CN101115047B - OFDM receiving and dispatching system for high speed mobile environment - Google Patents

OFDM receiving and dispatching system for high speed mobile environment Download PDF

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CN101115047B
CN101115047B CN200710119956.3A CN200710119956A CN101115047B CN 101115047 B CN101115047 B CN 101115047B CN 200710119956 A CN200710119956 A CN 200710119956A CN 101115047 B CN101115047 B CN 101115047B
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陆建华
龙毅
匡麟玲
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Tsinghua University
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Abstract

An orthogonal frequency division multiplexing OFDM transceiver system that is applicable to high speed mobile environment belongs to the technical field of digital communication and is characterized in that at the sending end, the data is segmented and goes through fast reverse fourier transform respectively, and OFDM sub-symbols after transformation are directly cascaded and are attached with a zero protective suffix, thus a relatively big sub-carrier interval is acquired and intercarrier interference caused by Doppler-spread is lessened, but the sensitivity of the system to inter sub-symbol interference. At the receiving end, an interference cancellation receiving device and method that uses sub-carrier given information is designed and the inter sub-symbol interference caused by multipath delay spread is eliminated. The invention causes little or no loss in spectral efficiency of OFDM system, and under the same channel condition, the system of the invention can improve the moving speed supported by traditional methods by about 1.6 times.

Description

A kind of OFDM receive-transmit system that is applicable to high-speed mobile environment
Technical field
The present invention relates to digital communication technology field, particularly a kind of OFDM (OFDM) modulating device and method of reseptance and device that improves the receiver translational speed.
Background technology
OFDM (hereinafter to be referred as OFDM) is as a kind of efficient broad band multicarrier transmission technology, paid attention to widely, adopted in European digital television broadcasting standard DVB-T, a plurality of wideband transmit technical standards such as WLAN standard IEEE802.11a, wireless metropolitan area network standard IEEE802.16.Yet, when obtaining broadband service, people constantly increase mobile demand, for example, in mobile application scenarios of high speed such as high-speed railways (speed per hour 350 kms/hour), also can enjoy the services such as HDTV (High-Definition Television) broadcast, WiMAX online.Therefore, improve the ability of OFDM wideband transmission system antagonism time-variant multipath channel, improve the translational speed of OFDM wideband transmission system receiver, become the subject matter of ofdm system.
Due to the broadband characteristics of signal and the movement of receiver, make transmission channel be rendered as the characteristic of large doppler spread and larger multidiameter delay expansion, cause ofdm system to be subject to disturbing between intersymbol interference and larger subcarrier the impact of (hereinafter to be referred as ICI) simultaneously.Ofdm system in the past will send sign map to one group of subcarrier by transmitting terminal, at receiving terminal, adopt self elimination method to alleviate the ICI introduced by carrier wave frequency deviation.But the method possible loss surpasses 50% throughput, and can not effectively alleviate the ICI introduced by doppler spread.The other method has proposed receiver and has suppressed ICI with the multilayer equalizer.But this equalizer needs desirable channel information usually, this will be difficult to guarantee in actual applications.
Summary of the invention
The present invention has designed a kind of OFDM receive-transmit system that is applicable to high-speed mobile environment.Its objective is the translational speed that improves OFDM wideband transmission system receiver under time-variant multipath channel.
Thinking of the present invention is; at transmitting terminal; by the transmitting terminal data are divided into to two parts; carry out respectively quick inverse-Fourier transform (hereinafter to be referred as IFFT), two OFDM subsymbols that produce after conversion, be called first subsymbol and second subsymbol; the two carries out cascade; and add zero protection suffix, thus obtaining larger subcarrier spacing, the ICI that doppler spread causes will alleviate thus.But also increased thus the sensitiveness of system antithetical phrase intersymbol interference (hereinafter to be referred as ISI).At receiving terminal, design one and utilized the interference of subcarrier Given information to eliminate receiving system and method, eliminated between the above-mentioned subsymbol caused by the multidiameter delay expansion and disturbed.
Specifically, data are divided into to two parts, are mapped as two parts subcarrier in frequency domain signal, suppose that above-mentioned two parts subcarrier in frequency domain signal is expressed as respectively the subcarrier in frequency domain signal X of first subsymbol 1the subcarrier in frequency domain signal X of [k] and second subsymbol 2[k], 0≤k<N, N is the ofdm system sub-carrier number, and N is even number.To above-mentioned subcarrier in frequency domain signal X 1[k] and x 2[k] carries out preliminary treatment, and preliminary treatment sub-carrier signal number is L, and L is the positive integer that is more than or equal to the maximum delay expansion, and L<N/2, and respective index is labeled as vectorial m.By X 1[k] and X 2[k] is expressed as respectively vectorial X 1and X 2.Thereafter, X 1[k] and X 2[k] inputs respectively two IFFT unit, and cascade is carried out in the output of IFFT, and now transmitted signal is
y [ n ] = x ~ 1 [ n ] + x ~ 2 [ n ] - - - ( 1 )
Wherein
x ~ 1 [ n ] = F - ( N 2 ) ( n , X 1 [ k ] ) , 0 &le; n < N / 2 0 , N / 2 &le; n < N (2)
x ~ 2 [ n ] = 0 , 0 &le; n < N / 2 F - ( N 2 ) ( n , X 2 [ k ] ) , N / 2 &le; n < N
Wherein, F (N)(k, x[n]) mean x[n]the DFT computing of N rank; F -(N)(n, X[k]) mean x[k]the contrary discrete Fourier transform (DFT) (hereinafter to be referred as IDFT) in N rank.
Above-mentioned transmitted signal after cascade forms new OFDM symbol and adds at afterbody the zero suffix that P is long, and wherein, P is the number of samples of zero suffix, and it is the positive integer that is more than or equal to the maximum delay expansion.
At receiving terminal, typical OFDM receiver all needs through frame synchronization, thereby determine the border of each OFDM symbol, thereafter, the long suffix of the P received first is added to OFDM symbol head, make the linear convolution in the OFDM symbol be equivalent to circular convolution, then received signal is carried out to N point fast Fourier conversion (hereinafter to be referred as FFT), the output of FFT just can be used interference of the present invention to eliminate the method and apparatus received.
