JPH07123043A - Communications system - Google Patents

Abstract

PURPOSE:To prevent increase in a communication time by selecting an error control system for an information channel depending on fluctuation in a channel state of a radio channel to prevent reduction in the transmission efficiency while suppressing undesired redundancy of the system. CONSTITUTION:A facsimile terminal equipment 1 is connected to a communication unit 3 provided in an automobile telephone exchange 4 via a equipment 1 and a signal conversion means 31 and stores picture signal data to a data storage means 34. Then the exchange station 4 connects the communication unit 3 to a communication unit 8 provided in a radio equipment 6 of a called destination. A line quality estimate means 7 detects line quality of a radio block sequentially based on a reception electric field strength and phase error data outputted from the radio equipment 6. A transmission control means 82 stores picture signal data to a data storage means 84 while selecting an error control system of an information channel depending on the quality of channel. The stored data are transferred to a facsimile terminal equipment 9 by a signal conversion means 83, in which the picture is drawn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to mobile communication such as mobile phones, and more particularly to a communication system for performing data communication using a wireless line.

[0002]

2. Description of the Related Art "Appendix 2 Standards for Data Transmission System of Digital Car Phone System" of "Digital Car Phone System Standards" (RCR STD-27B, Radio Wave System Development Center, December 1992) As described in (1), facsimile communication and data communication using a digital wireless line for mobile communication are put into practical use.

The standard defines a method of data communication by G3 facsimile communication and a modem (V.42ANNIX), and the system serves as a means for connecting a mobile terminal and an exchange to a data terminal as shown in FIG. It is configured by connecting a data communication unit.

The system shown in FIG. 9 has a transmission rate of 42 [kbp
[s] is a system that realizes a data communication service with an information transfer rate of 11.2 [kbps] by using a time division multiple access (TDMA) digital wireless line. FIG. 10 is a diagram for explaining an example of the reception (downlink radio line) signal format of the mobile device. One frame period to be time-divided is 20 [ms] and the number of multiplexing is 3. As shown in FIG. 10, the transmission rate of (20 ms / 3) × 42 k bits = 280 bits is provided in one frame period.

User information is assigned to 112 × 2 = 224 bits of an information channel referred to by the symbol TCH, and when converted into a transmission rate, 11.2 [kbps] (= 224/20).
ms).

The data communication unit operates as a connecting means for converting the communication data of the information channel TCH into a format capable of inputting / outputting a signal required for the data terminal, and has an error control function in the communication data of the information channel TCH. .

The communication mode in which a portable data terminal or an in-vehicle facsimile terminal is connected to a mobile unit for mobile communication has an advantage that it can be selected anywhere at any time. However, compared to wired communication, there are problems that the line quality is extremely deteriorated and that the talk time is restricted because it is driven by batteries.

The average bit error rate of wireless lines is 1% to
It is considered to be about 0.1%, which is four or more digits worse than a wired line. Moreover, this is a propagation path in which burst errors due to fading and multipath occur. Therefore, it is necessary for the error control for the wireless communication channel to have an error correction function using, for example, a BCH code, and further have an interleave function for rearranging blocks and bits to be transmitted for the purpose of spreading burst errors. For example, the mobile station side interleaves the data of the information channel and inputs / outputs the data to / from the data communication unit.

Further, the data communication unit performs error control on the information channel. The disclosure standard (RCR-ST
In D27B), Automatic Request Request
m, hereinafter ARQ). This is a method in which the receiving side determines the presence or absence of an error using an error detection code, and if the error is present, requests the transmitting side for retransmission.

If the application example of the described facsimile communication is shown, the maximum transmission rate of the image signal of the G3 facsimile standard is 9.6 [kbps], so 20 ms × 9.6.
An image signal of k bits = 192 bits, 16 bits of control information for ARQ, and 16 bits of CRC code for error detection coded to the control information and the image signal are added to make a total of 1
The information channel frame of 92 + 16 + 16 = 224 bits is configured. The disclosed example realizes high-quality facsimile communication by this retransmission function.

Now, the communication procedure of the wired G3 facsimile will be briefly described. This procedure is stipulated in CCITT (International Telegraph and Telephone Consultative Committee) Recommendation T.30. Connection procedure (Phase A), pre-message procedure (Phase B), image signal transmission procedure (Phase C), post-message procedure ( Phase D) and release procedure (Phase E). In the pre-message procedure, there is a period for sending a test signal for judging whether the modem speed is appropriate for the state of the connected line. If not, lower the modem speed (9.6 [kbps] ] To 7.2 [kbps] ((V.29)) Phase B processing is repeated.

