JP6912294B2 - Base stations, wireless communication systems and communication methods - Google Patents

Description

The present disclosure relates to base stations , wireless communication systems and communication methods.

Conventionally, an FPU (Field Pick-up Unit) is known as a device used for a wireless communication system that transmits images such as live television broadcasts and emergency news reports. This FPU is used for material transmission in the broadcasting field, transmits a UL (Up Link) signal of main line information from a mobile station (terminal) on the relay site side to a base station on the broadcasting station side, and bases on the broadcasting station side. The DL (Down Link) signal of the return information is transmitted from the station to the mobile station on the relay site side. The video captured by the camera is transmitted as a file in real time, transmitted as a UL signal from the mobile station to the base station, stored in a storage medium, and reproduced.

In the frame configuration in the FPU, in order to absorb the influence of the delay due to radio wave propagation and suppress the interference between the UL signal and the DL signal, a guard time (guard time) is used between the UL signal transmission period and the DL signal transmission period. GT: Guard Time) is provided. In GT, interference with other systems is measured (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 9-51327

In order to improve the transmission efficiency of the FPU, it is preferable that the GT is short, but on the other hand, if the GT is shortened, the number of samples required for measuring the interference cannot be secured, so that the accuracy of the interference measurement deteriorates. It ends up.

A non-limiting example of the present disclosure is to provide a base station, a wireless communication system, and a communication method capable of performing interference measurement without reducing transmission efficiency.

The base station according to one aspect of the present disclosure is a base station that performs radio communication with a terminal in a time division duplex system, and is a preamble signal or a null signal in the uplink preamble section at the beginning of the frame transmitted from the terminal. A receiving unit that receives the uplink signal in which is set, and an interference measuring unit that performs interference measurement at a time including the null signal section when the null signal is set in the uplink preamble section. Be prepared.

The wireless communication system according to one aspect of the present disclosure is a wireless communication system in which a terminal and a base station perform wireless communication in a time-division duplex system, and the terminal has a preamble signal in an uplink preamble section at the beginning of a frame. Alternatively, when the base station includes a transmitting unit for transmitting an uplink signal set with a null signal, the base station receives the uplink signal, and the null signal is set in the uplink preamble section. It is provided with an interference measuring unit that performs interference measurement at a time including a section of the null signal.

The communication method according to one aspect of the present disclosure is a communication method in a base station that performs time-division multiplex wireless communication with a terminal, and is a preamble signal in an uplink preamble section at the beginning of a frame transmitted from the terminal. Alternatively, when an uplink signal with a null signal set is received and the null signal is set in the uplink preamble section, interference measurement is performed at a time including the section of the null signal.

It should be noted that these comprehensive or specific embodiments may be realized in a system, an integrated circuit, a computer program, or a recording medium, and any combination of a system, a device, a method, an integrated circuit, a computer program, and a recording medium. It may be realized by.

According to one aspect of the present disclosure, the interference measurement can be performed without lowering the transmission efficiency.

Further advantages and effects in one aspect of the present disclosure will be apparent from the specification and drawings. Such advantages and / or effects are provided by some embodiments and features described in the specification and drawings, respectively, but not all need to be provided in order to obtain one or more identical features. There is no.

A block diagram showing a configuration example of a terminal according to the first embodiment of the present disclosure. A block diagram showing a configuration example of a base station according to the first embodiment of the present disclosure. The figure which shows an example of the frame structure in Embodiment 1 of this disclosure. Flowchart of the terminal according to the first embodiment of the present disclosure Flow chart of the base station according to the first embodiment of the present disclosure The figure which shows the frame structure in the modification 1 of Embodiment 1 of this disclosure. The figure which shows the frame structure in the modification 2 of Embodiment 1 of this disclosure. A block diagram showing a configuration example of a base station according to the second embodiment of the present disclosure. A block diagram showing a configuration example of a terminal according to a second embodiment of the present disclosure. The figure which shows an example of the frame structure in Embodiment 2 of this disclosure. The figure which shows the 1st example of the preamble and the correlation result in Embodiment 2 of this disclosure. The figure which shows the 2nd example of the preamble and the correlation result in Embodiment 2 of this disclosure. A block diagram showing a configuration example of a terminal according to a third embodiment of the present disclosure. Block diagram showing a configuration example of a base station according to the third embodiment of the present disclosure. The figure which shows an example of the frame structure in Embodiment 3 of this disclosure. The figure which shows an example of the frame structure in Embodiment 4 of this disclosure. The figure which shows another example of the frame structure in Embodiment 4 of this disclosure. The figure which shows an example of the frame structure in the modification of Embodiment 4 of this disclosure. A block diagram showing a configuration example of a base station according to the fifth embodiment of the present disclosure. A block diagram showing a configuration example of a terminal according to a fifth embodiment of the present disclosure. The figure which shows an example of the frame structure in Embodiment 5 of this disclosure.

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters and duplicate explanations for substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate the understanding of those skilled in the art.

It should be noted that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

(Embodiment 1)
The wireless communication system according to the first embodiment includes a terminal 100 shown in FIG. 1 and a base station 200 shown in FIG. The terminal 100 and the base station 200 are, for example, FPUs used for material transmission in the broadcasting field. That is, the terminal 100 transmits video information or the like as an uplink signal (UL (Uplink) signal) to the base station 200, and the base station 200 feeds back DL control information or the like as a downlink signal (DL (Downlink) signal). Send to 100. Further, in the wireless communication system according to the first embodiment, the UL signal and the DL signal are transmitted and received by using the Time Division Duplex (TDD) system.

<Terminal configuration>
Next, a configuration example of the terminal 100 according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration example of the terminal 100 according to the first embodiment.

As shown in FIG. 1, the terminal 100 includes a wireless reception unit 101, a baseband reception processing unit 102, an AGC / synchronization detection unit 103, a reception processing control unit 104, a determination unit 105, and a baseband transmission processing unit. It is mainly composed of 106, a preamble setting unit 107, an additional unit 108, and a wireless transmission unit 109.

The wireless reception unit 101 amplifies, filters, etc. the wireless signal (DL signal) received by the antenna based on the information of the AGC (Automatic Gain Control) one frame before acquired from the reception processing control unit 104, which will be described later. Performs wireless reception processing. Then, the radio reception unit 101 down-converts the signal after the radio reception processing to obtain a baseband signal. Then, the wireless receiving unit 101 outputs a baseband signal.

The baseband reception processing unit 102 performs FFT (Fast Fourier Transform) processing, demodulation processing, and error correction for the baseband signal acquired from the wireless reception unit 101 based on the timing information acquired from the reception processing control unit 104 described later. Performs baseband reception processing such as processing. Then, the baseband reception processing unit 102 outputs the received data in which the baseband reception processing has been performed. The received data includes the result of baseband reception processing of the selection signal transmitted from the base station 200. The result of the baseband reception processing of the selection signal is instruction information indicating whether or not the terminal 100 transmits a null signal in the UL preamble section.

Based on the preamble included in the baseband signal acquired from the radio reception unit 101, the AGC / synchronization detection unit 103 provides timing information for synchronization between transmission and reception, and gain control (AGC) in reception processing and the like. Information (for example, signal level) is detected. Then, the AGC / synchronous detection unit 103 outputs the detection result of the timing and information for the AGC to the reception processing control unit 104.

The reception processing control unit 104 controls the timing of reception processing and the AGC based on the detection result acquired from the AGC / synchronous detection unit 103. Specifically, the reception processing control unit 104 outputs timing information indicating the processing timing such as the start time and the end time of the baseband reception processing to the baseband reception processing unit 102. Further, the reception processing control unit 104 outputs the AGC information to the wireless reception unit 101.

The determination unit 105 extracts instruction information from the reception data output from the baseband reception processing unit 102. Then, the determination unit 105 determines whether or not to transmit a null signal to the preamble section based on the extracted instruction information. The determination unit 105 outputs the determination result to the preamble setting unit 107.

The baseband transmission processing unit 106 performs error correction coding and modulation on the transmission data (UL data), performs IFFT (Inverse Fast Fourier Transform) processing, and obtains a baseband signal of the transmission data. Then, the baseband transmission processing unit 106 outputs the baseband signal of the transmission data to the addition unit 108.

The preamble setting unit 107 sets a preamble signal or a null signal transmitted in the preamble section (UL preamble section) of the UL signal based on the determination result acquired from the determination unit 105. The preamble setting unit 107 includes a preamble generation unit 107a, a null signal generation unit 107b, and a switching unit 107c.

The preamble generation unit 107a generates a preamble and outputs it to the switching unit 107c. The preamble data is symbol data or the like in which the terminal 100 and the base station 200 are known in advance.

The null signal generation unit 107b generates a null signal and outputs it to the switching unit 107c.