Another aspect of the present invention, i.e. described interference is eliminated receiving system and is realized the output of above-mentioned FFT is carried out to interference elimination treatment.The output of receiving terminal FFT is divided into even number and odd number output, is expressed as respectively
Figure GFW00000082771600024
vector
Figure GFW00000082771600025
with
Figure GFW00000082771600026
right
Figure GFW00000082771600027
with
Figure GFW00000082771600028
be handled as follows:
R ^ p = R ~ e - - - ( 3 )
R ^ s = F e ( [ F 0 S ] ) - 1 [ R ~ 0 R known ] - - - ( 4 )
Wherein, F [N]∈ C n * Nmean the normalized discrete Fourier transform (DFT) in N rank (hereinafter to be referred as DFT) matrix, its element is
Figure GFW000000827716000211
Figure GFW000000827716000212
for the DFT matrix F (N)submatrix, its element
Figure GFW000000827716000213
Figure GFW000000827716000214
for the DFT matrix F (N)second half submatrix, its element
Figure GFW000000827716000215
s is F e's
Figure GFW000000827716000216
submatrix, its L is capable of F ecapable vector in choose, the corresponding above-mentioned transmitting terminal preliminary treatment index marker vector m of corresponding line index marker, its element S (i, j)=F e (m (i), j).R knownfrom accordingly
Figure GFW000000827716000217
the L that the subvector of middle extraction generates * 1 vector, extract the corresponding vectorial m of index marker.L is the positive integer that is more than or equal to the maximum delay expansion, and L<N/2.
The combinations thereof matrix it is a reversible Fan Demeng (Vandermonde) matrix.Because matrix S is chosen according to transmitting terminal known carrier wave insertion position, coefficient matrix
Figure GFW00000082771600032
can be when system calculated in advance, and the computing of matrix inversion can not cause the system operation time.
Described interference eliminate receiving system also comprise by simple plus and minus calculation from
Figure GFW00000082771600033
with
Figure GFW00000082771600034
in the subcarrier in frequency domain signal of first subsymbol of being restored
Figure GFW00000082771600035
subcarrier in frequency domain signal with second subsymbol recovered
Figure GFW00000082771600036
will
Figure GFW00000082771600037
with
Figure GFW00000082771600038
be expressed as respectively vector
Figure GFW00000082771600039
with computational methods are expressed as:
X ~ 1 = ( R ^ p + R ^ s ) / 2 - - - ( 5 )
X ~ 2 = ( R ^ p R ^ s ) / 2 - - - ( 6 )
So far, the purpose that receiving system has completed its design is eliminated in interference of the present invention, that is, eliminated between the subsymbol of introducing because of the cascade of transmitting terminal subsymbol and disturbed.Adopt traditional least square (LS) or least mean-square error (MMSE) method subcarrier in frequency domain signal to two subsymbols of above-mentioned recovery thereafter, with
Figure GFW000000827716000314
carry out channel estimating and equilibrium treatment.
The present invention is characterised in that and contains transmitter and receiver, wherein:
Transmitter contains: the first deserializer (102), and two pretreatment units (the first pretreatment unit 1031, the second pretreatment units 1032), N/2 point IFFT unit (1011,1012), the first parallel-to-serial converter (104), wherein,
The first deserializer (102), be used for the N-L of serial input data parallelization, N is the ofdm system number of sub carrier wave, N is even number, L is more than or equal to the zero integer that is less than N/2, for the sub-carrier signal number altogether increased in above-mentioned two pretreatment units processing, the output of deserializer is connected with above-mentioned two pretreatment unit inputs;
Two pretreatment units (1031,1032), carry out preliminary treatment for the parallel data stream that will be mapped to above-mentioned two N/2 point IFFT unit inputs, input is connected with the first deserializer output, exports respectively the subcarrier in frequency domain signal X of first subsymbol 1subcarrier in frequency domain signal X with second subsymbol 2to above-mentioned two N/2 point IFFT unit inputs; Described pretreatment unit is pressed following three step process for N-L the data from the first deserializer (102) input:
The first pretreatment unit (1031) first produces L 1the given data symbol of individual any appointment, comprising the remainder according to symbol, L 1be less than or equal to the L integer for being more than or equal to zero, and be placed at random subcarrier in frequency domain signal X 1subcarrier on, as X to be exported 1a part, the L that it is corresponding 1individual sub-carrier indices set is labeled as K 1, K 1the element span be to be more than or equal to 1 integer that is less than or equal to N/2; Then, the second pretreatment unit (1032) produces nonnegative integer L 2the individual known or remainder is according to symbol, L 2=L-L 1, and be placed at random subcarrier in frequency domain signal X 2subcarrier on, as X to be exported 2a part, the L that it is corresponding 2individual sub-carrier indices set is labeled as K 2, K 2the element span be to be more than or equal to 1 integer that is less than or equal to N/2, and
Figure GFW000000827716000315
be K 1and K 2not overlapping; If
Figure GFW000000827716000316
repeat to be placed at random X 2process, until
Figure GFW000000827716000317
again by K 1and K 2union K 1∪ K 2produce the sub-carrier indices vector m of L dimension;
The first deserializer (102) output N-L data to two pretreatment unit, pretreatment unit is placed into arbitrarily respectively X by it 1and X 2in on the subcarrier of the value of not putting, X wherein 1middle placement positive integer N/2-L 1individual data, X 2middle placement positive integer N/2-L 2individual data, meet the data subcarrier index and sub-carrier indices vector m is not overlapping;
Two pretreatment units (1031,1032) are exported respectively the X after processing 1and X 2;
Two N/2 point IFFT unit (1011,1012), for generation of two OFDM subsymbols, input respectively with two pretreatment units (1031,1032) output is connected, the IFFT unit be connected with the first pretreatment unit produces first subsymbol, and the IFFT unit be connected with the second pretreatment unit produces second subsymbol, and output is connected with the first parallel-to-serial converter (102) input;
The first parallel-to-serial converter (104), carry out serially concatenated for first subsymbol and second subsymbol by the output of above-mentioned two N/2 point IFFT unit, form new OFDM symbol and add zero suffix, input and above-mentioned two N/2 point IFFT unit (1011,1012) output is connected, the output transmitted signal;
Receiver contains: the second deserializer (204), and N point FFT unit (202), disturb and eliminate receiving system (201), two channel estimation and equalization unit (2031,2032), the second parallel-to-serial converter (205), wherein,
