JP2014011488A - Radio reception device and radio reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio reception device and a radio reception method which can enhance quality of reception data.SOLUTION: A smart phone 1 which receives data by an LTE system, comprises: an AGC (Automatic Gain Control) amplifier 614 which amplifies a received signal; an FFT (Fast Fourier Transform) processing unit 621 which demodulates the signal amplified by the AGC amplifier 614; and an AGC processing unit 622 which controls a gain of the AGC amplifier 614 on the basis of strength of the received signal and the number of resource blocks acquired as a processing result by the FFT processing unit 621.

Description

  The present invention relates to a radio reception apparatus and radio reception method that perform AGC control.

  Conventionally, in a wireless communication system, a multi-carrier scheme such as OFDMA (Orthogonal Frequency Division Multiple Access) is used.

  In addition, in a receiving circuit of a radio communication system, AGC (Automatic Gain Control) is performed in order to compensate for a receiving dynamic range such as ADC (A / D Converter) to cope with a strong electric field to a weak electric field. (For example, refer to Patent Document 1). This AGC adjusts the gain of the amplifier in accordance with RSSI (Receive Signal Strength Indication).

JP 2002-152173 A

  By the way, in the multi-carrier scheme such as LTE or WiMAX, the number of RBs (Resource Blocks) allocated to one wireless receiving device varies depending on the number of connected wireless receiving devices or the amount of communication data. . Here, when processing the received signal, the wireless reception device performs FFT (Fast Fourier Transform) processing at a fixed sampling frequency depending on the system bandwidth. For this reason, when the number of allocated RBs varies and the signal bandwidth varies, the gain of the FFT processing varies. When the gain of the FFT processing is increased, the processed signal is saturated and distorted, and the quality of received data may be deteriorated.

  An object of the present invention is to provide a wireless reception device and a wireless reception method capable of improving the quality of received data.

  A radio reception apparatus according to the present invention is a radio reception apparatus that receives data in a multi-carrier system, an amplifier that amplifies a reception signal, an FFT processing unit that demodulates a signal amplified by the amplifier, and the reception signal And a gain control unit that controls the gain of the amplifier based on the number of resource blocks obtained as a result of processing by the FFT processing unit.

  The gain controller preferably controls the gain of the amplifier to be smaller as the number of the resource blocks is smaller.

  The radio reception apparatus according to the present invention further includes a storage unit that stores an adjustment value for the amplifier associated with the strength of the reception signal and the number of the resource blocks, and the gain control unit includes the adjustment value. It is preferable to control the gain of the amplifier based on the above.

  In addition, it is preferable that a plurality of levels are provided for each of the received signal strength and the number of the resource blocks, and the storage unit stores adjustment values for combinations of the levels.

  A radio reception method according to the present invention is a radio reception method for receiving data in a multicarrier system, and includes an amplifier that amplifies a received signal and an FFT processing unit that demodulates a signal amplified by the amplifier. The apparatus controls the gain of the amplifier based on the intensity of the received signal and the number of resource blocks obtained as a processing result of the FFT processing unit.

  According to the present invention, it is possible to improve the quality of received data in a radio receiving apparatus.

It is a perspective view which shows the external appearance of the smart phone which concerns on embodiment. It is a front view which shows the external appearance of the smart phone which concerns on embodiment. It is a rear view which shows the external appearance of the smart phone which concerns on embodiment. It is a block diagram which shows the structure of the smart phone which concerns on embodiment. It is a block diagram which shows the detailed function of the communication unit which concerns on embodiment. It is a figure which shows typically the 1st example of the allocated subcarrier among system bands. It is a figure which shows typically the 2nd example of the allocated subcarrier among system bands. It is a figure which shows the sampling frequency corresponding to a system bandwidth, and the number of points of FFT processing. It is a figure which shows the relationship between the number of RBs, and the processing gain at the time of FFT processing. It is a figure which compares and shows an example of the signal strength in a time domain and a frequency domain. It is a figure which shows an AGC control table. It is a figure which shows the relationship between an antenna input level, the control voltage to an AGC amplifier, and the output of ADC. It is a figure which shows typically the output in the time domain and the frequency domain with respect to the reception power with an antenna.

