JP2001186024A - Error correction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an error correction device that can keep a prescribed level of reception quality and avoid useless repetition of turbo decoding thereby realizing small power consumption and reduction in a reception delay. SOLUTION: The error correction device is provided with a turbo decoder 106 that provides the output of a decoded result by repeating error correction processing to a received signal for a prescribed number of times, a turbo decoder performance characteristic table 105 that stores information denoting a signal with respect to an interruption ratio (SIR) of the received signal and a parameter to control the number of repetitive decoding times of the turbo decoder 106 in cross-reference with each other, an SIR measurement section 104 that detects the SIR of the received signal, and a control section 111 that controls the number of repetitive decoding times of the turbo decoder 106 according to the parameter selected from the turbo decoder performance characteristic table 105 in response to the detected SIR.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error correction device.

[0002]

2. Description of the Related Art Various error correction devices for performing error correction on a signal sequence received via a transmission path having an error and decoding the signal sequence have been known. A turbo decoder formed by connecting two recursive decoders is a decoder that can improve the error correction capability by performing iterative error correction, and is an error correction method suitable for space communication, satellite communication, and mobile communication. It is. However, the repetitive processing of the turbo decoder leads to an increase in power consumption and a large delay in the reception processing. Further, error correction may be performed more than required reception quality by performing excessive repetitive decoding. Also in this case, power consumption and reception delay increase.

One solution to this problem is to make a hard decision for each turbo decoding, perform a CRC check, and then terminate decoding if there is no error in the received sequence. A scheme for performing decoding continuously has been proposed. According to this method, the number of repetitions of the turbo decoder can be optimized, but the hard decision and the CRC check must be performed each time turbo decoding is performed, so that decoding time is further increased and reception delay is increased. Will increase.

[0004]

As described above, the conventional turbo decoder has a problem that power consumption is increased and reception processing delay is increased due to excessive repetitive decoding. Furthermore, control of iterative decoding including a CRC check must be performed for each turbo decoding, and there is a problem that a processing time is added to one turbo decoding and a reception delay increases.

The present invention has been made in view of such a problem, and an object of the present invention is to provide an error correction device capable of realizing low power consumption and reduction of reception delay.

[0006]

In order to solve the above-mentioned problems, an error correction apparatus according to a first aspect of the present invention provides a turbo decoder which outputs a decoding result by repeating an error correction process on a received signal a predetermined number of times. And information about the state of the received signal, storage means for storing the parameters for controlling the decoding process of the turbo decoder in association with each other, detecting means for detecting the state of the received signal, Control means for controlling a decoding process of the turbo decoder by using a parameter selected from the storage means according to a state of the received signal.

Further, an error correction device according to a second aspect of the present invention
In the first invention, the storage unit stores the signal-to-interference ratio (SIR) of the received signal and the number of times of iterative decoding of the turbo decoder in association with each other.

Further, an error correction device according to a third aspect of the present invention
In the first invention, the storage unit stores the reception electric field strength of the reception signal and the number of times of iterative decoding of the turbo decoder in association with each other.

Further, an error correction device according to a fourth aspect of the present invention comprises:
In the first invention, the storage unit stores information relating to the presence or absence of puncturing indicating the presence or absence of thinning of the received signal and the number of times of repetitive decoding of the turbo decoder in association with each other.

Further, an error correction device according to a fifth aspect of the present invention
In the first invention, the storage unit stores the thinning rate of the received signal and the number of times of iterative decoding of the turbo decoder in association with each other.