The second deserializer (204), for the input traffic parallelization by serial, input is the transmitter transmitted signal received, output is connected with above-mentioned N point FFT unit (202) input;
N point FFT unit (202), be converted to frequency-region signal for inputting time-domain signal, and input is connected with the second deserializer (204) output, and output is eliminated receiving system (201) input with above-mentioned interference and is connected;
Disturb and eliminate receiving system (201), for eliminate between subsymbol disturb and subcarrier between disturb, input is connected with N point FFT unit (202) output, and output and above-mentioned two channel estimation and equalization unit (2031,2032) input are connected; Described interference is eliminated receiving system and is contained even withdrawal device, strange withdrawal device, fixed coefficient linear filter, subcarrier withdrawal device, mends base subcarrier maker, adder and subtracter, wherein:
Even withdrawal device, be used for extracting subcarrier in frequency domain signal corresponding to even number index marker that the N point FFT unit (202) of receiving terminal is exported
Figure GFW00000082771600041
input is connected with the parallel output terminal of above-mentioned N point FFT unit (202), and output is connected with subcarrier withdrawal device input and adder input;
Strange withdrawal device, be used for extracting subcarrier in frequency domain signal corresponding to odd number index marker that the N point FFT unit (202) of receiving terminal is exported
Figure GFW00000082771600042
input is connected with the parallel output terminal of above-mentioned N point FFT unit (202), and output is connected with fixed coefficient linear filter input;
The fixed coefficient linear filter, be used for producing the difference signal of the subcarrier in frequency domain signal of first subsymbol with respect to the subcarrier in frequency domain signal of second subsymbol
Figure GFW00000082771600043
the fixed coefficient linear filter has two inputs, and an input is connected with benefit base subcarrier maker output, and an input is connected with strange withdrawal device output, and output is linked adder and subtracter input simultaneously; Described fixed coefficient linear filter produces by following three steps
Figure GFW00000082771600044
Generate the coefficient matrix of above-mentioned fixed coefficient linear filter
Figure GFW00000082771600051
comprise, according to the normalized DFT matrix F in N rank (N)'s
Figure GFW00000082771600052
submatrix F oand F e, its matrix element is respectively
Figure GFW00000082771600053
with
Figure GFW00000082771600054
regeneration F e's
Figure GFW00000082771600055
the s of submatrix, its L is capable of F ecapable vector in choose, the corresponding above-mentioned transmitting terminal preliminary treatment sub-carrier indices vector m of corresponding line index marker, its element S (i, j)=F e (m (i), j); Matrix F oconstitute one with matrix s
Figure GFW00000082771600056
combinatorial matrix
Figure GFW00000082771600057
calculate the inverse matrix of this combinatorial matrix
Figure GFW00000082771600058
and matrix F is multiplied by the right side e, obtain above-mentioned fixed coefficient linear filter
Figure GFW00000082771600059
coefficient matrix
Figure GFW000000827716000510
According to above-mentioned strange withdrawal device, obtain
Figure GFW000000827716000511
vector
Figure GFW000000827716000512
with the L that mends the generation of base subcarrier maker * 1 vectorial R known, constitute one
Figure GFW000000827716000513
the input combinatorial matrix
By above-mentioned input combinatorial matrix
Figure GFW000000827716000515
above-mentioned coefficient matrix is multiplied by the right side produce the output vector of fixed coefficient linear filter and output
Figure GFW000000827716000518
The subcarrier withdrawal device, be used for from the output signal of even withdrawal device the sub-carrier indices set mark K described by pretreatment unit 1and K 2extraction is no less than integer L known subcarrier, and input is connected with the output of above-mentioned even withdrawal device, and output is connected with benefit base subcarrier maker input;
Mend base subcarrier maker, being no less than integer L known subcarrier of being used for obtaining from above-mentioned subcarrier withdrawal device produces benefit base subcarrier R known, to meet the benefit base requirement that can solve; Input is connected with the output of above-mentioned subcarrier withdrawal device, and output is connected with the input of fixed coefficient linear filter; Described benefit base subcarrier maker produces R by following two steps known:
To the sub-carrier indices set mark K described in pretreatment unit 1corresponding sub-carrier signal get negative after as R to be exported knownthe sub-carrier signal element of middle manipulative indexing mark, to the sub-carrier indices set mark K described in pretreatment unit 2corresponding sub-carrier signal directly as R to be exported knownthe sub-carrier signal element of middle manipulative indexing mark;
Output R known;
Adder, be used for the output of the output of above-mentioned fixed coefficient linear filter and even withdrawal device is carried out to additional calculation, adder has two inputs, an input is connected with the output of above-mentioned even withdrawal device, an input is connected with above-mentioned fixed coefficient linear filter, is output as the subcarrier in frequency domain signal of first subsymbol after recovery the output of adder is for disturbing first output of eliminating receiving system (201);
Subtracter, be used for the output of the output of above-mentioned fixed coefficient linear filter and even withdrawal device is carried out to subtraction, subtracter has two inputs, an input is connected with the output of above-mentioned even withdrawal device, an input is connected with above-mentioned fixed coefficient linear filter output, is output as the subcarrier in frequency domain signal of second subsymbol after recovery
Figure GFW00000082771600061
the output of subtracter is for disturbing second output eliminating receiving system (201);
Two channel estimation and equalization unit (2031,2032), for by least square (LS) or Minimum Mean Square Error (MMSE) algorithm, estimating channel and balanced reception signal, input is connected with disturbing elimination receiving system output, and output is connected with the second parallel-to-serial converter (205) input;
The second parallel-to-serial converter (205), carry out serially concatenated for the parallel output by above-mentioned two channel estimation and equalization unit, and input is connected with two channel estimation and equalization unit outputs, is output as sub-carrier signal.
