CN203492047U - A receiver used for orthogonal frequency division multiplexing OFDM channel estimation - Google Patents
A receiver used for orthogonal frequency division multiplexing OFDM channel estimation Download PDFInfo
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- CN203492047U CN203492047U CN201320575099.9U CN201320575099U CN203492047U CN 203492047 U CN203492047 U CN 203492047U CN 201320575099 U CN201320575099 U CN 201320575099U CN 203492047 U CN203492047 U CN 203492047U
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Abstract
The utility model discloses a receiver used for orthogonal frequency division multiplexing OFDM channel estimation. The receiver comprise an analog-to-digital (A/D) converter, a frame detector, a fast Fourier transform (FFT) module, a channel estimation (CHEST) module, an equalizer (EQU), and a demodulator (DEMOD). The analog-to-digital (A/D) converter is used for providing an input signal. The frame detector is used for detecting the initial positions of the frames of the input signal. The fast Fourier transform (FFT) module is used for executing fast Fourier transform of N/M points on a lead code element in order to obtain channel frequency response estimation. The channel estimation (CHEST) module is used for performing interpolation on the lead code element and outputting interpolation channel frequency response estimation. The equalizer (EQU) is used for equalizing a frame header code element and the data code element of the fast Fourier transform (FFT) module. The demodulator (DEMOD) is used for extracting received information and outputting data bit streams carrying original information. By using the above technical scheme, distortion of interpolated value amplitude caused by overlarge phase difference in a channel estimating process can be decreased.
Description
Technical field
The utility model relates to channel estimating apparatus, relates in particular to a kind of receiver for orthogonal frequency division multiplex OFDM channel estimating.
Background technology
What prior art was conventional does in the method for initial channel estimation based on preamble symbol, the estimation of phase place is not all considered to the phase place that signal starting point error causes changes (or think and can ignore), because this error can be eliminated in follow-up channel equalization in not needing to do the communication system of channel interpolation.But in need to doing the system of channel interpolation, this phase difference can make the channel estimating performance after interpolation sharply worsen, therefore can not be ignored.
Due to ignoring for this error; in prior art, conventionally can cause the performance of channel frequency response to worsen; for this problem; what those skilled in the art adopted is the structure of feedback filter; belong to closed-loop system; need to do careful adjustment to filter loop parameter, be able to make trade-offs between performance and stability.
Therefore, be badly in need of a kind of method and apparatus of channel estimating, can reduce the distortion of the interpolate value amplitude causing because phase difference is excessive.
Utility model content
The purpose of this utility model is to provide a kind of receiver for orthogonal frequency division multiplex OFDM channel estimating, can reduce the distortion of the interpolate value amplitude causing because phase difference is excessive.
The utility model discloses a kind of receiver for orthogonal frequency division multiplex OFDM channel estimating, comprising: modulus (A/D) transducer, for input signal is provided; Frame detector, for detection of the arrival of described input signal frame and the original position of described input signal frame; Fast Fourier transform (FFT) module, for according to the signal receiving, carries out to preamble symbol the fast Fourier transform that N/M is ordered, and obtains channel frequency response and estimates; Channel estimating (CHEST) module, for estimating described preamble symbol to carry out interpolation according to described channel frequency response, and exports described interpolation channel frequency response and estimates; Equalizer (EQU), for estimating to come the data symbols of balanced frame head code element and described fast Fourier transform (FFT) module according to described interpolation channel frequency response; Demodulator (DEMOD), for extracting the information receiving and exporting the data bit flow that carries raw information.
Preferably, described channel estimating (CHEST) module comprises: frame detection module (DETECTOR), the interpolation X[M that described frame detection module (DETECTOR) is estimated prior to described channel frequency response], the starting point error " Δ " of the original position of described signal frame is done to estimate.
Preferably, described channel estimating (CHEST) module also comprises phase deviation generator (Phase ramp generators), described frame detection module (DETECTOR) calculates after described starting point error " Δ ", and described phase deviation generator (Phase ramp generators) is by take the exponential function that Δ is independent variable
obtain phase shift function.
Preferably, described channel estimating (CHEST) module also comprises delay (DELAY) module, for described phase shift function is compensated by the caused delay of described starting point error " Δ ".
Preferably, described channel estimating (CHEST) module is calculated the channel frequency response X[m that N/M is ordered], described phase deviation generator (Phase ramp generators) calculates N/M phase value and is multiplied by described channel frequency response X[m according to described starting point error " Δ "] obtain product, described product is done to N point interpolation and obtain the first channel frequency response.
Preferably, described phase deviation generator (Phase ramp generators) to a described N/M phase value get conjugation and in be inserted to N value and obtain N phase value
and a described N phase value is multiplied by the first channel frequency response, to obtain final channel frequency response estimated value.
