CN105656612A - Multi-user power line communication system resource distribution method based on bit swapping - Google Patents

Abstract

The invention discloses a multi-user power line communication system resource distribution method based on bit swapping. The method comprises the steps that on the condition that fairness among users is ensured, target rate proportion constraint conditions are introduced, subcarrier distribution and bit and power distribution are performed step by step, and in other words, subcarrier distribution is performed according to target rate proportion constraint coefficients corresponding to all the users at first; then, equal-bit distribution is performed on all subcarriers occupied by each user according to the target rate requirement of each user; then, according to the power minimization rule, remaining bits are distributed to the subcarrier with the lowest additional powder needed for increasing one bit; finally, on the condition that the total distribution bits of the users are not changed, bit swapping is performed on the subcarriers according to the bit swapping rule. According to the method, the fairness among the users are ensured, and the power distribution is optimal according to the bit swapping rule, so that the total emission power of a multi-user power line communication system is minimized.

Description

A kind of multi-user's electric line communication system resource allocation methods based on bit exchange

Technical field

The present invention relates to a kind of electric line communication system resource allocation techniques, especially relate to a kind of multi-user's electric line communication system resource allocation methods based on bit exchange.

Background technology

Power line communication (PowerLinecommunications, PLC) technology is on the basis of existing power line network, then installs some auxiliary equipments additional, the power line communication network become. Therefore, power line communication technology has that area coverage is wide, realize the features such as low, the plug and play of cost. At present, power line communication has become a study hotspot in present communications field.

But, power line network is not design exclusively for transmission data, and it does not substantially possess communication line characteristic essential to wire net. Power line channel has the features such as frequency selectivity, time variation, multipath, impedance mismatching and noise jamming are strong, and this makes power line communication still have many problems demand to solve. Realizing necessary its resource of Appropriate application of reliable power line communication at a high speed, therefore the resource allocation problem in electric line communication system is just particularly important. OFDMA (OrthogonalFrequencyDivisionMultipleAccess, orthogonal frequency-time multiple access) technology has good anti-multipath and noise characteristic, it is possible not only to improve the availability of frequency spectrum, and the frequency selectivity of power line channel can also be resisted. Self adaptation OFDMA dynamically can distribute according to the not equal sub-carrier of channel gain change and user's request, is more suitable in the communication of reality. Thus, self adaptation OFDMA technology combines with dynamic resource optimisation technique the resource allocation problem being widely used in electric line communication system.

Resource distribution in electric line communication system is broadly divided into the distribution of single user resource and multi-user resource distribution. The resources such as subcarrier in single user electric line communication system, bit and power are that a user owns, and are therefore absent from subcarrier assignment problem, only need to carry out bit and the power distribution of optimum on each subcarrier.Multi-user's electric line communication system must carry out on the basis of subcarrier distribution for each user, carry out bit and power distribution, its essence is how optimum for user distribution subcarrier and for subcarrier distribution power, and the problems such as fairness between user, subcarrier work and different service types can be introduced, therefore, the research of multi-user's electric line communication system resource allocation methods has very important significance in field of power line communication. Research worker is had to propose a kind of multi-user's electric line communication system resource allocation algorithm, this algorithm first requires to carry out number of sub carrier wave distribution according to ownership goal speed and conjunction targeted rate, then the user that channel condition is best is assigned subcarriers to, finally obtain the closed solutions of suboptimization bit distribution, this algorithm research system power minimization problem under closing targeted rate constraint, and be deduced the expression formula that suboptimization bit distributes, but this algorithm does not obtain the bit allocation result of optimum. Also research worker is had to propose another kind of multi-user's electric line communication system resource allocation algorithm, this algorithm is first pre-assigned to user on-demand for subcarrier and channel condition, bit and power is optimally distributed further according to genetic algorithm, and reduce its amount of calculation, multiple target resource allocation problem under this algorithm research different business, ensureing (RealTime in real time, RT) its resource taken is minimized under user's fixed rate, the speed of non real-time (NonRealTime, NRT) user is maximized again under system spare resource. The shortcoming of both algorithms is exactly all without the fairness considered between user.

Summary of the invention

The technical problem to be solved is to provide a kind of multi-user's electric line communication system resource allocation methods based on bit exchange, and it can not only ensure the fairness between user, and can be effectively reduced the energy consumption of multi-user's electric line communication system.

This invention address that the technical scheme that above-mentioned technical problem adopts is: a kind of multi-user's electric line communication system resource allocation methods based on bit exchange, it is characterised in that comprise the following steps:

1. set in multi-user's electric line communication system and have K user, and set multi-user's electric line communication system employing OFDM modulation technique, in each OFDM symbol, have N number of subcarrier, wherein, K > 1, N >=1;

2. according to theory of information knowledge, obtain the theoretical value of the speed that each user in multi-user's electric line communication system reaches on each subcarrier that it is shared, assume that the n-th subcarrier is shared by kth user, then be designated as r by the speed that kth user reaches on the n-th subcarrier_k,n, r_k,nTheoretical value beWherein, 1��k��K, 1��n��N, H_k,nRepresent kth user channel gain on the n-th subcarrier, P_k,nRepresent the power that kth user distributes on the n-th subcarrier,Representing kth user noise power on the n-th subcarrier, �� represents the signal to noise ratio difference on the n-th subcarrier;

