CN104837110A - Transfer strategy realization method based on interruption performance improvement in cellular D2D communication system - Google Patents

Abstract

The invention discloses a transfer strategy realization method based on interruption performance improvement in a cellular D2D communication system. According to the method, a base station is taken as a bidirectional amplify-forward (AF) relay in the D2D system, and the base station performs normal communication with other cellular users. The concrete steps comprise that in a first time slot, a D2D user 1 sends signals to a D2D user 2 and the relay (base station) via a direct link and a relay link respectively, and the base station also receives uplink signals from the other cellular users; in a second time slot, the D2D user 2 sends signals to the D2D user 1 and the relay (base station) via the direct link and the relay link respectively, and the base station sends downlink signals to the other cellular users; and in a third time slot, the relay (base station) amplifies mixed signals received in the previous time slots and forwards the processed signals to the two D2D users. Compared with the traditional D2D communication, D2D communication provided by the invention is advantaged in that interference from the cellular users is inhibited, and the interruption performance of the system is greatly improved.

Description

Based on the transmission policy implementation method that interruption performance promotes in honeycomb D2D communication system

Technical field

The present invention relates to the transmission policy implementation method based on interruption performance lifting in honeycomb D2D communication system, belong to communication technical field.

Background technology

Along with the fast development of modern communication technology, the radix of mobile subscriber is more and more huger, but frequency spectrum resource is limited, and this proposes stern challenge to the utilance of frequency spectrum resource.In order to address this problem, the D2D communications field based on cellular network causes increasing concern.D2D communication based on cellular network not only can promote utilance and the cell throughout of frequency spectrum resource, and in shorter distance, achieve the transmitting of information with lower transmitted power.

Although D2D communication has significant superiority, still there is the problem of fail safe and harmful interference.Therefore, the research how security performance of junction network being incorporated into D2D link becomes a new probing direction.In junction network, information source can utilize the increase of not authentic amplification forwarding relaying to be directly transferred to the security information of destination node, when declining, even if listener-in has better average signal-to-noise ratio than legitimate receiver, still safe information transmission can be realized.And Human disturbance node can be introduced in junction network, send artificial interference noise fascination eavesdropping node by it, avoid information to become to be ravesdropping in transmitting procedure.

For the harmful interference how avoided under D2D communication environment, have recently been proposed many schemes.Such as suitably select cellular device and D2D user to share Radio Resource, under the prerequisite not reducing cellular link performance, reduce the interference to D2D recipient; Utilize transmitting power and the Radio Resource of cellular network control D2D link, controlled by suitable power, coordinate interference between two service equipments and make whole system performance boost; In based on the D2D communication of cellular network, introduce two-way decoding and forwarding (DF) relaying, utilize Pa Tuolei optimization method to coordinate the interference of D2D and cellular link, maximize and speed.But the lifting of these agreements disconnected performance in systems in which has some limitations.And the present invention can solve problem above well.

Summary of the invention

The object of the invention is to provide a kind of being applied in honeycomb D2D communication system based on the transmission policy implementation method that interruption performance promotes, the method is by forwarding (that is: AF) relaying using base station as a Bi-directional amplifier, D2D communication user is made to utilize the combination of direct link and repeated link two kinds of modes to intercourse information, achieve and reduce interchannel harmful interference, significantly improve the interruption performance of system.

The present invention solves the technical scheme that its technical problem takes: for honeycomb D2D communication system scene, the present invention proposes and base station is forwarded (that is: AF) relaying as the Bi-directional amplifier of D2D link, achieve the approximate form under the expression formula of D2D link down probability closing form under this strategy and high s/n ratio, under the restriction that total transmitted power is fixing, construct system optimal power distribution problems, utilize SQP (SQP) algorithm to obtain optimal value.

Method flow:

Step 1: the D2D communication system based on cellular network comprises a pair D2D user (that is: D2D user 1 and D2D user 2), Bi-directional amplifier relaying (that is: base station), phone user.They use D2D respectively ₁, D2D ₂, R and CU represents, D2D ₁, D2D ₂, the transmitted power of R and CU is respectively P ₁, P ₂, P _r, P _c.

Step 2: when the first time slot, phone user CU sends upward signal S _cto base station; And D2D user 1 sends signal S by repeated link in D2D link ₁to relaying R (that is: base station), send signal S by direct link simultaneously ₁to D2D user 2.Now for D2D link, relaying R (that is: base station) and D2D user 2 are subject to the interference from phone user CU.

