CN101399564B - Dual-time collaboration detection method for sensing idle frequency spectrum in radio frequency - Google Patents

Abstract

The invention applies for protecting a double coordination detection method for vacant frequency spectrum detection in a cognitive radio system, relating to a radio communication system. The method is as follows: a plurality of cognitive users which take part in coordination in a traditional coordination detection algorithm are partitioned into different groups; a cognitive user needing communication is a group leader of the group; then the purposes of reducing spending of a control channel and improving detection performance of a system are gained by coordination within groups and coordination between groups. The users within the group locally judge by using an energy-check algorithm whether a master user signal exists in a certain frequency band authorized to the master user and transmits a local judgment result to the group leader. The group leader syncretizes the local judgments to make a group judgment result. A cognitive base station further syncretizes the group judgment result to make judgment, thus getting the final judgment of the system. Bit numbers of the judgment result transmitted to the cognitive base station are largely reduced by using the method, thus greatly saving bandwidth of the control channel, and detection performance is increased.

Description

Two cooperative detection methods of idle frequency spectrum in a kind of cognitive radio

Technical field

The present invention relates to wireless communication technology, relate in particular to the cognitive radio power technology.

Background technology

Cognitive radio is a kind of radio system, ambient conditions around it can automatically detect, the intelligently variation of the parameter of Adjustment System to conform, under the condition that authorized user (hereinafter referred is the primary user) is not caused interference from the space, utilize the idle frequency spectrum resource to communicate to the multidimensional such as frequency, time.In the system for cognitive radio, the idle frequency spectrum detection technique is the key technology that determines that can the cognitive radio power technology be realized.The idle frequency spectrum detection algorithm mainly can be divided into two large classes: the local frequency spectrum detection algorithm at the cooperative detection algorithm that the multi-user cooperates and alone family.

Whether in the cooperative detection algorithm, exist primary user's signal to judge the use state of frequency spectrum in primary user's transmitting terminal detects the signal that to be the perception user listen to by analysis, it is the detection under a kind of unknown primary user's receiving terminal situation.Algorithm commonly used has matched filter detection algorithm, energy detection algorithm and cyclostationary characteristic detection algorithm.Primary user's receiving terminal detects for primary user's transmitting terminal detects, it be by judge primary user's receiving terminal whether the in running order primary user of judgement system whether using the method for spectrum, of interest.The algorithm that primary user's receiving terminal commonly used detects: local oscillator leakage detects and based on the detection of interference temperature.

Owing to can not directly carry out Signalling exchange between cognitive radio user (hereinafter referred is the perception user) and the primary user, so the enforcement of frequency spectrum detection work can only lean on the perception user that the intercepting and capturing of primary user's signal are detected.In the process that primary user's signal is intercepted and captured, inevitably be subject to the impact of the factors such as multipath, shade and local interference, detect insecure phenomenon appearance thereby increased single perception user, in order to overcome this problem, a plurality of perception user collaborations have been detected as an urgent demand.Cooperative detection refers to that a plurality of perception users cooperate with each other and the detection carried out, and it judges more accurately by the detection information that merges a plurality of perception users whether the primary user exists.Tradition/single cooperative detection algorithm implementation was divided into for two steps: each user of the first step carries out first local detection algorithm, makes the primary user and exists or the non-existent judgement of primary user; Second step: perception user's court verdict is sent to aware base station, and the final the judgement whether primary user exists is made again by different fusion criterions in the base station.

Document [A.Ghasemi and E. S. Sousa, " Collaborative spectrumsensing for opportunistic access in fading environments; " in Proc.1st IEEE Symp.New Frontiers in Dynamic Spectrum Access Networks, Baltimore, USA, Nov.8-11,2005, pp:131-136] a kind of method of cooperative detection is disclosed, we are referred to as tradition/single cooperative detection.Tradition/single cooperative detection algorithm is better than local frequency spectrum detection algorithm in performance, but in cooperative detection, the perception user needs control channel to come to transmit court verdict to aware base station, and this control channel is that band is limit generally speaking.(simple scenario is 1 bit even each perception user is only with court verdict, as " 0 " or " 1 " respectively correspondence do not have the primary user or have the primary user) send aware base station to, when the number of users that participates in cooperation is very large, their required control channel bandwidth also can be very large, can too much busy channel resource.Here we have proposed a kind of two cooperative detection methods, and with the contrast of single cooperative detection algorithm, the bandwidth of not only having saved the control channel of system for cognitive radio, and the detection performance also is greatly improved.

