JP2002335201A - Communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate the deterioration of communication quality caused by radio wave attenuation in the case of rainfall without limiting a transmission distance, enlarging an antenna or increasing transmission output in communication equipment to be used for the base station or subscriber station in a fixed radio access system, in which a radio frequency higher than sub-millimeter wave band is used. SOLUTION: This communication equipment is provided with a first radio communication means 22 with which radio communication is enabled in a first frequency band higher than sub-millimeter wave, a second radio communication means 25 with which radio communication is enabled in a second frequency band less liable to attenuation of ratio wave caused by rainfall, a route cut examining means 28 for examining whether a communication route is cut or not, and a radio frequency switching means 27 for selecting one of first and second radio communication means 22 and 25, transmitting/receiving radio signal, preferentially selecting the radio communication means 22 at ordinary time and automatically switching it to the second radio communication means 25 when the cut of the communication route is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device used in a fixed wireless access system and the like, and more particularly, to a communication device provided in a base station and a subscriber station which perform communication using radio waves in a frequency band equal to or higher than a quasi-millimeter wave. Related to the device.

[0002]

2. Description of the Related Art As a system for providing an access service to a network such as an IP (Internet Protocol) network, for example, a fixed wireless access system is used. In a fixed wireless access system, a subscriber station and a base station are connected by a wireless communication line. The subscriber accesses the network from any terminal via the subscriber station and the base station.

By the way, since a very wide band can be secured in a high frequency band above the quasi-millimeter wave,
Frequencies are allocated to fixed wireless access systems and the like that require high-speed transmission. By performing wireless communication in a high frequency band equal to or higher than the quasi-millimeter wave, a very high-speed service can be realized by securing a wide band as a wireless communication line.

[0004] However, when a high frequency band of quasi-millimeter waves or higher is used, attenuation of radio waves is apt to occur due to the effects of rainfall and snowfall, and overcoming quality degradation due to this is greatly excessive. Therefore, in order to ensure communication quality even when radio wave attenuation due to rainfall has occurred conventionally, the transmission distance is limited, the size of the antenna is enlarged, and the transmission output is increased to operate, He had a certain rainfall margin.

[0005]

In the case of wireless communication using a frequency in the quasi-millimeter wave band, if the transmission distance is shortened, the influence of radio wave attenuation due to rainfall or snowfall can be suppressed. However, if the transmission distance is limited to a short distance, the area in which the wireless communication service can be provided becomes narrow, and it becomes difficult to provide the service in the entire required area.

Further, if the transmission distance is shortened to obtain a large rainfall margin, the radio communication line is not degraded due to radio wave attenuation even during rainfall or snowfall or when the weather is fine. In this case, the transmission distance is unnecessarily limited even though a communication error does not occur, and the area in which a service can be provided becomes narrower than the original capability of the communication system.

Further, even if the transmission distance is not limited, if the size of the transmission antenna or the reception antenna is increased or the transmission output is increased, the influence of the attenuation of radio waves due to rainfall or the like can be reduced. However, in the case of the fixed wireless access system, it is necessary to install the subscriber station directly at the user's house. Therefore, increasing the size of the antenna of the subscriber station is not preferable in appearance and leads to an increase in construction cost.

Further, in a radio apparatus using a high frequency such as a millimeter wave band, if the transmission output is increased, there is a high possibility that a commercially available mass-producible component cannot be used, and the cost of the component itself and adjustment of a high-frequency circuit are reduced. Such costs are increased, leading to an increase in the price of the equipment of the subscriber station.

The present invention relates to a communication device used for a base station or a subscriber station of a fixed radio access system using a radio frequency higher than the quasi-millimeter wave band, which limits the transmission distance, increases the size of the antenna, and increases the transmission output. An object of the present invention is to compensate for communication quality degradation due to radio wave attenuation at the time of rain without increasing the number of communications.

