JP2014039089A - Ofdm transmission device, ofdm transmission method, ofdm receiving device and ofdm receiving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an OFDM transmission device, an OFDM transmission method, an OFDM receiving device and an OFDM receiving method capable of optimally exhibit the frequency diversity effect in a case a disturbance power from neighboring channels is included to increase the durability against the disturbance from neighboring channels ensuring in a stable reception.SOLUTION: An identical data group is transmitted N times (N is an integer larger than 2). At least one time in the N times, the position of a BPSK or QAM modulated signal to be allocated to a sub-carrier is allocated to at least a position where is allocated in any time in the remaining N-1 times with respect to a center sub-carrier in an inverted order.

Description

  The present invention relates to a transmission apparatus or a transmission circuit that multiplexes and transmits a plurality of carriers like OFDM, a transmission method and program implemented by the transmission apparatus, and a reception apparatus that receives a signal transmitted by the OFDM or The present invention relates to a receiving circuit, a receiving method executed by the receiving device, and a program.

  Currently, in various digital communications such as terrestrial digital broadcasting and IEEE802.11a, an OFDM (Orthogonal Frequency Division Multiplexing) method is widely adopted as a transmission method. The OFDM scheme is a scheme that transmits a plurality of narrowband digitally modulated signals by frequency multiplexing using a plurality of subcarriers orthogonal to each other, and is therefore a transmission scheme with excellent frequency utilization efficiency.

  Further, in the OFDM system, one symbol section is composed of an effective symbol section and a guard interval section, and a part of the signal of the effective symbol section is copied and inserted into the guard interval section so as to have periodicity within the symbol. . For this reason, it is possible to reduce the influence of inter-symbol interference caused by multipath interference, and it has excellent resistance to multipath interference.

  Up to now, the wireless LAN standard in IEEE 802.11 has been mainly targeted at indoor communication, and the physical layer standards are 11b (maximum 11 Mbps), 11a and 11g (maximum 54 Mbps), 11n (maximum 600 Mbps), 11ac (maximum) 6.9 Gbps), and the addition of standards mainly based on the increase in transmission capacity continues. On the other hand, smart meters to realize smart grids have been fully studied, and accordingly, the need for low-rate transmission outdoors has increased, and the use of specific low-power radio for such applications has increased. Discussions such as possible frequency assignments continue. From these backgrounds, a study toward the establishment of a new communication standard using the sub-GHz band has started, and TGah, which is based on a wireless LAN standard using a frequency band of 1 GHz or less in IEEE 802.11, was launched in 2010. ing. The main required specifications in TGah are “data rate 100 kbps and maximum transmission distance 1 km”.

  In TGah, various technical proposals from the conventional wireless LAN standard have been proposed by various companies in order to satisfy this required specification. Above all, in order to secure a transmission distance of 1 km by a low power output, a method having the highest transmission error resistance (BPSK modulation / error correction (convolutional code) coding rate 1/2) used in a conventional wireless LAN. However, it is considered that a robust transmission method is necessary. For this reason, in TGah, increasing the robustness by repeatedly transmitting the same data is cited as an effective measure.

  There is Non-Patent Document 1 as a repetitive transmission method, and three patterns are presented as a repetitive method.

  First, as shown in FIG. 46, in symbol number p + 1 (p is an integer greater than or equal to 0), simply repeat transmission in the symbol direction while maintaining the same data arrangement as the subcarrier of symbol number p. Yes. The horizontal axis in FIG. 46 indicates the subcarrier direction, and the central subcarrier number is displayed as 0. Here, as a repetition, the same data is sent twice, and on the receiving side, the same data is received and the data is synthesized and decoded to obtain a power gain of 3 dB, which is robust. Increases nature. In addition, FIG. 47 shows an inter-axis domain signal obtained by inverse Fourier transform of an OFDM subcarrier that is a frequency domain signal. Here, since the same data is arranged at the same subcarrier position, the time domain signals of symbol number p and symbol number p + 1 have the same waveform. As described above, the OFDM signal has a guard interval obtained by copying a part of the signal. In the reception processing, generally, synchronization processing such as carrier frequency shift and symbol position is performed by correlating the guard interval and the copy source portion. If the two symbols are the same signal, the correlation between the symbol number p and the symbol number p + 1 can be taken to obtain a larger number of samples for calculating the correlation than the correlation only in the guard interval section. It is also possible to increase the calculation accuracy and increase the accuracy of the synchronization processing based on the correlation value.

  Second, as shown in FIG. 48, symbol number p and symbol number p + 1 are independent, and the same data is arranged in different subcarriers within the same symbol. Here, the data group on the plus side of the subcarrier number is also arranged on the minus side. As a repetition, the same data is sent twice, and on the receiving side, a power gain of 3 dB can be obtained by synthesizing and decoding in the same manner as before, and robustness is improved. Here, unlike the arrangement of FIG. 46, since the same data exists at different subcarrier positions, even if multipath interference exists and a specific subcarrier is lost and decoding is difficult, the same data at different subcarrier positions is used. If data is not lost, demodulation is possible using the data of the subcarrier, and a frequency diversity effect can be obtained.

  As shown in FIG. 49, the third is a configuration in which two data groups are exchanged and arranged in the subcarrier direction in symbol number p and symbol number p + 1. Again, the same data is sent twice as a repetition, and on the receiving side, by combining and decoding using the same data, a power gain of 3 dB can be obtained and the robustness can be improved. . Further, similar to the arrangement of FIG. 48, since the same data exists at different subcarrier positions, even when multipath interference exists and a specific subcarrier is lost and decoding is difficult, the same data at different subcarrier positions is obtained. If data is not lost, demodulation is possible using the data of the subcarrier, and a frequency diversity effect can be obtained.

  In Patent Document 1, when transmitting m pieces of data (m is an integer of 1 or more) over m symbols using a specific subcarrier within an OFDM frame, each of the specific subcarriers is transmitted. In contrast, the arrangement of data is changed in the symbol direction. As a result, even if a certain symbol disappears due to fading fluctuations, m data can be demodulated due to the time diversity effect using data in other symbols.

JP 2000-196559 A

Heejung Yu and two others, “Repetition Schemes for TGah”, November 7, 2011, IEEE, Internet (URL: https://mentor.ieee.org/802.11/documents?is_group=00ah,11-11-1490- 01-00ah-repetition-schemes-for-tgah.pptx)

  However, since Patent Document 1 correctly transmits data to be added to a specific subcarrier in a fading environment and the content of each data string in the transmission frame is the same, it is not a solution for data retransmission. .

  Further, the three arrangement patterns of Non-Patent Document 1 have the following problems. In wireless communication, information transmission is performed using various channels, and adjacent channels of a desired channel are used for different users and different purposes. Since the power of the transmitted radio wave is attenuated according to the distance, even if the transmission power is constant, each transmitter as a transmission source exists in various places. It varies greatly from one to another. For this reason, as shown in FIG. 50, the received power reaching the receiver may be extremely higher in the power of the adjacent channel than the power of the desired channel. In this case, the out-of-band signal of the adjacent channel becomes a large interference source in the desired channel and causes a transmission error. As shown in FIG. 50, the interference power from the adjacent channel is not uniform within the desired channel, and increases as the distance from the adjacent channel increases, and decreases as the distance from the adjacent channel increases. Here, in the first arrangement (see FIG. 46) in Non-Patent Document 1, data closer to a subcarrier closer to the adjacent channel is more likely to be erroneous due to the influence of adjacent channel interference. Since the data arrangement is exactly the same, as shown in FIG. 51, the same data at the same subcarrier position is also likely to be erroneous in symbol number p + 1, and the frequency diversity effect cannot be obtained at all, and the two data Even if the combined demodulation is performed, a data error due to adjacent channel interference cannot be reduced, and eventually a packet error occurs. In the second arrangement shown in FIG. 48, since the same data is retransmitted at a different carrier position, there is a frequency diversity effect. However, as shown in FIG. 52, the influence of the disturbance is not uniform with respect to the data position, and deviation occurs. The same applies to the third arrangement shown in FIG. 49. Since the same data is retransmitted at a different carrier position, there is a frequency diversity effect. However, as shown in FIG. 53, the influence of disturbance is not uniform. As a result, an error-prone carrier is generated, and a packet error is finally generated.

  In order to solve the above-described problem, an OFDM transmission apparatus according to one aspect of the present invention transmits the same data group N times (N is an integer of 2 or more). And a subcarrier modulation unit that assigns a BPSK or QAM modulated signal to an OFDM subcarrier, and the subcarrier modulation unit is configured to transmit a BPSK or QAM modulated signal at least once among the N times. The allocation positions to the subcarriers are configured such that the allocation positions are assigned in the opposite order around the center subcarrier with respect to the allocation positions at least once among the remaining N-1 times.

  According to the above aspect, when there is a disturbance from an adjacent channel in a desired channel band, the interference becomes stronger in a subcarrier closer to the adjacent channel, but the data groups are allocated in the opposite order. Therefore, the total interference level for the same data is the same for all data, and the frequency diversity effect can be maximized by the combining process on the receiving side, and the adjacent channel interference The tolerance is improved and stable reception is possible.

