CN108600991B - Car networking cooperation communication system, the power distribution method of roadside unit and system - Google Patents

Abstract

The invention discloses a collaborative communication system for Internet of Vehicles, a method and system for power distribution of roadside units. The roadside unit that uses RF energy collection replaces the roadbed equipment that needs to be laid vigorously to provide services for vehicles. The development of energy collection technology allows Install road-based equipment anywhere, regardless of the availability of power, so that the Internet of Vehicles infrastructure can cover a wider area. At the same time, the use of renewable energy instead of the grid has enabled the establishment of a green and intelligent transportation system.

Description

Cooperative communication system for Internet of Vehicles, power distribution method and system for roadside units

technical field

The present invention relates to the technical field of the Internet of Vehicles, in particular to a collaborative communication system for the Internet of Vehicles and a power distribution method and system for roadside units.

Background technique

Today's urban traffic, especially in traffic jams or vehicle accidents, will generate high-density traffic information transmission. The Internet of Vehicles uses technologies such as wireless communication and sensor detection to collect information on vehicles, roads, and the environment, and through vehicle-to-vehicle (V2V) and vehicle-to-road (V2R) information interaction and sharing, intelligent collaboration between vehicles and infrastructure can be achieved. In order to realize the integrated network of intelligent traffic management control, vehicle intelligent control and intelligent dynamic information service, it supports vehicle-to-vehicle (V2V) and vehicle-infrastructure (vehicle-to-in-vehicle, Collaborative communication between V2I). In the actual vehicle mobile environment, each vehicle can be considered as a mobile terminal, which can also help other vehicles to send information while communicating with the base station. In the traditional Internet of Vehicles cooperative communication system, it often costs a lot of money to use the power grid to build the roadbed equipment in the Internet of Vehicles. The roadbed equipment needs to lay the power grid vigorously to provide services for vehicles. In relatively remote areas, it costs a lot of money to use the power grid to build roadbeds in the Internet of Vehicles. Equipment is a waste of resources, and in some areas due to geographical factors, it will be very difficult to lay power grids. These factors hinder the construction and development of Internet of Vehicles in vast areas.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a collaborative communication system for the Internet of Vehicles, a power distribution method and system for roadside units, and provide services for vehicles by using roadside units collected by RF energy instead of roadbed equipment that requires extensive laying of power grids, so that the basis of the Internet of Vehicles Facilities can cover a wider area.

To achieve the above object, the present invention provides the following scheme:

A collaborative communication system for the Internet of Vehicles, the cooperative communication system for the Internet of Vehicles includes: a source node, a relay node, and a destination node;

Both the source node and the destination node are mobile vehicle nodes with independent physical locations;

The relay node is a passive roadside unit; the roadside unit can collect RF energy; the relay node uses the collected energy to send information;

The source node and the destination node perform information exchange through the relay node.

Optionally, the source node and the destination node perform information exchange through the relay node, specifically including:

the source node sends a send signal to the relay node;

The relay node amplifies the received transmission signal and forwards it to the destination node;

or the relay node decodes the received sending signal and judges whether the sending signal is received correctly, and obtains a first judgment result;

When the first judgment result is yes, the relay node forwards the sending signal to the destination node; when the first judgment result is no, it does not forward.

The present invention also provides a power distribution method of a roadside unit, the roadside unit is applied to a vehicle network cooperative communication system, and the vehicle network cooperative communication system includes a source node, a relay node and a destination node; Both the source node and the destination node are mobile vehicle nodes with independent physical locations; the relay node is a passive roadside unit; the roadside unit is capable of collecting RF energy; the relay node utilizes the collected energy Sending information; the source node and the destination node perform information interaction through the relay node; the power allocation method includes the following steps:

Obtain the channel fading coefficients of each link in the vehicle network cooperative communication system; the channel fading coefficients of each link include the channel fading coefficient of the link from the source node to the destination node, the channel fading coefficient of the link from the source node to the relay node coefficient and the channel fading coefficient of the link from the relay node to the destination node;

Determine the receiving signal-to-noise ratio of the destination node under the DF protocol or the AF protocol according to the channel fading coefficients of the links;

According to the receiving signal-to-noise ratio of the destination node, analyze the interruption probability of the system cooperation link under the DF protocol or the AF protocol; the interruption probability is related to the power allocation ratio;

determining the power allocation ratio when the outage probability reaches the minimum, as the optimal power allocation ratio;

Allocating the power of the RF signal received by the roadside unit according to the optimal power allocation ratio.

