JPH11355849A - Synchronizing signal detection method using pilot and tentative discrimination data symbol, mobile communication receiver and interference eliminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve estimating accuracy of a characteristic of a propagation path, when conducting synchronization detection by using a pilot symbol extrapolated in other channel than a channel for a data symbol for estimating the characteristics of a propagation path. SOLUTION: A device adopting this method is provided with a propagation path estimate section 5 by pilot that estimates the characteristics of a propagation path by using a pilot symbol that is separated through multiplication of an orthogonal code Y, a tentative discrimination section 8 that tentatively discriminates a received data symbol, based on a propagation path estimate value ξ1 by the propagation path estimate section 5, a propagation path estimate section 9 by pilot and tentative discrimination data, that uses a tentative discrimination data symbol by the tentative discrimination section 8 and the pilot symbol to estimate the characteristic of the propagation path, and a final discrimination section 13 that discriminates received data symbol, based on a propagation path estimate value ξ2 by the propagation path estimate section 9. Thus, the device regards the tentative discrimination data symbol as the pilot symbol to estimate the characteristic of the propagation path with high accuracy and to conduct synchronization detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for demodulating a phase modulated signal such as PSK, QPSK or MPSK or a multilevel QAM modulated signal in a digital mobile communication system. The present invention relates to a method for estimating propagation path characteristics using extrapolated pilot symbols and performing synchronous detection, and a mobile communication receiver and interference canceller.

[0002] In mobile communication, as a communication terminal moves in an environment in which a multipath (multipath) is formed, propagation path characteristics fluctuate due to fading.
When receiving and demodulating a data symbol in such a situation, a pilot symbol transmitted together with the data symbol is received and demodulated, and a channel characteristic is obtained from the pilot symbol.
(Fading complex envelope) is estimated, and the technique of performing synchronous detection of data symbols by removing the influence of the propagation path is widely used.

[0003] The above-mentioned pilot symbol is a known symbol having a predetermined amplitude and phase, and is inserted between data symbols or extrapolated to a channel different from the channel for the data symbol to be transmitted by the transmitting device. Sent from.

When a pilot symbol is interpolated, the pilot symbol is inserted at a predetermined position in the data frame and transmitted, and the receiving apparatus recognizes the position of the pilot symbol by synchronization using a preamble added before the data frame. Then, the symbol at that position is received and demodulated, and the characteristics of the propagation path are estimated from the amplitude and phase values.

On the other hand, when a pilot symbol is extrapolated, the pilot symbol and the data symbol are multiplexed and transmitted by mutually orthogonal channels. Since the pilot symbols are transmitted in parallel with the data symbols, the method of transmitting the extrapolated pilot symbols is also called a parallel pilot channel method.

In this method, for example, a data symbol and a pilot symbol are multiplied by mutually orthogonal codes,
By modulating each of them with the I and Q channels of QPSK, extrapolated pilot symbols can be transmitted. Such a scheme is called a pilot IQ multiplexing scheme.

[0007] Since the pilot extrapolation synchronous detection has a process of demultiplexing with a orthogonal code as described above, the DS-C
DMA (Direct Sequence Code Division Multiple Acc)
ess; direct spread spectrum code division multiplex access) is being studied for applications in the field of mobile communications.

[0008] Since the pilot symbol and the data symbol are orthogonal to each other, they can be separated from each other after demodulation on the receiving side, and the propagation path characteristics are estimated using the separated pilot symbols. Thus, synchronous detection of data symbols can be performed with high accuracy.

[0009] Here, propagation path estimation using pilot symbols will be described. Now, let the n-th transmission symbol be Z
n. Assuming that the propagation path characteristic at this time is Δn, the received symbol is Zn · Δn. It is assumed that the transmission symbol Zn is a symbol whose amplitude and phase are known in advance.

When the received symbol Zn · Δn received via the propagation path is multiplied by the known complex conjugate of the transmission symbol Zn ^* , the value becomes Δn · | Zn
| ^Two. Since the magnitude of the transmission symbol vector is known (| Zn | ≡1), the propagation path characteristic 路
n can be estimated by this calculation. The estimated value is {n}, and the estimated value {n} is expressed by the following equation. {n ^} = Zn {n · Zn ^* = {n · | Zn | ² ... (1)

In practice, received symbols are affected by noise and interference, and it is difficult to accurately estimate channel characteristics. Therefore, the average of the propagation path characteristics obtained from a plurality of pilot symbols is obtained, and the estimation accuracy is improved.
In general, a moving average is performed between a plurality of pilot symbols in a moving section in order to follow temporal fluctuation of a propagation path due to fading.

