CN101552763A - OFDM channel estimation technique - Google Patents
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Abstract
Orthogonal frequency division multiplexing OFDM receiver comprises a channel estimator for receiving one signal containing a plurality of symbols and each symbol comprises a plurality of pilot frequencies and a plurality of data sub carrier waves, wherein each symbol also comprises at least one pilot frequency sub carrier wave and the estimator uses the first channel response estimation of at least one pilot frequency sub carrier wave in the first symbol to select the first weight matrix in the weighting matrixes generated in advance and uses the channel estimation information of the data sub carrier wave in the first symbol generated by the selected first weighting matrix.
Description
Technical field
[0001] the present invention relates generally to OFDM (OFDM) system, particularly produce the OFDM receiver of channel estimating information.
Background of invention
[0002] OFDM (OFDM) system uses multichannel, can carry out the transmission of multichannel subcarrier simultaneously.The ofdm signal of an example comprises data subcarrier and pilot sub-carrier (pilot subcarrier) as shown in Figure 1.Fig. 1 has shown a frequency axis and a time shaft, and the subcarrier (pilot tone and data subcarrier) with identical time mark forms a symbol together.
[0003] when ofdm signal is transmitted and received by receiver subsequently, the signal that receives is different from the signal of transmission a bit, shown in equation 1, wherein (t k) is the sub-carrier that receives to y, x (t, k) be the sub-carrier of transmission, (t k) is the channel frequency response of this sub-carrier to H, (t k) is noise to n.Channel frequency response is provided by equation 2.Therefore, do not consider noise problem,, just can know the signal of transmission if know channel frequency response.The common calculating channel frequency response of OFDM receiver (being also referred to as " channel estimating ") is so that obtained the subcarrier of transmission before carrying out demodulation.
[0004] ofdm signal has the subcarrier of known attribute usually, so that assist the calculating channel frequency response.An example is training symbol (training symbol), such as the burst transfer that is used in the IEEE 802.11a/g.Another kind method is to use pilot sub-carrier to be distributed in the signal, as in WiMax, digital video broadcasting (DVB) etc.For example, Fig. 1 comprises pilot sub-carrier.Pilot tone is also referred to as known sound case, because to a given pilot tone, (t is known k) to x, and (t k) can be used to calculate the channel frequency response of given pilot tone, as equation 3 to known x.
[0005] DVB uses two kinds of pilot tones.At first, the pilot tone of dispersion is arranged, wherein per 12 sounds use a pilot tone in frequency domain.To each contiguous OFDM symbol, pilot frequency locations three subcarriers that periodically are shifted.The pilot tone of other type is a continuous pilot, wherein some sound of each OFDM symbol (be labeled as 0,48,54,87 ..., 1704 ... 6816) be known.
[0006] in DVB, scattered pilot is used for the channel frequency response of signal calculated mileage according to subcarrier.Use equation 3,, estimate channel frequency response in the scattered pilot position by least square method (LS).Estimate from the pilot tone LS of these acquisitions, further the channel frequency response of data estimator subcarrier.At present, the channel frequency response of many technology with cause pilot tone data estimator subcarrier arranged.
[0007] a kind of technology of the channel frequency response by pilot sub-carrier data estimator subcarrier is piecewise linear interpolation method and higher order polynomial match.This technology has been ignored noise effect, and does not need channel statistical information.Thereby provide low complexity and performance to moderate.
[0008] another kind of technology is transform domain method (transform domain method).The transform domain method needs channel statistical information (signal to noise ratio, time-frequency domain correlation), and uses fast Fourier transform (FFT) and contrary FFT/IFFT to calculate.During having, the transform domain method arrives the complexity and the performance of height.
[0009] also having another kind of technology is Minimum Mean Square Error (MMSE) method, and it uses channel statistical information usually, and has moderate complexity and higher performance.Traditional MMSE method is one dimension (1-D), time domain or frequency domain.1-D MMSE method is only seen the pilot tone with estimative data subcarrier same frequency or time mark.Some MMSE methods are not only used the 1-D time domain to estimate but also are used the 1-D frequency domain to estimate (being also referred to as sequence 1-D method), but be not genuine two dimension (2-D) method because and the pilot tone of estimative data subcarrier different frequency and time mark can not be used for estimating.But, in prior art, described real 2-D MMSE in a way and estimated.At present, the MMSE method that has can not obtain a suitable balance by carrying out unnecessary double counting and/or using and estimate than required more pilot between efficient and accuracy.
