JP4142259B2 - RAKE receiving apparatus and method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a RAKE receiving apparatus and method in spread spectrum communication, and more particularly to an apparatus and method for determining an effective path to be used in RAKE combining.
[0002]
[Prior art]
In recent years, mobile communication has been rapidly spreading, and various technologies for this purpose have been researched and developed.
[0003]
In mobile communications, as is well known to those skilled in the art, the phase and amplitude of the signal changes randomly depending on the speed of the mobile station and the carrier frequency, and fading occurs. For this reason, in mobile communication, it is difficult to stably receive a radio signal as compared with communication in which the position of each communication device is fixed.
[0004]
A spread spectrum communication system is effective as a method for reducing the influence of frequency selective fading as described above in mobile communication. In spread spectrum communication, the signal to be transmitted is spread to a wideband signal and then sent to the wireless network. Therefore, even if the received electric field strength decreases in a specific frequency range, the signal can be reproduced from another frequency range. It is like that. Note that as a spread spectrum communication method, a direct spread method, a frequency hopping method, and the like are known.
[0005]
By the way, in wireless communication, a receiver not only directly receives a signal wave transmitted from a transmitter, but also receives a reflected wave from a high-rise building or a mountain. Here, the propagation time of these reflected waves depends on the path. For this reason, the receiver normally receives a plurality of delayed waves. Such a communication environment is often called a “multipath fading environment”. In a multipath fading environment, if the direct spreading method is adopted, each delayed wave acts as an interference wave on the spreading code, resulting in degradation of reception characteristics.
[0006]
RAKE reception is known as a technique for avoiding deterioration of reception characteristics due to multipath fading. RAKE reception is a technique that actively uses the above-described delayed wave to improve reception characteristics. Specifically, in RAKE reception, a plurality of delayed waves are despread respectively, and the results of the plurality of despreading processes are appropriately added to synthesize demodulated signals corresponding to the plurality of delayed waves. Then, transmission data is reproduced from the synthesized signal.
[0007]
FIG. 16 is a configuration diagram of an existing RAKE receiving circuit. Here, a three-finger configuration is assumed. The I channel signal and the Q channel signal are signals obtained by decomposing a received signal into components orthogonal to each other.
[0008]
Received signals (I channel signal and Q channel signal) are applied to a path search unit and a demodulation / RAKE combining unit. In the path search unit, first, the matched filter 501 detects a correlation value indicating the correlation between the received signal and the spread code. This correlation value is detected one after another at intervals shorter than the chip period. Therefore, the correlation value output from the matched filter 501 changes every moment. The peak detection circuit 503 detects the peak of the correlation value (the timing at which the correlation value is maximized and its value). The sort circuit 504 selects three peaks having a large correlation value from a plurality of peaks detected by the peak detection circuit 503, for example, for each spreading code period. Then, the timing generation circuit 505 generates path timing information indicating the timing of the three peaks detected by the sort circuit 504 and delay amount information indicating the time difference between the timings of the three peaks, and modulates / RAKE-combines them. Give to the department. Note that the path search unit includes an integration circuit 502 that averages the correlation values of the peaks that appear periodically in order to improve the detection accuracy of the peak timing of the correlation values.
[0009]
A despreading circuit 511, a demodulation circuit 512, and a delay circuit 513 are provided for each finger. The despreading circuit 511 generates a spread code according to the path timing information given from the timing generation circuit 505, and despreads the received signal using it. Demodulation circuit 512 demodulates I channel and Q channel symbol data obtained by despreading processing. The delay circuit 513 delays the output of the demodulation circuit 512 according to the delay amount information given from the timing generation circuit 505. The adder circuit 514 synthesizes the output of the delay circuit 513. Then, transmission data is reproduced from the synthesized signal.
[0010]
Thus, in the existing RAKE receiving circuit, a plurality of correlation value peaks are detected, and signals received via different paths are synthesized using the timings of the plurality of correlation value peaks. Then, data is reproduced from this synthesized signal. Therefore, degradation of reception characteristics can be avoided even in a multipath fading environment.
[0011]
[Problems to be solved by the invention]
By the way, the difference in delay time of each path in a multipath environment depends on the communication environment. For example, as shown in FIG. 17A, in a suburban area where a signal wave is reflected by a mountain or the like, the difference in delay time of each path seems to be relatively large. In this case, the peak of the correlation value representing the correlation between the received signal and the spread code is detected corresponding to each path (paths 1 to 3) as shown in FIG.
[0012]
On the other hand, as shown in FIG. 17 (b), in the urban area where the signal wave is reflected by a nearby high-rise building or the like, the difference in delay time of each path seems to be small. In this case, the timings of correlation value peaks corresponding to a plurality of paths are close to each other. In the example shown in FIG. 18B, the correlation value peak timings corresponding to the path 1 and the path 2 are close to each other. However, when a plurality of correlation value peaks are close to each other in time, the peak detection circuit 503 actually has a plurality of correlation value peaks (correlation value peaks corresponding to path 1 and path 2). Regardless, only one correlation value peak can be detected. If the correlation value peak cannot be detected correctly, the characteristics (S / N ratio, etc.) of the synthesized signal obtained by synthesizing the signals obtained for each finger are degraded. In the above situation, it is difficult to accurately supplement each path even if, for example, DLL (Delay Locked Loop) is used.
[0013]
As described above, in the method of performing RAKE combining using the occurrence timing of the correlation value peak, the reception characteristics may not be improved in a communication environment where the difference in delay time of each path is small.
[0014]
An object of the present invention is to provide a RAKE reception method capable of obtaining good reception characteristics in any communication environment.
[0015]
[Means for Solving the Problems]
  The RAKE receiving apparatus of the present invention is an apparatus for despreading and combining signals received via a plurality of paths, and generating means for generating correlation power by despreading the received signal;Among the generated correlation powers, the N correlation powers appearing from the maximum correlation power to the Nth largest correlation power during the period of the spreading code.Detection means for detecting timing;Sorting means for sorting the detected N timings in descending order of correlation power;Setting means for setting a mask range determined based on a communication environment;Out of the N sorted timingsBased on timing difference and above mask rangen (1 <n <N)A determination means for determining the effective path of the determinednSynthesizing means for synthesizing the effective paths.