[0010]

A communication device is provided in a base station or a subscriber station for performing wireless communication between a fixed base station and at least one subscriber station. A first wireless communication means capable of performing wireless communication with a partner station using a first frequency band having a frequency equal to or higher than a quasi-millimeter wave, and a radio wave generated by rain having a lower frequency than the first frequency band. Whether or not the communication path is interrupted between the second wireless communication means capable of performing wireless communication with the other station using the second frequency band in which the attenuation of the communication path is small, and the communication partner or the relay device on the communication path For transmitting and receiving wireless signals by selectively using one of the first wireless communication means and the second wireless communication means, and performing the first wireless communication means in a normal state. Is selected preferentially, and the route cutoff inspection means is selected. When detecting the interruption of the communication path is characterized by comprising a radio frequency switching means for automatically switching to said second wireless communication means.

According to the first aspect, transmission and reception of a radio signal can be performed by selectively using either one of the first radio communication means and the second radio communication means. When the first wireless communication means is used, a high frequency of quasi-millimeter waves or higher is used, so that high-speed wireless transmission can be realized. On the other hand, the second
Since the wireless communication means uses a lower frequency than the first wireless communication means, the transmission speed is low, but the influence of radio wave attenuation due to rainfall is small.

The radio frequency switching means preferentially selects the first radio communication means in a normal state. Then, when radio wave attenuation due to rainfall occurs and normal communication cannot be performed due to a communication error, the route cutoff inspecting unit determines that the communication route is cutoff. When the communication path is interrupted, the radio frequency switching means automatically selects the second radio communication means.

When communication is performed using the second wireless communication means, communication can be continued without attenuation of radio waves even during rainfall or snowfall. Of course, the available transmission rate is lower than in the case of using the quasi-millimeter wave band, but the occurrence of a state in which communication is not possible is avoided. In other words, when the communication quality is degraded by rainfall, it is necessary to reduce the communication frequency by lowering the communication frequency. Therefore, it is necessary to limit the transmission distance, enlarge the antenna, and increase the transmission output in order to increase the rainfall margin in the quasi-millimeter wave band. Absent.

The frequency used by the second wireless communication means is, for example, an ISM (Industrial, Scientific and Medical: Industrial, Scientific and Medical) which does not require a license assigned to the 2.4 GHz band.
ificand Medical) bands are preferred. According to a second aspect of the present invention, in the communication device of the first aspect, the route cutoff inspection unit periodically transmits a test packet to and from a communication partner or a relay device on a communication route,
When the packet cannot be received within a predetermined time, it is recognized that the communication path is interrupted.

According to the second aspect, similarly to the routing protocol in the router, the interruption of the communication path is recognized by checking whether or not a test packet transmitted periodically is received. Therefore, the switching of the frequency can be controlled using the function of the router. A communication device provided in the base station or the subscriber station for performing wireless communication between a fixed base station and at least one subscriber station, wherein the communication device has a frequency of a quasi-millimeter wave or higher. A first wireless communication unit capable of performing wireless communication with a partner station using the first frequency band; and a second frequency band having a lower frequency than the first frequency band and having less attenuation of radio waves due to rainfall. A second wireless communication unit capable of performing wireless communication with a partner station using the first wireless communication unit, a reception level detection unit for detecting a level of a signal received by the first wireless communication unit, and the first wireless communication unit Means and the second wireless communication means are selectively used to transmit and receive wireless signals, and in a steady state, the first wireless communication means is preferentially selected and detected by the reception level detection means. If the reception level drops abnormally Characterized in that a radio frequency switching means for automatically switching to said second wireless communication means.

According to the third aspect, the transmission and reception of the radio signal can be performed by selectively using one of the first radio communication means and the second radio communication means. When the first wireless communication means is used, a high frequency of quasi-millimeter waves or higher is used, so that high-speed wireless transmission can be realized. On the other hand, the second
Since the wireless communication means uses a lower frequency than the first wireless communication means, the transmission speed is low, but the influence of radio wave attenuation due to rainfall is small.

The radio frequency switching means preferentially selects the first radio communication means in a normal state. Then, when the radio wave attenuation occurs due to the rainfall and the received signal level of the first wireless communication means decreases, the wireless frequency switching means automatically selects the second wireless communication means. When communication is performed using the second wireless communication means, communication can be continued without attenuation of radio waves even during rainfall or snowfall. Of course, the available transmission rate is lower than in the case of using the quasi-millimeter wave band, but the occurrence of a state in which communication is not possible is avoided.

