CN102523051A - Method for constructing cognitive radio simulation system on basis of complementary bridge function sequence - Google Patents

Abstract

Provided is a method for constructing a cognitive radio simulation system on the basis of a complementary bridge function sequence. The method comprises step 1 inputting a spectrum spreading sequence into a constructed simulation system with a walsh sequence with sequence values of '+1' and '-1' and a bridge function sequence with sequence values of '+1', '0' and '-1' serving as the spectrum spreading sequence; step 2 respectively inputting an m sequence and a bridge function sequence which serve as a spectrum spreading sequence into the constructed simulation system; step 3 considering capacity for suppressing multi-access interference of a multi-user system when the bridge function sequence with a zero correlation of a cross-correlation function is utilized to serve as the spectrum spreading sequence under the multi-user system, wherein the step 1 and the step 2 consider the capacity for suppressing multi-path interference of a single-user system. The method constructs the cognitive radio simulation system on the basis of the complementary bridge function sequence and utilizes the Underlay accessing technology. By utilizing the bridge function sequence to serve as the spectrum spreading sequence, a ternary sequence with a zero correlation zone is verified to have better multi-path interference resistance capacity than a binary sequence.

Description

A kind of construction method based on complementary bridge sequence of function cognitive radio analogue system

Technical field:

The present invention relates to a kind of construction method based on complementary bridge sequence of function cognitive radio analogue system.This system is transmitted pulse with the Gaussian pulse, is under the prerequisite of frequency expansion sequence with the walsh sequence and the bridge sequence of function, can judge through the calculating of the error rate, and the three value bridge sequences of function with zero correlation block have better bit error rate performance than walsh sequence.The invention belongs to the cognitive radio technology field.

Background technology:

In the recent two decades, along with social development, people increase sharply to the demand of radio communication, and wireless network increases fast.Distributed to certain applications because of many main wireless frequency spectrums, the rare of frequency spectrum becomes more and more serious.Therefore, how under limited frequency spectrum resources, satisfying people is important and difficult task of ten minutes of wireless communication field to the growing demand of radio communication.Test shows mandate frequency spectrum is not fully utilized recently.Under this background; One type of radiotechnics of reusing frequency spectrum resource is organized proposition in succession by some research institutions and standard formulation; This is wherein most typical be The Technology of Ultra (UltraWideband, UWB) and cognitive radio technology (Cognitive Radio, CR).These two kinds of technology develop rapidly because of its tempting application prospect.And because they are in the spectrum reuse mode, many differences such as technological realization aspect are paid close attention to the further research novelty that two kinds of technology combine.

Super-broadband tech has started one research boom in the world after last century, be applied to civil area the nineties, be considered to the revolutionary technology of next generation wireless communication.Ultra broadband has the wireless communication technology of a great difference as a kind of and conventional art, has two-forty, low cost, and low in power consumption makes UWB become the optimal candidate technology of short distance high-rate wireless communication of future generation.Super-broadband tech can be divided into two types at present: based on the impact class UWB of burst pulse formula with based on the carrier-class UWB of modulated carrier spread spectrum formula.

Cognitive radio can improve the utilization rate of frequency spectrum significantly as a kind of revolutionary smart frequency spectrum technology of sharing, has received people's extensive concern in recent years.The notion of cognitive radio be the further expansion of software radio as a kind of brand-new intelligent radio communication technology, it is more extensive that cognitive radio is contained face, the function of cognitive radio is also more powerful.

The present invention is the fundamental simulation environment through matrix experiment chamber/simulation software (MATLAB/SIMULINK); With substrate (Underlay) mode is access technology; With the Gaussian pulse is to send pulse; With the three value bridge sequences of function is frequency expansion sequence, erects the software emulation platform based on the ultra broadband cognitive radio, compares as frequency expansion sequence and to simulation result with the bridge sequence of function with different zero correlation section lengths through walsh sequence; Simulation result shows; The three value bridge sequences of function with zero correlation block have than walsh sequence and have better anti-multipath and multiple access interference capability, and the length of zero correlation is long more, and anti-multipath and multiple access interference capability are also strong more.

Summary of the invention:

The purpose of this invention is to provide a kind of construction method based on complementary bridge sequence of function cognitive radio analogue system; Under this system; Can see from simulation result; Through adopting different frequency expansion sequences, have three value frequency expansion sequences of zero correlation block, have better anti-multipath than walsh sequence and disturb and anti-multiple access interference capability.

For achieving the above object, the present invention adopts following technical scheme:

A kind of construction method of the present invention based on complementary bridge sequence of function cognitive radio analogue system, these method concrete steps are following:

Step 1; With sequential value is "+1 ", the walsh sequence of " 1 " and be "+1 " with sequential value, " 0 "; The bridge sequence of function of " 1 " is input in the constructed analogue system as frequency expansion sequence; And,, be that ber curve can be seen from the last resulting simulation result of system to increase the zero correlation block of bridge function through changing the shift parameters j of the bridge sequence of function; The bridge sequence of function with zero correlation block has better bit error rate performance than walsh sequence, promptly has better anti-multipath interference capability;

Step 2; The m sequence and the bridge sequence of function are input to respectively in the constructed analogue system as frequency expansion sequence, can see through simulation result, at bridge function shift parameters smaller be the zero correlation of bridge function smaller in; Adopt the system of m sequence better slightly than the system's anti-multipath interference capability that adopts the bridge sequence of function; This is because the auto-correlation function of m sequence is a constant value except that zero point, and very near 0, but along with the increase of bridge function shift parameters; Be under the elongated gradually situation of zero correlation, adopt the bridge sequence of function to have better bit error rate performance as the system of frequency expansion sequence;

Step 3, what above step 1 and step 2 were considered is that single user system suppresses the multipath interference capability; It suppresses multiple access interference capability when considering now to adopt under the multi-user system bridge letter sequence that cross-correlation function has a zero correlation as frequency expansion sequence; We have made up a ultra broadband cognitive radio system that has two users to exist; Making the bridge sequence of function with zero correlation block and one type of special cross-correlation function perseverance is 0 the bridge function smart code sequence frequency expansion sequence as system; Simulation result shows that along with the increase of shift parameters, zero correlation block is also increasing; It is also more and more stronger that system suppresses the multiple access interference capability; When employing cross-correlation function perseverance was 0 bridge function smart code sequence, the bit error rate performance of system was best, promptly suppresses the multiple access interference capability and reaches best.

Wherein, in the single user system in step 1, the bridge function uses in system as frequency expansion sequence.The bridge sequence of function is a kind of three value sequences, and tangible zero correlation block is arranged.And verified in a large amount of documents, contain zero correlation block frequency expansion sequence can significantly reduce multipath and disturb.And determined the length of the zero correlation block of bridge function as the shift parameters j in the bridge function, along with the increase of shift parameters j, the length of bridge function zero correlation block is also increasing gradually, and walsh function does not have similar character.So in the simulation process that step 1 adopted; We have adopted the bridge sequence of function and the walsh sequence of different shift parameters to compare; Along with the variation of shift parameters, the length of the zero correlation block of bridge function is also increasing gradually, and then system's anti-multipath interference capability is also more and more stronger.

Wherein, in the single user system in step 2, we adopt the bridge sequence of function of m sequence and different shift parameters to use in the system as frequency expansion sequence.The m sequence is a kind of frequency expansion sequence that widely uses, and its auto-correlation function is steady state values except locating to have the kurtosis at zero point at all the other some places, and very near zero.We mentioned in the described content of step 2, and when bridge sequence of function shift parameters j was smaller, when promptly the length of zero correlation block was smaller, the anti-multipath interference capability of the bridge sequence of function was not as the m sequence, be exactly because the auto-correlation function of m sequence very near 0.When the shift parameters j of bridge function increased gradually, zero correlation block increased gradually, and the anti-multipath interference performance strengthens naturally gradually.So when using the bigger bridge sequence of function of zero correlation block, its anti-multipath interference capability is better than m sequence.Under m sequence and the simultaneous situation of the bridge sequence of function, step 2 provides a criterion of selecting the better bridge sequence of function of performance.

Wherein, in the multi-user system described in the step 3, we have adopted two users' system.In this system, we have adopted the common bridge sequence of function and one type of special bridge sequence of function respectively is the frequency expansion sequence of bridge function smart code sequence as system.Numerous lists of references are verified, and existing multiple access disturbs the cross-correlation function decision by frequency expansion sequence in the multi-user system.Not homotactic cross-correlation function has tangible zero correlation block in the common bridge sequence of function family, can reduce the multiple access that exists between the multi-user and disturb.And one type of special bridge sequence of function, promptly its cross-correlation function perseverance of bridge function smart code sequence is 0.Can prove when the cross-correlation function perseverance is 0, should have the performance that best anti-multiple access disturbs in theory.We use this this type smart code sequence in 2 users' the system as frequency expansion sequence; Simulation result has been verified notional result; Adopt the system of smart code sequence to have better bit error rate performance than the common bridge sequence of function, promptly better anti-multiple access interference capability.

3, the present invention has following advantage and good effect:

1) the present invention has made up the cognitive radio software emulation system based on the employing Underlay access technology of the complementary bridge sequence of function.Through adopting the bridge sequence of function, can verify that three value sequences with zero correlation block have better anti-multipath interference capability than binary sequence as frequency expansion sequence.

2) the constructed cognitive radio system of the present invention adopt a kind of special bridge sequence of function be the smart code sequence as frequency expansion sequence, the cross-correlation function perseverance of this sequence is 0, effectively the anti-multiple access interference capability of enhanced system.

Description of drawings:

Fig. 1 user software of the present invention analogue system modular structure sketch map.

Fig. 2 adopts the error rate of system sketch map of 4 * 8 sequence matrix and ellipsoid wave function orthogonal pulses.

Fig. 3 adopts the error rate of system sketch map of 8 * 16 sequence matrix and ellipsoid wave function orthogonal pulses.

Fig. 4 is the bit error rate performance sketch map of multi-user system during as frequency expansion sequence with the common bridge sequence of function.

Fig. 5 is the bit error rate performance sketch map of smart code sequence multi-user system when being frequency expansion sequence with one type of special bridge sequence of function.

Fig. 6 is a FB(flow block) of the present invention.

Symbol description is following among the figure:

Wherein PSWF representes the ultra-wideband communications transceiver;

Wherein UWB representes The Technology of Ultra;

Wherein RAKE representes correlation receiver image rake;

Wherein Bit Error Rate representes bit error rate;

Wherein Walsh representes walsh function;

Wherein Bridge representes the bridge function;

Wherein User 1 representes user 1;

Wherein User 2 representes users 2.

Embodiment:

See Fig. 6, a kind of construction method of the present invention based on complementary bridge sequence of function cognitive radio analogue system, these method concrete steps are following:

Step 1; With sequential value is "+1 ", the walsh sequence of " 1 " and be "+1 " with sequential value, " 0 "; The bridge sequence of function of " 1 " is input in the constructed analogue system as frequency expansion sequence; And,, be that ber curve can be seen from the last resulting simulation result of system to increase the zero auto-correlation district of bridge function through changing the shift parameters j of the bridge sequence of function; The bridge sequence of function with zero correlation block has better bit error rate performance than walsh sequence, promptly has better anti-multipath interference capability;

Step 2; The m sequence and the bridge sequence of function are input to respectively in the constructed analogue system as frequency expansion sequence, can see through simulation result, at bridge function shift parameters smaller be the zero correlation of bridge function smaller in; Adopt the system of m sequence better slightly than the system's anti-multipath interference capability that adopts the bridge sequence of function; This is because the auto-correlation function of m sequence is a constant value except that zero point, and very near 0, but along with the increase of bridge function shift parameters; Be under the elongated gradually situation of zero correlation, adopt the bridge sequence of function to have better bit error rate performance as the system of frequency expansion sequence;

The ultra wideband of single user's direct sequence (DS-UWB) system is discussed.In Fig. 1; Data source (Data Source; DS) Bernoulli Jacob's binary signal generator (the Bernoulli Binary Generator in the subsystem; BBG) generate at random two and make information data 0 and 1 and pass through the U transducer (unipolar to bipolar converter, UBC) module becomes and is-1 and 1.In UWB pulse generator subsystem, produce the Gaussian pulse waveform.(DataModulation, DM) (Binary Phase Shift Keying BPSK) modulates the two-phase PSK that carries out in the subsystem output waveform in data-modulated.Then transmission signals can be expressed as

$s\left(t\right)=\underset{n=-\∞}{\overset{\∞}{\mathrm{\Σ}}}{d}_{\left[\frac{n}{G}\right]}{c}_{n}p(t-{\mathrm{nT}}_c)---\left(1\right)$

P (t) is the normalization impulse waveform, and the duration is T _cc _nBe to be the spreading code of G in the cycle, symbol period is T _s=GT _c, so spreading gain is G.Be sent to modulation signal the ultra-wideband channel of standard.

$h\left(t\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}\underset{k=0}{\overset{K-1}{\mathrm{\Σ}}}{\mathrm{\α}}_{k,l}(t-T_l-{\mathrm{\τ}}_{k,l})---\left(2\right)$

The l number that is bunch wherein, k is the number of bunch inner rays.α _{K, l}Be the multipath gain, T _lBe l bunch time-delay, τ _{K, l}Be the relative time delay of k bar ray in l bunch. be the derivation below convenient, the reduced form on can the employing formula

$h\left(t\right)=\underset{l=0}{\overset{\mathrm{KL}-1}{\mathrm{\Σ}}}{\mathrm{\α}}_{l^{\′}}\mathrm{\δ}(t-{\mathrm{\τ}}_{l^{\′}})---\left(3\right)$

Find out l '=lK+k easily, α _{L '}=α _k, τ _{L '}=T _l+ τ _{K, l}The reception signal does

$r\left(t\right)=s\left(t\right)*h\left(t\right)+n\left(t\right)=\underset{l=0}{\overset{\mathrm{KL}-1}{\mathrm{\Σ}}}{\mathrm{\α}}_{l^{\′}}\underset{n=-\∞}{\overset{\∞}{\mathrm{\Σ}}}{d}_{\left[\frac{n}{G}\right]}{c}_{n}p(t-{\mathrm{\τ}}_{l^{\′}}-{\mathrm{nT}}_c)+n\left(t\right)---\left(4\right)$

Receiving signal is the energy signal that contains many different delay paths; Adopt ultra-wideband communications transceiver (P-RAKE); Select the suitable L paths that arrives at first; Merge with least-mean-square-error criterion, in equalizer (Equalizer) module, adopt the recursive least-squares equalization algorithm to reduce the influence of multipath channel then.

Pass through a series of calculating of shifting onto, the variance that draws the multipath interference does

${{\mathrm{\σ}}^2}_{\mathrm{MPI}}=\frac{1}{G^2}\underset{l=0}{\overset{N-1}{\mathrm{\Σ}}}\underset{M+K\≠m}{\overset{M-1}{\underset{k=0}{\mathrm{\Σ}}}}{\mathrm{le}}^{-\mathrm{M\Δ\τ}/\mathrm{\Γ}}{e}^{-\mathrm{k\Δ\τ}/\mathrm{\γ}}({R_c}^2(m-M-k)+{\widehat{R_c}}^2(m-M-k))---\left(5\right)$

R _c(τ) be the autocorrelation of spreading code, $\widehat{R_c}\left(\mathrm{\τ}\right)=R_c(T_s-\mathrm{\τ})$

At last, can obtain the error probability with the synchronous matched filter receiver of m bar multipath according to the BPSK BER formulas

$P_e=Q\left[\sqrt{\frac{2E_m}{{\mathrm{\&sigma;}}_M{\mathrm{PI}}^2+{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HDA0000113606880000022.png"\; state="\{\{state\}\}">N</figure-callout>}}_0/2}}\right]---\left(6\right)$

E _mBe the received energy of each symbol of m bar multipath, wherein

$Q\left(a\right)={\&Integral;}_a^{\&infin;}\frac{1}{\sqrt{2\mathrm{\&pi;}}}{e}^{-x^2/2}\mathrm{dx}---\left(7\right)$

By (5), (6), (7) formula comprehensively can get, because R _c(τ) for being the autocorrelation of spreading code, because the increase of the k value of smart code sequence, zero correlation block is elongated gradually, can be known by (7) formula, and bit error rate performance is become better and better.Fig. 2, Fig. 3 can well explain this problem.

Step 3, what above step 1 and step 2 were considered is that single user system suppresses the multipath interference capability; It suppresses multiple access interference capability when considering now to adopt under the multi-user system bridge letter sequence that cross-correlation function has a zero correlation as frequency expansion sequence; We have made up a ultra broadband cognitive radio system that has two users to exist; Making the bridge sequence of function with zero cross-correlation district and one type of special cross-correlation function perseverance is 0 the bridge function smart code sequence frequency expansion sequence as system; Simulation result shows that along with the increase of shift parameters, zero cross-correlation district is also increasing; It is also more and more stronger that system suppresses the multiple access interference capability; When employing cross-correlation function perseverance was 0 bridge function smart code sequence, the bit error rate performance of system was best, promptly suppresses the multiple access interference capability and reaches best.

Transmitter section and single user system are similar, and just many users repeat no more at this, only consider receiver section at present.Specifically undertaken by following mode:

The acknowledge(ment) signal of receiver can be expressed as following form

$r\left(t\right)=\underset{k=1}{\overset{N_u}{\mathrm{\&Sigma;}}}{s^{\left(k\right)}}_{\mathrm{rec}}\left(t\right)+n\left(t\right)---\left(8\right)$

Wherein n (t) is an additive white Gaussian noise, N _uIt is number of users

Under multi-path environment

$s_{\mathrm{rec}}^{\left(k\right)}\left(t\right)=\sqrt{E_p}\underset{j=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\underset{n=0}{\overset{N_s-1}{\mathrm{\&Sigma;}}}\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{a}_l^{\left(k\right)}{d}_j^{\left(k\right)}{g}_n^{\left(k\right)}{w}_{\mathrm{rec}}(t^{\left(k\right)}-{\mathrm{jT}}_f-n{T}_c-{\mathrm{\&tau;}}_l)---\left(9\right)$

E wherein _PBe pulse energy,

Be the channel coefficients of the 1st paths,

It is multidiameter.

The template signal of the 1st correlator of P-Rake receiver can be written as following expression formula

$V_l\left(t\right)=\underset{n=0}{\overset{N_s-1}{\mathrm{\&Sigma;}}}{g}_n^{\left(k\right)}{w}_{\mathrm{rec}}(t^l-{\mathrm{jT}}_f-n{T}_c-\widehat{{\mathrm{\&tau;}}_l})---\left(10\right)$

Wherein

is the local pseudo random sequence that produces, be the channel estimating delay of the 1st paths.

When signal through L correlator, the expression formula of k user's signal does

$r_l^{\left(k\right)}={\&Integral;}_{j{T}_f}^{{\mathrm{jT}}_f+(N_s-1)T_c}{s}_{\mathrm{rec}}^{\left(k\right)}\left(t\right)v\left(t\right)\mathrm{dt}$

$={\&Integral;}_{j{T}_f}^{j{T}_f+(N_s-1)T_c}\left(\sqrt{E_p}\underset{j=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\underset{n=0}{\overset{N_s-1}{\mathrm{\&Sigma;}}}\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{a}_l^{\left(k\right)}{d}_j^{\left(k\right)}{g}_n^{\left(k\right)}{w}_{\mathrm{rec}}(t^{\left(k\right)}-{\mathrm{jT}}_f-n{T}_c-{\mathrm{\&tau;}}_l)\right)\left(\underset{n=0}{\overset{N_s-1}{\mathrm{\&Sigma;}}}{g}_n^{\left(k\right)}{w}_{\mathrm{rec}}(t^l-{\mathrm{jT}}_f-{\mathrm{nT}}_c-\widehat{{\mathrm{\&tau;}}_l})\right)\mathrm{dt}$

$=A\underset{n=0}{\overset{N_s-1}{\mathrm{\&Sigma;}}}{g}_n^{\left(k\right)}{g}_n^{\left(l\right)}R\left(\mathrm{\&Delta;}\right)\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}\widehat{{\mathrm{\&gamma;}}_l}---\left(11\right)$

Wherein $A=\sqrt{E_p}{N}_s\underset{j=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{d}_j^{\left(k\right)}\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{a}_l^{\left(k\right)},$ $R\left(\mathrm{\&Delta;}\right)={\&Integral;}_0^{T_c}\left(w_{\mathrm{Rec}}(t^{\left(k\right)}-{\mathrm{JT}}_f-n{T}_c-{\mathrm{\&tau;}}_l)\right)\left(w_{\mathrm{Rec}}(t^l-{\mathrm{JT}}_f-{\mathrm{NT}}_c-\widehat{{\mathrm{\&tau;}}_l})\right)\mathrm{Dt},$

It is the estimated value of weight estimator

The expression formula of k user's multiple access interference is:

$\mathrm{MAI}=A^2{\left(R\left(\mathrm{\&Delta;}\right)\right)}^2{\left(\underset{n=0}{\overset{N_s-1}{\mathrm{\&Sigma;}}}{g}_n^{\left(k\right)}{g}_n^{\left(l\right)}\right)}^2{\left(\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}\widehat{{\mathrm{\&gamma;}}_l}\right)}^2=A^2{\left(R\left(\mathrm{\&Delta;}\right)\right)}^2{R}_{\mathrm{lk}}{\left(\mathrm{\&tau;}\right)}^2{\left(\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}\widehat{{\mathrm{\&gamma;}}_l}\right)}^2=A^2{\mathrm{\&sigma;}}_{\mathrm{MAI}}{\left(\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}\widehat{{\mathrm{\&gamma;}}_l}\right)}^2---\left(12\right)$

σ wherein _MAI=(R (Δ)) ²R _Lk(τ) ², and R _Lk(τ) be the cross-correlation function of frequency expansion sequence when through after L correlator, the expression of white Gaussian noise does

$n^2={\mathrm{\&sigma;}}_n^2{N}_s^2{R}^2\left(0\right){\left(\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{\mathrm{\&gamma;}}_l\right)}^2---\left(13\right)$

Estimate that according to standard Gauss the expression formula of BER formulas can be written as

$P_e=Q\left[\sqrt{\frac{E_p{N}_S^2{R}^2\left(0\right){\left(\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{\mathrm{\&gamma;}}_l{a}_l^k\right)}^2}{E_p{N}_S^2{\mathrm{\&sigma;}}_{\mathrm{MAI}}{\left(\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{\mathrm{\&gamma;}}_l{a}_l^{\left(k\right)}\right)}^2+{\mathrm{\&sigma;}}_n^2{N}_S^2{R}^2\left(0\right){\left(\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{\mathrm{\&gamma;}}_l\right)}^2}}\right]---\left(14\right)$

Can see that by formula (14) cross-correlation function of frequency expansion sequence is more little, the bit error rate performance of system is good more, i.e. system's inhibition multiple access interference capability is also strong more.Fig. 4 and Fig. 5 contrast can well be explained this problem.Fig. 4 is the bit error rate performance of multi-user system during as frequency expansion sequence with the common bridge sequence of function.Fig. 5 is to be the bit error rate performance of smart code sequence multi-user system during as frequency expansion sequence with one type of special bridge sequence of function.Can be got by two figure contrasts, adopting the cross-correlation function perseverance is that 0 bridge function smart code sequence has better bit error rate performance than the common bridge sequence of function, promptly better anti-multiple access interference capability.

Claims (4)

1. construction method based on complementary bridge sequence of function cognitive radio analogue system, it is characterized in that: these method concrete steps are following:

Step 1: with sequential value is "+1 "; The walsh sequence of " 1 " and be "+1 " with sequential value, " 0 ", the bridge sequence of function of " 1 " is input in the constructed analogue system as frequency expansion sequence; And through changing the shift parameters j of the bridge sequence of function, to increase the zero correlation block of bridge function; From the last resulting simulation result of system is that ber curve is seen, the bridge sequence of function with zero correlation block has better bit error rate performance than walsh sequence, promptly has better anti-multipath interference capability;

Step 2; The m sequence and the bridge sequence of function are input to respectively in the constructed analogue system as frequency expansion sequence, see through simulation result, at bridge function shift parameters smaller be the zero correlation of bridge function smaller in; Adopt the system of m sequence better slightly than the system's anti-multipath interference capability that adopts the bridge sequence of function; This is because the auto-correlation function of m sequence is a constant value except that zero point, and very near 0, but along with the increase of bridge function shift parameters; Be under the elongated gradually situation of zero correlation, adopt the bridge sequence of function to have better bit error rate performance as the system of frequency expansion sequence;

Step 3, what above step 1 and step 2 were considered is that single user system suppresses the multipath interference capability; It suppresses multiple access interference capability when considering now to adopt under the multi-user system bridge letter sequence that cross-correlation function has a zero correlation as frequency expansion sequence; We have made up a ultra broadband cognitive radio system that has two users to exist; Making the bridge sequence of function with zero correlation block and one type of special cross-correlation function perseverance is 0 the bridge function smart code sequence frequency expansion sequence as system; Simulation result shows that along with the increase of shift parameters, zero correlation block is also increasing; It is also more and more stronger that system suppresses the multiple access interference capability; When employing cross-correlation function perseverance was 0 bridge function smart code sequence, the bit error rate performance of system was best, promptly suppresses the multiple access interference capability and reaches best.

2. a kind of construction method according to claim 1 based on complementary bridge sequence of function cognitive radio analogue system; It is characterized in that: in the single user system in step 1; The bridge function uses in system as frequency expansion sequence, and the bridge sequence of function is a kind of three value sequences that obvious zero correlation block is arranged, contain zero correlation block frequency expansion sequence can significantly reduce multipath and disturb; And determined the length of the zero correlation block of bridge function as the shift parameters j in the bridge function; Along with the increase of shift parameters j, the length of the zero correlation block of bridge function is also increasing gradually, and walsh function does not have similar character; So in the simulation process that step 1 adopted; Adopted the bridge sequence of function and the walsh sequence of different shift parameters to compare; Along with the variation of shift parameters, the length of the zero correlation block of bridge function is also increasing gradually, and then system's anti-multipath interference capability is also more and more stronger.

3. a kind of construction method according to claim 1 based on complementary bridge sequence of function cognitive radio analogue system; It is characterized in that: in the single user system in step 2, adopt the bridge sequence of function of m sequence and different shift parameters to use in the system as frequency expansion sequence; The m sequence is a kind of frequency expansion sequence, and its auto-correlation function is steady state values except locating to have the kurtosis at zero point at all the other some places, and very near zero; When bridge sequence of function shift parameters j was smaller, when promptly the length of zero correlation block was smaller, the anti-multipath interference capability of the bridge sequence of function was not as the m sequence, be exactly because the auto-correlation function of m sequence very near 0; When the shift parameters j of bridge function increased gradually, zero correlation block increased gradually, and the anti-multipath interference performance increases naturally gradually; So when using the bigger bridge sequence of function of zero correlation block, its anti-multipath interference capability is better than m sequence; Under m sequence and the simultaneous situation of the bridge sequence of function, step 2 provides a criterion of selecting the better bridge sequence of function of performance.

4. a kind of construction method based on complementary bridge sequence of function cognitive radio analogue system according to claim 1 is characterized in that: in the multi-user system described in the step 3, adopted two users' system; In this system, having adopted the common bridge sequence of function and one type of special bridge sequence of function respectively is the frequency expansion sequence of bridge function smart code sequence as system; Existing multiple access disturbs the cross-correlation function decision by frequency expansion sequence in the multi-user system; Not homotactic cross-correlation function has tangible zero correlation block in the common bridge sequence of function family, reduces the multiple access that exists between the multi-user and disturbs; And one type of special bridge sequence of function, promptly its cross-correlation function perseverance of bridge function smart code sequence is 0; Can prove when the cross-correlation function perseverance is 0, should have the performance that best anti-multiple access disturbs in theory; Use this this type smart code sequence in 2 users' the system as frequency expansion sequence; Simulation result has been verified notional result; Adopt the system of smart code sequence to have better bit error rate performance than the common bridge sequence of function, promptly better anti-multiple access interference capability.

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