Radio apparatus and radio communication system

Abstract

[Problem] To provide a radio apparatus and a radio communication system capable of continuously maintaining radio communication even when the communication environment changes due to precipitation or the like. [Solution] The radio apparatus and the radio communication system are provided with a frequency bandwidth control unit 31 with which communications are transmitted and received by a station, the frequency bandwidth of a transmission signal is changed in accordance with changes in the communication environment so as to maintain radio communication, transmission is performed at a fixed maximum transmission power, and the frequency bandwidth and the transmission power per unit frequency bandwidth is controlled in conjunction with each other. Under the condition that the transmission power is fixed, the frequency bandwidth is narrowed and the transmission power per unit frequency bandwidth is increased to maintain communication even if the communication environment worsens further from the state in which operation is running at the maximum frequency bandwidth.

Description

Wireless device and wireless communication system

[0001] The present invention relates to a wireless communication system that performs transmission and reception in opposite directions, and particularly to a wireless communication system that can continue to maintain communication even when the communication environment changes.

[0002] [Prior Art] 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 in securing a wide band, and because the wavelength is short, an antenna with a sharp directivity can be configured in a small size, and the frequency utilization efficiency can be increased by radiating only to the target propagation path.

[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 an adaptive modulation method has been introduced as a countermeasure in conventional wireless communication systems. The adaptive modulation method prevents communication disconnection and maintains the communication state by switching to a modulation method that enables 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.

[0005] [Configuration Example of Conventional Wireless Communication System: FIG. 7] A configuration example of a conventional wireless communication system using the adaptive modulation method will be described with reference to FIG. 7. FIG. 7 is an explanatory diagram showing a configuration example of a conventional wireless communication system. In FIG. 7, a configuration in which both the wireless device A and the wireless device B perform one-to-one opposite communication with one unit each is shown, but a configuration in which a plurality of wireless devices A or wireless devices B perform one-to-N opposite communication may also be used. As shown in FIG. 7, the conventional wireless communication system is a system in which the wireless device A and the wireless device B perform line-of-sight communication facing each other. Here, the wireless device A and the wireless device B have the same configuration, and the same reference numerals are given to the wireless device A and the wireless device B.

[0006] The configuration of a conventional radio will now be described. As shown in Figure 7, a conventional radio 7 comprises an antenna 71, a transmitter 72, a receiver 73, a modulation unit 74, a demodulator 75, and an adaptive modulation unit 76. The antenna 71 is a directional antenna, and the antennas 71 of radio A and radio B face each other to perform point-to-point transmission and reception. The transmitter 72 upconverts the transmission signal into a radio signal and outputs it to the antenna 71. The receiver 73 downconverts the radio signal received by the antenna 71 and outputs it to the demodulator 75.

[0007] The modulation unit 74 modulates the transmission data using the modulation scheme instructed by the adaptive modulation unit 76 and outputs it to the transmission unit 72. The demodulation unit 75 extracts the desired wave from the signal input from the receiving unit 73 based on the modulation scheme instructed by the adaptive modulation unit 76, demodulates it, and outputs it to the adaptive modulation unit 76. The adaptive modulation unit 76 calculates the communication quality from the received signal input from the demodulation unit 75, selects an appropriate modulation scheme based on the communication quality, and notifies the modulation unit 74 and the demodulation unit 75 of the selected modulation scheme.

[0008] In adaptive modulation schemes, when communication quality is good, the modulation level is increased to increase the transmission speed, while when communication quality is poor, the modulation level is decreased to prioritize the continuation of communication over transmission speed. This method is effective in preventing interruptions to the communication channel, but the communication speed will be slower when the communication environment is poor due to rain, etc.

[0009] For example, even if high-speed transmission with a channel capacity of 1 Gbps is being performed using the 4096QAM (Quadrature Amplitude Modulation) modulation scheme in clear weather, during heavy rain, the modulation scheme is switched to QPSK (Quadrature Phase Shift Keying) to maintain communication. As a result, even if communication is maintained, the communication speed drops significantly to 150 Mbps.

[0010] Furthermore, in conventional wireless communication systems, communication is performed using an allocated channel (usable frequency band), so the bandwidth used for communication is fixed.

[0011] [Related Technology] A related prior art document is Japanese Patent Publication No. 2008-167500, "Transmission Power Control Method and Wireless Access System" (Patent Document 1).

