JP2011029970A - Digital radio system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital radio system that prevents a sound that is hard to hear from being output from a terminal device that receives and demodulates frames even if data in the frames are delayed or missing. <P>SOLUTION: In the digital radio system including a radio relay device wherein two of first and second radio base station devices are connected via a communication line, one of the radio base station devices includes a means that receives and demodulates a digital radio signal transmitted from a first mobile communication terminal and transfers the obtained digital data to the other radio base station device via the communication line, while the other radio base station device includes a means that resends a frame signal including a rebuilt synchronization word as a digital radio signal to a second mobile communication terminal. The second mobile communication terminal performs a repetitious operation of a previously obtained normal demodulation sound when it receives an IDLE frame first, and performs a mute operation when IDLE continues for a predetermined number or more of multiple frames. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a digital radio system, and in particular, a digital radio system provided with means for preventing the occurrence of demodulated audio distortion on the mobile communication terminal side due to missing or delayed frame data when relaying a digital radio signal About.

In digital wireless communication, data to be transmitted is transmitted and received in frame units, but a synchronization word having a specific signal arrangement pattern at a predetermined position of each frame on the transmitter side (Frame Sync Word: hereinafter referred to as “FSW”) The receiver side establishes synchronization by detecting the synchronization word in the detection output signal. As described above, in digital wireless communication, the frame configuration and symbol timing are configured based on a predetermined communication protocol.
In digital wireless communication, signals to be transmitted such as audio signals and control signals on the transmitting side are transmitted as digital signals superimposed on a carrier wave, and processing on the receiving side is restored to the original audio signals and control signals. However, in order to increase the speed of signal processing in these processes, a DSP (Digital Signal Processor or Processing; digital signal processing device), which is a signal processing unit dedicated to signal processing, is used in addition to the CPU that controls the entire process. I have.
Also, in mobile communication systems, the transmission power on the mobile communication terminal side is reduced for effective use of frequencies and miniaturization of mobile communication terminals, and radio base station devices and radio relay devices are arranged everywhere, Those that are connected by a communication network are the mainstream.

FIG. 7 is a system outline diagram showing an example of a radio base station apparatus used in the digital radio system. As shown in FIG. 7, a radio wave transmitted from a digital radio A that is a mobile communication terminal is received and demodulated by a digital radio base station A that is the nearest radio base station apparatus. At that time, the FSW added to the head of the frame is detected, the subsequent data frame is demodulated, and then the nearest digital radio base station (base station) of the communication partner digital radio (mobile communication terminal) B is transmitted via the network. Station apparatus) B. Based on the received information, the digital radio base station B reconstructs a predetermined frame to which FSW is added, and superimposes it on a radio wave and transmits it to the digital radio B.
Further, the digital radio base station A can also operate as a relay station that transmits a frame reconstructed from the radio wave transmitted by the digital radio A to a mobile device (not shown) around the own station.
Each of the digital radio base stations A and B includes at least one controller for the control channel and a plurality of communication channel controllers, and both the digital radio base stations A and B have radio communication means, wired communication means, and optical communication. It is connected by a communication network such as a cable. In many cases, the communication network includes a circuit switch, and is configured so that the nearest digital radio base stations of a target radio communication terminal are connected to each other. ing.

FIG. 9 is a block diagram showing a general schematic configuration of the digital radios A and B. As a transmission system, a microphone 21 that converts voice into an electrical signal, a microphone amplifier 22, and a codec circuit that digitally encodes the voice signal (CODEC) 23, a press switch or a relay switch 24 for connecting an audio signal to the transmitter, an audio amplifier 25, a modulation level adjuster 26, a voltage controlled oscillator (modulator) 27, and the like. As a receiving system, an intermediate frequency amplifier 31 that converts a high frequency signal received by an antenna into an intermediate frequency signal, an amplifier 32 that amplifies the signal to a required level, an AD converter 33 that converts an analog signal into a digital signal, digital conversion The DSP 34 that functions as a vocoder, a microcomputer (CPU) 35 that controls the entire apparatus, an audio amplifier 36 that amplifies the audio signal supplied through the codec circuit 23, A level adjuster 37, a speaker 38, and the like are included.
Regarding speech coding in such digital wireless communication, for example, Patent Document 1 discloses a technique related to an inter-channel synchronization method in a digital wireless base station and an inter-channel synchronization program therefor, which can be referred to. .
As a frame configuration in the digital radio system, for example, the one shown in FIG. 10 is known. That is, FIG. 10A shows a configuration example of a voice frame. A synchronization word (FSW) at the head, a link information channel (LICH) indicating frame structure information, and control information are transmitted at a low speed. A slow associated channel (SACCH) is arranged, followed by a voice channel (VCH) for transmitting compressed voice encoded data. FIG. 10B shows a still frame that is configured to transmit control information at high speed instead of speech encoded data during normal speech frame transmission. Similarly, a synchronization word (FSW) is placed at the head. And a link information channel (LICH) and a low-speed associated channel (SACCH) are arranged, and a high-speed associated channel (FACCH1) having two data channels as one data structure follows.
Further, IDLE data is used as data applied to the accompanying channels (SACCH and FACCH1) for transmitting control information, which is used when there is no information to be notified, such as a standby operation during transmission. IDLE data is used by both mobile stations and base stations. Specifically, at the beginning of transmission of mobile stations, for several tens of milliseconds while voice is processed and converted into data, the base station The data that is used while the relay operation is switched while the transmission is continued (for example, when the voice is interrupted and data communication is started, or when multiple radios are talking alternately while the call channel is activated) is there.
JP 2007-235281 A

