JP2000031883A - Radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely insure data communication with low power even under a bad condition and to reduce the cost of the entire system by increasing and decreasing the number of channels, transmission cells, etc., in accordance with the communication state of a radio link due to rainfall, etc. SOLUTION: A controller 11 of a master station 1 controls a multiplexing device 3 and increases and decreases the number of channels that are subjected to time division multiplexing in accordance with the communication state of a radio link RF. The transmission rate of a multiple signal to be outputted to a modulator 5 is made 1/several, a needed exclusive band is made narrow and the density of frequency power is relatively made high by reducing the number of channels if a communication state is bad. A channel to be multiplexed is selected, based on a flag showing priority that is attached to the header information of each channel data. It is possible to surely transmit a channel that surely selects high SN ratio by means of the same transmission power and a high output is not needed uselessly even when a communication state is bad by adjusting the number of channels of transmission data in accordance with the communication state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication system, and more particularly, to a radio communication system connecting a master station and a plurality of slave stations.

[0002]

2. Description of the Related Art The demand for a high-speed network has been increasing with the rapid spread of the Internet connection and the like in recent years. However, high-speed lines provided by wired networks are still expensive for ordinary consumers, and local wireless communication networks capable of providing lower-cost services are being actively researched and developed. . This local wireless network uses quasi-millimeter waves (3 GHz to 30 GHz).
z), and also in the millimeter wave band (30 GHz to 300 GHz)
Is used to provide a high-speed two-way data communication line from a telephone exchange to a plurality of subscribers in a predetermined area, or to provide a local videophone service. . As shown in FIG. 9, in such a local wireless network (wireless communication system), a plurality of slave stations 100 installed in a general home or the like are wirelessly connected to a master station 200 having a radially communicable area 71 (cell). Connected via a line. In a high frequency band such as a quasi-millimeter wave band or a millimeter wave band, the line-of-sight distance is limited to about several kilometers, and the size of the cell 71 is also in accordance therewith.
To cover a relatively large area such as an urban area,
00 is provided for the area. Each parent station 200
Between the stations, a central office 72 installed in a telephone exchange or the like is connected via a high-speed line 73 such as an optical fiber, and communicates with a slave station 100 in another cell 71 via the master station 200 and the central office 73. It is also possible to do.

For example, as shown in a functional block diagram of FIG. 10, a transmitting side of each of a plurality of slave stations 100 in the wireless communication system includes an interface device 101, a modulator 102, and a modulator 102 which are connected to the outside. A frequency conversion device 103 for converting the modulated signal output from the above to an intermediate frequency for transmission, a frequency conversion device 104 for converting the intermediate frequency signal output from the frequency conversion device 103 to a radio frequency for transmission, A transmission high-output solid-state amplifier 105 for amplifying a wireless signal output from the frequency converter 104, a diplexer 106, and an antenna 107 for both transmission and reception are provided. The above slave station 1
00, a low-noise amplifier 108 for amplifying a radio signal received via the antenna 107 and the diplexer 106, and a frequency converter for converting a signal output from the low-noise amplifier to an intermediate frequency for reception. Apparatus 10
9, a tuner 110 and a demodulation device 111. On the other hand, a receiving antenna 201 is provided on the receiving side of the master station 200 connected to the plurality of slave stations 100 by a radio line using a microwave, quasi-millimeter wave, or millimeter wave band.
A low-noise amplifier 202 for amplifying a radio signal supplied from an antenna 201, a frequency converter 203 for converting a signal output from the low-noise amplifier 202 to an intermediate frequency for reception, a distributor 204, and a slave station. A plurality of tuners 205 for tuning to the intermediate frequency for reception in synchronization with 100
And a demodulation device 206 provided for each tuner 205
And an interface device 207 connected to the outside. The transmitting side of the master station 200 includes a plurality of modulators 208 for modulating transmission data supplied from the interface device 207, and a frequency for converting a signal output from the modulator 208 to an intermediate frequency for transmission. A converter 209, a synthesizer 210, a frequency converter 211 for converting a signal from the synthesizer 210 into a radio frequency for transmission, a transmission high-power solid-state amplifier 212 for amplifying an output of the frequency converter 211, Trust antenna 21
3 are provided.

