JP2011146938A - Radio transmitter and preamble generating method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive, high-quality and high-transmission-speed radio transmitter and a preamble generating method for the same which reduce a peak/average power ratio while securing downward compatibility with the conventional standard and securing a broadband width. <P>SOLUTION: The radio transmitter includes an OFDM generating means for transmitting a communication packet to a radio receiver by orthogonal frequency division multiplex modulation. The OFDM generating means transmits the communication packet including a first band and a second band serving as a compatible band, and a third band and a fourth band serving as an extended area of the compatible band. The OFDM generating means transmits a preamble signal A to the first band as an preamble signal A having no phase difference, transmits it to the second band as a preamble signal jA, transmits it to the third band as a preamble signal Ae<SP>jθ1</SP>, and transmits it to the fourth band as a preamble signal jAe<SP>jθ2</SP>. Preferably, θ1 is set to 0°, and θ2 is 180°. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radio transmission apparatus that performs packet communication by orthogonal frequency division multiplexing (hereinafter referred to as OFDM) modulation and a preamble generation method thereof.

  The speed of wireless LAN is increased every time a new standard is established. However, it is important for the new standard to ensure backward compatibility with the conventional standard.

  For example, in IEEE802.11a that can communicate at a maximum transmission rate of 54 Mbps using the 5 GHz band, STF (Short Training Field), LTF (Long Training Field), and SIG (Signal) as shown in FIG. Filed) and has a preamble of 20 MHz, and is used in a bandwidth of 20 MHz as shown in FIG.

  In IEEE802.11n established after IEEE802.11a, communication is possible at a maximum transmission rate of 600 Mbps using the 2.4 GHz band or 5 GHz band, but backward compatibility with IEEE802.11a is used because the same 5 GHz band is used. 18 (A), L (Legacy) -STF corresponding to STF, L-LTF corresponding to LTF, L-SIG corresponding to SIG, and extended HT (High Throughput), as shown in FIG. ) -SIG, HT-STF, HT-LTF1-N (1 ≦ N ≦ 4) are used.

In IEEE802.11n, a bandwidth of 20 MHz or 40 MHz is used. However, when communication is performed with a bandwidth of 40 MHz, as shown in FIG. 18B, the bandwidth of 20 MHz used in IEEE802.11a is used. On the other hand, a signal having a phase difference of about π / 2 is used in the expanded 20 MHz band. When new standards are formulated in this way, backward compatibility is ensured while increasing the bandwidth and speeding up.
As a wireless communication apparatus considering such backward compatibility, the one described in Patent Document 1 is known.

US Patent Application Publication No. 2005/0286474

Patent Document 1 describes the expansion of the bandwidth from 20 MHz to 40 MHz in the IEEE802.11a standard, but the peak-to-average power ratio (hereinafter referred to as PAPR). Is not considered. In wireless communication devices, it is important to reduce PAPR. When the PAPR is high, instantaneous high power is generated with respect to the average power. Therefore, since high linearity is required as the amplification characteristic of the signal amplifier in order to cope with instantaneous high power, the signal amplifier becomes expensive. In addition, when a signal amplifier having the same amplification characteristics as the conventional one is used, the radio signal includes a lot of distortion, so that not only the transmission quality is deteriorated but also the interference with the adjacent channel is concerned. In addition, a transmitter having a high PAPR is not suitable for a portable mobile terminal because power consumption increases.
Simply increasing the bandwidth from the 20 MHz bandwidth to the 40 MHz bandwidth and further increasing the bandwidth from the 40 MHz bandwidth to the 80 MHz bandwidth will increase the number of subcarriers, resulting in a high PAPR. It becomes a preamble.

  Accordingly, the present invention provides a wireless transmission device capable of low-cost and high-quality high-speed transmission by realizing a reduction in PAPR while ensuring a wide bandwidth while ensuring backward compatibility with conventional standards. Another object of the present invention is to provide a preamble generation method thereof.

The wireless transmission device of the present invention comprises OFDM generation means for transmitting communication packets to the wireless reception device by orthogonal frequency division multiplexing modulation, and control means for controlling the OFDM generation means to transmit communication packets in a predetermined order, The OFDM generation means is compatible with a first band in which the preamble signal A is transmitted as a preamble signal A without a phase difference and a second band that is set as an extension band of the first band and is transmitted as a preamble signal jA. A communication packet is transmitted using a third band and a fourth band that are arranged symmetrically with the compatible band and set as an extension band of the compatible band, and the first band and the second band. ^Yes , a preamble signal is generated in which the third band is a preamble signal Ae ^jθ1 and the fourth band is a preamble signal jAe ^jθ2. It has the function to perform.

