Radio equipment and wireless communication systems

Abstract

The present invention provides a radio and wireless communication system that can avoid interference with radios using nearby channels, even when the frequency bandwidth is expanded to compensate for attenuation during rainfall. [Solution] The present invention provides a wireless device that transmits and receives signals in opposition, and has a function to change the frequency bandwidth in accordance with changes in the communication environment to maintain a constant communication channel capacity, and when expanding the bandwidth in accordance with the changes in the communication environment would cause interference with other wireless devices using nearby channels, it determines whether it is possible to synchronize with the transmission timing of other wireless devices, and if it is possible to synchronize with the transmission timing, it controls the wireless device to transmit in accordance with that transmission timing, and a wireless communication system equipped with the wireless device.

Description

Technical Field

[0001] The present invention relates to a wireless device that performs transmission and reception in opposite directions. In particular, in an environment where interference with other wireless devices occurs by expanding the frequency bandwidth, the present invention relates to a wireless device and a wireless communication system that can perform optimal attenuation compensation during rainfall according to the level of interference.

Background Art

[0002] [Conventional Technology] Conventionally, there is a wireless system in which one-to-one or one-to-N wireless devices face each other and perform transmission and reception. Such a wireless system is used for broadband transmission applications as a relay line or an entrance line, and the quasi-millimeter wave band (3 GHz to 30 GHz) and the millimeter wave band (30 GHz to 300 GHz) are often used.

[0003] The quasi-millimeter wave band and the millimeter wave band are advantageous for long-distance high-speed transmission because it is easy to secure a wide bandwidth, and because the wavelength is short, it is possible to configure a small antenna with sharp directivity, and by radiating only to the target propagation path, the frequency utilization efficiency can be increased.

[0004] However, on the other hand, these frequency bands are greatly affected by the attenuation of radio waves due to moisture such as rainfall and snowfall, and in conventional wireless communication systems, an adaptive modulation method has been introduced as a countermeasure. The adaptive modulation method switches to a modulation method that can perform good transmission even when the line quality of the propagation path is low when the communication quality deteriorates due to the influence of rainfall attenuation or the like, thereby preventing communication interruption and maintaining the communication state.

[0005] In the adaptive modulation method, when the communication quality is good, the modulation order is increased to increase the transmission speed, while when the communication quality is bad, the modulation order is decreased to prioritize the continuation of communication over the transmission speed. This method is effective for preventing the communication path from being interrupted, but the communication speed becomes slow when the communication environment is bad due to precipitation or the like.

[0006] Therefore, in order to achieve high-speed transmission with stable communication quality while maintaining a constant communication channel capacity even when the communication environment deteriorates due to rainfall, etc., a wireless device has been proposed that expands the frequency bandwidth in accordance with rainfall attenuation (Patent Document 1).

[0007] [Conventional rainfall attenuation compensation process: Figure 7] The conventional rainfall attenuation compensation process will be explained using Figure 7. Figure 7 is a flowchart of the conventional rainfall attenuation compensation process. As shown in Figure 7, conventional wireless devices typically transmit and receive using TDD (Time Division Duplex) with self-propelled transmission and reception timing, and the frequency bandwidth used for communication is the standard bandwidth (S51). Typically, the timing of transmission and reception between opposing devices is determined as a closed timing between the communicating devices (a unique timing between the opposing devices).

[0008] Then, the system monitors whether or not there is rainfall (precipitation) and determines whether or not there is rainfall (S52). If there is no rainfall (sunny or cloudy), the system returns to process S52 and continues monitoring. Furthermore, if processing S52 determines that there is rainfall, the process is terminated by performing an adaptive bandwidth change process (S53) to adjust the frequency bandwidth according to the deterioration of communication quality in order to compensate for attenuation due to rainfall. This allows for reliable communication even during rainfall, while maintaining channel capacity. However, no measures have been taken to address the impact of bandwidth expansion.

[0009] [Interference due to frequency bandwidth expansion] When installing multiple radios in a wireless communication system, they should be installed at a sufficient distance (separation distance) to prevent interference. However, if the frequency bandwidth is expanded to compensate for rain attenuation, the required separation distance between radios using adjacent channels, and even the next adjacent channel, becomes larger. In other words, even if there is no interference between neighboring devices using adjacent channels or next-next

[0010] [Conventional interference handling process: Figure 8] The interference handling process in conventional wireless devices will be explained using Figure 8. Figure 8 is a flowchart showing the interference handling process in conventional wireless devices. As shown in Figure 8, conventional radios periodically measure the reception quality of their own channel (or the received power level of the guard bands at both ends of their own channel), which serves as an indicator of interference (S61).

