JPH0750631A - Digital radio communication equipment with pseudo background noise generation function - Google Patents

Abstract

PURPOSE:To simplify and miniaturize the circuit constitution of a device by generating pseudo background noise by a simple constitution and a little amount of calculation. CONSTITUTION:In a code book 211 provided within a sound decoding circuit 21, plural code vectors V1 (n), V2(n),... VM-1 (n) and VM (n) composed of unit variance random Gauss signals are already stored. The code vectors are selectively read from the code book 211 in a silent section by noting that these code vectors V1 (n), V2(n),... VM-1 (n) and VM (n) are not substantially used in the silent section. A psudo background noise signal bnkf (n) is generated by multiplying this code vector Z (n) by the energy level information Ekf complemented and corrected by an energy level complement circuit 222 and by letting the vector pass a spectrum filter 224.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system such as a digital cellular radio system, and in particular, inserting pseudo background noise in a silent section of a speech signal coming from a mobile station having a VOX function. The present invention relates to a digital wireless communication device including a means for performing

[0002]

2. Description of the Related Art In recent years, various wireless communication systems have been developed and operated with the development of wireless communication technology and the increase of communication needs. One of them is a digital cellular radio system.

FIG. 10 shows a schematic structure thereof.
This system is, for example, a control station CS connected to a wired telephone network NW, and a wired line C for each control station CS.
A plurality of base stations BS connected via L1, CL2, ...
1, BS2, ... And a plurality of mobile stations PS1, PS2 ,. Each of the base stations BS1, BS2, ...
Radio zones E1, E2, ... Called as cells are formed in different small areas within the respective service areas. Mobile station P
S1, PS2, ... consist of, for example, a car telephone device, a mobile phone, or a cordless phone. When these mobile stations PS1, PS2, ... Make a call with the far-end speaker who owns the telephone device accommodated in the wired telephone network NW, the mobile stations PS1, PS2 ,. It is connected via a digital radio communication channel to a base station provided in the cell in which it is located, and from this base station to the control station C
It is connected via S to the telephone device of the wired telephone network NW.

By the way, recently VOX has been added to this type of system.
It is advocated to have a function. The VOX function is to detect the silent section of the transmission voice signal during communication in the mobile stations PS1, PS2, ... And to stop the operation of the transmission system in this silent section. Generally, it is said that the ratio of speaking time to the total talking time is about 30%.
By using the OX function, the power consumption of the mobile station can be significantly saved. As a result, the battery life of the mobile station is extended, which makes it possible to extend the continuous use time and reduce the size of the battery to reduce the size and weight of the wireless device.

However, when a call is made using the VOX function, the background noise in the silent section of the mobile station is not transmitted to the far-end speaker. For this reason, the far-end speaker feels uncomfortable in receiving when changing from the voiced section to the silence section and from the silence section to the voiced section, which causes deterioration of the reception quality.

Therefore, recently, the base stations BS1, BS2,
It is proposed that pseudo background noise is generated in ... And this pseudo background noise is inserted into the silent section of the call signal coming from the mobile stations PS1, PS4, and sent to the far-end speaker of the wired telephone network NW. Has been done. In this way, pseudo background noise is sent to the far-end speaker in the silent section of the transmission signal, so that the far-end speaker is less likely to deteriorate the reception quality.

However, the conventional means for generating pseudo background noise uses, for example, a random number generator for generating a pseudo random binary sequence, and the pseudo random binary sequence generated by this random number generator is used as a basis. It produces white noise. However, in such a configuration, a high-order shift register is required for the random number generator that generates the pseudo-random binary sequence, which leads to an increase in the size and complexity of the circuit configuration. Also, the actual background noise is generally assumed to be Gaussian. Therefore, in order to generate background noise that is close to reality, it is necessary to combine some uniform random signals or perform Gaussian transformation of the random signals. However, in order to perform these signal synthesis processing and signal conversion processing, a considerable amount of calculation is required by the arithmetic circuit, which increases the load on the arithmetic circuit.

[0008]

As described above, in the digital radio communication apparatus provided with the pseudo background noise generating means conventionally considered, the circuit configuration for generating the pseudo background noise becomes complicated and large, and the Gaussian There is a problem that many operations are required to generate mold noise.

