JP6506596B2 - Wireless communication apparatus, wireless communication method, wireless communication system and chip - Google Patents

Description

  The present invention relates to technology for performing one-to-one bi-directional communication by Time Division Duplex (TDD), and in particular, efficiently and accurately detects frequency deviations on the transmission side and the reception side, Wireless communication apparatus, wireless communication method, wireless communication system, and chip for correcting

  Conventionally, OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme is compared with single carrier modulation scheme due to the error of the local oscillator between the radio communication apparatus on the transmitting side and the radio communication apparatus on the receiving side. It is known to be susceptible to frequency deviations that occur. In order not to be affected by the frequency deviation, an automatic frequency control (AFC) circuit that corrects the frequency deviation is essential.

  As a basic method for the wireless communication apparatus on the receiving side to detect the frequency deviation, there is one that detects the phase rotation amount between the repeatedly transmitted signals and detects the frequency deviation from the phase rotation amount. For example, in a wireless communication system based on a standard for broadcast material transmission (see Non-Patent Document 1 and Non-Patent Document 2), continuous OFDM symbols are transmitted without interruption in unidirectional communication.

  In this wireless communication system, the wireless communication apparatus on the receiving side has a complex correlation between a second half of the OFDM symbol and a GI (Guard Interval) period in which the second half is copied to the beginning of the OFDM symbol and added. Calculate the value. Then, the wireless communication apparatus on the receiving side calculates the amount of phase rotation from the complex correlation value, detects the frequency deviation from the amount of phase rotation, and feeds it back to the AFC circuit (see, for example, Patent Document 1 and Non-patent Document 3).

  On the other hand, in a wireless communication system such as a wireless LAN, a signal in the form of a burst-like OFDM signal with a defined frame length is used. According to the standards such as the standard IEEE802.11a, a known signal called a preamble is added to the head of the transmission signal in order to achieve various signal synchronization. The wireless communication apparatus on the receiving side calculates the phase rotation amount of the repetition section in the preamble, and detects the frequency deviation from the phase rotation amount (see, for example, Patent Document 2).

  In addition, in order not to be affected by the remaining frequency deviation, it is necessary to correct the frequency deviation completed on a frame basis. Therefore, the radio communication apparatus on the reception side performs phase tracking in an open loop configuration using a pilot carrier or the like to correct the frequency deviation (see, for example, Patent Document 3).

  Also in a time-division duplex wireless communication system in which transmission and reception are switched on a time axis to perform bi-directional communication, signals transmitted from a wireless communication apparatus are basically intermittent, that is, bursty. Various methods have been proposed for establishing signal synchronization (frame synchronization, symbol synchronization, frequency synchronization) based on this burst signal and extracting various information.

Unexamined-Japanese-Patent No. 2006-135861 JP, 2006-41722, A Patent No. 3534020

ARIB STD-B33, "Portable OFDM digital radio transmission system for transmitting television broadcasting program materials" ARIB STD-B57, "Portable OFDM digital radio transmission system for transmitting 1.2 GHz / 2.3 GHz band television broadcast program material" Seki, Taga, Ishikawa, “Consideration of new frequency synchronization method using guard period in OFDM”, Technical Report of the Institute of Television Engineers of Japan, ITE Technical Report Vol. 19, No. 38, p. 13-18

  In the method of detecting frequency deviation in a wireless communication system using time division duplexing as described above, a preamble is added to the beginning of a subframe, which is a burst signal, in units of frames in which transmission and reception of subframes are performed. , Establish frequency synchronization. Therefore, a preamble intended to establish frequency synchronization is always added to the subframe.

  Here, a bi-directional communication is performed in which a subframe is transmitted from the first wireless transmission device to the second wireless transmission device and a subframe is transmitted from the second wireless transmission device to the first wireless transmission device. The unit is called a frame.

  However, in the wireless communication system, there has been a problem that transmission of such a preamble reduces transmission efficiency. From the viewpoint of transmission efficiency in the wireless communication system, it is desirable not to transmit the preamble as much as possible.

  Therefore, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a wireless communication apparatus capable of realizing a time division duplex system with good transmission efficiency when transmitting and receiving subframes. A method, a wireless communication system and a chip are provided.

  In order to solve the problem, a wireless communication apparatus according to claim 1 transmits and receives subframes in a time division duplex system, and detects and corrects a frequency deviation of a received signal of the subframe. A transmitting unit for transmitting a subframe including a preamble for detecting a frequency deviation to another wireless communication device and transmitting a subframe not including the preamble as a subsequent subframe, and the other wireless communication device The preamble included in the received subframe is used to detect a first frequency deviation, and the first frequency deviation in the received signal of the subframe is corrected, and a subframe received from the other wireless communication apparatus is detected. A second frequency deviation is detected using a included pilot carrier, and the second in the received signal of the sub-frame is detected. A receiver for correcting a wave number deviation, the receiver receiving a sine wave digital signal of a predetermined oscillation frequency, and orthogonally demodulating the reception signal of the subframe based on the sine wave digital signal A demodulation unit, a fast Fourier transform operation unit that performs fast Fourier transform on the signal orthogonally demodulated by the orthogonal demodulation unit, and generates a signal in the frequency domain, and a preamble included in a subframe orthogonally demodulated by the orthogonal demodulation unit Using the first frequency deviation detecting unit for detecting the first frequency deviation, and the sine wave having the correction value as a result of subtracting a predetermined frequency from a predetermined frequency and the correction value as the predetermined oscillation frequency An oscillator that generates and outputs a digital signal, and a pilot that extracts a pilot carrier from the signal in the frequency domain generated by the fast Fourier transform operation unit A lot carrier extraction unit; and a second frequency deviation detection unit for detecting the second frequency deviation using the pilot carrier extracted by the pilot carrier extraction unit; When the sub-frame including the preamble is received, the oscillator subtracts the first frequency deviation detected by the first frequency deviation detection unit from the predetermined frequency as a correction value, and the correction value is used as the correction value. The sine wave digital signal having the predetermined oscillation frequency is generated and output, and the quadrature demodulation unit receives the sine wave digital signal from the oscillator, and the sub frame is generated based on the sine wave digital signal. The first frequency deviation in the reception signal of the sub-frame is corrected by orthogonal demodulation of the reception signal, and the other radio communication apparatus A first frequency deviation detected when the oscillator receives a sub-frame including the preamble from the predetermined frequency after receiving the sub-frame including the preamble; The sine wave digital signal is generated with a correction value obtained by subtracting the sum of the second frequency deviation detected by the second frequency deviation detection unit and a correction value as the predetermined oscillation frequency. The first frequency deviation is output by the quadrature demodulation unit inputting the sine wave digital signal from the oscillator and performing quadrature demodulation on the reception signal of the subframe based on the sine wave digital signal. Correcting the second frequency deviation in the corrected received signal of the sub-frame.

In the wireless communication apparatus according to claim 2, in the wireless communication apparatus according to claim 1, the waveform in the preamble formed by repeating the same waveform a plurality of times as the signal orthogonally demodulated by the orthogonal demodulation unit. And a plurality of correlation peaks on the time axis at which the cross correlation value calculated by the movement correlation unit is at the peak. A correlation peak detection unit that detects a position and detects the cross correlation value of the correlation peak position as a correlation peak value, and the correlation peak position based on a plurality of correlation peak values detected by the correlation peak detection unit And a first frequency deviation detection unit that calculates the phase rotation amount between the phase shift amount and the first frequency deviation from the phase rotation amount.

  The wireless communication apparatus according to claim 3 is the wireless communication apparatus according to claim 1 or 2, wherein the second frequency deviation detection unit is a predetermined one based on the pilot carrier extracted by the pilot carrier extraction unit. Calculating a complex division value of the symbol interval, calculating an average value of the complex division values in the subframe, setting a phase angle of the average value as a phase rotation amount, and detecting a second frequency deviation from the phase rotation amount To be characterized.

  A wireless communication apparatus according to claim 4 is the wireless communication apparatus according to any one of claims 1 to 3, further comprising: a frame for detecting a synchronization timing of the subframe and generating a frame synchronization timing signal. C / N based on a signal of a frequency domain generated by a synchronization detection unit, a symbol synchronization detection unit detecting a symbol synchronization timing of the sub frame, and generating a symbol synchronization timing signal, and the fast Fourier transform operation unit A C / N ratio calculator for calculating a ratio, and a reset signal generator for generating a reset signal for resetting the first frequency deviation, wherein the oscillator is generated by the reset signal generator Generating a sine wave digital signal having the predetermined frequency as the predetermined oscillation frequency based on a reset signal; The demodulator, on the basis of the sine-wave digital signal, the cause of the received signal of the sub-frame orthogonal demodulated, characterized in that.

  The wireless communication apparatus according to claim 5 is the wireless communication apparatus according to any one of claims 1 to 4, wherein the transmitting unit is configured to receive the first subframe and the second subframe at the start of communication. Transmitting the subframe including the preamble to the other wireless communication device, and transmitting the subframe not including the preamble as the third and subsequent subframes, and the receiving unit performs the other wireless communication From the device, a subframe including the preamble is received as a first subframe and a second subframe at the start of communication, and a subframe not including the preamble is received as third and subsequent subframes. The preamble included in the subframe is used to detect the first frequency deviation, and the received signal of the subframe is detected. Correcting the first frequency deviation, detecting the second frequency deviation using a pilot carrier included in the subframe, and correcting the second frequency deviation in the reception signal. I assume.

  In the wireless communication apparatus according to claim 6, in the wireless communication apparatus according to claim 5, the transmitting unit transmits a subframe not including the preamble as the third and subsequent subframes, and Transmitting the sub-frame including the preamble at a period of 1, the receiving unit receives a sub-frame not including the preamble as the third and subsequent sub-frames from the other wireless communication apparatus, and Receiving a subframe including the preamble in a cycle of

  Further, in the wireless communication method according to a seventh aspect of the present invention, in the wireless communication method of transmitting and receiving subframes in a time division duplex system and detecting and correcting a frequency deviation of a reception signal of the subframe Receiving a sub-frame including a preamble for decoding, quadrature-modulating a received signal of the sub-frame including the preamble, and detecting a first frequency deviation using the preamble included in the received signal; Generating a first sine wave digital signal having a correction value obtained by subtracting the first frequency deviation from a predetermined frequency and using the correction value as an oscillation frequency; and based on the first sine wave digital signal. Orthogonally demodulate a received signal of a subframe including the preamble, and fast Fourier transform the orthogonally demodulated signal to obtain a frequency domain Generating a signal, extracting a pilot carrier from the signal in the frequency domain, and detecting a 2-1st frequency deviation using the pilot carrier, and detecting the first frequency deviation from the predetermined frequency and the first frequency deviation. Generating a second sine wave digital signal using the correction value as a correction value and subtracting the sum of the frequency deviation of 2-1 and the sub-frame not including the preamble Step: orthogonally demodulate the received signal of the sub-frame not including the preamble based on the second sine wave digital signal, and fast Fourier transform the orthogonally demodulated signal to generate a signal in the frequency domain, A step of extracting a pilot carrier from a signal in the frequency domain and detecting a second frequency deviation using the pilot carrier And a third sine wave digital signal having a correction value obtained by subtracting an addition value of the first frequency deviation and the second frequency deviation from a predetermined frequency as a correction value, and using the correction value as an oscillation frequency. Generating a sine wave digital signal for orthogonally demodulating a received signal upon further receiving the subframe not including the preamble, and further receiving the subframe including the preamble Before or after transmitting the subframe including the preamble, and before or after receiving the subframe not including the preamble, including transmitting the subframe not including the preamble. It features.

