CN104812045A - Method for distributing cognitive user bandwidth and transmitting power in centralized cognitive wireless network - Google Patents

Abstract

The invention discloses a method for distributing cognitive user bandwidth and transmitting power in a centralized cognitive wireless network. The method is characterized by comprising the following steps that S1, a mathematical model with the cognitive user total channel capacity being the maximum value is built; S2, the transmitting power of each cognitive user is fixed, and the optimal distribution value of each cognitive user bandwidth is calculated; S3, the optimal distribution value of the transmitting power of each cognitive user is calculated according to the optimal distribution value of each cognitive user bandwidth. The method adopting the technical scheme has the advantages that the distribution values of the bandwidth and the transmitting power of each cognitive user are respectively optimized, the defects of bandwidth waste and lower system capacity caused by a bandwidth averaging method are overcome, the bandwidth can be more reasonably distributed, and the validity, the adaptability and the total channel capacity of the cognitive wireless network are improved.

Description

Cognitive user bandwidth sum transmitting power division method in centralized cognition wireless network

Technical field

The present invention relates to wireless communication technology field.More specifically, cognitive user bandwidth sum transmitting power division method in a kind of centralized cognition wireless network is related to.

Background technology

In centralized cognition wireless planar network architecture, have the infrastructure of centralization, i.e. master controller.The existence of central controller makes various resource to be combined with each other, combined optimization, to realize the optimum use of various resource.In general, the base station in network serves the effect of master controller, is responsible for the cognitive user in pool, coordination network, serves the effect of constraint cognitive user behavior.Due to the effect of master controller, cooperate with one another between the cognitive user in centralized cognitive wireless, based on the constraint of the agreement that all cognition wireless users obey, cognitive user not only considers self benefits, also considers the total revenue of whole system.Therefore, great for the Research Significance of optimization method in centralized cognition wireless network.

The current concern combined optimization technology that spectrum allocation may, allocated bandwidth etc. and power control to combine more and more being subject to researcher, have also been obtained the method for bandwidth optimization, but these methods do not consider that channeling is on the impact of system.Present invention employs associating power control method, overall system bandwidth is combined as optimum target with the transmitting power of cognitive user, optimum target be decomposed into the sub-optimization aim that is directed to bandwidth sum power respectively and solve one by one, realize the co-allocation of bandwidth and power in system, by this optimum allocation, cognitive radio system is made to reach optimum channel capacity and performance

Therefore, need to provide cognitive user bandwidth sum transmitting power division method in a kind of centralized cognition wireless network.

Summary of the invention

The object of the present invention is to provide cognitive user bandwidth sum transmitting power division method in a kind of centralized cognition wireless network, the method considers bandwidth and power to the impact of cognition wireless network overall channel capacity, and is that target function has carried out Multiple Optimization with overall channel capacity.For reducing the computation complexity of node further, multiobjective optimization problem is converted into two subproblems by dimension-reduction treatment and solves by the method, thus a kind of low complex degree bandwidth sum power distribution method is proposed, by solving target function, achieve the optimum allocation of bandwidth sum power simultaneously.The method can be applicable in existing centralized network architecture, has stronger practicality.

For achieving the above object, the present invention adopts following technical proposals:

Cognitive user bandwidth sum transmitting power division method in a kind of centralized cognition wireless network, the method comprises the steps:

S1, the overall channel capacity setting up cognitive user are the Mathematical Modeling of maximum;

S2, fixing each cognitive user transmitting power, calculate the optimum allocation value of each cognitive user bandwidth, formula is as follows:

$B_i=\frac{g_i{p}_i}{\underset{j=1}{\overset{N}{\mathrm{\Σ}}}{g}_j{p}_j}{B}_{\mathrm{total}};$

In formula, B _ifor cognitive wireless network system distributes to cognitive user SU _ibandwidth, g _ifor cognitive user SU _ito the link gain of its own base station, p _ifor cognitive user SU _itransmitting power, g _jfor cognitive user SU _jto the link gain of its own base station, p _jfor cognitive user SU _jtransmitting power, B _totalfor authorization channel total bandwidth, N is the number of cognitive user;

