JP4591969B2 - COMMUNICATION METHOD, RADIO DEVICE USING THE SAME, AND COMMUNICATION SYSTEM - Google Patents

Description

  The present invention relates to a communication technique, and more particularly to a communication method for executing communication according to transmission path characteristics between two wireless devices, and a wireless device and a communication system using the communication method.

  An OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, which is one of the multicarrier schemes, is a communication scheme that enables high-speed data transmission and is strong in a multipath environment. This OFDM modulation scheme is applied to IEEE802.11a, g and HIPERLAN / 2, which are standardized standards for wireless LAN (Local Area Network). A packet signal in such a wireless LAN is generally transmitted via a transmission path environment that fluctuates with time, and is affected by frequency selective fading. Therefore, a receiver generally performs transmission path estimation dynamically. Execute.

In order for the receiving apparatus to perform transmission path estimation, two types of known signals are provided in the packet signal. One is a known signal provided for all carriers at the beginning of the packet signal, which is a so-called preamble or training signal. The other is a known signal provided for some of the carriers in the data interval of the packet signal, which is a so-called pilot signal (see, for example, Non-Patent Document 1).
Sine Coleri, Mustafa Ergen, Anuj Puri, and Ahmad Bahai, “Channel Estimate Techniques Based on Pilot Arrangement in OFDM Systems”, IbnEnts. 48, no. 3, pp. 223-229, Sept. 2002.

  One technique for effectively using frequency resources in wireless communication is an adaptive array antenna technique. The adaptive array antenna technology controls the directivity pattern of an antenna by controlling the amplitude and phase of a signal to be processed in each of a plurality of antennas. There is a MIMO (Multiple Input Multiple Output) system as a technique for increasing the data rate by using such adaptive array antenna technology. In the MIMO system, each of a transmission apparatus and a reception apparatus includes a plurality of antennas, and sets packet signals to be transmitted in parallel (hereinafter, each of data to be transmitted in parallel in a packet signal is referred to as a “sequence”. ). That is, the data rate is improved by setting a sequence up to the maximum number of antennas for communication between the transmission device and the reception device.

  Furthermore, when such an MIMO system is combined with an OFDM modulation scheme, the data rate is further increased. In the MIMO system, the data rate can be adjusted by increasing or decreasing the number of antennas to be used for data communication. Furthermore, the adjustment of the data rate is made in more detail by applying adaptive modulation. In addition, the data rate is increased by the transmission apparatus performing beamforming. In adaptive modulation and beamforming, communication according to the transmission path characteristics between the transmission apparatus and the reception apparatus is executed, so that communication suitable for the transmission path characteristics is realized.

  In order to improve the processing accuracy of adaptive modulation and beamforming, it is preferable that the receiving device acquires the respective transmission path characteristics between the plurality of antennas included in the transmitting device and the plurality of antennas included in the receiving device. desirable. In order to improve the accuracy of acquisition of transmission path characteristics, the transmission apparatus or the reception apparatus transmits known signals for transmission path estimation from all antennas. Hereinafter, a known signal for channel estimation arranged in a plurality of sequences is referred to as a “training signal” regardless of the number of sequences in which data is arranged. For example, even when the data is arranged in two series, the training signal is arranged in four series.

  Under such circumstances, the present inventor has come to recognize the following problems. After acquiring the transmission path characteristics, the receiving apparatus transmits the acquired transmission path characteristics to the transmission apparatus. When the signal is a plurality of sequences and the OFDM modulation scheme is used, the transmission path characteristics are defined in units of sequences and subcarriers. That is, the amount of information of transmission path characteristics increases, and transmission efficiency decreases. On the other hand, higher transmission efficiency is desirable from the viewpoint of effective use of frequency.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a communication technique that suppresses deterioration in transmission efficiency when transmitting transmission path characteristics.

  In order to solve the above problems, a wireless device according to an aspect of the present invention includes a reception unit that receives a signal from a communication target wireless device, and a communication target wireless device based on a signal received by the reception unit. A derivation unit for deriving transmission line characteristics in the frequency domain, a conversion unit for converting the transmission line characteristic derived in the derivation unit from the frequency domain to the time domain, and a time domain transmission line characteristic converted by the conversion unit. A transmission unit that transmits to a wireless device to be communicated. The conversion unit assumes that the value of the component having a large delay time in the time domain transmission path characteristics is zero, and thereby converts the time domain transmission path characteristics from the number of components that should constitute the frequency domain transmission path characteristics. Reduce the number of components to be composed.

  According to this aspect, by assuming that the value of the component having a large delay time in the time domain transmission path characteristics is zero, the time domain transmission path characteristics having fewer components than the frequency domain transmission path characteristics are derived. it can.

  Another aspect of the present invention is also a wireless device. This device is a multicarrier signal from a wireless device to be communicated and receives a multicarrier signal formed by a plurality of sequences, and a multicarrier signal received by the receiving unit, A derivation unit for deriving transmission path characteristics for each of a plurality of sequences in units of carriers, a conversion unit for converting transmission line characteristics in units of carriers derived in the derivation unit into transmission line characteristics in units of delay time, and conversion in the conversion unit A transmission unit that transmits transmission path characteristics in units of delay time to a wireless device to be communicated. The conversion unit assumes that the value of the component having a large delay time out of the channel characteristics in the delay time unit is zero, so that the transmission path in the delay time unit is larger than the number of components that should constitute the carrier channel characteristic. Reduce the number of components that should constitute the characteristic.

  “Transmission path characteristics in units of carriers” are transmission path characteristics for each carrier, and “transmission path characteristics in units of delay times” are transmission path characteristics for different values of delay times. According to this aspect, by assuming that the value of the component having a large delay time among the channel characteristics of the delay time unit is zero, the channel characteristics of the delay time unit having a smaller number of components than the channel characteristics of the carrier unit. Can be derived.

  The multicarrier signal to be received by the receiving unit constitutes a packet signal, and a data signal is arranged in at least one of a plurality of series, and is known in the previous stage of the data signal in the series in which the data signal is arranged. An additional known signal is arranged at a timing other than the timing at which the known signal is arranged and the timing at which the data signal is arranged with respect to the series in which the data signal is not arranged while the signal is arranged. Using the known signal included in the received multicarrier signal and the previously stored known signal, the channel characteristics for the sequence in which the data signal is arranged are derived for each carrier and included in the received multicarrier signal. Sequence in which no data signal is allocated using the additional known signal stored in advance and the additional known signal stored in advance Channel characteristics against may also derive the carrier unit.

  The “pre-stored known signal” and the “pre-stored additional known signal” may be the same signal, not different signals. In this case, since the known signal is also arranged in the sequence where the data signal is not arranged, the transmission path characteristic for the sequence where the data signal is not arranged can be derived.

  The conversion unit is a conversion coefficient for converting transmission line characteristics in units of carriers into transmission line characteristics in units of delay times, and is formed by a plurality of components to be multiplied by the respective transmission line coefficient components in units of carriers. A storage unit for storing the conversion coefficient, and an execution unit for deriving the transmission line characteristic in a delay time unit by multiplying the conversion coefficient stored in the storage unit and the transmission line characteristic in a carrier unit in association with the component unit; May be provided. The conversion coefficient stored in the storage unit may be defined so as to include only a value corresponding to a component having a small delay time with respect to each component in a carrier unit. In this case, since the conversion coefficient is defined so that only the value corresponding to the component with a small delay time is included for each component in the carrier unit, the delay time unit in which the number of components is smaller than the transmission path characteristics in the carrier unit. The transmission line characteristics can be derived.

  Yet another aspect of the present invention is also a wireless device. This device is a transmission path characteristic with a wireless device to be communicated, and receives a time domain transmission line coefficient from the wireless device to be communicated, and a transmission path characteristic received at the reception unit as time. A conversion unit for converting from a region to a frequency region, and a setting unit for setting a condition for transmitting a data signal to a wireless device to be communicated based on transmission path characteristics of the frequency region converted by the conversion unit. In the time domain transmission line characteristics received by the receiver, the value of the component with a large delay time is assumed to be zero, so that the time domain transmission line characteristics are larger than the number of components that should constitute the frequency domain transmission line characteristics. The number of components that should constitute the time domain transmission line characteristics received by the receiving unit is the number of components that should constitute the frequency domain transmission path characteristics. The conversion is executed after supplementing a component having a predetermined value with respect to the transmission characteristics in the time domain received by the receiving unit so as to be equal.

  An example of the “predetermined value” is “zero”, and any value that does not affect the transmission path characteristics in the time domain may be used. According to this aspect, a component having a predetermined value is supplemented to the time domain transmission line characteristics, and then the conversion to the frequency domain is performed. Therefore, the number of time domain transmission line characteristics is equal to the frequency domain transmission. Even if there are fewer than the number of components of the path characteristics, the transmission path characteristics in the frequency domain can be acquired.

  Yet another aspect of the present invention is also a wireless device. This device has a transmission path characteristic for each of a plurality of sequences with a communication target wireless device, and a reception unit that receives a transmission path coefficient in units of delay time from the communication target wireless device, and a reception unit A transmission unit that converts the transmission path characteristics from a delay time unit to a carrier unit, and transmission of multiple sequences of multicarrier signals to a wireless device to be communicated based on the carrier unit transmission path characteristics converted by the conversion unit And a setting unit for setting the conditions. In the transmission path characteristics in the delay time unit received at the receiver, the value of the component with a large delay time is assumed to be zero, so that transmission in the delay time unit is performed rather than the number of components that should constitute the transmission path characteristics in the carrier unit. The number of components that should constitute the path characteristics is reduced, and the conversion unit is a component that the number of components that should constitute the channel characteristics in delay time received by the receiver should constitute the channel characteristics in carrier units. The conversion is executed after supplementing a predetermined value component to the transmission path characteristics in units of delay time received by the receiving unit so as to be equal to the number of.