It is a block diagram showing the structure of the OFDM transmitter 1 in Embodiment 1 of this invention. It is a schematic diagram showing the structure of the OFDM frame in Embodiment 1 of this invention. It is a schematic diagram showing an OFDM symbol. It is a schematic diagram showing the OFDM symbol structure of LTF. It is a schematic diagram showing the concept of waveform shaping. 3 is a block diagram illustrating a configuration of a subcarrier modulation unit 21 in the OFDM transmission device 1. FIG. It is a schematic diagram showing the mapping of BPSK and QPSK. It is a schematic diagram showing the data arrangement with respect to the subcarrier in Embodiment 1 of this invention. It is a block diagram showing the structure of the OFDM receiver 1001 in Embodiment 1 of this invention. 2 is a block diagram illustrating a configuration of a synthesis equalization unit 1201 in an OFDM receiver 1001. FIG. It is a schematic diagram showing a mode that adjacent channel interference is included. It is the schematic diagram (1) showing the data arrangement | positioning with respect to a subcarrier of the aspect different from FIG. It is a schematic diagram (2) showing the data arrangement with respect to a subcarrier of the aspect different from FIG. It is a block diagram showing the structure of the OFDM transmission apparatus 2 in Embodiment 2 of this invention. 3 is a block diagram illustrating a configuration of a subcarrier modulation unit 22 in the OFDM transmission device 2. FIG. It is a schematic diagram showing the data arrangement | positioning with respect to a subcarrier in Embodiment 2 of this invention. It is a block diagram showing the structure of the OFDM receiver 1002 in Embodiment 2 of this invention. 2 is a block diagram illustrating a configuration of a synthesis equalization unit 1202 in an OFDM receiving apparatus 1002. FIG. It is a schematic diagram showing a mode that adjacent channel interference is included. FIG. 17 is a schematic diagram (1) illustrating a data arrangement with respect to subcarriers in a manner different from that in FIG. 16. It is the schematic diagram (2) showing the data arrangement | positioning with respect to a subcarrier of the aspect different from FIG. It is a block diagram showing the structure of the OFDM transmission apparatus 3 in Embodiment 3 of this invention. 3 is a block diagram illustrating a configuration of a subcarrier modulation unit 23 in the OFDM transmission device 3. FIG. It is a figure showing the relationship between a data sequence and modulation in normal QPSK modulation and QPSK modulation of the present invention. It is a schematic diagram showing the data arrangement with respect to the subcarrier in Embodiment 3 of this invention. It is a block diagram showing the structure of the OFDM receiver 1003 in Embodiment 3 of this invention. FIG. 11 is a block diagram illustrating a configuration of an IQ combining unit 1401 in the OFDM receiving apparatus 1003. It is a block diagram showing the structure of the OFDM transmission apparatus 4 in Embodiment 4 of this invention. 3 is a block diagram illustrating a configuration of a subcarrier modulation unit 24 in the OFDM transmission device 4. FIG. It is a schematic diagram showing the data arrangement with respect to the subcarrier in Embodiment 4 of this invention. It is a block diagram showing the structure of the OFDM receiver 1004 in Embodiment 4 of this invention. 3 is a block diagram illustrating a configuration of a synchronization unit 1105 in the OFDM receiving apparatus 1001 according to Embodiment 1. FIG. It is a schematic diagram showing that the OFDM symbol is delayed by the OFDM effective symbol length. FIG. 10 is a block diagram illustrating a configuration of a synchronization unit 1505 in an OFDM receiving apparatus 1004 of a fourth embodiment. It is a schematic diagram showing having delayed the OFDM symbol length OFDM symbol length. It is a schematic diagram showing the data arrangement with respect to the subcarrier in Embodiment 4 of this invention. FIG. 37 is a schematic diagram showing a data arrangement for subcarriers in a different mode different from FIG. 36. It is a block diagram showing the structure of the OFDM receiver 1005 in Embodiment 5 of this invention. FIG. 11 is a block diagram illustrating a configuration of a transmission path characteristic estimation unit 1707 in the OFDM receiver 1005. It is a schematic diagram showing the data arrangement | positioning with respect to the subcarrier different from FIG. 12 which can apply calculation of CPE in Embodiment 5 of this invention. It is a block diagram showing the structure of the OFDM transmitter 6 in Embodiment 6 of this invention. 3 is a block diagram illustrating a configuration of a subcarrier modulation unit 26 in the OFDM transmission device 6. FIG. It is a schematic diagram showing the data arrangement | positioning with respect to a subcarrier in Embodiment 6 of this invention. It is a block diagram showing the structure of the OFDM receiver 1006 in Embodiment 6 of this invention. FIG. 11 is a block diagram illustrating a configuration of a transmission path characteristic estimation unit 1807 in the OFDM receiver 1006. It is a schematic diagram (1) of the data arrangement | positioning with respect to a subcarrier in a nonpatent literature 1. 6 is a schematic diagram showing an OFDM symbol (time domain signal) in Non-Patent Document 1. FIG. It is a schematic diagram (2) of the data arrangement | positioning with respect to a subcarrier in a nonpatent literature 1. It is a schematic diagram (3) of the data arrangement | positioning with respect to a subcarrier in a nonpatent literature 1. It is the schematic diagram which showed presence of the adjacent channel disturbance. FIG. 47 is a schematic diagram showing the presence of adjacent channel interference with respect to the data arrangement of FIG. 46. FIG. 49 is a schematic diagram showing the presence of adjacent channel interference with respect to the data arrangement of FIG. 48. FIG. 50 is a schematic diagram showing the presence of adjacent channel interference with respect to the data arrangement of FIG. 49.

A first transmission device, which is an aspect of the present invention, is a transmission device using an OFDM scheme,
In order to transmit the same data group N times (N is an integer equal to or greater than 2), a subcarrier modulation unit that assigns a BPSK or QAM modulated signal to the OFDM subcarrier based on a predetermined rule for the same data group And the subcarrier modulation unit assigns at least one of the N times the position of the BPSK or QAM modulated signal to the subcarrier at least one of the remaining N-1 times. The allocation positions are assigned in the opposite order with the center subcarrier as the center.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  The second transmitting apparatus, which is an aspect of the present invention, is configured such that the N is 2 in the first transmitting apparatus.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  According to a third transmitting apparatus, which is an aspect of the present invention, in the first transmitting apparatus, the subcarrier modulation unit divides the subcarrier of the OFDM1 symbol into N, and the same for each divided subcarrier. The data group is assigned.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  According to another aspect of the present invention, in the fourth transmission device, in the first transmission device, the subcarrier modulation unit allocates one data group to one OFDM symbol, and uses N OFDM symbols. , N identical data groups are allocated.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  According to another aspect of the present invention, in the fifth transmission device, in the first transmission device, the subcarrier modulation unit converts the signal allocated to the subcarrier to a complex conjugate at least once among the N times. , The configuration.

  According to this aspect, when there is interference from an adjacent channel, the frequency diversity effect can be maximized by combining processing on the reception side, resistance to adjacent channel interference is improved, and stable reception is possible. Furthermore, the time domain signal of at least one data group symbol is complex conjugate with the time domain signal of at least one symbol of the remaining data group, and the two symbols are synchronized based on the correlation with the OFDM symbol length. Since processing can be performed and the number of samples effective for correlation calculation increases, the accuracy of correlation calculation can be improved and the accuracy of synchronization processing can be expected to improve.

  A sixth transmitting apparatus, which is an aspect of the present invention, is configured such that, in the fifth transmitting apparatus, the data group allocated in the opposite order with the center subcarrier as the center is allocated in a complex conjugate.

  According to this aspect, when there is interference from an adjacent channel, the frequency diversity effect can be maximized by combining processing on the reception side, resistance to adjacent channel interference is improved, and stable reception is possible. Furthermore, the time domain signal of the symbol assigned with the inversion arrangement and complex conjugate becomes complex conjugate with respect to the time domain signal of at least one symbol of the remaining data group, and the correlation between the two symbols with the OFDM symbol length. Since synchronization processing can be performed based on the number of samples and the number of samples effective for correlation calculation increases, the accuracy of correlation calculation can be improved and the accuracy of synchronization processing can be expected to improve.

  In a seventh transmission device according to an aspect of the present invention, in the first transmission device, the subcarrier modulation unit further includes the same data, and further, the I-axis (in-phase component) and Q-axis (orthogonal component) of the subcarrier. ) So that it can be repeatedly transmitted using both axes, and the I axis and Q axis are mapped to the I axis and Q axis of different subcarriers, respectively.

  According to this aspect, when there is interference from an adjacent channel, the frequency diversity effect can be maximized by the combining process on the receiving side, and the frequency diversity effect can be exhibited even in multipath interference. The resistance to interference and multipath interference is improved, and stable reception is possible.

  An eighth transmission apparatus according to an aspect of the present invention is the first transmission apparatus, wherein the subcarrier modulation unit divides the data group into M groups (M is 2 or more) and uses predetermined symbols. The data group is allocated, and the M groups are allocated one by one to M symbols other than the predetermined symbol.

  According to this aspect, the phase rotation amount between symbols that are repeatedly transmitted can be calculated using the received signals of many data carriers other than the pilot, so the average parameter in the phase rotation calculation is Since the accuracy of final phase rotation calculation can be improved, phase tracking can be performed correctly even in a noise environment, high-precision equalization processing can be performed, and stable reception is possible.

  In a ninth transmission device according to an aspect of the present invention, in the eighth transmission device, the N is 2, the M is 2, and the M symbols other than the predetermined symbols are the predetermined symbols. The symbols are the symbols before and after the symbol.

  According to this aspect, the phase rotation amount between symbols that are repeatedly transmitted can be calculated using the received signals of many data carriers other than the pilot, so the average parameter in the phase rotation calculation is Since the accuracy of final phase rotation calculation can be improved, phase tracking can be performed correctly even in a noise environment, high-precision equalization processing can be performed, and stable reception is possible.

  The first receiving apparatus, which is an aspect of the present invention, includes a receiving unit that receives a transmission signal that transmits the same data group N times (N is an integer of 2 or more), and at least of the N times, At one time, the allocation position of the BPSK or QAM modulated signal to the subcarrier is in the opposite order with respect to the allocation position at least one of the remaining N-1 times, centering on the center subcarrier. Assign to the configuration.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  The second receiver, which is an aspect of the present invention, is the first receiver, wherein the transmission signal includes a known preamble signal at the head of the frame, and the receiver is configured to transmit a transmission line based on the preamble. A transmission path characteristic estimation unit that performs characteristic estimation, a disturbance detection unit that detects a disturbance signal existing in a desired band based on the preamble, and the N pieces of the same data are combined or selected, and a waveform A synthesis equalization unit that performs equalization, and in the synthesis equalization unit, the combining or selection includes transmission path characteristics estimated by the transmission path characteristic estimation section, and interference signals detected by the interference detection section. At least one of the detection results is used.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level received is the same for all data, and the frequency diversity effect is maximized on the receiving side by precise combining processing using the estimated channel characteristics and the interference detection result. Therefore, resistance to adjacent channel interference is improved and stable reception is possible.

  According to another aspect of the present invention, the third receiving device is the first receiving device, wherein the transmission signal assigns the data group to the complex conjugate at least once while the N data groups are allocated to the subcarriers. The reception unit has a correlation calculation unit, and the correlation calculation unit calculates a correlation by multiplying a signal delayed by an OFDM symbol length by a signal not delayed, and OFDM The interval integration is performed over the symbol length.

