JP2006211726A - Transmitting method and apparatus thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch configuration of preamble of a MIMO system. <P>SOLUTION: A storage unit 116 stores a preamble signal defined in a conventional system and a preamble signal defined in the MIMO system. A monitoring unit 112 monitors the existence of a communication apparatus corresponding not to the MIMO system but to the conventional system. A transmission channel characteristics acquiring unit 114 derives the characteristics of a radio transmission channel with a receiving apparatus. A selecting unit 110 selects a packet format on the basis of a monitoring result obtained by the monitoring unit 112. The selecting unit 110 further selects the arrangement of an LTS, on the basis of the characteristics of the radio transmission channel derived by the unit 114. <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 a packet format signal and receiving the packet format signal.

  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 is set for each antenna. 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. In general, the preamble signal is defined by a fixed pattern. However, if the preamble signal pattern changes in consideration of the characteristics of the wireless transmission path and the packet utilization efficiency, a flexible wireless communication system can be realized with respect to the characteristics of the wireless transmission path.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a transmission method and apparatus for changing the format of a preamble signal.

  In order to solve the above-described problem, a transmitting apparatus according to an aspect of the present invention includes a second radio communication different from the first radio communication system at a subsequent stage of the first known signal in the first radio communication system. A packet format in which a second known signal in the system is arranged is defined, using either the packet format or another packet format defined such that a portion of the packet format is extracted; A generation unit that generates a packet signal and a transmission unit that transmits the packet signal generated by the generation unit.

  According to this aspect, since either the predetermined packet format or another packet format defined so that a part of the packet format is extracted is switched, compatibility with the first wireless communication system or packet utilization efficiency is achieved. Can be improved.

  The part extracted from the packet format defined in the generation unit may include at least a part to be used for transmission path estimation in the second known signal. In this case, even if another packet format specified so that a part of the packet format is extracted is used, the wireless device corresponding to the second wireless communication system can receive the packet signal.

  The first known signal included in the packet format defined in the generation unit is defined so as to be related to each other among the plurality of antennas, and the second known signal is defined by the plurality of antennas. It may be defined while being associated with each. In this case, even if the first known signal is transmitted from a plurality of antennas, the first known signal can be received by the wireless device corresponding to the first wireless communication system.

  The first known signal included in the packet format defined in the generation unit is defined so as to be related to each of a plurality of sequences, and the second known signal is a plurality of sequences. It may be defined while being associated with each of the above. In this case, even if the first known signal is transmitted as a plurality of sequences, the first known signal can be received by the wireless device corresponding to the first wireless communication system.

  Another aspect of the present invention is a transmission method. In this method, a packet format in which a second known signal in a second wireless communication system different from the first wireless communication system is arranged after the first known signal in the first wireless communication system has a packet format. The packet signal is generated using any one of the packet formats defined and the other packet formats defined so that a part of the packet format is extracted.

  Another aspect of the present invention is also a transmission method. In this method, a packet format in which a second known signal in a second wireless communication system different from the first wireless communication system is arranged after the first known signal in the first wireless communication system has a packet format. A packet signal is generated using one of the defined packet formats and another packet format defined so that a part of the packet format is extracted, and the generated packet signal is transmitted. And a step of.

  The part extracted from the packet format defined in the generating step may include at least a part to be used for transmission path estimation in the second known signal. The first wireless communication system and the second wireless communication system corresponding to the packet format defined in the generating step may use a multicarrier signal. The first known signal included in the packet format defined in the generating step is defined to be related to each of the plurality of antennas, and the second known signal is a plurality of the plurality of antennas. It may be defined while being associated with each of the antennas.

  The first known signal included in the packet format defined in the generating step is defined to be related to each of the plurality of sequences, and the second known signal is a plurality of It may be defined while being associated with each of the series. A step of monitoring the presence of a communication apparatus compatible with the first wireless communication system without corresponding to the second wireless communication system, and the step of generating includes a packet format different from the packet format based on the monitoring result The packet signal may be generated while selecting either of the above.

  Yet another embodiment of the present invention is a receiving device. This apparatus has a packet format in which a second known signal in a second wireless communication system different from the first wireless communication system is arranged after the first known signal in the first wireless communication system. A receiving unit that receives a packet signal from a transmission device that uses one of the packet format and another packet format that is defined so that a part of the packet format is extracted; and Based on the second known signal in the received packet signal based on the portion to be used for channel estimation, the estimation unit for estimating the channel characteristic, and the channel characteristic estimated by the estimation unit And a processing unit for processing data included in the packet signal.

  According to this aspect, even if a packet signal to be received corresponds to a plurality of types of packet formats, such a packet signal can be received.

  For the packet signal to be received by the receiving unit, the relationship between the signal pattern included in the packet format and the signal pattern included in another packet format is stored in advance. The information processing apparatus may further include a specifying unit that specifies a packet format for the received packet signal, and the estimation unit and the processing unit may execute processing according to the packet format specified by the specifying unit. In this case, since the packet format for the packet signal is automatically specified from the received packet signal, the sequence for notifying the type of the packet format can be omitted.

  Yet another embodiment of the present invention is a reception method. In this method, a packet format in which a second known signal in a second wireless communication system different from the first wireless communication system is arranged after the first known signal in the first wireless communication system has a packet format. A reception method for receiving a packet signal from a transmission device that uses one of the packet format and another packet format defined so that a part of the packet format is extracted. Of the second known signal in the packet signal, the transmission path characteristic is estimated based on the portion to be used for transmission path estimation, and the data included in the packet signal is based on the estimated transmission path characteristic. Process.

  Yet another embodiment of the present invention is also a transmission device. The apparatus stores a first known signal defined in the first wireless communication system and a second known signal defined in a second wireless communication system different from the first wireless communication system. A selection unit that selects one of a packet format in which the second known signal is arranged at the head portion, and a packet format in which the first known signal is further arranged in a preceding stage of the second known signal, and a selection unit And a transmission unit that transmits a signal in the packet format selected in (1).

  According to this aspect, since the presence / absence of the first known signal is switched, compatibility with the first wireless communication system and improvement of packet utilization efficiency can be selected in the second wireless communication system.

  Yet another embodiment of the present invention is also a transmission device. This apparatus has the same number of first known signals defined in the first wireless communication system that should transmit signals using a plurality of carriers and the number of carriers for transmitting signals in the first wireless communication system. A storage unit for storing a second known signal defined by the second wireless communication system that should transmit signals from a plurality of antennas in parallel while using the same number of carriers, and the second known signal are arranged at the head part A selection unit that selects one of the received packet format, a packet format in which the first known signal is further arranged before the second known signal, and a transmission unit that transmits the signal in the packet format selected by the selection unit; .

  According to this aspect, since the presence / absence of the first known signal is switched, compatibility with the first wireless communication system and improvement of packet utilization efficiency can be selected in the second wireless communication system.

  A plurality of types of second known signals stored in the storage unit may be defined according to the number of antennas that should transmit signals in the second wireless communication system. Since the pattern of the second known signal is changed according to the number of antennas, the communication quality can be improved.

  When the selection unit selects a packet format in which the second known signal is arranged at the head part, if the number of antennas to which the signal is to be transmitted becomes one, a plurality of types of second known signals defined One of them may be arranged. Even if the number of antennas is changed from a plurality to one, since the second known signal corresponding to one of the plurality of antennas is used, switching to the first wireless communication system becomes unnecessary.

  When selecting a packet format in which the first known signal is further arranged before the second known signal, the selecting unit selects the second known signal between the first known signal and the second known signal. Information indicating that it is arranged may be arranged. Since the information indicating that the second known signal is arranged is inserted after the first known signal, it is possible to notify the communication device of the first wireless communication system of the content of the subsequent signal. it can.

  A monitoring unit that monitors the presence of a communication device that is not compatible with the second wireless communication system and that is compatible with the first wireless communication system, and the selection unit determines the packet format based on the monitoring result of the monitoring unit. You may choose. Since the switching of the presence / absence of the first known signal is performed based on the presence / absence of the terminal device of the first wireless communication system, even if the switching is performed, other communication devices are not affected.

  Another embodiment of the present invention is also a transmission device. This apparatus includes a transmission unit that transmits signals defined in a predetermined packet format in parallel from a plurality of antennas, a storage unit that stores a known signal to be placed at the beginning of the packet format, and a known signal that is stored in the packet format. When placing at the beginning, select either an arrangement in which known signals are transmitted from multiple antennas at the same timing, or an arrangement in which known signals are transmitted from multiple antennas at different timings A selection unit.

  According to this aspect, since the arrangement of known signals to be transmitted from a plurality of antennas is changed, signal transmission quality and packet utilization efficiency can be selected.

  The deriving unit that derives the characteristics of the radio transmission path to which the signal is to be transmitted and the selection unit may select the arrangement of the known signals based on the derived characteristics of the radio transmission path. Since the change of the configuration of the known signal to be transmitted from a plurality of antennas is executed based on the quality of the radio transmission path, the configuration of the known signal suitable for the quality of the radio transmission path can be selected.

  Yet another embodiment of the present invention is also a transmission method. This method is the same as the first known signal defined in the first wireless communication system to transmit signals using a plurality of carriers and the number of carriers for transmitting signals in the first wireless communication system. The second known signal defined by the second wireless communication system that should transmit signals from a plurality of antennas in parallel while using the number of carriers is defined, and the second known signal is arranged at the head portion. The packet format and the packet format in which the first known signal is further arranged in the previous stage of the second known signal are selected, and the signal is transmitted.

  Yet another embodiment of the present invention is also a transmission method. The method stores a first known signal defined in a first wireless communication system and a second known signal defined in a second wireless communication system different from the first wireless communication system. Selecting a packet format in which the second known signal is arranged at the head part, and a packet format in which the first known signal is further arranged in the preceding stage of the second known signal, and a step of selecting Transmitting a signal in the selected packet format.

  Yet another embodiment of the present invention is also a transmission method. This method is the same as the first known signal defined in the first wireless communication system to transmit signals using a plurality of carriers and the number of carriers for transmitting signals in the first wireless communication system. Storing a second known signal defined by the second wireless communication system to transmit signals from a plurality of antennas in parallel while using the number of carriers, and the second known signal is arranged at the head portion A packet format, a step of selecting one of the packet formats in which the first known signal is further arranged in the previous stage of the second known signal, and a step of transmitting the signal in the packet format selected in the selecting step. .

  The second known signal stored in the storing step may be defined in a plurality of types according to the number of antennas that should transmit signals in the second wireless communication system. The step of selecting, when selecting the packet format in which the second known signal is arranged at the head part, is provided with a plurality of types of second known signals if the number of antennas to transmit the signal is one. One of them may be arranged. The step of selecting includes selecting the second known signal between the first known signal and the second known signal when selecting a packet format in which the first known signal is further arranged before the second known signal. Information indicating that is placed may be placed.

  The method further comprises the step of monitoring the presence of a communication device compatible with the first wireless communication system without being compatible with the second wireless communication system, and the selecting step is based on the monitoring result in the monitoring step. May be selected. The second known signal stored in the storing step includes a plurality of portions having different signal patterns, and the selecting step transmits at least one of the plurality of portions from the plurality of antennas at the same timing. The arrangement of the second known signals and the arrangement of the second known signals that respectively transmit at least one of the plurality of portions at different timings from the plurality of antennas may be selected. In the step of deriving and selecting the characteristics of the wireless transmission path on which the signal is to be transmitted, the second known signal arrangement may be selected based on the derived characteristics of the wireless transmission path.

  Yet another embodiment of the present invention is also a transmission method. This method has an arrangement in which a known signal is transmitted from a plurality of antennas at the same timing with respect to a known signal to be arranged at the beginning of a packet format of a signal to be transmitted in parallel from a plurality of antennas One of arrangements is selected so that signals are transmitted from a plurality of antennas at different timings.

  Yet another embodiment of the present invention is also a transmission method. This method includes a step of transmitting a signal defined in a predetermined packet format in parallel from a plurality of antennas, a step of storing a known signal to be arranged at the head portion of the packet format, and a step of storing the known signal at the head portion of the packet format. Selecting an arrangement in which known signals are transmitted from a plurality of antennas at the same timing, and an arrangement in which known signals are transmitted from a plurality of antennas at different timings. Is provided. In the step of deriving the characteristics of the radio transmission path to which the signal is to be transmitted and the selection step, the arrangement of the known signals may be selected based on the derived characteristics of the radio transmission path.

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

  ADVANTAGE OF THE INVENTION According to this invention, the transmission method and apparatus which change the format of a preamble signal can be provided.

  Before describing the present invention in detail, an outline will be described. An embodiment 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 multi-carrier, specifically, OFDM (Orthogonal Frequency Division Multiplexing) modulation, and the transmitted signal is defined in a packet format. A preamble signal is arranged at the beginning of the packet format, and a receiving apparatus that receives the signal performs AGC (Automatic Gain Control) 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.

  On the other hand, there may be a receiving device that does not support the MIMO system around the transmitting device (hereinafter, a system that does not support the MIMO system is referred to as a “conventional system”). The conventional system transmits a signal by the OFDM modulation method as in the MIMO system. However, unlike the MIMO system, the signal is transmitted by setting one channel between the transmission device and the reception device. Here, if a preamble signal corresponding to only the MIMO system is added, the signal redundancy in the packet format in the MIMO system can be reduced. However, since the conventional system cannot recognize such a preamble signal, it recognizes the arrival of the signal. There are cases where it is not possible. At this time, if the conventional system uses CSMA, carrier sense is not accurately executed. As a result, since it is determined that no signal is transmitted and the signal is transmitted by itself, the probability of occurrence of signal collision increases.

  On the other hand, in a MIMO system, if a preamble signal corresponding to the conventional system is added before the preamble signal corresponding to only the MIMO system, the reception apparatus of the conventional system can also recognize the preamble signal. As a result, the above-described problems are less likely to occur. However, since the preamble signals corresponding to the two systems are added, the signal redundancy in the packet format of the MIMO system increases. In order to solve these problems, the transmitting apparatus according to the present embodiment adds a preamble signal corresponding to the conventional system to the head of the packet format if there is a receiving apparatus corresponding to the conventional system in the vicinity. On the other hand, if there is no receiving device corresponding to the conventional system in the vicinity, the preamble signal corresponding to the conventional system is not added to the head of the packet format.

  FIG. 1 shows a spectrum of a multicarrier signal according to an embodiment of the present invention. This corresponds to a multicarrier signal transmitted by the conventional system and a multicarrier signal transmitted from one antenna of the MIMO system. Here, it is assumed that the conventional system is a wireless LAN (Local Area Network) compliant with the IEEE 802.11a standard (hereinafter, the wireless LAN compliant with the IEEE 802.11a standard is also referred to as “conventional system”). 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 (Binary Phase Shift Keying), QSPK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), and 64QAM.

  On the other hand, in the MIMO system, subcarriers with subcarrier numbers “−28” to “28” are used. Therefore, the number of subcarriers used is “56”, and the subcarrier number “0” is set to null as described above.

  FIG. 2 shows a configuration of a packet format according to the embodiment of the present invention. This corresponds to the call channel of the conventional system. 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 conventional system, since the size of the Fourier transform is 64 (hereinafter, one FFT (Fast Fourier Transform) point is referred to as an “FFT point”) and the guard interval has 16 FFT points, the OFDM symbol is 80 FFT. It corresponds to a point.

  In the packet 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. The signal is a control signal, and the data is information to be transmitted from the transmission device to the reception device. 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. If such a notation is used, the STS of the conventional system is expressed as follows.

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

  FIG. 3 shows a concept of the communication system 100 according to the embodiment of the present invention. 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.

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, the problem when the preamble signal of the conventional system, for example, the STS is transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b in FIG. 3 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、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、従来システムのＳＴＳと別のＳＴＳが必要となり、かつ、それらの相互相関値は低い方が望ましい。 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 by the third term on the right side of Equation 4. As can be seen, when 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, an STS different from the STS of the conventional system is required for the MIMO system, and it is desirable that their cross-correlation values are low.

  Next, a problem when a preamble signal such as STS suitable for the MIMO system as described above is added to the head portion of the packet format will be described. When a packet signal to which a preamble signal suitable for the MIMO system is added is transmitted from the transmission device 10, the reception device 12 can receive the packet signal. On the other hand, a reception device of a conventional system (not shown) also receives a packet signal to which a preamble signal suitable for a MIMO system is added. However, since the preamble signal in the conventional system held in advance by the receiving apparatus is different from the preamble signal added to the packet signal, even if correlation processing is performed between them, the correlation value is higher than a predetermined value. Does not grow. As a result, the receiving device cannot detect the packet signal. Further, if the receiving device and the transmitting device integrally form a communication device, the above-described operation corresponds to the fact that no packet signal is detected by the communication device, so the communication device transmits a signal. This corresponds to the fact that carrier sense is not correctly executed in the communication device, and therefore, signal collision is likely to occur.

  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 according to 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 a preamble signal to the head of the packet signal. Here, a plurality of types of preamble signals to be added by the preamble adding unit 32 are defined, and one of them is selected based on an instruction from the control unit 26. Details thereof will be described later.

  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 signal. The GI unit 36 adds a guard interval to the time domain data. As shown in FIG. 2, guard intervals added to the preamble signal and the data signal 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, signals are transmitted from the plurality of transmitting antennas 14 in parallel. 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. The control unit 26 controls the timing and the like of the transmission apparatus 10 and selects a preamble signal to be added by the preamble adding unit 32.

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

  FIG. 5 shows the configuration of the control unit 26. The control unit 26 includes a selection unit 110, a monitoring unit 112, a transmission path characteristic acquisition unit 114, and a storage unit 116.

  The storage unit 116 stores a preamble signal specified in the conventional system and a preamble signal specified in the MIMO system. That is, the storage unit 116 stores a packet format in which the preamble signal in the MIMO system is arranged after the preamble signal in the conventional system. As described above, the conventional system and the MIMO system use multicarrier signals. In addition, the MIMO system transmits signals from a plurality of transmitting antennas 14 in parallel. Further, a plurality of types of preamble signals defined by the MIMO system are defined according to the number of transmitting antennas 14 to which signals are to be transmitted. A plurality of types of prescribed preamble signals will be described later. Similarly to the preamble signal of the conventional system shown in FIG. 2, the preamble signal of the MIMO system is defined to include STS and LTS. Here, STS and LTS have different signal patterns.

  The monitoring unit 112 monitors the presence of a communication device that does not correspond to the MIMO system but corresponds to the conventional system. Here, it is assumed that the transmission apparatus 10 and a reception apparatus (not shown) integrally constitute a communication apparatus, for example, a base station apparatus compatible with a MIMO system. The receiving device searches for the signal received from the communication device of the conventional system among the received signals. That is, it is determined whether the packet format of the received packet signal corresponds to the packet format of the conventional system shown in FIG. The monitoring unit 112 determines that there is no communication device corresponding to the conventional system when the receiving device does not detect a packet signal defined by the conventional system over a predetermined period. On the other hand, when the receiving apparatus detects a packet signal defined by the conventional system within a predetermined period, it is determined that there is a communication apparatus corresponding to the conventional system.

  The transmission path characteristic acquisition unit 114 derives the characteristics of the wireless transmission path with the receiving device 12. The characteristics of the wireless transmission path are measured by a predetermined method. One method is measurement by the reception device 12 of FIG. 3, and another method is measurement by a communication device including the transmission device 10. The former corresponds to the characteristic of the wireless transmission path from the transmission apparatus 10 to the reception apparatus 12, and the latter corresponds to the characteristic of the wireless transmission path from the reception apparatus 12 to the transmission apparatus 10. In the former case, the communication device including the receiving device 12 notifies the communication device including the transmitting device 10 of the measurement result. Here, the characteristics of the wireless transmission path include reception power, delay profile, delay spread, error rate, and the like.

  The selection unit 110 selects a packet format based on the monitoring result from the monitoring unit 112. Here, two types of packet formats are defined. 6A to 6B show packet formats selected by the selection unit 110. FIG. FIG. 6A shows a packet format in which a preamble signal corresponding to the MIMO system is arranged at the head portion (hereinafter referred to as “dedicated format”). Here, it is assumed that signals are transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b among the transmitting antennas 14, the packet format of the signal transmitted from the first transmitting antenna 14a is shown in the upper stage, 2 shows the packet format of the signal transmitted from the transmitting antenna 14b. “STS1” and “LTS1” are transmitted as preamble signals from the first transmitting antenna 14a, and “STSa” and “LTSa” are transmitted as preamble signals from the second transmitting antenna 14b. Here, “STS1” and “STSa”, and “LTS1” and “LTSa” are signals having different patterns. Details of these signals will be described later.

  FIG. 6B shows a packet format in which a preamble signal corresponding to the conventional system is further arranged before the preamble signal corresponding to the MIMO system (hereinafter referred to as “mixed format”). Here, the STS and LTS of the preamble signal corresponding to the conventional system are indicated as “conventional STS” and “conventional LTS”, respectively. Note that the pattern of the conventional STS is as described in FIG. The part corresponding to the preamble signal of the MIMO system is the same as that shown in FIG. Here, a “signal” is arranged between the preamble signal corresponding to the conventional system and the preamble signal corresponding to the MIMO system. “Signal” includes information indicating that a preamble signal corresponding to the MIMO system is arranged. Therefore, even if the communication apparatus of the conventional system receives the packet signal, the packet signal may be discarded from the content of “signal”. Further, the information indicating that the preamble signal is arranged may be the length of the packet signal, that is, it is only necessary to determine that some signal continues for a certain period of time. In the mixed format, the number of subcarriers in the “conventional STS”, “conventional LTS”, and “signal” portions is different from the subcarrier number in the subsequent portion.

  Since the dedicated format has few redundant signal components, the use efficiency of packets can be improved. On the other hand, the mixed format is detected by a communication apparatus compatible with the conventional system since a packet signal corresponding to the conventional system is added. If the monitoring unit 112 does not detect a communication device compatible with the conventional system, the selection unit 110 selects a dedicated format. If the monitoring unit 112 detects a communication device compatible with the conventional system, the selection unit 110 Select a mixed format.

  That is, the selection unit 110 generates a packet signal while selecting either the dedicated format or the mixed format based on the monitoring result of the monitoring unit 112. Here, it can be said that the dedicated format is a packet format defined such that a part of the mixed format is extracted. Further, the extracted part includes at least a part to be used for transmission path estimation in the preamble signal in the MIMO system. Here, the parts to be used for transmission path estimation correspond to “LTS1” and “LTSa” in FIGS. 6A to 6B.

  Further, the selection unit 110 selects an LTS arrangement based on the characteristics of the wireless transmission path derived by the transmission path characteristic acquisition unit 114. 7A to 7B show the format of the LTS selected by the selection unit 110. FIG. FIGS. 7A to 7B are described in a dedicated format, but may be a mixed format, in which case the preamble signal portion of the MIMO system is illustrated. FIG. 7A shows a case where LTSs are transmitted from a plurality of transmitting antennas 14 at the same timing (hereinafter, such a format is referred to as “continuous format”). "Is transmitted, and" LTSa "is transmitted from the second transmitting antenna 14b. FIG. 7B shows a case where LTSs are transmitted from a plurality of transmitting antennas 14 at different timings (hereinafter, such a format is referred to as “separation format”), and “LTS1” and “LTSa” are illustrated as shown. "Is transmitted at a different timing.

  Since the continuous format has few redundant signal components, the use efficiency of packets can be improved. On the other hand, in the separation format, “LTS1” and “LTSa” are transmitted at different timings, and interference between signals is reduced. Therefore, estimation of transmission path characteristics, response vectors, and weights performed by the receiving apparatus 12 described later are performed. Vector estimation is accurate and communication quality is improved. If the wireless channel characteristics acquired by the channel characteristics acquisition unit 114, for example, the error rate is not worse than the threshold value, the selection unit 110 selects the continuous format, and the error rate is worse than the threshold value. If so, the selection unit 110 selects the separation format.

  FIG. 8 shows the relationship used when selecting by the selection unit 110, and shows the relationship between the number of transmitting antennas and the STS pattern transmitted from the transmitting antenna. In addition, although description is abbreviate | omitted here about LTS, suppose that it selects similarly. 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”, the conventional STS is transmitted from the first transmitting antenna 14a. Note that, in the case of the dedicated format, the selection unit 110 may transmit “STS1” defined by the MIMO system if the number of transmission antennas 14 to which a signal is to be transmitted becomes one. Thereby, switching to the preamble signal corresponding to the conventional system can be omitted.

  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, “STS1”, “STSa”, “STS2”, and “STSb” are defined by values that reduce the cross-correlation value in order to solve the above-described problems.

  Further, “STSa” transmitted from the second transmitting antenna 14b when the number of transmitting antennas 14 is “2” and from the third transmitting antenna 14c when the number of transmitting antennas 14 is “3”. It has a function of notifying the receiving apparatus 12 of the number of transmitting antennas 14 that are transmitting signals, depending on the pattern difference between “STSb” to be transmitted. Therefore, these STSs are different to the extent that “STSa” and “STSb” can be identified from the signal received by the receiving device 12. That is, the cross-correlation value between “STSa” and “STSb” is defined to be small.

  The number of transmitting antennas 14 is determined by the control unit 26. The control unit 26 determines the number of transmission antennas 14 according to the characteristics of the wireless transmission path acquired by the transmission path characteristic acquisition unit 114. That is, if the characteristics of the wireless transmission path are good, the number of transmitting antennas 14 is increased. The control unit 26 may determine the number of transmission antennas 14 based on the capacity of information to be transmitted. For example, if the capacity of information to be transmitted is large, the number of transmitting antennas 14 is increased.

  FIG. 9 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 receiving device 12 receives a packet signal from the transmitting device 10 in FIG. 4 via the receiving antenna 16. 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, the radio frequency of the radio 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. That is, the processing unit 52 is a portion to be used for transmission path estimation in the preamble signal corresponding to the MIMO system in the received packet signal, that is, “LTS1” shown in FIGS. 6A and 6B. Based on the above, the channel characteristics are estimated. The processing unit 52 processes data included in the packet signal based on the estimated transmission path characteristics. 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. 10 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 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 converter 68 converts an analog signal into a digital signal. The quadrature detection unit 64 performs quadrature detection on the intermediate frequency signal, generates a baseband digital signal, and outputs it as the first baseband reception signal 202a. In general, a baseband signal contains two components, an in-phase component and a quadrature component, so it should be indicated by two signal lines. Shown by signal line. The same applies to the following.

  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. In the MIMO system, since the STS is set for each transmission antenna 14, the correlation unit 70 performs correlation processing on each of the plurality of STSs and outputs a plurality of correlation values. The correlation value is input to the control unit 58 in FIG. 9 through a signal line (not shown). The control unit 58 determines the reception start of the packet signal 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. 11 shows the configuration of the correlation unit 70. The correlation unit 70 includes a conventional STS correlation unit 330, an STSa correlation unit 332, an STSb correlation unit 334, and a selection unit 336.

  The STSa correlation unit 332 stores in advance a signal sequence obtained by converting STSa into the time domain, and calculates a correlation value between the stored signal sequence and the received signal sequence (hereinafter referred to as “two-antenna correlation value”). . The STSb correlation unit 334 stores in advance a signal sequence obtained by converting the STSb into the time domain, and calculates a correlation value between the stored signal sequence and the received signal sequence (hereinafter referred to as “3-antenna correlation value”). .

  Conventional STS correlation section 330 stores in advance a signal sequence obtained by converting the above-described conventional STS into the time domain, or a signal sequence obtained by converting some subcarrier signals of conventional STS into the time domain. Further, the conventional STS correlation unit 330 calculates a correlation value between the stored signal sequence and the received signal (hereinafter referred to as “correlation value for one antenna”). Note that the signal sequence stored by the conventional STS correlator 330 may correspond to an STS corresponding to the MIMO system, for example, STS1 in FIG.

  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 transmitting data based on the selected correlation value. That is, if the correlation value for two antennas is large, the number of transmission antennas 14 is determined as “2”. If the correlation value for three antennas is large, the number of transmission antennas 14 is determined as “3”. If the value is large, the number of transmitting antennas 14 is determined to be “1”.

FIG. 12 shows the 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 LTS1 and the like. In addition, it is assumed that the LTS is also selected according to the STS selected by the conventional STS correlation unit 330.

  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応答ベクトルが求められる。

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

受信ウエイト信号２０６は、受信応答ベクトルから導出される。なお、受信ウエイト信号２０６は、ＬＭＳアルゴリズムなどの適応アルゴリズムによって導出されてもよい。

The reception weight signal 206 is derived from the reception response vector. The reception weight signal 206 may be derived by an adaptive algorithm such as an LMS algorithm.

  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.

  FIG. 13 is a flowchart illustrating a procedure of transmission processing in the transmission device 10. The monitoring unit 112 monitors whether there is a communication device compatible with the conventional system. If there is a communication device compatible with the conventional system (Y in S10), the selection unit 110 selects a mixed format (S12). On the other hand, if there is no communication device compatible with the conventional system (N in S10), the selection unit 110 selects a dedicated format (S14). Further, the selection unit 110 selects STSs and LTSs corresponding to the number of transmission antennas 14 from the storage unit 116 (S16), and arranges them in the selected format. The transmission device 10 transmits a packet signal (S18).

  FIG. 14 is another flowchart showing the procedure of the transmission process in the transmission apparatus 10. The transmission path characteristic acquisition unit 114 acquires the characteristics of the wireless transmission path, for example, the error rate. If the characteristics of the wireless transmission path are good (Y in S50), that is, if the error rate is lower than the threshold value, the selection unit 110 selects a continuous format (S52). On the other hand, if the characteristics of the wireless transmission path are not good (N in S50), the selection unit 110 selects a separation format (S54). Further, the selection unit 110 selects STSs and LTSs corresponding to the number of transmission antennas 14 from the storage unit 116 (S56), and arranges them in the selected format. The transmission device 10 transmits a packet signal (S58).

  Described above is a modification of the embodiment described above. The transmission apparatus according to the modification is of the same type as the transmission apparatus 10 of FIG. 4, and the reception apparatus is of the same type as the reception apparatus 12 of FIG. Therefore, description of the configuration of the transmission device is omitted. FIGS. 15A to 15C show the structure of the packet format according to the modification of the present invention. FIG. 15A is a modification of FIG. 6B, which is a modification of the mixed format. The steps after “STS1” and “STSa” in FIG. 15A are the same as those in FIG. However, in FIG. 15A, “conventional STS”, “conventional LTS”, and “signal” are also assigned to the second transmitting antenna 14b. At that time, for example, CDD (Cyclic Delay Diversity) is applied to “conventional STS” or the like assigned to the second transmitting antenna 14b.

  That is, the conventional STS assigned to the second transmission antenna 14b is shifted in timing from the conventional STS assigned to the first transmission antenna 14a. Here, as shown in the figure, “conventional STS” in which CDD is performed is indicated as “conventional STS + CDD”. The same applies when “conventional STS” or the like is assigned to the third transmitting antenna 14c. As described above, the “conventional STS” and the “conventional LTS” included in the conventional format are defined so as to be related to each other among the plurality of transmitting antennas 14. Here, “relevant” is CDD as described above. Further, “STS1”, “STSa” and the like are defined while being associated with each of the plurality of transmitting antennas 14.

  FIG. 15B shows a dedicated format corresponding to the mixed format of FIG. The dedicated format shown in FIG. 15B is defined so that a part of the mixed format shown in FIG. Here, a part corresponds to “STS1”, “STSa”, “LTS1”, “LTSa”, “signal”, “data 1”, and “data 2”. That is, the preamble signal and signal corresponding to the conventional system are omitted. Note that FIG. 15B has the same configuration as FIG. FIG. 15C also shows a dedicated format corresponding to the mixed format of FIG. 15A, and corresponds to a modification of FIG. The dedicated format shown in FIG. 15C is defined by extracting a part of the mixed format shown in FIG. 15A different from that shown in FIG.

  Here, a part corresponds to “conventional STS”, “conventional STS + CDD”, “LTS1”, “LTSa”, “signal”, “data 1”, and “data 2”. That is, “conventional LTS”, “conventional LTS + CDD”, “signal”, “signal + CDD”, “STS1”, and “STSa” are omitted. Note that the receiving side recognizes in advance whether the packet format shown in FIG. 15B or the packet format shown in FIG. 15C is used as the dedicated format. And

  Further, in order to specify whether the packet signal to be received is a mixed format or a dedicated format, the correlation unit 70 in FIG. 11 may perform a correlation process. At this time, the correlation unit 70 stores in advance the relationship between the signal pattern included in the mixed format and the signal pattern included in the dedicated format. For example, when the mixed format is specified as shown in FIG. 15A and the dedicated format is specified as shown in FIG. 15B, the correlator 70 determines the signal pattern included in the mixed format as: “Conventional STS” is stored, and “STS1” or the like is stored as a signal pattern included in the dedicated format. That is, the above-mentioned “relation” corresponds to a signal pattern that can distinguish a difference in each packet format.

  The correlator 70 performs, in parallel, the correlation process with the “conventional STS” and the correlation process with “STS1” on the received packet signal. Further, if the former correlation value is large, the correlation unit 70 specifies that the received packet signal is in a mixed format, and if the latter correlation value is large, the correlation unit 70 indicates that the received packet signal is in a dedicated format. Is identified. Further, the processing unit 52, the demodulation unit 54, and the like in FIG. 9 execute processing according to the packet format specified by the correlation unit 70.

  Still another modification will be described. In the embodiments and the modifications so far, the packet format associated with each of the plurality of transmitting antennas 14 has been described. In another modification, a packet format associated with each of a plurality of streams will be described. The transmitting apparatus arranges preamble signals corresponding to the MIMO system in a plurality of sequences and arranges data in a plurality of sequences. On the other hand, in the prescription of the mixed format, the transmission apparatus arranges a preamble signal corresponding to the conventional system in at least one of a plurality of sequences. The transmission device multiplies the preamble signal and data corresponding to the MIMO system by a steering matrix, thereby increasing the number of sequences in which these are arranged to the number of the plurality of transmitting antennas 14. Further, when generating a mixed format packet signal, the transmission apparatus performs CDD on the preamble signal corresponding to the conventional system. Hereinafter, a plurality of series of packet signals subjected to steering matrix multiplication and CDD are also referred to as “a plurality of series of packet signals”.

  Note that the steering matrix described above includes a component for executing CDD in order to execute a cyclic time shift for each series. In addition, the amount of time shift in CDD is different in units of a plurality of series of packet signals. As described above, the transmission apparatus deforms a plurality of series of packet signals and transmits the plurality of modified packet signals from the plurality of transmission antennas 14, respectively.

  FIG. 16 shows a configuration of a transmission apparatus 300 according to another modification of the present invention. The transmission apparatus 300 includes an error correction unit 28, an interleaving unit 30, a modulation unit 314, a preamble addition unit 32, a spatial dispersion unit 318, a first radio unit 24a, a second radio unit 24b, and a third radio unit, collectively referred to as a radio unit 24. A first transmission antenna 14a, a second transmission antenna 14b, a third transmission antenna 14c, a fourth transmission antenna 14d, and a control unit 26. .

  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. Further, the interleaving 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 314 performs modulation on each of the two series of data. The preamble adding unit 316 adds a preamble signal to the modulated data. Depending on the preamble signal added by the preamble adding unit 316, the plurality of packet signals correspond to the conventional format or the dedicated format. Here, the packet format to which the preamble signal is added corresponds to FIGS. 6 (a)-(b) and FIGS. 15 (a)-(c). In the case corresponding to FIGS. 15A to 15C, it is assumed that CDD is not performed at this stage.

  Spatial dispersion section 318 multiplies the preamble signal and data corresponding to the MIMO system among the plurality of series of packet signals by the steering matrix to increase the number of preamble signals to the number of transmission antennas 14. And data. Here, the spatial distribution unit 318 extends the order of the input preamble signal and data to the number of multiple sequences before performing multiplication. The number of input preamble signals and data is “2”, and is represented by “Nin” here. Therefore, the input preamble signal and data are each indicated by a “Nin × 1” vector. The number of the plurality of transmitting antennas 14 is “4”, and is represented by “Nout” here. The spatial dispersion unit 318 extends the order of the input preamble signal and data from Nin to Nout. That is, the vector “Nin × 1” is expanded to the vector “Nout × 1”. At that time, “0” is inserted into the components from the Nin + 1 line to the Nout line.

ステアリング行列は、「Ｎｏｕｔ×Ｎｏｕｔ」の行列である。また、Ｗは、直交行列であり、「Ｎｏｕｔ×Ｎｏｕｔ」の行列である。直交行列の一例は、ウォルシュ行列である。ここで、ｌは、サブキャリア番号を示しており、ステアリング行列による乗算は、サブキャリアを単位にして実行される。さらに、Ｃは、以下のように示され、ＣＤＤのために使用される。

The steering matrix S is shown as follows.

The steering matrix is a “Nout × Nout” matrix. W is an orthogonal matrix, which is a “Nout × Nout” matrix. An example of an orthogonal matrix is a Walsh matrix. Here, l indicates a subcarrier number, and multiplication by the steering matrix is executed in units of subcarriers. In addition, C is shown as follows and is used for CDD.

  Here, δ represents the shift amount. That is, the spatial dispersion unit 318 performs a cyclic time shift on a sequence basis by the shift amount corresponding to each of the increased plurality of sequences. The shift amount is set to a different value for each series. As described above, the spatial dispersion unit 318 performs CDD on the preamble signal and signal corresponding to the conventional system. CDD is executed for each of the plurality of transmitting antennas 14 while changing the shift amount.

  For example, by executing CDD on “conventional STS”, “conventional STS”, “conventional STS + CDD1”, “conventional STS + CDD2”, and “conventional STS + CDD3” are generated. Here, “CDD1”, “CDD2”, and “CDD3” have different shift amounts. As described above, the preamble signals corresponding to the conventional system are defined so as to be related to each other among the plurality of sequences. As a result of the above processing, the spatial dispersion unit 318 transforms a plurality of series of burst signals.

  The same number of radio units 24 as the transmission antennas 14 are provided. The radio unit 24 transmits a plurality of modified packet signals. At that time, the wireless unit 24 transmits the modified packet signals of a plurality of series while corresponding to the plurality of transmission antennas 14. Note that the radio unit 24 may transmit a packet signal from some of the plurality of transmission antennas 14.

  FIGS. 17A to 17C show packet formats of signals transmitted from the transmission device 300. FIG. FIG. 17A corresponds to a mixed format, as in FIG. As described above, in the “conventional STS”, “conventional LTS” and “signal” which are preamble signals corresponding to the conventional system, the shift amounts defined as “CDD1”, “CDD2” and “CDD3” are defined. CDD is done based on this. “STS1 ′” to “STS4 ′” correspond to signals transformed from “STS1”, “STSa”, and the like in FIG. 6B by the spatial dispersion unit 318. That is, “STS1 ′” to “STS4 ′” correspond to signals obtained by multiplying “STS1”, “STSa”, and the like by a steering matrix. The same applies to “LTS 1 ′”, “signal 1 ′”, “data 1 ′”, and the like.

  FIG. 17B shows a dedicated format corresponding to the mixed format of FIG. The dedicated format shown in FIG. 17B is defined so that a part of the mixed format shown in FIG. Here, a part is defined similarly to FIG. That is, the preamble signal corresponding to the conventional system is omitted. FIG. 17C also shows a dedicated format corresponding to the mixed format of FIG. 17A, and corresponds to a modification of FIG. The dedicated format in FIG. 17C is defined by extracting a part of the mixed format in FIG. 17A different from that in FIG. Here, a part is defined similarly to FIG.

  According to the embodiment of the present invention, the preamble signal in the conventional system is added to the head part of the packet signal, so that the communication apparatus in the conventional system can receive the packet signal. In addition, compatibility with conventional systems can be maintained. In addition, it is possible to inform the communication device of the conventional system of the presence of the packet signal. Further, since signal transmission by the communication device of the conventional system can be prevented, the probability of signal collision can be improved. In addition, since the presence / absence of a preamble signal in the conventional system is switched, compatibility with the conventional system and improvement in packet utilization efficiency can be selected. Further, since the switching of the presence / absence of the preamble signal of the conventional system is executed based on the presence / absence of the terminal device of the conventional system, it does not affect other communication devices.

  Further, since the preamble signal pattern is changed according to the number of antennas, the communication quality can be improved. Even if the number of antennas is changed from a plurality to one, since a preamble signal corresponding to one of the plurality of antennas is used, switching to a conventional system is not necessary. Further, since the signal is inserted after the preamble signal of the conventional system, the content of the subsequent signal can be notified to the communication device of the conventional system. In addition, since the configuration of the preamble signal to be transmitted from a plurality of antennas is changed, the signal transmission quality and the packet utilization efficiency can be selected. Since the configuration of the preamble signal to be transmitted from the plurality of antennas is changed based on the quality of the wireless transmission path, a preamble configuration suitable for the quality of the wireless transmission path can be selected.