[0011] Then, the presence or absence of interference is determined based on the reception quality (S62). Specifically, if the quality of the local channel is higher than the threshold and the quality is good, it is determined that there is no interference and the process returns to S61. Furthermore, if the quality of the local channel is lower than the threshold in processing S62 and the quality is poor, interference is determined to be present, and adaptive modulation control is performed to increase the transmission power or decrease the modulation level according to the quality (S63), before returning to processing S61. Thus, conventional wireless devices were designed to perform corresponding processing when interference was detected.

[0012] However, the interference that arises from the expansion of the frequency bandwidth is a rapid change, and therefore cannot be adequately tracked by the processing described above. Furthermore, it is expected that the interference level will increase as both interfering devices increase their transmission power, further worsening the interference situation.

[0013] [Related technologies] Furthermore, a related prior art is Japanese Patent Publication No. 2024-179034, "Wireless device and wireless communication system" (Patent Document 1). Patent Document 1 describes a wireless device and wireless communication system that perform transmission and reception in opposition, and which change the frequency bandwidth to maintain a constant communication channel capacity even when there are changes in the communication environment due to rainfall or the like.

Prior Art Documents

Patent Documents

[0014]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0015] As described above, in conventional wireless devices, when the frequency bandwidth is expanded, the separation distance from wireless devices using adjacent channels or next-adjacent channels increases, resulting in interference and preventing good communication.

[0016] In addition, Patent Document 1 does not describe a configuration in which, for a wireless device that expands the frequency bandwidth for rainfall attenuation compensation, when interference occurs with other wireless devices using nearby channels when the frequency bandwidth is expanded, the transmission timing of the own device is linked to the transmission timing of the interfering party.

[0017] The present invention has been made in view of the above circumstances, and an object thereof is to provide a wireless device and a wireless communication system that can avoid interference with wireless devices using nearby channels even when the frequency bandwidth is expanded for attenuation compensation during rainfall.

Means for Solving the Problems

[0018] The present invention for solving the problems of the above conventional example is a wireless device that performs transmission and reception in opposite directions, and has a function of changing the frequency bandwidth so as to keep the communication path capacity constant according to changes in the communication environment. When interference is likely to occur with other wireless devices using nearby channels by expanding the bandwidth according to changes in the communication environment, it determines whether it can be linked to the transmission timing of other wireless devices, and when it can be linked to the transmission timing, it performs transmission in accordance with the transmission timing.

[0019] Further, in the wireless device of the present invention, when it is determined that it is impossible to synchronize with the transmission timing of another wireless device, the interference level during rainfall due to environmental changes is estimated, and when the estimated interference level is less than a specific threshold value, during rainfall, the communication path capacity is reduced and the frequency bandwidth is changed.

[0020] Further, in the wireless device of the present invention, when the estimated interference level is greater than or equal to a specific threshold value, during rainfall, the change of the frequency bandwidth is stopped, and adaptive modulation is performed with a fixed frequency bandwidth.

[0021] Further, the present invention is a wireless device that performs transmission and reception in opposite directions, has a function of changing the frequency bandwidth so as to keep the communication path capacity constant according to changes in the communication environment, and when interference will occur with other wireless devices using neighboring channels by expanding the bandwidth according to changes in the communication environment, it is characterized in that transmission is performed in accordance with the transmission timing of other wireless devices.

[0022] Further, the present invention is a wireless device that performs transmission and reception in opposite directions, has a function of changing the frequency bandwidth so as to keep the communication path capacity constant according to changes in the communication environment, and when interference will occur with other wireless devices using neighboring channels by expanding the bandwidth according to changes in the communication environment, the interference level during rainfall due to environmental changes is estimated, and when the estimated interference level is less than a specific threshold value, during rainfall, the communication path capacity is reduced and the frequency bandwidth is changed.

[0023] Further, the present invention is a wireless device that performs transmission and reception in opposite directions, has a function of changing the frequency bandwidth so as to keep the communication path capacity constant according to changes in the communication environment, and when interference will occur with other wireless devices using neighboring channels by expanding the bandwidth according to changes in the communication environment, the interference level during rainfall due to environmental changes is estimated, and when the estimated interference level is greater than or equal to a specific threshold value, during rainfall, the change of the frequency bandwidth is stopped, and adaptive modulation is performed with a fixed frequency bandwidth.

