CN101997799A - Orthogonal frequency division multiplexing (OFDM) channel estimation method based on filter bank - Google Patents
Orthogonal frequency division multiplexing (OFDM) channel estimation method based on filter bank Download PDFInfo
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- CN101997799A CN101997799A CN2009100567463A CN200910056746A CN101997799A CN 101997799 A CN101997799 A CN 101997799A CN 2009100567463 A CN2009100567463 A CN 2009100567463A CN 200910056746 A CN200910056746 A CN 200910056746A CN 101997799 A CN101997799 A CN 101997799A
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Abstract
The invention discloses an orthogonal frequency division multiplexing (OFDM) channel estimation method based on a filter bank, which comprises the following steps: generating the complex exponential pilot data having the same center frequency with the OFDM sampling sub-carrier, multiplexing with the information source data, filtering the pilot data corresponding to the pilot on the receiving terminal by a multiphase filter bank which is realized by the N point FFT, then performing the least squares estimation to the output data of each corresponding channel to obtain the initial channel frequency domain estimation data, and obtaining the initial channel frequency domain data of all the sub-carriers through the processing of linear interpolation, then performing the IFFT process, performing the zero fill and the FFT process to the L point major tap coefficients in the time domain, and finally obtaining the channel parameters corresponding to all the positions of the sub-carriers through the interpolation in the frequency domain. The method of the invention solves the defects of poor channel estimation under the condition of low signal to noise ratio in the existing schemes, and have the advantages of stable performance, low cost, low error code floor and the like.
Description
Technical field
The present invention relates to the signal of communication processing method in the radio communication, a kind of OFDM based on bank of filters (Orthogonal Frequency Division Multiplexing, OFDM) particularly is provided channel estimation methods.
Background technology
Now, third generation digital mobile communication (3G, The 3rd Generation) development is rapid, and the TD-SCDMA that China proposes also is one of global 3G standard, and the 3G portable terminal is about to extensive use, and the business service market of 3G portable terminal is also with flourish.Along with the continuous evolution of the third generation, back three generations and future mobile communication system, wireless communication system will provide more and more higher data rate and communication quality guarantee more reliably.Simultaneously, the residing environment of user terminal be along with the progress of modern science and technology also will become increasingly complex, high-speed mobile and various multipath reflection conditional decisions wireless communication system must be able to adapt to these abominable transmission environments.Ofdm system can become broadband multipath frequency-selective channel the parallel narrow band frequency flatness fading channel of one group of convolution, have and effectively to eliminate the characteristics that multipath disturbs, adaptive data rate is easy to adjust, balancing procedure is simple and spectrum efficiency is high, become one of core transmission technology in the physical layer in the future mobile communication system.But utilize effective coherent demodulation technology to obtain higher snr gain, just must carry out the estimation and the tracking of channel parameter at receiving terminal, particularly the time become and the low signal-to-noise ratio condition under the high-precision channel parameter estimation of realization, the low signal-to-noise ratio conditional decision precision of channel parameter estimation be difficult to reach actual instructions for use, simultaneously, complicated algorithm for estimating will use channel statistic property, and actual environment has determined in use can't obtain channel statistical characteristic accurately.
Summary of the invention
The present invention is directed to the deficiencies in the prior art, a kind of stable performance, the OFDM channel estimation methods based on bank of filters that cost is low are proposed, be used for from the pilot frequency sequence of reception antenna signal, estimating precise channels parameter information under the time varying channel condition, particularly have under the very low signal to noise ratio condition at receiving terminal, do not utilize any statistical property of channel, can realize high-precision channel parameter estimation and tracking.