  Furthermore, the wireless communication system according to claim 8 comprises a wireless communication system configured to transmit and receive subframes in a time division duplex system, and detect and correct a frequency deviation of received signals of the subframes. In the communication system, each of the pair of wireless communication devices is the wireless communication device according to claim 1.

  Furthermore, the chip according to claim 9 is a chip mounted on a wireless communication apparatus that transmits and receives subframes in a time division duplex system and detects and corrects frequency deviation of reception signals of the subframes. A first digital signal processing unit that generates a subframe including a preamble for causing a wireless communication device to detect a frequency deviation, and generates a subframe not including the preamble as a subsequent subframe, and the other wireless communication The preamble included in the subframe received from the device is used to detect a first frequency deviation, and the first frequency deviation in the received signal of the subframe is corrected, and the sub received from the other wireless communication device The pilot carrier included in the frame is used to detect a second frequency deviation, and the received signal in the subframe is detected. And a second digital signal processing unit that corrects the second frequency deviation, wherein the second digital signal processing unit receives a sine wave digital signal of a predetermined oscillation frequency, and generates a sine wave digital signal. Based on the orthogonal demodulation unit that orthogonally demodulates the received signal of the sub-frame, the fast Fourier transform operation unit that performs fast Fourier transform on the signal orthogonally demodulated by the orthogonal demodulation unit, and generates the signal in the frequency domain; A first frequency deviation detection unit for detecting the first frequency deviation using a preamble included in a sub-frame orthogonally demodulated by the demodulation unit, and a result obtained by subtracting a predetermined frequency from a predetermined frequency is used as a correction value. An oscillator for generating and outputting the sine wave digital signal having the correction value as the predetermined oscillation frequency, and a circumference generated by the fast Fourier transform operation unit A pilot carrier extraction unit that extracts a pilot carrier from a signal of several regions; and a second frequency deviation detection unit that detects the second frequency deviation using the pilot carrier extracted by the pilot carrier extraction unit. The first frequency deviation detecting unit detects the oscillator from the predetermined frequency when the wireless communication apparatus receives a subframe including the preamble from the other wireless communication apparatus. The result of subtracting the frequency deviation is used as a correction value, and the sine wave digital signal having the correction value as the predetermined oscillation frequency is generated and output, and the quadrature demodulation unit receives the sine wave digital signal from the oscillator. Receiving the subframe by orthogonally demodulating the received signal of the subframe based on the sine wave digital signal The oscillator corrects the first frequency deviation from the predetermined frequency after correcting the first frequency deviation in the signal and after the wireless communication apparatus receives a subframe including the preamble from the other wireless communication apparatus. The result of subtracting the addition value of the first frequency deviation detected by the detection unit and the second frequency deviation detected by the second frequency deviation detection unit is a correction value, and the correction value is the predetermined oscillation. The sine wave digital signal in frequency is generated and output, and the quadrature demodulation unit inputs the sine wave digital signal from the oscillator, and the reception signal of the sub frame is orthogonalized based on the sine wave digital signal. Demodulation is performed to correct the second frequency deviation in the reception signal of the sub-frame in which the first frequency deviation is corrected.

  As described above, according to the present invention, when transmitting and receiving subframes, it is not necessary to always transmit and receive subframes including a preamble, so a time division duplex system with good transmission efficiency can be realized. It becomes possible.

FIG. 1 is a schematic view showing an overall configuration of a wireless communication system including a wireless communication device according to an embodiment of the present invention. (1) is a figure which shows the structure of a TDD sub-frame (with a preamble). (2) is a figure which shows the structure of a TDD sub-frame (without a preamble). It is a figure which shows the waveform of a preamble. It is a block diagram which shows the structure of the radio | wireless communication apparatus by embodiment of this invention. It is a figure which shows the cross correlation value calculated by the movement correlation part. It is a figure which shows arrangement | positioning of a pilot carrier. It is a figure explaining the process of a 2nd frequency deviation detection part. It is a figure which shows a phase angle (phase rotation amount) on calculation in a process of a 2nd frequency deviation detection part. It is a figure which shows an actual phase angle (phase rotation amount) in the process of a 2nd frequency deviation detection part. It is a figure which shows the whole flow of the procedure which correct | amends a frequency deviation. It is a flowchart which shows the process of a preamble addition part. It is a flowchart which shows the procedure which correct | amends a frequency deviation. It is a flowchart which shows the procedure which correct | amends a frequency deviation (continuation of FIG. 12). It is a flowchart which shows the procedure which correct | amends a frequency deviation (continuation of FIG. 13).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention relates to a radio communication apparatus that transmits and receives subframes in a time division duplex system, transmits a subframe including a preamble, and then transmits a subframe not including the preamble, and a sub that includes the preamble. A frame is received, a frequency deviation is detected using a preamble included in the subframe, and it is corrected, and then a subframe not including the preamble is received, and a frequency deviation using a pilot carrier included in the subframe And a receiver for detecting and correcting the same.

  As a result, since it is not necessary to always transmit and receive subframes including a preamble, it is possible to reduce the number of preamble communications in the entire communication, and it is possible to realize a time division duplex system with good transmission efficiency.

[Wireless transmission system]
First, a wireless transmission system will be described. FIG. 1 is a schematic view showing an overall configuration of a wireless transmission system including a wireless communication device according to an embodiment of the present invention. The wireless transmission system includes a pair of wireless communication devices 1-1 and 1-2 that transmit and receive subframes in a time division duplex system. The signals transmitted by the wireless communication devices 1-1 and 1-2 are OFDM signals, and this wireless transmission system is specifically assumed to be the system described in the non-patent documents 1 and 2 described above. There is.

  The wireless communication devices 1-1 and 1-2 mutually transmit and receive TDD subframes. Within a predetermined frame period, a period of a subframe in which a TDD subframe is transmitted from the wireless communication device 1-1 to the wireless communication device 1-2, and from the wireless communication device 1-2 to the wireless communication device 1-1 The period of subframes in which TDD subframes are transmitted is preset. A subframe period in which a TDD subframe is transmitted from the wireless communication device 1-1 to the wireless communication device 1-2, and a subframe in which a TDD subframe is transmitted from the wireless communication device 1-2 to the wireless communication device 1-1 The term may be the same or different. The wireless communication device 1-1 transmits the TDD subframe to the wireless communication device 1-2 within the former subframe period, and the wireless communication device 1-2 transmits the TDD sub frame within the latter subframe period. The frame is transmitted to the wireless communication device 1-1.

  The wireless communication device 1-1 stores the transmission signal (data to be transmitted) in a TDD subframe, and transmits the TDD subframe to the wireless communication device 1-2, and the wireless communication device 1-2 transmits the TDD subframe. And a receiver for receiving the TDD subframes and extracting a reception signal from the TDD subframes. The wireless communication device 1-2 stores a transmission signal in a TDD subframe, and transmits a TDD subframe to the wireless communication device 1-1, and receives the TDD subframe transmitted by the wireless communication device 1-1. And a receiver for extracting a received signal from the TDD subframe.

  TDD subframes including a preamble under the time division duplex system in which the wireless communication devices 1-1 and 1-2 mutually switch between transmission and reception for each period of subframes on the time axis to perform bidirectional communication. To the other and receive TDD subframes containing the preamble from the other. Also, the wireless communication devices 1-1 and 1-2 transmit TDD subframes not including the preamble to the other, and receive TDD subframes not including the preamble from the other.

  FIG. 2A is a diagram showing the configuration of a TDD subframe (with a preamble). FIG. 2 (2) is a diagram showing the configuration of a TDD subframe (without a preamble). As shown in FIG. 2 (1), a TDD subframe including a preamble is composed of a preamble, a header portion and a payload portion, the preamble is disposed at the head, and then the header portion and the payload portion are respectively disposed. As shown in FIG. 2 (2), a TDD subframe not including a preamble is composed of a header part and a payload part. The subframe lengths of these TDD subframes are the same.

  The wireless communication device 1-1 generates a TDD subframe including the preamble of FIG. 2 (1) and transmits it to the wireless communication device 1-2, and transmits a TDD subframe including the preamble of the same configuration to the wireless communication device 1-2. Receive from Similarly, the wireless communication device 1-2 generates a TDD subframe including the preamble of FIG. 2 (1), transmits it to the wireless communication device 1-1, and transmits a TDD subframe including the preamble of the same configuration to the wireless communication device Receive from 1-1.

  Further, the wireless communication device 1-1 generates a TDD subframe not including the preamble of FIG. 2 (2) and transmits it to the wireless communication device 1-2, and wirelessly communicates the TDD subframe not including the preamble of the same configuration. It receives from the device 1-2. Similarly, the wireless communication device 1-2 generates a TDD subframe not including the preamble of FIG. 2 (2) and transmits it to the wireless communication device 1-1, and wirelessly transmits the TDD subframe not including the preamble of the same configuration. It receives from the communication apparatus 1-2.

  FIG. 3 is a diagram showing the waveform of the preamble shown in FIG. 2 (1). The horizontal axis shows time, and the vertical axis shows the amplitude of the signal of the preamble. As shown in FIG. 3, the preamble is a signal in which the same waveform is repeated eight times and is configured by eight identical waveforms.

[Wireless communication device]
Next, the wireless communication devices 1-1, 1-2 (collectively referred to as the wireless communication device 1) of the wireless transmission system shown in FIG. 1 will be described in detail. FIG. 4 is a block diagram showing the configuration of the wireless communication device 1 according to the embodiment of the present invention. The wireless communication device 1 includes an antenna 10, a switch 11, a transmitter 2, and a receiver 3.

  The transmitting unit 2 includes an inverse fast Fourier transform (IFFT) calculating unit 12, a GI adding unit 13, a preamble adding unit 14, an upsampling unit (US) 15, a low pass filter unit (LPF) 16, and a numerically controlled oscillator (NCO And 17, a quadrature modulation unit (QM) 18, a D / A conversion unit 19, and a frequency conversion unit (U / C) 20.

  The receiver 3 includes a frequency converter (D / C) 21, an A / D converter 22, an orthogonal demodulator (QDM) 23, a low pass filter (LPF) 24, a downsampling unit (DS) 25, and a preamble storage. Unit 26, movement correlation unit 27, correlation peak detection unit 28, frame synchronization detection unit 29, trigger signal generation unit 30, first frequency deviation detection unit 31, frequency deviation storage unit 32, addition unit 33, numerical control type oscillator ( NCO 34, symbol synchronization detection unit 35, FFT window timing unit 36, fast Fourier transform (FFT) operation unit 37, pilot carrier extraction unit 38, second frequency deviation detection unit 39, and reset signal generation unit 40 .

  .., NCO 17 and QM 18 in the transmission unit 2, and QDM 23, LPF 24,..., Second frequency deviation detection unit 39 and reset signal generation unit 40 in the reception unit 3. Thus, a digital signal processing unit that processes digital signals is configured.

