JP2005130122A - Frequency-hopping radio apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frequency-hopping radio apparatus for preferentially selecting a frequency channel, having the comparatively small degree of interference as a usable frequency channel using small amount of calculation. <P>SOLUTION: The apparatus is provided with a frequency-hopping radio communication section 11 for selecting one frequency channel from among a plurality of predetermined frequency channels, switching a frequency channel to be selected with the lapse of time, and assigning predetermined packet data to one frequency channel to perform radio communication; a frequency channel evaluation unit 12 for continuously determining whether or not each of the frequency channels selected by the frequency-hopping radio communication section is usable, according to a predetermined determining standard and controlling the frequency-hopping radio communication section to perform frequency hopping, while avoiding the frequency channels determined as being unavailable; and an evaluation standard deciding section 13 for updating the determining standard, of the frequency-channel evaluating section on the basis of the number of frequency channels determined as being unavailable by the frequency-channel evaluation unit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a frequency hopping radio apparatus, and more particularly to an evaluation criterion determining unit that determines a criterion for determining whether or not each frequency channel selected for communication is usable, and is used for, for example, a Bluetooth-compatible portable terminal. It is what is done.

  Bluetooth (Bluetooth) has been proposed as a new standard for wireless communication for mobile terminals to exchange data between mobile phones, PDAs (personal digital assistants), notebook computers, voice terminal devices (headphones, etc.) Using a 2.4 GHz band frequency, a maximum communication speed of, for example, 12 Mbps can be realized.

  With Bluetooth-compatible mobile devices (hereinafter referred to as Bluetooth devices), wireless communication is performed by switching one frequency channel selected from 79 frequency channels defined in the frequency band from 2.40 GHz to 2.48 GHz over time. The frequency hopping method is used. In this frequency hopping method, communication is performed by selecting a channel to repeat at a predetermined time interval (for example, 625 μs) based on a predetermined pseudo-random algorithm and assigning one packet data to one channel.

  By the way, the frequency band is used not only in Bluetooth devices but also in wireless LAN stations, for example. Unlike a Bluetooth device, a wireless LAN station does not perform frequency hopping and always uses a fixed frequency band (a continuous frequency width corresponding to approximately 20 channels of a Bluetooth device).

  FIG. 6 shows how a wireless LAN station interferes with a frequency hopping wireless device. When the frequency hopping wireless device 61 performs frequency hopping to perform Bluetooth communication, if data is transmitted to a frequency channel that overlaps the frequency band used in the wireless LAN station 62, the frequency hopping wireless device 61 transmits the data. Since the signal to be transmitted interferes with the signal transmitted by the wireless LAN station 62, there is a high possibility that one or both of the received data will be in error.

  Even when the frequency hopping wireless device 61 is affected by a noise signal leaked from an electronic device other than the wireless LAN station 62 (for example, a microwave oven), an error in received data may occur as described above. is there.

  In order to avoid such a data transfer error of the Bluetooth device, the frequency channel used by the wireless LAN station is autonomously detected by the Bluetooth device, and frequency hopping is performed by avoiding the detected frequency channel (the detected frequency channel). Are not used in Bluetooth communication), and two evaluation methods are roughly classified.

  (1) The first evaluation method continuously monitors errors in received data for each frequency channel, calculates a temporal average of errors, measures an error rate, and the measured error rate reaches a predetermined threshold value. When the frequency exceeds the frequency (the rate at which errors occur in the received data is high), the corresponding frequency channel is not used.

  (2) The second evaluation method is to continuously monitor RSSI (Received Signal Strength Indication) for each frequency channel, and when the frequency of RSSI value exceeding a predetermined threshold is high, the corresponding frequency channel Do not use.

  That is, as described above, the error rate and RSSI value of the received data are continuously measured, the frequency channel in which the error rate or RSSI value exceeds the predetermined threshold is specified, and the specified frequency channel is a wireless LAN station. May be determined not to be used for frequency hopping.

  On the other hand, when there are a plurality of devices that perform Bluetooth communication independently, since the plurality of Bluetooth devices perform frequency hopping of different sequences, the possibility of interference between them is low. is not. In addition, when the distance between the Bluetooth devices increases, the error rate of the received data increases.

  In this way, even when communicating between Bluetooth devices, the error rate and RSSI value of the received data are continuously measured as described above, and the frequency at which the error rate or RSSI value exceeds the predetermined criterion is high. The channel may be specified so that the specified frequency channel is not used in frequency hopping.

  However, in the evaluation method as described above, if a threshold value that is a criterion for determining the error rate or RSSI value is fixed, which frequency channel should be avoided when the number of frequency channels exceeding the threshold value increases? Cannot be specified.

  Also, when the number of frequency channels that can be used by a device that performs Bluetooth communication is very small, the error rate or RSSI value criterion is exceeded so that interference between devices that perform Bluetooth communication independently cannot be ignored. Even so, it is desirable to continue to use frequency channels with a relatively low degree of interference so that the number of usable frequency channels does not become extremely small.

  In this case, it is necessary to select a frequency channel that has a relatively low degree of interference by sorting the error rate or RSSI value from the frequency channels that exceed the error rate or RSSI value criteria. There is. However, the amount of calculation for sorting each piece of data (error rate or RSSI value) corresponding to a large number of frequency channels is generally large, and it has been difficult to achieve compatibility with the demand for lower power consumption of Bluetooth devices.

Non-Patent Document 1 discloses a method in which a device performing Bluetooth communication does not transmit / receive a packet when it is time to use a channel that is not used for frequency hopping.
N.Golmie, N.Chevrollier, and I.Elbakkouri, "Interference Aware Bluetooth Packet Scheduling", in Proceedings of GLOBECOM '01, IEEE Volume: 5, 2001, Page 2857-2863.

  As described above, the conventional frequency hopping wireless device fixes the determination criterion when not using the frequency channel in which the error rate or RSSI value of the received data frequently exceeds the predetermined determination criterion for frequency hopping. Therefore, when the number of unused frequency channels increases, there is a problem that it is impossible to specify which frequency channel is particularly desired to be avoided.

  In addition, when frequency channels with relatively low interference between devices that perform independent Bluetooth communication are used continuously, an error rate or RSSI can be used so that the number of usable frequency channels does not become extremely small. Sort the error rate or RSSI value size from frequency channels that exceed the value criterion. At this time, since the calculation amount for sorting is generally large, there is a problem that it is difficult to satisfy the demand for low power consumption of the Bluetooth device.

  The present invention has been made to solve the above-mentioned problems, and is not used when not using for frequency hopping a frequency channel whose received data error rate or RSSI value frequently exceeds a predetermined criterion. When the number of frequency channels increases, the number of frequency channels can be reduced, and it is easy to meet the demand for low power consumption when applied to Bluetooth devices without the need for sort calculations. An object of the present invention is to provide a frequency hopping radio apparatus.

  The frequency hopping radio apparatus according to the present invention selects one frequency channel from a plurality of predetermined frequency channels, switches the selected frequency channel with time, and transmits predetermined packet data to one frequency channel. A frequency hopping wireless communication unit that performs wireless communication by assignment and a frequency channel selected by the frequency hopping wireless communication unit are continuously determined according to a predetermined determination criterion, and determined as unusable. A frequency channel evaluation unit that controls the frequency hopping radio communication unit to perform frequency hopping while avoiding the frequency channel, and the frequency based on the number of frequency channels determined to be unusable by the frequency channel evaluation unit Update criteria for channel evaluation section Characterized by comprising a criterion determining unit.

  According to the frequency hopping radio apparatus of the present invention, by increasing the determination reference value as the number of usable frequency channels decreases, a frequency channel that can use a frequency channel with a small amount of calculation and a relatively small degree of interference. Can be preferentially selected.

<First Embodiment>
FIG. 1 is a block diagram schematically showing a first embodiment of a frequency hopping radio apparatus according to the present invention. In the frequency hopping radio apparatus 10 shown in FIG. 1, 11 is a frequency hopping radio communication unit, 12 is a frequency channel evaluation unit, 13 is an evaluation criterion determination unit, and 14 is a radio antenna.