Summary of the invention

The perception user needs control channel to come to transmit local court verdict to aware base station in the cooperative detection, and this control channel is that band is limit generally speaking.In tradition/single cooperative detection, the user of all cooperations needs to transmit local court verdict to aware base station, and when the number of users that participates in cooperation was very large, their required control channel bandwidth also can be very large.The present invention is directed to that a plurality of perception users send the court verdict of oneself to base station respectively in tradition/single cooperative detection algorithm, cause the heavy problem of band-limited control channel burden, a kind of two cooperative detection algorithms of idle frequency spectrum perception have been proposed, the system for cognitive radio that is fit to have aware base station.

The technical scheme that the present invention addresses the above problem is, a kind of two cooperation idle frequency spectrum cognitive methods are proposed, the method specifically comprises: two perception users of (1) needs communication shake hands by aware base station, success latter two perception user respectively around own certain limit (its radius is generally less than two distances between the perception user) send the idle frequency spectrum that cooperates and detect request, form a collaboration frequency spectrum all perception users of this scope and detect the group.Like this, have two collaboration frequency spectrums to detect the group, needing the perception user of communication is the cluster of this group.(2) collaboration frequency spectrum detects in the group each perception user and adopts the method such as energy detection algorithm as local frequency spectrum detection algorithm, locally judges whether there is primary user's signal on certain frequency range that licenses to the primary user, and local judged result is sent to cluster.Cluster is collected this locality judgement of each perception user in this group, merges these local court verdicts according to OR criterion or AND criterion and makes group court verdict.(3) cluster is sent group's court verdict into the aware base station fusion, forms the decision statistics of aware base station, at the aware base station place group's court verdict is further adopted OR criterion or the judgement of AND criterion, thereby obtains the conclusive judgement of system for cognitive radio.

In two cooperative detection methods, only has the perception user (cluster) who needs communication but not all perception users' court verdict is delivered to the base station, reduce to a great extent the court verdict bit number that passes to aware base station, so just greatly saved the bandwidth of control channel.Detect performance with the contrast of single cooperative detection algorithm and also be greatly improved, solve the problem of frequency spectrum resource scarcity.

Description of drawings

Two perception users of Fig. 1 shake hands and form collaboration frequency spectrum and detect group's schematic diagram.

The energy detection algorithm schematic diagram that the local detection algorithm of Fig. 2 adopts.

The schematic block diagram of two cooperative detection of Fig. 3.

Lower pair cooperative detection algorithm of Fig. 4 OR fusion rule and single cooperative detection algorithm ROC are relatively.

Lower pair cooperative detection algorithm of Fig. 5 AND fusion rule and single cooperative detection algorithm ROC are relatively.

Embodiment

The present invention proposes a kind of two cooperative detection methods, perception user in the group adopts the local judgements of conduct such as energy detection algorithm, this locality judges on certain frequency range that licenses to the primary user whether have primary user's signal, cluster is collected this locality judgement of each perception user in this group, and carry out the group and adjudicate, group's court verdict is sent to aware base station, as the decision statistics of aware base station.Now for accompanying drawing and instantiation enforcement of the present invention is further described in detail.

The first step, a perception user who needs communication sends communication request with another perception user to aware base station, and two perception users that need to communicate by letter by aware base station shake hands.Being illustrated in figure 1 as two perception users shakes hands and forms collaboration frequency spectrum and detect group's schematic diagram.As the perception user CRN among the group 1 need to group 2 in perception user CR1 communicate, the CRN of group in 1 sends communication request, shakes hands with CRN among the group 2 by aware base station.

Second step, after shaking hands successfully, among CR1 in two perception customer groups 2, the group 1 CRN respectively around own certain limit (its radius is generally less than two distances between the perception user) send the idle frequency spectrum that cooperates and detect request, all perception users that receive cooperation idle frequency spectrum detection request in this scope form a collaboration frequency spectrum and detect the group (if some perception users receive two cooperation idle frequency spectrums detection requests, then respond the cooperation idle frequency spectrum of at first receiving and detect request, and be classified to this collaboration frequency spectrum detection group).Like this, form two collaboration frequency spectrums in the system for cognitive radio and detect the group, comprise separately independently perception user CR1-CRN in the group, needing the perception user of communication is the cluster of this group, and in Fig. 1, CRN is the cluster user among the group 1, and CR1 is the cluster user among the group 2.

In the 3rd step, each perception user adopts energy detection algorithm as local frequency spectrum detection algorithm in each group.Being illustrated in figure 2 as the present invention adopts energy detection algorithm to carry out the schematic diagram of local judgement as local detection algorithm.

A collaboration frequency spectrum detects interior each the perception user of group the unknown signaling that receives is passed through a low pass filter filters out out-of-band noise and adjacent signal, then pass through successively A/D converter, squarer, after N the sampling summation, obtain detection statistic Y, itself and predefined threshold value are compared to judge.Can judge during greater than threshold value to have primary user's signal on this frequency range, local court verdict is set be " 1 ", it is masked as H1, show that the perception user is not suitable for working in this frequency range; When detection statistic Y can judge that noise is only arranged on this frequency range during less than threshold value, there is not primary user's signal, local court verdict is set is " 0 ", it is masked as HO, show that the perception user can use this frequency range.

In order to save the control channel bandwidth, each perception user only passes to cluster with the court verdict of 1bit in the group, and the sign of court verdict is deposited in the detection system memory.Have the primary user on the frequency range that wherein " 1 " expression perception user detects, " 0 " represents that there is not the primary user in this frequency range.

In the 4th step, the 1st cooperation also is cooperation in the group.Be illustrated in figure 3 as the schematic block diagram of two cooperative detection of the present invention, wherein the first half is cooperation in the group.

For certain section frequency spectrum that licenses to the primary user, in the group each perception user based on oneself local frequency spectrum detection algorithm according to detection statistic y ₁..., y _N, independently finish local judgement, adjudicate this section frequency spectrum and whether have the primary user, obtain respectively local court verdict u ₁..., u _N, and local court verdict delivered to cluster.Cluster utilizes OR criterion or AND criterion to make judgement in the group according to local court verdict, and its result is u _0j(j=1 ..., K).

The 5th step, for the second time cooperation: cooperation between the group, see the latter half among Fig. 3.

Two perception users (cluster) that need to communicate by letter detect two collaboration frequency spectrums respectively group's court verdict { u _0j(j=1,2), K=2} sends to aware base station here, and these court verdicts form the decision statistics of aware base station, and aware base station utilizes OR criterion or AND criterion to obtain final court verdict D based on these statistics.

In the cooperative detection, the perception user needs control channel to come to transmit local court verdict to aware base station, and this control channel is that band is limit generally speaking.In order to save the control channel bandwidth, the perception user only passes to aware base station with the court verdict (0 or 1) of 1bit.In tradition/single cooperative detection, the user of all cooperations needs to transmit local court verdict to aware base station, and when the number of users that participates in cooperation was very large, their required control channel bandwidth also can be very large.But two collaboration methods of the present invention only have two court verdicts of cluster to send into aware base station and adjudicate, and have greatly reduced the data volume that transmits, and save the control channel bandwidth.

Below OR fusion criterion or AND fusion criterion are further described in detail.

The OR criterion

As long as there is a perception User support judgement to be H1, the aware base station final judging result just is judged to this judgement H1, i.e. inclusive-OR operation criterion.Sign in the cooperative system detection of stored device as long as the H1 that is masked as that perception user arranges is arranged, namely supports the judgement primary user to exist, and cluster and base station make final justice and have the primary user in this frequency range, total with the court verdict sign be set to H1; Only having the sign in the memory all is HO, and namely all perception users' court verdict is when not having the primary user in the frequency range, and enter a judgement and do not have the primary user in this frequency range in cluster or base station, total court verdict sign is set to HO.

Namely the statistic Y when the cooperative system fusion center satisfies:

Describe as weighing the detection performance index in the system for cognitive radio with false alarm probability and detection probability, false alarm probability and the detection probability of carrying out after the OR criterion cooperates are respectively:

$P_F=1-\underset{i=1}{\overset{N}{\mathrm{\Π}}}(1-p_{\mathrm{fi}})---\left(2\right)$

$P_D=1-\underset{i=1}{\overset{N}{\mathrm{\Π}}}(1-p_{\mathrm{di}})---\left(3\right)$

Wherein, N is for participating in the perception user number of cooperation, p _Fi, p _DiThe local false alarm probability and the local detection probability that represent respectively i user, this integration program have less false dismissal probability and larger false alarm probability.

The AND criterion

When all perception users supported certain judgement for H1, the aware base station final judging result just was judgement H1, i.e. AND operation criterion.Sign in the cooperative system detection of stored device, only has the judgement of all making primary user's existence as all perception users, when the sign that arranges in the memory all was H1, cluster and base station made final justice and have the primary user in this frequency range, and total court verdict sign is set to H1.As long as the HO that is masked as that perception user arranges is arranged, namely support judgement not exist primary user, cluster and base station to make final justice and do not have the primary user in this frequency range, total and with the court verdict sign be set to HO.Namely the statistic Y when the cooperative system fusion center satisfies:

False alarm probability and detection probability after cooperating are respectively:

$P_F=\underset{i=1}{\overset{N}{\mathrm{\Π}}}{p}_{\mathrm{fi}}---\left(4\right)$

$P_D=\underset{i=1}{\overset{N}{\mathrm{\Π}}}{p}_{\mathrm{di}}---\left(5\right)$

Compare this integration program has sacrificed false dismissal probability and has exchanged reducing of false alarm probability for the OR rule.

In the cognitive radio frequency spectrum detection, mainly weigh the performance of system by the size of detection probability under the same terms.But false alarm probability refers to that primary user's signal does not exist is mistaken for the probability that has primary user's signal, and detection probability is exactly the correct probability of judging, and false dismissal probability and detection probability sum are 1.After introducing cooperative detection, the parameter that the measurement system that we consider detects performance then is global detection probability and overall empty probability.

In two cooperative detection systems, make P _{F, j}, P _{D, j}Represent respectively group's false alarm probability, detection probability among the group j, the global detection probability and the overall false alarm probability that draw the frequency spectrum detection system of twice cooperation under the OR rule by formula (2), (3) when group's number is K (K 〉=2) are:

$P_D=1-\underset{j=1}{\overset{K}{\mathrm{\Π}}}(1-P_{d,j})---\left(6\right)$

$P_F=1-\underset{j=1}{\overset{K}{\mathrm{\Π}}}(1-P_{f,j})---\left(7\right)$

Global detection probability and overall false alarm probability by the frequency spectrum detection system of twice cooperation under formula (4), (5) AND rule are:

$P_D=\underset{i=1}{\overset{K}{\mathrm{\Π}}}{P}_{d,j}---\left(8\right)$

$P_F=\underset{i=1}{\overset{K}{\mathrm{\Π}}}{P}_{f,j}---\left(9\right)$

We can regard the single cooperative detection as the special circumstances of the number (K=1) that hives off in two inferior cooperative detection algorithms.

The ROC curve that Fig. 4, Fig. 5 have provided respectively OR fusion rule, lower pair cooperative detection algorithm of AND fusion rule and single cooperative detection algorithm compares.

During the same terms, there are two groups in system under two the cooperative detection environment, and the user's number in each group is respectively 8,4, group only under the single cooperative detection environment, and user's number sum during user's number is got and detected for two times is 8.Wherein, Fig. 4 adopts the OR criterion for twice fusion in two the cooperations, and Fig. 5 adopts the AND criterion for twice fusion in two the cooperations.Can find out, under the identical overall false alarm probability condition, the overall false dismissal probability of two cooperative detection algorithms will be lower than the overall false dismissal probability of single cooperative detection algorithm, therefore has and detects preferably performance.

The above; be better embodiment of the present invention only, but protection scope of the present invention is not limited to this, anyly is familiar with the people of this technology in the disclosed technical scope of the present invention; the conversion that can expect easily and replacement all should be included in the protection category of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.

Two cooperative detection algorithms that adopt the present invention to propose are in the situation that the identical global detection probability that can improve system of overall false alarm probability; Secondly in two cooperative detection, only have cluster (only two) but not all perception users' court verdict is delivered to the base station, reduced to a great extent the court verdict bit number that passes to aware base station, so just greatly saved the bandwidth of control channel.

Claims (4)

1. a kind of two cooperative detection methods of idle frequency spectrum in the cognitive radio, it is characterized in that, need the perception user of communication to shake hands by aware base station, the perception user who successfully shakes hands sends the idle frequency spectrum that cooperates to radius less than the scope of distance between two perception users respectively and detects request; The collaboration frequency spectrum that forms respectively take the perception user of needs communication as cluster detects the group; Collaboration frequency spectrum detects interior each the perception user of group and carries out local frequency spectrum detection, and this locality judges on certain frequency range that licenses to the primary user whether have primary user's signal, and local court verdict is sent to cluster; Cluster merges above-mentioned local court verdict makes group court verdict, and send into aware base station as the decision statistics of aware base station, at the aware base station place group's court verdict is further adopted OR criterion or the judgement of AND criterion, thereby obtain the final judging result of system for cognitive radio, determine whether primary user's signal exists.

2. two inferior cooperative detection methods according to claim 1 is characterized in that, local frequency spectrum detecting method adopts energy detection algorithm, and each perception user adjudicates according to the detection statistic complete independently is local based on the local frequency spectrum detection of oneself in the group.

3. two cooperative detection methods according to claim 1 is characterized in that, each perception user only passes to cluster as the decision statistics of cluster with the court verdict of 1bit in the group; Each cluster is only passed to aware base station as the decision statistics of base station with the court verdict of 1bit.

4. two cooperative detection methods according to claim 1 is characterized in that, in the cluster judgement, can adopt OR criterion or AND criterion to the group in each perception user's local court verdict carry out amalgamation judging, obtain group court verdict; Can adopt OR criterion or AND criterion that group's court verdict is adjudicated in the amalgamation judging of base station, obtain total final judging result.

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