The present invention adopts following technical scheme, comprises the following steps:
(1) the information source data are carried out chnnel coding, modulation, string and conversion become
The valid data D to be transmitted of individual sub-carrier formats, wherein B is the subcarrier in frequency domain sampling interval of OFDM, the value of B is four times of time delay largest extension value,
Expression N rounds downwards divided by the result after the B;
(2) produce and channel frequency domain sampling position corresponding subcarrier pilot data P=exp (j2 π kBn/N),
The length of pilot data equals 1/4th of OFDM transmission system frame length, and it is multiplexing that pilot data and data to be transmitted structure are carried out data pilot according to the Comb Pilot form, forms OFDM transferring data frames X;
(3) OFDM transferring data frames X being carried out N point FFT handles, handle the back by launching through analog radio frequency after adding Cyclic Prefix, the length that adds Cyclic Prefix is the L point, counting of L is the maximum of channel delay expansion, the OFDM receiving terminal carries out simulation process and digitlization with the signal that receives, remove Cyclic Prefix simultaneously and do N point FFT processing, obtain received signal Frame Y;
(4) with received signal Frame Y according to carrying out demultiplexing, with the locational reception pilot data of corresponding OFDM frequency domain sampling with the multiplexing identical method of transmitting terminal
D ' separates with secured transmission of payload data, wherein
Be the channel coefficients on the corresponding pilot tone sample point;
(5) the reception pilot data P ' that demultiplexing is obtained sends into the channel estimation process device, carry out least-squares estimation through the data that respectively each sampling subcarrier obtained after the multiphase filter group Filtering Processing, and will estimate that the channel value that obtains carries out linear interpolation and obtains channel estimating initial coefficients on all sub-carrier positions
(6) with the channel estimating initial coefficients that obtains
Carry out N point IFFT and handle, obtain corresponding time domain tap coefficient
And will
According to the processing of sorting of tap watt level, and keep L maximum tap, wherein L is counting of OFDM Cyclic Prefix, and remaining tap coefficient is all carried out the zero setting processing;
(7) will carry out N point FFT frequency domain interpolation through L the non-zero channel tap that obtains after the zero setting processing and handle, obtain N OFDM time varying channel frequency domain sampling value of final moment corresponding
The channel frequency domain sampling value of utilizing estimation to obtain
Finish the data balancing on each subchannel of OFDM, the secured transmission of payload data D ' that is about to receive is divided by the channel frequency domain sampling value on the correspondence position
(8) will carry out and go here and there conversion through the valid data after the equilibrium treatment, and separate and be in harmonious proportion channel decoding and handle, finally be recovered the information source data.
The present invention has following conspicuous outstanding substantial characteristics and remarkable advantage compared with prior art:
Described inventive method utilizes the polyphase filter technology filtering noise to improve the OFDM time varying channel parameter Estimation precision under the low signal-to-noise ratio condition.And use the FFT technology to estimate channel frequency coefficient value on each subcarrier sample position therefore to adopt method and apparatus of the present invention to realize that OFDM time varying channel estimating system has the advantages that computation complexity is low, the error code floor is low.
Description of drawings
The inventive method is provided by the following drawings and exemplifying embodiment.
Fig. 1 transmits and receives system works flow process schematic diagram for the OFDM that uses the inventive method;
Fig. 2 is a filter bank structure schematic diagram of the present invention;
Embodiment
The present invention is further described below in conjunction with accompanying drawing and preferred embodiment.The specific implementation step of the inventive method is as follows:
(1) the information source data are carried out chnnel coding, modulation, string and conversion become
The valid data D to be transmitted of individual sub-carrier formats, wherein B is the subcarrier in frequency domain sampling interval of OFDM, the value of B is four times of time delay largest extension value,
Expression N rounds downwards divided by the result after the B;
(2) produce and channel frequency domain sampling position corresponding subcarrier pilot data P=exp (j2 π kBn/N),
The length of pilot data equals 1/4th of OFDM transmission system frame length, and it is multiplexing that pilot data and data to be transmitted structure are carried out data pilot according to the Comb Pilot form, forms OFDM transferring data frames X;
(3) OFDM transferring data frames X being carried out N point FFT handles, handle the back by launching through analog radio frequency after adding Cyclic Prefix, the length that adds Cyclic Prefix is the L point, counting of L is the maximum of channel delay expansion, the OFDM receiving terminal carries out simulation process and digitlization with the signal that receives, remove Cyclic Prefix simultaneously and do N point FFT processing, obtain received signal Frame Y;
(4) with received signal Frame Y according to carrying out demultiplexing, with the locational reception pilot data of corresponding OFDM frequency domain sampling with the multiplexing identical method of transmitting terminal
D ' separates with secured transmission of payload data, wherein
Be the channel coefficients on the corresponding pilot tone sample point;
(5) the reception pilot data P ' that demultiplexing is obtained sends into the channel estimation process device, carry out least-squares estimation through the data that respectively each sampling subcarrier obtained after the multiphase filter group Filtering Processing, and will estimate that the channel value that obtains carries out linear interpolation and obtains channel estimating initial coefficients on all sub-carrier positions
(6) with the channel estimating initial coefficients that obtains
Carry out N point IFFT and handle, obtain corresponding time domain tap coefficient
And will
According to the processing of sorting of tap watt level, and keep L maximum tap, wherein L is counting of OFDM Cyclic Prefix, and remaining tap coefficient is all carried out the zero setting processing;
(7) will carry out N point FFT frequency domain interpolation through L the non-zero channel tap that obtains after the zero setting processing and handle, obtain N OFDM time varying channel frequency domain sampling value of final moment corresponding
The channel frequency domain sampling value of utilizing estimation to obtain
Finish the data balancing on each subchannel of OFDM, the secured transmission of payload data D ' that is about to receive is divided by the channel frequency domain sampling value on the correspondence position
(8) will carry out and go here and there conversion through the valid data after the equilibrium treatment, and separate and be in harmonious proportion channel decoding and handle, finally be recovered the information source data.
