JP2002290294A - Waveform equalizer, frequency offset compensation method, program, recording medium, mobile station wireless unit using the waveform equalizer, base station wireless unit, and mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waveform equalizer whose equalization is enhanced. SOLUTION: An equalization filter section 120 eliminates inter-code interference of a received signal, a code discriminator 109 forms a coordinate axis on the basis of an equalization signal y(k-1) resulting from delaying an equalization signal y(k) outputted from the equalization filter section 120 by one symbol an determines a signal point d(k) of a present symbol from a signal point object with a prescribed angle to the coordinate axis. Then an error calculation unit 112 generates a phase error signal ϕ(k) denoting a phase difference between the signal point d(k) of the present symbol and the equalization signal y(k) outputted from the equalization filter section 120, a phase error vector accumulator 114 accumulates the phase error vectors ϕ(k) to generate a phase error accumulated vector Φ, and a complex multiplier 105 applies complex arithmetic operation to the phase error accumulation vector Φ and an input signal 12 applied to the equalization filter section 120 to compensate a frequency offset included in the input signal 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform equalizer, a frequency offset compensating method, a program for executing the frequency offset compensating method, a recording medium on which the program is recorded, and a method for controlling the waveform equalizer and the like. Mobile station radio devices, base station radio devices such as mobile phones, car phones, and private digital radio communication phones used for removing the effects of selective fading, and mobile communications composed of these mobile station radio devices and base station radio devices The present invention relates to a system, and particularly to a waveform equalizer, a frequency offset compensation method, a program, a recording medium, a mobile station radio apparatus using a waveform equalizer, and a base station radio apparatus that have good equalization performance even when the frequency offset is large. And a mobile communication system.

[0002]

2. Description of the Related Art In a mobile communication system or the like, a phenomenon called a multipath in which a plurality of radio wave propagation paths exist between a base station radio apparatus and a mobile station radio apparatus is observed. Therefore, the received wave arrives via a plurality of propagation paths, and the received waves arriving from each propagation path arrive with a delay time peculiar to each propagation path. The amplitude and phase variations are not uniform for each frequency in the band, resulting in frequency selective fading. Due to the influence of the frequency selective fading, problems such as occurrence of intersymbol interference have occurred.

As a countermeasure, a waveform equalizer compensates for waveform distortion due to frequency-selective fading from a received wave to prevent deterioration of transmission errors. However, in a waveform equalizer, when a frequency offset exists between the frequency of a carrier included in a received signal and a local oscillation frequency of a frequency synthesizer included in a wireless device, a phenomenon in which a phase rotates at a high speed occurs, and waveform equalization occurs. Since the adaptive algorithm of the detector cannot follow the rotation speed of the phase and the equalization ability is deteriorated,
Methods for eliminating this effect have been conventionally studied. Here, a conventional waveform equalizer is disclosed in
The waveform equalizer disclosed in Japanese Patent Publication No. 91 will be described. FIG. 12 is a configuration diagram showing a conventional waveform equalizer.
In FIG. 1, a conventional waveform equalizer includes a feedforward filter 1201 and a feedback filter 120.
2, adders 1203 and 1210, coordinate converter 1204
1211, switch 1205, delay unit 1206, subtractor 1207, sign decision unit 1208, data demodulator 120
9. Equalization error calculator 1212 and tap coefficient updater 1
213 is provided.

Next, the operation of the conventional waveform equalizer will be described. First, sampled time-series input data as an input signal is input to the feedforward filter 1201. Output signals of the feedforward filter 1201 and the feedback filter 1202 are added at an adder 1203 for each sampling, and the adder 1
The estimated signal output from the first coordinate converter 1
204 is input. In the first coordinate converter 1204, the input IQ signal is converted into a polar coordinate system (r (amplitude) and θ
(Phase)).

Next, one output signal of the output signal of the first coordinate converter 1204 is input to the symbol delay unit 1206 via the selection switch 1205, and the other output signal is input to the adder 1207. The signal of the current symbol and the signal delayed by one symbol by the symbol delay unit 1206 are input to the adder 1207. As a result, the adder 12
From 06, the transition amount of the phase angle between one symbol is output. This phase transition angle is input to the sign determiner 1208,
The code determiner 1208 performs data code determination at a transition angle corresponding to the modulation scheme, and outputs an ideal phase transition angle and an ideal amplitude value. The data is demodulated by the data demodulator 1209 based on the ideal phase transition angle. Further, this phase transition angle is added to the signal delayed by one symbol in the adder 1210, and the second coordinate converter 121
1 is input. The second coordinate converter 1211 converts the input signal into a rectangular coordinate system. The converted IQ signal is
It is input to the feedback filter 1202 and the equalization error calculator 1212.

[0006] Then, a difference between the equalized signal and the determination signal is obtained by an equalization error calculator 1212, and tap coefficient update operations are performed by tap coefficient updaters 1213 and 1214 based on the difference information, and Forward filter 1201 and feedback filter 1202
Are updated.

As described above, in the conventional waveform equalizer, the phase angle one symbol before the estimated signal and the data decision unit 1 are determined.
Adder 1210 calculates the sum with the output signal of 208, converts it into a rectangular coordinate signal by coordinate converter 1211 and then uses it as an input signal of filters 1201 and 1202. The characteristic is followed to suppress an increase in the equalization error.

[0008]

However, in the above-mentioned conventional waveform equalizer, when the frequency offset exceeds a certain amount, the characteristics of the filter can follow the phase rotation caused by the frequency offset. Because you ca n’t
The equalization performance deteriorated, and another solution was needed.

[0009] The present invention has been made in view of the above-described conventional circumstances, and enables a waveform equalizer to have a wider pull-in range for a frequency offset.
An object of the present invention is to provide a waveform equalizer, a frequency offset compensation method, a program, a recording medium, a mobile station radio apparatus, a base station radio apparatus, and a mobile communication system using the waveform equalizer, which further improve the equalization performance. I do.

[0010]

According to another aspect of the present invention, there is provided a waveform equalizer comprising: an equalizing filter for removing intersymbol interference of a received signal; Code determining means for forming a coordinate axis based on an equalized signal obtained by delaying the equalized signal output from the means by one symbol, and determining a signal point of a current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis; Error calculating means for generating a phase error signal representing a phase difference between the signal point of the current symbol and the equalized signal output from the equalizing filter means, and cumulatively adding the phase error signal A phase error signal accumulating means for generating a signal, a complex operation for performing a complex operation on the phase error accumulative addition signal and an input signal input to the equalizing filter means, and compensating for a frequency offset included in the input signal. And has a means.

According to a second aspect of the present invention, there is provided a waveform equalizer including a tapping delay unit, an equalization filter unit for removing intersymbol interference of a received signal, and an equalization signal output from the equalization filter unit. Sign determining means for forming a coordinate axis based on the equalized signal delayed by one symbol, and determining a signal point of the current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis; Error calculating means for generating an equalization error signal representing a difference from the equalization signal output from the equalization filter means, and a tap coefficient for updating a tap coefficient of the tapped delay means based on the equalization error signal Update means.

A waveform equalizer according to a third aspect of the present invention includes an equalizing filter means for removing intersymbol interference of a received signal and a signal point candidate at a predetermined angle with respect to a fixed coordinate axis. Fixed code determining means for determining a signal point; error calculating means for generating a phase error signal representing a phase difference between the signal point of the current symbol and the equalized signal output from the equalizing filter means; Phase error signal accumulating means for accumulating and adding signals to generate a phase error accumulative addition signal, and performing a complex operation on the phase error accumulative addition signal and an input signal input to the equalization filter means, and including the input signal. And a complex operation means for compensating for the frequency offset.

According to a fourth aspect of the present invention, there is provided a waveform equalizer for equalizing filter means for removing inter-symbol interference of a received signal, and equalizing the equalized signal output from the equalizing filter means by delaying one symbol. Sign determining means for forming a coordinate axis based on a signal and determining a signal point of the current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis, and a signal point forming a predetermined angle with respect to the fixed coordinate axis Fixed sign determination means for determining the signal point of the current symbol from the candidate; and the signal point of the current symbol determined by the code determination means or the fixed code determination means and the equalized signal output from the equalization filter means. Error calculating means for generating a phase error signal representing a phase difference between the current symbol and a signal point of the current symbol by the code determining means until a predetermined time has elapsed after the input of the equalized signal. Switching means for determining the signal point of the current symbol by the fixed code determination means after a lapse of time; phase error signal accumulating means for accumulating the phase error signal to generate a phase error accumulative addition signal; A complex operation unit for performing a complex operation on the accumulated signal and the input signal input to the equalization filter unit, and compensating for a frequency offset included in the input signal.

According to a fifth aspect of the present invention, in the waveform equalizer according to the first, third, or fourth aspect, the phase error signal accumulating means includes an accumulative time for the phase error signal. Weighting is performed according to the weight.

According to a sixth aspect of the present invention, in the waveform equalizer of the first, third, fourth, or fifth aspect, the error calculating means calculates a quadrature component of the phase error cumulative addition signal. It is multiplied by n (n is a positive natural number).

According to a seventh aspect of the present invention, in the waveform equalizer according to the first, third, fourth, fifth, or sixth aspect, frequency conversion means for converting the frequency of the received signal into an intermediate frequency. And a frequency control unit that controls the frequency of a local oscillation signal to the frequency conversion unit so as to compensate for the frequency offset included in the input signal based on the frequency offset estimated from the phase error cumulative addition signal. It has more.

The waveform equalizer according to claim 8 is the waveform equalizer according to claim 1, 2, 3, 4, 5, 6, or 7, wherein the equalization filter means includes a forward equalizer. And a rear equalizer.

In the frequency offset compensating method according to a ninth aspect of the present invention, there is provided an equalizing filter step for removing intersymbol interference of a received signal, and an equalization delaying the equalized signal output from the equalizing filter step by one symbol. Forming a coordinate axis based on the signal, determining a signal point of the current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis, and outputting from the signal point of the current symbol and the equalization filter step An error calculating step of generating a phase error signal representing a phase difference from the equalized signal, a phase error signal accumulating step of accumulating the phase error signal to generate a phase error accumulative addition signal, and the phase error accumulating step. Complex operation for performing a complex operation on the addition signal and the input signal input to the equalization filter step and compensating for a frequency offset included in the input signal It is intended to and a step.

A frequency offset compensating method according to a tenth aspect includes a delay step with tap, an equalizing filter step for removing intersymbol interference of a received signal, and an equalized signal output from the equalizing filter step. Forming a coordinate axis based on the equalized signal delayed by one symbol, and determining a signal point of a current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis; An error calculation step of generating an equalization error signal representing a difference from the equalization signal output from the equalization filter step, and a tap coefficient for updating a tap coefficient of the tapped delay step based on the equalization error signal Update step.

