CN102291191B - Frequency spectrum sensing method - Google Patents

Abstract

The invention discloses a frequency spectrum sensing method. The frequency spectrum sensing method comprises the following steps of: independently sensing minor user nodes in an energy detecting mode, and acquiring the use conditions of frequency spectrums of the peripheries of the minor user nodes; acquiring a latest detection result by diffusing the minor user nodes within a two-hop neighbour range; computing the local sensing information and the synergetic sensing information of the minor user nodes; acquiring a judgment threshold according to master user communication behavior priori knowledges and the synergetic sensing information, and judging. According to the frequency spectrum sensing method disclosed by the invention, special appointed sink nodes or clustering computation is not needed, the local sensing information diffusion of the minor user nodes is limited within the two-hop neighbour range, and the complexity and the synergetic spending of the synergetic detection of a distributed cognitive network are effectively reduced.

Description

A kind of frequency spectrum sensing method

Technical field

The invention belongs to the cognitive radio technology field, particularly a kind of frequency spectrum sensing method.

Background technology

Develop rapidly along with wireless technology, frequency spectrum resource is in short supply day by day, the main cause of discovering present frequency spectrum resource present situation in short supply is that traditional fixed frequency spectrum method of salary distribution makes major part authorize the utilance of frequency range low excessively, has caused the significant wastage of frequency spectrum resource.In order to improve the availability of frequency spectrum, alleviate the deficient problem of frequency spectrum, various dynamic spectrum access technologies are arisen at the historic moment.Wherein, cognitive radio is considered to have one of technology of application potential most.The basic thought of cognitive radio is: when the frequency range of distributing to main user (Primary User) was not used, inferior user (Secondary user) can not cause under the prerequisite of interference main user, and chance formula ground inserts this frequency range; When main user inserted the frequency range of just " being used " again, inferior user in time withdrawed to avoid to clash with main user.

The frequency spectrum detection technology is the basis of realizing cognitive radio technology.Energy measuring be wherein a kind of simple, use detection method more widely, particularly under the prerequisite of signal the unknown, energy measuring is a kind of optimal algorithm.The collaboration frequency spectrum detection mode that existing energy measuring mostly adopts a plurality of users to cooperate with each other, the influence with the factors such as multipath, shade and interference that reduce wireless channel provides and detects performance more accurately and reliably.In collaborative testing process, determining of each time user's cooperative mode and conclusive judgement thresholding all is the major issue that is worth research.

Existing cooperation spectrum based on energy detects the mode that mostly adopts the whole network collaborative, and namely time user node of all in the network is announced the independent perception information of this node to a certain appointment aggregation node, carries out conclusive judgement by aggregation node then.Another kind of common cooperative mode is the sub-clustering mode, in the network of being formed by inferior user node, elect a plurality of bunches of first nodes by node, non-bunch of first node announced perception information to a bunch head, again to the announcement of higher level's aggregation node, and finally form frequency spectrum and take the situation discriminative information after bunch first node gathers.

The cooperation spectrum perceptive mode of existing distributed cognition wireless network needs to set separately aggregation node, the situation that can not adapt to time user node network topology dynamic change, and existing cooperative mode reckons without the radio communication feature of distributed wireless networks, and mode simply collaborative by the whole network or that adopt sub-clustering to work in coordination with can produce bigger collaborative expense.

After aggregation node receives the energy sensing information that each time user node transmits, can a plurality of energy sensing information be weighted summation according to the weight of each time user node correspondence, and comparing judgement with threshold value, the detected energy value is higher than weight and puts and think that then channel is by main CU.Threshold value can fixedly install, and also can dynamically set according to indexs such as probability of false detection, and the frequency spectrum perception technology of double threshold also can be set: a high threshold is used for limiting false alarm probability, and a low threshold is used for limiting alarm dismissal probability.When receiving signal strength signal intensity and be lower than low threshold, judge that channel be idle, when the signal strength signal intensity that receives was higher than high threshold, the judgement channel was led with taking, when signal strength signal intensity is between low threshold and the high threshold, channel whether occupied uncertain.

And select technology for thresholding, fixed threshold or detect mode that index determines decision threshold according to theory all can not the behavior of dynamically adapting master user's communications, thereby reduced accuracy of detection.Based on the frequency spectrum detection technology of double threshold, though improved the frequency spectrum detection performance to a certain extent, to the variation of still not considering main telex network behavior of choosing of high and low thresholding.

