JP3223755B2 - Soft decision decoding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus used in a digital mobile radio communication system such as an automobile / mobile phone system employing a digital modulation / demodulation system.
In particular, the present invention relates to a soft-decision decoding method for an error correction code.

[0002]

2. Description of the Related Art Soft-decision decoding is a technique for estimating a digital signal by determining a signal to which noise has been added as a multilevel signal in a transmission system for transmitting a digital signal through a transmission path to which noise is added. The bit error rate can be improved as compared with hard decision decoding in which a binary signal of “0” or “1” is determined.

FIG. 7 shows a configuration of a receiving apparatus in a digital mobile radio communication system using a conventional soft decision decoding system disclosed in, for example, JP-A-6-21985. In the figure, reference numeral 10 denotes an antenna for receiving a radio signal generated by digitally modulating coded communication data that has been subjected to error correction coding by block coding using, for example, convolutional coding or BCH coding, using, for example, a π / 4 shift DQPSK method. , 11 are demodulators for digitally demodulating the received signal received by the antenna 10 in a process reverse to the digital modulation, for example, by a method such as delay detection. In the case of the π / 4DQPSK method, there are two types of I / Q. A demodulated signal is output. 1
Reference numeral 2 denotes a signal to be subjected to soft-decision decoding (a soft-decision-determined signal set, hereinafter, referred to as a soft-decision signal set) in the demodulated signal based on the result of the hard decision on the sign of the demodulated signal including the phase information output from the demodulation unit 11. (Referred to as “signal set”) and a signal set detection unit that performs a convolution-encoding process that is performed by tail bits input with a length equal to or longer than the constraint length in the case of a convolutional code. A bit sequence having a predetermined bit length, which is a group of data from the first bit to the last bit, and a bit sequence having a predetermined bit length, which is one block of block-coded block code, is included in the block code. One unit. Reference numeral 13 denotes a determination boundary (the signal boundary) of a demodulated signal portion corresponding to the signal set in the demodulated signal including the phase information output from the demodulator 11 based on the signal set instruction output from the signal set detector 12. (Corresponds to the hard decision threshold value at the time of hard decision performed by the set detection unit 12)
A phase reliability information generation unit that calculates a distance from the received signal, and outputs the distance as reliability information relating to the phase of the received signal (hereinafter referred to as “phase reliability information”). The respective phase reliability information is obtained. 14
Is a reception level detection unit that detects the reception level of the reception signal, that is, extracts a value having a dimension of the square of the envelope of the reception signal as a decibel value obtained by analog-to-digital conversion of the reception signal. Based on the signal set instruction output from the set detection unit 12, the reception level signal of the portion corresponding to the signal set among the reception level signals output from the reception level detection unit 14 is decibel-true converted, and the conversion is performed. A level reliability information generating unit that outputs a value as reliability information relating to the reception level of the received signal (hereinafter referred to as “level reliability information”); 16 includes each of the two types of phase reliability information and the level reliability information A multiplication unit which generates two types of final reliability information as signal set reliability information, and 17 is a hard decision result in the signal set detection unit 12. A soft decision unit for soft-deciding a decoded symbol of a certain signal set and signal set reliability information output from the multiplication unit 16, and an error correction decoding unit 18 for error-correcting decoding the soft decision data output from the soft decision unit Department.

Next, the operation will be described. In the soft decision section 17, a plurality of soft decision thresholds are fixedly set in advance. The larger the number, that is, the number of quantization bits, the more finely the signal set reliability information can be quantized, thereby improving the quantization accuracy. However, the increase in the number of bits complicates the configuration of the soft decision processing. Therefore, the number of soft decision thresholds is determined by a trade-off between the quantization accuracy and the soft decision processing configuration. The actual value of the soft decision threshold is assumed to cover the fluctuation range of the signal set reliability information (corresponding to the dynamic range of the reception level) to be subjected to the soft decision, and to cover the fluctuation range. The determination gain is set to be the maximum.

However, in a real environment in which a digital mobile radio communication system such as an automobile / mobile phone system is used, fading occurs due to a change in the communication environment, and the reception level fluctuates greatly. Therefore, the fluctuation range of the signal set reliability information is also affected by the fluctuation, and greatly deviates from the fluctuation range originally assumed. Therefore, the initially set soft decision threshold value of the soft decision unit 17 is not an appropriate value, resulting in a decrease in the soft decision gain and an increase in the bit error rate. In order to solve this problem, a method has been proposed in which the soft decision threshold value is variably controlled according to the change in the bit error rate caused by the change in the reception level.