[0024] Furthermore, the present invention is a wireless communication system in which wireless devices transmit and receive signals in opposition, and is characterized by comprising any of the wireless devices described above. [Effects of the Invention]

[0025] According to the present invention, a wireless device that transmits and receives signals in opposite directions has a function to change the frequency bandwidth in response to changes in the communication environment in order to maintain a constant communication channel capacity. When expanding the bandwidth in response to changes in the communication environment would cause interference with other wireless devices using nearby channels, the device determines whether it can synchronize with the transmission timing of the other wireless devices, and if it can synchronize with the transmission timing, it transmits in accordance with that transmission timing. Therefore, even when the frequency bandwidth is expanded during rainfall, interference with other wireless devices is prevented, and the communication channel capacity is maintained, enabling good communication.

[0026] Furthermore, according to the present invention, if it is determined that the transmission timing cannot be synchronized with that of other wireless devices, the interference level during rainfall due to environmental changes is estimated, and if the estimated interference level is below a certain threshold, the wireless device reduces the communication channel capacity and changes the frequency bandwidth during rainfall. Therefore, when the interference level during rainfall is small, the interference resistance is improved and the frequency bandwidth is expanded, which has the effect of maintaining a certain level of communication channel capacity and enabling good communication.

[0027] Furthermore, according to the present invention, if the estimated interference level exceeds a certain threshold, the radio stops changing the frequency bandwidth during rainfall and performs adaptive modulation with a fixed frequency bandwidth. Therefore, when the interference level is high during rainfall, interference caused by bandwidth expansion is not generated, and the effects of interference are suppressed, thereby maintaining communication. [Brief explanation of the drawing]

[0028] [Figure 1] This is a schematic diagram illustrating interference power associated with frequency bandwidth expansion. [Figure 2]This is a schematic diagram of the wireless communication system. [Figure 3] This is an explanatory diagram for cases where transmission timing can be synchronized. [Figure 4] This is an explanatory diagram for cases where the transmission timing cannot be synchronized. [Figure 5] This is a flowchart showing the first process in the rainfall attenuation compensation control unit. [Figure 6] This is a flowchart showing the second and third processes in the rainfall attenuation compensation control unit. [Figure 7] This is a flowchart showing the conventional rainfall attenuation compensation process. [Figure 8] This is a flowchart showing the interference handling process in conventional wireless devices. [Modes for carrying out the invention]

[0029] Embodiments of the present invention will be described with reference to the drawings. [Summary of the Embodiment] The wireless device according to an embodiment of the present invention (this wireless device) is a wireless device that transmits and receives signals in opposition to each other, and has a function to change the frequency bandwidth in order to maintain a constant communication channel capacity in response to changes in the communication environment, and when expanding the bandwidth in response to changes in the communication environment would cause interference with other wireless devices using nearby channels, it determines whether it is possible to synchronize with the transmission timing of the other wireless devices, and if it is possible to synchronize with the transmission timing, it transmits in accordance with that transmission timing, and even if the frequency bandwidth is expanded to compensate for rain attenuation, interference can be prevented by transmitting at the same timing, the effects of interference on adjacent channels and the next adjacent channel can be avoided, and good communication can be achieved.

[0030] Furthermore, if this radio cannot synchronize with the transmission timing of other radios, it can estimate the interference level during rainfall. If the estimated interference level is below a threshold, it can reduce the communication channel capacity to improve interference immunity and suppress the effects of interference. If the interference level is greater than the threshold, it can stop changing the frequency bandwidth to prevent interference from occurring. Thus, it can perform appropriate processing according to the interference level during rainfall.

[0031] Furthermore, the wireless communication system according to this embodiment (this wireless communication system) is a wireless communication system in which two wireless devices communicate with each other. In this embodiment, "rainfall" is not limited to rain, but includes all precipitation phenomena such as snow and hail.

[0032] [Interference power associated with frequency bandwidth expansion: Figure 1] Before describing the configuration of this system, we will explain the interference power when the frequency bandwidth is expanded using Figure 1. Figure 1 is a schematic diagram illustrating the interference power associated with frequency bandwidth expansion. As shown in Figure 1, in the absence of rainfall (standard time), the transmitted power spectrum is shown by the dotted line, and although leakage power extends to adjacent channels and the next adjacent channel (shown by the shaded lines), the impact is not very significant. For example, in the example in Figure 1, the leakage power (interference power) level in the adjacent channel is represented by L1, and in the next adjacent channel by L2.