Further, in the frequency offset compensating method according to the eleventh aspect, an equalizing filter step for removing intersymbol interference of a received signal, and a method for converting a current symbol from a signal point candidate forming a predetermined angle with respect to a fixed coordinate axis. A fixed code determination step of determining a signal point; an error calculation step of generating a phase error signal representing a phase difference between the signal point of the current symbol and the equalized signal output from the filter step; A phase error signal accumulating step of accumulatively adding to generate a phase error accumulative addition signal; and performing a complex operation on the phase error accumulative addition signal and an input signal input to the equalization filter step, and calculating a frequency included in the input signal. Complex operation step for compensating for the offset.

A frequency offset compensating method according to a twelfth aspect of the present invention provides an equalizing filter step for removing intersymbol interference of a received signal, and an equalization signal obtained by delaying the equalized signal output from the equalizing filter step by one symbol. A code determining step of forming a coordinate axis based on the signal and determining a signal point of the current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis; and a signal point forming a predetermined angle with respect to the fixed coordinate axis. A fixed code determination step of determining the signal point of the current symbol from the candidate, and the signal point of the current symbol determined by the code determination step or the fixed code determination step and the equalized signal output from the equalization filter step. An error calculating step of generating a phase error signal representing a phase difference between the signals; and A switching step of determining the signal point of the current symbol in the fixed step and determining the signal point of the current symbol in the fixed code determination step after the lapse of the predetermined time; and cumulatively adding the phase error signal to accumulate the phase error. Accumulating a phase error signal to generate a signal;
A complex operation of performing a complex operation on the phase error cumulative addition signal and an input signal input to the equalization filter step, and compensating for a frequency offset included in the input signal.

According to a thirteenth aspect of the present invention, in the frequency offset compensating method according to the ninth, eleventh or twelfth aspect, the phase error signal accumulating step includes accumulating the phase error accumulative addition signal. 9. The method according to claim 9, wherein weighting is performed according to time.
13. The frequency offset compensation method according to 1 or 12.

According to a fourteenth aspect of the present invention, in the frequency offset compensating method according to the ninth, eleventh, twelfth, or thirteenth aspect, the error calculating step includes calculating a quadrature component of the phase error cumulative addition signal. It is multiplied by n (n is a positive natural number).

According to a fifteenth aspect of the present invention, in the frequency offset compensating method according to the ninth, eleventh, twelfth, thirteenth, or fourteenth aspect, a frequency converting step of converting the frequency of the received signal into an intermediate frequency. And a frequency control step of controlling a frequency of a local oscillation signal to the frequency conversion step so as to compensate for a frequency offset included in the input signal based on the frequency offset estimated from the phase error cumulative addition signal. Have

According to another aspect of the present invention, there is provided a program for causing a computer to execute the program according to the ninth to tenth aspects.
It is a program for causing a computer to execute the frequency offset compensation method described in 12, 13, 14, or 15.

A computer-readable recording medium according to claim 17 is a computer-readable recording medium.
It is recorded as a program for causing a computer to execute the frequency offset compensation method described in 12, 13, 14 or 15.

A mobile station radio apparatus according to claim 18 is a waveform equalizer according to claim 1, 2, 3, 4, 5, 6, 7, or 8, a program according to claim 16, or The recording medium according to claim 17 is provided.

A base station radio apparatus according to claim 19 is a waveform equalizer according to claim 1, 2, 3, 4, 5, 6, 7 or 8, a program according to claim 16, or The recording medium according to claim 17 is provided.

A mobile communication system according to a twentieth aspect further comprises a waveform equalizer according to the first, second, third, fourth, fifth, sixth, seventh or eighth aspect, a program according to the sixteenth aspect, or A recording medium according to claim 17 is provided.

A waveform equalizer according to claim 1 of the present invention, a frequency offset compensation method according to claim 9, a program according to claim 16, a recording medium according to claim 17, and 18.
In the base station radio apparatus according to the first aspect, the mobile station radio apparatus according to the nineteenth aspect, and the mobile communication system according to the twentieth aspect, the intersymbol interference of the received signal is removed by the equalization filter means (equalization filter step). The determination unit (sign determination step) forms a coordinate axis based on the equalized signal delayed by one symbol from the equalized signal output from the equalization filter unit (equalization filter step), and forms a predetermined angle with respect to the coordinate axis. The signal point of the current symbol is determined from the signal point candidates forming Then, the error calculating means (error calculating step) generates a phase error signal representing a phase difference between the signal point of the current symbol and the equalized signal output from the equalizing filter means (equalizing filter step). The signal accumulation means (phase error signal accumulation step) accumulates and adds the phase error signals to generate a phase error accumulation addition signal, and the complex operation means (complex operation step) and the phase error accumulation addition signal and the equalization filter means ( The input signal input to the equalizing filter step) is subjected to a complex operation to compensate for a frequency offset included in the input signal.

In the conventional waveform equalizer, since the signal point of the current symbol is determined from signal point candidates forming a predetermined angle with respect to the fixed coordinate axis, the phase rotation due to the frequency offset of the signal point of the current symbol is performed. Although the amount is the accumulated phase rotation amount obtained by accumulating the phase rotation amount due to the frequency offset of the signal point of the symbol before the current symbol, the waveform equalizer of the present invention uses the sign judgment means (sign judgment step). Since the phase of the coordinate axis is rotated so as to compensate for the phase rotation amount due to the frequency offset of the signal point one symbol before, the phase rotation amount due to the frequency offset of the signal point of the current symbol becomes the symbol rotation amount before the signal point of the current symbol. Is reduced because the accumulated phase rotation amount due to the frequency offset of the signal point is compensated.

In the conventional waveform equalizer, when the frequency offset exceeds a predetermined amount, the phase rotation caused by the frequency offset increases, and the accumulated phase rotation is used. The signal phase rotates at high speed. As a result, the adaptive update algorithm of the equalization filter unit cannot follow the rotation speed of the phase of the received signal, and the equalization performance has deteriorated. On the other hand, in the waveform equalizer of the present invention, the phase rotation amount due to the frequency offset of the signal point of the symbol output from the code determination unit (code determination step) is compensated for by the accumulated phase rotation amount. Even if the frequency offset amount exceeds a predetermined amount, the phase of the received signal does not rotate at high speed. Therefore, an allowable frequency offset amount (hereinafter referred to as a frequency offset pull-in range) becomes large, and the adaptive algorithm can sufficiently follow the phase rotation speed, thereby improving the equalization performance of the waveform equalizer. Can be.

Here, the phase error accumulation addition signal output by the phase error signal accumulation means (phase error signal accumulation step) will be described with reference to the principle explanatory diagram shown in FIG.
The phase error cumulative addition signal is a phase output by the error calculating means (error calculating step) based on the phase difference between the signal point of the current symbol and the equalized signal output from the equalizing filter means (equalizing filter step). The error signal is obtained by accumulative addition. The phase error cumulative addition vector Φ (phase error cumulative addition signal), which is the result of the cumulative addition of the phase error signal, can be regarded as a frequency offset estimation vector as shown in FIG. Therefore, by performing complex operation on the phase error cumulative addition signal and the input signal input to the equalization filter unit (equalization filter step) by complex operation means (complex operation step), for example, By complexly multiplying the input signal by the complex conjugate vector, the amount of phase rotation due to the frequency offset included in the input signal can be compensated, so that the pull-in range for the frequency offset is further increased, and the adaptive algorithm is used to rotate the phase rotation. Since the speed can be sufficiently followed, the equalization performance of the waveform equalizer can be improved.

Further, since the amount of phase rotation due to the frequency offset can be reduced by the sign determining means (sign determining step) as described above, the phase error signal output from the error calculating means (error calculating step) is also relative. Become smaller. Therefore, the direction of the cumulative addition vector accumulated by the phase error accumulating means (phase error accumulating step) can be converged in a short time, and the equalization performance in the initial stage of the equalization can be improved.

Further, the waveform equalizer of the present invention is applied to either or both of the mobile station radio apparatus and the base station radio apparatus, and the apparatus is provided with either or both of the mobile station radio apparatus and the base station radio apparatus. In the mobile communication system configured as described above, the pull-in range for the frequency offset is increased, and the equalization performance can be improved, so that the reception performance can be improved for various propagation path conditions, and as a result, It is possible to construct a high-quality mobile communication system in which the influence of frequency selective fading is reliably removed. Further, since the system design constraint on the frequency offset amount is relaxed, the design of the mobile communication system can be facilitated.

Also, the waveform equalizer according to claim 2, the frequency offset compensation method according to claim 10, the program according to claim 16, the recording medium according to claim 17, and the claim 18
In the base station radio apparatus according to the first aspect, the mobile station radio apparatus according to the nineteenth aspect, and the mobile communication system according to the twentieth aspect, reception is performed by an equalization filter unit (equalization filter step) including a delay unit with a tap (delay step). The inter-symbol interference of the signal is removed, and the coordinate axis is formed by the code determination means (code determination step) based on the equalized signal output from the equalization filter means (equalization filter step) delayed by one symbol. Then, a signal point of the current symbol is determined from signal point candidates forming a predetermined angle with respect to the coordinate axis. Then, an error calculating means (error calculating step) generates an equalized error signal representing a difference between the signal point of the current symbol and the equalized signal output from the equalizing filter means (equalizing filter step). The updating means (tap coefficient updating step) updates the tap coefficient of the tapped delay means (delay step) based on the equalization error signal.

As described above, the coordinate axis is formed by the sign judging means (sign judging step) based on the equalized signal delayed by one symbol from the equalized signal output from the equalizing filter means (equalizing filter step). Since the signal point of the current symbol is determined from signal point candidates forming a predetermined angle with respect to the coordinate axis, the amount of phase rotation due to the frequency offset is reduced. Therefore, the equalization error signal output by the error calculating means (error calculating step) becomes relatively small, so that the tap coefficient updating speed in the tap coefficient updating means (tap coefficient updating step) increases, and the variation of the propagation path increases. Can be improved, and as a result, the performance of the waveform equalizer can be improved.

Sign determining means (sign determining step)
Accordingly, the phase of the coordinate axis is rotated so as to compensate for the phase rotation amount due to the frequency offset of the signal point one symbol before, so the phase rotation amount due to the frequency offset of the signal point of the current symbol is Since the accumulated phase rotation amount due to the frequency offset of the signal point of the symbol is compensated, the value is reduced. Therefore, even if the frequency offset amount in the received signal exceeds a predetermined amount, the phase of the received signal does not rotate at high speed. That is, the pull-in range for the frequency offset increases, and the adaptive algorithm can sufficiently follow the rotation speed of the phase, so that the equalization performance of the waveform equalizer can be improved.