FIG. 8 shows a configuration of a receiving apparatus in a digital mobile radio communication system using a conventional soft decision decoding system for variably controlling a soft decision threshold value disclosed in, for example, Japanese Patent Application Laid-Open No. 5-183450. . In the figure, reference numeral 17 denotes a decoded symbol of a signal set, which is a hard decision result in the signal set detection unit 12, and phase reliability information, which is an output of the phase reliability information generation unit 13 (in this case, the same as the signal set reliability information) And a soft decision unit that makes a soft decision using a variable soft decision threshold
Numeral 2 re-encodes the decoded data output from the error correction decoding section 18 again (hereinafter referred to as “re-encoding”), and outputs the re-coded data and the soft signal which is an input signal to the error correction decoding section 18. An error estimating unit 33 that compares the judgment data with the judgment data and estimates a bit error rate, which is a degree of the mismatch, based on an output of the error estimating unit 32, sets a soft decision threshold value of the soft decision unit 12 to the error estimating unit 32. Is a soft-decision threshold value control unit that variably controls so as to reduce the bit error rate estimated in (1). In this conventional example, unlike the conventional example of FIG. 8 described above, the signal set reliability information is generated using only the phase reliability information without using the level reliability information, thereby simplifying the entire configuration of the receiving apparatus. Is being planned.

Next, the operation will be described. The soft decision threshold value of the soft decision unit 17 is normally set so that the reception level does not fluctuate, so that when the fluctuation range of the signal set reliability information is a substantially constant standard level, the soft decision gain is maximized. ing. However, when fading occurs and the reception level fluctuates significantly, the initially set soft decision threshold value of the soft decision unit 12 is not an appropriate value. Therefore, in order to set the soft decision threshold value to a more appropriate value, the error estimating unit 32 compares the re-encoded data obtained by re-encoding the decoded data subjected to the error correction decoding with the soft decision data before the error correction decoding. The bit error rate is compared to estimate the soft error threshold, and the soft decision threshold control unit operates to sequentially increase and decrease the soft decision threshold so as to reduce the bit error rate and variably control the soft error threshold.

[0008]

Since the conventional soft decision decoding system is configured as described above, if the soft decision threshold value is fixedly set in advance, fading occurs and the reception level is reduced. If there is a large fluctuation, the fluctuation width of the signal set reliability information is also affected by the fluctuation, so that the initially set soft decision threshold value is not an appropriate value, resulting in a decrease in soft decision gain and an increase in the bit error rate. There was a problem. Further, when the soft decision threshold is variably controlled according to the fluctuation of the reception level in order to cope with the fluctuation of the signal set reliability information due to the fluctuation of the reception level, the error-correction decoded data is re-encoded and the code error rate is reduced. A feedback system such as an error estimating unit for estimating and a soft-decision threshold control unit for variably controlling the soft-decision threshold so as to reduce the bit error rate is required, and the circuit configuration is complicated. Also, since only phase reliability information is used as signal set reliability information, particularly when large fading occurs and the reception level further fluctuates, the phase reliability information is also affected. Is variably controlled, but there is a problem that the soft decision gain is reduced and the bit error rate is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. Even in a communication environment in which fading occurs and the reception level fluctuates greatly, the code error rate does not increase and the error correction capability is improved. It is an object of the present invention to provide a soft-decision decoding system that can sufficiently exhibit the above. It is another object of the present invention to provide a soft-decision decoding system having a simple circuit configuration that does not require a feedback system such as an error estimator and a soft-decision threshold controller.

[0010]

SUMMARY OF THE INVENTION A soft decision decoding system according to the present invention is a soft decision decoding system for an error correction code for performing a soft decision on a received signal and using signal set reliability information to obtain demodulated data. Means for instructing a signal set to be decoded; means for calculating phase reliability information from a demodulated signal including phase information obtained by demodulating a received signal based on the signal set instruction; and Means for calculating a standard reference value for each signal set from the reception level of the reception signal, and means for calculating level reliability information by normalizing the reception level of the reception signal with the standard reference value based on the signal set instruction. , Means for soft-decision based on the phase reliability information and the level reliability information.

