JPH11127208A - Synchronous detection method using pilot symbol and tentative decision data symbol, mobile object communication receiver and interference elimination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve estimation precision of propagation path transfer characteristics with regard to a synchronous detection method using a pilot symbol and a tentative decision data symbol and a mobile object transfer receiver and an interference elimination device. SOLUTION: This device estimates propagation path transfer characteristics and executes a synchronous detection by considering a tentative decision data symbol to be a pilot symbol by means of the first propagation path transfer characteristics estimation circuit 3 for estimating propagation path transfer characteristics by using the pilot symbol interpolated in a data frame at regular intervals, a tentative decision circuit 6 for making a tentative decision of a reception data symbol on the basis of the first estimated propagation path transfer characteristics by the first propagation path characteristics estimation circuit 3, the second propagation path transfer characteristics estimation circuit 7 for estimating the propagation path characteristics by using the tentative decision data symbol and the pilot symbol by the tentative decision circuit 6, and a final decision circuit 11 for deciding the reception data symbol on the basis of the second estimated propagation path transfer characteristics by the second propagation path transfer characteristics estimation circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to PSK, QPS
In a digital mobile communication system using a phase modulation signal such as K or MPSK or a multi-level QAM modulation signal, etc., pilot symbols and tentative determination are performed by estimating transmission characteristics of a propagation path using pilot symbols and data symbols themselves to perform synchronous detection. The present invention relates to a synchronous detection method using a data symbol, a mobile communication receiver, and an interference canceller.

[0002]

2. Description of the Related Art In a mobile communication, a received signal fluctuates due to fading as a terminal moves in an environment in which a multipath is formed. When demodulating a received signal in such a situation, a method of estimating a transfer characteristic (complex number) of a propagation path from a received pilot symbol and reducing the influence of fading due to the transfer characteristic of the propagation path to perform synchronous detection. Is widely used.

FIG. 12 is an explanatory diagram of a data frame in which pilot symbols are interpolated. FIG. 12A shows a data frame to be transmitted, and FIG. 12B shows a data symbol sequence and pilot symbols in encoded data. . In the figure, 12-1 is a data frame, 12-2 is a preamble,
12-3 is encoded data, 12-4 is a data symbol sequence, and 12-5 is a pilot symbol. One or a plurality of pilot symbols 12-5 are interpolated at regular intervals between data symbol strings 12-4 in the encoded data 12-3, and a portion 12-in which the pilot symbols are interpolated.
6 is called a pilot block.

[0004] The pilot symbol 12-5 is a predetermined known data symbol, and is transmitted at predetermined time intervals after transmitting the preamble 12-2 from the transmitting device. If the timing of the received signal transmitted from the transmitting apparatus and received via the propagation path is synchronized with that of the receiving apparatus, the receiving apparatus computes from the received signal at the time position of the pilot symbol 12-5. Thus, the transfer characteristic of the propagation path can be estimated.

[0005] The timing synchronization with the received signal in the receiving apparatus can be synchronized with the received signal by detecting the preamble 12-2 added before the data frame.

[0006] Now, the k-th pilot symbol in the n-th pilot block transmitted from the transmitting apparatus is represented by Z
nk. If the transfer characteristic of the propagation path at this time is ξnk,
The received symbol received via the propagation path is Znk / ξnk
Becomes

[0007] Since the transmission symbol at this time position is a pilot symbol Znk which is a known data symbol, Znk ^* which is a complex conjugate of the pilot symbol Znk ^.
Is multiplied by the received symbol, the value is ξnk · | Znk | ²
Since the magnitude (amplitude) of the pilot symbol is a known value (or | Znk | ≡1), the transfer characteristic 伝 達 nk of the propagation path at this time can be estimated. The estimated value is {nk}, and the estimated value {nk} is expressed by the following equation. ξnk ＾ = Znk ・ ξnk ・ Znk ^* = ξnk ・ ｜ Znk ｜ ²・ ・ ・ ・ (1)

However, actually, the received symbol is affected by noise and interference of other signals, so that the transfer characteristic of the propagation path cannot be accurately estimated. Therefore, a plurality of pilot symbols 12-5 are inserted into one pilot block 12-6 so that the transfer characteristics of the propagation path can be more accurately estimated. An estimated propagation path transfer characteristic is obtained, and the average value is used as an estimated value of the propagation path transfer characteristic in the pilot block 12-6. Here, the estimated value of the propagation path transfer characteristic in the n-th pilot block is {n}.