Optionally, the determining the signal-to-noise ratio of the destination node under the DF protocol or the AF protocol according to the channel fading coefficients of the links specifically includes:

According to the formula Determine the receiving signal-to-noise ratio of the destination node under the DF protocol; where γ _D represents the receiving signal-to-noise ratio of the destination node under the DF protocol; ^g _{0 =} |h _{0 |} The channel fading coefficient of the destination node link, c represents a constant related to the environment, τ represents the path loss index, d _SD represents the distance between the source node and the destination node; ρ represents the power distribution ratio of the roadside unit; η represents the energy conversion efficiency of the roadside unit; g ₁ = |h ₁ | ² obeys the exponential distribution with parameter λ ₁ , h ₁ represents the channel fading coefficient of the source node to the relay node link, d _SR represents the distance between the source node and the relay node; g ₂ =|h ₂ | ² obeys the exponential distribution with parameter λ ₂ , h ₂ represents the channel fading coefficient of the link from the relay node to the destination node, d _RD represents the distance between the relay node and the destination node; γ= _{P S} /N ₀ , PS represents the transmit power of the source node, and N ₀ represents the variance of the additive white Gaussian noise at the relay node and the destination node; μ represents the coefficient before the variance of the additive Gaussian white noise generated by the sampling of the RF to baseband conversion unit at the destination node; R correct indicates that the relay node correctly receives the signal transmitted by the source node; R error indicates that the relay node incorrectly receives the signal transmitted by the source node Signal.

Optionally, the determining the receiving signal-to-noise ratio of the destination node under the DF protocol or the AF protocol according to the channel fading coefficients of the links specifically includes:

According to the formula γ _D1 =g ₀ γ/(1+μ) determine the receiving signal-to-noise ratio of the destination node in the first time slot under the AF protocol;

According to the formula Determine the receiving signal-to-noise ratio of the destination node in the second time slot under the AF protocol;

According to the formula γ _D =γ _D1 +γ _D2 , determine the receiving signal-to-noise ratio of the destination node in the whole communication process under the AF protocol.

Optionally, the analyzing the interruption probability of the system cooperation link under the DF protocol or the AF protocol according to the receiving signal-to-noise ratio of the destination node specifically includes:

According to the formula Analyze the interruption probability of the system cooperation link under the DF protocol; the system cooperation link is a cooperation link from the source node to the relay node and then to the destination node; wherein R _T represents the target data rate; K ₁ (x) is the first-order modified Bessel function of the second kind;

Optionally, the analyzing the interruption probability of the system cooperation link under the DF protocol or the AF protocol according to the receiving signal-to-noise ratio of the destination node specifically includes:

According to the formula Analyze the interruption probability of the system cooperation link under the AF protocol; where, a=1+1/(1-ρ),

Optionally, the allocating the power of the RF signal received by the roadside unit according to the optimal power allocation ratio specifically includes:

According to the optimal power allocation ratio, the RF signal yR- _S received by the roadside unit R is divided into and section, of which partly for energy harvesting, Some are used for information processing.

The present invention also provides a roadside unit power distribution system, the power distribution system comprising:

The channel fading coefficient acquisition module is used to obtain the channel fading coefficient of each link in the Internet of Vehicles cooperative communication system; the channel fading coefficient of each link includes the channel fading coefficient of the source node to the destination node link, the source node to the destination node The channel fading coefficient of the relay node link and the channel fading coefficient of the relay node to the destination node link;

The receiving signal-to-noise ratio determination module is used to determine the receiving signal-to-noise ratio of the destination node under the DF protocol or the AF protocol according to the channel fading coefficient of each link;

The interruption probability analysis module is used to analyze the interruption probability of the system cooperation link under the DF protocol or the AF protocol according to the receiving signal-to-noise ratio of the destination node; the interruption probability is related to the power allocation ratio;

An optimal power allocation ratio determination module, configured to determine the power allocation ratio when the interruption probability reaches the minimum, as the optimal power allocation ratio;

A power allocation module, configured to allocate the power of the RF signal received by the roadside unit according to the optimal power allocation ratio.

Optionally, the power distribution module specifically includes:

A power allocation unit, configured to divide the RF signal y _RS received by the roadside unit R into and section, of which partly for energy harvesting, Some are used for information processing.

According to the specific embodiments provided by the invention, the invention discloses the following technical effects:

The invention discloses a collaborative communication system for Internet of Vehicles, a method and system for power distribution of roadside units. The roadside unit that uses RF energy collection replaces the roadbed equipment that needs to be laid vigorously to provide services for vehicles. The development of energy collection technology allows Install road-based equipment anywhere, regardless of the availability of power, so that the Internet of Vehicles infrastructure can cover a wider area. At the same time, the use of renewable energy instead of the grid has enabled the establishment of a green and intelligent transportation system.

In addition, the present invention provides a power distribution method and system for roadside units, which proposes a collaborative communication model for the Internet of Vehicles using roadside units as relays, adopts a relay protocol based on power distribution, and derives an Internet of Vehicles powered by energy harvesting The outage probability of the system is obtained, the optimal power distribution ratio is obtained, and the power distribution of the RF signal received by the roadside unit is realized according to the optimal power distribution ratio, and the cooperative communication performance of the communication system is improved.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without paying creative labor.

FIG. 1 is a schematic diagram of a vehicle networking cooperative communication system provided by the present invention;

Fig. 2 is a flow chart of a power distribution method for roadside units provided by the present invention;

Fig. 3 is a structural diagram of a power distribution system of a roadside unit provided by the present invention;

4 is a schematic diagram of the relationship between the interruption probability of the S→R→D link and ρ when the DF protocol is adopted according to the embodiment of the present invention;

5 is a schematic diagram of the relationship between the interruption probability of the S→R→D link and ρ when the AF protocol is adopted according to the embodiment of the present invention;

6 is a schematic diagram of the relationship between SNR and outage probability under DF direct transmission and different values of ρ provided by the embodiment of the present invention;

7 is a schematic diagram of the relationship between SNR and outage probability under AF direct transmission and different values of ρ provided by the embodiment of the present invention;

Fig. 8 is a schematic diagram of comparison of outage probabilities under the DF and AF protocols provided by the embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The purpose of the present invention is to provide a collaborative communication system for the Internet of Vehicles, a power distribution method and system for roadside units, and provide services for vehicles by using roadside units collected by RF energy instead of roadbed equipment that requires extensive laying of power grids, so that the basis of the Internet of Vehicles Facilities can cover a wider area.

In order to make the above objects, features and advantages of the present invention more comprehensible, the invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

FIG. 1 is a schematic diagram of a vehicle networking cooperative communication system provided by the present invention. Referring to Fig. 1, the IoV cooperative communication system provided by the present invention is composed of mobile vehicle nodes S and D independent of physical location, and passive roadside unit R. The roadside unit R acts as a relay to help S→D exchange information. Information is transmitted from source node S to destination node D through an energy-constrained relay node R. There is no direct communication link between two nodes. The roadside unit R is passive and can perform energy harvesting to send information. The relay R collects energy from the RF signal sent by the source node S, and then uses the collected energy as the transmission power to send the signal from the source node S to the destination node. d. The mobile vehicles S and D use the roadside unit R capable of collecting RF energy to assist them in completing the information interaction.