  Embodiments for carrying out the present invention will be described in detail with reference to the drawings. Hereinafter, a smartphone will be described as an example of a wireless reception device.

  The external appearance of the smartphone 1 according to the embodiment will be described with reference to FIGS. 1 to 3. As shown in FIGS. 1 to 3, the smartphone 1 has a housing 20. The housing 20 includes a front face 1A, a back face 1B, and side faces 1C1 to 1C4. The front face 1 </ b> A is the front of the housing 20. The back face 1 </ b> B is the back surface of the housing 20. The side faces 1C1 to 1C4 are side surfaces that connect the front face 1A and the back face 1B. Hereinafter, the side faces 1C1 to 1C4 may be collectively referred to as the side face 1C without specifying which face.

  The smartphone 1 includes a touch screen display 2, buttons 3A to 3C, an illuminance sensor 4, a proximity sensor 5, a receiver 7, a microphone 8, and a camera 12 on the front face 1A. The smartphone 1 has a camera 13 on the back face 1B. The smartphone 1 has buttons 3D to 3F and an external interface 14 on the side face 1C. Hereinafter, the buttons 3A to 3F may be collectively referred to as the button 3 without specifying which button.

  The touch screen display 2 includes a display 2A and a touch screen 2B. The display 2A includes a display device such as a liquid crystal display (Liquid Crystal Display), an organic EL panel (Organic Electro-Luminescence panel), or an inorganic EL panel (Inorganic Electro-Luminescence panel). The display 2A displays characters, images, symbols, graphics, and the like.

  The touch screen 2B detects contact of a finger, a stylus pen, or the like with respect to the touch screen display 2. The touch screen 2B can detect a position where a plurality of fingers, a stylus pen, or the like is in contact with the touch screen display 2.

  The detection method of the touch screen 2B may be any method such as a capacitance method, a resistive film method, a surface acoustic wave method (or an ultrasonic method), an infrared method, an electromagnetic induction method, and a load detection method. Hereinafter, for the sake of simplicity of explanation, a finger that the touch screen 2B detects contact with the touch screen display 2 or a stylus pen or the like may be simply referred to as a “finger”.

  The smartphone 1 determines the type of gesture based on the contact, contact position, contact time, or number of contacts detected by the touch screen 2B. The gesture is an operation performed on the touch screen display 2. The gesture determined by the smartphone 1 includes touch, long touch, release, swipe, tap, double tap, long tap, drag, flick, pinch in, pinch out, and the like.

  A touch is a gesture in which a finger contacts the touch screen display 2 (for example, a surface). The smartphone 1 determines a gesture in which a finger contacts the touch screen display 2 as a touch. The long touch is a gesture in which a finger contacts the touch screen display 2 for a predetermined time or more. The smartphone 1 determines a gesture in which a finger contacts the touch screen display 2 for a predetermined time or more as a long touch.

  A release is a gesture in which a finger leaves the touch screen display 2. The smartphone 1 determines a gesture in which a finger leaves the touch screen display 2 as a release. The swipe is a gesture that moves while the finger is in contact with the touch screen display 2. The smartphone 1 determines a gesture that moves while the finger is in contact with the touch screen display 2 as a swipe.

  A tap is a gesture for releasing following a touch. The smartphone 1 determines a gesture for releasing following a touch as a tap. The double tap is a gesture in which a gesture for releasing following a touch is continued twice. The smartphone 1 determines a gesture in which a gesture for releasing following a touch is continued twice as a double tap.

  A long tap is a gesture for releasing following a long touch. The smartphone 1 determines a gesture for releasing following a long touch as a long tap. The drag is a gesture for performing a swipe from an area where a movable object is displayed. The smartphone 1 determines, as a drag, a gesture for performing a swipe starting from an area where a movable object is displayed.

  The flick is a gesture that is released while the finger moves at high speed in one direction following the touch. The smartphone 1 determines, as a flick, a gesture that is released while the finger moves in one direction at high speed following the touch. Flick: Up flick that moves your finger up the screen, Down flick that moves your finger down the screen, Right flick that moves your finger right in the screen, Left flick that moves your finger left in the screen Etc.

  Pinch-in is a gesture that swipes in a direction in which a plurality of fingers approach each other. The smartphone 1 determines, as a pinch-in, a gesture that swipes in a direction in which a plurality of fingers approach each other. Pinch-out is a gesture that swipes a plurality of fingers away from each other. The smartphone 1 determines a gesture of swiping in a direction in which a plurality of fingers move away from each other as a pinch out.

  The smartphone 1 operates according to these gestures that are determined via the touch screen 2B. Therefore, operability that is intuitive and easy to use for the user is realized. The operation performed by the smartphone 1 according to the determined gesture differs depending on the screen displayed on the touch screen display 2.

  FIG. 4 is a block diagram illustrating the configuration of the smartphone 1. The smartphone 1 includes a touch screen display 2, a button 3, an illuminance sensor 4, a proximity sensor 5, a communication unit 6, a receiver 7, a microphone 8, a storage 9, a controller 10, and cameras 12 and 13. , An external interface 14, an acceleration sensor 15, an orientation sensor 16, and a rotation detection sensor 17.

  As described above, the touch screen display 2 includes the display 2A and the touch screen 2B. The display 2A displays characters, images, symbols, graphics, or the like. The touch screen 2B detects a gesture.

  The button 3 is operated by the user. The button 3 includes buttons 3A to 3F. The controller 10 detects an operation on the button by cooperating with the button 3. The operation on the button is, for example, click, double click, push, and multi-push.

  For example, the buttons 3A to 3C are a home button, a back button, or a menu button. For example, the button 3D is a power on / off button of the smartphone 1. The button 3D may also serve as a sleep / sleep release button. For example, the buttons 3E and 3F are volume buttons.

  The illuminance sensor 4 detects illuminance. For example, the illuminance is light intensity, brightness, luminance, or the like. The illuminance sensor 4 is used for adjusting the luminance of the display 2A, for example.

  The proximity sensor 5 detects the presence of a nearby object without contact. The proximity sensor 5 detects that the touch screen display 2 is brought close to the face, for example.

  The communication unit 6 communicates wirelessly. The communication method performed by the communication unit 6 is a wireless communication standard. For example, wireless communication standards include cellular phone communication standards such as 2G, 3G, and 4G. For example, communication standards for cellular phones include LTE (Long Term Evolution), W-CDMA, CDMA2000, PDC, GSM (registered trademark), PHS (Personal Handy-phone System), and the like. Examples of wireless communication standards include WiMAX (Worldwide Interoperability for Microwave Access), IEEE802.11, Bluetooth (registered trademark), IrDA, NFC (Near Field Communication), and the like. The communication unit 6 may support one or more of the communication standards described above.

  The receiver 7 outputs the audio signal transmitted from the controller 10 as audio. The microphone 8 converts the voice of the user or the like into a voice signal and transmits it to the controller 10. The smartphone 1 may further include a speaker in addition to the receiver 7. The smartphone 1 may further include a speaker instead of the receiver 7.

  The storage 9 stores programs and data. The storage 9 is also used as a work area for temporarily storing the processing result of the controller 10. The storage 9 may include any storage device such as a semiconductor storage device and a magnetic storage device. The storage 9 may include a plurality of types of storage devices. The storage 9 may include a combination of a portable storage medium such as a memory card and a storage medium reading device.

  The programs stored in the storage 9 include an application executed in the foreground or the background and a control program that supports the operation of the application. For example, the application displays a predetermined screen on the display 2A, and causes the controller 10 to execute processing according to the gesture detected by the touch screen 2B. The control program is, for example, an OS. The application and the control program may be installed in the storage 9 via wireless communication by the communication unit 6 or a storage medium.

  The storage 9 stores, for example, a control program 9A, a mail application 9B, a browser application 9C, and setting data 9Z. The mail application 9B provides an electronic mail function for creating, transmitting, receiving, and displaying an electronic mail. The browser application 9C provides a WEB browsing function for displaying a WEB page. The table 9D stores various tables such as a key assignment table. The arrangement pattern database 9E stores arrangement patterns such as icons displayed on the display 2A. The setting data 9Z provides various setting functions related to the operation of the smartphone 1.

  The control program 9A provides functions related to various controls for operating the smartphone 1. The control program 9A realizes a call by controlling the communication unit 6, the receiver 7, the microphone 8, and the like, for example. The function provided by the control program 9A includes a function of performing various controls such as changing information displayed on the display 2A according to a gesture detected via the touch screen 2B. Note that the functions provided by the control program 9A may be used in combination with functions provided by other programs such as the mail application 9B.

  The controller 10 is, for example, a CPU (Central Processing Unit). The controller 10 may be an integrated circuit such as a SoC (System-on-a-chip) in which other components such as the communication unit 6 are integrated. The controller 10 controls various operations of the smartphone 1 to realize various functions.

  Specifically, the controller 10 executes instructions included in the program stored in the storage 9 while referring to the data stored in the storage 9 as necessary, and the display 2A, the communication unit 6 and the like. Various functions are realized by controlling. The controller 10 may change the control according to detection results of various detection units such as the touch screen 2B, the button 3, and the acceleration sensor 15.

  For example, by executing the control program 9A, the controller 10 executes various controls such as changing information displayed on the display 2A according to a gesture detected via the touch screen 2B.

  The camera 12 is an in-camera that captures an object facing the front face 1A. The camera 13 is an out camera that captures an object facing the back face 1B.

  The external interface 14 is a terminal to which another device is connected. The external interface 14 may be a general-purpose terminal such as a universal serial bus (USB), a high-definition multimedia interface (HDMI), a light peak (thunderbolt), and an earphone microphone connector. The external interface 14 may be a dedicated terminal such as a dock connector. Devices connected to the external interface 14 include, for example, an external storage, a speaker, and a communication device.

  The acceleration sensor 15 detects the direction and magnitude of acceleration acting on the smartphone 1. The direction sensor 16 detects the direction of geomagnetism. The rotation detection sensor 17 detects the rotation of the smartphone 1. The detection results of the acceleration sensor 15, the orientation sensor 16, and the rotation detection sensor 17 are used in combination in order to detect changes in the position and orientation of the smartphone 1.

  The smartphone 1 configured as described above can improve the quality of data received by multicarrier wireless communication. A specific configuration will be described below.

FIG. 5 is a block diagram illustrating detailed functions of the communication unit 6 in the smartphone 1.
In addition, the smart phone 1 shall respond | correspond to LTE as a radio | wireless communications system which performs data communication.

The communication unit 6 includes an RF unit 61 and a signal processing unit 62.
The RF unit 61 amplifies the signal input from the antenna by the LNA 611 and converts it to the primary intermediate frequency by the RF mixer 612. Further, the RF unit 61 measures RSSI (intensity of the received signal) with respect to the received signal branched via the coupler 613 by the detection circuit, and provides it to the signal processing unit 62.

  Further, the RF unit 61 amplifies the signal by the AGC amplifier 614 whose gain is adjusted by the AGC, converts the signal to a secondary intermediate frequency by the IF mixer 615, digitizes the signal by the ADC 616, and provides the signal to the signal processing unit 62.

The signal processing unit 62 includes an FFT processing unit 621 and an AGC processing unit 622.
The FFT processing unit 621 performs FFT processing on the digital signal provided from the RF unit 61 and provides the demodulated result to the controller 10. Further, the FFT processing unit 621 provides the AGC processing unit 622 with a value corresponding to the number of RBs obtained as a result of the FFT processing.

  The AGC processing unit 622 controls the gain of the AGC amplifier 614 based on the RSSI (received signal strength) provided from the RF unit 61 and the number of RBs provided from the FFT processing unit 621.

Here, the relationship between the number of RBs and the gain in the FFT processing will be described.
FIG. 6 is a diagram schematically illustrating subcarriers (carrier waves) allocated to the smartphone 1 in the system band when only the smartphone 1 is connected to the base station.
In this case, the smartphone 1 can monopolize all subcarriers in the system band.

FIG. 7 is a diagram schematically illustrating subcarriers allocated to the smartphone 1 in the system band when a large number of terminals are connected to the base station.
For example, when the number of connections to the base station is maximum, the subcarrier that can be used by the smartphone 1 is a band corresponding to one RB.

FIG. 8 is a diagram showing the sampling frequency corresponding to the system bandwidth and the number of points of FFT processing.
As the bandwidth increases, the sampling frequency increases and the number of FFT processing points also increases. For example, in the case of a communication system having a bandwidth of 20 MHz, the sampling frequency is 30.72 MHz and the number of FFT processing points is 2048.
Here, since the bandwidth is fixed for each communication system, a constant value is adopted for the sampling frequency and the number of points of the FFT processing.

FIG. 9 is a diagram illustrating the relationship between the number of RBs and the processing gain at the time of FFT processing in a communication system having a system bandwidth (system_BW) of 20 MHz.
When the number of assigned RBs (signal_RB) is 100, that is, when 1200 subcarriers are used, the signal bandwidth (signal_BW) is 18 MHz, and the FFT sampling frequency is 30.72 MHz as described above. , FFT processing gain is 2.3 dB.

On the other hand, when the number of assigned RBs is 1, the signal bandwidth is 1.8 MHz, but the FFT sampling frequency does not change at 30.72 MHz as described above, so the FFT processing gain is 22.2. 3 dB.
Thus, the smaller the number of RBs, the higher the processing gain during FFT processing.

  FIG. 10 is a diagram showing a comparison of examples of signal strength in the process in the time domain (Time Domain) and the frequency domain (Freq Domain).

The output from the ADC 616, i.e., the distortion-free saturation point of the time domain IQ signal, is -3 dBFS. In a system with a system bandwidth of 20 MHz, when the output in the time domain of a signal received with 100 RBs is −10 dBFS, the FFT processing gain is 2.3 dB, so the output in the frequency domain is −7. 7 dBFS.
On the other hand, if the output in the time domain of the received signal with the number of RBs is -15 dBFS, the FFT processing gain is 22.3 dB, so the output in the frequency domain is 7.3 dBFS. Since the output in this frequency region exceeds the distortion-free saturation point, the signal after FFT processing is saturated.

When the AGC processing unit 622 performs control with only power in the time domain based on RSSI, when the number of RBs allocated to the smartphone 1 decreases, the FFT processing gain increases and the signal is saturated in the frequency domain. .
Therefore, the AGC processing unit 622 controls the gain of the AGC amplifier 614 to be smaller as the number of RBs is smaller.

FIG. 11 is a diagram showing an AGC control table stored in the storage 9.
In this AGC control table, adjustment values for the AGC amplifier 614 associated with the RSSI and the number of RBs, which are the strength of the received signal, are stored.

  A plurality of levels are provided for each of the RSSI and the number of RBs. Specifically, for example, RSSI has three levels of “High”, “Middle”, and “Low”, and “Gain_High” is used as an FFT processing gain calculated from the system bandwidth and the number of RBs. ”,“ Gain_Middle ”, and“ Gain_Low ”.

An adjustment value (AGC_Control) is stored for each combination of the RSSI level and the FFT processing gain level. The AGC processing unit 622 controls the gain of the AGC amplifier 614 based on this adjustment value.
Note that “AGC1”, “AGC2”, and “AGC3” in the adjustment value have a relationship of “AGC1 <AGC2 <AGC3” corresponding to the magnitude of RSSI. The AGC processing unit 622 adjusts the control voltage of the AGC amplifier 614 in accordance with an adjustment value obtained by subtracting the FFT processing gain from these values, thereby adjusting the level of the received signal.

  FIG. 12 is a diagram illustrating a relationship among the antenna input level, the control voltage to the AGC amplifier 614, and the output of the ADC 616.

  The control voltage VGCTL is higher as the slope is larger, and the AGC gain is higher. The AGC processing unit 622 performs control so that the output is constant in the frequency domain even if the antenna input level changes. Specifically, when performing control based on RSSI, the AGC processing unit 622 controls the output to a TYP lower than the saturation point (MAX on the vertical axis) when converted to the frequency domain. For example, when the antenna input level is TYP, the control voltage is VGCTL1. In addition, when the antenna input level is MAX, the AGC processing unit 622 decreases the gain of the AGC amplifier 614 by setting the control voltage as VGCTL2, and when the antenna input level is MIN, the AGC processing unit 622 increases the gain of the AGC amplifier 614 by setting the control voltage as VGCTL3.

