CN105451240A - Bidirectional cooperation anti-interference spectrum access method based on joint optimization of time and bandwidth - Google Patents

Abstract

The invention provides a bidirectional cooperation anti-interference spectrum access method based on the joint optimization of time and bandwidth. According to the method, a cognitive user is accessed to the frequency spectrum of a master user in the bidirectional cooperation manner. If a target rate is realized for the master user with the help of the cognitive user, the master user allocates one part of the time to the cognitive user to authorize the cognitive user to access to the frequency spectrum of the master user itself. Otherwise, the master user forbids the cognitive user to access to the frequency spectrum of the master user itself. After the cognitive user is accessed to the frequency spectrum of the master user, the information of the master user and the information of the cognitive user are sent out at different bandwidths respectively. According to the method, the spectrum loss caused by the mutual interference between the master user and the cognitive user and the bidirectional cooperation of the master user and the cognitive user in the half-duplex mode can be eliminated. Therefore, the user performance is improved.

Description

A kind of anti-interference frequency spectrum access method of two-way cooperation based on time and bandwidth combined optimization

Technical field

The invention belongs to the cognition wireless technical field of telecommunications in wireless communication field, especially a kind of frequency spectrum access method.

Background technology

Along with the development of radio communication, wireless communication user is on the increase, and business demand increases fast, and limited radio spectrum resources becomes the bottleneck of restriction development of wireless communication systems gradually.A large amount of research reports of FCC (FCC) show that the utilance of current wireless frequency spectrum is very low, only have 15% ~ 85%, major part frequency spectrum is not fully utilized when majority, and frequency spectrum service condition is very uneven, some unauthorized frequency ranges take too crowded, and some authorizes frequency range to be then often in idle condition.The visible main cause causing frequency spectrum resource in short supply is existing this static spectrum management mode and spectrum allocation strategy.Wireless communications environment around the perception of cognitive radio technology energy, under the impregnable prerequisite of guarantee primary user's proper communication, wait for an opportunity insertion authority frequency spectrum, by certain study and decision making algorithm, adaptively modifying system operational parameters adapts to the change of running environment, can to frequency spectrum in the time, frequency, spatially carry out multidimensional multiplexing, thus promote the utilance of frequency spectrum resource.

Coexist in formula frequency spectrum access method at cognitive radio, cognitive user is allowed to share same frequency range with primary user meeting under certain prerequisite.But in this cut-in method, between primary user and cognitive user, there is interference all the time, make originally just very limited frequency spectrum resource be not fully utilized, the performance of primary user and cognitive user also can be affected due to interference.And this frequency spectrum access method is unidirectional cooperation, there is the loss of eigenfrequency spectrum efficiency.

Summary of the invention

For the existing defect coexisted in formula frequency spectrum access technology, solve the problem of interference mutually between primary user and cognitive user, overcome the not high deficiency of the availability of frequency spectrum, the invention provides the problem of interference mutually between a kind of effective elimination primary user and cognitive user, improve the anti-interference frequency spectrum access method of two-way cooperation based on time and bandwidth combined optimization of the availability of frequency spectrum.

The technical solution adopted for the present invention to solve the technical problems is:

A kind of anti-interference frequency spectrum access method of two-way cooperation based on time and bandwidth combined optimization, radio communications system comprises a main system and a cognitive system, main system comprises primary user A and primary user B, cognitive system is made up of cognitive user transmitting terminal S and cognitive user receiving terminal D, can simulate the radio protocol in main system and system parameters; Described main system supports relay function, the mandate frequency spectrum be made up of one section of W bandwidth; The described anti-interference frequency spectrum access method of two-way cooperation based on time and bandwidth combined optimization comprises the following steps:

1) cognitive user is with the frequency spectrum of cooperation mode access primary user, after cognitive user receives the information of primary user, helps by decoding forward collaboration mode the information forwarding primary user;

2) the speed R obtained after primary user A and B is helped by cognitive user cooperation is calculated _aand R _b;

3) if R _a>=R _aTand R _b>=R _bT, then primary user will distribute portion of time to understanding user, authorizes it to access the frequency spectrum of oneself, after the frequency spectrum of cognitive user access main system, utilizes the bandwidth of a part to forward the information of primary user, utilizes remaining bandwidth to send the information of oneself; Otherwise primary user continues through to direct transfer and sends the information of oneself;

Time between primary user and cognitive user and bandwidth co-allocation problem are modeled as:

