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

Bidirectional cooperation anti-interference spectrum access method based on time and bandwidth joint optimization

Technical Field

The invention belongs to the technical field of cognitive radio communication in the field of wireless communication, and particularly relates to a frequency spectrum access method.

Background

With the development of wireless communication, wireless communication users are increasing, service requirements are rapidly increasing, and limited wireless spectrum resources gradually become bottlenecks that restrict the development of wireless communication systems. A lot of research reports of the Federal Communications Commission (FCC) in the united states indicate that the utilization rate of the current wireless spectrum is low, only 15% -85%, most of the spectrum is not fully utilized most of the time, the usage of the spectrum is unbalanced, some unlicensed bands are too crowded, and some licensed bands are often in an idle state. It can be seen that the main reasons for the shortage of spectrum resources are the existing static spectrum management method and spectrum allocation strategy. The cognitive radio technology can sense the surrounding wireless communication environment, the authorized spectrum is accessed opportunistically on the premise that the normal communication of a master user is not influenced, the working parameters of the system are changed adaptively to adapt to the change of the operating environment through a certain learning and decision algorithm, and the multidimensional multiplexing of the spectrum in time, frequency and space can be carried out, so that the utilization rate of the spectrum resource is improved.

In the cognitive radio coexistence type spectrum access method, a cognitive user is allowed to share the same frequency band with a master user on the premise of meeting a certain requirement. However, in the access method, interference always exists between the primary user and the cognitive user, so that originally very limited spectrum resources cannot be fully utilized, and the performances of the primary user and the cognitive user are also affected by the interference. And the spectrum access method is one-way cooperative, and has inherent loss of spectrum efficiency.

Disclosure of Invention

Aiming at the defects in the existing coexisting spectrum access technology, the problem of mutual interference between a master user and a cognitive user is solved, and the defect of low spectrum utilization rate is overcome.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a two-way cooperation anti-interference spectrum access method based on time and bandwidth joint optimization is disclosed, wherein a radio communication system comprises a main system and a cognitive system, the main system comprises a main user A and a main user B, the cognitive system consists of a cognitive user sending end S and a cognitive user receiving end D, and radio protocols and system parameters in the main system can be simulated; the main system supports a relay function and has an authorized frequency spectrum consisting of a section of W bandwidth; the bidirectional cooperation anti-interference spectrum access method based on the time and bandwidth joint optimization comprises the following steps:

1) the cognitive user accesses the frequency spectrum of the master user in a cooperative mode, and after receiving the information of the master user, the cognitive user helps to forward the information of the master user in a decoding and forwarding cooperative mode;

2) calculating the rate R obtained by the main users A and B after the cooperation help of the cognitive users_AAnd R_B；

3) If R is_A≥R_ATAnd R is_B≥R_BTThe master user can allocate a part of time to the cognitive user, authorize the cognitive user to access the frequency spectrum of the master user, and after the cognitive user accesses the frequency spectrum of the master system, the information of the master user is forwarded by using a part of bandwidth, and the information of the master user is sent by using the rest bandwidth; otherwise, the master user continues to send own information through direct transmission;

the problem of time and bandwidth joint allocation between a main user and a cognitive user is modeled as follows:

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

satisfies 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 is_ATAnd R_BTThe target rates of primary users A and B are respectively represented, T is { m, n }, B is { α }, m and n respectively represent the time occupied by the primary users A and B for transmitting own information in the first time slot and the second time slot, α and β respectively represent the bandwidth used for recognizing users to help the primary users A and B to forward information in the third time slot_A、R_BAnd R_SRespectively representing the rate obtained by a master user A, a master user B and a cognitive user S after the cognitive user accesses the master user frequency spectrum:

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_SRepresenting the transmit power, gamma, of the cognitive user S_SDIndicates the channel gain, sigma, of the link from the cognitive user sending end to the cognitive user receiving end²Representing noise power spectral density, R_ASAnd R_SBIndicating the rates achieved by primary user a in the first and second slots, 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_Aindicating the transmission power, gamma, of primary user A_AS,γ_SBAnd gamma_ABRespectively representing the channel gain of a link from a master user A to a cognitive user sending end, the channel gain of the link from the cognitive user sending end to a master user B and the channel gain of the link from the master user A to the master user B, R_BSAnd R_SAIndicating the rates achieved by primary user B in the first and second slots, 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_BIndicating the transmission power, gamma, of the primary user B_BS,γ_SAAnd gamma_BARespectively representing the channel gain of a link from a master user B to a cognitive user sending end, the channel gain of the link from the cognitive user sending end to a master user A and the channel gain of the link from the master user B to the master user A;

the above-mentioned optimal time allocation is obtained by a mathematical optimization method:

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

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

according to R_SBAnd R_SAObtaining the optimal bandwidth allocation under 4 different conditions:

① when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

② when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

③ when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

④ when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

further, in the step 2), the cognitive user accesses the frequency spectrum of the master user in a decoding and forwarding cooperation mode through three time slots;

in the 1 st time slot, a master user A sends information to a cognitive user S by using an m time slot, and the transmission rate of an A → S link is as follows:

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

in the 2 nd time slot, the master user B sends information to the cognitive user S end by using the n time slot, and the transmission rate of the B → S link is as follows:

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

in the 3 rd time slot, the cognitive user S utilizes α W bandwidth and P_SThe power of/3 is used for assisting the main user A to transmit information, and β W bandwidth and P are used_SThe power of/3 is used for helping the primary user B to transmit information, and after maximum ratio combination, the transmission rates of the S → B link and the S → A link are respectively as follows:

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

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

so the rates obtained by primary users a and B with the help of the cognitive user S through three slots are:

R_A＝min{R_AS,R_SB}(3)

R_B＝min{R_BS,R_SA}(4)

meanwhile, the cognitive user sends own information by using the rest (1-alpha-beta) W bandwidth and (1-m-n) time slot, so that the cognitive user obtains the following rate:

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

the technical conception of the invention is as follows: in the coexisting spectrum access method, the cognitive users and the master users use the same spectrum to communicate simultaneously, and interference always exists between the cognitive users and the master users, so that originally very limited spectrum resources cannot be fully utilized, and the performances of the master users and the cognitive users are influenced by the interference. Moreover, the spectrum access method uses a one-way cooperation mode, and the loss of spectrum efficiency is caused by the half-duplex working mode. According to the method, the cognitive user accesses the frequency spectrum of the master user in a two-way cooperation mode, the master user and the cognitive user send information through different time and bandwidth respectively, and the problem of interference between the master user and the cognitive user can be effectively solved. Meanwhile, the cognitive system is accessed to the frequency spectrum of the master user in a bidirectional cooperation mode, and the frequency spectrum utilization rate can be improved.

The invention has the following beneficial effects: (1) the interference problem of a master user and a cognitive user in the coexisting spectrum access method is solved; (2) the frequency spectrum utilization rate is improved.

Drawings

FIG. 1 is a schematic diagram of a bidirectional cooperative anti-interference spectrum access model of the method of the present invention, wherein h_ijI, j ∈ { A, B, S, D }, i ≠ j, is the channel coefficient of Rayleigh flat fading channel, and h_ij＝h_jiCompliance withWhere v is the path loss exponent, d_ijThe method comprises the steps of (a) broadcasting respective information for a main user A and a main user B, and (B) broadcasting the information of the main user and the information of the main user for a cognitive user S.

FIG. 2 is a graph of the time and bandwidth joint optimization coefficients α, β, m and n as a function of S position in the method of the present invention.

Fig. 3 is a graph of the transmission rate of a primary user and a cognitive user as a function of S-position when the cognitive user gains spectrum access.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Referring to fig. 1 to 3, a bidirectional cooperation anti-interference spectrum access method based on time and bandwidth joint optimization is realized based on an existing radio communication system, wherein the radio communication system comprises a main system and a cognitive system, the main system comprises a main user a and a main user B, the main system supports a relay function and has an authorized spectrum consisting of a section of W bandwidth, and the cognitive system comprises a cognitive user transmitting terminal S and a cognitive receiving terminal D. The cognitive system is able to model radio protocols and system parameters in the host system.

In the method of the embodiment, the cognitive user accesses the frequency spectrum of the master user in a bidirectional cooperation mode. After receiving the information of the master user, the cognitive user helps to forward the information of the master user in a decoding and forwarding cooperation mode. If the primary users A and B obtain the rate R after cooperative assistance of cognitive users_AAnd R_BAre all greater than their target rate, i.e. R_A≥R_ATAnd R_B≥R_BTThe master user can allocate a part of time to the cognitive user, authorize the cognitive user to access the frequency spectrum of the master user, transmit the information of the master user by using a part of bandwidth after the cognitive user accesses the frequency spectrum of the master system, and transmit the information of the master user by using the rest bandwidth(ii) a Otherwise, the master user continues to send own information through direct transmission.

In the embodiment, after the cognitive user accesses the primary user frequency spectrum, the transmission rates R of the primary users A and B_AAnd R_BAnd rate R obtained by cognitive user_SCan be obtained by the following method:

the cognitive user accesses the frequency spectrum of the master user in a decoding and forwarding cooperation mode through three time slots; in the 1 st time slot, a master user A sends information to a cognitive user S by using an m time slot, and the transmission rate of an A → S link is as follows:

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

in the 2 nd time slot, the master user B sends information to the cognitive user S end by using the n time slot, and the transmission rate of the B → S link is as follows:

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

in the 3 rd time slot, the cognitive user S utilizes α W bandwidth and P_SThe power of/3 is used for assisting the main user A to transmit information, and β W bandwidth and P are used_SThe power of/3 is used for helping the primary user B to transmit information, and after maximum ratio combination, the transmission rates of the S → B link and the S → A link are respectively as follows:

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

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

so the rates obtained by primary users a and B with the help of the cognitive user S through three slots are:

R_A＝min{R_AS,R_SB}(3)

R_B＝min{R_BS,R_SA}(4)

meanwhile, the cognitive user sends own information by using the rest (1-alpha-beta) W bandwidth and (1-m-n) time slot, so that the cognitive user obtains the following rate:

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

the time and bandwidth allocation method in this embodiment specifically includes:

the time and bandwidth allocation between the primary user and the cognitive user can be modeled as:

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

satisfies the following conditions

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

The above-mentioned optimal time allocation is obtained by a mathematical optimization method:

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

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

according to R_SBAnd R_SAObtaining the optimal bandwidth allocation under 4 different conditions:

① when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

② when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

③ when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

④ when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

the bidirectional cooperation anti-interference spectrum access method based on time and bandwidth joint optimization can effectively eliminate the interference problem of a master user and a cognitive user in the coexistence spectrum access method, and can improve the spectrum utilization rate.

In the spectrum access method of the embodiment, a cognitive user occupies time 1-m-n in a third time slot authorized by a primary user and accesses a spectrum of the primary user, the cognitive user utilizes α W bandwidth obtained by partial access to help forward information of the primary user A, utilizes β W bandwidth to help forward information of the primary user B, and utilizes the rest (1- α - β) W bandwidth to send own information, the primary user and the cognitive user respectively send information through different time and bandwidth and do not interfere with each other, in the embodiment, A, B and S are assumed to be positioned on the same straight line, A and B are respectively positioned at (0, 0) and (1, 0), S moves from A to B in an X positive half axis, and D is positioned at 0.4 directly above S, so D is D_AB＝1，d_BS＝1-d_AS，d_SD0.4. Assuming that the path loss exponent v is 4, the granted bandwidth W is 1, and the noise power spectral density σ²The transmission power of the main user and the transmission power of the cognitive user are respectively P (1)_A＝P_B10dB and P_S20 dB. Drawing (A)The optimal time and bandwidth joint allocation of the spectrum allocation method of the present invention is shown in fig. 2.

The spectrum access method of the embodiment effectively improves the spectrum utilization rate. Fig. 3 shows the rates of the master user and the cognitive user after the spectrum access method of the present invention is adopted, and it can be seen that after the spectrum access method of the present invention is adopted, the cognitive user can obtain a larger transmission rate while the master user can reach the target rate.

Claims (2)

1. A two-way cooperation anti-interference spectrum access method based on time and bandwidth joint optimization is disclosed, wherein a radio communication system comprises a main system and a cognitive system, the main system comprises a main user A and a main user B, the cognitive system consists of a cognitive user sending end S and a cognitive user receiving end D, and radio protocols and system parameters in the main system can be simulated; the method is characterized in that: the main system supports a relay function and has an authorized frequency spectrum consisting of a section of W bandwidth; the bidirectional cooperation anti-interference spectrum access method based on the time and bandwidth joint optimization comprises the following steps:

1) the cognitive user accesses the frequency spectrum of the master user in a cooperative mode, and after receiving the information of the master user, the cognitive user helps to forward the information of the master user in a decoding and forwarding cooperative mode;

2) calculating the rate R obtained by the main users A and B after the cooperation help of the cognitive users_AAnd R_B；

3) If R is_A≥R_ATAnd R is_B≥R_BTThe master user can allocate a part of time to the cognitive user, authorize the cognitive user to access the frequency spectrum of the master user, and after the cognitive user accesses the frequency spectrum of the master system, the information of the master user is forwarded by using a part of bandwidth, and the information of the master user is sent by using the rest bandwidth; otherwise, the master user continues to send own information through direct transmission;

the problem of time and bandwidth joint allocation between a main user and a cognitive user is modeled as follows:

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

satisfies 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 is_ATAnd R_BTAre respectively provided withThe target rates of primary users A and B are represented, T is { m, n }, B is { α }, m and n respectively represent the time occupied by the primary users A and B for transmitting own information in the first time slot and the second time slot, α and β respectively represent the bandwidth for recognizing users in the third time slot to help the primary users A and B to forward information, and R is the bandwidth used by the users in the third time slot for helping the primary users A and B to forward information_A、R_BAnd R_SRespectively representing the rate obtained by a master user A, a master user B and a cognitive user S after the cognitive user accesses the master user frequency spectrum:

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_SRepresenting the transmit power, gamma, of the cognitive user S_SDIndicates the channel gain, sigma, of the link from the cognitive user sending end to the cognitive user receiving end²Representing noise power spectral density, R_ASAnd R_SBRespectively representThe rate achieved by primary user a in the first and second slots:

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

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

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_Aindicating the transmission power, gamma, of primary user A_AS,γ_SBAnd gamma_ABRespectively representing the channel gain of a link from a master user A to a cognitive user sending end, the channel gain of the link from the cognitive user sending end to a master user B and the channel gain of the link from the master user A to the master user B, R_BSAnd R_SAIndicating the rates achieved by primary user B in the first and second slots, 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_BIndicating the transmission power, gamma, of the primary user B_BS,γ_SAAnd gamma_BARespectively representing the channel gain of a link from a master user B to a cognitive user sending end, the channel gain of the link from the cognitive user sending end to a master user A and the channel gain of the link from the master user B to the master user A;

the above-mentioned optimal time allocation is obtained by a mathematical optimization method:

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

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

according to R_SBAnd R_SAObtaining the optimal bandwidth allocation under 4 different conditions:

① when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

② when $\left\{\begin{array}{c}{m}^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

③ when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}\&GreaterEqual;(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

④ when $\left\{\begin{array}{c}{m}^{*}<(1-m^{*}-n^{*})\mathrm{\&alpha;}\\ n^{*}<(1-m^{*}-n^{*})\mathrm{\&beta;}\end{array}\right.$ When the temperature of the water is higher than the set temperature,

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

2. the cooperative spectrum access method with interference resistance based on joint optimization of time and bandwidth as claimed in claim 1, wherein: in the step 2), the cognitive user accesses the frequency spectrum of the authorized user in a decoding and forwarding cooperation mode through three time slots;

in the 1 st time slot, a master user A sends information to a cognitive user S by using an m time slot, and the transmission rate of an A → S link is as follows:

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

in the 2 nd time slot, the master user B sends information to the cognitive user S end by using the n time slot, and the transmission rate of the B → S link is as follows:

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

in the 3 rd time slot, the cognitive user S utilizes α W bandwidth and P_SThe power of/3 is used for assisting the main user A to transmit information, and β W bandwidth and P are used_SThe power of/3 is used for helping the primary user B to transmit information, and after maximum ratio combination, the transmission rates of the S → B link and the S → A link are respectively as follows:

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

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

so the rates obtained by primary users a and B with the help of the cognitive user S through three slots are:

R_A＝min{R_AS,R_SB}(3)

R_B＝min{R_BS,R_SA}(4)

meanwhile, the cognitive user sends own information by using the rest (1-alpha-beta) W bandwidth and (1-m-n) time slot, so that the cognitive user obtains the following rate:

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