Further, the waveform equalizer of the present invention is applied to one or both of a mobile station radio apparatus and a base station radio apparatus, and is provided with one or both of the mobile station radio apparatus and the base station radio apparatus. In the mobile communication system configured as described above, the pull-in range for the frequency offset is increased, the equalization performance can be improved, and the follow-up property to the fluctuation of the propagation path is improved. The performance can be improved, and as a result, a high quality mobile communication system in which the influence of frequency selective fading is removed can be constructed. Further, since the system design constraint on the frequency offset amount is relaxed, the design of the mobile communication system can be facilitated.

The waveform equalizer according to claim 3, the frequency offset compensation method according to claim 11, the program according to claim 16, the recording medium according to claim 17, and the claim 18.
In the base station radio apparatus according to the first aspect, the mobile station radio apparatus according to the nineteenth aspect, and the mobile communication system according to the twentieth aspect, the equalization filter means (equalization filter step) removes and fixes intersymbol interference of the received signal. The signal point of the current symbol is determined from the signal point candidates forming a predetermined angle with respect to the fixed coordinate axis by the code determination means (fixed code determination step), and the signal of the current symbol is determined by the error calculation means (error calculation step). A phase error signal representing a phase difference between the point and the equalized signal output from the equalization filter means (equalization filter step) is generated, and the phase error signal is accumulated by the phase error signal accumulation means (phase error signal accumulation step). Cumulative addition generates a phase error cumulative addition signal, and the complex error means (complex operation step) uses the phase error cumulative addition signal and the equalization filter means (equalization filter). An input signal input to the motor steps) and complex operation is to compensate the frequency offset included in the input signal.

As described above, the signal point of the current symbol is determined from the signal point candidates forming a predetermined angle with respect to the fixed coordinate axis by the fixed code determination means (fixed code determination step). The phase rotation amount reflecting the offset amount appears. Therefore, the phase error signal output by the error calculating means (error calculating step) also reflects the actual frequency offset amount, and the phase error signal accumulating means (phase error signal accumulating step) accumulates the phase error signals. You. Then, the accumulated phase error signal added from the phase error signal accumulating means (phase error signal accumulating step) can be regarded as a frequency offset estimation vector reflecting the actual frequency offset amount. Therefore, the complex operation means (complex operation step) performs a complex operation on the phase error cumulative addition signal and the input signal inputted to the equalization filter means (equalization filter step), thereby realizing the actual signal contained in the input signal. Can be compensated for the phase rotation amount reflecting the frequency offset amount of the above, so that the equalization performance of the waveform equalizer can be improved.

Further, the waveform equalizer of the present invention is applied to one or both of a mobile station radio apparatus and a base station radio apparatus, and is provided with one or both of the mobile station radio apparatus and the base station radio apparatus. In the mobile communication system configured as described above, the pull-in range for the frequency offset is increased, and the equalization performance can be improved, so that the reception performance can be improved for various propagation path conditions, and as a result, It is possible to construct a high-quality mobile communication system in which the influence of frequency selective fading is reliably removed. Further, since the system design constraint on the frequency offset amount is relaxed, the design of the mobile communication system can be facilitated.

Also, the waveform equalizer according to claim 4, the frequency offset compensation method according to claim 12, the program according to claim 16, the recording medium according to claim 17, and the claim 18.
In the base station radio apparatus according to the first aspect, the mobile station radio apparatus according to the nineteenth aspect, and the mobile communication system according to the twentieth aspect, the equalization filter means (equalization filter step) removes intersymbol interference of the received signal and performs switching. Means (switching step), the equalization signal output from the equalization filter means (equalization filter step) is input, and the equalization output from the equalization filter means (equalization filter step) until a predetermined time has elapsed. A coordinate axis is formed based on the equalized signal obtained by delaying the signal by one symbol, and the current symbol is determined by a code determination unit (code determination step) that determines a signal point of the current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis. After the lapse of the predetermined time, the signal point of the current symbol is determined from the signal point candidates forming a predetermined angle with respect to the fixed coordinate axis. Switch to the code decision unit (fixed code determining step) is determined a signal point of the current symbol. The signal point of the current symbol determined by the sign determining means (sign determining step) or the fixed sign determining means (fixed code determining step) is equalized by the error calculating means (error calculating step) with the equalizing filter means (equalizing filter step). )
A phase error signal representing a phase difference from the equalized signal output from the phase error signal is generated, and the phase error signal is cumulatively added by a phase error signal accumulating means (phase error signal accumulating step) to generate a phase error cumulative addition signal. Complex operation means (complex operation step) performs a complex operation on the phase error cumulative addition signal and the input signal input to the equalization filter means (equalization filter step) to compensate for a frequency offset included in the input signal. Like that.

As described above, the switching means (switching step) is performed until a predetermined time elapses after the input of the equalized signal output from the equalizing filter means (equalizing filter step).
When the signal point of the current symbol is determined by the code determination means (code determination step), the amount of phase rotation due to the frequency offset of the signal point of the symbol output by the code determination means (code determination step) is small. The phase error signal output by the means (error calculation step) also becomes relatively small. Therefore, the direction of the cumulative addition vector accumulated by the phase error accumulating means (phase error accumulating step) can be converged in a short time, and the equalization performance in the initial stage of the equalization can be improved. Further, since the amount of phase rotation due to the frequency offset is small, the pull-in range for the frequency offset increases.

When the operation is switched to the fixed code determination means (fixed code determination step) after the predetermined time has elapsed, the phase rotation amount reflecting the actual frequency offset amount appears. The phase error signal thus reflected also reflects the actual frequency offset amount, and the phase error cumulative addition signal from the phase error signal accumulating means (phase error signal accumulating step) estimates the frequency offset reflecting the actual frequency offset amount. It can be regarded as a vector. Since the phase error addition signal converges after a lapse of a predetermined time, the complex operation means (complex operation step) determines whether the phase error cumulative addition signal and the input signal input to the equalization filter means (equalization filter step) are equal to each other. Can be compensated for the phase rotation amount reflecting the actual frequency offset amount included in the input signal, so that the equalization performance of the waveform equalizer can be improved.

As a result, the pull-in range for the frequency offset can be increased, and furthermore, the deterioration of the equalization performance of the waveform equalizer due to the frequency offset can be prevented over the entire time zone from the beginning of the equalization. ,
And the equalization performance can be improved.

Further, the waveform equalizer of the present invention is applied to one or both of a mobile station radio apparatus and a base station radio apparatus, and is provided with one or both of the mobile station radio apparatus and the base station radio apparatus. According to the mobile communication system configured as described above, the pull-in range for the frequency offset is increased, and the equalization performance can be improved, so that the reception performance can be improved for various propagation path conditions. As a result, it is possible to construct a high-quality mobile communication system in which the influence of frequency selective fading is reliably removed. Further, since the system design constraint on the frequency offset amount is relaxed, the design of the mobile communication system can be facilitated.

Also, the waveform equalizer according to claim 5, the frequency offset compensation method according to claim 13, the program according to claim 16, the recording medium according to claim 17, and the claim 18.
In the base station radio apparatus according to the first aspect, the mobile station radio apparatus according to the nineteenth aspect, and the mobile communication system according to the twentieth aspect, the phase error signal accumulating means (phase error signal accumulating step) reduces the accumulated time with respect to the phase error signal. Weighting is performed in accordance with the weight.

As described above, the phase error signal accumulating means (phase error signal accumulating step) increases the reliability of the phase error signal with the lapse of the equalization time and the thermal noise with the lapse of the equalization time. By making use of the fact that the influence is reduced, the phase error signal is weighted in accordance with the accumulated time, thereby increasing the accuracy of the phase error accumulated addition signal. That is, the phase error cumulative addition signal can be regarded as a phase rotation amount due to a more actual frequency offset,
As a result, the equalization performance of the waveform equalizer can be improved.

Also, a waveform equalizer according to claim 6, a frequency offset compensation method according to claim 14, a program according to claim 16, a recording medium according to claim 17, and a recording medium according to claim 18.
In the base station radio apparatus according to the second aspect, the mobile station radio apparatus according to the nineteenth aspect, and the mobile communication system according to the twentieth aspect, the error calculating means (error calculating step) multiplies the quadrature component of the phase error cumulative addition signal by n times (n Is a positive natural number).

As described above, the sign judging means (sign judging step) performs the sign judging process by the switching means (switching step) until a predetermined time elapses, and after the elapse of the predetermined time, the fixed sign judging means (fixed sign judging means) When performing the sign determination process by switching to step (step), the quadrature component of the phase error cumulative addition signal is multiplied by n (n is a positive natural number) by the error calculation means (error calculation step). A phase error signal is cumulatively added based on the signal points obtained by the fixed sign determination means (fixed code determination step) from the phase error cumulative addition signal obtained by cumulatively adding the phase error signals based on the signal points obtained in step) It is possible to converge on the accumulated phase error added signal in a short time. That is, the phase error cumulative addition signal reflecting the actual frequency offset amount by the fixed code determining means (fixed code determining step) is converted from the phase error cumulative added signal having a fast convergence speed in the initial stage of equalization by the code determining means (sign determining step). Since the switching can be performed in a short time, the equalization performance can be improved.

The waveform equalizer according to claim 7, the frequency offset compensation method according to claim 15, the program according to claim 16, the recording medium according to claim 17, and the claim 18.
In the base station radio apparatus according to the first aspect, the mobile station radio apparatus according to the nineteenth aspect, and the mobile communication system according to the twentieth aspect, the frequency of the received signal is converted into the intermediate frequency by the frequency conversion means (frequency conversion step). The frequency control means (frequency control step) controls the frequency of the local oscillation signal used in the frequency conversion means (frequency conversion step) based on the frequency offset estimated from the phase error cumulative addition signal, so that the frequency is included in the input signal. Frequency offset is compensated.

As described above, the frequency of the local oscillation signal used for the frequency conversion means (frequency conversion step) is controlled by the frequency control means (frequency control step) based on the frequency offset estimated from the phase error cumulative addition signal. Thereby, the frequency offset included in the received signal can be compensated. As a result, the equalization performance of the waveform equalizer can be improved.

In the waveform equalizer according to the eighth aspect, it is desirable that the equalization filter means has a configuration including a front equalizer and a rear equalizer. As described above, by providing the equalizing filter means of the waveform equalizer with the forward equalizer and the backward equalizer, it is possible to cope with a severe fluctuation due to a function of time and place in the wireless transmission path. Can be.