The channel transfer characteristic at the position of the data symbol sequence sandwiched between the two pilot blocks 12-6 is obtained by averaging or linearly interpolating the channel transfer characteristics at the position of the two pilot blocks 12-6. Ask by

When an estimated value of the propagation path transfer characteristic is obtained, the transmission data symbol is demodulated as follows. Where n
Xni represents the i-th transmission data symbol of the transmission data symbol sequence interposed between the n-th pilot block and the (n + 1) -th pilot block, ξni represents the actual propagation path transfer characteristic,
Estimate transfer characteristic of transmission channel is {ni}, demodulated data symbol is X
ni ＾.

The data symbol received via the propagation path is
The value Xni · nini obtained by multiplying the transmission data symbol Xni by the actual propagation path transfer characteristic ξni is multiplied by the complex conjugate ξni ＾ ^* of the estimated path transfer characteristic ξni ＾ to obtain the estimated propagation path transfer characteristic ξni By dividing by the square of the absolute value of ＾,
The transmission data symbol Xni is demodulated as a demodulated data symbol Xni} in which the influence of the propagation path transfer characteristic {ni is reduced. This can be expressed as follows. Xni ＾ = Xniξniξniξ ^* / | ni ＾ | ² ... (2)

The data symbol demodulated in this manner is determined as a predetermined discrete data symbol by comparing it with a predetermined threshold by a determination circuit after diversity combining, and a decoding process such as deinterleaving and error correction is performed by a decoder. And is reproduced as data. FIG. 13 shows a conventional receiving apparatus including a synchronous detection circuit using pilot symbols.

In FIG. 13, an antenna (ANT) 13
Is received by the radio unit 14,
Amplifies the received signal by an amplifier (LNA) 14-1, removes components outside a predetermined band by a band-pass filter (BPF) 14-2, and multiplies the signal by a mixer 14-3 with a signal LO from a local oscillator. The signal is converted into a baseband band, high-frequency components are removed by a low-pass filter (LPF) 14-4, and the resultant signal is output to a circuit at the next stage.

An A / D conversion circuit (A / D) 15 at the next stage quantizes the received signal from the radio unit 14, converts it into a digital signal, and outputs the digital signal to a timing synchronization circuit 16. The timing synchronization circuit 16 The synchronization is performed by the signal, and the received signal is output to the synchronous detection circuit 17.

In the synchronous detection circuit 17, a propagation path estimating circuit 17-1 based on pilot symbols calculates an estimated value {ni} of the propagation path transfer characteristic by the above equation (1), and multiplies the complex conjugate {ni} ^* by the multiplier 17-. Output to 3.

A multiplier 17-3 multiplies the received signal passed through the delay circuit 17-2 by the complex conjugate {ni} ^* of the estimated propagation path transfer characteristic output from the propagation path estimation circuit 17-1 based on the pilot symbol. And the demodulated data symbol Xni ＾ is input to the diversity combining circuit 1.
Output to 7-4.

In the synchronous detection circuit 17, the demodulated data symbol Xni ＾ is calculated by multiplying the received signal Xniξξni by the complex conjugate ξni ＾ ^* of the estimated propagation path transfer characteristic. According to 2), the multiplication is ξ
ni ＾ ^* / | ξniξ | must be multiplied by ² ,
Since the calculation of the square of the absolute value of the estimated propagation path transfer characteristic | ξni ＾ | ² only affects the amplitude component of the demodulated data symbol Xni 、, the processing in other circuit units that handle the amplitude component is appropriately changed. By doing so, the multiplier 1
The multiplication by 7-3 can be the multiplication of the estimated value of the propagation path transfer characteristic by the complex conjugate {ni} ^* .

The demodulated data symbol Xni ＾ is diversity-combined with a demodulated data symbol by another similar circuit by a diversity combining circuit 17-4, and is compared with a predetermined threshold by a determination circuit 17-5 to determine a predetermined discrete data symbol. And outputs it to the decoder 18.

[0019]

As can be seen from the above equation (2), if the actual propagation path transmission characteristic {ni} and the estimated propagation path transmission characteristic {ni} are equal, the demodulated data symbol Xni
＾ matches the transmission data symbol Xni,
Actual propagation path transfer characteristics ξni and estimated propagation path transfer characteristics ξni ＾
Increases, the difference between the demodulated data symbol Xni ＾ and the transmission data symbol Xni also increases.

Accordingly, it is important to accurately estimate the actual propagation path transfer characteristics in order to accurately demodulate data symbols. To improve the estimation accuracy of propagation path transfer characteristics,
One method is to increase the number of pilot symbols to be interpolated. However, if the number of pilot symbols is increased, the number of data symbols to be transmitted is reduced by that amount. It gets worse.

When the propagation path transfer characteristic varies greatly between pilot blocks, that is, when the fading frequency is high, the method of estimating the propagation path transfer characteristic using fixed-period pilot symbols employs a data symbol sequence between pilot blocks. The propagation path transfer characteristic at the position cannot be correctly estimated corresponding to the fading frequency.

