JP5337746B2 - OFDM signal combining receiver and repeater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress interference waves and to receive desired waves even in an environment where a multipath of desired waves which are long in delay time and large in level are received together with the interference waves. <P>SOLUTION: A receiver for combining OFDM signals includes: an FFT (40) which converts the OFDM signals received by a reception antenna into reception carrier symbols in a frequency domain; an array combination section (50) which generates array combination signals by weighting and combining the reception carrier symbols for each subcarrier comprising the OFDM signals by a first weighting factor; weighting factor optimizing sections (61 and 63) which generate reference signals estimating transmission symbols and generate second weighting factors so that an error between the reference signals and the array combination signals may become minimum; and filter processing sections (62 and 64) which filter and process the reciprocal of the second weighting factor and then generate the re-reciprocal of the reciprocal of the filter processed second weighting factor as the first weighting factor. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a receiving apparatus for OFDM signal synthesis for digital broadcasting and digital transmission using an OFDM (Orthogonal Frequency Division Multiplexing) system, and in particular, fading and interference waves that are problematic when receiving radio waves in digital broadcasting or wireless LAN. The present invention relates to a receiving apparatus for OFDM signal synthesis and a relay apparatus that apply adaptive array antenna technology and diversity reception technology as countermeasures.

  2. Description of the Related Art Conventionally, there is known an OFDM signal combining receiver that applies adaptive array antenna technology or diversity reception technology and calculates a weighting factor for each subcarrier of each received OFDM signal output from each array element of the array antenna ( For example, see Patent Documents 1 to 3).

JP 2003-174427 A JP 2005-295506 A JP 2008-66982 A

  However, in the technique described in Patent Document 1, the weighting factor is directly calculated only for subcarriers that transmit SP (Scattered Pilot) signals, and for other subcarriers, subcarriers that transmit SP signals. Is obtained by interpolating the weighting factor calculated for. In order to give a correct value to the interpolation result of the weighting factor, the calculation of the weighting factor by the SP signal satisfies the sampling theorem, that is, the subcarrier interval (the subcarrier in which the SP signal is inserted) in which the weighting factor is calculated. This is limited when the carrier direction interval is equal to or less than the Nyquist interval for the change of the weighting factor in the subcarrier direction. The Nyquist interval for the change in the subcarrier direction of the weighting factor is the subcarrier interval for calculating the weighting factor, depending on the reception conditions such as the arrival time of the interference wave and the array element interval when receiving a multipath wave with a long delay time. In this case, even if the weighting factor for the subcarrier to which the SP signal is transmitted is accurately calculated, the weighting factor for the subcarrier to which only the data is transmitted is correctly calculated in the interpolation process. As a result, an optimum synthesized signal could not be obtained.

  In the technique described in Patent Document 2, the weight coefficient is obtained by optimizing the transmission line response obtained using the SP signal as an input vector and the undistorted response as a reference signal in all subcarriers. However, in order to optimize the weighting factor even in the subcarrier where the SP signal is not transmitted, many operations are required.

  In the techniques described in Patent Literature 2 and Patent Literature 3, weight coefficients are obtained for all subcarriers using a symbol determination value as a reference signal. However, when there is an error that is difficult to reduce in symbol determination, the interference coefficient may not be sufficiently suppressed because the weighting factor does not converge to the optimum value.

  An object of the present invention is an OFDM signal combining reception capable of receiving a desired wave by suppressing the interference wave even in an environment where a multipath of the desired wave having a long delay time and a large level is received together with the interference wave. It is to provide a device and a relay device.

  In order to solve the above-described problem, an OFDM signal combining receiver according to the present invention is an OFDM signal combining receiver that receives an OFDM signal by a receiving antenna including a plurality of array elements. An FFT unit that converts an OFDM signal into a frequency-domain received carrier symbol; and an array combining unit that generates an array combined signal by weighting and combining the received carrier symbol with a first weighting factor for each subcarrier constituting the OFDM signal. A weighting factor optimizing unit that generates a reference signal for estimating a transmission symbol and generates a second weighting factor so that an error between the reference signal and the array combined signal is minimized, and an inverse number of the second weighting factor Then, the reciprocal of the reciprocal of the filtered second weighting factor is set as the first weighting factor. Characterized in that it comprises a generation filtering unit.

