JP2022131172A - Communication device and communication method - Google Patents

Abstract

To provide a technique for suppressing deterioration of voice quality when data transmission in a predetermined time slot is stopped in TDMA communication.SOLUTION: A transmission data generation unit 26 encodes audio data as data of a first time slot. An interruption control unit 28 interrupts data transmission in a second time slot different from the first time slot. A discarded data selection unit 30 selects audio data for the second time slot from a plurality of discontinuous sections in the audio data. A transmission data generation unit 26 joins audio data before and after the audio data selected by the discarded data selection unit 30 and encodes the audio data joined, as data of the first time slot.SELECTED DRAWING: Figure 2

Description

The present invention relates to communication technology, and more particularly to a TDMA (Time Division Multiple Access) communication apparatus and communication method.

A technology has been proposed in which a radio device on the transmitting side that performs TDMA communication stops data transmission in a predetermined time slot and receives data during that time (see, for example, Patent Document 1).

U.S. Patent Application Publication No. 2009/0303923

Until now, when data transmission in a predetermined time slot was stopped, continuous voice data was lost, and the voice quality at the receiving end was sometimes degraded.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a technique for suppressing deterioration of voice quality when data transmission in a predetermined time slot is stopped in TDMA communication.

In order to solve the above problems, a communication device according to one aspect of the present invention is a communication device of a TDMA (Time Division Multiple Access) system, which generates transmission data by encoding audio data as data of a first time slot. an interruption control unit that interrupts data transmission in a second time slot different from the first time slot; and discard data that selects audio data for the second time slot from a plurality of discontinuous sections in the audio data. and a selection unit. The transmission data generation unit concatenates the audio data before and after the audio data selected by the discard data selection unit and encodes it as data of the first time slot.

Another aspect of the invention is a communication method. This method is a communication method executed by a TDMA communication device, and when a time slot for data transmission is called a first time slot and a time slot for interrupting data transmission is called a second time slot, a discard data selection step of selecting audio data for a second time slot from a plurality of discontinuous sections of the audio data; encoding as data for the slot; and suspending data transmission for the second time slot.

Any combination of the above-described constituent elements, and expressions of the present invention converted between a system, a computer program, a recording medium storing the computer program, and the like are also effective as embodiments of the present invention.

According to the present invention, deterioration of voice quality can be suppressed when data transmission in a predetermined time slot is stopped in TDMA communication.

It is a figure which shows the structure of the communication system of an Example. 2 is a block diagram showing functional blocks included in the communication device of FIG. 1; FIG. It is a flow chart showing the operation of the communication device. FIG. 2 is a timing chart regarding data transmission of a conventional transmitter; FIG. 4 is a timing chart regarding data transmission of the communication device of the embodiment; 4 is a timing chart regarding data transmission of the communication device of the embodiment;

First, an outline of the embodiment will be described. A transmitter that performs wireless communication using the TDMA method has a call interruption function that stops data transmission in response to a request from the receiver (hereinafter also referred to as a "transmission interruption instruction") during a call with the receiver. there is something Call interruption is realized by switching between transmission and reception for only one time slot at the same timing during a call between the transmitter and the receiver. Conventionally, when a transmitter stops transmitting data in a predetermined time slot, continuous audio data is lost, and the audio quality at the receiving end may be degraded.

The transmitter (communication device 12 described later) of the embodiment is configured to be able to receive a transmission suspension instruction from the receiver in a time slot during which transmission of audio data is suspended. In addition, the transmitter (communication device 12 described later) of the embodiment selects audio data for the time slot at which data transmission is to be interrupted, from a plurality of discontinuous intervals in the audio data, in other words, from a plurality of discrete intervals. . As a result, when data transmission in a predetermined time slot is stopped in TDMA communication, it is possible to suppress dropout of continuous voice data and suppress deterioration of voice quality on the receiving side.

The details of the embodiment will be described. FIG. 1 shows the configuration of a communication system 10 of an embodiment. Communication system 10 includes communication device 12 and communication device 14 . The communication device 12 and the communication device 14 are wireless communication devices that transmit and receive data using the TDMA method. In an embodiment, communication device 12 operates primarily as a transmitter of audio data, and communication device 14 operates primarily as a receiver of audio data. When the communication device 12 receives the transmission interruption instruction from the communication device 14, the communication device 12 stops subsequent data transmission.