Generally, when the fading frequency is low,
For example, assuming that the maximum Doppler frequency is fd and the interpolation period of the pilot block is Tp, the propagation path at the position of the two pilot blocks is in a region where the value of the normalized fading frequency fd · Tp is about 0.1 or less. It is known that the estimation accuracy when the average value of the transfer characteristics is used as the propagation path transfer characteristic therebetween is better than the estimation accuracy when linear interpolation is performed.

Conversely, in a region where the fading frequency is high and the value of the normalized fading frequency fd · Tp is about 0.1 or more, the estimation accuracy in the case of performing linear interpolation is superior. However, even when linear interpolation is performed, the accuracy of estimating the propagation path transfer characteristics is lower in a region where the normalized fading frequency fd · Tp is high than in a region where the standardized fading frequency is low, and as a result, the data error rate is large.

An object of the present invention is to estimate propagation path transfer characteristics with high accuracy without increasing the number of pilot symbols and even when the fading frequency is high, and to reduce the error rate of received data.

[0025]

According to the present invention, there is provided a synchronous detection method using a pilot symbol and a provisionally determined data symbol. (1) In receiving a data symbol in mobile communication, data is interpolated at regular intervals into a data frame. Estimating a propagation path transfer characteristic using a pilot symbol, performing a tentative determination of a received data symbol based on the estimated propagation path transfer characteristic using the pilot symbol, and using the tentatively determined data symbol and the pilot symbol to perform a propagation path transfer characteristic And finally determining the received data symbol based on the estimated propagation path transfer characteristic of the tentatively determined data symbol and the pilot symbol.

Also, (2) a step of repeating the tentative decision of the data symbol several times based on the estimated propagation path transfer characteristic based on the tentative decision data symbol and the pilot symbol is included.

(3) In the determination of a received data symbol sandwiched between two pilot symbols, the received data symbol is determined based on a propagation path transfer characteristic estimated using a tentatively determined data symbol near the center of the two pilot symbols. It includes a process of determining a data symbol.

(4) In estimating the propagation path transfer characteristic of a data symbol position sandwiched by two pilot symbols, the two pilot symbols and the two
Based on the propagation path transfer characteristic estimated by the tentative decision data symbol near the center of one pilot symbol or the propagation path transfer characteristic estimated by the two pilot symbols and a plurality of tentative decision data symbols between the two pilot symbols, The method includes a step of interpolating a propagation path transfer characteristic at a data symbol position sandwiched between the two pilot symbols.

(5) A first propagation path transfer characteristic estimating circuit for estimating a transfer path characteristic using pilot symbols interpolated at equal intervals in a data frame. And a tentative decision circuit for tentatively determining a received data symbol based on a first estimated propagation path transfer characteristic by the first propagation path transfer characteristic estimating circuit, and a tentative decision data symbol and the pilot symbol by the tentative decision circuit. A second propagation path transfer characteristic estimating circuit based on pilot symbols and tentative decision data symbols for estimating propagation path transfer characteristics using the same, and receiving based on a second estimated propagation path transfer characteristic by the second propagation path transfer characteristic estimating circuit. And a final determination circuit for determining a data symbol.

(6) A plurality of provisional decision circuits for provisionally determining data symbols based on the estimated propagation path transfer characteristics of the provisionally determined data symbols and pilot symbols are provided.

(7) A first propagation path transfer characteristic estimating circuit for estimating a propagation path transfer characteristic by using pilot symbols interpolated at equal intervals in a data frame. A temporary determination circuit for performing a temporary determination of a received data symbol based on a first estimated propagation path transfer characteristic by a first propagation path transfer characteristic estimating circuit, and a propagation path using the temporary determination data symbol and the pilot symbol by the temporary determination circuit. A second propagation path transfer characteristic estimating circuit based on pilot symbols and provisionally determined data symbols for estimating transfer characteristics, and a received data symbol is determined based on a second estimated propagation path transfer characteristic by the second propagation path transfer characteristic estimating circuit. And a final determination circuit that performs the determination.

(8) A plurality of provisional decision circuits for provisionally determining data symbols based on the estimated propagation path transfer characteristics of the provisionally determined data symbols and pilot symbols are provided.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention regards a data symbol demodulated and determined using an interpolated pilot symbol as a pilot symbol, and uses the data symbol in the same manner as in the case of a pilot symbol to obtain propagation path transfer characteristics. Is performed, the propagation path transfer characteristic is estimated with higher accuracy than the conventional estimation using only the pilot symbol.

Then, using the propagation path transfer characteristics estimated by the above method, the data symbol is demodulated and determined again, and the data is decoded. Therefore, 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.