  According to this aspect, when there is interference from an adjacent channel, the frequency diversity effect can be maximized by combining processing on the reception side, resistance to adjacent channel interference is improved, and stable reception is possible. Furthermore, the time domain signal of at least one data group symbol is complex conjugate with the time domain signal of at least one symbol of the remaining data group, and the two symbols are synchronized based on the correlation with the OFDM symbol length. Since processing can be performed and the number of samples effective for correlation calculation increases, the accuracy of correlation calculation can be improved and the accuracy of synchronization processing can be expected to improve.

  According to another aspect of the present invention, in a fourth receiver, the first receiver includes a transmission signal including a known preamble signal at the head of the frame, and further including the same data group as a subcarrier I. Mapping is performed so that transmission can be further repeated using both axes (in-phase component) and Q-axis (quadrature component), and the mapping of the I-axis and Q-axis is performed for the I-axis and Q-axis of different subcarriers, respectively. Mapping, the receiving unit, a transmission path characteristic estimation unit that performs estimation of transmission path characteristics based on the preamble, a disturbance detection unit that detects a disturbance signal existing in a desired band based on the preamble, With respect to the N times of the same data, for each subcarrier, synthesis or selection is performed for waveform equalization, and for the same data group of the I axis and Q axis, I axis information and Q An IQ combining unit for combining or selecting information, wherein the combining or selecting includes: the transmission path characteristic estimated by the transmission path characteristic estimation unit; and the interference detected by the interference detection unit. At least one of the signal detection results is used, and in the IQ combining unit, the combination or selection of the I axis and the Q axis is performed based on the transmission path characteristics estimated by the transmission path characteristic estimation section and the interference detected by the interference detection section. At least one of the signal detection results is used.

  According to this aspect, when there is interference from an adjacent channel, the frequency diversity effect can be maximized by the accurate combining process using the transmission path characteristic estimation value and the interference detection result on the receiving side, and transmission By combining accurate I-axis information and Q-axis information using estimated path characteristics and interference detection results, frequency diversity effects can be achieved even in multipath interference, improving resistance to adjacent channel interference and multipath interference. , Stable reception becomes possible.

  According to another aspect of the present invention, in the fifth receiver, in the first receiver, the receiver includes a CPE calculator that calculates a phase rotation between symbols, and the CPE calculator includes the center The symbol using at least a part of signals of the data group allocated in the opposite order centering on the subcarrier and at least a part of signals of at least one data group among the other N-1 data groups The phase rotation between them is calculated.

  According to this aspect, the phase rotation amount between symbols that are repeatedly transmitted can be calculated using the received signals of many data carriers other than the pilot, so the average parameter in the phase rotation calculation is Since the accuracy of final phase rotation calculation can be improved, phase tracking can be performed correctly even in a noise environment, high-precision equalization processing can be performed, and stable reception is possible.

  A tenth transmission device, which is an aspect of the present invention, is a transmission device using an OFDM system, and in order to transmit the same data group twice, the same data group is based on a predetermined rule, A subcarrier modulation unit that allocates a BPSK or QAM modulated signal to an OFDM subcarrier, the subcarrier modulation unit assigning a position of the BPSK or QAM modulated signal to the subcarrier with respect to the first data group; The second data group is assigned in such an order that the level at which interference in the band is received becomes uniform when viewed in terms of the total level of two identical data.

  According to this aspect, when interference exists in the desired channel band, the same data group is set so that the total level of the interference received for the same data is the same level for any data. Repeated transmission is possible, and the frequency diversity effect can be maximized by combining processing on the receiving side, resistance to in-band interference is improved, and stable reception is possible.

  A first transmission method, which is an aspect of the present invention, is a transmission method using the OFDM method, and transmits the same data group N times (N is an integer of 2 or more). A subcarrier modulation step of allocating a BPSK or QAM modulated signal to an OFDM subcarrier based on a predetermined rule, wherein the subcarrier modulation step includes BPSK or QAM at least once among the N times The allocation positions of the modulated signals to the subcarriers are configured so as to be allocated in the opposite order around the center subcarrier with respect to the allocation positions in at least one of the remaining N-1 times.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  A first transmission circuit, which is an aspect of the present invention, is a transmission circuit using an OFDM system, and transmits the same data group N times (N is an integer of 2 or more). A subcarrier modulation circuit for assigning a BPSK or QAM modulated signal to an OFDM subcarrier based on a predetermined rule, wherein the subcarrier modulation circuit is BPSK or QAM at least one of the N times The allocation positions of the modulated signals to the subcarriers are configured so as to be allocated in the opposite order around the center subcarrier with respect to the allocation positions in at least one of the remaining N-1 times.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  A first transmission program, which is an aspect of the present invention, is a transmission program using the OFDM method, and the same data is transmitted in order to transmit the same data group N times (N is an integer of 2 or more). A subcarrier modulation step of allocating a BPSK or QAM modulated signal to an OFDM subcarrier based on a predetermined rule, wherein the subcarrier modulation step includes BPSK or QAM at least once among the N times The allocation positions of the modulated signals to the subcarriers are configured so as to be allocated in the opposite order around the center subcarrier with respect to the allocation positions in at least one of the remaining N-1 times.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  A first reception method, which is an aspect of the present invention, includes a reception step of receiving a transmission signal for transmitting the same data group N times (N is an integer of 2 or more), and at least of the N times, At one time, the allocation position of the BPSK or QAM modulated signal to the subcarrier is in the opposite order with respect to the allocation position at least one of the remaining N-1 times, centering on the center subcarrier. Assign to the configuration.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  The first receiving circuit, which is an aspect of the present invention, includes a receiving circuit that receives a transmission signal for transmitting the same data group N times (N is an integer of 2 or more), and at least of the N times, At one time, the allocation position of the BPSK or QAM modulated signal to the subcarrier is in the opposite order with respect to the allocation position at least one of the remaining N-1 times, centering on the center subcarrier. Assign to the configuration.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  A first reception program, which is an aspect of the present invention, includes a reception step of receiving a transmission signal for transmitting the same data group N times (N is an integer of 2 or more), and at least of the N times, At one time, the allocation position of the BPSK or QAM modulated signal to the subcarrier is in the opposite order with respect to the allocation position at least one of the remaining N-1 times, centering on the center subcarrier. Assign to the configuration.

  According to this aspect, when there is interference from an adjacent channel, the interference becomes stronger in the subcarrier closer to the adjacent channel. However, by assigning data groups in the opposite order, the same data can be assigned to the same data. On the other hand, the total interference level is the same for all data, and by combining processing on the receiving side, the frequency diversity effect can be maximized, the resistance to adjacent channel interference is improved, and stable. Reception is possible.

  A second transmission method, which is an aspect of the present invention, is a transmission method using the OFDM method, and in order to transmit the same data group twice, the same data group is based on a predetermined rule. A subcarrier modulation step of assigning a BPSK or QAM modulated signal to an OFDM subcarrier, wherein the subcarrier modulation step assigns an allocation position of the BPSK or QAM modulated signal to the subcarrier with respect to the first data group. The second data group is assigned in such an order that the level at which interference in the band is received becomes uniform when viewed in terms of the total level of two identical data.

  According to this aspect, when interference exists in the desired channel band, the same data group is set so that the total level of the interference received for the same data is the same level for any data. Repeated transmission is possible, and the frequency diversity effect can be maximized by combining processing on the receiving side, resistance to in-band interference is improved, and stable reception is possible.

  The second transmission circuit, which is an aspect of the present invention, is a transmission circuit using the OFDM method, and transmits the same data group twice based on a predetermined rule in order to transmit the same data group twice. A subcarrier modulation circuit for allocating a BPSK or QAM modulated signal to an OFDM subcarrier, wherein the subcarrier modulation circuit assigns an allocation position of the BPSK or QAM modulated signal to a subcarrier with respect to a first data group; The second data group is assigned in such an order that the level at which interference in the band is received becomes uniform when viewed in terms of the total level of two identical data.

  According to this aspect, when interference exists in the desired channel band, the same data group is set so that the total level of the interference received for the same data is the same level for any data. Repeated transmission is possible, and the frequency diversity effect can be maximized by combining processing on the receiving side, resistance to in-band interference is improved, and stable reception is possible.

  The second transmission program, which is an aspect of the present invention, is a transmission program using the OFDM system, and in order to transmit the same data group twice, the same data group is based on a predetermined rule. A subcarrier modulation step of assigning a BPSK or QAM modulated signal to an OFDM subcarrier, wherein the subcarrier modulation step assigns an allocation position of the BPSK or QAM modulated signal to the subcarrier with respect to the first data group. The second data group is assigned in such an order that the level at which interference in the band is received becomes uniform when viewed in terms of the total level of two identical data.

  According to this aspect, when interference exists in the desired channel band, the same data group is set so that the total level of the interference received for the same data is the same level for any data. Repeated transmission is possible, and the frequency diversity effect can be maximized by combining processing on the receiving side, resistance to in-band interference is improved, and stable reception is possible.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
A first embodiment of an OFDM transmitter and receiver according to the present invention will be described with reference to FIGS. Here, a part of the 802.11ah format under study by TGah in IEEE 802.11 is described as an example, but the application destination is not limited to this. In addition, since it is in the standard formulation stage, the 802.11ah format given as an example is not limited to this format because it may be changed in the future.

  FIG. 1 is a block diagram showing a configuration of OFDM transmission apparatus 1 according to Embodiment 1 of the present invention. The OFDM transmitter 1 according to the first embodiment of the present invention includes an OFDM modulator 11, a D / A converter 107, an RF output unit 108, and an antenna 109. The OFDM modulation unit 11 includes an error correction coding unit 101, an interleaving unit 102, a subcarrier modulation unit 21, a synchronization signal generation unit 103, an inverse Fourier transform unit 104, a guard interval addition unit 105, and a symbol shaping unit 106.

  The data to be transmitted is input to the error correction encoding unit 101, and is encoded after adding redundant bits for error correction. As an example, convolutional coding is performed here. The error-corrected encoded signal is input to the interleave unit, and the signal order is rearranged and output to the subcarrier modulation unit 21. Subcarrier modulation section 21 maps the interleaved signal to each OFDM subcarrier using digital modulation such as BPSK or QAM, and outputs the result to inverse Fourier transform section 104.

