CN101848480A - Signal-to-interference ratio decision method in actual ICI (Inter-Carrier Interference) elimination of high-mobility OFDM (Orthogonal Frequency Division Multiplexing) cooperative system - Google Patents

Abstract

The invention discloses a signal-to-interference ratio decision method in actual ICI (Inter-Carrier Interference) elimination of a high-mobility OFDM (Orthogonal Frequency Division Multiplexing) cooperative system, which comprises the following steps of: (1) establishing a signal-to-interference ratio model of the capacity of the cooperative system, and analyzing the influence degree of the signal-to-interference ratio on the capacity of the system; (2) determining a value get method of the signal-to-interference ratio of the cooperative method according to a direct channel and the channel characteristics of the cooperative system; (3) calculating a signal-to-interference ratio range which can satisfy system performance requirements according to the signal-to-interference ratio model of the capacity of the cooperative system and the value get method of the signal-to-interference ratio; and (4) determining the elimination process of an elimination algorithm and evaluating the algorithm performance of the elimination algorithm according to the threshold of the signal-to-interference ratio. The method effectively solves the problem of the evaluation on elimination effect during the actual ICI elimination process by using the scheme of evaluating system performance by the signal-to-interference ratio, and the method greatly reduces calculation on the premise of having the same effect with a bit error index measurement elimination algorithm.

Description

Signal interference ratio determination methods in the actual elimination of high-speed mobile OFDM cooperative system ICI

Technical field

The present invention relates to the signal processing method in the radio communication, particularly relate to the signal interference ratio determination methods of interference eliminated between a kind of OFDM cooperative system subcarrier.

Background technology

According to the medium-term and long-term development plan of Chinese Railway, to the year two thousand twenty, the high speed railway construction mileage of 200 kilometers in China and above speed per hour will will account for the over half of world's high speed total kilometrage above 1.8 ten thousand kilometers.So the research that with the high-speed railway is the ground ultrahigh speed mobility system of broadband wireless communication of representative more and more is subjected to people's attention.Since ofdm system have availability of frequency spectrum height, can effective anti-intersymbol interference advantages such as (ISI), make the OFDM broadband system can be used as the alternative of high-speed mobile communication system.For ofdm system, become the influence of factor when channel Doppler frequency shift, transmitting-receiving carrier wave frequency deviation (CFO), oscillator phase etc., can cause between subcarrier orthogonality to be destroyed, produce the interference (ICI) between subcarrier, under high-speed mobile environment, Doppler frequency shift is directly proportional with the speed of moving body, becomes the key factor that influences systematic function under the high-speed mobile environment.And bullet train is in order to adapt to the requirement of high-speed cruising, aspect sealing and the compartment material very big variation is being arranged all, increased the loss of wireless signal, make up the communication for coordination system for this reason, reduce the influence of car body to wireless signal loss as far as possible, obtain simultaneously the collaboration diversity gain again, and high-speed railway moves when ofdm system ICI eliminates and has following factor to exist: (1) Doppler frequency shift constantly changes along with the speed of service of train changes, so ICI also is continuous variation; (2) channel estimating, Doppler estimate it is that error is arranged certainly; (3) removing method of ICI is because factors such as multipath also are impossible eliminate ICI fully.The ICI elimination algorithm of research is a lot of at present, Kim Byung-Chul, the ICI elimination algorithm that utilizes Doppler's diversity of Lu I-Tai design, the unifrequency backoff algorithm, combined estimation method, the balancing technique algorithm, these methods are eliminated the back error performance and are improved, but the difficulty in computation of the error rate is big in actual the elimination, and is difficult to know the elimination degree.

Summary of the invention

Problem and shortage in view of above prior art existence, the object of the present invention is to provide the signal interference ratio determination methods in the actual elimination of a kind of high-speed mobile OFDM cooperative system ICI, this method has been simplified calculating greatly under the prerequisite that the effect with error rate index measurement elimination algorithm is equal to, solved and eliminated the Evaluation on effect problem in the actual ICI elimination process.