In the above wireless communication system, the slave station 10
In the uplink where a signal is transmitted from 0 to the master station 200, first, transmission data supplied from an external network or the like is
The signal is supplied to the modulation device 102 via the interface device 101. The transmission data is converted into a modulation signal having a predetermined occupied frequency bandwidth BW1 by the modulator 102. The modulated signal output from the modulator 102 is converted to an intermediate frequency for transmission by the frequency converter 103 and further converted to a radio frequency for transmission by the frequency converter 104. The radio signal output from the frequency converter 104 is transmitted by the high-power solid-state amplifier 10 for transmission.
After being amplified to the required transmission output level by 5, it is supplied to the transmission / reception antenna 107 and transmitted to the master station 200. Communication wave RF transmitted from antenna of slave station 100
−U is received by the receiving antenna 201 of the master station 200,
After being amplified by the receiving low-noise amplifier 202, the signal is converted into a receiving intermediate frequency by the frequency converter 203.
The signal of the intermediate frequency for reception is distributed by the distributor 204 and supplied to the tuner 205 group. The intermediate frequency for reception is selected by a tuner 205 tuned to the slave station 100, and is supplied to demodulators 206 provided for the respective tuners 205. The modulated wave demodulated by the demodulator 206 returns to the original transmission data, is connected to an external network via the interface device 207, or becomes transmission data to another slave station.

In a downlink where a signal is transmitted from the master station 200 to the slave station 100, first, transmission data from an external network or another slave station is transmitted to the interface device 207.
Is supplied to the modulation device 208 via the. The modulator 208 converts the transmission data into a predetermined occupied frequency bandwidth BW.
2 modulated signals. The modulated signal output from the modulator 208 is converted by the frequency converter 209 into an intermediate frequency for transmission, and the combiner 210 combines the signal with another intermediate frequency signal for transmission. The signal of the intermediate frequency synthesized by the synthesizer 210 is further converted to a radio frequency for transmission by a frequency converter 211 and amplified to a required transmission output level by a high-power solid-state amplifier 212 for transmission. And transmitted to the slave station 100. Transmission antenna 2 of master station 200
The communication wave RF-D transmitted from the mobile station 13 is received by the transmission / reception antenna 107 of the slave station 100, and is transmitted to the diplexer 10.
6 separates from the transmission signal. The reception signal output from the diplexer 106 is amplified by the reception low-noise amplifier 108, and is converted by the frequency converter 109 into a signal of the reception intermediate frequency. The tuner 110 selects the signal of the intermediate frequency for reception and supplies the signal to the demodulation device 111. The modulated wave demodulated by the demodulation device 111 returns to the original transmission data, and the interface device 1
01 is connected to an external network or the like.

In the above-described radio communication system, since a high frequency band such as a quasi-millimeter wave or a millimeter wave is used, a communication wave RF-U communicated between a master station and a slave station due to, for example, rainfall. , RF-D are attenuated. In order to perform highly reliable wireless communication, the line design of the wireless system is important. Of course, besides rain, the above communication waves RF-U, RF
−D undergoes various amplifications and attenuations. For example, if the transmission power per communication wave from the transmission high-output solid-state amplifier 105 is Pt1, the transmission power is uniformly distributed to the occupied frequency bandwidth BW1 of the communication wave RF-U, and the power density is Pt1.
/ BW1. The communication wave RF-U is amplified by the transmitting antenna 107 with the directivity gain Gat, and then a distance attenuation lossD × d1 proportional to the square of the communication distance.
Attenuated by ² . At the same time, if there is rain or the like, it is attenuated by the rain attenuation lossR × d1 proportional to the communication distance. When receiving the communication wave RF-U, the signal is amplified by the receiving antenna 201 with the directional gain Gar, and then input to the receiving low-noise amplifier 202. Here, for example, in the case of 26 GHz radio in the quasi-millimeter wave band, the distance attenuation amount is about 100 dB at a point 250 m away from the master station 200, about 106 dB at a point 500 m away, and about 112 dB at a point 1 km away. . Further, the rain attenuation amount is, for example, 100 m which is generated for about 7 minutes a year when a 26 GHz radio in the quasi-millimeter wave band is used in Japan.
If it corresponds to m / h, it is about 20 dB / km. From these amplifications and attenuations, the power density P at the input of the low-noise amplifier 202 for reception of the communication wave RF-U is obtained.
D1 is PD1 = (Pt1 / BW1) × Gat / (lossD × d1
² ) / (lossR × d1) × Gar By the power density PD1 and the signal-to-noise ratio S / N determined by the power density NP of the noise at the input of the reception low noise amplifier 202, the communication wave RF-
The reliability of U can be evaluated. Signal to noise ratio S /
N can be represented by the following equation. S / N = PD1 / NP = (Pt1 / BW1) × Gat / (lossD × d1 ² ) / (lossR × d1) × Gar / NP The power density NP of the noise at the input of the receiving low noise amplifier 202 is It is determined by the absolute temperature and noise figure of the amplifier. By modifying the above equation, the signal-to-noise ratio S / N can be expressed as follows. S / N = constant × Pt1 / (BW1 × (lossD × d1 ² )
× (lossR × d1)) That is, the signal-to-noise ratio S / N is proportional to the transmission power Pt1, inversely proportional to the occupied frequency bandwidth BW1, inversely proportional to the square of the distance d1, and if there is rainfall, Rainfall lossR
And the attenuation is inversely proportional to the distance d1. The communication wave R
The same applies to FD.