[0055]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a waveform equalizer, a frequency offset compensating method, a program, a recording medium, a mobile station radio apparatus, a base station radio apparatus and a mobile communication system using a waveform equalizer according to the present invention will be described. Regarding the form, [First Embodiment], [Second Embodiment], [Modifications of First and Second Embodiments], [Third Embodiment], [Fourth Embodiment] This will be described in detail with reference to the drawings. In the description of each embodiment, the waveform equalizer and the frequency offset compensation method according to the present invention will be described in detail, and a mobile station radio apparatus, a base station radio apparatus, and a mobile communication system using the waveform equalizer will be referred to. However, the program according to the present invention is a program for executing the frequency offset compensation method, and the recording medium according to the present invention is a recording medium on which a program for executing the frequency offset compensation method is recorded. Therefore, the description is included in the following description of the frequency offset compensation method.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a configuration diagram illustrating a configuration of a waveform equalizer according to the embodiment. In FIG. 1, a waveform equalizer according to the present embodiment corresponds to a portion surrounded by a broken line, and includes a complex multiplier 105, a feedforward filter 106, and a feedback filter 10.
7, an adder 108, a sign decision unit 109, a symbol delay unit 110, a data demodulator 111, an equalization error calculator 112,
A tap coefficient updating unit 113 and a phase error vector accumulator 114 are provided.

The feedforward filter 106 and the feedback filter 107 may be configured to use hardware such as a delay circuit with a tap, or may be configured to be incorporated in a DSP (Digital Signal Processor). Is also possible. The feedforward filter 106 operates in such a manner that, in the impulse response of the wireless transmission path, the contribution of the delayed wave is higher when the arrival level of the delayed wave is higher than that of the preceding wave, and the delayed wave cancels the direct wave. On the other hand, the feedback filter 107 has a high contribution when the arrival level of the preceding wave is higher than that of the delayed wave, and the filter operates in such a manner that the direct wave cancels the delayed wave.

The adder 108 performs an addition operation on the output from the feed-forward filter 106 and the output from the feedback filter 107 to obtain an equalized output y (k).
Is output. Note that the feedforward filter 106, the feedback filter 107, and the adder 108 correspond to the equalization filter unit, and correspond to the equalization filter means recited in the claims. Further, the symbol delay unit 110 outputs the equalized output y output from the adder 108.
Equalized output y delayed by one symbol time with respect to (k)
(K-1).

The sign determiner 109 can realize its function by a program on a DSP, for example.
08 and the equalizer output y (k) and the adder 10
8 and the equalized output y (k-1) delayed by one symbol through the symbol delay unit 110,
An Ir-Qr plane is formed based on the equalized output y (k-1), and a signal point d () for demodulating the current symbol is determined by a phase transition angle between one symbol according to a modulation scheme on the Ir-Qr plane. k), which corresponds to the sign determination means in the claims.

The data demodulator 111 outputs a signal point d for demodulating the current symbol output from the code decision unit 109.
The transmission bit string is reproduced as demodulated data based on (k).

The equalization error calculator 112 represents the phase between the signal point d (k) for demodulation output from the sign determiner 109 and the equalized output y (k) output from the adder 108. Phase error vector φ (k) and sign decision unit 109
Signal point d (k) for demodulation output from
It calculates an equalization error vector e (k) representing a difference from the equalization output y (k) output from the device, and corresponds to an error calculation unit described in claims.

The tap coefficient updater 113 outputs the equalization error vector e output from the equalization error calculator 112.
Based on (k), the update amount of the tap coefficient is determined using various adaptive algorithms, and the feedforward filter 1
06 and the tap coefficient of the feedback filter, and corresponds to the tap coefficient updating means described in the claims. The adaptive algorithm used when determining the update amount of the tap coefficient based on the equalization error includes, for example, an adaptive algorithm such as a steepest descent method, an LMS algorithm, and an RLS algorithm.

Further, the phase error vector accumulator 114
The phase error vector φ (k) is cumulatively added to generate a phase error cumulative addition vector Φ, which corresponds to a phase error signal accumulating means described in claims.

The complex multiplier 105 performs a complex operation on the phase error cumulative addition vector Φ generated by the phase error vector accumulator 114 and the input signal input to the complex multiplier 105. It corresponds to the complex multiplication means in the range.

Furthermore, the root Nyquist filter limits the Nyquist band in order to reduce the occupied bandwidth of the modulated wave.

Next, the operation of the waveform equalizer of this embodiment will be described with reference to FIG. In the present embodiment, a π / 4 shift QPSK (Quadrature Pha
A description will be given of an example in which se shift keying is used.
First, the reception signal 11 received by the antenna is input to the mixer 101 and down-converted. The down-converted signal is input to the quadrature demodulator 102, and the quadrature demodulated IQ signal is output. This IQ signal is A
When input to the D converter 103, it is sampled,
It is converted from an analog IQ signal to a digitized IQ signal. The band of the digitized IQ signal is limited by the root Nyquist filter 104, and the band-limited IQ signal 12 is input to the complex multiplier 105.

In the complex multiplier 105, the input IQ signal 12 is complex-multiplied by a complex conjugate vector of a frequency offset amount estimation vector based on the phase error cumulative addition vector Φ generated by the phase error vector accumulator 114. , Are input to the feedforward filter 106 of the waveform equalizer. The convolution operation is performed in the feedforward filter 106, and the output signal is input to the adder 108. On the other hand, an output signal similarly obtained from the feedback filter 107 is also input to the adder 108, and the equalizer 108 outputs an equalized output y (k). Here, the equalized output y (k) is a complex number having an I component and a Q component.

Then, the equalized output y (k) of the current symbol and the equalized output y (k−1) delayed by one symbol time by the symbol delay unit 110 are input to the code decision unit 109. The sign determiner 109 forms a coordinate axis based on the equalized output y (k-1) delayed by one symbol time, and signal point candidates forming angles of ± π / 4 and ± 3π / 4 with respect to the coordinate axis. To the signal point d (k) for demodulation of the current symbol
Is output.

Here, the operation of the sign determination unit 109 will be described in more detail with reference to FIGS. First, the operation of a conventional code determiner (hereinafter, referred to as a fixed code determiner) in a π / 4 shift QPSK modulation / demodulation scheme will be described with reference to FIG. FIG. 2 is an explanatory diagram showing a conventional method for determining a signal point for demodulation of a fixed code determiner in a π / 4 shift QPSK modulation / demodulation system. In the figure, (a) shows four signal sets at a certain time, and (b) shows four signal sets at the next time. Each of the four asterisks in FIGS. 2A and 2B is a candidate position of a signal point d (k) for demodulation, and one of them is output from the code determiner 109.

As shown in FIG. 2, the signal point d (k) for demodulating the current symbol is fixedly allocated in the IQ plane. For example, on the IQ plane, at a certain time, any one of the four symbols in FIG.
At the next time, one of the four symbols in FIG. 2B is received and demodulated. That is, the combination of FIGS. 2A and 2B is used alternately for each symbol.

Next, with reference to FIG. 3, the operation of the code determiner 109 of the present embodiment will be described. FIG. 3 is an explanatory diagram showing a method for determining a signal point for demodulation by the code determiner. First, 1
When the equalized output y (k-1) before the symbol time is received,
The direction of the equalized output y (k-1) one symbol time before is defined as a new I axis (Ir axis), and a direction forming 90 degrees with the direction is defined as a new Q axis (Qr axis). (See the broken line in FIG. 3). And ± π with respect to this Ir axis.
/ 4 and ± 3π / 4 are defined as candidate positions of the signal point d (k) for demodulation of the current symbol (4 in FIG.
Candidate positions closest to the received equalized output y (k) as signal points d for demodulating the current symbol.
(K) (black star in FIG. 3).

Here, a description will be given of a calculation example of the method of determining the signal point for demodulation by the code decision unit 109. First, as described above, the code determiner 109 forms an Ir-Qr plane based on the equalized output y (k-1) one symbol time earlier. Then, on the Ir-Qr surface, the following step 1) and step 2) (2a) to 2d) are executed. Step 1) Phase transition vector z (k) = y (k) · y
^* Calculate (k-1). (However, y ^* (k-1) is y
It is a conjugate complex number of (k-1). Step 2a) When the real part of z (k) is positive and the imaginary part is positive,
d (k) = (y (k-1) / | y (k-1) |) exp
[jπ / 4]. End. Step 2b) When the real part of z (k) is negative and the imaginary part is positive,
d (k) = (y (k-1) / | y (k-1) |) exp
[j3π / 4]. End. Step 2c) When the real part of z (k) is negative and the imaginary part is negative,
d (k) = (y (k-1) / | y (k-1) |) exp
[j (-3π / 4)]. End. Step 2d) When the real part of z (k) is positive and the imaginary part is negative,
d (k) = (y (k-1) / | y (k-1) |) exp
[j (-π / 4)]. End. Although the input data and the calculation result are always in the orthogonal coordinate system, coordinate conversion may be performed when necessary during the calculation.

Next, referring again to FIG.
09 for demodulating the current symbol output from the signal point d
(K) is input to the data demodulator 111, the feedback filter 107, and the error calculator 112. In the data demodulator 111, a signal point d for demodulating the current symbol
When (k) is input, a transmission bit string is reproduced as demodulated data. Further, in the equalization error calculator 112, the signal point d (k) for demodulating the current symbol output from the code determiner 109 and the equalization output y output from the adder 108 are output.
(K) is input.

In the equalization error calculator 112, the equalization output y
(K) and the equalization error e (k) representing the difference between the current symbol demodulation signal point d (k) and the equalization output y (k) and the current symbol demodulation signal point d (k). And a phase error vector φ (k) representing the phase difference between Then, the equalization error calculation equalization error e (k) is input to the tap coefficient updater 113, and the phase error vector φ (k) is input to the phase error vector accumulator 114.

Here, the equalization error e (k) and the phase error vector φ (k) calculated by the equalization error calculator 112 will be described with reference to FIG. FIG. 4 shows an equalization error e (k).
FIG. 4 is an explanatory diagram showing a phase error vector φ (k).
In the figure, the equalization error e (k) indicates the difference between the signal point d (k) and the equalization output y (k). If the angle formed by the equalized output y (k) and the signal point d (k) for demodulation is Δθ (k), the phase error vector φ (k) is represented by Expression (1).

Φ (k) = | y (k) | exp [jΔθ (k)] (1)

In equation (1), the phase error vector φ
By (k), the frequency offset amount per symbol time can be estimated. The phase error vector φ (k) may be only exp [jΔθ (k)], but | y (k) |
Is small, the reliability of exp [jΔθ (k)] is low. Therefore, by multiplying this by | y (k) |, the contribution of the phase error vector to the accumulated value is increased.

