CN100375397C - Signal detector - Google Patents
Signal detector Download PDFInfo
- Publication number
- CN100375397C CN100375397C CNB2005101076992A CN200510107699A CN100375397C CN 100375397 C CN100375397 C CN 100375397C CN B2005101076992 A CNB2005101076992 A CN B2005101076992A CN 200510107699 A CN200510107699 A CN 200510107699A CN 100375397 C CN100375397 C CN 100375397C
- Authority
- CN
- China
- Prior art keywords
- signal
- signals
- unit
- band
- replica
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Abstract
A signal detector arranged in a receiver of a wireless communication device includes a variable passband bandpass filter configured to bandlimit a received signal using a variable passband; a signal parameter detection unit configured to detect a signal parameter of each of a plurality of signals contained in the received signal; a detection order determination unit configured to determine a detection order for detecting the signals from the received signal based on the signal parameter; a parameter control unit configured to control the passband of the variable passband bandpass filter based on the detection order and the signal parameter; and an equalization and decision unit configured to equalize and decide the bandlimited signal output from the variable passband bandpass filter. The signals contained in the received signal are successively detected from the received signal according to the detection order by means of the variable passband bandpass filter and the equalization and decision unit.
Description
Technical Field
The present invention relates to a signal detector used in a radio receiver constituting a radio communication system.
Background
In a wireless communication system, a technique for suppressing the amount of interference received is very important in order to effectively use limited frequency resources. As a conventional technique for improving the frequency use efficiency, there is a replica generation type interference canceller which generates a replica of a reception signal to effectively remove interference as shown in fig. 1 (for example, see non-patent document 1).
In the replica generation type interference canceller shown in fig. 1, channels of a desired signal and an interfering signal are successively estimated by a channel estimation unit a using an estimation error and a reference signal, a desired signal replica generator b and an interfering signal replica generator c perform convolution operation on all symbol sequence candidates that can be acquired by the desired signal and the interfering signal and respective channel estimation values, thereby generating a desired signal replica and an interfering signal replica and a received signal replica that is the sum of them for all symbol sequence candidates, a maximum likelihood sequence estimation unit d determines a symbol sequence candidate that can provide a desired signal and an interfering signal of a received signal replica closest to an actual received signal, and outputs the symbol sequence candidate of the desired signal as a determination result of the received signal, thereby effectively removing interference. The reference signal uses a known symbol sequence in the training interval and uses the determined symbol in the data interval.
By removing the interference signal from the received signal as appropriate, a plurality of different signals can use the same frequency at the same time, and frequency use efficiency can be improved.
On the other hand, as another conventional technique for improving the frequency utilization efficiency, a successive multi-user detection method based on an MMSE (Minimum Mean Square Error) filter for a plurality of user signals having the same signal bandwidth as shown in fig. 2 has been studied (non-patent document 3).
In the multiuser detection method based on the MMSE filter for a plurality of user signals having the same signal bandwidth shown in fig. 2, first, the 1 st detected signal (hereinafter, the k-th detected signal is referred to as the k-th detection target signal) is started, and the first detection target signal is equalized by the MMSE filter using the channel information of all the detection target signals stored in advance. Then, signal detection and replica generation of the first detection target signal are performed based on the equalized signal. Then, the second detection target signal is equalized, detected, and the replica generation process is performed. At this time, the processing is performed using a signal obtained by subtracting the replica signal of the first detection target signal from the input signal. Thus, the second detection target signal can be subjected to signal detection processing while suppressing interference from the first detection target signal, and a highly reliable detection result can be obtained. The MMSE filter-based multi-user detection method is also similar to the band-limiting successive multi-user detection method, and performs signal detection processing using a signal obtained by subtracting replica signals of the first to k-1-th detection target signals from the input signal in the k-th detection target signal.
In this way, by sequentially detecting other signals which are interference sources with respect to the signal to be detected, and generating and removing duplicates, the same frequency can be used at the same time by a plurality of different signals, and frequency utilization efficiency can be improved.
Non-patent document 1 discloses "refractory なる signal profile capable of separating refractory boundary better, namely, outer corner communication
Congratulation president collection, B-5-174 (3 months 2004)
Non-patent document 3' an effective square-root algorithm for BLAST, ' International conference on Acoustics, speech, and Signal Processing (ICASSP) '00 (6 months 2000)
Non-patent document 4'Fractional Tap-Spacing Equalizer and sequences for Clock Recovery in Dala models,' IEEE Transaction on Communications, (8 months 1976)
Although the replica generation type interference canceller shown in fig. 1 can generate a replica of a signal included in a received signal and detect the signal, when the number of signals to be used increases, the amount of calculation increases exponentially, and there is a problem that it is difficult to complete the processing within a practical calculation time. In particular, when a plurality of narrow band signals are superimposed on the same frequency as a wide band signal and transmitted, it is necessary to simultaneously process the plurality of narrow band signals in order to separate and extract the wide band signal, and it is difficult to separate and detect the signals.
In addition, the multiuser detection method based on the MMSE filter for a plurality of user signals having the same signal bandwidth shown in fig. 2 can maintain high signal detection accuracy and replica generation accuracy because the MMSE filter performs signal equalization using channel information of an interference signal. At this time, the channel information generally described uses a value estimated at the receiver side. However, when signals having different signal bandwidths are superimposed on the same frequency in the received signal, the sampled signal is affected by intersymbol Interference (ISI) because each signal is band-limited using a filter (not shown) having a different passband from that of the transmitting side. With regard to this ISI, since the signal bandwidths of the transmission-side band limiting filter and the reception-side band limiting filter for the detection target signal itself contained in the received signal are the same, in an environment where there is no delayed wave, it is possible to make ISI not occur by using the band limiting filter employed so far. However, since a reception-side band limiting filter for a signal to be detected band-limits a reception signal with respect to a signal of another user having a signal bandwidth different from that of the signal to be detected, the signal bandwidth of the transmission-side band limiting filter and that of the reception-side band limiting filter are different from each other, which causes ISI. The ISI varies greatly according to the sampling timing, and the state of the channel also varies greatly according to each sampling timing. Although such a variation can be estimated by performing channel estimation using a fractionally spaced coefficient variable filter (non-patent document 4), the number of taps (tap) of the filter becomes extremely large, the amount of calculation increases, and the channel estimation accuracy deteriorates.
Disclosure of Invention
The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a signal detector capable of separating and detecting signals with a small amount of calculation under the condition that a plurality of signals are superimposed on the same frequency, and capable of improving frequency utilization efficiency.
In order to solve the above-described problems, a signal detector according to one aspect of the present invention is a signal detector in a wireless communication system, which is provided in a receiver of a wireless communication device used in a wireless communication environment in which a plurality of wireless communication devices communicate with each other using different signal bandwidths and different carrier frequencies, the signal detector including: a variable passband bandpass filter that limits signals outside a frequency band in the received signal with a variable passband; a signal parameter detection unit that detects a signal parameter of each of a plurality of signals included in the received signal; a detection order determining unit configured to determine a detection order for detecting the signal from the received signal based on the signal parameter; a parameter control unit that controls a pass band of the band pass filter whose pass band is variable according to the detection order and the signal parameter; an equalization determination unit that equalizes and determines the band-limited signal from the band-pass variable bandpass filter, and a replica generator that generates a replica of the received signal using the determination result and the channel estimation value generated by the equalization determination unit, the signal detector including a plurality of stages of signal separation, each stage being defined as a combination of the band-pass variable bandpass filter, the equalization determination unit, and the replica generation unit, at each stage, the replica signal generated at a preceding stage is subtracted from the received signal, and band-limiting, equalization, and determination are performed using a residual signal after the subtraction, the plurality of signals included in the received signal being sequentially separated from the received signal by the band-pass variable bandpass filter and equalization determination unit in detection order. With this configuration, when various signals share a frequency band, signals included in the received signal can be separated and extracted by a process with a small amount of calculation on the receiving side.
In addition, according to a second aspect of the present invention, there is provided a signal detector, wherein the detection order determining unit includes: a mutual interference amount estimation unit configured to estimate a mutual interference amount when a plurality of signals included in the received signal interfere with each other, based on the received signal and the signal parameter; and a quality estimation and order determination unit that determines an order of separating and extracting signals included in the received signal from the received signal using the estimated mutual interference amount estimated by the mutual interference amount estimation unit, wherein the quality estimation and order determination unit may calculate a quality as a reference when determining a signal of a predetermined detection order by setting an estimated mutual interference amount of a signal preceding the detection order in the predetermined detection order to a predetermined value or less, and determine the order. Thus, the detection can be performed sequentially from a high-quality signal.
Further, according to a third aspect of the present invention, there is provided a signal detector according to the second aspect, wherein the mutual interference amount estimation unit includes: a signal power estimation unit that estimates received powers of a plurality of signals included in the received signal; a power per unit bandwidth calculation unit that calculates a power per unit bandwidth of each of the plurality of signals included in the received signal, based on the signal parameter and the estimated power value of each of the plurality of signals included in the received signal estimated by the signal power estimation unit; a signal overlap state estimation unit that estimates a bandwidth of a frequency in which a plurality of signals included in the received signal overlap in frequency and interfere with each other, based on the signal parameter; and an interference power calculating unit that calculates an estimated mutual interference amount based on a signal power calculation value per unit bandwidth of each of the plurality of signals included in the received signal calculated by the power per unit bandwidth calculating unit and an overlap frequency bandwidth between the plurality of signals included in the received signal estimated by the signal overlap state estimating unit. This makes it possible to easily estimate the amount of interference between a plurality of signals included in the received signal.
