WO2008010283A1

WO2008010283A1 - Signal detecting apparatus

Info

Publication number: WO2008010283A1
Application number: PCT/JP2006/314415
Authority: WO
Inventors: Tsuyoshi Kobayashi
Original assignee: Mitsubishi Electric Corporation
Priority date: 2006-07-20
Filing date: 2006-07-20
Publication date: 2008-01-24
Also published as: JPWO2008010283A1; JP4685937B2

Abstract

A signal detecting apparatus for detecting a desired OFDM modulated signal from among received signals. The signal detecting apparatus comprises an FFT part that converts received signals to first frequency domain signals of the respective carriers; a preamble pattern generating part (51) that generates second frequency domain information of the respective carriers, based on signals which include predetermined known information, have different frequencies and different initial phases and which are obtained by multiplexing signals of a plurality of carriers; complex conjugators (52) that generate complex conjugates of the second frequency domain information for the respective carriers; complex multipliers (53) that multiply the first frequency domain signals of the respective carriers by the complex conjugates of the respective carriers generated by the complex conjugators; a complex summing amplifier (54) that adds together a part or all of multiplication outputs from the multiplying means; and a signal detecting means (an absolute value calculating part (55), a carrier detecting/determining part (56)) that calculates an absolute value of an addition result or calculates a square value of the addition result and uses a predetermined threshold value to detect/determine a desired signal.

Description

Specification

Signal detection device

Technical field

TECHNICAL FIELD [0001] The present invention relates to a signal detection device that performs detection of a desired signal and the like in a receiver that constitutes a communication device, and in particular, detects a desired signal and a symbol timing using a known signal. It is related with the signal detection apparatus to perform.

Background art

[0002] In a communication system using the CSMA (Carrier Sense Multiple Access) method, a known signal waveform is added before a signal for transmitting data, and the known signal waveform is transmitted to a communication device belonging to the communication system. It constantly monitors whether or not it exists on the transmission line. And when a communication device detects the presence of a known signal waveform, it does not transmit even if there is transmission data, and performs a receiving operation. Also, in the case of a communication system using the TDMA (Time Division Multiple Access) method, the base station periodically transmits a known signal waveform so that the terminal can synchronize with the basic period and timing of time division. In some cases, the terminal performs synchronization by detecting this known signal waveform. Such a known signal waveform is called a preamble, and the operation of detecting whether or not the signal of the communication system of the device is present on the transmission path is called carrier detection or carrier sense. is there.

[0003] In conventional carrier detection, a communication device simply receives received signal power (RSSI).

Strength Indicator) was measured, and the presence or absence of a signal was judged based on the measurement result. Specifically, the RSSI measurement result is compared with a certain threshold value, and if the RSSI measurement value is larger than the threshold value, it is determined that a signal is present, and the RSSI measurement value is smaller than the threshold value V, In case it was judged that there was no signal, it was.

[0004] Further, the correlation value between the signal waveform on the transmission line and the preamble signal waveform which is a known waveform is constantly monitored, and when the correlation value is greater than a certain threshold, it is determined that a signal exists, A method for more reliably detecting the presence of a signal in the target communication system by determining that the signal does not exist when the correlation value is smaller than the threshold value. (For example, Patent Document 1).

[0005] Furthermore, in a communication system using OFDM (Orthogonal Frequency Division Multiplexing) as a modulation method, the time at which different information is placed on multiple frequencies using fast inverse Fourier transform (IFFT) on the transmission side. A waveform is generated, and information on each frequency is separated on the receiving side by Fast Fourier Transform (FFT). The processing unit of this IFFTZFFT is called a symbol, etc. In the FFT processing at the time of reception, it is necessary to cut out the received signal using an appropriate symbol timing and use it as the FFT input. The preamble signal is also used to detect this symbol timing. The reception side obtains the correlation value of the received waveform in the same manner as the carrier detection described above, and the symbol timing is determined based on the timing of the peak position where the correlation value is maximum. Detection methods are used (for example, Non-Patent Document 1).

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-295085 (Page 3-6, Fig. 1)

Non-Patent Document 1: Supervised by Masahiro Moriya and Shuji Kubota “Revised 802.11 High-Speed Wireless LAN Textbook” Impress Inc., January 1, 2005, P206-212

Disclosure of the invention

Problems to be solved by the invention

However, since the detection determination based on the conventional RSSI is based only on the power, even if the power of other system signals or noises exceeds the threshold, the carrier is detected. O There is a problem that it is judged to be a detection, that is, there is a high possibility of performing a false detection.

[0008] In addition, there are a method using autocorrelation and a method using cross-correlation as a method using a correlation value. In autocorrelation, a signal repeatedly transmitted is multiplied by a signal delayed by a repetition period. The correlation value is obtained by integrating the result. On the other hand, in cross-correlation, the correlation value is obtained by integrating the multiplication results of each sample of the known preamble signal waveform and received waveform. In general, in autocorrelation, multiplication circuit power is sufficient, but only moderate and strong peaks are obtained, and timing detection accuracy is inferior to cross-correlation. Cross-correlation requires as many multiplier circuits as the number of samples for which correlation is to be obtained. However, since a steep peak is obtained, timing detection accuracy is high. For both auto-correlation and cross-correlation, the integration results are multiplied by the number of samples. An adder circuit for obtaining the sum is required. In either case, the longer the period for obtaining the correlation value, the higher the detection accuracy, but the problem is that the circuit scale increases.

[0009] The present invention has been made in view of the above, and an object of the present invention is to obtain a signal detection device that realizes highly accurate carrier detection and timing detection.

Means for solving the problem

In order to solve the above-described problems and achieve the object, a signal detection apparatus according to the present invention is a signal detection apparatus for detecting a desired signal modulated by a medium power OFDM system of a received signal. The signal conversion means for converting the received signal into frequency domain information (first frequency domain signal) for each carrier, and signals of a plurality of carriers that include predetermined known information and have different frequencies and initial phases are multiplexed. Based on the converted signal, known frequency information generating means for generating frequency domain information (second frequency domain information) for each carrier, and complex of the second frequency domain information output from the known frequency information generating means The complex conjugate generating means for generating a conjugate for each carrier, the first frequency domain signal for each carrier, and the complex conjugate for each carrier generated by the complex conjugate generating means have the same frequency. A multiplication means for multiplying the areas, an addition means for adding a part or all of the multiplication outputs of the multiplication means, an absolute value of the addition result or a square value of the addition result, Signal detecting means for performing detection determination of a desired signal using a prescribed predetermined threshold value.

