CN102572922A - Quality of service (QoS) requirement and confidence-based multi-channel spectrum sensing mechanism for cognitive radio - Google Patents

Abstract

The invention discloses a quality of service (QoS) requirement and confidence-based multi-channel spectrum sensing mechanism for cognitive radio. A central node equally divides a wideband to be sensed in a network unit into a plurality of non-overlapped sub-channels, determines the number of sub-channels to be sensed by each of different cognitive user according to QoS requirements and confidence reported by each cognitive user, and allocates the sub-channels to be sensed to each cognitive user in an interval insertion way; and each cognitive user performs energy detection on the sub-channels allocated by the center node, and transmits a detection result to the center node, and the center node performs data fusion according to the detection result and confidence of each cognitive user, and finally judges whether a primary user signal exists on each sub-channel or not. Whether the primary user signal exists in a wideband range or not is rationally judged from the association between the cognitive users and the sensed channels in multi-channel spectrum sensing by fully combining the fairness and reliability of the multi-channel spectrum sensing.

Description

Cognitive radio multichannel frequency spectrum perception mechanism based on QoS demand and confidence level

Technical field

The invention belongs to wireless communication technology field, relate to the multichannel frequency spectrum perception mechanism in a kind of cognitive radio networks.Specifically, the multichannel frequency spectrum perception is a kind of key technology of cognitive radio, and cognitive user need dynamically be carried out perception to the broadband of certain limit in the process of searching frequency spectrum cavity-pocket, and not only to a certain fixed frequency range.The present invention combines the perception of single channel cooperation spectrum, multichannel frequency spectrum perception and data fusion technology; Take all factors into consideration service quality (the Quality of Service of cognitive user; QoS) ability of demand and frequency spectrum perception; Under the prerequisite that guarantees feasibility, improve the reliability and the fairness of cognitive radio multichannel frequency spectrum perception.

Background technology

(Cognitive Radio, notion CR) originates from Joseph doctor's Mitola of Sweden KTH in 1999 the sex work of laying a foundation to cognitive radio, for solving the low problem of the availability of frequency spectrum a kind of reliable solution thinking is provided.Its core concept be cognitive user promptly time user ((PrimaryUser, appearance PU) can insert instant available spectrum adaptively to survey the promptly main user of authorized user for Secondary User, SU) perceived spectral environment reliably on broadband.Its key technology comprises frequency spectrum perception, dynamic frequency spectrum deployment and power control.

In the frequency spectrum perception problem, detect the unstable properties problem for solving " concealed terminal ", the electromagnetic environment single cognitive user that causes such as abominable, need a plurality of cognitive user carry out cooperation spectrum and detect.The thought that cooperation spectrum detects is the environment around cognitive user is constantly surveyed, and utilizes local detection algorithm to draw testing result and is sent to Centroid, judges according to suitable blending algorithm whether main subscriber signal exists by Centroid.At present, local detection method has energy measuring, matched filtering detection, the detection of circulation spectrum signature etc., and wherein energy measuring does not need main user's prior information because of it and realizes simple by extensively employing.

The blending algorithm that cooperation spectrum detects generally include with merge or merge, most fusions etc.Cognitive user in the certain limit is sent local testing result to Centroid, and Centroid judges according to above-mentioned several method whether main user exists.Wherein, can reduce false alarm probability, but require too high the detection probability of local testing result with blending algorithm; Or blending algorithm then can bring higher false alarm probability, the reduction availability of frequency spectrum; Most fusions can be regarded the compromise of preceding two kinds of methods as, but its uncertainty is too high; Thereby said method is not the most feasible cooperation spectrum detection method.

In practical application; On the one hand, at present IEEE 802.22 mainly is used for hyperfrequency with cognitive radio (Very High Frequency is VHF) with very high frequency(VHF) (Ultra High Frequency; UHF) radio and television frequency range concentrates on 30～300MHz and 300MHz～3GHz.Along with the increase of carrier frequency, the cognitive user wideer frequency range of perception of having to; On the other hand, the density degree that idle frequency spectrum distributes in the practical application is different, and idle frequency spectrum distributes when comparatively disperseing, and cognitive user need perception in the band limits of broad, supplies different cognitive user to insert so that find abundant idle frequency spectrum.With the broadband shared band of treating perception be divided into uniformly-spaced, nonoverlapping a plurality of subchannels, on single channel joint spectrum perception basis, accomplish the multichannel frequency spectrum perception by cognitive user, have important researching value.

In multichannel frequency spectrum perception problem, mainly contain two kinds at present and solve thinking: the one, adopt method (for example broadcast band being carried out tuning search) by scan channel; The 2nd, realize the comprehensive of knowledge to the observed result of part through rational inference step.First kind of thinking can produce tangible perception time delay, is difficult to satisfy the requirement that frequency is shared dynamic and real-time.Second kind of thinking is a kind of suitable solution, mainly studies to reasonable derivation two aspects of Global Information to the selection of channel perception with by the part perception information from cognitive user at present.

To the selection of cognitive user, can be divided into for two steps to channel perception:

At first, confirm that different cognitive users needs the number of channel perception.The factor that influences this number is a lot, like cognitive user distribution etc. in the service bandwidth demand of the perceptual performance of the restriction of cognitive user terminal hardware condition, cognitive user self, cognitive user, the NE.

Secondly, under the restricted number in a last step, selected to treat the channel of perception.Equally, the foundation of selection also has multiple, like cognitive user distribution in selection, cognitive user hardware constraints, the NE at random etc.In addition, also need guarantee each channel, to improve the accuracy of sensing results simultaneously by a plurality of cognitive user perception as far as possible.

The association of the present invention cognitive user and channel perception from the multichannel frequency spectrum perception, it is good and bad to take into full account cognitive user QoS demand and self perception, and it is machine-processed to propose a kind of cognitive radio multichannel frequency spectrum perception of taking into account reliability and fairness.

Summary of the invention

The purpose of this invention is to provide a kind of cognitive radio multichannel frequency spectrum perception mechanism, be used for judging at cognitive radio system whether main subscriber signal exists on the broad frequency range based on QoS demand and confidence level.The present invention is from the selection of cognitive user to channel perception; Confirm that according to the perception (being the confidence level of different cognitive users frequency spectrum perception) of the QoS demand and the cognitive user self of different cognitive users cognitive user needs the number of channel perception and the channel of concrete perception by Centroid; And further utilize the confidence level of cognitive user that sensing results is merged; Take into full account the fairness and the reliability of multichannel frequency spectrum perception, whether main subscriber signal in the broad frequency range is existed make reasonable judgement.

In order to achieve the above object, the invention provides a kind of cognitive radio multichannel frequency spectrum perception mechanism, it is characterized in that, may further comprise the steps based on QoS demand and confidence level:

Step 1: the broadband of treating perception in the cognition network unit is divided into N nonoverlapping subchannel, and stipulates the once multipotency perception c of each cognitive user _MaxSubchannel is to guarantee short detecting period.

Step 2: cognitive user SU _jWith QoS demand R _jWith confidence level P _jSend to Centroid, wherein

(2A) the QoS demand is presented as that cognitive user communicates needed subchannel number, R _j∈ N;

(2B) confidence level of cognitive user characterizes the ability of cognitive user frequency spectrum perception, for cognitive user in the historical data is directed against the percentage that the correct number of times of single subchannel perception accounts for total perception number of times, P _j∈ [0,1].