  According to this aspect, the component of the predetermined value is supplemented to the transmission path characteristic in the delay time unit, and then the conversion to the carrier unit is performed. Therefore, the number of the transmission path characteristic component in the delay time region is the carrier unit. Even if the number of the transmission path characteristics is less than the number of the transmission path characteristics, the transmission path characteristics in units of carriers can be obtained.

  Yet another embodiment of the present invention is a communication method. The method includes a step of receiving a signal from a wireless device to be communicated, a step of deriving a transmission path characteristic with the wireless device to be communicated in a frequency domain based on the received signal, and The method includes a step of converting the transmission path characteristic from the frequency domain to the time domain, and a step of transmitting the converted transmission path characteristic of the time domain to a wireless device to be communicated. The converting step assumes that the value of the component having a large delay time among the time domain transmission line characteristics is zero, so that the time domain transmission line characteristics are larger than the number of components to constitute the frequency domain transmission line characteristics. The number of components that should be made is reduced.

  Yet another embodiment of the present invention is also a communication method. This method includes a step of receiving a multicarrier signal that is a multicarrier signal from a wireless device to be communicated and formed by a plurality of sequences, and a plurality of sequences based on the received multicarrier signals. Deriving the transmission path characteristics for each carrier in units of carriers, converting the derived transmission path characteristics in units of carriers into transmission path characteristics in units of delay time, and converting the converted transmission path characteristics in units of delay time to the wireless communication target Transmitting to the device. The converting step assumes that the value of the component having a large delay time out of the channel characteristics in the delay time unit is zero, so that the transmission in the delay time unit is larger than the number of components that should constitute the carrier channel characteristic. You may reduce the number of the components which should comprise a road characteristic.

  The multicarrier signal to be received in the receiving step constitutes a packet signal, the data signal is arranged in at least one of a plurality of sequences, and the data signal in the sequence in which the data signal is arranged is preceded by the data signal. An additional known signal is arranged at a timing other than the timing at which the known signal is arranged and the timing at which the data signal is arranged with respect to a sequence in which the known signal is arranged but the data signal is not arranged. The step uses the known signal included in the received multicarrier signal and the known signal stored in advance to derive the channel characteristics for the sequence in which the data signal is arranged for each carrier, and receives the received multicarrier signal. Data signals using the additional known signals included in and the previously stored additional known signals. There the channel characteristics to the arrangement that are not sequence may be derived to the carrier unit.

  The converting step is a conversion coefficient for converting the transmission line characteristic of the carrier unit into the transmission line characteristic of the delay time unit, and is formed by a plurality of components to be multiplied by each component of the transmission line coefficient of the carrier unit. The transmission coefficient in delay time unit is derived by multiplying the conversion coefficient and the transmission path characteristic in units of carriers in correspondence with the component unit while referring to the converted conversion coefficient. May be defined to include only values corresponding to components having a small delay time.

  Yet another embodiment of the present invention is also a communication method. This method includes a step of receiving a transmission path characteristic from a wireless device to be communicated with a wireless device to be communicated and having a time domain transmission line coefficient from the wireless device to be communicated. And a step of setting a condition for transmitting a data signal to a wireless device to be communicated based on the converted channel characteristics of the frequency domain. In the time domain transmission path characteristics received in the receiving step, the value of the component with a large delay time is assumed to be zero, so that the time domain transmission path is greater than the number of components that should constitute the frequency domain transmission path characteristics. The number of components that should constitute the characteristic has been reduced, and the step of converting is such that the number of components that should constitute the received time domain transmission line characteristic is equal to the number of components that should constitute the frequency domain transmission line characteristic. As described above, the conversion is executed after supplementing a component having a predetermined value for the received time domain transmission line characteristics.

  Yet another embodiment of the present invention is also a communication method. The method includes transmission path characteristics for each of a plurality of sequences with a communication target wireless apparatus, and a step of receiving a transmission path coefficient in a delay time unit from the communication target wireless apparatus; and the received transmission path characteristics Converting the delay time unit to the carrier unit, and setting the conditions for transmitting a multi-carrier signal of a plurality of sequences to the wireless device to be communicated based on the converted channel characteristics of the carrier unit. Prepare. In the channel characteristics of the delay time unit received in the receiving step, the value of the component having a large delay time is assumed to be zero, so that the number of components of the delay time unit is larger than the number of components that should constitute the channel characteristics of the carrier unit. The number of components that should constitute the transmission path characteristics is reduced, and the step of converting is performed in such a manner that the number of components that should constitute the transmission path characteristics in units of delay time is the number of components that should constitute the transmission path characteristics in units of carriers. The conversion may be executed after supplementing a component having a predetermined value with respect to the transmission path characteristics in units of delay time so as to be equal to the number.

  Yet another embodiment of the present invention is a communication system. The communication system includes means for receiving a signal from the first radio apparatus, means for deriving a transmission path characteristic with the first radio apparatus in the frequency domain based on the received signal, and derivation A second wireless device comprising: means for converting the transmission path characteristics from the frequency domain to the time domain; and means for transmitting the converted time domain transmission path characteristics to the first wireless device; A means for receiving a transmission line coefficient, a means for converting the received transmission line characteristic from the time domain to the frequency domain, and transmitting a data signal to the second radio apparatus based on the converted transmission line characteristic in the frequency domain And a first wireless device including means for setting a special condition. The second radio apparatus assumes that the value of the component having a large delay time in the time domain transmission path characteristics is zero, thereby transmitting the time domain transmission more than the number of components that should constitute the frequency domain transmission path characteristics. The first radio apparatus reduces the number of components that should constitute the path characteristics, and the number of components that should constitute the received time domain transmission path characteristics is equal to the number of components that should constitute the frequency domain transmission path characteristics. The conversion is executed after supplementing a component of a predetermined value with respect to the received time domain transmission path characteristics so as to be equal.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the deterioration of the transmission efficiency at the time of transmitting a transmission line characteristic can be suppressed.

  Before describing the present invention in detail, an outline will be described. Embodiments of the present invention relate to a MIMO system composed of at least two wireless devices. One of the wireless devices corresponds to a base station device, and the other corresponds to a terminal device. The base station apparatus performs beam forming when transmitting a packet signal. Therefore, the terminal device derives in advance the transmission path characteristics with the base station apparatus, and the base station apparatus acquires the transmission path characteristics from the terminal apparatus. In addition, the base station device transmits a training signal to cause the terminal device to derive the transmission path characteristics. In the following description, a packet signal in which a training signal is arranged is also referred to as a “training signal”.

  When the terminal device receives the training signal, the terminal device estimates transmission path characteristics between a plurality of antennas included in the terminal device in units of sequences included in the MIMO system. Note that the transmission path characteristics are estimated in units of subcarriers. Further, the base station apparatus transmits a signal requesting the derived transmission path characteristics (hereinafter referred to as “request signal”) to the terminal apparatus. When the terminal device receives the request signal, it transmits the transmission path characteristics. However, the estimated transmission path characteristics have a value in units of subcarriers for each combination of the sequence and the antenna, so that the data amount becomes large. For this reason, the amount of data of a signal (hereinafter referred to as “response signal”) that is a signal from the terminal device to the base station device and that includes information on transmission path characteristics increases. As a result, the transmission efficiency of the entire system is deteriorated. In order to cope with this, the base station apparatus and the terminal apparatus according to the embodiment execute the following processing.

  Here, in particular, a process from when the terminal device receives the training signal to when the transmission path characteristic is transmitted will be described. Therefore, a known technique may be used for the beam forming process in the base station apparatus. When the terminal device receives the training signal, the terminal device estimates the transmission path characteristics for each subcarrier for each combination of the sequence and the antenna. Also, the terminal device converts the transmission path characteristics in units of subcarriers into transmission path characteristics in units of delay times. That is, the transmission path characteristics are converted from the frequency domain to the time domain. At that time, the terminal apparatus excludes the component from the transmission path characteristics to be transmitted by assuming that the value for the component with the long delay time is zero among the transmission path characteristics in the delay time unit. As a result, the data amount of the response signal is reduced.

  FIG. 1 shows a spectrum of a multicarrier signal according to an embodiment of the present invention. In particular, FIG. 1 shows the spectrum of a signal in the OFDM modulation scheme. One of a plurality of carriers in the OFDM modulation system is generally called a subcarrier, but here, one subcarrier is designated by a “subcarrier number”. In the MIMO system, 56 subcarriers from subcarrier numbers “−28” to “28” are defined. The subcarrier number “0” is set to null in order to reduce the influence of the DC component in the baseband signal. On the other hand, in a system that does not support the MIMO system (hereinafter referred to as “conventional system”), 52 subcarriers from subcarrier numbers “−26” to “26” are defined. An example of a conventional system is a wireless LAN compliant with the IEEE802.11a standard. Further, one signal unit composed of a plurality of subcarriers and one signal unit in the time domain is referred to as an “OFDM symbol”.

  Each subcarrier is modulated by a variably set modulation method. As the modulation method, any one of BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), 64QAM, and 256QAM is used.

