JP2003273842A - Data transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: when a phasing frequency is lowered to result in a drop segment length becoming long in data transmission, an error- burst length by phasing becomes long relative to an interleave size N; this hampers sufficient diffusion of error bursts, degrading an error correction capability and thus an error rate. <P>SOLUTION: The phasing frequency depends on a traveling speed of a movable station. The state of a transmission path is determined based on speed information provided by a speedometer and received field strength indication (RSSI). This information is transmitted, together with ACK/NACK data, to a transmitter station, thereby reducing instability of data transmission caused by phasing. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission system in a digital mobile radio communication system.

[0002]

2. Description of the Related Art In a digital mobile radio communication system, when data transmission is performed, it is necessary to add redundancy to transmission information and correct and detect a channel error caused by fading or the like. The conventional technique will be described with reference to FIG. The encoding and decoding processes in the conventional technology are based on FACCH (Fast Associated) in the ARIB STD-T61 standard.
In accordance with Control CHannel) processing, ARQ (Automatic Re
Since the peat reQuest) method is simplex communication, SAW (Stop
An example using the And Wait method will be described.

In FIG. 2, 101 is a data input terminal,
102 is an input buffer, 103 is a transmitting station disassembly / assembly information adding unit, and 104 is a transmitting station CRC (Cyclic Redundancy Chec).
k) Coding unit, 105 is a transmission station convolutional coding unit, 106
Is a transmitting station interleave processing unit, 107 is a transmitting station frame assembling unit, 108 is a transmitting station transmitting unit, 109 is a transmitting signal output terminal, 110 is a receiving station receiving signal input terminal, 111 is a receiving station receiving unit, and 112 is a receiving station frame. Decomposing section, 113 is a receiving station deinterleave processing section, 114 is a receiving station Viterbi decoding section, 115 is a receiving station CRC verification section, 116 is a receiving station disassembly and assembly information verification section, 117 is an output buffer, 118 is a data output terminal, 119. Is ACK (ACKnowledgment) / NAC
K (Negative ACKnowledgment) data generator, 120 receiving station disassembly / assembly information adding section, 121 receiving station CRC coding section, 122 receiving station convolutional coding section, 123 receiving station interleave processing section, and 124 receiving station frame Assembling unit, 125 is a receiving station transmitting unit, 126 is a receiving station transmitting signal output terminal, 127 is a transmitting station receiving signal input terminal, 128 is a transmitting station receiving unit, 129 is a transmitting station frame disassembling unit, and 130 is a transmitting station deinterleaving process. Part, 131 is a transmitting station Viterbi decoding part, 132 is a transmitting station CRC verification part, and 133 is ACK /
The NACK data determination unit and 134 indicate a data transmission control unit.

The data input from the data input terminal 101 is fetched into the buffer 102, and when the data for one frame is accumulated, it is output to the transmitting station disassembly / assembly information adding section 103. The transmitting station disassembly / assembly information adding unit 103 adds the position (information such as the head and the end) in the upper layer of the transmission data, and the transmitting station CRC (Cyclic Redundancy Chec).
k) Output to the encoding unit 104. Transmission station CRC encoding unit 1
04, CRC for the purpose of error detection in transmission information
After adding the code, the code is output to the transmission station convolutional coding unit 105. The transmission station convolutional coding unit 105 performs convolutional coding with a constraint length K = 6 and a coding rate R = 1/2 for the purpose of error correction. The transmission station interleave processing unit 106 performs a 16-bit depth interleaving process on the encoded data. The data after the interleave processing is incorporated in the FACCH section in the frame shown in FIG. The transmitting station transmitting unit 108 performs modulation processing and high frequency conversion on the input data and transmits the input data from the transmitting station signal output terminal 109. The transmitting station follows A from the receiving station according to the SAW method.
The next signal transmission is not performed until the CK / NACK signal is received.

