JP2003273799A - Radio access system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio access system for securing high communication quality by allowing communication equipment to changeover a plurality of set frequencies for usage, and to perform communication by radio wave. <P>SOLUTION: In the communication equipment, receiving means 11 and 12 receive radio signals, and reception frequency changeover means 14-16 changeover the frequencies of the radio signals received by the receiving means 11 and 12 within the plurality of set frequencies. A interference situation detecting means 13 detects the situation of interference concerning the signals received by the receiving means 11 and 12 at each frequency. Then, the frequency to be used for radio communication by the communication equipment is changed- over based on the detection result of the interference situation detecting means 13 in the communication equipment. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a subscriber radio access system mainly composed of a plurality of communication devices, and more particularly to a radio access for ensuring high communication quality by switching frequencies used for radio communication by the communication devices. Regarding the system.

[0002]

2. Description of the Related Art With the progress of advanced information technology in recent years, the sophistication of communication networks has become an issue. However, it is difficult to secure a sufficient communication capacity that can meet the demand in the conventional communication network mainly composed of metallic cables. Further, there is a communication network using an optical fiber cable as a communication network having a larger capacity, but it is not always necessarily promptly developed because there are many restrictions in terms of construction cost and land use.

For example, WLL (Wireless Local Loop)
Alternatively, a subscriber wireless access system called FWA (Fixed Wireless Access) or the like (in the present specification, such a system is also simply referred to as “wireless access system”) is provided as compared with a communication system using a wired network. It is easy to implement, and its spread is expected as an early promotion of regional network development.

Generally, as a method of a radio access system, a base station device and a user (subscriber station device) are in a one-to-one correspondence.
There is a P-P (Point to Point) system in which wireless communication is performed by connecting to a wireless LAN and a P-MP (Point to Multip1e Point) system in which one base station device and a plurality of users simultaneously perform wireless communication. A mesh type wireless access system, which is an advanced version of these existing systems from the viewpoint of flexibility in network construction and fault tolerance, is being studied and researched.

Here, FIG. 8 shows a configuration example of a mesh type wireless access system. In FIG. 8 (a),
An example of the overall configuration of the mesh type wireless access system is shown. As shown in FIG. 1A, the mesh type wireless access system is configured by connecting a plurality of wireless station devices 21 and 22 with a wireless link 23. This is to construct a mesh type network topology. One or more wireless station devices 22 forming a network are connected to a backbone network 24.

FIG. 8B shows a configuration example of the above-mentioned wireless station devices 21 and 22. As shown in FIG. 8B, the wireless station devices 21 and 22 are routers 31. When,
A plurality of (four in four directions in this example) wireless devices 32 used for wireless communication with each adjacent direction, and each of these wireless devices 3
2 and the same number of antennas 33 whose directivity is narrowed toward adjacent directions.
Is wirelessly connected to the opposite radio equipment provided in the adjacent radio station device.

Further, the router 31 described above is a local I
It is connected to the P network 34, exchanges data with the local IP network 34, and relays data addressed to other wireless station devices, that is, in the direction in which the wireless station device to be transmitted exists. The data to be relayed is transmitted by the wireless device. Thus, in the configuration of the mesh type wireless access system, each wireless link 23 is of the PP type, but the mesh type network topology is used as a whole.

In FIG. 8 (a), the same reference numeral "21" is assigned to a plurality of radio station apparatuses, and different reference numeral "2" is given to the radio station apparatuses connected to the backbone network 24.
2 ". Further, in FIG. 8A, the same reference numeral" 23 "is attached to a plurality of wireless links. In addition, in FIG. To the plurality of antennas, and the same reference numeral “33” is attached to the plurality of antennas.
For example, a base station device and a subscriber station device are fixedly installed and used as 1 and 22.

Here, as an example of a radio access system, in the "base station apparatus and radio access system" described in Japanese Patent Laid-Open No. 2001-169338, the received radio wave is changed based on the received electric field strength for each frequency while switching the frequency. The presence or absence of interfering waves in the interior is detected to determine the suitability of equipment installation. In the technique of this document, when compared with the present invention described later, for example, detecting the level of the interference wave for each frequency, determining the frequency of good communication quality based on the detection result, the determination result The frequency used for wireless communication by the communication device is switched based on the above, the switching is appropriately performed during wireless communication, and the null symbol is included in the wireless frame, and the level of the interference wave is detected using the null symbol. Nothing has been done.

Although not related to the gist of the present invention described later, for example, "subscriber wireless access system" of Japanese Patent No. 3087836 and "ISD of Japanese Patent No. 3045161" are disclosed.
N-corresponding subscriber radio access system and B channel packet transmission method "and" Access control within the subscriber station radio access system and subscriber radio access system "in Japanese Patent No. 3022864. Various studies have been made on the system.

[0011]

However, in the conventional radio access system as shown in the above-mentioned conventional example,
For example, at the time when the wireless station device is installed, an optimum line state can be realized so that interference does not occur, but after that, changes in the propagation environment due to buildings newly installed around the wireless station device and other There was a problem that the line quality might deteriorate due to the installation of a new wireless line by the operator.

