JP4685937B2 - Signal detection device - Google Patents

Description

  The present invention relates to a signal detection apparatus that detects a desired signal in a receiver that constitutes a communication apparatus, and more particularly to a signal detection apparatus that detects a desired signal and a symbol timing using a known signal. Is.

  In a communication system using a CSMA (Carrier Sense Multiple Access) method, a known signal waveform is added before a signal for sending data, and the communication apparatus belonging to the communication system transmits the known signal waveform on the transmission path. Whether or not it exists is constantly monitored. When the communication device detects the presence of a known signal waveform, it does not perform transmission even if there is transmission data, and performs a reception operation. Also, in the case of a communication system using a TDMA (Time Division Multiple Access) system, the base station periodically transmits a known signal waveform so that the terminal can synchronize with the period and timing that are the basis of time division, and the terminal May synchronize by detecting this known signal waveform. Such a known signal waveform is called a preamble or the like, and an operation for detecting whether or not a signal of a communication system of its own device is present on a transmission path may be called carrier detection or carrier sense.

  In conventional carrier detection, a communication device simply measures received signal strength (RSSI) and determines the presence or absence of a signal 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 exists, and if the RSSI measurement value is smaller than the threshold value, Judged that there was no signal.

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

  Furthermore, in a communication system using OFDM (Orthogonal Frequency Division Multiplexing) as a modulation method, a time waveform in which different information is placed on a plurality of frequencies is generated on the transmission side using an inverse fast Fourier transform (IFFT). On the receiving side, processing for separating information of individual frequencies is performed by Fast Fourier Transform (FFT). This IFFT / FFT processing unit is called a symbol or the like, and in the FFT processing at the time of reception, it is necessary to cut out a received signal using an appropriate symbol timing and make it an FFT input. A preamble signal is also used to detect this symbol timing, and the reception side obtains the correlation value of the received waveform in the same manner as the carrier detection described above, and detects the symbol timing based on the timing of the peak position where the correlation value is maximum. (For example, Non-Patent Document 1).

JP 2005-295085 A (page 3-6, FIG. 1) Supervised by Masahiro Moriya and Shuji Kubota “Revised 802.11 High-Speed Wireless LAN Textbook”, Impress Inc., January 1, 2005, P206-212

  However, since the detection determination based on the conventional RSSI is detection based only on power, even if it is power such as a signal or noise of another system, if it exceeds a threshold value, it will be determined as carrier detection. That is, there is a problem that the possibility of erroneous detection is high.

  There are two methods of using correlation values: autocorrelation and cross-correlation. In autocorrelation, the product of repeated transmission is integrated with the signal delayed by the repetition period. Thus, the correlation value is obtained. On the other hand, in cross-correlation, the correlation value is obtained by integrating the multiplication result of each sample of the known preamble signal waveform and the received waveform. In general, only one multiplication circuit is required for autocorrelation, but only a gentle peak is obtained, and the timing detection accuracy is inferior to that of cross-correlation. The cross-correlation requires a multiplication circuit as many as the number of samples for which the correlation is obtained. For both autocorrelation and cross-correlation, integration requires an adder circuit that calculates the sum of the multiplication results for the number of samples. In either case, the longer the period for calculating the correlation value, the higher the detection accuracy. There is a problem that the circuit scale increases.

  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.

In order to solve the above-described problems and achieve the object, a signal detection device according to the present invention is a signal detection device for detecting a desired signal modulated by an OFDM (Orthogonal Frequency Division Multiplexing) method from received signals. 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 are multiplexed. Based on the received signal, known frequency information generating means for generating frequency domain information (second frequency domain information) for each carrier, and complex conjugate of the second frequency domain information output from the known frequency information generating means For each carrier, a first frequency domain signal for each carrier, and a carrier for each carrier generated by the complex conjugate generator. Multiplying means for multiplying prime conjugates in the same frequency domain, adding means for adding a part or all of the multiplication output by the multiplying means, and the absolute value of the addition result or the square value of the addition result And a signal detection means for performing detection determination of a desired signal using the calculation result and a predetermined threshold value defined in advance, and the multiplication means includes at least two of the multiplication results Selecting a multiplication result, generating a complex conjugate of the selected multiplication result, multiplying each of the generated complex conjugates by the multiplication result in a frequency domain separated by a fixed interval, and the adding means, A part or all of the multiplication results are added to calculate a final addition result, and the signal detection unit uses the final addition result to perform detection determination processing of the desired signal, and , The signal When the detection means detects the desired signal, the Rukoto a timing judging means judges correct reception timing of the desired signal based on the calculated final addition result of the phase, the obtained phase Features.