If the signal-to-noise ratio S / N is larger than a threshold determined by the modulation scheme, highly reliable communication is possible. For example, four-phase modulation (QPSK)
In the case of, if the signal-to-noise ratio S / N is 14 dB or more,
The error rate is less than 0.0001%. In the wireless system, the slave stations 100 are scattered in the cell 71,
The distance to 0 differs for each slave station 100. For example, when the slave station A is installed at a distance of 250 m (distance d1) from the master station 200 and the slave station B is installed at a distance of 1 km (distance d2) from the master station 200 farther from the slave station A, If the distance attenuation D1 of A is 100 dB, the distance is quadrupled, so that the distance attenuation D2 of the slave station B is 112 dB.
B. Also, the rain attenuation R1, R2 is the distance d1,
d2 is approximately proportional to the amount of rainfall. When the amount of rainfall is 100 mm / h and the frequency of the communication wave is 26 GHz, the attenuation is about 5 dB at a distance of 250 m and about 20 dB at a distance of 1 km. The amount of attenuation of the communication wave to the slave station is 2 in clear weather and in heavy rain.
0 dB = 100 times the change.

[0008] Thus, the slave station 10 in the same cell 71
Even when communication is performed with 0, the signal-to-noise ratio S / N greatly varies depending on the distance between each slave station 100 and the master station 200 and environmental conditions such as rainfall. For this reason, the transmission power and the bandwidth of the communication wave in the wireless communication system are assumed to be the worst conditions, for example, when the communication is performed between the farthest slave station 100 and the master station 200 during the maximum rainfall. Is determined. For example, in order to obtain a communication speed of 1.5 Mbps, a frequency bandwidth of about 1 MHz is required in the QPSK modulation method, but in a quasi-millimeter wave band of 26 GHz, a horn having a directivity gain of about 14 dBi is provided to the master station 200. A parabolic antenna with a gain of about 34 dBi is used for the
When performing highly reliable communication with a maximum of 10 slave stations 100 at a distance of 100 km / h in a heavy rain of about 100 mm / h, the slave station 10
The high power solid-state amplifier 105 for transmission of 0 has a maximum power of 1
A transmission power of about 1 m is required for the transmission high-output amplifier 212 of the master station 200.

[0009]

However, the quasi-millimeter-wave and millimeter-wave transmission high-output solid-state amplifiers having the maximum power as described above are expensive and consume large power. There was a problem of rising. Furthermore, in areas where annual rainfall is relatively large and rainfall fluctuations are large, such as in Japan, if the transmission power margin is included in the design at the time of design so that communication is not interrupted during the worst rainfall, almost all year round In this period, the operation was performed with very low power relative to the maximum power, resulting in a wasteful system. The present invention improves a wireless communication system in order to solve such problems in the conventional technology. For example, when wideband communication cannot be expected due to the weather or the like, a channel is set according to a communication state of a wireless link. It is an object of the present invention to provide a wireless communication system capable of reliably communicating digital data by increasing or decreasing the number or the number of cells to be transmitted.

