from the transmitting terminal 100 is decoded in the transmitting side SDU (Selection and Distribution Unit) 110 and transmitted to the receiving SDU 120 through a wired network. The receiving side SDU 120 transmits the data through an encoding process in order to transmit the data to the receiving terminal 130 through a wireless network, and the receiving terminal 130 decodes the data by its own vocoder. (Decoding) to receive a voice signal.

Meanwhile, in the mobile communication service, MtoM (Mobile to Mobile) refers to communication in the case where both the calling subscriber and the called subscriber are mobile terminals. In the M2M communication, a 'vocoder bypass mode (Vocoder Bypass Mode)' method has been proposed to improve sound quality in the same carrier. The vocoder bypass mode method refers to a method in which a voice compressed at 8 Kbps in a public network is transmitted to a counterpart receiver without being converted to 64 Kbps PCM. As such, if both the calling terminal and the called terminal are mobile terminals, and both mobile terminals use the same voice compression scheme in the public network, the sound quality can be improved by using the above-described vocoder bypass mode.

However, if the voice frame is lost due to a problem such as degradation of the public network, the voice frame must be generated by itself in order to transmit the voice frame to the receiving terminal. In this case, conventionally, an 1/8 rate null frame is generated and transmitted. In this case, the 1/8 rate null frame means a 1/8 rate frame in which the data contents are all '1', which is an EVRC (Enhanced Variable Rate Coder) standard in order for the receiving terminal to restore voice normally. According to the standard (3GPP2 C-0014).

2 is a diagram illustrating an error frame processing method for voice data in a conventional mobile communication system. Referring to FIG. 2, when a frame is lost due to a deterioration of a channel environment between a transmitting terminal MS1 200 and a transmitting base station BTS 210, the transmitting base station 210 controls the control station. An 'erasure frame' is transmitted to (RNC) 220, and the control station 220 transmits a 1/8 rate null frame 250 to the receiving base station 230 according to the EVRC standard as described above. Will be sent.

However, as a result of the experiment, when the 1/8 rate null frame is used as described above, when the voice frames are continuously lost in the public network due to the poor voice recovery efficiency of the receiving terminal 240, severe sound quality degradation occurs. . The original 1/8 rate frame is used as a silent frame, and in the case of only an 1/8 rate null frame, the EVRC standard treats the error rate as an 1/8 rate null frame. However, when the receiving terminal receives the 1/8 rate null frame continuously as described above, the sound quality is degraded by being processed as a silent frame despite the error occurrence condition instead of silentness.

Accordingly, an object of the present invention is to provide an apparatus and a method for improving sound quality of voice data transmitted in a mobile communication system which prevents degradation of sound quality by transmitting a 1/4 rate frame when an error frame occurs.

Apparatus for achieving the above object; In a mobile communication system for transmitting a voice data frame transmitted from a transmitting mobile terminal to a receiving mobile terminal, an error determination unit for determining whether or not an error with respect to the received voice frame; A rate determining unit determining to generate a quarter rate frame when it is determined that the received voice frame is an error frame as a result of the determination of the error determining unit; And a frame forming unit generating a frame according to the determination of the rate determining unit.

The method for achieving the above object; A mobile communication system for transmitting a voice data frame transmitted from a transmitting mobile terminal to a receiving mobile terminal, the method comprising: receiving a voice data frame from the transmitting terminal; Checking whether the received frame is an error frame; Generating a quarter rate frame when the determination result is an error frame; And transmitting the generated quarter rate frame to a receiving terminal.

The present invention transmits using 1/4 rate frames instead of lost frames in order to ensure the best sound quality even when a lost voice frame occurs due to a problem such as degradation of a public network in a mobile communication system.

In general, according to the EVRC standard, it is prescribed to process an error frame when the following frame is received.

1/4 rate frame

2. 1/8 rate null frame

3. Blank frame (signaling frame)

4. erasure frame

On the other hand, the terminal receiving the frame is to restore the speech by the speech restoration algorithm of the terminal itself (for example, interpolation of the previously received speech signal, etc.). However, when an error frame occurs, when the 1/8 rate null frame is continuously received as in the conventional case, the sound quality is degraded due to the silent processing. Therefore, the present invention is implemented to transmit the 1/4 rate frame when the error frame occurs.

Accordingly, the terminal receiving the 1/4 rate frame does not mute the received frame, and determines that the received frame is an error frame and restores the normal frame by the voice reconstruction algorithm, thereby overcoming the degradation of sound quality.