A preamble signal generation method for a wireless transmission device according to the present invention is a preamble signal generation method for a wireless transmission device that transmits a communication packet to a wireless reception device by orthogonal frequency division multiplexing modulation, in which the preamble signal A has no phase difference. The first band transmitted as the first band and the second band transmitted as the preamble signal jA are set as compatible bands, arranged symmetrically with the compatible band, and expanded the compatible band. For the third band and the fourth band set as bands, a preamble signal is generated with the third band as a preamble signal Ae ^jθ1 and the fourth band as a preamble signal jAe ^jθ2, and is transmitted as a communication packet. And

The wireless transmission device of the present invention is obtained by further expanding the bandwidth to the third band and the fourth band from the first band and the second band, which are compatible bands. In the first band, the preamble signal A is transmitted as the preamble signal A having no phase difference. In the second band, the preamble signal A is transmitted as the preamble signal jA. Then, for the third band and the fourth band, the OFDM generation means generates a preamble signal having the third band as the preamble signal Ae ^jθ1 and the fourth band as the preamble signal jAe ^jθ2 . For θ1 and θ2, a value that reduces the PAPR is set. By doing so, it is a subordinate of the wireless receiving device that receives any of the first band from the first band and the wireless receiving device that receives any of the first band, the second band, the third band, and the fourth band. PAPR can be reduced while maintaining compatibility.

The OFDM generation means is configured such that PAPR is smaller than that when a signal having the first band and the third band as a preamble signal A and a signal having the second band and the fourth band as a preamble signal jA is transmitted. Thus, it is possible to provide a function of generating a preamble signal.
When the band is extended from the first band and the second band, which are compatible bands, to the third band and the fourth band, which are extension bands, the preamble signal in the third band is transmitted as the same preamble signal A as the first band, It is conceivable to transmit the preamble signal in the fourth band as the same preamble signal jA as in the second band. However, in the present invention, the OFDM generation means generates a preamble signal having the third band as the preamble signal Ae ^jθ1 and the fourth band as the preamble signal jAe ^jθ2, and the third band is preambleed for θ1 and θ2 at this time. The angle is such that the PAPR is lower than when the signal A is used and the fourth band is the preamble signal jA. By doing so, it is possible to further reduce the PAPR by extending the phase of the preamble signal from the compatible band to the extended band as it is, so that high-speed data transmission, low-cost signal amplifiers, and high communication performance can be achieved. Quality can be improved.

The OFDM generation means preferably generates a preamble signal with a phase in which θ1 is set to 0 ° and θ2 is set to 180 °. By setting such θ1 and θ2, the third low band becomes the preamble signal A and the fourth band becomes the preamble signal −jA. By using such a preamble signal, a substantially minimum PAPR can be achieved. Therefore, it is possible to further reduce the PAPR while ensuring backward compatibility. Further, when θ1 is set to 0 °, the value of ^ejθ1 is 1, and when θ2 is set to 180 °, the value of ^ejθ2 is −1. ^Therefore , it is easy to calculate a phase difference when generating a preamble signal. It is.
Further, the OFDM generation means can also generate a preamble signal with a phase in which θ1 is set to 180 ° and θ2 is set to 0 °. By doing so, the PAPR can be almost minimized, and when θ1 is 180 °, the value of e ^jθ1 is −1, and when θ2 is 0 °, the value of e ^jθ2 is 1. It is easy to calculate the phase difference when generating the preamble signal.

  Each of the first to fourth bands is a band corresponding to the IEEE802.11a standard and the IEEE802.11n standard, and the first and second bands or the third and fourth bands are the IEEE802.11n standard. It can be set as a band corresponding to. By doing so, although each of the first to fourth bands has a phase change, it is possible to maintain backward compatibility with the IEEE802.11a standard and the IEEE802.11n standard, respectively. Also, the first and second bands and the third and fourth bands can maintain backward compatibility with the IEEE 802.11n standard although there is a phase change. Therefore, the communication packet from the wireless transmission device of the present invention can be received by the wireless reception device compliant with the IEEE802.11a standard or the wireless reception device communication compliant with the IEEE802.11n standard.