The present invention has been made paying attention to such a point, and an object thereof is to enable generation of pseudo background noise with a simple configuration and a small amount of calculation, whereby a simple and compact circuit configuration is achieved. An object of the present invention is to provide a digital wireless communication device having a pseudo background noise generating function that can realize the above-mentioned features.

Another object of the present invention is to generate a pseudo background noise having a smooth level change and a more realistic pseudo background noise, thereby further improving the reception quality of a far-end speaker. It is to provide a digital wireless communication device provided with.

[0011]

In order to achieve the above object, the present invention detects a silent section of a transmission voice signal and uses a part of this silent section to detect a signal existing in this silent section. A code is used in a digital wireless communication device that transmits information indicating a configuration and communicates via a wireless channel with a mobile station that has a function of stopping operations related to transmission in other periods of the silent section. A code vector is read from a code book in which the vector is stored, a first signal is generated based on the code book, and the generated first signal is adjusted based on the information sent from the mobile station. Then, a pseudo background noise signal is generated, and this pseudo background noise is output instead of the received signal from the mobile station during the period corresponding to the silent section detected by the mobile station. That.

The present invention also generates a pseudo random sequence when generating the first signal, and selectively selects one of a plurality of code vectors from the code book according to the generated pseudo random sequence. Is read out and the read code vector is output as a first signal.

The present invention further comprises means for generating first and second pseudo-random sequences to generate the first signal, reading a plurality of code vectors from a codebook to obtain these codes. The vector is first transformed according to the first pseudo-random sequence, then the modified plurality of vector signals are calculated with the second pseudo-random sequence, and the plurality of vector signals obtained by this calculation are mutually It is also characterized in that the first signal is generated by combining.

Further, according to the present invention, when the second signal is generated, the energy level of the first signal generated by the first signal generating means is adjusted based on the information sent from the mobile station. And at least one of the second signal processing for adjusting the spectrum of the first signal based on the information sent from the mobile station.

On the other hand, in order to achieve the above-mentioned other object, another aspect of the present invention detects a silent section of a transmission voice signal, and outputs information indicating at least a signal energy level of the silent section for a predetermined time during the silent section. In a digital wireless communication device that performs transmission via a wireless channel with a mobile station that has a function of transmitting at intervals and stopping operations related to transmission in other periods of the above-mentioned silent section, first from a codebook. A code vector is read out and a first signal is generated based on this code vector. Then, based on the information received from the mobile station at fixed time intervals, a change in the signal energy level between the respective reception timings is obtained, and the energy level of the first signal is obtained based on the obtained change. Is complemented and adjusted, and this complemented and adjusted signal is output as a pseudo background noise signal.

According to another aspect of the present invention, when generating a pseudo background noise signal, each time information is received from a mobile station, the following information is received based on the information received now and the information received in the past. The change in the signal energy level of the background noise during the period until the signal is received, and based on this estimation result, the first
It is characterized in that pseudo background noise is generated by complementarily adjusting the energy level of the signal.

[0017]

As a result, according to the present invention, pseudo background noise is generated by adding the signal state of the silent section received from the mobile station to this code vector based on the code vector stored in the codebook. . Therefore, the circuit configuration is simplified and the amount of calculation is reduced as compared with the case of using the conventional pseudo background noise generating means that uses a high-order shift register and further requires a calculation for Gaussian conversion. .

In particular, a digital wireless communication device is generally equipped with a CELP type voice codec, and this voice codec includes a codebook in which white Gaussian drive signal vectors are stored. Therefore, when the present invention is implemented in a digital wireless communication device, pseudo background noise can be generated by using the drive signal vector of the codebook already provided in the voice codec. That is, the pseudo background noise can be generated by using the existing circuit as it is.
Therefore, the increase in the circuit configuration can be suppressed to an extremely small level.

Further, according to the present invention, a plurality of code vectors stored in the codebook are selectively read according to the pseudo random sequence and used for generating pseudo background noise. Therefore, compared to the case where the pseudo background noise is always generated based on one specific type of code vector, it is possible to generate the pseudo background noise that is highly random and closer to the actual condition.

