JP2013232855A - Base station, interference suppression device, and interference suppression method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base station, an interference suppression device, and an interference suppression method that can suppress an interference signal generated by frequency conversion of a radio signal in frequency band different from a radio signal received from a communication terminal.SOLUTION: When a base station is receiving a radio signal in a first frequency band (1.5 GHz band) including a desired signal and an interference signal, the base station receives a radio signal in a second frequency band (11 GHz band) before it was frequency converted to an interference signal in the first frequency band, and generates a reference signal d(t) in the first frequency band by frequency converting the received signal in the second frequency band. The base station generates an interference replica signal corresponding to the interference signal on the basis of the reference signal d(t) and the received signal in the first frequency band. The interference signal included in the received signal in the first frequency band is suppressed by subtracting the generated interference replica signal from the received signal in the first frequency band.

Description

  The present invention relates to a base station capable of wireless communication with a communication terminal, an interference apparatus that can use the base station, and an interference suppression method.

  2. Description of the Related Art Conventionally, a base station that obtains good communication quality with a communication terminal by suppressing an interference signal included in a reception signal when receiving a radio signal transmitted from the communication terminal is known. For example, a base station that generates an interference replica signal from a known signal (for example, a pilot symbol in a CDMA system) and subtracts the generated interference replica signal from a received signal is known (see, for example, Patent Document 1). In this base station, it is possible to suppress interference signals from adjacent base stations and interference signals from communication terminals other than the reception request target existing in the same base station cell.

The interference signal suppressed by the conventional base station is an interference signal between the communication terminal and the base station, such as an interference signal from an adjacent base station or an interference signal from a communication terminal existing in the same base station cell. It is a radio signal transmitted and received in a radio communication network. For this reason, it is considered that interference signals can be suppressed using the above-described known signals (for example, pilot symbols in the CDMA system). However, the received signal received by the base station may include other interference signals that are difficult to predict other than the radio signals transmitted and received by the wireless communication network. Then, when this inventor investigated about such another interference signal, it turned out that the interference signal resulting from the radio broadcast wave transmitted from the broadcast satellite exists as shown below. In FIG. 15, since the frequency band of the radio broadcast wave d _RF from the broadcast satellite 90 is normally 11 MHz band, it is considered that there is no interference with the 1.5 MHz band radio signal x _MS transmitted from the communication terminal 80. It is done. However, the received signal (BS-RF signal) received by the BS receiving system 95 from the broadcasting wave d _RF from the broadcasting satellite 90 is basically frequency conversion incorporated in the receiving device 97 mounted on the parabolic antenna 96. A signal converted to an intermediate frequency (BS-IF) signal by an apparatus (LNB: Low Noise Block Converter) (hereinafter, a signal converted to an intermediate frequency (BS-IF) by the LNB is referred to as an LNB BS-IF signal). ), And transmitted to a broadcast receiver (not shown) via the coaxial cable 98. Further, the BS-IF signal by the LNB takes into account the transmission loss of the coaxial cable 98 and the distribution loss when the received signal is distributed in the apartment house, and the like, and the amplification device (booster) 99 provided near the antenna 96 is used. In some cases, the signal is amplified (hereinafter, the signal amplified by the booster 99 is referred to as “BS-IF signal by the booster”). BS-IF signal by the BS-IF signal and boosters by the LNB is in the same 1.5MHz band the radio signal _{x MS} to be transmitted to the base station 100 from the communication terminal 80. For this reason, if the radio wave shielding (shielding) of these devices 97 and 99 is insufficient or there is a connection error with the connector of the coaxial cable 98, the intermediate frequency signal xBS _-IF after frequency conversion is transmitted to the space as radio waves. It was found that the leaked radio wave was received by the base station 100 and became an interference signal.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a base capable of suppressing an interference signal generated by frequency conversion from a radio signal having a frequency band different from that of a radio signal received from a communication terminal. It is to provide a station, an interference suppression device, and an interference suppression method.

A base station according to the present invention corresponds to a first receiving means for receiving a radio signal in a first frequency band including a desired signal transmitted from a communication terminal and an interference signal that interferes with the desired signal, and corresponds to the interference signal. An interference suppression unit that suppresses an interference signal included in the received signal in the first frequency band by subtracting an interference replica signal from the received signal in the first frequency band, the base station comprising the desired signal and Second receiving means for receiving a radio signal in the second frequency band before being frequency-converted to the interference signal in the first frequency band when receiving a radio signal in the first frequency band including the interference signal; Based on the reference signal generating means for generating a reference signal of the first frequency band by frequency-converting the received signal of the second frequency band, the interference replica signal based on the reference signal and the received signal of the first frequency band Produce dried It includes a replica signal generating means.
Further, the interference suppression apparatus according to the present invention generates an interference replica signal corresponding to an interference signal from a received signal in a first frequency band including a desired signal transmitted from a communication terminal and an interference signal that interferes with the desired signal. An interference suppression apparatus that suppresses an interference signal included in the reception signal of the first frequency band by subtracting, and when receiving a radio signal of the first frequency band including the desired signal and the interference signal, The radio signal of the second frequency band is input from the radio receiver that receives the radio signal of the second frequency band before the frequency conversion to the interference signal of the first frequency band, and the received signal of the second frequency band is Reference signal generating means for generating a reference signal of the first frequency band by frequency conversion, and the received signal of the first frequency band are input, and the interference based on the reference signal and the received signal of the first frequency band Replica signal Comprising an interference replica signal generation means for generating for the.
In addition, the interference suppression method according to the present invention provides an interference replica signal corresponding to an interference signal from a received signal in a first frequency band including a desired signal transmitted from a communication terminal and an interference signal that interferes with the desired signal. An interference suppression method for suppressing an interference signal included in a reception signal of the first frequency band by subtracting, when receiving a radio signal of the first frequency band including the desired signal and the interference signal, Receiving a radio signal of a second frequency band before being frequency-converted to an interference signal of the first frequency band; and generating a reference signal of the first frequency band by frequency-converting the received signal of the second frequency band And generating the interference replica signal based on the reference signal and the received signal in the first frequency band.

  According to each of the base station, the interference suppression device, and the interference suppression method, when a radio signal in the first frequency band is received, a radio signal in the second frequency band is simultaneously received, and a received signal in the second frequency band is received. To generate a reference signal in the first frequency band, and based on the generated reference signal and the received signal in the first frequency band, the interference corresponding to the interference signal included in the received signal in the first frequency band A replica signal can be generated. By subtracting the interference replica signal from the received signal in the first frequency band, it is possible to suppress the interference signal contained in the received signal in the first frequency band, so that the radio signal received from the communication terminal has a different frequency band. It is possible to suppress the interference signal generated by frequency conversion from the signal.