Referring to Fig. 1, transmitting terminal carries out chnnel coding with the information source data, modulation, string and conversion, data to be transmitted that obtains and pilot data carry out the data multiplex processing according to the comb form, then data are sent into the IFFT unit, add Cyclic Prefix again, launch after handling through analog radio frequency.Receiving terminal carries out the analog signal that receives simulation process and finishes digitlization, sew with FFT through past circulation embedding more afterwards and handle, the data that obtain carry out obtaining pilot data and valid data respectively behind the data pilot demultiplexing, the pilot data that obtains is sent into channel estimating apparatus of the present invention, obtain corresponding time varying channel estimated parameter, and utilize the channel estimating parameter that the valid data that receive are carried out channel equalization, and then respectively through and string conversion, separate and be in harmonious proportion channel decoding and handle the information source data that are restored at last.
As shown in Figure 2, the FFT computing that the inventive method has utilized N to order realizes bank of filters, bank of filters is achieved like this: at first design a normalization cut-off frequecy of passband and stopband cut-off frequency respectively at the wave digital lowpass filter prototype h (n) of 1/N and 2/N, n=0, M-1, the N phase component that i filter among the present invention just in time is this low pass filter prototype, i.e. h
i(n)=and h (Nk+n), k=0 ..., M/N, n=0 ..., N-1 handles through N times of zero insertion again.Then, the data of output are carried out the least-squares estimation processing in each bank of filters passage, obtain the channel coefficients on each corresponding pilot sub-carrier frequency, the process linear interpolation obtains the initial channel frequency coefficient on other valid data subcarrier correspondence positions again.To obtain N initial channel frequency coefficient then and handle the time domain tap coefficient that obtains correspondence through N point IFFT, because on most of tap coefficient all is noise, the present invention carries out important tap to this N corresponding time domain tap coefficient and obtains and follow the tracks of processing, N tap coefficient of time domain sorted according to watt level, keep a prominent L tap coefficient, and other N-L coefficient all carried out the zero setting denoising Processing.Carry out the processing of N point FFT frequency domain interpolation after again L the important tap coefficient that remains being mended N-L individual zero at last, obtain frequency domain channel coefficient corresponding on final whole subcarriers
In sum, the invention provides a kind of OFDM channel estimation methods based on bank of filters, by producing the identical complex exponential pilot data of OFDM sampling subcarrier center frequency point, and carry out multiplexing with the transmitting terminal data to be transmitted according to the pectination form, pilot data on the corresponding pilot frequency locations that receiving terminal will obtain is sent into a multiphase filter group of utilizing N point FFT to realize, respectively each respective channel output data are carried out least-squares estimation then, obtain processing through linear interpolation again behind the initial channel frequency domain data estimator on the corresponding pilot sub-carrier, obtain the initial channel frequency domain data on all subcarriers, carry out again IFFT and process, and carry out the important tap of L point in time domain and obtain and follow the tracks of. At last the important tap coefficient of L point is carried out zero padding and FFT and process, obtain channel parameter corresponding on all sub-carrier positions at Frequency domain interpolation. The present invention utilizes the bank of filters filtering noise to improve the OFDM time varying channel Parameter Estimation Precision under the Low SNR, the advantage such as have stable performance, cost is low and the error code floor is low.
Claims (3)
1. OFDM channel estimation methods based on bank of filters, described method are used for estimating from ofdm signal the channel parameter of corresponding time-frequency position, it is characterized in that utilizing the multiphase filter group to obtain the filter factor of each passage; Comprise the following steps:
(1) the information source data are carried out chnnel coding, modulation, string and conversion become
The valid data D to be transmitted of individual sub-carrier formats, wherein B is the subcarrier in frequency domain sampling interval of OFDM,
Expression N rounds downwards divided by the result after the B;
(2) produce and channel frequency domain sampling position corresponding subcarrier pilot data P=exp (j2 π kBn/N),
It is multiplexing that pilot data and data to be transmitted structure are carried out data pilot according to the Comb Pilot form, forms OFDM transferring data frames X;
(3) OFDM transferring data frames X being carried out N point FFT handles, handle the back by launching through analog radio frequency after adding Cyclic Prefix, the length that adds Cyclic Prefix is the L point, the OFDM receiving terminal carries out simulation process and digitlization with the signal that receives, remove Cyclic Prefix simultaneously and do N point FFT processing, obtain received signal Frame Y;
(4) with received signal Frame Y according to carrying out demultiplexing, with the locational reception pilot data of corresponding OFDM frequency domain sampling with the multiplexing identical method of transmitting terminal
D ' separates with secured transmission of payload data, wherein
Be the channel coefficients on the corresponding pilot tone sample point;
(5) the reception pilot data P ' that demultiplexing is obtained sends into the channel estimation process device, carry out least-squares estimation through the data that respectively each sampling subcarrier obtained after the multiphase filter group Filtering Processing, and will estimate that the channel value that obtains carries out linear interpolation and obtains channel estimating initial coefficients on all sub-carrier positions
(6) with the channel estimating initial coefficients that obtains
Carry out N point IFFT and handle, obtain corresponding time domain tap coefficient
And will
According to the processing of sorting of tap watt level, and keep L maximum tap, wherein L is counting of OFDM Cyclic Prefix, and remaining tap coefficient is all carried out the zero setting processing;
(7) will carry out N point FFT frequency domain interpolation through L the non-zero channel tap that obtains after the zero setting processing and handle, obtain N OFDM time varying channel frequency domain sampling value of final moment corresponding
The channel frequency domain sampling value of utilizing estimation to obtain
Finish the data balancing on each subchannel of OFDM, the secured transmission of payload data D ' that is about to receive is divided by the channel frequency domain sampling value on the correspondence position
(8) will carry out and go here and there conversion through the valid data after the equilibrium treatment, and separate and be in harmonious proportion channel decoding and handle, finally be recovered the information source data.