The OFDM receive-transmit system that is applicable to high-speed mobile environment as described above, is characterized in that, transmitter comprises M pretreatment unit and M N/M point IFFT unit, and M is more than or equal to 2 positive integers that are less than or equal to N.Wherein the difference signal in the fixed coefficient linear filter contains M-1 subsignal, respectively subcarrier in frequency domain signal poor of the subcarrier in frequency domain signal of first subsymbol and second subsymbol, the subcarrier in frequency domain signal of the subcarrier in frequency domain signal of second subsymbol and the 3rd subsymbol poor, the like until the subcarrier in frequency domain signal of the subcarrier in frequency domain signal of M-1 subsymbol and M subsymbol poor.
An advantage of the invention is and effectively reduced the sensitivity of system to ICI, improve the translational speed of receiver, theory analysis and emulation show, at the same terms, during signal to noise ratio 20dB, system of the present invention can improve the approximately translational speed of 1.6 times than conventional method.In addition, described modulation and method of reseptance and device also have advantages of that flexible structure, algorithm are simple, are easy to realize.
It should be noted that most practical ofdm systems have inserted zero subcarrier for outer interference of inhibition zone, these subcarrier information can be used for above-mentioned disturbance eliminating and receiving method and device, eliminate between subsymbol and disturb.In addition, when existing zero subcarrier deficiency, can the parton carrier wave be preset as to zero at transmitting terminal and reach same purpose.Thereby, than self elimination method in the past, the expense of OFDM wideband transmission system of the present invention can significantly descend.
Above-described goal of the invention and advantage are in the OFDM wideband transmission system, signal is carried out the OFDM modulation and disturbs in the method and apparatus of eliminating and realize, wherein, digital information symbols has adopted data sectional has been carried out to IFFT when carrying out the OFDM modulation, is used for producing a plurality of OFDM subsymbols and carries out direct cascade.From Fig. 7 performance comparison diagram, can find out, compare not do and disturb the ofdm system of eliminating and two kinds of methods of ofdm system of applying self elimination method, method proposed by the invention is at two kinds of doppler spread situation (f dt s=0.126 and F dt s=0.081) all obtain better performance in, method proposed by the invention is at F dt sthe performance of=0.126 o'clock and conventional method are at F dt sthe performance of=0.081 o'clock is close.Consider a large amount of zero subcarriers of ubiquity in ofdm system, the present invention does not seldom even lose the spectrum efficiency of ofdm system, and in same channel conditions, system of the present invention can improve approximately 1.6 times than the translational speed of conventional method support.
The accompanying drawing explanation
Fig. 1 is the structural representation of OFDM modulating device of the present invention.
Fig. 2 is the schematic diagram that receiving system position in the OFDM receiver is eliminated in interference of the present invention.
Fig. 3 is the structural representation that receiving system is eliminated in interference of the present invention.
Fig. 4 is the operational flowchart of a kind of preprocess method in OFDM modulating device of the present invention.
Fig. 5 is that a kind of benefit base subcarrier R that mends base subcarrier maker in receiving system is eliminated in interference of the present invention knownthe operational flowchart of generation method.
Fig. 6 is the operational flowchart that fixed coefficient linear filter computational methods in receiving system are eliminated in interference of the present invention.
Fig. 7 is the method for the invention and the performance comparison diagram of not doing interference elimination method and self elimination method.
Embodiment
According to an aspect of the present invention, provide a kind of OFDM modulating device (referring to accompanying drawing 1), comprise two N/2 point IFFT unit, N is the ofdm system number of sub carrier wave, and N is even number, for generation of two OFDM subsymbols; Deserializer, for the data flow parallelization by serial; Two pretreatment units, carry out preliminary treatment for the parallel data stream that will be mapped to above-mentioned two N/2 point IFFT unit inputs, and the first pretreatment unit is exported the subcarrier in frequency domain signal X of first subsymbol 1, the subcarrier in frequency domain signal X of second subsymbol of the second pretreatment unit output 2; Parallel-to-serial converter, carry out serially concatenated for first subsymbol and second subsymbol by the output of above-mentioned two N/2 point IFFT unit, forms new OFDM symbol and add zero suffix.
The present invention also provides a kind of transmitting terminal to carry out pretreated method (referring to accompanying drawing 4), and described method comprises: L subcarrier is at random from subcarrier in frequency domain signal X 1and X 2middle selection zero setting or given value, its sub-carrier indices set is labeled as respectively K 1and K 2, and meet
Figure GFW00000082771600071
two index marker union of sets collection produce sub-carrier indices vector m.Specifically, the first pretreatment unit (1031) first produces L 1the given data symbol of individual any appointment, comprising the remainder according to symbol, L 1be less than or equal to the L integer for being more than or equal to zero, and be placed at random subcarrier in frequency domain signal X 1subcarrier on, as X to be exported 1a part, its corresponding L 1individual sub-carrier indices set is labeled as K 1, K 1the element span be to be more than or equal to 1 integer that is less than or equal to N/2; Then, the second pretreatment unit (1032) produces nonnegative integer L 2the individual known or remainder is according to symbol, L 2=L-L 1, and be placed at random subcarrier in frequency domain signal X 2subcarrier on, as X to be exported 2a part, its corresponding L 2individual sub-carrier indices set is labeled as K 2, K 2the element span be to be more than or equal to 1 integer that is less than or equal to N/2, and that is, K 1and K 2not overlapping; If
Figure GFW00000082771600073
repeat to be placed at random X 2process, until
Figure GFW00000082771600074
again by K 1and K 2union K 1∪ K 2produce the sub-carrier indices vector m of L dimension.Due to many zero subcarriers being arranged in Practical OFDM Systems, suppose that ofdm system has S zero subcarrier, if SL, vectorial m can choose in above-mentioned these zero subcarriers.If S<L, except above-mentioned S zero subcarrier is selected, L-S subcarrier at transmitting terminal by zero setting.A N-L data to two pretreatment unit of the first deserializer output, pretreatment unit is placed into arbitrarily respectively X by it 1and X 2in on the subcarrier of the value of not putting, X wherein 1middle placement positive integer N/2-L 1individual data, X 2middle placement positive integer N/2-L 2individual data, meet the data subcarrier index and sub-carrier indices vector m is not overlapping; Two pretreatment units are exported respectively the X after processing 1and X 2.
