JP4593435B2 - Transmission method and apparatus, and communication system using the same - Google Patents

Description

  The present invention relates to a transmission technique, and more particularly to a transmission method and apparatus for transmitting packet signals formed in a plurality of streams, and a communication system using the same.

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

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

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

  Furthermore, when such an MIMO system is combined with an OFDM modulation scheme, the data rate is further increased. In the MIMO system, the data rate can be adjusted by increasing or decreasing the number of antennas to be used for data communication. Furthermore, the adjustment of the data rate is made in more detail by applying adaptive modulation. In order to reliably execute such adjustment of the data rate, the transmission device acquires information (hereinafter referred to as “rate information”) on the data rate suitable for the wireless transmission path between the transmission device and the reception device. Should. In order to improve the accuracy of such rate information, in the receiving apparatus, it is preferable to acquire the transmission path characteristics between the plurality of antennas included in the transmitting apparatus and the plurality of antennas included in the receiving apparatus. desirable.

  Further, combinations of antenna directivity patterns in the transmission apparatus and the reception apparatus in the MIMO system are as follows, for example. One is a case where the antenna of the transmission device has an omni pattern and the antenna of the reception device has a pattern in adaptive array signal processing. Another case is when both the antenna of the transmitting device and the antenna of the receiving device have patterns in adaptive array signal processing. This is also called beam forming. The former can simplify the system, but the latter can improve the characteristics because the directivity pattern of the antenna can be controlled in more detail. In the latter case, in order to perform adaptive array signal processing for transmission in the transmission device, in the reception device, each of the transmission paths between the plurality of antennas included in the transmission device and the plurality of antennas included in the reception device It is desirable to acquire characteristics.

  In order to improve the accuracy of rate information and the accuracy of beam forming in the above requirements, it is necessary to acquire the characteristics of the transmission path characteristics with high accuracy. In order to improve the accuracy of acquisition of transmission path characteristics, the transmission apparatus or the reception apparatus transmits known signals for transmission path estimation from all antennas. Hereinafter, a known signal for channel estimation arranged in a plurality of sequences is referred to as a “training signal” regardless of the number of sequences in which data is arranged. For example, even when the data is arranged in two series, the training signal is arranged in four series.

  Under such circumstances, the present inventor has come to recognize the following problems. When a training signal is transmitted, the number of sequences including a known signal for channel estimation (hereinafter referred to as “known signal for channel estimation”) is different from the number of sequences including data. In addition, a known signal (hereinafter, referred to as “AGC known signal”) for setting a receiving side AGC (Automatic Gain Control) is arranged in the preceding stage of the transmission path estimation known signal. When the AGC known signal is arranged only in the sequence in which data is arranged, a part of the transmission path estimation known signal is received in a state where the AGC known signal is not received in the preceding stage. In particular, if the reception strength of the known signal for AGC is not large on the reception side, the gain in AGC is set to a value that is somewhat large. At this time, if the strength of the transmission path estimation known signal of the sequence in which the AGC known signal is not arranged is large, the transmission path estimation known signal may be amplified so as to cause distortion by AGC. As a result, a transmission path estimation error based on the transmission path estimation known signal increases.

  On the other hand, when AGC known signals are arranged in a sequence in which transmission path estimation known signals are arranged, the number of sequences in which AGC known signals are arranged differs from the number of sequences in which data is arranged. The gain set by the known signal may not be suitable for data demodulation. As a result, errors are likely to occur in the demodulated data. In particular, these problems become more important as the difference between the number of sequences in which known signals for transmission path estimation are arranged and the number of sequences in which data is arranged increases.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a transmission technique that improves the accuracy of channel estimation while suppressing a decrease in transmission efficiency when transmitting a known signal for channel estimation. Is to provide.

  In order to solve the above-described problem, a transmitting apparatus according to an aspect of the present invention is a transmitting apparatus that transmits a packet signal formed by a plurality of streams, and is a data signal to be arranged in at least one of the plurality of streams. , A first known signal arranged in a sequence in which a data signal inputted in the input unit is arranged, and a second known signal arranged in a plurality of sequences in the subsequent stage of the first known signal And a generation unit that generates a packet signal from the data signal, and a transmission unit that transmits the packet signal generated in the generation unit. When the second known signal is arranged in a plurality of sequences, the generation unit combines the plurality of sequences into a plurality of groups, with a number of sequences larger than the number of sequences in which the data signals are arranged as one group. In addition, the timing at which the second known signal is to be arranged is shifted from each other for each of the plurality of groups.

  According to this aspect, since a plurality of sequences are grouped into a plurality of groups and the timings at which each of the plurality of groups should be arranged are shifted from each other, the number of sequences per group can be reduced, and the first known signal and the first The difference in intensity between the two known signals can be reduced.

  In the second known signal included in the packet signal generated by the generation unit, a predetermined unit is repeated in the time domain, and a combination of codes of the predetermined unit has an orthogonal relationship between sequences in the group. May be. In this case, since the number of sequences in the group is smaller than the total number of sequences, the number of sequences to be orthogonally related is also reduced, and the number of units for forming the second known signal can be reduced.

  The input unit inputs data signals to be arranged in one sequence, and the generation unit arranges the four sequences while arranging the two sequences as one group when arranging the second known signal in the four sequences. The two known groups may be combined, the timings at which the second known signals are to be arranged are shifted from each other, and the second known signals may be formed by repeating the two units. . In this case, even if the first known signal is arranged in one series, the second known signal is only arranged in two series at a predetermined timing, so that the first known signal and the second known signal are arranged. The difference in intensity with the signal can be reduced.

  The generation unit generates another packet signal by arranging the first known signal, the second known signal, and the data signal in one series, and the second known signal is also generated in the other packet signal. May be formed by repeating two units. In this case, when the second known signal is arranged in one sequence and when the second known signal is arranged in a plurality of sequences, the configuration of one sequence is similar. Can be executed easily.

  Another aspect of the present invention is a transmission method. This method is a transmission method for transmitting a packet signal formed by a plurality of sequences, in which a first known signal is arranged in a sequence in which a data signal to be arranged in at least one of the plurality of sequences is arranged. The packet signal is generated by arranging the second known signal in a plurality of series and the number of series in which the data signal is arranged when the second known signal is arranged in the plurality of series. While a larger number of sequences are grouped into one group, a plurality of sequences are grouped into a plurality of groups, and the timing at which the second known signal is to be arranged is shifted from each other for each of the plurality of groups. .

  In the second known signal included in the generated packet signal, a predetermined unit is repeated in the time domain, and a combination of codes of the predetermined unit has an orthogonal relationship between sequences in the group. Good. The data signals are arranged in one series, and when the second known signal is arranged in four series, the two series are grouped into one group, and the four series are grouped into two groups. The timing at which the second known signal is to be arranged may be shifted from each other as a unit, and the second known signal may be formed by repeating two units. Another packet signal is also generated by arranging the first known signal, the second known signal, and the data signal in one series, and the second known signal is also two units in the other packet signal. You may form by repeating.

  Yet another embodiment of the present invention is a communication system. The communication system includes a transmission device that transmits a packet signal formed by a plurality of streams, and a reception device that receives a packet signal from the transmission device. The transmitting device arranges the first known signal in the sequence in which the data signal to be arranged in at least one of the plurality of sequences is arranged, and then arranges the second known signal in the plurality of sequences, When a packet signal is generated and the second known signal is arranged in a plurality of series, a plurality of series are arranged with a number of series larger than the number of series in which the data signal is arranged as one group. And the timing at which the second known signal is to be arranged is shifted from each other in units of each of the plurality of groups, and the receiving apparatus includes the second known signal included in the received packet signal. From the above, the transmission path characteristic with the transmitting apparatus is estimated.

  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, when transmitting the known signal for transmission path estimation, the precision of transmission path estimation can be improved, suppressing the fall of transmission efficiency.

  Before describing the present invention in detail, an outline will be described. Embodiments of the present invention relate to a MIMO system composed of at least two wireless devices. One of the wireless devices corresponds to a transmitting device, and the other corresponds to a receiving device. The transmission device generates a packet signal composed of a plurality of sequences. Here, in particular, processing when the transmission apparatus transmits a training signal will be described. For this reason, the adaptive modulation processing based on the above-described rate information and the beam forming are performed based on the received training signal. However, a known technique may be used for these, and description thereof is omitted here. Under the above circumstances, there is a possibility that the estimation accuracy of transmission path characteristics in the receiving apparatus may deteriorate due to the difference between the number of sequences in which known signals for AGC are arranged and the number of sequences in which known signals for transmission path estimation are arranged. There is. In addition, even when a training signal is transmitted, it is desired to suppress a decrease in transmission efficiency. Therefore, in this embodiment, the following processing is executed.

  The transmitting apparatus arranges AGC known signals in a sequence in which data is arranged. Therefore, when the data is arranged in one series, the AGC known signal is also arranged in one series. As a result, the amplification factor set in the receiving apparatus corresponds to the data reception intensity, so that the data reception characteristics are improved. In addition, when generating a training signal, the transmission apparatus arranges transmission path estimation known signals in a plurality of sequences, and at that time, the plurality of sequences are grouped into a plurality of groups. One group is defined so as to include a larger number of sequences than the number of sequences in which data is arranged. For example, when data is arranged in one series and the number of series is “4”, one group is formed by two series. Therefore, two groups are formed from the four sequences.

  Further, the transmission apparatus generates a packet signal by arranging the transmission path estimation known signals included in each of the two groups while shifting the timing. Therefore, at the timing when the known signal for channel estimation included in one group is arranged, the known signal for channel estimation contained in another group is not arranged, and the known channel for channel estimation in one group is known. The number of signal sequences can be reduced. As a result, the number of sequences in which the transmission path estimation known signal is arranged can be reduced at a predetermined timing. As a result, even if the number of sequences in which the AGC known signals are arranged is small, the number of sequences in which the transmission path estimation known signals are arranged is also reduced. Is done.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  4A and 4B show packet formats when the number of sequences is one in the communication system 100. FIG. FIGS. 4A to 4B correspond to the case where the number of packet signal sequences shown in FIGS. 3A to 3C is “1”. The difference between the two is the number of “HT-LTF” included in the packet signal. FIG. 4A is similar to the first stream in the packet format shown in FIG. Here, one “HT-LTF” is included in the packet format. On the other hand, FIG. 4B corresponds to the first stream in the packet format shown in FIG. That is, two “HT-LTF” are included in the packet signal. If the packet format of FIG. 4A is used, the period of “HT-LTF” can be shortened, so that transmission efficiency can be improved. On the other hand, if the packet format of FIG. 4B is used, it is a part of the packet format when the number of sequences is “2”, so that the packet format can be easily switched. Here, it is assumed that the packet format of FIG. 4B is used.