  However, if data is transmitted through the communication line in this way, data in the frame may be lost due to various reasons such as noise mixing or phase delay. growing. Therefore, as described above, when a radio signal including digitally encoded information is received and demodulated (or received and decoded), and then digitally encoded again and retransmitted, data loss in a frame due to reception decoding or transmission may occur. When a delay occurs, it becomes impossible to reconstruct those frames, and the frames are lost.

FIG. 11 is a diagram for explaining a problem associated with frame relay processing in such a conventional radio base station apparatus or radio relay apparatus. FIG. 11 (a) shows that the digital radio base station B is connected via a network. FIG. 11B shows an example of the frame configuration received in this case, and FIG. 11B shows an example of the frame configuration when re-encoding or re-framing for re-transmission to the digital radio equipment B. .
That is, in the frame shown in FIG. 11 (a), among the frames (Frames) received by the digital radio base station B via the network, the frames 1 to 4 and the frame 8 have been demodulated normally. In this example, there is a delay from frame 4 to frame 5 (Frame L), and data is lost (Frame ×) in frames 5 to 7. When such received and demodulated data is reconstructed into a frame signal, as shown in FIG. 11 (b), the frame cannot be reconstructed for a frame with a delay or data missing, and is lost (blank). .
When the digital wireless device B receives and decodes a signal with a missing frame in this way, normal audio decoding is impossible in the demodulator (Vocoder) of the receiver, and a very unpleasant sound is output from the speaker.

In general, in a digital mobile communication terminal, even when data loss or delay is included in a received and demodulated frame, sound recovery can be performed normally by performing data restoration by error correction. In addition, in the unlikely event that restoration is not possible, the data is discarded by error detection, but in general, by repeating and outputting a normal audio signal received and demodulated before that, sound interruption is prevented, Further, when data is discarded for a long period of time, a mute process is performed to prevent generation of difficult sounds. However, as described above, if the frame itself is lost, error correction and error detection become impossible, so that sound cut-off prevention and mute processing are not performed, and it is not possible to prevent the output of difficult sounds.
Such troubles not only occur in radio base station apparatuses, but also in repeater apparatuses and radio relay apparatuses that similarly include a radio relay function, and those similar to radio base station apparatuses in multi-access (cellular) cellular phone systems. Can also be a problem.
The present invention has been made to solve the problems of the conventional digital radio system, radio base station apparatus, and radio relay apparatus, and is a digital radio system, radio base station apparatus, and radio with improved sound quality. An object is to provide a relay device.

In order to solve this problem, the present invention provides a digital wireless system including a wireless relay device in which two first and second wireless base station devices are connected via a communication line. One of these radio base station apparatuses receives and demodulates a digital radio signal configured as a frame signal including a synchronization word transmitted from the first mobile communication terminal, and transmits the obtained digital data via the communication line. Means for transferring to the other radio base station apparatus, the other radio base station apparatus determining whether or not the data of the frame to be transmitted in the transferred digital signal has been acquired before transmission; If the data is acquired, means for reconstructing the data as data of the frame, and if the data cannot be acquired, IDLE data, C Means for reconstructing a frame by setting either data indicating C error or data indicating FEC error, and a frame signal including the reconstructed synchronization word as a digital radio signal to the second mobile communication terminal When the received frame is an IDLE frame and the IDLE frame is received for the first time in the radio relay apparatus comprising means for retransmitting and the second mobile communication terminal, It is configured to perform a mute operation when IDLE continues for a plurality of predetermined frames or more after repeated operations.
According to a second aspect of the present invention, there is provided a digital radio system including a radio relay apparatus in which two first and second radio base station apparatuses are connected via a communication line. Means for receiving and demodulating a digital radio signal configured as a frame signal including a synchronization word transmitted by the mobile communication terminal and transferring the obtained digital data to the other radio base station apparatus via the communication line And the other radio base station apparatus determines whether or not the data of the frame to be transmitted in the transferred digital signal has been acquired before transmission, and if the data is acquired, Means for reconstructing as frame data, and if the data could not be acquired, IDLE data, data indicating CRC error, FEC error A radio comprising: means for reconstructing a frame by setting any of the indicated data; and means for retransmitting a frame signal including the reconstructed synchronization word as a digital radio signal to the second mobile communication terminal When the received frame is a frame in which the CRC error and the FEC error are set in the relay device and the second mobile communication terminal, the frame in which the CRC error and the FEC error are set is received first A normal demodulated sound that was acquired previously is repeated, and a frame that has been set with the CRC error and FEC error continuously for a plurality of predetermined frames continues to be muted.