It is assumed that a channel characteristic estimated by averaging a plurality of pilot symbols before and after the n-th pilot symbol is {n}. Let the n-th transmission data symbol be Z
n, the actual data channel is {n}, and the received data symbol is Zn · {n. Therefore, this is multiplied by the complex conjugate of the estimated channel characteristic {n ^{} *} to obtain the square of the absolute value of the vector of the estimated channel characteristic {n}. , The transmission data symbol Zn obtained by removing the influence of the transmission path from the reception data symbol is demodulated. This demodulated data symbol is defined as Zn ＾, and the above operation is represented by the following equation. Zn ＾ = Znξ {nξ {n ^{} *} / | ξn ＾ | ² (2)

[0013] The data symbols thus synchronously detected are subjected to diversity combining and then determined for their phases, and in the case of multi-valued QAM or the like, their amplitudes are also determined. After undergoing decoding processing such as correction, it is reproduced as information data.

[0014]

2. Description of the Related Art FIG. 10 is a diagram showing a configuration of a conventional receiving apparatus for performing synchronous detection using pilot symbols. In the figure, a signal received from an antenna (ANT) 10-1 is input to a radio unit (Rx) 10-2, and the radio unit 10-
2 amplifies the received signal by an amplifier (LNA) 10-21, removes a component outside a predetermined band by a band-pass filter (BPF) 10-22, and multiplies the signal LO from a local oscillator by a mixer 10-23. The low-pass filter (LPF) 10-24 removes high-frequency components and outputs the result to a signal processing unit in the next stage.

Next-stage A / D converter (A / D) 10-3
Quantizes the received signal from the radio unit (Rx) 10-2 and converts it into a digital signal,
Performs synchronization based on the received signal output from the A / D converter (A / D) 10-3, and outputs the received signal to the synchronous detector 10-5.

In the synchronous detector 10-5, the multiplier 10
A received signal is extracted by multiplying the received signal by the orthogonal code X by −51, and a received pilot symbol is extracted by multiplying the received signal by the orthogonal code Y by the multiplier 10-52. Here, the orthogonal code X and the orthogonal code Y are codes orthogonal to each other, and it is assumed that the data symbol and the pilot symbol are modulated and multiplexed by these orthogonal codes, respectively.

The received data symbol output from multiplier 10-51 is given a predetermined delay by delay section (D) 10-53, and then output to multiplier 10-54.
On the other hand, the received pilot symbols output from multiplier 10-52 are
0-55, and the channel estimation unit 10-55 calculates the estimated value {n} of the channel characteristic by the above equation (1),
The complex conjugate {n ^{} *} is output to the multiplier 10-54.

The multiplier 10-54 includes a delay unit (D) 10-
The received data symbol provided with a delay corresponding to the calculation time for the propagation path estimation by 53 is added to the propagation path estimation unit 10-
The complex conjugate {n} of the propagation path characteristic estimated value output from 55
^* , The demodulated data symbol Zn ＾ obtained by performing the operation of the above equation (2) to remove the influence of the propagation path.
To the diversity combining unit 10-56.

In the multiplier 10-54, the demodulated data symbol Zn ＾ is replaced with the received data symbol Zn ·
ξn is multiplied by the complex conjugate of the estimated value of the propagation path characteristic ξn ＾ ^* , whereas according to the above equation (2),
The multiplication by the multiplier 10-54 is performed by using Zn · {n and {n ^{} *.}
/ | {N} | ² , but the square of the absolute value of the estimated value of the propagation path characteristic | {n} |
² only affects the amplitude component of the demodulated data symbol Zn ＾, so that the multiplier 10-
54 multiplies the complex conjugate {n
乗 算^* can be multiplied.

The demodulated data symbol Zn ＾ is diversity-combined with the demodulated data symbol by another similar circuit by the diversity combining section 10-56, and the decision section 10-56.
According to −57, the phase (and also the amplitude in the case of multi-level QAM) is compared with a predetermined threshold value, determined as a predetermined discrete data symbol, and output to the decoder 10-6.

[0021]

As can be seen from the above equation (2), if the difference between the estimated propagation path characteristic {n} and the actual propagation path characteristic {n} is large, the transmission data symbol Zn
And the demodulated data symbol Zn ＾ also increases. Therefore, it is important to accurately estimate the propagation path characteristics Δn in order to correctly reproduce data.