Then build the minimum power problem in multi-user's electric line communication system, be expressed as: $\begin{array}{cc}\min & \underset{k=1}{\overset{K}{\Σ}}\underset{n=1}{\overset{N}{\Σ}}{\mathrm{\β}}_{k,n}{p}_{k,n}\\ s.t.& C1:\underset{k=1}{\overset{K}{\Σ}}{\mathrm{\β}}_{k,n}=1,\∀n;\\ & C2:r_{k,n}\∈Z_0^b,\∀k,n;\\ & C3:\underset{n=1}{\overset{N}{\Σ}}{r}_{k,n}=R_k,\∀n;\underset{k=1}{\overset{K}{\Σ}}{R}_k=R;\\ & C4:R_1:R_2:\mathrm{...}:R_K={\mathrm{\γ}}_1:{\mathrm{\γ}}_2:\mathrm{...}{\mathrm{\γ}}_K;\end{array},$ Wherein, min represents " minimizing ", 1��k��K, 1��n��N, ��_k,nValue be 0 or be 1, ��_k,n=1 represents kth CU the n-th subcarrier, ��_k,n=0 represents vacant n-th subcarrier of kth user, p_k,nRepresenting the power that distributes on the n-th subcarrier of kth user, s.t. represents " constrained in ", symbolRepresent " arbitrarily ",Representing the set that is made up of all integers in 0��b, b represents the upper limit of the bit number that each user transmits on each subcarrier that it is shared, R_kRepresenting the targeted rate requirement of kth user, R represents the conjunction targeted rate requirement of multi-user's electric line communication system, ��₁����₂����_KIt is positive integer, ��₁Represent the targeted rate ratio constraint factor that the 1st user is corresponding, ��₂Represent the targeted rate ratio constraint factor that the 2nd user is corresponding, ��_KRepresenting the targeted rate ratio constraint factor that k-th user is corresponding, constraints C1 represents that each subcarrier at most can only shared by a user;Constraints C2 represents that each user speed on each subcarrier is the integer in 0��b; Constraints C3 represents that each user needs to meet its targeted rate requirement, and multi-user's electric line communication system need to meet it and close rate requirement; Constraints C4 represents that the targeted rate between each user need to meet non-linear ratio's constraint;

3. number of sub carrier wave is distributed for each user, and distribute subcarrier for each user, detailed process is: 3. _ 1, according to each self-corresponding targeted rate ratio constraint factor of all users, tentatively distribute number of sub carrier wave for each user, the number of sub carrier wave tentatively distributing to kth user is designated as cm_k,Wherein, symbolFor rounding downwards symbol, ��_kRepresent the targeted rate ratio constraint factor that kth user is corresponding; 3. _ 2, under the principle preferentially subcarrier being distributed to the user making its channel gain maximum, distribute, for each user, the subcarrier that channel condition is best, until the sum of subcarrier that each user is assigned to reaches tentatively to distribute to the number of sub carrier wave of this user; 3. _ 3, remaining unassigned each subcarrier is distributed to the user making its channel gain maximum with the form of sub-carrier selection user, then add up the sum of the subcarrier finally distributing to each user, the sum finally distributing to the subcarrier of kth user is designated as m_k;