Further, in a soft decision decoding method of an error correction code for performing a soft decision from a received signal having received spatial diversity using signal set reliability information to obtain demodulated data, a soft decision decoding is performed in response to a result of the spatial diversity reception. and means for instructing the subject to signal set, means for calculating the phase reliability information from the demodulation signal including the phase information obtained by demodulating the received signal based on the signal set instruction, received from multiple antennas Means for comparing a signal to select a reception signal indicating a maximum level, outputting the received signal as a reception level of the reception signal, and a standard reference value for each signal set from the reception level of the selected reception signal based on the signal set instruction. Calculating means, and standardizing a reception level of the selected reception signal with the standard reference value based on the signal set instruction. Means for calculating the Le reliability information, soft on the basis of said phase reliability information and the level reliability information
Determining means.

Means for instructing a signal set to be subjected to soft-decision decoding in a soft-decision decoding method of an error-correcting code for obtaining soft-decision data by performing soft-decision using signal set reliability information from a TDMA received signal; Means for calculating phase reliability information from a demodulated signal including phase information obtained by demodulating the received signal based on the signal set instruction; and a signal to be subjected to soft decision decoding based on TDMA slot timing of the received signal. Means for detecting the reception level of the set portion, calculating a standard reference value for each signal set from the reception level, and leveling the reception level of the reception signal with the standard reference value based on the signal set instruction. means for calculating reliability information, which was provided with a soft determining means based on said phase reliability information and the level reliability information That.

The TDMA slot timing is generated by predicting from the position of the synchronization word in the TDMA slot data which is a received signal or the position of the TDMA reference timing.

The signal set includes a bit string having a predetermined bit length, which is a group of data from the first bit to the last bit, which is convolutionally coded and generated by tail bits input over a constraint length, or a block code. It is composed of any one of bit strings having a predetermined bit length, which is data of one block of the converted block code.

The standard reference value is one of a maximum value, a minimum value of the received signal, a value obtained by subtracting a predetermined offset from the maximum value, a value obtained by adding a predetermined offset to the minimum value, and an average value. It is composed.

The apparatus further comprises means for selecting a decoding algorithm of the error correction code, and subtracts a predetermined reference from a standard reference value according to the selected decoding algorithm from a maximum value, a minimum value, and a maximum value of a reception level of a reception signal. The selected value is selected from any one of a calculated value, a value obtained by adding a predetermined offset to the minimum value, and an average value.

The level reliability information is calculated from the decibel value of the reception level.

[0018]

The soft decision decoding system according to the present invention calculates a standard reference value from a reception level of a received signal based on a signal set instruction, and normalizes the reception level of the received signal with the standard reference value to thereby obtain level reliability. Since the information is calculated, the fluctuation range of the level reliability information becomes small.

In the soft-decision decoding system for spatial diversity reception, received signals from a plurality of antennas are compared to select a received signal having a maximum level, and to selectively output the received signal as a received signal level. A standard reference value is calculated from the signal reception level, and the level reliability information is calculated by normalizing the reception level of the received signal with the standard reference value. Become.

The received signal is related to the TDMA communication system.
Since the TDMA slot timing indicating the range of the reception level signal for calculating the standard reference value is generated and the standard reference value is calculated based on the TDMA slot timing, the standard reference value calculation process based on the signal set instruction is performed. Becomes unnecessary.

The TDMA slot timing is generated by predicting from the position of the synchronization word in the TDMA slot data which is the received signal or the position of the TDMA reference timing, and the TD is calculated.
Since the standard reference value is calculated based on the MA slot timing, the standard reference value calculation process based on the signal set instruction becomes unnecessary.

The signal set is a bit string having a predetermined bit length, which is a group of data from the first bit to the last bit, which is convolutionally coded and generated by tail bits input over the constraint length, or a block code. Since it is composed of any one of bit strings having a predetermined bit length, which is data of one block of the converted block code, level reliability information and phase reliability information corresponding to a signal set are generated.

The standard reference value is one of a maximum value, a minimum value, a value obtained by subtracting a predetermined offset from the maximum value, a value obtained by adding a predetermined offset to the minimum value, and an average value. With this configuration, the level reliability information is calculated by normalizing the reception level of the reception signal using this value.

The apparatus further comprises means for selecting a decoding algorithm of the error correction code, and subtracts a predetermined reference from a standard reference value according to the selected decoding algorithm from a maximum value, a minimum value, and a maximum value of a reception level of a reception signal. Value, a predetermined value added to the minimum value, or an average value, and the selected value is used to standardize the reception level of the received signal to obtain the level reliability. Degree information is calculated.