[0016]
In a multipath environment, correlation power caused by signals received via each path appears in a predetermined range in terms of time. For this reason, when effective paths close to each other are combined, the same noise may overlap, and reception characteristics may deteriorate. Therefore, when the correlation power corresponding to each path is distributed discretely, signals that are close to each other should not be synthesized. On the other hand, when there are a plurality of paths having a small delay time difference, in order to improve reception characteristics by combining these paths, it is necessary to combine signals that are close to each other.
[0017]
Therefore, in the RAKE receiving apparatus of the present invention, the mask range is determined based on the communication environment, and the effective path interval to be used for RAKE combining is limited using the mask range. Accordingly, it is possible to appropriately select an effective path that improves reception characteristics in consideration of the communication environment. That is, good reception characteristics can be obtained in any communication environment.
[0018]
The mask range may be fixedly set according to the predicted communication environment, or may be dynamically changed according to the communication state. When the mask range is dynamically changed, for example, it is performed based on a correlation power profile.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a wireless communication apparatus in which a RAKE reception method according to an embodiment of the present invention is used. Here, it is assumed that the data is transmitted by spread spectrum communication of the direct spread method.
[0020]
The encoder 1 encodes transmission data. Here, the “code” is not particularly limited. For example, error correction coding, voice coding, image coding, and the like are assumed. The mapping circuit 2 modulates the output of the encoder 1 and further spreads data obtained by the modulation. Here, “modulation” is, for example, QPSK. In QPSK, data is arranged and transmitted at corresponding signal points on the phase plane. At this time, this signal point is represented by the I component and Q component of the phase plane. “Spreading” is a process of multiplying modulation data (I component data and Q component data in QPSK) by a spreading code.
[0021]
The output of the mapping circuit 2 is given to the D / A converter 4 after passing through the waveform shaping filter 3. The D / A converter 4 converts the output (spread I component data and Q component data) of the mapping circuit 2 into an analog signal. The quadrature modulation circuit 5 synthesizes a set of analog signals that are orthogonal to each other. The frequency conversion circuit 6 converts the IF band signal output from the quadrature modulation circuit 5 into an RF band signal. The output of the frequency conversion circuit 6 is sent to the wireless network using the antenna 11.
[0022]
On the other hand, a radio signal transmitted from another radio communication device is received by the antenna 11. Then, the signal received by the antenna 11 is given to the frequency conversion circuit 21. A signal transmitted from this wireless communication device and a signal transmitted from another wireless communication device are appropriately separated by the duplexer 12.
[0023]
The frequency conversion circuit 21 converts an RF band received signal into an IF band signal. The quadrature detection circuit 22 converts the output of the frequency conversion circuit 21 into a set of analog signals orthogonal to each other. This set of analog signals corresponds to the spread I component data and Q component data. The A / D converter 23 converts the output of the quadrature detection circuit 22 into digital data, and gives the conversion result to the path search circuit 24 and the demodulation / RAKE combining circuit 25.
[0024]
The path search circuit 24 detects a predetermined number of effective paths to be used in the RAKE combining based on the output of the A / D converter 23. In this embodiment, it is assumed that three effective paths are detected. The demodulation / RAKE combining circuit 25 despreads the received signal for each effective path detected by the path search circuit 24, and further demodulates the result of the despreading process. Note that the despreading process and the demodulation process correspond to the spreading process and the modulation process executed in the mapping circuit 2, respectively. Then, the demodulated signal obtained for each effective path is combined in consideration of the delay time of each path. The configuration and operation of the path search circuit 24 and the demodulation / RAKE combining circuit 25 will be described in detail later.
[0025]
The decoder 26 reproduces data from the output of the demodulation / RAKE combining circuit 25. Note that the operation of the decoder 26 corresponds to the operation of the encoder 1.
In the wireless communication apparatus having the above configuration, the RAKE reception method of the present embodiment is implemented in the path search circuit 24 and the demodulation / RAKE combining circuit 25.
[0026]
FIG. 2 is a configuration diagram of the path search circuit 24 and the demodulation / RAKE combining circuit 25. Here, RAKE is assumed to be 3 fingers. That is, it is assumed that three effective path signals are extracted and combined. The path search circuit 24 and the demodulation / RAKE combining circuit 25 of this embodiment are based on the existing circuit shown in FIG. However, the path search circuit 24 of this embodiment includes a sort circuit 31 and a valid path determination circuit 32 instead of the peak detection circuit 503 and the sort circuit 504 provided in the existing circuit.
[0027]
Received signals (I channel signal and Q channel signal) are applied to path search circuit 24 and demodulation / RAKE combining circuit 25. This received signal is the output of the A / D converter 23 shown in FIG. It is assumed that the A / D converter 23 operates in the 4-times oversampling mode. That is, the A / D converter 23 samples the input analog signal at an interval of a quarter of the chip period, and converts the analog signal into digital data each time and outputs it. Here, the “chip period” refers to a time allocated to each chip constituting the spreading code. The sampling period (that is, the time of one quarter of the chip period) by the A / D converter 23 is referred to as “sampling time”.
[0028]
In the path search circuit 24, first, the matched filter 501 detects the correlation between the received signal and the spread code. The matched filter 501 includes a predetermined number of stages of shift registers and sequentially stores digital signals output from the A / D converter 23. Each time a new signal is given to the shift register, that is, every sampling time, the signal stored in the shift register is multiplied by the spreading code to express the correlation between the received signal and the spreading code. Generate correlation values. As described above, the matched filter 501 outputs a correlation value indicating the correlation between the received signal and the spread code at each sampling time.
[0029]
In this embodiment, it is assumed that QPSK is adopted as the modulation method. In this case, matched filter 501 detects a correlation value for each of the I channel signal and the Q channel signal. Then, the correlation power (or reception power) is detected by calculating the square sum of the set of correlation values.
[0030]
FIG. 3 is a block diagram of the matched filter 501. Shift registers 41a and 41b store an I channel signal and a Q channel signal, respectively. The multiplying circuits 42a and 42b calculate correlation values by multiplying the signals stored in the shift registers 41a and 41b and the spreading codes, respectively. And the electric power detection circuit 43 calculates | requires correlation electric power by calculating the square sum of each correlation value produced | generated by the multiplication circuits 42a and 42b. The output of the power detection circuit 43 is given to the sort circuit 31 as “power information”.
[0031]
The timing counter 44 is counted up by a clock generated every sampling time. The count value of the timing counter 44 is given to the sort circuit 31 as “timing information”.
[0032]
Thus, the matched filter 501 generates power information and timing information for each sampling time. Note that the timing information is not necessarily generated by the matched filter 501, and may be generated by the sort circuit 31.
