JP2011114386A - Base station device, radio communication system and frequency correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base station device providing a high transmission frequency accuracy without the need of providing an oscillator with the high absolute accuracy of a frequency and without using signals transmitted from a mobile terminal. <P>SOLUTION: The base station device, which has an oscillator for generating reference frequency signals and generates transmission signals on the basis of the reference frequency signals, has: frequency deviation calculation parts 21-1 to 21-N for obtaining a frequency deviation on the basis of reception signals received from peripheral base station devices; and a frequency deviation estimation part 22 for obtaining a frequency correction amount for correcting the reference frequency signals on the basis of the frequency deviation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a base station apparatus in a wireless communication system including a mobile terminal such as a car phone or a mobile phone.

  In order to achieve high transmission frequency accuracy, a conventional base station apparatus generates a transmission signal using an oscillator with high absolute frequency accuracy. An oscillator with a high absolute frequency accuracy is expensive and large as a component, which causes an increase in the cost and size of the base station apparatus.

  On the other hand, when a transmission signal is generated by using an oscillator having a low absolute accuracy of the frequency, a signal leaks to another channel adjacent to the frequency, causing a problem that the adjacent channel is disturbed.

  Further, in Patent Document 1 below, when the base station apparatus does not have an oscillator with high frequency absolute accuracy, a clock signal is extracted from an uplink signal from a predetermined mobile terminal in order to improve transmission frequency accuracy. Thus, a method for adjusting the transmission frequency of the local station is disclosed.

JP 2006-295263 A

  However, according to the above-described conventional technique, as described above, there is a problem that the cost and size of the base station apparatus increase when an oscillator having a high frequency absolute accuracy is used. In addition, when an oscillator having a low frequency accuracy is used, there is a problem that adjacent channels are disturbed.

  Further, in the method described in Patent Literature 1, when the base station apparatus does not have an oscillator with high frequency accuracy, the accuracy of the transmission frequency is improved based on the clock signal extracted from the uplink signal of the mobile terminal. Yes. Therefore, there is a problem that at least one of the mobile terminals that perform radio communication with the base station apparatus needs to be a mobile terminal that transmits a frequency signal with high absolute accuracy.

  The present invention has been made in view of the above, and it is not necessary to provide an oscillator with high frequency absolute accuracy, and can achieve high transmission frequency accuracy without using a signal transmitted from a mobile terminal. An object of the present invention is to obtain a base station apparatus, a radio communication system, and a frequency correction method.

  In order to solve the above-described problems and achieve the object, the present invention is a base station apparatus that includes an oscillator that generates a reference frequency signal, and that generates a transmission signal based on the reference frequency signal. A frequency deviation calculating means for obtaining a frequency deviation between the reference frequency signal and a reference frequency signal of the other base station apparatus based on a received signal received from another base station apparatus which is the base station apparatus; and based on the frequency deviation Frequency deviation estimating means for obtaining a frequency correction amount for correcting the reference frequency signal.

  According to the present invention, since the base station apparatus corrects the frequency of its own oscillator using a common known signal transmitted by neighboring base station apparatuses, it is necessary to provide an oscillator with a high absolute accuracy of the frequency. And there is an effect that high transmission frequency accuracy can be realized without using a signal transmitted from the mobile terminal.

FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to the first embodiment. FIG. 2 is a diagram illustrating a functional configuration example of the base station apparatus according to the first embodiment. FIG. 3 is a diagram illustrating a functional configuration example of the digital receiving unit according to the first embodiment. FIG. 4 is a diagram illustrating an example of a received symbol string and a timing change position detected by the path search unit. FIG. 5 is a diagram illustrating an example of the frequency deviation θ (k) and the received symbol power P (k) obtained by the frequency deviation calculator. FIG. 6 is a diagram illustrating a functional configuration example of a digital reception unit of the base station apparatus according to the second embodiment. FIG. 7 is a diagram illustrating a functional configuration example of a digital reception unit of the base station apparatus according to the third embodiment. FIG. 8 is a diagram illustrating an example of a frequency band of the wireless communication system according to the fourth embodiment.

  Hereinafter, embodiments of a base station apparatus, a wireless communication system, and a frequency correction method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a first embodiment of a wireless communication system according to the present invention. As shown in FIG. 1, the radio communication system according to the present embodiment includes base station apparatuses 2-1 to 2-6. The base station device 1 can receive signals transmitted from the base station devices 2-1 to 2-6 to the terminals. 1 shows a case where the total number of base station apparatuses including the base station apparatus 1 is seven, the number of base station apparatuses is not limited to this, and may be any number. .

