JP2000078110A - Rake receiver, radio receiver and path detection method in rake receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reception performance by obtaining an optimum threshold value even in the case that an interference amount is changed and the gain is changed. SOLUTION: A matched filter 11 of a base band demodulator being a RAKE receiver obtains a correlation output (I and Q signals), a level measurement device 12 measures a level of the correlation output, a threshold value calculator 13 obtains respectively a mean value and a standard deviation based on a level measured by the level measurement device 12, adds the mean value to a value applying a prescribed weight to the standard deviation to obtain a threshold value, and a threshold value discrimination device 14 detects a path with a level over the threshold value obtained by the threshold value calculator 13 among levels measured by the level measurement device 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique of a spread spectrum communication system, and more particularly, to a RAKE receiver, a radio receiver, and a path detecting method of a RAKE receiver for performing RAKE combining by despreading a received signal. Things.

[0002]

2. Description of the Related Art In a spread spectrum communication system used in the DS-CDMA system, a RAKE reception is performed on the receiving side, so that a signal power ratio to thermal noise can be improved.

[0003] RAKE reception is a method of separating a preceding wave and a delayed wave by despreading from a received signal on which a preceding wave and a delayed wave having different delay times and undergoing independent fading fluctuations are superimposed on a multipath propagation path. The delay effect of the preceding wave and the delayed wave is made uniform, the phases are made in-phase, and weighting is performed on the received signal level to perform RAKE combining (maximum ratio combining), thereby obtaining a diversity effect.

In wideband DS-CDMA, since the chip rate can be increased, a received signal is separated into many multipaths, and the effect of RAKE reception is great.

FIG. 10 is a block diagram of a RAKE receiver using a two-step threshold multipath selection method. Conventional RA
As shown in FIG. 10, the KE receiver includes a matched filter 41, a propagation path fluctuation estimating unit 42, a level measuring unit 43, a complex conjugate unit 44, a multiplier 45, a two-stage multipath selecting unit 4
6, RAKE combining section 47, and threshold setting section 48
It has. The two-step threshold multipath selection method is described in Akira Fukumoto and two others, “IEICE Technical Report RCS97-119” (1997-10) p. 43-4
It is known as 8 mag.

In RAKE reception, it is necessary to separate a noise component and a multipath component from a correlation output obtained by despreading a received signal, and to perform diversity combining of only the multipath component. In the configuration shown in the figure, a threshold value is set in two stages to select a multipath input signal to be subjected to diversity combining.

FIG. 10 shows an example of a configuration in which a spectrum-spread received signal is despread in a matched filter 41 to output a correlation waveform (delay profile), and a RAKE combining unit 47 performs RAKE reception. I have. Note that the received signal is obtained by QPSK-modulating transmission data and further spreading-modulating with QPSK.

[0008] The matched filter 41 is a circuit that matches the spread code of the received signal. Matched filter 4
The correlation output of 1 is output to the propagation path fluctuation estimating unit 42, the level measuring unit 43, and the multiplier 45. Propagation path fluctuation estimation unit 42
In PSA, the PSA (Pi
lot symbol averaging cohe
The propagation path fluctuation is estimated by channel evaluation using a “rent detection” method, and the phase of each multipath for performing phase in-phase necessary for RAKE combining is obtained.

The level measuring section 43 measures the received signal level of each multipath from the correlation output. The complex conjugate unit 44 and the multiplier 45 take the complex conjugate of the estimation result by the propagation path fluctuation estimation unit 42 for the above-mentioned phase in-phase,
This is multiplied by the correlation output.

The two-stage multi-path selecting section 46 includes a multiplier 4
5 is input, multi-path selection is performed using two-stage threshold values, and the result is output to the RAKE combining unit 47. The threshold setting unit 48 is a block for inputting the output of the level measuring unit 43 and setting the two-step threshold.

Next, the frame format will be described. FIG. 11 is a diagram illustrating a frame configuration of a received signal. In FIG. 11, one frame is composed of a plurality of slots, and one slot has several pilot symbols at the beginning, followed by data symbols.

Here, the pilot symbol is a symbol used for measuring the state of the propagation path, and is composed of data known between the transmitting side and the receiving side. The data symbol is a symbol for transmitting transmission information.

Next, the operation of the receiving section shown in FIG. 10 will be described with reference to FIG. The received signal having the frame configuration shown in FIG. 11 is input to the matched filter 41 shown in FIG. 10, and the spectrum is despread. This despreading,
This corresponds to correlating the reference signal preset in the matched filter 41 with the received signal. The reference sequence is a sequence that matches the spreading code of the received signal.

In the correlation output output from the matched filter 41, each multipath of the propagation path of the received signal is output in a time-separated state. At this time, the amplitude and phase of each multipath are changed for each multipath due to the change of the propagation path, and the correlation waveform is output in a form including the amplitude and phase fluctuation.

The propagation path fluctuation estimating section 42 separates each multipath of the propagation path from the correlation output, detects a pilot symbol shown in FIG. 11 in the received signal, and detects information (amplitude, phase, etc.) of the pilot symbol. ) Is known to the receiving side, the amplitude and the phase variation of the fading variation in each multipath are measured, and the fading variation of each multipath in the data symbol is estimated based on the measurement result.

The complex conjugate unit 44 takes the complex conjugate of the fading fluctuation of each multipath obtained by the propagation path fluctuation estimating unit 42 and converts the result into a correlation output which is an output of the matched filter 41 in a multiplier 45. Multiply. In the correlation output of the matched filter 41, the preceding wave due to the multipath propagation path,
Each multipath such as a delayed wave is separated and output by a delay time difference, and each multipath fluctuates in amplitude and phase due to independent fading fluctuation.

A propagation path fluctuation estimating unit 42 is provided for each multipath.
By multiplying the complex conjugate of the estimated value of the amplitude and the phase variation of each multipath estimated in the above, the phase variation and the amplitude variation can be removed. Removing the phase fluctuation corresponds to equalizing the phase fluctuation of each multipath. Further, the operation of multiplying the estimated value of the amplitude fluctuation by multiplication corresponds to performing weighting of each multipath at the time of RAKE combining.