  The control means generates L-STF, L-LTF, L-SIG, HT-SIG corresponding to the IEEE 802.11n standard as the communication packet in the predetermined order, and as the L-SIG and the HT-SIG By using the communication packet to which dummy information is added so that the subsequent communication packet is received as data by the wireless receiver of the IEEE802.11a standard or the IEEE802.11n standard, backward compatibility with the IEEE802.11a standard or the IEEE802.11n standard is achieved. Can increase the sex.

According to the present invention, a wireless receiver that receives any one of the first to fourth bands by setting the third band as the preamble signal Ae ^jθ1 and the fourth band as the preamble signal jAe ^jθ2 , PAPR can be reduced while maintaining backward compatibility with a radio receiving apparatus that receives any of the second band, the third band, and the fourth band. Therefore, the present invention can realize a reduction in PAPR even if a wide bandwidth is ensured while ensuring backward compatibility with the conventional standard, so that inexpensive and high-quality high-speed transmission is possible. is there.

It is a figure which shows the state which the radio | wireless communication apparatus which concerns on embodiment of this invention is communicating with another radio | wireless communication apparatus. It is a figure which shows the structure of the radio | wireless transmitter shown in FIG. It is a figure which shows an example of a structure of the OFDM signal production | generation means shown in FIG. It is a figure which shows the packet format of the communication packet which the radio | wireless transmitter shown in FIG. 1 transmits. It is a figure which shows an example of a preamble signal, (A) shows the subcarrier information of the preamble signal transmitted as L-STF, (B) shows the subcarrier information of the preamble signal transmitted as L-LTF. FIG. It is a figure which shows an example of the format of VHT-SIG of the communication packet shown in FIG. FIG. 5 is a diagram for explaining backward compatibility of communication packets shown in FIG. 4. It is a figure which shows the reception flow of the radio | wireless receiving apparatus based on IEEE802.11a specification. It is a figure which shows an example of L-SIG. It is a figure which shows the reception flow of the radio | wireless receiving apparatus based on IEEE802.11n specification. It is a figure which shows an example of HT-SIG1 and HT-SIG2. (A) to (C) are diagrams for explaining the bandwidth of a communication packet transmitted by the wireless transmission device shown in FIG. It is a graph which shows PAPR of L-STF. It is a graph which shows PAPR of L-LTF. It is a table | surface which shows PAPR of L-LTF. 3 is a table comparing PAPR between the wireless transmission device shown in FIG. 1 and a transmitter compliant with the IEEE 802.11n standard. It is a figure for demonstrating the IEEE802.11a standard, (A) is a figure which shows a communication packet format, (B) is a figure which shows the band to be used. 2A and 2B are diagrams for explaining the IEEE 802.11n standard, in which FIG. 1A is a diagram illustrating a communication packet format, and FIG. 2B is a diagram illustrating a band to be used.

A wireless communication apparatus according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, radio communication apparatus R1 according to the present embodiment includes radio transmission apparatus 1 and radio reception apparatus 2, and a plurality of antennas by other radio communication apparatus R2 and MIMO-OFDM modulation. Packet communication is performed via In the present embodiment, the wireless communication device R1 and another wireless communication device R2 communicate with each other by four antennas 3a to 3d and 3e to 3h. FIG. 1 shows an example in which the number of antennas on the transmission side, the number of antennas on the reception side, the number of spatial streams, and the number of FEC encoders used are four.
Further, the wireless communication device R1 can reduce PAPR while maintaining backward compatibility between the IEEE802.11a standard and the IEEE802.11n standard. The wireless transmission device 1 has a transmission bandwidth of 80 MHz and has a maximum transmission rate of 1 Gbps or more using a 5 GHz band.
Since the present invention relates to the preamble signal and the packet format of the communication packet transmitted by the wireless transmission device 1, the description of the wireless reception device 2 is omitted.

  Next, the configuration of the wireless transmission device 1 will be described with reference to FIG. As shown in FIG. 2, the wireless transmission device 1 includes a control unit 10a and an OFDM signal generation unit 10b. The control unit 10a has a function of controlling the OFDM signal generation unit 10b to generate communication packets in a predetermined order, or to generate transmission data and output it to the OFDM signal generation unit 10b.

  The OFDM signal generation unit 10b has a function of transmitting a preamble signal and transmission data from the control unit 10a by OFDM modulation. As shown in FIG. 3, the OFDM signal generation means 10b includes a preamble pilot memory section 11, a scrambler section 12, an encoder parser section 13, an FEC (Forward Error). Correction) Encoder unit (FEC encoder) 14, Spatial stream parser unit 15, Interleaver unit 16, Mapper unit 17, STBC (Space-Time Block Code) encoder unit (STBC encoder) 18.

  Further, the OFDM signal generation means 10b includes a multiplexer unit (Mux) 19, a first CS (Cyclic Shift) inserter unit (CS inserter) 20, a spatial mapper unit (Spatial mapper) 21, and a PTS unit (Partial Transmit Sequence) 22. Inverse Fast Fourier Transform (IFFT) 23, second CS inserter section (CS inserter) 24, GI (Guard interval) inserter section (GI inserter) 25, and windowing section (Windowing) 26 And a transmission filtering unit (TX filter) 27.

The preamble pilot memory unit 11 is a memory in which a preamble signal transmitted prior to transmission information (Data) and a pilot signal inserted into the transmission information are stored. The preamble pilot memory unit 11 outputs a preamble signal instructed by the control means 10a.
The scrambler unit 12 randomizes the bits “0” and “1” using a generator polynomial of G (X) = X ⁷ + X ⁴ +1 for the transmission bit sequence from the control means, ”And“ 1 ”should not appear continuously.
The encoder parser unit 13 divides the scrambled transmission information into four FEC encoder units 14 and distributes them.
The FEC encoder unit 14 performs forward error correction encoding to enable error correction. The FEC encoder unit 14 performs encoding by BCC (Binary Convolutional Codes) calculated using a generator polynomial of rate 1/2 G ₀ = 133 ₈ and G ₁ = 171 ₈ .

The spatial stream parser unit 15 distributes transmission information to a spatial stream used in MIMO-OFDM modulation by decomposing the encoded data from the FEC encoder unit 14 into four blocks.
The interleaver unit 16 rearranges the arrangement of the transmission information distributed by the spatial stream parser unit 15 according to a predetermined rule.
The mapper unit 17 transmits BPSK (Binary Phase Shift Keying) modulation, QPSK (Quadrature Phase Shift Keying) modulation, and QAM (Quadrature Amplitude Modulation) modulation in order to transmit transmission information that is interleaved bit information as a radio signal. For example, bit information is mapped to symbols.

The STBC encoder unit 18 uses the space-time block code (STBC) to change the array points from the spatial stream (Spatial Stream: SS) to the space-time stream (Space-Time Stream: STS) for the mapped transmission information (symbol). ), It is possible to obtain a greater diversity gain.
The multiplexer unit 19 selects transmission information from the STBC encoder unit 18 and a preamble signal or pilot signal from the preamble pilot memory unit 11.

The first CS inserter unit 20 adds a cyclic shift to the transmission information (symbol). By adding a cyclic shift to the transmission information, unintended beam forming of the radio signal is prevented.
The spatial mapper unit 21 maps the transmission information (symbol) to which the cyclic shift is added according to the spatial mapping matrix.
The PTS unit 22 performs different phase rotation for each of the first to fourth bands to reduce PAPR.

The inverse fast Fourier transformer 23 performs OFDM modulation by performing inverse Fourier transform (IFFT) on the signal from the PTS unit 22.
Similar to the first CS inserter unit 20, the second CS inserter unit 24 adds a cyclic shift to the transmission information (symbol). The second CS inserter unit 24 is used exclusively with the first CS inserter unit 20.
The GI inserter unit 25 adds a guard interval to the OFDM-modulated symbol output from the second CS inserter unit 24.
Since the out-of-band spectrum increases when the signal periodicity changes greatly between adjacent symbols, the windowing unit 26 increases the attenuation of the spectrum by performing smoothing so that the change between adjacent symbols is small. And suppress the out-of-band spectrum. The transmission filtering unit 27 performs band limitation on the transmission signal from the windowing unit 26.

  Next, communication packets transmitted by the wireless transmission device 1 will be described with reference to FIG. In this specification, the packet format of a communication packet transmitted by the wireless transmission device 1 according to the present embodiment is referred to as a “VHT (Very High Throughput) Mixed Mode” packet format, and is hereinafter simply abbreviated as a VTH packet format. .

  As shown in FIG. 4A, in the VHT packet format, the preamble format is set to L-STF (8 μS), L-LTF (8 μS), L-SIG (4 μS), HT-SIG (8 μS), and HT. -It can be any packet format following SIG. In this embodiment, as shown in FIG. 4B, as an example of an arbitrary packet format, VHT-SIG (8 μS), VHT-STF (4 μS), VHT-LTF1 to 4 (4 μS), Data (4 μS). /3.6 μS).

L-STF, L-LTF, and L-SIG correspond to the IEEE802.11a STF, LTF, and SIG shown in FIG. 17 (A), and also the IEEE802.11n L-STF, L shown in FIG. 18 (A). -Corresponds to LTF and L-SIG. The HT-SIG corresponds to the IEEE 802.11n HT-SIG shown in FIG.
The preamble signals transmitted as the L-STF and L-LTF are stored as subcarrier information in the preamble pilot memory unit 11. For example, the L-STF can be expressed by the equation shown in FIG. 5A, and subcarrier information of −122 to −70, −58 to −6, 6 to 58, and 70 to 122 is IEEE802.11a. The same subcarrier information as STF. The L-LTF can be expressed by the equation shown in FIG. 5B. The subcarrier information of −122 to −70, −58 to −6, 6 to 58, and 70 to 122 is the IEEE802.11a LTF. Is the same subcarrier information.

  Moreover, about VHT-SIG, it can be set as the information parameter of a format as shown in FIG. 6 as an example. Here, VHT-SIG1 indicates the first symbol, and VHT-SIG2 indicates the second symbol.

Next, the backward compatibility of the VHT packet format will be described with reference to FIGS.
The VHT packet format can be received without problems by either a wireless transmission device (hereinafter referred to as a receiver) compliant with the IEEE 802.11a standard or a wireless communication device (hereinafter referred to as n receiver) compliant with the IEEE 802.11n standard. Is desirable.

As shown in FIG. 7, in the VHT packet format, the head of the VHT packet format is L-STF, L-LTF, and L-SIG in accordance with the IEEE802.11a standard and the IEEE802.11n standard.
In the IEEE802.11a standard, SIG, which is the first symbol after 16 μS from the beginning of a communication packet, is defined as BPSK modulation, and subsequent packet data is received using transmission parameter information included in this SIG. Accordingly, not only L-SIG in the VHT packet format is BPSK modulated, but also dummy information for continuously receiving communication packets following L-SIG is stored in L-SIG. For example, as the dummy information, as shown in FIG. 9, an arbitrary rate is stored as “Rate” so that signals after HT-SIG are handled as simple transmission information (Data), and communication packets after HT-SIG are stored. Is stored in the L-SIG as “Length” (length). Also, 0 information is “R” (Reserved bit), 0 or 1 information calculated from “Rate”, “R”, and “Length” is “P” (Parity bit), and all 0 information is It is stored in “Tail”.

  By doing so, as shown in FIG. 8, when the receiver a receives the L-SIG in the VHT packet format that is the first symbol after 16 μS from the beginning as the SIG (step S100), the L− The communication packet following SIG is mistakenly recognized as simple transmission information (Data), and reception is continued (step S110). The receiver a performs various processes on the received transmission information (Data) (step S120). Thus, the VHT packet format can ensure backward compatibility with the IEEE 802.11a standard.

  On the other hand, the n receiver receives communication packets according to a reception flow called auto detection. This auto-detection is a function for discriminating a communication packet conforming to the IEEE802.11a standard or a communication packet conforming to the IEEE802.11n standard by determining the modulation method of the communication packet. Therefore, in order to ensure backward compatibility even in the n receiver, it is important that the VHT packet format is not determined as abnormal data in the reception flow of the auto detection function.

  In the auto detection in the n receiver, as shown in FIG. 10, first, the first symbol and the second symbol after 16 μS from the beginning of the communication packet are received (steps S200 and S210). The second symbol is BPSK modulation or M-QAM modulation (M = 4, 16, 64) in the IEEE802.11a standard, and QBPSK modulation in the IEEE802.11n standard. Therefore, in step S220, if the second symbol is BPSK modulation or M-QAM modulation, it is determined that the communication packet conforms to the IEEE802.11a standard, and if it is QBPSK modulation, it conforms to the IEEE802.11n standard. It is determined that the communication packet is compliant. Therefore, if the received communication packet is a communication packet conforming to the IEEE 802.11a standard, the transmission information (Data) following SIG is received (step S230). In this case, the n receiver operates as an a receiver (step S240).

