CN108599881A - A kind of radio dynamic spectrum access method for multi-user and multi-channel - Google Patents
A kind of radio dynamic spectrum access method for multi-user and multi-channel Download PDFInfo
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Abstract
The present invention relates to a kind of radio dynamic spectrum access methods for multi-user and multi-channel, include the following steps：S1：The subcarrier load strategy and data packet arrival rate of each Virtual User are obtained according to the ACK/NACK message that cluster head in cognitive radio networks in the unit interval is broadcasted based on Di Li Cray processes；S2：Define the collision probability of target Secondary Users' data packet；S3：Obtain the probability density function that the data packet transmission delay of target Secondary Users is obeyed；S4：The relationship between data packet transmission delay and the queue time delay of target Secondary Users' data packet is established, the overall delay characteristic of multimedia transmission is obtained；S5：In conjunction with data packet retransmission number, the channel capacity characteristic of multimedia transmission is obtained；S6, binding capacity characteristic and delay character build service quality evaluation system, and by maximizing service quality, optimal data packet load mode is formulated for target Secondary Users.Compared with prior art, the present invention has many advantages, such as to reduce expense, highly practical.
Description
Technical field
The present invention relates to cognitive radio frequency spectrum access technology field, more particularly, to a kind of for multi-user and multi-channel
Radio dynamic spectrum access method.
Background technology
Frequency spectrum perception is the core technology in cognitive radio, needs the wireless environment around monitoring in real time, is unauthorized
User provides usable spectrum resource, while ensureing to find that authorized user to the occupancy of current frequency range, avoids interfering in time.Cause
This, the accuracy of frequency spectrum perception plays cognitive radio networks very crucial effect.For the big of frequency spectrum perception technology
Quantity research work provides many detection methods based on signal processing, these detection methods can mainly be divided into non-cooperating frequency
Spectrum perception and collaborative spectrum sensing two major classes.
With the development of wireless communication technique, demand rapid growth of the people to radio communication service so that wireless frequency spectrum
As more and more nervous resource.In wireless communications, frequency spectrum resource is very limited and expensive, ability after being only authorized to
It is legal to use wireless frequency spectrum.However, studies have shown that some radio band communication loads are excessive, and there are some frequency ranges almost empty
It is not busy.Therefore, there is an urgent need for a kind of new wireless-access mode to utilize these idle frequency ranges by people, wireless so as to alleviate
The problem of frequency spectrum growing tension, and popular research technology of the cognitive radio technology as future wireless system field, Neng Gouyou
Effect improves the spectrum utilization efficiency of radio resource.
Federal Communications Commission (Federal Communications Commission, FCC) was issued in 2003
Frequency spectrum with milestone significance reports that report confirms the low present situation of authorized spectrum band utilization rate, and emphasizes cognition wireless
Power technology serves as key player in following FCC policies.It is shown according to report, 3GHz authorized spectrum bands below do not obtain fully
The probability used is up to 70%, and traditional this frequency spectrum method of salary distribution results in the waste of frequency spectrum resource over time and space.
Cognitive radio technology is suggested in the case where this frequency spectrum resource is serious nervous, in the utilization ratio for improving frequency spectrum resource
It is made that tremendous contribution.Cognitive radio technology has its unique advantages, it can realize dynamic frequency spectrum distribution, effectively
Alleviate the situation of frequency spectrum resource anxiety.Although at present mostly still in research state, technology is not mature enough, cognition wireless
Power technology can centainly have by feat of its flexible radio characteristics and dynamic frequency spectrum partition characteristic in wireless communication field
There is powerful development prospect.
With the development of cognitive radio technology, research and application are no longer initial scopes, different researchers from
Different angles has carried out deeper elaboration to cognitive radio.The concept of cognitive radio is initially by imperial family of Sweden technology
What the doctor Joseph Mitola III of institute were proposed, be software radio (Software Defined Radio, SDR) skill
A kind of intelligentized extension of art.Doctor Mitola successively proposes a kind of description radio network internal construction module, equipment
With " radio knowledge representation language (RKRL) " and spectrum pool (Spectrum Pooling) concept of radio environment.Mitola
Doctor thinks cognitive radio technology based on software radio, but with software radio again there is essence difference,
It is mainly manifested in：Cognitive radio can be removed cognition radio frequency environment, air interface, led to by the inferential capability of radio module
Believe the use model of agreement and frequency spectrum, and intelligent AC is carried out by RKRL language and network, it is logical to greatly improve
More personalized communication mode is realized in the flexibility of letter.
FCC is known as recognizing from the angle of spectrum management, any radio with adaptive spectrum sensing capability
Radio, therefore FCC has also been proposed the cognitive radio definition of narrow sense.In order to overcome current radio spectrum resources utilization ratio low
Under problem, Federal Communications Commission proposes " secondary use " wireless frequency spectrum system to open authorized spectrum band, is at this
Authorized user has the priority using radio spectrum resources in system, and unauthorized user must be vacant wireless in authorized user
The access of opportunistic when frequency spectrum resource, and exited in time when authorized user resumes.According to the definition of FCC, nothing is recognized
Line electricity be a kind of its transmitting terminal according to its residing for the interaction of working environment adjust the wireless device of emission parameter,
Therefore cognitive radio is also referred to as " opportunistic frequency spectrum accesses radio ".
It is another whenever an authorized user sends a successfully data packet in system in traditional collaboration frequency spectrum access scheme
A unauthorized user will beam back a data packet after receiving and confirm again, and whole radio network users are numerous, and transmission connects
That receives frequently appoints information exchange to result in great expense.
Invention content
It is more for multi-user that it is an object of the present invention to overcome the above-mentioned drawbacks of the prior art and provide one kind
The radio dynamic spectrum access method of channel.
The purpose of the present invention can be achieved through the following technical solutions：
A kind of radio dynamic spectrum access method for multi-user and multi-channel includes the following steps：
S1：Based on the on-line study method of Di Li Cray processes, according to cluster head in cognitive radio networks in the unit interval
The ACK/NACK message of broadcast obtains the subcarrier load strategy and data packet arrival rate of each Virtual User；
S2：According to the data packet arrival rate of Virtual User, the collision probability of target Secondary Users' data packet is defined；
S3：According to when data packet collides in the collision probability of target Secondary Users' data packet and S-ALOHA systems
Retransmission mechanism is made a concession, the probability density function that the data packet transmission delay of target Secondary Users is obeyed is obtained；
S4：The relationship between data packet transmission delay and the queue time delay of target Secondary Users' data packet is established, is obtained more
The overall delay characteristic of media transmission；
S5：According to the step S3 data-bag lost probability obtained multimedia transmission is obtained in conjunction with data packet retransmission number
Capacity characteristic and the characteristic of channel；
S6：The delay character that binding capacity characteristic, the characteristic of channel and step S4 are obtained, builds service quality evaluation standard,
Optimal data packet load mode is formulated for target Secondary Users, completes dynamic spectrum access.
Preferably, the step S1 specifically includes following steps：
101) regard other Secondary Users in cognitive radio networks in addition to target Secondary Users as a Virtual User；
102) when Virtual User is properly received or sends a data packet, cluster head broadcasts an ACK/NACK message；
103) the ACK/NACK message counts broadcasted within the unit interval according to cluster head obtain the subcarrier load of Virtual User
Strategy, and calculate the data packet arrival rate of other Virtual User in addition to target Secondary UsersIts calculation formula is as follows：
Wherein, E { μjIt is load ratio of the Virtual User on subcarrier j, K is the ACK/NACK message of cluster head broadcast
Number,The probability of channel is not take up for authorized user.
Preferably, in the step S2, the definition procedure of the collision probability of target Secondary Users' data packet is：
Assuming that the arrival rate and retransmission rate of Virtual User data packet obey Poisson distribution, then do not connect in t moment in channel
The probability for receiving data packet is equal to target Secondary Users one new data packet of every t moment generation, then target Secondary Users are per t
Moment generates the probability F of a new data packetij(T >=t, 0) is：
In formula, T is data packet interarrival time, obeys parameter and isExponential distribution, then target Secondary Users number
According to the collision probability p of packetijExpression formula be：
Wherein, τ is that data packet receives successfully required minimum time unit from being sent to.
Preferably, the step S3 specifically includes following steps：
301) data packet after colliding or conflicting is retransmitted, the conflict according to target Secondary Users' data packet is general
Rate obtains data-bag lost probability and probability density function of the target Secondary Users on subcarrier j under different propagation delay times；
302) according to transmission probability and probability density function, the mixed exponential distribution that total propagation delay time is obeyed is obtained.
Preferably, the particular content of the step 301) is：
Assuming that each re-transmission time is respectively T1,T2,T3,…,Tk, target Secondary Users SUiData on subcarrier j
Packet loss probability is ωj(k-1), then have：
As propagation delay time TpWhen=τ, target Secondary Users SUiData-bag lost probability on subcarrier j is ωj1=
pij, probability density function is：
f1(Tp)=δ (Tp-τ)
As propagation delay time Tp=τ+T1When, target Secondary Users SUiData-bag lost probability on subcarrier j is ωj2=
(1-pij)·pij, probability density function is：
As propagation delay time Tp=τ+T1+T2When, target Secondary Users SUiData-bag lost probability on subcarrier j is
ωj3=(1-pij)2·pij, probability density function is：
When propagation delay time is Tp=τ+T1+T2+T3+…+TkWhen, target Secondary Users SUiData packet on subcarrier j is lost
Mistake probability is ωjk=(1-pij)k-1·pij, probability density function is：
When propagation delay time is TpWhen=∞, indicate that data packet is dropped, target Secondary Users SUiData on subcarrier j
Packet loss probability isIts probability density function is：
f∞(Tp)=δ (Tp-τ)
Wherein, δ () is impulse function.
Preferably, in the step 302), the expression formula for the mixed exponential distribution that total propagation delay time is obeyed is：
Tp~ωj1×f1(Tp)+ωj2×f2(Tp)+ωj3×f3(Tp)+…+ωjk×fk(Tp)+…+ωj∞×f∞(Tp)
Preferably, the step S4 specifically includes following steps：
401) according to Bu Laqieke-Qin Xin formula, queue time delay T is obtainedq：
Tq=XTp+r
In formula, X TpTarget Secondary Users SU in timeiIn the first-class data packet numbers to be transmitted of subcarrier j, r is current
The data packet residue transmission time that moment Virtual User transmits on sub-carriers；Utilize the mean value of rIndicate r,
Wherein,For target Secondary Users SUiThe time second order that is transmitted on subcarrier j of data packet away from then queue time delay Tq's
Expression formula becomes：
Wherein, λi·For target Secondary Users SUiData packet arrival rate, sijFor SUiLoad ratio on subcarrier j；
402) according to the queue time delay T of data packetqWith propagation delay time Tp, obtain the overall delay in transmission of data packets
dij：
403) assume target Secondary Users SUiMulti-medium data packet maximum restrain oneself time delay be Di, transmitted according to data packet
Overall delay d in the processij, then target Secondary Users SUiThe queue time delay loaded on subcarrier j is less than DiProbability be：
In formula：
Wherein, ψ, which is system, allows the maximum times retransmitted, T0For TpUpper limit value, expression formula is：
Preferably, the step S5 specifically includes following steps：
501) the data-bag lost probability obtained according to step S3 obtains the capacity characteristic of multimedia transmission, i.e. target time
Want user SUiData packet transfer rate PDRi：
502) according to different modulation systems, the characteristic of channel of multimedia transmission is obtained, i.e. different modulating mode is corresponding
Transmission power.
Preferably, the step S6 specifically includes following steps：
601) according to multimedia transmission when extend to the spectrum utilization efficiency performance of subcarrier, define service quality evaluation mark
Quasi- Ui(S, L) is：
In formula, θiFor weight coefficient, i.e., preference of the user for capacity characteristic and delay character in system；LjIt is every
The bit number of a symbol；
602) power limitation condition, channel capacity restrictive condition and the subcarrier of setting service quality evaluation standard load plan
Slightly restrictive condition；
603) according to restrictive condition, service quality standard is maximized, the optimal data packet of target Secondary Users is obtained and adds
Load mode completes dynamic spectrum access.
Preferably, the particular content of the step 602) is：
Power limitation condition：
Wherein,For the power of sometime user's transmission packet, PiFor the transmission power of user, the limitation item
Part requires the transmission power of the sum of power of user's simultaneous transmission data packet no more than user in sometime；
Channel capacity restrictive condition：
Wherein, B is the bit capacity of channel each second, and L is the length of each data packet, when which requires unit
The active volume that the packet size that interior Virtual User and target user load on subcarrier j cannot exceed the subcarrier is big
It is small；
The tactful restrictive condition of subcarrier load：
The restrictive condition requires subcarrier load strategy limitation that the subcarrier of target Secondary Users is required to load the sum of strategy
Less than 1.
Compared with prior art, the present invention has the following advantages：
One, expense is reduced：Entire radio network system is divided into several mutually independent clustering architectures by the present invention, often
Cluster head all is delivered a packet to when member needs transmission data packet in cluster in the presence of a cluster head in a clustering architecture, by cluster head
It is responsible for collecting data packet and forwards, an ACK message can be broadcasted when cluster head is successfully received data packet to member in cluster, and
When error of transmission or cluster head can broadcast a NACK message when colliding, these ACK messages can be used for estimating each secondary
Whether the data packet arrival rate of user, the i.e. present invention only need to judge data packet by success by transmitting and receiving ACK/NACK message
It receives, can effectively avoid expense caused by frequent information exchange in traditional collaboration frequency spectrum access scheme；
Two, highly practical：Service assessment system defined in the present invention enables to user can be according to itself clock synchronization
Different weight coefficients is arranged in the preference of delay characteristics and capacity characteristic, has in terms of time delay and spectrum utilization efficiency
There is certain flexibility.
Description of the drawings
Fig. 1 is the dynamic spectrum access schematic diagram in cognitive radio networks；
Fig. 2 is queue time delay schematic diagram of the data packet in certain channel；
Fig. 3 is a kind of flow chart of radio dynamic spectrum access method for multi-user and multi-channel；
Fig. 4 is maximum in the embodiment of the present invention to restrain oneself time delay for propagation delay time distribution function under different collision probabilities
Influence relational graph；
Fig. 5 is that target Secondary Users load strategy for propagation delay time distribution function in not syn-collision in the embodiment of the present invention
Influence relational graph under probability；
Fig. 6 is the influence relational graph that transmission power loads target Secondary Users strategy in the embodiment of the present invention；
Fig. 7 is influence relational graph of the channel availability for data-bag lost probability in the embodiment of the present invention；
Fig. 8 is that maximum restrains oneself influence relational graph of the time delay for data-bag lost probability in the embodiment of the present invention；
Fig. 9 is transmission power in the embodiment of the present invention for the influence relational graph of time delay and handling capacity；
Figure 10 is the weights system of a certain channel in the embodiment of the present invention under method proposed by the present invention and uniform load method
Influence relationship comparison diagram of the number when different authorized users are not take up the probability of channel to service quality；
Figure 11 is the weights system of a certain channel in the embodiment of the present invention under method proposed by the present invention and uniform load method
Influence relationship comparison diagram of the number in the case where different maximums restrain oneself case propagation delays to service quality；
Figure 12 is that maximum restrains oneself influence relational graph of the time delay to time delay and handling capacity in the embodiment of the present invention；
Figure 13 is original video frame design sketch in the embodiment of the present invention；
Figure 14 is in the embodiment of the present invention using the video frame design sketch after intelligent cross-layer method demodulation；
Figure 15 is in the embodiment of the present invention using the video frame design sketch after being demodulated with dynamic study method；
Figure 16 is in the embodiment of the present invention using the video frame design sketch after the demodulation of dynamic least interference method；
Figure 17 is in the embodiment of the present invention using the video frame design sketch after the method for the present invention demodulation.
Specific implementation mode
The present invention is described in detail with specific embodiment below in conjunction with the accompanying drawings.
Embodiment
As shown in Figure 1, Figure 2, Figure 3 shows, the present invention relates to a kind of radio dynamic spectrum access for multi-user and multi-channel
Method includes the following steps：
Step 1: on-line study process：
11) regard other Secondary Users in addition to target Secondary Users as a Virtual User.
12) whenever being properly received or sending a data packet, cluster head can broadcast an ACK/NACK message, ACK
(Acknowledgement) indicate that confirmation signal, NACK (Negative ACKnowledgment) indicate not confirmation signal.
13) the K ACK/NACK message count sent within the unit interval by observing Virtual User, obtains Virtual User
Subcarrier load strategy, and the data packet arrival rate of Virtual User is calculated, specific formula is as follows：
Wherein,For the data packet arrival rate of the other users other than target Secondary Users, E { μjBe Virtual User in son
Load ratio on carrier wave j, K are the ACK/NACK message counts of cluster head broadcast,The probability of channel is not take up for authorized user,
The subcarrier load strategy of Virtual User is a set of load proportional loading ratio of each user on subcarrier j.
Step 2: the collision probability definition of target Secondary Users' data packet：
21) arrival rate and retransmission rate for assuming Virtual User obey Poisson distribution, then not connect in t moment in channel
The probability for receiving data packet is equivalent to Secondary Users' one new data packet of every t moment generation, and probability is：
Wherein, Fij(T >=t, 0) indicates that Secondary Users generate the probability of a new data packet per t moment；
22) it is because data packet interarrival time T obeys parameterExponential distribution, then target Secondary Users data
The collision probability p of packetiiExpression formula be：
Wherein, pijThe data packet of target Secondary Users is indicated not by the probability to conflict, τ is one in TDMA technologies
The length of time slot, which is data packet, receives successfully required minimum time unit from being sent to.
Step 3: obtaining propagation delay time distribution probability density function：
31) after data packet collides or conflicts, maximum retransmission is 3 times, it is assumed that each re-transmission time is T1、T2With
T3, the propagation delay time and data-bag lost probability of data packet be as shown in table 1：
The transmission time of data packet and corresponding probability in the case of 1 maximum retransmission of table is 3 times
32) it is since time interval t obeys parameterExponential distribution, it can thus be derived that data packet transmission delay
For τ, τ+T1、τ+T1+T2、τ+T1+T2+T3, ∞ when probability density function, be shown below：
f1(Tp)=δ (Tp-τ),Tp=τ
f5(Tp)=δ (Tp- τ), Tp=∞
Wherein, TpFor the propagation delay time of data packet, δ () is impulse function.Therefore, the mixing that total propagation delay time is obeyed
Exponential distribution can be expressed as：
Tp~ωj1×f1(Tp)+ωj2×f2(Tp)+ωj3×f3(Tp)+ωj4×f4(Tp)+ωj5×f5(Tp)
Step 4: obtaining overall delay characteristic：
41) T is adopted when the queue for assuming the data packetqIt indicates, then according to Bu Laqieke-Qin Xin formula (P-K formula), team
Row time delay TqIt can be expressed as：
Tq=XTp+r
Wherein, X indicates TpTarget Secondary Users SU in timeiIn the first-class data packet numbers to be transmitted of subcarrier j, TpFor
The transmission time of data packet on sub-carriers, the mixed exponential distribution obeyed have obtained in front, and r indicates that current time is used
The data packet residue transmission time that family is transmitted on sub-carriers.
42) due to r≤XTp, in order to calculate simplicity, the present embodiment is with the mean value of rIndicate r, whereinFor user SUiThe time second order that is transmitted on subcarrier j of data packet away from.Therefore, above-mentioned queue time delay TqExpression formula
It can be expressed as：
Wherein, λiIndicate target Secondary Users SUiData packet arrival rate, sijIndicate SUiLoad on subcarrier j
Ratio.
43) since the time delay of data packet includes queue time delay and propagation delay time, consider the data packet newly loaded certainly
The propagation delay time of body, this makes it possible to obtain the overall delay d in transmission of data packetsijFor：
44) assume user SUiMulti-medium data packet maximum restrain oneself time delay be Di, then its load is on subcarrier j
Queue time delay is less than DiProbability can be expressed as：
In formula：
Wherein, ψ, which is system, allows the maximum times retransmitted, T0For TpUpper limit value, expression formula is：
Step 5: obtaining capacity characteristic：
51) assume that the probability that data-bag lost is had been presented in table 1 isThen target Secondary Users
SUiData packet transfer rate be：
52) in actual communication process, different the having differences property between leading to channel of fading characteristic between channel,
Therefore cluster head is different with the characteristics of radio channels between each user in cluster, it is assumed that Secondary Users believe with the ISI between cluster head
The time domain CIR in road is h=[0.80.6], also different according to the different required transmission powers of modulation system transmission data packet,
Assuming that bit error rate p of the data packet in transmission process0For constant, then the transmission power of each modulation system is fixed
, the corresponding transmission power of various modulation systems is as shown in table 2.
2 modulation system of table and transmission power
In table 2, Q (x) is mathematics common integral, and expression formula is：
Wherein, HjFor the frequency domain CIR on subcarrier j.
Step 6: structure service quality evaluation standard, obtains the optimal data packet load mode of target Secondary Users：
61) consider multimedia transmission when extend to the spectrum utilization efficiency performance of subcarrier, define service quality evaluation mark
Standard is：
Wherein, θiFor weight coefficient, which reflects preference of the user data package for time delay or spectrum utilization efficiency
Degree, LjFor the bit number of each symbol,
62) restrictive condition of service quality evaluation is set；
Set power limitation condition, channel capacity restrictive condition and the tactful restrictive condition of subcarrier load, expression formula point
It is not：
Power limitation condition：
Wherein,For the power of sometime user's transmission packet, PiFor the transmission power of user, the limitation item
Part describes the transmission power of the sum of power of user's simultaneous transmission data packet no more than user in sometime；
Channel capacity restrictive condition：
The restrictive condition indicates the packet size that Virtual User and target user load on subcarrier j in the unit interval
The active volume size of the subcarrier cannot be exceeded；
The tactful restrictive condition of subcarrier load：
The restrictive condition requires the sum of subcarrier load strategy of target Secondary Users to be less than 1.
63) under the restrictive condition that step 62) is proposed, maximization steps 61) in service quality, to obtain target
The optimal data packet load mode of Secondary Users, completes the access of dynamic spectrum.
To verify the validity of frequency spectrum access method of the present invention, the multimedia that the present embodiment has carried out multi-user and multi-channel passes
Defeated scene simulation experiment.
Assuming that cognition wireless spot net is divided into several mutually independent clustering architectures, and by a cluster in each cluster
Member composition in head and four clusters.Consider that one is gathered around there are four channel, the field of four Secondary Users SU and a main users PU
Scape.It is limited according to conditions such as intra-system channels capacity, the data packet transmission bit rate of four Secondary Users is in cluster
0.4Mbps, and the size L of each data packet is 1000bit, the bandwidth B of channel is 1MHz, and the length τ of each time slot is 1ms,
The probability of main users PU unoccupied channelsIt is 0.85, threshold bit error rate when multimedia transmission is set as 10^ (- 5).
The present embodiment simulates the performance of propagation delay time function first, and the maximum by changing system restrains oneself time delay DiAnd mesh
Mark the load ratio s of Secondary Usersij, to observe the distribution situation of propagation delay time.The distribution performance of propagation delay time such as Fig. 4 and Fig. 5
It is shown.Abscissa is data packet collisions probabilityFor 0~1 value, ordinate is that propagation delay time is less than threshold T0Distribution it is general
Rate.In Fig. 4, maximum restrains oneself time delay and is respectively set to 6ms, 8ms, 10ms and 12ms.Figure 4, it is seen that identical
Maximum is restrained oneself under time delay value, and with the increase of collision probability, the probability that propagation delay time is less than threshold value is gradually lowered；Identical
Collision probability in the case of, propagation delay time is restrained oneself the increase of time delay and is increased with maximum less than the probability of threshold value.In Fig. 5
In, target Secondary Users SUiData packet LOADING RATES on channel j is respectively set to 0.1,0.3,0.5 and 0.7.It can from Fig. 5
To find out, under identical data packet load ratio, with the increase of collision probability, propagation delay time be less than the probability of threshold value by
Gradually reduce；In identical collision probability, propagation delay time subtracts less than the probability of threshold value with the increase of load ratio
It is small.
The throughout characteristic of the method for the present invention is verified below.By the method for the present invention it is found that four kinds of reasons can lead to data packet
It loses.The first is still failed after data packet clashes re-transmission three times；Second is to ensure that the time delay of system is special
Property, a part of data packet can be abandoned actively；The third is caused by the power limited of target Secondary Users；4th kind is
Caused by finite channel capacity.In this emulation, it is assumed that the noise in channel is white Gaussian noise, and noise power is
1, the transmission power of target Secondary Users is respectively 5,10,20 and 30dB.Specific throughout characteristic is as shown in Fig. 6~9.Fig. 6
It illustrates under different transmission power, the data packet load mode of target Secondary Users, since the channel that data packet is transmitted declines
Characteristic is fallen, the channel quality of third channel is worst, so when transmission power is relatively low, target Secondary Users load is believed in third
Data packet ratio on road is minimum；Fig. 7 is illustrated under different transmission power, and different maximums are restrained oneself the data packet corresponding to time delay and lost
Lose probability, it can be seen that as maximum restrains oneself the increase of time delay, data-bag lost probability declines therewith.Fig. 8 illustrates different hairs
It penetrates under power, the data-bag lost probability corresponding to different main users free time probability, it can be seen that with the increasing of idle probability
Greatly, data-bag lost probability also declines therewith.Fig. 9 is illustrated under different transmission power, the delay character in the present patent application
And throughout characteristic, and in that case, selected best modulation system, it can be seen from the figure that with power
Increase, best modulation system becomes BPSK, QPSK, 16QAM, 64QAM successively.
Then performance of the analysis the method for the present invention under difference preference's coefficient.When in system data packet transmission delay require compared with
Gao Shi, it is therefore desirable to abandon some data packets to meet delay requirement, at the same time the throughout characteristic in system may reach
Less than requiring, therefore have to weigh between propagation delay time and handling capacity.Specific performance simulation is as shown in Figure 10~12.
Figure 10 and Figure 11 illustrates frequency spectrum dynamic access method proposed by the invention and uniform load method and does not sympathize in preference coefficient
Under condition, i.e. the asynchronous performance of weight coefficient compares.It can be seen from fig. 10 that the method for the present invention performance is better than uniform load
Method, and in the method, with the increase of main users free time probability, performance is also promoted therewith.It can be with from Figure 11
To find out, the method for the present invention is under the conditions of different maximums restrain oneself time delay, the method that performance will generally be better than uniform load, and with
Maximum restrains oneself the increase of time delay, and performance is also promoted therewith.Figure 12 is illustrated under different transmission power, in the present patent application when
Delay characteristics and throughout characteristic, and in that case, selected best modulation system, it can be seen from the figure that with
The maximum increase for restraining oneself time delay, best modulation system becomes BPSK, QPSK, 16QAM, 64QAM successively.
Further to prove that the validity of the method for the present invention, the present embodiment are verified by standard video sequence, and
The method of the present invention and other existing several methods are compared, including intelligent cross-layer algorithm, dynamic learning algorithm and
Dynamic least interference algorithm.For simulation result as shown in Figure 13~17, Figure 13 show original video frame, Figure 14 be using intelligence across
Demodulation design sketch after layer algorithm, Figure 15 are using the demodulation design sketch after dynamic study method, and Figure 16 is minimum using dynamic
Demodulation design sketch after algorithm of interference, Figure 16 are the demodulation effect after the dynamic access method that is proposed using the present patent application
Figure.From Figure 13~17 it can be found that video frame after being demodulated using the method for the present invention, visual effect are best.
The above description is merely a specific embodiment, but scope of protection of the present invention is not limited thereto, any
The staff for being familiar with the art in the technical scope disclosed by the present invention, can readily occur in various equivalent modifications or replace
It changes, these modifications or substitutions should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with right
It is required that protection domain subject to.
Claims (10)
1. a kind of radio dynamic spectrum access method for multi-user and multi-channel, for optimizing in cognitive radio networks
Dynamic spectrum access process, which is characterized in that include the following steps：
S1：Based on the on-line study method of Di Li Cray processes, broadcasted according to cluster head in cognitive radio networks in the unit interval
ACK/NACK message, obtain each Virtual User subcarrier load strategy and data packet arrival rate；
S2：According to the data packet arrival rate of Virtual User, the collision probability of target Secondary Users' data packet is defined；
S3：According to yielding when data packet collides in the collision probability of target Secondary Users' data packet and S-ALOHA systems
Retransmission mechanism obtains the probability density function that the data packet transmission delay of target Secondary Users is obeyed；
S4：The relationship between data packet transmission delay and the queue time delay of target Secondary Users' data packet is established, multimedia is obtained
The overall delay characteristic of transmission；
S5：According to the step S3 data-bag lost probability obtained the capacity of multimedia transmission is obtained in conjunction with data packet retransmission number
Characteristic and the characteristic of channel；
The delay character that S6, binding capacity characteristic, the characteristic of channel and step S4 are obtained, builds service quality evaluation standard, is mesh
Mark Secondary Users formulate optimal data packet load mode, complete dynamic spectrum access.
2. a kind of radio dynamic spectrum access method for multi-user and multi-channel according to claim 1, feature
It is, the step S1 specifically includes following steps：
101) regard other Secondary Users in cognitive radio networks in addition to target Secondary Users as a Virtual User；
102) when Virtual User is properly received or sends a data packet, cluster head broadcasts an ACK/NACK message；
103) the ACK/NACK message counts broadcasted within the unit interval according to cluster head obtain the subcarrier load plan of Virtual User
It omits, and calculates the data packet arrival rate of other Virtual User in addition to target Secondary UsersIts calculation formula is as follows：
Wherein, E { μjIt is load ratio of the Virtual User on subcarrier j, K is the ACK/NACK message counts of cluster head broadcast,
The probability of channel is not take up for authorized user.
3. a kind of radio dynamic spectrum access method for multi-user and multi-channel according to claim 2, feature
It is, in the step S2, the particular content for defining the collision probability of target Secondary Users' data packet is：
Assuming that the arrival rate and retransmission rate of Virtual User data packet obey Poisson distribution, then do not received in t moment in channel
The probability of data packet is equal to target Secondary Users and generates a new data packet per t moment, then target Secondary Users are per t moment
Generate the probability F of a new data packetij(T >=t, 0) is：
In formula, T is data packet interarrival time, obeys parameter and isExponential distribution, then target Secondary Users data packet
Collision probability pijExpression formula be：
Wherein, τ is that data packet receives successfully required minimum time unit from being sent to.
4. a kind of radio dynamic spectrum access method for multi-user and multi-channel according to claim 3, feature
It is, the step S3 specifically includes following steps：
301) data packet after colliding or conflicting is retransmitted, according to the collision probability of target Secondary Users' data packet,
Obtain data-bag lost probability and probability density function of the target Secondary Users on subcarrier j under different propagation delay times；
302) according to transmission probability and probability density function, the mixed exponential distribution that total propagation delay time is obeyed is obtained.
5. a kind of radio dynamic spectrum access method for multi-user and multi-channel according to claim 4, feature
It is, the particular content of the step 301) is：
Assuming that each re-transmission time is respectively T1,T2,T3,…,Tk, target Secondary Users SUiData packet on subcarrier j is lost
Mistake probability is ωj(k-1), then have：
As propagation delay time TpWhen=τ, target Secondary Users SUiData-bag lost probability on subcarrier j is ωj1=pij,
Probability density function is：
f1(Tp)=δ (Tp-τ)
As propagation delay time Tp=τ+T1When, target Secondary Users SUiData-bag lost probability on subcarrier j is ωj2=(1-
pij)·pij, probability density function is：
As propagation delay time Tp=τ+T1+T2When, target Secondary Users SUiData-bag lost probability on subcarrier j is ωj3=
(1-pij)2·pij, probability density function is：
When propagation delay time is Tp=τ+T1+T2+T3+…+TkWhen, target Secondary Users SUiData-bag lost on subcarrier j
Probability is ωjk=(1-pij)k-1·pij, probability density function is：
When propagation delay time is TpWhen=∞, indicate that data packet is dropped, target Secondary Users SUiData packet on subcarrier j is lost
Losing probability isIts probability density function is：
f∞(Tp)=δ (Tp-τ)
Wherein, δ () is impulse function.
6. a kind of radio dynamic spectrum access method for multi-user and multi-channel according to claim 5, feature
It is, in the step 302), the expression formula for the mixed exponential distribution that total propagation delay time is obeyed is：
Tp~ωj1×f1(Tp)+ωj2×f2(Tp)+ωj3×f3(Tp)+…+ωjk×fk(Tp)+…+ωj∞×f∞(Tp) 。
7. a kind of radio dynamic spectrum access method for multi-user and multi-channel according to claim 6, feature
It is, the step S4 specifically includes following steps：
401) according to Bu Laqieke-Qin Xin formula, queue time delay T is obtainedq：
Tq=XTp+r
In formula, X TpTarget Secondary Users SU in timeiIn the first-class data packet numbers to be transmitted of subcarrier j, r is current time
The data packet residue transmission time that Virtual User transmits on sub-carriers；Utilize the mean value of rIndicate r,
In,For target Secondary Users SUiThe time second order that is transmitted on subcarrier j of data packet away from then queue time delay TqTable
Become up to formula：
Wherein, λi·For target Secondary Users SUiData packet arrival rate, sijFor SUiLoad ratio on subcarrier j；
402) according to the queue time delay T of data packetqWith propagation delay time Tp, obtain the overall delay d in transmission of data packetsij：
403) assume target Secondary Users SUiMulti-medium data packet maximum restrain oneself time delay be Di, according to transmission of data packets
In overall delay dij, then target Secondary Users SUiThe queue time delay loaded on subcarrier j is less than DiProbability be：
In formula：
Wherein, ψ, which is system, allows the maximum times retransmitted, T0For TpUpper limit value, expression formula is：
。
8. a kind of radio dynamic spectrum access method for multi-user and multi-channel according to claim 7, feature
It is, the step S5 specifically includes following steps：
501) the data-bag lost probability obtained according to step S3 obtains the capacity characteristic of multimedia transmission, the i.e. secondary use of target
Family SUiData packet transfer rate PDRi：
502) according to different modulation systems, the characteristic of channel of multimedia transmission, the i.e. corresponding transmitting of different modulating mode are obtained
Power.
9. a kind of radio dynamic spectrum access method for multi-user and multi-channel according to claim 8, feature
It is, the step S6 specifically includes following steps：
601) according to multimedia transmission when extend to the spectrum utilization efficiency performance of subcarrier, define service quality evaluation standard Ui
(S, L) is：
In formula, θiFor weight coefficient, i.e., preference of the user for capacity characteristic and delay character in system；LjFor each symbol
Number bit number；
602) power limitation condition, channel capacity restrictive condition of setting service quality evaluation standard and subcarrier load strategy limit
Condition processed；
603) the three kinds of restrictive conditions set according to step 602), service quality standard is maximized, and obtains target Secondary Users
Optimal data packet load mode completes dynamic spectrum access.
10. a kind of radio dynamic spectrum access method for multi-user and multi-channel according to claim 9, feature
It is, in the step 602), sets power limitation condition, channel capacity restrictive condition and the son of service quality evaluation standard
The particular content of the tactful restrictive condition of carrier wave load is：
Power limitation condition：
Wherein,For the power of sometime user's transmission packet, PiFor the transmission power of user, restrictive condition requirement
Sometime transmission power of the sum of the power of interior user's simultaneous transmission data packet no more than user；
Channel capacity restrictive condition：
Wherein, B is the bit capacity of channel each second, and L is the length of each data packet, which required in the unit interval
The packet size that Virtual User and target user load on subcarrier j cannot exceed the active volume size of the subcarrier；
The tactful restrictive condition of subcarrier load：
The restrictive condition requires subcarrier load strategy limitation that the sum of subcarrier load strategy of target Secondary Users is required to be less than
1。
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