[0033] However, if the bandwidth is expanded to compensate for rainfall attenuation, the spectrum will be as shown by the solid line, and adjacent channels will output power equivalent to the transmission power of the channel itself. In Figure 1, the interference power of adjacent channels during bandwidth expansion (i.e., during rainfall) is estimated to be L3. Furthermore, the leakage power is also large in the next adjacent channel, and the interference power during rainfall is estimated to be L4. In other words, compared to standard time, after the frequency bandwidth expansion, interference power increases in adjacent channels and the next adjacent channel by the amount indicated by the arrows.

[0034] In this wireless communication system, as described later, I / N (Interference to Noise: interference power to noise power ratio) is used as an indicator of the degree of interference (interference level) when the bandwidth is expanded. By assuming a constant noise level, it becomes possible to estimate the I / N when the bandwidth is expanded (during rainfall). Processing using the estimated I / N during rainfall (estimated I / N during rainfall) will be described later.

[0035] [Configuration of this wireless communication system: Figure 2] The configuration of this wireless communication system will be explained with reference to Figure 2. Figure 2 is a schematic diagram of the wireless communication system. Note that while Figure 2 shows a configuration where each of the two radios, Radio A and Radio B, is a single unit performing one-to-one communication, it is also possible to use multiple units of Radio A or Radio B to perform one-to-many communication. As shown in Figure 2, this wireless communication system is a system in which radio A and radio B communicate face-to-face in line of sight. In this case, radio A and radio B have the same configuration and are assigned the same designation.

[0036] The configuration of this radio will be explained. As shown in Figure 2, the radio 1 comprises an antenna 11, a transmitting unit 12, a receiving unit 13, a modulation unit 14, a demodulation unit 15, and a rain attenuation compensation control unit 16. It operates based on the transmission timing, frequency bandwidth, modulation method, transmission power, etc., set by the rain attenuation compensation control unit 16.

[0037] Antenna 11 is a directional antenna, and the antennas 11 of radio A and radio B face each other to perform point-to-point transmission and reception. The transmitting unit 12 upconverts the transmission signal into a wireless signal and outputs it to the antenna 11. The receiving unit 13 down-converts the wireless signal received by the antenna 11 and outputs it to the demodulation unit 15.

[0038] The modulation unit 14 modulates the transmission data using the modulation scheme instructed by the rainfall attenuation compensation control unit 16 and outputs it to the transmission unit 12. The demodulation unit 15 extracts and demodulates the desired waveform from the signal input from the receiving unit 13 using a demodulation method corresponding to the modulation method instructed by the rainfall attenuation compensation control unit 16, and outputs it to the rainfall attenuation compensation control unit 16.

[0039] The rainfall attenuation compensation control unit 16 is a distinctive feature of this radio, and it performs control to compensate for rainfall attenuation by changing the frequency bandwidth while avoiding interference with adjacent channels and the next adjacent channel. In particular, the rainfall attenuation compensation control unit 16 of this wireless communication system performs three different types of processing depending on the installation status of the wireless device and the interference conditions during rainfall.

[0040] The first process involves controlling the transmission timing to match that of the other party's radio that is causing interference. Specifically, the rainfall attenuation compensation control unit 16 expands the frequency bandwidth to maintain a constant communication channel capacity in order to ensure stable communication speeds even when the communication environment deteriorates. However, when the frequency bandwidth is expanded, it determines whether interference will occur with radio equipment using adjacent channels and the next adjacent channel before actual rainfall occurs, and if interference occurs, it controls the transmission timing to synchronize in order to prevent such interference.

[0041] The second process is to improve interference immunity when interference avoidance through control of transmission timing is difficult. Specifically, the rainfall attenuation compensation control unit 16 estimates the interference level during rainfall before actual rainfall occurs. If the interference level is low, it reduces the communication channel capacity to lower the required quality, improves interference immunity, and then performs rainfall attenuation compensation by expanding the frequency bandwidth.

[0042] The third process is interference suppression, in which, if the estimated interference level is higher, the frequency bandwidth modification for rainfall attenuation compensation is stopped, and adaptive modulation is performed with a fixed bandwidth. When interference levels are high, reducing the communication channel capacity cannot completely avoid interference. Therefore, this system controls the system to prevent interference from occurring as a result of bandwidth expansion. The processes performed in the rainfall attenuation compensation control unit 16 will be described later.