In order to achieve the above object, the present invention has adopted with following technical proposals:

Signal interference ratio determination methods in the actual elimination of a kind of ICI, its step comprises as follows:

(1) sets up the signal interference ratio model of cooperative system capacity, analyze the influence degree of signal interference ratio power system capacity;

(2), determine the obtaining value method of cooperative system signal interference ratio according to the characteristic of channel of cooperative system direct channels and cooperative system;

(3), calculate and satisfy the signal interference ratio scope that systematic function requires according to the signal interference ratio model and the signal interference ratio obtaining value method of cooperative system capacity;

(4), determine the elimination process of elimination algorithm, and estimate the elimination performance of elimination algorithm according to the thresholding of signal interference ratio.

The signal interference ratio of setting up cooperative system described in the above-mentioned steps (1) is expressed as:

$\mathrm{SIR}=\frac{E\left\{\frac{{\sin }^2\left(\mathrm{\π\ϵ}\right)}{\mathrm{si}{n}^2\left(\frac{\mathrm{\π\ϵ}}{N}\right)}\right\}}{\underset{k=0,k\≠m}{\overset{N-1}{\mathrm{\Σ}}}E\left\{\frac{{\sin }^2\mathrm{\π}(k-m+\mathrm{\ϵ})}{{\sin }^2\mathrm{\π}\left(\frac{k-m+\mathrm{\ϵ}}{N}\right)}\right\}}$

Wherein N is a sub-carrier number, and ε is the normalization frequency deviation of relative subcarrier spacing, and k, m are the subcarrier sequence numbers, and k-m refers to the spacing of k bar and m bar subcarrier, and E{} represents the peek term of the content in the bracket is hoped.

The wide B of being of the regiment commander that sets up departments, the capacity when not existing ICI to disturb in the system is

Wherein S is a signal power, N ₀Be noise power, and when existing ICI to disturb, signal is write as S=S ₀+ S _ICI, S wherein ₀Be useful signal part, S _ICIBe the ICI interference sections.This moment, the signal interference ratio SIR of system was:

The channel capacity that obtains this moment is:

$C_I=B{\log }_2(1+\frac{S_0}{S_{\mathrm{ICI}}+N_0})$

$={B\log }_2(1+\frac{\frac{\mathrm{SIR}}{\mathrm{SIR}+1}\mathrm{SNR}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HSA00000114822100032.png,HSA00000114822100041.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}{\frac{1}{\mathrm{SIR}+1}\mathrm{SNR}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HSA00000114822100032.png,HSA00000114822100041.png"\; state="\{\{state\}\}">N</figure-callout>}}_0+N_0})$

$=B{\log }_2(1+\mathrm{SNR}-\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})$

Therefore the signal interference ratio model that obtains power system capacity is:

$\frac{{\mathrm{<figure-callout\; id="0"\; label="C\; I\; C"\; filenames="HSA00000114822100032.png,HSA00000114822100041.png"\; state="\{\{state\}\}">C</figure-callout>}}_I}{C_{}}=\frac{{\log }_2(1+\mathrm{SNR}-\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})}{{\log }_2(1+\mathrm{SNR})}$

Here C _I/ C ₀Be capacity that has the ICI interference and the ratio that does not have the capacity of ICI interference.

The signal interference ratio SINR1 and the SINR2 of direct channels and co-channel were respectively when above-mentioned steps (2) sub-carriers number was big:

$\mathrm{SINR}1=\frac{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)}}{(1-\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)})+\frac{1}{a_1}\&CenterDot;\frac{1}{{\mathrm{SNR}}_1}}$

$\mathrm{SINR}2=\frac{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)}}{(1-\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)})+\frac{1}{a_2}\&CenterDot;\frac{1}{{\mathrm{SNR}}_2}}$

Wherein SNR1 and SNR2 are respectively the signal to noise ratio of direct channels and co-channel, a ₁And a ₂Be respectively the pad value of direct channels and co-channel.By emulation as can be seen under identical signal interference ratio situation, the Capacity Ratio direct channel of collaborative passage much higher.Therefore cooperative system signal interference ratio value can be carried out from collaborative passage.

C in the above-mentioned steps (3) _I/ C ₀Increase with signal interference ratio SIR increases, but its rate of change diminishes gradually, and the definition rate of change is Cv, then can push away by the signal interference ratio model:

$\mathrm{Cv}=\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\ln 2\&CenterDot;{\log }_2(1+\mathrm{SNR})}\&CenterDot;\frac{1}{(1+\mathrm{SNR}-\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})\&CenterDot;{(\mathrm{SNR}+\mathrm{SIR}+1)}^2}$

To different signal to noise ratios, the variation of Cv all diminishes gradually along with the increase of signal interference ratio, that is to say C _I/ C ₀Increase with signal interference ratio SIR is fewer and feweri, but the transformation rate difference of the different Cv of signal to noise ratio, therefore can determine the scope of signal interference ratio according to different signal to noise ratios.

According to the thresholding of signal interference ratio, determine the elimination process of elimination algorithm in the above-mentioned steps (4), and estimate the elimination performance of elimination algorithm.The signal of cooperative system purpose user and collaborative point can be expressed as:

$Y_{\mathrm{sd}}\left(k\right)=H_{\mathrm{sd}}\left(k\right)V\left(k\right)S\left(0\right)+\underset{l=0,l\&NotEqual;k}{\overset{N-1}{\mathrm{\&Sigma;}}}{H}_{\mathrm{sd}}\left(l\right)V\left(l\right)S(l-k)+n_{\mathrm{sd}}\left(k\right)$

H wherein _Sd(k) be the channel gain of source node S and destination node D, n _SdIt is noise.First of following formula is useful signal, and second is because the distracter of the ICI that Doppler frequency shift produces passes through estimated signal V (k) for following formula, thereby can calculates the signal interference ratio of system easily.Promptly just can obtain the transmission performance of its system by the signal interference ratio of judging system.

Signal interference ratio determination methods in the actual elimination of ICI of the present invention has the following advantages compared with prior art: this method is after the relation of research signal interference ratio and Doppler frequency shift, set up the signal interference ratio model of ICI to the channel capacity influence, on this basis, in conjunction with high-speed mobile OFDM cooperative system model and channel selection algorithm, signal interference ratio model and signal interference ratio obtaining value method according to the cooperative system capacity, the signal interference ratio scope that systematic function requires is satisfied in calculating, show by emulation, this signal interference ratio determination methods and error rate index are weighed the elimination algorithm effect and are equal to, and in actual elimination process, its easier calculating has solved and has eliminated the Evaluation on effect problem in the actual ICI elimination process.

Description of drawings

Fig. 1 is the flow chart of the signal interference ratio evaluation method in the actual elimination of ICI of the present invention;

Fig. 2 is the analogous diagram that 1024 o'clock signal interference ratios change with relative frequency deviation for sub-carrier number;

C when Fig. 3 is respectively 10dB, 20dB, 30dB for signal to noise ratio _I/ C ₀Analogous diagram with signal interference ratio (dB) relation;

Fig. 4 is the mode figure of cooperative system;

The capacity comparison analogous diagram of cooperative system direct channel and collaborative passage when Fig. 5 is 10dB, 20dB, 50dB, 100dB respectively for signal to noise ratio;

C when Fig. 6 is respectively 10dB, 20dB, 30dB for signal to noise ratio _I/ C ₀Rate of change Cv and the analogous diagram of signal interference ratio (dB) relation;

Fig. 7 is respectively 10dB, 20dB, 30dB for signal to noise ratio, the analogous diagram of the Cv of correspondence when signal interference ratio changes from 40dB to 50dB;

The analogous diagram of relative frequency deviation and bit error rate relation when Fig. 8 is respectively 10dB, 20dB, 30dB for signal to noise ratio.

Embodiment

Below in conjunction with accompanying drawing embodiments of the invention are described in further detail.

As shown in Figure 1, the signal interference ratio evaluation method in the actual elimination of ICI, its concrete steps are as follows:

(1) sets up the signal interference ratio model of cooperative system capacity, analyze the influence degree of signal interference ratio: suppose that Y (m), X (m) are the output and the input signal of ofdm system to power system capacity, H (m) is a channel transfer function, and W (m) is an additive noise, and then the signal of receiving terminal can be expressed as:

$Y\left(m\right)=H\left(m\right)X\left(m\right)S\left(0\right)+\underset{k=0,k\&NotEqual;m}{\overset{N-1}{\mathrm{\&Sigma;}}}H\left(k\right)X\left(k\right)S(k-m)+W\left(m\right)$

Wherein

$S(k-m)=\frac{\sin \mathrm{\&pi;}(k-m+\mathrm{\&epsiv;})}{N\sin \frac{\mathrm{\&pi;}}{N}(k-m+\mathrm{\&epsiv;})}\exp \left[\mathrm{j\&pi;}(1-\frac{1}{N})(k-m+\mathrm{\&epsiv;})\right]$

$S\left(0\right)=\frac{\sin \mathrm{\&pi;\&epsiv;}}{N\sin \frac{\mathrm{\&pi;\&epsiv;}}{N}}\exp \left[\mathrm{j\&pi;}(1-\frac{1}{N})\mathrm{\&epsiv;}\right]$

First of formula is the useful signal item, and second is the interference signal item, and N is a sub-carrier number, and ε is the normalization frequency deviation of relative subcarrier spacing, and k, m are the subcarrier sequence numbers, and k-m refers to the spacing of k bar and m bar subcarrier.Then when sub-carrier number was big, signal interference ratio SIR can be expressed as:

$\mathrm{SIR}=\frac{E\left\{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{\mathrm{si}{n}^2\left(\frac{\mathrm{\&pi;\&epsiv;}}{N}\right)}\right\}}{\underset{k=0,k\&NotEqual;m}{\overset{N-1}{\mathrm{\&Sigma;}}}E\left\{\frac{{\sin }^2\mathrm{\&pi;}(k-m+\mathrm{\&epsiv;})}{{\sin }^2\mathrm{\&pi;}\left(\frac{k-m+\mathrm{\&epsiv;}}{N}\right)}\right\}}$

If the OFDM symbol period is with the 4 μ s of 802.11e, the highest running speed of bullet train was with 500km/ hour, carrier frequency is that 2.4GHz is an example, its normalization Doppler frequency deviation is about 0.004, thus Fig. 2 emulation ε get 0.001 to 0.01 change curve, as can be seen from the figure, increase along with ε, the signal interference ratio of system descends rapidly, the variation of signal interference ratio reaction Doppler frequency deviation, and corresponding one by one.

Suppose channel capacity:

Do not exist this moment ICI to disturb in the system, signal to noise ratio is Then when existing ICI to disturb in the system, signal can be write as S=S ₀+ S _ICI, S wherein ₀Be useful signal part, S _ICIBe the ICI interference sections.This moment, the signal interference ratio SIR of system was:

The channel capacity that can obtain this moment is:

$C_I=B{\log }_2(1+\frac{S_0}{S_{\mathrm{ICI}}+N_0})$

$={B\log }_2(1+\frac{\frac{\mathrm{SIR}}{\mathrm{SIR}+1}\mathrm{SNR}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HSA00000114822100032.png,HSA00000114822100041.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}{\frac{1}{\mathrm{SIR}+1}\mathrm{SNR}\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HSA00000114822100032.png,HSA00000114822100041.png"\; state="\{\{state\}\}">N</figure-callout>}}_0+N_0})$

$=B{\log }_2(1+\mathrm{SNR}-\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})$

So have the capacity of ICI interference and do not exist the ratio of the capacity of ICI interference to be:

Definition C _I/ C ₀Be the signal interference ratio model of channel capacity, expression ICI is to the influence degree of system, C _I/ C ₀Be 1, expression does not have influence to system, C _I/ C ₀The serious more Fig. 3 of more little influence has simulated signal to noise ratio C when being respectively 10dB, 20dB, 30dB _I/ C ₀With the relation of signal interference ratio, as can be seen from Figure 3 SIR is more little, C _I/ C ₀More little, under the identical SIR, the big more C of SNR _I/ C ₀More little, it is more little to illustrate that interchannel noise disturbs, and the ICI influence is just big more.For example if as can be seen from Figure 2 ε=0.004, SIR also is about 43dB, according to Fig. 3 when the SNR=30dB, C _I/ C ₀≈ 0.993, and promptly channel capacity drops to originally 99.3%, and reflection ICI disturbs the influence degree to broadband system.

(2), determine that cooperative system mode that the obtaining value method of cooperative system signal interference ratio: this paper sets up as shown in Figure 4 according to the characteristic of channel of cooperative system direct channels and cooperative system.User among the figure is the portable terminal in the compartment, and collaborative partner is the collaborative point that is provided with.In the transfer of data, collaborative point and terminal are made high-speed mobile like this, and collaborative point does not have high-speed mobile with terminal room, and is static relatively.The signal of direct channel can produce big loss when passing the compartment, calculate sub-carrier number when big the signal interference ratio SINR1 and the SINR2 of direct channels and co-channel be respectively:

$\mathrm{SINR}1=\frac{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)}}{(1-\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)})+\frac{1}{a_1}\&CenterDot;\frac{1}{{\mathrm{SNR}}_1}}$

$\mathrm{SINR}2=\frac{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)}}{(1-\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)})+\frac{1}{a_2}\&CenterDot;\frac{1}{{\mathrm{SNR}}_2}}$

A in the formula ₁, a ₂Be the transmission factor of direct channels and co-channel, SNR ₁, SNR ₂Be the signal to noise ratio of direct channels and co-channel, Fig. 5 has simulated under the different signal to noise ratios, the relation of signal interference ratio and channel capacity when adopting collaborative passage and adopting direct channel.As seen from Figure 5 under identical signal interference ratio situation, the Capacity Ratio direct channel of collaborative passage much higher.Therefore cooperative system signal interference ratio value can be carried out from collaborative passage.

(3), calculate and satisfy the signal interference ratio scope that systematic function requires: C according to the signal interference ratio model and the signal interference ratio obtaining value method of cooperative system capacity _I/ C ₀Increase with signal interference ratio SIR increases, but its rate of change diminishes gradually, and the definition rate of change is Cv, then can push away by the signal interference ratio model:

$\mathrm{Cv}=\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\ln 2\&CenterDot;{\log }_2(1+\mathrm{SNR})}\&CenterDot;\frac{1}{(1+\mathrm{SNR}-\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})\&CenterDot;{(\mathrm{SNR}+\mathrm{SIR}+1)}^2}$

Fig. 6 has simulated the relation of Cv and signal interference ratio, and as can be seen from the figure, to different signal to noise ratios, the variation of Cv all diminishes gradually along with the increase of signal interference ratio, that is to say C _I/ C ₀Increase with signal interference ratio SIR is fewer and feweri, but the transformation rate difference of the different Cv of signal to noise ratio, therefore can determine the scope of signal interference ratio according to different signal to noise ratios.Signal interference ratio is amplified its corresponding Cv of back as shown in Figure 7 from 40dB to 50dB, as can be seen if signal to noise ratio is 20dB, signal interference ratio greater than 48dB after, the variation of Cv is very little, promptly systematic function changes very little.Therefore we can be provided with the signal interference ratio value according to system's specific requirement, as the condition of convergence of elimination algorithm, can estimate the elimination effect of judging elimination algorithm simultaneously.

(4) according to the thresholding of signal interference ratio, determine the elimination process of elimination algorithm, and estimate the elimination performance of elimination algorithm: for system shown in Figure 4, the signal of purpose user and collaborative point can be expressed as:

$Y_{\mathrm{sd}}\left(k\right)=H_{\mathrm{sd}}\left(k\right)V\left(k\right)S\left(0\right)+\underset{l=0,l\&NotEqual;k}{\overset{N-1}{\mathrm{\&Sigma;}}}{H}_{\mathrm{sd}}\left(l\right)V\left(l\right)S(l-k)+n_{\mathrm{sd}}\left(k\right)$

H wherein _Sd(k) be the channel gain of source node S and destination node D, n _SdIt is noise.First of following formula is useful signal, and second is because the distracter of the ICI that Doppler frequency shift produces passes through estimated signal V (k) for following formula, thereby can calculates the signal interference ratio of system.Therefore, this paper has proposed the signal interference ratio determination methods that system ICI eliminates, and promptly just can obtain the transmission performance of its system by the signal interference ratio of judging system.Fig. 8 has simulated the relation curve of the error rate and frequency deviation when signal to noise ratio is respectively 10dB, 20dB, 30dB, is that 20dB, the error rate are 10 with the signal to noise ratio ^-4Be example, the frequency deviation of this moment is about 0.002, is 0.002 o'clock according to Fig. 1 frequency deviation, and its corresponding signal interference ratio is about 48dB, i.e. signal interference ratio determination methods and error rate index measurement elimination algorithm effect is equal to.Therefore we can determine that the value of signal interference ratio judges systematic function according to different channel characteristics.

In sum, signal interference ratio determination methods in the actual elimination of high-speed mobile OFDM cooperative system ICI provided by the invention and error rate index are weighed the elimination algorithm effect and are equal to, and in actual elimination process, its easier calculating has solved and has eliminated the Evaluation on effect problem in the actual ICI elimination process.

Claims (5)

1. the signal interference ratio determination methods that a high-speed mobile OFDM cooperative system ICI is actual in eliminating, it is as follows to it is characterized in that operating procedure comprises:

(1) sets up the signal interference ratio model of cooperative system capacity, analyze the influence degree of signal interference ratio power system capacity;

(2), determine the obtaining value method of cooperative system signal interference ratio according to the characteristic of channel of cooperative system direct channels and cooperative system;

(3), calculate and satisfy the signal interference ratio thresholding that systematic function requires according to the signal interference ratio model and the signal interference ratio obtaining value method of cooperative system capacity;

(4), determine the elimination process of elimination algorithm, and estimate the elimination performance of elimination algorithm according to the thresholding of signal interference ratio.

2. the signal interference ratio determination methods in the actual elimination of high-speed mobile OFDM cooperative system ICI according to claim 1 is characterized in that the signal interference ratio of setting up cooperative system in the described step (1) is expressed as:

$\mathrm{SIR}=\frac{E\left\{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{{\sin }^2\left(\frac{\mathrm{\&pi;\&epsiv;}}{N}\right)}\right\}}{\underset{k=0,k\&NotEqual;m}{\overset{N-1}{\mathrm{\&Sigma;}}}E\left\{\frac{{\sin }^2\mathrm{\&pi;}(k-m+\mathrm{\&epsiv;})}{{\sin }^2\mathrm{\&pi;}\left(\frac{k-m+\mathrm{\&epsiv;}}{N}\right)}\right\}}$

Wherein N is a sub-carrier number, and ε is the normalization frequency deviation of relative subcarrier spacing, and k, m are the subcarrier sequence numbers, and k-m refers to the spacing of k bar and m bar subcarrier, and E{} represents the peek term of the content in the bracket is hoped.

The wide B of being of the regiment commander that sets up departments, the capacity when not existing ICI to disturb in the system is

Wherein S is a signal power, N ₀Be noise power, and when existing ICI to disturb, signal is write as S=S ₀+ S _ICI, S wherein ₀Be useful signal part, S _ICIBe the ICI interference sections.This moment, the signal interference ratio SIR of system was:

The channel capacity that obtains this moment is:

$C_I={B\log }_2(1+\frac{S_0}{S_{\mathrm{ICI}}+N_0})$

$={B\log }_2(1+\frac{\frac{\mathrm{SIR}}{\mathrm{SIR}+1}\mathrm{SNR}\&CenterDot;N_0}{\frac{1}{\mathrm{SIR}+1}\mathrm{SNR}\&CenterDot;N_0+N_0})$

$={B\log }_2(1+\mathrm{SNR}-\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})$

Therefore the signal interference ratio model that obtains power system capacity is:

$\frac{C_I}{C_0}=\frac{{\log }_2(1+\mathrm{SNR}-\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})}{{\log }_2(1+\mathrm{SNR})}$

Here C _I/ C ₀Be capacity that has the ICI interference and the ratio that does not have the capacity of ICI interference.

3. the signal interference ratio determination methods that high-speed mobile OFDM cooperative system ICI according to claim 2 is actual in eliminating is characterized in that the signal interference ratio SINR1 and the SINR2 of direct channels and co-channel was respectively when described step (2) sub-carriers number was big:

$\mathrm{SINR}1=\frac{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)}}{(1-\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)})+\frac{1}{a_1}\&CenterDot;\frac{1}{{\mathrm{SNR}}_1}}$

$\mathrm{SINR}2=\frac{\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)}}{(1-\frac{{\sin }^2\left(\mathrm{\&pi;\&epsiv;}\right)}{N^2{\sin }^2(\mathrm{\&pi;\&epsiv;}/N)})+\frac{1}{a_2}\&CenterDot;\frac{1}{{\mathrm{SNR}}_2}}$

Wherein SNR1 and SNR2 are respectively the signal to noise ratio of direct channels and co-channel, a ₁And a ₂Be respectively the pad value of direct channels and co-channel.By emulation as can be seen under identical signal interference ratio situation, the Capacity Ratio direct channel of collaborative passage much higher.Therefore cooperative system signal interference ratio value can be carried out from collaborative passage.

4. the signal interference ratio determination methods in the actual elimination of high-speed mobile OFDM cooperative system ICI according to claim 3 is characterized in that the C in the described step (3) _I/ C ₀Increase with signal interference ratio SIR increases, but its rate of change diminishes gradually, and the definition rate of change is Cv, then can push away by the signal interference ratio model:

$\mathrm{Cv}=\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\ln 2\&CenterDot;{\log }_2(1+\mathrm{SNR})}\&CenterDot;\frac{1}{(1+\mathrm{SNR}-\frac{{\mathrm{SNR}}^2+\mathrm{SNR}}{\mathrm{SNR}+\mathrm{SIR}+1})\&CenterDot;{(\mathrm{SNR}+\mathrm{SIR}+1)}^2}$

To different signal to noise ratios, the variation of Cv all diminishes gradually along with the increase of signal interference ratio, that is to say C _I/ C ₀Increase with signal interference ratio SIR is fewer and feweri, but the transformation rate difference of the different Cv of signal to noise ratio, therefore can determine the scope of signal interference ratio according to different signal to noise ratios.

5. the signal interference ratio determination methods in the actual elimination of high-speed mobile OFDM cooperative system ICI according to claim 4, it is characterized in that the thresholding in the described step (4) according to signal interference ratio, determine the elimination process of elimination algorithm, and estimate the elimination performance of elimination algorithm.The signal of cooperative system purpose user and collaborative point can be expressed as:

$Y_{\mathrm{sd}}\left(k\right)=H_{\mathrm{sd}}\left(k\right)V\left(k\right)S\left(0\right)+\underset{l=0,l\&NotEqual;k}{\overset{N-1}{\mathrm{\&Sigma;}}}{H}_{\mathrm{sd}}\left(l\right)V\left(l\right)S(l-k)+n_{\mathrm{sd}}\left(k\right)$

H wherein _Sd(k) be the channel gain of source node S and destination node D, n _SdIt is noise.First of following formula is useful signal, and second is because the distracter of the ICI that Doppler frequency shift produces passes through estimated signal V (k) for following formula, thereby can calculates the signal interference ratio of system easily.Promptly just can obtain the transmission performance of its system by the signal interference ratio of judging system.

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