In order to improve the estimation accuracy of the propagation path characteristics,
It is conceivable to increase the transmission power of the pilot channel, but if the power of the pilot symbol is increased,
This will increase the power consumption of the mobile communication terminal. In order to keep the total transmission power constant and not increase the power consumption, the power of the data channel is reduced. However, this lowers the S / N ratio of the data symbol and deteriorates the reception characteristics.

Also, an increase in the transmission power of the pilot channel causes an increase in interference with the data channel,
In particular, in DS-CDMA mobile communication, this becomes a factor for deteriorating the channel capacity characteristics.

In addition, a method of increasing the number of pilot symbols to be averaged can be considered to improve the estimation accuracy of the channel characteristics. However, if the fluctuation of the channel characteristics is large with respect to the average section of pilot symbols, the channel estimation accuracy is adversely degraded, and the number of pilot symbols that can be averaged has an upper limit.

The present invention estimates the propagation path characteristics with high accuracy without increasing the transmission power of the pilot channel and without increasing the number of pilot symbols, and demodulates the data symbols from which the influence of the propagation path has been removed. It is another object of the present invention to reduce the error rate of received data.

[0026]

In order to solve the above-mentioned problems, a synchronous detection method using a pilot and a provisionally determined data symbol according to the present invention comprises: (1) receiving a data symbol in mobile communication; A channel characteristic is maintained by using a pilot symbol extrapolated to another channel, and synchronous detection is performed on the basis of a channel estimation value based on the pilot symbol to temporarily determine a received data symbol. Estimating propagation path characteristics using the tentatively determined data symbol and the pilot symbol, and synchronously detecting based on the tentatively determined data symbol and the propagation path estimated value based on the pilot symbol to finally determine a received data symbol. .

As described above, when performing pilot extrapolation synchronous detection, the data symbol is temporarily determined using the channel estimation value estimated using the pilot symbol. By using both the pilot symbols and the pilot symbols, the channel characteristics (fading complex envelope) are accurately estimated.

That is, the data symbols determined by the pilot extrapolation synchronous detection are regarded as pilot symbols, and the propagation path characteristics are estimated in the same manner as the pilot symbols, so that only the conventional pilot symbols are used. The propagation path characteristics can be estimated with higher accuracy than the propagation path estimation method. Then, using the more accurate channel estimation value obtained in this way, data symbols can be synchronously detected again, and data can be decoded with high accuracy.

(2) The received data symbol is tentatively determined a plurality of times by performing synchronous detection based on the channel estimation value based on the tentatively determined data symbol and pilot symbol, and the data symbol and pilot symbol based on the tentative determination are determined. And repeating the estimation of the propagation path characteristics a plurality of times. In this way, by repeating the tentative determination and the estimation of the propagation path characteristic a plurality of times, it is possible to further improve the accuracy of the tentative determination data and the propagation path estimated value.

The mobile communication receiving apparatus of the present invention comprises:
(3) A channel estimation unit using a pilot symbol for estimating channel characteristics using a pilot symbol extrapolated to a channel different from the data symbol, and a reception data symbol based on a channel estimation value based on the pilot symbol. A tentative determination unit for performing a tentative determination, a tentative determination data symbol by the tentative determination unit and a propagation path estimating unit using a pilot and a tentative determination data symbol for estimating a channel characteristic using the pilot symbol, and the pilot and the tentative determination data And a final determination unit that determines a received data symbol based on a channel estimation value using a symbol.

(4) The mobile communication receiving apparatus according to the present invention includes a plurality of propagation path estimating units based on the pilots and the tentatively determined data symbols, and performs propagation path estimation using the pilot symbols and the tentatively determined data symbols. It is provided with a plurality of determination units for determining a received data symbol based on a value.

Further, the interference elimination device of the present invention is provided with (5) DS
In a multi-stage interference canceller used in a CDMA mobile communication base station, a pilot symbol extrapolated to a channel different from a data symbol is used for an interference replica generation unit or a final-stage receiver of each stage. A channel estimation unit using pilot symbols for estimating propagation path characteristics, a provisional determination unit for performing provisional determination of a received data symbol based on a propagation path estimation value based on the pilot symbols, and a provisional determination data symbol by the provisional determination unit. And a channel estimating unit for estimating channel characteristics using the pilot symbols and a provisionally determined data symbol.