  The switch 11 receives the switching signal from the frame synchronization detection unit 29 and switches the internal switch to the transmitting unit 2 side or the receiving unit 3 side based on the switching signal. Specifically, when the switching signal indicates a period during which the switching signal transmits a TDD subframe, the switch 11 connects the antenna 10 and the transmitting unit 2, inputs a transmission signal of the TDD subframe from the transmitting unit 2, and transmits the antenna 10. Send through. On the other hand, when the switching signal indicates a period in which the switching signal receives a TDD subframe, the switch 11 connects the antenna 10 and the receiving unit 3, inputs the received signal of the TDD subframe via the antenna 10, and Output.

(Transmission unit 2)
Next, the transmitter 2 shown in FIG. 4 will be described in detail. When the switch 11 receives a switching signal indicating a period for transmitting a TDD subframe from the frame synchronization detection unit 29, the antenna 10 and the transmission unit 2 are connected. During a period in which a TDD subframe is transmitted, the antenna 10 and the transmitter 2 are connected via the switch 11.

  The IFFT operation unit 12 receives the modulated modulation signal (transmission signal) after mapping from a component (not shown), performs IFFT (Inverse Fast Fourier Transform) on the modulation signal in the frequency domain, and modulates the modulation signal in the time domain. Generate Then, the IFFT operation unit 12 outputs the modulation signal in the time domain to the GI addition unit 13.

  The GI addition unit 13 receives the modulation signal in the time domain from the IFFT operation unit 12, adds the GI to the modulation signal in the time domain, and outputs the modulation signal to which the GI is added to the preamble addition unit 14.

  The preamble adding unit 14 receives the modulated signal to which GI is added from the GI adding unit 13, adds a preamble to the modulated signal according to a predetermined rule, and generates a TDD subframe including the preamble, or a modulated signal And TDD subframes not including the preamble are generated.

  As a predetermined rule, for example, a TDD subframe (a TDD subframe including a preamble) added with a preamble is generated for the first and second TDD subframes to be transmitted at the start of communication, and the third at the start of communication For TDD subframes to be transmitted later, a rule is used to generate TDD subframes not including a preamble (TDD subframes not including a preamble).

  FIG. 11 is a flowchart showing the process of the preamble adder 14. The preamble addition unit 14 determines whether or not it is the first or second TDD subframe to be transmitted at the start of communication according to the above-mentioned rule (step S1101). When the preamble adding unit 14 determines that the TDD subframe to be transmitted first or second at the start of communication is determined to be the first or second TDD subframe at the start of communication (step S1101: Y), the preamble is added to the modulated signal and TDD including the preamble A subframe is generated (step S1102).

  On the other hand, if the preamble adding unit 14 determines in step S1101 that it is not the first or second TDD subframe to be transmitted at the start of communication (step S1101: N), ie, after the third at the start of communication. If it is determined that this is a TDD subframe to be transmitted, a TDD subframe not including a preamble is generated without adding a preamble to the modulated signal (step S1103). Then, the preamble adding unit 14 outputs a transmission signal of a TDD subframe (a TDD subframe including a preamble or a TDD subframe not including a preamble) to the US 15.

  In US15, the transmission signal of the TDD subframe is input from the preamble adding unit 14, the transmission signal is subjected to an upsampling process, and the transmission signal after the upsampling is output to the LPF 16.

The LPF 16 receives the up-sampled transmission signal from US 15 and filters the transmission signal so that components higher than a predetermined frequency are stepped down and allows components below a predetermined frequency to pass. Output to The NCO 17 is a local oscillator, and outputs a sine wave digital signal having an oscillation frequency of a predetermined value f _c to the QM 18.

  The QM 18 receives the filtered transmission signal from the LPF 16 and receives a sine wave digital signal from the NCO 17, performs digital quadrature modulation on the transmission signal based on the sine wave digital signal, and transmits the digital quadrature modulation signal. Are output to the D / A converter 19.

  The D / A conversion unit 19 receives the digital transmission signal after digital quadrature modulation from the QM 18, converts the digital signal into an analog signal, and outputs an analog transmission signal to the U / C 20.

  The U / C 20 receives an analog transmission signal from the D / A converter 19 and converts the frequency of the transmission signal from an intermediate frequency band to a radio frequency band. Then, the transmission signal converted into the radio frequency band is transmitted from the antenna 10 via the switch 11.

  Thus, the TDD subframe including the preamble is transmitted as the first and second TDD subframes at the start of communication from the transmitter 2 of the wireless communication device 1, and the preambles are transmitted as the third and subsequent TDD subframes. TDD subframes not including T are transmitted.

(Receiver 3)
Next, the receiver 3 shown in FIG. 4 will be described in detail. When the switch 11 receives a switching signal indicating a period for receiving a TDD subframe from the frame synchronization detection unit 29, the antenna 10 and the reception unit 3 are connected. During a period in which a TDD subframe is received, the antenna 10 and the receiver 3 are connected via the switch 11.

  The D / C 21 receives the received signal of the TDD subframe received by the antenna 10 via the switch 11, and converts the frequency of the received signal of the TDD subframe from the radio frequency band to the intermediate frequency band. Then, the D / C 21 outputs the reception signal converted into the intermediate frequency band to the A / D conversion unit 22.

  The A / D converter 22 receives an analog reception signal of an intermediate frequency band from the D / C 21, converts the analog signal into a digital signal, and outputs a digital reception signal to the QDM 23.

The QDM 23 receives a digital received signal from the A / D converter 22 and also receives from the _NCO 34 a sine wave digital signal whose oscillation frequency is a predetermined value f _NCO , and based on the sine wave digital signal, the received signal Digital quadrature demodulation, and outputs the received signal after digital quadrature demodulation to the LPF 24.

  The LPF 24 receives the received signal after digital quadrature demodulation from the QDM 23, performs a filtering process on the received signal so as to reduce components higher than a predetermined frequency, and passes components of a predetermined frequency or less, and outputs the filtered received signal Output to DS25.

  The DS 25 receives the filter-processed received signal from the LPF 24, down-samples the received signal, and performs down-sampling on the received signal as a moving correlation unit 27, a frame synchronization detection unit 29, a symbol synchronization detection unit 35, and an FFT operation Output to section 37.

  The preamble storage unit 26 stores a digital signal (a basic signal of the preamble) corresponding to the waveform of the repetition unit among the waveforms of the preamble shown in FIG. The basic signal of this preamble is 1/8 of the signal of the preamble composed of eight identical waveforms repeated the same waveform eight times, and is a signal of a repeating unit.

  The moving correlation unit 27 receives the down-sampled received signal from the DS 25, reads the basic signal of the preamble from the preamble storage unit 26, performs moving correlation calculation between the received signal and the basic signal of the preamble, and performs cross correlation Calculate the value. In the time axis of the received signal, when the cross correlation is high between the received signal and the basic signal of the preamble, ie, at the time point of the preamble in the received signal, the cross correlation value becomes a large value. The movement correlation unit 27 outputs the cross correlation value on the time axis of the received signal to the correlation peak detection unit 28.

  The correlation peak detection unit 28 receives the cross correlation value on the time axis of the received signal from the moving correlation unit 27 and detects the correlation peak position (the timing of the correlation peak) on the time axis at which the cross correlation value peaks. The cross correlation value of the correlation peak position is detected as a correlation peak value. The correlation peak position indicates a time position at which the cross correlation value peaks within a predetermined time range on the time axis of the received signal. The correlation peak detection unit 28 outputs the correlation peak position to the frame synchronization detection unit 29 and outputs the correlation peak value to the first frequency deviation detection unit 31.

  FIG. 5 is a diagram showing the cross correlation value calculated by the moving correlation unit 27. As shown in FIG. The horizontal axis shows time, and the vertical axis shows cross correlation value. The preamble is composed of eight identical waveforms, in which the same waveform is repeated eight times in one TDD subframe, as described in FIG. Therefore, eight correlation peaks in the cross correlation value between the received signal and the base signal of the preamble will be detected in the time range of the preamble in the TDD subframe. In FIG. 5, it can be seen that eight correlation peak positions are detected. In the example of FIG. 5, the correlation peak detection unit 28 outputs eight correlation peak positions (time positions of correlation peaks) to the frame synchronization detection unit 29, and eight correlation peak values (each correlation peak on the time axis) Value) is output to the first frequency deviation detection unit 31.

  Referring back to FIG. 4, the frame synchronization detection unit 29 receives the downsampled received signal from the DS 25 and also receives the correlation peak position from the correlation peak detection unit 28. The frame synchronization detection unit 29 detects, based on the correlation peak position, the timing at which FFT processing is started from the beginning of the header portion, that is, the timing of frame synchronization of the received signal. When the wireless communication device 1 receives a TDD subframe including a preamble, the correlation peak position is detected by the correlation peak detector 28. Thus, the timing of frame synchronization with respect to the TDD subframe including the preamble is detected.

  On the other hand, when the wireless communication device 1 receives a TDD subframe not including a preamble, that is, the frame synchronization detection unit 29 receives the downsampled received signal from the DS 25, but the correlation peak position from the correlation peak detection unit 28 If the timing of frame synchronization to be detected is the same as the timing of frame synchronization detected (based on the correlation peak position) when receiving a TDD subframe including a preamble, the timing of frame synchronization is Estimate (detect). Specifically, the frame synchronization detection unit 29 causes the wireless communication device 1 to receive the TDD subframe including the preamble twice in a row, and based on the respective correlation peaks, to perform two frame synchronization timings. To detect. Then, the frame synchronization detection unit 29 estimates the timing of frame synchronization when the wireless communication device 1 receives a TDD subframe not including a preamble at the same time interval as the time interval of two frame synchronization timings. .

  When the wireless communication device 1 receives a TDD subframe that does not include a preamble, the symbol synchronization detection unit 35 described later may estimate the frame synchronization timing.

  The frame synchronization detection unit 29 generates a frame synchronization timing signal indicating the timing of frame synchronization of the received signal, and generates a frame synchronization timing signal as a trigger signal generation unit 30, symbol synchronization detection unit 35, FFT window timing unit 36, and reset signal generation. Output to section 40.

  Further, based on the detected frame synchronization timing, the frame synchronization detection unit 29 determines the subframe period in which the wireless communication device 1 transmits a TDD subframe and the subframe period in which the TDD subframe is received, The timing of switching of these periods is determined. For example, the frame synchronization detection unit 29 determines that a period from a predetermined time before to a predetermined time after the detected frame synchronization timing is a subframe period in which a TDD subframe is received, and the other period is It is determined that it is a period of subframes transmitting TDD subframes.

  The frame synchronization detection unit 29 is a switching signal for switching transmission / reception of TDD subframes (a switching signal indicating a period of subframes transmitting TDD subframes, or a switching signal indicating a period of subframes receiving TDD subframes) Are generated, and a switching signal is output to the switch 11 at that timing.

  The trigger signal generation unit 30 receives the frame synchronization timing signal from the frame synchronization detection unit 29, and when the input frame synchronization timing signal is a frame synchronization timing signal corresponding to the first TDD subframe at the start of communication, the trigger signal Are generated and output to the frequency deviation storage unit 32. When the input frame synchronization timing signal is a frame synchronization timing signal corresponding to the second TDD subframe at the start of communication, the trigger signal generation unit 30 removes the frame synchronization timing signal and does not output the trigger signal. .

