JP7270858B2 - Transmitter, receiver, communication system, transmission method, timing synchronization method, control circuit and storage medium - Google Patents

Description

The present disclosure relates to a transmitter, a receiver, a communication system, a transmission method, a timing synchronization method, a control circuit and a storage medium.

As a wireless communication technology for IoT (Internet of Things) and M2M (Machine to Machine), LPWA (Low Power Wide Area), which realizes long-distance communication with low power consumption, is attracting attention. LoRaWAN, Sigfox, and Wi-SUN (Wireless Smart Utility Network) included in LPWA use the unlicensed ISM (Industry Science Medical) band. is an issue. Therefore, it is effective to apply direct sequence spread spectrum (hereinafter referred to as DS-SS (Direct Sequence Spread Spectrum)) communication, which is excellent in interference resistance, jamming resistance, confidentiality of communication, etc., to LPWA.

Since DS-SS communication performs despreading on the receiving side, the DS-SS receiver needs to detect the timing at which the information is multiplied by the spreading code at the transmitter. This process is also called timing synchronization. As a method of timing synchronization in the DS-SS system, initial synchronization (initial synchronization, initial acquisition) generally ensures that the spread code time lag between transmitters and receivers is, for example, within 1/2 chip. After rough synchronization with high precision, residual timing errors, ie, time shifts, are corrected with high precision by fine timing synchronization.

Timing synchronization in DS-SS communication is performed on signals that have been spread over a wide frequency band before despreading, so it is important to be able to achieve high-precision synchronization with a low SNR (Signal-to-Noise Ratio). Become. As a method for high-precision synchronization with a low SNR, space-time block code (hereinafter sometimes referred to as STBC (Space Time Block Code)) that transmits by manipulating the transmission order and code, It is effective to apply transmission diversity techniques such as delay diversity for simultaneously transmitting delayed signals.

When delay diversity is applied to a preamble signal for synchronization, synchronization performance is degraded because the delayed signal and the original signal are the same signal. Also, when applying transmit diversity such as frequency offset diversity that sends uncorrelated signals between transmit antennas, the initial synchronization method using a matched filter (MF) requires as many matched filters as there are transmit antennas. Therefore, the circuit size increases according to the number of transmitting antennas. On the other hand, since STBC is a process of only inverting the phase and sign of signals transmitted at the same time, initial synchronization can be realized with one matched filter without degrading performance. Also, in order to perform correct despreading in a DS-SS communication receiver, a plurality of synchronization processes such as spreading code timing synchronization, frame synchronization, and frequency synchronization are required. A DS-SS communication system intended for IoT/M2M communication is required to reduce the circuit scale and the amount of calculation per terminal. If the synchronization processes are performed by independent circuits, the circuit scale will increase. Therefore, it is desirable to reduce the circuit scale, such as by implementing various synchronization processes in the same circuit.

In Patent Document 1, frame timing is estimated by searching for the maximum value position using the process of autocorrelation characteristics of a preamble signal that is repeated periodically, and autocorrelation is performed within a specific interval from the estimated frame timing. A method for performing calculations and estimating symbol timing is disclosed.

Japanese Patent Publication No. 2007-520931

However, the technology described in Patent Literature 1 does not take into consideration the case where transmission diversity technology and STBC are applied, and there is concern that synchronization performance may deteriorate when STBC is applied.

The present disclosure has been made in view of the above, and an object of the present disclosure is to obtain a transmission device capable of improving synchronization performance in a communication system to which STBC is applied.

In order to solve the above-described problems and achieve an object, a transmission device according to the present disclosure performs encoding processing on a preamble signal to generate a first space-time block code, A space-time block encoder for generating a second space-time block code having a configuration in which the first half and the second half of the space block code are interchanged, and spectrally spreading the first space-time block code and the second space-time block code. A preamble spreader, and a frame generator for generating a frame including the first space-time block code after spectrum-spreading and the second space-time block code after spectrum-spreading.

The transmission device according to the present disclosure has the effect of being able to improve synchronization performance in a communication system to which STBC is applied.

A diagram showing a configuration example of a communication system according to an embodiment Flowchart showing the operation of the transmitter FIG. 4 is a diagram showing a configuration example of frames transmitted and received in a communication system; Flowchart showing the operation of the receiving device The figure which shows the structural example of the 1st synchronous processing part with which a receiving apparatus is equipped. Flowchart showing the operation of the first synchronization processing section provided in the receiving device FIG. 4 is a diagram showing an example of a first cross-correlation function calculated by an up-chirp correlation value calculator of a first synchronization processor provided in a receiver; FIG. 4 is a diagram showing an example of a first cross-correlation function calculated by an up-chirp correlation value calculator of a first synchronization processor provided in a receiver; FIG. 4 is a diagram showing an example of a first cross-correlation function calculated by an up-chirp correlation value calculator of a first synchronization processor provided in a receiver; A diagram showing an example of a second cross-correlation function calculated by a down-chirp correlation value calculation section of a first synchronization processing section provided in a receiving device. A diagram showing an example of a second cross-correlation function calculated by a down-chirp correlation value calculation section of a first synchronization processing section provided in a receiving device. A diagram showing an example of a second cross-correlation function calculated by a down-chirp correlation value calculation section of a first synchronization processing section provided in a receiving device. FIG. 4 is a diagram showing an image of threshold setting in the threshold determination unit of the first synchronization processing unit included in the receiving device; FIG. 4 is a diagram showing a configuration example of a processing circuit provided in a receiving device when the processing circuit is realized by a processor and a memory; A diagram showing an example of a processing circuit in a case where the processing circuit included in the receiving device is configured with dedicated hardware.

A transmitting device, a receiving device, a communication system, a transmitting method, a timing synchronization method, a control circuit, and a storage medium according to embodiments of the present disclosure will be described below in detail with reference to the drawings.

Embodiment.
FIG. 1 is a diagram showing a configuration example of a communication system 3 according to an embodiment. A communication system 3 includes a transmitter 1 and a receiver 2 . In the communication system 3, frame communication is assumed, and uniform block fading is assumed in one frame on the communication path between the transmission device 1 and the reception device 2. FIG. Although not shown in FIG. 1, the transmitting device 1 constitutes a communication device that transmits a radio signal of two communication devices that communicate in the communication system 3, and the receiving device 2 , constitute a communication device that receives a radio signal. In general, a communication device includes both a transmitter 1 and a receiver 2, and transmits and receives radio signals to and from a communication device of a communication partner.

First, the configuration and operation of the transmission device 1 will be described. Transmitter 1 includes modulator 11, space-time block encoder 12, spectrum spreaders 13 and 14, preamble generator 15, frame generator 16, transmission filters 17 and 18, transmission antenna 19 and 20 and. Spectrum spreading sections 13 and 14 constitute data spreading section 30 . Preamble generation section 15 also includes modulation section 151 , space-time block coding section 152 , and spectrum spreading sections 153 and 154 . Spectrum spreading sections 153 and 154 constitute preamble spreading section 50 .

