Wireless system, transmitting station, receiving station, and control method

Abstract

To address the problem of the passband characteristics of a bandpass filter changing with temperature change by eliminating the need for a temperature sensor that detects the ambient temperature of the bandpass filter and by eliminating the need for the passband characteristics of the bandpass filter to be variable.SOLUTION: A transmitting station includes: a bandpass filter having a passband of a specific IF band; a first frequency conversion unit that frequency converts an RF band input signal to the bandpass filter to the IF band; a second frequency conversion unit that frequency converts an IF band output signal from the bandpass filter to an RF band; and a frequency conversion control unit that causes the first frequency conversion unit and the second frequency conversion unit to change the center frequency of the IF band on the basis of frequency correction information from a receiving station.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wireless system, a transmitting station, a receiving station, and a control method. [Background technology]

[0002] Conventionally, as a method for dealing with the problem that the passband characteristics of a bandpass filter (BPF) change due to temperature changes, for example, a method described in Patent Document 1 is known. In the method described in Patent Document 1, in a narrowband bandpass filter device composed of multiple stages of crystal filter blocks, temperature compensation data is extracted from a temperature compensation table based on a temperature signal from a temperature sensor that detects the ambient temperature, and a variable capacitance diode that compensates for the tuning frequency of the crystal filter is controlled by the temperature compensation data. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-7366 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the method described in the above-mentioned Patent Document 1 requires a temperature sensor to detect the ambient temperature. In addition, since it is necessary to install the temperature sensor at a location where the ambient temperature of the bandpass filter can be detected, there are mounting restrictions on the device equipped with the bandpass filter. In addition, since the passband characteristics of the bandpass filter are changed according to temperature changes, the passband characteristics of the bandpass filter need to be variable.

[0005] The present invention has been made in consideration of the above circumstances, and its object is to provide a technique for addressing the problem that the passband characteristics of a bandpass filter change with temperature, by eliminating the need for a temperature sensor that detects the ambient temperature of the bandpass filter, and by eliminating the need for the passband characteristics of the bandpass filter to be variable. [Means for solving the problem]

[0006] One aspect of the present invention is a method for transmitting a radio signal in a radio frequency (RF) band, comprising: a transmitting station for transmitting a radio signal in a radio frequency (RF) band; and a receiving station for receiving the radio signal transmitted from the transmitting station. The transmitting station is a specific IF (Intermediate Frequency (IF)) band. a first frequency conversion unit that performs frequency conversion to the IF band for an RF band input signal to the bandpass filter, a second frequency conversion unit that performs frequency conversion to the RF band for an IF band output signal from the bandpass filter, and a frequency conversion control unit that controls the first frequency conversion unit and the second frequency conversion unit, wherein the transmitting station wirelessly transmits the radio signal resulting from the frequency conversion by the second frequency conversion unit, and the receiving station comprises a determination unit that determines a decrease in power levels at both ends of the passband of the bandpass filter based on the received radio signal, and a frequency correction instruction unit that transmits to the transmitting station frequency correction information for correcting a center frequency of the IF band in the frequency conversion of the first frequency conversion unit and the second frequency conversion unit when a predetermined condition that a change has occurred in the passband characteristic of the bandpass filter is satisfied based on a determination result of the determination unit, and the frequency conversion control unit causes the first frequency conversion unit and the second frequency conversion unit to change the center frequency of the IF band based on the frequency correction information. One aspect of the present invention is a wireless system in which, in the above-mentioned wireless system, the wireless signal is a modulated wave composed of a plurality of modulated wave subcarriers, and the judgment unit judges a relative decrease in power level for subcarriers at an edge portion among the plurality of modulated wave subcarriers. One aspect of the present invention is a wireless system in which, in the above-mentioned wireless system, the judgment unit judges whether a power level ratio between a subcarrier in an edge portion and other subcarriers other than the edge portion, among the plurality of modulated wave subcarriers, exceeds a predetermined threshold value. One aspect of the present invention is the wireless system, wherein the wireless signal is a modulated wave in accordance with an Orthogonal Frequency Division Multiplexing (OFDM) modulation method.

