JPH11313047A - Data communication equipment and mobile terminal equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable efficient error correction without wasting the retransmission of data even in the case of limiting transmission delay. SOLUTION: In the case of receiving a data frame with no error by sending a transmission error detected data frame again according to an ARQ protocol through an ARQ control circuit 713, it is monitored whether the data frame with no error is received within prescribed limit time T of transmission delay or not and when such a data frame is not received within the limit time T, the data frame received within the limit time T while having errors not less than three is read out of a data frame storage part 73 by a majority error correction circuit 714. Then, majority processing is performed for the unit of a bit and the data frame provided after this majority processing is transferred to a control part 5 as a received data frame.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to, for example, PHS
(Personal Handy-phone System) is used as a mobile terminal device in a data communication system that enables mobile data communication between the mobile terminal device and a server device or the like connected to a wired communication network. Data communication device.

[0002]

2. Description of the Related Art In recent years, digital mobile communication systems typified by cellular telephone systems and PHS have rapidly become widespread. In this type of system, in addition to a voice communication service, provision of a data communication service using a personal computer connected to a mobile phone or a portable information terminal having a wireless communication function has been started.

For example, when a user attempts to obtain desired information or the like from a server device on a computer network such as the Internet, a call is made from the portable information terminal to the desired server device. Then, first, the portable information terminal and the nearest base station are connected via a wireless link, and subsequently the base station accesses a data relay device such as a gateway via a wired communication network such as a public network. When a data communication connection is established between the base station and the data relay device, information transmitted from the server device to the data relay device via the Internet is transmitted from the data relay device to the base station via the connection. And transmitted from the base station to the calling portable information terminal via a wireless link.

[0004] The data communication service using the mobile communication system is very convenient because it can send and receive e-mails and browse Web information on the Internet anytime and anywhere.

[0005] In this type of mobile data communication system, an automatic retransmission request (A) is required in order to combat a transmission error occurring in a radio transmission section between a base station and a mobile terminal.
Error correction control employing an RQ (Automatic request for repetition) method is performed. The ARQ scheme uses an error detection code, and when an error is detected in received data on the receiving side, automatically transmits a retransmission request signal and retransmits the erroneous data. Very effective for temporary cases. However, if the transmission quality deteriorates constantly, the data retransmission procedure is repeated until error-free data is received on the receiving side, which increases the data transmission delay and increases the transmission path quality. However, there is a problem that the delay amount changes in accordance with the change of.

On the other hand, in the above-mentioned mobile data communication system, when data requiring immediacy such as voice or moving image is transmitted, signal reproduction is performed without causing a large delay in an upper layer such as an application layer. In order to perform the processing, it is necessary to limit the data transmission delay in the data link layer.

[0007] Therefore, it is difficult to apply the above-mentioned ARQ scheme as it is to a system in which the data transmission delay needs to be limited. Therefore, conventionally, for example, retransmission of data is repeated only within a time limit of a transmission delay requested by an upper layer, and if no error-free data cannot be received within the time limit, the latest received data within the time limit is received It has been considered that this data is used as received data for reproduction processing by an upper layer.

[0008]

However, in such a system, if error-free data cannot be received within the time limit, the data retransmission performed within the time limit cannot be used at all, resulting in a transmission delay. The error was not corrected only by the occurrence of, and the improvement of the transmission quality could not be expected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a data which can perform effective error correction without wasting data retransmission even when transmission delay is limited. A communication device and a mobile terminal device are provided.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a data communication apparatus or a mobile terminal apparatus which detects an error in received data and executes a retransmission procedure based on the detection result. A determination unit for determining whether or not the error correction of the data by the retransmission procedure is completed within a predetermined period of time for reproducing the data, and an error correction unit; When it is determined that the data is not completed, the error correction means performs a majority process on a plurality of received data received within the predetermined time, and outputs the processing result as error-corrected received data. Things.

Therefore, according to the present invention, if the error correction processing by the retransmission procedure is not completed within the time limit of the transmission delay requested by the upper layer, a plurality of mutually corresponding received messages within the time limit are received. The majority decision processing of the data is performed, and the result of the majority decision processing is provided to the upper layer processing as received data. For this reason, it is possible to obtain error-corrected data without wasting a plurality of retransmission data received within the time limit, thereby suppressing transmission delay and performing effective error correction. it can.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a mobile data communication system according to an embodiment of the present invention,
CS1 to CSn indicate PHS base stations. These base stations CS1 to CSn are geographically distributed in a service area covered by the system, and one or a plurality of them form a wireless area.