[0012] Patent Document 1 describes a wireless access system in which a base station device measures the reception level from a subscriber base station and transmits it to the subscriber base station, and the subscriber base station calculates the optimal transmission power and adjusts the transmission power.

[0013] Japanese Patent Publication No. 2008-167500

[0014] However, conventional wireless communication systems, while they change their modulation scheme to continue communication in response to changes in the communication environment, suffer from a decrease in communication speed, and if the communication environment deteriorates further, it becomes difficult to maintain communication.

[0015] Furthermore, Patent Document 1 does not describe a configuration in which the maximum transmission power is kept constant and the frequency bandwidth or the transmission power per unit frequency bandwidth is changed in response to changes in the communication environment.

[0016] This invention has been made in view of the above circumstances, and aims to provide a wireless device and wireless communication system that can prevent a reduction in communication speed as much as possible even when the communication environment changes due to rainfall, etc., and can maintain wireless communication even when the communication environment further deteriorates.

[0017] To solve the problems of the above-mentioned conventional example, the present invention provides a wireless device that transmits and receives signals in opposition, and which has a frequency bandwidth control unit that changes the frequency bandwidth of the transmitted signal in response to changes in the communication environment to maintain wireless communication, and transmits with a constant maximum transmission power, and controls the frequency bandwidth and the transmission power per unit frequency bandwidth in conjunction with each other.

[0018] Furthermore, the present invention provides a wireless device that, after the frequency bandwidth has been changed, includes a channel capacity control unit that changes the channel capacity of the transmitted data signal in accordance with the change in the communication environment.

[0019] Furthermore, the present invention provides a repeat transmission control unit in the above-mentioned wireless device that, after the frequency bandwidth has been changed, changes the number of times the same wireless frame is transmitted in accordance with the change in the communication environment.

[0020] Furthermore, the present invention includes an antenna control unit that, after the frequency bandwidth has been changed, changes the ratio of the number of antennas used for transmission in accordance with changes in the communication environment.

[0021] Furthermore, the present invention includes a communication quality measurement unit in the above-mentioned wireless device that measures the communication quality of the received signal and determines changes in the communication environment.

[0022] Furthermore, the present invention includes a received power measurement and attenuation calculation unit that calculates the amount of attenuation of radio waves in the transmission path from the change in the level of received power to determine changes in the communication environment.

[0023] Furthermore, the present invention relates to a wireless communication system that performs transmission and reception between opposing parties, wherein the wireless devices are used for both transmission and reception, and the transmitting wireless device and the receiving wireless device maintain wireless communication by performing the same control in response to changes in the communication environment.

[0024] According to the present invention, a wireless device that transmits and receives signals in opposite directions has a frequency bandwidth control unit that changes the frequency bandwidth of the transmitted signal in response to changes in the communication environment to maintain wireless communication, and transmits at a constant maximum transmission power, thereby controlling the frequency bandwidth and the transmission power per unit frequency bandwidth in conjunction. For example, even if the communication environment deteriorates from a state where it is operating at the maximum frequency bandwidth, it is possible to maintain communication.

[0025] This is an explanatory diagram showing the configuration of this wireless communication system. This is an explanatory diagram showing an overview of the communication maintenance control in this radio. This is an explanatory diagram showing an example configuration of the wireless communication maintenance control unit 16 (1). This is an explanatory diagram showing an example configuration of the wireless communication maintenance control unit 16 (2). This is an explanatory diagram showing an example of a control table in the wireless communication maintenance control unit 16. This is an explanatory diagram showing an example configuration of this wireless communication system. This is an explanatory diagram showing an example configuration of a conventional wireless communication system.

[0026] Embodiments of the present invention will be described with reference to the drawings. [Summary of Embodiments] 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, and is equipped with a frequency bandwidth control unit that keeps the maximum transmission power constant and changes the frequency bandwidth of the transmission signal and the transmission power per unit frequency bandwidth in conjunction with the communication environment in order to maintain wireless communication in response to changes in the communication environment, and under the condition that the transmission power is fixed, communication can be maintained even if the communication environment deteriorates from a state in which it is operating at the maximum frequency bandwidth.

[0027] Furthermore, the wireless communication system according to the embodiment of the present invention (this wireless communication system) is a system in which two of these wireless devices face each other and perform transmission and reception.