Specifically, in a radio access system, a band of several tens of MHz is allocated to a communication carrier, and the communication carrier generally allocates its own communication channel within the range. For example, FIG. 9 shows a system having a system bandwidth from the lower limit frequency fL to the upper limit frequency fU, and using five communication channels of frequencies f1 to f5 in the bandwidth. An example of a signal waveform when there is an interference wave that affects the frequency f1 and the frequency f5 is shown. In addition,
The horizontal axis of the figure shows the frequency, and the vertical axis shows the power of the signal.

As shown in the figure, conventionally, when the local station (wireless station apparatus) is receiving on a channel of frequency f1, for example, FER (Frame Error Rate) is applied to the interference at the frequency f1. And BER (Bit Error
Although it is possible to detect from the relationship between the communication quality and the received power that can be determined by Rate) etc., the interference wave existing in the vicinity of another frequency f5 cannot be predicted from the communication quality of the own station. In addition, the above problem is P
This is a technical problem common to all wireless access systems such as the P method, the P-MP method, and the mesh type.

Therefore, in the present invention, in order to solve the above problems, for example, it is considered to configure a system in which each radio station device automatically sets a frequency used for radio communication so as to avoid an interference wave. It was In such a configuration, it is considered necessary to identify the frequency band with less interference among the frequency bands occupied by the system.

The present invention has been made to solve the above conventional problems, and when a communication device switches and uses a plurality of frequencies to communicate wirelessly, for example, an interference wave exists at a certain frequency. An object of the present invention is to provide a wireless access system capable of ensuring high communication quality even in such a case.

[0016]

In order to achieve the above object, in the wireless access system according to the present invention, a communication apparatus switches and uses a plurality of set frequencies to perform wireless communication as follows. That is, in the communication device, the receiving means receives the wireless signal, and the receiving frequency switching means switches the frequency of the wireless signal received by the receiving means among the plurality of set frequencies described above, and the interference state detecting means switches the switching. The state of interference with respect to the signal received by the receiving means is detected for each frequency. Then, in the wireless access system, the frequency used for wireless communication by the communication device is switched based on the detection result of the interference condition detection means of the communication device.

Therefore, in the wireless access system,
The frequency of the wireless signal received by the communication device is switched, the interference situation is detected for each frequency, and the frequency used for wireless communication by the communication device is switched based on the detection result. Even in the presence of waves, high communication quality can be ensured by switching the frequency with no or less interference waves to be used for wireless communication by the communication device.

As a specific example, when two or more communication devices wirelessly communicate with each other, the two or more communication devices are communicated based on the interference situation detected by one or more communication devices of the two or more communication devices. The frequency used for wireless communication by the device is switched to a frequency with good communication quality. In such a configuration, the wireless communication is performed using the frequency at which the information signal communicated between these two or more communication devices is switched. Be communicated.

As the frequency, for example, a value at one point (frequency value) may be used, or a frequency band having a width may be used, for example. In normal wireless communication, a frequency band having a predetermined spread on each of the high band side and the low band side around a center frequency that is a frequency value of one point is used for communication.

Here, as the radio access system,
Various configurations may be used. The communication device may have various configurations, and is applied to, for example, a fixedly installed base station device or a fixedly installed subscriber station device. In addition, various communication methods may be used as a communication method of wireless communication performed by the communication device.

Various frequencies may be used as the set plurality of frequencies, and various numbers may be used as the plurality of frequencies. Further, the plurality of frequencies are preset in the system, for example. Also,
As a mode of wirelessly communicating by switching a plurality of frequencies, for example, not only a mode of switching each frequency as a frequency used for wireless communication but also simultaneously switching two or more frequencies as a frequency used for wireless communication There may be cases like this.

Various modes may be used as a mode for switching the frequency of the radio signal received by the receiving means among a plurality of set frequencies. For example, when detecting an interference situation, a plurality of modes may be used. It is possible to use a mode in which the frequencies are switched one by one in order, and when the frequency used for wireless communication is fixed based on the detection result of the interference situation, the frequency is switched to be used for wireless communication.

Further, as a mode for detecting the interference situation regarding the signal received by the received signal for each frequency,
Various modes may be used, and for example, it is preferable to use a mode that detects the state of interference for each received signal of each frequency for all of the plurality of set frequencies. Further, as the interference situation regarding the received signal, various things may be detected as long as it is possible to judge the quality of the communication quality for each frequency,
Specifically, the interference wave power and the like can be detected.

As a mode for switching the frequency used for wireless communication by the communication device based on the detection result of the interference condition detecting means of the communication device, for example, a mode for switching the frequency having the best communication quality to be used for wireless communication or Alternatively, it is possible to use a mode in which a frequency whose communication quality value exceeds a predetermined threshold value is switched to be used for wireless communication. In addition, as the timing for performing such interference situation detection processing and frequency switching processing for wireless communication,
For example, a mode that is always performed, or a mode that is performed when the value indicating the communication quality of the frequency used for wireless communication becomes less than a predetermined threshold value can be used.