When the determination result acquired from the determination unit 105 indicates that the null signal is transmitted to the UL preamble section, the switching unit 107c outputs the null signal acquired from the null signal generation unit 107b to the addition unit 108. When the determination result acquired from the determination unit 105 indicates that the null signal is not transmitted to the UL preamble section, the switching unit 107c outputs the preamble acquired from the preamble generation unit 107a to the addition unit 108.

The addition unit 108 adds a signal acquired from the switching unit 107c, that is, a preamble or null signal, to the stage before the baseband signal of the transmission data based on a predetermined frame configuration. Then, the addition unit 108 outputs a baseband transmission signal to which a preamble or null signal is added in front of the baseband signal of the transmission data to the radio transmission unit 109.

The wireless transmission unit 109 performs wireless transmission processing such as amplification and filtering on the baseband transmission signal acquired from the additional unit 108. Then, the wireless transmission unit 109 up-converts the signal after the wireless transmission process to obtain a wireless signal (UL signal). Then, the wireless transmission unit 109 transmits the UL signal from the antenna.

<Base station configuration>
Next, a configuration example of the base station 200 according to the first embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing a configuration example of the base station 200 according to the first embodiment.

As shown in FIG. 2, the base station 200 includes a determination unit 201, a selection signal generation unit 202, a baseband transmission processing unit 203, a preamble generation unit 204, an additional unit 205, a radio transmission unit 206, and a radio. It is mainly composed of a reception unit 207, a baseband reception processing unit 208, an AGC / synchronization detection unit 209, an AGC / synchronization holding unit 210, a reception processing control unit 211, and an interference measurement unit 212.

The determination unit 201 determines whether or not to cause the terminal 100 to transmit a null signal in the preamble section of the UL signal. In the following, a request for the terminal 100 to transmit a null signal in the preamble section of the UL signal is appropriately referred to as a null signal request. That is, the determination unit 201 determines whether or not to request a null signal. For example, the determination unit 201 determines that a null signal request is performed when the length of the guard time provided between the UL signal and the DL signal is equal to or less than the threshold value. Alternatively, the determination unit 201 determines that a null signal request is made when the distance between the base station 200 and the terminal 100 is equal to or less than the threshold value (that is, when the distance is short). The determination unit 201 outputs the determination result to the selection signal generation unit 202. This means that when the distance between the base station 200 and the terminal 100 is equal to or greater than the threshold value (that is, when the distance is long), the guard time for avoiding collision between the UL signal and the DL signal must be set to a long value. This is because sufficient interference detection performance can be obtained even if interference detection is performed using the guard time for avoiding collision between the originally inserted UL signal and DL signal. It is also possible to periodically request a null signal. For example, a null signal request may be made at a fixed cycle, such as a null signal request only once in 20 frames, or a null signal request may be made at a variable cycle. When the cycle for making a null signal request is variable, it is possible to change the cycle for making a null signal request by using information such as the line fluctuation speed, but a dedicated control signal indicating the cycle for making a null signal request. Need to be notified from the base station to the mobile station. However, since the amount of information of the dedicated control signal indicating the cycle of requesting the null signal may be about 1 bit to 3 bits at most, the increase in the amount of information of the control signal is small and the influence on the transmission efficiency is small. Of course, a plurality of methods may be combined as a method for requesting a null signal.

The selection signal generation unit 202 generates a selection signal based on the determination result acquired from the determination unit 201. Specifically, the selection signal generation unit 202 sets the 1-bit selection signal to "1" when making a null signal request. The selection signal generation unit 202 sets the 1-bit selection signal to "0" when the null signal request is not performed. The selection signal generation unit 202 outputs the selection signal to the baseband transmission processing unit 203.

The baseband transmission processing unit 203 performs error correction coding and modulation on the transmission data including the selection signal, performs IFFT (Inverse Fast Fourier Transform) processing, and obtains a baseband signal. Then, the baseband transmission processing unit 203 outputs the baseband signal to the additional unit 205.

The preamble generation unit 204 generates a preamble and outputs it to the addition unit 205. The preamble data is symbol data or the like in which the terminal 100 and the base station 200 are known in advance.

The addition unit 205 adds a preamble acquired from the preamble generation unit 204 to the front stage of the baseband signal of the transmission data based on a predetermined frame configuration. Then, the addition unit 205 outputs the baseband transmission signal to which the preamble is added in front of the baseband signal of the transmission data to the radio transmission unit 206.

The wireless transmission unit 206 performs wireless transmission processing such as amplification and filtering on the baseband transmission signal including the preamble. Then, the wireless transmission unit 206 up-converts the signal after the wireless transmission process to obtain the wireless signal. Then, the wireless transmission unit 206 transmits a wireless signal (DL signal) from the antenna.

Further, the wireless transmission unit 206 may perform control such as switching of the transmission frequency based on the measurement result indicating the interference level with another system acquired from the interference measurement unit 212 described later.

The wireless reception unit 207 performs wireless reception processing such as amplification and filtering on the wireless signal (UL signal) received by the antenna based on the AGC information one frame before acquired from the reception processing control unit 211 described later. conduct. Then, the radio reception unit 207 down-converts the signal after the radio reception processing to obtain a baseband signal. Then, the radio receiving unit 207 outputs a baseband signal.

The baseband reception processing unit 208 performs FFT (Fast Fourier Transform) processing, demodulation processing, and error correction for the baseband signal acquired from the wireless reception unit 207 based on the timing information acquired from the reception processing control unit 211 described later. Performs baseband reception processing such as processing. Then, the baseband reception processing unit 208 outputs the received data in which the baseband reception processing has been performed.

Based on the preamble included in the baseband signal acquired from the radio reception unit 207, the AGC / synchronization detection unit 209 provides timing information for synchronization between transmission and reception, and gain control (AGC) in reception processing and the like. Information (for example, signal level) is detected. Then, the AGC / synchronization detection unit 209 outputs the detection result of the timing and information for the AGC to the AGC / synchronization holding unit 210 and the reception processing control unit 211.

When the terminal 100 transmits a null signal to the preamble section, the AGC / synchronous detection unit 209 does not execute the detection process and does not output the detection result because the preamble does not exist.

The AGC / synchronization holding unit 210 holds the latest detection results of AGC and timing detected by the AGC / synchronization detection unit 209.

The reception processing control unit 211 controls the timing of reception processing and the AGC. Specifically, the reception processing control unit 211 outputs timing information indicating the processing timing such as the start time and the end time of the baseband reception processing to the baseband reception processing unit 208. Further, the reception processing control unit 211 outputs timing information indicating the processing timing such as the start time and the end time of the interference measurement to the interference measurement unit 212. Further, the reception processing control unit 211 outputs the AGC information to the wireless reception unit 207.

At that time, when the reception processing control unit 211 acquires the detection result from the AGC / synchronous detection unit 209, the reception processing control unit 211 generates timing information and AGC information based on the acquired detection result. Further, when the reception processing control unit 211 does not acquire the detection result from the AGC / synchronization detection unit 209, that is, when a null signal is transmitted in the preamble section, the reception processing control unit 211 is based on the detection result held by the AGC / synchronization holding unit 210. To generate timing information and AGC information.

Based on the timing information acquired from the reception processing control unit 211, the interference measurement unit 212 sets the guard time section or the section obtained by combining the guard time section and the preamble section to which the null signal is transmitted as the interference measurement section. The reception level (interference amount, for example, Received Signal Strength Indicator (RSSI)) in the interference measurement section is measured. For example, the interference measurement unit 212 outputs the measurement result to the wireless transmission unit 206.

<Frame configuration>
Next, the frame configuration in the wireless communication system according to the first embodiment will be described with reference to FIG. FIG. 3 is a diagram showing an example of a frame configuration according to the first embodiment.

FIG. 3 shows a frame configuration when the terminal 100 transmits a preamble to the UL preamble section (during normal preamble transmission), and the terminal 100 transmits a null signal to the UL preamble section. The frame configuration of the case (when transmitting a null signal) is shown.

FIG. 3 shows a UL signal transmission period, a DL signal transmission period, and a guard time (GT: Guard Time). As described above, in the wireless communication system according to the first embodiment, communication is performed using the time division duplex system. Therefore, as shown in FIG. 3, the UL signal transmission period and the DL signal transmission period are different. It is provided by time division via guard time.

The terminal 100 transmits the UL signal to the base station 200 during the UL signal transmission period shown by the frame configuration as shown in FIG. Similarly, the base station 200 transmits the DL signal to the terminal 100 during the DL signal transmission period shown by the frame configuration as shown in FIG.

The UL signal mainly includes a UL Data signal and a UL Preamble provided in front of the UL data signal. The DL signal mainly includes a preamble (DL Preamble) and a DL data (DL Data) signal.

Then, the DL data includes the selection signal generated by the selection signal generation unit 202. The selection signal at the time of preamble transmission is "0", and the selection signal at the time of null signal transmission is "1".