  Specifically, the trigger signal generation unit 30 counts an elapsed time from the frame synchronization timing signal input last time to the frame synchronization timing signal input this time, and compares the elapsed time with a predetermined time, and the elapsed time If T exceeds the predetermined time, the trigger signal is output, assuming that the input frame synchronization timing signal is a frame synchronization timing signal corresponding to the first TDD subframe at the start of communication. If the elapsed time does not exceed the predetermined time, the trigger signal generation unit 30 determines that the input frame synchronization timing signal is a frame synchronization timing signal corresponding to the second and subsequent TDD subframes at the start of communication. Do not output a signal. Here, the predetermined time is a time from the first reception of a TDD subframe including a preamble at the start of communication to the second reception of a TDD subframe including a preamble.

Thus, the trigger signal is output to the frequency deviation storage unit 32 at the timing when the frame synchronization is first established. The trigger signal generation unit 30 generates a trigger signal in the frequency deviation storage unit 32 at a timing later than the timing at which the first frequency deviation detection unit 31 outputs the first frequency deviation Δf ₁ to the frequency deviation storage unit 32. Output.

  The symbol synchronization detection unit 35 receives the down-sampled received signal from the DS 25 and also receives a frame synchronization timing signal from the frame synchronization detection unit 29, obtains GI correlation from the received signal, and generates a frame synchronization timing signal and GI correlation. Based on the timing of symbol synchronization of the received signal is detected. Then, the symbol synchronization detection unit 35 generates a symbol synchronization timing signal indicating the timing of symbol synchronization of the received signal, and outputs the symbol synchronization timing signal to the FFT window timing unit 36 and the reset signal generation unit 40.

  The FFT window timing unit 36 receives the frame synchronization timing signal from the frame synchronization detection unit 29 and also receives the symbol synchronization timing signal detected by the symbol synchronization detection unit 35 based on the frame synchronization timing signal and the GI correlation. Then, the FFT window timing unit 36 corrects the frame synchronization timing signal using the symbol synchronization timing signal, and uses the corrected frame synchronization timing signal to start FFT processing from the beginning of the header portion of the received signal. To detect Then, the FFT window timing unit 36 generates an FFT window timing signal reflecting the timing, and outputs the signal to the FFT operation unit 37. As a result, the frame synchronization timing signal is corrected using the symbol synchronization timing signal to be an accurate timing signal, and as a result, an accurate timing FFT window timing signal can be generated.

  The FFT operation unit 37 receives the downsampled received signal from the DS 25 and receives the FFT window timing signal from the FFT window timing unit 36, and at the timing when the FFT window timing signal is input, the received signal in the time domain. FFT (Fast Fourier Transform) is performed to generate a reception signal in the frequency domain. Then, the FFT operation unit 37 outputs the received signal in the frequency domain to the pilot carrier extraction unit 38 and a configuration unit (not shown) that performs demodulation processing of the header portion and the payload portion of the TDD subframe.

Here, when the QDM 23 performs digital quadrature demodulation on the received signal based on a sine wave digital signal whose oscillation frequency is a predetermined value f _NCO (= f _c −Δf ₁ ), the FFT operation unit 37 generates a frequency error Δf. Input the down-sampled received signal whose ₁ is corrected. When the QDM 23 performs digital quadrature demodulation on the received signal based on a sine wave digital signal whose oscillation frequency is a predetermined value f _NCO (= f _c −Δf ₁ −Δf ₂ ), the FFT operation unit 37 The down-sampled received signal with the error (Δf ₁ + Δf ₂ ) corrected is input.

  The reset signal generation unit 40 receives the frame synchronization timing signal from the frame synchronization detection unit 29 and also receives the symbol synchronization timing signal from the symbol synchronization detection unit 35. Further, the reset signal generation unit 40 is a C / N ratio (Carrier to Noise Ratio) calculation unit (not shown) (provided at a stage subsequent to the FFT operation unit 37, which calculates the C / N ratio based on the reception signal in the frequency domain. Input the C / N ratio from

  The reset signal generation unit 40 determines whether or not the input cycle of the frame synchronization timing signal is a predetermined cycle, and determines whether or not the input cycle of the symbol synchronization timing signal is a predetermined cycle. It is determined whether the N ratio is equal to or greater than a predetermined threshold value.

  The reset signal generation unit 40 determines that the input cycle of the frame synchronization timing signal is a predetermined cycle, determines that the input cycle of the symbol synchronization timing signal is a predetermined cycle, and the C / N ratio is a predetermined threshold. If it is determined that the value is equal to or more than the value, it is determined that the communication is normal.

  On the other hand, when the reset signal generation unit 40 determines that the input period of the frame synchronization timing signal is not a predetermined period, determines that the input period of the symbol synchronization timing signal is not a predetermined period, or the C / N ratio is predetermined. If it is determined that it is not above the threshold value (less than the predetermined threshold value), it is determined that the communication is abnormal (the communication is interrupted), and the reset signal is detected as the frequency deviation storage unit 32 and the second frequency deviation detection. Output to section 39.

  When the input cycle of the frame synchronization timing signal is not a predetermined cycle, it indicates that frame synchronization is not established, and when the input cycle of the symbol synchronization timing signal is not a predetermined cycle, it indicates that symbol synchronization is not established. In any case, it is determined that the communication is abnormal.

As a result, the reset signal is output to the frequency deviation storage unit 32, the frequency deviation Δf ₁ held in the frequency deviation storage unit 32 is reset, and a null signal is output from the frequency deviation storage unit 32 to the addition unit 33. Further, a reset signal is output to the second frequency deviation detecting unit 39, a second frequency deviation Delta] f ₂ is reset, the null signal is output to the adder 33 in which the second frequency deviation detecting unit 39 outputs .

The first frequency deviation detection unit 31 receives the correlation peak value from the correlation peak detection unit 28, calculates the phase rotation amount between the correlation peak positions based on the correlation peak value, and calculates the frequency deviation Δf ₁ from the phase rotation amount. To detect Then, the first frequency deviation detection unit 31 outputs the frequency deviation Δf ₁ to the frequency deviation storage unit 32.

In the example of FIG. 5, the first frequency deviation detection unit 31 receives eight correlation peak values from the correlation peak detection unit 28, and calculates the difference of the phase angle of each correlation peak value. For example, eight correlation peak values are respectively set as a first correlation peak value, a second correlation peak value,..., And an eighth correlation peak value. When the correlation peak detection unit 28 calculates the difference of the phase angle of each correlation peak value, the difference between the phase angle of the first correlation peak value and the phase angle of the second correlation peak value, The difference between the phase angle of the correlation peak value and the phase angle of the third correlation peak value,..., The difference between the phase angle of the first correlation peak value and the phase angle of the eighth correlation peak value Etc. are calculated respectively. Then, the first frequency deviation detection unit 31 calculates the phase rotation amount between the correlation peak positions from the difference of the phase angle, and converts the phase rotation amount into the frequency deviation Δf ₁ by a predetermined conversion formula. In addition, since the conversion equation for converting the phase rotation amount into the frequency deviation Δf ₁ is known, the detailed description is omitted here.

The frequency deviation storage unit 32 receives the frequency deviation Δf ₁ from the first frequency deviation detection unit 31, and receives the trigger signal from the trigger signal generation unit 30. The frequency deviation storage unit 32 also receives a reset signal from the reset signal generation unit 40.

When the trigger signal is input (when the trigger signal is ON), the frequency deviation storage unit 32 stores and holds the input frequency deviation Δf ₁ . The trigger signal is input from the trigger signal generation unit 30 when frame synchronization is established in the first TDD subframe at the start of communication, and when frame synchronization is established in the second TDD subframe at the start of communication. It is not input. It is not input even when frame synchronization is estimated in the third and subsequent TDD subframes at the start of communication. The frequency deviation Δf ₁ is detected in the first TDD subframe at the start of communication, and is already input from the first frequency deviation detection unit 31 when the trigger signal is input. Then, the frequency deviation storage unit 32 outputs the held frequency deviation Δf ₁ to the addition unit 33.

As a result, only the frequency deviation Δf ₁ detected in the first TDD subframe at the start of communication is held in the frequency deviation storage unit 32 and output to the addition unit 33. The frequency deviation Δf ₁ detected in the second and subsequent TDD subframes is not held in the frequency deviation storage unit 32. The addition unit 33 described later outputs the frequency deviation Δf ₁ to the NCO 34, and the _NCO 34 described later outputs a sine wave digital signal having the correction value (f _NCO = f _c −Δf ₁ ) as the oscillation frequency to the QDM 23.

When the frequency deviation storage unit 32 receives the reset signal, the frequency deviation storage unit 32 deletes the stored and held frequency deviation Δf ₁ . Then, the frequency deviation storage unit 32 outputs a null signal to the addition unit 33.

As a result, when frame synchronization can not be established, when symbol synchronization can not be established, or when the C / N ratio is smaller than a predetermined threshold value, it is determined that communication is interrupted, and frequency deviation storage unit 32 be deleted frequency deviation Delta] f ₁ which is held (is reset). Then, the frequency deviation storage unit 32 holds a new frequency deviation Δf ₁ detected in the first TDD subframe when the communication becomes normal and resumes (at the start of communication).

When a reset signal is output from the reset signal generation unit 40, a null signal is output to the addition unit 33 also from the second frequency deviation detection unit 39 described later. Therefore, the addition unit 33 described later outputs a null signal to the NCO 34 described later, and the NCO 34 outputs a sine wave digital signal having the predetermined value f _c as the oscillation frequency to the QDM 23 described later, and the QDM 23 has the predetermined value f. _The received signal is digital quadrature demodulated based on a sine wave digital signal whose oscillation frequency is _c .

Thus, the frequency deviation Delta] f ₁ is detected by using the first TDD subframe at the start of communication, in QDM23, frequency deviation Delta] f ₁ of the received signal is corrected. The correction of the frequency deviation Δf ₁ is performed from the beginning of the header following the preamble included in the first TDD subframe at the start of communication, and the header part and the payload part after the correction of the frequency deviation Δf ₁ are the LPF 24 and DS 25. The signal is input to the FFT operation unit 37 via

The accuracy of the frequency deviation Δf ₁ depends on the length of the preamble included in the TDD subframe. When the preamble is long, although the frequency deviation Δf ₁ with high accuracy is detected as compared with the case where the preamble is short, the transmission efficiency is lowered. On the other hand, when the length of the preamble is set to the minimum length necessary for detection of frame synchronization and the like in order to avoid a decrease in transmission efficiency, it is possible to detect the frequency deviation Δf ₁ with sufficient accuracy. Can not. For this reason, only by correcting the frequency deviation Δf ₁ with respect to the reception signal, the frequency deviation remains and further correction is required.

Therefore, in the second frequency deviation detection unit 39, the remaining frequency error is detected as frequency deviation Δf ₂ using the pilot carrier extracted by the pilot carrier extraction unit 38, and the addition unit 33 described later is a frequency deviation The (Δf ₁ + Δf ₂ ) is output to the _NCO 34, and the _NCO 34 described later outputs to the QDM 23 a sine wave digital signal whose oscillation frequency is the correction value (f _NCO = f _c −Δf ₁ −Δf ₂ ).