Summary of the invention

To the objective of the invention is to work in coordination with or adopt the collaborative mode of sub-clustering can produce the problem of bigger collaborative expense in order solving in the existing distributed cognition wireless network frequency spectrum perception by the whole network, to have proposed a kind of frequency spectrum sensing method.

Technical scheme of the present invention is: a kind of frequency spectrum sensing method specifically comprises the steps:

S1. each time user node adopts the energy measuring mode to carry out independent perception, obtains the frequency spectrum operating position of this node periphery;

S2. each time user node spreads up-to-date testing result in the two-hop neighbors scope;

S3. calculate local perception information and the collaborative perception information of each time user node;

S4. obtain decision threshold according to main telex network behavior priori and collaborative perception information and adjudicate.

Further, the local perception information of described each time of calculating of step S3 user node and the concrete computational process of collaborative perception information are:

I the energy detection value E of time user node after merge n this locality constantly _{I, local (}N) be:

$E_{i,\mathrm{local}}\left(n\right)=\mathrm{\γ}{E}_{i,\mathrm{local}}(n-1)+s_i\left(n\right)=\underset{k=n-K+1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\γ}}^{n-k}{s}_i\left(k\right)$

Wherein, s _i(k) be i user node in k local energy detection value constantly, γ is forgetting factor, K is local perception information employed historical perception information number when merging;

When i time user node carries out internodal collaborative perception, be about to local perception information E _i(n)=E _{I, local}When (n) merging again with the perception information that obtains from neighbor node, according to each perception information the contribution amount of conclusive judgement is weighted summation, the weight calculation formula of the perception information of j node when information fusion is:

J=1 ... M, wherein, M participates in the interstitial content of current information fusion, E for all _j(n) energy detection value that merges of the participation that obtains from node j of expression when j=i, is represented the energy detection value E of i time user node after the fusion of this locality of moment n _{I, local}(n); When j ≠ i, expression is from the current perception data of the moment n that j neighbor node transmits,

According to each perception information and respective weights, try to achieve the collaborative perception information E of i time user node _Co(n) be

$E_{\mathrm{co}}\left(n\right)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\ω}}_m\left(n\right)E_m\left(n\right).$

Further, the described judgement of step S4 is specially: try to achieve decision threshold E according to main telex network behavior priori and collaborative perception information _Th(n):

, wherein, Λ ₀=P (H ₀) P (H ₁), P (H ₁) and P (H ₀) represent main CU respectively or do not use the probability of channel resource,

δ ²Be noise power;

According to decision threshold, with itself and energy sensing information relatively after, whether draw channel by main CU;

Judging process is divided into two kinds of situations: as collaborative perception information E _Co(n) greater than

The time, select E _Co(n) with the local perception information E of judgement node _{I, local}(n) the higher value person in and decision threshold E _Th(n) compare, if greater than decision threshold, channel is by main CU, otherwise, channel idle; As collaborative perception information E _Co(n) less than

The time, then according to P (H ₁) and P (H ₀) ratio select, if P (H ₁)/P (H ₀Collaborative perception information E is selected in) 〉=1 _Co(n) with the local perception information E of judgement node _{I, local}(n) higher value person and decision threshold E in _Th(n) compare, otherwise then select wherein smaller value and decision threshold E _Th(n) compare, if greater than thresholding, channel is by main CU, otherwise, channel idle.

Beneficial effect of the present invention: frequency spectrum sensing method of the present invention does not need to specify specially aggregation node or carries out the sub-clustering computing, the local perception information diffusion of inferior user node is limited within its double bounce scope, effectively reduces complexity and the collaborative expense of the collaborative detection in the distributed cognition network.Method of the present invention has well adapted to the use characteristic of distributed cognition wireless network topology dynamically changeable and communication channel, effectively reduces collaborative detection overhead and complexity; Adopt the dual weighting amalgamation mode that perception information merges between the local historical perception information fusion of time user node and node, effectively utilized time and space diversity, reduced wireless channel multipath fading and the influence of disturbing perception data; According to main telex network behavioural characteristic priori and collaborative perception information, the use of self adaptation dynamic decision thresholding and decision method effectively reduces average probability of false detection and to main user's interference, and has improved the availability of frequency spectrum.

Description of drawings

Fig. 1 distributed cognition Radio Network System illustraton of model.

Fig. 2 is frequency spectrum sensing method schematic flow sheet of the present invention.

Fig. 3 is based on two-hop neighbors collaborative perception process schematic diagram.

Embodiment

The invention will be further elaborated below in conjunction with accompanying drawing and specific embodiment.

In distributed network, because the correspondence between each time user node is reciprocity, and be a kind of incomplete network structure between node, so each node can adopt the mode of distributed collaboration channel-aware, select a bunch first node to carry out the overhead that the sub-clustering perception brings thereby can save, consider simultaneously in the distributed cognition wireless communication, under the approximate situation of the wireless coverage of each node, the frequency spectrum of a certain node uses other node that only can have influence in its double bounce scope, uses frequency range to get final product so the sensing range of node only needs to be limited in its two-hop neighbors.

The present invention proposes in the distributed cognition wireless network, and by collaborative perception form between energy measuring and secondary nodes two-hop neighbors, whether by the detection method of main CU, the system model of its application scenarios as shown in Figure 1 to channel.

Frequency spectrum sensing method schematic flow sheet of the present invention may further comprise the steps as shown in Figure 2:

S1. each time user node adopts the energy measuring mode to carry out independent perception, obtains the frequency spectrum operating position of this node periphery.

Inferior user node periodically carries out frequency spectrum perception, and here, the energy measuring mode of employing can be asked mould for directly time-domain signal being sampled, and carries out then square; Also can utilize fast fourier transform that signal is transformed into frequency domain from time domain, then to frequency-region signal ask mould and square.Inferior user node is stored each time energy detection results, if the storage capacity of node self is limited, can adopt the form of circular buffer, the historical testing result of part that a buffer memory is nearest apart from current time.

S2. each time user node spreads up-to-date testing result in the two-hop neighbors scope.

In this step, the spectrum energy information that each time user node at first independently perceives the last time is announced to a hop neighbor time user node of oneself with the form of " the energy intensity value list of detected channel, this node MAC Address ".

In order to realize the diffusion in time user node two-hop neighbors scope, the hop neighbor node perceived information that each time user node also need be received oneself is transmitted to other hop neighbor node except this information source node.Wireless bandwidth occupancy when reducing diffuse information also in order to reduce the perception information loss, to improve the conclusive judgement precision, has adopted the data fusion mode of local many bit decisions simultaneously.For example can adopt the dibit blending algorithm, each time user node arranges three energy threshold T1, T2, T3 to the energy sensing value that oneself hop neighbor node transmits, after the channel energy that transmits quantized, again quantized value (dibit) is spread to one hop neighbor node with " neighbor node channel perception energy quantizes value list; neighbor node MAC Address tabulation; this node MAC Address " form, recover the energy measuring approximation at the destination node place by quantized value at last.The schematic diagram of this process as shown in Figure 3.

S3. calculate local perception information and the collaborative perception information of each time user node.

After the mutual diffusion of the perception information between inferior user node in the distributed cognition network, each time user node should have two kinds of perception informations: a kind of is the repeatedly local perception information that node self obtains by independent perception; Another kind is by the perception information of cooperation interaction process from current (or approximate current) other node of the moment of neighbor node acquisition, this part information is divided into the primary energy detected value that directly obtains from a hop neighbor again, also has the two-hop neighbors energy sensing quantized value that quantizes and forward by a hop neighbor.These perception informations all can exert an influence to the judgement of final channel occupancy situation, but consider time that perception information obtains and to the difference of the contribution of conclusive judgement precision etc., given different weights to these perception datas.

What at first consider is the influence of perception information acquisition time.Each time user's buffer memory the historical data that detect of part.Because the complexity of wireless transmission environment, the single frequency spectrum detecting result of inferior user node may produce flase drop because being interfered, consider simultaneously in general scene, main user to channel take or idling cycle is a bigger value with respect to inferior user's sense cycle, so can utilize the mode of historical perception information and current awareness information synthetic determination to overcome the single flase drop to the influence of final result, but the historical data more remote apart from current time is more little to the contribution amount of the result of determination of current time.Here adopt forgetting factor method, be the number less than 1 that index law reduces and alleviate historical data gradually to the influence of current time court verdict by multiply by one in the frequency spectrum detection value.

$E_{i,\mathrm{local}}\left(n\right)=\mathrm{\γ}{E}_{i,\mathrm{local}}(n-1)+s_i\left(n\right)=\underset{k=n-K+1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\γ}}^{n-k}{s}_i\left(k\right)---\left(1\right)$

In the formula (1), E _{I, local}(n) be the energy detection value of i time user node after merge n this locality constantly, be local perception information, K is local perception information employed historical perception information number when merging, here only used preceding n to detect K nearest moment data of data middle distance current time constantly, Yi Zhi, K≤n, s _i(k) be i user node in k local energy detection value constantly, γ is forgetting factor, is generally greater than 0.9 less than 1 constant.By the iteration of (1) formula, its weights of more old data are more little, and the weights γ of up-to-date one-time detection value ^N-kFor 1(namely when the k=n), thereby played the effect of eliminating the influence of historical data.

Next considers the collaborative perception of neighbor node, be example with i user node, the interstitial content of information fusion this time that participates in i time user node is M, and M comprises i time user node self, namely has M-1 neighbor node around i time user node.The computational process of the collaborative perception information of i time user node is as follows:

Local perception information E with i time user node _i(n)=E _{I, local}When (n) merging again with the perception information that obtains from M-1 neighbor node, according to each perception information the contribution amount of conclusive judgement is weighted summation, the calculating of its weight as the formula (2), ω wherein _j(n) be the weight of perception information when information fusion of j node, M participates in the interstitial content of current information fusion, E for all _j(n) energy detection value that merges of the participation that obtains from node j of expression when j=i, is represented the energy detection value E of i time user node after the fusion of this locality of moment n _{I, local}(n); When j ≠ i, expression is from the current perception data of the moment n that j neighbor node transmits.

${\mathrm{\ω}}_j\left(n\right)=E_j\left(n\right)/\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{E}_m\left(n\right)j=1,\·\·\·M---\left(2\right)$

According to each perception information and respective weights, try to achieve the collaborative perception information E of i time user node _Co(n), as the formula (3).

$E_{\mathrm{co}}\left(n\right)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\ω}}_m\left(n\right)E_m\left(n\right)---\left(3\right)$

S4. obtain decision threshold according to main telex network behavior priori and collaborative perception information and adjudicate.

In the cognitive radio operational environment of reality, (for example: communication behavior cable TV signal) has certain rules to main user usually, can obtain the prior probability of main CU channel resource according to historical statistics information.If P is (H ₁) and P (H ₀) represent main CU respectively or do not use the probability of channel resource.According to main telex network behavior priori and collaborative perception information, can try to achieve decision threshold E according to the form of formula (4) _Th(n), Λ in the formula ₀=P (H ₀) P (H ₁),

δ ²Be noise power, K is local perception information employed historical perception information number when merging.

According to decision threshold, with itself and energy sensing information relatively after, whether draw channel by the conclusion of main CU.Judging process is divided into two kinds of situations: as collaborative perception information E _Co(n) greater than

The time, select E _Co(n) with the local perception information E of judgement node _{I, local}(n) the higher value person in and decision threshold E _Th(n) compare, if greater than decision threshold, channel is by main CU, otherwise, channel idle; As collaborative perception information E _Co(n) less than

The time, then according to P (H ₁) and P (H ₀) ratio select, if P (H ₁)/P (H ₀Collaborative perception information E is selected in) 〉=1 _Co(n) with the local perception information E of judgement node _{I, local}(n) higher value person and decision threshold E in _Th(n) compare, otherwise then select wherein smaller value and decision threshold E _Th(n) compare, if greater than thresholding, channel is by main CU, otherwise, channel idle.

According to cognitive method of the present invention, its collaborative perception probability of false detection is obeyed:

Distribute, wherein E _Judge(n) for being used for and decision threshold E _Th(n) detected value that compares.As collaborative perception information E _Co(n) greater than

The time, P _{Co, error}(n) be monotone decreasing, so select E _Co(n) with the local perception information E of judgement node _{I, local}(n) the higher value person in is as E _Judge(n) with decision threshold E _Th(n) compare; If collaborative perception information E _Co(n) less than

The time, P _{Co, error}(n) the previous Q function in the formula is monotonically increasing, and a back Q function is monotone decreasing, and this just need see the proportion of these two parts in whole formula, i.e. the ratio P (H of two Q function coefficients ₁)/P (H ₀) next definite E that selects _Co(n) with the local perception information E of judgement node _{I, local}(n) higher value in or smaller value are as E _Judge(n) with decision threshold E _Th(n) compare.

To sum up, the contribution of method of the present invention is as can be seen:

1. adopt distributed collaborative detection mode, do not need to specify specially aggregation node or carry out the sub-clustering computing, and the local perception information diffusion of inferior user node is limited within its double bounce scope, effectively reduces complexity and the collaborative expense of the collaborative detection in the distributed cognition network;

2. adopt the dual weighting amalgamation mode that perception information merges between the local historical perception information fusion of time user node and node, according to the space-time characteristic in perception information source and to the otherness of the contribution degree of frequency spectrum detection, for each collaborative perception information arranges different weight coefficients, effectively utilize time and space diversity, reduced wireless channel multipath fading and interference to the influence of perception data;

3. introduced the priori of main telex network behavior, under the acting in conjunction of collaborative perception information and priori, try to achieve self-adaptive decision threshold, finally the channel operating position is made judgement, according to main telex network behavioural characteristic priori and collaborative perception information, the use of self adaptation dynamic decision thresholding and decision method effectively reduces average probability of false detection and to main user's interference, has improved the availability of frequency spectrum.

Those of ordinary skill in the art will appreciate that embodiment described here is in order to help reader understanding's principle of the present invention, should to be understood that the protection range of inventing is not limited to such special statement and embodiment.Everyly make various possible being equal to according to foregoing description and replace or change, all be considered to belong to the protection range of claim of the present invention.

Claims (3)

1. a frequency spectrum sensing method specifically comprises the steps:

S1. each time user node adopts the energy measuring mode to carry out independent perception, knows the frequency spectrum operating position of this node periphery;

S2. each time user node spreads up-to-date testing result in the two-hop neighbors scope;

S3. calculate local perception information and the collaborative perception information of each time user node;

S4. obtain decision threshold according to main telex network behavior priori and collaborative perception information and adjudicate;

Local perception information and the concrete computational process of collaborative perception information of described each time of calculating of step S3 user node are:

I the energy detection value E of time user node after merge n this locality constantly _{I, local}(n) be:

$E_{i,\mathrm{local}}\left(n\right)=\mathrm{\γ}{E}_{i,\mathrm{local}}(n-1)+s_i\left(n\right)=\underset{k=n-K+1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\γ}}^{n-k}{s}_i\left(k\right)$

Wherein, s _i(k) be i user node in k local energy detection value constantly, γ is forgetting factor, K is local perception information employed historical perception information number when merging;

When i time user node carries out internodal collaborative perception, be about to local perception information E _i(n)=E _{I, local}When (n) merging again with the perception information that obtains from neighbor node, according to each perception information the contribution amount of conclusive judgement is weighted summation, the weight calculation formula of the perception information of j node when information fusion is:

, wherein, M participates in the interstitial content of current information fusion, E for all _j(n) energy detection value that merges of the participation that obtains from node j of expression when j=i, is represented the energy detection value E of i time user node after the fusion of this locality of moment n _{I, local}(n); When j ≠ i, expression is from the current perception data of the moment n that j neighbor node transmits,

According to each perception information and respective weights, try to achieve the collaborative perception information E of i time user node _Co(n) be:

$E_{\mathrm{co}}\left(n\right)=\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\ω}}_m\left(n\right)E_m\left(n\right).$

2. frequency spectrum sensing method according to claim 1 is characterized in that, what the described diffusion of step S2 was specifically adopted is the data fusion mode of local many bit decisions.

3. frequency spectrum sensing method according to claim 1 and 2 is characterized in that, the described judgement of step S4 is specially:

Try to achieve decision threshold E according to main telex network behavior priori and collaborative perception information _Th(n):

, wherein, Λ ₀=P (H ₀) P (H ₁), P (H ₁) and P (H ₀) represent main CU respectively or do not use the probability of channel resource, , δ ²Be noise power;

According to decision threshold, with itself and energy sensing information relatively after, whether draw channel by main CU;

Judging process is divided into two kinds of situations: as collaborative perception information E _Co(n) greater than

The time, select E _Co(n) with the local perception information E of judgement node _{I, local}(n) the higher value person in and decision threshold E _Th(n) compare, if greater than decision threshold, channel is by main CU, otherwise, channel idle; As collaborative perception information E _Co(n) less than The time, then according to P (H ₁) and P (H ₀) ratio select, if P (H ₁)/P (H ₀Collaborative perception information E is selected in) 〉=1 _Co(n) with the local perception information E of judgement node _{I, local}(n) higher value person and decision threshold E in _Th(n) compare, otherwise then select wherein smaller value and decision threshold E _Th(n) compare, if greater than thresholding, channel is by main CU, otherwise, channel idle.

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