When there is no decision error in the tentative decision of the data symbol, the data symbol after the tentative decision can be used equally as a pilot symbol,
By using the data symbols, the accuracy of estimating the propagation path transfer characteristics can be further improved.

However, if there is a decision error in the tentative decision, the accuracy of estimating the propagation path transfer characteristics is degraded. Therefore, when using the tentatively determined data symbols, it is necessary to appropriately select the number of tentatively determined data symbols to be used or their positions in accordance with the error rate and fading frequency of the tentative determination.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram of a synchronous detection circuit according to a first embodiment of the present invention. FIG. 2 is a flowchart thereof. In FIG. 1, 100 is a synchronous detection circuit, 1 is a timing synchronization circuit, 2 is a first delay circuit, 3 is a first propagation path estimating circuit using pilot symbols, 4 is a first multiplier, and 5 is a first multiplier. A diversity combining circuit, 6 a tentative decision circuit, 7 a second propagation path estimating circuit based on pilot symbols and tentative decision data symbols, 8 a second delay circuit, 9
Is a second multiplier, 10 is a second diversity combining circuit, 11 is a final decision circuit, and 12 is a decoder.

FIG. 1 shows the configuration after the output portion after the received signal is dropped to the baseband and subjected to A / D conversion. The configuration of the wireless portion is the same as the configuration of the above-described conventional example. The A / D-converted received signal is transmitted to the timing synchronization circuit 1
, And the timing position of the pilot symbol and the data symbol is specified by the timing synchronization circuit 1.

The pilot symbol and the data symbol whose time position is specified are input to a first delay circuit 2, a second delay circuit 8, and a first propagation path estimating circuit 3 using pilot symbols.

The first propagation path estimation circuit 3 based on pilot symbols estimates propagation path transfer characteristics using pilot symbols in the same manner as in the above-described conventional example (see step (1) in FIG. 2). Assuming that the estimated propagation path transfer characteristic is { ₁ ^} , the first propagation path estimating circuit 3 outputs the complex conjugate { ₁ ^{} *} of the estimated propagation path transfer characteristic, and this output and the first delay circuit 2
The multiplication is performed by the first multiplier 4 with the received data symbol that has passed through the step (2) to perform synchronous detection (see step (2) in FIG. 2), thereby reducing the effect of the actual propagation path transfer characteristic that is the output. The first demodulated data symbol obtained is
Is output to the diversity combining circuit 5.

The first diversity combining circuit 5 performs diversity combining of the first demodulated data symbol and a demodulated data symbol generated by another similar circuit (see step (3) in FIG. 2), and performs diversity combining. It is determined whether or not the input signal is equal to or greater than the specified number of branches (see step (4) in FIG. 2).

The tentative decision circuit 6 makes a tentative decision as a predetermined discrete data symbol by comparing the first demodulated data symbol output from the first diversity combining circuit 5 with a predetermined threshold (step (FIG. 2)). 5)), and outputs the data symbol to the second propagation path estimation circuit 7 using pilot symbols and provisionally determined data symbols.

The second propagation path estimating circuit 7 regards the data symbol determined by the tentative decision circuit 6 as a pilot symbol, and determines the propagation path transmission characteristic by the same method as the above-described estimation of the propagation path transmission characteristic using the pilot symbol. Estimate (see step (6) in FIG. 2).

That is, assuming that the actual propagation path transfer characteristic of the data symbol receiving position is ξ and the transmission data symbol is X, the data determined by the tentative determination circuit 6 is added to the received data symbol X · ξ via the propagation path. By multiplying the complex conjugate of the symbol X by X ^* , the estimated propagation path transfer characteristic の of the data symbol reception position is obtained.

Next, the second propagation path estimating circuit 7 calculates the estimated propagation path transfer characteristic か ら estimated from the provisionally determined data symbol.
And a second estimated channel transfer characteristic { ₁ } based on the estimated channel transfer characteristic { ₁ } estimated from the pilot symbol.
₂ ＾ is calculated, and its complex conjugate ξ ₂ ＾ ^* is calculated by the second multiplier 9.
Output to

The second multiplier 9 receives the complex conjugate { ₂ ^{} *} of the second estimated propagation path transfer characteristic output from the second propagation path estimating circuit 7 via the second delay circuit 8. Synchronous detection is performed by multiplying by the data symbol (see FIG. 2).
(7)), and outputs the second demodulated data symbol to the second diversity combining circuit 10 in which the influence of the propagation path transfer characteristic is further reduced.

The second diversity combining circuit 10 diversity-combines the second demodulated data symbol from the second multiplier 9 and the demodulated data symbol from another similar circuit (step (8) in FIG. 2). Then, it is determined whether or not the input signal in the diversity combining is equal to or more than the specified number of branches (see step (9) in FIG. 2).