4. each subcarrier distribution bit shared by each user, and calculate the power that each user distributes on each subcarrier that it is shared; For kth user, each subcarrier distribution bit shared by kth user, and the detailed process calculating the power that kth user distributes on each subcarrier that it is shared is: 4. _ 1, the targeted rate requirement according to kth user, carry out all subcarriers shared by kth user waiting bit distribution, make the speed that kth user reaches on each subcarrier that it is shared identical, assume that the n-th subcarrier is shared by kth user, then makeWherein, symbolFor rounding downwards symbol; 4. _ 2, calculate kth user and increase the power increment needed for 1 bit on each subcarrier that it is shared, it is assumed that the n-th subcarrier is shared by kth user, then the power increment needed for kth user being increased by 1 bit on the n-th subcarrier is designated as e_k,n(r_k,n+ 1), $e_{k,n}(r_{k,n}+1)=(2^{r_{k,n}+1}-1){\mathrm{\σ}}_{k,n}^2\mathrm{\Γ}/H_{k,n}-(2^{r_{k,n}}-1){\mathrm{\σ}}_{k,n}^2\mathrm{\Γ}/H_{k,n};$ If the bit needed for 4. _ 3 kth users is all assigned, then directly perform step 4. _ 5; If the bit needed for kth user is not all assigned, then perform step 4. _ 4; 4. the minimum power increment in all power increments that kth user is corresponding and subcarrier corresponding to this minimum power increment _ 4, are first found out, it is assumed that this subcarrier is n-th^*Individual subcarrier, then distribute to n-th by 1 bit in remaining unappropriated all bits^*Individual subcarrier, then recalculates kth user n-th^*Individual subcarrier increases the power increment needed for 1 bitReturn again to step 4. _ 3 continue executing with; Wherein, n^*�� [1, N]; 4. _ 5, calculate kth user and reduce the power reduction needed for 1 bit on each subcarrier that it is shared, it is assumed that m-th subcarrier is shared by kth user, then the power reduction needed for kth user being reduced 1 bit on m-th subcarrier is designated as e_k,m(r_k,m), $e_{k,m}\left(r_{k,m}\right)=(2^{r_{k,m}}-1){\mathrm{\σ}}_{k,m}^2\mathrm{\Γ}/H_{k,m}-(2^{r_{k,m}-1}-1){\mathrm{\σ}}_{k,m}^2\mathrm{\Γ}/H_{k,m},$ Wherein, 1��m��N, r_k,mRepresent the speed that kth user reaches on m-th subcarrier,Represent kth user noise power on m-th subcarrier, H_k,mRepresent kth user channel gain on m-th subcarrier;4. the minimum power increment in all power increments that kth user is corresponding _ 6, is found out, and find out the peak power decrement in all power reduction that kth user is corresponding, it is assumed that minimum power increment corresponding to kth user is the power increment e that kth user increases needed for 1 bit on the i-th subcarrier that it is shared_k,i(r_k,i+ 1) the peak power decrement that, kth user is corresponding is the power reduction e that kth user reduces by 1 bit on the jth subcarrier that it is shared_k,j(r_k,j), if then e_k,j(r_k,j)>e_k,i(r_k,i+ 1), then perform step 4. _ 7; If e_k,j(r_k,j)��e_k,i(r_k,i+ 1), then perform step 4. _ 8; Above-mentioned, i �� [1, m_k], j �� [1, m_k], i �� j; 4. _ 7,1 bit on jth subcarrier is loaded on i-th subcarrier; Then recalculate kth user on the i-th subcarrier that it is shared, increase the power increment e needed for 1 bit_k,i(r_k,i+ 1) the power reduction e and needed for minimizing 1 bit_k,i(r_k,i), kth user on the jth subcarrier that it is shared, increase the power increment e needed for 1 bit_k,j(r_k,j+ 1) the power reduction e and needed for minimizing 1 bit_k,j(r_k,j), in the process recalculated, if the number of the bit on jth subcarrier is 0, then directly make e_k,j(r_k,j)=0, if the number of the bit on i-th subcarrier is b, then directly makes e_k,i(r_k,i+ 1)=��; It is then returned to step 4. _ 6 continue executing with, to complete bit exchange in the constant situation of total bit ensureing kth user distribution; Above-mentioned, �� represents infinitely great; 4. _ 8, according to water-filling algorithm, the power that kth user distributes on each subcarrier that it is shared is calculated, it is assumed that the n-th subcarrier shared by kth user, then calculates the power p that kth user distributes on the n-th subcarrier_k,n, $p_{k,n}=(2^{r_{k,n}}-1){\mathrm{\σ}}_{k,n}^2\mathrm{\Γ}/H_{k,n}.$

Described step 2. in set all subcarriers in multi-user's electric line communication system and all adopt quadrature amplitude modulation and the bit error rate identical, then the signal to noise ratio difference on each subcarrier is identical, namelyQ^-1() is the inverse function of Q (), the right tail function that Q () is standard normal distribution, P_eRepresent the bit error rate of each subcarrier.

The detailed process of described step 3. _ 2 is:

3. _ 2a, make �� represent all subcarriers sequence number constitute set, ��=1,2 ..., N}; And make ��_kThe set that the sequence number of the subcarrier that expression kth user is assigned to is constituted, ��_kInitial value be empty set, 1��k��K; Make c_kThe sum of the subcarrier that expression kth user has been assigned to, c_kInitial value be 0;

3. _ 2b, orderN-th * subcarrier is distributed to kth user, wherein, n^*�� [1, N],Represent and take so that H_k,nThe maximum n value of value;

3. _ 2c, by n-th^*The sequence number n of individual subcarrier^*Delete from ��, and make ��_k=��_k��{n^*, make c_k=c_k+ 1, wherein, " �� " is set union symbol, c_k=c_kIn+1 "=" for assignment;

If 3. _ 2d c_kWith cm_kEqual, then show that the sum of the subcarrier that kth user has been assigned to has reached tentatively to distribute to the number of sub carrier wave of kth, terminate the subcarrier assigning process of kth user; If c_kLess than cm_k, then return step 3. _ 2b continues executing with.

Described step 3. _ 3 assumes n-th^*Individual subcarrier is remaining one of them unassigned subcarrier, then makeDetermine n-th^*Individual subcarrier distributes to kth^*Individual user, wherein, n^*�� [1, N], k^*�� [1, K],Represent that kth user is n-th^*Channel gain on individual subcarrier,Represent take so thatThe maximum k value of value.

Compared with prior art, it is an advantage of the current invention that: the inventive method is when ensureing fairness between user, introduce targeted rate ratio constraints, and substep carries out subcarrier distribution and bit and power allocation, namely first carry out subcarrier distribution according to each self-corresponding targeted rate ratio constraint factor of all users; All subcarriers shared by each user are carried out waiting bit distribution by the then targeted rate requirement according to each user; Then according to power minimization criteria, remaining bits is distributed to the subcarrier that needed for increasing by 1 bit, excess power is minimum;Finally distribute in the constant situation of total bit each user, between subcarrier, bit exchange is carried out according to bit exchange criterion, the inventive method not only ensure that the fairness between user, and according to bit exchange criterion, power distribution is made to reach optimum, so that total transmitting power of multi-user's electric line communication system reaches minimum.