S3, optimum allocation value according to each cognitive user bandwidth, calculate the optimum allocation value of each cognitive user transmitting power, formula is as follows:

$p_i=\left\{\begin{array}{cc}{p}_i^{\max },& 1\≤i\≤k-1\\ \min \{p_i^{\max },(Q^{\max }-\underset{j=1}{\overset{k-1}{\mathrm{\Σ}}}{h}_j{p}_j^{\max })/h_j\},& i=k\\ 0,& k+1\≤i\≤N\end{array}\right.;$

In formula, h _ifor cognitive user SU _ito the link gain of authorized user, h _jfor cognitive user SU _jto the link gain of authorized user, Q ^maxfor the transmitting power of each cognitive user is to the threshold value of total interference that authorized user produces, k is defined as:

There is integer k and meet 1≤k≤N, make:

$\begin{array}{cc}{q}_i=h_i{p}_i^{\max },& \∀i\∈[1,k-1]\end{array}$

$0\≤q_k\≤h_k{p}_k^{\max }$

$\begin{array}{cc}{q}_i=0,& \∀i\∈[k+1,N]\end{array}$

In formula, q _i=h _ip _i, for cognitive user SU _ireflector transmitting power restriction, q _k=h _kp _k, for cognitive user SU _kreflector transmitting power restriction.

Preferably, in step S1 the overall channel capacity of cognitive user to be the model formation of the Mathematical Modeling of maximum be:

$\underset{B_i,p_i}{\max }\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{B}_i{\log }_2(1+\frac{g_i{p}_i}{n_0{B}_i})$

$\begin{array}{cccccc}s.t.& \underset{i=1}{\overset{N}{\mathrm{\Σ}}}{B}_i\≤B_{\mathrm{total}},& B_i\≥0,& p_i\≤p_i^{\max },& \underset{i=1}{\overset{N}{\mathrm{\Σ}}}{h}_i{p}_i\≤Q^{\max },& \∀i\∈N\end{array};$

In formula, n ₀for noise power spectral density.

Beneficial effect of the present invention is as follows:

Technical scheme application scenarios of the present invention is centralized cognition wireless network, various resource can be combined with each other, combined optimization, to realize the optimum use of various resource.Technical scheme of the present invention proposes the method that bandwidth sum power joint is optimized, and improve on the basis of tradition research, bandwidth power is optimized respectively, overcome bandwidth and divide equally the bandwidth waste that causes and the lower defect of power system capacity, more reasonably can distribute bandwidth, improve power system capacity.The technical scheme of the present invention and then optimization problem of complexity is divided into two sub-optimization problems, reduce the computation complexity of node, by solving target function, achieve the optimum allocation of bandwidth sum power simultaneously, improve the validity of cognitive wireless network system, adaptability and overall channel capacity.

Accompanying drawing explanation

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.

Fig. 1 illustrates cognitive user bandwidth sum transmitting power division method flow chart in centralized cognition wireless network.

Fig. 2 illustrates the power division schematic diagram of cognitive user transmitting power optimal solution.

Fig. 3 illustrates cognitive user overall channel capacity and maximum transmission power relation simulation result.

Fig. 4 illustrates cognitive user overall channel capacity and interference temperature relation simulation result.

Fig. 5 illustrates the simulation result of cognitive user overall channel capacity and bandwidth relationship.

Embodiment

In order to be illustrated more clearly in the present invention, below in conjunction with preferred embodiments and drawings, the present invention is described further.Parts similar in accompanying drawing represent with identical Reference numeral.It will be appreciated by those skilled in the art that specifically described content is illustrative and nonrestrictive, should not limit the scope of the invention with this below.

In the centralized cognition wireless network that the present embodiment provides, cognitive user bandwidth sum transmitting power division method adopts a Universal Model, the i.e. centralized cognition wireless network of a frequency spectrum share, cognitive wireless network system, an authorized user (primary user) and N number of cognitive user (secondary user's) is had, cognitive user then random uniform distribution in the community covered by cognition wireless network in network.Cognitive user in network adopts frequency division multiple access (frequency decision multiple access, FDMA) mode carries out frequency spectrum access, and cognitive user when transmitting power is less than threshold value to total interference that authorized user produces with the frequency spectrum resource of authorized user simultaneously use authority channel, when each cognitive user carries out information transmission, the frequency band of use is not overlapping with other cognitive user.In order to simplify intermediate computations, the present embodiment hypothesis channel circumstance is the most basic additive white Gaussian noise (AWGN) channel.

As shown in Figure 1, the method comprises the steps:

Step1, the overall channel capacity setting up cognitive user are the Mathematical Modeling of maximum;

Step2, fixing each cognitive user transmitting power, calculate the optimum allocation value of each cognitive user bandwidth;

Step3, optimum allocation value according to each cognitive user bandwidth, calculate the optimum allocation value of each cognitive user transmitting power.

Wherein

The detailed process of step Step1 is:

Setting cognitive user SU _ilink gain to authorized user is h _i, cognitive user SU _itransmitting terminal is to the receiving terminal of its correspondence---i.e. cognitive user SU _ilink gain to its own base station is g _i, authorization channel total bandwidth is B _total, cognitive wireless network system distributes to cognitive user SU _ibandwidth be B _i, the number of cognitive user is N, then allocated bandwidth constraint can be written as:

$\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{B}_i\≤B_{\mathrm{total}}$ Formula (1)

Suppose cognitive user SU _itransmitting power be p _i, then it is subject to the constraint of emitter and interference temperature two aspects simultaneously: first aspect is that the instantaneous peak value transmitting power of cognitive user is less than cognitive user SU _ireflector transmitting power restriction second aspect is that the transmitting power of each cognitive user should be less than threshold value Q to total interference that authorized user produces ^max.Then the Mathematical Modeling of transmitting power is:

$\begin{array}{cc}{p}_i\≤p_i^{\max },& \∀i\∈N\end{array}$ Formula (2)

$\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{h}_i{p}_i\≤Q^{\max }$ Formula (3)

Cognitive user SU _ithe apportioning cost of bandwidth be B _i, the apportioning cost of transmitting power is p _iawgn channel environmental condition under, the channel capacity obtained is:

$C_i=B_i{\log }_2(1+\frac{g_i{p}_i}{n_0{B}_i})$ Formula (4)

Wherein, C _ifor cognitive user SU _ithe channel capacity obtained, n ₀for noise power spectral density.

The target of the present embodiment is that maximize the overall channel capacity of cognitive user, then the overall channel capacity maximum of cognitive user can be modeled as under the constraint of formula (2) and (3):

$\underset{B_i,p_i}{\max }\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{B}_i{\log }_2(1+\frac{g_i{p}_i}{n_0{B}_i})$

$\begin{array}{cccccc}s.t.& \underset{i=1}{\overset{N}{\mathrm{\Σ}}}{B}_i\≤B_{\mathrm{total}},& B_i\≥0,& p_i\≤p_i^{\max },& \underset{i=1}{\overset{N}{\mathrm{\Σ}}}{h}_i{p}_i\≤Q^{\max },& \∀i\∈N\end{array}$ Formula (5)

The detailed process of step Step2 is:

Fixing each cognitive user transmitting power, the optimum allocation value problem calculating each cognitive user bandwidth can be converted into:

$\underset{B_i}{\min }\{-\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{B}_i{\log }_2(1+\frac{g_i{p}_i}{n_0{B}_i})\}$

$\begin{array}{ccc}s.t.& \underset{i=1}{\overset{N}{\mathrm{\Σ}}}{B}_i\≤B_{\mathrm{total}},& \∀i\∈N\end{array}$ Formula (6)

