CN105451322A - Channel allocation and power control method based on QoS in D2D network - Google Patents

Abstract

The invention provides a channel allocation and power control method based on subscriber's QoS. The channel allocation and power control method comprises the following steps: constructing a system model based on capacity maximum of D2D subscribers, and selecting a candidate cellular subscriber set meeting requirements for the D2D subscribers according to the minimal signal-interference-noise ratio requirement of the D2D subscribers; optimizing the transmission power of cellular subscribers and the D2D subscribers according to the method of Lagrange multipliers under the premises of meeting QoS requirements of the cellular subscribers and limiting subscriber's power; and calculating capacities of all the D2D subscribers according to the optimal transmission power of the subscribers, and allocating a channel to a D2D subscriber whose capacity is the largest, so as to realize D2D communication in a cellular network. Through joint optimization of subscriber's channel allocation and power control, the channel allocation and power control method has the advantages that each subscriber is allocated with optimal transmission power, and the channel is allocated to the D2D subscriber whose capacity is the largest, so that the energy loss of the cellular subscribers and the D2D subscribers is reduced, and the total capacity of the D2D subscribers is improved.

Description

A kind of channel allocation based on QoS and Poewr control method in D2D network

Technical field

The present invention relates to a kind of resource allocation methods, particularly relate to a kind of channel allocation based on user QoS and Poewr control method, belong to communication technical field.

Background technology

Along with developing rapidly of wireless communication technology, frequency spectrum resource shortage becomes mobile communication facing challenges.In conventional cellular network, do not allow direct communication between user.Communication process by base station transfer be divided into two stages: mobile terminal to base station, i.e. up link; Base station to mobile terminal, i.e. down link.This centralized working method is convenient to manage the interference of resource and control, but the level of resources utilization is low.The D2D communication technology is arisen at the historic moment in this context.

D2D communication is a kind of under cellular system controls, and allows short-range terminal user to carry out the new technology of direct communication by sharing local resource.Introduce D2D communication in cellular networks, base station burden can be alleviated, reduce communication delay.Compared with conventional cellular communication, D2D communication only takies the frequency spectrum resource of half.And in-plant D2D communication can reduce through-put power, energy efficient, increases the cruising time of mobile phone.D2D communication has obvious technical characteristic, and compared to short-range communication technique such as bluetooth and WLAN (wireless local area network) (WLAN), its maximum advantage is to be operated in mandate frequency range, and transfer of data has higher reliability.In addition, D2D communicates the coupling also not needing bluetooth and WLAN loaded down with trivial details like that, can provide better experience for user.

Cellular system, when distributing the D2D communication resource, can distribute the frequency spectrum resource of user in special, orthogonal with community user or reuse pattern.When cell load is lower, when having remaining frequency spectrum resource after meeting cell user communication, can distribute quadrature spectrum resource to D2D user, the two can not disturb mutually.When cell load is higher, the resource of D2D user reuse pattern user.Now sharing the phone user of same resource and D2D user can interference mutually, and the allocated channel that base station is communicated by control D2D and transmitted power control the interference brought community.Therefore for user distributes the interference between rational resource reduction user, improving entire system performance is a current study hotspot.The present invention, ensureing under phone user and D2D user's qos requirement, phone user's transmitted power is limited and D2D user's gross power is limited condition, constructs with the maximum majorized function turning to target of D2D user capacity.Adopt the transmitted power of method of Lagrange multipliers to phone user and D2D user to be optimized distribution, and communicate for D2D user distributes rational channel.Have and reduce user's energy consumption expense, improve the advantage of D2D user's total capacity.

Summary of the invention

Technical problem: the object of this invention is to provide a kind of channel allocation based on QoS and Poewr control method, by optimizing the transmitted power of phone user and D2D user, saves user's energy; And distribute rational channel for D2D user, reduce the interference between phone user and D2D user, improve the systematic function of D2D communication in cellular network.