  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 the known preamble pattern is received. Since carrier detection and timing determination are performed by determining the similarity between the preamble signal and the preamble pattern, the frequency of erroneous detection compared to the case where carrier detection or the like is performed using only power that has been conventionally used. And the carrier detection accuracy can be increased.

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 the first embodiment of the communication device (receiver) including the signal detection device according to the present invention. FIG. 3 is a diagram illustrating a configuration example of the carrier detection timing determination unit of the first embodiment. FIG. 4 is a diagram illustrating a configuration example of a carrier detection timing determination unit according to the second embodiment. FIG. 5 is a diagram illustrating an example of the relationship between the preamble signal head position and θ _Z with respect to the FFT input range. 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 the carrier detection timing determination unit of 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

DESCRIPTION OF SYMBOLS 1 Transmitter 2 Transmission path 3, 3b, 3c Receiver 10 Transmission information 11 Modulation part 12 IFFT part 13 Digital / analog conversion part (D / A)
14 Transmission signal 30 Reception information 31 Demodulation unit 32 FFT unit 33 Analog / digital conversion unit (A / D)
34 reception signal 35 time signal averaging unit 36 frequency information averaging unit 40 preamble generation unit 50, 50a, 50d, 50e carrier detection timing determination unit 51 preamble pattern generation unit 52 complex conjugate unit 53 complex multiplier 54 complex summation unit 55 absolute Value calculation unit 56 Carrier detection determination unit 57 Phase calculation unit 58 Timing determination unit 59 Time averaging unit

  Embodiments of a signal detection apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a communication apparatus (transmitter) that transmits data by performing OFDM modulation on a communication apparatus including a signal detection apparatus according to the present invention. Reference numeral 1 denotes a transmitter. This transmitter 1 receives transmission information 10 consisting of a bit sequence, outputs a modulation result, a modulation unit 11, an IFFT unit 12 that converts the output of the modulation unit 11 from a frequency domain to a time domain, and an IFFT unit 12. A digital / analog conversion unit (D / A) 13 that converts the output of the signal into an analog format and a known preamble (hereinafter referred to as a preamble) for performing carrier detection and timing determination, which are the original preambles A preamble generation unit 40 that generates a pattern is provided. Reference numeral 14 denotes an analog converted transmission signal, and reference numeral 2 denotes a transmission path.

  FIG. 2 is a diagram illustrating a configuration example of the first embodiment of the communication device (receiver) including the signal detection device according to the present invention, and 3 represents the receiver. The receiver 3 includes an analog / digital conversion unit (A / D) 33 that converts a received signal 34 from a transmission side into a digital format, and an FFT that converts an output of the A / D conversion unit 33 from a time domain to a frequency domain. Unit 32, demodulator 31 that demodulates the output of FFT unit 32 to generate reception information 30 including a bit string, carrier detection timing determination unit 50 that performs carrier detection and timing detection based on the output of FFT unit 32, and . Reference numeral 2 denotes the same transmission path as that 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 the signal to generate the reception signal 30 (restoring the transmission information 10). ) Explain the operation.

  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 generating unit 40 generates a predetermined known preamble pattern. This preamble pattern is a pseudo-random pattern composed of bit sequences of '0' and '1', for example, called an M sequence. The generated preamble pattern is input to the modulation unit 11, and the modulation unit 11, for example, according to a modulation method such as BPSK (Binary Phase Shift Keying), QPSK (Quadrate Phase Shift Keying), or QAM (Quadrate Amplitude Modulation) The input preamble pattern (bit sequence) is divided for each subcarrier, and further mapped on the complex plane. For example, if the preamble pattern is to be BPSK modulated, the bit string input from the preamble generation unit 40 is divided by 1 bit, and is “−1 + 0j” if it is “0”, and “1 + 0j” if it is “1”. Thus, it is converted into complex data representing two points on the complex plane.

  The complex data generated by the modulation unit 11 is input to the IFFT 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 / analog converter (hereinafter referred to as a D / A converter) 13 and sent to the transmission line 2 as a transmission signal 14.

  The preamble pattern may be assigned to all subcarriers or may be assigned using only some subcarriers.

