CN108848558A - A kind of SWIPT system self-adaption time slot signal method of reseptance collected based on nonlinear energy - Google Patents

Abstract

The invention discloses a SWIPT system adaptive time slot signal receiving method based on nonlinear energy collection. First, aiming at the scene of point-to-point communication of the nonlinear energy SWIPT system in a flat fading channel, it solves the problem that the nonlinear energy receiver of the SWIPT system is in a certain The power saturation of the input signal in the time slot leads to the waste of receiving energy and the rough allocation of resources at the receiving end; secondly, for the nonlinear energy SWIPT system, it is proposed to adaptively switch the collected information or energy according to the channel state. Optimizing the switching coefficients of the information receiver and the energy receiver, the constructed objective function has a simple form, and some parameters can be adjusted according to different requirements in different scenarios, which improves the flexibility of the application; the solution of the objective function is obtained by the optimization algorithm , the process is simple, there is no complicated mathematical analysis process, it is easy to operate in practice, and it can optimize two important indicators of the energy obtained by the receiving end and the system interruption probability at the same time.

Description

A SWIPT system adaptive time slot signal reception based on nonlinear energy harvesting method

technical field

The invention relates to the technical field of wireless communication, in particular to a wireless information and energy coordinated transmission (SWIPT) system based on nonlinear energy collection, and an adaptive time slot signal receiving method.

Background technique

In some traditional energy-constrained wireless networks, the life of the network often depends on the battery capacity of the network nodes, so the sustainability of the battery energy of the nodes is very important, and it is usually necessary to periodically charge the battery or replace the battery. For energy-constrained networks with harsh working environments, it is difficult or even impossible to charge or replace the batteries of its nodes, so the development of wireless energy transmission/harvesting technology has become an urgent need.

SWIPT is a technology that combines wireless information transmission and wireless energy transmission. The receiving end is composed of an information receiver and an energy receiver, so that the receiver can decode the information of the same radio frequency signal without adding additional time and frequency resources. (ID) while extracting energy (EH) from it. Compared with traditional wind energy, solar energy, tidal energy and other energy harvesting technologies that depend on the natural environment such as climate and are therefore uncontrollable, SWIPT can provide stable, controllable and reliable energy harvesting, and has become the focus of research and attention in the industry in recent years. In the SWIPT system, energy reception and information decoding at the receiving end use the same received signal. How to allocate system resources reasonably is a key issue that affects system performance.

At present, many researches have proposed various methods for SWIPT system resource allocation, but the existing methods are mainly aimed at linear energy receivers. The publication number is CN105611633A, and the publication date is May 25, 2016. The invention patent "Receiver Resource Allocation Method Based on SWIPT Beamforming Method" provides a method that combines beamforming design with SWIPT system resource allocation. A method for reducing the transmit power of the base station, but this invention is aimed at a linear energy receiver and aims at the minimum transmit power of the base station. The publication number is CN105119644A, and the publication date is December 2, 2015. The invention patent "SWIPT-based single-user MIMO system space division switching method" provides two modes of energy reception and information decoding for the SWIPT system using MIMO space division switching technology However, this invention is also aimed at a linear energy receiver, without considering the nonlinearity of the energy receiver.

The actual SWIPT energy receiver has nonlinear characteristics: when the power of the received signal increases to a certain value, the output power of the energy receiver will reach saturation and remain unchanged. The resource allocation method of the existing SWIPT system cannot solve the problem of waste of received energy when the output power of the energy receiver is saturated.

Contents of the invention

The purpose of the present invention is to solve the above-mentioned defects in the prior art, and provide a method for receiving adaptive time slot signals of a SWIPT system based on nonlinear energy collection. This method adopts an energy harvesting mode based on a time slot switching architecture, takes minimizing the outage probability as the optimization goal, and optimizes the switching coefficients of the information receiver and the energy receiver, aiming to provide a realistic resource allocation for the SWIPT system method.

The purpose of the present invention can be achieved by taking the following technical solutions:

A kind of SWIPT system adaptive time slot signal receiving method based on nonlinear energy harvesting, described receiving method comprises the following steps:

S1. The sending end S sends a signal x to the energy-limited receiving node D. The receiving node D divides a resource block into K sub-slots for reception. The signal received in the kth time slot is: In the formula, 1≤k≤K, h _k indicates that the channel coefficient of the kth time slot obeys flat fading, P _k indicates the transmitted signal power of this time slot, and n is the additive white Gaussian noise at the receiving end;

S2. Define the switching coefficient ρ between the information receiver and the energy receiver of the receiving node D. In the kth time slot, the switching coefficient between the information receiver and the energy receiver of the receiving node D is defined as ρ(k) , in the kth time slot, the optimal switching coefficient, that is, the optimal value of ρ(k) is denoted as ρ ^* (k), and the receiving node D performs information reception or energy collection according to the value of ρ ^* (k);

S3. According to the received signal y _rk , calculate its power value P _rk = |h _k | ² P _k , where |h _k | ² is the modulus of the complex channel coefficient h _k , representing the channel power of the kth time slot gain;

S4. According to the power value P _rk of the received signal, calculate the input power of the energy receiver of the destination node in the kth time slot

S5, input power to the energy receiver Multiplied by _η and the output power saturation value of the energy receiver For comparison, where, _η is the energy conversion efficiency of the energy receiver of the destination node, if Then ρ ^* (k)=1, the receiving node D switches the signal to the information receiver, and this time slot only performs information reception; otherwise, the following sequential steps are performed;

S6. Taking the minimization of the system outage probability as the optimization goal, and the switching coefficient ρ(k) as the optimization object, define the objective function in is the instantaneous outage probability of the kth time slot of the system, and is a function of ρ(k);

S7, using the Lagrange multiplier method, combined with the binary search method, for the objective function Solve to obtain the optimal information receiver and energy receiver switching coefficient ρ ^* (k);

S8. Perform adaptive time slot signal reception according to the obtained value of switching coefficient ρ ^* (k) between the information receiver and the energy receiver for each sub-slot.

Further, the switching coefficient ρ(k) has a value of 0 or 1, wherein ρ(k)=1 indicates that the receiving end of the time slot uses signals for information reception, and ρ(k)=0 indicates that the time slot The receiver uses the signal for energy harvesting.

Further, the formula of the interruption probability is as follows: where r _k =ρ(k)log(1+γ _k ) is the instantaneous information receiving rate of the kth time slot of the system, and r ₀ is the minimum information receiving rate threshold for normal communication of the system, where is the signal-to-noise ratio of the receiving end in the kth time slot, and σ ² is the noise power of the receiving end.

Further, the optimal switching coefficient ρ ^* (k) between the information receiver and the energy receiver in the step S7 is as follows:

(1) when , then ρ ^* (k) = 0;

(2) when , then ρ ^* (k) = 1;

(3) when , then ρ ^* (k) = 0;

where λ ^* is the optimal Lagrangian multiplier.

Further, the energy conversion efficiency η of the energy receiver of the destination node takes a value of 1.

Further, the adaptive time slot signal reception in the step S8 means that when ρ ^* (k)=1, the sub-time slot only performs information reception, and when ρ ^* (k)=0, the sub-time slot Only energy harvesting is done.

Further, the receiving method is aimed at the point-to-point wireless communication scenario of the SWIPT system, the channel type is a flat fading channel, the sending node S has a fixed and continuous energy supply, and the receiving node D has limited energy and no fixed energy supply , the receiver of the receiving node D is composed of two parts: an information receiver and an energy receiver, and the energy receiver obtains energy from the radio frequency signal of the surrounding environment.

Compared with the prior art, the present invention has the following advantages and effects:

1. The present invention aims at the scene of point-to-point communication of the nonlinear energy SWIPT system in the flat fading channel, and solves the problem that the input signal power saturation of the nonlinear energy receiver of the SWIPT system in a certain time slot leads to the waste of received energy.

2. The present invention considers that it is more in line with actual needs, solves the problem of rough allocation of resources at the receiving end of the nonlinear energy SWIPT system, makes the nonlinear energy SWIPT system use signals for information or energy collection and distribution methods more finely, and improves the nonlinear energy Operational efficiency of SWIPT system receivers.

3. For the nonlinear energy SWIPT system, the present invention proposes to adaptively switch the collected information or energy according to the channel state. Optimizing the switching coefficients of the information receiver and the energy receiver, the constructed objective function has a simple form, and some parameters can be adjusted according to different requirements in different scenarios, which improves the flexibility of the application; the solution of the objective function is obtained by the optimization algorithm , the process is simple, there is no complicated mathematical analysis process, it is easy to operate in practice, and it can optimize two important indicators of the energy obtained by the receiving end and the system interruption probability at the same time.