The final determination circuit 11 determines the second demodulated data symbol output from the second diversity combining circuit 10 as a predetermined discrete data symbol by comparing it with a predetermined threshold (step (FIG. 2) 10)), and outputs the data symbol to the decoder 12 (see step (11) in FIG. 2).

FIG. 3 is an explanatory diagram of a synchronous detection circuit according to a second embodiment of the present invention. The circuits denoted by reference numerals 1 to 12 in FIG. 3 are the same as the circuits denoted by reference numerals 1 to 12 in FIG. 200 is a synchronous detection circuit, 21 is a second provisional decision circuit, 22 is a third propagation path estimation circuit based on pilot symbols and provisional decision data symbols, 23 is a third delay circuit, 24 is a third multiplier, 25 Is a third diversity combining circuit, and 26 is a final decision circuit.

The synchronous detection circuit according to the second embodiment of the present invention shown in FIG. 3 comprises a first provisional decision circuit 6 and a second provisional decision circuit 2.
The provisional determination is performed twice according to 1. The first provisional decision circuit 6 makes a provisional decision on the data symbol based on the estimated propagation path transfer characteristic { ₁ } based on the pilot symbol, and further performs a second estimation propagation based on the provisional decision data symbol and the pilot symbol. Based on the path transfer characteristic { ₂ }, the second provisional decision circuit 21 makes a provisional decision on the data symbol, and the third propagation path estimation circuit 22 based on the pilot symbol and the provisional decision data symbol makes the second provisional decision. A complex conjugate { ₃ ^{} *} of a _third estimated propagation path transfer characteristic based on the tentative decision data symbol from the circuit 21 and the pilot symbol is generated.

The third multiplier 24 multiplies the received data symbol passed through the third delay circuit 23 by the complex conjugate { ₃ ^{} * of} the third estimated propagation path transfer characteristic, and The third demodulated data symbol having a reduced effect is output to the third diversity combining circuit 25.

The third diversity combining circuit 25 diversity-combines the third demodulated data symbol from the third multiplier 24 and the demodulated data symbol from another similar circuit, and outputs the result to a final decision circuit 26. Output to

In the first and second embodiments of the present invention, since the same number of diversity combining circuits as the number of decision circuits are provided, diversity combining is performed by the respective diversity combining circuits preceding the respective decision circuits. In some cases, the characteristics are greatly improved.

As described above, according to the first and second embodiments of the present invention, it is possible to use the data symbols after the tentative determination in the same manner as the pilot symbols, and to improve the estimation accuracy of the propagation path transfer characteristics. .

However, as described above, when the tentative decision data symbol is used as a pilot symbol, the position and the number of the tentative decision data symbol to be used for estimation must be properly selected according to the magnitude of fluctuation such as fading frequency. No. Hereinafter, the position and the number of the provisionally determined data symbols used for estimation will be described.

FIG. 4 is an explanatory diagram of the provisionally determined data symbol used for estimating the propagation path transfer characteristic, and shows the relationship between the position on the data frame and the change in the absolute value of the propagation path transfer characteristic. Actually, the propagation path transfer characteristic is a complex number, but for simplicity in the figure, only the absolute value is shown on the vertical axis and the phase is omitted, but the phase also fluctuates according to the position on the frame. I do.

In FIG. 4, the actual transmission path characteristics and the estimated transmission path characteristics of pilot block n are {n and {n}, respectively, and the actual transmission path characteristics and the estimated transmission path transmission characteristics of pilot block n + 1 are {n + 1}. And {n + 1}.

Assuming that the estimated propagation path transfer characteristic at the position of the data symbol sequence sandwiched between the two pilot blocks shown in FIG. 4 is the average value of {n} and {n + 1}, the transmission symbol is sandwiched between the pilot symbols. All of the data symbols thus demodulated are demodulated using the same estimated propagation path transfer characteristic, and are provisionally determined after diversity combining.

Here, when the difference between the actual propagation path transfer characteristics ξn and ξn + 1 of the two pilot blocks is small,
Even if the propagation path transfer characteristic is estimated using the provisionally determined data symbol at any position in the data symbol sequence, there is no large difference in estimation accuracy.

However, when the difference between the actual propagation path transfer characteristics ξn and ξn + 1 of the two pilot blocks is large,
The estimated propagation path transfer characteristic as an average value of the estimated propagation path transfer characteristics {n} and {n + 1} in the two pilot blocks, and the actual propagation path transfer characteristic are significantly different at a position near the end of the data symbol sequence. It will be something.

Accordingly, when the tentatively determined data symbol at a position near the end of the data symbol sequence is used for estimating the propagation path transfer characteristic, the error rate of the tentative determination increases, and the estimation accuracy of the propagation path transfer characteristic deteriorates. I will let you do it.