FIG. 2 is a flow chart showing the operation of the transmission device 1. As shown in FIG.

The modulation unit 11 modulates transmission data obtained from a host device (not shown) (step S101). The modulation unit 11 uses, for example, PSK (Phase Shift Keying) as a modulation method. Modulator 11 outputs the modulated transmission data to space-time block encoder 12 .

The space-time block coding unit 12 performs space-time block coding on the data signal, which is the modulated transmission data acquired from the modulation unit 11 . The space-time block coding unit 12, for example, continuously acquires the modulated signals s1 and s2 from the modulation unit 11, and performs STBC coding, that is, space-time block coding, as shown in the following equation (1) (step S102 ).

In equation (1), (·) ^* indicates a complex conjugate. Each row of Equation (1) corresponds to the modulated signal transmitted by the transmitting antennas 19 and 20 provided in the transmitting device 1, and each column corresponds to the transmission time of each modulated signal. That is, at time t1, the transmitting antenna 19 transmits the modulated signal s1 and the transmitting antenna 20 transmits the modulated signal s2. At the next time t2, the transmitting antenna 19 transmits the modulated signal −s2 ^* and the transmitting antenna 20 transmits the modulated signal s1 ^* . The space-time block coding unit 12 outputs the STBC-coded modulated signal to be transmitted from the transmitting antenna 19 to the spectrum spreading unit 13, and outputs the STBC-coded modulated signal to be transmitted from the transmitting antenna 20 to the spectrum spreading unit 14. Output. In the following description, the modulated signal may be simply referred to as "signal".

The spectrum spreading units 13 and 14 perform spectrum spreading for each signal to be transmitted from the respective transmitting antennas 19 and 20 on the STBC-encoded signals input from the space-time block coding unit 12 (step S103). . Specifically, the spectrum spreading unit 13 spreads the spectrum of the signal transmitted by the transmitting antenna 19 corresponding to the first line of the equation (1), and the spectrum spreading unit 14 performs the second line of the equation (1). Spectrum spreading is performed in the same manner as the spectrum spreading section 13 for the signal transmitted by the transmitting antenna 20 corresponding to the eye. It is also assumed that the spreading codes used by the spectrum spreading sections 13 and 14 are common. As this spreading code, for example, a Zadoff-Chu sequence that can be generated by setting M=3 in the following equation (2) is used. Equation (2) represents the t-th element C(t) of the Zadoff-Chu sequence C when the code length _Nc of the spreading code is an even number.

Here, M is the number of increments from the minimum frequency fmin to the maximum frequency fmax at the code length _Nc , and is coprime to _Nc . When M=1, the frequency increases once from the minimum frequency fmin to the maximum frequency fmax at the code length _Nc . When M=2, the frequency increases from the minimum frequency fmin to the maximum frequency fmax at the code length _Nc , and then further increases from the minimum frequency fmin to the maximum frequency fmax. That is, when M=2, the frequency increases twice from the minimum frequency fmin to the maximum frequency fmax at the code length _Nc . On the other hand, when M=-1, the frequency decreases once from the maximum frequency fmax to the minimum frequency fmin at the code length _Nc . Spectrum spreading sections 13 and 14 output the spectrum-spread signals to frame generating section 16 . In the following description, the signals generated by spectrum spreading sections 13 and 14 may be referred to as data.

The preamble generator 15 generates a preamble (step S104). Specifically, the preamble generator 15 generates a preamble by performing STBC coding and spectrum spreading on a known preamble signal. The preamble generator 15 performs STBC coding and spectrum spreading on the preamble signal by a method different from the method by the space-time block coding unit 12 and the spectrum spreading units 13 and 14 . In the following description, the signal generated by the preamble generator 15 may be called a preamble.

Details of the operations of modulation section 151, space-time block coding section 152, and spectrum spreading sections 153 and 154 of preamble generation section 15 will be described.

Modulation section 151 modulates the preamble signal in the same manner as modulation section 11 described above. For example, the same signal as 0, 0, 0, 0, . . . is input to the modulation section 151 . The modulation unit 151 uses, for example, QPSK (Quadrature Phase Shift Keying) as a modulation method. Modulating section 151 outputs the modulated signal to space-time block coding section 152 . In the following description, one element of the modulated signal modulated by modulation section 151 may be referred to as a symbol.

Space-time block coding section 152 performs STBC coding on the modulated signal obtained from modulating section 151 . For example, when the modulated signals s1 and s2 are continuously obtained from the modulating unit 151, the space-time block coding unit 152 performs STBC coding as shown in the above formula (1) or the following formula (3). .

Each row of Equation (3) corresponds to the modulated signal transmitted by the transmitting antennas 19 and 20 provided in the transmitting device 1, and each column corresponds to the transmission time of each modulated signal. In the case of the STBC encoding method shown in equation (3), at time t1, transmitting antenna 19 transmits modulated signal −s2 ^* and transmitting antenna 20 transmits modulated signal s1 ^* . At the next time t2, the transmitting antenna 19 transmits the modulated signal s1 and the transmitting antenna 20 transmits the modulated signal s2. That is, the STBC encoding method indicated by Equation (3) is obtained by replacing the STBC encoding method indicated by Equation (1) on the time axis. Hereinafter, for convenience of explanation, the STBC encoding method indicated by Equation (1) is referred to as first STBC encoding or first space-time block encoding, and the STBC encoding method indicated by Equation (3) is referred to as second It is called STBC coding or second space-time block coding.

For example, as shown in FIG. 3, space-time block coding section 152 performs first STBC coding on the first half of the preamble, and second STBC coding on the second half of the preamble. FIG. 3 is a diagram showing a configuration example of frames transmitted and received in the communication system 3. As shown in FIG. Space-time block coding section 152 outputs the STBC-encoded signal to be transmitted from transmitting antenna 19 to spectrum spreading section 153 , and outputs the STBC-coded signal to be transmitted from transmitting antenna 20 to spectrum spreading section 154 . .