  FIG. 2 is a diagram illustrating a functional configuration example of the base station apparatus 1 according to the present embodiment. The base station devices 2-1 to 2-6 may have the same configuration as the base station device 1 or different configurations. As shown in FIG. 2, the base station apparatus 1 includes an antenna 11, a circulator 12, an analog receiver 13, an oscillator 14, a digital receiver 15, a digital receiver 16, a digital transmitter 17, and an analog transmitter 18. .

  Next, the overall operation of the base station apparatus 1 will be described. The oscillator 14 outputs a frequency signal (reference frequency signal) having a predetermined frequency. A high-frequency reception signal received by the antenna 11 is input to the analog reception unit 13 via the circulator 12. The analog receiver 13 down-converts the received signal into a baseband signal based on the frequency signal output from the oscillator 14, further adjusts the gain of the baseband signal after down-conversion, and converts the baseband signal after gain adjustment into It converts into a digital reception signal by analog / digital conversion, and outputs a digital reception signal. The analog receiver 13 generates a sampling clock used in the analog / digital conversion process based on the frequency signal output from the oscillator 14.

  The digital receiving unit 15 performs digital processing such as demodulation processing, channel decoding, and error correction on the digital received signal converted by the analog receiving unit 13. The digital receiver 16 adjusts the frequency of the oscillator 14 based on the digital received signal converted by the analog receiver 13.

  The digital transmission unit 17 performs encoding, channel coding, modulation processing, and the like on transmission data input from the network to which the base station apparatus 1 is connected, and outputs the result as a digital transmission signal. The analog transmission unit 18 converts the digital transmission signal output from the digital transmission unit 17 into an analog transmission signal by digital / analog conversion. The analog transmission unit 18 further up-converts the analog transmission signal based on the frequency signal output from the oscillator 14 and transmits the analog transmission signal from the antenna 11 via the circulator 12 as a high-frequency transmission signal. Further, the digital transmission unit 17 generates a sampling clock for digital / analog conversion processing based on the frequency signal output from the oscillator 14.

  The base station apparatus 1 of this Embodiment adjusts the frequency of the frequency signal which the reference | standard oscillator 14 outputs based on the signal transmitted from the surrounding base station apparatuses 2-1 to 2-6. Therefore, there is no problem of preventing leakage of signals to other channels adjacent to each other due to the occurrence of frequency deviation and disturbing the adjacent channels.

  Next, the frequency adjustment method of the present embodiment will be described. FIG. 3 is a diagram illustrating a functional configuration example of the digital receiving unit 16 according to the present embodiment. In FIG. 3, components around the digital receiver 16 are also shown, but the circulator 12 is omitted for the sake of simplicity.

  As shown in FIG. 3, the digital reception unit 16 includes a frequency deviation calculation unit (frequency deviation calculation unit) 21-1 to 21 -N (N is a positive integer) and a frequency deviation estimation unit 22. . The frequency deviation calculation units 21-1 to 21-N have the same configuration. Moreover, since the frequency deviation calculation units 21-1 to 21-N perform processing for each of the surrounding base station apparatuses 2-1 to 2-6, N is equal to or greater than the number of surrounding base station apparatuses. For example, in the configuration of FIG. 1, since the number of peripheral base station apparatuses is 6, N is 6 or more. The frequency deviation calculation unit 21-k (k = 1, 2,..., N) includes a path search unit (path search in the figure) 31, a despreading unit 32, a frequency estimation unit 33, and a level measurement unit 34. The

  The received high frequency reception signal is input to the analog reception unit 13 via the antenna 11 and the circulator 12. The analog receiving unit 13 converts the received signal into a baseband digital received signal by the above-described processing, and outputs it to the digital receiving unit 16.

  In the digital receiver 16, the frequency deviation calculator 21-k calculates a frequency deviation with the own apparatus based on a common known signal (a signal including a known symbol) received from the surrounding base station apparatus 2-k. . It is assumed that the peripheral base station apparatuses 2-1 to 2-6 transmit a common known signal. The signals transmitted from the base station devices 2-1 to 2-6 are spread by the spreading code assigned to each base station to identify the source base station devices 2-1 to 2-6. Based on the spreading code, the frequency deviation calculation unit 21-k processes the received signal transmitted from the base station apparatus each responsible for processing.