The invention's effect

According to the present invention, the received preamble signal is converted into frequency domain information by FFT, and the result obtained by multiplying the converted information by the complex conjugate value of a known preamble pattern is used. Thus, carrier detection and timing determination are performed by determining the similarity between the received preamble signal and the preamble pattern, compared with the case where carrier detection is performed only with the power that was conventionally used. As a result, the frequency of erroneous detection can be suppressed, and the carrier detection accuracy can be increased.

Brief Description of Drawings

FIG. 1 is a diagram illustrating a configuration example of a communication device (transmitter) on a side that transmits data to a communication device including a signal detection device according to the present invention. FIG. 2 is a diagram illustrating a configuration example of a first embodiment of a communication device (receiver) including a signal detection device according to the present invention.

FIG. 3 is a diagram illustrating a configuration example of a carrier detection timing determination unit according to Embodiment 1. FIG. 4 is a diagram illustrating a configuration example of a carrier detection timing determination unit according to Embodiment 2. [Figure 5] Figure 5 shows an example of the relationship between the leading position of the preamble signal and Θ relative to the FFT input range.

Z

FIG.

FIG. 6 is a diagram illustrating a configuration example of a receiver according to the fourth embodiment.

FIG. 7 is a diagram illustrating a configuration example of a receiver according to the fifth embodiment.

FIG. 8 is a diagram illustrating a configuration example of a carrier detection timing determination unit according to the sixth embodiment.

FIG. 9 is a diagram illustrating another configuration example of the carrier detection timing determination unit according to the sixth embodiment.

Explanation of symbols

1 Transmitter

2 Transmission path

3, 3b, 3c receiver

10 Transmission information

11 Modulator

12 IFFT

13 Digital Z analog converter (DZA)

14 Transmission signal

30 Received information

31 Demodulator

32 FFT

33 Analog Z to Digital Converter (AZD)

34 Received signal 35 Time signal averaging section

36 Frequency information averaging unit

40 Preamble generator

50, 50a, 50d, 50e Carrier detection timing judgment unit

51 Preamble pattern generator

52 Complex conjugate

53 Complex multiplier

54 Total

55 Absolute value calculator

56 Carrier detection judgment part

57 Phase calculator

58 Timing judgment section

59 Time averaging section

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of a signal detection device according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

[0015] Embodiment 1.

FIG. 1 is a diagram showing a configuration example of a communication apparatus (transmitter) that transmits data by OFDM modulation to a communication apparatus including a signal detection apparatus according to the present invention, and 1 indicates a transmitter. This transmitter 1 has transmission information 10 that also has bit string power as input, a modulation section 11 that outputs the modulation result, an IFFT section 12 that converts the output of the modulation section 11 into frequency domain power, and I FFT The digital Z / analog converter (D / A) 13 that converts the output of the unit 12 into an analog format and the known signal (hereinafter called the preamble) for carrier detection and timing determination A preamble generation unit 40 for generating a preamble pattern to be 14 is an analog converted transmission signal, and 2 is a transmission path.

FIG. 2 is a diagram showing a configuration example of the first embodiment of the communication device (receiver) including the signal detection device according to the present invention, and 3 shows the receiver. The receiver 3 includes an analog Z / digital converter (A / D) 33 that converts the received signal 34 from the transmission side into a digital format, and A An FFT unit 32 that converts the output of the ZD conversion unit 33 from the time domain to the frequency domain, a demodulator 31 that demodulates the output of the FFT unit 32 and generates reception information 30 that also has bit string power, and an FFT unit 32 And a carrier detection timing determination unit 50 that performs carrier detection and timing detection based on the output of. 2 is the same transmission path as shown in FIG. 1, and the transmitter 1 and the receiver 3 forming the communication system exchange signals via this transmission path 2.

Next, detailed operations of the transmitter 1 and the receiver 3 configured as described above will be described. Here, the transmitter 1 generates a transmission signal based on the transmission information 10, the receiver 3 receives the generated signal, and demodulates it to generate the reception signal 30 (restore the transmission information 10). ) The operation will be described.

First, a signal transmission operation in which the transmitter 1 includes transmission of a preamble signal will be described with reference to FIG. When transmitting a preamble signal, the preamble generation unit 40 generates a known preamble pattern that is determined in advance. This preamble pattern is a pseudo-random pattern consisting of a bit string of “0” and “1”, for example, called an M-sequence. The generated preamble pattern is input to the modulation unit 11. The modulation unit 11 is in accordance with a modulation scheme such as BPSK (Binary Phase Shift Keying), QPSK (Quadrate Phase Shift Keying), or QAM (Quadrate Amplitude Modulation). The input preamble pattern (bit string) is divided for each subcarrier and further mapped onto the complex plane. For example, if the preamble pattern is to be BPSK modulated, the bit string that is also input to the preamble generator 40 is divided into lbits. If it is “0”, it is “—l + 0j”, if it is “1”, it is “1”. + Oj "to convert to complex data representing two points on the complex plane.

[0019] The complex data generated by the modulation unit 11 is input to the I FFT unit 12 as frequency domain information for each subcarrier. The IFFT unit 12 converts the input information into time domain information, and outputs digital time waveform information equal to a combined wave obtained by combining waveforms for each subcarrier. Further, the digital time waveform information is converted into an analog signal by a digital Z analog conversion unit (hereinafter referred to as a DZA conversion unit) 13 and sent to the transmission path 2 as a transmission signal 14.

[0020] Note that the preamble pattern may be assigned to all subcarriers or only some of the subcarriers may be used. [0021] Also, when transmitting the transmission information 10, the input to the modulation unit 11 becomes an arbitrary transmission information bit string (transmission information 10) instead of the known pattern input from the preamble generation unit 40. The basic operations of the modulation unit 11, the IFFT unit 12, and the DZA conversion unit 13 are the same as the operations at the time of preamble signal transmission described above. However, the transmission information modulation scheme need not be the same as the preamble modulation scheme, and other modulation schemes may be used.