Thus, the frequency deviation Δf ₂ is detected using the first TDD subframe at the start of communication, and the frequency deviation (Δf ₁ + Δf ₂ ) of the received signal is corrected in the QDM 23. Correction of the frequency deviation (Δf ₁ + Δf ₂₎ is performed from the second TDD subframe at the start of communication, the header portion and a payload portion that frequency deviation (Δf ₁ + Δf ₂₎ is corrected, the LPF24 and DS25 The signal is input to the FFT operation unit 37 via This process is also performed for the third and subsequent TDD subframes, and the residual frequency error gradually decreases, and the accuracy of the frequency deviation (Δf ₁ + Δf ₂ ) gradually increases.

  The pilot carrier extraction unit 38 receives the reception signal in the frequency domain from the FFT operation unit 37, extracts a pilot carrier at a predetermined position from the carrier of the reception signal, and outputs the pilot carrier to the second frequency deviation detection unit 39.

The second frequency deviation detection unit 39 receives the pilot carrier from the pilot carrier extraction unit 38 and receives the reset signal from the reset signal generation unit 40. When the pilot carrier is input, the second frequency deviation detection unit 39 calculates a complex division value of a predetermined symbol interval based on the pilot carrier, calculates the phase rotation amount from the complex division value, and calculates the frequency from the phase rotation amount The deviation Δf ⁱ ₂ is detected. i represents the number of a TDD subframe. Then, the second frequency deviation detection unit 39 accumulates the frequency deviation Δf ⁱ ₂ detected for each subframe, and outputs the accumulated frequency deviation Δf ₂ to the addition unit 33.

When the second frequency deviation detection unit 39 receives the reset signal, the second frequency deviation detection unit 39 deletes the frequency deviation Δf ₂ and outputs a null signal to the addition unit 33.

Adding unit 33 inputs the frequency deviation Delta] f ₁ from the frequency deviation memory 32, enter the frequency deviation Delta] f ₂ from the second frequency deviation detecting unit 39 adds a frequency deviation Delta] f ₁ and frequency deviation Delta] f _2, The addition result (Δf ₁ + Δf ₂ ) is output to the NCO 34.

The NCO 34 is a local oscillator, receives the addition result (Δf ₁ + Δf ₂ ) from the addition unit 33, and corrects it by subtracting the default value f _c with the addition result (Δf ₁ + Δf ₂ ) to obtain a correction value (f _NCO = a f _c -Δf ₁ -Δf ₂₎ generates a sine-wave digital signal and the oscillation frequency, and outputs a sine-wave digital signal to QM18.

Here, when frequency deviation Δf ₁ is detected using the first TDD subframe at the start of communication, addition unit 33 receives frequency deviation Δf ₁ from frequency deviation storage unit 32, and A null signal is input from the frequency deviation detection unit 39, and the addition result Δf ₁ is output to the NCO 34. Then, the _NCO 34 outputs a sine wave digital signal having the correction value (f _NCO = f _c −Δf ₁ ) as an oscillation frequency to the QDM 23. Thereby, in the QDM 23, the frequency deviation Δf ₁ of the received signal is corrected.

In addition, when frequency deviation Δf ₂ is detected using the first TDD subframe at the start of communication, addition unit 33 receives frequency deviation Δf ₁ from frequency deviation storage unit 32 and the second frequency. The frequency deviation Δf ₂ is input from the deviation detection unit 39, and the addition result (Δf ₁ + Δf ₂ ) is output to the NCO 34. Then, the _NCO 34 outputs a sine wave digital signal having the correction value (f _NCO = f _c −Δf ₁ −Δf ₂ ) as an oscillation frequency to the QDM 23. Thus, the frequency deviation (Δf ₁ + Δf ₂ ) of the received signal is corrected in the QDM 23. The same applies when the frequency deviation Δf ₂ is detected using the second and subsequent TDD subframes at the start of communication.

(Second frequency deviation detection unit 39)
Next, the second frequency deviation detection unit 39 shown in FIG. 4 will be described in detail. As described above, the second frequency deviation detection unit 39 calculates the complex division value of the predetermined symbol interval based on the pilot carrier, calculates the phase rotation amount from the complex division value, and calculates the frequency deviation Δf from the phase rotation amount. Detect ₂

FIG. 6 is a diagram showing the arrangement of pilot carriers. The horizontal axis shows subcarrier arrangement, and the vertical axis shows symbol arrangement. A black circle is a pilot carrier of the first transmission system in a 2-stream Multiple-Input Multiple-Output (MIMO) -OFDM transmission system, and a cross circle is a pilot carrier of the second transmission system. This is a pilot carrier arrangement of the bi-directional digital FPU system described in the non-patent document shown below.
"Mitsuyama, Serizawa, Izumi," Prototype and evaluation of interactive digital FPU experimental device based on time division duplex system ", EIT Bulletin, BCT 2013-101, pp. 25-28, Oct. 2013.

  In this bidirectional digital FPU system, a 2-stream MIMO-OFDM transmission system is assumed, and pilot carriers of each substream are distributed in the subcarrier direction and the symbol direction. Focusing on the same subcarrier, pilot carriers are inserted every four symbols. The wireless communication device 1 receives a signal including a pilot carrier of the arrangement shown in FIG.

The pilot carrier extraction unit 38 extracts a pilot carrier at a predetermined position from the carriers of the received signal shown in FIG. Here, in the kth pilot carrier of subcarrier arrangement, pilot carriers in the case where pilot carriers extracted every four symbols are arranged in symbol order are p ^k _n . p ^k _n denotes the k-th pilot carriers of the subcarrier arrangement, the complex amplitude value of the n-th pilot carrier from the first symbol.

FIG. 7 is a diagram for explaining the process of the second frequency deviation detection unit 39, in which pilot carriers extracted every four symbols are arranged in symbol order in the kth pilot carrier of subcarrier arrangement. . T _s is the symbol length. In the kth pilot carrier of subcarrier arrangement, pilot carriers p ^k ₁ , p ^k ₂ , p ^k ₃ , p ^k ₄ , p ^k ₅ ,..., P ^k _{i + 1} are arranged every four symbols. It is done.

The second frequency deviation detection unit 39 performs complex division between two pilot carriers separated by 4 × i symbols for the kth pilot carrier of subcarrier arrangement, and performs the jth complex division obtained in the symbol direction The value α ^k _{i, j} is calculated by the following equation.

When complex division is performed between two pilot carriers separated by 4 (4 × i = 4 × 1) symbols, the jth complex division value obtained in the symbol direction is α ^k _{1, j} . Further, when complex division is performed between two pilot carriers separated by 8 (4 × i = 4 × 2) symbols, the jth complex division value obtained in the symbol direction is α ^k _{2, j} . Similarly, when complex division is performed between two pilot carriers separated by 4 × i symbols, the first obtained complex division value in the symbol direction is α ^k _{i, 1} .

The second frequency deviation detection unit 39 sets K as the total number of pilot carriers in the subcarrier allocation (the total number of subcarrier positions where pilot carriers exist in subcarrier allocation) as the maximum value of the parameter j for the parameter _i as J _i The average value α _i of the complex division values α ^k _{i, j} for the parameter i (symbol interval 4 × i) is calculated by the following equation.

Mean value alpha _i of the complex division value alpha ^k _{i, j} in the formula (2), in FIG. 6, the two complex division value alpha ^k _{i, j} of the pilot carrier of 4 × i symbol intervals, subcarriers direction and It is a value obtained by averaging in the symbol direction.

Second frequency deviation detecting unit 39, the phase angle phi _i of the parameters i (symbol interval 4 × i), i.e. the phase angle phi _i of the average value alpha _i of the complex division value alpha ^k _{i, j,} the following equation Calculated by

The phase angle φ _i for the parameter i (symbol interval 4 × i) in the equation (3) corresponds to the amount of phase rotation of 4 × i symbol intervals caused by the remaining frequency deviation.

Thus, the second frequency deviation detecting unit 39, the phase angle (phase rotation amount) phi _i are calculated for each parameter i. The detection range of the frequency deviation is limited as the value of the parameter i is larger, but the remaining frequency deviation can be detected with high accuracy. However, if it is outside the actual detection range, that is, if the phase angle (phase rotation amount) φ _i exceeds ± π, false detection occurs.

8, in the process of the second frequency deviation detecting unit 39, the phase angle of the calculated illustrates a (phase rotation amount) phi _i. The horizontal axis represents the symbol interval i of the pilot carrier, which is a parameter i, the vertical axis represents the phase angle (phase rotation amount) phi _i. From FIG. 8, the values of the phase angles φ ₁ to φ ₃ calculated by the equation (3) take values on substantially the same straight line in the range of ± π or less, but the phase angles φ ₄ to φ ₆ the value is folded within the following range ± [pi, it can be seen that between the phase angle phi ₃ and the phase angle phi ₄ is discontinuous. The actual value of the phase angle phi ₄ to phi ₆ is beyond the scope of the following ± [pi.

For this reason, the second frequency deviation detection unit 39 does not monotonously increase or decrease from the values of the phase angles φ _{1 to} φ ₃ in the range of ± π or less as in the phase angles φ ₄ to φ _6. If, so that the phase angle phi ₄ to [phi] ₆ is closest to a straight line connecting the phase angle phi ₁ to [phi] _3, 2 [pi] n to a phase angle φ ₄ ~φ ₆ (n: an integer) the addition or subtraction of. That is, the second frequency deviation detecting unit 39, in the range of ± [pi, the phase angle phi _i parameter i that do not monotonically increase or decrease the value of such a phase angle phi _1, the value of such a phase angle phi ₁ A new phase angle φ _i is calculated by adding and subtracting 2πn (n: integer) to and from the phase angle φ _i calculated by the equation (2) so as to be closest to a monotonously increasing or decreasing straight line.

FIG. 9 is a diagram showing an actual phase angle (phase rotation amount) φ _i in the processing of the second frequency deviation detection unit 39, and this phase angle φ _i is finalized by the second frequency deviation detection unit 39. Is a value calculated in Similar to FIG. 8, the horizontal axis represents the symbol interval i of the pilot carrier, which is a parameter i, the vertical axis represents the phase angle (phase rotation amount) phi _i. As shown in FIG. 9, the second frequency deviation detecting unit 39, as the value of the phase angle phi ₄ to phi _6, according to the equation (2), calculates a value wrap range of ± [pi, the formula An actual value exceeding the range of ± π or less is calculated by adding 2πn (n: integer) to the calculation result of (2).

The second frequency deviation detection unit 39 calculates the phase angle φ calculated when parameter i = 1 (the symbol interval of pilot carriers is 4 × i = 4 × 1), where I is the maximum value of parameter i in one TDD subframe. By using ₁ , the frequency deviation Δf ₂ which is the remaining frequency deviation is calculated according to the following equation.