The level measuring section 43 measures the received signal level of each multipath from the output of the matched filter 41. The two-stage multipath selecting unit 46 uses the measurement result of the received signal level of each multipath and the threshold value set in the threshold value setting unit 48 to convert the output of the multiplier 45 into a multilevel signal used for RAKE combining. Select a path.

Next, details of the multipath selection will be described with reference to FIG.
This will be described with reference to FIG. FIG. 12 is a diagram illustrating received signal levels for describing operations of the threshold value setting unit and the two-stage multipath selection unit. 12, the vertical axis indicates the received signal level, and the horizontal axis indicates the time axis indicating the delay time of each multipath of the preceding wave and the delayed wave. Also, a to p are obtained by averaging and sampling the received signal levels of the respective multipaths output from the level measuring unit 3, and are hereinafter simply referred to as samples a to p.

The level of each sample a to p indicates the level of multipath or noise. Here, sample a, sample b, sample d, and sample k are set as samples indicating the received signal levels of the preceding wave and the delayed wave by the multipath, and the other samples are set as the sample values of the noise component.

In order for communication to be established, the preceding wave and the delayed wave due to multipath need to be higher than the noise level. Therefore, the two-stage multipath selector 46 and the threshold setting unit 48 select a path in the following procedure. In the samples a to p in FIG. 12, when the number of samples is L, the minimum reception power Smin and the maximum reception power Smax are detected in the L samples. Next, a threshold △ noise is set (に 対 し noise ≧ 0) in order not to synthesize a sample of only a noise component with the minimum received power Smin.

On the other hand, for the maximum received power Smax, RA
To select a sample having a signal effective for KE synthesis, a threshold value △ RAKE is set (△ RAKE ≧
0). From the samples a to p, only those samples whose level S (1) satisfies the following conditions are selected. S (j) ≧ max ｛Smin + △ noise, Smax
− {RAKE} Here, the symbol of max {A, B} means that A or B takes a larger value.

As a result, assuming that the settings of △ RAKE and △ noise are correctly set, it is possible to select only the samples indicating the reception signal levels of the preceding wave and the delayed wave by the multipath from the samples a to p, and It is possible not to select a sample by In the example of FIG. 11, (Smin + {noise) <(Smax− △)
(RAKE), a sample having a higher level than (Smax− △ RAKE) is selected, and a sample a, a sample b, a sample d, and a sample k indicating a multipath received signal level are selected.

The two-stage multipath selecting section 46 selects a multipath sample in the above-described manner, and outputs the output of the multiplier 45 at the same timing as the selected sample to RA.
Output to the KE combiner 47. In the RAKE combining unit 47, the multiplier 4 corresponding to the timing of the multipath sample selected by the two-stage multipath selecting unit 46 is used.
5 is input, and by synthesizing the signals,
It is possible to exclude only a signal consisting of noise and perform combining only with a signal effective for RAKE combining.

However, in an actual propagation path, the magnitude of the level fluctuation due to fading and the noise level differ depending on the propagation path. Therefore, if the propagation environment changes, these level fluctuations and noise fluctuations greatly differ. Therefore, in a conventional RAKE receiver,
If both of the above-mentioned parameters $ RAKE and $ noise are not properly selected, there is the following problem.

(1) When ΔRAKE is smaller than the optimal value, Smax−ΔRAK is smaller than the minimum value of the samples a to p indicating the multipath received signal level.
Since E increases, all of the samples that can be used for RAKE synthesis cannot be used for RAKE synthesis, and the characteristics deteriorate. (2) △ RAKE is larger than the optimum value and △ noise
Is smaller than the optimum value, the value of the sample of the noise level becomes larger than Smax- △ RAKE, and a noise component that cannot be used for RAKE synthesis is originally synthesized, and the characteristics are deteriorated. (3) When ｏnoise is larger than the optimum value, Smin + △ noise becomes larger than the minimum value of the levels of the samples a to p indicating the received signal level of the multipath, and all the samples that can be originally used for RAKE combining are RAKE.
It cannot be used for synthesis and its properties deteriorate.

Because of such a problem, it is difficult to exclude only noise-only signals and combine only signals effective for RAKE combining.

However, in an actual propagation path, the magnitude of the level fluctuation due to fading and the noise level differ depending on the propagation path. Therefore, if the propagation environment changes, these level fluctuations and noise fluctuations greatly differ.

[0029]

Therefore, as described above, in the conventional RAKE receiver, the parameter △
If both RAKE and $ noise are not properly selected, there is the following problem.

First, when ΔRAKE is smaller than the optimum value, Smax−ΔRA is smaller than the minimum value of the samples a to p indicating the multipath received signal level.
Since the KE increases, all of the samples that can be used for RAKE synthesis cannot be used for RAKE synthesis, and the characteristics deteriorate. Second, when △ RAKE is greater than the optimal value and △ noise is less than the optimal value, the value of the noise level sample is Smax− △ RAK.
The noise component becomes larger than E, and a noise component that cannot be used for RAKE combining is originally combined, so that the characteristics are deteriorated. Third, when △ noise is larger than the optimum value, Smin + △ noise becomes larger than the minimum value of the levels of the samples a to p indicating the received signal level of the multipath, and all of the samples that can be originally used for RAKE combining are removed. RAKE
It cannot be used for synthesis and its properties deteriorate.

Since such a problem occurs, it is difficult to exclude only noise-only signals and perform synthesis using only signals effective for RAKE synthesis.

The present invention has been made in order to solve the above-described problems, and it is possible to set an optimum threshold value to improve the reception performance even when the amount of interference changes or the gain changes. It is an object of the present invention to obtain a possible RAKE receiver, a radio receiving apparatus and a path detecting method of a RAKE receiver.

[0033]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, a RAKE receiver according to the present invention is a RAKE receiver for performing RAKE combining according to path detection equal to or greater than a threshold value, wherein the level measuring device measures a level based on a correlation output; A threshold calculator for determining an average value and a standard deviation based on the level measured by the measuring device, and adding a mean value to a value obtained by applying a predetermined weight to the standard deviation; And a threshold value judging unit for detecting a path of a level equal to or higher than the threshold value obtained by the threshold value calculator among the levels measured by the threshold value calculator.