Hereinafter, a detailed description of a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

3 is a diagram illustrating an error frame processing method for voice data according to the present invention.

Referring to FIG. 3, unlike the prior art described with reference to FIG. 2, when receiving an error frame, the control station 220 transmits a 1/4 rate frame 300 instead of a 1/8 rate null frame. Accordingly, the receiving terminal 240 determines that the frame is received as an error state rather than a silent state and recovers the sound quality by restoring it by a normal speech restoring algorithm.

4 is a diagram illustrating an error frame processing apparatus for voice data according to an embodiment of the present invention.

Referring to FIG. 4, the error frame processing apparatus of the control station 220 may include an error determining unit 400, a rate determining unit 410, a packet forming unit 420, and the like.

The error determining unit 400 determines whether an error is received with respect to the received voice frame. If the determination result is an error frame, the rate determining unit 410 determines to generate a 1/4 rate frame according to the present invention instead of a conventional 1/8 rate null frame.

Therefore, when the received frame is an error frame, the packet forming unit 420 forms a quarter rate frame according to the determination of the rate determining unit 410.

5 is a diagram illustrating an error frame processing procedure for voice data according to an embodiment of the present invention.

Referring to FIG. 5, when a voice data frame is received from the transmitting terminal (S501), it is checked whether the received frame is an error frame (S502). The presence or absence of the error frame may be determined by a status bit of an error flag included in the frame, or may be determined by an error check for the frame.

As a result of the determination, if it is not an error frame, the process is processed by a normal frame process (S505) and transmitted to the receiving terminal.

On the other hand, if the determination result is an error frame, according to the present invention, a new quarter rate frame is generated (S503), and the generated quarter rate frame is transmitted to the receiving terminal (S504).

In this way, the receiving terminal receiving the quarter rate frame determines the frame as an error frame according to the EVRC standard and outputs a speech signal by a normal speech reconstruction algorithm.

6 is a graph showing sound quality of received data according to a conventional error frame processing method, and FIG. 7 is a graph showing sound quality of received data according to an error frame processing method of the present invention. That is, FIG. 6 is a graph decoded by a receiving terminal by transmitting an 1/8 rate null frame when an error frame is generated according to the prior art, and FIG. 7 transmits a 1/4 rate frame when an error frame is generated according to the present invention. This is a graph decoded by the receiving terminal. In this case, the transmitted voice is voice data corresponding to the human voice 'ah'.

Referring to FIGS. 6 and 7, in FIG. 6, a sound error is deteriorated by determining that a continuous error frame in the middle of the voice signal is a silent signal and the voice is cut off. However, in FIG. 7, it can be seen that the degradation of sound quality due to an error frame can be significantly overcome by processing according to the present invention.

On the other hand, in the embodiment of the present invention has been described with respect to specific embodiments, various modifications are possible without departing from the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the appended claims, but also by those equivalent to the claims.

According to the present invention, by transmitting a quarter-rate frame when an error frame is generated in a mobile communication system, it is possible to overcome the degradation of sound quality caused by the conventional silent process.

Claims (7)

In a mobile communication system for transmitting a voice data frame transmitted from a transmitting mobile terminal to a receiving mobile terminal, An error determining unit determining whether an error is received with respect to the received voice frame; A rate determining unit determining to generate a quarter rate frame when it is determined that the received voice frame is an error frame as a result of the determination of the error determining unit; And And a frame forming unit configured to generate a frame according to the rate determining unit. The method of claim 1, wherein the rate determining unit, If the received voice frame is not an error frame as a result of the determination of the error determining unit, the sound quality improvement apparatus for the voice data transmitted in the mobile communication system, characterized in that the processing. The method of claim 1, wherein the error determination unit, And a voice frame processing method according to a vocoder bypass mode method. In a mobile communication system for transmitting a voice data frame transmitted from a transmitting mobile terminal to a receiving mobile terminal, Receiving a voice data frame from the transmitting terminal; Checking whether the received frame is an error frame; Generating a quarter rate frame when the determination result is an error frame; And Transmitting the generated quarter rate frame to a receiving terminal; and a sound quality improvement method for voice data transmitted from a mobile communication system. The method of claim 4, wherein in the checking of whether the error frame is an error frame, if the error frame is not an error frame, the sound frame is processed by a normal frame processing process. . 5. The method of claim 4, wherein the presence of the error frame is determined by status bits of an error flag included in the frame. 5. The method of claim 4, wherein the presence of the error frame is determined by an error check algorithm for the frame.

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