The transmitting signal is received by the receiving station receiving signal input terminal 110.
Is input to the receiving station receiving unit 111 via. The receiving station receiving unit 111 amplifies the received signal and band-limits it, then performs data reproduction processing, and outputs the reproduced received data to the receiving station frame decomposing unit 112. The receiving station frame decomposing unit 112 decomposes the received data for each channel and outputs the FACCH portion data to the receiving station deinterleaving processing unit 113.
The receiving station deinterleaving processing unit 113 performs deinterleaving processing so that the arrangement of the received data is the same as that before input to the transmitting station interleaving processing unit 106, and then outputs to the receiving station Viterbi decoding processing unit 114. The receiving station Viterbi decoding processing unit 114 performs Viterbi decoding on the received data, performs error correction, and outputs the received data to the receiving station CRC verification unit 115. The receiving station CRC verification unit 115 performs a CRC check to check the validity of the received data. At that time,
If there is no error, the received data is output to the receiving station disassembly / assembly information verification unit 116. Receiving station disassembly / assembly information verification unit 116
Then, the data is output to the output buffer 117 according to the data position information added on the transmitting station side. Output buffer 1
17 outputs the data to the data output terminal 118 when the data input is completed.

On the contrary, the receiving station CRC verification section 115
If an error is detected in, the received data is not output to the receiving station disassembly / assembly information adding unit 116. The error detection information from the reception station CRC verification unit 115 is also output to the ACK / NACK data generation unit 119, and the ACK / NACK data generation unit 119 generates data indicating ACK / NACK according to the input information, and the reception station disassembled and assembled. The information is output to the information adding unit 120. The generated ACK / NACK data includes the receiving station CRC encoding processing unit 121, the receiving station convolutional encoding processing unit 122, the receiving station interleaving processing unit 123, and the receiving station frame assembling unit 12 as in the encoding processing at the transmitting station.
After being stored in the frame as FACCH data via 4, the data is transmitted via the receiving station transmitter 125.

The transmission data is input from the transmission station reception signal input terminal 127 via the reception antenna, and the transmission station reception unit 1
Input to 28. Hereinafter, similarly to the receiving station decoding unit, the ACK / NACK data is reproduced via the transmitting station frame decomposing unit 129, the transmitting station deinterleave processing unit 130, the transmitting station Viterbi decoding unit 131, and the transmitting station CRC verification unit 132.
The data is output to the ACK / NACK data determination unit 133. AC
The K / NACK data determination unit 133 determines whether the receiving station has successfully received the data based on the ACK / NACK signal. When the ACK is confirmed, the reception success information is output to the data transmission control unit 134, and when the NACK is confirmed or the CRC error is detected by the transmission station CRC verification unit 132, the reception failure information is transmitted to the data transmission control unit 134. Send information. The data transmission control unit 134 performs processing in accordance with the received reception correctness information. If it is successful, the input buffer 102 is controlled to permit data input, and the signal position information is sent to the transmitting station disassembly / assembly information adding unit 103. If unsuccessful, the input buffer 102 and the transmitting station disassembly / assembly information addition 103 are controlled so that the previously transmitted data is transmitted. Data transmission is realized by repeating the above procedure until the end of data transmission.

[0008]

FIG. 4 shows an example of the FACCH error rate with respect to the received power in a fading environment. As is clear from the figure, the error rate deteriorates as the fading frequency decreases. This is because the fading period is long with respect to the interleave size of 16 bits, burst errors are not sufficiently dispersed, and the error correction capability by Viterbi decoding is reduced. The signal flow between the transmitting and receiving stations in such a case is shown in FIG. During data transmission, the fading frequency is lowered and the error correction capability is lowered, so that the data M is repeatedly transmitted. The data M is retransmitted until the fading frequency becomes high and the error correction capability is improved. Therefore, even if the received power is the same, if the fading frequency is different, the error correction capability is different, and there is a problem that stable data transmission cannot be performed. It is an object of the present invention to provide a data transmission system that solves the above problems and eliminates instability due to fading frequencies.

[0009]

A change in error rate due to a difference in fading frequency occurs because burst errors cannot be diffused sufficiently and error correction in Viterbi decoding is insufficient. In order to spread the error sufficiently, it is necessary to detect the fading frequency and reflect it in the interleave size. When the fading frequency is low, the number of drops per unit time due to fading is small, but the drop time is large and the burst error generation length is long, so the interleave size is increased and the spreading factor is increased. In addition, when the fading frequency is high, the drop time is short, but the number of drops per unit time is large, so reduce the interleave size to avoid concentration of errors that have already spread due to interleaving. Take control. Generally, the fading frequency depends most on the moving speed of the mobile station.