According to the present invention, the threshold calculator calculates
An average value and a standard deviation are obtained based on the level measured by the level measuring device, and the average value is added to a value obtained by applying a predetermined weight to the standard deviation to obtain a threshold value. Therefore, among the levels measured by the level measuring device, the path that is equal to or higher than the threshold value obtained by the threshold calculator is detected as a path, so there is no optimum even when the amount of interference changes or the gain changes. The threshold is set,
It is possible to improve reception performance.

A RAKE receiver according to the next invention is a RAKE receiver for performing RAKE combining according to detection of a path equal to or greater than a threshold value, wherein the level measuring device measures a level based on a correlation output; A threshold calculator for obtaining an average value based on the measured levels and applying a predetermined weight to the average value to obtain a threshold value; and a threshold value calculator among the levels measured by the level measurement device. And a threshold value judging device for detecting a path at a level equal to or higher than the threshold value obtained in the step (c).

According to the present invention, in the threshold calculator,
An average value is obtained based on the level measured by the level measuring device, and a predetermined weight is applied to the average value to obtain a threshold value.
Since the threshold value judging device detects a path that is equal to or higher than the threshold value obtained by the threshold value calculator among the levels measured by the level measuring device, the interference amount changes with a simple configuration. The optimum threshold value is set even when the gain changes or when the gain changes, whereby it is possible to improve the reception performance.

A RAKE receiver according to the next invention is a RAKE receiver for performing RAKE combining in accordance with detection of a path equal to or greater than a threshold value, wherein a matched filter for obtaining a correlation output from a received signal and a correlation output of the matched filter are provided. A level measuring instrument for measuring the level, a mean value based on the level of the received signal, a threshold calculator for obtaining a threshold value by applying a predetermined weight to the mean value, and measuring with the level measuring device. And a threshold value judging unit for detecting a path of a level equal to or higher than the threshold value obtained by the threshold value calculator.

According to the present invention, the level is measured by the level measuring device based on the correlation output of the matched filter.
In the threshold calculator, an average value is obtained based on the level of the received signal, a predetermined weight is applied to the average value to obtain a threshold value, and the threshold value is measured by the level measuring device in the threshold value judging device. Of the levels, the path that is equal to or higher than the threshold value obtained by the threshold calculator is detected as a path, so even if the amount of interference changes or the gain changes with a simple configuration, the optimum threshold value is set. As a result, it is possible to improve the reception performance.

A radio receiving apparatus according to the next invention is a radio receiving apparatus for obtaining a demodulated signal in accordance with path detection equal to or greater than a threshold value, wherein the level measuring means for measuring a level based on a correlation output; Threshold value calculating means for obtaining an average value and a standard deviation based on the measured level, and adding the average value to a value obtained by applying a predetermined weight to the standard deviation to obtain a threshold value; Threshold value determining means for detecting a path of a level equal to or higher than the threshold value obtained by the threshold value calculating means among the measured levels;
RAKE combining means for obtaining a demodulated signal by performing AKE combining.

According to the present invention, the level is measured based on the correlation output, an average value and a standard deviation are respectively obtained based on the measured level, and the average value is added to a value obtained by applying a predetermined weight to the standard deviation. When the interference amount changes, a demodulated signal is obtained by obtaining a threshold value, detecting a path above the threshold value among the measured levels, and performing RAKE combining according to the detected path. Even when the gain or the gain changes, an optimal threshold value is set for RAKE combining, thereby making it possible to improve reception performance.

According to another aspect of the present invention, there is provided a radio receiving apparatus for obtaining a demodulated signal in accordance with detection of a path equal to or greater than a threshold value, the level measuring means for measuring a level based on a correlation output, and the level measuring means. A threshold value calculating means for obtaining an average value based on the measured levels and applying a predetermined weight to the average value to obtain a threshold value; and a threshold value calculating means among the levels measured by the level measuring means. Threshold value determining means for detecting a path equal to or higher than the threshold value obtained in step (a), and RA RA for obtaining a demodulated signal by performing RAKE combining in accordance with the path detection of the threshold value determining means.
And KE combining means.

According to the present invention, a level is measured based on the correlation output, an average value is obtained based on the measured level, a predetermined weight is applied to the average value, and a threshold value is obtained.
Of the measured levels, a path that is equal to or higher than the threshold is detected, and a demodulated signal is obtained by performing RAKE combining in accordance with the detected path. RAK even if you do
An optimal threshold value is set for E-combining, which makes it possible to improve reception performance.

A radio receiving apparatus according to the next invention is a radio receiving apparatus for obtaining a demodulated signal in accordance with path detection equal to or more than a threshold value, wherein matched filter means for obtaining a correlation output from the received signal, and correlation output of the matched filter means Level measuring means for measuring the level based on the received signal level, an average value is obtained based on the level of the received signal, threshold value calculating means for applying a predetermined weight to the average value to obtain a threshold value,
Threshold value determining means for detecting a path equal to or higher than the threshold value obtained by the threshold value calculating means among the levels measured by the level measuring means; And RAKE combining means for obtaining a demodulated signal by performing

According to the present invention, the level is measured based on the matched filter correlation output, the average value is obtained based on the level of the received signal, a predetermined weight is applied to the average value to obtain a threshold value, and the measurement is performed. Of the levels, a path equal to or higher than a threshold is detected, and RAKE is performed in accordance with the detected path.
Since the demodulated signal is obtained by performing the combination, the optimum threshold value for RAKE combining is set even when the amount of interference changes or the gain changes with a simple configuration, thereby improving the reception performance. It becomes possible to plan.

A path detection method for a RAKE receiver according to the next invention is characterized in that the RAKE receiver detects a path in accordance with a path detection equal to or greater than a threshold value.
In a path detection method of a RAKE receiver for performing KE combining, an average value and a standard deviation are respectively obtained based on the level of the correlation output, and a value obtained by applying a predetermined weight to the obtained standard deviation is added to the average obtained above. A threshold is obtained by adding the values, and a path that is equal to or higher than the threshold obtained above among the levels of the correlation output is path-detected.