Summary of the invention
[0010] each embodiment of the present invention relates to provides system, method and the computer programmed product that effect technique is estimated channel frequency response in OFDM uses.In an object lesson, signal is divided into a plurality of windows (as the length of each window on time domain is 5 subcarriers, and length is 25 subcarriers on frequency domain).In addition, two or more weighting matrixs are calculated in advance, and the corresponding channel condition feature of each weighting matrix (as corresponding bigger channel delay spread of first weighting matrix and slower rate of fading, and corresponding less channel delay spread of second weighting matrix and rate of fading faster).
[0011] continues this example, in a window, the continuous pilot subcarrier in a part of window is carried out the MMSE channel frequency response estimate, wherein estimate to be to use each precalculated weighting matrix to carry out.The channel frequency response of continuous pilot subcarrier is known (normally by using a kind of LS algorithm).Each MMSE is estimated, use known response to calculate a variance (SE), the line item of going forward side by side.Window slides into another position on frequency domain, wherein more estimates, and record SE.Repeat this process up to the arrival band end, and on the set of records ends of SE, calculate MSE.MSE is a unmatched mean value between two groups of numerical value.The MMSE that the relatively MSE on the whole frequency band, and hypothesis has minimum MSE estimates more to represent real channel condition, and selects and use the corresponding weighting matrix that MMSE estimates that approaches most, estimates the channel frequency response of the data subcarrier in a symbol.
[0012] select in the finite aggregate of the weighting matrix that produces in advance, can help to reduce or reduces the double counting weighting matrix of complexity and costliness, complexity and double counting are the features of some prior aries.Therefore, the advantage of some embodiment is to reduce complexity and cost.Each embodiment of the present invention can be applied to 1-D and 2-D MMSE technology and carry out frequency response and estimate.
[0013] by adopting the LS channel frequency response to come direct estimation at the locational channel frequency response of data tones on the pilot tone position, each embodiment pays close attention to and how to use known distribution pilot tone to estimate channel response.In other words, this example reduces the transform domain method of using, and wherein the channel frequency response of pilot tone at first is transformed into time domain (channel impulse response CIR), is converted back to frequency domain again then after some is handled.The direct channel frequency response technology of this example adopts a weighted sum process, and promptly the channel frequency response of data tones is the weighted sum of one group of channel frequency response on pilot frequency locations.
[0014] when using each embodiment of the present invention, can consider some factor.For example, the number of pilots of using in the time of can determining in advance to estimate.Generally, use more pilot tones can be more accurate, but can increase complexity of calculation.In addition, the pilot tone of using during estimation can be to select in identical time mark, identical frequency marker, different time and/or frequency marker, thereby 1-D and 2-D method belong in the scope of embodiment.As a rule, the 1-D method of sequence will produce and the true identical performance of 2-D method.But sequence 1-D method should be followed an order and analyze time domain and frequency domain.For example, in a channel that fails more slowly, preferably at first analyze time domain.In the channel of a very fast decline, preferably at first analyze frequency domain.By contrast, in a real 2-D method, order information is included in the weighted factor.
[0015] under different channel characteristics, the weight vectors of MMSE standard is different.When the channel characteristics of channel characteristics of supposing and reality mates, will approach optimum performance.By using the precalculated weight vectors of a clear and definite channel characteristics set, each embodiment obtains the MMSE weight vectors of an actual channel characteristic.Based on the MSE of MMSE channel frequency response with at continuous pilot locational known (as LS) channel frequency response, precalculated weight vectors is used in the competition algorithm, and the continuous pilot set of wherein single OFDM symbol is used to calculate MSE.Precalculated weight vectors is competed once each OFDM symbol, and the victor is used to estimate the channel of an OFDM symbol.
[0016] above example provides a kind of and determines the method for weight vectors by the competition algorithm, and other method also belongs in the scope of embodiment.Weight vectors can be vied each other in a plurality of scopes, as one or several window, whole OFDM symbol or a full frame.The consideration of some reality is also arranged.Competition more among a small circle may cause unnecessary relatively calculating, and the competition of (as on full frame) may cause bigger delayed impact and bigger buffering requirement in a big way.Analog simulation shows the scope of an OFDM symbol, is rational and consistent with the receiver chain signal processing.
[0017] aforementioned feature of the present invention and the technical advantage set forth quite widely is so that can understand following detailed description of the present invention better.Further feature of the present invention and advantage will be described subsequently, and it constitutes claim of the present invention.The notion and the specific embodiment that one skilled in the art would recognize that disclosure can easily be used, and are used for revising or designing other structure so that carry out identical purpose of the present invention as a basis.Those skilled in the art should be realized that also this equivalent constructions does not have to break away from the spirit and scope of the present invention of setting forth in accessory claim.No matter novel features of the present invention is its structure or method of operation, with other purpose and advantage, from the description below in conjunction with accompanying drawing, will be better understood.But, should recognize profoundly that each feature that provides only is as the description purposes, rather than is intended to as restriction definition of the present invention.
