CN104601287A - Relay pre-coding method for information and energy transmission in wireless cognitive network - Google Patents

Abstract

The invention provides a relay pre-coding method for information and energy transmission in wireless cognitive network. The method involves at least one base station, a plurality of relays and a user; the information sent by the base station is transferred to the user through the relay, and the relay synchronously sends energy to the user. The method comprises the steps of estimating uplink and downlink channels through the base station and sending the signal to the relay; performing robust pre-coding through the relay by considering the channel error of the relay and the user; sending the processed information and energy to be transmitted to a receiving end through the relay; receiving the information and energy signals from the relay. According to the method, a relay node transmits energy to the user to meet the demand requirement of the user; the emission power of the relay is less than a threshold; in addition, the probability limitation method is performed for the SNR of the receiving end and the received energy value is feasible.

Description

The relaying method for precoding of transmission information and energy in wireless cognition network

Technical field

What the present invention relates to is wireless communication technology field, the relaying method for precoding of transmission information and energy while of specifically in a kind of wireless cognition network.

Background technology

Along with the development of wireless network, the information between equipment and the wireless transmission of energy receive increasing concern.In order to meet the growing experience requirements of people, the function of intelligent terminal also constantly increases, and the thing followed is that the power consumption of intelligent terminal is also increasing.Energy limited has become a key factor of restriction intelligent terminal service time.Although change the service time that battery can extend intelligent terminal, this will lower the convenience of intelligent terminal, and promotes the use cost of user.More convenient, safe, a green alternative method obtains energy from environment.This is almost wireless terminal and provides eternal energy source.Usual solar energy, wind energy can be used as energy source, and in addition, radio frequency signal can be used as a kind of available new energy source.It should be noted that the energy obtained from radio frequency signal is generally applicable to the low network of consumed power, such as sensing network.If but establish special wireless energy transfer network, so radio frequency signal just can as a kind of reliable and stable Power supply source.This topic not only obtains academicly and studies widely, is also quite paid attention in the application of industrial application.The problem that the method effectively transmitted between designing apparatus helps the transmission solving information and energy in reality is an important topic urgently to be resolved hurrily.

The present invention first proposed a kind of transfer process based on carrying out information and Energy Transfer while in wireless relay network.Channel wherein between base station and relaying is ideal communication channel, but the channel between relaying and user has the limited error of norm.The robustness Precoding Design scheme of a kind of information and Energy Transfer precoding is the present invention proposes for existing error.The program compares non-robust Precoding Design scheme, effectively can reduce the power that relaying consumes, and can ensure again service quality and the energy harvesting amount of receiving terminal.

Summary of the invention

The object of the invention is to overcome above-mentioned the deficiencies in the prior art, the relaying method for precoding of transmission information and energy in a kind of wireless cognition network is proposed, by via node transmitting energy to user, meet the energy requirement of user, ensure that the transmitting power of relaying is less than a threshold value.

Technical solution of the present invention is as follows:

A relaying method for precoding for transmission information and energy in wireless cognition network, its feature is, this network at least comprises a base station, multiple relaying and a user, wherein, the information that base station sends is through relay forwarding to user, and relaying sends energy to user simultaneously, and concrete steps are as follows:

Uplink and downlink channel estimating is carried out in step 1. base station, and signal is sent to relaying;

Step 2. relaying is under consideration continue and channel errors between user when, carry out robustness precoding, be about to the information from base station that receives and expectation sends the energy of receiving terminal to through robustness precoding, obtain the robustness pre-coding matrix W of the information received, expect the robustness pre-coding matrix of the energy sending receiving terminal to;

Described robustness pre-coding matrix is the signal to noise ratio snr >S making user _ththe pre-coding matrix of maximum probability, wherein S _thit is the preset value of SNR;

The energy that information after process and expectation send receiving terminal to sends by step 3. relaying;

Step 4. user receives information and the energy signal of relaying transmission.

Information sends to relaying to be the channel condition information that base station can measure between itself and relaying by described base station, and information is sent to relaying.Relay reception to signal be

y _r＝Hs+n _r(1)

In formula, s is the data that base station sends, and H is the channel between base station and relaying, n _rfor Gaussian noise.