Spectrum spreading sections 153 and 154 perform spectrum spreading on the STBC-encoded signal input from space-time block coding section 152 by up-chirp and down-chirp. Specifically, spectrum spreading section 153 spreads the spectrum of the first signal to be transmitted from transmitting antenna 19, and spectrum spreading section 154 spreads the spectrum of the second signal to be transmitted from transmitting antenna 20. Spectrum spreading is performed in the same manner as in section 153 . It is also assumed that the spreading code used by spectrum spreading sections 153 and 154 is common. An up-chirp referred to in this embodiment is a signal whose frequency increases over time. In this embodiment, this up-chirp is a Zadoff-Chu sequence generated by setting M=1 in the above equation (2). Down chirp referred to in this embodiment is a signal whose frequency decreases over time. In this embodiment, this down-chirp is a Zadoff-Chu sequence generated by setting M=−1 in the above equation (2). For example, as shown in FIG. 3, spectrum spreading sections 153 and 154 use the first half of the preamble as a signal obtained by spectrum-spreading the STBC-encoded first signal by up-chirp, and the second half as , and a signal obtained by spectrum-spreading the STBC-encoded second signal by down-chirp. Spectrum spreading sections 153 and 154 output the spectrum-spread signals to frame generating section 16 .

The frame generation unit 16 frames the data obtained by spectrum spreading by the spectrum spreading units 13 and 14 and the preamble generated by the preamble generation unit 15 for each information transmitted by the transmission antennas 19 and 20 ( step S105). Specifically, the frame generating section 16 frames the preamble generated by the preamble generating section 15 to be transmitted from the transmitting antenna 19 and the data generated by the spectrum spreading section 13 , and transfers the frames to the transmission filter 17 . Similarly, the frame generation unit 16 frames the preamble generated by the preamble generation unit 15 to be transmitted from the transmission antenna 20 and the data generated by the spread spectrum unit 14 , and passes the frame to the transmission filter 18 . The frame generation unit 16 frames the signals transmitted by the transmission antennas 19 and 20 as shown in FIG. 3, for example. As described above, FIG. 3 shows an example of a preamble generated by the preamble generator 15, and also shows an example of a signal after framing by the frame generator 16. FIG. The signal generated by the spread spectrum section 153 or the signal generated by the spread spectrum section 154 is arranged in the "preamble" part shown in FIG. Alternatively, data generated by the spectrum spreading section 14 is arranged. That is, the frame transmitted by the transmitting antenna 19 has a configuration in which the signal generated by the spread spectrum section 153 is arranged in the "preamble" portion and the data generated by the spread spectrum section 13 is arranged in the "data" portion. . The frame transmitted by the transmitting antenna 20 has a configuration in which the signal generated by the spread spectrum section 154 is arranged in the "preamble" portion and the data generated by the spread spectrum section 14 is arranged in the "data" portion.

The transmission filters 17 and 18 band-limit the signal framed by the frame generator 16 (step S106). Transmit filters 17 and 18 output band-limited signals to transmit antennas 19 and 20, respectively.

The transmitting antennas 19 and 20 respectively transmit the band-limited signals obtained from the transmitting filters 17 and 18 (step S107).

Next, the configuration and operation of the receiving device 2 will be described. As shown in FIG. 1, the receiving device 2 includes a receiving antenna 21, a receiving filter 22, a first synchronization processing unit 23, a second synchronization processing unit 24, a frequency offset correction unit 25, and a despreading unit. 26, an STBC decoding unit 27, and a demodulation unit 28. FIG. FIG. 4 is a flow chart showing the operation of the receiving device 2. As shown in FIG.

The receiving antenna 21 receives the signal transmitted from the transmitting device 1 (step S201). A signal received by the receiving antenna 21 , that is, a received signal is a signal transmitted from the transmitting device 1 . Receiving antenna 21 outputs a received signal to receiving filter 22 .

The reception filter 22 performs filtering on the reception signal acquired from the reception antenna 21 (step S202). The reception filter 22 passes the filtered signal to the first synchronization processing section 23 and the frequency offset correction section 25 .

The first synchronization processing unit 23 performs initial synchronization and frame synchronization based on the filtered signal obtained from the reception filter 22 (step S203). In this embodiment, the first synchronization processing unit 23 performs rough estimation of the timing multiplied by the spreading code in the transmitting device 1 and rough estimation of the frequency offset generated by the frequency shift of the local oscillator between the transmitting and receiving devices. I do. In the following description, the timing at which the spreading code is multiplied by the transmitting apparatus 1 may be referred to as spreading code timing. The coarse estimation of the spread code timing means the estimation of the spread code timing performed with coarser precision than the spread code timing estimation precision of the second synchronization processing unit 24, which will be described later. Further, the rough estimation of the frequency offset is the estimation of the frequency offset with coarser accuracy than the estimation accuracy of the frequency offset by the second synchronization processing unit 24, which will be described later. Initial synchronization is the process of roughly estimating the spreading code timing and roughly estimating the frequency offset. The first synchronization processing unit 23 further performs frame synchronization for estimating frame timing based on the result of rough estimation of the spreading code timing. The first synchronization processing unit 23 outputs the coarse estimation result of the spreading code timing, the coarse estimation result of the frequency offset, and the estimation result of the frame timing to the second synchronization processing unit 24 . A detailed configuration and operation of the first synchronization processing unit 23 will be described later.

Based on the three estimation results obtained from the first synchronization processing unit 23, the second synchronization processing unit 24, that is, the spreading code timing coarse estimation result, the frequency offset coarse estimation result, and the frame timing estimation result. Based on , a fine synchronization process is performed (step S204). The fine synchronization process estimates the spreading code timing error remaining in the rough spreading code timing estimation result and the frequency offset amount remaining in the rough frequency offset estimation result. This is a process for correcting the offset estimation result with high accuracy. Correction of the frequency offset estimation result is performed by multiple open loop AFC (Automatic Frequency Control). The spread code timing estimation result is corrected using the corrected frequency offset estimation result. The second synchronization processing unit 24 outputs the corrected frequency offset estimation result to the frequency offset correction unit 25 and outputs the corrected spreading code timing estimation result to the despreading unit 26 .

The frequency offset correction unit 25 corrects the frequency offset of the signal from the reception filter 22 based on the corrected frequency offset estimation result obtained from the second synchronization processing unit 24 (step S205). The frequency offset correction unit 25 outputs the corrected filtered signal to the despreading unit 26 .

The despreading unit 26 despreads the frequency offset-corrected signal input from the frequency offset correcting unit 25 based on the corrected spreading code timing estimation result obtained from the second synchronization processing unit 24 . (Step S206). Despreading section 26 outputs the despread signal to STBC decoding section 27 .

The STBC decoding unit 27 performs STBC decoding on the despread signal obtained from the despreading unit 26 (step S207).

The demodulator 28 demodulates the STBC-decoded signal obtained from the STBC decoder 27 (step S208).

Next, the configuration and operation of the first synchronization processing section 23 included in the receiving device 2 will be described in detail. FIG. 5 is a diagram showing a configuration example of the first synchronization processing section 23 included in the receiving device 2. As shown in FIG. As shown in FIG. 5, the first synchronization processing unit 23 includes an up-chirp correlation value calculation unit 231, a down-chirp correlation value calculation unit 232, decoding processing units 233 and 234, power value calculation units 235, 235a, and 236. and 236a, power value combiners 237 and 237a, correlation power memories 238 and 238a, threshold decision units 239 and 239a, timing and frequency offset estimator 240, power combiner 241, and frame timing estimator 242. , provided. Power value calculators 235 and 235 a and power value combiner 237 constitute a first power calculator 250 . Power value calculators 236 , 236 a and power value combiner 237 a constitute a second power calculator 251 .