[0033]
The sort circuit 31 monitors the power information and timing information for a certain period. Then, a predetermined number of timings with high correlation power are detected during the period. For example, in the example shown in FIG. 4, “6” is obtained as the timing for obtaining the maximum power, “7” is obtained as the timing for obtaining the second power, and “5” is obtained as the timing for obtaining the third power. . In addition, the said fixed period is a period of a spreading code, for example. Further, although the correlation power is schematically shown in FIG. 4, the timing information and the power information are stored in a table or the like provided on the memory as shown in FIG. 5, for example. Then, by searching this table, a predetermined number of timings with large correlation power are extracted.
[0034]
Further, the sort circuit 31 sorts and outputs the detected timing information in the order of correlation power. At this time, power information corresponding to each timing information is also output together. As described above, the sort circuit 31 sorts and outputs the timing information and the power information in the order of the correlation power.
[0035]
In this embodiment, considering that RAKE has a three-finger configuration, the sort circuit 31 detects 15 sets of timing information and power information. That is, if it is assumed that power appears until 3 sampling times before and after the impulse response, it is necessary to monitor the correlation power for each path for 7 sampling times. As a result, if the correlation power is monitored for 7 sampling times for each of the three effective paths, 21 sets of timing information and power information are detected. However, it is considered sufficient to detect only the peak of the three effective paths with the minimum correlation power. Accordingly, seven sets of timing information and power information are detected for the first and second paths, and one set of timing information and power information are detected for the third path. Thereby, 15 sets of timing information and power information are detected.
[0036]
The valid path determination circuit 32 determines three valid paths to be used in the RAKE combining based on the 15 sets of timing information and power information detected by the sort circuit 31, and the valid paths corresponding to these valid paths. Output information. Here, the valid path information is represented using, for example, the timing information described above. The configuration and operation of the valid path determination circuit 32 will be described later in detail.
[0037]
The timing generation circuit 505 modulates / RAKE combines the path timing information indicating the timing of the three effective paths determined by the effective path determination circuit 32 and the delay amount information indicating the difference between the delay amounts of the three effective paths. This is given to the circuit 25.
[0038]
The path search circuit 24 includes an integration circuit 502 that averages the correlation value or the correlation power in order to improve the timing detection accuracy.
The demodulation / RAKE combining circuit 25 can basically use an existing circuit. That is, the despreading circuit 511, the demodulation circuit 512, and the delay circuit 513 are provided for each effective path. The despreading circuit 511 generates a spread code according to the path timing information given from the timing generation circuit 505, and despreads the received signal using it. Demodulation circuit 512 demodulates I channel and Q channel symbol data obtained by despreading processing. The delay circuit 513 delays the output of the demodulation circuit 512 according to the delay amount information given from the timing generation circuit 505. The adder circuit 514 synthesizes the output of the delay circuit 513. Then, transmission data is reproduced from the synthesized signal.
[0039]
In the path search circuit 24 and the demodulation / RAKE combining circuit 25 configured as described above, one feature of the present invention is a method for determining an effective path. Hereinafter, the concept of a method for determining a predetermined number of effective paths in the effective path determination circuit 32 will be described.
[0040]
In RAKE combining, basically, it is desirable to combine signals received via paths with large correlation power. Therefore, in a three-finger configuration RAKE receiving circuit, if three timings at which the correlation power increases are detected, and the received signals are despread and synthesized at each detected timing, good reception characteristics should be obtained. It is.
[0041]
However, in practice, if the effective path is determined based only on the magnitude of the correlation power, the following problem occurs. For example, in the example illustrated in FIG. 4, “time 6”, “time 7”, and “time 5” are detected as timings at which the largest, second, and third largest correlation power is obtained. However, considering the characteristics of the roll-off filter, the correlation power appearing during the period from time 2 to time 10 is considered to be due to the signal at time 6. That is, it is considered that the correlation power appearing at time 5, time 6, and time 7 is caused by a signal transmitted through a specific path. Therefore, if the signals obtained by despreading the received signals at time 5, time 6 and time 7 are combined, noise generated in a specific path is superimposed, so that the S / N is replaced by RAKE combining. The ratio may deteriorate. Note that the roll-off filter is a filter for avoiding intersymbol interference, and is designed so that the impulse response becomes zero when separated by one chip period time as shown in FIG. . The roll-off filter is provided between the frequency conversion circuit 21 and the quadrature detection circuit 22, for example.
[0042]
In order to deal with this problem, it is only necessary not to detect the effective path in the vicinity of the timing when the large correlation power appears. For example, in the example shown in FIG. 4, since a large correlation power appears at time 6, the effective path is not detected in a predetermined period before and after time 6. Here, assuming that the above-described roll-off filter is used, the correlation power caused by the signal received through a certain path is almost present at a timing separated from the signal by one chip period time (that is, four sampling times). Disappear. Therefore, in this case, for example, “three sampling times” is set as the predetermined period. If this configuration is introduced, noise generated in a specific path is not superimposed, so that deterioration of the S / N ratio is avoided.
[0043]
By the way, the delay time (signal propagation time) of each path depends on the communication environment. Then, under an environment where the difference between the delay times of the paths is small, as shown in FIG. 7, the correlation powers caused by the signals received via the paths 1 to 4 overlap each other. In this case, the sort circuit 31 detects in order the timing with the large combined power drawn by the solid line in FIG. In this example, the maximum to fifth largest correlation power is detected at time 6, time 7, time 8, time 9, and time a. If the effective path is not detected within 3 sampling times from the timing at which the maximum correlation power appears (that is, time 6), time 7, time 8 and time 9 are not determined as effective path timings. It is determined that a is the second effective path timing.
[0044]
In this case, an effect by avoiding the superposition of specific noise is expected, but the effect by appropriately combining signals received via adjacent paths cannot be enjoyed. In an environment where the difference between the delay times of each path is small, the demerit due to the fact that the latter effect cannot be obtained usually becomes larger than the merit due to the former effect. Therefore, in such a communication environment, an effective path should be detected even in the vicinity of the timing at which large correlation power appears.
[0045]
In the RAKE reception method of the present embodiment, based on the above-described problem, the reference for detecting an effective path to be used in RAKE reception is changed according to the communication environment. Hereinafter, an embodiment of a method for detecting a valid path will be described.
