JP2004104717A - Receiver, error-correction decoding device, and error-correction decoding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver, an error-correction decoding device and an error-correction decoding method in which error-correction processing is performed by rightly calculating the likelihood value in the communication environment where a received signal power is fluctuated but an S/N is not fluctuated or in the communication environment where the received signal power and a noise power are independently fluctuated. <P>SOLUTION: Whether or not a soft decision likelihood value is to be corrected is decided based on the fluctuation quantity of a noise power component in a received signal or presence/absence of fluctuation of the S/N and based on the decided result, the soft decision likelihood value is corrected as needed, so that an error-correction capability is prevented from being lowered by the unwanted correction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a receiving apparatus, an error correction decoding apparatus, and the like used in a communication environment such as a CDMA communication system in which the received signal power fluctuates, but the ratio between a desired signal component and a noise component of the received signal does not fluctuate. It is suitable for application to an apparatus and an error correction decoding method.
[0002]
[Prior art]
In a receiving apparatus used in a conventional mobile communication system or the like, a received signal is temporarily input to an AGC (Automatic Gain Control) circuit because an input range of an analog-to-digital conversion circuit provided in the receiving circuit is determined. Here, after the power of the received signal is made constant, this is subjected to analog-to-digital conversion.
[0003]
The AGC output signal whose signal level is made constant in the AGC circuit is output to the error correction decoder. This error correction decoder performs maximum likelihood determination such as Viterbi decoding executed in response to a convolutional code on the transmission side. The calculated soft decision likelihood value has a large S / N ratio. The soft decision likelihood value is corrected by multiplying the soft decision likelihood value by a weighting factor depending on the signal level (instantaneous reception amplitude) of the received signal so that is reflected. As a result, in a communication environment in which noise power does not fluctuate and only received signal power fluctuates due to fading, a reduction in error correction capability is suppressed (for example, see Patent Document 1).
[0004]
That is, the likelihood in the error correction decoding changes depending on the S / N of a signal (received signal) to be subjected to error correction. Therefore, the ratio of the soft decision likelihood values at each time point must be equal to the S / N ratio (the ratio between the desired wave component and the noise component) at each time point.
[0005]
FIG. 13 is a signal waveform diagram showing an example of fluctuations in noise power and received signal power in a communication environment in which only received signal power fluctuates due to fading without fluctuation in noise power. Then, the S / N at each time point in this case can be represented by the received signal power / noise power, and the result is as shown in FIG. As shown in FIG. 14, the S / N of the received signal becomes “2” at time t, becomes “11” at time t + 1, and becomes “3” at time t + 2.
[0006]
On the other hand, in the receiving apparatus, an AGC circuit is used for keeping the total received power (the sum of the received signal power and the noise power) constant for the above-described reason. FIG. 15 is a signal waveform diagram showing variations in noise power and received signal power when the total received power at each time point is adjusted to “12” using the AGC circuit under the conditions of the signal waveform diagram shown in FIG. is there.
[0007]
In addition, the soft decision likelihood value in this case is given by the fact that the ratio of the soft decision likelihood value at each time point and the ratio of the received signal power are equal, and the proportional constant to the received signal power is k, as shown in FIG. It becomes as shown in. As shown in FIG. 16, the soft decision likelihood value (without correction) of the received signal becomes “8k” at time t, becomes “11k” at time t + 1, and becomes “9k” at time t + 2.
[0008]
In this case, the ratio of the soft decision likelihood values at each time point shown in FIG. 16 does not match the S / N ratio at each time point shown in FIG. 14, and the correct soft decision likelihood value is calculated. Absent.
[0009]
This is because the SGC does not reflect on the soft decision likelihood value because the AGC circuit keeps the total received power constant, although the S / N at each time varies. .
[0010]
Therefore, in such a communication environment, if an AGC circuit is used, it is difficult to correctly calculate a soft decision likelihood value, and the error correction capability is reduced. In such a case, conventionally, correction is performed by multiplying the soft decision likelihood value by a weight coefficient depending on the instantaneous reception amplitude so that the magnitude of S / N is reflected on the soft decision likelihood value.
[0011]
This correction is not a correction in S / N but a correction using a weighting factor depending on the instantaneous reception amplitude. However, in an environment where the noise power does not fluctuate, the S / N ratio at each time and the instantaneous reception Since the ratios of the weighting factors depending on the amplitude are in the same relationship, correct correction is performed as long as the noise power does not fluctuate.
[0012]
FIG. 17 is a diagram illustrating the soft decision likelihood values at each time point when the soft decision likelihood values are multiplied by a weight coefficient depending on the instantaneous reception amplitude. However, in this case, the total received power value which is the square value of the instantaneous reception amplitude is used as the weighting factor depending on the instantaneous reception amplitude.
[0013]
As shown in FIG. 17, the ratio of the soft decision likelihood value at each time point matches the value of S / N at each time point in FIG. 2, and as long as it is used in an environment where the noise power does not fluctuate as described above. In, the soft decision likelihood value can be correctly calculated, and as a result, a decrease in error correction capability can be suppressed.
[0014]
[Patent Document 1]
JP-A-5-315977 (page 6, FIG. 8)
[0015]
[Problems to be solved by the invention]
However, in a mobile communication system of the CDMA (Code Division Multiple Access) system or the like, interference from other cells is composed of many signals, and therefore has almost constant power without fluctuation. However, a received signal is transmitted through a plurality of paths. The received multipath signal fluctuates in power due to fading. Therefore, when the main component of the noise power is due to multipath in a fading environment, the noise power (interference component) fluctuates.
[0016]
In such a case, the multipath signal also becomes signal power by rake combining reception, so that the fluctuations in the noise power and the fluctuations in the received signal power substantially match, and as a result, the fluctuations in the received signal power Even so, the communication environment is such that the S / N (the ratio between the desired wave component and the noise component) does not greatly change.
[0017]
Another condition for establishing such a communication environment is transmission power control. In this transmission power control, when noise power or received signal power fluctuates due to fading, transmission power is controlled on the transmission side such that the S / N on the reception side is always constant. Accordingly, a communication environment in which the S / N does not fluctuate even when the received signal power fluctuates.
[0018]
FIG. 18 shows an example of fluctuations in noise power and received signal power in such a communication environment. FIG. 19 shows the S / N at each point in the fluctuation state of the noise power and the received signal power shown in FIG. As shown in FIG. 19, the S / N of the received signal becomes “2” at time t, becomes “2” at time t + 1, and becomes “2” at time t + 2.
[0019]
That is, in the variation example of the noise power and the received signal power shown in FIG. 18, the S / N is not changed even though the total received signal power is changed.
[0020]
FIG. 20 shows a state in which the received signal whose total received signal power fluctuates is subjected to gain control by the AGC circuit to adjust the total received signal power to “12”.