FIG. 6 is a flow chart showing the operation of the first synchronization processing section 23 included in the receiving device 2. As shown in FIG. The flowchart shown in FIG. 6 shows the details of the operation of step S203 in the flowchart shown in FIG. In FIG. 6, steps S301, S303, S305, S307, S309, and S311 include an up-chirp correlation value calculator 231, a decoding processor 233, power value calculators 235 and 235a, a power value combiner 237, a correlation power memory. 238 and a threshold determination unit 239. FIG. Steps S302, S304, S306, S308, S310, and S312 include the down-chirp correlation value calculator 232, the decoding processor 234, the power value calculators 236 and 236a, the power value combiner 237a, the correlation power memory 238a, and the threshold decision unit 239a. shows the processing performed in the block consisting of

The up-chirp correlation value calculation unit 231, which is the first correlation value calculation unit, uses a matched filter to spread the filtered signal acquired from the reception filter 22 and the spectrum in the preamble generation unit 15 of the transmission device 1. A cross-correlation function with the up-chirp obtained is calculated (step S301). Let the cross-correlation function calculated by the up-chirp correlation value calculation unit 231 be the first cross-correlation function. FIG. 7 is a diagram showing an example of the first cross-correlation function calculated by the up-chirp correlation value calculator 231 of the first synchronization processor 23 included in the receiver 2. As shown in FIG. FIG. 7 shows the power value of the first cross-correlation function when the number of symbols N _s of the modulated signal output by the modulation section 151 is N _s =8 (up-chirp spread first half 4 symbols, down-chirp spread last 4 symbols). An example is shown. The horizontal axis of FIG. 7 is the symbol number of the preamble in the signal that passes through the matched filter (signal after passing through the reception filter 22). 8 and 9 show the first cross-correlation function in terms of power values when channel response values different from the example shown in FIG. 7 are obtained.

A channel response value between the transmitting antenna 19 of the transmitting device 1 and the receiving antenna 21 of the receiving device 2 and a channel response value between the transmitting antenna 20 of the transmitting device 1 and the receiving antenna 21 of the receiving device 2 Depending on the phase relationship, the symbol numbers for obtaining large correlation power values shown in FIGS. 7 to 9 change. For example, as described in the description of the modulation unit 151, when a signal such as 0, 0, 0, 0, ... is input and QPSK modulation is performed, the example shown in FIG. This is obtained when the phase relationship of the channel response values is close to anti-phase, and the example shown in FIG. 8 is obtained when the two channel response values are close to in-phase. The example shown in FIG. 9 is obtained when the phase relationship between the two channel response values is neither close to the same phase nor close to the opposite phase. Also, as shown in FIGS. 7 and 8, when the phase relationship between the two channel response values is close to in-phase or out-of-phase, in the first four symbols to which up-chirp spreading is applied, , a large correlation is observed. Up-chirp correlation value calculation section 231 outputs the calculated first cross-correlation function to decoding processing section 233 .

The down-chirp correlation value calculation unit 232, which is the second correlation value calculation unit, uses a matched filter to spread the filtered signal obtained from the reception filter 22 and the spectrum spread in the preamble generation unit 15 of the transmission device 1. A cross-correlation function with the down chirp is calculated (step S302). The cross-correlation function calculated by the down-chirp correlation value calculator 232 is set as the second cross-correlation function. FIG. 10 is a diagram showing an example of the second cross-correlation function calculated by the down-chirp correlation value calculator 232 of the first synchronization processor 23 included in the receiver 2. As shown in FIG. The example shown in FIG. 10 is the second cross-correlation function when the number of symbols N _s of the modulated signal output by the modulation section 151 is N _s =8 (up-chirp spread first half 4 symbols, down-chirp spread second half 4 symbols). is shown as a power value. The horizontal axis of FIG. 10 is the symbol number of the preamble in the signal that passes through the matched filter, as in FIGS. 7 to 9 described above. 11 and 12 show the second cross-correlation function in terms of power values when channel response values different from the example shown in FIG. 10 are obtained. In the examples shown in FIGS. 10 and 11, similar to the examples shown in FIGS. 7 and 8 described above, in the latter four symbols to which down-chirp spreading is applied, a large correlation is observed once every two symbols. be done. However, in the preamble generation unit 15 of the transmission device 1, the encoding method is switched between the preamble for which up-chirp spreading is performed and the space-time block encoding unit 152 on the time axis. That is, the coding method for the latter four symbols to which down-chirp spreading is applied is obtained by replacing the coding method for the first half four symbols to which up-chirp spreading is applied on the time axis. Therefore, if the symbol numbers for which the correlation is large are odd numbers in the examples shown in FIGS. 7 to 9, the symbol numbers for which the correlation is large are even numbers in the examples shown in FIGS. In the example shown in FIG. 10 to FIG. 12, if the number of symbols with high correlation is even, the number of symbols with high correlation in the examples shown in FIGS. 10 to 12 is odd. Down chirp correlation value calculation section 232 outputs the second cross-correlation function to decoding processing section 234 . Note that the first synchronization processing unit 23 performs the operation of the down-chirp correlation value calculation unit 232 in parallel with the operation of the up-chirp correlation value calculation unit 231 .

The decoding processing unit 233, which is the first decoding processing unit, decodes the first cross-correlation function calculated by the up-chirp correlation value calculation unit 231 (step S303). Specifically, decoding processing section 233 performs first mutual Multiply the correlation function. For example, the number of symbols N _s of the modulated signal output from the modulating unit 151 of the preamble generating unit 15 in the transmitting device 1 is set to N _s =8, and s1, s2, s1, s2, s1, s2, s1, and s2 are the modulated signals. Suppose you get In addition, space-time block coding section 152 and preamble spreading section 50 of preamble generation section 15 perform STBC coding shown in the above equation (1) on the first four symbols and perform up-chirp spreading, and , STBC encoding shown in the above equation (3) and down-chirp spreading are performed on the latter four symbols. In this case, decoding processing section 233 multiplies the matrix shown in Equation (4) below by the first cross-correlation function.

Each row of Equation (4) corresponds to signals transmitted by the transmitting antennas 19 and 20 provided in the transmitting device 1, and each column corresponds to symbol time. Further, when decoding processing section 233 multiplies the matrix shown in Equation (4) by the first cross-correlation function, for each column of the matrix, decoding processing section 233 multiplies the first cross-correlation function by the code length of the spreading code N _c × Multiply every oversample number N _ovs intervals. That is, decoding processing section 233 multiplies the matrix shown in equation (4) by the first cross-correlation function shown in equation (5) below.

