JP4350544B2 - Transmission path characteristic estimation apparatus and computer program - Google Patents

Description

  The present invention relates to a transmission path characteristic estimation apparatus in a wireless communication system and a computer program for realizing the transmission path characteristic estimation apparatus using a computer.

  Suppressing self-path interference due to multipath propagation in a wireless communication system is important for realizing high-speed transmission. For example, a frequency domain equalization method is known as an effective self-path interference suppression technique in a wireless communication system using single carrier transmission. In particular, the frequency domain equalization method using the Minimum Mean Square Error norm can suppress noise enhancement in frequency components with a small channel gain, and is known as an effective equalization algorithm ( Hereinafter, the frequency domain equalization method based on this least mean square error criterion is referred to as an MMSE frequency equalization method).

  FIG. 6 is a block diagram showing a schematic configuration of a wireless communication system including a conventional receiver 300 using the MMSE frequency equalization method. In FIG. 6, a transmitter 1 inserts a cyclic prefix (hereinafter referred to as CP) by CP inserters 11a and 11b at the heads of transmission data and a transmission pilot signal, and then inserts these CPs. The subsequent transmission data and the transmission pilot signal are time-multiplexed by the time multiplexer 12, and the time-multiplexed signal is wirelessly transmitted from the antenna 13. FIG. 7 is a diagram illustrating a configuration example of a transmission frame of the transmission signal. In the example of FIG. 7, the last 32 symbols of the pilot signal are copied to the head part (CP part) of the pilot signal, and the last 32 symbols of the data are copied to the head part (CP part) of the data. The pilot signal is a known signal that is preliminarily matched with the receiver side.

  In receiver 300, CPs are removed by CP removers 22a and 22b from the received data and the received pilot signal of the signal received by antenna 21, respectively. Next, the transmission path estimator 310 obtains a transmission path characteristic estimation value and a noise power estimation value from the received pilot signal after CP removal. The MMSE frequency equalizer 24 equalizes and outputs the received data after CP removal in the frequency domain by using the transmission channel characteristic estimation value and the noise power estimation value according to the equation (1).

Here, d _r (n) is the received data after CP removal, d _r ′ (n) is the received data after MMSE frequency equalization, H _a (f) is the frequency domain channel characteristic estimation value, and N _a is the noise. Power estimation value, F {x} is a discrete Fourier transform of x, F ⁻¹ {x} is an inverse discrete Fourier transform of x, and ^* is a complex conjugate notation.

FIG. 8 is a block diagram showing a configuration of the conventional transmission path estimator 310 of FIG. 8, first, a discrete Fourier transformer 231a is CP after removal of the received pilot signal _p r (n), (n is from 0 _(integer N until p -1)) discrete Fourier transform of _{N p} points for (See equation (2)). However, N _p is the sequence length of the received pilot signal p _r (n) after CP removal, and p _r (f) is the signal after the discrete Fourier transform.

Next, the converted pilot signal P _r (f) is multiplied by a predetermined signal by the multiplier 234c, thereby obtaining a frequency domain transmission line characteristic estimated value H _a (f) shown in the equation (3). . However, P _t (f) is a frequency characteristic of a known pilot signal.

Here, since the channel characteristic estimated value H _a (f) is _a channel characteristic estimated value to which noise has been added, it is necessary to remove the influence of noise. To this end, the inverse discrete Fourier transformer 233 performs inverse discrete Fourier transform on the transmission path characteristic estimated value H _a (f) to obtain _a time domain transmission path characteristic estimated value h _a (n). The time domain transmission line characteristic estimated value h _a (n) represents the estimated delay profile. In general, the CP length N _CP is set to be longer than the maximum delay time of the transmission path, so that all components in the time domain longer than the CP length N _CP can be regarded as noise components. Thereby, the multiplier 234a multiplies the transmission line characteristic estimation value h _a (n) by the filter 235e having the coefficient g _NE (n) for extracting only the component within the CP length N _CP , thereby estimating the transmission line characteristic. The noise component is removed from the value h _a (n). Next, the transmission path estimation value interpolator 236 performs data interpolation on the transmission path characteristic estimation value after the noise removal. In general, the pilot length is shorter than the data length in order to reduce the overhead. Therefore, the shortage is interpolated with the data value “0” by the transmission line estimated value interpolator 236 to obtain a transmission line characteristic estimated value having the same length as the data length. Next, the discrete Fourier transformer 231c performs a discrete Fourier transform on the transmission path characteristic estimation value after the data interpolation, and outputs a frequency domain transmission path characteristic estimation value H _a ′ (f) ((4), (5). ) See formula). This channel characteristic estimation value H _a ′ (f) is input to the MMSE frequency equalizer 24 and used as the frequency domain channel characteristic estimation value H _a (f) in the above equation (1).

