CN105119861A - BER improvement method of interleaved carrier index modulation N-order continuous OFDM system - Google Patents

Abstract

The invention belongs to the technical field of wireless communication, and relates to orthogonal frequency division multiplexing and interleaved carrier index modulation technology, N-order continuous interleaved carrier index modulation technology and related signal detection technology. A BER improvement method of an interleaved carrier index modulation N-order continuous OFDM system comprises: firstly carrying out interleaved subcarrier index modulation on a sending symbol after digital modulation, and carrying out N-order continuous processing on the obtained symbol to obtain an NC noise mean in the step; calculating an energy adjustment factor capable of keeping a ratio of signal sending power and noise power on various frequency points as a constant value through the noise mean, and multiplying sending data after ISIM modulation to finish the processing procedure. The method is used for inhibiting noise at positions with higher frequency points on both ends generated by NC processing, which not only effectively reduces the error rate of an NC-ISIM-OFDM system, but also achieves efficient out-of-band rejection of an NC-OFDM system, so that the spectral performance and the transmission efficiency of the system is improved relatively balanced. The method provided by the invention is used for effectively reducing the error rate of the NC-ISIM-OFDM system to improve the system performance.

Description

A kind of intertexture carrier index modulation N rank continuous ofdm system BER ameliorative way

Technical field

The invention belongs to wireless communication technology field, relate to OFDM (OrthogonalFrequencyDivisionMultiplexing), the modulation of intertexture carrier index (InterweaveSubcarrierIndexModulation, ISIM) technology, N rank continuous OFDM (NOrderContinuousOrthogonalFrequencyDivisionMultiplexing) technology and coherent signal detection technique.

Background technology

In the last few years, a kind of based on sub-carrier indices modulation (SubcarrierIndexModulation, SIM) OFDM technology is suggested as novel multi-carrier transmission scheme (SIM-OFDM), and the program can be regarded as the expansion of spatial modulation thought at frequency domain.The information bit of SIM-OFDM system comprises two parts, and a part is called " index bit ", for selecting the position activating subcarrier in sub-block; Another part is as " modulation bit ", and for being modulated into constellation point symbol and being sent by activation subcarrier selected above, remaining subcarrier does not send data.Compared with OFDM, the system configuration that SIM-OFDM is special, makes it have the ability of better anti-inter-carrier interference (Inter-CarrierInterface, ICI), and this point is verified in relevant research.A kind of transmitter schemes (hereinafter referred to as ISIM-OFDM) of intertexture SIM-OFDM system of improvement is suggested recently, by improving the mapping method of sub-carrier indices modulation, namely introducing carrier wave interleaving block makes between the subcarrier in each sub-block separate, which increase the minimum Eustachian distance between constellation point, thus improve systematic function.ISIM-OFDM system block diagram as shown in Figure 1.Compared with ofdm system and SIM-OFDM system, ISIM-OFDM system has better bit error rate performance.As a kind of multicarrier system, also there is the high-energy leakage problem brought by high secondary lobe in ISIM-OFDM.N-continuousOFDM (NC-OFDM) obtains the technology of efficient Sidelobe Suppression by making continuous print symbol become level and smooth, but under the noise effect that can produce in processing procedure due to N-continuous signal, loses a part of bit error rate performance.The system combined by NC-OFDM and ISIM-OFDM, as Fig. 2, can keep good Sidelobe Suppression effect, can obtain again than the low bit error rate performance of NC-OFDM.But generally, the error rate that causes of the combination of these two kinds of technology is still undesirable.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, propose a kind of intertexture carrier index modulation N rank continuous ofdm system BER ameliorative way.