According to another aspect of the present invention, receiving system is eliminated in a kind of interference be provided in OFDM wideband transmission system receiver.Described interference is eliminated the position of receiving system in the OFDM receiver referring to accompanying drawing 2.At first typical ofdm system receiver needs to determine the border of OFDM symbol, and thereafter, the long suffix of the P received first is added to OFDM symbol head, makes the linear convolution in the OFDM symbol be equivalent to circular convolution, and each OFDM symbol carries out N point FFT again.The input that receiving system is eliminated in interference of the present invention is connected with the parallel output terminal of above-mentioned N point FFT unit, and its output is connected with the channel estimation and equalization unit.
Interference provided by the present invention is eliminated receiving system (referring to accompanying drawing 3) and being comprised: even withdrawal device, for extracting subcarrier in frequency domain signal corresponding to above-mentioned N point FFT unit output even number index marker, is expressed as vector
Figure GFW00000082771600081
strange withdrawal device, for extracting subcarrier in frequency domain signal corresponding to above-mentioned N point FFT unit output odd number index marker, be expressed as vector
Figure GFW00000082771600082
the subcarrier withdrawal device, for extracting subcarrier in frequency domain signal corresponding to above-mentioned sub-carrier indices vector m from above-mentioned even withdrawal device; Mend base subcarrier maker, for the subcarrier in frequency domain signal extracted from above-mentioned subcarrier withdrawal device, produce and mend base sub-carrier vector R known; The fixed coefficient linear filter, for the vectorial R obtained from above-mentioned benefit base subcarrier maker knownvector with above-mentioned strange withdrawal device acquisition
Figure GFW00000082771600083
middle employing formula (4) compute vector adder, for from vector
Figure GFW00000082771600085
the vector that employing formula (3) obtains
Figure GFW00000082771600086
with the vector obtained from the fixed coefficient linear filter
Figure GFW00000082771600087
carry out addition, obtain the subcarrier in frequency domain signal that disturbs first subsymbol after eliminating
Figure GFW00000082771600088
subtracter, for from vector
Figure GFW00000082771600089
the vector that employing formula (3) obtains
Figure GFW000000827716000810
with the vector obtained from the fixed coefficient linear filter
Figure GFW000000827716000811
subtracted each other, obtained the subcarrier in frequency domain signal that disturbs second subsymbol after eliminating
Figure GFW000000827716000812
The present invention also provides a kind of benefit base subcarrier R in above-mentioned benefit base subcarrier maker knownthe generation method, the corresponding above-mentioned transmitting terminal of described method carries out pretreated method.Comprise the following steps: for vector
Figure GFW000000827716000813
middle index marker is k 1the sub-carrier signal element, get negative after as vectorial R knownmiddle index marker is k 1the sub-carrier signal element,
Figure GFW000000827716000814
for vector
Figure GFW000000827716000815
middle index marker is k 2the sub-carrier signal element, directly as vectorial R knownmiddle index marker is k 2the sub-carrier signal element, R known [ k 2 ] = R ~ e [ k 2 ] .
The present invention also provides the above-mentioned fixed coefficient linear filter of a kind of use compute vector method.Described computational methods comprise the following steps: at first, generate the coefficient matrix of above-mentioned fixed coefficient linear filter, comprise, according to above-mentioned DFT matrix F (N)'s
Figure GFW000000827716000818
submatrix F oand F e's submatrix s, form one
Figure GFW000000827716000820
combinatorial matrix
Figure GFW000000827716000821
calculate combinations thereof inverse of a matrix matrix
Figure GFW000000827716000822
and above-mentioned DFT matrix F is multiplied by the right side (N)submatrix F e, obtain above-mentioned fixed coefficient linear filter coefficient matrix
Figure GFW000000827716000824
the calculating of above-mentioned coefficient matrix can first be carried out in the system current events; Then, according to above-mentioned strange withdrawal device, obtain
Figure GFW000000827716000825
vector
Figure GFW000000827716000826
the L produced with above-mentioned benefit base subcarrier maker * 1 vectorial R known, form one
Figure GFW00000082771600091
the input combinatorial matrix
Figure GFW00000082771600092
finally, by above-mentioned input combinatorial matrix
Figure GFW00000082771600093
above-mentioned coefficient matrix is multiplied by the right side
Figure GFW00000082771600094
(referring to formula 4), obtain vector
Figure GFW00000082771600095
By below in conjunction with accompanying drawing, to OFDM modulating device of the present invention and for this device, at receiving terminal, disturbing the embodiment that eliminates the method and apparatus received to be described in detail, other purpose, characteristic and the advantage that the present invention may be better understood.
With reference to figure 1, OFDM modulating device proposed by the invention is described.Shown in Fig. 1 is the OFDM modulating device that produces the cascade of two OFDM subsymbols, and it comprises: a deserializer (102), for the data flow parallelization by serial; Two N/2 point IFFT unit (1011,1012), for generation of two OFDM subsymbols; Two pretreatment units (the first pretreatment unit 1031, the second pretreatment units 1032), carry out preliminary treatment for the parallel data stream to being mapped to above-mentioned two IFFT unit inputs; A parallel-to-serial converter (104), carry out serially concatenated for the output to above-mentioned two IFFT unit (1011,1012), forms new OFDM symbol and add zero suffix.
Now, the subcarrier in frequency domain signal of the first deserializer (102) output is divided into two parts, delivers in two pretreatment units and carries out preliminary treatment, exports respectively the subcarrier in frequency domain signal X of first subsymbol 1subcarrier in frequency domain signal X with second subsymbol 2.Thereafter, X 1and X 2input respectively above-mentioned two IFFT unit, first subsymbol of IFFT unit output and second subsymbol input parallel-to-serial converter (104), parallel-to-serial converter 104 carries out serially concatenated and adds zero suffix the output of IFFT unit according to formula (1) and formula (2).
Describe interference proposed by the invention below with reference to Fig. 2 and eliminate the embodiment of receiving system in the receiver installation site.As shown in Figure 2, the input that receiving system (201) is eliminated in interference of the present invention is connected with the parallel output terminal of N point FFT unit (202), and its output and two channel estimation and equalization unit (2031,2032) are connected.At first, determine the OFDM character boundary and the reception signal that carries out after suffix copies is input to deserializer (204); Then, deserializer (204), by the reception signal parallel of serial, outputs to a N point FFT unit (202); Then, the parallel output of N point FFT unit (202) is connected to the input that receiving system (201) is eliminated in interference of the present invention; Then, the output that receiving system (201) is eliminated in interference of the present invention is input to two channel estimation and equalization unit (2031,2032), to disturbing the subcarrier in frequency domain signal after eliminating, carries out respectively channel estimating and equilibrium; Finally, the output of above-mentioned two channel estimation and equalization unit is input to parallel-to-serial converter (205), and the parallel data serialization is exported.