According to the present invention, an average value and a standard deviation are respectively obtained based on the level of the correlation output, and the average value is added to a value obtained by weighting the standard deviation by a predetermined value to obtain a threshold value. Thus, among the levels of the correlation output, a path that is equal to or higher than the threshold value is detected, so that even when the amount of interference changes or the gain changes, the optimum threshold value for RAKE combining is set. Thereby, it is possible to improve reception performance.

A path detection method for a RAKE receiver according to the next invention is characterized in that the RAKE receiver detects
In a path detection method of a RAKE receiver for performing KE combining, an average value is obtained based on a level of a correlation output, a predetermined weight is applied to the obtained average value to obtain a threshold value, and a level of the level of the correlation output is obtained. Among them, the path detection is performed at a level higher than the threshold value obtained above.

According to the present invention, an average value is obtained based on the level of the correlation output, a predetermined weight is applied to the average value to obtain a threshold value, and the threshold value of the correlation output level is equal to or higher than the threshold value. Is detected, the optimum threshold value for RAKE combining is set only by the average value even when the amount of interference changes or the gain changes, thereby improving the reception performance. It becomes possible.

A path detecting method of a RAKE receiver according to the next invention is characterized in that the RAKE receiver detects
In a path detection method of a RAKE receiver that performs KE combining, an average value is obtained based on the level of a received signal, a predetermined weight is applied to the obtained average value to obtain a threshold value, and a level of a correlation output level is obtained. Among them, the path detection is performed at a level higher than the threshold value obtained above.

According to the present invention, an average value is obtained based on the level of a received signal, a predetermined weight is applied to the average value to obtain a threshold value, and the correlation output level is equal to or higher than the threshold value. Is detected, the optimum threshold value for RAKE combining is set only by the average value even when the amount of interference changes or the gain changes, thereby improving the reception performance. It becomes possible.

[0051]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the accompanying drawings, a RAKE receiver, a radio receiver and an RA according to the present invention will be described below.
A preferred embodiment of the path detection method of the KE receiver will be described in detail.

Embodiment 1 First, the overall configuration will be described. FIG. 1 is a block diagram showing a configuration example of the wireless reception device according to the first embodiment of the present invention. Embodiment 1
As shown in FIG. 1, the wireless receiving device includes an antenna 1 for receiving a wireless signal, an RF amplifier 2 for amplifying a received signal,
Mixer 3 for mixing the intermediate frequency signal and the local oscillation signal
A, 3B, a local oscillator 5 for oscillating a local oscillation signal, a 90 ° phase shifter 4 for delaying the phase by 90 °, a low-pass filter (LPF) 6 for extracting a desired signal from a baseband signal
A, 6B, A / D converters 7A and 7B for converting a desired signal from an analog signal to a digital signal, and a RAKE receiver for despreading I and Q to perform RAKE combining, that is, a baseband demodulator 8 and RAKE combining. A digital processing circuit 9 for performing processing such as error correction on the obtained demodulated signal is provided.

In the radio receiving apparatus shown in FIG. 1, the intermediate frequency signal input via the antenna 1 and the RF amplifier 2 is divided into two channels, and the mixers 3A, 3A respectively
3B. On the other hand, a local oscillation signal output from the local oscillator 5 and having a frequency substantially equal to the desired signal is input to the mixer 3A and the 90 ° phase shifter 4
Is input to the mixer 3B.

In the mixers 3A and 3B, the intermediate frequency signal and the local oscillation signal are mixed and converted into baseband signals, respectively, and then only the desired signal is selected by the LPFs 6A and 6B. Then, the filtered desired signal of the baseband signal is A / D-converted by A / D converters 7A and 7B, and then demodulated by a baseband demodulator 8 corresponding to a RAKE receiver. It is output to a digital processing circuit 9 that performs such operations.

Next, the baseband demodulator 8 corresponding to the RAKE receiver will be described in detail. FIG. 2 shows the first embodiment.
FIG. 2 is a block diagram showing a configuration example of a baseband demodulator 8 (RAKE receiver) according to the present invention. Baseband demodulator 8
Is, for example, as shown in FIG.
1, a level measuring device 12, a threshold calculator 13, a threshold judging device 14, and a phase compensation and RAKE combiner 1.
5 is comprised.

The matched filter 11 includes the A / D converter 7
The received signals digitized by A and 7B are subjected to spectrum despreading to perform correlation output (output of I signal and Q signal). That is, this matched filter 1
In reference numeral 1, a reference sequence is set in advance, and the received signal is correlated using the reference sequence. Note that the reference sequence is a sequence that matches the spreading code of the received signal.

The level measuring device 12 has a power calculator 101A.
And a cyclic integrator 102, and measures the received signal level of each multipath based on the I signal and Q signal output from the matched filter 11. The power calculator 101A obtains the received signal level by adding the square of I and the square of Q. Also, at a timing with a path, a level obtained by noise + interference + signal is measured, and at a timing without a path, a level obtained by noise + interference is measured.

The threshold calculator 13 is provided with the average calculator 10
3. It has a standard deviation σ calculator 104, a β weighter 105, and an adder 106, and measures an average and a standard deviation from the measurement level of the level measuring device 12 to obtain a threshold value. The average value calculator 103 calculates an average value from the measurement level, and the standard deviation σ calculator 104 calculates a standard deviation σ from the measurement level. The β weighter 105 adds β to the standard deviation σ
, And the adder 106 calculates the threshold by adding the average value and σ × β.

The threshold value judging unit 14 comprises the threshold value calculator 1
Path detection is performed from the measurement level based on the threshold value obtained in step 3 to obtain a detected path. Phase compensation and RAKE
The combiner 15 performs phase compensation and RAKE combining from the detection path and the I signal and the Q signal to obtain a demodulated signal.

In the above configuration, the A / D converter 7A,
The received signal digitized by 7B is subjected to spectrum despreading by matched filter 11. As a result, the I signal and the Q signal are output to the level measurement device 12 and the phase compensation and RAKE combiner 15 as correlation outputs.