[0007] One aspect of the present invention is a wireless system comprising a transmitting station that transmits a radio signal in an RF (Radio Frequency) band and a receiving station that receives the radio signal transmitted from the transmitting station, the transmitting station comprising: a bandpass filter having a passband of a specific IF (Intermediate Frequency) band; a first frequency conversion unit that performs frequency conversion to the IF band on an RF band input signal to the bandpass filter; a second frequency conversion unit that performs frequency conversion to the RF band on an IF band output signal from the bandpass filter; and a frequency conversion control unit that controls the first frequency conversion unit and the second frequency conversion unit, wherein the transmitting station wirelessly transmits the radio signal resulting from frequency conversion by the second frequency conversion unit, and the frequency conversion control unit causes the first frequency conversion unit and the second frequency conversion unit to change the center frequency of the IF band based on frequency correction information notified by the receiving station.

[0008] One aspect of the present invention is a receiving station of a wireless system including a transmitting station that transmits a radio signal in an RF (Radio Frequency) band and a receiving station that receives the radio signal transmitted from the transmitting station, wherein the transmitting station includes a bandpass filter having a passband of a specific IF (Intermediate Frequency) band, the transmitting station performs a first frequency conversion to an IF band on an RF band input signal to the bandpass filter, performs a second frequency conversion to an RF band on an IF band output signal from the bandpass filter, and wirelessly transmits the radio signal resulting from the second frequency conversion, and the receiving station includes a determination unit that determines a decrease in the power level of each of both ends of the passband of the bandpass filter based on the received radio signal, and a frequency correction instruction unit that transmits frequency correction information to the transmitting station for correcting the center frequency of the IF band in the first frequency conversion and the second frequency conversion when a predetermined condition that the passband of the bandpass filter has changed is met based on a determination result of the determination unit.

[0009] One aspect of the present invention is a control method for a wireless system including a transmitting station that transmits a radio signal in an RF (Radio Frequency) band and a receiving station that receives the radio signal transmitted from the transmitting station, the transmitting station receiving a specific IF (Intermediate Frequency) a first frequency conversion step in which the transmitting station performs frequency conversion on an RF band input signal to the bandpass filter to the IF band, a second frequency conversion step in which the transmitting station performs frequency conversion on an IF band output signal from the bandpass filter to the RF band, a transmission step in which the transmitting station wirelessly transmits the radio signal resulting from the frequency conversion performed in the second frequency conversion step, a determination step in which the receiving station determines, based on the received radio signal, a decrease in power levels at both ends of the passband of the bandpass filter, a frequency correction instruction step in which the receiving station transmits, to the transmitting station, frequency correction information for correcting a center frequency of the IF band in the frequency conversions of the first frequency conversion step and the second frequency conversion step, when a predetermined condition that the passband of the bandpass filter has changed is satisfied based on a determination result of the determination step, and a frequency conversion control step in which the transmitting station changes the center frequency of the IF band for the first frequency conversion step and the second frequency conversion step, based on the frequency correction information. Effect of the Invention

[0010] According to the present invention, as a method for dealing with the problem that the passband characteristics of a bandpass filter change due to temperature changes, it is possible to eliminate the need for a temperature sensor to detect the ambient temperature of the bandpass filter, and also to eliminate the need for the passband characteristics of the bandpass filter to be variable. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of a wireless system according to an embodiment. [Diagram 2]1 is a diagram illustrating an example of a schematic configuration of a wireless system according to an embodiment. [Diagram 3] FIG. 11 is a diagram for explaining a control method according to an embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of a procedure of a control method according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 are diagrams showing an example of a schematic configuration of a wireless system according to an embodiment. A relay station 100 as an example of a transmitting station according to the embodiment transmits a wireless signal in an RF (Radio Frequency) band. A base station 300 as an example of a receiving station according to the embodiment receives the wireless signal transmitted from the relay station 100.