Technical scheme: based on the channel allocation of QoS and Poewr control method in D2D network of the present invention, comprise the following steps:

1) use C={1 respectively, 2 ..., M} and D={1,2 ..., N} represents that phone user collects and D2D user's collection, and M be phone user's number, N be D2D to number of users, K represents number of available channels, defines S and represents the channel set of the multiplexing phone user of D2D user;

2) D2D user j (1≤j≤N) Signal to Interference plus Noise Ratio on channel k (1≤k≤K) is calculated p in formula _totfor the total transmitted power of D2D user, g _jfor D2D user is to the channel gain of j, N ₀represent noise power, represent the maximum transmit power of phone user, h _i,jrepresent the channel gain between phone user i and D2D user j;

3) according to the minimum Signal to Interference plus Noise Ratio requirement of D2D user j be included in set omega by the channel k met the demands, wherein Ω is the candidate channel set of D2D user, represent the Signal to Interference plus Noise Ratio threshold value of D2D user;

4) initialization t=1 and λ (t)=2, wherein t is iterations, and λ is Lagrange multiplier;

5) according to formula ${\tilde{p}}_{j,k}^d={\[\frac{\sqrt{\mathrm{\Δ}}}{2{g_{i,B}}^2\·B(g_j+B)}-\frac{A}{2B}-\frac{A}{2(g_j+B)}\]}_0^{\mathrm{\τ}}$ Calculate D2D user j (1≤j≤N) transmitted power on channel k (k ∈ Ω), wherein ${\[\·\]}_x^y=\min \left(max\right(\·,),y),\mathrm{\τ}=\frac{1}{h_{j,B}}(\frac{g_{i,B}}{{\mathrm{\γ}}_{th}^c}\·P_{max}^c-N_0),$ H in formula _j,Brepresent the channel gain between D2D user j and base station, g _i,Brepresent the channel gain between phone user i and base station, for the Signal to Interference plus Noise Ratio threshold value of phone user; And $\mathrm{\Δ}=g_j{g_{i,B}}^{2}A(g_j{g_{i,B}}^{2}A+\frac{4}{\mathrm{\λ}ln2}{g_{i,B}}^{2}B(g_j+B\left)\right),$ Wherein $A=N_0\·(1+\frac{{\mathrm{\γ}}_{th}^c\·h_{i,j}}{g_{i,B}}),B=\frac{{\mathrm{\γ}}_{th}^c\·h_{j,B}\·h_{i,j}}{g_{i,B}};$

6) according to described step 5) in the transmitted power of D2D user j (1≤j≤N) that obtains will substitute into formula in, obtain the transmitted power of phone user i (1≤i≤M);

7) according to formula calculate D2D user j (1≤j≤N) capacity on channel k (1≤k≤K), and channel k is distributed to be worth maximum D2D user j*, then channel k is included into D2D user's multipling channel S set;

8) according to formula with t=t+1 respectively iteration upgrade λ (t) and t, θ (t) they are step series, and the conventional expression formula of θ (t) is or in formula, η is constant;

9) according to described step 8) in the λ (t) that obtains, repeat described step 5) to 8), until satisfy condition | λ (t+1)-λ (t) |≤exp, wherein exp is the constant that a numerical value is very little, and value is exp=10 ^-8.

In combined optimization cellular network of the present invention, the power of D2D communication controls and channel allocation, according to the minimum Signal to Interference plus Noise Ratio requirement of phone user and D2D user, by building with the maximum Optimized model turning to target of D2D user capacity.Adopt method of Lagrange multipliers to solve the optimum transmit power of D2D user and phone user, and calculate D2D user capacity according to user's optimum transmit power, by channel allocation to the maximum D2D user of capability value.Achieve optimal resource allocation, the interference between phone user and D2D user can be reduced, reduce the energy expense of phone user and D2D user, improve D2D user capacity and network spectrum utilance.

Beneficial effect

The present invention compared with prior art, has the following advantages:

1. the inventive method turns to optimization aim so that D2D user capacity is maximum, carries out optimum allocation to the transmitted power of phone user and D2D user, and compared with constant power distribution method, energy distribution is optimized rationally more, avoids the energy dissipation of phone user and D2D user.

2. be different from traditional resource allocation methods, the combined optimization channel allocation that the present invention proposes and Poewr control method can be user's optimal scheme resource, thus greatly improve the availability of frequency spectrum, also improve network performance.