Further, according to the present invention, a plurality of code vectors are read from the codebook, these code vectors are first converted by the first pseudo-random sequence, and each code vector after this conversion and the second code vector are converted. The pseudo random sequence is calculated and then synthesized with each other. For this reason, it is possible to generate pseudo background noise with higher randomness and closer to reality.

Further, according to the present invention, at the time of generating the pseudo background noise, at least one of the energy level and the spectrum of the first signal generated based on the code vector is corrected. Therefore, it is possible to generate pseudo background noise that is closer to the background noise of the mobile station and is less discomfort for the far-end speaker.

On the other hand, according to another aspect of the present invention, the change in the signal energy level of the background noise between the respective reception timings is obtained based on the information received from the mobile station at constant time intervals, and this change is calculated. Based on this, level-adjusted pseudo background noise is generated. That is, the level of the pseudo background noise between the reception timings is complementarily corrected based on the information of the silent section notified from the mobile station at a constant time interval. For this reason, the pseudo background noise level changes smoothly without stepwise change each time information is received, which makes it possible to generate pseudo background noise with less discomfort that is close to reality.

According to still another aspect of the present invention, each time information is received from the mobile station, a change in the signal level of the background noise during the period until the next information is received is estimated based on this information, Pseudo background noise is generated based on this estimation result. That is, the level of pseudo background noise during the period until the next information is received is controlled by using the so-called extrapolation method. Therefore, pseudo background noise can be generated without causing delay.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, prior to the description of the pseudo background noise generation circuit in the cellular base stations BS1, BS2, ...
The VOX operation in S1, PS2, ... Will be described.

In the mobile station, during a call, for example, as shown in FIG. 5A, the voiced / silent section of the transmitted voice signal is monitored. Then, when a change from the voiced section to the silence section is detected, a silence section start pattern indicating the start timing of the silence section is transmitted in the first time slot for transmitting this silence section. When a change from a silent section to a sound section is detected, a silent section end pattern indicating the end timing of the silent section is transmitted in the last time slot for transmitting the silent section.

Further, the mobile stations PS1, PS2, ... Have a fixed time with respect to the cellular base stations BS1, BS2, ... In the silent section from the transmission of the silent section start pattern to the transmission of the silent section end pattern. Send change information at intervals. The change information includes information indicating the energy level of the background noise in the silent section and information indicating the spectrum. The transmission interval of the change information is set to 100 msec, for example. FIG. 5B shows the transmission timing of the change information, and the hatched slots 1, 2, ..., K-2, k-1, k, k + 1, ... Are the change information transmission slots. .

Further, in the TDMA method adopted in the cellular radio system of this embodiment, one transmission frame length is set to 20 msec as shown in FIG. 5 (c). Then, three time slots, each of which is used as a radio communication channel, are time-division multiplexed in this one transmission frame. Therefore, the change information is transmitted once every five transmission frames as shown in FIG. 5 (c). In the other four transmission frames in which the change information is not transmitted, the mobile stations PS1, PS2, ... Stop the operation of the transmission system for battery saving.

Next, the configuration of the cellular base station including the pseudo background noise generation circuit according to this embodiment will be described. FIG. 1 is a circuit block diagram showing a configuration of a receiving system of a cellular base station having a pseudo background noise generating function according to an embodiment of the present invention.

Radio frequency signals sent from the mobile stations PS1, PS2, ... Via digital communication channels are received by an antenna 11 and then an antenna duplexer (DUP) 12 is received.
Is input to the receiving circuit (RX) 13 via. In the reception circuit 13, the radio frequency signal is mixed with the reception local oscillation signal output from the frequency synthesizer (SYN) 14 and frequency-converted into an intermediate frequency signal. In addition,
The frequency of the reception local oscillation signal generated from the frequency synthesizer 14 is designated by the channel designation data SYC output from the control circuit 20.

The reception intermediate frequency signal is converted into a digital signal in the A / D converter 16 after the excess high frequency component is removed by the low pass filter (LPF) 15, and then the digital demodulation circuit (DEM). 17 is input. In the digital demodulation circuit 17, the received intermediate frequency signal is digitally demodulated and converted into a digital baseband signal. The digital baseband signal output from the digital demodulation circuit 17 includes a digital call signal and a digital control signal. Of these, the digital control signal is taken into the control circuit 20 and identified.