[0021]
As shown in FIG. 20, when a received signal originally having no variation in S / N is subjected to gain control by an AGC circuit so that the total received signal power becomes constant, the result is included in the total received signal power. The noise power and the received signal power have constant values so as to keep the same S / N.
[0022]
FIG. 21 shows the soft decision likelihood values at each point in this case. As shown in FIG. 21, the soft decision likelihood value (without correction) of the received signal is “2k” at time t, “2k” at time t + 1, and “2k” at time t + 2. That is, for a received signal whose S / N does not fluctuate even though the total received signal power fluctuates, in a state where the AGC circuit keeps the total received signal power constant (FIG. 21), FIG. And the same result as the S / N shown in FIG. 19 can be obtained.
[0023]
Then, the received signal subjected to gain control by the AGC circuit is multiplied by a weight coefficient (using the total received power as in the case of FIG. 17) of the soft decision likelihood value depending on the instantaneous received amplitude. FIG. 22 shows a case in which the correction is performed. As shown in FIG. 22, the soft decision likelihood value (with correction) of the received signal becomes “6k” at time t, becomes “24k” at time t + 1, and becomes “12k” at time t + 2.
[0024]
As shown in FIG. 22, for a received signal whose S / N does not fluctuate even though the total received signal power fluctuates, the AGC circuit keeps the total received signal power constant ( If weighting correction using the instantaneous amplitude value is further performed from FIG. 21), the result becomes different from the S / N at each time point shown in FIG.
[0025]
That is, it is difficult to calculate a correct soft decision likelihood value by performing weight correction on a received signal in which the total received signal power fluctuates while maintaining a state in which the S / N does not fluctuate. However, there has been a problem that the error correction capability of the device has been reduced.
[0026]
This is because when the noise power fluctuates, the ratio of the weighting factor depending on the instantaneous reception amplitude at each time point and the S / N ratio at each time point are uncorrelated, and thus depend on the instantaneous reception amplitude. This is because even when the soft decision likelihood value is multiplied by the weight coefficient, the ratio of the soft decision likelihood value at each time point is not equal to the S / N ratio at each time point.
[0027]
Further, even in a communication environment in which the noise power and the received signal power fluctuate independently (when the S / N is not constant), when the correction by multiplying by the weight coefficient depending on the instantaneous amplitude value is performed, the soft decision likelihood is correctly calculated. There was a problem that it was difficult to calculate the value.
[0028]
That is, FIG. 23 is a signal waveform diagram illustrating an example of fluctuations in noise power and received signal power in a communication environment in which noise power and received signal power vary independently. FIG. 24 is a diagram showing the S / N at each time point in FIG.
[0029]
As shown in FIG. 24, the S / N of the received signal becomes “2” at time t, becomes “2” at time t + 1, and becomes “0.5” at time t + 2.
[0030]
FIG. 25 shows a signal waveform diagram in the case where the received signal shown in FIG. 23 is subjected to gain control by the AGC circuit so that the total received signal power is kept at a constant value “18”. FIG. 26 shows the soft decision likelihood values.
[0031]
FIG. 26 is a diagram illustrating a case where the gain is controlled by the AGC circuit and then a correction is performed by multiplying by a weighting factor depending on the instantaneous amplitude value, and a case where the correction is not performed. As shown in FIG. 26, the soft decision likelihood value at each time point does not match the S / N ratio shown in FIG. 24 in both the case where the correction is performed and the case where the correction is not performed. .
[0032]
That is, when the noise power and the received signal power fluctuate independently, it is difficult to correctly calculate the soft decision likelihood value if the soft decision likelihood value is corrected, and the error correction capability is reduced. Further, even when the soft decision likelihood value is not corrected, similarly, it becomes difficult to correctly calculate the soft decision likelihood value, and the error correction capability is reduced.
[0033]
In this case, when the noise power and the received power fluctuate independently and the S / N is not constant, the ratio of the weight coefficient depending on the instantaneous reception amplitude at each time and the ratio of the S / N at each time are uncorrelated. Therefore, even if a correction is made such that the soft decision likelihood value is multiplied by a weight coefficient depending on the instantaneous reception amplitude, the ratio of the soft decision likelihood value at each time point is the S / N ratio at each time point. By not being equal to
[0034]
The AGC circuit does not make the ratio of the soft decision likelihood values at each time point close to the S / N ratio at each time point, but keeps the total received signal power constant without correlation with the S / N. It is. Therefore, it is difficult to correctly calculate the soft decision likelihood value even when the correction is not performed.
[0035]
The present invention has been made in view of such a point, and while the received signal power fluctuates, the ratio between the desired wave component and the noise component does not fluctuate, or the received signal power and the noise component are not changed. An object of the present invention is to provide a receiving apparatus, an error correction decoding apparatus, and an error correction decoding method that can correctly calculate a likelihood value and perform error correction processing in a communication environment that changes independently.
[0036]
[Means for Solving the Problems]
A receiving apparatus according to the present invention includes a gain control unit that keeps a total signal power of a received signal constant, and a maximum likelihood decoding of a reception code sequence of a signal whose total received signal power is kept constant by the gain control unit. At this time, for each received code, the likelihood of the candidate code is given as a multi-level likelihood, and the likelihood value calculating means for correcting the likelihood as necessary, and a noise component included in the received signal. Noise component fluctuation detecting means for detecting fluctuations in the likelihood, and correction for determining whether to perform the correction depending on the instantaneous amplitude of the received signal with respect to the likelihood based on the detection result of the noise component fluctuation detecting means. And control means.
[0037]
According to this configuration, when the noise component of the received signal fluctuates by a certain amount or more, the main component of the noise component can be determined to be a multipath signal. In this case, the ratio between the desired wave component and the noise component of the received signal (for example, Since S / N) does not vary, the soft decision likelihood value is not multiplied by a weighting factor that depends on the instantaneous received signal amplitude. As a result, a correct soft decision likelihood value can be calculated according to the ratio between the desired wave component and the noise component of the received signal, and a decrease in error correction capability can be suppressed.
[0038]
A receiving apparatus according to the present invention includes a gain control unit that keeps a total signal power of a received signal constant, and a maximum likelihood decoding of a reception code sequence of a signal whose total received signal power is kept constant by the gain control unit. At this time, for each received code, the likelihood of the candidate code is given as a multi-level likelihood, and the likelihood value calculating means for correcting the likelihood as necessary, and a desired wave included in the received signal. Correction control means for determining whether or not to perform the correction depending on the instantaneous amplitude of the received signal with respect to the likelihood based on information indicating a change in the ratio between the component and the noise component. Take.
[0039]
According to this configuration, it is determined whether or not to perform the correction depending on the instantaneous amplitude of the received signal on the likelihood based on the information indicating the change in the ratio between the desired wave component and the noise component of the received signal. This makes it possible to accurately correct the soft decision likelihood based on the type of the noise component included in the received signal.