Next, referring again to FIG. 1, the tap coefficient updating unit 113 calculates a tap coefficient based on the equalization error e (k) so that the next symbol can be satisfactorily equalized. As a result, the tap coefficients of the feedforward filter 106 and the feedback filter 107 are updated. Further, the phase error vector accumulator 11
In step 4, the phase error vector φ (k) is cumulatively added to generate a phase error cumulative addition vector Φ.

Here, the frequency offset will be described in detail with reference to FIG. FIG. 5A shows a π / 4 shift Q
This is a transmission symbol sequence according to the PSK modulation method, and (b) is a reception symbol sequence according to the π / 4 shift QPSK demodulation method. Here, assuming that the symbol rate of the signal is fs [Hz] and the frequency offset is foff [Hz], the phase rotation amount per symbol due to the frequency offset Ψ [rad].
Can be expressed as in equation (2).

Ψ = 2π * foff / fs (2)

Therefore, the symbol sequence of the transmission signal is s
(N), when a symbol sequence as shown in FIG. 5A is transmitted, since the frequency offset amount is foff [Hz], as shown in FIG.
_i (n) (corresponding to ○ in the figure) is the amount of phase rotation Ψ [ra
Due to d], a received symbol sequence whose phase is rotated by {, 2}, 3},... with respect to the transmitted symbol sequence (corresponding to ● in the figure) is received. At this time, the transmission path is an ideal transmission path without any fading, and it is assumed that there is no thermal noise in the receiver.

Next, referring again to FIG. 1, phase error cumulative addition vector Φ output from phase error vector accumulator 114 can be regarded as an estimated vector of the frequency offset amount. Therefore, the complex multiplier 105 performs an operation to cancel the frequency offset by performing a complex multiplication of the complex conjugate vector of the phase error cumulative addition vector Φ and the input signal 12. Here, the phase error cumulative addition vector Φ will be described with reference to FIG. 6 for reference. FIG. 6 is a principle explanatory diagram for explaining the phase error cumulative addition vector Φ in principle. In the figure, the phase error cumulative addition vector Φ is obtained by cumulatively adding the phase error vector φ (k), and can be regarded as an estimated vector of the frequency offset amount. The phase Θ is a phase rotation amount (estimated value) per symbol due to the frequency offset.

Next, an example of a specific calculation process in the complex multiplier 105 will be described. The phase error cumulative addition vector Φ of the phase error vector up to a certain reception slot is represented by Expression (3).

Φ = {φ (k) = Y exp [j}] (3)

When the sample sequence r _i (n) of the output signal of the root Nyquist filter 104 in the next reception slot is given by the following equation (4):

R _i (n) = I (n) + jQ (n) (4)

In the complex multiplier 105, the operation shown in the equation (5) is performed, and an output r _o (n) is obtained.

R _o (n) = r _i (n) exp [−j (nΘ / N)] (5)

Note that N is the number of oversampling of the received signal. Here, the oversampling number N will be described with reference to FIGS. First, N = 1
(No oversampling) will be described.

In FIG. 6, when Θ = Ψ, r _i (n) is phase-rotated in the direction opposite to the phase rotation direction due to the frequency offset by the calculation of equation (5), and r _o (n)
Is obtained. Therefore, r _o (n) is equal to s in FIG.
(N). That is, r _o (n) = s (n)
Therefore, the frequency offset is compensated. But,
In practice, due to various effects such as fluctuations in the propagation path, r
_{Since o} (n) = s (n) does not hold, this is repeated to follow the change in the frequency offset.

For reference, FIG. 7 shows a transmission data sequence and a reception data sequence oversampled at four times the symbol rate.

As described above, in the waveform equalizer in the present embodiment, the intersymbol interference of the received signal is removed by the equalization filter unit 120, and the signal output from the equalization filter unit 120 is output by the code determination unit 109. The equalized signal y (k) is set to 1
A coordinate axis (Ir-Qr axis) is formed based on the symbol-delayed equalized signal y (k-1), and a signal point d (k) of the current symbol is calculated from signal point candidates forming a predetermined angle with respect to the coordinate axis.
To determine. Then, the error calculator 112 generates a phase error signal φ (k) representing the phase difference between the signal point d (k) of the current symbol and the equalized signal y (k) output from the equalization filter unit 120. , The phase error vector accumulator 114 accumulates the phase error vector φ (k) to generate a phase error cumulative addition vector Φ, and the complex multiplier 105 generates the phase error cumulative addition vector Φ and the equalization filter unit 12.
A complex operation is performed on the input signal 12 input to 0 and the frequency offset included in the input signal 12 is compensated.

In the conventional waveform equalizer, the signal point d (k) of the current symbol is determined from the signal point candidates forming a predetermined angle with respect to the fixed coordinate axes (I-Q axes). The amount of phase rotation due to the frequency offset of the signal point d (k) of the symbol is determined by the signal point d (k) of the symbol before the current symbol.
Although the phase rotation amount due to the frequency offset of -1) is the accumulated phase rotation amount, the waveform equalizer according to the present embodiment uses the sign determination unit 109 to output the signal point d (k−1 ), The phase of the coordinate axis (Ir-Qr axis) is rotated so as to compensate for the phase rotation amount due to the frequency offset. Therefore, the phase rotation amount due to the frequency offset of the signal point d (k) of the current symbol is equal to the signal point of the current symbol. Is reduced because the accumulated phase rotation amount due to the frequency offset of the signal point d (k-1) of the symbol before the symbol is compensated.

In the conventional waveform equalizer, when the frequency offset exceeds a predetermined amount, the phase rotation due to the frequency offset increases, and the accumulated phase rotation is used. The signal phase rotates at high speed. As a result, the adaptive update algorithm of the equalization filter unit cannot follow the rotation speed of the phase of the received signal, and the equalization performance has deteriorated. On the other hand, in the waveform equalizer according to the present embodiment, the phase rotation amount due to the frequency offset of the signal point d (k) of the symbol output from the code determiner 109 is compensated for the accumulated phase rotation amount. Even if the frequency offset exceeds a predetermined amount, the phase of the received signal does not rotate at high speed. Therefore, an allowable frequency offset amount (hereinafter referred to as a frequency offset pull-in range) becomes large, and the adaptive algorithm can sufficiently follow the phase rotation speed, thereby improving the equalization performance of the waveform equalizer. Can be.

Since the phase error cumulative addition vector Φ (phase error cumulative addition signal) can be regarded as a frequency offset estimation vector, the complex multiplier 105 converts the conjugate complex vector of the phase error cumulative addition vector By complexly multiplying the signal 12, the phase rotation amount due to the frequency offset included in the input signal 12 can be compensated, so that the pull-in range for the frequency offset is further increased, and the adaptive algorithm sufficiently follows the phase rotation speed. Therefore, the equalization performance of the waveform equalizer can be improved.

Further, since the amount of phase rotation due to the frequency offset is reduced by the sign determiner 109, the phase error vector φ (k) output from the error calculator 112 is relatively reduced. Therefore, the direction of the phase error cumulative addition vector Φ generated by the phase error vector accumulator 114 can be converged in a short time, and the equalization performance in the initial stage of equalization can be improved.

In the waveform equalizer according to the present embodiment, the sign deciding unit 109 delays the equalized signal y (k) output from the equalizing filter unit 120 by one symbol and outputs an equalized signal y (k−1). ) Based on the coordinate axis (Ir-Qr axis)
Is formed, and the signal point d (k) of the current symbol is determined from the signal point candidates forming a predetermined angle with respect to the coordinate axis, and the signal point d (k) of the current symbol and the equalization filter are determined by the error calculator 112. An equalization error signal e (k) representing a difference from the equalization signal y (k) output from the unit 120 is generated, and a tap coefficient updating unit 113 generates a tap coefficient based on the equalization error signal e (k). Is to be updated.

As described above, the sign judging unit 109 uses the coordinate axis (Ir-I) based on the equalized signal y (k-1) obtained by delaying the equalized signal y (k) output from the equalizing filter unit 120 by one symbol. Qr), and the signal point d (k) of the current symbol is calculated from the signal point candidates forming a predetermined angle with respect to the coordinate axis.
Is determined, the amount of phase rotation due to the frequency offset is reduced. Therefore, the equalization error vector e (k) output from the error calculator 112 becomes relatively small.
The update speed of the tap coefficient in the tap coefficient update unit 113 is increased, and the followability to the fluctuation of the propagation path can be improved. As a result, the performance of the waveform equalizer can be improved.

Further, according to the sign determination unit 109, the phase of the coordinate axis (Ir-Qr axis) is rotated so as to compensate the phase rotation amount due to the frequency offset of the signal point d (k-1) one symbol before. Since the amount of phase rotation by the frequency offset of the signal point d (k) of the current symbol is compensated for by the amount of accumulated phase rotation by the frequency offset of the signal point d (k-1) of the symbol before the signal point of the current symbol. Become smaller. Therefore, even if the frequency offset amount in the input signal 12 exceeds a predetermined amount, the phase of the input signal 12 does not rotate at high speed. That is, the pull-in range for the frequency offset increases, and the adaptive algorithm can sufficiently follow the rotation speed of the phase, so that the equalization performance of the waveform equalizer can be improved.

Further, a sign judging unit 109 is a fixed sign judging unit that determines a signal point d (k) of the current symbol from signal point candidates forming a predetermined angle with respect to a fixed coordinate axis (I-Q axis). Even if there is, the equalization filter unit 120 removes intersymbol interference of the received signal, and the fixed code determiner determines the signal point of the current symbol from signal point candidates forming a predetermined angle with respect to the fixed coordinate axis. The error calculator 112 calculates the signal point d (k) of the current symbol and the equalization filter unit 12.
A phase error vector e (k) representing a phase difference from the equalized signal y (k) output from 0 is generated, a phase error vector accumulator 114 generates a phase error cumulative addition vector Φ, and a complex multiplier 105, the phase error cumulative addition vector Φ and the input signal 1 input to the equalization filter unit 120
2 is subjected to a complex operation to compensate for the frequency offset included in the input signal 12.

As described above, since the fixed sign determiner determines the signal point d (k) of the current symbol from the signal point candidates forming a predetermined angle with respect to the fixed coordinate axis (I-Q axis). , A phase rotation amount reflecting the actual frequency offset amount appears. Therefore, the phase error vector φ (k) output from the error calculator 112 also reflects the actual frequency offset amount, and the phase error vector accumulator 114
In, the phase error vector φ (k) is cumulatively added. The phase error cumulative addition vector Φ output from the phase error vector accumulator 114 can be regarded as a frequency offset estimation vector reflecting the actual frequency offset amount. Therefore, by the complex multiplier 105,
By performing complex multiplication of the complex conjugate vector of the phase error cumulative addition vector Φ and the input signal 12 input to the equalization filter unit 120, the phase rotation amount reflecting the actual frequency offset amount included in the input signal 12 Can be compensated, so that the equalization performance of the waveform equalizer can be improved.