  Further, since the dedicated format is defined so as to extract a part of the mixed format, a plurality of types of dedicated formats can be defined by changing the extracted part. Also, even if the number of data series is smaller than the number of transmitting antennas, multiplication by an orthogonal matrix and cyclic time shift processing are executed, so the number of data series increases to the number of transmitting antennas. it can. In addition, since the LTS corresponding to the MIMO system executes the same processing as that of the data series, the LTS corresponding to the MIMO system can be used when receiving data of the wireless device to be communicated. Further, since the packet format for the packet signal is automatically specified from the received packet signal, the sequence for notifying the type of the packet format can be omitted. Further, since the sequence for notifying the type of packet format can be omitted, transmission efficiency can be improved.

  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 the embodiment of the present invention, a wireless LAN conforming to the IEEE 802.11a standard is illustrated as a conventional system. However, the present invention is not limited to this, and other communication systems may be used. Furthermore, although the communication system 100 has been described as a MIMO system, it may be another communication system. Moreover, it is not necessary to transmit a multicarrier signal. According to this modification, the present invention can be applied to various communication systems 100. That is, the conventional system and the communication system 100 only need to have some compatibility such as the same radio frequency.

  In the embodiment of the present invention, a dedicated format is defined so as to extract a part of the mixed format as shown in FIGS. That is, the dedicated format is defined as a format obtained by extracting a part of the mixed format. Further, when extracting a part, at least one of the plurality of components included in the mixed format, such as “STS1” in FIG. 15B and “LTS1” in FIG. A dedicated format is defined so that elements such as “LTS1” are extracted as they are. That is, the predetermined component is either included in the dedicated format as it is or not included in the dedicated format at all. However, the present invention is not limited to this, and for example, a dedicated format may be defined so that some of predetermined components are extracted.

  Specifically, the latter half of “LTS1” or the like may be extracted as a dedicated format. Also, when “STS1” is formed by concatenating a plurality of signals having a period of a predetermined period, only a predetermined number of signals having a period of a predetermined period are extracted. A format may be defined. When “STS1” is formed by concatenating five signals having a predetermined period, the latter two signals may be extracted as a dedicated format. Note that signals having a predetermined period may not be the same pattern. The above is also applicable to “LTS1” and the like. According to this modification, various dedicated formats can be defined. Further, the period of the preamble signal included in the dedicated format can be adjusted in detail. That is, it suffices if the dedicated format includes a preamble signal that can be received.

It is a figure which shows the spectrum of the multicarrier signal which concerns on the Example of this invention. It is a figure which shows the structure of the packet format which concerns on the Example of this invention. It is a figure which shows the concept of the communication system which concerns on the Example of this invention. It is a figure which shows the structure of the transmitter of FIG. It is a figure which shows the structure of the control part of FIG. 6A to 6B are diagrams illustrating packet formats selected by the selection unit in FIG. FIGS. 7A to 7B are diagrams showing the format of the LTS selected by the selection unit of FIG. FIG. 6 is a diagram illustrating a relationship used when selecting by the selection unit in FIG. 5 and a relationship between the number of transmitting antennas and an STS pattern transmitted from the transmitting antenna. 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 correlation part of FIG. It is a figure which shows the structure of the 1st process part of FIG. It is a flowchart which shows the procedure of the transmission process in the transmitter of FIG. It is another flowchart which shows the procedure of the transmission process in the transmitter of FIG. FIGS. 15A to 15C are diagrams showing the configuration of the packet format according to the modification of the present invention. It is a figure which shows the structure of the transmitter which concerns on another modification of this invention. FIGS. 17A to 17C are diagrams illustrating packet formats of signals transmitted from the transmission apparatus of FIG.

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 section, 36 GI section, 38 orthogonal modulation section, 40 frequency conversion section, 42 amplification section, 100 communication system, 110 selection section, 112 monitoring section, 114 transmission path characteristic acquisition section, 116 storage section.

Claims (5)

A packet format in which the second known signal in the second wireless communication system different from the first wireless communication system is arranged at the subsequent stage of the first known signal in the first wireless communication system is defined. A generation unit that generates a packet signal while using the packet format;
A transmission unit for transmitting the packet signal generated in the generation unit,
The first known signal included in the packet format defined in the generation unit is defined so as to be related to each other between the plurality of antennas, and the second known signal is defined as the plurality of antennas. A transmitting apparatus characterized by being defined while being associated with each of the above. A packet format in which the second known signal in the second wireless communication system different from the first wireless communication system is arranged at the subsequent stage of the first known signal in the first wireless communication system is defined. A generation unit that generates a packet signal while using the packet format;
A transmission unit for transmitting the packet signal generated in the generation unit,
The first known signal included in the packet format defined in the generation unit is defined so as to be related to each other among the plurality of sequences, and the second known signal is defined as the plurality of sequences. A transmission apparatus characterized by being defined while being associated with each of the above.   The transmission according to claim 1 or 2, wherein the first radio communication system and the second radio communication system corresponding to the packet format defined in the generation unit use multicarrier signals. apparatus. A packet format in which the second known signal in the second wireless communication system different from the first wireless communication system is arranged at the subsequent stage of the first known signal in the first wireless communication system is defined. A transmission method for generating a packet signal while using the packet format,
The first known signal included in the defined packet format is defined so as to be related to each other among the plurality of antennas, and the second known signal corresponds to each of the plurality of antennas. A transmission method characterized in that it is specified while being attached. A packet format in which the second known signal in the second wireless communication system different from the first wireless communication system is arranged at the subsequent stage of the first known signal in the first wireless communication system is defined. A transmission method for generating a packet signal while using the packet format,
The first known signal included in the defined packet format is defined so as to be related to each other among the plurality of sequences, and the second known signal corresponds to each of the plurality of sequences. A transmission method characterized in that it is specified while being attached.

Images