A fourth aspect of the present invention is the signal detector according to the third aspect of the present invention, wherein the mutual interference amount estimation unit includes a channel estimation unit configured to estimate a channel estimation value, which is a state of a channel in which a plurality of signals included in the received signal are spread along a time axis, using the received signal and the signal parameter, and the signal power estimation unit is configured to estimate power using the channel estimation value for the main wave of each signal estimated by the channel estimation unit. This makes it possible to estimate the power of each signal with high accuracy.
Further, according to a fifth aspect of the present invention, in the signal detector according to the third aspect of the present invention, the signal power estimating unit may estimate the power of each signal by performing correlation detection using known symbol sequences corresponding to a plurality of signals included in the received signal. Thus, the power of each signal can be estimated with a simple configuration.
Further, a sixth aspect of the present invention is the signal detector according to the third aspect of the present invention, wherein the power-per-unit-bandwidth calculating means may calculate the signal power per unit bandwidth of each signal by averaging values of the signal power of each signal estimated by the signal power estimating means for a predetermined time, using the signal bandwidth included in the signal parameter of each signal. Thus, the amount of interference per unit bandwidth that each signal generates to other signals can be estimated.
Further, a seventh aspect of the present invention is the signal detector according to the third aspect of the present invention, wherein the signal overlapping state estimating means calculates an upper limit and a lower limit of a frequency band used for each signal based on center frequency information and signal bandwidth information included in the signal parameter, and compares the calculated upper limit and lower limit of the frequency band between all signals included in the received signal to calculate the overlapping frequency width between the signals. Thus, the signal band in which the respective signals interfere with each other can be obtained by simple calculation.
Further, according to the signal detector of the third aspect of the present invention, the interference power calculating means may calculate the interference power between the plurality of signals included in the received signal by multiplying the signal power per unit bandwidth of each signal calculated by the power per unit bandwidth calculating means by the overlapping frequency bandwidth between the signals calculated by the signal overlapping state estimating means. Thus, the interference power between the respective signals can be estimated by a simple calculation.
Further, a ninth aspect of the present invention is the signal detector according to any one of the first to third aspects of the present invention, wherein the detection order determining unit includes: a mutual interference amount estimation unit configured to estimate a mutual interference amount when a plurality of signals included in the received signal overlap each other on a frequency axis and interfere with each other, based on the received signal and the signal parameter; a noise estimation unit configured to estimate noise powers received by a plurality of signals included in the received signal, respectively, based on the received signal and the signal parameter; and a quality estimation and order determination unit that determines an order of separating and extracting signals included in the received signal from the received signal using the estimated mutual interference amount estimated by the mutual interference amount estimation unit and the estimated noise power estimated by the noise estimation unit, wherein the quality estimation and order determination unit may determine the order by calculating a quality as a reference when determining a signal of a predetermined detection order by setting an estimated mutual interference amount of a signal preceding the detection order in the predetermined detection order to a predetermined value or less. In this way, the detection order can be determined using the communication quality in consideration of the noise included in the received signal, and the signal can be separated and detected with high accuracy.
Further, a tenth aspect of the present invention is the signal detector according to the ninth aspect of the present invention, wherein the noise estimation unit includes: a replica signal generation unit that generates a replica of the received signal based on the received signal and the signal parameter; a subtractor that subtracts the replica signal generated by the replica signal generation means from the received signal and outputs a residual signal; a band-pass filter that band-limits the residual signal using a signal bandwidth of each of a plurality of signals included in the reception signal; and a noise power estimating unit that calculates power of noise band-limited by the band-pass filter, estimates a noise signal waveform included in the reception signal, and performs band limitation, thereby obtaining and outputting power of noise affecting a plurality of signals included in the reception signal for each signal. This makes it possible to easily obtain the power of noise affecting each signal included in the received signal.
Further, an eleventh aspect of the present invention is the signal detector according to any one of the first to tenth aspects of the present invention, wherein the detection order determining means may set the higher the detection order of the signal having the higher communication quality is. This reduces a determination error in a signal having a higher detection order, and can separate and detect the signal with high accuracy.
A twelfth aspect of the present invention is the signal detector according to any one of the first to eleventh aspects of the present invention, wherein the signal parameter detecting unit may estimate and detect the signal parameter of each signal included in the received signal based on the received signal. This makes it possible to perform signal separation in advance without information on each signal.
A thirteenth aspect of the present invention is the signal detector according to any one of the first to twelfth aspects of the present invention, wherein the signal parameter detecting unit may be notified of the signal parameter of each signal by the wireless station on the transmitting side in advance. In this way, by acquiring the signal parameters of the respective signals in advance, the signal separation operation can be easily performed.
A fourteenth receiver according to the present invention is a receiver of a wireless communication device used in a wireless communication environment in which a plurality of wireless communication devices communicate with each other using different transmission signal bandwidths, the receiver including a multiuser detector including: a plurality of band limiting filters having different pass bands respectively corresponding to a plurality of signals included in the input signal transmitted from the other wireless communication apparatus having a plurality of transmitting side filters having different pass bands; a channel estimation unit which estimates channel state information of each of the plurality of signals, using signal information, in consideration of intersymbol interference caused by the plurality of transmission side filters and a reception side filter of the receiver; a minimum mean square error filter that calculates a filter coefficient using the estimated channel state information and the signal information, and equalizes the associated band-limited signal; a soft input-output decoder that determines each user data item contained in the signal from the signal information and calculates a likelihood of each symbol mapped to a signal space; a replica generator that generates a symbol sequence replica according to the likelihood and generates a received signal replica using the symbol sequence replica and the signal information, the symbol sequence replica being provided to the minimum mean square error filter and used in equalization of the band-limited signal; and a subtractor that subtracts the received signal replica from the input signal. This makes it possible to perform equalization processing in consideration of large fluctuation in ISI due to filters of signals having different signal bandwidths, and to separate signals with high accuracy.
A fifteenth aspect of the present invention is a receiver according to the fourteenth aspect of the present invention, wherein the radio receiver includes a multi-stage multi-user detection unit in which a plurality of the multi-user detection units are connected in a vertical direction, and the multi-user detection unit is configured to perform signal detection and replica generation using a replica signal generated by a multi-user detection unit at a preceding stage of the vertical connection. This improves the accuracy of replica generation, and can separate signals with higher accuracy.
According to the signal detector of the present invention, under the condition that a plurality of signals having different signal parameters share the same frequency for communication, the signals can be separated and detected with a small amount of calculation.
Drawings
Fig. 1 is a block diagram showing a structure of a conventional replica generation interference canceller.
Fig. 2 is a block diagram showing the structure of a successive multi-user detection method (conventional method) based on an MMSE filter.
Fig. 3 is a block diagram showing an example of the configuration of a receiver including the signal detector according to embodiment 1 of the present invention.
Fig. 4 is a schematic diagram of a signal processing procedure of the signal detector.
Fig. 5 is a block diagram showing an example of the configuration of a receiver including the signal detector according to embodiment 2 of the present invention.
Fig. 6 is a block diagram showing an example of the configuration of the detection order determining unit.
Fig. 7 is a flowchart showing the operation of the quality estimation and order determination means in fig. 6.
Fig. 8 is a block diagram showing another configuration example of the detection order determining unit.
Fig. 9 is a flowchart showing the operation of the quality estimation and sequence determination unit in fig. 8.
Fig. 10 is a block diagram showing an example of the configuration of the mutual interference amount estimating unit.
Fig. 11 is a block diagram showing another configuration example of the mutual interference amount estimating unit.
Fig. 12 is a block diagram showing an example of the structure of a power-per-unit-bandwidth calculating unit.
Fig. 13 is a schematic diagram showing the relationship between the power of each signal and the signal power per unit bandwidth.
Fig. 14 is a diagram showing a relationship between a usage bandwidth of a signal and an overlapping frequency bandwidth.
Fig. 15 is a schematic diagram showing the amount of mutual interference.
Fig. 16 is a block diagram showing another configuration example of the detection order determining unit.
Fig. 17 is a flowchart showing the operation of the quality estimation and order determination unit in fig. 16.
Fig. 18 is a block diagram showing another configuration example of the detection order determining unit.
Fig. 19 is a flowchart showing the operation of the quality estimation and sequence determination means in fig. 18.
Fig. 20 is a block diagram showing an example of the configuration of the noise estimation unit.
Fig. 21 is a schematic diagram showing an operation of the noise estimation unit.
Fig. 22 is a block diagram showing an example of the configuration of a receiver including the signal detector according to embodiment 3 of the present invention.
Fig. 23 is a block diagram showing an example of the configuration of the signal detector according to embodiment 4 of the present invention.
