CN102186232A - Power distribution method for multi-district OFDMA (Orthogonal Frequency Division Modulation) system - Google Patents

Abstract

The invention discloses a power distribution method for a multi-district OFDMA (Orthogonal Frequency Division Modulation) system, comprising the following steps of establishing a constrain optimization model for multi-district OFDMA system power distribution; simplifying the power optimization distribution as the solution of target linear equations; working out the linear equations in the step b; the obtained power distribution matrix is the optimum solution if the power distribution matrix meets the constrain conditions; the obtained power distribution matrix is adjusted by iteration if failing to meet the constrain conditions, thus obtaining the final result for power distribution; the power value Pi(j) in the row i and line j in the power distribution matrix is distributed to the sub-carrier wave j of a user i. The solving complexity of the method is only equal to the solution of the linear equations; and the method has low complexity, is suitable for concentrative processing, and can improve system performance, thereby having strong real-time characteristic.

Description

The power distribution method of a kind of multi-cell OFDMA system

Technical field

The present invention relates to the allocation of radio resources field in the mobile communication system, be specifically related to the power distribution method of a kind of multi-cell OFDMA (orthogonal frequency division multiplexing multiple access) system.

Background technology

Along with the rapidly increase of people to the business demand of wireless and mobile communication, radio spectrum resources is more and more nervous.How effectively Radio Resource to be distributed and become more and more important problem.For Radio Resource optimized distribution problem, can be divided into two classes according to optimization aim: the first kind is to satisfy under the condition of user rate the transmitting power of minimization system; Second class is under the limited condition of system emission power, all users' of maximization system total data rate.

The achievement in research majority of OFDMA system resource allocation all is to belong to about the aforementioned second class problem under present many cell scenario, and less relatively for the achievement in research of aforementioned first kind problem.Just the optimized Algorithm about aforementioned first kind problem has been proposed in the following application for a patent for invention.

(1) Liao Xuewen, Lv Gangming, Zhu Shihua, Ren Pinyi, a kind of resource allocation and power distribution method that is used for honeycomb multi-cell OFDMA system, Chinese invention patent application, application number 201010213897.8

(2) Chen Xiaodong, Xiong Shangkun, Wang Qingyang etc., the combined distributing method of local resource and device in the OFDMA system, Chinese invention patent application, application number 201010255740.1

Foregoing invention patent application (1) is the method that adopts Distributed Calculation, comes the user in each sub-district is carried out subcarrier and power division by iteration.Each sub-district is calculated interference cost factor and is also sent to neighbor cell, the interference cost factor that sends of reception of neighboring cell simultaneously, the interference cost factor of each cell update neighbor cell, and the power division in each sub-district when calculating next iteration according to this.This method only needs to exist between the base station limited cooperation, and by sharing of the interference cost factor, each cell base station can the independent allocation transmitted power.But simulate the actual conditions of presence of intercell interference by the interference cost factor, then the account form of the interference cost factor directly has influence on the performance of allocation result, and the formula of the interference cost factor that proposed in should inventing is very complicated, along with increasing of number of users and carrier number, can cause amount of calculation very big, bring bigger load to cell base station.

The subcarrier of multi-cell OFDMA and the combined optimization assignment problem of power are considered in foregoing invention patent application (2), are equally to adopt the distributed mode of finding the solution.In the power division part, original allocation is carried out based on single sub-district under the co-channel interference situation of other sub-district not considering, sub-district in the collaboration region is by mutual exchange channel information of data-interface and power allocation information separately then, each cell base station utilizes iterative program independently to calculate co-channel interference from other sub-district again, and the power division of upgrading each sub-district is by judging whether the Signal to Interference plus Noise Ratio of user on certain subcarrier of Serving cell determines greater than specified threshold whether iteration continues.Each cell base station carries out parallel work-flow simultaneously, though amount of calculation is disperseed to each base station, reduced complexity, but be to rely on each other in fact because use the power that on this carrier wave, distributes of the different user of same carrier wave, dependent variable each other is so directly adopt the parallel computation meeting to cause the result who finally tries to achieve not necessarily accurate.

In general, there is following problem in existing multi-cell OFDMA power distribution algorithm: 1) from the Optimum Theory angle, utilize classic algorithm to find the solution, implementation complexity is big, is unfavorable for adopting centralized processing; 2) the employing Distributed Problem Solving Algorithm is disperseed amount of calculation, has reduced complexity, but owing to complementary relation between each sub-district, distributed finding the solution can not really be planned as a whole the resource optimization distribution of many sub-districts from the overall situation.At the problems referred to above, it is extremely low that the present invention proposes a kind of complexity, is fit to centralized processing and well behaved power distribution method.

Summary of the invention

Purpose of the present invention overcomes the prior art above shortcomings, proposes the power distribution method of a kind of multi-cell OFDMA system, reaches preferable performance with low complex degree, is applicable to the centralized processing of network, and concrete technical scheme is as follows.