That is, when the communication quality is degraded due to rainfall, the problem is dealt with by lowering the communication frequency. Therefore, in order to increase the rainfall margin in the quasi-millimeter wave band, the transmission distance is limited, the antenna is enlarged, the transmission output is increased, and the like. No need to do. According to a fourth aspect of the present invention, in the communication device of the third aspect, the radio frequency switching means suppresses or shuts off a radio transmission output of the first radio communication means when the second radio communication means is selected. Features.

According to the fourth aspect, when the own station switches to a lower frequency, the wireless transmission output of the first wireless communication means is suppressed or cut off, so that the reception level of the quasi-millimeter wave band also decreases at the partner station. . Therefore, when the configuration of the communication device of the other station is the same as that of the own station, the other station automatically changes the frequency in accordance with the change of the frequency of the own station.

According to a fifth aspect of the present invention, in the communication device of the third aspect, the radio frequency switching means selects the first wireless communication means again when a predetermined time has elapsed after the selection of the second wireless communication means. And confirming the reception level by using this method. In a fifth aspect, when a predetermined time elapses after switching the communication frequency to a lower frequency, the first wireless communication means is selected again and the reception level is confirmed. Therefore, when the reception level is recovered due to the recovery of the weather or the like, it is possible to automatically return the communication frequency to the frequency in the quasi-millimeter wave band and perform high-speed transmission.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) One embodiment of a communication device according to the present invention will be described with reference to FIGS. This embodiment corresponds to claims 1 and 2. FIG. 1 is a block diagram showing the configuration of the communication system of this embodiment. FIG. 2 is a flowchart showing the operation of each station in this embodiment.

In this embodiment, the first wireless communication means, the second wireless communication means, the path cutoff inspection means, and the radio frequency switching means of the first aspect are each a quasi-millimeter wave band transmission / reception circuit.
2, 2.4 GHz band transmission / reception circuit 25, communication line diagnostic unit 2
8 and the path selection circuit 27. In this embodiment, it is assumed that the present invention is applied to a communication system as shown in FIG. 1 used for a fixed wireless access service.
That is, the fixed base station 12 is connected to the IP network 13 by wire, and the subscriber station 11 installed in each home or the like is provided.
And the base station 12 are connected by a wireless communication line. A terminal 10 such as a personal computer is connected to the subscriber station 11.

Although one subscriber station 11 is shown in the example of FIG. 1, a plurality of subscriber stations 11 can perform radio communication with one base station 12 at the same time. Since it is assumed that bidirectional communication is performed, the subscriber station 11 and the base station 1
TDD (Time Div.)
ision Duplex) or FDD (Frequency Division Du)
plex) may be used.

In this example, the subscriber station 11 and the base station 12 have the same components. That is, the subscriber station 11
And the base station 12 respectively include a quasi-millimeter wave band modulation / demodulation circuit 21, a quasi-millimeter wave band transmission / reception circuit 22, antennas 23, 2,.
A 4 GHz band modulation / demodulation circuit 24, a 2.4 GHz band transmission / reception circuit 25, an antenna 26, a path selection circuit 27, and a communication line diagnosis unit 28 are provided.

The subscriber station 11 and the base station 12 perform radio communication using the frequency in the quasi-millimeter wave band by using the quasi-millimeter wave band modulation / demodulation circuit 21, the quasi-millimeter wave band transmitting / receiving circuit 22, and the antenna 23. be able to. In addition, 2.4GH
By using the z-band modulation / demodulation circuit 24, the 2.4-GHz band transmission / reception circuit 25, and the antenna 26, wireless communication can be performed using the frequency of the 2.4-GHz band. In addition,
As a frequency in the 2.4 GHz band, a radio license is not required.
It is desirable to use the SM band.