[0028] [Configuration of this wireless communication system: Figure 1] The configuration of this wireless communication system will be explained with reference to Figure 1. Figure 1 is an explanatory diagram showing the configuration of this wireless communication system. As shown in Figure 1, this wireless communication system is used in which two radios, A and B, which have the same configuration, communicate with each other. In Figure 1, both radios A and B are shown as one unit each for one-to-one communication, but it is also possible to use multiple radios A or B to perform one-to-N communication. Both radios A and B are the same radios, and in Figure 1, radios A and B are given the same reference numerals.

[0029] As shown in Figure 1, the radio 1 used as radio A and radio B in this wireless communication system comprises an antenna 11, a transmitting unit 12, a receiving unit 13, a modulation unit 14, a demodulation unit 15, and a wireless communication maintenance control unit 16. Of these, the antenna 11 is the same as that of the conventional radio shown in Figure 7, but it may also be a MIMO (Multiple Input Multiple Output) radio equipped with multiple antennas 11. Furthermore, the basic operation of the transmitting unit 12, receiving unit 13, modulation unit 14, and demodulation unit 15 is the same as that of the conventional radio shown in Figure 7, but a feature of the radio 1 is that it operates based on the frequency bandwidth, modulation method, transmission power, etc. selected by the wireless communication maintenance control unit 16.

[0030] The wireless communication maintenance control unit 16 performs communication maintenance control by controlling various items such as frequency bandwidth, communication channel capacity, number of repetitions, and number of MIMO antennas in order to ensure stable communication at a stable communication speed even when the communication environment deteriorates, and to maintain communication even if it deteriorates further. The communication maintenance control will be described later.

[0031] [Outline of Communication Maintenance Control in This Radio: Figure 2] An overview of the communication maintenance control in this radio will be explained using Figure 2. Figure 2 is an explanatory diagram showing an overview of the communication maintenance control in this radio. As shown in Figure 2(a), for example, when the weather is sunny / cloudy / light rain and the deterioration of communication quality is within a certain range, the control is made to maintain the communication speed by keeping the communication channel capacity constant. Specifically, the wireless communication maintenance control unit 16 controls the frequency bandwidth to be progressively wider as the communication environment deteriorates while maintaining the communication channel capacity. In this case, the maximum bandwidth is 400 MHz. This makes it possible to communicate while maintaining the communication speed. Figure 2(a) shows the state in which the frequency bandwidth has been controlled to the maximum width (400 MHz).

[0032] If the communication environment deteriorates further due to rainfall or other factors after the frequency bandwidth has reached its maximum, the wireless communication maintenance control unit 16 performs control aimed at maintaining communication rather than communication speed. Specifically, the wireless communication maintenance control unit 16 sequentially narrows the frequency bandwidth while continuously transmitting radio waves at maximum transmission power. The maximum transmission power is a constant value. As a result, although the frequency bandwidth is sequentially narrowed as the communication environment deteriorates, the transmission power per unit bandwidth increases, allowing communication to continue.

[0033] In the example in Figure 2, if the communication environment deteriorates due to, for example, rainfall, when the frequency bandwidth is at its maximum as in (a), the wireless communication maintenance control unit 16 reduces the frequency bandwidth to half of (a), 200 MHz, as in (b). In addition, by setting the transmission power to the set maximum transmission power, the transmission power per unit bandwidth becomes twice that of (a). This results in a 3 dB increase in the power ratio.

[0034] Furthermore, if heavy rain causes further deterioration of the communication environment, the wireless communication maintenance control unit 16 will, as shown in (c), set the frequency bandwidth to 100 MHz, which is half that of (b), and the transmission power per unit bandwidth will be double that of (b) (an additional 3 dB increase).

[0035] Furthermore, if the communication environment deteriorates further due to heavy rain or other reasons, the wireless communication maintenance control unit 16 will, as shown in (d), set the frequency bandwidth to 50 MHz, which is half of (c), and the transmission power per unit bandwidth will be twice that of (c) (an additional 3 dB increase).

[0036] In this way, by controlling the frequency bandwidth to be gradually narrowed in response to the deterioration of the communication environment, and by transmitting with a fixed maximum transmission power, it is possible to increase the transmission power per unit bandwidth in conjunction with the frequency bandwidth, thereby maintaining communication.