[0013] As an example of the wireless signal according to the present embodiment, the wireless signal is an OFDM (Orthogonal Frequency Division Multiplexing) modulated wave (OFDM modulated wave). The OFDM modulated wave is a modulated wave composed of a plurality of subcarriers (modulated wave subcarriers).

[0014] [Relay station (transmitting station)] The configuration of the relay station 100 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing a schematic configuration example of the relay station 100 according to this embodiment. The relay station 100 receives a radio signal RF1 in a first RF band transmitted from a mobile station. As an example of the radio signal RF1 according to this embodiment, the radio signal RF1 is a frequency division multiplexed signal in which four signals a, b, c, and d are subjected to FDM (Frequency Division Multiplexing). Each of the signals a, b, c, and d corresponds to an OFDM modulated wave. Therefore, the frequency band of each of the signals a, b, c, and d is the band of the OFDM modulated wave.

[0015] In relay station 100, a received radio signal RF1 (RF band input signal) is frequency-converted to an IF (Intermediate Frequency) band signal IF1 by mixer 101. A local oscillator 102 supplies a local frequency to mixer 101 for frequency-converting a radio signal in a first RF band to an IF band. Mixer 101 and local oscillator 102 correspond to a first frequency conversion unit.

[0016] The signal IF1 is input to the bandpass filter BPF. The bandpass filter BPF is a bandpass filter having a passband of a specific IF band. As an example of the passband of the specific IF band according to this embodiment, the passband of the bandpass filter BPF is the frequency band of the signal b included in the signal IF1. Therefore, the bandpass filter BPF attenuates the power levels of the signals a, c, and d other than the signal b included in the signal IF1. As a result, the IF band signal IF2 (IF band output signal) output from the bandpass filter BPF is a signal obtained by attenuating the power levels of the signals a, c, and d other than the signal b from the signal IF1.

[0017] The frequency band of the signal b included in the signal IF1 is the frequency band of the OFDM modulated wave, and therefore the passband of the bandpass filter BPF corresponds to the frequency band of the signal b included in the signal IF1, that is, the frequency band of the OFDM modulated wave.

[0018] The signal IF2 is frequency converted to a radio signal RF2 in the second RF band by the mixer 111. The local oscillator 112 supplies a local frequency for frequency converting the signal in the IF band to a radio signal in the second RF band to the mixer 111. The mixer 111 and the local oscillator 112 correspond to a second frequency conversion unit.

[0019] The relay station 100 wirelessly transmits a radio signal RF2. The radio signal RF2 wirelessly transmitted from the relay station 100 is received by the base station 300.

[0020] The frequency conversion control unit 120 controls the local frequencies oscillated by the local oscillator 102 and the local oscillator 112 based on the frequency correction information 200. The frequency correction information 200 is notified from the base station 300.

[0021] [Base station (receiving station)] The configuration of the base station 300 according to this embodiment will be described with reference to Fig. 2. Fig. 2 is a diagram showing a schematic configuration example of the base station 300 according to this embodiment. The base station 300 receives a radio signal RF2 wirelessly transmitted from the relay station 100.

[0022] 2 shows a received signal 401 (OFDM modulated wave) of the radio signal RF2 in a normal state and a received signal 402 (OFDM modulated wave) of the radio signal RF2 in a state where suppression occurs. The normal OFDM modulated wave is a case where the passband characteristics of the bandpass filter BPF of the relay station 100 are normal, and has a uniform power level in all subcarriers.

[0023] On the other hand, when suppression occurs in the OFDM modulated wave, the passband characteristics of the bandpass filter BPF become abnormal due to temperature changes, and the power level of the subcarriers at one edge is suppressed more than that of the other subcarriers outside the edge. This point will be explained with reference to Figure 3.

[0024] 3 is a diagram for explaining a control method according to this embodiment. At normal temperature, the bandpass filter BPF of the relay station 100 has a passband characteristic BPTF (center frequency Fa) at normal temperature. Therefore, at normal temperature, the OFDM modulated wave that has passed through the bandpass filter BPF has a uniform power level in all subcarriers (corresponding to a received signal 401 (OFDM modulated wave) at normal temperature).

[0025] On the other hand, when a temperature change occurs and the temperature around the bandpass filter BPF deviates from normal temperature, the passband characteristic of the bandpass filter BPF changes from the normal temperature passband characteristic BPTF (center frequency Fa) to the passband characteristic BPTF' (center frequency Fa') due to the temperature change. Due to the shift in the center frequency of this passband characteristic (shift from center frequency Fa to center frequency Fa'), the power level of the subcarriers at one edge portion is suppressed more than the other subcarriers outside the edge portion (corresponding to the received signal 402 (OFDM modulated wave) when suppression occurs).

[0026] In order to eliminate the suppression of the power level of the subcarriers at the edge portions, in this embodiment, the center frequency of the IF band in the frequency conversion of mixers 101 and 111 is corrected from the center frequency Fi at room temperature to center frequency Fi'. As a result, even if the passband characteristic of the bandpass filter BPF changes due to a temperature change and remains at the passband characteristic BPTF' (center frequency Fa'), the OFDM modulated wave is frequency shifted, and thus the suppression of the power level of the subcarriers at the edge portions does not occur. Therefore, the frequency-shifted OFDM modulated wave 403 has a uniform power level in all subcarriers.

[0027] Information on the correction of the center frequency of the IF band in the frequency conversion of mixer 101 and mixer 111 is notified from base station 300 to relay station 100 as frequency correction information 200. The frequency correction information 200 will be described below.

[0028] In FIG. 2, base station 300 includes a determination unit 301 and a frequency correction instruction unit 302 .

[0029] The base station 300 receives a radio signal RF2 wirelessly transmitted from the relay station 100. The received signal is called a target received signal. The determination unit 301 monitors the power level of the subcarriers of the target received signal (OFDM modulated wave). The determination unit 301 determines a relative decrease in power level of the subcarriers of the edge portion among the subcarriers of the target received signal (OFDM modulated wave). Specifically, the determination unit 301 determines whether the power level ratio between the subcarriers of the edge portion and the other subcarriers other than the edge portion exceeds a predetermined threshold. In this threshold determination, the determination unit 301 may calculate a moving average value of the power level of each subcarrier, and determine whether the ratio of the moving average value between the subcarriers of the edge portion and the other subcarriers other than the edge portion exceeds a predetermined threshold.

[0030] The passband of the bandpass filter BPF corresponds to the frequency band of the signal b included in the signal IF1, i.e., the band of the OFDM modulated wave. Therefore, the subcarriers at the edges of the target received signal (OFDM modulated wave) correspond to both ends of the passband of the bandpass filter.

[0031] The determination unit 301 notifies the frequency correction instruction unit 302 of the determination result.

[0032] If a predetermined condition that the passband characteristic of the bandpass filter BPF has changed is satisfied based on the determination result of the determination unit 301, the frequency correction instruction unit 302 transmits frequency correction information 200 to the relay station 100 using a control line between the relay station 100 and the base station 300. The frequency correction information 200 is information for correcting the center frequency of the IF band in the frequency conversion of the first frequency conversion unit (mixer 101 and local oscillator 102) and the second frequency conversion unit (mixer 111 and local oscillator 112). The frequency correction information 200 includes, for example, information indicating the direction (positive or negative) in which the center frequency of the IF band is shifted and the amount of shift (N ppm).

[0033] The frequency correction instruction unit 302 generates frequency correction information 200 using a predetermined method (e.g., a conversion table or a function) from the determination result of the determination unit 301 (information of the subcarriers of the edge portion where the power level is reduced (subcarrier number, amount of reduction in power level, etc.)).

[0034] The predetermined condition for the change in the passband characteristics of the bandpass filter BPF is, for example, when the determination that there is a relative decrease in the power level of the subcarriers in the edge portion occurs a predetermined number of times (m times) or more consecutively, where m can be set to any value equal to or greater than 1.

[0035] In the relay station 100, the frequency conversion control unit 120 changes the local frequency at which the local oscillator 102 and the local oscillator 112 oscillate, based on the frequency correction information 200 notified from the base station 300. By changing the local frequency, the center frequency of the IF band in the frequency conversion of the mixers 101 and 111 is corrected from the center frequency Fi at room temperature to the center frequency Fi', as shown in Fig. 3. As a result, even if the passband characteristic of the bandpass filter BPF changes due to a temperature change and remains at the passband characteristic BPTF' (center frequency Fa'), the OFDM modulated wave is frequency shifted, and thus suppression of the power level of the subcarriers at the edge portions does not occur. Therefore, the frequency-shifted OFDM modulated wave 403 has a uniform power level in all subcarriers.

[0036] Next, the procedure of the control method according to this embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram showing an example of the procedure of the control method according to this embodiment.

[0037] The relay station 100 receives a radio signal RF1 in the first RF band transmitted from a mobile station, frequency-converts the received radio signal RF1 to an IF band signal IF1 and then passes the signal through a bandpass filter BPF, frequency-converts the IF band signal IF2 output from the bandpass filter BPF to a radio signal RF2 in the second RF band, and wirelessly transmits the radio signal RF2 to the base station 300. The base station 300 receives the radio signal RF2 wirelessly transmitted from the relay station 100.

[0038] (Step S1) In the relay station 100, the ambient temperature of the bandpass filter BPF changes.

[0039] (Step S2) The passband characteristics of the bandpass filter BPF change due to a change in temperature, which causes a suppression of the power level of subcarriers at edge portions in the IF band signal IF2 output from the bandpass filter BPF.

[0040] (Step S3) In the base station 300, the determining unit 301 determines whether or not to suppress the power level of the subcarriers at the edge portions in the received signal (target received signal) of the radio signal RF2.

[0041] (Step S4) In base station 300, when determination section 301 determines that the power levels of the subcarriers in the edge portion are to be suppressed, frequency correction instruction section 302 transmits frequency correction information 200 to relay station 100 to instruct it to correct the center frequency of the IF band.

[0042] (Step S5) In the relay station 100, the frequency conversion control unit 120 corrects the center frequency of the IF band based on the frequency correction information 200 notified from the base station 300. This eliminates the suppression of the power level of the subcarriers at the edge portions.

[0043] (Step S6) In the base station 300, the determining unit 301 confirms that the suppression of the power level of the subcarriers in the edge portion of the received signal (target received signal) of the radio signal RF2 has been eliminated.

[0044] As described above, according to this embodiment, as a method for dealing with the problem that the passband characteristics of the bandpass filter BPF change due to temperature change, the center frequency of the IF band is corrected, so that the suppression of the power level of the subcarriers at the edge portions can be eliminated even if the passband characteristics remain unchanged due to temperature change. This makes it possible to eliminate the need for a temperature sensor that detects the ambient temperature of the bandpass filter, and also makes it unnecessary for the passband characteristics of the bandpass filter to be variable.

[0045] In the above-described embodiment, the relay station 100 is used as a transmitting station, and the base station 300 is used as a receiving station, but the transmitting station and the receiving station are not limited to this.

[0046] This will, for example, make it possible to improve the overall service quality in wireless systems, thereby contributing to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is to "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0047] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not deviate from the gist of the present invention are also included. [Explanation of symbols]

[0048] 100... relay station (transmitting station), 101, 111... mixers, 102, 112... local oscillators, BPF... band pass filters, 120... frequency conversion control section, 300... base station (receiving station), 301... determination section, 302... frequency correction instruction section

Claims

1. A transmitting station for transmitting a radio signal in an RF (Radio Frequency) band; a receiving station for receiving the wireless signal transmitted from the transmitting station, The transmitting station, A bandpass filter having a passband of a specific IF (Intermediate Frequency) band; a first frequency conversion unit that performs frequency conversion of an RF band input signal to the bandpass filter to an IF band; a second frequency conversion unit that performs frequency conversion of an IF band output signal from the band pass filter to an RF band; a frequency conversion control unit that controls the first frequency conversion unit and the second frequency conversion unit, the transmitting station wirelessly transmits the radio signal resulting from the frequency conversion by the second frequency conversion unit; The receiving station, a determination unit that determines a decrease in the power level at each of both ends of a pass band of the band pass filter based on the received radio signal; a frequency correction instruction unit that transmits, to the transmitting station, frequency correction information for correcting a center frequency of an IF band in frequency conversion by the first frequency conversion unit and the second frequency conversion unit when a predetermined condition that a passband characteristic of the bandpass filter has changed is satisfied based on a determination result by the determination unit, The frequency conversion control unit causes the first frequency conversion unit and the second frequency conversion unit to change a center frequency of an IF band based on the frequency correction information. Radio system.

