JP2022105797A - Wireless communication system - Google Patents

Abstract

To demodulate a modulation wave of a frequency shift keying method while suppressing occurrence of beat interference regardless of a power ratio of a signal transmitted from each base station.SOLUTION: An offset frequency Δf is set between a frequency in modulation processing of a wireless communication device of a first base station (base station 2A) and a frequency in modulation processing of a wireless communication device of a second base station (base station 2B). A receiving station 3 uses a known signal XA' transmitted during a learning period to obtain a propagation environment HA between the first base station (base station 2A) and the receiving station 3, a propagation environment HB between the second base station (base station 2B) and the receiving station 3, and an offset frequency Δf and obtain a signal XA transmitted from one base station (base station 2A in this embodiment) by removing a signal XB transmitted from the other base station (base station 2B) from a received signal Y at the receiving station 3.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wireless communication system, and more particularly to a technique suitable for application to a wireless communication system using a narrow band signal.

In a commercial wireless system that uses a narrow band signal, it is difficult to allocate a new frequency due to the exhaustion of the frequency band. Therefore, there is a commercial wireless system that transmits the same signal from a plurality of base stations to a terminal at the same frequency. However, in this method, when a plurality of radio signals have the same level and opposite phase at a certain reception point, the signals are lost due to the same wave interference (that is, beat interference). As a countermeasure against such signal loss, a method of changing the mapping rule for each base station is known (Patent Document 1).

Japanese Unexamined Patent Publication No. 2018-166293

However, the method of Patent Document 1 has a problem that it cannot cope with the situation of receiving two signals having different amplitudes.

Therefore, the present invention provides a wireless communication system capable of demodulating a modulated wave of a frequency shift keying system while suppressing the occurrence of beat interference regardless of the power ratio of the signal transmitted from each base station. The purpose is.

In order to solve the above problems, the invention according to claim 1 comprises a first base station and a second base station each including a wireless communication device for transmitting a signal modulated by a frequency shift modulation method, and the first base station. It has a receiving station that receives a signal transmitted from the first base station and also receives a signal transmitted from the second base station, and is used in the modulation process of the wireless communication device of the first base station. An offset frequency is set between the frequency and the frequency in the modulation process of the radio communication device of the second base station, and the receiving station utilizes the known signal transmitted during the learning period to use the first The propagation environment between the base station and the receiving station, the propagation environment between the second base station and the receiving station, and the offset frequency are obtained, and one base station is obtained from the received signal at the receiving station. It is a wireless communication system characterized in that a signal transmitted from is removed from the other base station and a signal transmitted from the other base station is acquired.

The invention according to claim 2 is characterized in that, in the wireless communication system according to claim 1, the offset frequency is equal to or less than a tolerance with respect to a reference value of mapping in the modulation process.

According to the third aspect of the present invention, in the wireless communication system according to the first or second aspect, the frequency shift keying method is a four-value frequency shift keying method having a multivalue number of four. It is a feature.

According to the first aspect of the present invention, since a constant offset frequency is set for each frequency shift assigned in the modulation process in each base station, the signal is transmitted from each base station. It is possible to suppress the occurrence of beat interference.

According to the invention of claim 1, it is also transmitted from one of the base stations by utilizing the known signal transmitted during the learning period and utilizing the fact that the frequency offset between the base stations is constant. By removing the signal from the received signal at the receiving station and acquiring the signal transmitted from the other base station, the occurrence of beat interference is suppressed regardless of the power ratio of the signal transmitted from each base station. It is possible to demodulate the modulated wave of the frequency shift modulation method.

According to the second aspect of the present invention, the offset frequency is set to an appropriate value, whereby the present invention can be applied without any trouble and good wireless communication can be performed.

According to the third aspect of the present invention, it is possible to exert the above-mentioned effects in a wireless communication system that performs wireless communication by using a quaternary frequency shift keying method.