On the other hand, the digital speech signal is input to the time division multiple access (TDMA) circuit 18. This TDMA
In the circuit 18, the three time slots are separated for each transmission frame, and the digital speech signal is extracted for each of these time slots. Each of the extracted digital speech signals is an error correction decoding circuit (CH-D
EC) 19 is input. The error correction decoding circuit 19 performs an error correction decoding process on the digital call signal, and the error correction decoded digital call signal is input to a voice decoding circuit (SP-DEC) 21. The voice decoding circuit 21 performs a voice decoding process on the digital call signal. The digital speech signal output from the voice code decoding circuit 21 is used in the switching circuit 2 described later.
4 is input to the D / A converter 25, converted into an analog call signal by the D / A converter 25, and then transmitted to the wired line CL via the hybrid circuit 26.

In an actual circuit, the error correction decoding circuit 19 and the speech decoding circuit 21 are integrally formed with the error correction coding circuit and the speech coding circuit of the transmission system, which are called a channel codec and a speech codec, respectively. ing.

By the way, the cellular base station BS of this embodiment is
1, BS2, ...
An X control circuit 23 and a switching circuit 24 are provided. VO
The X control circuit 23 shifts the switching circuit 24 from the voice decoding circuit 21 side to the pseudo background noise generation circuit 22 side when the silent section start pattern indicating the start timing of the silent section arrives from the mobile stations PS1, PS2, .... The switching circuit 24 is switched from the pseudo background noise generating circuit 22 side to the voice decoding circuit 21 side when a silent period end pattern indicating the end timing of the silent period arrives from the mobile station in this state. Further, the VOX control circuit 23 gives a pseudo background noise generation instruction to the pseudo background noise generation circuit 22 while the switching circuit 24 is being switched to the pseudo background noise generation circuit 22 side.

Now, the pseudo background noise generation circuit 22 selects one of a plurality of code vectors read from the codebook provided in the speech decoding circuit 21, and selects the energy level of the selected code vector. And the spectrum is variably controlled based on the update information sent from the mobile stations PS1, PS2, ... At a constant time interval (100 msec) to generate and output a pseudo background noise signal.

FIG. 2 is a circuit block diagram showing the configuration of the pseudo background noise generation circuit 22. The pseudo background noise generating circuit 22 includes a code vector selecting circuit 221, an energy level complementing circuit 222, a signal synthesizing circuit 223, and
And a spectral filter 224.

First, the code vector selection circuit 22
1 has a random number generation circuit 225 and a switching selection circuit 226 as shown in FIG. 3, for example. Random number generation circuit 225
Is a shift register circuit 225 as shown in FIG.
a and a buffer circuit 225b. And
With these circuits, the pseudo random sequence R _N-2 , R
_N-1 , _RN , ... Are generated. The switching selection circuit 226 is composed of a multiplexer, and the pseudo random sequences R _N-2 , R _{N- 1} and R output from the random number generation circuit 225.
_The codebook 21 of the speech decoding circuit 21 according to _N.
A plurality of code vectors V ₁ (n), V stored in _{1
2 (n), ..., V} M-1 (n), and selects one from among V _M (n) and outputs. Here, the voice decoding circuit 21 is CELP.
In the codebook 211, a plurality of driving codevectors V ₁ (n), which are random Gaussian white sequences independent of unit variance, are used in the codebook 211.
V ₂ (n), ..., V _M-1 (n), V _M (n) are stored in advance. Therefore, the code vector stored in the codebook 211 is
It can be used as it is as the noise vector Z (n) which is the basis of the background noise.

The energy level complementing circuit 222 receives the change information slot received each time the change information slot arrives from the mobile stations PS1, PS2, ... At regular time intervals (100 msec) as shown in FIG. an energy level information EOk included in k, two changes on the slot k-2, k-1 energy level information EO _k-2 contained in, EO _k-1 and based on the previously received, the following changes Estimate the change, or slope, of the energy level during the period until the information slot k + 1 is received. Then, the energy level information E that changes according to the estimated inclination
kf is generated in time series and supplied to the signal synthesis circuit 223. That is, the energy level between the update information slots is complemented by the linear extrapolation method. The advantage of the extrapolation method is that the change in the energy level of the pseudo background noise can be delayed. Note that f = 1 to F, and F represents the number of transmission frames (5 frames) between the two update information slots k and k + 1.