The guard time (GT) is provided between the transmission period of the UL signal and the transmission period of the DL signal in order to absorb the influence of the delay due to radio wave propagation and suppress the interference between the UL signal and the DL signal. ..

Then, as shown in the frame configuration at the time of null signal transmission, when the selection signal is “1”, the terminal 100 transmits the null signal to the UL preamble section of the UL signal following the guard time. The base station 200 performs interference measurement with a section in which the guard time section and the UL preamble section of the UL signal to which the null signal is transmitted are combined as an interference measurement section.

Next, the processing flow of the terminal in the first embodiment will be described. FIG. 4 is a flowchart showing a processing flow of the terminal according to the first embodiment. FIG. 4 shows a processing flow in the DL signal reception processing of the nth frame and the UL signal transmission processing of the n + 1th frame.

The terminal 100 receives the DL signal of the nth frame transmitted from the base station 200 (S101).

Then, the terminal 100 extracts instruction information from the selection signal included in the DL signal (S102).

Based on the extracted instruction information, the terminal 100 determines whether or not to transmit a null signal to the UL preamble section of the n + 1st frame (that is, whether or not a null signal is requested) (S103).

When transmitting a null signal to the UL preamble section (YES in S103), the terminal 100 sets a null signal in the UL preamble section (S104).

When the null signal is not transmitted to the UL preamble section (NO in S103), the terminal 100 sets the preamble in the UL preamble section (S105).

Then, the terminal 100 transmits the n + 1th UL signal (S106). A null signal or a preamble is set in the UL preamble section of the n + 1th UL signal.

Next, the processing flow of the base station according to the first embodiment will be described. FIG. 5 is a flowchart showing a processing flow of the base station according to the first embodiment. FIG. 5 shows a processing flow in the DL signal transmission processing of the nth frame and the UL signal reception processing of the n + 1th frame.

The base station 200 determines whether or not to cause the terminal 100 to transmit a null signal (that is, whether or not to request a null signal) in the UL preamble section of the n + 1th frame (S201).

When a null signal is transmitted to the UL preamble section of the n + 1st frame (YES in S201), the base station 200 generates a selection signal “1” as a selection signal included in the UL signal of the nth frame (YES in S201). S202).

Then, the base station 200 transmits the DL signal of the nth frame including the generated selection signal (S203).

Then, the base station 200 receives the UL signal of the n + 1st frame (S204).

The base station 200 performs the interference measurement in the interference measurement section including the UL preamble section in which the null signal is transmitted (S205).

When the null signal is not transmitted to the UL preamble section of the n + 1st frame (NO in S201), the base station 200 generates the selection signal “0” as the selection signal included in the UL signal of the nth frame. (S206).

Then, the base station 200 transmits the DL signal of the nth frame including the generated selection signal (S207).

Then, the base station 200 receives the UL signal of the n + 1st frame (S208).

Then, the base station 200 detects the preamble in the UL preamble section (S209).

In S209, the base station 200 may perform interference measurement with the guard time section as the interference measurement section.

As described above, according to the first embodiment, when the base station 200 executes the interference measurement, the base station 200 transmits a selection signal indicating that a null signal is transmitted to the preamble section of the UL signal to the terminal 100. The terminal 100 transmits a null signal to the preamble section of the UL signal based on the received selection signal. As a result, the base station 200 can perform the interference measurement with the section of the guard time section and the preamble section of the UL signal to which the null signal is transmitted as the interference measurement section, so that the guard time is made longer. It is possible to prevent deterioration of the accuracy of interference measurement without doing so.

In the first embodiment, an example in which the selection signal is transmitted to the terminal 100 when the base station 200 executes the interference measurement has been described, but the present disclosure is not limited to this. For example, the period in which the terminal 100 transmits a null signal in the preamble section of the UL signal (for example, once every 20 frames) may be known in advance between the base station 200 and the terminal 100. In that case, since the base station 200 can perform interference measurement in a known cycle, the section obtained by combining the guard time section and the preamble section of the UL signal to which the null signal is transmitted is set as the interference measurement section. The station 200 does not have to transmit the selection signal.

Further, the period for transmitting the null signal in the preamble section of the UL signal may be variable according to the fluctuation speed of the line or the like. In that case, the base station 200 may determine the cycle for transmitting the null signal based on the fluctuation speed of the line, and may transmit a control signal indicating the determined cycle instead of the selection signal.

As described above, the guard time is provided to absorb the influence of the delay due to radio wave propagation, so that the longer the distance between the base station 200 and the terminal 100, the longer the guard time is set. Therefore, when the distance between the base station 200 and the terminal 100 is long, the interference measurement can be performed in the guard time section, so that the null signal may be controlled not to be transmitted in the preamble section of the UL signal.

For example, the base station 200 sets the selection signal to "0" when the distance between the base station 200 and the terminal 100 is larger than the threshold value, and sets the selection signal to "1" when the distance is smaller than the threshold value. May be set.

Further, the timing at which the base station 200 transmits the selection signal indicating that the null signal is transmitted in the preamble section of the UL signal and / or the timing at which the terminal 100 receives the selection signal and transmits the null signal are appropriate. , May be changed. Hereinafter, as a modification of the present embodiment, an example of changing the timing of transmitting the selection signal by the base station 200 and an example of changing the timing of transmitting the null signal by the terminal 100 will be described.

(Modification 1 of Embodiment 1)
In the first modification of the first embodiment, an example of controlling the interval between frames for transmitting a null signal will be described.

FIG. 6 is a diagram showing a frame configuration in a modification 1 of the first embodiment. FIG. 6 shows the DL signal of the nth frame (Flame # n), the UL signal and DL signal of the n + 1th frame (Flame # n + 1), and the n + 2nd at the time of preamble transmission and null signal transmission, respectively. Frame (Flame # n + 2) is shown. For convenience of illustration, the UL signal of the nth frame and the n + 2nd DL signal are omitted in FIG.

Since the frame configuration at the time of preamble transmission shown in FIG. 6 is the same as the frame configuration described in FIG. 3, detailed description thereof will be omitted.

In the frame configuration at the time of transmitting the null signal shown in FIG. 6, the base station 200 transmits the DL data signal including the selection signal “1” in the nth frame. The terminal 100 receives the DL data signal of the nth frame and transmits a null signal to the UL preamble section of the n + 1th frame.

Then, when the base station 200 transmits the DL data signal indicating the selection signal "1" in the nth frame, the base station 200 is next to the n + 1th frame (that is, the frame in which the DL data signal indicating the selection signal "1" is transmitted. In the frame), a DL data signal including the selection signal “0” is transmitted. The terminal 100 receives the DL data signal of the n + 1st frame, and transmits the preamble without transmitting the null signal in the UL preamble section of the n + 2nd frame.

An example of control having a frame configuration as shown in FIG. 6 will be described. This control is executed, for example, by changing the determination process of the determination unit 201.

When the determination unit 201 determines that the terminal 100 is to transmit the null signal in the preamble section of the UL signal of the nth frame, the determination unit 201 does not cause the terminal 100 to transmit the null signal in the preamble section of the UL signal of the n + 1th frame. , Is determined.

By controlling the frame configuration as shown in FIG. 6, the base station 200 can prevent consecutive frames that do not include the preamble in the preamble section of the UL signal, thus preventing deterioration of the characteristics of AGC and timing information. can.

(Modification 2 of Embodiment 1)
In the second modification of the first embodiment, after the terminal 100 notifies the base station 200 of the result (for example, ACK / NACK information) indicating whether or not the selection signal can be received, in the UL preamble section. An example of transmitting a null signal will be described.

FIG. 7 is a diagram showing a frame configuration in the second modification of the first embodiment. FIG. 7 shows the DL signal of the nth frame (Flame # n), the UL signal and DL signal of the n + 1th frame (Flame # n + 1), and the n + 2nd at the time of preamble transmission and null signal transmission, respectively. Frame (Flame # n + 2) is shown. For convenience of illustration, the UL signal of the nth frame and the n + 2nd DL signal are omitted.

Since the frame configuration at the time of preamble transmission has been described with reference to FIG. 3, detailed description thereof will be omitted.

At the time of null signal transmission, the base station 200 transmits the DL data signal including the selection signal “1” in the nth frame. The terminal 100 transmits a UL data signal including a determination result indicating whether or not the selection signal has been received in the n + 1th frame.

For example, when the terminal 100 can receive the selection signal, it transmits a UL data signal including ACK in the n + 1st frame, and transmits a null signal in the UL preamble section in the n + 2nd frame. Then, when the UL data signal contains ACK, the base station 200 executes the interference measurement in the n + 2nd frame.

On the other hand, when the terminal 100 cannot receive the selection signal, it transmits a UL data signal including NACK in the n + 1st frame, and transmits a preamble in the UL preamble section in the n + 2nd frame. Then, when the UL data signal contains NACK, the base station 200 may retransmit the DL data signal including the selection signal “1” in the n + 1th frame.

An example of control having a frame configuration as shown in FIG. 7 will be described. This control is executed, for example, by changing the processing of the determination unit 105.

At the nth frame, the determination unit 105 determines whether or not the instruction information can be extracted from the reception data output from the baseband reception processing unit 102. The case where the instruction information can be extracted corresponds to the case where the selection signal can be received, and the case where the instruction information cannot be extracted, that is, the case where the selection signal cannot be received.

When the instruction information can be extracted in the nth frame, the determination unit 105 notifies the additional unit 108 to transmit ACK in the n + 1th frame, and a null signal in the UL preamble section of the n + 2nd frame. The determination result of switching to is output to the switching unit 107c.

If the instruction information cannot be extracted in the nth frame, the determination unit 105 notifies the additional unit 108 to transmit NACK in the n + 1th frame, and preambles in the UL preamble section of the n + 2nd frame. The determination result of switching to is output to the switching unit 107c.

By controlling the frame configuration as shown in FIG. 7, the base station 200 can receive the determination result (ACK / NACK). Therefore, when the base station 200 performs the interference measurement, the UL preamble is performed. It is possible to avoid the situation where the null signal is not transmitted in the section. Therefore, it is possible to avoid a deviation in operation between the base station 200 and the terminal 100.

(Embodiment 2)
In the first embodiment described above, an example of adding a selection signal for notifying the terminal 100 whether or not to transmit a null signal in the UL preamble section to the DL data signal has been described. In the second embodiment, an example in which the base station changes the DL preamble in order to notify the terminal whether or not to transmit a null signal in the UL preamble section will be described.

<Base station configuration>
A configuration example of the base station according to the second embodiment will be described with reference to FIG. FIG. 8 is a block diagram showing a configuration example of the base station 300 according to the second embodiment. Note that, in FIG. 8, the same configuration as that of FIG. 2 is assigned the same reference numeral, and the description thereof will be omitted.

The base station 300 adopts a configuration in which the selection signal generation unit 202 of the base station 200 shown in FIG. 2 is deleted and the preamble generation unit 204 is replaced with the preamble generation unit 304. Then, the determination unit 201 adopts a configuration in which it is connected to the preamble generation unit 304.

The determination unit 201 determines whether or not to transmit a null signal to the terminal 400 described later in the preamble section of the UL signal. The determination unit 201 outputs the determination result to the preamble generation unit 304.

The preamble generation unit 304 generates a preamble and outputs it to the addition unit 205. At that time, the preamble generation unit 304 changes the polarity of a part of the preamble based on the determination result acquired from the determination unit 201.

The preamble generation unit 304 has an arrangement unit 304a, an inverse Fourier transform unit 304b, and a polarity changing unit 304c.

The arrangement unit 304a arranges the preamble data in a subcarrier group composed of some subcarriers of the subcarrier group used for OFDM transmission.

For example, when the number of subcarriers for OFDM transmission is 2N + 1 (N is an integer of 1 or more) and each subcarrier is assigned a subcarrier number from # -N to #N in order from the subcarrier with the lowest frequency. , The arrangement unit 304a is arranged in the subcarrier group corresponding to the subcarrier number (subcarrier number # -16, # -8, # 8, # 16, etc.) which is a multiple of 8 excluding 0. When the arrangement unit 304a performs such an arrangement, the preamble time signal output from the inverse Fourier transform unit 304b, which will be described later, becomes a periodic signal in which eight signal components that are the same as each other are arranged in the time axis direction.

The inverse Fourier transform unit 304b performs an IFFT (Inverse Fast Fourier Transform) process on the preamble arranged by the arrangement unit 304a to obtain a baseband preamble. Then, the inverse Fourier transform unit 304b outputs the baseband preamble to the polarity changing unit 304c.

The polarity changing unit 304c changes the polarity of a part of the signal component of the baseband preamble based on the determination result acquired from the determination unit 201. Specifically, when the polarity changing unit 304c causes the terminal 400 to transmit a null signal in the preamble section of the UL signal, the polarity changing unit 304c changes the polarity of a part of the signal component of the baseband preamble and adds the changed preamble. Output to unit 205. When the terminal 100 is not allowed to transmit the null signal in the preamble section of the UL signal, the polarity changing unit 304c outputs the polarity to the addition unit 205 without changing the polarity of a part of the signal component of the baseband preamble. The polarity change of the preamble in the polarity change unit 304c will be described later.

<Terminal configuration>
Next, a configuration example of the terminal 400 according to the second embodiment will be described with reference to FIG. FIG. 9 is a block diagram showing a configuration example of the terminal 400 according to the second embodiment. Note that, in FIG. 9, the same configuration as in FIG. 1 is assigned the same reference numerals and the description thereof will be omitted.

The terminal 400 adopts a configuration in which the determination unit 105 of the terminal 100 shown in FIG. 1 is replaced with the determination unit 405.

The determination unit 405 determines whether or not to transmit a null signal to the preamble section of the UL signal based on the preamble included in the baseband signal acquired from the radio reception unit 101. Specifically, the determination unit 405 extracts the preamble and performs cross-correlation processing on the preamble. As described above, the base station 300 changes the polarity of a part of the baseband preamble depending on whether or not the terminal 400 transmits the null signal in the preamble section of the UL signal. Therefore, the determination unit 405 detects whether or not the polarity of a part of the preamble has been changed by performing cross-correlation processing on the preamble, and determines whether or not to transmit a null signal to the preamble section of the UL signal. judge. The determination unit 405 outputs the determination result to the preamble setting unit 107 (specifically, the switching unit 107c). The cross-correlation process in the determination unit 405 will be described later.

<Frame configuration>
Next, the frame configuration in the wireless communication system according to the second embodiment will be described with reference to FIG. FIG. 10 is a diagram showing an example of a frame configuration according to the second embodiment.

The difference between the frame configuration in the second embodiment shown in FIG. 10 and the frame configuration in the first embodiment shown in FIG. 3 is that the DL preamble is used instead of the selection signal being included in the DL data signal in FIG. This is a point that changes between when the preamble is transmitted and when the null signal is transmitted. Next, the DL preamble that is changed between the time of preamble transmission and the time of null signal transmission will be described.

<Composite of preamble and correlation processing>
FIG. 11A is a diagram showing a first example of the preamble and the correlation result in the second embodiment. FIG. 11B is a diagram showing a second example of the preamble and the correlation result in the second embodiment.

As described above, the DL preamble is a periodic signal in which eight signal components that are the same as each other are arranged in the time axis direction. In FIGS. 11A and 11B, the eight signal components of the preamble added to the front stage of the DL data signal are designated as Premium (# 1) to Premium (# 8), respectively. Further, in FIG. 11B, when the polarity changing unit 304c causes the terminal 400 to transmit a null signal in the preamble section of the UL signal, the polarity of the signal component at the rear end in the time axis direction of the eight signal components is inverted. As an example, the signal component in which the polarity of the preamble (# 8) is inverted is shown as the preamble (# 8)'.

Further, as an example of the cross-correlation processing, the determination unit 405 is based on a set of a signal component (hereinafter, referred to as a preamble (# 1)') in which the polarities of the preamble (# 1) and the preamble (# 1) are inverted. As a signal, this reference signal and a pair of two adjacent signal components in the preamble (for example, Premium (# 1) and Premium (# 2)) are cross-correlated in order.

The example shown in FIG. 11A is the result of the preamble when the terminal 400 is not allowed to transmit the null signal in the preamble section of the UL signal and the result of the correlation processing for the preamble. As shown in FIG. 11A, the polarity of the preamble is not changed when the terminal 400 is not allowed to transmit the null signal in the preamble section of the UL signal. In this case, for example, the cross-correlation between the reference signal and the set of Preamble (# 1) and Preamble (# 2) is a signal component in which the reference signal's Preamble (# 1)'and Preamble (# 2) have different polarities. Therefore, no peak occurs in the cross-correlation. Similarly, for other signal component sets, there is no peak in the cross-correlation, so there is no peak in the result of the cross-correlation with respect to the preamble.

The example shown in FIG. 11B is the result of the preamble when the terminal 400 is made to transmit the null signal in the preamble section of the UL signal and the result of the correlation processing for the preamble. As shown in FIG. 11B, the polarity of the preamble (# 8), which is a signal component at the end of the preamble when the terminal 400 is made to transmit a null signal in the preamble section of the UL signal, is inverted. In this case, the cross-correlation between the reference signal and the pair of the preamble (# 7) and the preamble (# 8)'is that the preamble (# 1)'and the preamble (# 8)' are signal components having the same polarity. Therefore, a peak occurs at a position corresponding to the end position of the preamble.

As a result of the cross-correlation, the determination unit 405 determines that the null signal is not transmitted to the preamble section when the peak does not occur at the position corresponding to the terminal position of the received DL preamble. The determination unit 405 determines that a null signal is transmitted to the preamble section when a peak occurs at a position corresponding to the terminal position of the received DL preamble as a result of cross-correlation.

As described above, according to the second embodiment, when the base station 300 executes the interference measurement, it transmits a DL preamble indicating that a null signal is transmitted to the preamble section of the UL signal. The terminal 400 transmits a null signal to the preamble section of the UL signal based on the received DL preamble. As a result, the base station 300 can perform the interference measurement with the section obtained by combining the guard time section and the preamble section of the UL signal to which the null signal is transmitted as the interference measurement section, so that the guard time is made longer. It is possible to prevent deterioration of the accuracy of interference measurement without doing so.

Further, according to the second embodiment, the base station 300 is instructed to transmit a null signal in the preamble section of the UL signal without adding a selection signal to the DL data signal (that is, a null signal request). Can be transmitted to the terminal 400.

Further, according to the second embodiment, the base station 300 transmits a periodic DL preamble to the terminal 400. Therefore, for example, the preamble detection accuracy in the terminal 400 can be improved even in a multipath environment.

In the second embodiment, the DL preamble has described an example of a periodic signal in which eight signal components that are the same as each other are arranged in the time axis direction, but the present disclosure is not limited to this. The period of the DL preamble may be changed by changing the subcarrier in which the preamble data is arranged in the arrangement unit 304a. For example, when the placement unit 304a is placed in a subcarrier group corresponding to a subcarrier number (subcarrier number # -8, # -4, # 4, # 8, etc.) that is a multiple of 4 excluding 0, the DL preamble is set. It becomes a periodic signal in which four signal components that are the same as each other are arranged in the time axis direction. Even in this case, the polarity changing unit 304c notifies the terminal 400 of transmitting a null signal in the preamble section of the UL signal by changing the polarity of a part of the signal component of the preamble. Can be sent.

Further, the arrangement unit 304a may be arranged in the subcarrier corresponding to the subcarrier number of 0.

Further, the polarity changing unit 304c does not change the polarity of a part of the signal components when transmitting a null signal to the terminal 400 in the preamble section of the UL signal, and sends a null signal to the terminal 100 in the preamble section of the UL signal. When not transmitting, the polarity of a part of the signal component may be changed. Further, the polarity changing unit 304c is a signal for changing the polarity depending on whether the terminal 400 transmits a null signal in the preamble section of the UL signal or the terminal 400 does not transmit the null signal in the preamble section of the UL signal. The ingredients may be different. Further, the position of the signal component whose polarity is changed by the polarity changing unit 304c is not limited to the rear end of the preamble. Further, the number of signal components whose polarity is changed by the polarity changing unit 304c is not limited to one.

(Embodiment 3)
In the first and second embodiments described above, the configuration in which the terminal switches between transmitting a null signal and transmitting a preamble in all of the UL preamble sections has been described. In the third embodiment, a configuration in which the terminal transmits a null signal to a part of the UL preamble section will be described.

<Terminal configuration>
The configuration of the terminal according to the third embodiment will be described with reference to FIG. FIG. 12 is a block diagram showing a configuration example of the terminal 500 according to the third embodiment. Note that, in FIG. 12, the same configuration as that of FIG. 9 is given the same number and the description thereof will be omitted.

The terminal 500 adopts a configuration in which the preamble setting unit 107 of the terminal 400 shown in FIG. 9 is replaced with the preamble setting unit 507.

The preamble setting unit 507 generates a preamble composed of a plurality of signal components that are the same as each other as a UL preamble, and replaces a part of the signal components of the preamble with a null signal based on the determination result acquired from the determination unit 405. do.

Specifically, the preamble setting unit 507 includes an arrangement unit 507a, an inverse Fourier transform unit 507b, and a null signal replacement unit 507c.

The arrangement unit 507a arranges the preamble data in a subcarrier group composed of some subcarriers of the subcarrier group used for OFDM transmission.

For example, when the number of subcarriers for OFDM transmission is 2N + 1 (N is an integer of 1 or more) and each subcarrier is assigned a subcarrier number from # -N to #N in order from the subcarrier with the lowest frequency. , The arrangement unit 507a is arranged in the subcarrier group corresponding to the subcarrier number (subcarrier number # -16, # -8, # 8, # 16, etc.) which is a multiple of 8 excluding 0. When the arrangement unit 507a performs such an arrangement, the preamble time signal output from the inverse Fourier transform unit 507b, which will be described later, becomes a periodic signal in which eight signal components that are the same as each other are arranged in the time axis direction.

The inverse Fourier transform unit 507b performs an IFFT (Inverse Fast Fourier Transform) process on the preamble arranged by the arrangement unit 507a to obtain a baseband preamble. Then, the inverse Fourier transform unit 507b outputs the baseband preamble to the null signal replacement unit 507c.

The null signal replacement unit 507c replaces a part of the signal component of the baseband preamble with a null signal based on the determination result acquired from the determination unit 405. Specifically, when the null signal replacement unit 507c transmits a null signal in the preamble section of the UL signal, the null signal replacement unit 507c replaces a part (for example, the head portion) of the signal component of the baseband preamble with the null signal. The latter preamble is output to the addition unit 108. When the null signal replacement unit 507c does not transmit the null signal in the preamble section of the UL signal, the null signal replacement unit 507c outputs the null signal to the addition unit 108 without replacing the null signal. The preamble configuration in which the null signal is replaced by the null signal replacement unit 507c will be described later.

<Base station configuration>
A configuration example of the base station according to the third embodiment will be described with reference to FIG. FIG. 13 is a block diagram showing a configuration example of the base station 600 according to the third embodiment. Note that, in FIG. 13, the same configuration as that of FIG. 8 is assigned the same reference numeral, and the description thereof will be omitted.

In the base station 600, the AGC / synchronization holding unit 210 of the base station 300 shown in FIG. 8 has been deleted, and the AGC / synchronization detection unit 209, the reception processing control unit 211, and the interference measurement unit 212 have the AGC / synchronization detection unit 609, respectively. A configuration is adopted in which the reception processing control unit 611 and the interference measurement unit 612 are replaced.

Based on the preamble included in the baseband signal acquired from the radio reception unit 207, the AGC / synchronization detection unit 609 provides timing information for synchronization between transmission and reception, and gain control (AGC) in reception processing and the like. Information (for example, signal level) is detected. In the third embodiment, as described above, the terminal 500 may transmit a UL preamble in which a part is replaced with a null signal, or may transmit a UL preamble in which the terminal 500 is not replaced with a null signal. Therefore, the AGC / synchronous detection unit 609 acquires timing information indicating the length of the preamble section from the reception processing control unit 611 described later, and performs preamble detection based on the timing information. Then, the AGC / synchronous detection unit 609 outputs the AGC and timing detection results to the reception processing control unit 611.

The reception processing control unit 611 controls the timing of reception processing and the AGC based on the detection result acquired from the AGC / synchronous detection unit 609. Specifically, the reception processing control unit 611 outputs timing information indicating the processing timing such as the start time and the end time of the baseband reception processing to the baseband reception processing unit 208.

Further, the reception processing control unit 611 determines the preamble section and the interference measurement section based on whether or not the terminal 500 transmits the UL preamble in which a part is replaced with a null signal, and the timing indicating each section is indicated. The information is output to the AGC / synchronous detection unit 609 and the interference measurement unit 612. Further, the reception processing control unit 611 outputs the AGC information to the wireless reception unit 207.

Based on the timing information acquired from the reception processing control unit 611, the interference measurement unit 612 sets the guard time section or the section obtained by combining the guard time section and the preamble section in which the null signal is transmitted as the interference measurement section. Measure the reception level in the interference measurement section. The interference measurement unit 612 outputs the measurement result to the wireless transmission unit 206.

<Frame configuration>
Next, the frame configuration in the wireless communication system according to the third embodiment will be described with reference to FIG. FIG. 14 is a diagram showing an example of the frame configuration according to the third embodiment.

The difference between the frame configuration in the third embodiment shown in FIG. 14 and the frame configuration in the second embodiment shown in FIG. 10 is a periodic signal in which eight signal components having the same UL preamble are arranged in the time axis direction. At a certain point, when a null signal is transmitted, a null signal is transmitted in a part of the UL preamble section instead of transmitting the null signal in the entire UL preamble section.

By communicating in the frame configuration shown in FIG. 14, when transmitting a null signal, the base station 600 measures interference in a section in which the guard time section and a part of the preamble section in which the null signal is transmitted are combined. Interference measurement can be performed as a section, and even when a null signal is transmitted, preamble detection can be performed in a section in which the signal component of the preamble is transmitted without transmitting the null signal.

As described above, according to the third embodiment, when the base station 600 executes the interference measurement, the DL preamble indicating that the null signal is transmitted in the preamble section of the UL signal is transmitted to the terminal 500. Based on the received DL preamble, the terminal 500 transmits a preamble in which a part of the UL signal is replaced with a null signal in the preamble section of the UL signal. As a result, the base station 600 can perform the interference measurement with the section including the guard time section and the preamble section of the UL signal to which the null signal is transmitted as the interference measurement section, and is not replaced with the null signal. Preamble can be detected. That is, since the latest AGC information and timing information can be acquired while preventing deterioration of the accuracy of interference measurement, for example, even when the terminal moves at high speed and the propagation environment fluctuates rapidly, the AGC information can be obtained. It is possible to prevent deterioration of the accuracy of timing information.

In the terminal 500, the number of signal components to be replaced with the null signal (that is, the section in which the null signal is transmitted) is not limited to the example shown in FIG. 14, and may be changed as appropriate. For example, the base station 600 may instruct the terminal 500 of the section for transmitting the null signal, so that the terminal 500 may change the section for transmitting the null signal. For example, when the distance between the base station 600 and the terminal 500 is equal to or less than the threshold value (that is, when the distance is short), the section for transmitting the null signal can be set to a longer value. In this case, it is necessary for the base station to notify the mobile station of a dedicated control signal indicating a section for transmitting the null signal. However, since the amount of dedicated control signal information indicating this null signal section may be about 1 bit to 3 bits at most, the increase in the amount of control signal information is small and the influence on the transmission efficiency is small.

(Embodiment 4)
In each of the above-described embodiments, an example in which a wireless communication system including a base station and a terminal communicates using one frequency band has been described, but in the present disclosure, the wireless communication system uses a plurality of frequency bands. It can be applied even when communicating. In the fourth embodiment, an example in which the wireless communication system described in the first embodiment uses two frequency bands will be described. In the following description, an example in which the wireless communication system uses two frequency bands, a first frequency band (f1) and a second frequency band (f2), will be described as an example. Then, the UL signal and DL signal transmitted and received using the first frequency band are used as the first UL signal and the first DL signal, respectively, and the UL signal and DL signal transmitted and received using the second frequency band are used. This will be described as a second UL signal and a second DL signal, respectively.

The terminal according to the fourth embodiment performs the transmission processing of the first UL signal and the transmission processing of the second UL signal in parallel while ensuring synchronization with each other. Further, the terminal according to the fourth embodiment performs the reception processing of the first DL signal and the reception processing of the second DL signal in parallel while ensuring synchronization with each other. Since the first UL signal transmission process and the second UL signal transmission process are the same as the UL signal transmission process in the terminal 100 according to the first embodiment, detailed description thereof will be omitted. Further, since the first DL signal reception process and the second DL signal reception process are the same as the DL signal reception process in the terminal 100 according to the first embodiment, detailed description thereof will be omitted.

The base station according to the fourth embodiment performs the transmission processing of the first DL signal and the transmission processing of the second DL signal in parallel while ensuring synchronization with each other. Further, the base station according to the fourth embodiment performs the reception processing of the first UL signal and the reception processing of the second UL signal in parallel while ensuring synchronization with each other. Since the first DL signal transmission process and the second DL signal transmission process are the same as the DL signal transmission process in the base station 200 according to the first embodiment, detailed description thereof will be omitted. Further, since the first UL signal reception process and the second UL signal reception process are the same as the UL signal reception process in the base station 200 according to the first embodiment, detailed description thereof will be omitted. ..

<Frame configuration>
Next, the frame configuration in the wireless communication system according to the fourth embodiment will be described with reference to FIG. FIG. 15 is a diagram showing an example of a frame configuration according to the fourth embodiment. In FIG. 15, detailed description of the same configuration as in FIG. 3 will be omitted.

FIG. 15 shows the frame configurations of the first frequency band and the second frequency band, respectively. Then, in each frame configuration, a null signal or a preamble is transmitted in the preamble section of the UL signal according to the selection signal included in the DL signal.

Further, in FIG. 15, a null signal is transmitted in the preamble section of the second UL signal of the n + 1th frame (Flame # n + 1), and the preamble is transmitted in the preamble section of the first UL signal. Similarly, a null signal is transmitted in the preamble section of the first UL signal of the n + second frame (Flame # n + 2), and a preamble is transmitted in the preamble section of the second UL signal. That is, when a null signal is transmitted in one of the UL preamble sections of the two frequency bands, the preamble is transmitted in the other.

With such a frame configuration, the AGC and timing information obtained in the reception processing of the UL signal to which the preamble is transmitted can be used for the reception processing of the UL signal to which the null signal is transmitted.

When a null signal is transmitted in one of the UL preamble sections of the two frequency bands, the control of transmitting the preamble in the other is executed, for example, by the determination unit of the base station (determination unit 201 in FIG. 2). NS.

Specifically, when the determination unit determines that the terminal is to transmit the null signal in the preamble section of the first UL signal, the determination unit determines that the terminal is not to transmit the preamble in the preamble section of the second UL signal. do. Similarly, when the determination unit determines that the terminal is to transmit the null signal in the preamble section of the second UL signal, it determines that the terminal is not allowed to transmit the preamble in the preamble section of the first UL signal. That is, the determination unit makes a determination so that the null signal is not transmitted at the same time in the preamble section of the UL signals of the two frequency bands.

As described above, in the fourth embodiment, when the terminal transmits the null signal to the preamble section of the first UL signal, the base station transmits the guard time section and the null signal in the first frequency band. Interference measurement can be performed by using the section including the preamble section of the first UL signal as the interference measurement section. Similarly, when the terminal transmits a null signal in the preamble section of the second UL signal, the base station can transmit the guard time section and the null signal in the second frequency band of the second UL signal. Interference measurement can be performed by using the section including the preamble section as the interference measurement section.

In the fourth embodiment described above, an example in which the wireless communication system described in the first embodiment uses two frequency bands has been described, but the present disclosure is not limited to this. Hereinafter, an example in which the wireless communication system described in the second embodiment uses two frequency bands will be described. Since the configuration of the terminal and the base station in this example is the same as that of the terminal and the base station of the second embodiment, detailed description thereof will be omitted. In the following, a frame configuration in an example in which the wireless communication system described in the second embodiment uses two frequency bands will be described.

FIG. 16 is a diagram showing another example of the frame configuration according to the fourth embodiment. In FIG. 16, a detailed description of the same configuration as in FIG. 10 will be omitted.

FIG. 16 shows the frame configurations of the first frequency band and the second frequency band, respectively. Then, in each frame configuration, a null signal or a preamble is transmitted in the preamble section of the UL signal according to the DL preamble included in the DL signal.

Even with such a frame configuration, the base station can be set in the first frequency band by transmitting a null signal to the preamble section of the first UL signal, as in the fourth embodiment described above. The interference measurement can be performed by setting the section in which the guard time section and the preamble section of the first UL signal to which the null signal is transmitted are combined as the interference measurement section. Similarly, when the terminal transmits a null signal in the preamble section of the second UL signal, the base station can transmit the guard time section and the null signal in the second frequency band of the second UL signal. Interference measurement can be performed by using the section including the preamble section as the interference measurement section.

In the frame configuration described above, there is an example in which the base station performs a DL signal using both the first frequency band (frequency f1) and the second frequency band (frequency f2) in the DL signal transmission section. explained. The DL signal is control information that the base station feeds back to the terminal, and its size is smaller than that of the UL signal. Further, in the FPU, the transmission section of the DL signal may be shortened in order to improve the transmission efficiency of the UL signal. Therefore, when the wireless communication system communicates using a plurality of frequency bands, the base station may transmit a DL signal using at least one of the plurality of frequency bands. In this case, in the frequency band in which the DL signal is not transmitted, the terminal may transmit the UL signal instead of the DL signal in the DL signal transmission section.

In the following, as a modification of the fourth embodiment, the DL signal is transmitted using the first frequency band among the first frequency band and the second frequency band, and the DL signal is transmitted in the second frequency band. An example in which a UL signal is transmitted instead of a DL signal will be described in the transmission section of.

(Modified Example of Embodiment 4)
FIG. 17 is a diagram showing a frame configuration in a modified example of the fourth embodiment. FIG. 17 shows the frame configurations of the first frequency band and the second frequency band, respectively.

As shown in the frame configuration of the first frequency band (frequency f1) in FIG. 17, in the transmission section of the UL signal of the nth frame (Frame # n), the terminal uses the first frequency band to generate the UL signal. To send. Then, in the DL signal transmission section of the nth frame, the base station transmits the DL signal using the first frequency band. At that time, the base station transmits a DL preamble indicating that a null signal is transmitted in the preamble section of the UL signal in order to perform the interference measurement.

As shown in the frame configuration of the second frequency band (frequency f2) of FIG. 17, in the transmission section of the DL signal of the nth frame, the base station does not transmit the DL signal using the second frequency band. On the other hand, the terminal transmits the UL signal using the second frequency band in the UL signal transmission section and the DL signal transmission section (reception section in the terminal) of the nth frame. At that time, since the terminal does not need to change the length of the UL preamble, the UL data signal of the UL signal transmitted using the second frequency band can be lengthened.

Then, the terminal receives the DL signal including the DL preamble transmitted by the base station using the first frequency band, and in the next frame (n + 1th frame (Flame # n + 1)), the preamble section of the UL signal. Sends a null signal to.

Specifically, as shown in FIG. 17, the terminal is null in a part of the preamble section of the UL signal transmitted using the second frequency band, which is continuous with the guard time provided at the boundary of the frame. Send a signal. Then, the terminal transmits the UL preamble in the preamble section in which the null signal is not transmitted. The configuration in which the null signal is transmitted in a part of the preamble section of the UL signal and the UL preamble is transmitted in the remaining part has been described in the third embodiment, and thus the description thereof will be omitted.

The base station performs interference measurement with a section obtained by combining a section of the guard time provided at the frame boundary and a part of the preamble section to which the null signal is transmitted as an interference measurement section.

As described above, in the modified example of the fourth embodiment, the base station transmits the DL signal using the first frequency band among the first frequency band and the second frequency band, and in the second frequency band, the DL signal is transmitted. When the terminal transmits the UL signal in the DL signal transmission section, the terminal transmits a null signal using the second frequency band in a part of the preamble section of the UL signal. As a result, the base station can perform the interference measurement with the section obtained by combining the guard time section and the preamble section of the UL signal to which the null signal is transmitted as the interference measurement section, so that the guard time is made longer. It is possible to prevent deterioration of the accuracy of interference measurement without any problem.

Further, in the modified example of the fourth embodiment, as shown in the frame configuration of the second frequency band in FIG. 17, the guard time is set because the UL signal and the DL signal are not switched within one frame. It suffices to be provided only at the boundary of the frame, and there is no need for time for switching transmission / reception at each of the base station and the terminal. Therefore, in the frame configuration of the second frequency band, the guard time at the frame boundary can be set long, and the interference measurement section can be lengthened. Further, by setting the guard time at the frame boundary to be long, the section of the null signal for securing the interference measurement section required in the base station can be set to be short. As a result, since the terminal can transmit the UL preamble in at least a part of the preamble section of the UL signal, the accuracy of interference detection in the base station is improved, and the AGC and timing information obtained by receiving the UL preamble are obtained. It is possible to prevent deterioration of characteristics.

In the modified example of the fourth embodiment, the example using two frequency bands has been described, but the present disclosure is not limited to this. The frequency band used for transmitting and receiving the UL signal and / or the DL signal may be three or more. In this case, the base station uses at least one of the plurality of frequency bands to transmit a DL signal including a DL preamble indicating that a null signal is transmitted in the preamble section of the UL signal. Further, the terminal transmits the UL signal in the UL signal transmission section and the DL signal transmission section using at least one of the frequency bands in which the base station does not transmit the DL signal. At that time, the terminal transmits the UL signal in the UL signal transmission section in the frequency band in which the base station transmits the DL signal. Then, the terminal receives the DL signal and transmits a null signal in a part of the preamble section of the UL signal transmitted using at least one of the frequency bands in which the base station does not transmit the DL signal.

Further, in the modified example of the fourth embodiment, the example in which the terminal transmits a null signal in a part of the preamble section of the UL signal and the UL preamble is transmitted in the remaining part has been described, but the terminal uses the UL signal. A null signal may be transmitted in all of the preamble sections of the above.

Further, in the modified example of the fourth embodiment, an example in which the base station transmits a DL preamble indicating that a null signal is transmitted in the preamble section of the UL signal in order to perform the interference measurement has been described. Disclosure is not limited to this. For example, as described in the first embodiment, the base station may transmit a DL signal including a selection signal in order to perform the interference measurement.

The frequency band in which only the UL signal is transmitted (the second frequency band in FIG. 17) can be set to any frequency band. For example, normally, one of the frequency bands is fixedly set to the frequency band in which only the UL signal is transmitted, and the other frequency band is set to the UL signal only when the base station wants to perform interference measurement on the other frequency band. It may be set to the frequency band in which only is transmitted. Alternatively, each frequency band may be alternately set to a frequency band in which only the UL signal is transmitted.

Although the fourth embodiment and its modifications described above have been described as an example using two frequency bands, the present disclosure is not limited to this. The frequency band used for transmitting and receiving the UL signal and / or the DL signal may be three or more.

(Embodiment 5)
In each of the above-described embodiments, an example in which the base station requests the terminal to transmit a null signal in order to perform the interference measurement and the terminal transmits the null signal in the UL preamble section has been described. However, the present disclosure is not limited to the example in which the base station performs interference measurement. In the fifth embodiment, an example in which the base station transmits a null signal in the DL preamble section will be described in order for the terminal to also perform interference measurement.

<Base station configuration>
The configuration of the base station according to the fifth embodiment will be described with reference to FIG. FIG. 18 is a block diagram showing a configuration example of the base station 700 according to the fifth embodiment. Note that, in FIG. 18, the same configuration as that of FIG. 2 is assigned the same reference numeral, and the description thereof will be omitted.

The base station 700 adopts a configuration in which the preamble generation unit 204 of the base station 200 shown in FIG. 2 is replaced with the preamble setting unit 704. Then, the determination unit 201 outputs the determination result to the preamble setting unit 704 (specifically, the switching unit 704d described later).

The preamble setting unit 704 sets the preamble based on the determination result acquired from the determination unit 201. The preamble setting unit 704 includes a preamble generation unit 704a, a null signal generation unit 704b, a determination result holding unit 704c, and a switching unit 704d.

The preamble generation unit 704a generates a preamble and outputs it to the switching unit 704d. The preamble data is symbol data or the like in which the base station 700 and the terminal 800, which will be described later, are known in advance.

The null signal generation unit 704b generates a null signal and outputs it to the switching unit 704d.

The determination result holding unit 704c holds the determination result acquired from the determination unit 201 and holds one frame. For example, the determination result holding unit 704c holds the determination result of the determination unit 201 at the time of the DL signal generation processing of the nth frame until the DL signal generation processing of the n + 1st frame, and the DL of the n + 1th frame. When the signal is generated, it is output to the switching unit 704d.

When the determination result acquired from the determination unit 201 indicates that the null signal is transmitted to the UL preamble section, the switching unit 704d outputs the null signal acquired from the null signal generation unit 704b to the addition unit 205. When the determination result acquired from the determination unit 201 indicates that the null signal is not transmitted to the preamble, the switching unit 704d outputs the preamble acquired from the preamble generation unit 704a to the addition unit 205.

<Terminal configuration>
Next, a configuration example of the terminal 800 according to the fifth embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration example of the terminal 800 according to the fifth embodiment. Note that, in FIG. 19, the same configuration as that of FIG. 1 is assigned the same number and the description thereof will be omitted.

In the terminal 800, the AGC / synchronization detection unit 103 and the reception processing control unit 104 of the terminal 100 shown in FIG. 1 are replaced with the AGC / synchronization detection unit 809 and the reception processing control unit 811, and the AGC / synchronization holding unit 810 and the interference measurement are performed. The configuration in which the part 812 is added is adopted. Then, the determination unit 105 adopts a configuration in which the determination result is output to the reception processing control unit 811.

Based on the preamble included in the baseband signal acquired from the radio reception unit 101, the AGC / synchronization detection unit 809 provides timing information for synchronization between transmission and reception, and gain control (AGC) in reception processing and the like. Information (for example, signal level) is detected. Then, the AGC / synchronization detection unit 809 outputs the detection result of the timing and information for the AGC to the AGC / synchronization holding unit 810 and the reception processing control unit 811.

When the base station 700 transmits a null signal to the preamble section, the AGC / synchronous detection unit 809 does not execute the detection process and does not output the detection result because the preamble does not exist.

The AGC / synchronization holding unit 810 holds the latest detection results of AGC and timing detected by the AGC / synchronization detection unit 809.

The reception processing control unit 811 controls the timing of reception processing and the AGC. Specifically, the reception processing control unit 811 outputs timing information indicating the processing timing such as the start time and the end time of the baseband reception processing to the baseband reception processing unit 102. Further, the reception processing control unit 811 outputs timing information indicating the processing timing such as the start time and the end time of the interference measurement to the interference measurement unit 812. Further, the reception processing control unit 811 outputs the AGC information to the wireless reception unit 101.

