Transmission device, reception device, communication method, control circuit, and storage medium

Abstract

This transmission device (1) is characterized by comprising: a preamble generation unit (101) that generates a preamble signal configured from a multi-channel signal in which the channel interval, which is the frequency interval between adjacent channels, is not constant, the preamble signal including a combination of channel intervals in which the channel interval of one channel is not a natural number multiple of the channel interval of another channel; and a transmission unit (105) that performs a packet transmission by means of a transmission signal including the preamble signal.

Description

Transmitter, receiver, communication method, control circuit, and storage medium

[0001] This disclosure relates to a transmitting device, a receiving device, a communication method, a control circuit, and a storage medium for packet transmission.

[0002] In packet transmission communication systems, the receiving device synchronizes with the signal transmitted from the transmitting device in order to receive and demodulate it. Synchronization includes symbol synchronization to detect symbol timing, packet detection to detect packet timing, and frequency synchronization to estimate and correct frequency offset.

[0003] The communication standard for wireless LAN (Local Area Network) employs the OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, and a preamble signal is defined for synchronization processing in wireless LAN as well.

[0004] Patent Document 1 discloses a technique for performing synchronization processing by utilizing the fact that the time-domain signal of a short training field (STF) of a wireless LAN is a repeating signal, and by performing autocorrelation processing using the repeating portion of the signal to create a time-shifted signal.

[0005] Patent No. 5961109

[0006] However, the conventional technology described above had a problem in that when dips occurred due to frequency fluctuations in the propagation path caused by multipath, the synchronization accuracy could be significantly reduced.

[0007] For example, in a wireless LAN STF (Single-Track Function), subcarriers are spaced four subcarriers apart. If the period of a dip caused by frequency fluctuations in the propagation path due to multipath coincides with the subcarrier spacing, all subcarriers will be significantly degraded, resulting in a substantial decrease in synchronization accuracy at the receiving end.

[0008] This disclosure has been made in view of the above, and aims to provide a transmitting device that can suppress a decrease in synchronization accuracy.

[0009] In order to solve the above-described problems and achieve the object, a transmission apparatus according to the present disclosure includes a preamble signal composed of a multi-channel signal in which a channel interval, which is a frequency interval between adjacent channels, is not constant, and a combination of channel intervals is included such that the other channel interval is not a natural number multiple of one channel interval. The preamble generation unit generates a preamble signal, and a transmission unit performs packet transmission using a transmission signal including the preamble signal.

[0010] According to the present disclosure, an effect of suppressing a decrease in synchronization accuracy can be achieved.

[0011] FIG. showing the functional configuration of the transmission apparatus according to Embodiment 1, FIG. showing the functional configuration of the reception apparatus that receives the transmission signal of the transmission apparatus shown in FIG. 1, FIG. showing a configuration example of the preamble generation unit shown in FIG. 1, FIG. showing a configuration example of the preamble signal generation apparatus, FIG. explanatory diagram of an example of the preamble signal, FIG. showing the propagation path when the dip period due to the frequency fluctuation of the propagation path is 4 superimposed on the preamble signal of FIG. 5, FIG. showing the propagation path when the dip period due to the frequency fluctuation of the propagation path is 4 superimposed with the preamble signal of the comparative example, FIG. showing an example of the functional configuration of the synchronization unit, FIG. showing an example of the preamble signal of Embodiment 3, FIG. showing a configuration example of the multi-channel filter unit in the reception apparatus of Embodiment 3, FIG. showing dedicated hardware for realizing the functions of the transmission apparatus and the reception apparatus according to Embodiments 1 to 3 of the present disclosure, FIG. showing the configuration of the control circuit for realizing the functions of the transmission apparatus and the reception apparatus according to Embodiments 1 to 3 of the present disclosure

[0012] Hereinafter, a transmission apparatus, a reception apparatus, a communication method, a control circuit, and a storage medium according to embodiments of the present disclosure will be described in detail based on the drawings.

[0013] Embodiment 1. FIG. 1 is a diagram showing the functional configuration of a transmission apparatus 1 according to Embodiment 1. The transmission apparatus 1 includes a modulation unit 100, a preamble generation unit 101, a selector unit 102, a transmission filter unit 103, a frequency conversion unit 104, and a transmission unit 105.