[0037] During operation, for example, if the communication environment deteriorates when the frequency bandwidth is at its maximum, as in (a), adaptive modulation is performed while maintaining the frequency bandwidth at its upper limit, using a slower modulation method to maintain communication. However, if the communication environment deteriorates further, this radio controls the frequency bandwidth as in (b) to (d), and also transmits at maximum transmission power to control the transmission power per unit frequency bandwidth. In particular, in the state of (a), even if the modulation method is changed from QPSK to BPSK, for example, the effect on maintaining communication is limited (about 3 dB), so the communication maintenance control of this radio is effective.

[0038] [Configuration Example of Wireless Communication Maintenance Control Unit (1): Figure 3] Next, Configuration Example (1) of the Wireless Communication Maintenance Control Unit 16 will be explained using Figure 3. Figure 3 is an explanatory diagram showing Configuration Example (1) of the Wireless Communication Maintenance Control Unit 16. As shown in Figure 3, the Wireless Communication Maintenance Control Unit 16 in Configuration Example (1) will be referred to as Wireless Communication Maintenance Control Unit 16a. The Wireless Communication Maintenance Control Unit 16a includes a communication quality measurement unit 21, a frequency bandwidth switching control unit 31, a communication channel capacity switching control unit 32, a repetitive transmission switching control unit 33, and a MIMO antenna switching control unit 34.

[0039] The communication quality measurement unit 21 measures the communication quality based on the input signal (desired signal) from the demodulation unit 15 and the noise level. As the communication quality, the level of the desired signal and the level of the noise component are detected, and the ratio between them (S / N ratio, etc.) is used.

[0040] The frequency bandwidth switching control unit 31 selects a frequency bandwidth corresponding to the communication quality measured by the communication quality measurement unit 21 from among a plurality of frequency bandwidths stored in advance, and notifies each part of the radio. Specifically, the frequency bandwidth switching control unit 31 has a frequency bandwidth table that associates communication quality with frequency bandwidth in advance, and selects a frequency bandwidth based on this table. Examples of the frequency bandwidth table, as well as the communication channel capacity table, repetitive transmission table, and MIMO antenna table described later, will be described later.

[0041] Similarly, the channel capacity switching control unit 32 is equipped with a channel capacity table, and from among the multiple channel capacities stored in the table, it selects a channel capacity corresponding to the communication quality measured by the communication quality measurement unit 21 and notifies each unit. When the communication environment deteriorates, wireless communication may be interrupted or errors associated with communication may occur more easily. Therefore, in the control of channel capacity, when the communication quality deteriorates, the ratio of the SYNC signal / preamble signal and error correction code for wireless synchronization is increased and transmitted. This controls the system to maintain communication even if the transmission speed is reduced. For this reason, the channel capacity table is set so that the lower the communication quality, the smaller the channel capacity used for data communication.

[0042] The repetitive transmission switching control unit 33 is equipped with a repetitive transmission table, and from among the multiple repetitive transmission counts stored in the table, it selects the number of repetitive transmissions corresponding to the communication quality measured by the communication quality measurement unit 21 and notifies each unit. The repetitive transmission table is set to increase the number of repetitive transmissions of the same frame when the communication quality is low. By repetitive transmission, the receiving side receives the same frame multiple times and increases the probability of correct reception by, for example, comparing and combining them.

[0043] The MIMO antenna switching control unit 34 includes a MIMO antenna table, selects the one corresponding to the communication quality measured by the communication quality measurement unit 21 from among the plurality of MIMO antenna numbers stored in the table, and notifies each unit. In the case of a MIMO radio having a plurality of antennas 11, when the communication environment deteriorates, the number of antennas is restricted to increase the transmission power from one antenna and control is performed to increase the reception power of the opposing device. That is, in the MIMO antenna table, when the communication quality becomes low, the number of antennas is set to be reduced.

[0044] Here, each switching control unit of the communication path capacity switching control unit 32, the repeated transmission switching control unit 33, and the MIMO antenna switching control unit 34 in the wireless communication maintenance control unit 16 is assumed to operate independently. In the radio 1, it is assumed that only one of the switching control units operates according to the deterioration of the communication environment, and as the communication environment deteriorates, the frequency bandwidth switching control unit 31, the communication path capacity switching control unit 32, the repeated transmission switching control unit 33, and the MIMO antenna switching control unit 34 operate in this order. Note that a configuration may be adopted in which a plurality of switching control units perform control in conjunction with each other.

[0045] In this wireless communication system, the opposing radios A and B may each independently perform the above-described control. If both radios are operating normally, the determination of the communication quality is the same in either radio, and the same control is performed. Alternatively, with one radio as the master and the other as the slave, when the master radio performs control, the content may be notified to the slave radio so that the slave radio performs the same control. In the case of one-to-N opposing communication, one radio opposing N radios may be set as the master radio and the N radios may be set as slave radios, and the same control may be performed overall.