  As described above, in the digital radio system including the radio relay apparatus in which the first and second radio base station apparatuses are connected via the communication line, one of these radio base station apparatuses is Receives and demodulates a digital radio signal configured as a frame signal including a synchronization word transmitted from one mobile communication terminal, and transfers the obtained digital data to the other radio base station apparatus via the communication line And the other radio base station apparatus determines whether or not the data of the frame to be transmitted in the transferred digital signal has been acquired before transmission, and if the data is acquired, Means for reconstructing the data of the frame, and if the data cannot be acquired, IDLE data, data indicating a CRC error, FEC Means for reconstructing the frame by setting any of the data indicating the error, and means for retransmitting the frame signal including the reconstructed synchronization word as a digital radio signal to the second mobile communication terminal. When the received frame is an IDLE frame in the second mobile communication terminal and the second mobile communication terminal, when the IDLE frame is received for the first time, it repeats normal demodulated audio obtained previously and decides in advance. When the IDLE continues for a plurality of frames, the mute operation is performed. Accordingly, it is possible to provide a digital radio system, a radio base station apparatus, and a radio relay apparatus with improved sound quality.

The flowchart which shows one Example of the relay process of the data frame in the radio base station apparatus which concerns on this invention. The frame block diagram which shows an example of the relay process of the data frame in the radio base station apparatus which concerns on this invention. The figure which shows the specific example of the frame structure in the radio base station apparatus to which this invention is applied. The flowchart which shows the other Example of the relay process of the data frame in the radio base station apparatus to which this invention is applied. The frame block diagram in the other Example of the relay method of the data frame of this invention. The frame block diagram which shows the other specific example to which this invention is applied. 1 is a schematic block diagram illustrating an example of a digital wireless relay device to which the present invention is applied. The flowchart which shows an example of the reception process of the digital radio to which this invention is applied. 1 is a schematic block diagram illustrating an example of a digital wireless device to which the present invention is applied. The figure which shows an example of the frame structure in a digital radio system. It is a figure for demonstrating the conventional malfunction, (a) is the frame figure which the digital radio base station received via the network, (b) is the figure of the frame which a digital radio base station reconstructs and resends.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .
FIG. 1 is a flowchart showing an example of data frame relay processing (method) in a radio base station apparatus according to the present invention. This example shows the processing in the above-described digital radio base station B shown in FIG. 7, that is, the radio base station nearest to the mobile communication terminal (digital radio B) which is the communication partner side.
At this time, the digital radio base station B acquires data from the network and secures data for a certain number of frames before starting transmission. If the number of frame data secured is large, it leads to audio delay. If the number of frame data is too small, data loss is likely to occur. Therefore, data is secured on the basis of no problem in normal operation. When transmission is started, frames are continuously transmitted until transmission is completed.

When the process starts, first, data is acquired from the network (S1). When it is determined that the frame transmission is started when retransmitted to the digital wireless device B (S2), it is determined whether or not data on the frame to be transmitted is obtained from the network (S3). If frame data is obtained, it is determined that “data is present” (S3, Yes), and the process proceeds to step S4. The obtained data is set as frame data (S4) and frame transmission is performed (S5). If the frame data is missing, the determination in the process S3 is “no data for the corresponding frame” (S3, No), and therefore “IDLE data” is set for the frame (S6). Is transmitted (S5).
Data acquired from the network is reconstructed as a frame and counted in units of frames. If the frame count is less than the specified value, the corresponding frame data cannot be obtained.