It is a figure which shows the outline of the wireless communication system which concerns on embodiment of this invention. It is a functional block diagram which shows the schematic structure of the modulation part provided in the base station of the wireless communication system of FIG. It is a figure explaining the offset frequency added in a base station. It is a functional block diagram which shows the schematic structure of the demodulation part provided in the receiving station of the wireless communication system of FIG. It is a functional block diagram which shows the schematic structure of the interference canceller part of the demodulation part of FIG.

Hereinafter, the present invention will be described based on the illustrated embodiment. In the following, the characteristic configuration of the present invention will be described, and the description of the conventional mechanism for performing wireless communication will be omitted. Further, in each figure, the signal line and the imaginary part (Q signal; in other words, the orthogonal component and the Q signal component) that transmit the real part (I signal; in other words, the in-phase component and the I signal component) constituting the complex signal are transmitted. ) Is displayed as one signal line together with the signal line to be transmitted.

FIG. 1 is a diagram showing an outline of a wireless communication system 1 according to an embodiment of the present invention.

In this embodiment, data is altered and demodulated by a wireless communication device including a modulation unit 20 provided in the base stations 2A and 2B and a wireless communication device including a demodulation unit 30 provided in the receiving station 3, and these base stations 2A are used. , 2B and the receiving station 3 perform wireless communication. Data modulation / demodulation is performed by a frequency shift keying (FSK) method.

The base stations 2A and 2B generate a transmission signal including information to be transmitted, and transmit the transmission signal to the receiving station 3. At this time, the base station 2A and the base station 2B simultaneously transmit / wirelessly transmit (that is, broadcast) the same signal.

The transmission signal transmitted from the base station 2A reaches the receiving station 3 via the radio propagation path 5A, and the transmission signal transmitted from the base station 2B reaches the receiving station 3 via the radio propagation path 5B.

The receiving station 3 receives a signal transmitted from the base station 2A and transmitted via the radio propagation path 5A, and also receives a signal transmitted from the base station 2B and transmitted via the radio propagation path 5B. The received signal is subjected to predetermined processing and the information to be transmitted is output.

The wireless communication system 1 according to the embodiment has a first base station (base station 2A) and a second base station (base station) each including a wireless communication device for transmitting a signal modulated by a frequency shift modulation method. 2B) and a receiving station 3 that receives a signal transmitted from a first base station (base station 2A) and also receives a signal transmitted from a second base station (base station 2B). An offset frequency Δf is set between the frequency in the modulation process of the radio communication device of the first base station (base station 2A) and the frequency in the modulation process of the radio communication device of the second base station (base station 2B). The receiving station 3 uses the known signal _{XA'transmitted} during the learning period to provide a propagation environment _HA between the first base station (base station 2A) and the receiving station 3 and a second base station (base station 2A). The propagation environment HB between the base station 2B) and the receiving station 3 and the offset frequency _Δf are obtained from the received signal Y in the receiving station 3 from one of the base stations (base station 2B in this embodiment). The transmitted signal X _B is removed to acquire the signal X _A transmitted from the other base station (base station 2A in this embodiment).

FIG. 2 is a functional block diagram showing a schematic configuration of a modulation unit 20 provided in base stations 2A and 2B of the wireless communication system 1 according to the embodiment of the present invention.

The mapping unit 21 of the modulation unit 20 provided in the base stations 2A and 2B performs predetermined processing (for example, analog-digital conversion processing, error correction coding processing, frequency conversion) as necessary for the information / data to be transmitted. The input of the binary data string subjected to the processing (processing and amplification processing) is received, and the modulation mapping processing is performed on the binary data string by the frequency shift modulation (FSK) method to generate and output the symbol string.

In this embodiment, the mapping unit 21 specifically describes the "municipal digital mobile communication system (SCPC / 4-value FSK)" which is a standard related to a wireless system using the 4-value FSK method among the narrow-band digital mobile communication methods. Method) ”(Association of Radio Industries and Businesses, Standard No .: ARIB STD-T116), and the modulation mapping process is performed. In the above standard (ARIB STD-T116), quaternary FSK mapping is performed with the contents shown in Table 1 below.