(6) The interference elimination apparatus of the present invention includes a plurality of propagation path estimating units based on the pilot and the tentatively determined data symbols, and uses a propagation path estimation value using the pilot symbols and the tentatively determined data symbols. Is provided with a plurality of determination units for determining a received data symbol.

[0034]

FIG. 1 is a diagram showing a configuration of a synchronous detection unit according to a first embodiment of the present invention. FIG. 1 shows a configuration for processing a signal after A / D conversion output after converting a received signal into a base band. The relatives of the wireless section in the preceding stage may be the same as those in the conventional receiving apparatus shown in FIG.

In FIG. 1, 100 is a synchronous detection unit, 1 is a timing synchronization unit, 2 and 3 are multiplication units for multiplying orthogonal codes, 4 is a delay unit that gives a delay corresponding to the operation time for estimating the propagation path by the pilot, Reference numeral 5 denotes a pilot channel estimation unit, 6 denotes a multiplication unit for multiplying a pilot channel estimation value, 7 denotes a diversity combining unit, 8 denotes a tentative determination unit, 9 denotes a channel estimation unit by pilot and temporary determination data, and 10 denotes a pilot. , A delay unit for delaying the operation time for the propagation path estimation and the propagation path estimation by the pilot and the tentative decision data, 11 is a multiplication unit that multiplies the propagation path estimation value by the pilot and the tentative decision data, 12 is a diversity combining unit, 13 is a final decision unit, and 14 is a decoder.

The synchronous detector 100 according to the embodiment of the present invention
As in the conventional example, after the timing synchronization using the preamble is performed by the timing synchronization unit 1,
A baseband received signal is input. The received signal is
A data symbol and a pilot symbol are signals multiplexed by an orthogonal code, and a multiplier 2 and a multiplier 3 multiply the received signal by orthogonal codes X and Y orthogonal to each other to obtain a data symbol and a pilot symbol. And separated.

Now, it is assumed that a data symbol is output from the multiplier 2 that multiplies the orthogonal code X, and a pilot symbol is output from the multiplier 3 that multiplies the orthogonal code Y. The data symbol output from the multiplier 2 is input to the delay unit 4 and the delay unit 10. The delay unit 4 gives the input data symbol a delay corresponding to the operation time for estimating the propagation path by the pilot as described above, and inputs the output to the multiplier 6.

On the other hand, the pilot output from the multiplier 3
The symbol is input to the channel estimation unit 5 by the pilot.
The propagation path estimating unit 5 performs the calculation of the above equation (1).
Channel estimation using pilot symbols, and
Estimate of ξ₁Complex conjugate of ξ ₁＾^*With the multiplier 6 and the pie
Output to the propagation path estimation unit 9 based on the lot and the tentative judgment data
I do.

The multiplier 6 multiplies the complex conjugate { ₁ ^{} *} of the estimated value of the propagation path by the output signal of the delay unit 4 to demodulate the data symbol, and outputs the output signal to the diversity combining unit 7.
After the diversity combining, the tentative determination unit 8 tentatively determines the data symbol as a data symbol.

If there is no decision error in the tentative decision, the data symbol after the tentative decision can be used exactly as a pilot symbol, and by using the data symbol, the accuracy of estimating the propagation characteristic of the propagation path is further improved. Can be done.

Therefore, using the tentative decision data symbol determined by the tentative decision unit 8, the propagation path characteristic is estimated in the pilot and temporary decision data propagation path estimation unit 9,
Based on the channel estimation value and the above-described channel estimation value { ₁ } using the pilot symbol, a highly accurate channel estimation value {
₂ Find 求 め る.

[0042] Then, by using the estimated value xi] ₂ ^ of the more accurate channel characteristics, demodulates data symbols by the multiplier 11 again, and diversity combining by diversity combining unit 12, a data symbol by the final judging section 13 Is finally determined, and decoded by the decoder 14 as data.

FIG. 2 is a diagram showing the procedure of the synchronous detection according to the first embodiment of the present invention. In the figure, ()
The symbols in the parentheses indicate each procedure, the solid-line arrows indicate the flow of the synchronous detection procedure, and the dotted-line arrows indicate the paths of information transmitted and received between the procedures.

First, in step (1), the orthogonal code X
, And Y, the pilot symbol and the data symbol are separated from each other. In step (2), the propagation path is estimated based on the pilot symbol, and in step (3), the pilot symbol obtained in step (2) is used. The data symbol is multiplied by the propagation path estimation value to perform synchronous detection. In step (4), diversity combining is performed. In step (5), it is determined whether the number of input signals in diversity combining is equal to or greater than a prescribed number of branches. If the number of branches is equal to or more than the number of branches, the data symbol is provisionally determined in step (6), and in step (7), the channel estimation value estimated using the provisionally determined data symbol obtained in step (6) and the procedure ( A channel estimation value is obtained based on the pilot channel estimation value obtained in 2).