  When the n receiver receives the VHT packet format, first, the first symbol L-SIG and the second symbol HT-SIG1 after 16 μS from the beginning of the communication packet are received (step S200, step S210). ). The second symbol is QBPSK modulation in the VHT packet format. Therefore, in step S220, it is determined that the IEEE 802.11n standard.

  In the VHT packet format, since HT-SIG stores dummy information for continuing to receive communication packets (communication packets after VHT-SIG) following HT-SIG, HT-SIG has HT-SIG stored in HT-SIG. The subsequent communication packet is continuously received (step S250). In this case, the n receiver operates as an n receiver as it is (step S260).

  As described above, in the reception flow in the n receiver, backward compatibility can be ensured by misidentifying that the VHT packet format is a communication packet conforming to the IEEE802.11n standard. For example, for HT-SIG1 and HT-SIG2 as shown in FIG. 11, information defined as HT-SIG of the IEEE802.11n standard can be used as dummy information. For example, the data length after VHT-SIG is stored in “HT Length”, and an error detection code corresponding to the communication packet is stored in CRC.

  Next, the operation of radio transmitting apparatus 1 according to the present embodiment when transmitting L-SIG, L-LTF, L-SIG, and HT-SIG in the VTH packet format is based on FIG. 3 and FIG. explain.

For transmission of the L-STF, subcarrier information determined by the equation shown in FIG. 5A is read from the preamble pilot memory unit 11 according to an instruction from the generation unit 10b. For transmission of L-LTF, subcarrier information determined by the equation shown in FIG. 5B is read from the preamble pilot memory unit 11.
Then, the read subcarrier information passes through the multiplexer unit 19 and passes through the first CS inserter unit 20 and the spatial mapper unit 21 without being processed, and passes through the PTS unit 22, the inverse fast Fourier transformer 23, and the like. The second CS inserter unit 24, the GI inserter unit 25, the windowing unit 26, and the transmission filtering unit 27 respectively process and transmit from the antennas 3a to 3d.

  The L-SIG is a bit sequence in which dummy information is added to transmission parameter information (L-Data rate, L-Length, etc.) defined as SIG in the IEEE 802.11a standard, and includes an FEC encoder unit 14 and an interleaver. Unit 16, mapper unit 17, PTS unit 22, inverse fast Fourier transformer 23, second CS inserter unit 24, GI inserter unit 25, windowing unit 26, and transmission filtering unit 27. Are transmitted from the antennas 3a to 3d.

  In the HT-SIG, a bit sequence in which dummy information is added to transmission parameter information (MCS, Length, etc.) defined by the IEEE 802.11n standard includes an FEC encoder unit 14, an interleaver unit 16, and a mapper unit 17. , PTS unit 22, inverse fast Fourier transformer 23, second CS inserter unit 24, GI inserter unit 25, windowing unit 26, and transmission filtering unit 27, and transmitted from antennas 3 a to 3 d. Is done.

Next, PAPR of the wireless transmission device 1 will be described based on FIG. 12 and FIG.
In the wireless transmission device 1, as shown in FIG. 12A, 64 subcarriers are used as one band, and four bands are used every 20 MHz. By using the third band and the fourth band symmetrically across the center frequency with the first band and the second band, the total bandwidth is 80 MHz.
The first band from -128 to -65, the second band from -64 to -1, the third band from 0 to 63, and the fourth band from 64 to 127, respectively. Can be a band corresponding to the IEEE802.11a standard and the IEEE802.11n standard. The first band and the second band, or the third band and the fourth band can be bands corresponding to the IEEE 802.11n standard.

In the wireless transmission device 1 according to the present embodiment, when the PTS unit 22 rotates the phase of the preamble signal A for each subcarrier, as shown in FIG. The signal A is a preamble signal jA whose phase is advanced by 90 ° in the second band, the third band is a preamble signal Ae ^jθ1, and the fourth band is a preamble signal jAe ^jθ2 . However, θ1 and θ2 are rotation angles (phase differences) rotated by the PTS unit 22.

As described above, when the PTS unit 22 rotates and transmits the phase of the preamble signal A, the PAPR calculated by the following equation changes as shown in the graphs shown in FIGS. 13 and 14 and the table shown in FIG. . However, in the formula, S is a transmission signal, and n is an integer from 0 to N-1, which indicates sampling. max is a function for calculating the peak power, and E is a function for calculating the average electrode. FIG. 13 is a graph showing PAPR in L-STF, and FIG. 14 is a graph showing PAPR in L-LTF. FIG. 15 is a table showing PAPR in L-LTF.

It can be seen from the graphs shown in FIGS. 13 and 14 or the table shown in FIG. 15 that when θ1 is 0 ° and θ2 is 180 °, the PAPR is almost the minimum.
Therefore, in the PTS unit 22 of the wireless transmission device 1 according to the present embodiment, by setting the rotation angle of the preamble signal A to 0 ° and θ2 to 180 °, as shown in FIG. In the third band, the preamble signal A is transmitted as the preamble signal A having no phase difference, and in the fourth band, the preamble signal jA is transmitted as the preamble signal -jA in which the phase of the preamble signal jA is rotated by 180 °.

Thus, by setting θ1 to 0 ° and θ2 to 180 ° as the phase rotation angles of the PTS unit 22, it is possible to reduce PAPR. Therefore, since the PAPR can be reduced, it is possible to suppress the momentary large power from being added to the average power, so that even if the signal amplifier has low linearity, signal amplification is performed in a range without distortion. be able to. Therefore, since the wireless transmission device 1 can transmit a wireless signal without distortion, it is possible to prevent deterioration in transmission quality and interference between adjacent channels, and thus high-quality wireless communication can be performed. In addition, the wireless transmission device 1 is suitable for a mobile terminal because power consumption can be kept low.
Here, in the table shown in FIG. 15, there is an angle at which a lower PAPR can be obtained when θ1 is 0 ° and θ2 is 180 °. However, when θ1 is 0 °, the value of ^ejθ1 is 1, and when θ2 is 180 °, the value of ^ejθ2 is −1, and the phase difference is calculated when the PTS unit 22 generates the preamble signal. Therefore, it is preferable to set θ1 to 0 ° and θ2 to 180 °. As long as the calculation in the PTS unit 22 is possible, an angle at which the PAPR is lower than that when θ1 is 0 ° and θ2 is 180 ° may be set.

Further, with respect to the rotation angle of the preamble signal by the PTS unit 22, θ1 can be set to 180 ° and θ2 can be set to 0 °. By doing so, it is possible to achieve a low PAPR, and when θ1 is 180 °, the value of e ^jθ1 is −1, and when θ2 is 0 °, the value of e ^jθ2 is 1. Calculation of the phase difference when the unit 22 generates the preamble signal can be facilitated. In this case, as shown in FIG. 12C, the preamble signal -A is transmitted in the third band, and the preamble signal jA is transmitted in the fourth band.

  Here, in addition to setting θ1 to 0 °, θ2 to 180 °, θ1 to 180 °, and θ2 to 0 °, θ1 and θ2 are the preamble signal A in the first band and the preamble signal in the second band. It is also possible to make the angle smaller than when a signal conforming to the IEEE802.11n standard is set to jA. By doing so, the wireless transmission device 1 can be set to a low PAPR while having a bandwidth twice that of a transmitter compliant with the IEEE 802.11n standard.

  Also, θ1 and θ2 can be set to angles smaller than when a signal having the first band and the third band as the preamble signal A and the second band and the fourth band as the preamble signal jA is transmitted. By doing so, it is possible to reduce the PAPR as compared with the third band and the fourth band, which are duplicates of the first band and the second band, in the same way as when the IEEE 802.11a standard is expanded to the IEEE 802.11n standard. Can do.

That is, the PAPR of the signal having the first band and the third band as the preamble signal A and the second band and the fourth band as the preamble signal jA is represented by the third band θ1 as the preamble signal Ae ^jθ1 in the graph shown in FIG. Is the same as the case where the second band θ2 is 0 °, which is 0 ° and the preamble signal jAe ^jθ2 (indicated by a point Z in FIG. 13). Therefore, in order to reduce the PAPR, it is understood that θ1 and θ2 set in the wireless transmission device 1 may be set to an angle that becomes a PAPR smaller than the virtual plane L. The angle at which the PAPR is smaller than the virtual plane L is shown as a shaded portion in the table shown in FIG. Within such a range of θ1 and θ2, a low PAPR can be achieved.

  Here, FIG. 16 shows a table comparing the PAPR at the time of transmission of L-STF and L-LTF for the wireless transmission device 1 according to the present embodiment and the transmission device compliant with the IEEE 802.11n standard. It can also be seen from the table shown in FIG. 16 that PAPR can be reduced.

  Thus, in the wireless transmission device 1 according to the embodiment of the present invention, the PAPR can be reduced while ensuring backward compatibility by further expanding the bandwidth from the IEEE 802.11a standard or the IEEE 802.11n standard. Inexpensive and high-quality high-speed transmission is possible.

  In this embodiment, -128 to -65 is the first band, -64 to -1 is the second band, 0 to 63 is the third band, and 64 to 127 is the fourth band. As described above, the first band may be any band from -128 to -63, -64 to -1, 0 to 63, and 64 to 127. The second band is from -128 to -63 when the first band is from -64 to -1, from 64 to 127 when from 0 to 63, and from 0 to 63 when from 64 to 127. It can be. Furthermore, as for the third and fourth bands, two bands of −128 to −1 can be allocated when the first band is 0 to 63 and the second band is 64 to 127.

  The present invention is capable of high-speed transmission at low cost and high quality by realizing a reduction in PAPR even if a wide bandwidth is ensured while ensuring backward compatibility with conventional standards, so that next-generation wireless communication is possible. It is suitable for a transmission device, and particularly suitable for high-definition video distribution because it enables high-speed transmission.

R1 Wireless communication apparatus 1 Wireless transmission apparatus 10a Control means 10b OFDM signal generation means 11 Preamble pilot memory part 12 Scrambler part 13 Encoder parser part 14 FEC encoder part 15 Spatial stream parser part 16 Interleaver part 17 Mapper part 18 STBC encoder part 19 Multiplexer unit 20 First CS inserter unit 21 Spatial mapper unit 22 PTS unit 23 Inverse fast Fourier transform 24 Second CS inserter unit 25 GI inserter unit 26 Windowing unit 27 Transmission filtering unit 2 Radio reception devices 3a to 3h Antenna R2 Other radio communication apparatus

Claims (7)

OFDM generating means for transmitting a communication packet to a wireless receiver by orthogonal frequency division multiplexing modulation, and control means for controlling the OFDM generating means to transmit communication packets in a predetermined order,
The OFDM generation means is compatible with a first band in which the preamble signal A is transmitted as a preamble signal A without a phase difference and a second band that is set as an extension band of the first band and is transmitted as a preamble signal jA. A communication packet is transmitted using a third band and a fourth band that are arranged symmetrically with the compatible band and set as an extension band of the compatible band, and the first band and the second band. A wireless transmission device having a function of generating a preamble signal in which the third band is a preamble signal Ae ^jθ1 and the fourth band is a preamble signal jAe ^jθ2 .   The OFDM generating means has a peak-to-average power ratio that is smaller than that in the case of transmitting a signal in which the first band and the third band are a preamble signal A and the second band and the fourth band are a preamble signal jA. The radio transmission apparatus according to claim 1, further comprising a function of generating a preamble signal based on and θ2.   The radio transmission apparatus according to claim 1 or 2, wherein the OFDM generation means generates a preamble signal with a phase in which θ1 is set to 0 ° and θ2 is set to 180 °.   The radio transmission apparatus according to claim 1 or 2, wherein the OFDM generation means generates a preamble signal with a phase in which θ1 is set to 180 ° and θ2 is set to 0 °.   Each of the first to fourth bands is a band corresponding to the IEEE802.11a standard and the IEEE802.11n standard, and the first and second bands or the third and fourth bands are the IEEE802.11n standard. The wireless transmission device according to any one of claims 1 to 4, wherein the wireless transmission device has a bandwidth corresponding to.   The control means generates L-STF, L-LTF, L-SIG, HT-SIG corresponding to the IEEE 802.11n standard as the communication packet in the predetermined order, and as the L-SIG and the HT-SIG 6. The wireless transmission device according to claim 5, wherein the subsequent communication packet is a communication packet to which dummy information is added so that the wireless reception device of the IEEE802.11a standard or the IEEE802.11n standard receives the data as data. In a preamble generation method of a wireless transmission device that transmits a communication packet to a wireless reception device by orthogonal frequency division multiplexing modulation,
A compatible band is a first band in which the preamble signal A is transmitted as a preamble signal A without a phase difference and a second band that is set as an extension band of the first band and is transmitted as a preamble signal jA. For the third band and the fourth band set as the extension bands of the compatible band, a preamble signal in which the third band is a preamble signal Ae ^jθ1 and the fourth band is a preamble signal jAe ^jθ2 A method of generating a preamble signal of a wireless transmission device, wherein the method generates and transmits as a communication packet.