[0046] [Configuration Example (2) of Wireless Communication Maintenance Control Unit: FIG. 4] Next, a configuration example (2) of the wireless communication maintenance control unit 16 will be described using FIG. 4. FIG. 4 is an explanatory diagram showing a configuration example (2) of the wireless communication maintenance control unit 16. As shown in FIG. 4, the wireless communication maintenance control unit 16 in configuration example (2) is denoted as the wireless communication maintenance control unit 16b. The wireless communication maintenance control unit 16b is configured by providing a received power measurement attenuation amount calculation unit 22 instead of the communication quality measurement unit 21 in the wireless communication maintenance control unit 16a shown in FIG. 3.

[0047] The received power measurement attenuation amount calculation unit 22 measures the received power of the received signal input from the demodulation unit 15, and calculates the attenuation amount by comparing it with the received power in a case where the communication environment is good (for example, on a sunny day). When there is rain attenuation, the attenuation amount increases. The frequency bandwidth switching control unit 31, communication path capacity switching control unit 32, repeated transmission switching control unit 33, and MIMO antenna switching control unit 34 perform control based on the attenuation amount from the received power measurement attenuation amount calculation unit 22.

[0048] And the frequency bandwidth switching control unit 31 of the wireless communication maintenance control unit 16b has a table storing the frequency bandwidth corresponding to the attenuation amount, selects the frequency bandwidth corresponding to the attenuation amount from the received power measurement attenuation amount calculation unit 22, and notifies each unit.

[0049] Similarly, the communication path capacity switching control unit 32, repeated transmission switching control unit 33, and MIMO antenna switching control unit 34 also have tables storing the communication path capacity, repeated transmission times, and MIMO antenna numbers corresponding to the attenuation amount respectively, and make selections based on each table according to the attenuation amount from the received power measurement attenuation amount calculation unit 22.

[0050] [Example of Control Table of Wireless Communication Maintenance Control Unit: FIG. 5] An example of the control table in the wireless communication maintenance control unit 16 will be described using FIG. 5. FIG. 5 is an explanatory diagram showing an example of the control table in the wireless communication maintenance control unit 16. In FIG. 5, an example of the control table in the wireless communication maintenance control unit 16a described in FIG. 4 is shown, which collectively shows the above-mentioned frequency bandwidth table, communication path capacity table, repeated transmission table, and MIMO antenna table.

[0051] The control table 50 stores the frequency bandwidth 52, channel capacity 53, number of repetitions 54, and number of MIMO antennas 55, corresponding to the communication quality 51. The frequency bandwidth table includes the communication quality 51 and frequency bandwidth 52, the channel capacity table includes the communication quality 51 and channel capacity 53, the repetition table includes the communication quality 51 and number of repetitions 54, and the MIMO antenna table includes the communication quality 51 and number of MIMO antennas 55.

[0052] In the example in Figure 5, the communication quality 51 is divided into seven categories: A or higher (Category 1), B to A (B or higher but less than A, Category 2), C to B (Category 3), D to C (Category 4), E to D (Category 5), F to E (Category 6), and below F (Category 7), the lowest quality. However, the number of communication quality categories is not limited to these, and there may be more or fewer categories.

[0053] Each threshold value from A to F represents a communication quality value determined by actual measurements or simulations. Furthermore, to introduce hysteresis, different values ​​may be used for the direction in which communication quality deteriorates (from category 1 to category 7) and the direction in which it improves (from category 7 to category 1). Note that in the example in Figure 5, the communication quality categories are common to all control items, but they may be different for each control item.

[0054] The control based on the control table 50 in Figure 5 will be explained in detail. The frequency bandwidth switching control unit 31 controls the frequency bandwidth by referring to the frequency bandwidth 52 in the control table 50. As shown in Figure 5, the frequency bandwidth switching control unit 31 controls the frequency bandwidth to be progressively wider from section 1, where the communication quality is good, to section 4, where it has deteriorated to some extent. Specifically, in section 1, the frequency bandwidth is set to the minimum of 50 MHz, in section 2, where the communication quality has deteriorated slightly, it is set to 100 MHz, in section 3 to 200 MHz, and in section 4 to the maximum of 400 MHz. Within this range of sections, the communication channel capacity is not controlled and is kept constant, allowing communication to be performed without changing the transmission speed, thus achieving good communication.