The mobile terminal devices PS1 to PSm are connected to the nearest base station via a radio line in the cell formed by each of the base stations CS1 to CSn. As a wireless access method between the base station and the mobile terminal device, for example, TDMA-TDD (Time Division Multiple Access)
-Time Division Duplex) method is used. The mobile terminal devices PS1 to PSm include a mobile information terminal having a data communication function and a wireless access function, and a mobile terminal device having a personal computer PC connected to the mobile phone, in addition to a mobile phone having only a call function.

Each of the base stations CS1 to CSn is connected to an I 'interface network (hereinafter referred to as I') via a subscriber line.
(Referred to as a network) IN2 and connected to a dedicated line network PN via a dedicated line. I 'net IN2 is PHS
And a public network composed of a circuit switching network together with the integrated services digital network (ISDN) IN1. Many wired terminal devices (not shown) are connected to the ISDN network IN1. The leased line network PN forms a packet network. The packet exchange is performed according to the protocol specified in 25.

A gateway GW as a data communication device is connected to the ISDN network IN1 and the private line network PN, and a server device AS is connected to the gateway GW via the Internet, for example. Server device AS
Has a function as a mail server when e-mail is transmitted between the mobile terminal devices PS1 to PSm and the wired terminal device, and transmits Web information such as news and advertisements to the mobile terminal devices PS1 to PSm and the wired terminal device. Has a function as a content server for notifying the user. For information transmission between the gateway GW and the server device AS,
The TCP / IP protocol is used.

Note that the gateway GW and the server device AS
Can be connected via a network, and further, a function as a server device can be implemented in the gateway GW.

By the way, among the devices constituting the above mobile data communication system, the mobile terminal devices PS1 to PS1 are provided.
PSm is configured as follows. FIG. 2 is a functional block diagram showing the configuration.

The mobile terminals PS1 to PSm include a radio unit 1 having an antenna 11, a modem unit 2, and a TDMA unit 3.
, A communication unit 4, a control unit 5, an information storage unit 6, a data communication unit 7, a display unit 8, and a key input unit 9.

That is, the radio carrier signals arriving from the base stations CS1 to CSn are received by the antenna 11 and then input to the receiving unit 13 via the high frequency switch (SW) 12 of the radio unit 1. In the receiving unit 13, the received radio carrier signal is mixed with the local oscillation signal generated from the synthesizer 14 and down-converted into a received intermediate frequency signal. The local oscillation signal frequency generated from the synthesizer 14 is set to a value corresponding to the radio channel frequency according to an instruction from the control unit 5. Also, the radio unit 1 includes a reception field strength detection unit (RSSI) 16
Is provided. In this reception electric field strength detection unit 16,
The received electric field strengths of the radio carrier signals arriving from the base stations CS1 to CSn are detected, and the detected values are reported to the control unit 5 for, for example, determining and displaying the reception quality.

The received intermediate frequency signal output from the receiving unit 13 is input to the demodulation unit 21 of the modem unit 2. The demodulation section 21 performs digital demodulation of the received intermediate frequency signal, thereby reproducing a digital demodulated signal.

The TDMA decoding section 31 of the TDMA section 3
Separates the digital demodulated signal for each reception time slot. If the data of the separated slot is audio data, the audio data is transmitted to the interface unit 4.
To enter. On the other hand, if the data of the separated slot is packet data or control data, these data are input to the data communication unit 7.

The communication unit 4 has an ADPCM (Adaptive Diffe
rential Pulse Code Modulation) Transcoder 41
, A PCM codec 42, a speaker 43, and a microphone 44. The ADPCM transcoder 41 decodes the audio data output from the TDMA decoding unit 31. The PCM codec 42 uses the A
The digital audio signal output from the DPCM transcoder 41 is converted into an analog signal, and this audio signal is output from the speaker 43 as loudspeaker.

The data communication unit 7 receives the data output from the TDMA decoding unit 31 and supplies the data to the control unit 5. If the received data is control data, the control unit 5 analyzes the control data and performs necessary control.
On the other hand, if the received data is packet data arriving from a server device or the like, the packet data is depacketized, stored in the information storage unit 6, and supplied to the display unit 8 including, for example, a liquid crystal display (LCD). Display.