This is because the bit error rate for an equivalent S / N is the same in the modulation method (16QAM) used when the modem speed is 9.6 [kbps] and the modulation method (8QAM) used when the modem speed is 7.2 [kbps]. This is because better characteristics are obtained in the case of 7.2 [kbps]. That is, when the line quality is good, the transmission speed is emphasized and 9.6 [kbp
[s] communication is selected, and if the line condition is poor, the error rate characteristic is emphasized and the communication at 7.2 [kbps] is selected.

The above standard (RCR ST
The D-27B) G3 facsimile regulations also specify that the communication procedures for phases B, C, and D except for the connection and disconnection of the wireless line should be the same.

[0014]

As described above, when the data communication unit is provided in the mobile unit and the exchange and the data communication service is carried out by using the user information channel, the line prior to the communication of the information signal such as the image signal is used. The quality is tested and the transmission procedure is switched, for example by reducing the modem speed of the facsimile terminal. The disclosed standard (RCR STD-27B) is intended to obtain consistency with the existing G3 facsimile communication procedure.

By the way, the quality of the wireless section varies remarkably with the movement of the mobile unit, unlike the case of the wired one. Therefore, even if the line quality is deteriorated at the beginning of connection, there is a possibility that the line quality may be improved during communication or, conversely, the good line condition may be extremely deteriorated.

For example, it is possible to consider an error control in which the transmission rate of the information signal is lowered within a range where the data terminal application can be prepared and the redundant signal such as the error correction code is added to the margin of the communication capacity in preparation for the deterioration of the quality of the wireless section. In this case, while the line quality is improving, there is a problem that the transmission efficiency is deteriorated due to excessive error control and the communication time is unnecessarily increased.

When the ARQ system defined in the above standard (RCR STD-27B) is used, the number of retransmission requests may increase and the transmission efficiency may decrease due to the deterioration of the line quality.

Since the mobile device limits the talk time on the assumption that it is driven by a battery due to its portability, it is not preferable to reduce the transmission efficiency for a certain amount of data, that is, increase the communication required time. Further, there is a problem that it is not desirable from the viewpoint of effective use of frequencies and an increase in billing to users.

The object of the present invention is to cope with the fluctuation of the line quality due to the movement of the mobile unit, and by selecting an appropriate error control, the unnecessary deterioration of the transmission efficiency is prevented, and the communication with the increase of the communication time is prevented. To provide a system.

[0020]

To achieve the above object, the present invention performs radio management, mobility management, and call control, and performs bidirectional communication using a set information channel.
A mobile communication means comprising a single or a plurality of mobile telephone exchange stations, a fixed base station, and a mobile radio station is provided, and (1) the mobile telephone exchange station includes at least an information signal transmitted using an information channel. First signal converting means for converting a signal required for the data terminal into a signal format that can be input to and output from the data terminal, and inputting and outputting the converted signal corresponding to a communication procedure required by the data terminal, and an information signal, respectively. Error control processing means having a plurality of error control functions having different transmission rates, and an error in the first error control processing means in response to an "error control switching request signal" received using the information channel. A first terminal connection including a first transmission control means for outputting a control selection signal and transmitting an "error control switching response signal" corresponding to the request signal, and a first data storage means. Means (data communication unit), (2) the mobile radio station, the line quality estimation means for estimating the quality of the reception line in the wireless section and outputting the line quality data showing the quality stepwise, At least a second signal converting means, which is the same as that provided in the exchange, and a second
Of the error control processing means, the second data storage means, and the value of the line quality data, the "error control switching request signal" is transmitted to the information channel, and the "error control switching response signal" is transmitted. After the reception, the second terminal connection means (data communication unit) is provided, which comprises the second transmission control means for outputting the error control selection signal according to the line quality data to the second error control processing means.

However, each transmission frame used by the plurality of error control functions included in the first and second error control processing means has the same number of bits in one frame, and is for control information relating to switching of the error control functions. In addition, an area having a common arrangement and number of bits in the frame is provided.

[0022]

When transmitting from the first data terminal connected to the public network to the second data terminal connected to the mobile radio station, each of the above means operates as follows.

The first data terminal is connected to the first terminal connecting means provided in the car switching center via the public network.