Further, the multiplier 234b, with respect to the channel estimation value _h a (n), by multiplying the filter 235f having a coefficient of inverse characteristics of the coefficient _{g NE (n) (1-} g NE (n)) Then, a component outside the CP length N _CP is extracted from the transmission path characteristic estimated value h _a (n). Next, the noise power estimator 237 calculates and outputs _a noise power estimation value Na by integrating the output of the multiplier 234b (see equation (6)).

A. Czylwik, “Low Overhead Pilot-Aided Synchronization for Single Carrier Modulation with Frequency Domain Equalization,” Proc. GLOBECOM '98, pp. 2068-2073, Sydney, Australia, Nov. 1998.

  However, in the above-described conventional technique, in a wireless communication system using a pilot signal whose frequency characteristics are not constant, there is a problem that the accuracy of the transmission path characteristic estimated value deteriorates due to noise being emphasized during the transmission path estimation. . This problem will be described. When the frequency characteristic of noise is N (f), the above equation (3) can be replaced with the equation (7). However, H (f) is an actual transmission path characteristic value in the frequency domain.

As a result, the noise power spectral density | N _a (f) | ² added to the channel characteristic estimation value H _a (f) in the frequency domain is expressed by equation (8).

From this equation (8), it can be seen that the noise power spectral density added to the transmission path characteristic estimated value H _a (f) varies depending on the frequency characteristic P _t (f) of the transmission pilot signal. FIG. 9 is a diagram showing a reciprocal 1 / | P _t (f) | ² of the normalized power spectral density | P _t (f) | ² of the pilot signal by the pseudo noise (hereinafter referred to as PN) code. is there. The PN code is generally used as a pilot signal of the existing standard. The PN code is a series of constant power in the time domain, but as shown in FIG. 9, its frequency characteristic is not constant and varies greatly. For this reason, the noise of the transmission path characteristic estimated value H _a (f) is emphasized in the frequency component in which the inverse 1 / | P _t (f) | ^{2 of} the normalized power spectral density exceeds “1”. Therefore, the accuracy of the transmission path characteristic estimation value is deteriorated. Thereby, even if the MMSE frequency equalization method is applied to the received data, a sufficient effect cannot be obtained.

  In addition, changing the existing pilot signal from a PN code whose frequency characteristics are not constant to a series of signals whose frequency characteristics are constant is to maintain backward compatibility with receivers compliant with existing standards. Is practically impossible.

  The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a transmission path capable of improving the accuracy of a transmission path characteristic estimation value in a wireless communication system using a pilot signal having a non-constant frequency characteristic. The object is to provide a characteristic estimation apparatus.

  Another object of the present invention is to provide a computer program for realizing the transmission path characteristic estimation apparatus of the present invention using a computer.

In order to solve the above problems, a transmission path characteristic estimation apparatus according to the present invention estimates a transmission path characteristic in a wireless communication system that transmits one continuous known signal from a transmitter to a receiver. A signal dividing means for dividing the received known signal received by the receiver into a plurality of signals, a plurality of divided received known signals, and transmission known signals respectively corresponding to the received known signals, to generate signal-to-noise power Transmission path estimation value calculation means for calculating a transmission path characteristic estimation value so that the ratio is maximized, and the transmission path estimation value calculation means includes the frequency characteristics of the received known signal divided into the plurality and the transmission Multiply each by the complex conjugate value of the frequency characteristic of the known signal, add the multiplication results, and divide the addition result by the sum of the power spectral density of the transmission known signal, And calculates the serial channel estimation value.

A transmission path characteristic estimation apparatus according to the present invention is a transmission path characteristic estimation apparatus that estimates transmission path characteristics in a wireless communication system that transmits a plurality of continuous known signals from a transmitter to a receiver. and a transmitting known signals, each corresponding to a plurality of received known signal and these received known signals, comprising a channel estimation value calculating means for signal-to-noise power ratio is calculated channel estimation value so as to maximize the transmission The path estimation value calculation means multiplies the frequency characteristic of the received known signal by the complex conjugate value of the frequency characteristic of the transmitted known signal, adds the multiplication results, and adds the addition result to the power spectrum of the known transmission signal. The transmission path characteristic estimated value is calculated by dividing by the sum of densities .