In equation (5), k is an arbitrary integer and x(.) is the first cross-correlation function obtained with the sample number in brackets. Therefore, the output of the decoding processing unit 233 is the product of the matrix shown in Equation (4) and the matrix shown in Equation (5), and is given by Equation (6) below.

Here, the 1st line of Formula (6) becomes an output to the power value calculation part 235, and the 2nd line becomes an output to the power value calculation part 235a. The decoding processing unit 233 outputs the first line of the formula (6), which is the result of multiplying the formulas (4) and (5), to the power value calculation unit 235, and calculates the power value of the second line of the formula (6). Output to the unit 235a.

The decoding processing unit 234, which is the second decoding processing unit, decodes the second cross-correlation function calculated by the down-chirp correlation value calculation unit 232 (step S304). Decoding processor 234 decodes the second cross-correlation function in the same manner as decoding processor 233 decodes the first cross-correlation function. Specifically, the decoding processing unit 234 performs the second mutual Multiply the correlation function. That is, decoding processing section 234 multiplies the matrix shown in Equation (4) above by the second cross-correlation function. The decoding processing unit 234 outputs the first row of the multiplication result to the power value calculation unit 236, and outputs the second row of the multiplication result to the power value calculation unit 236a.

The power value calculators 235 and 235a calculate the power value of the decoding result input from the decoding processor 233 (step S305). Specifically, the power value calculator 235 calculates the power value by squaring the absolute value of the output in the first row of the multiplication result of the above equation (4) and the first cross-correlation function. The power value calculator 235a calculates the power value by squaring the absolute value of the output in the second row of the multiplication result of the above equation (4) and the first cross-correlation function. Power value calculator 235 outputs the calculated power value to power value synthesizer 237 , and power value calculator 235 a outputs the calculated power value to power value synthesizer 237 .

The power value calculators 236 and 236a calculate the power value of the decoding result input from the decoding processor 234 (step S306). Specifically, the power value calculator 236 calculates the power value by squaring the absolute value of the output in the first row of the multiplication result of the above equation (4) and the second cross-correlation function. The power value calculation unit 236a calculates the power value by squaring the absolute value of the output in the second row of the multiplication result of the above equation (4) and the second cross-correlation function. The power value calculator 236 outputs the calculated power value to the power value synthesizer 237a, and the power value calculator 236a outputs the calculated power value to the power value synthesizer 237a.

The power value synthesizer 237 synthesizes the power values input from the power value calculators 235 and 235a (step S307). For example, if ^the power value calculated by the power value calculator 235 is |b1| ² and the power value calculated by the power value calculator 235a is | ^b2 | | Compose as shown in ² . The power value synthesizing section 237 causes the correlation power memory 238 to store the synthesizing result. The power value synthesizing section 237 also outputs the synthesizing result to the power synthesis processing section 241 .

The power value synthesizer 237a synthesizes the power values input from the power value calculators 236 and 236a (step S308). The power value synthesizing unit 237 a synthesizes two power values in the same manner as the power value synthesizing unit 237 . The power value synthesis unit 237a stores the synthesis result in the correlation power memory 238a. In addition, the power value synthesizing unit 237 a outputs the synthesizing result to the power synthesis processing unit 241 .

Correlation power memories 238 and 238a are configured to hold power values of a number corresponding to spreading code length x number of oversamples. (1 symbol period) is stored (steps S309 and S310). The processing up to the power value synthesizing units 237 and 237a operates in sample time units, but the processing after the correlation power memories 238 and 238a changes to the operation in symbol time units.

The threshold determination unit 239 reads out the power value for one cycle of the spreading code from the correlation power memory 238, and estimates the timing of the up-chirp based on the power value for one cycle of the spreading code (step S311). The up-chirp timing is the timing at which spectrum spreading section 153 of preamble generating section 15 in transmitting apparatus 1 multiplies the preamble signal by the up-chirp. Specifically, in step S311, the threshold determination unit 239 detects the maximum power value from the power values for one cycle of the spreading code and compares it with the threshold. When the maximum power value exceeds the threshold value, the threshold determination unit 239 estimates that the sample timing corresponding to the maximum power value is the up-chirp timing. That is, the threshold determination section 239 operates as an up-chirp timing estimation section. In addition, the threshold determination unit 239 stores the timing of the symbol for which the up-chirp timing estimation is completed, that is, the timing for which the threshold is exceeded, and obtains an up-chirp estimation completion symbol. The threshold determination unit 239 passes the up-chirp timing estimation result, that is, the sample timing corresponding to the maximum power value exceeding the threshold, to the timing and frequency offset estimation unit 240 as the up-chirp estimated timing n1. In addition, the threshold determination unit 239 transfers the up-chirp estimated timing n1 to the power synthesis processing unit 241 . Further, the threshold determination section 239 transfers the up-chirp estimation completion symbol to the frame timing estimation section 242 .

The threshold decision unit 239a reads out the power value for one cycle of the spreading code from the correlation power memory 238a, and estimates the down-chirp timing based on the power value for one cycle of the spreading code (step S312). The down-chirp timing is the timing at which spectrum spreading section 154 of preamble generating section 15 in transmitting apparatus 1 multiplies the preamble signal by the down-chirp. The threshold determination unit 239a estimates the down-chirp timing by a method similar to the method by which the threshold determination unit 239 estimates the up-chirp timing. That is, the threshold determination section 239a operates as a down-chirp timing estimation section. The threshold determination unit 239a passes the down-chirp timing estimation result to the timing and frequency offset estimation unit 240 as the estimated down-chirp timing n2. Further, the threshold determination unit 239 a passes the down-chirp timing estimation result, that is, the estimated down-chirp timing n<b>2 to the power synthesis processing unit 241 .

The thresholds used for determination by the threshold determination units 239 and 239a are generated, for example, by the following method. The threshold determination units 239 and 239a calculate the average of the power values for one cycle of the spreading code read from the correlation power memories 238 and 238a, and set the average value to a constant α times as the threshold (see FIG. 13). Note that the first synchronization processing unit 23 may perform the operation of the threshold determination unit 239 before or after the operation of the threshold determination unit 239a. Further, the operation of the threshold determination unit 239 and the operation of the threshold determination unit 239a may be performed in parallel. FIG. 13 is a diagram showing an image of threshold setting in the threshold determination units 239 and 239a of the first synchronization processing unit 23 included in the receiving device 2. As shown in FIG.