[0014] The modulation unit 100 modulates the transmission data and outputs the modulated signal to the selector unit 102. The preamble generation unit 101 generates a preamble signal and outputs the generated preamble signal to the selector unit 102. The selector unit 102 selects either the modulated signal output by the modulation unit 100 or the preamble signal output by the preamble generation unit 101, and outputs the selected signal to the transmission filter unit 103. The transmission filter unit 103 filters the signal output by the selector unit 102 with a filter for transmission, and outputs the filtered signal to the frequency conversion unit 104. The frequency conversion unit 104 frequency-converts the signal output by the transmission filter unit 103, and outputs the frequency-converted signal to the transmission unit 105. The transmission unit 105 transmits the signal output by the frequency conversion unit 104.

[0015] FIG. 2 is a diagram showing the functional configuration of the receiving apparatus 2 that receives the transmission signal of the transmission apparatus 1 shown in FIG. 1. The receiving apparatus 2 includes a receiving unit 200, a frequency conversion unit 201, a receiving filter unit 202, a synchronization unit 203, and a demodulation unit 204.

[0016] The receiving unit 200 receives the transmission signal transmitted by the transmission apparatus 1 and outputs the received signal to the frequency conversion unit 201. The frequency conversion unit 201 frequency-converts the received signal output by the receiving unit 200 into a baseband signal and outputs the baseband signal to the receiving filter unit 202. The receiving filter unit 202 filters the baseband signal with a filter for reception in the communication band and outputs the filtered signal to the synchronization unit 203. The synchronization unit 203 performs synchronization processing such as symbol synchronization for detecting symbol timing, packet detection for detecting packet timing, and frequency synchronization for matching the clock frequencies between transmission and reception by detecting a preamble signal from the signal output by the receiving filter unit 202, and outputs the signal after the synchronization processing to the demodulation unit 204. The demodulation unit 204 performs demodulation processing for demodulating the received signal excluding the preamble signal based on the symbol timing and packet timing detected by the synchronization unit 203. The demodulation unit 204 outputs the demodulated data generated by the demodulation processing.

[0017] Figure 3 shows an example configuration of the preamble generation unit 101 shown in Figure 1. The preamble generation unit 101 includes, for example, a memory unit 110 and a memory read control unit 111. Since the preamble signal is constructed based on a known sequence in the receiving device 2, the preamble signal generated in advance is stored in the memory unit 110, and the preamble signal is read out from the memory unit 110 according to the read control of the memory read control unit 111.

[0018] Here, we will explain how to generate the preamble signal. As described above, the transmitting device 1 reads the preamble signal that has been pre-stored in the memory unit 110. The preamble signal used by the transmitting device 1 can be generated, for example, by the preamble signal generation device 3 shown in Figure 4.

[0019] Figure 4 shows an example of the configuration of the preamble signal generation device 3. The preamble signal generation device 3 includes a known sequence generation unit 120 for preamble, a modulation processing unit 121, a roll-off filter unit 122, a frequency shift unit 123, and an adder unit 124.

[0020] The preamble known sequence generation unit 120 generates known sequences for channels #1 to #N, corresponding to the number of channels in the preamble signal. For example, a Gold sequence with good cross-correlation characteristics can be used as the known sequence. Here, the known sequence used by the preamble known sequence generation unit 120 is not limited to the Gold sequence, but may also be an M sequence, a PN (Pseudo-random Noise) sequence, etc. The preamble known sequence generation unit 120 generates Ns bits of known sequences for each channel, corresponding to the number of symbols Ns in the preamble signal. The preamble known sequence generation unit 120 outputs the generated known sequences to the modulation processing unit 121.

[0021] The modulation processing unit 121 modulates the known sequence for each channel. The modulation processing unit 121 can use DBPSK (Differential Binary Phase Shift Keying) as the modulation method. However, the modulation method used by the modulation processing unit 121 is not limited to DBPSK, and other modulation methods may be used. When modulating the known sequence, the modulation processing unit 121 uses the symbol rate R per channel of the preamble signal. s A modulated signal is generated according to the following. Here, when the communication wave bandwidth is B, the modulation processing unit 121 calculates B / R s The modulated signal is generated at double the oversampling rate. The modulation processing unit 121 outputs the multiple modulated signals, each generated by modulating one of the multiple known sequences, to the roll-off filter unit 122.