  Next, the operation of the frequency deviation calculator 21-k will be described. The path search unit 31 detects the timing (reception timing) of the received signal corresponding to each path of the multipath generated in the propagation path using the known symbol included in the received signal transmitted from the base station apparatus 2-k. To do. As a method for detecting this timing, for example, the method described in “Ishioka et al.,“ W-CDMA compatible path search LSI ”(1999 Annual Conference of the Institute of Electronics, Information and Communication Engineers B-5-12) is used. be able to.

  Here, for simplicity of explanation, the case where the path search unit 31 detects one path will be described. However, the case where a plurality of paths are detected can also be handled by performing the processing described later. .

Based on the timing detected by the path search unit 31, the despreading unit 32 performs a despreading process on the received signal using a spreading code assigned to a common known symbol, and generates a received symbol. Specifically, for example, when the spreading factor is 256, a reception symbol is generated according to the following equation (1).
r (k, m) = Σx (256 × m + i) × CONJG (C (k, 256 × m + i))
... (1)

  The above sum Σ is the sum for i = 1, 2,... CONJG () represents the complex conjugate of the value in parentheses. X (n) is a received signal sampled at a chip rate based on the timing detected by the path search unit 31, and n represents a sample number. C (k, i) is a spreading code of the base station apparatus 2-k assigned to a common known symbol, and r (k, m) is the m-th reception transmitted from the base station apparatus 2-k. Symbol.

The frequency estimation unit 33 uses the received symbol generated by the despreading unit 32 to calculate an average value of frequency deviations from the own station according to the following equations (2) and (3).
Θ (k) = Σarctan (r (k, m) × CONJG (r (k, m−1)))
... (2)
θ (k) = Θ (k) / M ′ (3)

  Note that the above sum Σ is the sum for m = 2, 3,. When there is no discontinuous change in phase deviation as will be described later, M ′ = M−1. M represents the number of phase deviations (number of received symbols) used for the averaging process, and is a sufficiently large positive integer suitable for the averaging process. arctan () is a function that represents an angle when a complex number is converted into polar coordinates from −π ≦ to <π. Θ (k) represents the sum of the phase deviations corresponding to the base station apparatus 2-k (phase deviations from the own station determined based on the signal transmitted from the base station apparatus 2-k), and θ ( k) represents an average value of phase deviations corresponding to the base station apparatus 2-k.

  However, when the timing detected by the path search unit 31 is changed during the calculation of the above equations (2) and (3), the phase deviation of the received symbol becomes discontinuous, and therefore the phase deviation is Received symbols that have changed discontinuously are excluded from treatment. FIG. 4 is a diagram illustrating an example of a received symbol string and a timing change position detected by the path search unit 31. Assume that an average value of phase deviations is obtained using a reception symbol string 41 composed of reception symbols r1 to rM. At this time, it is assumed that the timing change 42 occurs between the reception symbol r10 and the reception symbol r11, and the timing change 43 occurs between the reception symbol r29 and the reception symbol r30.

In this case, Θ (k) is calculated without using the phase deviation between the received symbols r10 and r11 and the phase deviation between the received symbols 29 and 30. Specifically, it calculates | requires according to the following formula | equation (4). In this case, M ′ = M−3 in the calculation of the above equation (3).
Θ (k) = arctan (r2 × CONJG (r1))
+ Arctan (r3 x CONJG (r2))
:
+ Arctan (r10 x CONJG (r9))
+ Arctan (r12 x CONJG (r11))
:
+ Arctan (r29 x CONJG (r28))
+ Arctan (r31 x CONJG (r30))
:
+ Arctan (rM × CONJG (rM−1)) (4)

  Whether or not a discontinuous change has occurred in the phase deviation can be determined by comparing each phase deviation before summation and whether or not the difference from other phase deviations is a predetermined value or more. Alternatively, the change in timing detected by the path search unit 31 may be detected and determined.