  On the other hand, the synchronization signal generation unit 103 generates a synchronization preamble signal such as STF (Short Training Field) or LTF (Long Training Field) and outputs the same to the inverse Fourier transform unit 104. Here, FIG. 2 shows an example of a frame format that is a temporal relationship between the STF, the LTF, and the transmission data group. As shown in FIG. 2, the frame format starts with STF and then becomes LTF. The LTF is followed by a SIGNAL symbol, followed by a data symbol. The signal included in the SIGNAL symbol includes parameter information necessary for demodulation.

  The inverse Fourier transform unit 104 performs inverse Fourier transform on the OFDM subcarriers generated by the subcarrier modulation unit 21 and the synchronization signal generation unit 103 to convert the frequency domain signal into a time domain signal, and a guard interval addition unit 105. Output to. As shown in FIG. 3, the guard interval adding unit 105 copies the latter half of the OFDM effective symbol and adds it to the head. However, in the LTF, as shown in FIG. 4, one guard interval is added to two OFDM effective symbols. The signal to which the guard interval is added is input to the symbol shaping unit 106, and the process of halving the amplitude of each sample before and after the OFDM symbol is performed on the first and last samples of the OFDM symbol as shown in FIG. Then, shaping is performed to suppress out-of-band power of the spectrum. The signal of the symbol shaping unit 106 is input to the D / A conversion unit 107, converted from a digital signal to an analog continuous signal, converted to a predetermined carrier frequency by the RF output unit 108, and transmitted by the antenna 109. Here, the OFDM transmission device 1 according to the first embodiment of the present invention is characterized by the subcarrier modulation unit 21.

  The configuration of the subcarrier modulation unit 21 is shown in FIG. The subcarrier modulation unit 21 includes a data holding unit 111, a mapping unit 112, and a subcarrier assignment unit 113. In the data holding unit 111, the input data of the subcarrier modulation unit 21 is held in a necessary section, which will be described later, and output to the multi-level modulation unit 112. The multi-level modulation unit 112 maps to BPSK, QPSK, 16QAM, 64QAM, etc. based on the input data. Here, for convenience of explanation, BPSK is also included in the multilevel modulation. An example of the mapping of BPSK and QPSK to input data is shown in FIG. 7 (16QAM and 64QAM are omitted). The complex signal after mapping is represented as x_n (n is an integer). The multi-level modulated signal is input to the subcarrier assignment unit 113, and the multi-level modulated signal x_n is arranged for each subcarrier number based on a predetermined rule, and is output to the inverse Fourier transform unit 104. Here, in the subcarrier modulation unit 21, the same data is used for the symbol number p (p is an integer of 0 or more) and the symbol number p + 1. Specifically, multi-level modulation is performed on the symbol number p based on the data input to the subcarrier modulation unit 21, and multi-level modulation is performed on the subcarrier number based on a predetermined rule. 2, multi-level modulation is performed on the same data as the symbol number p held in the data holding unit 111, and the multi-level modulation is performed on the subcarrier number based on a predetermined rule. Here, there is a feature in the arrangement rule of the multilevel modulation signal with respect to the subcarrier number in the symbol number p and the symbol number p + 1.

  FIG. 8 shows the rules for the arrangement of multilevel modulation signals with respect to the subcarrier numbers in symbol number p and symbol number p + 1. Here, for the sake of simplicity, subcarrier numbers are set to −13 to +13, and subcarrier number 0 corresponding to DC is set to Null. In addition, multilevel modulation signals from x_1 to x_26 are used. As shown in FIG. 8, the point that symbol number p and symbol number p + 1 are arranged in reverse order with respect to the subcarrier number and is repeatedly transmitted differs greatly from the previous example. When the symbol number p + 2 is reached, the data holding unit 111 holds new input data and arranges the multi-value modulated signal based on the data in the order of the subcarrier numbers opposite to each other with the symbol numbers p + 2 and p + 3. To do.

  Using the above repeating method, the OFDM transmitter 1 generates an OFDM signal and transmits it.

  FIG. 9 is a block diagram showing a configuration of OFDM receiving apparatus 1001 according to Embodiment 1 of the present invention. An OFDM receiver 1001 includes an antenna 1101, a tuner 1102, an A / D converter 1103, and an OFDM demodulator 1011. The OFDM demodulator 1011 includes an orthogonal transform unit 1104, a synchronization unit 1105, a Fourier transform unit 1106, a transmission path characteristic estimation unit 1107, a disturbance detection unit 1108, a synthesis equalization unit 1201, a demapper unit 1109, a demapper unit 1109, An interleave unit 1110 and an error correction unit 1111 are included.

  A tuner 1102 selects a received signal of a desired reception channel from a signal received by the antenna 1101, and an output of the tuner 1102 is converted from an analog signal to a digital signal by an A / D converter 1103, and an orthogonal demodulator 1104. The quadrature demodulation is performed at a fixed frequency, and the IF signal is converted into a complex baseband signal. The complex baseband signal is input to the synchronization unit 1105, and synchronization processing such as carrier frequency synchronization and signal timing synchronization is performed using the STF signal, the LTF signal, and the like, and then input to the Fourier transform unit 1106. Fourier transform section 1106 performs Fourier transform on the effective OFDM symbol period portion, and outputs the result to transmission path estimation section 1107, interference detection section 1108, and synthesis equalization section 1201. Here, the Fourier transform is assumed to be configured by FFT, but is not limited thereto.

  Transmission path characteristic estimation section 1107 estimates the distortion characteristics of the amplitude and phase that the received signal has received on the transmission path for each subcarrier, and outputs it to synthesis equalization section 1201. Here, transmission path characteristics are estimated using a pilot signal included in the LTF signal. In addition, the interference detection unit 1108 detects the interference wave in which the received signal is mixed in the transmission path for each subcarrier. Here, the pilot signal included in the LTF signal is used to calculate the difference between two symbols of the transmission path characteristics of the pilot signal. However, the present invention is not limited to this. The synthesis equalization unit 1201 performs amplitude phase correction (equalization) using the transmission path characteristics estimated by the transmission path characteristic estimation unit 1107 and the interference detection result detected by the interference detection unit 1108, and repeatedly transmits them. The same data in the processed signals is synthesized and output to the demapper unit 1109. The demapper unit 1109 performs a hard decision or a soft decision on the multi-level modulated signal based on the multi-level mapping, inputs the signal to the de-interleave unit 1110, performs de-interleave, and inputs it to the error correction unit 1111 To do. The error correction unit 1111 corrects the transmission error for the deinterleaved signal and restores the transmission information data.

  Here, the configuration of the synthesis equalization unit 1201 is shown in FIG. The synthesis equalization unit 1201 includes a data holding unit 1211 and a synthesis calculation unit 1212. The output signal of the Fourier transform unit 1106 is input to the data holding unit 1211, the necessary data is output to the synthesis operation unit 1212, the transmission path estimation value that is the output signal of the transmission path characteristic estimation unit 1107, and the interference detection unit 1108. Based on the output signal, equalization processing and synthesis processing are performed. Here, since the transmission signals are arranged as shown in FIG. 8, these same data are combined. For example, since the data of the subcarrier number “13” of the symbol number p and the data of the subcarrier number “−13” of the symbol number p + 1 are the same data, the two are combined as a pair. Specifically, the received signal at the corresponding symbol / subcarrier position is read from the data held in the data holding unit 1211, and the channel characteristic estimation value and the interference detection result at each symbol / subcarrier position are used. Then, equalization and synthesis are performed as in the following formula 1.

In Equation 1, the received signal is represented as Y, the transmission path characteristic estimation value as H, and the disturbance detection value as I. k represents a subcarrier number, and p represents a symbol number.

  Here, as shown in FIG. 11, consider a case where there is interference from an adjacent channel. At this time, since the repetitive transmission as shown in FIG. 8 is performed, for example, the level of interference received by the multilevel modulation signal x_26 at the symbol number p is the level of interference received by the multilevel modulation signal x_1 at the symbol number p. Although it is larger than the level, the symbol number p + 1 has an inverse relationship, and the total interference level using two symbols is the same level for any multi-level modulation signal. For this reason, the frequency diversity effect can be maximized by combining processing on the receiving side, resistance to adjacent channel interference is improved, and stable reception is possible.

  The subcarrier modulation unit 21 is configured to perform multi-level modulation with each symbol based on the data held by the data holding unit 111 at the symbol number p and symbol number p + 1. After performing the value modulation, the multi-level modulation signal may be held and used as the symbol number p + 1, or any configuration that can realize the arrangement of FIG.

  Note that although the synthesis operation unit 1212 is configured to combine two signals, it may be a process of selecting one of the two signals based on the interference detection value. That is, only the data with the smaller interference detection value level may be selected from the two identical data, and the equalization processing may be performed on the data with the transmission path characteristic value. Further, the composition operation is not limited to Equation 1, and any composition can be used as long as the composition can reduce the influence of interference.

  Note that the data arrangement in the first embodiment is configured using all subcarriers excluding the center subcarrier as shown in FIG. 8, but is not limited to this, and some subcarriers are used as shown in FIG. May be a pilot signal, and as shown in FIG. 13, the pilots may not be symmetrically arranged with respect to the center subcarrier, and may not be present on the same subcarrier in the symbol direction. . Further, the number of pilots may not be the same number on the left and right with respect to the center subcarrier, and the number of subcarriers may not be the same on the left and right.

(Embodiment 2)
Embodiment 2 of the OFDM transmitter and receiver according to the present invention will be described with reference to FIGS. The same constituent elements as those in FIGS. 1 to 13 are denoted by the same symbols, and the description thereof is omitted. The OFDM transmission apparatus 2 shown in FIG. 14 is significantly different from the OFDM transmission apparatus 1 according to Embodiment 1 with respect to the arrangement of multilevel modulation signals on subcarriers in the subcarrier modulation unit 22.

  FIG. 15 shows a configuration diagram of the subcarrier modulation unit 22. The subcarrier modulation unit 22 includes a data holding unit 121, a multilevel modulation unit 112, and a subcarrier assignment unit 123. The data holding unit 121 holds input data, and the multilevel modulation unit 112 multilevel modulation. Then, the subcarrier assignment unit 123 arranges the multi-level modulation signal for the subcarrier number according to a predetermined rule.