[0022] The roll-off filter unit 122 applies a roll-off filter according to the roll-off ratio to each of the multiple modulated signals output by the modulation processing unit 121, generating a spectrally shaped modulated signal. The preamble signal generated by the preamble signal generator 3 is a multi-channel signal composed of multiple channels. Therefore, the processing by the roll-off filter unit 122 is performed in order to control the influence on other channels within the communication bandwidth. The roll-off filter unit 122 outputs the multiple modulated signals after processing to the frequency shift unit 123.

[0023] The frequency shift unit 123 performs channel-specific frequency shift processing on the spectrally shaped modulated signal for each channel. The frequency shift amount f is set for channel number n. n This is predetermined. Channel number n takes values ​​from 1 to N. Also, the frequency interval between adjacent channels is called the channel interval, and the channel interval between channel number x+1 and x is Δf x If defined as such, the channel number x takes values ​​from 1 to N-1, and Δf x = f x+1 -f x The channel numbers are assigned in ascending order from the lowest frequency channel. In this case, for any two different a and b (a ≠ b), Δfa and Δf b such that there exists a frequency shift amount f where the relationship with natural number multiples does not hold for Δf n is determined. In other words, for one channel interval Δf a and the other channel interval Δf b there exists at least one combination of a and b such that it does not become a natural number multiple, and the frequency shift amount f n is determined.

[0024] FIG. 5 is an explanatory diagram of an example of a preamble signal. In FIG. 5, a preamble signal composed of 12 channels 300, that is, a preamble signal with the number of channels N = 12 is shown. In FIG. 5, the communication bandwidth B is divided into 64 parts, and B / 64 is expressed as 1. For the channel intervals Δf x corresponding to the channel numbers x = 1 to 11 in FIG. 5, specifically, Δf1 = 5, Δf2 = 4, Δf3 = 4, Δf4 = 6, Δf5 = 4, Δf6 = 8, Δf7 = 4, Δf8 = 5, Δf9 = 3, Δf 10 = 6, Δf 11 = 4. In this case, for example, Δf1 = 5 and Δf2 = 4 do not have a relationship of natural number multiples.

[0025] Here, the effects of using the preamble signal shown in FIG. 5 will be described. As shown in FIG. 5, by setting the frequency shift amount f a such that there exists at least one combination of a and b such that the other channel interval Δf b does not become a natural number multiple with respect to one channel interval Δf n even if dips due to frequency fluctuations in the propagation path occurring in a multipath environment occur periodically, it becomes possible to suppress a deterioration in reception quality.

[0026] Figure 6 shows the preamble signal in Figure 5 overlaid with the propagation path 301 when the dip period D due to frequency fluctuations in the propagation path is 4. In Figure 6, dip positions due to propagation path 301 occur at intervals of 4 from frequency -30. However, the channels where degradation due to dips occurs are channel numbers n = 2, 3, 4, 11, and 12, and no significant degradation due to dips occurs in the other channels. Propagation path 301 is just one example, and when the dip period D of the propagation path is greater than 1, the dip positions will not overlap with all channels in the preamble signal in Figure 5.

[0027] Here, the dip period D due to frequency fluctuations in the propagation path depends on the maximum delay time of the multipath. For example, in the case of a multipath with two equal-power waves, the maximum delay time of the delayed wave in the assumed multipath environment is τ max In this case, the dip period D [Hz] due to frequency fluctuations in the propagation path is expressed by the following formula (1).

[0028] D = 1 / τ max ... (1)

[0029] In other words, the dip period D due to frequency fluctuations in the propagation path exceeds 1 when the delay wave reaches its maximum delay time τ. max This is when the delay time is less than or equal to 64 / B [sec]. For example, when the communication wave bandwidth B = 20 MHz, the maximum delay time τ of the delayed wave is less than or equal to 64 / B [sec]. max When the time interval is 3.2 μsec or less, the dip period D due to frequency fluctuations in the propagation path will be greater than 1. In this case, using a preamble signal as shown in Figure 5 can avoid a situation where "the dip position overlaps across all channels."

[0030] Furthermore, if all channel spacings are natural multiples of the dip period D, the dip positions will overlap across all channels. Therefore, the channel spacing of the preamble signal should be set to the maximum delay time τ of the delayed wave in the assumed multipath environment. max It is desirable to include values ​​that are not natural multiples of 1 / 2.