When wireless communication is performed using a frequency in the quasi-millimeter wave band, a wide bandwidth can be secured, so that high-speed communication becomes possible. However, since the frequency is high, in the case of rainfall or snowfall, the communication quality tends to deteriorate due to attenuation of radio waves. On the other hand, when wireless communication is performed using a frequency in the 2.4 GHz band, a wide bandwidth cannot be secured, so that a reduction in communication speed is inevitable. However, since the frequency is relatively low, even in the case of rainfall or snowfall, attenuation of radio waves hardly occurs, and high communication quality can be maintained.

The path selection circuit 27 and the communication line diagnosis unit 28
Provides a function similar to a general router. The path selection circuit 27 transmits a packet transmitted / received by the terminal 10 to a path passing through the quasi-millimeter wave band modulation / demodulation circuit 21, the quasi-millimeter wave band transmission / reception circuit 22, and the antenna 23, and the 2.4 GHz band modulation / demodulation circuit 2
It is connected to either one of the path passing through the 4, 2.4 GHz band transmitting / receiving circuit 25 and the antenna 26. In an initial state or a steady state, the route selection circuit 27 selects the former route.
Wireless communication is performed at a frequency in the quasi-millimeter wave band.

The route selection circuit 27 has a function of managing a communication route like a general router. Further, the communication path can be switched on a packet basis. The communication line diagnosing unit 28 periodically (for example, once every 30 seconds) transmits a known hello packet to an adjacent router. Further, the communication line diagnosis unit 28 periodically monitors whether or not a hello packet is received from an adjacent router.

In the example of FIG. 1, the adjacent router to the communication line diagnosis unit 28 of the subscriber station 11 corresponds to the communication line diagnosis unit 28 of the base station 12. A router adjacent to the communication line diagnosis unit 28 of the base station 12 corresponds to the communication line diagnosis unit 28 of the subscriber station 11. For example, if the radio wave of the quasi-millimeter wave band is attenuated due to rainfall or snowfall and the communication quality is deteriorated,
Since the hello packet transmitted by the adjacent router does not reach the communication line diagnostic unit 28 on the receiving side, the communication line diagnostic unit 28
Can detect that the communication line has been disconnected.

When the communication line diagnostic unit 28 detects that the communication line has been disconnected, the path selection circuit 27 automatically sets the communication path to a path passing through the 2.4 GHz band modulation / demodulation circuit 24, the 2.4 GHz band transmission / reception circuit 25, and the antenna 26. Switch
Therefore, the frequency of the wireless line transmitting the packet is switched from the quasi-millimeter wave band to the 2.4 GHz band. When wireless communication is performed at a frequency of the 2.4 GHz band, attenuation of radio waves due to rainfall or snowfall does not easily occur. Therefore, even when a communication line is interrupted in the quasi-millimeter wave band, a new communication path is performed at a frequency of the 2.4 GHz band. Can be established and communication can be continued.

The route selection circuit 27 selects one of a route for performing wireless communication at a frequency in the quasi-millimeter wave band and a route for performing wireless communication at a frequency in the 2.4 GHz band to transfer traffic to the terminal 10 or the IP network. Flow to 13.

The path selection circuit 27 and the communication line diagnosis unit 28
, Each of the subscriber station 11 and the base station 12 performs the operation shown in FIG. Steps S11 and S12 are executed first, so that a path using a quasi-millimeter wave band wireless line is preferentially selected in the initial state. In the steady state, steps S13 and S14 are periodically repeated, and it is confirmed that the communication path is normal. Therefore, the communication is continued on the same path using the quasi-millimeter wave band wireless line as the initial state. .

On the other hand, if the radio wave of the quasi-millimeter wave band is greatly attenuated by rainfall or snowfall and the communication quality deteriorates, it becomes impossible to receive the hello packet transmitted from the adjacent router. Therefore, the process proceeds from step S14 to S15. Step S15
Then, the path selection circuit 27 selects a communication path using a frequency in the 2.4 GHz band. Therefore, when the communication quality is degraded due to rainfall or snowfall, the communication line is automatically switched to the wireless line of the 2.4 GHz band.

In step S16, when the reduction in the reception level due to rainfall or the like is resolved and the hello packet from the communication path using the frequency in the quasi-millimeter wave band is received normally, the quasi-millimeter wave band is again transmitted. A route using a wireless line is selected. In the subscriber station 11 and the base station 12, 2.4G
Traffic always flows to both the Hz band system and the quasi-millimeter wave band system, and the receiving side receives a hello packet from the transmitting side and switches to a transmission path with good communication quality. However, a communication path using a quasi-millimeter wave band having a large transmission capacity is selected by default.

(Second Embodiment) Another embodiment of the communication apparatus of the present invention will be described with reference to FIGS. This embodiment corresponds to claims 3 to 5. FIG. 3 is a block diagram showing the configuration of the communication system of this embodiment. FIG. 4 is a flowchart showing the operation of each station in this embodiment.

This embodiment is a modification of the first embodiment. 3, elements corresponding to those in FIG. 1 are denoted by the same reference numerals. The description of the same elements as those in the first embodiment will be omitted. In this embodiment, the first wireless communication means, the second wireless communication means, the reception level detecting means and the wireless frequency switching means of the third aspect are respectively a quasi-millimeter wave band transmitting / receiving circuit 22 and a 2.4 GHz band transmitting / receiving circuit 2.
5, corresponding to the reception level detection unit 31 and the path selection circuit 27.

As shown in FIG. 3, a reception level detection unit 31 is connected to the quasi-millimeter wave band transmission / reception circuit 22. The reception level detector 31 detects the reception level of the quasi-millimeter wave band radio wave received by the quasi-millimeter wave band transmission / reception circuit 22 via the antenna 23. The communication line diagnosis unit 28 compares the reception level detected by the reception level detection unit 31 with a predetermined threshold Rv to identify whether or not the communication path has been interrupted.

That is, when the attenuation of radio waves increases due to the influence of rainfall or snowfall, and the communication quality deteriorates, the reception level detected by the reception level detection unit 31 abnormally decreases. Therefore, the reception level is compared with the threshold value Rv. This makes it possible to identify the deterioration of the communication quality, that is, the interruption of the communication line. In this embodiment, the subscriber station 11 and the base station 1
Each station 2 performs the operation shown in FIG. 4 by using the functions of the path selection circuit 27, the communication line diagnosis unit 28, and the reception level detection unit 31.

As shown in FIG. 4, initially, step S2
1 and S22, the quasi-millimeter wave band modulation / demodulation circuit 2 in the initial state and the steady state as in the first embodiment.
1, a communication path passing through the quasi-millimeter wave band transmitting / receiving circuit 22 and the antenna 23 is used for communication of the terminal 10, and communication is performed using frequencies in the quasi-millimeter wave band. In step S23, the reception level detected by the reception level detection unit 31 is compared with a threshold value Rv. When the reception level is equal to or higher than the threshold value Rv, communication is continued using the frequency in the quasi-millimeter wave band.

The reception level of the radio wave in the quasi-millimeter wave band decreases due to the influence of rainfall or snowfall, and when the reception level falls below the threshold value Rv, the process proceeds from step S23 to S24. If the state in which the reception level is less than the threshold value Rv continues for a predetermined time Tm, it is considered that the communication path using the quasi-millimeter wave band wireless line has been interrupted, and step S24 is performed.
Then, the process proceeds to S25.

Therefore, when the communication quality of the quasi-millimeter wave band radio line is degraded due to the influence of rainfall or snowfall, 2.4G
It automatically switches to a wireless line with a frequency in the Hz band. For this reason, although the transmission speed is limited, it is possible to avoid deterioration of communication quality. Further, even when the radio line is switched to the 2.4 GHz band radio line, when the predetermined time Tp elapses, the process returns from step S28 to S21, switches to the quasi-millimeter wave band radio line and checks the reception level. So
When the communication quality of the quasi-millimeter-wave band wireless line becomes better due to the recovery of the weather or the like, the wireless line is automatically switched to the quasi-millimeter wave band wireless line.

If the communication quality remains degraded, the process proceeds to steps S23 and S24 again to step S25.
A wireless line of a frequency in the 4 GHz band is used for communication. It should be noted that the configuration and operation of the parts whose description is omitted are described in the first section.
This is the same as the embodiment.