Fig. 24 is a block diagram showing an example of a parameter information generation method.
Fig. 25 is a block diagram showing an example of the configuration of the signal parameter detection unit.
Fig. 26 is a block diagram showing an example of the configuration of a radio receiver including the radio transmitter and the multi-user detector according to embodiment 5 of the present invention.
Fig. 27 is a block diagram showing an example of the structure of the multi-user detector in fig. 26.
Fig. 28 is a block diagram showing an example of the configuration of the channel calculating section in fig. 27.
Fig. 29 is a block diagram showing an example of the structure of a multiuser detector in the case where channel estimation is performed simultaneously on all signals.
Fig. 30 is a block diagram showing an example of the configuration of a multiuser detector in a case where channel estimation is performed individually on each signal.
Fig. 31 is a block diagram showing an example of the configuration of the channel calculating section in fig. 30.
Fig. 32 is a block diagram showing an example of the structure of a wireless receiver having a multi-stage multi-user detector.
Fig. 33 is a block diagram showing an example of the structure of a multi-user detector constituting a multi-stage multi-user detector.
Fig. 34 is a block diagram showing an example of the configuration of the channel calculating section in fig. 33.
Description of the symbols
1. 2: a transmitter; 10: a receiver; 11: a band pass filter with a variable pass band; 12: a signal parameter detection unit; 13: a detection order determining unit; 14: a parameter control unit; 15: an equalization judgment unit; 16: a copy generation unit; 17: and a subtracter.
Detailed Description
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
(embodiment 1)
Fig. 3 is a block diagram showing an example of the configuration of a receiver including the signal detector according to embodiment 1 of the present invention. Fig. 4 is a schematic diagram of a signal processing procedure of the signal detector.
In fig. 3, the receiver 10 is composed of: a band-pass filter 11 (11) for limiting the frequency band of the received signal and making the pass band variable 1 、11 2 ) (ii) a A signal parameter detection unit 12 that detects signal parameters of a plurality of signals included in the received signal; a detection order determining unit 13 for determining the detection order of the received signals based on the received signals and the signal parameters detected by the signal parameter detecting unit 12; a parameter control unit 14 that controls the passband of the variable passband bandpass filter 11 based on the detection order determined by the detection order determining unit 13 and the signal parameter detected by the signal parameter detecting unit 12; equalization determining section 15 (15) 1 、15 2 ) An equalizer that equalizes and determines an output signal from the band-pass filter 11 having a variable passband; auxiliary setA present generation unit 16 that generates a replica of the received signal using the determination result of the equalization determination unit 15 and the channel estimation value estimated in the equalization process; a subtractor 17 that subtracts the replica signal from the received signal.
The transmitter 1 and the transmitter 2 transmit signals having different transmission signal parameters, respectively, and the receiver 10 receives a reception signal a obtained by adding these signals. The reception signal A is inputted to a band pass filter 11 with a variable passband 1 A detection order decision unit 13 and a subtractor 17. The signal parameters such as the signal bandwidth, center frequency, and modulation scheme of the signal 1 and the signal 2 are transmitted and notified to the signal parameter detecting section 12 of the receiver 10 before communication. As an example, use of common doesThe line channel notifies the signal parameter before starting communication by a radio control signal. Here, an example of a case of notification in advance before starting communication is shown.
The signal parameter detecting section 12 detects signal parameters of the signal 1 and the signal 2 included in the received signal, and inputs the detected signal parameters to the detection order determining section 13 and the parameter control section 14. In detection order determining section 13, an order of detecting signals (signal 1 and signal 2) included in the received signal is determined based on received signal a and signal parameter B, and detection order C is input to parameter control section 14. The parameter control unit 14 controls the band pass filter #1 (11) whose pass band is variable according to the information of the center frequency and the signal bandwidth detected in the signal parameter detection unit 12 1 ) In the same manner as above, parameters necessary for equalizing and determining the modulation scheme, symbol rate, and the like of the signal having the detection order of 1 st are input to equalization determination section #1 (15) 1 ). Similarly, the band-pass variable band-pass filter #2 (11) is controlled using the signal parameter of the signal whose detection order is 2 nd 2 ) And an equalization judgment unit #2 (15) 2 )。
Band pass filter #1 (11) having a variable pass band 1 ) As shown in the band-limited signal G of FIG. 4, or to suppressSignals of signal components in frequency bands other than the frequency band of the signal of the 1 st order are detected. The band-limited signal G is input to an equalization determination unit #1 (15) 1 ) Equalization and decision are performed. At this time, the determination result #1 (D) obtained in the equalization processing 1 ) And the channel estimation value E are input to the replica generating unit 16. In the replica generating unit 16, according to the determination result #1 (D) 1 ) And a channel estimation value E, and generates a replica signal F of the signal having the detection order 1, and inputs the replica signal to the subtractor 17. The subtractor 17 subtracts the replica signal F from the received signal a, and inputs the result to the band-pass filter #2 (11) with a variable passband 2 ). At this time, the signal is input to a band pass filter #2 (11) with a variable passband 2 ) As shown in fig. 4, the signal (2) is a signal obtained by subtracting the signal in the detection order 1, that is, a signal composed of the signal in the detection order 2 and noise, from the received signal. Band pass filter #2 (11) with variable passband 2 ) The pass band is changed so that the signal whose detection order designated by the parameter control unit 14 is 2 nd passes, and the output of the filter is input to the equalization determination unit #2 (15) 2 ). Equalization determination unit #2 (15) 2 ) Equalization and determination of the signal whose detection order is 2 are performed based on the inputted signal, and determination result #2 (D) is outputted 2 )。
In this way, under the condition that the signal with the detection order of 1 can be accurately determined, the signal with the detection order of 2 can be determined in a state where the amount of interference received by the signal with the detection order of 1 is small, and therefore, the signals included in the received signal a can be separated and detected with high accuracy.
(embodiment 2)
Fig. 5 is a block diagram showing an example of the configuration of a receiver including the signal detector according to embodiment 2 of the present invention, and the configuration example in which two transmitters are provided in embodiment 1 shown in fig. 3 is extended to a configuration example in which 1 to K transmitters are provided. Functional blocks that perform the same operations as those shown in fig. 3 are assigned the same reference numerals, and description thereof will be omitted.
In the receiver 10, K band-pass filters 11 (11) with variable pass bands are provided 1 、 11 2 、～、11 K ) And an equalization judgment unit 15 (15) 1 、15 2 、～、15 K ) Having K-1 copy generating units 16 (16) 1 、16 2 、～、16 K-1 ) And subtractor 17 (17) 1 、17 2 、～、17 K-1 ). Band pass filter #1 (11) with variable passband 1 ) Band-pass filter #2 (11) with variable passband 2 ) Band pass filter # K (11) with variable passband K ) The pass bands of the filters are changed so that a signal with the detection order of 1 st, a signal with the detection order of 2 nd, and a signal with the detection order of K th pass through the filters. The signals having passed through bandpass filters # 1, #2, # 38 zxft 3238, # K of which the pass band is variable are input to equalization determination sections # 1, #2, # 62 zxft 3262, # K, respectively. Equalization decision units # 1, #2, … and # K equalize and decide the input signal, and channel estimation value E obtained in the equalization process 1 、E 2 … and determination result D 1 、D 2 … inputs replica generation units # 1, #2, …. The replica generation units # 1, #2, and … generate replicas of the signals whose detection orders are 1 st, 2 nd, and …, respectively, and input the replicas to the subtractor 17 1 、17 2 …. Subtractor #1 (17) 1 ) Subtracting a replica signal F of the signal with the detection order 1 from the received signal A 1 The subtraction result is input to a band-pass filter #2 (11) whose passband is variable 2 ) And subtractor #2 (17) 2 ). Subtractor #2 (17) 2 ) The replica signal F of the signal with the detection order 2 is subtracted from the signal input from the subtractor # 1 2 The subtraction result is input to a band pass filter and a subtractor of the next stage, the pass band of which is variable. In this way, by sequentially removing the signals from the received signal starting from the signal having a high detection order, the signal input to the band-pass filter having a variable pass band of a predetermined level becomes a signal obtained by subtracting the replica signal of the signal having a higher detection order from the target signal passed through the filterThe signals can be separated and extracted with high accuracy.
Fig. 6 is a block diagram showing an example of the configuration of detection order determining section 13, and is composed of mutual interference amount estimating section 131 and quality estimating and order determining section 132.
Mutual interference amount estimation section 131 estimates the mutual interference amount (estimated mutual interference amount I) between a plurality of signals included in the received signal from received signal a and signal parameter B, and inputs the estimated mutual interference amount I to quality estimation and order determination section 132. Here, the estimated value of the interference amount of the signal a with respect to the signal b is represented by I (a, b), and the estimated mutual interference amount I can be expressed by the following expression (1). The interference amount estimation value I (a, a) is the power of the signal a.
[ equation 1]
Fig. 7 is a flowchart showing the operation of the quality estimation and sequence determination unit 132 in fig. 8. The quality estimation and order determination unit 132 determines the detection order according to the flow shown in fig. 7.