[0010]

To achieve the above object, the invention according to claim 1 comprises a multiplexing means for multiplexing digital data from one or more digital data channels, and the multiplexing means. A modulator for superimposing the digital data multiplexed by the multiplexing means on a communication wave communicated via a wireless link, and a demodulator for extracting the digital data from the communication wave communicated via the wireless link And a multiplexing / demultiplexing unit for multiplexing / demultiplexing the digital data demodulated by the demodulator, the multiplexing unit multiplexes the digital data according to the communication state of the radio link. The wireless communication system is characterized by adjusting a transmission rate of digital data to the modulator. In addition, the invention according to claim 2 is based on claim 1 described above.
In the wireless communication system described in (1), the gist is that the transmission rate is adjusted by increasing or decreasing the number of digital data channels multiplexed by the multiplexing means. According to a third aspect of the present invention, in the wireless communication system according to the first aspect,
The digital data is transmitted at a predetermined frame period in the digital data channel, and the multiplexing means transmits the digital data at a rate corresponding to an amount of data selected for each frame period of the digital data. The gist is that the transmission rate is adjusted by performing the conversion. According to a fourth aspect of the present invention, in the wireless communication system according to the first aspect, the digital data channel is a virtual channel formed by asynchronously transmitting fixed-length cells, and The gist is that the transmission rate is adjusted by the device changing the transmission amount of the cells to the modulator. According to a fifth aspect of the present invention, in the wireless communication system according to any one of the first to fourth aspects, the multiplexing means uses the control channel provided on the wireless link to perform the multiplexing. The gist is that the transmission rate of the digital data multiplexed by the means is transmitted to the demultiplexing means.

According to a sixth aspect of the present invention, in the wireless communication system according to any one of the first to fifth aspects, the communication state of the wireless link is determined based on rainfall. This is the gist. According to a seventh aspect of the present invention, in the wireless communication system according to any one of the first to fifth aspects, a communication state of the wireless link is determined based on a signal-to-noise ratio of the communication wave. Is the gist. According to an eighth aspect of the present invention, in the wireless communication system according to any one of the first to seventh aspects, the modulator is controlled according to a communication state of the wireless link, and communication of the communication wave is performed. The gist is to change the band or the modulation method. According to the wireless communication system of any one of claims 1 to 8, even when the communication state of the wireless link changes due to, for example, rainfall, the number of channels of the digital data multiplexed by the multiplexing means is reduced. The transmission rate of the multiplexed signal transmitted to the modulator is increased or decreased, by performing speed conversion according to the data amount selected for each frame, or by changing the number of cells transmitted to the modulator. Since the adjustment is made according to the communication state of the wireless link, communication via the wireless link can be reliably performed. Therefore, it is not necessary to use an expensive transmission amplifier or the like in order to maintain the reliability of communication, and the cost of the entire system can be reduced.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
This embodiment is a specific example of the present invention.
It is not intended to limit the technical scope of the present invention. Here, FIG. 1 is a diagram showing a schematic configuration of a wireless communication system according to an embodiment of the present invention, FIG. 2 is a diagram for explaining a configuration of a master station and a slave station of the wireless communication system, and FIG. FIG. 4 is a diagram for explaining the operation of the wireless communication system, and FIG. 4 is a time chart for specifically explaining a multiplexing process in the wireless communication system. The wireless communication system according to the present embodiment is, for example, as shown in FIG.
And the slave station 2 are realized as a wireless communication system for performing two-way wireless communication via the wireless link RF.
As shown in FIGS. 1 and 2, the master station 1 and slave station 2 in the wireless communication system each include multiplexing devices 3 and 4 for multiplexing digital data from a plurality of digital data channels. Modulators 5 and 6 for superimposing the digital data multiplexed by the devices 3 and 4 on a communication wave communicated via the radio link RF;
Demodulators 7 and 8 for extracting the digital data from the communication wave communicated via the radio link RF, and demultiplexers 9 and 10 for demultiplexing the digital data demodulated by the demodulators 7 and 8. And control devices 11 and 12 for controlling the modulators 5 and 6, demodulators 7 and 8, multiplexers 3 and 4, and demultiplexers 9 and 10. Then, as shown in FIGS. 3 (a) to 3 (c) or FIGS. 4 (a) to 4 (c), the control devices 11 and 12 control the multiplexing devices 3 and 3 in accordance with environmental conditions such as rainfall.
By changing the number of channels of digital data to be multiplexed by 4, the transmission rate of the multiplexed signal sent to the modulators 5 and 6 is adjusted.