Accompanying drawing explanation

Fig. 1 is the topological structure block diagram of multi-user's electric line communication system;

Fig. 2 closes in difference to adopt the inventive method to compare schematic diagram with the resource allocation performance of existing resource allocation methods under targeted rate;

Fig. 3 adopts the inventive method to compare schematic diagram with the resource allocation performance of existing resource allocation methods under different user quantity;

Fig. 4 be the inventive method totally realize block diagram.

Detailed description of the invention

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

Fig. 1 gives the topological structure block diagram of multi-user's electric line communication system, and the present invention proposes a kind of multi-user's electric line communication system resource allocation methods based on bit exchange on this basis, and it totally realizes block diagram as shown in Figure 4, and it comprises the following steps:

1. set in multi-user's electric line communication system and have K user, and set multi-user's electric line communication system employing OFDM (OrthogonalFrequencyDivisionMultiple) modulation technique, there is N number of subcarrier in each OFDM symbol, wherein, K > 1, N >=1.

2. according to theory of information knowledge, obtain the theoretical value of the speed that each user in multi-user's electric line communication system reaches on each subcarrier that it is shared, assume that the n-th subcarrier is shared by kth user, then be designated as r by the speed that kth user reaches on the n-th subcarrier_k,n, r_k,nTheoretical value beWherein, 1��k��K, 1��n��N, H_k,nRepresent kth user channel gain on the n-th subcarrier, P_k,nRepresent the power that kth user distributes on the n-th subcarrier, P_k,nValue given by multi-user's electric line communication system,Representing kth user noise power on the n-th subcarrier, �� represents the signal to noise ratio difference on the n-th subcarrier, and the value of �� is relevant with modulation system and the bit error rate.

Then build the minimum power problem in multi-user's electric line communication system, i.e. resource allocator model, be expressed as: $\begin{array}{cc}\min & \underset{k=1}{\overset{K}{\Σ}}\underset{n=1}{\overset{N}{\Σ}}{\mathrm{\β}}_{k,n}{p}_{k,n}\\ s.t.& C1:\underset{k=1}{\overset{K}{\Σ}}{\mathrm{\β}}_{k,n}=1,\∀n;\\ & C2:r_{k,n}\∈Z_0^b,\∀k,n;\\ & C3:\underset{n=1}{\overset{N}{\Σ}}{r}_{k,n}=R_k,\∀n;\underset{k=1}{\overset{K}{\Σ}}{R}_k=R;\\ & C4:R_1:R_2:\mathrm{...}:R_K={\mathrm{\γ}}_1:{\mathrm{\γ}}_2:\mathrm{...}{\mathrm{\γ}}_K;\end{array},$ Wherein, min represents " minimizing ", 1��k��K, 1��n��N, ��_k,nValue be 0 or be 1, ��_k,n=1 represents kth CU the n-th subcarrier, ��_k,n=0 represents vacant n-th subcarrier of kth user, p_k,nRepresenting the power that distributes on the n-th subcarrier of kth user, s.t. represents " constrained in ", symbolRepresent " arbitrarily ",Representing the set that is made up of all integers in 0��b, b represents the upper limit of the bit number that each user transmits on each subcarrier that it is shared, b=8, R in the present embodiment_kRepresenting the targeted rate requirement of kth user, R represents the conjunction targeted rate requirement of multi-user's electric line communication system, R₁Represent the targeted rate requirement of the 1st user, R₂Represent the targeted rate requirement of the 2nd user, R_KRepresent the targeted rate requirement of k-th user, ��₁����₂����_KIt is positive integer, ��₁Represent the targeted rate ratio constraint factor that the 1st user is corresponding, ��₂Represent the targeted rate ratio constraint factor that the 2nd user is corresponding, ��_KRepresenting the targeted rate ratio constraint factor that k-th user is corresponding, constraints C1 represents that each subcarrier at most can only shared by a user;Constraints C2 represents that each user speed on each subcarrier is the integer in 0��b; Constraints C3 represents that each user needs to meet its targeted rate requirement, and multi-user's electric line communication system need to meet it and close rate requirement; Constraints C4 represents that the targeted rate between each user need to meet non-linear ratio's constraint.

In this particular embodiment, step 2. in set all subcarriers in multi-user's electric line communication system and all adopt quadrature amplitude modulation and the bit error rate identical, then the signal to noise ratio difference on each subcarrier is identical, namelyQ^-1() is the inverse function of Q (), the right tail function that Q () is standard normal distribution, P_eRepresent the bit error rate of each subcarrier.