First, as an initial setting, the detection order i is set to '1' (step S10). Then, it is determined whether i is equal to the number of signals included in the received signal (step S11). If they are not equal, the process proceeds to step S12, and if they are equal, the process ends. In step S12, the estimated mutual interference amount estimated by mutual interference amount estimation section 131 is used to estimate the communication quality of each signal. Then, SIR, which is a ratio of desired signal power to interference signal power corresponding to signals included in the received signal, is calculated by the following equation (2) est The signal whose value is the largest is set as the detection order i (step S13).
[ equation 2]
Then, in step S13, the interference amount of the signal with the best quality with respect to other signals and the desired signal power of the signal itself are all set to '0' (step S14). Here, although the power is set to '0', the power may be set to a very small value in consideration of a condition that it is difficult to completely remove the signal due to a generation error of the replica signal. Then, the detection order i is incremented by 1 to i +1 (step S15), and the process returns to step S11.
The detection order is determined by the above actions. This makes it possible to sequentially detect signals with less influence of interference and with good communication quality.
Fig. 8 is a block diagram showing another configuration example of the detection order determining unit 13. In FIG. 8The detection order determining means 13 includes a mutual interference amount estimating means 131, a quality estimating and order determining means 133, and (E) b /I o ) BER correspondence table 134. Fig. 9 shows a flowchart of the operation of the quality estimation and sequence determination unit 133.
Mutual interference amount estimation section 131 estimates mutual interference amounts (estimated mutual interference amounts) between a plurality of signals included in the received signal based on received signal a and signal parameter B, and inputs the estimated mutual interference amounts to quality estimation and order determination section 133.
The quality estimation and order determination unit 133 operates according to the flowchart of fig. 9. That is, as the initial setting, the detection order i is set to '1' (step S20). Then, it is determined whether i is equal to the number (K) of signals included in the received signal (step S21). The process proceeds to step S22 if they are not equal to each other, and the process ends if they are equal to each other. In step S22, the ratio of signal power to interference power (E) per 1 bit is estimated based on the estimated mutual interference amount I and the modulation scheme information X included in the signal parameter B b /I o ). Then, based on the estimation (E) b /I o ) (Y) and modulation scheme information X, with reference to (E) b /I o ) A BER correspondence table 134 for determining estimated bit error rates [ BER (1), BER (2) ] of the respective signals included in the received signal A)，…BER(K)]Z (step S23). Here, BER (p) is an estimated bit error rate of the signal p. Then, the detection order of the signal with the lowest estimated bit error rate is set to 'i' (step S24), and the interference amount of the signal with the detection order of 'i' with other signals and the desired signal power of the signal itself are all set to '0' (step S25). Note that, although the power is set to '0', the power may be set to a small value in consideration of a condition that it is difficult to completely remove the signal due to a generation error of the replica signal. Then, the detection order i is incremented by 1 to i +1 (step S26), and the process returns to step S21.
The detection order is determined by the above actions. According to this configuration, it is possible to sequentially detect from a signal whose bit error rate is expected to be low, and to separate and detect a signal included in the received signal a with high accuracy.
Fig. 10 is a block diagram showing an example of the configuration of mutual interference amount estimation section 131, and includes: a transmission path estimation unit 1311, a signal power estimation unit 1312, a power per unit bandwidth calculation unit 1313, a signal overlap state estimation unit 1314, and an interference power calculation unit 1315.
Transmission path estimation section 1311 estimates transmission paths of a plurality of signals included in received signal a, and estimated transmission path estimation value J is input to signal power estimation section 1312. Here, the training sequence of the signal parameters is input to transmission channel estimation section 1311 and used, but a transmission channel may be estimated using pilot symbols. The signal power estimation unit 1312 estimates the power of each signal from the input transmission path estimation value J.
As shown in fig. 11, transmission path estimation section 1311 in fig. 10 may be omitted, and signal power estimation section 1312 may perform correlation detection on received signal a using a known symbol sequence (training sequence is used as an example in fig. 11) in correlation detector 13121, and power estimation section 13122 may estimate the power of each signal from the correlation value detected by correlation detector 13121.
In fig. 10 and 11, the power estimation value L of each signal is input to the power per unit bandwidth calculation section 1313, the power per unit bandwidth calculation section 1313 calculates the signal power per unit bandwidth of each signal using the information of the signal bandwidth, and the calculation result is input to the interference power calculation section 1315. Here, wu (p) represents the power per unit bandwidth of the signal p. At this time, power per unit bandwidth calculation section 1313, as shown in fig. 12, obtains a calculated signal power per unit bandwidth by integrating the instantaneous value P (t) of the power of each signal estimated by signal power estimation section 1312 with time, averaging the power for each observation time, and dividing the power by signal bandwidth information BW in signal parameter B. At this time, a signal power calculation value per unit bandwidth of the signal p is obtained by the following equation (3).
[ equation 3]
Here, fig. 13 shows an example of the relationship between the power of each signal and the signal power per unit bandwidth. FIG. 13 shows a superimposed received signal 1 (A) 1 ) And Signal 2 (A) 2 ) And signal 3 (A) 3 ) For the example of 3 signals, the power of each signal is the area of the region representing each signal. The power per unit bandwidth is approximately the height of the region representing each signal in the figure. In addition, the power per 1 bit is the result of dividing the power per unit bandwidth by the number of transmittable bits per unit bandwidth.
The signal overlapping state estimation unit 1314 calculates the bandwidth of the frequency at which the signals included in the received signal a overlap each other, based on the information of the center frequency and the signal bandwidth, and inputs the calculated value to the interference power calculation unit 1315. Here, the frequency bandwidth in which the signal p and the signal q overlap is defined as B overlay (p、q)。
This will be described with reference to fig. 13. Here, signal 1 is repeated with signal 2Region O of the stack 1 (the region of mutual interference) is located at the left end of the frequency band of signal 1, and the overlapping bandwidth is defined as B overlay (1, 2). At this time, it is clear that equation B overlay (1、2)＝B overlay (2, 1) is true. The bandwidth in which the signal p is superimposed on the signal p, i.e., the signal bandwidth of the signal p, is represented by B overlay (p, p). In this case, the region O where the signal 1 and the signal 3 overlap 2 Is equal to the frequency band of signal 3, so B overlay (1、 3)＝B overlay (3、1)＝B overlay (3, 3). And, due to the region O where signal 2 and signal 3 overlap 3 Do not exist, so B overlay (2、3)＝B overlay (3, 2) =0. The frequency bandwidth to be overlapped is divided into the cases shown in fig. 14 based on the center frequency and the signal bandwidth, and is obtained by the following equations 4 to 7. Here, the center frequencies of the signals p and q are respectively denoted by f cp And f cq Setting the signal bandwidth as BW p And BW q . The signal p and the signal q are arbitrary signals included in the received signal, and the following equations may be applied by substituting the signal p and the signal q.
(a) When the used frequency band of the signal p contains the used frequency band of the signal q
(i.e., when f cq +BW q /2≤f cp +BW p 2 and f cp -BW p /2≤f cq -BW q When 2
[ equation 4]
B overlay (p，q)＝BW q Calculator (4)
(b) When the upper limit of the used frequency band of the signal p is within the used frequency band of the signal q
(i.e., when f cp +BW p /2≤f cq +BW q 2 and f cp -BW p /2≤f cq -B Wq When 2
[ equation 5]
B overlay (p，q)＝(f cp +BE p /2)-(f cp -BW q /2 calculation formula (5)
(c) When the lower limit of the use frequency band of the signal p is within the use frequency band of the signal q
(i.e., when f cq +BW q /2≤f cp +BW p 2 and f cq -BW q /2≤f cp -BW p When 2
[ equation 6]
B overlay (p，q)＝(f cp +BW q /2)-(f cp -BW p /2 calculation formula (6)
(d) When the frequency band of signal p does not overlap with the frequency band of signal q
(i.e., when f cq +BW q /2≤f cp -BW p /2 or f cp +BW p /2≤f cq -BW q When 2
[ equation 7]
B overlay (p, q) =0 equation (7)
Interference power calculation section 1315 calculates estimated mutual interference amount I from input signal power calculation value M for each unit bandwidth of each signal and overlapping frequency bandwidth O between a plurality of signals. At this time, the amount of interference of the signal p with the signal q can be obtained by multiplying the frequency bandwidth in which the signal p overlaps the signal q by the power per unit bandwidth of the signal p. That is, the estimated mutual interference amount I (p, q) can be calculated by the following equation (8).
[ equation 8]
I(p，q)＝W U (p)B overlay (p, q) formula (8)
Fig. 15 is a schematic diagram showing the amount of mutual interference. The region P in the diagram represents the portion of the signal where signal 2 interferes with signal 1, and the power in this region is approximately Wu (2) B overlay (2,1) = I (2,1). In the figure, the region Q represents a signal portion where signal 3 interferes with signal 1, and the power in this region is approximately Wu (3) B overlay (3,1) = I (3,1). That is, the total interference received by signal 1 is I (2,1) + I (3,1). This is achieved byWhen the power of signal 1 is Wu (1) B overlay (1,1) = I (1,1), the estimated communication quality (in this case, the estimated SIR) of the signal 1 can be expressed by the following equation (9).
