JP2000078111A - Channel estimate device for cdma synchronous detection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a channel with higher accuracy by controlling a weighted coefficient at channel estimate based on also correlation between pilot signals not only on the correlation between an estimated value of channel information to be obtained and each pilot signal. SOLUTION: The channel estimate device is provided with a channel estimate value generating section 11 that generates a channel estimate value as to channel information by multiplying a prescribed weighting coefficient Wj (j=0-3) with each of plurality of pilot signals and summing the resulting pilot signals and with a weighting coefficient control section 10 that controls the weighting coefficient Wj in the channel estimate value generating section 11 based on a correlation among plurality of the pilot signals and the correlation between plurality of the pilot signals and the estimated value of the channel information to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

(Contents) Technical field to which the present invention pertains Prior art (FIGS. 13 to 16) Problems to be Solved by the Invention Means for Solving the Problems Embodiment of the Invention (A) Description of First Embodiment ( (B) Description of the second embodiment (FIGS. 10 and 11) (C) Description of the third embodiment (FIG. 12) (D) Other effects of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA synchronous detection channel estimating apparatus for performing channel estimation for synchronous detection of a received signal for CDMA (Code Division Multiple Access) communication using a pilot signal.

[0003]

2. Description of the Related Art In recent years, CDMA (particularly, direct spread CDMA (DS-CDMA)) has been actively researched and developed as a promising access system in the next-generation mobile communication system. Here, in the DS-CDMA system, as is well known, the communication capacity and the number of users accommodated are limited by interference of other users who perform communication in the same frequency band. , RAKE demodulation].

FIG. 13 is a block diagram showing an example of a configuration focusing on a reception system (synchronous detection part) in a DS-CDMA mobile station. The reception system 100 shown in FIG. Sections 102-1 to 102-n (n is a natural number), channel estimation sections 103-1 to 103-n, complex conjugate sections 104-1 to 104-n, and multipliers 105-1 to 105-1
Fingers 100-1 to 100-n having 105-n
And a RAKE combining unit 106 and a signal processing unit 107.

Here, demodulation section 101 converts the received signal into a QP
The demodulation is performed by a required demodulation method such as SK. The despreading unit 102-i in each finger 100-i (where i = 1 to n) receives a different propagation environment (path) (multipath). By subjecting each of the signals to despreading individually, a multipath signal component included in the received signal is separated.

The channel estimator 103-i of each finger 100-i is connected to the above despreader 102-i.
The channel estimation for each multipath is performed based on a signal after despreading by i (multipath signal component: hereinafter, referred to as a despread signal). This channel estimation is usually performed, for example, as shown in FIG. This is performed by weighting and averaging a plurality of pieces of known data such as a pilot signal (hereinafter, sometimes simply referred to as “pilot”) inserted into the received signal (data signal) at a fixed period (slot unit).

For this reason, the channel estimating section (CDMA synchronous detection channel estimating apparatus) 103-i includes a switch 2, a delay element (T _s ) 3, an adder 4, and a delay element, as shown in FIG. (T _slot ) 5, a multiplier 6 and an adder 7. Here, the switch 2 is ON-controlled by a searcher or the like who knows the pilot timing only when the despread signal is a pilot, and the delay element 3 delays the input pilot by one symbol. The adder 4 averages a plurality of pilots by sequentially adding the pilot one symbol before to the input pilot,
The delay element 5 delays the input pilot by one slot.

A multiplier 6 multiplies a plurality of pilots obtained by the delay element 5 with a predetermined weighting coefficient w _j (j = 0 to 3 in FIG. 14). Numeral 7 is for generating a channel estimation value by adding and averaging the pilot signals multiplied by the weighting coefficients w _j in the multiplier 6 described above.

That is, the above-mentioned portion including the delay element 5, the multiplier 6 and the adder 7 multiplies a plurality of pilots by a predetermined weighting coefficient and adds each pilot, thereby obtaining the channel information of the data signal. And a function as a channel estimation value generation unit 11 that generates the channel estimation value. With such a configuration, in channel estimation section 103-i, pilot (pilot block) of each slot of the despread signal is averaged in a symbol unit by delay element 112 and adder 113, and then channel estimation value generation section 11 performs. , Each pilot is delayed by a delay element 114 by one slot, and the obtained pilots are each multiplied by a predetermined weighting coefficient w _j by each multiplier 115 and added by an adder 116 to obtain a channel estimation value (complex Amplitude signal).

Next, each finger 100-i shown in FIG.
, The complex conjugate units 104-i take complex conjugates of the channel estimation values obtained by the channel estimation unit 103-i as described above to generate complex conjugate signals of the channel estimation values, respectively. 105-i detects the data signal by multiplying the complex conjugate signal obtained by the complex conjugate unit 104-i by the despread signal (data signal) from the despread unit 102-i, respectively. , The channel information (the amount of phase rotation) is corrected according to the channel estimation result.

The RAKE combining section 106 RAKE-combines the data signals detected as described above and averages them, and the signal processing section 107 performs processing on the data signal obtained by the RAKE combining section 106. Then, by performing necessary signal processing such as deinterleaving processing and Viterbi decoding processing, signal reproduction processing is performed. The reproduced signal (data) is appropriately output to a speaker, a display, or the like of the mobile station.

With such a structure, the above-mentioned DS-CD
In the receiving system 100 for MA, in each finger 100-i, the channel estimation unit 103-i performs channel estimation for each multipath of the received signal, and based on the estimation result, the complex conjugate signal generation unit 104-i. And multiplier 1
05-i, the channel information of the received signal is corrected for each multipath, and the received signal from each finger 100-i is RAKE-combined by the RAKE combining unit 106 and averaged, thereby achieving efficient synchronization. Detection can be performed.

By the way, in a mobile communication environment, multipath fading is affected. Therefore, in order to perform stable communication even in a situation where a mobile station such as a mobile phone moves at high speed, the mobile station follows a fast fading fluctuation (adaptive). It is necessary to carry out channel estimation. However, the above-described reception system 100 (channel estimation section 103-
In i), since the weighting coefficient _wj and the number of pilots used for channel estimation in each finger 100-i are constant (fixed) regardless of the fluctuation of fading, optimal channel estimation cannot be performed. Therefore, in a mobile communication environment, there is a very high possibility that signal quality will be degraded.

Therefore, for example, the Technical Report of IEICE. SS published by the Institute of Electronics, Information and Communication Engineers
E98-20, RCS98-20 (1998-04)) p67-p74 (hereinafter referred to as publicly known literature) adaptively adjusts the weighting factor at the time of channel estimation according to the speed of fading fluctuation. Control techniques have been proposed. Specifically, in the technique of this known document, for example, as shown in FIG. 16, the channel estimation vector ξ _l (n) obtained by weighted averaging and the channel estimation vector ξ _l ′ (n + i) of each pilot are By calculating the inner product, a correlation value between the channel estimation value (estimated value of channel information to be obtained) obtained by weighted averaging and the channel estimation value of each pilot is obtained, and the real part is used as a weighting coefficient for each pilot. (The real part of the correlation value calculated up to a certain slot is used as a weight coefficient of the next slot).

[0015]

However, even in such a technique according to the known document, the weighting coefficient is controlled based only on the correlation value between the channel estimation value obtained by weighted averaging and the channel estimation value of each pilot. Since there is no channel estimation (correlation between pilots is not taken into account), it is difficult to say that channel estimation with sufficient accuracy can be performed, especially in a mobile communication environment.

Further, since there is no suggestion to actively control the number of pilots used at the time of channel estimation in each finger, it is considered from this point that channel estimation with sufficient accuracy has not been performed. The present invention has been devised in view of such a problem, and controls a weighting coefficient at the time of channel estimation based on not only a correlation between an estimated value of channel information to be obtained and each pilot, but also a correlation between pilots. Accordingly, it is an object of the present invention to provide a CDMA synchronous detection channel estimating apparatus capable of performing more accurate channel estimation.

Also, by actively controlling the number of pilots used in channel estimation, it is possible to perform more accurate channel estimation, or to calculate the product of a complex conjugate signal of a pilot and another pilot at a certain moment. It is another object of the present invention to provide a CDMA synchronous detection channel estimating apparatus that can perform high-speed channel estimation by using it as a weighting coefficient.

[0018]

For this reason, the CD of the present invention
The MA synchronous detection channel estimating device (claim 1) includes a plurality of rake combining multiple rake combining units for synchronous detection of a received signal for CDMA communication having a pilot signal (hereinafter, simply referred to as "pilot") and a data signal. The fingers each obtain an estimated value for the channel information of the data signal from a plurality of pilots, and multiply each of the plurality of pilots by a predetermined weighting coefficient and add each pilot, A channel estimation value generation unit that generates a channel estimation value for the channel information; and the channel estimation based on the correlation between the plurality of pilots and the correlation between the plurality of pilots and the estimated value of the channel information to be obtained. It has a weighting coefficient control unit that controls the weighting coefficient in the value generation unit. It is set to.

Here, the weighting coefficient control unit, for example, calculates an inverse matrix of a correlation matrix composed of correlation values between pilots and a correlation vector composed of correlation values between each pilot and an estimated value of channel information to be obtained. The weighting coefficient may be determined by calculating the product of Also, the present CDMA synchronous detection channel estimating apparatus (hereinafter simply referred to as “channel estimating apparatus”) includes a moving speed detecting unit for detecting its own moving speed, and the weighting coefficient control unit is configured to May be obtained from the moving speed detected by the moving speed detecting unit.

Further, the present channel estimating apparatus includes a tentative determination unit for performing a tentative determination of the data signal based on the channel estimation value generated by the channel estimation value generation unit, and the weighting coefficient control unit includes The correlation may be obtained in consideration of the correlation between the data signals for which the provisional determination is performed by the provisional determination unit (claim 4). Further, the channel estimation value generation section may be configured to use the data signal, for which the provisional determination has been performed by the provisional determination section, for generating a channel estimation value.

Further, the present channel estimating apparatus is provided with a common correlation generator for obtaining and averaging the correlation common to the respective fingers, and the weighting coefficient controller is provided with a common correlation generator. The channel estimation value generation unit may be configured to control a weighting coefficient based on the averaged correlation (claim 6).

The channel estimating apparatus also includes a signal-to-interference / noise power ratio estimating unit for estimating a signal-to-interference / noise power ratio based on the received signal.
The weighting coefficient control unit is configured to remove an interference / noise component included in a correlation between pilots based on the signal-to-interference / noise power ratio obtained by the signal-to-interference / noise power ratio estimation unit. (Claim 7).

Next, the channel estimation apparatus of the present invention (claim 8) generates a channel estimation value for channel information by multiplying each of a plurality of pilots by a predetermined weighting coefficient and adding each pilot. A channel estimation value generator, and a pilot number for controlling the number of pilots used for generating the channel estimation value in the channel estimation value generator based on the correlation value between the plurality of pilots and the estimated value of the channel information to be obtained. It is characterized by having a control unit.

Here, the number-of-pilots control section is configured to use, for example, only the pilots whose correlation values are equal to or more than a predetermined value for generating the channel estimation value in the channel estimation value generation section. Good (claim 9). The channel estimation apparatus further includes a signal-to-interference / noise power ratio estimating unit for estimating a signal-to-interference / noise power ratio based on the received signal, and the pilot number control unit includes: The interference / noise component included in the correlation between the pilots may be removed based on the signal-to-interference / noise power ratio obtained by the interference / noise power ratio estimator.

Further, a channel estimating apparatus according to the present invention (Claim 11) comprises a complex conjugate signal generating section for generating a complex conjugate signal at a certain moment of a part of a plurality of pilots, and a complex conjugate signal A correlation value calculator for calculating a correlation value between the complex conjugate signal and another pilot by taking a product of the pilot value and other pilots other than some pilots. A weighted multiplier that multiplies the weighted coefficients of the pilots, and a channel estimation value for the channel information is generated by adding some of the above pilots and other pilots multiplied by the weighted coefficients by the weighted multiplier. It is characterized by having an adding section for performing the operation.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. (A) Description of First Embodiment FIG. 1 is a block diagram showing a configuration of a channel estimation device for CDMA synchronous detection as a first embodiment of the present invention. The channel estimation device 1 shown in FIG. Each of the fingers 100-
i, an estimated value for channel information of a data signal from a plurality of pilot signals at each finger 100-i for synchronous detection of a received signal for CDMA communication having a pilot signal and a data signal. This embodiment is different from the one shown in FIG. 13 in that a correlation estimating unit 8, an SIR estimating unit 9, and a weight determining unit 10 are provided. Note that in FIG. 1, components denoted by the same reference numerals as those shown in FIG. 13 are the same as those described above with reference to FIG. 13.

Here, the correlation estimating section 8 converts a pilot signal (hereinafter, simply referred to as “pilot”) averaged for each symbol by the delay element 3 and the adder 4 between pilots or a pilot block (a plurality of pilots). SIR estimating unit 9 obtains a correlation value between blocks (hereinafter, also referred to as correlation data) between signals (see hatched portions in FIG. 15). Power ratio (SIR: Signal to Interfer)
ence and noise power Ratio).

A weight determining unit (weighting coefficient control unit) 10 calculates the correlation between the pilots obtained by the correlation estimating unit 8 and the SIR obtained by the SIR estimating unit 9.
And calculating and determining the optimum values of the weighting coefficients w _j to be multiplied to each pilot in each multiplier 6 of the channel estimation value generating unit 11, and controls the respective weighting coefficients w _j. Here, an algorithm for determining the weighting coefficient w _j will be described.

First, each pilot (or pilot block)
V)_m ^(k)= Α_m ^(k)+ N_m ^(k) (1) Where m is the pilot (or pilot
H) and k is the finger (or diversity) number.
Symbol (= i), α_m ^(k)Is the complex amplitude of the channel, n_m ^(k)Is
Represents noise and interference components.

Therefore, a channel estimation value v ^(k) using a plurality of pilots or pilot blocks (hereinafter, simply “pilot” includes the case of “pilot block” ⁾ is given by: v ^(k) = Σ w _m ^(k) v _m ^(k) (2) Here, Σ represents the sum of _m , and w _m ^(k) is a weighting coefficient. The weighting coefficient is determined so that the root mean square of the difference between the channel estimation value v ^(k) obtained by equation (2) and the complex amplitude v _r ^(k) of the actual channel is minimized. Here, the mean square of ^{the, 2σ 2 = <| v (} k) - v r (k) | 2> When (3), since the equation (3) is a quadratic function, weighted differential value is 0 for the coefficient w _m ^(k), that _{^{is, ∂σ 2 / ∂ w m0 (}} k) = Σ w m (k) Real [<v m (k) * v m0 (k)>] -Real ^{_{[<v r (k) *}} v m0 (k)>] = 0 ··· (4) should be satisfied. Here, Real [] indicates that a real part is taken, <> indicates an averaging operation, and * indicates a complex conjugate. Therefore, the weighting coefficient vector w ^(k) can be obtained as ^{w (k) = R (k} ) -1 r 0 (k) ··· (5). Here, in the equation (5), R ^{(k) -1} represents an inverse matrix of the correlation matrix R ^(k) , and r ₀ ^(k) represents a correlation vector. The correlation matrix R ^(k) is composed of the correlation between pilots. For example, in the case of 4 rows and 4 columns (when a channel estimation value is obtained from four pilots (blocks) as shown in FIG. 1),

[0031]

(Equation 1)

Where each element is the average power of noise σ^{(k) 2}
And r_p ^(k)= <Real [α_{m + p} ^{(k) *}α_m ^{( k)}]> (Just
And p is an integer). Note that noise
Average power σ^{(k) 2}Is obtained by the SIR estimator 9
It can be removed based on SIR. On the other hand, the correlation vector
R₀ ^(k)Is the channel estimation for each pilot above
Value v _m ^(k)And the complex amplitude of the actual channel v_r ^(k)Correlation with
Value. However, this v_r ^{(k )}Is not known data
By estimating from the correlation value of each pilot (if
In other words, using the temporary determination result
Ask).

For example, the correlation value between the same pilots is represented by r
₀Between the pilot and the pilot one slot away
The correlation value is r₁Then, between each of these pilots
The actual channel at the center of the detected data signal (detected data)
The correlation value r₀₁Is r₀₁= (R ₀+ R₁) / 2
be able to. However, at this time, r₀, R₁Is SIR
Noise / interference based on the SIR obtained by the estimation unit 9
Component average power σ^{(k) 2}Use the value from which
You.

That is, the weight determination section 10 generates a correlation matrix R ^(k) composed of correlation values between pilots based on the correlation data between pilots obtained by the correlation estimation section 8 as shown in FIG. 2, for example. Then, a correlation vector r ₀ ^(k) consisting of a correlation value between each pilot and an estimated value of a channel to be ^obtained is generated based on the correlation data between the pilots and the SIR obtained by the SIR estimator 9 (step S1). and (step S2), and by calculating the product of the inverse matrix R ^{(k) -1} of the correlation matrix R ^(k) as shown in the above equation (5) and the correlation vector r ₀ ^(k), the weighting factor w _j (weighting coefficient vector w ^(k) ) is obtained (step S3).

As described above, according to the channel estimation apparatus 1 of the present embodiment, the correlation between the pilots (correlation matrix R ^(k) ) and the correlation between each pilot and the estimated value of the channel to be obtained (correlation vector r) ₀ ^(k) ), the root mean square of the difference between the channel estimation value v ^(k) and the complex amplitude v _r ^(k) of the actual channel is obtained by performing the calculation shown in the above equation (5). and controls to determine the smallest weighting coefficient w _j, each finger for each 100-i, it is possible to always provide the optimum weighting coefficient w _j adapted to fading fluctuation, an increase in improvement or transmission capacity of the communication quality Becomes possible.

Particularly, in the present embodiment, the weight determining unit 1
0 removes noise / interference components included in the elements of the correlation matrix R ^(k) based on the SIR obtained by the SIR estimator 9 and then estimates and obtains the correlation vector r ₀ ^(k). Therefore, the determination of the weighting coefficient w _j can be realized with higher accuracy. Note that the above-described correlation vector r ₀ ^(k) can also be obtained by using a technique described in the above-mentioned known document.

(A1) Description of First Modification of First Embodiment FIG. 3 is a block diagram showing a first modification of the above-described channel estimating apparatus 1. The channel estimating apparatus 1 shown in FIG. 1 is different from that shown in FIG. 1 in that a moving speed detecting unit 12 that detects a moving speed of the mobile station (that is, the mobile station) is provided. In the present embodiment, the correlation estimating unit 8
The maximum Doppler frequency of Rayleigh fading is obtained from the moving speed v detected by the moving speed detection unit 12, and the correlation data r (t _{q, r} ) between the pilots is calculated as r (t _{q, r} ) = J ₀ [2πf _c (V / c) t _{q, r} ] (7) However, this equation (7)
In, t _{q, r} is the time difference between the pilot, J ₀ () is the zero order Bessel function, f _c the RF carrier frequency, c is the representative of the speed of light.

As a result, the weight determination unit 10
In the same manner as in the above-described channel estimation apparatus 1, the correlation estimation unit 8 calculates the correlation data r obtained from the moving speed v.
A correlation matrix R ^(k) and a correlation vector r ₀ ^(k) based on (t _{i, j} ⁾
Can be requested. That is, as shown in FIG. 4, the weight determination unit 10 of the present modification uses the correlation data r (t _{i, j} ) obtained from the moving speed v by the correlation estimation unit 8 and S
A correlation matrix R ^(k) and a correlation vector r ₀ ^(k) are obtained from the SIR obtained by the IR estimator 9 (step S4).
The weighting coefficient w _j is determined by calculating the equation (5) (step S5).

In this case, in the CDMA mobile station, transmission power control according to reception power called TPC (Transmitter Power Control) is performed. (T
_{i, j} ), the calculated weighting coefficient w _j
Since the value does not take the PC into consideration, it is necessary to correct the weighting coefficient w _j according to the TPC (step S
6).

As described above, according to the channel estimating apparatus 1 (weight determining unit 10) of the present modification, the correlation between the pilots is obtained from the moving speed v detected by the moving speed detecting unit 12, so that the actual moving by performing decision and control of the weighting coefficients w _j in accordance with the fading variation due to the movement velocity v of the stations it can be performed with higher accuracy channel estimation.

(A2) Description of Second Modification of First Embodiment FIG. 5 is a block diagram showing a second modification of the channel estimation device 1 described above with reference to FIG. 1. The channel estimation device shown in FIG. 1 is a switch 2 compared to that shown in FIG.
In that a switch 2 ′ is provided in place of, and a provisional determination unit 13 is provided.

Here, the switch 2 'outputs the pilot to the adder 4 when the despread signal is a pilot, and outputs the data signal to the tentative decision unit 13 when the despread signal is a data signal. The provisional determination unit 13 performs provisional determination of the data signal based on the channel estimation value generated by the channel estimation value generation unit 11 (addition unit 7), and the provisional determination result is The correlation estimator 8 is used to generate correlation data between pilots.

That is, in the second modified example, in a certain fading environment, the correlation value between the signals is determined by the interval between the signals. They also use it. Thus, the weight determination unit 10 can obtain the correlation matrix R ^(k) and the correlation vector r ₀ ^(k) in consideration of the correlation between the data signals that have undergone the tentative determination by the tentative determination unit 13.

That is, the weight determination section 10 is, for example, shown in FIG.
As shown in ⁽¹⁾ , a correlation matrix R ^(k) is generated from correlation data between pilots and between data signals tentatively determined by the tentative determination unit 13 (hereinafter, referred to as tentative determination signals). However, at this time, the component in which the correlation of the noise and interference appears is the same as the number of symbols averaged first in the pilot block in order to equalize the average power of the noise and interference. Are also averaged first (step S7).

Hereinafter, the algorithm described above with reference to FIG.
In the same manner as described above, the SIR determined by the SIR
To the correlation matrix R^(k)Noise and interference components
And the correlation vector r₀ ^(k)(Step S
8), these correlation matrices R^(k) And the correlation vector r₀ ^(k)
Is used to perform an operation according to equation (5), and the weighting coefficient
 w_jIs obtained (step S9).

As described above, according to the channel estimating apparatus 1 (weight determining section 10) of the second modification, not only the pilot but also the data signal portion are used as the material at the time of determining the weighting coefficient w _j , so that the accuracy is further improved. Can be generated. (A3) Description of Third Modification of First Embodiment FIG. 7 is a block diagram showing a third modification of the channel estimation device 1 described above with reference to FIG. 1. The channel estimation device 1 shown in FIG. As compared with the switch shown in FIG. 1, a switch 2 'and a tentative determination unit 1 similar to those described above in the second modified example
3, a delay element 5 'and a multiplier 6' are provided in place of the delay element 5 and the multiplier 6, and the output of the tentative decision unit 13 is connected to a signal line 14 to the delay element 5 '. Is different.

Here, each of the delay elements 5 ′ delays, by one symbol, a tentative judgment signal obtained by tentatively judging an input pilot or a data portion before the channel information desired by the tentative judgment unit 13. The multiplier 6 'assigns a predetermined weighting coefficient w _j (j = 0 to k in FIG. 7) to a plurality of pilots or temporary decision signals obtained by being delayed by one symbol by each of the delay elements 5'.
-1: k is a natural number of 2 or more). The other components are the same as those described above with reference to FIG.

That is, the channel estimation apparatus 1 of the present modification
Is the channel estimation value generation unit 1 in the configuration shown in FIG.
1 uses the data signal for which the tentative determination has been made in generating the channel estimation value. However, in this case, since the temporary decision signal may be occurring error, weighting determination unit 10, weighting coefficient w _j value smaller than the weighting coefficient w _j of example pilot for multiplying the temporary decision signal To be corrected.

That is, the weight determining unit 10 is, for example, shown in FIG.
As shown in FIG. 6, steps S7 to S9 described above with reference to FIG.
In the same manner as described above, the weighting coefficient w _j is obtained by performing the calculation according to the equation (5) based on the correlation data between the pilots and between the data signals tentatively determined by the tentative determination unit 13 (hereinafter referred to as the tentative determination signal). After that (steps S10 to S12), the weighting coefficient w _j for the pilot is set to a% (where 0 ≦
a ≦ 100) is set as the weighting coefficient w _j of the temporary determination signal (step S13).

As described above, according to the channel estimation apparatus 1 of the third modified example, not only the pilot but also the data signal portion is used for the channel estimation in the channel estimation value generation section 11, so that a more accurate channel An estimate can be obtained. (A4) Description of Fourth Modification of First Embodiment FIG. 9 is a block diagram showing a fourth modification of the channel estimation device 1 described above with reference to FIG. 1. The channel estimation device 1 shown in FIG. Compared to the one shown in FIG.
A correlation estimating unit 8 (correlation estimating unit) 8 ′ for obtaining the above-mentioned correlation data in common for each finger 100-i
In that correlation data is obtained from the pilot of each finger 100-i and averaged.

The RAKE combiner 106, the despreader 102-i in each finger 100-i, and the multiplier 105
−i are the same as those described above with reference to FIG. 13, and the delay adjustment unit 15 calculates the delay time difference between the channel estimation value obtained by the channel estimation device 1 and the despread signal from the despreading unit 102-i. Are adjusted to match.

That is, the channel estimating apparatus 1 of the present modified example
In a Rayleigh fading environment, the correlation data should be determined by the fading speed and time interval, and RA
The correlation estimation unit 8 'should be equal in the fingers 100-i (or diversity) for performing KE combining.
In (2), correlation data (SIR for each finger) is obtained from the pilot in each finger 100-i and averaged. Since the SIR is different for each finger 100-i, each finger 100-i
i for each finger 100-i by the SIR estimator 9 for i.

As a result, the weighting determination unit 10 determines (controls) the weighting coefficient w _j in the channel estimation value generation unit 11 based on the correlation data whose accuracy has been improved by the averaging in the correlation estimation unit 8 ′. Highly accurate channel estimation can be performed. The algorithm for determining the weighting coefficient w _j at this time is the same as that described with reference to FIG.

(B) Description of Second Embodiment FIG. 10 is a block diagram showing a configuration of a channel estimation device for CDMA synchronous detection according to a second embodiment of the present invention. The channel estimation device 1A shown in FIG. Is different from that of the first embodiment shown in FIG.
In that a weight determining unit 10A is provided in place of. The other components (the components having the same reference numerals as those shown in FIG. 1) are the same as those described above with reference to FIG.

Here, the weighting decision unit (pilot signal number control unit) 10A of the second embodiment determines the correlation value between the plurality of pilots and the estimated value of the channel information to be obtained (that is, the correlation vector r ₀ ^{( k)} ), the number of pilots used for generating the channel estimation value in the channel estimation value generation unit 11 is controlled. In this case, only the pilots whose correlation values are equal to or more than a predetermined value (reference value) are controlled. Is used in the generation of the channel estimation value in the channel estimation value generation unit 11.

As a result, in the weight determining section 10A,
For example, as shown in FIG. 11, first, a correlation vector r ₀ ^(k) is obtained based on correlation data between pilots obtained by the correlation estimator 8 and SIR obtained by the SIR estimator 9 (step S14). However, in this case, for example,
When the correlation value between the same pilots (or pilot blocks) is r ₀ , and the correlation value between the pilot and the pilot (or pilot block) one slot away is r ₁ , each of these pilots (or pilot blocks) actual channel of the center of the sandwiched data signals to the correlation value r ₀₁ of the (detection _{data), r 01 = (r 0} + r 1)
/ 2. At this time, r ₀ and r ₁ are SIR
A value from which the average power σ ^{(k) 2 of} the noise / interference component is removed based on the SIR obtained by the estimator 9 is used.

Then, the weight determining unit 10A uses only the elements larger than the reference value, that is, only the pilots with high correlation among the elements of the obtained correlation vector r ₀ ^(k) for channel estimation (step S15). For example, when the reference value is “0.5”, the weighting coefficient w _{j is set} to “0” for pilots less than “0.5”, and “0.
For pilots 5 and above, their weighting factors w _j
It can be considered to be "1.0".

As described above, according to the channel estimation apparatus 1A of the second embodiment, the number of pilots used for channel estimation is actively controlled in accordance with the correlation value between a plurality of pilots and the estimated value of the channel information to be obtained. By doing so, only pilots with a high correlation can be used for channel estimation, so that highly accurate channel estimation can be performed. In particular, here, since the calculation of Expression (5) described above in the first embodiment is not necessary, high-speed channel estimation can be realized.

Also in the present embodiment, the noise and interference components included in the elements of the correlation matrix R ^(k) are removed based on the SIR obtained by the SIR estimator 9 and then the correlation vector r _{0 is obtained.}
^{Since (k)} is estimated and calculated, a more accurate weighting coefficient
The decision of w _j can be realized. The above-described control of the number of pilots can be applied to the above-described first embodiment and the first to fourth modifications of the first embodiment.

(C) Description of Third Embodiment FIG. 12 is a block diagram showing the configuration of a channel estimation device for CDMA synchronous detection according to a third embodiment of the present invention. The channel estimation device 1B shown in FIG. Includes a switch 2, a delay element (T _s ) 3 for each symbol, an adder 4 and a delay element (T _slot ) 5 for each slot, which are the same as those described above with reference to FIG. It comprises the adders 6A, 6B, 19A, 19B, the adder 16, the averaging unit 17, the complex conjugate unit 18 and the like.

Here, the adder 16 adds some of the pilots at a certain moment obtained by the delay element (T _slot ) 5 to each other, and the averaging unit 17 The pilot obtained by the adder 16 is averaged, and the complex conjugate section 18 generates a complex conjugate signal by taking the complex conjugate of the pilot averaged by the averaging section 17.

That is, the adder 16 and the averaging unit 17
The complex conjugate unit 18 functions as a complex conjugate signal generation unit 20 that generates a complex conjugate signal at a certain moment of some of the plurality of pilots. Further, a multiplier (correlation value calculation unit) 19A, 1
9B calculates the correlation value between the complex conjugate signal and another pilot by taking the product of the complex conjugate signal obtained by the complex conjugate unit 18 and other pilots other than the above-mentioned some pilots, respectively. The multipliers (weighting multipliers) 6A and 6B are provided with these multipliers 19A and 19B.
The correlation value obtained in B is multiplied as a weighting coefficient of the other pilot signal.

The adder 7 generates a channel estimation value by adding a part of the above pilots and other pilots multiplied by the weighting coefficients by the multipliers 6A and 6B. With such a configuration, in the channel estimation device 1B of the third embodiment, the first and second channels are estimated.
Instead of the correlation value observed for a long time as in the embodiment, a value (correlation value) obtained by averaging one of the pilots at a certain moment and performing complex conjugate can be used as the weight of the other pilot. . By using the instantaneous value as the correlation value in this way, it is possible to perform channel estimation adapted to fading fluctuation at high speed.

(D) Others In the first and second embodiments described above,
Although the SIR is used, the above-described weight determination control (pilot number control) can be realized without using the SIR. Further, the number of pilots used for channel estimation may be controlled based only on the SIR. For example, when the noise / interference component is large, the channel estimation value is inaccurate, but when the noise / interference component is small, the estimation value obtained from pilots for a small number of symbols (slots) is also accurate. It is also possible to control the number of pilot symbols (the number of slots) used for channel estimation according to the amounts of noise and interference components.

Further, such control can be applied in combination with each of the above embodiments. And
The present invention is not limited to the above-described embodiment and each modified example, and can be variously modified and implemented without departing from the gist of the present invention.

[0066]

As described in detail above, the CDMA of the present invention
According to the channel estimation apparatus for synchronous detection, based on the correlation between each pilot signal and the correlation between each pilot signal and the estimated value of the channel to be obtained, the difference between the channel estimated value and the complex amplitude of the actual channel is calculated. Since the weighting coefficient that minimizes the root mean square is determined and controlled, an optimal weighting coefficient that is always adapted to fading fluctuations can be given to each finger, and communication quality can be improved or transmission capacity can be increased. (Claims 1 to 7).

According to the CDMA synchronous detection channel estimating apparatus of the present invention, the number of pilots used for channel estimation is positively controlled according to the correlation value between a plurality of pilot signals and the estimated value of channel information to be obtained. As a result, only highly correlated pilots can be used for channel estimation, so that highly accurate channel estimation can be performed at high speed (claims 8 to 10).

Further, according to the channel estimation apparatus for CDMA synchronous detection of the present invention, a value (correlation value) obtained by averaging one complex between pilots at a certain moment and complex conjugate is used as the weight of the other pilot. To use
Channel estimation adapted to fading fluctuation at high speed can be performed (claim 11).

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a channel estimation device for CDMA synchronous detection according to a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation (weighting determination algorithm) of the channel estimation device of the first embodiment.

FIG. 3 is a block diagram showing a first modification of the channel estimation device of the first embodiment.

FIG. 4 is a flowchart for explaining the operation (weighting determination algorithm) of the channel estimation device of the first modification.

FIG. 5 is a block diagram showing a second modification of the channel estimation device of the first embodiment.

FIG. 6 is a flowchart illustrating an operation (weighting determination algorithm) of a channel estimation device according to a second modification.

FIG. 7 is a block diagram showing a third modification of the channel estimation device of the first embodiment.

FIG. 8 is a flowchart illustrating an operation (weighting determination algorithm) of a channel estimation device according to a third modification.

FIG. 9 is a block diagram showing a fourth modification of the channel estimation device of the first embodiment.

FIG. 10 is a block diagram showing a configuration of a channel estimation device for CDMA synchronous detection as a second embodiment of the present invention.

FIG. 11 is a flowchart for explaining the operation (control of the number of pilots) of the channel estimation device of the second embodiment.

FIG. 12 is a block diagram illustrating a configuration of a CDMA synchronous detection channel estimation device according to a third embodiment of the present invention.

FIG. 13 is a block diagram illustrating an example of a configuration focusing on a reception system (synchronous detection portion) in a DS-CDMA mobile station.

FIG. 14 is a block diagram illustrating a configuration of a channel estimation unit in a reception system.

FIG. 15 is a diagram illustrating a data configuration example of a radio signal using a pilot signal.

FIG. 16 is a phase vector diagram for explaining conventional weight control.

[Explanation of symbols]

1, 1A, 1B CDMA synchronous detection channel estimation device 2, 2 'switch 3 delay elements (T _s) 4,16 adder 5,5' delay elements (T _slot) 6,6 ', 105-1~105- n Multiplier 6A, 6B Multiplier (weighting multiplication unit) 7 Addition unit 8 Correlation estimation unit 8 'Correlation estimation unit (common correlation generation unit) 9 SIR estimation unit 10 Weight determination unit (weighting coefficient control unit) 10A Weight determination unit ( Pilot signal number control unit) 11 Channel estimation value generation unit 12 Moving speed detection unit 13 Temporary judgment unit 14 Signal line 15 Delay adjustment unit 17 Average unit 18 Complex conjugate unit 19A, 19B Multiplier (correlation value calculation unit) 20 Complex conjugate signal Generators 100-1 to 100-n Fingers 102-1 to 102-n Despreader 106 RAKE combiner

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Matsuyama 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Yoshihiko Asano 4-chome Kami-Odanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Fujitsu Limited (72) Inventor Kazama Hamada 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture F-term within Fujitsu Limited (reference) 5K004 AA05 FA05 FB00 FD06 FF00 5K022 EE02 EE13 EE35 EE36 5K052 AA02 BB08 CC06 DD03 EE38 FF29 GG03 GG19 GG20 GG42 5K059 AA08 BB08 CC03 DD33

Claims (11)

[Claims] 1. For synchronous detection of a received signal for CDMA communication having a pilot signal and a data signal, each of a plurality of fingers for rake combining uses a plurality of pilot signals to determine the channel information of the data signal from the plurality of pilot signals. A channel estimating apparatus for obtaining an estimated value, comprising: multiplying each of the plurality of pilot signals by a predetermined weighting factor and adding each pilot signal to generate a channel estimated value for the channel information. Weighting factor control for controlling the weighting factor in the channel estimation value generation unit based on a correlation between the plurality of pilot signals and a correlation between the plurality of pilot signals and an estimated value of channel information to be obtained. A channel estimating apparatus for CDMA synchronous detection, comprising: 2. A weight coefficient control unit comprising: a product of an inverse matrix of a correlation matrix composed of correlation values between the pilot signals and a correlation vector composed of correlation values between the pilot signals and estimated channel information to be obtained; 2. The channel estimation apparatus for CDMA synchronous detection according to claim 1, wherein the weighting coefficient is determined by calculating the following equation. 3. A moving speed detecting unit for detecting a moving speed of the vehicle, wherein the weighting coefficient control unit obtains a correlation between the pilot signals from the moving speed detected by the moving speed detecting unit. 2. The channel estimation device for CDMA synchronous detection according to claim 1, wherein the channel estimation device is configured. 4. A provisional decision section for making a provisional decision on the data signal based on the channel estimation value generated by the channel estimation value generation section, and wherein the weighting coefficient control section includes a provisional decision section 2. The CDMA synchronous detection channel estimator according to claim 1, wherein the correlation is determined in consideration of the correlation between the determined data signals. 5. The channel estimation value generation section, wherein the data signal which has been provisionally determined by the provisional determination section is also used for generating the channel estimation value. The channel estimation device for CDMA synchronous detection according to the above. 6. A common correlation generator for obtaining and averaging the correlation in common for each of the fingers, and the weighting coefficient controller based on the correlation averaged by the common correlation generator. 2. The CDMA synchronous detection channel estimating apparatus according to claim 1, wherein the weighting coefficient is controlled by the channel estimation value generating section. 7. A signal-to-interference / noise power ratio estimator for estimating a signal-to-interference / noise power ratio based on the received signal, and the weighting coefficient controller comprising: The apparatus according to claim 1, wherein an interference / noise component included in a correlation between the pilot signals is removed based on the signal-to-interference / noise power ratio obtained by the ratio estimating unit. 7. The channel estimation device for CDMA synchronous detection according to any one of 6. 8. For synchronous detection of a received signal for CDMA communication having a pilot signal and a data signal, each of a plurality of fingers for rake combining uses a plurality of pilot signals to determine the channel information of the data signal from the plurality of pilot signals. A channel estimating apparatus for obtaining an estimated value, comprising: multiplying each of the plurality of pilot signals by a predetermined weighting factor and adding each pilot signal to generate a channel estimated value for the channel information. And a pilot signal number control unit that controls the number of pilot signals used for generating a channel estimation value in the channel estimation value generation unit based on a correlation value between the plurality of pilot signals and an estimation value of channel information to be obtained. A channel estimating apparatus for CDMA synchronous detection, comprising: 9. The method according to claim 1, wherein the pilot signal number control unit is configured to use only pilot signals having the correlation value equal to or greater than a predetermined value for generating a channel estimation value in the channel estimation value generation unit. 9. The channel estimation device for CDMA synchronous detection according to claim 8, wherein: 10. A signal-to-interference / noise power ratio estimator for estimating a signal-to-interference / noise power ratio based on the received signal, and wherein the pilot signal number control unit comprises: 9. The apparatus according to claim 8, wherein an interference / noise component included in a correlation between the pilot signals is removed based on the signal-to-interference / noise power ratio obtained by the power ratio estimator. Or a channel estimation device for CDMA synchronous detection according to claim 9. 11. For synchronous detection of a received signal for CDMA communication having a pilot signal and a data signal, each of a plurality of rake combining fingers converts a plurality of pilot signals into channel information about channel information of the data signal. A channel estimating apparatus for obtaining an estimated value, comprising: a complex conjugate signal generation unit that generates a complex conjugate signal at a certain moment of a part of the plurality of pilot signals; A correlation value calculator for calculating a correlation value between the complex conjugate signal and the other pilot signal by taking a product of the other pilot signals other than the pilot signal of A weight multiplication unit for multiplying a value as a weighting coefficient of the other pilot signal; By adding the said other pilot signal multiplied by, characterized in that it includes an addition unit for generating a channel estimate for the channel information, CDMA synchronous detection channel estimation device.