First embodiment
FIG. 8 is a configuration diagram of an effective path determination circuit in the first embodiment. The effective path determination circuit 32 determines three effective paths to be used in the RAKE combining using a preset mask width.
[0046]
The flip-flop circuits 51 (1) to 51 (15) store 15 sets of timing information selected by the sort circuit 31. Here, timing information representing the timing at which the correlation power is maximized is stored in the flip-flop circuit 51 (1). Hereinafter, each timing information representing the timing at which the correlation power is the second to fifteenth largest is the flip-flop circuit. 51 (2) to 51 (15).
[0047]
The mask circuits 52 and 53 are set with a predetermined mask width. Here, the mask width is determined based on, for example, a communication environment in which the wireless communication apparatus is used. Specifically, in an environment where a small delay time difference is likely to exist (such as an urban area), a small mask width is set, and in an environment where a large delay time difference is likely to exist (such as a suburban area) A large mask width is set. As an example, “2 sampling time” is set in the urban area, and “3 sampling time” is set in the suburban area.
[0048]
The mask circuit 52 sets a predetermined mask range for the timing information stored in the flip-flop circuit 51 (1), and the timing information stored in the flip-flop circuit 51 (2) falls within the mask range. Check if it is located. At this time, if the timing information stored in the flip-flop circuit 51 (2) is located within the mask range, the mask circuit 52 outputs a pulse signal. This pulse signal is given to the flip-flop circuit 51 (2) and also given to the flip-flop circuits 51 (3) to 51 (15) via the OR circuit 55. By this pulse signal, the timing information stored in the flip-flop circuits 51 (3) to 51 (15) is shifted to the preceding flip-flop circuit. On the other hand, when the timing information stored in the flip-flop circuit 51 (2) is located outside the mask range, the mask circuit 52 does not output a pulse signal.
[0049]
The operation of the mask circuit 53 is basically the same as that of the mask circuit 52. However, the mask circuit 53 sets a predetermined mask range for the timing information selected by the selection circuit 54, and whether the timing information stored in the flip-flop circuit 51 (3) is located within the mask range. Check for no. Here, the selection circuit 54 selects the output of the flip-flop circuit 51 (1) or the flip-flop circuit 51 (2) according to selection information (not shown). The output of the mask circuit 53 is given to the flip-flop circuits 51 (3) to 51 (15) via the OR circuit 55, but is not given to the flip-flop circuit 51 (2).
[0050]
Next, the operation of the valid path determination circuit 32 configured as described above will be described. The effective path determination circuit 32 determines three effective paths in the following procedure.
First, the timing at which the correlation power is maximum (maximum timing) is determined as the effective path timing. That is, the timing information stored in the flip-flop circuit 51 (1) is output as “valid timing information 1”.
[0051]
Subsequently, it is determined whether or not the timing at which the second largest correlation power is obtained (second timing) is the effective path timing. In this case, the mask range is set with respect to the maximum timing, and it is determined whether or not the second rank timing is located within the mask range. This determination is executed by the mask circuit 52. If the second timing is located outside the mask range, it is determined that the second timing is an effective path timing. That is, the timing information stored in the flip-flop circuit 51 (2) is output as “valid timing information 2”.
[0052]
On the other hand, when the second timing is located within the mask range, the mask circuit 52 generates a pulse signal. As a result, the timing information stored in the flip-flop circuits 51 (3) to 51 (15) is shifted to the preceding flip-flop circuit, and the third timing is stored in the flip-flop circuit 51 (2). . At this time, the timing information indicating the second timing is discarded. Then, it is determined whether or not the third place timing is an effective path timing. That is, it is determined whether or not the third timing is within the mask range.
[0053]
At this time, if the third timing is located outside the mask range, the third timing is determined as the effective path timing and is output as “effective timing information 2”. On the other hand, when the third timing is located within the mask range, the above-described processing is repeated until a valid path is detected. As a result, the second effective path is determined.
[0054]
The method for determining the third effective path is basically the same as the method for determining the second effective path. However, when the third effective path is determined, a mask range is set for each timing of the two determined effective paths. That is, when the selection circuit 54 selects the output of the flip-flop circuit 51 (1), the mask range is set for the timing of the first effective path, and the timing stored in the flip-flop circuit 51 (3). It is examined whether or not the timing represented by the information is located within the mask range. When the selection circuit 54 selects the output of the flip-flop circuit 51 (2), the mask range is set for the timing of the second effective path, and the timing stored in the flip-flop circuit 51 (3). It is examined whether or not the timing represented by the information is located within the mask range. When the timing represented by the timing information stored in the flip-flop circuit 51 (3) is located outside both mask ranges, the timing is determined as the valid path timing, and the “valid path information” 3 "is output.
[0055]
FIG. 9 is a configuration diagram of the mask circuit. The adder 61 adds the mask width M to the timing information T1, and the subtracter 62 subtracts the mask width M from the timing information T1. Here, the timing information T 1 is the output of the flip-flop circuit 51 (1) in the mask circuit 52 and the output of the selection circuit 54 in the mask circuit 53. The comparison circuit 63 compares the output of the adder 61 with the timing information T2, and outputs “H” when the output of the adder 61 is greater. On the other hand, the comparison circuit 64 compares the output of the subtractor 62 with the timing information T2, and outputs “H” when the output of the subtractor 62 is smaller. Here, the timing information T2 is the output of the flip-flop circuit 51 (2) in the mask circuit 52, and the output of the flip-flop 51 (3) in the mask circuit 53. The AND circuit 65 calculates the logical product of the outputs of the comparison circuits 63 and 64.
[0056]
By the above circuit, a mask range is set for the timing information T1, and it is determined whether or not the timing information T2 is located within the mask range.
Next, a specific example will be shown with reference to FIGS. 4 and 7, the symbols “1” to “15” attached to the graphs indicating the correlation power indicate the order of the correlation power. That is, “1” represents the maximum timing, and “2” to “15” represent the second timing to the fifteenth timing.
[0057]
The example shown in FIG. 4 represents the correlation power in the wireless communication device used in the suburban area. Further, it is assumed that “mask width = 3” is set in the mask circuits 52 and 53.
[0058]
First, the maximum timing is determined as the timing of the first effective path. That is, “time 6” is determined as the timing of the first effective path. Then, a mask range is set for “time 6”. Here, the mask width is “3”. Therefore, “time 3” to “time 9” are the mask range.