[ equation 9]
Calculator (9)
Similarly, the estimated communication quality can be easily obtained for the signal 2 and the signal 3.
The signal detector of fig. 3 may be configured to input the channel estimation value J obtained in fig. 10 to the equalization determining section 15 and use the channel estimation value J.
Fig. 16 is a block diagram showing an example of the configuration of the detection order determining unit 13 in the case where a signal for communication using a spreading code is included in a received signal. Fig. 17 is a flowchart showing the operation of quality estimation and order determination section 132 in fig. 16.
In fig. 16, the estimated mutual interference amount I is obtained in mutual interference amount estimating section 131 as in fig. 6, but at this time, input spreading factor information R is used as signal parameter B, and power I (p, p) of each signal is a value SF (p) I (p, p) obtained by multiplying spreading factor SF (p). In this configuration, even for a signal not using a spreading code, it is possible to cope with the signal by setting the spreading rate information to '1'. In this case, the ratio of the desired signal power to the interference signal power in the comparison of the communication quality (step S32) in the operation flow of fig. 17 can be calculated by the following equation (10), and the detection order can be determined in consideration of the spreading gain. Thus, even for a received signal in which a signal using a spreading code and a signal not using a spreading code are mixed, the detection order can be determined efficiently, and the signals can be separated and extracted with high accuracy.
[ equation 10]
Calculator (10)
Fig. 18 is a block diagram showing another configuration example of the detection order determining unit 13. In this configuration, noise estimation section 135 is added to detection order determination section 13 in fig. 6, and the operation of the other sections is the same, so that the description thereof is omitted.
Mutual interference amount estimation section 131 estimates mutual interference amounts of a plurality of signals included in received signal a from received signal a and signal parameter B, and inputs estimated mutual interference amount I to quality estimation and order determination section 132. Noise estimation section 135 estimates noise powers received by a plurality of signals included in received signal a based on received signal a and signal parameter B, and inputs estimated noise power T to quality estimation and order determination section 132. The quality estimation/order determination unit 132 determines the detection order in accordance with the operation flow 33 of fig. 19, based on the input estimated mutual interference amount I and estimated noise power T. The operation flow of fig. 19 is the same as the operation flow of fig. 7, and differs only in whether or not noise is considered for the communication quality as a reference for determining the order. Specifically, as an initial setting, the detection order i is set to '1' (step S40). Then, it is determined whether i is equal to the number of signals included in the received signal (step S41). The process proceeds to step S42 if they are not equal to each other, and the process ends if they are equal to each other. In step S42, the ratio of the signal power of each of the plurality of signals included in the received signal a to the interference signal power + the noise power is obtained, and the signal having the highest ratio is set as the detection order i. Then, in step S42, the power of the signal with the best quality is set to '0'. That is, the interference amount of the signal with other signals and the desired signal power of the signal itself are all set to '0' (step S43). Then, the detection order i is incremented by 1 to i +1 (step S44), and the process returns to step S41. In this way, when a plurality of signals having different signal bandwidths use a frequency band repeatedly, the influence of noise received by each signal can be estimated with high accuracy, and the detection order can be determined efficiently.
In the present embodiment, the obtained influence of noise is used to calculate the 1-to-1 ratio in the same manner as in fig. 8Specific signal power to interference and noise power ratio E b /(I o +N o )， The estimated bit error rate is obtained using the value, and the detection order can be determined based on this.
Fig. 20 is a block diagram showing an example of the configuration of noise estimation section 135, and includes replica signal generation section 1351, subtractor 1352, and band-pass filter 1353 (1353) 1 、1353 2 、～、1353 k ) And a noise power estimation unit 1354. Fig. 21 is a schematic diagram showing the operation of noise estimation section 135.
Replica signal generation section 1351 generates replicas of a plurality of signals included in received signal a from received signal a and the training sequence in signal parameter B, outputs replica U of the received signal as the sum of them, and inputs replica U to subtractor 1352. The subtractor 1352 subtracts the received signal replica U from the received signal a. By subtracting the reception signal replica U from the reception signal a in this way, only the noise component remains, and the residual signal V can be obtained. The residual signal V is then input to a band pass filter 1353. The band-pass filter 1353 band-limits the residual signal V according to the frequency bands of the plurality of signals included in the received signal. Specifically, a bandpass filter 1353 corresponding to the signal p is provided after Fourier transformation of the residual signal is performed to N (f) p Is H p (f) Then, the following formula (11) (N) can be used H (p, f)) to obtain the noise after passing through the band-pass filter.
[ equation 11]
N H (p，f)＝N(f)H p (f) Calculator (11)
Wherein H p (f) Indicating the frequency band used (i.e., f) with the pass band being the signal p cp -BW p /2 ≤f≤f cp +BW p /2). At this time, as shown in fig. 21, the band-pass filter 1353 outputs the noise W (W) whose band is limited in accordance with the frequency band of each signal included in the received signal a 1 、W 2 、 W 3 ). Thus, the band-pass filter 11 of fig. 3 with a variable passband can be estimatedThe remaining noise component. The output band-limited noise W is input to noise power estimation section 1354, and noise power estimation section 1354 estimates the power of noise received by each signal included in received signal a using the following equation and outputs the result.
[ equation 12]
By the above processing, it is possible to estimate the noise contained in the received signal a and the noise power received by each signal.
(embodiment 3)
Fig. 22 shows a receiver including a signal detector according to embodiment 3 of the present inventionA block diagram of an example of a structure of (1). Thus, the present invention may be formed by adding an error correction decoder 151 (151) 1 、151 2 ) And the structure of the error correction encoder 152. In this case, the output of the equalization determining unit # 1 is input to the error correction decoder 151 1 The decoding is performed according to the error correction coding method transmitted as the transmission signal parameter, and the result is output as the determination result #1 (D1). The determination result #1 (D1) is input to the error correction encoder 152, encoded by the same encoding method as that on the transmission side, and the encoded signal is input to the replica generating unit 16. In this way, since the replica signal is generated using the signal with few errors after error correction, it is possible to prevent deterioration in the generation accuracy of the replica signal due to a determination error, and to separate and detect the signal with high accuracy.
(embodiment 4)
Fig. 23 is a block diagram showing an example of the configuration of the signal detector according to embodiment 4 of the present invention, and includes a band pass filter 11 (11) having a variable passband 1 、11 2 、11 3 、～、11 k ) And an equalization judging unit 15 (15) 1 、15 2 、15 3 、～、15 k ) And a copy generation unit 16 (16) 1 、16 2 、 16 3 、～、16 k ) Formed of a plurality of stages 18 (18) 1 、18、～、18 N ). In this figure, as in the configuration of fig. 3, the signal parameter detection section 12, the detection order determination section 13, and the parameter control section 14 control the operations of the variable passband bandpass filter 11 and the equalization determination section 15.
At stage 1 18 1 In the above-described manner, similarly to the signal detector of fig. 3, the equalization determination is performed on the signal subjected to the band limitation via the band-pass filter 11 with a variable pass band in accordance with the detection order determined by the detection order determining unit 13, and the determination result (primary determination result) is obtained. The replica generating unit 16 generates replicas of the signals of the 2 nd and subsequent detection orders included in the received signal a based on the primary determination result and the channel estimation value, and inputs the replicas to the 2 nd stage 18 2 . At stage 2 18 2 Will be subtracted from the received signal a at stage 1 18 1 The signal generated in (1) is a signal obtained by duplicating the 2 nd and subsequent signals, and the bandpass filter #1b having a variable passband corresponding to the signal having the detection order of 1 st is input. In band pass filter #1b with a variable passband, an input signal is band-limited, the band-limited signal is input to equalization determining section #1b, the equalization determining section #1b performs equalization determination on the input signal, and the determination result (secondary determination result) and a channel estimation value are input to replica generating section #1b. At this time, the signal input to the variable passband bandpass filter #1a contains an interference signal in the received signal, and the signal input to the variable passband bandpass filter #1b is subtractedAt stage 1 18 1 The signal obtained by copying the signal generated in (1) is a signal in which the influence of interference is suppressed. Therefore, the influence of the interference signal in the equalization determining section 15 is suppressed, and more accurate channel estimation values can be obtained than in the 1 st stage. Then, in the replica generating unit #1b, the detection order is generated to be the first order from the input secondary determination result and the channel estimation value1, is a replica of the signal.
The residual signal obtained by subtracting the signal copies having the detection order of 3 rd and 3 rd generated at the 1 st stage and the signal copy having the detection order of 1 st generated at the copy generation unit #1b from the received signal a is input to the band pass filter #2b having a variable pass band. Similarly, a band pass filter # nb having a variable passband corresponding to the signal having the detection order of the nth is inputted with a residual signal obtained by subtracting the signal replica having the detection order of the (n + 1) th and subsequent signal replicas having the detection order of the (n-1) th and previous signal replicas having the detection order of the (n-1) th and subsequent signal replicas having the detection order of the (2) th stages from the received signal a. These input signals are subjected to band limitation and equalization determination, and replica generating section 16 generates a replica signal from the secondary determination result of equalization determining section 15 and the channel estimation value.