3. number of sub carrier wave is distributed for each user, and distribute subcarrier for each user, detailed process is: 3. _ 1, according to each self-corresponding targeted rate ratio constraint factor of all users, tentatively distribute number of sub carrier wave for each user, the number of sub carrier wave tentatively distributing to kth user is designated as cm_k,Wherein, symbolFor rounding downwards symbol, ��_kRepresent the targeted rate ratio constraint factor that kth user is corresponding; 3. _ 2, under the principle preferentially subcarrier being distributed to the user making its channel gain maximum, the subcarrier that channel condition is best is distributed for each user, until the sum of subcarrier that each user is assigned to reaches tentatively to distribute to the number of sub carrier wave of this user, in the assignment procedure, it is necessary to assure each subcarrier can only distribute to a user; 3. _ 3, generallyAfter carrying out the distribution of subcarrier of step 3. _ 2, still haveIndividual subcarrier remains, remaining unassigned each subcarrier is distributed to the user making its channel gain maximum with the form of sub-carrier selection user, then add up the sum of the subcarrier finally distributing to each user, the sum finally distributing to the subcarrier of kth user is designated as m_k, m_k��cm_k��

In this particular embodiment, the detailed process of step 3. _ 2 is:

3. _ 2a, make �� represent all subcarriers sequence number constitute set, ��=1,2 ..., N}; And make ��_kThe set that the sequence number of the subcarrier that expression kth user is assigned to is constituted, ��_kInitial value be empty set, 1��k��K; Make c_kThe sum of the subcarrier that expression kth user has been assigned to, c_kInitial value be 0;

3. _ 2b, orderBy n-th^*Individual subcarrier distributes to kth user, wherein, and n^*�� [1, N],Represent and take so that H_k,nThe maximum n value of value;

3. _ 2c, by n-th^*The sequence number n of individual subcarrier^*Delete from ��, and make ��_k=��_k��{n^*, make c_k=c_k+ 1, wherein, " �� " is set union symbol, c_k=c_kIn+1 "=" for assignment;

If 3. _ 2d c_kWith cm_kEqual, then show that the sum of the subcarrier that kth user has been assigned to has reached tentatively to distribute to the number of sub carrier wave of kth, terminate the subcarrier assigning process of kth user; If c_kLess than cm_k, then return step 3. _ 2b continues executing with.

In this particular embodiment, step 3. _ 3 assumes n-th^*Individual subcarrier is remaining one of them unassigned subcarrier, then makeDetermine n-th^*Individual subcarrier distributes to kth^*Individual user, wherein, n^*�� [1, N], k^*�� [1, K],Represent that kth user is n-th^*Channel gain on individual subcarrier,Represent take so thatThe maximum k value of value.

4. each subcarrier distribution bit shared by each user, and calculate the power that each user distributes on each subcarrier that it is shared;For kth user, each subcarrier distribution bit shared by kth user, and the detailed process calculating the power that kth user distributes on each subcarrier that it is shared is: 4. _ 1, the targeted rate requirement according to kth user, carry out all subcarriers shared by kth user waiting bit distribution, make the speed that kth user reaches on each subcarrier that it is shared identical, assume that the n-th subcarrier is shared by kth user, then makeWherein, symbolFor rounding downwards symbol; 4. _ 2, calculate kth user and increase the power increment needed for 1 bit on each subcarrier that it is shared, it is assumed that the n-th subcarrier is shared by kth user, then the power increment needed for kth user being increased by 1 bit on the n-th subcarrier is designated as e_k,n(r_k,n+ 1), $e_{k,n}(r_{k,n}+1)=(2^{r_{k,n}+1}-1){\mathrm{\σ}}_{k,n}^2\mathrm{\Γ}/H_{k,n}-(2^{r_{k,n}}-1){\mathrm{\σ}}_{k,n}^2\mathrm{\Γ}/H_{k,n};$ If the bit needed for 4. _ 3 kth users is all assigned, then directly perform step 4. _ 5; If the bit needed for kth user is not all assigned, then perform step 4. _ 4; 4. the minimum power increment in all power increments that kth user is corresponding and subcarrier corresponding to this minimum power increment _ 4, are first found out, it is assumed that this subcarrier is n-th^*Individual subcarrier $(n^{*}=\arg \underset{1\≤n\≤N}{min}\left(e_{k,n}\left(r_{k,n}+1\right)\right),\arg \underset{1\≤n\≤N}{min}\left(e_{k,n}\left(r_{k,n}+1\right)\right)$ Represent and make e_k,n(r_k,n+ 1) n value during minima is taken), then 1 bit in remaining unappropriated all bits is distributed to n-th^*Individual subcarrier, then recalculates kth user n-th^*Individual subcarrier increases the power increment needed for 1 bitReturn again to step 4. _ 3 continue executing with; Wherein, n^*�� [1, N]; 4. _ 5, calculate kth user and reduce the power reduction needed for 1 bit on each subcarrier that it is shared, it is assumed that m-th subcarrier is shared by kth user, then the power reduction needed for kth user being reduced 1 bit on m-th subcarrier is designated as e_k,m(r_k,m), $e_{k,m}\left(r_{k,m}\right)=(2^{r_{k,m}}-1){\mathrm{\σ}}_{k,m}^2\mathrm{\Γ}/H_{k,m}-(2^{r_{k,m}-1}-1){\mathrm{\σ}}_{k,m}^2\mathrm{\Γ}/H_{k,m},$ Wherein, 1��m��N, r_k,mRepresent the speed that kth user reaches on m-th subcarrier,Represent kth user noise power on m-th subcarrier, H_k,mRepresent kth user channel gain on m-th subcarrier; 4. the minimum power increment in all power increments that kth user is corresponding _ 6, is found out, and find out the peak power decrement in all power reduction that kth user is corresponding, it is assumed that minimum power increment corresponding to kth user is the power increment e that kth user increases needed for 1 bit on the i-th subcarrier that it is shared_k,i(r_k,i+ 1) the peak power decrement that, kth user is corresponding is the power reduction e that kth user reduces by 1 bit on the jth subcarrier that it is shared_k,j(r_k,j), if then e_k,j(r_k,j)>e_k,i(r_k,i+ 1), then perform step 4. _ 7; If e_k,j(r_k,j)��e_k,i(r_k,i+ 1), then perform step 4. _ 8; Above-mentioned, i �� [1, m_k], j �� [1, m_k], i �� j; 4. _ 7,1 bit on jth subcarrier is loaded on i-th subcarrier; Then recalculate kth user on the i-th subcarrier that it is shared, increase the power increment e needed for 1 bit_k,i(r_k,i+ 1) the power reduction e and needed for minimizing 1 bit_k,i(r_k,i), kth user on the jth subcarrier that it is shared, increase the power increment e needed for 1 bit_k,j(r_k,j+ 1) the power reduction e and needed for minimizing 1 bit_k,j(r_k,j), in the process recalculated, if the number of the bit on jth subcarrier is 0, then directly make e_k,j(r_k,j)=0, if the number of the bit on i-th subcarrier is b, then directly makes e_k,i(r_k,i+ 1)=��; It is then returned to step 4. _ 6 continue executing with, to complete bit exchange in the constant situation of total bit ensureing kth user distribution; Above-mentioned, �� represents infinitely great; 4. _ 8, according to water-filling algorithm, the power that kth user distributes on each subcarrier that it is shared is calculated, it is assumed that the n-th subcarrier shared by kth user, then calculates the power p that kth user distributes on the n-th subcarrier_k,n, $p_{k,n}=(2^{r_{k,n}}-1){\mathrm{\σ}}_{k,n}^2\mathrm{\Γ}/H_{k,n}.$