[0059]
Next, it is checked whether or not “time 7” as the second timing is located in the mask range. Here, “time 7” is located within the mask range. Similarly, “time 6”, which is the third timing, is also within the mask range. However, “time k”, which is the fourth timing, is located outside the mask range. Therefore, “time k” is determined as the timing of the second effective path. Then, a mask range is set for “time k”. Thereby, “time h” to “time n” also become the mask range.
[0060]
Thereafter, the third valid path is detected in the same procedure as when the second valid path is detected. In this case, the fifth timing and the sixth timing are located in the mask range corresponding to the first effective path. Further, the seventh timing and the eighth timing are located in the mask range corresponding to the second effective path. However, “time u” as the ninth timing is located outside the two mask ranges. Therefore, it is determined that “time u” is the timing of the third effective path.
[0061]
As a result, “time 6”, “time k”, and “time u” are output as the valid path information 1 to 3.
The example shown in FIG. 7 represents correlation power in a wireless communication device used in an urban area. Further, it is assumed that “mask width = 2” is set in the mask circuits 52 and 53.
[0062]
First, “time 6” which is the maximum timing is determined as the timing of the first effective path. Then, a mask range is set for “time 6”. However, in this example, the mask width is “2”. Therefore, “time 4” to “time 8” are the mask range.
[0063]
Subsequently, the second effective path is searched. In this example, the second place timing and the third place timing are located within the mask range. Therefore, “time a” that is the fourth timing is determined as the timing of the second effective path. Then, a mask range is set for “time a”. As a result, “time 8” to “time c” also become the mask range.
[0064]
After this, the third effective path is searched. In this example, the fifth place timing and the sixth place timing are located in the mask range corresponding to the second effective path. Therefore, “time d” that is the seventh timing is determined as the timing of the third effective path.
[0065]
As a result, “time 6”, “time a”, and “time d” are output as the valid path information 1 to 3.
Thus, in the first embodiment, a mask range is set according to a predetermined mask width, and an effective path is determined using the mask range. On the other hand, in the following embodiment, the mask range is dynamically determined according to the communication environment (or communication state).
Second embodiment
In the second embodiment, the mask range is determined according to the communication environment (or communication state). This communication environment is recognized based on the correlation power profile. That is, the mask width is dynamically determined based on the correlation power profile.
[0066]
For example, in an environment where the difference in delay time of each path is large, as shown in FIG. 4, the correlation power corresponding to each path is distributed discretely. When a roll-off filter or the like is provided, the correlation power becomes sufficiently small when the sampling power is separated by about 3 sampling times from the peak timing. Therefore, when the correlation power at a timing three sampling times away from the peak timing of the correlation power is sufficiently small compared to the peak of the correlation power, the wireless communication device is placed in an environment where the difference in delay time between the paths is large. Can be regarded as being. In this case, if signals having timings close to each other are combined, reception characteristics deteriorate due to superposition of the same noise, so the mask range needs to be widened.
[0067]
On the other hand, in an environment where the difference in delay time of each path is small, as shown in FIG. 7, since the correlation power corresponding to a plurality of paths overlaps, the combined correlation power changes gently. For this reason, the correlation power remains relatively high even if it is separated from the peak timing by about 3 sampling times. Therefore, when the correlation power at a timing three sampling times away from the peak timing is relatively large compared to the peak of the correlation power, the wireless communication device is placed in an environment where the delay time difference between the paths is small. Can be considered. In this case, if signals having timings close to each other are combined, the reception characteristics are improved by combining signals of different paths, so it is advantageous to narrow the mask range to some extent.
[0068]
The effective path determination circuit of the second embodiment uses the above-described characteristics. Hereinafter, the configuration and operation of the effective path determination circuit of the second embodiment will be described.
FIG. 10 is a configuration diagram of an effective path determination circuit in the second embodiment. The effective path determination circuit 32 determines three effective paths to be used in the RAKE combining using a mask width that dynamically changes according to the communication environment.
[0069]
10, the flip-flop 51, the mask circuits 52 and 53, the selection circuit 54, and the OR circuit 55 are the same as those in the first embodiment shown in FIG. However, the mask width information given to the mask circuits 52 and 53 is dynamically generated.
[0070]
The flip-flop circuits 71 (1) to 71 (15) store 15 sets of power information selected by the sort circuit 31. Here, the power information representing the maximum correlation power is stored in the flip-flop circuit 71 (1), and the power information representing the second to fifteenth largest correlation power is respectively the flip-flop circuits 71 (2) to 71 (71). Stored in 15). The information stored in the flip-flop circuits 71 (2) to 71 (15) is shifted together when the information stored in the flip-flop circuits 51 (2) to 51 (15) is shifted. Is done.
[0071]
The detection circuit 72 has a timing three sampling times away from the timing represented by the timing information stored in the flip-flop 51 (1) and the timing represented by the timing information stored in the flip-flop 51 (2). The timing 3 sampling time away from is detected. When the corresponding timing is detected, the selection circuit 73 is notified of it.
[0072]
Upon receiving the notification from the detection circuit 72, the selection circuit 73 selects and outputs the power information stored in the flip-flop 71 (1), and selects and outputs the power information corresponding to the notification. For example, when the timing represented by the timing information stored in the flip-flop 51 (1) and the timing represented by the timing information stored in the flip-flop 51 (15) are 3 sampling times apart from each other Then, “15” is notified from the detection circuit 72 to the selection circuit 73, and the selection circuit 73 selects and outputs the power information stored in the flip-flop 71 (1) and the flip-flop 71 (15). When the selection circuit 73 does not receive the notification from the detection circuit 72, for example, the selection circuit 73 outputs the power information stored in the flip-flop 71 (1) and “zero”.
[0073]
The power comparison circuit 74 calculates a power ratio represented by the power information output from the selection circuit 73. Then, the mask width is determined based on this ratio. Specifically, if this ratio is larger than a predetermined threshold value, a larger mask width (for example, “3”) is used, and if this ratio is smaller than the threshold value, a smaller mask width (for example, “2”). ) Is used. When “zero” is output from the selection circuit 73, a large mask width (for example, “3”) is used.
[0074]
Mask width holding circuits 75 and 76 hold the mask width determined by the power comparison circuit 74. The mask width holding circuit 75 holds the mask width determined by the power comparison circuit 74 when the detection circuit 72 searches for the timing corresponding to the timing information stored in the flip-flop 51 (1). On the other hand, the mask width holding circuit 76 holds the mask width determined by the power comparison circuit 74 when the detection circuit 72 searches for the timing corresponding to the timing information stored in the flip-flop 51 (2).