Description of drawings
[0018] for a more complete understanding of the present invention, existing in conjunction with the accompanying drawings also with reference to following description, wherein:
[0019] Fig. 1 describes an example ofdm signal;
[0020] Fig. 2 describes a canonical system of one embodiment of the invention;
[0021] Fig. 3 describes a typical 2-D channel estimating can using in various embodiments of the invention;
[0022] Fig. 4 describe can use in the various embodiments of the invention on the time domain across 5 carrier waves and on frequency domain across a typical 2-D window of 25 carrier waves.
[0023] Fig. 5 describes a representative channel feature hypothesis can using and is used for the weight vectors that equation 7 calculates so that calculate in advance in one embodiment of the invention.
[0024] Fig. 6 describes a typical window of one embodiment of the invention;
[0025] Fig. 7 describes a typical sliding window pattern that is used in the some embodiments of the invention;
[0026] Fig. 8 describes a typical sliding window technique in the band edge use of one embodiment of the invention;
[0027] Fig. 9 describes a canonical process of one embodiment of the invention; With
[0028] Figure 10 describes a typical computer system of one embodiment of the invention.
Detailed Description Of The Invention
[0029] Fig. 2 describes the canonical system 200 of one embodiment of the invention.System 200 comprises OFDM receiver 201, and it is the part of digital television receiver 202 in this embodiment.OFDM receiver 201 is not limited to be used in the television receiver, and other use also is possible, as handheld device (as mobile phone, personal digital assistant, on knee/desktop computer etc.).
[0030] OFDM receiver 201 receives a signal, and this signal is included in the subcarrier of expanding on time and the frequency domain.Channel estimator 210 is handled this signal, produces channel frequency response and estimates that this will be in following detailed description.Demodulator 220 uses channel frequency response to carry out the coherent demodulation of data tones.Demodulator 220 utilizes the data tones and the frequency channels that receive to respond the data symbol (as BPSK, QPSK, qam symbol) that recovers to transmit.Then, the data recovered symbol is flowed into channel decoder 230 to do further processing and to show the user then by soft mapping (soft-demapped) the one-tenth bit information of separating.
[0031] Fig. 3 describes a typical 2-D channel estimating can using in various embodiment of the present invention.In this example, use the interior pilot tone in zone to come the channel frequency response of data estimator subcarrier 301, even this pilot tone does not have common time or frequency marker with data subcarrier 301.Square frame 302 has been described the cross-correlation calculation of two pilot tones of typical use.To each data subcarrier, can calculate the MMSE channel estimating according to equation 4, wherein H is the vector of pilot channel frequency response, w is a weight vectors, it multiply by pilot channel frequency response matrix, and SNR is a signal to noise ratio, and θ is a cross-correlation vector, R is the auto-correlation vector, and I is unit matrix (identity matrix).
[0032] various embodiment of the present invention sets a 2-D window in the OFDM symbol, and it is used to select the channel frequency response of weight vectors and data estimator subcarrier.Fig. 4 has described typical 2-D window 400, its on the time domain across 5 OFDM symbols on frequency domain across 25 subcarriers.
[0033] window 400 is subclass of subcarrier in 5 OFDM symbols, and part 401 is subclass of subclass.401 parts are subclass of data subcarrier, use window 400 will estimate channel frequency response thus, and this will be in following detailed description.A notable feature of window 400 is subcarriers that the number to 12 of its restriction scattered pilot is used to estimate 401 parts.Equation 7 has shown the channel estimation calculation of 401 partial data subcarriers.Matrix W is one
Matrix, it comprises 11 weight vectors w, each data subcarrier of corresponding 401 parts of each w, and each weight vectors w comprises a weighted factor of each pilot tone in 400 li 12 pilot tones of window.Therefore, be that 12 weight vectors is stocked in the calculating shown in the equation 7 to 400,11 length of window, use 12 multiplication to calculate and an additional calculation to each data subcarrier in 11 data subcarriers in 400 parts.
[0034] some embodiments of the present invention can be fitted to the frame of different size and the window of different size.Usually can expect to have a large-size window that comprises more pilot tone result more accurately can be provided more to assess the cost.The window by analog simulation displayed map 4 can provide acceptable result to be used for the DVB-T/H application.