  Further, when transmitting the transmission information 10, the only difference is that 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 D / A conversion unit 13 are the same as the operations during the 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.

  As a method of realizing the preamble generation unit 40, if a pseudo-random sequence such as an M sequence is used, a preamble pattern is generated using a shift register and an XOR operation circuit, or a preamble pattern is stored in advance as a memory. There are methods. Further, 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 D / A conversion unit 13.

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

  The preamble signal reception process is the same as the data reception process until the FFT unit 32 performs an operation for converting the input of the A / D conversion unit 33 from the time domain to the 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.

  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 converts a complex number into a complex conjugate value, and a preamble pattern generation unit 51 that generates frequency information for each subcarrier of the same known signal (preamble signal) transmitted from the transmitter 1. A complex conjugate 52, a complex multiplier 53, a complex summation unit 54 that calculates the sum of a plurality of complex numbers, an absolute value calculation unit 55 that calculates the absolute value of the complex number, and an absolute value of the calculated complex number in advance A carrier detection determination unit that determines that a carrier has been detected when the absolute value is equal to or greater than the threshold value compared to a predetermined threshold value.

The complex number information for each subcarrier input from the FFT unit 32 to the carrier detection timing detection unit 50 is assumed to be X _i (i is a subcarrier number). In the carrier detection timing detection unit 50, a preamble pattern generation unit 51 corresponding to a known frequency information generation unit generates complex number information P _i (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 _i ^* . Thereafter, the complex multiplier 53 corresponding to the multiplication means multiplies the above P _i ^* by the complex number information X _i of the received signal to obtain Y _i . Further, the total sum Z of Y _i is calculated by the complex summation device 54 corresponding to the adding means. Z thus obtained can be expressed by the following formula (1).

・・・（１）

... (1)

  Then, the absolute value calculation unit 55 obtains 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 thereof is expressed by the following equation (2).

・・・（２）

... (2)

Further, instead of the absolute value (corresponding to the amplitude) shown in the above equation (2), the absolute value calculating unit 55 calculates the square value (corresponding to the electric power) of the total value Z as shown in the following equation (3). For example, the carrier detection determination unit 56 may perform carrier detection using the square value of the total value Z.
Z ² = A ² + B ² (3)

Also, instead of using the sum values (the sum of all the multiplication result Y _i) for all subcarriers, those selected portion from the added value (multiplication result Y _i for only some of the subcarriers It is also possible to calculate the added value) for the above and perform the subsequent processing 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 _i of the received signal by the complex conjugate value P _i ^* of the preamble pattern, if the received signal is a preamble signal, the multiplication result Y _i becomes “1 + 0j” in any subcarrier, and the total value thereof is “K + 0j”, the absolute value of the total value is k. On the other hand, if the received signal is a signal different from the preamble signal, Y _i has a different value for each subcarrier, and the absolute value of the total value is smaller than k. If a pseudo-random pattern such as an M-sequence is used as a preamble pattern, the larger the number of subcarriers, the closer the absolute value of the sum value when a signal other than the preamble signal is received approaches 0 (zero).

  In an actual environment where communication is performed, the amplitude and phase change depending on the transmission path characteristics, so even if a preamble signal is received, the absolute value is not always k, but the sum of a plurality of subcarriers is taken. As a result, 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 value for signal detection determination in consideration of transmission path characteristics and the like. Can be detected. The case where the preamble pattern is BPSK-modulated has been described as an example, but the same applies when another modulation scheme is used.

The threshold value for signal detection determination is determined based on the relationship between the absolute value of the total value when the preamble signal is received and the absolute value of the total value when other than the preamble signal is received. For example, the bit pattern used as the preamble pattern, the comparison target at the time of carrier detection determination (whether the absolute value of the total value or the square value of the absolute value is used as the target to be compared with the threshold value), The type of information to be added when calculating the total value (what kind of processing is performed on the input X _i to be input to the carrier detection timing determination unit), and when calculating the total value This is determined in consideration of the number to be added (number of information to be added). It should be noted that an optimal threshold may be selected and used as appropriate according to the transmission path characteristics from among a plurality of thresholds determined in advance in consideration of the transmission path characteristics. The previously set threshold value may be used while being adjusted as appropriate according to the transmission path characteristics.