In the base station, the interference replica signal generation means calculates values of each of a plurality of parameters necessary for generating the interference replica signal that can be calculated from the reference signal and the received signal of the first frequency band, The interference replica signal may be generated based on the calculated value of the parameter.
In the interference suppression method, the step of generating the interference replica signal predetermines a plurality of parameters necessary for generating the interference replica signal that can be calculated from the reference signal and the received signal in the first frequency band. Calculating a value of each of the plurality of parameters based on the reference signal and the received signal of the first frequency band, and generating the interference replica signal based on the calculated values of the plurality of parameters And may be included.
In these base stations and the interference suppression method, the interference necessary for suppressing the interference signal is obtained by using a plurality of parameters necessary for generating an interference replica signal that can be calculated from the reference signal and the received signal in the first frequency band. The replica signal generation process is simplified.
In the base station, the parameters used for generating the interference replica signal may be a frequency offset, a delay time, and an amplitude of the interference signal. In this base station, the interference replica signal can be accurately generated by using the frequency offset, delay time, and amplitude of the interference signal to generate the interference replica signal, so that the interference signal suppression processing at a predetermined timing can be performed. Accuracy and efficiency can be improved.
Further, in the base station, the interference replica signal generating means sets a correlation between the reference signal and the received signal in the first frequency band while setting a plurality of sets of frequency offset, delay time and amplitude for the reference signal. By calculating a value and comparing a correlation value calculated for each of a plurality of combinations of the frequency offset, delay time, and amplitude with a preset threshold value, the frequency offset, delay time, and amplitude of the interference signal are estimated. Also good. In this base station, the frequency of the interference signal is accurately calculated by calculating a correlation value between the reference signal and the received signal in the first frequency band while setting a plurality of sets of frequency offset, delay time and amplitude for the reference signal. Offset, delay time and amplitude can be estimated. Further, since the frequency offset, delay time and amplitude of the interference signal are estimated by comparing the correlation value with a preset threshold value, the influence of noise can be eliminated.
Further, in the base station, the interference replica signal generation means generates the interference replica signal based on an offset reference signal in which the frequency offset and delay time are set in the reference signal and a weight corresponding to the amplitude. The weight difference may be calculated based on the difference between the received signal in the first frequency band and the interference replica signal and the offset reference signal, and the weight may be updated using the difference. . In this base station, it is possible to improve the accuracy of the interference replica signal as the generation of the interference replica signal is repeated while suppressing the processing load when generating the interference replica signal.
The base station further includes storage means for storing the estimated value of the parameter, and the interference replica signal generation means includes the parameter value stored in the storage means and the reference signal of the first frequency band. The interference replica signal may be generated based on In this base station, since the interference signal can be suppressed by reusing the estimated value of the parameter, the interference signal can be suppressed by simpler processing.
The base station may further include an update unit that repeatedly updates the estimated value of the parameter stored in the storage unit at a predetermined timing, and the update timing may be changeable. In this base station, the estimated value of the parameter can be updated according to changes in the communication environment such as the source of the interference signal and the transmission path, so that the accuracy of the interference signal suppression process over time can be improved.
Further, in the base station, the path of the received signal received by the first receiving unit is divided into a first path on which interference signal suppression processing is performed by the interference suppression unit, and interference signal suppression processing by the interference suppression unit. Reception path switching means for switching between the second path that is not performed may be provided. In this base station, when the interference suppression means stops functioning due to a failure or the like, the received signal can be processed without going through the interference suppression means.
In particular, in this base station, the reception path switching means is configured to switch the path of the reception signal from the first path to the second path when the intensity of the reference signal is less than or less than a threshold. You may provide the control means to control. In this base station, when the interference suppression unit does not function normally due to insufficient reference signal strength, the interference suppression unit prevents the accuracy of interference suppression from being reduced, or inappropriate interference suppression processing is performed. Can be prevented in advance.
In the base station, the received signal in the first frequency band may include a plurality of interference signals having at least one of frequency offset, delay time, and amplitude different from each other. In this base station, even when a plurality of interference signals having different frequency offsets, delay times, and amplitudes are included in the received signal of the first frequency band, each interference signal can be reliably suppressed. .
In the base station, the first frequency band radio signal received by the first receiving means is a 1.5 GHz band radio signal transmitted from the communication terminal and received by the second receiving means. The second frequency band radio signal may be an 11 GHz band radio broadcast signal transmitted from a broadcast satellite. In this base station, it is possible to suppress a 1.5 GHz band interference signal obtained by frequency conversion from an 11 GHz band radio broadcast signal having a frequency band different from that of the 1.5 GHz band radio signal received from the communication terminal.
In the base station, the interference signal included in the radio signal in the first frequency band received by the first receiving means is a frequency converter for converting a radio broadcast signal into an intermediate frequency signal and an intermediate frequency signal The leaked signal may be leaked from at least one of the amplifying devices for amplifying the signal. In this base station, it is possible to suppress an interference signal caused by a frequency-converted signal leaked from a booster that amplifies an intermediate-frequency signal obtained by frequency-converting a radio broadcast wave reception signal.

  According to the present invention, an interference replica signal corresponding to an interference signal included in a reception signal in the first frequency band is generated, and the reception of the first frequency band is performed by subtracting the interference replica signal from the reception signal in the first frequency band. Since the interference signal included in the signal can be suppressed, it is possible to suppress the interference signal generated by frequency conversion from a radio signal having a frequency band different from that of the radio signal received from the communication terminal.

The schematic block diagram which shows an example of the whole structure of the base station which concerns on one Embodiment of this invention. (A) is explanatory drawing which shows typically the frequency spectrum of the received signal x before interference signal BS-IF is suppressed. (B) is explanatory drawing which shows typically the frequency spectrum of the received signal (output signal) z by which interference signal BS-IF was suppressed. The block diagram which shows the example of 1 structure of an interference suppression process part. The block diagram which shows the other structural example of an interference suppression process part. FIG. 3 is a block diagram illustrating interference suppression processing according to the first embodiment. (A) And (b) is explanatory drawing which illustrates the some BS-IF interference signal whose magnitude | size of an amplitude is more than a threshold value, respectively. 9 is a flowchart illustrating a procedure of interference suppression processing according to the second embodiment. Explanatory drawing which shows the BS-IF interference signal arranged in order of the magnitude | size of the amplitude in the interference suppression process of Example 2. FIG. Explanatory drawing which shows the mode of the search of the interference signal in the interference suppression process of Example 3. FIG. FIG. 9 is a block diagram illustrating interference suppression processing according to the fourth embodiment. FIG. 10 is a block diagram illustrating interference suppression processing according to a fifth embodiment. The schematic block diagram which shows an example of the whole structure of the base station which concerns on other embodiment of this invention. The schematic block diagram which shows an example of the whole structure of the base station which concerns on further another embodiment of this invention. The schematic block diagram which shows an example of the whole structure of the base station which concerns on further another embodiment of this invention. Explanatory drawing for demonstrating the subject in the conventional base station.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1
FIG. 1 is a schematic configuration diagram illustrating an example of the overall configuration of a base station according to an embodiment of the present invention. In FIG. 1, a base station 10 according to the present embodiment includes a radio signal (1.5 MHz band) in a first frequency band (1.5 MHz band) from a base station apparatus 20 as a main body, an interference suppression apparatus 30, and a mobile device 80 as a communication terminal. A base station antenna 40 as first receiving means for receiving radio waves), and duplexers (DUPlexers) 50 and 51 for sharing the base station antenna 40 for transmission and reception. The interference suppression device 30 receives an interference suppression processing unit 300 (to be described later) serving as interference suppression means and a radio signal (radio wave) d _RF (t) of a satellite broadcast BS in the second frequency band (11 MHz band) used for interference suppression. BS receiving system 350.

The BS reception system 350 includes a mobile communication signal x _MS that is a desired signal and its IF interference signal (hereinafter referred to as “BS-IF interference signal”) x _BS-IF generated by a plurality of BS receivers. When receiving a radio signal x in the first frequency band (1.5 MHz band), it is a radio signal in the second frequency band (11 MHz band) before being converted into an interference signal in the first frequency band. It functions as a second receiving means for receiving a radio signal (radio wave) d _RF (t) of the satellite broadcast BS. Furthermore, the BS reception system 350 also functions as a reference signal generation unit that generates a reference signal d ₀ (t) in the first frequency band by performing frequency conversion on the reception signal d _RF (t) in the second frequency band. As the BS reception system 350, for example, as shown in the figure, a parabolic antenna (hereinafter referred to as “interference suppression BS antenna”) 351 that is an antenna body, and a BS-RF mounted on the interference suppression BS antenna 351. An existing BS receiving system with a receiver 352 can be used. The BS-RF receiver 352 of the BS receiving system 350 converts the frequency of the received signal d _RF (t) in the second frequency band (11 MHz band) to generate a signal d ₀ (t in the first frequency band (1.5 MHz band)). LNB (Low Noise Block Converter). The signal d ₀ (t) output from the BS-RF receiver 352 is sent to the interference suppression device 30 via a coaxial cable. Hereinafter, the BS-IF signal d ₀ (t) frequency-converted to the intermediate frequency BS-IF by the BS-RF receiver 352 is referred to as “BS-IF reference signal” or simply “reference signal”.

The received signal x ₀ (t) in the first frequency band received by the base station antenna 40 is sent to the interference suppression device 30 via the duplexer 50 and processed. The received signal z ₀ (t) processed by the interference suppression device 30 is sent to the base station device 20 via the duplexer 51. The base station antenna 40 and duplexers 50 and 51 are also used when transmitting mobile communication radio signals to the mobile device 80, and mobile communication transmission signals output from the base station apparatus 20. Is sent to the detour path 52 via the duplexer 51 and then sent to the base station antenna 40 via the duplexer 50.