FIG. 2 is a block diagram showing functional blocks included in the communication device 12 of FIG. Each block shown in the block diagrams of this specification can be implemented by computer processors, CPUs, memory and other elements, electronic circuits, and mechanical devices in terms of hardware, and can be implemented by computer programs and the like in terms of software. However, here, the functional blocks realized by their cooperation are drawn. Therefore, those skilled in the art will understand that these functional blocks can be realized in various ways by combining hardware and software.

The communication device 12 includes a CPU 20 , an antenna 34 , an antenna switching section 36 , a demodulation circuit 38 , an A/D converter 40 , a microphone 42 , an A/D converter 44 , a D/A converter 46 and a modulation circuit 48 .

The CPU 20 includes a reception data analysis section 22 , a transmission/reception control section 24 , a transmission data generation section 26 and a discard data selection section 30 . The transmission data generator 26 includes an interruption controller 28 . The discarded data selection section 30 includes a silence detection section 32 . A computer program in which the functions of the plurality of functional blocks provided by the CPU 20 are implemented may be stored in a storage unit (not shown) of the communication device 12 . The CPU 20 may exert the functions of the plurality of functional blocks by reading the computer program into a main memory (not shown) and executing it.

The antenna 34 transmits and receives RF (Radio Frequency) signals. The antenna switching unit 36 is controlled by the transmission/reception control unit 24, connects the antenna 34 and the demodulation circuit 38 during reception, and connects the antenna 34 and the modulation circuit 48 during transmission. Demodulation circuit 38 demodulates the RF signal received by antenna 34 and outputs the demodulated analog signal to A/D converter 40 . A/D converter 40 converts the analog signal input from demodulation circuit 38 into a digital signal (hereinafter also referred to as “received data”) and outputs the received data to received data analysis section 22 .

The received data analysis unit 22 uses a predetermined filter to remove unnecessary band signal components from the received data input from the A/D converter 40, detect bits, and correct errors. Parse the content of the data. If the received data includes synchronous data or control data, the received data analysis unit 22 outputs the synchronous data or control data to the transmission/reception control unit 24 .

At the time of transmission, the transmission/reception control unit 24 controls the antenna switching unit 36 to connect the antenna 34 to the modulation circuit 48, switch the power supply of the modulation circuit 48 on, and transmit the RF signal. During reception, the transmission/reception control unit 24 controls the antenna switching unit 36 to connect the antenna 34 to the demodulation circuit 38 and turn on the demodulation circuit 38 to receive the RF signal.

The microphone 42 converts the speaker's voice into an analog signal and outputs the converted analog signal to the A/D converter 44 . The A/D converter 44 converts the analog signal input from the microphone 42 into a digital signal (hereinafter also referred to as “audio data”) and outputs the audio data to the discard data selection unit 30 .

The discarded data selection unit 30 accepts audio data input from the A/D converter 44 (hereinafter also referred to as “input audio data”). The input audio data may be divided into a plurality of sections in units of 20 milliseconds of data for encoding. Also, the audio data output from the A/D converter 44 may be temporarily stored in a predetermined storage area (buffer) (not shown), and the discard data selection unit 30 reads out the audio data from the storage area. may

Hereinafter, among the plurality of time slots in the TDMA system, the first time slot for transmitting data is also called "normal time slot". A second time slot which is different from the normal time slot and which interrupts data transmission when the call interruption function is enabled is called a "transmission interruption time slot". The discarded data selection unit 30 selects audio data for the transmission interruption time slot from a plurality of discontinuous sections in the input audio data. The audio data selected by the discarded data selection unit 30 as the audio data for the transmission suspension time slot is discarded without being transmitted, and is hereinafter also referred to as "discarded data".

The silence detection unit 32 detects silence intervals in the input audio data. For example, the silence detection unit 32 may detect, as a silence section, a section in which the absolute value of the amplitude is equal to or less than a predetermined threshold for a preset time (for example, 20 milliseconds) from the input audio data. An appropriate value for this threshold value may be determined based on the knowledge of the developer of the communication device 12, an experiment using the communication system 10, or the like. The discarded data selection unit 30 preferentially selects the audio data of the silent period detected by the silence detector 32 from the input audio data as the audio data for the transmission interruption time slot (that is, discarded data).

The discard data selection unit 30 replaces the audio data selected as discard data from the input audio data with a predetermined value (in other words, a predetermined bit string) indicating discard data. The discarded data selection unit 30 outputs the input audio data in which the values of some sections are replaced with values indicating discarded data to the transmission data generation unit 26 .