The first signal converting means receives the information signal transmitted by the first data terminal according to the communication procedure of the data terminal. The received information signal is temporarily stored in the first data storage means. The first data terminal releases the public line when the signal transmission is completed. Then, the car switching center calls the mobile radio station of the call destination, and sets a bidirectional information channel between the first terminal connecting means and the second terminal connecting means provided in the mobile radio station.

The first terminal connecting means uses the information signal data accumulated in the first data accumulating means by using the error control function of the first error control processing means which has been initialized. Initiate the communication to send to.

At this time, the second terminal connection means performs the reception error processing using the similarly initialized second error control processing means, and temporarily processes the processed image signal data to the second transmission control means. It operates so as to be stored in the second data storage means via.

During communication, the line quality estimating means provided in the mobile radio station successively monitors the state of the downlink radio section between the fixed base station and the mobile radio station, and outputs the line quality data to the second transmission control means. .

The second transmission control means determines the switching of the error control function using the line quality data, and carries out the switching processing.

This determination algorithm operates so as to suppress the redundancy of error control when the line condition is good, improve the transmission efficiency, and increase the redundancy of error control when the quality deteriorates.

The switching timing of error control is the second
The "error control switching request signal" transmitted by the transmission control means and the "error control switching response signal" transmitted by the first transmission control means can be synchronized between the terminal connection means.

As described above, the communication between the first and second terminal connecting means using the wireless channel eventually becomes the communication between the first and second data accumulating means, and the information signal data by switching the error control function. The change in the transmission speed is solved by adjusting the access speed of the data storage means and does not pose a problem. Then, by switching the error control function, the transmission efficiency is adjusted according to the fluctuation of the line quality in the wireless section, and the increase of the wireless communication time due to unnecessary redundant signals can be prevented.

The information signal data stored in the second data storage means is stored in the second data storage at the arbitrary time and place desired by the user.
Data terminal 2 according to the data communication procedure by the signal conversion means of
Transferred to.

Since real-time communication between data terminals is not performed in this manner, error control of the information channel can be arbitrarily switched during communication.

When the user selects not to switch the error control function, the mobile communication means composed of the exchange, the fixed base station and the mobile radio station sets up a bidirectional information channel between the data terminals. Works like. The error control method of the first and second error control processing means is fixed as the initial setting, and each signal conversion means does not execute the data procedure by looping back, but relays for performing real-time communication between the data terminals. By carrying out the signal conversion operation, each of the terminal connection means operates so as to perform communication using the information channel without going through the data storage means.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining the system configuration of an embodiment of the present invention. 1 and 9 are facsimile terminals, 2 is a public network, 3 and 8 are data communication units serving as terminal connecting means for facsimiles, 4 Is a mobile telephone exchange, 5 is a fixed base station, 6 is a wireless device, and 7 is a line quality estimating means.

The data communication units 3 and 8 respectively include signal conversion means 31 and 83, transmission control means 32 and 82, error control means 33 and 81, and data storage means 34.
And 84. This is between the public network 2 and the car switching office 4 (and between the wireless station 6 and the facsimile terminal 9).
To execute a facsimile communication procedure, convert a facsimile signal and digital data, temporarily store digital data, and perform data error control.

It is also assumed that the wireless device 6, the line quality estimating means 7 and the data communication unit 8 constitute a portable mobile station of a digital car telephone.

The system shown in FIG. 1 is for performing mutual data communication between the facsimile terminals 1 and 9 using the communication line of the digital car telephone.

In particular, in the present invention, when communication is performed by using the facsimile terminal 1 as a sender of image signals and the facsimile terminal 9 as a receiver, the error control method of the error control processing means 33 and 81 is applied to the fluctuation of the line quality in the wireless section. Corresponding and has a function to switch in stages.

First, the system configuration will be described, and then the error control method switching function will be described.

The fax terminal 1 is connected to the data communication unit 3 provided in the car telephone exchange 4 via the public network 2. In the data communication unit 3, the signal conversion means 31 is connected to the facsimile terminal 1 under the control of the transmission control means 32. A data storage means 34 and an error control processing means 33 are also connected to the transmission control means 32, and the communication data of the phase-modulated signal of the facsimile and the digital data are mutually converted by the signal conversion means 31. Responsible for storage and error control.