  Here, as repeated transmission, different data is transmitted for each symbol, and the same data is transmitted twice within the same symbol. A specific arrangement rule of the subcarrier assignment unit 123 is shown in FIG. As shown in FIG. 16, the multilevel modulation signals are arranged so as to be bilaterally symmetric about the center subcarrier (subcarrier number 0), which is different from the OFDM transmitter 1 in the first embodiment. It is.

  Using the above iterative method, the OFDM transmitter 2 generates and transmits an OFDM signal.

  FIG. 17 is a block diagram showing a configuration of OFDM receiving apparatus 1002 according to Embodiment 2 of the present invention. Compared with OFDM receiving apparatus 1001 in Embodiment 1, OFDM receiving apparatus 1002 differs in combining equalization of combining and equalizing section 1202 depending on the transmission format being different from that in Embodiment 1.

  The configuration of the synthesis equalization unit 1202 is shown in FIG. The synthesis equalization unit 1202 includes a data holding unit 1221 and a synthesis calculation unit 1222. The output signal of the Fourier transform unit 1106 is input to the data holding unit 1221, the necessary data is output to the synthesis operation unit 1222, the transmission path estimation value that is the output signal of the transmission path characteristic estimation unit 1107, and the interference detection unit 1108. Based on the output signal, equalization processing and synthesis processing are performed. Here, since the transmission signals are arranged as shown in FIG. 16, the same data in these symbols are combined. For example, since the data of the subcarrier number “13” and the data of the subcarrier number “−13” are the same data, the two are combined as a pair. Specifically, the received signal at the corresponding symbol / subcarrier position is read from the data held by the data holding unit 1221, and the channel characteristic estimation value and the interference detection result at each symbol / subcarrier position are used. Then, equalization and synthesis are performed as in the following formula 2.

In Expression 2, the received signal is represented as Y, the transmission path characteristic estimation value is represented as H, and the interference detection value is represented as I. k represents a subcarrier number, and p represents a symbol number.

  Here, as shown in FIG. 19, consider a case where there is interference from an adjacent channel. At this time, since the repetitive transmission as shown in FIG. 16 is performed, the level of interference received by the multi-level modulation signal x_1 is the level of interference received by the multi-level modulation signal x_13 when the region with the positive carrier number is seen. However, in the region where the carrier number is negative, the relationship is reversed, and the level of disturbance received by the total of two identical multi-level modulation signals is the same level for all multi-level modulation signals. For this reason, the frequency diversity effect can be maximized by combining processing on the receiving side, resistance to adjacent channel interference is improved, and stable reception is possible.

  The subcarrier modulation unit 22 is configured to perform multilevel modulation based on the data stored in the data storage unit 121. However, after performing multilevel modulation from x_1 to x_13, the multilevel modulation signal is stored. Then, it may be configured to use it repeatedly, and any configuration that can realize the arrangement of FIG. 16 may be used.

  In addition, although the synthetic | combination calculating part 1222 was set as the synthetic | combination process of two signals, it is good also as a selection process based on a disturbance detection value. That is, only the data with the smaller interference detection value level may be selected from the two identical data, and the equalization processing may be performed on the data with the transmission path characteristic value. Further, the composition operation is not limited to the expression 2, and any composition can be used as long as the composition can reduce the influence of interference.

  The data arrangement in the second embodiment is configured using all subcarriers except for the center subcarrier as shown in FIG. 16, but is not limited to this, and some subcarriers are used as shown in FIG. May be a pilot signal. Further, as shown in FIG. 21, the pilot may not be arranged symmetrically with respect to the center.

(Embodiment 3)
Embodiment 3 of the OFDM transmitter and receiver according to the present invention will be described with reference to FIGS. In addition, the same component as FIGS. 1-21 uses the same symbol, and description is abbreviate | omitted. The OFDM transmission apparatus 3 shown in FIG. 22 is significantly different from the OFDM transmission apparatus 1 according to Embodiment 1 with respect to the arrangement of multilevel modulation signals on subcarriers in the subcarrier modulation unit 23.

  FIG. 23 shows the configuration of the subcarrier modulation unit 23. The subcarrier modulation unit 23 includes a data holding unit 131, an I / Q retransmission QPSK modulation unit 132, a modulation signal holding unit 134, and a subcarrier assignment unit 133. The data holding unit 131 holds input data and inputs it to the I / Q retransmission QPSK modulation unit 132. The modulation in the I / Q retransmission QPSK modulation unit 132 will be described. As shown in FIG. 24, in normal QPSK modulation, when there are 6 bits of input data, QPSK modulation is performed 2 bits at a time, and there are three modulated signals. On the other hand, in I / Q retransmission QPSK, as shown in FIG. 24, 6 bits of input data are allocated to the I axis (in-phase component) and the Q axis (quadrature component) (however, the same data is not paired). QPSK modulation is performed in such a manner that retransmission is performed on the I axis and the Q axis so that six modulation signals are obtained. Such QPSK modulation is performed, input to the modulation signal holding unit 134, held for a predetermined time, input to the subcarrier assignment unit 133, and a modulation signal is arranged for the subcarrier number according to a predetermined rule. Next, the arrangement of modulation signals for subcarrier numbers in subcarrier assignment section 133 will be described. Here, similarly to subcarrier assignment section 113 in the first embodiment, as shown in FIG. 25, symbol number p and symbol number p + 1 are arranged in reverse order with respect to the subcarrier number and repeatedly transmitted. . Here, for 26 types of QPSK from x_1 to x_26, the original transmission bits are transmitted twice on the I axis and the Q axis, and the modulation signal is retransmitted on symbol number p and symbol number p + 1. Therefore, the transmission data is transmitted four times per bit.

  Using the above repetition method, the OFDM transmitter 3 generates an OFDM signal and transmits it.

  FIG. 26 is a block diagram showing a configuration of OFDM receiving apparatus 1003 according to Embodiment 3 of the present invention. Compared with OFDM receiving apparatus 1001 in the first embodiment, OFDM receiving apparatus 1003 has IQ combining section 1401 added in place of demapping section 1109 in response to the transmission format being different from that in the first embodiment. Different.

  Here, as shown in FIG. 25, the QPSK modulation signal is arranged in the subcarrier, and the synthesis and equalization of the multilevel modulation signal is the same as in the first embodiment. The IQ combining unit 1401 includes a data holding unit 1411 and a combining calculation unit 1412. The signal synthesized and equalized by the synthesis equalization unit 1201 is held in a necessary section by the data holding unit 1411, and QPSK is divided into I-axis information and Q-axis information. Combining operation unit 1412 combines a pair of the same bits out of the I-axis information and the Q-axis information arranged on different subcarriers, and performs combining. For example, in the case of QPSK modulation as shown in FIG. 24, since the I axis of x_1 and the Q axis of x_4 are based on the same bit b0, a pair is formed by combining both. At this time, as a weighting, the transmission channel characteristic estimated value and the interference detection value at the subcarrier position where x_1 and x_4 are arranged are combined and output as in the following Expression 3.

Here, “Re” indicates an I-axis component, and “Im” indicates a Q-axis component.

  In the repetitive transmission subcarrier arrangement shown in FIG. 8 shown in FIG. 8, as described above, when adjacent channel interference occurs, the subcarrier arrangement is uniform for each subcarrier. In the symbol number p + 1, x_13 at the center subcarrier position is very close to each other, and if frequency selectivity due to multipath interference occurs at the center carrier, it is difficult to obtain a frequency diversity effect and an error occurs. End up. On the other hand, by repeating transmission using the concept of transmitting with another carrier on the Q axis, the same information bits are arranged on various carriers, and combining them, frequency diversity for adjacent channels is obtained. In addition to enhancing the effect, it also has the effect of obtaining a frequency diversity effect with respect to multipath, improves resistance to adjacent channel interference and multipath interference, and enables stable reception.

  Here, when QPSK is used, BPSK loses 3 dB of error resistance against thermal noise when viewed with one subcarrier, but the same information is transmitted with other subcarriers, so combining is performed. Since a diversity gain of 3 dB is obtained, the loss is canceled out in total.

  Note that the synthesis operation unit 1412 performs the synthesis process of the two signals, but may perform the selection process based on the interference detection value. That is, you may make it select only the data with the smaller level of a disturbance detection value among two identical data. In addition, the composition operation is not limited to Equation 3, and any composition may be used as long as the composition reduces the influence of interference. Furthermore, the selection process may be a selection process based on the value of the transmission path characteristic. That is, only the data having the smaller absolute value level of the transmission path characteristics may be selected from the two identical data. Further, the composition operation is not limited to Equation 3, and any composition may be used as long as it is a composition that reduces the influence of noise.

  Note that the data arrangement in the third embodiment is configured to use all subcarriers except the center subcarrier as shown in FIG. 25, but is not limited to this, and as described in the first embodiment, the data arrangement is one. Some of the subcarriers may be pilot signals, and the pilots may not be symmetrically arranged with respect to the center, and may not exist on the same subcarrier in the symbol direction. Further, the number of pilots may not be the same number on the left and right with respect to the center subcarrier, and the number of subcarriers may not be the same on the left and right.

  In the third embodiment, QPSK modulation using I / Q retransmission and repeated transmission using a plurality of symbols are used. However, the present invention is not limited to this, and QPSK modulation using I / Q retransmission and A configuration using repeated transmission within one symbol as shown in FIG. 16 may be adopted.

(Embodiment 4)
Embodiment 4 of the OFDM transmitter and receiver according to the present invention will be described with reference to FIGS. In addition, the same component as FIGS. 1-27 uses the same symbol, and abbreviate | omits description.

  The OFDM transmission apparatus 4 shown in FIG. 28 is significantly different from the OFDM transmission apparatus 1 in Embodiment 1 with respect to the arrangement of the multilevel modulation signal on the subcarriers in the subcarrier modulation unit 24.

  FIG. 29 shows the configuration of the subcarrier modulation unit 24. The subcarrier modulation unit 24 includes a data holding unit 111, a multilevel modulation unit 112, and a subcarrier assignment unit 143. Subcarrier assignment section 143 arranges multilevel modulation signals in the reverse order of symbol number p and symbol number p + 1 with respect to the subcarrier number, similarly to subcarrier assignment section 113 in the first embodiment. Send repeatedly. However, as shown in FIG. 30, in the symbol number p + 1, it is different from the first embodiment in that it is arranged in the reverse order and the multilevel modulation signal is arranged in a complex conjugate. The relationship of the time domain signal between symbol number p and symbol number p + 1 in such an arrangement will be described using equations 4 and 5.