2. the OFDM channel estimation methods based on bank of filters as claimed in claim 1 is characterized in that: the value of B is decided by the time delay largest extension value of transmission wireless channel in the step (1), is four times of time delay largest extension value.
3. the OFDM channel estimation methods based on bank of filters as claimed in claim 1 is characterized in that: the length that produces pilot data in the step (2) equals 1/4th of OFDM transmission system frame length.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012109928A1 (en) * | 2011-02-15 | 2012-08-23 | 中兴通讯股份有限公司 | Method, device, and system for processing signal |
| CN103326972A (en) * | 2013-07-01 | 2013-09-25 | 重庆邮电大学 | Filter bank multicarrier modulation system and design method thereof |
| CN103346983A (en) * | 2013-06-13 | 2013-10-09 | 电子科技大学 | OFDM self-adaption complex interpolation channel estimation method based on comb-type pilot frequency |
| CN104038271A (en) * | 2014-05-16 | 2014-09-10 | 中国人民解放军空军工程大学 | OFDM technology-based airborne two-antenna simultaneous communication method |
| CN109302367A (en) * | 2018-10-09 | 2019-02-01 | 重庆会凌电子新技术有限公司 | Multi channel signals analog demodulator system and method |
| CN114629750A (en) * | 2020-12-10 | 2022-06-14 | 宸芯科技有限公司 | Channel estimation enhancement method, device, equipment and medium |
| CN115801504A (en) * | 2023-01-17 | 2023-03-14 | 南京创芯慧联技术有限公司 | Time domain tap storage method and device, computer equipment and storage medium |
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2009
- 2009-08-20 CN CN2009100567463A patent/CN101997799A/en active Pending
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012109928A1 (en) * | 2011-02-15 | 2012-08-23 | 中兴通讯股份有限公司 | Method, device, and system for processing signal |
| CN103346983A (en) * | 2013-06-13 | 2013-10-09 | 电子科技大学 | OFDM self-adaption complex interpolation channel estimation method based on comb-type pilot frequency |
| CN103346983B (en) * | 2013-06-13 | 2015-12-23 | 电子科技大学 | The multiple Channel Estimation Interpolation Methods of a kind of OFDM self adaptation based on Comb Pilot |
| CN103326972A (en) * | 2013-07-01 | 2013-09-25 | 重庆邮电大学 | Filter bank multicarrier modulation system and design method thereof |
| CN104038271A (en) * | 2014-05-16 | 2014-09-10 | 中国人民解放军空军工程大学 | OFDM technology-based airborne two-antenna simultaneous communication method |
| CN104038271B (en) * | 2014-05-16 | 2018-02-09 | 中国人民解放军空军工程大学 | Airborne two slave antenna based on OFDM technology while communication means |
| CN109302367A (en) * | 2018-10-09 | 2019-02-01 | 重庆会凌电子新技术有限公司 | Multi channel signals analog demodulator system and method |
| CN109302367B (en) * | 2018-10-09 | 2021-09-17 | 重庆会凌电子新技术有限公司 | Multichannel signal analog demodulation system and method thereof |
| CN114629750A (en) * | 2020-12-10 | 2022-06-14 | 宸芯科技有限公司 | Channel estimation enhancement method, device, equipment and medium |
| CN115801504A (en) * | 2023-01-17 | 2023-03-14 | 南京创芯慧联技术有限公司 | Time domain tap storage method and device, computer equipment and storage medium |
| CN115801504B (en) * | 2023-01-17 | 2023-06-13 | 南京创芯慧联技术有限公司 | Time domain tap storage method, device, computer equipment and storage medium |
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Application publication date: 20110330 |