JP2006197648A - Method and apparatus for transmitting signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately receive a plurality of known signals by a receiver. <P>SOLUTION: A data separating unit 20 separates data to be transmitted into the number of data equal to that of antennas. An error correcting unit 28 performs a coding for error correction. An interleave unit 30 interleaves data after the convolutional coding. A preamble adding unit 32 adds an STS to the head of a burst signal. The preamble adding unit 32 is to store respectively a plurality of STSs corresponding respectively to a plurality of the transmitting antennas 14 and to be transmitted for a prescribed period. An IFFT unit 34 performs Inverse Fast Fourier Transform (IFFT). A GI unit 36 adds a guard interval to data in time domain. A quadrature modulation unit 38 carries out quadrature modulation. A frequency conversion unit 40 performs a frequency conversion. An amplification unit 42 is a power amplifier for amplifying radio-frequency signals. Finally, signals are transmitted from a plurality of the transmitting antennas 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transmission technique, and more particularly to a transmission method and apparatus for transmitting signals from a plurality of antennas.

  In wireless communication, effective use of limited frequency resources is generally desired. One of the technologies for effectively using frequency resources is the adaptive array antenna technology. In the adaptive array antenna technology, the antenna directivity pattern is formed by controlling the amplitude and phase of signals transmitted and received by a plurality of antennas. That is, an apparatus equipped with an adaptive array antenna changes the amplitude and phase of signals received by a plurality of antennas, adds the changed plurality of received signals, respectively, and changes the amplitude and phase (hereinafter referred to as the amount of change). A signal equivalent to a signal received by an antenna having a directivity pattern corresponding to “weight” is received. In addition, a signal is transmitted by an antenna directivity pattern corresponding to the weight.

In the adaptive array antenna technology, an example of a process for calculating a weight is a method based on a minimum mean square error (MMSE) method. In the MMSE method, a Wiener solution is known as a condition for giving an optimum weight value, and a recurrence formula with a smaller amount of calculation than directly solving the Wiener solution is also known. As the recurrence formula, for example, an adaptive algorithm such as an RLS (Recursive Least Squares) algorithm or an LMS (Least Mean Squares) algorithm is used. On the other hand, for the purpose of increasing the data transmission rate and improving the transmission quality, there are cases where data is subjected to multicarrier modulation and a multicarrier signal is transmitted (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-2110099

  There is a MIMO (Multiple Input Multiple Output) system as a technique for increasing the data transmission speed using the adaptive array antenna technology. In the MIMO system, the transmission device and the reception device each include a plurality of antennas, and one channel corresponding to each antenna is set. That is, for the communication between the transmission device and the reception device, channels up to the maximum number of antennas are set to improve the data transmission rate. Furthermore, if a technology for transmitting a multicarrier signal is combined with such a MIMO system, the data transmission speed can be further increased. On the other hand, since the signal transmitted from the transmission apparatus is accurately received by the reception apparatus, the transmission signal generally includes a preamble that is a known signal. However, when the receiving device of the MIMO system receives the preamble, the weight for adaptive array signal processing may not be derived. In such a case, there is interference between the preambles output from the plurality of antennas. The signal received by the receiving device is likely to be erroneous. In particular, since the AGC setting based on the received preamble is performed at the initial stage of the reception process, it is easily affected by interference due to the preamble transmitted from an undesired antenna.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a transmission method and a method for reducing interference between known signals on a receiving side when transmitting multicarrier known signals from a plurality of antennas, respectively. To provide an apparatus.

  One embodiment of the present invention is a transmission device. This apparatus should transmit a plurality of antennas, a transmission unit that transmits signals using a plurality of carriers via the plurality of antennas, and a plurality of antennas, and transmit from the transmission unit in a predetermined period. And a storage unit for storing a plurality of known signals. In this device, a known signal corresponding to one of the plurality of antennas out of a plurality of known signals stored in the storage unit is a known signal relative to a known signal corresponding to the other antenna of the plurality of antennas. A carrier having at least a part of which may be different may be used.

  With the above apparatus, since at least some of the plurality of known signals are transmitted with different carriers, the cross-correlation between the plurality of known signals is reduced, and the transmitted plurality of known signals can be accurately received by the receiving apparatus. it can.

  Another aspect of the present invention is a transmission method. This method transmits a plurality of known signals respectively corresponding to a plurality of antennas over a predetermined period of time when a signal using a plurality of carriers is transmitted from a plurality of antennas. The known signal transmitted from the above uses a carrier in which at least a part of the known signal is different from the known signal transmitted from the other antenna among the plurality of antennas.

  Yet another aspect of the present invention is also a transmission method. The method includes a step of transmitting a signal using a plurality of carriers from a plurality of antennas, a step of storing a plurality of known signals respectively corresponding to the plurality of antennas, and a plurality of stored known signals over a predetermined period. Transmitting. In this method, the step of storing includes, for a known signal corresponding to one of the plurality of antennas, a known signal corresponding to the other antenna of the plurality of antennas. Thus, a carrier in which at least a part of the known signal is different may be used.

  In the storing step, among the plurality of known signals, the autocorrelation characteristic of the known signal corresponding to one of the plurality of antennas is more than the autocorrelation characteristic of the known signal corresponding to the other antenna of the plurality of antennas. It may be specified to be higher. The number of the plurality of antennas is 3 or more, and the storing step includes a known signal corresponding to one of the plurality of antennas and a remaining corresponding to the other antenna of the plurality of antennas. The cross-correlation characteristics between each of the known signals may be defined to be lower than the cross-correlation characteristics between each of the remaining known signals corresponding to the other antennas.

  The plurality of known signals in the storing step has, as a first value, the number of carriers used only for the known signals corresponding to one of the plurality of antennas among the plurality of carriers to be transmitted in the transmitting step. The first value may be defined to be larger than the second value when the number of carriers used only for known signals corresponding to the other antennas of the plurality of antennas is the second value. . The number of the plurality of antennas is 3 or more, and for the plurality of known signals in the storing step, the second value is the number of carriers used only for the known signals corresponding to one of the other antennas. Also good. The second value may be zero for a plurality of known signals in the storing step.

  Each of the plurality of known signals in the storing step may use a different carrier. Each of the plurality of known signals in the storing step may use a predetermined number of carriers discretely selected from the plurality of carriers. Each of the plurality of known signals in the storing step is defined so that a frequency difference between a highest frequency carrier and a lowest frequency carrier among a predetermined number of discretely selected carriers is equal to each other. Also good. Each of the plurality of known signals in the storing step may use a different carrier. The plurality of known signals of the storing step may be defined such that the number of carriers to be used for each of the known signals is equal. The storing step uses the number of carriers to be used for a known signal corresponding to one of a plurality of antennas among a plurality of known signals for a known signal corresponding to another antenna of the plurality of antennas. There may be more than the number of carriers to be done. The plurality of carriers used for the plurality of known signals in the storing step are predefined in a part of the plurality of carriers to be transmitted in the transmitting step, and the plurality of known signals in the storing step are At least one carrier selected from a plurality of predefined carriers may be used. In the plurality of known signals in the storing step, the value of the in-phase component of the waveform of the known signal corresponding to one of the plurality of antennas is the quadrature component of the waveform of the known signal corresponding to the other antenna of the plurality of antennas. The value of the quadrature component of the waveform of the known signal corresponding to one of the plurality of antennas is equal to the value of the in-phase component of the waveform of the known signal corresponding to the other antenna of the plurality of antennas. It may be specified that

  Determining a number of antennas to which signals should be transmitted among the plurality of antennas, and the step of transmitting includes transmitting and storing signals via the antennas according to the determined number of antennas. If one of the antennas that should transmit the signal is the main antenna and the other is the sub antenna, the number of carriers used only for the known signal corresponding to the main antenna is the known signal corresponding to one of the sub antennas. The number of stored known signals is defined so that the number of carriers is more than the number of carriers used only, and the known signals corresponding to the main antenna are the same for the plurality of carriers to be used regardless of the determined number of antennas. However, it may be defined by different known signal values depending on the determined number of antennas.

  Of the known signals in the storing step, the known signal corresponding to the main antenna and the known signal corresponding to the sub-antenna may use different carriers. Among the known signals in the storing step, the known signal corresponding to the main antenna is defined by a value that reduces the cross-correlation characteristics between the known signals corresponding to the main antenna when the number of antennas to which the signal should be transmitted is different. May be. Among the known signals of the storage step, the known signal corresponding to the main antenna has an in-phase component and a quadrature component in the time domain, and the first type is different from the two types of antennas to which the signal is to be transmitted. The value of the in-phase component in the time domain of the known signal is equal to the value of the quadrature component in the time domain of the second type of known signal, and the value of the quadrature component in the time domain of the first type of known signal is It may be defined to be equal to the value of the in-phase component in the time domain.

  Among the plurality of known signals in the storing step, the known signal corresponding to the main antenna has an in-phase component and a quadrature component in the time domain, and is 1 for two types of antennas to which signals should be transmitted. The absolute value of the in-phase component in the time domain of the second type of known signal is equal to the absolute value of the quadrature component in the time domain of the second type of known signal, and the sign is inverted, and the quadrature in the time domain of the first type of known signal It may be defined that the absolute value of the component is equal to the absolute value of the in-phase component in the time domain of the second type of known signal, and the sign is inverted. Among the plurality of known signals in the storing step, the known signals corresponding to the sub-antennas may be defined by values that reduce the mutual correlation characteristics. Among the known signals in the storing step, a plurality of carriers to be used for the known signal corresponding to the main antenna and the known signal corresponding to the sub antenna are a plurality of carriers used when transmitting the known signal from one antenna. It may be defined to correspond to any of the carriers.

  In the plurality of known signals in the storing step, the absolute value of the in-phase component of the waveform of the known signal corresponding to one of the plurality of antennas is orthogonal to the waveform of the known signal corresponding to the other antenna of the plurality of antennas. The absolute value of the orthogonal component of the waveform of the known signal corresponding to one of the plurality of antennas is equal to the absolute value of the component, and the sign is inverted. It may be defined so that it is equal to the absolute value of the in-phase component of the waveform and the sign is inverted.

  Yet another embodiment of the present invention is a program. The program includes a step of transmitting a signal using a plurality of carriers from a plurality of antennas, a step of storing a plurality of known signals respectively corresponding to the plurality of antennas in a memory, and a plurality of signals stored in the memory over a predetermined period. Transmitting the known signals to the wireless network from a plurality of antennas. In this program, the step of storing in the memory includes a known signal corresponding to one of the plurality of antennas among a plurality of known signals stored in the memory, and a known signal corresponding to another antenna of the plurality of antennas. On the other hand, a carrier in which at least a part of the known signal is different may be used.

  The step of storing in the memory is that the autocorrelation characteristic of a known signal corresponding to one of a plurality of antennas among a plurality of known signals is the autocorrelation characteristic of a known signal corresponding to another antenna of the plurality of antennas May be defined to be higher. The number of the plurality of antennas is 3 or more, and the step of storing in the memory corresponds to the known signal corresponding to one of the plurality of antennas and the other antenna of the plurality of antennas among the plurality of known signals. The cross-correlation characteristics between each of the remaining known signals may be defined to be lower than the cross-correlation characteristics between each of the remaining known signals corresponding to the other antennas.

  The plurality of known signals in the step of storing in the memory has a first number of carriers used only for the known signals corresponding to one of the plurality of antennas among the plurality of carriers to be transmitted in the transmitting step. If the second value is the number of carriers used only for known signals corresponding to other antennas of the plurality of antennas, the first value is defined to be larger than the second value. Also good. The number of the plurality of antennas is 3 or more, and for the plurality of known signals in the step of storing in the memory, the second value is the number of carriers used only for the known signals corresponding to one of the other antennas. It may be a number. The second value may be zero for a plurality of known signals in the step of storing in the memory.

  Each of the plurality of known signals stored in the memory may use a different carrier. Each of the plurality of known signals in the step of storing in the memory may use a predetermined number of carriers discretely selected from the plurality of carriers. Each of the plurality of known signals in the step of storing in the memory is defined so that the frequency difference between the highest frequency carrier and the lowest frequency carrier among the predetermined number of discretely selected carriers is equal to each other. May be. Each of the plurality of known signals stored in the memory may use different carriers. The plurality of known signals in the step of storing in the memory may be defined such that the number of carriers used for each of the known signals is equal. In the step of storing in the memory, the number of carriers to be used for a known signal corresponding to one of a plurality of antennas among a plurality of known signals is a known signal corresponding to another antenna of the plurality of antennas. There may be more than the number of carriers to be used. The plurality of carriers used for the plurality of known signals in the step of storing in the memory are defined in advance in a part of the plurality of carriers to be transmitted in the step of transmitting, and the plurality of known in the steps of storing in the memory The signal may use at least one carrier selected from the plurality of predefined carriers. In the plurality of known signals stored in the memory, the value of the in-phase component of the waveform of the known signal corresponding to one of the plurality of antennas is equal to the waveform of the known signal corresponding to the other antenna of the plurality of antennas. The value of the quadrature component of the waveform of the known signal corresponding to one of the plurality of antennas is equal to the value of the quadrature component, and the value of the in-phase component of the waveform of the known signal corresponding to the other antenna of the plurality of antennas May be defined to be equal to

  A step of determining the number of antennas to which signals should be transmitted among the plurality of antennas, and the step of transmitting includes the step of transmitting signals via the antennas according to the determined number of antennas and storing them in the memory The number of carriers used only for known signals corresponding to the main antenna corresponds to one of the sub-antennas when one of the antennas to transmit signals is the main antenna and the rest is the sub-antenna. A plurality of stored known signals are defined such that the number of stored known signals is equal to or greater than the number of carriers used only for known signals, and the known signals corresponding to the main antenna should be used regardless of the determined number of antennas. May be defined by different known signal values depending on the determined number of antennas.

  Of the plurality of known signals stored in the memory, the known signal corresponding to the main antenna and the known signal corresponding to the sub-antenna may use different carriers. Among the plurality of known signals stored in the memory, the known signal corresponding to the main antenna reduces the cross-correlation characteristic between the known signals corresponding to the main antenna when the number of antennas to which the signal should be transmitted is different. It may be defined by a value. Among the plurality of known signals stored in the memory, the known signal corresponding to the main antenna has an in-phase component and a quadrature component in the time domain, and for two types of antennas to which signals should be transmitted. The value of the in-phase component in the time domain of the first known signal is equal to the value of the quadrature component in the time domain of the second known signal, and the value of the quadrature component in the time domain of the first known signal is two. It may be defined to be equal to the value of the in-phase component in the time domain of the known signal of the eye.

  Of the plurality of known signals stored in the memory, the known signal corresponding to the main antenna has an in-phase component and a quadrature component in the time domain, and for two types of antennas to which signals should be transmitted The absolute value of the in-phase component in the time domain of the first type of known signal is equal to the absolute value of the quadrature component in the time domain of the second type of known signal, and the sign is inverted, and the time domain of the first type of known signal It may be specified that the absolute value of the quadrature component in is equal to the absolute value of the in-phase component in the time domain of the second type of known signal and the sign is inverted. Of the plurality of known signals in the step of storing in the memory, the known signals corresponding to the sub-antennas may be defined by values that reduce the mutual correlation characteristics. Among the multiple known signals stored in the memory, multiple carriers that should be used for the known signal corresponding to the main antenna and the known signal corresponding to the sub antenna are used when transmitting the known signal from one antenna. It may be defined to correspond to any of a plurality of carriers.

  In the plurality of known signals stored in the memory, the absolute value of the in-phase component of the waveform of the known signal corresponding to one of the plurality of antennas is the waveform of the known signal corresponding to the other antenna of the plurality of antennas. The absolute value of the orthogonal component of the waveform of the known signal corresponding to one of the plurality of antennas is known corresponding to the other antenna of the plurality of antennas. It may be defined so that it is equal to the absolute value of the in-phase component of the signal waveform and the sign is inverted.

  Yet another embodiment of the present invention is a receiving device. This device includes a receiving unit that receives a plurality of signals respectively transmitted from a plurality of antennas on a transmission side when one of the plurality of antennas on a transmission side is a main antenna and the other is a sub antenna, and a reception unit A detection unit that detects a known signal included in the signal transmitted from the main antenna, and a plurality of antennas including a transmission-side main antenna and sub-antenna according to the value of the detected known signal. And an estimation unit that estimates the number of antennas that are transmitting signals, and a processing unit that processes received signals according to the estimated number of antennas. In this apparatus, the known signal included in the signal transmitted from the main antenna among the plurality of signals respectively transmitted from the plurality of antennas on the transmission side to be received by the receiving unit is the signal of the antenna transmitting the signal. The estimator stores in advance the relationship between the value of the known signal contained in the signal transmitted from the main antenna and the number of antennas transmitting the signal. The number of antennas transmitting signals may be estimated by associating the values of known signals detected with the relationship.

  According to the above apparatus, the number of antennas to which data is transmitted can be specified (estimated) on the transmission side according to the received known signal, so that the number of antennas to which data is transmitted from the transmission apparatus to the reception apparatus is notified. Is no longer necessary.