According to a sixth aspect of the present invention, there is provided an error correction apparatus in a CDMA radio communication system, comprising: a turbo decoder for outputting a decoding result by repeating an error correction process on a received signal a predetermined number of times; Detecting means for detecting a signal-to-interference ratio (SIR), transmitting means for transmitting control information for controlling transmission power generated based on the detected SIR to a transmitting side, based on the control information, A parameter generation unit that generates a parameter for controlling a decoding process of the turbo decoder; and a control unit that controls a decoding process of the turbo decoder using the generated parameter.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an outline of the present embodiment will be described. In the present embodiment, a performance characteristic table of a turbo decoder is provided. When the turbo decoder performs decoding, a corresponding parameter is selected from the performance characteristic table according to the state of a received signal, and error correction is performed using the selected parameter. . Here, the performance characteristic table of the turbo decoder includes (1) the number of iterative decodings corresponding to the received signal's SIR (signal interference ratio), and (2) the number of iterative decodings corresponding to the received signal strength of the received signal. , (3) the number of repetitive decodings corresponding to the presence or absence of puncturing of the encoded data, and (5) the number of repetitive decodings corresponding to the thinning rate of the encoded data. By using such a table, control is performed such that the number of times of decoding at the time of turbo decoding becomes the optimum number of times of iterative decoding.

In a CDMA radio communication system, when error correction is performed by a turbo decoder, the number of repetitions of the turbo decoder is optimized by controlling the number of repetitions of the turbo decoder using information (TPC bit) of closed loop power control. Therefore, low power consumption and reduction of reception delay can be realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a CDMA wireless terminal equipped with the turbo decoder according to the present embodiment. FIG.
In, the data received by the antenna 101 is
The multipath is separated in the matched filter 102. The separated multipaths are combined by the rake combiner 103. The combined signal is sent to SIR measurement section 104. The SIR measuring section 104 measures the SIR of the combined signal. Also, the rake synthesizer 103
Is sent to the turbo decoder 106 and subjected to error correction. At this time, control section 111 sets the optimum decoding parameters selected from turbo decoder performance characteristic table 105 in turbo decoder 106 based on the signal from SIR measurement section 104 or protocol control section 107.

On the other hand, TPC control section 109 adds TPC to received data based on the measurement result in SIR measurement section 104.
The control information is sent to the modulator 110 after being added. Modulator 1
At 10, the received signal is modulated, spread, and frequency-modulated, and then transmitted via the antenna 101.

(First Embodiment) FIG. 2 is a configuration diagram for explaining a first embodiment of the present invention. Turbo decoder 20
3 has two decoders 2031 and 2032,
The soft output error correction in the two decoders 2031 and 2032 is defined as one decoding process of the turbo decoder 203. The decoder 1 (2031) receives the signal 1 as the information bit I and the signal 2 as the first parity bit p1.
And the output of the deinterleave circuit 2036 as input, performs soft output error correction, and sends the result to the interleave circuit 2035. The interleave circuit 2035 is a part that rearranges input signals according to a predetermined rule. The deinterleave circuit 2036 is a part that performs a process of returning the rearranged signals to the original arrangement. Decoder 2 (2032) outputs a signal obtained by rearranging information bits I as received signal 1 by interleave circuit 2034,
Soft output error correction is performed using the output of the interleave circuit 2035 and the received signal 3 as the second parity bit p2 as inputs, and the result is deinterleaved by the deinterleave circuit 203.
6 to the decoder 1 (2031). As a result, the decoding process is repeatedly performed.

After a predetermined number of decodings, the decoding result of the decoder 2 (2032) is sent to the hard decision unit 2033, and the soft output result from the decoder 2 (2032) is
It is output after the hard decision processing for converting to the corresponding binary data is performed.

In this case, the number of times of iterative decoding in turbo decoder 203 is controlled by control section 204 as follows. That is, the present embodiment includes the turbo decoder performance characteristic table 201 in which the signal-to-interference ratio (SIR) of the received signal is stored in association with the number of repetitive decodings as a parameter for controlling decoding of the turbo decoder 203. Of the received signal measured by the SIR measurement unit 202
When the IR value is sent, the number of times of repeated decoding corresponding to the SIR value is searched and sent to the control unit 204. The control unit 204 determines the number of times of iterative decoding as the hard decision unit 2033.
Set to. After performing the decoding process for the set number of times, the turbo decoder 203 performs a hard decision on the output of the decoder 2 (2032) by the hard decision unit 2033 and outputs the result.

Thus, when the SIR value is small,
That is, when the reception quality is poor, control is performed so as to increase the number of repetitive decodings. When the SIR value is large, that is, when the reception quality is good, the control is performed so that the number of repetitive decodings is reduced. It is possible to realize a reduction in delay.

(Second Embodiment) FIG. 3 is a configuration diagram for explaining a second embodiment of the present invention. Turbo decoder 30
3 is a decoder 1 (3031) and a decoder 2 (3031)
2) It is composed of interleave circuits 3034 and 3035, deinterleave circuit 3036, and hard decision section 3033, and the operation is the same as that of the first embodiment.

The second embodiment is characterized in that a turbo decoder performance characteristic table 301 is provided in which SIR values are associated with the number of times of iterative decoding of turbo decoding. S
IR measuring section 302 first obtains the received electric field strength of the received signal, and then obtains the interference power by obtaining the variance of the received electric field strength. Finally, the SIR value is obtained by taking the ratio of the received electric field strength to the interference power. The received electric field strength measured by the SIR measuring section 302 is based on the turbo decoder performance characteristic table 30.
Sent to 1. In the turbo decoder performance characteristic table 301, the number of times of repeated decoding corresponding to the received received field strength is searched and sent to the control unit 304. Control unit 304
Sets the number of times of iterative decoding in the hard decision unit 3033. After performing the decoding process for the set number of times, the turbo decoder 303 performs a hard decision on the output of the decoder 2 (3032) by the hard decision unit 3033 and outputs the result.

In the present embodiment, taking into account that the time required to obtain the interference power may cause a time lag between the currently received signal and its SIR value, the reception is considered. By controlling the number of times of iterative decoding of turbo decoding based on the electric field strength, it is possible to minimize a time lag.

(Third Embodiment) A third embodiment of the present invention will be described below. FIG. 4 is a diagram showing a configuration of a turbo encoder to which the third embodiment of the present invention is applied, wherein an interleave circuit 200 and two recursive systematic convolutional code generation units 2
01 and 202. In a turbo encoder, since two parity bits are usually added to input information bits, the coding rate is 1/3.

However, as shown in FIG.
3, a parity bit p1 and p2 are alternately selected and transmitted (punctured) to reduce the coding rate to 、, thereby improving the channel capacity. On the other hand, the performance of the turbo decoder has a coding rate of 1/3.
The coding rate of 1/2 is more deteriorated when turbo decoding is performed. Therefore, in the third embodiment, in order to compensate for this drawback, if there is puncturing, the number of times of repeated decoding of turbo decoding is increased.

FIG. 6 is a configuration diagram for explaining a third embodiment of the present invention. The turbo decoder 603 is the decoder 1
(6031), decoder 2 (6032), interleave circuits 6034 and 6035, deinterleave circuit 60
36, a hard decision unit 6033, the operation of which is the first
This is the same as the embodiment.

The third embodiment is characterized in that a turbo decoder performance characteristic table 601 in which information on the presence or absence of puncturing is associated with the number of times of iterative decoding of turbo decoding is provided. The presence or absence of puncturing is determined by performing negotiation with the transmitting side before starting communication.

When information about the presence or absence of puncturing is notified from the protocol control unit 602, the number of repetitive decodings corresponding to the presence or absence of puncturing is retrieved from the turbo decoder performance characteristic table 601 and sent to the control unit 604. The control unit 604 determines the number of times of iterative decoding by the hard decision unit 6.
By setting to 033, the number of times of iterative decoding in the turbo decoder 603 is controlled. In this way, even if the coding rate is 1/2 due to puncturing, decoding can be performed without deteriorating the error correction rate. As a result, good reception quality can be maintained.
Unnecessary repetition of turbo decoding can be avoided, and power consumption can be reduced and reception delay can be reduced.

(Fourth Embodiment) Hereinafter, a fourth embodiment of the present invention will be described. If the transmission rate of information after turbo encoding does not match the actual transmission rate of wireless communication, in order to maintain consistency, part of the turbo encoded data is thinned out or the same code is repeatedly transmitted. However, the present embodiment is an embodiment that takes this into consideration.