The level measuring device 12 measures the received signal level of each multipath based on the I signal and the Q signal output from the matched filter 11. The measurement level signal, which is the measurement result, is output to the threshold calculator 13 and the threshold determiner 14. In the threshold calculator 13,
The average and the standard deviation are measured from the measurement level of the level measuring device 12, and a threshold value is obtained from the addition result of these measured values. This threshold is output to the threshold determiner 14.

In the threshold value judging unit 14, a path is detected from the measurement level supplied from the level measuring unit 12 based on the threshold value obtained by the threshold value calculator 13, and a detected path is obtained. This path detection involves phase compensation and RAK
It is output to the E synthesizer 15. The phase compensation and RAKE combiner 15 performs phase compensation and RAKE combining from the detection path from the threshold value determiner 14 and the I signal and Q signal from the matched filter 11 to obtain a demodulated signal. This demodulated signal is output to the digital processing circuit 9 as described above.

Here, a specific configuration of the standard deviation σ calculator 104 will be described. FIG. 3 is a diagram illustrating a configuration example of the standard deviation σ calculator 104 according to the first embodiment.
The standard deviation σ calculator 104 includes, for example, as shown in FIG.
2, 1003, adder 1005, and route circuit 1
006.

The standard deviation σ calculator 104 shown in FIG.
In the first system, the measurement levels output from the level measuring device 12 are averaged and squared by the averaging circuit 1001 and the squaring circuit 1002, respectively, and are squared in the second system.
Each of them is squared and averaged by an averaging circuit 1004. The standard deviation σ calculator 104 further subtracts the value obtained in the second system from the value obtained in the first system to obtain the square root of the result, and sets it as the standard deviation σ.

Next, a method for determining β will be described in detail. FIG.
FIG. 3 is a graph for explaining a method of determining β in the present embodiment, wherein FIG. 4A shows a frequency distribution, FIG. 4B shows required Eb / No, and FIG. FIG. 4D shows an erroneous detection probability, and FIG. 4D shows an error function.

In FIG. 4A, the vertical axis indicates frequency, and the horizontal axis indicates level. In FIG. 4B, the vertical axis represents required Eb / No [dB] (representing required quality and corresponding to the S / N ratio per information bit) at a bit error rate of 10 ⁻³ , and the horizontal axis represents a threshold value. Indicates the level. In FIG. 9C, the vertical axis indicates the probability of erroneous detection, and the horizontal axis indicates the threshold level. FIG.
In (c), E indicates the edge of the interference + noise distribution, and D
Indicates the position of the optimum level (threshold level). In FIG. 3D, the vertical axis represents an error function erfc.
(X), the horizontal axis indicates x.

In the path detection for RAKE combining, if the threshold is smaller than the optimum threshold, noise and interference are RAKE-combined, and the performance deteriorates.
On the other hand, if the threshold value is larger than the optimum threshold value, the paths to be combined are not combined, and the performance deteriorates. Therefore, it is necessary to find an optimal threshold value for separating the path from the interference and noise.

FIG. 4A shows the frequency distribution of the output of the level measuring device 12. In FIG. 4A, the level is divided into a noise and interference side and a path side at a position D of the optimum threshold level. Since the ratio of the path to the whole is small, the average level can be almost regarded as the level of noise + interference. The distribution of interference + noise is spread as shown in FIG. 4A because the interference and noise themselves vary.

Accordingly, if the threshold level is set at the edge E (right end in the figure) of the interference + noise distribution as in the position D of the threshold level shown in FIG. Threshold levels can be obtained. The edge E of the interference + noise distribution can be defined, for example, as m + β × σ. Here, m is the average value of the level obtained by the average value calculator 103, σ is the standard deviation obtained by the standard deviation σ calculator 104 as described above, and β is a weighting coefficient of the standard deviation σ. If the optimal value of β is, for example, “3”, then
The edge E of the interference + noise distribution can be determined by m + 3σ.

As described above, the reason for finding the optimum threshold level is that there is an erroneous detection for detecting a timing when there is no path when the threshold value is low, and there is a path to be detected when the threshold value is high. This is to prevent non-detection that cannot be detected.

Degradation due to non-detection varies depending on the propagation environment. Deterioration due to erroneous detection is determined by the power of noise and interference, and in this case does not depend on the propagation environment. Therefore, an optimal threshold value can be obtained by setting the minimum threshold value that sufficiently suppresses deterioration due to erroneous detection. Therefore, as shown in FIG. 4 (b), the required Eb /
The position D at which No [DB] is lowest may be set as the threshold level.

Deterioration due to erroneous detection is determined by the erroneous detection probability. By setting the erroneous detection probability to about 5% or less, the influence of deterioration due to erroneous detection is almost eliminated.
The false detection probability is P
₁ , if the total false detection probability is Ptotal, P
The total is obtained by the following equation (1). Ptotal = 1− (1−P ₁ ) ⁿ (1) where n is the number of observation delay profile observation window length chips.

Further, assuming that Ptotal = 0.05, the false detection probability P ₁ is obtained by the following equation (2). P ₁ = 1− (1−0.05) ^{1 / n} (2)

The erroneous detection probability P at each timing
₁ is determined by the distribution of noise and interference. For example, when cyclic integration is performed sufficiently (about several tens of times), a Gaussian distribution is obtained. Note that the distribution can be calculated even when the number of cyclic integrations is small. In the case of a Gaussian distribution, if the mean is m and the standard deviation is σ, the distribution is

(Equation 1) The probability that the threshold is exceeded at the timing when there is no path,

(Equation 2) It is expressed as Here, Th is a threshold value.

[0075]

(Equation 3) Using,

(Equation 4) Becomes

Therefore, 1/2 × er shown in FIG.
From the graph of fc (x), ×× erfc (x) = P ₁
When obtaining the x ₁ serving as, Th = √2 × σ × x 1 + m , and it suffices as beta = √2 × x _1. Thus, the weighting coefficient can be obtained.

As described above, according to the first embodiment, the average value m and the standard deviation σ of the power delay profile are obtained, and the weight coefficient β obtained in advance for the standard deviation σ is obtained.
Is weighted and added to the average value m to obtain a threshold value for path detection, so that an optimal threshold value is set for RAKE combining even when the amount of interference changes or the gain changes. be able to. Further, an optimum threshold value can be set even when the averaging number or the forgetting factor is changed. As a result, it is possible to improve the performance as a spread spectrum receiver.

Next, a modification of the first embodiment will be described. First, a modified example of the power calculator will be described.
FIG. 5 is a diagram showing a modification of the power calculator according to the first embodiment. In the first embodiment, the power calculator 101A obtains the power value from the sum of the square of I and the square of Q. However, as shown in FIG. 5, the power calculator 101B obtains the power value. The power value may be obtained from the square root of the sum of the square of Q and the square of Q. In this way, if the circuit configuration for obtaining the square root is used, the number of output bits can be halved as compared with the case of a simple sum, and the size of a subsequent circuit can be reduced thereafter. In addition, in the case of this modification, the accuracy can be improved.

FIG. 6 shows another modification of the power calculator. FIG. 6 shows a configuration in which the sum of the absolute values of I and Q is used as the power value. As described above, since the calculation is simplified by taking the absolute value by the power calculator 101C, the circuit scale can be reduced in this case as well.

Next, a modification of the standard deviation σ calculator will be described. FIG. 7 is a diagram showing a modification of the standard deviation σ calculator in the first embodiment. In the modification shown in FIG. 7, the standard deviation σ calculator includes an averaging circuit 2001, an adder 2002, an absolute value circuit 2003, and an averaging circuit 2004. In this case, the operation is simplified as compared with the configuration of FIG. 3, so that the circuit scale can be reduced.

Embodiment 2 In the first embodiment, the threshold value calculator 13 has the standard deviation σ calculator 10
4, a β weighting unit 105 and an adder 106 are provided to observe the standard deviation σ and set the threshold value. However, the present invention is not limited to this, and the second embodiment described below will be described. As described above, the threshold value may be set without observing the standard deviation σ. Note that also in the second embodiment,
Since the entire configuration is the same as that of FIG. 1, its illustration and description are omitted.

Here, a baseband demodulator corresponding to a RAKE receiver will be described. FIG. 8 shows a baseband demodulator (RAKE receiver) according to Embodiment 2 of the present invention.
FIG. 3 is a block diagram showing an example of the configuration of FIG. The baseband demodulator according to the second embodiment, for example, as shown in FIG.
It comprises a matched filter 11, a level measuring device 12, a threshold value calculator 21, a threshold value judging device 14, and a phase compensation and RAKE combiner 15. Here, the configuration other than the threshold value calculator 21 is the same as the configuration in FIG. 2 (Embodiment 1), and thus detailed description is omitted.

The threshold calculator 21 has an average calculator 20.
1 and an α weighting device 202, and obtains a threshold value by measuring an average from the measurement level of the level measurement device 12. The average value calculator 201 calculates the average value from the measurement level, and the α weighting unit 202 weights the average value m with α.

In the above configuration, the A / D converter 7A,
The received signal digitized by 7B is subjected to spectrum despreading by matched filter 11. As a result, the I signal and the Q signal are output to the level measurement device 12 and the phase compensation and RAKE combiner 15 as correlation outputs.

The level measuring device 12 measures the received signal level of each multipath based on the I signal and the Q signal output from the matched filter 11. The measurement level signal, which is the measurement result, is output to the threshold calculator 21 and the threshold determiner 14. In the threshold calculator 21,
The average value calculator 201 is obtained from the measurement level of the level measurement device 12.
The average is measured according to
The threshold value is obtained by multiplying α by 2. This threshold is output to the threshold determiner 14.

In the threshold value judging unit 14, a path is detected from the measurement level supplied from the level measuring unit 12 based on the threshold value obtained by the threshold value calculator 21, and a detected path is obtained. This path detection involves phase compensation and RAK
It is output to the E synthesizer 15. The phase compensation and RAKE combiner 15 performs phase compensation and RAKE combining from the detection path from the threshold value determiner 14 and the I signal and Q signal from the matched filter 11 to obtain a demodulated signal. This demodulated signal is output to the digital processing circuit 9 as described above.

In the above operation, since the spread of noise + interference is caused by noise and interference, it is proportional to the level of noise + interference. Therefore, assuming that the average value of the level is m and the standard deviation indicating the spread is σ, σ = k × m. Therefore, if m + β × σ = (1 + k × β) m and 1 + k × β = α, the optimal threshold Th is Th = α × m.

As described above, according to the second embodiment, the coefficient α can be optimally determined in advance from the averaged number of the matched filter output, the erroneous detection rate, the non-detection rate, and the like. Can be optimally set for RAKE synthesis even if the value of the input signal changes or the gain changes. As described above, since the standard deviation σ is not observed, it is possible to suppress the circuit scale to be smaller than in the first embodiment and to realize a simplified operation.

Embodiment 3 In the second embodiment described above, the threshold value calculator is provided after the matched filter and the level measurement device, and the threshold value is set based on the cyclically integrated measurement level. However, the threshold value may be set independently of the received signal without using a matched filter as in the third embodiment described below. Note that, also in the third embodiment, since the overall configuration is the same as that of FIG. 1, the illustration and description thereof are omitted.

Here, a baseband demodulator corresponding to a RAKE receiver will be described. FIG. 9 shows a baseband demodulator (RAKE receiver) according to Embodiment 3 of the present invention.
FIG. 3 is a block diagram showing an example of the configuration of FIG. The baseband demodulator according to the third embodiment, for example, as shown in FIG.
It comprises a matched filter 11, a level measuring device 12, a threshold value calculator 31, a threshold value judging device 14, and a phase compensation and RAKE combiner 15. Here, the configuration other than the threshold value calculator 31 is the same as the configuration in FIG. 8 (Embodiment 2), and thus detailed description is omitted.

The threshold calculator 31 includes a power calculator 301
A, average value calculator 302, and α weighter 303
The average is measured from the level immediately before the matched filter 11 to obtain a threshold. Power calculator 301A
Calculates the received signal level by adding the square of I and the square of Q. The average value calculator 302 calculates the average value from the measurement level, and the α weighting unit 303 weights the average value m with α.

