CN103987050A - Anti-interference frequency spectrum access method based on full duplex OFDM cooperation - Google Patents

Abstract

Provided is an anti-interference frequency spectrum access method based on full duplex OFDM cooperation. According to the method, if the speed during direct transmission of an authorized user is lower than the target speed, cooperation request signals will be sent to surrounding cognitive users for seeking the cooperation of the cognitive users. The cognitive user which can help the authorized user to obtain the maximum speed can be found out from all the cognitive users receiving the cooperation request signals, if the user can help the authorized user to achieve the target speed, the user will be allowed to have access to the frequency spectrum of the authorized user in a full duplex OFDM cooperation mode, and otherwise, the authorized user continues to send own information through direct transmission. After the cognitive user has access to the frequency spectrum of the authorized user, the cognitive user helps the authorized user to forward the information of the authorized user by using one part of subcarriers and power in a second time slot, and sends own information by using the other part of subcarriers and power in a first time slot and a second time slot. The anti-interference frequency spectrum access method based on the full duplex OFDM cooperation effectively solves the problem of mutual interference between the authorized user and the cognitive users, and improves the throughput of a cognitive system.

Description

A kind of anti-interference frequency spectrum access method based on full duplex OFDM cooperation

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

Since entering 21 century, the communication technology has obtained development widely, especially with wireless communication technology, develops rapidly the most outstanding.Along with the fast development of wireless communication technology, the problem of frequency spectrum resource scarcity is also day by day serious.According to the research report of frequency spectrum policy taskforce of FCC, the utilance of existing mandate frequency spectrum only has 15%～85%, these frequency spectrums of distributing to authorized user are not all fully used on time and space, in a lot of degree of shortage of visible spectrum resource because irrational radio spectrum management mode causes.Due to most of frequency spectrums authorized user assignment, the ultimate challenge facing is at present share spectrum resources under the prerequisite of not disturbing authorized user transmission how, promotes the utilance of frequency spectrum resource.Cognitive radio indicates an effective direction to the research that solves frequency spectrum resource scarcity, it is by wireless environment around self-adapting detecting, real-time regulating system parameter (as modulation technique, operating frequency and through-put power etc.), guaranteeing under the impregnable prerequisite of proper communication of authorized user, wait for an opportunity insertion authority frequency spectrum, thereby make full use of limited frequency spectrum resource.

At cognitive radio, coexist in formula frequency spectrum access method, cognitive user, by the transmitted power drawing oneself up, is not affecting under the prerequisite of authorized user proper communication, insertion authority user's frequency spectrum, and authorized user communicates simultaneously.Yet in this frequency spectrum access method, owing to being familiar with user and authorized user, use identical frequency spectrum to communicate simultaneously, between them, exist and disturb all the time, the performance of authorized user and cognitive user all can be because interference is affected.And cognitive user is operated in semiduplex mode, when receiving authorization user information, can not send own information simultaneously, make originally with regard to very limited frequency spectrum resource, to be not fully utilized, bring the loss of throughput.

Summary of the invention

In order to overcome in the existing formula frequency spectrum access method that coexists the problem of phase mutual interference and the deficiency of the loss of throughput problem that semiduplex mode causes between authorized user and cognitive user, the invention provides between a kind of effective elimination authorized user and cognitive user the anti-interference frequency spectrum access method based on full duplex OFDM cooperation of interference problem and loss of throughput problem mutually.

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

A kind of anti-interference frequency spectrum access method based on full duplex OFDM cooperation, radio communications system comprises an authoring system and a cognitive system, wherein, authoring system is by an authorized user transmitting terminal PT and authorize receiving terminal PR to form, and described authoring system is supported relay function; Cognitive system is by L cognitive user transmitting terminal ST _i, i ∈ L={1,2,3 ..., L} and a common receiving terminal SR form, and described cognitive system can be simulated radio protocol and the system parameters in main system; The described anti-interference frequency spectrum access method based on full duplex OFDM cooperation comprises following process:

1) authorized user transmitting terminal PT calculates when direct transferring to the speed R that authorizes receiving terminal PR _k, with its targeted rate R _trelatively, if R _k< R _t, authorize receiving terminal PR cognitive user transmission towards periphery cooperation request rtc signal to seek the cooperation of cognitive user;

2) receive after rtc signal, authorized user transmitting terminal PT sends a cooperation response ATC signal;