FIG. 7 is a block diagram showing a configuration for performing speed adjustment after turbo coding. For example, when the wireless transmission rate is lower than the information rate after turbo coding, the coded bits from the turbo encoder 250 are thinned out based on the adjustment rate setting from the adjustment rate setting unit 254, and then transmitted. I do. That is, the encoded information bit I and the first,
For each of the second parity bits p1 and p2, a bit pattern to be thinned out is calculated by the speed adjustment units 251 to 253, and thinning processing is performed. The adjustment rate at this time is determined by performing negotiation with the transmitting side before starting communication.

Since the error correction capability at the time of reception is degraded as the rate at which the information after turbo encoding is thinned out increases, the error correction ability is increased by increasing the number of turbo decodings according to the thinning rate. It is possible to improve and maintain good reception quality.

FIG. 8 is a block diagram for explaining a fourth embodiment of the present invention. Turbo decoder 803 is decoder 1
(8031), decoder 2 (8032), interleave circuits 8034 and 8035, deinterleave circuit 80
36, a hard decision unit 8033, the operation of which is the first
This is the same as the embodiment.

The fourth embodiment is characterized in that a turbo decoder performance characteristic table 801 in which information on a speed adjustment rate is associated with the number of times of iterative decoding of turbo decoding is provided. Before starting communication, a predetermined speed adjustment rate is notified to the turbo decoder performance characteristic table 801. In the turbo decoder performance characteristic table 801, the number of times of iterative decoding corresponding to this rate adjustment rate is searched and sent to the control unit 804. The control unit 804 controls the number of times of iterative decoding in the turbo decoder 803 by setting the number of times of iterative decoding in the hard decision unit 8033.

In this way, the number of repetitive decodings of the turbo decoder 803 is controlled according to the rate adjustment rate, so that good reception quality can be maintained and unnecessary turbo decoding repetition can be avoided. it can. As a result, it is possible to reduce power consumption and reduce reception delay.

(Fifth Embodiment) Hereinafter, a fifth embodiment of the present invention will be described. In a CDMA wireless communication system, reception quality is kept constant by performing closed-loop power control, and further, interference is not given to other terminals or base stations. This closed loop power control is generally performed by adding a predetermined TPC bit to transmission data in a TCB control unit.

FIG. 9 is a block diagram for explaining a fifth embodiment of the present invention. The turbo decoder 903 is the decoder 1
(9031), decoder 2 (9032), interleave circuits 9034 and 9035, deinterleave circuit 90
36, a hard decision unit 9033, the operation of which is the first
This is the same as the embodiment. The fifth embodiment is characterized in that it includes a repetition number generation unit 901 that generates the number of repetition decodings of the turbo decoder 903 based on the TPC value.

The SI measured by the SIR measuring unit 902
When the R value is larger than a preset value, the TPC control section 109 inserts a TPC bit for instructing the transmitting side to reduce the transmission power into transmission data and transmits the transmission data. When the measured SIR value is smaller than a preset value, the TPC control unit 109 inserts a TPC bit for instructing the transmitting side to increase the transmission power into the transmission data and transmits the transmission data. I do. Where TP
If the C bit is set to increase the transmission power on the transmitting side, it means that the reception quality is not good, and T
If the PC bit is set to lower the transmission power on the transmitting side, it means that the reception quality is good. Therefore, in the fifth embodiment, this information is used to make iterative decoding of the turbo decoder 903. Try to control the number of times.

The TPC control unit 905 has an SIR measurement unit 902
TPC to be inserted into transmission data based on SIR from
Generate a value. The TPC bit is 2 bits, and "00"
In the case of, the transmission power is not changed, and "1"
If it is "0", it is a request to increase the transmission power, and if it is "01", it is a request to decrease the transmission power.

The number-of-repetitions generator 9 that has received the TPC value
In 01, when the value of TPC is "10", a value obtained by increasing the number of times of repetitive decoding by 1 is generated and output. Control unit 904
Sets this value in the hard decision unit 9033. Also, TP
When the value of C is "01", a value is generated by reducing the number of times of repetitive decoding by 1 and output. The control unit 901 sets this value in the hard decision unit 9033. When the value of TPC is “00”, the number of times of repetitive decoding is not updated.