Equation 4 represents the inverse Fourier transform for the symbol number p, where the subcarrier information is Xk.

This equation 5 represents the inverse Fourier transform for the symbol number p + 1 using the subcarrier information Xk in consideration of the reverse order and the complex conjugate, and the equation 5 is transformed into the equation. Finally, the complex conjugate of the time domain signal of symbol number p is obtained. That is, with the arrangement shown in FIG. 30, the time domain signals of symbol number p and symbol number p + 1 have a complex conjugate relationship. For the sake of convenience, in the equation, the subcarrier multilevel signal is represented by Xk, and the subcarrier number and the index k are used in common in the symbol number p. Therefore, the notation different from x_n in FIG. 30 is used. (That is, X13 = x_26).

  Using the above repetition method, the OFDM transmitter 4 generates an OFDM signal and transmits it.

  FIG. 31 is a block diagram showing a configuration of OFDM receiving apparatus 1004 according to Embodiment 4 of the present invention. Compared with OFDM receiving apparatus 1001 in Embodiment 1, OFDM receiving apparatus 1004 differs in the calculation method of time domain signal correlation in synchronization section 1505 according to the transmission format being different from that in Embodiment 1. Here, in order to clarify the difference between them, the synchronization unit 1105 in the OFDM receiving apparatus 1001 of Embodiment 1 will be described. The synchronization unit 1105 includes a correlation calculation unit 1601 and a synchronization establishment unit 1605. The correlation calculation unit 1601 includes an effective symbol length delay unit 1602, a complex conjugate calculation unit 1603, an interval integration unit 1604, and a multiplication unit 1606. Composed. As shown in FIG. 3, the OFDM symbol is the same signal as a copy of the rear part of the OFDM effective symbol is inserted as a guard interval. In order to obtain the correlation between the copy part and the guard interval part by using this fact, the effective symbol length delay unit 1602 delays the OFDM effective symbol length, and as shown in FIG. Match the timing. Then, the complex conjugate calculation unit 1603 takes the complex conjugate, multiplies the received signal, and the interval integration unit 1604 performs interval integration for the guard interval length in accordance with the correlation value between the copy portion and the guard interval portion. A peak occurs in the interval integral value. Based on this information, the synchronization establishing unit 1605 performs synchronization processing such as carrier frequency synchronization and signal timing synchronization. On the other hand, FIG. 34 shows a configuration diagram of synchronization section 1505 in OFDM receiving apparatus 1004 of the fourth embodiment. The synchronization unit 1505 includes a correlation calculation unit 1611 and a synchronization establishment unit 1615. The correlation calculation unit 1611 includes a symbol length delay unit 1612, an interval integration unit 1614, a multiplication unit 1616, and a synchronization establishment unit 1615. . As described above, in the transmission signal of the OFDM transmitter 4, the symbol number p and the symbol number p + 1 have a complex conjugate relationship. For this reason, the symbol length delay unit 1612 delays the OFDM symbol length including the guard interval, thereby matching the signal timings of the symbol number p and the symbol number p + 1 as shown in FIG. Here, since the symbol number p + 1 is a complex conjugate with respect to the symbol number p, the correlation can be calculated by multiplying the signal delayed by the symbol length delay unit 1612 without taking the complex conjugate. . Then, the interval integration unit 1614 performs interval integration for the OFDM symbol length, thereby causing a peak in the interval integration value according to the correlation value between the two symbols. Based on this information, the synchronization establishment unit 1615 performs synchronization processing such as carrier frequency synchronization and signal timing synchronization.

  The synthesis equalization unit 1201 considers the fact that the symbol number p + 1 is arranged in a complex conjugate, and differs from equation 1 to perform synthesis equalization as in the following equation 6, but is not limited thereto.

  With the above configuration, the frequency diversity effect can be exhibited to the maximum by combining processing on the receiving side, the resistance to adjacent channel interference can be improved, and stable reception can be performed as in the first embodiment. Furthermore, this embodiment also has the following effects. In the first embodiment, the synchronization process is performed based on the correlation of the guard interval, but in this embodiment, the synchronization process can be performed based on the correlation with the OFDM symbol length, and the sample is effective for calculating the correlation. Since the number increases, the accuracy of correlation calculation can be improved and the accuracy of synchronization processing can be expected to improve. Furthermore, if narrowband interference exists in the desired band, the synchronization unit 1105 in the first embodiment also adds correlation between narrowband interference waves in the correlation calculation between the guard interval and the copy portion. However, in this embodiment, the time domain signal is a complex conjugate signal, and the correlation of the OFDM signal is obtained by multiplying without taking the complex conjugate. On the other hand, since it is not a multiplication with a complex conjugate signal for the narrowband interference wave component, there is an advantage that the value after the interval integration is difficult to correlate, offset is not easily generated, and the peak is easily detected. .

  Note that the data arrangement in the second embodiment is configured to use all subcarriers except the center subcarrier as shown in FIG. 15, but is not limited to this, and some subcarriers are used as shown in FIG. May be a pilot signal. Further, as shown in FIG. 37, the pilot may not be arranged symmetrically with respect to the center. However, since the time domain signal of the symbol number p + 1 has a complex conjugate relationship with the time domain signal of the symbol number p, the symbol number p + 1 is different from the subcarrier position “k” that was the pilot at the symbol number p. , It is necessary to place a complex conjugate pilot at the subcarrier position of “−k”.

  Further, although the symbol number p + 1 is a complex conjugate, the symbol number p may be assigned as a complex conjugate.

  In addition, this embodiment may be combined with the retransmission by the I axis and the Q axis shown in the third embodiment.

(Embodiment 5)
A fifth embodiment of the OFDM receiving apparatus of the present invention will be described with reference to FIGS. In addition, the same component as FIGS. 1-37 uses the same symbol, and abbreviate | omits description. Note that the transmitting apparatus in the present embodiment is equivalent to the OFDM transmitting apparatus 1 in the first embodiment, and the mapping of multi-level modulation to subcarriers is as shown in FIG. 11 with subcarrier numbers “7” and “ It is assumed that there is a pilot at “-7”. As multi-level modulation, BPSK or QPSK is used.

  FIG. 38 is a block diagram showing a configuration of OFDM receiving apparatus 1005 in the fifth embodiment of the present invention. The OFDM receiving apparatus 1005 differs from the OFDM receiving apparatus 1001 in Embodiment 1 regarding the estimation of transmission path characteristics in the transmission path estimation unit 1707. FIG. 39 shows the configuration of transmission path characteristic estimation section 1707.

  The transmission path characteristic estimation unit 1707 includes a known signal generation unit 1711, a division unit 1712, a CPE calculation unit 1713, and a CPE correction unit 1714. Known signal generating section 1711 generates pilots in all subcarriers of LTF and pilot signals in subcarrier numbers “7” and “−7” included in the data symbols, outputs them to dividing section 1712, and knows the received signals. The transmission path characteristics are estimated by dividing by the signal. The transmission line characteristic calculated by LTF is used as the transmission line characteristic of the subsequent data symbols. However, if there is a carrier frequency error, phase rotation common to the subcarriers occurs as the symbol progresses. Therefore, it is necessary to follow phase rotation with respect to the transmission path characteristics obtained by LTF. This phase rotation is called CPE (Common Pilot Error). The CPE calculation unit 1713 calculates this CPE. The CPE calculating unit 1713 estimates the phase rotation common to the subcarriers using the transmission path characteristics of the pilots with the subcarrier numbers “7” and “−7” existing in each symbol. Specifically, assuming that there is a phase rotation θ between symbol number p and symbol number p + 1, and the transmission path characteristic is H, as shown in the following equation 7, with respect to pilot subcarrier number k, between symbols The phase rotation amount common to the subcarriers is calculated by calculating the phase difference of the transmission path characteristics.

  Here, since there are a plurality of pilots of subcarrier numbers “7” and “−7”, the calculated phases are averaged as shown in the following equation 8, and all subcarriers are calculated based on the calculated phase rotation. By correcting the LTF transmission line characteristic, which is the transmission line characteristic, for each symbol by the CPE correction unit 1714, the phase rotation of the transmission line characteristic of all subcarriers is tracked and used for synthesis equalization.

  Here, in the calculation of the phase rotation amount, accuracy is given by taking the average of the phase calculated by the subcarrier number “7” and the phase calculated by “−7”. However, since there are only two pilot signals per symbol, the accuracy improvement by averaging cannot be expected greatly. Therefore, a major feature of the present embodiment is that CPE calculating section 1713 calculates CPE using received signals other than pilots.

  The symbol number p and the symbol number p + 1 are transmitted as shown in FIG. 11. Here, as an example, the subcarrier numbers “13” and “−13” of the symbol number p and the subcarrier of the symbol number p + 1 are used. This will be described using received signals with numbers “13” and “−13”. Here, assuming that symbol number p and symbol number p + 1 have a phase rotation of θ and the transmission path characteristic is H, the received signal is represented by multiplication of H and multi-level modulation signal x_n. As described above, the phase rotation can be calculated by calculation using the received signal.

  In the expression expansion, since it is BPSK or QPSK, the point that the amplitude r of the multilevel modulation signal can be regarded as the same regardless of the subcarrier is used. In this way, the phase is also calculated for the other subcarriers using the received signal, and the average phase rotation is calculated by averaging.

  With the above configuration, the phase rotation can be calculated using the received signals of many data carriers other than the pilots in symbol number p and symbol number p + 1 where repeated transmission is performed. Since the accuracy of final phase rotation calculation can be improved, phase tracking can be performed correctly even in a noise environment, high-precision equalization processing can be performed, and stable reception is possible.

  In this embodiment, the pilot positions are “7” and “−7”. However, the present invention is not limited to this, and any subcarrier may be used, and it may not be a fixed subcarrier in the symbol direction. .