[0040]
The receiving apparatus according to the present invention, in the above configuration, employs a configuration in which the correction control unit determines whether or not the correction is performed based on whether or not the received signal is transmitted under transmission power control.
[0041]
According to this configuration, the information indicating whether or not the transmission power control has been performed is used as the information indicating the change in the ratio between the desired wave component and the noise component of the received signal, so that the desired wave included in the received signal is used. It can be easily determined whether or not the ratio between the component and the noise component is constant. This makes it possible to easily determine whether or not to correct the soft decision likelihood.
[0042]
The receiving apparatus of the present invention, in the above configuration, wherein the correction control means determines the presence or absence of the correction based on whether a main component of a noise component included in the received signal is due to multipath. Take.
[0043]
According to this configuration, it is possible to determine whether or not the ratio between the desired wave component and the noise component included in the received signal is constant, based on whether or not a noise component due to multipath is included.
[0044]
A receiving apparatus according to the present invention includes a gain control unit that keeps a total signal power of a received signal constant, and a maximum likelihood decoding of a reception code sequence of a signal whose total received signal power is kept constant by the gain control unit. At the same time, for each received code, the likelihood of the candidate code is given as a multi-level likelihood, and the likelihood is multiplied by a weighting factor depending on the instantaneous amplitude of the received signal and the received signal is multiplied by the likelihood. And a likelihood value calculating means for performing division by the included noise component value.
[0045]
According to this configuration, the soft decision likelihood value can be correctly calculated even when the desired wave component and the noise component of the received signal fluctuate independently.
[0046]
The error correction decoding apparatus of the present invention, when performing the maximum likelihood decoding of the received code sequence of the received signal, gives the likelihood of the candidate code for each received code as a multi-level level likelihood. A likelihood value calculating means for multiplying by a weighting factor depending on the instantaneous amplitude of the received signal and dividing by a noise component value included in the received signal, based on the likelihood value calculated by the likelihood value calculating means. And a decoding means for performing error correction decoding by means of a decoding means.
[0047]
According to this configuration, the soft decision likelihood value can be correctly calculated even when the desired wave component and the noise component of the received signal fluctuate independently.
[0048]
The error correction decoding method of the present invention, when performing maximum likelihood decoding of a received code sequence of a received signal, gives likelihood of a candidate code for each received code as a multi-level likelihood, and A likelihood value calculating step of multiplying by a weighting factor depending on the instantaneous amplitude of the received signal and dividing by a noise component value included in the received signal, based on the likelihood value calculated by the likelihood value calculating means. And a decoding step of performing error correction decoding.
[0049]
According to this method, the soft decision likelihood value can be correctly calculated even when the desired wave component and the noise component of the received signal fluctuate independently.
[0050]
BEST MODE FOR CARRYING OUT THE INVENTION
The gist of the present invention is to judge the necessity of the soft decision likelihood value correction based on the fluctuation amount of the noise component of the received signal or the presence or absence of the fluctuation of the ratio between the desired wave component and the noise component, and to perform the unnecessary correction. The purpose of the present invention is to prevent the error correction ability from being lowered due to the error. Here, the noise component means all unnecessary components regardless of the factor.
[0051]
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0052]
(Embodiment 1)
FIG. 1 is a block diagram illustrating a configuration of a receiving device according to an embodiment of the present invention.
[0053]
In FIG. 1, reference numeral 100 denotes a CDMA receiving apparatus as a whole, and a reception signal received via an antenna 101 is received by a reception RF (Radio Frequency) unit 102. The receiving RF unit 102 converts a received signal of a radio frequency into a signal of a baseband, and outputs this to the AGC circuit 103.
[0054]
The AGC circuit 103 performs gain control to keep the total received signal power (sum of the received signal power and noise power) of the received signal constant. The received signal whose total received signal power is kept constant is output from AGC circuit 103 to demodulation section 104.
[0055]
Demodulation section 104 performs demodulation processing such as despreading and RAKE combining on the received signal (total received signal power) having a constant amplitude output from AGC circuit 103, and then demodulates the demodulated signal resulting from the demodulation as an error. The signals are output to the correction decoder 106 and the noise power fluctuation amount measurement unit 105, respectively.
[0056]
Also, the AGC circuit 103 outputs the received signal after the AGC processing as described above, and in the AGC processing, the weighting coefficient (gain) obtained by multiplying the fluctuating received signal so that the signal level is constant. The adjustment coefficient is output to the error correction decoder 106 and the noise power fluctuation amount measurement unit 105, respectively. This weight coefficient is a coefficient that depends on the instantaneous reception amplitude. Specifically, the magnitude of the signal (received signal) input to the AGC circuit 103, such as the square of the magnitude of the received signal input to the AGC circuit 103, may be used. The reason for using the value of the square of the magnitude of the received signal is that when the likelihood value is obtained in the error correction decoder 106, the received signal must be input in a size that reflects the ratio of noise power. .
[0057]
The error correction decoder 106 receives the demodulated signal output from the demodulation unit 104 and the weight coefficient output from the AGC circuit 103 in the soft decision likelihood value calculation unit 107. Soft decision likelihood value calculating section 107 performs a soft decision likelihood value calculating process based on the control signal output from reception amplitude weight multiplication control section 108.
[0058]
That is, in this receiving apparatus 100, the demodulated signal output from demodulation section 104 and the weighting factor output from AGC circuit 103 are supplied to noise power variation measurement section 105. FIG. 2 is a block diagram illustrating a configuration of the noise power fluctuation amount measurement unit 105. The noise power fluctuation measuring section 105 receives the demodulated signal and the weighting factor in the noise power measuring section 111, and first measures instantaneous noise power, which is a noise component of the demodulated signal. In this case, the noise power measuring unit 111 measures the noise power from the X signals, for example, by subtracting the square of the average of the X signals from the average of the square of the X signals. As noise power.
[0059]
Here, since the demodulated signal is controlled by the AGC circuit 103 so that the total received power becomes constant, it is difficult to measure a correct instantaneous noise power as it is. Therefore, the noise power measurement unit 111 multiplies the measured instantaneous noise power by the weight coefficient supplied from the AGC circuit 103. Since this weighting factor depends on the instantaneous reception amplitude, by multiplying the instantaneous noise power by this weighting factor, a change in the noise power given by the AGC circuit so that the total reception power becomes constant is obtained. Can be removed.
[0060]
The result of the multiplication is output to the delay unit 112 and the comparison and division unit 113 as an instantaneous noise power value. The delay unit 112 delays the input instantaneous noise power value for a predetermined time, and then outputs the delayed power value to the comparison / division unit 113. The comparison / division unit 113 compares the current instantaneous noise power value output from the noise power measuring unit 111 with the instantaneous noise power value output from the delay unit 112 after a predetermined time delay, and compares the two instantaneous noise power values. The small instantaneous noise power value is divided from the large instantaneous noise power value among the values.
[0061]
The result of the division in this manner is a measured value indicating the amount of change in the instantaneous noise power value (hereinafter, this is referred to as the amount of change in noise power). The noise power fluctuation amount obtained by the noise power fluctuation amount measuring section 105 is output to the reception amplitude weight multiplication control section 108 (FIG. 1).
[0062]
The reception amplitude weight multiplication control unit 108 compares the noise power variation output from the noise power variation measurement unit 105 with a preset threshold, and if the noise power variation is smaller than the threshold, A control signal for multiplying the soft decision likelihood value by a weight coefficient depending on the instantaneous reception amplitude is output to decision likelihood value calculating section 107.
[0063]
On the other hand, if the noise power variation output from the noise power variation measuring unit 105 is larger than a preset threshold, the reception amplitude weight multiplication control unit 108 The control unit 107 outputs a control signal to the calculation unit 107 to prevent the soft decision likelihood value from being multiplied by a weight coefficient depending on the instantaneous reception amplitude.
[0064]
If the control signal output from reception amplitude weight multiplication control section 108 is a control signal for multiplying the weight coefficient, soft decision likelihood value calculation section 107 calculates the soft signal based on the demodulated signal at this time. The soft decision likelihood value is multiplied by a weight coefficient depending on the instantaneous reception amplitude. On the other hand, if the control signal output from reception amplitude weight multiplication control section 108 is a control signal for not multiplying the weight coefficient, soft decision likelihood value calculation section 107 The calculated soft decision likelihood value is used without multiplying the soft decision likelihood value calculated based on the weight coefficient depending on the instantaneous reception amplitude.
[0065]
FIG. 3 is a schematic diagram for explaining a method of calculating a soft decision likelihood value based on a demodulated signal in soft decision likelihood calculating section 107. FIG. 3 gives the soft decision likelihood for a one-dimensional (one-bit) code. In the case of two-dimensional (two-bit) codes, it is sufficient to apply to each bit and add.
[0066]
The demodulated signal level + V corresponds to the code “0”, and the demodulated signal level −V corresponds to the code “1”. FIG. 3 shows the likelihood for the code “0”. As this likelihood, for example, multiple values from 0 to 16 are assigned according to the demodulated signal amplitude value. That is, if a signal having an amplitude such as the demodulated signal amplitude A in FIG. 3 is input, the likelihood in the case of hard decision becomes zero. In other words, it can be understood that the hard decision is that the demodulated signal is close to the candidate code "0", but its certainty cannot be determined with sufficient accuracy.
[0067]
On the other hand, the likelihood is given as 6 in the soft decision according to the present embodiment. Since this is a value close to 8 (an intermediate point between two code levels), it can be determined that the value is close to the candidate code “0” but the reliability is low.
[0068]
The soft decision likelihood calculation section 107 calculates the soft decision likelihood of the demodulated signal by the method shown in FIG. 3, and further weights the calculated soft decision likelihood value depending on the instantaneous reception amplitude. Whether or not correction by coefficient multiplication is possible is determined based on a control signal from reception amplitude weight multiplication control section 108. Then, based on the control signal, if correction is necessary, the soft decision likelihood value is corrected by multiplying by a weighting coefficient. The likelihood value is not multiplied by the weight coefficient.
[0069]
In this way, the soft decision likelihood value calculated by the soft decision likelihood value calculation section 107 and corrected as necessary is output to the addition / comparison / selection section 121 in the error correction decoder 106 shown in FIG. Is done.
[0070]
Upon receiving the soft decision likelihood value output from the soft decision likelihood value calculating section 107, the addition / comparison / selection section 121 sets the value of the state likelihood at the immediately preceding time stored in the state likelihood memory 122 to a possible value. The soft decision likelihood value of the state transition is added to obtain a new state likelihood. Then, the addition / comparison / selection unit 121 compares the state likelihoods of a plurality of state transitions leading to one state, selects a transition having the maximum state likelihood from among them, and selects the state likelihood of the selected transition. The state likelihood memory 122 is updated using the degree as a new state likelihood.
[0071]
Further, the addition / comparison / selection unit 121 outputs to the path memory 123 the information j (i) of the simultaneously selected transition (representing the transition from the state j to the state i). The path memory 123 sequentially stores the transition information j (i) or the state number of the transition, and obtains a decoding result from the state transition selected and left at the final point in the maximum likelihood determination unit 124.
[0072]
In the above configuration, the likelihood in error correction decoding generally changes depending on S / N. Therefore, the ratio of the soft decision likelihood values at each time point must be equal to the S / N ratio at each time point.
[0073]
In this regard, as described above with reference to FIG. 13, when the noise power included in the received signal is substantially constant, the ratio of the S / N at each time point and the ratio of the weighting factor depending on the instantaneous reception amplitude are as follows. They are in equal relation. Therefore, in such a communication environment, the receiving apparatus 100 multiplies the soft decision likelihood value calculated based on the output signal of the AGC circuit by the weighting coefficient, thereby obtaining an accurate signal matching the S / N ratio. The soft ratio of likelihood values can be determined.
[0074]
On the other hand, when the noise power included in the received signal fluctuates, the ratio of the weight coefficient depending on the instantaneous reception amplitude at each time point and the S / N ratio at each time point are uncorrelated. Therefore, in such a communication environment, the receiving apparatus 100 obtains a noise fluctuation amount equal to or larger than a predetermined threshold value as a measurement result of the noise power fluctuation amount measuring unit 105, and based on the detection result of the noise fluctuation amount. Thus, control is performed so that the reception amplitude weight multiplication control unit 108 does not multiply the soft decision likelihood value of the weight coefficient (correction of the soft decision likelihood value).
[0075]
In this case, as shown in FIG. 18, assuming that the received signal input to the AGC circuit fluctuates while maintaining its S / N ratio, the demodulated signal output from the AGC circuit is: Since the total received signal power is kept constant, the noise power component is also kept constant. That is, the S / N ratio of the demodulated signal in this case is kept constant. Therefore, this demodulated signal meets the above-mentioned condition that the ratio of the soft decision likelihood values at each time point must be equal to the S / N ratio at each time point.
[0076]
Therefore, in such a case, an accurate soft decision likelihood value can be obtained by not multiplying the soft decision likelihood value by the weight coefficient (correction of the soft decision likelihood value). Incidentally, an example of a communication environment that results in fluctuation while maintaining the S / N ratio of the received signal will be described below.