3) cognitive user transmitting terminal ST _ireceive after RTC and ATC signal, calculate the own complete relaying as authorized user transmitting terminal PT, speed when accessible while using whole subcarriers and power to help to forward PT information

4) in all cognitive user, find out and can obtain maximum cognitive user ST _b, and find out the speed that this cognitive user can help authorized user to reach

5) if sT _bcTC signal is confirmed in broadcast cooperation, the mode insertion authority user's who cooperates with full duplex OFDM frequency spectrum; Otherwise authorized user continues to send by direct transferring the information of oneself;

6) authorized user is received after CTC signal, distributes a part of subcarrier to ST _b, allow its mode with full duplex OFDM cooperation to access the frequency spectrum of oneself; ST _bobtain the authorization after user's frequency spectrum access, at second time slot, utilize a part of subcarrier and power to help to forward the information of authorized user, utilize other a part of subcarrier and power at first and second time slot, to send the information of oneself.

Further, the subcarrier of cognitive user and power division are modeled as:

$\underset{\{G,p\}}{\max }{R}_s---\left(1\right)$

Meet the following conditions $\left\{\begin{array}{c}{R}_p\&GreaterEqual;R_T\\ {\mathrm{\&Sigma;}}_{k\&Element;{\stackrel{\&OverBar;}{G}}_p}{p}_{\mathrm{ss},b}^k\&le;P_s\\ {\mathrm{\&Sigma;}}_{k^{\&prime;}\&Element;G_s}{p}_{\mathrm{sp},b}^{k^{\&prime;}}+{\mathrm{\&Sigma;}}_{k^{\&prime;}\&Element;{\stackrel{\&OverBar;}{G}}_s}{p}_{\mathrm{ss},b}^{k^{\&prime;}}\&le;P_s\end{array}\right.---\left(2\right)$

Wherein, G={G _p, G _sand the subcarrier and the power division that represent respectively cognitive user, G _pand G _srepresent to distribute to respectively the subcarrier set of authorized user and cognitive user, with represent respectively G _pand G _ssupplementary set, with represent respectively ST _bat second time slot power for relaying authorization user information and while sending own information on subcarrier k', represent ST _bat first time slot power when sending information on subcarrier k, P _sthe maximum transmit power that represents cognitive user, R _pand R _srepresent respectively after cognitive user insertion authority user frequency spectrum the speed that authorized user and cognitive user obtain:

R _p＝min{R ₁,R ₂} （3）

$R_s=R_s^1+R_s^2---\left(4\right)$

Wherein, R ₁and R ₂represent respectively the speed that authorized user obtains at first and second time slot:

$R_1=\frac{1}{2}\underset{k\&Element;G_p}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{1,b}^k{p}_p^k)---\left(5\right)$

$R_2=\frac{1}{2}\underset{k^{\&prime;}\&Element;G_s}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}{p}_{\mathrm{sp},b}^{k^{\&prime;}})---\left(6\right)$

Wherein with represent respectively subcarrier k at link PT to ST _bwith subcarrier k' at link ST _bto the channel gain on PR, be illustrated in the upper power when sending authorization user information of subcarrier k, according to water-filling algorithm, distribute;

with represent respectively the speed that cognitive user obtains at first time slot and second time slot:

$R_s^1=\frac{1}{2}\underset{k\&Element;{\stackrel{\&OverBar;}{G}}_p}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{3,b}^k{p}_{\mathrm{ss},b}^k)---\left(7\right)$

$R_s^2=\frac{1}{2}\underset{k^{\&prime;}\&Element;{\stackrel{\&OverBar;}{G}}_s}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}{p}_{\mathrm{ss},b}^{k^{\&prime;}})---\left(8\right)$

Wherein with represent that respectively subcarrier k and k' are at link ST _bto the channel gain on SR.

By method of Lagrange multipliers, obtain above-mentioned optimum subcarrier and power division:

$p_{\mathrm{ss},b}^{k^{*}}={(\frac{1}{2{\mathrm{\&beta;}}_{P_1}}-\frac{1}{{\mathrm{\&gamma;}}_{3,b}^k})}^{+}---\left(9\right)$

$p_{\mathrm{sp},b}^{k^{\&prime;*}}={(\frac{{\mathrm{\&beta;}}_{R_2}}{2{\mathrm{\&beta;}}_{P_2}}-\frac{1}{{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}})}^{+}---\left(10\right)$

$p_{\mathrm{ss},b}^{k^{\&prime;*}}={(\frac{1}{2{\mathrm{\&beta;}}_{P_2}}-\frac{1}{{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}})}^{+}---\left(11\right)$

$G_p^{*}=\arg \underset{G_p}{\max }\underset{k\&Element;G_p}{\mathrm{\&Sigma;}}{F}_k---\left(12\right)$

$G_s^{*}=\arg \underset{G_s}{\max }\underset{k^{\&prime;}\&Element;G_s}{\mathrm{\&Sigma;}}{F}_{k^{\&prime;}}---\left(13\right)$

Wherein

$F_k=\frac{{\mathrm{\&beta;}}_{R_1}}{2}\ln (1+{\mathrm{\&gamma;}}_{1,b}^k{p}_p^k)-\frac{1}{2}\ln (1+{\mathrm{\&gamma;}}_{3,b}^k{p}_{\mathrm{ss},b}^{k^{*}})+{\mathrm{\&beta;}}_{P_1}{p}_{\mathrm{ss},b}^{k^{*}}---\left(14\right)$

$F_{k^{\&prime;}}=\frac{{\mathrm{\&beta;}}_{R_2}}{2}\ln (1+{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}{p}_{\mathrm{sp},b}^{k^{\&prime;*}})-\frac{1}{2}\ln (1+{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}{p}_{\mathrm{ss},b}^{k^{\&prime;*}})+{\mathrm{\&beta;}}_{P_2}(p_{\mathrm{ss},b}^{k^{\&prime;*}}-p_{\mathrm{sp},b}^{k^{\&prime;*}})---\left(15\right)$

Wherein with represent Lagrange multiplier.

Further, in described step 5), cognitive user is by two time slot full duplex decoding forward collaboration mode insertion authority users' frequency spectrum;

At first time slot, ST _butilize G _pin subcarrier receive the information of authorized user transmitting terminal PT, authorized user transmitting terminal PT is to ST _bspeed be:

$R_1=\frac{1}{2}\underset{k\&Element;G_p}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{1,b}^k{p}_p^k)---\left(5\right)$

Meanwhile, ST _butilize remaining in subcarrier send oneself information, ST _bspeed to common receiving terminal SR is:

$R_s^1=\frac{1}{2}\underset{k\&Element;{\stackrel{\&OverBar;}{G}}_p}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{3,b}^k{p}_{\mathrm{ss},b}^k)---\left(7\right)$

At second time slot, ST _bthe information of decoding authorized user, and utilize G _sin subcarrier forward authorization user information to authorizing receiving terminal PR, ST _bto authorizing the speed of receiving terminal PR to be:

$R_2=\frac{1}{2}\underset{k^{\&prime;}\&Element;G_s}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}{p}_{\mathrm{sp},b}^{k^{\&prime;}})---\left(6\right)$

Meanwhile, ST _butilize remaining in subcarrier send oneself information, ST _bto authorizing the speed of receiving terminal SR to be:

$R_s^2=\frac{1}{2}\underset{k^{\&prime;}\&Element;{\stackrel{\&OverBar;}{G}}_s}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}{p}_{\mathrm{ss},b}^{k^{\&prime;}})---\left(8\right)$

So the rate representation that authorized user and cognitive user obtain by two time slots is:

R _p＝min{R ₁,R ₂} （3）

$R_s=R_s^1+R_s^2---\left(4\right).$

Technical conceive of the present invention is: due in the formula frequency spectrum access method that coexists, understanding user uses identical frequency spectrum to send authorized user and the information of oneself, between authorized user and cognitive user, exist and disturb all the time, both sides' performance all can be because interference is affected.And cognitive user is operated in semiduplex mode, when receiving authorization user information, can not send own information simultaneously, make originally with regard to very limited frequency spectrum resource, to be not fully utilized, bring the loss of throughput.In this patent method, cognitive user is by the mode insertion authority user's of cooperation frequency spectrum, and authorized user and cognitive user are carried out transmission information with the subcarrier of quadrature respectively, can effectively solve the interference problem between authorized user and cognitive user.Meanwhile, cognitive system is operated in full-duplex mode at first time slot, can effectively solve the problem that semiduplex mode throughput is low.

Beneficial effect of the present invention is mainly manifested in: (1) has eliminated the interference problem between authorized user and cognitive user; (2) promoted the throughput of cognitive user.

Accompanying drawing explanation

Fig. 1 is the anti-interference frequency spectrum access model schematic diagram based on full duplex OFDM cooperation of the inventive method, wherein, with represent respectively subcarrier k at link PT to PR, PT is to ST _iand ST _ito the channel coefficients on SR, with represent that respectively subcarrier k' is at link ST _ito PR and ST _ito the channel coefficients on SR;

Fig. 2 is that the Mean Speed of authorized user and cognitive user is along with P _s/ σ ²variation diagram, σ wherein ²represent noise power;

Fig. 3 is that cognitive user frequency spectrum access probability is with P _s/ σ ²variation diagram.

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 based on full duplex OFDM cooperation, based on existing radio communications system, realize, described radio communications system comprises an authoring system and a cognitive system, wherein authoring system is by an authorized user transmitting terminal (primary transmitter, PT) and authorize receiving terminal (primary receiver, PR) to form.Authoring system is supported relay function, and cognitive system is by L cognitive user transmitting terminal (secondary transmitter, ST _i, i ∈ L={1,2,3 ..., L}) form with cognitive receiving terminal (secondary receiver, SR).Cognitive system can be simulated radio protocol and the system parameters in main system;

In anti-interference frequency spectrum access method based on full duplex OFDM cooperation, PT calculates when direct transferring the speed R of PR _k, with its targeted rate R _trelatively, if R _k< R _t, PR cognitive user transmission towards periphery cooperation request rtc signal is to seek the cooperation of cognitive user.Receive after rtc signal, PT sends a cooperation response ATC signal.ST _ireceive after RTC and ATC signal, calculate the own complete relaying as PT, speed when accessible while using whole subcarriers and power to help to forward PT information in all cognitive user, find out and can obtain maximum cognitive user ST _b, and find out the speed that this cognitive user can help authorized user to reach if sT _bcTC signal is confirmed in broadcast cooperation, with full duplex decoding forward collaboration mode insertion authority user's frequency spectrum; Otherwise authorized user continues to send by direct transferring the information of oneself.Authorized user is received after CTC signal, distributes a part of subcarrier to ST _b, allow its mode with full duplex OFDM cooperation to access the frequency spectrum of oneself.ST _bobtain the authorization after user's frequency spectrum access, at second time slot, utilize a part of subcarrier and power to help to forward the information of authorized user, utilize other a part of subcarrier and power at first and second time slot, to send the information of oneself.

In present embodiment, speed RK when authorized user direct transfers can obtain by the following method:

$R_K=\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\ln (1+{\mathrm{\&gamma;}}_0^k{p}_p^k)---\left(16\right)$

Wherein for subcarrier k at link PT to the channel gain on PR.

ST in present embodiment _ihelp the accessible maximum instantaneous speed of authorized user can obtain by the following method:

$R_i^{\max }=\min \{R_{1,i}^{\max },R_{2,i}^{\max }\}---\left(17\right)$

Wherein $R_{1,i}^{\max }=\frac{1}{2}{\mathrm{\&Sigma;}}_{k=1}^K\ln (1+{\mathrm{\&gamma;}}_{1,i}^k{p}_p^k),$ $R_{2,i}^{\max }=\frac{1}{2}{\mathrm{\&Sigma;}}_{k^{\&prime;}=1}^K\ln (1+{\mathrm{\&gamma;}}_{2,i}^{k^{\&prime;}}{p}_{\mathrm{sp},i}^{k^{\&prime;}}),$ represent subcarrier k at link PT to ST _ion channel gain, represent that subcarrier k' is at link ST _ito the channel gain on SR, represent ST _ipower on subcarrier k' during for relaying authorization user information.

The speed R that in present embodiment, after cognitive user insertion authority user frequency spectrum, authorized user and cognitive user obtain _scan obtain by the following method:

Cognitive user is by two time slot full duplex decoding forward collaboration mode insertion authority users' frequency spectrum.At first time slot, ST _butilize G _pin subcarrier receive the information of PT, PT is to ST _bspeed be:

$R_1=\frac{1}{2}\underset{k\&Element;G_p}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{1,b}^k{p}_p^k)---\left(5\right)$

Wherein represent subcarrier k at link PT to ST _bon channel gain, be illustrated in the upper power when sending authorization user information of subcarrier k, according to water-filling algorithm, distribute.

Meanwhile, ST _butilize remaining in subcarrier send oneself information, ST _bspeed to SR is:

$R_s^1=\frac{1}{2}\underset{k\&Element;{\stackrel{\&OverBar;}{G}}_p}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{3,b}^k{p}_{\mathrm{ss},b}^k)---\left(7\right)$

Wherein represent that subcarrier is at link ST _bto the channel gain on SR, represent ST _bpower on subcarrier k when sending own information.

At second time slot, ST _bthe information of decoding authorized user, and utilize G _sin subcarrier forward authorization user information to PR, ST _bspeed to PR is:

$R_2=\frac{1}{2}\underset{k^{\&prime;}\&Element;G_s}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}{p}_{\mathrm{sp},b}^{k^{\&prime;}})---\left(6\right)$

Wherein for subcarrier k' is at link ST _bto the channel gain on PR, power while being illustrated in subcarrier k' above for relaying authorization user information

Meanwhile, ST _butilize remaining in subcarrier send oneself information, ST _bspeed to SR is:

$R_s^2=\frac{1}{2}\underset{k^{\&prime;}\&Element;{\stackrel{\&OverBar;}{G}}_s}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}{p}_{\mathrm{ss},b}^{k^{\&prime;}})---\left(8\right)$

Wherein represent that subcarrier k' is at link ST _bto the channel gain on SR, represent ST _bpower on subcarrier k' when sending own information.

The speed that authorized user and cognitive user obtain is:

R _p＝min{R ₁,R ₂} （3）

$R_s=R_s^1+R_s^2---\left(4\right)$

Subcarrier and power distribution method in present embodiment are specially:

The subcarrier of cognitive user and power division can be modeled as:

$\underset{\{G,p\}}{\max }{R}_s---\left(1\right)$

Meet the following conditions $\left\{\begin{array}{c}{R}_p\&GreaterEqual;R_T\\ {\mathrm{\&Sigma;}}_{k\&Element;{\stackrel{\&OverBar;}{G}}_p}{p}_{\mathrm{ss},b}^k\&le;P_s\\ {\mathrm{\&Sigma;}}_{k^{\&prime;}\&Element;G_s}{p}_{\mathrm{sp},b}^{k^{\&prime;}}+{\mathrm{\&Sigma;}}_{k^{\&prime;}\&Element;{\stackrel{\&OverBar;}{G}}_s}{p}_{\mathrm{ss},b}^{k^{\&prime;}}\&le;P_s\end{array}\right.---\left(2\right)$

Wherein, G={G _p, G _sand the subcarrier and the power division that represent respectively cognitive user, G _pand G _srepresent to distribute to respectively the subcarrier set of authorized user and cognitive user, with represent respectively G _pand G _ssupplementary set, P _sthe maximum transmit power that represents cognitive user.

By method of Lagrange multipliers, we can obtain above-mentioned optimum subcarrier and power division:

$p_{\mathrm{ss},b}^{k^{*}}={(\frac{1}{2{\mathrm{\&beta;}}_{P_1}}-\frac{1}{{\mathrm{\&gamma;}}_{3,b}^k})}^{+}---\left(9\right)$

$p_{\mathrm{sp},b}^{k^{\&prime;*}}={(\frac{{\mathrm{\&beta;}}_{R_2}}{2{\mathrm{\&beta;}}_{P_2}}-\frac{1}{{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}})}^{+}---\left(10\right)$

$p_{\mathrm{ss},b}^{k^{\&prime;*}}={(\frac{1}{2{\mathrm{\&beta;}}_{P_2}}-\frac{1}{{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}})}^{+}---\left(11\right)$

$G_p^{*}=\arg \underset{G_p}{\max }\underset{k\&Element;G_p}{\mathrm{\&Sigma;}}{F}_k---\left(12\right)$

$G_s^{*}=\arg \underset{G_s}{\max }\underset{k^{\&prime;}\&Element;G_s}{\mathrm{\&Sigma;}}{F}_{k^{\&prime;}}---\left(13\right)$

Wherein

$F_k=\frac{{\mathrm{\&beta;}}_{R_1}}{2}\ln (1+{\mathrm{\&gamma;}}_{1,b}^k{p}_p^k)-\frac{1}{2}\ln (1+{\mathrm{\&gamma;}}_{3,b}^k{p}_{\mathrm{ss},b}^{k^{*}})+{\mathrm{\&beta;}}_{P_1}{p}_{\mathrm{ss},b}^{k^{*}}---\left(14\right)$

$F_{k^{\&prime;}}=\frac{{\mathrm{\&beta;}}_{R_2}}{2}\ln (1+{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}{p}_{\mathrm{sp},b}^{k^{\&prime;*}})-\frac{1}{2}\ln (1+{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}{p}_{\mathrm{ss},b}^{k^{\&prime;*}})+{\mathrm{\&beta;}}_{P_2}(p_{\mathrm{ss},b}^{k^{\&prime;*}}-p_{\mathrm{sp},b}^{k^{\&prime;*}})---\left(15\right)$

Wherein with represent Lagrange multiplier.

On average can the reaching speed and can be obtained by following formula of cognitive user in present embodiment:

${\stackrel{\&OverBar;}{R}}_s=E\left[R_s\right]\&CenterDot;P_{\mathrm{access}}---\left(18\right)$

Wherein probability for cognitive user insertion authority frequency spectrum.

On average can the reaching speed and can be obtained by following formula of authorized user in present embodiment:

${\stackrel{\&OverBar;}{R}}_p=E\left[R_K\right|\{R_K\&GreaterEqual;R_T\}\&cup;\{R_b^{\max }<R_T\}]\&CenterDot;(1-P_{\mathrm{access}})+E[R_p]\&CenterDot;P_{\mathrm{access}}---\left(19\right)$

The anti-interference frequency spectrum access method based on full duplex OFDM cooperation of the present embodiment, can effectively eliminate the interference problem of authorized user and cognitive user in the formula frequency spectrum access method that coexists, and can effectively promote the throughput of cognitive user.

In the frequency spectrum access method of this enforcement, cognitive user can send the information of oneself in two time slots.At first time slot, cognitive user G _pin subcarrier receive the information of authorized user, and utilize residue in subcarrier send oneself information.At second time slot, cognitive user G _sin subcarrier forward authorization user information, utilize residue simultaneously in subcarrier send oneself information.Cognitive user can send the information of oneself in two time slots, and authorized user and cognitive user send information by disjoint subcarrier respectively, can not produce interference between mutually.In the present embodiment, we make P _p/ σ ²=10dB, sub-carrier number K=32, cognitive user sends terminal number L=20, the channel static frequency selectivity rayleigh fading channel that is as the criterion.Unless otherwise indicated, with at-5dB, between 5dB, be uniformly distributed.

The anti-interference frequency spectrum access method based on OFDM cooperation of the present embodiment has promoted the performance of authorized user and cognitive user.In Fig. 2, shown at R _tduring=2bps/Hz, adopt the Mean Speed of authorized user and cognitive user after frequency spectrum access method of the present invention, can find out and adopt after frequency spectrum access method of the present invention, not only cognitive user can obtain frequency spectrum access, and the performance of authorized user also can get a promotion.And can find out and adopt the cognitive system Mean Speed of full-duplex mode of the present invention higher than the cognitive system Mean Speed that adopts semiduplex mode.Fig. 3 has shown the probability of the cognitive user access frequency spectrum in the present invention, and has compared with and R _t=2bps/Hz and R _tduring=3bps/Hz, access the probability of frequency spectrum, can find out less, R _tlarger, the probability of cognitive user access frequency spectrum is larger.

Claims (5)

1. the anti-interference frequency spectrum access method based on full duplex OFDM cooperation, radio communications system comprises an authoring system and a cognitive system, wherein, authoring system is by an authorized user transmitting terminal PT and authorize receiving terminal PR to form, and described authoring system is supported relay function; Cognitive system is by L cognitive user transmitting terminal ST _i, i ∈ L={1,2,3 ..., L} and a common receiving terminal SR form, and described cognitive system can be simulated radio protocol and the system parameters in main system; It is characterized in that: the described anti-interference frequency spectrum access method based on full duplex OFDM cooperation comprises the following steps:

1) authorized user transmitting terminal PT calculates when direct transferring to the speed R that authorizes receiving terminal PR _k, with its targeted rate R _trelatively, if R _k< R _t, authorize receiving terminal PR cognitive user transmission towards periphery cooperation request signal to seek the cooperation of cognitive user;

2) receive after cooperation request signal, authorized user transmitting terminal PT sends a cooperation response signal;

3) cognitive user transmitting terminal ST _ireceive after cooperation request signal and cooperation response signal, calculate oneself completely as the relaying of authorized user transmitting terminal PT, accessible speed while using whole subcarriers and power to help to forward authorized user transmitting terminal PT information

4) in all cognitive user, find out and can obtain maximum cognitive user ST _b, and find out the speed that this cognitive user can help authorized user to reach

5) if sT _bbroadcast cooperation confirmation signal, the mode insertion authority user's who cooperates with full duplex OFDM frequency spectrum; Otherwise authorized user continues to send by direct transferring the information of oneself;

6) authorized user is received after cooperation confirmation signal, distributes a part of subcarrier to ST _b, allow its mode with full duplex OFDM cooperation to access oneself frequency spectrum, ST _bobtain the authorization after user's frequency spectrum access, at second time slot, utilize a part of subcarrier and power to help to forward the information of authorized user, utilize other a part of subcarrier and power at first and second time slot, to send the information of oneself.

2. a kind of anti-interference frequency spectrum access method based on full duplex OFDM cooperation as claimed in claim 1, is characterized in that: subcarrier and the power division of cognitive user are modeled as:

$\underset{\{G,p\}}{\max }{R}_s---\left(1\right)$

Meet the following conditions $\left\{\begin{array}{c}{R}_p\&GreaterEqual;R_T\\ {\mathrm{\&Sigma;}}_{k\&Element;{\stackrel{\&OverBar;}{G}}_p}{p}_{\mathrm{ss},b}^k\&le;P_s\\ {\mathrm{\&Sigma;}}_{k^{\&prime;}\&Element;G_s}{p}_{\mathrm{sp},b}^{k^{\&prime;}}+{\mathrm{\&Sigma;}}_{k^{\&prime;}\&Element;{\stackrel{\&OverBar;}{G}}_s}{p}_{\mathrm{ss},b}^{k^{\&prime;}}\&le;P_s\end{array}\right.---\left(2\right)$

Wherein, G={G _p, G _sand the subcarrier and the power division that represent respectively cognitive user, G _pand G _srepresent to distribute to respectively the subcarrier set of authorized user and cognitive user, with represent respectively G _pand G _ssupplementary set, with represent respectively ST _bat second time slot power for relaying authorization user information and while sending own information on subcarrier k', represent ST _bat first time slot power when sending information on subcarrier k, P _sthe maximum transmit power that represents cognitive user; R _pand R _srepresent respectively after cognitive user insertion authority user frequency spectrum the speed that authorized user and cognitive user obtain:

R _p＝min{R ₁,R ₂} （3）

$R_s=R_s^1+R_s^2---\left(4\right)$

Wherein, R ₁and R ₂represent respectively the speed that authorized user obtains at first and second time slot:

$R_1=\frac{1}{2}\underset{k\&Element;G_p}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{1,b}^k{p}_p^k)---\left(5\right)$

$R_2=\frac{1}{2}\underset{k^{\&prime;}\&Element;G_s}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}{p}_{\mathrm{sp},b}^{k^{\&prime;}})---\left(6\right)$

Wherein with represent respectively subcarrier k at link PT to ST _bwith subcarrier k' at link ST _bto the channel gain on PR, be illustrated in the upper power when sending authorization user information of subcarrier k, according to water-filling algorithm, distribute;

with represent respectively the speed that cognitive user obtains at first time slot and second time slot:

$R_s^1=\frac{1}{2}\underset{k\&Element;{\stackrel{\&OverBar;}{G}}_p}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{3,b}^k{p}_{\mathrm{ss},b}^k)---\left(7\right)$

$R_s^2=\frac{1}{2}\underset{k^{\&prime;}\&Element;{\stackrel{\&OverBar;}{G}}_s}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}{p}_{\mathrm{ss},b}^{k^{\&prime;}})---\left(8\right)$

Wherein with represent that respectively subcarrier k and k' are at link ST _bto the channel gain on SR;

By method of Lagrange multipliers, obtain above-mentioned optimum subcarrier and power division:

$p_{\mathrm{ss},b}^{k^{*}}={(\frac{1}{2{\mathrm{\&beta;}}_{P_1}}-\frac{1}{{\mathrm{\&gamma;}}_{3,b}^k})}^{+}---\left(9\right)$

$p_{\mathrm{sp},b}^{k^{\&prime;*}}={(\frac{{\mathrm{\&beta;}}_{R_2}}{2{\mathrm{\&beta;}}_{P_2}}-\frac{1}{{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}})}^{+}---\left(10\right)$

$p_{\mathrm{ss},b}^{k^{\&prime;*}}={(\frac{1}{2{\mathrm{\&beta;}}_{P_2}}-\frac{1}{{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}})}^{+}---\left(11\right)$

$G_p^{*}=\arg \underset{G_p}{\max }\underset{k\&Element;G_p}{\mathrm{\&Sigma;}}{F}_k---\left(12\right)$

$G_s^{*}=\arg \underset{G_s}{\max }\underset{k^{\&prime;}\&Element;G_s}{\mathrm{\&Sigma;}}{F}_{k^{\&prime;}}---\left(13\right)$

Wherein

$F_k=\frac{{\mathrm{\&beta;}}_{R_1}}{2}\ln (1+{\mathrm{\&gamma;}}_{1,b}^k{p}_p^k)-\frac{1}{2}\ln (1+{\mathrm{\&gamma;}}_{3,b}^k{p}_{\mathrm{ss},b}^{k^{*}})+{\mathrm{\&beta;}}_{P_1}{p}_{\mathrm{ss},b}^{k^{*}}---\left(14\right)$

$F_{k^{\&prime;}}=\frac{{\mathrm{\&beta;}}_{R_2}}{2}\ln (1+{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}{p}_{\mathrm{sp},b}^{k^{\&prime;*}})-\frac{1}{2}\ln (1+{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}{p}_{\mathrm{ss},b}^{k^{\&prime;*}})+{\mathrm{\&beta;}}_{P_2}(p_{\mathrm{ss},b}^{k^{\&prime;*}}-p_{\mathrm{sp},b}^{k^{\&prime;*}})---\left(15\right)$

Wherein with represent Lagrange multiplier.

3. the anti-interference frequency spectrum access method based on full duplex OFDM cooperation as claimed in claim 1 or 2, is characterized in that: in described step 5), cognitive user is by two time slot full duplex decoding forward collaboration mode insertion authority users' frequency spectrum;

At first time slot, ST _butilize G _pin subcarrier receive the information of PT, PT is to ST _bspeed be:

$R_1=\frac{1}{2}\underset{k\&Element;G_p}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{1,b}^k{p}_p^k)---\left(5\right)$

Meanwhile, ST _butilize remaining in subcarrier send oneself information, ST _bspeed to SR is:

$R_s^1=\frac{1}{2}\underset{k\&Element;{\stackrel{\&OverBar;}{G}}_p}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{3,b}^k{p}_{\mathrm{ss},b}^k)---\left(7\right)$

At second time slot, ST _bthe information of decoding authorized user, and utilize G _sin subcarrier forward authorization user information to PR, ST _bspeed to PR is:

$R_2=\frac{1}{2}\underset{k^{\&prime;}\&Element;G_s}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{2,b}^{k^{\&prime;}}{p}_{\mathrm{sp},b}^{k^{\&prime;}})---\left(6\right)$

Meanwhile, ST _butilize remaining in subcarrier send oneself information, ST _bspeed to SR is:

$R_s^2=\frac{1}{2}\underset{k^{\&prime;}\&Element;{\stackrel{\&OverBar;}{G}}_s}{\mathrm{\&Sigma;}}\ln (1+{\mathrm{\&gamma;}}_{3,b}^{k^{\&prime;}}{p}_{\mathrm{ss},b}^{k^{\&prime;}})---\left(8\right).$

4. the anti-interference frequency spectrum access method based on full duplex OFDM cooperation as claimed in claim 1 or 2, is characterized in that: in described step 1), and speed R when authorized user transmitting terminal direct transfers _kobtain by the following method:

$R_K=\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}\ln (1+{\mathrm{\&gamma;}}_0^k{p}_p^k)---\left(16\right)$

Wherein for subcarrier k at link PT to the channel gain on PR.

5. the anti-interference frequency spectrum access method based on full duplex OFDM cooperation as claimed in claim 1 or 2, is characterized in that: in described step 3), obtain by the following method:

$R_i^{\max }=\min \{R_{1,i}^{\max },R_{2,i}^{\max }\}---\left(17\right)$

Wherein $R_{1,i}^{\max }=\frac{1}{2}{\mathrm{\&Sigma;}}_{k=1}^K\ln (1+{\mathrm{\&gamma;}}_{1,i}^k{p}_p^k),$ $R_{2,i}^{\max }=\frac{1}{2}{\mathrm{\&Sigma;}}_{k^{\&prime;}=1}^K\ln (1+{\mathrm{\&gamma;}}_{2,i}^{k^{\&prime;}}{p}_{\mathrm{sp},i}^{k^{\&prime;}}),$ represent subcarrier k at link PT to ST _ion channel gain, represent that subcarrier k' is at link ST _ito the channel gain on SR, represent ST _ipower on subcarrier k' during for relaying authorization user information.