  In the OFDM signal combining receiver according to the present invention, the weighting factor optimization unit receives an SP signal having a predetermined symbol number transmitted from a subcarrier having a predetermined subcarrier number from the received carrier symbol. A received SP signal extracting unit that extracts signals, a synthesized SP signal extracting unit that extracts an SP signal after array synthesis from the array synthesized signal, and a true value of a known SP signal as the reference signal (transmitted SP signal) A transmission SP signal generation unit for generating, an error calculation unit for calculating an error signal obtained by subtracting the SP signal after the array synthesis from the reference signal, and the error signal is minimized by using the received SP signal. A weighting factor control unit that calculates the second weighting factor for a subcarrier on which an SP signal is transmitted, and the filter processing unit includes the second weighting factor control unit. A first reciprocal calculating unit for calculating a reciprocal of the coefficient; an interpolation LPF for interpolating the reciprocal of the second weighting factor and generating a filtered reciprocal weighting factor; and a reciprocal of the corrected reciprocal weighting factor. And a second reciprocal number calculation unit for calculating as a first weighting factor.

  In the OFDM signal combining receiver according to the present invention, the weighting factor optimization unit estimates a transmission symbol from the reception carrier symbol and generates the reference signal, and the reference signal generation unit An error calculation unit that calculates an error signal obtained by subtracting an array composite signal, and a weighting factor control unit that calculates the second weighting factor for the subcarrier so that the error signal is minimized using the received carrier symbol. The filter processing unit includes: a first reciprocal calculating unit that calculates the reciprocal of the second weighting factor; an LPF unit that generates a corrected reciprocal weighting factor obtained by filtering the reciprocal of the second weighting factor; and the corrected reciprocal And a second reciprocal number calculating unit that calculates the reciprocal of the weighting factor as the first weighting factor.

  Also, in the OFDM signal combining receiver according to the present invention, the reference signal generation unit performs weighted combining on the received carrier symbol using the first weighting factor in the subcarrier to be processed, and the first reference A first reference array combining unit that generates an array combined signal; an inverse interpolation unit that generates an interpolation weight coefficient obtained by performing an inverse interpolation of the first weight coefficient in a subcarrier adjacent to a subcarrier to be processed; and the received carrier symbol Are subjected to weighting combining using the interpolation weighting coefficient to generate a second reference array combined signal, and each of the first reference array combined signal and the second reference array combined signal is subjected to symbol determination. A symbol determination unit for generating a symbol determination signal and a modulation error for calculating a modulation error ratio of each symbol determination signal A calculation unit; a maximum value detection unit that generates an instruction signal that specifies a larger modulation error ratio among the modulation error ratios; and a value that has a large modulation error ratio indicated by the instruction signal among the symbol determination signals. And a selection unit that selects the symbol determination signal as the reference signal.

  Furthermore, a relay apparatus according to the present invention is characterized by including the above-described OFDM signal combining receiver.

  According to the present invention, in an environment where a multipath of a desired wave having a long delay time and a large level is received together with the interference wave, the receiver for OFDM signal synthesis capable of suppressing the interference wave and receiving the desired wave And a relay device can be provided.

It is a block diagram which shows the structure of the receiver for OFDM signal synthesis | combination of Example 1 by this invention. It is a block diagram which shows the structure of the weight optimization part of the receiver for OFDM signal synthesis | combination of Example 1 by this invention. It is a block diagram which shows the structure of the filter process part of the receiver for OFDM signal synthesis of Example 1 by this invention. It is a figure explaining operation | movement of the filter process part of the receiver for OFDM signal synthesis of Example 1 by this invention. It is a block diagram which shows the structure of the receiver for OFDM signal synthesis | combination of Example 2 by this invention. It is a block diagram which shows the structure of the weight optimization part of the receiver for OFDM signal synthesis of Example 2 by this invention. It is a block diagram which shows the structure of the reference signal production | generation part of the receiver for OFDM signal synthesis of Example 2 by this invention. It is a block diagram which shows the structure of the filter process part of the receiver for OFDM signal synthesis of Example 2 by this invention. It is a figure explaining operation | movement of the filter process part of the receiver for OFDM signal synthesis of Example 2 by this invention. It is a figure which shows the interference removal characteristic in the multipath environment of the receiver for OFDM signal synthesis of Example 2 by this invention. It is a block diagram which shows the structure of a relay apparatus provided with the receiver for OFDM signal synthesis by this invention. It is a figure explaining arrangement | positioning of SP signal.

  In the following description, the number of array elements is L, and the array element number assigned to an arbitrary array element is l (0 ≦ l ≦ L−1). Further, the number of subcarriers constituting the OFDM signal is K, the carrier number assigned to an arbitrary subcarrier is k (0 ≦ k ≦ K−1), and the number of subcarriers on which an SP (Scattered Pilot) signal is transmitted is K ( SP), a carrier number assigned to an arbitrary subcarrier in which an SP signal is transmitted is k (SP) (0 ≦ k (SP) ≦ K (SP) −1). Further, i is a symbol number assigned to an arbitrary symbol constituting the OFDM signal.

The OFDM signal combining receiver according to the first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a receiving apparatus 1 for OFDM signal synthesis according to a first embodiment of the present invention. The OFDM signal combining receiver 1 includes a receiving antenna 10 (10 ₀ to 10 _L-1 ) including a plurality of array elements, reception filters 20 (20 _{0 to} 20 _L-1 ) corresponding to the number of array elements, Receive conversion units 30 (30 ₀ to 30 _L-1 ) for the number of array elements, FFT units 40 (40 ₀ to 40 _L-1 ) for the number of array elements, and array combining units 50 (50 for the number of subcarriers) ₀ to 50 _K-1 ) and a weighting factor calculation unit 60. The weighting factor calculation unit 60 includes weighting factor optimization units 61 (61 _{0 to} 61 _{K (SP) -1} ) corresponding to the number of subcarriers to which SP signals are transmitted, and filter processing units 62 (62 _{0 corresponding to the} number of array elements). ~ 62L _-1 ).

  The reception antenna 10 receives the OFDM signal and outputs it to the reception filter 20.

  The reception filter 20 removes unnecessary signal components outside the frequency band of the desired wave from the signal input from the reception antenna 10 and outputs the signal component to the reception conversion unit 30.

  The reception conversion unit 30 frequency-converts the signal input from the reception filter 20 to generate an IF (Intermediate Frequency) signal. Subsequently, the digital IF signal obtained by A / D converting the IF signal is quadrature demodulated, and an equivalent baseband signal is output to the FFT unit.

  The FFT unit 40 performs FFT (Fast Fourier Transform) processing on the equivalent baseband signal input from the reception conversion unit 30 and converts it into a carrier symbol (hereinafter referred to as “reception carrier symbol”) of a frequency domain signal. And output to the array synthesis unit 50 and the weight coefficient optimization unit 61.

  As shown in the following equations (1) to (3), array combining section 50 receives the received carrier symbol input from FFT section 40 for each subcarrier constituting the OFDM signal, and the weight input from filter processing section 62. An array combined signal (hereinafter also referred to as “combined carrier symbol”) is generated by weighting and combining with coefficients (that is, correction weighting coefficient described later), and output to the weighting coefficient optimizing unit 61 and the outside.

  The weight coefficient optimization unit 61 generates a reference signal in which a transmission symbol is estimated using the reception carrier symbol input from the FFT unit 40, and an error between the reference signal and the array combined signal input from the array combining unit 50. The weighting factor optimized so as to be minimized is generated and output to the filter processing unit 62. Details of the weight coefficient optimization unit 61 will be described later.

  The filter processing unit 62 corrects the weighting factor input from the weighting factor optimization unit 61 by performing interpolation and filtering, and corrects the weighting factor after correction (hereinafter referred to as “correction weighting factor”). The data is output to the array composition unit 50. Details of the filter processing unit 62 will be described later.

FIG. 2 is a block diagram illustrating a configuration of the weight optimization unit 61 according to the first embodiment of the present invention. The weight optimization unit 61 includes reception SP signal extraction units 611 (611 _{0 to} 611 _L-1 ), a transmission SP signal generation unit 612, a combined SP signal extraction unit 613, and an error calculation unit 614 corresponding to the number of array elements. And a weight coefficient control unit 615.

The reception SP signal extraction unit 611 uses, as a reception SP signal, an SP signal having a predetermined symbol number transmitted by a subcarrier having a predetermined subcarrier number among the reception carrier symbols input from the FFT unit 40. The extracted received SP signal x ′ _{k (SP)} is output to the weight coefficient control unit 615. FIG. 12 is a diagram for explaining the arrangement of SP signals. SP signals are indicated by black circles, and other carrier symbols are indicated by white circles. The SP signal is a signal having a predetermined amplitude and phase at the time of signal generation. For example, an IDSB-T (Integrated Services Digital Broadcasting-Terrestrial) system, which is a broadcasting system for digital terrestrial television broadcasting, or DVB- In the T (Digital Video Broadcasting-Terrestrial) system, it is inserted as a reference signal. In the case of the IDSB-T system, the reception SP signal extraction unit 611 extracts a carrier symbol satisfying the following expression (4) from among the carrier symbols input from the FFT unit 40 as a reception SP signal.

k mod12 = 3 (i mod4) (4)
Here, mod represents the remainder. In the following, symbol number i is omitted for simplicity.

  Since the amplitude and phase of the SP signal are predetermined on the transmission side, the same SP signal as the transmission side (hereinafter referred to as “transmission SP signal”) is also generated in the OFDM signal combining receiver 1 on the reception side. can do. The transmission SP signal generation unit 612 generates a true transmission SP signal that satisfies Equation (4), and outputs the transmission SP signal to the error calculation unit 614.

  The synthesized SP signal extraction unit 613 extracts a carrier symbol satisfying Expression (4) from the synthesized carrier symbols input from the array synthesis unit 50 as a synthesized SP signal, and outputs the extracted synthesized SP signal to the error calculation unit 614. To do.

  The error calculation unit 614 calculates an error signal obtained by subtracting the combined SP signal input from the combined SP extraction unit 613 from the transmission SP signal input from the transmission SP signal generation unit 612, as shown in the following equation (5). And output to the weight coefficient control unit 615.

e _{k (SP)} = r _{k (SP)} −d _{k (SP)} (5)
Here, r _{k (SP)} is a transmission SP signal of carrier number k (SP), d _{k (SP)} is a combined SP signal of carrier number k (SP), and e _{k (SP)} is carrier number k. (SP) error signal.

The weight coefficient control unit 615 uses the reception SP signal x ′ _{k (SP)} input from the reception SP signal extraction unit 611 so that the error signal e _{k (SP)} input from the error calculation unit 614 is minimized. The weight coefficient w _{k (SP)} is optimized and output to the filter processing unit 62. As an optimization method, an algorithm such as LMS (Least Mean Square) or RLS (Recursive Least-Squares) which is a least square error method can be used. In the LMS algorithm, the error signal _{ek (SP)} is minimized by updating the weighting factor w (n + 1) as shown by the following equation (6) using the weighting factor w (n) at time n. can do.

ここで、μは更新前後の変化量を規定するステップサイズであり、上付きの＊は複素共役を表す。

Here, μ is the step size that defines the amount of change before and after the update, and the superscript * represents the complex conjugate.

  In the RLS algorithm, the weighting coefficient is updated using the following equations (7) to (9).

ここで、ｇ(ｎ)はゲインベクトル、Ｐ(ｎ)は相関逆行列、λは忘却係数である。ＬＭＳやＲＬＳは公知の技法であるため、説明は省略する。

Here, g (n) is a gain vector, P (n) is a correlation inverse matrix, and λ is a forgetting factor. Since LMS and RLS are well-known techniques, description thereof is omitted.

FIG. 3 is a block diagram illustrating the configuration of the filter processing unit 62 according to the first embodiment of the present invention. The filter processing unit 62 includes first reciprocal calculation units 621 (621 _{0 to} 621 _{K (SP) -1} ) corresponding to the number of subcarriers to which SP signals are transmitted, an interpolation LPF (Low Pass Filter) unit 622, and subcarriers. The second reciprocal calculation unit 623 (623 _{0 to} 623 _K−1 ) for several minutes.

As shown in the following equation (10), the first reciprocal calculation unit 621 is the reciprocal of the weight coefficient w _{k (SP)} input from the weight coefficient control unit 615 (hereinafter referred to as “reciprocal weight coefficient”) v _{k ( SP)} is calculated and output to the interpolation LPF unit 622.

ここで、↑はアップサンプリングを表し、↑３は３倍のアップサンプリングを意味する。また、ＬＰＦはＬＰＦ処理を表す。

Here, ↑ represents upsampling, and ↑ 3 represents three times upsampling. LPF represents LPF processing.

FIG. 4 is a diagram for explaining the operation of the filter processing unit 62 in an environment where a multipath of a desired wave having a long delay time and a high level is received. FIG. 4A shows values obtained when IFFT (Inverse Fast Fourier Transform) processing is performed on the complex conjugate value of the weighting coefficient w _{k (SP)} input to the first reciprocal calculation unit 621. FIG. 4B shows values when IFFT processing is performed on the complex conjugate value of the reciprocal weight coefficient v _{k (SP)} output from the first reciprocal number calculation unit 621. In FIG. 4A, the multipath component of the desired wave included in the received signal appears cyclically, whereas in FIG. 4B, it appears acyclically. Then, the reciprocal weight coefficient v _{k (SP)} is interpolated and the second reciprocal calculation unit 623 takes the reciprocal again, whereby the weight coefficient of the subcarrier to which the SP signal is not transmitted can be obtained correctly. .

  Therefore, according to the OFDM signal combining receiver 1 of the first embodiment, the desired wave can be received while suppressing the interference wave with a small amount of calculation and a small processing circuit.

  Next, the OFDM signal combining receiver 2 according to the second embodiment of the present invention will be described in detail with reference to the drawings. In addition, the same reference number is attached | subjected to the same component as Example 1, and description is abbreviate | omitted.

FIG. 5 is a block diagram illustrating the configuration of the OFDM signal combining receiver 2 according to the second embodiment of the present invention. The OFDM signal combining receiver 2 according to the second embodiment includes a receiving antenna 10 (10 ₀ to 10 _L-1 ) configured by a plurality of array elements and reception filters 20 (20 _{0 to} 20 _L− ) corresponding to the number of array elements. ₁ ), receiving conversion units 30 (30 ₀ to 30 _L-1 ) for the number of array elements, FFT units 40 (40 ₀ to 40 _L-1 ) for the number of array elements, and array combining for the number of subcarriers Unit 50 (50 ₀ to 50 _K−1 ) and a weighting factor calculation unit 60. The weighting factor calculation unit 60 includes weighting factor optimization units 63 (63 _{0 to} 63 _K−1 ) for the number of subcarriers and filter processing units 64 (64 ₀ to 64 _L−1 ) for the number of array elements. . The OFDM signal combining receiver 2 according to the second embodiment is different from the OFDM signal combining receiver 1 according to the first embodiment (see FIG. 1) in the internal processing of the weight coefficient calculation unit 60. The weighting factor calculation unit 60 of the second embodiment will be described.

  The weighting factor optimizing unit 63 generates a reference signal in which a transmission symbol is estimated using the received carrier symbol input from the FFT unit 40 and the correction weighting factor input from the filter processing unit 64, and this reference signal and array synthesis A weighting factor optimized so as to minimize an error from the array composite signal input from the unit 50 is generated and output to the filter processing unit 64. Details of the weight coefficient optimization unit 63 will be described later.

  The filter processing unit 64 corrects the weighting factor input from the weighting factor optimizing unit 63 by performing filter processing, and the corrected weighting factor (hereinafter referred to as “correction weighting factor”) is the array synthesizing unit 50. Output to. Details of the filter processing unit 64 will be described later.

  FIG. 6 is a block diagram illustrating a configuration of the weight optimization unit 63 according to the second embodiment of the present invention. The weight optimization unit 63 includes a reference signal generation unit 631, an error calculation unit 632, and a weight coefficient control unit 633.

  The reference signal generation unit 631 estimates the transmission symbol from the reception carrier symbol using the reception carrier symbol input from the FFT unit 40 and the weighting coefficient input from the filter processing unit 64 (that is, a correction weighting coefficient described later). A reference signal is generated and output to the error calculator 632.

Carrier error calculation unit 632, error calculator 614, which is input as shown in the following equation (13), from the reference signal r _k of the carrier number k which is inputted from the reference signal generating unit 631, from the array combining section 50 subtracting the synthetic carrier symbols d _k of number k, calculates an error signal e _k of the carrier number k, and outputs the weighting factor controller 633.

e _k = r _k −d _k (13)

ここで、μは更新前後の変化量を規定するステップサイズであり、上付きの＊は複素共役を表す。

Here, μ is the step size that defines the amount of change before and after the update, and the superscript * represents the complex conjugate.

  In the RLS algorithm, the weighting coefficient is updated using the following equations (15) to (17).

ここで、ｇ(ｎ)はゲインベクトル、Ｐ(ｎ)は相関逆行列、λは忘却係数である。

Here, g (n) is a gain vector, P (n) is a correlation inverse matrix, and λ is a forgetting factor.

  FIG. 7 is a block diagram illustrating a configuration of the reference signal generation unit 631 of the OFDM signal combining receiver 2 according to the second embodiment of the present invention. The reference signal generation unit 631 includes an inverse interpolation unit 6311, two reference array synthesis units 6312 (6312-1 and 6312-2), two symbol determination units 6313 (63313-1 and 6313-2), and two A modulation error ratio (MER) calculation unit 6314 (6314-1 and 6314-2), a maximum value detection unit 6315, and a selection unit 6316 are provided.

As shown in the following equation (21), the symbol determination unit 6313-1 performs demapping and remapping of the array composite signal input from the reference array synthesis unit 6312, performs symbol determination, and generates a symbol determination signal d _k ¹ . The result is output to the modulation error ratio calculation unit 6314 and the selection unit 6316. Similarly, symbol determination section 6313-2 outputs symbol determination signal d _k ² subjected to symbol determination to modulation error ratio calculation section 6314 and selection section 6316 as shown in the following equation (22). In symbol determination, a given combined carrier symbol is compared with a transmission carrier symbol, and a transmission carrier symbol having the smallest norm is used as a symbol determination signal.

ここで、ｄｅｃはシンボル判定を行う関数を表す。

Here, dec represents a function for performing symbol determination.

The modulation error ratio calculator 6314-1 uses the array combined signal y _k ¹ input from the reference array combiner 6312-1 and the symbol determination value d _k ¹ input from the symbol determiner 63313-1, 23), the modulation error ratio R ¹ is calculated and output to the maximum value detector 6315. Similarly, the modulation error ratio calculator 6314-2 uses the array composite signal y _k ² input from the reference array combiner 6312-2 and the symbol determination value d _k ² input from the symbol determination unit 6313-2. The modulation error ratio R ² is calculated by the following equation (24) and output to the maximum value detection unit 6315. Note that the calculation of the modulation error ratio is a known technique as described in, for example, ETR 290: “Measurement guidelines for DVB Systems”, ETSI Technical Report, may 1997, and thus description thereof is omitted.

ここで、arg maxは変調誤差値Ｒ^mのうち、変調誤差比が最大であるｍの値を返す関数である。 The maximum value detection unit 6315 receives an instruction signal for specifying the larger modulation error ratio among the modulation error values R ¹ and R ² input from the modulation error ratio calculation unit 6314 as shown in the following equation (25). The data is output to the selection unit 6315.

Here, arg max is a function that returns the value of m having the maximum modulation error ratio among the modulation error values R ^m .

As shown in the following equation (26), the selection unit 6316 is based on the instruction signal input from the maximum value detection unit 6315 among the symbol determination signals input from the symbol determination unit 6313, and the modulation error ratio indicated by the instruction signal select the symbol decision signal is the value, and outputs the error calculating section 632 as a reference signal r _k.

FIG. 8 is a block diagram illustrating the configuration of the filter processing unit 64 of the OFDM signal combining receiver according to the second embodiment of the present invention. The filter processing unit 64 includes a first reciprocal calculation unit 641 (641 _{0 to} 641 _K−1 ) for the number of subcarriers, an LPF unit 642, and a second reciprocal calculation unit 643 (643 _{0 to} 643 _{K for the} number of subcarriers). _-1 ).

The first reciprocal number calculation unit 641 calculates the reciprocal number of the weighting factor w _k input from the weighting factor control unit 633 (hereinafter referred to as “reciprocal weighting factor”) v _k by the following equation (27), and the LPF unit 642. To enter.

ここで、ＬＰＦはＬＰＦ処理を表す。

Here, LPF represents LPF processing.

FIG. 9 is a diagram for explaining the operation of the filter processing unit 64 in an environment where a multipath of a desired wave having a long delay time and a high level is received. FIG. 9A shows a value when IFFT processing is performed on the complex conjugate value of the weighting coefficient w _k input to the first reciprocal calculation unit 641, and FIG. 9B shows the first reciprocal calculation unit 641. 2 shows a value when IFFT processing is performed on the complex conjugate value of the reciprocal weighting coefficient v _k output from. In FIG. 9A, the multipath component of the desired wave included in the received signal appears cyclically, whereas in FIG. 9B, it appears acyclically. Then, by removing high-frequency components by LPF processing, it is possible to draw a weighting factor that has not converged into the optimal solution.

  FIG. 10 is a diagram showing interference cancellation characteristics in a multipath environment obtained by computer simulation. The horizontal axis represents the multipath D / U ratio (desired to undesired ratio), and the vertical axis represents BER (Bit Error Rate). Show. For comparison, the interference cancellation characteristics of the OFDM signal combining receiver according to the present invention and the OFDM signal combining receiver in which the phase correction value calculator described in Patent Document 3 is combined with the receiver described in Patent Document 2 are combined. Show. The transmission parameters are ISDB-T mode 3 which is a broadcasting system of terrestrial digital broadcasting, GI ratio 1/8 (126 μs), carrier modulation is 64QAM, and the encoding rate of the inner code is 3/4. In particular, when the multipath D / U ratio is small (the level is large), it can be seen that the OFDM signal combining receiver of the present invention has a good interference cancellation effect.

  Next, a relay apparatus including the OFDM signal combining receiver according to the present invention will be described in detail with reference to the drawings.

  FIG. 11 is a block diagram illustrating a configuration of a relay apparatus 3 including the OFDM signal combining receiver 1 according to the first embodiment or the OFDM signal combining receiver 2 according to the second embodiment. The relay device 3 includes an external reception antenna 10, an OFDM signal synthesis reception device 1 or 2, an IFFT unit 70, a GI addition unit 80, a transmission conversion unit 90, a power amplifier 100, a transmission filter 110, A transmission antenna 120;

  The receiving antenna 10 receives the OFDM signal transmitted from the master station and outputs it to the receiving apparatus 1 or 2 for OFDM signal synthesis.

  The OFDM signal combining receiver 1 or 2 performs array combining processing on the carrier symbols after FFT to remove multipath distortion and interference waves in the same frequency band as the desired wave, and outputs the result to the IFFT unit 70.

  The IFFT unit 70 performs IFFT processing on the array combined signal input from the OFDM signal combining receiving apparatus 1 or 2 to convert it into a time domain signal, and outputs it to the GI adding unit 80.

  The GI adding unit 80 adds a GI to the head of the OFDM symbol with respect to the time domain signal input from the IFFT unit 70 and outputs the signal to the transmission conversion unit 90 as an IF signal having the same frequency as the input signal.

  The transmission conversion unit 90 frequency-converts the IF signal input from the GI addition unit 508 to generate an RF (Radio Frequency) signal, amplifies the signal to a certain level, and outputs the amplified signal to the power amplifier 100.

  The power amplifier 100 amplifies the RF signal input from the transmission conversion unit 90 to obtain a transmission signal having a desired output, and outputs the amplified signal to the transmission filter 110.

  The transmission filter 110 removes unnecessary radiation components outside the band from the transmission signal input from the power amplifier 100 and outputs the signal to the transmission antenna 120.

  The transmission antenna 120 radiates a transmission signal from which unnecessary components outside the band are removed by the transmission filter 110.

  Each of the above embodiments has been described as a representative example, but it will be apparent to those skilled in the art that many changes and substitutions can be made within the spirit and scope of the invention. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and changes can be made without departing from the scope of the claims.

  As described above, according to the present invention, the interference wave can be suppressed and the desired wave can be received even in an environment where a multipath of the desired wave having a long delay time and a large level is received together with the interference wave. Useful for any application where signals are received by multiple array antennas.

1, 2 OFDM signal combining receiver 10 receiving antenna 20 receiving filter 30 receiving conversion unit 40 FFT unit 50 array combining unit 60 weighting factor calculating unit 61, 63 weighting factor optimizing unit 611 receiving SP signal extracting unit 612 transmitting SP signal generation Unit 613 synthesized SP signal extraction unit 614, 632 error calculation unit 615, 633 weight coefficient control unit 62, 64 filter processing unit 621, 641 first reciprocal number calculation unit 622 interpolation LPF unit 623, 643 second reciprocal number calculation unit 63 weight coefficient optimum Conversion unit 631 reference signal generation unit 6311 reciprocal interpolation unit 6312 reference array synthesis unit 6313 symbol determination unit 6314 modulation error ratio calculation unit 6315 maximum value detection unit 6316 selection unit 642 LPF unit 3 relay device 70 IFFT unit 80 GI addition unit 90 transmission conversion Part 100 Power amplifier 110 Shin filter 120 transmitting antenna

Claims (5)

An OFDM signal combining receiver for receiving an OFDM signal by a receiving antenna including a plurality of array elements,
An FFT unit for converting an OFDM signal received by a receiving antenna into a received carrier symbol in a frequency domain;
An array combining unit that generates an array combined signal by weighting and combining the received carrier symbol with a first weighting factor for each subcarrier constituting the OFDM signal;
A weighting factor optimizing unit that generates a reference signal that estimates a transmission symbol and generates a second weighting factor so that an error between the reference signal and the array combined signal is minimized;
A filter processing unit that performs a filtering process on the reciprocal of the second weighting factor, and then generates a reciprocal of the reciprocal of the filtered second weighting factor as the first weighting factor;
An OFDM signal combining receiver characterized by comprising: The weight coefficient optimization unit includes:
A received SP signal extraction unit that extracts, as a received SP signal, an SP signal of a predetermined symbol number transmitted by a subcarrier of a predetermined subcarrier number from the received carrier symbol;
A synthesized SP signal extraction unit that extracts an SP signal after array synthesis from the array synthesized signal;
A transmission SP signal generation unit that generates a true value of a known SP signal as the reference signal;
An error calculation unit for calculating an error signal obtained by subtracting the SP signal after the array synthesis from the reference signal;
A weighting factor control unit that calculates the second weighting factor for a subcarrier on which the SP signal is transmitted so that the error signal is minimized using the received SP signal;
The filter processing unit
A first reciprocal calculator for calculating the reciprocal of the second weighting factor;
An interpolation LPF unit that interpolates the reciprocal of the second weighting factor and generates a filtered reciprocal weighting factor,
2. The OFDM signal combining receiver according to claim 1, further comprising: a second reciprocal number calculation unit configured to calculate a reciprocal number of the corrected reciprocal weighting factor as the first weighting factor. The weight coefficient optimization unit includes:
A reference signal generator for estimating a transmission symbol from the received carrier symbol and generating the reference signal;
An error calculation unit for calculating an error signal obtained by subtracting the array composite signal from the reference signal;
A weighting factor control unit that calculates the second weighting factor for the subcarrier so that the error signal is minimized using the received carrier symbol;
The filter processing unit
A first reciprocal calculator for calculating the reciprocal of the second weighting factor;
An LPF unit for generating a corrected inverse weighting coefficient obtained by filtering the inverse of the second weighting coefficient;
2. The OFDM signal combining receiver according to claim 1, further comprising: a second reciprocal number calculation unit configured to calculate a reciprocal number of the corrected reciprocal weighting factor as the first weighting factor. The reference signal generator is
A first reference array combining unit that performs weighted combining on the received carrier symbol using the first weighting factor in a subcarrier to be processed, and generates a first reference array combined signal;
A reciprocal interpolation unit that generates an interpolation weight coefficient obtained by reciprocal interpolation of the first weight coefficient in a subcarrier adjacent to a subcarrier to be processed;
A second reference array combining unit that performs weighted combining on the received carrier symbol using the interpolation weighting coefficient to generate a second reference array combined signal;
A symbol determination unit for generating a symbol determination signal by performing symbol determination on each of the first reference array combined signal and the second reference array combined signal;
A modulation error ratio calculation unit for calculating a modulation error ratio of each symbol determination signal;
A maximum value detecting unit for generating an instruction signal for specifying a larger modulation error ratio among the modulation error ratios;
A selection unit that selects a symbol determination signal having a large modulation error ratio indicated by the instruction signal from the symbol determination signals, and sets the reference determination signal;
The OFDM signal combining receiver according to claim 3, further comprising:   A relay apparatus comprising the OFDM signal combining receiver according to any one of claims 1 to 4.

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