JP5577904B2 - Transceiver and transmitter - Google Patents

Description

  The present invention relates to a receiver and a transmitter, and more particularly to a receiver and a transmitter that transmit and receive signals including a preamble for establishing synchronization.

  In a TDMA (Time Division Multiple Access) system, a signal with a preamble added in front of a data portion is generally transmitted in order to synchronize the timing of the data portion. The receiver detects the preamble and establishes symbol timing synchronization.

  In mobile radio communications, received waves are subject to frequency fluctuations due to factors such as a frequency error of a crystal oscillator mounted on a transceiver and a Doppler shift due to movement of a transceiver terminal. This frequency offset correction is performed using the preamble described above, and the preamble needs a certain length.

  Patent Document 1 describes that an instantaneous phase difference of a correlation peak value between a received signal and a known preamble pattern is obtained, and a frequency offset is estimated from the relationship between the instantaneous phase difference and time, that is, from the angular velocity of the correlation peak value. ing.

JP 2007-228332 A

  As described above, the technique described in Patent Document 1 obtains a correlation peak for estimating a frequency offset. However, since the correlation peak cannot be obtained when the frequency offset is large, the detectable frequency offset is limited.

  An object of the present invention is to solve the above-described problems and provide a receiver and a transmitter capable of detecting a large frequency offset with a short preamble.

  A receiver according to the present invention is a receiver that receives a signal including a synchronization establishment preamble transmitted from a transmitter, and is modulated so that a transition for each modulation period does not pass through a zero point included in the preamble. Calculation means for obtaining a rotation speed of the signal point from a frequency offset detection pattern comprising a specific pattern in which the signal point transitions so as to rotate in a certain direction in the measurement, and an estimation means for estimating the frequency offset based on the rotation speed And the frequency offset is corrected.

  The transmitter according to the present invention is a transmitter that transmits a signal including a preamble for establishing synchronization, and is modulated so that the transition for each modulation period does not pass through the zero point, and the signal point rotates in a constant direction in the constellation. And generating means for generating the preamble including a frequency offset detection pattern composed of a specific pattern that makes such a transition.

  According to the present invention, it is possible to detect a large frequency offset with a short preamble.

(A) is a figure which shows schematic structure of the receiver for demonstrating the principle of this invention, (b) is a figure which shows schematic structure of the transmitter for demonstrating the principle of this invention. It is a figure which shows the structure of the transmitter by embodiment of this invention. It is a figure which shows the structure of the receiver by embodiment of this invention. It is a figure which shows the structure of the frequency offset correction | amendment and preamble detection part of FIG. It is a figure which shows the example of the preamble pattern produced | generated by the preamble production | generation part of FIG. (A) is a figure which shows the pattern for frequency offset detection of FIG. 5, (b) is the figure which divided and showed this frequency offset detection pattern for I component and Q component. FIG. 7 is a diagram illustrating a constellation of π / 2 shift BPSK indicating signal transition of the frequency offset detection pattern of FIG. 6. It is a figure which shows the angular velocity which changes according to a frequency offset. It is a flowchart which shows operation | movement of the receiver of FIG.

  Before describing embodiments of the present invention, the principle of the present invention will be described with reference to the drawings in order to help understanding of the present invention. 1A is a diagram showing a schematic configuration of a receiver for explaining the principle of the present invention, and FIG. 1B is a diagram showing a schematic configuration of a transmitter for explaining the principle of the present invention. is there.

  The receiver shown in FIG. 1A is a receiver that receives a signal including a preamble for establishing synchronization transmitted from a transmitter, and the transition for each modulation period included in the preamble does not pass through the zero point. The calculation unit 101 that obtains the rotational speed of the signal point from the frequency offset detection pattern consisting of a specific pattern that is modulated so that the signal point rotates in a constant direction in the constellation, and the frequency based on the rotational speed And an estimation unit 102 that estimates an offset, and corrects the frequency offset.

  The transmitter shown in FIG. 1B is a transmitter that transmits a signal including a preamble for establishing synchronization, and is modulated so that the transition for each modulation period does not pass the zero point, and the signal point is constant in the constellation. A generation unit 111 that generates a preamble including a frequency offset detection pattern including a specific pattern that changes so as to rotate in the direction of.