The signal synthesizing circuit 223 comprises, for example, a multiplier. In this multiplier, the code vector Z (n) composed of the unit variance random Gaussian signal selectively output from the code vector selection circuit 221 is multiplied by the energy level information E _kf output from the energy level complementing circuit 222. The energy level-corrected code vector Z '(n) is thus obtained.

Each time the above-mentioned update information slot is received, the spectrum filter 224 receives the update information slot k just received and the update information transmitted by the update information slot k-1 received immediately before. The included spectral information αj _k and αj _k-1 are given as filter coefficients. The spectral filter 224 is

[Equation 1] It has the following transfer characteristic H (Z). Then, the spectrum filter 224 performs a filtering operation on the complementary code vector Z '(n) output from the signal synthesis circuit 223 according to the transfer characteristic H (Z).
The signal obtained by this calculation is used as a pseudo background noise signal bn _kf.
Output as (n).

Next, the pseudo background noise generating operation by the cellular base station configured as described above will be described. For example, during communication with the mobile station PS1, the VOX control circuit 23 monitors arrival of a silent section start pattern and a silent section end pattern from the mobile station PS1. When the silent section start pattern arrives, the VOX control circuit 23 provides a switching control signal to the switching circuit 24 at that time. This switching control signal causes the switching circuit 24 to switch from the voice decoding circuit 21 side to the pseudo background noise generation circuit 22 side. At the same time, the VOX control circuit 23 gives an instruction to generate a pseudo background noise signal to the pseudo background noise generation circuit 22.

Upon receiving the instruction to generate the pseudo background noise signal, the pseudo background noise generating circuit 22 starts generating the pseudo background noise signal as follows. That is, first, in the code vector selection circuit 221, a random number is generated from the random number generation circuit 225, and the switching selection circuit 226 is switched according to this random number. Therefore, the plurality of code vectors V ₁ (n), V ₂ (n), ... V _M-1 (n), stored in the codebook 211,
V _M (n) is selectively read out through the switching selection circuit 226. At this time, the codebook 211 is
Since the digital call signal does not arrive from the mobile station PS1, it is not used for the decoding process. Therefore, there is no problem even if the codebook 211 is used for generating pseudo background noise.

On the other hand, in the energy level complementing circuit 222, every time a change information slot is received from the mobile station PS1, the energy level information E0 _k transmitted by the received change information slot k and the energy level information E0 _k received in the past are received. Two
Based on the energy level information E0 _k-1 , E0 _k-2 transmitted in one change information slot k-1, k-2, the energy level of the energy level in the period until the next change information slot k + 1 is received. The slope is estimated. The energy level information E _kf corrected according to this inclination is supplied to the signal synthesizing circuit 223 for adjusting the energy level of the code vector Z (n) output from the code vector selecting circuit 221.

If there is no change information slot received in the past, or if there is only one, there is only the energy level information E0 _k of the change information slot k that has been received, or this change information slot. energy level information E0 of k and one past change information slot k-1
_{Based on k} and E0 _k-1 , the slope of the energy level during the period until the next change information slot k + 1 is received is estimated.

In the signal synthesizing circuit 223, the code vector Z (n) output from the code vector selecting circuit 221 is multiplied by the complementary energy level information E _kf output from the energy level complementing circuit 222, and the energy The level-corrected code vector Z '(n) is output. This corrected code vector Z '(n) is subsequently input to the spectral filter 224. Then, in the spectrum filter 224, the change information slot k and one change information slot k in the past.
, The spectral information α j _k respectively transmitted by −1,
Filtering is performed using _α j _k-1 as a filter coefficient, and the filtered code vector is output as a pseudo background noise signal bn _kf (n).

This pseudo background noise signal bn _kf (n)
Is output to the D / A converter 25 in place of the signal output from the voice decoding circuit 21 by passing through the switching circuit 24, converted into an analog signal in the D / A converter 25, and then converted to the far signal. It is sent to the telephone of the wired telephone network NW, which is the end speaker.