The level measurement unit 34 calculates the power of the received symbol. For example, it calculates according to the following formula | equation (5). P (k) represents power (received power), and the following sum is the sum of m = 1, 2,... || ² represents the square of the absolute value of the complex number.
P (k) = Σ | r (k, m) | ² / M (5)

  Based on the averaged frequency deviation θ (k) obtained by the frequency deviation calculators 21-1 to 21 -N and the power P (k) of the received symbol, the frequency deviation estimator 22 Calculate the frequency correction amount. Specifically, the frequency correction amount is calculated by, for example, obtaining an average value of the frequency deviation θ (k) corresponding to the power P (k) that is equal to or greater than a predetermined threshold value, and setting the obtained value as the estimated frequency deviation. , The correction amount of the oscillator 14. This correction amount indicates how much the frequency of the own station is different from that of the surrounding base station apparatus. It is necessary to increase or decrease the frequency of the oscillator 14 by a value proportional to the correction amount. Adjust the amount to zero. Any method of adjusting the frequency of the oscillator 14 may be used. For example, a method of correcting (or decreasing) the frequency of the oscillator 14 by a predetermined value until the correction amount becomes zero. Etc.

  FIG. 5 is a diagram illustrating an example of the frequency deviation θ (k) and the received symbol power P (k) obtained by the frequency deviation calculators 21-1 to 21 -N. FIG. 5 shows the frequency deviation θ (k) and the received symbol power P (k) obtained by each of the frequency deviation calculators 21-1 to 21 -N. In this case, the number of surrounding base station apparatuses is seven, and calculation results 51 to 57 indicate combinations of frequency deviation θ (k) and received symbol power P (k) corresponding to each base station apparatus. ing. In the case of FIG. 5, there are three calculation results 53, 54, and 55 where the power P (k) of the calculation results 51 to 57 is equal to or greater than the threshold value 50. Therefore, the average value of the frequency deviation θ (k) of the calculation results 53, 54, and 55 is set as the correction amount.

  Here, the average value of the frequency deviations of the base station apparatuses 2-1 to 2-6 in which the power P (k) is equal to or greater than the threshold value 50 is used as the correction amount. A predetermined number of base station apparatuses 2-1 to 2-6 may be selected, and the correction amount may be obtained based on the frequency deviation θ (k) of the selected base station apparatuses 2-1 to 2-6.

  Further, the frequency deviation θ (k) corresponding to the base station apparatus in which the power P (k) of the received symbol is larger than the threshold value 50 and the power P (k) of the received symbol is maximum may be used as the correction amount. If there is no calculation result in which the power P (k) of the received symbol is greater than the threshold value 50, the frequency deviation of the oscillator 14 may not be corrected.

Further, the frequency deviation θ (k) of the calculation result (the calculation results 53, 54, and 55 in the case of FIG. 5) where the power P (k) of the received symbol is larger than the threshold value 50 is shown in the following equation (6). Thus, the correction amount may be calculated by weighted addition using P (k).
(P (1) × θ (1) + P (2) × θ (2) + P (3) × θ (3))
/ (P (1) + P (2) + P (3)) (6)

  Further, in the present embodiment, the frequency deviation calculation unit 21-k is also provided with a function for obtaining the power P (k), that is, a power calculation function, but the power P (k) is obtained for each peripheral base station apparatus. A power calculation unit is separately provided, and the frequency deviation estimation unit 22 uses the power P (k) obtained by the power calculation unit and the frequency deviation θ (k) obtained by the frequency deviation calculation unit 21-k as a set of calculation results. The correction amount may be obtained in the same manner as described above.

  In the above description, the path search unit 31 detects only one timing. However, when there are a plurality of paths, the path search unit 31 includes a frequency deviation calculation unit for each path. The frequency deviation calculation unit performs the same processing as described above for each detected timing of each path, and obtains the calculation results (reception symbol power P (k) and frequency deviation θ (k)) for each path. Good.

  In addition, the method by which the frequency deviation calculation units 21-1 to 21-N described above obtain the frequency deviation is an example, and is not limited to this, and any method may be used as a method for obtaining the frequency deviation.

  As described above, in the present embodiment, base station apparatus 1 corrects the frequency of its own oscillator using a common known signal transmitted by neighboring base station apparatuses 2-1 to 2-6. did. Therefore, even when the frequency accuracy of the oscillator 14 is low, the base station apparatus 1 can generate a transmission signal with high frequency absolute accuracy by correcting the frequency of the oscillator 14. Further, since the transmission signals from the peripheral base station apparatuses 2-1 to 2-6 are used, it is not necessary to use signals transmitted from the mobile terminals, and mobile terminals with high frequency accuracy are provided in the radio communication system. There is no need.