Adopt after technique scheme, preamble symbol based on channel strip information is only provided is carried out the method for estimation of interpolation processing, utilize the channel sampling subset that preamble symbol provides to recover the channel frequency response that OFDM code element is complete, make interpolation be poised for battle starting point and detect no longer sensitivity of error, improve stability and the accuracy of the channel estimation value based on preamble symbol, reduced the probability of the distortion of interpolate value amplitude in interpolation process.
Simultaneously, the setting of above method median filter belongs to open loop structure, because the implementation complexity of construction of switch is less than closed-loop structure, existence and stability problem not, existing technical staff is without the performance that reduces the receiver of this household network communication system in order to improve stability.
Accompanying drawing explanation
Fig. 1 is for being used the schematic diagram of the frame structure of OFDM (OFDM) communication system;
Fig. 2 is linear interpolation schematic diagram;
Fig. 3 is the system block diagram of OFDM receiver;
Fig. 4 is the different conditions conversion schematic diagram of OFDM receiver;
Fig. 5 is the channel response interpolating circuit circuit diagram of OFDM receiver;
Embodiment
Below in conjunction with accompanying drawing and specific embodiment, further set forth advantage of the present utility model.
Consult Fig. 1, Fig. 1 is for being used the schematic diagram of the frame structure of OFDM (OFDM) communication system.The frame structure of orthogonal frequency-division multiplex singal comprises one or more preamble symbol, the data symbols signal of one or more OFDM frames first code units and one or more OFDMs.OFDM receiver detects and estimated frame original position by the preamble symbol of frame structure, and the training sequence of channel estimating is provided to OFDM inner receiver.Preamble symbol is used a predefined signal to OFDM receiver, and this predefine signal can be simplified the estimation of channel frequency response.OFDM frame head code element comprises supplementary signal, and how this supplementary signal encodes to the described data symbols in frame structure if having defined.The data symbols of described ofdm signal has comprised the data of transmitting.
Consulting Fig. 2, is two plural X[M
0] and X[M
0+ 1] linear interpolation schematic diagram, shows amplitude distortion and how to form.Two complex vector X[M
0] and X[M
0+ 1] M between is distributed in the interpolation point on this point-to-point transmission string.This M the interpolation point being distributed on string will affect the accuracy of the amplitude of these linear interpolation points.Accuracy degree of susceptibility depends on the corresponding central angle of arc that 2 linear interpolation points form, the i.e. phase difference of this 2 linear interpolation point.So the angle that increases progressively of the frame starting point of estimation is φ [m
0+1]-φ [m
0]=2 π M Δ/N.Correct way is to produce M point on the circular arc between these two complex vectors, and the amplitude of these points will be more accurate.
Consulting Fig. 3, is the system block diagram of OFDM receiver.The system block diagram of this OFDM receiver comprises modulus (A/D) transducer, frame detector, fast Fourier transform (FFT) module, equalizer (EQU), channel estimating (CHEST) module and demodulator (DEMOD).Modulus (A/D) transducer provides input signal to OFDM receiver.The arrival of frame detector detection signal frame and its original position.From original position, frame detector is fft block by signal segmentation, and the signal of cutting apart is sent to FFT module.FFT module receives after the signal of cutting apart, and preamble symbol is carried out to the fast Fourier transform that N/M is ordered, and obtaining sub-carrier frequencies index is m=0, and 1,2 ..., the estimation of the channel impulse response of N/M.The fast Fourier transform that why adopts N/M to order is because only used N/M equally spaced subcarrier in the definition of preamble symbol.This M frequency corresponding with frame head code element and OFDM data code element in the middle of frequency indices N=0, M-1,2M-1 ..., N-M+1.Therefore, the relation of these two sub-carrier set is channel frequency response functions that a sample rate is M.The fast Fourier transform of preamble symbol is the channel frequency response function that channel estimating (CHEST) module provides a M point.
Channel estimating (CHEST) module is carried out after interpolation preamble symbol, and the interpolation channel frequency response that can obtain a N point is estimated.Equalizer estimates to come the data symbols of balanced frame head code element and FFT module with the interpolation channel frequency response of this N point.Equalizer provides piece after equilibrium to demodulator.Demodulator extracts the information receiving and exports the data bit flow that carries raw information.