  As described above, in the present embodiment, the transmission side transmits, as a preamble signal, a predetermined preamble pattern assigned to a plurality of predetermined frequencies. On the other hand, at the time of reception of the preamble signal, on the receiving side, as in the case of data demodulation, information is separated for each frequency using the FFT, and the result obtained by multiplying each by the complex conjugate value of the preamble pattern is used. The carrier detection and the timing determination are performed by determining the similarity between the received preamble signal and the preamble pattern. Thereby, compared with the case where carrier detection etc. are performed only with the electric power used conventionally, possibility of performing an erroneous detection can be made small.

  The FFT unit 32 and the complex multiplier 53 are circuits that are 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. It can be used for carrier detection. In other words, 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.

Embodiment 2. FIG.
Next, the signal detection apparatus according to the second embodiment will be described. In Embodiment 1 described above, carrier detection is determined 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, but in this embodiment, When the preamble signal reception timing is determined in a unit smaller 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 conjugate complex multiplication between two subcarriers. Will be described.

  The transmitter according to the present embodiment has the same configuration (see FIG. 1) as the transmitter according to the first embodiment described above. 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. For this reason, in the present embodiment, description of portions other than the carrier detection timing determination unit is omitted, and only the operation of the timing detection determination unit (in this embodiment, the timing detection determination unit 50a) is described. Do.

  FIG. 4 is a diagram illustrating a configuration example of the carrier detection timing determination unit 50a according to the second embodiment. The carrier detection timing determination unit 50a further includes a (second) complex conjugate 52 and a (second) complex multiplier after the complex multiplier 53 with respect 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 description thereof is omitted.

In the carrier detection timing determination unit 50a having the above-described configuration, the subsequent complex conjugate unit 52 uses a complex conjugate value other than Y _k (that is, Y ₁ , Y ₂ ,..., Y _k−1 ) output from the preceding complex multiplier 53. (Y ₁ ^* , Y ₂ ^* ,..., Y _k-1 ^* ). The rear stage complex multiplier 53 includes outputs from the rear stage complex conjugater 52 (Y ₁ ^* , Y ₂ ^* ,..., Y _k-1 ^* ) and Y ₁ other than the output from the front stage complex multiplier 53 (ie, Y ₂ , Y ₃ ,..., Y _k ). The complex summation unit 54 calculates the summation value Z of the output of the subsequent complex multiplier 53. Here, when the output of the complex multiplier 53 at the subsequent stage is Y ′ _{i− (i−1)} , the total value Z can be expressed by the following equation (4).

・・・（４）

... (4)

Here, the reason why the latter complex conjugate 52 and the latter complex multiplier 53 are added will be described. When 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 Y of the complex number information X _i of the preamble signal and the complex conjugate value P _i ^* of the preamble pattern _When viewed as a vector, _i 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 each Y _i is complex-added as it is, components that cancel each other out due to the difference in phase are generated. Therefore, Y ^′ _{i− (i−1)} obtained by further complex-multiplying Y _i to the complex conjugate value Y _i−1 ^{* of} the adjacent subcarrier has a phase rotation amount corresponding to the subcarrier interval frequency. If it is a vector and the subcarrier interval frequency is constant, it becomes a vector (complex number information) having the same phase between any 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. However, the threshold value for signal detection determination used by the 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 total value (the complex conjugate 52 and the complex multiplier 53 correspond to the input X _i 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 performed and adding the information obtained by the processing.

  In the first embodiment, in the carrier detection determination 56, the time when the input value (the output of the absolute value calculation unit 55) exceeds the threshold value is set 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, the phase calculator 57 first obtains the phase of the total value Z using the following equation (5).

・・・（５）

... (5)

FIG. 5 is a diagram illustrating an example of the relationship between the preamble signal head position and θ _Z with respect to the FFT input range. As described above, when the output range of the IFFT unit 12 at the time of preamble signal generation and the input range of the FFT unit 32 at the time of reception do not match, Y ^′ _{i− (i−1)} is the amount of deviation of the input range of the FFT unit 32. And phase rotation corresponding to the subcarrier interval frequency. Therefore, the timing determiner 58 calculates the amount of deviation ΔT _FFT between the current received signal input range to the FFT unit 32 and the preamble start position using the following equation (6), and uses ΔT _FFT to determine the reception timing. judge. Here, T _FFT is a time corresponding to the input range of the FFT unit 32. The phase calculation unit 57 and the timing determination unit 58 constitute a timing determination unit.

・・・（６）

... (6)

By adjusting the reception timing based on the ΔT _FFT , the receiver can demodulate data at a more accurate timing.