[0062] Therefore, the difference between the estimated propagation path transfer characteristic as an average value of the estimated propagation path transmission characteristics {n} and {n + 1} in the two pilot blocks and the actual propagation path transmission characteristic is small, and the center of the data symbol is small. By using the provisionally determined data symbols in the vicinity of the portion for estimating the propagation path transfer characteristics, stable and accurate estimation of the propagation path transfer characteristics can be obtained even when the fluctuation of the propagation path transfer characteristics becomes large.

FIG. 5 is an explanatory diagram of the estimated propagation path transfer characteristic based on the tentatively determined data symbol, and shows the relationship between the position on the data frame and the change in the absolute value of the propagation path transfer characteristic. As in the case of FIG. 4, for the sake of simplicity, only the absolute value is shown on the vertical axis, and the phase is omitted. Ξn and ξn
{, {N + 1} and {n + 1} are propagation path transfer characteristics in two pilot blocks and their estimated values, as in the case of FIG.

In FIG. 5, the estimated propagation path transfer characteristic obtained from the tentatively determined data symbol according to the first or second embodiment of the present invention is denoted by {d}. When the propagation path transfer characteristic at the position of the data symbol sequence sandwiched between the two pilot blocks is obtained from the estimated propagation path transfer characteristics {n} and {n + 1} in the two pilot blocks, the fading frequency is high and the propagation path transfer characteristic is high. In the conventional case, when the fluctuations of the two pilot blocks are large, linear interpolation using only the estimated propagation path transfer characteristics {n} and {n + 1} in the two pilot blocks is used to obtain the estimated propagation path transfer characteristic at the data symbol sequence position between them. But not the first or second of the present invention.
According to the embodiment of the present invention, the propagation path transfer characteristic value {d} estimated from the tentative decision data symbol is also used for the interpolation, and the estimated propagation path transfer characteristic in the pilot block and the propagation path transfer characteristic value estimated from the tentative decision data symbol are used. By performing linear interpolation using the three estimated propagation path transfer characteristics {n}, {d}, and {n + 1}, highly accurate propagation path transfer characteristics at the data symbol string position can be estimated.

The accuracy of three-point interpolation is higher than that of two-point interpolation, and it is also possible to apply an interpolation method such as quadratic interpolation or three-dimensional spline. Although only the interpolation of the amplitude component is shown in FIG. 5, the interpolation is similarly performed for the phase component.

FIG. 6 is an explanatory diagram of the estimated propagation path transfer characteristics based on a plurality of temporarily determined data symbols, and shows the relationship between the position on the data frame and the change in the absolute value of the propagation path transfer characteristics. As in the case of FIG. 4, for the sake of simplicity, only the absolute value is shown on the vertical axis, and the phase is omitted. {N} and {n}, {n + 1} and {n + 1} are propagation path transfer characteristics in two pilot blocks and their estimated values, as in the case of FIG.

In FIG. 6, a plurality of estimated propagation path transfer characteristics obtained from the provisionally determined data symbols according to the first or second embodiment of the present invention are denoted by {d 1} and {d 2}. As shown in the figure, the position of the estimation of the propagation path transfer characteristic by the provisionally determined data symbol is not limited to the center of the data symbol sequence,
Two or more places, using the estimated propagation path transfer characteristics obtained by the tentative decision data symbol at each position and the estimated propagation path transfer properties {n} and {n + 1} calculated by the pilot block. By performing the interpolation, it is possible to accurately estimate the propagation path transfer characteristic at the data symbol position.

FIG. 6 shows an example in which the propagation path transfer characteristics are estimated at two places by the provisionally determined data symbols, and data interpolation is performed at a total of four points. Although only the interpolation of the amplitude component of the propagation path transfer characteristic is shown in the figure, the interpolation is similarly performed for the phase component.

FIG. 7 shows a receiver for mobile communication according to an embodiment of the present invention. Antenna (ANT) 1 in FIG.
3, the radio unit 14, the A / D conversion circuit (A / D) 15, the timing circuit 16, and the decoder 18 are the antenna (ANT) 13, radio unit 14, and A
The same components as those of the A / D conversion circuit (A / D) 15, the timing circuit 16 and the decoder 18 are denoted by the same reference numerals as those in FIG. 13, and their operations are the same as those described above. Omitted. The configuration of the synchronous detection circuit 100 shown in FIG. 7 is the same as that of the synchronous detection circuit 100 according to the first embodiment of the present invention shown in FIG. Is the same as the operation described above, and the description is omitted.

FIG. 8 is an explanatory diagram of a multi-stage type interference canceller. This multi-stage interference canceller is DS
-Used in a CDMA mobile communication base station to remove interference from other users (mobile stations).