[0075]
When setting the mask range corresponding to the timing information stored in the flip-flop 51 (1), the selection circuit 77 selects the mask width held in the mask holding circuit 75, and the flip-flop 51 (2 When the mask range corresponding to the timing information stored in (1) is set, the mask width held in the mask holding circuit 76 is selected.
[0076]
Thus, the mask width determined by the power comparison circuit 74 is given to the mask circuits 52 and 53. The operation after the mask width is given is basically the same as that in the first embodiment.
[0077]
FIG. 11 is a configuration diagram of the detection circuit 72. The adder 81 adds “+3” to the timing information T1, and the adder 82 adds “−3” to the timing information T1. Here, the timing information T1 is timing information stored in the flip-flop 51 (1) or 51 (2). The selector 83 selects and outputs the timing information T2 to T15 one by one in order. Here, the timing information T2 to T15 is timing information stored in the flip-flops 51 (2) to 51 (15). Match detection circuits 84 and 85 detect timing information that matches the outputs of adders 81 and 82, respectively. The coincidence detection circuits 84 and 85 are constituted by, for example, exclusive OR circuits. When the coincidence is detected in at least one of the coincidence detection circuits 84 or 85, the OR circuit 86 outputs a signal indicating that fact.
[0078]
From the above circuit, it is detected whether or not there is a timing that is three sampling times away from the timing stored in the flip-flop circuit 51 (1) or 51 (2).
[0079]
Next, a specific example of the procedure for determining the mask width will be described with reference to FIGS.
In the example illustrated in FIG. 4, first, “time 6”, which is the maximum timing, is determined as the timing of the first effective path. In this case, the detection circuit 72 checks whether or not the timing information indicating the timing three sampling times away from “time 6” is stored in the flip-flop circuits 51 (2) to 51 (15). In this example, “time 9” as the 14th timing and “time 3” as the 15th timing are detected. The selection circuit 73 selects and outputs the power information stored in the flip-flop 71 (1), and selects the power information stored in the flip-flops 71 (14) and 71 (15). Output. Here, it is assumed that the power information stored in the flip-flop 71 (14) is selected first.
[0080]
Subsequently, the power comparison circuit 74 compares the power information selected by the selection circuit 73. That is, the correlation power at time 6 and the correlation power at time 9 are compared. Here, the correlation power at time 9 is sufficiently smaller than the correlation power at time 6. Therefore, the power comparison circuit 74 outputs a large mask width (mask width = 3). The mask width is held by the mask width holding circuit 75 and further supplied to the mask circuit 52.
[0081]
The operation after the mask width is given to the mask circuit 52 is the same as that of the first embodiment. Therefore, in the example shown in FIG. 4, “time k” is obtained as the timing of the second effective path.
[0082]
Further, the detection circuit 72 checks whether or not the timing information indicating the timing three sampling times away from the “time k” is stored in the flip-flop circuits 51 (2) to 51 (15). In this example, such timing information is not stored. Therefore, the selection circuit 73 selects and outputs power information representing the correlation power at time k, and outputs “zero”. In this case, the power comparison circuit 74 outputs a large mask width (mask width = 3). The information indicating the mask width is held by the mask width holding circuit 76 and further supplied to the mask circuit 53 as necessary.
[0083]
The operation after the mask width is given to the mask circuit 53 is the same as that of the first embodiment. Therefore, in the example shown in FIG. 4, “time u” is obtained as the timing of the third effective path.
[0084]
Also in the example illustrated in FIG. 7, first, “time 6” which is the maximum timing is determined as the timing of the first effective path. Then, the detection circuit 72 searches for timing information representing a timing three sampling times away from “time 6” in the same manner as the procedure described with reference to FIG. As a result, in this example, “time 9” which is the fourth timing is detected. The selection circuit 73 selects and outputs the power information stored in the flip-flop 71 (1), and selects and outputs the power information stored in the flip-flop 71 (4).
[0085]
Subsequently, the power comparison circuit 74 compares the power information selected by the selection circuit 73. That is, the correlation power at time 6 and the correlation power at time 9 are compared. However, the correlation power at time 9 is not sufficiently smaller than the correlation power at time 6. Therefore, the power comparison circuit 74 outputs a small mask width (mask width = 2). The mask width is held by the mask width holding circuit 75 and further supplied to the mask circuit 52.
[0086]
Thereafter, the second effective path is determined using the mask width. Then, similarly to the procedure described with reference to FIG. 4, the mask width corresponding to the second effective path is determined, and further, the third effective path is determined using these mask widths. A description of these procedures is omitted.
[0087]
As described above, in the second embodiment, the effective path is determined using the mask range that is dynamically determined according to the communication environment (or communication state).
Third embodiment
In the second embodiment, as described above, the correlation power at the timing of the effective path is compared with the correlation power at a timing three sampling times away from the timing, and the mask width is determined based on the comparison result. . Specifically, the mask width is determined based on whether the ratio of these powers exceeds a predetermined threshold value. At this time, if the received power of a signal received through a single path is sufficiently large, the power ratio can be expected to be 10 times or more, depending on the characteristics of the roll-off filter. .
[0088]
However, in the state where the C / N ratio (Carrier / Noise Ratio) of the received signal is low, the ratio of noise to the received power is high, and thus the above power ratio is small. Therefore, in the third embodiment, the power ratio is automatically corrected according to the reception level of the signal.
[0089]
FIG. 12 is a configuration diagram of an effective path determination circuit in the third embodiment. The effective path determination circuit of the third embodiment is realized by adding a multiplication circuit 91 to the circuit of the second embodiment shown in FIG.
[0090]
Multiplication circuit 91 multiplies one of the correlation powers compared in power comparison circuit 74 by a coefficient corresponding to the reception level. Specifically, for example, when the correlation power corresponding to the effective path is compared with the correlation power at a timing three sampling times away from the timing of the effective path, the coefficient is multiplied by the correlation power of the effective path. The
[0091]
The signal reception level is detected by an existing technique. However, since the reception level constantly fluctuates, an average over a certain period may be used.
In the above example, the output of the selection circuit 73 is corrected. However, the threshold used in the power comparison circuit 74 may be dynamically corrected in accordance with the reception level of the signal.