  In the present embodiment, Y ′ is obtained between adjacent subcarriers and the total value thereof is used, but Y ′ may be obtained between arbitrary subcarriers. Further, only some of the subcarriers may be used. However, when obtaining Y ′ between arbitrary subcarriers, the sum value is obtained by setting the phase of Y ′ as a value corresponding to the phase rotation at the frequency interval between one subcarrier according to the frequency interval between the subcarriers. Corrections such as calculating Z are necessary.

  As described above, in the present embodiment, the transmission side transmits, as a preamble signal, a predetermined preamble pattern assigned to a plurality of predetermined frequencies. On the other hand, at the time of reception of the preamble signal, on the receiving side, as in the case of data demodulation, information is separated for each frequency using the FFT, and the result obtained by multiplying each by the complex conjugate value of the preamble pattern is used. The carrier detection and the timing determination are performed by determining the similarity between the received preamble signal and the preamble pattern. Thereby, compared with the case where carrier detection etc. are performed only with the electric power used conventionally, possibility of performing an erroneous detection can be made small.

  The FFT unit 32 and the complex multiplier 53 are circuits that are 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. It can be used for carrier detection. In other words, 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.

  Furthermore, paying attention to the phase rotation of the FFT output when the output range of the IFFT unit 12 at the time of preamble signal generation does not match the input range of the FFT unit 32 at the time of reception, the phase deviation amount between the subcarriers to the FFT unit 32 It is possible to know at which timing within the time of the input range the head of the preamble signal has been received.

Embodiment 3 FIG.
Next, the signal detection apparatus according to the third embodiment will be described. In the above embodiment, the case where a preamble signal generated from a predetermined known preamble pattern without repetition is used is described. In the present embodiment, the preamble pattern is continuously generated a plurality of times. Carrier detection and timing determination when using a preamble signal generated based on repetitions will be described.

  The transmitter of the present embodiment has the same configuration as that of the transmitter of the first embodiment (see FIG. 1), and only the preamble signal generation operation is different from that of 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 with a focus on differences from the first embodiment.

  The transmitter differs from the transmitter of the first embodiment 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. Note that the number of repetitions of the preamble pattern is L. Other operations are the same as those in the first embodiment.

  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 instead of Z (M ≦ L) consecutive FFT processing results. The carrier detection is determined when the absolute value (or the square value of the absolute value) of the complex summation device 54 exceeds the threshold value N times (N ≦ M).

In addition, when the structure of the carrier detection timing determination part with which a receiver is provided is the same as that of the receiver shown in Embodiment 2, the timing determination part 58 is a carrier detection determination part among M continuous FFT process results. The average value of the _Z phase θ _Z when it is determined that 56 exceeds the threshold value is obtained. When the carrier detection determination unit 56 determines carrier detection, ΔT _FFT is calculated using the average value of θ _Z and the reception timing is determined. Alternatively, the timing determination unit 58 calculates ΔT _FFT from the Z phase θ _Z when the carrier detection determination unit 56 determines that the threshold value has been exceeded, and further calculates the average value of ΔT _FFT . And when the carrier detection determination part 56 determines with carrier detection, you may make it determine a reception timing using the average value of (DELTA) _TFFT .

  As described above, in the present embodiment, the transmission side assigns a predetermined preamble pattern to each of a plurality of predetermined frequencies and uses the result of continuous transmission a plurality of times as a preamble signal. On the other hand, at the time of receiving a preamble signal, on the receiving side, information is separated for each frequency by using FFT similarly to data demodulation, and using the result obtained by multiplying them by 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 a plurality of times. As a result, compared to the case where carrier detection is performed using only power used in the past or the case where carrier detection or the like is performed based on the determination result only once shown in the first and second embodiments, erroneous detection is performed. The possibility of doing it can be reduced.

  The FFT unit 32 and the complex multiplier 53 are circuits that are 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. It can be used for carrier detection. In other words, 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.

  Further, when the configuration of carrier detection timing determination unit 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 output of IFFT unit 12 at the time of preamble signal generation Paying attention to the phase rotation of the FFT output when the input range does not match the input range of the FFT unit 32 at the time of reception, at any timing within the time of the input range to the FFT unit 32 from the phase deviation amount between the subcarriers You can know if you have received the head.