  Furthermore, the AGC processing unit 622 controls the output in the time domain to be TYP ′ in order to suppress an increase in output due to the FFT processing gain. That is, the control voltages VGCTL1, VGCTL2, and VGCTL3 are lowered to VGCTL1 ', VGCTL2', and VGCTL3 ', respectively.

  FIG. 13 is a diagram schematically showing output in the time domain and frequency domain with respect to the received power at the antenna.

The range of received power from the antenna is a to d, and the processable range in the time domain and the frequency domain is b to c. When the received power from the antenna is high, the smartphone 1 performs a process of decreasing the gain by decreasing the AGC voltage, and when the received power is low, the smartphone 1 performs a process of increasing the gain by increasing the AGC voltage. In the AGC control considering only the time domain based on the conventional RSSI, the output is adjusted to a broken line range b to c that can be processed in the time domain. As a result, the output becomes a broken line range b to d in the frequency domain and exceeds the processable solid line range b to c, and saturation occurs in the processing process. By the control based on the adjustment, adjustment is performed so that the output is reduced by an amount (dc) corresponding to the processing gain of FFT.
As a result, the output in the frequency domain is suppressed to the target solid line range b to c, compared to the broken line range b to d when the FFT processing gain is not considered.

  As described above, according to the present embodiment, the smartphone 1 performs AGC in consideration of the processing gain of FFT in addition to RSSI. Therefore, even when the number of assigned RBs decreases during communication, the received signal is saturated. Therefore, it is possible to prevent signal quality deterioration and improve the quality of received data.

  Moreover, since the smart phone 1 can determine the control voltage easily by managing the adjustment amount by AGC with a control table, it can reduce a processing load. Furthermore, since a plurality of levels are provided for each of the RSSI and the number of RBs, and adjustment values are set for the combinations thereof, the data amount and the processing load are reduced.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to embodiment mentioned above. Further, the effects described in the embodiments of the present invention only list the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the above-described embodiments. Absent.

The configuration of the smartphone 1 shown in FIGS. 4 and 5 is an example, and may be changed as appropriate within a range that does not impair the gist of the present invention.
In addition, the communication unit 6 has been described as corresponding to LTE, but is not limited thereto, and may be WiMAX or another wireless communication system.

  In the above-described embodiment, a smartphone has been described as an example of a wireless reception device, but the wireless reception device is not limited to a smartphone. For example, the wireless reception device may be a mobile phone, a portable personal computer, a digital camera, a media player, an electronic book reader, a portable electronic device such as a navigator or a game machine, or a communication-dedicated module specialized for a communication function. The wireless reception device may be a stationary electronic device such as a desktop personal computer or a television receiver.

1 Smartphone (wireless receiver)
6 Communication unit 9 Storage 10 Controller 61 RF unit 62 Signal processing unit 611 LNA
612 RF mixer 613 Coupler 614 AGC amplifier 615 IF mixer 616 ADC
621 FFT processing unit 622 AGC processing unit (gain control unit)

Claims (5)

A wireless receiver for receiving data in a multicarrier system,
An amplifier that amplifies the received signal;
An FFT processing unit for demodulating the signal amplified by the amplifier;
A radio receiving apparatus comprising: a gain control unit that controls a gain of the amplifier based on the intensity of the received signal and the number of resource blocks obtained as a processing result of the FFT processing unit.   The radio reception apparatus according to claim 1, wherein the gain control unit controls the gain of the amplifier to be smaller as the number of the resource blocks is smaller. A storage unit for storing an adjustment value for the amplifier, which is associated with the intensity of the received signal and the number of the resource blocks;
The radio reception apparatus according to claim 1, wherein the gain control unit controls a gain of the amplifier based on the adjustment value.   The radio reception apparatus according to claim 3, wherein a plurality of levels are provided for each of the received signal strength and the number of the resource blocks, and the storage unit stores adjustment values for combinations of the levels. A wireless reception method for receiving data in a multicarrier system,
The number of resource blocks obtained as a result of the processing of the FFT processing unit by the wireless reception device having an amplifier that amplifies the received signal and an FFT processing unit that demodulates the signal amplified by the amplifier A wireless reception method for controlling the gain of the amplifier based on the above.

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