Embodiment 2. FIG.
FIG. 6 is a diagram illustrating a functional configuration example of the digital reception unit of the base station apparatus according to the second embodiment of the present invention. The configuration of the base station apparatus (referred to as base station apparatus 1a) of the present embodiment is the same as that of the base station apparatus 1 of the first embodiment except that the digital receiver 16a of the present embodiment is provided instead of the digital receiver 16 of the first embodiment. This is the same as the base station apparatus 1 of the first embodiment. The configuration of the radio communication system of the present embodiment is the same as that of the radio communication system of the first embodiment, except that the base station apparatus 1 of the first embodiment is replaced with the base station apparatus 1a of the present embodiment. . Components having the same functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted. Hereinafter, differences from the first embodiment will be described.

  The digital receiver 16a includes frequency deviation calculators 21a-1 to 21a-N and a frequency deviation estimator 22a. Frequency deviation calculators 21a-1 to 21a-N process signals received from different base station apparatuses 2-1 to 2-6, respectively. The configuration of the frequency deviation calculator 21a-k is the same as the frequency deviation calculator 21-k of the first embodiment except that the despreading unit 35 and the level (power) comparison unit 36 are added and the level measurement unit 34 is deleted. This is the same as the frequency deviation calculation unit 21-k of the first embodiment. Since the processes of the path search unit 31, the despreading unit 32, and the frequency estimation unit 33 have the same configuration as that of the first embodiment, the description thereof is omitted.

  The peripheral base station apparatuses 2-1 to 2-6 may be base station apparatuses having a large radius to cover, such as macro base station apparatuses, and base station apparatuses having a small radius to cover such as femtocells (small base stations). (Station equipment). In general, the macro base station apparatus has a high absolute accuracy of the oscillator, and the small base station apparatus has a low absolute accuracy of the oscillator. Therefore, a base station device that can be expected to have a high absolute accuracy of the oscillator is selected from the neighboring base station devices 2-1 to 2-6, and the frequency deviation is calculated using the signal transmitted from the selected base station device. When obtained, the frequency of the own station can be accurately corrected.

  On the other hand, it is conceivable that power ratios between different channels (between different frequencies) transmitted from the same base station apparatus are different between base station apparatuses that cover different radii. For example, a base station device that needs to have a large radius to cover, such as a macro base station device, may set the power of a specific channel such as a broadcast channel larger. On the other hand, in a small base station, there is a possibility that the power of a specific channel such as a broadcast channel is set to be small. In such a case, when the power of the signal transmitted with the known symbol described in Embodiment 1 is compared with the power of the specific channel, the macro base station apparatus knows the power of the specific channel such as the broadcast channel. The power ratio of the signal transmitted with the symbol is reduced. Therefore, by using such a power ratio, a base station apparatus with high absolute accuracy of the oscillator can be selected.

  Next, the operation of the present embodiment will be described. Based on the timing detected by the path search unit 31, the despreading unit 35 performs despreading processing on a specific channel multiplexed with a code different from the spreading code used for the despreading processing of the despreading unit 32. The specific process is the same as that of the despreading unit 32, and only the code used for the despreading process is different. In addition, as a specific code that the despreading unit 35 despreads, a code used in transmission processing of a specific channel used for transmission of broadcast information or the like is used.

The level comparison unit 36 calculates the power ratio of received symbols obtained by the despreading unit 32 and the despreading unit 35, respectively. For example, the power ratio H (k) is calculated according to the following equation (7).
H (k) = (Σ | r (k, m) | ² ) / (Σ | r ′ (k, m) | ² ) (7)

  The above sum Σ is the sum for m = 1, 2,. In addition, r (k, m) is a reception symbol output from the despreading unit 32, and r '(k, m) is a reception symbol output from the despreading unit 35.

  The frequency deviation estimation unit 22a is based on the calculation results (frequency deviation θ (k) and received symbol power ratio H (k)) output from the frequency deviation calculation units 21a-1 to 21a-N, respectively. The frequency correction amount of the oscillator 14 is calculated. For example, in the system in which the power of a specific channel such as a broadcast channel is set large in the macro base station apparatus as described above, the frequency deviation estimation unit 22a selects the base station apparatus having the smallest power ratio H (k) as the macro base. The frequency correction amount is determined using the frequency deviation θ (k) corresponding to the calculation result that is identified as the station device and has the smallest power ratio H (k).

  Conversely, when the power of a specific channel of the macro base station apparatus is set to be smaller than the power of the known signal in system operation, the base station apparatus with the largest power ratio H (k) is identified as the macro base station apparatus. You just have to do it.

  Also, a power ratio threshold for the power ratio is provided, and a base station apparatus having a power ratio larger than the power ratio threshold is determined as a macro base station apparatus, or a base station apparatus having a power ratio smaller than the power ratio threshold May be determined as a macro base station apparatus. When there are a plurality of base station apparatuses that have determined the macro base station apparatus, the average value of the frequency deviation θ (k) corresponding to these base station apparatuses may be used as the correction amount of the oscillator 14. Further, the correction amount may be obtained by averaging the weights as in the above formula (6) of the first embodiment using the frequency deviation θ (k) corresponding to these base station apparatuses. The operations of the present embodiment other than those described above are the same as those of the first embodiment.

  As described above, in the present embodiment, a macro base station apparatus is identified using a power ratio between a specific channel and a known symbol, and based on a signal transmitted by the identified base station apparatus, The frequency of the oscillator was corrected. Therefore, the same effect as in the first embodiment can be obtained, and the frequency correction of the own station can be performed with higher accuracy than in the first embodiment.

Embodiment 3 FIG.
FIG. 7 is a diagram illustrating a functional configuration example of the digital reception unit of the base station apparatus according to the third embodiment of the present invention. The configuration of the base station apparatus (referred to as base station apparatus 1b) of the present embodiment is that except that the digital receiver 16b of the present embodiment is provided instead of the digital receiver 16 of the base station apparatus 1 of the first embodiment. This is the same as the base station apparatus 1 of the first embodiment. The configuration of the radio communication system of the present embodiment is the same as that of the radio communication system of the first embodiment except that the base station apparatus 1 of the first embodiment is replaced with the base station apparatus 1b of the present embodiment. . Components having the same functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted. Hereinafter, differences from the first embodiment will be described.

  The digital receiver 16b includes frequency deviation calculators 21b-1 to 21b-N and a frequency deviation estimator 22b. Frequency deviation calculators 21b-1 to 21b-N process signals received from different base station apparatuses 2-1 to 2-6, respectively. The configuration of the frequency deviation calculation unit 21b-k is the same as that of the frequency deviation calculation unit 21-k of the first embodiment, except that the despreading unit 37 and the notification information acquisition unit 38 are added. Same as -k. Since the processing of the path search unit 31, the despreading unit 32, the frequency estimation unit 33, and the level measurement unit 34 has the same configuration as that of the first embodiment, the description thereof is omitted.

  In the second embodiment, the macro base station apparatus is identified based on the power ratio. However, in the present embodiment, it is included in the broadcast channel signal transmitted from the neighboring base station apparatuses 2-1 to 2-6. Based on the broadcast information, the macro base station and the small base station are identified.

  Next, the operation of the present embodiment will be described. Based on the timing detected by the path search unit 31, the despreading unit 37 performs despreading processing on the broadcast channel multiplexed with a code different from the spreading code used for the despreading processing of the despreading unit 32. The specific process is the same as that of the despreading unit 32, and only the code used for the despreading process is different.

  The broadcast information acquisition unit 38 extracts the base station identification information of the transmission source base station device from the received symbol of the broadcast channel obtained by the despreading unit 37, and based on the base station identification information, for example, the macro base station device. It is identified whether it is a small base station device or not, and the identification result is output to the frequency deviation estimator 22b. The frequency deviation estimation unit 22 holds the base station identification information and the correspondence information as to whether the base station apparatus is a macro base station apparatus in advance. Here, it is assumed that the macro base station apparatus includes an oscillator with high frequency accuracy. However, the present invention is not limited to this, and correspondence information for identifying a base station apparatus including an oscillator with high frequency accuracy is stored in advance. In addition, it is determined whether the base station apparatus includes an oscillator with high frequency accuracy based on the base station identification information and the corresponding information, and correction is performed based on the phase deviation of the base station apparatus including the oscillator with high frequency accuracy. What is necessary is just to ask for quantity.

  In addition, when the base station identification information of the source base station apparatus does not exist in the broadcast information, the macro base station apparatus extracts the transmission power information from the received symbol instead of the identification information of the base station apparatus. Or a small base station apparatus may be identified.