Embodiment 4 FIG.
Next, the signal detection apparatus according to the fourth embodiment will be described. In the third embodiment described above, carrier detection and timing determination in the case where the preamble signal transmitted by the transmitter is generated based on a preamble pattern that is repeatedly repeated a plurality of times have been described. In this embodiment, Describes a case where the received time waveform is averaged and carrier detection is determined using the averaged time waveform.

  The transmitter according to the present embodiment has the same configuration as the transmitter according to the first embodiment described above, and only the preamble signal generation operation is different from that of the first embodiment. This transmitter is different from the transmitter according to the first embodiment in that in the operation of transmitting a preamble signal, a signal in which the same preamble pattern is continuously repeated a plurality of times is generated and transmitted as a preamble signal. Note that the number of repetitions of the preamble pattern is L. 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. Since other parts are the same as those of the receiver of the first embodiment, the same reference numerals are given and description thereof is omitted. Henceforth, the receiver of this Embodiment is described as the receiver 3b.

  The operation of the receiver 3b will be described based on FIG. First, when receiving data, the receiver 3b performs the same operation as the receiver 3 of the first embodiment. That is, when the received signal 34 is input, the A / D converter 33 converts it into digital time waveform information, and inputs the converted received signal to the FFT unit 32. The subsequent operations are the same as those shown in the first embodiment.

  Next, when receiving the preamble signal and performing carrier detection and timing determination, the time signal averaging unit 35 immediately precedes the output of the A / D conversion unit 33 for every time corresponding to the input range of the FFT unit 32. 1 times (l ≦ L) are averaged, and the A / D conversion unit 33 output after the averaging is output to the FFT unit 32.

When digital time waveform information corresponding to the time T _{FFT for} the input range of the FFT unit 32 obtained from the A / D conversion unit 33 at time t is expressed as S (t) as in the following equation (7), at time t: The output S _avr (t) from the time signal averaging unit 35 can be expressed by the following equation (8).

・・・（７）

... (7)

・・・（８）

... (8)

The FFT unit 32 converts the _averaged time waveform S _avr (t) expressed by the above equation (8) into frequency domain information and outputs the frequency domain information to the carrier detection timing determination unit 50. The subsequent operations are the same as those shown in the first embodiment.

  In the present embodiment, the time signal averaging unit 35 is added to the receiver of the first embodiment. However, the present invention is not limited to this, and the receiver of the second embodiment is used. The time signal averaging unit 35 may be added. In 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.

  As described above, in the present embodiment, the transmission side assigns a predetermined preamble pattern to each of a plurality of predetermined frequencies and uses the result of continuous transmission a plurality of times as a preamble signal. On the other hand, in the case of preamble signal reception, after the received time waveform is averaged, information is separated for each frequency using FFT in the same manner as in 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 result obtained by the multiplication. As a result, erroneous detection is performed as compared with the case where carrier detection is performed using only power that has been used in the past, or the case where carrier detection or the like is performed without averaging time waveforms as described in the above-described embodiment. The possibility can be reduced.

  The FFT unit 32 and the complex multiplier 53 are circuits that are 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. It can be used for carrier detection. In other words, 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.

  Further, when the configuration of carrier detection timing determination unit 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 output of IFFT unit 12 at the time of preamble signal generation Paying attention to the phase rotation of the FFT output when the input range does not match the input range of the FFT unit 32 at the time of reception, at any timing within the time of the input range to the FFT unit 32 from the phase deviation amount between the subcarriers You can know if you have received the head.

Embodiment 5 FIG.
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 the present embodiment, frequency information after FFT processing is averaged and used to perform carrier detection. A case where detection determination is performed will be described.

  The transmitter according to the present embodiment has the same configuration as the transmitter according to the first embodiment described above, and only the preamble signal generation operation is different from that of the first embodiment. This transmitter is different from the transmitter according to the first embodiment in that in the operation of transmitting a preamble signal, a signal in which the same preamble pattern is continuously repeated a plurality of times is generated and transmitted as a preamble signal. Note that the number of repetitions of the preamble pattern is L. Other operations are the same as those in the first embodiment.

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

  The operation of the receiver 3c will be described based on 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 averages the frequency information (complex data) for the previous l times (l ≦ L) for each frequency band corresponding to the output range of the FFT unit 32, and carrier detection is performed on the frequency information after the averaging. Output to the timing determination unit 50.

When the frequency information for the frequency band F _FFT of the output range of the FFT unit 32 obtained from the FFT unit 32 at time t is expressed as D (t) as shown in the following equation (9), from the FFT unit 32 at time t: The output D _avr (t) can be expressed by the following equation (10).