The received signal x in the first frequency band (1.5 MHz band) received by the base station antenna 40 is a mobile communication signal that is a desired signal transmitted from the mobile device 80 as illustrated in FIG. x _MS and a plurality of BS-IF interference signals x _BS-IF . Each of the plurality of BS-IF interference signals x _BS-IF is a signal caused by a leaked radio wave having an intermediate frequency of a satellite broadcast receiving system installed in a home, office, various facilities, or the like. The satellite broadcast receiving system includes a parabolic antenna (hereinafter referred to as “BS antenna”) that receives a radio signal of a satellite broadcast BS in a second frequency band (11 MHz band), and a second satellite broadcast BS received by the BS antenna. An LNB that converts the frequency band BS received signal d _RF (t) to an intermediate frequency, and an amplifier (hereinafter referred to as “BS booster”) that is provided near the BS antenna so as to amplify the intermediate frequency signal after frequency conversion. .). The BS booster amplifies a BS-IF signal having the same frequency as the first frequency band. Here, when the radio wave shielding (shielding) of the BS booster is insufficient or there is a connection error between the BS booster and the coaxial cable connector, the BS-IF signal may leak from the BS booster to the space as radio waves. Since the radio waves leaked from each BS booster travel through different transmission paths, they reach the base station antenna 40 as a plurality of radio signals having different delay times and intensities. In addition, when a radio signal (BS-RF signal) received by the BS antenna is converted into an intermediate frequency signal (BS-IF signal), a frequency offset due to the frequency deviation of the local transmitter for conversion to the intermediate frequency is set. Arise. In this way, a radio signal including a plurality of leaked radio waves having different delay times, intensities, and frequencies is received by the base station antenna 40 as a BF-IF interference signal x _BS-IF included in the received signal x in the first frequency band. The

The received signal x in the first frequency band received by the base station antenna 40 is amplified by the duplexer 50 and then input to the interference suppression device 30, and the interference suppression device 30 receives the BS-IF interference signal x _BS-IF. Received signal z (see FIG. 2B) is input to base station apparatus 20.

The interference suppression device 30 is an interference suppression processing unit that performs processing to suppress the BF-IF interference signal x _BS-IF included in the received signal x in the first frequency band (1.5 MHz band) received by the base station antenna 40. 300. The interference suppression processing unit 300 subtracts replicas of a plurality of BF-IF interference signals x _BS-IF (hereinafter referred to as “interference replica signals”) from the reception signal x of the first frequency band to receive the first frequency band. It acts as an interference suppression means for suppressing the BF-IF interference signal _{x BS-IF} included in the signal x. The interference suppression processing unit 300 functions to cancel the interference signal included in the received signal, and is also referred to as an “interference canceller”. In addition, the interference suppression processing unit 300, based on the reference signal d ₀ (t) generated by the BS receiving system 350 and the received signal x ₀ (t) of the first frequency band received by the base station antenna 40, It also functions as an interference replica signal generation means for generating an interference replica signal.

  FIG. 1 shows an example in which an existing BS reception system 350 having a BS antenna 351 for interference suppression and a BS-RF receiver 352 with a built-in LNB is used as the second reception means and the reference signal generation means. However, it is not limited to this configuration. For example, an existing parabolic antenna may be used only for the BS antenna 351 for interference suppression, and separate devices having high frequency stability may be used for the BS-RF receiver and the frequency converter (LNB). . Further, the interference suppression device 30 may be configured to include a BS-RF receiver and a frequency converter (LNB) configured as individual devices having high frequency stability without including an existing parabolic antenna. .

FIG. 3 is a block diagram illustrating a configuration example of the interference suppression processing unit 300. The interference suppression processing unit 300 of FIG. 3 includes a parameter value estimation unit 301, a parameter value storage unit 302, an interference replica signal generation unit 303, and a subtraction processing unit 304.
The parameter value estimation unit 301 uses an input signal x ₀ (t) that is a received signal in the first frequency band (1.5 MHz band) received by the base station antenna 40 at a predetermined timing, and an interference suppression BS antenna 351. Based on the received signal d _RF (t) of the second frequency band (11 MHz band) received and the reference signal d ₀ (t) of the first frequency band (1.5 MHz band) obtained by frequency conversion, the received signal x A value of a parameter used to generate an interference replica signal corresponding to the BF-IF interference signal x _BS-IF included in ₀ (t) is estimated. The parameters for this estimation target, for example, the reference signal _d 0 (t) BF-IF interference signal _{x BS-IF} the delay time for, and the like amplitude or frequency offset.
The parameter value storage unit 302 stores the parameter estimation value estimated by the parameter value estimation unit 301 until the next parameter value is estimated and updated so that it can be used for a plurality of subsequent interference suppression processes. Is.
The interference replica signal generation unit 303 receives the received signal x ₀ (t) based on the parameter value stored in the parameter value storage unit 302 and the reference signal d ₀ (t) in the first frequency band (1.5 MHz band). corresponding to BF-IF interference signal _{x BS-IF} contained in t) to generate an interference replica signal y (t).
The subtraction processing unit 304 subtracts the interference replica signal y (t) generated by the interference replica signal generation unit 303 from the input signal x ₀ (t) that is the received signal in the first frequency band (1.5 MHz band). I do. The reception signal in the first frequency band in which the BF-IF interference signal xBS _-IF is suppressed by the subtraction processing of the subtraction processing unit 304 is output to the base station apparatus 20 as the output signal z ₀ (t).

In the interference suppression processing unit 300 in FIG. 3, the parameter estimation value estimated by the parameter value estimation unit 301 is stored in the parameter value storage unit 302, and therefore can be used continuously for a plurality of subsequent interference suppression processing. . Therefore, the number of parameter value estimation processes by the parameter value estimation unit 301 can be minimized, and the signal processing amount of the interference suppression processing unit 300 can be greatly reduced.
By the way, the estimated value of the parameter may not change greatly even with time. For example, when the interference suppression processing unit 300 is restarted, the estimated value of the parameter does not change significantly from before the restart, so that the parameter estimated value stored in the parameter value storage unit 302 or its surrounding values is changed thereafter. You may make it use for an interference suppression process.

FIG. 4 is a block diagram illustrating another configuration example of the interference suppression processing unit 300. Unlike the configuration example of FIG. 3, the interference suppression processing unit 300 of FIG. 4 is configured to update parameters sequentially, and the estimated value of the parameter estimated by the parameter value estimation unit 301 is estimated for the next parameter value. In addition, the parameter value storage unit 302 that stores data until updating is not provided.
The parameter value estimation unit 301 uses an input signal x ₀ (t) that is a received signal in the first frequency band (1.5 MHz band) received by the base station antenna 40 at a predetermined timing, and an interference suppression BS antenna 351. The BF− included in the received signal x is based on the reference signal d ₀ (t) of the first frequency band (1.5 MHz band) obtained by frequency-converting the received signal of the second frequency band (11 MHz band). IF interference signal x Estimates the value of a parameter used to generate an interference replica signal corresponding to _BS-IF .
The interference replica signal generation unit 303 receives the received signal x ₀ (t) based on the parameter value estimated by the parameter value estimation unit 301 and the reference signal d ₀ (t) in the first frequency band (1.5 MHz band). generating a BF-IF interference signal _{x BS-IF} interference replica signal corresponding to y (t) included in).
The subtraction processing unit 304 subtracts the interference replica signal y (t) generated by the interference replica signal generation unit 303 from the input signal x ₀ (t) that is the received signal in the first frequency band (1.5 MHz band). I do. The reception signal in the first frequency band in which the BF-IF interference signal xBS _-IF is suppressed by the subtraction processing of the subtraction processing unit 304 is output to the base station apparatus 20 as the output signal z ₀ (t).

In the interference suppression processing unit 300 in FIG. 4, the parameter estimation value estimated by the parameter value estimation unit 301 is not stored in the parameter value storage unit, but interference with the mobile communication signal x itself used for the parameter value estimation is stored. Since it can be used for suppression processing, the accuracy of interference suppression increases. Also, the time zone during which the mobile communication signal x ₀ (t) is received, the BS booster 91 such as a home that is the source of the interference signal, and the BF-IF interference signal x between the BS booster 91 and the base station 10 _When the transmission characteristics of the _BS-IF change, it is possible to respond quickly to the change.

Hereinafter, a more specific example of the interference suppression processing in the interference suppression processing unit 300 according to the present embodiment will be described.
[Example 1 of interference suppression processing]
FIG. 5 is a block diagram illustrating an example of interference suppression processing in the interference suppression processing unit 300. In the first embodiment, the mobile communication signal including the BS-IF interference signal is frequency-converted (down-converted) from the first frequency band (1.5 GHz band) to a predetermined frequency band (baseband). An interference replica signal that is a replica of the BS-IF interference signal in the frequency band is generated, and the generated interference replica signal is subtracted from the received mobile communication signal in which the delay time for generating the interference replica is compensated by the processing delay. Thereafter, the frequency is converted (up-converted) to the original first frequency (1.5 GHz band) and output.

In order to generate the interference replica signal, it is necessary to estimate a complex amplitude that is an amplitude including a frequency offset f _offset , a delay time τ, and a phase of each of a plurality of BS-IF interference signals included in the received signal. In particular, the value of the frequency offset f _offset of the BS-IF interference signal varies greatly for each BS booster (BS receiver) that is the source of the BS-IF interference signal. Therefore, highly accurate estimation of the value of the frequency offset f _offset and its correction are very important.