In this way, in the q-th stage, the channel estimation value is made highly accurate using the replica signal generated in the q-1-th stage, and the accuracy of the determination result is made higher. When the number of stages is N, the determination result of the balance determination unit 15 of the nth stage is output as the final determination result.
By adopting the above configuration, it is possible to suppress errors in channel estimation values and determination errors due to the influence of interference signals in the configuration shown in fig. 3, and to separate signals with high accuracy.
Fig. 24 and 25 are diagrams showing an example of a signal parameter detection method. In fig. 24 and 25, the same table as in the information reception and transmission regarding the modulation scheme, the signal bandwidth, the center frequency, and the like that may be used is stored in the transceiver. The transmitting side selects a sequence number corresponding to a signal parameter to be used from the table, generates a data sequence, and transmits the data sequence before communication. For example, when a signal having a QPSK modulation scheme, a BWc signal bandwidth, and a fcB center frequency is transmitted, the "No." "2", "3", and "2" are modulated by data serialization and transmitted before communication. On the receiving side, as shown in fig. 25, using the same table, sequences are also generated and modulated for all combinations of parameters that are likely to be used, and used for correlation detection in the correlation detector 121. The parameter determination unit 122 uses the signal parameters such as the modulation scheme, the signal bandwidth, and the center frequency corresponding to the sequence determined to have the highest correlation detection result, and outputs the signal parameters as the signal parameters B. In this way, since it is not necessary to transmit the signal parameter using a separate control channel, it is possible to effectively use the frequency resource.
(embodiment 5)
Since the equalization process is performed on the signal preceding the detection sequence by processing the signal following the detection sequence as noise, the detection accuracy and the accuracy of the generated replica are degraded.
Next, fig. 26 is a block diagram showing an example of the configuration of a radio transmitter and a radio receiver having a multi-user detector according to embodiment 5 of the present invention.
In fig. 26, the transmitter 5-1 (5-1 a, 5-1b, 5-1 c) is constituted by: modulators 5 to 11 (5 to 11a, 5 to 11b, 5 to 11 c), band limiting filters 5 to 12 (5 to 12a, 5 to 12b, 5 to 12 c), transmission-side low-pass filters 5 to 13 (5 to 13a, 5 to 13b, 5 to 13 c), baseband-RF (Radio Frequency) converters 5 to 14 (5 to 14a, 5 to 14b, 5 to 14 c), antennas 5 to 15 (5 to 15a, 5 to 15b, 5 to 15 c), and encoding units 5 to 16 (5 to 16a, 5 to 16 b). The encoding section 5-16 is omitted in the case where error correction is not performed.
The receiver 5-2 is constituted by: RF-baseband conversion sections 5-20 (5-20 a, 5-20 b), reception-side low-pass filters 5-21 (5-21 a, 5-21 b), multi-user detectors 5-22, high-output amplifiers 5-26 (5-26 a, 5-26 b), and antennas 5-25 (5-25 a, 5-25 b). Fig. 26 shows a case where the number of receiving antennas is 2.
The transmitter 5-1 inputs transmission data 5-10 (5-10 a, 5-10b, 5-10 c) or data error-correction-coded by the coding section 5-16 to the modulator 5-11, and the modulator 5-11 modulates the input data and maps the data to a point on a signal space. The band limiting filter 5-12 performs waveform shaping on the signal modulated in the modulator 5-11. The baseband-RF converters 5 to 14 amplify and frequency-convert the baseband signal whose band has been limited to an RF band signal. The transmission-side low-pass filters 5 to 13 suppress high-frequency components of the frequency-converted signal. The signal with the high frequency component suppressed by the transmission side low pass filter 5-13 is transmitted via the transmission antenna 5-15.
The signal transmitted from the transmission antenna 5-15 is received by the reception antenna 5-25 of the receiver 5-2 through the transmission path 5-3 (5-3 a, 5-3b, 5-3 c). The received signal is amplified by a high output amplifier 5-26, and then, noise outside the received signal band is suppressed by a receiving low pass filter 5-21, and then, the signal is converted into a baseband signal by an RF-baseband converter 5-20. The baseband signal is input to a multi-user detector 5-22. The multiuser detector 5-22 refers to the signal information 5-24 relating to the signal included in the received signal, and outputs the received data determination result 5-23 (5-23 a, 5-23b, 5-23 c) from the baseband signal.
Fig. 27 shows an example of the structure of the multiuser detector 5-22. In fig. 27, the multiuser detectors 5-22 are composed of: band limiting filters 220 (220 a, 220b, 220 c), channel calculation sections 221 (221 a, 221b, 221 c), MMSE filters 222 (222 a, 222b, 222 c), soft input-output decoders 223 (223 a, 223b, 223 c), replica generators 224 (224 a, 224 b), and subtracters 225 (2253 a, 225 b).
In the multiuser detector 5-22, first, the band-limiting filter 220a for detecting a signal in order 1 (hereinafter, the signal in order k is referred to as a signal to be detected in order k) performs band-limiting on the input signal r, and the band-limited signal is input to the MMSE filter 222a. The channel calculating unit 221a calculates a channel state of the signal of each user included in the input signal r, taking into account the ISI state from the transmission-side band limiting filter 5-12 to the band limiting filter 220a of the 1 st detection target signal on the receiving side, based on the reception filter information of the 1 st detection target signal from the band limiting filter 220a, the symbol rate information, timing information, information of the transmission path 5-3, and the transmission-side filter information of the signal of each user included in the reception signal.
Here, when it is assumed that the low-pass filters 5-13, 5-21 of the reception and transmission ideally operate and there is no signal distortion, when the modulation signal vector of the k-th detection signal is set to b k Setting the transmission filter matrix to G TX，k Setting the matrix of the state of the transmission path 5-3 as H p，k When n is the noise vector and K is the total number of signals to be detected, the input signal r can be expressed by the following expression. In addition, τ k represents the arrival timing of each signal.
[ equation 13]
Calculator (13)
In this case, the input signal r can be expressed by the following equation.
[ equation 14]
r＝[r * (0)，...，r * (D 1 )] H Calculator (14)
At this time, D 1 The +1 indicates the number of sample points of the 1 st detection target signal, and "+" and "H" indicated in the upper right corner of the vector or matrix indicate complex conjugate and complex conjugate transpose, respectively. And r (m) represents time mT s1 Of the received signal, T Sk Represents the time interval of the sample of the kth detection object signal. Here, when the number of symbols of the transmitted modulated signal is set to M k When it is ready, b k The expression can be expressed by the following equation. b k (m) represents the m +1 th modulated signal of the k-th detection target signal.
[ equation 15]
And, a transmission filter matrix G TX，k Comprises the following steps:
[ equation 16]
Calculator (16)
In this case, gk (t) represents a time response function of the band limiting filter 5-12 in transmission of the kth detection target signal, and is determined according to the passing bandwidth of the kth detection target signal. Tk denotes a symbol time of the kth detection target signal, and a symbol rate is given in accordance with 1/Tk.
Matrix H of transmission path states p，k The expression can be expressed by the following equation.
[ equation 17]
At this time, hk (p, q) represents a q-th delayed wave (delay time: qT) received in the received signal r (p) S1 ) The amplitude and phase rotation of the phase.
At this time, a matrix G representing the band limiting filter 220a is used Rx，1 ：
[ equation 18]
Calculator (18)
The signal having passed through the band limiting filter 220a on the receiving side becomes:
[ equation 19]
At this time, when the received signal is sampled in accordance with the arrival timing of the 1 st detection target signal, that is, when the received signal is sampled at the time mTS + τ 1, the arrival timings of the 2 nd to K th received signals are shifted relatively by the time τ 1. That is, the signal after passing through the reception filter 220 a:
[ equation 20] equation (20)
In this case, the channel calculating unit 221a calculates the channel matrix of the k-th detection target signal as the following equation based on equation (20).
[ equation 21]
Similarly, the channel calculating unit 221 in the processing block of the m-th detection target signal calculates the channel matrix of the k-th detection target signal as the following expression.
[ equation 22]
Fig. 28 shows an example of a block diagram configuration of a channel calculating unit in a processing block of an m-th detection target signal.
For simplicity, the channel matrix for processing the mth detection target signal of the kth detection target signal is:
[ equation 23]
Calculator (23)
This makes it possible to easily calculate a channel state in which ISI is caused by a difference in the pass band of the filter that is not considered in the method of non-patent document 3, and to suppress an increase in the amount of calculation and deterioration in the channel estimation accuracy as compared with the case where a fractional interval coefficient variable filter is used according to the method of non-patent document 4.
From the channel matrix calculated as described above, MMSE filter 222a calculates a filter coefficient w (u) for the u-th symbol of the 1 st detection target signal by the following formula.
[ equation 24]
Here, eu denotes a vector for detecting only the u-th row component of the matrix, σ 2 Representing the average power of the noise, I 1 Represents M 1 ×M 1 The identity matrix of (2). Λ k denotes a symbol sequence bk on the actually transmitted signal space of the kth detection target signal and a symbol sequence replica generated after modulation:
[ equation 25]
The covariance matrix of the dispersion of (a) is:
[ equation 26]
In addition, the covariance matrix is an identity matrix when no replica of the symbol sequence is generated at all, that is, when a replica signal of the k-th detection target signal is not subtracted from the input signal, whereas the covariance matrix is an approximate zero matrix when a replica can be generated with high accuracy and a replica is subtracted with high accuracy. Here, when the 1 st detection target signal is processed, since subtraction of any signal replica is not performed, Λ k is a unit matrix for all k.