[0077]
A first example in which the S / N ratio of a received signal fluctuates while being maintained will be described. In CDMA communication, a multipath signal or the like may cause interference, and the multipath signal may be a main component of noise power. In such a case, since the multipath signal also becomes signal power by rake combining reception, the fluctuation of the noise power and the power of the received signal are almost the same. Of the ratio is small.
[0078]
Next, a second example will be described. In some cases, transmission power control is performed on the signal received by the receiving device at the transmission source. In the transmission power control, the transmission power is controlled on the transmission side so that the S / N on the reception side is always constant even if the noise power or the received signal power fluctuates due to fading. Is changed, the communication environment does not change the S / N.
[0079]
Therefore, when the noise power fluctuates by a certain amount or more and the fluctuation state is detected based on the noise power fluctuation amount measured by the noise power fluctuation amount measuring unit 105 of the receiving device 100, the receiving device 100 Based on the detection result, it can be determined that the main component of the noise power is a multipath signal or that the received signal is a signal subjected to transmission power control.
[0080]
In such a case, even if gain control is performed by the AGC circuit 103 so that the value of the total received signal power is constant, the soft decision likelihood value obtained based on the result is not corrected. Thus, an accurate soft decision likelihood value can be obtained.
[0081]
FIG. 5 is a flowchart illustrating an error correction decoding process performed by the receiving apparatus 100. As shown in FIG. 5, receiving apparatus 100 measures a noise power value of a received signal in step ST101, and obtains a fluctuation amount of the noise power value in step ST102. Then, the receiving apparatus 100 proceeds to the subsequent step ST103, and determines whether or not the fluctuation amount of the noise power value obtained in the above-described step ST102 is larger than a threshold.
[0082]
If a positive result is obtained in step ST103, this means that the amount of change in the noise power value is larger than the threshold, that is, when the soft decision likelihood value is corrected, a correct soft decision likelihood value cannot be obtained. As a result, this means a state in which the error correction capability may be reduced due to the correction of the soft decision likelihood value. At this time, the receiving apparatus 100 proceeds to step ST104 and performs the soft decision. Error correction processing is performed without correcting the likelihood value.
[0083]
On the other hand, if a negative result is obtained in step ST103, this indicates that the variation in the noise power value is smaller than the threshold, that is, the correct soft decision likelihood is obtained by correcting the soft decision likelihood value. This means that the state can be obtained, and as a result, a certain error correction capability can be maintained. At this time, the receiving apparatus 100 proceeds to step ST105 and sets the soft decision likelihood value Error correction processing with a correction for.
[0084]
As described above, according to the receiving apparatus of the present embodiment, by controlling whether to perform the weighting process based on the variation of the noise power component of the received signal, the accurate soft decision likelihood The value can be calculated.
[0085]
In the above-described embodiment, the method for measuring the amount of noise power fluctuation is to compare the instantaneous noise power value measured last time with the noise power value measured this time and divide the smaller value from the larger value. However, the present invention is not limited to this.For example, an average of the measured noise power values for a predetermined number of times in the past is obtained, and the average value is compared with the current measured noise power value. In other words, other methods, such as dividing the smaller one, can be used as long as they represent the amount of change in noise power.
[0086]
Further, in the above-described embodiment, as a method of correcting the soft decision likelihood value, the case where a weight coefficient depending on the instantaneous reception amplitude is used has been described. However, the present invention is not limited to this. Adjustment coefficient (a coefficient for multiplying the received signal amplitude so as to keep the total received power constant. In an AGC circuit for temporarily maintaining the power K, K = (gain adjustment coefficient / received signal) ² (Where K is the power and the square is established), the inverse of the square may be used. As described above, since the gain adjustment coefficient of the AGC circuit 103 is the reciprocal of the coefficient that depends on the instantaneous reception amplitude, it is necessary to newly calculate a coefficient that depends on the instantaneous reception amplitude by using this gain adjustment coefficient. Therefore, the soft decision likelihood value can be easily corrected.
[0087]
Further, in the above-described embodiment, the case where S / N is used as the ratio between the desired wave component and the noise component of the received signal by paying attention to the noise power has been described, but this S / N is SIR (Signal Interference). Ratio) is also included.
[0088]
Further, in the above embodiment, the case where a Viterbi decoder is used as the error correction decoder 106 has been described. However, the present invention is not limited to this. For example, turbo encoding is performed on the transmission side, and Other encoding and decoding methods may be used, such as performing turbo decoding on the receiving side.
[0089]
(Embodiment 2)
FIG. 6 is a block diagram showing the configuration of receiving apparatus 200 according to Embodiment 2 of the present invention. However, components having the same configuration as in FIG. 1 are denoted by the same reference numerals as in FIG. 1, and detailed description is omitted.
[0090]
The receiving apparatus 200 illustrated in FIG. 6 determines whether or not transmission power control is performed instead of measuring the noise power value as compared to the receiving apparatus 100 described above with reference to FIG. The difference is that it is determined whether or not correction of the soft decision likelihood value is possible based on this.
[0091]
That is, in FIG. 6, receiving apparatus 200 outputs a demodulated signal obtained as a result of demodulation in demodulation section 104 to soft decision likelihood value calculation section 107 of error correction decoder 106 and to transmission power control section 201 I do.
[0092]
Transmission power control section 201 outputs control information, which is included in the demodulated signal and indicates whether or not transmission power control is being performed, to reception amplitude weight multiplication control section 208. Here, the transmission power control means that the received signal received by the receiving device 200 is transmitted from the transmission source under the transmission power control. The reception amplitude weight multiplication control unit 208 determines whether or not transmission power control is performed based on the control information output from the transmission power control unit 201. When the transmission power control is not performed, A control signal for multiplying the soft decision likelihood value by a weight coefficient depending on the instantaneous reception amplitude is output to soft decision likelihood value calculating section 107.
[0093]
On the other hand, when the transmission power control is performed, the reception amplitude weight multiplication control unit 208 sends the soft decision likelihood value to the soft decision likelihood value A control signal for preventing multiplication by the dependent weight coefficient is output.
[0094]
With this, when the transmission power control is performed, the S / N of the received signal is always constant, and the soft decision likelihood value is multiplied by a weight coefficient depending on the instantaneous received signal amplitude (the soft decision likelihood value). Correction) is not performed. As a result, the correct soft-decision likelihood value is calculated in accordance with the S / N, so that even when a signal for which transmission power control is performed is received, a decrease in the error correction capability can be suppressed. it can.
[0095]
FIG. 7 is a flowchart illustrating an error correction decoding processing procedure in the receiving apparatus 200. As shown in FIG. 7, receiving apparatus 200 extracts control information indicating whether transmission power control is performed from a received signal (demodulated signal) in step ST201, and in step ST202, transmits the received signal based on the control information. It is determined whether the data is transmitted under the power control.