  The plurality of signals transmitted from the plurality of antennas on the transmission side to be received by the receiving unit respectively use a plurality of carriers, and the number of carriers used only for the known signals transmitted from the main antenna is the sub antenna. More than the number of carriers used only for known signals transmitted from and the known signals transmitted from the main antenna use multiple identical carriers regardless of the number of antennas transmitting the signals May be. Among a plurality of signals transmitted from a plurality of transmitting-side antennas to be received by the receiving unit, a known signal to be transmitted from the main antenna and a known signal to be transmitted from the sub-antenna use different carriers. May be.

  Of the plurality of signals transmitted from the plurality of transmitting antennas to be received by the receiving unit, the known signal to be transmitted from the main antenna is different from the main antenna when the number of antennas transmitting the signals is different. May be defined by a value that reduces the cross-correlation characteristics between known signals to be transmitted. Of the plurality of signals transmitted from the plurality of transmitting antennas to be received by the receiving unit, the known signal to be transmitted from the main antenna has an in-phase component and a quadrature component in the time domain, and For the two types of antennas to be transmitted, the value of the in-phase component in the time domain of the first known signal is equal to the value of the quadrature component in the time domain of the second known signal. It may be specified that the value of the quadrature component in the time domain of the signal is equal to the value of the in-phase component in the time domain of the second known signal.

  Among the plurality of signals transmitted from the plurality of antennas on the transmission side to be received by the receiving unit, the known signal to be transmitted from the main antenna has an in-phase component and a quadrature component in the time domain, and For the two types of antennas to be transmitted, the absolute value of the in-phase component in the time domain of the first known signal is equal to the absolute value of the quadrature component in the time domain of the second known signal, and the sign is It may be specified that the absolute value of the quadrature component in the time domain of the first type of known signal is equal to the absolute value of the in-phase component in the time domain of the second type of known signal and the sign is inverted.

  Of the plurality of signals transmitted from the plurality of transmitting antennas to be received by the receiving unit, the known signals to be transmitted from the sub-antennas may be defined by values that reduce the mutual correlation characteristics. Among a plurality of signals respectively transmitted from a plurality of transmitting antennas to be received by the receiving unit, a plurality of carriers to be used for a known signal to be transmitted from the main antenna and a known signal to be transmitted from the sub-antenna May be defined to correspond to any of a plurality of carriers used when a known signal is transmitted from one antenna.

  Yet another embodiment of the present invention is a reception method. This method is a case where one of a plurality of antennas on the transmission side is a main antenna and the other is a sub-antenna, and a known signal included in a signal transmitted from the main antenna transmits a signal. When it is specified with different values depending on the number of antennas, it is included in the signal transmitted from the main antenna from the signal received and received from the multiple antennas on the transmitting side. A known signal is detected, and the number of antennas transmitting a signal among the antennas including the main antenna and the sub antenna on the transmission side is estimated according to the value of the detected known signal.

  Yet another embodiment of the present invention is also a reception method. The method includes a step of receiving a plurality of signals respectively transmitted from a plurality of antennas on the transmission side when one of the plurality of antennas on the transmission side is a main antenna and the other is a sub antenna. A step of detecting a known signal included in a signal transmitted from a main antenna from a signal, and a signal among a plurality of antennas including a main antenna and a sub antenna on a transmission side according to the value of the detected known signal And estimating the number of antennas transmitting the signal and processing the received signal according to the estimated number of antennas. In this method, the known signal included in the signal transmitted from the main antenna among the plurality of signals respectively transmitted from the plurality of antennas on the transmission side to be received in the receiving step is the antenna transmitting the signal. In the estimation step, the relationship between the value of the known signal included in the signal transmitted from the main antenna and the number of antennas transmitting the signal is stored in advance. Therefore, the number of antennas transmitting signals may be estimated by associating the values of known signals detected with the relationship.

  A plurality of signals respectively transmitted from a plurality of antennas on the transmitting side to be received in the receiving step use a plurality of carriers, and the number of carriers used only for the known signal transmitted from the main antenna More than the number of carriers used only for known signals transmitted from the antennas, and the known signals transmitted from the main antenna have multiple identical carriers regardless of the number of antennas transmitting the signals. May be used. Of the plurality of signals transmitted from the plurality of transmitting antennas to be received in the receiving step, the known signal to be transmitted from the main antenna and the known signal to be transmitted from the sub-antenna are different carriers. May be used.

  Among the plurality of signals transmitted from the plurality of transmitting antennas to be received in the receiving step, the known signal to be transmitted from the main antenna is the main signal when the number of antennas transmitting the signals is different. You may prescribe | regulate by the value which makes the cross correlation characteristic between the known signals which should be transmitted from an antenna small. Of the plurality of signals transmitted from the plurality of transmitting antennas to be received in the receiving step, the known signal to be transmitted from the main antenna has an in-phase component and a quadrature component in the time domain, and the signal Is equal to the value of the quadrature component in the time domain of the second known signal is equal to the value of the quadrature component in the time domain of the second known signal. It may be specified that the value of the quadrature component in the time domain of the known signal is equal to the value of the in-phase component in the time domain of the second type of known signal.

  Of the plurality of signals transmitted from the plurality of transmitting antennas to be received in the receiving step, the known signal to be transmitted from the main antenna has an in-phase component and a quadrature component in the time domain, and the signal , The absolute value of the in-phase component in the time domain of the first known signal is equal to the absolute value of the quadrature component in the time domain of the second known signal, and the code May be defined such that the absolute value of the quadrature component in the time domain of the first known signal is equal to the absolute value of the in-phase component in the time domain of the second known signal, and the sign is inverted. .

  Among the plurality of signals transmitted from the plurality of antennas on the transmitting side to be received in the receiving step, the known signals to be transmitted from the sub-antennas may be defined by values that reduce the mutual correlation characteristics. Among a plurality of signals transmitted from a plurality of antennas on the transmitting side to be received in the receiving step, a plurality of signals to be used for a known signal to be transmitted from the main antenna and a known signal to be transmitted from the sub-antenna, respectively. The carrier may be defined so as to correspond to any of a plurality of carriers used when a known signal is transmitted from one antenna.

  Yet another embodiment of the present invention is a program. This program receives a plurality of signals respectively transmitted from a plurality of antennas on the transmission side via a wireless network when one of the plurality of antennas on the transmission side is a main antenna and the other is a sub antenna. Detecting a known signal included in the signal transmitted from the main antenna from the received signal and storing it in a memory; and depending on the value of the stored known signal, the main antenna and sub-antenna on the transmission side And a step of processing a received signal according to the estimated number of antennas. In this program, the known signal included in the signal transmitted from the main antenna among the plurality of signals respectively transmitted from the plurality of transmitting antennas to be received in the receiving step is the antenna transmitting the signal. In the determining step, the relationship between the value of the known signal included in the signal transmitted from the main antenna and the number of antennas transmitting the signal is stored in advance in the memory. The number of antennas transmitting signals may be estimated by associating the values of known signals stored with the relationship stored in the memory.

  A plurality of signals respectively transmitted from a plurality of antennas on the transmitting side to be received in the receiving step use a plurality of carriers, and the number of carriers used only for the known signal transmitted from the main antenna More than the number of carriers used only for known signals transmitted from the antennas, and the known signals transmitted from the main antenna have multiple identical carriers regardless of the number of antennas transmitting the signals. May be used. Of the plurality of signals transmitted from the plurality of transmitting antennas to be received in the receiving step, the known signal to be transmitted from the main antenna and the known signal to be transmitted from the sub-antenna are different carriers. May be used. Among the plurality of signals transmitted from the plurality of transmitting antennas to be received in the receiving step, the known signal to be transmitted from the main antenna is the main signal when the number of antennas transmitting the signals is different. You may prescribe | regulate by the value which makes the cross correlation characteristic between the known signals which should be transmitted from an antenna small.

  Of the plurality of signals transmitted from the plurality of transmitting antennas to be received in the receiving step, the known signal to be transmitted from the main antenna has an in-phase component and a quadrature component in the time domain, and the signal Is equal to the value of the quadrature component in the time domain of the second known signal is equal to the value of the quadrature component in the time domain of the second known signal. It may be specified that the value of the quadrature component in the time domain of the known signal is equal to the value of the in-phase component in the time domain of the second type of known signal. Of the plurality of signals transmitted from the plurality of transmitting antennas to be received in the receiving step, the known signal to be transmitted from the main antenna has an in-phase component and a quadrature component in the time domain, and the signal , The absolute value of the in-phase component in the time domain of the first known signal is equal to the absolute value of the quadrature component in the time domain of the second known signal, and the code May be defined such that the absolute value of the quadrature component in the time domain of the first known signal is equal to the absolute value of the in-phase component in the time domain of the second known signal, and the sign is inverted. .

  Of the plurality of signals respectively transmitted from the plurality of transmitting-side antennas to be received in the receiving step, the known signals to be transmitted from the sub-antennas may be defined by values that reduce the mutual correlation characteristics. Among a plurality of signals transmitted from a plurality of antennas on the transmitting side to be received in the receiving step, a plurality of signals to be used for a known signal to be transmitted from the main antenna and a known signal to be transmitted from the sub-antenna, respectively. The carrier may be defined so as to correspond to any of a plurality of carriers used when a known signal is transmitted from one antenna.

  Yet another embodiment of the present invention is a communication system. This system includes a transmission device having a plurality of antennas, and a reception device that receives signals transmitted from the transmission devices by the plurality of antennas. In this system, the transmission device includes a transmission unit that transmits signals using a plurality of carriers via a plurality of antennas, and a plurality of transmission units that correspond to each of the plurality of antennas and that should be transmitted from the transmission unit in a predetermined period. A known signal corresponding to one of the plurality of antennas among the plurality of known signals stored in the storage unit corresponds to the other antenna of the plurality of antennas. A carrier in which at least a part of the known signal is different from the known signal may be used.

  Among the plurality of known signals stored in the storage unit, the autocorrelation characteristic of the known signal corresponding to one of the plurality of antennas is more than the autocorrelation characteristic of the known signal corresponding to the other antenna of the plurality of antennas. It may be specified to be higher. The number of the plurality of antennas is three or more, and among the plurality of known signals stored in the storage unit, the known signal corresponding to one of the plurality of antennas and the remaining corresponding to the other antenna of the plurality of antennas The cross-correlation characteristics between each of the known signals may be defined to be lower than the cross-correlation characteristics between each of the remaining known signals corresponding to the other antennas.

  The plurality of known signals stored in the storage unit has, as a first value, the number of carriers used only for the known signal corresponding to one of the plurality of antennas among the plurality of carriers to be transmitted from the transmission unit. The first value may be defined to be larger than the second value when the number of carriers used only for known signals corresponding to the other antennas of the plurality of antennas is the second value. . The number of the plurality of antennas is 3 or more, and for the plurality of known signals stored in the storage unit, the second value is the number of carriers used only for the known signals corresponding to one of the other antennas. It is good. The second value may be zero for a plurality of known signals stored in the storage unit.

  Each of the plurality of known signals stored in the storage unit may use different carriers. Each of the plurality of known signals stored in the storage unit may use a predetermined number of carriers discretely selected from a plurality of carriers. Each of the plurality of known signals stored in the storage unit is defined so that the frequency difference between the highest frequency carrier and the lowest frequency carrier among the predetermined number of discretely selected carriers is equal to each other. May be. Each of the plurality of known signals stored in the storage unit may use different carriers. The plurality of known signals stored in the storage unit may be defined so that the number of carriers to be used for each of the known signals is equal. Of a plurality of known signals stored in the storage unit, the number of carriers to be used for a known signal corresponding to one of a plurality of antennas is used for a known signal corresponding to another antenna of the plurality of antennas. There may be more than the number of carriers to be done. The plurality of carriers used for the plurality of known signals stored in the storage unit are defined in advance as a part of the plurality of carriers to be transmitted from the transmission unit, and the plurality of known signals stored in the storage unit are Alternatively, at least one carrier selected from the plurality of carriers defined in advance may be used. In the plurality of known signals stored in the storage unit, the value of the in-phase component of the waveform of the known signal corresponding to one of the plurality of antennas is orthogonal to the waveform of the known signal corresponding to the other antenna of the plurality of antennas. The value of the quadrature component of the waveform of the known signal corresponding to one of the plurality of antennas is equal to the value of the component to the value of the in-phase component of the waveform of the known signal corresponding to the other antenna of the plurality of antennas. It may be defined to be equal.

  A determination unit configured to determine the number of antennas to which signals should be transmitted among the plurality of antennas, wherein the transmission unit transmits signals via the antennas according to the determined number of antennas, and the storage unit The number of carriers used only for known signals corresponding to the main antenna is only known signals corresponding to one of the sub-antennas, where one of the antennas to transmit is the main antenna and the remaining is the sub-antenna. The number of stored known signals is defined so that the number of carriers used is equal to or greater than the number of carriers used, and the number of carriers to be used is the same for known signals corresponding to the main antenna regardless of the determined number of antennas. However, it may be defined by different known signal values depending on the determined number of antennas.

  Of the plurality of known signals stored in the storage unit, the known signal corresponding to the main antenna and the known signal corresponding to the sub-antenna may use different carriers. Among the plurality of known signals stored in the storage unit, the known signal corresponding to the main antenna is a value that reduces the cross-correlation characteristics between the known signals corresponding to the main antenna when the number of antennas to which the signal should be transmitted is different. May be defined by Among the plurality of known signals stored in the storage unit, the known signal corresponding to the main antenna has an in-phase component and a quadrature component in the time domain, and for two types of antennas to which the signal should be transmitted, The value of the in-phase component in the time domain of the first known signal is equal to the value of the quadrature component in the time domain of the second known signal, and the value of the quadrature component in the time domain of the first known signal is the second type. May be defined to be equal to the value of the in-phase component in the time domain of the known signal.

  Among the plurality of known signals stored in the storage unit, the known signal corresponding to the main antenna has an in-phase component and a quadrature component in the time domain, and for two types of antennas to which the signal should be transmitted, The absolute value of the in-phase component in the time domain of the first type of known signal is equal to the absolute value of the quadrature component in the time domain of the second type of known signal, and the sign is inverted, and in the time domain of the first type of known signal It may be defined that the absolute value of the quadrature component is equal to the absolute value of the in-phase component in the time domain of the second type of known signal, and the sign is inverted. Of the plurality of known signals stored in the storage unit, the known signals corresponding to the sub-antennas may be defined by values that reduce the mutual correlation characteristics. Among a plurality of known signals stored in the storage unit, a plurality of carriers to be used for a known signal corresponding to the main antenna and a known signal corresponding to the sub antenna are used when transmitting a known signal from one antenna. It may be defined to correspond to any of a plurality of carriers.

  The receiving device includes a receiving unit that receives a plurality of signals respectively transmitted from a plurality of antennas on a transmitting side when one of a plurality of antennas on a transmitting side is a main antenna and the other is a sub antenna, and a receiving unit A detection unit that detects a known signal included in the signal transmitted from the main antenna, and a plurality of antennas including a transmission-side main antenna and sub-antenna according to the value of the detected known signal. A plurality of antennas on the transmission side that are to be received by the receiving unit, and an estimation unit that estimates the number of antennas that are transmitting signals in the processing unit, and a processing unit that processes received signals according to the estimated number of antennas Among the plurality of signals respectively transmitted from, the known signal included in the signal transmitted from the main antenna is defined with different values depending on the number of antennas transmitting the signal, The relationship between the value of the known signal included in the signal transmitted from the main antenna and the number of antennas transmitting the signal is stored in advance, and the value of the known signal detected in the relationship is associated with the signal. The number of transmitting antennas may be estimated.

  Among a plurality of signals respectively transmitted from a plurality of transmitting antennas to be received by the receiving unit, a plurality of carriers to be used for a known signal to be transmitted from the main antenna and a known signal to be transmitted from the sub-antenna Is defined to correspond to one of a plurality of carriers used when a known signal is transmitted from one antenna, and the known signal to be transmitted from the main antenna transmits a signal. Regardless of the number of antennas, a plurality of identical carriers are used, and the detection unit targets a plurality of carriers used for known signals transmitted from the main antenna and is included in the signals transmitted from the main antenna. You may detect the signal or the known signal in the case of transmitting from one antenna.

  The plurality of signals transmitted from the plurality of antennas on the transmission side to be received by the receiving unit respectively use a plurality of carriers, and the number of carriers used only for the known signals transmitted from the main antenna is the sub antenna. More than the number of carriers used only for known signals transmitted from and the known signals transmitted from the main antenna use multiple identical carriers regardless of the number of antennas transmitting the signals May be. Among a plurality of signals transmitted from a plurality of transmitting-side antennas to be received by the receiving unit, a known signal to be transmitted from the main antenna and a known signal to be transmitted from the sub-antenna use different carriers. May be.

  Of the plurality of signals transmitted from the plurality of transmitting antennas to be received by the receiving unit, the known signal to be transmitted from the main antenna is different from the main antenna when the number of antennas transmitting the signals is different. May be defined by a value that reduces the cross-correlation characteristics between known signals to be transmitted. Among the plurality of signals transmitted from the plurality of antennas on the transmission side to be received by the receiving unit, the known signal to be transmitted from the main antenna has an in-phase component and a quadrature component in the time domain, and For the two types of antennas to be transmitted, the value of the in-phase component in the time domain of the first known signal is equal to the value of the quadrature component in the time domain of the second known signal. The value of the quadrature component in the time domain of the signal may be defined to be equal to the value of the in-phase component in the time domain of the second known signal.