  Also, convolutional coding is applied to these signals as an error correction method. The coding rate of convolutional coding is set to 1/2, 3/4, and the like. Furthermore, the number of data to be transmitted in parallel is set variably. As a result, the data rate is also variably set by variably setting the modulation scheme, coding rate, and number of sequences. The “data rate” may be determined by any combination of these, or may be determined by one of them. In the conventional system, when the modulation method is BPSK and the coding rate is 1/2, the data rate is 6 Mbps. On the other hand, when the modulation method is BPSK and the coding rate is 3/4, the data rate is 9 Mbps.

  FIG. 2 shows a configuration of the communication system 100 according to the embodiment of the present invention. The communication system 100 includes a first wireless device 10a and a second wireless device 10b collectively referred to as a wireless device 10. The first radio apparatus 10a includes a first antenna 12a, a second antenna 12b, a third antenna 12c, and a fourth antenna 12d, which are collectively referred to as an antenna 12, and the second radio apparatus 10b is collectively referred to as an antenna 14. A first antenna 14a, a second antenna 14b, a third antenna 14c, and a fourth antenna 14d are included. Here, the first radio apparatus 10a corresponds to a base station apparatus, and the second radio apparatus 10b corresponds to a terminal apparatus.

  As a configuration of the communication system 100, an outline of a MIMO system will be described. It is assumed that data is transmitted from the first radio apparatus 10a to the second radio apparatus 10b. The first radio apparatus 10a transmits a plurality of series of data from each of the first antenna 12a to the fourth antenna 12d. As a result, the data rate is increased. The second radio apparatus 10b receives a plurality of series of data by the first antenna 14a to the fourth antenna 14d. Furthermore, the second radio apparatus 10b separates the received data by adaptive array signal processing and independently demodulates a plurality of series of data.

  Here, since the number of antennas 12 is “4” and the number of antennas 14 is also “4”, the combination of transmission paths between the antennas 12 and 14 is “16”. A transmission path characteristic between the i-th antenna 12i and the j-th antenna 14j is denoted by hij. In the figure, the transmission path characteristic between the first antenna 12a and the first antenna 14a is h11, the transmission path characteristic between the first antenna 12a and the second antenna 14b is h12, the second antenna 12b and the first antenna. 14a, the transmission path characteristic between the second antenna 12b and the second antenna 14b is h22, and the transmission path characteristic between the fourth antenna 12d and the fourth antenna 14d is h44. Has been. Note that transmission lines other than these are omitted for clarity of illustration. Here, it is assumed that the first radio apparatus 10a is performing beamforming. Therefore, a training signal is transmitted in advance from the first radio apparatus 10a to the second radio apparatus 10b. Further, the first radio apparatus 10a and the second radio apparatus 10b may be reversed.

  3A to 3C show packet formats in the communication system 100. FIG. FIGS. 3A to 3C show a format of a normal packet signal, not a training signal. Here, FIG. 3A corresponds to the case where the number of series is “4”, FIG. 3B corresponds to the case where the number of series is “3”, and FIG. Corresponds to the case where the number of series is “2”. In FIG. 3A, it is assumed that data included in the four sequences is to be transmitted, and packet formats corresponding to the first to fourth sequences are shown in order from the top to the bottom.

  In the packet signal corresponding to the first stream, “L-STF”, “HT-LTF”, and the like are arranged as preamble signals. “L-STF”, “L-LTF”, “L-SIG”, “HT-SIG” are known signals for AGC setting, known signals for transmission path estimation, control signals, MIMO systems corresponding to conventional systems Correspond to the control signals corresponding to. The control signal corresponding to the MIMO system includes, for example, information on the number of sequences and the destination of the data signal. “HT-STF” and “HT-LTF” correspond to a known signal for AGC setting and a known signal for channel estimation corresponding to the MIMO system. On the other hand, “data 1” is a data signal. Note that L-LTF and HT-LTF are used not only for AGC setting but also for timing estimation.

  Also, in the packet signal corresponding to the second stream, “L-STF (−50 ns)”, “HT-LTF (−400 ns)” and the like are arranged as preamble signals. Further, in the packet signal corresponding to the third stream, “L-STF (−100 ns)”, “HT-LTF (−200 ns)”, and the like are arranged as preamble signals. In the packet signal corresponding to the fourth stream, “L-STF (−150 ns)”, “HT-LTF (−600 ns)”, and the like are arranged as preamble signals.

  Here, “−400 ns” or the like indicates a timing shift amount in CDD (Cyclic Delay Diversity). CDD is a process in which a waveform in the time domain is shifted backward by a shift amount in a predetermined section, and a waveform pushed out from the last part of the predetermined section is cyclically arranged at the head portion of the predetermined section. That is, “L-STF (−50 ns)” is cyclically shifted with a delay amount of −50 ns with respect to “L-STF”. The L-STF and the HT-STF are configured by repeating a period of 800 ns, and the other HT-LTFs are configured by a repeating part of a period of 3.2 μs and a GI part of 0.8 μs. Here, “data 1” to “data 4” are also CDDed, and the timing shift amount is the same value as the timing shift amount in the HT-LTF arranged in the preceding stage.

  In the first stream, HT-LTFs are arranged in the order of “HT-LTF”, “−HT-LTF”, “HT-LFT”, and “−HT-LTF” from the top. Here, these are sequentially referred to as “first component”, “second component”, “third component”, and “fourth component” in all series. If the calculation of the first component-second component + third component-fourth component is performed on all series of received signals, the receiving apparatus extracts a desired signal for the first series. Further, if the calculation of the first component + second component + third component + fourth component is performed on all series of received signals, the receiving apparatus extracts a desired signal for the second series. Further, if the calculation of the first component-second component-third component + fourth component is performed on all series of received signals, the receiving apparatus extracts a desired signal for the third series. Also, if the calculation of the first component + second component−third component−fourth component is performed on the received signals of all sequences, the desired signal for the fourth sequence is extracted in the receiving apparatus. These correspond to the combination of codes of predetermined components having an orthogonal relationship between sequences. The addition / subtraction process is executed by vector calculation.

  In the part from “L-LTF” to “HT-SIG” and the like, “52” subcarriers are used as in the conventional system. Of the “52” subcarriers, “4” subcarriers correspond to pilot signals. On the other hand, “56” subcarriers are used in the subsequent parts such as “HT-LTF”.

  In FIG. 3A, the sign of “HT-LTF” is defined as follows. The codes are arranged in the order of “+”, “−”, “+”, “−” in order from the top of the first sequence, and the codes are “+”, “+”, “+” in order from the top of the second sequence. Arranged in the order of “+” and “+”, the codes are arranged in the order of “+”, “−”, “−” and “+” in order from the top of the third series, and from the top of the fourth series. In order, the codes are arranged in the order of “+”, “+”, “−”, and “−”. However, the code | symbol may be prescribed | regulated as follows. The codes are arranged in the order of “+”, “−”, “+”, “+” in order from the top of the first sequence, and the codes are “+”, “+”, “+” in order from the top of the second sequence. Arranged in the order of “−” and “+”, the codes are arranged in the order of “+”, “+”, “+”, “−” in order from the top of the third series, and from the top of the fourth series. In order, the symbols are arranged in the order of “−”, “+”, “+”, “+”. Even such a code corresponds to a combination of codes of predetermined components having an orthogonal relationship between sequences.

  FIG. 3B corresponds to the first to third series in FIG. FIG. 3C is similar to the first series and the second series in the packet format shown in FIG. Here, the arrangement of “HT-LTF” in FIG. 3B is different from the arrangement of “HT-LTF” in FIG. That is, the HT-LTF includes only the first component and the second component. In the first sequence, HT-LTFs are arranged in the order of “HT-LTF” and “HT-LTF” from the top, and in the second sequence, HT-LTFs are arranged from the top to “HT-LTF”, “− They are arranged in the order of “HT-LTF”. If the calculation of the first component + the second component is performed on the reception signals of all sequences, the reception device extracts the desired signal for the first sequence. Also, if the first component-second component calculation is performed on all series of received signals, the receiving apparatus extracts a desired signal for the second series. These can also be said to be orthogonal as described above. For example, the packet signals shown in FIGS. 3A to 3C are transmitted from the first radio apparatus 10a while being beam-formed.

  4A to 4D show packet formats for training signals in the communication system 100. FIG. FIGS. 4A to 4D are training signals for packet signals when FIGS. 3B to 3C and data are arranged in one sequence. In the following, for the sake of clarity, “L-STF” to “HT-SIG” included in the packet format are omitted. That is, the configuration after “HT-STF” is shown. FIG. 4A shows a case where the number of sequences (hereinafter referred to as “main sequences”) in which data signals are arranged is “3”, and FIG. 4B shows that the number of main sequences is “2”. FIGS. 4C to 4D show a case where the number of main sequences is “1”. That is, in FIG. 4A, data signals are arranged from the first series to the third series, and in FIG. 4B, data signals are arranged in the first series and the second series, 4C to 4D, data signals are arranged in the first series.

  The arrangement related to HT-LTF among the first to third series in FIG. 4A is the same as the arrangement in FIG. 3B. However, in the subsequent stage, blank periods are provided from the first series to the third series. On the other hand, in a blank period from the first series to the third series, HT-LTF is arranged in the fourth series. Further, following the HT-LTF arranged in the fourth series, data is arranged from the first series to the third series. In the fourth series, one HT-LTF is arranged.