[0022] It should be noted that the implementation method of the preamble generation unit 40 includes a method of generating a preamble pattern using a shift register and an XOR operation circuit if it is a pseudo-random sequence such as an M sequence, or a preamble as a memory. There is a method of storing patterns. When the preamble generation unit 40 has a memory configuration, digital time waveform information of the preamble signal may be stored. In this case, the output of the preamble generation unit 40 is directly input to the DZA conversion unit 13.

Next, an operation when the receiver 3 receives a signal (received signal 34) via the transmission path 2 will be described. At the time of data reception, if there is an input of the reception signal 34, an analog Z digital conversion unit (hereinafter referred to as AZD conversion unit) 33 converts it into digital time waveform information. The FFT unit 32 corresponding to the signal conversion means generates complex data as frequency domain information for each subcarrier by converting the input from the AZD conversion unit 33 into the frequency domain. The demodulator 31 demaps the input from the AZD converter 33 to a bit string for each subcarrier according to a predetermined demodulation method such as BPSK, QPSK, QAM, etc. Receive information 30 is generated.

[0024] The preamble signal reception process is the same as the data reception process until the FFT unit 32 converts the input of the AZD conversion unit 33 into a time domain power frequency domain. When receiving the preamble signal, the complex data for each subcarrier generated by the FFT unit 32 is input to the carrier detection timing determination unit 50, and the carrier detection timing determination unit 50 performs carrier detection and timing determination.

[0025] Next, the operation of the carrier detection timing detection unit 50 will be described. FIG. 3 is a diagram illustrating a configuration example of the carrier detection timing determination unit 50 included in the receiver according to the present embodiment. The carrier detection timing detection unit 50 is the same as that transmitted from the transmitter 1. A preamble pattern generator 51 that generates frequency information for each subcarrier of a known signal (preamble signal), a complex conjugate 52 that converts complex numbers to complex conjugate values, a complex multiplier 53, and a sum of multiple complex numbers The complex summation unit 54 for calculating the absolute value, the absolute value calculation unit 55 for calculating the absolute value of the complex number, and the absolute value of the calculated complex number are compared with a predetermined threshold value. A carrier detection determination unit 56 that determines that a carrier has been detected in the above case.

[0026] The complex number information for each subcarrier input from the FFT unit 32 to the carrier detection timing detection unit 50 is X (i is a subcarrier number). In the carrier detection timing detection unit 50, a preamble pattern generation unit 51 corresponding to known frequency information generation means generates complex number information P (i is a subcarrier number) for each subcarrier in the preamble signal, and generates complex conjugate thereof. A complex conjugate 52 corresponding to the means converts to a complex conjugate value P *. Thereafter, the complex multiplier 53 corresponding to the multiplication means multiplies the P * by the complex number information X of the received signal to obtain Y. Further, the sum total value Z of Y is calculated by the complex summation device 54 corresponding to the adding means. Z thus obtained can be expressed by the following equation (1).

[0027] [Equation 1]

i = 0 i = 0

••• (1)

[0028] Then, the absolute value calculation unit 55 calculates the absolute value of the total value Z output from the complex totalizer 54. Z is also a complex number, and when it is “Z = A + Bj”, the absolute value of this is given by the following equation (2).

[0029] [Equation 2]

| Z | = VA ² + B ²

••• (2)

[0030] Instead of the absolute value (corresponding to amplitude) shown in the above equation (2), the absolute value of the square value of the total value Z (corresponding to power) as shown in the following equation (3) is calculated. The carrier detection / determination unit 56 may perform carrier detection using the square value of the total value Z, for example, by the calculation by the unit 55. Z ² = A ² + B ² --(3)

[0031] In addition, the total value for all the subcarriers (the sum of all the multiplication results Y _; ) is used as V, and instead of only some of the subcarriers (the multiplication result Y _; (Addition value for a part selected from the above) may be calculated, and the subsequent processing may be performed using the addition result. The absolute value calculation unit 55 and the carrier detection unit 56 constitute a signal detection unit.

Here, the reason why carrier detection is possible using the above formula (2) or (3) will be described. By multiplying the complex number information X of the received signal by the complex conjugate value P * of the preamble pattern, if the received signal is a preamble signal, the multiplication result Y is “Ι + Oj” for any subcarrier, and the sum is “ k + Oj ", the absolute value of the sum is k. On the other hand, if the received signal is a signal different from the preamble signal, Y _; will have a different value for each subcarrier, and the absolute value of the total value will be smaller than k. If a pseudo-random pattern such as an M-sequence is used as the preamble pattern, the larger the number of subcarriers, the closer to 0 (zero) the absolute value of the total value when other than the preamble signal is received.

[0033] In an actual environment in which communication is performed, the amplitude and phase change depending on the transmission path characteristics. Therefore, even when a preamble signal is received, the absolute value is not necessarily k. By taking the sum of the carriers, there is a clear difference between the absolute values when the preamble signal is received and when other signals are received. Therefore, the carrier detection determination unit 56 can determine carrier detection when the absolute value exceeds a predetermined threshold for signal detection determination in consideration of transmission path characteristics and the like. The timing when the preamble signal is present can be detected. The case where the preamble pattern is BPSK modulated has been described as an example, but the same applies when other modulation schemes are used.

[0034] The threshold for signal detection determination is determined based on the relationship between the absolute value of the total value when a preamble signal is received and the absolute value of the total value when a signal other than the preamble signal is received! / To do. For example, the bit pattern used as the preamble pattern, the comparison target at the time of carrier detection judgment (LV, whether to use the absolute value of the total value or the square value of the absolute value as the value to be compared), Type of information to be added when calculating the total value (what kind of processing is performed on the input X to the carrier detection timing judgment unit) To be calculated) and the number of objects to be added when calculating the total value (number of information to be added). It is also possible to select and use the optimum threshold value as appropriate according to the transmission path characteristics from a plurality of threshold values determined in advance in consideration of the transmission path characteristics. Decide it in advance and use it while adjusting the appropriate value according to the transmission path characteristics.