An embodiment of the interference elimination receiving system of the present invention's proposition is described below with reference to Fig. 3.As shown in Figure 3, as a preferred embodiment, disturb the elimination receiving system to comprise an even withdrawal device (301) and a strange withdrawal device (302), their input is connected with the parallel output terminal of above-mentioned N point FFT unit (202), is used for extracting respectively subcarrier in frequency domain signal vector corresponding to even number index marker that above-mentioned N point FFT unit (202) is exported
Figure GFW00000082771600096
the subcarrier in frequency domain signal vector corresponding with the odd number index marker
Figure GFW00000082771600097
a subcarrier withdrawal device (303), its input is connected with the output of above-mentioned even withdrawal device (301), is used for extracting being no less than L known subcarrier; A benefit base subcarrier maker (304), its input is connected with the output of above-mentioned subcarrier withdrawal device (303), utilizes from vector
Figure GFW00000082771600101
the individual known subcarrier of L that is no less than of middle extraction produces vectorial R known; A fixed coefficient linear filter (305), it has two inputs, an input is connected with benefit base subcarrier maker (304) output, an input is connected with strange withdrawal device (302) output, utilizes the output of above-mentioned benefit base subcarrier maker (304) and strange withdrawal device (302) to produce combinatorial matrix
Figure GFW00000082771600102
and the right fixed coefficient matrix that is multiplied by calculated in advance produce output vector
Figure GFW00000082771600104
an adder (306), it has two inputs, an input is connected with the output of above-mentioned even withdrawal device (301), an input is connected with above-mentioned fixed coefficient linear filter (305), carry out add operation, be output as the subcarrier in frequency domain signal of first subsymbol after recovery
Figure GFW00000082771600105
a subtracter (307), it has two inputs, an input is connected with the output of above-mentioned even withdrawal device (301), an input is connected with above-mentioned fixed coefficient linear filter (305), carry out subtraction, be output as the subcarrier in frequency domain signal of second subsymbol after recovery
Figure GFW00000082771600106
Fig. 4 describes an embodiment of a kind of preprocess method of transmitting terminal proposed by the invention.As shown in Figure 4, a kind of preprocess method of described transmitting terminal comprises the following steps: at first, in step S401, the first pretreatment unit first produces nonnegative integer L 1the individual known or remainder is according to symbol, and L 1≤ L, and be placed at random subcarrier in frequency domain signal X 1subcarrier on, its corresponding L 1individual sub-carrier indices set is labeled as K 1; Then, in step S402, the second pretreatment unit produces nonnegative integer L 2the individual known or remainder is according to symbol, L 2=L-L 1, and be placed at random subcarrier in frequency domain signal X 2subcarrier on, its corresponding L 2individual sub-carrier indices set is labeled as K 2, and
Figure GFW00000082771600107
two set marks intersect for sky, the phase non-overlapping copies; If
Figure GFW00000082771600108
repeat to be placed at random X 2process, until
Figure GFW00000082771600109
in step S403, by K 1and K 2union produces the sub-carrier indices vector m of L dimension.Finally, in step S404, the first deserializer is exported a N-L data to two pretreatment unit, and pretreatment unit is placed into respectively X by it 1and X 2in on the subcarrier of the value of not putting, X wherein 1middle placement positive integer N/2-L 1individual data, X 2middle placement positive integer N/2-L 2individual data, meet the data subcarrier index and sub-carrier indices vector m is not overlapping; Two pretreatment units are exported respectively the X after processing 1and X 2.
Fig. 5 describes a kind of benefit base subcarrier R in benefit base subcarrier maker proposed by the invention knownan embodiment of generation method.The method correspondence a kind of preprocess method of above-mentioned transmitting terminal.As shown in Figure 5, described a kind of R knownthe generation method comprises the following steps: at first, and in step S501, for the vector of subcarrier withdrawal device (303) output
Figure GFW000000827716001010
middle index marker is k 1the sub-carrier signal element, get negative after as vectorial R knownmiddle index marker is k 1the sub-carrier signal element,
Figure GFW000000827716001011
then, in step S502, for the vector of subcarrier withdrawal device (303) output
Figure GFW000000827716001012
middle index marker is k 2the sub-carrier signal element, directly as vectorial R knownmiddle index marker is k 2the sub-carrier signal element, R known [ k 2 ] = R ~ e [ k 2 ] .
An embodiment of fixed coefficient linear filter computational methods of the present invention is described below with reference to Fig. 6.As shown in Figure 6, described computational methods comprise the following steps: at first, in step S601, calculate the coefficient matrix of above-mentioned fixed coefficient linear filter this step can first be carried out in the system current events; Then, in step S602, by strange withdrawal device (302) output, obtain subcarrier in frequency domain signal vector corresponding to odd number index marker
Figure GFW00000082771600112
then, in step S603, by above-mentioned benefit base subcarrier maker 304 outputs, obtain vectorial R known; Then, in step S604, by vector
Figure GFW00000082771600113
with vectorial R knowncombination results filter output matrix
Figure GFW00000082771600114
then, in step S605, the fixed coefficient matrix of step S601 calculated in advance is multiplied by the filter input matrix right side that step S604 produces produce the output vector of fixed coefficient linear filter
Figure GFW00000082771600116
The description of above-mentioned preferred embodiment can make any technical staff of this area can use the present invention.Clearly, these embodiment can also have various modification, and basic principle of the present invention also can be applied to other embodiment.So the present invention is not limited only to above-described embodiment, the new feature that should understand principle of the present invention and disclose from wide region.