The transmission data generation unit 26 performs voice encoding processing on the input voice data input from the discard data selection unit 30 using a vocoder or the like. In the embodiment, the transmission data generator 26 encodes input audio data in units of predetermined intervals (20 milliseconds). Also, the transmission data generator 26 generates transmission data in which the encoded audio data, synchronization data, and control data are arranged. The transmission data generation unit 26 also removes signal components in unnecessary bands using a predetermined filter. The transmission data generator 26 outputs transmission data from which signal components in unnecessary bands have been removed to the D/A converter 46 .

The D/A converter 46 converts the transmission data input from the transmission data generator 26 into an analog signal and outputs the converted analog signal to the modulation circuit 48 . The modulation circuit 48 modulates the carrier wave based on the analog signal input from the D/A converter 46 and outputs the modulated RF signal to the antenna 34 .

The transmission data generator 26 will be described in detail. The transmission data generation unit 26 encodes the input audio data input from the discard data selection unit 30 as normal time slot data. The transmission data generation unit 26 identifies the portion of the input audio data that has the predetermined value indicating the discarded data as the discarded data selected by the discarded data selection unit 30, and connects the audio data before and after the discarded data in the input audio data. are encoded as normal time slot data.

Interruption control section 28 interrupts data transmission in a predetermined transmission interruption time slot. The transmission data generation unit 26 suppresses encoding and discards a section in which a value indicating discarded data is set in the input audio data. That is, no transmission data is generated in the transmission interruption time slot.

In addition, the transmission data generation unit 26 includes information indicating acceptance of the transmission stop instruction in the data of the normal time slot immediately before the transmission interruption time slot. The information to the effect that the transmission stop instruction is accepted can be said to be information indicating that the transmitter will suspend the transmission operation in the next time slot and perform the reception operation, and can also be said to be information indicating the timing of the call interruption.

The operation of the communication device 12 configured as above will be described.
FIG. 3 is a flow chart showing the operation of the communication device 12. As shown in FIG. The discarded data selection unit 30 acquires input voice data based on the voice input to the microphone 42 (S10). The silence detection unit 32 of the discarded data selection unit 30 detects silent intervals in the input audio data (S11). The discard data selection unit 30 selects discard data, which is audio data for the transmission interruption time slot, from a plurality of discontinuous sections in the input audio data (S12).

In S12, the discarded data selection unit 30 preferentially selects the audio data in the silent period as discarded data. Further, as will be described later, if there is no silent section within a predetermined period (for example, within 80 milliseconds), the discard data selection unit 30 forcibly discards the audio data of one section within that period as discard data. select.

The interruption control section 28 of the transmission data generating section 26 determines whether or not it is transmission interruption timing (transmission interruption time slot). If it is not the transmission interruption timing (N of S13), the transmission data generation unit 26 encodes the input audio data input from the discard data selection unit 30 as normal time slot data to generate transmission data (S14). When discarded data is included in the section to be processed, the transmission data generator 26 connects and encodes the audio data before and after the discarded data to generate transmission data. The transmission data is transmitted from the antenna 34 through D/A conversion and modulation (S15).

If the next time slot is a transmission interruption time slot, the transmission data generation unit 26 includes information indicating acceptance of a transmission stop instruction in the data of the normal time slot immediately before the transmission interruption time slot.

If it is transmission interruption timing (transmission interruption time slot) (Y of S13), the interruption control unit 28 interrupts data processing. Specifically, the interruption control unit 28 causes the transmission/reception control unit 24 to perform switching processing from the transmission mode to the reception mode (S16). If the transmission stop instruction transmitted from the communication device 14 is received at the transmission interruption timing (transmission interruption time slot) (Y in S17), the transmission/reception control unit 24 stops data transmission in subsequent time slots (S18 ). If the transmission stop instruction has not been received (N of S17), the transmission/reception control unit 24 switches from the reception mode to the transmission mode, and the transmission data generation unit 26 resumes data transmission in the next normal time slot.

FIG. 4 is a timing chart for data transmission of a conventional transmitter that does not have the features of the communication device 12 of the embodiment. As shown in FIG. 4, the conventional transmitter compresses the audio data to be transmitted by performing audio encoding processing in units of 20 milliseconds. That is, one section of the audio data to be transmitted is 20 milliseconds. In addition, the conventional transmitter combines the compressed three-section audio data and the synchronization/control data to generate transmission data for one time slot. The conventional transmitter outputs the generated transmission data for one time slot to the D/A converter at intervals of 30 milliseconds.