The mapping unit 21 performs conversion processing into symbols according to Table 1 for the dibits constituting the input binary data string (in other words, every 2 bits), and outputs the symbol string.

The ROF unit 22 has a roll-off filter function, receives an input of a symbol string output from the mapping unit 21, and performs band limiting processing on the symbol string in order to reduce / eliminate intersymbol interference. Output.

The frequency offset unit 23 receives the input of the symbol string output from the ROF unit 22, and is a numerical value representing a frequency obtained by adding the offset frequency Δf to the value of the frequency shift corresponding to each symbol, and is transferred to the NCO unit 24. A numerical value representing the input frequency is calculated and output.

Here, the above standard (ARIB STD-T116) defines that the tolerance of frequency deviation is ± 10% or less with respect to the reference value of mapping. In consideration of this, in this embodiment in which the modulation mapping process is performed according to the above standard (ARIB STD-T116), the offset frequency Δf is set in the range where the absolute value is 31.5 Hz or less.

Based on the above, specifically, in this embodiment, the offset frequency Δf of the base station 2A is set to 0 Hz, and the offset frequency Δf of the base station 2B is set to 30 Hz (see FIG. 3). Here, the value of the offset frequency Δf added to each of the frequency deviation values corresponding to each symbol is constant for any frequency deviation.

For example, the offset frequency Δf of the base station 2A is set to 0 Hz, the offset frequency Δf of the base station 2B is set to -30 Hz, the offset frequency Δf of the base station 2A is set to -15 Hz, and the base is set. The offset frequency Δf of the station 2B may be set to +15 Hz.

The NCO unit 24 has a function of a numerically controlled oscillator (NCO: an abbreviation for Numerically Controlled Oscillator), receives a numerical value representing a predetermined frequency output from the frequency offset unit 23, and receives an oscillation signal of a frequency corresponding to the numerical value. Is output.

The quadrature modulation unit 25 receives the input of the oscillation signal output from the NCO unit 24, performs quadrature modulation processing using the oscillation signal, and outputs a transmission signal (baseband signal).

The transmission signal output from the quadrature modulation unit 25 is subjected to predetermined processing (for example, amplification processing, frequency conversion processing) as necessary, and then transmitted / wirelessly transmitted via the antenna 26. At this time, as described above, the base station 2A and the base station 2B simultaneously transmit / wirelessly transmit the same signal.

In this embodiment, the transmission signal X _A (baseband signal) is transmitted from the base station 2A, and the transmission signal X _B (baseband signal) is transmitted from the base station 2B.

The receiving station 3 receives the signal transmitted from the base station 2A and the signal transmitted from the base station 2B via the antenna 31.

FIG. 4 is a functional block diagram showing a schematic configuration of a demodulation unit 30 provided in the receiving station 3 of the wireless communication system 1 according to the embodiment of the present invention.

The signal received via the antenna 31 is subjected to predetermined processing (for example, band limiting processing, amplification processing, frequency conversion processing) as necessary, and then orthogonal to the demodulation unit 30 provided in the receiving station 3. It is input to the detection unit 32.

The orthogonal detection unit 32 performs orthogonal detection using a local oscillation signal supplied from a local oscillator (not shown), and generates and outputs a complex signal composed of an I signal having an in-phase component and a Q signal having an orthogonal component. do.

The interference canceller unit 4 has a constant offset frequency Δf for each frequency shift assigned in the modulation mapping process in each of the base stations 2A and 2B (specifically, in this embodiment, the offset frequency Δf = 30 Hz in the base station 2B). With respect to the signal transmitted from the base stations 2A and 2B with the addition of, one of the base stations (this embodiment) by utilizing the fact that the frequency offset between the base station 2A and the base station 2B is constant. Specifically, it is a mechanism for removing the signal transmitted from the base station 2B) from the received signal.

FIG. 5 is a functional block diagram showing a schematic configuration of the interference canceller unit 4 according to this embodiment.