In order to achieve the above object, the present invention determines the state of the propagation path based on the information from the speedometer and calculates the optimum interleave size when an error is detected in the transmission data. The information is configured to be transmitted to the transmitting station together with the ACK / NACK data so as to reduce the change in the error correction capability due to fading.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. 1 is an example of a functional block showing an embodiment of the present invention. In FIG. 1, 135 is a speedometer, 136 is an analog digital converter (ADC),
37 indicates an interleave size setting unit, 138 indicates a data generation unit and 139 interleave size determination unit. Also,
The same numbers are given to the functional elements having the same functions as the constituent elements described in the related art.

In FIG. 1, the data input from the data input terminal 101 is taken into the buffer 102, and when the data for one frame is accumulated, it is output to the transmitting station disassembly / assembly information adding unit 103. In the transmitting station disassembly / assembly information adding unit 103, the position (information such as the head and the end) in the upper layer of the transmission data is added, and the transmitting station CRC (Cyclic
Redundancy Check) Output to the encoding unit 104. The transmitting station CRC encoding unit 104 adds a CRC code for the purpose of error detection to the transmission information, and then outputs the transmission information to the transmitting station convolutional encoding unit 105. Transmission station convolutional coding unit 10
In 5, convolutional coding with a constraint length K = 6 and a coding rate R = 1/2 is performed for the purpose of error correction. The interleave size determination unit 139 controls the interleave processing unit 106 to perform interleaving with a specified value of 16 bits at the start of transmission. The encoded data is subjected to an interleaving process with an interleave size of 16 bits in the transmission station interleave processing unit 106 under the control of the interleave size determination unit 139. The data after the interleaving processing is incorporated in the FACCH part in the frame shown in FIG. The transmitting station transmitting unit 108 performs modulation processing and high frequency conversion on the input data, and transmits the transmitting station signal output terminal 1
Sent from 09.

The transmission signal is received by the reception signal input terminal 110 of the reception station.
Is input to the receiving station receiving unit 111 via. The receiving station receiving unit 111 amplifies the received signal and band-limits it, then performs data reproduction processing, and outputs the reproduced received data to the receiving station frame decomposing unit 112. The receiving station frame decomposing unit 112 decomposes the received data for each channel and outputs the FACCH portion data to the receiving station deinterleaving processing unit 113. At the start of reception, the interleave size setting unit 137 controls the receiving station deinterleave processing unit 113 to perform deinterleaving with a specified value of 16 bits. The receiving station deinterleave processing unit 113 performs deinterleaving processing according to the control from the interleave size setting unit 137 to make the arrangement of the received data similar to the state before inputting to the transmitting station interleave processing unit 106, and then the receiving station Viterbi Decoding processing unit 114
Output to. The receiving station Viterbi decoding processing unit 114 performs Viterbi decoding on the received data, corrects the error, and then receives the receiving station CR.
Output to the C verification unit 115. Receiving station CRC verification unit 115
Then, a CRC check is performed to check the validity of the received data.

When there is no error, the received data is output to the receiving station disassembly / assembly information verification unit 116, the interleave size setting unit 137 is controlled to maintain the current interleave size, and the data generation unit 138 is sent ACK data. Control to generate. The receiving station disassembly / assembly information verification unit 116 outputs the data to the output buffer 117 according to the data position information added on the transmitting station side. The output buffer 117 outputs the data to the data output terminal 118 when the data input is completed.

On the contrary, the receiving station CRC verification unit 115
If an error is detected in step 1, the received data is not output to the receiving station disassembly / assembly information adding unit 116, an interleave size change instruction is output to the interleave size generation unit 137, and NACK data is output to the data generation unit 138. Control to generate. Interleave size setting unit 137
Then, the speed information of the speedometer 135 is acquired via the ADC 136, the current propagation path state is determined, the optimum interleave size is determined, and the data is output to the data generation unit 138. The data generation unit 138 generates the information of the CRC verification unit 115 and the interleave size setting unit 137 as transmission data. The generated data is received by the receiving station CRC encoding processing unit 121, the receiving station convolutional encoding processing unit 122, and the receiving station interleaving processing unit 123, as in the encoding processing at the transmitting station.
After storing the FACCH data in the frame via the receiving station frame assembling unit 124, the receiving station transmitting unit 125
To send via.

