JP3588043B2 - Receiver and automatic frequency control method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a receiving device and an automatic frequency control method used in a CDMA wireless communication system.
[0002]
[Prior art]
2. Description of the Related Art In recent years, wireless communication systems such as mobile phones and car phones have rapidly become widespread. In the communication terminal apparatus of this wireless communication system, the receiving apparatus performs automatic frequency control (hereinafter, referred to as "AFC") in order to compensate for a difference in carrier frequency with the transmitting apparatus.
[0003]
Hereinafter, a conventional receiving apparatus will be described with reference to FIGS. FIG. 7 is a diagram illustrating a slot configuration of data transmitted from the transmission device. FIG. 8 is a block diagram showing a configuration of a conventional receiving apparatus.
[0004]
As shown in FIG. 7, a transmitting device (not shown) transmits a signal including a known symbol 11 and a known symbol 12 spread by CodeA and CodeB, respectively. Here, the code lengths of CodeA and CodeB are respectively t_CAAnd t_CBAnd the interval between the known symbols 11 and 12 is t_gapAnd
[0005]
The signal transmitted from the transmitting device is received by the receiving device shown in FIG. In FIG. 8, a signal (received signal) received by antenna 21 is frequency-converted from a carrier frequency to a baseband by reception RF section 22. At this time, the reception RF section 22 uses a local signal oscillated from an oscillator 38 described later. The in-phase component (I-ch) and the quadrature component (Q-ch) of the baseband signal (reception baseband signal) output from the reception RF unit 22 are respectively A / D converters 23 and A / D converters 24. Is converted into a digital signal, and is output to the searcher 25, the correlator 26, the correlator 27, and the correlator 28.
[0006]
The searcher 25 correlates the received baseband signal converted into a digital signal with CodeA, which is a known code, and the timing at which the power of the correlation value exceeds a threshold (that is, the reception timing of CodeA) t_AIs detected. In searcher 25, t_A+ T_gap, The reception timing t of CodeB_BIs calculated. In searcher 25, t_A+ T_CA/ 2, the reception timing t at the beginning of the data part_DataIs calculated.
[0007]
The searcher 25 outputs the reception timing of the head of the data section to the correlator 26 and the synchronous detector 29, the searcher 25 outputs the CodeA reception timing to the correlator 27, and the searcher 25 transmits the CodeA reception timing to the correlator 28. Thus, the reception timing of CodeB is output.
[0008]
The correlator 26 correlates the data portion of the received baseband signal with a predetermined spreading code (a spreading code assigned to the receiving device) based on the reception timing at the beginning of the data portion from the searcher 25. The data part of the received baseband signal after the correlation processing is output to the synchronous detector 29.
[0009]
The correlator 27 correlates the known symbol 11 of the received baseband signal with CodeA based on the reception timing of CodeA from the searcher 25. Similarly, the correlator 28 correlates the known symbol 12 of the received baseband signal with the CodeB based on the reception timing of the CodeB from the searcher 25.
[0010]
The synchronous detection unit 29 performs a synchronous detection process on the data portion of the received baseband signal that has been subjected to the correlation process based on the reception timing of the head of the data portion from the searcher 25. The data part of the received baseband signal after the synchronous detection is demodulated by the demodulation unit 30 and the received data is extracted.
[0011]
The in-phase component of the known symbol 11 of the received baseband signal subjected to the correlation processing is calculated by the delay unit 31 at t_AB(= T_CA/ 2 + t_gap+ T_CB/ 2; see FIG. 7) and output to the complex correlation operation unit 33. Similarly, the orthogonal component of the known symbol 11 of the received baseband signal subjected to the correlation processing is calculated by the delay unit 32 at t_AB(= T_CA/ 2 + t_gap+ T_CB/ 2), and then output to the complex correlation operation unit 33. The in-phase component and the quadrature component of the known symbol 12 of the received baseband signal subjected to the correlation processing are output to the complex correlation calculator 33, respectively.
[0012]
The complex correlation calculator 33 performs a complex correlation process using the in-phase components of the known symbols 11 and 12 of the received baseband signal subjected to the correlation process. Further, the complex correlation operation unit 33 performs a complex correlation process using the orthogonal components of the known symbols 11 and the known symbols 12 of the received baseband signal subjected to the correlation process. The in-phase component and the quadrature component of the received baseband signal after the complex correlation processing are output to phase estimating section 34.
