JP7798201B2 - Relay radio device and radio relay method - Google Patents

Description

This disclosure relates to a relay radio device and a radio relay method that relay a carrier wave transmitted by a radio signal from a higher-level radio station.

In relay radio equipment that relays carrier waves transmitted as radio signals from a higher-level radio station, the antenna installed on the tower and the radio equipment installed indoors are often far apart. As a result, losses in the power feeder line connecting the two (hereafter referred to as power feeder loss) tend to increase. One way to address power feeder loss is to place an amplifier inside the radio equipment. This makes it possible to amplify the received signal level that has been attenuated by power feeder loss.

On the other hand, Non-Patent Document 1 discloses a method of placing a low noise amplifier (LNA) as a preamplifier immediately adjacent to the antenna in a communications receiver. This makes it possible to amplify a weak desired signal to a predetermined reception level.

"Knowledge Base 4 Groups, Part 1, Chapter 11, Receivers" (Kenji Ito, Institute of Electronics, Information and Communication Engineers, Ver. 1/2010.11.9)

However, because amplifiers amplify not only the power level of the desired signal contained in the carrier wave but also the noise power level at the same time, no matter where the amplifier is placed within the relay radio equipment, it is not possible to expect an improvement in the C/N (carrier-to-noise ratio). Therefore, if there is significant feeder loss, the carrier signal will not meet the required C/N, causing a degradation in the BER (Bit Error Rate).

In order to solve the above-mentioned problems, the primary objective of this disclosure is to provide a relay radio device in which the carrier signal meets the required C/N ratio and the BER does not degrade even when there is power loss of the carrier wave due to the power supply line.

A second object of this disclosure is to provide a wireless relay method in which the carrier signal meets the required C/N ratio and the BER does not degrade even when there is power loss of the carrier wave due to the power supply line.

A first aspect of the present disclosure is a relay radio device that relays a carrier wave transmitted as a radio signal from an upper radio station, the relay radio device comprising:
a modulation method conversion process for converting the modulation method of the carrier wave into a modulation method with a lower multi-value;
a bandwidth conversion process for expanding the frequency band of the carrier wave so that the transmission capacity of the carrier wave is equal before and after the modulation method conversion process;
Preferably, the system is configured to perform the following:

A second aspect of the present disclosure is a wireless relay method for relaying a carrier wave transmitted as a wireless signal from an upper wireless station, the method comprising:
a modulation method conversion process for converting the modulation method of the carrier wave into a modulation method with a lower multi-value;
a bandwidth conversion process for expanding the frequency band of the carrier wave so that the transmission capacity of the carrier wave is equal before and after the modulation method conversion process;
It is preferable to perform the following.

The first and second aspects of the present disclosure provide a relay radio device and a radio relay method in which the carrier signal meets the required C/N ratio and the BER does not degrade even when there is power loss of the carrier wave due to the power supply line.

10 is a schematic diagram illustrating a conventional relay wireless device and a modulation method of a carrier wave received by the relay wireless device according to a comparative example of the present disclosure. FIG. 10 is a schematic diagram illustrating a conventional relay radio device including an LNA as a pre-amplifier, and a modulation method of a carrier wave received by the relay radio device, according to a comparative example of the present disclosure. FIG. 10A and 10B are schematic diagrams illustrating configuration examples of a higher-level station, a relay wireless device, and a lower-level station according to a comparative example of the present disclosure, and a modulation method of a carrier wave relayed by the relay wireless device. FIG. 10 is a schematic diagram illustrating an example of a functional configuration of a conventional relay wireless device according to a comparative example of the present disclosure. 1 is a schematic diagram illustrating a relay wireless device and a modulation method of a carrier wave received by the relay wireless device according to a first embodiment of the present disclosure; FIG. 2 is a diagram illustrating an example of a functional configuration of a relay wireless device according to a first embodiment of the present disclosure. FIG. 10 is a schematic diagram illustrating a relay radio device including an LNA and a carrier modulation method according to a second embodiment of the present disclosure. FIG. 10 is a diagram illustrating an example of a functional configuration of a relay wireless device according to a second embodiment of the disclosure. 11 is a schematic diagram illustrating an example of the configuration of a higher-level station, a relay wireless device, and a lower-level station according to a third embodiment of the present disclosure, and a modulation method of a carrier wave relayed by the relay wireless device. FIG. FIG. 2 is a diagram illustrating an example of a functional configuration of a transmitting device that performs wireless communication with a relay wireless device. FIG. 11 is a schematic diagram illustrating an example of a functional configuration of a relay wireless device according to a third embodiment of the present disclosure. 13 is a schematic diagram illustrating an example of the configuration of a higher-level station, a relay wireless device, and a lower-level station according to a fourth embodiment of the present disclosure, and a modulation method of a carrier wave relayed by the relay wireless device. FIG. 13 is a flowchart of a process performed by a relay wireless device according to a fourth embodiment of the present disclosure.