Since the level reliability information is calculated from the decibel value of the reception level, the decibel-true value conversion becomes unnecessary.

[0026]

【Example】

Embodiment 1 FIG. FIG. 1 shows a configuration of a receiving apparatus in a digital mobile radio communication system using a soft decision decoding system according to an embodiment of the present invention. In the figure, those having the same or equivalent functions as those of the conventional example are indicated by the same numbers. In the figure, 20
Is a standard reference value generation unit that generates a standard reference value corresponding to the signal set from a reception level signal output from the reception level detection unit 14 based on a signal set instruction output from the signal set detection unit 12. A standard reference value corresponding to the error correction method is generated. For example, when it is desired to directly incorporate the fluctuation of the received signal into the level reliability information, the maximum value of the received level within the time corresponding to the signal set may be set as the standard reference value. Reference numeral 15 denotes a standard which is a decibel-true value conversion of a reception level signal of a portion corresponding to the signal set in the reception level signal, based on the signal set instruction, and converts the converted value into an output of the standard reference value generation unit 20. A level reliability information generation unit that normalizes the reference value with a converted value obtained by performing decibel-true value conversion and outputs the result as level reliability information. That is, this corresponds to considering the standard reference value as the maximum value of the level reliability information. The other parts are the same as those of the conventional example shown in FIG.

Next, the operation of this embodiment will be described. FIGS. 2A and 2B show time variations of the reception level. Hereinafter, the fluctuation range of the signal set reliability information and the required number of bits of the soft decision threshold value in the soft decision decoding method will be described with reference to FIG. In the figure, the reception level on the vertical axis is LO
Shown in G units. Here, for ease of explanation, it is assumed that the content of data in each signal set is the same, that is, the phase reliability information of each signal set is the same and does not change. Therefore, the change in the signal set reliability information is proportional to the change in the level reliability information. As shown in FIG. 2A, in a real environment in which fading occurs, the reception level undergoes a level fluctuation of 40 dB or more with time. In the conventional soft-decision decoding method described with reference to FIG.
Therefore, the signal set reliability information changes. In the figure, the signal set reliability information corresponding to signal set 1 is 0 dB to-.
The signal set reliability information corresponding to 10 dB and the signal set 2 has a fluctuation range of −30 dB to −40 dB, each of 10 dB. Therefore, if the soft decision threshold value is set so as to cover the fluctuation of the signal set reliability information, for example, the accuracy of soft decision of the signal set 1 with the true value in ten steps (4 bits) of the soft decision threshold value is obtained. Therefore, when the soft decision threshold value of the signal set 2 is to be provided, since the relative level difference between the signal set 1 and the signal set 2 is 30 dB, the true value is 1
A soft decision threshold value of 0000 steps (14 bits) is required, which makes implementation difficult. On the other hand, in the case of this embodiment, FIG.
As shown in (b), a standard reference value (the maximum value of the reception level in the signal set in this case) is set for each signal set, and the result of standardizing the reception level with the standard reference value is used as level reliability information. Considering the same received signal as 2 (a), the reception level (0 dB to -10 dB) of the signal set 1 has the standard reference value of 0 dB, and the reception level (-30 dB to -40 dB) corresponding to the signal set 2 has the standard value. Reference value -30d
B, the fluctuation width of the level reliability information, that is, the fluctuation width of the signal set reliability information is 0 dB to -10 dB for both the signal sets 1 and 2. Therefore, even when the soft decision threshold value of the signal set 2 is provided with the accuracy of soft decision in the soft decision threshold value of the signal set 1 with the true value in 10 steps (4 bits), the soft decision threshold value is 10 steps (4 bits). ). As described above, in this embodiment,
Since the level reliability information is standardized by the standard reference value for each signal set, the fluctuation of the reception level within the signal set (10 dB in this embodiment) is not the fluctuation of the reception level over the entire time in the actual environment. It is sufficient that the soft decision threshold value is set to cover the threshold value, and the required number of bits of the soft decision threshold value can be reduced, and the circuit configuration can be simplified.