A computer program according to the present invention is a computer program for performing transmission path characteristic estimation processing for estimating transmission path characteristics in a wireless communication system that transmits one continuous known signal from a transmitter to a receiver. The signal-to-noise power ratio is maximized from the function of dividing the received known signal received by the machine into the plurality of divided known received signals and the transmitted known signals respectively corresponding to the received known signals. A computer program for causing a computer to realize a calculation function for calculating a transmission path characteristic estimation value , wherein the calculation function is a complex of the frequency characteristic of the received known signal divided into the plurality and the frequency characteristic of the transmission known signal. A function of multiplying the conjugate values respectively, a function of adding the multiplication results, and the addition result of the transmission known signal. And having a function of dividing the sum of the spectral density, the.

A computer program according to the present invention is a computer program for performing transmission path characteristic estimation processing for estimating transmission path characteristics in a wireless communication system that transmits a plurality of continuous known signals from a transmitter to a receiver. A computer has an arithmetic function that calculates a channel characteristic estimate from a plurality of received known signals received by the transmitter and known transmission signals corresponding to the received known signals so that the signal-to-noise power ratio is maximized. A computer program , wherein the arithmetic function includes a function of multiplying a frequency characteristic of the received known signal by a complex conjugate value of a frequency characteristic of the transmitted known signal, a function of adding the multiplication results, and a result of the addition. And the function of dividing by the sum of the power spectral densities of the transmission known signals .
As a result, the transmission path characteristic estimation apparatus described above can be realized using a computer.

  According to the present invention, even in a wireless communication system using a known signal (pilot signal) whose frequency characteristics are not constant, it is possible to obtain a transmission path estimation value with a smaller noise power spectrum density, and to improve the accuracy of the transmission path characteristic estimation value. Can be achieved. As a result, it is possible to obtain transmission channel characteristic estimation accuracy equivalent to that when using a pilot signal having a constant frequency characteristic, and an excellent effect of being able to perform highly reliable wireless communication with a low error rate. can get.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a schematic configuration of a wireless communication system including a receiver 2 including a transmission path estimator (transmission path characteristic estimation apparatus) according to an embodiment of the present invention. In FIG. 1, the transmitter 1 is the same as the conventional configuration of FIG. In transmitter 1, CP inserter 11a inserts a CP at the beginning of transmission data, and CP inserter 11b inserts a CP at the beginning of a transmission pilot signal. Next, the time multiplexer 12 time-multiplexes the transmission data and the transmission pilot signal after the CP insertion, and this time-multiplexed signal is wirelessly transmitted from the antenna 13. The configuration of the transmission frame of the transmission signal with CP is, for example, the configuration shown in FIG. The pilot signal is a known signal that is preliminarily matched with the receiver side.

In the receiver 2 shown in FIG. 1, only the transmission path estimator 23 is different from the conventional configuration of FIG. 6, and the other configurations are the same as the conventional configuration.
In the receiver 2, the CP remover 22 a removes the CP from the received data of the signal received by the antenna 21, and the CP remover 22 b removes the CP from the received pilot signal of the signal received by the antenna 21. Next, the transmission path estimator 23 obtains a transmission path characteristic estimation value and a noise power estimation value from the received pilot signal after CP removal. The MMSE frequency equalizer 24 equalizes and outputs the received data after CP removal in the frequency domain by using the transmission channel characteristic estimation value and the noise power estimation value according to the above equation (1).

  Hereinafter, the transmission path estimator (transmission path characteristic estimation apparatus) according to each embodiment of the present invention will be sequentially described.

First, the first embodiment will be described.
FIG. 2 is a block diagram showing the configuration of the transmission path estimator 23 according to the first embodiment of the present invention. In FIG. 2, the transmission path estimation unit 23 receives a received pilot signal p _r (n) having a sequence length N _p from which CP has been removed. The received pilot signal p _r (n) is divided into a plurality of pilot signals by the switch SW. As this division method, there may be an overlapping portion if the divided signals are not the same. In this embodiment, as shown in FIG. 2, two pilot signals p _r1 (m) and p _r2 (m) of sequence length M _p (where M _p <N _p ) are received pilot signals p _r (n) is divided (see equation (9)).