Using the filter coefficient w1 (u) thus obtained, the following equalization processing is performed on the received signal.
[ equation 27]
s 1 (u)＝w 1 (u) H G Rx、1 r calculation formula (27)
Thus, unlike the method shown in non-patent document 2 in which the signal of another user that is interfering is treated as noise, the signal of another user that is interfering is subjected to equalization processing based on the MMSE reference that minimizes the square error, and therefore a more accurate signal detection result can be obtained.
The signal after such equalization processing is input to the soft input-output decoder 223a. The soft input/output decoder 223a determines the received data and calculates the likelihood for the transmission symbol, taking into account the coding of the 1 st detection target signal after the equalization processing, if the transmission side performs coding. Here, when the modulation scheme is BPSK, log likelihood ratio λ 1 (u), which is a logarithmic value of the likelihood ratio, is expressed as follows.
[ equation 28]
Then, the replica generator 224 generates a replica of the symbol sequence using the likelihood obtained by the soft input-output decoder 223. If the copy of the sequence of symbols is assumed to be:
[ equation 29]
The copy of the u-th symbol can be calculated by the following equation.
[ equation 30]
The replica of the symbol sequence is input to an MMSE filter of a processing unit of a signal to be detected later. Then, a replica of the received signal of the 1 st detection target signal is obtained by the following formula in consideration of the transmission filtering and the reception timing,
[ equation 31]
The subtractor 225 disposed at the previous stage of the band limiting filter of the 2 nd detection target signal is input.
Then, the process proceeds to signal processing of the 2 nd detection target signal.
In the 2 nd detection target signal processing, first, a replica of the 1 st detection target signal is subtracted from the input signal. Then, using the subtraction result expressed by the following equation,
[ equation 32]
Calculator (32)
The same processing as that of the 1 st detection target signal is performed. Similarly, the m-th detection target signal is subjected to signal processing using the following equation.
[ equation 33]
In the detection process of the m-th detection target signal, the signal may be sequentially demodulated, a replica of the m-th detection target signal may be generated from the signal of the demodulation result, and the ISI component caused by the influence of the delayed wave may be removed using the replica.
In the present embodiment, the example in which only the influence of the transmission-side band limiting filter 5-12 and the reception-side band limiting filter 220 is considered has been described, but it is considered that the ISI may occur due to distortion of the signal waveform in the low pass filter for reception and transmission. In this case, the k-th detection target signal is setThe matrix of the impulse response of the low-pass filter 5-13 on the transmitting side is L Tx，k Let L be a matrix representing the impulse response of the low-pass filters 5-21 on the receiving side Rx，k In this case, the channel calculation unit 221 for processing the m-th detection target signal calculates the channel matrix of the k-th detection target signal according to the following equation:
[ equation 34]
Whereby multi-user detection can be performed taking into account the influence of the low-pass filters 5-13, 5-21.
And, if the matrix is large, the amount of computation of the inverse matrix calculation becomes extremely large. Therefore, ISI symbols that affect only when the power is equal to or lower than a predetermined power are not considered in the channel matrix for the symbols to be demodulated, and the channel matrix can be made small and the amount of computation can be reduced.
Fig. 29 is a block diagram showing an example of a configuration when channel states are estimated simultaneously for all signals to be detected. In the present configuration example, the transmission path information is estimated by the transmission path estimation section 226:
[ equation 35]
[H p，1 ，...，H p，K ]Calculator (35)
Instead of the actual transmission path information, estimated transmission path estimation values are used:
[ equation 36]
The same operation as in fig. 27 is performed. The transmission path estimation unit 226 multiplies a transmission filter matrix by reference symbols such as training symbols and pilot symbols in consideration of the reception timing of each signal, and performs transmission path estimation using an RLS (Recursive Least Square) algorithm or an LMS (Least Mean Square) algorithm. By multiplying the transmission filter matrix in advance, the influence of ISI caused by the filter is not reflected in the transmission path estimation. This makes it possible to estimate the state of the transmission path with high accuracy.
Fig. 30 is a block diagram showing an example of a configuration when channel states are individually estimated for respective detection target signals. In the present configuration, the processing unit of the m-th detection target signal estimates the transmission path of the m-th detection target signal after passing through the band limiting filter 220. The transmission path estimation is performed by using the RLS algorithm or the LMS algorithm, taking into account ISI caused by the influence of the filter on the transmission side, as in the simultaneous estimation.
Fig. 31 is a block diagram showing an example of the configuration of the channel calculating section in fig. 30. In the channel calculation unit 221 for processing the m-th detection target signal, since the propagation path estimation is performed only up to the m-th detection target signal, the propagation path estimation values of the m + 1-th and subsequent detection target signals are calculated as 0.
Fig. 32 is a block diagram showing an example of the structure of a receiver having a multi-user detector. In the present structural example, the receiver 5-2 has a multi-stage multi-user detector 5-27 constituted by connecting a plurality of multi-user detectors 5-28 (5-28 a, 5-28b, 5-28 c) in tandem. In the multi-stage multi-user detector 5-27, the symbol sequence replica generated in the detection process of the multi-user detector 5-28 of stage 1 is used in the stage 1+1 multi-user detector:
[ equation 37]
Calculator (37)
And a replica signal:
[ equation 38]
The accuracy of multi-user detection is improved by performing repeated signal detection processing.
Fig. 33 is a block diagram showing an example of the structure of the multi-user detector 5-28 inside the multi-stage multi-user detector 5-27. Fig. 33 shows an example in which the number of receiving antennas is 2. The level 1 multiuser detector 5-28 subtracts, in the detection process of the level 1 detection object signal, the replica signal generated by the level 1-1 multiuser detector from the input signal r, and uses the signal of the subtraction result:
[ equation 39]
Calculator (39)
To perform signal detection processing. In the detection process of the m-th detection target signal, since the replica of the m-1 th and m-1 th previous detection target signals is updated, a signal expressed by the following equation is used as a result of subtracting the updated replica.
[ equation 40]
Calculator (40)
Fig. 34 shows an example of the configuration of the channel calculation section of the multi-stage multi-user detectors 5 to 27. In the channel calculation unit 221 of the mth detection target signal, since the channel estimation values of the detection target signals before the mth and mth are updated, the channel matrix is calculated using the updated values. Thus, when the channel estimation value is updated successively, the channel matrix is also updated simultaneously, and highly accurate signal separation can be achieved.
The present invention has been described above based on preferred embodiments thereof. Although the present invention has been described by showing specific examples, it is needless to say that various modifications and changes can be made to these specific examples without departing from the spirit and scope of the present invention defined by the claims. That is, the detailed description and drawings of the specific examples should not be construed as limiting the invention.
Claims (15)
1. A signal detector provided in a receiver of a wireless communication apparatus used in a wireless communication environment in which a plurality of wireless communication apparatuses communicate with each other using different signal bandwidths and different carrier frequencies, the signal detector comprising:
a variable pass band pass filter that limits a signal out of a frequency band in the reception signal with a variable pass band;
a signal parameter detection unit that detects a signal parameter of each of a plurality of signals included in the received signal;
a detection order determining unit configured to determine a detection order for detecting the signal from the received signal, based on the signal parameter;
a parameter control unit that controls a pass band of the variable pass band pass filter according to the detection order and the signal parameter;
an equalization determination unit that equalizes and determines the band-limited signal from the band-pass filter with a variable passband, and
a replica generator that generates a replica of the received signal using the determination result and the channel estimation value generated by the equalization determination unit,
the signal detector includes a plurality of stages of signal separation, each stage being defined as a combination of the band pass filter whose pass band is variable, the equalization decision unit, and the replica generation unit,
at each stage, the replica signal generated at a previous stage is subtracted from the received signal, and band limiting, equalization, and decision are performed using the subtracted residual signal,
the plurality of signals included in the reception signal are sequentially separated from the reception signal by the band pass filter whose pass band is variable and the equalization decision unit in the detection order.
2. The signal detector according to claim 1, wherein the detection order deciding unit has:
a mutual interference amount estimation unit that estimates a mutual interference amount between the plurality of signals included in the received signal; and
and a quality estimation and order determination unit that determines a detection order for detecting the plurality of signals from the received signal based on the estimated mutual interference amount, determines a quality to be used as a reference when determining the signals in a predetermined detection order, and estimates the quality when determining the detection order, considering that the mutual interference amount caused by the signals preceding the predetermined detection order is equal to or less than a predetermined level.
3. The signal detector according to claim 2, wherein the mutual interference amount estimation unit has:
a power estimation unit that estimates received powers of the plurality of signals included in the received signal;
a power per unit bandwidth calculation unit that calculates a power per unit bandwidth of each of the plurality of signals based on the signal parameter and the power estimated by the power estimation unit;
a signal overlap estimation unit that estimates an overlap frequency bandwidth in which the plurality of signals overlap and interfere with each other, based on the signal parameter; and
and an interference amount calculation unit that calculates the mutual interference amount based on the signal power per unit bandwidth and the overlap frequency bandwidth.