Fig. 7 has compared the bit error rate performance that adopts apparatus and method of the present invention to obtain, with the bit error rate performance of not doing interference elimination method (document [1]) and self elimination method (document [2]).Wherein, document [1] can be published in referring to Y.Li international IEEE communication proceedings (IEEE in 1998, Transaction, on, Communication) " OFDM channel estimating (the Robust of robust under quick disperse fading channel of the article on, channel, estimation, for, OFDM, systems, with, rapid, dispersive, fading, channels) ", document [2] can be published in the article " inter-carrier interference self elimination method (Intercarrier in the OFDM GSM on international IEEE communication proceedings in calendar year 2001 referring to Y.Zhao, interference, self-cancellation, scheme, for, OFDM, mobile, communication, systems) ".Emulation is with reference to the 802.16e-2006 standard, and whole 20MHz system bandwidth is divided into n=2048individual subcarrier, wherein comprise 319zero subcarrier.The long T of OFDM symbol s=102.4 μ s.System is used the QPSK modulation.Multipath channel meets wide steady irrelevant scattering hypothesis (WSSUS).Multipath meets index and postpones the envelope distribution, and its respective channel power is
Figure GFW00000082771600117
wherein k=(L+1)/l.g(2L+2)， L＝127。The time varying characteristic in each footpath meets Jakes Doppler envelope.Emulation has comprised two kinds of normalization doppler spreads, i.e. f dt s=0.126 and f dt s=0.081, the maximum receiver speed that these two kinds of normalization doppler spreads are corresponding under the 3.8GHz carrier frequency is respectively 350km/s and 225km/s.In order to compare, we are the traditional self elimination method of not doing interference elimination method and document [2] of emulation document [1] also, and its number of sub carrier wave is all identical.Fig. 7 abscissa is bit signal to noise ratio E b/ N o, ordinate is bit error rate BER, in figure, six performance curves are from top to bottom respectively: left triangle dotted line is that document [1] is not done interference elimination method at f dt scurve under=0.126; The cross pecked line is that document [2] self elimination method is at f dt scurve under=0.126; Right triangle dotted line is that document [1] method is at f dt scurve under=0.081; The Magen David solid line is that method proposed by the invention is at f dt scurve under=0.126; Lower triangulation point dotted line is that document [2] method is at f dt scurve under=0.081; The five-pointed star solid line is that method proposed by the invention is at f dt scurve under=0.081.As seen from Figure 7, than above-mentioned two kinds of methods, method proposed by the invention all obtains better performance in two kinds of doppler spread situations, and method proposed by the invention is at f dt sthe performance of=0.126 o'clock with do not do interference elimination method at f dt sthe performance of=0.081 o'clock is close.Consider in system 319 zero subcarriers are arranged, number is much larger than the time delay expansion of channel, and method proposed by the invention does not need to choose extra zero subcarrier.Than self elimination method, it does not lose spectrum efficiency, and the translational speed of receiver can be improved to nearly 1.6 times.

Claims (2)

1. an OFDM receive-transmit system that is applicable to high-speed mobile environment, is characterized in that containing transmitter and receiver, wherein:
Transmitter contains: the first deserializer (102), and two pretreatment units (the first pretreatment unit 1031, the second pretreatment units 1032), N/2 point IFFT unit (1011,1012), the first parallel-to-serial converter (104), wherein,
The first deserializer (102), be used for the N-L of serial input data parallelization, N is the ofdm system number of sub carrier wave, N is even number, L is more than or equal to the zero integer that is less than N/2, for the sub-carrier signal number altogether increased in above-mentioned two pretreatment units processing, the output of the first deserializer is connected with above-mentioned two pretreatment unit inputs;
Two pretreatment units (1031,1032), carry out preliminary treatment for the parallel data stream that will be mapped to above-mentioned two N/2 point IFFT unit inputs, input is connected with the first deserializer output, exports respectively the subcarrier in frequency domain signal X of first subsymbol 1subcarrier in frequency domain signal X with second subsymbol 2to above-mentioned two N/2 point IFFT unit inputs; Described pretreatment unit is pressed following three step process for N-L the data from the first deserializer input:
The first pretreatment unit (1031) first produces L 1the given data symbol of individual any appointment, comprising the remainder according to symbol, L 1be less than or equal to the integer of L for being more than or equal to zero, and be placed at random subcarrier in frequency domain signal X 1subcarrier on, as X to be exported 1a part, the L that it is corresponding 1individual sub-carrier indices set is labeled as K 1, K 1the element span be to be more than or equal to 1 integer that is less than or equal to N/2; Then, the second pretreatment unit (1032) produces nonnegative integer L 2the individual known or remainder is according to symbol, L 2=L-L 1, and be placed at random subcarrier in frequency domain signal X 2subcarrier on, as X to be exported 2a part, the L that it is corresponding 2individual sub-carrier indices set is labeled as K 2, K 2the element span be to be more than or equal to 1 integer that is less than or equal to N/2, and
Figure FFW00000082771500011
be K 1and K 2not overlapping; If
Figure FFW00000082771500012
repeat to be placed at random X 2process, until
Figure FFW00000082771500013
again by K 1and K 2union K 1∪ K 2produce the sub-carrier indices vector m of L dimension;
A first deserializer output N-L data to two pretreatment unit, pretreatment unit is placed into arbitrarily respectively X by it 1and X 2in on the subcarrier of the value of not putting, X wherein 1middle placement positive integer N/2-L 1individual data, X 2middle placement positive integer N/2-L 2individual data, meet the data subcarrier index and sub-carrier indices vector m is not overlapping;
Two pretreatment units are exported respectively the X after processing 1and X 2;
Two N/2 point IFFT unit (1011,1012), for generation of two OFDM subsymbols, input respectively with two pretreatment units (1031,1032) output is connected, the IFFT unit be connected with the first pretreatment unit produces first subsymbol, and the IFFT unit be connected with the second pretreatment unit produces second subsymbol, and output is connected with the first parallel-to-serial converter input;
The first parallel-to-serial converter (104), carry out serially concatenated for first subsymbol and second subsymbol by the output of above-mentioned two N/2 point IFFT unit, form new OFDM symbol and add zero suffix, input is connected with above-mentioned two N/2 point IFFT unit outputs, the output transmitted signal;
Receiver contains: the second deserializer (204), and N point FFT unit (202), disturb and eliminate receiving system (201), two channel estimation and equalization unit (2031,2032), the second parallel-to-serial converter (205), wherein,