  The frequency deviation estimator 22b outputs the calculation results (frequency deviation θ (k) and received symbol power P (k)) obtained by the frequency deviation calculators 21b-1 to 21b-N and the broadcast information acquisition unit 38. The frequency correction amount of the oscillator 14 of the own station is obtained based on the identification result. For example, an average value of the frequency deviation θ (k) corresponding to the base station device identified as the macro base station device may be obtained as the frequency correction amount. Further, the maximum frequency deviation θ (k) among the frequency deviations θ (k) of the base station apparatus identified as the macro base station apparatus may be obtained as the frequency correction amount. The operations of the present embodiment other than those described above are the same as those of the first embodiment.

  As described above, in the present embodiment, the base station identification information included in the broadcast information is used to identify the macro base station apparatus, and based on the signal transmitted by the identified base station apparatus, the local station oscillator The frequency of was corrected. Therefore, the same effect as in the first embodiment can be obtained, and the frequency correction of the own station can be performed with higher accuracy than in the first embodiment.

Embodiment 4 FIG.
FIG. 8 is a diagram illustrating an example of a frequency band of the wireless communication system according to the fourth embodiment of the present invention. A transmission frequency band 61 indicates a transmission frequency band, and a correction frequency band 62 indicates a frequency band for correcting the frequency of the oscillator. The configuration of the base station apparatus of the present embodiment is the same as the configuration of base station apparatus 1 of the first embodiment. Further, the configuration of the wireless communication system of the present embodiment is the same as that of the first embodiment. Hereinafter, differences from the first embodiment will be described.

  When the transmission signal of the own station and the transmission signals of the neighboring base station apparatuses are in the same frequency band, it is necessary to stop the transmission signal of the own station and receive the transmission signals of other base station apparatuses. In contrast, in the present embodiment, the transmission signal of the local station is corrected by using the transmission signal of the base station apparatus in a frequency band different from the transmission frequency band, so that the transmission signal of the local station is not stopped. Correction of the oscillator 14 of the station can be performed. In this case, for example, the peripheral base station apparatuses 2-1 to 2-6 transmit a signal including a common known symbol in the correction frequency band 62 different from the transmission signal.

  As a method for correcting the frequency of the oscillator 14, any of the methods in the first to third embodiments may be used. The operations of the present embodiment other than those described above are the same as those of the first embodiment.

  The example of FIG. 8 shows the case where the frequency band for correcting the frequency of the oscillator is one, but Embodiments 1 to 3 using a plurality of frequency bands as the frequency band for correcting the frequency of the oscillator. The same processing may be performed. For example, the same processing as in Embodiments 1 to 3 is performed based on known symbols transmitted in different frequency bands for each of the neighboring base station apparatuses 2-1 to 2-6.

  Further, the oscillator 14 can be corrected by using a signal of a communication method different from the communication method in which the local station communicates. In this case, the analog reception unit 13 outputs a signal transmitted by the communication method for communication received via the antenna 11 and the circulator 12 to the digital reception unit 15, and at the same time, transmits the signal by a communication method different from the communication method for communication. The signal (referred to as a correction signal) is output to the digital receiver 16. For example, when a communication method such as LTE (Long Term Evolution) is used as the communication method of the local station, W-CDMA (Wideband Code Division Multiple Access) is used as the communication method for correcting the frequency of the oscillator 14 of the local station. In other words, the frequency may be corrected using a transmission signal from a base station apparatus that transmits a signal by the W-CDMA system.

  As described above, in this embodiment, the frequency of the oscillator 14 of the local station is corrected using a frequency different from the frequency at which the local station is transmitting the transmission signal. Therefore, the same effect as in the first embodiment can be obtained without stopping the transmission signal of the own station. Further, by using signals from base station apparatuses of a plurality of frequency bands, the number of candidates for signals of the base station apparatus used for the oscillator correction of the own station increases, and correction with higher accuracy can be performed.

  As described above, the base station apparatus and communication method according to the present invention are useful for a base station apparatus in a radio communication system including mobile terminals, and are particularly suitable for a base station apparatus including an oscillator with low frequency accuracy.

1, 2-1 to 2-6 Base station apparatus 11 Antenna 12 Circulator 13 Analog receiver 14 Oscillator 15, 16, 16a, 16b Digital receiver 17 Digital transmitter 18 Analog transmitter 21-1 to 21-N, 21a- 1 to 21a-N, 21b-1 to 21b-N Frequency deviation calculation unit 22, 22a, 22b Frequency deviation estimation unit 31 Path search unit 32, 35, 37 Despreading unit 33 Frequency estimation unit 34 Level measurement unit 36 Level comparison unit 38 Broadcast Information Acquisition Unit 61 Transmission Frequency Band 62 Correction Frequency Band

Claims (17)

A base station apparatus comprising an oscillator for generating a reference frequency signal, and generating a transmission signal based on the reference frequency signal,
Based on a received signal received from another base station apparatus that is a base station apparatus other than the own station, a frequency deviation calculating means for obtaining a frequency deviation between the reference frequency signal and the reference frequency signal of the other base station apparatus;
A frequency deviation estimating means for obtaining a frequency correction amount for correcting the reference frequency signal based on the frequency deviation;
A base station apparatus comprising: The received signal is down-converted based on the frequency generated based on the reference signal,
The frequency deviation calculating means obtains a phase deviation of a received signal after down-conversion received from the other base station apparatus as the frequency deviation.
The base station apparatus according to claim 1. Power calculating means for obtaining the power of the received signal received from the other base station apparatus;
Further comprising
The frequency deviation estimation means selects a correction target base station apparatus from the other base station apparatus based on the power, and obtains the frequency correction amount based on the frequency deviation corresponding to the correction target base station apparatus.
The base station apparatus according to claim 1 or 2, characterized in that The frequency deviation estimation means selects the other base station apparatus whose power is greater than a predetermined threshold as the correction target base station apparatus.
The base station apparatus according to claim 3. The frequency deviation estimation means selects a predetermined number of the other base station devices as the correction target base station device in order of increasing power.
The base station apparatus according to claim 3. The frequency deviation estimation means obtains an average value of the frequency correction amounts corresponding to the correction target base station device as the frequency correction amount.
The base station apparatus according to claim 3, 4 or 5. The frequency deviation estimation means selects, as the correction target base station apparatus, the other base station apparatus in which the power is greater than a predetermined threshold and the power is maximum.
The base station apparatus according to claim 3. Power comparison means for calculating a power ratio between the specific signal transmitted from the other base station apparatus that transmits the broadcast information and the transmission signal received from the other base station apparatus that is spread with a spreading code different from the specific signal. ,
Further comprising
Selecting a correction target base station device from the other base station device based on the power ratio, and obtaining the frequency correction amount based on the frequency deviation corresponding to the correction target base station device;
The base station apparatus according to claim 1 or 2, characterized in that The frequency deviation estimation means selects the other base station apparatus having the minimum or maximum power ratio as the correction target base station apparatus.
The base station apparatus according to claim 8. The frequency deviation estimation means selects the other base station apparatus whose power ratio is greater than a predetermined threshold as the correction target base station apparatus.
The base station apparatus according to claim 8. Broadcast information acquisition means for acquiring predetermined information based on broadcast information received from the other base station device;
The frequency deviation estimation means selects a correction target base station apparatus from the other base station apparatus based on the predetermined information, and obtains the frequency correction amount based on the frequency deviation corresponding to the correction target base station apparatus. ,
The base station apparatus according to claim 1, wherein the base station apparatus is a base station apparatus. The frequency deviation estimating means maintains correspondence between base station identification information for identifying a base station apparatus and information for identifying whether or not the frequency accuracy of a signal transmitted by the base station apparatus is high. ,
The predetermined information is base station identification information for identifying a base station device,
The base station apparatus according to claim 11. The predetermined information is transmission power information indicating transmission power,
The base station apparatus according to claim 11. The frequency deviation calculating means obtains the frequency deviation based on a received signal received from the other base station apparatus in a frequency band different from the frequency band used for transmission by the own apparatus.
The base station apparatus according to claim 1, wherein: The frequency deviation calculating means obtains the frequency deviation based on a received signal received from the other base station apparatus in a communication method different from the communication method used by the own device for communication.
The base station apparatus according to claim 1, wherein the base station apparatus is a base station apparatus. A first base station apparatus which is the base station apparatus according to any one of claims 1 to 15;
A second base station apparatus capable of receiving a signal transmitted by the own apparatus by the first base station apparatus;
A wireless communication system comprising: A frequency correction method in a base station apparatus that includes an oscillator that generates a reference frequency signal and generates a transmission signal based on the reference frequency signal,
Based on a received signal received from another base station apparatus which is a base station apparatus other than the own station, a frequency deviation calculating step for obtaining a frequency deviation between the reference frequency signal and the reference frequency signal of the other base station apparatus;
A frequency deviation estimating step for obtaining a frequency correction amount for correcting the reference frequency signal based on the frequency deviation;
A frequency correction method comprising:

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