  Moreover, in order to obtain | require CPE, although it was set as the structure which uses the data of all the subcarriers, it is not restricted to this, You may use only one part signal. In addition, the data arrangement for the subcarriers is reversed from x_1 to x_24 as shown in FIG. 12, but as shown in FIG. On the other hand, only a part of the data arrangement may be used, and in this case, the CPE may be calculated using a part of the signals that form the pair.

  Further, this embodiment may be combined with the repetitive transmission within the same symbol shown in the second embodiment or the re-transmission using the I axis and Q axis shown in the third embodiment.

(Embodiment 6)
A sixth embodiment of the OFDM transmitter and receiver according to the present invention will be described with reference to FIGS. In addition, the same component as FIGS. 1-40 uses the same symbol, and abbreviate | omits description.

  41 is significantly different from the OFDM transmission apparatus 1 according to Embodiment 1 with respect to the arrangement of multilevel modulation signals on subcarriers in the subcarrier modulation unit 26. FIG. 42 shows a configuration of the subcarrier modulation unit 26. The subcarrier modulation unit 26 includes a data holding unit 161, a multilevel modulation unit 162, and a subcarrier assignment unit 163.

  The data holding unit 161 holds input data of the subcarrier modulation unit 26 in a necessary section, which will be described later, and outputs it to the multilevel modulation unit 162. The multi-level modulation unit 162 maps to BPSK, QPSK, etc. based on the input data. The multi-level modulated signal is input to subcarrier assignment section 163, and multi-level modulated signal x_n is arranged for each subcarrier number based on a predetermined rule, and is output to inverse Fourier transform section 104.

  In the first embodiment, the same data is used for the symbol number p and the symbol number p + 1. However, the sixth embodiment is characterized in that the same data is transmitted over three or more symbols.

  FIG. 43 shows the arrangement rule of multilevel modulation signals with respect to the subcarrier numbers in symbol number p, symbol number p + 1, and symbol number p + 2. 43 mainly describes x_1 to x_24 transmitted by symbol number p + 1, and blank subcarriers in symbol number p and symbol number p + 2 are paired with another symbol. The signal is assigned, but regularly follows the contents described below.

  First, paying attention to the symbol number p and symbol number p + 1, except for the pilot, the subcarrier number jumps one subcarrier at a time, such as “−13”, “13”, “−11”, and “11”. The subcarrier positions are arranged in pairs that are inverted between symbols. Next, paying attention to the symbol number p + 1 and the symbol number p + 2, when the pilot carrier is excluded, the subcarrier numbers are “−12”, “12”, “−10”, “10”, and so on. The subcarrier positions other than the subcarrier positions paired with the symbol number p + 1 are arranged so that the subcarrier position is a pair that is inverted between symbols. In this way, multilevel modulation signals are arranged on all subcarriers of symbol number p + 1. In accordance with this rule, a blank subcarrier in symbol number p + 2 is paired with subcarrier numbers “−13”, “13”, “−11”, and “11” of symbol number p + 3 (not shown). A part of the multilevel modulation signal transmitted at p + 3 is assigned.

  Using the above repeating method, the OFDM transmitter 6 generates and transmits an OFDM signal.

  FIG. 44 is a block diagram showing a configuration of OFDM receiving apparatus 1006 according to Embodiment 6 of the present invention. Compared with OFDM receiving apparatus 1005 in the fifth embodiment, OFDM receiving apparatus 1006 differs in transmission path characteristic estimation in transmission path estimating section 1807 depending on the transmission format being different from that in the fifth embodiment. FIG. 45 shows the configuration of transmission path characteristic estimation section 1807 in OFDM receiving apparatus 1006.

  The transmission path characteristic estimation unit 1807 includes a known signal generation unit 1711, a division unit 1712, a CPE calculation unit 1813, and a CPE correction unit 1814. Here, CPE calculation for symbols in CPE calculation section 1813 is different from transmission path characteristic estimation section 1707 in the fifth embodiment. In the CPE calculation unit 1713 in the fifth embodiment, in addition to the CPE calculation by the pilot, the CPE is calculated using data. However, the symbol number p and the symbol number p + 1 are used to perform phase rotation between the symbols. The phase rotation between the symbols is calculated by using the symbol number p + 2 and the symbol number p + 3, and the phase rotation between the symbols of the symbol number p + 1 and the symbol number p + 2 cannot be calculated using the data. It is only calculation by. On the other hand, based on the transmission format of FIG. 43, the CPE calculation unit 1813 according to Embodiment 6 of the present invention calculates the phase rotation between symbols using data over all symbols. For example, the phase rotation amount at symbol number p and symbol number p + 1 is calculated by subcarrier numbers “−13”, “13”, “−11”, “11”, etc., and the phase rotation amount at symbol number p + 1 and symbol number p + 2 Is calculated using subcarrier numbers “−12”, “12”, “−10”, “10”, and the like. The calculated phase rotation is averaged within the symbol, and the CPE correction unit 1814 performs phase correction on the transmission path characteristic calculated by LTF.

  With the above configuration, phase rotation can be calculated using received signals of many data carriers other than pilots in symbol number p and symbol number p + 1 where repeated transmission is performed, and also in symbol number p + 1 and symbol number p + 2. Since the phase rotation can be calculated using the received signals of many data carriers other than the pilot, the average parameter in the phase rotation calculation can be increased for any symbol, and the final phase rotation calculation Since the accuracy is improved, phase tracking can be performed correctly even in a noise environment, high-precision equalization processing can be performed, and stable reception is possible.

  In FIG. 43, the pilot is included. However, since the CPE can be calculated using data in any symbol, the pilot may be deleted. If the symbol number p is a signal immediately after the LTF, the blank subcarrier in FIG. 43 may be assigned as an LTF pilot as a repetitive transmission so as to be paired with the LTF pilot signal, or a dummy subcarrier may be used. A carrier may be assigned as a dummy value (for example, a bit is set to 0).

  In the OFDM transmitters and receivers shown in the first to sixth embodiments, as repeated transmission, the symbol number p and symbol number p + 1 and the repeated transmission arrangement using consecutive symbols are described. Regardless, the data group may be repeatedly transmitted with the symbol number p and the symbol number p + 2, and another data group may be repeatedly transmitted with the symbol number p + 1 and the symbol number p + 3. Further, the data group may be repeatedly transmitted as a symbol group such that the data group is transmitted over N symbols and the same data group is transmitted over the subsequent N symbols.

  In the OFDM transmitters and receivers described in Embodiments 1 to 6, the description has been given focusing on the leakage signal from the adjacent channel as the interference source, but is not limited thereto. For example, the present invention may be applied to a spurious existing in the same channel.

  In the OFDM transmitters and receivers shown in the first to sixth embodiments, the description has been given of the configuration in which the multi-level modulation signal is transmitted twice. Times. Furthermore, for example, a configuration may be adopted in which transmission is performed twice in an inversion arrangement, a pair group of the inversion relation is repeated again in the arrangement, and transmission is performed four times in total.

Note that the OFDM transmitters and receivers shown in Embodiments 1 to 6 may be applied not only to data symbols but also to STFs and LTFs that are pilot symbols.
Note that the OFDM transmitter and receiver shown in Embodiments 1 to 6 are described separately as devices, but the present invention is not limited to this, and may be configured as a device having both the described transmission processing and reception processing. In that case, it is also possible to employ a configuration in which at least a part of each component related to the transmission process and at least a part of each component related to the reception process is shared.

  Further, each component of the OFDM transmitter and receiver in Embodiments 1 to 6 may be realized by an LSI that is an integrated circuit. At this time, each component may be individually made into one chip, or may be made into one chip so as to include a part or all of them. Further, although it is referred to as LSI here, it may be referred to as IC, system LSI, super LSI, or ultra LSI depending on the degree of integration. Further, the method of circuit integration is not limited to LSI, and implementation with a dedicated circuit or a general-purpose processor is also possible. Further, the method of circuit integration is not limited to LSI, but may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) or a reconfigurable processor capable of reconfiguring connection and setting of circuit cells inside the LSI may be used. Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Possible applications include biotechnology.

  In addition, at least a part of the operation procedure of the receiving apparatus described in the above-described core embodiment is described in the reception program, and for example, a CPU (Central Processing Unit) reads and executes the program stored in the memory. Alternatively, the program may be stored in a recording medium and distributed.

  Further, the OFDM transmitter and receiver according to Embodiments 1 to 6 may be realized using a transmission method or a reception method that performs at least a part of the described transmission process or reception process.

  Further, any OFDM transmission device, transmission method, transmission circuit, reception device, reception method, reception circuit, or program that performs a part of the transmission processing or reception processing that realizes the first to sixth embodiments is implemented. Forms 1 to 6 may be realized. For example, a part of the configuration of the receiving device described in each of the above embodiments is realized by the receiving device or the integrated circuit, and an operation procedure performed by the configuration excluding the part is described in the receiving program. It may be realized by reading out and executing the program stored in.

  Further, although Embodiments 1 to 6 refer to the 802.11ah scheme that is under formulation, the present invention is not limited to this.

  The OFDM transmitter and receiver according to the present invention have an effect of reducing transmission errors with respect to interference from adjacent channels due to data arrangement during repeated transmission, and in fields such as future next-generation wireless LANs It is beneficial.

