CN101043486A - Symbol estimation method using de-dot frequency domain linear equalization - Google Patents
Symbol estimation method using de-dot frequency domain linear equalization Download PDFInfo
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Abstract
The provided signal estimation method in communication system comprises: obtaining the frequency signal on every frequency point for the received signal; calculating inversion to the signal on every frequency point; removing the frequency point with lower channel attenuation; and taking inverse Fourier transform to obtain the signal estimation.
Description
Technical field
The present invention relates to a kind of symbol estimation method that in communication system, adopts de-dot frequency domain linear equalization,,, eliminated the distortion that the channel zero frequency is caused for whole fft block signal by having removed frequency domain channel pairing frequency at zero point according to the present invention.The present invention is specially adapted to carrier wave communication system.
Background technology
Along with the raising of 3G (Third Generation) Moblie transmission rate, each symbol continues the reduction in cycle, and the subject matter that system of broadband wireless communication faces is exactly the time delay expansion that how to resist the dozens or even hundreds of symbol that causes owing to multipath fading.For in the environment of high-speed communication, contrary frequency selectivity decline effectively, every motion of 3GPP (third generation partner plan) has concentrated on the mode of employing frequency division multiplexing (FDM).Each user's frequency orthogonal in the fdma system, the symbol period that each subscriber signal continued can not reduce along with increasing of number of users, can not aggravate the influence of the intersymbol interference that produces owing to multidiameter.
In 3GPP tissue, some company proposes to adopt OFDM (OFDM) mode, and its benefit is to adopt the mode of orthogonal frequency that the user is composed to overlap, can effectively improve bandwidth availability ratio.Yet orthogonal frequency division multiplex OFDM needs strict synchronism between the user, and its peak-to-average force ratio (PAPR) is higher, makes the requirement of power amplifier dynamic range of ustomer premises access equipment (UE) improve, thereby has improved the cost of power amplifier.
The single-carrier modulated (SC) that has Cyclic Prefix can reduce peak-to-average force ratio effectively, and aspect the anti-multipath interference, have similar performance to OFDM, therefore, in the discussion of 3GPP standardization body, single-carrier system is accepted by each major company, thereby will be applied to up-link wireless communication.
In ofdm system, because each carrier wave symbol difference of carrying, so input carries out at frequency domain usually, respectively each frequency handled according to flat decline.In single-carrier system, because the influence of multidiameter, the content of current sign can postpone several symbols of back, therefore need carry out equilibrium treatment, and equalization algorithm is divided into time domain equalization and frequency domain equalization.Time-domain equalizer carries out convolution algorithm with the time domain filtering and the received signal of several taps, and frequency equalizer transforms to frequency domain with received signal, removes the influence of channel then at each frequency, and realizes balanced after carrying out inverse Fourier transform.The implementation complexity of frequency domain equalization algorithm is lower, and in the frequency domain equalization algorithm, the linear equalization algorithm is more simple, and convergence is to adopt more equalization algorithm at present fast.
But there is problem as described below in prior art.
Frequency domain linear equalization and frequency domain decision feedback equalization algorithm are to use two kinds of more equalization algorithms at present.David Falconer, what people such as Sirikiat Lek Arisyavisitakul delivered is entitled as, the article and the DavidFalconer of " White Paper:Frequency domain equalization forsingle-carrier broadband wireless systems ", the article that is entitled as " Frequencydomain equalization for single-carrier broadband wirelesssystems " that people such as Sirikiat Lek Arisyavisitakul deliver on the 58th ~ 66 page of the IEEEcommunication magazine in April in 2004 is introduced this.The frequency linearity equilibrium treatment realizes block diagram as shown in Figure 1.Send signal and arrive reception antenna, at first,, form filtering to the received signal,, carry out Fourier transform, obtained being positioned at the signal on each frequency then at step S102 at step S101 through behind the channel fading.At step S103, on each frequency, channel is inverted respectively, promptly to the received signal of frequency domain respectively divided by the channel fading value of corresponding frequency, then can obtain sending the frequency domain estimated value of symbol, at step S104, carry out inverse Fourier transform then, thereby obtain the sign estimation result under the single-carrier system, at step S105, the symbol that estimates is carried out the estimated value that demodulation obtains each bit.
The frequency DFF also is to pay close attention to more equalizer at present, and its processing realizes block diagram as shown in Figure 2.Send signal and arrive reception antenna, at first,, form filtering,, carry out Fourier transform, obtained being positioned at the signal on each frequency then at step S202 to receiving signal at step S201 through behind the channel fading.At step S203, utilize the frequency filter coefficient sequence W try to achieve respectively with each frequency on signal multiplication, that is, and with the received signal on the frequency domain respectively divided by the coefficient W at corresponding frequency place
1, then at step S204, carry out inverse Fourier transform, thereby obtain single-carrier system sign estimation z, at step S205, carry out the subtracter operation, just, from z, deduct the output of the time domain feedback filter that obtains at step S207.At step S206, the difference of subtraction is detected, detect the output result and be input to feedback filter on the one hand, be input to the input (step S208) of demodulator on the other hand, last, after demodulation, obtain sending the estimated value of each bit of signal.
From above introduction as can be seen, the realization of frequency domain linear equalization algorithm is simple especially.But, because it is when handling, with the received signal on each frequency divided by channel fading, therefore, channel fading on this frequency hour, for example, channel fading approaches zero, and then the noise component(s) in the received signal is divided by after approaching zero channel fading, will be very big, thereby bring bigger distortion for whole fast fourier transform, thereby in single-carrier system, can influence the detection of all signals in the whole fft block.
List of references
[1]David?Falconer，Sirikiat?Lek?Arisyavisitakul，etc，“White?Paper：Frequency?domain?equalization?for?single-carrierbroadband?wireless?systems.”
[2]David?Falconer，Sirikiat?Lek?Arisyavisitakul，etc，“Frequency?domain?equalization?for?single-carrier?broadbandwireless?systems，”IEEE?communication?magazine，April，2002，pp.58~66.
[3]H.Sari，G.Karam，and?I.Jeanclaude，“FrequencyDomain?Equalization?of?Mobile?Radio?and?Terrestrial?BroadcastChannels，”Proc.Globecom’94，San?Francisco，CA，Nov.-Dec.1994，pp.1-5
[4]H.Sari，G.Karam，and?I.Jeanclaude，“TransmissionTechniques?for?Digital?Terrestrial?TV?Broadcasting，”IEEECommun.Mag.，Vol?33，no.2，Feb.1995，pp.100-109
Summary of the invention
In order to overcome above-mentioned defective of the prior art the present invention has been proposed.Therefore, the present invention proposes a kind of symbol estimation method that in communication system, adopts de-dot frequency domain linear equalization, according to the present invention,, eliminated the distortion that the channel zero frequency is caused for whole fft block signal by having removed frequency domain channel pairing frequency at zero point.
To achieve these goals, according to the present invention, proposed a kind of symbol estimation method that adopts de-dot frequency domain linear equalization in communication system, described method comprises step: the frequency-region signal that is positioned at each frequency that obtains received signal; At described frequency-region signal, on each frequency, each channel is inverted respectively; A processing is gone in described frequency-region signal execution, remove the estimation frequency of the low corresponding transmission symbol of channel fading; And to going the described frequency-region signal after the processing to carry out inverse Fourier transform, so that obtain the sign estimation that sends symbol.
Preferably, the described step of obtaining the frequency-region signal that is positioned at each frequency of received signal comprises: carry out contrary shaping filter to received signal, to obtain the convolution signal that sends symbol and each channel fading vector; And to described convolution signal execution Fourier transform, to obtain the frequency-region signal that is positioned at each frequency of received signal.
Preferably, at described frequency-region signal, comprise in the step of on each frequency each channel being inverted respectively: utilize described frequency-region signal to realize inverting each channel divided by the channel fading value on each frequency.
Preferably, described described frequency-region signal is carried out goes the step of a processing may further comprise the steps: the received signal to noise ratio of estimating communication system; First thresholding is set, and described first thresholding is the inverse of described received signal to noise ratio; Compare the channel fading value and first thresholding on each frequency successively; If the channel fading value on the frequency is less than first thresholding, then the transmission sign estimation value on this frequency is set to zero; And if the channel fading value then makes the transmission sign estimation value on this frequency remain unchanged less than first thresholding.
Preferably, described described frequency-region signal is carried out goes the step of a processing may further comprise the steps: second thresholding is set, and described second thresholding is a fixed value; Compare the channel fading value and second thresholding on each frequency successively; If the channel fading value on the frequency is less than second thresholding, then the transmission sign estimation value on this frequency is set to zero; And if the channel fading value then makes the transmission sign estimation value on this frequency remain unchanged less than second thresholding.
Preferably, described communication system is a carrier wave communication system.
Therefore, the present invention proposes a kind of symbol estimation method that in communication system, adopts de-dot frequency domain linear equalization.The present invention is based on the linear equalization algorithm and proposed to go a Processing Algorithm, it is by removing frequency domain channel pairing frequency at zero point, eliminated the distortion that channel is caused for whole fft block signal zero point, simulation result shows by this and goes a Processing Algorithm, can improve performance 1 ~ 2dB than traditional linear frequency territory equalization algorithm.
Description of drawings
Below in conjunction with the detailed description of preferred embodiment of accompanying drawing to being adopted, above-mentioned purpose of the present invention, advantage and feature will become apparent by reference, wherein:
Fig. 1 shows the schematic diagram according to the frequency domain linear equalizer of prior art;
Fig. 2 shows the schematic diagram according to the frequency domain DFF of prior art;
Fig. 3 shows the schematic diagram of the single-carrier system transmitting terminal that has Cyclic Prefix;
Fig. 4 shows the schematic diagram that the piece in the single carrier frequency domain equalization is handled;
Fig. 5 shows the schematic diagram according to the symbol estimation method of employing de-dot frequency domain linear equalization of the present invention;
Fig. 6 shows according to the schematic diagram of handling example that goes in the symbol estimation method of the present invention;
Fig. 7 shows according in the symbol estimation method of the present invention another and removes a schematic diagram of handling example; And
The performance that Fig. 8 shows the inventive method and conventional method compares.
Embodiment
Below with reference to Fig. 3 the applied system configuration of the present invention is described.
As example, the present invention has adopted the single-carrier system that has Cyclic Prefix, as shown in Figure 3, at transmitting terminal, at step S301, inserts Cyclic Prefix in sending signal, then at step S302, it is sent after forming filtering.
At step S303, the signal that sends will be through the influence (referring to document 3 and 4) of channel fading.When circulation prefix processing and FFT handle when combining, the balancing technique of frequency domain can obtain the complexity same low with ofdm system, close performance, identical reception and lower peak-to-average force ratio.
The single-carrier signal that has a Cyclic Prefix as shown in Figure 4, back P symbol of a data block has been added to the front of data block and formed Cyclic Prefix.
If the transmission symbol sebolic addressing in fft block is s=[s
1s
2S
N], the symbol numbers in the fft block is N, and the signal that is loaded with this transmission symbol arrives receiving terminal through channel fading, and wherein the order of channel fading is L, and in addition, establishing corresponding received signal is y, then
y＝h*s+n
Wherein * is the convolution algorithm symbol, and n represents white Gaussian noise.
Below with reference to Fig. 5 and 6 symbol estimation method according to the employing de-dot frequency domain linear equalization of first embodiment of the invention is described.
As shown in Figure 5.Send signal and arrive reception antenna through behind the channel fading.At first,, carry out contrary shaping filter, obtain sending the convolution signal of symbol and channel fading matrix receiving signal at step S501.At step S502, it is carried out Fourier transform, obtain being positioned at the signal on each frequency.
At receiving terminal, after y carries out Fourier transform to the received signal, then obtain frequency-region signal Y and be
Y＝HS+N
At step S503, on each frequency, channel is inverted respectively, promptly to the received signal Y of frequency domain
iDivided by the channel fading value of corresponding frequency, then obtained sending the estimated value of symbol respectively
At step S504, go a processing then.
The operation of going a processing among first embodiment as shown in Figure 6.At first at step S601, estimated snr then at step S602, is provided with the inverse that thresholding b is a signal to noise ratio.At step S603, frequency sequence number index is initialized as 1.Afterwards, at step S604, judge the size of channel fading value and b.If H
i＜b,, then at step S605, make the estimate symbol on this frequency
If H
i＞b, then the transmission sign estimation value on this frequency remains unchanged, promptly
At step S606, i is added 1 then,, judge whether that all frequencies all handle,, then get back to step 604 if be untreated at step S607.
At step S505, carry out inverse Fourier transform above-mentioned going after a processing all handles all frequencies, thereby obtain the sign estimation result of single-carrier system, last, at step S506, the symbol that estimates is carried out demodulation, thereby obtain the estimated value of each bit of this symbol.
Below with reference to Fig. 5 and 7 symbol estimation method according to the employing de-dot frequency domain linear equalization of second embodiment of the invention is described.
As shown in Figure 5.Send signal and arrive reception antenna, at first,, carry out contrary shaping filter to the received signal, obtain sending the convolution signal of symbol and channel fading matrix at step S501 through behind the channel fading.At step S502, it is carried out Fourier transform, obtain being positioned at the signal on each frequency.
At receiving terminal, after y carries out Fourier transform to the received signal, obtain frequency-region signal Y and be
Y＝HS+N
At step S503, on each frequency, channel is inverted respectively, promptly to the received signal Y of frequency domain
iDivided by the channel fading value of corresponding frequency, then obtained sending the estimated value of symbol respectively
At step S504, go a processing then.
The operation of going a processing among second embodiment as shown in Figure 7.At first at step S701, it is a fixed value that thresholding a is set, and this value can be tabled look-up or rule of thumb try to achieve.At step S702, frequency sequence number index is initialized as 1.Afterwards, at step S703, judge the size of channel fading value and a.If H
i＜a then at step S704, makes the transmission sign estimation value on this frequency
If H
i＞a, then the transmission sign estimation value on this frequency remains unchanged, promptly
At step S705, i is added 1 then,, judge whether that all frequencies all handle,, then get back to step 703 if be untreated at S706.
At step S505, carry out inverse Fourier transform above-mentioned going after a processing all handles all frequencies, thereby obtain the sign estimation result of single-carrier system, last, at step S506, the symbol that estimates is carried out demodulation, thereby obtain the estimated value of each bit of this symbol.
The present invention proposes a kind of symbol estimation method that in communication system, adopts de-dot frequency domain linear equalization.In single-carrier system, frequency domain linear equalization algorithm realizes that owing to having advantage simple, fast convergence rate is widely adopted.The present invention is based on the linear equalization algorithm and proposed to go a Processing Algorithm, it eliminates the distortion that the channel zero frequency is caused for whole fft block signal by removing frequency domain channel pairing frequency at zero point.
Simulated conditions of the present invention can adopt the 64QAM modulation, and fft block length is 512 symbols, and channel fading is Rayleigh fading, and the multipath number is 5, and noise is a white Gaussian noise, and simulation times is 800 times.Thus, simulation result as shown in Figure 8, Fig. 8 is the performance comparison diagram of comparing with traditional linear frequency domain equalization algorithm.As can be seen from Figure 8, the de-dot frequency equalization algorithm can improve about performance 1 ~ 2dB than traditional linear frequency territory equalization algorithm by simply going a processing.
Although below show the present invention in conjunction with the preferred embodiments of the present invention, one skilled in the art will appreciate that under the situation that does not break away from the spirit and scope of the present invention, can carry out various modifications, replacement and change to the present invention.Therefore, the present invention should not limited by the foregoing description, and should be limited by claims and equivalent thereof.
Claims (6)
1, a kind of symbol estimation method that in communication system, adopts de-dot frequency domain linear equalization, described method comprises step:
Obtain the frequency-region signal that is positioned at each frequency of received signal;
At described frequency-region signal, on each frequency, each channel is inverted respectively;
A processing is gone in described frequency-region signal execution, remove the low frequency of described frequency-region signal channel fading; And
To going the described frequency-region signal after the processing to carry out inverse Fourier transform, so that obtain the sign estimation that sends symbol.
2, method according to claim 1 is characterized in that the described step of obtaining the frequency-region signal that is positioned at each frequency of received signal comprises:
Carry out contrary shaping filter to received signal, to obtain the convolution signal that sends symbol and each channel fading vector; And
Described convolution signal is carried out Fourier transform, to obtain the frequency-region signal that is positioned at each frequency of received signal.
3, method according to claim 1, it is characterized in that comprising in the step of on each frequency each channel being inverted respectively: utilize described frequency-region signal to realize inverting to each channel divided by the channel fading value on each frequency at described frequency-region signal.
4, method according to claim 1 is characterized in that described described frequency-region signal is carried out go the step of a processing may further comprise the steps:
Estimate the received signal to noise ratio of communication system;
First thresholding is set, and described first thresholding is the inverse of described received signal to noise ratio;
Compare the channel fading value and first thresholding on each frequency successively;
If the channel fading value on the frequency is less than first thresholding, then the transmission sign estimation value on this frequency is set to zero; And
If the channel fading value less than first thresholding, then makes the transmission sign estimation value on this frequency remain unchanged.
5, method according to claim 1 is characterized in that described described frequency-region signal is carried out go the step of a processing may further comprise the steps:
Second thresholding is set, and described second thresholding is a fixed value;
Compare the channel fading value and second thresholding on each frequency successively;
If the channel fading value on the frequency is less than second thresholding, then the transmission sign estimation value on this frequency is set to zero; And
If the channel fading value less than second thresholding, then makes the transmission sign estimation value on this frequency remain unchanged.
6, method according to claim 1 is characterized in that described communication system is a carrier wave communication system.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105119857A (en) * | 2015-07-17 | 2015-12-02 | 电子科技大学 | Radar inter-station low-jitter anti-interference signal communication link technology |
| CN107113257A (en) * | 2015-01-30 | 2017-08-29 | 华为技术有限公司 | The method and apparatus of data processing |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107113257A (en) * | 2015-01-30 | 2017-08-29 | 华为技术有限公司 | The method and apparatus of data processing |
| CN107113257B (en) * | 2015-01-30 | 2020-07-10 | 南通数动互联科技有限公司 | Data processing method and device |
| CN105119857A (en) * | 2015-07-17 | 2015-12-02 | 电子科技大学 | Radar inter-station low-jitter anti-interference signal communication link technology |
| CN105119857B (en) * | 2015-07-17 | 2018-03-20 | 电子科技大学 | Low jitter, anti-jamming signal communication link technologies between a kind of radar station |
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