On the other hand, the voice signal of the user input to the microphone 44 is PCM-coded by the PCM codec 42, and is further compression-coded by the ADPCM transcoder 41. Then, the encoded audio data is TDM
It is input to the A encoding unit 32. The control data and packet data output from the control unit 5 are input to the TDMA encoding unit 32 via the data communication unit 7.

[0025] The TDMA encoding section 32
The digital audio data of each channel output from the CM transcoder 41 and the control data and packet data output from the data communication unit 7 are inserted into a transmission time slot designated by the control unit 5 and multiplexed. The modulation unit 22 digitally modulates the transmission intermediate frequency signal with the multiplexed digital communication signal output from the TDMA encoding unit 32, and inputs the modulated transmission intermediate frequency signal to the transmission unit 15.

The transmitting section 15 mixes the modulated transmission intermediate frequency signal with a local oscillation signal generated from the synthesizer 14, upconverts the mixed signal into a radio carrier frequency, and further amplifies the signal to a predetermined transmission power level. The radio carrier signal output from the transmitting unit 15 is transmitted from the antenna 11 via the high frequency switch 12 to the base stations CS1 to CSn.
Sent to

The control unit 5 controls the operation of the apparatus as a whole by using a microcomputer as a main control unit. In particular, a telephone directory management function and a wireless link between the base stations CS1 to CSn in connection with incoming and outgoing calls are connected. And a data reproduction processing function in the application layer.

The data communication section 7 has a data communication processing function in the data link layer, and is configured as follows, for example. FIG. 3 is a functional block diagram showing the configuration. That is, the data communication section 7 includes a data transmission / reception section 71, an interface section 72, and a data frame storage section 73, which are mutually connected via a data bus 74.

First, the interface section 72 exchanges a transmission data frame and a reception data frame with the control section 5. Further, the data frame storage unit 73 performs primary storage of the data frame received by the data transmission / reception unit 71 and temporary storage of the transmission data frame transferred from the control unit 5.

On the other hand, the data transmission / reception unit 71 includes a data frame transmission / reception circuit 711, an error detection circuit 712,
A Q control circuit 713 and a majority error correction circuit 714 are provided.

The data frame transmission / reception circuit 711 performs transmission / reception processing of data frames with the base stations CS1 to CSn according to the protocol specified in the data link layer. And stores the received data frame in the data frame storage circuit 73. At the same time, the transmission data frame transferred from the control unit 5 is read out from the data frame storage circuit 73 and output to the TDMA encoding unit 32.

The error detection circuit 712 detects an error in the data frame received by the data frame transmission / reception circuit 711. Then, the detection result is transmitted to the ARQ control circuit 7.
13 is notified.

When a data error is notified from the error detection circuit 712, the ARQ control circuit 713 generates a retransmission request for the target data frame, and sends the retransmission request from the data frame transmission / reception circuit 711 to the base station. And send it out. Also, the ARQ control circuit 713 determines whether or not an error-free received data frame has been received within the transmission delay time limit required by the control unit 5 during the ARQ control period. Then, when a received data frame having no error can be received within the time limit, the received data frame is read from the data frame storage unit 73 and transferred to the control unit 5 via the interface unit 72. On the other hand, when a received data frame having no error is not received within the time limit, an error correction instruction is given to the majority error correction circuit 714.

The majority error correction circuit 714 uses the ARQ
When an error correction instruction is given from the control circuit 713,
For three or more mutually corresponding data frames received within the time limit by the ARQ control, a majority decision process is performed by comparing in a bit unit. Then, the data frame obtained as a result of the majority decision processing is transferred to the interface unit 72 as an error-corrected received data frame, and transferred from the interface unit 72 to the control unit 5.

Next, the operation of the apparatus configured as described above will be described. Here, the data transmitted from the gateway GW is transferred to the mobile terminal device P via the base station CS1.
The case of receiving in S1 will be described as an example.

In the data communication mode, the mobile terminal P
The data communication unit 7 in S1 performs a data frame receiving operation according to the ARQ protocol. FIG. 4 shows an example of a data frame format in the ARQ protocol. That is, one data frame includes a control field, an information field, and a frame check sequence (FCS). Control information such as the sequence number and type of the data frame is inserted into the control field. In the information field, information data to be processed by the control unit 5 in the upper layer is inserted. FCS is
Used to detect data errors in data frames.

FIG. 6 shows an example of a data transmission operation according to the ARQ protocol, and shows a case where a selective retransmission (SR) system in consideration of a response delay time is applied. The number described on the transmission side corresponds to the transmission sequence number sequentially incremented and assigned for each data frame to be transmitted, and the number described on the reception side corresponds to the transmission sequence number assigned on the transmission side Respectively indicate transmission request numbers for the data frames to be transmitted.

For example, assume that a transmission error has occurred in the data frame of the transmission sequence number "2" as shown in FIG. 6 after the mobile terminal device PS1 starts receiving the data frame. Then, this transmission error is detected by the error detection circuit 712.
And the ARQ control circuit 713 is notified that an error has been detected. Upon receiving this notification, the ARQ control circuit 713
Repeatedly transmits the retransmission request of the transmission request number "2" to the base station CS1 at regular intervals.

On the other hand, upon receiving the retransmission request from mobile terminal apparatus PS1, base station CS1 on the transmission side updates the transmission request number of the requested data frame even if the response delay time has elapsed since the reception. If not, the data frame having the transmission sequence number requested by the retransmission request is retransmitted.

When a transmission error also occurs in the retransmitted data frame having the transmission sequence number “2”, the mobile terminal apparatus PS1 sends the transmission request number “2” to the ARQ control circuit 713.
Is repeatedly transmitted to the base station CS1 again. Upon receiving the retransmission request, the base station CS1 retransmits the data frame having the transmission sequence number requested by the retransmission request as described above.

Thereafter, the retransmission procedure for the data frame with the transmission sequence number "2" is repeatedly executed until the data frame with the transmission sequence number "2" without error can be received in the mobile terminal device PS1 on the receiving side. The data frames D21, D22,... Having errors received by repeating this retransmission procedure are all stored in the data frame storage unit 73.

When an error-free data frame of transmission sequence number "2" is received by the retransmission, ARQ
The control circuit 713 ends the retransmission procedure at that time. Then, the error-free data frame is read from the data frame storage unit 73, and the data frame is transferred to the control unit 5 via the interface unit 72.

On the other hand, during the repetition of the retransmission procedure,
The ARQ control circuit 713 measures the execution time,
If the time exceeds the transmission delay time limit T allowed by the control unit 5, the subsequent retransmission procedure for the data frame of the transmission sequence number "2" is abandoned, and the error correction instruction to the majority error correction circuit 714 is issued. give.

Then, the majority error correction circuit 714
A plurality of erroneous data frames received within the time limit T by repeating the retransmission procedure are read from the data frame storage unit 73, respectively. Then, these data frames are compared on a bit-by-bit basis to perform a majority decision process.

For example, as shown in FIG.
Of the three erroneous data frames D21, D2
Assuming that D2 and D23 have been received, the majority error correction circuit 714 performs majority processing on a bit-by-bit basis as shown in FIG. 5 to obtain a majority-taken data frame D20. Then, the majority data frame D20 is transferred from the interface unit 72 to the control unit 5.

As described above, in the present embodiment, when the ARQ control circuit 713 retransmits a data frame in which a transmission error has been detected in accordance with the ARQ protocol to receive an error-free data frame, no error is detected. It monitors whether or not the data frame is received within the transmission delay time limit T determined for the reason of the received data reproduction processing of the control unit 5. If the data frame is received within the time limit T, the received data frame is transferred as it is to the control unit 5 via the interface unit 72, and if no error-free data frame is received within the time limit, Reads a data frame having three or more errors received within the time limit T from the data frame storage unit 73 by the majority error correction circuit 714, performs a majority process on a bit-by-bit basis, and obtains the data after the majority process. The received data frame is transferred to the control unit 5 as a received data frame.

Therefore, according to this embodiment, if the error correction processing by the retransmission procedure is not completed within the transmission delay time limit T requested by the control unit 5, the retransmission procedure is abandoned at that time, and the majority decision is made. The error is corrected by the processing. For this reason, a problem in which the retransmission procedure is repeated endlessly is prevented, and error correction can be performed by effectively using a plurality of data frames including an error received within the time limit T. Therefore, as compared with the conventional method in which the reproduction procedure is repeated endlessly or the method in which the data frame received last within the time limit is supplied to the control unit 5 as the received data frame as it is, the transmission delay is more effectively suppressed. Error correction can be performed. FIG. 7 shows a conventional operation in which the reproduction procedure is repeated endlessly, in comparison with the operation of the present embodiment shown in FIG.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the case where the error correction is performed using only the ARQ scheme has been described.
The RQ scheme and an error correction scheme using an error correction code may be used together. In this case, for example, if an error is detected in a received data frame, the error is corrected by an error correction decoding process, and if the error cannot be corrected even by this process, a retransmission procedure by the ARQ scheme is executed. Good to do.

In the majority error correction process, when a large number of data frames containing an error are received within the time limit, the majority process is not performed using all the data frames, but a part of them is performed. May be selected to perform majority processing. In this way, the time required for the majority processing can be reduced.

Further, when performing the majority decision processing, first, a plurality of data frames received within the time limit are roughly compared, for example, in units of a plurality of bits to obtain an average. The exclusion may be made, and majority processing may be performed between the remaining data frames.

In addition, the type and configuration of the data transmission system, the configuration of the mobile terminal device, the configuration of the data communication unit, the content of the majority error correction process, and the like are variously modified without departing from the gist of the present invention. it can.

[0052]

As described above in detail, according to the present invention, in a data communication apparatus for detecting an error in received data and executing a retransmission procedure based on the detection result, a predetermined value is set for reproducing the received data. Determining means for determining whether error correction of data by the retransmission procedure has been completed within the given predetermined time, comprising error correction means, when it is determined that error correction is not completed by the determination means, The error correction means performs majority processing on the received data received a plurality of times within the predetermined time, and outputs the processing result as error-corrected received data.

Therefore, according to the present invention, it is possible to provide a data communication device and a mobile terminal device capable of performing effective error correction without wasting data retransmission even when transmission delay is limited.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a mobile data communication system according to the present invention.

FIG. 2 is a circuit block diagram showing a configuration of a mobile terminal device used in the system shown in FIG.

3 is a circuit block diagram showing a configuration of a data communication unit of the mobile terminal device shown in FIG.

FIG. 4 is a diagram showing an example of a data frame format used in the ARQ protocol.

FIG. 5 is a view for explaining the operation of the data communication unit shown in FIG. 3;

FIG. 6 is a view showing an example of a retransmission procedure by the data communication unit shown in FIG. 3;

FIG. 7 is a diagram showing a conventional retransmission procedure in which a reproduction procedure is repeated endlessly.

[Explanation of symbols]

 CS1 to CSn base station PS1 to PSm mobile terminal device IN1 ISDN network IN2 I 'network PN private line network AS server device GW gateway 1 radio unit 2 modem unit 3 TDMA unit 4 communication unit 5 ... Control unit 6 ... Information storage unit 7 ... Data communication unit 8 ... Display unit 9 ... Input unit 11 ... Antenna 12 ... High frequency switch (SW) 13 ... Reception unit 14 ... Synthesizer 15 ... Transmission unit 16 ... Reception electric field strength detection unit (RSSI) 21 demodulation unit 22 modulation unit 31 TDMA decoding unit 32 TDMA encoding unit 41 ADPCM transcoder 42 PCM codec 43 speaker 44 microphone 71 data frame transmitting / receiving unit 72 interface unit 73 data frame Storage unit 74 Data bus 711 Data frame transmission / reception circuit 71 ... error detecting circuit 713 ... ARQ control circuit 714 ... majority error correction circuit

Claims (4)

[Claims] 1. A data communication apparatus for detecting an error in received data and executing a retransmission procedure based on a result of the detection, wherein the data communication apparatus performs the retransmission procedure within a predetermined time for reproducing the received data. Judging means for judging whether or not the error correction of the data has been completed; and, when the judging means judges that the error correction has not been completed, the majority decision processing of the corresponding plurality of received data received within the predetermined time is performed. A data communication apparatus comprising: an error correction unit that outputs a result of the processing as received data with error correction. 2. The data communication apparatus according to claim 1, wherein said error correction means compares a plurality of pieces of received data bit by bit and performs majority processing. 3. A mobile station connected to at least one base station forming a wireless area via a wireless channel, performing error detection on data received from the base station, and executing a retransmission procedure based on the detection result. A terminal device for determining whether or not the error correction of the data by the retransmission procedure is completed within a predetermined time which is predetermined in reproducing the received data; and the error correction is not completed by the determination unit. When it is determined that, the error correction means that performs majority processing of the corresponding plurality of times of received data received within the predetermined time and outputs the processing result as error-corrected received data. Mobile terminal device. 4. The mobile terminal device according to claim 3, wherein said error correction means compares a plurality of pieces of received data bit by bit and performs majority processing.