Next, in step (8), the data symbols are multiplied by the channel and channel estimation values obtained in step (7) to perform synchronous detection, and in step (9), diversity combining is performed. Procedure (10)
In step (1), it is determined whether or not the input signal in the diversity combining is equal to or greater than the specified number of branches.

As described above, the present invention regards a data symbol demodulated and determined using a pilot symbol as a pilot symbol, and estimates the propagation path characteristics using the data symbol as a pilot symbol.
Even when the fluctuation of the propagation path characteristics is large (when the fading frequency is high), it is possible to obtain a highly accurate estimated value of the propagation path characteristics compared to the conventional estimation using only the pilot symbol.

FIG. 3 is a diagram showing the configuration of the synchronous detection unit according to the second embodiment of the present invention. This embodiment shows an example in which the tentative determination is performed twice. The basic configuration is based on a channel estimation value { ₁ } using only pilot symbols,
A tentative determination of the data symbol is performed, and a more accurate channel estimation value is calculated based on the channel estimation value estimated using the tentatively determined data symbol and the previously determined channel estimation value. The tentative determination of the data symbol is performed again using the higher-accuracy channel estimation value, and the channel estimation is performed again using the second-time tentatively-determined data symbol with a smaller error, thereby gradually increasing the accuracy of the channel vertebral constant value. It is something to improve.

In the second embodiment of the present invention, the provisional
In this example, the number of tentative determinations is set to be longer than that, so that a more accurate channel estimation value can be obtained. As described above, in the present invention, data symbol determination is performed twice or more. Here, the final determination is referred to as final determination, and the previous determination is referred to as temporary determination.

The circuits denoted by reference numerals 1 to 14 in FIG. 3 are the same as the components denoted by reference numerals 1 to 14 in FIG. 200 is a synchronous detection unit, 21 is a tentative determination unit, 22 is a channel estimation unit based on pilot and temporary determination data, and 23 is a channel estimation in the channel estimation unit 5, channel estimation unit 9, and channel estimation unit 22. , A delay unit for multiplying the data symbol by a delay corresponding to the total operation time for the data symbol, a multiplication unit for multiplying a propagation path estimation value based on pilot and temporary decision data, and a diversity combining unit 25.

The synchronous detection unit according to the second embodiment of the present invention shown in FIG. 3 includes a provisional decision unit 8 for provisional decision of a first data symbol and a provisional decision unit 21 for provisional decision of a second data symbol. And a channel is estimated using the provisionally determined data symbol and the pilot symbol.

[0051] That is, performs temporary decision of data symbols by the temporary decision unit 8 based on the estimated value xi] ₁ ^ of the propagation path by pilot symbols, further, a second propagation path by a tentative decision data symbols and the pilot symbols Is temporarily determined by the tentative determination unit 21 on the basis of the estimated value { ₂ }, and using the tentatively determined data symbol output from the tentative determination unit 21, the propagation path estimation unit 22 similarly performs Estimation is performed, and based on the estimated value and the channel estimation value { ₁ } based on pilot symbols, a more accurate channel estimation value { ₃ } is calculated by moving average or the like as described above.

Then, the multiplier 24 multiplies the received data symbol passed through the delay unit 23 by the complex conjugate { ₃ ^{} *} of the channel estimation value { ₃ ^} calculated by the channel estimation unit 22, and outputs the diversity combining unit 25. , And the final decision unit 13 makes the final decision on the data symbol.

In the first and second embodiments of the present invention, the same number of diversity combining sections as the number of determining sections are provided at the preceding stage of each determining section, and each diversity combining section performs diversity combining. The characteristics are greatly improved.

As described above, according to the first and second embodiments of the present invention, by estimating the propagation path characteristics using the data symbols after the tentative determination equivalent to the pilot symbols, The channel characteristics can be estimated, and the estimation accuracy of the channel characteristics can be improved.

[0055] However, the channel estimation value by the pilot symbols xi] ₁ ^ a temporary decision data symbol channel estimation value xi] _d1 ^ and by, more accurate channel estimation value xi] ₂ ^
When obtaining (or { ₃ }), the pilot symbol is known, while the provisionally determined data symbol contains an error with a certain probability. Therefore, the accuracy is further improved by averaging the weights in accordance with the respective degrees of reliability instead of averaging the two as they are.