The timing and frequency offset estimation unit 240 estimates the timing of the spreading code based on the up-chirp estimation timing n1 obtained from the threshold value determination unit 239 and the down-chirp estimation timing n2 obtained from the threshold value determination unit 239a (step S313). . Specifically, the timing and frequency offset estimating section 240 sets the timing n0 between the up-chirp estimation timing n1 and the down-chirp estimation timing n2 as the spreading code timing. The timing and frequency offset estimating section 240 rounds off the timing n0 when it becomes a decimal, and uses it as the estimation result of the spreading code timing.

In addition, the timing and frequency offset estimator 240 calculates the frequency offset between the transmitter 1 and the receiver 2 from the difference between the estimated up-chirp timing n1 and the estimated down-chirp timing n2, as shown in the following equation (7). is roughly estimated (step S314).

The timing and frequency offset estimating section 240 outputs the estimated spreading code timing and the roughly estimated frequency offset to the second synchronization processing section 24 as a coarse spreading code timing estimation result and a coarse frequency offset estimation result, respectively. Timing and frequency offset estimating section 240 also outputs the spread code timing rough estimation result to power combining processing section 241 and frame timing estimating section 242 .

The power synthesizing unit 241 shifts the signal from the power value synthesizing unit 237 and the signal from the power value synthesizing unit 237a by different sample timings and synthesizes them (step S315). Specifically, the power combining processing section 241 converts the signal from the power value combining section 237 into [(difference of symbols STBC-encoded by different preamble generating section 15 of transmitting apparatus 1)×(spreading code period)+d1 ] sample timings. Here, d1 is an integer representing the sample timing difference between the estimated up-chirp timing n1 and the intermediate timing n0, and d1 can be calculated by the following equation (8).

In Equation (8), the first line on the right side is the ceiling function, and the second line is the floor function. That is, d1 calculated by equation (8) is the smallest integer greater than or equal to (n1-n0) when "n1-n0≧0" holds, and (n1- n0) is the largest integer below. The power synthesizing unit 241 also shifts the signal from the power value synthesizing unit 237a by the number of sample timings of d2 and synthesizes it with the signal from the power value synthesizing unit 237 after the shift. Here, d2 is an integer representing the sample timing difference between the estimated down-chirp timing n2 and the intermediate timing n0. d2 can be calculated by a formula in which "1" in the above formula (8) is replaced with "2", that is, a formula in which "n1" on the right side is replaced with "n2". For example, as in the above example, when the number of symbols of the modulated signal output by the modulating unit 151 of the preamble generating unit 15 is set to N _s = 8, and the STBC encoding method is changed by four symbols each in the first half and the second half, the power value is combined. The signal from the unit 237 is shifted by 4×N _c ×N _ovs +d1 samples and synthesized with the signal from the power value synthesizing unit 237a shifted by the number of d2 sample timings. The power synthesizing unit 241 transfers the synthesized signal to the frame timing estimating unit 242 .

Frame timing estimating section 242 uses the combined power value input from power combining processing section 241 , the rough spread code timing estimation result input from timing and frequency offset estimating section 240 , and the up-chirp input from threshold determining section 239 . Frame timing is estimated based on the estimated completion symbol (step S316). Specifically, the frame timing estimator 242 receives the signal from the power combiner 241 at several sample timings before and after the spread code timing coarse estimation result in the window corresponding to the preamble symbol section represented by the up-chirp estimation completion symbol. The timing at which the maximum input composite power value is obtained is detected and used as the frame timing estimation result. The frame timing estimation unit 242 outputs the frame timing estimation result to the second synchronization processing unit 24 .

Next, the hardware configuration of the receiving device 2 will be explained. In the receiving device 2, the receiving antenna 21 is realized by an antenna device. The receive filter 22 is realized by a filter circuit. The first synchronization processing section 23, the second synchronization processing section 24, the frequency offset correction section 25, the despreading section 26, the STBC decoding section 27 and the demodulation section 28 are realized by processing circuits. The processing circuitry may be a processor and memory executing programs stored in the memory, or may be dedicated hardware. Processing circuitry is also called control circuitry.

FIG. 14 is a diagram showing a configuration example of a processing circuit 90 when the processing circuit included in the receiving device 2 is realized by a processor and memory. A processing circuit 90 shown in FIG. 14 is a control circuit and includes a processor 91 and a memory 92 . When the processing circuit 90 is composed of the processor 91 and the memory 92, each function of the processing circuit 90 is implemented by software, firmware, or a combination of software and firmware. Software or firmware is written as a program and stored in memory 92 . In the processing circuit 90, each function is realized by the processor 91 reading and executing the program stored in the memory 92. FIG. That is, the processing circuitry 90 includes a memory 92 for storing programs that result in the processing of the receiving device 2 being executed. This program can also be said to be a program for causing the receiving device 2 to execute each function realized by the processing circuit 90 . This program may be provided by a storage medium storing the program, or may be provided by other means such as a communication medium.

Here, the processor 91 is, for example, a CPU (Central Processing Unit), a processing device, an arithmetic device, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor). The memory 92 is a non-volatile or volatile memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), EEPROM (registered trademark) (Electrically EPROM). This corresponds to semiconductor memory.

FIG. 15 is a diagram showing an example of the processing circuit 93 when the processing circuit included in the receiving device 2 is configured with dedicated hardware. The processing circuit 93 shown in FIG. 15 is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. thing applies. The processing circuit may be partly implemented by dedicated hardware and partly implemented by software or firmware. Thus, the processing circuitry may implement each of the functions described above through dedicated hardware, software, firmware, or a combination thereof.

Although the hardware configuration of the receiving device 2 has been described, the hardware configuration of the transmitting device 1 is the same. In the transmission device 1, the transmission antennas 19, 20 are realized by antenna devices. The transmission filters 17 and 18 are realized by filter circuits. Modulator 11, space-time block encoder 12, spectrum spreaders 13 and 14, preamble generator 15, and frame generator 16 are implemented by processing circuits. The processing circuitry may be a processor and memory executing programs stored in the memory, or may be dedicated hardware.

As described above, in the communication system 3 according to the present embodiment, the preamble generation unit 15 of the transmission device 1 performs STBC encoding on half of the preambles, and the phase relationship of the signals transmitted by the two transmission antennas 19 and 20 is are exchanged on the time axis of the STBC-encoded two symbols to generate a preamble signal. The first synchronization processing unit 23 of the receiving device 2 calculates the cross-correlation function between the spreading code of the receiving device 2 and the received signal, and calculates the complex conjugate of the matrix representing the STBC encoding performed by the preamble generating unit 15 , by the calculated cross-correlation function, and combining the multiplication results among the multiple preamble signals. Also, the first synchronization processing unit 23 detects the spread code timing from the multiplication result obtained by synthesizing a plurality of preamble signals. Further, the first synchronization processing unit 23 further synthesizes the multiplication result obtained by synthesizing the preamble signals between symbols subjected to different STBC encoding. After that, the first synchronization processing unit 23 searches for a portion where the maximum combined cross-correlation power value is obtained within a window ranging from the symbol for which the up-chirp timing estimation is completed to the preamble symbol length, thereby estimating the frame timing. To detect.