In the above description, the case where the maximum value of the reception level in the signal set is used as the standard reference value and this value is regarded as the maximum value of the level reliability information has been described. You can change it. For example, when the fluctuation of the received signal is directly taken into the level reliability information as in the above, the minimum value of the reception level in the set may be set as the standard reference value, and this value may be regarded as the minimum value of the level reliability information. In order to reduce the influence of the error of the sampling value due to the deviation of the sampling timing of the analog / digital conversion in the reception level detection unit 14 and the error due to the saturation of the reception level due to the excessive reception signal input, the maximum value of the reception level in the signal set The value obtained by subtracting the fixed offset from the standard reliability value is used as the standard reference value, and this value may be regarded as the maximum value of the level reliability information. When reducing the effect of errors due to reception level saturation as described above, a value obtained by adding a fixed offset to the minimum value of the reception level in the signal set is regarded as the standard reference value, and this value is regarded as the minimum value of the level reliability information. You may. Further, when the time of one signal set is long and the fluctuation of the reception level in the signal set is averaged, the average value of the reception levels in the signal set may be set as the standard value.

Embodiment 2 FIG. In the TDMA communication system, one coded signal set is divided into a plurality of sub-signal sets and divided into the same slot or over a plurality of slots as a countermeasure against burst errors of communication data due to an instantaneous change in a communication environment due to fading. There is a case of distributed arrangement (interleaving). FIG. 3 shows a configuration of a receiving apparatus in a digital mobile radio communication system using a soft decision decoding system according to another embodiment of the present invention in such a TDMA communication system. In the figure, those having the same or equivalent functions as those of the conventional example are indicated by the same numbers. In the figure, reference numeral 21 denotes T indicating the position of a signal set to be subjected to soft-decision decoding.
A TDMA slot timing supply unit 20 for generating a DMA slot timing predicts a signal set portion from the TDMA slot timing, and
Is a standard reference value generation unit that obtains a standard reference value corresponding to a signal set from the reception level output from the unit, and sets, for example, the maximum value of the reception level in the signal set as the standard reference value.

Next, the operation of this embodiment will be described. FIG. 4 is a diagram for explaining the TDMA slot timing generated by the TDMA slot timing supply unit. In FIG. 5, (a) shows an example of a slot data signal format. Here, TDMA3 multiplexing (full rate) / communication physical channel uplink / slot 0 /
The signal format at the time of mobile station reception is shown. In (a), R is a guard time for burst transient response, P is a preamble, TCH is a communication channel, SW is a synchronization word, CC is a color code, SF is a steel flag, SACCH is a low-speed ACCH, RCH is a housekeeping bit, and G is Indicates guard time. In PDC, speech data in the speech channel TCH is convolutionally coded. When soft-decision decoding is performed on the speech channel TCH, the TDMA slot timing supply unit 21 outputs, for example, the following TDMA slot timing. (B) is a case where only the communication channel TCH is instructed as a standard reference generation target.
(C) is a case in which all slot data including the synchronization word SW excluding the guard time R and the guard time G for burst transient response before and after the slot are specified as targets for generating the standard reference. The TDMA slot timing is simply configured, and the standard reference value generation unit 2
Processing at 0 is simplified. As a method of generating the TDMA slot timing, for example, a method of predicting a signal set position in a slot from a synchronization word SW of received slot data and generating the position so as to include the position, a method of generating a public signal such as a receiving device in a base station, and the like. There is a method of predicting a signal set position in a slot using the TDMA reference timing on the network side, and generating a signal to include the position. In the latter method, the prediction of the signal set position does not depend on the received signal. PD
In C, since the speech data is interleaved with the speech channel TCH across two slots after being convolutionally coded, the standard reference value generation unit 20 uses one slot 0 and slot 0 three slots later. Then, each sub-signal set is extracted from the number, and the entire signal set is recognized. Further, a standard reference value is generated from the reception level corresponding to this signal set. As described above, in the present embodiment, TD is used instead of the signal set instruction.
The standard reference value is generated based on the MA slot timing, and the level reliability information is standardized by the standard reference value for each signal set. Therefore, the number of necessary bits of the soft decision threshold can be reduced, and the circuit configuration can be reduced. Simplification can be achieved.