Fourth embodiment
In the fourth embodiment, as in the second and third embodiments, the mask range is dynamically determined according to the communication environment, but the communication environment recognition method is different. The basic concept of the method for recognizing the communication environment in the fourth embodiment will be briefly described below.
[0092]
A wireless communication apparatus normally includes a roll-off filter having characteristics as shown in FIG. Here, the circuit of this embodiment operates in the 4 × oversampling mode. Therefore, as shown in FIG. 4, the correlation power of the signal received through a certain path should be substantially zero at a timing four sampling times away from the peak timing. In other words, as shown in FIG. 7, when a large correlation power is continuously obtained from the peak timing of the correlation power over 4 sampling times, it can be considered that a plurality of paths are close to each other.
[0093]
The effective path determination circuit of the fourth embodiment uses the above-described characteristics. The configuration and operation of the second embodiment will be described below.
FIG. 13 is a configuration diagram of an effective path determination circuit in the fourth embodiment. The effective path determination circuit of the fourth embodiment is realized by providing mask width holding circuits 75 and 76, a selection circuit 77, and a continuous detection circuit 101 in the circuit shown in FIG. The mask width holding circuits 75 and 76 and the selection circuit 77 are the same as those shown in FIG.
[0094]
The continuous detection circuit 101 checks whether the second to fifteenth timings are continuously present within the range of four sampling times from the effective path timing as a reference. Timing information corresponding to the second to fifteenth timings is stored in the flip-flops 51 (2) to 51 (15). If the second to fifteenth timings are continuously present within the range of four sampling times from the timing of the effective path, it is assumed that a path with a small delay time difference exists adjacently, A small mask width (mask width = 2) is output. On the other hand, when the second to fifteenth timings do not exist continuously within the range of four sampling times from the effective path timing, it is considered that there is no path having a small delay time difference, and a large mask width (Mask width = 3) is output.
[0095]
FIG. 14 is a configuration diagram of the continuous detection circuit 101. The adders 111 to 114 add “+1”, “+2”, “+3”, and “+4” to the timing information T1, respectively, and the adders 115 to 118 add “−1”, “−2”, “−” to the timing information T1, respectively. 3 ”and“ −4 ”are added. Here, the timing information T1 is timing information corresponding to the effective path, and is stored in the flip-flop 51 (1) or 51 (2). The selector 119 selects and outputs the timing information T2 to T15 one by one in order. Here, the timing information T2 to T15 is timing information stored in the flip-flops 51 (2) to 51 (15). The coincidence detection circuits 121 to 128 are constituted by, for example, exclusive OR circuits, and detect timing information that coincides with the outputs of the adders 111 to 118, respectively. The AND circuit 131 outputs “H” when a coincidence is detected in all of the coincidence detection circuits 121 to 124, and the AND circuit 132 outputs “H” when a coincidence is detected in all of the coincidence detection circuits 125 to 128. H "is output. The OR circuit 133 calculates and outputs a logical sum of the outputs of the AND circuits 131 and 132.
[0096]
From the above circuit, it is detected whether or not the maximum timing to the fifteenth timing are present continuously for four sampling times.
Next, a specific example of the procedure for determining the mask width will be described with reference to FIGS.
[0097]
In the example illustrated in FIG. 4, first, “time 6”, which is the maximum timing, is determined as the timing of the first effective path. In this case, the continuous detection circuit 101 determines whether “time 7”, “time 8”, “time 9”, and “time a” are all stored in the flip-flops 51 (2) to 51 (15), and “time It is checked whether all of “5”, “time 4”, “time 3”, and “time 2” are stored. In this example, “time 2” and “time a” are not registered. Therefore, the continuous detection circuit 101 regards that there is no path having a small delay time difference, and outputs “3” as the mask width.
[0098]
Thereafter, the second effective path is determined using the mask width, and after the mask width corresponding to the second effective path is determined, the third effective path is determined using those mask widths. However, the description is omitted.
[0099]
Also in the example illustrated in FIG. 7, the continuous detection circuit 101 searches for timing information corresponding to “time 6” in the same manner as the procedure described with reference to FIG. 4. In this example, “time 7”, “time 8”, “time 9”, and “time a” are all stored. Therefore, in this case, the continuous detection circuit 101 regards that there is a path with a small delay time difference, and outputs “2” as the mask width.
Fifth embodiment
In the fourth embodiment, it is determined that there is a path with a small delay time difference when large correlation power appears continuously over a certain period with reference to the timing of the effective path. However, considering the characteristics of the roll-off filter, it can be determined whether there is a path with a small difference in delay time based on the magnitude of the correlation power at a position away from the effective path timing by a certain time. Specifically, when a large correlation power appears at a position away from the effective path timing by a certain time, it is determined that there is a path with a small delay time difference, and when a large correlation power does not appear, the delay time It is determined that no path with a small difference exists. The effective path determination circuit of the fifth embodiment uses this characteristic.
[0100]
FIG. 15 is a configuration diagram of an effective path determination circuit in the fifth embodiment. This valid path determination circuit includes a detection circuit 141 instead of the continuous detection circuit 101 in the fourth embodiment shown in FIG.
[0101]
The detection circuit 141 checks whether the second to fifteenth timings appear at a position four sampling times away from the effective path timing as a reference. Here, timing information corresponding to the 2nd to 15th timings is stored in the flip-flops 51 (2) to 51 (15). When the corresponding timing information is detected, it is assumed that a path with a small delay time difference exists adjacently, and a small mask width (mask width = 2) is output. On the other hand, when such timing information is not detected, it is assumed that there is no path with a small delay time difference, and a large mask width (mask width = 3) is output.
[0102]
The detection circuit 141 basically has the same configuration as the detection circuit 72 shown in FIG. However, in the detection circuit 141, “+4” and “−4” are added to the adders 81 and 82, respectively.
[0103]
Thus, in the RAKE receiving apparatus of this embodiment, the mask range is determined according to the communication environment, and a plurality of effective paths are appropriately selected using the mask range. In the above-described embodiments (the first to fifth embodiments), two types of mask ranges are used. However, the present invention is not limited to this, and three or more types of mask ranges are used. The structure used may be sufficient.
[0104]
In the above-described embodiment, the effective path is determined using the timing at which large correlation power appears, but the present invention is not limited to this. That is, for example, a correlation value representing the correlation between the received signal and the spread code may be used. Here, the correlation value is data obtained by multiplying a received signal by a spreading code.