This communication data is connected from the car telephone exchange 4 to the fixed base station 5, and is connected to the wireless device 6 of the portable mobile station via the wireless line of the digital car telephone. Then, the communication data is interconverted between the phase-modulated signal of the facsimile and the digital data via the data communication unit 8 and connected to the facsimile terminal 9. The above path is the communication path between the facsimile terminal 1 and the facsimile terminal 9.

Among the above routes, the line quality of the communication lines between the public network 2, the car telephone exchange 4 and the fixed base station 5 is relatively stable from the time the lines are set up. However, the quality of the wireless section fluctuates drastically as the portable mobile station moves.

In this embodiment, this radio channel uses π / 4 shift QPSK as a modulation method, a transmission rate of 42 [kbps],
It is a time division multiplex line of 3 multiplexes. Time division frame is 2
It is set to 0 [ms], and this is divided into three, and about 6.67 [ms] is used as a time slot unit, and 280 bits are transmitted in one time slot. This is a standard value defined in the above-mentioned "Digital Car Telephone System Standard" (RCR STD-27B), and the wireless device 6 complies with this standard.

In this case, the transmission rate using the information channel in the wireless section is 11.2 [kbps], and 224 bits of the 280 bits are allocated, and data communication is performed using this.

In the construction of the portable mobile station, as shown in FIG. 1, the wireless device 6 decodes and modulates the wireless signal, and the data communication unit 8 is connected by digital data. The signal supplied from the wireless device 6 is a data clock signal, a received data signal, and a transmitted / received frame timing signal corresponding to the time slot, and the signal output from the data communication unit 8 is transmitted data. These are connected to the error control processing means 81 of the data communication unit 8. A bidirectional control interface is also provided between the transmission control means 82 of the data communication unit 8 and the wireless device 6. Further, the transmission control means 8
2 inputs line quality data. The transmission control means 82
The error control processing means 81 according to the line quality data.
The configuration is such that an error control selection signal is output to. The line quality data is multilevel data supplied from the line quality estimating unit 7 which receives the received electric field strength and the phase error data from the wireless device 6.

Further, the transmission control means 82 is connected to the data storage means 84 and temporarily stores the image signal data. The image signal data accumulated here is the transmission control means 82.
Can be supplied to the facsimile terminal 9 via the signal conversion means 83.

The above is the outline of the system configuration of the present embodiment.

Next, an example of a communication procedure for transmitting an image signal from the fax terminal 1 to the facsimile terminal 9 will be described. FIG. 2 is a diagram for explaining the communication procedure. The communication is divided into three phases, and the steps 1 to 3 are assigned to the respective phases.

Step 1 is the transmission of image signals between the fax terminal 1 and the car telephone exchange 4, and step 2 is the car telephone exchange 4.
From the portable mobile station to the mobile terminal, step 3 is the transmission of the image signal from the mobile station to the facsimile terminal 9.

In order to perform transmission divided into these three phases,
The fax terminal 1 and the facsimile terminal 2 do not perform real-time communication. Communication is time-divided through the data storage means 34 and 84. It is assumed that the phase of step 2 is activated by the management of the mobile telephone switching center 4, and the activation of the phase of step 3 is controlled by the operation of the user of the mobile mobile station.

Facsimile terminal 1 and facsimile terminal 2
The reason for disconnecting the communication in time is as follows. That is, the error control method used for the information channels of the car telephone exchange 4 and the mobile mobile station can be arbitrarily switched according to the line quality in the wireless section independently of the transmission procedure of the facsimile.

Since the data storage means 84 used for this purpose is based on the assumption that the portable mobile station is driven by a battery, a non-volatile storage function which does not require a backup power source is required for low power consumption. In addition, it is necessary that the mobile station is made into an IC because the mobile station is required to be downsized at the same time.

The image signal data of the facsimile may be collectively erased as unnecessary data after the drawn image is printed. In this case, the data storage means 84 is flash RO.
M is convenient.

In order to freely switch the error control, FIG.
Although the communication procedure as shown in FIG. 2 is carried out, real-time communication can be carried out without interposing the data storage means 32 and 84 in the configuration shown in FIG. In this case, the information transmission rate is determined according to the result of the training period at the time of line connection (pre-phase procedure of G3 facsimile) according to the facsimile communication procedure, and the error control processing means 33 and 81 perform automatic repeat request data communication. The selection of such a communication procedure is made by the sender at the time of facsimile transmission or by the user of the portable mobile station selecting the communication procedure in advance.