The signal that described relaying will forward comprises information signal and energy signal two parts.Relaying can carry out Precoding Design to these two kinds of signals respectively.The transmission signal of relaying is as follows:

x _r＝WHs+Wn _r+Va (2)

W in formula is the pre-coding matrix of relaying to the information received, and V relaying is to the pre-coding matrix a of energy signal.The energy that relaying sends, it meets

The signal that described user receives comprises signal and noise two parts of relay forwarding.The signal that user receives can be written as:

y _d＝G(WHs+Wn _r+Va)+n _d(3)

In formula, G represents the down channel between receiving terminal and user.N _dit is the additive white Gaussian noise between user and relaying.

The ideal communication channel when channel information of whole model is the signal between base station and relaying, and there is error in the channel between relaying and user, then the channel matrix between relaying and user is modeled as

$G=\hat{G}+\mathrm{\ΔG}---\left(4\right)$

Wherein, be that CSI estimates, Δ G is corresponding channel condition information error.

If each node has perfect channel information, then have in matrix Δ G is all independent identically distributed gaussian variables,

The SNR of user is expressed as

$\mathrm{SNR}=\frac{{\mathrm{\σ}}_s^2{\left|\right|(\hat{G}+\mathrm{\ΔG})\mathrm{WH}\left|\right|}^2}{{\mathrm{\σ}}_r^2{\left|\right|(\hat{G}+\mathrm{\ΔG})W\left|\right|}^2+{\mathrm{\σ}}_d^2}---\left(5\right)$

The energy that receiving terminal receives is y _e=GVa, the following condition of demand fulfillment:

$E\left[{\left|\right|y_E\left|\right|}^2\right]={\mathrm{\σ}}_a^2{\left|\right|\mathrm{GV}\left|\right|}^2\≥P---\left(6\right)$

Z=ww ^h, Y=vv ^h, wherein, w and v is the diagonal matrix of W and V respectively, then uses formula Xyy ^hx ^h=Yxx ^hy ^h(5), (6) are converted, wherein X=diag (x), Y=diag (y).

The robustness Precoding Design of described retransmit is the maximum probability rate in order to make the SNR value of user be greater than predetermined value, ensures service quality and the energy acceptance amount of user simultaneously, gives following optimization problem (P1):

$\begin{array}{cc}\underset{W,V,t}{\max }& \mathrm{Prob}\{\mathrm{SNR}\≥S_{\mathrm{th}}\}---\left(7a\right)\end{array}$

s.t.E(||x _r|| ²)≤P _r(7b)

Prob{E(||y _e|| ²)≥P _th}≥r (7c)

The present invention replaces probability limited with strict norm is limited, and the SNR that user receives and the energy that receiving terminal receives can be rewritten as

SNR-S _th＝ΔGQ ₁ΔG ^H+2Re(ΔGr ₁)+s ₁≥0 (8)

E[||y _E|| ²]-P _th＝ΔGQ ₂ΔG ^H+2Re(ΔGr ₂)+s ₂≥0 (9)

Wherein, $Q_1={\mathrm{HZH}}^H-S_{\mathrm{th}}{\mathrm{\σ}}_r^{2}Z,$ $r_1=Q_1{\stackrel{\‾}{g}}^H,$ $s_1=\stackrel{\‾}{g}{Q}_1{\stackrel{\‾}{g}}^H-S_{\mathrm{th}}{\mathrm{\σ}}_d^2,$ $s_2=\stackrel{\‾}{g}{Q}_2\stackrel{\‾}{g}-P_{\mathrm{th}},$ Q ₂＝Y， $r_2=Q_2{\stackrel{\‾}{g}}^H$

According to S-lemma, (7) (8) can be restricted to further:

$\left[\begin{array}{cc}{Q}_1& r_1\\ r_1^H& S_1\end{array}\right]+t_1\left[\begin{array}{cc}{I}_R& 0\\ 0& -d_1\end{array}\right]\≥0---\left(10\right)$

$\left[\begin{array}{cc}{Q}_2& r_2\\ r_2^H& S_2\end{array}\right]+t_2\left[\begin{array}{cc}{I}_R& 0\\ 0& -d_2\end{array}\right]\≥0---\left(11\right)$