  In this way, the correlation peak between the received signal and the known preamble pattern is not obtained for frequency offset estimation, but the signal transition speed of the frequency offset detection pattern made up of the specific pattern included in the preamble of the received signal is determined. Since the frequency offset is estimated and obtained, a large frequency offset can be detected with a short preamble.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 2 is a diagram showing a configuration of a transmitter according to the embodiment of the present invention. 2, the transmitter according to the embodiment of the present invention includes a preamble generation unit 1, a π / 2 shift BPSK (Binary Phase Shift Keying) modulation unit 2, a data generation unit 3, and a QPSK (quadrature phase shift keying). A modulation unit 4, a D / A converter 5, an RF (Radio Frequency) unit 6, and an antenna 7 are included.

  The preamble generation unit 1 generates preamble data including a frequency offset detection pattern and a synchronization establishment (synchronization timing detection) pattern. FIG. 5 is a diagram showing an example of a preamble pattern generated by the preamble generator 1 of FIG. As shown in FIG. 5, the preamble is configured such that a frequency offset detection pattern is arranged in the first half and a synchronization establishment pattern is arranged in the second half.

  A blank of several symbols determined in advance based on a frequency offset correction processing time in a receiver described later is set between the frequency offset detection pattern and the synchronization establishment pattern. The pattern for establishing synchronization is a signal sequence that can take a correlation peak by an analog matched filter, and includes, for example, a PN (Pseudo Noise) code.

  FIG. 6A is a diagram showing the frequency offset detection pattern of FIG. 5, and FIG. 6B is a diagram showing the frequency offset detection pattern divided into an I component and a Q component. The preamble including the frequency offset detection pattern generated by the preamble generation unit 1 is modulated by the π / 2 shift BPSK modulation unit 2 using the π / 2 shift BPSK method, and the modulated frequency offset detection pattern is shown in FIG. ).

  FIG. 7 is a diagram illustrating a constellation of π / 2 shift BPSK indicating signal transition of the frequency offset detection pattern of FIG. By making the frequency offset detection pattern shown in FIG. 6, the signal transition of π / 2 shift BPSK changes so that the signal point rotates in a certain direction as shown in FIG. In the embodiment of the present invention, the frequency offset is estimated by obtaining the speed (angular velocity) of this signal transition in the receiver described later.

  As described above, the frequency offset detection pattern generated by the preamble generation unit 1 is modulated using the π / 2 shift BPSK method and is changed from a specific pattern in which a signal point changes in a constellation so as to rotate in a certain direction. Become.

  The data generation unit 3 generates user data. The QPSK modulation unit 4 modulates the data generated by the data generation unit 3 using the QPSK method. The D / A converter 5 converts the transmission signal composed of the preamble from the π / 2 shift BPSK modulation unit 2 and the data from the subsequent QPSK modulation unit 4 into an analog signal. The RF unit 6 converts the transmission signal from the D / A converter 5 into a high frequency signal and transmits it through the antenna 7.

  FIG. 3 is a diagram showing a configuration of a receiver according to the embodiment of the present invention. In FIG. 3, the receiver according to the embodiment of the present invention includes an antenna 11, an RF unit 12, an A / D converter 13, a frequency offset correction / preamble detection unit 14, and a QPSK demodulation unit 15. The RF unit 12 converts the signal from the transmitter of FIG. 2 received via the antenna 11 into an intermediate frequency signal using a local oscillation signal of a LO (local oscillator) 121. The A / D converter 13 converts the received signal from the RF unit 12 into a digital signal.

  FIG. 4 is a diagram showing the configuration of the frequency offset correction and preamble detection unit 14 of FIG. In FIG. 4, the frequency offset correction and preamble detection unit 14 includes a calculation unit 21, an estimation unit 22, and a correction control unit 23 for frequency offset correction. The frequency offset correction / preamble detector 14 includes correlators 31 and 32, absolute value circuits 33 and 34, an adder 35, and a detector 36 for preamble detection (symbol timing detection).