[0055] Furthermore, if the communication environment deteriorates to categories 5 through 7, the frequency bandwidth switching control unit 31 sequentially narrows the frequency bandwidth, as shown in Figure 5. At the same time, it controls the transmission power to the set maximum transmission power. Specifically, it sets it to 200 MHz in category 5, 100 MHz in category 6, and 50 MHz in category 7. This increases the transmission power per unit bandwidth, thereby increasing the received power at the receiving end and maintaining communication. In addition, when the rain stops and the propagation path environment returns to good conditions, the original frequency bandwidth can be quickly returned, preventing the use of unnecessary frequency resources and increased power consumption.

[0056] Furthermore, the communication channel capacity switching control unit 32 controls the communication channel capacity by referring to the communication channel capacity 53 in the control table 50. Specifically, as shown in Figure 5, in sections 1 to 4, the capacity is kept constant at a maximum of 1 Gbps. Then, in sections 5 to 7, where the communication environment has deteriorated, the ratio of synchronization signals and error correction codes is increased, and the proportion of data is reduced to decrease the transmission channel capacity. In section 5, the transmission capacity is set to 1 / 2 of that of sections 1 to 4 (500 Mbps), in section 6, to 1 / 4 (250 Mbps), and in section 7, to 1 / 8 (250 Mbps).

[0057] For example, even if the frequency bandwidth switching control unit 31 controls the frequency bandwidth, if wireless communication cannot be maintained and the connection is lost, the control unit can increase the preamble to facilitate wireless synchronization, thereby reducing the communication channel capacity used for data communication, shortening the wireless disconnection time, and accelerating reconnection.

[0058] The repetitive transmission switching control unit 33 controls the number of repetitive transmissions by referring to the number of repetitive transmissions 54 in the control table 50. As shown in Figure 5, in sections 1 to 4, the control is set so that repetitive transmission is not performed. Then, in section 5, the control is set so that transmission is performed twice per frame, in section 6 four times, and in section 7 eight times.

[0059] The MIMO antenna switching control unit 34 controls the number of MIMO antennas by referring to the number of MIMO antennas 55 in the control table 50. In sections 1 to 4, transmission is performed with all antennas; in section 5, transmission is performed with half of the antennas; in section 6, transmission is performed with 1 / 4 of the antennas; and in section 7, transmission is performed with 1 / 8 of the antennas. This aims to concentrate the transmission power on fewer antennas and increase the reception level.

[0060] In this radio, in response to communication quality, the frequency bandwidth is first controlled, then the channel capacity is controlled if maintaining communication is still difficult, the number of repeated transmissions is controlled if maintaining communication is still unstable, and finally the number of MIMO antennas is controlled.

[0061] Specifically, in the control table 50, the frequency bandwidth, communication channel capacity, number of repeated transmissions, and number of MIMO antennas may be controlled for each row of the communication quality, or the frequency bandwidth may be controlled first from section 1 to section 7 for each column of the control table 50, and then the communication channel capacity, number of repeated transmissions, and number of MIMO antennas may be controlled.

[0062] Furthermore, the system may be configured to control multiple items in combination. If the communication environment improves, the settings may be restored to their original values ​​in the following order: MIMO antenna count, repetition count, channel capacity, and frequency bandwidth.

[0063] [Example Configuration of this Wireless Communication System: Figure 6] An example configuration of this wireless communication system will be explained using Figure 6. Figure 6 is an explanatory diagram showing an example configuration of this wireless communication system. In the example configuration of Figure 6, two radios, A and B (both radios 10), with the same configuration, communicate with each other, and each radio 10 is equipped with four MIMO antennas. In addition, a wireless communication maintenance control unit 16a equipped with a communication quality measurement unit 21 is provided as the wireless communication maintenance control unit 16.

[0064] Then, as described above, the switching control units 31 to 34 of the wireless communication maintenance control unit 16a control the frequency bandwidth, communication capacity, number of repetitions, and number of MIMO antennas based on the communication quality values ​​from the communication quality measurement unit 21. Alternatively, instead of the wireless communication maintenance control unit 16a, the system may be configured to include a wireless communication maintenance control unit 16b that calculates the amount of attenuation of received power and performs the respective controls.