Therefore, in the interference suppression process of FIG. 5, first, the frequency offset f _offset , delay time τ, and complex amplitude of the BS-IF interference signal are estimated. Now, a received signal including the mobile communication signal received by the base station 10 and the BS-IF interference signal is set as x ₀ (t) as a function of time t. The received signal x ₀ (t) is frequency-converted to a predetermined frequency by a down converter (DC) 311 and then sampled at a time interval ΔT by an analog-digital converter (ADC) 312 to receive a received signal x (i) comprising a digital signal. ). Here, i is a natural number representing the sampling order. The sampling time interval ΔT is generally sufficient if a time of about 1/2 or 1/4 of the symbol length (= 1 / radio transmission bandwidth) of the radio signal is sufficient.

On the other hand, in the first frequency band (1.5 MHz band) obtained by frequency-converting the BS received signal d _RF (t) in the second frequency band (11 MHz band) received by the BS antenna 351 for interference suppression provided in the base station 10. The BS-IF signal is set as a reference signal d ₀ (t) as a function of time t. The reference signal d ₀ (t) is frequency-converted to a predetermined frequency by the down converter (DC) 313 and then sampled by the analog-to-digital converter (ADC) 314 at a time interval ΔT to be a digital reference signal d (i ). Here, i is a natural number representing the sampling order.

The estimation processing unit 315 detects a BS-IF interference signal that is frequency offset based on the reference signal d (i). For this purpose, first, a reference signal that is frequency offset by a value obtained by discretizing the frequency offset amount f _offset with respect to the received reference signal d (i) at a frequency interval Δf is denoted as d _off (i, m). _off (i, m) can be expressed by the following equation (1). Here, “j” in equation (1) represents an imaginary number (√−1), and “m” is a natural number representing the order of frequency offsets discretized by Δf. “MΔf” is a discretized frequency offset amount.

Next, the estimation processing unit 315 detects the BS-IF interference signal by obtaining a correlation between the frequency-offset reference signal d _off (i, m) and the received signal x ₀ (i). Now, a reference signal shifted by n is set as d _off (i−n, m). If the correlation calculation value between the received signal x ₀ (i) and the reference signal d _off (i−n, m) is r (n, m), r (n, m) can be expressed by the following equation (2) ( (See FIG. 6). Here, “ ^* ” in equation (2) represents a complex conjugate, and “N _s ” is the number of data used for correlation calculation.

Now, assuming that the range of n is N _{min to} N _max and the range of m is M _{min to} M _max , the estimation processing unit 315 has (N _max −N _min +1) × (M _max −M _min +1) ways. Correlation calculation is performed. Then, the estimation processing unit 315, the calculated correlation value r (n, m) the magnitude of | r (n, m) | is compared with a threshold value _{L th} that predetermines, as shown in the following equation (3) R (n, m) that is equal to or greater than the threshold Lth is _{defined as} the complex amplitude of the BS-IF interference signal.

Now, let K _max be the number of BS-IF interference signals that are equal to or greater than the threshold value L _th , arrange the BS-IF interference signals in order from the largest, and BS-IF interference that has the kth magnitude. Let r (n _k , m _k ) be the complex amplitude of the signal. In this case, r (n _k , m _k ) is the complex amplitude of the kth BS-IF interference signal and has the following three elements.
Delay time τ: _nk ΔT
Frequency offset f _offset : m _k Δf
Amplitude: r (n _k , m _k )

FIGS. 6A and 6B are explanatory diagrams illustrating a plurality of BS-IF interference signals each having an amplitude greater than or _equal to a threshold value Lth. In FIG. 6, in the coordinate space of the frequency offset and the delay time, the amplitudes are r (n ₁ , m ₁ ), r (n ₂ , m ₁ ), r (n ₃ , m ₂ ), r (n ₄ , m ₂ ), R (n ₄ , m ₃ ), r (n ₅ , m ₃ ), and six BS-IF interference signals having amplitudes greater than or equal to the threshold L _th are illustrated.

If the k-th BS-IF interference signal generated by the interference replica signal generation units 316 and 317 is y _{nk, mk} (i), y _{nk, mk} (i) is the next using the reference signal d (i). It is represented by Formula (4). This BS-IF interference signal y _{nk, mk} (i) is an interference replica signal corresponding to the BS-IF interference signal included in the received signal x (i).

However, the equation h (n _k , m _k ) in the equation (4) is expressed by the following equation (5) using the complex amplitude r (n _k , m _k ).

Next, the addition processing unit 318 adds all BS-IF interference signals (interference replica signals) y _{nk, mk} (i) from 1 to Kmax. In the subtraction processing unit 320, all BS-IF interference signals (interference replica signals) y _{nk, mk} (i) added by the addition processing unit 318 are received signals x (i) subjected to delay processing by the processing delay unit 319. By subtracting from, it is possible to obtain an output signal z (i) composed of a digital signal output to the base station apparatus 20. This output signal z (i) is expressed by the following equation (6).

The output signal z (i) output from the subtraction processing unit 320 is converted into an analog signal by the digital analog converter (DAC) 321 and then the first frequency band (1.5 GHz band) by the up converter (UC) 322. By performing frequency conversion to a predetermined frequency, an output signal z ₀ (t) output to the base station device 20 is obtained.

[Embodiment 2 of interference suppression processing]
FIG. 7 is a flowchart illustrating a procedure of interference suppression processing according to another embodiment in the interference suppression processing unit 300. In the second embodiment, from the plurality of BS-IF interference signals detected by the correlation calculation process in the estimation processing unit 315, the magnitude of amplitude | r (n _k , m _k ) as shown in the above equation (3). A BS-IF interference signal with | being _{equal to} or greater than the threshold L _th is selected (step 101). Here, when the number Kmax of BS-IF interference signals whose amplitude | r (n _k , m _k ) | is equal to or greater than a threshold value is large, the signal processing capability causes the selected BS-IF interference signal to There are cases where interference suppression processing cannot be executed for all. Therefore, in the second embodiment, as illustrated in FIG. 8, amplitude magnitudes | r (of a plurality of BS-IF interference signals selected so as to satisfy | r (n _k , m _k ) | ≧ L _th. n _k , m _k ) | are arranged in descending order (step 102), and BS-IF interference signals are further selected by the required number K _need (≦ Kmax) in the descending order of | r (n _k , m _k ) | (Step 103). Thus the BS-IF interference signal of the selected required number K _need only generate an interference replica signal to perform interference suppression processing (step 104).
In the second embodiment, the BS-IF interference signals detected based on the result of the correlation calculation process are arranged in order of magnitude of the amplitude, and the interference suppression process is executed only for a required number of BS-IF interference signals in the descending order. Thus, it becomes possible to cancel the optimum BS-IF interference signal in consideration of the signal processing capability, and the BS-IF interference signal cancellation can be made more efficient.
Since other processes in the second embodiment are the same as those in the first embodiment, the description thereof is omitted.

[Third embodiment of interference suppression processing]
The third embodiment is intended to speed up the search for the BS-IF interference signal in the interference suppression processing in the interference suppression processing unit 300. Note that the description of the same processing as in the first embodiment will be omitted in the processing in the third embodiment.

In the third embodiment, _{assuming that} the maximum range of the frequency offset amount f _offset is f _wide , N _max = f _wide / Δf is the number of times of searching when discretized by the frequency interval Δf. If the maximum range of the delay time is T _wide , M _max = T _wide / ΔT is the number of searches when discretized at a time interval ΔT. Therefore, N _max × M _max is the total number of searches.

Further, the processing time of the correlation calculations per time is proportional to the number of data N _s to be used for the calculation. Therefore, it is necessary to calculate N _max × M _max × N _s . As N _max , M _max , and N _s are increased, the detection accuracy of the BS-IF interference signal is improved. However, the processing time increases and the processing delay increases accordingly. As a result, the detection of the BS-IF interference signal is delayed.

Therefore, in the third embodiment, first, then the frequency interval as shown Delta] f, the time interval [Delta] T, a plurality sets of data number N _s of the correlation calculation. And those values are adaptively changed.
Frequency interval: Δf = Δf ₁ , Δf ₂ , ---. However, (Δf ₁ > Δf ₂ > −−−−)
Time interval: ΔT = ΔT ₁ , ΔT ₂ , ---. However, (ΔT ₁ > Δf ₂ > −−−−)
Number of data for correlation calculation: N _s = N _s1 , N _s2 , ---. However, (N _s1 <N _s2 <----)

Here, it sets larger frequency interval Delta] f, and the time interval [Delta] T, is set to be smaller the number of data N _s of the correlation calculation. Specifically, the frequency interval is set to Δf ₁ , the time interval ΔT ₁ , the number of correlation calculation data is set to N _s1 , the correlation value is calculated, the amplitude is compared with the threshold value L _th, and the following equation (7 ) when a and (8) are shown as the threshold _{L th} or more, the _n 1, _m is provisionally determined that there is a BS-IF interference signal to a value of _1, the frequency offset value _{n 1} Delta] f at that time _1. Record the delay time m ₁ ΔT ₁ .