Hereinafter, the details of the wireless communication system will be described by taking as an example a case where data is transmitted from the master station 1 to the slave station 2. In the above wireless communication system, for example, three channels CH1, CH2,
The digital data channel corresponding to CH3 is terminated by a T1 framer 14 for each channel via an I / F device 13 provided on the master station 1 side. Here, the T1 line is a serial communication line capable of accommodating 24 communication channels of 64 kbps. For example, if each channel is an audio signal, the T1 line is sampled at a frame period of 125 μsec and quantized by 8 bits. It is possible to transmit. In the T1 framer 14, T1
Effective data corresponding to each channel is extracted from the frame and output to the multiplexer 3. In the multiplexer 3, the digital data input from the plurality of T1 framers 14 are time-division multiplexed and output as one multiplexed signal. That is, each channel CH1, CH2,
The time slot of CH3 (here, the frame period) is
For example, as shown in FIG.
It is changed to 67 μsec, and data of three channels is temporally arranged within one frame period (125 μsec) of the multiplexed signal. Then, the multiplexed signal output from the multiplexing device 3 is supplied to the modulator 5 and superimposed on the carrier. The modulation method at this time includes, for example, QPSK or 16Q
AM or the like is used. The digital data modulated by the modulator 5 is transmitted to the demodulator 8 in the slave station 2 using the radio link RF, and the demodulator 8 demodulates the digital data. The digital data demodulated by the demodulator 8 is demultiplexed by the demultiplexer 10 and supplied to each T1 framer 14.

By the way, when multiplexing a plurality of (three) data channels having the same transmission rate as described above, a transmission rate that is a plurality of (3) times is required as shown in FIG. When the signal is output to the modulator 5 as it is, the occupied bandwidth of the communication wave transmitted via the radio link RF is relatively widened, and the power density of the communication wave is relatively reduced. However, when the communication state of the wireless link RF deteriorates due to environmental conditions such as rainfall, it may be difficult to reliably perform communication at a relatively low power density. Therefore, in the wireless communication system according to the present embodiment, the control device 11 controls the multiplexer 3 in accordance with the communication state of the wireless link RF due to environmental conditions such as rainfall, for example, to perform time-division multiplexing. Change the number. For example, when the communication state of the wireless link RF is worse than usual, as shown in FIG. 3B, the multiplexing device 3 controls two channels CH1 and CH2 of the three channels under the control of the control device 11. Multiplexing is performed only for CH2. That is, as shown in FIG.
The time slots of channels CH1 and CH2 are 125
μsec is changed to 62.5 μsec and multiplexed into one frame of the multiplexed signal. Further, when the communication state is poor, only one channel CH1 of the three channels is selected and output to the modulator 5 as shown in FIGS. 3 (c) and 4 (c).

As a result, the transmission rate of the multiplexed signal output to the modulator 5 is 2/3, 1/3 as compared with the case where all three channels are multiplexed, and the required occupied bandwidth is reduced. It becomes relatively narrow. Therefore, when the same transmission power is used, as shown in FIG. 3, the frequency power densities relatively increase, and even when the communication state of the radio link RF is poor due to environmental conditions such as rainfall. , Communication is performed reliably. Here, a flag indicating a priority is added as header information to the digital data of each channel, and the control device 11 selects a channel to be multiplexed by the multiplexer 3 based on the priority. . The change in the communication state due to the rainfall is determined based on, for example, the relationship between the rainfall measured in the past and the signal attenuation ratio, and the current rainfall measured by the rain gauge. The number of digital data channels multiplexed by the multiplexer 3 is the control channel C.
It is transmitted to the demultiplexing device 10 of the slave station 2 using C. The demultiplexer 10 demultiplexes digital data based on control information transmitted via the control channel CC. In the wireless communication system, the number of channels of digital data transmitted via a wireless link is adjusted according to the communication state due to rainfall or the like as described above. If the number of channels is increased or decreased, if the transmission power is constant, the occupied band increases and decreases, and the signal-to-noise ratio decreases and increases. For this reason, if the number of channels is reduced when the communication condition deteriorates, the occupied bandwidth required is reduced accordingly, and a high signal-to-noise ratio can be secured with the same transmission power.
Therefore, the selected channel is transmitted reliably. As a result, it is not necessary to use an expensive high-power transmission amplifier to perform reliable communication under the worst rain conditions,
The cost of the entire system can be reduced.