The power distribution method of a kind of multi-cell OFDMA system may further comprise the steps:

A sets up the Constraint Anchored Optimization that the multi-cell OFDMA system power distributes;

Target function in the Constraint Anchored Optimization that b, analytical procedure a obtain and constraints are distributed power optimization to be simplified to and are found the solution the target system of linear equations;

C, the system of linear equations among the solution procedure b obtains the power division matrix, the capable j column element of this matrix i p _i(j) performance number that on subcarrier j, is assigned to for user i, user's performance number on its unappropriated subcarrier all is 0, and wherein i is a Customs Assigned Number, and j is a subcarrier number;

The power division matrix that d, step c obtain is if satisfy described constraints, and then it is optimal solution, finds the solution end; If do not satisfy described constraints, then it is carried out the iteration adjustment, obtain the final result of power division;

E, the performance number p of the capable j row of i in the power division matrix that steps d is tried to achieve _i(j) distribute to user i divide subcarrier j.

In the power distribution method of above-mentioned multi-cell OFDMA system, step a may further comprise the steps:

A1) obtain target function: the power division target of multi-cell OFDMA system is to reach under the default rate conditions total transmitting power of base station in the minimization system all users, promptly minimize the transmitting power sum on all users' the subcarrier, therefore, the target function of power division Constraint Anchored Optimization is

Wherein U is the numbering set of all users in the system, and M is the numbering set of all subcarriers in the system, p _i(j) performance number that on subcarrier j, is assigned to for user i;

A2) obtain constraints: the prerequisite of power division described in the step 1) is that all users reach described default speed, therefore one of constraints of power division Constraint Anchored Optimization is that user's actual speed rate is greater than or equals described default speed, then require the Signal to Interference plus Noise Ratio of all users on the subcarrier that is assigned to all to be not less than the target Signal to Interference plus Noise Ratio of user's correspondence, promptly arbitrary user i is had SINR _i(j) 〉=SINR _i, i ∈ S (j), wherein SINR _i(j) be the Signal to Interference plus Noise Ratio of user i on certain subcarrier j, SINR _iTarget Signal to Interference plus Noise Ratio for user i; Suppose that subcarrier assigns before power division, different user does not distribute identical subcarrier in the same sub-district, and each user i has identical target spectrum utilance η on the subcarrier that is distributed _i, and the transmission rate R of expectation _i, the number of sub carrier wave r that distributes of user i then _iNeed satisfy r _i〉=R _i/ (B η _i), r _iGet the smallest positive integral that satisfies aforementioned inequality, S (j) is the Customs Assigned Number collection that is assigned to the different districts of subcarrier j; Since in the reality performance number be on the occasion of, so the constraints of power division Constraint Anchored Optimization two be the power of all users that try to achieve on its assigned carrier wave all greater than 0, i.e. p _i(j)＞0, i ∈ S (j).

In the power distribution method of above-mentioned multi-cell OFDMA system, step b may further comprise the steps:

B1) obtain arbitrary user i measurable Signal to Interference plus Noise Ratio SINR on subcarrier j _i(j) calculation expression, because the OFDMA system multiplexing factor of medium frequency is 1, the user of different districts can use same subcarrier, exists co-channel interference so SINR between different districts _i(j) available following formula calculates:

${\mathrm{SINR}}_i\left(j\right)=\frac{p_i\left(j\right)G_i\left(j\right)}{\underset{h\∈S\left(j\right),h\≠i}{\mathrm{\Σ}}{G}_i^{b\left(h\right)}\left(j\right)p_h\left(j\right)+{\mathrm{BN}}_0},i\∈S\left(j\right)$

Wherein b (h) is a user h place cell number, and S (j) is the user's collection that is assigned to the different districts of subcarrier j, p _i(j) represent the performance number that user i is assigned to, p on subcarrier j _h(j) represent the performance number that user h is assigned to, G on subcarrier j _i(j) channel gain of expression user i on subcarrier j,

Be illustrated in the channel gain between the base station that subcarrier j goes up user i and sub-district k (k ≠ b (i)), B is the bandwidth of system subcarrier, N ₀It is the power spectral density of white noise;

B2) obtain the target Signal to Interference plus Noise Ratio SINR of arbitrary user i _i, each user i has identical target spectrum utilance η in the supposing the system on the subcarrier that is distributed _i, and the transmission rate R of expectation _i, then η is arranged for user i _i=log ₂(1+SINR _i), then the target Signal to Interference plus Noise Ratio of user i is

B3) with above-mentioned b1), b2) two go on foot one of constraints of the described power division Constraint Anchored Optimization of expression formula substitution step a that obtains, SINR _i(j) 〉=SINR _iCan change into p _i(j) with user's target spectrum utilance η _iBetween inequality constraints relation

$p_i\left(j\right)\≥(2^{{\mathrm{\η}}_i}-1)=\frac{\underset{h\∈S\left(j\right),h\≠i}{\mathrm{\Σ}}{G}_i^{b\left(h\right)}\left(j\right)p_h\left(j\right)+{\mathrm{BN}}_0}{G_i\left(j\right)},i\∈S\left(j\right);$

B4) to make the target function value minimum of the described power division Constraint Anchored Optimization of step a, be the transmitting power sum minimum of all users on the subcarrier that is assigned in the system, then require the performance number of each user on the carrier wave that is assigned to all to get minimum, also promptly for arbitrary user i in the system, requirement above-mentioned steps b3) inequality in is got equal sign, like this for the power p of each user i on the subcarrier j that is assigned to _i(j) can both obtain an equation, also just obtain one group with p _i(j) be the system of linear equations of unknown quantity, i.e. the target system of linear equations $p_i\left(j\right)\≥(2^{{\mathrm{\η}}_i}-1)=\frac{\underset{h\∈S\left(j\right),h\≠i}{\mathrm{\Σ}}{G}_i^{b\left(h\right)}\left(j\right)p_h\left(j\right)+{\mathrm{BN}}_0}{G_i\left(j\right)},i\∈S\left(j\right).$

In the power distribution method of above-mentioned multi-cell OFDMA system, steps d comprises:

D1) whether all elements is all greater than zero for the determining step c power division matrix of trying to achieve, and not have the power of the distribution of certain user on all subcarriers all be 0, if satisfy, then this power division matrix is the optimal solution of power division, finds the solution end; If do not satisfy, then jump to steps d 2);

D2) separating of trying to achieve among the step c carried out the iteration adjustment, step is as follows: d1) whether all elements is all greater than zero for the determining step c power division matrix of trying to achieve, and the power that does not have the distribution of certain user on all subcarriers all is 0, if satisfy, then this power division matrix is the optimal solution of power division, finds the solution end; If do not satisfy, then jump to steps d 2);

D2) separating of trying to achieve among the step c carried out the iteration adjustment, step is as follows:

D21) all the negative power values in the power division matrix all are adjusted into 0;

D22) be steps d 21 with the left side in the full scale equation group) in the equation of controlled negative power value all remove, be that the right of the equation of positive expresses that negative power all becomes 0 in the formula simultaneously with the left side, so just obtain a new equation group;

D23) with the negative equation group of separating element of having of each carrier wave correspondence d21 set by step all), d22) adjust, statistics is adjusted the sub-carrier number of each user's service of back then, promptly each user performance number of distributing on each subcarrier is greater than zero number; If the service sub-carrier number of certain user i is reduced to r ' _i, then with its availability of frequency spectrum η _iBe updated to η ' _i,

Sub-carrier number does not have the user who changes then need not upgrade the availability of frequency spectrum; In the equation group that availability of frequency spectrum substitution step I i after upgrading is obtained, the new equation group of getting back;

D24) solution procedure d23 respectively) each the new equation group that obtains obtains new power division matrix, if this matrix all elements is all non-negative and be not zero row entirely, then adjusts and stops, and the separating of gained is the optimal solution of the power division that this method tries to achieve; If it is zero entirely that certain row appears in the power division matrix of trying to achieve, the then adjustment of going up in limited time that perhaps reaches iterations stops, otherwise goes to d21) go on foot and continue to adjust successively.

In the power distribution method of above-mentioned multi-cell OFDMA system, in the described multi-cell OFDMA system central controller is arranged, each cell base station is all given central controller with feedback of channel information, and the channel gain between each terminal and the base station calculates by central controller.

Above-mentioned steps d is adjusted into 0 with negative performance number, finds the solution thereby obtain new equation group again, is actually the subcarrier that eliminates bad channel conditions from user's sub-carrier set like this, and good subcarrier improves the availability of frequency spectrum to allow channel condition, and carrying is more professional.And on the good subcarrier of channel condition, reaching identical speed, its required power is also less relatively.

Compared with prior art, the power distribution method of the multi-cell OFDMA system that the present invention proposes, after obtaining Constraint Anchored Optimization, not from the optimum theory angle of complexity, but adopt abovementioned steps b to obtain system of linear equations, find the solution by abovementioned steps c again, more irrational separating according to abovementioned steps d adjusted, carry out power division at last.The core of power division is to find the solution the power division matrix, and the complexity of finding the solution of the method that the present invention proposes only is equivalent to find the solution system of linear equations, and complexity is low, is fit to centralized processing, can improve systematic function, so practicality is stronger.

Description of drawings

Fig. 1 is the flow chart of the power distribution method of the present invention's proposition.

Fig. 2 finds the solution system of linear equations in the execution mode, obtains the flow chart of power division matrix.

Fig. 3 is that execution mode neutral line solution of equations element is adjusted flow chart.

Embodiment

Below in conjunction with accompanying drawing concrete enforcement of the present invention is described further, but enforcement of the present invention is not limited thereto.

The multi-cell OFDMA system model that the present invention is based on has following feature:

1) there is a central controller in this OFDMA system, and a plurality of sub-districts are arranged, and there are a plurality of users each sub-district.Each cell base station is all given central controller with feedback of channel information, by it channel gain between each terminal and the base station is calculated, and then manages the power division of a plurality of sub-districts concentratedly.

2) carrier wave assigns before power division, and different user does not distribute identical subcarrier in the same sub-district.

3) this OFDMA system multiplexing factor of medium frequency is 1.

4) each user i has identical target spectrum utilance η on the subcarrier that is distributed _i, and default transmission rate R _i, then the number of sub carrier wave of user i distribution need satisfy r _i〉=R _i/ (B η _i), r _iGet the smallest positive integral that satisfies aforementioned inequality.

According to above-mentioned feature 3), the user of different districts can use same subcarrier, so exists co-channel interference between different districts.Then for user i measurable Signal to Interference plus Noise Ratio SINR on subcarrier j _i(j) be:

${\mathrm{SINR}}_i\left(j\right)=\frac{p_i\left(j\right)G_i\left(j\right)}{\underset{h\∈S\left(j\right),h\≠i}{\mathrm{\Σ}}{G}_i^{b\left(h\right)}\left(j\right)p_h\left(j\right)+{\mathrm{BN}}_0},i\∈S\left(j\right)---\left(1\right)$

According to above-mentioned feature 4), utilize the relation of the availability of frequency spectrum and Signal to Interference plus Noise Ratio, for user i η is arranged _i=log ₂(1+SINR _i), the target Signal to Interference plus Noise Ratio SINR of user i then _iFor:

${\mathrm{SINR}}_i=2^{{\mathrm{\η}}_i}-1---\left(2\right)$ The symbol of using among the present invention is carried out as giving a definition and illustrating:

1) sub-carrier set of define system is M={1, L, and m}, cell set is C={1, L, N}, user's collection of sub-district k correspondence is U _k=1, L n _k, all users' of whole system set is used

Represent.Above-mentioned M, C, U _kBe the nature manifold.

2) definition b (i) is a user i place cell number,

3) definition S (j) is the user's collection that is assigned to the different districts of subcarrier j,

4) p _i(j) represent the performance number that user i is assigned on subcarrier j; p _h(j) represent the performance number that user h is assigned on subcarrier j; G _i(j) channel gain of expression user i on subcarrier j comprises antenna gain, path loss, shadow fading etc.; Be illustrated in the channel gain between the base station that subcarrier j goes up user i and sub-district k (k ≠ b (i)); B is the bandwidth of system subcarrier; N ₀It is the power spectral density of white noise; G _i(j) and

Can calculate by the central controller of system.

The actual user of being i and use interference measure between other community users of subcarrier j equally.

Giving an example below describes the power distribution method that the present invention carries in detail, and idiographic flow is referring to accompanying drawing 1.At first obtain the target function and the constraints of power division problem Constraint Anchored Optimization, be described below:

$\min \underset{i\∈U,j\∈M}{\mathrm{\Σ}}{p}_i\left(j\right)---\left(3\right)$

$\frac{G_i\left(j\right)p_i\left(j\right)}{\underset{h\∈S\left(j\right),h\≠i}{\mathrm{\Σ}}{G}_i^{b\left(h\right)}\left(j\right)p_h\left(j\right)+{\mathrm{BN}}_0}\≥{\mathrm{SINR}}_i,i\∈S\left(j\right)---\left(4\right)$

p _i(j)＞0，i∈S(j) (5)

Wherein can rewrite (4) formula as follows:

$p_i\left(j\right)\≥(2^{{\mathrm{\η}}_i}-1)=\frac{\underset{h\∈S\left(j\right),h\≠i}{\mathrm{\Σ}}{G}_i^{b\left(h\right)}\left(j\right)p_h\left(j\right)+{\mathrm{BN}}_0}{G_i\left(j\right)},i\∈S\left(j\right)---\left(6\right)$

Work as p _i(j) all get minimum value, when promptly the inequality in the formula (6) was all got equal sign, the formula that adds up of formula (3) just can obtain minimum value, and promptly target function can be got minimum value.That is to say, under the restriction of constraints (5) and (6), find the solution the optimal solution of target function (3), can be simplified to all non-negative approximate solution problem of element of separating of the system of linear equations shown in the formula of finding the solution (7).

$p_i\left(j\right)\≥(2^{{\mathrm{\η}}_i}-1)=\frac{\underset{h\∈S\left(j\right),h\≠i}{\mathrm{\Σ}}{G}_i^{b\left(h\right)}\left(j\right)p_h\left(j\right)+{\mathrm{BN}}_0}{G_i\left(j\right)},i\∈S\left(j\right)---\left(7\right)$

For each carrier wave j, can obtain the system of linear equations shown in one group of formula (7), unknown number p _i(j) number and equation number are the number of users of the different districts that uses carrier wave j, and the equation number and the unknown number number of all carrier wave correspondences then are Wherein n is a total number of users in the system.

