CN102625315A - Horizontal concurrent spectrum allocation method in cognitive wireless system - Google Patents

Abstract

The invention discloses a horizontal concurrent spectrum allocation method in a cognitive wireless system. The invention relates to a spectrum allocation method belonging to the field of communication, and aims to solve the problem of poor fairness of the original concurrent method in spectrum allocation. The spectrum allocation method comprises the following steps of: I, establishing a topological graph according to the wireless network of the cognitive wireless system, and initializing, wherein the available spectrum number is M greater than or equal to 1; II, decomposing the topological graph into M sub-graphs; III, calculating the label number in each sub-graph Gk=(Vk, Ek) according to respective standards, calculating the cognitive user label for M*alpha sub-graphs in M sub-graphs by use of the collaborative maximum system total efficiency standard, and calculating the cognitive user label for the remaining M*(1-alpha) sub-graphs by use of the collaborative maximum proportional fairness standard; IV, allocating the spectrum j to the user realizing maximum label i and label j; V, removing the allocated spectrum and updating the topological graph; VI, judging whether the spectra in the graph are completely allocated, and if so, ending the process; and VII, otherwise, returning to the step II. The method disclosed by the invention is applied to the spectrum allocation in wireless communication.

Description

The parallel frequency spectrum distributing method of level in a kind of cognitive radio system

Technical field

The present invention relates to a kind of frequency spectrum distributing method, belong to the communications field.

Background technology

The algorithm of the spectrum allocation may of using at present is a parallel algorithm, and it is with being decomposed into a plurality of subgraphs based on the graph theory model topology diagram, on these subgraphs, carries out independently spectrum allocation may then:

In cognitive radio system, owing to be use authority user's the frequency spectrum of selecting a good opportunity, the usable spectrum of cognitive radio users receives the authorized user operating state, the influence of position and coverage, the characteristic that tool changes at one's leisure.Therefore, in cognitive radio system, adopt the graph theory coloring models to carry out the spectrum allocation may analysis, need be to the constraints of spectrum allocation may, distribution target etc. is carried out necessary revision.The prerequisite of cognitive radio users use authority frequency range is: use if current channel is authorized to the user, then for fear of the interference to authorized user, this channel can not be used by near cognitive family.Fig. 1 is the network topology structure of a cognitive radio system.

Unified graph theory model is by idle matrix, the benefit matrix, and interference matrix and allocation matrix are described.

Idle frequency spectrum is meant in certain time and space, the untapped frequency spectrum of main user.Because locus and the isoparametric difference of through-put power, for different cognitive user, whether the same frequency band free time maybe be different.Whether the free time is used idle matrix notation to frequency spectrum for cognitive user.If the distribution time is very short with respect to the environmental change time, each matrix remains unchanged in assignment period.

The benefit that the user obtains is used the benefit matrix notation: benefit matrix B={ b _{N, m}} _{P * Q}, b _{N, m}Characterize the benefit weight that user n uses frequency spectrum m to be brought, like spectrum capabilities etc., P is a number of users, and subscript is from 0 to P-1, and Q is total frequency band number, subscript from 0 to Q-1.Matrix L is combined with matrix B, can draw the benefit L of effective spectrum _B={ l _{N, m}B _{N, m}} _{P * Q}

Interference between cognitive radio users is represented with interference matrix: interference matrix set C={c _{N, k}| c _{N, k}∈ 0,1}} _{P * P}, c _{N, k}=1 expression user n and user k can produce interference when using same frequency spectrum at the same time, when n=k, and c _{N, k}=0.

Glitch-free spectrum allocation may matrix A={ a _{N, m}| a _{N, m}∈ 0,1}} _{P * Q}, a _{N, m}=1 expression frequency spectrum m is assigned to user n.A must satisfy noiseless condition:

$a_{n,m}\&CenterDot;a_{k,m}=0\mathrm{if}{c}_{n,k}=1,\&ForAll;n,k<N,m<M---\left(1\right)$

The main standard that parallel method is used is MSB and MPF.

Introduced the benefit of each frequency range, can obtain with maximization frequency spectrum benefit be target the optimum allocation standard (correspondingly system's mathematic(al) representation of reaching the maximum spectrum benefit becomes for Max-Sum-Bandwidth, expression formula MSB):

$\underset{A\&Element;{\mathrm{\&Lambda;}}_{P\&times;Q}}{\max }\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{Q-1}{\mathrm{\&Sigma;}}}{a}_{n,m}\&CenterDot;b_{n,m}---\left(2\right)$

Λ in the formula _{P * Q}---the set of the noiseless spectrum allocation may matrix A that all satisfy condition.