Wherein, $d_1={\mathrm{\σ}}_g\sqrt{0.5\×{\mathrm{\Φ}}_{{\mathrm{\χ}}_{2R}^2}^{-1}t},$ $d_{\text{2}}={\mathrm{\σ}}_g\sqrt{0.5\×{\mathrm{\Φ}}_{{\mathrm{\χ}}_{2R}^2}^{-1}r}.$

The transmitting power of relaying will meet

$\begin{array}{c}E\left[{\left|\right|x_r\left|\right|}^2\right]={\mathrm{\σ}}_s^2{\left|\right|\mathrm{WH}\left|\right|}^2+{\mathrm{\σ}}_r^2{\left|\right|W\left|\right|}^2+{\mathrm{\σ}}_a^2{\left|\right|V\left|\right|}^2\\ =\mathrm{tr}\left(Q_{r}Z\right)+\mathrm{tr}\left(Q_2\right)\≤P_r\end{array}---\left(12\right)$

Wherein, $Q_r={\mathrm{HH}}^H+{\mathrm{\σ}}_r^2{I}_R,$ Q ₂＝Y。

Therefore, optimization problem (P1) can be expressed as (P2):

$\begin{array}{cc}\underset{Z,Y,t_1,t_2,t}{\max }& t---\left(13a\right)\end{array}$

s.t.Tr(Q _rZ)+Tr(Q ₂)≤P _r(13b)

$\left[\begin{array}{cc}{Q}_1& r_1\\ r_1^H& s_1\end{array}\right]+t_1\left[\begin{array}{cc}{I}_R& 0\\ 0& -d_1\end{array}\right]\≥0---\left(13c\right)$

$\left[\begin{array}{cc}{Q}_2& r_2\\ r_2^H& s_2\end{array}\right]+t_2\left[\begin{array}{cc}{I}_R& 0\\ 0& -d_2\end{array}\right]\≥0---\left(13d\right)$

t ₁≥0,t ₂≥0,0≤t≤1 (13e)

Rank(Y)＝1,Rank(Z)＝1 (13f)

Because the order of the Y in (13f), Z is 1, making is not the problem of a convex optimization in (P2), and the present invention uses that positive semidefinite is lax abandons matrix restriction, first keeps optimization problem to be convex, then uses dichotomy to find the optimal solution of problem.Specific algorithm is as follows:

1: initialization:

1) t is introduced _min, t _max, n, η and N _max, they are corresponding respectively the search lower bound of dichotomy algorithm, the upper bound of dichotomy algorithm, iterations technology, the precision of dichotomy algorithm and maximum iteration time.

2) formula is utilized to calculate Q respectively ₁, r ₁, S ₁, d ₁, Q ₂, r ₂, S ₂, d ₂, Q _r, Z.

2: iterative step:

1)t＝(t _min+t _max)/2；

2) Y in CVX calculating (P2) is used ⁽ⁿ⁾, Z ⁽ⁿ⁾;

3) if step 2) can feasible solution be found, t _min=t, otherwise, t _max=t;

3: termination condition:

Work as t _max-t _min≤ η or n > N _maxdichotomy algorithm terminates, and wherein η is a default threshold value, N _maxbe

Maximum iterations, exports t ^opt=t, Y ^opt=Y ⁽ⁿ⁾, Z ^opt=Z ⁽ⁿ⁾.Otherwise, n=n+1, and return step 2.

The invention has the beneficial effects as follows the power that effectively can reduce relaying and consume, service quality and the energy harvesting amount of receiving terminal can be ensured again.It should be noted that, the method for probability of use restriction more easily can obtain larger feasible value relative to strict restriction.

Accompanying drawing explanation

By embodiments of the invention being described below in conjunction with accompanying drawing, above-mentioned and other objects, features and advantages of the present invention will be made clearly, wherein:

Fig. 1 is the communication means flow chart based on wireless communication relay system according to the better enforcement of the present invention;

Fig. 2 is wireless messages according to the better enforcement of the present invention and energy relay transmission network schematic diagram.

Fig. 3 works as S _th=5, P _thwhen=2, for different r values, the distribution situation of the throughput of user.

Fig. 4 is different S _th, P _ththe situation of the power that relaying consumes under condition.

Fig. 5 works as S _th=5, P _thwhen=2, for different r values, the distribution situation of the energy that user receives.

Embodiment

Elaborate to embodiments of the invention below, the present embodiment is being implemented premised on technical solution of the present invention, give detailed execution mode and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

Specific implementation step comprises following steps:

The first step, initializes system parameters and constraints.A base station, a user and two relayings are included in the present embodiment.Base station, relaying and user are single antenna.Up channel H ∈ C ^{m × 1}be the ideal communication channel of obeying Ruili distribution, down channel is except obeying Ruili channel G ∈ C ^{1 × M}outside also comprise the limited error term Δ G of norm.The present embodiment emulates the result of different up-downgoing channels 10000.

Second step, calculates Z and Y.Circular is, the energy requirement of user feedback oneself, SNR limit feedback are to relaying, and relaying, again according to the power limitation condition of oneself, can obtain each formula in (13), then uses convex optimization tool CVX, can calculate Z and Y.

3rd step, the transmitting power calculating relaying and the SNR meeting user and the energy received.According to formula (5) and (6), calculate the SNR of user in robustness and non-robust scheme and the energy received respectively.The power of relaying consumption can be calculated according to formula (12).

4th step, is emulated by matlab, and the probability for the user SNR obtained in the 3rd step, energy and relaying consumption carries out the comparison of robustness and non-robust performance.

Fig. 3 works as S _th=5, P _thwhen=2, for different r values, the distribution situation of the throughput of user.Illustrate that robustness precoding can ensure the service quality of recipient relative to non-robust.

Fig. 4 is different S _th, P _ththe situation of the power that relaying consumes under condition.As can be seen from the figure, robustness scheme power more more than the consumption of non-robust scheme, this is because consider the poor situation of channel in robustness scheme.

Fig. 5 works as S _th=5, P _thwhen=2, for different r values, the distribution situation of the energy that user receives.As can be seen from the figure, along with the increase of threshold value r, the energy that user absorbs is relatively many.

It should be noted last that, above embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although with reference to preferred embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that, can modify to the technical scheme of invention or equivalent replacement, and not departing from the spirit and scope of technical solution of the present invention, it all should be encompassed in the middle of right of the present invention.

Claims (3)

1. the relaying method for precoding of transmission information and energy in wireless cognition network, it is characterized in that, this network at least comprises a base station, multiple relaying and a user, wherein, the information that base station sends is through relay forwarding to user, and relaying sends energy to user simultaneously, and concrete steps are as follows:

Uplink and downlink channel estimating is carried out in step 1. base station, and signal is sent to relaying;

Step 2. relaying is under consideration continue and channel errors between user when, carry out robustness precoding, be about to the information from base station that receives and expectation sends the energy of receiving terminal to through robustness precoding, obtain the robustness pre-coding matrix W of the information received, expect the robustness pre-coding matrix of the energy sending receiving terminal to;

Described robustness pre-coding matrix is the signal to noise ratio snr >S making user _ththe pre-coding matrix of maximum probability, wherein S _thit is the preset value of SNR;

The energy that information after process and expectation send receiving terminal to sends by step 3. relaying;

Step 4. user receives information and the energy signal of relaying transmission.

2. the relaying method for precoding of transmission information and energy in wireless cognition network according to claim 1, it is characterized in that, the existing channel errors between described step 2. relaying and user refers to: the down channel between relaying and user exists Gaussian error in formula, be estimate channel, Δ G is channel estimation errors.

3. the relaying method for precoding of transmission information and energy in wireless cognition network according to claim 1, it is characterized in that, in the measure error situation of described step 2. existing for specifically between relaying and user, user by the energy requirement of oneself, SNR limit feedback to relaying, relaying, again according to the power limitation condition of oneself, obtains the robustness pre-coding matrix V to the energy that robustness pre-coding matrix pre-coding matrix W and the centering secondary of the information received are sent by convex optimization method.