  With such an arrangement, the number of sequences in which “HT-STF” is arranged becomes equal to the number of sequences in which data signals are arranged, and therefore included in the amplification factor set by “HT-STF” in the receiving apparatus. Error can be reduced, and deterioration of data signal reception characteristics can be prevented. In addition, since “HT-LTF” arranged in the fourth sequence is only arranged in one sequence, the “HT-LTF” arranged in the fourth sequence in the receiving apparatus is so distorted as to be caused by AGC. The situation where it is amplified can be reduced. Therefore, it is possible to prevent deterioration in accuracy of transmission path estimation.

  Of the first sequence and the second sequence in FIG. 4B, the arrangement related to HT-LTF is the same as the arrangement in FIG. However, in the subsequent stage, blank periods are provided in the first series and the second series. On the other hand, in the blank period in the first sequence and the second sequence, HT-LTF is arranged in the third sequence and the fourth sequence. Further, following the HT-LTF arranged in the third series and the fourth series, data is arranged in the first series and the second series. The arrangement of HT-LTFs in the third series and the fourth series is the same as the arrangement in FIG.

  Here, with respect to the timing shift amount, it is assumed that the priority is defined such that the priority decreases in the order of “0 ns”, “−400 ns”, “−200 ns”, and “−600 ns”. That is, it is defined that “0 ns” has the highest priority and “−600 ns” has the lowest priority. Therefore, in the first series and the second series, values of “0 ns” and “−400 ns” are used as timing shift amounts. On the other hand, values of “0 ns” and “−400 ns” are also used as timing shift amounts in the third and fourth series. As a result, the combination of “HT-LTF” and “HT-LTF” in the first sequence is also used in the third sequence, and “HT-LTF (−400 ns)” and “−HT in the second sequence are used. Since the combination of “−LTF (−400 ns)” is also used in the fourth stream, the processing becomes simple.

  The arrangement related to the HT-LTF in the first series in FIG. 4C is equivalent to the arrangement for the first series in FIG. Here, two “HT-LTF” are arranged. However, in the subsequent stage, a blank period is provided in the first series. On the other hand, in the blank period in the first sequence, HT-LTF is arranged in the second sequence to the fourth sequence. Further, following the HT-LTF arranged from the second series to the fourth series, data is arranged in the first series. Here, the arrangement of HT-LTFs arranged from the second series to the third series is similar to the arrangement in FIG.

  FIG. 4D is configured in the same manner as FIG. 4C, but the combination of symbols “HT-LTF” in FIG. 4D is different from that in FIG. Here, the combination of codes “HT-LTF” is defined such that an orthogonal relationship is established between sequences. Further, in FIG. 4D, it is defined that the combination of “HT-LTF” codes is fixed for each of a plurality of sequences. Here, in FIG. 4D, as in FIG. 4C, “0 ns”, “−400 ns”, and “−200 ns” having high priorities even in the second to fourth series. Is used.

  One “HT-LTF” is arranged in the fourth series in FIG. 4A, that is, a series in which data is not arranged (hereinafter referred to as “sub-sequence”). Also, two “HT-LTF” are arranged in the third series and the fourth series in FIG. Further, four “HT-LTFs” are arranged from the second series to the fourth series in FIGS. When these are compared, the length of “HT-LTF” arranged in the subsequence in FIGS. 4C to 4D is the longest. That is, when the number of main sequences in the packet signal for which a training signal is to be generated increases, the length of the sub-sequence decreases and transmission efficiency improves. It is assumed that the training signal is transmitted without beamforming.

  FIGS. 5A to 5D show other packet formats for training signals in the communication system 100. FIG. FIGS. 5A to 5D correspond to FIGS. 4A to 4D, respectively. In FIGS. 5A to 5D, the timing shift amount is defined while being associated with each of the plurality of sequences. Here, a timing shift amount “0 ns” is defined for the first sequence, a timing shift amount “−400 ns” is defined for the second sequence, and a timing shift amount “−” is defined for the third sequence. 200 ns ”is defined, and the timing shift amount“ −600 ns ”is defined for the fourth stream.

  Therefore, in FIG. 5A, “−600 ns” is used instead of the timing shift amount “0 ns” in the fourth stream in FIG. 4A. In FIG. 5B, instead of the timing shift amounts “0 ns” and “−400 ns” in the third sequence and the fourth sequence in FIG. 4B, “−200 ns” and “−600 ns”. Is used. On the other hand, in FIGS. 5C to 5D, timing shift amounts “0 ns”, “−400 ns”, and “−200 ns” from the second series to the fourth series in FIGS. 4C to 4D are used. Instead of “−400 ns”, “−200 ns”, “−600 ns” are used.

  FIG. 5D is configured in the same manner as FIG. 5C, but the combination of symbols “HT-LTF” in FIG. 5D is different from that in FIG. Priorities are provided in advance for combinations of signs of “HT-LTF”. That is, the code combination in the first sequence in FIG. 3A has the highest priority, and the code combination in the fourth sequence has the lowest priority. In addition, a combination of codes is used in order from a combination of codes with higher priority for a sequence in which a data signal is arranged, and a code in order from a combination of codes with a higher priority is also used for a sequence in which no data signal is arranged. Use a combination of In this way, if the combination of codes is the same, calculation of transmission path characteristics for the “HT-LTF” portion of the sequence in which no data is arranged when the receiving apparatus performs the + − operation to extract each component. In addition, a common circuit can be used for the calculation of the transmission path characteristics for the “HT-LTF” portion of the sequence in which data is arranged.

  FIG. 6 shows a packet format of a training signal that is finally transmitted in the communication system 100. FIG. 6 corresponds to a case where the packet signals of FIG. 4B and FIG. 5B are modified. An operation using an orthogonal matrix (described later) is performed on “HT-STF” and “HT-LTF” arranged in the first sequence and the second sequence in FIGS. 4B and 5B. As a result, “HT-STF4” is generated from “HT-STF1”. The same applies to “HT-LTF”. Further, CDD with timing shift amounts “0 ns”, “−50 ns”, “−100 ns”, and “−150 ns” is performed for each of the first to fourth streams. The absolute value of the timing shift amount at the second CDD is set to be smaller than the absolute value of the timing shift amount at the first CDD for HT-STF and HT-LTF. Similar processing is executed for “HT-LTF” arranged in the third series and the fourth series, “data 1” of the first series, and the like.

  FIG. 7 shows the configuration of the first radio apparatus 10a. The first radio apparatus 10a includes a first radio unit 20a, a second radio unit 20b, a fourth radio unit 20d, a baseband processing unit 22, a modem unit 24, an IF unit 26, and a control unit 30, which are collectively referred to as a radio unit 20. Including. Also, as signals, a first time domain signal 200a, a second time domain signal 200b, a fourth time domain signal 200d, which are collectively referred to as a time domain signal 200, a first frequency domain signal 202a, a second, which are collectively referred to as a frequency domain signal 202, A frequency domain signal 202b and a fourth frequency domain signal 202d are included. The second radio apparatus 10b is configured in the same manner as the first radio apparatus 10a. Therefore, in the following description, the explanation regarding the transmission of the training signal and the execution of the beamforming corresponds to the processing in the first radio apparatus 10a, and the explanation about the estimation of the transmission path characteristics and the notification of the transmission path characteristics is the second radio. This corresponds to the processing in the apparatus 10b.

  As a reception operation, the radio unit 20 performs frequency conversion on a radio frequency signal received by the antenna 12 and derives a baseband signal. The radio unit 20 outputs the baseband signal to the baseband processing unit 22 as a time domain signal 200. In general, baseband signals are formed by in-phase and quadrature components, so they should be transmitted by two signal lines. Here, for clarity of illustration, only one signal line is used. Shall be shown. An AGC and A / D converter are also included. The AGC sets the amplification factor in “L-STF” and “HT-STF”.

  As a transmission operation, the radio unit 20 performs frequency conversion on the baseband signal from the baseband processing unit 22 and derives a radio frequency signal. Here, a baseband signal from the baseband processing unit 22 is also shown as a time domain signal 200. The radio unit 20 outputs a radio frequency signal to the antenna 12. That is, the radio unit 20 transmits a radio frequency packet signal from the antenna 12. Further, a PA (Power Amplifier) and a D / A converter are also included. The time domain signal 200 is a multicarrier signal converted into the time domain, and is a digital signal.

  As a reception operation, the baseband processing unit 22 converts each of the plurality of time domain signals 200 into the frequency domain, and performs adaptive array signal processing on the frequency domain signal. The baseband processing unit 22 outputs the result of adaptive array signal processing as the frequency domain signal 202. One frequency domain signal 202 corresponds to each of a plurality of transmitted sequences. Further, as a transmission operation, the baseband processing unit 22 receives a frequency domain signal 202 as a frequency domain signal from the modulation / demodulation unit 24, converts the frequency domain signal to the time domain, and transmits the frequency domain signal to each of the plurality of antennas 12. The time domain signal 200 is output while being associated.

  It is assumed that the number of antennas 12 to be used in the transmission process is specified by the control unit 30. Here, the frequency domain signal 202, which is a frequency domain signal, includes a plurality of subcarrier components as shown in FIG. For the sake of clarity, it is assumed that the frequency domain signals are arranged in the order of subcarrier numbers to form a serial signal.