Next, FIG. 9 and the following equation (9), as shown in (10), recorded frequency offset value _{n 1} Delta] f _1, the periphery of the delay time _{m 1 ΔT 1 Δf 1} is smaller than the frequency interval Delta] f _2, [Delta] T ₁ Correlation values are calculated with a smaller time interval ΔT ₂ and with a correlation calculation data number N _s2 greater than N _s1 .

However, n ₂ and m ₂ in the above formulas (9) and (10) are limited to the vicinity of the frequency offset value n ₁ Δf ₁ and delay time m ₁ ΔT ₁ recorded as shown in the following formula (11). To do.

Here, Δf _w and ΔT _w correspond to a frequency offset width and a delay time width for limiting the search range, respectively. By limiting the search range in this way, the processing time can be shortened. Further, by searching with a smaller frequency interval Δf ₂ and a smaller time interval ΔT ₂ , it is possible to estimate a highly accurate frequency offset value and delay time, and to increase the number of correlation calculation data N _s2 . A high amplitude r (n _k , m _k ) can be estimated. As a result, the BS-IF interference signal cancellation effect can be increased.

As described above, in the third embodiment, it is possible to search for a highly accurate BS-IF interference signal at high speed and to reduce the processing amount. In the description of the third embodiment, the two search range limiting methods have been described. However, by limiting the search range in the same manner as the three or four methods, the processing time can be further shortened and the accuracy is high. (N _k , m _k ) can be estimated.

[Embodiment 4 of interference suppression processing]
FIG. 10 is a block diagram showing still another embodiment of the interference suppression processing in the interference suppression processing unit 300. Note that description of the same processing as in the first embodiment (see FIG. 5) is omitted.
In the first embodiment, the received signal x ₀ (t) including the BS-IF interference signal received by the base station 10 is frequency-converted (down-converted) and processed in a low frequency band. Specifically, after canceling the BS-IF interference signal in a low frequency band, the frequency is converted (up-converted) to the original mobile communication frequency band (first frequency band: 1.5 GHz band) and output. Yes.

In the fourth embodiment, the received signal x0 (t) including the BS-IF interference signal is amplified by the amplifier 323 without frequency conversion, and the interference replica signal y (i), which is a replica of the BS-IF interference signal, is used in a low frequency band. Is generated. Then, the interference replica signal y (i) is frequency-converted (up-converted) to generate an interference replica signal y (t), and the up-converted interference replica signal y (t) is used to change the frequency of mobile communication. The BS-IF interference signal is canceled in the band (first frequency band: 1.5 GHz band). According to the fourth embodiment, the received signal x ₀ (t) received by the base station antenna 40 is output to the base station device 20 even if the estimation processing unit 315 or the interference replica signal generation unit does not function due to a failure or the like. can do.

[Embodiment 5 of interference suppression processing]
FIG. 11 is a block diagram illustrating still another embodiment of the interference suppression processing in the interference suppression processing unit 300. Note that description of the same processing as in the first embodiment (see FIG. 5) is omitted.
In the fifth embodiment, the BS reception signal d _RF (t) in the second frequency band (11 MHz band) is received by the BS antenna 351 for interference suppression installed in the base station 10 as in the first embodiment, and the received BS signal d _RF (t) is received by the BS. The reference signal d ₀ (t) is generated by frequency conversion to the same frequency as the IF interference signal. Based on this reference signal d ₀ (t), an interference replica signal y (t) that is a replica of a plurality of BS-IF interference signals received by the base station 10 is created, and the interference replica signal y (t) is received signal. The BS-IF interference signal is canceled by adding x ₀ (t) in reverse phase.

  In particular, in the fifth embodiment, the weight calculation unit (estimation processing unit) 324 sequentially calculates the weight w for creating the interference replica signal y (t) as described below. The weight used here is a weighting coefficient to be applied to the reference signal when generating the interference replica signal y (t), and corresponds to the complex amplitude h in the first embodiment.

First, the weight calculation unit 324 needs to detect a BS-IF interference signal having a frequency offset based on the reference signal d (i). For this purpose, first, a reference signal that is frequency offset by a value obtained by discretizing the frequency offset amount f _offset with respect to the received reference signal d (i) at a frequency interval Δf is denoted as d _off (i, m). _off (i, m) can be expressed by the following equation (12). Here, “j” in Equation (12) represents an imaginary number (√−1), and “m” is a natural number representing the order of frequency offsets discretized by Δf. “MΔf” is a discretized frequency offset amount. The sampling time interval ΔT is generally sufficient if a time of about 1/2 or 1/4 of the symbol length (= 1 / radio transmission bandwidth) of the radio signal is sufficient.

First, a method for generating weights for creating an interference replica signal will be described. Now, assuming that the weight for creating the interference replica signal is w (n, m), the interference replica signal y (i), which is a replica of the BS-IF interference signal, has the weight w (n, m) and the reference signal d. It is given by the following equation (13) using _off (i, m). Note that n and m are the same variables as in equation (2).

Next, the update of the weight w (n, m) will be described. A weight difference Δw (n, m) is calculated by performing the calculation shown in the following equation (14) on the signal obtained by subtracting the interference replica signal y (i) from the received signal x (i). In Expression (14), “ ^* ” represents a complex conjugate, and “N _s ” represents the number of data used for calculating the weight difference Δw.

The weight w (n, m) obtained by correcting the difference Δw (n, m) with respect to the current weight w (n, m) is given by the following equation (15).

By the way, in the fifth embodiment, first, the presence / absence of a BS-IF interference signal is determined. Here, determination of the presence / absence of a BS-IF interference signal will be described.
As an example, the initial value of the weight is given by the following equation (16).

When the weight difference Δw (n, m) is calculated, the weight difference Δw (n, m) is expressed by the following equation (17).

Therefore, the next weight w (n, m) is represented by the following equation (18) because the initial weight is w (n, m) = 0.

The weight calculation unit 324 detects a BS-IF interference signal that is frequency-offset based on the reference signal d (i) based on the weight of Expression (18).
As in the first embodiment, when the range of n is N _{min to} N _max and the range of m is M _{min to} M _max , the weight calculation unit 324 has (N _max −N _min +1) × (M _max -M _min +1) correlation calculations are performed. The magnitude of the calculated weights w (n, m) | w (n, m) | is compared with a threshold value _{L th} have preset the threshold _{L th} or more is w (n, m) the BS-IF Simultaneously with the complex amplitude of the interference signal, it is determined that there is a BS-IF interference signal at the position (nΔT, mΔf).
If the same control as in the third embodiment is performed, it is possible to cancel the optimum BS-IF interference signal in consideration of the signal processing capability, and the BS-IF interference signal cancellation efficiency can be improved. it can.
Incidentally, the number of BS-IF interference signal becomes the threshold value _{L th} or more and _{K max.} Let w (n _k , m _k ) be the weight of the k-th BS-IF interference signal arranged in order. The kth BS-IF interference signal has the following elements.
Delay time τ: _nk ΔT
Frequency offset f _offset : m _k Δf
Weight (equivalent to amplitude): w (n _k , m _k )

Then, an interference replica signal y (i) that is a replica of the BS-IF interference signal is sequentially generated as shown in the following equation (19) with respect to K _max BS-IF interference signals determined to have interference. , Subtract from the received signal x (i).

The output signal z (i) is expressed by the following equation (20).

As in the second embodiment, | w (n _k , m _k ) | is arranged in descending order, and the required number K _need (≦ Kmax) is increased in the order in which | w (n _k , m _k ) | select BS-IF interference signal, executes the generated and interference suppression processing an interference replica signal only BS-IF interference signal required number K _need chosen. Thereby, the amount of signal processing can be reduced without significantly reducing the interference suppression processing.

[Embodiment 2]
FIG. 12 is a schematic configuration diagram illustrating an example of the overall configuration of a base station according to another embodiment of the present invention. Note that, in the configuration of the base station according to the present embodiment, the same parts as those shown in FIGS.