The function of switching the frequency used for wireless communication by the communication device based on the detection result of the interference condition detecting means of the communication device may be provided in any place of the wireless access system. It is possible to provide all or part of the above in a communication device, and the communication device can be configured to automatically switch and set a frequency used for wireless communication to a favorable frequency.

Further, in the wireless access system according to the present invention, the wireless communication by the communication device is performed using the wireless frame including null symbols having a signal level of zero at predetermined intervals, and the interference condition of the communication device. The detecting means detects the interference situation in the null symbol included in the signal received by the receiving means. Therefore, the interference situation regarding the received signal is detected by using the null symbol whose signal level (for example, the amplitude of the signal) is zero, so that the interference situation can be accurately detected.

Here, as the radio frame, frames having various configurations may be used. Also, as the predetermined interval in which the null symbol is included in the radio frame,
Various intervals may be used, for example a constant interval is preferred. Further, the null symbol included in one place in the radio frame may be, for example, one symbol, or may be two or more symbols. Note that, in the radio frame, a portion other than the null symbol includes, for example, a symbol of information to be communicated (information symbol) and a symbol of information for performing control (control symbol).

Various modes may be used as a mode for detecting the interference situation regarding the received signal in the null symbol. For example, a communication device may be provided for each null symbol provided at a constant interval in the radio frame. A mode in which the frequency is switched to detect the interference situation, or, for example, a frequency to be switched is assigned in advance to each null symbol in the radio frame, and the communication device switches the frequency according to the allocation to detect the interference situation. Aspects and the like can be used.

Next, a more specific configuration example of the present invention will be shown. In a wireless access system according to the present invention, as a preferable configuration example, a plurality of frequencies for which a communication device is set are switched and used for wireless communication as follows. That is, in the communication device, the antenna inputs the radio signal, the reception processing means receives the signal of the frequency corresponding to the local frequency signal from the signal input by the antenna, detects the level of the received signal, and detects the interference signal. The level detection means detects the interference signal level based on the reception signal level detected by the reception processing means, and the local frequency signal switching supply means sets the frequencies of the local frequency signals to the reception processing means to a plurality of frequencies (local frequencies). The local frequency signal is switched over to supply the local frequency signal to the reception processing means. Then, in the wireless access system, based on the detection result of the interference signal level detection means of the communication device,
The frequency used for wireless communication by the communication device is switched.

In this configuration example, the receiving means is composed of the antenna and the reception processing means, the receiving frequency switching means is composed of the local frequency signal switching supply means, and the interference condition detecting means is composed of the interference signal level detecting means. It

Here, as the antenna, various antennas may be used, for example, an antenna having no directivity (omnidirectional type) may be used, or an antenna having directivity may be used. May be. Further, as a function of receiving a signal of a frequency corresponding to a local frequency signal from a signal input by an antenna, for example, a signal of all frequencies that can be input by the antenna input from the air by the antenna and a local frequency signal It is possible to configure by using a mixer that is generated by mixing the signals of the frequency corresponding to the local frequency signal as a signal to be received and a filter that extracts the signal of the frequency.

Various levels such as power and amplitude may be detected as the level of the received signal and the level of the interference signal. Further, as a mode of switching the frequency used for wireless communication by the communication device based on the detection result of the interference signal level detection means of the communication device, for example, the frequency with the smallest detected interference signal level is switched to be used for wireless communication. It is possible to use a mode, or a mode in which the frequency at which the detected interference signal level becomes less than a predetermined threshold value is switched to be used for wireless communication.
Further, the timing of performing the detection processing of the interference signal level and the switching processing of the frequency used in the wireless communication is, for example, a mode in which it is always performed, or the interference signal level of the frequency used in the wireless communication is predetermined. A mode that is performed when the threshold value is exceeded can be used. Generally, it can be said that the smaller the interference signal level, the better the communication quality.

Further, in the radio access system according to the present invention, as a preferable configuration example, in the local frequency signal switching supply means, the fixed frequency signal output means outputs the signal of the frequency set fixedly and outputs the variable frequency signal. The means switches and outputs signals of a plurality of frequencies corresponding to the set plurality of frequencies (local frequencies), and the mixing means mixes the signal from the fixed frequency signal output means and the signal from the variable frequency signal output means. Then, the local frequency signal obtained by the mixing is output and supplied to the reception processing means.

Various frequencies may be used as the fixedly set frequency. As the plurality of frequencies corresponding to the set plurality of frequencies (local frequencies), for example, a local frequency signal of the set plurality of frequencies (local frequencies) can be obtained as a result of mixing by the mixing unit. Such frequencies are used.