  First, the frequency offset correction process will be described. The calculation unit 21 calculates an angular velocity that is a rotational speed of signal transition in the constellation shown in FIG. 7 from the frequency offset detection pattern included in the preamble of the received signal from the A / D converter 13. The calculation formula of the angular velocity ω (t) is shown below. X (t) is an I component and y (t) is a Q component.

  In order to reduce the influence of noise, the calculation unit 21 takes an average value of angular velocities in the frequency offset detection pattern section. The estimation unit 22 estimates a frequency offset based on the angular velocity calculated by the calculation unit 21. FIG. 8 is a diagram showing the angular velocity that changes in accordance with the frequency offset. As shown in FIG. 8, the original angular velocity ωs of the signal transition when there is no frequency offset changes to the angular velocity ωs + ωoffset according to the frequency offset, so that the frequency offset is obtained from the angular velocity calculated by the calculation unit 21. Can do.

  The correction control unit 23 corrects the frequency offset by controlling the local oscillation frequency of the LO 121 based on the frequency offset amount obtained by the estimation unit 22. Next, preamble detection processing will be described. The correlator 31 correlates the received signal from the A / D converter 13 with the I component signal of a known reference pattern (preamble synchronization establishment pattern). The correlator 32 correlates the received signal from the A / D converter 13 with the Q component signal of a known reference pattern.

  The correlation values obtained by the correlators 31 and 32 are summed up by the absolute value circuits 33 and 34 and the adder 35 and inputted to the detection unit 36. The detection unit 36 performs threshold determination on the input value to detect a correlation peak position, and outputs the detected correlation peak position to the QPSK demodulation unit 15 as a symbol timing. The QPSK demodulator 15 performs QPSK demodulation processing on the data part of the received signal using this symbol timing.

  Between the preamble synchronization establishment pattern correlated by the correlators 31 and 32 and the frequency offset detection pattern arranged in the first half of the preamble, based on the frequency offset correction processing time as shown in FIG. A predetermined number of blanks having a predetermined number of symbols are provided. Therefore, the preamble detection process described above is performed on the received signal after the frequency offset correction.

  FIG. 9 is a flowchart showing the operation of the receiver of FIG. In FIG. 9, when a signal is received from the transmitter of FIG. 2, the calculation unit 21 calculates an angular velocity from the frequency offset detection pattern included in the preamble of the received signal (step S1). The estimation unit 22 estimates the frequency offset amount based on the angular velocity calculated by the calculation unit 21 (step S2). Then, the correction control unit 23 corrects the frequency offset based on the frequency offset amount obtained by the estimation unit 22 (step S3).

  Next, the symbol timing is detected by the detection unit 36 using the synchronization establishment pattern subsequent to the frequency offset detection pattern (step S4), and is notified to the QPSK demodulation unit 15 (step S5).

  As described above, in the embodiment of the present invention, instead of obtaining a correlation peak between a received signal and a known preamble pattern for estimating a frequency offset, a frequency composed of a specific pattern included in the preamble of the received signal. Since the frequency offset is estimated by obtaining the signal transition speed of the offset detection pattern, a large frequency offset can be detected with a short preamble.

  In the embodiment of the present invention, π / 2 shift BPSK is used as a preamble modulation scheme, but the present invention is not limited to this, and a digital modulation scheme (for example, OQPSK) in which transition for each modulation period does not pass through a zero point is used. (Offset QPSK) or the like. It is also possible to use a carrier wave (can be considered as modulation by direct current). That is, the frequency offset detection pattern generated by the preamble generation unit 1 is composed of a specific pattern that is modulated so that the transition for each modulation period does not pass through the zero point and the signal point changes in a constant direction in the constellation. .

  A part or all of the above embodiment can be described as in the following supplementary notes, but is not limited to the following description.

[Appendix 1]
A frequency offset correction method for a receiver that receives a signal including a preamble for establishing synchronization transmitted from a transmitter,
Rotation of the signal point from a frequency offset detection pattern comprising a specific pattern that is included in the preamble and modulated so that the transition for each modulation period does not pass through the zero point and the signal point in the constellation transitions to rotate in a certain direction. A calculation step for determining the speed;
An estimation step of estimating a frequency offset based on the rotation speed;
And a correction step for correcting the frequency offset.

[Appendix 2]
The frequency offset detection pattern is arranged at the beginning of the preamble,
The supplementary note 1, further comprising a detection step of detecting a synchronization timing by performing a correlation operation between the synchronization establishment pattern of the preamble arranged after the frequency offset detection pattern and a known reference pattern. Frequency offset correction method.

[Appendix 3]
The frequency offset correction method according to claim 2, wherein the synchronization establishment pattern of the preamble is arranged with a predetermined number of symbols from the frequency offset detection pattern.

[Appendix 4]
4. The frequency offset correction method according to appendix 3, wherein the interval of the predetermined number of symbols is determined based on a time required for the frequency offset correction process.

[Appendix 5]
An operation control method of a transmitter for transmitting a signal including a preamble for establishing synchronization,
Including a generation step of generating the preamble including a frequency offset detection pattern including a specific pattern in which a transition for each modulation period is modulated so as not to pass through a zero point and a signal point in the constellation changes so as to rotate in a certain direction. An operation control method characterized by the above.

[Appendix 6]
6. The operation control method according to appendix 5, wherein the frequency offset detection pattern is arranged at the head of the preamble.

[Appendix 7]
The operation according to claim 6, wherein the synchronization establishment pattern of the preamble arranged after the frequency offset detection pattern is arranged at a predetermined number of symbols from the frequency offset detection pattern. Control method.

[Appendix 8]
The interval of the predetermined number of symbols is determined based on a time required for correction processing of the frequency offset in a receiver that estimates the frequency offset using the frequency offset detection pattern and corrects the frequency offset. The operation control method according to appendix 7.

1 Preamble generator
2 π / 2 shift BPSK modulator
3 Data generator
4 QPSK modulator
5 D / A converter 6,12 RF unit 7,11 Antenna
13 A / D converter
14 Frequency offset correction and preamble detector
15 QPSK demodulator 21, 101 calculator 22, 102 estimator
23 Correction control unit 31, 32 Correlator 33, 34 Absolute value circuit
35 Adder
36 detector 111 generator 121 LO

Claims (8)

Means for generating a preamble including a frequency offset detection pattern and a synchronization timing detection pattern;
Means for transmitting a signal including the preamble;
Means for receiving the signal;
Means for calculating a rotation speed in a constellation of the frequency offset detection pattern included in the received signal;
Wherein the rotational speed, and estimates the frequency offset based on the original rotational speed and, of the difference between when the frequency offset is not, see containing and means for correcting the frequency offset,
The frequency offset detection pattern is a pattern for generating a modulation symbol that rotates around a zero point in a constant direction in a constellation by being combined with a predetermined modulation method.
Transceiver. The frequency offset detection pattern is arranged at the beginning of the preamble,
2. The transceiver according to claim 1, further comprising means for detecting a synchronization timing by performing a correlation operation between the synchronization timing detection pattern arranged after the frequency offset detection pattern and a known reference pattern. .   3. The transceiver according to claim 2, wherein the synchronization timing detection pattern is spaced apart from the frequency offset detection pattern by a predetermined number of symbols.   4. The transceiver according to claim 3, wherein the interval of the predetermined number of symbols is determined based on a time required for the correction process of the frequency offset. It means for generating a preamble comprising a frequency offset detection pattern and synchronization timing detection pattern seen including,
The frequency offset detection pattern is a pattern for generating a modulation symbol that rotates around a zero point in a constant direction in a constellation by being combined with a predetermined modulation method.
Transmitter.   6. The transmitter according to claim 5, wherein the frequency offset detection pattern is arranged at the head of the preamble.   7. The transmitter according to claim 6, wherein the synchronization timing detection pattern arranged after the frequency offset detection pattern is arranged with a predetermined number of symbols from the frequency offset detection pattern.   The interval of the predetermined number of symbols is determined based on a time required for correction processing of the frequency offset in a receiver that estimates the frequency offset using the frequency offset detection pattern and corrects the frequency offset. The transmitter according to claim 7.

Images