[0031] To explain the effect of the preamble signal shown in Figure 5, we will use a comparative example. Figure 7 is a diagram in which the preamble signal of the comparative example is superimposed on the propagation path 302 when the dip period D due to frequency fluctuations of the propagation path is 4. The preamble signal of the comparative example does not satisfy the conditions explained using Figure 5. That is, in the preamble signal of the comparative example, one channel spacing Δf a In contrast, the other channel spacing Δf b The frequency shift amount f exists such that there is no combination of a and b that does not result in a natural number multiple. n This is the setting. Specifically, in the preamble signal of the comparative example shown in Figure 7, the channel spacing Δf6 = 8, and the other channel spacings are 4. In this case, if a propagation path 302 with a dip period D = 4 occurs, the dip position will overlap with all channels, and all channels will be degraded.

[0032] Returning to the explanation of Figure 4, the frequency shift unit 123 sets a set frequency shift amount f for each of the multiple channels. n After performing frequency shift processing and generating signals for each channel, the generated signals are output to the summing unit 124.

[0033] The summing unit 124 adds up all the multiple signals that have been frequency-shifted for each channel. This generates a multi-channel preamble signal. The summing unit 124 outputs the generated preamble signal.

[0034] Next, as explained above, the channel spacing Δf a In contrast, the other channel spacing Δf b This section describes the synchronization process in a receiving device 2 that receives a transmission signal containing a preamble signal composed of a multi-channel signal where there is one or more combinations of a and b such that the result is not a natural number multiple. Note that the synchronization method described here is just one example and is not limited to the example described.

[0035] Figure 8 shows an example of the functional configuration of the synchronization unit 203. The synchronization unit 203 includes a multi-channel filter unit 210, a demodulation unit 211, a correlation accumulation unit 212, a peak detection unit 213, and a frequency offset estimation unit 214. Each part of the synchronization unit 203 will be described below.

[0036] The multi-channel filter unit 210 filters the received signal output by the receiving filter unit 202 to extract a signal for each channel and performs downsampling according to the symbol rate per channel. For example, when the transmitting device 1 transmits a transmission signal including the preamble signal shown in Figure 5, the number of channels N = 12, so the multi-channel filter unit 210 filters to extract 12 channels. The multi-channel filter unit 210 outputs the 12 filtered signals at a sampling rate oversampled relative to the symbol rate per channel through downsampling processing. The multi-channel filter unit 210 outputs the 12 filtered and downsampled signals as a time signal. Note that the multi-channel filter unit 210 may also output the signal at a sampling rate equal to the symbol rate without oversampling during the downsampling process. The multi-channel filter unit 210 outputs the signals for the number of channels after processing to the demodulation unit 211.

[0037] The demodulation unit 211 performs demodulation processing on the time signals extracted for each channel output by the multi-channel filter unit 210. The demodulation unit 211 performs demodulation processing according to the modulation scheme used when generating the preamble signal. For example, if DBPSK is used as the modulation scheme when generating the preamble signal, the demodulation unit 211 performs demodulation processing for DBPSK. In the case of DBPSK, demodulation processing is performed by complex multiplication by a signal with a 1-symbol delay and complex conjugate in order to perform differential decoding processing. The demodulation unit 211 performs demodulation processing on the time signals for the number of channels and outputs the demodulation result signals, which are the demodulation results for the number of channels, to the correlation accumulation unit 212.

[0038] The correlation accumulation unit 212 performs cross-correlation processing using a known sequence on the demodulated result signals for the number of channels. The correlation accumulation unit 212 performs correlation processing on the demodulated result signals for the length of the known sequence and accumulates the correlation results for the length of the sequence. At this time, the correlation results are complex signals, so the correlation accumulation unit 212 accumulates them as complex signals. Furthermore, since there are as many accumulated results as there are channels, the accumulated results for each channel are also accumulated as complex signals. The correlation accumulation unit 212 performs the above cross-correlation processing and accumulation processing on a unit-by-unit basis of the input symbol. If the input signal is oversampled, the correlation accumulation unit 212 performs cross-correlation processing and accumulation processing on a unit-by-unit basis of the oversampled signal. After performing the cross-correlation processing and accumulation processing, the correlation accumulation unit 212 outputs the accumulated results to the peak detection unit 213 and the frequency offset estimation unit 214, respectively.