The physical meaning of expression formula is that spectrum allocation may is the maximum spectrum benefit that system brings, the common representative of consumer of benefit matrix obtainable transmission rate on each frequency band.

For the fairness of distinct methods relatively, method has also been introduced the module of relevant spectrum allocation may fairness, promptly maximum ratio fairness tolerance (Max-Proportional-Fair, MPF):

$\underset{A\&Element;{\mathrm{\&Lambda;}}_{N\&times;M}}{\max }{(\underset{n=0}{\overset{P-1}{\mathrm{\&Pi;}}}\underset{m=0}{\overset{Q-1}{\mathrm{\&Sigma;}}}{a}_{n,m}\&CenterDot;b_{n,m})}^{\frac{1}{N}}---\left(3\right)$

Because parallel method is to be decomposed into a plurality of subgraphs to original topology diagram; On these subgraphs, carry out independently spectrum allocation may then; Do not carry out the exchange of information between each subgraph; So each subgraph can't be considered the distribution condition of other subgraphs when distributing, can't use the information of having distributed frequency spectrum, this is the basic reason of parallel method fairness difference.

Summary of the invention

When the present invention seeks to spectrum allocation may, the problem of original parallel method fairness difference provides the parallel frequency spectrum distributing method of level in a kind of cognitive radio system.

The parallel frequency spectrum distributing method of level in a kind of cognitive radio system of the present invention, realize steps of the method are:

Step 1, set up topological diagram according to the wireless network of cognitive radio system, and this topological diagram is carried out initialization, the usable spectrum number in this topological diagram is M, M >=1;

Step 2, topological diagram is counted M by usable spectrum be decomposed into the M sub-graphs;

Step 3, at each subgraph G _k=(V _k, E _k) in according to separately criterion calculation index value; M* α sub-graphs in the M sub-graphs is adopted collaboration type maximization system total benefit criterion calculation cognitive user label; All the other M* (1-α) sub-graphs adopts collaboration type maximization equitable proportion criterion calculation cognitive user label simultaneously

Wherein, α is defined as level and row coefficient, 0≤α≤1; V _kBe subgraph G _kThe set on summit, i.e. the set of cognitive user in the subgraph; E _kBe subgraph G _kThe set on limit, i.e. subgraph G _kIn adjacent a pair of cognitive user between the set of the interference that exists; K=1 ..., M;

Step 4, at each subgraph G _k=(V _k, E _k) in select to make label label _{I, j}The maximum cognitive user of value

And frequency spectrum j distributed to this cognitive user, and 1≤j≤M, 0≤i≤N, N are subgraph G _kMiddle cognitive user number;

Step 5, remove the frequency spectrum that has assigned, upgrade topology diagram then;

Step 6, judge whether the frequency spectrum in the topological diagram assigns, if then, execution in step seven if not, then, turns back to step 2;

Step 7, the spectrum allocation may that finishes.

Advantage of the present invention is: the present invention is based on the basis of parallel algorithm and proposes, and this algorithm uses two kinds of various criterions in allocated channel: collaboration type maximization system's total benefit standard maximizes the equitable proportion standard with collaboration type; Make parallel algorithm when distributing frequency spectrum, per minute is joined a secondary channel can both carry out an information exchange between subgraph, uses the spectrum information that has distributed on other subgraphs; Improved the fairness of spectrum allocation may; Promptly

wherein i be cognitive user, j is that spectrum number prevents that a large amount of spectrum allocation may from giving a cognitive user, and is as shown in Figure 7; The horizontal parallel algorithm of this paper has been accomplished the increase with spectrum number in addition; Time overhead changes little, compares original parallel algorithm, and the horizontal parallel algorithm of this paper shortens the time of spectrum allocation may; Improve spectrum allocation may efficient, as shown in Figure 8.