4. The signal detector according to claim 3, wherein the mutual interference amount estimation unit has a transmission path estimation section that estimates, for each signal included in the reception signal, a transmission path estimation value representing a state of a transmission path that widens along a time axis,
the power estimation unit estimates power using a transmission path estimation value of a main wave of the respective signals.
5. The signal detector of claim 3, wherein the power estimation unit uses a known sequence of symbols for correlation detection to estimate the power of the respective signal.
6. The signal detector according to claim 3, wherein the power per unit bandwidth calculating unit calculates the signal power per unit bandwidth of each of the signals by averaging the estimated values of the signal power for the estimated predetermined time period using a signal bandwidth included in the signal parameter.
7. The signal detector according to claim 3, wherein the signal overlap estimation unit calculates an upper limit and a lower limit of a frequency band of each signal from carrier frequency information and signal bandwidth information contained in the signal parameter, and compares the upper limit and the lower limit between all signals contained in the received signal to estimate the overlap frequency bandwidth.
8. The signal detector according to claim 3, wherein the interference amount calculation unit multiplies the signal power per unit bandwidth of the respective signals by the overlapping frequency bandwidth, thereby calculating the inter-signal interference power contained in the received signal.
9. The signal detector according to claim 1, wherein the detection order deciding unit has:
a mutual interference amount estimation unit that estimates a mutual interference amount caused by the signals included in the reception signal, which overlap on a frequency axis and mutually interfere, based on the signal parameters of the reception signal and the respective signals;
a noise estimation unit that estimates noise of each of the signals based on the received signal and the signal parameter; and
and a quality estimation and order determination unit that determines an order of detecting signals from the received signal using the estimated mutual interference amount and noise, estimates a quality used as a reference when determining signals in a predetermined detection order, and estimates the quality by considering that the mutual interference amount caused by signals whose detection order is earlier than the predetermined order is equal to or less than a predetermined level.
10. The signal detector according to claim 9, wherein the noise estimation unit has:
a replica signal generation unit that generates a replica signal of the received signal based on the received signal and the signal parameter;
a subtractor that subtracts the replica signal from the received signal and outputs a residual signal;
a band-limiting filter that band-limits the residual signal to a signal bandwidth of the signal contained in the received signal according to an estimated noise waveform contained in the received signal; and
a noise calculation unit that calculates and outputs the noise removed by the band limiting filter for each signal included in the reception signal.
11. The signal detector according to claim 1, wherein the detection order decision unit provides a higher detection order for the signal with higher communication quality.
12. The signal detector of claim 1, wherein the signal parameters of the signals are estimated from the received signals.
13. The signal detector according to claim 1, wherein the signal parameter of each signal is obtained in advance from a wireless communication apparatus on a transmission side.
14. A receiver of a wireless communication device for use in a wireless communication environment in which a plurality of wireless communication devices communicate with each other using different transmission signal bandwidths, the receiver having a multi-user detector comprising:
a plurality of band limiting filters having different pass bands respectively corresponding to a plurality of signals included in the input signal transmitted from the other wireless communication apparatus having a plurality of transmit-end filters having different pass bands;
a channel estimation unit that estimates channel state information of each of the plurality of signals, using signal information, in consideration of intersymbol interference caused by the plurality of transmitting-side filters and a receiving-side filter of the receiver;
a minimum mean square error filter that calculates a filter coefficient using the estimated channel state information and the signal information, and equalizes the associated band-limited signal;
a soft input-output decoder that determines each user data item contained in the signal from the signal information and calculates a likelihood of each symbol mapped to a signal space;
a replica generator that generates a symbol sequence replica according to the likelihood, and generates a received signal replica using the symbol sequence replica and the signal information, the symbol sequence replica being provided to the minimum mean square error filter and used in equalization of the band-limited signal; and
a subtractor that subtracts the received signal replica from the input signal.
15. The receiver according to claim 14, wherein said receiver has a multi-stage multi-user detection unit comprising 2 or more than 2 of said multi-user detectors, each of said multi-user detectors performing signal detection and replica generation using replica signals generated by said multi-user detector of a preceding stage.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004287234 | 2004-09-30 | ||
| JP2004287234 | 2004-09-30 | ||
| JP2005255083 | 2005-09-02 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1756096A CN1756096A (en) | 2006-04-05 |
| CN100375397C true CN100375397C (en) | 2008-03-12 |
Family
ID=36689098
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2005101076992A Expired - Fee Related CN100375397C (en) | 2004-09-30 | 2005-09-30 | Signal detector |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN100375397C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105407063A (en) * | 2014-09-10 | 2016-03-16 | 三星电子株式会社 | Apparatus and method for mitigating interference in a wireless communication system |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4246755B2 (en) * | 2006-05-30 | 2009-04-02 | 株式会社エヌ・ティ・ティ・ドコモ | Received signal frequency band detector |
| US9819442B2 (en) | 2012-03-16 | 2017-11-14 | Intel Deutschland Gmbh | Internal interference signaling |
| CN103647743B (en) * | 2013-12-29 | 2017-12-26 | 联想(北京)有限公司 | A kind of signal processing method and relevant apparatus |
| CN111226478A (en) * | 2018-01-12 | 2020-06-02 | Oppo广东移动通信有限公司 | Data sending method, device and system |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2003039012A1 (en) * | 2001-10-25 | 2003-05-08 | Infineon Technologies Ag | Adaptive channel filter for a mobile radio receiver, and method for adaptive channel filtering |
| US20030216122A1 (en) * | 2002-05-17 | 2003-11-20 | Cordone Sean S. | Multiple carrier adaptive notch filter |
| US20040141565A1 (en) * | 2002-07-19 | 2004-07-22 | Interdigital Technology Corporation | Groupwise successive interference cancellation for block transmission with reception diversity |
-
2005
- 2005-09-30 CN CNB2005101076992A patent/CN100375397C/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2003039012A1 (en) * | 2001-10-25 | 2003-05-08 | Infineon Technologies Ag | Adaptive channel filter for a mobile radio receiver, and method for adaptive channel filtering |
| US20030216122A1 (en) * | 2002-05-17 | 2003-11-20 | Cordone Sean S. | Multiple carrier adaptive notch filter |
| US20040141565A1 (en) * | 2002-07-19 | 2004-07-22 | Interdigital Technology Corporation | Groupwise successive interference cancellation for block transmission with reception diversity |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105407063A (en) * | 2014-09-10 | 2016-03-16 | 三星电子株式会社 | Apparatus and method for mitigating interference in a wireless communication system |
| CN105407063B (en) * | 2014-09-10 | 2020-09-08 | 三星电子株式会社 | Apparatus and method for mitigating interference in a wireless communication system |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1756096A (en) | 2006-04-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP1643657B1 (en) | Signal detector used in wireless communication system | |
| KR100765873B1 (en) | Groupwise successive interference cancellation for block transmission with reception diversity | |
| US6944245B2 (en) | Multi-pass interference reduction in a GSM communication system | |
| JP3210343B2 (en) | Method and apparatus for receiving and decoding communication signals in a CDMA receiver | |
| US6137843A (en) | Methods and apparatus for canceling adjacent channel signals in digital communications systems | |
| JP4578376B2 (en) | Signal separation device | |
| JP4913043B2 (en) | Apparatus and method for optimally estimating distortion caused by transmission media by sequential firing of pairs of orthogonal complementary sequences | |
| JP4503442B2 (en) | Decision feedforward equalizer system and method | |
| US8315342B2 (en) | Method and apparatus for simplified expected symbol value computation and interference cancellation in communication signal processing | |
| JP4778007B2 (en) | Apparatus and associated method for filtering received signal by adaptive operation of input noise whitening filter | |
| KR20000069434A (en) | Method and apparatus for digital symbol detection using transmission medium response estimates | |
| NO317331B1 (en) | Method and apparatus for digital radio signal reception | |
| KR20050098026A (en) | Scaling using gain factors for use in data detection for wireless code division multiple access communication systems | |
| CN100375397C (en) | Signal detector | |
| KR20070081786A (en) | An apparatus and method for multiple input multiple output in communication | |
| KR20080050205A (en) | Iterative reception method and iterative receiver | |
| JP2008503140A (en) | Adaptive main digital ultra wideband receiver | |
| WO2010070350A2 (en) | Multiple output multiple user methods and/or systems of underwater accoustic communication | |
| TW432843B (en) | Receiver for a digital transmission system | |
| US6760374B1 (en) | Block decision feedback equalization method and apparatus | |
| EP0656162A1 (en) | Cdma communication system | |
| US10193712B2 (en) | Mobile terminal device and method for processing signals | |
| JP4635200B2 (en) | CDMA transmission apparatus and method | |
| JP7264260B2 (en) | Wireless communication system, wireless communication method, transmitting station device and receiving station device | |
| CN1672379B (en) | Differential decoder followed by non-linear compensator |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20080312 Termination date: 20190930 |