Consulting Fig. 4, is the different conditions conversion schematic diagram of OFDM receiver.As shown in the figure, the different conditions of OFDM receiver can be state A, state B, state C, has described respectively under each state the different operating state of OFDM receiver.Described state A, for OFDM receiver is intercepted arrival and its original position of the signal that receives detection signal frame.Described state B, for signal frame is detected and after its original position determines, adopts preamble symbol to carry out Initial Channel Assignment estimated value.Described state C, for the frame consisting of frame head code element and OFDM data symbols signal is carried out to equilibrium and demodulation, and output information bit stream.
Under state A, the frame detector of OFDM receiver intercept digital-to-analogue (A/D) transducer input signal until a complete frame be listened.Once frame is detected, after the starting point of this frame is estimated by frame detector, OFDM receiver will jump to state B.Under state B, the fast Fourier transform that OFDM receiver is ordered with N/M in preamble symbol obtains the estimated value of channel frequency response.While transmitting due to preamble symbol, only use M subcarrier of N available subcarrier, channel estimating (CHEST) module is carried out interpolation according to channel frequency response, and this interpolation channel frequency response is sent to equalizer.Now, OFDM receiver frame head code element and the data symbols that C comes demodulation to receive that get the hang of.Under state C, all signals after preamble symbol of ofdm signal are split into OFDM piece, and Cyclic Prefix is removed and carries out fast Fourier transform to being divided into the data block that N orders.Resulting frequency-region signal will be by equilibrium and demodulation.After demodulation, the data that obtain are a string data bit flows that carry raw information.
Consulting Fig. 5, is the channel response interpolating circuit circuit diagram of OFDM receiver.The channel estimating of OFDM receiver (CHEST) module is state of activation when state B, and carries out the estimation of channel frequency response.Frame detection module (DETECTOR) in channel estimating (CHEST) module is prior to the interpolation X[M of channel frequency response], starting point error " Δ " is done to estimate.In estimation procedure, in order to determine starting point error, frame detection module calculates X[M] phase place and by it divided by M.Once obtain after starting point error " Δ ", phase deviation generator (Phase ramp generators) is by take the exponential function that Δ is independent variable
obtain phase shift function, channel estimating (CHEST) module is calculated the channel frequency response X[m that N/M is ordered], phase deviation generator (Phase ramp generators) calculates N/M phase value and is multiplied by channel frequency response X[m according to starting point error " Δ "] obtain product, product is done to N point interpolation and obtain the first channel frequency response.Phase deviation generator has been eliminated phase difference before channel frequency response is interpolated, and on channel frequency response, reinserts interpolation phase deviation.Postponement module " DELAY " is used for compensation by the caused delay of error " Δ ".
The consequential signal of channel estimating (CHEST) module, by being carried out the interpolation that multiplying power is M, obtains all n=0, and 1 ..., the first interpolation channel frequency response of N-1 is estimated (not comprising phase place).Channel estimating (CHEST) module is carried out interpolation with polynomial interpolation algorithm, phase deviation generator (Phase ramp generators) to N/M phase value get conjugation and in be inserted to N value and obtain N phase value
and N phase value is multiplied by the first channel frequency response, to obtain final channel frequency response estimated value.
Adopt after technique scheme, preamble symbol based on channel strip information is only provided is carried out the method for estimation of interpolation processing, utilize the channel sampling subset that preamble symbol provides to recover the channel frequency response that OFDM code element is complete, make interpolation be poised for battle starting point and detect no longer sensitivity of error, improve stability and the accuracy of the channel estimation value based on preamble symbol, reduced the probability of the distortion of interpolate value amplitude in interpolation process.
Simultaneously, the setting of above method median filter belongs to open loop structure, because the implementation complexity of construction of switch is less than closed-loop structure, existence and stability problem not, existing technical staff is without the performance that reduces the receiver of this household network communication system in order to improve stability.
Should be noted that, embodiment of the present utility model has preferably implementation, and not the utility model is done to any type of restriction, any person skilled in art of being familiar with may utilize the technology contents change of above-mentioned announcement or be modified to the effective embodiment being equal to, in every case do not depart from the content of technical solutions of the utility model, any modification or equivalent variations and the modification above embodiment done according to technical spirit of the present utility model, all still belong in the scope of technical solutions of the utility model.
Claims (6)
1. for a receiver for orthogonal frequency division multiplex OFDM channel estimating, it is characterized in that:
Comprise:
Modulus (A/D) transducer, for converted input signal;
Frame detector, for detection of the arrival of described input signal frame and the original position of described input signal frame; Fast Fourier transform (FFT) module, for according to the signal receiving, carries out to preamble symbol the fast Fourier transform that N/M is ordered, and obtains channel frequency response and estimates;
Channel estimating (CHEST) module, for estimating described preamble symbol to carry out interpolation according to described channel frequency response, and exports described interpolation channel frequency response and estimates;
Equalizer (EQU), for estimating to come the data symbols of balanced frame head code element and described fast Fourier transform (FFT) module according to described interpolation channel frequency response;
Demodulator (DEMOD), for extracting the information receiving and exporting the data bit flow that carries raw information.