  FIG. 8 shows the configuration of a signal in the frequency domain. Here, one combination of subcarrier numbers “−28” to “28” shown in FIG. 1 is referred to as an “OFDM symbol”. In the “i” th OFDM symbol, subcarrier components are arranged in the order of subcarrier numbers “1” to “28” and subcarrier numbers “−28” to “−1”. Also, the “i−1” th OFDM symbol is arranged before the “i” th OFDM symbol, and the “i + 1” th OFDM symbol is arranged after the “i” th OFDM symbol. And In the part such as “L-SIG” in FIG. 3A and the like, a combination of subcarrier numbers “−26” to “26” is used for one “OFDM symbol”.

  Returning to FIG. The baseband processing unit 22 included in the first radio apparatus 10a performs CDD in order to generate a training signal corresponding to the packet formats of FIGS. 4 (a)-(d) and FIGS. 5 (a)-(d). Execute. Further, the baseband processing unit 22 performs steering matrix multiplication in order to perform transformation into the packet signal shown in the packet format of FIG. Details of these processes will be described later. On the other hand, when the baseband processing unit 22 included in the second radio apparatus 10b receives the training signal, the baseband processing unit 22 derives transmission path characteristics from the received training signal.

  That is, the baseband processing unit 22 receives a multicarrier signal that is a multicarrier signal from the first radio apparatus 10a and formed by a plurality of sequences. Here, in the training signal, data is arranged in at least one of the plurality of sequences. Further, other than the timing at which the HT-LTF is arranged and the timing at which the data is arranged with respect to the series in which the data is not arranged while the HT-LTF is arranged in the preceding stage of the data in the series in which the data is arranged. HT-LTF is also arranged at the timing. The derived transmission path characteristics are transformed by the control unit 30 described later, and then transmitted from the baseband processing unit 22 to the first radio apparatus 10a in the packet format of FIGS. 3 (a) to 3 (c). Further, the baseband processing unit 22 included in the first radio apparatus 10a performs beamforming based on the transmission path characteristics received from the second radio apparatus 10b, and the packets shown in FIGS. 3 (a) to 3 (c). A packet signal corresponding to the format is transmitted.

  The modem unit 24 performs demodulation and deinterleaving on the frequency domain signal 202 from the baseband processing unit 22 as reception processing. Note that demodulation is performed in units of subcarriers. The modem unit 24 outputs the demodulated signal to the IF unit 26. Further, the modem unit 24 performs interleaving and modulation as transmission processing. The modem unit 24 outputs the modulated signal to the baseband processing unit 22 as the frequency domain signal 202. It is assumed that the modulation scheme is specified by the control unit 30 during the transmission process.

  As reception processing, the IF unit 26 combines signals from the plurality of modulation / demodulation units 24 to form one data stream. Furthermore, one data stream is decoded. The IF unit 26 outputs the decoded data stream. In addition, the IF unit 26 receives and encodes one data stream as transmission processing, and then separates it. Further, the IF unit 26 outputs the separated data to the plurality of modulation / demodulation units 24. It is assumed that the coding rate is specified by the control unit 30 during the transmission process. Here, an example of encoding is convolutional encoding, and an example of decoding is Viterbi decoding.

  The control unit 30 controls the timing of the first radio apparatus 10a. First, the operation when the control unit 30 included in the first radio apparatus 10a generates a training signal will be described. The control unit 30 cooperates with the IF unit 26, the modulation / demodulation unit 24, and the baseband processing unit 22 in FIGS. 3 (a)-(c), 4 (a)-(d), and FIG. 5 (a)-( d) Generate a packet signal having a packet format as shown in FIG. 6 and execute control for transmitting the generated packet signal. Here, the processing for generating the packet format shown in FIGS. 4B and 5B will be mainly described, but the same processing is executed for other packet formats.

  In the IF unit 26, data to be arranged in at least one of a plurality of series is input. Here, as shown in FIGS. 4B and 5B, data to be arranged in two series is input. The control unit 30 provides the baseband processing unit 22 with “HT-STF” and “HT-STF” sequences in which the input data is arranged, that is, the first sequence and the second sequence. An instruction is given to generate a packet signal from “HT-LTF” arranged in a plurality of series in the subsequent stage and data arranged in the first series and the second series. As shown in FIGS. 3A to 3C, the control unit 30 includes “L-STF”, “L-LTF”, “L-SIG”, and “HT-SIG” in the previous stage of the HT-STF. An instruction is output to the baseband processing unit 22 so as to be arranged.

  Here, as described in FIG. 4B and FIG. 5B, the case where two “HT-LTFs” are arranged for one series will be described. That is, the entire “HT-LTF” is formed by repeating “HT-LTF” in the time domain. Further, the combination of codes “HT-LTF” is defined so that an orthogonal relationship between main sequences or sub-sequences is established. As a result, as described above, if the first component and the second component are added in the main sequence, the HT-LTF for the first sequence is extracted. Further, if the second component is subtracted from the first component in the main sequence, the HT-LTF for the second sequence is extracted.

  Note that the number of “HT-LTFs” arranged in one sequence is determined by the number necessary to establish the orthogonal relationship. Therefore, if the number of sequences to establish the orthogonal relationship is “2”, the number of “HT-LTF” per sequence is “2”. On the other hand, if the number of sequences to establish the orthogonal relationship is “3” or “4”, the number of “HT-LTF” per sequence is “4”.

  The control unit 30 causes the baseband processing unit 22 to execute CDD on HT-LTF or the like. Note that CDD corresponds to causing the HT-LTF arranged in another series to perform a cyclic timing shift in the HT-LTF based on the HT-LTF arranged in one series. The control unit 30 provides a priority in advance for the timing shift amount. Here, as described above, the priority of the timing shift amount “0 ns” is set to the highest priority, and subsequently, the priority is decreased in the order of “−400 ns”, “−200 ns”, and “−600 ns”. Set.

  Furthermore, the control unit 30 causes the baseband processing unit 22 to use the timing shift amount in order from the timing shift amount with the highest priority for the main sequence. For example, in the case of FIG. 4B, “0 ns” is used for the first sequence and “−400 ns” is used for the second sequence. Also, the control unit 30 causes the timing shift amounts to be used in order from the timing shift amount with the highest priority for the subsequences. For example, in the case of FIG. 4B, “0 ns” is used for the third sequence, and “−400 ns” is used for the fourth sequence. Through the above processing, a packet signal having the packet format shown in FIG. 4B is generated.

  On the other hand, different timing shift amounts may be set for a plurality of sequences. For example, “0 ns” is set as the timing shift amount of the first sequence, “−400 ns” is set as the timing shift amount of the second sequence, and “−200 ns” is set as the timing shift amount of the third sequence. Is set, and “−600 ns” is set as the timing shift amount of the fourth stream. Through the above processing, a packet signal having the packet format shown in FIG. 5B is generated.

  After the packet signal of the packet format as shown in FIGS. 4A to 4D and FIGS. 5A to 5D is generated by the above processing, the control unit 30 transmits the packet signal to the baseband processing unit 22. These packet signals are deformed. That is, the control unit 30 transforms the packet format shown in FIGS. 4B and 5B into the packet format shown in FIG. The baseband processing unit 22 performs CDD on the extended sequence after extending the number of sequences to the number of multiple sequences. Further, the control unit 30 causes the radio unit 20 to transmit the modified packet signal.

  Further, the control unit 30 causes a request signal to be transmitted from the baseband processing unit 22 or the like. Here, the request signal may be included in the training signal, or may be included in a packet signal different from the training signal. For simplification of description, in the following description, it is assumed that the request signal is included in the training signal.

  Next, the operation of the control unit 30 included in the second radio apparatus 10b that should receive the training signal will be described. The control unit 30 causes the baseband processing unit 22 to derive transmission path characteristics for each of a plurality of sequences in units of subcarriers based on the received training signal. That is, the baseband processing unit 22 uses the HT-LTF included in the received training signal and the prestored HT-LTF to determine the channel characteristics for the sequence in which the data signal is arranged by correlation or the like. Derived in subcarrier units. As shown in FIG. 1, since 56 subcarriers are used, the transmission path characteristics in units of subcarriers are derived for 56 subcarriers. The above processing is executed not only for the main sequence but also for the sub sequence. Further, the transmission path characteristics are derived in units of paths or sequences as shown in FIG.

  The control unit 30 performs the Fourier transform to convert the derived transmission path characteristics in units of subcarriers into transmission path characteristics in units of delay time. For example, a 64-point FFT is performed. At this time, zeros are inserted into subcarriers for which transmission path characteristics are not derived. As a result of the above processing, transmission path characteristics having values corresponding to 64 types of delay times are derived. In addition, the control unit 30 assumes that the value of the component with the large delay time in the transmission path characteristics in the delay time unit is zero. For example, of 64 types of delay times, values corresponding to the 16th and later delay times from the smallest are assumed to be zero.

  As a result, the transmission path characteristic in units of delay time has 16 components. In addition, since the transmission path characteristics in units of subcarriers have “56” components and the transmission path characteristics in units of delay times have “16” components, the amount of data is reduced by the above processing. . FIG. 9 shows the concept of conversion processing in the control unit 30. The horizontal axis indicates the delay time, and the vertical axis indicates the signal intensity. The numbers shown on the horizontal axis are assigned such that the shorter the delay time, the smaller the value. Therefore, in the above example, only the values for the numbers “1” to “16” are valid. Returning to FIG.