  Among the plurality of signals transmitted from the plurality of antennas on the transmission side to be received by the receiving unit, the known signal to be transmitted from the main antenna has an in-phase component and a quadrature component in the time domain, and For the two types of antennas to be transmitted, the absolute value of the in-phase component in the time domain of the first known signal is equal to the absolute value of the quadrature component in the time domain of the second known signal, and the sign is It may be specified that the absolute value of the quadrature component in the time domain of the first type of known signal is equal to the absolute value of the in-phase component in the time domain of the second type of known signal and the sign is inverted. Of the plurality of signals transmitted from the plurality of transmitting antennas to be received by the receiving unit, the known signals to be transmitted from the sub-antennas may be defined by values that reduce the mutual correlation characteristics. Among a plurality of signals respectively transmitted from a plurality of transmitting antennas to be received by the receiving unit, a plurality of carriers to be used for a known signal to be transmitted from the main antenna and a known signal to be transmitted from the sub-antenna May be defined to correspond to any of a plurality of carriers used when a known signal is transmitted from one antenna.

  Yet another embodiment of the present invention is also a transmission device. The apparatus includes an output unit that outputs a plurality of series of signals, a plurality of known signals corresponding to each of the plurality of series of signals, and is included in a predetermined period of each of the plurality of series of signals. And a storage unit for storing a plurality of known signals respectively. A plurality of series of signals output from the output unit uses a plurality of carriers, and among the plurality of known signals stored in the storage unit, a known signal corresponding to one of the plurality of series of signals is A carrier that is at least partially different from a known signal corresponding to a signal of another sequence among a plurality of sequences of signals may be used.

  With the above apparatus, since a plurality of known signals are output at least partially by different carriers, the cross-correlation between the plurality of known signals is reduced, and the receiving apparatus accurately receives the plurality of output known signals. be able to.

  Yet another aspect of the present invention is also a transmission method. In this method, a plurality of known signals are acquired from a memory in which a plurality of known signals corresponding to each of a plurality of series of signals are stored, and the plurality of known signals are included in a predetermined period. A plurality of series of signals that use a plurality of carriers, and one of a plurality of series of signals among a plurality of stored known signals. The known signal corresponding to す る uses a carrier that is at least partially different from the known signal corresponding to the other series of signals among the plurality of series of signals.

  Yet another aspect of the present invention is also a transmission method. The method includes a step of acquiring a plurality of known signals from a memory storing a plurality of known signals corresponding to each of a plurality of series of signals, and including the acquired plurality of known signals in a predetermined period. Outputting a series of signals. The plurality of series of signals output in the outputting step use a plurality of carriers, respectively, and one of the plurality of series of signals among the plurality of known signals stored in the memory in the obtaining step. The known signal corresponding to す る uses a carrier that is at least partially different from known signals corresponding to signals of other sequences among a plurality of sequences of signals.

  Among the plurality of known signals stored in the memory in the obtaining step, the autocorrelation characteristic of the known signal corresponding to one of the signals of the plurality of sequences is the signal of the other sequences of the signals of the plurality of sequences. It may be defined to be higher than the autocorrelation characteristic of the corresponding known signal. Each of the plurality of known signals stored in the memory in the obtaining step may use a different carrier. Each of the plurality of known signals stored in the memory in the obtaining step may use a predetermined number of carriers discretely selected from the plurality of carriers. In each of the plurality of known signals stored in the memory in the obtaining step, the frequency difference between the highest frequency carrier and the lowest frequency carrier among the predetermined number of discretely selected carriers is equal to each other. May be defined as follows. Each of the plurality of known signals stored in the memory in the obtaining step may use a different carrier. In the plurality of known signals stored in the memory in the obtaining step, the number of carriers to be used for each of the known signals may be defined to be equal.

  Among the plurality of known signals stored in the memory in the obtaining step, the number of carriers to be used for the known signal corresponding to one of the plurality of series of signals is different from the other of the plurality of series of signals. It may be greater than the number of carriers to be used for known signals corresponding to the sequence. The plurality of carriers used for the plurality of known signals stored in the memory in the obtaining step are defined in advance as a part of the plurality of carriers to be output, and the plurality of known signals stored in the storage unit May use at least one carrier selected from the plurality of carriers defined in advance.

  In the plurality of known signals stored in the memory in the obtaining step, the value of the in-phase component of the waveform of the known signal corresponding to one of the plurality of series of signals is the other series of the plurality of series of signals. The value of the orthogonal component of the waveform of the known signal corresponding to one of the signals of the plurality of sequences is equal to the value of the orthogonal component of the waveform of the known signal corresponding to the signal, It may be defined to be equal to the value of the in-phase component of the waveform of the known signal corresponding to the signal of the series.

  In the plurality of known signals stored in the memory in the obtaining step, the absolute value of the in-phase component of the waveform of the known signal corresponding to one of the plurality of series of signals is the other series of the plurality of series of signals. Is equal to the absolute value of the quadrature component of the waveform of the known signal corresponding to the signal, and the sign is inverted, and the absolute value of the quadrature component of the waveform of the known signal corresponding to one of the signals of the plurality of sequences is It may be specified that the signal is equal to the absolute value of the in-phase component of the waveform of the known signal corresponding to the other series of signals, and the sign is inverted.

  Yet another embodiment of the present invention is also a program. The program includes a step of acquiring a plurality of known signals from a memory storing a plurality of known signals respectively corresponding to a plurality of series of signals, and including a plurality of acquired known signals in a predetermined period. Outputting a series of signals. The plurality of series of signals output in the outputting step use a plurality of carriers, respectively, and one of the plurality of series of signals among the plurality of known signals stored in the memory in the obtaining step. Is a program for causing a computer to use at least a portion of a carrier different from a known signal corresponding to a signal of another sequence among a plurality of sequences of signals.

  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.

  Advantageous Effects of Invention According to the present invention, it is possible to provide a transmission method and apparatus in which interference between known signals is reduced on the receiving side when multicarrier known signals are transmitted from a plurality of antennas, respectively.

Example 1
Before describing the present invention in detail, an outline will be described. Embodiment 1 of the present invention relates to a MIMO system configured by a transmission apparatus having a plurality of antennas and a reception apparatus having a plurality of antennas. In addition, the MIMO system according to the present embodiment transmits a signal by a multi-carrier, specifically, OFDM (Orthogonal Frequency Division Multiplexing) modulation method, and the transmitted signal forms a burst signal. A preamble signal is arranged at the head of the burst signal, and a receiving apparatus that receives the signal performs AGC setting, timing synchronization, carrier reproduction, and the like based on the preamble signal. In a MIMO system, independent signals are transmitted from a plurality of antennas of a transmission apparatus, and a reception apparatus demodulates a desired signal by separating the received signals by adaptive array signal processing. However, during the preamble signal period, the weight for adaptive array signal processing is not completed, so that signal separation by adaptive array signal processing is not sufficient. The transmission apparatus according to the present embodiment defines a plurality of preamble signals such that the correlation between the plurality of preamble signals transmitted from the plurality of antennas becomes small. As a result, even if signal separation by adaptive array signal processing is not sufficient, the preamble signals of each other do not become interference.

  FIG. 1 illustrates a spectrum of a multicarrier signal according to the first embodiment. FIG. 1 shows a signal spectrum in a wireless LAN (Local Area Network) compliant with the IEEE802.11a standard as a wireless system to which the OFDM modulation method is applied. One of a plurality of carriers in the OFDM system is generally called a subcarrier, but here, one subcarrier is designated by a “subcarrier number”. As shown in the figure, the IEEE 802.11a standard defines 53 subcarriers from subcarrier numbers “−26” to “26”. The subcarrier number “0” is set to null in order to reduce the influence of the DC component in the baseband signal. Each subcarrier is modulated by BPSK, QSPK, 16QAM, and 64QAM.

  FIG. 2 illustrates a concept of the communication system 100 according to the first embodiment. The communication system 100 includes a transmission device 10 and a reception device 12. Further, the transmission device 10 includes a first transmission antenna 14 a and a second transmission antenna 14 b that are collectively referred to as a transmission antenna 14, and the reception device 12 is a first reception antenna 16 a that is generally referred to as a reception antenna 16. And the second receiving antenna 16b.

  The transmitting apparatus 10 transmits a predetermined signal, but transmits different signals from the first transmitting antenna 14a and the second transmitting antenna 14b. The receiving device 12 receives signals transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b by the first receiving antenna 16a and the second receiving antenna 16b. Furthermore, the receiving device 12 separates the received signals by adaptive array signal processing, and independently demodulates the signals transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b. Here, the transmission path characteristic between the first transmission antenna 14a and the first reception antenna 16a is h11, the transmission path characteristic between the first transmission antenna 14a and the second reception antenna 16b is h12, 2 If the transmission path characteristic between the transmission antenna 14b and the first reception antenna 16a is h21, and the transmission path characteristic between the second transmission antenna 14b and the second reception antenna 16b is h22, the receiving apparatus 12 operates by enabling only h11 and h22 by adaptive array signal processing and independently demodulating the signals transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b.

  FIG. 3 shows the configuration of the burst format according to the first embodiment, which does not correspond to the MIMO system. This burst format corresponds to a speech channel of the IEEE 802.11a standard. In the OFDM modulation system, generally, the total of the Fourier transform size and the number of symbols in the guard interval is used as one unit. This single unit is an OFDM symbol in this embodiment. In the IEEE 802.11 standard, the size of the Fourier transform is 64 (hereinafter, one FFT (Fast Fourier Transform) point is referred to as an “FFT point”), and the number of FFT points in the guard interval is 16, so the OFDM symbol Corresponds to 80 FFT points.

  In the burst signal, “preamble” of “4 OFDM symbol”, “signal” of “1 OFDM symbol”, and “data” of an arbitrary length are arranged from the head. The preamble is a known signal transmitted for AGC setting, timing synchronization, carrier reproduction, and the like in the receiving apparatus 12. The signal is a control signal, and the data is information to be transmitted from the transmission device 10 to the reception device 12. Further, as shown in the figure, the “preamble” of “4 OFDM symbol” is separated into “STS (Short Training Sequence)” of “2 OFDM symbol” and “LTS (Long Training Sequence)” of “2 OFDM symbol”. The STS is composed of ten signal units “t1” to “t10”, and one unit “t1” or the like is 16 FFT points. As described above, the STS uses the unit of the time domain as 16 FFT points, but uses 12 subcarriers among the 53 subcarriers shown in FIG. 1 in the frequency domain. The STS is particularly used for AGC setting and timing synchronization. On the other hand, the LTS is composed of two signal units “T1” and “T2” and a guard interval “GI2” that is twice as long, and one unit “T1” is 64 FFT points. “GI2” is 32 FFT points. The LTS is particularly used for carrier reproduction.

「１+ｊ」は、ＱＰＳＫ変調されたＳＴＳの信号点を示す。 The signal in the frequency domain as shown in FIG. 1 is indicated as S− ₂₆ , _26, and the subscript indicates the subcarrier number. Using such a notation, the STS of the IEEE 802.11a standard is expressed as follows.

“1 + j” indicates a signal point of STS subjected to QPSK modulation.

第１受信用アンテナ１６ａで受信した信号の１６ＦＦＴ単位での強度は、次のように示される。

Here, a problem when the STS of the IEEE802.11a standard is transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b of FIG. 2 will be described. If the signal transmitted from the first transmitting antenna 14a is S1 (t), the signal transmitted from the second transmitting antenna 14b is S2 (t), and the noise is n1 (t) and n2 (t), A signal received by the first receiving antenna 16a is represented by X1 (t), and a signal received by the second receiving antenna 16b is represented by X2 (t) as follows.

The intensity in units of 16 FFT of the signal received by the first receiving antenna 16a is shown as follows.

送信される信号Ｓ１（ｔ）とＳ２（ｔ）が同一であり、さらにh１１＝−h２１の場合は、受信した信号の強度が０になるので、受信装置１２のＡＧＣは正確に動作しない。さらに、一般的にはデータ区間ではＸｃが０とみなせる程度に小さくなるので、データ区間の受信電力は｜ｈ１１｜^２＋｜ｈ２２｜^２となる。従って、データ区間とＳＴＳ区間の受信電力の差は、（数４）の右辺第３項で示されるように、２Ｒｅ［ｈ１１ｈ*２１X*ｃ］となる。これから分かるように、Ｓ1（ｔ）とＳ２（ｔ）が異なる場合でも、ＳＴＳ区間のＸｃが大きい場合には、ＳＴＳ区間の電力とデータ区間の電力が大きく異なるため、ＡＧＣが正常に動作しない。従って、ＭＩＭＯシステムに対して、ＩＥＥＥ８０２．１１ａ規格のＳＴＳと別のＳＴＳが必要となり、かつ、それらの相互相関は低い必要がある。 Here, using the relationship of ΣS * 1 (t) S2 (t) = Xc, ΣS * i (t) nj (t) = 0, | nj (t) | ² ≈0, the intensity is as follows: Shown in

When the transmitted signals S1 (t) and S2 (t) are the same, and h11 = −h21, the received signal strength becomes 0, so the AGC of the receiving device 12 does not operate correctly. Further, generally, Xc becomes small enough to be regarded as 0 in the data interval, so the received power in the data interval becomes | h11 | ² + | h22 | ² . Therefore, the difference in received power between the data section and the STS section is 2Re [h11h * 21X * c] as shown in the third term on the right side of (Equation 4). As can be seen from this, even when S1 (t) and S2 (t) are different, if Xc in the STS section is large, the power in the STS section and the power in the data section are greatly different, and AGC does not operate normally. Therefore, for the MIMO system, an STS different from the IEEE 802.11a standard STS is required, and their cross-correlation needs to be low.

  FIG. 4 shows the configuration of the transmission apparatus 10. The transmission device 10 includes a data separation unit 20, a first modulation unit 22a, a second modulation unit 22b, an Nth modulation unit 22n, which are collectively referred to as a modulation unit 22, a first radio unit 24a, a second radio unit 24, and a second radio unit 24. A radio unit 24b, an Nth radio unit 24n, a control unit 26, and an Nth transmission antenna 14n are included. The first modulation unit 22a includes an error correction unit 28, an interleaving unit 30, a preamble addition unit 32, an IFFT unit 34, a GI unit 36, and an orthogonal modulation unit 38. The first radio unit 24a includes a frequency conversion unit 40, An amplification unit 42 is included.

  The data separator 20 separates data to be transmitted into the number of antennas. The error correction unit 28 performs encoding for error correction on the data. Here, it is assumed that convolutional encoding is performed, and the encoding rate is selected from predetermined values. The interleave unit 30 interleaves the convolutionally encoded data. The preamble adding unit 32 adds an STS to the head of the burst signal. It is assumed that the preamble adding unit 32 stores a plurality of STSs corresponding to each of the plurality of transmission antennas 14 and to be transmitted in a predetermined period. Although details of the plurality of STSs will be described later, at least an STS corresponding to one of the plurality of transmitting antennas 14 is at least partially different from an STS corresponding to another transmitting antenna 14. A carrier shall be used. That is, the STS uses subcarriers that have the same number of subcarriers to be used for each STS and that are different from each other.

  The IFFT unit 34 performs IFFT (Inverse Fast Fourier Transform) in units of FFT points, and converts a frequency domain signal using a plurality of subcarrier carriers into a time domain. The GI unit 36 adds a guard interval to the time domain data. As shown in FIG. 3, guard intervals added to the preamble and data are different. The quadrature modulation unit 38 performs quadrature modulation. The frequency converter 40 converts the orthogonally modulated signal into a radio frequency signal. The amplifying unit 42 is a power amplifier that amplifies a radio frequency signal. Finally, it is transmitted from a plurality of transmitting antennas 14. The control unit 26 controls the timing of the transmission device 10 and the like. In this embodiment, it is assumed that the directivity of the transmission antenna 14 is non-directional, and the transmission apparatus 10 does not perform adaptive array signal processing.

  FIG. 5 shows the configuration of the receiving device 12. The receiving device 12 includes an N-th receiving antenna 16n, a first wireless unit 50a collectively referred to as a wireless unit 50, a second wireless unit 50b, an N-th wireless unit 50n, and a first processing unit 52a collectively referred to as a processing unit 52. A second processing unit 52b, an N-th processing unit 52n, a first demodulating unit 54a, a second demodulating unit 54b, an N-th demodulating unit 54n, a data combining unit 56, and a control unit 58, which are collectively referred to as a demodulating unit 54, are included. Further, as signals, a first radio reception signal 200a, a second radio reception signal 200b, an Nth radio reception signal 200n, which are collectively referred to as a radio reception signal 200, and a first baseband reception signal 202a, which is generically referred to as a baseband reception signal 202, A second baseband received signal 202b, an Nth baseband received signal 202n, a first synthesized signal 204a collectively referred to as a synthesized signal 204, a second synthesized signal 204b, and an Nth synthesized signal 204n are included.