[0035] present, discuss and get back to the calculating of weighting matrix W, and return description all data subcarriers generation channel responses in the symbol are estimated.One of feature of some embodiments of the invention be exactly weighting matrix be in one group of weighting matrix that produces in advance, to select.This feature can provide bigger efficient because can reduce or reduce each data subcarrier weight vectors recomputate cost.
[0036] a kind of exemplary method that produces weighting matrix in advance comprises they and channel characteristics hypothesis (channel profile assumptions) is associated.In addition, use known relevant position of data subcarrier and in window the scattered pilot in pilot sub-carrier structure, set up weighting matrix.This will be described following, be identical on the pattern of scattered pilot each window in entire frame, thereby the weighting matrix that produces in advance can be used for all symbols in this example signal.
[0037] in this example embodiment, use the weighting matrix of reasonable number, each weighting matrix is associated with a hypothesis channel characteristics, supposes that wherein the set of channel characteristics almost covers all possible Real-time Channel condition.Fig. 5 has described a representative channel feature hypothesis can using in some embodiments, is used for calculation equation 7 to produce weighting matrix in advance.In the embodiment of Fig. 5, be the hypothesis of having considered fading rate and having postponed expansion, it is the feature that is associated with the cross-correlation and the auto-correlation of equation 5 and 6.Quadrant 501 expressions expand to a moderate delay expansion and a channel characteristics from zero rate of fading to high rate of fading from zero-lag.Quadrant 502 expressions expand to a high delay expansion and a channel characteristics from zero rate of fading to medium rate of fading from zero-lag.Quadrant 503 expression quadrants 501 and 502 channel characteristics that occur simultaneously.The channel characteristics of quadrant 504 fast fading rates of expression and high latency expansion.In this example embodiment, a weighting matrix (W1) is associated with the feature of quadrant 501, and another weighting matrix (W2) is associated with the feature of quadrant 502.Two weighting matrixs all are effectively when channel characteristics respective quadrants 503, and quadrant 504 is useless (are signal quality too poor and can't use).
[0038] Fig. 6 has described the typical window 600 of one embodiment of the invention.Be similar to window 400 (Fig. 4), window 600 is set 12 scattered pilots, will be used for the channel estimating of the data subcarrier of part 601.Fig. 6 has also described continuous pilot 602 (having in one group of continuous pilot of same frequency mark).In this example, continuous pilot 602 is used to select in the method for a weighting matrix.
[0039] as mentioned above, use, be easy to calculate the channel frequency response estimation of a pilot sub-carrier such as a kind of LS method (equation 3).In this example, use a kind of LS method, the channel frequency response of estimating pilot frequency 602, and storage numerical value.Also can use a kind of MMSE technology,, calculate the channel frequency response of pilot tone 602 equally each weighting matrix W1 and W2 that produces in advance.Then, window is moved to a reposition, and at new the window's position continuous pilot is calculated once more.Repeat the process of the sliding window pattern and the MMSE of the continuous pilot of calculating two different matrixes, up to covering whole frequency band.Two groups of MMSE that obtained continuous pilot estimate.Estimate that with LS two groups of MMSE estimate to be used to calculate MSE.For example, MSE1 and MSE2 represent respectively that first group of MMSE estimates and second group of MMSE estimation in error.If MSE1＜MSE2 then selects W1, if MSE1＞MSE2 then selects W2.Sometimes, can use a deviation factors (alpha).For example, if MSE1＜MSE2*alpha then selects W1.Deviation factors alpha can be used to consider the noise effect of LS estimation.
[0040] relatively be to describe by equation 8, wherein J is the frequency marker set of continuous pilot.Equation 8 has calculated the mean value of two groups of SE in the symbol, and they are compared.Because scale factor 1/ size (J) does not influence comparative result usually, some embodiment can use accumulated value rather than mean value to avoid division arithmetic.Therefore, example embodiment comprises a mechanism so that two or more channel characteristics hypothesis is at war with, and wherein each channel characteristics hypothesis is associated with a different weighting matrix.Best channel characteristics hypothesis will " win " competition, thereby provide a weighting matrix to be used for the interior a plurality of data subcarriers of equation 7.
[0041] embodiment selects the optimum weighting matrix to estimate to comprise the channel frequency response of data subcarrier in the symbol of part 601.After selecting suitable weighting matrix, the data tones in the symbol is carried out the MMSE channel frequency response estimate.Window scheme slides on frequency band once more, by using " winner " matrix of selecting, the channel frequency response of data tones in the estimate symbol (as the symbol around 601 parts).