Step 3: in the second time slot, base station sends downstream signal S _rto phone user CU; And D2D user 2 sends signal S by repeated link in D2D link ₂to relaying R (that is: base station), send signal S by direct link simultaneously ₂to D2D user 1.

Step 4: in the 3rd time slot, the mixed signal that the first two time slot receives is amplified by relaying R (that is: base station), and gain amplifier is the arithmetic square root that G, G are expressed as relaying transmitted power and the ratio of mixed signal power.Amplifying signal is sent to D2D user 1 and D2D user 2 by relaying R (base station) respectively.

Step 5: the signal received at the second time slot and the 3rd time slot according to D2D user 1, can obtain the reception Signal to Interference plus Noise Ratio of D2D user 1; According to the signal that D2D user 2 receives at the first time slot and the 3rd time slot, the reception Signal to Interference plus Noise Ratio of D2D user 2 can be obtained.

Step 6: the D2D user 1 determined according to above-mentioned steps 5 and the Signal to Interference plus Noise Ratio of D2D user 2, the outage probability P of definition D2D link _outfor: P _out=P [min (SINR ₁, SINR ₂)≤γ _th].Wherein SINR ₁for the Signal to Interference plus Noise Ratio of D2D user 1; SINR ₂for the Signal to Interference plus Noise Ratio of D2D user 2; γ _thfor the threshold value preset.

Step 7: according to the method for subregion integration, the outage probability P that above-mentioned steps 6 is defined _outthe form of two integration sums is decomposed into by integral domain.Obtain the results added of two integrations respectively, obtain the outage probability of the D2D transmission policy proposed.Consider that D2D user side in high s/n ratio situation will be far longer than the power of noise from the interference of phone user CU again, obtain the approximate form of system break probability under high s/n ratio.

Step 8: minimum for optimization aim with system break probability, proposes optimal power allocation problem, and optimization object is that D2D user is to the transmitted power P with relaying ₁, P ₂, P _r, constraints is P ₁+ P ₂+ P _r=P, wherein P is fixing total transmitted power.SQP (that is: SQP) algorithm is utilized to solve the optimal power allocation scheme of optimal value as system.

Said method of the present invention is applied in honeycomb D2D communication system.

Beneficial effect:

1, direct link and repeated link combine by the present invention, under guarantee phone user and D2D user share identical frequency spectrum resource prerequisite, reduce and affect the harmful interference of D2D link, increase the throughput of community.

2, the present invention is using base station as Bi-directional amplifier (that is: AF) relaying support transmission, and compared with traditional D2D communication strategy, interruption performance obtains and promotes significantly.

Accompanying drawing explanation

Fig. 1 is system model schematic diagram of the present invention.

Fig. 2 is method flow diagram of the present invention.

Embodiment

Below in conjunction with Figure of description, further detailed description is gone out to the invention.

As shown in Figure 1, honeycomb D2D communication system of the present invention comprise a pair D2D user, phone user, one as the base station of AF relaying, use D2D respectively ₁, D2D ₂, CU, R represent.Suppose a single cell scenario, channel condition is rayleigh fading channel, and all node work in a half-duplex mode, what be equipped with is single antenna, uplink and downlink channel is reciprocal constant, and in high s/n ratio situation, will be far longer than noise power from phone user to the interference of D2D link.

Use P _irepresent the transmitted power of i node, wherein i ∈ { 1,2, R, C}.For rayleigh fading channel, use h _ijrepresent that node i arrives the channel coefficients between node j, wherein i, j ∈ { 1,2, R, C}, i ≠ j.Because channel is reciprocal constant, there is h _ij=h _ji.The noise n of i (i ∈ { 1,2, R, C}) node _ibe assumed to be additive white Gaussian noise (AWGN), have n _i~ CN (0, N ₀).D _ijrepresent the distance between node i to node j, easily obtain d _ij=d _ji.α represents path fading coefficient.At j node from the received power of sending node i be use S _irepresent the transmission signal from node i (i ∈ { 1,2, R, C}).