For synchronization and control data, the transmitted data for timeslot 1 is populated with a synchronization word that is used by the receiver to synchronize to the slot timing. In the transmission data of time slot 2, control data including source and destination IDs are arranged. Null data is arranged in the transmission data of time slot 3 . During transmission, these three types of synchronization/control data are repeatedly arranged in transmission slots. In FIG. 4, time slots 1 to 5 are normal time slots, and time slot 6 is a transmission interruption time slot.

Describe procedures for call interruptions.
The conventional transmitter inserts information to the effect of accepting a transmission stop instruction in the control data placed in the time slot 5, in other words, inserts information to the effect that the transmission will be stopped and the reception operation will be performed in the next time slot. A receiver that receives this can transmit a transmission interruption instruction (call interruption information) in the next time slot so that the transmitter will stop transmitting and perform the receiving operation in the next time slot. Recognize that.

The conventional transmitter stops the transmission operation at the time slot 6 and performs the reception operation. At this timing, when the receiver stops data transmission from the transmitter, it generates transmission data including a transmission interruption instruction (also called "call interruption information"), and transmits the transmission data to the conventional transmitter. Send. When data transmission from the transmitter is to be continued, the receiver continues the reception operation without transmitting a transmission interruption instruction.

Conventional transmitters immediately stop transmission when receiving a transmission interruption instruction in time slot 6 . On the other hand, the conventional transmitter resumes data transmission in time slot 7 if no transmission interruption instruction is received in time slot 6 . After time slot 7, the conventional transmitter repeats the operations of time slots 1 to 6 until it receives a transmission interruption instruction from the receiver. That is, the data transmission is periodically interrupted and the reception operation is performed. The operation of the conventional transmitter described above is similarly executed in the communication device 12 of the embodiment.

In FIG. 4, "silent" in the input audio data indicates a silent section. As shown in FIG. 4, a conventional transmitter that does not have the features of the communication device 12 of the embodiment discards voice data in a plurality of continuous sections when transmission is interrupted at time slot 6. FIG. In FIG. 4, the audio data of three consecutive sound segments are discarded. Since the voice data of continuous multiple sections cannot reach the receiver, the voice quality on the receiving side deteriorates.

FIG. 5 is a timing chart regarding data transmission of the communication device 12 of the embodiment. The discarded data selection unit input in FIG. "Discard" in the discard data selection section output indicates that a value indicating discard data is set.

In the example of FIG. 5, the silence detector 32 of the discarded data selector 30 detects three silent intervals from the input audio data, and the discarded data selector 30 selects these three silent intervals as discarded data. The transmission data generation unit 26 concatenates the audio data other than the discarded data to generate transmission data for the normal time slot. According to the communication device 12 of the embodiment, since the voice data of the silent section is not transmitted, the interval between words may be shortened. That is, it is possible to suppress deterioration of voice quality on the receiving side.

FIG. 6 is also a timing chart regarding data transmission of the communication device 12 of the embodiment. The figure is a timing chart when there is no silent section for the transmission interruption time slot when the call interruption function is executed. In the example of FIG. 6, the silence detection unit 32 of the discarded data selection unit 30 detects one silence period.

If there is no silent section in the audio data for a predetermined period (here, 80 milliseconds), the discard data selection unit 30 forcibly selects one section (here, the last section) in that period as discard data. select. In the example of FIG. 6, since there is no silent section in the first period of 80 milliseconds, the discarded data selection unit 30 selects the last section of this period as discarded data. Since a silent section exists in the second period of 80 milliseconds, the discarded data selection unit 30 preferentially selects the silent section as discarded data. Since there is no silent section in the third period of 80 milliseconds, the discarded data selection unit 30 selects the last section of this period as discarded data.

The transmission data generator 26 concatenates the audio data before and after the discarded data. Generate transmission data for normal time slots. According to the communication device 12 of the embodiment, even when there are few silent intervals, discarded data is selected from a plurality of discontinuous intervals, so deterioration of voice quality on the receiving side can be suppressed. Also, to preferentially select silent intervals as discarded data. It is possible to reduce the frequency of missing voiced segments and suppress deterioration of voice quality on the receiving side.

The present invention has been described above based on the examples. Those skilled in the art will understand that the contents described in the embodiment are examples, and that various modifications can be made to combinations of the components and processing processes of the embodiment, and such modifications are within the scope of the present disclosure. By the way.