[0065] [Effects of the Embodiment] This wireless device is a wireless device that transmits and receives signals in opposite directions, and is equipped with a frequency bandwidth switching control unit 31 that keeps the maximum transmission power constant and changes the frequency bandwidth of the transmission signal and the transmission power per unit frequency bandwidth in conjunction with the change in the communication environment in order to maintain wireless communication. Therefore, even if the communication environment deteriorates further from the state in which the transmission power is fixed and the device is operating at the maximum frequency bandwidth, it has the effect of being able to maintain communication by narrowing the frequency bandwidth and increasing the transmission power per unit frequency bandwidth.

[0066] Furthermore, according to this wireless device, in addition to the above configuration, the frequency bandwidth switching control unit 31 controls the communication channel capacity to remain constant if the deterioration of communication quality is within a certain range, and increases the frequency bandwidth as the communication environment deteriorates. Therefore, if the deterioration of communication quality is within a certain range, it prevents a reduction in communication speed, and even if the communication environment deteriorates further, it has the effect of being able to continue wireless communication.

[0067] Furthermore, this radio has the added benefit of being able to maintain communication even more effectively, as it includes a communication channel capacity switching control unit 32 that controls the communication channel capacity in response to changes in the communication environment after controlling the frequency bandwidth, a repeat transmission switching control unit 33 that controls the number of repeat transmissions, and a MIMO antenna switching control unit 34 that controls the number of MIMO antennas.

[0068] Furthermore, this wireless communication system uses two radio units, one for transmitting and the other for receiving, and they transmit and receive signals in a two-way communication system. The transmitting and receiving radio units maintain wireless communication by performing the same control in response to changes in the communication environment, so even if the communication environment deteriorates, communication can be maintained.

[0069] The present invention is suitable for wireless devices and wireless communication systems that can maintain wireless communication even when the communication environment changes due to precipitation or other factors.

[0070] 1...This radio, 7...Conventional radio, 11, 71...Antenna, 12, 72...Transmitter, 13, 73...Receiver, 14, 74...Modulation unit, 15, 75...Demodulation unit, 16...Wireless communication maintenance control unit, 21...Communication quality measurement unit, 22...Received power measurement attenuation calculation unit, 31...Frequency bandwidth switching control unit, 32...Communication channel capacity switching control unit, 33...Repetitive transmission switching control unit, 34...MIMO antenna switching control unit, 50...Control table, 51...Communication quality, 52...Frequency bandwidth, 53...Communication channel capacity, 54...Number of repetitive transmissions, 55...Number of MIMO antennas, 76...Adaptive modulation unit

Claims

1. A wireless device for two-way transmission and reception, having a frequency bandwidth control unit that changes the frequency bandwidth of the transmitted signal in response to changes in the communication environment to maintain wireless communication, and transmits at a constant maximum transmission power, thereby controlling the frequency bandwidth and the transmission power per unit frequency bandwidth in conjunction.

2. The radio according to claim 1, further comprising a channel capacity control unit that changes the channel capacity of the transmitted data signal in accordance with the change in the communication environment after the frequency bandwidth has been changed.

3. The radio according to claim 1, which has a repeat transmission control unit that changes the number of times the same radio frame is transmitted in accordance with the change in the communication environment after the frequency bandwidth has been changed.

4. The radio according to claim 1, which has an antenna control unit that changes the ratio of the number of antennas used for transmission in accordance with changes in the communication environment after the frequency bandwidth has been changed.

5. The wireless device according to claim 1, which has a communication quality measuring unit that measures the communication quality of a received signal and determines changes in the communication environment.

6. The radio device according to claim 1, which has a received power measurement and attenuation calculation unit that calculates the amount of attenuation of radio waves in the transmission line from a change in the level of received power and determines a change in the communication environment.

7. A wireless communication system for two-way communication, wherein the wireless device described in claim 2 is used for both transmitting and receiving, and the transmitting wireless device and the receiving wireless device maintain wireless communication by performing the same control in response to changes in the communication environment.

8. A wireless communication system for two-way communication, wherein the wireless device described in claim 3 is used for both transmission and reception, and the transmitting wireless device and the receiving wireless device maintain wireless communication by performing the same control in response to changes in the communication environment.

9. A wireless communication system for sending and receiving signals in opposite directions, wherein the wireless device described in claim 4 is used for both transmitting and receiving, and the transmitting wireless device and the receiving wireless device maintain wireless communication by performing the same control in response to changes in the communication environment.

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