This makes it possible to improve frame detection uncertainty due to STBC encoding, and regardless of the phase relationship between the channel response values between each of the two transmitting antennas 19 and 20 and the receiving antenna 21, Since frame timing can be detected, frame synchronization can be performed while suppressing performance deterioration due to STBC encoding. In addition, frame synchronization is performed using the result of synthesizing the result of the cross-correlation function between the received signal used in the initial synchronization and the spreading code of the receiving device 2 in all preamble sections. can be performed, and the circuit scale can be suppressed.

In this embodiment, a configuration has been described in which all known preamble signals having the same value are input to modulation section 151 and the STBC encoding method is switched on the time axis, but the present invention is not limited to this. For example, by setting the known preamble signal to 0, 0, 0, 0, ..., 1, 0, 0, 1, ..., and performing the same STBC encoding on all preambles, an equivalent STBC-encoded signal may be configured to obtain As a result, the configuration of the space-time block encoder 152 of the preamble generator 15 of the transmitter 1 and the configuration of the decoders 233 and 234 of the first synchronization processor 23 of the receiver 2 can be simplified. can.

Further, in the present embodiment, the spreading codes used by the spectrum spreading sections 153 and 154 of the preamble generating section 15 provided in the transmitting apparatus 1 are generated with the sequence parameters M=1, -1 in the above equation (2). Up-chirp and down-chirp are mentioned, but not limited to this. A Zadoff-Chu sequence with M=3, 5 in Equation (2), a Zadoff-Chu sequence in which the center frequencies of up-chirp and down-chirp are combined, and the like may be used. Alternatively, only up-chirp or only down-chirp may be used. However, by using both the up-chirp and the down-chirp generated with the sequence parameter M = 1, -1 in Equation (2), even if a frequency offset occurs due to the frequency shift of the local oscillator between the transmitting and receiving devices, the accuracy can be improved. Good synchronization is possible. Also, by using a Zadoff-Chu sequence whose sequence parameter is not M=1, it is possible to perform synchronization while suppressing degradation of accuracy even during multiple access.

In addition, the preamble generation unit 15 included in the transmitting device 1 arranges the first preamble generated by combining STBC coding and up-chirp spreading according to the above equation (1) in the first half, and according to the above equation (3) Although the second preamble generated by combining STBC coding and down-chirp spreading is arranged in the latter half to configure the preamble, the method is not limited to this. For example, STBC coding and down-chirp spreading according to equation (1) are combined to generate the first half of the preamble, and STBC coding and up-chirp spreading according to equation (3) are combined to generate the second half of the preamble. , the combination of STBC coding and spread spectrum may be changed. In addition, instead of dividing the preamble for STBC encoding according to equation (1) and the preamble for STBC encoding according to equation (3) into the first half and the second half, these two STBC encodings are alternately performed by two symbols. may be By doing so, when up-chirp spreading and down-chirp spreading are used together, the symbol difference for performing up-chirp spreading or down-chirp spreading can be doubled, and multiple opening in the second synchronization processing unit 24 can be performed. The estimation accuracy of frequency offset fine synchronization using loop AFC can be improved.

Further, in the first synchronization processing unit 23 of the receiving device 2, the up-chirp correlation value calculation unit 231 and the down-chirp correlation value calculation unit 232 calculate the cross-correlation function between the spreading code and the received signal, and the decoding processing unit 233 and 234 sequentially perform STBC decoding processing, but the present invention is not limited to this. A configuration may be employed in which the decoding of STBC and the calculation of the cross-correlation function are performed simultaneously. However, with this configuration, the size of the circuit increases because the shift register length of the matched filter for calculating the cross-correlation function is equal to the number of preamble symbols×spreading code length. By sequentially performing the calculation of the cross-correlation function and the decoding of the STBC as in the present embodiment, the circuit scale does not depend on the number of preamble symbols, and the circuit scale of the first synchronization processing unit 23 increases. can be suppressed.

The configurations shown in the above embodiments are only examples, and can be combined with other known techniques, or can be combined with other embodiments, without departing from the scope of the invention. It is also possible to omit or change part of the configuration.

1 transmitter 2 receiver 3 communication system 11 151 modulator 12 152 space-time block encoder 13 14 153 154 spectrum spreader 15 preamble generator 16 frame generator 17 , 18 transmission filter, 19, 20 transmission antenna, 21 reception antenna, 22 reception filter, 23 first synchronization processing unit, 24 second synchronization processing unit, 25 frequency offset correction unit, 26 despreading unit, 27 STBC decoding unit , 28 demodulator, 30 data spreader, 50 preamble spreader, 231 up-chirp correlation value calculator, 232 down-chirp correlation value calculator, 233, 234 decoding processor, 235, 235a, 236, 236a power value calculator, 237,237a power value synthesizing unit, 238,238a correlation power memory, 239,239a threshold determining unit, 240 timing and frequency offset estimating unit, 241 power synthesizing processing unit, 242 frame timing estimating unit, 250 first power calculating unit, 251 second power calculator;

Claims (16)