The base station 10 according to the present embodiment is a configuration example in the case where diversity reception is performed using two base station antennas 40 (# 1) and 40 (# 2). In FIG. 12, the signals received by the base station antennas 40 (# 1) and 40 (# 2) are x ₀ (t) and x ₀ ′ (t), respectively. In addition, the first interference suppression processing unit (BS-IF interference canceller) 300 (# 1) and the second interference suppression processing unit (BS-IF interference canceller) 300 (# 2) constituting the interference suppression device 30 are completely different. It is the same configuration. Also, the BS broadcast RF signal d _RF (t) received by the interference suppression BS antenna 351 installed in the base station 10 is frequency-converted to the same frequency as the BS-IF interference signal to generate the reference signal d ₀ (t). doing. Then, the generated reference signal d ₀ (t) is branched into two, the first interference suppression processing unit 300 (# 1) and the second one provided for each of the base station antennas 40 (# 1) and 40 (# 2). Each is input to the interference suppression processing unit 300 (# 2).

  Note that the interference suppression processing in each of the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) in FIG. 12 is any interference suppression illustrated in the first to fifth embodiments. It does not matter if it is a process. Further, when communication is performed from the base station apparatus 20 to the mobile device, the mobile communication signal is transmitted from the base station antenna 40 (# 1) by switching the signal path by the duplexer (DUP: Duplexer) 50, 51. Can be sent.

[Embodiment 3]
FIG. 13 is a schematic configuration diagram illustrating an example of the overall configuration of a base station according to still another embodiment of the present invention. Note that, in the configuration of the base station according to the present embodiment, the same parts as those shown in FIGS.

The base station 10 of the present embodiment is a configuration example in the case where diversity reception is performed by two base station antennas 40 (# 1) and 40 (# 2), as in the embodiment of FIG. In FIG. 14, the signals received by the base station antennas 40 (# 1) and 40 (# 2) are x ₀ (t) and x ₀ ′ (t), respectively. In addition, the first interference suppression processing unit (BS-IF interference canceller) 300 (# 1) and the second interference suppression processing unit (BS-IF interference canceller) 300 (# 2) constituting the interference suppression device 30 are completely different. It is the same configuration. In addition, switches 70 and 71 that directly pass the received signals x ₀ (t) and x ₀ ′ (t) are provided for each of the base station antennas 40 (# 1) and 40 (# 2). The switch 70 uses the path of the received signal x ₀ (t), the first path where the interference signal suppression process is performed by the first interference suppression processing unit 300 (# 1), and the first interference suppression processing unit 300 (# 1). ) Functions as reception path switching means for switching to and from the second path where interference signal suppression processing is not performed. Similarly, the switch 71 uses a path of the reception signal x ₀ ′ (t) as a first path where the interference signal suppression process is performed by the second interference suppression processing unit 300 (# 2), and a second interference suppression process. It functions as a reception path switching means for switching to and from the second path where the interference signal suppression processing by the unit 300 (# 2) is not performed. When the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) do not function due to a failure or the like, the control device 74 as the control unit receives the received signal x ₀ (t), By performing control to switch the switches 70 and 71 so as to directly pass x ₀ ′ (t), the received signals x ₀ (t) and x ₀ ′ (t) are respectively sent to the interference suppression processing units 300 (# 1). ), 300 (# 2) can be output directly to the base station apparatus 20 without going through.

In addition, the control device 74 detects each received signal x ₀ (t) when the intensity of the reference signal d ₀ (t) (for example, the power of the reference signal or SNR: Signal to Noise Ratio) is less than or less than the threshold. ), And the switch 70 and 71 may be controlled so that the route x ₀ ′ (t) is switched from the first route to the second route. When the control causes the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) to stop functioning normally due to insufficient strength of the reference signal d ₀ (t). In addition, it is possible to prevent the accuracy of interference suppression in each interference suppression processing unit 300 (# 1) and 300 (# 2) from being lowered, and to prevent inappropriate interference suppression processing from being performed in advance.

In the present embodiment, when the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) do not function simultaneously due to a failure or the like, the following restoration algorithm is used. It can be recovered. When failures occur in the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) at the same time, the control device 74 receives the received signals x ₀ (t) and x ₀ ′ (t). The switches 70 and 71 are switched so as to pass directly. Thereby, communication to the base station apparatus 20 is securable. Next, the control device 74 tries to recover the function by resetting both the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2). Then, by switching one of the switches 70 and 71, the signal from one of the plurality of interference suppression processing units (for example, the first interference suppression processing unit 300 (# 1)) is changed to the base station device 20 side. To monitor the status. This monitoring can be performed in the base station apparatus 20. If the state can be recovered, the switch is kept switched so that the signal from the interference suppression processing unit is output to the base station apparatus 20 side. Next, the other switch is controlled so that a signal from the other of the plurality of interference suppression processing units (for example, the second interference suppression processing unit 300 (# 2)) is output to the base station device 20 side, Monitor status. If the state can be recovered, the switch is kept switched so that the signal from the interference suppression processing unit is output to the base station apparatus 20 side. By this control, it is possible to prevent both of the diversity receptions from being cut off at the same time, and the reliability of the base station can be improved.

  Note that the interference suppression processing in each of the first interference suppression processing unit 300 (# 1) and the second interference suppression processing unit 300 (# 2) in FIG. 13 is any interference suppression illustrated in the first to fifth embodiments. It does not matter if it is a process. When communication is performed from the base station apparatus 20 to the mobile device, the mobile communication signal can be transmitted from the base station antenna 40 (# 1) by switching the signal path by the duplexers 50 and 51. it can.

  1, 12, and 13, the example in which the interference suppression device 30 including the interference suppression processing unit 300 and the like is provided separately from the base station device 20 has been described. However, the interference suppression processing unit 300 Or the like may be incorporated in the base station apparatus 20.

FIG. 14 is a schematic configuration diagram showing an example of the overall configuration of a base station that is a base station according to still another embodiment of the present invention and in which the interference suppression device 30 is incorporated in the base station device 20. Note that, in the configuration of the base station according to the present embodiment, the same parts as those shown in FIG.
In FIG. 14, a base station apparatus 20 provided in the base station 10 includes a receiving apparatus 200 and a transmitting apparatus 210, and the above-described interference suppression apparatus 30 is incorporated. The interference suppression processed reception signal z ₀ (t) output from the interference suppression device 30 is sent to the reception device 200. The mobile communication signal output from the transmission device 210 is sent to the base station antenna 40 via the duplexer 50 and transmitted toward the mobile device.

As described above, according to each of the above embodiments, the interference replica signals corresponding to the plurality of BS-IF interference signals x _BS-IF included in the reception signal x in the first frequency band (1.5 MHz band) are generated, respectively. By subtracting the interference replica signal from the received signal x in the first frequency band, a plurality of BS-IF interference signals x _BS-IF included in the received signal x in the first frequency band can be suppressed. Therefore, a plurality of BS-IFs in the first frequency band (1.5 MHz band) generated by frequency conversion from a radio signal in the second frequency band (11 MHz band) having a frequency band different from that of the radio signal received from the mobile device 80. The interference signal xBS _-IF can be suppressed.

In each of the above embodiments, the first frequency band is the 1.5 GHz band, the second frequency band is the 11 GHz band for BS broadcasting, and a radio wave that is leaked from the BS booster 91 installed in a home or the like. Although the case where the signal is an interference signal has been described, the present invention is not limited to this. In addition, the present invention can be applied in the same manner as long as the base station 10 can receive the radio signal in the second frequency band before the frequency conversion that is the source of the interference signal in the first frequency band. The effect is obtained.
Further, the estimation and generation of interference replica signals are not limited to the above embodiments. For example, a least mean square (LMS) algorithm, a recursive least square (RLS) algorithm, an ultra-high resolution algorithm such as MUSIC (Multiple Signal Classification), and a two-dimensional LMS algorithm are similarly used. In some cases, similar effects can be obtained.