Although the second frequency deviation detection unit 39 calculates the frequency deviation Δf ₂ using only the phase angle φ _{1 according} to the equation (4), other parameters may be used instead of the phase angle φ _1. The phase angle φ _i when i = 2 or the like may be used. Specifically, the second frequency deviation detection unit 39 uses the phase angle φ _i calculated when the parameter i (the symbol interval of the pilot carrier is i) to calculate the frequency deviation Δf _{2, i} as the following equation Calculated by

Further, the second frequency deviation detection unit 39 calculates the frequency deviations Δf _{2 and 2 for} each parameter i according to the equation (5), averages these for the parameter i, and calculates the frequency deviation as the average value obtained by averaging. It may be calculated as Δf _{2, i} . Further, the second frequency deviation detection unit 39 calculates the frequency deviation Δf _{2, i} for each parameter i according to the equation (5), obtains the median of these, and calculates the median as the frequency deviation Δf _{2, i} You may do it.

Thus, the frequency deviation Δf ₂ calculated by the second frequency deviation detection unit 39 is output to the addition unit 33. Then, the addition result (Δf ₁ + Δf ₂ ) is output from the addition unit 33 to the _NCO 34, and the sine wave digital signal whose oscillation frequency is the correction value (f _NCO = f _c −Δf ₁ −Δf ₂ ) is output from the _NCO 34 to the QDM 23. The frequency deviation (Δf ₁ + Δf ₂ ) of the received signal is corrected in the QDM 23.

[Frequency deviation correction procedure]
Next, a procedure in which the wireless communication device 1 corrects the frequency deviation of the received signal will be described. As described above, for the reception signal of the first TDD subframe at the start of communication, the NCO 34 is updated using the frequency deviation Δf ₁ detected by the first frequency deviation detection unit 31 (Sine generated by NCO 34 Wave digital signal is updated) and the frequency deviation Δf ₁ of the received signal is corrected. This frequency deviation Δf ₁ is then treated as a fixed frequency deviation. For the reception signals of the second and subsequent TDD subframes at the start of communication, the frequency deviation Δf ₁ detected in the second and subsequent TDD subframes by the first frequency deviation detection unit 31 is not used and is fixed. in addition to the frequency deviation Delta] f ₁ (first frequency detected by the TDD subframe deviation Delta] f _1), by using the frequency deviation Delta] f ₂ detected by the second frequency deviation detecting unit 39, NCO34 is updated, The frequency deviation Δf ₂ of the received signal is further corrected. That is, the frequency deviation (Δf ₁ + Δf ₂ ) of the received signal is corrected.

  FIG. 10 is a diagram showing an overall flow of a procedure for correcting the frequency deviation. 12 to 14 are flowcharts showing the procedure of correcting the frequency deviation. In the following description, the wireless communication device 1 that transmits a TDD subframe first at the start of communication is taken as a master, and the wireless communication device 1 that receives the TDD subframe is taken as a slave. Also, the TDD subframes transmitted first by the master and the slave are referred to as initial frame No. 1, and the second TDD subframe to be transmitted is an initial frame No. Set to 2. These initial frame numbers. 1, No. 2 is a signal for connection setup for establishing communication between the master and the slave.

  Initial frame No. 1, No. A preamble is added to the beginning of 2 and its payload section is composed of dummy data other than actual transmission data, such as a pseudo random code. It is assumed that no preamble is added to the beginning of the third and subsequent TDD subframes, and that the payload portion is configured by actual transmission data.

  The second TDD subframe to be transmitted is an initial frame No. 1 which is a TDD subframe including a preamble. The purpose of 2 is to enable frame synchronization estimation for the third and subsequent TDD subframes that do not include a preamble. That is, initial frame No. 1, No. The frame synchronization of the third and subsequent TDD subframes is estimated using the timing of frame synchronization detected in 2 respectively. As shown in the lower part of FIG. 1, No. The frame synchronization positions in the third and subsequent TDD subframes are estimated at the same time intervals as those of the frame synchronization positions after the frame synchronization positions are respectively detected using the preambles included in No. 2 Be done.

  As described above, the FFT window timing unit 36 corrects the frame synchronization timing signal using the symbol synchronization timing signal, and uses the corrected frame synchronization timing signal to perform FFT processing from the beginning of the header portion of the received signal. To detect when to start. By correcting the frame synchronization timing using the symbol synchronization timing signal, a highly accurate frame synchronization position can be obtained, and an FFT window timing signal with accurate timing can be detected.

(Receive processing of initial frame No. 1 by slave)
At the start of communication, the master stores dummy data in the payload section, stores predetermined data in the header section, and generates a TDD subframe to which a preamble is added at the beginning. Send to slave as 1.

Referring to FIGS. 10 and 12, the slave transmits the initial frame No. 1 transmitted by the master. 1 is received (step S1001), and the initial frame No. 1 is received. Using one of the preamble, and detects a frequency deviation Delta] f ¹ ₁ at a first frequency deviation detecting unit 31 (step S1002). In the frequency deviation Delta] f ¹ _1, subscript above indicates the number of TDD subframes received, indicating that under the indices detected by the first frequency deviation detecting unit 31.

The slave updates the _NCO 34 with the frequency deviation Δf ₁ = Δf ¹ ₁ and the frequency deviation Δf ₂ = 0, and in the _NCO 34, a sine wave digital signal whose oscillation frequency is the correction value (f _NCO = f _c −Δf ¹ ₁ ) It generates (step S1003). Then, in the QDM 23, the slave receives the initial frame No. 1 based on the sine wave digital signal. 1 of a header portion and a payload portion, the updated correction value ^{_{(f NCO = f c -Δf 1}} 1) for digital quadrature demodulation. Thus, the initial frame No. 1 of the header portion and a payload portion, the frequency deviation Delta] f ¹ ₁ is corrected.

In the pilot carrier extraction unit 38, the slave receives the initial frame number no. Extracts pilot carriers included in the header portion and a payload portion of 1, the second frequency deviation detecting unit 39 detects the frequency deviation Delta] f ¹ ₂ remaining (step S1004).

The slave updates the _NCO 34 as the frequency deviation Δf ₁ = Δf ¹ ₁ and the frequency deviation Δf ₂ = Δf ¹ ₂ , and in the _NCO 34, makes the correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ ) the oscillation frequency Generate a sine wave digital signal. In this process, initial frame number. It is performed at the end timing of 1. Then, the slave receives the next TDD subframe so that the QDD 23 performs digital quadrature demodulation on the next TDD subframe with the updated correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ ) (Step S1005).

In addition, initial frame No. 1 of the header portion and the payload portion is only the frequency deviation Delta] f ¹ ₁ detected by the first frequency deviation detecting unit 31 is corrected by the influence of residual frequency deviation, the appropriate digital quadrature demodulation in QDM23 It may not happen. However, as described above, since the payload portion of the initial frame No. 1 is configured by dummy data other than actual transmission data such as a pseudo random code, there is no influence on communication itself.

Further, the timing of the process of updating the NCO 34, that is, the timing at which the second frequency deviation detection unit 39 outputs the frequency deviation Δf ₂ is referred to as initial frame No. Although the end timing of 1 is used, it may be any timing until the wireless communication device 1 receives the next TDD subframe. Initial frame No. The same applies to the reception process of No. 2 and the reception process of the third and subsequent TDD subframes, and also to the master.

(Master's initial frame No. 1 reception process)
The slave starts with the initial frame No. from the master. 1 and receive the above-described processing, the initial frame No. 1 is received. Generate 1 and send it to the master. Specifically, the slave stores dummy data in the payload section, stores predetermined data in the header section, and generates a TDD subframe to which a preamble is added at the beginning, as in the master. . Send to master as 1.

The master transmits the initial frame No. transmitted by the slave. 1 is received, and processing similar to that of the slave is performed (steps S1001 to S1005). That is, the master detects the frequency deviation Delta] f ¹ ₁ at the first frequency deviation detecting unit 31, the correction value to update the _{NCO34 (f NCO = f c -Δf} 1 1) sine-wave digital signal to the oscillation frequency Generate Then, in the QDM 23, the master receives the initial frame No. 1 of a header portion and a payload portion, the updated correction value ^{_{(f NCO = f c -Δf 1}} 1) for digital quadrature demodulation.

In the pilot carrier extraction unit 38, the master receives the initial frame No. Extracts pilot carriers included in the header portion and a payload portion of 1, the second frequency deviation detecting unit 39 detects the frequency deviation Delta] f ¹ ₂ remaining, correction values to update the NCO34 (f _NCO = f _c A sine wave digital signal having an oscillation frequency of −Δf ¹ ₁ −Δf ¹ ₂ ) is generated. Then, the master receives the next TDD subframe so that the QDD 23 performs digital quadrature demodulation on the next TDD subframe with the updated correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ ) Prepare for

(Receive processing of initial frame No. 2 by slave)
The master, from slave to initial frame no. 1 and receive the above-described processing, the initial frame No. 1 is received. Generate 2 and send it to the slave.

Referring to FIGS. 10 and 13, the slave transmits the initial frame No. 1 transmitted by the master. 2 is received (step S1006), and the initial frame No. 2 is received. With 2 of the preamble, and detects the frequency deviation Delta] f ² ₁ at a first frequency deviation detecting unit 31 (step S1007).

In this case, the frequency deviation Delta] f ² ₁ detected by the first frequency deviation detecting unit 31, the initial frame No. Unlike at the reception of 1, it is not fed back to the NCO 34 and is not used for its processing. That is, the frequency deviation storage unit 32 stores the initial frame No. 1 the frequency deviation Delta] f ¹ _1, which is detected when it receives as it holds and outputs the NCO34.

The slave does not update the NCO 34 (does not update the sine wave digital signal generated by the _NCO 34), and in the _NCO 34, a sine whose oscillation frequency is the same correction value (f _NCO = f _c -Δ f ¹ ₁ -Δ f ¹ ₂ ) Output wave digital signal. Then, in the QDM 23, the slave receives the initial frame No. 1 based on the sine wave digital signal. Digital quadrature demodulation is performed on the header part and the payload part of ^No. ₂ with the same correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ ). Thus, the initial frame No. The frequency deviation (Δf ¹ ₁ + Δf ¹ ₂ ) of the header portion and the payload portion of ₂ is corrected.

In the pilot carrier extraction unit 38, the slave receives the initial frame number no. The pilot carrier included in the header part and the payload part of No. 2 is extracted, and the second frequency deviation detection unit 39 detects the remaining frequency deviation Δf ² ₂ (step S1008).

The slave updates the _NCO 34 with a frequency deviation Δf ₁ = Δf ¹ ₁ and a frequency deviation Δf ₂ = (Δf ¹ ₂ + Δf ² ₂ ), and the _NCO 34 corrects the correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ A sine wave digital signal having an oscillation frequency of −Δf ² ₂ ) is generated. In this process, initial frame number. It is performed at the end timing of 2. Then, the slave performs digital quadrature demodulation on the next TDD subframe in QDM 23 with the updated correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ −Δf ² ₂ ) Prepare to receive subframes (step S1009).

(Master's initial frame No. 2 reception process)
The slave starts with the initial frame No. from the master. 2 and receive the above-described processing, the initial frame No. 2 is received. Generate 2 and send it to the master.

The master transmits the initial frame No. transmitted by the slave. 2 is received, and processing similar to that of the slave is performed (steps S1006 to S1009). That is, the master is to detect the frequency deviation Delta] f ² ₁ at the first frequency deviation detecting unit 31, the frequency deviation Delta] f ² ₁ is not used. The master outputs, at the _NCO 34, a sine wave digital signal whose oscillation frequency is the same correction value as before (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ ).

