CN107454033B - Out-of-band rejection method for the continuous ofdm system of time domain N rank - Google Patents

Out-of-band rejection method for the continuous ofdm system of time domain N rank Download PDF

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CN107454033B
CN107454033B CN201710795520.XA CN201710795520A CN107454033B CN 107454033 B CN107454033 B CN 107454033B CN 201710795520 A CN201710795520 A CN 201710795520A CN 107454033 B CN107454033 B CN 107454033B
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precoding
time domain
domain
band
rank
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CN107454033A (en
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苑杰
但黎琳
肖悦
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University of Electronic Science and Technology of China
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University of Electronic Science and Technology of China
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/2605—Symbol extensions, e.g. Zero Tail, Unique Word [UW]
    • H04L27/2607—Cyclic extensions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03343—Arrangements at the transmitter end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H04L27/2628—Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Discrete Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)

Abstract

The invention belongs to wireless communication technology field, it is related to the time domain and frequency domain combined precoding adaptive approach for the continuous ofdm system of time domain N rank.Method of the invention is mainly in the off-line calculation stage, pass through the spectral leakage under calculated NC-OFDM system different rank, cooperate the preserved sub-carrier number of precoding it is adaptively selected go out most appropriate order of modulation and preserved sub-carrier number scheme, reach the demand for both meeting Out-of-band rejection, it is the scheme of high spectrum utilization efficiency and low complex degree simultaneously, to obtained in the continuous ofdm system of time domain N rank of low interference to neighbouring Sidelobe Suppression effect time domain and frequency domain combined precoding adaptive approach that is good, while being promoted on bit error rate performance.

Description

Out-of-band rejection method for the continuous ofdm system of time domain N rank
Technical field
The invention belongs to wireless communication technology fields, are related to orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing), the continuous orthogonal frequency division multiplexing of N rank (N Order Continuous Orthogonal Frequency Division Multiplexing) technology and precoding Out-of-band rejection technology (Precoding), specifically It is to be related to the time domain and frequency domain combined code self-adapting Out-of-band rejection method that prelists.
Background technique
In recent years, a kind of continuous (the N Order Continuous) OFDM technology of N rank is proposed as novel overloading Wave transmission plan, for inhibiting out-of-band power to reveal (hereinafter referred to as NC-OFDM).NC-OFDM technology is by promoting adjacent OFDM Intersymbol range value and phase value continuity, the discontinuous point between smooth adjacent OFDM symbol, greatly improve The spectrum leakage problem of ofdm system.But as a kind of technology inhibited by introducing smooth signal with outward leakage, NC- Ofdm system has been also subjected to the problem of smooth signal bring interference increases, error rate of system deteriorates.And according to theory deduction, The interference is in user's frequency range and non-uniform Distribution.NC-OFDM is accomplished into the new signal procesing in time domain technology of one of time domain, It is called the continuous OFDM of time domain N (Time-Domain N-continuous OFDM, TD-NC-OFDM), is not only able to inhibit overloading The spectrum leakage of wave signal, the advantage not having with some tradition NC-OFDM technologies also.The technology of this time domain NC passes through benefit With the inhomogeneities of smooth signal distributions, the noise being added to original symbol is effectively controlled by being suitably truncated Influence reduce Sidelobe Suppression to the shadow of bit error rate performance to simplify receiving end in the case where not reducing out-band performance It rings.
Precoding class method reaches the mesh for reducing spectrum leakage using having the frequency domain precoder of optimization function matrix 's.Precoding class method or the frequency band zero setting of frequency point will be fixed or will can be occupied by increase system on a small quantity as precoding Number of sub carrier wave, so such method can cause the loss of a small amount of message transmission rate.Certainly total number of sub carrier wave very When big, which can ignore.The advantage of precoding technique be the inhibitory effect in the neighbouring secondary lobe of symbol main lobe it is obvious that and In receiver signal directly by the way that pre-coding matrix is inverted directly to restore original signal, and this recovery is not have to the bit error rate It is influential.
Method for precoding is applied in the continuous OFDM method of time domain N, so that the inhibitory effect of preferable adjacent frequency band is obtained, But in the case where given optimization range and practical preserved sub-carrier number, it is unable to get an optimal parameters adjusting, from And reach the scheme that high spectrum efficiency and low complex degree are obtained in the case where realizing Out-of-band rejection.Thus propose time-frequency domain Combine the code self-adapting Out-of-band rejection method that prelists.
Summary of the invention
It is to be solved by this invention, aiming at the above problem, propose the TD-NC- of precoding technique and low interference OFDM technology combines, so that the significant Sidelobe Suppression ability of NC-OFDM technology bring can be obtained, while also benefiting from and prelisting Rejection ability and bit error rate gain of the code bring adjacent to secondary lobe, provide more balanced performance on the whole for system.This hair Bright method first carries out precoding to data subcarrier, then to the subcarrier after precoding calculate its N it is continuous required for it is low dry TD-NC-OFDM noise is disturbed, in subcarrier by mapping, IFFT transformation will be calculated before after adding a series of processing such as CP Noise is added on time domain transmission symbol and is sent.
The technical scheme is that
It is smooth after truncation in the continuous ofdm system of N rank for the Out-of-band rejection method of the continuous ofdm system of N rank Noise is integrated in the performance of effect and the bit error rate for Out-of-band rejection due to traditional continuous OFDM of N rank, but for The Sidelobe Suppression performance of adjacent frequency band is bad.In the preserved sub-carrier number R given pre-coding matrixmaxUnder target band Out-of-band rejection target E to be achievedaimIn the case where, it prelists code self-adapting with combining and reaches high spectrum utilization and low The property regulation of complexity.Fig. 1 is the transmitting terminal block diagram of whole system.This time domain and frequency domain combined code self-adapting Out-of-band rejection that prelists Method the following steps are included:
S1, pre-coding matrix P is calculated according to subcarrier maps position, initial precoding preserved sub-carrier number is Rbeg:
To acquire the data subcarrier after precoding are as follows:The spectral leakage for calculating target band is
fsIt is entire frequency band,It is the frequency point of target band.
E is worked as in S2, judgementd>EaimWhen, enable R=Rbeg+ 2, repeat S1 step；
E is worked as in judgementd<EaimWhen, continue to execute S3 step downwards；
S3, by the subcarrier after precodingBe mapped on entire symbol, the subcarrier after mapping is carried out IFFT is to time domain, in addition cyclic prefix, the time-domain expression for obtaining OFDM symbol is xi；
S4, according to data subcarrier diIt calculates and reveals E in the frequency band that continuous order is Nx(n), it and calculates and target frequency Difference △ E with leakage:
△ E=| Ex(n)-Eaim|
And choose the continuous order n=argmin of time-domain symbol { △ E }, n ∈ { 2,4,6,8,10 }
△ E (n) < 0 is worked as in S5, judgement, continues to execute S6 step；When △ E (n) > 0, returns to and execute S2 step；
S6, the smooth noise signal acquired is added to composition transmission signal on the time-domain signal of precodingIt sends.
Smooth signal is acquired by the TD-NC-OFDM of low interference
It is the basic matrix in the TD-NC-OFDM method of low interference,P2It is relevant parameter type matrix.
Smooth signal is added on time-domain signalIt sends.
Beneficial effects of the present invention are, in the preserved sub-carrier number R given pre-coding matrixmaxUnder target band Out-of-band rejection target E to be achievedaimIn the case where, make spectral efficient and low complex degree by adaptively having acquired Scheme, relative to precoding algorithms, method of the invention significantly reduces the platform of Sidelobe Suppression, relative to low interference TD-NC-OFDM algorithm, the present invention effectively improve the Out-of-band rejection performance of neighbouring secondary lobe, and the gain on BER.
Detailed description of the invention
Fig. 1 is time domain and frequency domain combined precoding adaptive approach transmitter block diagram；
Fig. 2 is that time domain and frequency domain combined precoding adaptive approach is schemed in Out-of-band rejection performance PSD；
Fig. 3 is that the invention of this hair and the bit error rate of traditional algorithm compare under EVA channel.
Specific embodiment
Technical solution of the present invention has been described in detail in Summary, has been said below by emulation experiment The authenticity of bright effect of the present invention:
It is tested using Matlab2014a emulation platform.Experiment simulation parameter setting is as follows: number of sub carrier wave K= Continuous order Adaptive Modulation obtains N between signal in 256, signal modulation mode 16QAM, NC processing when being 4, in emulation Signal passes through EVA channel.The present invention carries out experiment simulation using above-mentioned parameter on Matlab, and this method has more outstanding comprehensive Close performance: by Fig. 2 it can be seen that Out-of-band rejection performance, when it is CP length that length, which is truncated, neighbouring secondary lobe when R=8 Inhibitory effect is optimal, and the performance of this method bit error rate is better than the bit error rate performance of TD-NC-OFDM as seen from Figure 3；Mentioned side Method bit error rate ratio TD-NC-OFDM after SNR=30dB is significantly reduced.Shown in following analogous diagram, mentioned method can be adaptive It adjusts to realize the performance of preferable Out-of-band rejection performance and the bit error rate.

Claims (1)

1. being used for the Out-of-band rejection method of the continuous ofdm system of time domain N rank, this method is used for given the pre- of pre-coding matrix Stay number of sub carrier wave RmaxWith the Out-of-band rejection target E to be achieved under target bandaimIn the case where, certainly with joint precoding It adapts to reach the property regulation of high spectrum utilization and low complex degree；Characterized by comprising the following steps:
S1, pre-coding matrix P is calculated according to subcarrier maps position, if initial precoding preserved sub-carrier number is Rbeg, from And acquire the data subcarrier after precoding are as follows:Calculate the spectral leakage of target band are as follows:
fsIt is entire frequency band,It is the frequency point of target band, NCPFor cyclic prefix symbolic number；
E is worked as in S2, judgementd>EaimWhen, enable R=Rbeg+ 2, repeat S1 step；
E is worked as in judgementd<EaimWhen, continue to execute S3 step downwards；
S3, by the subcarrier after precodingBe mapped on entire symbol, IFFT is carried out to the subcarrier after mapping and is arrived Time domain, in addition cyclic prefix, the time-domain expression for obtaining OFDM symbol is xi；
S4, according to data subcarrier diIt calculates and reveals E in the frequency band that continuous order is nx(n), it and calculates and is let out with target band The difference △ E of dew:
△ E=| Ex(n)-Eaim|
And choose the continuous order n=argmin of time-domain symbol { △ E }, n ∈ { 2,4,6,8,10 }
△ E (n) < 0 is worked as in S5, judgement, into S6 step；When △ E (n) > 0, step S2 is returned to；
S6, the smooth noise signal acquired is added to composition transmission signal on the time-domain signal of precodingIt sends:
Smooth signal is acquired by the TD-NC-OFDM method of low interference
It is the basic matrix in the TD-NC-OFDM method of low interference,V=n, P2It is relevant parameter type matrix:
The smooth noise signal acquired is added to constitute on the time-domain signal of precoding and sends signal
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Citations (4)

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Publication number Priority date Publication date Assignee Title
CN104022983A (en) * 2014-05-09 2014-09-03 国家电网公司 CPE inhibition method in OFDM system
CN105049386A (en) * 2015-05-26 2015-11-11 浙江大学 Active interference elimination method in UFMC system
CN105119861A (en) * 2015-08-31 2015-12-02 电子科技大学 BER improvement method of interleaved carrier index modulation N-order continuous OFDM system
CN106789806A (en) * 2016-11-24 2017-05-31 哈尔滨工业大学 WFRFT mixed carrier system out-of-band power suppressing methods based on frequency domain precoding

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Publication number Priority date Publication date Assignee Title
CN104022983A (en) * 2014-05-09 2014-09-03 国家电网公司 CPE inhibition method in OFDM system
CN105049386A (en) * 2015-05-26 2015-11-11 浙江大学 Active interference elimination method in UFMC system
CN105119861A (en) * 2015-08-31 2015-12-02 电子科技大学 BER improvement method of interleaved carrier index modulation N-order continuous OFDM system
CN106789806A (en) * 2016-11-24 2017-05-31 哈尔滨工业大学 WFRFT mixed carrier system out-of-band power suppressing methods based on frequency domain precoding

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