Embodiment 3 FIG. In a digital mobile radio communication system, a plurality of error correction schemes may be used together in error correction coding. For example, in the case of the PDC, the mobile station is set to receive the BCCH (broadcast channel) on the control physical channel immediately after the power is turned on.
The CH is error-correction-coded by a BCH code which is a type of block code. The subsequent communication channel TCH on the communication physical channel is error-correction-coded by a convolutional code. In such a case, a plurality of decoding units corresponding to the respective error correction decoding algorithms are provided in the receiving device. FIG. 5 shows a configuration of a receiving apparatus in a digital mobile radio communication system using a soft decision decoding system according to another embodiment of the present invention in such a case. Here, an example using two types of decoding algorithms 1 and 2 will be described. In the figure,
Those having the same or equivalent functions as those of the conventional example are indicated by the same numbers. In the figure, reference numeral 22 denotes a decoding algorithm selection unit for selecting and indicating which decoding algorithm the received signal corresponds to in accordance with a procedure predetermined for each digital mobile radio communication system, and 12 denotes an output of the demodulation unit 11. A signal set detection unit for hard-deciding a demodulated signal including certain phase information and detecting a signal set corresponding to the decoding algorithm indicated by the decoding algorithm selection unit 22 in the demodulated signal from the hard decision result;
Reference numeral 20 denotes a standard reference value generator for obtaining a standard reference value corresponding to a signal set from the signal set instruction signal output from the signal set detector 12 and the reception level output from the reception level detector 14. A standard reference value suitable for the decoding algorithm selected by the decoding algorithm selection unit 22 is generated. Reference numeral 15 denotes a part of the reception level signal output from the reception level detection part 14, which generates a reception level signal corresponding to the signal set, based on the signal set instruction output from the signal set detection part 12. A level reliability information generating unit for normalizing the result with a standard reference value output from the unit 20 and outputting the result as level reliability information; and a level reliability corresponding to the decoding algorithm selected by the decoding algorithm selecting unit 22. Output information. Reference numerals 16a and 16b denote multiplication units for multiplying each of the two types of I / Q phase reliability information by the level reliability information and converting them into two types of final signal reliability signal set reliability information. It is provided corresponding to the types of decoding algorithms 1 and 2. 17a and 17b are the signal set detector 1
2 is a soft-decision section for soft-deciding the decoded symbol of the signal set as the result of the hard decision in step 2 and the signal set reliability information output from the multiplication sections 16a and 16b. Selected according to the signal. Reference numerals 18a and 18b denote error correction decoding units for error correcting and decoding the soft decision data output from the soft decision units 17a and 17b.

Next, the operation of this embodiment will be described. The standard reference value generator 20 subtracts a predetermined offset from, for example, the maximum value, the minimum value, and the maximum value of the reception level in the signal set in accordance with the decoding algorithm selected by the decoding algorithm selection unit 22 from the reception level signal. An optimum value is generated as a standard reference value from a value, a value obtained by adding a predetermined offset to a minimum value, or an average value. In the case of this embodiment, for example, when the decoding algorithm 1 is selected, the maximum value of the reception level is generated as the standard reference value, and when the decoding algorithm 2 is selected, the minimum value of the reception level is generated as the standard reference value. As described above, in the present embodiment, since the standard reference value is optimized according to the decoding algorithm, the accuracy of error correction decoding is improved.

Embodiment 4 FIG. As a technique for reducing the effect of fading, there is a space diversity receiving method that uses received signals received by two or more antennas that are spatially separated sufficiently. FIG. 6 shows a configuration of a receiving apparatus in a digital mobile radio communication system using a soft decision decoding system according to another embodiment of the present invention in such a spatial diversity receiving system. Here, for the sake of simplicity, a description will be given as a two-system (systems A and B) spatial diversity receiving system. In the figure, those having the same or equivalent functions as those of the conventional example are indicated by the same numbers. In the figure, reference numeral 18 denotes a demodulated signal a from systems A and B,
b, and the reception level detectors 14a and 14b
Is a diversity unit that weights with the reception level detected in step (1) and then performs vector synthesis to generate a synthesized demodulated signal. Reference numeral 23 denotes a maximum reception level detection unit that selects and outputs the reception level having the higher level among the systems A and B. Processing using the combined demodulated signal output from the diversity unit and the maximum reception level signal output from the maximum reception level detection unit is the same as in the first embodiment, and a description thereof will be omitted. As described above, in the present embodiment, when generating the level reliability information, the reception level of each system is simply compared and the maximum reception level is selected, so that the circuit configuration can be simplified.

In the first to fourth embodiments, the level reliability information generation unit 15 converts the reception level and the standard reference value into
As in the prior art, the decibel-true value conversion is performed, and the level reliability information is calculated using the converted value. However, in order to simplify the configuration, this conversion is omitted and the decibel value (LOG unit) is used.
May be used as it is.