DESCRIPTION OF SYMBOLS 10 Base station 20 Base station apparatus 30 Interference suppression apparatus 40 Base station antenna 50, 51 Duplexer 70, 71 Switch 74 Control apparatus 80 Mobile device 300 Interference suppression processing part 301 Parameter value estimation part 302 Parameter value storage part 303 Interference replica signal Generation unit 304 Subtraction processing unit 350 BS reception system 351 Interference suppression BS antenna (parabolic antenna)
352 BS-RF receiver

Japanese Patent Laid-Open No. 2001-267942

The interference signal suppressed by the conventional base station is an interference signal between the communication terminal and the base station, such as an interference signal from an adjacent base station or an interference signal from a communication terminal existing in the same base station cell. It is a radio signal transmitted and received in a radio communication network. For this reason, it is considered that interference signals can be suppressed using the above-described known signals (for example, pilot symbols in the CDMA system). However, the received signal received by the base station may include other interference signals that are difficult to predict other than the radio signals transmitted and received by the wireless communication network. Then, when this inventor investigated about such another interference signal, it turned out that the interference signal resulting from the radio broadcast wave transmitted from the broadcast satellite exists as shown below. 15, usually, the frequency band of the radio broadcast wave _{d RF} from broadcasting satellite 90 is 11 G Hz band, interfering with radio signals _{x MS} of 1.5 G Hz band transmitted from the communication terminal 80 It is not considered. However, the received signal (BS-RF signal) received by the BS receiving system 95 from the broadcasting wave d _RF from the broadcasting satellite 90 is basically frequency conversion incorporated in the receiving device 97 mounted on the parabolic antenna 96. A signal converted to an intermediate frequency (BS-IF) signal by an apparatus (LNB: Low Noise Block Converter) (hereinafter, a signal converted to an intermediate frequency (BS-IF) by the LNB is referred to as an LNB BS-IF signal). ), And transmitted to a broadcast receiver (not shown) via the coaxial cable 98. Further, the BS-IF signal by the LNB takes into account the transmission loss of the coaxial cable 98 and the distribution loss when the received signal is distributed in the apartment house, and the like, and the amplification device (booster) 99 provided near the antenna 96 is used. In some cases, the signal is amplified (hereinafter, the signal amplified by the booster 99 is referred to as “BS-IF signal by the booster”). BS-IF signal by the BS-IF signal and boosters by the LNB is in the same 1.5 G Hz band and a radio signal _{x MS} to be transmitted to the base station 100 from the communication terminal 80. For this reason, if the radio wave shielding (shielding) of these devices 97 and 99 is insufficient or there is a connection error with the connector of the coaxial cable 98, the intermediate frequency signal xBS _-IF after frequency conversion is transmitted to the space as radio waves. It was found that the leaked radio wave was received by the base station 100 and became an interference signal.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1
FIG. 1 is a schematic configuration diagram illustrating an example of the overall configuration of a base station according to an embodiment of the present invention. In Figure 1, the base station 10 according to this embodiment includes a base station apparatus 20 of the main body, the interference suppression device 30, from the mobile station 80 as a communication terminal of the first frequency band (1.5 G Hz band) radio A base station antenna 40 as first receiving means for receiving a signal (radio wave), and duplexers (DUPlexers) 50 and 51 for sharing the base station antenna 40 for transmission and reception are provided. Interference suppression unit 30 includes an interference suppression processing unit 300 described later as an interference suppression unit, a radio signal of satellite BS of the second frequency band used in the interference suppression (11 G Hz band) and _{(radio) d} RF (t) BS receiving system 350 for receiving.

The BS reception system 350 includes a mobile communication signal x _MS that is a desired signal and its IF interference signal (hereinafter referred to as “BS-IF interference signal”) x _BS-IF generated by a plurality of BS receivers. when receiving a radio signal x of the first frequency band (1.5 G Hz band), a second frequency band before it is frequency-converted to an interference signal of the first frequency band (11 G Hz band) It functions as a second receiving means for receiving a radio signal (radio wave) d _RF (t) of a satellite broadcast BS that is a radio signal. Furthermore, the BS reception system 350 also functions as a reference signal generation unit that generates a reference signal d ₀ (t) in the first frequency band by performing frequency conversion on the reception signal d _RF (t) in the second frequency band. As the BS reception system 350, for example, as shown in the figure, a parabolic antenna (hereinafter referred to as “interference suppression BS antenna”) 351 that is an antenna body, and a BS-RF mounted on the interference suppression BS antenna 351. An existing BS receiving system with a receiver 352 can be used. BS-RF receiver 352 of the BS receiver system 350, the signal of the second frequency band the first frequency band by frequency conversion of the received signal _d RF (t) of (11 G Hz band) (1.5 G Hz band) An LNB (Low Noise Block Converter) that generates d ₀ (t) is included. The signal d ₀ (t) output from the BS-RF receiver 352 is sent to the interference suppression device 30 via a coaxial cable. Hereinafter, the BS-IF signal d ₀ (t) frequency-converted to the intermediate frequency BS-IF by the BS-RF receiver 352 is referred to as “BS-IF reference signal” or simply “reference signal”.

Received signal x of the first frequency band received at the base station antenna 40 (1.5 G Hz band), as illustrated in FIG. 2 (a), the moving body is a desired signal transmitted from the mobile station 80 The communication signal x _MS and a plurality of BS-IF interference signals x _BS-IF are included. Each of the plurality of BS-IF interference signals x _BS-IF is a signal caused by a leaked radio wave having an intermediate frequency of a satellite broadcast receiving system installed in a home, office, various facilities, or the like. Satellite systems, parabolic antenna for receiving radio signals of a satellite broadcasting BS of the second frequency band (11 G Hz band) (hereinafter referred to as "BS antenna".) And the satellite BS received by BS antenna An LNB that converts the BS received signal d _RF (t) in the second frequency band to an intermediate frequency and an amplifier (hereinafter referred to as “BS booster”) that is provided near the BS antenna so as to amplify the intermediate frequency signal after frequency conversion. "). The BS booster amplifies a BS-IF signal having the same frequency as the first frequency band. Here, when the radio wave shielding (shielding) of the BS booster is insufficient or there is a connection error between the BS booster and the coaxial cable connector, the BS-IF signal may leak from the BS booster to the space as radio waves. Since the radio waves leaked from each BS booster travel through different transmission paths, they reach the base station antenna 40 as a plurality of radio signals having different delay times and intensities. In addition, when a radio signal (BS-RF signal) received by the BS antenna is converted into an intermediate frequency signal (BS-IF signal), a frequency offset due to the frequency deviation of the local transmitter for conversion to the intermediate frequency is set. Arise. In this way, a radio signal including a plurality of leaked radio waves having different delay times, intensities, and frequencies is received by the base station antenna 40 as a BF-IF interference signal x _BS-IF included in the received signal x in the first frequency band. The

Interference suppression unit 30, interference suppression to perform processing for suppressing the BF-IF interference signal _{x BS-IF} included in the received signal x of the first frequency band received at the base station antenna 40 (1.5 G Hz band) A processing unit 300 is provided. The interference suppression processing unit 300 subtracts replicas of a plurality of BF-IF interference signals x _BS-IF (hereinafter referred to as “interference replica signals”) from the reception signal x of the first frequency band to receive the first frequency band. It acts as an interference suppression means for suppressing the BF-IF interference signal _{x BS-IF} included in the signal x. The interference suppression processing unit 300 functions to cancel the interference signal included in the received signal, and is also referred to as an “interference canceller”. In addition, the interference suppression processing unit 300, based on the reference signal d ₀ (t) generated by the BS receiving system 350 and the received signal x ₀ (t) of the first frequency band received by the base station antenna 40, It also functions as an interference replica signal generation means for generating an interference replica signal.

FIG. 3 is a block diagram illustrating a configuration example of the interference suppression processing unit 300. The interference suppression processing unit 300 of FIG. 3 includes a parameter value estimation unit 301, a parameter value storage unit 302, an interference replica signal generation unit 303, and a subtraction processing unit 304.
Parameter value estimation unit 301, a predetermined timing, an input signal _x 0 is the received signal of the first frequency band received at the base station antenna 40 (1.5 G Hz band) (t), the interference suppression BS antenna 351 second frequency band received by the (11 G Hz band) of the received signal _d RF (t) is in the reference signal _d 0 of the first frequency band frequency-converted (1.5 G Hz band) (t) based on estimates the values of the parameters used to generate the interference replica signal corresponding to the BF-IF interference signal _{x BS-IF} included in the received signal _x 0 (t). The parameters for this estimation target, for example, the reference signal _d 0 (t) BF-IF interference signal _{x BS-IF} the delay time for, and the like amplitude or frequency offset.
The parameter value storage unit 302 stores the parameter estimation value estimated by the parameter value estimation unit 301 until the next parameter value is estimated and updated so that it can be used for a plurality of subsequent interference suppression processes. Is.
Interference replica signal generation unit 303, based on the reference signal _d 0 of the parameter values the values in the first frequency band parameter stored in the storage unit 302 (1.5 G Hz band) (t), the received signal x ₀ generates an interference replica signal y corresponding to the BF-IF interference signal _{x BS-IF} contained in (t) (t).
Subtraction processing unit 304, an interference replica signal generation unit 303 interference replica signal y generated by (t), from a received signal of a first frequency band (1.5 G Hz band) input signal _x 0 (t) Perform the subtraction process. The reception signal in the first frequency band in which the BF-IF interference signal xBS _-IF is suppressed by the subtraction processing of the subtraction processing unit 304 is output to the base station apparatus 20 as the output signal z ₀ (t).

