JP3760705B2 - Wireless communication device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless communication device, and more particularly to an SS-type wireless communication device.
[0002]
[Prior art]
In recent years, spread spectrum (SS) type wireless communication devices that are less affected by interference waves and have a high transmission speed have been used. As the spread spectrum system, a direct spread (DS) system, a frequency hopping (FH) system, and the like are known. The SS type wireless communication apparatus performs communication using one of a plurality of communication channels in an ISM (Industrial Scientific and Medical) band (2.4 to 2.5 GHz).
The frequency of this ISM band is also used for wireless devices other than SS wireless communication devices, such as wireless tags (RF-IDs).
In such a SS type radio communication device, if communication is performed on a communication channel used by another radio device, communication of other radio devices is disturbed. Therefore, communication channels (not used by other radio devices ( Communication is performed using an available communication channel. Whether or not a communication channel is usable is determined based on a received electric field strength signal (RSSI) indicating a level of a received signal in the communication channel.
[0003]
[Problems to be solved by the invention]
Incidentally, electrical devices such as microwave ovens and medical high-frequency heaters generate ISM band noise during operation.
The SS wireless communication device can receive data transmitted from the transmission side by means of a spreading code, a frequency hopping pattern, or the like even if ISM band noise is generated from such an electric device.
However, since the conventional wireless communication device determines whether each communication channel can be used based on the received electric field strength signal of each communication channel, not only the communication channel used by the wireless tag but also noise. It is determined that the communication channel in which the error occurs is also unusable. That is, it is determined that the communication channel cannot be used even though it is a usable communication channel. For this reason, there are problems that the number of usable communication channels is reduced and communication efficiency is poor.
As a result of various studies to solve the problems of the conventional wireless communication device, the present inventor has found that the frequency band of a signal transmitted from a wireless device such as a wireless tag is narrow, and the SS wireless communication device We found that the frequency band of noise generated from electronic devices such as frequency bands and microwave ovens is wide. That is, by determining the width of the frequency band, the communication channel is used by the wireless tag, or the communication channel is used by another SS type wireless communication device or the communication channel. It has been found that it is possible to determine whether noise is occurring.
Therefore, the present invention is configured to be able to determine whether the communication channel is a communication channel used by another radio having a narrow frequency band or a communication channel in which noise is generated, thereby improving communication efficiency. It is an object to provide a good wireless communication device.
[0004]
[Means for Solving the Problems]
A first aspect of the present invention for solving the above-described problems is an SS type radio communication apparatus as set forth in claim 1.
2. The SS wireless communication device according to claim 1, wherein when the received electric field strength in the communication channel set by the communication channel setting circuit is equal to or higher than a predetermined level , the processor has two or more adjacent to the set communication channel. If the received electric field strength in the communication channel is equal to or higher than the set level, communication is performed via the set communication channel.
As a result, when noise is generated in the communication channel set by the communication channel setting circuit, the set communication channel is used, so that the communication efficiency is improved.
According to a second aspect of the present invention, there is provided a SS type radio communication device as defined in claim 2.
Oite the radio communication apparatus SS system according to claim 2, the processor, when the received electric field intensity at two or more adjacent communication channel is not set level or more, based on the past reception field strength signals of the respective communication channels Select a new communication channel. As a result, the possibility that the new communication channel becomes unusable is reduced, and the process of resetting the communication channel can be reduced.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an embodiment of a wireless communication device of the present invention. The wireless communication device shown in FIG. 1 is a DS-SS wireless communication device using a superheterodyne method.
The antenna 10 is connected to a common contact 12 a of a transmission / reception change-over switch 12 via a filter 11 such as a bandpass filter, and a reception-side contact 12 b of the transmission / reception change-over switch 12 is connected to a mixer 13.
The mixer 13 mixes the received signal with the first local oscillation signal output from the first local oscillator 15 and outputs an intermediate frequency signal.
The intermediate frequency signal output from the mixer 13 is supplied to the mixers 18 and 19 of the quadrature demodulator 17 via the amplifier 16. The mixer 18 mixes the intermediate frequency signal and the second local oscillation signal output from the second local oscillator 20 and outputs an in-phase reception signal Ir. The mixer 19 mixes the intermediate frequency signal and the second local oscillation signal output from the second local oscillator 20 whose phase is shifted by 90 degrees by the transfer circuit 23, and outputs a quadrature-phase received signal Qr. .
The baseband processor 21 determines the received signal based on the in-phase received signal Ir and the quadrature-phase received signal Qr.
[0006]
On the other hand, the baseband processor 21 divides the transmission signal into an in-phase transmission signal It and a quadrature transmission signal Qt, and supplies the transmission signal to a quadrature modulator 22 having the same configuration as the quadrature demodulator 17. The quadrature modulator 22 combines a signal obtained by modulating the in-phase transmission signal It with the second local oscillation signal and a signal obtained by modulating the quadrature phase transmission signal Qt with the second local oscillation signal whose phase is shifted by 90 degrees. Output intermediate frequency signal.
The mixer 14 modulates the intermediate frequency signal with the first local oscillation signal. The mixer 14 is connected to the transmission side contact 12 c of the transmission / reception selector switch 12.
The baseband processor 21 supplies a transmission switching signal to the transmission / reception change-over switch 12 during the reception operation to connect the common contact 12a to the reception-side contact 12b, and supplies a transmission switching signal to the transmission / reception change-over switch 12 during the transmission operation. The common contact 12a is connected to the transmission side contact 12c.
Further, as will be described later, the baseband processor 21 performs processing for determining the level of the received signal of each communication channel based on the received electric field strength signal (RSSI) indicating the level of the received signal, and the first channel scan signal. The local oscillator 15 is supplied to the local oscillator 15 to scan the communication channel, and the communication channel for communication is determined.
The first local oscillator 15 of the present embodiment corresponds to the communication channel setting circuit of the present invention, and the amplifier 16 corresponds to the received electric field strength detection circuit of the present invention.
[0007]
First, the basic principle of the present invention will be described.
Currently, in the SS system, communication channels are set at intervals of 5 MHz in the ISM band (2.4 GHz to 2.5 GHz). For example, the communication channel 1 is set to 2.407 GHz, the communication channel 2 is set to 2.412 MHz, the communication channel 3 is set to 2.417 MHz, and the like.
Here, the frequency band of the wireless tag is about 1 MHz, that is, occupies one or two channels of the SS communication channel.
On the other hand, the frequency band of the SS system occupies 15 to 26 MHz, that is, the above-described SS system communication channels are occupied by 3 to 5 channels.
Further, noise generated from electrical equipment such as a microwave oven occupies 60 to 70 MHz, that is, occupies 12 to 14 channels of the SS communication channel.
Therefore, when a signal is detected in the communication channel n (the level of the received electric field strength signal RSSI in the communication channel n is equal to or higher than the set level), based on the level of the received electric field strength signal RSSI in the communication channel adjacent to the communication channel n, It is possible to determine whether the communication channel n is a communication channel used by an SS wireless communication device, a communication channel in which noise is generated, or a communication channel used by a wireless tag.
For example, when a signal is detected in three or more communication channels adjacent to the communication channel n (for example, the level of the received electric field strength signal RSSI in the communication channel n + 1, the communication channel n + 2, and the communication channel n + 3 is equal to or higher than the set level). It can be seen that the communication channel n is either a communication channel used by the SS wireless communication device or a communication channel in which noise is generated. On the other hand, when a signal is detected in a communication channel less than 3 channels adjacent to the communication channel n (for example, the level of the received electric field strength signal RSSI in the communication channel n + 1 is equal to or higher than the set level, but the received electric field strength in the communication channel n + 2 It can be seen that the communication channel n is a communication channel used by the wireless tag when the level of the signal RSSI is less than the set level.
[0008]
Next, the first embodiment of the operation for determining the communication channel in the wireless communication device of the present invention will be described with reference to the flowchart shown in FIG. Here, it is assumed that the first local oscillator 15 outputs a first local oscillation signal corresponding to the communication channel n.