In the pilot carrier extraction unit 38, the master receives the initial frame No. Extracts pilot carriers included in the header portion and a payload portion of 2, in a second frequency deviation detecting unit 39 detects the frequency deviation Delta] f ² ₂ remaining, correction values to update the NCO34 (f _NCO = f _c A sine wave digital signal having an oscillation frequency of −Δf ¹ ₁ −Δf ¹ ₂ −Δf ² ₂ ) is generated. Then, the master performs digital quadrature demodulation on the next TDD subframe in QDM 23 with the updated correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ −Δf ² ₂ ) Prepare to receive subframes.

(Receive processing of the third TDD subframe by the slave)
The master, from slave to initial frame no. After receiving 2 and performing the above-described process, the third TDD subframe is generated and transmitted to the slave. Specifically, the master stores transmission data in the payload section, stores predetermined data in the header section, generates a TDD subframe without adding a preamble at the beginning, and generates the third TDD subframe. Send to slave as

Referring to FIGS. 10 and 14, the slave receives the third TDD subframe transmitted by the master (step S1010). Since the third TDD subframe is not added preamble, frequency deviation Delta] f ³ ₁ at the first frequency deviation detecting unit 31 is not detected. The frequency deviation storage unit 32 stores the initial frame No. 1 the frequency deviation Delta] f ¹ _1, which is detected when it receives as it holds and outputs the NCO34.

The slave does not update the _NCO 34, and outputs, at the _NCO 34, a sine wave digital signal whose oscillation frequency is the same correction value (f _NCO = f _c -Δ f ¹ ₁ -Δ f ¹ ₂ -Δ f ² ₂ ). Then, the slave uses the same correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ −Δf ₂₎ in the QDM 23 based on the sine wave digital signal in the header portion and the payload portion of the third TDD subframe. Digital quadrature demodulation is performed in ² ₂ ). Thus, the frequency deviation (Δf ¹ ₁ + Δf ¹ ₂ + Δf ² ₂ ) of the header and payload of the third TDD subframe is corrected.

The slave, in the pilot carrier extraction unit 38, the pilot carrier included in the header portion and a payload portion of the third TDD subframe extracted, in a second frequency deviation detecting unit 39, the frequency deviation Delta] f ³ ₂ remaining It detects (step S1011).

Slave updates the NCO34 as frequency deviation Δf ^₁ = Δf _{1 1} and frequency deviation ^{_{Δf 2 = (Δf 1 2 +}} Δf 2 2 + Δf 3 2), in NCO34, the correction value ^{_{(f NCO = f c -Δf 1}} 1 - A sine wave digital signal having an oscillation frequency of Δf ¹ ₂ −Δf ² ₂ −Δf ³ ₂ ) is generated. This process is performed at the end timing of the third TDD subframe. Then, the slave performs digital quadrature demodulation of the next TDD subframe in QDM 23 with the updated correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ −Δf ² ₂ −Δf ³ ₂ ) , Prepare to receive the next TDD subframe (step S1012).

(Master 3rd TDD subframe reception process)
The slave starts with the initial frame No. from the master. After receiving 2 and performing the above-mentioned processing, a third TDD subframe is generated and transmitted to the master. Specifically, the slave stores transmission data in the payload section, stores predetermined data in the header section, generates a TDD subframe without adding a preamble at the beginning, and generates this as a third TDD subframe Send to the master as

The master receives the third TDD subframe transmitted by the slave and performs processing similar to that of the slave (steps S1010 to S1012). That is, the master outputs a sine wave digital signal whose oscillation frequency is the same correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ −Δf ² ₂ −Δf ³ ₂ ) in NCO 34, and in QDM 23, Based on the sinusoidal digital signal, the header and payload parts of the third TDD subframe are given the same correction value (f _NCO = f _c- Δ f ¹ _1- Δ f ¹ _2- Δ f ² _2- Δ f ³ ₂ ) Digital quadrature demodulation.

The master in a pilot carrier extraction unit 38, the pilot carrier included in the header portion and a payload portion of the third TDD subframe extracted, in a second frequency deviation detecting unit 39, the frequency deviation Delta] f ³ ₂ remaining To detect. Then, the slave generates a sine wave digital signal whose oscillation frequency is the correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ −Δf ² ₂ −Δf ³ ₂ ) in the NCO 34, and in the QDM 23 In order to perform digital quadrature demodulation on the TDD subframe of T with the updated correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ −Δf ² ₂ −Δf ³ ₂ ), at the next TDD subframe reception Prepare.

(4th and subsequent TDD subframe reception processing)
The frequency deviation (Δf ¹ ₁ + Δf ¹ ₂ + Δf ² ₂ + Δf ³ ₂ ) of the header and payload of the fourth TDD subframe is corrected. Then, for the fourth TDD subframe, in the QDM 23, the next fifth TDD subframe is updated with the updated correction value (f _NCO = f _c −Δf ¹ ₁ −Δf ¹ ₂ −Δf ² ₂ −Δf ³ ₂ -Prepare for the reception of the next TDD subframe so as to perform digital quadrature demodulation in Δf ⁴ ₂ ). As described above, also for the fourth and subsequent TDD subframes, processing similar to the reception processing of the third TDD subframe is repeated in the slave and the master. In this way, communication can be continued while always performing high-precision frequency deviation correction without using a preamble.

  As described above, according to the wireless communication device 1 according to the embodiment of the present invention, the transmitter 2 transmits TDD subframes including a preamble as the first and second TDD subframes at the start of communication, TDD subframes not including a preamble are transmitted as the third and subsequent TDD subframes.

When the wireless communication device 1 receives a TDD subframe including a preamble at the start of communication, the first frequency deviation detection unit 31 of the reception unit 3 detects the correlation peak position based on the correlation peak value calculated from the preamble. The phase rotation amount is calculated, and the frequency deviation Δf ₁ is detected from the phase rotation amount. The frequency deviation Δf ₁ is then used as a fixed value. Then, the _NCO 34 generates a sine wave digital signal whose oscillation frequency is the correction value (f _NCO = f _c −Δf ₁ ), and the QDM 23 performs digital quadrature demodulation on the received signal based on the sine wave digital signal. Thereby, the frequency deviation Δf ₁ of the received signal is corrected.

Further, the second frequency deviation detection unit 39 calculates a complex division value of a predetermined symbol interval based on the pilot carrier included in the reception signal in which the frequency deviation Δf ₁ is corrected, and the phase rotation amount from the complex division value. It is calculated, and to detect the frequency deviation Delta] f ⁱ ₂ remaining from the phase rotation amount. Then, the _NCO 34 generates a sine wave digital signal whose oscillation frequency is the correction value (f _NCO = f _c −Δf ₁ −Δf ₂ ), and the QDM 23 digitally quadratures the received signal based on the sine wave digital signal. Demodulate. Thus, the frequency deviation Δf ₂ remaining in the received signal is corrected. That is, the frequency deviation (Δf ₁ + Δf ₂ ) of the received signal is corrected.

Furthermore, when the wireless communication device 1 receives a TDD subframe not including a preamble, the second frequency deviation detection unit 39 determines the frequency deviation (Δf ₁ + Δf ₂ ) based on the pilot carrier included in the received signal corrected. detects the frequency deviation Delta] f ⁱ _2, obtains a frequency deviation Delta] f ₂ obtained by accumulating the frequency deviation Delta] f ⁱ _2, sine wave NCO34 is that correction value _{(f NCO = f c -Δf 1} -Δf 2) and the oscillation frequency A digital signal is generated, and the QDM 23 performs digital quadrature demodulation on the received signal based on this sine wave digital signal. By repeating such processing, the frequency deviation Δf ⁱ ₂ remaining in the received signal is corrected for each received TDD subframe.

  Thus, TDD subframes including a preamble are transmitted and received only at the start of communication, and thereafter TDD subframes not including a preamble are transmitted and received. Therefore, since it is not necessary to always transmit and receive subframes including a preamble, it is possible to reduce the number of preamble communications in the entire communication, and it is possible to realize a time division duplex system with good transmission efficiency.

In general, when the preamble period is set longer in the TDD subframe, the first frequency deviation detection unit 31 can detect the frequency deviation Δf ₁ with high accuracy than when the preamble period is set shorter. . However, even if the preamble period is set short in the TDD subframe, the second frequency deviation detection unit 39 determines the remaining frequency deviation Δf ₂ after the frequency deviation Δf ₁ is corrected from the received signal. Can be detected with high accuracy. This is because the second frequency deviation detection unit 39 detects the frequency deviation Δf ₂ based on the pilot carrier. Therefore, since the preamble period in the TDD subframe can be set short, it becomes possible to realize a time division duplex system with good transmission efficiency.

  The present invention has been described above by the embodiment. However, the present invention is not limited to the embodiment, and can be variously modified without departing from the technical concept thereof. In the above embodiment, the wireless communication device 1 transmits TDD subframes including a preamble as the first and second TDD subframes at the start of communication, and does not include the preamble as the third and subsequent TDD subframes. Made to transmit TDD subframes. On the other hand, the wireless communication device 1 may periodically generate (at a predetermined cycle) TDD subframes including a preamble for the third and subsequent TDD subframes and transmit the TDD subframes. Specifically, the wireless communication device 1 generates and transmits a TDD subframe including a preamble as the nth TDD subframe, where n is an integer of 3 or more corresponding to a predetermined cycle. A TDD subframe including a preamble is generated and transmitted as the (n + 1) th TDD subframe.

  Thus, even after the wireless communication apparatus 1 receives a TDD subframe not including a preamble, the frame synchronization detection unit 29 uses the TDD subframe including the preamble at a predetermined cycle to generate a frame synchronization timing signal. Is updated. Therefore, even if, for example, the distance between the pair of wireless communication devices 1 changes with the passage of time and the timing of frame synchronization changes, the accuracy of the frame synchronization timing signal does not decrease.

  In the embodiment, the digital signal processing unit (the IFFT operation unit 12 in the transmission unit 2, the GI addition unit 13,..., NCO 17 and QM 18 of the wireless communication device 1 shown in FIG. Processing of each component of QDM 23, LPF 24,..., Second frequency deviation detection unit 39 and reset signal generation unit 40) is realized by a chip of an LSI which is an integrated circuit mounted on the wireless communication device 1. You may do so. The processing of each component of the digital signal processor, the D / A converter 19 and the A / D converter 22 may be realized by a chip of an LSI. These may be individually made into one chip, or some or all of them may be made into one chip.

  Also, instead of LSI, it may be realized by a chip such as VLSI or ULSI having different degree of integration. Furthermore, the present invention is not limited to chips such as LSIs, and dedicated circuits or general purpose processors may be used, or FPGAs (Field Programmable Gate Arrays) may be used.

