JP2010232857A - Transmitter and communication system equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter for suppressing power leakage to an adjoining channel and for reducing a peak power relative to an average power. <P>SOLUTION: In a transmitter 1, band pass filters BPF1-BPF4 divides transmission spectrum Σδ(t-nTs)a<SB>n</SB>into division transmission spectrums DVS1-DVS4 by transmission functions H<SB>1</SB>(ω)-H<SB>4</SB>(ω) respectively. The division transmission spectrums DVS1-DVS4 are subjected to convolution to limit a band. Multipliers MP1-MP4 multiply the division transmission spectrums DVS1-DVS4 supplied from the band pass filters BPF1-BPF4 by e<SP>jω1t</SP>to e<SP>jω4t</SP>for frequency conversion. An adder SUM1 arranges in series division transmission spectrums DVS1'-DVS4' each of which frequency has been converted for transmission. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transmitter and a communication system including the transmitter, and more particularly to a transmitter that divides a transmission spectrum into a vacant communication band and transmits the transmission spectrum and a communication system including the transmitter.

  With the development of communication systems for the realization of ubiquitous networks, indoor and short-range personal wireless systems such as wireless LAN (Local Area Network) and RF-ID (Radio Frequency Identification) are spreading and developing. Demand for radio waves is expected to increase further in the future.

  However, frequency resources are limited, and radio waves are imminent in a band of 6 GHz or less suitable for mobile communication and the above-described wireless system, so that it is difficult to assign a new frequency band.

  On the other hand, it is desirable that a self-operated indoor or short-range wireless system as described above does not require a license, and is normally operated in an ISM (Industry-Science-Medical) band such as 2,4 GHz. For this reason, with the increase in radio wave usage in the future, there are concerns about an increase in transmission delay due to shortage of radio channels, a decrease in transmission speed, and an increase in transmission errors due to interference.

  The ISM band is shared by various radio systems, and various radio systems confirm the availability of radio channels of any frequency and bandwidth by carrier sense and secure their radio resources (frequency and time slot). Are used. For this reason, a lot of fragmented free radio resources, that is, a large number of “gaps” in the spectrum are left unnecessarily.

  In order to solve this problem, a dynamic spectrum access (DSA) system concept and a control channel configuration in which fragmented free spectrum is accumulated and used as one radio channel have been proposed (Non-patent Documents 1 and 2). .

  As a method of dividing the transmission spectrum into a plurality of bands and making them discontinuous, OFDMA (Orthogonal Frequency Division Multiplexing Access) (non-Frequency Division Multiplexing Access) OFDMA (Orthogonal Frequency Division Multiplexing Access) (OFDM) 3) Fast Fourier Transform (FFT) for single carrier modulation, mapping of discrete spectrum corresponding to OFDM subcarriers on the frequency axis, and inverse Fast Fourier Transform (IFFT: Inverse Fast Fourier Transform) Single carrier transmission method (non-transmission) Patent Document 4) it has been proposed.

  In any of these systems, a CP (Cyclic Prefix) is added to the head of the FFT block for transmission.

  Further, in the ISM band and the like, asynchronous other systems are generally operated between adjacent channels, and power leakage to the adjacent channels directly causes interference. And reception of the own system is equivalent to reception with a matched filter of a sinc function, and interference from other systems of adjacent channels also occurs.

  In order to solve this problem, a method has been proposed in which subcarriers are band-limited by wavelet transform or filters to reduce power leakage to adjacent channels (Non-Patent Document 5).

Taro Maruma, Hitoshi Yano, Seiji Tsukamoto, Masazumi Kamiha, “Proposal of Dynamic Spectrum Access System for Highly Efficient Frequency Sharing in ISM Band,” IEICE Technical Report, SR2008-07, March 2009. Hitoshi Yano, Hideyoshi Tsuji, Yasuo Suzuki, Seiji Tsukamoto, Makoto Taro, Masazumi Ueha, “Examination of physical channel configuration of dynamic spectrum access system for high-efficiency frequency sharing in ISM band,” IEICE Technical Report, SR2008- 08, March 2009. Noriyuki Fukui, Hiroki Kubo, “Evolved UTRA frequency scheduling and CQI transmission method,” 2008 Shingaku Sodai, BS-4-8, pp. S-45-46, Sep. 2008. Shingo Sasashima and Seiichi Sampei, “Study on Wideband Single-Carrier Transmission System Using Dynamic Spectrum Access Control,” IEICE Technical Report, RCS 2006-233, Jan. 2007. Tetsuo Ohori, Junichi Onodera, Kenji Gojima, Takeshi Terao, Kei Suyama, Hiroshi Suzuki, “Evaluation of Feasibility of Gaussian Multicarrier Transmitter by FPGA Implementation,” IEICE Tech. RCS2007-220, March. 2008. K. Takeba, H. Tomeda, and F. Adachi, “Iterative overlap FDE for DS-CDMA without GI,” Proc. IEEE Vch. Technol. Conf. (VTC 2006 fall), Montreal, Sep. 2006.

  However, the methods described in Non-Patent Documents 3 and 4 have a problem that power leakage to the adjacent channel is increased.

  In addition, the method described in Non-Patent Document 5 has a problem that the peak power with respect to the average power is increased.

  Accordingly, the present invention has been made to solve such a problem, and an object thereof is to provide a transmitter capable of suppressing power leakage to an adjacent channel and reducing peak power with respect to average power. It is.

  Another object of the present invention is to provide a communication system including a transmitter capable of suppressing power leakage to an adjacent channel and reducing peak power with respect to average power.