In the radio access system according to the present invention, as a preferred configuration example, radio communication by a communication device is performed using radio frames including null symbols whose signal level is zero at regular intervals, and In the communication device, the reception processing means detects the reception timing of the null symbol based on the signal input by the antenna, and the interference signal level detection means detects the local frequency signal based on the reception timing of the null symbol detected by the reception processing means. The switching supply means is controlled to sequentially switch the frequency of the signal received by the reception processing means in each null symbol, and the interference signal level based on the reception signal level detected by the reception processing means in each null symbol is detected. .

Here, various intervals may be used as the constant interval in which the null symbol is included in the radio frame. Also, as the reception timing of the null symbol,
As an example, it is possible to specify the reception timing of one or more null symbols and the cycle in which the null symbols are included in the radio frame.

Various methods may be used to detect the interference signal level based on the received signal level in the null symbol. For example, in the null symbol, the signal level is zero (for example, during transmission). Therefore, it is possible to use a method in which the result of subtracting the level of noise other than the interference signal from the received signal level is regarded as the level of the interference signal (interference signal level) and detected.

Further, the local frequency signal switching supply means is controlled based on the reception timing of the null symbol detected by the reception processing means, and the frequency of the signal received by the reception processing means in each null symbol is switched in order. As for the local frequency signal supplied to the reception processing means by the local frequency signal switching supply means, for example, the signal of each frequency can be received at the timing of each null symbol and the interference signal level of each frequency can be detected. It is possible to use a mode that controls the frequency of the.

In the radio access system according to the present invention, as a preferred configuration example, in the communication device, the interference signal level detection result storage means stores the detection result of the interference signal level detection means for each frequency. As a result, in the wireless access system, the interference state detection result for each frequency stored by the communication device can be used for various purposes. Here, as the interference signal level detection result storage means, for example, a memory can be used.

In addition to the radio access system, the technique according to the present invention as described above is, for example, a communication device such as a subscriber station device or a base station device provided in the radio access system, or such a communication device. It is possible to realize it as a communication device provided in the device, a wireless access system, a communication device, a method of processing performed in the communication device, or the like.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described with reference to the drawings. FIG. 1 shows a configuration example of a transceiver according to the embodiment of the present invention. The transceiver of this example applies the communication device of the present invention, and is provided in a subscriber wireless access system to which the wireless access system of the present invention is applied.

As shown in the figure, the transceiver of this example is provided with a frame configuration circuit 1, a radio transmitter 2, and an antenna 3 as the configuration of the transmission side (transmission unit). Further, as shown in the figure, in the transceiver of this example, an antenna 11, a radio receiver 12, an interference wave power detection storage circuit 13, and a direct digital synthesizer (a reception side (reception unit)) are provided. DDS: Direct Digital
Synthesizer) 14, local oscillator 15, and mixer 16
And are provided.

First, an operation example on the transmitting side of the transceiver of this example will be described. That is, the data to be transmitted (transmission data)
Is input to the frame configuration circuit 1. The frame configuration circuit 1 performs symbol mapping processing on input transmission data according to a modulation method applied to communication, and further adds a control signal, a synchronization signal, or the like to configure a radio frame, and the radio frame A null symbol of zero amplitude having no information is inserted into the frame at a constant interval with a length of 1 symbol or more to generate a transmission baseband signal a, and the generated transmission baseband signal a is wirelessly transmitted. Transmitter 2
Output to.

Here, FIG. 2 shows a configuration example of a radio frame used for radio communication performed by the transceiver of the present example provided in the radio access system of the present example.
In the radio frame shown in the figure, the signal of the null symbol N is inserted at every constant time interval T corresponding to the insertion interval of the null symbol, and in other portions, for example, information (data ) Signals such as symbols and control symbols are arranged.

FIG. 3 shows an example of null symbol mapping in this example. In this example, QPSK (Quadrature Phase Shift Keyin) is used as an example of a modulation method.
g) method is used. When the QPSK method is used as the modulation method, the normal data is the four symbol points Sd1 to Sd on the constellation shown in FIG.
4 is mapped according to the data,
The null symbol is mapped to the symbol point Sn having an amplitude of 0. The abscissa of the figure (a) indicates the I phase component (In P
hase), and the vertical axis represents the Q-phase component (Quadrature Pha
se) is shown.

Further, as shown in FIG. 7B, when viewed on the time axis, the amplitude of other symbols (that is, other than the null symbol) is ± A (A is a predetermined value which is not zero). On the other hand, only the null symbol Sn has zero amplitude. The horizontal axis of FIG. 7B shows time (Time) t, and the vertical axis shows the level of signal amplitude.

As the insertion interval T of the null symbol N shown in FIG. 2, for example, it is preferable to set the detection interval of the interference wave which is considered necessary in the operation of the applied system, but a simple setting method. For example, since the null symbol N is inserted into the control signal portion of the radio frame in synchronization with the radio frame, the null symbol N
, And a method of setting the insertion interval T of the null symbol N in units of a superframe composed of a plurality of radio frames, for example. it can.

When the transmission baseband signal a is output from the frame configuration circuit 1 to the radio transmitter 2 as described above, the radio transmitter 2 next quadrature-modulates the input transmission baseband signal a. Then, the signal is frequency-converted into a desired radio frequency band usable in the system, and then the frequency-converted radio frequency signal is power-amplified and wirelessly output to the space by the antenna 3.

Next, an operation example of the receiving side of the transceiver of this example will be shown. That is, after receiving the radio wave from the space by the antenna 11, the radio receiver 12 extracts a signal in a desired frequency band from the received radio wave signal and performs processing such as quadrature detection and demodulation. Outputting the received data obtained, reproducing the synchronization timing of the radio frame related to the extracted signal to estimate the position of the null symbol N, and detecting the interference wave power by using the estimated position and the symbol timing as information b of the null symbol timing. Information on the detected received power (received power information) which is output to the memory circuit 13 and detects the received power related to the extracted signal.
c is output to the interference wave power detection storage circuit 13.

The received power information c is as follows.
For example, RSSI (Received Signal Strength Indicator)
It is possible to use various kinds of information, such as information using the above-mentioned information or information in which the absolute value of the symbol known in the transceiver is obtained. Further, it is assumed that the null symbol timing indicated by the above-mentioned null symbol timing information b is adjusted according to the delay of the detection method, for example.

In the radio receiver 12 described above, frequency conversion is performed on the signal input from the antenna 11 in order to extract the signal in the desired frequency band. In this example, the local frequency used for such frequency conversion is such that the local oscillator 15 oscillates a signal at a fixed frequency, the DDS 14 generates a signal at a variable frequency, and the mixer 16 outputs the signal from the local oscillator 15. And the output from the DDS 14 are combined (mixed) to be generated and supplied to the wireless receiver 12.

Here, the DDS 14 is, for example, several tens of ns.
It is a device capable of switching the frequency in a short period of time of about ec, and the wireless receiver 1 has the configuration as in this example.
Frequency of local frequency signal to 2 (local frequency)
Is generated, the frequency received by the wireless receiver 12 can be switched in a short time. For example, when the transmission speed is 10 Msymbol / sec,
Since the symbol interval is 100 nsec, it is possible to switch the reception frequency for each symbol.

In this example, the transmitting side (for example, the transmitter 2 or the like) and the receiving side (for example, the receiver 1) used for wireless communication are used.
2) to detect interference in a frequency used for communication and interference in a usable frequency in the vicinity of the frequency assigned to the radio access system, the reception side uses the DDS 14 to switch the reception frequency. is there.

Here, FIG. 4 shows an example of the structure of the radio channel used in the radio access system of this example, in which the horizontal axis represents frequency and the vertical axis represents signal power. Shows the level. As shown in the figure, in this example, the system to be applied has a lower limit frequency fL ~
There are five wireless channels in the band of the upper limit frequency fU, and five center frequencies f1 to f5 are set corresponding to these five wireless channels.

In this case, by controlling the DDS 14 so that the center frequencies used for wireless communication can be set to the frequencies f1, f2, f3, f4, and f5, respectively, the interference status is grasped in all the wireless channels in the system. In addition, wireless communication can be performed on all wireless channels.

In the interference wave power detection storage circuit 13, null symbol timing information b input from the radio receiver 12 is received.
DD according to the null symbol timing indicated by
While controlling the DDS 14 by outputting a control signal d for performing a desired frequency setting to S14, the power of the interference wave is detected based on the received power information c input from the wireless receiver 12, Information on the detected interference wave power (interference wave power information) is stored in a memory circuit.

The capacity of the storage circuit is appropriately prepared according to the operating mode of the system to which it is applied. Further, the content of the information stored in the storage circuit is, for example,
In the operation of the wireless access system, it can be used for changing the wireless channel used and controlling the transmission power.

Next, with reference to FIG. 5, an example of a method for detecting the interference wave power by the receiving side of the transceiver of this example will be conceptually described. FIG. 5A shows an example of a signal (transmission signal) transmitted from the transmission side using the radio frame as shown in FIG. 2, and FIG. 5B shows that there is no interference wave. FIG. 5C shows an example of a reception signal when the transmission signal is received by the reception side when the above-mentioned situation occurs. When there is no interference wave, FIG. FIG. 5D shows an example of the detected received power, FIG. 5D shows an example of the interference wave signal received by the receiving side, and FIG. An example of the reception signal when the transmission signal is received by the reception side is shown. FIG. 5 (f) shows that the interference wave signal is detected by the radio receiver 12 on the reception side based on the reception signal. An example of received power is shown. In Fig. 5 (g), the receiving side receives Timing t0, t1, t2, t3 of the null symbol N for the signal to be,
... is shown as an example. 5 (a) to 5 (g)
The horizontal axis of indicates the time.

Further, in FIG. 5, with respect to the reception power (with an interference wave) shown in FIG. 5F, the reception power at the null symbol timing at time t0 and the reception power at the null symbol timing at time t3 are enlarged. Is shown,
The horizontal axis represents time (Time), and the vertical axis represents power [d
B] is shown.

When a radio signal on the receiving side receives a transmission signal in which a null symbol N is inserted as shown in FIG. 5A, when no interference wave exists, it is shown in FIG. 5B. A received signal in which the power of such a null symbol portion is only a noise component is obtained, and as shown in FIG. 5C, the received power is a null symbol insertion period T between fixed reception power levels. A drop in power is observed at.

Next, assume an environment in which an interference wave exists. When there is an interference wave signal as shown in FIG. 5 (d), the reception signal on the receiving side is in a state in which the interference wave signal is superimposed on the reception signal as shown in FIG. 5 (e),
The received power is also affected by the influence, and an increase in the power of the interference wave signal can be seen as shown in FIG.

For example, assuming that the noise power is n [dB], the reception power (with an interference wave) is enlarged as shown in FIG. 5 at null symbol timings t1, t2, and t3 in the time zone in which the interference wave exists. Is observed to be I [dB], the interference wave power can be expressed as (I−n) [dB], and the situation of the interference wave can be grasped.

On the other hand, at the null symbol timings t3 and t4 in which no interference wave exists, as shown in an enlarged view in FIG. 5, as the received power (no interference wave), the noise level itself of n [dB] is observed. , The interference power is (n-
It can be determined that n) = 0 [dB] (that is, no interference wave). Such a method of detecting the interference wave power can be effectively used as a method of detecting the state of a wireless channel to be observed other than the wireless channel during communication.

Next, an example of a DDS control method performed to detect the interference wave condition will be described. First, an example of a method of controlling the DDS 14 on the receiving side will be described with reference to FIG.
The horizontal axis of FIGS. 6A to 6D indicates the time (Tim).
e) and t1 to t7 indicate predetermined times. In this example, it is assumed that there are three frequency bands f1, f2, and f3 as wireless channels usable in the system, and normal data communication is performed using the frequency band f1.

First, on the transmitting side, as shown in FIG. 6A, three null symbols N1, which are arranged consecutively,
Information is transmitted by inserting N2 and N3 in a radio frame at regular intervals. Here, as the number of the plurality of null symbols, for example, the same number as the number of radio channels to be observed is prepared, and the cycle of inserting the null symbols may be appropriately set according to the system, for example. .

Next, on the receiving side, as shown in FIG. 6B, the three frequency bands f1, f2, f3 are set in accordance with the timing of the null symbols N1, N2, N3 detected by the radio receiver 12. The DDS 14 is controlled by the control signal from the interference wave power detection / storage circuit 13 so that the reception frequencies are sequentially received. Where the null symbol N
The time of the start position of 1 is t1, and the time of the start position of the null symbol N2 and the start position of the null symbol N2 is t1.
2 and the time of the end position of the null symbol N2 and the start position of the null symbol N3 is t3, and the null symbol N
The time at the end position of 3 is t4. Note that FIG.
In (b), as the symbol timing, only the symbol timing corresponding to the null symbol is explicitly shown, and symbol timings of other information symbols and the like are omitted.

The null symbols N1 to N shown in FIG.
This will be described more specifically with reference to the insertion position of No. 3 and the symbol timings t5, t6, and t7 shown in FIG. In this example, the time such as the center of each symbol having a time width is set to the symbol timing t5 to t7 of each symbol.
To consider.

First, the time t1 at the beginning of the null symbol N1
At symbol timing t5 immediately after, the interference wave power regarding the currently communicating wireless channel (frequency band f1) is detected and held in the interference wave power detection storage circuit 13. Next, normal information data is received from the symbol timing t5 to the time t2 at the beginning of the next null symbol N2.

After that, the time t at the beginning of the null symbol N2
2 to receive signals in the frequency band f2, D
The frequency of the DS 14 is switched, and the interference wave power in the frequency band f2 is detected and stored at the symbol timing t6 immediately after that. Next, at time t3 at the beginning of the null symbol N3, the frequency of the DDS 14 is switched so as to receive a signal in the frequency band f3, and immediately after that, the interference wave power in the frequency band f3 is detected and recorded. .

By the processing up to this point, all radio channels used in the system (three frequency bands f1 to f3)
For, it is possible to grasp the interference situation. Next, at the timing of the end time t4 of the null symbol N3, the DD of the frequency band f1 is received.
The frequency of S14 is switched, and normal information data is received until the next null symbol position.

After that, the same processing as described above is repeated for each null symbol insertion period. As a method of holding the information about the interference wave power inside the interference wave power detection storage circuit 13, for example, the stored contents are obtained by the interference wave power detection value of each new frequency band depending on the level fluctuation state in the system. For example, a method of updating, a method of equipping a plurality of memories for each radio channel to enable processing such as averaging of interference wave power detection values, and the like can be used.

Next, referring to FIG. 7, DDS1 on the receiving side
Another example of the method of controlling the No. 4 will be described. Note that FIG.
~ The horizontal axis of FIG. 7 (d) indicates time (Time),
t1 to t12 indicate predetermined times. In this example, it is assumed that there are three frequency bands f1, f2, and f3 as wireless channels usable in the system, and normal data communication is performed using the frequency band f1.

First, on the transmitting side, as shown in FIG. 7A, one null symbol N is inserted into each radio frame to transmit information. In the example shown in FIG. 6, the interference wave powers of all the wireless channels are detected in the same fixed period as the period of the wireless frame, whereas in the present example,
As shown in FIG. 7B, the observation period for each wireless channel is set to (the constant period × the number of wireless carriers), which allows frequency switching of the DDS 14 as compared with the example shown in FIG. Allows you to do it slowly.

The insertion position of the null symbol N shown in FIG. 7C and the symbol timing t9-shown in FIG. 7D.
This will be described more specifically with reference to t12. In this example, the time such as the center of each symbol having a time width is regarded as the symbol timing t9 to t12 of each symbol.

On the receiving side, first, the first null symbol N
Symbol timing t9 immediately after time t1 at the beginning position of
, The wireless channel currently in communication (frequency band f
The interference wave power relating to 1) is detected and held in the interference wave power detection storage circuit 13. Then, at time t2 at the ending position of the null symbol N, normal information data reception is restarted.

Next, the frequency of the DDS 14 is switched so as to receive the signal in the frequency band f2 at the time t3 at the head position of the second null symbol N, and the interference wave power in the frequency band f2 is immediately after that at the symbol timing t10. Detect and save. Then, at time t4 at the end position of the null symbol N, the frequency band f1
The frequency of the DDS 14 is switched so as to receive the signal of, and normal information data is received until time t5 at the start position of the next null symbol N.

Next, the frequency of the DDS 14 is switched so as to receive the signal in the frequency band f3 at the time t5 at the start position of the third null symbol, and at the symbol timing t11 immediately after that, the interference wave power in the frequency band f3 is set. Detect and save. After that, at time t6 at the end position of the null symbol N, the frequency of the DDS 13 is switched so as to receive the signal in the frequency band f1, and normal information is provided until time t7 at the start position N of the next null symbol N. Receive data.

By the processing up to this point, all radio channels used in the system (three frequency bands f1 to f3)
For, it is possible to grasp the interference situation. After that, the same processing as described above is repeated in units of (null symbol insertion period × number of wireless carriers).

As described above, in this example, in the subscriber radio access system composed of a plurality of communication devices,
The transmitter of the communication device performs a symbol mapping process and a process of inserting null symbols of zero amplitude having no information at regular intervals with a length of one symbol or more to generate and output a transmission baseband signal a. A frame configuration circuit 1, a radio transmitter 2 for orthogonally modulating the transmission baseband signal a, performing frequency conversion into a radio band, and then outputting a power-amplified radio signal to an antenna, and outputting the radio signal to space. And the antenna 3 that operates.

Further, in this example, the receiving section of the communication device includes an antenna 11 for receiving radio waves from the space and outputting a reception radio signal, and a quadrature detection for extracting a desired frequency band from the reception radio signal. A radio receiver 12 having a function of performing processing such as demodulation and outputting received data, detecting a null symbol estimated position in the received radio signal and detecting received power, and outputting the information b and c; DDS by the control signal d according to the null symbol estimated position
The interference wave power detection memory circuit 13 and the interference wave power detection memory for controlling and controlling the reception frequency and observing the reception power in each frequency band and observing the interference situation in each frequency band. A DDS 14 that outputs a variable frequency signal for adjusting the center frequency of wireless communication to a desired frequency under the control of the circuit 13 and a fixed frequency signal for frequency conversion in the wireless receiver 12 are generated. It is composed of a local oscillator 15 and a mixer 16 which synthesizes an output from the DDS 14 and an output from the local oscillator 15 to generate a signal of a local frequency used for frequency conversion in the radio receiver 12.

In this example, even when the communication quality of the wireless channel used for wireless communication is deteriorated by the interference wave, the DDS 14 capable of switching the frequency at high speed is used to allocate the system. The interference situation of each wireless channel is searched for a plurality of wireless channels for communication that are configured in the same frequency band, and a wireless channel that can maintain communication quality is searched for, and the searched wireless channel is used. To make wireless communication.

Further, in this example, as such a channel search, π / 4Q is set for every fixed number of bits as a symbol for establishing temporal synchronization in the transmission / reception channel.
Differently from the transition of the signal point array such as in the PSK method, a null symbol whose amplitude is reduced to zero is inserted, and a search is performed in the null symbol, whereby all the frequencies within the allocated frequency band are searched. Investigate the condition of interference waves on the wireless channel.

With this configuration, in the present example, for example, a plurality of fixed station devices corresponding to a plurality of subscriber station devices and one fixed station device corresponding to one base station device are wirelessly connected. In a subscriber wireless access system having such a network configuration, it is possible to improve the communication quality of wireless communication performed by a communication station device such as a subscriber station device or a base station device.