[0013]
The phase estimator 34 estimates the amount of phase rotation per unit time using the in-phase component and the quadrature component of the received baseband signal after the complex correlation processing output from the complex correlation calculator 33. In the smoothing unit 35, the frequency offset is calculated using the phase rotation amount estimated by the phase estimating unit 34. The calculated frequency offset is output to the control voltage converter 36.
[0014]
The control voltage converter 36 outputs a signal having a predetermined control voltage applied to the oscillator 38 in order to compensate for the calculated frequency offset. The signal output from the control voltage converter 36 is converted to an analog signal by a D / A converter 37 and then output to an oscillator 38. Thus, the frequency of the local signal in the oscillator 38 is controlled so as to compensate for the frequency offset.
[0015]
As described above, the conventional receiving apparatus estimates the amount of phase rotation between known symbols in a received signal, calculates a frequency offset, and performs AFC so as to compensate for the frequency offset.
[0016]
[Problems to be solved by the invention]
However, since the known symbols after correlation are affected by the cross-correlation of the spreading code and the noise, the above-mentioned conventional receiving apparatus cannot accurately estimate the amount of phase rotation between known symbols. It is difficult, and there is a problem that the accuracy of AFC is deteriorated.
[0017]
The present invention has been made in view of such a point, and it is possible to highly accurately estimate the amount of phase rotation between known symbols by suppressing the influence of cross-correlation of a spreading code and the influence of noise. It is an object of the present invention to provide a receiving apparatus and an automatic frequency control method capable of realizing the above.
[0018]
[Means for Solving the Problems]
The receiving device of the present invention includes:Searching means for calculating a first correlation value that is a correlation value between the received signal in which a known symbol including a part of a predetermined basic code is inserted and the basic code, and a first correlation value exceeding a predetermined threshold value; Determining means for determining the number and type of known symbols time-multiplexed based on the number and the time zone to which the reception timing belongs; a received signal portion in which the first half of the known symbol is inserted; A second correlation value, which is a correlation value with a known symbol determined to be multiplexed, and a third correlation value, which is a correlation value between the latter half of the known symbol and the determined known symbol,A correlation value calculating means for calculating,From the phase difference between the addition result of the second correlation value and the addition result of the third correlation value,The configuration includes a phase rotation amount estimating unit for estimating the phase rotation amount, and a frequency control unit for controlling the frequency of the oscillator so as to compensate for the frequency offset based on the phase rotation amount.
[0022]
According to these configurations, the amount of phase rotation can be estimated using a value obtained by adding the correlation values of a plurality of known symbols. Therefore, in the estimation of the amount of phase rotation, the influence of cross-correlation of spread codes and the influence of noise are suppressed. A high-precision AFC can be realized.
[0023]
In the receiving apparatus according to the present invention, the correlation value calculating means may include a fourth correlation value which is a correlation value between the received signal part in which the known symbol is inserted and the known symbol determined to be time-multiplexed by the determination means. A fifth correlation value, which is a correlation value between the received signal and the spreading code of the control channel, is calculated, and the phase rotation amount estimating means calculates the fourth correlation value when the number of time-multiplexed known symbols is one. A configuration for estimating the amount of phase rotation from the phase difference with the fifth correlation value is employed.
[0024]
With this configuration, stable AFC can be performed even when the number of time-multiplexed known symbols is one.
[0025]
The receiving apparatus of the present invention employs a configuration in which the correlation value calculating means calculates a fifth correlation value using a cell-specific control channel.
[0026]
With this configuration, the amount of phase rotation is not erroneously estimated using the control channel of another cell, so that the stability of the system is improved.
[0027]
In the receiving apparatus according to the present invention, the phase rotation amount estimating means may be configured such that, even when the number of the time-multiplexed known symbols is 1, if the control channel and the known symbols are temporally close, the second A configuration is employed in which the amount of phase rotation is estimated from the phase difference between the correlation value and the third correlation value.
[0028]
With this configuration, even if the number of known symbols that are time-multiplexed is 1, and the control channel and the known symbols are temporally close, a certain degree of stable AFC can be realized.
[0029]
A communication terminal device according to the present invention has a configuration in which any one of the receiving devices described above is mounted.take.Further, a base station apparatus according to the present invention has a configuration in which any of the above-described receiving apparatuses is mounted.take.
[0030]
With these configurations, it is possible to suppress the influence of cross-correlation of spread codes and the influence of noise in estimating the amount of phase rotation, and realize high-precision AFC. Therefore, high-quality wireless communication can be performed. it can.
[0031]
The automatic frequency control method according to the present invention includes: a step of calculating a first correlation value that is a correlation value between a received signal in which a known symbol including a part of a predetermined basic code is inserted and the basic code; Determining the number, type and correlation processing timing of known symbols time-multiplexed based on the number of the first correlation values that have exceeded and the time zone to which the reception timing belongs; and the number of the determined known symbols. Calculating a correlation value of one or a plurality of time-multiplexed received signals based on the type and timing of the correlation processing; estimating a phase rotation amount using an added value of the correlation values; Controlling the frequency of the oscillator to compensate for the frequency offset based on the amount of rotation. Also,The automatic frequency control method of the present invention calculates a first correlation value that is a correlation value between a received signal in which a known symbol including a part of a predetermined basic code is inserted and the basic code, and exceeds a predetermined threshold. The number and type of known symbols that are time-multiplexed are determined based on the number of the first correlation value and the time zone to which the reception timing belongs, and the time-multiplexed with the received signal portion in which the first half of the known symbol is inserted. Calculating a second correlation value that is a correlation value with the known symbol determined to be present and a third correlation value that is a correlation value between the second half of the known symbol and the determined known symbol, and calculating the second correlation value. A method of estimating the amount of phase rotation from the phase difference between the result of addition of the third correlation value and the result of addition of the third correlation value, and controlling the frequency of the oscillator so as to compensate for the frequency offset based on the amount of phase rotation.
[0032]
According to this method, the amount of phase rotation can be estimated using a value obtained by adding the correlation values of a plurality of known symbols. Therefore, in the estimation of the amount of phase rotation, the effect of cross-correlation of spread codes and the effect of noise can be suppressed. A high-precision AFC can be realized.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
The gist of the present invention is that the transmitting side inserts a known symbol consisting of a spread code obtained by code shift into transmission data and performs multiplex transmission, and the receiving side uses a value obtained by adding the correlation values of a plurality of known symbols to obtain a phase rotation amount. Is to estimate
[0034]
Prior to the description of each embodiment, first, a method of generating a spread code of a known symbol part inserted into transmission data by the transmission side in the present invention will be described with reference to FIG.
[0035]
In FIG. 1, the length of a basic code is P (chip), and the maximum delay profile length of a wireless channel is W (chip). Also, two identical basic codes are arranged in series, and the basic code BC₁And the back is the basic code BC₂And
[0036]
The spreading code Code1 for the user 1 is the basic code BC₁Basic code BC₂Is created by adding the part of W from the beginning of. The spreading code Code2 for the user 2 is the basic code BC₁Basic code BC is obtained by removing W from the beginning of₂Is created by adding a 2 × W portion from the beginning of That is, the spreading code Code2 is the basic code BC₁, BC₂In FIG. 7, the portion corresponding to the spread code Code1 is moved (shifted) backward by W.
[0037]
Similarly, assuming that the number of users is k, the spreading code Codei for the user i (i = 1, 2,..., K) is the basic code BC₁The basic code BC is obtained by removing the (i-1) × W part from the head of₂Is created by adding the i × W part from the beginning of Each spreading code Codei has a length of Lm = P + W (chip).
[0038]
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the transmitting side is a base station apparatus and the receiving side is a communication terminal apparatus. In the following description, a delayed wave is not considered. In the following description, a spread code generated by the method shown in FIG. 1 is referred to as a “shift code”.
[0039]
(Embodiment 1)
FIG. 2 is a diagram illustrating a slot configuration of data transmitted from a base station apparatus that performs wireless communication with the communication terminal apparatus according to Embodiment 1 of the present invention. As shown in FIG. 2, a known symbol is inserted substantially at the center of the slot. This known symbol is a spread code generated by the method shown in FIG. The data part is multiplied by a spreading code unique to each user.
[0040]
The base station apparatus multiplexes and transmits a signal having the slot configuration shown in FIG. 2 to each communication terminal apparatus (user) during communication. Also, the basic code and the shift amount are notified to each communication terminal device in advance by transmitting and receiving the control signal.
[0041]
FIG. 3 is a block diagram showing a configuration of the communication terminal device according to the present embodiment. FIG. 3 shows the configuration on the receiving side of the communication terminal apparatus, and the configuration on the transmitting side is omitted.
[0042]
Receiving antenna 101 receives a radio signal transmitted from the base station device. The reception RF unit 102 multiplies the reception signal of the reception antenna 101 by a local signal oscillated by an oscillator 123 described later, and converts the frequency of the reception signal to baseband.
[0043]
The A / D converter 103 performs A / D conversion on an in-phase component (I-ch) of a baseband signal (hereinafter, referred to as “reception baseband signal”) output from the reception RF unit 102. Similarly, A / D converter 104 performs A / D conversion on the quadrature component (Q-ch) of the received baseband signal.
[0044]
The searcher 105 creates a delay profile of the known symbol portion of the received baseband signal converted into a digital signal using the basic code shown in FIG. Is received and output to the code number / type determination unit 106. Also, the searcher 105 calculates the reception timing at the head of the data part based on the reception timing of the known symbol, and outputs the calculated reception timing to the correlator 107 and the synchronous detection unit 110.
[0045]
The code number / type determination unit 106 determines the number and type of the currently used shift codes based on the reception timing of the known symbols from the searcher 105, and determines the correlators 108-1 to n and the correlators 109-1. To n (n is a natural number of 2 or more) indicating the timing of the correlation process. The details of the determination of the number of codes and the type in the code number / type determination unit 106 will be described later.
[0046]
Correlator 107 correlates the data portion of the received baseband signal with a predetermined spreading code (spreading code assigned to its own device) based on the reception timing at the beginning of the data portion from searcher 105, and performs a correlation process. The data part of the subsequent received baseband signal is output to synchronous detection section 110.
[0047]
Correlators 108-1 to 108-n respectively provide a correlation value between the known symbol first half of the received baseband signal and the shift code (hereinafter, referred to as "symbol first half correlation value") in accordance with an instruction from code number / type determination section 106. Is calculated. Similarly, correlators 109-1 to n correspond to the correlation value between the latter half of the known symbol of the received baseband signal and the shift code (hereinafter referred to as the “symbol second half correlation value”) in accordance with the instruction from code number / type determination section 106, respectively. ").
[0048]
Synchronous detection section 110 performs synchronous detection processing on the data section of the received baseband signal after the correlation processing based on the reception timing of the head of the data section from searcher 105, and outputs the result to demodulation section 111. Demodulation section 111 performs demodulation processing on the data part of the received baseband signal that has been synchronously detected, and extracts received data.
[0049]
The adder 112 adds the in-phase components of the first half symbol correlation values calculated by the correlators 108-1 to 108-n, respectively. Similarly, the adder 113 adds the orthogonal components of the first-half symbol correlation values calculated by the correlators 108-1 to 108-n, respectively.
[0050]
The adder 114 adds the in-phase components of the symbol second-half correlation values calculated by the correlators 109-1 to 109-n, respectively. Similarly, the adder 115 adds the orthogonal components of the symbol second-half correlation values calculated by the correlators 109-1 to 109-n, respectively.
[0051]
The delay unit 116 delays the in-phase component of the symbol first half correlation value added by the adder 112 by a predetermined amount, and then outputs the delayed component to the complex correlation operation unit 118. Similarly, delay section 117 delays the orthogonal component of the first-half symbol correlation value added by adder 113 by a predetermined amount, and outputs the result to complex correlation operation section 118.
[0052]
Complex correlation operation section 118 performs a complex correlation process using the in-phase component of the symbol first half correlation value after addition and the in-phase component of the symbol second half correlation value after addition. Further, the complex correlation operation unit 118 performs a complex correlation process using the orthogonal component of the symbol first half correlation value after addition and the orthogonal component of the symbol second half correlation value after addition.
[0053]
The phase estimating unit 119 estimates the amount of phase rotation per unit time using the in-phase component and the quadrature component of the correlation value after the complex correlation processing output from the complex correlation calculating unit 118. The details of the estimation of the amount of phase rotation by the phase estimation unit 119 will be described later.
[0054]
The smoothing unit 120 calculates the frequency offset by smoothing the phase rotation amount estimated by the phase estimation unit 119. The control voltage converter 121 outputs a signal having a predetermined control voltage applied to the oscillator 123 to the D / A converter 122 to compensate for the calculated frequency offset. The D / A converter 122 converts a signal output from the control voltage converter 121 into an analog signal. The oscillator 123 oscillates a local signal having a frequency corresponding to the voltage of the output signal of the D / A converter 122.
[0055]
Next, the operation of the AFC in the communication terminal device shown in FIG. 1 will be described.
[0056]
The radio signal transmitted from the base station apparatus is received by the reception antenna 101, and is multiplied by the reception RF section 102 by the local signal oscillated by the oscillator 123 to be converted into a baseband frequency.
[0057]
The in-phase component of the received baseband signal is converted to a digital signal by the A / D converter 103, and the quadrature component of the received baseband signal is converted to a digital signal by the A / D converter 104. The received baseband signal converted to a digital signal is output to searcher 105, correlator 107, correlators 108-1 to n, and correlators 109-1 to n.
[0058]
In the searcher 105, a delay profile of a known symbol portion of the received baseband signal converted into a digital signal is created based on the basic code shown in FIG. 1, the reception timing of the known symbol is detected, and the code number / type determining unit is used. At 106, the number and type of shift codes currently used are determined.
[0059]
The correlator 107 correlates the data portion of the received baseband signal with a predetermined spreading code (a spreading code assigned to the own device) based on the reception timing at the head of the data portion. Then, synchronous detection section 110 performs synchronous detection processing on the data section of the received baseband signal after the correlation processing based on the reception timing at the beginning of the data section, and demodulation section 111 performs synchronous detection. A demodulation process is performed on the data portion of the received baseband signal to extract the received data.
[0060]
Further, in correlators 108-1 to 108-n, the first half correlation value of the symbol is calculated based on the second half of the known symbol and the shift code of the received baseband signal. Similarly, in correlators 109-1 to 109-n, the latter half symbol correlation value is calculated based on the latter half of the known symbol and the shift code of the received baseband signal.
[0061]
The in-phase and quadrature components of the symbol first half correlation values calculated by the correlators 108-1 to 108-n are added by adders 112 and 113, and delayed by delay units 116 and 117 by a predetermined amount. The in-phase component and the quadrature component of the symbol second-half correlation values calculated by the correlators 109-1 to 109-n are added by adders 114 and 115.
[0062]
Then, complex correlation operation section 118 adds the in-phase component of the symbol first half correlation value after the addition and the in-phase component of the symbol second half correlation value after the addition, and adds the quadrature component of the symbol first half correlation value after the addition. A complex correlation process is performed with the orthogonal component of the later symbol second half correlation value.
[0063]
Then, the phase estimation unit 119 estimates the amount of phase rotation per unit time based on the in-phase component and the quadrature component of the correlation value after the complex correlation processing, and the smoothing unit 120 smoothes the amount of phase rotation to reduce the frequency offset. Is calculated. The calculated frequency offset is output to control voltage conversion section 121.
[0064]
In the control voltage conversion unit 121, a signal having a predetermined control voltage is output to the D / A converter 122, converted into an analog signal, and then output to the oscillator 123 in order to compensate for the calculated frequency offset. . The oscillator 123 oscillates a local signal having a frequency corresponding to the voltage of the output signal of the D / A converter 122.
[0065]
Next, details of the determination of the number of codes and the type in the code number / type determination unit 106 will be described with reference to the diagram showing the delay profile in FIG. FIG. 4 is a diagram showing a delay profile created by the communication terminal device according to the present embodiment. In FIG. 4, the horizontal axis is time, and the vertical axis is power.
[0066]
When the base station apparatus multiplexes the data shown in FIG. 2 to a plurality of communication terminal apparatuses, the base station uses the basic code on the receiving side of the communication terminal apparatus to generate a known symbol part of the received baseband signal. When a delay profile is created, peaks exceeding the threshold value are detected by the number of communication terminal devices that are currently communicating.
[0067]
Then, when the base station apparatus is performing wireless communication with the communication terminal apparatus using the shift code Codei, the time at which the base station apparatus transmits data is set to 0, and the time (i−1) × W to the time i × W The peak exceeding the threshold appears in the range of the time zone Ti that is less than.
[0068]
For example, in the case of FIG. 4, since the peaks P1 and P3 exceeding the threshold appear within the range of T1 and T3, the base station apparatus performs wireless communication with the communication terminal apparatus using the shift code Code1 and the shift code Code3. It turns out that it is.
[0069]
The number-of-codes / type determining unit 106 determines the number of communication terminals with which the base station apparatus is currently performing wireless communication based on the number of peaks exceeding the threshold, and based on the time zone to which the timing of the peak belongs, The base station device determines a shift code used for a known symbol of a transmission signal.
[0070]
In the case of FIG. 4, the code number / type determination unit 106 instructs the correlator 108-1 to use the time P1 as the timing of the correlation processing, and instructs the correlator 108-2 to use the time P3 as the timing of the correlation processing. To indicate. The number-of-codes / type determining unit 106 determines the length of the known symbol part by t._kThen, the time (P1 + t) is given to the correlator 109-1._k/ 2) as the timing of the correlation processing, and the time (P3 + t) is given to the correlator 109-2._k/ 2) is designated as the timing of the correlation processing.
[0071]
Next, details of the estimation of the amount of phase rotation by the phase estimating unit 119 will be described with reference to FIG. FIG. 5 is a diagram showing the amount of phase rotation estimated by the communication terminal device according to the present embodiment. In FIG. 5, the correlation value is represented by a vector on the IQ plane.
[0072]
In FIG. 5A, a vector 201 is a symbol first half correlation value between the known symbol first half of the received baseband signal and the shift code Code1, and a vector 202 is a known symbol first half of the received baseband signal and the shift code Code3. , And the vector 203 is a composite vector obtained by adding the vector 201 and the vector 202.
[0073]
In FIG. 5B, a vector 211 is a correlation value of the latter half of the known symbol of the received baseband signal and the shift code Code1, and a vector 212 is a correlation of the second half of the known symbol of the received baseband signal and the shift code. This is a symbol second half correlation value with Code3, and the vector 213 is a composite vector obtained by adding the vector 211 and the vector 212.
[0074]
In FIG. 5C, the angle difference θ between the combined vector 203 and the combined vector 213 indicates the amount of phase rotation. The phase estimating unit 119 estimates a phase rotation amount using a value obtained by adding the correlation values of a plurality of known symbols.
[0075]
As described above, the transmitting side inserts the known symbol composed of the spread code obtained by the code shift into the transmission data and performs multiplex transmission, so that the receiving side can calculate the correlation value of a plurality of known symbols.
[0076]
Here, since the cross-correlation and noise of the spread code affecting the correlated known symbols are random, the cross-correlation of the spread code is estimated in the estimation of the amount of phase rotation by adding the correlation values of a plurality of known symbols. The effect of noise and the effect of noise are suppressed.
[0077]
Therefore, the transmitting side inserts a known symbol consisting of a spread code obtained by code shifting into transmission data and performs multiplex transmission, and the receiving side estimates the amount of phase rotation using a value obtained by adding the correlation values of a plurality of known symbols. Accordingly, the amount of phase rotation between known symbols can be estimated with high accuracy, and highly accurate AFC can be realized.
[0078]
It is preferable that the number n of the correlators 108-1 to n and the number n of the correlators 109-1 to n is equal to the number of codes that can be communicated at the same time. Holds. In this case, the code number / type determination unit 106 sequentially selects the shift codes having the highest peak among the shift codes currently used, and sends them to the correlators 108-1 to n and the correlators 109-1 to n. Indicates the timing of the correlation process.
[0079]
(Embodiment 2)
Here, in the first embodiment, when only one communication terminal device is currently communicating with the base station device, the feature of adding the correlation value of the known symbol cannot be utilized, and However, since the phase rotation amount is estimated in the first half and the second half of the known symbol portion that are close in time, the estimation accuracy of the phase rotation amount is considered to deteriorate rather than in the related art.
[0080]
In the second embodiment, in order to solve the above problem, a case will be described in which the correlation value used for estimating the amount of phase rotation is switched according to the number of shift codes currently used.
[0081]
FIG. 6 is a block diagram showing a configuration of a communication terminal device according to Embodiment 2 of the present invention. In the communication terminal device shown in FIG. 6, the same components as those in the communication terminal device shown in FIG.
[0082]
The communication terminal device shown in FIG. 6 differs from the code number / type determination unit 106 of the communication terminal device shown in FIG. The communication terminal device shown in FIG. 6 has a configuration in which correlators 302 and 303 and a switching unit 304 are added, as compared with the communication terminal device shown in FIG.
[0083]
The searcher 105 detects the timing at which the power of the correlation value exceeds the threshold (that is, the reception timing of the known symbol), and outputs it to the code number / type determination unit 301.
[0084]
The code number / type determining unit 301 determines the number and type of the currently used shift code based on the reception timing of the known symbol from the searcher 105. When the number of currently used shift codes is plural, the code number / type determining unit 301 sends the code to the correlators 108-1 to n and the correlators 109-1 to n (n is a natural number of 2 or more). On the other hand, it instructs the timing of the correlation processing, and when it is a singular number, instructs the correlator 302 to indicate the timing of the correlation processing and instructs the correlator 303 to execute the correlation processing.
[0085]
Further, the code number / type determining unit 301 controls the switching unit 304 to perform switch switching based on the number of currently used shift codes. Specifically, when the number of shift codes currently used is plural, the adder 112 and the delay unit 116, the adder 113 and the complex correlation operation unit 118, the adder 114 and the delay unit 117 and the adder 115 Switching control is performed so as to connect to the complex correlation operation unit 118, respectively. On the other hand, if the number of currently used shift codes is singular, the correlator 302 and the delay unit 116, the correlator 302 and the complex correlation operation unit 118, the correlator 303 and the delay unit 117, and the correlator 303 and the complex correlation operation Switching control is performed so as to connect the respective sections 118.
[0086]
Correlator 302 calculates a correlation value (hereinafter, referred to as “entire symbol correlation value”) between the entire known symbol portion of the received baseband signal and the shift code in accordance with an instruction from code number / type determination section 301.
[0087]
Correlator 303 calculates a correlation value (hereinafter, referred to as “control channel correlation value”) between the received received signal of the control channel for synchronization and the spread code of the control channel in accordance with an instruction from code number / type determination section 301. I do.
[0088]
The switching unit 304 switches the connection according to the control of the code number / type determining unit 301 described above.
[0089]
As a result, when the number of currently used shift codes is singular, phase estimating section 119 estimates the amount of phase rotation from the angle difference between the overall symbol correlation value and the synchronization control channel correlation value.
[0090]
As described above, by switching the correlation value used for estimating the amount of phase rotation according to the number of currently used shift codes, the same effect as in the first embodiment can be obtained when the number of shift codes is plural. Thus, stable AFC can be performed even when the number of shift codes is single.
[0091]
Here, when a common control channel for synchronization is used in all cells, there is a possibility that the amount of phase rotation is erroneously estimated using the control channel of another cell. In this case, the accuracy of pulling in the frequency offset is large. Will deteriorate. Therefore, by estimating the amount of phase rotation using the synchronization control channel unique to each cell, the stability of the system is improved.
[0092]
Further, the offset amount of the synchronization control channel with respect to the head of the slot differs from cell to cell, and the position of the synchronization control channel may be temporally closer to the position of the known symbol part. In this case, AFC can be performed with higher accuracy by estimating the amount of phase rotation in the former half and the latter half of the known symbol part as described in the first embodiment. Therefore, the communication terminal apparatus knows the position of the control channel for synchronization before the line is established, and appropriately switches the signal used for estimating the amount of phase rotation based on the positional relationship between the position of the control channel for synchronization and the known symbol part. This makes it possible to always achieve a certain degree of stable AFC.
[0093]
By combining the above embodiments with space diversity reception and path diversity reception, more stable and highly accurate AFC can be performed.
[0094]
Further, in each of the above embodiments, the transmitting side is described as a base station apparatus and the receiving side is described as a communication terminal apparatus. However, the present invention can be applied even when the receiving side is a base station apparatus and the transmitting side is a communication terminal apparatus. .
[0095]
Further, in each of the above embodiments, a delayed wave is not taken into account for simplicity of description. However, the present invention includes a component for performing channel estimation, RAKE combining, and the like in a receiving apparatus. The above effects can be obtained even in an existing propagation environment.
[0096]
In each of the above embodiments, the correlation value of a known symbol in another time slot is also added to perform a complex correlation operation, and the amount of phase rotation is estimated. The influence can be suppressed, and more accurate AFC can be realized.
[0097]
【The invention's effect】
As described above, according to the present invention, since the correlation values of a plurality of known symbols can be added, the influence of the cross-correlation of the spread code and the influence of noise can be suppressed to reduce the amount of phase rotation between the known symbols. Estimation can be performed with high accuracy, and highly accurate AFC can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a method of generating a spread code of a known symbol part used in the present invention.
FIG. 2 is a diagram illustrating a slot configuration of data transmitted from a base station apparatus that performs wireless communication with a communication terminal apparatus according to Embodiment 1 of the present invention.
FIG. 3 is a block diagram showing a configuration of a communication terminal device according to the embodiment.
FIG. 4 is a diagram showing a delay profile created by the communication terminal device according to the embodiment.
FIG. 5 is a diagram showing a phase rotation amount estimated by the communication terminal device according to the embodiment.
FIG. 6 is a block diagram showing a configuration of a communication terminal device according to Embodiment 2 of the present invention.
FIG. 7 is a diagram showing a slot configuration of data transmitted from a transmission device.
FIG. 8 is a block diagram showing a configuration of a conventional receiving apparatus.
[Explanation of symbols]
102 RF receiver
105 Searcher
106, 301 Code number / type determination unit
107, 108, 109, 302, 303 correlator
112-115 adder
118 Complex correlation operation unit
119 Phase estimation unit
121 control voltage converter
123 oscillator
304 switching unit

Claims (8)

Search means for calculating a first correlation value that is a correlation value between a received signal in which a known symbol including a part of a predetermined basic code is inserted and the basic code;
Determining means for determining the number and type of known symbols time-multiplexed based on the number of the first correlation values exceeding a predetermined threshold and the time zone to which the reception timing belongs;
A second correlation value that is a correlation value between a received signal portion in which the first half of the known symbol is inserted and a known symbol determined to be time-multiplexed by the determination unit; Correlation value calculating means for calculating a third correlation value that is a correlation value with the obtained known symbol ;
Phase rotation amount estimating means for estimating a phase rotation amount from a phase difference between the addition result of the second correlation value and the addition result of the third correlation value ;
A frequency control means for controlling a frequency of an oscillator so as to compensate for a frequency offset based on the phase rotation amount. The correlation value calculating means includes a fourth correlation value which is a correlation value between the received signal portion in which the known symbol is inserted and the known symbol determined to be time-multiplexed by the determination means, and spread of the received signal and the control channel. A fifth correlation value, which is a correlation value with the code, is calculated, and the phase rotation amount estimating means calculates the difference between the fourth correlation value and the fifth correlation value when the number of time-multiplexed known symbols is one. The receiving apparatus according to claim 1, wherein the amount of phase rotation is estimated from the phase difference. The receiving apparatus according to claim 2 , wherein the correlation value calculating means calculates a fifth correlation value using a cell-specific control channel. Even when the number of known symbols time-multiplexed is one, the phase rotation amount estimating means may determine that the second correlation value and the third correlation value are equal when the control channel and the known symbol are temporally close to each other. The receiving device according to claim 2, wherein the amount of phase rotation is estimated from a phase difference from the value. A communication terminal device comprising the receiving device according to any one of claims 1 to 4 . A base station device comprising the receiving device according to claim 1 . Calculating a first correlation value that is a correlation value between the received signal in which a known symbol including a part of a predetermined basic code is inserted and the basic code;
  Determining the number, type and correlation processing timing of known symbols time-multiplexed based on the number of the first correlation values exceeding a predetermined threshold and the time zone to which the reception timing belongs;
  Calculating a correlation value of one or a plurality of time-multiplexed received signals based on the determined number of known symbols, type and timing of the correlation process;
  Estimating the amount of phase rotation using the sum of the correlation values,
  Controlling the frequency of the oscillator so as to compensate for the frequency offset based on the phase rotation amount. Calculating a first correlation value that is a correlation value between the received signal in which a known symbol including a part of a predetermined basic code is inserted and the basic code, and calculating the number of the first correlation values exceeding a predetermined threshold value and The number and type of known symbols that are time-multiplexed are determined based on the time zone to which the reception timing belongs. A second correlation value that is a correlation value and a third correlation value that is a correlation value between the second half of the known symbol and the determined known symbol are calculated, and a result of adding the second correlation value and the third correlation value are calculated. An automatic frequency control method comprising: estimating a phase rotation amount from a phase difference from a result of addition of the oscillator; and controlling a frequency of an oscillator to compensate for a frequency offset based on the phase rotation amount.

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