[0039] The peak detection unit 213 converts the cumulative result output by the correlation accumulation unit 212 in units of one symbol or one oversample into an amplitude, compares the amplitude value with a threshold, and determines that a packet has been detected if it exceeds the threshold. The unit outputs the timing at which the amplitude value exceeds the threshold as the packet detection and symbol timing detection result. Here, the threshold is a predetermined value.

[0040] The frequency offset estimation unit 214 estimates the frequency offset using the cumulative timing results obtained by the peak detection unit 213 for packet detection and symbol timing detection. Specifically, in the case of differential coding modulation such as DBPSK, the demodulation unit 211 performs complex multiplication by complex conjugate with a signal with a one-symbol delay. Therefore, the cumulative result can be treated as the amount of phase change per symbol. Accordingly, the frequency offset estimation unit 214 obtains the phase by performing an arctangent operation on the cumulative result, normalizes the obtained phase θ [rad] by 2π, and calculates the time per symbol 1 / R. s The frequency offset q is estimated by dividing by . The frequency offset estimation unit 214 can calculate the frequency offset q using the following formula (2).

[0041] q = θ / (2π) × R s ... (2)

[0042] The frequency offset estimation unit 214 outputs the estimated frequency offset value to the demodulation unit 204.

[0043] As described above, according to Embodiment 1, a transmission device 1 is provided that comprises a preamble generation unit 101 that generates a preamble signal composed of a multi-channel signal in which the channel intervals, which are the frequency intervals between adjacent channels, are not constant, and which includes a combination of channel intervals such that the channel interval of one channel is not a natural number multiple of the channel interval of the other channel; and a transmission unit 105 that performs packet transmission with a transmission signal including the preamble signal having the above characteristics.

[0044] As described above, by using a preamble signal composed of a multi-channel signal that includes channel spacing combinations such that the channel spacing of one channel is not a natural number multiple of the channel spacing of the other, it is possible to reduce the degradation of the preamble signal. In particular, it is possible to prevent significant preamble signal degradation where dip positions overlap across all channels in a particular transmission line.

[0045] Furthermore, the channel spacing of the preamble signal included in the transmission signal of the transmitter 1 includes channels that are not natural multiples of the dip period D due to frequency fluctuations in the propagation path. In other words, the channel spacing of the preamble signal is equal to the maximum delay time τ of the delayed wave in the assumed multipath environment. max This includes values ​​that are not natural multiples of 1 / 2. In this case, it is possible to prevent the situation where "the dip position overlaps across all channels of the preamble signal due to dips caused by frequency fluctuations in the propagation path."

[0046] Embodiment 2. Embodiment 1 reduces the degradation of the preamble signal by avoiding, as much as possible, the occurrence of the dip period D due to frequency fluctuations in the propagation path coinciding with the channel spacing. However, even if the overlap between the dip position and the channel due to frequency fluctuations in the propagation path is avoided, if a delay wave exists in a multipath environment, the maximum delay time τmax Intersymbol interference occurs accordingly. Adaptive equalization is an effective countermeasure against intersymbol interference. However, since synchronization processing using preamble signals is usually required to operate with an open aperture, performing adaptive equalization processing before synchronization processing is extremely difficult from a computational standpoint. For this reason, in Embodiment 2, the effect of intersymbol interference is reduced by adjusting the symbol rate per channel of the preamble signal. The configuration of the transmitting device 1 and receiving device 2 in Embodiment 2 is the same as in Embodiment 1, and the following will mainly describe the parts that differ from Embodiment 1.

[0047] Intersymbol interference is caused by the symbol length T per channel of the preamble signal. s (= 1 / R) s ) Maximum delay time τ of the delayed wave max This is determined by the following. Therefore, in Embodiment 2, the maximum delay time τ max to, τ max ≦T s By multiplying by 2, the effects of intersymbol interference can be reduced. In other words, the maximum delay time τ in a multipath environment for environments using wireless communication. max If this is assumed, the symbol rate R per channel of the preamble s R s ≤ 1 / (2τ) max ) . In this case, the dip period D [Hz] (= 1 / τ) due to frequency fluctuations in the propagation path is assumed to be ). max ) is D≧2R s This is the result.

[0048] Next, let's consider the channel spacing of the preamble signal. As explained in Embodiment 1, if the channel spacing of the preamble signal includes channels that are not natural multiples of the dip period D, even if dips occur due to frequency fluctuations in the propagation path, it is possible to avoid the situation where "the dip positions overlap across all channels of the preamble signal."