Here, the transmission signal _XA (baseband signal) transmitted from the base station 2A is expressed by the following formula 1 in consideration of the fact that the offset frequency Δf is 0 Hz.

Further, the transmission signal X _B (baseband signal) transmitted from the base station 2B is expressed by the following mathematical formula 2 in consideration of the fact that the offset frequency Δf is 30 Hz (that is, Δf ≠ 0).

The meanings of each symbol / variable in Equations 1 and 2 are as follows.
X _A : Transmission signal (baseband signal) transmitted from base station 2A
X _B : Transmission signal (baseband signal) transmitted from base station 2B
f _A : Frequency of transmission signal transmitted from base station 2A [Hz]
Δf: Offset frequency [Hz] added by base station 2B
t: Time (sampling time)
j: Imaginary unit

The propagation environment H _A in the radio propagation path 5A from the base station 2A to the receiving station 3 is expressed by the following mathematical formula 3, and the propagation environment H _B in the radio propagation path 5B from the base station 2B to the receiving station 3 is expressed. , It is expressed as the following formula 4.

The meanings of the symbols / variables in Equations 3 and 4 are as follows.
_HA : Propagation environment between base station 2A and receiving station 3 H _B : Propagation environment between base station 2B and receiving station 3 α: Amplitude fluctuation in propagation environment _HA β: Amplitude fluctuation in propagation environment H _B Φ _A : Phase fluctuation in propagation environment H _A Φ _B : Phase fluctuation in propagation environment H _B

Based on the above, the received signal Y in the receiving station 3 is expressed by the following mathematical formula 5. The meaning of each symbol / variable in the following formulas 5 to 11 is the same as the meaning of each symbol / variable in the above formulas 1 to 4.

The interference canceller unit 4 uses the known signal _XA'included / added to the received signal periodically (or repeatedly at a predetermined timing) at a predetermined time interval to form a base station 2A and a receiving station 3. The values of the propagation environment _HA between the base station _2B , the propagation environment HB between the base station 2B and the receiving station 3, and the offset frequency Δf [Hz] added by the base station 2B are obtained and updated as appropriate. Based on the value, the transmission signal X _B transmitted from the base station 2B is removed from the reception signal Y in the reception station 3 (see the above equation 5), and the transmission signal X _A transmitted from the base station 2A is acquired. .. The transmission signal X _A transmitted from the base station 2A may be removed to acquire the transmission signal X _B transmitted from the base station 2B.

The known signal X _A '(including a signal called a reference signal, a pilot signal, a training signal, etc.) is, for example, predetermined and shared by both the base stations 2A and 2B and the receiving station 3. It is a predetermined bit sequence, and is stored in a storage unit (not shown) in the receiving station 3 for processing in the receiving station 3. Further, in the following description, the symbol / variable with "'" indicates that the symbol / variable is related to the known signal X _A '.

The first dividing unit 401 of the interference canceller unit 4 receives the input of the received signal Y (see the above formula 5 and the following formula 6) in the receiving station 3 received via the antenna 31, and also receives the input of the storage unit (illustrated). The input of the known signal X _{A'supplied from (omitted) is received, the received signal Y is divided by the known signal X A '} , and the signal expressed by the following formula 7 is output. Here, when the transmission signals transmitted from the base stations 2A and 2B are known signals (in other words, period, timing), X _A in Equation 6 is X _A '(in this case, the “learning period”). Called).

The LPF unit 402 has a function of a low-pass filter, receives an input of a signal output from the first division unit 401 (see the above equation 7), and among the signals, between the base station 2A and the receiving station 3. The propagation environment H _A of is a low frequency component, and the component related to the propagation environment H _B between the base station 2B and the receiving station 3 (that is, the second term in the above equation 7) is a higher frequency component. Utilizing the fact that there is, the propagation environment _HA between the base station 2A and the receiving station 3 is output.

The first propagation environment update control unit 403 receives the input of the propagation environment _HA between the base station 2A and the receiving station 3 output from the LPF unit 402, and uses the propagation environment _HA in the learning period for the learning period. In other words, it is output to the addition unit 404 as a propagation environment _HA'for interference cancellation processing while being held until the next learning period.

The first addition / subtraction unit 405 receives the input of the propagation environment _HA between the base station 2A and the reception station 3 output from the LPF unit 402, and the signal output from the first division unit 401 (above). (Refer to Equation 7), the signal output from the first dividing unit 401 is subtracted from the propagation environment _HA ( _HA'in the case of the learning period), and the result is as shown in Equation 8 below. Outputs the signal represented by.

The phase angle calculation unit 406 receives the input of the signal output from the first addition / subtraction unit 405 (see the above equation 8), and takes the inverse tangent function (that is, tan ^-1 ) of the signal to obtain the phase angle θ. Is calculated.

The delay unit 407 receives the input of the phase angle θ output from the phase angle calculation unit 406, delays the phase angle θ by one sampling cycle, and outputs the delayed phase angle θ. The phase angle output from the phase angle calculation unit 406 is expressed as “θ _t ”, and the delayed phase angle output from the delay unit 407 is delayed by one sampling period with respect to the phase angle θ _t and is “θ _t ”. Notated as _-1 ".

The frequency calculation unit 408 subtracts the phase angle θ _t-1 output from the delay unit 407 from the phase angle θ _t output from the phase angle calculation unit 406 to obtain the phase angle change amount Δθ _t in the sampling period. The frequency calculation unit 408 further calculates the offset frequency Δf using the relationship of Δf = Δθ _t × fs / 2π (where fs: sampling frequency [Hz]).

The frequency update control unit 409 receives the input of the offset frequency Δf output from the frequency calculation unit 408, and paraphrases the offset frequency Δf in the learning period as the offset frequency Δf'for interference cancellation processing during the period other than the learning period. And, while holding until the next learning period, a numerical value representing the offset frequency Δf', which represents a frequency to be input to the NCO unit 411, is calculated and output.

The amplification unit 410 has an amplifier function, receives an input of a numerical value (signal) representing an offset frequency Δf' output from the frequency update control unit 409, performs a predetermined amplification process, and outputs the input.

The NCO unit 411 has a function of a numerically controlled oscillator, receives an input of a numerical value representing the offset frequency Δf' output from the amplification unit 410, and according to the numerical value representing the offset frequency Δf', is as shown in the following mathematical formula 9. Generates and outputs the signal represented by.

The multiplication unit 412, the second addition / subtraction unit 413, the estimation unit 414, and the second propagation environment update control unit 415 provide a processing loop for estimating the propagation environment _HB between the base station 2B and the receiving station 3. Configure.

The multiplying unit 412 receives the input of the signal output from the NCO unit 411 (see the above formula 9), and is between the base station 2B and the receiving station 3 output from the second propagation environment update control unit 415. It receives the input of the propagation environment, multiplies the signal by the propagation environment, and outputs it.

The second addition / subtraction unit 413 receives the input of the signal output from the first addition / subtraction unit 405 (see the above equation 8), and also receives the input of the signal output from the multiplication unit 412, and receives the input of the signal and the two signals. Subtract and output the difference as an error signal. That is, the second addition / subtraction unit 413 uses the signal output from the first addition / subtraction unit 405 (see the above equation 8) as a reference signal, and the difference between the signals output from the multiplication unit 412 with respect to the reference signal is an error signal. Is output as.

The estimation unit 414 has a function of, for example, a transversal type equalizer, receives an input of a signal output from the NCO unit 411 (see the above equation 9), and an error signal output from the second addition / subtraction unit 413. The signal output from the NCO unit 411 (above) based on the error signal output from the second addition / subtraction unit 413 using, for example, the minimum average square (LMS: Least Mean Square) algorithm. The propagation environment H _B (see equation 9) between the base station 2B and the receiving station 3 is made to converge to the signal output from the first addition / subtraction unit 405 (see equation 8 above; reference signal). Estimate (see Equation 4 above).

The second propagation environment update control unit 415 receives the input of the propagation environment H _B between the base station 2B and the receiving station 3 output from the estimation unit 414, and uses the propagation environment H _B in the learning period as the learning period. In other words, it is output to the multiplication unit 412 as a propagation environment H _B'for interference cancellation processing while being held until the next learning period. The initial value of the propagation environment H _B when starting the estimation process (in other words, the convergence process) in the estimation unit 414 is set to, for example, 1.

As a result of the above, the propagation environment _HA'between the base station 2A for interference cancellation processing and the receiving station 3 is output from the first propagation environment update control unit 403, and the frequency update control unit 409 outputs the base for interference cancellation processing. The offset frequency Δf'added by the station 2B is output, and further, the propagation environment H _B'between the base station 2B for interference cancellation processing and the receiving station 3 is output from the second propagation environment update control unit 415. To.

Then, during the period other than the learning period, the propagation environment _HA'between the base station 2A and the receiving station 3 and the propagation environment _HB'between the base station 2B and the receiving station 3 are added. The transmission signal X _B (base band signal) transmitted from the base station 2B is removed from the reception signal Y (see the above equations 5 and 6) in the reception station 3 based on the value of the offset frequency Δf'. The transmission signal _XA (baseband signal) transmitted from the base station 2A is acquired.

Specifically, when the propagation environment H _B'for interference cancellation processing is output from the second propagation environment update control unit 415, the signal represented by the following formula 10 is output from the multiplication unit 412. Will be done. The NCO unit 411 generates and outputs a signal represented by the above equation 9 even during a period other than the learning period.

The addition unit 404 receives the input of the propagation environment _HA'for interference cancellation processing output from the first propagation environment update control unit 403, and receives the input of the signal output from the multiplication unit 412 (see the above equation 10). Upon receiving the input, the two signals are added and the signal represented by the following formula 11 is output.

The second division unit 416 receives the input of the received signal Y (see the above formula 6) and the input of the signal output from the adding unit 404 (see the above formula 11), and uses the received signal Y as described above. The transmission signal _XA (baseband signal) transmitted from the base station 2A is output by dividing by the signal output from the addition unit 404.

As a result, the interference canceller unit 4 outputs the transmission signal _XA (baseband signal) transmitted from the base station 2A.

The delay detection unit 33 receives the input of the signal output from the interference canceller unit 4, performs delay detection between consecutive symbols using the signal as an input, and generates and outputs a detection signal.

The ROF unit 34 has a roll-off filter function having the same characteristics as the ROF unit 22 of the base stations 2A and 2B, receives the input of the detection signal output from the delay detection unit 33, and performs band limitation processing on the detection signal. Is applied and output.

The rigidity determination unit 35 and the demapping unit 36 receive the input of the detection signal output from the ROF unit 34, and based on the detection signal, the modulation method used in the mapping unit 21 of the base stations 2A and 2B (of this embodiment). Specifically, according to the above-mentioned standard (ARIB STD-T116), a four-value FSK method) is used to perform hard determination on a symbol-by-symbol basis, perform demapping processing, and output a dibit value.

The binary data string output from the demapping unit 36 is data in which the binary data string input to the mapping unit 21 of the base stations 2A and 2B is reproduced (in other words, a digital signal returned to the original data array). Is.

According to the radio communication system 1 according to the embodiment, a constant offset frequency Δf for each frequency shift assigned in the modulation mapping process in the base stations 2A and 2B (in the above embodiment, the offset frequency in the base station 2B). Since the signal is transmitted from each of the base stations 2A and 2B after Δf = 30 Hz) is set, it is possible to suppress the occurrence of beat interference.

According to the wireless communication system 1 according to the embodiment, the known signal transmitted during the learning period is used, and the frequency offset between the base station 2A and the base station 2B is constant. The signal transmitted from one base station (base station 2B in the above embodiment) is removed from the received signal Y in the receiving station 3 from the other base station (base station 2A in the above embodiment). By acquiring the transmitted signal, it is possible to demolish the modulated wave of the frequency shift modulation method while suppressing the occurrence of beat interference regardless of the power ratio of the signal transmitted from each base station 2A, 2B. It becomes.