FIG. 6B shows the waveform of the pseudo background noise signal generated by the pseudo background noise generation circuit 22 of this embodiment and sent to the far-end speaker. As is apparent from the figure, the change characteristics of the signal level between the change information slots are complementarily adjusted, and are close to the actual background noise in the mobile station shown in FIG. 6A.
By the way, the change characteristic of the signal level when the complementary correction is not performed changes stepwise as shown in FIG. 7B, and the quality thereof deteriorates as compared with the case where the complementary correction is performed.

As described above, in this embodiment, the speech decoding circuit 21
In the codebook 211 provided therein, a plurality of code vectors V ₁ (n), V ₂ (n), ... V _M-1 (n), V _M (n) composed of unit variance random Gaussian signals are already present. Are stored, and these code vectors V ₁ (n)
, V ₂ (n), ... V _M-1 (n), V _M (n) are not used in the silent section, and code vectors are selectively selected from the codebook 211 in the silent section. This code vector Z (n) is read out and used as a noise vector which is a basis for generating a pseudo background noise signal.

For this reason, it is not necessary to synthesize some uniform random signals or to perform Gaussian conversion of random signals as in the conventional case in order to generate pseudo background noise that is close to the actual one. Can be greatly simplified and downsized, and the amount of calculation can be reduced.

Further, in the present embodiment, every time the energy level complementing circuit 222 receives the change information slot k from the mobile station at a constant time interval, it receives the energy level information E0 _{k of the} received change information slot. , The energy level gradient during the period until the next change information slot k + 1 is received is estimated based on the energy level information E0 _k-1 and E0 _{k-2 of the two} change information slots received in the past. , Complementary energy level information Ekf that changes according to this inclination is generated. Then, the code vector Z (n) is multiplied by the complementary energy level information Ekf in the signal synthesizing circuit 223 to generate a level-corrected code vector Z '(n).

Therefore, it is possible to generate a pseudo background noise signal in which the level between the change slots is complemented, so that not only the level value has an appropriate value, but also the level change characteristic is the actual background in the mobile station. Pseudo background noise close to noise can be generated, which allows the far-end speaker to hear pseudo background noise with less discomfort.

Moreover, in this embodiment, the change in the energy level during the period until the next change information slot is received is estimated based on the energy level information transmitted in the past change information slot as described above, The level of pseudo background noise is complementarily corrected. That is, the level of the pseudo background noise is complementarily corrected by the extrapolation method. Therefore, there is no large delay in level change,
A pseudo background noise signal can be generated that is closer to the actual background noise at the mobile station.

[0052] Further, in this embodiment, the level correction code vector Z '(n) is, the change information slots k and spectral information .alpha.j _k transmitted respectively by one change information slot k-1 of the past, The spectrum filter 224 performs a filtering process using _α j _k−1 as a filter coefficient, and the filtered code vector is output as a pseudo background noise signal bn _kf (n). Therefore, it is possible to generate pseudo background noise with excellent naturalness close to the actual background noise in the mobile station in terms of not only the level characteristics but also the spectrum characteristics.

The present invention is not limited to the above embodiment. For example, in the above embodiment, a random number is generated from the random number generation circuit 225 as shown in FIG. However, this noise vector may be generated using overlap and vector sum. FIG. 8 is a circuit block diagram showing the configuration.

That is, this circuit includes an overlap code vector generation circuit 41, a code vector temporary storage circuit 42, a vector sum code vector generation circuit 43,
And an adder circuit 44. The overlap code vector generation circuit 41 includes a random number generation circuit 411 and a cycle circuit 412.

[0055] From the random number generation circuit 411, a random number gamma ₁ to? _M of the number of bits corresponding to the stored code vector number M is generated in the codebook 211, the random number gamma ₁ to? _M
Are supplied to the cycle circuit 412. Cycle circuit 41
In 2, the code vector V is read from the codebook _{211 1 (n), V 2} (n), ... V M-1 (n), V M (n)
Are converted according to the random numbers γ ₁ to γ _M , respectively. For example, as shown in FIG. 9, the codebook V _m (n) is divided into four blocks, and these blocks are cyclically shifted according to a random number γ _m in the cycle circuit 412, and a new overlapped code is created. The vector becomes V _m ′ (n). The figure shows the case where γ _m = 2.