  The radio unit 50 performs frequency conversion processing, amplification processing, AD conversion processing, and the like between the radio frequency radio reception signal 200 and the baseband baseband reception signal 202. Here, since a wireless LAN conforming to the IEEE 802.11a standard is assumed as the communication system 100, the wireless frequency of the wireless reception signal 200 corresponds to the 5 GHz band. Furthermore, correlation processing is also performed for timing detection. The processing unit 52 performs adaptive array signal processing on the baseband received signal 202 and outputs a composite signal 204 corresponding to the transmitted plurality of signals. The demodulator 54 demodulates the composite signal 204. Further, guard interval removal, FFT, deinterleaving, and decoding are also executed. The data combiner 56 combines the signals output from the demodulator 54 corresponding to the data separator 20 in FIG. The control unit 58 controls the timing of the receiving device 12 and the like.

  FIG. 6 shows a configuration of the first radio unit 50a. The first radio unit 50 a includes an LNA unit 60, a frequency conversion unit 62, an orthogonal detection unit 64, an AGC 66, an AD conversion unit 68, and a correlation unit 70.

  The LNA unit 60 amplifies the first radio reception signal 200a. The frequency conversion unit 62 performs frequency conversion between a radio frequency 5 GHz band and an intermediate frequency on a signal to be processed. The quadrature detection unit 64 performs quadrature detection on the intermediate frequency signal to generate a baseband analog signal. The AGC 66 automatically controls the gain so that the amplitude of the signal is within the dynamic range of the AD converter 68. In the initial setting of the AGC 66, the STS of the received signal is used, and control is performed so that the strength of the STS approaches a predetermined value. The AD conversion unit 68 converts the baseband analog signal into a digital signal and outputs the digital signal as the first baseband received signal 202a.

  In order to detect STS from first baseband received signal 202a, correlator 70 performs correlation processing using first baseband received signal 202a and previously stored STS, and outputs a correlation value. Although details will be described later, since the STS is set for each transmission antenna 14, the correlation unit 70 performs correlation processing on a plurality of STSs and outputs a plurality of correlation values. The correlation value is input to the control unit 58 in FIG. 5 through a signal line (not shown). The control unit 58 determines the start of burst signal reception based on the plurality of correlation values input from the plurality of correlation units 70, and notifies the processing unit 52, the demodulation unit 54, and the like to that effect. In addition, in order to demodulate a plurality of signals, assignment of the processing unit 52 and the demodulation unit 54 to each signal is determined and notified to the processing unit 52, the demodulation unit 54, and the like.

FIG. 7 shows a configuration of the first processing unit 52a. The first processing unit 52a includes a synthesis unit 80, a reception response vector calculation unit 82, and a reference signal storage unit 84. The synthesizer 80 includes a first multiplier 86a, a second multiplier 86b, an Nth multiplier 86n, and an adder 88, which are collectively referred to as a multiplier 86. The signal includes a first reception weight signal 206a, a second reception weight signal 206b, an Nth reception weight signal 206n, and a reference signal 208, which are collectively referred to as a reception weight signal 206.
The reference signal storage unit 84 stores the LTS.

  The reception response vector calculation unit 82 calculates a reception weight signal 206 from the baseband reception signal 202 and the reference signal 208 as reception response characteristics of the reception signal with respect to the transmission signal. The calculation method of the reception weight signal 206 may be arbitrary, but is executed based on correlation processing as shown below as an example. It is assumed that the reception weight signal 206 and the reference signal 208 are input not only from within the first processing unit 52a but also from the second processing unit 52b and the like through a signal line (not shown). The first baseband received signal 202a is denoted by x1 (t), the second baseband received signal 202b is denoted by x2 (t), the reference signal 208 corresponding to the first transmitting antenna 14a is S1 (t), and the second transmitting band is transmitted. If the reference signal 208 corresponding to the antenna 14b is expressed as S2 (t), x1 (t) and x2 (t) are expressed by the following equations.

ここで、雑音は無視する。第１の相関行列Ｒ１は、Ｅをアンサンブル平均として、次の式で示される。

Here, noise is ignored. The first correlation matrix R1 is expressed by the following equation, where E is an ensemble average.

参照信号２０８間の第２の相関行列Ｒ２も次の式のように計算される。

The second correlation matrix R2 between the reference signals 208 is also calculated as follows:

最終的に、第２の相関行列Ｒ２の逆行列と第１の相関行列Ｒ１を乗算し、次の式で示される受信ウエイト信号２０６が求められる。

Finally, the inverse matrix of the second correlation matrix R2 and the first correlation matrix R1 are multiplied to obtain a reception weight signal 206 represented by the following equation.

  Multiplier 86 weights baseband received signal 202 with received weight signal 206, and adder 88 adds the outputs of multiplier 86 and outputs synthesized signal 204.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of an arbitrary computer, and in terms of software, it is realized by a program having a reservation management function loaded in memory. The functional block realized by those cooperation is drawn. 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.

  FIGS. 8A to 8C show the structure of the burst format according to the first embodiment. Here, it is assumed that the number of transmitting antennas 14 in FIG. FIG. 8A shows a case where two burst signals are transmitted in an overlapping manner. As described above, it is assumed that the first STS and the second STS are different signal sequences. On the other hand, the first LTS, the second LTS, the first signal, and the second signal are arbitrary signal sequences, but the description thereof is omitted here. In FIG. 8B, of the two bursts, the first STS and the second STS are transmitted at the same timing, but the first LTS, the first signal, the second LTS, and the second signal are transmitted at different timings. The first data and the second data are transmitted again at the same timing. As described above, it is assumed that the first STS and the second STS are different signal sequences. On the other hand, the first LTS, the second LTS, the first signal, and the second signal are transmitted at different timings here, and therefore may be the same signal series. FIG. 8C shows a case where STS is added to only one signal. Other than that, it is the same as FIG.

ｈ１１＝−ｈ１２Ｘｃの場合、Ｘ１（ｔ）とＳ１（ｔ）の相互相関は「０」になる。一方、Ｘｃが小さければ、一般的にｈ１１＝−ｈ１２Ｘｃとならない。すなわち、Ｓ１（ｔ）とＳ２（ｔ）の相互相関が小さくなるようなＳＴＳがＭＩＭＯシステムに適している。なお、ここでの相互相関とは、ＳＴＳが配置されるべき１２サブキャリアを対象にした相互相関である。このような関係の一例には、複数のＳＴＳが配置されるサブキャリア番号が異なる場合があり、以下に示す。 Here, an STS suitable for the MIMO system will be described. Note that the same reference numerals as those in FIG. 3 are used. The cross-correlation between X1 (t) and S1 (t) performed by the correlation unit 70 in FIG. 6 is shown as follows.

When h11 = −h12Xc, the cross-correlation between X1 (t) and S1 (t) is “0”. On the other hand, if Xc is small, h11 = −h12Xc is not generally obtained. That is, an STS that reduces the cross-correlation between S1 (t) and S2 (t) is suitable for a MIMO system. Here, the cross-correlation is a cross-correlation for 12 subcarriers where STS should be arranged. As an example of such a relationship, subcarrier numbers in which a plurality of STSs are arranged may be different, and are shown below.

すなわち、複数のＳＴＳは、ＩＥＥＥ８０２．１１ａ規格で規定されたＳＴＳの中から選択されている。このような規則によって、ふたつのＳＴＳ間の相互相関は０になる。さらに、数１に示したＩＥＥＥ８０２．１１ａ規格のＳＴＳとの相互相関も小さくなる。 FIGS. 9A to 9B show waveforms of known signals transmitted from the transmission apparatus 10. Here, the number of transmitting antennas 14 is 2, FIG. 9A shows an STS to be transmitted from the first transmitting antenna 14a, and FIG. 9B is transmitted from the second transmitting antenna 14b. Indicates the power STS. In both cases, the vertical axis indicates “amplitude”, the horizontal axis indicates “FFT point number”, and the in-phase (I) component and the quadrature (Q) component of the STS are separately illustrated. The STS shown in FIGS. 9A to 9B is shown as follows in the frequency domain.

That is, a plurality of STSs are selected from STSs defined in the IEEE 802.11a standard. With this rule, the cross-correlation between the two STSs becomes zero. Furthermore, the cross-correlation with the STS of the IEEE802.11a standard shown in Equation 1 is also reduced.

このような規則によって、３つのＳＴＳ間の相互相関は０になる。さらに、数１に示したＩＥＥＥ８０２．１１ａ規格のＳＴＳとの相互相関も小さくなる。 FIGS. 10A to 10C are diagrams illustrating waveforms of known signals transmitted from the transmission apparatus 10 of FIG. FIGS. 10A to 10C are obtained by extending FIGS. 9A to 9B to three transmitting antennas 14. The STS shown in FIGS. 10A to 10C is shown as follows in the frequency domain.

With such a rule, the cross-correlation between the three STSs becomes zero. Furthermore, the cross-correlation with the STS of the IEEE802.11a standard shown in Equation 1 is also reduced.

  FIG. 11 is a flowchart illustrating a procedure of a reception operation by the reception device 12. The radio unit 50 receives the signal, and the AGC 66 sets the AGC based on the STS included in the received signal (S10). If the control unit 58 can detect the STS as a result of the correlation processing in the correlation unit 70 (Y in S12), the assignment of the processing unit 52 and the demodulation unit 54 to the plurality of transmitted signals is further determined (S14). On the other hand, if the control part 58 cannot detect STS (N of S12), it will return to step 10 again. The processing unit 52 starts adaptive array signal processing by deriving the reception weight signal 206 based on the LTS included in the received signal (S16). The demodulator 54 starts demodulating the synthesized signal 204 output from the data combiner 56 (S18).

  According to the embodiment of the present invention, since different subcarriers are used for a plurality of known signals among a plurality of predetermined subcarriers, the cross-correlation between the plurality of known signals can be reduced. In addition, since the cross-correlation between the plurality of known signals is small, the detection accuracy of the plurality of known signals by the receiving device can be improved. In addition, since the cross-correlation between a plurality of known signals is small, the accuracy of AGC setting by the receiving apparatus can be improved.

(Example 2)
A second embodiment of the present invention relates to a preamble signal to be applied to a MIMO system, similar to the first embodiment of the present invention, and aims to reduce interference between a plurality of transmitted preamble signals. In the first embodiment, in order to set the cross-correlation between a plurality of preamble signals to “0”, the subcarriers to which the preambles are assigned are not matched, and the number of subcarriers to which the preambles are assigned is the same. . The transmission apparatus according to the second embodiment does not have the same number of subcarriers to which each preamble is allocated, that is, allocates a large number of subcarriers to one preamble and allocates a few subcarriers to another preamble. As a result, the autocorrelation value is different for each preamble.

  The transmission device 10 and the reception device 12 according to the second embodiment are the same as the transmission device 10 of FIG. 4 and the reception device 12 of FIG.

  In the first embodiment, the number of subcarriers assigned to each STS is the same. As a result, the cross-correlation is reduced and the AGC setting accuracy is increased. Since the number of subcarriers per STS is reduced, the autocorrelation of the STS itself is reduced. On the other hand, timing detection and frequency offset estimation (not shown) by the receiving device 12 are performed based on the STS autocorrelation, so that the detection accuracy and the estimation accuracy generally increase as the STS autocorrelation increases. That is, in one aspect of the second embodiment, the STS autocorrelation characteristic corresponding to one of the plurality of transmission antennas 14 in FIG. 4 is more than the STS autocorrelation characteristics corresponding to the other transmission antennas 14. Specify to be higher. Further, the number of subcarriers to be used for the STS corresponding to one of the plurality of transmission antennas 14 is larger than the number of subcarriers to be used for the STS corresponding to the other transmission antennas 14. Stipulate.

  Specifically, in the case where the transmission apparatus 10 includes three transmission antennas 14, when transmitting a signal using only the first transmission antenna 14a and the second transmission antenna 14b, the transmission apparatus 10 corresponds to the first transmission antenna 14a. Six subcarriers are allocated to the STS, and six subcarriers are allocated to the STS corresponding to the second transmission antenna 14b. On the other hand, when transmitting signals using the three transmitting antennas 14, six subcarriers are allocated to the STS corresponding to the first transmitting antenna 14a, and three subcarriers are allocated to the STS corresponding to the second transmitting antenna 14b. Allocation, and three subcarriers are allocated to the STS corresponding to the third transmitting antenna 14c. As a result, the receiving apparatus 12 in FIG. 5 performs AGC setting based on each STS. In addition, based on the STS having the largest number of subcarriers among the plurality of STSs, the reception device 12 performs timing detection and frequency offset estimation.

  In another aspect of the second embodiment, subcarriers used by different STSs are partially overlapped. Compared to the previous examples, the cross-correlation is increased, but the autocorrelation is also increased. That is, among the plurality of subcarriers used in the STS defined in the IEEE 802.11a standard, the number of subcarriers used only in the STS corresponding to one of the plurality of transmission antennas 14 is the first value. When the number of carriers used only for STSs corresponding to other transmitting antennas 14 is the second value, the plurality of STSs are defined such that the first value is larger than the second value. Yes. For example, eight subcarriers are allocated to the STS corresponding to the first transmission antenna 14a, and six subcarriers are allocated to the STS corresponding to the second transmission antenna 14b. This is the case when they overlap.

  When the number of transmission antennas 14 is 3, the second value is the number of subcarriers used only for the STS corresponding to one of the other transmission antennas 14. In such a case, the cross-correlation characteristics between the second transmitting antenna 14b and the third transmitting antenna 14c with respect to the STS corresponding to the first transmitting antenna 14a correspond to the second transmitting antenna 14b. It is defined to be lower than the cross-correlation characteristics between the STS and the STS corresponding to the third transmitting antenna 14c. That is, all of the STSs corresponding to the three transmitting antennas 14 are 6 subcarriers, one of which exclusively uses 4 subcarriers, the other exclusively uses 2 subcarriers, Another case is when all subcarriers are not used exclusively.

  Further, subcarriers may be allocated so that the second value described above becomes “0”. That is, 6 subcarriers are exclusively allocated to the STS corresponding to the first transmission antenna 14a, and the STSs corresponding to the second transmission antenna 14b and the third transmission antenna 14c share the remaining 6 subcarriers, respectively. . At that time, those STSs use signal sequences that have a small cross-correlation.

  According to the embodiment of the present invention, the number of subcarriers to be used for a plurality of known signals among the predetermined subcarriers is different for each of the plurality of known signals. A plurality of known signals can be designed to have a value of. Further, since the autocorrelation value for a predetermined known signal is increased, the timing detection accuracy and frequency offset estimation accuracy in the receiving apparatus can be improved.

(Example 3)
The third embodiment of the present invention relates to a MIMO system as in the first embodiment of the present invention. However, the third embodiment relates to correlation processing in the receiving apparatus. As described above, when a plurality of known signals are transmitted in parallel from a plurality of antennas of the transmission device, the reception device detects a timing from the plurality of received known signals, and detects a plurality of signals corresponding to each of the plurality of known signals. A correlator is required. Here, when a plurality of correlators are provided, the circuit scale of the receiving device increases. The MIMO system according to this embodiment defines a predetermined relationship between a plurality of time domain known signal sequences (hereinafter referred to as “time domain known signals”). The transmitting device transmits the plurality of defined time domain known signals, and the receiving device reduces the amount of correlation processing based on the relationship between the plurality of time domain known signals. That is, in general, correlation processing is executed by multiplication and addition, but here, among the correlation processing related to two known signal sequences, the multiplication is made common, and the multiplication results are added in different combinations, and the two are combined. Output the correlation value.

  The transmission device 10 and the reception device 12 according to the third embodiment are the same as the transmission device 10 of FIG. 4 and the reception device 12 of FIG.

  FIGS. 12A to 12B show waveforms of known signals transmitted from the transmission apparatus 10 according to the third embodiment. Here, the number of transmitting antennas 14 is 3, and the STS corresponding to the first transmitting antenna 14a is subcarrier numbers “−24, −16, −12, −8, −4, 4, 8, 12, 16 and 24 ”, the STS corresponding to the second transmission antenna 14b is allocated to the subcarrier number“ 20 ”, and the STS corresponding to the third transmission antenna 14c is the subcarrier number“ −20 ”. Is arranged. 12A corresponds to the STS waveform corresponding to the second transmitting antenna 14b, and FIG. 12B corresponds to the STS waveform corresponding to the third transmitting antenna 14c. The value of the in-phase component of the STS waveform corresponding to the second transmitting antenna 14b is equal to the value of the quadrature component of the STS waveform corresponding to the third transmitting antenna 14c, and the STS corresponding to the second transmitting antenna 14b. Is equal to the value of the in-phase component of the STS waveform corresponding to the third transmitting antenna 14c.

  FIG. 13 illustrates a configuration of the correlation unit 70 according to the third embodiment. The correlation unit 70 includes a first I delay unit 300a, a second I delay unit 300b, a third I delay unit 300c, and a Q delay unit 302, which are collectively referred to as an I delay unit 300, and a first Q delay unit 302a and a second Q delay unit 302b. The first Q storage unit 304a, the second I storage unit 304b, the third I storage unit 304c, the fourth I storage unit 304d, and the Q storage unit 306 are collectively referred to as the third Q delay unit 302c and the I storage unit 304. Unit 306a, second Q storage unit 306b, third Q storage unit 306c, fourth Q storage unit 306d, first multiplication unit 308a, second multiplication unit 308b, third multiplication unit 308c, fourth multiplication unit collectively referred to as multiplication unit 308 308d, fifth multiplier 308e, sixth multiplier 308f, seventh multiplier 308g, eighth multiplier 308h, ninth multiplier 308i, tenth multiplier 308j, eleventh multiplier 3 8k, twelfth multiplier 308l, thirteenth multiplier 308m, fourteenth multiplier 308n, fifteenth multiplier 308o, sixteenth multiplier 308p, and first adder 310a and second adder 310b collectively referred to as adder 310. , Third adder 310c, fourth adder 310d, fifth adder 310e, sixth adder 310f, seventh adder 310g, eighth adder 310h, ninth adder 310i, tenth adder 310j, 11 adder 310k, twelfth adder 310l, thirteenth adder 310m, fourteenth adder 310n, fifteenth adder 310o, sixteenth adder 310p, first adder 312a and second adder 312 collectively An adder 312b, a third adder 312c, and a fourth adder 312d are included. The signal also includes a first correlated in-phase value 210, a first correlated quadrature value 212, a second correlated in-phase value 214, and a second correlated quadrature value 216.

  The first baseband received signal 202a output from the AD conversion unit 68 of FIG. 6 is input to the correlation unit 70. In FIG. 6, the signal line to which the first baseband received signal 202a is to be transmitted is shown as one straight line, but in reality, it is a signal having an in-phase component and a quadrature component. Show. In order to simplify the explanation and the drawings, the number of I delay units 300 and Q delay units 302 is three, that is, the correlation processing is executed based on the four first baseband received signals 202a. Assume that the correlation processing is executed based on the other number of first baseband received signals 202a. Further, the correlator 70 also executes correlation processing for the STS corresponding to the first transmission antenna 14a described above, and includes a circuit for this, but is omitted here.

  The I delay unit 300 and the Q delay unit 302 successively delay the in-phase component value and the quadrature component value of the input first baseband received signal 202a. The I storage unit 304 and the Q storage unit 306 are components of the STS waveform corresponding to the first transmitting antenna 14a, that is, the STS converted into the time domain (hereinafter referred to as “time domain STS”). It may be used in the same meaning as “known signal”). Note that the I storage unit 304 and the Q storage unit 306 store the in-phase component and the quadrature component of the time domain STS, respectively.

  The multiplication unit 308 performs multiplication in the correlation process. That is, the first multiplier 308a multiplies the value of the quadrature component of the first baseband received signal 202a and the value of the in-phase component of the time domain STS, and the second multiplier 308b calculates the in-phase component of the first baseband received signal 202a. The third multiplication unit 308c multiplies the value of the in-phase component in the time domain STS by the value of the quadrature component of the first baseband received signal 202a and the value of the quadrature component in the time domain STS. Is multiplied by the value of the in-phase component of the first baseband received signal 202a and the value of the in-phase component of the time domain STS. The fifth multiplier 308e, the ninth multiplier 308i, and the thirteenth multiplier 308m correspond to the first multiplier 308a, and the sixth multiplier 308f, the tenth multiplier 308j, and the fourteenth multiplier 308n are the second multiplier. The seventh multiplier 308g, the eleventh multiplier 308k, and the fifteenth multiplier 308o correspond to the third multiplier 308c, the eighth multiplier 308h, the twelfth multiplier 308l, and the sixteenth multiplier 308p. Corresponds to the fourth multiplier 308d. That is, the multiplication for the two time domains STS is made common.

  The addition unit 310 adds the multiplication results output from the multiplication unit 308, and the addition unit 312 further adds the addition results. As a result, correlation values for the two time domain STSs are generated in a form having an in-phase component and a quadrature component, respectively. The first addition unit 310a subtracts the multiplication result of the fourth multiplication unit 308d from the multiplication result of the first multiplication unit 308a, and the second addition unit 310b performs the multiplication result of the second multiplication unit 308b and the third multiplication unit 308c. The multiplication result is added, the third addition unit 310c adds the multiplication result of the second multiplication unit 308b and the multiplication result of the third multiplication unit 308c, and the fourth addition unit 310d calculates the multiplication result of the first multiplication unit 308a. The multiplication result of the fourth multiplication unit 308d is subtracted. In addition, the fifth addition unit 310e, the ninth addition unit 310i, and the thirteenth addition unit 310m correspond to the first addition unit 310a, and the sixth addition unit 310f, the tenth addition unit 310j, and the fourteenth addition unit 310n perform the second addition. The seventh adder 310g, the eleventh adder 310k, and the fifteenth adder 310o correspond to the third adder 310c, the eighth adder 310h, the twelfth adder 310l, and the sixteenth adder 310p. Corresponds to the fourth adder 310d.

  The first adding unit 312a calculates a quadrature component of the correlation value for one time domain STS and outputs a first correlation quadrature value 212, and the second adding unit 312b is an in-phase component of the correlation value for one time domain STS. And outputs the first correlation in-phase value 210, the third adder 312c calculates the quadrature component of the correlation value for the other time domain STS and outputs the second correlation quadrature value 216, and the second adder 312b calculates the in-phase component of the correlation value for the other time domain STS and outputs the second correlation in-phase value 214. Here, the first addition unit 312a adds the addition results of the fourth addition unit 310d, the eighth addition unit 310h, the twelfth addition unit 310l, and the sixteenth addition unit 310p, and the second addition unit 312b performs the third addition. 310c, seventh addition unit 310g, eleventh addition unit 310k, and fifteenth addition unit 310o are added, and the third addition unit 312c is a second addition unit 310b, a sixth addition unit 310f, and a tenth addition unit. 310j adds the addition results of the fourteenth addition unit 310n, and the fourth addition unit 312d adds the subtraction results of the first addition unit 310a, the fifth addition unit 310e, the ninth addition unit 310i, and the thirteenth addition unit 310m. .

  FIGS. 14A to 14B illustrate waveforms of known signals transmitted from the transmission apparatus 10 according to the third embodiment. 14 (a)-(b), in the same manner as FIGS. 12 (a)-(b), the value of the in-phase component in the time domain STS corresponding to the second transmission antenna 14b is applied to the third transmission antenna 14c. The value of the quadrature component of the time domain STS corresponding to the third transmission antenna 14c is equal to the value of the quadrature component of the corresponding time domain STS and the value of the quadrature component of the time domain STS corresponding to the second transmission antenna 14b It has the relationship which becomes equal to. Therefore, the correlation unit 70 in FIG. 13 is effective as a circuit for executing the correlation processing on the signal.

  According to the embodiment of the present invention, since the delay unit for delaying the input signal, the storage unit for storing the reference signal, and the multiplication unit in the correlation processing can be shared by processing for a plurality of reference signals, the circuit scale can be reduced. it can.

Example 4
The fourth embodiment of the present invention relates to the correlation processing in the receiving apparatus as in the third embodiment. The fluctuation period of one waveform among the plurality of time domain known signals according to the present embodiment is twice the fluctuation period of the other. Furthermore, only the time domain known signal having the longer fluctuation period is stored. The correlation process for the time domain known signal that is not stored is executed after a predetermined value is selected from the stored values of the time domain known signal. Therefore, it is possible to share part of the correlation processing for two time domain known signals.

  The transmission device 10 and the reception device 12 according to the fourth embodiment are the same as the transmission device 10 of FIG. 4 and the reception device 12 of FIG. In the present embodiment, two time domains STS are transmitted from the two transmitting antennas 14 such that the fluctuation period of one time domain STS is ½ of the fluctuation period of the other time domain STS. Here, the time region STS having the longer fluctuation cycle is referred to as “first time region STS”, and the time region STS having the shorter fluctuation cycle is referred to as “second time region STS”. Furthermore, it is assumed here that the period of the second time region STS is ½ of the period of the first time region STS.

  FIG. 15 illustrates a configuration of the correlation unit 70 according to the fourth embodiment. FIG. 15 shows a first multiplication unit 314a, a second multiplication unit 314b, a third multiplication unit 314c, a fourth multiplication unit 314d, and a fifth multiplication unit 314e, which are collectively referred to as a multiplication unit 314, with respect to the correlation unit 70 in FIG. , Sixth multiplier 314f, seventh multiplier 314g, eighth multiplier 314h, ninth multiplier 314i, tenth multiplier 314j, eleventh multiplier 314k, twelfth multiplier 314l, thirteenth multiplier 314m, 14th multiplication unit 314n, 15th multiplication unit 314o, 16th multiplication unit 314p, first addition unit 316a, second addition unit 316b, third addition unit 316c, fourth addition unit 316d, fifth An adder 316e, a sixth adder 316f, a seventh adder 316g, and an eighth adder 316h are included.

  The I storage unit 304 and the Q storage unit 306 store the first time region STS. Here, the processing until the second correlated in-phase value 214 and the second correlated quadrature value 216 are output is the same as the processing until the second correlated in-phase value 214 and the second correlated quadrature value 216 in FIG. 13 are output. Omitted.

  Regarding the processing until the first correlated in-phase value 210 and the second correlated quadrature value 216 are output, the multiplying unit 314 applies the value of the I storage unit 304 and the Q storage unit 306 to the delayed first baseband received signal 202a. Multiply by the value of. However, only the first I storage unit 304a and the third I storage unit 304c of the I storage unit 304 are used. That is, the multiplication unit 314 that performs multiplication using the I storage unit 304 is arranged in order of the second multiplication unit 314b, the sixth multiplication unit 314f, the tenth multiplication unit 314j, and the fourteenth multiplication unit 314n in time series. Yes. The second multiplication unit 314b performs multiplication using the first I storage unit 304a, while the sixth multiplication unit 314f performs multiplication using the third I storage unit 304c instead of the second I storage unit 304b. That is, the ratio of the period of the second time domain STS to the first time domain STS, here, a value obtained by reversing 1/2, that is, a value of the I storage unit 304 is selected for each integer such as “2”. The same applies to the Q storage unit 306.

  According to the embodiment of the present invention, since the delay unit for delaying the input signal and the storage unit for storing the reference signal can be shared by the processing for the plurality of reference signals, the circuit scale can be reduced.

(Example 5)
The fifth embodiment of the present invention relates to the correlation processing in the receiving apparatus as in the third embodiment. One of the plurality of time domain known signals according to the present embodiment has a waveform such that either the in-phase component or the quadrature component is 0 and the amplitude is constant. Furthermore, the other of the time domain known signals has a value obtained by inverting one orthogonal component. A receiving apparatus that has received such a time domain known signal can share part of the correlation processing for the two time domain known signals, and also eliminates the need for multiplication.

  FIG. 16 illustrates a waveform of a known signal transmitted from the transmission apparatus 10 according to the fifth embodiment. Here, the number of transmitting antennas 14 is 3, and the STS corresponding to the first transmitting antenna 14a is subcarrier numbers “−24, −20, −12, −8, −4, 4, 8, 12, 20, 24 ”, the STS corresponding to the second transmission antenna 14 b is allocated to the subcarrier number“ −16 ”, and the STS corresponding to the third transmission antenna 14 c is the subcarrier number“ 16 ”. Is arranged. FIG. 16 shows a time domain STS with respect to the STS corresponding to the second transmitting antenna 14b. On the other hand, the time domain STS for the STS corresponding to the third transmitting antenna 14c has a waveform obtained by inverting the orthogonal component of FIG.

FIG. 17 illustrates a configuration of the correlation unit 70 according to the fifth embodiment. The correlation unit 70 is different from the correlation unit 70 of FIG. 13 in that the first inversion unit 318a, the second inversion unit 318b, the third inversion unit 318c, the fourth inversion unit 318d, and the fifth inversion unit are collectively referred to as the inversion unit 318. 318e and a sixth reversing unit 318f.
The inversion unit 318 inverts the value of the input signal. That is, a positive value is converted into a negative value, and a negative value is converted into a positive value.
The adding unit 312 adds the first baseband received signal 202a, the output signal of the I delay unit 300, and the output signal of the inverting unit 318, and adds the first correlated in-phase value 210, the first correlated quadrature value 212, and the second correlated in-phase value. 214, the second correlation orthogonal value 216 is output.

  According to the embodiment of the present invention, a delay unit for delaying an input signal can be shared by processing for a plurality of reference signals, and a multiplication unit in correlation processing can be deleted, so that the circuit scale can be reduced.

(Example 6)
The sixth embodiment of the present invention relates to a MIMO system as in the previous embodiments. As described above, in the MIMO system, independent signals are transmitted from a plurality of transmitting antennas. In the embodiments so far, the number of transmitting antennas is fixed to a constant value. However, the number of transmitting antennas may be changed according to the capacity of data to be transmitted. That is, when the capacity of data to be transmitted is small, the number of transmitting antennas is reduced, and when the capacity of data to be transmitted is large, the number of transmitting antennas is increased. When the number of transmitting antennas that transmit signals is appropriately changed by the transmitting apparatus, the receiving apparatus needs to recognize the number of transmitting antennas that have been changed in order to accurately receive data. If the transmitting apparatus notifies the receiving apparatus of the number of transmitting antennas transmitting data by a predetermined control signal, the data transmission efficiency is reduced by the control signal. Therefore, even if there is no control signal, it is only necessary for the receiving apparatus to recognize the number of transmitting antennas that are transmitting data.

  The transmitting apparatus according to the present embodiment changes the STS pattern according to the number of transmitting antennas that transmit data, and the receiving apparatus detects the changed STS pattern to transmit data to be transmitted. Recognize the number of trusted antennas. That is, a plurality of transmission antennas are divided into one (hereinafter referred to as “main antenna”) and the rest (hereinafter referred to as “sub antenna”), and the STS pattern transmitted from the main antenna is changed according to the number of transmission antennas. To do. Also, different subcarriers are used in the STS transmitted from the main antenna and the STS transmitted from the sub-antenna so that the change in the pattern of the STS transmitted from the main antenna is accurately received. That is, each STS is defined so that the cross-correlation value between them becomes small.

  As described above, the receiving apparatus according to the present embodiment detects the STS pattern transmitted from the main antenna. This detection is performed by correlation processing between the received signal and a previously stored STS pattern. For example, when the number of transmitting antennas is 2 and 3, a correlation unit corresponding to each STS pattern is required. In the present embodiment, the STS patterns transmitted from the main antenna when the number of transmitting antennas is 2 and 3 are defined such that the phases are reversed from each other as in the third embodiment. Therefore, if the receiving apparatus includes the correlation unit described in the third embodiment, it is possible to detect a change in the STS pattern transmitted from the main antenna. Furthermore, it is not necessary to provide a correlation unit corresponding to each STS pattern.

  The transmission device 10 according to the sixth embodiment is the same type as the transmission device 10 of FIG. The transmission device 10 includes a determination unit (not shown). The determining unit determines the number of transmitting antennas 14 to which a signal is to be transmitted among the N transmitting antennas 14 based on a predetermined instruction. Here, the predetermined instruction may be arbitrary. For example, the predetermined instruction may be received from an application according to the type and amount of application for transmitting data in the communication system 100, or between the transmission device 10 and the reception device 12. The measurement unit (not shown) may measure the quality of the transmission path, and the measurement unit may input an instruction according to the measurement result to the determination unit. Further, the modulation unit 22 and the radio unit 24 corresponding to the number of transmission antennas 14 determined by the transmission antenna 14 operate to transmit signals.

  As described above, the preamble adding unit 32 stores the STS and LTS in advance, and adds the STS and LTS to the head portion of the burst signal. Furthermore, the preamble adding unit 32 selects a predetermined STS from a plurality of types of STS stored in advance according to the number of transmitting antennas 14 determined by the determining unit. For example, the preamble adding unit 32 included in the modulation unit 22 corresponding to the main antenna selects an STS corresponding to the main antenna. Further, the STS corresponding to the main antenna is stored according to the number of transmission antennas 14 that may be determined, and the STS corresponding to the number of transmission antennas 14 determined by the determination unit is selected. . For example, when “2” or “3” can be determined as the number of transmitting antennas 14, the preamble adding unit 32 performs the STS corresponding to the number “2” of transmitting antennas 14 and the number “3” of transmitting antennas 14. ”Is stored. Further, when the determining unit determines the number of transmitting antennas 14 to be “2”, the preamble adding unit 32 selects the STS corresponding to “2” and adds it to the burst signal. On the other hand, the preamble adding unit 32 included in one or more modulation units 22 corresponding to the sub antenna selects an STS corresponding to the sub antenna. When there are a plurality of sub-antennas, the STS patterns corresponding to them are different so as to reduce mutual interference.

  FIG. 18 illustrates the relationship between the number of transmitting antennas 14 that transmit data according to the sixth embodiment and the STS pattern transmitted from the transmitting antenna 14. Here, the number of transmission antennas 14 is shown in the vertical direction in the figure, and the transmission antenna 14 to be used and the STS corresponding thereto are shown in the horizontal direction in the figure according to the number of transmission antennas 14. Yes. That is, when the number of transmitting antennas 14 is “1”, an STS defined in the above-mentioned IEEE 802.11a standard (hereinafter referred to as “Legacy STS”) is transmitted from the first transmitting antenna 14a. When the number of transmitting antennas 14 is “2”, “STS1” is transmitted from the first transmitting antenna 14a, and “STSa” is transmitted from the second transmitting antenna 14b. Further, when the number of transmitting antennas 14 is “3”, “STS1” is transmitted from the first transmitting antenna 14a, “STS2” is transmitted from the second transmitting antenna 14b, and the third transmitting antenna 14c. “STSb” is transmitted. Here, the second transmitting antenna 14b when the number of transmitting antennas 14 is "2" corresponds to the main antenna, and the third transmitting antenna 14c when the number of transmitting antennas 14 is "3" corresponds to the main antenna. Other than that corresponds to the sub-antenna.