[0042] as mentioned above, each embodiment is included in sliding window on the frequency domain.Fig. 7 has described a typical sliding window pattern that is used in the some embodiments of the invention.Fig. 7 shows a plurality of window 701-704, is appreciated that in this example, in the entire frame all is to set unified window, thereby between the data subcarrier of window and window and the scattered pilot consistent spatial relationship is arranged.Each window 701-704 comprises sub-carrier subset 711-714 separately.Selecting a weighting matrix to be used for after the channel frequency response of data estimator subcarrier, this weighting matrix is used to other subclass of all frequency bands in the symbol.Sliding window technique is used to the channel frequency response (as the symbol around subclass 711-713) of data subcarrier in the estimate symbol.In other words, use the scattered pilot in the window 701, the weighting matrix of selection is applied to window 701 to estimate 711 partial data subcarriers.Identical process can be applied to other window (not shown) on window 702,703 and the frequency band.In some embodiments, also can use this weighting matrix (as subclass 714) to other symbol in the frame.
[0043] should be noted that, is not that each window all comprises continuous pilot.This window is not used for selecting a weighting matrix, but is used for the channel frequency response of data estimator subcarrier.
[0044] uses sliding window technique at band edge, do some allotments, as shown in Figure 8.Fig. 8 has shown two sliding windows 801 and 802, the edge situation that their each self-described is different.Window 801 is on the left hand edge of frame, thereby window 801 and subclass 811 are cut off.In the case, with the size of window 801 make with frame in other window measure-alike, and use virtual subnet carrier wave (comprising virtual pilot frequency) to fill up the space of being set up.Window 801 comprises 12 virtual subnet carrier waves of each symbol.In addition, subclass 811 comprises 5 virtual subnet carrier waves.In this example, the numerical value of virtual subnet carrier wave is set to 0, and is the same with above example, estimates channel frequency response.
[0045] window 802 is on the right hand edge of symbol frequency band, as described in relevant window 801, is suitable for same notion.Once more, insert the virtual subnet carrier wave be set to 0 numerical value, as placeholder (placeholder), thereby the size of window 802 and subclass 811 respectively with frame in other window and subclass unified mutually.
[0046] various embodiment comprise the method for carrying out according to above example.Fig. 9 has described the canonical process 900 of one embodiment of the invention.Process 900 can be carried out as the OFDM receiver shown in Fig. 2 by one.
[0047] in module 901, received signal, some symbols are cushioned to do further processing.In this example, when window on time domain during across 5 OFDM symbols, 5 OFDM symbols of system buffer, n-4, n-3, n-2, n-1, n.When receiving n OFDM symbol, system can estimate the channel frequency response of n-2 OFDM symbol.When receiving n+1 OFDM symbol, system can estimate the channel frequency response of n-1 OFDM symbol, and the rest may be inferred.When receiving n OFDM symbol,, there are 5 OFDM symbols to be cushioned (, the sound matrix of one 5 row 6817 row being arranged) as in the DVB example as an example.In this example, buffering is a continuous process, and wherein all symbols that receive are cushioned, and then further handles.Signal can normally be carried out by computer storage and cushion by wireless or wired receiving.
[0048], continuous pilot and scattered pilot are carried out the LS estimation in module 902.In some embodiments, be known at the LS channel frequency response of pilot tone (comprise disperse and continuous pilot), so do not calculate in module 902, module 902 produces the channel LS frequency response of pilot tones and estimates.
[0049] in module 903 and 904, use two different weighting matrix W1 and W2, continuous pilot is calculated two different MMSE estimate, the corresponding different channel characteristics hypothesis of each weighting matrix.The MMSE that the LS channel estimating of scattered pilot is used in module 903 and 904 estimates, shown in equation 7.Other embodiment can use the channel characteristics hypothesis more than two.More channel characteristics hypothesis can provide bigger accuracy usually, assesses the cost and complexity but also increase.Analog simulation shows that corresponding fading rate and two different weights vectors that postpone to expand can enough be used for some DVB and use.
[0050] in module 905, relatively the LS of MMSE estimation and continuous pilot calculates.The calculating of corresponding first matrix W 1 is first set, and the calculating of corresponding second matrix W 2 is second set.Having minimum MSE selects which weighting matrix W1 and W2 to be used for the channel estimating of data subcarrier about that MMSE set of computations demonstration of LS.In some embodiments, introduce a deviation factors and be used to alleviate noise effect.