A new code vector V _m ′ (n) output from the overlap code vector generation circuit 41.
Is temporarily stored in the code vector temporary storage circuit 42 and then input to the vector sum code vector generation circuit 43. This vector sum code vector generation circuit 43
It is composed of a random number generation circuit 431 and a synthesis circuit 432.

From the random number generation circuit 431, the number M of code vectors stored in the code vector temporary storage circuit 211.
Random numbers β _{1 to} β _M having the number of bits corresponding to are generated. The random numbers β _{1 to} β _M are, for example, {−1,1} and are supplied to the synthesis circuit 432. The synthesizing circuit 432 reads the code vectors V ₁ ′ (n), V ₂ ′ (n), ... VM ₋₁ ′ (n), V read from the code vector temporary storage circuit 42.
_M ′ (n) is multiplied by the random numbers β _{1 to} β _M , respectively. Therefore, from the synthesis circuit 432, VSELP
Similar to the case of the (Vector sum excited linear prediction) method, M vectors whose markers have been changed are output.
These vectors are added together in the adder circuit 44 and output as a noise vector.

With such a configuration, it is possible to generate a noise vector having a higher randomness, which makes it possible to generate pseudo background noise that is closer to the actual background noise.

As the energy level complementary correction method, an interpolation method may be used in addition to the extrapolation method, and the energy level complementing circuit, the spectrum filter, the random number generating circuit, the cellular base station, and the like. The type of digital wireless communication device to be applied can be variously modified and implemented without departing from the scope of the present invention.

[0060]

As described in detail above, according to the present invention, a code vector is read from a code book in which the code vector is stored, a first signal is generated based on this code book, and the generated first signal is generated. The signal is adjusted based on the above information sent from the mobile station to generate a pseudo background noise signal, and this pseudo background noise is converted into a received signal from the mobile station during a period corresponding to a silent section detected by the mobile station. The output is made instead.

Therefore, according to the present invention, the pseudo background noise can be generated with a simple structure and a small amount of calculation, whereby the digital radio communication having the pseudo background noise generating function can realize the simplification of the circuit structure. A device can be provided.

According to another aspect of the present invention, a code vector is read from a code book and the first code vector is read based on this code vector.
Signal is generated, the change in the signal energy level between the respective reception timings is obtained based on the information received from the mobile station at fixed time intervals, and the first signal is obtained based on the obtained change. The energy level of is complementarily adjusted and the signal subjected to the complementary adjustment is output as a pseudo background noise signal.

Therefore, according to another aspect of the present invention, it is possible to generate a pseudo background noise whose level changes smoothly and which is closer to the actual one, and thereby to further improve the reception quality of the far-end speaker. A digital wireless communication device having a generation function can be provided.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a configuration of a reception system of a cellular base station having a pseudo background noise generation function according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram showing a configuration of a pseudo background noise generation circuit shown in FIG.

FIG. 3 is a circuit block diagram showing a configuration of a code vector selection circuit shown in FIG.

4 is a diagram showing an example of a circuit configuration of the random number generation circuit shown in FIG.

FIG. 5 is a signal format diagram for explaining an operation of transmitting change information from a mobile station to a cellular base station.

FIG. 6 is a signal waveform diagram of pseudo background noise generated by the device of this embodiment.

FIG. 7 is a signal waveform diagram of pseudo background noise generated by a conventional device.

FIG. 8 is a circuit block diagram showing a part of the configuration of a pseudo background noise generation circuit according to another embodiment of the present invention.

9 is a diagram showing an operation example of the circuit shown in FIG.

FIG. 10 is a schematic configuration diagram of a cellular radio system.

[Explanation of symbols]

 CS ... Control station BS1, BS2, ... Cellular base station PS1, PS2, ... Mobile station 11 ... Antenna 12 ... Antenna duplexer (DUP) 13 ... Receiving circuit (RX) 14 ... Frequency synthesizer (SYN) 15 ... Low pass filter (LPF) 16 ... A / D converter 17 ... Digital demodulation circuit (DEM) 18 ... Time division multiple access circuit (TDMA) 19 ... Error correction decoding circuit (CH-DEC) 20 ... Control circuit 21 ... Speech decoding circuit (SP) -DEC) 22 ... Pseudo background noise generation circuit 23 ... VOX control circuit 24 ... Switching circuit 25 ... D / A converter 26 ... Hybrid circuit 41 ... Overlap code vector generation circuit 42 ... Code vector temporary storage circuit 43 ... Vector sum code Vector generation circuit 44 ... Addition circuit 211 ... Codebook 221 ... Code vector selection circuit 22 2 ... Energy level complementing circuit 223 ... Signal synthesizing circuit 224 ... Spectral filter 225 ... Random number generating circuit 225a ... Shift register 225b ... Buffer circuit 226 ... Switching selecting circuit 411, 431 ... Random number generating circuit 412 ... Cycle circuit 432 ... Combining circuit

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[Procedure amendment]

[Submission date] October 7, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

Claims (6)

[Claims] 1. A silent section of a transmitted voice signal is detected, information representing the structure of a signal existing in this silent section is transmitted by using a partial period of this silent section, and another section of the silent section is transmitted. In a digital wireless communication device that communicates via a wireless channel with a mobile station that has a function of stopping operations related to transmission during a period, a codebook in which code vectors are stored, and a code vector from this codebook. And a first signal generating means for generating a first signal based on the read codebook, and a first signal generated by the first signal generating means for the mobile station. Second signal generation means for generating a pseudo background noise signal by adjusting based on the information received from the pseudo background noise signal, and the pseudo background noise signal generated by the second signal generation means. A pseudo background noise generating function, comprising: signal selecting means for outputting in place of a received signal from the mobile station during a period corresponding to a silent section detected by the mobile station. Digital wireless communication device. 2. The first signal generating means has means for generating a pseudo-random sequence, and selectively selects one of a plurality of code vectors from a codebook according to the pseudo-random sequence generated by the means. 2. The digital radio communication apparatus having the pseudo background noise generating function according to claim 1, wherein the code vector read out to the above is output as the first signal. 3. The first signal generating means includes a first random sequence generating means for generating a first pseudo random sequence, a second random sequence generating means for generating a second pseudo random sequence, and a code. Means for reading a plurality of code vectors from the book and changing these code vectors according to the first pseudo-random sequence; and a plurality of vectors for calculating the changed plurality of vector signals with the second pseudo-random sequence. The pseudo background noise generating function according to claim 1, further comprising: a means for obtaining a signal and a means for synthesizing a plurality of vector signals obtained by the means with each other to generate a first signal. Wireless communication device equipped with. 4. The first signal processing, wherein the second signal generating means adjusts the energy level of the first signal generated by the first signal generating means based on the information sent from the mobile station, The pseudo background noise generating function according to claim 1, wherein at least one of a second signal processing for adjusting the spectrum of the first signal based on information transmitted from a mobile station is performed. Equipped digital wireless communication device. 5. A silent section of a transmitted voice signal is detected, information representing at least a signal energy level of this silent section is transmitted at fixed time intervals in the silent section, and is transmitted in other periods of the silent section. In a digital wireless communication device that communicates via a wireless channel with a mobile station having a function of stopping the operation related to, a codebook in which code vectors are stored, and a code vector is read from this codebook, First signal generating means for generating a first signal based on the read code vector, and based on the information received from the mobile station at constant time intervals, between the respective reception timings. The change in the signal energy level is obtained, the energy level of the first signal is complementarily adjusted based on the change, and the complementary adjustment is performed. Second signal generating means for outputting the signal as a pseudo background noise signal, and a pseudo background noise signal output from the second signal generating means in a period corresponding to a silent section detected by the mobile station. A digital radio communication apparatus having a pseudo background noise generating function, comprising: a signal selecting means for outputting instead of a received signal from the mobile station. 6. The second signal generating means receives the next information based on the information received now and the information received in the past every time the information is received from the mobile station at a constant time interval. The change in the signal energy level of the background noise during the period until the time is reached, the energy level of the first signal is complementarily adjusted based on this estimation result, and this interpolation-corrected signal is output as a pseudo background noise signal. 6. A digital wireless communication device having a pseudo background noise generating function according to claim 5.