[0096]
If a positive result is obtained in step ST202, this means that transmission power control is being performed, that is, if the S / N of the received signal is constant and the soft decision likelihood value is corrected, correct soft decision is performed. This means that the likelihood value is not obtained, and as a result, there is a possibility that the error correction capability may be degraded due to the correction of the soft decision likelihood value. Moving to ST203, error correction processing is performed without correcting the soft decision likelihood value.
[0097]
On the other hand, if a negative result is obtained in step ST202, this means that the transmission power control is not performed, that is, the S / N of the received signal is not constant, and the correction of the soft decision likelihood value is performed. By doing so, it is possible to obtain a correct soft decision likelihood value, and as a result, it is in a state where a certain error correction capability can be maintained. At this time, the receiving apparatus 200 proceeds to step ST204. Then, an error correction process involving correction of the soft decision likelihood value is performed.
[0098]
As described above, according to the receiving apparatus of the present embodiment, based on the control information of a received signal, it is determined whether or not the received signal is transmitted under transmission power control, and the determination result is obtained. By controlling whether to perform the weighting process based on the above, accurate calculation of the soft decision likelihood value can be performed.
[0099]
In the above-described embodiment, the case where a weight coefficient depending on the instantaneous reception amplitude is used as a method for correcting the soft decision likelihood value has been described, but the present invention is not limited to this, and the gain in the AGC circuit 103 Adjustment coefficient (a coefficient for multiplying the received signal amplitude so as to keep the total received power constant. In an AGC circuit for temporarily maintaining the power K, K = (gain adjustment coefficient / received signal) ² (Where K is the power and the square is established), the inverse of the square may be used. As described above, since the gain adjustment coefficient of the AGC circuit 103 is the reciprocal of the coefficient that depends on the instantaneous reception amplitude, it is necessary to newly calculate a coefficient that depends on the instantaneous reception amplitude by using this gain adjustment coefficient. Therefore, the soft decision likelihood value can be easily corrected.
[0100]
Further, in the above-described embodiment, the case where S / N is used as the ratio between the desired wave component and the noise component of the received signal by paying attention to noise power has been described, but this S / N includes SIR. .
[0101]
Further, in the above-described embodiment, the case where a Viterbi decoder is used as the error correction decoder 106 has been described. However, the present invention is not limited to this. For example, turbo encoding is performed on the transmission side, and Other encoding and decoding methods may be used, such as performing turbo decoding on the receiving side.
[0102]
(Embodiment 3)
FIG. 8 is a block diagram showing a configuration of receiving apparatus 300 according to Embodiment 3 of the present invention. However, components having the same configuration as in FIG. 1 are denoted by the same reference numerals as in FIG. 1, and detailed description is omitted.
[0103]
The receiving apparatus 300 shown in FIG. 8 is different from the receiving apparatus 100 described above with reference to FIG. 1 in that, instead of measuring the noise power value, other cell interference is performed based on the received power from the currently communicating cell and other cells. The difference is that the amount is calculated and the demodulation section 104 determines whether or not to correct the soft decision likelihood value based on the number of fingers used for data demodulation and the amount of interference from other cells.
[0104]
That is, in FIG. 8, receiving apparatus 300 includes cell search section 301 and finger assignment control section 302, and cell search section 301 divides the received power from another cell by the received power from the cell currently communicating. , And outputs the result of the division to the reception amplitude weight multiplication control section 308 as the other cell interference amount.
[0105]
In addition, finger assignment control section 302 outputs the number of fingers used in the rake combining reception processing at the time of data demodulation in demodulation section 104 to reception amplitude weight multiplication control section 308.
[0106]
Receiving amplitude weight multiplication control section 308 compares the other cell interference amount output from cell search section 301 with a preset threshold value, and determines that the other cell interference amount is smaller than the threshold value and finger allocation control section 302 If the number of fingers output from is more than one, the soft decision likelihood value calculation section 107 outputs a control signal for preventing the soft decision likelihood value from being multiplied by a weighting factor depending on the instantaneous reception amplitude.
[0107]
On the other hand, if at least one of the other cell interference amount is smaller than the threshold value or the number of fingers is not satisfied, the reception amplitude weight multiplication control unit 308 determines the soft decision likelihood. A control signal for multiplying the soft decision likelihood value by a weight coefficient depending on the instantaneous reception amplitude is output to degree value calculating section 107.
[0108]
As described above, when the other cell interference amount is small and the number of fingers is plural, the main component of the noise power value of the received signal is due to multipath. In this case, the S / N of the received signal is high. Can be determined not to vary, and the soft decision likelihood value calculation unit 107 does not multiply the soft decision likelihood value by the weighting coefficient (correction of the soft decision likelihood value). Therefore, a correct soft decision likelihood value according to S / N can be calculated, and a decrease in error correction capability can be suppressed.
[0109]
FIG. 9 is a flowchart illustrating an error correction decoding processing procedure in the receiving apparatus 300. As shown in FIG. 9, receiving apparatus 300 reads the other cell interference amount and the number of fingers related to the received signal in step ST301, and in step ST302, based on the other cell interference amount and the number of fingers, the other cell interference amount is smaller than a threshold. It is determined whether both are small and the number of fingers is plural.
[0110]
If a positive result is obtained in step ST302, this means that the main component of the noise power value of the received signal is due to multipath, that is, the S / N of the received signal is constant and the soft decision likelihood value When the correction is performed, a correct soft decision likelihood value cannot be obtained, and as a result, a state in which the error correction capability may be reduced due to the correction of the soft decision likelihood value may be caused. At this time, the receiving apparatus 300 moves to step ST303 and performs error correction processing without performing correction on the soft decision likelihood value.
[0111]
On the other hand, if a negative result is obtained in step ST302, this means that the main component of the noise power value of the received signal is not due to multipath, that is, the S / N of the received signal is not constant, By correcting the soft decision likelihood value, it is possible to obtain a correct soft decision likelihood value, and as a result, it is in a state where a certain error correction capability can be maintained. The receiving apparatus 300 proceeds to step ST304 and performs error correction processing involving correction of the soft decision likelihood value.
[0112]
As described above, according to the receiving apparatus of the present embodiment, based on the other cell interference amount and the number of fingers related to a received signal, it is determined whether or not the main component of the noise power value of the received signal is due to multipath. By judging and controlling whether or not to perform the weighting process based on the judgment result, it is possible to accurately calculate the soft decision likelihood value.
[0113]
In the above-described embodiment, the case where a weight coefficient depending on the instantaneous reception amplitude is used as a method for correcting the soft decision likelihood value has been described, but the present invention is not limited to this, and the gain in the AGC circuit 103 Adjustment coefficient (a coefficient for multiplying the received signal amplitude so as to keep the total received power constant. In an AGC circuit for temporarily maintaining the power K, K = (gain adjustment coefficient / received signal) ² (Where K is the power and the square is established), the inverse of the square may be used. As described above, since the gain adjustment coefficient of the AGC circuit 103 is the reciprocal of the coefficient that depends on the instantaneous reception amplitude, it is necessary to newly calculate a coefficient that depends on the instantaneous reception amplitude by using this gain adjustment coefficient. Therefore, the soft decision likelihood value can be easily corrected.