  Further, in association with the above description, the STS corresponding to the main antenna when the number of transmitting antennas 14 is “2” is “STSa” and the number of transmitting antennas 14 is “3”. The STS corresponding to the main antenna is “STSb”. On the other hand, the STS corresponding to the sub-antenna when the number of transmitting antennas 14 is “2” is “STS1”, and the STS corresponding to the sub-antenna when the number of transmitting antennas 14 is “3” is “STS1”. And “STS2”. For convenience of explanation, “STSa” and “STSb” are collectively referred to as “main antenna STS”, and “STS1” and “STS2” are collectively referred to as “sub-antenna STS”. Although the number of transmitting antennas 14 for transmitting signals has been described as “2” or “3”, the number may be other than these.

  Referring to the relationship between these STS and legacy STS, the plurality of carriers to be used for the main antenna STS and the sub-antenna STS respectively correspond to any of the 12 subcarriers used in the legacy STS. It is prescribed. Here, the STS for the main antenna and the STS for the sub-antenna use 6 subcarriers different from each other among the 12 subcarriers of the Legacy STS. With such a definition, the cross-correlation value between the main antenna STS and the sub-antenna STS is “0”. Note that the 6 subcarriers used by the main antenna STS are constant regardless of the number of transmission antennas 14 that transmit data, and the 6 subcarriers used by the main antenna STS are transmission channels that transmit data. It is assumed that it is constant regardless of the number of trusted antennas 14. Therefore, when there are a plurality of sub-antennas, for example, when the number of transmitting antennas 14 is “3”, “STS1” and “STS2” use the same 6 subcarriers.

  The main antenna STS includes “STSa” and “STSb”, but the number of transmitting antennas 14 transmitting signals is notified to the receiving device 12 by the difference in the pattern of “STSa” and “STSb”. It has a function to tighten. Therefore, these STSs need to be different to the extent that “STSa” and “STSb” can be identified from the signal received by the receiving device 12. That is, the main antenna STS is defined as a different main antenna STS when the number of transmitting antennas 14 to which signals are to be transmitted is different, and more specifically, between “STSa” and “STSb”. It is defined by a value that reduces the cross-correlation characteristics. These specific values will be described later.

  On the other hand, the sub-antenna STS uses the same sub-carrier, particularly when there are a plurality of sub-antennas, and thus “STS 1” and “STS 2” are defined in a pattern that reduces interference between them. The sub-antenna STSs are defined by values that reduce the cross-correlation characteristics. From the above, even if the number of transmitting antennas 14 used for signal transmission increases, the number of subcarriers used only for the main antenna STS remains constant at “6”. The number of subcarriers used only for STS is reduced to “0”.

また、「ＳＴＳｂ」は、周波数領域で以下のとおりに示される。

FIG. 19 shows the waveform of STSa, and FIG. 20 shows the waveform of STSb. That is, these correspond to the time domain values of the main antenna STS when the number of transmitting antennas 14 that transmit signals is “2” and “3”. The STS for the main antenna has an in-phase component and a quadrature component in the time domain, and the in-phase of “STSa” with respect to two types of antennas to transmit signals, ie, “2” and “3”. It is specified that the value of the component is equal to the value of the quadrature component of “STSb”, and the value of the quadrature component of “STSa” is equal to the value of the in-phase component of “STSb”. On the other hand, “STSa” is indicated as follows in the frequency domain.

Further, “STSb” is indicated in the frequency domain as follows.

また、「ＳＴＳ２」は、周波数領域で以下のとおりに示される。

FIG. 21 shows the waveform of STS1, and FIG. 22 shows the waveform of STS2. That is, these correspond to the time domain values of the sub-antenna STS. “STS1” is indicated as follows in the frequency domain.

Further, “STS2” is indicated in the frequency domain as follows.

The receiving device 12, the first radio unit 50a, the first processing unit 52a, and the correlation unit 70 according to the sixth embodiment are the receiving device 12 in FIG. 5, the first radio unit 50a in FIG. 6, and the first processing unit 52a in FIG. This is the same type as the correlation unit 70 in FIG.
The radio unit 50 receives signals transmitted from the plurality of transmitting antennas 14 respectively. The correlator 70 detects the STS from the received signal. Here, the operation for detecting the STS for the main antenna will be described. The correlation unit 70 stores the value of “STSa” in the I storage unit 304 and the Q storage unit 306. The multiplier 308 and the adder 310 perform correlation between the received signal and the stored value, and the correlation value between the received signal and “STSa” is output as the first correlation in-phase value 210 and the first correlation quadrature value 212. The correlation value between the received signal and “STSb” is output as the second correlation in-phase value 214 and the second correlation quadrature value 216.

  An estimation unit (not shown) inputs the first correlated in-phase value 210, the first correlated quadrature value 212, the second correlated in-phase value 214, and the second correlated quadrature value 216, and the first correlated in-phase value 210 and the first correlated quadrature value 212 are input. , The magnitude calculated from the second correlation in-phase value 214 and the second correlation quadrature value 216 (hereinafter referred to as “second magnitude”). Is derived. Further, if the first size is larger than the second size, the estimation unit estimates that the transmitted main antenna STS is “STSa”, and the number of transmitting antennas 14 transmitting signals. Is determined to be “2”. On the other hand, if the first size is not larger than the second size, it is estimated that the transmitted main antenna STS is “STSb”, and the number of transmitting antennas 14 transmitting signals is “ 3 ”. In accordance with the determined number of transmitting antennas 14, the receiving device 12 performs settings for demodulation. That is, if the number of transmitting antennas 14 is “2”, the first demodulator 54a and the second demodulator 54b are operated, and if the number of transmitting antennas 14 is “3”, the first demodulator 54a 3 The demodulator 54c is operated.

  FIG. 23 is a flowchart illustrating a procedure of a reception operation by the reception device 12. The radio unit 50 receives the signal, and the AGC 66 sets the AGC based on the STS included in the received signal (S50). The STS is detected by correlation processing in the correlation unit 70 (S52). If the detected STS is “STSa” (Y in S54), the estimation unit determines reception of two series of signals (S56). The first demodulator 54a and the second demodulator 54b are operated. On the other hand, if the detected STS is not “STSa” (N in S54) but “STSb”, the estimation unit determines reception of three sequences of signals (S58), and the third demodulation unit 54a performs third demodulation. The unit 54c is operated. The processing unit 52 starts the adaptive array signal processing by deriving the reception weight signal 206 based on the LTS included in the received signal (S60). The demodulator 54 starts demodulating the synthesized signal 204 output from the data combiner 56 (S62).

  According to the embodiment of the present invention, even if the transmitting apparatus does not notify the receiving apparatus of the number of antennas that transmit signals, the receiving apparatus can recognize the number of antennas that the transmitting apparatus transmits signals. In addition, since the delay unit for delaying the input signal, the storage unit for storing the reference signal, and the multiplication unit in the correlation processing can be shared by the processing for the two STSs, the circuit scale can be reduced.

(Example 7)
In the MIMO system as in the sixth embodiment, the seventh embodiment of the present invention changes the STS pattern according to the number of transmitting antennas that transmit data in the MIMO system, and the receiving device changes the changed STS pattern. The present invention relates to a technique for recognizing the number of transmitting antennas that transmit data by detecting the data. Further, as in the sixth embodiment, the STS pattern transmitted from the main antenna has a predetermined relationship according to the number of transmitting antennas that transmit data. The receiving apparatus detects a plurality of correlation values with one correlation unit using the relationship. In the sixth embodiment, the above-described predetermined relationship is a relationship in which the phases are reversed, whereas in the seventh embodiment, the absolute value of each component is exchanged and the relationship is reversed in sign. .

これ以外は、実施例６と同一であるので、説明を省略する。 FIG. 24 illustrates the relationship between the number of transmitting antennas 14 that transmit data according to the seventh embodiment and the pattern of STS transmitted from the transmitting antenna 14. Similarly to FIG. 18, the number of transmitting antennas 14 is shown in the vertical direction of the figure, and the transmitting antenna 14 to be used and the STS corresponding thereto are shown in the horizontal direction of the figure according to the number of transmitting antennas 14. Show. In FIG. 24, the STS transmitted from the third transmitting antenna 14c for the number “3” of transmitting antennas 14 that transmit signals, that is, the STS for the main antenna is “STSb ′”. Here, “STSb ′” is indicated in the frequency domain as follows.

Except this, it is the same as the sixth embodiment, and thus the description is omitted.

  FIG. 25 shows the waveform of STSb '. STSb 'has a relationship in which the sign is inverted with respect to STSb. STSb ′ has an in-phase component and a quadrature component in the time domain, and the absolute value of the in-phase component of “STSa” with respect to two types of antennas to which signals should be transmitted, ie, “2” and “3”. The value is equal to the absolute value of the quadrature component of “STSb ′”, the sign is further inverted, the absolute value of the quadrature component of “STSa” is equal to the absolute value of the in-phase component of “STSb ′”, and the sign is further inverted. It is stipulated in.

  FIG. 26 shows a configuration of the correlation unit 70. The correlation unit 70 includes a first inversion unit 320a and a second inversion unit 320b, which are collectively referred to as an inversion unit 320 with respect to the correlation unit 70 in FIG. The inversion unit 320 inverts the signs of the addition results of the third addition unit 312c and the fourth addition unit 312d. That is, the correlation value between the STSb 'whose sign is inverted with respect to the STSb and the input signal is calculated. Since the other operations are the same as those in FIG. With these, the multiplication between the in-phase component value and the quadrature component value possessed by the plurality of delayed signals and the in-phase component value and the quadrature component value possessed by the plurality of stored reference signals is made common, Since a plurality of multiplication results generated by multiplication are added in different combinations, the amount of processing can be reduced.

  According to the embodiment of the present invention, even if the transmitting apparatus does not notify the receiving apparatus of the number of antennas that transmit signals, the receiving apparatus can recognize the number of antennas that the transmitting apparatus transmits signals. In addition, since the delay unit for delaying the input signal, the storage unit for storing the reference signal, and the multiplication unit in the correlation processing can be shared by the processing for the two STSs, the circuit scale can be reduced. It can also be realized by changing the pattern of the main antenna STS from that of the sixth embodiment.

(Example 8)
In the MIMO system as in the sixth and seventh embodiments, the eighth embodiment of the present invention changes the STS pattern according to the number of transmitting antennas that transmit data in the MIMO system, and the receiving device changes the STS. The present invention relates to a technique for recognizing the number of transmitting antennas that transmit data by detecting a pattern. In the sixth and seventh embodiments, the description has been made on the change of the number of transmitting antennas such as “2” and “3” for the number of transmitting antennas for transmitting data. However, in the eighth embodiment, the number of transmission antennas that transmit data is “1” to “3”, that is, the number of transmission antennas is one. Here, when the number of transmitting antennas is one, it is assumed that the wireless LAN conforms to the IEEE802.11a standard, and therefore, the STS corresponding thereto is a Legacy STS. The transmitting apparatus transmits Legacy STS, STSa, and STSb from the main antenna according to the number of transmitting antennas that transmit data. As described above, Legacy STS uses 12 subcarriers, and STSa and STSb use 6 subcarriers.

  On the other hand, the receiving apparatus has correlation units corresponding to Legacy STS, STSa, and STSb, respectively, performs correlation processing with the signals received by them, and outputs a correlation value. Further, the correlation values are compared, and the number of transmission antennas is specified according to the STS having the largest correlation value. The receiving apparatus according to the present embodiment does not hold a value corresponding to Legacy STS of 12 subcarriers as a correlation unit corresponding to Legacy STS, but is STSa or STSb among Legacy STSs of 12 subcarriers. Six used subcarriers are selected, and values corresponding to the selected subcarriers are held.

  FIG. 27 illustrates a configuration of the correlation unit 70 according to the eighth embodiment. The correlation unit 70 includes a legacy STS correlation unit 330, an STSa correlation unit 332, an STSb correlation unit 334, and a selection unit 336. In addition, although the correlation part corresponding to a subantenna may be provided, it abbreviate | omits here.

  The STSa correlation unit 332 stores in advance a plurality of signals obtained by converting STSa into the time domain, and calculates a correlation value between the stored signal and the received signal (hereinafter referred to as “two-antenna correlation value”). The STSb correlation unit 334 stores in advance a plurality of signals obtained by converting the STSb into the time domain, and calculates a correlation value between the stored signal and the received signal (hereinafter referred to as “correlation value for three antennas”). Here, the STSa correlation unit 332 and the STSb correlation unit 334 are described as different configurations, but may be configured as one correlation unit 70 as in the sixth embodiment.

  The Legacy STS correlator 330 stores in advance a signal obtained by converting only the subcarrier signals used in STSa and STSb into the time domain in the Legacy STS described above. Furthermore, Legacy STS correlation section 330 calculates a correlation value between the stored signal and the received signal (hereinafter referred to as “correlation value for one antenna”).

  The selection unit 336 compares the magnitudes of the two-antenna correlation value, the three-antenna correlation value, and the one-antenna correlation value, and selects the maximum correlation value. An estimation unit (not shown) determines the number of transmission antennas 14 that are transmitting data corresponding to the selected correlation value.

  According to the embodiment of the present invention, when there are a plurality of transmitting antennas transmitting signals, the correlation value is calculated by the signal corresponding to only the subcarrier to be used by the STS corresponding to the main antenna. Therefore, the influence from other subcarriers can be excluded, and the accuracy of the correlation value to be compared can be improved. In addition, since the accuracy of the correlation value to be compared can be improved, the estimation accuracy of the number of transmitting antennas transmitting signals can be improved. Further, the correlation unit as described above can also be used for timing detection and the like.

Example 9
The ninth embodiment of the present invention relates to a preamble signal to be applied to the MIMO system, similarly to the first embodiment of the present invention. In particular, the present invention relates to the arrangement of preamble signals that can improve the accuracy of gain control by AGC even in a frequency selective fading environment. If the MIMO system is affected by frequency selective fading, a plurality of portions where the attenuation of the received signal is large and small portions appear in the frequency band of the signal. For example, from a low frequency to a high frequency, a portion where the signal attenuation is large and a portion where the signal attenuation is small appear alternately at predetermined intervals. If this is made to correspond to the multicarrier in MIMO, the signal attenuation increases for a predetermined number of subcarriers from a subcarrier at a low frequency to a subcarrier at a high frequency, and then for a predetermined number of subcarriers. Thus, the signal attenuation is reduced at random.

  In the MIMO system, as described above, it is desirable that the cross-correlation between STSs transmitted from a plurality of antennas is small. Even if the cross-correlation is small, if the subcarriers in which the STSs transmitted from the respective antennas are substantially continuous are used, that is, among the subcarriers used by one STS, the subcarrier having the highest frequency and the smallest subcarrier are used. If the frequency difference from the subcarrier frequency is small, the signal strength may increase in all subcarriers corresponding to the received STS. On the contrary, the signal strength may be low. If the gain is set in AGC in such a situation, when data having a larger number of subcarriers than STS is received, the gain is not an appropriate value, and the quality of the received signal may be degraded. . This is because an increase in the number of subcarriers includes a case where the signal strength increases and a case where the signal strength decreases.

  The STS corresponding to each of the plurality of antennas according to the present embodiment uses a predetermined number of discretely selected subcarriers. For example, every 8th subcarrier in the subcarrier number is used. As a result, even if the number of subcarriers of the STS is smaller than the number of subcarriers of the data, since the STS uses the entire signal band, it is not affected locally by the frequency-selective fading but instead is locally affected. be able to. In consideration of cross-correlation, STSs respectively corresponding to a plurality of antennas use different subcarriers. Furthermore, if the frequency difference between the subcarrier of the maximum frequency and the frequency of the minimum subcarrier among subcarriers used by one STS is defined as a bandwidth, the bandwidth for a plurality of STSs can be increased. It is stipulated to be the same.

  If the subcarriers used in the plurality of STSs are arranged as described above, even if the number of subcarriers used in the STS is smaller than the number of subcarriers used in the data, under a frequency selective fading environment. An appropriate gain can be derived at. Note that the arrangement of the subcarriers as described above may overlap with the description of the first embodiment.

  The transmission device 10 and the reception device 12 according to the ninth embodiment are the same as the transmission device 10 of FIG. 4 and the reception device 12 of FIG.

  FIGS. 28A to 28D are diagrams illustrating an outline of known signals arranged on subcarriers according to the ninth embodiment. FIGS. 28A to 28D show the signal spectrum as in FIG. 1, with the horizontal axis corresponding to the subcarrier number and the vertical axis corresponding to the signal intensity. A solid line indicates a subcarrier signal at the time of transmission, and a dotted line indicates a transfer function of the transmission path. The transfer function of the transmission line is affected by frequency selective fading as shown in the figure, and there are a part where the signal strength is high and a part where the signal strength is low. Here, a portion where the signal strength in the transfer function is high corresponds to a portion where the signal attenuation in the transmission path is small, and a portion where the signal strength in the transfer function is low corresponds to a portion where the signal attenuation in the transmission path is large. Note that, unlike FIG. 1, here, the number of subcarriers is set to 20 to simplify the description. In addition, the transmission apparatus 10 uses two transmission antennas 14 including a first transmission antenna 14a and a second transmission antenna 14b, and an STS transmitted from each transmission antenna 14 uses four subcarriers. To do.

  FIG. 28A shows an arrangement of STS subcarriers to be transmitted from the first transmission antenna 14a to be compared with the subcarrier arrangement in this embodiment. Here, subcarriers with subcarrier numbers “1 to 4” are used. As shown in the figure, the signal strength of the STS received by the receiving apparatus 12 is relatively large because the signal attenuation in the transmission path is small compared to the STS transmitted from the transmitting apparatus 10.

  FIG. 28B shows the arrangement of STS subcarriers transmitted from the second transmitting antenna 14b in the same case as FIG. Here, subcarriers with subcarrier numbers “17 to 20” are used. Here, as in FIG. 28A, the receiving apparatus 12 receives an STS having a relatively large signal strength. As a result, if the STS is arranged as shown in FIGS. 28A and 28B, the receiving apparatus 12 sets the gain of the AGC 66 based on the STS having a relatively large signal strength. Get smaller.

  However, as shown in the figure, in the frequency region corresponding to the subcarrier number “4 to 17”, the signal attenuation in the transmission path is large. As a result, the signal strength of data using such frequency domain subcarriers is smaller than in the case of STS. That is, the gain value set based on the STS is smaller than the gain value suitable for the transfer function, and an error may occur in the received signal.

  FIG. 28C shows an arrangement of STS subcarriers transmitted from the first transmitting antenna 14a in the present embodiment. As shown in the figure, the STS uses a predetermined number of subcarriers discretely selected from a plurality of subcarriers. That is, 4 subcarriers selected every 5 out of 20 subcarriers are used. The corresponding subcarrier numbers are “5”, “10”, “15”, and “20”. The bandwidth is a band corresponding to 15 subcarriers.

  FIG. 28D shows the arrangement of STS subcarriers transmitted from the second transmitting antenna 14b in the same case as FIG. FIG. 28 (d) uses four subcarriers selected every five out of the 20 subcarriers as in FIG. 28 (c). However, the corresponding subcarrier numbers are “3”, “8”, “13”, and “18”. That is, the STS transmitted from the first transmitting antenna 14a and the STS transmitted from the second transmitting antenna 14b use different subcarriers. This is to reduce the cross-correlation between these STSs. On the other hand, the bandwidth is equal to the bandwidth in the STS transmitted from the first transmitting antenna 14a.

  In FIG. 28 (c), the signal strength for the subcarriers with subcarrier numbers “5” and “20” increases, and the signal strength for the subcarriers with subcarrier numbers “10” and “15” decreases. In FIG. 28D, the signal strength for the subcarriers with subcarrier numbers “3” and “18” increases, and the signal strength for the subcarriers with subcarrier numbers “8” and “13” decreases. Such an arrangement of subcarriers includes a subcarrier having a high signal strength and a subcarrier having a low signal strength, which qualitatively reflects a transfer function in a frequency selective fading environment. Therefore, according to the subcarrier arrangement as shown in FIGS. 28C and 28D, the gain value is close to the gain value suitable for the transfer function. As a result, errors that occur in the received signal can be reduced.

  Based on specific parameters of the MIMO system, for example, the STS is arranged on the following subcarriers. The STS transmitted from the first transmitting antenna 14a uses subcarriers with subcarrier numbers “−24”, “−16”, “−8”, “4”, “12”, and “20”. 2 The STS transmitted from the transmitting antenna 14b uses subcarriers with subcarrier numbers “−20”, “−12”, “−4”, “8”, “16”, and “24”. Apart from this, the arrangement as shown in Formula 10 of Example 1 may be used. Such an STS is stored in the preamble adding unit 32 as described above.

  According to the embodiment of the present invention, it is possible to provide a preamble signal that improves gain estimation accuracy even in a frequency selective fading environment. Further, the cross-correlation between preamble signals in a plurality of antennas can be reduced. In addition, since the number of subcarriers used for the preamble is small, the signal period in the time domain can be shortened. For this reason, gain estimation can be performed at high speed. Further, since the gain estimation can be improved, the quality of the received signal can be improved.

(Example 10)
Example 10 relates to a transmission apparatus in a MIMO system. In the embodiments so far, the transmission apparatus transmits an independent signal from each of the plurality of transmission antennas. In addition, a plurality of STSs are used so as to correspond to each of the signals. For example, four types of signals are transmitted by transmitting signals from each of four antennas. In addition, four types of STSs are used so as to correspond to each of the four types of signals. Hereinafter, each of the four types of signals is referred to as a series of signals, and so far, it corresponds to the four types of series of signals. As a result, in the embodiments so far, the number of series signals and the number of transmitting antennas are the same.

  In the tenth embodiment, the number of series signals and the number of transmitting antennas are different. Here, the case where the number of series signals is smaller than the number of transmitting antennas is targeted. For example, the number of series signals is “2”, and the number of transmitting antennas is “4”. The transmission apparatus according to the present embodiment distributes a plurality of series of signals to each of a plurality of transmission antennas by multiplying a plurality of series of signals by a steering matrix. Further, the transmission device transmits a dispersed signal from each of the plurality of transmission antennas.

  FIG. 29 illustrates the configuration of the transmission apparatus 10 according to the tenth embodiment. The transmission apparatus 10 includes an error correction unit 28, an interleaving unit 30, a first modulation unit 110a generically called a modulation unit 110, a second modulation unit 110b, a first preamble addition unit 112a generically called a preamble addition unit 112, a second Preamble adding section 112b, spatial dispersion section 114, first radio section 24a, second radio section 24b, third radio section 24c, fourth radio section 24d, and transmission antenna 14 collectively referred to as radio section 24. 1 transmission antenna 14a, 2nd transmission antenna 14b, 3rd transmission antenna 14c, and 4th transmission antenna 14d are included.

  The error correction unit 28 and the interleaving unit 30 respectively perform convolutional coding and interleaving similarly to the error correction unit 28 and the interleaving unit 30 of FIG. However, the error correction unit 28 and the interleaving unit 30 in FIG. 4 perform processing on the data separated by the data separation unit 20, whereas here, the error correction unit 28 and the interleaving unit 30 perform processing on the signal before separation. ing. FIG. 4 may be configured as shown in FIG. The interleave unit 30 outputs the data after separating it into a plurality of sequences. Here, it is separated into two series. The two series of data can be said to be independent of each other.

  Modulation section 110 performs modulation on each of the two series of data. The preamble adding unit 112 adds a preamble to the modulated data. Therefore, preamble adding section 112 stores a plurality of STSs corresponding to each of a plurality of series of data and to be transmitted in a predetermined period. Here, the STS stored in the preamble adding unit 112 is the same as in the previous embodiments. That is, the STS corresponding to one of the plurality of series of data uses a carrier that is at least partially different from the STS corresponding to the other series of data of the plurality of series of data. Here, a combination of data, STS, and the like is referred to as a “signal” as one unit. Note that either data or STS is called a signal and is used without distinction. Finally, two series of signals are output in parallel from the two preamble addition units 112. Note that the burst format of the signal output from the preamble adding unit 112 may be defined as shown in FIGS.

  Spatial dispersion section 114 receives two series of signals and multiplies the signals by a steering matrix to generate signals of the number of transmitting antennas 14. That is, the transmission antenna 14 generates a signal having a number larger than the number of signals of the plurality of sequences and the number of signals of the transmission antenna 14 by multiplying the signals of the plurality of sequences by the steering matrix. To do. Spatial dispersion section 114 expands the order of the input series of signals to the number of transmitting antennas 14 before performing multiplication. The input series of signals is “2”, and is represented here by “Nin”. Therefore, the input series of signals is indicated by a vector of “Nin × 1”. The number of transmitting antennas 14 is “4”, and is represented here by “Nout”. Spatial dispersion section 114 extends the order of the input series of signals 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.

ステアリング行列は、「Ｎｏｕｔ×Ｎｏｕｔ」の行列である。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、以下のように示され、ＣＤＤ（Ｃｙｃｌｉｃ Ｄｅｌａｙ Ｄｉｖｅｒｓｉｔｙ）のために使用される。

ここで、δは、シフト量を示す。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。 The steering matrix S is shown as follows.

The steering matrix is a “Nout × Nout” matrix. Here, l indicates a subcarrier number, and multiplication by the steering matrix is executed in units of subcarriers. Further, C is shown as follows and is used for CDD (Cyclic Delay Diversity).

Here, δ represents the shift amount. W is an orthogonal matrix, and is a “Nout × Nout” matrix. An example of an orthogonal matrix is a Walsh matrix.

  The same number of radio units 24 as the transmission antennas 14 are provided. The radio unit 24 includes an IFFT unit 34, a GI unit 36, and an orthogonal modulation unit 38 in addition to the radio unit 24 in FIG. Note that the space dispersion unit 114 may be provided after the IFFT unit 34 (not shown). Finally, the radio unit 24 transmits a signal spread to the number of transmitting antennas 14.

  The plurality of STSs stored in the preamble adding unit 112 may be defined in the same manner as in FIGS. 9A to 9B of the first embodiment. That is, each of the plurality of STSs uses a different carrier. Each of the plurality of STSs uses a predetermined number of carriers discretely selected from the plurality of carriers. Further, the plurality of STSs are defined so that the number of carriers to be used for each STS is equal. Further, a plurality of carriers used for a plurality of STSs are defined in advance in a part of the plurality of carriers to be transmitted, and the plurality of STSs are selected from the plurality of carriers defined in advance. Use at least one carrier. Since these details are the same as those in the first embodiment, description thereof is omitted.

  The STS stored in the preamble adding unit 112 may be defined in the same manner as in the second embodiment. That is, among the plurality of STSs, the autocorrelation characteristic of the STS corresponding to one of the plurality of series of signals is more than the autocorrelation characteristic of the STS corresponding to the other series of signals among the plurality of series of signals. It is stipulated to be higher. In addition, the number of carriers to be used for an STS corresponding to one of a plurality of sequences of signals among the plurality of STSs is used for an STS corresponding to another sequence of the plurality of sequences of signals. It is stipulated to be more than the number of carriers that should be. Since these details are the same as those in the second embodiment, description thereof is omitted.

  Further, the STS stored in the preamble adding unit 112 may be defined in the same manner as in FIGS. 12A to 12B of the third embodiment. That is, in a plurality of STSs, the value of the in-phase component of the STS waveform corresponding to one of the plurality of series signals is orthogonal to the STS waveform corresponding to the other series of signals in the plurality of series signals. The value of the quadrature component of the STS waveform corresponding to one of a plurality of series of signals that is equal to the value of the component is the same phase of the STS waveform corresponding to the other series of signals of the plurality of series of signals. It is specified to be equal to the value of the component. Since this detail is the same as that of Example 3, description is abbreviate | omitted.

  Further, the STS stored in the preamble adding unit 112 may be defined in the same manner as in FIGS. 28C to 28D of the ninth embodiment. That is, in each of the plurality of STSs, the difference in frequency between the highest frequency carrier and the lowest frequency carrier among the predetermined number of discretely selected carriers is defined to be equal to each other. Each of the plurality of STSs uses different carriers. Since these details are the same as those of the ninth embodiment, description thereof is omitted.

  According to the embodiment of the present invention, since a plurality of STSs use different subcarriers among a plurality of predetermined subcarriers, the cross-correlation between the plurality of STSs can be reduced. Moreover, since the cross correlation between several STS is small, the detection accuracy of several STS by a receiver can be improved. In addition, since the cross-correlation between the plurality of STSs is small, the accuracy of AGC setting by the receiving apparatus can be improved. In addition, when a plurality of series of signals are transmitted from a plurality of transmission antennas, the number of the plurality of transmission antennas is increased from the number of the plurality of series of signals to be transmitted from one transmission antenna. Signal strength can be reduced. Further, since the strength of the signal transmitted from one transmitting antenna is reduced, distortion caused by the power amplifier can be reduced with respect to the transmitted signal. Also, open loop transmission diversity can be performed.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  In Embodiments 1 to 10 of the present invention, the STS defined in the IEEE 802.11a standard is targeted as a reference signal. However, the present invention is not limited to this, and other signals may be used. That is, any known signal may be used as long as it is arranged and transmitted on a plurality of subcarriers.

  In the ninth embodiment of the present invention, the plurality of STSs stored in the transmission apparatus 10 use different subcarriers. However, the present invention is not limited to this. For example, subcarriers that are partially overlapped or subcarriers that are all overlapped may be used. In that case, since the cross-correlation between the plurality of STSs may increase, it is desirable to use an STS pattern that reduces the cross-correlation. According to this modification, the effect of Example 2 can be obtained. That is, it is sufficient that the bandwidth is wide to some extent.

  In the ninth embodiment of the present invention, the plurality of STSs stored in the transmission apparatus 10 are defined so that the bandwidths are equal. However, the present invention is not limited to this. For example, the bandwidth may be defined to have different values. According to this modification, the present invention can be applied even when the number of transmitting antennas 14 is increased. That is, it is sufficient that the bandwidth is wide to some extent.

  In the seventh embodiment of the present invention, the transmitting apparatus 10 changes the STS pattern according to the number of transmitting antennas 14 to be used, and the receiving apparatus 12 is used by detecting the changed STS pattern. The number of transmitting antennas 14 is recognized. Furthermore, a predetermined relationship is given to the STS pattern transmitted from the main antenna according to the number of transmitting antennas 14 that transmit data. In particular, the predetermined relationship is defined as a relationship in which the absolute value of each component is exchanged and the sign is inverted. However, the present invention is not limited to this. For example, a predetermined relationship may be defined for each of the plurality of transmitting antennas 14. That is, in the plurality of STSs stored in the preamble adding unit 32, the absolute value of the in-phase component of the STS waveform corresponding to one of the plurality of transmission antennas 14 is the other transmission value of the plurality of transmission antennas 14. It is defined to be equal to the absolute value of the orthogonal component of the waveform of the STS corresponding to the trusted antenna 14 and further to reverse the sign.

  In addition, the absolute value of the orthogonal component of the STS waveform corresponding to one of the plurality of transmission antennas 14 is equal to the in-phase component of the STS waveform corresponding to the other transmission antenna 14 of the plurality of transmission antennas 14. It is specified that it is equal to the absolute value of and the sign is inverted. According to the third embodiment, the STS waveform corresponding to one of the plurality of transmission antennas 14 corresponds to the STS waveform corresponding to the second transmission antenna 14b. The STS waveform corresponding to the other transmitting antenna 14 corresponds to the STS waveform corresponding to the third transmitting antenna 14c.

  Further, the above modification may be applied to the tenth embodiment. That is, in the STS stored in the preamble adding unit 112, the absolute value of the in-phase component of the STS waveform corresponding to one of the plurality of series of signals corresponds to the signal of the other series of the plurality of series of signals. It is specified to be equal to the absolute value of the orthogonal component of the waveform of the STS and the sign is inverted. Further, the absolute value of the orthogonal component of the STS waveform corresponding to one of the plurality of series signals is the absolute value of the in-phase component of the STS waveform corresponding to the other series of signals of the plurality of series signals. And the sign is further inverted. According to this modification, the correlation between STSs corresponding to each of the plurality of transmitting antennas 14 can be reduced.

The features of the invention described in Examples 3 to 7 may be defined by the following items.
(Item 3-1)
For a sequence in which a plurality of reference signals are arranged on the time axis, a plurality of sequences are defined in advance by changing the values of the plurality of reference signals in the sequence, and the plurality of sequences are combined. An input unit for sequentially inputting the received signal;
A plurality of delay units for successively delaying the input signal;
A plurality of storage units each storing a plurality of reference signals corresponding to one of the plurality of series;
A correlation processing unit that performs correlation processing based on the values of the plurality of delayed signals and the stored values of the plurality of reference signals, and outputs a plurality of correlation values between the input signal and the plurality of sequences, respectively. And
The plurality of sequences included in the signal input to the input unit have a predetermined relationship,
The correlation processing unit performs the correlation processing by a combination of multiplication and addition corresponding to the predetermined relationship.