[Second Embodiment] Next, a waveform equalizer according to a second embodiment of the present invention will be described. In the second embodiment, a demodulation signal point d is added to the configuration of the first embodiment.
A fixed code determiner that allocates (k) fixedly to the IQ plane is added, and the control unit switches between the code determiner and the fixed determiner. With reference to FIG. 8, the waveform equalizer of the present embodiment will be described. FIG. 8 is a configuration diagram showing a code determination unit that includes a code determination unit and a fixed code determination unit and can be switched by a switch.

In FIG. 8, a code determining unit 800 includes a code determining unit 801, a fixed code determining unit 802, and a control unit 803 a.
And switches sw1a and sw1b. First, the code determiner 801 forms an Ir-Qr surface based on the equalized output y (k-1) one symbol before, and
Signal point d for demodulating the current symbol with reference to the r-Qr plane
(K) is determined, and has the same function and operation as the sign determination unit 109 described in the first embodiment, and thus detailed description will be omitted.

The fixed code decision unit 802 converts the signal point d (k) for demodulating the current symbol from a signal point candidate at a predetermined angle with respect to the fixed IQ axis for demodulating the current symbol. To determine the signal point d (k). For example,
In the π / 4 shift QPSK, on the fixed IQ plane, a candidate closest to the equalized output y (k) is used for each symbol from the symbol set shown in FIGS. The position is determined to be a signal point d (k) for demodulation of the current symbol.

Further, the control unit 803a sends the fixed sign decision unit 802 from the sign decision unit 801 after a lapse of a predetermined time from the input of the equalized output y (k) from the equalization filter unit 120.
Switch signal CNT to switch s
w1a and sw1b. Here, the control unit 803a may be configured by hardware such as a counter for counting a predetermined number of reception slots or a delay circuit having a delay of a predetermined time, or may be switched by software based on a timer or the like in a DSP or MPU. The signal CNT may be generated. Further, the switches sw1a and sw1b switch between the code determiner 801 and the fixed code determiner 802 based on the switching signal CNT from the controller 803a.

Referring to FIG. 6 and equation (3), Θ represents the amount of phase rotation (scalar amount) per symbol time due to the frequency offset, but Θ is smaller than the actual frequency offset amount. This is the amount of phase rotation.
This is because, in the code decision unit 109 shown in FIG. 1, the demodulation signal point d (k) of the equalized output of the current symbol is not fixedly assigned to the IQ plane. This is because the Ir-Qr plane is formed based on the equalized output y (k-1) one symbol before.

Therefore, the phase error cumulative addition vector Φ
The convergence of the direction of the (estimated vector of the frequency offset amount) is fast because the signal point d (k) for demodulation of the current symbol rotates in phase with the frequency offset, but the direction of the converged phase error cumulative addition vector Φ is actually Since the direction becomes a direction corresponding to the smaller frequency offset amount, error bits are likely to be constantly generated even after the convergence of the phase error cumulative addition vector Φ. Therefore, the waveform equalizer of the present embodiment includes the control unit 8
03a, the code determiner 801 and the fixed code determiner 80
2 to improve the equalization performance over the entire time period from the beginning of the equalization.

Next, referring to FIG.
The operation for switching from to the fixed code determiner 802 will be described. Until a predetermined time from the input of the equalized output y (k) from the equalization filter unit 120, the code determination unit 801 performs a code determination process. , Sw1b
Is operated to switch from the code determiner 801 to the fixed determiner 802, and the fixed code determiner 802 performs a code determination process. At this time, the phase error vector accumulator 114 sequentially accumulates the input phase error vectors φ (k) irrespective of the difference between the two code determiners 801 and 802.

Next, with reference to FIG. 9, the features of the present embodiment will be described by describing changes in the phase error cumulative addition vector due to switching of the code determiner of the present embodiment. FIG. 9A is an explanatory diagram showing a phase error cumulative addition vector when the code discriminator 801 is used and a phase error cumulative addition vector when the fixed sign discriminator 802 is used, and FIG. FIG. 10 is an explanatory diagram showing a phase error cumulative addition vector when switching from the code determiner 801 to the fixed code determiner 802 after a lapse of time. It should be noted that the phase error cumulative addition vector shown in the figure is data obtained under fast Doppler fading conditions, but the same applies under slow Doppler fading conditions.

Referring to FIG. 9A, plot プ ロ ッ ト is
14 shows a phase error cumulative addition vector when the sign determiner 801 is used. Looking at the plot ○, it can be seen that the direction of the phase error cumulative addition vector is determined (converged) in a relatively short time from the start of the equalization processing. Sign decision unit 8
01, the signal point for demodulation of the current symbol is phase-rotated together with the frequency offset, so that the frequency offset amount may appear smaller than the actual value. Therefore, the phase error accumulation addition vector (frequency offset The convergence of the direction of the quantity estimation vector) is fast.

However, since the direction of the converged phase error cumulative addition vector does not correspond to the actual frequency offset (smaller than the actual frequency offset amount) in the sign determination unit 801, the locus of the plot ○ indicates the actual offset. It is smaller than the slope corresponding to the amount.

On the other hand, the plot △ indicates the fixed sign
2 shows a phase error cumulative addition vector when the number 2 is used. The slope of the plot 傾 き has a variation in the initial stage of the equalization process compared to the plot ○. However, once the slope is determined, the slope well reflects the actual frequency offset.

That is, in the sign determinator 802, the convergence of the direction of the accumulated phase error vector in the phase error vector accumulator 114 is slow, but the direction of the accumulated vector of the converged phase error vector depends on the actual frequency offset amount. It reflects well, and the equalization performance after convergence is stabilized.

Therefore, the waveform equalizer of the present embodiment utilizes the advantage of the time zone in which each of the sign determiner 801 and the fixed sign determiner 802 is superior.
As shown by the plot □ in (b), immediately after the start of equalization, the sign determinator 801 in which the convergence of the phase error cumulative addition vector is fast.
Is used, the equalization performance in the initial stage of the equalization processing is improved, and after a predetermined time has elapsed and the phase error cumulative addition vector has converged, the fixed code decision unit 802 having better equalization performance is used. Switching.

Further, in the waveform equalizer of the present embodiment, after a predetermined time has passed, the sign decision unit 801 switches from the fixed sign decision unit 80
However, at the timing when the sign decision unit 801 is switched to the fixed sign decision unit 802, only the Q component may be multiplied with respect to the cumulative addition vector of the phase error vector.

The plot x in FIG. 9B is a phase error cumulative addition vector when the orthogonal component of the phase error cumulative addition vector is multiplied at a certain timing. In the figure, a plot □ is a phase error cumulative addition vector when the orthogonal component is not multiplied, and a plot X is a phase error cumulative addition vector when the orthogonal component of the phase error cumulative addition vector is multiplied. In the figure, the plot x is
It can be seen that the vehicle is riding on the line (plot に お け る in FIG. 9A) by the fixed code determiner 802 faster than the plot □. In other words, by multiplying the orthogonal component,
It is possible to quickly converge to the value of the phase error cumulative addition vector expected by the fixed sign determiner 802.

As described above, according to the waveform equalizer of this embodiment, the intersymbol interference of the received signal is removed by the equalizing filter unit 120, and the equalization is performed by the control unit 803a and the switches sw1a and sw1b. Filter unit 12
Until a predetermined time elapses after the equalized signal y (k) output from 0 is input, the equalized signal output from the equalizing filter unit 120 is delayed based on the equalized signal y (k−1) by one symbol. To form a coordinate axis (Ir-Qr axis), and determine a signal point d (k) of the current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis. k), and after a lapse of the predetermined time, a fixed code determination for determining a signal point d (k) of the current symbol from signal point candidates forming a predetermined angle with respect to a fixed coordinate axis (I-Q axis). Switch 802 to determine the signal point d (k) of the current symbol. And the error calculator 11
2, the code determiner 801 or the fixed code determination 802
Generates a phase error vector φ (k) representing a phase difference between the signal point d (k) of the current symbol determined by the above equation and the equalized signal y (k) output from the equalization filter unit 120, By the accumulator, the phase error vector φ (k)
Is cumulatively added to generate a phase error cumulative addition vector Φ,
By the complex multiplier 105, the phase error cumulative addition vector Φ
And the input signal 12 input to the equalization filter unit 120 by complex multiplication to compensate for the frequency offset included in the input signal.

As described above, the control unit 803a and the switch sw1 are kept until a predetermined time elapses after the equalization signal y (k) output from the equalization filter unit 120 is input.
When the signal point d (k) of the current symbol is determined by the code determiner 801 based on a and sw1b, the code determiner 801
Since the amount of phase rotation due to the frequency offset of the signal point d (k) of the symbol output from is small, the error calculator 11
2, the phase error vector φ (k) also becomes relatively small. Therefore, the phase error vector accumulator 114
Can converge in a short time the direction of the accumulated phase error cumulative addition vector Φ, and the equalization performance in the initial stage of equalization can be improved. Further, since the amount of phase rotation due to the frequency offset is small, the pull-in range for the frequency offset increases.

When the operation is switched to the fixed code decision unit 802 after the lapse of the predetermined time, a phase rotation amount reflecting the actual frequency offset amount appears, so that the phase error vector φ (k) output from the error calculator 112 is output. Also reflects the actual frequency offset amount, and the phase error cumulative addition vector Φ from the phase error vector accumulator 114
Can be regarded as a frequency offset estimation vector reflecting the actual frequency offset amount. After a lapse of a predetermined time, the accumulated phase error addition vector Φ converges. Therefore, the complex multiplier 105 converts the complex conjugate of the accumulated phase error addition vector Φ and the input signal 12 input to the equalization filter unit 120 into a complex signal. By multiplying, the phase rotation amount reflecting the actual frequency offset amount included in the input signal 12 can be compensated, so that the equalization performance of the waveform equalizer can be improved.

As a result of the above, it is possible to widen the pull-in range for the frequency offset and to prevent the deterioration of the equalization performance of the waveform equalizer due to the frequency offset from the beginning of the equalization over the entire time zone. ,
And the equalization performance can be improved.

In the waveform equalizer of this embodiment, the error calculator 112 multiplies the orthogonal component of the accumulated phase error addition vector Φ (k).
From the phase error cumulative addition vector Φ obtained by cumulatively adding the phase error vector φ (k) based on the demodulation signal point d (k) obtained in step 1 phase error vector φ (k) based on d (k)
Can be converged in a short time to a phase error cumulative addition vector Φ obtained by cumulatively adding That is, the sign determination unit 80
Since the phase error cumulative addition vector Φ having a high convergence speed at the initial stage of equalization by 1 can be switched in a short time to the phase error cumulative addition vector Φ reflecting the actual frequency offset amount by the fixed sign determiner 802, the equalization can be performed. Performance can be improved.