Transmission policy provided by the invention comprises three time slots, in the first slot, and D2D ₁with transmitted power P ₁send signal S simultaneously ₁to relaying R (base station) and D2D ₂, phone user CU is with transmitted power P _csend signal S _cto relaying R (base station).Therefore the via node R (base station) of D2D link and D2D ₂be subject to the interference effect from CU, the first time slot is at D2D ₂, the Received signal strength of relaying R (base station) is expressed as:

$y_2\left(1\right)=\sqrt{P_{12}}{h}_{12}{S}_1+\sqrt{P_{C2}}{h}_{C2}{S}_2+n_2\left(1\right)---\left(1\right)$

$y_R\left(1\right)=\sqrt{P_{1R}}{h}_{1R}{S}_1+\sqrt{P_{\mathrm{CR}}}{h}_{\mathrm{CR}}{S}_2+n_R\left(1\right)---\left(2\right)$

Wherein in above-mentioned expression formula, (1) represents the first time slot in three time slots.

In the second time slot, D2D ₂with transmitted power P ₂send signal S simultaneously ₂to relaying R (base station) and D2D ₁, base station sends the downstream signal of cellular link to CU simultaneously.Second time slot is at D2D ₁be expressed as with the Received signal strength of relaying R (base station):

$y_1\left(2\right)=\sqrt{P_{21}}{h}_{21}{S}_2+n_1\left(2\right)---\left(3\right)$

$y_R\left(2\right)=\sqrt{P_{2R}}{h}_{2R}{S}_2+n_R\left(2\right)---\left(4\right)$

Wherein in above-mentioned expression formula, (2) represent the second time slot in three time slots.

Relaying R (base station), in conjunction with the Received signal strength of the first two time slot, amplifies mixed signal and is transmitted to two D2D users at the 3rd time slot simultaneously.In the mixed signal of relaying R (base station) be then:

$y_R=\sqrt{P_{1R}}{h}_{1R}{S}_1+\sqrt{P_{2R}}{h}_{2R}{S}_2+\sqrt{P_{\mathrm{CR}}}{h}_{\mathrm{CR}}{S}_C+n_R\left(1\right)+n_R\left(2\right)---\left(5\right)$

The amplification coefficient of relaying R (base station) is expressed as:

$G=\sqrt{\frac{P_R}{P_{1R}{\left|h_{1R}\right|}^2+P_{2R}{\left|h_{2R}\right|}^2+P_{\mathrm{CR}}{\left|h_{\mathrm{CR}}\right|}^2+2N_0}}---\left(6\right)$

Amplification coefficient G can guarantee that the transmitted power of relaying R (base station) is P _r.

In the 3rd time slot, D2D ₁, D2D ₂receive the amplification forwarding signal from relaying R (base station), be expressed as:

$y_1\left(3\right)=G{y}_R{h}_{R1}\sqrt{d_{R1}^{-\mathrm{\α}}}+n_1\left(3\right)---\left(7\right)$

$y_2\left(3\right)=G{y}_R{h}_{R2}\sqrt{d_{R2}^{-\mathrm{\α}}}+n_2\left(3\right)---\left(8\right)$

Wherein in above-mentioned expression formula, (3) represent the 3rd time slot in three time slots.

In formula (7), in (8), substitute into (5), after elimination self-interference, D2D ₁, D2D ₂end can be written as at the Received signal strength of the 3rd time slot:

$\begin{array}{c}{y}_1\left(3\right)={\mathrm{Gh}}_{R1}\sqrt{P_{2R}}{h}_{2R}\sqrt{d_{R1}^{-\mathrm{\α}}}{S}_2+{\mathrm{Gh}}_{R1}\sqrt{P_{\mathrm{CR}}}{h}_{\mathrm{CR}}\sqrt{d_{R1}^{-\mathrm{\α}}}{S}_C\\ +{\mathrm{Gh}}_{R1}{n}_R\left(1\right)\sqrt{d_{R1}^{-\mathrm{\α}}}+{\mathrm{Gh}}_{R1}{n}_R\left(2\right)\sqrt{d_{R1}^{-\mathrm{\α}}}+n_1\left(3\right)\end{array}---\left(9\right)$