なお、行列Ｆ_{６４×６４}は、サブキャリア単位の伝送路特性と遅延時間単位の伝送路特性との間の変換係数に相当する。前述のごとく、遅延時間単位の伝送路特性が１６個の成分を有している場合、遅延時間単位の伝送路特性は、以下のように１６行１列の行列ｈ’_１６によって示される。

The conversion process in the control unit 30 will be described in further detail. Transmission path characteristics in units of subcarriers are indicated by a matrix H ′ ₆₄ of 64 rows and 1 column, and transmission path characteristics in units of delay times are indicated by a matrix h ′ ₆₄ of 64 rows and 1 column. Here, “′” means an estimated value. _'64 matrix h' matrix H and ₆₄ are related by the matrix _{F 64 × 64} in 64 rows 64 columns as follows.

Note that the matrix F _{64 × 64} corresponds to a conversion coefficient between the transmission path characteristics in units of subcarriers and the transmission path characteristics in units of delay times. As described above, when the transmission line characteristic in delay time unit has 16 components, the transmission line characteristic in delay time unit is represented by a matrix h ′ ₁₆ of 16 rows and 1 column as follows.

ここで、Ｆ_{６４×６４}の一般化逆行列は、以下のように示される。

The matrix of transform coefficients F _{64 × 16} has 64 rows and 16 columns. Further, the matrix h ′ ₁₆ is shown as follows by using the F _{64 × 64} generalized inverse matrix and the matrix H ′ ₆₄ .

Here, the generalized inverse matrix of F _{64 × 64} is shown as follows.

  Since each component of the matrix is a known value, it is stored in the control unit 30 in advance. That is, the control unit 30 is a conversion coefficient for changing the transmission path characteristics in units of subcarriers to the transmission path characteristics in units of delay time, and a plurality of components to be multiplied by the respective transmission path coefficient components in units of subcarriers. The conversion coefficient formed by is stored. As described above, the transform coefficient is defined so as to include only a value corresponding to a component having a small delay time with respect to each subcarrier component. Further, the control unit 30 multiplies the stored conversion coefficient and transmission path characteristics in units of subcarriers while associating them with component units, thereby deriving transmission path characteristics in units of delay time. The control unit 30 included in the second radio apparatus 10b causes the baseband processing unit 22 and the like to transmit the transmission path characteristics in units of delay time derived as described above.

  Next, the operation of the control unit 30 included in the first radio apparatus 10a that should receive the transmission path characteristics from the second radio apparatus 10b will be described. The control unit 30 acquires transmission path characteristics in units of delay time via the baseband processing unit 22 and the like. As described above, in the channel characteristics of the delay time unit, the value of the component having a large delay time is assumed to be zero, so that the number of components of the delay time unit is larger than the number of components that should constitute the channel characteristics of the subcarrier unit. The number of components that should constitute the transmission path characteristics is reduced. The control unit 30 applies the delay time unit transmission path characteristics so that the number of components to configure the acquired delay time unit transmission path characteristics is equal to the number of components to form the carrier unit transmission path characteristics. Replenish ingredients.

  That is, the acquired transmission path characteristics in units of delay time between one antenna 12 and one series in the second radio apparatus 10b have 16 components. The control unit 30 extends the number of transmission path characteristic components in units of delay time to “64” by inserting 48 “0” s after 16 components. Further, the control unit 30 converts the expanded transmission path characteristics from a delay time unit to a subcarrier unit by executing FFT. As a result, the control unit 30 acquires transmission path characteristics in units of subcarriers. Further, the control unit 30 causes the baseband processing unit 22 to perform beam forming based on the transmission path characteristics in units of subcarriers. The description regarding beam forming will be described later.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a communication function loaded in the memory. Describes functional blocks realized by collaboration. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 10 shows the configuration of the baseband processing unit 22. The baseband processing unit 22 includes a reception processing unit 50 and a transmission processing unit 52. The reception processing unit 50 executes a part corresponding to the reception operation among the operations in the baseband processing unit 22. That is, the reception processing unit 50 performs adaptive array signal processing on the time domain signal 200, and for that purpose, derivation of the weight vector of the time domain signal 200 is performed. Further, the reception processing unit 50 outputs the result of array synthesis as the frequency domain signal 202. The reception processing unit 50 estimates the above-described transmission path characteristics based on the frequency domain signal 202 corresponding to the training signal. Here, the transmission path characteristics are transmission path characteristics in units of subcarriers.

  The transmission processing unit 52 executes a part corresponding to the transmission operation among the operations in the baseband processing unit 22. That is, the reception processing unit 50 generates the time domain signal 200 by converting the frequency domain signal 202. In addition, the transmission processing unit 52 associates a plurality of sequences with the plurality of antennas 12, respectively. Further, the transmission processing unit 52 executes CDD as shown in FIGS. 3A to 3C, FIGS. 4A to 4D, and FIGS. 5A to 5D. The steering matrix calculation as shown in FIG. Note that the transmission processing unit 52 finally outputs the time domain signal 200. In addition, the transmission processing unit 52 performs beam forming with respect to FIGS.

  FIG. 11 shows the configuration of the reception processing unit 50. The reception processing unit 50 includes an FFT unit 74, a weight vector deriving unit 76, a first combining unit 80a, a second combining unit 80b, a third combining unit 80c, and a fourth combining unit 80d, which are collectively referred to as a combining unit 80.

  The FFT unit 74 converts the time domain signal 200 into a frequency domain value by performing FFT on the time domain signal 200. Here, the frequency domain values are configured as shown in FIG. That is, the frequency domain value for one time domain signal 200 is output on one signal line.

  The weight vector deriving unit 76 derives a weight vector for each subcarrier from the value in the frequency domain. The weight vector is derived so as to correspond to each of a plurality of sequences, and the weight vector for one sequence has an element corresponding to the number of antennas 12 for each subcarrier. An adaptive algorithm may be used to derive the weight vector corresponding to each of a plurality of sequences, or transmission path characteristics may be used. For these processes, known techniques are used. Therefore, the description is omitted here. As described above, the weight vector deriving unit 76 calculates the first component−the second component + the third component−the fourth component, the first component + the second component, and the like as described above. Finally, as described above, weights are derived in units of subcarriers, antennas 12 and sequences. Note that the weight vector deriving unit 76 derives the weight vector and derives the above-described transmission path characteristics in units of subcarriers. The transmission path characteristics in units of subcarriers are derived between the antenna 12 of the second radio apparatus 10b and one series.

  The synthesizing unit 80 performs synthesis using the frequency domain value converted by the FFT unit 74 and the weight vector from the weight vector deriving unit 76. For example, among the weight vectors from the weight vector deriving unit 76, the weight corresponding to one subcarrier and the weight corresponding to the first series are selected as one multiplication target. The selected weight has a value corresponding to each of the antennas 12.

  As another multiplication target, a value corresponding to one subcarrier is selected from the values in the frequency domain converted by the FFT unit 74. The selected value has a value corresponding to each of the antennas 12. Note that the selected weight and the selected value correspond to the same subcarrier. While being associated with each of the antennas 12, the selected weight and the selected value are respectively multiplied, and the multiplication result is added, whereby a value corresponding to one subcarrier in the first sequence is obtained. Derived. In the first synthesizing unit 80a, the above processing is also performed on other subcarriers, and data corresponding to the first stream is derived. Further, in the second synthesis unit 80b to the fourth synthesis unit 80d, data corresponding to the fourth series is derived from the second series by the same processing. The derived first to fourth sequences are output as the first frequency domain signal 202a to the fourth frequency domain signal 202d, respectively.

ここで、δは、シフト量を示し、ｌは、サブキャリア番号を示している。さらに、行列Ｃと系列との乗算は、サブキャリアを単位にして実行される。すなわち、分散部６６は、Ｌ−ＳＴＦ等内での循環的なタイミングシフトを系列単位に実行する。また、タイミングシフト量は、図３（ａ）−（ｃ）、図４（ａ）−（ｄ）、図５（ａ）−（ｄ）のごとく設定される。 FIG. 12 shows the configuration of the transmission processing unit 52. The transmission processing unit 52 includes a distribution unit 66 and an IFFT unit 68. The dispersion unit 66 associates the frequency domain signal 202 with the antenna 12. First, processing when beamforming is not executed, for example, processing when transmitting a training signal will be described. The distribution unit 66 uses the CDD to generate packet signals corresponding to the packet formats in FIGS. 3A to 3C, 4A to 4D, and 5A to 5D. Execute. CDD is performed as matrix C as follows.

Here, δ indicates a shift amount, and l indicates a subcarrier number. Further, the multiplication of the matrix C and the sequence is executed in units of subcarriers. That is, the distribution unit 66 performs a cyclic timing shift within the L-STF or the like on a sequence basis. The timing shift amount is set as shown in FIGS. 3A to 3C, FIGS. 4A to 4D, and FIGS. 5A to 5D.

  The distribution unit 66 multiplies the training signals generated as shown in FIGS. 4A to 4D and FIGS. 5A to 5D by the steering matrix, thereby obtaining the number of training signal sequences. Is increased to the number of series. Here, the dispersion unit 66 extends the order of the input signal to the number of a plurality of sequences before performing multiplication. In the case of FIG. 4B and FIG. 5B, since “HT-STF” and the like arranged in the first sequence and the second sequence are input, the number of input signals is “2”. Yes, represented here by “Nin”.