Next, the configurations of the radio equipment 6 and the channel quality estimating means 7 will be shown, and the channel quality data will be described.

FIG. 3 is a diagram for explaining an example of the configuration of the wireless device 6. In the figure, reference numeral 60 designates a transmission / reception shared antenna,
61 is a demultiplexer, 62 is a reception front end unit, 63 is a reception IF unit, 64 is a demodulation unit, 65 is a reception processing unit, 66 is a transmission processing unit, 67 is an IQ generation unit, 68 is a quadrature modulation unit, 69
Is a power amplification unit, 600 is a control unit, 601 is an oscillator, 60
2 is a frequency synthesizer, and 603 is a phase locked loop (hereinafter referred to as PLL).

810 MHZ to 8 propagated in the wireless section
The 26 MHz π / 4 shift QPSK modulation signal is input to the reception front end section 62 via the transmission / reception shared antenna 60 and the demultiplexer 61, where it is amplified and mixed from 940 MHz to 956 MHz supplied from the frequency synthesizer 602. The frequency is converted according to the frequency and is output to the reception IF unit 63 as a first IF signal of 130 MHz. Reception IF unit 63
Outputs the first IF signal from the PLL 603 12
It is mixed with 9.550MHz and converted to the second IF signal of 450MHz. Further, band limiting and amplification are performed by a roll-off filter of π / 4 shift QPSK modulation, and a signal whose waveform has been shaped by a limiter is output to the demodulation unit 64.

In the amplification operation in the reception IF section 63, gain control for amplifying a radio signal having a large dynamic range to a constant level is performed, and the gain control voltage at this time is used as a signal representing the reception electric field strength to estimate the line quality. Means 7
Output to.

The demodulation unit 64 performs delay detection on the reception signal subjected to the limiter shaping, decodes it into binary digital data, and then outputs it to the reception processing unit 65. Along with this detection operation, a deviation amount of the reception phase from the ideal modulation phase is detected, and phase error data obtained by quantizing this is output to the line quality estimating means 7. Further, the symbol timing cycle (in this case, the symbol is 2 bits) is extracted from the fluctuation of the reception phase, and the bit clock signal 42 kHz having a frequency twice this is reproduced and supplied to the reception processing unit 65 and the transmission processing unit 66.

The reception processing unit 65 detects frame synchronization from the decoded bit string, performs deinterleaving for the purpose of spreading burst errors, and outputs information channel data to the data communication unit 8. Further, the control channel information is output to the control unit 600.

The control unit 600 processes radio management, mobility management and call control according to the control channel information. The tuning frequency of the frequency synthesizer 602 is set to the designated wireless channel, and the gain of the power amplification unit 69 is controlled according to the transmission output control from the fixed base station 5. Further, the quantized received electric field strength and channel quality data output from the channel quality estimation means 7 are input to estimate the bit error rate of the reception (downlink) wireless channel, and the transmission control channel (transmission CCH in FIG. 3).
To the base station via.

Communication data of the information channel from the data communication unit 8 is input to the transmission processing section 66. The transmission processing unit 66 performs interleaving processing and frame processing of a wireless channel, and outputs it to the IQ generation unit 67.

The IQ generating section 67 outputs π / corresponding to the bit string.
The 4-shift QPSK modulation signal is output to the quadrature modulation unit 68 as a two-dimensional vector signal of the in-phase component (I component) and the quadrature component (Q component). The quadrature modulator 68 directly quadrature-modulates the carrier signal of 940 to 956 MHz output from the frequency synthesizer 602 with the vector signal and outputs it to the power amplifier 69. The power-amplified transmission signal is the demultiplexer 6
It is radiated from the transmission / reception shared antenna 60 via 1.

The power consumed by the power amplifier 69 occupies most of the power consumed by the wireless device 6. Therefore, the fixed base station 5 detects the state of the uplink in the wireless section, and instructs the wireless device 6 to change the transmission output as necessary. For example, when the line condition is good, the transmission output of the wireless device 6 is reduced to reduce power consumption. As a result, regarding the upstream radio line, power control is performed according to the line state, and the system does not consume unnecessary power.

Next, the downlink channel quality will be explained a little more. FIG. 4 is a diagram for explaining the configuration of the line quality estimating means 7. In the figure, 70 is a timer unit and 71 is A.
/ D section, 72 is an occurrence frequency counting section, 73 is an averaging circuit, 7
4 is a decoder.