When determining a communication channel for communication, the baseband processor 21 supplies a reception switching signal to the transmission / reception selector switch 12 to connect the antenna 10 to the mixer 13.
Then, the baseband processor 21 determines whether or not the level of the received electric field strength signal RSSI in the communication channel n is equal to or higher than the set level Vr (step S1). The setting level Vr is set to a level at which a signal or noise is not received and a signal or noise is received in each communication channel.
When the received electric field strength signal RSSI in the communication channel n is equal to or higher than the set level Vr, the communication channel is scanned (step S2). For example, a channel scan signal is supplied from the baseband processor 21 to the first local oscillator 15, and a first local oscillation signal corresponding to the communication channel n + 1 is output.
After scanning the communication channel, “1” is added to the number of channels (step S3). At the start of the process shown in FIG. 2, the number of channels is reset to “0”. The direction of scanning the channel can be set as appropriate.
[0009]
Next, it is determined whether or not the number of channels is equal to or greater than the set number Nr (step S4). As the set number Nr, for example, a value capable of discriminating between the frequency band of the SS wireless communication device, the frequency band of noise, and the frequency band of the wireless tag is set. For example, when the frequency band of the SS radio is 3 to 5 communication channels, the frequency band of noise is 12 to 14 communication channels, and the frequency band of the wireless tag is 2 communication channels or less, the number of settings “3” is set as Nr.
If the number of channels is less than the set number Nr, it is determined whether or not the received electric field strength signal RSSI in the communication channel after scanning (for example, communication channel n + 1) is equal to or higher than the set level Vr (step S5).
If the received electric field strength signal RSSI in the communication channel after scanning is equal to or higher than the set level Vr, the process returns to step S2 to scan the communication channel again. For example, the first local oscillation signal corresponding to the communication channel n + 2 is output.
[0010]
On the other hand, if the level of the received electric field strength signal of the communication channel n is less than the set level Vr in step S1, the communication channel n is not used by other radio devices or other SS radio communication devices, and noise Neither has occurred. Therefore, in this case, it is determined that the communication channel n is used as a communication channel (step S6).
In step S4, when the number of channels is equal to or larger than the set number Nr, that is, when the level of the received electric field strength signal RSSI in three or more communication channels adjacent to the communication channel n is equal to or higher than the set level, the communication channel n. Is used in the SS radio or there is a high possibility that noise is generated in the communication channel n. Therefore, in this case, it is determined that the communication channel n is used as a communication channel (step S6).
After it is determined in step S6 that the communication channel n is used, communication is performed in step S7, and then the process ends.
In step S5, if the level of the received electric field strength signal RSSI in the scanned communication channel (for example, communication channel n + 1) is lower than the set level, that is, the received electric field strength signal in three or more communication channels adjacent to the communication channel n. When the RSSI level is not higher than the set level, there is a high possibility that the communication channel n is used by a radio device having a frequency band narrower than the frequency band of the SS type radio communication device such as a radio tag. Therefore, in this case, after determining that the communication channel n is not used as a communication channel (step S8), the process is terminated. If it is determined in step S8 that the communication channel n is not used, a process of scanning the communication channel and searching for a usable communication channel is executed.
The determination of “whether or not” in steps S1, S4, and S5 may or may not include an equal sign.
[0011]
In the above embodiment, every time communication is performed, a usable communication channel is set. For this reason, for example, the communication channel n can be used because the other wireless device using the communication channel n was not operating at the previous communication, but the other wireless device using the communication channel n was used at the current communication. It is possible that the communication channel n cannot be used because of the operation. In this case, it is necessary to search for another available communication channel. Also, when another communication channel that can be used at that time is set, the same situation as described above may occur.
Therefore, it is less likely that the communication channel becomes unusable by determining a communication channel that has been used by another wireless device and setting a communication channel that is less likely to be used by another wireless device. The second embodiment will be described with reference to the flowchart shown in FIG.
The processing in steps S1 to S8 in the flowchart shown in FIG. 3 is the same as the processing in the flowchart shown in FIG.
In the present embodiment, every time the processing shown in the flowchart of FIG. 3 is executed during communication, the level of the received electric field strength signal RSSI in each communication channel is stored in the storage means.
After determining that the channel n is not used in step S8, the history of the level of the received electric field strength signal RSSI in each communication channel stored in the storage unit is referred to (step S9).
Based on the history of the received electric field strength signal RSSI in each communication channel, a new communication channel is selected from communication channels other than communication channels that have been used by other wireless devices whose frequency band is narrower than the SS wireless communication device. Is selected (step S10). The baseband processor 21 outputs a first local oscillation signal corresponding to the communication channel selected from the first local oscillator 15. In addition, the newly selected communication channel is notified to the wireless communication device of the communication partner via the control channel.
[0012]
As described above, in the second embodiment, a communication channel other than a communication channel that has been used by another wireless device having a frequency band narrower than that of the SS wireless communication device is selected and set. The possibility that the channel will be used by another wireless device is reduced, and the processing and time required to set the communication channel again can be reduced.
In the second embodiment, the processes in steps S9 and S10 are executed after the process in step S8. However, the processes in steps S9 and S10 are performed before the process in step S6, after the process in step S7, and the like. It can be executed at any point.
In step S10, it is preferable to select a communication channel other than the communication channel in which another wireless device has communicated and the communication channel in which noise has occurred.
As a method for selecting a communication channel, various selection methods such as the order of the number of communication channels and the order of the number of times used in the past are possible.
[0013]
In the above embodiment, the case where the SS wireless communication device is operated so as not to use the communication channel of the frequency band used in the wireless tag has been described. However, the present invention is not limited to the SS wireless communication device. The present invention is not limited to wireless tags, and can be applied to wireless devices having different frequency bands.
Further, although the super heterodyne system and SS system radio communication apparatuses have been described as the radio communication apparatus, the radio communication apparatus is not limited to the SS system radio communication apparatus and the super heterodyne system radio communication apparatus, and has various configurations. A machine can be used.
In addition, although a part of the receiving circuit and the transmitting circuit are shared, the receiving circuit and the transmitting circuit can be provided separately. In this case, the transmission / reception selector switch can be omitted.
Further, the reception field strength detection circuit for detecting the reception field strength of each communication channel is not limited to the intermediate frequency amplifier 16, and various detection circuits can be used.
[0014]
【The invention's effect】
As described above, if the SS type radio communication device according to claim 1 is used, it is set if the received electric field strength in two or more communication channels adjacent to the set communication channel is equal to or higher than a set level. The communication efficiency is improved because the communication is performed through the communication channel .
Further, if the SS type wireless communication device according to claim 2 is used, the possibility that the set communication channel becomes unusable is reduced, and the processing and time for resetting the communication channel can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an embodiment of a wireless communication device of the present invention.
FIG. 2 is a flowchart showing the first embodiment of the operation of the wireless communication device of the present invention.
FIG. 3 is a flowchart showing a second embodiment of the operation of the wireless communication device of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Antenna 12 Transmission / reception changeover switch 13, 14, 18, 19 Mixer 15, 20 Local oscillator 21 Baseband processor

Claims (2)

A communication channel setting circuit for setting any one of a plurality of communication channels, a reception field strength detection circuit for detecting a reception field strength in each communication channel, and a processor,
The processor sequentially detects reception field strengths of communication channels adjacent to the set communication channel when the reception field strength in the communication channel set by the communication channel setting circuit is equal to or higher than a predetermined level, and is adjacent to the communication channel setting circuit. An SS type radio communication device that performs communication via the set communication channel when the received electric field strength in two or more communication channels is equal to or higher than a set level. 2. The SS type radio communication apparatus according to claim 1, wherein a reception electric field strength signal of each communication channel is stored, and the processor has a reception electric field strength in two or more adjacent communication channels not higher than a set level. Sometimes a SS type radio communication device that selects a new communication channel based on the received field strength signal of each stored communication channel.

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