2. receiver as claimed in claim 1, is characterized in that:
Described channel estimating (CHEST) module comprises: frame detection module (DETECTOR), described frame detection module (DETECTOR) is estimated X[M prior to described channel frequency response], the starting point error " Δ " of the original position of described signal frame is done to estimate.
3. receiver as claimed in claim 2, is characterized in that:
Described channel estimating (CHEST) module also comprises phase deviation generator (Phase ramp generators), described frame detection module (DETECTOR) calculates after described starting point error " Δ ", and described phase deviation generator (Phase ramp generators) is by take the exponential function that Δ is independent variable
obtain phase shift function.
4. receiver as claimed in claim 3, is characterized in that:
Described channel estimating (CHEST) module also comprises delay (DELAY) module, for described phase shift function is compensated by the caused delay of described starting point error " Δ ".
5. receiver as claimed in claim 4, is characterized in that:
Described channel estimating (CHEST) module is calculated the channel frequency response X[m that N/M is ordered], described phase deviation generator (Phase ramp generators) calculates N/M phase value and is multiplied by described channel frequency response X[m according to described initial point error " Δ "] obtain product, described product is done to N point interpolation and obtain the first channel frequency response.
6. receiver as claimed in claim 5, is characterized in that:
Described phase deviation generator (Phase ramp generators) to a described N/M phase value get conjugation and in be inserted to N value and obtain N phase value
and a described N phase value is multiplied by the first channel frequency response, to obtain final channel frequency response estimated value.
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| US201361763394P | 2013-02-11 | 2013-02-11 | |
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| CN201310423194.1A Active CN103986678B (en) | 2013-02-11 | 2013-09-16 | A kind of receiver and its method of estimation for orthogonal frequency division multiplex OFDM channel estimation |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103986678A (en) * | 2013-02-11 | 2014-08-13 | 芯迪半导体科技（上海）有限公司 | A receiver used for orthogonal frequency division multiplexing OFDM channel estimation and estimation method thereof |
| CN106302299A (en) * | 2015-05-20 | 2017-01-04 | 中兴通讯股份有限公司 | A kind of multiple-user access method and device |
| CN110192379A (en) * | 2017-01-19 | 2019-08-30 | 高通股份有限公司 | The low peak average power of channeling for multiple streams compares Waveform Design |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR100865469B1 (en) * | 2005-03-08 | 2008-10-27 | 삼성전자주식회사 | Apparatus and method for channel estimation in sdma-ofdm systems |
| WO2010055981A1 (en) * | 2008-11-16 | 2010-05-20 | Lg Electronics Inc. | Apparatus for transmitting and receiving a signal and method of transmitting and receiving a signal |
| CN101662434B (en) * | 2009-09-27 | 2012-05-02 | 上海大学 | WiMAX channel estimation method designed by utilizing pilot frequency format |
| CN101764643A (en) * | 2009-12-31 | 2010-06-30 | 北京交通大学 | Channel equalization method and system based on physical layer Mesh to combining precursor and pilot frequency |
| CN203492047U (en) * | 2013-02-11 | 2014-03-19 | 芯迪半导体科技（上海）有限公司 | A receiver used for orthogonal frequency division multiplexing OFDM channel estimation |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103986678A (en) * | 2013-02-11 | 2014-08-13 | 芯迪半导体科技（上海）有限公司 | A receiver used for orthogonal frequency division multiplexing OFDM channel estimation and estimation method thereof |
| CN103986678B (en) * | 2013-02-11 | 2017-12-26 | 芯迪半导体科技（上海）有限公司 | A kind of receiver and its method of estimation for orthogonal frequency division multiplex OFDM channel estimation |
| CN106302299A (en) * | 2015-05-20 | 2017-01-04 | 中兴通讯股份有限公司 | A kind of multiple-user access method and device |
| CN106302299B (en) * | 2015-05-20 | 2020-06-05 | 中兴通讯股份有限公司 | Multi-user access method and device |
| CN110192379A (en) * | 2017-01-19 | 2019-08-30 | 高通股份有限公司 | The low peak average power of channeling for multiple streams compares Waveform Design |
| CN110192379B (en) * | 2017-01-19 | 2022-04-19 | 高通股份有限公司 | Low peak-to-average power ratio waveform design for frequency multiplexing of multiple streams |
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| CN103986678B (en) | 2017-12-26 |
| CN103986678A (en) | 2014-08-13 |
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Granted publication date: 20140319 |