Further, in this example, since it is possible to monitor the interference state for all the radio channels in the subscriber radio access system, for example, a new radio station can be installed and a frequency used for radio communication can be changed. It is possible to obtain the effect that the parameters can be safely and promptly changed when the transmission power control or the like is performed.

In this example, the function of the antenna 11 and the function of the radio receiver 12 constitute the receiving means, and the function of the DDS 14, the function of the local oscillator 15 and the function of the mixer 16 constitute the receiving frequency switching means. Therefore, the function of the interference wave power detection storage circuit 13 constitutes an interference state detection means.

Here, the configuration of the radio access system, the communication device and the like according to the present invention is not necessarily limited to the ones described above, and various configurations may be used. Further, the application fields of the present invention are not necessarily limited to those shown above, and the present invention can be applied to various fields. The technology according to the present invention can be applied to various wireless communication systems in which a plurality of communication devices perform wireless communication, for example.

As various processes performed in the wireless access system and the communication device according to the present invention, for example, in a hardware resource including a processor and a memory, a control in which the processor is stored in a ROM (Read Only Memory) A configuration controlled by executing a program may be used, or, for example, each functional unit for executing the process may be configured as an independent hardware circuit. Further, the present invention is a floppy (registered trademark) disk or a CD storing the above control program.
(Compact Disc) -It can be understood as a computer-readable recording medium such as a ROM or the program (itself), and by inputting the control program into the computer from the recording medium and causing the processor to execute the program, the present invention can be realized. Such processing can be performed.

[0088]

As described above, in the radio access system according to the present invention, the communication device receives the radio signal by switching the frequency of the radio signal to be received among a plurality of set frequencies, and performs the switching. The situation of interference related to a signal received for each frequency is detected, and a frequency selected based on the detection result is used for wireless communication in a manner such that the set plurality of frequencies are switched and used. Therefore, even if there is an interference wave at a certain frequency, for example, even if there is an interference wave at a certain frequency, by switching the frequency with no or less interference wave to be used for the wireless communication by the communication device, the wireless communication by the communication device can be performed. High communication quality can be secured.

Further, in the radio access system according to the present invention, radio communication is performed by the communication device using radio frames including null symbols having a signal level of zero at predetermined intervals, and the signal received by the communication device is received. Since the interference situation is detected in the null symbol included in, the interference situation can be accurately detected by using the radio frame portion in which the signal level from the transmission side becomes a constant zero.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a transceiver according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a radio frame.

FIG. 3 is a diagram showing an example of null symbol mapping.

FIG. 4 is a diagram showing an example of a configuration of wireless channels in a wireless access system.

FIG. 5 is a diagram for explaining an example of a method of detecting interference wave power.

FIG. 6 is a diagram for explaining an example of a mode in which a frequency for detecting interference wave power is switched.

FIG. 7 is a diagram for explaining another example of a mode in which the frequency for detecting the interference wave power is switched.

FIG. 8 is a diagram showing a configuration example of a mesh type wireless access system.

FIG. 9 is a diagram showing an example of generation of an interference wave.

[Explanation of symbols]

1 ... Frame configuration circuit, 2 ... Wireless transmitter, 3, 1
1, 33 ... Antenna, 12 ... Radio receiver, 13 ...
.Interference wave power detection memory circuit, 14 ... DDS, 15
..Local oscillators, 16..Mixers, Sd1 to Sd4 ..
・ Symbol points, Sn ・ ・ Null symbol points, 21, 22
..Wireless stations, 23 .., wireless links, 24 ..
31 ... Router, 32 ... Radio, 34 ... Local IP network,

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Konishi             2-15-1 Ohara, Kamifukuoka City, Saitama Stock             Company CAD Research Institute (72) Inventor Shinichi Nomoto             2-15-1 Ohara, Kamifukuoka City, Saitama Stock             Company CAD Research Institute F-term (reference) 5K022 EE21 EE31                 5K067 AA03 BB02 CC02 CC04 DD11                       DD41 DD51 EE02 EE10 JJ11                       JJ31 JJ37 JJ38

Claims (2)

[Claims] 1. A wireless access system in which a communication device wirelessly communicates by switching a plurality of set frequencies, wherein the communication device includes receiving means for receiving a wireless signal, and wireless communication for receiving by the receiving means. A reception frequency switching unit that switches the frequency of the signal among a plurality of set frequencies, and an interference state detection unit that detects the state of interference related to the signal received by the receiving unit for each frequency are provided. A radio access system, characterized in that a frequency used for radio communication by the communication device is switched based on a detection result of the interference situation detecting means. 2. The radio access system according to claim 1, wherein the radio communication by the communication device is performed by using a radio frame including null symbols having a signal level of zero at predetermined intervals, and the interference situation of the communication device. The wireless access system is characterized in that the detecting means detects an interference situation in the null symbol included in the signal received by the receiving means.