CN101754234B - Opportunistic spectrum access method based on Markov chain and CSMA - Google Patents

Abstract

An opportunistic spectrum access method based on Markov chain and CSMA includes that the access predication statistical module method of the Markov chain is combined with the CSMA access protocol to adopt different access modes according to different induction areas, before the user access is recognized, the spectrum detection is carried out according to spectrum induction method, and the first and second dual thresholds Lambda 1 and Lambda 2 of the interference temperature of the master user, the judgment area whether the master user exists is divided according to the two thresholds, when the interference temperature value is less than the Lambda 1, the user is recognized and accessed directly; when the interference temperature value is more than the Lambda 2, the CSMA access mode is adopted for back-off access; when the interference temperature is between the Lambda 1 and Lambda 2, a Markov chain access predication statistical module with the master user as the priority is built in queuing and non-queuing modes, and the Markov chain module is adopted to describe the opportunistic spectrum access. During access process, the first and second interference temperature thresholds are regulated dynamically to realize the maximization of the whole network throughput.

Description

Opportunistic spectrum access method based on Markov Chain and Carrier Sense Multiple Access

Technical field

The present invention relates to cognitive radio opportunistic spectrum access technology, especially a kind of opportunistic spectrum access method based on Markov Chain and Carrier Sense Multiple Access belongs to radio communication and signal processing technology field.

Background technology

Opportunistic spectrum inserts (OSA, Opportunistic Spectrum Access) allow unauthorized user (claiming cognitive user again) on spatial domain or time domain, to share and authorize frequency spectrum, have only when authorized user (claiming main user again) when not taking these frequency spectrums cognitive user just can insert.Especially, the dynamic of spectrum environment makes the design of opportunistic spectrum access scheme be faced with several important problem, and promptly what ground mode is cognitive user need determine when in and insert which channel and send/receive data and do not influence main user's proper communication.From the technological challenge that OSA-MAC (Medium Access Control) design faces, existing scheme can not solve rightly and make full use of spectrum issue.Simultaneously, for protecting main user's proper communication, these algorithms defective of various degrees all aspect spectrum utilization and the protection of main user performance compromise does not also have a kind of opportunistic spectrum access method can satisfy the requirement of cognitive radio system fully at present.The existing opportunistic spectrum access scheme that divides chain based on Ma Erke is owing to the probabilistic existence of sensing results, thereby the blindness that will cause cognitive user to insert influences the performance of system, and amount of calculation is very big.On the other hand, along with development of wireless communication devices, the rare problem of frequency spectrum has become the problem that presses for solution.The opportunistic spectrum access technology in this field of cordless communication network, has become research focus in recent years as a kind of effective means that improves the availability of frequency spectrum.In the case, the frequency spectrum that can fully improve the availability of frequency spectrum of research innovation inserts algorithm, has great using value.Achievement in research can be used for the sparse occasions such as wireless-transmission network of population.

Summary of the invention

The present invention proposes a kind of opportunistic spectrum access method based on Markov Chain and Carrier Sense Multiple Access, can improve the availability of frequency spectrum effectively, alleviates the rare problem of wireless application research field frequency spectrum resource.Obtain sensing results more accurately by setting interference temperature double threshold value, and cognitive user is taked different access waies according to different perception zones, reduced amount of calculation than greatly with Markov Chain cut-in method only, and take into full account main user's priority, realize that better frequency spectrum inserts.

Realize that technical scheme of the present invention is: a kind of opportunistic spectrum access method based on Markov Chain and Carrier Sense Multiple Access, it is characterized in that: markovian access prediction statistical model method and Carrier Sense Multiple Access access protocol are combined, take different access waies according to different perception zones, realize that better frequency spectrum inserts, improve the availability of frequency spectrum; Before cognitive user inserts, cognitive user is carried out frequency spectrum detection by frequency spectrum sensing method, and set first, second two-door limit value of main user's interference temperature, first threshold value is less than second threshold value, divide the decision region whether main user exists with these two threshold values, guarantee the reliability of frequency spectrum detection, in access procedure, according to dynamic first, second interference temperature threshold value of adjusting of perception cycle, to realize the entire throughput maximization of network; When main user's interference temperature during less than first threshold value, confirm that main user does not exist, cognitive user directly inserts; When interference temperature during greater than second threshold value, confirm main user's existence, adopt the Carrier Sense Multiple Access access module to keep out of the way access; When interference temperature is between first, second threshold value, cognitive user can't be judged main user's existence accurately, setting up with main user by queueing form is that the Markov of priority is linked into the prediction statistical model, describes the behavior that opportunistic spectrum inserts and carries out channel estimating and insert with Markov chain model.

In with one-period, the method for determining and dynamically adjusting of first, second interference temperature threshold value is:

Set first, second interference temperature threshold value and be respectively λ ₁=λ ₀-Δ and λ ₂=λ ₀+ Δ;

λ wherein ₀Be optimum interference temperature threshold value, Δ is represented dynamic interval, and establishes Δ=1/2 (λ _Max-λ _Min), λ _Max, λ _MinBe respectively the main user's that cognitive user records by frequency spectrum sensing method minimum and maximum interference temperature value;

Optimum interference temperature threshold value λ ₀By minimise false probability Q _eAsk for

${\mathrm{\λ}}_0=\underset{\mathrm{\λ}}{\arg }\max \left(Q_e\right)---\left(1\right)$

$Q_e=Q_f+Q_m$

$=\mathrm{Prob}(E>E_{\mathrm{\λ}}|H_0)+(1-\mathrm{Prob}(E>E_{\mathrm{\λ}}|H_1))$

$=\frac{\mathrm{\Γ}(u,E_{\mathrm{\λ}}/2)}{\mathrm{\Γ}\left(u\right)}+1-Q(\sqrt{2\mathrm{\γ}},\sqrt{E_{\mathrm{\λ}}})---\left(2\right)$

In the formula, E is the main subscriber signal that cognitive user receives, E _λThe main subscriber signal of correspondence when being λ for interference temperature, H ₀And H ₁For not having situation according to binary system hypothesis testing decision method corresponding respectively main user's existence and main user in the frequency spectrum perception, Prob () represents probability function, u=TW is the time and the bandwidth product of main subscriber signal, and γ is the signal to noise ratio of cognitive user received signal, and Γ () represents gamma function.First, second interference temperature threshold value λ ₁And λ ₂Frequency spectrum detection corresponding dynamic according to the cycle is adjusted.

Advantage of the present invention and remarkable result: the present invention predicts that by adopting Markov to be linked into statistical model method and CSMA access protocol improve the frequency spectrum access strategy, by setting the two-door limit value of dynamic interference temperature, with these two decision region that threshold value is divided main user, according to perception information, when interference temperature is outside two threshold values, confirm under the situation that whether main user exist, adopt directly access or CSMA (Carrier Sense Multiple Access, Carrier Sense Multiple Access) pattern to keep out of the way access.And when interference temperature was got involved between two threshold values, setting up with main user was that the Markov chain chance access model of priority carries out channel estimating and inserts.Obtain sensing results more accurately, effectively raised the perception correctness, improved access efficiency.

Existing Markov is linked into the prediction statistical model mainly based on cognitive user, and the access of having ignored main user with withdraw from, and opportunistic spectrum inserts the proper communication that must guarantee main user, therefore need guarantee that main user has than the higher priority of cognitive user use frequency spectrum, the present invention takes into full account main user's priority, having set up with main user is that the Markov Chain forecast model of priority inserts more effective description opportunistic spectrum, and the access of having considered main user with withdraw from the influence that cognitive user is caused.Markov is linked into prediction statistical model method in the present invention and the CSMA access protocol combines, take different access waies according to different perception zones, reduced amount of calculation than greatly with Markov Chain cut-in method only, owing to taken into full account main user's access and withdrawed from the influence that cognitive user is caused, adopt main user's priority, better realize the frequency spectrum access, improved the availability of frequency spectrum, had stronger practicality.And the less consideration of existing opportunistic spectrum access scheme has the access strategy of main User Priority, is difficult to the robustness of assurance system and the contradiction of protection original system.

Description of drawings

Fig. 1 has the cut-in method of two-door limit value;

Fig. 2 is to be the Markov chain chance access model (is example with two cognitive user situations) of priority with main user:

Fig. 3 is to be the state table of the Markov chain chance access model of priority with main user among Fig. 2.

Embodiment

With reference to above-mentioned accompanying drawing, the specific embodiment of the present invention is described in further detail:

As Fig. 1, abscissa is represented the interference temperature value υ of main user's receiving terminal, λ among the figure ₁, λ ₂Be respectively the threshold value of first, second interference temperature, satisfy λ ₁＜λ ₂, when the value of the interference temperature that records less than λ ₁The time, represent that main subscriber signal does not exist, cognitive user can directly insert; And when the value of interference temperature greater than λ ₂The time, represent that main subscriber signal exists, adopt the CSMA access module to keep out of the way access.When the value of interference temperature between λ ₁, λ ₂Between the time, be the uncertain region, cognitive user can't be judged main user's existence accurately, by queuing with not have that the queuing dual mode sets up with main user be that the Markov of priority is linked into the prediction statistical model, describe the behavior that opportunistic spectrum inserts with Markov chain model, improve access efficiency.Δ is represented dynamic interval among the figure, Δ=1/2 (λ _Max-λ _Min), λ _Max, λ _MinBe respectively the main user's that cognitive user records minimum and maximum interference temperature value, λ ₁=λ ₀-Δ, λ ₂=λ ₀+ Δ is by minimise false probability Q _eObtain optimum interference temperature threshold value λ ₀

It is the Markov chain chance access model (is example with two cognitive user situations) and the state table of priority that Fig. 2 and Fig. 3 have described with main user.Reflected that when main user turns back to the frequency spectrum that cognitive user using cognitive user is at state SU_A, SU_B and all needed in 2 o'clock to keep out of the way, and the frequency spectrum that will use gives back main user, having demonstrated fully with main user is the access characteristic of priority.

Claims (1)

1. opportunistic spectrum access method based on Markov Chain and Carrier Sense Multiple Access, it is characterized in that: markovian access prediction statistical model method and Carrier Sense Multiple Access access protocol are combined, take different access waies according to different perception zones, realize that better frequency spectrum inserts, improve the availability of frequency spectrum; Before cognitive user inserts, cognitive user is carried out frequency spectrum detection by frequency spectrum sensing method, and set first, second two-door limit value of main user's interference temperature, first threshold value is less than second threshold value, divide the decision region whether main user exists with these two threshold values, guarantee the reliability of frequency spectrum detection, in access procedure, according to dynamic first, second interference temperature threshold value of adjusting of perception cycle, to realize the entire throughput maximization of network; When main user's interference temperature during less than first threshold value, confirm that main user does not exist, cognitive user directly inserts; When interference temperature during greater than second threshold value, confirm main user's existence, adopt the Carrier Sense Multiple Access access module to keep out of the way access; When interference temperature is between first, second threshold value, cognitive user can't be judged main user's existence accurately, setting up with main user by queueing form is that the Markov of priority is linked into the prediction statistical model, describes the behavior that opportunistic spectrum inserts and carries out channel estimating and insert with Markov chain model;

The method of determining and dynamically adjusting of described first, second interference temperature threshold value is:

Set first, second interference temperature threshold value and be respectively λ ₁=λ ₀-Δ and λ ₂=λ ₀+ Δ;

λ wherein ₀Be optimum interference temperature threshold value, Δ is represented dynamic interval, and establishes Δ=1/2 (λ _Max-λ _Min), λ _Max, λ _MinBe respectively the main user's that cognitive user records by frequency spectrum sensing method minimum and maximum interference temperature value;

Optimum interference temperature threshold value λ ₀By minimise false probability Q _eAsk for

${\mathrm{\λ}}_0=\underset{\mathrm{\λ}}{\arg }\max \left(Q_e\right)---\left(1\right)$

$Q_e=Q_f+Q_m$

$=\mathrm{Prob}(E>E_{\mathrm{\λ}}|H_0)+(1-\mathrm{Prob}(E>E_{\mathrm{\λ}}|H_1))$

$=\frac{\mathrm{\Γ}(u,E_{\mathrm{\λ}}/2)}{\mathrm{\Γ}\left(u\right)}+1-Q(\sqrt{2\mathrm{\γ}},\sqrt{E_{\mathrm{\λ}}})---\left(2\right)$

In the formula, E is the main subscriber signal that cognitive user receives, E _λThe main subscriber signal of correspondence when being λ for interference temperature, H ₀And H ₁For not existing according to the corresponding respectively main user of binary system hypothesis testing decision method in the frequency spectrum perception and there is situation in main user, Prob () represents probability function, and u=TW is the time and the bandwidth product of main subscriber signal, and γ is the signal to noise ratio of cognitive user received signal, Γ () represents gamma function, Q _fRepresent pre-alarm probability, Q _mThe expression false dismissal probability, Q () expression Marcum Q function, first, second interference temperature threshold value λ ₁And λ ₂Frequency spectrum detection corresponding dynamic according to the cycle is adjusted.

Images