DESCRIPTION OF SYMBOLS 1 OFDM transmitter 2 OFDM transmitter 3 OFDM transmitter 4 OFDM transmitter 6 OFDM transmitter 11 OFDM demodulator 12 OFDM demodulator 13 OFDM modulator 14 OFDM modulator 16 OFDM modulator 21 Subcarrier modulator 22 Subcarrier modulator 23 subcarrier modulation unit 24 subcarrier modulation unit 26 subcarrier modulation unit 101 error correction coding unit 102 interleave unit 103 synchronization signal generation unit 104 inverse Fourier transform unit 105 guard interval addition unit 106 symbol shaping unit 107 D / A conversion unit 108 RF output unit 109 Antenna 111 Data holding unit 112 Multi-level modulation unit 113 Subcarrier assignment unit 121 Data holding unit 123 Subcarrier assignment unit 131 Data holding unit 132 I / Q retransmission QPSK modulation Modulation unit 133 Subcarrier assignment unit 134 Modulation signal holding unit 143 Subcarrier assignment unit 161 Data holding unit 162 Multi-level modulation unit 163 Subcarrier assignment unit 1001 OFDM receiving device 1002 OFDM receiving device 1003 OFDM receiving device 1004 OFDM receiving device 1005 OFDM receiving Apparatus 1006 OFDM receiver 1011 OFDM demodulator 1012 OFDM demodulator 1013 OFDM demodulator 1014 OFDM demodulator 1015 OFDM demodulator 1016 OFDM demodulator 1101 antenna 1102 tuner 1103 A / D converter 1104 orthogonal transform unit 1105 synchronization unit 1106 Fourier transform unit 1107 Transmission path characteristic estimation unit 1108 Interference detection unit 1109 Demapper unit 1110 Deinterleave unit 1111 Error correction unit 1201 Combining equalization unit 1202 Combining equalization unit 1211 Data holding unit 1212 Combining operation unit 1221 Data holding unit 1222 Combining operation unit 1401 IQ combining unit 1411 Data holding unit 1412 Combining operation unit 1505 Synchronizing unit 1601 Correlation calculating unit 1602 Effective symbol length delay Unit 1603 complex conjugate calculation unit 1604 interval integration unit 1605 synchronization establishment unit 1606 multiplication unit 1611 correlation calculation unit 1612 symbol length delay unit 1614 interval integration unit 1615 synchronization establishment unit 1616 multiplication unit 1707 transmission line characteristic estimation unit 1711 known signal generation unit 1712 division Unit 1713 CPE calculating unit 1714 CPE correcting unit 1807 transmission path characteristic estimating unit 1813 CPE calculating unit 1814 CPE correcting unit

Claims (24)

A transmitter using the OFDM method,
In order to transmit the same data group N times (N is an integer equal to or greater than 2), a subcarrier modulation unit that assigns a BPSK or QAM modulated signal to the OFDM subcarrier based on a predetermined rule for the same data group Have
The subcarrier modulation unit assigns a BPSK or QAM modulated signal to a subcarrier at least once among the N times, and assigns at least one of the remaining N-1 times. Assign the opposite order around the center subcarrier for the position,
An OFDM transmitter characterized by the above. N is 2;
The OFDM transmitter according to claim 1. The subcarrier modulation unit divides an OFDM1 symbol subcarrier into N, and assigns the same data group to each divided subcarrier.
The OFDM transmitter according to claim 1. The subcarrier modulation unit allocates one data group to one OFDM symbol, and allocates N identical data groups using N OFDM symbols.
The OFDM transmitter according to claim 1. The subcarrier modulation unit makes a signal to be allocated to a subcarrier complex conjugate at least once among the N times.
The OFDM transmitter according to claim 1. Centering on the center subcarrier, assigning it in a complex conjugate to the data group assigned in the opposite order,
The OFDM transmitter according to claim 5. The subcarrier modulation unit maps the same data so that it can be repeatedly transmitted using both the I-axis (in-phase component) and Q-axis (orthogonal component) axes of the subcarrier,
The mapping of the I axis and the Q axis maps to the I axis and the Q axis of different subcarriers, respectively.
The OFDM transmitter according to claim 1. The subcarrier modulation unit divides the data group into M groups (M is 2 or more), assigns the data group with a predetermined symbol, and generates M data for M symbols other than the predetermined symbol. Assign one group at a time,
The OFDM transmitter according to claim 1. The N is 2, the M is 2,
M symbols other than the predetermined symbol are symbols before and after the predetermined symbol.
The OFDM transmitter according to claim 8. A reception unit that receives transmission signals for transmitting the same data group N times (N is an integer of 2 or more);
At least one of the N times, the allocation position of the BPSK or QAM modulated signal to the subcarrier is the center subcarrier relative to the allocation position of at least one of the remaining N-1 times. Assign to the opposite order,
An OFDM receiver characterized by that. The transmission signal includes a known preamble signal at the beginning of the frame,
The receiver is configured to estimate a channel characteristic based on the preamble;
A disturbance detection unit for detecting a disturbance signal existing in a desired band based on the preamble;
A synthesis equalization unit that performs synthesis or selection and waveform equalization on the N same data,
In the synthesis equalization unit, the synthesis or selection uses at least one of the transmission path characteristic estimated by the transmission path characteristic estimation unit and the interference signal detection result detected by the interference detection unit,
The OFDM receiver according to claim 10. The transmission signal assigns the data group to the subcarrier in a complex conjugate at least once, among the N data groups assigned to the subcarrier.
The receiving unit includes a correlation calculating unit,
The correlation calculation unit calculates the correlation by multiplying the signal delayed by the OFDM symbol length and the signal not delayed, and performs interval integration over the OFDM symbol length.
The OFDM receiver according to claim 10. The transmission signal includes a known preamble signal at the beginning of the frame,
Further, the same data group is mapped so that it can be repeatedly transmitted using both the I axis (in-phase component) and the Q axis (orthogonal component) of the subcarrier,
The mapping of the I axis and the Q axis maps to the I axis and Q axis of different subcarriers, respectively.
The receiver is configured to estimate a channel characteristic based on the preamble;
A disturbance detection unit for detecting a disturbance signal existing in a desired band based on the preamble;
A synthesis equalization unit that performs synthesis or selection and waveform equalization for each subcarrier with respect to the N times of the same data;
An IQ combining unit that combines or selects I axis information and Q axis information for the same data group of the I axis and the Q axis,
In the synthesis equalization unit, the synthesis or selection uses at least one of the transmission path characteristic estimated by the transmission path characteristic estimation unit and the interference signal detection result detected by the interference detection unit,
In the IQ combining unit, the combination or selection of the I axis and the Q axis uses at least one of the transmission path characteristic estimated by the transmission path characteristic estimation unit and the interference signal detection result detected by the interference detection unit.
The OFDM receiver according to claim 10. The receiving unit includes a CPE calculating unit that calculates a phase rotation between symbols,
The CPE calculating unit includes at least a part of signals assigned to the center subcarrier in the opposite order and at least a part of at least one data group among the other N-1 data groups. Signal to calculate a phase rotation between the symbols,
The OFDM receiver according to claim 10. A transmitter using the OFDM method,
In order to transmit the same data group twice, a subcarrier modulation unit that assigns the BPSK or QAM modulated signal to the OFDM subcarrier based on a predetermined rule for the same data group,
The subcarrier modulation unit assigns a position where the BPSK or QAM modulated signal is assigned to the subcarrier to the first data group, and a level at which interference in the band is received with respect to the assignment position of the second data group. Assign them in an order that is uniform when viewed at the total level of two identical data.
An OFDM transmitter characterized by the above. A transmission method using the OFDM method,
In order to transmit the same data group N times (N is an integer equal to or greater than 2), a subcarrier modulation step of assigning a BPSK or QAM modulated signal to the OFDM subcarrier based on a predetermined rule for the same data group Have
In the subcarrier modulation step, at least one of the N times, the allocation position of the BPSK or QAM modulated signal to the subcarrier is at least one of the remaining N-1 times. Assign the opposite order around the center subcarrier for the position,
An OFDM transmission method characterized by the above. A transmission circuit using an OFDM system,
In order to transmit the same data group N times (N is an integer of 2 or more), a subcarrier modulation circuit that assigns a BPSK or QAM modulated signal to the OFDM subcarrier based on a predetermined rule for the same data group Have
The subcarrier modulation circuit assigns a BPSK or QAM modulated signal to a subcarrier at least once among the N times, and assigns at least one of the remaining N-1 times. Assign the opposite order around the center subcarrier for the position,
An OFDM transmission circuit characterized by the above. A transmission program using the OFDM method,
In order to transmit the same data group N times (N is an integer equal to or greater than 2), a subcarrier modulation step of assigning a BPSK or QAM modulated signal to the OFDM subcarrier based on a predetermined rule for the same data group Have
In the subcarrier modulation step, at least one of the N times, the allocation position of the BPSK or QAM modulated signal to the subcarrier is at least one of the remaining N-1 times. Assign the opposite order around the center subcarrier for the position,
A program to be executed by an OFDM transmitter. A reception step of receiving a transmission signal for transmitting the same data group N times (N is an integer of 2 or more);
At least one of the N times, the allocation position of the BPSK or QAM modulated signal to the subcarrier is the center subcarrier relative to the allocation position of at least one of the remaining N-1 times. Assign to the opposite order,
An OFDM receiving method characterized by the above. A receiving circuit for receiving a transmission signal for transmitting the same data group N times (N is an integer of 2 or more);
At least one of the N times, the allocation position of the BPSK or QAM modulated signal to the subcarrier is the center subcarrier relative to the allocation position of at least one of the remaining N-1 times. Assign to the opposite order,
An OFDM receiver circuit. A reception step of receiving a transmission signal for transmitting the same data group N times (N is an integer of 2 or more);
At least one of the N times, the allocation position of the BPSK or QAM modulated signal to the subcarrier is the center subcarrier relative to the allocation position of at least one of the remaining N-1 times. Assign to the opposite order,
A program to be executed by an OFDM receiver. A transmission method using the OFDM method,
A subcarrier modulation step of assigning a BPSK or QAM modulated signal to an OFDM subcarrier based on a predetermined rule in order to transmit the same data group twice;
In the subcarrier modulation step, the allocation position of the BPSK or QAM modulated signal to the subcarrier with respect to the first data group, and the level at which interference in the band is received with respect to the allocation position of the second data group, Assign them in an order that is uniform when viewed at the total level of two identical data.
An OFDM transmission method characterized by the above. A transmission circuit using an OFDM system,
A subcarrier modulation circuit for allocating a BPSK or QAM modulated signal to an OFDM subcarrier based on a predetermined rule in order to transmit the same data group twice;
The subcarrier modulation circuit has a level at which an BPSK or QAM modulated signal is assigned to a subcarrier with respect to a first data group, and a level that is subject to in-band interference with respect to an assignment position of a second data group. Assign them in an order that is uniform when viewed at the total level of two identical data.
An OFDM transmission circuit characterized by the above. A transmission program using the OFDM method,
A subcarrier modulation step of assigning a BPSK or QAM modulated signal to an OFDM subcarrier based on a predetermined rule in order to transmit the same data group twice;
In the subcarrier modulation step, the allocation position of the BPSK or QAM modulated signal to the subcarrier with respect to the first data group, and the level at which interference in the band is received with respect to the allocation position of the second data group, Assign them in an order that is uniform when viewed at the total level of two identical data.
A program to be executed by an OFDM transmitter.