  FIGS. 5A to 5D show training signal packet formats in the communication system 100. FIG. 5 (a)-(d) are training signals for the packet signals in FIGS. 3 (a)-(c) and FIG. 4 (b). In the following, for the sake of clarity, “L-STF” to “HT-SIG” included in the packet format are omitted. That is, the configuration after “HT-STF” is shown. FIG. 5A shows a case where the number of sequences (hereinafter referred to as “main sequences”) in which data signals are arranged is “3”, and FIG. 5B shows that the number of main sequences is “2”. FIGS. 5C to 5D show the case where the number of main sequences is “1”. That is, in FIG. 5 (a), data signals are arranged from the first series to the third series, and in FIG. 5 (b), data signals are arranged in the first series and the second series, In FIGS. 5C to 5D, data signals are arranged in the first series.

  The arrangement from the first series to the third series in FIG. 5A to the arrangement related to HT-LTF is the same as the arrangement in FIG. However, in the subsequent stage, blank periods are provided from the first series to the third series. On the other hand, in a blank period from the first series to the third series, HT-LTF is arranged in the fourth series. Further, following the HT-LTF arranged in the fourth series, data is arranged from the first series to the third series. Note that the arrangement of HT-LTFs in the fourth series is the same as the arrangement in FIG.

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

  Of the first sequence and the second sequence in FIG. 5B, the arrangement related to HT-LTF is the same as the arrangement in FIG. However, in the subsequent stage, blank periods are provided in the first series and the second series. On the other hand, in the blank period in the first sequence and the second sequence, HT-LTF is arranged in the third sequence and the fourth sequence. Further, following the HT-LTF arranged in the third series and the fourth series, data is arranged in the first series and the second series. The arrangement of HT-LTFs in the third series and the fourth series is the same as the arrangement in FIG.

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

  The arrangement related to HT-LTF in the first series of FIG. 5C is equivalent to the arrangement for the first series of FIG. Here, two “HT-LTF” are arranged. However, in the subsequent stage, a blank period is provided in the first series. On the other hand, in the blank period in the first sequence, HT-LTF is arranged in the second sequence to the fourth sequence. Further, following the HT-LTF arranged from the second series to the fourth series, data is arranged in the first series. Here, the arrangement of HT-LTFs arranged from the second series to the third series is similar to the arrangement in FIG.

  FIG. 5D is configured in the same manner as FIG. 5C, but the combination of symbols “HT-LTF” in FIG. 5D is different from that in FIG. Here, the combination of codes “HT-LTF” is defined such that an orthogonal relationship is established between sequences. Further, in FIG. 5D, it is defined that the combination of “HT-LTF” codes is fixed for each of a plurality of sequences. Here, in FIG. 5D, as in FIG. 5C, “0 ns”, “−400 ns”, and “−200 ns” having high priorities even in the second to fourth series. Is used.

  One “HT-LTF” is arranged in the fourth series in FIG. 5A, that is, a series in which data is not arranged (hereinafter referred to as “sub-sequence”). Also, two “HT-LTFs” are arranged in the third series and the fourth series in FIG. Furthermore, four “HT-LTFs” are arranged from the second series to the fourth series in FIGS. When these are compared, the length of “HT-LTF” arranged in the subsequence in FIGS. 5C to 5D is the longest. That is, when the number of main sequences in a packet signal for which a training signal is to be generated decreases, the length of the sub sequence increases and transmission efficiency decreases. In particular, in FIGS. 5C to 5D, four “HT-LTFs” similar to the case of four sequences are arranged even though the number of subsequences is “3”. The present embodiment proposes a packet format for suppressing a reduction in transmission efficiency even in such a case.

  6A to 6D show other packet formats for training signals in the communication system 100. FIG. FIGS. 6A to 6D correspond to FIGS. 5A to 5D, respectively. In FIGS. 6A to 6D, the timing shift amount is defined while being associated with each of the plurality of sequences. Here, a timing shift amount “0 ns” is defined for the first sequence, a timing shift amount “−400 ns” is defined for the second sequence, and a timing shift amount “−” is defined for the third sequence. 200 ns ”is defined, and the timing shift amount“ −600 ns ”is defined for the fourth stream.

  Therefore, in FIG. 6A, “−600 ns” is used instead of the timing shift amount “0 ns” in the fourth series in FIG. 5A. In FIG. 6B, instead of the timing shift amounts “0 ns” and “−400 ns” in the third sequence and the fourth sequence in FIG. 5B, “−200 ns” and “−600 ns”. Is used. On the other hand, in FIGS. 6C to 6D, timing shift amounts “0 ns”, “−400 ns”, and “−200 ns” from the second series to the fourth series in FIGS. 5C to 5D are used. Instead of “−400 ns”, “−200 ns”, “−600 ns” are used.

  FIG. 6D is configured in the same manner as FIG. 6C, but the combination of symbols “HT-LTF” in FIG. 6D is different from that in FIG. Priorities are provided in advance for combinations of signs of “HT-LTF”. That is, the code combination in the first sequence in FIG. 3A has the highest priority, and the code combination in the fourth sequence has the lowest priority. In addition, a combination of codes is used in order from a combination of codes with higher priority for a sequence in which a data signal is arranged, and a code in order from a combination of codes with a higher priority is also used for a sequence in which no data signal is arranged. Use a combination of In this way, if the combination of codes is the same, calculation of transmission path characteristics for the “HT-LTF” portion of the sequence in which no data is arranged when the receiving apparatus performs the + − operation to extract each component. In addition, a common circuit can be used for the calculation of the transmission path characteristics for the “HT-LTF” portion of the sequence in which data is arranged.

  FIGS. 7A to 7D show still another packet format for training signals in the communication system 100. FIG. As described above, when the number of main sequences in a packet signal for which a training signal is to be generated decreases, the length of sub sequences increases and transmission efficiency decreases. FIGS. 7A and 7B are packet formats for solving such a problem. 7A is a packet format corresponding to FIGS. 5C to 5D, and FIG. 7B is a packet format corresponding to FIGS. 6C to 6D. FIGS. 7C to 7D show packet formats to be compared with FIGS. 7A to 7B. In FIG. 7A, a plurality of sequences forming packet signals, that is, “4” sequences are grouped into a plurality of groups. One group is defined to include a larger number of sequences than the number of sequences in which data is arranged. Here, one group is defined to include two sequences. That is, a first group is formed from the first series and the second series, and a second group is formed from the third series and the fourth series. That is, two groups are formed from “4” series.

  The first series of the first group includes “HT-STF” and “data”. In addition, “HT-LTF” in the first group and “HT-LTF” in the second group are arranged at different timings. Therefore, at the timing when “HT-LTF” in the first group is arranged, “HT-LTF” in the second group is not arranged, and vice versa. Therefore, the signal strength of “HT-LTF” in the first group and the signal strength of “HT-LTF” in the second group are set to a close value. As a result, in the receiving apparatus, the reception strengths of both are also close. In addition, since the number of sequences in which “HT-LTF” is arranged in both groups is “2”, and the number of sequences in which “HT-STF” is arranged is “1”, “HT-LTF”. ”And“ HT-STF ”are close to each other. Therefore, the amplification factor derived by “HT-STF” is close to the amplification factor suitable for the two groups of HT-LTFs. Thereby, in the receiving apparatus, the accuracy of channel estimation by “HT-LTF” is improved.

  Further, the arrangement of “HT-LTF” in the second group is defined in the same manner as in FIG. That is, since the arrangement when the number of sequences is two is made, the number of “HT-LTF” in the second group is “2”. Therefore, a decrease in transmission efficiency is suppressed. In FIG. 7B, “HT-LTF” is arranged as in FIG. The difference between the two is the value of the timing shift amount in CDD, but since this has already been described, the description thereof is omitted.

  The effects of the packet format of FIGS. 7A to 7B will be described in comparison with FIGS. 7C to 7D. As described above, the packet format shown in FIGS. 7A to 7B is higher than the packet format shown in FIGS. 5C to 5D and 6C to 6D. -LTF "can be reduced. On the other hand, a packet format having the same number of “HT-LTF” as the packet format of FIGS. 7A to 7B is shown as FIGS. 7C to 7D. In FIG. 7C, “HT-STF” and “Data 1” are arranged in the first series. On the other hand, “HT-LTF” is arranged from the first series to the fourth series, as in FIG. That is, “HT-LTF” based on four sequences is arranged. However, according to such a packet format, “HT-STF” is arranged in one sequence, but “HT-LTF” is arranged in four sequences, so the “HT-LTF” portion. Is likely to be larger than the received power of the “HT-STF” portion. For this reason, if amplification is performed at a gain set based on one HT-STF in the receiving apparatus, the “HT-LTF” portion is likely to be distorted. As a result, an error occurs when data 1 is received, and reception quality deteriorates.

  FIG. 7D is similar to FIG. 7C, but “HT-STF” is arranged from the first sequence to the fourth sequence. Therefore, the reception power of the “HT-STF” portion and the reception power of the “HT-LTF” portion are close to each other. As a result, even if amplification is performed at the set amplification factor, the “HT-LTF” portion is less likely to be distorted. However, since “Data 1” is arranged in one sequence, the received power of that portion is likely to be different from the received power of the “HT-STF” portion. As a result, the set amplification factor is not an appropriate value for the reception of the “data 1” portion, so an error occurs when data 1 is received, and reception quality deteriorates.

  In summary, according to the packet format as shown in FIGS. 7 (c)-(d), the “HT-LTF” per sequence is similar to the packet format of FIGS. 7 (a)-(b). The number decreases. However, the quality of channel estimation and reception quality in the cases of FIGS. 7C to 7D are worse than those in FIGS. 7A to 7B. On the other hand, the quality of channel estimation and reception quality in the cases of FIGS. 5 (c)-(d) and 6 (c)-(d) are the same as those in FIGS. 7 (a)-(b). However, as described above, the number of “HT-LTF” per sequence increases. Therefore, it can be said that the packet format shown in FIGS. 7A and 7B is a format for improving the transmission efficiency and suppressing the deterioration of the quality of the channel estimation and the reception quality.

  FIG. 8 shows a packet format of a packet signal finally transmitted in the communication system 100. FIG. 8 corresponds to a case where the packet signal of FIGS. 7A to 7B is modified. An arithmetic operation using an orthogonal matrix described later is performed on “HT-STF” and “HT-LTF” arranged in the first sequence and the second sequence in FIGS. As a result, “HT-STF4” is generated from “HT-STF1”. The same applies to “HT-LTF”. Further, CDD with timing shift amounts “0 ns”, “−50 ns”, “−100 ns”, and “−150 ns” is performed for each of the first to fourth streams. The absolute value of the timing shift amount at the second CDD is set to be smaller than the absolute value of the timing shift amount at the first CDD for HT-STF and HT-LTF. Similar processing is executed for “HT-LTF” arranged in the third series and the fourth series, “data 1” of the first series, and the like.

  FIG. 9 shows the configuration of the first radio apparatus 10a. The first radio apparatus 10a includes a first radio unit 20a, a second radio unit 20b, a fourth radio unit 20d, a baseband processing unit 22, a modem unit 24, an IF unit 26, and a control unit 30, which are collectively referred to as a radio unit 20. Including. Also, as signals, a first time domain signal 200a, a second time domain signal 200b, a fourth time domain signal 200d, which are collectively referred to as a time domain signal 200, a first frequency domain signal 202a, a second, which are collectively referred to as a frequency domain signal 202, A frequency domain signal 202b and a fourth frequency domain signal 202d are included. The second radio apparatus 10b is configured in the same manner as the first radio apparatus 10a. Therefore, in the following description, the description related to the reception operation corresponds to the process in the second radio apparatus 10b, and the description related to the transmission operation corresponds to the process in the first radio apparatus 10a.

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

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

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

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

  FIG. 10 shows the structure of a signal in the frequency domain. Here, one combination of subcarrier numbers “−28” to “28” shown in FIG. 1 is referred to as an “OFDM symbol”. In the “i” th OFDM symbol, subcarrier components are arranged in the order of subcarrier numbers “1” to “28” and subcarrier numbers “−28” to “−1”. Also, the “i−1” th OFDM symbol is arranged before the “i” th OFDM symbol, and the “i + 1” th OFDM symbol is arranged after the “i” th OFDM symbol. And In the part such as “L-SIG” in FIG. 3A and the like, a combination of subcarrier numbers “−26” to “26” is used for one “OFDM symbol”.

  Returning to FIG. In addition, the baseband processing unit 22 performs the packets shown in FIGS. 3A to 3C, 5A to 5B, 6A to 6B, and 7A to 7B. CDD is performed to generate a packet signal corresponding to the format. Further, the baseband processing unit 22 performs a steering matrix multiplication in order to perform transformation into the packet signal shown in the packet format of FIG. Details of these processes will be described later.

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

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

  The control unit 30 controls the timing of the first radio apparatus 10a. The control unit 30 cooperates with the IF unit 26, the modulation / demodulation unit 24, and the baseband processing unit 22 in FIGS. 3 (a)-(c), 4 (a)-(b), and FIG. 5 (a)-( b), packet signals having packet formats as shown in FIGS. 6 (a)-(b), 7 (a)-(b), and FIG. 8 are generated, and control for transmitting the generated packet signals is executed. . Here, the processing for generating the packet format shown in FIGS. 7A to 7B will be mainly described, but the same processing is executed for other packet formats.

  In the IF unit 26, data to be arranged in at least one of a plurality of series is input. Here, as shown in FIGS. 7A to 7B, data to be arranged in one series is input. The control unit 30 provides the baseband processing unit 22 with a series in which input data is arranged, that is, “HT-STF” arranged in the first series and a plurality of series in the subsequent stage of “HT-STF”. Is instructed to generate a packet signal from “HT-LTF” arranged in the data and data arranged in the first stream. As shown in FIGS. 3A to 3C, the control unit 30 includes “L-STF”, “L-LTF”, “L-SIG”, and “HT-SIG” in the previous stage of the HT-STF. An instruction is output to the baseband processing unit 22 so as to be arranged.

  When arranging “HT-LTF” in a plurality of sequences, the control unit 30 collects a plurality of sequences into a plurality of groups while making a number of sequences larger than the number of sequences in which data is arranged as one group. . In FIGS. 7A and 7B, since the two sequences are made one group, the four sequences are grouped into two groups. In addition, the control unit 30 shifts the timings at which “HT-LTF” should be arranged in units of each of the plurality of groups. That is, “HT-LTF” in the first group and “HT-LTF” in the second group are arranged at different timings.

  Here, as described in FIGS. 7A to 7B, two “HT-LTFs” are arranged for one series. That is, the entire “HT-LTF” is formed by repeating “HT-LTF” in the time domain. In addition, the combination of codes “HT-LTF” is defined so that an orthogonal relationship is established between sequences in the group. As a result, as described above, if the first component and the second component are added in the first group, the HT-LTF for the first sequence is extracted. Further, if the second component is subtracted from the first component in the first group, the HT-LTF for the second sequence is extracted.

  Note that the number of “HT-LTFs” arranged in one sequence is determined by the number necessary to establish the orthogonal relationship. Therefore, if the number of sequences to establish the orthogonal relationship is “2”, the number of “HT-LTF” per sequence is “2”. On the other hand, if the number of sequences to establish the orthogonal relationship is “3” or “4”, the number of “HT-LTF” per sequence is “4”. Therefore, when the number of sub-sequences is “3” as shown in FIGS. 5B to 5C, an orthogonal relationship is required between them, so that “4” “HT-LTFs” are Will be placed. In FIGS. 7A to 7B in the present embodiment, the number of sequences that need an orthogonal relationship is reduced by reducing the number of sequences included in one group. As a result, the number of “HT-LTF” per series is reduced.

  On the other hand, the control unit 30 arranges “HT-STF”, “HT-LTF”, and “data” in one series with respect to the baseband processing unit 22 as shown in FIG. Another packet signal is generated. Note that another “HT-LTF” is also included in another packet signal. For example, when the number of sequences in which data is arranged is “1”, the control unit 30 selects the packet format shown in FIGS. 7A to 7B when generating the training signal, and generates the training signal. When not, the packet format shown in FIG. 4B is selected. Among these, since the configuration of the first series is similar, switching of the packet format is easily realized.

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

  Furthermore, the control unit 30 causes the baseband processing unit 22 to use the timing shift amount in order from the timing shift amount with the highest priority for the first group. For example, in the case of FIG. 7A, “0 ns” is used for the first sequence and “−400 ns” is used for the second sequence. In addition, the control unit 30 causes the second group to use the timing shift amount in order from the timing shift amount with the highest priority. For example, in the case of FIG. 7A, “0 ns” is used for the third series, and “−400 ns” is used for the fourth series. Through the above processing, a packet signal having the packet format shown in FIG. 7A is generated.

  On the other hand, different timing shift amounts may be set for a plurality of sequences. For example, “0 ns” is set as the timing shift amount of the first sequence, “−400 ns” is set as the timing shift amount of the second sequence, and “−200 ns” is set as the timing shift amount of the third sequence. Is set, and “−600 ns” is set as the timing shift amount of the fourth stream. Through the above processing, a packet signal having the packet format shown in FIGS. 7B to 7D is generated.

  After the packet signal of the packet format as shown in FIGS. 5A to 5B, 6A to 6B, and 7A to 7B is generated by the above processing, the control unit 30 causes the baseband processing unit 22 to transform such packet signals. Further, the control unit 30 causes the radio unit 20 to transmit the modified packet signal. That is, the control unit 30 converts the packet format shown in FIGS. 5A to 5B, 6A to 6B, and 7A to 7B into the packet format shown in FIG. Deform. The baseband processing unit 22 performs CDD on the extended sequence after extending the number of sequences to the number of multiple sequences.

  On the other hand, the receiving device receives a packet signal from the transmitting device. The receiving device estimates transmission path characteristics with the transmitting device from the HT-LTF included in the received packet signal. The transmission path characteristics are derived, for example, by calculating the correlation between the HT-LTF included in the received packet signal and the HT-LTF stored in advance in the receiving apparatus. Further, the transmission path characteristics are derived in units of paths or sequences as shown in FIG. Therefore, the transmission path characteristics are generally shown as a matrix. Further, the reception device generates rate information from the derived transmission path characteristics and notifies the transmission device of the rate information. The control unit 30 of the transmission apparatus causes the modulation / demodulation unit 24 to set a modulation scheme based on the received rate information. Further, based on the received rate information, the control unit 30 causes the baseband processing unit 22 to set the number of sequences and causes the IF unit 26 to set the coding rate.

  Further, the receiving apparatus may perform beam forming at the time of transmission based on the derived transmission path characteristics. Alternatively, the reception device may notify the transmission device of the derived transmission path characteristics, and the transmission device may perform beamforming at the time of transmission.

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

  FIG. 11 shows the configuration of the baseband processing unit 22. The baseband processing unit 22 includes a reception processing unit 50 and a transmission processing unit 52. The reception processing unit 50 executes a part corresponding to the reception operation among the operations in the baseband processing unit 22. That is, the reception processing unit 50 performs adaptive array signal processing on the time domain signal 200, and for that purpose, derivation of the weight vector of the time domain signal 200 is performed. Further, the reception processing unit 50 outputs the result of array synthesis as the frequency domain signal 202. Note that the reception processing unit 50 may generate rate information based on the frequency domain signal 202. Since the generation of rate information may be a known technique as described above, the description thereof is omitted.

  The transmission processing unit 52 executes a part corresponding to the transmission operation among the operations in the baseband processing unit 22. That is, the reception processing unit 50 generates the time domain signal 200 by converting the frequency domain signal 202. In addition, the transmission processing unit 52 associates a plurality of sequences with the plurality of antennas 12, respectively. Further, the transmission processing unit 52 executes CDD as shown in FIGS. 5 (a)-(b), 6 (a)-(b), and 7 (a)-(b). The steering matrix calculation as shown in FIG. Note that the transmission processing unit 52 finally outputs the time domain signal 200. On the other hand, the transmission processing unit 52 transmits the packet signals shown in FIGS. 5A to 5B, 6A to 6B, and 7A to 7B. Beam forming may be performed. Since beam forming may be a known technique as described above, description thereof is omitted.

  FIG. 12 shows the configuration of the reception processing unit 50. The reception processing unit 50 includes an FFT unit 74, a weight vector deriving unit 76, a first combining unit 80a, a second combining unit 80b, a third combining unit 80c, and a fourth combining unit 80d, which are collectively referred to as a combining unit 80.

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

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

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

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

ここで、δは、シフト量を示し、ｌは、サブキャリア番号を示している。さらに、行列Ｃと系列との乗算は、サブキャリアを単位にして実行される。すなわち、分散部６６は、Ｌ−ＳＴＦ等内での循環的なタイミングシフトを系列単位に実行する。また、タイミングシフト量は、図３（ａ）−（ｃ）、図５（ａ）−（ｂ）、図６（ａ）−（ｂ）、図７（ａ）−（ｂ）のごとく設定される。 FIG. 13 shows the configuration of the transmission processing unit 52. The transmission processing unit 52 includes a distribution unit 66 and an IFFT unit 68. The dispersion unit 66 associates the frequency domain signal 202 with the antenna 12. The distribution unit 66 corresponds to the packet formats in FIGS. 3A to 3C, 5A to 5B, 6A to 6B, and 7A to 7B. CDD is performed to generate a packet signal. CDD is performed as matrix C as follows.

Here, δ indicates a shift amount, and l indicates a subcarrier number. Further, the multiplication of the matrix C and the sequence is executed in units of subcarriers. That is, the distribution unit 66 performs a cyclic timing shift within the L-STF or the like on a sequence basis. Further, the timing shift amount is set as shown in FIGS. 3A to 3C, 5A to 5B, 6A to 6B, and 7A to 7B. The

  The distribution unit 66 multiplies the training signal generated as shown in FIGS. 5A to 5B, 6A to 6B, and 7A to 7B by a steering matrix. By doing so, the number of training signal sequences is increased to the number of multiple sequences. Here, the dispersion unit 66 extends the order of the input signal to the number of a plurality of sequences before performing multiplication. In the case of FIGS. 7A to 7B, since “HT-STF” and the like arranged in the first sequence and the second sequence are input, the number of input signals is “2”. Here, it is represented by “Nin”.

  Therefore, the input data is indicated by a vector “Nin × 1”. Further, the number of the plurality of series is “4”, and is represented by “Nout” here. The distribution unit 66 extends the order of the input data from Nin to Nout. That is, the vector “Nin × 1” is expanded to the vector “Nout × 1”. At that time, “0” is inserted into the components from the Nin + 1 line to the Nout line. On the other hand, with respect to “HT-LTF” arranged in the third sequence and the fourth sequence in FIGS. 7A to 7B, the components up to Nin are “0”, and Nout + 1 to Nout HT-LTF or the like is inserted in the components up to the line.

ステアリング行列は、「Ｎｏｕｔ×Ｎｏｕｔ」の行列である。また、Ｗは、直交行列であり、「Ｎｏｕｔ×Ｎｏｕｔ」の行列である。直交行列の一例は、ウォルシュ行列である。ここで、ｌは、サブキャリア番号を示しており、ステアリング行列による乗算は、サブキャリアを単位にして実行される。さらに、Ｃは、前述のごとく、ＣＤＤを示す。ここで、ＣＤＤにおけるタイミングシフト量は、複数の系列のそれぞれに対して異なるように規定されている。すなわち、第１の系列に対して「０ｎｓ」、第２の系列に対して「−５０ｎｓ」、第３の系列に対して「−１００ｎｓ」、第４の系列に対して「−１５０ｎｓ」のようにタイミングシフト量が規定される。ＩＦＦＴ部６８は、分散部６６からの信号に対してＩＦＦＴを実行し、時間領域信号２００として出力する。 The steering matrix S is shown as follows.

The steering matrix is a “Nout × Nout” matrix. W is an orthogonal matrix, which is a “Nout × Nout” matrix. An example of an orthogonal matrix is a Walsh matrix. Here, l indicates a subcarrier number, and multiplication by the steering matrix is executed in units of subcarriers. Further, C represents CDD as described above. Here, the timing shift amount in the CDD is defined to be different for each of the plurality of sequences. That is, “0 ns” for the first sequence, “−50 ns” for the second sequence, “−100 ns” for the third sequence, “−150 ns” for the fourth sequence, etc. The amount of timing shift is defined in FIG. The IFFT unit 68 performs IFFT on the signal from the dispersion unit 66 and outputs it as a time domain signal 200.

  The operation of the wireless device 10 having the above configuration will be described. When the IF unit 26 receives data to be arranged in one sequence, the control unit 30 causes the baseband processing unit 22 to arrange the HT-STF in the sequence in which the data signal is arranged. In addition, the control unit 30 defines two groups as four groups and defines two groups for the four sequences, and arranges an HT-LTF in each of the two groups. At that time, the two groups of HT-LTFs are arranged at different timings. The baseband processing unit 22 transforms the packet signal by multiplying the packet signal thus generated by a steering matrix. The radio unit 20 transmits the modified packet signal from the plurality of antennas 12.

  According to the embodiment of the present invention, a plurality of sequences are grouped into a plurality of groups, and the timing at which each of the plurality of groups is to be arranged is shifted from each other. Therefore, the number of sequences per group can be reduced, and HT-STF And the difference in strength between HT-LTF can be reduced. Further, since the difference in intensity between HT-STF and HT-LTF is reduced, the amplification factor derived for HT-STF can be close to a value suitable for HT-LTF. In addition, since the amplification factor derived for HT-STF is close to a value suitable for HT-LTF, the accuracy of channel estimation based on HT-LTF can be improved. In addition, since the accuracy of channel estimation is improved, the accuracy of rate information can be improved.

  Further, since the accuracy of channel estimation is improved, the accuracy of beamforming control can be improved. Further, since the number of sequences in the group is smaller than the total number of sequences, the number of sequences to be orthogonally related is also reduced, and the number of HT-LTFs included in one sequence can be reduced. Since the number of HT-LTFs included in one sequence is reduced, transmission efficiency can be improved. Further, even if HT-STFs are arranged in one sequence, HT-LTFs are arranged in two sequences at a predetermined timing, so that the difference in strength between HT-STF and HT-LTF can be reduced. In addition, since the configuration of one sequence is similar between when the HT-LTF is arranged in one sequence and when the HT-LTF is arranged in a plurality of sequences, it is easy to switch between the two. Can be executed.

  In addition, when generating the training signal, the number of sequences in which HT-STF is arranged and the number of sequences in which data is arranged are the same, so that the gain set by HT-STF is the data. Correspondingly, deterioration of data reception characteristics can be suppressed. In addition, by defining a priority for the amount of timing shift and using each of a plurality of groups in order from the highest priority, the same amount of timing shift can be used. Further, the processing can be simplified by using a large amount of the same timing shift. In addition, when the number of a plurality of sequences is “2” and the number of sequences in which data is arranged is “1”, the receiving apparatus can be assigned to one of the plurality of sequences according to the reception status of HT-LTF. It can instruct the transmitting device whether data should be arranged. That is, transmission diversity can be executed.

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

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

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

  In the embodiment of the present invention, HT-LTFs are arranged at different timings in units of groups. However, the present invention is not limited to this, and may be arranged at the same timing, for example. FIG. 14 shows another packet format for training signals in the communication system 100. Data is arranged from the first series to the third series. The training signal is the same as that shown in FIG. According to this modification, since the HT-LTF period can be shortened, the transmission efficiency can be improved.

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

It is a figure which shows the spectrum of the multicarrier signal which concerns on the Example of this invention. It is a figure which shows the structure of the communication system which concerns on the Example of this invention. FIGS. 3A to 3C are diagrams showing packet formats in the communication system of FIG. 4A and 4B are diagrams showing packet formats when the number of sequences is one in the communication system of FIG. FIGS. 5A to 5D are diagrams showing a packet format for training signals in the communication system of FIG. FIGS. 6A to 6D are diagrams showing another training signal packet format in the communication system of FIG. FIGS. 7A to 7D are diagrams showing still another training signal packet format in the communication system of FIG. FIG. 3 is a diagram illustrating a packet format of a packet signal that is finally transmitted in the communication system of FIG. 2. It is a figure which shows the structure of the 1st radio | wireless apparatus of FIG. FIG. 10 is a diagram illustrating a configuration of a frequency domain signal in FIG. 9. It is a figure which shows the structure of the baseband process part of FIG. It is a figure which shows the structure of the process part for reception of FIG. It is a figure which shows the structure of the process part for transmission of FIG. It is a figure which shows the packet format for another training signal in the communication system of FIG.

Explanation of symbols

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

Claims (6)

A transmission device that transmits a packet signal formed by a plurality of sequences,
An input unit for inputting a data signal to be arranged in at least one of a plurality of series;
From the first known signal arranged in the series in which the data signal input in the input unit is arranged, the second known signal arranged in a plurality of series in the subsequent stage of the first known signal, and the data signal A generator for generating a packet signal;
A transmission unit for transmitting the packet signal generated in the generation unit,
When the second known signal is arranged in a plurality of sequences, the generating unit sets a plurality of sequences to a plurality of groups while setting a number of sequences larger than the number of sequences in which data signals are arranged as one group. A transmission apparatus characterized in that the timings at which the second known signals are to be arranged are shifted from each other in units of each of the plurality of groups.   In the second known signal included in the packet signal generated by the generation unit, a predetermined unit is repeated in the time domain, and a combination of codes of the predetermined unit has an orthogonal relationship between sequences in the group. The transmission apparatus according to claim 1, further comprising: The input unit inputs data signals to be arranged in one series,
When the second known signal is arranged in four sequences, the generating unit combines the four sequences into two groups, and groups each of the two groups, 3. The transmission apparatus according to claim 2, wherein the timing at which the second known signal is to be arranged is shifted from each other, and the second known signal is formed by repeating two units.   The generation unit generates another packet signal by arranging the first known signal, the second known signal, and the data signal in one series, and the second known signal is also generated in the other packet signal. 4. The transmission apparatus according to claim 3, wherein the signal is formed by repeating two units. A transmission method for transmitting a packet signal formed by a plurality of sequences,
A packet signal is generated by arranging a first known signal in a series in which a data signal to be arranged in at least one of a plurality of series is arranged, and then arranging a second known signal in the plurality of series. When the second known signals are arranged in a plurality of series, the plurality of series are grouped into a plurality of groups while a number of series larger than the number of series in which the data signal is arranged is made one group. The transmission method is characterized in that the timings at which the second known signals are to be arranged are shifted from each other in units of a plurality of groups. A transmission device for transmitting a packet signal formed by a plurality of sequences;
A receiving device for receiving a packet signal from the transmitting device;
The transmitting device arranges a first known signal in a sequence in which a data signal to be arranged in at least one of a plurality of sequences is arranged, and then arranges a second known signal in the plurality of sequences. Generating a packet signal and arranging the second known signal in a plurality of sequences, a plurality of sequences having a number larger than the number of sequences in which the data signal is arranged as one group, The timings at which the second known signals are to be arranged are shifted from each other in a plurality of groups and in units of each of the plurality of groups.
The communication apparatus, wherein the reception apparatus estimates a transmission path characteristic with the transmission apparatus from a second known signal included in the received packet signal.

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