[0049] Considering the regulations on antenna power under the Radio Law, for example, in the 2.4 GHz band, if antenna power is defined as the average power per MHz, then if the minimum channel spacing is 1 MHz or more, the average power per channel is limited by the regulations on antenna power under the Radio Law, regardless of the symbol rate per channel. However, if the symbol rate per channel decreases, the bandwidth narrows, and consequently, the noise power received by each channel also decreases. As a result, by reducing the symbol rate when the minimum channel spacing is 1 MHz or more, the signal power to noise power ratio per channel increases, improving the synchronization performance of the receiver using the preamble signal. However, when frequency synchronization is performed on the receiver side using the preamble signal, the frequency offset is estimated by the phase change between symbols, so the estimated allowable frequency offset F e is, "-R s / 2 < F e <R s The range is " / 2". Therefore, the symbol rate R depends on the expected frequency offset. s We need to decide that.

[0050] As described above, according to Embodiment 2, the symbol rate per channel of the preamble signal included in the transmission signal of the transmitting device 1 is 1, and the maximum delay time τ of the delayed wave in the assumed multipath environment is 1. max It is less than or equal to the value obtained by dividing by twice the value. This reduces intersymbol interference due to multipath. Furthermore, by setting the minimum channel spacing of the preamble signal to the unit frequency of the antenna power specification in the Radio Law, for example, 1 MHz or more, the signal-to-noise power ratio per channel can be increased according to the symbol rate, thereby improving the synchronization performance using the preamble signal on the receiving side.

[0051] Embodiment 3. The transmitting device 1 according to Embodiment 2 can avoid the dip period D due to frequency fluctuations in the propagation path and the channel spacing being the same, similar to Embodiment 1. Furthermore, in Embodiment 2, intersymbol interference due to multipath was reduced by adjusting the symbol rate value per channel of the preamble signal, and synchronization performance on the receiving side was improved by making the minimum channel spacing of the preamble signal equal to or greater than the unit frequency specified in the antenna power regulations under the Radio Law. However, in the above transmitting device 1, since a preamble signal composed of a multichannel signal with non-constant channel spacing is used, the amount of computation in the multichannel filter unit 210 within the synchronization unit 203 on the receiving side increases. Specifically, in the multichannel filter unit 210, if the signal is extracted for each channel, downsampled, and output, filtering and downsampling are required for each channel, which increases the amount of computation.

[0052] It is known that when the channel spacing is constant, the computational load can be reduced by using a polyphase filter bank with FFT (Fast Fourier Transform). However, as mentioned above, keeping all channel spacings constant can cause significant degradation of the preamble signal. Therefore, in Embodiment 3, multiple groups of adjacent channels are provided, and the channel spacing within each group is adjusted so that a polyphase filter bank using FFT can be used on a group-by-group basis.

[0053] Figure 9 shows an example of a preamble signal in Embodiment 3. Here, the 12 channels included in the preamble signal are divided into three groups: Group #1 to Group #3. Each group consists of four channels. Specifically, Group #1 consists of channels 1 to 4, Group #2 consists of channels 5 to 8, and Group #3 consists of channels 9 to 12. The group numbers are assigned in ascending order from the lowest frequency. Here, the channel spacing between the closest channels in two adjacent groups, Group #x and Group #x+1, is Δg.x For example, the channel spacing between group #1 and group #2 is Δg1 = Δf4 = 6, and the channel spacing between group #2 and group #3 is Δg2 = Δf8 = 6.

[0054] Here, the channel spacing within a group is set to be a natural number multiple of the minimum channel spacing within that group. This allows the multi-channel filter unit 210 at the receiving end to process channels on a group-by-group basis, enabling the use of a polyphase filter bank using FFT on a group-by-group basis and reducing the computational load. In the example in Figure 9, the channel spacings within group #1 are Δf1, Δf2, Δf3. The channel spacings within group #2 are Δf5, Δf6, Δf7. The channel spacings within group #3 are Δf9, Δf 10 , Δf 11 That is the case.

[0055] Furthermore, the channel spacing Δg between groups x The group is set to include elements that are not natural multiples of the minimum channel spacing within the group. This ensures that even if the dip period D due to propagation path frequency fluctuations matches the channel spacing within a group, the matching of channel spacing and dip period D between groups can be avoided.