  The frequency hopping wireless communication unit 11 selects one frequency channel from a plurality of predetermined frequency channels, switches the selected frequency channel with time, and assigns, for example, one packet data to one frequency channel. Wireless communication function. In this case, as a method of switching the frequency channel to be selected with the passage of time, the frequency channel is normally selected so as to be repeated at regular time intervals based on a predetermined pseudo-random algorithm.

  The frequency channel evaluation unit 12 has a determination function that continuously determines whether or not each frequency channel selected by the frequency hopping radio communication unit 11 can be used according to a predetermined determination criterion, and cannot be used (or not used). A control function for controlling the frequency hopping radio communication unit 11 so as to perform frequency hopping while avoiding the frequency channel determined to be.

  Specific example 1 of the determination function measures the frequency at which the RSSI value exceeds a predetermined threshold for each selected frequency channel, and determines whether the frequency exceeds a predetermined determination criterion to determine whether each frequency channel is This is a function for determining whether or not it can be used.

  The specific example 2 of the determination function measures the frequency of occurrence of an error in received data for each selected frequency channel and determines whether the frequency of the error exceeds a predetermined criterion by determining whether the frequency of the error exceeds a predetermined criterion. This is a function for determining whether or not it can be used.

  The evaluation criterion determination unit 13 has an update function for updating the determination criterion (threshold value) of the frequency channel evaluation unit 12 based on the number of frequency channels determined to be unusable (or not used) by the frequency channel evaluation unit 12 . This update function has a characteristic of updating the determination criterion so that the value (threshold value) of the determination criterion is monotonously increased in accordance with the number of frequency channels determined to be unusable (or not used).

  FIG. 2 shows a specific example of the criterion (threshold) update characteristic by the update function of the evaluation criterion determination unit 13 in FIG. FIG. 3 shows an example of the relationship between the criterion (threshold) updated by the update characteristic of FIG. 2 and the degree of interference in each selected frequency channel.

  As shown in FIG. 2, the number n of frequency channels (frequency channels determined to be unusable or not used) determined to exceed a threshold that is a criterion is equal to or lower than the lower limit value n_lo of the frequency channel number control range. In this case, it is not necessary to update the threshold value because Bluetooth communication can be performed without any problem.

  In addition, when the number n of frequency channels determined to exceed the threshold value that is the determination criterion is equal to or greater than the upper limit value n_hi of the frequency channel number control range, Bluetooth communication cannot be performed. There is no need to update.

  On the other hand, if the number n of frequency channels determined to exceed the threshold value that is the determination criterion is within the range between the lower limit value n_lo and the upper limit value n_hi of the frequency channel number control range, the determination is made. By increasing the threshold monotonously (proportional in this example) in accordance with the number n of frequency channels determined to exceed the reference threshold, the frequency channels determined to exceed the determination threshold It is possible to suppress the number n to a certain number or less, that is, to secure a certain number or more of frequency channels determined to be usable.

  Note that the frequency channel evaluation unit 12 and the evaluation criterion determination unit 13 exchange data and control signals between each other, and are preferably mounted on the same integrated circuit chip. In addition, a storage circuit unit for storing data of frequency channels determined to be usable by the frequency channel evaluation unit 12 and data of determination criteria updated by the evaluation criterion determination unit 13 (a storage circuit unit 42 in FIG. 4 described later). ) Is preferably mounted on the same integrated circuit chip.

  The update function of the evaluation criterion determination unit 13 as described above can be realized using a microprocessor (MPU) and a control program mounted on the same integrated circuit chip as the frequency channel evaluation unit 12.

  FIG. 4 schematically shows a part of an example of the configuration of the evaluation criterion determination unit 13 in FIG. In FIG. 4, 41 is an MPU (microprocessor), 42 is a storage circuit section for storing a control program and related data, and 43 is a signal bus.

  FIG. 5 shows an example of a control flow by the control program stored in the storage circuit unit 42 in FIG. As shown in FIG. 5, first, as Bluetooth communication parameters, the minimum value per_min and maximum value per_max of the error rate (or RSSI value) in the packet data, and the lower limit of the frequency channel number control range corresponding to this error rate range Value n_lo and upper limit value n_hi, threshold values th_min and th_max set corresponding to lower limit value n_lo and upper limit value n_hi For example, the rate and the threshold value ref_th serving as a determination criterion are set as follows, for example.

per_min = 8%, per_max = 98%, n_lo = 40, n_hi = 59,
rate = (th_max−th_min) / (n_hi−n_lo)
ref_th = th_min
Next, it is determined whether or not the frequency channel number n exceeding the initial threshold value ref_th is smaller than the lower limit channel number n_lo (n <n_lo). If the determination result is n <n_lo (Yes) , Ref_th = th_min is set and the next update is started.

  If the determination result is not n <n_lo (No), it is determined whether the frequency channel number n is larger than the upper limit channel number n_hi (n> n_hi). If the determination result is n> n_hi (Yes ), Ref_th = th_max is set and the next update is started.

  When the determination result is not n> n_hi (No), the threshold value ref_th is set to be optimized by setting ref_th = th_min + (n−n_lo) * rate, and the next update is performed.

  As described above, this frequency hopping wireless device compares a measurement value indicating the degree of interference of each frequency channel such as an error rate or RSSI value with a determination criterion to identify a usable frequency channel. The criterion value is changed according to the number of usable frequency channels. In this case, as the number of usable frequency channels decreases, the determination reference value is changed in a direction in which usable frequency channels increase. As a result, it becomes easy to realize low power consumption required when this apparatus is applied to a Bluetooth device without requiring a sort calculation that generally increases the amount of calculation.

1 is a block diagram schematically showing a first embodiment of a frequency hopping radio apparatus according to the present invention. FIG. The characteristic view which shows a specific example of the determination reference | standard (threshold value) update characteristic by the update function of the evaluation reference determination part in FIG. The figure which shows an example of the relationship between the criteria (threshold value) updated by the update characteristic of FIG. 2, and the grade of the interference in each selected frequency channel. The figure which shows typically a part of example of a structure of the evaluation criteria determination part in FIG. The figure which shows an example of the control flow by the control program stored in the memory | storage circuit part in FIG. The figure which shows a mode that a wireless LAN station gives interference to a frequency hopping radio | wireless apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Frequency hopping radio | wireless apparatus, 11 ... Frequency hopping radio | wireless communication part, 12 ... Frequency channel evaluation part, 13 ... Evaluation criteria determination part, 14 ... Radio antenna.

Claims (5)

Frequency hopping radio that selects one frequency channel from a plurality of predetermined frequency channels, switches the selected frequency channel with time, assigns predetermined packet data to one frequency channel, and performs wireless communication A communication department;
For each frequency channel selected by the frequency hopping radio communication unit, it is continuously determined whether or not it can be used according to a predetermined criterion, and frequency hopping is performed while avoiding the frequency channel determined to be unusable. A frequency channel evaluation unit for controlling the frequency hopping radio communication unit;
A frequency hopping radio apparatus comprising: an evaluation criterion determination unit that updates a determination criterion of the frequency channel evaluation unit based on the number of frequency channels determined to be unusable by the frequency channel evaluation unit.   The frequency channel evaluation unit measures whether the received signal strength exceeds a predetermined threshold and determines whether the frequency channel is usable by determining whether the frequency exceeds a predetermined criterion. The frequency hopping radio apparatus according to claim 1, wherein:   The frequency channel evaluation unit determines whether or not the frequency channel is usable by measuring the frequency of occurrence of errors in received data and determining whether or not the frequency of occurrence of errors exceeds a predetermined criterion. The frequency hopping radio apparatus according to claim 1.   The evaluation criterion determination unit determines the determination when the number of frequency channels determined to exceed the determination criterion value is within a range between a lower limit value and an upper limit value of a frequency channel number control range. 4. The number of unusable frequency channels is suppressed by increasing a threshold according to the number of frequency channels determined to exceed a reference value. The frequency hopping radio apparatus according to the item.   5. A storage circuit unit that stores data of frequency channels determined to be usable by the frequency channel evaluation unit and data of determination criteria to be updated and determined by the evaluation criterion determination unit. The frequency hopping radio apparatus according to any one of the above.

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