3. channel allocation of the present invention and Poewr control method are under the QoS condition ensureing phone user and D2D user, can improve the D2D user capacity under different phone user's number, reduce power consumption and the expense of user, thus serve better for user provides.

Accompanying drawing explanation

Fig. 1 is the schematic flow sheet of the inventive method.

Fig. 2 is the network model schematic diagram of the inventive method.

Fig. 3 is the D2D user capacity comparison diagram under different resource allocative decision.

Fig. 4 is the D2D user capacity variation diagram along with D2D increases spacing.

Specific implementation method

Below in conjunction with embodiment and Figure of description, the technical scheme to invention is described in detail:

The D2D traffic model of shared cellular system uplink resource of the present invention as shown in Figure 2, it is positioned at the base station of center of housing estate by one, M the phone user and the N that are randomly distributed in community form D2D user, and use C={1 respectively, 2 .., M} and D={1,2 ..., N} represents that phone user collects and collects with D2D user.Definition comprises the array of M × K variable and N × K variable, is respectively used to the transmitted power depositing phone user and D2D user, and initialization array P _c=Ο _{m × K}and P _d=Ο _{n × K}.Phone user i (1≤i≤M) busy channel k (1≤k≤K) communicates, multiplexing K the channel having distributed to phone user of D2D user, and wherein K represents number of available channels, and definition S is the multiplexing phone user's channel set of D2D user.

On channel k, phone user i sends signal x to base station _c,i, the transmission signal of D2D user j is x _d,j, the Received signal strength of signal and D2D user j that base station receives phone user i is respectively:

$y_{c,i}=\sqrt{p_{i,k}^c}{g}_{i,B}{x}_{c.i}+\sqrt{p_{j,k}^c}{g}_{j,B}{x}_{c,j}+n_1---\left(1\right)$

$y_{d,j}=\sqrt{p_{j,k}^d}{g}_j{x}_{d,j}+\sqrt{p_{i,k}^c}{h}_{i,j}{x}_{c.i}+n_2---\left(2\right)$

Wherein with that the transmitted power of the phone user i of shared channel k and D2D are to the transmitted power of j transmitting terminal respectively.G _i,Brepresent the channel gain between phone user i and base station, g _i,Bg can be expressed as _i,B=κ d _i,B ^-α| g ₀| ², in formula, d _i,Bbe the distance between phone user i transmitting terminal to base station, κ and α is channel fading constant and the channel fading factor respectively, g ₀obey average to be 0 variance be the complex exponential distribution of 1.Same, the channel gain g of D2D user j transmitting terminal and receiving terminal can be obtained _j, the channel gain h between D2D user j and base station _j,B, take the channel gain h between the phone user i of same channel and D2D user j _i,j.N ₁and n ₂that phone user is to the additive white Gaussian noise on base station link and D2D receiving terminal link respectively.Without loss of generality, suppose that all communication links all have identical noise power N ₀.

According to calculate D2D user j (1≤j≤N) Signal to Interference plus Noise Ratio on channel k (1≤k≤K), will satisfy condition the channel k that takies of phone user i be included into set omega, otherwise be not included into set omega, wherein Ω is the candidate channel set of D2D user, namely ${\mathrm{\Ω}}_j=\left\{k\right|{\mathrm{\Γ}}_{j,k}^d>{\mathrm{\γ}}_{th}^d,k=i,i=1,2,\mathrm{...},M\},\∀j\∈D$ And Ω={ Ω _j| j=1,2 ..., N}.P _totrepresent total transmitted power of D2D user, the maximum transmit power of phone user, represent the Signal to Interference plus Noise Ratio threshold value of D2D user.The present invention, to maximize D2D user capacity, builds following optimization aim problem:

$\underset{\{p_{i,k}^c,p_{j,k}^d,{\mathrm{\π}}_{j,k}\}}{\max }\underset{k\∈\mathrm{\Ω}}{\Σ}\underset{j\∈D}{\Σ}{\log }_2(1+\frac{p_{j,k}^d{g}_j}{N_0+p_{i,k}^c{h}_{i,j}})\·{\mathrm{\π}}_{j,k}---\left(3\right)$

Subjectto:

$0\≤p_{i,k}^c\≤P_{max}^c,\∀i\∈C---\left(4\right)$

$p_{j,k}^d\·h_{j,B}-\frac{p_{i,k}^c\·g_{i,B}}{{\mathrm{\γ}}_{th}^c}+N_0\≤0---\left(5\right)$

$\underset{k\∈\mathrm{\Ω}}{\Σ}\underset{j\∈D}{\Σ}{\mathrm{\π}}_{j,k}\·p_{j,k}^d\≤P_{tot}---\left(6\right)$

$\underset{j\∈D}{\Σ}{\mathrm{\π}}_{j,k}\≤1,{\mathrm{\π}}_{j,k}\∈\{0,1\},k=1,2,\mathrm{...},K---\left(7\right)$

Wherein with be respectively the transmitted power of phone user i and D2D user j on channel k, π _j,kthe Channel assignment factor, π _j,k=1 represents that channel k is multiplexing by D2D user j, π _j,k=0 represents that channel k is not multiplexing by D2D user j, the Signal to Interference plus Noise Ratio of phone user i on channel k, represent the Signal to Interference plus Noise Ratio threshold value of phone user.Formula (5) is by the minimum Signal to Interference plus Noise Ratio requirement of phone user transform and obtain.

Problem (3) relative to the Lagrangian of constraints (6) is:

$L\left(\right\{p_{i,k}^c,p_{j,k}^d,{\mathrm{\π}}_{j,k}\},\mathrm{\λ})=\underset{k\∈\mathrm{\Ω}}{\Σ}\underset{j\∈D}{\Σ}{\log }_2(1+\frac{p_{j,k}^d{g}_j}{N_0+p_{i,k}^c{h}_{i,j}}){\mathrm{\π}}_{j,k}-\mathrm{\λ}(\underset{k\∈\mathrm{\Ω}}{\Σ}\underset{j\∈D}{\Σ}{\mathrm{\π}}_{j,k}\·p_{j,k}^d-P_{tot})---\left(8\right)$

Wherein λ is Lagrange multiplier, and Lagrange duality function can be expressed as:

Wherein be defined as g _k(λ) be:

For given λ, formula (15) can be decomposed into K question of independence, the channel k that each problem correspondence one is given, the problem namely in formula (16). represent G when channel k being distributed to D2D user j _k(λ) value, now π _j,k=1.So for given λ, former majorized function can be converted into following expression:

$G_k^j\left(\mathrm{\λ}\right)=\underset{\{p_{i,k}^c,p_{j,k}^d\}}{\max }{\log }_2(1+\frac{p_{j,k}^d\·g_j}{N_0+p_{i.k}^c\·h_{i,j}})-\mathrm{\λ}\·p_{j,k}^d---\left(11\right)$

Subjectto:

$0\≤p_{i,k}^c\≤P_{max}^c---\left(12\right)$

$p_{j,k}^d\·h_{j,B}-\frac{p_{i,k}^c\·g_{i,B}}{{\mathrm{\γ}}_{th}^c}+N_0\≤0---\left(13\right)$

In the problems referred to above with coupling, can by decomposition method to this problem solving.For given the target function of (11) of can pinpointing the problems is monotonous descending function.The target function that this describes the problem (11) exists maximum can be reached when obtaining minimum value.Constraint (12) and (13) is rewritten as compacter form:

$\frac{{\mathrm{\γ}}_{th}^c}{g_{i,B}}(p_{j,k}^d\·h_{j,B}+N_0)\≤p_{i,k}^c\≤P_{\max }^c---\left(14\right)$

Therefore, optimum for:

${\tilde{p}}_{i,k}^c=\frac{{\mathrm{\γ}}_{th}^c}{g_{i,B}}(p_{j,k}^d\·h_{j,B}+N_0)---\left(15\right)$

Then as follows by problem (11) can be simplified in the target function of formula (15) substitution problem (11):

$G_k^j\left(\mathrm{\λ}\right)=\underset{p_{j,k}^d}{\max }{\log }_2(1+\frac{p_{j,k}^d\·g_j}{N_0(1+\frac{{\mathrm{\γ}}_{th}^c\·h_{i,j}}{g_{i,B}})+\frac{{\mathrm{\γ}}_{th}^c\·h_{j,B}\·h_{i,j}}{g_{i,B}}\·p_{j,k}^d})-\mathrm{\λ}\·p_{j,k}^d---\left(16\right)$

Subjectto:

$p_{j,k}^d\≤\frac{1}{h_{j,B}}(\frac{g_{i,B}}{{\mathrm{\γ}}_{th}^c}\·P_{\max }^c-N_0)---\left(17\right)$

Constraints (17) is transformed by constraints (14) and obtains, in order to prove that the problems referred to above are convex problem, in the derivation of equation (16) right second dervative, can obtain:

$\frac{d^2{G}_k^j\left(\mathrm{\λ}\right)}{d{\left(p_{j,k}^d\right)}^2}=\frac{-A\·g_j\·(A\·(2\·B+g_j)+2\·B(B+g_j)\·p_{j,k}^d)}{{(A+B\·p_{j,k}^d+g_j\·p_{j,k}^d)}^2\·{(A+B\·p_{j,k}^d)}^2}---\left(18\right)$

Wherein:

$A=N_0\·(1+\frac{{\mathrm{\γ}}_{th}^c\·h_{i,j}}{g_{i,B}})---\left(19\right)$

$B=\frac{{\mathrm{\γ}}_{th}^c\·h_{j,B}\·h_{i,j}}{g_{i,B}}---\left(20\right)$

Formula (18) perseverance is less than 0, so be convex function, optimal solution can be obtained by convex optimization method.

According to KKT condition, obtain right first derivative and make it equal 0 can obtaining:

$\frac{1}{\ln 2}\·\frac{g_j{g_{i,B}}^2\·A}{g_{i,B}\·A+g_{i,B}(g_j+B)\·p_{j,k}^d}\·\frac{1}{g_{i,B}\·A+g_{i,B}\·B\·p_{j,k}^d}-\mathrm{\λ}=0---\left(21\right)$

The optimum transmit power of D2D user is obtained by formula (21):

${\tilde{p}}_{j,k}^d={\[\frac{\sqrt{\mathrm{\Δ}}}{2{g_{i,B}}^2\·B(g_j+B)}-\frac{A}{2B}-\frac{A}{2(g_j+B)}\]}_0^{\mathrm{\τ}}---\left(22\right)$

Wherein ${\[\·\]}_x^y=min\left(max\right(\·,x),y),\mathrm{\τ}=\frac{1}{h_{j,B}}(\frac{g_{i,B}}{{\mathrm{\γ}}_{th}^c}\·P_{max}^c-N_0)$ And Δ has following expression:

$\mathrm{\Δ}=g_j{g_{i,B}}^2\·A\·(g_j{g_{i,B}}^2\·A+\frac{4}{\mathrm{\λ}\·ln2}\·{g_{i,B}}^2\·B(g_j+B\left)\right)---\left(23\right)$

Formula (22) is substituted in formula (15) optimum transmit power of phone user i on channel k can be obtained try to achieve optimum with afterwards, can in the hope of for:

$G_k^j\left(\mathrm{\λ}\right)={\log }_2(1+\frac{{\tilde{p}}_{j,k}^d\·g_j}{N_0+{\tilde{p}}_{i.k}^c\·h_{i,j}})-\mathrm{\λ}\·{\tilde{p}}_{j,k}^d---\left(24\right)$

Corresponding by all candidate D2D users trying to achieve channel k value, distributes to channel k be worth maximum D2D user j*, namely and π _{j*, k}=1, and channel k is included into S set.And on channel k, for D2D user j ≠ j*, its π _j,k=0, then can obtain the transmitted power collection of optimum phone user and D2D user with try to achieve all K channel afterwards, dual function G (λ) can try to achieve by through type (9).Finally, need to try to achieve optimum λ >=0 maximizing G (λ).Initialization t=1 and λ (t)=2, and λ carries out iteration renewal according to following formula:

$\mathrm{\λ}(t+1)=\mathrm{\λ}\left(t\right)-\mathrm{\θ}\left(t\right)(P_{tot}-\underset{k}{\Σ}\underset{j}{\Σ}{\tilde{p}}_{j,k}^d)---\left(25\right)$

θ (t) > 0 in formula is a series of step series, and some popular θ (t) selection rules are with wherein η is constant.

The present invention is based on the idiographic flow of the channel allocation of QoS and Poewr control method as shown in Figure 1.

In sum, the present invention is considering the qos requirement of phone user and D2D user, under phone user's power limited and the limited condition of D2D user's gross power, to maximize D2D user capacity for optimization aim, optimum allocation is carried out to the transmitted power of phone user and D2D user, and has distributed rational channel for D2D user.The D2D user capacity comparison diagram of the channel allocation that proposes of the present invention and Poewr control method and constant power resource allocation methods as shown in Figure 3.As can be seen from the figure the inventive method can obtain better systematic function; Be as shown in Figure 4 the present invention propose along with D2D user capacity when D2D user distance increases, and the design sketch compared with other resource allocation methods, as can be seen from the figure this method can improve D2D user capacity further.

Claims (1)

1. A kind of channel allocation based on QoS and Poewr control method in 1.D2D network, it is characterized in that, the method comprises the following steps:

   1) use C={1 respectively, 2 ..., M} and D={1,2 ..., N} represents that phone user collects and D2D user's collection, and M be phone user's number, N be D2D to number of users, K represents number of available channels, defines S and represents the channel set of the multiplexing phone user of D2D user;

   2) D2D user j (1≤j≤N) Signal to Interference plus Noise Ratio on channel k (1≤k≤K) is calculated p in formula _totfor the total transmitted power of D2D user, g _jfor D2D user is to the channel gain of j, N ₀represent noise power, represent the maximum transmit power of phone user, h _i,jrepresent the channel gain between phone user i and D2D user j;

   3) according to the minimum Signal to Interference plus Noise Ratio requirement of D2D user j be included in set omega by the channel k met the demands, wherein Ω is the candidate channel set of D2D user, represent the Signal to Interference plus Noise Ratio threshold value of D2D user;

   4) initialization t=1 and λ (t)=2, wherein t is iterations, and λ is Lagrange multiplier;

   5) according to formula ${\tilde{p}}_{j,k}^d={\[\frac{\sqrt{\mathrm{\Δ}}}{2{g_{i,B}}^2\·B(g_j+B)}-\frac{A}{2B}-\frac{A}{2(g_j+B)}\]}_0^{\mathrm{\τ}}$ Calculate D2D user j (1≤j≤N) transmitted power on channel k (k ∈ Ω), wherein ${\[\·\]}_x^y=min\left(max\right(\·,x),y),\mathrm{\τ}=\frac{1}{h_{j,B}}(\frac{g_{i,B}}{{\mathrm{\γ}}_{th}^c}\·P_{max}^c-N_0),$ H in formula _j,Brepresent the channel gain between D2D user j and base station, g _i,Brepresent the channel gain between phone user i and base station, for the Signal to Interference plus Noise Ratio threshold value of phone user; And $\mathrm{\Δ}=g_j{g_{i,B}}^{2}A(g_j{g_{i,B}}^{2}A+\frac{4}{\mathrm{\λ}ln2}{g_{i,B}}^{2}B(g_j+B\left)\right),$ Wherein $A=N_0\·(1+\frac{{\mathrm{\γ}}_{th}^c\·h_{i,j}}{g_{i,B}}),B=\frac{{\mathrm{\γ}}_{th}^c\·h_{j,B}\·h_{i,j}}{g_{i,B}};$

   6) according to described step 5) in the transmitted power of D2D user j (1≤j≤N) that obtains will substitute into formula in, obtain the transmitted power of phone user i (1≤i≤M);

   7) according to formula calculate D2D user j (1≤j≤N) capacity on channel k (1≤k≤K), and channel k is distributed to be worth maximum D2D user j*, then channel k is included into D2D user's multipling channel S set;

   8) according to formula with t=t+1 respectively iteration upgrade λ (t) and t, θ (t) they are step series, and the conventional expression formula of θ (t) is or in formula, η is constant;

   9) according to described step 8) in the λ (t) that obtains, repeat described step 5) to 8), until satisfy condition | λ (t+1)-λ (t) |≤exp, wherein exp is the constant that a numerical value is very little, and value is exp=10 ^-8.