In the above configuration, the A / D converter 7A,
The received signal digitized by 7B is subjected to spectrum despreading by matched filter 11. As a result, the I signal and the Q signal are output to the level measurement device 12 and the phase compensation and RAKE combiner 15 as correlation outputs. The I signal and Q signal immediately before the matched filter 11 are output to the threshold calculator 31.

The level measuring device 12 measures the received signal level of each multipath based on the I signal and the Q signal output from the matched filter 11. The measurement level signal, which is the measurement result, is output to the threshold value determiner 14. In the threshold calculator 31, an average is measured from the input I and Q levels, and the measured value is multiplied by α to obtain a threshold. This threshold value is determined by the threshold
Output to

In the threshold value judging unit 14, a path is detected from the measurement level supplied from the level measuring unit 12 based on the threshold value obtained by the threshold value calculator 31, and a detected path is obtained. This path detection involves phase compensation and RAK
It is output to the E synthesizer 15. The phase compensation and RAKE combiner 15 performs phase compensation and RAKE combining from the detection path from the threshold value determiner 14 and the I signal and Q signal from the matched filter 11 to obtain a demodulated signal. This demodulated signal is output to the digital processing circuit 9 as described above. In the above operation, the optimum threshold value Th is equal to T as in the second embodiment.
h = α × m.

As described above, according to the third embodiment, the standard deviation σ is equal to the average number of the matched filter output,
The optimum threshold can be determined in advance from the erroneous detection rate, the non-detection rate, and the like. Therefore, even when the amount of interference changes or the gain changes, it is possible to set an optimum threshold value for RAKE combining. .

As described above, even when the average is measured from the level immediately before the matched filter and the threshold value is set, a configuration in which the standard deviation σ is not observed can be realized as in the second embodiment. Therefore, compared to the first embodiment, it is possible to reduce the circuit scale and realize simplified processing.

The present invention has been described with reference to Embodiments 1, 2 and 3.
However, various modifications are possible within the scope of the present invention, and these are not excluded from the scope of the present invention.

[0098]

As described above, according to the present invention, the threshold value calculator calculates the average value and the standard deviation based on the level measured by the level measuring device, and determines the standard deviation as a predetermined value. The average value is added to the weighted value to obtain a threshold value. Since the level is detected as a path, an optimum threshold value is set even when the amount of interference changes or the gain changes, thereby obtaining a RAKE receiver capable of improving reception performance. This has the effect.

According to the next invention, an average value is obtained by the threshold value calculator based on the level measured by the level measuring device, and a predetermined weight is applied to the average value to obtain a threshold value. Since the threshold value judging device detects a path that is equal to or higher than the threshold value obtained by the threshold value calculator among the levels measured by the level measuring device, the interference amount changes with a simple configuration. The optimum threshold value is set even when the gain or the gain changes, thereby providing an effect of obtaining a RAKE receiver capable of improving the reception performance.

According to the next invention, a level measuring device
The level is measured based on the correlation output of the matched filter, a threshold calculator calculates an average value based on the level of the received signal, and a predetermined weight is applied to the average value to obtain a threshold value. In the case where the amount of interference changes with a simple configuration, the threshold judgment unit detects paths that are equal to or higher than the threshold value obtained by the threshold value calculator, out of the levels measured by the level measurement device. The optimum threshold value is set even when the gain or the gain changes, whereby a rake receiver capable of improving the reception performance is obtained.

According to the next invention, a level is measured based on the correlation output, an average value and a standard deviation are respectively obtained based on the measured level, and the average value is added to a value obtained by applying a predetermined weight to the standard deviation. Then, a threshold is obtained, and a path equal to or higher than the threshold among the measurement levels is detected, and a demodulated signal is obtained by performing RAKE combining in accordance with the detected path, so that the amount of interference varies. Even when the gain changes, the optimum threshold value is set for RAKE combining, thereby providing an effect that a wireless receiving apparatus capable of improving the receiving performance can be obtained.

According to the next invention, a level is measured based on the correlation output, an average value is obtained based on the measured level, a predetermined weight is applied to the average value, and a threshold value is obtained.
Of the measured levels, a path that is equal to or higher than the threshold is detected, and a demodulated signal is obtained by performing RAKE combining in accordance with the detected path. RAK even if you do
An optimum threshold value is set for E-combining, and this has the effect of providing a radio receiving apparatus capable of improving reception performance.

According to the next invention, a level is measured based on the matched filter correlation output, an average value is obtained based on the level of the received signal, a predetermined weight is applied to the average value, and a threshold value is obtained. Among the measurement levels, a path that is equal to or higher than the threshold is detected, and RAK is performed according to the detected path.
Since a demodulated signal is obtained by performing E-combining, even when the amount of interference changes or the gain changes with a simple configuration, an optimum threshold value for RAKE combining is set.
Thereby, there is an effect that a wireless receiving apparatus capable of improving the receiving performance can be obtained.

According to the next invention, an average value and a standard deviation are respectively obtained based on the level of the correlation output, and the average value is added to a value obtained by applying a predetermined weight to the standard deviation, thereby setting a threshold value. Then, among the levels of the correlation output, a path that is equal to or higher than the threshold value is detected, so that even when the amount of interference changes or the gain changes, RAKE is performed.
An optimum threshold value is set for the combination, thereby providing an effect that a path detection method of a RAKE receiver that can improve reception performance is obtained.

According to the next invention, an average value is obtained based on the level of the correlation output, a predetermined weight is applied to the average value to obtain a threshold value, and the threshold value among the correlation output levels is obtained. Since the above levels are detected as paths,
Even when the amount of interference changes or the gain changes, the optimum threshold value for RAKE combining is set only by the average value, and as a result, RAKE capable of improving reception performance
There is an effect that a path detection method of the receiver can be obtained.