(Item 3-2)
The signal input to the input unit and the plurality of reference signals have an in-phase component and a quadrature component, and the predetermined relationship included in the plurality of sequences is a reference signal included in one of the plurality of sequences. Is equal to the value of the quadrature component of the reference signal included in the other, and the value of the quadrature component of the reference signal included in one is the value of the in-phase component of the reference signal included in the other. Is an equal relationship,
The correlation processing unit multiplies the in-phase component value and the quadrature component value included in the plurality of delayed signals, and the in-phase component value and the quadrature component value included in the plurality of stored reference signals. And a plurality of multiplication results generated by the multiplication are added in different combinations. The correlator according to item (3-1),

(Item 3-3)
The correlation processing unit sets an integration result of the value of the in-phase component included in the signal and the value of the in-phase component included in the reference signal as a first value, and the value of the quadrature component included in the signal and the reference signal are The result of integration with the value of the quadrature component possessed is the second value, the result of summation of the value of the in-phase component possessed by the signal and the value of the quadrature component possessed by the reference signal is the third value, and the signal is present. When the integration result of the value of the quadrature component and the value of the in-phase component included in the reference signal is the fourth value, as the correlation process, the first value and the second value are obtained for one of the two sequences. , The difference between the fourth value and the third value, and the difference between the third value and the fourth value and the difference between the second value and the first value for the other of the two sequences. The correlator according to item (3-2), wherein:

(Item 6-1)
The signal to be input to the input unit is transmitted while changing the number of antennas from a plurality of antennas on the transmission side, and one of the plurality of antennas is a main antenna and the rest is a sub antenna. In this case, the sequence to be transmitted from the main antenna according to the number of antennas to which the signal is transmitted is the value of the in-phase component of the reference signal included in the sequence corresponding to the predetermined number of antennas to which the signal is transmitted. Is equal to the value of the quadrature component of the reference signal included in the sequence corresponding to the number of different antennas, and the value of the quadrature component of the reference signal included in the sequence corresponding to the predetermined number of antennas is The relation that should be equal to the value of the in-phase component of the reference signal included in the series corresponding to the number of
The storage unit stores a plurality of reference signals included in a sequence corresponding to the number of predetermined antennas to which a signal is transmitted among sequences to be transmitted from the main antenna,
The correlator according to item (3-2) or (3-3), further comprising a determination unit that determines the number of antennas to which a signal is transmitted based on the plurality of correlation values.

(Item 7-1)
The signal input to the input unit and the plurality of reference signals have an in-phase component and a quadrature component, and the predetermined relationship included in the plurality of sequences is a reference signal included in one of the plurality of sequences. Is equal to the absolute value of the quadrature component of the reference signal included in the other, the sign is inverted, and the absolute value of the quadrature component of the reference signal included in one is included in the other. Is equal to the absolute value of the in-phase component of the reference signal, and the sign should be inverted.
The correlation processing unit multiplies the in-phase component value and the quadrature component value included in the plurality of delayed signals, and the in-phase component value and the quadrature component value included in the plurality of stored reference signals. And a plurality of multiplication results generated by the multiplication are added in different combinations. The correlator according to item (3-1),

(Item 7-2)
The correlation processing unit sets an integration result of the value of the in-phase component included in the signal and the value of the in-phase component included in the reference signal as a first value, and the value of the quadrature component included in the signal and the reference signal are The result of integration with the value of the quadrature component possessed is the second value, the result of summation of the value of the in-phase component possessed by the signal and the value of the quadrature component possessed by the reference signal is the third value, and the signal is present. When the integration result of the value of the quadrature component and the value of the in-phase component included in the reference signal is the fourth value, as the correlation process, the first value and the second value are obtained for one of the two sequences. And the difference between the fourth value and the third value, and for the other of the two sequences, a value obtained by inverting the sign from the sum of the third value and the fourth value, the second value, and the first value The correlator according to item (7-1), wherein a value obtained by inverting a sign from a value difference is calculated.

(Item 7-3)
The signal to be input to the input unit is transmitted while changing the number of antennas from a plurality of antennas on the transmission side, and one of the plurality of antennas is a main antenna and the rest is a sub antenna. In this case, the sequence to be transmitted from the main antenna according to the number of antennas to which signals are transmitted is the absolute value of the in-phase component of the reference signal included in the sequence corresponding to the predetermined number of antennas to which signals are transmitted. The value is equal to the absolute value of the orthogonal component of the reference signal included in the sequence corresponding to the number of other antennas, the sign is inverted, and the reference signal included in the sequence corresponding to the predetermined number of antennas The absolute value of the quadrature component is equal to the absolute value of the in-phase component of the reference signal included in the sequence corresponding to the number of other antennas, and the sign should be inverted.
The storage unit stores a plurality of reference signals included in a sequence corresponding to the number of predetermined antennas to which a signal is transmitted among sequences to be transmitted from the main antenna,
The correlator according to item (7-1) or item (7-2), further comprising a determination unit that determines the number of antennas to which a signal is transmitted based on the plurality of correlation values.

(Item 4-1)
The plurality of sequences included in the signal input from the input unit are defined such that each value fluctuates in a predetermined cycle, and the predetermined relationship that the plurality of sequences has is the relationship between the plurality of sequences. When one of them is used as a reference, the reference series has a relationship that should be an integral multiple of the period of a series other than the reference series.
The plurality of storage units respectively store a plurality of reference signals corresponding to the standard series.
The correlation processing unit selects a part of the plurality of stored reference signals for a sequence other than the standard sequence according to a difference from a cycle of the standard sequence, and selects the selected reference signal. The correlator according to item (3-1), wherein multiplication is performed between the reference signal and the plurality of delayed input signals.

(Item 5-1)
The signal input to the input unit and the plurality of reference signals have an in-phase component and a quadrature component, and the predetermined relationship of the plurality of sequences is that only one of the in-phase component or the quadrature component of the reference signal is present. A relationship having a predetermined value,
The storage unit stores information for inverting the sign of the delayed signal in a form corresponding to the plurality of reference signals,
The correlator according to item (3-1), wherein the correlation processing unit adds the signal inverted based on the information and the delayed signal as the correlation processing.

(Item 3-4)
For a sequence in which a plurality of reference signals are arranged on the time axis, a plurality of sequences are defined in advance by changing the plurality of reference signals in the sequence, and a signal obtained by synthesizing the plurality of sequences An input unit for sequentially inputting
A plurality of delay units for successively delaying the input signal;
A plurality of storage units each storing a plurality of reference signals corresponding to one of the plurality of series;
A correlation processing unit that performs correlation processing based on the values of the plurality of delayed signals and the stored values of the plurality of reference signals, and outputs a plurality of correlation values between the input signal and the plurality of sequences, respectively. When,
A controller that detects the timing of the input signal based on the plurality of correlation values;
The plurality of sequences included in the signal input to the input unit have a predetermined relationship,
The correlation processing unit executes the correlation processing by a combination of multiplication and addition according to the predetermined relationship.

(Item 3-5)
The signal input to the input unit and the plurality of reference signals have an in-phase component and a quadrature component, and the predetermined relationship included in the plurality of sequences is a reference signal included in one of the plurality of sequences. Is equal to the value of the quadrature component of the reference signal included in the other, and the value of the quadrature component of the reference signal included in one is the value of the in-phase component of the reference signal included in the other. Is an equal relationship,
The correlation processing unit multiplies the in-phase component value and the quadrature component value included in the plurality of delayed signals, and the in-phase component value and the quadrature component value included in the plurality of stored reference signals. And a plurality of multiplication results generated by the multiplication are added in different combinations. The receiving apparatus according to item (3-4),

(Item 3-6)
The correlation processing unit sets an integration result of the value of the in-phase component included in the signal and the value of the in-phase component included in the reference signal as a first value, and the value of the quadrature component included in the signal and the reference signal are The result of integration with the value of the quadrature component possessed is the second value, the result of summation of the value of the in-phase component possessed by the signal and the value of the quadrature component possessed by the reference signal is the third value, and the signal is present. When the integration result of the value of the quadrature component and the value of the in-phase component included in the reference signal is the fourth value, as the correlation process, the first value and the second value are obtained for one of the two sequences. , The difference between the fourth value and the third value, and the difference between the third value and the fourth value and the difference between the second value and the first value for the other of the two sequences. The receiving device according to item (3-5), wherein:

(Item 6-2)
The signal to be input to the input unit is transmitted while changing the number of antennas from a plurality of antennas on the transmission side, and one of the plurality of antennas is a main antenna and the rest is a sub antenna. In this case, the sequence to be transmitted from the main antenna according to the number of antennas to which the signal is transmitted is the value of the in-phase component of the reference signal included in the sequence corresponding to the predetermined number of antennas to which the signal is transmitted. Is equal to the value of the quadrature component of the reference signal included in the sequence corresponding to the number of different antennas, and the value of the quadrature component of the reference signal included in the sequence corresponding to the predetermined number of antennas is The relation that should be equal to the value of the in-phase component of the reference signal included in the series corresponding to the number of
The storage unit stores a plurality of reference signals included in a sequence corresponding to the number of predetermined antennas to which a signal is transmitted among sequences to be transmitted from the main antenna,
The receiving device according to item (3-5) or item (3-6), further comprising a determining unit that determines the number of antennas to which a signal is transmitted based on the plurality of correlation values.

(Item 7-4)
The signal input to the input unit and the plurality of reference signals have an in-phase component and a quadrature component, and the predetermined relationship included in the plurality of sequences is a reference signal included in one of the plurality of sequences. Is equal to the absolute value of the quadrature component of the reference signal included in the other, the sign is inverted, and the absolute value of the quadrature component of the reference signal included in one is included in the other. Is equal to the absolute value of the in-phase component of the reference signal, and the sign should be inverted.
The correlation processing unit multiplies the in-phase component value and the quadrature component value included in the plurality of delayed signals, and the in-phase component value and the quadrature component value included in the plurality of stored reference signals. And a plurality of multiplication results generated by the multiplication are added in different combinations. The receiving apparatus according to item (3-4),

(Item 7-5)
The correlation processing unit sets an integration result of the value of the in-phase component included in the signal and the value of the in-phase component included in the reference signal as a first value, and the value of the quadrature component included in the signal and the reference signal are The result of integration with the value of the quadrature component possessed is the second value, the result of summation of the value of the in-phase component possessed by the signal and the value of the quadrature component possessed by the reference signal is the third value, and the signal is present. When the integration result of the value of the quadrature component and the value of the in-phase component included in the reference signal is the fourth value, as the correlation process, the first value and the second value are obtained for one of the two sequences. And the difference between the fourth value and the third value, and for the other of the two sequences, a value obtained by inverting the sign from the sum of the third value and the fourth value, the second value, and the first value The receiving apparatus according to item (7-4), wherein a value obtained by inverting a sign from a value difference is calculated.

(Item 7-6)
The signal to be input to the input unit is transmitted while changing the number of antennas from a plurality of antennas on the transmission side, and one of the plurality of antennas is a main antenna and the rest is a sub antenna. In this case, the sequence to be transmitted from the main antenna according to the number of antennas to which signals are transmitted is the absolute value of the in-phase component of the reference signal included in the sequence corresponding to the predetermined number of antennas to which signals are transmitted. The value is equal to the absolute value of the orthogonal component of the reference signal included in the sequence corresponding to the number of other antennas, and the sign is inverted, and the orthogonality of the reference signal included in the sequence corresponding to the predetermined number of antennas The value of the component is equal to the value of the in-phase component of the reference signal included in the sequence corresponding to the number of other antennas, and the sign should be inverted.
The storage unit stores a plurality of reference signals included in a sequence corresponding to the number of predetermined antennas to which a signal is transmitted among sequences to be transmitted from the main antenna,
The receiving device according to item (7-4) or item (7-5), further comprising a determining unit that determines the number of antennas to which a signal is transmitted based on the plurality of correlation values.

It is a figure which shows the spectrum of the multicarrier signal which concerns on Example 1. FIG. 1 is a diagram illustrating a concept of a communication system according to a first embodiment. It is a figure which shows the structure of the burst format which concerns on Example 1. FIG. It is a figure which shows the structure of the transmitter of FIG. It is a figure which shows the structure of the receiver of FIG. It is a figure which shows the structure of the 1st radio | wireless part of FIG. It is a figure which shows the structure of the 1st process part of FIG. FIGS. 8A to 8C are diagrams illustrating a configuration of a burst format according to the first embodiment. FIGS. 9A and 9B are diagrams illustrating waveforms of known signals transmitted from the transmission apparatus of FIG. FIGS. 10A to 10C are diagrams illustrating waveforms of known signals transmitted from the transmission apparatus of FIG. It is a flowchart which shows the procedure of the reception operation | movement by the receiver of FIG. 12A to 12B are diagrams illustrating waveforms of known signals transmitted from the transmission apparatus according to the third embodiment. FIG. 10 is a diagram illustrating a configuration of a correlation unit according to a third embodiment. FIGS. 14A to 14B are diagrams illustrating waveforms of known signals transmitted from the transmission apparatus according to the third embodiment. FIG. 10 is a diagram illustrating a configuration of a correlation unit according to a fourth embodiment. FIG. 10 is a diagram illustrating a waveform of a known signal transmitted from a transmission apparatus according to a fifth embodiment. FIG. 10 is a diagram illustrating a configuration of a correlation unit according to a fifth embodiment. It is a figure which shows the relationship between the number of the transmitting antennas which transmit the data which concern on Example 6, and the pattern of STS transmitted from a transmitting antenna. It is a figure which shows the waveform of STSa of FIG. It is a figure which shows the waveform of STSb of FIG. It is a figure which shows the waveform of STS1 of FIG. It is a figure which shows the waveform of STS2 of FIG. 16 is a flowchart illustrating a procedure of a receiving operation by a receiving device according to a sixth embodiment. It is a figure which shows the relationship between the number of the transmitting antennas which transmit the data which concern on Example 7, and the pattern of STS transmitted from a transmitting antenna. It is a figure which shows the waveform of STSb 'of FIG. FIG. 10 is a diagram illustrating a configuration of a correlation unit according to a seventh embodiment. FIG. 10 is a diagram illustrating a configuration of a correlation unit according to an eighth embodiment. FIGS. 28A to 28D are diagrams illustrating an outline of known signals arranged on subcarriers according to the ninth embodiment. FIG. 10 is a diagram illustrating a configuration of a transmission device according to Embodiment 10.

Explanation of symbols

  10 transmitting apparatus, 12 receiving apparatus, 14 transmitting antenna, 16 receiving antenna, 20 data separating section, 22 modulating section, 24 radio section, 26 controlling section, 28 error correcting section, 30 interleave section, 32 preamble adding section, 34 IFFT unit, 36 GI unit, 38 quadrature modulation unit, 40 frequency conversion unit, 42 amplification unit, 50 radio unit, 52 processing unit, 54 demodulation unit, 56 data combination unit, 58 control unit, 60 LNA unit, 62 frequency conversion unit 64 quadrature detection unit, 66 AGC, 68 AD conversion unit, 70 correlation unit, 80 synthesis unit, 82 reception response vector calculation unit, 84 reference signal storage unit, 86 multiplication unit, 88 addition unit, 100 communication system, 200 wireless reception Signal, 202 baseband received signal, 204 Generated signal, 206 received weight signal, 208 reference signal, 210 first correlated in-phase value, 212 first correlated quadrature value, 214 second correlated in-phase value, 216 second correlated quadrature value, 300 I delay unit, 302 Q delay unit, 304 I storage unit, 306 Q storage unit, 308 multiplication unit, 310 addition unit, 312 addition unit, 314 multiplication unit, 316 addition unit, 318 inversion unit, 320 inversion unit, 330 Legacy STS correlation unit, 332 STSa correlation unit 334 STSb correlation unit, 336 selection unit.

Claims (7)

Multiple antennas,
A transmitter for transmitting an OFDM signal using a plurality of subcarriers via the plurality of antennas;
A storage unit corresponding to each of the plurality of antennas and storing a plurality of known signals to be transmitted from the transmission unit in a predetermined period;
Among the plurality of known signals stored in the storage unit, a known signal corresponding to one of the plurality of antennas is different from a known signal corresponding to another antenna of the plurality of antennas. A transmission apparatus using a subcarrier.   A plurality of subcarriers used for a plurality of known signals stored in the storage unit are defined in advance in a part of the plurality of subcarriers to be transmitted from the transmission unit, and stored in the storage unit The transmission apparatus according to claim 1, wherein the plurality of known signals use at least one subcarrier selected from the plurality of subcarriers defined in advance. An output unit for outputting a plurality of sequences of OFDM signals;
A plurality of known signals corresponding to each of the plurality of OFDM signals, and a storage unit that stores a plurality of known signals included in a predetermined period of each of the plurality of OFDM signals. Prepared,
Of the plurality of known signals stored in the storage unit, a known signal corresponding to one of the plurality of series of OFDM signals corresponds to another series of OFDM signals among the plurality of series of OFDM signals. A transmission apparatus using different subcarriers for a known signal.   A plurality of subcarriers used for a plurality of known signals stored in the storage unit are defined in advance in a part of the plurality of subcarriers to be output from the output unit, and stored in the storage unit The transmitting apparatus according to claim 3, wherein the plurality of known signals use at least one subcarrier selected from the plurality of predetermined subcarriers.   Each of the plurality of known signals stored in the storage unit uses a predetermined number of subcarriers discretely selected from a plurality of subcarriers. The transmitting device according to 1. A transmission method for transmitting an OFDM signal using a plurality of subcarriers from a plurality of antennas and transmitting a plurality of known signals corresponding to each of the plurality of antennas in a predetermined period,
A transmission method characterized in that a known signal corresponding to one of a plurality of antennas uses different subcarriers from a known signal corresponding to another antenna of the plurality of antennas. A transmission method for outputting a plurality of sequences of OFDM signals each using a plurality of subcarriers, and outputting a plurality of known signals corresponding to each of the plurality of sequences of OFDM signals in a predetermined period,
A transmission method characterized in that a known signal corresponding to one of a plurality of sequences uses different subcarriers with respect to a known signal corresponding to another sequence of the plurality of sequences.

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