The frame synchronization signal output from the reception processing unit 65 is sent to the timer unit 70, the received electric field strength detected by the reception IF unit 63 is sent to the A / D unit 71, and the phase error data detected by the demodulation unit 64 is sent to the A / D unit 71. It is input to the occurrence frequency counting unit 72, respectively.

The timer section 70 outputs to the A / D section 71 the timing of periodically sampling the received electric field strength with the frame synchronization signal as a reference. The A / D unit 71 quantizes the received electric field intensity, and the control unit 600 and the averaging circuit 73 are quantized.
Output to.

The averaging circuit 73 obtains an average value of the quantized received electric field strength in a predetermined short section, updates the average value with the latch timing signal output from the timer section 70, and outputs the average value to the decoder 73. .

Further, the timer section 70 generates a gate signal indicating that the allocated time slot is being received, and the generation frequency counting section 7
2, the occurrence frequency counter 72 counts the number of occurrences of a specific value of the phase error data, and outputs it to the decoder 73.

The phase error data has values as shown in FIG. 5, for example.

In FIG. 5, the range of π / 4 [rad] for each of the lead phase region and the lag phase region is divided into four equal to the center of the ideal phase point of the π / 4 shift QPSK modulation signal, and the phase distance from the ideal point is The values of ± 0, ± 1, ± 2, ± 3 are assigned to each step as the distance increases. This division can be obtained by counting the reception phase using a clock of 32 (8 × 4) times the second IF frequency of 450 kHz.
The demodulation unit 64 outputs the corresponding phase error data from the detected reception phase.

Such phase error data is ± π / 4 [ra
If it exceeds the area of [d], it means that a data error has occurred. Therefore, there is a correlation between the line quality and the probability distribution of the phase error data, and FIG. 6 shows an example of the relationship between the phase error data and the bit error rate obtained by computer simulation. This shows the relationship between the occurrence frequency of the phase error data ± 3 and the bit error rate shown in FIG. 5, using a clock 32 times 450 kHz for counting the reception phase. In FIG. 6, as the bit error rate deteriorates, the occurrence frequency of ± 3 tends to monotonically increase. The occurrence frequency counting unit 72 counts and outputs the number of occurrences of ± 3 and ± 2 for each gate period output by the timer unit 70.

A method of estimating the line quality based on the phase error data is described in detail in, for example, "Line Monitor Circuit" described in Japanese Patent Laid-Open No. 2-353748.

The decoder 74 gives stepwise line quality data from the received electric field strength output from the averaging circuit 73 and the output count value of the occurrence frequency counter 72.

The error control method of the data communication units 3 and 8 is switched according to the thus obtained line quality data. Next, the error control switching procedure will be described.

FIG. 7 is a flow chart showing an example of the error control switching algorithm executed by the transmission control means 82 of the data communication unit 8. However, in FIG.
Is a variable indicating the level of error control, the larger the number, the higher the redundancy of the error control method and the initial value is 1. q is a value indicating the line quality level, and the larger the number, the deteriorated line state. Is a variable that indicates.

Now, when the line in the wireless section is set up and the data communication using the information channel is started, the transmission control means 82
Inputs the line quality data every time it receives a frame of the information channel and obtains the line quality level q (process e1).
Next, Q-q is calculated, the code is checked, and if Q> q, the process e3 is performed (process e2). The shift to the process e3 indicates an instantaneous improvement of the line quality. Therefore, the frame deterioration count value is cleared (process e3), and the frame improvement count value is incremented by 1 (process e4).

Next, the frame-improved count value is a predetermined value a.
(Process e5), and if the condition is satisfied, a process e6 is performed to switch to an error control system that places importance on transmission efficiency with lower redundancy than the current error control.

Then, the frame improvement count value is cleared,
The value of Q indicating the error control level is reduced by one level (process e7), and the process returns to process e1.

When q≤Q is determined in the process e2, the process moves to process e9 except when q = Q. Processing e
9 to 13 are processes when the line quality of the frame is deteriorated. First, the frame improvement count value is cleared (process e).
9) The frame deterioration count value is incremented by one. Then, when the count value of deterioration reaches the predetermined value b, the processing e12 for switching the error control method to a method with higher redundancy is executed this time.

The above switching algorithm operates so that the line quality level q is equal to the error control level Q. This makes it possible to adjust the redundancy of error control according to the fluctuation of the line quality due to the movement of the mobile mobile station, and prevent the transmission efficiency from being extremely deteriorated and the communication time being increased.