$\begin{array}{c}{y}_2\left(3\right)={\mathrm{Gh}}_{R2}\sqrt{P_{1R}}{h}_{1R}\sqrt{d_{R2}^{-\mathrm{\α}}}{S}_1+{\mathrm{Gh}}_{R2}\sqrt{P_{\mathrm{CR}}}{h}_{\mathrm{CR}}\sqrt{d_{R2}^{-\mathrm{\α}}}{S}_C\\ +{\mathrm{Gh}}_{R2}{n}_R\left(1\right)\sqrt{d_{R2}^{-\mathrm{\α}}}+{\mathrm{Gh}}_{R2}{n}_R\left(2\right)\sqrt{d_{R2}^{-\mathrm{\α}}}+n_2\left(3\right)\end{array}---\left(10\right)$

D2D ₁signal is received, D2D at the second time slot and the 3rd time slot ₂signal is received, therefore D2D at the first time slot and the 3rd time slot ₁, D2D ₂reception Signal to Interference plus Noise Ratio (SINR) be respectively:

${\mathrm{SINR}}_1=\frac{P_{21}{\left|h_{21}\right|}^2}{N_0}+\frac{G^2{P}_{2R}{\left|h_{R1}\right|}^2{\left|h_{2R}\right|}^2{d}_{R1}^{-\mathrm{\α}}}{G^2{P}_{\mathrm{CR}}{\left|h_{R1}\right|}^2{\left|h_{\mathrm{CR}}\right|}^2{d}_{R1}^{-\mathrm{\α}}+2G^2{\left|h_{R1}\right|}^2{N}_0{d}_{R1}^{-\mathrm{\α}}+N_0}---\left(11\right)$

${\mathrm{SINR}}_2=\frac{P_{12}{\left|h_{12}\right|}^2}{P_{C2}{\left|h_{C2}\right|}^2+N_0}+\frac{G^2{P}_{1R}{\left|h_{R2}\right|}^2{\left|h_{1R}\right|}^2{d}_{R2}^{-\mathrm{\α}}}{G^2{P}_{\mathrm{CR}}{\left|h_{R2}\right|}^2{\left|h_{\mathrm{CR}}\right|}^2{d}_{R2}^{-\mathrm{\α}}+2G^2{\left|h_{R2}\right|}^2{N}_0{d}_{R2}^{-\mathrm{\α}}+N_0}---\left(12\right)$

Outage probability is defined as the threshold gamma that instantaneous SINR is less than a setting _th, namely

P _out＝P[SINR≤γ _th] (13)

The present invention is based on traditional D2D communication theory, on existing cellular network basis, both effectively suppress the harmful interference of interchannel, again can significantly elevator system interruption performance, specifically show that under this strategy, interruption performance step comprises as follows:

1) system break probability

Two D2D communication user D2D ₁, D2D ₂all must correctly Received signal strength, therefore the tolerance of interruption performance must consider D2D simultaneously ₁with D2D ₂end-to-end SINR.Then the outage probability of D2D link can be written as:

P _out＝P[min(SINR ₁,SINR ₂)≤γ _th] (14)

By by formula X=P _1R| h _1R| ², Y=P _2R| h _2R| ², Z=P _cR| h _cR| ², W=P ₁₂| h ₁₂| ², V=P ₂₁| h ₂₁| ²and T=P _c2| h _c2| ²substitute in (11) and (12), two D2D users receive SINR and are reduced to respectively:

${\mathrm{SINR}}_1=\frac{V}{N_0}+\frac{\mathrm{aXY}}{\mathrm{aX}(Z+2N_0)+N_0}---\left(15\right)$

${\mathrm{SINR}}_2=\frac{W}{{T+N}_0}+\frac{\mathrm{bXY}}{\mathrm{bY}(Z+2N_0)+N_0}---\left(16\right)$

Wherein a=G ²/ P ₁, b=G ²/ P ₂.

Therefore the outage probability of D2D link is expressed as:

$P_{\mathrm{out}}=1-\stackrel{\‾}{P}[\frac{V}{N_0}+\frac{\mathrm{aXY}}{\mathrm{aX}(Z+2N_0)+N_0}>{\mathrm{\γ}}_{\mathrm{th}},\frac{W}{T+N_0}+\frac{\mathrm{bXY}}{\mathrm{bY}(Z+2N_0)+N_0}>{\mathrm{\γ}}_{\mathrm{th}}]---\left(17\right)$

The expression formula releasing non-interrupted probability according to (17) is:

$\stackrel{\‾}{P}\left({\mathrm{\γ}}_{\mathrm{th}}\right)=P[Y>K+\frac{L}{X},X>M+\frac{N}{Y}]---\left(18\right)$

Wherein, $K=\frac{({\mathrm{\γ}}_{\mathrm{th}}{N}_0-V)(Z+2N_0)}{N_0},L=\frac{{\mathrm{\γ}}_{\mathrm{th}}{N}_0-V}{a},M=\frac{[{\mathrm{\γ}}_{\mathrm{th}}(T+N_0)-W](Z+2N_0)}{T+N_0},$

$N=\frac{[{\mathrm{\γ}}_{\mathrm{th}}(T+N_0)-W]N_0}{(T+N_0)b}.$

X and Y is independently exponential random variable, and the integral domain therefore in (18) formula is the key obtaining non-interrupted probability.Simultaneous Equations with calculating solves solution of equations and crosspoint (X ₀, Y ₀) be:

$X_0=\frac{N+\mathrm{KM}-L+\sqrt{{(L-\mathrm{KM}-N)}^2+4\mathrm{KML}}}{2K}---\left(19\right)$

$Y_0=\frac{L+\mathrm{KM}-N+\sqrt{{(N-\mathrm{KM}-L)}^2+4\mathrm{KMN}}}{2M}---\left(20\right)$

Straight line x is just through crosspoint (X ₀, Y ₀), integral domain is divided into two parts.Therefore according to integral domain, non-interrupted probability expression can be expressed as two integration sums:

${\stackrel{\‾}{P}}_{\mathrm{out}}=\underset{X_0}{\overset{\∞}{\∫}}\underset{K+\frac{L}{x}}{\overset{\frac{Y_0}{X_0}x}{\∫}}{f}_Y\left(y\right)f_X\left(x\right)\mathrm{dydx}+\underset{Y_0}{\overset{\∞}{\∫}}\underset{M+\frac{N}{y}}{\overset{\frac{X_0}{Y_0}y}{\∫}}{f}_X\left(x\right)f_Y\left(y\right)\mathrm{dxdy}---\left(21\right)$

Wherein X=P _1R| h _1R| ²~ CN (1/P _1R), Y=P _2R| h _2R| ²~ CN (1/P _2R).

Carry out integral and calculating to (21), the expression formula releasing non-interrupted probability is:

$\begin{array}{c}{\stackrel{\‾}{P}}_{\mathrm{out}}=-\frac{P_{2R}{X}_0}{X_0{P}_{2R}+Y_0{P}_{1R}}\exp (-\frac{X_0{P}_{2R}+Y_0{P}_{1R}}{P_{1R}{P}_{2R}})-\frac{Y_0{P}_{1R}}{Y_0{P}_{1R}+X_0{P}_{2R}}\exp (-\frac{Y_0{P}_{1R}+X_0{P}_{2R}}{P_{1R}{P}_{2R}})\\ +\frac{1}{P_{1R}}\exp (-\frac{K}{P_{2R}})\underset{X_0}{\overset{\∞}{\∫}}\exp (-\frac{1}{P_{1R}}x-\frac{L}{x{P}_{2R}})\mathrm{dx}+\frac{1}{P_{2R}}\exp (-\frac{M}{P_{1R}})\underset{Y_0}{\overset{\∞}{\∫}}\exp (-\frac{y}{P_{2R}}-\frac{N}{y{P}_{1R}})\mathrm{dy}\end{array}---\left(22\right)$

Therefore the expression formula obtaining D2D outage probability is:

$\begin{array}{c}{P}_{\mathrm{out}}=1-{\stackrel{\‾}{P}}_{\mathrm{out}}=1+\frac{P_{2R}{X}_0}{X_0{P}_{2R}+Y_0{P}_{1R}}\exp (-\frac{X_0{P}_{2R}+Y_0{P}_{1R}}{P_{1R}{P}_{2R}})+\frac{Y_0{P}_{1R}}{Y_0{P}_{1R}+X_0{P}_{2R}}\exp (-\frac{Y_0{P}_{1R}+X_0{P}_{2R}}{P_{1R}{P}_{2R}})\\ -\frac{1}{P_{1R}}\exp (-\frac{K}{P_{2R}})\underset{X_0}{\overset{\∞}{\∫}}\exp (-\frac{1}{P_{1R}}x-\frac{L}{x{P}_{2R}})\mathrm{dx}-\frac{1}{P_{2R}}\exp (-\frac{M}{P_{1R}})\underset{Y_0}{\overset{\∞}{\∫}}\exp (-\frac{y}{P_{2R}}-\frac{N}{y{P}_{1R}})\mathrm{dy}\end{array}---\left(23\right)$

After substituting into above-mentioned defined K, L, M, N, expression formula (23) becomes:

$P_{\mathrm{out}}=1+\frac{P_{2R}{X}_0}{X_0{P}_{2R}+Y_0{P}_{1R}}\exp (-\frac{X_0{P}_{2R}+Y_0{P}_{1R}}{P_{1R}{P}_{2R}})+\frac{Y_0{P}_{1R}}{Y_0{P}_{1R}+X_0{P}_{2R}}\exp (-\frac{Y_0{P}_{1R}+X_0{P}_{2R}}{P_{1R}{P}_{2R}})-\frac{1}{P_{1R}}$

$\exp (-\frac{({\mathrm{\γ}}_{\mathrm{th}}{N}_0-V)(Z+2N_0)}{N_0{P}_{2R}})\underset{X_0}{\overset{\∞}{\∫}}\exp (-\frac{1}{P_{1R}}x-\frac{{\mathrm{\γ}}_{\mathrm{th}}{N}_0-V}{P_{2R}\mathrm{ax}})\mathrm{dx}-\frac{1}{P_{2R}}\exp (-\frac{[{\mathrm{\γ}}_{\mathrm{th}}(T+N_0)-W](Z+2N_0)}{P_{1R}(T+N_0)})$

$\underset{Y_0}{\overset{\∞}{\∫}}\exp (-\frac{y}{P_{2R}}-\frac{[{\mathrm{\γ}}_{\mathrm{th}}(T+N_0)-W]N_0}{y{P}_{1R}(T+N_0)b})\mathrm{dy}---\left(24\right)$

(24) formula is exactly the accurate expression of D2D link down probability under this strategy.

2) approximate form of outage probability under high s/n ratio

In the present invention in hypothesis high s/n ratio situation, the power of noise will be far longer than from the interference of phone user for D2D user, but can not ignore noise is exaggerated at relaying R (base station).Therefore, according to the conclusion of formula (24), show that the approximate expression of outage probability during high s/n ratio is:

$P_{\mathrm{out}}\≈1+\frac{P_{2R}{X}_0}{X_0{P}_{2R}+Y_0{P}_{1R}}\exp (-\frac{X_0{P}_{2R}+Y_0{P}_{1R}}{P_{1R}{P}_{2R}})+\frac{Y_0{P}_{1R}}{Y_0{P}_{1R}+X_0{P}_{2R}}\exp (-\frac{Y_0{P}_{1R}+X_0{P}_{2R}}{P_{1R}{P}_{2R}})-\frac{1}{P_{1R}}$

$\exp (-\frac{({\mathrm{\γ}}_{\mathrm{th}}{N}_0-V)(Z+2N_0)}{N_0{P}_{2R}})\underset{X_0}{\overset{\∞}{\∫}}\exp (-\frac{1}{P_{1R}}x-\frac{{\mathrm{\γ}}_{\mathrm{th}}{N}_0-V}{P_{2R}\mathrm{ax}})\mathrm{dx}-\frac{1}{P_{2R}}\exp (-\frac{({\mathrm{\γ}}_{\mathrm{th}}T-W)(Z+2N_0)}{P_{1R}T})$

$\underset{Y_0}{\overset{\∞}{\∫}}\exp (-\frac{y}{P_{2R}}-\frac{({\mathrm{\γ}}_{\mathrm{th}}T-W)N_0}{y{P}_{1R}\mathrm{Tb}})\mathrm{dy}---\left(25\right)$

3) optimal power allocation scheme

For transmission policy provided by the invention, use outage probability to distribute the optimization that D2D link carries out power as tolerance, object is by optimal power allocation scheme reasonably allocation of transmit power P ₁, P ₂, P _rmake outage probability reach minimum, constraints is fixing total transmitted power P.

Therefore optimization problem is described as:

$(P_1,P_2{,P}_R)=\arg \underset{P_1,P_2,P_R}{\min }{P}_{\mathrm{outage}}---\left(26\right)$

s.t. P ₁+P ₂+P _R＝P

According to the conclusion of described formula (14), above-mentioned optimization problem is converted to:

$(P_1,P_2{,P}_R)=\arg \underset{P_1,P_2,P_R}{\max }\min ({\mathrm{SINR}}_1,{\mathrm{SINR}}_2)---\left(27\right)$

s.t. P ₁+P ₂+P _R＝P

Introducing auxiliary variable t makes problem easily process: t=min (SINR ₁, SINR ₂), target function becomes therefore optimal power allocation problem is expressed as again:

$(P_1,P_2{,P}_R)=\arg \underset{P_1,P_2,P_R}{\max }t$

s.t. P ₁+P ₂+P _R＝P (28)

SINR ₁≥t,SINR ₂≥t

Above-mentioned formula (28) is a Solution of Nonlinear Optimal Problem, adopt SQP (SQP) algorithm solve optimal value be this transmission policy under optimal power allocation scheme.

In sum, the present invention is the mode adopting direct link and repeated link to combine, using the Bi-directional amplifier forward relay of base station as D2D link, make D2D user can receive echo signal in two different time-gaps, improve the interruption performance of system significantly.

Claims (3)

1. in honeycomb D2D communication system based on interruption performance promote transmission policy implementation method, it is characterized in that, said method comprising the steps of:

Step 1: the D2D communication system in cellular network comprises a pair D2D user, Bi-directional amplifier relaying, that is: base station, phone user; They use D2D respectively ₁, D2D ₂, R and CU represents, D2D ₁, D2D ₂, the transmitted power of R and CU is respectively P ₁, P ₂, P _r, P _c;

Step 2: when the first time slot, phone user CU sends upward signal S _cto base station; And D2D user 1 sends signal S by repeated link in D2D link ₁to relaying R, that is: base station, send signal S by direct link simultaneously ₁to D2D user 2; Now for D2D link, relaying R, that is: base station and D2D user 2 are subject to the interference from phone user CU;

Step 3: in the second time slot, base station sends downstream signal S _rto phone user CU; And D2D user 2 sends signal S by repeated link in D2D link ₂to relaying R, that is: base station, send signal S by direct link simultaneously ₂to D2D user 1;

Step 4: in the 3rd time slot, relaying R, that is: the mixed signal that the first two time slot receives is amplified by base station, and gain amplifier is the arithmetic square root that G, G are expressed as relaying transmitted power and the ratio of mixed signal power; Relaying R, that is: amplifying signal is sent to D2D user 1 and D2D user 2 by base station respectively;

Step 5: the signal received at the second time slot and the 3rd time slot according to D2D user 1, obtains the reception Signal to Interference plus Noise Ratio of D2D user 1; According to the signal that D2D user 2 receives at the first time slot and the 3rd time slot, obtain the reception Signal to Interference plus Noise Ratio of D2D user 2;

Step 6: the D2D user 1 determined according to above-mentioned steps 5 and the Signal to Interference plus Noise Ratio of D2D user 2, the outage probability P of definition D2D link _outfor: P _out=P [min (SINR ₁, SINR ₂)≤γ _th]; Wherein SINR ₁for the Signal to Interference plus Noise Ratio of D2D user 1; SINR ₂for the Signal to Interference plus Noise Ratio of D2D user 2; γ _thfor the threshold value preset;

Step 7: according to the method for subregion integration, the outage probability P that above-mentioned steps 6 is defined _outthe form of two integration sums is decomposed into by integral domain; Obtain the results added of two integrations respectively, obtain the outage probability of the D2D transmission policy proposed; Consider that D2D user side in high s/n ratio situation will be far longer than the power of noise from the interference of phone user CU again, obtain the approximate form of system break probability under high s/n ratio;

Step 8: minimum for optimization aim with system break probability, proposes optimal power allocation problem, and optimization object is that D2D user is to the transmitted power P with relaying ₁, P ₂, P _r, constraints is P ₁+ P ₂+ P _r=P, wherein P is fixing total transmitted power, utilizes sequential quadratic programming algorithm to solve the optimal power allocation scheme of optimal value as system.

2. in a kind of honeycomb D2D communication system according to claim 1 based on interruption performance promote transmission policy implementation method, it is characterized in that: described method is the mode adopting direct link and repeated link to combine, using the Bi-directional amplifier forward relay of base station as D2D link, make D2D user can receive echo signal in two different time-gaps.

3. in a kind of honeycomb D2D communication system according to claim 1 based on interruption performance promote transmission policy implementation method, it is characterized in that: described method is applied to honeycomb D2D communication system.