System of linear equations to all carrier wave correspondences is found the solution, and idiographic flow is referring to accompanying drawing 2.Be example explanation Solving Linear process with the pairing equation group of carrier wave j below.Suppose S (j)={ i ₁, i ₂, L i _k, then can obtain a following K equation:

$\left\{\begin{array}{c}{p}_{i_1}\left(j\right)G_{i_1}\left(j\right)-(2^{{\mathrm{\η}}_{i_1}}-1)\underset{n=2}{\overset{k}{\mathrm{\Σ}}}{G}_{i_1}^{b\left(i_n\right)}\left(j\right)p_{i_n}\left(j\right)=(2^{{\mathrm{\η}}_{i_1}}-1)\·{\mathrm{BN}}_0\\ p_{i_2}\left(j\right)G_{i_2}\left(j\right)-(2^{{\mathrm{\η}}_{i_2}}-1)\underset{n=1,n\≠2}{\overset{k}{\mathrm{\Σ}}}{G}_{i_2}^{b\left(i_n\right)}\left(j\right)p_{i_n}\left(j\right)=(2^{{\mathrm{\η}}_{i_2}}-1)\·{\mathrm{BN}}_0\\ M\\ p_{i_k}\left(j\right)G_{i_k}\left(j\right)-(2^{{\mathrm{\η}}_{i_k}}-1)\underset{n=1}{\overset{k-1}{\mathrm{\Σ}}}{G}_{i_k}^{b\left(i_n\right)}\left(j\right)p_{i_n}\left(j\right)=(2^{{\mathrm{\η}}_{i_k}}-1)\·{\mathrm{BN}}_0\end{array}\right.$

K rank system of linear equations to above-mentioned likeness in form Ax=b is found the solution with Gaussian elimination method.Wherein

$A=\left[\begin{array}{cccc}{G}_{i_1}\left(j\right)& -(2^{{\mathrm{\η}}_{i_1}}-1)G_{i_1}^{b\left(i_2\right)}& L& -(2^{{\mathrm{\η}}_{i_1}}-1)G_{i_1}^{b\left(i_k\right)}\\ -(2^{{\mathrm{\η}}_{i_2}}-1)G_{i_2}^{b\left(i_1\right)}& G_{i_2}\left(j\right)& L& -(2^{{\mathrm{\η}}_{i_2}}-1)G_{i_k}^{b\left(i_k\right)}\\ & M& & \\ -(2^{{\mathrm{\η}}_{i_k}}-1)G_{i_k}^{b\left(i_1\right)}& -(2^{{\mathrm{\η}}_{i_k}}-1)G_{i_k}^{b\left(i_2\right)}& L& G_{i_k}\left(j\right)\end{array}\right]$

$b={\left[\begin{array}{cccc}(2^{{\mathrm{\η}}_{i_1}}-1){\mathrm{BN}}_0& (2^{{\mathrm{\η}}_{i_2}}-1){\mathrm{BN}}_0& L& (2^{{\mathrm{\η}}_{i_k}}-1){\mathrm{BN}}_0\end{array}\right]}^{\′}$

$x={\left[\begin{array}{cccc}{p}_{i_1}\left(j\right)& p_{i_2}\left(j\right)& L& p_{i_k}\left(j\right)\end{array}\right]}^{\′}$

Coefficient matrices A is carried out the elementary row conversion, make it become a upper triangular matrix, so just can obtain the equation group of an equivalence.And then utilize backward steps just can try to achieve separating of full scale equation group.

All can try to achieve unique solution according to the method described above for the equation group that each carrier wave is relevant, these be separated the power division matrix that is combined into a n * m, the performance number p that the capable j column element of matrix i is assigned on subcarrier j for user i _i(j), the performance number of user on its unappropriated subcarrier all is 0.If it is all non-negative that the power matrix that obtains like this satisfies all elements, and incomplete zero row, then this matrix is the optimal solution of target function.If do not satisfy then it is carried out the iteration adjustment, step is as follows:

I. all the negative power values in the power division matrix to be adjusted all are adjusted into 0.

Ii. the equation that with the left side in the full scale equation group is controlled negative power value in the step I all removes, and is that the right of the equation of positive expresses that negative power all becomes 0 in the formula simultaneously with the left side.So just obtain a new equation group.

Iii. the negative equation group of separating element of having of each carrier wave correspondence is all adjusted by above-mentioned steps, statistics is adjusted the sub-carrier number of each user's service of back then, and promptly each user performance number of distributing on each carrier wave is greater than zero number.If the service subcarrier of certain user i is reduced to r ' _i, then with the availability of frequency spectrum η of its distributing carrier wave _iBe updated to η ' _i,

Carrier number does not have the user who changes then need not upgrade frequency spectrum

Utilance.In the equation group that availability of frequency spectrum substitution step I i after these are upgraded obtains, for each subcarrier new equation group of getting back.