Next, the error control switching procedure will be described. The transmission control means 82 transmits an "error control switching request signal" for requesting the transmission control means 32 of the data communication unit 3 to change the error control level according to the error control information incorporated in the frame of the information channel.

Only when the transmission control means 32 detects the change in the error control level, the transmission control means 32 returns an "error control switching response signal" indicating the response and the error control level of the change destination to the transmission control means 82. . Transmission control means 82
Detects the response signal, and switches the error control system when the change error control level coincidence is detected.

The above "error control switching request signal"
Shall be repeatedly notified with a predetermined timeout period.

Next, a plurality of error control methods will be described for the case of this embodiment. FIG. 8 is a diagram for explaining the frame structure of the information channel of the present embodiment, which corresponds to three error control levels of error control levels Q = 1 to 3, and is referred to by symbols F1, F2a to F2c, F3, respectively. It has three types of frame configurations.

As described above, the larger the error control level Q, the higher the redundancy. In FIG. 8, CRC indicates a cyclic code and has a function of detecting the occurrence of an error. ECC indicates that a correction code having an error correction capability is added.

In the present embodiment, as described above, 2 in 1 frame.
An 11.2 [kbps] information channel that transmits 24 bits in 20 [ms] is used. It is also assumed that the facsimile terminals 1 and 9 are terminals having a transmission rate of 2.4 [kbps]. In this case, the transmission rate is 48 bits in the period of 20 [ms].

The error control level Q = 1 is used when the channel condition is good, and the frame configuration F1 uses the above-mentioned automatic retransmission request method. When a data error is detected by the error control processing means 33, 81 by the CRC code, the retransmission of the error frame is requested. When the line condition is good, the transmission efficiency is very good, but when the line deteriorates, the number of retransmission requests increases and the transmission efficiency deteriorates. .

When Q = 2, the same image signal is continuously transmitted three times, and the receiving side performs majority processing to correct the data error. F2a, F2b, and F2c having a frame structure are repeatedly transmitted in this order. (A), (B), (C), and (D) attached to the image signals of F2a to F2c in FIG. 8 indicate that the contents of the blocks are the same.

In the case of Q = 3 (F3), the redundancy is further increased, and the error correction code indicated by ECC is added. After being corrected by the error correction calculation, the receiving side performs majority processing on the image signals that have been further transmitted three times. Even if the line condition is extraordinarily deteriorated by this error control, 2.
The transmission rate of 4 kbps is maintained and the increase of communication time is prevented. The average transmission speed of such image signals can be selectively and easily changed by using the data storage units 34 and 84 in the data communication units 3 and 8 without performing real-time communication between the facsimile terminals 1 and 9 and using the wireless section. Is the result of independent transmission of the. That is, the change in the transmission rate of the information channel is adjusted by the access rate between the transmission control means 32 (82) and the data storage means 34 (84).

According to this embodiment, when the image signal is transmitted from the facsimile terminal 1 to the facsimile terminal 9, the error control method of the information channel is switched according to the fluctuation of the line quality in the wireless section to prevent the deterioration of the transmission efficiency. This has the effect of preventing an increase in call time. Further, since the portable mobile station is provided with the data storage means 84, there is an effect that the user can output a facsimile image at his / her arbitrary time.

[0093]

As described above, according to the present invention, it is possible to switch the error control system of the information channel in response to fluctuations in the quality of the wireless line of mobile communication, and excessive redundancy for the line quality. It is possible to prevent the transmission efficiency from being lowered because the code is not transmitted. Therefore, it is possible to prevent an increase in communication time required for transmitting a certain amount of data, and it is effective in power saving of a communication system using a battery-driven portable terminal whose use time is limited.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an embodiment.

FIG. 2 is an explanatory diagram of a communication procedure according to the embodiment.

FIG. 3 is a configuration diagram of a wireless device 6 according to an embodiment.

FIG. 4 is a configuration diagram of channel quality estimation means 7 of the embodiment.

FIG. 5 is an explanatory diagram of mapping of phase error data according to the embodiment.

FIG. 6 is a relationship diagram between the phase error data and the bit error rate according to the embodiment.

FIG. 7 is a flowchart illustrating an error control switching algorithm according to an embodiment.

FIG. 8 is a frame configuration diagram of an embodiment.