At that time, when the reception processing control unit 811 acquires the detection result from the AGC / synchronous detection unit 809, the reception processing control unit 811 generates timing information and AGC information based on the acquired detection result. Further, when the reception processing control unit 811 does not acquire the detection result from the AGC / synchronization detection unit 809, that is, when a null signal is transmitted in the preamble section, the reception processing control unit 811 is based on the detection result held by the AGC / synchronization holding unit 810. To generate timing information and AGC information.

Based on the timing information acquired from the reception processing control unit 811, the interference measurement unit 812 sets the guard time section or the section obtained by combining the guard time section and the preamble section in which the null signal is transmitted as the interference measurement section. The reception level (interference amount, for example, Received Signal Strength Indicator (RSSI)) in the interference measurement section is measured. The interference measurement unit 812 outputs the measurement result to the wireless transmission unit 109.

<Frame configuration>
Next, the frame configuration in the wireless communication system according to the fifth embodiment will be described with reference to FIG. FIG. 20 is a diagram showing an example of a frame configuration according to the fifth embodiment.

The difference between the frame configuration in the fifth embodiment shown in FIG. 20 and the frame configuration in the first embodiment shown in FIG. 3 is that a null signal is transmitted to the DL preamble section of the n + 1th frame.

As shown in FIG. 20, when the base station 700 causes the terminal 800 to transmit a null signal in the UL preamble section of the n + 1st frame, the base station 700 transmits the selection signal “1” in the nth frame and the n + 1th frame. A null signal is transmitted in the DL preamble section of the frame. The terminal 800 transmits a null signal in the UL preamble section of the n + 1th frame. Then, the base station 700 performs the interference measurement with the section including the n + 1st UL preamble section as the interference measurement section, and the terminal 800 performs the interference measurement with the section including the n + 1th DL preamble section as the interference measurement section. be able to.

As described above, according to the fifth embodiment, the base station 700 transmits a selection signal indicating that a null signal is transmitted to the preamble section of the UL signal to the terminal 800 when performing the interference measurement, and selects the terminal 800. A null signal is transmitted in the DL preamble section in the next frame in which the signal is transmitted. The terminal 800 transmits a null signal to the preamble section of the UL signal based on the received selection signal, and performs interference measurement in the preamble section of the DL signal received after transmitting the UL signal. As a result, the base station 700 can perform the interference measurement with the section in which the guard time section and the preamble section of the UL signal to which the null signal is transmitted are combined as the interference measurement section, and the terminal 800 can perform the interference measurement. Since the interference measurement can be performed by using the section that combines the section and the preamble section of the DL signal to which the null signal is transmitted as the interference measurement section, the accuracy of the interference measurement is deteriorated without lengthening the guard time. Can be prevented.

In addition, each embodiment described above and a modification thereof may be combined appropriately or may be switched appropriately.

Further, in each of the embodiments described above and examples thereof, the base station mainly requests the terminal to transmit a null signal in the preamble section of the UL signal when performing the interference measurement. Although examples have been described, the present disclosure is not limited to this. When the terminal having the configuration described as the configuration of the base station in each of the above embodiments and the modified examples thereof executes the interference measurement, the terminal transmits a null signal to the base station in the preamble section of the DL signal. You may make a request. In that case, the preamble section of the DL signal is based on the request that the base station having the configuration described as the configuration of the terminal in each of the above embodiments and the modified examples thereof transmits a null signal to the preamble section of the DL signal. A null signal is transmitted to the terminal, and the terminal performs interference measurement with the section including the null signal in the preamble section of the DL signal as the interference measurement section.

Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the claims, which naturally belong to the technical scope of the present disclosure. Understood. In addition, each component in the above embodiment may be arbitrarily combined as long as the purpose of disclosure is not deviated.

In each of the above embodiments, the present disclosure has been described for an example of configuring using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

Further, each functional block used in the description of the above embodiment is typically realized as an LSI which is an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiment and include an input and an output. These may be individually integrated into one chip, or may be integrated into one chip so as to include a part or all of each functional block. Although it is referred to as an LSI here, it may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration.

Further, the method of making an integrated circuit is not limited to LSI, and may be realized by using a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor in which the connection and settings of the circuit cells inside the LSI can be reconfigured may be used.

Furthermore, if an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology or another technology derived from it, it is naturally possible to integrate functional blocks using another technology. The application of biotechnology, etc. is possible.

The present disclosure can be expressed as a control method executed in a wireless communication device or a control device. The present disclosure can also be expressed as a program for operating such a control method by a computer. Further, the present disclosure can also be expressed as a recording medium in which such a program is recorded in a state in which it can be read by a computer. That is, the present disclosure can be expressed in any category of devices, methods, programs, and recording media.

Further, the present disclosure is not limited to the above-described embodiment in terms of the type, arrangement, number, etc. of the members, and deviates from the gist of the invention, such as appropriately replacing the constituent elements with those having the same effect and effect. It can be changed as appropriate to the extent that it does not.

The present disclosure is suitable for use in terminals such as FPUs and base stations.

100, 400, 500, 800 Terminals 101, 207 Wireless receiver 102, 208 Baseband reception processing unit 103, 209, 609, 809 AGC / synchronous detection unit 104, 211, 611, 811 Reception processing control unit 105, 201, 405 Judgment unit 106, 203 Baseband transmission processing unit 107, 507, 704 Preamble setting unit 107a, 204, 304, 704a Preamble generation unit 107b, 704b Null signal generation unit 107c, 704d Switching unit 108, 205 Addition unit 109, 206 Wireless transmission Part 200, 300, 600, 700 Base station 202 Selection signal generation part 210, 810 AGC / Synchronous holding part 212, 612, 812 Interference measurement part 304a, 507a Arrangement part 304b, 507b Inverse Fourier transform part 304c Polarity change part 507c Null signal Replacement part 704c Judgment result holding part

Claims (13)

A base station that performs time division duplex wireless communication with terminals.
A receiver that receives an uplink signal that is transmitted from the terminal and has a preamble signal or a null signal set in the uplink preamble section at the beginning of the frame.
When the null signal is set in the uplink preamble section, the interference measurement unit that performs interference measurement at the time including the section of the null signal and
Base station with. A transmission unit for transmitting a downlink signal including an instruction indicating whether or not to set the null signal in the uplink preamble section is further provided.
The base station according to claim 1. The transmitter changes the preamble included in the downlink signal based on whether or not the null signal is set in the uplink preamble section.
The base station according to claim 2. The downlink signal preamble is a signal in which signal components are periodically arranged.
The transmitter inverts at least one polarity of the signal component based on whether or not the null signal is set in the uplink preamble section.
The base station according to claim 3. When the transmission unit transmits an instruction indicating that the null signal is set in the uplink preamble section of the nth frame (n is an integer of 1 or more), the null is in the uplink preamble section of the n + 1th frame. Send an instruction not to set the signal,
The base station according to claim 2. In the nth frame (n is an integer of 1 or more), the transmission unit transmits a downlink signal including an instruction indicating that the null signal is set in the uplink preamble section.
The receiving unit performs interference measurement at a time including the section of the null signal in the n + 2nd frame.
The base station according to claim 2. The uplink signal preamble is a signal in which signal components are periodically arranged.
At least one of the signal components is replaced by the null signal.
The base station according to claim 1. The receiving unit receives a plurality of uplink signals transmitted by the terminal using a plurality of frequency bands, and receives the plurality of uplink signals.
The interference measurement unit performs interference measurement at a time including a section of the null signal of at least one uplink signal.
The base station according to claim 1. The receiving unit performs synchronous detection using a preamble signal set in an uplink preamble section of an uplink signal different from the at least one uplink signal.
The base station according to claim 8. Further, a transmission unit for transmitting a downlink signal including an instruction indicating whether or not to set the null signal in the uplink preamble section using the first frequency band among the plurality of frequency bands is provided.
The receiving unit receives the uplink signal transmitted by the terminal in a section including a transmission section of the downlink signal using at least one frequency band different from the first frequency band.
The interference measurement unit performs interference measurement at a time including the null signal of the at least one uplink signal transmitted by the terminal using the at least one frequency band.
The base station according to claim 8. The transmitter sets a null signal in the downlink preamble section of the downlink signal and transmits the downlink signal.
The base station according to claim 2. A wireless communication system in which a terminal and a base station perform time division duplex radio communication.
The terminal
A transmitter that transmits an uplink signal with a preamble signal or a null signal set in the uplink preamble section at the beginning of the frame.
With
The base station
A receiver that receives the uplink signal and
When the null signal is set in the uplink preamble section, the interference measurement unit that performs interference measurement at the time including the section of the null signal and
To prepare
Wireless communication system. It is a communication method in a base station that performs time division duplex wireless communication with a terminal.
Receives an uplink signal with a preamble signal or null signal set in the uplink preamble section at the beginning of the frame, which is transmitted from the terminal.
When the null signal is set in the uplink preamble section, the interference measurement is performed at the time including the section of the null signal.
Communication method.

Images