FIG. 4 is a block diagram illustrating another configuration example of the interference suppression processing unit 300. Unlike the configuration example of FIG. 3, the interference suppression processing unit 300 of FIG. 4 is configured to update parameters sequentially, and the estimated value of the parameter estimated by the parameter value estimation unit 301 is estimated for the next parameter value. In addition, the parameter value storage unit 302 that stores data until updating is not provided.
Parameter value estimation unit 301, a predetermined timing, an input signal _x 0 is the received signal of the first frequency band received at the base station antenna 40 (1.5 G Hz band) (t), the interference suppression BS antenna 351 based on the reference signal _d 0 of the second frequency band received first frequency band received signal is frequency conversion (11 G Hz band) (1.5 G Hz band) (t), the received signal A value of a parameter used to generate an interference replica signal corresponding to the BF-IF interference signal x _BS-IF included in x is estimated.
Interference replica signal generation unit 303, based on the reference signal _d 0 of the estimated parameters of the values in the first frequency band by the parameter value estimation unit 301 (1.5 G Hz band) (t), the received signal _{x 0} An interference replica signal y (t) corresponding to the BF-IF interference signal x _BS-IF included in (t) is generated.
Subtraction processing unit 304, an interference replica signal generation unit 303 interference replica signal y generated by (t), from a received signal of a first frequency band (1.5 G Hz band) input signal _x 0 (t) Perform the subtraction process. The reception signal in the first frequency band in which the BF-IF interference signal xBS _-IF is suppressed by the subtraction processing of the subtraction processing unit 304 is output to the base station apparatus 20 as the output signal z ₀ (t).

On the other hand, the first frequency band (1.5 G, which second frequency band received by the interference suppression BS antenna 351 provided in the base station 10 a BS reception signal _d RF of (11 G Hz band) (t) to frequency conversion (Hz band) BS-IF signal is set as a reference signal d ₀ (t) as a function of time t. The reference signal d ₀ (t) is frequency-converted to a predetermined frequency by the down converter (DC) 313 and then sampled by the analog-to-digital converter (ADC) 314 at a time interval ΔT to be a digital reference signal d (i ). Here, i is a natural number representing the sampling order.

[Embodiment 5 of interference suppression processing]
FIG. 11 is a block diagram illustrating still another embodiment of the interference suppression processing in the interference suppression processing unit 300. Note that description of the same processing as in the first embodiment (see FIG. 5) is omitted.
In Example 5, receives a BS reception signal _d RF of the second frequency band by the interference suppression BS antenna 351 installed in the base station 10 as in the above first embodiment (11 G Hz band) (t), it Is converted to the same frequency as the BS-IF interference signal to generate the reference signal d ₀ (t). Based on this reference signal d ₀ (t), an interference replica signal y (t) that is a replica of a plurality of BS-IF interference signals received by the base station 10 is created, and the interference replica signal y (t) is received signal. The BS-IF interference signal is canceled by adding x ₀ (t) in reverse phase.

As described above, according to the above embodiments, the first frequency band interference replica signals corresponding to a plurality of BS-IF interference signal _{x BS-IF} included in the received signal x (1.5 G Hz band) respectively generated By subtracting the interference replica signal from the received signal x in the first frequency band, a plurality of BS-IF interference signals x _BS-IF included in the received signal x in the first frequency band can be suppressed. Thus, a plurality of second frequency band in which the frequency band is different from the radio signal received from the mobile station 80 frequency-converted by the first frequency band generated from the radio signal (11 G Hz band) (1.5 G Hz band) BS-IF interference signal x _BS-IF can be suppressed.

Claims (15)

First receiving means for receiving a radio signal in a first frequency band including a desired signal transmitted from a communication terminal and an interference signal that interferes with the desired signal;
Interference suppression means for suppressing an interference signal included in the received signal in the first frequency band by subtracting an interference replica signal corresponding to the interference signal from the received signal in the first frequency band. And
A second radio signal receiving a radio signal in the second frequency band before being frequency-converted to the interference signal in the first frequency band when receiving the radio signal in the first frequency band including the desired signal and the interference signal; Receiving means;
A reference signal generation means for generating a reference signal of the first frequency band by frequency-converting the received signal of the second frequency band;
An interference replica signal generation unit configured to generate the interference replica signal based on the reference signal and the received signal in the first frequency band. In the base station of claim 1,
The interference replica signal generation means calculates values of a plurality of parameters necessary for generating the interference replica signal that can be calculated from the reference signal and the received signal of the first frequency band, and the calculated values of the plurality of parameters Generating the interference replica signal based on the base station. The base station of claim 2,
The base station characterized in that the parameters used for generating the interference replica signal are a frequency offset, a delay time, and an amplitude of the interference signal. In the base station of claim 3,
The interference replica signal generation means includes
Calculating a correlation value between the reference signal and the received signal in the first frequency band while setting a plurality of sets of frequency offset, delay time and amplitude for the reference signal;
A base that estimates the frequency offset, delay time, and amplitude of the interference signal by comparing a correlation value calculated for each of the plurality of combinations of the frequency offset, delay time, and amplitude with a preset threshold value Bureau. In the base station of claim 3,
The interference replica signal generation means includes
Based on an offset reference signal in which the frequency offset and delay time are set in the reference signal and a weight corresponding to the amplitude, the interference replica signal is generated,
The weight difference is calculated based on the difference between the received signal in the first frequency band and the interference replica signal and the offset reference signal, and the weight is updated using the difference. base station. In the base station according to any one of claims 2 to 5,
Storage means for storing the estimated value of the parameter;
The base station characterized in that the interference replica signal generation means generates the interference replica signal based on the value of the parameter stored in the storage means and the reference signal of the first frequency band. The base station of claim 6,
Update means for repeatedly updating the estimated value of the parameter stored in the storage means at a predetermined timing;
The base station characterized in that the update timing can be changed. In the base station according to any one of claims 1 to 7,
The path of the received signal received by the first receiving means is a first path where interference signal suppression processing is performed by the interference suppression means, and a second path where interference signal suppression processing is not performed by the interference suppression means. A base station characterized by comprising reception path switching means for switching between and. The base station of claim 8,
Control means for controlling the reception path switching means to switch the path of the reception signal from the first path to the second path when the intensity of the reference signal is equal to or less than a threshold value or less than a threshold value; A base station characterized by that. In the base station according to any one of claims 1 to 9,
The received signal of the first frequency band includes a plurality of interference signals having different frequency offsets, delay times, and amplitudes from each other. In the base station according to any one of claims 1 to 10,
The first frequency band radio signal received by the first receiving means is a 1.5 GHz band radio signal transmitted from the communication terminal,
The base station, wherein the second frequency band radio signal received by the second receiving means is an 11 GHz band radio broadcast signal transmitted from a broadcast satellite. In the base station according to any one of claims 1 to 11,
The interference signal included in the first frequency band radio signal received by the first receiving means is at least a frequency converter that converts a radio broadcast signal into an intermediate frequency signal and an amplifier that amplifies the intermediate frequency signal. A base station characterized by a leaked signal leaked from one device. By subtracting the interference replica signal corresponding to the interference signal from the reception signal of the first frequency band including the desired signal transmitted from the communication terminal and the interference signal that interferes with the desired signal, reception of the first frequency band is performed. An interference suppression device for suppressing an interference signal included in a signal,
Radio reception for receiving a radio signal in the second frequency band before frequency conversion to the interference signal in the first frequency band when receiving a radio signal in the first frequency band including the desired signal and the interference signal A reference signal generating means for receiving a radio signal of the second frequency band from an apparatus and generating a reference signal of the first frequency band by frequency-converting the received signal of the second frequency band;
An interference replica signal generating unit configured to receive the first frequency band reception signal and generate the interference replica signal based on the reference signal and the first frequency band reception signal; Interference suppression device. By subtracting the interference replica signal corresponding to the interference signal from the reception signal of the first frequency band including the desired signal transmitted from the communication terminal and the interference signal that interferes with the desired signal, reception of the first frequency band is performed. An interference suppression method for suppressing an interference signal included in a signal,
Receiving a radio signal in the second frequency band before being frequency-converted to the interference signal in the first frequency band when receiving a radio signal in the first frequency band including the desired signal and the interference signal; ,
Generating a first frequency band reference signal by frequency-converting the received signal of the second frequency band;
Generating the interference replica signal based on the reference signal and the received signal in the first frequency band. A method for suppressing interference. The interference suppression method of claim 14,
Generating the interference replica signal comprises:
Predetermining a plurality of parameters necessary for generating the interference replica signal that can be calculated from the reference signal and the received signal in the first frequency band;
Calculating a value of each of the plurality of parameters based on the reference signal and the received signal in the first frequency band;
Generating the interference replica signal based on the calculated values of the plurality of parameters.

Images