According to the next invention, an average value is obtained based on the level of the received signal, a predetermined weight is applied to the average value to obtain a threshold value, and the threshold value among the correlation output levels is obtained. Since the above levels are detected as paths,
Even when the amount of interference changes or the gain changes, the optimum threshold value for RAKE combining is set only by the average value, and as a result, RAKE capable of improving reception performance
There is an effect that a path detection method of the receiver can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a wireless reception device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a RAKE receiver according to Embodiment 1 of the present invention.

FIG. 3 is a diagram illustrating a configuration example of a standard deviation σ calculator according to the first embodiment;

FIG. 4 is a diagram for explaining a method of determining β in a graph.

FIG. 5 is a diagram showing a modification of the power calculator according to the first embodiment.

FIG. 6 is a diagram showing another modified example of the power calculator in the first embodiment.

FIG. 7 is a diagram showing a modification of the standard deviation σ calculator in the first embodiment.

FIG. 8 is a block diagram illustrating a configuration example of a RAKE receiver according to a second embodiment of the present invention.

FIG. 9 is a block diagram illustrating a configuration example of a RAKE receiver according to a third embodiment of the present invention.

FIG. 10 is a configuration diagram of a RAKE receiver using a two-step threshold multipath selection method.

FIG. 11 is a diagram illustrating a frame configuration of a received signal in DS-CDMA.

FIG. 12 is a diagram illustrating received signal levels for describing operations of a threshold value setting unit and a two-stage multipath selection unit.

[Explanation of symbols]

1 antenna, 2 RF amplifier, 3A, 3B mixer,
4. 90 ° phase shifter, 5 local oscillators, 6A, 6B LP
F, 7A, 7B A / D converter, 8 baseband demodulator, 9 digital processing circuit, 11 matched filter,
12 level determiner, 13 threshold calculator, 14 threshold determiner, 15 phase compensation and RAKE combiner,
21 threshold calculator, 31 threshold calculator, 101
A, 101B, 101C, 301A Power calculator, 10
2 cyclic integrator, 103 average value calculator, 104 standard deviation σ calculator, 105 β weighter, 105 adder, 201, 302 average value calculator, 202, 303
α weighter.

Claims (9)

[Claims] 1. According to detection of a path equal to or more than a threshold value, R
In a RAKE receiver for performing AKE combining, a level measuring device for measuring a level based on a correlation output, an average value and a standard deviation are respectively obtained based on the level measured by the level measuring device, and a predetermined weight is assigned to the standard deviation. A threshold calculator that obtains a threshold value by adding an average value to the value obtained by applying the threshold value; A rake receiver comprising: a threshold detector for detecting a path; 2. The method according to claim 1, wherein R
In a RAKE receiver that performs AKE combining, a level measuring device that measures a level based on a correlation output, an average value is determined based on the level measured by the level measuring device, and a predetermined weight is given to the average value. A threshold calculator that obtains a threshold value; and a threshold determiner that detects a path equal to or higher than the threshold obtained by the threshold calculator among the levels measured by the level calculator. A RAKE receiver, characterized in that: 3. The method according to claim 3, wherein the detection of a path equal to or greater than a threshold value
A rake receiver that performs AKE combining, a matched filter that obtains a correlation output from a received signal, a level measuring device that measures a level based on the correlation output of the matched filter, and an average value that is obtained based on a level of the received signal. A threshold calculator that obtains a threshold by applying a predetermined weight to the average value; and a path detection unit that detects a level equal to or higher than the threshold obtained by the threshold calculator among the levels measured by the level meter. A rake receiver, comprising: 4. A radio receiving apparatus for obtaining a demodulated signal in accordance with detection of a path equal to or more than a threshold value, wherein: a level measuring means for measuring a level based on a correlation output; and an average based on the level measured by the level measuring means. A threshold value calculating means for obtaining a threshold value by calculating a value and a standard deviation, and adding an average value to a value obtained by applying a predetermined weight to the standard deviation; and, among the levels measured by the level measuring means, Threshold value determining means for detecting a path above a threshold value obtained by the threshold value calculating means;
And a RAKE combining means for obtaining a demodulated signal by performing combining. 5. A radio receiving apparatus for obtaining a demodulated signal in accordance with detection of a path equal to or more than a threshold value, comprising: level measuring means for measuring a level based on a correlation output; and averaging based on the level measured by said level measuring means. Threshold value calculating means for obtaining a threshold value and applying a predetermined weight to the average value to obtain a threshold value; Threshold value determining means for detecting a level of a path;
And a RAKE combining means for obtaining a demodulated signal by performing combining. 6. A radio receiving apparatus for obtaining a demodulated signal in accordance with detection of a path equal to or greater than a threshold value, a matched filter means for obtaining a correlation output from the received signal, and a level for measuring a level based on the correlation output of the matched filter means. Measuring means, an average value based on the level of the received signal, a threshold calculating means for obtaining a threshold value by applying a predetermined weight to the average value, and a threshold value of the level measured by the level measuring means. Threshold value determining means for detecting a level above a threshold value obtained by the threshold value calculating means;
And a RAKE combining means for obtaining a demodulated signal by performing combining. 7. The method according to claim 7, wherein the detection of a path equal to or greater than a threshold value
In a path detecting method of a RAKE receiver performing AKE combining, an average value and a standard deviation are respectively obtained based on a level of a correlation output, and a value obtained by applying a predetermined weight to the obtained standard deviation is added to the obtained average value. To obtain a threshold,
A path detection method for a rake receiver, wherein a path of a level of the correlation output that is equal to or higher than the threshold value obtained above is detected. 8. The method according to claim 7, further comprising the steps of:
In a path detecting method of a RAKE receiver for performing AKE combining, an average value is obtained based on a level of a correlation output, a predetermined weight is applied to the obtained average value to obtain a threshold value, and a level of the level of the correlation output is obtained. A path detection method for a rake receiver, wherein the path is detected at a level equal to or higher than the threshold value obtained above. 9. According to detection of a path equal to or greater than a threshold value, R
In a path detecting method of a RAKE receiver performing AKE combining, an average value is obtained based on a level of a received signal, a predetermined weight is applied to the obtained average value to obtain a threshold value, and a correlation output level is obtained. A path detection method for a rake receiver, wherein the path is detected at a level equal to or higher than the threshold value obtained above.