  Therefore, the input data is indicated by a vector “Nin × 1”. Further, the number of the plurality of series is “4”, and is represented by “Nout” here. The distribution unit 66 extends the order of the input data from Nin to Nout. That is, the vector “Nin × 1” is expanded to the vector “Nout × 1”. At that time, “0” is inserted into the components from the Nin + 1 line to the Nout line. On the other hand, with respect to “HT-LTF” arranged in the third series and the fourth series in FIGS. 4B and 5B, the components up to Nin are “0”, and the Nin + 1th row HT-LTF and the like are inserted in the components from to the Nout line.

ステアリング行列は、「Ｎｏｕｔ×Ｎｏｕｔ」の行列である。また、Ｗは、直交行列であり、「Ｎｏｕｔ×Ｎｏｕｔ」の行列である。直交行列の一例は、ウォルシュ行列である。ここで、ｌは、サブキャリア番号を示しており、ステアリング行列による乗算は、サブキャリアを単位にして実行される。さらに、Ｃは、前述のごとく、ＣＤＤを示す。ここで、ＣＤＤにおけるタイミングシフト量は、複数の系列のそれぞれに対して異なるように規定されている。すなわち、第１の系列に対して「０ｎｓ」、第２の系列に対して「−５０ｎｓ」、第３の系列に対して「−１００ｎｓ」、第４の系列に対して「−１５０ｎｓ」のようにタイミングシフト量が規定される。 The steering matrix S is shown as follows.

The steering matrix is a “Nout × Nout” matrix. W is an orthogonal matrix, which is a “Nout × Nout” matrix. An example of an orthogonal matrix is a Walsh matrix. Here, l indicates a subcarrier number, and multiplication by the steering matrix is executed in units of subcarriers. Further, C represents CDD as described above. Here, the timing shift amount in the CDD is defined to be different for each of the plurality of sequences. That is, “0 ns” for the first sequence, “−50 ns” for the second sequence, “−100 ns” for the third sequence, “−150 ns” for the fourth sequence, etc. The amount of timing shift is defined in FIG.

Next, processing when performing beamforming will be described. As described above, the transmission path characteristics in units of delay time from the second radio apparatus 10b are converted into transmission path characteristics in units of subcarriers by the control unit 30. In order to clarify the description, the processing for one subcarrier will be described below, but the same processing may be executed for other subcarriers. Here, the matrix of the transmission path characteristics taking into account a plurality of sequences and converted by the control unit 30 is indicated as H ′. On the other hand, if the actual transmission line characteristic matrix is denoted by H, the two have the following relationship.

さらに、分散部６６は、積算結果を以下のように固有値分解する。

ここで、Σが固有値であり、Ｖが固有ベクトルである。分散部６６は、Ｖを送信ウエイトベクトルに設定することによって、複数の系列に対してビームフォーミングを実行する。ＩＦＦＴ部６８は、分散部６６からの信号に対してＩＦＦＴを実行し、時間領域信号２００として出力する。 Here, S is the aforementioned steering matrix. The dispersion unit 66 calculates the product of H Hermitian conjugate of H and H as follows.

Furthermore, the dispersion unit 66 performs eigenvalue decomposition on the integration result as follows.

Here, Σ is an eigenvalue and V is an eigenvector. The dispersion unit 66 performs beam forming on a plurality of sequences by setting V as a transmission weight vector. The IFFT unit 68 performs IFFT on the signal from the dispersion unit 66 and outputs it as a time domain signal 200.

  FIG. 13 is a sequence diagram illustrating a procedure for notification of transmission path characteristics in the communication system 100. The first radio apparatus 10a transmits a training signal to the second radio apparatus 10b, and includes a request signal in the training signal (S10). The second radio apparatus 10b estimates transmission path characteristics in units of subcarriers based on the training signal (S12). Further, the second radio apparatus 10b converts the estimated transmission path characteristic into a transmission path characteristic in units of delay time (S14), includes the converted transmission path characteristic in the response signal, and transmits the response signal to the first radio apparatus 10a ( S16). The first radio apparatus 10a converts the transmission path characteristics included in the response signal into transmission path characteristics in units of subcarriers, and derives a transmission weight vector from the converted transmission path characteristics (S18). The first radio apparatus 10a transmits data by performing beamforming using the transmission weight vector (S20).

  According to the embodiment of the present invention, by assuming that the value of the component having a large delay time among the transmission line characteristics in the delay time unit is zero, the delay time having a smaller number of components than the transmission line characteristic in the subcarrier unit. The unit transmission line characteristics can be derived. Further, since the number of transmission path characteristic components in delay time units is smaller than the number of transmission path characteristic components in subcarrier units, the amount of data included in the response signal can be reduced. In addition, since the amount of data included in the response signal is reduced, transmission efficiency can be improved. In general, a component having a large delay time in the transmission path characteristics in units of delay time includes a small number of delayed waves, so that deterioration in estimation accuracy is suppressed even if the value of the component is assumed to be zero. it can. In addition, it is possible to suppress deterioration in estimation accuracy and improve transmission efficiency.

  In addition, since the conversion coefficient is defined so that only the value corresponding to the component having a small delay time is included for each component in the subcarrier unit, the delay time in which the number of components is smaller than the transmission path characteristics in the subcarrier unit. The unit transmission line characteristics can be derived. Further, since the conversion coefficient is stored after being calculated in advance, the processing can be simplified. In addition, since the component of zero value is supplemented to the transmission path characteristics in the delay time unit, and the conversion to the subcarrier unit is executed, the number of transmission path characteristic components in the delay time region is the subcarrier unit. Even if there are fewer than the number of components of the transmission path characteristics, the transmission path characteristics in units of subcarriers can be acquired.

  Further, since HT-LTF is also arranged in a sequence in which no data is arranged, it is possible to derive transmission path characteristics for a sequence in which no data is arranged. Further, since the difference in intensity between HT-STF and HT-LTF is reduced, the amplification factor derived for HT-STF can be close to a value suitable for HT-LTF. In addition, since the amplification factor derived for HT-STF is close to a value suitable for HT-LTF, the accuracy of channel estimation based on HT-LTF can be improved. In addition, when generating the training signal, the number of sequences in which HT-STF is arranged and the number of sequences in which data is arranged are the same, so that the gain set by HT-STF is the data. Correspondingly, deterioration of data reception characteristics can be suppressed. Further, the processing can be simplified by using a large amount of the same timing shift. In addition, when the number of a plurality of sequences is “2” and the number of sequences in which data is arranged is “1”, the receiving apparatus can be assigned to one of the plurality of sequences according to the reception status of HT-LTF. It can instruct the transmitting device whether data should be arranged. That is, transmission diversity can be executed.

  In addition, since the timing shift amount for each of the HT-LTFs arranged in a plurality of series has the same value, even if the series in which the data is arranged is changed, the receiving apparatus can easily cope with it. In addition, since different timing shift amounts are set for each of the plurality of streams, the processing can be executed uniformly. In addition, since the processing can be executed uniformly, the processing can be simplified. Further, even if the number of sequences in which data is arranged increases in the subsequent packet signal, the HT-LTF for the increased sequence has already been transmitted with the same timing shift amount. The receiving device can use the already derived timing or the like. In addition, since the already derived timing or the like can be used, the receiving apparatus can easily cope with an increase in the number of sequences in which data is arranged.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the case where the number of the plurality of sequences is “4” has been described. However, the present invention is not limited to this. For example, the number of the plurality of sequences may be smaller than “4” or larger than “4”. Accordingly, in the former case, the number of antennas 12 may be smaller than “4”, or the number of antennas 12 may be larger than “4”. In these cases, the number of sequences included in one group may be greater than “2”, or the number of groups may be greater than “2”. According to this modification, the present invention can be applied to various numbers of series.

  In the embodiment of the present invention, a matrix in which each component has an orthogonal relationship is shown as the sign relationship of “HT-LTF” in the training signal. However, the present invention is not limited to this. For example, a matrix having a code relationship that allows each desired component to be extracted by a simple operation such as addition or subtraction even if the components are not orthogonal. That's fine. According to this modification, various code relationships can be used as the code of “HT-LTF” in the training signal.

  In the embodiment of the present invention, the control unit 30 arranges the training signal in the packet signal including the request signal. However, the present invention is not limited to this. For example, the control unit 30 may transmit a packet signal including a request signal after transmitting a packet signal in which a training signal is arranged. According to this modification, the second radio apparatus 10b can extend the period from the timing at which the training signal is received to the timing at which the response signal should be transmitted. That is, it is only necessary to transmit a packet signal in which a training signal is arranged.

  In the embodiment of the present invention, the first radio apparatus 10a performs beam forming based on the transmission path characteristics. However, the present invention is not limited to this. For example, the first radio apparatus 10a may perform adaptive modulation based on the transmission path characteristics. The control unit 30 of the first radio apparatus 10a stores in advance a rule that associates the transmission path characteristic with the transmission rate, and identifies the transmission rate from the received transmission path characteristic while referring to the rule. Here, the transmission path characteristic may be a signal strength or delay spread that can be derived from the transmission path characteristic, and the transmission rate may be a value determined by a modulation scheme, a coding rate, and the number of sequences. Further, the control unit 30 may store a threshold for signal strength and delay spread while associating with a modulation scheme, a coding rate, and the number of sequences as a rule. According to this modification, adaptive modulation can be performed. That is, it is only necessary that the transmission path characteristic is transmitted from the second radio apparatus 10b to the first radio apparatus 10a.

