CN102595491B - Data transmission method in cognitive radio network - Google Patents

Abstract

The invention provides a data transmission method in a cognitive radio network, which comprises the following steps: in an initialized subframe, enabling all k secondary users to report the perception results, setting an ordinary subframe number into 1 in a data fusion center, determining to enable an optimal secondary user to report a set Omega according to the perception results reported by all the k secondary users, judging whether a main user exists or not and enabling all the k secondary users to carry out data transmission if the main user exists; and in an ordinary subframe, enabling the secondary users in the set omega reported by the optimal secondary user to report the perception results, judging whether the main user exists or not in the data fusion center according to the perception results reported by the secondary users in the set omega reported by the optimal secondary user and enabling all the k secondary users to carry out data transmission if the main user does not exist. By applying the invention, on the premise that the main user is not disturbed, the report signaling cost is reduced, so that the throughout capacity of the secondary users in the cognitive radio network is improved.

Description

Data transmission method in a kind of cognitive radio networks

Technical field

The present invention relates to wireless communication technology field, relate in particular to the data transmission method in a kind of cognitive radio networks.

Background technology

Along with the fast development of broadband wireless communication technique, future communications network increases day by day to the demand of various ubiquitous wireless traffics, the rare problem demanding prompt solution of wireless communication field that becomes of radio spectrum resources.In recent years, academia has proposed cognitive radio (CR, cognitive radio) technology, make secondary user's (SU, secondary user) can access idle frequency range (also referred to as frequency spectrum cavity-pocket), in order to improve the rare problem of frequency spectrum resource, described secondary user's refers to the user who does not obtain some wireless frequency spectrum legal authorization.

Wherein, frequency spectrum cavity-pocket is defined in special time period and the authorized frequency bands not used by primary user (PU, primary user) in specific geographical area, and described primary user refers to the legal authorization user who obtains some wireless frequency spectrum.When primary user does not temporarily use certain wireless frequency spectrum, secondary user's can be passed through frequency spectrum perception and access procedure, uses this wireless frequency spectrum.For example, yet imperfect due to channel condition, exists shadow fading, high-penetration loss and multipath fading etc., for a secondary user's, carry out separately frequency spectrum perception and obtain rapidly accurate sensing results, and this is very difficult.Therefore for overcoming this shortcoming, collaborative spectrum sensing technology is suggested to improve the performance of frequency spectrum perception.In centralized cooperation sensing network, comprise a primary user, a plurality of secondary user's and a data fusion center (FC, fusion center), wherein data fusion center refers to the control node with data processing and Function of Information Fusion, secondary user's is distributed in the control range at data fusion center, and it is responsible for processing the perception information of secondary user's submission and makes the sensing results finally whether existing about primary user.

According to the mode of secondary user's access idle frequency spectrum, access style can be divided into three classes, comprise chance formula frequency spectrum access (OSA, opportunistic spectrum access), frequency spectrum share access (SS, spectrum sharing) and the access of novel mixed frequency spectrum.Chance formula frequency spectrum access strategy refer to secondary user's first cognitive radio frequency range be idle or busy, only having when perceiving wireless frequency spectrum is that idle condition can access.Frequency spectrum share access refers to that secondary user's can coexist with primary user, as long as guarantee, primary user is not caused to harmful interference.The access of novel mixed frequency spectrum require secondary user's first cognitive radio frequency range be idle or busy (being similar to the access of chance formula frequency spectrum), again according to the sensing results that provided by data fusion center, adjust self transmitting power to avoid bringing harmful interference (being similar to frequency spectrum share access) to primary user.

Yet, in above-mentioned three kinds of access waies, all comprise a significant process in collaborative spectrum sensing, be that secondary user's need to report perception information to the process at data fusion center, because the quantity of secondary user's is larger, numerous secondary user's all reports perception information can take larger running time-frequency resource to data fusion center simultaneously, be that actual report signaling consumption is larger, thereby reduced reached at the throughput of secondary user's in cognitive radio networks, wherein said report signaling consumption represents secondary user's shared running time-frequency resource when reporting perception information.

Summary of the invention

(1) technical problem that will solve

The technical problem to be solved in the present invention is, for above-mentioned defect, how the data transmission method in a kind of cognitive radio networks is provided, it can be under the prerequisite of interfere with primary users not, reduce report signaling consumption, thereby improve the throughput of secondary user's in cognitive radio networks.

(2) technical scheme

For solving the problems of the technologies described above, the invention provides the data transmission method in a kind of cognitive radio networks, in the cognitive radio networks that is applicable to be formed by a primary user, data fusion center and K secondary user's, its frame structure comprises an initialization subframe and M common subframe, comprises step:

A: in initialization subframe, all K secondary user's is carried out sensing results and reported;

B: in initialization subframe, it is 1 that data fusion center arranges common subframe numbers, the sensing results reporting according to all K secondary user's determines that optimum secondary user's reports set omega, and judge whether that primary user exists, if there is no, all K secondary user's is carried out transfer of data, and enters step C; Otherwise, directly enter step C;

C: in common subframe, optimum secondary user's reports the secondary user's in set omega to carry out sensing results and reports;

D: in common subframe, the sensing results that data fusion center reports the secondary user's in set omega to report according to optimum secondary user's judges whether that primary user exists, if there is no, all K secondary user's is carried out transfer of data, and enters step e; Otherwise, directly enter step e;

E: whether the common subframe numbers that pre-treatment is worked as in judgement is greater than M, if so, returns to steps A; Otherwise after being added to 1, the common subframe numbers when pre-treatment returns to step C.

Wherein, the length of described initialization subframe and M common subframe fix and length identical.

Wherein, described initialization subframe and M common subframe forms by perception stage, report stage and data transfer phase 3 parts.

Wherein, in described step B, the sensing results that described data fusion center reports according to all K secondary user's judges whether that primary user exists and comprises:

The sensing results that described data fusion center reports all K secondary user's is carried out logical AND and is operated to judge whether that primary user exists.

Wherein, in described step B, the sensing results that described data fusion center reports according to all K secondary user's determines that optimum secondary user's reports set omega to comprise:

Described data fusion center, by the detection probability descending of all secondary user's, is chosen detection probability in optimum secondary user's set omega higher than the secondary user's of the first predetermined threshold α.

Wherein, described the first predetermined threshold α is 0.9.

Wherein, in described step B, the sensing results that described data fusion center reports according to all K secondary user's determines that optimum secondary user's reports set omega to comprise:

The false alarm probability ascending order of all secondary user's is arranged at described data fusion center, and false alarm probability is chosen in optimum secondary user's set omega lower than the secondary user's of the second predetermined threshold β.

Wherein, described the second predetermined threshold β is 0.1.

(3) beneficial effect

The invention discloses the data transmission method in a kind of cognitive radio networks, it provides a kind of novel frame structure, and this frame structure is comprised of M+1 subframe, comprises an initialization subframe and M common subframe.Each subframe lengths is fixed and is identical, by perception, report and data transfer phase, forms.The difference of initialization subframe and common subframe is, carries out the secondary user's number difference that sensing results reports in the report stage, brings report signaling consumption different, thereby causes the throughput of system during each subframe different.The inventive method is based on this new frame structure, in the report stage of initialization subframe, by all secondary user's, carrying out sensing results reports, by the processing procedure of initialization subframe, data fusion center is that follow-up M common subframe determines that optimum secondary user's reports set omega, wherein the secondary user's number in set omega is less than or equal to total secondary user's number K, report stage in follow-up M common subframe, secondary user's in above-mentioned set omega is carried out sensing results and is reported, thereby under the prerequisite of interfere with primary users not, reduced report signaling consumption, improved the throughput of secondary user's in cognitive radio networks, make limited Radio Resource obtain efficient utilization, there is stronger practicality.

Accompanying drawing explanation

Fig. 1 is the frame structure schematic diagram in the data transmission method described in the embodiment of the present invention;

Fig. 2 is the flow chart of the data transmission method in the cognitive radio networks described in the embodiment of the present invention.

Embodiment

Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples are used for illustrating the present invention, but are not used for limiting the scope of the invention.

The applicable cognitive radio networks of data transmission method of the present invention is comprised of a primary user, a data fusion center and K secondary user's.

As shown in Figure 1, the frame structure of data transmission method application of the present invention is comprised of M+1 subframe, comprises an initialization subframe and M common subframe.Each subframe lengths is fixed and is identical, by perception stage, report stage and data transfer phase 3 parts, forms.Described perception stage refers to that secondary user's for example adopts the frequency spectrum sensing method based on energy detection to survey the stage whether primary user exists, because the channel situation between each secondary user's and primary user is not quite similar, based on energy detection scheme, can obtain detection probability and the false alarm probability of each secondary user's; The described report stage refers to that secondary user's sends perception information to the stage at data fusion center, adopts time division multiple access way during transmission, by each secondary user's, sends in turn perception information separately to data fusion center; Described data transfer phase refers to the final sensing results that obtains data fusion center when all secondary user's, whether exist after primary user, according to final sensing results, determine whether to carry out transfer of data in this subframe, if come from the final sensing results at data fusion center, show that primary user exists, all secondary user's all do not send data, otherwise all secondary user's are all carried out data transmission.The difference of initialization subframe and common subframe is, carries out the secondary user's number difference that sensing results reports in the report stage, brings report signaling consumption different, thereby causes the throughput of system during each subframe different.

As shown in Figure 2, the data transmission method in cognitive radio networks of the present invention comprises step:

A: in initialization subframe, all K secondary user's is carried out sensing results and reported;

In this step, all K secondary user's is in the report stage of initialization subframe, to carry out sensing results to report.

Before this step, also comprise that all K secondary user's carries out local frequency spectrum perception in the perception stage of initialization subframe, survey the step whether primary user exists.

In perception stage, all K secondary user's is carried out local frequency spectrum perception, and perception stage is very important, and the accuracy of frequency spectrum perception directly affects the reliability of communication.Initialization subframe is the same with the perception stage of follow-up M common subframe, by all secondary user's, carries out local frequency spectrum perception.Local frequency spectrum perception is a dualism hypothesis problem, and the probability when primary user does not exist can be set as H ₀, the probability when primary user exists can be set as H ₁, H wherein ₀+ H ₁=1, at moment t, the reception signal at each secondary user's i place can be expressed as:

H ₀：y _i(t)＝u _i(t)， (1)

H _i：y _i(t)＝h _is _i(t)+u _i(t).

Wherein i ∈ 1,2,3 ..., K}, y _i(t) represent the reception signal of i secondary user's.S _i(t) being transmitting of primary user, is that zero-mean variance is E[|S _i(t) | ²=σ _s ²independent random process.In addition, additive white Gaussian noise u _i(t) be modeled as stochastic variable, E[|u _i(t) | ²]=σ _u ², h _ibe the channel coefficients between primary user and i secondary user's, obeying average is μ h _sidepoor is σ _h ²rayleigh fading.In the multiple method for frequency spectrum perception, energy detection for example, matched filtering detection and loop detection, it is the simplest that energy detection is proved to be, and surveys rapidly primary user's signal.Therefore, applied energy detecting strategy of the present invention, the predicted value at each secondary user's place received signal power can be represented by the formula:

$T\left(y_i\right)=\frac{1}{N}\underset{t=1}{\overset{N}{\mathrm{\Σ}}}{\left|y_i\left(t\right)\right|}^2---\left(2\right)$

Wherein, y _i(t) be t sampled point of received signal, the sample frequency of received signal is f _s, τ is available detecting period.Sampling number N is not more than τ f _smaximum integer, for simplifying, suppose N=τ f _s, therefore, the false alarm probability of each secondary user's and detection probability can be expressed as:

$P_{f,i}=P(T\left(y_i\right)>{\mathrm{\ϵ}}_i|H_0)=Q\left((\frac{{\mathrm{\ϵ}}_i}{{\mathrm{\σ}}_u^2}-1)\sqrt{\mathrm{\τ}{f}_s}\right)---\left(3\right)$

$P_{f,i}=P(T\left(y_i\right)>{\mathrm{\ϵ}}_i|H_1)=Q\left((\frac{{\mathrm{\ϵ}}_i}{{\mathrm{\σ}}_u^2}-\mathrm{\γ}{\left|h_i\right|}^2-1)\sqrt{\frac{\mathrm{\τ}{f}_s}{2\mathrm{\γ}{\left|h_i\right|}^2+1}}\right)---\left(4\right)$

Described false alarm probability refers to when primary user does not exist, and secondary user's is surveyed the probability that primary user exists mistakenly; Described detection probability refers to when primary user exists, and secondary user's is correctly surveyed the probability that primary user exists; ε wherein _ithresholding is surveyed in representative, and Q () represents Gauss Q function, is expressed as at hypothesis H ₁situation under, all secondary user's have identical value γ=σ _s ²/ σ _u ², and γ | h _i| ²primary user's Signal-to-Noise SNR that representative measures at i secondary user's place.For a given detection probability by substitution, survey thresholding ε _ithe expression formula that can obtain false alarm probability is as follows:

$P_{f,i}=Q(\sqrt{2\mathrm{\γ}{\left|h_i\right|}^2+1}{Q}^{-1}\left({\tilde{P}}_{d,i}\right)+\sqrt{\mathrm{\τ}{f}_s}\mathrm{\γ}{\left|h_i\right|}^2)---\left(5\right)$

B: in initialization subframe, it is 1 that data fusion center arranges common subframe numbers, the sensing results reporting according to all K secondary user's determines that optimum secondary user's reports set omega, and judge whether that primary user exists, if there is no, all K secondary user's is carried out transfer of data, and enters step C; Otherwise, directly enter step C;

In this step, the sensing results that described data fusion center reports according to all K secondary user's judges whether that primary user exists and comprises:

The sensing results that described data fusion center reports all K secondary user's is carried out logical AND and is operated to judge whether that primary user exists.

In this step, described optimum secondary user's reports the secondary user's number in set omega to be less than or equal to total secondary user's number K.

In this step, data fusion center can be used two kinds of methods to judge that whether primary user exists, and determines fusion method and data fusion method.Described decision fusion method is also referred to as hard decision, the mode of each secondary user's by energy detection and make local perception and determine, and feedback " 1-bit " information is to data fusion center.Data fusion is also referred to as soft information and merges, and the accurate energy sensing of different secondary user's sends to data fusion center to combine and makes final perception decision.Yet soft information merges and needs the accurate energy sensing value of each secondary user's, can bring more overhead, therefore, the present invention adopts hard-decision method.Because a secondary user's sends perception information to data fusion center, suppose the signaling consumption δ of the unit of taking.In the report stage of initialization subframe, by all secondary user's, carry out reporting of perception information, therefore the report signaling consumption bringing is H δ; And in report stage of follow-up M common subframe, to report set omega to carry out reporting of perception information by optimum secondary user's, with L, represent to report the secondary user's number in set omega, report that signaling consumption is L δ (L≤K), the signaling consumption of hence one can see that M common subframe report stage is less than initialization subframe.Data fusion center, according to the definite final sensing results of logical AND operation, can obtain system detection probability and the false alarm probability of sensing network, is expressed as:

$Q_d(\mathrm{\τ},L)=\underset{i\∈\mathrm{\Ω}}{\mathrm{\Π}}{P}_{d,i}---\left(6\right)$

$Q_f(\mathrm{\τ},L)=\underset{i\∈\mathrm{\Ω}}{\mathrm{\Π}}{P}_{f,i}---\left(7\right)$

Wherein, there are two kinds of methods can determine that optimum secondary user's reports set omega: first method is by the detection probability descending of all secondary user's, detection probability is chosen in optimum secondary user's set omega higher than the secondary user's of the first predetermined threshold α; Second method is that the false alarm probability ascending order of all secondary user's is arranged, and false alarm probability is chosen in optimum secondary user's set omega lower than the secondary user's of the second predetermined threshold β.The the first predetermined threshold α relating in this step can be made as 0.9, the second predetermined threshold β can be made as 0.1, also can to α and β, carry out respective design according to requirement in practical systems.

C: in common subframe, optimum secondary user's reports the secondary user's in set omega to carry out sensing results and reports;

In this step, to report the secondary user's in set omega be in the report stage of common subframe, to carry out sensing results to report to optimum secondary user's.

Before this step, also comprise that all K secondary user's carries out local frequency spectrum perception in the perception stage of initialization subframe, survey the step whether primary user exists.

D: in common subframe, the sensing results that data fusion center reports the secondary user's in set to report according to optimum secondary user's judges whether that primary user exists, if there is no, all K secondary user's is carried out transfer of data, and enters step e; Otherwise, directly enter step e;

In this step, the sensing results that described data fusion center reports the secondary user's in set omega to report according to optimum secondary user's judges whether that primary user exists and comprises:

Described data fusion center reports sensing results that the secondary user's in set omega reports to carry out logical AND optimum secondary user's and operates to judge whether that primary user exists.

E: whether the common subframe numbers that pre-treatment is worked as in judgement is greater than M, if so, returns to steps A; Otherwise after being added to 1, the common subframe numbers when pre-treatment returns to step C.

In sum, the invention discloses the data transmission method in a kind of cognitive radio networks, it provides a kind of novel frame structure, and this frame structure is comprised of M+1 subframe, comprises an initialization subframe and M common subframe.Each subframe lengths is fixed and is identical, by perception, report and data transfer phase, forms.The difference of initialization subframe and common subframe is, carries out the secondary user's number difference that sensing results reports in the report stage, brings report signaling consumption different, thereby causes the throughput of system during each subframe different.The inventive method is based on this new frame structure, in the report stage of initialization subframe, by all secondary user's, carrying out sensing results reports, by the processing procedure of initialization subframe, data fusion center is that follow-up M common subframe determines that optimum secondary user's reports set omega, wherein the secondary user's number in set omega is less than or equal to total secondary user's number K, report stage in follow-up M common subframe, secondary user's in above-mentioned set omega is carried out sensing results and is reported, thereby under the prerequisite of interfere with primary users not, reduced report signaling consumption, improved the throughput of secondary user's in cognitive radio networks, make limited Radio Resource obtain efficient utilization, there is stronger practicality.

Above execution mode is only for illustrating the present invention; and be not limitation of the present invention; the those of ordinary skill in relevant technologies field; without departing from the spirit and scope of the present invention; can also make a variety of changes and modification; therefore all technical schemes that are equal to also belong to category of the present invention, and scope of patent protection of the present invention should be defined by the claims.

Claims (5)

1. the data transmission method in a cognitive radio networks, in the cognitive radio networks that is applicable to be formed by a primary user, data fusion center and K secondary user's, its frame structure comprises an initialization subframe and M common subframe, it is characterized in that, comprises step:

A: in initialization subframe, all K secondary user's is carried out sensing results and reported;

B: in initialization subframe, it is 1 that data fusion center arranges common subframe numbers, the sensing results reporting according to all K secondary user's determines that optimum secondary user's reports set omega, and judge whether that primary user exists, if there is no, all K secondary user's is carried out transfer of data, and enters step C; Otherwise, directly enter step C;

Wherein, the described sensing results reporting according to all K secondary user's determines that optimum secondary user's reports set omega to comprise: maybe arrange the detection probability descending of all secondary user's at described data fusion center by the false alarm probability ascending order of all secondary user's, and detection probability is chosen in optimum secondary user's set omega lower than the secondary user's of the second predetermined threshold β higher than the first predetermined threshold α or false alarm probability;

The described primary user of judging whether exists and comprises: the sensing results that described data fusion center reports all K secondary user's is carried out logical AND and operated to judge whether that primary user exists;

C: in common subframe, optimum secondary user's reports the secondary user's in set omega to carry out sensing results and reports;

D: in common subframe, the sensing results that data fusion center reports the secondary user's in set omega to report according to optimum secondary user's judges whether that primary user exists, if there is no, all K secondary user's is carried out transfer of data, and enters step e; Otherwise, directly enter step e;

Wherein, the described sensing results that reports the secondary user's in set omega to report according to optimum secondary user's judges whether that primary user exists and comprises: described data fusion center reports sensing results that the secondary user's in set omega reports to carry out logical AND optimum secondary user's and operates to judge whether that primary user exists;

E: whether the common subframe numbers that pre-treatment is worked as in judgement is greater than M, if so, returns to steps A; Otherwise after being added to 1, the common subframe numbers when pre-treatment returns to step C.

2. data transmission method according to claim 1, is characterized in that, the length of described initialization subframe and M common subframe fix and length identical.

3. data transmission method according to claim 1, is characterized in that, described initialization subframe and M common subframe forms by perception stage, report stage and data transfer phase 3 parts.

4. data transmission method according to claim 1, is characterized in that, described the first predetermined threshold α is 0.9.

5. data transmission method according to claim 1, is characterized in that, described the second predetermined threshold β is 0.1.