FIG. 2 is a diagram showing an IDLE frame as a result of the above processing. After setting FSW (frame synchronization word) and link channel information (LICH), a low-speed associated channel (SACCH), a high-speed associated channel (FACCH) ) Is set to “IDLE data”.
FIG. 3 shows an example of a frame structure when the present invention is applied to the demodulated data shown in FIG. 11. In frames 1 to 4, it is determined that “data is present” (S3, Yes), The process proceeds to step S4, where the obtained data is set in a frame (S4) and frame transmission is performed (S5). Further, since data is missing for the frames 5 to 7, the determination in the process S3 is “no data of the corresponding frame” (S3, No), and “IDLE data” is set for the frame (S6). ) And frame transmission (S5). As a result, even if the digital radio base station B demodulates a frame including a data delay or loss as shown in FIG. 3A, as shown in FIG. ) Will be retransmitted in the absence of a frame.
Therefore, in the digital wireless device B that receives and demodulates these digital signals, the “IDLE data” is subjected to a process of repeatedly outputting a normal demodulated sound obtained previously or a mute process. If a delay frame or a missing frame occurs instantaneously, if the mute process is selected, the sound will be interrupted, so the repeated process is more suitable. However, if the delay frame or missing frame continues for a relatively long time, the repetition process becomes unnatural. Specifically, the state of the received frame is stored, and two or more “IDLE frames” continue. In the case of (that is, when both the previous frame and the current frame are IDLE), mute is selected. A control flow of such a digital wireless device B is shown in FIG.

When the processing starts, the digital wireless device B receives data via wireless communication (S21). If it is determined that the current frame is IDLE (S22 Yes), it is determined whether or not the previous frame is IDLE (S23). If the previous frame is also IDLE (S23 Yes), a mute process is performed (S24). On the other hand, when the previous frame is not IDLE (No in S23), a process of repeatedly outputting the normal demodulated sound acquired previously is performed (S26). When the current frame is not IDLE (No at S22), or when the mute process (S24) or the repetition process (S26) is completed, the current data state is stored (S25), and the process is terminated.
In addition, in FIG. 8, only one frame before is targeted, so it is an explanation of muting when there are 2 consecutive IDLE frames, but when multiple frames are consecutive by storing past several frames Can be changed to mute. In addition, it may be detected by a method of providing a counter to determine whether or not the IDLE frame is +1 in the case of continuous, and clearing other than that.
In FIG. 3, the IDLE frame is set due to omission and delay after frame 4, and the radio that has received this is in a mute state continuously after repeated processing, and when frame data is obtained in frame 8, Audio output has been resumed. By operating in this way, it is possible to solve the problem that meaningless or hard to hear sound is output from a speaker or the like.
The present invention is not limited to this example and can be variously modified. FIG. 4 is a flowchart showing another embodiment of the present invention. In the data frame relay method in the radio base station apparatus shown in this example, when frame data cannot be obtained, “FEC error” data is inserted instead.

FIG. 4 also shows processing in the digital radio base station B shown in FIG. 7 described above, that is, the radio base station apparatus on the communication counterpart side. When the process starts, data is acquired from the network (S11). If it is determined that it is the start of frame transmission when retransmitting to the digital radio B (S12), it is determined whether data is obtained for the frame to be transmitted (S13). If frame data is obtained, it is determined that “data is present” (S13, Yes), and the process proceeds to processing S14, where the obtained data is set as a frame (S14) and frame transmission is performed (S15).
On the other hand, if it is determined in S13 that frame data is missing (S13, No), “FSW” is set for the frame (S16), and then the CRC error low-speed associated channel (SACCH) and After setting data such that the number of FEC error bits is determined to be an error (in the digital radio terminal) as “error voice data” in the voice channel (VCH) (S17, S18), frame transmission is executed (S15). ). FEC (Forward Error Correction) is a forward error detection / correction method in which redundant data for error detection / correction is added before data transmission and correction is performed on the receiving side if there is an error. However, in this example, using this function, data selected so as to be judged as “FEC error” on the receiving side is inserted.
FIG. 5 is a frame diagram showing an example of the result of the above processing, which is a low-speed associated channel (SACCH) following FSW (frame synchronization word) and link channel information (LICH), and data cannot be obtained. Data indicating “CRC error” is inserted into the frame, and data indicating “FEC error” is inserted into the voice channel (VCH) from which subsequent data cannot be obtained.