Iv. each new equation group of obtaining of solution procedure iii obtains new power division matrix, if this matrix all elements is all non-negative and do not have non-zero capable, then adjusts and stops, and the separating of gained is the optimal solution of the power division that this method tries to achieve; If it is zero entirely that certain row appears in the power division matrix of trying to achieve, the then adjustment of going up in limited time that perhaps reaches iterations stops, and adjusts successively otherwise go to i step continuation.

The set-up procedure idiographic flow of irrational power division matrix of obtaining referring to accompanying drawing 3, is specified adjustment process below for example.Suppose that the irrational power division matrix P that tries to achieve is n * m rank matrix as follows, Customs Assigned Number is 1～n, and subcarrier number is 1～m.

$P=\left[\begin{array}{ccccc}{p}_1\left(1\right)L& p_1\left(j_1\right)L& p_1\left(j_2\right)L& p_1\left(j_3\right)L& p_1\left(m\right)\\ & & M& & \\ p_{i_1}\left(1\right)L& p_{i_1}\left(j_1\right)L& p_{i_1}\left(j_2\right)L& p_{i_1}\left(j_3\right)L& p_{i_1}\left(m\right)\\ & & M& & \\ p_{i_2}\left(1\right)L& p_{i_2}\left(j_1\right)L& p_{i_2}\left(j_2\right)L& p_{i_2}\left(j_3\right)L& p_{i_2}\left(m\right)\\ & & M& & \\ p_{i_k}\left(1\right)L& p_{i_k}\left(j_1\right)L& p_{i_k}\left(j_2\right)L& p_{i_k}\left(j_3\right)L& p_{i_k}\left(m\right)\\ & & M& & \\ p_n\left(1\right)L& p_n\left(j_1\right)L& p_n\left(j_2\right)L& p_n\left(j_3\right)L& p_n\left(m\right)\end{array}\right]$

Each element that matrix P i is capable is represented the power division value of i user on each subcarrier respectively, and each element of j row is then represented each user's who is assigned to j subcarrier power division value, then p respectively _i(j) performance number that on subcarrier j, is assigned to of representative of consumer i.Because the number of sub carrier wave that each user i is assigned to is r _iSo, the no more than r of nonzero element that i is capable among the matrix P _iIndividual, the user of the no more than subcarrier j of the nonzero element correspondence of j row collects the number of user among the S (j).

For convenience of description, suppose to have only subcarrier j ₁, j ₂, j ₃Corresponding equation group has negative separating, and establishes subcarrier j ₁Corresponding equation group has following negative separating

And S (j ₁)={ i ₁, i ₂, L, i _k, i _a, i _b, L, i _c∈ S (j ₁).With the example that is adjusted into, describe the adjustment process of iteration in detail below to above-mentioned irrational power division matrix P.Concrete steps are as follows:

1) with j among the P ₁Negative element in the row, promptly All be adjusted into 0.

2) subcarrier j by abovementioned steps b as can be known, ₁The coefficient matrices A of corresponding equation group, constant term vector b and unknown quantity vector x are respectively:

$A=\left[\begin{array}{cccc}{G}_{i_1}\left(j_1\right)& -(2^{{\mathrm{\η}}_{i_1}}-1)G_{i_1}^{b\left(i_2\right)}& L& -(2^{{\mathrm{\η}}_{i_1}}-1)G_{i_1}^{b\left(i_k\right)}\\ -(2^{{\mathrm{\η}}_{i_2}}-1)G_{i_2}^{b\left(i_1\right)}& G_{i_2}\left(j_1\right)& L& -(2^{{\mathrm{\η}}_{i_2}}-1)G_{i_k}^{b\left(i_k\right)}\\ & M& & \\ -(2^{{\mathrm{\η}}_{i_k}}-1)G_{i_k}^{b\left(i_1\right)}& -(2^{{\mathrm{\η}}_{i_k}}-1)G_{i_k}^{b\left(i_2\right)}& L& G_{i_k}\left(j_1\right)\end{array}\right]$

$b={\left[\begin{array}{cccc}(2^{{\mathrm{\η}}_{i_1}}-1){\mathrm{BN}}_0& (2^{{\mathrm{\η}}_{i_2}}-1){\mathrm{BN}}_0& L& (2^{{\mathrm{\η}}_{i_k}}-1){\mathrm{BN}}_0\end{array}\right]}^{\′}$

$x={\left[\begin{array}{cccc}{p}_{i_1}\left(j_1\right)& p_{i_2}\left(j_1\right)& L& p_{i_k}\left(j_1\right)\end{array}\right]}^{\′}$

Now it is done following adjustment, in the deletion matrix A

The row and column at place respectively, obtain new coefficient matrices A '; Corresponding to the row of deleting in the matrix A, corresponding row among the delete columns vector b obtains new constant term vector b '; In the delete columns vector x

The row at place, obtain new unknown quantity vector x '.Can obtain j like this ₁Pairing new equation group.