Description of drawings

Fig. 1 is the graph theory model of cognitive radio system; The i.e. network topology structure of a cognitive radio system; Six summit su1～su6 among the figure represent six different cognitive user; Four summit puA～puD represent four different authorisation users, and suppose that the mandate frequency range that each authorized user uses is respectively frequency spectrum A, frequency spectrum B, frequency spectrum C and frequency spectrum D;

Fig. 2 is the flow chart of the horizontal parallel algorithm of the present invention;

Fig. 3 is the sketch map of system's fairness along with the situation of change of α;

is 10 for number of users N among the figure; Number of channel M is the value of 10 o'clock α;

is 10 for number of users N among the figure; Number of channel M is the value of 20 o'clock α

Among the figure

to count N be 20 for cognitive user; Number of channel M is the value of 10 o'clock α; Among the figure to count N be 20 for cognitive user, number of channel M is the value of 20 o'clock α;

Fig. 4 is the extreme value of the α that obtains of 50 tests;

Fig. 5 is fixed as under 5 the situation optimum alpha along with the Changing Pattern emulation sketch map of spectrum number for the cognitive user number;

Fig. 6 is fixed as under 20 the situation optimum alpha along with the emulation sketch map of the Changing Pattern of cognitive user number for spectrum number.

Fig. 7 is the comparison of the justice of horizontal parallel method and original parallel algorithm;

is original fairness value among the figure, and

is fairness value of the present invention among the figure.

Fig. 8 is the comparison of the time overhead of horizontal parallel method and original parallel algorithm;

is the value of time overhead of the present invention among the figure, and

is the value of original time overhead among the figure.

Embodiment

Embodiment one: below in conjunction with Fig. 2 this execution mode is described,

The parallel frequency spectrum distributing method of level in a kind of cognitive radio system, realize steps of the method are:

Step 1, set up topological diagram according to the wireless network of cognitive radio system, and this topological diagram is carried out initialization, the usable spectrum number in this topological diagram is M, M >=1;

Step 2, topological diagram is counted M by usable spectrum be decomposed into the M sub-graphs;

Step 3, at each subgraph G _k=(V _k, E _k) in according to separately criterion calculation index value; M* α sub-graphs in the M sub-graphs is adopted collaboration type maximization system total benefit criterion calculation cognitive user label; All the other M* (1-α) sub-graphs adopts collaboration type maximization equitable proportion criterion calculation cognitive user label simultaneously

Wherein, α is defined as level and row coefficient, 0≤α≤1; V _kBe subgraph G _kThe set on summit, i.e. the set of cognitive user in the subgraph; E _kBe subgraph G _kThe set on limit, i.e. subgraph G _kIn adjacent a pair of cognitive user between the set of the interference that exists; K=1 ..., M;

Step 4, at each subgraph G _k=(V _k, E _k) in select to make label label _{I, j}The maximum cognitive user of value And frequency spectrum j distributed to this cognitive user, and 1≤j≤M, 0≤i≤N, N are subgraph G _kMiddle cognitive user number;

Step 5, remove the frequency spectrum that has assigned, upgrade topology diagram then;

Step 6, judge whether the frequency spectrum in the topological diagram assigns, if then, execution in step seven if not, then, turns back to step 2;

Step 7, the spectrum allocation may that finishes.

Embodiment two: below in conjunction with Fig. 2 this execution mode is described, this execution mode is for to the further specifying of execution mode one,

The parallel alpha of level in the step 3 of the present invention is meant uses subgraph number of maximization system total benefit standard to take turns the ratio of total subgraph number of branch timing with this when each takes turns the calculating label.

Embodiment three: below in conjunction with Fig. 2 this execution mode is described, this execution mode is for to the further specifying of execution mode one,

The method of calculating the cognitive user label when employing of the present invention maximizes system's total benefit standard is:

After cognitive user i has been assigned with frequency spectrum j, the D adjacent with this cognitive user _{I, j}Individual node can't use this frequency spectrum j that has distributed, and current spectrum allocation may is b to the contribution margin of whole system total bandwidth _{I, j}/ (D _{I, j}+ 1); ${\mathrm{Label}}_{i,j}=\frac{b_{i,j}}{D_{i,j}+1},$

D in the formula _{I, j}For containing the cognitive user number of frequency spectrum j, 0≤i≤N, 0≤j≤M in and the usable spectrum adjacent with cognitive user i;

b _{I, j}Be defined as spectrum capabilities, can get by mountain farming formula:

$b_{i,j}={\mathrm{band}}_j\&CenterDot;{\log }_2(1+K\&CenterDot;\frac{p_{i,j}\&CenterDot;{\left|H_{i,j}\right|}^2}{{\mathrm{band}}_j\&CenterDot;{\mathrm{\&sigma;}}_0^2}),$

Band in the formula _jBandwidth for frequency spectrum j; p _{I, j}Be the transmitting power of cognitive user i on frequency spectrum j;

| H _{I, j}| ²Be the spectrum gain of frequency spectrum j, suppose that every frequency spectrum is all identical to the gain of each cognitive user, promptly has cognitive user i:

Be the noise power on the unit bandwidth;

K is a constant, the error rate requirement of expression cognitive user, and K is expressed as:

$K=-\frac{1.5}{\ln (5\&CenterDot;\mathrm{BER})}.$

Embodiment four: below in conjunction with Fig. 2 this execution mode is described, this execution mode is for to the further specifying of execution mode one,

When employing of the present invention maximization system total benefit standard is distributed frequency spectrum, when when calculating the cognitive user label, several nodes occurring and having identical label, the node that bandwidth is little will be given higher index value.

Embodiment five: below in conjunction with Fig. 2 this execution mode is described, this execution mode is for to the further specifying of execution mode one,

The method of employing collaboration type maximization equitable proportion criterion calculation cognitive user label of the present invention is:

${\mathrm{label}}_{i,j}=\frac{b_{i,j}}{(D_{i,j}+1)\&CenterDot;\underset{j=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{a}_{i,j}\&CenterDot;b_{i,j}}$

b _{I, j}Be defined as spectrum capabilities, D _{I, j}For containing the cognitive user number of frequency spectrum j, 0≤i≤N, 0≤j≤M in and the usable spectrum adjacent with cognitive user i.

Specific embodiment:

Step 1, set up topological diagram according to the wireless network of cognitive radio system, and this topological diagram is carried out initialization, the usable spectrum number in this topological diagram is M, M >=1;

Step 2, topological diagram is counted M by usable spectrum be decomposed into the M sub-graphs;

Step 3, at each subgraph G _k=(V _k, E _k) in according to separately criterion calculation index value, the M* α sub-graphs in the M sub-graphs is adopted collaboration type maximization system total benefit criterion calculation user label, all the other M* (1-α) sub-graphs adopts collaboration type maximization equitable proportion criterion calculation user label simultaneously;

Confirming of step 4, level and row coefficient

In horizontal parallel criterion algorithm, the parallel alpha of level is defined as each subgraph number of taking turns use CMSB standard when calculating label and takes turns the ratio of total subgraph number of branch timing with this.

For the influence to system's fairness of analysis level and row coefficient, this paper carries out emulation to system's fairness under following four kinds of situation with the situation of change of level and row coefficient.Average system fairness when α gets different value

(1) to count N be 10 to cognitive user, and number of channel M is 10;

(2) to count N be 10 to cognitive user, and number of channel M is 20;

(3) to count N be 20 to cognitive user, and number of channel M is 10;

(4) to count N be 20 to cognitive user, and number of channel M is 20.

Generate 1000 topological diagrams under every kind of situation at random; When calculation of alpha is got different value; The mean value of system's fairness of 1000 topological diagrams, for a certain fixing situation, there is an extreme value that makes that system's fairness is maximum in the parallel alpha of level between 0～1; For condition of different, the maximum extreme value of fairness also is not quite similar.

For example for situation (2), when α=0.15, can make the fairness of system maximum.In fact,, just can find,, because the finiteness of the randomness of its topological structure and the topological number that produces at random, make the extreme value of the α of its fairness maximum neither be identical even for a certain fixing situation if carry out emulation repeatedly.For example, ask the extreme value of α according to the method described above for situation (2), duplicate test 50 times, the extreme value of α is not what fix, its value is different in different tests.But the extreme value of α neither continually varying, but between several values value, therefore,, can under this kind situation, repeatedly find the solution the extreme value of α in order to confirm the extreme value of the α under a certain situation, get mode in many numerical value then as the optimum alpha of this kind situation.For example in test shown in Figure 5, the extreme value of α is got 0.15 test and is occurred 32 times, gets 0.2 test and occurs 6 times, gets 0.3 test and occurs 5 times, and the test of getting other values occurs 7 times, therefore can think that the optimum alpha of situation (2) is 0.15.

Because the optimum alpha of the different cognitive users number and the situation of different channels number is also different; This paper is fixed as under 5 the situation optimum alpha along with the Changing Pattern of the number of channel to the cognitive user number, and the number of channel is fixed as optimum alpha under 20 the situation and has carried out emulation along with the Changing Pattern of cognitive user number.From analogous diagram, can find out; Optimum alpha when the different cognitive users number is counted with different channels is different, and does not have clear regularity property, so in order to confirm the optimum alpha of different situations in the emulation hereinafter; This paper is with cognitive user number value successively between 5 to 20; The number of channel 5 between 20 successively the optimum alpha value in the value obtain, and its tabulation is preserved, use during in order to the civilian emulation in back.The optimum alpha list of values is seen appendix table 1.

The optimum level and the row coefficient of the horizontal parallel method of appendix table 1

The present invention is not limited to above-mentioned execution mode, can also be the reasonable combination of technical characterictic described in above-mentioned each execution mode.

Claims (5)

1. the parallel frequency spectrum distributing method of level in the cognitive radio system is characterized in that: realize steps of the method are:

Step 1, set up topological diagram according to the wireless network of cognitive radio system, and this topological diagram is carried out initialization, the usable spectrum number in this topological diagram is M, M >=1;

Step 2, topological diagram is counted M by usable spectrum be decomposed into the M sub-graphs;

Step 3, at each subgraph G _k=(V _k, E _k) in according to separately criterion calculation index value; M* α sub-graphs in the M sub-graphs is adopted collaboration type maximization system total benefit criterion calculation cognitive user label; All the other M* (1-α) sub-graphs adopts collaboration type maximization equitable proportion criterion calculation cognitive user label simultaneously

Wherein, α is defined as level and row coefficient, 0≤α≤1; V _kBe subgraph G _kThe set on summit, i.e. the set of cognitive user in the subgraph; E _kBe subgraph G _kThe set on limit, i.e. subgraph G _kIn adjacent a pair of cognitive user between the set of the interference that exists; K=1 ..., M;

Step 4, at each subgraph G _k=(V _k, E _k) in select to make label label _{I, j}The maximum cognitive user of value

And frequency spectrum j distributed to this cognitive user, and 1≤j≤M, 0≤i≤N, N are subgraph G _kMiddle cognitive user number;

Step 5, remove the frequency spectrum that has assigned, upgrade topology diagram then;

Step 6, judge whether the frequency spectrum in the topological diagram assigns, if then, execution in step seven if not, then, turns back to step 2;

Step 7, the spectrum allocation may that finishes.

2. based on the parallel frequency spectrum distributing method of level in a kind of cognitive radio system of claim 1, it is characterized in that: the parallel alpha of the level in the step 3 is meant uses subgraph number of maximization system total benefit standard to take turns the ratio of total subgraph number of branch timing with this when each takes turns the calculating label.

3. the frequency spectrum distributing method parallel according to level in a kind of cognitive radio system of claim 1 is characterized in that: the method for calculating the cognitive user label when adopting maximization system total benefit standard is:

${\mathrm{label}1}_{i,j}=\frac{b_{i,j}}{D_{i,j}+1},$

D in the formula _{I, j}For containing the cognitive user number of frequency spectrum j, 0≤i≤N, 0≤j≤M in and the usable spectrum adjacent with cognitive user i;

b _{I, j}Be the spectrum capabilities of user i, can get by mountain farming formula:

$b_{i,j}={\mathrm{band}}_j\&CenterDot;{\log }_2(1+K\&CenterDot;\frac{p_{i,j}\&CenterDot;{\left|H_{i,j}\right|}^2}{{\mathrm{band}}_j\&CenterDot;{\mathrm{\&sigma;}}_0^2}),$

In the formula, band _jBandwidth for frequency spectrum j; p _{I, j}Be the transmitting power of cognitive user i on frequency spectrum j;

| H _{I, j}| ²Be the spectrum gain of frequency spectrum j to cognitive user i, it is all identical to the gain of each cognitive user to establish every frequency spectrum, promptly has:

Be the noise power on the unit bandwidth;

K is a constant, the error rate requirement of expression cognitive user, and K is expressed as:

$K=-\frac{1.5}{\ln (5\&CenterDot;\mathrm{BER})}.$

4. the frequency spectrum distributing method parallel according to level in a kind of cognitive radio system of claim 1; It is characterized in that: when adopting maximization system total benefit standard to distribute frequency spectrum; When calculating the cognitive user label, several nodes occurring and having identical label, then give bandwidth minimum cognitive user spectrum allocation may.

5. the frequency spectrum distributing method parallel according to level in a kind of cognitive radio system of claim 1 is characterized in that: adopt the method for collaboration type maximization equitable proportion criterion calculation cognitive user label to be:

${\mathrm{label}}_{i,j}=\frac{b_{i,j}}{(D_{i,j}+1)\&CenterDot;\underset{j=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{a}_{i,j}\&CenterDot;b_{i,j}},$

b _{I, j}Be the spectrum capabilities of user i, D _{I, j}For containing the cognitive user number of frequency spectrum j, 0≤i≤N, 0≤j≤M in and the usable spectrum adjacent with cognitive user i.

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