$\underset{T,B}{\max }{R}_S---\left(1\right)$

Meet the following conditions

$\left\{\begin{array}{c}{R}_A\&GreaterEqual;R_{AT}\\ R_B\&GreaterEqual;R_{BT}\\ 0<\mathrm{\&alpha;}+\mathrm{\&beta;}<1\\ 0<n+m<1\\ 0<\mathrm{\&alpha;}<1\\ 0<\mathrm{\&beta;}<1\\ 0<m<1\\ 0<n<1\end{array}\right.---\left(2\right)$

Wherein R _aTand R _bTrepresent the targeted rate of primary user A and B respectively, T={m, n}, B={ α, β }, m and n represents that primary user A and B sends the time shared by oneself information at the first time slot and the second time slot respectively, α and β represents that understanding user helps primary user A and B forwarding information bandwidth used at the 3rd time slot respectively.R _a, R _band R _safter representing cognitive user access primary user frequency spectrum respectively, the speed that primary user A, primary user B and cognitive user S obtain:

R _A＝min{R _AS,R _SB}(3)

R _B＝min{R _BS,R _SA}(4)

$R_S=(1-m-n)(1-\mathrm{\&alpha;}-\mathrm{\&beta;}){\mathrm{Wlog}}_2(1+\frac{P_S{\mathrm{\&gamma;}}_{SD}}{3{\mathrm{\&sigma;}}^2})---\left(5\right)$

Wherein, P _srepresent the transmitting power of cognitive user S, γ _sDrepresent the channel gain of cognitive user transmitting terminal to cognitive user receiving terminal link, σ ²represent noise power spectral density, R _aSand R _sBrepresent the speed that primary user A obtains first and second time slot respectively:

$R_{AS}={\mathrm{mWlog}}_2(1+\frac{P_A{\mathrm{\&gamma;}}_{AS}}{{\mathrm{\&sigma;}}^2})---\left(6\right)$

$R_{SB}=\left\{\begin{array}{cc}\&lsqb;m-\left(1-m-n\right)\mathrm{\&alpha;}\&rsqb;R_{A1}+\left(1-m-n\right){\mathrm{\&alpha;R}}_{A2}& m\&GreaterEqual;\left(1-m-n\right)\mathrm{\&alpha;}\\ \&lsqb;\left(1-m-n\right)\mathrm{\&alpha;}-m\&rsqb;R_{A3}+{\mathrm{mR}}_{A2}& m<\left(1-m-n\right)\mathrm{\&alpha;}\end{array}\right.---\left(7\right)$

Wherein, $R_{A1}={\mathrm{Wlog}}_2(1+\frac{P_A{\mathrm{\&gamma;}}_{AB}}{{\mathrm{\&sigma;}}^2}),R_{A2}={\mathrm{Wlog}}_2(1+\frac{P_S{\mathrm{\&gamma;}}_{SB}}{3{\mathrm{\&sigma;}}^2}+\frac{P_A{\mathrm{\&gamma;}}_{AB}}{{\mathrm{\&sigma;}}^2}),$ p _arepresent the transmitting power of primary user A, γ _aS, γ _sBand γ _aBrepresent the primary user A channel gain to cognitive user transmitting terminal link respectively, cognitive user transmitting terminal to the channel gain of primary user B link and primary user A to the channel gain of primary user B link, R _bSand R _sArepresent the speed that primary user B obtains first and second time slot respectively:

$R_{BS}={\mathrm{nWlog}}_2(1+\frac{P_B{\mathrm{\&gamma;}}_{BS}}{{\mathrm{\&sigma;}}^2})---\left(8\right)$

$R_{SA}=\left\{\begin{array}{cc}\&lsqb;n-\left(1-m-n\right)\mathrm{\&beta;}\&rsqb;R_{B1}\left(1-m-n\right){\mathrm{\&beta;R}}_{B2}& n\&GreaterEqual;\left(1-m-n\right)\mathrm{\&beta;}\\ \&lsqb;\left(1-m-n\right)\mathrm{\&beta;}-n\&rsqb;R_{B3}+{\mathrm{nR}}_{B2}& n<\left(1-m-n\right)\mathrm{\&beta;}\end{array}\right.---\left(9\right)$

Wherein $R_{B1}={\mathrm{Wlog}}_2(1+\frac{P_B{\mathrm{\&gamma;}}_{BA}}{{\mathrm{\&sigma;}}^2}),R_{B2}={\mathrm{Wlog}}_2(1+\frac{P_S{\mathrm{\&gamma;}}_{SA}}{3{\mathrm{\&sigma;}}^2}+\frac{P_B{\mathrm{\&gamma;}}_{BA}}{{\mathrm{\&sigma;}}^2}),$ p _brepresent the transmitting power of primary user B, γ _bS, γ _sAand γ _bArepresent the primary user B channel gain to cognitive user transmitting terminal link respectively, cognitive user transmitting terminal is to the channel gain of primary user A link and primary user B to the channel gain of primary user A link;

Obtain above-mentioned optimal time by Mathematics Optimization Method to distribute:

$m^{*}=\frac{R_{AT}}{{\mathrm{Wlog}}_2(1+\frac{P_A{\mathrm{\&gamma;}}_{AS}}{{\mathrm{\&sigma;}}^2})}---\left(10\right)$

$n^{*}=\frac{R_{BT}}{{\mathrm{Wlog}}_2(1+\frac{P_B{\mathrm{\&gamma;}}_{BS}}{{\mathrm{\&sigma;}}^2})}---\left(11\right)$

According to R _sBand R _sAdifferent values, obtain the optimal bandwidth allocation under 4 kinds of different situations:

1. when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\left\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}{R}_{A1}}{(1-m^{*}-n^{*})(R_{A2}-R_{A1})}\\ \mathrm{\&beta;}=\frac{R_{BT}-n^{*}{R}_{B1}}{(1-m^{*}-n^{*})(R_{B2}-R_{B1})}\end{array}\right.---\left(12\right)$

2. when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\left\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}{R}_{A1}}{(1-m^{*}-n^{*})(R_{A2}-R_{A1})}\\ \mathrm{\&beta;}=\frac{R_{BT}-n^{*}\left(R_{B2}-R_{B3}\right)}{(1-m^{*}-n^{*})R_{B3}}\end{array}\right.---\left(13\right)$

3. when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\left\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}\left(R_{A2}-R_{A3}\right)}{(1-m^{*}-n^{*})R_{A3}}\\ \mathrm{\&beta;}=\frac{R_{BT}-n^{*}{R}_{B1}}{(1-m^{*}-n^{*})(R_{B2}-R_{B1})}\end{array}\right.---\left(14\right)$

4. when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\left\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}\left(R_{A2}-R_{A3}\right)}{(1-m^{*}-n^{*})R_{A3}}\\ \mathrm{\&beta;}=\frac{R_{BT}-n^{*}\left(R_{B2}-R_{B3}\right)}{(1-m^{*}-n^{*})R_{B3}}\end{array}\right.---\left(15\right).$

Further, described step 2) in, cognitive user accesses the frequency spectrum of primary user by three slot decoder forward collaboration modes;

At the 1st time slot, primary user A m time slot sends information to cognitive user S, and the transmission rate of A → S link is:

$R_{AS}={\mathrm{mWlog}}_2(1+\frac{P_A{\mathrm{\&gamma;}}_{AS}}{{\mathrm{\&sigma;}}^2})---\left(6\right)$

At the 2nd time slot, primary user B n time slot holds transmission information to cognitive user S, and the transmission rate of B → S link is:

$R_{BS}={\mathrm{nWlog}}_2(1+\frac{P_B{\mathrm{\&gamma;}}_{BS}}{{\mathrm{\&sigma;}}^2})---\left(8\right)$

At the 3rd time slot, cognitive user S utilizes α W bandwidth sum P _sthe power of/3 helps primary user A transmission information, with β W bandwidth sum P _sthe power of/3 helps primary user B transmission information, and through maximum-ratio combing, the transmission rate of S → B link and S → A link is respectively:

$R_{SB}=\left\{\begin{array}{cc}\&lsqb;m-\left(1-m-n\right)\mathrm{\&alpha;}\&rsqb;R_{A1}+\left(1-m-n\right){\mathrm{\&alpha;R}}_{A2}& m\&GreaterEqual;\left(1-m-n\right)\mathrm{\&alpha;}\\ \&lsqb;\left(1-m-n\right)\mathrm{\&alpha;}-m\&rsqb;R_{A3}+{\mathrm{mR}}_{A2}& m<\left(1-m-n\right)\mathrm{\&alpha;}\end{array}\right.---\left(9\right)$

$R_{SA}=\left\{\begin{array}{cc}\&lsqb;n-\left(1-m-n\right)\mathrm{\&beta;}\&rsqb;R_{B1}+\left(1-m-n\right){\mathrm{\&beta;R}}_{B2}& n\&GreaterEqual;\left(1-m-n\right)\mathrm{\&beta;}\\ \&lsqb;\left(1-m-n\right)\mathrm{\&beta;}-n\&rsqb;R_{B3}+{\mathrm{nR}}_{B2}& n<\left(1-m-n\right)\mathrm{\&beta;}\end{array}\right.---\left(7\right)$

So the speed that primary user A and B is obtained under the help of cognitive user S by three time slots is respectively:

R _A＝min{R _AS,R _SB}(3)

R _B＝min{R _BS,R _SA}(4)

Meanwhile, cognitive user utilizes remaining (1-alpha-beta) W bandwidth sum (1-m-n) time slot to send the information of oneself, so the speed that cognitive user obtains is:

$R_S=(1-m-n)(1-\mathrm{\&alpha;}-\mathrm{\&beta;}){\mathrm{Wlog}}_2(1+\frac{P_S{\mathrm{\&gamma;}}_{SD}}{3{\mathrm{\&sigma;}}^2})---\left(5\right).$

Technical conceive of the present invention is: owing to coexisting in formula frequency spectrum access method, cognitive user and primary user use identical frequency spectrum to communicate simultaneously, all the time interference is there is mutually, make originally to be not fully utilized with regard to very limited frequency spectrum resource, the performance of primary user and cognitive user also can be affected due to interference.And this frequency spectrum access method uses unidirectional cooperation mode, because its semiduplex mode of operation causes the loss of spectrum efficiency.In this patent method, cognitive user accesses the frequency spectrum of primary user by the mode of two-way cooperation, and primary user and cognitive user send information respectively by different time and bandwidth, effectively can solve the interference problem between primary user and cognitive user.Meanwhile, cognitive system, with the frequency spectrum of two-way cooperation mode access primary user, can improve the availability of frequency spectrum.

Beneficial effect of the present invention is mainly manifested in: (1) eliminates the interference problem of primary user and cognitive user in the formula frequency spectrum access method that coexists; (2) improve the availability of frequency spectrum.

Accompanying drawing explanation

Fig. 1 is the two-way cooperation anti-interference frequency spectrum access model schematic diagram of the inventive method, wherein h _ij, i, j ∈ A, B, S, D}, i ≠ j is the channel coefficients of Rayleigh flat fading channel, and h _ij=h _ji, obey wherein v is path loss index, d _ijfor the normalized cumulant between each transmitting terminal and receiving terminal, (a) broadcasts respective information for primary user A and B, and (b) is that cognitive user S broadcasts primary user and the information of oneself.

Fig. 2 is that time and bandwidth combined optimization factor alpha in the inventive method, β, m and n are with the variation diagram of S position.

Fig. 3 is that the transmission rate of primary user and cognitive user is with the variation diagram of S position when cognitive user obtains frequency spectrum access.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.

With reference to Fig. 1 ~ Fig. 3, a kind of anti-interference frequency spectrum access method of two-way cooperation based on time and bandwidth combined optimization, realize based on existing radio communications system, described radio communications system comprises a main system and a cognitive system, wherein main system is made up of primary user A and primary user B, main system supports relay function, and the mandate frequency spectrum be made up of one section of W bandwidth, cognitive system is made up of a cognitive user transmitting terminal S and cognitive receiving terminal D.Cognitive system can simulate radio protocol in main system and system parameters.

In the method for present embodiment, cognitive user is with the frequency spectrum of two-way cooperation mode access primary user.After cognitive user receives the information of primary user, help by decoding forward collaboration mode the information forwarding primary user.If the speed R that primary user A and B is obtained after being helped by cognitive user cooperation _aand R _ball be greater than the targeted rate of oneself, i.e. R _a>=R _aTand R _b>=R _bT, then primary user will distribute portion of time to understanding user, authorizes it to access the frequency spectrum of oneself, after the frequency spectrum of cognitive user access main system, utilizes the bandwidth of a part to forward the information of primary user, utilizes remaining bandwidth to send the information of oneself; Otherwise primary user continues through to direct transfer and sends the information of oneself.

The transmission rate R of primary user A and B after cognitive user access primary user frequency spectrum in present embodiment _aand R _b, and the speed R that cognitive user obtains _scan obtain by the following method:

Cognitive user accesses the frequency spectrum of primary user by three slot decoder forward collaboration modes; At the 1st time slot, primary user A m time slot sends information to cognitive user S, and the transmission rate of A → S link is:

$R_{AS}={\mathrm{mWlog}}_2(1+\frac{P_A{\mathrm{\&gamma;}}_{AS}}{{\mathrm{\&sigma;}}^2})---\left(6\right)$

At the 2nd time slot, primary user B n time slot holds transmission information to cognitive user S, and the transmission rate of B → S link is:

$R_{BS}={\mathrm{nWlog}}_2(1+\frac{P_B{\mathrm{\&gamma;}}_{BS}}{{\mathrm{\&sigma;}}^2})---\left(8\right)$

At the 3rd time slot, cognitive user S utilizes α W bandwidth sum P _sthe power of/3 helps primary user A transmission information, with β W bandwidth sum P _sthe power of/3 helps primary user B transmission information, and through maximum-ratio combing, the transmission rate of S → B link and S → A link is respectively:

$R_{SB}=\left\{\begin{array}{cc}\&lsqb;m-\left(1-m-n\right)\mathrm{\&alpha;}\&rsqb;R_{A1}+\left(1-m-n\right){\mathrm{\&alpha;R}}_{A2}& m\&GreaterEqual;\left(1-m-n\right)\mathrm{\&alpha;}\\ \&lsqb;\left(1-m-n\right)\mathrm{\&alpha;}-m\&rsqb;R_{A3}+{\mathrm{mR}}_{A2}& m<\left(1-m-n\right)\mathrm{\&alpha;}\end{array}\right.---\left(9\right)$

$R_{SA}=\left\{\begin{array}{cc}\&lsqb;n-\left(1-m-n\right)\mathrm{\&beta;}\&rsqb;R_{B1}+\left(1-m-n\right){\mathrm{\&beta;R}}_{B2}& n\&GreaterEqual;\left(1-m-n\right)\mathrm{\&beta;}\\ \&lsqb;\left(1-m-n\right)\mathrm{\&beta;}-n\&rsqb;R_{B3}+{\mathrm{nR}}_{B2}& n<\left(1-m-n\right)\mathrm{\&beta;}\end{array}\right.---\left(7\right)$

So the speed that primary user A and B is obtained under the help of cognitive user S by three time slots is respectively:

R _A＝min{R _AS,R _SB}(3)

R _B＝min{R _BS,R _SA}(4)

Meanwhile, cognitive user utilizes remaining (1-alpha-beta) W bandwidth sum (1-m-n) time slot to send the information of oneself, so the speed that cognitive user obtains is:

$R_S=(1-m-n)(1-\mathrm{\&alpha;}-\mathrm{\&beta;}){\mathrm{Wlog}}_2(1+\frac{P_S{\mathrm{\&gamma;}}_{SD}}{3{\mathrm{\&sigma;}}^2})---\left(5\right)$

Time in present embodiment and bandwidth allocation methods are specially:

Time between primary user and cognitive user and allocated bandwidth can be modeled as:

$\underset{T,B}{\max }{R}_S---\left(1\right)$

Meet the following conditions

$\left\{\begin{array}{c}{R}_A\&GreaterEqual;R_{AT}\\ R_B\&GreaterEqual;R_{BT}\\ 0<\mathrm{\&alpha;}+\mathrm{\&beta;}<1\\ 0<n+m<1\\ 0<\mathrm{\&alpha;}<1\\ 0<\mathrm{\&beta;}<1\\ 0<m<1\\ 0<n<1\end{array}\right.---\left(2\right)$

Obtain above-mentioned optimal time by Mathematics Optimization Method to distribute:

$m^{*}=\frac{R_{AT}}{{\mathrm{Wlog}}_2(1+\frac{P_A{\mathrm{\&gamma;}}_{AS}}{{\mathrm{\&sigma;}}^2})}---\left(10\right)$

$n^{*}=\frac{R_{BT}}{{\mathrm{Wlog}}_2(1+\frac{P_B{\mathrm{\&gamma;}}_{BS}}{{\mathrm{\&sigma;}}^2})}---\left(11\right)$

According to R _sBand R _sAdifferent values, obtain the optimal bandwidth allocation under 4 kinds of different situations:

1. when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\left\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}{R}_{A1}}{(1-m^{*}-n^{*})(R_{A2}-R_{A1})}\\ \mathrm{\&beta;}=\frac{R_{BT}-n^{*}{R}_{B1}}{(1-m^{*}-n^{*})(R_{B2}-R_{B1})}\end{array}\right.---\left(12\right)$

2. when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\left\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}{R}_{A1}}{(1-m^{*}-n^{*})(R_{A2}-R_{A1})}\\ \mathrm{\&beta;}=\frac{R_{BT}-n^{*}\left(R_{B2}-R_{B3}\right)}{(1-m^{*}-n^{*})R_{B3}}\end{array}\right.---\left(13\right)$

3. when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\left\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}\left(R_{A2}-R_{A3}\right)}{(1-m^{*}-n^{*})R_{A3}}\\ \mathrm{\&beta;}=\frac{R_{BT}-n^{*}{R}_{B1}}{(1-m^{*}-n^{*})(R_{B2}-R_{B1})}\end{array}\right.---\left(14\right)$

4. when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\left\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}\left(R_{A2}-R_{A3}\right)}{(1-m^{*}-n^{*})R_{A3}}\\ \mathrm{\&beta;}=\frac{R_{BT}-n^{*}\left(R_{B2}-R_{B3}\right)}{(1-m^{*}-n^{*})R_{B3}}\end{array}\right.---\left(15\right).$

The anti-interference frequency spectrum access method of two-way cooperation based on time and bandwidth combined optimization of the present embodiment, effectively can eliminate the interference problem of primary user and cognitive user in the formula frequency spectrum access method that coexists, and can improve the availability of frequency spectrum.

In the frequency spectrum access method of the present embodiment, cognitive user licenses to its 3rd time slot primary user, holding time 1-m-n, the frequency spectrum of access primary user.The α W bandwidth that cognitive user utilizes part access to obtain helps the information forwarding primary user A, utilizes β W bandwidth to help to forward the information of primary user B, utilizes remaining (1-alpha-beta) W bandwidth to send the information of oneself.Primary user and cognitive user send information respectively by different time and bandwidth, can not produce interference mutually.In the present embodiment, suppose A, B and S is located on the same line, A and B lays respectively at (0,0) and (1,0) place.S is moved to B by A in X positive axis, and D is positioned at 0.4 place directly over S.Therefore d _aB=1, d _bS=1-d _aS, d _sD=0.4.Suppose path loss index v=4, authorize bandwidth W=1, noise power spectral density σ ²=1, primary user's transmitted power and cognitive user transmitted power are respectively P _a=P _b=10dB and P _s=20dB.Optimal time and the bandwidth co-allocation of intermediate frequency spectrum distribution method of the present invention is shown in Fig. 2.

The frequency spectrum access method of the present embodiment effectively improves the availability of frequency spectrum.Show the speed adopting primary user and cognitive user after frequency spectrum access method of the present invention in Fig. 3, can find out that after adopting frequency spectrum access method of the present invention, while primary user's Danone reaches targeted rate, cognitive user also can obtain larger transmission rate.

Claims (2)

1. the anti-interference frequency spectrum access method of two-way cooperation based on time and bandwidth combined optimization, radio communications system comprises a main system and a cognitive system, main system comprises primary user A and primary user B, cognitive system is made up of cognitive user transmitting terminal S and cognitive user receiving terminal D, can simulate the radio protocol in main system and system parameters; It is characterized in that: described main system supports relay function, the mandate frequency spectrum be made up of one section of W bandwidth; The described anti-interference frequency spectrum access method of two-way cooperation based on time and bandwidth combined optimization comprises the following steps:

1) cognitive user is with the frequency spectrum of cooperation mode access primary user, after cognitive user receives the information of primary user, helps by decoding forward collaboration mode the information forwarding primary user;

2) the speed R obtained after primary user A and B is helped by cognitive user cooperation is calculated _aand R _b;

3) if R _a>=R _aTand R _b>=R _bT, then primary user will distribute portion of time to understanding user, authorizes it to access the frequency spectrum of oneself, after the frequency spectrum of cognitive user access main system, utilizes the bandwidth of a part to forward the information of primary user, utilizes remaining bandwidth to send the information of oneself; Otherwise primary user continues through to direct transfer and sends the information of oneself;

Time between primary user and cognitive user and bandwidth co-allocation problem are modeled as:

$\underset{T,B}{max}{R}_S---\left(1\right)$

Meet the following conditions

$\left\{\begin{array}{c}{R}_A\&GreaterEqual;R_{AT}\\ R_B\&GreaterEqual;R_{BT}\\ 0<\mathrm{\&alpha;}+\mathrm{\&beta;}<1\\ 0<n+m<1\\ 0<\mathrm{\&alpha;}<1\\ 0<\mathrm{\&beta;}<1\\ 0<m<1\\ 0<n<1\end{array}\right.---\left(2\right)$

Wherein R _aTand R _bTrepresent the targeted rate of primary user A and B respectively, T={m, n}, B={ α, β }, m and n represents that primary user A and B sends the time shared by oneself information at the first time slot and the second time slot respectively, α and β represents that understanding user helps primary user A and B forwarding information bandwidth used at the 3rd time slot respectively, R _a, R _band R _safter representing cognitive user access primary user frequency spectrum respectively, the speed that primary user A, primary user B and cognitive user S obtain:

R _A＝min{R _AS,R _SB}(3)

R _B＝min{R _BS,R _SA}(4)

$R_S=(1-m-n)(1-\mathrm{\&alpha;}-\mathrm{\&beta;}){\mathrm{Wlog}}_2(1+\frac{P_S{\mathrm{\&gamma;}}_{SD}}{3{\mathrm{\&sigma;}}^2})---\left(5\right)$

Wherein, P _srepresent the transmitting power of cognitive user S, γ _sDrepresent the channel gain of cognitive user transmitting terminal to cognitive user receiving terminal link, σ ²represent noise power spectral density, R _aSand R _sBrepresent the speed that primary user A obtains first and second time slot respectively:

$R_{AS}={\mathrm{mWlog}}_2(1+\frac{P_A{\mathrm{\&gamma;}}_{AS}}{{\mathrm{\&sigma;}}^2})---\left(6\right)$

$R_{SB}=\left\{\begin{array}{cc}\&lsqb;m-(1-m-n)\mathrm{\&alpha;}\&rsqb;R_{A1}+(1-m-n){\mathrm{\&alpha;R}}_{A2}& m\&GreaterEqual;(1-m-n)\mathrm{\&alpha;}\\ \&lsqb;(1-m-n)\mathrm{\&alpha;}-m\&rsqb;R_{A3}+{\mathrm{mR}}_{A2}& m<(1-m-n)\mathrm{\&alpha;}\end{array}\right.---\left(7\right)$

Wherein, $R_{A1}={\mathrm{Wlog}}_2(1+\frac{P_A{\mathrm{\&gamma;}}_{AB}}{{\mathrm{\&sigma;}}^2}),$ $R_{A2}={\mathrm{Wlog}}_2(1+\frac{P_S{\mathrm{\&gamma;}}_{SB}}{3{\mathrm{\&sigma;}}^2}+\frac{P_A{\mathrm{\&gamma;}}_{AB}}{{\mathrm{\&sigma;}}^2}),$ p _arepresent the transmitting power of primary user A, γ _aS, γ _sBand γ _aBrepresent the primary user A channel gain to cognitive user transmitting terminal link respectively, cognitive user transmitting terminal to the channel gain of primary user B link and primary user A to the channel gain of primary user B link, R _bSand R _sArepresent the speed that primary user B obtains first and second time slot respectively:

$R_{BS}={\mathrm{nWlog}}_2(1+\frac{P_B{\mathrm{\&gamma;}}_{BS}}{{\mathrm{\&sigma;}}^2})---\left(8\right)$

$R_{SA}=\left\{\begin{array}{cc}\&lsqb;n-(1-m-n)\mathrm{\&beta;}\&rsqb;R_{B1}+(1-m-n){\mathrm{\&beta;R}}_{B2}& n\&GreaterEqual;(1-m-n)\mathrm{\&beta;}\\ \&lsqb;(1-m-n)\mathrm{\&beta;}-n\&rsqb;R_{B3}+{\mathrm{nR}}_{B2}& n<(1-m-n)\mathrm{\&beta;}\end{array}\right.---\left(9\right)$

Wherein $R_{B1}={\mathrm{Wlog}}_2(1+\frac{P_B{\mathrm{\&gamma;}}_{BA}}{{\mathrm{\&sigma;}}^2}),$ $R_{B2}={\mathrm{Wlog}}_2(1+\frac{P_S{\mathrm{\&gamma;}}_{SA}}{3{\mathrm{\&sigma;}}^2}+\frac{P_B{\mathrm{\&gamma;}}_{BA}}{{\mathrm{\&sigma;}}^2}),$ p _brepresent the transmitting power of primary user B, γ _bS, γ _sAand γ _bArepresent the primary user B channel gain to cognitive user transmitting terminal link respectively, cognitive user transmitting terminal is to the channel gain of primary user A link and primary user B to the channel gain of primary user A link;

Obtain above-mentioned optimal time by Mathematics Optimization Method to distribute:

$m^{*}=\frac{R_{AT}}{{\mathrm{Wlog}}_2(1+\frac{P_A{\mathrm{\&gamma;}}_{AS}}{{\mathrm{\&sigma;}}^2})}---\left(10\right)$

$n^{*}=\frac{R_{BT}}{{\mathrm{Wlog}}_2(1+\frac{P_B{\mathrm{\&gamma;}}_{BS}}{{\mathrm{\&sigma;}}^2})}---\left(11\right)$

According to R _sBand R _sAdifferent values, obtain the optimal bandwidth allocation under 4 kinds of different situations:

1. when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}{R}_{A1}}{(1-m^{*}-n^{*})(R_{A2}-R_{A1})}\\ \mathrm{\&beta;}=\frac{R_{AB}-n^{*}{R}_{B1}}{(1-m^{*}-n^{*})(R_{B2}-R_{B1})}\end{array}---\left(12\right)$

2. when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}{R}_{A1}}{(1-m^{*}-n^{*})(R_{A2}-R_{A1})}\\ \mathrm{\&beta;}=\frac{R_{AB}-n^{*}(R_{B2}-R_{B3})}{(1-m^{*}-n^{*})R_{B3}}\end{array}---\left(13\right)$

3. when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}(R_{A2}-R_{A3})}{(1-m^{*}-n^{*})R_{A3}}\\ \mathrm{\&beta;}=\frac{R_{BT}-n^{*}{R}_{B1}}{(1-m^{*}-n^{*})(R_{B2}-R_{B1})}\end{array}---\left(12\right)$

4. when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ Time,

$\{\begin{array}{c}\mathrm{\&alpha;}=\frac{R_{AT}-m^{*}(R_{A2}-R_{A3})}{(1-m^{*}-n^{*})R_{A3}}\\ \mathrm{\&beta;}=\frac{R_{BT}-n^{*}(R_{B2}-R_{B3})}{(1-m^{*}-n^{*})R_{B3}}\end{array}---\left(15\right).$

2., as claimed in claim 1 based on the anti-interference frequency spectrum access method of cooperation of time and bandwidth combined optimization, it is characterized in that: described step 2) in, cognitive user is by the frequency spectrum of three slot decoder forward collaboration mode insertion authority users;

At the 1st time slot, primary user A m time slot sends information to cognitive user S, and the transmission rate of A → S link is:

$R_{AS}={\mathrm{mWlog}}_2(1+\frac{P_A{\mathrm{\&gamma;}}_{AS}}{{\mathrm{\&sigma;}}^2})---\left(6\right)$

At the 2nd time slot, primary user B n time slot holds transmission information to cognitive user S, and the transmission rate of B → S link is:

$R_{BS}={\mathrm{nWlog}}_2(1+\frac{P_B{\mathrm{\&gamma;}}_{BS}}{{\mathrm{\&sigma;}}^2})---\left(8\right)$

At the 3rd time slot, cognitive user S utilizes α W bandwidth sum P _sthe power of/3 helps primary user A transmission information, with β W bandwidth sum P _sthe power of/3 helps primary user B transmission information, and through maximum-ratio combing, the transmission rate of S → B link and S → A link is respectively:

$R_{SB}=\left\{\begin{array}{cc}\&lsqb;m-(1-m-n)\mathrm{\&alpha;}\&rsqb;R_{A1}+(1-m-n){\mathrm{\&alpha;R}}_{A2}& m\&GreaterEqual;(1-m-n)\mathrm{\&alpha;}\\ \&lsqb;(1-m-n)\mathrm{\&alpha;}-m\&rsqb;R_{A3}+{\mathrm{mR}}_{A2}& m<(1-m-n)\mathrm{\&alpha;}\end{array}\right.---\left(9\right)$

$R_{SA}=\left\{\begin{array}{cc}\&lsqb;n-(1-m-n)\mathrm{\&beta;}\&rsqb;R_{B1}+(1-m-n){\mathrm{\&beta;R}}_{B2}& n\&GreaterEqual;(1-m-n)\mathrm{\&beta;}\\ \&lsqb;(1-m-n)\mathrm{\&beta;}-n\&rsqb;R_{B3}+{\mathrm{nR}}_{B2}& n<(1-m-n)\mathrm{\&beta;}\end{array}\right.---\left(7\right)$

So the speed that primary user A and B is obtained under the help of cognitive user S by three time slots is respectively:

R _A＝min{R _AS,R _SB}(3)

R _B＝min{R _BS,R _SA}(4)

Meanwhile, cognitive user utilizes remaining (1-alpha-beta) W bandwidth sum (1-m-n) time slot to send the information of oneself, so the speed that cognitive user obtains is:

$R_S=(1-m-n)(1-\mathrm{\&alpha;}-\mathrm{\&beta;}){\mathrm{Wlog}}_2(1+\frac{P_S{\mathrm{\&gamma;}}_{SD}}{3{\mathrm{\&sigma;}}^2})---\left(5\right).$