[0051] in module 906, the weight vectors of selection (is called W here
*) be used to the channel frequency response of data estimator subcarrier.In some embodiments, module 906 can comprise uses a kind of sliding window technique with all frequency spectrums at frame (or partial frame) at least, with in addition time-domain on use identical weighting matrix W
*
[0052] in module 907, the channel frequency response of the data subcarrier of frame estimates to be used to demodulation.Then, the transmission restituted signal is to do further processing.For example, restituted signal can be passed to decoding signals.Process 900 operations are to convert an ofdm signal to a demodulation coded signal, and wherein data content can be used to provide the user perceptible information, as the voice of mobile phone or the sound and the image of TV.
[0053] process 900 is examples, and various embodiment can increase, ignore, revise and/or the module of layout process again 900.For example, as mentioned above, can use the channel estimating of carrying out continuous pilot more than the set of two different weights matrix.In addition, some embodiment can be to the action of each symbol Executive Module 903-905, and every several symbols are carried out once, and every frame is carried out once, or frequently carries out in special the application.The weighting matrix candidate's of Chan Shenging identity set can be used to entire frame or a plurality of frame in advance, in some embodiments, can only be set up once and be used for all calculating subsequently.Although above embodiment has described the signal of relevant DVB, the OFDM that can allocate in these are implemented and be used for any kind uses, and uses the application of the signal of scattered pilot and continuous pilot as WiMax, mobile broadband wireless, China Mobile multimedia broadcasting standard or other.Process 900 is implemented in real time, thus the imperceptible delay of user.
[0054] each embodiment of the present invention provides the advantage that is better than the existing channel estimation technique.For example, set a plurality of unified windows and select one in a frame from the weighting matrix candidate of a reasonable number, this can save cushion space, and reduces number of computations.Form 1 has shown that the buffer of an embodiment uses and complexity analyzing, and this embodiment uses
Window (as Fig. 4) produces a set of two weighting matrixs in advance to a DVB signal, selects one in two identical weighting matrixs that produce in advance in entire frame.In addition, the weighting matrix that produces in advance and in the middle of their, select to reduce or greatly reduce dependence to real-time matrix inversion and Real-time Channel statistics (as SNR and time/frequency domain correlation).In addition, the buffer that is provided by some embodiment uses and the reduction of complexity can have imperceptible performance loss.
N: the number B of useful subcarrier
d: the bit width of each subcarrier
N
d: the number B of data subcarrier
c: the bit width of channel estimating
N
Cp: the number B of continuous pilot
m: the bit width of composite weighted matrix element
N
Sp: the number of scattered pilot
[0055] when implementing by computer executable instructions, the various elements of the embodiment of the invention are actually the software code of these various element operations of definition.Executable instruction or software code can obtain (as hard disk media, light media, RAM, EPROM, EEPROM, tape media, cassette tape media, flash memory, ROM, memory stick etc.) from readable medium.In fact, readable medium can comprise can stored information any media.
[0056] Figure 10 describes an example computer system 1000 of one embodiment of the invention.Be that computer system 1000 comprises the example system that can implement the embodiment of the invention (television receiver of implementing as the example of Fig. 2 202 or other comprise the equipment of OFDM receiver, as mobile phone or cellular telephone base stations).CPU (CPU) 1001 is connected to system bus 1002.CPU 1001 can be any universal or special CPU.But the present invention is not subjected to the restriction of CPU 1000 frameworks, as long as CPU 1001 supports the present invention's operation described herein.According to embodiments of the invention, CPU1001 can carry out various logical instructions.For example, in conjunction with the described typical operation flow process of Fig. 9, one or more CPU as CPU 1001, can carry out machine level instruction according to above.
[0057] preferably, computer system 1000 also comprises random asccess memory (RAM) 1003, and it can be SRAM, DRAM, SDRAM etc.In this example, computer system 1000 is used the buffer 302 of RAM 1003 as Fig. 3.Preferably, computer system 1000 comprises read-only memory (ROM) 1004, and it can be PROM, EPROM, EEPROM etc.As known in prior art, RAM 1003 and ROM 1004 keep user and system data and program.
[0058] preferably, computer system 1000 also comprises I/O (I/O) adapter 1005, communication adapter 1011, user interface adapter 1008 and display adapter 1009.In some embodiment, I/O adapter 1005, user interface adapter 1008 and/or communication adapter 1011 can make the user and computer system 1000 carries out interaction so that input information, as the television channel of expectation, the telephone number that expectation is called out, the information of text message etc.
[0059] preferably, I/O adapter 1005 is connected to computer system 1000 with memory devices 1006 as one or more hard disk drives, CD (CD) driver, floppy disk, magnetic tape type driver etc.When RAM 1003 can not satisfy the memory requirement of relevant storage medium data, can utilize memory devices.Preferably, communication adapter 1011 is arrived network 1012 (as the Internet, local area network (LAN), cellular network, wired telephone network etc.) by adaptive to connect computer system 1000.User interface adapter 1008 connects user input devices, as keyboard 1013, positioning equipment 1007 and microphone 1014 and/or output equipment such as loud speaker 1015 to computer system 1000.Display adapter 1009 is to be driven to be controlled at the demonstration on the display device 1010 by CPU 1001, for example show media when playing.
[0060] according to various embodiment, the actual configuration of part system may be shown in above.For example, the embodiment of the invention may be implemented within application-specific integrated circuit (ASIC) (ASICs) or ultra-large integrated (VLSI) circuit.Some embodiment can be used in special chip group and/or the software/firmware encapsulation.In fact, those skilled in the art can utilize the suitable construction of any number, and it can carry out the logical operation of the embodiment of the invention.
[0061] though described the present invention and superiority thereof in detail, should be understood that under the condition of the present invention that does not break away from the claims definition and can make various changes, replace and variation.In addition, the application's scope is not limited to the processing method of describing in the specification herein, and machine is made, and material constitutes, means, the specific embodiment of method and step etc.As can be easily understood from the description, can utilize carried out in fact with here the explanation corresponding embodiment identical function or realized the present existing of identical result or the processing method of developing in the future, machine, make, material constitutes, means, method and step.Therefore, appending claims is intended to comprise these processing methods, and machine is made, and material constitutes, means, method or step.
Claims (24)
1. an OFDM (OFDM) receiver comprises:
A channel estimator, it receives a signal that comprises a plurality of symbols, each symbol comprises a plurality of data subcarriers, this estimator uses first channel response of at least one pilot sub-carrier in the signal to estimate to select first weighting matrix in a plurality of weighting matrixs that produce in advance, and first weighting matrix that use is selected is that at least one data subcarrier subclass produces the channel response estimated information; With
A demodulator, it receives the channel response estimated information of at least one data sub-carrier subset from channel estimator, and the signal that uses the channel response estimated information of at least one data subcarrier subclass to come demodulate reception to arrive.
2. a digital television receiver comprises the described OFDM receiver of claim 1.
3. digital television receiver according to claim 2, wherein the OFDM receiver is to move according to digital video broadcast-terrestrial (DVB-T) standard.
4. digital television receiver according to claim 2, wherein the OFDM receiver is to move according to handheld terminal digital video broadcasting (DVB-H) standard.
5. a cellular telephone base stations comprises the described OFDM receiver of claim 1.
6. OFDM receiver according to claim 1, wherein signal is a wireless receiving.
7. OFDM receiver according to claim 1, wherein signal is wired reception.
8. OFDM receiver according to claim 1, wherein a plurality of weighting matrixs that produce in advance produce according to the known relevant position of a plurality of data subcarriers in the pilot sub-carrier structure.
9. OFDM receiver according to claim 1, wherein a plurality of weighting matrixs that produce are in advance explained the delay expansion of channel and the potential difference on the rate of fading.
10. OFDM receiver according to claim 1, wherein channel estimator uses first weighting matrix of selecting, and carries out a plurality of channel estimating along frequency band in first symbol.
11. OFDM receiver according to claim 1, wherein channel estimator is set up a two dimension (2-D) window in signal, this window comprises the first pilot sub-carrier subclass of first character subset, this channel estimator uses first weighting matrix of selecting and the channel response of the first pilot sub-carrier subclass, at least one data subcarrier subclass is carried out the 2-D channel estimating.
12. OFDM receiver according to claim 1, wherein channel estimator is set up a two dimension (2-D) window in signal, window comprises first pilot sub-carrier of first character subset, channel estimator uses each weighting matrix that produces in advance and the first pilot sub-carrier subclass, at least one pilot sub-carrier in the window is produced other channel response to be estimated, the other channel response of each weighting matrix that produces is in advance estimated to estimate to compare with first channel response of at least one pilot sub-carrier, and in the middle of the weighting matrix that produces in advance, make one's options based on the comparison.
13. OFDM receiver according to claim 12, wherein selecting is to be undertaken by selecting a weighting matrix that produces in advance, and this produces first channel response estimation that a channel response estimates to approach most this at least one pilot sub-carrier.
14. OFDM receiver according to claim 13, wherein the channel response estimated information comprises channel frequency response information.