Description of drawings

Fig. 1 is the non-linear energy harvesting SWIPT system adaptive timeslot receiving flowchart of the present invention;

Figure 2 is a supplementary flowchart of Figure 1;

Fig. 3 is a schematic diagram of an information or energy receiver based on time slot switching in the SWIPT system involved in the present invention;

Fig. 4 is the SWIPT system nonlinear energy receiver energy collection model figure that the present invention relates to;

Fig. 5 is a collection schematic diagram of the relationship between received signal power and nonlinear energy involved in the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example

This embodiment discloses a SWIPT system adaptive time slot signal receiving method based on nonlinear energy collection. The specific implementation process mainly includes: optimizing the switching coefficient between the information receiver and the energy receiver, and performing adaptive time slot reception according to the optimization result Signal.

In this embodiment, as shown in Fig. 1 and Fig. 2, the process flow of the core steps of non-linear energy harvesting SWIPT system adaptive time slot reception, the information or energy of the SWIPT system involved in the present invention shown in Fig. 3 is based on time slot switching Receiver, FIG. 4 shows the SWIPT system nonlinear energy receiver energy collection model involved in the present invention, and FIG. 5 shows a collection schematic diagram of the relationship between received signal power and nonlinear energy involved in the present invention.

The implementation steps of this embodiment are as follows:

Step S1, the sending end S sends a signal x to the energy-limited receiving node D, and the receiving node D divides a resource block into K sub-slots for reception, and the signal received in the kth (1≤k≤K) time slot is : In the formula, h _k indicates that the channel coefficient of the kth time slot obeys flat fading, P _k indicates the transmitted signal power of this time slot, and n is the additive white Gaussian noise at the receiving end.

In this embodiment, the transmission time of one resource block is 60s, one resource block is divided into K=60 time slots for reception, and the power P k of the kth sub-slot (1≤k≤60) sub-slot is P _k =5mw.

Step S2, defining the switching coefficient ρ between the information receiver and the energy receiver of the receiving node D. In the kth time slot, the switching coefficient between the information receiver and the energy receiver of the receiving node D is defined as ρ(k). In the kth time slot, the optimal value of the optimal switching coefficient ρ(k) is denoted as ρ ^* (k), and the receiving node D performs information reception or energy collection according to the value of ρ ^* (k). The possible values of the switching coefficient ρ(k) are only 0 and 1, where ρ(k)=1 means that the receiving end of the time slot uses the signal for information reception, and ρ(k)=0 means that the receiving end of the time slot uses the signal for In the collection of energy.

Step S3, according to the received signal y _rk described in step S1, calculate its power value P _rk = |h _k | ² P _k , where |h _k | ² is the modulus of the complex channel coefficient h _k described in step S1, expressing Channel power gain for the kth time slot.

Step S4, according to the power value P _rk of the received signal described in step S3, calculate the input power of the energy receiver of the destination node in the kth time slot

Step S5, input power to the energy receiver described in step S4 Multiplied by η and the output power saturation value of the energy receiver To compare, if Then ρ ^* (k)=1, the receiving node D switches the signal to the information receiver, and only information reception is performed in this time slot; otherwise, the following sequential steps are performed. Described η is the energy conversion efficiency of destination node energy receiver, and among the present invention η=1, the output power saturation value of energy receiver

Step S6. Taking the minimization of the system outage probability as the optimization goal, and the switching coefficient ρ(k) as the optimization object, define the objective function in is the instantaneous outage probability of the kth time slot of the system, and is a function of ρ(k). Examples, the outage probability is given by the formula give. Where r _k =ρ(k)log(1+γ _k ) is the instantaneous information receiving rate of the kth time slot of the system, r ₀ =1.61bits/s/Hz is the minimum information receiving rate threshold for normal communication of the system, here is the signal-to-noise ratio of the receiving end at the kth time slot, and σ ² =0.5mw is the noise power of the receiving end.

Step S7, utilize Lagrangian multiplier method, and in conjunction with binary search method, to the objective function described in step S6 Solve. The value of the optimal Lagrangian multiplier obtained is λ ^* = 0.32; the value of the optimal information receiver and energy receiver switching coefficient ρ ^* (k) (1≤k≤K) is as follows:

(1) when , then ρ ^* (k) = 0;

(2) when , then ρ ^* (k) = 1;

(3) when , then ρ ^* (k)=0.