1 is a schematic diagram showing a conventional relay wireless device and a modulation method of a carrier wave received by the relay wireless device according to a comparative example of the present disclosure.

In Figure 1, relay radio device 100 relays carrier wave 140 transmitted as a radio signal from a higher-level radio station (hereinafter referred to as the higher-level station). Antenna 110 of relay radio device 100 receives carrier wave 140 transmitted from the higher-level station and reaching the relay radio device. Carrier wave 140 received by antenna 110 passes through feeder line 120 and is sent to radio device 130.

The radio device 130 is a receiver that performs demodulation and error correction coding on the carrier wave 140 received by the antenna 110 and transmitted via the feeder line 120. Furthermore, the radio device 130 transmits the demodulated and error correction coded signal to the terminal.

Carrier wave 140 occupies a certain range of frequency band, but the occupied frequency band is not limited. The modulation method of carrier wave 140 is, for example, 64QAM (QAM: Quadrature Amplitude Modulation). Here, panel P11 in Figure 1 shows the frequency characteristics of carrier wave 140 power when received by the antenna. Also, the C/N of the carrier wave here is assumed to be A.

In panel P11, only one carrier wave 140 is shown, but the wireless transmission method may be multi-carrier transmission with multiple carrier waves 140. Or, as in panel P11, it may be single-carrier transmission with only one carrier wave 140. This point is assumed to be common to the comparative examples and embodiments that follow.

When carrier wave 140 passes through feeder line 120, feeder loss L occurs. Panel P12 in Figure 1 shows the frequency characteristics of carrier wave 140 power after passing through feeder line 120. After passing through feeder line 120, the power of carrier wave 140 decreases by the amount of feeder loss L. Therefore, the C/N after passing through feeder line 120 can be expressed as (C/N = A - L).

In wireless communications, the C/N at which the BER becomes a specified value is calculated for each modulation method. For example, in the case of 64QAM, the required C/N is 24.2 dB. If the C/N of the carrier 140 input to the wireless device 130 does not meet this required C/N, degradation of the BER will occur.

Therefore, even if the C/N (= A) is equal to or greater than the required C/N when receiving through antenna 110 (panel P11), if the feeder line loss L is large and the C/N (= A-L) after passing through feeder line 120 is lower than the required C/N (panel P12), BER degradation will occur.

In the prior art, an amplifier is placed within the radio device 130, but even if the signal of the carrier wave 140 (panel P12) after passing through the power supply line 120 is amplified, the amplifier itself does not have the effect of improving the C/N ratio, so degradation of the BER is unavoidable.

As such, in the conventional relay radio device 100, degradation of BER due to power supply line losses of the carrier wave 140 was unavoidable.

Figure 2 is a schematic diagram showing a conventional relay radio device equipped with an LNA as a pre-amplifier, and the modulation method of the carrier wave received by the relay radio device, which is a comparative example of the present disclosure. The relay radio device 200 is similar to the relay radio device 100 of Figure 1, but an LNA 210 with good internal noise characteristics is installed as a pre-amplifier immediately adjacent to the antenna 110. The LNA 210 is used when the antenna 110 receives weak radio waves, such as in satellite communications.

In Figure 2, panels P21 and P22 show the frequency characteristics of the carrier 140 power when received by the antenna 110 and after amplification by the LNA 210, respectively. The weak carrier signal when received by the antenna 110 is amplified by the LNA 210. In this way, by amplifying the carrier 140 signal immediately adjacent to the antenna 110, it is possible to avoid amplifying the noise power generated within the feeder line 120.

However, even if a pre-amplifier is installed close to the antenna 110 as shown in Figure 2, the amplifier itself does not have the effect of improving the C/N ratio, and therefore, if a large feeder loss L occurs, the C/N ratio will deteriorate. Therefore, in this case as well, as in Figure 1, the carrier wave 140 input to the radio device 130 will not meet the required C/N ratio, and deterioration of the BER will be unavoidable (panel P23 in Figure 2).

Figure 3 is a schematic diagram showing an example configuration of a higher-level station, a relay radio device, and a lower-level radio station (hereinafter referred to as a lower-level station) in a comparative example of the present disclosure, and the modulation method of the carrier wave relayed by the relay radio device.