[0043]

According to the present invention, when radio waves in the quasi-millimeter wave band are attenuated by rainfall or snowfall, the frequency is automatically switched to a low frequency such as the 2.4 GHz band which is hardly affected by rainfall or snowfall. Deterioration of communication quality can be avoided.

Accordingly, the rainfall margin required for compensating for the radio wave attenuation can be reduced as compared with the conventional case.
It is possible to reduce the cost and size of the wireless device. In practicing the present invention, it is necessary to add a communication device using a low frequency such as the 2.4 GHz band in addition to the quasi-millimeter wave band, but the 2.4 GHz band which is distributed at a low price in the market. Since the wireless access system can be used as it is, the cost of the wireless device can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a communication system according to a first embodiment.

FIG. 2 is a flowchart illustrating an operation of each station according to the first embodiment.

FIG. 3 is a block diagram illustrating a configuration of a communication system according to a second embodiment.

FIG. 4 is a flowchart illustrating an operation of each station according to the second embodiment.

[Explanation of symbols]

 Reference Signs List 10 terminal 11 subscriber station 12 base station 13 IP network 21 quasi-millimeter wave band modulation / demodulation circuit 22 quasi-millimeter wave band transmission / reception circuit 23 antenna 24 2.4 GHz band modulation / demodulation circuit 25 2.4 GHz band transmission / reception circuit 26 antenna 27 route selection circuit 28 communication Line diagnosis unit 31 Received level detection unit

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukihide Mizumoto 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-term (reference) in Nippon Telegraph and Telephone Corporation 5K067 AA01 DD44 EE06 EE10 GG01 GG11 KK11 LL01 LL02

Claims (5)

[Claims] 1. A communication device provided in a base station or a subscriber station for performing wireless communication between a fixed base station and at least one subscriber station, wherein the communication device has a frequency of a quasi-millimeter wave or higher. A first wireless communication unit capable of performing wireless communication with a partner station using the first frequency band; and a second frequency band having a lower frequency than the first frequency band and having less attenuation of radio waves due to rainfall. A second wireless communication unit capable of performing wireless communication with a partner station by using a communication path, and a path cutoff check unit for checking whether a communication path is cut off with a communication partner or a relay device on a communication path, The radio signal is transmitted and received by selectively using one of the first radio communication means and the second radio communication means, and the first radio communication means is preferentially selected in a steady state, The interruption inspection means detects interruption of the communication path. Communication apparatus characterized by comprising a radio frequency switching means for automatically switching to said second wireless communication means when. 2. The communication apparatus according to claim 1, wherein the path cutoff inspection means periodically transmits a test packet to a communication partner or a relay apparatus on a communication path, and transmits the packet for a predetermined time. A communication device for recognizing interruption of a communication path when reception is not possible within a period of time. 3. A communication device provided in a base station or a subscriber station for performing wireless communication between a fixed base station and at least one subscriber station, wherein the communication device has a frequency of a quasi-millimeter wave or higher. A first wireless communication unit capable of performing wireless communication with a partner station using the first frequency band; and a second frequency band having a lower frequency than the first frequency band and having less attenuation of radio waves due to rainfall. A second wireless communication unit capable of performing wireless communication with a partner station using the first wireless communication unit; a reception level detection unit configured to detect a level of a signal received by the first wireless communication unit; Means and the second wireless communication means are selectively used to transmit and receive wireless signals, and in a steady state, the first wireless communication means is preferentially selected and detected by the reception level detection means. When the reception level drops abnormally The communication apparatus according to claim automatically switched to the provision of a radio frequency switching means to the second wireless communication means. 4. The communication device according to claim 3, wherein said radio frequency switching means suppresses or shuts off a radio transmission output of said first radio communication means when said second radio communication means is selected. Characteristic communication device. 5. The communication apparatus according to claim 3, wherein the radio frequency switching means selects the first wireless communication means again when a predetermined time has elapsed after selecting the second wireless communication means, and sets the reception level. A communication device characterized in that: