CN100442681C - Wraparound canceller, relay system, and wraparound cancelling method - Google Patents

Wraparound canceller, relay system, and wraparound cancelling method Download PDF

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CN100442681C
CN100442681C CNB2003801007648A CN200380100764A CN100442681C CN 100442681 C CN100442681 C CN 100442681C CN B2003801007648 A CNB2003801007648 A CN B2003801007648A CN 200380100764 A CN200380100764 A CN 200380100764A CN 100442681 C CN100442681 C CN 100442681C
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transmission path
output
reference carrier
path characteristic
circuit
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CN1695320A (en
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国枝贤德
四方英邦
河合庆士
林健一郎
铃木一章
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H04B7/15564—Relay station antennae loop interference reduction
    • H04B7/15585—Relay station antennae loop interference reduction by interference cancellation

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Abstract

A wraparound canceller capable of performing adaptive operation to follow a wraparound wave, a parent station wave phase, and temporal level fluctuation at a high speed and with a high accuracy as well as reducing the device size. By limiting the number of data items of the transmission path characteristic estimation section and performing the extension to the entire band by 0 insert at the frequency region and windowing after the time region conversion instead of performing interpolation, the speed of adaptive operation of the wraparound canceller is increased because of the reduction in the number of processing data items. Accordingly, it is possible to realize a high capability to follow the wraparound wave, parent station wave phase, and the temporal level fluctuation and the internal processing becomes more accurate. Consequently, a highly accurate canceling operation can be performed and the circuit size is reduced, thereby realizing the reduced size of the device as a beneficial effect.

Description

Loop interference eliminator, relay system and loop interference elimination method
Technical field
The present invention relates to a kind of utilization from OFDM (Orthogonal Frequency DivisionMultiplexing, OFDM) propagation path characteristic that estimates of signal is come the loop interference eliminator that cancellation loop disturbs, refer in particular to a kind of like this loop interference eliminator, relay system and loop interference elimination method: accelerate the speed of the self adaptation operation of loop interference eliminator by reducing the number of data points of handling, realization is to the height trackability of the time variation of loop disturbing wave and main website wave phase and level, carry out high-precision inter-process, thereby can carry out high-precision elimination operation, and with the miniaturization of the circuit scale implement device that reduces.
Background technology
In recent years, in the execution as broadcast wave relaying SFN (Single FrequencyNetwork, single-frequency net) such as terrestrial digital broadcasting, the use of OFDM transmission means was studied.The OFDM transmission means is that a kind of numerical data with transmission is modulated the carrier wave of many mutually orthogonals, and modulating wave is carried out mode multiplexing and that send.The OFDM transmission means is characterised in that: just great lengthened code elementary time when the carrier number that uses is brought up to hundreds if not thousands of; Further, add the duplicating of rear portion signal during the effective code element before during the effective code element, thereby do not allow to be subject to postpone the influence of ripple as the guard period signal.
These features cause the radio network that can construct single-frequency, the possibility of SFN just, and therefore as mentioned above, the OFDM transmission means causes concern as a kind of transmission means of terrestrial digital broadcasting.
Method as realizing SFN adopts following method easier technically: to come to each repeat broadcast point transmission signals with the channel that is different from broadcast wave as optical fiber and microwave etc., and send signal with identical frequency.Yet, utilize the method for optical fiber to exist the problem of channel cost, adopt the method for microwave to need to guarantee new frequency resource.
Therefore, need to realize a kind ofly both on cost, having superiority, do not need the SFN through the broadcast wave relaying of the frequency resource of adding again.
Because the broadcast wave of launching from transmitting antenna is surrounded on the phenomenon of reception antenna, in the realization of broadcast wave relaying SFN, the possibility of problems such as causing repeating signal deterioration and amplifier vibration is arranged.
For the loop that prevents broadcast wave relaying SFN disturbs, can take following measure:
(1) configured separate by transmitting antenna and reception antenna, and utilize conducts such as high mountain or building to cover to reduce loop and disturb,
(2) directional characteristic that improves send/receive antenna reduces the loop interference,
(3) come cancellation loop to disturb by signal processing technology.
Yet, because there are various situation in high mountain and building, and the measure that only rely on to improve the directional characteristic of antenna can not fully suppress loop to be disturbed, and therefore just can compare effectively be used the again loop interference eliminator of the signal processing technology in the employing (3) of the measure in (1) and (2).
Traditionally, as a kind of like this signal processing technology, following method has been proposed: estimate that from the ofdm signal that receives loop disturbs the frequency characteristic of transmission path, disturb the frequency characteristic data of transmission path to carry out IFFT (Inverse Fast Fourier Transform to the loop that estimates, invert fast fourier transformation) to be converted into the impulse response data on the time shaft, this impulse response data is set at the filter factor of transversal filter, thereby create the reproducing signals that loop disturbs, and come cancellation loop to disturb (for example, referring to the flat 11-355160 communique of Japanese Patent Application Laid-Open) by deduct this reproducing signals with received signal.In addition, as its supercomputing treatment technology, the method (for example, referring to Japanese Patent Application Laid-Open 2001-223663 communique) that has sparse treatment circuit in the transmission path characteristic estimation section is arranged also.Below with reference to the accompanying drawings an example of signal processing technology in the loop interference eliminator is described.
Fig. 1 is the ideograph of pilot signal configuration example, represented to be used for terrestrial digital broadcast mode DVB-T (the Digital Video Broadcasting-Terrestrial in Europe, digital video broadcasting-land) and be used for the configuration of pilot signal of the terrestrial digital broadcast mode ISDB-T (Integrated Services Digital Broadcasting-Terrestrial, integrated service digital broadcasting-land) etc. of Japan.
The circle representative data carrier wave of white among Fig. 1, the circle of black is represented the pilot frequency carrier wave of decentralized configuration (SP:Scattered Pilot, scattered pilot)
In addition, the k on the transverse axis among Fig. 1 (frequency axis) represents carrier index, and the n on the longitudinal axis (time shaft) represents symbol number.At this moment, be that the carrier wave of k=kp transmits the SP signal with the carrier index that satisfies following (formula 1).(wherein, " mod " expression complementation in the expression formula, " p " represents nonnegative integer.)
Kp=3 (n mod 4)+12p ... (formula 1)
Can find out obviously that from (formula 1) configuration of SP is determined divided by the remainder of 4 gained by symbol number n.
In addition, the SP signal is based on that the pseudorandomcode character string modulates, and its amplitude and phase place are only determined by the carrier index k that is disposed, and do not rely on symbol number n.How to determine amplitude and phase place unimportant, therefore omit it and specify, but also as the SP configuration, determined divided by 4 remainders that obtain by symbol number n to the explanation here.
In addition, at the right-hand member of carrier wave, dispose pilot signal independently with symbol signal.This pilot signal also is based on the pseudorandomcode character string and modulates, and its amplitude and phase place are determined divided by 4 remainders that obtain by symbol number n.When symbol number n was 0 divided by 4 remainder, this pilot signal also met (formula 1), therefore from here on, pilot signal was contained in the definition of pilot frequency carrier wave or SP.
Fig. 2 is the block diagram of an example of expression loop interference eliminator 3.
In the inside of filter factor generating unit 33, transmission path characteristic estimation portion 331 estimates transmission path characteristic F (ω) from the output s (t) of subtraction portion 31, simultaneously output is offered residual error property calculation circuit 3309 as input.
Inside in transmission path characteristic estimation portion 331, FFT (Fast Fourier Transform, fast fourier transform) circuit 3301 extracts signal corresponding to length during the effective code element from the output s (t) of subtraction portion 31, carry out the FFT conversion, thereby s (t) is transformed to frequency-region signal from time-domain signal, and will export s (ω) and offer symbol number and extract circuit 3302 as input, also offer first input that SP extracts circuit 3303 simultaneously.
Symbol number extract circuit 3302 from be contained in input s (ω) (TransmissionMultiplexing Configuration Control, the control of transmission multiplexing structure) waits about extracting the configuration of symbol number with appointment SP in the information of code element as TMCC.In case after symbol number is extracted out, also can replaces extracting and handle with symbol number phase Calais.Symbol number as the minimum necessary information of the configuration that will determine SP, amplitude and phase place is output divided by 4 remainders that obtain, and this output is provided for SP respectively and extracts second input separately of circuit 3303, transmission path characteristic counting circuit 3304 and SP combiner circuit 3305.Below, symbol number can directly not used again, therefore symbol number is renamed as " symbol number " divided by 4 remainders that obtain.
According to the appointment that the code element coding extracts circuit 3302, SP extracts circuit 3303 and extract the signal Sp (ω) that has only the SP signal from the output s (ω) of fft circuit 3301, and will export first input that Sp (ω) offers the transmission path characteristic counting circuit.
Extract the appointment of circuit 3302 according to symbol number, transmission path characteristic counting circuit 3304 generates the SP signal Xp (ω) of the known appointment of its amplitude and phase place in inside, SP signal Sp (ω) by SP being extracted circuit 3303 output calculates transmission path characteristic Fp (ω) to SP divided by Xp (ω), and this output is provided for first input of SP combiner circuit 3305.
The transmission path characteristic Fp (ω) that SP combiner circuit 3305 is preserved corresponding to 4 code elements of SP, the SP that the indication of extracting circuit 3302 according to symbol number will be allocated in 4 code elements synthesizes the original configuration of carrier wave, and exports again corresponding to the transmission path characteristic Fp ' of synthetic SP (ω).That is to say, according to the left end of the Fp (ω) of the left end of the Fp (ω) of the left end of the Fp (ω) of the left end of the Fp (ω) of symbol number 0, symbol number 1, symbol number 2, symbol number 3, the Fp of symbol number 0 (ω) from the 2nd of left end ... order reconfigure.(ω) be provided for interpolation circuit 3306 according to the transmission path characteristic Fp ' that obtains of synthetic SP of output.
The transmission path characteristic Fp ' that interpolation circuit 3306 only obtains dispersedly to synthetic SP interpolation (ω) and estimates the transmission path characteristic of signal band integral body.
That is to say that interpolation circuit 3306 usefulness are to the transmission path characteristic of the SP that calculated, interpolation is from the transmission path characteristic of the position of data carrier deleted between the SP, the transmission path characteristic of picked up signal frequency band integral body.Also can come interpolation, carry out low-pass filtering as direction at carrier wave with different feasible methods.Thereby this method realizes interpolation by carry out convolution algorithm according to the impulse response of low pass filter.Yet from the angle of accuracy and stability, impulse response need be set to finite length could be useful.Interpolation circuit 3306 is exported all transmission path characteristic of signal band that obtained, and output is offered sparse circuit 3308.
Sparse circuit 3308 is thinning thin with data, and reduces number of data points, to shorten the processing time of back circuit.It is in order to prevent that when IFFT circuit 3310 carries out the conversion of time shaft phase relation produces skew that sparse processing is carried out by this way, and the carrier data position that prevents to become the centre frequency that IFFT handles produces skew.By the restriction that IFFT handles, time sparse data of the power with per 2 is counted.The data slice number reduces along with sparsely spaced increase, but described in Japanese Patent Application Laid-Open 2001-223663 communique, is that actual boundary is arranged, and approximately is limited in 2 or 4.In addition, when data not when sparse, sparse circuit can omit.Data F after sparse (ω) exports from transmission path characteristic estimation portion 331, and this output is offered residual error property calculation circuit 3309.
Fig. 3 shows the pattern of the built-in function of transmission path characteristic estimation portion 331.This operation illustrated, therefore only with this figure with for referencial use and omission explanation wherein.
Residual error property calculation circuit 3309 calculates elimination residual error E (ω) according to the output F (ω) of transmission path characteristic estimation portion 331, and output is offered IFFT circuit 3310.
The output E (ω) of 3310 pairs of residual error property calculation of IFFT circuit circuit 3309 carries out IFFT, thereby the residual error E (ω) of frequency domain is converted to the residual error e (t) of time domain, and output is offered coefficient update circuit 3311.
Coefficient update circuit 3311 is according to the output e (t) of IFFT circuit 3310, calculate filter factor w_new (t) based on predetermined coefficient update expression formula, and will export second input that offers FIR filter 32 as the output w_fir (t) of filter factor generating unit 33.
Next, the condition that explanation loop interference eliminator 3 cancellation loops are disturbed.
At first, the output F (ω) of transmission path characteristic estimation portion 331 represents with (formula 2):
F ( ω ) = w _ in ( ω ) 1 - w _ in ( ω ) w _ o ut ( ω ) w _ loo p ( ω ) - w _ fir ( ω ) (formula 2)
Therefore, the loop interference signal can be represented with (formula 3) by the condition that subtraction portion 31 is eliminated:
W_in (ω) w_out (ω) w_loop (ω)=w_fir (ω) ... (formula 3)
Here, when eliminate residual error E (ω) such as (formula 4) during definition,
E (ω)=w_in (ω) w_out (ω) w_loop (ω)-w_fir (ω) ... (formula 4)
(formula 2) is out of shape, obtains (formula 5).
E ( ω ) = 1 - w _ in ( ω ) F ( ω ) (formula 5)
Here, make model simplification, when smooth, its transfer function w_in (ω) becomes constant D to the frequency characteristic of supposing receiving-member, and can be calculated in residual error property calculation portion 3309 based on (formula 6) in the signal band.
D = Σ ω F ( ω ) (formula 6)
At this moment, elimination residual error E (ω) is represented by (formula 7).
E ( ω ) = 1 - D F ( ω ) (formula 7)
In addition, the coefficient update expression formula of coefficient update circuit 3311 is defined by (formula 8).
W_new (t)=w_old (t)+μ e (t) ... (formula 8)
Wherein, the coefficient before upgrading during w_old (t) in (formula 8), μ is the non-negative constant smaller or equal to 1.
In said structure, thereby need carry out feedback control manipulation makes loop disturb poor between the transfer function w_fir (ω) of transfer function w_loop (ω) w_out (ω) and FIR filter 32, promptly eliminate residual error E (ω), can converge to 0, and have only main wave component to be output to the output s (t) of loop interference eliminator 3.
Fig. 4 is the block diagram that the data slice number that each parts of loop interference eliminator 3 are handled has been added note.The connection of each parts and handle all with Fig. 2 in identical, therefore omit the explanation of its operation.The situation that the data slice number can transmit the mode 3 of foregoing ISDB-T mode is an example.
In the I/O of fft circuit 3301, the input of symbol number extraction circuit 3302 and first input that SP extracts circuit 3303, number of data points is 8192 points.Extract the output of circuit 3303, first input and output of transmission path characteristic counting circuit 3304 and first input of SP combiner circuit 3305 at SP, number of data points is 469 points, just is contained in a SP number in the code element.In the output of SP combiner circuit 3305 and the input of interpolation circuit 3306, number of data points is 1873 points, just corresponding to the SP number (still, the pilot signal of right-hand member is public) of 4 code elements.In the output of interpolation circuit 3306 and the input of sparse circuit 3308, number of data points is represented the configuration of carrier wave, and therefore the same with the I/O of fft circuit 3301 also is 8192 points.In the output of sparse circuit 3308, the I/O of residual error property calculation circuit 3309 and the I/O of IFFT circuit 3310, how number of data points is reduced by sparse processing according to data and changes, but number of data points is identical, is actually or or 8192 points at 2048 at 4096.
Here require the loop interference eliminator can provide to height trackability, the high-precision elimination operation of the time variation of loop disturbing wave or main website wave phase and level and the miniaturization of installing.
Yet, in said structure, earlier by the transmission path characteristic with SP is carried out the transmission path characteristic that interpolation estimates signal band integral body, calculate the residual error characteristic then, therefore increase the number of the data point that is used to handle and hinder processing at a high speed, the imperfection (for example limited length) of impulse response that is used for the low pass filter of interpolation in addition reduces the estimated accuracy of transmission path characteristic, and exists low pass filter to need the problem of large-scale circuit.
Summary of the invention
The objective of the invention is with reducing the speed that the number of data points of handling improves the self adaptation operation of loop interference eliminator, thereby realize the height trackability that phase place and level to loop disturbing wave and main website ripple changed the time, carry out high-precision elimination operation by the accuracy that improves inter-process, thus and the miniaturization of the scale implement device of minimizing circuit.
Theme of the present invention is not adopt to synthetic SP (Scattered Pilot, scattered pilot) transmission path characteristic is calculated the residual error characteristic after carrying out interpolation, then this residual error characteristic being carried out IFFT handles to be converted into the structure of time-domain signal, earlier the transmission path characteristic of synthetic SP is calculated the residual error characteristic and adopt, this residual error characteristic is inserted 0 and carry out IFFT and handle and be converted to the structure of carrying out the window processing after the time-domain signal.
Like this, by reducing the speed that the number of data points of handling improves the operation of loop interference eliminator self adaptation, the height trackability that realization changed time of the phase place of loop disturbing wave and main website ripple and level, improve the precision of inter-process, carry out high accuracy and eliminate operation and reduce circuit scale, thereby can obtain the advantageous effects of implement device miniaturization.
According to the loop interference eliminator of the embodiment of the invention is to be used for when to send when receiving identical frequency relaying and have the multi-carrier signal of reference carrier uniformly-spaced, eliminate the loop interference eliminator that the loop between the send/receive antenna disturbs, comprise: elimination portion, eliminate the loop that is contained in the received signal with the filter of having set coefficient and disturb; Transmission path characteristic estimation portion offsets except the signal transmission path estimation characteristic after the described loop interference; Residual error property calculation portion calculates based on the estimated result of described transmission path characteristic estimation portion and to eliminate residual error; Zero insertion portion inserts remainder certificate to the output of described residual error property calculation portion; Invert fast fourier transformation portion is converted to time-domain signal with the output of described zero insertion portion; Window portion to the output of described invert fast fourier transformation portion, extracts and removes that transmission path characteristic repeats the scope of composition and by the scope of the described filter coefficient appointment smaller in the two; And renewal portion, upgrade the coefficient of described filter based on the output of described window portion.
The loop interference elimination method is a kind of when to send when receiving identical frequency relaying and have the multi-carrier signal of equally spaced reference carrier according to another embodiment of the present invention, eliminate the loop interference elimination method that the loop between transmission and the reception antenna disturbs, comprise: removal process, eliminate the loop that is contained in the received signal with the filter of having set coefficient and disturb; The transmission path characteristic estimating step offsets except the signal transmission path estimation characteristic after the described loop interference; The residual error characteristic calculation steps is eliminated residual error based on the estimated result calculating of described transmission path characteristic estimating step; The zero insertion step is inserted remainder certificate in the output result of described residual computations step; The invert fast fourier transformation step is converted to time-domain signal with the output result of described zero insertion step; The window step to the output of described invert fast fourier transformation step, is extracted the scope of the repetition composition remove transmission path characteristic and by the scope of the described filter coefficient appointment smaller in the two; And step of updating, based on the output result of described window step the coefficient of described filter is upgraded.
Description of drawings
Fig. 1 is the ideograph of an example of expression pilot signal configuration;
Fig. 2 is the block diagram of an example of expression loop interference eliminator structure;
Fig. 3 is the sketch map that the filter factor of explanation loop interference eliminator shown in Figure 2 generates the operation of parts;
Fig. 4 is the block diagram that the filter factor to the number of data points of each parts additional treatments of expression loop interference eliminator shown in Figure 2 generates parts;
Fig. 5 is the theory structure block diagram of expression use according to repeat broadcast system one example of the loop interference eliminator of the embodiment of the invention;
Fig. 6 is the block diagram of expression according to the loop interference eliminator of the embodiment of the invention;
The operator scheme figure of the filter factor generation parts that Fig. 7 is explanation when supposition is used for code element number according to the loop interference eliminator of the embodiment of the invention and is 1;
The operator scheme figure of the filter factor generation parts that Fig. 8 is explanation when supposition is used for code element number according to the loop interference eliminator of the embodiment of the invention and is 2;
The operator scheme figure of the filter factor generation parts that Fig. 9 is explanation when supposition is used for code element number according to the loop interference eliminator of the embodiment of the invention and is 4; And
To be expression generate the block diagram of parts according to the filter factor to the number of data points of each parts additional treatments of the loop interference eliminator of the embodiment of the invention to Figure 10.
Embodiment
With reference to the accompanying drawings embodiments of the present invention are described.
Fig. 5 is the block diagram that the SFN relay system model of loop interference eliminator is used in expression.Mark among the figure " * " expression convolution algorithm.In addition, except that specifying, following signal or response are all handled according to plural number.Suppose " (t) " the expression time-domain signal, " (w) " the expression frequency-region signal, determine definition on another territory simultaneously with the definition in the territory.
Acceptance division 2 among Fig. 5 is a baseband signal with the conversion of signals of RF (Radio Frequency, wireless frequency) band, and on the contrary, sending part 4 is converted to the RF band signal with baseband signal.Yet these frequency inverted, are therefore removed the special instruction without any in essence influence hereinafter to the present invention, can not mention these frequency inverted again.
In Fig. 5, x (t) expression master station signal, the input signal of r (t) expression acceptance division 2, the input signal of s (t) expression sending part 4, the impulse response of w_in (t) expression acceptance division 2, the impulse response of w_out (t) expression sending part 4, w_loop (t) expression loop disturbs the impulse response of transmission path 6, the impulse response of FIR (Finite Impulse Response, the finite impulse response (FIR)) filter 32 of w_fir (t) expression loop interference eliminator 3a inside.
In Fig. 5, reception antenna 1 receives and comes from loop and disturb the signal x of master station (t) of transmission path and the composite signal of loop interference signal w_loop (t) * w_out (t) * s (t), and will export r (t) and offer acceptance division 2.Acceptance division 2 r (t) is to received signal carried out processing such as filtering, frequency inverted and gain adjustment, and will export first input that w_in (t) * r (t) offers the subtraction portion 31 among the loop interference eliminator 3a.
In loop interference eliminator 3a, output w_in (t) the * r (t) of subtraction portion 31 usefulness acceptance divisions 2 deducts output w_fir (t) the * s (t) of FIR filter 32, and will export first input and the filter coefficient generating unit 33 that s (t) offers FIR filter 32, the while also offers sending part 4 as the output of loop interference eliminator 3a.
Filter coefficient generating unit 33 from the output s (t) of subtraction portion 31 thus the characteristic that estimates transmission path generates filter coefficient, and will export w_fir (t) and offer second of FIR filter 32 and import.
FIR filter 32 with the output w_fir (t) of the output s (t) of subtracter 31 and filter coefficient generating unit 33 carry out that thus convolution algorithm generates the loop interference signal duplicate w_fir (t) * s (t), and output is offered second input of subtraction portion 31.
Thereby the output s (t) of 4 pairs of subtraction portion 31 of sending part carry out that filtering, frequency inverted and gain are adjusted etc. handles and generates repeating signal w_out (t) * s (t), and output is offered transmitting antenna 5.
Transmitting antenna 5 is launched output w_out (t) the * s (t) of sending part 4, and the part of output is disturbed transmission path 6 and is surrounded on reception antenna 1 as loop interference signal w_loop (t) * w_out (t) * s (t) through loop.
Here, will the condition that loop interference eliminator 3a cancellation loop disturbs be described.
At first, the output Fp ' of the 331a of transmission path characteristic estimation portion is (ω) represented by (formula 9).Notice that all for OFDM, the output of being not only SP and all data carriers is all represented by the F (ω) shown in (formula 2), but under the situation of this execution mode, the output that only has pilot frequency carrier wave (SP) frequency is represented by Fp (ω).Then, the output of a code element of this output Fp (ω) expression, then (ω) represented when a plurality of code elements are synthetic by Fp '.
F p , ( ω ) = w _ in ( ω ) 1 - w _ in ( ω ) w _ o ut ( ω ) w _ loo p ( ω ) - w _ fir ( ω ) (formula 9)
Therefore, the condition eliminated by subtraction portion 31 of loop interference signal is represented by (formula 10).
W_in (ω) w_out (ω) w_loop (ω)=w_fir (ω) ... (formula 10)
Here, if eliminate residual error E (ω) shown in (formula 11) and define,
E (ω)=w_in (ω) w_out (ω) w_loop (ω)-w_fir (ω) ... (formula 11)
Substitution (formula 9) is out of shape, and just obtains (formula 12).
E ( ω ) = 1 - w _ in ( ω ) F p , ( ω ) (formula 12)
Here, make model simplification, when smooth, its transfer function w_in (ω) becomes constant D to the frequency characteristic of supposing acceptance division 2, and can be calculated in residual error property calculation circuit 3309 inside based on (formula 13) in signal band.
D = Σ ω F p , ( ω ) (formula 13)
At this moment, elimination residual error E (ω) is represented by (formula 14).
E ( ω ) = 1 - D F p , ( ω ) (formula 14)
In addition, the coefficient update expression formula with coefficient update circuit 3311 is defined as (formula 15).
W_new (t)=w_old (t)+μ e (t) ... (formula 15)
Wherein, the w_old (t) in (formula 15) is the coefficient before upgrading, and μ is the non-negative constant smaller or equal to 1.Under these conditions, converge to 0 thereby need to carry out the feasible elimination residual error E (ω) of FEEDBACK CONTROL, and have only main wave component to be output to the output s (t) of loop interference eliminator 3 as the difference between the transfer function w_fir (ω) of loop interference transfer function w_loop (ω) w_out (ω) and FIR filter 32.
Fig. 6 is the block diagram of expression according to the loop interference eliminator 3a of embodiment of the present invention 1.In Fig. 6, enclose same label with part identical among Fig. 2 and be used for explanation.
In filter coefficient generating unit 33a inside, the transmission path characteristic F (ω) that the transmission path characteristic estimation 331a of portion will estimate from the output s (t) of subtraction portion 31 exports as first, and this output is offered the input of residual error property calculation circuit 3309.The transmission path characteristic estimation 331a of portion will determine the needed minimal information of configuration, amplitude and phase place of SP---symbol number is as second output, and will export and offer 0 insertion circuit 3312 and phase place rotation compensation circuit 3314 second importing separately respectively.
Inside at the transmission path characteristic estimation 331a of portion, FFT (Fast Fourier Transform, fast fourier transform) circuit 3301 extracts the signal corresponding to length during the effective code element from the output s (t) of subtraction portion 31, carry out FFT time-domain signal s (t) is converted to frequency-region signal, and will export s (ω) and offer symbol number and extract the input of circuit 3302 and SP and extract first of circuit 3303 and import.
Symbol number extract circuit 3302 from be contained in input s (ω) as extracting the symbol number that is used to specify the SP configuration in the TMCC code element information such as (TransmissionMultiplexing Configuration Control transmit multiplexing control structure).In case extract after the symbol number, can replace extracting with symbol number phase Calais and handle.Symbol number will determine that divided by 4 remainder conduct the minimum necessary information of configuration, amplitude and the phase place of SP is output, and this output is provided for SP extraction circuit 3303, transmission path characteristic counting circuit 3304, SP combiner circuit 33051,0 insertion circuit 3312 and phase place rotation compensation circuit 3,314 second input separately respectively.Below, no longer directly use symbol number, therefore symbol number is renamed as " symbol number " divided by 4 remainders that obtain.
According to the appointment that symbol number is extracted circuit 3302, SP extracts circuit 3303 and extracts the signal Sp (ω) that has only the SP signal from the output S (ω) that exports fft circuit 3301, and will export first input that Sp (ω) offers the transmission path characteristic counting circuit.
Extract the appointment of circuit 3302 according to symbol number, transmission path characteristic counting circuit 3304 generates the SP signal Xp (ω) of the known appointment of its amplitude and phase place in inside, SP signal Sp (ω) by SP being extracted circuit 3303 output divided by SP signal Xp (ω) thus obtain transmission path characteristic Fp (ω) for SP, and output is offered first input of SP combiner circuit 33051.
SP combiner circuit 33051 is for the transmission path characteristic Fp (ω) of a plurality of code elements preservations corresponding to SP, the SP that the appointment of extracting circuit 3302 according to the symbol number of preassigned regular R will be distributed in a plurality of code elements synthesizes the original configuration at ripple, and again the synthetic SP of output transmission path characteristic Fp ' (ω).The back will be described in detail regular R.
When according to regular R with 4 continuous code elements when synthetic, adopt the processing identical with SP combiner circuit illustrated in fig. 2 3305.
In addition, when only using a code element according to regular R, obviously do not need to synthesize, SP combiner circuit 33051 can omit.
The output Fp ' of described SP combiner circuit 33051 (ω) exports as first of the transmission path characteristic estimation 331a of portion, and this output is provided for residual error property calculation circuit 3309.
Residual error property calculation circuit 3309 (ω) calculates and eliminates residual error E (ω) according to the output Fp ' of the transmission path characteristic estimation 331a of portion, as output, and output is offered 0 first input of inserting circuit 3312 with the elimination residual error E (ω) that calculates.
0 inserts circuit 3312, IFFT circuit 3310, window circuit 3313 and phase place rotation compensation circuit 3314 for the characteristic between elimination residual error E (ω) the insertion SP of first input that offers 0 insertion circuit 3312, is converted into time-domain signal e (t).
At first, 0 insert circuit 3312 and insert 0 in the position of the data carrier of deletion between as the elimination residual error E (ω) of the synthetic SP of first input.0 the method how inserted depends on regular R.In brief, insert two 0 simultaneously.The back will be specifically described regular R.
When according to synthetic 4 the continuous code elements of regular R, 0 inserts circuit 3312 inserts 0 in the position of the data carrier of deletion in the middle of synthetic SP.That is to say,, therefore insert simultaneously two 0 (referring to the interpolation processing of Fig. 3) owing to per three carrier waves of synthetic SP dispose.
In addition, number of data points need be made as 2 power, thereby can be handled by the IFFT circuit 3310 of back, therefore signal band outside data about insertion continuous 0.These insertions also depend on regular R, and in brief, data are expanded by inserting 0, thereby make frequency bandwidth and fft circuit 3301 handled signal bands have same width.
These have inserted 00 output of inserting circuit 3312 and have been provided for IFFT circuit 3310.
3310 pairs in IFFT circuit by 0 insert circuit 3312 inserted 0 elimination residual error E (ω) thus carry out IFFT with the residual error e (t) that the residual error E (ω) of frequency domain is converted to time domain, then output is offered window circuit 3313.
Window circuit 3313 is according to regular R, from the time-domain signal of IFFT circuit 3310 outputs, perhaps remove a scope of the repetition composition of transmission path characteristic, perhaps be limited to an interior scope of coefficient scope of FIR filter 32, extract the smaller among both.The back will be described in detail regular R.
The output of window circuit 3313 is provided for first input of phase place rotation compensation circuit 3314.
Phase place rotation compensation circuit 3314 is according to the appointment of extracting circuit 3302 as the symbol number of second input, and the phase place rotation that the offset that time-domain signal received, become the carrier data of the centre frequency that IFFT handles in IFFT circuit 3310 inputs by first input is brought compensates.Because the input dependence of IFFT circuit 3310 is in regular R, phase compensation also depends on regular R.In brief, the skew of supposing centre frequency is Δ ω, and each moment t as first time-domain signal of importing be multiply by exp (j Δ ω t), and wherein j is an imaginary unit.The back will be described in detail regular R.
When comprising the code element of symbol number 0 according to regular R use, become the not skew of carrier data of the centre frequency of IFFT processing in the input of IFFT circuit 3310, therefore do not need to carry out phase compensation, thereby phase place rotation compensation circuit 3314 can omit.
The time-domain signal of phase rotation circuit 3314 outputs becomes eliminates residual error e (t), and output is provided for coefficient update circuit 3311.
Next will the processing of regular R and relative SP combiner circuit 33051,0 insertion circuit 3312, window circuit 3313 and phase place rotation compensation circuit 3314 be described in detail.
Rule R can be divided into following several situation substantially: use 1 code element, use 2 code elements and use 4 code elements.
The processing of each parts in the time of at first, will using the situation of 1 code element to regular R describes.Fig. 7 shows the operator scheme under the situation of using 1 code element.
When only using a code element, SP combiner circuit 33051 is unwanted, and the output of the transmission path characteristic estimation 331a of portion is the transmission path characteristic with per 12 carrier extracts.0 inserts the greatest common divisor that circuit 3312 is considered the power time of 12 carrier waves and 2, per 4 carrier extract transmission path characteristic, thus before handling, IFFT circuit 3310 generates the transmission path characteristic that per 2 power extracts, and in 12 carrier waves, insert 20.In addition, make data be expanded by inserting 0, thereby obtain and the identical bandwidth of fft circuit 3301 handled signals in the data outside.In this case, according to the SP configuration rule of symbol number, bandwidth may not meet with original bandwidth.
In particular, do not have band bending, the carrier shift of (3) is arranged, the carrier shift of (6) is arranged, the carrier shift of (9) is arranged for symbol number 3 for symbol number 2 for symbol number 1 for symbol number 0.When 0 insertion circuit 3312 keeps these skews output is offered the input of IFFT circuit 3310.These signals have increased data by inserting 0, but their still signals in 12 carrier spacings in essence, therefore based on well-known sampling thheorem, in the output of IFFT circuit 3310, every (1/12) the individual symbol time of time domain just electricity around.For this reason, IFFT circuit 3310 provides the window circuit 3313 of output only to propose since the signal of time 0 (1/12) code element to it.
Next the situation of using 2 code elements is described.Fig. 8 shows the operator scheme under the situation of using two code elements.Suppose that these two code elements are not two continuous code elements but cross the group that two code elements of 1 intermediate symbol constitute.In particular, just symbol number 0 and 2 groups that constitute, or symbol number 1 and 3 groups that constitute.The transmission path characteristic Fp corresponding to SP (ω) that SP combiner circuit 33051 will offer first input preserves as the group that 2 code elements constitute, and keeps the order of original SP that they are synthetic.In the groups that symbol number 0 and 2 constitutes, according to Fp (ω) left end of symbol number 0, the Fp of symbol number 2 (ω) left end, the Fp of symbol number 0 (ω) is from second of left end ... order reconfigure.Situation for symbol number 1 and 3 combination also is the same.The output of the transmission path characteristic estimation 331a of portion becomes the transmission path characteristic with per 6 carrier extracts.Under the situation of symbol number 1 and 3, the pilot signal of right-hand member does not meet the rule of per 6 carrier extracts, and is therefore deleted.
Generate the transmission path characteristic that every (2 power) extracts for before handling at IFFT circuit 3310,0 insert that circuit 3312 is considered 6 carrier waves (with 2 power) thus per 2 the carrier extract transmission path characteristic of greatest common divisor, and in 6 carrier waves, insert two 0.In addition, come growth data, thereby obtain the identical bandwidth of signal handled with fft circuit 3301 by insert 0 in the data outsides.In this case, according to the SP configuration rule, some symbol number may not match with original bandwidth.Specifically, do not have band bending for the combination of symbol number 0 and 2, and the band bending of (3) is arranged for the combination of symbol number 1 and 3.When 0 insertion circuit 3312 keeps these skews output is offered the input of IFFT circuit 3310.These signals have increased data by inserting 0, but their still signals in 6 carrier spacings in essence, therefore based on well-known sampling thheorem, in the output of IFFT circuit 3310 every (1/6) symbol time time domain just electricity around.For this reason, IFFT circuit 3310 provides the window circuit 3313 of output only to extract from the signal of the moment 0 (1/6) code element to it.Yet (1/6) symbol time also might surpass the protection period that guarantees the normal reception of code element, is not very practical therefore, but might be limited in the coefficient scope of FIR filter 32.
3314 pairs of phase place rotations that brought by above-mentioned carrier shift of phase place rotation compensation circuit under the situation that is used to use a code element or use two code elements compensate.As mentioned above, as the time-domain signal of phase place rotation compensation circuit 3,314 first input because the phase place rotation that above-mentioned carrier shift is accepted is proportional with time of delay from the moment 0, and under situation, just be (27/8192) times of carrier shift according to the transmission of the mode 3 of ISDB-T pattern.For example, be under the situation of (3) in carrier shift, proportionality coefficient becomes (3) * (2 π/8192), and if suppose that proportionality coefficient is Δ ω, the delay t from the moment 0 multiply by exp (j* Δ ω * t) as phase compensation.
Next the situation when using 4 code elements is described.Fig. 9 shows the operator scheme of using 4 code elements.When using 4 continuous code elements, as mentioned above, the processing of the SP combiner circuit 3305 among the operation of SP combiner circuit 33051 and Fig. 2 is identical.With the situation of using a code element or use the situation of two code elements different be can not produce carrier shift.0 inserts the input that circuit 3312 offers output in IFFT circuit 3310.These signals increase data by inserting 0, but these signals still signal in 3 carrier spacings in essence, therefore based on well-known sampling thheorem, in the output of IFFT circuit 3310, every (1/3) symbol time of time domain just electric around.For this reason, IFFT circuit 3310 provides the window circuit 3313 of output only to extract from the signal of (1/3) code element of the moment 0 beginning to it.Yet (1/3) symbol time might surpass the guard time that guarantees the normal reception of code element, is not very practical therefore, but might be defined in the coefficient scope of FIR filter 32.
Rule R can and limit by multiple combination and define.For example, under the situation of using 1 code element, thereby only use symbol number 0 not need phase place rotation compensation circuit 3314.Under the situation of using 2 code elements, only use the combination of code element 0 and 2, thereby do not need phase place rotation compensation circuit 3314.
In addition, can be by in zero hour of loop interference eliminated or restart and constantly improve the precision that code element number improves calculating, and it is few and the code element number still less of update time is shortened in expectation to set the number of data points of handling when a predetermined level is exceeded is counted in the renewal of coefficient update circuit 3311.During normal running, increase code element number, and when the index variation of coefficient update circuit 3311 is relatively more violent, can shorten update time, thereby can reduce code element number by reducing the number of data points of handling.
Figure 10 is the block diagram that the data slice number that each parts of loop interference eliminator 3a are handled is added note.Therefore the connection of each parts and processing thereof and shown in Figure 6 identical omit the wherein explanation of operation.The situation that the data slice number will transmit according to the mode 3 of described ISDB-T mode is an example.
In the I/O of fft circuit 3301, the input of symbol number extraction circuit 3302 and first input that SP extracts circuit 3303, the data slice number is 8192 points.Extract the output of circuit 3303, first input and output of transmission path characteristic counting circuit 3304 and first input of SP combiner circuit 33051 at SP, number of data points is 469 points of the SP number that comprises in 1 code element.Insert first input of circuit 3312 in the output of SP combiner circuit 33051, the input and output and 0 of residual error property calculation portion 3309, number of data points changes along with the code element number M that is used for regular R, suppose comprise right-hand member pilot signal then number of data points for (M*468+1) point.In 0 output, the I/O of IFFT circuit 3310 and the input of window circuit 3313 of inserting circuit 3312, number of data points changes along with the code element that is used for regular R, is 2048 points during 1 code element, is 4096 points during 2 code elements, is 8192 points during 4 code elements.In the parts of the back of window output, number of data points depends on the window processing.In fact, when the code element number that is used for regular R was 1, the number of data slice was for approaching 682 points of (8192/12); And when code element number was 2 or 4, number of data points was 1024 points corresponding to typical guard time (1/8) symbol time.Therefore, compare the conventional example shown in Fig. 4, the number of data points of Chu Liing significantly reduces here, so can shorten the processing time of each parts and the data I/O time between each parts.
In addition, obtain all transmission path characteristic of frequency band with respect to the output in the transmission path characteristic estimation section in the loop interference eliminator shown in Fig. 2 with interpolation, can only use the output of SP part in the present embodiment, obtain to insert 0 again after the residual error characteristic, carry out IFFT, carry out windowization and use sampling thheorem to obtain time-domain signal corresponding to all residual error characteristics of frequency band as the transmission path characteristic estimation section.In addition, the incomplete expansion all of the limited wordlength low-pass filtering of difference and use interpolation to frequency band, the expansion of using above-mentioned sampling thheorem is the most accurate in theory expansion all to frequency band.In addition, viewpoint from the circuit scale of the connection of ignoring each parts, this is the structure that a kind of usefulness 0 insertion and windowization replace interpolation, but because the processing of 0 data and the processing that windowization is just extracted data are just inserted in 0 insertion, so this circuit scale is far smaller than the interpolation of carrying out calculating.
Therefore, loop interference eliminator 3a according to present embodiment, number of data points by the restriction transmission path characteristic estimation 331a of portion, and by without interpolation frequency domain carry out 0 insert and the time domain conversion after the window operation to expand to frequency band all, thereby can reach favourable effect, promptly by reducing the speed that the number of data points of handling improves the self adaptation operation of loop interference eliminator, the height trackability that realization changed time of the phase place of loop disturbing wave or main website ripple and level, by carrying out inter-process more accurately, carry out high accuracy and eliminate operation, and pass through the miniaturization of reduction circuit scale implement device.
As mentioned above, can realize advantageous effects according to the present invention, promptly, reduce the speed of the self adaptation operation that improves the loop interference eliminator by the number of data points of handling, realization by carrying out high-precision inter-process, is carried out high-precision elimination operation to the height trackability that time of the phase place of loop disturbing wave or main website ripple and level changes, and by the reduction circuit scale, the implement device miniaturization.
Present embodiment has illustrated the loop interference eliminator in the SFN relay system, but as long as adopt the system of OFDM transmission means, and present embodiment also can be applied to as the transponder in WLAN and the wireless telecommunication system etc.
This specification is willing to 2002-299523 Japanese patent application and on October 1st, 2003 submit special Japanese patent application of being willing to 2003-343412 number to based on the spy who submitted on October 11st, 2002, and its full content all is contained in this for reference.
Industrial applicibility of the present invention is, the present invention relates to a kind of use from OFDM (Orthogonal Frequency Division Multiplexing, OFDM) transmission path characteristic that goes out of Signal estimation The loop interference eliminator that comes cancellation loop to disturb, and can be applicable to loop interference eliminator, relay system With the loop interference elimination method, be used for the repeat broadcast that terrestrial digital broadcasting realizes broadcast wave relaying SFN Stand and radio communication in transponder etc. in.

Claims (11)

1. loop interference eliminator, when to send when receiving identical frequency relaying and have the multi-carrier signal of reference carrier uniformly-spaced, the loop of eliminating between the send/receive antenna disturbs, and comprising:
Elimination portion eliminates the loop that is contained in the received signal with the filter of having set coefficient and disturbs;
Transmission path characteristic estimation portion offsets except the signal transmission path estimation characteristic after the described loop interference;
Residual error property calculation portion calculates based on the estimated result of described transmission path characteristic estimation portion and to eliminate residual error;
Zero insertion portion inserts remainder certificate to the output of described residual error property calculation portion;
Invert fast fourier transformation portion is converted to time-domain signal with the output of described zero insertion portion;
Window portion to the output of described invert fast fourier transformation portion, extracts and removes that transmission path characteristic repeats the scope of composition and by the scope of the described filter coefficient appointment smaller in the two; And
Renewal portion upgrades the coefficient of described filter based on the output of described window portion.
2. loop interference eliminator as claimed in claim 1, wherein, described transmission path characteristic estimation portion comprises:
Fast fourier transform portion will be converted to frequency-region signal as the output of the described elimination portion of time-domain signal;
The reference carrier information extraction portion is extracted the information of configuration of expression reference carrier and signal component from the output of described fast fourier transform portion;
The reference carrier extraction unit according to the reference carrier configuration that obtains from the output of described reference carrier information extraction portion, only extracts reference carrier from the output of described fast fourier transform portion;
The transmission path characteristic calculating part, configuration and signal component by reference carrier that the output of described fast fourier transform portion and output from described reference carrier information extraction portion are obtained compare, thereby calculate the transmission path characteristic of reference carrier.
3. loop interference eliminator as claimed in claim 2, wherein, described transmission path characteristic estimation portion only uses one group of described transmission path characteristic calculating part to export the transmission path estimation characteristic.
4. loop interference eliminator as claimed in claim 2, wherein, described transmission path characteristic estimation portion also comprises: reference carrier synthesizes portion, store many groups of outputs of described transmission path characteristic calculating part, and according to the configuration of the reference carrier that obtains from the output of described reference carrier extraction unit, the group that has different reference carrier configurations in the many groups of outputs of being stored is synthesized
Two groups of outputs that the synthetic portion of described reference carrier only will uniformly-spaced dispose reference carrier are synthesized, and
Output with the synthetic portion of described reference carrier comes the transmission path estimation characteristic.
5. loop interference eliminator as claimed in claim 2, wherein, described transmission path characteristic estimation portion also comprises: reference carrier synthesizes portion, store many groups of outputs of described transmission path characteristic calculating part, and according to the configuration of the reference carrier that obtains from the output of described reference carrier extraction unit, the group that has different reference carrier configurations in the many groups of outputs of being stored is synthesized
4 groups of outputs that the synthetic portion of described reference carrier only will uniformly-spaced dispose reference carrier are synthesized, and
Use the output of the synthetic portion of described reference carrier to come the transmission path estimation characteristic.
6. loop interference eliminator as claimed in claim 1 wherein, when the transmission path characteristic of described transmission path characteristic estimation portion output is estimated, uses the combination that does not need the specific reference carrier that the phase place rotation compensation handles.
7. loop interference eliminator as claimed in claim 1 also comprises: phase place rotation compensation portion, and according to the output excute phase rotation compensation of the carrier wave configuration that is used to estimate described transmission path characteristic to described window portion,
Wherein, described renewal portion generates the coefficient of described filter according to the output of described phase place rotation compensation portion.
8. loop interference eliminator as claimed in claim 4, wherein, the synthetic portion of described reference carrier changes the output group number of the described transmission path characteristic calculating part that is synthesized starting constantly or moment of restarting or according to the state of described filter coefficient.
9. as loop interference eliminator according to claim 5, wherein, the synthetic portion of described reference carrier changes the group number of the output of the described transmission path characteristic calculating part that is synthesized starting constantly or moment of restarting or according to the state of described filter coefficient.
10. a relay system has loop interference eliminator as claimed in claim 1.
11. a loop interference elimination method, when to send when receiving identical frequency relaying and have the multi-carrier signal of equally spaced reference carrier, the loop of eliminating between the send/receive antenna disturbs, and comprising:
Removal process is eliminated the loop that is contained in the received signal with the filter of having set coefficient and is disturbed;
The transmission path characteristic estimating step offsets except the signal transmission path estimation characteristic after the described loop interference;
The residual error characteristic calculation steps is eliminated residual error based on the estimated result calculating of described transmission path characteristic estimating step;
The zero insertion step is inserted remainder certificate in the output result of described residual computations step;
The invert fast fourier transformation step is converted to time-domain signal with the output result of described zero insertion step;
The window step to the output of described invert fast fourier transformation step, is extracted the scope of the repetition composition remove transmission path characteristic and by the scope of the described filter coefficient appointment smaller in the two; And
Step of updating is upgraded the coefficient of described filter based on the output result of described window step.
CNB2003801007648A 2002-10-11 2003-10-06 Wraparound canceller, relay system, and wraparound cancelling method Expired - Fee Related CN100442681C (en)

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