The relay radio device 300 relays signals between the upper and lower radio stations. The relay radio device 300 receives the carrier wave 140 transmitted from the antenna 310 of the transmitting device 301, which is the upper station, using the receiving antenna 320. It then transmits the carrier wave 140 to the radio device 340 via the power feeder 330. The radio device 340 amplifies the received carrier wave 140, demodulates it once, and then modulates it again. It then transmits the re-modulated carrier wave 140 to the transmitting antenna 360 via the power feeder 350.

The lower-level stations are relay radio devices 100 and 200 that receive the carrier wave 140 transmitted from relay radio device 300. The functions of relay radio devices 100 and 200 are the same as those described in Figures 1 and 2, so further description will be omitted.

In Figure 3, panel P31 shows the power frequency characteristics of the carrier 140 after passing through the feeder line 330. As with panel P11 in Figure 1, the C/N of the carrier is reduced by the amount of the feeder line loss L. Also, panel P32 shows the frequency characteristics of the carrier 140 power at the transmitting antenna 360. Here too, a reduction in C/N occurs due to the feeder line 350.

Furthermore, carrier wave 140 transmitted from transmitting antenna 360 is affected by fading while propagating through the wireless section. Therefore, the power of carrier wave 140 at radio device 130 of relay radio devices 100 and 200 that receives carrier wave 140 is reduced not only by the feeder line loss L due to feeder line 120 but also by the propagation loss _L0 of carrier wave 140 in the wireless section (panel P33).

Therefore, even if the C/N ratio of the carrier 140 is equal to or greater than the required C/N ratio at the transmitting antenna 360 of the relay radio apparatus 300 (panel P32), if the propagation loss _L0 is large, the required C/N ratio cannot be met at the relay radio apparatuses 100 and 200 (panel P33). This results in BER degradation. Note that the longer the wireless section, the greater the propagation loss _L0. Therefore, the effect of BER degradation is particularly noticeable when the relay radio apparatus 300 and the relay radio apparatuses 100 and 200 are far apart.

Note that Figure 3 describes the case where the higher-level station is the transmitting device 301. However, the higher-level station may be any radio station equipped with a radio transmission function, such as a radio base station or a radio relay station. Similarly, the lower-level station does not have to be the relay radio device 100 or 200, but may be a radio station equipped with a radio receiving function, such as a radio base station or a radio relay station. This point is also common to the comparative examples and embodiments that follow.

Figure 4 is a schematic diagram showing an example of the functional configuration of a conventional relay radio device according to a comparative example of the present disclosure. In Figure 4, a receiving antenna 320 transmits a received carrier wave 140 to a radio device 340 via a power supply line 330. The radio device 340 demodulates, corrects errors in, and remodulates the received carrier wave 140. The radio device 340 includes an RF reception processing unit 370, a DEM unit 380, a MOD unit 390, an RF transmission processing unit 400, and a monitoring control unit 410.

The RF reception processing unit 370 processes the radio frequency (RF) signal input from the receiving antenna 320. The RF reception processing unit 370 includes a reception AMP unit 371, an AGC (Automatic Gain Control) unit 372, and a C/N detection unit 373. The reception AMP unit 371 amplifies the received radio frequency signal. The AGC unit 372 automatically corrects the reception gain according to the level of the received signal. The C/N detection unit 373 detects the C/N of the input carrier wave 140.

The DEM unit 380 performs demodulation and error correction, and monitors and controls the BER for the signal input from the RF reception processing unit 370. The DEM unit 380 has a waveform equalization unit 381, a signal demodulation unit 382, an error correction unit 383, and a BER monitoring unit 384. The waveform equalization unit 381 equalizes the waveform of the received signal to the desired waveform. The signal demodulation unit 382 demodulates the waveform of the received signal. The error correction unit 383 performs error correction decoding. The BER monitoring unit 384 monitors whether or not there is any degradation in the BER based on the modulation method of the input carrier.

The MOD unit 390 is a unit that re-modulates the signal input from the DEM unit 380. The MOD unit 390 comprises a waveform shaping unit 391, an FEC (Forward Error Correction) encoding unit 392, and a signal modulation unit 393. The waveform shaping unit 391 is a unit that shapes the waveform of the signal. The FEC encoding unit 392 is a unit that assigns an error correction code to the signal. The signal modulation unit 393 is a unit that performs re-modulation.

The RF transmission processing unit 400 performs transmission processing on the transmission signal input from the MOD unit 390. The RF transmission processing unit 400 comprises a transmission AMP unit 401 and a filter unit 402. The transmission AMP unit 401 amplifies the transmission signal. The filter unit 402 removes unnecessary frequency components from the transmission signal.