[0043] [Obtaining interference indices] The interference index is a value used to determine whether or not interference occurs during bandwidth expansion. In this wireless communication system, the received power of the adjacent channel and the next adjacent channel (sometimes collectively referred to as the neighboring channel) is used. Specifically, the rainfall attenuation compensation control unit 16 periodically measures the received power of adjacent channels and the next adjacent channel in the state before actual rainfall occurs, that is, before frequency bandwidth expansion, to obtain an interference index.

[0044] Then, if the reception level of a nearby channel is above a set reference value, the rainfall attenuation compensation control unit 16 determines that when its own device and the other device expand their frequency bandwidth during rainfall, they will interfere with each other. Therefore, it performs control to avoid interference or control to reduce the effects of interference before performing rainfall attenuation compensation to expand the frequency bandwidth. These processes are the first to third processes described above, and their details will be described later.

[0045] [Calculation of Interference Level (I / N)] Furthermore, as shown in Figure 1, the rainfall attenuation compensation control unit 16 calculates the I / N during standard time (when there is no frequency bandwidth expansion) and the I / N during rainfall (when the frequency bandwidth is expanded) (estimated I / N during rainfall) based on the received power of the acquired neighboring channels. The estimated I / N during rainfall is a value that indicates the magnitude of interference during rainfall, and as will be described later, it is used to decide whether to perform interference-resistant operation (second process) or interference-suppression operation (third process).

[0046] [Detection of the interfering party's transmission timing] Furthermore, the rainfall attenuation compensation control unit 16 detects the transmission timing of radios using adjacent channels and next-next-next channels when acquiring the interference index described above (before frequency bandwidth expansion). The intervals in which adjacent channels and next-next-next-next channels can be received are defined as the transmission timing of the interfering party on each channel. Furthermore, if the interfering device has the same specifications as the device itself, the transmission timing may be detected by directly detecting the synchronization signals and control signals of the adjacent channel or the next adjacent channel.

[0047] [Transmission timing control] Furthermore, if interference occurs with adjacent channels or the next adjacent channel due to the expansion of the frequency bandwidth during rainfall, the rainfall attenuation compensation control unit 16 first attempts to avoid interference by matching the transmission timing with the interfering radio (synchronizing the transmission timing).

[0048] [When transmission timing can be synchronized: Figure 3] First, we will explain the case where the transmission timing can be synchronized with that of the interfering party using Figure 3. Figure 3 is an explanatory diagram of the case where the transmission timing can be synchronized. Figure 3 illustrates a system in which radio A and radio B communicate with each other, where, in the event of rainfall and an expansion of the frequency bandwidth, radio A is subjected to interference from radio C.

[0049] In this case, radio A detects the transmission timing of radio C and synchronizes its own transmission timing with that timing. This prevents interference between radio A and radio C. Furthermore, before changing its transmission timing, radio A notifies the opposing radio B that it will change its transmission timing in conjunction with radio C.

[0050] [If transmission timing cannot be synchronized: Figure 4] Next, we will explain the case where the transmission timing cannot be synchronized with the interference partner, using Figure 4. Figure 4 is an explanatory diagram of the case where the transmission timing cannot be synchronized. As shown in Figure 4(a), when radio A is subjected to interference from multiple radios (in this case, radios C and D), radios C and D transmit at independent timings. Therefore, adjusting to one will not synchronize the transmission timing with the other, resulting in interference.

[0051] Furthermore, as shown in Figure 4(b-1), if opposing radios A and B are subjected to interference from the same radio C, for example, even if radio A is synchronized with radio C, the opposing radio B cannot be synchronized, resulting in interference. Furthermore, as shown in Figure 4(b-2), if radio A interferes with radio D, and radio B interferes with radio C, since radio C and radio D transmit at their own independent timings, either radio A or radio B cannot synchronize with the interfering party, resulting in interference.

[0052] [Processing in the rainfall attenuation compensation control unit 16] Next, the rainfall attenuation compensation process in the rainfall attenuation compensation control unit 16 of this wireless communication system will be described. [First process: Figure 5] First, the first process in the rainfall attenuation compensation control unit 16 will be explained using Figure 5. Figure 5 is a flowchart showing the first process in the rainfall attenuation compensation control unit 16. As shown in Figure 5, first, under normal operating conditions (no rainfall), this radio communicates with the opposing device using a self-propelled transmission and reception timing, and the frequency bandwidth is set to the standard bandwidth (S11).