REFERENCE SIGNS LIST 1 wireless communication apparatus 2 transmission unit 3 reception unit 10 antenna 11 switch 12 inverse fast Fourier transform (IFFT) operation unit 13 GI addition unit 14 preamble addition unit 15 up sampling unit (US)
16, 24 low pass filter (LPF)
17, 34 Numerically Controlled Oscillator (NCO)
18 Quadrature Modulation (QM)
19 D / A converter 20 Frequency converter (U / C)
21 Frequency converter (D / C)
22 A / D converter 23 Quadrature demodulator (QDM)
25 down sampling unit (DS)
26 preamble storage unit 27 moving correlation unit 28 correlation peak detection unit 29 frame synchronization detection unit 30 trigger signal generation unit 31 first frequency deviation detection unit 32 frequency deviation storage unit 33 addition unit 35 symbol synchronization detection unit 36 FFT window timing unit 37 Fast Fourier transform (FFT) operation unit 38 Pilot carrier extraction unit 39 Second frequency deviation detection unit 40 Reset signal generation unit

Claims (9)

A wireless communication apparatus that transmits and receives subframes in a time division duplex scheme and detects and corrects frequency deviations of received signals of the subframes.
A transmitting unit that transmits a subframe including a preamble for causing another wireless communication device to detect a frequency deviation, and transmits a subframe not including the preamble as a subsequent subframe;
A first frequency deviation is detected using a preamble included in a subframe received from the other wireless communication apparatus, and the first frequency deviation in a received signal of the subframe is corrected, and the other wireless communication is performed. And a receiver configured to detect a second frequency deviation using a pilot carrier included in a subframe received from the apparatus, and correct the second frequency deviation in a received signal of the subframe.
The receiving unit is
An orthogonal demodulation unit which receives a sine wave digital signal of a predetermined oscillation frequency and orthogonally demodulates the reception signal of the subframe based on the sine wave digital signal;
A fast Fourier transform operation unit that performs fast Fourier transform on the signal orthogonally demodulated by the orthogonal demodulation unit to generate a signal in a frequency domain;
A first frequency deviation detection unit that detects the first frequency deviation using a preamble included in a subframe orthogonally demodulated by the orthogonal demodulation unit;
An oscillator that generates and outputs the sine wave digital signal with a correction value obtained by subtracting a predetermined frequency from a predetermined frequency and using the correction value as the predetermined oscillation frequency;
A pilot carrier extraction unit that extracts a pilot carrier from the signal in the frequency domain generated by the fast Fourier transform operation unit;
A second frequency deviation detection unit that detects the second frequency deviation using the pilot carrier extracted by the pilot carrier extraction unit;
When a subframe including the preamble is received from the other wireless communication device,
The oscillator is
Generating a sine wave digital signal with the correction value as the correction value and the correction value as the predetermined oscillation frequency, by subtracting the first frequency deviation detected by the first frequency deviation detection unit from the predetermined frequency Output
The quadrature demodulation unit
The sine wave digital signal is input from the oscillator, and the first frequency deviation in the reception signal of the subframe is corrected by performing orthogonal demodulation on the reception signal of the subframe based on the sine wave digital signal. ,
After receiving a subframe containing the preamble from the other wireless communication device,
The oscillator is
A first frequency deviation detected when the first frequency deviation detection unit receives a subframe including the preamble from the predetermined frequency, and a second frequency deviation detected by the second frequency deviation detection unit The sine wave digital signal is generated and output, with the result of subtracting the addition value with the frequency deviation as the correction value, and the correction value as the predetermined oscillation frequency.
The quadrature demodulation unit
The sine wave digital signal is input from the oscillator, and the received signal of the subframe is orthogonally demodulated based on the sine wave digital signal to obtain the received signal of the subframe in which the first frequency deviation is corrected. And correcting the second frequency deviation in the wireless communication device. In the wireless communication device according to claim 1,
A moving correlation operation is performed between the signal orthogonally demodulated by the orthogonal demodulation unit and the basic signal of the repeating unit of the waveform in the preamble formed by repeating the same waveform a plurality of times to calculate a cross correlation value Mobile correlation unit,
A correlation peak detection unit that detects a plurality of correlation peak positions on the time axis at which the cross correlation value calculated by the movement correlation unit peaks and detects the cross correlation value of the correlation peak position as a correlation peak value; ,
A first frequency deviation for calculating a phase rotation amount between the correlation peak positions based on the plurality of correlation peak values detected by the correlation peak detection unit, and detecting the first frequency deviation from the phase rotation amount. A wireless communication device comprising: a detection unit. The wireless communication device according to claim 1 or 2
The second frequency deviation detection unit
Based on the pilot carrier extracted by the pilot carrier extraction unit, a complex division value of a predetermined symbol interval is calculated, an average value of the complex division values in the subframe is calculated, and a phase angle of the average value is phased. A wireless communication device, wherein a second frequency deviation is detected from the phase rotation amount as a rotation amount. The wireless communication device according to any one of claims 1 to 3.
Furthermore, a frame synchronization detection unit that detects synchronization timing of the subframes and generates a frame synchronization timing signal;
A symbol synchronization detection unit that detects symbol synchronization timing of the subframe and generates a symbol synchronization timing signal;
A C / N ratio calculation unit that calculates a C / N ratio based on the signal in the frequency domain generated by the fast Fourier transform operation unit;
A reset signal generation unit that generates a reset signal for resetting the first frequency deviation;
The oscillator is
The sine wave digital signal having the predetermined frequency as the predetermined oscillation frequency is generated based on the reset signal generated by the reset signal generation unit, and the quadrature demodulation unit generates the sine wave digital signal based on the reset signal generation unit. A radio communication apparatus characterized by quadrature-demodulating a received signal of the sub-frame. The wireless communication device according to any one of claims 1 to 4.
The transmission unit is
A sub-frame including the preamble is transmitted to the other wireless communication device as the first sub-frame and the second sub-frame at the start of communication, and the sub-frame does not include the preamble as the third and subsequent sub-frames. Send a frame,
The receiving unit is
A sub-frame including the preamble is received as the first sub-frame and the second sub-frame at the start of communication from the other wireless communication device, and the sub-frame does not include the preamble as the third and subsequent sub-frames A frame is received, a preamble included in the subframe is used to detect the first frequency deviation, a first frequency deviation in a received signal of the subframe is corrected, and a pilot included in the subframe A wireless communication apparatus, comprising: using a carrier to detect the second frequency deviation; and correcting the second frequency deviation in the received signal. In the wireless communication device according to claim 5,
The transmission unit is
As the third and subsequent subframes, a subframe not including the preamble is transmitted, and a subframe including the preamble is transmitted at a predetermined cycle,
The receiving unit is
A subframe not including the preamble is received as the third and subsequent subframes from the other wireless communication apparatus, and a subframe including the preamble is received at a predetermined cycle. Wireless communication device. A wireless communication method for transmitting and receiving subframes in a time division duplex system and detecting and correcting a frequency deviation of a received signal of the subframe,
Receiving a subframe including a preamble for detecting the frequency deviation;
Quadrature demodulating a received signal of a subframe including the preamble and detecting a first frequency deviation using the preamble included in the received signal;
Generating a first sine-wave digital signal with an oscillating frequency as a result of subtracting the first frequency deviation from a predetermined frequency as a correction value;
Based on the first sine wave digital signal, the received signal of the subframe including the preamble is orthogonally demodulated, and the orthogonally demodulated signal is fast Fourier transformed to generate a signal in the frequency domain, and the signal in the frequency domain Extracting a pilot carrier from the signal and detecting a 2-1st frequency deviation using the pilot carrier;
A second sine wave digital signal having an oscillation frequency with the correction value as a correction value is generated by subtracting the sum of the first frequency deviation and the (2-1) th frequency deviation from a predetermined frequency. Step and
Receiving subframes that do not include the preamble;
Based on the second sine wave digital signal, the received signal of the subframe not including the preamble is orthogonally demodulated, and the orthogonally demodulated signal is fast Fourier transformed to generate a signal in the frequency domain, Extracting a pilot carrier from the signal and detecting a second frequency deviation using the pilot carrier;
A third sine wave digital signal having a correction value obtained by subtracting an addition value of the first frequency deviation and the second frequency deviation from a predetermined frequency, and the correction value being an oscillation frequency, Generating a sine wave digital signal for orthogonally demodulating a received signal when the subframe not including the preamble is further received.
Furthermore, before or after the step of receiving a subframe including the preamble,
Transmitting a subframe including the preamble;
Before or after the step of receiving subframes not including the preamble,
Transmitting a subframe not including the preamble. A wireless communication system comprising a pair of wireless communication devices that transmit and receive subframes in a time division duplex scheme and detect and correct frequency deviations of received signals in the subframes,
A wireless communication system, wherein each of the pair of wireless communication devices is the wireless communication device according to claim 1. In a chip mounted on a wireless communication apparatus that transmits and receives subframes in a time division duplex system and detects and corrects frequency deviation of received signals of the subframes,
A first digital signal processing unit that generates a subframe including a preamble for causing another wireless communication device to detect a frequency deviation, and generates a subframe not including the preamble as a subsequent subframe;
A first frequency deviation is detected using a preamble included in a subframe received from the other wireless communication apparatus, and the first frequency deviation in a received signal of the subframe is corrected, and the other wireless communication is performed. A second digital signal processing unit that detects a second frequency deviation using a pilot carrier included in a subframe received from the device, and corrects the second frequency deviation in the received signal of the subframe; Equipped
The second digital signal processing unit
An orthogonal demodulation unit which receives a sine wave digital signal of a predetermined oscillation frequency and orthogonally demodulates the reception signal of the subframe based on the sine wave digital signal;
A fast Fourier transform operation unit that performs fast Fourier transform on the signal orthogonally demodulated by the orthogonal demodulation unit to generate a signal in a frequency domain;
A first frequency deviation detection unit that detects the first frequency deviation using a preamble included in a subframe orthogonally demodulated by the orthogonal demodulation unit;
An oscillator that generates and outputs the sine wave digital signal with a correction value obtained by subtracting a predetermined frequency from a predetermined frequency and using the correction value as the predetermined oscillation frequency;
A pilot carrier extraction unit that extracts a pilot carrier from the signal in the frequency domain generated by the fast Fourier transform operation unit;
A second frequency deviation detection unit that detects the second frequency deviation using the pilot carrier extracted by the pilot carrier extraction unit;
When the wireless communication device receives a subframe including the preamble from the other wireless communication device,
The oscillator is
Generating a sine wave digital signal with the correction value as the correction value and the correction value as the predetermined oscillation frequency, by subtracting the first frequency deviation detected by the first frequency deviation detection unit from the predetermined frequency Output
The quadrature demodulation unit
The sine wave digital signal is input from the oscillator, and the first frequency deviation in the reception signal of the subframe is corrected by performing orthogonal demodulation on the reception signal of the subframe based on the sine wave digital signal. ,
After the wireless communication device receives a subframe including the preamble from the other wireless communication device,
The oscillator is
Correct the result of subtracting the sum of the first frequency deviation detected by the first frequency deviation detection unit and the second frequency deviation detected by the second frequency deviation detection unit from the predetermined frequency Generating and outputting the sine wave digital signal having a value and the correction value as the predetermined oscillation frequency,
The quadrature demodulation unit
The sine wave digital signal is input from the oscillator, and the received signal of the subframe is orthogonally demodulated based on the sine wave digital signal to obtain the received signal of the subframe in which the first frequency deviation is corrected. Correcting the second frequency deviation at.