According to the wireless communication system 1 according to the embodiment, there are further advantages as follows.
1) It is applicable to the 4-value FSK method, which is being introduced one after another in commercial wireless systems.
2) The device does not become large like the transmission diversity.
3) Since the code is not made redundant as in the case of the differential space-time block code, the information transmission rate does not decrease.
4) Since it is realized by a frequency offset of several tens of Hz, the frequency utilization efficiency is high.
5) Even if the power ratios of the signals transmitted from each base station are close, no bit error occurs.

Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above-described embodiment, and even if there is a design change or the like within a range that does not deviate from the gist of the present invention. Included in the invention.

Specifically, in the above embodiment, the configurations of the base stations 2A and 2B of the wireless communication system 1 according to the present invention are shown in FIG. 2, and the configurations of the receiving station 3 are shown in FIG. However, the configurations of the base stations 2A and 2B and the receiving station 3 of the wireless communication system 1 according to the present invention are not limited to the configurations shown in FIGS. 2 and 4, and the configurations of the base stations 2A and 2B and the receiving station 3 are not limited to those shown in FIGS. May be configured in other embodiments. That is, the main point of the wireless communication system 1 according to the present invention is that the frequency shift in the modulation mapping process at each base station is offset, the known signal is used at the receiving station, and the frequency offset is constant. Is to remove the signal transmitted from one base station from the received signal and acquire the signal transmitted from the other base station, and the specific configuration for realizing this point is specific. It is not limited to the embodiment.

Further, in the above embodiment, the modulation mapping process is performed according to the "municipal digital mobile communication system (SCPC / 4-value FSK method)" (Association of Radio Industries and Businesses, standard number: ARIB STD-T116). However, following the above standard (ARIB STD-T116) is not an essential requirement in the present invention, and frequency shift keying may be performed according to other standards and specifications. In addition, the multi-valued number of frequency shift keying is not limited to 4, but may be any other multi-valued number.

1 Wireless communication system 2A Base station 2B Base station 20 Modulation unit 21 Mapping unit 22 ROF unit 23 Frequency offset unit 24 NCO unit 25 Orthogonal modulation unit 26 Antenna 3 Receiving station 30 Demodulation unit 31 Antenna 32 Orthogonal detection unit 33 Delay detection unit 34 ROF Part 35 Hardness determination part 36 Demapping part 4 Interference canceller part 401 First division part 402 LPF part 403 First propagation environment update control part 404 Addition part 405 First addition / subtraction part 406 Phase angle calculation part 407 Delay part 408 Frequency Calculation unit 409 Frequency update control unit 410 Amplification unit 411 NCO unit 412 Multiplication unit 413 Second addition / subtraction unit 414 Estimating unit 415 Second propagation environment update control unit 416 Second division unit 5A From base station 2A to receiving station 3 Radio propagation path to reach 5B Radio propagation path from base station 2B to receiving station 3

Claims (3)

A first base station and a second base station each equipped with a wireless communication device that transmits a signal modulated by a frequency shift keying method, and
It has a receiving station that receives a signal transmitted from the first base station and also receives a signal transmitted from the second base station.
An offset frequency is set between the frequency in the modulation process of the wireless communication device of the first base station and the frequency in the modulation process of the wireless communication device of the second base station.
The receiving station uses a known signal transmitted during the learning period to propagate between the first base station and the receiving station, and between the second base station and the receiving station. Obtaining the environment and the offset frequency, removing the signal transmitted from one base station from the received signal at the receiving station, and acquiring the signal transmitted from the other base station.
A wireless communication system characterized by that. The offset frequency is less than or equal to the tolerance for the reference value of the mapping in the modulation process.
The wireless communication system according to claim 1. The frequency shift keying method is a four-value frequency shift keying method in which the number of multiple values is four.
The wireless communication system according to claim 1 or 2.

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