  According to the present invention, the transmitter is a transmitter that transmits data using a free communication band, and includes a detection unit, a division filter, a band limiting filter, and a transmission unit. The detecting means detects a plurality of free communication bands that are communication bands that are not used for data communication. The division filter divides a transmission spectrum obtained by frequency-modulating transmission data into j (j is a positive integer) free communication bands including a minimum number of free communication bands as many as possible. The band limiting filter performs band limiting processing by performing a convolution operation on j divided transmission spectra divided into j free communication bands. The transmission means transmits the j divided transmission spectrums subjected to the band limitation process.

  Preferably, the band limiting filter is a root cosine roll-off filter.

  Preferably, the j free communication bands are free communication bands selected from a plurality of free communication bands in order of increasing bandwidth.

  Preferably, the division filter maintains an order of a plurality of discrete frequency components of the transmission spectrum, and a free communication band included in the plurality of free communication bands so that the plurality of frequency components are as continuous as possible. The transmission spectrum is divided into j free communication bands.

  Preferably, the division filter includes a serial / parallel converter, a Fourier transformer, a mapper, and an inverse Fourier transformer. The serial / parallel converter divides the transmission spectrum into a plurality of blocks each composed of N (N is an integer of 2 or more) symbols, and converts the plurality of blocks from a serial arrangement to a parallel arrangement. The Fourier transformer performs a fast Fourier transform on a plurality of blocks. The mapper multiplies the output signal of the Fourier transformer by a mapping matrix composed of LN rows × N columns (L is an integer that is a power of 2 equal to or greater than 2). The inverse Fourier transformer performs an inverse fast Fourier transform on the output signal of the mapper. The band limiting filter includes a convolution filter and a parallel / serial converter. The convolution filter limits the band of the output signal by performing a convolution operation on the output signal of the inverse Fourier transformer. The parallel / serial converter converts the operation result by the convolution filter from the parallel array to the serial array. Each column of the mapping matrix corresponds to the frequency component of the output signal from the Fourier transformer. Each row of the mapping matrix corresponds to an input frequency component to the inverse Fourier transformer. Furthermore, the mapper converts the frequency components at both ends of the inverse Fourier transformer to a null spectrum, maintains the order of the discrete spectrum received from the Fourier transformer, and further converts the discrete spectrum so that the frequency components of the discrete spectrum are as continuous as possible. Map.

  According to the present invention, the communication system is a communication system that transmits and receives data using a vacant communication band, and includes a transmitter and a receiver. The transmitter transmits the transmission data to j (j is a positive integer) free communication bands, which are composed of as few free communication bands as possible, among a plurality of free communication bands which are communication bands not used for data communication. The frequency-modulated transmission spectrum is divided, and the band limiting process is performed by performing a convolution operation on the j divided transmission spectrums divided into j free communication bands. Transmit the divided transmission spectrum. The receiver receives the j divided transmission spectra transmitted from the transmitter, and obtains a received signal by equalizing the received j divided transmission spectra on the frequency axis.

  In the present invention, the transmission spectrum is divided into j free communication bands, which are as small as possible, among a plurality of free communication bands in the wireless communication space, and each of the divided j divided transmission spectra is divided. On the other hand, the band is limited by performing a convolution operation. Then, j divided transmission spectra whose bandwidths are limited are transmitted.

  As a result, by dividing the transmission spectrum into j free communication bands, that is, by reducing the number of divisions of the transmission spectrum as much as possible, each divided transmission spectrum becomes a kind of partial response signal, The peak power with respect to the average power decreases as the number of transmission spectrum divisions decreases. Further, by performing convolution operation on each of the j divided transmission spectra to limit the band, the side lobe of each divided transmission spectrum is lowered.

  Therefore, according to the present invention, power leakage to an adjacent channel can be suppressed, and peak power with respect to average power can be reduced.

1 is a schematic diagram of a communication system according to an embodiment of the present invention. It is the schematic which shows the structure of the transmitter shown in FIG. It is the schematic which shows the structure of the receiver shown in FIG. It is a conceptual diagram of an operating frequency band. It is a conceptual diagram for demonstrating operation | movement in the serial / parallel converter and Fourier-transformer of the transmitter 1 shown in FIG. It is a conceptual diagram of mapping and convolution. It is a conceptual diagram for demonstrating the operation | movement in an inverse Fourier transformer, a convolution filter, and a parallel / serial converter shown in FIG. It is a conceptual diagram of overlap FDE. It is a conceptual diagram of the transmitter shown in FIG. It is a conceptual diagram of a transmission signal. It is a conceptual diagram of the receiver shown in FIG. It is a conceptual diagram of the output signal of a matched filter.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic diagram of a communication system according to an embodiment of the present invention. Referring to FIG. 1, a communication system 10 according to an embodiment of the present invention includes a transmitter 1 and a receiver 2. The transmitter 1 and the receiver 2 are arranged in a wireless communication space. Although not shown in FIG. 1, there are other communication devices that perform wireless communication using various wireless systems.

  The transmitter 1 divides the transmission data into a vacant communication band in a wireless communication space that is not used for data transmission by other communication devices and transmits the data to the receiver 2 by a method described later.

  The receiver 2 receives transmission data from the transmitter 1 and processes the received transmission data by a method described later.

  FIG. 2 is a schematic diagram showing the configuration of the transmitter 1 shown in FIG. Referring to FIG. 2, the transmitter 1 includes a modulator 11, a serial / parallel converter 12, a Fourier transformer 13, a mapper 14, a detection unit 15, an inverse Fourier transformer 16, and a convolution filter. 17, a parallel / serial converter 18, transmission means 19, and an antenna 20.

  The modulator 11 receives transmission data composed of a digital signal, and frequency-modulates the received transmission data according to a predetermined method. Then, the modulator 11 outputs the frequency-modulated transmission spectrum to the serial / parallel converter 12.

  The serial / parallel converter 12 receives the transmission spectrum from the modulator 11, blocks the received transmission spectrum for each N (N is an integer of 2 or more) symbols, and blocks M (an integer consisting of an odd number). , The generated M blocks are converted from a serial array to a parallel array, and the M blocks including the parallel array are output to the Fourier transformer 13.

  The Fourier transformer 13 receives M blocks arranged in parallel from the serial / parallel converter 12, and performs M fast Fourier transform on the N symbols included in each of the received M blocks. Perform in parallel on the block. Then, the Fourier transformer 13 outputs a signal D, which is a result of the fast Fourier transform process for the M blocks, to the mapper 14. This signal D is composed of M divided transmission spectrum blocks, and each of the M divided transmission spectrum blocks is composed of N frequency components.

  The mapper 14 receives M divided transmission spectrum blocks from the Fourier transformer 13 and receives a plurality of vacant communication bands in the wireless communication space from the detection means 15. Then, the mapping device 14 uses, as a minimum, free communication of N frequency components included in each of the M divided transmission spectrum blocks based on a plurality of free communication bands. A mapping matrix <P> for dividing into bands is generated.

  In this specification, the notation <A> represents the matrix A.

  When the mapping unit 14 generates the mapping matrix <P>, the mapping unit <P> generates N frequency components included in each of the M divided transmission spectrum blocks using the generated mapping matrix <P>. Is divided into free communication bands consisting of as few as possible. Then, the mapping unit 14 outputs the signal S as a result of the division to the inverse Fourier transformer 16. This signal S is composed of M mapping blocks, and each of the M mapping blocks is composed of LN (L is an integer made up of a power of 2 of 2 or more) frequency components.

  The detection means 15 detects a plurality of vacant communication bands in the wireless communication space by performing carrier sense via the antenna 20 at all times or periodically at a predetermined time interval. Then, the detection means 15 outputs the detected plurality of free communication bands to the mapping device 14.

  The inverse Fourier transformer 16 receives the signal S from the mapper 14 and performs inverse fast Fourier transform on the LN frequency components included in each of the M mapping blocks constituting the received signal S to obtain time axis data. The signal is converted, and a signal s as a result of the conversion is output to the convolution filter 17.

  The convolution filter 17 performs a convolution operation on the signal s received from the inverse Fourier transformer 16 by a method described later, and outputs the operation result to the parallel / serial converter 18.

  The parallel / serial converter 18 converts the operation result received from the convolution filter 17 from a parallel array to a serial array, and outputs a baseband signal having the serial array to the transmission unit 19.

  The transmission means 19 converts the baseband signal received from the parallel / serial converter 18 from a digital signal to an analog signal, converts the baseband signal composed of the analog signal into a predetermined frequency band, and receives the signal via the antenna 20. Transmit to machine 2.

  FIG. 3 is a schematic diagram showing the configuration of the receiver 2 shown in FIG. Referring to FIG. 3, the receiver 2 includes an antenna 21, an AD converter 22, a serial / parallel converter 23, a convolution filter 24, a Fourier transformer 25, a detection unit 26, and a demapping unit 27. And an inverse Fourier transformer 28 and a symbol determiner 29.

  The antenna 21 receives a baseband signal from the transmitter 1 and outputs the received baseband signal to the AD converter 22.

  The AD converter 22 receives a baseband signal from the antenna 21, converts the received baseband signal from an analog signal to a digital signal, and outputs the baseband signal composed of the converted digital signal to the serial / parallel converter 23. To do.

  The serial / parallel converter 23 converts the baseband signal received from the AD converter 22 from a serial array to LN parallel arrays, and outputs the converted baseband signal including the LN parallel arrays to the convolution filter 24. To do.

  The convolution filter 24 performs a convolution operation on the baseband signal composed of LN parallel arrays received from the serial / parallel converter 23, and outputs the operation result to the Fourier transformer 25.

  The Fourier transformer 25 performs a fast Fourier transform on the calculation result of the convolution filter 24 and outputs a baseband signal composed of frequency components to the demapping unit 27.

  The detecting means 26 always senses the carrier via the antenna 21 and detects a plurality of free communication bands in the wireless communication space. Then, the detection unit 26 outputs the detected plurality of free communication bands to the demapping unit 27.

The demapping unit 27 generates a mapping matrix <P> by the same method as the mapping unit 14 based on a plurality of free communication bands received from the detecting means 26, and a demapping matrix that is a transposed matrix of the generated mapping matrix <P>. Mapping matrix <P> ^T is calculated. Then, the demapping unit 27 performs equalization on the frequency selective propagation path on the frequency axis with respect to the baseband signal received from the Fourier transformer 25 by a method described later, and demapping the signal after the equalization. The matrix <P> ^T is multiplied to convert a signal composed of LN frequency components into a signal composed of N frequency components. Thereafter, the demapping unit 27 outputs a signal composed of L frequency components to the inverse Fourier transformer 27.

  The inverse Fourier transformer 28 performs inverse fast Fourier transform on the signal received from the demapping unit 27 and outputs the converted signal to the symbol determination unit 29.

  The symbol determiner 29 determines a signal from the inverse Fourier transformer 28 and acquires received data.

  FIG. 4 is a conceptual diagram of the operating frequency band. Referring to FIG. 4, the operating frequency band is a frequency band such as a 2.4 GHz band. The communication bands B1 to B4 included in the operation frequency band are used by different wireless systems, and empty communication bands EB1 to EB5 exist in the gaps between the communication bands B1 to B4.

  Assuming that the bandwidth of the transmission data is W, the empty communication bands EB1 to EB5 have bandwidths W1 to W5 that are narrower than the bandwidth W, respectively. Therefore, transmission data of the bandwidth W cannot be transmitted using one free communication band (any of the free communication bands EB1 to EB5) out of the free communication bands EB1 to EB5.

  However, the total of the bandwidths W1 to W5 of the free communication bands EB1 to EB5 is larger than the bandwidth W. Accordingly, among the bandwidths W1 to W5 of the vacant communication bands EB1 to EB5, the vacant communication band (at least two or more vacant communication bands of the vacant communication bands EB1 to EB5) whose total bandwidth is equal to or greater than the bandwidth W is used. For example, transmission data of bandwidth W can be transmitted.

  Therefore, in the embodiment of the present invention, the transmitter 1 divides transmission data into as few free communication bands as possible selected from the free communication bands EB1 to EB5 and transmits the divided transmission data to the receiver 2.

  Hereinafter, detailed operations in the transmitter 1 will be described in the case of N = 8, L = 2, and J = 4. J represents the number of free communication bands used for transmission data division among the free communication bands EB1 to EB5, and consists of an integer of 2 or more.

  FIG. 5 is a conceptual diagram for explaining operations in the serial / parallel converter 12 and the Fourier transformer 13 of the transmitter 1 shown in FIG.

  Referring to FIG. 5, serial / parallel converter 12 modulates a complex baseband signal DA (see FIG. 5A) in symbol units modulated by BPSK, QPSK, QAM or the like according to transmission data. 11 is divided into M blocks BLK_1 to BLK_M for every N symbols (see (b) of FIG. 5).

  Then, the serial / parallel converter 12 converts the M blocks BLK_1 to BLK_M from the serial array to the parallel array, and Fourier-transforms the M blocks BLK_1 to BLK_M (see FIG. 5C) including the parallel array. Output to the device 13.

  The Fourier transformer 13 performs fast Fourier transform on the M blocks BLK_1 to BLK_M having a parallel arrangement in parallel, and M blocks BLK_1_f to BLK_M_f having a parallel arrangement (each block BLK_1_f to BLK_M_f is generated from N frequency components). 5 (see (d) of FIG. 5) is output to the mapper 14.

  FIG. 6 is a conceptual diagram of mapping and convolution. FIG. 7 is a conceptual diagram for explaining operations in the inverse Fourier transformer 16, the convolution filter 17, and the parallel / serial converter 18 shown in FIG.

  Referring to FIG. 6, mapping device 14 maps N frequency components FSS of blocks BLK_1_f to BLK_M_f to frequency component FSSM using mapping matrix <P>.

  When mapping N (= 8) frequency components FSS to LN (= 16) frequency components FSSM, (LN)! / {(L-1) N}! There is a street mapping. Therefore, in the embodiment of the present invention, the following restriction is provided.

  (A) The frequency index at both ends of the inverse Fourier transformer 16 is set to a null spectrum.

  (B) The order of the discrete spectrum is not changed.

(C) The discrete spectrum is mapped so that the index is as continuous as possible, and the number of divisions is J or less (J is an integer of 2 or more).

  The above limitation (a) means that when N = 8 and LN = 16, no spectrum is mapped to the index IDX1 and the index IDX16.

  In addition, the restriction (b) means that mapping is performed while maintaining the order of the N frequency components constituting the frequency component FSS.

  Further, the above restriction (c) selects as few free communication bands as possible in the order of wide bandwidth from a plurality of free communication bands, and divides the discrete spectrum (frequency component FSS) into the selected free communication bands. Means that.

  As a result of applying the above restrictions (a) to (c), the four frequency components FSS1 are mapped to the four frequency components FSSM1 composed of the indices IDX2 to IDX5, and the one frequency component FSS2 is mapped to the index IDX7. Is mapped to one frequency component FSSM2 and one frequency component FSS3 is mapped to one frequency component FSSM3 consisting of an index IDX10, and two frequency components FSS4 are mapped to two frequency indexes FSX4 and IDX14 Maps to frequency component FSSM4. In this case, the number J of free communication bands is four.

  A mapping matrix <P> for mapping the frequency components FSS1 to FSS4 to the frequency components FSSM1 to FSSM4 is expressed by the following equation.

  The mapping matrix <P> has a size of LN rows and N columns in which unit matrices corresponding to the divided J (= 4) subspectrums (frequency components FSSM1 to FSSM4) are arranged. Each column of the mapping matrix <P> corresponds to the frequency index of the output of the N-point Fourier transformer 13, and each row corresponds to the frequency index of the input of the LN-point inverse Fourier transformer 16. Each column is composed of different unit vectors in which only one element is “1” and the others are “0”. Furthermore, the zero vector row corresponds to the index of the null spectrum, and the first row and the LN row are zero vectors by the restriction (a).

  The mapper 14 generates a mapping matrix <P> shown in Expression (1) based on the plurality of free communication bands received from the detection means 15 and the above-described restrictions (a) to (c), and the generated mapping The frequency components FSS1 to FSS4 are mapped to the frequency components FSSM1 to FSSM4 by multiplying the frequency component FSS of each block BLK_m_f (m is an integer satisfying 1 ≦ m ≦ M) received from the Fourier transformer 13 by the matrix <P>. To do.

  That is, the mapping unit 14 maintains the order of a plurality of discrete frequency components of the transmission spectrum, and the transmission spectrum is included in the plurality of unused communication bands so that the plurality of frequency components are as continuous as possible. The transmission spectrum is divided into four free communication bands. In this case, the four free communication bands are free communication bands selected from a plurality of free communication bands in order of increasing bandwidth.

  By this division, each divided transmission spectrum becomes a kind of partial response signal, and the peak power with respect to the average power becomes lower as the number of divisions of the transmission spectrum decreases.

  Referring to FIG. 7, block BLKM_m mapped by mapper 14 is composed of a matrix of LN rows and 1 column (see (a) of FIG. 7).

  Then, the inverse Fourier transformer 16 performs an inverse Fourier transform on each LN frequency component of the block BLKM_m to generate a block BLKM_m.

  The convolution filter 17 includes a root cosine roll-off filter, and performs a convolution operation on each component of the block BLKM_m. As shown in FIG. 6, this convolution operation performs band limitation on four sub-spectrums so that power does not leak between adjacent sub-spectrums in four sub-spectrums composed of frequency components FSSM1 to FSSM4. It is. Due to this band limitation, the side lobe of each divided sub-spectrum is lowered.

  The parallel / serial converter 18 receives the block BLKM_m on which the convolution operation has been performed from the convolution filter 17, and converts the received block BLKM_m from the parallel array to serial data suitable for DA conversion.

  More specifically, the parallel / serial converter 18 converts each element of the block BLKM_m from the parallel array to serial data suitable for DA conversion, and from the converted block BLKM_m (see FIG. 7B). A baseband output signal is generated.

The baseband output signal is y (t), and the kth k corresponding to the mth FFT block (the block input to the Fourier transformer 13) of the output of the convolution filter 17 (k is −LN / 2− ( Integer satisfying LN / 2) -1) When the sample value is ym _{, k} , the following equations (2) to (5) are obtained.

Here, h _k = h (kTs / L) and h (t) are impulse responses of the convolution filter 17 (= band limiting filter), and Ts is a symbol period. Further, sm _{, k} is an output of the kth inverse Fourier transformer 16 for the mth FFT block (block inputted to the Fourier transformer 13). Further, S _{m, k ′} is the frequency index of the k′-th inverse Fourier transformer 17. Furthermore, D _{m, n} is the output of the Fourier transform 13 of the nth frequency index for the mth FFT block (the block input to the Fourier transform 13). M ′ is the number of blocks corresponding to the length of the impulse response h _k of the convolution filter 17, and the impulse response length is equal to NM′Ts.

  Hereinafter, in the embodiment of the present invention, M ′ is an odd number of 3 or more. The convolution filter 17 stores the output data of the inverse Fourier transformer 16 for a total of M ′ blocks of the block and the preceding and following (M′−1) / 2 blocks with respect to the m-th block to be calculated. A buffer memory is provided, and the calculation of Expression (2) is performed on the data of M ′ blocks.

  Specifically, M ′ = 3 to 5 is selected. Note that M ′ may be an even number. In this case, the buffer memory and the calculation are performed by the m-th block, the previous (M ′ / 2) −1 block, and the subsequent M ′ / 2 block. This may be performed for a total of M ′ blocks, or a total of M ′ blocks including the block, M ′ / 2 blocks before, and (M ′ / 2) −1 blocks after. .

Therefore, Fourier transformer 13, i (i is a positive integer) receiving a d _i is the modulation complex amplitude of th transmit symbol from the modulator 11, assigns the received modulated complex amplitude d _i in equation (5) Then, D _{m, n} is calculated, and the calculated D _{m, n} is output to the mapper 14.

The mapper 14 generates a mapping matrix <P> shown in the expression (1) based on the plurality of free communication bands and the restrictions (a) to (c) received from the detecting unit 15, and the generated mapping matrix <P > And D _{m, n} received from the Fourier transformer 13 are substituted into the equation (4) to calculate S _m, and the calculated S _m is output to the inverse Fourier transformer 16.

The inverse Fourier transformer 16 calculates S _{m, k} by substituting S _m received from the mapper 14 into Equation (3), and outputs the calculated s _{m, k} to the convolution filter 17. The convolution filter 17 performs a convolution operation by substituting s _{m, k} received from the inverse Fourier transformer 17 into Equation (2), and outputs ym _{, k} to the parallel / serial converter 18. The parallel / serial converter 18 converts _{ym, k} from the parallel array to the serial array and outputs the baseband output signal y (t) to the transmission means 19.

  Then, the transmission means 19 converts the baseband output signal y (t) from a digital signal to an analog signal, and transmits the baseband output signal y (t) composed of the analog signal to the receiver 2 via the antenna 20.

  In the above description, when N = 8, L = 2, and J = 4, it has been described that the mapping matrix <P> is composed of Equation (1). However, the mapping matrix <P> is generally It consists of an expression.

In Expression (6), O _{M, N} is a zero matrix of M rows and N columns, and I _M is an M-th order unit matrix. M _j is a frequency index proportional to the bandwidth of the j-th (j = 1, 2,..., J) sub-spectrum, and M ₀ ′ is the lower side of the first sub-spectrum. The number of null frequency indexes, M _J ′ is the number of null frequency indexes on the upper side of the j-th sub-spectrum, and M _j ′ is the j-th and j + 1-th (where 1 ≦ j ≦ J−1). Null frequency index number between sub-spectrums. M ₀ ′ and M _j ′ satisfy the following expression.

  Next, the operation in the receiver 2 will be described. First, the operation in the receiver 2 will be conceptually described. In the receiver 2, the AD converter 22 converts the baseband signal received from the antenna 21 from an analog signal to a digital signal, and the baseband signal composed of the digital signal (see (c) in FIG. 7) is serial / parallel. Output to the converter 23.

  The serial / parallel converter 23 converts the M blocks BLKM_1 to BLKM_M constituting the baseband signal from the serial arrangement to the parallel arrangement, and convolves the blocks BLKM_1 to BLKM_M (see FIG. 7B) having the parallel arrangement. Output to the filter 24.

  The convolution filter 24 receives the blocks BLKM_1 to BLKM_M from the serial / parallel converter 23, and applies the convolution operation of Expression (9) to the input data of M 'blocks per output of one block.

  The Fourier transformer 25 performs fast Fourier transform on the LN frequency components of each of the blocks BLKM_1 to BLKM_M on which the convolution operation has been performed, and outputs the blocks BLKM_1_f to BLKM_M_f (see FIG. 7A) to the demapping unit 27. To do.