In the first to fourth embodiments, the reception level is normalized by the standard reference value to obtain level reliability information, and the signal set reliability information which is the product of the level reliability information and the phase reliability information is obtained. Although the case where the soft decision is made using the fixed soft decision threshold has been described, the standard reference value may be used for scaling the soft decision threshold. That is, there is a basic soft decision threshold value corresponding to a certain basic standard reference value, and the basic soft decision threshold value is scaled by a ratio of the generated standard reference value to the basic standard reference value, and a new soft decision threshold value is obtained. Generate a soft decision threshold.

[0036]

As described above, the present invention has the following effects.

[0037] By standardizing the reception level of the received signal with the standard reference value calculated from the reception level of the received signal based on the signal set instruction and calculating the level reliability information, the fluctuation range of the level reliability information is reduced. Because it becomes smaller,
Even in a communication environment in which the reception level fluctuates greatly, the number of bits of the soft decision threshold can be reduced, the configuration can be simplified, and the error correction capability can be sufficiently exhibited without increasing the bit error rate.

In the soft-decision decoding system for performing spatial diversity reception, reception signals received from a plurality of antennas are compared, and a reception signal having the maximum level is received at a standard reference value calculated from the reception level of the selected reception signal. Since the level is standardized and the level reliability information is calculated, the fluctuation range of the level reliability information is reduced, so that even in a communication environment where the reception level fluctuates greatly, the bit of the soft decision threshold value is set. The number can be reduced, the configuration can be simplified, and the error correction capability can be sufficiently exhibited without increasing the code error rate.

The received signal is related to the TDMA communication system.
A TDMA slot timing indicating a range of a reception level signal for calculating a standard reference value is generated, and a standard reference value is calculated based on the TDMA slot timing, thereby calculating a standard reference value based on a signal set instruction. Is unnecessary, so that the circuit configuration can be simplified.

The TDMA slot timing is generated by predicting from either the position of the synchronizing word in the TDMA slot data which is a received signal or the position of the TDMA reference timing, and based on the TDMA slot timing, By calculating the value, the process of calculating the standard reference value based on the signal set instruction is not required, so that the circuit configuration can be simplified.

The signal set includes a bit string having a predetermined bit length, which is a group of data from the first bit to the last bit, which is convolutionally coded and generated by tail bits input over the constraint length, or a block code. Level reliability information corresponding to the signal set, which is composed of any one of bit strings having a predetermined bit length, which is data of one block of the converted block code,
Since the phase reliability information is generated, even in a communication environment in which the reception level fluctuates greatly, the code error rate does not increase and the error correction capability can be sufficiently exhibited.

The standard reference value is one of a maximum value, a minimum value, a value obtained by subtracting a predetermined offset from the maximum value, a value obtained by adding a predetermined offset to the minimum value, and an average value of the reception level of the received signal. And the level reliability information is calculated by normalizing the reception level of the reception signal using this value. Therefore, even in a communication environment where the reception level fluctuates greatly, the soft decision threshold value can be set. The number of bits can be reduced, the configuration can be simplified, and the error correction capability can be sufficiently exhibited without increasing the code error rate.

The apparatus further comprises means for selecting a decoding algorithm for the error correction code, and subtracts a predetermined reference from a standard reference value according to the selected decoding algorithm from a maximum value, a minimum value, and a maximum value of a reception level of a reception signal. Level, the value obtained by adding a predetermined offset to the minimum value, or the average value. The level reliability information is obtained by normalizing the reception level of the reception signal using the selected value. , The number of bits of the soft decision threshold can be reduced and the configuration can be simplified even in a communication environment where the reception level fluctuates greatly, and the code error rate does not increase and the error correction capability is sufficient. Can be demonstrated in.

Further, the level reliability information is calculated from the decibel value of the reception level, and the decibel-true value conversion becomes unnecessary, so that the circuit configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a soft decision decoding system according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams for explaining the operation of the soft-decision decoding system according to the embodiment of the present invention shown in FIG. 1, wherein FIG. 2A shows the fluctuation of conventional level reliability information, and FIG. Indicates a change in information.

FIG. 3 is a block diagram showing a configuration of a soft decision decoding system according to another embodiment of the present invention.

4A and 4B are diagrams for explaining the operation of the soft decision decoding system according to the embodiment of the present invention shown in FIG. 3, wherein FIG. 4A shows an example of a slot data signal format, and FIGS.
An example of slot timing is shown.