FIG. 6 shows an example of a frame configuration when the modification of the present invention is applied to the demodulated data shown in FIG. That is, it is determined that “data is present” in frames 1 to 4 (S13, Yes), the process proceeds to step S14, the obtained data is set as a frame (S14), and frame transmission is performed (S15). ). On the other hand, since the data for frame 5 is delayed, the determination in the process S13 is “no data for the corresponding frame” (S13, No), and data indicating “CRC error” is set for the frame (S17). ) In the subsequent VCH, “error frame” data having a large number of error bits such as “FEC error” is inserted. As a result, even if the digital radio base station B demodulates a frame including a data delay or omission as shown in FIG. 6A, as shown in FIG. ) Is not transmitted, and data indicating “CRC error” and “FEC error” is embedded in that portion and retransmitted.
Therefore, in the digital radio B that receives and demodulates these digital signals, the process of repeatedly outputting the normal demodulated sound acquired previously is the same as the embodiment described with reference to FIGS. 1 to 3 and FIG. Alternatively, since the mute process controls the sound muting state, it is possible to solve the problem that a meaningless or hard to hear sound is output from a speaker or the like that occurs when a frame is transmitted in a blank state. In particular, in this modified embodiment, all frames for which data cannot be obtained are filled with data that causes them to be processed as errors, so that they can be used for general purposes.

In the above-described embodiment, since the correct symbol data is added to the FSW and LICH of the frame to be retransmitted, the IDLE process is performed while maintaining the synchronization in the receiving digital radio, and other data and Audio can be made an error.
In the above-described embodiment, the case where data loss or delay occurs in communication between wireless base stations connected by the network in FIG. 7 has been described. However, this operation can also be applied to data transmitted from a mobile station. It is. In other words, if the frame data transmitted by the digital radio A is lost or delayed for some reason (such as radio interference or multipath), the digital radio base station A that receives it has the operations described above. Similarly, transmission data to be relayed and data to be transmitted to the digital base station B can be replaced with IDLE data, data indicating a CRC error, and data indicating an FEC error.

Although an example of the present invention has been described above, it goes without saying that application to other systems and various modifications are possible without being limited to this example.
Further, by programming the frame relay processing procedure of the present invention in accordance with an OS that can be controlled by a computer, any computer equipped with the OS can be controlled by the same processing method. Further, these programs are written on a recording medium such as a CD-ROM, and the CD-ROM or the like is mounted on a medium driving device such as a CD-ROM drive mounted on the computer. It goes without saying that the object of the present invention is achieved by storing in a memory or storage device and executing it.
As a recording medium for storing the program, a semiconductor medium (for example, ROM, nonvolatile memory card, etc.), an optical medium (for example, DVD, MO, MD, CD, etc.), a magnetic medium (for example, magnetic tape, flexible disk, etc.) ) Or the like.

  10, 11 digital radio, 12, 13 digital radio base station (device), 23 codec circuit, 34 DSP, 25 CPU (microcomputer), FSW frame synchronization word

Claims (2)

In a digital radio system including a radio relay apparatus in which two first and second radio base station apparatuses are connected via a communication line, one of these radio base station apparatuses is transmitted by a first mobile communication terminal Means for receiving and demodulating a digital radio signal configured as a frame signal including a synchronization word, and transferring the obtained digital data to the other radio base station apparatus via the communication line; The station apparatus determines whether or not the data of the frame to be transmitted in the transferred digital signal has been acquired before transmission, and means for reconstructing the data as data of the frame when the data is acquired If the data cannot be acquired, IDLE data, data indicating a CRC error, or data indicating an FEC error is included in the frame. A radio relay apparatus comprising: means for reconstructing a frame; and means for retransmitting a frame signal including the reconstructed synchronization word as a digital radio signal to the second mobile communication terminal; In the second mobile communication terminal, if the received frame is an IDLE frame, when the IDLE frame is received for the first time, it repeats normal demodulated sound acquired previously, and IDLE continues for more than a predetermined number of frames. If so, a digital radio system configured to perform a mute operation. In a digital radio system including a radio relay apparatus in which two first and second radio base station apparatuses are connected via a communication line, one of these radio base station apparatuses is transmitted by a first mobile communication terminal Means for receiving and demodulating a digital radio signal configured as a frame signal including a synchronization word, and transferring the obtained digital data to the other radio base station apparatus via the communication line; The station apparatus determines whether or not the data of the frame to be transmitted in the transferred digital signal has been acquired before transmission, and means for reconstructing the data as data of the frame when the data is acquired If the data cannot be acquired, IDLE data, data indicating a CRC error, or data indicating an FEC error is included in the frame. A radio relay apparatus comprising: means for reconstructing a frame; and means for retransmitting a frame signal including the reconstructed synchronization word as a digital radio signal to the second mobile communication terminal; In the second mobile communication terminal, when the received frame is a frame in which the CRC error and the FEC error are set, if the frame in which the CRC error and the FEC error are set is received for the first time, A digital wireless system configured to repeat a demodulated sound and perform a mute operation when frames having the CRC error set continuously for a plurality of predetermined frames or more continue.