2. the radio signal is a modulated wave composed of a plurality of modulated wave subcarriers, the determination unit determines a relative decrease in power level of subcarriers in edge portions among the plurality of modulated wave subcarriers; 2. The wireless system of claim 1.

3. the determination unit determines whether a power level ratio between a subcarrier in an edge portion and another subcarrier other than the edge portion, among the plurality of modulated wave subcarriers, exceeds a predetermined threshold value.

3. The wireless system according to claim 2.

4. The wireless signal is a modulated wave of an OFDM (Orthogonal Frequency Division Multiplexing) modulation method.

4. A wireless system according to claim 2 or 3.

5. A transmitting station for transmitting a radio signal in an RF (Radio Frequency) band; a receiving station that receives the wireless signal transmitted from the transmitting station, A bandpass filter having a passband of a specific IF (Intermediate Frequency) band; a first frequency conversion unit that performs frequency conversion of an RF band input signal to the bandpass filter to an IF band; a second frequency conversion unit that performs frequency conversion of an IF band output signal from the band pass filter to an RF band; a frequency conversion control unit that controls the first frequency conversion unit and the second frequency conversion unit, the transmitting station wirelessly transmits the radio signal resulting from the frequency conversion by the second frequency conversion unit; the frequency conversion control unit causes the first frequency conversion unit and the second frequency conversion unit to change a center frequency of an IF band based on frequency correction information notified from the receiving station. Transmitting station.

6. A transmitting station for transmitting a radio signal in an RF (Radio Frequency) band; a receiving station for receiving the wireless signal transmitted from the transmitting station, the transmitting station includes a bandpass filter having a passband of a specific IF (Intermediate Frequency) band; the transmitting station performs a first frequency conversion to an IF band on an RF band input signal to the bandpass filter, performs a second frequency conversion to an RF band on an IF band output signal from the bandpass filter, and wirelessly transmits the radio signal resulting from the second frequency conversion; The receiving station, a determination unit that determines a decrease in the power level at each of both ends of a pass band of the band pass filter based on the received radio signal; and a frequency correction instruction unit that transmits, to the transmitting station, frequency correction information for correcting a center frequency of an IF band in the first frequency conversion and the second frequency conversion when a predetermined condition that a pass band of the band pass filter is changed is satisfied based on a determination result of the determination unit. Receiving station.

7. A transmitting station for transmitting a radio signal in an RF (Radio Frequency) band; a receiving station that receives the wireless signal transmitted from the transmitting station, the transmitting station includes a bandpass filter having a passband of a specific IF (Intermediate Frequency) band; a first frequency conversion step in which the transmitting station performs frequency conversion of an RF band input signal to the bandpass filter into an IF band; a second frequency conversion step in which the transmitting station performs frequency conversion on the IF band output signal from the bandpass filter to an RF band; a transmitting step of the transmitting station wirelessly transmitting the radio signal resulting from the frequency conversion in the second frequency conversion step; a determining step of determining, by the receiving station, a decrease in the power level at each of both ends of the pass band of the band pass filter based on the received radio signal; a frequency correction instruction step of transmitting, to the transmitting station, frequency correction information for correcting a center frequency of an IF band in frequency conversion in the first frequency conversion step and the second frequency conversion step, when a predetermined condition that a pass band of the band pass filter has changed is satisfied based on a result of the determination step; a frequency conversion control step of the transmitting station changing a center frequency of an IF band for the first frequency conversion step and the second frequency conversion step based on the frequency correction information; A control method comprising:

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