In each stage shown in FIG. 8, an interference replica generation unit (ICU) 30 corresponding to the user and a receiver (ReC) 40 at the final stage receive the error signal e and the interference replica signal s from the previous stage, and perform interference cancellation. Processing is performed, and the interference residual estimation signal d and the corrected interference replica signal s are output to the next stage.

The combiner 50 at each stage includes an interference replica generation unit (ICU) 30 corresponding to the user at each stage.
Is synthesized, and the synthesized interference residual estimation signal is combined with a delay circuit (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 is improved, and a rake (RAKE) reception process using the error signal e and the interference replica signal s of the final stage is performed. Thus, 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 a maximum ratio combination of signals of each propagation path by diversity combination. Means that.

FIG. 9 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, 41-2, channel estimation circuit 3
1-3, 41-3 and multipliers 31-4, 41-4 are provided.

The error signal e and the interference replica signal s are inputted to the despreading units 31 and 41 from the previous stage, and the error signal e is despread by despreaders 31-1 and 41-1. The signal obtained by adding the obtained signal and the interference replica signal s from the previous stage by the adders 31-2 and 41-2 is the same as the signal having the data frame configuration in FIG.

The channel estimation circuits 31-3 and 41-3
Is used to estimate the propagation path transfer characteristic (channel). When estimating the propagation path transfer characteristic (channel) from the output signals of the adders 31-2 and 41-2, the first or second embodiment of the present invention is performed. By applying the channel transfer characteristic (channel) estimating means using the pilot symbols and the tentatively determined data symbols according to the embodiment, highly accurate estimated channel transfer characteristics can be obtained.

The outputs of the adders 31-2 and 41-2 are:
Multipliers 31-4 and 41-4 multiply the complex conjugate of the estimated propagation path transfer characteristics by the channel estimation circuits 31-3 and 41-3, and output the result to the interference replica generation unit (I
CU) 30 or diversity combiners 32 and 42 in the final stage receiver (ReC) 40 and combiner 32 in interference replica generation unit (ICU) 30.
Is provisionally determined by the provisional decision unit 33, and the output of the combiner 42 in the final stage receiver (ReC) 40 is subjected to soft decision by the soft decision decoder 43 and decoded. The soft decision is to output a decision result holding the amplitude of the received data symbol.

Interference replica generation unit (ICU) 30
In the re-spreading unit 34, the output from the tentative decision unit 33 is multiplied by the output of the channel estimation circuit 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. At the same time, 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 are added by the adder 34-2.
-2 is respread by the respreader 34-3. The output from the re-spreading unit 34 is diversity-combined by the combiner 35 and output to the next stage as an interference residual estimation signal d.

As described above, the multiplier 3
The multiplication by 4-1 uses the propagation path transfer characteristics estimated by the channel estimation circuit 31-3, and the accuracy of the estimated propagation path transfer characteristics by the channel estimation circuit 31-3 is determined by the first or second embodiment of the present invention. By applying and improving the second embodiment, the characteristics of interference removal can be significantly improved.

FIG. 10 shows a despreading unit 31 in an interference replica generation unit (ICU) 30 of an interference canceller incorporating a synchronous detection circuit according to the first embodiment of the present invention. FIG.
At 0, a portion 100 surrounded by a dotted line is the same as that of the synchronous detection circuit according to the first embodiment of the present invention, and each circuit portion constituting the synchronous detection circuit is denoted by the same reference numeral as in FIG. Since the operation is the same as the operation described above, a duplicate description will be omitted.

FIG. 11 shows a despreading section 41 in a receiver (ReC) 40 in the final stage of the interference canceller incorporating the synchronous detection circuit according to the first embodiment of the present invention. FIG.
Similarly to FIG. 11, a portion 100 surrounded by a dotted line is the same as the synchronous detection circuit of the first embodiment of the present invention, and each circuit portion constituting the synchronous detection circuit has the same configuration as that of FIG. The reference numerals are used, and the operation is the same as the operation described above, and thus the duplicated description will be omitted.

[0082]

As described above, according to the present invention,
Considering the provisionally determined data symbol demodulated by reducing the influence of the actual channel transfer characteristic using the estimated channel transfer characteristic by the pilot symbol, as a pilot symbol,
By estimating the propagation path transfer characteristic of the data symbol column position using the tentatively determined data symbol and estimating the propagation path transfer characteristic using the pilot symbol and the tentatively determined data symbol, a highly accurate estimated propagation path transfer characteristic is obtained. And the error rate of the received data can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a synchronous detection circuit according to a first embodiment of the present invention.