3) to j among the P ₂, j ₃The element of row and corresponding equation group thereof are copied above-mentioned j ₁The method of adjustment of row is adjusted, and repeats no more here.Like this for subcarrier j ₁, j ₂, j ₃, can obtain a new equation group.The equation group of other subcarrier correspondence remains unchanged.

4) will be designated as r ' by the capable nonzero element number of i among the power division matrix P that obtains after the above-mentioned steps adjustment _i, order

The availability of frequency spectrum of upgrading user i is η ' _i=β η _i

Find the solution in each equation group that availability of frequency spectrum substitution step 3) after upgrading is obtained, obtain new power division matrix, if this matrix all elements is all non-negative and be not zero row entirely, then to adjust and stop, separating of gained is the power division optimal solution that this method is tried to achieve; If it is zero entirely that certain row appears in the power division matrix of trying to achieve, the upper limit that perhaps reaches iterations is then adjusted and is stopped, otherwise goes to the 1st) step continues to adjust successively.

After normally finishing, adjustment obtains the optimal power allocation matrix, the capable j column element of i p in this matrix _i(j) be the performance number that user i should be assigned on subcarrier j.

The power distribution method complexity of multi-cell OFDMA system proposed by the invention is low, and often also approaches systematic function under this kind power distribution method based on the systematic function that the power division that optimum theory is tried to achieve is separated gained.

Claims (5)

1. the power distribution method of a multi-cell OFDMA system is characterized in that may further comprise the steps:

A sets up the Constraint Anchored Optimization that the multi-cell OFDMA system power distributes;

Target function in the Constraint Anchored Optimization that b, analytical procedure a obtain and constraints are distributed power optimization to be simplified to and are found the solution the target system of linear equations;

C, the system of linear equations among the solution procedure b obtains the power division matrix, the capable j column element of this matrix i p _i(j) performance number that on subcarrier j, is assigned to for user i, user's performance number on its unappropriated subcarrier all is 0, and wherein i is a Customs Assigned Number, and j is a subcarrier number;

The power division matrix that d, step c obtain is if satisfy described constraints, and then it is optimal solution, finds the solution end; If do not satisfy described constraints, then it is carried out the iteration adjustment, obtain the final result of power division; E, the performance number p of the capable j row of i in the power division matrix that steps d is tried to achieve _i(j) distribute to user i divide subcarrier j.

2. the power distribution method of multi-cell OFDMA according to claim 1 system is characterized in that step a may further comprise the steps:

A1) obtain target function: the power division target of multi-cell OFDMA system is to reach under the default rate conditions total transmitting power of base station in the minimization system all users, promptly minimize the transmitting power sum on all users' the subcarrier, therefore, the target function of power division Constraint Anchored Optimization is

Wherein U is the numbering set of all users in the system, and M is the numbering set of all subcarriers in the system, p _i(j) performance number that on subcarrier j, is assigned to for user i;

A2) obtain constraints: the prerequisite of power division described in the step 1) is that all users reach described default speed, therefore one of constraints of power division Constraint Anchored Optimization is that user's actual speed rate is greater than or equals described default speed, then require the Signal to Interference plus Noise Ratio of all users on the subcarrier that is assigned to all to be not less than the target Signal to Interference plus Noise Ratio of user's correspondence, promptly arbitrary user i is had SINR _i(j) 〉=SINR _i, i ∈ S (j), wherein SINR _i(j) be the Signal to Interference plus Noise Ratio of user i on certain subcarrier j, SINR _iTarget Signal to Interference plus Noise Ratio for user i; Suppose that subcarrier assigns before power division, different user does not distribute identical subcarrier in the same sub-district, and each user i has identical target spectrum utilance η on the subcarrier that is distributed _i, and default transmission rate R _i, the number of sub carrier wave r that distributes of user i then _iNeed satisfy r _i〉=R _i/ (B η _i), r _iGet the smallest positive integral that satisfies aforementioned inequality, S (j) is the Customs Assigned Number collection that is assigned to the different districts of subcarrier j; Since in the reality performance number be on the occasion of, so the constraints of power division Constraint Anchored Optimization two be the power of all users that try to achieve on its assigned carrier wave all greater than 0, i.e. p _i(j)＞0, i ∈ S (j).