[0105]
(Appendix 1) A RAKE receiver that despreads and combines signals received through a plurality of paths,
Generating means for generating correlation power by despreading the received signal;
Detection means for detecting the timing at which the maximum correlation power to the Nth largest correlation power appears;
Setting means for setting a mask range determined based on a communication environment;
Determining means for determining a plurality of effective paths based on the detected timing difference and the mask range;
A combining means for combining a plurality of determined effective paths;
A RAKE receiving apparatus.
[0106]
(Appendix 2) The RAKE receiver according to Appendix 1,
The determining means determines the timing of the first effective path based on the timing when the maximum correlation power appears, sets the mask range based on the determined timing of the effective path, and at a timing not masked by the mask range. Therefore, the second effective path is determined based on the timing at which the largest correlation power among the second to Nth largest correlation powers appears.
[0107]
(Supplementary note 3) The RAKE receiver according to supplementary note 1, wherein
The setting means sets the mask range based on a ratio of two predetermined correlation powers from the maximum correlation power to the Nth largest correlation power.
[0108]
(Supplementary note 4) The RAKE receiver according to supplementary note 3, wherein
The setting means corrects the ratio of the correlation power based on the reception level of the received signal, and sets the mask range based on the corrected ratio.
[0109]
(Supplementary note 5) The RAKE receiver according to supplementary note 1, wherein
The setting means sets the mask range based on whether or not a predetermined number of consecutive timings are detected by the detection means.
[0110]
(Appendix 6) The RAKE receiver according to Appendix 1,
The setting means sets the mask range based on whether or not the detection means detects timings separated from each other by a predetermined interval.
[0111]
(Appendix 7) The RAKE receiver according to Appendix 1,
The setting means dynamically changes the mask range based on a correlation power profile.
[0112]
(Supplementary note 8) A path determination apparatus for determining a plurality of paths to be used in RAKE reception,
Generating means for generating correlation power by despreading the received signal;
Detection means for detecting the timing at which the maximum correlation power to the Nth largest correlation power appears;
Setting means for setting a mask range determined based on a communication environment;
Determining means for determining a plurality of effective paths to be RAKE based on the detected timing difference and the mask range;
A path determination device having
[0113]
(Supplementary note 9) A RAKE receiving method for despreading and combining signals received via a plurality of paths,
Generate correlation power by despreading the received signal,
Detect the timing when the largest correlation power to the Nth largest correlation power appears,
Set the mask range determined based on the communication environment,
Determining a plurality of valid paths based on the detected timing difference and the mask range;
A RAKE reception method for combining a plurality of determined effective paths.
[0114]
(Supplementary Note 10) A path determination method for determining a plurality of paths to be used in RAKE reception,
Generate correlation power by despreading the received signal,
Detect the timing when the largest correlation power to the Nth largest correlation power appears,
Set the mask range determined based on the communication environment,
A path determination method for determining a plurality of effective paths to be RAKE-matched based on the detected timing difference and the mask range.
[0115]
【The invention's effect】
According to the present invention, the effective path determination criterion to be used in the RAKE combining is determined according to the communication environment, so that the gain obtained in the RAKE combining is always good.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a wireless communication apparatus in which a RAKE receiving method according to an embodiment of the present invention is used.
FIG. 2 is a configuration diagram of a path search circuit and a demodulation / RAKE combining circuit.
FIG. 3 is a block diagram of a matched filter.
FIG. 4 is a diagram illustrating a method for detecting timing with large correlation power.
FIG. 5 is an example of a table storing timing information and power information.
FIG. 6 is a diagram illustrating characteristics of a roll-off filter.
FIG. 7 is an example of correlation power when the difference between delay times of each path is small.
FIG. 8 is a configuration diagram of an effective path determination circuit in the first embodiment.
FIG. 9 is a configuration diagram of a mask circuit.
FIG. 10 is a configuration diagram of an effective path determination circuit in the second embodiment.
FIG. 11 is a configuration diagram of a detection circuit.
FIG. 12 is a configuration diagram of an effective path determination circuit in the third embodiment.
FIG. 13 is a configuration diagram of an effective path determination circuit according to a fourth embodiment.
FIG. 14 is a configuration diagram of a continuous detection circuit.
FIG. 15 is a configuration diagram of an effective path determination circuit in a fifth embodiment;
FIG. 16 is a configuration diagram of an existing RAKE receiving circuit.
FIG. 17 is a diagram illustrating an example of a communication environment.
18 is a diagram illustrating a correlation between a received signal and a spread code in the communication environment illustrated in FIG.
[Explanation of symbols]
24 path search circuit
25 Demodulation / RAKE synthesis circuit
31 Sort circuit
32 Valid path determination circuit
52, 53 Mask circuit
72 Detection circuit
73 Selection circuit
74 Power comparison circuit
91 Multiplier circuit
101 Continuous detection circuit
141 detection circuit

Claims (6)

A RAKE receiver that despreads and combines signals received via a plurality of paths,
Generating means for generating correlation power by despreading the received signal;
Detecting means for detecting N timings at which the maximum correlation power to the Nth largest correlation power appear in the period of the spreading code period from the generated correlation power ;
Sorting means for sorting the detected N timings in descending order of correlation power;
Setting means for setting a mask range determined based on a communication environment;
Determining means for determining n (1 <n <N) effective paths from the sorted N timings based on a timing time difference and the mask range;
A synthesis means for synthesizing the determined n effective paths;
A RAKE receiving apparatus. The RAKE receiver according to claim 1,
The number N of the detected timings is determined based on the number n of the effective paths. The RAKE receiver according to claim 1,
The setting means is a RAKE receiver that sets the mask range based on a ratio of two predetermined correlation powers among the sorted correlation powers of N timings . The RAKE receiver according to claim 1,
The RAKE receiving apparatus , wherein the setting means sets the mask range based on whether a predetermined number of consecutive timings are detected by the detection means. The RAKE receiver according to claim 1,
The RAKE receiver that sets the mask range based on whether or not the setting means detects timings separated from each other by a predetermined interval. A RAKE receiving method for despreading and combining signals received through a plurality of paths,
Generate correlation power by despreading the received signal,
From the generated correlation power, N timings at which the largest correlation power to the Nth largest correlation power appear in the period of the spreading code period are detected,
Sort the detected N timings in descending order of correlation power,
Set the mask range determined based on the communication environment,
From the sorted N timings, n (1 <n <N) effective paths are determined based on the timing time difference and the mask range,
Combining the determined n effective paths
RAKE receiving method.

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