[0053] Then, when there is no rainfall, the rainfall attenuation compensation control unit 16 periodically measures the received power of the adjacent channel and the next adjacent channel (neighboring channel) and uses it as an interference index (S12). Furthermore, the rainfall attenuation compensation control unit 16 determines whether there are any adjacent channels or next adjacent channels that would cause interference if there were rainfall (S13). Specifically, the rainfall attenuation compensation control unit 16 determines that interference will occur due to the expansion of the frequency bandwidth during rainfall if the received power acquired in processing S12 is equal to or greater than a preset reference value ("Yes"), and determines that no interference will occur during rainfall if the received power is less than the reference value ("No").

[0054] If there are channels in processing S13 where interference occurs during rainfall (in the case of "Yes"), the rainfall attenuation compensation control unit 16 determines whether it is possible to synchronize the transmission timing with the radio device that is causing the interference (S14).

[0055] Specifically, the rainfall attenuation compensation control unit 16 determines that interoperation is possible and proceeds to process S15 if there is only one radio interfering with its own device, and furthermore, the opposing device of its own device is not interfering with the interfering device or any other radio.

[0056] Furthermore, if there are multiple radios interfering with the device itself, or if the device's interfering partner also interferes with the opposing device, or if the device itself and the opposing device interfere with different partners, the system will determine that interoperation is impossible and proceed to (A). Furthermore, this radio 1 notifies the opposing device of information about the device's interference partner and transmission timing, and the rainfall attenuation compensation control unit 16 determines whether or not the transmission timing can be synchronized based on this information.

[0057] Then, in process S14, if it is possible to synchronize the transmission timing with the interfering device ("possible"), the rainfall attenuation compensation control unit 16 detects the transmission timing of the interfering device and performs interference avoidance processing to synchronize its own device's transmission timing with the interfering device's transmission timing (S15), and then proceeds to process S16. Before synchronizing the transmission timing, the opposing device is notified of the change in transmission and reception timing.

[0058] On the other hand, if there are no channels that cause interference during rainfall in process 13 (i.e., "none"), the rainfall attenuation compensation control unit 16 does not control the transmission timing and performs a rainfall determination (S16). If there is no rainfall in process S16 (if it is sunny / cloudy), the process returns to the judgment in process S16 and continues monitoring for rainfall.

[0059] Furthermore, if rainfall occurs during processing S16 (in the case of rainfall), the rainfall attenuation compensation control unit 16 performs adaptive bandwidth modification processing to change the frequency bandwidth according to the reception quality from the opposing device as rainfall attenuation compensation (S17), and then terminates the processing. In this way, the first process is carried out.

[0060] As a result, in the first process, when there is a risk of interference occurring in adjacent channels or the next adjacent channel during rainfall, control is performed to synchronize the transmission timing with the radio equipment communicating using the interfering channel before the rain falls, thereby preventing interference. If rainfall actually occurs, the frequency bandwidth can be expanded without interference, and good communication can be maintained while preserving the communication channel capacity.

[0061] In the process shown in Figure 5, the system determines whether or not the transmission timing can be synchronized in process S14. However, instead of making a determination in process S14, the system may proceed to process S15 in process S13 if there are channels where interference occurs during rainfall, in order to perform interference avoidance processing.

[0062] [Second process, third process: Figure 6] Next, the second and third processes in the rainfall attenuation compensation control unit 16 will be explained using Figure 6. Figure 6 is a flowchart showing the second and third processes in the rainfall attenuation compensation control unit 16. Note that the process in Figure 6 follows the process shown in Figure 5 (A). Processes S21 to S23 are the second process, and processes S21, S24, and S25 are the third process.

[0063] As shown in Figure 6, in the second process, if it is not possible to synchronize the transmission timing with the interfering partner in process S14 of Figure 5 (case A), the rainfall attenuation compensation control unit 16 estimates the interference level I / N, which indicates the effect of interference during rainfall, based on the received power of the nearby channel where interference is determined to occur, and compares the estimated I / N during rainfall with a preset threshold (S21).

[0064] Then, if the estimated interference level during rainfall, which is the estimated I / N during rainfall, is smaller than the threshold ("small"), the rainfall attenuation compensation control unit 16 performs a rainfall determination (S22). If there is no rainfall (sunny / cloudy), it continues monitoring in process S22. If it rains during processing S22, interference tolerance processing is performed (S23) to reduce the communication channel capacity and then change the adaptive bandwidth as compensation for rain attenuation, and then the processing ends.