FIG. 4 is an explanatory diagram of a propagation path estimating unit for performing weighted averaging according to the embodiment of the present invention. This figure shows the internal configuration of the propagation path estimation unit 9 and the propagation path estimation unit 22 based on the pilot and temporary decision data shown in FIGS. In the figure, 4-1 is a tentative determination unit, 4-2 is a channel estimation unit that outputs a channel estimation value { ₁ } by pilot, 4-3 is a channel estimation unit by pilot and tentative determination data,
31 is a channel estimation unit that outputs a channel estimation value { _d1 } based on the tentative determination data, 4-32 is a multiplication unit that multiplies the channel estimation value { _d1 } by a weight coefficient Wa, and 4-33 is a channel estimation value { ₁
乗 算 is multiplied by a weight coefficient Wb, and 4-34 is a weighted average calculator.

[0057] provisional decision weighting coefficients Wa to be multiplied to the channel estimation value xi] _d1 ^ by data symbols, and set smaller than the weighting coefficient wb multiplying the channel estimation value xi] ₁ ^ by the pilot symbols, their propagation path estimated value Is weighted by a weighted average calculation unit 4-34 to obtain a channel estimation value ξ ₂
The accuracy of ＾ (or ξ ₃ ＾) can be improved.

[0058] The ratio of the weight coefficient wa and the weight factor wb is by setting in accordance with the error rate of the tentative decision data symbols, to optimize the accuracy of the channel estimation value xi] ₂ ^ (or xi] ₃ ^) it can. The error rate of the tentative decision data symbol is
If the required error rate of the final decision data symbol is determined by comparing and comparing the provisional decision data symbol with the final decision data symbol, the required error rate is naturally determined and can be obtained in advance by simulation or the like.

Next, a receiver for mobile communication incorporating the above-described synchronous detection unit will be described. FIG. 5 is a diagram showing a configuration of a mobile communication receiving apparatus incorporating the synchronous detection unit of the present invention. In the figure, an antenna (ANT) 1
0-1, radio section (Rx) 10-2, A / D converter (A / D
D) 10-3, timing synchronization section 10-4 and decoder 1
Since 0-6 are the same as those in the conventional receiving apparatus of FIG. 10 described above, they are denoted by the same reference numerals as in FIG. 10 and duplicate description is omitted.

The configuration of the synchronous detector 100 in FIG. 5 is the same as that of the synchronous detector 100 according to the first embodiment of the present invention shown in FIG. The operation is the same as the operation described above, and the description is omitted.

A receiving apparatus for mobile communication receives a transmission signal affected by a large change in propagation path characteristics due to fading. However, by incorporating a synchronous detection unit according to the present invention, the propagation path characteristics can be accurately detected. Estimate and synchronously detect (demodulate) the transmission signal from which the influence of the propagation path is removed by the estimated value
Therefore, a high-accuracy receiving device with a low data error rate can be configured.

Next, a description will be given of a multi-stage interference canceller incorporating the synchronous detector according to the present invention. The multi-stage interference canceller is used in a DS-CDMA mobile communication base station, and cascade-connects a plurality of stages of interference replica generation units (ICUs) corresponding to user channels by combining them in multiple stages, and gradually increasing each stage. Is a device that receives signals by removing interference from other user channels.

FIG. 6 is a diagram showing the configuration of a multi-stage interference canceller. The interference replica generation unit (ICU) 30 corresponding to the user and the receiver (ReC) 40 at the final stage at each stage in FIG. 6 receive the error signal e and the interference replica signal s from the previous stage, and perform interference removal processing. , Interference replica generation unit (ICU) 30
Outputs the interference residual estimation signal d and the corrected interference replica signal s to the next stage.

The combiner 50 of each stage includes an interference replica generation unit (ICU) 30 corresponding to the user of each stage.
Are synthesized, and the synthesized interference residual estimation signal d is combined with a delay unit (De
lay) 60, a new error signal e is output by subtracting from the error signal e of the previous stage.

By repeating this operation for each stage, the error signal approaches zero, the accuracy of the interference replica signal s is improved, and rake (RAKE) reception using the error signal e of the final stage and the interference replica signal s is performed. By processing
Interference between users can be eliminated. Here, the rake (RAKE) reception processing is to multiply received data symbols corresponding to each multipath by a complex conjugate of an estimated propagation path transfer characteristic, and perform maximum ratio combining of signals of each propagation path by diversity combining. Means that.