[Modifications of First and Second Embodiments] Next, modifications of the first and second embodiments will be described. As shown in FIGS. 1 and 8,
The configuration is the same as that of the first and second embodiments. However, in the phase error vector accumulators 114 of the first and second embodiments, the phase error vector is simply added irrespective of the equalization time. However, in this modification, the phase error vector φ (k) is Weighting according to the accumulated time. For this reason, the reliability of the phase error vector increases according to the equalization time, so that the phase error vector reflects the actual frequency offset amount, and as a result, the equalization performance improves.

Further, the phase error vector accumulator 114 performs weighting according to the equalization time and performs addition, so that the longer the equalization time, the greater the influence of thermal noise.
(K), that is, the effect of thermal noise is reduced, so that the reliability of the phase error vector is increased, and as a result, the equalization performance is improved.

As described above, in the waveform equalizer of this embodiment, the phase error vector accumulator 114 increases the reliability of the phase error vector φ (k) as the equalization time elapses, and the equalization. Using the fact that the influence of thermal noise is reduced with the passage of time, the phase error vector φ (k)
Is weighted according to the accumulated time,
The accuracy of the phase error cumulative addition vector Φ becomes higher. That is, since the phase error cumulative addition vector Φ can be regarded as a phase rotation amount due to a more actual frequency offset,
The equalization performance of the waveform equalizer can be improved.

[Third Embodiment] Next, a waveform equalizer according to a third embodiment of the present invention will be described. The waveform equalizer of the present embodiment has a configuration in which a frequency synthesizer and a control unit are added to the configurations of the first and second embodiments (see FIGS. 1 and 8). FIG. 10 is a configuration diagram showing the waveform equalizer of the present embodiment. In the figure,
1 are denoted by the same reference numerals and description thereof is omitted.

The control section 803b estimates the frequency offset amount from the phase error cumulative addition vector Φ output from the phase error vector accumulator 114, and controls the local oscillation generated by the frequency synthesizer 1000 to compensate for the frequency offset amount. It controls the frequency of the signal, and corresponds to the frequency control means described in the claims.
Further, the frequency synthesizer 1000 includes a control unit 803b.
A local oscillation signal having a frequency corresponding to the control signal from the controller 101 is generated and supplied to the mixer unit 101. The mixer unit 101 converts the frequency of a received signal into an intermediate frequency, and corresponds to a frequency conversion unit described in the claims.

Next, the operation of the waveform equalizer of this embodiment will be described with reference to FIG. First, the phase error cumulative addition vector Φ output from the phase error vector accumulator 114
Is input to the control unit 803b. Then, the control unit 80
3b estimates the frequency offset amount from the phase error cumulative addition vector Φ, and controls the frequency of the local oscillation signal generated by the frequency synthesizer 1000 so as to compensate for the frequency offset amount.

Here, a method of estimating the frequency offset amount from the phase error cumulative addition vector Φ will be described with reference to FIG. Since the phase error accumulated vector Φ is generated by the phase error vector accumulator 114, the phase Θ can be obtained. As described in the first embodiment, in equation (2), the symbol rate of the signal is fs
[Hz] and the frequency offset as foff [Hz], the phase rotation amount per symbol due to the frequency offset Ψ
[rad] is Ψ = 2π * foff / fs.

As shown in FIG. 6, when the phase error cumulative addition vector Φ is estimated, the amount of phase rotation per symbol due to the frequency offset is estimated to be Θ [rad]. The estimated amount of the frequency offset est-foff [Hz] can be obtained by Expression (6).

Est-foff = Θ * fs / 2π (6)

As described above, the frequency of the local oscillation signal generated by frequency synthesizer 1000 is controlled so as to compensate for the frequency offset amount estimated by control section 803b. Then, by inputting a local oscillation signal having a controlled frequency to the mixer section 101, the frequency offset amount of the reception signal 11 is compensated. After controlling the frequency of the local transmission signal, the phase error cumulative addition vector Φ in the phase error vector accumulator 114 is reset to zero.

As described above, according to the waveform equalizer in the present embodiment, the local oscillator used in the mixer 101 so as to compensate the frequency offset estimated from the phase error cumulative addition vector Φ by the controller 803b. By controlling the frequency of the signal, the frequency offset included in the received signal 11 can be compensated, and as a result, the equalization performance of the waveform equalizer can be improved.

The first embodiment, the second embodiment,
Further, in the modified examples of the first and second embodiments, the phase rotation of the input signal to the waveform equalizer is realized by providing the complex multiplier 105 after the root Nyquist filter 104. Since the signal having the offset is input to the root Nyquist filter, a part of the in-band signal is deleted.

In order to cope with such a situation, a configuration may be adopted in which the complex multiplier 105 is arranged in a stage preceding the root Nyquist filter 104. With this configuration, since the frequency offset amount of the output signal of the complex multiplier 105 is reduced, the in-band signal removed by the root Nyquist filter 104 is reduced, and the equalization performance can be improved. As a result, the reception performance can be improved. Can be improved.

[Fourth Embodiment] Next, a mobile station radio apparatus, a base station radio apparatus and a mobile communication system according to a fourth embodiment of the present invention will be described. In a large-zone mobile communication system, a high-speed mobile communication system, and the like, a plurality of radio wave propagation paths connecting a base station and a mobile station are observed. Therefore, received waves arrive from a plurality of propagation paths, and the received waves arriving from each of the propagation paths arrive with a delay time peculiar to each propagation path. The amplitude and phase fluctuations are not uniform for each frequency, and frequency selective fading occurs. Due to the effect of the frequency selective fading,
Problems such as occurrence of intersymbol interference occur. As a countermeasure, a waveform equalizer is used to cancel the waveform distortion due to frequency selective fading from the received wave, thereby preventing the transmission error from deteriorating.

If there is a frequency offset between the frequency of the carrier wave included in the arriving received wave and the local oscillation frequency provided in the mobile station radio apparatus, the phase will be high if there is a variation in the local oscillation frequency among individuals. In this case, there is a problem peculiar to a mobile communication system that an equalization performance is deteriorated because an equalization updating algorithm cannot follow a phase rotation speed.

In the present embodiment, the waveform equalizer described in the first embodiment, the second embodiment, and the modified example of the first and second embodiments is used in a mobile station radio apparatus and a base station radio apparatus. And a mobile communication system including the mobile station radio apparatus and the base station radio apparatus.
FIG. 11 shows a configuration example of the mobile communication system of the present embodiment. The position where the waveform equalizer is provided is, for example,
It can be provided in one or both of the demodulation section of the mobile station radio apparatus and the demodulation section of the base station radio apparatus (in FIG. 11, within the reception section of the base station BS1).

As described above, the waveform equalizers according to the first embodiment, the second embodiment, and the modified examples of the first and second embodiments are used for the mobile station radio apparatus or the base station radio apparatus. In a mobile communication system configured with these mobile station radio apparatus and base station radio apparatus applied to one or both of them, the pull-in range for the frequency offset becomes large, and the equalization performance can be improved. The receiving performance can be improved for various propagation path conditions. Therefore, a mobile communication terminal and a base station infrastructure having good reception performance are provided. By combining these, a high-quality mobile communication system resistant to frequency selective fading and frequency offset can be constructed. Furthermore, since the system design constraints on the amount of frequency offset are relaxed,
The design of the mobile communication system can be facilitated, and as a result, a high-quality mobile communication system can be constructed.

[0139]

As described above, the waveform equalizer, the frequency offset compensating method, the program, the recording medium, the mobile station radio apparatus, the base station radio apparatus and the mobile communication system using the waveform equalizer of the present invention are provided. According to this, the inter-symbol interference of the received signal is removed by the equalizing filter means (equalizing filter step), and the signal output from the equalizing filter means (equalizing filter step) by the sign determining means (sign determining step). A coordinate axis is formed based on the equalized signal obtained by delaying the equalized signal by one symbol, and a signal point of the current symbol is determined from signal point candidates forming a predetermined angle with respect to the coordinate axis. Then, the error calculating means (error calculating step) generates a phase error signal representing a phase difference between the signal point of the current symbol and the equalized signal output from the equalizing filter means (equalizing filter step). The signal accumulation means (phase error signal accumulation step) accumulates and adds the phase error signals to generate a phase error accumulation addition signal, and the complex operation means (complex operation step) and the phase error accumulation addition signal and the equalization filter means ( The input signal input to the equalizing filter step) is subjected to a complex operation to compensate for the frequency offset included in the input signal, and the code determination means (code determination step) performs the frequency offset of the signal point one symbol before. The phase of the coordinate axis is rotated so that the amount of phase rotation caused by the current symbol is compensated. The amount is reduced by compensating for the accumulated phase rotation amount due to the frequency offset of the signal point of the symbol before the signal point of the current symbol, and as a result, even if the frequency offset amount exceeds a predetermined amount, the phase of the received signal is high Without rotation, the allowable frequency offset amount (that is, the pull-in range for the frequency offset) increases, and the adaptive algorithm can sufficiently follow the phase rotation speed. Can be provided.

According to the present invention, the phase error cumulative addition vector (phase error cumulative addition signal) can be regarded as a frequency offset estimation vector. By performing a complex operation on the addition signal and the input signal input to the equalization filter means (equalization filter step), the amount of phase rotation due to the frequency offset included in the input signal can be compensated. The pull-in range is further increased, the adaptive algorithm can sufficiently follow the rotation speed of the phase, and a waveform equalizer with further improved equalization performance can be provided.

Further, according to the present invention, the amount of phase rotation due to the frequency offset can be reduced by the sign determining means (sign determining step), and the phase error signal output from the error calculating means (error calculating step) is also reduced. As a result, the direction of the accumulative addition vector accumulated by the phase error accumulating means (phase error accumulating step) can be converged in a short time, and a waveform having improved equalization performance in the initial stage of equalization An equalizer can be provided.

Further, the waveform equalizer of the present invention is applied to one or both of the mobile station radio apparatus and the base station radio apparatus, and the mobile station radio apparatus and the base station radio apparatus are provided with one or both of them. According to the mobile communication system configured as described above, the pull-in range for the frequency offset is increased, and the equalization performance can be improved, so that the reception performance can be improved for various propagation path conditions. As a result, it is possible to construct a high-quality mobile communication system in which the influence of frequency selective fading is reliably removed. Further, since the system design constraint on the frequency offset amount is relaxed, the design of the mobile communication system can be facilitated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of a waveform equalizer according to a first embodiment.