[0065] The second process allows for improved interference immunity and expanded frequency bandwidth, even if the transmission timing cannot be synchronized. This is possible if the interference caused by the frequency bandwidth expansion is within a certain range, although the channel capacity is slightly reduced. The channel capacity can then be maintained at that level, enabling good communication.

[0066] Furthermore, in processing S21, if the estimated I / N during rainfall is greater than or equal to a threshold ("large"), the rainfall attenuation compensation control unit 16 performs a rainfall determination and monitors for rainfall (S24). If rainfall occurs, as interference suppression processing, it stops changing the bandwidth and performs adaptive modulation (S25). When the estimated I / N ratio during rainfall is high and interference is expected to persist, reducing the channel capacity will not completely avoid interference. Therefore, adaptive modulation is performed with a fixed bandwidth to prevent interference.

[0067] In the third process, although the effect of keeping the communication channel capacity constant through frequency bandwidth expansion is not achieved, interference to adjacent channels and the next adjacent channel does not occur, making it possible to continue communication.

[0068] Alternatively, instead of branching the second and third processes from process S14 in Figure 5, the processes S11 to S13 in Figure 5 may be performed in the same way as the first process, and if it is determined in process S13 that there is an interference channel during rainfall, the process may be configured to proceed to S21 in Figure 6.

[0069] [Examples of interference tolerance / interference suppression control] Here, we will explain an example of control that determines whether to perform interference resistance or interference suppression based on the estimated I / N during rainfall. For example, if the bandwidth is doubled as the first stage (first expansion step) of rain attenuation compensation (frequency bandwidth expansion) in order to keep the communication channel capacity constant, interference with adjacent channels becomes a problem. Switching the primary modulation scheme from 1024QAM (Quadrature Amplitude Modulation) to 256QAM reduces the channel capacity (by about 20%), which lowers the required quality by about 7dB. Therefore, if the estimated I / N during rainfall is less than 7dB (I / N < 7dB), it is preferable to switch the primary modulation scheme and expand the frequency bandwidth as an interference-resistant operation (processing S23 in Figure 6).

[0070] Furthermore, if the estimated I / N during rainfall is 7 dB or higher (I / N ≥ 7 dB), it is preferable to operate with adaptive modulation without bandwidth expansion as interference suppression (processing S25 in Figure 6). By not expanding the bandwidth, interference to adjacent channels is not increased. Furthermore, by reducing the modulation depth from 1024QAM to 64QAM through adaptive modulation, the required quality is reduced by approximately 12dB, thus mitigating the impact even if the interference source expands its bandwidth.

[0071] Reducing the modulation depth from 1024QAM to 16QAM lowers the required quality by approximately 17dB, and further reducing it to QPSK (Quadrature Phase Shift Keying) lowers it by approximately 19dB, thus significantly reducing the impact of interference.

[0072] Furthermore, when considering interference with the next adjacent channel and the channel next to that in the second stage (second extension step) of rainfall attenuation compensation, a lower I / N value may be set as the threshold for processing S21 in Figure 6 to determine interference resistance / interference suppression.

[0073] In the first stage of rainfall attenuation compensation, for example, if 64QAM is used, switching the primary modulation scheme from 64QAM to 16QAM will reduce the required quality by about 4dB. Therefore, if the estimated I / N during rainfall is less than 4dB (I / N < 4dB), interference-resistant operation is performed, and if the estimated I / N during rainfall is 4dB or more (I / N ≥ 4dB), interference-resistant suppression operation is performed, and it is preferable to operate with adaptive modulation while maintaining the frequency bandwidth of the first stage of rainfall attenuation compensation. In other words, if the estimated interference level during rainfall exceeds a threshold, the frequency bandwidth change is stopped, and adaptive modulation is performed with a fixed bandwidth.

[0074] By not expanding the bandwidth any further, we not only avoid increasing interference to the next adjacent channel and even further down the line, but by reducing the modulation depth from 64QAM to QPSK using adaptive modulation, the required quality is reduced by about 6dB, thus mitigating the impact even if the interference source expands its bandwidth.

