CN105979590B - User's scheduling and power distribution method in cognitive radio system based on available capacity - Google Patents
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Abstract
User's scheduling and power distribution method in a kind of cognitive radio system of the present invention based on available capacity, can adapt to the guarantee of otherness time delay QoS.The cognitive radio system include a main transmitting terminal, a secondary emission end, at least two can interoperable SU and several MU that cannot be cooperated to each other, secondary emission end can be used as fusion center, the data of SU are handled；Described method includes following steps, step 1, and secondary user's carry out frequency spectrum perception, judges the use state of channel, and obtains the detection probability that different detecting states occur；Step 2, the expression formula of the available capacity of SU is obtained according to the parameter of cognitive radio system, establish the relationship of detection probability Yu SU available capacity, and mean power it is limited and to PU it is interference-limited under conditions of available capacity is optimized, target is turned to available capacity maximum and obtains final user's scheduling and power allocation scheme.
Description
Technical field
The present invention relates to the resource allocation methods of cognitive radio system in wireless communication field, specially cognitive radio
User's scheduling and power distribution method in system based on available capacity.
Background technique
The fast development of wireless communication technique, it is desirable that various communication equipments are gone with higher efficiency using limited frequency spectrum,
But the fixed frequency spectrum method of salary distribution of existing authorized spectrum band but fails that frequency spectrum resource is made to be fully utilized.Cognitive radio
Technology is to solve the problems, such as the effective way of radio spectrum resources scarcity.In cognitive radio system, unauthorized user (Second
User, SU) i.e. secondary user's, by the use state of perceived spectral, dynamic, the adaptive configured transmission for changing itself,
When frequency spectrum is in the access frequency spectrum of " frequency spectrum cavity-pocket " Shi Zeji, the utilization efficiency of frequency spectrum can be promoted effectively in this way to maximum
Change power system capacity or meets the quality of service requirement of user.
However, equipment unknown in cognition network can dynamically access frequency spectrum, this feature faces cognition network
More special safety problem.Counterfeit main customer attack (Primary User Emulation Attack, PUEA) is wherein
A kind of common form: certain malicious users (Malicious User, MU) present in system are being awarded for hostile purpose
User (Primary User, PU) is weighed when i.e. primary user is not take up channel, imitates signal characteristic (modulation system, the coding staff of PU
Formula, power etc.) signal is sent, so that legal SU takes for PU and is occupying frequency spectrum and avoiding using the frequency range, thus significantly
Spectrum efficiency is reduced, so that service quality (Quality of Service, QoS) demand of SU can not be satisfied, and
Different users often has a different delay requirements, such as audio signal is stringenter than the delay requirement that data are transmitted, institute
It is had great significance with the security problem research to otherness time delay QoS.Available capacity is defined as meeting certain QoS requirement
The maximum arrival rate of lower system, the system of characterize provide the ability of real-time sex service.So the available capacity of lifting system can
Effectively to ensure the time delay QoS demand of user.
Since the limited performance of cognition network is in maximum transmission power, and the communication quality in order to ensure PU, SU's is logical
Letter receives many limitations, so cannot guarantee the QoS of SU, reasonable resource allocation side only by transimission power is promoted
Case can effectively promote the system performance of cognition network, however, the resource allocation algorithm in existing cognitive radio system
Time delay qos requirement is not mostly considered or only considers very strict or very loose situation, therefore studies otherness time delay QoS
Security problem has great significance.
Summary of the invention
Aiming at the problems existing in the prior art, the present invention is provided in a kind of cognitive radio system based on available capacity
User's scheduling and power distribution method, can adapt to the guarantee of otherness time delay QoS, in the limited system call of capacity, into
Row optimal user's scheduling and power distribution.
The present invention is to be achieved through the following technical solutions:
User's scheduling and power distribution method in cognitive radio system based on available capacity, the cognitive radio
System include a main transmitting terminal, a secondary emission end, at least two can interoperable SU and several to each other
The MU that cannot be cooperated, secondary emission end can be used as fusion center, handle the data of SU；Include the following steps,
Step 1, secondary user's carry out frequency spectrum perception, judge the use state of channel, and obtain different detecting states and occur
Detection probability；
Step 2 obtains the expression formula of the available capacity of SU according to the parameter of cognitive radio system, establishes detection probability
With the relationship of SU available capacity, and mean power it is limited and to PU it is interference-limited under conditions of available capacity is carried out it is excellent
Change, target is turned to available capacity maximum and obtains final user's scheduling and power allocation scheme.
Preferably, using the double threshold energy detection method of cooperation among users, channel status is detected, carries out frequency spectrum
Perception, specifically comprises the following steps；
Step 1, two secondary user's arbitrarily chosen in cognitive radio system sample current Received Signal, obtain
To the energy detection value for two secondary user's being selected；
Step 2, energy measuring statistic is obtained by cooperation among users according to two energy detection values that step 1 obtainsIt is shown below respectively with d_Y；
Wherein:J=1,2, N be sampling number, and y [i] is the signal of i-th sampling,WithIt is
In cognitive radio system when main transmitting terminal transmitting signal, signal energy that two secondary user's receive；
Step 3, determine that energy measuring statistic is preset accordingly by limiting the theoretical value of detection probability in a variety of situations
Thresholding；Pre-determined threshold includes energy measuring statisticPre-determined threshold λ up and down1And λ2And energy measuring statistic d_Y
Pre-determined threshold ε；By energy detection statisticWith upper and lower pre-determined threshold λ1And λ2Compared as follows,On if
Formula is set up, and thens follow the steps 4, no to then follow the steps 5；
Step 4, compared with energy detection statistic d_Y being carried out as follows with pre-determined threshold ε, d_Y < ε；If above formula is set up,
Then it is determined as that primary user occupies frequency spectrum；Otherwise it is determined as that malicious user occupies frequency spectrum, i.e. frequency spectrum current state is PUEA；
Step 5, by energy detection statisticWith upper and lower pre-determined threshold λ1And λ2Compared as follows,On if
Formula is set up, then is determined as the frequency spectrum free time；Otherwise it is determined as that malicious user occupies frequency spectrum, i.e. frequency spectrum current state is PUEA；
Step 6, the case where being occupied according to frequency spectrum in step 4 and step 5 completes frequency spectrum perception, and judge channel uses shape
State.
Further, in step 3, the theoretical value by limiting detection probability in a variety of situations determines energy measuring statistic phase
The pre-determined threshold answered, specific step is as follows,
Step 3.1, the process of primary user and malicious user access frequency spectrum are modeled；
Step 3.2, by the analysis to modeling, the prior probability of primary user and malicious user access frequency spectrum are obtained；
Step 3.3, the distribution for receiving signal obedience is carried out it is assumed that obtaining the combination of all channel status and detecting state
In the case of detection probability theoretical value, and solve obtain the corresponding pre-determined threshold of energy measuring statistic.
Further, in step 3.1, when modeling, the process model building by primary user and malicious user access frequency spectrum is Poisson
Process.
Preferably, the probability of different detecting states is obtained according to central-limit theorem.
Preferably, the available capacity expression formula are as follows:
Wherein, θ is QoS index；K is the channel status number of limited channel model；P(sj) it be channel virtual condition is sj's
Probability；Be channel virtual condition be sjAnd testing result isProbability；It is for testing resultWhen function
Rate distribution coefficient；For the rate of information throughput under the power partition coefficient.
Further, with mean power it is limited and to PU it is interference-limited under conditions of maximize the available capacity of system into
The modeling of row optimization problem, expression formula are as follows:
0≤β≤1
Wherein, β indicates ratio shared by the available capacity of two SU from 0 to 1；θ1And θ2It is respective to respectively indicate two SU
QoS index；P4 is the probability that PU busy channel is detected as to channel idle, and P6 is that PU busy channel is detected as MU busy channel
Probability.
Further, it according to limited channel model and optimization problem model, obtains objective function and constraint condition indicates
Optimization problem；The optimization method of fixed schedule matrix and optimization power alternating iteration when being dispatched using user, obtains some letter
Optimal user scheduling and probability assignments scheme under road state.
Further, the optimal of the optimization problem of objective function and constraint condition expression is obtained by solution dual problem
Solution；The optimal solution of dual problem is obtained using gradient descent method.
Compared with prior art, the invention has the following beneficial technical effects:
First, the present invention consider to primary user it is interference-limited under the premise of, occupied in channel idle and malicious user
Information transmission is carried out using different power when channel, when channel idle, using lesser transimission power, malicious user occupies letter
It is larger due to interfering when road, so can effectively promote the information transmission of secondary user's in this way using biggish power transmission
Rate.
Second, the present invention considers the otherness time delay qos requirement of different user, the no longer simple angle from information theory
It sets out, only goes to realize power distribution as optimization aim using the ergodic capacity of system or outage capacity.The present invention is by available capacity
Theory is applied in cognitive radio system, and the size of available capacity characterizes the guarantee situation of user's time delay QoS, the present invention
The relationship of user's available capacity and detection probability is established under the scene there are PUEA, and in the case where different QoS index
User's scheduling and power distribution are realized, is that there are realize otherness time delay QoS under the scene of PUEA in cognitive radio system
Guarantee provides feasible method.
Further, combined optimization processing is carried out with power to user's scheduling by using the method for alternating iteration, and most
Optimal user's scheduling and power allocation scheme are obtained eventually.It can be realized simultaneously the combined optimization of user's scheduling and power distribution,
Different power is used in the case where channel idle and malicious user busy channel, and according to the current letter of two secondary user's
Road state is scheduled user, and the different time delay QoS constraint requirements of user have also been fully considered in scheduling process.
Detailed description of the invention
Fig. 1 is the flow chart of the double threshold frequency spectrum perception of cooperation among users described in present example.
Fig. 2 is the system available capacity comparison of each scheme under identical QoS constraint condition described in present example.
Fig. 3 is the system available capacity comparison of each scheme under difference QoS constraint condition described in present example.
Fig. 4 is the system available capacity bound pair ratio of each scheme under identical QoS constraint condition described in present example.
Fig. 5 is the system available capacity bound pair ratio of each scheme under difference QoS constraint condition described in present example.
Specific embodiment
Below with reference to specific embodiment, the present invention is described in further detail, it is described be explanation of the invention and
It is not to limit.
User's scheduling and power distribution method in cognitive radio system of the present invention based on available capacity, there are PUEA's
When user under scene towards available capacity is dispatched with power distribution, the first step is examined using the double threshold energy of cooperation among users
Survey scheme carries out frequency spectrum perception, detects to channel status, judges the use state of channel, and obtains various different detection shapes
The detection probability that state occurs；Second step establishes the relationship of detection probability Yu SU available capacity, and turns to mesh with available capacity maximum
Mark obtains user's scheduling and power allocation scheme.Wherein, the table of SU available capacity is obtained according to the parameter of cognitive radio system
Up to formula, and mean power it is limited and to PU it is interference-limited under conditions of the available capacity is optimized, obtain most
The available capacity of bigization system.
Specific embodiment is as follows:
Consider a cognitive radio system, includes a main transmitting terminal in the system, a secondary emission end, two can
With interoperable SU and several MU that cannot be cooperated to each other, secondary emission end can be used as fusion center, to SU's
Data are handled.PU and MU occupies frequency spectrum resource with certain probability, in this way, secondary user's can use reasonable frequency spectrum
Perceptual strategy detects whether channel is occupied by PU or MU, and reasonably utilizes channel according to testing result.Assuming that channel is auspicious
The time duration of sharp bulk nanometer materials, a frame is T, wherein the preceding T of each frame0Second is used for frequency spectrum perception, remaining T-T0Duration
It is transmitted for information.Channel status is detected using the double threshold case of energy detection schemes of cooperation among users in this programme.
1) the double threshold case of energy detection schemes of cooperation among users
In view of the transmission power of MU and the random mobility of position, the reception signal energy to multiple SU cannot achieve
It is imitated, this programme is distinguished by the way of cooperation among users to signal is received, as shown in Figure 1, two thresholdings of setting
λ1And λ2And λ1<λ2, detection statistic are as follows:
Wherein:
N is sampling number, and y [i] is the signal of i-th sampling,WithIt is main transmitting terminal in cognitive radio system
When emitting signal, signal energy that two secondary user's receive.
SU is by Y1,Y2Fusion center is passed to, fusion center calculatesWith d_Y, and by its with preset thresholding into
Row comparison.It first determines whetherWhether it is located between two thresholdings, ifThen think that channel is idle state, ifThen think that channel is occupied by MU, it is assumed here that main transmitting terminal sends signal with firm power, and the position of SU is protected
Hold constant, and the transmission power of MU and position be by random fluctuation, so when MU transmission power is excessive or MU distance SU is closer
The energy value that secondary user's are detected is greater than thresholding λ2。
When the energy value detected is located between two thresholdings, the unstability of position and transmission power based on MU is led to
Two user collaborations are crossed to distinguish whether signal comes from MU, when the energy of two SU detection and the work of known PU signal energy are poor
When difference afterwards is greater than some thresholding ε, it is believed that signal comes from MU, thinks that signal carrys out spontaneous emission when energy differences are less than thresholding ε
The main transmitting terminal of power stability.
2) determination of various detection probabilities
Consider actual communication process, it is assumed that the process that PU accesses frequency spectrum is Poisson process, arrival rate λP, occupy every time
It is μ that the time of channel, which obeys parameter,PQuantum condition entropy；MU cannot be accounted for persistently when the channel is idle due to power limited
With channel, but in the case where channel idle, frequency spectrum, arrival rate λ are accessed with Poisson processM, each busy channel when
Long parameter of obeying is μMQuantum condition entropy.
Assuming that the state transition probability of PU busy channel isIndicate that channel status is transformed into state j by state i, wherein
I, j ∈ 0,1, state 0 indicate that channel idle, state 1 indicate PU busy channel, then available following transition probability:
By the prior probability of the available PU busy channel of the above transition probability are as follows:
It is similarly available when PU is not take up channel, the prior probability of MU busy channel are as follows:
WhereinCalculation method reference
In order to obtain the theoretical value of various detection probabilities, following hypothesis is done:
A) signal that two SU receive next autonomous transmitting terminal obeys the circulation multiple Gauss distribution of 0 mean value, and variance is divided intoWithAnd these information of SU a priori known；
B) two SU receive the circulation multiple Gauss distribution that the signal from MU obeys 0 mean value, and variance is divided intoWithWhereinValue the energy value that detects can be utilized to carry out according to when testing result is MU busy channel
Estimation, it is assumed herein that the two values can be estimated correctly out；When testing result is that channel is occupied by MU, can use as follows
Mode pair(wherein i=1,2) is estimated:
Wherein, N is using points, yjFor the obtained signal of jth time sampling.When n is large,Can accurately it be estimated
Meter comes out.
C) additive noise 0 mean variance of obedience in channel isCirculation multiple Gauss distribution.
According to central-limit theorem, it is known that channel it is idle, occupied by PU, these three states occupied by MU under, inspection
Survey statisticWith the equal Gaussian distributed of d_Y.
Any moment, the virtual condition of channel and testing result there are three types of may, all situations as listed in table 1:
1 channel status of table and detecting state.
According to the detection scheme proposed, this available nine kinds of probability happened are as shown in table 2:
The theoretical value of detection probability under the various states of table 2.
Wherein
3) towards the optimization problem of available capacity
Available capacity is defined as under the requirement for meeting certain statistics QoS, the maximum arrival rate that system can achieve,
The system of characterize provides the ability of real-time sex service.After determining cognitive user for transmission plan corresponding to different sensing results
The expression of available cognitive radio system available capacity, to be modeled and be solved to optimization problem, finally
Obtain optimal user's scheduling and power allocation scheme.The expression of available capacity is as follows:
Wherein:Expectation is asked in expression, and S (t) indicates accumulation service process, i.e. the bit of service user in 0~t time
Number, θ indicates QoS index, for biggish θ, it is desirable that system has lower time delay rate of violation, i.e. qos requirement is stringenter, institute
Attainable available capacity is lower；For lesser θ, the requirement to QoS is more loose, and the attainable available capacity of institute is higher.
In order to obtain available capacity expression formula of the secondary user's based on detection probability, will test result and actual conditions can be with
It is expressed as follows:
Then the available capacity of secondary user's can be expressed as follows:
Wherein:
Testing result isWhen power partition coefficient
Testing result isThe rate of information throughput, institute
Can obtain:
Wherein: P1~P9 is the detection probability of various states in table 1.
1) finite-state channel model.
In order to realize to the mean value computation of channel status, this programme uses finite-state channel model in (14): assuming that
Channel is Rayleigh bulk nanometer materials, and the channel gain z of two SU is independent of one another, and z is remained unchanged in a time slot T, no
Change at random with the interior z of time slot.Channel status is divided into K sections according to signal-to-noise ratio (Signal Noise Ratio, SNR), is drawn
The boundary divided is { σ0,...,σK, if signal-to-noise ratio falls within section [σk-1,σk), then think that channel status is mk, so can will believe
The set expression of road state is M={ m1,m2,...,mK}.After the partition strategy of SNR determines, various channel shapes can be obtained
Probability corresponding to state is π={ π0,π1,...,πK-1}.According to finite-state channel model, (13) can be expressed as follows:
2) interference of PU is limited.
When testing result is channel idle or is MU busy channel, secondary emission end will pass through reasonable Scheme Choice
Information is sent for secondary user's, but testing result is with certain risk, namely in practical PU busy channel, frequency spectrum
The possible channel idle of the result of perception either MU busy channel, the communication of secondary user's will interfere PU at this time.For
The communication quality for guaranteeing PU limits the interference desired value to PU are as follows:
Wherein: PupFor the average interference upper limit.
3) optimization problem is established and is solved.
The present invention establishes following optimization problem to maximize system available capacity as target:
0≤β≤1
Wherein: β indicates ratio shared by the available capacity of two users from 0 to 1；θ1And θ2Respectively indicate two SU respectively
QoS index.
In order to obtain user's scheduling scheme under different channels state, it is assumed that S (m1,m2) be SU scheduling function, wherein
(m1,m2) be respectively two SU channel status.S(m1,m2)=1 indicates that secondary emission end is that user 1 sends information, S (m1,m2)
=0 indicates that secondary emission end is that user 2 sends information, defines dispatch matrix SK×K, whereinIndicate different
User's scheduling scheme under channel status.For any time slot, there is following situation:
One: testing result is PU busy channel, at this point, SU will stop communicating.
Two: testing result is channel idle or MU busy channel, will dispatch a SU at this time and communicates.
According to limited channel model, the objective function of (17) and constraint condition can be expressed as follows:
0≤β≤1
Optimization problem solving:
It can prove to fix when user's dispatch matrix, the objective function of optimization problem described in formula (18) is convex function, and
Restrictive condition is linear, so being a convex optimization problem.The optimization thought that alternating iteration can be used, has respectively obtained difference
User's scheduling and probability assignments scheme under channel status:
Step 1. finds optimal dispatch matrix S (in K for fixed β, fixed transmission powers, traversal2It is found in kind).
For step 2. for fixed dispatch matrix and β, formula (18) can be by solving the available former problem of dual problem
(18) optimal solution, detailed process is as follows:
The dual problem of former problem can indicate are as follows:
s.t.λ≥0 (19)；
Can by using gradient descent method obtain problem (19) optimal solution, gradient descent method be when user dispatch determine with
This convex optimization problem of power optimization, specific steps are solved afterwards are as follows:
Step 2.1: Initialize installation
The number of iterations t=1 is enabled, and the initial value D of dual function is set(0)And the initial value λ of Lagrange multiplier(0)
Step 2.2: update optimized variable:
Step 2.3: updating Graded factor Δ f(t), dual function D(t)And Lagrange multiplier λ(t):
λ(t)=λ(t-1)+step*Δf(t)(23)；
Wherein step is iteration step length；
Step 2.4: judge whether iteration terminates:
ξ=| D(t)-D(t-1)|；T=t+1 (24)；
If ξ > 10-4, meet iterated conditional, then repeat step 2.1 to step 2.4, until iteration terminates, obtain optimal
Power distribution strategies function.
Then step 3. brings the power after optimization in step 1 into, repeat step 1 and arrive step 3, by power distribution and user
Scheduling is iterated, and obtains optimal joint optimization result.Namely by the iteration of scheduling and optimization, that is, after determining dispatch matrix
Optimize power, then goes to obtain new dispatch matrix with the power after this optimization, then remove optimization power with new dispatch matrix, according to
It is secondary to carry out several times,
The present invention simulates the scheduling of the user under the mentioned scene there are PUEA towards available capacity and power distribution side
Case is compared in performance, and with random schedule user, constant power allocation plan.Simulation parameter reference table 3.
The configuration of 3 simulation parameter of table
| Simulation parameter | Configuration |
| Frame length | 1 second |
| Perceive duration | 0.1 second |
| PU arrival rate λP | 0.01 |
| μP | 0.01 |
| MU arrival rate λM | 0.005 |
| λ1 | 0.9405 |
| λ2 | 12.207 |
| ε | 0.223 |
| K | 5 |
It is respectively 10dB and 12dB that main transmitting terminal is set in emulation to two putting down signal-to-noise ratio for SU, and noise power is set as 1.
The value that identical QoS and otherness QoS constrains lower F is set forth in Fig. 2 and Fig. 3, as can be seen that constant power is random from two figures
It is minimum to dispatch available capacity obtained, and the performance of optimal power random schedule has slight raising, when using constant power
When optimal scheduling, the available capacity of system is very significantly improved, and uses the scheme of proposed scheduling and power joint optimization
System can be made to obtain optimal performance.Can also be obtained by Fig. 2 and Fig. 3, the F value under random schedule be it is linear, this be because
For β and F is linear relationship in formula (18) after dispatch matrix is fixed.Because the QoS of two users constrains identical, institute in Fig. 2
Curve with optimal scheduling is symmetrical, and the inclination of the curve of random schedule is since the unjustness of random schedule causes
's.In Fig. 3, θ2<θ1, when β is smaller, optimal scheduling is tended to dispatch user 2, and the resulting available capacity of system is larger, and works as β
When larger, optimal scheduling is tended to dispatch user 1, and the resulting available capacity of system is smaller, this meets the theory of available capacity, i.e.,
QoS index is smaller, can obtain higher available capacity.
Available capacity boundary value under the identical QoS of Fig. 4 and Fig. 5 and otherness QoS constraint, i.e., optimizing place to (18)
The curve drawn when reason using the available capacity of two SU as coordinate, characterize that two SU can obtain jointly it is maximum effectively
The boundary of capacity.Compared to constant power optimal scheduling scheme it can be seen from Fig. 4 and Fig. 5, optimal power optimal scheduling scheme
Available capacity circle is bigger, and in Fig. 4, due to θ1=θ2So curve is symmetrical, and curve is not symmetrical in Fig. 5, equally
Meet under same case, QoS index is smaller, the maximum theory of user's available capacity obtained.
Side of the optimal power optimal scheduling scheme mentioned it can be seen from simulation result compared to constant power random schedule
Case can make system obtain higher available capacity, advantageously ensure that the communication quality for the system that different delay requires.
Claims (7)
1. user's scheduling and power distribution method in cognitive radio system based on available capacity, the cognitive radio system
System includes a main transmitting terminal, a secondary emission end, at least two can interoperable SU and several to each other not
The MU that can be cooperated, secondary emission end can be used as fusion center, handle the data of SU；It is characterised in that it includes as follows
Step,
Step 1, secondary user's carry out frequency spectrum perception, judge the use state of channel, and obtain the inspection that different detecting states occur
Survey probability；
Step 2 obtains the expression formula of the available capacity of SU according to the parameter of cognitive radio system, establishes detection probability and SU
The relationship of available capacity, and mean power it is limited and to PU it is interference-limited under conditions of available capacity is optimized,
Target, which is turned to, with available capacity maximum obtains final user's scheduling and power allocation scheme；
The available capacity expression formula are as follows:
Wherein, θ is QoS index；K is the channel status number of limited channel model；P(sj) it be channel virtual condition is sjProbability；Be channel virtual condition be sjAnd testing result isProbability；It is for testing resultWhen power point
Distribution coefficient；For the rate of information throughput under the power partition coefficient；Assuming that channel is Rayleigh bulk nanometer materials, a frame
Time duration be T, wherein the preceding T of each frame0Second is used for frequency spectrum perception, remaining T-T0Duration is transmitted for information；
With mean power it is limited and to PU it is interference-limited under conditions of maximize the available capacity of system and optimize problem
Modeling, expression formula are as follows:
Wherein, β indicates ratio shared by the available capacity of two SU from 0 to 1；θ1And θ2Respectively indicate two respective QoS of SU
Index；P4 is the probability that PU busy channel is detected as to channel idle, and P6 is that PU busy channel is detected as MU busy channel
Probability, PupFor the average interference upper limit.
2. user's scheduling and power distribution side in cognitive radio system according to claim 1 based on available capacity
Method, which is characterized in that using the double threshold energy detection method of cooperation among users, channel status is detected, carries out frequency spectrum
Perception, specifically comprises the following steps；
Step 1, arbitrarily choose cognitive radio system in two secondary user's current Received Signal is sampled, obtain by
The energy detection value for two secondary user's chosen；
Step 2, energy measuring statistic is obtained by cooperation among users according to two energy detection values that step 1 obtainsWith
D_Y is shown below respectively；
Wherein:N is sampling number, and y [i] is the signal of i-th sampling,WithIt is cognition
In radio system when main transmitting terminal transmitting signal, signal energy that two secondary user's receive；
Step 3, the corresponding pre-determined threshold of energy measuring statistic is determined by limiting the theoretical value of detection probability in a variety of situations；
Pre-determined threshold includes energy measuring statisticPre-determined threshold λ up and down1And λ2And the pre- gating of energy measuring statistic d_Y
Limit ε；By energy detection statisticWith upper and lower pre-determined threshold λ1And λ2Compared as follows,If above formula is set up,
Then follow the steps 4, it is no to then follow the steps 5；
Step 4, compared with energy detection statistic d_Y being carried out as follows with pre-determined threshold ε, d_Y < ε；If above formula is set up, sentence
It is set to primary user and occupies frequency spectrum；Otherwise it is determined as that malicious user occupies frequency spectrum, i.e. frequency spectrum current state is PUEA；
Step 5, by energy detection statisticWith upper and lower pre-determined threshold λ1And λ2Compared as follows,If above formula at
It is vertical, then it is determined as the frequency spectrum free time；Otherwise it is determined as that malicious user occupies frequency spectrum, i.e. frequency spectrum current state is PUEA；
Step 6, the case where being occupied according to frequency spectrum in step 4 and step 5 completes frequency spectrum perception, judges the use state of channel.
3. user's scheduling and power distribution side in cognitive radio system according to claim 2 based on available capacity
Method, which is characterized in that in step 3, the theoretical value by limiting detection probability in a variety of situations determines energy measuring statistic phase
The pre-determined threshold answered, specific step is as follows,
Step 3.1, the process of primary user and malicious user access frequency spectrum are modeled；
Step 3.2, by the analysis to modeling, the prior probability of primary user and malicious user access frequency spectrum are obtained；
Step 3.3, the distribution for receiving signal obedience is carried out it is assumed that obtaining the combined situation of all channel status and detecting state
The theoretical value of lower detection probability, and solve and obtain the corresponding pre-determined threshold of energy measuring statistic.
4. user's scheduling and power distribution side in cognitive radio system according to claim 3 based on available capacity
Method, which is characterized in that in step 3.1, when modeling, the process model building by primary user and malicious user access frequency spectrum is Poisson mistake
Journey.
5. user's scheduling and power distribution side in cognitive radio system according to claim 1 based on available capacity
Method, which is characterized in that the probability of different detecting states is obtained according to central-limit theorem.
6. user's scheduling and power distribution side in cognitive radio system according to claim 1 based on available capacity
Method, which is characterized in that according to limited channel model and optimization problem model, obtain the optimization of objective function and constraint condition expression
Problem；The optimization method of fixed schedule matrix and optimization power alternating iteration when being dispatched using user, obtains some channel shape
Optimal user scheduling and probability assignments scheme under state.
7. user's scheduling and power distribution side in cognitive radio system according to claim 6 based on available capacity
Method, which is characterized in that the optimal solution for obtaining the optimization problem of objective function and constraint condition expression by solving dual problem；It adopts
The optimal solution of dual problem is obtained with gradient descent method.
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