・・・（９）

... (9)

・・・（１０）

... (10)

The carrier detection timing determination unit 50 performs carrier detection and timing determination based on the _averaged frequency information D _avr (t) expressed by the above equation (10). Note that the carrier detection operation and the timing determination operation are the same as those shown in the first embodiment.

  In this 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 receiver of the second embodiment is used. The frequency information averaging unit 36 may be added. In 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.

  As described above, in the present embodiment, the transmission side assigns a predetermined preamble pattern to each of a plurality of predetermined frequencies and uses the result of continuous transmission a plurality of times as a preamble signal. On the other hand, in the case of receiving a preamble signal, the receiving side separates information for each frequency using FFT, further averages the separated information, and multiplies the averaged information by the complex conjugate value of the preamble pattern. Using the results obtained in this way, carrier detection and timing determination are performed by determining the similarity between the received preamble signal and the preamble pattern. As a result, erroneous detection is performed as compared with the case where carrier detection is performed using only power that has been used in the past or the case where carrier detection or the like is performed without averaging frequency information described in the above-described embodiment. The possibility can be reduced.

  The FFT unit 32 and the complex multiplier 53 are circuits that are 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. It can be used for carrier detection. In other words, 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.

  Further, when the configuration of carrier detection timing determination unit 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 output of IFFT unit 12 at the time of preamble signal generation Paying attention to the phase rotation of the FFT output when the input range does not match the input range of the FFT unit 32 at the time of reception, at any timing within the time of the input range to the FFT unit 32 from the phase deviation amount between the subcarriers You can know if you have received the head.

Embodiment 6 FIG.
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 frequency information after FFT are averaged to determine carrier detection. However, in this embodiment, immediately before carrier detection and A case where information immediately before timing determination is averaged and carrier detection and timing determination are performed using the averaged information will be described.

  The transmitter according to the present embodiment has the same configuration as the transmitter according to the first embodiment described above, and only the preamble signal generation operation is different from that of the first embodiment. This transmitter is different from the transmitter according to the first embodiment in that in the operation of transmitting a preamble signal, a signal in which the same preamble pattern is continuously repeated a plurality of times is generated and transmitted as a preamble signal. Note that the number of repetitions of the preamble pattern is L. Other operations are the same as those in the first embodiment.

  The configuration of the receiver is the same as that of the receiver of the first embodiment, but the detailed configuration of the carrier detection timing determination unit is partially different. For this reason, in the present embodiment, description of parts other than the carrier detection timing determination unit is 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. The carrier detection timing determination unit 50 (see FIG. 3) described in the first embodiment is immediately before carrier detection. A time averaging unit 59 for averaging information is added. In the description of the operation 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.

  FIG. 9 is a diagram illustrating another configuration example of the carrier detection timing determination unit according to the sixth embodiment. Compared to the carrier detection timing determination unit 50a (see FIG. 4) described in the second embodiment, FIG. A time averaging unit 59 for averaging information immediately before detection is added. In the description of the operation 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.

In both of the carrier detection timing determination units 50d and 50e, the time averaging unit 59 corresponding to the addition result averaging unit averages the frequency information for the previous l times (l ≦ L) from the output of the complex summation device 54. Output. It should be _noted that information Z _avr (t) output from the time averaging unit 59 at time t, where Z (t) is the total value obtained at time t and T _FFT is the time for the input range of the FFT unit 32. Can be expressed by the following formula (11).

・・・（１１）

(11)

  In both carrier detection timing determination units 50d and 50e, absolute value calculation unit 55 and phase calculation unit 57 execute the processing described in the first or second embodiment based on the output from time averaging unit 59. To do. Then, the carrier detection unit 56 and the timing determination unit 58 respectively execute the processing described in the first or second embodiment based on the output from the absolute value calculation unit 55 and the output from the phase calculation unit 57. .

  In the present embodiment, the time averaging unit 59 is added to the carrier detection timing determination unit provided in the receiver of the first or second embodiment. However, the present invention 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 FIG.

  As described above, in the present embodiment, the transmission side assigns a predetermined preamble pattern to each of a plurality of predetermined frequencies and uses the result of continuous transmission a plurality of times as a preamble signal. On the other hand, in the case of preamble signal reception, the information used for carrier detection and timing detection is time-averaged, and carrier detection and timing determination are performed using the results. As a result, carrier detection or the like is performed without averaging the information used when performing carrier detection and timing detection shown in the above-described embodiment when performing carrier detection using only power that has been conventionally used. Compared to the case, the possibility of erroneous detection can be reduced.