As described above, in the fifth embodiment, the number of times of iterative decoding of the turbo decoder 903 is updated in conjunction with the closed loop power control, so that a constant reception quality can be maintained and unnecessary turbo decoding is performed. Can be avoided, thereby reducing power consumption and reducing reception delay.

Note that the turbo decoder performance characteristic table is
It may be configured by an interleave length and a corresponding number of times of iterative decoding.

[0041]

According to the present invention, a constant reception quality can be maintained, and unnecessary turbo decoding can be avoided, thereby realizing low power consumption and reduction of reception delay. An error correction device can be provided.

[Brief description of the drawings]

FIG. 1 shows a C equipped with a turbo decoder to which the present invention is applied.
FIG. 2 is a diagram illustrating a configuration of a DMA wireless terminal.

FIG. 2 is a configuration diagram for explaining a first embodiment of the present invention.

FIG. 3 is a configuration diagram for explaining a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a configuration of a turbo encoder to which a third embodiment of the present invention has been applied.

FIG. 5 is a diagram illustrating a configuration when parity bits p1 and p2 are alternately selected and transmitted.

FIG. 6 is a configuration diagram for explaining a third embodiment of the present invention.

FIG. 7 is a block diagram illustrating a configuration for performing speed adjustment after turbo encoding.

FIG. 8 is a configuration diagram for explaining a fourth embodiment of the present invention.

FIG. 9 is a configuration diagram for explaining a fifth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 101 antenna 102 matched filter 103 rake combiner 104 SIR measuring section 105 turbo decoder performance characteristic table 106 turbo decoder 107 protocol control section 108 transmission data 109 TPC control section 110 modulator 111 control section 201 turbo decoder performance characteristic table 202 SIR Measurement unit 203 Turbo decoder 204 Control unit 301 Turbo decoder performance characteristic table 302 SIR measurement unit 303 Turbo decoder 304 Control unit 601 Turbo decoder performance characteristic table 602 Protocol control unit 603 Turbo decoder 604 Control unit 801 Turbo decoder performance Characteristic table 802 Protocol control unit 803 Turbo decoder 804 Control unit 901 Turbo decoder performance characteristic table 902 SIR measurement unit 903 Turbo decoder 904 Control unit 9 5 TPC controller

Claims (6)

[Claims] 1. A turbo decoder that outputs a decoding result by repeating an error correction process on a received signal a predetermined number of times, information on a state of the received signal, and a parameter for controlling a decoding process of the turbo decoder. Storage means for associating and storing the received signal state; detecting means for detecting the state of the received signal; and decoding processing of the turbo decoder according to a parameter selected from the storage means in accordance with the detected state of the received signal. Control means for controlling the error correction device. 2. The error correction according to claim 1, wherein said storage means stores a signal-to-interference ratio (SIR) of the received signal and the number of times of repetitive decoding of the turbo decoder in association with each other. apparatus. 3. The error correction device according to claim 1, wherein the storage unit stores the received electric field strength of the received signal and the number of times of repetitive decoding by the turbo decoder in association with each other. 4. The storage unit according to claim 1, wherein the storage unit stores information relating to the presence or absence of puncturing indicating whether or not the received signal is thinned, and the number of times of repetitive decoding of the turbo decoder in association with each other. Error correction device. 5. The error correction device according to claim 1, wherein the storage unit stores the thinning rate of the received signal and the number of times of iterative decoding of the turbo decoder in association with each other. 6. An error correction device in a CDMA wireless communication system, comprising: a turbo decoder that outputs a decoding result by repeating an error correction process on a received signal a predetermined number of times; and a signal-to-interference ratio (SIR) of the received signal. ), Transmitting means for transmitting control information for controlling transmission power to the transmitting side based on the detected SIR, and controlling decoding processing of the turbo decoder based on the control information. An error correction apparatus in a CDMA wireless communication system, comprising: a parameter generation unit that generates a parameter for performing a decoding process; and control means that controls a decoding process of the turbo decoder based on the generated parameter.