[0016]

In the above embodiment, the communication state is determined based on environmental conditions such as rainfall. However, the present invention is not limited to this. For example, the communication state may be determined by directly measuring the signal-to-noise ratio. Alternatively, the control device 11 may temporally change according to a predetermined schedule based on past signal-to-noise ratio data or the like. Such a wireless communication system is also an example of the wireless communication system in the present invention. Further, in the above embodiment, the channel to be communicated via the wireless link RF is selected according to the priority added to the data of each channel.
The present invention is not limited to this, and for example, a preset channel may be selected. It should be noted that, in addition to not performing transmission at all, a channel that is not selected is provided, for example, by providing a buffer in the device, storing it in the buffer, and transmitting it via the radio link RF after the communication state is restored. Alternatively, transmission may be performed via another communication path such as a wired line. Such a wireless communication system is also an example of the wireless communication system in the present invention. In the above embodiment, the communication speed of the communication wave communicated via the wireless link RF is changed by adjusting the transmission rate to the modulator 5 according to the communication state of the wireless link RF. However, it is also possible to perform the adjustment by changing the modulation method of the modulator 5. If communication cannot be reliably performed even if the number of channels is changed, for example, the modulation of the modulator 5 is performed. The modulation method may be changed. Such a wireless communication system is also an example of the wireless communication system in the present invention.

In the above embodiment, the number of channels of digital data communicated via the radio link is changed according to the communication state. However, the present invention is not limited to this. For example, as shown in FIGS. Alternatively, the transmission rate of the multiplexed signal sent to the modulators 5 and 6 may be adjusted by converting the speed of each frame of a certain channel. Here, FIG. 5 is a diagram showing a schematic configuration of a wireless communication system according to one embodiment of the present invention, FIG. 6 is a diagram for explaining an operation of the wireless communication system according to the above embodiment, and FIG. 6 is a time chart for specifically explaining multiplexing in the wireless communication system according to the first embodiment. In the example of FIG. 5, it is assumed that only one channel is communicated by the wireless communication system. The wireless communication system according to one embodiment of the present invention has substantially the same configuration as the wireless communication system according to the above-described embodiment, except that the multiplexers 3 and 4 have an input / output speed conversion buffer function. Is used. In the wireless communication system according to the above embodiment, digital data of each frame supplied via the I / F device 13 and the T1 framer 14 is temporarily stored in a buffer provided in the multiplexer 3.
Therefore, in the wireless communication system according to the above embodiment, when the communication state of the wireless link RF deteriorates, the control device 1
In accordance with the control of 1, the multiplexer 3 selects only a part of the 24 lines accommodated in T1 and performs speed conversion. As a result, for example, as shown in FIGS. 6A and 6B or FIGS. 7A and 7B, the transmission rate to the modulators 5 and 6 is relatively small, and the occupied bandwidth of the communication wave is reduced. Narrowed,
As a result, the power density increases even with the same transmission power. As a result, even when the communication state deteriorates, it is possible to reliably perform communication.