  The FFT unit 32 and the complex multiplier 53 are circuits that are 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. It can be used for carrier detection. In other words, 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.

  Furthermore, in the receiver including the carrier detection timing determination unit 50e, pay attention to the phase rotation of the FFT output when the output range of the IFFT unit 12 at the time of preamble signal generation and the input range of the FFT unit 32 at the time of reception do not match, It is possible to know at which timing within the time of the input range to the FFT unit 32 the head of the preamble signal is received from the phase deviation amount between the subcarriers.

  As described above, the signal detection apparatus according to the present invention is useful for a communication system, and in particular, a receiver included in a communication apparatus that detects a desired signal and symbol timing with high accuracy with a small circuit scale based on a known signal. Suitable for

Claims (8)

A signal detection device for detecting a desired signal modulated by an OFDM (Orthogonal Frequency Division Multiplexing) method from received signals,
Signal converting means for converting the received signal into frequency domain information (first frequency domain signal) for each carrier;
Known frequency information generating means for generating frequency domain information (second frequency domain information) for each carrier based on a signal obtained by multiplexing signals of a plurality of carriers having predetermined known information and having different frequencies. ,
Complex conjugate generation means for generating, for each carrier, a complex conjugate of the second frequency domain information output from the known frequency information generation 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;
Adding means for adding a part or all of the multiplication output by the multiplication means;
Signal detection means for calculating an absolute value of the addition result or a square value of the addition result, and performing detection determination of a desired signal using the calculation result and a predetermined threshold defined in advance;
Equipped with a,
The multiplication means is
Two or more multiplication results are selected from the multiplication results, a complex conjugate of the selected multiplication results is generated, and the multiplication results in the frequency domain separated by a fixed interval from the generated complex conjugates Respectively multiplied by
The adding means adds a part or all of the multiplication results to calculate a final addition result,
The signal detection means performs detection determination processing of the desired signal using the final addition result,
further,
A timing determination unit that calculates a phase of the final 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;
Signal detection apparatus according to claim Rukoto equipped with. 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 for the desired signal a plurality of times within a range not exceeding the number of repetitions of the bit string, and finally determines whether the desired signal is detected based on the execution result of the plurality of times. signal detection apparatus according to claim 1, characterized in that to determine the. Said signal detecting means, when the detection number of the desired signal in the plurality of times of execution result is a prescribed number of times or more, and finally according to claim 2, characterized in that it is determined that detects a desired signal Signal detection device. further,
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
The signal detection apparatus according to claim 1 , wherein the signal conversion unit converts the output of the time signal averaging unit into frequency domain information. further,
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 averaged for each carrier Frequency information averaging means,
With
The multiplying unit uses the averaged output for each carrier of the frequency information averaging unit instead of the signal conversion output, and each averaged output and the complex conjugate for each carrier generated by the complex conjugate generating unit. The signal detection device according to claim 1 , wherein the signal frequency is multiplied by the same frequency region. further,
When the predetermined known information is a repetition of a bit string of a specific pattern, an addition result obtained by acquiring the addition output of the addition means a plurality of times within a range not exceeding the number of repetitions of the bit string and averaging the acquired addition output Averaging means,
With
The signal detection unit calculates an absolute value of the averaged result in the addition result averaging unit or a square value of the averaged result, and performs detection determination of a desired signal using the calculation result and the threshold value. The signal detection device according to claim 1 . further,
When the predetermined known information is a repetition of a bit string of a specific pattern, an addition result obtained by acquiring the addition output of the addition means a plurality of times within a range not exceeding the number of repetitions of the bit string and averaging the acquired addition output Averaging means,
With
The signal detection means calculates an absolute value of the averaged result in the addition result averaging means or a square value of the averaged result, and performs detection determination of a desired signal using the calculation result and the threshold value. ,
It said timing determination means according to claim 1, wherein the addition result to calculate the phase of the averaged result of the averaging means, to determine the accurate reception timing of the desired signal based on the obtained phase Signal detector. The predetermined threshold value is determined based on a bit pattern forming the predetermined known information, a content of processing executed by the multiplication unit, and a number of multiplication outputs to be added by the addition unit. signal detection apparatus according to any one of claims 1-7, characterized.

Images