FIG. 5 is a block diagram showing a configuration of a soft decision decoding system according to another embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a soft decision decoding system according to another embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a conventional soft decision decoding system.

FIG. 8 is a block diagram showing a configuration of another conventional soft decision decoding system.

[Explanation of symbols]

 10, 10a, 10b Receiving antenna 11, 11a, 11b Demodulation unit 12 Signal set detection unit 13 Phase reliability information generation unit 14, 14a, 14b Reception level detection unit 15 Level reliability information generation unit 16, 16a, 16b Multiplication unit 17 , 17a, 17b Soft decision section 18, 18a, 18b Error correction decoding section 20 Standard reference value generation section 21 TDMA slot timing supply section 22 Decoding algorithm selection section 23 Maximum reception level detection section 32 Error estimation section 33 Soft decision threshold control Department

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 27/00-27/38 H03M 13/23

Claims (8)

(57) [Claims] A means for designating a signal set to be subjected to soft-decision decoding in a soft-decision decoding method for an error-correcting code for performing soft-decision from received signals and using signal-set reliability information to obtain demodulated data, Means for calculating phase reliability information from a demodulated signal including phase information obtained by demodulating a received signal based on a signal set instruction; and a standard reference value for each signal set from a reception level of the received signal based on the signal set instruction. means for calculating and means for calculating the level reliability information by normalizing at the standard reference value the reception level of the received signal based on the signal setting instruction, to said phase reliability information and the level reliability information soft decision decoding method is characterized in that a soft determining <br/> means based. 2. A soft-decision decoding method for an error-correcting code for performing a soft-decision using signal set reliability information from a received signal having received spatial diversity and obtaining demodulated data. and means for instructing the subject to signal set, means for calculating the phase reliability information from the demodulation signal including the phase information obtained by demodulating the received signal based on the signal set instruction, received from multiple antennas Means for comparing a signal to select a reception signal indicating a maximum level, outputting the received signal as a reception level of the reception signal, and a standard reference value for each signal set from the reception level of the selected reception signal based on the signal set instruction. Means for calculating, and standardizing the reception level of the selected reception signal with the standard reference value based on the signal set instruction, thereby obtaining a level signal. Means for calculating reliability information, and soft decision based on the phase reliability information and the level reliability information
Soft decision decoding method is characterized in that a means for. 3. A means for instructing a signal set to be subjected to soft-decision decoding in a soft-decision decoding scheme for an error-correcting code that obtains demodulated data by performing soft-decision using signal set reliability information from a TDMA received signal; Means for calculating phase reliability information from a demodulated signal including phase information obtained by demodulating the received signal based on the signal set instruction; and a signal to be subjected to soft decision decoding based on TDMA slot timing of the received signal. Means for detecting the reception level of the set portion, calculating a standard reference value for each signal set from the reception level, and leveling the reception level of the reception signal with the standard reference value based on the signal set instruction. Means for calculating reliability information; and means for soft- decision based on the phase reliability information and the level reliability information. Soft decision decoding method. 4. The TDMA slot timing is generated by predicting from a position of a synchronization word in a TDMA slot data which is a received signal or a position of a TDMA reference timing. 2. The soft decision decoding method according to 1. 5. A signal set includes a bit string or a block having a predetermined bit length, which is a group of data from a first bit to a last bit, which are convolutionally coded and generated by tail bits input over a constraint length. The soft-decision decoding method according to any one of claims 1 to 4, wherein the bit code is one of bit strings having a predetermined bit length, which is data of one block of the encoded block code. 6. The standard reference value is one of a maximum value, a minimum value, a value obtained by subtracting a predetermined offset from the maximum value, a value obtained by adding a predetermined offset to the minimum value, and an average value of the reception level of the received signal. The soft-decision decoding method according to any one of claims 1 to 5, wherein 7. A means for selecting a decoding algorithm of an error correction code, wherein a standard reference value is set in accordance with the selected decoding algorithm, and a predetermined offset from a maximum value, a minimum value, and a maximum value of a reception level of a reception signal. The soft decision decoding method according to claim 1, wherein the selected value is selected from one of a value obtained by adding a predetermined offset to a minimum value, a value obtained by subtracting the minimum value, and an average value. 8. The soft decision decoding method according to claim 1, wherein the level reliability information is calculated from a decibel value of a reception level.