[0114]
Further, in the above-described embodiment, the case where S / N is used as the ratio between the desired wave component and the noise component of the received signal by paying attention to noise power has been described, but this S / N includes SIR. .
[0115]
Further, in the above-described embodiment, the case where a Viterbi decoder is used as the error correction decoder 106 has been described. However, the present invention is not limited to this. For example, turbo encoding is performed on the transmission side, and Other encoding and decoding methods may be used, such as performing turbo decoding on the receiving side.
[0116]
(Embodiment 4)
FIG. 10 is a block diagram showing the configuration of receiving apparatus 400 according to Embodiment 4 of the present invention. However, components having the same configuration as in FIG. 1 are denoted by the same reference numerals as in FIG. 1, and detailed description is omitted.
[0117]
The receiving apparatus 400 shown in FIG. 10 measures the instantaneous noise power value instead of measuring the noise power fluctuation amount as compared with the receiving apparatus 100 described above with reference to FIG. By correcting the soft-decision likelihood value based on the weighting coefficient depending on the instantaneous reception amplitude, even if the noise power value and the received signal power value fluctuate independently, the S / N can be determined. The difference is that a correct soft decision likelihood value is calculated.
[0118]
That is, in FIG. 10, receiving apparatus 400 includes noise power fluctuation amount measuring section 401 that measures the instantaneous noise power value. The noise power fluctuation amount measuring section 401 receives the demodulated signal output from the demodulating section 104 and a weight coefficient depending on the instantaneous reception amplitude output from the AGC circuit 103.
[0119]
Since the demodulated signal is controlled by the AGC circuit 103 so that the total received power becomes constant, it is difficult to measure the correct instantaneous noise power as it is. Therefore, the noise power fluctuation measuring section 401 multiplies the measured instantaneous noise power by the weight coefficient supplied from the AGC circuit 103. Since the weighting factor depends on the instantaneous reception amplitude, the instantaneous noise power is multiplied by the weighting factor, so that the change in the noise power given by the AGC circuit 103 so that the total reception power is constant. Can be removed. The result of this multiplication is output to the soft decision likelihood value calculation section 407 of the error correction decoder 106 as the instantaneous noise power value.
[0120]
Soft decision likelihood value calculating section 407 calculates a soft decision likelihood value based on a demodulated signal (a demodulated signal based on a received signal subjected to AGC control) output from demodulating section 104, and calculates the calculated soft decision likelihood value. The degree value is multiplied by a weighting factor depending on the instantaneous reception amplitude, and the multiplication result is further divided by the instantaneous noise power value output from the noise power fluctuation amount measuring section 401.
[0121]
Accordingly, even when the received signal power value and the noise power value included in the total received signal power fluctuate independently, the variation of the total received signal power value is multiplied by the weighting factor depending on the instantaneous reception amplitude. And the fluctuation of the noise power value is compensated by division by the instantaneous noise power.
[0122]
Thus, even when the noise power value and the received signal power value fluctuate independently, it is possible to calculate a correct soft decision likelihood value according to the S / N, and suppress a decrease in error correction capability. be able to.
[0123]
Incidentally, FIG. 11 is a flowchart illustrating a procedure for correcting the soft decision likelihood value in the soft decision likelihood value calculation unit 407 of the receiving apparatus 400. As shown in FIG. 11, soft decision likelihood value calculating section 407 acquires a demodulated signal, a weight coefficient (weight coefficient depending on instantaneous reception amplitude) and an instantaneous noise power value regarding a received signal in step ST401, and then proceeds to step ST402. , A soft decision likelihood value is calculated based on the demodulated signal.
[0124]
Then, the soft decision likelihood value calculating section 407 proceeds to step ST403, where the soft decision likelihood value calculated in step ST402 is multiplied by a weighting factor depending on the instantaneous reception amplitude and the instantaneous noise power value. Division by. As described above, by multiplying the soft decision likelihood value by the weight coefficient depending on the instantaneous reception amplitude, the AGC circuit 103 applies the AGC signal to the received signal whose total received signal power is kept constant. By restoring the state before processing by the circuit 103 and further dividing the restored signal by the instantaneous noise power value, a soft decision likelihood value based on the received signal power value in a state where the noise power value does not fluctuate, That is, the ratio of the soft decision likelihood value equal to the S / N ratio at each time point can be obtained.
[0125]
Incidentally, FIG. 12 shows a correction in which the soft decision likelihood value is multiplied by a weight coefficient depending on the instantaneous reception amplitude and further divided by the noise power when the received signal power value and the noise power value fluctuate independently. FIG. 11 is a diagram showing a corrected soft decision likelihood value at each point in time when.
[0126]
As shown in FIG. 12, the ratio of the soft decision likelihood value after correction at each time point is the case of the received signal power and the noise power which fluctuate while maintaining the constant S / N ratio described above with reference to FIG. The result is similar to the above, and it can be seen from this result that the soft decision likelihood value was correctly calculated.
[0127]
Thus, even when the received signal power value and the noise power value fluctuate independently, a correct soft decision likelihood value according to S / N can be calculated.
[0128]
As described above, according to the receiving apparatus of the present embodiment, the instantaneous noise power value is measured, and the soft decision likelihood value is calculated based on the measured instantaneous noise power value and the weight coefficient depending on the instantaneous reception amplitude. , It is possible to calculate a correct soft decision likelihood value in accordance with the S / N even when the noise power value and the received signal power value fluctuate independently.
[0129]
In the above-described embodiment, the case where a weight coefficient depending on the instantaneous reception amplitude is used as a method for correcting the soft decision likelihood value has been described, but the present invention is not limited to this, and the gain in the AGC circuit 103 Adjustment coefficient (a coefficient for multiplying the received signal amplitude so as to keep the total received power constant. In an AGC circuit for temporarily maintaining the power K, K = (gain adjustment coefficient / received signal) ² (Where K is the power and the square is established), the inverse of the square may be used. As described above, since the gain adjustment coefficient of the AGC circuit 103 is the reciprocal of the coefficient that depends on the instantaneous reception amplitude, it is necessary to newly calculate a coefficient that depends on the instantaneous reception amplitude by using this gain adjustment coefficient. Therefore, the soft decision likelihood value can be easily corrected.
[0130]
Further, in the above-described embodiment, the case where S / N is used as the ratio between the desired wave component and the noise component of the received signal by paying attention to noise power has been described, but this S / N includes SIR. .