FIG. 2 is a flowchart of the synchronous detection circuit according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a synchronous detection circuit according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a temporary determination data symbol used for estimating a propagation path transfer characteristic according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of estimated propagation path transfer characteristics based on provisionally determined data symbols according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram of estimated propagation path transfer characteristics based on a plurality of temporarily determined data symbols according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram of a receiving device for mobile communication according to an embodiment of the present invention.

FIG. 8 is an explanatory diagram of a multi-stage interference canceller.

FIG. 9 is an explanatory diagram of an interference replica generation unit and a receiver of the multi-stage interference canceller.

FIG. 10 is an explanatory diagram of a despreading unit of the interference replica generation unit of the multi-stage interference canceller incorporating the first embodiment of the present invention.

FIG. 11 is an explanatory diagram of a despreading unit of a receiver of the multi-stage interference canceller incorporating the first embodiment of the present invention.

FIG. 12 is an explanatory diagram of a data frame in which pilot symbols are interpolated.

FIG. 13 is an explanatory diagram of a receiving device including a conventional synchronous detection circuit using pilot symbols.

[Description of Signs] 100 Synchronous detection circuit 1 Timing synchronization circuit 2 First delay circuit 3 First propagation path estimation circuit using pilot symbols 4 First multiplier 5 First diversity synthesis circuit 6 Temporary decision circuit 7 Pilot symbol Second propagation path estimating circuit based on tentative decision data symbol 8 Second delay circuit 9 Second multiplier 10 Second diversity combining circuit 11 Final decision circuit 12 Decoder

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shugaku Kobayakawa 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Takeshi Ken Toda 4-chome, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture No. 1 in Fujitsu Limited

Claims (8)

[Claims] When receiving a data symbol in mobile communication, a propagation path transfer characteristic is estimated using a pilot symbol inserted in a data frame, and a received data symbol is estimated based on the estimated propagation path transfer characteristic based on the pilot symbol. The transmission path characteristics are estimated using the provisionally determined data symbols and the pilot symbols, and the final decision is made on the received data symbols based on the estimated transmission path characteristics using the provisionally determined data symbols and the pilot symbols. A synchronous detection method using a pilot symbol and a provisionally determined data symbol. 2. The pilot symbol and the tentatively-determined data symbol according to claim 1, wherein the tentatively-determined data symbol is repeated several times based on the estimated propagation path transfer characteristic of the tentatively-determined data symbol and the pilot symbol. Synchronous detection method using. 3. A method for determining a received data symbol sandwiched by two pilot symbols, the method comprising: determining a received data symbol based on a propagation path transfer characteristic estimated using a tentatively determined data symbol near the center of the two pilot symbols; 3. The synchronous detection method using pilot symbols and provisionally determined data symbols according to claim 1 or 2, wherein the determination is performed. 4. Estimation of propagation path transfer characteristics at a data symbol position sandwiched by two pilot symbols, wherein said two pilot symbols and a propagation path transfer estimated by a tentatively determined data symbol near the center of the two pilot symbols. A propagation path transmission characteristic at a data symbol position sandwiched between the two pilot symbols based on characteristics or propagation path transmission characteristics estimated from the two pilot symbols and a plurality of provisionally determined data symbols between the two pilot symbols. 3. The synchronous detection method using pilot symbols and provisionally determined data symbols according to claim 1 or 2, wherein 5. A first propagation path transfer characteristic estimating circuit for estimating a transfer path characteristic using a pilot symbol interpolated in a data frame, and a first estimation by the first propagation path transfer characteristic estimating circuit. A tentative determination circuit that performs a tentative determination of a received data symbol based on a propagation path transfer characteristic; By the second
And a final determination circuit for determining a received data symbol based on a second estimated propagation path transfer characteristic by the second propagation path transfer characteristic estimation circuit. Body communication receiver. 6. The mobile communication according to claim 5, wherein a plurality of provisional decision circuits for provisionally determining a data symbol based on an estimated propagation path transfer characteristic based on the provisionally determined data symbol and the pilot symbol are provided. For receiving device. 7. A first propagation path transfer characteristic estimating circuit for estimating a transfer path characteristic using a pilot symbol interpolated in a data frame, and a first estimation by the first propagation path transfer characteristic estimating circuit. A tentative decision circuit for tentatively determining a received data symbol based on a propagation path transfer characteristic, a pilot symbol and a tentative decision data symbol for estimating a propagation path transfer characteristic using the tentative decision data symbol and the pilot symbol by the tentative decision circuit By the second
And a final determination circuit that determines a received data symbol based on a second estimated propagation path transfer characteristic of the second propagation path transfer characteristic estimation circuit. Removal device. 8. The interference canceller according to claim 7, wherein a plurality of provisional decision circuits for provisionally determining a data symbol based on the estimated propagation path transfer characteristics of the provisionally determined data symbol and the pilot symbol are provided. .