The constraints formula (1) of sub-majorized function is Linear Constraints, so optimization problem formula (6) is convex optimization problem.So the present embodiment need prove for given { p _i, the optimum allocation value problem formulations (6) calculating each cognitive user bandwidth is convex optimization, then solves convex optimization problem at utilization method of Lagrange multipliers, then

$\begin{array}{cc}\frac{g_i{p}_i}{n_0{B}_i}=\frac{g_j{p}_j}{n_0{B}_j},& \∀i,j\∈N\end{array}$ Formula (7)

From formula (7), as cognitive user SU _itransmitting power { p _ifixing time, for reaching optimum target, must strict proportionate relationship be had between the optimum bandwidth that each cognitive user is distributed.The then optimum allocation value B of each cognitive user bandwidth under this condition _ifor:

$B_i=\frac{g_i{p}_i}{\underset{j=1}{\overset{N}{\mathrm{\Σ}}}{g}_j{p}_j}{B}_{\mathrm{total}}$ Formula (8)

The detailed process of step Step3 is:

The apportioning cost B of each cognitive user bandwidth that formula (8) is tried to achieve _isubstitute in the overall channel capacity maximization problems of the cognitive user of formula (5), just can obtain the optimum allocation value problem of each cognitive user transmitting power:

$\underset{p_i}{\max }{B}_{\mathrm{total}}{\log }_2(1+\underset{j=1}{\overset{N}{\mathrm{\Σ}}}\frac{g_j{p}_j}{n_0{B}_{\mathrm{total}}})$

$\begin{array}{ccc}s.t.& p_i\≤{p_i}^{\max },& \∀i\∈N\end{array}$

$\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{h}_i{p}_i\≤Q^{\max }$ Formula (9)

Due to authorization channel total bandwidth B _totalfor positive definite value, noise power spectral density n ₀also be on the occasion of.Clearly this sub-majorized function is about variable increasing function.Make q _i=h _ip _i, then the optimum allocation value problem (9) of each cognitive user transmitting power can be converted into:

$\underset{p_i}{\max }\underset{j=1}{\overset{N}{\mathrm{\Σ}}}\frac{g_j}{h_j}{q}_j$

$\begin{array}{cccc}s.t.& q_i\≤h_i{p_i}^{\max },& \underset{i=1}{\overset{N}{\mathrm{\Σ}}}{q}_i\≤Q^{\max },& \∀i\∈N\end{array}$ Formula (10)

For the optimum allocation value problem formulations (10) of new each cognitive user transmitting power, by optimization coefficient g _i/ h _ifrom large to small to each cognitive user SU _ibe numbered, that is:

G ₁/ h ₁>=g ₂/ h ₂>=...>=g _n/ h _nformula (11)

The present embodiment proves under the prioritization of formula (11) formula, can obtain the feasible solution set of the optimal solution of the optimum allocation value problem (10) of each cognitive user transmitting power: there is integer k and meet 1≤k≤N, make:

$\begin{array}{cc}{q}_i=h_i{p}_i^{\max },& \∀i\∈[1,k-1]\end{array}$

$0<q_k\&le;h_k{p}_k^{\max }$

$\begin{array}{cc}{q}_i=0,& \&ForAll;i\&Element;[k+1,N]\end{array}$ Formula (12)

In formula, q _k=h _kp _k, for cognitive user SU _kreflector transmitting power restriction.

Suppose to there is above-mentioned feasible solution set, the optimized results of target function G is

$G=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{g_k}{h_k}{q}_k$ Formula (13)

The present embodiment changes the transmitting power of arbitrary neighborhood two user j and j+1, can obtain new optimum results

$G^{*}=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{g_k}{h_k}{q}_k^{*}$ Formula (14)

At formula G ^*in except k=j and k=j+1, the transmitting power of other users is all constant, so obtain:

$G^{*}-G=\frac{g_j}{h_j}{q}_j^{*}+\frac{g_{j+1}}{h_{j+1}}{q}_{j+1}^{*}-\frac{g_j}{h_j}{q}_j-\frac{g_j}{h_j}{q}_j$ Formula (15)

Under optimal condition, from formula (14):

Because except k=j and k=j+1, the transmitting power of other users is all constant, then have:

$q_j^{*}+q_{j+1}^{*}=q_j+q_{j+1}$ Formula (17)

Defined variable Δ q is thus:

$\mathrm{\&Delta;q}=q_{j+1}^{*}-q_{j+1}=q_j-q_j^{*}$ Formula (18)

Formula (18) formula is substituted into formula (16) obtain:

$G^{*}-G=\mathrm{\&Delta;q}(\frac{g_{j+1}}{h_{j+1}}-\frac{g_j}{h_j})$ Formula (19)

To ensure that G is optimum operable result, then demand fulfillment G ^*-G<0.Because g _j/ h _j>=g _j+1/ h _j+1, so require Δ q>0.

There is above-mentioned feasible optimal solution set in optimization problem (10), therefore the Optimal Transmitting Power target of the present embodiment is exactly find optimum k value, makes:

$q_{\mathrm{si}}=\left\{\begin{array}{cc}{h}_i{p}_i^{\max },& 1\&le;i\&le;k-1\\ \min \{{h_{i}p}_i^{\max },Q^{\max }-\underset{j=1}{\overset{k-1}{\mathrm{\&Sigma;}}}{h}_j{p}_j^{\max }\},& i=k\\ 0,& k+1\&le;i\&le;N\end{array}\right.$ Formula (20)

The optimum allocation value disaggregation that then can obtain formula (20) each cognitive user transmitting power of equal value is:

$p_i=\left\{\begin{array}{cc}{p}_i^{\max },& 1\&le;i\&le;k-1\\ \min \{p_i^{\max },(Q^{\max }-\underset{j=1}{\overset{k-1}{\mathrm{\&Sigma;}}}{h}_j{p}_j^{\max })/h_j\},& i=k\\ 0,& k+1\&le;i\&le;N\end{array}\right.$ Formula (21)

The actual performance of the distribution method of the bandwidth sum power of user in the centralized cognition wireless network provided to check the present embodiment, utilizes MATLAB R2012a to emulate the method.Optimal power allocation value as shown in Figure 2.

To the method that utilized bandwidth under fixed-bandwidth B=10MHz condition is divided equally, the simulation result of the relation between the overall channel capacity of cognitive user and maximum transmission power and interference temperature respectively as shown in Figure 3,4.The method that the overall channel capacity that the joint distributed method that the present embodiment proposes obtains is divided equally higher than bandwidth, particularly along with the continuous increase of maximum transmission power, the overall channel capacity that the method that bandwidth is divided equally realizes can reach a threshold value very soon, no longer increases.Mainly because total bandwidth is averagely allocated to each cognitive user by the method that bandwidth is divided equally, but the bandwidth taken required for each cognitive user transmission information is not identical, tape tolerance system when this will cause a part of cognitive user information transmission and another part cognitive user only needs fractional bandwidth transmission information and causes the situation of bandwidth waste.Like this, along with the raising of each user emission power or interference temperature limit, cognitive user can in order to carry out the transmitting power also corresponding increase communicated, and bandwidth allocation problems is tending towards obvious gradually.Allocated bandwidth is combined with power division by this method, carries out allocated bandwidth dynamically, can well solve this problem.

For fixing interference temperature Q ^maxthe method that under=10dB condition, utilized bandwidth is divided equally, to the simulation result of the relation between the overall channel capacity of cognitive user and bandwidth as shown in Figure 5.The present embodiment can be good at carrying out allocated bandwidth, optimization system performance.When interference temperature, total bandwidth are identical, the channel capacity that this method obtains all is greater than the power system capacity not using this method.This shows, this method has stronger adaptability for environment, can carry out adaptive adjustment to obtain maximized channel total capacity, improves systematic function.In addition, when maximum transmission power or interference temperature one timing, total bandwidth is larger, and the overall system capacity of cognitive user is larger, and the QoS of each cognitive user is higher.