FIG. 7 is an explanatory diagram of the interference replica generation unit and the final stage receiver of the multi-stage interference canceller. Interference replica generation unit (ICU) 30
And the receiver (ReC) 40 at the final stage is provided with a number of despreading units 31 and 41 corresponding to the propagation paths, respectively.
Each of the despreading units 31 and 41 includes a despreader 31-1 and 41.
-1, adders 31-2 and 41-2, channel estimation unit 31
-3, 41-3, and multipliers 31-4, 41-4.

The error signal e and the interference replica signal s are input to the despreading units 31 and 41 from the preceding stage, and the error signal e is despread by despreaders 31-1 and 41-1. The added signal and the interference replica signal s from the previous stage are added by adders 31-2 and 41-2 to become a baseband reception signal, which is the same as the reception signal input to the synchronous detection unit 100 in FIG. Signal.

The channel estimators 31-3 and 41-3 estimate the channel transfer characteristics (channels), and estimate the channel characteristics from the output signals of the adders 31-2 and 41-2. At this time, it is possible to obtain a highly accurate channel estimation value by applying the channel characteristic estimating means using the pilot symbols and the provisionally determined data symbols according to the first or second embodiment of the present invention.

The outputs of the adders 31-2 and 41-2 are:
Multipliers 31-4 and 41-4 multiply the complex conjugates of the channel estimation values by the channel estimators 31-3 and 41-3, and output the result to an interference replica generation unit (ICU).
Diversity combining is performed by the combiners 32 and 42 in the receiver 30 (ReC) 40 or the final stage receiver 30, and the output of the combiner 32 in the interference replica generation unit (ICU) 30 is provisionally determined by the provisional determination unit 33. The output of the combiner 42 in the receiver (ReC) 40 is the soft decision decoder 4
3 and is decoded. The soft decision is to output a decision result holding the amplitude value of the received data symbol.

The interference replica generation unit (ICU) 30
In the re-spreading unit 34, the output from the tentative determination unit 33 is multiplied by the output of the channel estimation unit 31-3 by the multiplier 34-1, and the output of the multiplier 34-1 is used as the interference replica signal s to the next stage. And the adder 34-2 adds the output of the multiplier 34-1 and the signal obtained by inverting the sign of the interference replica signal s from the previous stage, and calculates the difference between the received data symbol and the interference replica signal s. Then, the difference (the output of the adder 34-2) is re-spread by the re-spreader 34-3. The output from the re-spreading unit 34 is diversity-combined by the combiner 35 and output to the next stage as the interference residual estimation signal d.

As described above, the multiplier 3
In the multiplication by 4-1, the channel characteristics estimated by the channel estimation unit 31-3 are used.
By improving the accuracy of the channel estimation value according to 1-3 by applying the embodiment of the present invention, it is possible to greatly improve the characteristics of interference cancellation.

FIG. 8 shows an interference replica generation unit (ICU) 30 of an interference canceller incorporating the synchronous detector of the present invention.
FIG. 3 is a diagram showing a despreading unit 31 in FIG. In FIG. 8, a portion 100 surrounded by a dotted line is the same as the synchronous detection unit of the first embodiment of the present invention, and each circuit unit constituting the synchronous detection unit is denoted by the same reference numeral as in FIG. Since the operation is the same as the above-mentioned operation, a duplicate description will be omitted.

In the despreading unit 31 in the interference replica generation unit (ICU) 30 shown in FIG. 8, the data channel and the pilot channel are spread by different codes. Despreads the received signal to separate data symbols and pilot symbols.

However, in order to avoid complicating the drawing, the data channel and the pilot channel after despreading are drawn by the same line. Further, data symbols and pilot symbols may be time-multiplexed on one signal line and sent to each circuit.

FIG. 9 is a diagram showing a despreading section 41 in a receiver (ReC) 40 in the final stage of the interference canceling apparatus incorporating the synchronous detection section of the present invention. In FIG. 9, similarly to FIG. 8, a portion 100 surrounded by a dotted line is the same as the synchronous detector of the first embodiment of the present invention, and each circuit constituting the synchronous detector is the same as FIG. The same reference numerals are given, and the operation is the same as the operation described above, and thus the duplicated description will be omitted.