Below by way of Computer Simulation, further illustrate feasibility and the effectiveness of the inventive method.

Assume that power line channel multipath model selects classical four footpath channel model, i.e. M=4, and set a₀=0, a₁=7.8 �� 10^-10Second/rice, ��=1, g₁=0.64, g₂=0.38, g₃=-0.15, g₄=0.05, d₁=200.0 meters, d₂=222.4 meters, d₃=244.8 meters, d₄=267.5 meters, v_p=1.5 �� 10^-8Meter per second, the frequency band range of multi-user's electric line communication system is 0��20MHz, and the number of subcarrier is 128, i.e. N=128, and the bit error rate is P_e=10^-4,Q^-1() is the inverse function of Q () function, the right tail function that Q () is standard normal distribution, $Q\left(x\right)=\underset{x}{\overset{+\mathrm{\∞}}{\∫}}\frac{1}{\sqrt{2\mathrm{\π}}}\exp (-\frac{1}{2}{t}^2)dt,Q\left(x\right)=\underset{x}{\overset{+\mathrm{\∞}}{\∫}}\frac{1}{\sqrt{2\mathrm{\π}}}\exp (-\frac{1}{2}{t}^2)dt$ In x represent the input parameter of Q (), exp () represents that t is integration variable, P with the natural radix e exponential function being the end_eRepresenting the bit error rate requirement of each subcarrier, on subcarrier, the maximum number bits of distribution is 8.

In order to obtain more stable reliable simulation result, simulation result is averaged through 1000 Monte-Carlo (Monte Carlo) emulation and obtains.

Fig. 2 gives the inventive method and algorithm (1) under different conjunction targeted rate, and (this algorithm first requires to carry out number of sub carrier wave distribution according to ownership goal speed and conjunction targeted rate, then the user that channel condition is best is assigned subcarriers to, finally obtain the closed solutions of suboptimization bit distribution), (this algorithm is first pre-assigned to user on-demand for subcarrier with channel condition to algorithm (2), optimally distribute bit and power further according to genetic algorithm, and reduce its amount of calculation) resource allocation performance compare. In this simulation process, number of users is 6, i.e. K=6, and the targeted rate ratio constraint factor of its correspondence is ��₁:��₂:��₃:��₄:��₅:��₆=2:2:3:3:5:5. From figure 2 it can be seen that for a fixing conjunction targeted rate, adopt total transmitting power of the inventive method to consume minimum; Along with closing being continuously increased of targeted rate, adopt total transmitting power consumption of each method all to increase to some extent, but total transmitting power curve of employing the inventive method is always situated in bottom. This demonstrate and close under targeted rate in difference, compare existing method, adopt total transmitting power consumption of the inventive method to be always up minimum.