If have multiple authorized user in centralized cognition wireless network, cognitive user bandwidth sum transmitting power division method in the centralized cognition wireless network provided of the present embodiment then should be provided, when the authorization channel of this authorized user is shared to each cognitive user and each authorized user, calculate the optimum allocation value of each cognitive user bandwidth and the optimum allocation value of transmitting power.

Obviously; the above embodiment of the present invention is only for example of the present invention is clearly described; and be not the restriction to embodiments of the present invention; for those of ordinary skill in the field; can also make other changes in different forms on the basis of the above description; here cannot give exhaustive to all execution modes, every belong to technical scheme of the present invention the apparent change of extending out or variation be still in the row of protection scope of the present invention.

Claims (2)

1. a cognitive user bandwidth sum transmitting power division method in centralized cognition wireless network, it is characterized in that, the method comprises the steps:

S1, the overall channel capacity setting up cognitive user are the Mathematical Modeling of maximum;

S2, fixing each cognitive user transmitting power, calculate the optimum allocation value of each cognitive user bandwidth, formula is as follows:

$B_i=\frac{g_i{p}_i}{\underset{j=1}{\overset{N}{\mathrm{\&Sigma;}}}{g}_j{p}_j}{B}_{\mathrm{total};}$

In formula, B _ifor cognitive wireless network system distributes to cognitive user SU _ibandwidth, g _ifor cognitive user SU _ito the link gain of its own base station, p _ifor cognitive user SU _itransmitting power, g _jfor cognitive user SU _jto the link gain of its own base station, p _jfor cognitive user SU _jtransmitting power, B _totalfor authorization channel total bandwidth, N is the number of cognitive user;

S3, optimum allocation value according to each cognitive user bandwidth, calculate the optimum allocation value of each cognitive user transmitting power, formula is as follows:

$p_i=\left\{\begin{array}{cc}{p}_i^{\max },& 1\&le;i\&le;k-1\\ \min \{p_i^{\max },(Q^{\max }-\underset{j=1}{\overset{k-1}{\mathrm{\&Sigma;}}}{h}_j{p}_j^{\max })/h_i\},& i=k\\ 0,& k+1\&le;i\&le;N\end{array}\right.$

In formula, h _ifor cognitive user SU _ito the link gain of authorized user, h _jfor cognitive user SU _jto the link gain of authorized user, Q ^maxfor the transmitting power of each cognitive user is to the threshold value of total interference that authorized user produces, k is defined as:

There is integer k and meet 1≤k≤N, make:

$\begin{array}{cc}{q}_i=h_i{p}_i^{\max },& \&ForAll;i\&Element;[1,k-1]\end{array}$

$0<q_k\&le;h_k{p}_k^{\max };$

$\begin{array}{cc}{q}_i=0,& \&ForAll;i\&Element;[k+1,N]\end{array}$

In formula, q _i=h _ip _i, p _i ^maxfor cognitive user SU _ireflector transmitting power restriction, q _k=h _kp _k, p _k ^maxfor cognitive user SU _kreflector transmitting power restriction.

2. method according to claim 1, is characterized in that, in described step S1, to be the model formation of the Mathematical Modeling of maximum be the overall channel capacity of cognitive user:

$\underset{B_i,p_i}{\max }\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{B}_i{\log }_2(1+\frac{g_i{p}_i}{n_0{B}_i})$

$s.t.\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{B}_i\&le;B_{\mathrm{total}},B_i\&GreaterEqual;0,p_i\&le;p_i^{\max },\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{h}_i{p}_i\&le;Q^{\max },\&ForAll;i\&Element;N;$

In formula, n ₀for noise power spectral density.