This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2019-173474 filed on Sep. 24, 2019; the entire contents of which are incorporated herein by reference.
An embodiment described herein relates generally to a reception device.
In recent years, an azimuth estimation function has been added to a next generation standard BLE5.1 (Bluetooth Low Energy 5.1) of Bluetooth (registered trademark) that is a wireless communication standard. This enables position tracking of objects and persons using radio waves of BLE. A reception device provided with such a BLE standard is required to have durability against a multipath environment in consideration of indoor use.
Although it is possible to alleviate degradation of signals due to influences of multiple paths by using a multipath canceller or the like as a countermeasure, there is a problem that the device becomes expensive. The capacity of a storage unit increases and the device becomes expensive as well, although it is possible to improve accuracy of azimuth estimation by increasing the number of packets used for azimuth estimation and performing weighted time multiplexing.
A reception device according to an embodiment in a system that performs wireless communication while switching a frequency channel includes a channel selecting unit, a generation unit, and a determination unit. The channel selecting unit converts a received signal of the frequency channel into a channel signal of an intermediate frequency. The generation unit generates a received channel number by a predetermined scheme. The determination unit determines whether or not to save a signal used for azimuth estimation in a storage unit from the channel signal based on the received channel number.
Hereinafter, the embodiment will be described in detail with reference to drawings.
First, a configuration of a reception device according to an embodiment will be described based on
The antenna 11 receives a signal in a wireless frequency band and outputs the signal to the tuner 12.
The tuner 12 that serves as the channel selecting unit selects a channel for the signal received by the antenna 11 in accordance with a received channel number from the received channel number generation unit 17, converts the signal into a signal of an intermediate frequency, and outputs the signal to the ADC 13. Note that the tuner 12 may convert the signal received by the antenna 11 into a signal of an intermediate frequency regardless of the received channel number.
The ADC 13 performs analog-to-digital conversion on the signal of the intermediate frequency and outputs the signal to the quadrature detection unit 14.
The quadrature detection unit 14 converts the digital signal of the intermediate frequency into a baseband signal and outputs the signal to the extraction unit 15.
The extraction unit 15 extracts a signal (field) used for azimuth estimation from the baseband signal and outputs the signal to the storage unit 18. Although the signal for azimuth estimation is a constant tone extension (CTE), the signal is not limited to a CTE but may be another signal.
In a case in which the received channel number from the received channel number generation unit 17 and a received channel number, which is received in the past, a signal for azimuth estimation of which is saved in the storage 18, are compared, if the result shows that, the received channel numbers are separated from each other by N channels or more, the determination unit 16 outputs to the storage unit 18 a command for saving the signal for azimuth estimation. Note that N is a predetermined number that can arbitrarily be set. The received channel number, which is received in the past, a signal for azimuth estimation of which is saved in the storage unit 18, may be a received channel number received in the past.
The received channel number generation unit 17 outputs the received channel number generated in a predetermined scheme to the tuner 12 and the determination unit 16. The received channel number is a signal indicating a channel number of a channel as a target of reception performed by the reception device 1. The received channel number can be replaced with an arbitrary signal that can uniquely specify the channel as a target of reception performed by the reception device 1 and the channel number of the channel. According to the BLE standard, a channel switching sequence is defined in advance by a communication protocol. Therefore, the received channel number generation unit 17 generates the received channel number in accordance with the channel switching sequence.
The reception device 1 according to the embodiment has thirty eight channels. Channel numbers CH0, CH1, . . . , CH37 that are continuous in an order from a low frequency band to a high frequency band are applied to the respective channels. In this specification, a channel of a channel number Chin (n is 0 to 37) will be referred to as a channel Chin. Note that the channel numbers in the embodiment indicate height relationships of frequency bands of the respective channels. Therefore, it is not necessary for the respective channels to be managed with numbers, and it is possible to manage the respective channels in an arbitrary scheme in which the channel numbers can be specified in the reception device 1.
The received channel number generation unit 17 generates received channel numbers in an order of the channel CH8, the channel CH1, the channel CH7, the channel CH20, the channel CH15, . . . in the embodiment.
The storage unit 18 saves the signal for azimuth estimation in accordance with the command from the determination unit 16. The storage unit 18 does not save the signal for azimuth estimation in a case in which no command is provided from the determination unit 16.
The azimuth estimation unit 19 performs azimuth estimation processing based on a plurality of signals for azimuth estimation saved in the storage unit 18. In the embodiment, the azimuth estimation unit 19 performs the azimuth estimation processing based on four signals, for example. If the azimuth estimation unit 19 executes the azimuth estimation processing, then the plurality of signals for azimuth estimation saved in the storage unit 18 are deleted.
Next, operations of the reception device 1 configured as described above will be described using
In a case in which the reception device 1 is used indoors, for example, inclusion of a notch in a frequency due to influences of multiple paths is conceivable. In a case in which a notch is included in the frequency of the channel CH7, for example, there is a high probability that reception quality of the channels CH6 and CH8 before and after CH7 is also degraded.
According to the embodiment, azimuth estimation is thus performed using channels in a plurality of frequency bands.
The channel CH7 is not separated from the channel CH8 received in the past by five channels or more, the signal of the channel CH7 is neither saved nor used for azimuth estimation. In this manner, the reception device 1 does not perform azimuth estimation using a plurality of signals with degraded reception quality, and accuracy of the azimuth estimation is thus improved.
In
The packet P8 has a field A8 configured of a preamble access address protocol data unit (PDU) and a CRC. A signal used for azimuth estimation is applied to the field A8. In the following description, the signal for azimuth estimation will be referred to as a constant tone extension (CTE), and the signal for azimuth estimation of the packet P8 will be described as CTE_B8.
The other packets P1, P7, P20, and P15 also have configurations that are similar to the configuration of the packet P8. The packet P1 has a field A1 and CTE_B1, the packet P7 has a field A7 and CTE_B7, the packet P20 has a field A20 and CTE_B20, and the packet P15 has a field A15 and CTE_B15.
In the case of
On the other hand, according to the embodiment, CTEs of channels that are close to a channel received in the past are not saved in the storage unit 18 with reference to a channel history as illustrated in
First, a received channel number of the channel CH8 is input from the received channel number generation unit 17 to the determination unit 16. The determination unit 16 compares the input received channel number (channel CH8) with a past received channel number, and no past received channel number is found. The determination unit 16 provides a command for saving CTE_B8 to the storage unit 18. In this manner, CTE_B8 is saved in the storage unit 18.
Next, a received channel number of the channel CH1 is input from the received channel number generation unit 17 to the determination unit 16. The determination unit 16 compares the input received channel number (channel CH1) with the past received channel number (channel CH8). Since the channel CH1 is separated from the channel CH8 by five channels or more, the determination unit 16 provides a command for saving CTE_B1 to the storage unit 18. In this manner, CTE_B1 is saved in the storage unit 18.
Next, a received channel number of the channel CH7 is input from the received channel number generation unit 17 to the determination unit 16. The determination unit 16 compares the input received channel number (channel CH7) with the past received channel numbers (the channel CH8 and the channel CH1). Although the channel CH7 is separated from the channel CH1 by five channels or more, the channel CH7 is not separated from the channel CH8 by five channels or more. Therefore, the determination unit 16 provides a command for not saving CTE_B7 to the storage unit 18. In this manner, CTE_B7 is not saved in the storage unit 18. Similarly, the determination unit 16 compares the received channels CH20 and CH15 with the past received channel numbers and provides commands for saving or not saving CTEs to the storage unit 18. In this manner, CTE_B8, CTE_B1, CTE_B20, and CTE_B15 are saved in the storage unit 18. The azimuth estimation unit 19 performs azimuth estimation using the four saved CTEs, namely CTE_B8, CTE_B1, CTE_B20, and CTE_B15.
As described above, the reception device 1 saves in the storage unit 18 CTEs of channels that are separated from past received channel numbers by N channels or more and performs azimuth estimation. In other words, the received channel numbers of the channels that are close to the channels received in the past are neither saved in the storage unit 18 nor used for azimuth estimation. As a result, the reception device 1 does not perform azimuth estimation using a plurality of signals with reception quality degraded by inclusion of a notch in a frequency due to influences of multiple paths. Therefore, it is possible to improve accuracy of azimuth estimation without significantly increasing the capacity of the storage unit even in a multipath environment according to the reception device in the embodiment.
Note that the determination unit 16 compares the received channel number from the received channel number generation unit 17 with the received channel numbers received in the past and determines whether or not to save the CTE in the storage unit 18 in the embodiment, but the embodiment is not limited thereto.
For example, the determination unit 16 may sequentially save CTEs of received channels in the storage unit 18, and in a case in which a channel with higher reception quality than reception quality of CTEs saved in the storage unit 18 is received, the determination unit 16 may replace the CTE of a channel with degraded reception quality with a CTE of a channel with higher reception quality. Alternatively, the determination unit 16 may save CTEs of channels from received signals with power that is higher than a predetermined threshold value in the storage unit 18. At this time, the determination unit 16 receives a signal selected by the tuner 12 and measures reception quality and power of the received signal.
Alternatively, the determination unit 16 may save a history, specifically, channels, the saving of which in the storage unit 18 is ordered through commands in the past and may save CTEs of the saved channels in the storage unit 18. Alternatively, the determination unit 16 may save an experimental rule in the past, specifically, channels with high accuracy in azimuth estimation performed in the past and may save CTEs of the saved channels in the storage unit 18. At this time, the determination unit 16 receives a result of azimuth estimation processing from the azimuth estimation unit 19 and measures accuracy of the azimuth estimation.
The determination unit 16 may select CTEs of channels to be saved in the storage unit 18 from a wide range. In a case in which there are thirty eight channels from the channel CH0 to the channel CH37, for example, the determination unit 16 may always save in the storage unit 18 a CTE of the channel CH0 and a CTE of the channel CH37, which are the outermost channels. In a case in which there are a plurality of channels the channel numbers are typically applied to the channels from a lower frequency band in an order of channels CH0, CH1, . . . , CH37. Therefore, the determination unit 16 always saves, in the storage unit 18, the CTE of the channel in the lowest frequency band and the CTE of the channel in the highest frequency band as the outermost channels.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2019-173474 | Sep 2019 | JP | national |