A first modified example will be described. The sound quality improvement technique of the above embodiment can be applied to functions other than the call interruption function. For example, while the communication device 14 (receiver) is receiving data on one frequency, it can be applied to monitor (also referred to as scanning) another frequency in a specific time slot. The purpose of monitoring another frequency is to periodically monitor if there is a higher priority voice communication occurring on another frequency, and if so, use that frequency to hear that voice. It is conceivable that the In a receiver that can receive only one frequency at a time, if it periodically switches to another frequency, the received sound at the original frequency will be interrupted, resulting in deterioration of sound quality.

Therefore, the communication device 12 (transmitter) of this modified example is provided with a transmission interruption time slot as in the embodiment, and stops data transmission in the transmission interruption time slot. In addition, the transmission data generation unit 26 of the communication device 12 adds a message to the transmission data of the normal time slot immediately before the transmission suspension time slot (for example, time slot 5 in FIGS. 5 and 6) that the transmission stop instruction of the embodiment is accepted. information permitting scanning of other channels (also referred to as "priority communication monitor information").

Also in this modification, the discarded data selection unit 30 of the communication device 12 selects audio data (ie, discarded data) for the transmission interruption time slot from a plurality of discontinuous sections in the input audio data. According to the communication device 12 of this modified example, when the communication device 14 (receiver) periodically scans another channel, deterioration of voice quality on the receiving side can be suppressed.

A second modification will be described. In the above embodiment, the discarded data selection unit 30 preferentially selects the audio data of the silent section in the input audio data as discarded data. As a modified example, the discard data selection unit 30 may preferentially select audio data (long sounds, etc.) in sections with little change in the input audio data as discard data. For example, the discard data selection unit 30 may detect the amount of change in one or both of the amplitude and frequency of the audio data in each section of the input audio data. The discarded data selection unit 30 may identify a section in which the amount of change in one or both of amplitude and frequency is equal to or less than a predetermined threshold as a section with little change. An appropriate value for this threshold value may be determined based on the knowledge of the developer of the communication device 12, an experiment using the communication system 10, or the like.

According to the communication device 12 of this modification, by preferentially selecting audio data in a section with little change in the input audio data as discarded data, the frequency of discarding meaningful audio can be reduced. deterioration of voice quality can be suppressed. Note that the discard data selection unit 30 selects audio data in silent intervals in the input audio data as discard data with the first priority, and audio data in intervals with little change in the input audio data has a lower priority than the first priority. It may be selected as discarded data with a second priority. Furthermore, if there is neither a silent section nor a section with little change in the audio data for a predetermined period (for example, 80 milliseconds), the discard data selection unit 30 selects one section (for example, the last section) in that period. may be forcibly selected as discarded data.

Any combination of the above-described examples and modifications is also useful as an embodiment of the present invention. A new embodiment resulting from the combination has the effects of each combined embodiment and modified example. It should also be understood by those skilled in the art that the functions to be fulfilled by each constituent element described in the claims are realized by each constituent element shown in the embodiments and modified examples singly or in conjunction with each other.

10 communication system 12 communication device 14 communication device 26 transmission data generation unit 28 suspension control unit 30 discard data selection unit 32 silence detection unit.

Claims (5)

A TDMA (Time Division Multiple Access) communication device,
a transmission data generation unit that encodes voice data as data in the first time slot;
an interruption control unit that interrupts data transmission in a second time slot different from the first time slot;
a discard data selection unit that selects audio data for the second time slot from a plurality of discontinuous sections in the audio data,
The communication device, wherein the transmission data generation unit concatenates audio data before and after the audio data selected by the discard data selection unit and encodes it as data of the first time slot. 2. The communication apparatus according to claim 1, wherein said transmission data generation unit includes information indicating acceptance of a transmission stop instruction in the data of said first time slot immediately before said second time slot. 2. The communication apparatus according to claim 1, wherein said transmission data generator includes information permitting scanning of another channel in data of said first time slot immediately before said second time slot. Further comprising a silence detection unit that detects a silence interval in the audio data,
4. The communication apparatus according to any one of claims 1 to 3, wherein the discarded data selection unit preferentially selects audio data in a silent period detected by the silence detection unit as audio data for the second time slot. . A communication method executed by a TDMA communication device,
When a time slot in which data transmission is performed is called a first time slot and a time slot in which data transmission is interrupted is called a second time slot,
a discarded data selection step of selecting audio data for the second time slot from a plurality of discontinuous sections of audio data;
a step of concatenating the audio data before and after the audio data selected in the discard data selection step and encoding them as data of the first time slot;
suspending data transmission in the second timeslot;
A communication method comprising:

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