Next, these two pilot signals p _r1 (m) and p _r2 (m) are subjected to discrete Fourier transform by discrete Fourier transformers 231a and 231b, respectively. Thereby, the frequency characteristics P _r1 (f), P _r2 (f) of the two pilot signals p _r1 (m), p _r2 (m) obtained by dividing the received pilot signal p _r (n) are calculated (( (See 10)). Where F {x} is a discrete Fourier transform of x.

Next, the transmission path estimated value calculator 232 calculates a frequency domain transmission path characteristic estimated value H _a (f) from the frequency characteristics P _r1 (f) and P _r2 (f) according to the equation (11). Thereby, even when the frequency characteristics of the pilot signal are not constant, it is possible to obtain a transmission path characteristic estimation value with a small noise power spectral density. Details of this point will be described later.

However, ^* is a complex conjugate notation. Also, P _t1 (f) and P _t2 (f) are 2 of the sequence length M _{p obtained} by dividing the known pilot signal, similarly to the divided pilot signals p _r1 (m) and p _r2 (m). It is the frequency characteristic of one signal. These frequency characteristics P _t1 (f) and P _t2 (f) are stored in advance in a memory (not shown) in the transmission path estimated value calculator 232.

The transmission path characteristic estimated value H _a (f) calculated by the transmission path estimated value calculator 232 is multiplied by the filter 235a after the inverse discrete Fourier transform, as in FIG. Here, the filter 235a has a coefficient for extracting only a component within a predetermined length N _delay that is equal to or longer than the maximum delay time of the transmission path. For example, it has a coefficient g _NE (n) for extracting only the component within the CP length N _CP . Next, the transmission path estimation value interpolator 236 interpolates the data value “0” with respect to the transmission path characteristic estimation value after the noise removal, and outputs a transmission path characteristic estimation value having the same length as the data length. Next, the discrete Fourier transformer 231c performs a discrete Fourier transform on the transmission path characteristic estimation value after data interpolation, and outputs a frequency domain transmission path characteristic estimation value H _a ′ (f). This channel characteristic estimation value H _a ′ (f) is input to the MMSE frequency equalizer 24 of FIG. 1 and used as the frequency domain channel characteristic estimation value H _a (f) in the above equation (1). .

Further, the channel characteristic estimation value H _a (f) is multiplied by the filter 235b after the inverse discrete Fourier transform. Here, the filter 235b has a coefficient for extracting a component outside the predetermined length N _delay that is equal to or longer than the maximum delay time of the transmission path. For example, it has a coefficient (1-g _NE (n)) for extracting a component outside the CP length N _CP . Next, the noise power estimator 237 calculates and outputs _a noise power estimated value Na by integrating the output of the multiplier 234b (see the above equation (6)).

Next, by calculating the channel characteristic estimation value H _a (f) in the frequency domain by the above equation (11), even if the frequency characteristic of the pilot signal is not constant, the channel characteristic estimation with a small noise power spectral density is performed. The point which can obtain | require a value is demonstrated in detail.
Similarly to the substitution from the above expression (3) to the expression (7), the above expression (11) can be replaced by the expression (12) when the noise frequency characteristic is N (f). However, H (f) is an actual transmission path characteristic value in the frequency domain.

As a result, the noise power spectral density | N _a (f) | ² added to the channel characteristic estimation value H _a (f) in the frequency domain is expressed by equation (13).

In this equation (13), frequency characteristics P _t1 (f) and P _t2 (f) are frequency characteristics of a signal obtained by dividing one pilot signal into two, but are uncorrelated. Therefore, the second term of the above equation (13) can be approximately regarded as “0”. Thereby, the above expression (13) becomes the expression (14).

From this equation (14), the noise power spectral density added to the transmission path characteristic estimation value H _a (f) varies according to 1 / (| P _t1 (f) | ² + | P _t2 (f) | ² ). I understand that FIG. 3 shows the normalized power spectral density | P _t1 (f) | ² , | P _t2 (f) related to the frequency characteristics P _t1 (f) and P _t2 (f) of the pilot signal of the existing standard using the PN code. ) | ² of the reciprocal _{1 / | P t1 (f)} | 2, 1 / | a diagram illustrating a ² | _P t2 (f). As shown in FIG. 3, the frequency characteristics P _t1 (f) and P _t2 (f) are uncorrelated and show different frequency characteristics.

FIG. 4 shows the reciprocal 1 / (| P _t1 (f) | ² + | P _t2 (f) | of the sum of the normalized power spectral densities related to the frequency characteristics P _t1 (f) and P _t2 (f) of FIG. ² ). As shown in FIG. 4, there are few frequency components in which the reciprocal of the sum of the normalized power spectral densities exceeds 1, and even if it exceeds 1, the value is small. For example, even if the power spectral density of the frequency characteristic P _t1 (f) is very small, if the power spectral density of the frequency characteristic P _t2 (f) is large, the frequency component is averaged and noise is generated in the frequency component. Not emphasized. Further, since the frequency characteristics P _t1 (f) and P _t2 (f) are uncorrelated, the probability that both power spectral densities of the frequency characteristics P _t1 (f) and P _t2 (f) are small is correlated. Small compared to some cases. Thereby, by calculating the channel characteristic estimation value H _a (f) in the frequency domain by the above equation (11), even when the frequency characteristic of the pilot signal is not constant, noise enhancement can be suppressed efficiently, A channel characteristic estimation value with a smaller noise power spectral density can be obtained.

  According to the first embodiment described above, one continuous received pilot signal (received known signal) is divided into a plurality of received pilot signals. Then, from the plurality of divided reception pilot signals and transmission pilot signals (transmission known signals) respectively corresponding to these signals, the transmission line characteristics are set so that the signal-to-noise power ratio is maximized by the above equation (11). Calculate an estimate. Thereby, even when the frequency characteristics of the pilot signal are not constant, it is possible to obtain a transmission path characteristic estimation value with a small noise power spectral density.

In the above-described embodiment, the first embodiment has been described with an example in which one reception pilot is divided into two. However, one reception pilot signal may be divided into three or more. The effect of can be obtained.
Further, in a wireless communication system in which a plurality of pilot signals are transmitted, one received pilot signal may be divided into a plurality as in the above-described embodiment, or a plurality of received pilot signals may be expressed by the above equation (11). You may apply to.

  In the first embodiment described above, when one received pilot signal is divided into a plurality of pilot signals, no CP is inserted on the divided pilot signal on the transmission side. The transmission path characteristic estimated value calculated by the estimated value calculator 232 includes an interference component. However, this interference component is included only from the beginning of the received pilot signal before division to the portion corresponding to the maximum delay time of the transmission path. Therefore, in the transmission path estimator 23 of FIG. 2 described above, before performing the discrete Fourier transform on the divided received pilot signal, the interference mixed portion is compensated with, for example, a temporary transmission path characteristic estimation value, thereby transmitting the transmission path. It is possible to further improve the accuracy of characteristic estimation.

Next, a second embodiment will be described.
FIG. 5 is a block diagram showing the configuration of the transmission path estimator 23 according to the second embodiment of the present invention. In FIG. 5, the same reference numerals are given to portions corresponding to the respective portions in FIG. Note that the filters 235c and 235d in FIG. 5 correspond to the filters 235a and 235b in FIG. 2, respectively.
5, the transmission path estimation unit 23 performs discrete Fourier transform on the received pilot signal p _r (n) of the sequence length N _p from which CP has been removed by the discrete Fourier transformer 231a in the same manner as in FIG. The pilot signal P _r (f) is multiplied by a predetermined signal by the multiplier 234c to obtain the frequency domain transmission line characteristic estimated value H _a (f) shown in the above equation (3).

In this transmission line characteristic estimated value H _a (f), as indicated by the above equations (7) and (8), the added noise power spectral density varies depending on the frequency characteristic P _t (f) of the transmission pilot signal. In addition, noise is emphasized in frequency components having a large inverse 1 / | P _t (f) | ^{2 of} the normalized power spectral density.

In the transmission path estimator 23 of FIG. 5, the transmission path estimation value replacement unit 301 emphasizes noise by determining the threshold value of the inverse 1 / | P _t (f) | ² of the normalized power spectral density. Select frequency components. Then, by replacing the channel characteristic estimation value of the selected frequency component with a certain value, a channel characteristic estimation value with reduced noise power spectral density is obtained.

The transmission path estimated value replacement unit 301 replaces the transmission path characteristic estimated value according to equation (15), and outputs the replaced transmission path characteristic estimated value H _pmt (f). However, P _TH is a threshold value for determining the frequency component to be replaced, and H _TH (f) is a value for replacing the estimated channel characteristic value in the frequency component to be replaced.

Although noise emphasis can be suppressed by the replacement operation according to equation (15), information on the transmission path itself is lost. For example, if the threshold value _PTH is set too low, noise enhancement is difficult to occur, but a lot of information on the transmission path itself is lost, leading to deterioration in transmission path characteristic estimation accuracy. Therefore, the transmission path estimated value replacement unit 301 sets the optimum threshold P _TH corresponding to the transmission path state by _obtaining the threshold P _TH based on the noise power estimated in the past (noise power estimated value N _a ). To do. For example, the threshold value P _TH is calculated and set by the equation (16), where k is a constant.

Thereby, in the transmission line in which the noise power is more dominant than the own-path interference power, the threshold _PTH is set low, so that noise enhancement is suppressed. On the other hand, in a transmission line whose own path interference power is larger than noise power, the threshold value _PTH is set high, and information on the transmission path is not lost, so that own path interference can be efficiently suppressed.

For the replacement value H _TH (f), for example, a constant represented by the equation (17) is set. Or it calculates and sets as what interpolates from the value before and behind by (18) Formula.

In addition, when “H _TH (f) = 0” is substituted according to equation (17), the channel gain of the replaced frequency component is lost. For this reason, when using the equation (17), it is preferable to use the equation (15) after being transformed into the equation (19).

N _TH is the number of frequency components to be replaced.
According to the above equation (19), a reduction in channel gain due to substitution can be suppressed by correcting the power spectral density of frequency components that are not substituted.

Note that the bit error rate in the received data after frequency equalization varies depending on the setting algorithm for the replacement value H _TH (f), so that the setting algorithm is not limited to the above-described example, and is appropriately selected according to the transmission path state and the like. do it.

  According to the second embodiment described above, the frequency component in which noise is emphasized in the transmission path characteristic estimated value is selected by determining the threshold value of the power spectral density of the transmission pilot signal (transmission known signal). Replace the estimated channel characteristics of the frequency component. Thereby, even when the frequency characteristics of the pilot signal are not constant, it is possible to obtain a transmission path characteristic estimation value with a small noise power spectral density.

  As described above, according to the embodiment of the present invention, it is possible to obtain a transmission path estimation value with a smaller noise power spectrum density even in a wireless communication system using a pilot signal with a non-constant frequency characteristic. As a result, it is possible to obtain transmission channel characteristic estimation accuracy equivalent to that when using a pilot signal having a constant frequency characteristic, and an excellent effect of being able to perform highly reliable wireless communication with a low error rate. can get.

  In each of the above-described embodiments, the transmission path estimator 23 shown in FIGS. 2 and 5 may be realized by dedicated hardware, and the transmission path estimator 23 may be a memory and a DSP. It may be configured by an arithmetic processing unit such as a (digital signal processor), and the function may be realized by loading a program for realizing the function of the transmission path estimator 23 into a memory and executing it.

Also, a program for realizing each function performed by the transmission path estimator 23 shown in FIGS. 2 and 5 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system. The transmission path characteristic estimation process may be performed by executing the process. Here, the “computer system” may include an OS and hardware such as peripheral devices.
Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” means a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a CD-ROM, a hard disk built in a computer system, etc. This is a storage device.

Further, the “computer-readable recording medium” refers to a volatile memory (for example, DRAM (Dynamic DRAM)) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. Random Access Memory)), etc., which hold programs for a certain period of time.
The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.
For example, the present invention can be applied to various wireless communication systems such as a wireless communication system using multicarrier transmission in addition to a wireless communication system using single carrier transmission.
In the above-described embodiment, the present invention is applied to the wireless communication system using the CP. However, the present invention can be similarly applied to the wireless communication system not using the CP. An effect can be obtained.

It is a block diagram which shows schematic structure of the radio | wireless communications system which comprises the receiver 2 provided with the transmission path estimator (transmission path characteristic estimation apparatus) which concerns on embodiment of this invention. It is a block diagram which shows the structure of the transmission path estimator 23 which concerns on the 1st Embodiment of this invention. Reciprocals 1 / | P _t1 (f) | ² and 1 / | P _t2 (f) | ² of normalized power spectral densities related to frequency characteristics P _t1 (f) and P _t2 (f) of pilot signals by PN codes FIG. It is a figure which shows the reciprocal 1 / (| _Pt1 (f) | ² ++ _Pt2 (f) | ² ) of the sum of the normalized power spectrum density concerning the same frequency characteristic _Pt1 (f), _Pt2 (f). is there. It is a block diagram which shows the structure of the transmission path estimator 23 which concerns on the 2nd Embodiment of this invention. 1 is a block diagram showing a schematic configuration of a wireless communication system including a conventional receiver 300. FIG. It is a figure which shows the structural example of the transmission frame of a transmission signal. It is a block diagram which shows the structure of the conventional transmission path estimator 310 shown in FIG. It is a figure which shows the reciprocal 1 / | _Pt (f) | ² of the normalized power spectrum density of the pilot signal by a PN code.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Receiver, 21 ... Antenna, 22a, 22b ... CP remover, 23 ... Transmission path estimator (transmission path characteristic estimation apparatus), 24 ... MMSE frequency equalizer, 231a-c ... Discrete Fourier transform, 232 ... Transmission path estimation value calculator, 233... Inverse discrete Fourier transformer, 234 a to c... Multiplier, 235 a to d. Replacer, SW ... switch.

Claims (4)

In a transmission path characteristic estimation device for estimating transmission path characteristics in a wireless communication system that transmits one continuous known signal from a transmitter to a receiver,
Signal dividing means for dividing the received known signal received by the receiver into a plurality of signals;
A transmission path estimated value calculating means for calculating a transmission path characteristic estimated value so that a signal-to-noise power ratio is maximized from the plurality of divided known reception signals and transmission known signals respectively corresponding to the received known signals; , equipped with a,
The transmission path estimation value calculating means multiplies the frequency characteristic of the received known signal divided into the plurality and the complex conjugate value of the frequency characteristic of the transmitted known signal, adds these multiplication results, and adds the addition result. A transmission path characteristic estimation apparatus that calculates the transmission path characteristic estimated value by dividing by a sum of power spectrum densities of the transmission known signals. In a transmission path characteristic estimation device that estimates transmission path characteristics in a wireless communication system that transmits a plurality of continuous known signals from a transmitter to a receiver,
A channel estimation value for calculating a channel characteristic estimation value from the plurality of reception known signals received by the receiver and transmission known signals respectively corresponding to the reception known signals so as to maximize the signal-to-noise power ratio. Computation means ,
The transmission path estimation value calculating means multiplies the frequency characteristic of the received known signal and the complex conjugate value of the frequency characteristic of the known transmission signal, adds the multiplication results, and adds the addition result to the known transmission signal. A transmission path characteristic estimation apparatus that calculates the transmission path characteristic estimated value by dividing by a sum of power spectrum densities. A computer program for performing transmission path characteristic estimation processing for estimating transmission path characteristics in a wireless communication system that transmits one continuous known signal from a transmitter to a receiver,
A function of dividing the received known signal received by the receiver into a plurality of;
A computing function for calculating a channel characteristic estimation value from the plurality of divided known reception signals and transmission known signals respectively corresponding to the reception known signals so as to maximize the signal-to-noise power ratio, A computer program to be realized ,
The calculation function is
A function of multiplying the frequency characteristic of the received known signal divided into a plurality and the complex conjugate value of the frequency characteristic of the known transmission signal;
A function for adding these multiplication results,
A function of dividing the addition result by the sum of the power spectral density of the transmission known signal;
A computer program characterized by comprising: A computer program for performing transmission path characteristic estimation processing for estimating transmission path characteristics in a wireless communication system that transmits a plurality of continuous known signals from a transmitter to a receiver,
A computer having a calculation function for calculating a channel characteristic estimation value from a plurality of reception known signals received by the receiver and transmission known signals respectively corresponding to the reception known signals so as to maximize a signal-to-noise power ratio. is a computer program to be implemented,
The calculation function is
A function of multiplying the frequency characteristic of the received known signal and the complex conjugate value of the frequency characteristic of the known transmission signal, respectively;
A function for adding these multiplication results,
A function of dividing the addition result by the sum of the power spectral density of the transmission known signal;
A computer program characterized by comprising:

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