The transmission data is input from the transmission station reception signal input terminal 127 through the reception antenna, and the transmission station reception unit 12
Input to 8. Hereinafter, similar to the receiving station decoding section, the transmitting station frame disassembling section 129 and the transmitting station deinterleave processing section 13
0, the transmission station Viterbi decoding unit 131, and the transmission station CRC verification unit 132 to reproduce the received data, and ACK / NACK
The data is output to the data determination unit 133. The ACK / NACK data determination unit 133 determines whether the receiving station has successfully received the data, based on the ACK / NACK signal. If the ACK is confirmed, the reception success information is sent to the data transmission control unit 134.
Output to. If NACK is confirmed, the received data is output to the interleave size determination unit 139, and the reception failure information is transmitted to the data transmission control unit 134.

Interleave determination section 139 acquires the interleave size from the received data and outputs it to transmitting station interleave processing section 106. When a CRC error is detected, the interleave size is not changed and the data transmission control unit 134 is controlled to transfer the same data again. The data transmission control unit 134 performs processing according to the received reception correctness information. If successful, the input buffer 102 is controlled to allow data input, and
The signal position information is sent to the transmitting station disassembly / assembly information adding unit 103. If unsuccessful, the input buffer 102 and the transmitter disassembly / assembly information adding unit 103 are controlled so as to send the previously sent data. Data transmission is realized by repeatedly executing the above procedure until the end of data transmission.

FIG. 6 shows a signal flow of the above processing.
At the start of transmission, the interleave size is the specified value (16 bi
In step t), when the fading frequency is lowered and an error is detected in the receiving station, the receiving station sends the interleave size A (A has a value of 16 bits or more) together with the NACK signal. The transmitting station reads the interleave size A and reflects it in the next transmission. Further, when the fading frequency changes and an error occurs, the interleave size is changed from A to B again (A <B if the fading frequency becomes low, B> A if the fading frequency becomes high),
Achieve stable data transmission.

[0019]

According to the present invention, it is possible to reduce the deterioration of the reception error rate and the instability of data transmission due to fading, and to realize stable data transmission.

[Brief description of drawings]

FIG. 1 is a block diagram showing a data transmission system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional data transmission method.

FIG. 3 is a block diagram of a data transmission frame.

FIG. 4 shows an example of FACCH error rate characteristics.

FIG. 5 shows an example of a signal flow according to the related art.

FIG. 6 shows an example of a signal flow according to the present invention.

[Explanation of symbols]

101: data input terminal, 102: input buffer, 10
3: Transmission station disassembly / assembly information addition unit, 104: Transmission station CRC
(Cyclic Redundancy Check) coding unit, 105: transmission station convolutional coding unit, 106: transmission station interleave processing unit, 107: transmission station frame assembly unit, 108: transmission station transmission unit, 109: transmission signal output terminal, 110: Reception station reception signal input terminal, 111: reception station reception section, 112: reception station frame decomposition section, 113: reception station deinterleave processing section, 114: reception station Viterbi decoding section, 115: reception station CR
C verification unit, 116: receiving station disassembly and assembly information verification unit, 11
7: output buffer, 118: data output terminal, 119:
ACK / NACK data generation unit, 120: receiving station disassembly / assembly information adding unit, 121: receiving station CRC encoding unit, 12
2: receiving station convolutional encoding unit, 123: receiving station interleaving processing unit, 124: receiving station frame assembling unit, 125:
Receiving station transmitting unit, 126: Receiving station transmission signal output terminal, 12
7: transmitter station reception signal input terminal, 128: transmitter station receiver,
129: transmitting station frame disassembling unit, 130: transmitting station deinterleaving processing unit, 131: transmitting station Viterbi decoding unit, 13
2: Transmission station CRC verification unit, 133: ACK / NACK data determination unit, 134: Data transmission control unit, 135: Speedometer, 136: Analog-digital converter, 137: Interleave size setting unit, 138: Data generation unit, 139 :
Interleave size determination unit.

Claims (4)

[Claims] 1. A data transmission system, characterized in that, in a mobile station of a digital radio communication system of a simplex communication system, a channel characteristic is detected and an error correction capability is optimized during data transmission. 2. The data transmission method according to claim 1, further comprising: a speedometer and means for changing an interleave size (depth) corresponding to speed information detected by the speedometer. Transmission method. 3. The data transmission method according to claim 2, wherein the interleave size is increased when the speed of the mobile station is high, and the interleave size is decreased when the speed of the mobile station is low. 4. The data transmission method according to claim 3, wherein the interleave size is ARQ (Automatic Repeat re).
Quest) ACK (ACKnowledgment) / NACK (Negative A
CKnowledgment) signal is transmitted together with the data transmission method.