Step S8, according to step S4 and step S7, each sub-slot information receiver and energy receiver switch the value of the coefficient ρ ^* (k) to perform adaptive time slot signal reception.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (7)

1. a kind of SWIPT system self-adaption time slot signal method of reseptance collected based on nonlinear energy, which is characterized in that described Method of reseptance include the following steps：

S1, transmitting terminal S send signal x to the receiving node D of energy constraint, and a resource block is divided into the K period of the day from 11 p.m. to 1 a.m by receiving node D Gap is received, and the signal that k-th of time slot receives is：In formula, 1≤k≤K, h_kWhen indicating k-th The channel coefficients of gap obey flat fading, P_kIndicate the transmission signal power of the time slot, n is receiving end additive white Gaussian noise；

S2, the handoff factor ρ defined between the intelligence receiver and energy receiver of receiving node D are received in k-th of time slot Handoff factor between the intelligence receiver and energy receiver of node D is defined as ρ (k), in k-th of time slot, optimal switching system Number is that the optimal value of ρ (k) is denoted as ρ^*(k), receiving node D is according to ρ^*(k) value carries out information reception or collection of energy；

S3, according to the reception signal y_rk, calculate its performance number P_rk=| h_k|²P_k, wherein | h_k|²It is complex channel coefficient h_k's Mould indicates the channel power gain of k-th of time slot；

S4, according to receive signal performance number P_rk, calculate input power of the energy receiver in k-th of time slot of destination node P_k ^ER=(1- ρ (k)) | h_k|²P_rk；

S5, by energy receiver input power P_k ^ERMultiplied by the output power saturation value after η with energy receiverIt is compared, Wherein, η is the energy conversion efficiency of destination node energy receiver, ifThen ρ^*(k)=1, receiving node D will Signal is switched to intelligence receiver, which only carries out information reception；Otherwise, following sequential steps are executed；

S6, optimization aim is minimised as with system break probability, handoff factor ρ (k) is optimization object, objective functionWhereinIt is the momentary interruption probability of k-th of time slot of system, is the function of ρ (k)；

S7, using method of Lagrange multipliers, and combine binary search method, to the objective functionIt is asked Solution obtains optimal intelligence receiver and energy receiver handoff factor ρ^*(k)；

The each sub-slots intelligence receiver and energy receiver handoff factor ρ that S8, basis obtain^*(k) value carries out adaptive Time slot signal receives.

2. a kind of SWIPT system self-adaption time slot signal collected based on nonlinear energy according to claim 1 is received Method, which is characterized in that the value of the handoff factor ρ (k) is 0 or 1, and wherein ρ (k)=1 indicates that the time slot receiving end will Signal is received for information, and ρ (k)=0 indicates that signal is used for energy and connects collection by the time slot receiving end.

3. a kind of SWIPT system self-adaption time slot signal collected based on nonlinear energy according to claim 1 is received Method, which is characterized in that the formula of the outage probability is as follows：Wherein r_k=ρ (k) log (1+γ_k) be k-th of time slot of system instant message reception rate, r₀It is the minimal information receiving velocity door of system normal communication Limit value, hereinSignal-to-noise ratio for receiving end in k-th of time slot, σ²It is the noise power of receiving end.

4. a kind of SWIPT system self-adaption time slot signal collected based on nonlinear energy according to claim 1 is received Method, which is characterized in that optimal intelligence receiver and energy receiver handoff factor ρ in the step S7^*(k) value is such as Under：

(1) whenWhen, then ρ^*(k)=0；

(2) whenWhen, then ρ^*(k)=1；

(3) whenWhen, then ρ^*(k)=0；

Wherein λ^*It is best Lagrange multiplier.

5. a kind of SWIPT system self-adaption time slot signal collected based on nonlinear energy according to claim 1 is received Method, which is characterized in that the energy conversion efficiency η value of the destination node energy receiver is 1.

6. a kind of SWIPT system self-adaption time slot signal collected based on nonlinear energy according to claim 1 is received Method, which is characterized in that self-adapting time slot letter signal receives in the step S8, refers to ρ^*(k)=1 when, the sub-slots are only Carry out information reception, ρ^*(k)=0 when, which only carries out collection of energy.

7. a kind of SWIPT system self-adaption time slot letter collected based on nonlinear energy according to any one of claims 1 to 5 Number method of reseptance, which is characterized in that the method for reseptance is directed to SWIPT system in point-to-point wireless communication scene, Channel type is flat fading channel, and sending node S has a fixed and lasting energy supply, receiving node D energy constraint and The receiver of the energy supply that do not fix, receiving node D consists of two parts：Intelligence receiver and energy receiver, energy Receiver obtains energy from the radiofrequency signal of ambient enviroment.