Fig. 3 gives the inventive method and algorithm (1) under different user quantity, and (this algorithm first requires to carry out number of sub carrier wave distribution according to ownership goal speed and conjunction targeted rate, then the user that channel condition is best is assigned subcarriers to, finally obtain the closed solutions of suboptimization bit distribution), (this algorithm is first pre-assigned to user on-demand for subcarrier with channel condition to algorithm (2), optimally distribute bit and power further according to genetic algorithm, and reduce its amount of calculation) resource allocation performance compare. In this simulation process, conjunction targeted rate is 500bits/s/Hz, and the targeted rate ratio constraint factor of its correspondence is ��₁:��₂:��:��_K=1:1: ...: 1. From figure 3, it can be seen that for a fixing number of users, adopt total transmitting power of the inventive method to consume minimum; Along with being continuously increased of number of users, the total transmitting power consumption adopting each method is all in rising trend, but, comparatively speaking, adopt total transmitting power of the inventive method to consume increasing degree minimum.

It is feasible and effective that above-mentioned simulation analysis fully indicates the inventive method.

Claims (4)

1. the multi-user's electric line communication system resource allocation methods based on bit exchange, it is characterised in that comprise the following steps:

1. set in multi-user's electric line communication system and have K user, and set multi-user's electric line communication system employing OFDM modulation technique, in each OFDM symbol, have N number of subcarrier, wherein, K > 1, N >=1;

2. according to theory of information knowledge, obtain the theoretical value of the speed that each user in multi-user's electric line communication system reaches on each subcarrier that it is shared, assume that the n-th subcarrier is shared by kth user, then be designated as r by the speed that kth user reaches on the n-th subcarrier_k,n, r_k,nTheoretical value beWherein, 1��k��K, 1��n��N, H_k,nRepresent kth user channel gain on the n-th subcarrier, P_k,nRepresent the power that kth user distributes on the n-th subcarrier,Representing kth user noise power on the n-th subcarrier, �� represents the signal to noise ratio difference on the n-th subcarrier;

Then build the minimum power problem in multi-user's electric line communication system, be expressed as:

C4:R₁:R₂:...:R_K=��₁:��₂:...��_K; , wherein, min represents " minimizing ", 1��k��K, 1��n��N,

��_k,nValue be 0 or be 1, ��_k,n=1 represents kth CU the n-th subcarrier, ��_k,n=0 represents vacant n-th subcarrier of kth user, p_k,nRepresenting the power that distributes on the n-th subcarrier of kth user, s.t. represents " constrained in ", symbolRepresent " arbitrarily ",Representing the set that is made up of all integers in 0��b, b represents the upper limit of the bit number that each user transmits on each subcarrier that it is shared, R_kRepresenting the targeted rate requirement of kth user, R represents the conjunction targeted rate requirement of multi-user's electric line communication system, ��₁����₂����_KIt is positive integer, ��₁Represent the targeted rate ratio constraint factor that the 1st user is corresponding, ��₂Represent the targeted rate ratio constraint factor that the 2nd user is corresponding, ��_KRepresenting the targeted rate ratio constraint factor that k-th user is corresponding, constraints C1 represents that each subcarrier at most can only shared by a user; Constraints C2 represents that each user speed on each subcarrier is the integer in 0��b; Constraints C3 represents that each user needs to meet its targeted rate requirement, and multi-user's electric line communication system need to meet it and close rate requirement; Constraints C4 represents that the targeted rate between each user need to meet non-linear ratio's constraint;

3. number of sub carrier wave is distributed for each user, and distribute subcarrier for each user, detailed process is: 3. _ 1, according to each self-corresponding targeted rate ratio constraint factor of all users, tentatively distribute number of sub carrier wave for each user, the number of sub carrier wave tentatively distributing to kth user is designated as cm_k,Wherein, symbolFor rounding downwards symbol, ��_kRepresent the targeted rate ratio constraint factor that kth user is corresponding; 3. _ 2, under the principle preferentially subcarrier being distributed to the user making its channel gain maximum, distribute, for each user, the subcarrier that channel condition is best, until the sum of subcarrier that each user is assigned to reaches tentatively to distribute to the number of sub carrier wave of this user; 3. _ 3, remaining unassigned each subcarrier is distributed to the user making its channel gain maximum with the form of sub-carrier selection user, then add up the sum of the subcarrier finally distributing to each user, the sum finally distributing to the subcarrier of kth user is designated as m_k;

4. each subcarrier distribution bit shared by each user, and calculate the power that each user distributes on each subcarrier that it is shared; For kth user, each subcarrier distribution bit shared by kth user, and the detailed process calculating the power that kth user distributes on each subcarrier that it is shared is: 4. _ 1, the targeted rate requirement according to kth user, carry out all subcarriers shared by kth user waiting bit distribution, make the speed that kth user reaches on each subcarrier that it is shared identical, assume that the n-th subcarrier is shared by kth user, then makeWherein, symbolFor rounding downwards symbol;4. _ 2, calculate kth user and increase the power increment needed for 1 bit on each subcarrier that it is shared, it is assumed that the n-th subcarrier is shared by kth user, then the power increment needed for kth user being increased by 1 bit on the n-th subcarrier is designated as e_k,n(r_k,n+ 1),If the bit needed for 4. _ 3 kth users is all assigned, then directly perform step 4. _ 5; If the bit needed for kth user is not all assigned, then perform step 4. _ 4; 4. the minimum power increment in all power increments that kth user is corresponding and subcarrier corresponding to this minimum power increment _ 4, are first found out, it is assumed that this subcarrier is n-th^*Individual subcarrier, then distribute to n-th by 1 bit in remaining unappropriated all bits^*Individual subcarrier, then recalculates kth user n-th^*Individual subcarrier increases the power increment needed for 1 bitReturn again to step 4. _ 3 continue executing with; Wherein, n^*�� [1, N]; 4. _ 5, calculate kth user and reduce the power reduction needed for 1 bit on each subcarrier that it is shared, it is assumed that m-th subcarrier is shared by kth user, then the power reduction needed for kth user being reduced 1 bit on m-th subcarrier is designated as e_k,m(r_k,m),Wherein, 1��m��N, r_k,mRepresent the speed that kth user reaches on m-th subcarrier,Represent kth user noise power on m-th subcarrier, H_k,mRepresent kth user channel gain on m-th subcarrier; 4. the minimum power increment in all power increments that kth user is corresponding _ 6, is found out, and find out the peak power decrement in all power reduction that kth user is corresponding, it is assumed that minimum power increment corresponding to kth user is the power increment e that kth user increases needed for 1 bit on the i-th subcarrier that it is shared_k,i(r_k,i+ 1) the peak power decrement that, kth user is corresponding is the power reduction e that kth user reduces by 1 bit on the jth subcarrier that it is shared_k,j(r_k,j), if then e_k,j(r_k,j)>e_k,i(r_k,i+ 1), then perform step 4. _ 7; If e_k,j(r_k,j)��e_k,i(r_k,i+ 1), then perform step 4. _ 8; Above-mentioned, i �� [1, m_k], j �� [1, m_k], i �� j; 4. _ 7,1 bit on jth subcarrier is loaded on i-th subcarrier; Then recalculate kth user on the i-th subcarrier that it is shared, increase the power increment e needed for 1 bit_k,i(r_k,i+ 1) the power reduction e and needed for minimizing 1 bit_k,i(r_k,i), kth user on the jth subcarrier that it is shared, increase the power increment e needed for 1 bit_k,j(r_k,j+ 1) the power reduction e and needed for minimizing 1 bit_k,j(r_k,j), in the process recalculated, if the number of the bit on jth subcarrier is 0, then directly make e_k,j(r_k,j)=0, if the number of the bit on i-th subcarrier is b, then directly makes e_k,i(r_k,i+ 1)=��; It is then returned to step 4. _ 6 continue executing with, to complete bit exchange in the constant situation of total bit ensureing kth user distribution; Above-mentioned, �� represents infinitely great; 4. _ 8, according to water-filling algorithm, the power that kth user distributes on each subcarrier that it is shared is calculated, it is assumed that the n-th subcarrier shared by kth user, then calculates the power p that kth user distributes on the n-th subcarrier_k,n,

2. a kind of multi-user's electric line communication system resource allocation methods based on bit exchange according to claim 1, it is characterized in that all subcarriers setting in multi-user's electric line communication system during described step is 2. all adopt quadrature amplitude modulation and the bit error rate identical, then the signal to noise ratio difference on each subcarrier is identical, namelyQ^-1() is the inverse function of Q (), the right tail function that Q () is standard normal distribution, P_eRepresent the bit error rate of each subcarrier.

3. a kind of multi-user's electric line communication system resource allocation methods based on bit exchange according to claim 1 and 2, it is characterised in that the detailed process of described step 3. _ 2 is:

3. _ 2a, make �� represent all subcarriers sequence number constitute set, ��=1,2 ..., N}; And make ��_kThe set that the sequence number of the subcarrier that expression kth user is assigned to is constituted, ��_kInitial value be empty set, 1��k��K; Make c_kThe sum of the subcarrier that expression kth user has been assigned to, c_kInitial value be 0;

3. _ 2b, orderBy n-th^*Individual subcarrier distributes to kth user, wherein, and n^*�� [1, N],Represent and take so that H_k,nThe maximum n value of value;

3. _ 2c, by n-th^*The sequence number n of individual subcarrier^*Delete from ��, and make ��_k=��_k��{n^*, make c_k=c_k+ 1, wherein, " �� " is set union symbol, c_k=c_kIn+1 "=" for assignment;

If 3. _ 2d c_kWith cm_kEqual, then show that the sum of the subcarrier that kth user has been assigned to has reached tentatively to distribute to the number of sub carrier wave of kth, terminate the subcarrier assigning process of kth user; If c_kLess than cm_k, then return step 3. _ 2b continues executing with.

4. a kind of multi-user's electric line communication system resource allocation methods based on bit exchange according to claim 3, it is characterised in that assume n-th in described step 3. _ 3^*Individual subcarrier is remaining one of them unassigned subcarrier, then makeDetermine n-th^*Individual subcarrier distributes to kth^*Individual user, wherein, n^*�� [1, N], k^*�� [1, K],Represent that kth user is n-th^*Channel gain on individual subcarrier,Represent take so thatThe maximum k value of value.