[0131]
Further, in the above-described embodiment, the case where a Viterbi decoder is used as the error correction decoder 106 has been described. However, the present invention is not limited to this. For example, turbo encoding is performed on the transmission side, and Other encoding and decoding methods may be used, such as performing turbo decoding on the receiving side.
[0132]
【The invention's effect】
As described above, according to the present invention, while the received signal power fluctuates, the ratio of the desired signal component to the noise component of the received signal does not fluctuate, or the received signal power and the noise component power are not changed. In a communication environment that fluctuates independently, it is possible to correctly calculate a likelihood value and perform error correction processing.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a noise power fluctuation amount measuring unit according to the first embodiment.
FIG. 3 is a schematic diagram for explaining a process of calculating a soft decision likelihood value;
FIG. 4 is a block diagram showing a configuration of an error correction decoder according to Embodiment 1.
FIG. 5 is a flowchart showing an error correction decoding processing procedure according to the first embodiment.
FIG. 6 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 2 of the present invention.
FIG. 7 is a flowchart showing an error correction decoding processing procedure according to the second embodiment.
FIG. 8 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 3 of the present invention.
FIG. 9 is a flowchart showing an error correction decoding processing procedure according to the third embodiment.
FIG. 10 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 4 of the present invention.
FIG. 11 is a flowchart showing a procedure for correcting a soft decision likelihood value according to the fourth embodiment;
FIG. 12 is a diagram showing a correction result of a soft decision likelihood value according to the fourth embodiment.
FIG. 13 is a signal waveform diagram showing a received signal waveform in a communication environment in which noise power does not fluctuate.
FIG. 14 is a diagram showing S / N (received signal power / noise power) in a communication environment in which noise power does not fluctuate.
FIG. 15 is a signal waveform diagram showing a waveform of a received signal after AGC processing in a communication environment where there is no fluctuation in noise power.
FIG. 16 is a diagram illustrating a soft decision likelihood value (without correction) of a signal after AGC processing of a received signal in a communication environment in which there is no fluctuation in noise power.
FIG. 17 is a diagram showing a soft decision likelihood value (with correction) of a signal after AGC processing of a received signal in a communication environment in which there is no fluctuation in noise power.
FIG. 18 is a signal waveform diagram showing a received signal waveform in a communication environment in which received signal power and noise power fluctuate while maintaining S / N.
FIG. 19 is a diagram showing S / N in a communication environment in which received signal power and noise power fluctuate while maintaining S / N.
FIG. 20 is a signal waveform diagram showing a waveform of a received signal waveform after AGC processing in a communication environment in which received signal power and noise power fluctuate while maintaining S / N.
FIG. 21 is a diagram showing a soft decision likelihood value (without correction) of a signal after AGC processing of a received signal waveform in a communication environment in which received signal power and noise power fluctuate while maintaining S / N.
FIG. 22 is a diagram showing a soft decision likelihood value (with correction) of a signal after AGC processing of a received signal waveform in a communication environment in which received signal power and noise power fluctuate while maintaining S / N.
FIG. 23 is a signal waveform diagram showing a received signal waveform in a communication environment in which received signal power and noise power vary independently.
FIG. 24 is a diagram showing the S / N of a received signal in a communication environment in which the received signal power and the noise power vary independently.
FIG. 25 is a signal waveform diagram showing a waveform after AGC processing of a received signal in a communication environment in which the received signal power and the noise power vary independently.
FIG. 26 is a diagram illustrating a soft decision likelihood value (with and without correction) of a signal after AGC processing of the received signal in a communication environment in which the received signal power and the noise power vary independently.
[Explanation of symbols]
100, 200, 300, 400 receiving device
101 antenna
102 RF receiver
103 AGC circuit
104 demodulation unit
105 Noise power fluctuation measurement unit
106 error correction decoder
107, 407 Soft decision likelihood value calculation unit
108, 208, 308 Receive amplitude weight multiplication control unit
111, 401 Noise power measurement unit
112 delay unit
113 Comparison Division
201 transmission power control unit
301 Cell Search Unit
302 Finger Assignment Control Unit

Claims (7)

Gain control means for keeping the total signal power of the received signal constant;
When the received code sequence is subjected to maximum likelihood decoding for a signal whose total received signal power is kept constant by the gain control means, the likelihood of the candidate code for each received code is represented by a multi-level likelihood. And a likelihood value calculating means for correcting the likelihood as necessary.
Noise component fluctuation detecting means for detecting a fluctuation of a noise component included in the received signal,
Correction control means for determining whether or not to perform the correction depending on the instantaneous amplitude of the received signal, based on the detection result of the noise component fluctuation detection means,
A receiving device comprising: Gain control means for keeping the total signal power of the received signal constant;
When the received code sequence is subjected to maximum likelihood decoding for a signal whose total received signal power is kept constant by the gain control means, the likelihood of the candidate code for each received code is represented by a multi-level likelihood. And a likelihood value calculating means for correcting the likelihood as necessary.
A correction for determining whether or not to perform the correction depending on the instantaneous amplitude of the received signal on the likelihood based on information indicating a change in a ratio between a desired wave component and a noise component included in the received signal. Control means;
A receiving device comprising: The receiving apparatus according to claim 2, wherein the correction control unit determines whether or not the correction is performed based on whether or not the received signal is transmitted under transmission power control. 3. The receiving apparatus according to claim 2, wherein the correction control unit determines whether or not the correction is performed based on whether a main component of a noise component included in the received signal is due to multipath. . Gain control means for keeping the total signal power of the received signal constant;
When the received code sequence is subjected to maximum likelihood decoding for a signal whose total received signal power is kept constant by the gain control means, the likelihood of the candidate code for each received code is represented by a multi-level likelihood. A likelihood value calculating means for multiplying the likelihood by a weighting factor depending on the instantaneous amplitude of the received signal and dividing by a noise component value included in the received signal,
A receiving device comprising: When the received code sequence of the received signal is subjected to maximum likelihood decoding, the likelihood of the candidate code is given as a multilevel likelihood for each received code, and the likelihood depends on the instantaneous amplitude of the received signal. Likelihood value calculating means for multiplying the weighted coefficient and dividing by the noise component value included in the received signal,
Decoding means for performing error correction decoding based on the likelihood value calculated by the likelihood value calculation means,
An error correction decoding device comprising: When the received code sequence of the received signal is subjected to maximum likelihood decoding, the likelihood of the candidate code is given as a multilevel likelihood for each received code, and the likelihood depends on the instantaneous amplitude of the received signal. A likelihood value calculating step of multiplying by the weighted coefficient and dividing by a noise component value included in the received signal,
A decoding step of performing error correction decoding based on the likelihood value calculated by the likelihood value calculation means,
An error correction decoding method comprising:

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