[0075] [Effects of the embodiment] This radio is a two-way radio that transmits and receives signals and has a function to change the frequency bandwidth in response to changes in the communication environment to maintain a constant communication channel capacity. When expanding the bandwidth in response to changes in the communication environment would cause interference with other radios using nearby channels, the radio is equipped with a rain attenuation compensation control unit 16 that determines whether it can synchronize with the transmission timing of other radios, and if it can synchronize with the transmission timing, controls the radio to transmit in accordance with that transmission timing. As a result, even if the frequency bandwidth is expanded by rain attenuation compensation, interference can be prevented by transmitting at the same timing, the effects of interference on nearby channels can be avoided, and good communication can be achieved while maintaining communication channel capacity.

[0076] Furthermore, according to this radio, if the rainfall attenuation compensation control unit 16 cannot synchronize with the transmission timing of other radios, it calculates the estimated I / N during rainfall as the interference level during rainfall. If the estimated I / N during rainfall is smaller than a threshold, the radio reduces the channel capacity to improve interference immunity and then expands the frequency bandwidth. Therefore, when the estimated interference level during rainfall is small, it is possible to expand the frequency bandwidth while suppressing the effects of interference, thereby maintaining a certain level of channel capacity and achieving good communication.

[0077] Furthermore, according to this radio, the rainfall attenuation compensation control unit 16 calculates the estimated I / N during rainfall as the interference level during rainfall, and if the estimated I / N during rainfall is greater than a threshold, the radio stops changing the frequency bandwidth and performs adaptive modulation with a fixed frequency bandwidth. Therefore, when the estimated interference level during rainfall is large, it is possible to maintain communication by suppressing the effects of interference without generating interference associated with frequency bandwidth expansion. [Industrial applicability]

[0078] The present invention is suitable for radio transceivers and wireless communication systems that can avoid interference with radio transceivers using nearby channels even when the frequency bandwidth is expanded as compensation for attenuation during rainfall. [Explanation of Symbols]

[0079] 1...Radio unit, 11...Antenna, 12...Transmitter, 13...Receiver, 14...Modulator, 15...Demodulator, 16...Rainfall attenuation compensation control unit

Claims

1. A radio that transmits and receives signals in opposite directions, It has a function to change the frequency bandwidth in order to maintain a constant communication channel capacity in response to changes in the communication environment. A radio device characterized in that, when expanding the bandwidth in response to a change in the communication environment would cause interference with other radio devices using nearby channels, it determines whether it can synchronize with the transmission timing of the other radio devices, and if it can synchronize with the transmission timing, it transmits in accordance with that transmission timing.

2. The radio according to claim 1, characterized in that, if it is determined that it cannot be synchronized with the transmission timing of the other radio, it estimates the interference level during rainfall due to the environmental change, and if the estimated interference level is below a certain threshold, it reduces the communication channel capacity and changes the frequency bandwidth during rainfall.

3. The radio according to claim 2, characterized in that, if the estimated interference level exceeds a certain threshold, the frequency bandwidth change is stopped during rainfall, and adaptive modulation is performed with a fixed frequency bandwidth.

4. A radio that transmits and receives signals in opposite directions, It has a function to change the frequency bandwidth in order to maintain a constant communication channel capacity in response to changes in the communication environment. A radio device characterized by transmitting in accordance with the transmission timing of other radio devices when expanding the bandwidth in response to changes in the communication environment would cause interference with other radio devices using nearby channels.

5. A wireless device that transmits and receives signals in opposite directions, It has a function to change the frequency bandwidth in order to maintain a constant communication channel capacity in response to changes in the communication environment. A radio characterized in that, when expanding the bandwidth in response to a change in the communication environment would cause interference with other radios using nearby channels, the radio estimates the interference level during rainfall due to the change in the environment, and if the estimated interference level is below a certain threshold, it reduces the communication channel capacity and changes the frequency bandwidth during rainfall.

6. A wireless device that transmits and receives signals in opposite directions, It has a function to change the frequency bandwidth in order to maintain a constant communication channel capacity in response to changes in the communication environment. A radio characterized in that, when expanding the bandwidth in response to a change in the communication environment would cause interference with other radios using nearby channels, the radio estimates the interference level during rainfall due to the environmental change, and if the estimated interference level exceeds a certain threshold, it stops changing the frequency bandwidth during rainfall and performs adaptive modulation with a fixed frequency bandwidth.

7. A wireless communication system in which radios transmit and receive signals to each other, A wireless communication system characterized by comprising a wireless device according to any one of claims 1 to 6.

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