The demapping unit 27 performs equalization on the frequency axis for each of the blocks BLKM_1_f to BLKM_M_f using the demapping matrix <P> ^T by a method to be described later, and converts the blocks BLKM_1_f to BLKM_M_f after the equalization. The demapping matrix <P> ^T is multiplied to convert the blocks BLKM_1_f to BLKM_M_f composed of LN frequency components into blocks BLK_1_f to BLK_M_f composed of N frequency components (see (d) of FIG. 5).

  The inverse Fourier transformer 28 performs inverse fast Fourier transform on each of the N frequency components of the blocks BLK_1_f to BLK_M_f received from the demapping unit 27, and the blocks BLK_1 to BLK_M after the transformation (see (c) of FIG. 5). Is output to the symbol determiner 29.

  As a result, the symbol determiner 29 receives blocks BLK_1 to BLK_M blocked in the transmitter 1. Therefore, the symbol determiner 29 obtains received data by determining each component of the blocks BLK_1 to BLK_M.

When the complex baseband signal of the received signal received by the receiver 2 is r (t) and the kth sample value of the mth block of the signal is rm _{, k} , the sample value rm _{, k} is It is expressed by the following formula.

  Then, the following expressions (9) to (12) are obtained.

  Note that the matrix <W> is a frequency axis equalization weight, and is determined based on, for example, a minimum square error method (MMSE) (Non-Patent Document 6).

In the receiver 2, the serial / parallel converter 23 receives rm _{, k} from the AD converter 22, converts the received rm _{, k} from the serial array to the parallel array, and outputs it to the convolution filter 24.

The convolution filter 24 performs a convolution operation by substituting rm _{, k} received from the serial / parallel converter 23 into the equation (9), and supplies the q _{m, k} obtained by the convolution operation to the Fourier transformer 25. Output.

  When M ′ is an odd number, the output for each block is input data for a total of M ′ blocks of the block and the preceding and following (M′−1) / 2 blocks as shown in Equation (9). Is calculated from Accordingly, the convolution filter 24 has a buffer memory for storing input data for M ′ blocks, like the convolution filter 17. M ′ may be an even number. In this case, the buffer memory and the operation are performed by calculating the total M ′ of the m-th block, the previous (M ′ / 2) −1 block, and the subsequent M ′ / 2 blocks. This may be done for a total of M ′ blocks, that is, a block, the block, the previous M ′ / 2 blocks, and the subsequent (M ′ / 2) −1 blocks.

The Fourier transformer 25 substitutes q _{m, k} received from the convolution filter 24 into the equation (10), performs fast Fourier transform, and outputs the converted Q _{m, k ′} to the demapping unit 27.

Demapper 27, Q _m received from Fourier transformer _25, the _{k 'into} Equation (12) calculates a Z _m, and outputs the calculated Z _m to the inverse Fourier transformer 28.

Inverse Fourier transformer 28, calculates the _{z m, n} and _{Z m} received from the demapper 27 are substituted into equation (11), and outputs the computed _{z m,} the _n to the symbol determiner 29.

The symbol determiner 29 determines z _{m, n} received from the inverse Fourier transformer 28 to obtain received data.

  The equalization performed by the demapping unit 27 using the equation (12) is called an overlap FDE (Frequency Domain Equalizer). FIG. 8 is a conceptual diagram of the overlap FDE.

  Since the demapping unit 27 receives the blocks BLKM_1_f to BLKM_M_f (see FIG. 7A) from the Fourier transformer 25, the three consecutive blocks are represented as BLKM_t_f, BLKM_t + 1_f, and BLKM_t + 2_f.

  Then, the demapping unit 27 arranges the target block (any one of BLKM_t_f, BLKM_t + 1_f, and BLKM_t + 2_f) in the center of the point FFT interval, and performs frequency domain equalization (FDE). Then, the demapping unit 27 extracts only the center block from the obtained post-FDE blocks, and performs frequency domain equalization (FDE) while overlapping the FFT sections in order to equalize the next block. The demapping unit 27 performs this repeatedly to equalize the blocks BLKM_1_f to BLKM_M_f.

  FIG. 9 is a conceptual diagram of the transmitter 1 shown in FIG. FIG. 10 is a conceptual diagram of a transmission signal. Referring to FIG. 9, transmitter 1 conceptually includes bandpass filters BPF1 to BPF4, multipliers MP1 to MP4, and an adder SUM1.

  Each of the bandpass filters BPF1 to BPF4 includes a bandpass filter having a low side lobe to an adjacent channel (adjacent frequency band). The bandpass filters BPF1 to BPF4 are bandpass filters that divide the transmission spectrum into as few free communication bands as possible out of a plurality of free communication bands in the wireless communication space.

More specifically, the band-pass filter BPF1 are transmitted signal Σδ (t-nTs) be represented using any of a modulation symbol _{a n} undergo _{a n,} transmits the received transmission signal Σδ (t-nTs) _{a n} The band is divided by the function H ₁ (ω), and the divided transmission spectrum DVS1 obtained by the band division is output to the multiplier MP1.

Further, the band-pass filter BPF2 receives the transmission signal Σδ (t-nTs) _{a n,} and band-divided by the received transmission signal Σδ (t-nTs) transmitting _{a n} function _{H 2 (ω),} the band division The divided transmission spectrum DVS2 is output to the multiplier MP2.

Further, the band-pass filter BPF3 receives the transmission signal Σδ (t-nTs) _{a n,} and band-divided by the received transmission signal Σδ (t-nTs) transmitting _{a n} function _{H 3 (ω),} the band division The divided transmission spectrum DVS3 is output to the multiplier MP3.

Further, the band pass filter BPF4 receives the transmission signal Σδ (t-nTs) _{a n,} and band-divided by the received transmission signal Σδ (t-nTs) transmitting _{a n} function _{H 4} (omega), the band division The divided transmission spectrum DVS4 is output to the multiplier MP4.

  In this case, the bandpass filters BPF1 to BPF4 limit the bands of the divided transmission spectra DVS1 to DVS4, respectively, by the above-described convolution operation.

Multiplier MP1 multiplies ^{e Jomega1t} split transmission spectrum DVS1 received from the band-pass filter BPF1, and outputs a multiplication result divided transmission spectrum DVS1 '(see FIG. 10) to the adder SUM1.

Also, the multiplier MP2 multiplies ^{e Jomega2t} split transmission spectrum DVS2 received from the band-pass filter BPF2, and outputs a multiplication result divided transmission spectrum DVS2 '(see FIG. 10) to the adder SUM1.

Furthermore, the multiplier MP3 multiplies ^{e Jomega3t} split transmission spectrum DVS3 received from the band-pass filter BPF 3, and outputs a multiplication result divided transmission spectrum DVS3 '(see FIG. 10) to the adder SUM1.

Furthermore, the multiplier MP4 multiplies ^{e Jomega4t} split transmission spectrum DVS4 received from the band-pass filter BPF 4, and outputs a multiplication result divided transmission spectrum DVS4 '(see FIG. 10) to the adder SUM1.

In this way, the multipliers MP1 to MP4 convert the frequencies of the divided transmission spectra DVS1 to DVS4 by the frequencies ω ₁ / (2π) to ω ₄ / (2π), respectively, to obtain the divided transmission spectra DVS1 ′ to DVS4 ′ (FIG. 10) is output to the adder SUM1.

  The frequency of the divided transmission spectrums DVS1 to DVS4 is converted by the multipliers MP1 to MP4 so that the divided transmission spectra DVS1 to DVS4 do not overlap with the adjacent divided transmission spectra.

  The adder SUM1 receives four divided transmission spectra DVS1 ′ to DVS4 ′ from the multipliers MP1 to MP4, and generates the baseband signal by arranging the received four divided transmission spectra DVS1 ′ to DVS4 ′ in series. To do.

In this case, the sum of the passbands of the transfer functions H ₁ (ω) to H ₄ (ω) is equal to the bandwidth W of single carrier modulation of a normal continuous spectrum with respect to the symbol period Ts, and satisfies the following equation. Each of the transfer functions H ₁ (ω) to H ₄ (ω) has a root cosine roll-off characteristic.

  FIG. 11 is a conceptual diagram of the receiver 2 shown in FIG. FIG. 12 is a conceptual diagram of the output signal of the matched filter. Referring to FIG. 11, receiver 2 conceptually includes matched filters MTHF1 to MTHF4, multipliers MP5 to MP6, and an adder SUM2.

  Each of the matched filters MTHF1 to MTHF4 is a matched filter that performs overlap frequency domain equalization by the above-described method.

  The matched filter MTHF1 receives the received signal and passes only the divided reception spectrum DVS1 ″ (see (a) of FIG. 12) of the received signal to the multiplier MP5.

  The matched filter MTHF2 receives the received signal and passes only the divided reception spectrum DVS2 ″ (see FIG. 12A) of the received signal to the multiplier MP6.

  Further, the matched filter MTHF3 receives the received signal, and passes only the divided reception spectrum DVS3 ″ (see FIG. 12A) of the received signal to the multiplier MP7.

  Further, the matched filter MTHF4 receives the received signal, and passes only the divided reception spectrum DVS4 ″ (see FIG. 12A) of the received signal to the multiplier MP8.

  In this case, the matched filters MTHF1 to MTHF4 perform equalization on the frequency axis by the above-described overlap frequency domain equalization.

The multiplier MP5 multiplies the divided reception spectrum DVS1 ″ received from the matched filter MTHF1 by e ^−jω1t, and ^supplies the division reception spectrum DVS1 ′ ″ (see FIG. 12B), which is the multiplication result, to the adder SUM2. Output.

The multiplier MP6 multiplies the divided reception spectrum DVS2 ″ received from the matched filter MTHF2 by e ^−jω2t, and ^adds the division reception spectrum DVS2 ′ ″ (see FIG. 12B) as the multiplication result. Output to SUM2.

Furthermore, the multiplier MP7 multiplies the divided reception spectrum DVS3 ″ received from the matched filter MTHF3 by e ^−jω3t, and ^adds the divided reception spectrum DVS3 ′ ″ (see FIG. 12B) as the multiplication result. Output to SUM2.

Further, the multiplier MP8 multiplies the divided reception spectrum DVS4 ″ received from the matched filter MTHF4 by e ^−jω4t, and ^adds the divided reception spectrum DVS4 ′ ″ (see FIG. 12B) as the multiplication result. Output to SUM2.

Thus, the multiplier MP5~MP8, respectively, the frequency of the divided received spectrum DVS1 "~DVS4" converted by the frequency -ω ₁ ~-ω ₄ divided reception spectrum DVS1 '''~DVS4''' ( FIG. 12 (see (b)) is output to the adder SUM2.

  The reason why the frequencies of the divided reception spectra DVS1 ″ to DVS4 ″ are converted by the multipliers MP5 to MP8 is to return the converted frequencies so as not to overlap in the transmitter 1.

  The adder SUM2 receives the four divided reception spectrums DVS1 ′ ″ to DVS4 ′ ″ from the multipliers MP5 to MP8 and serially receives the four divided reception spectra DVS1 ′ ″ to DVS4 ′ ″. Arrange the received baseband signals.

  In the transmitter 1 shown in FIG. 9, four bandpass filters BPF1 to BPF4 are shown. This is because the transmission spectrum is divided into four free communication bands. In the case of dividing into free communication bands other than four, the transmitter 1 includes a bandpass filter and a multiplier according to the number of divisions of the transmission spectrum.

  For the same reason, the receiver 2 shown in FIG. 11 also includes a matched filter and a multiplier according to the number of divisions of the transmission spectrum.

  The transmitter according to the embodiment of the present invention is not limited to the configuration shown in FIG. 2, and generally has only to have the configuration shown in FIG. 9. Further, the receiver according to the embodiment of the present invention is not limited to the configuration shown in FIG. 3, and generally only has to have the configuration shown in FIG. 11.

  As described above, the transmitter 1 divides the transmission spectrum into j (j = 1 to J) free communication bands, which are the smallest possible number of the plurality of free communication bands in the wireless communication space, and Each of the divided j divided transmission spectra is subjected to a convolution operation to limit the band, and the j divided transmission spectrums with the band limited are transmitted to the receiver 2.

  As a result, by dividing the transmission spectrum into as few free communication bands as possible, that is, by reducing the number of transmission spectrum divisions as much as possible, each divided transmission spectrum is converted into a kind of partial response signal. Thus, the peak power with respect to the average power decreases as the number of transmission spectrum divisions decreases.

  Further, by performing convolution operation on each of the j divided transmission spectra to limit the band, the side lobe of each divided transmission spectrum is lowered.

  Therefore, according to the present invention, the leakage power to the adjacent channel can be suppressed, and the peak power with respect to the average power can be lowered.

  In the above description, the transmission spectrum is divided and transmitted in four free communication bands. However, in the embodiment of the present invention, the present invention is not limited to this, and there is a free space other than the four free communication bands. Even when the transmission spectrum is divided into the communication bands for transmission, the transmission spectrum is divided by the method described above and transmitted from the transmitter 1 to the receiver 2.

  In the above description, the case of transmitting data by wireless communication has been described. However, in the embodiment of the present invention, the present invention is not limited to this, and the communication system 10 described above also transmits data by wired communication. It can be applied, and is particularly applicable to power line carrier communications.

  In the embodiment of the present invention, the serial / parallel converter 12, the Fourier transformer 13, the mapper 14 and the inverse Fourier transformer 16 constitute a “divided filter”.

  In the embodiment of the present invention, convolution filter 17 and parallel / serial converter 18 constitute a “band limiting filter”. The band limiting filter is a root cosine roll-off filter.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a transmitter capable of suppressing power leakage to an adjacent channel and reducing peak power with respect to average power. The present invention is also applied to a communication system including a transmitter capable of suppressing power leakage to an adjacent channel and reducing peak power with respect to average power.

  DESCRIPTION OF SYMBOLS 1 Transmitter, 2 Receiver, 10 Communication system, 11 Modulator, 12,23 Serial / parallel converter, 13,25 Fourier transformer, 14 Mapper, 15,26 Detection means, 16,28 Inverse Fourier transformer, 17, 24 convolution filter, 18 parallel / serial converter, 19 transmission means, 20, 21 antenna, 27 demapping unit, 29 symbol determination unit.

Claims (6)

A transmitter for transmitting data using a vacant communication band,
Detecting means for detecting a plurality of free communication bands which are communication bands not used for communication of the data;
A division filter that divides a transmission spectrum obtained by frequency-modulating transmission data into j (j is a positive integer) free communication bands each including a minimum number of free communication bands among the plurality of free communication bands;
A band limiting filter that performs a band limiting process by performing a convolution operation on the j divided transmission spectrums divided into the j free communication bands;
A transmitter comprising: a transmission unit configured to transmit j divided transmission spectrums on which the band limitation process has been performed.   The transmitter according to claim 1, wherein the band limiting filter is a root cosine roll-off filter.   2. The transmitter according to claim 1, wherein the j free communication bands include free communication bands selected in descending order of bandwidth from the plurality of free communication bands.   The division filter maintains an order of a plurality of discrete frequency components of the transmission spectrum, and the transmission spectrum is included in the plurality of unused communication bands so that the plurality of frequency components are as continuous as possible. The transmitter according to claim 3, wherein the transmission spectrum is divided into the j free communication bands by dividing the transmission spectrum into communication bands. The split filter is
A serial / parallel converter that divides the transmission spectrum into a plurality of blocks each consisting of N (N is an integer of 2 or more) symbols, and converts the plurality of blocks from a serial arrangement to a parallel arrangement;
A Fourier transformer for fast Fourier transforming the plurality of blocks;
A mapping unit that multiplies the output signal of the Fourier transformer by a mapping matrix consisting of LN rows × N columns (L is an integer that is a power of 2 that is 2 or more);
An inverse Fourier transformer that performs an inverse fast Fourier transform on the output signal of the mapper,
The band limiting filter is:
A convolution filter that convolves the output signal of the inverse Fourier transformer to limit the bandwidth of the output signal;
A parallel / serial converter that converts a result of operation by the convolution filter from a parallel array to a serial array;
Each column of the mapping matrix corresponds to the frequency component of the output signal from the Fourier transformer,
Each row of the mapping matrix corresponds to an input frequency component to the inverse Fourier transformer,
The mapper sets the frequency components at both ends of the inverse Fourier transformer to a null spectrum, maintains the order of the discrete spectrum received from the Fourier transformer, and further keeps the frequency components of the discrete spectrum as continuous as possible. The transmitter of claim 4, mapping a discrete spectrum. A communication system that transmits and receives data using a vacant communication band,
The transmission data is frequency-modulated into j (j is a positive integer) free communication bands that are as small as possible among a plurality of free communication bands that are not used for data communication. And the band limitation process is performed by performing a convolution operation on the j divided transmission spectrums divided into the j free communication bands, and the j band limitation processes are performed. A transmitter for transmitting a divided transmission spectrum of
A communication system comprising: a receiver that receives j divided transmission spectrums transmitted from the transmitter and obtains a received signal by equalizing the received j divided transmission spectra on a frequency axis.

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