As described above, in the present embodiment, the transmission side transmits, as preamble signals, signals that have been assigned a predetermined preamble pattern to a plurality of predetermined frequencies. On the other hand, at the time of receiving the preamble signal, on the other hand, when the preamble signal is received, information is separated for each frequency using the FFT, and the result obtained by multiplying them with the complex conjugate value of the preamble pattern is used. Thus, carrier detection and timing determination are performed by determining the similarity between the received preamble signal and the preamble pattern. As a result, the possibility of erroneous detection can be reduced compared to the case where carrier detection or the like is performed using only power that has been conventionally used.

[0036] Further, the FFT unit 32 and the complex multiplier 53 are circuits normally provided for data reception by a general OFDM receiver, and it is not necessary to perform carrier detection and data demodulation at the same time. The same circuit can be used for carrier detection. That is, the above-described receiver can be realized with a small circuit scale as compared with the conventional carrier detection based on correlation in the time domain.

[0037] Embodiment 2.

Next, the signal detection apparatus according to the second embodiment will be described. In the first embodiment described above, the carrier detection determination is performed by using the sum of the FFT result of the received signal and the complex multiplication result of the conjugate complex value of the preamble pattern. The preamble signal reception timing is determined in finer units than the time interval input to the FFT using the result of the complex multiplication of the conjugate complex value of the preamble pattern and the result of conjugate complex multiplication between the two subcarriers. The case where it does is demonstrated.

[0038] The transmitter of the present embodiment has a configuration similar to that of the transmitter of the first embodiment described above (see FIG. 1). The receiver has the same configuration as that of the receiver of Embodiment 1 (see FIG. 2), but the detailed configuration of the carrier detection timing determination unit is partially different. Therefore, this embodiment In the above, description of parts other than the carrier detection timing determination unit will be omitted, and only the operation of the timing detection determination unit (in this embodiment, the timing detection determination unit 50a) will be described.

FIG. 4 is a diagram illustrating a configuration example of the carrier detection timing determination unit 50a according to the second embodiment. This carrier detection timing determination unit 50a further adds a (second) complex conjugate 52 and a (second) complex multiplication after the complex multiplier 53 to the carrier detection timing determination unit 50 of the first embodiment. And a phase calculation unit 57 and a timing determination unit 58 are added. Other portions are denoted by the same reference numerals as those of the carrier detection timing determination unit 50, and the description thereof is omitted.

[0040] In the carrier detection timing determination unit 50a having the above-described configuration, the subsequent complex conjugate unit 52 converts a complex conjugate value (Y, Y, ..., Y) other than Y (ie, Y, Y, ..., Y) from the output of the preceding complex multiplier 53. k 1 2 k-1

Y *, Y *, ..., Y *). The downstream complex multiplier 53 is connected to the complex conjugate 52

1 2 k-1

Force (Y *, Y *, ..., Y *) and complex multiplier in the previous stage, except for 53 output Y (ie, Y, Y, ...

1 2 k-1 1 2 3

Y) respectively. The complex summation unit 54 is the summation value Z k of the output of the complex multiplier 53 in the subsequent stage.

Is calculated. Here, assuming that the output of the subsequent complex multiplier 53 is Y ′, the total value Z is given by the following equation (

i- (i-l)

4).

[0041] [Equation 3] z = ∑Y '-(i-i) = ∑. Y = ∑ (x) · (Xi-i · Pi- i = l i = l i = l Γ) *

•••(Four)

Here, the reason why the latter complex conjugate 52 and the latter complex multiplier 53 are added will be described. If the input range when the received preamble signal is input to the FFT unit 32 does not match the output range at the time of generation on the transmission side, the multiplication result of the complex number information X of the preamble signal and the complex conjugate value P * of the preamble pattern When viewed as a vector, Y causes a phase rotation corresponding to the amount of deviation between the output range of the IFFT unit 12 and the input range of the FFT unit 32 during reception and the frequency of each subcarrier. As a result, if Y is complex-added as it is, components that cancel each other out due to the difference in phase will occur. Therefore, Y ′ obtained by further complex multiplication of Y to the complex conjugate value Y * of the adjacent subcarrier is subcarrier

i-1 i iG-1) The vector has a phase rotation amount according to the interval frequency. If the subcarrier interval frequency is constant, it becomes a vector (complex number information) having the same phase between all subcarriers.

The output of the complex summation device 54 is input to the absolute value calculation unit 55 and the phase calculation unit 57. The processing in absolute value calculation unit 55 and carrier detection determination unit 56 is the same as that in the first embodiment described above. However, the threshold for signal detection determination used by carrier detection determination unit 56 is different from that used in the first embodiment. That is, the carrier detection determination unit 56, for example, the type of information to be added when the complex summation unit 54 calculates the summation value (the complex multiplier 52 and the complex multiplier 53 are input to the input X to the carrier detection timing determination unit). The information obtained by modifying the threshold value used in the first embodiment is used in consideration of what kind of processing is executed and adding the information obtained by the processing.

In the first embodiment, the timing at which the input value (the output of the absolute value calculation unit 55) exceeds the threshold in the carrier detection determination 56 is used as the preamble signal detection timing. However, the time waveform input to the FFT unit 32 has a time interval width corresponding to the input range of the FFT unit 32, and timing information beyond this time interval cannot be obtained (detection accuracy cannot be increased). . Therefore, in the present embodiment, in order to obtain more detailed timing, first, the phase calculator 57 obtains the phase of the total value Z using the following equation (5).

[0045] [ ^Equation 4] tan ^_1 (B / A) (if Α> 0)

tan 1 ¹ (Β / Α) + π (if A <0 & B≥0)

ί3η ^_1 (Β / Α)-π (if A <0 & B <0)

•••(Five)

Figure 5 shows the relationship between the preamble signal start position and 0 for the FFT input range.

Z

It is a figure which shows an example. As described above, if the output range of IFFT section 12 at the time of preamble signal generation does not match the input range of FFT section 32 at the time of reception, Y is the input range of FFT section 32.

i- (i-l)

Phase rotation corresponding to the amount of deviation of the surroundings and the subcarrier interval frequency occurs. Therefore, the timing determiner 58 uses the following equation (6) to calculate the deviation ΔΤ between the current received signal input range to the FFT unit 32 and the start position of the preamble, and uses ΔΤ to determine the reception timing.

FFT FFT

Determine. Here, T is a time corresponding to the input range of the FFT unit 32. The phase The calculation unit 57 and the timing determination unit 58 constitute the timing determination means _c [Equation 5]

(If θ _ζ > 0)

2π

^ ^ FFT

FFT

1 FFT + ^ ⁷ X (θ _ζ <0)

2π

••• (6)

[0048] By adjusting the reception timing based on the above ΔΤ, the receiver is more accurate.

FFT

Data can be demodulated at the timing.

[0049] In the present embodiment, Y 'may be obtained between adjacent subcarriers, and the sum value may be used. Y' may be obtained between arbitrary subcarriers. Only some of the subcarriers may be used. However, when Y ′ is obtained between arbitrary subcarriers, the phase of Y ′ is set to a value corresponding to the phase rotation at the frequency interval between one subcarrier according to the frequency interval between the subcarriers. Correction such as calculating the total value 算出 is required.

[0050] Thus, in the present embodiment, the transmission side transmits, as preamble signals, signals that have been assigned a predetermined preamble pattern to a plurality of predetermined frequencies. On the other hand, at the time of receiving the preamble signal, on the other hand, when the preamble signal is received, information is separated for each frequency using the FFT, and the result obtained by multiplying them with the complex conjugate value of the preamble pattern is used. Thus, carrier detection and timing determination are performed by determining the similarity between the received preamble signal and the preamble pattern. As a result, the possibility of erroneous detection can be reduced compared to the case where carrier detection or the like is performed using only power that has been conventionally used.

[0051] Also, the FFT unit 32 and the complex multiplier 53 are circuits that a general OFDM receiver normally includes for data reception, and it is not necessary to perform carrier detection and data demodulation at the same time. The same circuit can be used for carrier detection. That is, the above-described receiver can be realized with a small circuit scale as compared with the conventional carrier detection based on correlation in the time domain.

[0052] Furthermore, the output range of the IFFT unit 12 at the time of preamble signal generation and the FFT unit 32 at the time of reception Pay attention to the phase rotation of the FFT output when the input ranges do not match, and know the timing of the preamplifier signal at which timing within the input range to the FFT unit 32. Can do.

[0053] Embodiment 3.

Next, the signal detection apparatus according to the third embodiment will be described. The above embodiment describes the case where a preamble signal generated from a predetermined known preamble pattern is used without repetition. In this embodiment, the preamble pattern is continuously repeated a plurality of times. The carrier detection and timing determination in the case where the blemble signal generated based on the repetition is used will be described.

The transmitter of the present embodiment has the same configuration as the transmitter of the first embodiment described above (see FIG. 1), and only the preamble signal generation operation is different from the first embodiment. The receiver also has the same configuration as that of the receiver of the first embodiment (see FIG. 2), and only the carrier determination operation is different from that of the first embodiment. The configuration of the carrier detection timing determination unit provided in the receiver may be the same as that in the second embodiment. Hereinafter, the operations of the transmitter and the receiver will be described focusing on the differences from the first embodiment.

[0055] The transmitter differs from the transmitter of Embodiment 1 in that, in the preamble signal transmission operation, a signal is generated by repeatedly repeating the same preamble pattern a plurality of times and transmitted as a preamble signal. The number of preamble pattern repetitions is L. Other operations are the same as those in the first embodiment.

[0056] On the other hand, in the receiver, the carrier detection determination unit 56 does not immediately determine carrier detection when the threshold value is exceeded only once, but based on M (M≤L) consecutive FFT processing results. If the absolute value (or the square value of the absolute value) of Z (the output of the complex summer 54) exceeds the threshold value N times (N≤M), it is determined that the carrier is detected.

[0057] When the configuration of the carrier detection timing determination unit provided in the receiver is the same as that of the receiver described in Embodiment 2, the timing determination unit 58 includes the M consecutive FFT processing results, Average of phase Θ of Z when carrier detection determination unit 56 determines that the threshold value is exceeded

Z

Find the value. Then, when the carrier detection determination unit 56 determines that carrier detection, Θ

Z

ΔΤ is calculated using the average value of and the reception timing is determined. Or timing The determination unit 58 determines the phase of Z when the carrier detection determination unit 56 determines that the threshold value has been exceeded.

Z

From this, ΔΤ is obtained, and the average value of ΔΤ is obtained. The carrier detection determination unit 56

FFT FFT

Determines the carrier timing, the reception timing is determined using the average value of Δ 判定

FFT

Please do it.

As described above, in the present embodiment, the transmitting side uses a signal that is assigned a predetermined preamble pattern to a plurality of predetermined frequencies and continuously transmitted a plurality of times as a preamble signal. To do. On the other hand, at the time of receiving a preamble signal, on the other hand, the information obtained by separating the information for each frequency using the FFT and multiplying it by the complex conjugate value of the preamble pattern is used, as in demodulating data. Thus, carrier detection and timing determination are performed by determining the similarity between the received preamble signal and the preamble pattern multiple times. As a result, compared to the case where carrier detection is performed using only power that has been used in the past, or the case where carrier detection is performed based on the determination result only once shown in the first and second embodiments, the error is detected. The possibility of performing detection can be reduced.

[0059] Also, the FFT unit 32 and the complex multiplier 53 are circuits that a general OFDM receiver normally includes for data reception, and it is not necessary to perform carrier detection and data demodulation at the same time. The same circuit can be used for carrier detection. That is, the above-described receiver can be realized with a small circuit scale as compared with the conventional carrier detection based on correlation in the time domain.

[0060] Furthermore, when the configuration of carrier detection timing determination section 50 is as shown in Fig. 4 (when the configuration of the receiver is the same as that of the receiver of the second embodiment), the IF FT at the time of preamble signal generation Pay attention to the phase rotation of the FFT output when the output range of the unit 12 and the input range of the FFT unit 32 at the time of reception do not match, and the phase deviation amount power between subcarriers Any timing within the time of the input range to the FFT unit 32 It is possible to know whether or not the beginning of the preamble signal has been received.

[0061] Embodiment 4.

Next, the signal detection apparatus according to the fourth embodiment will be described. In Embodiment 3 described above, the preamble signal transmitted by the transmitter continues the preamble pattern a plurality of times. In the present embodiment, the case where the received time waveform is averaged and used to determine the carrier detection is described. To do.

[0062] The transmitter of the present embodiment has the same configuration as that of the transmitter of the first embodiment described above, and only the operation of generating a preamble signal is different from that of the first embodiment. This transmitter is the same as the transmitter of Embodiment 1 in that it generates a signal in which the same preamble pattern is repeated a plurality of times in succession and transmits this as a preamble signal in the preamble signal transmission operation. Different. The number of repetitions of the preamble pattern is L times. Other operations are the same as those in the first embodiment.

FIG. 6 is a diagram illustrating a configuration example of a receiver according to the fourth embodiment. The receiver according to the present embodiment has a configuration in which a time signal averaging unit 35 is added to the receiver according to the first embodiment described above. The other parts are the same as those of the receiver of the first embodiment, so the same reference numerals are given and the description thereof is omitted. Henceforth, the receiver of this Embodiment is described as the receiver 3b.

[0064] The operation of the receiver 3b will be described with reference to FIG. First, when receiving data, the receiver 3b performs the same operation as the receiver 3 of the first embodiment. That is, when there is an input of the received signal 34, the AZD conversion unit 33 converts it into digital time waveform information and inputs the converted received signal to the FFT unit 32. Subsequent operations are the same as those shown in the first embodiment.

[0065] Next, when receiving the preamble signal and performing carrier detection and timing determination, the time signal averaging unit 35 outputs the output of the AZD conversion unit 33 unit every time corresponding to the input range of the FFT unit 32. The previous time waveform (1≤L) is averaged, and the averaged AZD conversion unit 33 unit output is output to the FFT unit 32.

[0066] At time t, time T for the input range of FFT unit 32 obtained from AZD conversion unit 33

FFT

If the digital time waveform information of minutes is expressed as S (t) as shown in the following equation (7), the output S (t) from the time signal averaging unit 35 at time t can be expressed as the following equation (8). it can.

avr

[0067] [Equation 6]

S (t) = {s ₀ (t), _{S l} (t), s ₂ (t), _--- , s _TFFT (t)} • (7)

[0068] [Equation 7]

••• (8)

[0069] The FFT unit 32 converts the averaged time waveform S (t) expressed by the above equation (8) into frequency domain information.

avr

And output to the carrier detection timing determination unit 50. Subsequent operations are the same as those described in the first embodiment.

[0070] Although the present embodiment has been described as a configuration in which the time signal averaging unit 35 is added to the receiver of the first embodiment, the present invention is not limited to this. A configuration in which a time signal averaging unit 35 is added to the receiver of form 2 may be adopted. In carrier detection and timing determination, carrier detection may be performed based on a plurality of determination results as described in the third embodiment.

[0071] Thus, in this embodiment, the transmission side assigns a predetermined preamble pattern to each of a plurality of predetermined frequencies and uses a signal that is continuously transmitted a plurality of times as a preamble signal. To do. On the other hand, in the case of preamble signal reception, after the received time waveform is averaged, the information is separated for each frequency using the FFT as in the case of data demodulation, and the information is separated from the complex conjugate value of the preamble pattern. Carrier detection and timing determination are performed by determining the similarity between the received preamble signal and the preamble pattern using the results obtained by multiplying each. As a result, compared to the case where carrier detection is performed using only power that has been used in the past or the case where carrier detection is performed without averaging the time waveform described in the above-described embodiment, erroneous detection is performed. The possibility of doing it can be reduced.

[0072] Also, the FFT unit 32 and the complex multiplier 53 are circuits that a general OFDM receiver normally includes for data reception, and it is not necessary to perform carrier detection and data demodulation at the same time. The same circuit can be used for carrier detection. In other words, compared with the conventional carrier detection based on correlation in the time domain, the above-described receiver can be realized with a small circuit scale. Can be realized.

[0073] Furthermore, when the configuration of carrier detection timing determination section 50 is as shown in Fig. 4 (when the configuration of the receiver is the same as that of the receiver of the second embodiment), the IF FT at the time of preamble signal generation Pay attention to the phase rotation of the FFT output when the output range of the unit 12 and the input range of the FFT unit 32 at the time of reception do not match, and the phase deviation amount power between subcarriers Any timing within the time of the input range to the FFT unit 32 It is possible to know whether or not the beginning of the preamble signal has been received.

[0074] Embodiment 5.

Next, the signal detection apparatus according to the fifth embodiment will be described. In Embodiment 4 described above, the received time waveform is averaged to determine carrier detection. However, in this embodiment, frequency information after FFT processing is averaged and used to perform keying. A case where determination of carrier detection is performed will be described.

The transmitter of the present embodiment has the same configuration as that of the transmitter of the first embodiment described above, and only the operation for generating a preamble signal is different from that of the first embodiment. This transmitter is the same as the transmitter of Embodiment 1 in that it generates a signal in which the same preamble pattern is repeated a plurality of times in succession and transmits this as a preamble signal in the preamble signal transmission operation. Different. The number of repetitions of the preamble pattern is L times. Other operations are the same as those in the first embodiment.

[0076] FIG. 7 is a diagram illustrating a configuration example of a receiver in the fifth embodiment. The receiver of the present embodiment has a configuration in which a frequency information averaging unit 36 is added to the receiver of the first embodiment described above. The other parts are the same as those of the receiver of the first embodiment, so the same reference numerals are given and the description thereof is omitted. Henceforth, the receiver of this Embodiment is described as the receiver 3c.

[0077] The operation of the receiver 3c will be described with reference to FIG. First, when receiving data, the receiver 3c performs the same operation as the receiver 3 of the first embodiment.

Next, when receiving a preamble signal and performing carrier detection and timing determination, complex data for each subcarrier, which is an output from the FFT unit 32, is input to the frequency information averaging unit 36. The frequency information averaging unit 36 has a frequency for the output range of the FFT unit 32. The frequency information (complex data) of the immediately preceding (1≤L) is averaged for each band, and the averaged frequency information is output to the carrier detection timing determination unit 50.

[0079] The frequency band F for the output range of FFT unit 32 obtained from FFT unit 32 at time t

FFT

When the frequency information is expressed as D (t) as shown in the following equation (9), the output D (t) from the FFT unit 32 at time t can be expressed as the following equation (10).

avr

[0080] [Equation 8]

D (t)-(d ₀ (t), d, (t), d ₂ (t),-, d _FFFi (t)

••• (9)

[0081] [Equation 9]

1-1 1—】 1-1 1—1

Xd ₀ (t-iF _FFT ) — iF _FFr ) _J d ₂ (t-iF _FFT ) ∑α _Ρρρτ (t-iF _FFT ) i-0 i = 0 i-0 i = 0

D _avr (t):

••• do)

The carrier detection timing determination unit 50 performs carrier detection and timing determination based on the averaged frequency information D (t) expressed by the above equation (10). Carrier detection motion avr

The operation and timing determination operation are the same as those shown in the first embodiment.

In the present embodiment, the frequency information averaging unit 36 is added to the receiver of the first embodiment. However, the present invention is not limited to this, and the reception of the second embodiment is performed. A frequency information averaging unit 36 may be added to the machine. Also, when performing carrier detection and timing determination, carrier detection or the like may be performed based on a plurality of determination results as described in the third embodiment.

[0084] Thus, in the present embodiment, the transmission side assigns a predetermined preamble pattern to each of a plurality of predetermined frequencies and uses a signal that is continuously transmitted a plurality of times as a preamble signal. To do. On the other hand, in the case of preamble signal reception, information is separated for each frequency using an FFT, the information after separation is averaged, and the averaged information is multiplied by the complex conjugate value of the preamble pattern. Using the results obtained in this way, the received preamble signal and preamble pattern Carrier detection and timing determination are performed by determining similarity. As a result, compared to the case where carrier detection is performed using only power that has been used in the past or the case where carrier detection is performed without averaging frequency information as described in the above-described embodiment, erroneous detection is performed. The possibility of doing it can be reduced.

Further, the FFT unit 32 is a complex multiplier 53, which is a circuit normally provided for data reception by a general OFDM receiver, and it is not necessary to perform carrier detection and data demodulation at the same time. The same circuit can be used for carrier detection. That is, the above-described receiver can be realized with a small circuit scale as compared with the conventional carrier detection based on correlation in the time domain.

[0086] Furthermore, when the configuration of carrier detection timing determination section 50 is as shown in Fig. 4 (when the configuration of the receiver is the same as that of the receiver of the second embodiment), the IF FT at the time of preamble signal generation Pay attention to the phase rotation of the FFT output when the output range of the unit 12 and the input range of the FFT unit 32 at the time of reception do not match, and the phase deviation amount power between subcarriers Any timing within the time of the input range to the FFT unit 32 It is possible to know whether or not the beginning of the preamble signal has been received.

[0087] Embodiment 6.

Next, the signal detection apparatus according to the sixth embodiment will be described. In Embodiments 4 and 5 described above, the received time waveform and the frequency information after FFT are averaged to determine carrier detection. In this embodiment, immediately before carrier detection and A case will be described in which information immediately before timing determination is averaged and carrier detection and timing determination are performed using the averaged information.

The transmitter of the present embodiment has the same configuration as that of the transmitter of the first embodiment described above, and only the preamble signal generation operation is different from that of the first embodiment. This transmitter is the same as the transmitter of Embodiment 1 in that it generates a signal in which the same preamble pattern is repeated a plurality of times in succession and transmits this as a preamble signal in the preamble signal transmission operation. Different. The number of repetitions of the preamble pattern is L times. Other operations are the same as those in the first embodiment.

[0089] The configuration of the receiver is the same as that of the receiver of Embodiment 1, but the carrier detection timing is The detailed configuration of the ring determination unit is partially different. For this reason, in the present embodiment, description of parts other than the carrier detection timing determination unit will be omitted, and only the operation of the timing detection determination unit will be described.

FIG. 8 is a diagram illustrating a configuration example of the carrier detection timing determination unit according to the sixth embodiment. Compared to the carrier detection timing determination unit 50 (see FIG. 3) described in the first embodiment, FIG. A time averaging unit 59 is added to average the information immediately before detection. In the description of operations to be described later, the carrier detection timing determination unit having this configuration is referred to as a carrier detection timing determination unit 50d. Further, portions other than the time averaging unit 59 are denoted by the same reference numerals as those of the carrier detection timing determination unit 50, and description thereof is omitted.

[0091] FIG. 9 is a diagram illustrating another configuration example of the carrier detection timing determination unit according to the sixth embodiment. FIG. 9 illustrates the carrier detection timing determination unit 50a according to the second embodiment (see FIG. 4). Thus, a time averaging unit 59 for averaging information immediately before carrier detection is added. In the description of operations to be described later, the carrier detection timing determination unit having this configuration is referred to as a carrier detection timing determination unit 50e. Further, portions other than the time averaging unit 59 are denoted by the same reference numerals as those of the carrier detection timing determination unit 50, and description thereof is omitted.

[0092] Even if the carrier detection timing determination units 50d and 50e are shifted, the time averaging unit 59 corresponding to the addition result averaging unit outputs the output of the complex summation unit 54 once (1≤L ) Minute frequency information is averaged and output. If the total value obtained at time t is Z (t) and the time for the input range of the FFT unit 32 is T, the time averaging unit 59 at time t

FFT

The output information Z (t) can be expressed by the following equation (11).

avr

[0093] [Equation 10]

Z _avr (t Z (t-iT _FFT )

i = 0

••• (11)

[0094] In both carrier detection timing determination units 50d and 50e, absolute value calculation unit 55 and phase calculation unit 57 show the above-described embodiment 1 or 2 based on the output from time averaging unit 59. Execute the process. And carrier detection unit 56, Taimin Based on the output from the absolute value calculation unit 55 and the output from the phase calculation unit 57, the determination unit 58 executes the process shown in the first or second embodiment described above, respectively. .

[0095] In the present embodiment, the power of adding time averaging section 59 to the carrier detection timing determining section provided in the receiver of Embodiment 1 or 2 is not limited to this. A time averaging unit 59 may be added to the carrier detection timing determination unit that performs the operation shown in form 3.

[0096] As described above, in the present embodiment, the transmitting side assigns a predetermined preamble pattern to each of a plurality of predetermined frequencies, and uses a signal that is continuously transmitted a plurality of times as a preamble signal. To do. On the other hand, in the case of preamble signal reception, information used for carrier detection and timing detection is time-averaged, and the results are used to perform carrier detection and timing determination. As a result, the carrier detection is performed without averaging the information used for carrier detection and timing detection shown in the above-described embodiment when carrier detection is performed using only power that has been conventionally used. The possibility of erroneous detection can be reduced compared to the case where detection or the like is performed.

[0097] Further, the FFT unit 32 is a complex multiplier 53, which is a circuit that is generally provided for data reception by a general OFDM receiver, and it is not necessary to perform carrier detection and data demodulation at the same time. The same circuit can be used for carrier detection. That is, the above-described receiver can be realized with a small circuit scale as compared with the conventional carrier detection based on correlation in the time domain.

[0098] Furthermore, in a receiver equipped with carrier detection timing determination unit 50e, the phase rotation of the FFT output when the output range of IFFT unit 12 at the time of preamble signal generation and the input range of FFT unit 32 at the time of reception do not match With regard to the power of phase deviation between subcarriers, it is possible to know the key that received the beginning of the preamble signal at any timing within the input range to the FFT unit 32.

Industrial applicability

[0099] As described above, the signal detection apparatus according to the present invention is useful for a communication system, and in particular, based on a known signal, a desired signal and symbol timing can be increased with a small circuit scale. It is suitable for a receiver provided in a communication device that detects accurately.

Claims

The scope of the claims

[1] A signal detection device for detecting a desired signal modulated by an OFDM (Orthogonal Frequency Division Multiplexing) method from received signals,

A signal conversion means for converting the received signal into frequency domain information (first frequency domain signal) for each carrier;

Known to generate frequency domain information (second frequency domain information) for each carrier on the basis of a signal in which signals of a plurality of carriers that include predetermined known information and have different frequencies and initial phases are multiplexed. Frequency information generating means;

Complex conjugate generating means for generating for each carrier a complex conjugate of the second frequency domain information output from the known frequency information generating means;

Multiplication means for multiplying the first frequency domain signal for each carrier by the complex conjugate for each carrier generated by the complex conjugate generation means in the same frequency domain, and a part of the multiplication output by the multiplication means Alternatively, an addition means for adding all together, and an absolute value of the addition result or a square value of the addition result are calculated, and detection determination of a desired signal is performed using the calculation result and a predetermined threshold value defined in advance. Signal detection means for performing

A signal detection apparatus comprising:

[2] The multiplication means includes

Two or more multiplication results are selected from the multiplication results, and complex conjugates of the selected multiplication results are generated. The multiplications in the frequency domain separated by a fixed interval are generated for the generated complex conjugates. Multiply each result,

The signal detection apparatus according to claim 1, wherein the adding means adds a part or all of the multiplication results.

[3] In addition,

A timing determination unit that calculates a phase of the addition result when the signal detection unit detects a desired signal, and determines an accurate reception timing of the desired signal based on the obtained phase;

The signal detection device according to claim 2, further comprising:

[4] When the predetermined known information is a repetition of a bit string of a specific pattern,

The signal detection means executes the detection determination process of the desired signal a plurality of times within a range not exceeding the number of repetitions of the bit string, and finally determines whether or not the desired signal is detected based on the execution result of the plurality of times. 4. The signal detection apparatus according to claim 1, 2 or 3, wherein the determination is performed on an as-needed basis.

[5] The signal detection means may determine that the desired signal is finally detected when the number of times of detection of the desired signal is equal to or greater than a predetermined number in the execution result of the plurality of times. 4. The signal detection device according to 4.

[6] In addition,

When the predetermined known information is a repetition of a bit string of a specific pattern, a received signal in a time domain is acquired a plurality of times within a range not exceeding the number of repetitions of the bit string for each section on which the bit string is placed, Time signal averaging means for averaging the acquired signals;

With

4. The signal detection device according to claim 1, wherein the signal conversion unit converts the output of the time signal averaging unit into frequency domain information.

[7] In addition,

When the predetermined known information is a repetition of a bit string of a specific pattern, each output of the signal conversion means is acquired a plurality of times within a range not exceeding the number of repetitions of the bit string, and the acquired output is obtained. Frequency information averaging means for averaging for each carrier,

The multiplication means uses the averaged output for each carrier of the frequency information averaging means instead of the signal conversion output, and each of the averaged outputs and the complex for each carrier generated by the complex conjugate generating means. 4. The signal detection device according to claim 1, wherein the conjugate is multiplied by the same frequency region.

[8] In addition,

When the predetermined known information is a repetition of a bit string of a specific pattern, the addition output of the addition means is taken multiple times within a range not exceeding the number of repetitions of the bit string. Addition result averaging means for averaging the obtained addition outputs,

With

The signal detecting means calculates an absolute value of the averaged result in the addition result averaging means or a square value of the averaged result, and uses the calculated result and the threshold and the value of the desired signal. 3. The signal detection device according to claim 1, wherein detection determination is performed.

[9] In addition,

When the predetermined known information is a repetition of a bit string of a specific pattern, the addition output of the addition means is obtained a plurality of times within a range not exceeding the number of repetitions of the bit string, and the obtained addition output is averaged. Addition result averaging means,

With

The signal detecting means calculates an absolute value of the averaged result in the addition result averaging means or a square value of the averaged result, and uses the calculated result and the threshold and the value of the desired signal. Make a detection decision,

4. The timing determination unit according to claim 3, wherein the phase of the averaging result in the addition result averaging unit is calculated, and an accurate reception timing of the desired signal is determined based on the obtained phase. The signal detection apparatus as described.

[10] Based on the predetermined threshold !, the value based on the bit pattern forming the predetermined known information, the contents of the processing executed by the multiplication means, and the number of multiplication outputs to be added by the addition means The signal detection device according to claim 1, wherein the signal detection device is determined.