The monitoring control unit 410 monitors the RF reception processing unit 370, DEM unit 380, MOD unit 390, and RF transmission processing unit 400. It also receives an alarm and performs control if a specific process cannot be performed in each unit. It also controls each unit in cases where power interference with other radio stations becomes a problem and it is necessary to urgently stop the processing of the local station.

The transmitting antenna 360 transmits the carrier wave 140 transmitted from the RF transmission processing unit 400 via the power supply line 350 to the lower-level station as a radio signal.

In this way, conventional relay radio devices 300 demodulated the received carrier wave 140 once, re-modulated it, and then transmitted it to the downstream station. Demodulation and re-modulation required a large radio device 340, and due to maintenance and other issues, the radio device 340 had to be installed indoors. This resulted in a large distance between the antenna and radio device 340, and significant power feeder losses occurred in the power feeders 330 and 340 connecting the two.

As explained above using Figures 1 to 4, in the conventional relay radio devices 100, 200, and 300, when the feeder line loss and propagation loss were large, the carrier C/N did not meet the required C/N, resulting in BER degradation.

First Embodiment
5 is a schematic diagram illustrating a relay radio device and a modulation method of a carrier wave received by the relay radio device according to the first embodiment of the present disclosure. The relay radio device 500 further includes a modulation conversion device 510 immediately after the antenna 110 in the configuration example of the relay radio device 100 in FIG. 1 described as a comparative example.

The modulation conversion device 510 converts the modulation method of the carrier wave 140 received by the antenna 110 from 64QAM to QPSK (Quarter Phase Shift Keying), which has a smaller number of modulation levels. While 64QAM can carry 6 bits of information per modulation (per symbol) using 64 symbols, QPSK can only carry 2 bits using 4 values. Therefore, the modulation conversion device 510 expands the frequency band of the carrier wave 140 by three times, ensuring the same transmission capacity after conversion to QPSK as before (panel P52 in Figure 5).

Furthermore, the modulation conversion device 510 transmits the modulated and converted carrier wave 140 with an expanded frequency band to the radio device 130 via the feeder line 120. Since there are no restrictions imposed by the Radio Law within the waveguide or coaxial cable that constitutes the feeder line 120, the modulation method and bandwidth can be freely set.

When receiving a radio signal, the C/N required for the received signal to meet the specified BER is calculated as the required C/N. The lower the modulation level, the smaller the required C/N. In the case of QPSK, the required C/N is 11.2 dB, which is lower than the required C/N for 64QAM (= 24.2 dB).

In this disclosure, the modulation conversion device 510 converts to a modulation format with a lower multi-level number, thereby lowering the required C/N ratio in the radio device 130. By the amount of the lower required C/N ratio, a degradation margin of 13 dB or more can be provided in the C/N ratio of the carrier 140. This makes it possible to produce an improvement in the BER.

Figure 6 is a diagram showing an example functional configuration of a relay radio device according to embodiment 1 of the present disclosure. The antenna 110 transmits the received carrier wave 140 to the modulation conversion device 510. The RF reception processing unit 370 within the modulation conversion device 510 is similar to the RF reception processing unit 370 in the prior art shown in Figure 4, and therefore a description thereof will be omitted.

The modulation conversion unit 530 performs modulation conversion and frequency bandwidth conversion on the RF signal amplified by the RF reception processing unit 370. The modulation conversion unit 530 includes a modulation method conversion unit 531 and a bandwidth conversion unit 532. The modulation conversion unit 530 converts the carrier wave 140 from 64QAM to QPSK. The bandwidth conversion unit 532 expands the frequency bandwidth by three times.

The modulation method monitoring control unit 540 is the part that monitors the RF reception processing unit 370 and the modulation conversion unit 530. It also receives an alarm and performs control if the specified processing cannot be performed in each monitored unit.

The radio device 130 is the part that demodulates the carrier wave modulated and converted by the modulation conversion device 510 and input via the power supply line 120, and transmits the user signal to the terminal. The DEM unit 550 within the radio device 130 is the same as the DEM unit 380 in the prior art. However, the BER monitoring unit 554 monitors the deterioration of the BER based on the required C/N (= 11.2 dB) of QPSK.

The deframing unit 560 includes a buffering unit 561 that temporarily buffers transmitted and received signals. The user interface unit 570 includes a connection unit 571 that sends user signals to the terminal.

The monitoring control unit 580 is the part that monitors and controls the DEM unit 550 and the deframing unit 560. It also receives an alarm and performs control if the DEM unit 550 is unable to perform a specified process.

In this way, the relay radio device 500 performs modulation conversion and bandwidth expansion in the modulation conversion device 510. The carrier wave 140 converted from 64QAM to QPSK is demodulated in the radio device 130, and the degradation of the BER is monitored based on the required C/N (= 11.2 dB) of QPSK.

As explained above, in the relay radio device 500 of this embodiment, the modulation conversion device 510 installed immediately after reception by the antenna 110 converts the carrier wave 140 to a modulation method with fewer multi-levels and expands the bandwidth. This makes it possible to lower the required C/N while maintaining the transmission capacity of the carrier wave 140, thereby improving the BER.

Note that either the processing performed by the modulation method conversion unit 531 or the processing performed by the bandwidth conversion unit 532 described in this embodiment can be performed first. This point is also common to the following embodiments.

Embodiment 2
7 is a schematic diagram illustrating a relay radio device including an LNA and a carrier modulation method according to a second embodiment of the present disclosure. The relay radio device 600 is similar to the relay radio device 500 in FIG. 5, but further includes an LNA 210. The LNA 210 is placed immediately adjacent to the antenna 110 and performs pre-amplification of a weak carrier signal.

In this way, by further adding the LNA 210, in addition to the effect of the first embodiment, it becomes possible to amplify a weak carrier signal at the pre-stage.

Figure 8 is a diagram showing an example functional configuration of a relay radio device according to embodiment 2 of the present disclosure. In the relay radio device 600 of Figure 8, in addition to the example functional configuration of Figure 6, an LNA 210 is added immediately adjacent to the antenna 110.

In this way, the relay radio device 600 of this embodiment can be provided with a pre-amplification function using the LNA 210.

Embodiment 3
FIG. 9 is a schematic diagram illustrating an example of the configuration of a higher-level station, a relay wireless device, and a lower-level station according to the third embodiment of the present disclosure, and a modulation method of a carrier wave relayed by the relay wireless device.

The relay radio device 700, like the conventional relay radio device 300 in Figure 3 described as a comparative example, includes a receiving antenna 320, a transmitting antenna 360, and a radio device 710. The radio device 710 includes a modulation conversion unit 530.

The carrier wave received by the receiving antenna 320 of the relay radio device 700 is transmitted to the radio device 710 via the power feeder 720. The radio device 710 modulates and converts the frequency band of the received carrier wave 140. The modulated and converted carrier wave 140 is then transmitted to the transmitting antenna 360 via the power feeder 730.

In Figure 9, details of the transmitting device 301, which is the upper station, will be described later. Also, the relay radio devices 500 and 600, which are the lower stations, are the same as those in Figures 5 and 7, so their explanation will be omitted.

Panel P91 in Figure 9 shows the frequency characteristics of the carrier wave 140 power at the receiving antenna 320. Here, a carrier wave modulated using the 64QAM method is received. Panel P92 shows that the radio device 710 converts the modulation from 64QAM to QPSK, expanding the frequency band three times. The transmitting antenna 360 transmits the carrier wave 140 modulated using the QPSK method (panel P93).

The power loss of the carrier 140 in the radio device 130 of the relay radio device 500, 600 includes the feeder loss L due to the feeder 120 and the propagation loss _L0 , as explained in Fig. 3 (panel P94). However, as explained in the first and second embodiments, changing the modulation method to QPSK reduces the required C/N ratio, and there is a degradation margin of 13 dB or more in the C/N ratio of the carrier 140. This can produce the effect of improving BER degradation even when a large propagation loss _L0 occurs in the wireless section.

Figure 10 shows an example of the functional configuration of a transmitting device that performs wireless communication with a relay wireless device. The transmitting device 301, which is the upper station, has an antenna 310 and a wireless device 740.

The user interface unit 750 of the wireless device 740 has a connection unit 751 that receives user signals transmitted from the terminal. The framing unit 760 has a buffering unit 761 that temporarily stores signals transmitted from the user interface unit 750. Furthermore, the functions of the MOD unit 390 and the RF transmission processing unit 400 are the same as those described in Figure 4, so their description will be omitted.

The monitoring control unit 770 is the part that monitors and controls the framing unit 760, MOD unit 390, and RF transmission processing unit 400. It also receives an alarm and performs control when the MOD unit 390 and RF transmission processing unit 400 are unable to perform the specified processing. It also controls each unit when there is a problem with power interference with other radio stations, etc., and it is necessary to urgently stop the processing of the own station.

The transmitting antenna 360 transmits the carrier wave 140 transmitted from the RF transmission processing unit 400 via the power supply line 730 to the relay radio device 700.

As described above, the transmitting device 301 of this embodiment receives a user signal, encodes and modulates it, and then transmits a carrier wave 140 from the transmitting antenna.

Figure 11 is a schematic diagram showing an example functional configuration of a relay radio device according to embodiment 3 of the present disclosure. Similar to the conventional relay radio device 300 of Figure 4 described as a comparative example, the relay radio device 700 includes a receiving antenna 320, a transmitting antenna 360, and a radio device 710. The radio device 710 includes an RF reception processing unit 370, a modulation conversion unit 530, an RF transmission processing unit 400, and a monitoring control unit 780. The functions of the RF reception processing unit 370 and the RF transmission processing unit 400 are the same as those in Figure 4, and therefore their explanations are omitted. Furthermore, the function of the modulation conversion unit 530 is the same as those in Figure 6, and therefore their explanations are omitted.

The monitoring control unit 780 is the part that monitors and controls the RF reception processing unit 370, modulation conversion unit 530, and RF transmission processing unit 400. It also receives an alarm and performs control when a specific process cannot be performed in each unit. It also controls each unit in cases where power interference with other radio stations becomes a problem and it becomes necessary to urgently stop the processing of the local station.

As explained above, the relay radio device 700 of this embodiment converts the received carrier wave 140 into a modulation method with fewer multi-levels and expands the frequency bandwidth. This makes it possible to lower the required C/N and improve the BER while maintaining the transmission capacity of the carrier wave 140 that the relay radio device 700 transmits as a radio signal to the downstream station.

In addition, the relay radio device 700 in this embodiment does not need to perform demodulation and remodulation, as does the relay radio device 300 in the prior art, so a smaller radio device 710 can be provided than in the prior art.

The miniaturization of the wireless device 710 creates a new advantage in that it can now be installed outdoors, whereas conventional technology required that the wireless device 710 be installed indoors. This means that the distance between the receiving antenna 320 and the transmitting antenna 360 and the wireless device 710 can be shortened, and the power feed lines 330 and 340 connecting them can also be shortened. This results in the effect of suppressing power feed line losses.

[Variations]
In the radio relay device 700, the LNA 210 may be arranged in close proximity to the receiving antenna 320 to provide a pre-amplification function.

Embodiment 4
FIG. 12 is a schematic diagram illustrating an example of the configuration of a higher-level station, a relay wireless device, and a lower-level station according to the fourth embodiment of the present disclosure, and a modulation method of a carrier wave relayed by the relay wireless device.

Like the relay radio device 700 of embodiment 3, the relay radio device 800 includes a receiving antenna 320, a transmitting antenna 360, and a radio device 810. The radio device 810 includes a modulation conversion unit 530.

In the relay radio device 800 of Figure 12, the radio device 810 detects changes over time in the propagation environment of the carrier wave 140 by detecting changes over time in the communication quality of the wireless communication. The communication quality is measured, for example, by the C/N ratio of the signal received by the receiving antenna 320. Furthermore, the radio device 810 converts the modulation method according to the communication quality. In addition, in conjunction with the modulation conversion, the frequency band is expanded or narrowed to ensure the transmission capacity of the carrier wave 140.

Figure 12(a) shows the function of the relay radio device 800 when communication quality is degraded. In this case, the radio device 810 of the relay radio device 800 converts the modulation method of the carrier wave 140 from the current 64QAM to 16QAM, which has a lower multi-level. Furthermore, the frequency bandwidth is expanded, ensuring the same transmission capacity for the carrier wave after modulation conversion as before conversion (panel P121).

Here, for 16QAM, the required C/N is 18.1 dB, which is lower than the required C/N (= 24.2 dB) for 64QAM. Therefore, a C/N degradation margin of 6.1 dB can be provided for the carrier wave 140 received by the relay radio devices 500 and 600, which are lower-level stations.

On the other hand, Figure 12(b) shows the function of the relay radio device 800 when communication quality deteriorates further than during wireless communication in (a) due to rain attenuation or interference waves. In this case, the radio device 810 converts the modulation method of the carrier wave 140 to QPSK, which has an even lower modulation level than the current 16QAM. It also expands the bandwidth to ensure transmission capacity (panel P124).

By converting the modulation method to a lower order, it is possible to provide an additional C/N degradation margin in the lower-level relay radio devices 500 and 600. Therefore, even if the propagation loss from relay radio device 800 to the lower-level station is twice as large as in case (a), it is still possible to improve BER degradation by the margin (panel P126).

As described above, the relay radio device 800 of this embodiment performs modulation conversion and expands or reduces the frequency band depending on the communication quality. Conventionally, technology has been used to adaptively change the modulation method depending on the communication quality, but because the bandwidth is fixed, the transmission capacity fluctuates with the modulation conversion. In this regard, the present disclosure makes it possible to relay to a lower station while maintaining the transmission capacity at the upper station.

Here, the relay radio device 800 of this embodiment is particularly suitable for medical, aviation, and military applications. As mentioned earlier, in conventional technology, transmission capacity fluctuates due to adaptive modulation. While this is not a problem for best-effort data communications such as IP (Internet Protocol) communications, it is a problem for medical, aviation, and military applications, where transmission capacity must be guaranteed.

Figure 13 is a flowchart of the processing performed by the relay radio device according to embodiment 4 of the present disclosure. First, the relay radio device 800 starts processing (step S131). Next, the C/N of the signal received by the receiving antenna is acquired (step S132). Next, the acquired C/N is compared with the C/N acquired last time to determine whether there has been a change (step S133). If it is determined that there has been no change in the C/N, this means that there has been no change in the propagation environment of the carrier 140. Therefore, the modulation multi-level number and frequency bandwidth are held (step S134). After processing step S134, the process proceeds to step S132 to continue communication.

On the other hand, if it is determined in step S133 that there has been a change in the C/N, further processing is performed to determine whether the C/N has deteriorated (step S135). If the C/N has not deteriorated, this means that the C/N has improved and the propagation environment has improved. Therefore, in this case, the modulation method conversion unit 531 in the modulation conversion unit 530 performs processing to increase the modulation multi-level number (step S136). Furthermore, the bandwidth conversion unit 532 performs processing to narrow the frequency bandwidth (step S137). After processing step S137, the process proceeds to step S132 and communication continues.

On the other hand, if the C/N ratio deteriorates in step S135, this means that the propagation environment has deteriorated. In this case, the modulation method conversion unit 531 performs processing to reduce the modulation multi-level number (step S138). Furthermore, the bandwidth conversion unit 532 performs processing to expand the frequency bandwidth (step S139). After processing step S139, the process proceeds to step S132 and communication continues.

As explained above using the flowchart, the relay radio device 800 of this embodiment detects changes in the C/N ratio over time and continuously performs the process of controlling the modulation multi-level number and bandwidth in response to the changes over time. This not only enables adaptive control of the modulation method in response to changes in communication quality over time, as in conventional technology, but also makes it possible to relay to lower-level stations while maintaining the transmission capacity at the higher-level station.

As described above, the present disclosure provides a relay radio device and a radio relay method that meet the required C/N ratio and do not degrade the BER of the received signal, even when there is power loss of the carrier wave due to the power feed line.

[Variations]
In the first to third embodiments of the present disclosure, the relay radio devices 500, 600, and 700 are described as being equipped with a modulation conversion unit 530 and performing modulation conversion from 64QAM to QPSK. However, the modulation schemes shown here are merely examples and do not limit the technical scope of the present disclosure. The modulation conversion unit 530 of the relay radio devices 500, 600, and 700 only needs to perform conversion to a modulation scheme with a smaller number of multi-level values, and can select a suitable modulation scheme depending on the usage environment.

Similarly, in the fourth embodiment of the present disclosure, it has been described that the relay radio device 800 includes a modulation conversion unit 530 and performs modulation conversion in response to changes in communication quality over time. However, the modulation method may be a different modulation method from that exemplified in the fourth embodiment, and an appropriate modulation method may be selected in response to communication quality.

In embodiment 4 of the present disclosure, it has been described that the relay radio device 800 detects changes in the C/N ratio over time. However, changes in other communication qualities over time may also be detected. For example, the signal-to-interference-plus-noise power ratio C/(N+I) may be used, where I is the interference power. Furthermore, changes over time can also be detected by monitoring the BER or the amount of rainfall on the transmission path. In particular, the impact of rain attenuation is significant for radio waves with frequencies above 10 GHz, so monitoring the amount of rainfall is effective. Changes over time can also be detected using ACK frames and NACK frames.

In addition, communication quality does not have to be measured by the relay radio device 800. For example, communication quality may be measured at a higher-level station or a lower-level station and notified to the relay radio device 800.

This disclosure is applicable not only to microwave bands but also to all frequency bands. It is also applicable not only to fixed microwave relay applications, but also to mobile backhaul, wireless access, wireless LAN, simple wireless, weak wireless, drone control, and more.

In the present disclosure, the processing performed by relay radio devices 500, 600, 700, and 800 may be executed by a program using a computer equipped with a CPU and memory and storing a program in the memory. Alternatively, the processing may be executed by a program using an integrated circuit such as an FPGA (Field Programmable Gate Array). The program may be provided by being recorded on a storage medium or via a network.

[Correspondence to terms in claims]
The processing performed by the modulation method converter 531 included in the relay radio devices 500, 600, and 700 described in the first to third embodiments of the present disclosure is referred to as modulation method conversion processing. Furthermore, the processing performed by the bandwidth converter 532 is referred to as bandwidth conversion processing.

In addition, the processing performed by the signal demodulation unit 552 and error correction unit 553 provided in the relay radio devices 500 and 600, as described in embodiments 1 and 2 of the present disclosure, is referred to as the demodulation and decoding processing.

Furthermore, as described in the fourth embodiment of the present disclosure, when the relay radio device 800 detects an improvement in communication quality, the processing performed by the modulation method conversion unit 531 is called the multi-level number raising processing. The multi-level number raising processing is the processing of step S136.

100, 200, 300, 500, 600, 700, 800 Relay radio devices 110, 310 Antennas 120, 330, 350, 720, 730 Feed lines 130, 340, 710, 740, 810 Radio device 140 Carrier wave 210 LNA
301 Transmitting device 320 Receiving antenna 360 Transmitting antenna 370 RF receiving processing unit 371 Receiving AMP unit 372 AGC unit 373 C/N detection unit 380, 550 DEM unit 381, 551 Waveform equalization unit 382, 552 Signal demodulation unit 383, 553 Error correction unit 384, 554 BER monitoring unit 390 MOD unit 391 Waveform shaping unit 392 FEC encoding unit 393 Signal modulation unit 400 RF transmission processing unit 401 Transmission AMP unit 402 Filter unit 410, 580, 770, 780 Monitoring and control unit 510 Modulation conversion device 530 Modulation conversion unit 531 Modulation method conversion unit 532 Bandwidth conversion unit 540 Modulation method monitoring and control unit 560 Deframing unit 561, 761 Buffering unit 570, 750 User interface units 571, 751 Connection unit 760 Framing unit

Claims (8)

receiving a carrier wave having a first modulation method and a first frequency band as a radio signal from a higher-level radio station;
a modulation method conversion process for converting the modulation method of the carrier wave into a second modulation method having a lower multi-level number than the first modulation method ;
a bandwidth conversion process of expanding the frequency band of the carrier wave to a second frequency band wider than the first frequency band so that the transmission capacity before and after the modulation format conversion process is equal;
a demodulation and decoding process for demodulating and error correcting the carrier wave having the second modulation method and the second frequency band obtained by the modulation method conversion process and the bandwidth conversion process;
a relay radio device configured to perform the steps of: 2. The relay radio device according to claim 1, configured to execute a transmission process for transmitting the carrier wave processed by the demodulation and decoding process to a downstream radio station . 3. The radio relay device according to claim 2 , wherein the carrier wave transmitted in the transmission process has the second modulation method and the second frequency band . further comprising a low noise amplifier;
3. The radio relay device according to claim 1, wherein the low noise amplifier performs pre-amplification of a carrier wave having the first modulation method and the first frequency band transmitted from the upper radio station. further executing a process of detecting a change over time in communication quality of the wireless communication performed by the wireless communication device itself;
If the communication quality has improved,
a modulation level raising process for converting the modulation method of the carrier wave transmitted from the higher-level radio station into a third modulation method having a higher modulation level than the first modulation method ;
a reduction process of reducing the frequency band of the carrier wave to a third frequency band narrower than the first frequency band so that the transmission capacity before and after the multi-level number raising process is equal;
a process of transmitting a carrier wave having the third modulation method and the third frequency band obtained by the multi-level number raising process and the reduction process to the lower radio station as a radio signal using the third modulation method and the third frequency band;
Run
If the communication quality is degraded,
the modulation format conversion process;
the bandwidth conversion process;
the demodulation and decoding process;
the transmission process;
4. The relay radio device according to claim 3, wherein the relay radio device executes the following. By using a relay radio device,
receiving a carrier wave having a first modulation method and a first frequency band as a radio signal from a higher-level radio station;
a modulation method conversion process for converting the modulation method of the carrier wave into a second modulation method having a lower multi-level number than the first modulation method ;
a bandwidth conversion process of expanding the frequency band of the carrier wave to a second frequency band wider than the first frequency band so that the transmission capacity before and after the modulation format conversion process is equal;
a demodulation and decoding process for demodulating and error correcting the carrier wave having the second modulation method and the second frequency band obtained by the modulation method conversion process and the bandwidth conversion process;
A wireless relay method comprising: The relay radio device
7. The wireless relay method according to claim 6, further comprising: executing a transmission process of transmitting the carrier wave processed by the demodulation and decoding process to a downstream wireless station . The wireless relay method according to claim 7 , wherein the carrier wave transmitted in the transmission process has the second modulation method and the second frequency band .