[0056] In the example shown in Figure 9, Δf1 = 4, Δf2 = 4, Δf3 = 4, so the minimum channel spacing for group #1 is 4. Also, Δf5 = 4, Δf6 = 8, Δf7 = 4, so the minimum channel spacing for group #2 is 4. Furthermore, Δf9 = 4, Δf 10 = 4, Δf 11 Since Δg1 = 4, the minimum channel spacing for group #3 is 4. Because the channel spacings between groups are Δg1 = 6 and Δg2 = 6, it can be seen that the preamble signal has a configuration that satisfies the above conditions. In the example in Figure 9, the minimum channel spacing for each group was the same at 4, but the minimum channel spacing for each group may be different.

[0057] Figure 10 shows an example of the configuration of the multi-channel filter unit 210 in the receiving device 2 of Embodiment 3. Although only the multi-channel filter unit 210 is shown in Figure 10, the receiving device 2 according to Embodiment 3 has the configuration shown in Figure 2, and the synchronization unit 203 has the configuration shown in Figure 8. Detailed explanations of parts of the receiving device 2 that are the same as those in Embodiment 1 are omitted.

[0058] The multi-channel filter section 210 includes frequency shift sections 220-1 to 220-M, polyphase filter bank sections 221-1 to 221-M, and a selector section 222. Hereinafter, when it is not necessary to distinguish between multiple components having similar functions, only the common designation will be used in the description. When it is necessary to distinguish between multiple components having similar functions, a hyphen will be followed by a different designation to indicate the common designation. For example, when it is not necessary to distinguish between the frequency shift sections 220-1 to 220-M, they will be referred to as frequency shift section 220.

[0059] The multi-channel filter unit 210 has the same number of frequency shift units 220 and polyphase filter bank units 221 as the number of groups M included in the preamble signal. The M frequency shift units 220 and polyphase filter bank units 221 are arranged in parallel. The frequency shift units 220 and polyphase filter bank units 221 process each group. For example, in group #1, the frequency shift unit 220 shifts the frequency to a position where the preamble signal of group #1 can be extracted, and the polyphase filter bank unit 221 extracts channels from the frequency-shifted received signal, downsamples them, and outputs them. After performing the above processing for each group, the selector unit 222 selects and outputs the channels corresponding to the group from the outputs of the polyphase filter bank units 221-1 to 221-M for each group.

[0060] As described above, according to Embodiment 3, the channels of the preamble signal are divided into multiple groups, each containing multiple adjacent channels. The channel spacing within a group is set to a natural number multiple of the minimum channel spacing within that group, while the channel spacing between groups is set to include those that are not natural number multiples of the minimum channel spacing within a group. This makes it possible to use a polyphase filter bank using FFT on a group-by-group basis when extracting channels in the multi-channel filter unit 210 of the receiving device 2, thereby reducing the amount of computation. Furthermore, while there is a possibility that the dip period D due to frequency fluctuations in the propagation path and the channel spacing may coincide within a group, it is possible to avoid the dip period D and channel spacing coinciding between groups.

[0061] Next, a hardware configuration for realizing the functions of the transmitting device 1 and receiving device 2 according to embodiments 1 to 3 of this disclosure will be described. The functions of the transmitting device 1 and receiving device 2 are realized by processing circuits. These processing circuits may be realized by dedicated hardware or by control circuits using a CPU (Central Processing Unit).

[0062] When the above processing circuits are implemented using dedicated hardware, they are implemented by the processing circuit 90 shown in Figure 11. Figure 11 is a diagram showing dedicated hardware for implementing the functions of the transmitting device 1 and receiving device 2 according to embodiments 1 to 3 of this disclosure. The processing circuit 90 is 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.

[0063] When the above processing circuit is implemented using a control circuit with a CPU, this control circuit is, for example, a control circuit 91 with the configuration shown in Figure 12. Figure 12 is a diagram showing the configuration of a control circuit 91 for realizing the functions of a transmitting device 1 and a receiving device 2 according to embodiments 1 to 3 of this disclosure. As shown in Figure 12, the control circuit 91 comprises a processor 92 and a memory 93. The processor 92 is a CPU, also called a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, DSP (Digital Signal Processor), etc. The memory 93 is, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), EEPROM (Registered Trademark) (Electrically EPROM), magnetic disk, flexible disk, optical disk, compact disk, minidisc, DVD (Digital Versatile Disk), etc.