FIG. 9 is a diagram illustrating a conventional example of a data transmission system configuration using a digital car telephone system.

FIG. 10 is a diagram illustrating a signal format in a downlink wireless section of a digital mobile phone system.

[Explanation of symbols]

 1, 9 ... Facsimile terminal, 2, 106 ... Public network, 3, 8 ... Data communication unit, 4 ... Automobile telephone exchange station, 5 ... Fixed base station, 6 ... Radio equipment, 7 ... Line quality estimating means, 31, 83 ... signal conversion means, 32, 82 ... transmission control means, 33, 81 ... error control processing means, 34, 84 ... data storage means, 60 ... shared antenna, 61 ... duplexer, 62 ... reception front end section, 63 ... reception IF section, 64 ... demodulation section, 65 ... reception processing section, 66 ... transmission processing section, 67 ... IQ generation section, 68 ... quadrature modulation section, 69 ... power amplification section, 70 ... timer section, 71 ... A / D Reference numeral 72 ... Occurrence frequency counter, 73 ... Averaging circuit, 74 ... Decoder, 600 ... Control unit, 601 ... Oscillator, 602 ... Frequency synthesizer, 603 ... Phase locked loop.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H04N 1/00 104 Z 107 Z 7304-5K H04B 7/26 109 M 9297-5K H04L 27/00 A (72) Inventor Toyota Honda, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd.

Claims (6)

[Claims] 1. A communication system for transmitting an information signal between a data terminal connected to a public network and a data terminal connected to a land mobile station, the information signal being transferred to an information channel set in a wireless section interface. An error control processing unit having a plurality of error control functions having different information signal data transfer rates per unit frame is provided, and the plurality of error control functions are selectively operated according to fluctuations in channel quality in the downlink radio section. A communication system characterized in that information signal data is switched to perform communication of information signal data. 2. A communication system for transmitting an information signal between a data terminal connected to a public network and a data terminal connected to a land mobile station, the information signal being transferred to an information channel set in a wireless section interface. Error signal processing means having a plurality of error control functions having the same S / N ratio and different transmission efficiencies with respect to the information signal data to be transmitted. The plurality of error control functions are provided in accordance with fluctuations in channel quality in the downlink radio section. A communication system characterized by selectively switching to perform communication of information signal data. 3. A communication system for transmitting image signals between a first facsimile terminal connected to a public network and a second facsimile terminal connected to a land mobile station, wherein data is stored in a switching center. Means and signal conversion means for demodulating the received image signal into digital data by performing a facsimile communication procedure. The image signal transmitted from the first facsimile terminal is demodulated into digital data and stored in the data storage means. 3. The communication system according to claim 1, wherein the exchange station transfers the image signal data accumulated in the data accumulating means to the land mobile station via an information channel set in a wireless section interface. . 4. A data accumulating means for accumulating image signal data transferred through an information channel in a land mobile station, and a signal for converting the accumulated image signal data into a signal format that can be input to a second facsimile terminal. The communication system according to claim 3, further comprising conversion means. 5. The communication system according to claim 4, wherein the data storage means provided in the land mobile station is a non-volatile storage element that can be electrically erased collectively. 6. Radio management, mobility management, and call control are performed, and bidirectional communication is performed using a set information channel.
Mobile communication means comprising a single or a plurality of mobile telephone exchanges, fixed base stations, and mobile radio stations, (1) The mobile telephone exchange is provided with at least an information signal transmitted using an information channel. First signal converting means for converting a signal required for a facsimile terminal into a signal format that can be input / output to / from the facsimile terminal, and inputting / outputting a converted signal corresponding to a communication procedure required by the facsimile terminal; and an information signal, respectively. Error control processing means having a plurality of error control functions having different transmission rates, and an error in the first error control processing means depending on an "error control switching request signal" received using the information channel. First transmission control means for outputting a control selection signal and transmitting an "error control switching response signal" corresponding to the request signal, and first data storage means And (2) a line quality estimating unit for estimating the quality of a reception line in a wireless section and outputting line quality data indicating the quality stepwise to the mobile radio station. And at least a second signal converting means similar to that provided in the exchange,
Second error control processing means, second data storage means, and, in accordance with the value of the line quality data, transmits the "error control switching request signal" to an information channel, and the "error control switching response signal". And a second terminal connection means including a second transmission control means for outputting an error control selection signal according to the line quality data to the second error control processing means. Communication system.