The second deserializer (204), for the input traffic parallelization by serial, input is the transmitter transmitted signal received, output is connected with above-mentioned N point FFT unit input;
N point FFT unit (202), be converted to frequency-region signal for inputting time-domain signal, and input is connected with the second deserializer output, and output is connected with disturbing elimination receiving system (201) input;
Disturb to eliminate receiving system (201), for eliminate between subsymbol disturb and subcarrier between disturb, input is connected with N point FFT unit (202) output, output is connected with above-mentioned two channel estimation and equalization unit inputs; Described interference is eliminated receiving system and is contained: even withdrawal device, strange withdrawal device, fixed coefficient linear filter, subcarrier withdrawal device, benefit base subcarrier maker, adder and subtracter, wherein:
Even withdrawal device, be used for extracting subcarrier in frequency domain signal corresponding to even number index marker that the N point FFT unit (202) of receiving terminal is exported
Figure FFW00000082771500021
input is connected with the parallel output terminal of above-mentioned N point FFT unit (202), and output is connected with subcarrier withdrawal device input and adder input;
Strange withdrawal device, be used for extracting subcarrier in frequency domain signal corresponding to odd number index marker that the N point FFT unit (202) of receiving terminal is exported
Figure FFW00000082771500022
input is connected with the parallel output terminal of above-mentioned N point FFT unit, and output is connected with fixed coefficient linear filter input;
The fixed coefficient linear filter, be used for producing the difference signal of the subcarrier in frequency domain signal of first subsymbol with respect to the subcarrier in frequency domain signal of second subsymbol
Figure FFW00000082771500023
the fixed coefficient linear filter has two inputs, and an input is connected with benefit base subcarrier maker output, and an input is connected with strange withdrawal device output, and output is connected to adder and subtracter input simultaneously; Described fixed coefficient linear filter produces by following three steps
Generate the coefficient matrix of above-mentioned fixed coefficient linear filter comprise, according to N rank normalization DFT matrix F (N)'s
Figure FFW00000082771500026
submatrix F oand F e, its matrix element is respectively with regeneration F e's
Figure FFW00000082771500029
submatrix S, its L is capable of F ecapable vector in choose, the corresponding above-mentioned transmitting terminal preliminary treatment sub-carrier indices vector m of corresponding line index marker, its element S (i, j)=F e (m (i), j); Matrix F oconstitute one with matrix S
Figure FFW000000827715000210
combinatorial matrix
Figure FFW000000827715000211
calculate the inverse matrix of this combinatorial matrix
Figure FFW000000827715000212
and matrix F is multiplied by the right side e, obtain above-mentioned fixed coefficient linear filter
Figure FFW000000827715000213
coefficient matrix
According to above-mentioned strange withdrawal device, obtain
Figure FFW000000827715000215
vector
Figure FFW000000827715000216
with the L that mends the generation of base subcarrier maker * 1 vectorial R known, constitute one
Figure FFW000000827715000217
the input combinatorial matrix
Figure FFW000000827715000218
By above-mentioned input combinatorial matrix above-mentioned coefficient matrix is multiplied by the right side produce the output vector of fixed coefficient linear filter
Figure FFW00000082771500033
and output
Figure FFW00000082771500034
The subcarrier withdrawal device, be used for from the output signal of even withdrawal device the sub-carrier indices set mark K described by pretreatment unit 1and K 2extraction is no less than integer L known subcarrier, and input is connected with the output of above-mentioned even withdrawal device, and output is connected with benefit base subcarrier maker input;
Mend base subcarrier maker, being no less than integer L known subcarrier of being used for obtaining from above-mentioned subcarrier withdrawal device produces benefit base subcarrier R known, to meet
Figure FFW00000082771500035
the benefit base requirement that can solve; Input is connected with the output of above-mentioned subcarrier withdrawal device, and output is connected with the input of fixed coefficient linear filter; Described benefit base subcarrier maker produces R by following two steps known:
To the sub-carrier indices set mark K described in pretreatment unit 1corresponding sub-carrier signal get negative after as R to be exported knownthe sub-carrier signal element of middle manipulative indexing mark, to the sub-carrier indices set mark K described in pretreatment unit 2corresponding sub-carrier signal directly as R to be exported knownthe sub-carrier signal element of middle manipulative indexing mark;
Output R known;
Adder, be used for the output of the output of above-mentioned fixed coefficient linear filter and even withdrawal device is carried out to additional calculation, adder has two inputs, an input is connected with the output of above-mentioned even withdrawal device, an input is connected with above-mentioned fixed coefficient linear filter, is output as the subcarrier in frequency domain signal of first subsymbol after recovery
Figure FFW00000082771500036
the output of adder is for disturbing first output of eliminating receiving system (201);
Subtracter, be used for the output of the output of above-mentioned fixed coefficient linear filter and even withdrawal device is carried out to subtraction, subtracter has two inputs, an input is connected with the output of above-mentioned even withdrawal device, an input is connected with above-mentioned fixed coefficient linear filter output, is output as the subcarrier in frequency domain signal of second subsymbol after recovery
Figure FFW00000082771500037
the output of subtracter is for disturbing second output eliminating receiving system (201);
Two channel estimation and equalization unit (2031,2032), for by least square (LS) or Minimum Mean Square Error (MMSE) algorithm, estimating channel and balanced reception signal, input is connected with disturbing elimination receiving system output, and output is connected with the second parallel-to-serial converter input;
The second parallel-to-serial converter (205), carry out serially concatenated for the parallel output by above-mentioned two channel estimation and equalization unit, and input is connected with two channel estimation and equalization unit outputs, the output sub-carrier signal.
2. the OFDM receive-transmit system that is applicable to high-speed mobile environment as claimed in claim 1, it is characterized in that, transmitter comprises M pretreatment unit and M N/M point IFFT unit, M is more than or equal to 2 positive integers that are less than or equal to N, wherein the difference signal in fixed coefficient linear filter (305) contains M-1 subsignal, respectively subcarrier in frequency domain signal poor of the subcarrier in frequency domain signal of first subsymbol and second subsymbol, the subcarrier in frequency domain signal of the subcarrier in frequency domain signal of second subsymbol and the 3rd subsymbol poor, the like until the subcarrier in frequency domain signal of the subcarrier in frequency domain signal of M-1 subsymbol and M subsymbol poor.
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