3. the power distribution method of multi-cell OFDMA according to claim 1 system is characterized in that step b may further comprise the steps:

B1) obtain arbitrary user i measurable Signal to Interference plus Noise Ratio SINR on subcarrier j _i(j) calculation expression, because the OFDMA system multiplexing factor of medium frequency is 1, the user of different districts can use same subcarrier, exists co-channel interference so SINR between different districts _i(j) available following formula calculates:

${\mathrm{SINR}}_i\left(j\right)=\frac{p_i\left(j\right)G_i\left(j\right)}{\underset{h\∈S\left(j\right),h\≠i}{\mathrm{\Σ}}{G}_i^{b\left(h\right)}\left(j\right)p_h\left(j\right)+{\mathrm{BN}}_0},i\∈S\left(j\right)$

Wherein b (h) is a user h place cell number, and S (j) is the user's collection that is assigned to the different districts of subcarrier j, p _i(j) represent the performance number that user i is assigned to, p on subcarrier j _h(j) represent the performance number that user h is assigned to, G on subcarrier j _i(j) channel gain of expression user i on subcarrier j,

Be illustrated in the channel gain between the base station that subcarrier j goes up user i and sub-district k (k ≠ b (i)), B is the bandwidth of system subcarrier, N ₀It is the power spectral density of white noise;

B2) obtain the target Signal to Interference plus Noise Ratio SINR of arbitrary user i _i, each user i has identical target spectrum utilance η in the supposing the system on the subcarrier that is distributed _i, and the transmission rate R of expectation _i, then η is arranged for user i _i=log ₂(1+SINR _i), then the target Signal to Interference plus Noise Ratio of user i is

B3) with above-mentioned b1), b2) two go on foot one of constraints of the described power division Constraint Anchored Optimization of expression formula substitution step a that obtains, SINR _i(j) 〉=SINR _iCan change into p _i(j) with user's target spectrum utilance η _iBetween inequality constraints relation

$p_i\left(j\right)\≥(2^{{\mathrm{\η}}_i}-1)=\frac{\underset{h\∈S\left(j\right),h\≠i}{\mathrm{\Σ}}{G}_i^{b\left(h\right)}\left(j\right)p_h\left(j\right)+{\mathrm{BN}}_0}{G_i\left(j\right)},i\∈S\left(j\right);$

B4) to make the target function value minimum of the described power division Constraint Anchored Optimization of step a, be the transmitting power sum minimum of all users on the subcarrier that is assigned in the system, then require the performance number of each user on the carrier wave that is assigned to all to get minimum, also promptly for arbitrary user i in the system, requirement above-mentioned steps b3) inequality in is got equal sign, like this for the power p of each user i on the subcarrier j that is assigned to _i(j) can both obtain an equation, also just obtain one group with p _i(j) be the system of linear equations of unknown quantity, i.e. the target system of linear equations $p_i\left(j\right)=(2^{{\mathrm{\η}}_i}-1)=\frac{\underset{h\∈S\left(j\right),h\≠i}{\mathrm{\Σ}}{G}_i^{b\left(h\right)}\left(j\right)p_h\left(j\right)+{\mathrm{BN}}_0}{G_i\left(j\right)},i\∈S\left(j\right).$

4. the power distribution method of multi-cell OFDMA according to claim 1 system is characterized in that steps d comprises:

D1) whether all elements is all greater than zero for the determining step c power division matrix of trying to achieve, and not have the power of the distribution of certain user on all subcarriers all be 0, if satisfy, then this power division matrix is the optimal solution of power division, finds the solution end; If do not satisfy, then jump to steps d 2);

D2) separating of trying to achieve among the step c carried out the iteration adjustment, step is as follows:

D21) all the negative power values in the power division matrix all are adjusted into 0;

D22) be steps d 21 with the left side in the full scale equation group) in the equation of controlled negative power value all remove, be that the right of the equation of positive expresses that negative power all becomes 0 in the formula simultaneously with the left side, so just obtain a new equation group;

D23) with the negative equation group of separating element of having of each carrier wave correspondence d21 set by step all), d22) adjust, statistics is adjusted the sub-carrier number of each user's service of back then, promptly each user performance number of distributing on each subcarrier is greater than zero number; If the service sub-carrier number of certain user i is reduced to r ' _i, then with its availability of frequency spectrum η _iBe updated to η ' _i,

Sub-carrier number does not have the user who changes then need not upgrade the availability of frequency spectrum; In the equation group that availability of frequency spectrum substitution step I i after upgrading is obtained, the new equation group of getting back;

D24) solution procedure d23 respectively) each the new equation group that obtains obtains new power division matrix, if this matrix all elements is all non-negative and be not zero row entirely, then adjusts and stops, and the separating of gained is the optimal solution of the power division that this method tries to achieve; If it is zero entirely that certain row appears in the power division matrix of trying to achieve, the then adjustment of going up in limited time that perhaps reaches iterations stops, otherwise goes to d21) go on foot and continue to adjust successively.

5. according to the power distribution method of each described multi-cell OFDMA system of claim 1～4, it is characterized in that in the described multi-cell OFDMA system central controller being arranged, each cell base station is all given central controller with feedback of channel information, and the channel gain between each terminal and the base station calculates by central controller.

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