Encoding processing is performed on the preamble signal to generate a first space-time block code, and a second space-time block code is generated in which the first half and the second half of the first space-time block code are interchanged. a space-time block encoder to generate;
a preamble spreader that spectrum-spreads the first space-time block code and the second space-time block code;
a frame generation unit that generates a frame including the first space-time block code after spectrum-spreading and the second space-time block code after spectrum-spreading;
A transmitting device comprising: The space-time block coding unit performs a first coding process on half of the preamble signal to generate the first space-time block code, and generates the first space-time block code on the remaining half of the preamble signal. generating the second spatio-temporal block code by executing a second encoding process in which the first encoding process is replaced on the time axis;
2. The transmitter according to claim 1, characterized by: The preamble signal is composed of a plurality of identical symbols,
The space-time block coding unit executes the first coding process on symbols in the first half of the preamble signal, and executes the second coding process on symbols in the second half of the preamble signal. do,
3. The transmitter according to claim 2, characterized by: The preamble signal is composed of a plurality of identical symbols,
The space-time block coding unit executes the first coding process on odd-numbered symbols of the preamble signal and the second coding process on even-numbered symbols of the preamble signal. do,
3. The transmitter according to claim 2, characterized by: The space-time block coding unit performs one coding process on all of the preamble signals,
A symbol string whose coding result by the space-time block coding unit includes the first space-time block code and the second space-time block code is input to the space-time block coding unit as the preamble signal. let
2. The transmitter according to claim 1, characterized by: The preamble spreader is
spectrally spreading the first space-time block code using one of an up-chirp that is a spreading code whose frequency increases with the lapse of time and a down-chirp that is a spreading code whose frequency decreases with the lapse of time, and the up-chirp and spectrum-spreading the second space-time block code with the other of the down-chirps;
6. The transmitting device according to any one of claims 1 to 5, characterized in that: The preamble spreader is
spectrum-spreading the first space-time block code using one of the two spreading codes with low correlation, and spectrum-spreading the second space-time block code using the other of the two spreading codes;
6. The transmitting device according to any one of claims 1 to 5, characterized in that: A first preamble generated by spectrum-spreading a first space-time block code generated by encoding a preamble signal and a first half symbol and a second half symbol of the first space-time block code are exchanged. and a second preamble generated by spectrum-spreading a second space-time block code having a configuration comprising:
a first correlation value calculator that calculates a first cross-correlation function that is a cross-correlation function between the spreading code used in the spectrum spreading and the first preamble;
a second correlation value calculator that calculates a second cross-correlation function that is a cross-correlation function between the spreading code and the second preamble;
a first decoding processing unit that decodes the first cross-correlation function;
a second decoding processing unit that decodes the second cross-correlation function;
a first power value calculator that calculates the power value of the decoding result of the first cross-correlation function;
a second power value calculator that calculates the power value of the decoding result of the second cross-correlation function;
a timing and frequency offset estimator for estimating spreading code timing and frequency offset based on the power value calculated by the first power value calculator and the power value calculated by the second power value calculator;
a power synthesis processing unit that combines the power value calculated by the first power value calculation unit and the power value calculated by the second power value calculation unit;
a frame timing estimation unit for estimating frame timing based on the combined power value;
A receiving device comprising: The spectrum spreading of the first space-time block code uses an up-chirp, which is a spreading code whose frequency increases over time, and the spectrum spreading of the second space-time block code uses a frequency that increases over time. A down-chirp, which is a decreasing spreading code, is used,
an up-chirp timing estimating unit that estimates the multiplication timing of the up-chirp based on the power value of the decoding result of the first cross-correlation function;
a down-chirp timing estimation unit that estimates the down-chirp multiplication timing based on the power value of the decoding result of the second cross-correlation function;
with
The timing and frequency offset estimator estimates the spreading code timing and the frequency offset based on the up-chirp multiplication timing and the down-chirp multiplication timing.
9. The receiving apparatus according to claim 8, characterized by: a transmitter according to claim 1;
a receiving device according to claim 8;
A communication system comprising: A transmission method executed by a transmission device,
Encoding processing is performed on the preamble signal to generate a first space-time block code, and a second space-time block code is generated in which the first half and the second half of the first space-time block code are interchanged. a first step of generating;
a second step of spectrally spreading the first space-time block code and the second space-time block code;
a third step of generating a frame including the first space-time block code after spectrum spreading and the second space-time block code after spectrum spreading;
A transmission method comprising: A first preamble generated by spectrum-spreading a first space-time block code generated by encoding a preamble signal and a first half symbol and a second half symbol of the first space-time block code are exchanged. a second preamble generated by spectrum-spreading a second space-time block code having a configuration of:
a first step of calculating a first cross-correlation function that is a cross-correlation function between the spreading code used in the spectrum spreading and the first preamble;
a second step of calculating a second cross-correlation function between the spreading code and the second preamble;
a third step of decoding the first cross-correlation function;
a fourth step of decoding the second cross-correlation function;
a fifth step of calculating a power value of the decoding result of said first cross-correlation function;
a sixth step of calculating a power value of the decoding result of the second cross-correlation function;
a seventh step of estimating spreading code timing and frequency offset based on the power values calculated in the fifth step and the power values calculated in the sixth step;
an eighth step of synthesizing the power value calculated in the fifth step and the power value calculated in the sixth step;
a ninth step of estimating frame timing based on the combined power values;
A timing synchronization method, comprising: A control circuit for controlling a transmitter,
Encoding processing is performed on the preamble signal to generate a first space-time block code, and a second space-time block code is generated in which the first half and the second half of the first space-time block code are interchanged. a first step of generating;
a second step of spectrally spreading the first space-time block code and the second space-time block code;
a third step of generating a frame including the first space-time block code after spectrum spreading and the second space-time block code after spectrum spreading;
A control circuit that causes the transmitting device to execute: A first preamble generated by spectrum-spreading a first space-time block code generated by encoding a preamble signal and a first half symbol and a second half symbol of the first space-time block code are exchanged. a second preamble generated by spectrum-spreading a second space-time block code having a configuration of:
a first step of calculating a first cross-correlation function that is a cross-correlation function between the spreading code used in the spectrum spreading and the first preamble;
a second step of calculating a second cross-correlation function between the spreading code and the second preamble;
a third step of decoding the first cross-correlation function;
a fourth step of decoding the second cross-correlation function;
a fifth step of calculating a power value of the decoding result of said first cross-correlation function;
a sixth step of calculating a power value of the decoding result of the second cross-correlation function;
a seventh step of estimating spreading code timing and frequency offset based on the power values calculated in the fifth step and the power values calculated in the sixth step;
an eighth step of synthesizing the power value calculated in the fifth step and the power value calculated in the sixth step;
a ninth step of estimating frame timing based on the combined power values;
A control circuit that causes the receiving device to execute: A storage medium storing a program for controlling a transmission device,
Said program
Encoding processing is performed on the preamble signal to generate a first space-time block code, and a second space-time block code is generated in which the first half and the second half of the first space-time block code are interchanged. a first step of generating;
a second step of spectrally spreading the first space-time block code and the second space-time block code;
a third step of generating a frame including the first space-time block code after spectrum spreading and the second space-time block code after spectrum spreading;
A storage medium characterized by causing the transmitting device to execute: A first preamble generated by spectrum-spreading a first space-time block code generated by encoding a preamble signal and a first half symbol and a second half symbol of the first space-time block code are exchanged. a second preamble generated by spectrum-spreading a second space-time block code having a configuration that stores a program for controlling a receiving device that receives a signal containing
Said program
a first step of calculating a first cross-correlation function that is a cross-correlation function between the spreading code used in the spectrum spreading and the first preamble;
a second step of calculating a second cross-correlation function between the spreading code and the second preamble;
a third step of decoding the first cross-correlation function;
a fourth step of decoding the second cross-correlation function;
a fifth step of calculating a power value of the decoding result of said first cross-correlation function;
a sixth step of calculating a power value of the decoding result of the second cross-correlation function;
a seventh step of estimating spreading code timing and frequency offset based on the power values calculated in the fifth step and the power values calculated in the sixth step;
an eighth step of synthesizing the power value calculated in the fifth step and the power value calculated in the sixth step;
a ninth step of estimating frame timing based on the combined power values;
A storage medium characterized by causing the receiving device to execute:

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