Technical scheme of the present invention is:

At the transmitting terminal of system, first the modulation of intertexture sub-carrier indices is carried out to the transmission symbol after digital modulation, carry out N rank to the symbol obtained to process continuously, NC noise average is obtained in this step, go out can make each frequency sends by this noise mean value computation the energy adjusting factor that signal power and the ratio of noise power are definite value, the transmission data after modulating with ISIM have been multiplied processing procedure.This method makes the noise of the two ends higher-frequency point produced by NC process be suppressed, not only significantly reduce the error rate of NC-ISIM-OFDM system, and achieve the Out-of-band rejection of NC-OFDM system high efficiency, thus the spectral performance of the comparatively balanced system that improves and efficiency of transmission.

A kind of intertexture carrier index modulation N rank continuous ofdm system BER ameliorative way, comprises the steps:

S1, set system subcarrier number as K, index bit length is M, OFDM constellation point signal is X=[X ₀..., X _k-1] ^h, described signal X length is K, carries out n and selects the interleaving index of 1 to modulate, be divided into by described signal X described signal X individual sub-block, namely every n subcarrier forms a sub-block, selects 1 subcarrier in each sub-block to send data, obtains the frequency-region signal after ISIM modulation 2≤n≤K and n is even number;

S2, according to formula to modulating the ofdm signal obtained through ISIM carry out N-continuous process, wherein, I is unit matrix, P=Φ ^ha ^h(AA ^h) ^-1a Φ, $A=\left[\begin{array}{cccc}1& 1& ...& 1\\ k_0& k_1& ...& k_{K-1}\\ ...& ...& ...& ...\\ k_0^N& k_1^N& ...& k_{K-1}^N\end{array}\right],$ represent the OFDM symbol of input, the symbol obtained after representing i-th (-∞ < i <+∞) individual N continuous rank process, N represents the continuous exponent number between continuous OFDM symbol, k _urepresent the position that u subcarrier maps, u=0,1 ..., K-1;

S3, according to formula draw the noise that NC process produces, wherein, the symbol obtained after representing the i-th-1 N continuous rank process;

S4, make i=i+1, return step S3, until recycle time is n time, obtains the statistical average of noise ω square, obtain average $\stackrel{\&OverBar;}{\mathrm{\&omega;}}=({\mathrm{\&omega;}}_1+{\mathrm{\&omega;}}_2+...+{\mathrm{\&omega;}}_n)/n;$

S5, according to equation group $\left\{\begin{array}{c}\frac{|G_k{|}^2}{|\stackrel{\&OverBar;}{{\mathrm{\&omega;}}_k}{|}^2}\stackrel{\mathrm{\&Delta;}}{=}u\\ |G_1{|}^2+|G_2{|}^2+...+|G_K{|}^2=K\end{array}\right.$ Solve energy adjusting factor G _kunique solution wherein, k=1 ..., K represents the ordinal number of a kth subcarrier, and u is proportionality coefficient, ω _kfor the noise on a kth subcarrier;

S6, by described in S1 with G described in S5 _kbe multiplied, obtain input frequency domain signal

S7, according to formula by X described in S6 _newas new incoming symbol carry out N-continuous process, obtain the signal X ' with good Out-of-band rejection performance _new;

S8, subsequent step are the common process of ofdm system, specific as follows:

S81, by X ' described in S7 _newcarry out OFDM modulation to obtain sending signal, described OFDM modulation process comprises over-sampling, IFFT conversion, parallel-serial conversion and adds Cyclic Prefix;

S82, by S81 prime number send signal sent by transmitting antenna, described transmission signal arrives receiving terminal after Gaussian channel;

S83, carry out Cyclic Prefix, serioparallel exchange at receiving terminal by sending signal described in the S82 received, then transform to frequency domain through IFFT, then utilize ML to detect, draw and separate carrier wave index modulation and demodulation, recovery obtains message bit stream compared with original bit stream, and then calculates the error rate.

Further, n ∈ { 2,4,8} described in S1.

The invention has the beneficial effects as follows:

The present invention introduces an energy adjusting factor G at transmitting terminal between processing continuously in the modulation of intertexture sub-carrier indices and N rank, the noise of the higher-frequency point produced by NC process is suppressed, the method significantly reduces the error rate of NC-ISIM-OFDM system, thus improves the performance of system.

Accompanying drawing explanation

Fig. 1 is ISIM intertexture sub-carrier indices modulation schematic diagram.

Fig. 2 is NC-ISIM-OFDM system block diagram.

Fig. 3 the present invention is directed to the flow chart that NC-ISIM-OFDM system reduces error rate algorithm.

Embodiment

Below in conjunction with embodiment and accompanying drawing, describe technical scheme of the present invention in detail.

Present embodiment adopts Matlab2014a emulation platform to test.Experiment simulation optimum configurations is as follows: number of sub carrier wave K=256, sub-carrier configuration (L=2, J=1), signal madulation mode is QPSK, over-sampling multiple D=2, continuous print top step number V=4 between signal in N-continuous process, the signal in emulation is merely through Gaussian white noise channel, and detection algorithm is that ML detects.The present invention utilizes above-mentioned parameter to carry out experiment simulation on Matlab, this algorithm has more outstanding combination property: simulation result shows, at (L=2, under the environment of J=1), QPSK modulation, order of modulation V=4, institute's extracting method not only significantly reduces the error rate, realizes good Out-of-band rejection performance simultaneously.

A kind of intertexture carrier index modulation order continuous ofdm system BER ameliorative way, comprises the steps:

S1, set system subcarrier number as K, index bit length is M, OFDM constellation point signal is X=[X ₀..., X _k-1] ^h, described signal X length is K, carries out n and selects the interleaving index of 1 to modulate, be divided into by described signal X described signal X individual sub-block, namely every n subcarrier forms a sub-block, selects 1 subcarrier in each sub-block to send data, obtains the frequency-region signal after ISIM modulation n=4;

S2, according to formula to modulating the ofdm signal obtained through ISIM carry out N-continuous process, wherein, I is unit matrix, P=Φ ^ha ^h(AA ^h) ^-1a Φ, $A=\left[\begin{array}{cccc}1& 1& ...& 1\\ k_0& k_1& ...& k_{K-1}\\ ...& ...& ...& ...\\ k_0^N& k_1^N& ...& k_{K-1}^N\end{array}\right],$ represent the OFDM symbol of input, the symbol obtained after representing i-th (-∞ < i <+∞) individual N continuous rank process, N represents the continuous exponent number between continuous OFDM symbol, k _urepresent the position that u subcarrier maps, u=0,1 ..., K-1;

S3, according to formula draw the noise that NC process produces, wherein, the symbol obtained after representing the i-th-1 N continuous rank process;

S4, make i=i+1, return step S3, until recycle time is n time, obtains the statistical average of noise ω square, obtain average succinct for formulation, now omits the subscript i in above formula;

S5, according to equation group $\left\{\begin{array}{c}\frac{|G_k{|}^2}{|\stackrel{\&OverBar;}{{\mathrm{\&omega;}}_k}{|}^2}\stackrel{\mathrm{\&Delta;}}{=}u\\ |G_1{|}^2+|G_2{|}^2+...+|G_K{|}^2=K\end{array}\right.$ Solve energy adjusting factor G _kunique solution wherein, k=1 ..., K represents the ordinal number of a kth subcarrier, and u is proportionality coefficient, ω _kfor the noise on a kth subcarrier;

S6, by described in S1 with G described in S5 _kbe multiplied, obtain input frequency domain signal

S7, according to formula by X described in S6 _newas new incoming symbol carry out N-continuous process, obtain the signal X ' with good Out-of-band rejection performance _new;

S8, subsequent step are the common process of ofdm system, specific as follows:

S81, by X ' described in S7 _newcarry out OFDM modulation to obtain sending signal, described OFDM modulation process comprises over-sampling, IFFT conversion, parallel-serial conversion and adds Cyclic Prefix;

S82, by S81 prime number send signal sent by transmitting antenna, described transmission signal arrives receiving terminal after Gaussian channel;

S83, carry out Cyclic Prefix, serioparallel exchange at receiving terminal by sending signal described in the S82 received, then transform to frequency domain through IFFT, then utilize ML to detect, draw and separate carrier wave index modulation and demodulation, recovery obtains message bit stream compared with original bit stream, and then calculates the error rate.

Claims (2)

1. an intertexture carrier index modulation N rank continuous ofdm system BER ameliorative way, is characterized in that, comprise the steps:

S1, set system subcarrier number as K, index bit length is M, OFDM constellation point signal is X=[X ₀..., X _k-1] ^h, described signal X length is K, carries out n and selects the interleaving index of 1 to modulate, be divided into by described signal X described signal X individual sub-block, namely every n subcarrier forms a sub-block, selects 1 subcarrier in each sub-block to send data, obtains the frequency-region signal after ISIM modulation 2≤n≤K and n is even number;

S2, according to formula to modulating the ofdm signal obtained through ISIM carry out N-continuous process, wherein, I is unit matrix, P=Φ ^ha ^h(AA ^h) ^-1a Φ, $A=\left[\begin{array}{cccc}1& 1& ...& 1\\ k_0& k_1& ...& k_{K-1}\\ ...& ...& ...& ...\\ k_0^N& k_1^N& ...& k_{K-1}^N\end{array}\right],$ represent the OFDM symbol of input, the symbol obtained after representing i-th (-∞ < i <+∞) individual N continuous rank process, N represents the continuous exponent number between continuous OFDM symbol, k _urepresent the position that u subcarrier maps, u=0,1 ..., K-1;

S3, according to formula draw the noise that NC process produces, wherein, the symbol obtained after representing the i-th-1 N continuous rank process;

S4, make i=i+1, return step S3, until recycle time is n time, obtains the statistical average of noise ω square, obtain average $\stackrel{\&OverBar;}{\mathrm{\&omega;}}=({\mathrm{\&omega;}}_1+{\mathrm{\&omega;}}_2+...+{\mathrm{\&omega;}}_n)/n;$

S5, according to equation group $\left\{\begin{array}{c}\frac{|G_k{|}^2}{|\stackrel{\&OverBar;}{{\mathrm{\&omega;}}_k}{|}^2}\stackrel{\mathrm{\&Delta;}}{=}u\\ |G_1{|}^2+|G_2{|}^2+...+|G_K{|}^2=K\end{array}\right.$ Solve energy adjusting factor G _kunique solution wherein, k=1 ..., K represents the ordinal number of a kth subcarrier, and u is proportionality coefficient, ω _kfor the noise on a kth subcarrier;

S6, by described in S1 with G described in S5 _kbe multiplied, obtain input frequency domain signal

S7, according to formula by X described in S6 _newas new incoming symbol carry out N-continuous process, obtain the signal X ' with good Out-of-band rejection performance _new;

S8, subsequent step are the common process of ofdm system, specific as follows:

S81, by X ' described in S7 _newcarry out OFDM modulation to obtain sending signal, described OFDM modulation process comprises over-sampling, IFFT conversion, parallel-serial conversion and adds Cyclic Prefix;

S82, by S81 prime number send signal sent by transmitting antenna, described transmission signal arrives receiving terminal after Gaussian channel;

S83, carry out Cyclic Prefix, serioparallel exchange at receiving terminal by sending signal described in the S82 received, then transform to frequency domain through IFFT, then utilize ML to detect, draw and separate carrier wave index modulation and demodulation, recovery obtains message bit stream compared with original bit stream, and then calculates the error rate.

2. a kind of intertexture carrier index modulation N rank according to claim 1 continuous ofdm system BER ameliorative way, is characterized in that: n ∈ { 2,4,8} described in S1.