Further, in the above embodiment, the T1 line is used for transmitting digital data.
It is also possible to perform transmission by ATM (asynchronous transfer mode) using fixed-length cells of bytes. In this case, the digital data channel is formed by a virtual channel, and the multiplexers 3 and 4 are provided with an ATM interface. The cells in the ATM are supplied asynchronously to the multiplexers 3 and 4. For example, when the communication state of the radio link RF is good and broadband communication can be expected, as shown in FIG. Since the cells are received densely and the data input to the modulators 5 and 6 after multiplexing are transmitted at a high clock rate corresponding to a wide band, the number of ATM cells per unit time is relatively large. Become. In a situation where the communication state of the radio link RF is not good and the communication band is relatively limited, the number of ATM cells per unit time after multiplexing is small as shown in FIG. Become. Further, when the communication state deteriorates, the number of ATM cells per unit time after multiplexing is reduced as shown in FIG. As described above, according to the wireless communication system according to another embodiment of the present invention, the communication speed can be changed by adjusting the number of ATM cells according to the communication state of the wireless link. A high signal-to-noise ratio can always be ensured by the transmission power. Therefore, the communication speed can be reduced, but the communication can be performed reliably. As a result, it is not necessary to use an expensive high-output transmission amplifier in order to perform reliable communication under the worst rain conditions, and the cost of the entire system can be reduced. Further, in the above-described embodiments and examples, the case where communication is performed from the master station 1 to the slave station 2 has been described.
The present invention can also be applied to a case where communication is performed to a user. Further, the present invention can be applied to not only the case of performing two-way communication but also the case of performing one-way communication. Furthermore, the present invention can be applied to a wireless communication system that performs not only one-to-one communication but also one-to-many communication.

[0019]

According to the radio communication system according to any one of the first to eighth aspects, even when the communication state of the radio link changes due to, for example, rainfall, the digital multiplexed by the multiplexing means. Multiplexing transmitted to the modulator by increasing or decreasing the number of data channels, performing speed conversion according to the amount of data selected for each frame, or changing the number of cells transmitted to the modulator Since the transmission rate of the signal is adjusted according to the communication state of the wireless link, it is possible to reliably perform communication via the wireless link. Therefore, it is not necessary to use an expensive transmission amplifier or the like in order to maintain the reliability of communication, and the cost of the entire system can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining a configuration of a master station and a slave station of the wireless communication system.

FIG. 3 is a diagram illustrating an operation of the wireless communication system.

FIG. 4 is a time chart for specifically explaining a multiplexing process in the wireless communication system.

FIG. 5 is a diagram showing a schematic configuration of a wireless communication system according to an embodiment of the present invention.

FIG. 6 is a diagram for explaining the operation of the wireless communication system according to the embodiment.

FIG. 7 is a time chart for specifically explaining a multiplexing process in the wireless communication system according to the embodiment.

FIG. 8 is a time chart for specifically explaining a multiplexing process in a wireless communication system according to another embodiment of the present invention.

FIG. 9 illustrates an example of a local wireless network.

FIG. 10 is a diagram showing an example of a conventional wireless communication system.

[Explanation of symbols]

 3,4 ... multiplexer 5,6 ... modulator 7,8 ... demodulator 9,10 ... demultiplexer

Claims (8)

[Claims] 1. A multiplexing means for multiplexing digital data from one or more digital data channels, and a communication in which the digital data multiplexed by the multiplexing means is communicated via a radio link. A modulator for superimposing on the wave, a demodulator for extracting the digital data from the communication wave communicated via the radio link, and a demultiplexing means for demultiplexing the digital data demodulated by the demodulator. Wherein the transmission rate of digital data multiplexed by the multiplexing means to the modulator is adjusted according to the communication state of the radio link. Wireless communication system. 2. The wireless communication system according to claim 1, wherein said transmission rate is adjusted by increasing or decreasing the number of channels of digital data multiplexed by said multiplexing means. 3. The digital data is transmitted on the digital data channel at a predetermined frame period, and the multiplexing means according to an amount of data selected for each frame period of the digital data. 2. The wireless communication system according to claim 1, wherein the transmission rate is adjusted by performing speed conversion of the digital data. 4. The digital data channel is a virtual channel formed by asynchronously transmitting fixed-length cells, and the multiplexing device changes the transmission amount of the cells to the modulator. The wireless communication system according to claim 1, wherein the transmission rate is adjusted by: 5. The multiplexing means transmits a transmission rate of digital data multiplexed by the multiplexing means to the demultiplexing means using a control channel provided on the radio link. The wireless communication system according to any one of claims 1 to 4. 6. The wireless communication system according to claim 1, wherein a communication state of the wireless link is determined based on a rainfall amount. 7. The communication state of the wireless link is determined based on a signal-to-noise ratio of the communication wave.
The wireless communication system according to claim 1. 8. The wireless communication according to claim 1, wherein the modulator is controlled according to a communication state of the wireless link to change a communication band or a modulation method of the communication wave. system.