  In the embodiment of the present invention, the communication system 100 targets multicarrier signals. However, the present invention is not limited to this. For example, the communication system 100 may process a single carrier signal. In that case, the second radio apparatus 10b derives the transmission path characteristic in the frequency domain based on the received signal. Similarly to the embodiment, the second radio apparatus 10b converts the derived transmission path characteristics from the frequency domain to the time domain, and transmits the converted time domain transmission path characteristics to the first radio apparatus 10a. At that time, by assuming that the value of the component having the large delay time in the time domain transmission line characteristics is zero, the time domain transmission line characteristics are more than the number of components that should constitute the frequency domain transmission line characteristics. The number of components to be configured is reduced. On the other hand, the first radio apparatus 10a converts the received transmission path characteristic from the time domain to the frequency domain. At this time, similarly to the embodiment, the received time domain transmission is performed so that the number of components that should constitute the received time domain transmission path characteristics is equal to the number of components that should constitute the frequency domain transmission path characteristics. The conversion is executed after a component having a predetermined value is supplemented to the road characteristics. According to this modification, by assuming that the component of the delay time component of the time domain transmission channel characteristic is zero, the time domain transmission channel characteristic having a smaller number of components than the frequency domain transmission channel characteristic Can be derived. In addition, since a component of a predetermined value is supplemented to the time domain transmission line characteristics and then conversion to the frequency domain is performed, the number of time domain transmission line characteristics components is equal to the frequency domain transmission line characteristics. Even if the number of components is smaller than the number of components, the transmission path characteristics in the frequency domain can be acquired.

  In the embodiment of the present invention, the baseband processing unit 22 derives the channel characteristics in the time domain by deriving the channel characteristics in units of subcarriers and then executing IFFT. However, the present invention is not limited to this. For example, the baseband processing unit 22 may directly derive the time domain transmission path characteristics from the received signal. At that time, for example, the transmission path characteristic of only 16 sample points is estimated by the least square method. The processing at this time is “Tomohiro Imai, Yasutaka Ogawa, Takeo Ogane,“ Study on Adaptive Array in OFDM Communication System, ”IEICE Technical Report, A.P2001-115, RCS2001-154, Oct. 2001.” , "Y. Ogawa, K. Nishio, T. Nishimura, and T. Ohgane," Channel Estimation and Signal Detection for Space Division Multiplexing in a MIMO-OFDM System, "IEICE Trans. Commun., Vol. E88-B, no 1, pp. 10-18, Jan. 2005. " According to the present modification, the number of unknowns can be reduced compared with the estimation of transmission path characteristics in units of subcarriers, so that characteristics can be improved.

It is a figure which shows the spectrum of the multicarrier signal which concerns on the Example of this invention. It is a figure which shows the structure of the communication system which concerns on the Example of this invention. FIGS. 3A to 3C are diagrams showing packet formats in the communication system of FIG. FIGS. 4A to 4D are diagrams showing a packet format for training signals in the communication system of FIG. FIGS. 5A to 5D are diagrams showing another training signal packet format in the communication system of FIG. FIG. 3 is a diagram illustrating a packet format of a training signal that is finally transmitted in the communication system of FIG. 2. It is a figure which shows the structure of the 1st radio | wireless apparatus of FIG. It is a figure which shows the structure of the signal of the frequency domain in FIG. It is a figure which shows the concept of the conversion process in the control part of FIG. It is a figure which shows the structure of the baseband process part of FIG. It is a figure which shows the structure of the process part for reception of FIG. It is a figure which shows the structure of the process part for transmission of FIG. FIG. 3 is a sequence diagram showing a procedure for notification of transmission path characteristics in the communication system of FIG. 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 radio | wireless apparatus, 12 antenna, 14 antenna, 20 radio | wireless part, 22 baseband process part, 24 modem part, 26 IF part, 30 control part, 100 communication system.

Claims (6)

A receiving unit that receives a multicarrier signal that is a multicarrier signal from a wireless device to be communicated and is formed of a plurality of sequences;
A deriving unit for deriving transmission path characteristics for each of the plurality of sequences in units of carriers based on the multicarrier signal received by the receiving unit;
A conversion unit for converting the transmission path characteristics in units of carriers derived in the deriving section into transmission path characteristics in units of delay time;
A transmission unit that transmits the transmission path characteristics in units of delay time converted by the conversion unit to the wireless device to be communicated;
The conversion unit assumes that the value of the component having a large delay time among the transmission line characteristics in the delay time unit is zero, so that the transmission in the delay time unit is larger than the number of components that should constitute the transmission line characteristic in the carrier unit. Reduce the number of components that should constitute the road characteristics ,
The multicarrier signal to be received by the receiving unit constitutes a packet signal, the data signal is arranged in at least one of a plurality of series, and the data signal in the series in which the data signal is arranged An additional known signal is arranged at a timing other than the timing at which the known signal is arranged and the timing at which the data signal is arranged with respect to the series in which the data signal is not arranged while the known signal is arranged,
The deriving unit derives a channel characteristic for a sequence in which the data signal is arranged, using a known signal included in the received multicarrier signal and a previously stored known signal, and receives the carrier characteristic. The transmission path characteristic for a sequence in which the data signal is not arranged is derived for each carrier while using the additional known signal included in the multicarrier signal and the additional known signal stored in advance. Wireless device. The converter is
A conversion coefficient for converting a transmission path characteristic of a carrier unit into a transmission path characteristic of a delay time unit, and a conversion coefficient formed by a plurality of components to be multiplied by each of the transmission path coefficient components of the carrier unit. A storage unit for storing;
An execution unit for deriving transmission path characteristics in units of delay times by multiplying the conversion coefficients stored in the storage unit and transmission path characteristics in units of carriers in association with component units;
2. The radio according to claim 1 , wherein the conversion coefficient stored in the storage unit is defined to include only a value corresponding to a component having a small delay time with respect to each component in a carrier unit. apparatus. A receiving unit that is a transmission path characteristic with a wireless device to be communicated, and that receives a transmission path coefficient in a time domain from the wireless device to be communicated;
A converter that converts the transmission path characteristics received by the receiver from the time domain to the frequency domain;
Based on the frequency domain transmission path characteristics converted by the conversion unit, comprising a setting unit for setting a condition for transmitting a data signal to the wireless device to be communicated,
In the time domain transmission path characteristics received by the receiving unit, the value of the component having a large delay time is assumed to be zero, so that the time domain transmission path is larger than the number of components that should constitute the frequency domain transmission path characteristics. The number of components that should constitute the characteristic is reduced,
The converter receives at the receiver so that the number of components that should constitute the time domain transmission path characteristics received by the receiver is equal to the number of components that should constitute the frequency domain transmission path characteristics. A radio apparatus that performs conversion after supplementing a component having a predetermined value with respect to a transmission path characteristic in a time domain. A receiver that is a transmission line characteristic for each of a plurality of series with a wireless device to be communicated, and that receives a transmission line coefficient in units of delay time from the wireless device to be communicated;
A conversion unit that converts the transmission path characteristics received in the reception unit from a delay time unit to a carrier unit;
A setting unit that sets conditions for transmitting a multi-carrier signal of a plurality of sequences to the wireless device to be communicated based on the transmission path characteristics in units of carriers converted by the conversion unit;
In the transmission path characteristics in delay time units received by the receiving unit, the value of the component having a large delay time is assumed to be zero, so that the number of delay time units is larger than the number of components that should constitute the transmission path characteristics in carrier units. The number of components that should constitute the transmission path characteristics is reduced,
The converter receives at the receiver so that the number of components that should constitute the transmission path characteristics in delay units received by the receiver is equal to the number of components that should constitute the transmission path characteristics in units of carriers. A radio apparatus that performs conversion after supplementing a component having a predetermined value for the transmission path characteristics in units of delay time. Receiving from the communication target wireless device a transmission path characteristic between the communication target wireless device and a time domain transmission line coefficient;
Converting received channel characteristics from time domain to frequency domain;
Based on the converted frequency domain transmission path characteristics, comprising the step of setting a condition for transmitting a data signal to the wireless device to be communicated,
In the time domain transmission line characteristics received in the receiving step, the value of the component having a large delay time is assumed to be zero, so that the time domain transmission is larger than the number of components that should constitute the frequency domain transmission line characteristics. The number of components that should constitute the road characteristics has been reduced,
The step of converting the received time domain transmission path characteristics so that the number of components to constitute the received time domain transmission path characteristics is equal to the number of components to constitute the frequency domain transmission path characteristics. On the other hand, the communication method is characterized in that the conversion is executed after a component having a predetermined value is replenished. Means for receiving a signal from the first radio apparatus; means for deriving a transmission path characteristic with the first radio apparatus in the frequency domain based on the received signal; and a derived transmission path characteristic A second wireless device comprising: means for converting the frequency domain into the time domain; and means for transmitting the converted time domain transmission path characteristics to the first wireless device;
Based on the means for receiving the channel coefficient from the second radio apparatus, the means for converting the received channel characteristic from the time domain to the frequency domain, and the second radio channel based on the converted channel characteristic of the frequency domain. A first wireless device including means for setting conditions for transmitting a data signal to the device,
The second radio apparatus assumes that the value of the component having a large delay time in the time domain transmission path characteristics is zero, thereby transmitting the time domain transmission more than the number of components that should constitute the frequency domain transmission path characteristics. Reduce the number of components that should constitute the road characteristics,
The first radio apparatus receives the time domain transmission path characteristics so that the number of components to configure the received time domain transmission path characteristics is equal to the number of components to configure the frequency domain transmission path characteristics. A communication system is characterized in that the conversion is executed after a component having a predetermined value is supplemented.

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