FIG. 2 is an explanatory diagram showing a method for determining a signal point for demodulation in a fixed code determiner using a π / 4 shift QPSK modulation / demodulation scheme.

FIG. 3 is an explanatory diagram showing a method for determining a signal point for demodulation in the code determiner of the first embodiment.

FIG. 4 is an explanatory diagram of an equalization error and a phase error vector.

FIG. 5A is an explanatory diagram illustrating a transmission symbol sequence according to a π / 4 shift QPSK modulation scheme, and FIG.
FIG. 4 is an explanatory diagram illustrating a received symbol sequence according to a π / 4 shift QPSK demodulation method.

FIG. 6 is a diagram illustrating the principle of a phase error cumulative addition vector.

FIG. 7 is an explanatory diagram illustrating a transmission data sequence and a reception data sequence oversampled at four times the symbol rate.

FIG. 8 is a partial configuration diagram illustrating a switching configuration of a code determiner and a fixed code determiner of a waveform equalizer according to a second embodiment.

FIG. 9A is an explanatory diagram illustrating a phase error cumulative addition vector when a sign determinator 801 is used and a phase error cumulative addition vector when a fixed sign determinator 802 is used, and FIG. After a predetermined time has passed,
FIG. 11 is an explanatory diagram illustrating a phase error cumulative addition vector when switching from 1 to a fixed code determiner 802;

FIG. 10 is a configuration diagram illustrating a waveform equalizer according to a third embodiment.

FIG. 11 is a configuration diagram of a mobile station radio apparatus and a base station radio apparatus according to a fourth embodiment, and a mobile communication system including the mobile station radio apparatus and the base station radio apparatus.

FIG. 12 is a configuration diagram showing a configuration of a conventional waveform equalizer.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 reception signal 12 input signal 101 mixer unit 102 quadrature demodulator 103 AD converter 104 root Nyquist filter 105 complex multiplier 106 feedforward filter 107 feedback filter 108 adder 109 sign determiner 110 symbol delay unit 111 data demodulator 112 equalization Error calculator 113 Tap coefficient updater 114 Phase error vector accumulator 120 Equalization filter unit 800 Sign judgment unit 801 Sign judgment unit 802 Fixed sign judgment unit 803a Control unit 803b Control unit 1000 Frequency synthesizer 1201 Feedforward filter 1202 Feedback filter 1203 1210 Adder 1204, 1211 Coordinate converter 1205 Switch 1206 Delayer 1207 Subtractor 1208 Sign decision unit 1209 Data demodulator 1212 equalization error calculator 1213 tap coefficient updater sw1a, sw1b switch CNT control signal d (k) signal point for demodulation of current symbol y (k) equalization output y (k-1) 1 symbol time Delayed equalized output φ (k) phase error signal

Continuation of front page (72) Inventor Ken Akiyama 4-3-1 Tsunashimahigashi, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture F-term in Matsushita Communication Industrial Co., Ltd. 5K004 AA05 FC02 FD02 FG00 FG02 FG02 FH01 5K046 AA05 EE01 EE06 EE37 EE47 EE55 EF54

Claims (20)

[Claims] 1. An equalizing filter means for removing inter-symbol interference of a received signal, and a coordinate axis is formed based on an equalized signal obtained by delaying the equalized signal output from the equalizing filter means by one symbol. Sign determining means for determining a signal point of the current symbol from signal point candidates forming a predetermined angle with respect to a signal point representing the phase difference between the signal point of the current symbol and the equalized signal output from the equalizing filter means. Error calculating means for generating a phase error signal; phase error signal accumulating means for accumulating and adding the phase error signal to generate a phase error accumulative addition signal; input to the phase error accumulative addition signal and the equalization filter means. Complex operation means for performing a complex operation on the input signal and compensating for a frequency offset included in the input signal. 2. An equalizing filter comprising tapping delay means for removing inter-symbol interference of a received signal, and an equalization signal output from the equalization filter means being delayed by one symbol based on the equalization signal. Sign determination means for forming a coordinate axis and determining a signal point of a current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis; and an equalization output from the signal point of the current symbol and the equalization filter means. An error calculating means for generating an equalization error signal representing a difference from the signal; and a tap coefficient updating means for updating a tap coefficient of the delay means with tap based on the equalization error signal. Waveform equalizer. 3. Equalizing filter means for removing inter-symbol interference of a received signal; fixed code determining means for determining a signal point of a current symbol from signal point candidates forming a predetermined angle with respect to a fixed coordinate axis; Error calculating means for generating a phase error signal representing a phase difference between the signal point of the current symbol and the equalized signal output from the equalizing filter means; and Phase error signal accumulating means for generating, and complex operation means for performing a complex operation on the phase error accumulated addition signal and an input signal input to the equalization filter means, and compensating for a frequency offset included in the input signal, A waveform equalizer, comprising: 4. An equalizing filter means for removing intersymbol interference of a received signal, and a coordinate axis is formed based on an equalized signal obtained by delaying the equalized signal output from the equalizing filter means by one symbol. Sign determining means for determining the signal point of the current symbol from the signal point candidates forming a predetermined angle with respect to the fixed point, and determining the signal point of the current symbol from the signal point candidates forming a predetermined angle with respect to the fixed coordinate axis. Sign determining means for generating a phase error signal representing a phase difference between a signal point of the current symbol determined by the sign determining means or the fixed code determining means and an equalized signal output from the equalizing filter means; An error calculating means, and a code point determining means for determining a signal point of a current symbol until a predetermined time elapses after the equalized signal is input, and after the predetermined time elapses, the fixed code Switching means for determining the signal point of the current symbol by the determining means; phase error signal accumulating means for accumulating and adding the phase error signal to generate a phase error accumulative addition signal; the phase error accumulative addition signal and the equalizing filter Complex arithmetic means for performing a complex operation on an input signal input to the means and compensating for a frequency offset included in the input signal. 5. The waveform equalizer according to claim 1, wherein the phase error signal accumulating means weights the phase error signal according to an accumulation time. 6. The waveform equalizer according to claim 4, wherein said error calculating means multiplies the quadrature component of said phase error cumulative addition signal by n (n is a positive natural number). 7. A frequency conversion means for converting a frequency of the received signal into an intermediate frequency, and compensating for a frequency offset included in the input signal based on a frequency offset estimated from the phase error cumulative addition signal. 7. The waveform equalizer according to claim 1, further comprising frequency control means for controlling a frequency of a local oscillation signal to said frequency conversion means. 8. The apparatus according to claim 1, wherein said equalization filter means includes a forward equalizer and a rear equalizer.
The waveform equalizer according to 2, 3, 4, 5, 6, or 7. 9. An equalizing filter step for removing inter-symbol interference of a received signal;
Forming a coordinate axis based on the symbol-delayed equalized signal,
A code determining step of determining a signal point of the current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis; and a phase difference between the signal point of the current symbol and the equalized signal output from the equalization filter step. An error calculating step of generating a phase error signal representing: a phase error signal accumulating step of accumulatively adding the phase error signal to generate a phase error accumulative addition signal; and A complex operation step of performing a complex operation on an input signal to be input and compensating for a frequency offset included in the input signal. 10. An equalization filter step comprising a delay step with taps for removing intersymbol interference of a received signal, and an equalization signal output from the equalization filter step is set to 1
Forming a coordinate axis based on the symbol-delayed equalized signal,
A code determination step of determining a signal point of the current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis; anda difference between the signal point of the current symbol and the equalized signal output from the equalization filter step. An error calculating step of generating a represented equalization error signal, and a tap coefficient updating step of updating a tap coefficient of the tapped delay step based on the equalization error signal,
A frequency offset compensation method comprising: 11. An equalizing filter step for removing inter-symbol interference of a received signal; a fixed code determining step for determining a signal point of a current symbol from signal point candidates forming a predetermined angle with respect to a fixed coordinate axis; An error calculating step of generating a phase error signal representing a phase difference between the signal point of the current symbol and the equalized signal output from the filtering step; and cumulatively adding the phase error signal to generate a phase error cumulative addition signal A phase error signal accumulating step, and a complex operation step of performing a complex operation on the phase error accumulated addition signal and an input signal input to the equalization filter step and compensating for a frequency offset included in the input signal. A frequency offset compensation method, characterized in that: 12. An equalizing filter step for removing inter-symbol interference of a received signal;
Forming a coordinate axis based on the symbol-delayed equalized signal,
A code determining step of determining a signal point of the current symbol from signal point candidates forming a predetermined angle with respect to the coordinate axis; and determining a signal point of the current symbol from signal point candidates forming a predetermined angle with respect to the fixed coordinate axis. And a phase error signal representing a phase difference between the signal point of the current symbol determined in the code determination step or the fixed code determination step and the equalized signal output from the equalization filter step. An error calculating step to generate, and a signal point of a current symbol is determined by the code determining step until a predetermined time has elapsed after the equalized signal is input, and after the predetermined time has elapsed, the current symbol is determined by the fixed code determining step. A switching step of determining a signal point of the phase error; and a phase error of cumulatively adding the phase error signal to generate a phase error cumulative addition signal. A signal accumulation step, and a complex operation step of performing a complex operation on the phase error accumulation addition signal and an input signal input to the equalization filter step, and compensating for a frequency offset included in the input signal. Frequency offset compensation method. 13. The phase error signal accumulating step, wherein the phase error accumulative addition signal is weighted according to an accumulation time.
3. The frequency offset compensation method according to 1. 14. The error calculating step multiplies an orthogonal component of the phase error cumulative addition signal by n (n is a positive natural number).
14. The frequency offset compensation method according to claim 12, wherein 15. A frequency conversion step of converting a frequency of the received signal into an intermediate frequency, and compensating for a frequency offset included in the input signal based on a frequency offset estimated from the phase error cumulative addition signal. A frequency control step of controlling a frequency of a local oscillation signal used in the frequency conversion step.
15. The frequency offset compensation method according to 2, 13, or 14. 16. The method of claim 9, 10, 11, 12, 13,
A program for causing a computer to execute the frequency offset compensation method according to 14 or 15. 17. The method of claim 9, 10, 11, 12, 13,
A computer-readable recording medium recorded as a program for causing a computer to execute the frequency offset compensation method according to 14 or 15. 18. A waveform equalizer according to claim 1, 2, 3, 4, 5, 6, 7, or 8, a program according to claim 16, or a recording medium according to claim 17. A mobile station radio apparatus characterized by the above-mentioned. 19. A waveform equalizer according to claim 1, 2, 3, 4, 5, 6, 7, or 8, a program according to claim 16, or a recording medium according to claim 17. A base station wireless device. 20. A waveform equalizer according to claim 1, 2, 3, 4, 5, 6, 7 or 8, a program according to claim 16, or a recording medium according to claim 17. A mobile communication system, comprising: