Communication terminal and channel estimate method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a CDMA communication terminal device and a channel estimation method used in a wireless communication system such as a car phone or a mobile phone.

【0002】

[Conventional technology]

In a wireless communication system, in order to increase the reception power of an individual channel transmission signal (hereinafter referred to as "individual channel signal") at a communication terminal on the base station side, individual channel signals from a plurality of diversity antennas for one communication terminal. In some cases, a transmission diversity is used to transmit.

【0003】

Figure 8 shows the system configuration diagram of the system disclosed in 3GPP WG1TSG-RAN WG1 R1-99832 (Physical channels and mapping of transport channels onto physical channels (FDD)) as an example of a wireless communication system using transmission diversity. is there.

【0004】

As shown in FIG. 8, the base station 1 transmits a transmission signal of the common pilot channel (hereinafter referred to as common pilot channel signal) A from the antenna A, and transmits a common pilot channel signal B from the antenna B. At the same time, the base station 1 transmits the individual channel signal A from the antenna A to the communication terminal 2 to the communication terminal 2, and transmits the individual channel signal B from the antenna B to the communication terminal 2.

【0005】

In the base station 1, the individual channel signal A and the individual channel signal B are multiplied by the same diffusion code. Therefore, in the communication terminal 2, the individual channel signal A and the individual channel signal B are separated as one signal that cannot be separated. Received.

【0006】

On the other hand, in base station 1, the common pilot channel signal A and the common pilot channel signal B are multiplied by different diffusion codes. Alternatively, some method is adopted that is separable even when multiplied by the same diffusion code. Therefore, they can be separated in the communication terminal 2. Further, since the individual channel signal A and the common pilot channel signal A, and the individual channel signal B and the common pilot channel signal B are received through the same propagation path, the common pilot channel signal A and the common pilot channel signal are received. By estimating the channel of B, the phase rotation angle of the individual channel signal B with respect to the individual channel signal A can be known.

【0007】

FIG. 9 is a block diagram showing a configuration of a conventional communication terminal. In the communication terminal shown in FIG. 9, the antenna 11 receives the signal transmitted from the base station and transmits the signal to the base station. The duplexer 12 switches between transmission and reception time zones. The receiving RF unit 13 amplifies the received signal that has passed through the duplexer 12 and frequency-converts it into a baseband signal.

【0008】

The despreading unit 14 despreads the output signal of the receiving RF unit 13 with the spreading code of the individual channel signal, and extracts the modulated signal of the individual channel signal. Similarly, the despreading unit 15 despreads the output signal of the receiving RF unit 13 with the spreading code of the common pilot channel signal A, and extracts the modulated signal of the common pilot channel signal A. Similarly, the despreading unit 16 despreads the output signal of the receiving RF unit 13 with the spreading code of the common pilot channel signal B, and extracts the modulated signal of the common pilot channel signal B.

【0009】

The channel estimation unit 17 estimates the phase and amplitude of the propagation path (so-called channel estimation) by using the pilot symbol in the modulated signal of the individual channel signal output from the reverse diffusion unit 14. In the following description, the estimated phase and amplitude of the channel are referred to as channel estimates.

【0010】

Similarly, the channel estimation unit 18 performs channel estimation using the pilot symbol in the modulated signal of the common pilot channel signal A output from the reverse diffusion unit 15, and the channel estimation unit 19 outputs from the reverse diffusion unit 16. Channel estimation is performed using the pilot symbol in the modulated signal of the common pilot channel signal B.

【0011】

The demodulation unit 20 demodulates the modulated signal of the individual channel signal output from the dediffusion unit 14 based on the channel estimation value output from the channel estimation unit 17, and extracts the received signal.

【0012】

The phase rotation control unit 21 has a phase rotation amount with respect to the base station based on the phase difference between the common pilot channel signal A output from the channel estimation unit 18 and the common pilot channel signal B output from the channel estimation unit 19. Generates a phase rotation control signal that indicates.

【0013】

The multiplexing unit 22 multiplexes the phase rotation control signal output from the phase rotation control unit 21 with the transmission signal. The modulation unit 23 performs a primary modulation process such as QPSK on the output signal of the multiplexing unit 22. The spreading unit 24 multiplies the output signal of the modulation unit 23 by a unique spreading code to spread the signal. The transmission RF unit 25 converts the output signal of the diffusion unit 24 into a radio frequency, amplifies it, and wirelessly transmits it from the antenna 11 via the duplexer 12.

【0014】

Next, the relationship between the phase difference δ of the individual channel signal and the channel estimated value estimated by the channel estimation unit 17 will be described with reference to FIG.

【0015】

In FIG. 10, the channel estimate β (n) is the channel estimate β of the individual channel signal A._aChannel estimate β of (n) and individual channel signal B_{b b}It is expressed as a composite vector of (n).

【0016】

In addition, in FIG. 10, β_{b b}Value obtained by rotating (n) by 180 ° -β_{b b}(n) and β_aThe channel estimate obtained by combining (n) is represented by β'(n).

【0017】

FIG. 10 (a) shows each channel estimate when the phase difference δ between the individual channel signal A and the individual channel signal B is -90 ° δ <90 °, and FIG. 10 (b) shows individual channel estimates. The estimated value of each channel when the phase difference δ between the channel signal A and the individual channel signal B is 90 ° δ <270 ° is shown.

【0018】

As shown in FIG. 10 (a), when the phase difference δ between the individual channel signal A and the individual channel signal B is -90 ° δ <90 °, β (n) is β'(n). Become larger. On the other hand, as shown in FIG. 10 (b), when the phase difference δ between the individual channel signal A and the individual channel signal B is 90 ° δ <270 °, β'(n) is β (n). ) Will be larger.

【0019】

That is, when 90 ° δ <270 °, the received power in the communication terminal can be increased by rotating the individual channel signal B by 180 ° and transmitting it.

【0020】

In this way, in the wireless communication system in which the transmission diversity is introduced, the communication terminal estimates the channels of the common pilot channel signal A and the common pilot channel signal B to control the phase rotation amount, and the base station side determines the phase rotation control amount. By appropriately rotating the phase of the individual channel signal B and transmitting the signal B based on the above, it is possible to increase the reception power of the individual channel signal in the communication terminal and improve the reception quality.

【0021】

[Problems to be Solved by the Invention]

However, if the individual channel signals are appropriately phase-rotated for each slot on the base station side, the receiving slots in the communication terminal become discontinuous. Therefore, in the conventional communication terminal, the channel estimates are averaged over a plurality of slots. There is a problem that the reliability of the channel estimation value becomes lower than that in the case where the transmission diversity is not used.

【0022】

The present invention has been made in view of this point, and an object of the present invention is to provide a communication terminal device and a channel estimation method capable of improving the reliability of channel estimation values in a wireless communication system in which transmission diversity is introduced. To do.

【0023】

[Means for solving problems]

The communication terminal device of the present invention estimates the first channel estimation means that estimates the common pilot channel in the first antenna of the base station device and outputs the first estimated value, and the common pilot channel in the second antenna of the base station device. The second channel estimation means that outputs the second estimated value, the third channel estimation means that estimates the individual channels and outputs the third estimated value, the first estimated value, the second estimated value, and the second estimated value. A phase rotation amount estimation means that estimates the phase rotation amount of each channel in the second antenna based on the relationship of the three estimated values, a value obtained by rotating the second estimated value by the phase rotation amount, and the first estimated value. A configuration is adopted in which a channel estimation value synthesis means for synthesizing and outputting a synthesis estimation value is provided.

【0024】

Further, the phase rotation amount estimating means of the communication terminal device of the present invention calculates the first synthesized value by synthesizing the value obtained by rotating the second estimated value by the candidate phase rotation amount and the first estimated value, and calculates the candidate phase. Among the rotation amounts, the one having the highest orthogonality between the first composite value and the third estimated value is estimated as the phase rotation amount of the individual channel in the second antenna, and the channel estimation value synthesis means is only the phase rotation amount. A configuration is adopted in which the value obtained by rotating the second estimated value and the first estimated value are combined and the combined estimated value is output.

【0025】

With these configurations, channel estimation can be performed based on the phase rotation amount and the channel estimation value of the common pilot channel. Therefore, since the signal of the common pilot channel has a larger transmission power than the signal of the individual channel, the channel estimation The reliability of the value can be improved.

【0026】

Further, the phase rotation amount estimation means of the communication terminal device of the present invention combines the value obtained by rotating the second estimated value by the candidate phase rotation amount and multiplying by the candidate amplitude coefficient with the first estimated value, and the first synthesized value. Is calculated, and among the combinations of the candidate phase rotation amount and the candidate amplitude coefficient, the one having the highest orthogonality between the first composite value and the third estimated value is the phase rotation amount and amplitude coefficient of the individual channels in the second antenna. The channel estimation value synthesizing means synthesizes the value obtained by multiplying the value obtained by rotating the second estimation value by the phase rotation amount by the amplitude coefficient and the first estimation value, and outputs the synthesis estimation value. Take the composition.

【0027】

With this configuration, channel estimation can be performed based on the amplitude coefficient, phase rotation amount, and channel estimation value of the common pilot channel signal, so that the channel can be transmitted even when the amplitude of the individual channel signal is changed on the base station side. The reliability of the estimated value can be improved.

【0028】

Further, the communication terminal device of the present invention adopts a configuration including a multi-channel estimated value combining means for synthesizing a value obtained by correcting the phase rotation amount with respect to the combined estimated value of the previous reception slot and the current combined estimated value.

【0029】

With this configuration, channel estimates can be synthesized over a plurality of slots, and the reliability of channel estimates can be improved.

【0030】

Further, the base station device of the present invention adopts a configuration in which wireless communication is performed with any of the above communication terminal devices by transmission diversity.

【0031】

With this configuration, the reliability of channel estimates can be improved in a wireless communication system using transmission diversity.

【0032】

In the channel estimation method of the present invention, the common pilot channel in the first antenna of the base station apparatus is estimated to calculate the first estimated value, the common pilot channel in the second antenna is estimated, and the second estimated value is calculated. The individual channels are estimated to calculate the third estimated value, the value obtained by rotating the second estimated value by the candidate phase rotation amount and the first estimated value are combined to calculate the first synthesized value, and the candidate phase rotation amount is described. Among them, the one having the highest orthogonality between the first composite value and the third estimated value is estimated as the phase rotation amount of the individual channel in the second antenna, and the value obtained by rotating the second estimated value by this phase rotation amount. A method is adopted in which the first estimated value is combined with the first estimated value and the combined estimated value is output.

【0033】

By this method, channel estimation can be performed based on the phase rotation amount and the channel estimation value of the common pilot channel. Therefore, since the signal of the common pilot channel has a higher transmission power than the signal of the individual channel, the channel estimation value. Can improve the reliability of.

【0034】

Further, in the channel estimation method of the present invention, the common pilot channel in the first antenna of the base station apparatus is estimated to calculate the first estimated value, and the common pilot channel in the second antenna is estimated to calculate the second estimated value. Then, the individual channels are estimated, the third estimated value is calculated, the second estimated value is rotated by the candidate phase rotation amount, the value obtained by multiplying the candidate amplitude coefficient, and the first estimated value are combined to form the first synthesized value. Is calculated, and among the combinations of the candidate phase rotation amount and the candidate amplitude coefficient, the one having the highest orthogonality between the first composite value and the third estimated value is the phase rotation amount and amplitude coefficient of the individual channels in the second antenna. The method is adopted in which the combined estimated value is output by synthesizing the value obtained by multiplying the value obtained by rotating the second estimated value by the phase rotation amount by the amplitude coefficient and the first estimated value.

【0035】

By this method, channel estimation can be performed based on the amplitude coefficient, the amount of phase rotation, and the channel estimation value of the common pilot channel signal, so that the channel can be transmitted even when the amplitude of the individual channel signal is changed on the base station side. The reliability of the estimated value can be improved.

【0036】

Further, the channel estimation method of the present invention adopts a method of synthesizing a value obtained by correcting the phase rotation amount with respect to the composite estimated value of the previous reception slot and the current composite estimated value.

【0037】

By this method, the channel estimates can be synthesized over a plurality of slots, and the reliability of the channel estimates can be improved.

【0038】

BEST MODE FOR CARRYING OUT THE INVENTION

The gist of the present invention is to estimate the phase rotation amount of the common pilot channel signal with respect to the individual channel signal, and to estimate the channel using the common pilot channel signal having a larger transmission power than the individual channel signal.

【0039】

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

【0040】

FIG. 1 is a block diagram showing a configuration on a transmitting side of a base station that performs wireless communication with the communication terminal of the present invention.

【0041】

In the base station shown in FIG. 1, the modulation unit 101 performs a primary modulation process such as QPSK on the transmission signal. The modulation unit 102 performs a primary modulation process such as QPSK on the common pilot channel signal A. The modulation unit 103 performs a primary modulation process such as QPSK on the common pilot channel signal B.

【0042】

The spreading unit 104 multiplies the output signal of the modulation unit 101 by a unique spreading code to spread the signal. The spreading unit 105 multiplies the output signal of the modulation unit 102 by a unique spreading code to spread the signal. The spreading unit 106 multiplies the output signal of the modulation unit 103 by a unique spreading code to spread the signal.

【0043】

The phase rotation unit 107 rotates the phase of the output signal of the diffusion unit 104 by a predetermined amount based on the phase rotation control signal that indicates the phase rotation amount included in the signal transmitted from the communication terminal.

【0044】

The multiplexing unit 108 multiplexes the output signal of the spreading unit 104 and the output signal of the spreading unit 105. The multiplexing unit 109 multiplexes the output signal of the phase rotating unit 107 and the output signal of the spreading unit 106.

【0045】

The transmission RF unit 110 converts the output signal of the multiplexing unit 108 into a radio frequency, amplifies it, and wirelessly transmits it from the antenna 112. The transmission RF unit 111 converts the output signal of the multiplexing unit 109 into a radio frequency, amplifies it, and wirelessly transmits it from the antenna 113.

【0046】

In the following description, the phase rotation amount in the phase rotation unit 107 of the base station is two types, 0 ° and 180 °.

【0047】

(Embodiment 1) The first embodiment is a mode in which the base station transmits the individual channel signal A and the individual channel signal B without changing the amplitudes.

【0048】

FIG. 2 is a block diagram showing a configuration of a communication terminal according to the first embodiment of the present invention.

【0049】

In the communication terminal shown in FIG. 2, the antenna 201 receives the signal transmitted from the base station and transmits the signal to the base station. The duplexer 202 switches between transmission and reception time zones. The receiving RF unit 203 amplifies the received signal that has passed through the duplexer 202 and frequency-converts it into a baseband signal.

【0050】

The despreading unit 204 despreads the output signal of the receiving RF unit 203 with the spreading code of the individual channel signal, and extracts the modulated signal of the individual channel signal. Similarly, the despreading unit 205 despreads the output signal of the receiving RF unit 203 with the spreading code of the common pilot channel signal A, and extracts the modulated signal of the common pilot channel signal A. Similarly, the despreading unit 206 despreads the output signal of the receiving RF unit 203 with the spreading code of the common pilot channel signal B to take out the modulated signal of the common pilot channel signal B.

【0051】

The channel estimation unit 207 estimates the phase and amplitude of the propagation path (so-called channel estimation) by using the pilot symbol in the modulated signal of the individual channel signal output from the reverse diffusion unit 204.

【0052】

Similarly, the channel estimation unit 208 performs channel estimation using the pilot symbol in the modulated signal of the common pilot channel signal A output from the reverse diffusion unit 205, and the channel estimation unit 209 is output from the reverse diffusion unit 206. Channel estimation is performed using the pilot symbol in the modulated signal of the common pilot channel signal B.

【0053】

The phase rotation amount estimation unit 210 estimates the phase rotation amount based on the channel estimation values output from the channel estimation units 207, 208, and 209. A specific method for estimating the phase rotation amount in the phase rotation amount estimation unit 210 will be described later.

【0054】

The channel estimation value synthesis unit 211 synthesizes the channel estimation value of the common pilot channel signal based on the phase rotation amount estimated by the phase rotation amount estimation unit 210, and outputs the final channel estimation value. The specific method of synthesizing the channel estimates in the channel estimation value synthesizing unit 211 will be described later.

【0055】

The demodulation unit 212 demodulates the modulated signal of the individual channel signal output from the despreading unit 204 based on the channel estimated value output from the channel estimated value combining unit 211, and extracts the received signal.

【0056】

The phase rotation control unit 213 has a phase rotation amount with respect to the base station based on the phase difference between the common pilot channel signal A output from the channel estimation unit 208 and the common pilot channel signal B output from the channel estimation unit 209. Generates a phase rotation control signal that indicates.

【0057】

In the case of the present embodiment, since the phase rotation amount in the phase rotation unit 107 of the base station is "0 °" and "180 °", the phase rotation control unit 213 is the common pilot channel signal A. When the phase difference δ from the common pilot channel signal B is -90 ° δ <90 °, the phase rotation amount is set to "0 °", and in other cases, the phase rotation amount is set to "180 °". Outputs the phase rotation control signal.

【0058】

The multiplexing unit 214 multiplexes the phase rotation control signal output from the phase rotation control unit 213 with the transmission signal. The modulation unit 215 performs a primary modulation process such as QPSK on the output signal of the multiplexing unit 214. The spreading unit 216 multiplies the output signal of the modulation unit 215 by a unique spreading code to spread the signal. The transmission RF unit 217 converts the output signal of the diffusion unit 216 into a radio frequency, amplifies it, and wirelessly transmits it from the antenna 201 via the duplexer 202.

【0059】

Next, the relationship between the channel estimates estimated by the channel estimation units 207, 208, and 209 will be described with reference to FIG.

【0060】

FIG. 3 (a) shows the relationship between the estimated values of each channel when the phase rotation amount is 0 °, and FIG. 3 (b) shows the estimated values of each channel when the phase rotation amount is 180 °. Show the relationship.

【0061】

In the following description, the channel estimate value of the individual channel signal A is β._aLet (n) be, and set the channel estimate of the individual channel signal B to β._{b b}Let it be (n). In this case, the channel estimate β (n) of the individual channel signal is β._a(n) and β_{b b}Represented as a composite vector of (n) Also, the channel estimate of the common pilot channel signal A is α_aLet (n) and set the channel estimate of the common pilot channel signal B to α._{b b}Let it be (n).

【0062】

As shown in Fig. 3 (a), when the phase rotation amount is "0 °", the phase and propagation path of the individual channel signal A and the common pilot channel signal A are the same, so β_aVector (n) and α_aIt points in the same direction as the vector in (n). Similarly, β_{b b}Vector (n) and α_{b b}It points in the same direction as the vector in (n).

【0063】

If the base station does not change the amplitudes of the individual channel signal A and the individual channel signal B, β_aα for (n)_aAmplitude ratio of (n) and β_{b b}α for (n)_{b b}The amplitude ratios of (n) are equal.

【0064】

Therefore, the channel estimate β (n) of the individual channel signal is α._a(n) and α_{b b}The composition result of (n) faces the same direction as α (n).

【0065】

That is, when the phase rotation amount is "0 °", the channel can be estimated by synthesizing the channel estimated value of the common pilot channel signal A and the channel estimated value of the common pilot channel signal B.

【0066】

On the other hand, when the phase rotation amount is "180 °" as shown in Fig. 3 (b), the phase of the individual channel signal B is rotated 180 ° with respect to the common pilot channel signal B, so β_{b b}Vector (n) and α_{b b}It points in a different direction from the vector in (n). Therefore, unlike the case where the phase rotation amount is 0 °, the channel cannot be estimated using the composite result of the channel estimates of the common pilot channel signal.

【0067】

However, α_{b b}Value of (n) rotated 180 ° -α_{b b}The vector of (n) is β_{b b}It points in the same direction as the vector in (n). Therefore, β (n) is α_a(n) and -α_{b b}The composition result of (n) faces the same direction as α'(n).

【0068】

That is, when the phase rotation amount is "180 °", the channel can be estimated by synthesizing the channel estimated value of the common pilot channel signal A and the channel estimated value of the common pilot channel signal B rotated by 180 °.

【0069】

If the phase rotation amount can be estimated in this way, the channel estimation can be performed based on the channel estimation value of the common pilot channel signal. Since the common pilot channel signal has a higher transmission power than the individual channel signal, the reliability of the channel estimate is higher than that of using the individual channel signal.

【0070】

Hereinafter, a method for estimating the phase rotation amount in the phase rotation amount estimation unit 210 will be described.

【0071】

When two channel estimates are parallel, the complex conjugate of one channel estimate and the other channel estimate are orthogonal. The amplitudes of the two channel estimates are then minimized when they are orthogonal to each other.

【0072】

For example, when the phase rotation amount is 0 °, as described above, the channel estimated value β (n) of the individual channel signal is in the same direction as the composite result α (n) of the channel estimated value of the common pilot channel signal. Since it faces, the complex conjugate α of β (n) and α (n)^*It is orthogonal to (n).

【0073】

From this relationship, the phase rotation amount estimation unit 210 first determines the channel estimation value α of the common pilot channel signal A._a(n) and the channel estimate α of the common pilot channel signal B_{b b}The combined value α'(n) with the value obtained by phase-rotating (n) by θ is calculated by the following equation (1).

【0074】

(Number 1) α'(n) = α_a(n) + exp (jθ) × α_{b b}(n) (1) [0075]

Then, the phase rotation amount estimation unit 210 has an amplitude for each predetermined candidate value of θ (in the case of this embodiment, two types of θ = 0 ° and 180 °) according to the following equation (2). X (θ) is calculated, the candidate value with the minimum X (θ) is estimated as the phase rotation amount θ, and the phase rotation amount θ is output to the channel estimation value synthesizer 211.

【0076】

(Number 2) X (θ) = Re [α'^*(n)] × Re [β (n)] + Im [α'^*(n)] × Im [β (n)] (2) [0077]

here,(·)^*Indicates the complex conjugate, Re [] indicates the real part, and Im [] indicates the imaginary part.

【0078】

Since the communication terminal knows the phase rotation control signal transmitted to the base station, the phase rotation amount estimation unit 210 first evaluates X (θ) using the phase rotation control signal, and then X (θ). When θ) is smaller than the threshold value, the θ may be estimated as the phase rotation amount θ. As a result, there is a high possibility that the phase rotation amount can be estimated by one calculation, so that the estimation time of the phase rotation amount can be shortened.

【0079】

Next, a method of calculating the channel estimated value in the channel estimated value synthesizing unit 211 will be described.

【0080】

The channel estimation value synthesis unit 211 receives the channel estimation value β (n) of the individual channel signal from the channel estimation unit 207 and the channel estimation value α of the common pilot channel signal A from the channel estimation unit 208._a(n) is the channel estimation value α of the common pilot channel signal B from the channel estimation unit 209._{b b}For (n), the phase rotation amount θ is input from the phase rotation amount estimation unit 210.

【0081】

Then, the final channel estimated value ξ (n) is calculated by the following equation (3) and output to the demodulation unit 212.

【0082】

(Number 3) ξ (n) = α_a(n) + exp (jθ) × α_{b b}(n) + β (n) (3) [0083]

In this way, since the common pilot channel signal has a larger transmission power than the individual channel signal, the reliability of the channel estimation value is obtained by performing the channel estimation based on the phase rotation amount and the channel estimation value of the common pilot channel signal. Can be improved.

【0084】

(Embodiment 2) The second embodiment is a mode in which the base station transmits the individual channel signal A and the individual channel signal B with different amplitudes.

【0085】

Hereinafter, the relationship between the channel estimates in the present embodiment will be described with reference to FIG.

【0086】

When the amplitude of the individual channel signal B is a times the individual channel signal A (hereinafter, this a is referred to as the "amplitude coefficient") at the base station, β_aα for (n)_aIf the amplitude ratio of (n) is k, then β_{b b}α for (n)_{b b}The amplitude ratio of (n) is (k × a).

【0087】

In this case, as shown in FIG. 4, the channel estimated value β (n) of the individual channel signal and the combined value α (n) of the channel estimated values of the common pilot channel signal A and the common pilot channel signal B point in the same direction. There is no.

【0088】

Therefore, when transmitting by changing the amplitudes of the individual channel signal A and the individual channel signal B in the base station, α (n) cannot be used as it is for channel estimation, and it is necessary to consider the amplitude coefficient a.

【0089】

FIG. 5 is a block diagram showing a configuration of a communication terminal according to the second embodiment of the present invention. In the communication terminal shown in FIG. 5, the components common to the communication terminal shown in FIG. 2 are designated by the same reference numerals as those in FIG. 2 and the description thereof will be omitted.

【0090】

The communication terminal shown in FIG. 5 has a configuration in which an amplitude / phase rotation amount estimation unit 301 is added instead of the phase rotation amount estimation unit 210 to the communication terminal shown in FIG.

【0091】

The amplitude / phase rotation amount estimation unit 301 first first estimates the channel estimation value α of the common pilot channel signal A._a(n) and the channel estimate α of the common pilot channel signal B_{b b}The combined value α'(n) with the value obtained by phase-rotating (n) by θ is calculated by the following equation (4).

【0092】

(Number 4) α'(n) = α_a(n) + a × exp (jθ) × α_{b b}(n) (4) [0093]

Then, the amplitude / phase rotation amount estimation unit 301 uses a predetermined candidate value for each θ by the following equation (5) (in the case of this embodiment, there are two types, θ = 0 ° and 180 °). , And the amplitude X (a, θ) is calculated for each predetermined candidate value of the amplitude coefficient a (for example, a = 0.5, 1.0, 2.0, etc.), and the candidate value in which X (θ) is minimized is calculated. Is estimated as the amplitude coefficient a and the phase rotation amount θ, and the amplitude coefficient a and the phase rotation amount θ are output to the channel estimation value synthesis unit 211.

【0094】

(Number 5) X (a, θ) = Re [α'^*(n)] × Re [β (n)] + Im [α'^*(n)] × Im [β (n)] (5) [0095]

The channel estimation value synthesis unit 211 receives the channel estimation value β (n) of the individual channel signal from the channel estimation unit 207 and the channel estimation value α of the common pilot channel signal A from the channel estimation unit 208._a(n) is the channel estimation value α of the common pilot channel signal B from the channel estimation unit 209._{b b}For (n), the amplitude coefficient a and the phase rotation amount θ are input from the amplitude / phase rotation amount estimation unit 301, respectively.

【0096】

Then, the final channel estimated value ξ (n) is calculated by the following equation (6) and output to the demodulation unit 212.

【0097】

(Number 6) ξ (n) = α_a(n) + a × exp (jθ) × α_{b b}(n) + β (n) (6) [0098]

In this way, by performing channel estimation based on the amplitude coefficient, phase rotation amount, and channel estimation value of the common pilot channel signal, the channel estimation value is transmitted even when the amplitude of the individual channel signal is changed and transmitted on the base station side. The reliability of the can be improved.

【0099】

(Embodiment 3) When the maximum fading Doppler frequency is low and the fading fluctuation is gradual, the reliability of the channel estimated value can be improved by averaging the fading estimated value across a plurality of receiving slots. ..

【0100】

However, as described above, when the transmission diversity is introduced into the wireless communication system, the reception slots become discontinuous, so that the channel estimation value cannot be averaged over a plurality of slots.

【0101】

The third embodiment is for solving this problem, and is a mode in which channel estimates are synthesized over a plurality of slots when transmission diversity is introduced.

【0102】

FIG. 6 is a block diagram showing a configuration of a communication terminal according to a third embodiment of the present invention. In the communication terminal shown in FIG. 6, the components common to the communication terminal shown in FIG. 2 are designated by the same reference numerals as those in FIG. 2 and the description thereof will be omitted.

【0103】

The communication terminal shown in FIG. 6 has a configuration in which a multi-channel estimation value synthesis unit 401 is added to the communication terminal shown in FIG.

【0104】

FIG. 7 is a block diagram showing the internal configuration of the multi-channel estimated value synthesizing unit 401.

【0105】

In FIG. 7, the delay circuit 501 stores the channel estimate at the current time (n), and the delay circuit 502 stores the channel estimate at the time (n-1) one slot before.

【0106】

Further, the delay circuit 503 stores the phase rotation amount at the current time (n), and the delay circuit 504 stores the phase rotation amount at the time (n-1) one slot before. Then, the addition circuit 505 calculates the difference between the phase rotation amount at time (n) and the phase rotation amount at time (n-1).

【0107】

In the phase rotation circuit 506, the phase from the time (n-1) to the time (n) based on the calculation result of the addition circuit 505 with respect to the channel estimation value of the time (n-1) output from the delay circuit 502. Correct the amount of rotation.

【0108】

Then, the synthesis circuit 507 synthesizes the corrected channel estimated value output from the phase rotation circuit 506 and the corrected time (n) channel estimated value output from the delay circuit 502. ..

【0109】

In this way, by correcting the channel estimate of the time one slot before and synthesizing this correction result with the channel estimate of the current time, it is possible to synthesize the channel estimate over a plurality of slots. The reliability of channel estimates can be improved.

【0110】

In the present embodiment, the case where the channel estimated value of the time one slot before is corrected and combined with the channel estimated value of the current time has been described, but the present invention is not limited to one slot before, and which Even in the pre-reception slot, the same correction processing can be performed and combined with the channel estimate value at the current time.

【0111】

It should be noted that the third embodiment can be combined with the second embodiment, and the channel estimates can be synthesized over a plurality of slots even when the base station side transmits the individual channel signals with different amplitudes.

【0112】

[Effect of the invention]

As described above, according to the communication terminal device and the channel estimation method of the present invention, the reliability of the channel estimation value in the wireless communication system using the transmission diversity by using the channel estimation value of the common pilot channel signal and the like. Can be improved.

[Simple explanation of drawings]

[Figure 1]

A block diagram showing a configuration on the transmitting side of a base station that performs wireless communication with the communication terminal of the present invention. [Figure 2]

A block diagram showing a configuration of a communication terminal according to a first embodiment of the present invention. [Fig. 3]

The figure which shows the relationship of the channel estimated value which concerns on the said embodiment. [Fig. 4]

The figure which shows the relationship of the channel estimated value which concerns on Embodiment 2 of this invention. [Fig. 5]

Block diagram showing the configuration of the communication terminal according to the above embodiment [Fig. 6]

A block diagram showing a configuration of a communication terminal according to a third embodiment of the present invention. [Fig. 7]

A block diagram showing an internal configuration of a multi-channel estimated value synthesizer of a communication terminal according to the above embodiment. [Fig. 8]

System configuration diagram of wireless communication system using transmission diversity [Fig. 9]

Block diagram showing the configuration of a conventional communication terminal [Fig. 10]

The figure which shows the relationship between the phase rotation amount and a channel estimate value. [Explanation of symbols]

107 Phase rotating part 207, 208, 209 channel estimator 210 Phase rotation amount estimation unit 211 Channel estimate synthesizer 212 Demodulator 213 Phase rotation control unit 301 Amplitude / Phase Rotation Estimator 401 Multi-channel estimate synthesizer 506 Phase rotation circuit 507 synthesis circuit