[0076]

As described above, according to the present invention,
The provisional decision data symbol synchronously detected by removing the influence of the actual propagation path characteristic using the propagation path estimation value by the pilot symbol is regarded as a pilot symbol, and the propagation path characteristic is estimated using the provisional decision data symbol. By estimating the propagation path characteristics based on the propagation path estimation value using the symbol and the propagation path estimation value using the tentative decision data symbol, a highly accurate propagation path estimation value can be obtained. Rate can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a synchronous detection unit according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a procedure of synchronous detection according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of a synchronous detection unit according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a propagation path estimating unit that performs weighted averaging according to the embodiment of this invention.

FIG. 5 is a diagram showing a configuration of a mobile communication receiving device incorporating the synchronous detection unit of the present invention.

FIG. 6 is a diagram illustrating a configuration of a multi-stage interference canceller.

FIG. 7 is an explanatory diagram of an interference replica generation unit and a final stage receiver of the multi-stage interference canceller.

FIG. 8 is a diagram showing a despreading unit in an interference replica generation unit (ICU) of the interference canceller incorporating the synchronous detection unit of the present invention.

FIG. 9 is a diagram showing a despreading unit in a receiver (ReC) at the final stage of the interference canceller incorporating the synchronous detection unit of the present invention.

FIG. 10 is a diagram illustrating a configuration of a conventional receiving apparatus that performs synchronous detection using pilot symbols.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 100 Synchronous detection part 1 Timing synchronization part 2, 3 Multiplication part which multiplies with orthogonal code 4 Delay part which gives delay for operation time for propagation path estimation by pilot 5 Propagation path estimation part by pilot 6 Propagation path estimation value by pilot Multiplying unit 7 Diversity combining unit 8 Temporary decision unit 9 Propagation path estimation unit based on pilot and provisional decision data 10 Delay unit that gives a delay of operation time for propagation path estimation by pilot and propagation path estimation by pilot and provisional decision data Reference Signs List 11 Multiplier for multiplying a channel estimation value based on pilot and tentative decision data 12 Diversity combining unit 13 Final decision unit 14 Decoder

Claims (6)

[Claims] When receiving a data symbol in mobile communication, a channel characteristic is estimated by using a pilot symbol extrapolated to a channel different from the data symbol, and a channel estimation value based on the pilot symbol is used. A synchronous detection is performed to temporarily determine a received data symbol. Further, a channel characteristic is estimated using the temporarily determined data symbol and the pilot symbol, and a channel estimation value based on the temporarily determined data symbol and the pilot symbol is used. A synchronous detection method using a pilot and a provisionally determined data symbol, wherein the received data symbol is finally determined by performing synchronous detection. 2. A method for performing synchronous detection based on a channel estimation value based on the tentatively determined data symbol and the pilot symbol to tentatively determine a received data symbol a plurality of times, and using the data symbol and the pilot symbol based on the tentative determination. 2. The synchronous detection method according to claim 1, wherein the estimation of the propagation path characteristics is repeated a plurality of times. 3. A channel estimation unit using pilot symbols for estimating channel characteristics using a pilot symbol extrapolated to a channel different from a data symbol, and receiving data based on a channel estimation value based on the pilot symbols. A tentative determination unit for tentatively determining symbols; a tentative determination data symbol by the tentative determination unit; and a propagation path estimation unit based on tentative determination data symbols for estimating propagation path characteristics using the pilot symbols; A receiving unit for mobile communication, comprising: a final determining unit that determines a received data symbol based on a propagation path estimation value using the determined data symbol. 4. A plurality of determination units for determining a received data symbol based on a propagation path estimation value using the pilot symbol and the tentatively determined data symbol, comprising: a plurality of channel estimation units based on the pilot and the tentatively determined data symbol. The receiving device for mobile communication according to claim 4, wherein the receiving device is provided. 5. A multi-stage interference canceling apparatus used in a base station of DS-CDMA mobile communication, wherein an interference replica generation unit of each stage or a final stage receiver is extrapolated to a channel different from a data symbol. A channel estimation unit using a pilot symbol for estimating a channel characteristic using the pilot symbol obtained; a temporary determination unit for performing a temporary determination of a received data symbol based on a channel estimation value based on the pilot symbol; And a channel estimating unit for estimating propagation path characteristics using the tentatively determined data symbol and the pilot symbol. 6. A plurality of determination units for determining a received data symbol based on a channel estimation value using the pilot symbol and the tentatively determined data symbol, comprising: a plurality of propagation path estimating units based on the pilot and the tentatively determined data symbol. The interference canceling device according to claim 7, further comprising: