JP7681293B2 - Method for generating database for full-duplex communication and method for full-duplex wireless communication - Google Patents

Description

The present invention relates to a method for generating a database for full-duplex communication, and a full-duplex wireless communication method, for wireless communication by full-duplex wireless communication.

In the conventional frequency band below 6 GHz, the average throughput has increased by approximately 1.5 times per year due to the increase in mobile phone lines, and the problem of frequency congestion has become a common occurrence. In addition, with the introduction of the fifth generation mobile communication system (5G), the use of high SHF (Super High Frequency) bands and other bands will also begin, but it is not necessarily possible to secure a large number of channels, and it is thought that the problem of frequency congestion will not be resolved.

For this reason, B5G (Beyond 5G), the next generation communication standard after 5G, needs to respond to the further rapid increase in mobile traffic caused by the increase in mobile phone lines. In particular, in recent years, various technologies have been developed with the goal of improving the effective use of frequencies. One of these technologies is full-duplex wireless communication technology, which is a type of wireless multiplexing technology that simultaneously transmits and receives wireless signals.

Full-duplex wireless communication technology transmits and receives wireless signals simultaneously, so in principle it can double the efficiency of frequency usage. For this reason, it is highly useful in 5G and B5G wireless communication systems, including IoT systems.

The technology disclosed in Non-Patent Document 1 performs full-duplex wireless communication between multiple wireless terminals and a base station, thereby achieving effective use of frequency resources to expand radio wave resources.

Bharadia, E. McMilin, and S. Katti, “Full duplex radios.” In Proceedings of the ACM SIGCOMM 2013 conference on SIGCOMM’13, pages 375-386, NewYork, NY, USA, 2013.

However, this full-duplex wireless communication technology transmits and receives wireless signals simultaneously and at the same frequency, so the transmitted signal sent by the device can get into the receiving circuit and become mixed with the received signal, resulting in degradation of communication quality due to so-called self-interference. For this reason, in wireless communication systems that implement full-duplex wireless communication technology, it is essential to implement self-interference cancellation technology to fully cancel this self-interference.

As shown in Figure 6, self-interference cancellation is generally realized by targeting antenna isolation, a high-frequency analog canceller, and a baseband digital canceller, and by carrying out optimal design and development according to the frequency. It is relatively easy to achieve antenna isolation 9 by adjusting the distance and arrangement of the transmitting antenna 71 and the receiving antenna 72, and by achieving isolation of several tens of dB. The baseband digital canceller 73 is an interference canceller in the digital domain, and although it is system-dependent, it is not frequency-dependent, and the input signal level is also converged to a certain range by the analog circuit in the previous stage, so the same interference canceller can be applied to systems of different frequencies.

The high-frequency analog canceller 74 implements a feedback circuit between the transmission circuit 75 and the reception circuit 76, and uses its own transmission signal as a reference signal to perform optimal gain (signal level) and delay correction so that the feedback signal from the transmission antenna 71 has the same amplitude and opposite phase, and cancels the feedback signal by mixing the reference signal and the feedback signal.

However, in such a self-interference canceller in a high-frequency analog circuit, the target interference signal changes depending on, for example, the distance and arrangement of the transmitting antenna 71 and the receiving antenna 72. For this reason, it is necessary to create a database 77 in which the reference interference signal that is transmitted from the transmitting antenna 71 to the receiving antenna 72 is recorded in advance, and to refer to the reference interference signal recorded in the database 77 to perform optimal gain and delay correction and generate a reference signal.

In such cases, the amount of information required for database 77 to stably cancel looping signals changes due to temporal fluctuations in the communication environment and differences in the communication environment between terminals. For example, the optimal amount of information required differs between a daytime communication environment where communication volume is high and a nighttime communication environment where communication volume is low. If the amount of information is less than the optimal amount required, the accuracy of communication becomes unstable, and if the amount of information is more than the optimal amount required, extra communication costs are incurred. For this reason, in order to stably cancel looping signals, it is necessary to apply database 77 with an amount of information that matches the communication environment.

In addition, for example, a typical transmitting antenna 71 and receiving antenna 72 have directivity that changes the accuracy of communication depending on the direction of the communication device performing wireless communication. Therefore, the amount of information required to stably cancel the feedback signal varies depending on the above-mentioned direction. Therefore, in order to stably cancel the feedback signal, it is necessary to apply a database 77 with an amount of information that matches the antenna directivity.

However, in the technology disclosed in Non-Patent Document 1, the same database 77 is operated even when the communication environment fluctuates over time, differs between terminals, or the direction of the communication device is different, so it is not possible to stably cancel the echo signal in the face of such fluctuations and differences.

The present invention has been developed to solve the above-mentioned problems, and aims to provide a database generation method for full-duplex communication and a full-duplex wireless communication method that can stably cancel loop interference signals despite temporal fluctuations and differences in the communication environment.

A database generating method for full-duplex communication according to a first aspect of the present invention uses a communication device having a transmitting antenna for transmitting a transmission signal and a receiving antenna for receiving a reception signal, and which communicates wirelessly with an external terminal using full-duplex wireless communication, to generate a database for canceling a loop signal received by the receiving antenna from a transmission signal transmitted by the transmitting antenna. The method includes a loop receiving step for receiving only a reference loop signal received by the receiving antenna from a reference transmission signal transmitted by the transmitting antenna , and a generation step for sampling the reference loop signal received by the loop receiving step and generating the database for recording the reference loop signal, characterized in that the generation step performs a process of sequentially generating the databases so that the amount of information varies depending on one or more of period information regarding the length of the period during which the reference loop signal is received by the receiving antenna and period information regarding the period for sampling the reference loop signal.

The second invention relates to a method for generating a database for full-duplex communication according to the first invention, characterized in that the loop reception step acquires directional information related to the direction of the transmitting antenna or the receiving antenna in the direction from the external terminal to the communication device, and the generation step performs processing to determine one or more of the period information and the cycle information according to the directional information acquired by the loop reception step.

The third invention relates to a method for generating a database for full-duplex communication according to the second invention, and is characterized in that, in the generation step, if the directional information acquired in the wraparound reception step is identical to other directional information, a database is generated with the same amount of information as the database generated for the other directional information.

The full-duplex wireless communication method according to the fourth aspect of the present invention is characterized in that in the second aspect of the present invention, when the directional information acquired in the wraparound reception step is identical to other directional information, the generating step shares the database generated for the other directional information.

A full-duplex wireless communication method according to a fifth aspect of the present invention is a full-duplex wireless communication method for performing full-duplex wireless communication between a communication device having a transmitting antenna for transmitting a transmission signal and a receiving antenna for receiving a reception signal, and an external terminal, the method comprising: a loop receiving step for receiving only a reference loop signal received by the receiving antenna from a reference transmission signal transmitted by the transmitting antenna; a generation step for sampling the reference loop signal received by the loop receiving step and sequentially generating a database for recording the reference loop signal; a communication receiving step for newly receiving a reception signal including a loop signal by the receiving antenna; and a processing step for referring to one or more of the databases generated by the generation step and canceling the loop signal included in the reception signal received by the communication receiving step, characterized in that the generation step sequentially generates the databases so that the amount of information varies depending on one or more of period information regarding the length of the period during which the reference loop signal is received by the receiving antenna and period information regarding the period for sampling the reference loop signal.

The full-duplex wireless communication method according to the sixth invention is the fifth invention, characterized in that the generating step generates a database for each of the external terminals, the communication receiving step acquires, for each of the external terminals, directional information relating to the direction of the transmitting antenna or the receiving antenna relative to the direction toward the communication device, and the processing step, when the directional information of the external terminal newly acquired in the communication receiving step is the same as the directional information of another external terminal, refers to the database generated for the other external terminal.

According to the first to sixth inventions, databases are generated sequentially so that the amount of information varies depending on one or more of period information regarding the length of the period during which the reference interference signal is received by the receiving antenna and period information regarding the period at which the reference interference signal is sampled. This makes it possible to generate multiple databases with different amounts of information depending on the period information or period information, making it possible to refer to databases with appropriate amounts of information for fluctuations and differences in the communication environment. This makes it possible to stably cancel interference signals despite fluctuations and differences in the communication environment.

In particular, according to the second invention, the generating step determines one or more of the period information and the cycle information according to the directional information acquired by the loop reception step. This makes it possible to determine an appropriate amount of information in the database according to the directional information, thereby enabling stable cancellation of the loop signal against fluctuations and differences due to changes in directivity.

In particular, according to the third invention, in the generation step, if the directional information acquired in the wraparound reception step is identical to other directional information, a database with the same amount of information as the database generated for the other directional information is generated. This allows the amount of information in the database to be determined univocally, for example, in cases where the directional information is identical, thereby reducing the burden of generating the database.

In particular, according to the fourth aspect of the invention, the generating step is characterized in that, if the directional information acquired in the wraparound receiving step is identical to other directional information, the database generated for the other directional information is shared. This allows the same database to be shared between external terminals having the same directional information, thereby reducing the burden of generating the database.

In particular, according to the sixth aspect of the present invention, if the directional information of the external terminal newly acquired in the communication reception step is identical to the directional information of another external terminal, the processing step refers to the database generated for that other external terminal. As a result, when wireless communication is performed with multiple external terminals, for example, if the directional information is identical, the external terminals can share the same database, thereby reducing the burden of canceling the feedback signal.

FIG. 1 is an overall schematic diagram of a wireless communication system to which a database generating device and a self-interference cancellation circuit according to the present invention are applied. FIG. 2 shows a block diagram of a self-interference cancellation circuit. FIG. 3 shows a block diagram of the database generating device. FIG. 4 shows a flow chart of a full-duplex wireless communication method to which the present invention is applied. FIG. 5 shows the directivity of the antenna. FIG. 6 is a diagram for explaining a general self-interference cancellation method.

The self-interference cancellation circuit to which the present invention is applied will be described in detail below with reference to the drawings.

Figure 1 is an overall schematic diagram of a wireless communication system 1 to which the present invention is applied. The wireless communication system 1 includes a base station 2 and multiple user terminals 3. The wireless communication system 1 will be described using an example in which a full-duplex wireless communication method is adopted, which is a duplex method that uses the same frequency and the same time slot to simultaneously transmit and receive, but the present invention is not limited to this, and a general half-duplex wireless communication method may also be adopted.

The base station 2 serves as a wireless access point between the user terminal 3 and the base station 2, and serves as an interface between the base station 2 and public communication networks such as the Internet. In other words, the base station 2 serves as a relay means that enables the user terminal 3 to transmit and receive data between the base station 2 and public communication networks such as the Internet. The base station 2 performs wireless communication with the user terminal 3 based on the above-mentioned full-duplex wireless communication method. The base station 2 also includes a self-interference cancellation circuit 10 for canceling loopback signals.

The user terminal 3 is composed of a terminal device capable of wireless communication, such as a notebook personal computer (PC), a mobile terminal, a smartphone, a tablet terminal, a wearable terminal, etc. Such a user terminal 3 transmits and receives packet data between the base station 2 via wireless communication, using a transmission signal or a reception signal made of a radio frequency.

Figure 2 shows the block configuration of the self-interference cancellation circuit 10. The self-interference cancellation circuit 10 is roughly classified into a database generating device 4, a receiving circuit 5 and a transmitting circuit 6 connected to the database generating device 4, and a local oscillator circuit 8 connected to the receiving circuit 5 and the transmitting circuit 6. This self-interference cancellation circuit 10 applies a so-called superheterodyne circuit configuration, and the receiving circuit 5 band-converts the radio frequency of the received signal received from the user terminal 3 to generate a converted signal, which is then output to the inside of the base station 2. The transmitting circuit 6 band-converts the converted signal output from the inside of the base station 2 to a radio frequency, converts it into a transmission signal, and transmits it to the user terminal 3. The local oscillator circuit 8 supplies the reference signal to be mixed in each band conversion to the receiving circuit 5 and the transmitting circuit 6, respectively. Each of these configurations will be described in detail below.

The receiving circuit 5 includes a receiving antenna 11, a processor 31 connected to the receiving antenna 11 and the database generating device 4, a coupler 32 connected to the receiving antenna 11 and the processor 31, an amplifier 12 connected to the coupler 32, a receiving band filter 13 connected to the amplifier 12, an attenuator 14 connected to the receiving band filter 13, a mixer 15 connected to the attenuator 14, a filter 16 connected to the mixer 15, a high gain amplifier 18 connected to the filter 16, and an attenuator 19 connected to the high gain amplifier 18, and the attenuator 19 is connected inside the base station 2.

The transmission circuit 6 includes an attenuator 21 connected inside the base station 2, a mixer 22 connected to the attenuator 21, a bandpass filter 23 connected to the mixer 22, a buffer amplifier 24 connected to the bandpass filter 23, a variable attenuation circuit 25 connected to the buffer amplifier 24, a driver amplifier 26 connected to the variable attenuation circuit 25, a power amplifier 28 connected to the driver amplifier 26, an isolator 29 connected to the power amplifier 28, and a database generation device 4 and a transmission antenna 30 connected to the isolator 29.

The local oscillator circuit 8 includes a reference clock 41 and voltage-controlled oscillators 42 and 43 connected to the reference clock 41. The voltage-controlled oscillator 42 is connected to the mixer 15 in the receiving circuit 5, and the voltage-controlled oscillator 43 is connected to the mixer 22 in the transmitting circuit 6.

The receiving antenna 11 is an antenna for receiving a higher radio frequency signal transmitted from the user terminal 3. The components of the received signal received by this receiving antenna 11 include components that may be self-interference, which are caused by a loop signal received by the transmission signal transmitted from the transmitting antenna 30 looping around. The receiving antenna 11 converts the radio signal of the received signal, including such a loop signal, into an electrical signal, and outputs it to the coupler 32, the database generating device 4, and the processor 31.

The processor 31 refers to the database 55 (described later) recorded by the database generator 4, and outputs to the coupler 32 a reference signal that has been subjected to optimal gain and delay correction so that the feedback signal contained in the received signal has the same amplitude but the opposite phase.

The coupler 32 receives an electrical signal of the received signal including the feedback signal from the receiving antenna 11. A reference signal is also input to the coupler 32 from the processor 31. The coupler 32 performs a process of mixing the electrical signal with the reference signal. This allows the feedback signal itself to be cancelled by superimposing the reference signal, which has been subjected to optimal gain and delay compensation so that the feedback signal contained in the electrical signal has the same amplitude but the opposite phase as the feedback signal. The coupler 32 outputs the electrical signal from which the feedback signal has been cancelled to the amplifier 12.

The amplifier 12 amplifies the electrical signal output from the coupler 32 and outputs it to the receive band filter 13.

The receiving band filter 13 limits the band of the electrical signal from the amplifier 12 to a predetermined range and outputs it to the attenuator 14.

The attenuator 14 attenuates the electrical signal input from the receiving band filter 13 and outputs it to the mixer 15.

The mixer 15 mixes the reference signal output from the local oscillator circuit 8 with the electrical signal to generate a conversion signal. The mixer 15 outputs this conversion signal to the filter 16.

Filter 16 extracts specific frequency components from the converted signal input from mixer 15 and applies band limitation to other frequency components. Band limitation is performed in the receiving band filter 13, but since this is performed in the high-frequency radio frequency band, unnecessary frequency components are cut by applying band limitation again in this specific frequency range. Filter 16 outputs the band-limited converted signal to high-gain amplifier 18.

The high-gain amplifier 18 is a circuit that performs high-gain amplification on the converted signal input from the filter 16. The high-gain amplifier 18 outputs the amplified converted signal to the attenuator 19.

The attenuator 19 attenuates the converted signal input from the high gain amplifier 18, then transmits it to the base station 2 and utilizes the various information contained therein.

The attenuator 21 attenuates the converted signal input from inside the base station 2 and outputs it to the mixer 22.

The mixer 22 mixes the reference signal output from the local oscillator circuit 8 with the converted signal to generate an electrical signal of the transmission signal converted to a high-frequency radio frequency. The mixer 22 outputs the transmission signal converted to a radio frequency component to the bandpass filter 23.

The bandpass filter 23 performs filtering on the transmission signal output from the mixer 22, passing only a specified band and restricting other bands, and outputs the result to the buffer amplifier 24.

The buffer amplifier 24 amplifies the transmission signal output from the bandpass filter 23 and outputs it to the variable attenuation circuit 25.

The variable attenuation circuit 25 adjusts the amount of attenuation so that the transmission signal input from the buffer amplifier 24 has an appropriate output level, and outputs this to the driver amplifier 26.

The driver amplifier 26 amplifies the transmit signal to the desired voltage level and outputs it to the power amplifier 28.

The power amplifier 28 amplifies the power of the transmission signal supplied from the driver amplifier 26 and outputs it to the isolator 29.

The isolator 29 is a device for isolating the circuit that generates a transmission signal as needed and leads it to the transmission antenna 30. When the transmission signal from the power amplifier 28 passes through the isolator 29, it is output to the transmission antenna 30.

The reference clock 41 is a clock that is used as a reference when actually generating the reference signal. The voltage-controlled oscillator 42 refers to the time information from the reference clock 41 when oscillating the reference signal to be supplied to the mixer 15. Similarly, the voltage-controlled oscillator 43 refers to the time information from the reference clock 41 when oscillating the reference signal to be supplied to the mixer 22.

Next, the configuration of the database generating device 4 for generating the database 55 for canceling the loop interference signal will be described. The database 55 for canceling the loop interference signal is a database in which sampled reference loop interference signals are recorded, and which is used to create reference signals necessary for canceling the loop interference signal.

Figure 3 is a diagram showing a block configuration of the database generating device 4. The database generating device 4 includes a reception information acquisition unit 50 connected to the transmitting antenna 30, a directionality information acquisition unit 51, a period information determination unit 52 connected to the reception information acquisition unit 50 and the directionality information acquisition unit 51, a period information determination unit 53 connected to the directionality information acquisition unit 51, a database generating unit 54 connected to the receiving antenna 11, the period information determination unit 52, and the period information determination unit 53, and a recording unit 56 connected to the database generating unit 54. The recording unit 56 is also connected to the processor 31.

The reception information acquisition unit 50 acquires reception information related to the reception status of the receiving antenna 11, and outputs a reference transmission signal to the transmitting antenna 30 according to the reception information. The reception information acquisition unit 50 may also output the acquired reception information to the period information determination unit 52.

The directivity information acquisition unit 51 acquires directivity information regarding the directivity of the transmitting antenna 30 or the receiving antenna 11 in the direction from the user terminal 3 to the base station 2. The directivity information acquisition unit 51 outputs the acquired directivity information to the period information determination unit 52 and the period information determination unit 53.

The period information determination unit 52 acquires period information regarding the length of the period during which the reference loop signal is received by the receiving antenna 11, according to the reception information output from the reception information acquisition unit 50 or the directionality information output from the directionality information acquisition unit 51. The period information determination unit 52 outputs the acquired period information to the database generation unit 54.

The period information determination unit 53 acquires period information regarding the period for sampling the reference loop signal according to the directivity information output from the directivity information acquisition unit 51. The period information determination unit 53 outputs the acquired period information to the database generation unit 54.

The database generation unit 54 receives the reference loop signal through the receiving antenna 11 in accordance with the period information output from the period information determination unit 52. The database generation unit 54 samples the received reference loop signal in accordance with the period information output from the period information determination unit 53. The database generation unit 54 creates multiple databases 55 that record the sampled reference loop signals, the amount of information of which differs in accordance with at least one of the period information and the period information. The database generation unit 54 outputs the generated databases 55 to the recording unit 56.

The recording unit 56 stores the generated database 55 and outputs the database 55 to the processing unit 31 as necessary.

Next, the operation of canceling a loop signal in full-duplex wireless communication in this embodiment will be described with reference to FIG. 4. The operation of canceling a loop signal in this embodiment generates a database 55 for canceling the loop signal through a loop reception step S11 for receiving a reference loop signal and a generation step S12 for generating a database 55. Thereafter, the operation of canceling the loop signal is completed by referring to the database 55 through a communication reception step S13 for receiving a new received signal and a processing step S14 for canceling the loop signal. Each step will be described in detail below.

First, in the wraparound reception step S11, the directional information acquisition unit 51 acquires directional information regarding the direction of the transmitting antenna 30 or the receiving antenna 11 in the direction from the user terminal 3 to the base station 2. The directional information acquisition unit 51 acquires directional information based on the GPS position information of the user terminal 3, or the relative positional relationship between the base station 2 and the user terminal 3, etc. In such a case, the user terminal 3 may not actually be communicating, but may be a user terminal 3 that is intended to communicate wirelessly using the generated database 55, for example. The directional information acquisition unit 51 outputs the acquired directional information to the period information determination unit 52 and the period information determination unit 53.

As shown in FIG. 5, the directional information may be, for example, information indicating the angle of the direction B from the user terminal 3 to the base station 2 with respect to the direction A in which the receiving antenna 11 is oriented, the position of the user terminal 3 with respect to the direction A in which the receiving antenna 11 is oriented, or the degree of energy loss of the transmission signal or the reception signal in the wireless communication between the receiving antenna 11 oriented in the direction A and the user terminal 3 located in the direction B from the base station 2. The accuracy of communication of a directional antenna such as the receiving antenna 11 changes depending on the change in the direction B from the user terminal 3 to the base station 2 with respect to the direction A in which the antenna is oriented. For example, the energy loss of the reception signal received by the receiving antenna 11 when communicating with the user terminal 3b located in the direction B2, which is larger than the angle of the direction B1 with respect to the direction A, is larger than when communicating with the user terminal 3a located in the direction B1 using the receiving antenna 11 oriented in the direction A. Therefore, the amount of information required in the database 55 differs depending on the directional information between the receiving antenna 11 or the transmitting antenna 30 and the user terminal 3.

Next, the reception information acquisition unit 50 acquires reception information regarding the reception status of the reception signal by the receiving antenna 11. The reception information may be, for example, information indicating whether the receiving antenna 11 is receiving a reception signal, information indicating the degree of reception of the reception signal by the receiving antenna 11, or information indicating the source of the reception signal received by the receiving antenna 11. The reception information acquisition unit 50 controls the transmission of the reference transmission signal by the transmitting antenna 30 according to the reception information. It is preferable that the reception information acquisition unit 50 transmits the reference transmission signal to the transmitting antenna 30 and receives the reference loop signal by the receiving antenna 11 according to the reception information, for example, when the receiving antenna 11 is not receiving a reception signal, but this is not limited to this. For example, when the degree of reception of the reception signal by the receiving antenna 11 is lower than a preset threshold, the reception information acquisition unit 50 may transmit the reference transmission signal to the transmitting antenna 30 and receive the reference loop signal by the receiving antenna 11. Furthermore, when the source of the received signal received by the receiving antenna 11 is only the transmitting antenna 30, the receiving information acquisition unit 50 may transmit a reference transmission signal to the transmitting antenna 30 and receive the reference loopback signal by the receiving antenna 11. Furthermore, the receiving information acquisition unit 50 may output the receiving information to the period information determination unit 52.

The reference transmission signal is a transmission signal transmitted from the transmitting antenna 30 in order to generate the database 55. The reference interference signal is a interference signal received by the receiving antenna 11 from the reference transmission signal transmitted from the transmitting antenna 30 in order to generate the database 55.

Next, in the generation step S12, the period information determination unit 52 determines and acquires period information regarding the length of the period during which the reference loop signal is received by the receiving antenna 11 in accordance with the reception information output from the reception information acquisition unit 50 or the directional information output from the directional information acquisition unit 51. The period information may be, for example, the date and time when reception of the reception signal by the receiving antenna 11 starts and the date and time when reception ends, or the length of the period from the date and time when reception starts to the date and time when reception ends. When the reception information is input by the reception information acquisition unit 50, the period information determination unit 52 determines and acquires the period information so that, for example, the receiving antenna 11 receives only the reference transmission signal transmitted from the transmitting antenna 30. In addition, when the directional information is input by the directional information acquisition unit 51, the period information determination unit 52 may determine and acquire the period information in accordance with the directional information. In such a case, for example, when the input directional information is information indicating the degree of energy loss of the received signal in wireless communication, the period information determination unit 52 may determine the length of the period from the date and time when reception starts to the date and time when reception ends in accordance with the degree of energy loss. This makes it possible to generate a database 55 with an appropriate amount of information depending on the directional information between the receiving antenna 11 or transmitting antenna 30 and the user terminal 3.

The period information determination unit 52 may also acquire period information without receiving reception information and directional information. In such a case, for example, the period information determination unit 52 may determine the period information so that the reference loop signal is received for a long period of time during the daytime when communication volume is high, and may determine the period information so that the reference loop signal is received for a short period of time during the nighttime when communication volume is low. This makes it possible to generate a database 55 with an appropriate amount of information for each fluctuation and difference in the communication environment.

The periodic information determination unit 53 also determines and acquires periodic information regarding the period for sampling the reference loop signal. The periodic information is information regarding the period for sampling the reference loop signal, and may be, for example, information indicating that sampling is performed once every 10 seconds, but is not limited to this. The periodic information determination unit 53 may determine periodic information such that the sampling period is short during daytime hours when communication volume is high, and may determine periodic information such that the sampling period is long during nighttime hours when communication volume is low. In generating the database 55, the amount of information in the database 55 increases when the sampling period is short and sampling is performed frequently, so that it is possible to generate a database 55 with an appropriate amount of information for each fluctuation and difference in the communication environment.

The period information determination unit 53 may also determine and acquire period information according to the directional information output from the directional information acquisition unit 51. In this case, for example, when the input directional information is information indicating the degree of energy loss of a received signal in wireless communication, the period information determination unit 53 may determine the period of the reference loop signal according to the degree of energy loss. This makes it possible to generate a database 55 with an appropriate amount of information according to the directional information between the receiving antenna 11 or transmitting antenna 30 and the user terminal 3.

Next, the database generating unit 54 controls the reception of the reference loop signal by the receiving antenna 11 based on the period information output from the period information determining unit 52. In such a case, the database generating unit 54 may control the reception of the reference loop signal only during the period indicated by the period information. In addition, the database generating unit 54 may acquire only the reference loop signal received during the period indicated by the period information among the reference loop signals received by the receiving antenna 11. After that, the database generating unit 54 samples the received or acquired reference loop signal based on the period information, and then sequentially generates a database 55 that records the sampled reference loop signal. The database generating unit 54 sequentially generates the databases 55 so that the amount of information differs depending on the period information or period information. The database generating unit 54 may sequentially generate databases 55 with different amounts of information for each period information or period information from the reference loop signal indicating the same information. In addition, the database generating unit 54 may generate databases 55 with different amounts of information for each type of reference loop signal, such as a reference loop signal indicating an image or a reference loop signal indicating a sound. This allows multiple databases 55 with different amounts of information to be generated according to the period information or cycle information, so that appropriate databases 55 can be referenced for each variation or difference in the communication environment. This makes it possible to stably cancel loop interference signals even when the communication environment varies or differs.

In addition, in the generation step S12, if the acquired directional information is the same as other directional information in the wraparound reception step S11, the database 55 may be generated with the same amount of information as the database 55 corresponding to the other directional information. This allows the amount of information in the database 55 to be determined uniquely, for example, when the directional information is the same, so the burden of generating the database 55 is reduced. In addition, in the generation step S12, if the acquired directional information is the same as other directional information, the database 55 generated for the other directional information may be shared. This allows the same database 55 to be shared between external terminals with the same directional information, so the burden of generating the database 55 is reduced. In addition, the database 55 may be generated so as to correspond to each user terminal 3 with which communication is expected. In addition, the database 55 may be created in advance before starting new communication, or may be generated immediately before communication is performed.

Next, we will explain the operation of the self-interference cancellation circuit 10, which refers to the database 55 and cancels the sneak interference signal.

The self-interference cancellation circuit 10 first creates a conversion signal under a full-duplex wireless communication system, which is a duplex system that simultaneously transmits and receives. The conversion signal is generated inside the base station 2 and is supplied to the attenuator 21.

The converted signal supplied to the attenuator 21 is attenuated and then output to the mixer 22. The converted signal output to the mixer 22 is mixed with a reference signal supplied from the local oscillator circuit 8 to become a transmission signal converted to a high radio frequency. The transmission signal is band-limited in the bandpass filter 23, amplified in the buffer amplifier 24, and attenuated in the variable attenuation circuit 25. The transmission signal is further amplified in the driver amplifier 26, amplified in the power amplifier 28, and sent to the transmission antenna 30 via the isolator 29. The transmission antenna 30 emits the transmission signal, which is then conveyed to the user terminal 3 as a radio signal in the radio frequency band.