15. a computer programmed product has a computer readable medium, it has the computer programming logic of record, and so that an OFDM (OFDM) conversion of signals is become a restituted signal, this computer programmed product comprises:
Determine the code of a plurality of windows in the ofdm signal, wherein each window comprises a plurality of pilot tones;
Store a plurality of weighting matrix candidates' that produce in advance code;
In the middle of at least some windows, obtain the code of first channel estimating response of first pilot set;
The weighting matrix candidate who uses each to produce in advance produces the code of the other channel response estimation of first pilot set;
Based on the comparison that other channel response is estimated and first channel response is estimated, select a weighting matrix candidate's who produces in advance code;
Use the weighting matrix of selecting that produces in advance to come the code of the channel response of data subcarrier in the estimate symbol; With
Use the code of the estimation channel response demodulation ofdm signal of data carrier in the symbol.
16. computer programmed product according to claim 15, wherein the weighting matrix that produces in advance is associated with the channel characteristics hypothesis.
17. computer programmed product according to claim 15, wherein the channel characteristics hypothesis comprises:
The hypothesis of the delay expansion of a relevant channel; With
The hypothesis of a relevant channel fading speed.
18. computer programmed product according to claim 15 wherein uses the weighting matrix of selecting that produces in advance to come the code of data subcarrier channel response in the estimate symbol to comprise:
Use at least some pilot tones in a plurality of windows, produce the code of a two dimension (2-D) the channel frequency response estimation of data subcarrier.
19. computer programmed product according to claim 15, wherein first channel response is estimated to comprise:
The least square method of channel frequency response is estimated.
20. the method for a restituted signal, the method comprises:
Receive a signal;
Set a plurality of windows in signal, these a plurality of windows comprise a plurality of continuous pilot subcarriers;
Use a known transmission feature of pilot sub-carrier, first channel response that obtains the continuous pilot subcarrier is estimated;
The a plurality of other channel response that produces the continuous pilot subcarrier estimates that this other channel response is estimated to be to use a plurality of weighting matrix candidates to produce, and each other channel response is estimated corresponding weighting matrix candidate;
Relatively this other channel response is estimated and the estimation of first channel response;
Based on the comparison, select a weighting matrix candidate;
Use the weighting matrix candidate who selects, the channel response of data subcarrier in the estimate symbol; With
Use the estimation channel response demodulation signal of data subcarrier.
21. method according to claim 20, wherein signal comprises:
An OFDM (OFDM) signal.
22. method according to claim 20, wherein signal also comprises scattered pilot.
23. method according to claim 20 estimates that wherein the channel response of at least one subclass of a plurality of data subcarriers comprises:
The execution two dimensional channel is estimated.
24. method according to claim 20, wherein each weighting matrix candidate comprises:
A plurality of vectors, a data subcarrier of at least one data subcarrier subclass in the corresponding symbol of each vector;
Wherein each vector is included in one group of weighted value that will be applied to pilot sub-carrier during the channel estimating.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
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| CNA2009101393134A CN101552763A (en) | 2009-04-29 | 2009-04-29 | OFDM channel estimation technique |
| CN200910225718XA CN101771651B (en) | 2009-04-29 | 2009-11-27 | OFMD (Orthogonal Frequency Division Multiplexing) channel estimation technology |
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| Application Number | Priority Date | Filing Date | Title |
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| CNA2009101393134A CN101552763A (en) | 2009-04-29 | 2009-04-29 | OFDM channel estimation technique |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104253777A (en) * | 2013-06-28 | 2014-12-31 | 英特尔移动通信有限责任公司 | Method and device for channel estimation with colliding interference cancellation |
| CN107248967A (en) * | 2016-07-21 | 2017-10-13 | 武汉芯泰科技有限公司 | A kind of channel estimation methods and device applied to ofdm system |
| CN114598576A (en) * | 2022-03-14 | 2022-06-07 | Oppo广东移动通信有限公司 | Spur subcarrier channel estimation method, device, chip, terminal and storage medium |
-
2009
- 2009-04-29 CN CNA2009101393134A patent/CN101552763A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104253777A (en) * | 2013-06-28 | 2014-12-31 | 英特尔移动通信有限责任公司 | Method and device for channel estimation with colliding interference cancellation |
| CN104253777B (en) * | 2013-06-28 | 2017-12-26 | 英特尔德国有限责任公司 | The method and apparatus of the channel estimation eliminated using conflict interference |
| CN107248967A (en) * | 2016-07-21 | 2017-10-13 | 武汉芯泰科技有限公司 | A kind of channel estimation methods and device applied to ofdm system |
| CN107248967B (en) * | 2016-07-21 | 2023-09-01 | 武汉芯泰科技有限公司 | Channel estimation method and device applied to OFDM system |
| CN114598576A (en) * | 2022-03-14 | 2022-06-07 | Oppo广东移动通信有限公司 | Spur subcarrier channel estimation method, device, chip, terminal and storage medium |
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