Step 3: the subchannel number c of QoS demand that Centroid reports according to each cognitive user in the step 2 and the perception of confidence level decision different cognitive users needs _j, wherein

(3A) if the QoS demand R that cognitive user reports _j=0, even the present cognitive user does not need communication, and the confidence level size that Centroid reports according to this cognitive user is given this knowledge user a virtual QoS demand R ' _j, to make things convenient for the number of this cognitive user perception subchannel of Centroid decision:

$R_j^{\′}=\left\{\begin{array}{cc}\underset{i}{\max }\left\{R_i\right\},& P_j>P_{\mathrm{high}}\\ \underset{i\≠j}{\min }\left\{R_i\right\},& \mathrm{others}\end{array}\right.$

P wherein _HighFor cognitive system is divided the sufficiently high thresholding confidence level of cognitive user perception;

(3B) pass through the R that (3A) step guarantees each cognitive user _jAll greater than zero, Centroid decision cognitive user needs the subchannel number of perception

C wherein _MinThe>=1st, can be in order to guarantee each subchannel by the perception of a plurality of cognitive user institute, symbol Expression is not more than the maximum integer of x.

Step 4; The result that Centroid draws according to step 3 is the subchannel of cognitive user distribution needs perception according to the mode of inserting at interval, and record distribution s as a result _Ij∈ 0,1}, and send it to cognitive user, s _IjBeing to represent cognitive user j perception subchannel i at 1 o'clock, is to represent not perception of cognitive user j subchannel i at 0 o'clock.Wherein

The interval of the expression cognitive user j institute perception subchannel that (4A) makes

;

(4B) Centroid is according to following rule decision cognitive user j perception subchannel i whether:

$s_{\mathrm{ij}}=\left\{\begin{array}{cc}1,& i={(j+k\·{\mathrm{\Δ}}_j)}_{\mathrm{mod}N}\\ 0,& \mathrm{others}\end{array}\right.$

K=0 wherein, 1 ..., c _j-1.

Step 5: cognitive user is carried out energy measuring to the subchannel that Centroid distributes, and with testing result u _IjSend to Centroid, u _Ij{+1 ,-1} representes the testing result of cognitive user j to subchannel i, u to ∈ _Ij=+1 expression cognitive user j thinks that main subscriber signal exists on subchannel i, otherwise, u _Ij=-1 expression thinks that main subscriber signal does not exist, and Centroid carries out conclusive judgement according to following rule, and court verdict is sent to each cognitive user:

(5A), get

the confidence level normalization of cognitive user

(5B) make conclusive judgement, the court verdict of subchannel i is used z whether there being main subscriber signal to exist on each subchannel _iExpression:

$z_i=\left\{\begin{array}{cc}1,& \underset{j}{\mathrm{\Σ}}{\stackrel{\‾}{P}}_j{u}_{\mathrm{ij}}>0\\ 0,& \mathrm{others}\end{array}\right.$

Z wherein _i=1 is illustrated in and has main subscriber signal to exist on the subchannel i, otherwise, do not exist.

Advantage of the present invention is, judges the subchannel number of cognitive user needs perception on the one hand according to the different QoS requirements of cognitive user, and the demand of cognitive user is big more, and the contribution that need pay is also many more; To the cognitive user that does not temporarily have communication requirement, also give its suitable perception task according to the ability of its frequency spectrum perception; Centroid adopts the mode of inserting at interval when treating the subchannel of perception for the cognitive user distribution on the other hand, can be by the purpose of a plurality of different cognitive users detections to reach subchannel; In addition, when Centroid is done conclusive judgement, take all factors into consideration the frequency spectrum perception ability of different cognitive users, adopted the weighting fusion algorithm, guaranteed the accuracy of perception.

Description of drawings

Fig. 1 is that sketch map is formed in the cognitive radio networks unit of using multichannel frequency spectrum perception mechanism of the present invention.

Fig. 2 shines upon sketch map between cognitive user and the subchannel.

Fig. 3 is the operating procedure schematic flow sheet of multichannel frequency spectrum perception mechanism of the present invention.

Embodiment

For making technical scheme of the present invention and advantage clearer, the present invention is made further detailed description below in conjunction with accompanying drawing and specific embodiment.

Referring to shown in Figure 1, the cognitive radio networks unit that the present invention relates to comprises several main users (PU), a Centroid and several cognitive user (SU).The spendable band limits of main subscriber signal distributes extensively, and cognitive user need be carried out perception to the frequency range of broadband range, makes the judgement whether main subscriber signal exists, and makes conclusive judgement by Centroid.Limit by hardware condition and detecting period, therefore the impossible whole frequency bands of perception of single cognitive user are divided into non-overlapping copies, mutual incoherent N subchannel with whole frequency, carry out the multichannel frequency spectrum perception.

Referring to shown in Figure 2; In the multichannel perception; Cognitive user with treat that channel perception can constitute bigraph (bipartite graph), promptly the vertex set among the figure can be divided into two mutually disjoint subclass, and the summit that every limit depends among the figure all belongs to this two mutually disjoint subclass; Be that cognitive user and interchannel have corresponding relation, and not contact between the different cognitive users, between the different channels.For guaranteeing the fairness and the reliability of frequency spectrum perception mechanism, the corresponding relation between cognitive user and the subchannel needs Centroid to confirm according to certain criterion.

Referring to shown in Figure 3, the cognitive radio multichannel frequency spectrum perception mechanism that the present invention is based on QoS demand and confidence level has following operating procedure:

Step 1: the broadband of treating perception in the cognition network unit is divided into a nonoverlapping N=10 subchannel, and stipulates the once multipotency perception c of each cognitive user _Max=5 subchannel are supposed total K=8 cognitive user.

Step 2: on behalf of signal post, all cognitive user will need the QoS demand R and the confidence level P of subchannel number to send to Centroid, for further specifying situation, suppose R=[0,1,4,2 here; 2,3,0,2], P=[0.92,0.73; 0.76,0.82,0.66,0.95,0.63,0.93].

Step 3: establish cognitive system and divide the sufficiently high thresholding confidence level of cognitive user perception P _High=0.9, giving demand according to following rule is virtual demand of cognitive user of 0:

$R_j^{\′}=\left\{\begin{array}{cc}\underset{i}{\max }\left\{R_i\right\},& P_j>P_{\mathrm{high}}\\ \underset{i\≠j}{\min }\left\{R_i\right\},& \mathrm{others}\end{array}\right.,i,j=\mathrm{1,2},...,K$

Become [4,1,4,2,2,3,1,2] through amended virtual QoS demand, establish c _Min=3, Centroid is according to the subchannel number of following formula decision cognitive user needs perception

Get c=[5,2,5,4,4,5,2,4].

Step 4: the result that Centroid draws according to step 3 is the subchannel of cognitive user distribution needs perception, and record distribution s as a result _Ij∈ 0,1}, s _IjBe to represent cognitive user j perception subchannel i, s at 1 o'clock _IjBe to represent not perception of cognitive user j subchannel i at 0 o'clock.Get Δ=[2,5,2 by

; 2,2,2; 5,2], then by

$s_{\mathrm{ij}}=\left\{\begin{array}{cc}1,& i={(j+k\·{\mathrm{\Δ}}_j)}_{\mathrm{mod}N}\\ 0,& \mathrm{others}\end{array}\right.,k=\mathrm{0,1},\·\·\·,c_j-1$

Can get

$s=\left[\begin{array}{cccccccc}1& 0& 1& 0& 1& 0& 0& 0\\ 0& 1& 0& 0& 0& 1& 1& 1\\ 1& 0& 1& 0& 0& 0& 0& 0\\ 0& 0& 0& 1& 0& 1& 0& 1\\ 1& 0& 1& 0& 1& 0& 0& 0\\ 0& 0& 0& 1& 0& 1& 0& 0\\ 1& 1& 1& 0& 1& 0& 1& 0\\ 0& 0& 0& 1& 0& 1& 0& 1\\ 1& 0& 1& 0& 1& 0& 0& 0\\ 0& 0& 0& 1& 0& 1& 0& 1\end{array}\right]$

Thus, visible 10 subchannel are respectively [3,4,2,3,3,2,5,3,3,3] by the number of times of perception, and each subchannel is all at least by the perception of two cognitive user institutes.

Step 5: cognitive user is carried out energy measuring to the subchannel that Centroid distributes, and with testing result u _IjSend to Centroid, u _Ij{+1 ,-1} representes the testing result of cognitive user j to subchannel i, u to ∈ _Ij=+1 representes that cognitive user j thinks in main subscriber signal existence on the channel i, otherwise, u _Ij=-1 expression thinks that main subscriber signal does not exist, and Centroid is with the confidence level normalization of cognitive user

And calculate

Judge that it is positive and negative, if just, judge that then main subscriber signal exists on subchannel i, note is made z _i=1; Otherwise, not existing, note is made z _i=0.

Through above step, the cognitive radio multichannel frequency spectrum perception mechanism that the present invention is based on QoS demand and confidence level is achieved.The present invention is not limited to the embodiment of said system, all any modifications of within spirit of the present invention and principle, being done, is equal to replacement etc., all is included in protection scope of the present invention.

Claims (4)

1. the cognitive radio multichannel frequency spectrum perception mechanism based on QoS demand and confidence level is characterized in that, comprises following operating procedure:

Step 1: Centroid is divided into N nonoverlapping subchannel with the broadband of treating perception in the NE, and stipulates the once multipotency perception c of each cognitive user _MaxSubchannel;

Step 2: each cognitive user sends to Centroid with its QoS demand and confidence level;

Step 3: the subchannel number of QoS demand that Centroid reports according to each cognitive user in the step 2 and the perception of confidence level decision different cognitive users needs;

Step 4: Centroid is that cognitive user is distributed the subchannel of treating perception according to the result who draws in the step 3 according to the mode of inserting at interval, and allocation result is informed cognitive user;

Step 5: cognitive user is carried out energy measuring to the subchannel that Centroid distributes; And testing result sent to Centroid; Carry out data fusion by Centroid according to the testing result and the confidence level of each cognitive user; Make the conclusive judgement that whether main user exists on each subchannel, and court verdict is sent to each cognitive user.

2. method according to claim 1 is characterized in that, the QoS demand in the step 2 shows as cognitive user and communicates needed subchannel number.

3. method according to claim 1 is characterized in that, step 3 further comprises the following operations content:

(1) if the QoS demand R that cognitive user j reports _j=0, Centroid is through judging its confidence level P _jSize give a virtual QoS demand for this cognitive user:

$R_j^{\′}=\left\{\begin{array}{cc}\underset{i}{\max }\left\{R_i\right\},& P_j>P_{\mathrm{high}}\\ \underset{i\≠j}{\min }\left\{R_i\right\},& \mathrm{others}\end{array}\right.$

P wherein _HighFor cognitive system is divided the sufficiently high thresholding confidence level of cognitive user perception;

(2) the QoS demand (or virtual QoS demand) that guarantees each cognitive user is all greater than after zero, and Centroid decision cognitive user needs the subchannel number c of perception _j:

C wherein _MinBe value, satisfy c in order to guarantee that each subchannel can be established by a plurality of cognitive user institute's perception _Min>=1, symbol

Expression is not more than the maximum integer of x.

4. method according to claim 1 is characterized in that, step 4 further comprises the following operations content:

The interval of the expression cognitive user j institute perception subchannel that (1) makes ;

(2) Centroid is according to following rule decision cognitive user j perception subchannel i whether:

$s_{\mathrm{ij}}=\left\{\begin{array}{cc}1,& i={(j+k\·{\mathrm{\Δ}}_j)}_{\mathrm{mod}N}\\ 0,& \mathrm{others}\end{array}\right.$

K=0 wherein, 1 ..., c _j-1, s _IjBeing to represent cognitive user j perception subchannel i at 1 o'clock, is to represent not perception of cognitive user j subchannel i at 0 o'clock.

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