In the communication reception step S13, a part of the transmission signal sent from the transmission antenna 30 may be received by the receiving antenna 11 as a return signal, and the return signal may be superimposed on the transmission signal sent from the user terminal 3. The receiving antenna 11 outputs the received signal to the processing unit 31 and the coupler 32.

In addition, in the communication reception step S13, directional information of the transmitting antenna 30 or the receiving antenna 11 in the direction from an external terminal such as the user terminal 3 to a communication device such as the base station 2 may be acquired for each user terminal 3.

The received signal sent to the coupler 32 still contains a loop signal. In processing step S14, the coupler 32 performs processing to cancel the loop signal contained in the received signal. Specifically, the reference signal input from the processor 31 is mixed with the received signal containing the loop signal.

This reference signal is generated in processing step S14 with reference to the database 55 described above. For example, the processor 31 may extract a loop signal from the received signal, refer to one or more of the databases 55 generated in generation step S12, and generate a reference signal from the reference loop signals contained in the database 55 that has the same amplitude and opposite phase as a reference loop signal that is equivalent to or similar to the extracted loop signal. For this reason, the database 55 previously generated in generation step S12 is referenced to generate a reference signal that has the same amplitude and opposite phase as the reference loop signal, and the loop signal can be canceled by superimposing this on the loop signal.

The unit for processing the loop signal, including the coupler 32 and the processing unit 31, may be provided in any part of the receiving circuit 5. For example, the coupler 32 and the processing unit 31 may be connected to the mixer 15, and the filter 16 may be connected to the coupler 32. Any well-known method may be used to extract the loop signal from the received signal. It is not essential to obtain the loop signal from the received signal each time, and before the start of actual communication, a reference loop signal contained in a database 55 generated in advance may be assumed to be the loop signal, and its amplitude and phase may be detected in advance.

In addition, when the processing unit 31 refers to one or more of the databases 55 generated in the generation step S12, the database 55 to be referred to may be selected, for example, according to the communication environment. In such a case, for example, during times when the accuracy of wireless communication is low, such as during the day when communication volume is high, or when the reception and transmission sensitivity of the communication partner is low, a database 55 with a large amount of information is selected from the multiple databases 55 and referred to, thereby enabling stable cancellation of loop interference signals.

In addition, when the processing unit 31 refers to one or more of the databases 55 generated in the generation step S12, the database 55 to be referred to may be selected according to the directional information acquired in the communication reception step S13, for example. In such a case, it is possible to select an appropriate database 55 according to the directional information with the user terminal 3 that performs wireless communication. Therefore, it is possible to cancel the loop signal stably against fluctuations and differences due to changes in directivity. In addition, in the processing unit 31, in the communication reception step S11, if the directional information of the user terminal 3 is the same as the directional information of another user terminal 3, the same database 55 as the database 55 corresponding to the other user terminal 3 may be referenced. For example, after the user terminal 3a and the base station 2 refer to the database 55a and cancel the loop signal to perform wireless communication, when the base station 2 performs wireless communication with the user terminal 3b having the same directional information as the user terminal 3a, the database 55a is referenced and the loop signal is canceled. In such a case, wireless communication may be performed with user terminal 3b immediately after user terminal 3a, but this is not limited thereto. For example, when wireless communication with user terminal 3a is performed followed by wireless communication with user terminal 3c, and then wireless communication with user terminal 3b, the same database 55a may be referenced. As a result, when wireless communication is performed with multiple user terminals 3, the same database can be shared between the user terminals 3 if the directional information is the same, and the burden of canceling the loopback signal is reduced.

The amplitude of the feedback signal may be measured via a power detector (not shown). As for the phase, the processing unit 31 provisionally sets the phase based on the reference feedback signal, and then superimposes this on the feedback signal. As a result, the user or system may visually check to what extent the feedback signal has been canceled, or the program may automatically detect the degree to which the feedback signal has been reduced.

Then, the processing unit 31 resets the phase and similarly detects the degree of reduction in the loop signal compared to the previous time. As a result, if the loop signal has further decreased compared to the previous time, if the phase was increased during the resetting process, it is increased further, and if the phase was decreased during the resetting process, it is decreased further. Also, if the loop signal has increased compared to the previous time, if the phase was increased during the resetting process, it is decreased conversely, and if the phase was decreased during the resetting process, it is increased conversely.

In this way, the reference signal corresponding to the detected feedback signal may be generated before the signal is amplified by the amplifier 12, but this is not limited to the above. For example, the local oscillator circuit 8 may extract the feedback signal from the received signal, refer to the database 55, and generate the above reference signal corresponding to the phase of the extracted feedback signal. The local oscillator circuit 8 may be equipped with a function to extract the feedback signal from the received signal in the same manner as described above. Then, the local oscillator circuit 8 may generate a reference signal so that the phase is the same as the feedback signal, and the mixer 15 may mix the reference signal with the received signal to generate a converted signal. Through mixing with this reference signal, the phase has already been adjusted to match the feedback signal, so the processor 21 only needs to adjust the amplitude of the reference signal in the same manner as described above to match the feedback signal.

In this way, the processing operation for canceling the loopback signal can be classified into a method in which all adjustments of the amplitude and phase of the reference signal are performed on the receiving circuit 5 side, and a method in which the phase of the reference signal is adjusted and only the amplitude of the reference signal is adjusted on the receiving circuit 5 side.

The processor 31 may also refer to the database 55 and generate a reference signal based on the transmission signal. In such a case, the reference loop signal and the reference transmission signal may be linked and recorded in the database 55, a reference transmission signal similar to or matching the transmission signal transmitted by the transmission circuit 6 may be selected from the database, and a reference signal may be generated that has the same amplitude and opposite phase as the reference loop signal linked to the selected reference transmission signal. This enables stable cancellation of the loop signal against fluctuations and differences in the communication environment.

Although an embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. Such a novel embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

1 Wireless communication system 2 Base station 3 User terminal 4 Database generation device 5 Receiving circuit 6 Transmitting circuit 8 Local oscillator circuit 9 Antenna isolation 10 Self-interference cancellation circuit 11 Receiving antenna 12 Amplifier 13 Receiving band filter 14 Attenuator 15 Mixer 16 Filter 18 High gain amplifier 19 Attenuator 21 Attenuator 22 Mixer 23 Bandpass filter 24 Buffer amplifier 25 Variable attenuation circuit 26 Driver amplifier 28 Power amplifier 29 Isolator 30 Transmitting antenna 31 Processor 32 Coupler 41 Reference clock 42 Voltage controlled oscillator 43 Voltage controlled oscillator 50 Receiving information acquisition unit 51 Directivity information acquisition unit 52 Period information determination unit 53 Period information determination unit 54 Database generation unit 55 Database 56 Recording unit 71 Transmitting antenna 72 Receiving antenna 73 Baseband digital canceller 74 High frequency analog canceller 75 Transmitting circuit 76 Receiving circuit 77 Database S11 Wraparound reception step S12 Generation step S13 Communication reception step S14 Processing step

Claims (6)

A database generation method for full-duplex communication, using a communication device having a transmitting antenna for transmitting a transmitting signal and a receiving antenna for receiving a receiving signal, and wirelessly communicating with an external terminal using full-duplex wireless communication, for generating a database for canceling a loop interference signal received by the receiving antenna from a transmitting signal transmitted by the transmitting antenna, comprising:
a loop reception step of receiving only a reference loop signal received by the receiving antenna from the reference transmission signal transmitted by the transmitting antenna ;
a generation step of sampling the reference wraparound signal received by the wraparound reception step, and generating the database for recording the reference wraparound signal;
a generation step of generating the database for full-duplex communication, the generation step being characterized in that the database is sequentially generated so that the amount of information varies depending on at least one of period information regarding the length of a period during which the reference loop signal is received by the receiving antenna and period information regarding a period for sampling the reference loop signal. The wraparound reception step acquires directional information regarding a direction of the transmitting antenna or the receiving antenna in a direction from the external terminal to the communication device,
2. The method for generating a database for full-duplex communication according to claim 1, wherein the generating step determines at least one of the period information and the period information according to directional information acquired by the wraparound reception step. 3. The method for generating a database for full-duplex communication according to claim 2, wherein the generating step generates a database having the same amount of information as a database generated for another piece of directional information when the directional information acquired in the wraparound receiving step is the same as the other piece of directional information. 3. The method for generating a database for full-duplex communication according to claim 2, wherein, in the generating step, if the directional information acquired in the wraparound receiving step is identical to other directional information, the database generated for the other directional information is shared. 1. A full-duplex wireless communication method for performing full-duplex wireless communication between a communication device having a transmitting antenna for transmitting a transmission signal and a receiving antenna for receiving a reception signal, and an external terminal, comprising:
a loop reception step of receiving only a reference loop signal received by the receiving antenna from the reference transmission signal transmitted by the transmitting antenna;
a generating step of sampling the reference wraparound signal received by the wraparound signal receiving step, and sequentially generating a database for recording the reference wraparound signal;
a communication receiving step of receiving a new reception signal including a loop interference signal by the receiving antenna;
a processing step of referring to one or more of the databases generated in the generating step and canceling a loop interference signal included in the reception signal received in the communication receiving step;
the generating step sequentially generates the database so that the amount of information varies depending on at least one of period information regarding a length of a period during which the reference loop signal is received by the receiving antenna and period information regarding a period for sampling the reference loop signal. The generating step generates a database for each of the external terminals,
The communication receiving step includes acquiring, for each of the external terminals, directivity information regarding a directivity of the transmitting antenna or the receiving antenna with respect to a direction toward the communication device;
6. The full-duplex wireless communication method according to claim 5, wherein the processing step refers to a database generated for the other external terminal when the directional information of the external terminal newly acquired in the communication receiving step is identical to directional information of the other external terminal.

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