[0064] When the above processing circuit is implemented by the control circuit 91, it is implemented by the processor 92 reading and executing the program corresponding to the processing of each component, which is stored in the memory 93. The memory 93 is also used as temporary memory for each process executed by the processor 92. The program may be provided stored on a storage medium or provided via a communication channel such as the internet.

[0065] The configurations shown in the embodiments described above are merely examples of the content of this disclosure and can be combined with other known technologies, and parts of the configuration can be omitted or modified without departing from the gist of this disclosure.

[0066] 1 Transmitter, 2 Receiver, 3 Preamble signal generator, 90 Processing circuit, 91 Control circuit, 92 Processor, 93 Memory, 100 Modulation unit, 101 Preamble generation unit, 102, 222 Selector unit, 103 Transmit filter unit, 104, 201 Frequency conversion unit, 105 Transmit unit, 110 Memory unit, 111 Memory read control unit, 120 Known sequence generation unit for preamble, 121 Modulation processing unit, 122 Roll-off filter unit, 123, 220, 220-1, 220-M Frequency shift unit, 124 Adder, 200 Receiver, 202 Receiver filter unit, 203 Synchronization unit, 204, 211 Demodulation unit, 210 Multi-channel filter unit, 212 Correlation accumulation unit, 213 Peak detection unit, 214 Frequency offset estimation section, 221, 221-1, 221-M Polyphase filter bank section, 301, 302 Propagation path, B Communication wave bandwidth, D Dip period, F e Estimated tolerance, f n Frequency shift amount, M number of groups, N number of channels, N s Symbol count, q frequency offset, R s Symbol rate, T s Symbol length, τ max Maximum delay time.

Claims

1. A transmitting device comprising: a preamble generation unit that generates a preamble signal composed of a multi-channel signal in which the channel intervals, which are the frequency intervals between adjacent channels, are not constant, and which includes a combination of channel intervals such that the channel interval of one channel is not a natural number multiple of the channel interval of the other; and a transmitting unit that performs packet transmission using a transmission signal including the preamble signal.

2. The transmitting device according to claim 1, characterized in that the channel spacing of the preamble signal includes values ​​that are not natural number multiples of 1 of the maximum delay time of the delayed wave in the assumed multipath environment.

3. The transmitting device according to claim 1 or 2, characterized in that the symbol rate per channel of the preamble signal is less than or equal to the value obtained by dividing 1 by twice the maximum delay time of the delayed wave in the assumed multipath environment.

4. The transmitting device according to any one of claims 1 to 3, characterized in that the minimum channel spacing of the preamble signal is equal to or greater than the unit frequency specified for antenna power.

5. The transmitting device according to any one of claims 1 to 4, characterized in that the channels of the preamble signal are divided into a plurality of groups including a plurality of adjacent channels, the channel spacing within a group is a natural number multiple of the minimum channel spacing within that group, and the channel spacing between groups is not a natural number multiple of the minimum channel spacing within a group.

6. A receiving device comprising: a receiving unit that receives the transmission signal transmitted by the transmitting device described in claim 5; and a synchronization unit that extracts the channels using a polyphase filter bank based on a fast Fourier transform on a group basis.

7. A communication method comprising the steps of: generating a preamble signal composed of a multi-channel signal in which the channel intervals, which are the frequency intervals between adjacent channels, are not constant, and which includes a combination of channel intervals such that the channel interval of one channel is not a natural number multiple of the channel interval of the other; and performing packet transmission with a transmission signal including the preamble signal.

8. A control circuit for controlling a transmitting device that performs packet transmission, characterized in that it causes the transmitting device to perform the step of generating a preamble signal which is composed of a multi-channel signal in which the channel intervals, which are the frequency intervals between adjacent channels, are not constant, and which includes a combination of channel intervals such that the channel interval of one channel is not a natural number multiple of the channel interval of the other.

9. A storage medium for storing a program for controlling a transmitting device that performs packet transmission, wherein the program causes the transmitting device to perform the following steps: generate a preamble signal which is composed of a multi-channel signal in which the channel intervals, which are the frequency intervals between adjacent channels, are not constant, and which includes a combination of channel intervals such that the channel interval of one channel is not a natural number multiple of the channel interval of the other.

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