Relay protocols based on energy harvesting include time switch relay (Time switch relay, TSR) protocol and power allocation based relay (Power switch relay, PSR) protocol.

In this paper, S represents the source node, R represents the relay node, D represents the destination node, and the "→" between the letters represents the link from the node in front of the arrow to the node behind the arrow, for example, S→D represents the source node to the destination node link. RF is the abbreviation of Radio Frequency (radio frequency).

Energy Harvesting (EH), the process of extracting energy from the surrounding environment as an alternative method to provide energy, extending the life of energy-constrained communication networks, can utilize a variety of harvestable energies such as heat, light, waves and wind and other energy sources for energy harvesting in wireless networks. Recently, energy harvesting from ambient radio frequency (RF) signals has received increasing attention due to its convenience of providing energy self-sufficiency for low-power communication systems. With recent advances in low-power device technology in industry and academia, it is expected that energy harvesting from RF signals will provide a practical solution for future applications, especially for networking of low-power devices, such as wireless sensor networks ( WSN) node. People are starting to pay attention to energy-constrained networks such as wireless sensor networks and the Internet of Things, where wireless devices are usually neither connected to the grid nor frequently recharged or replaced. For the above-mentioned network, on the premise of satisfying the basic communication service, how to obtain a stable and continuous energy supply so as to prolong the network lifetime has become the focus of attention. Even harvesting energy from man-made phenomena such as wireless energy transfer for sustainable networks. RF signals radiated by ambient transmitters can be a viable source for energy harvesting. On the one hand, RF signals are widely available in the ambient atmosphere and can carry energy and information simultaneously; on the other hand, RF signals have been widely used as carriers for information transmission. Since the simultaneous transmission of wireless information and power enables high efficiency of RF signals, potentially providing great convenience to mobile users.

In the vehicle networking cooperative communication system, roadside unit power distribution method and system provided by the present invention, the roadside unit that uses RF energy collection replaces the roadbed equipment that needs to lay a large power grid to provide services for vehicles, so that the vehicle network infrastructure can Cover a wider area.

Specifically as shown in Figure 1, the vehicle networking cooperative communication system includes: a source node S, a relay node R, and a destination node D; both the source node S and the destination node D are mobile vehicle nodes with independent physical locations . The characteristic of the system is that the relay node R is a passive roadside unit, and the roadside unit R can collect RF energy. The roadside unit R uses the collected energy to send information. The source node S and the destination node D perform information exchange through the relay node R.

The source node S sends the sending signal x _s to the relay node R;

Under the AF protocol, the relay node R amplifies the received transmission signal x _s and forwards it to the destination node D;

Under the DF protocol, the relay node R decodes the received transmission signal x _s and judges whether the transmission signal x _s is received correctly, and obtains a first judgment result;

When the first judgment result is yes, the relay node R forwards the sending signal to the destination node D; when the first judgment result is no, it does not forward.

Each node in Fig. 1 is a single antenna in a half-duplex mode. Assuming that the transmission power of the mobile vehicle _S is PS, the roadside unit R obtains energy from the received RF signal, and η∈(0,1) represents the energy efficiency, which depends on the rectification efficiency and the energy harvesting circuit at R. Assume that S→R and R→D initial distances are denoted by D _SR and D _DR . (h ₀ ,d _SD ), (h ₁ ,d _SR ), (h ₂ ,d _RD ) denote the channel fading coefficient and distance of S→D, S→R and R→D links respectively. In the Gaussian random variable of , Assume variables c=1, τ=2, d representing environment-related constants, path loss exponents, and inter-node distances, respectively. The variable g _i =|h _i | ² , i∈{0,1,2} obeys the exponential distribution with parameters λ _i , i∈{0,1,2}.

According to the power distribution ratio ρ∈(0,1), the RF signal y _RS received by the roadside unit R is divided into two parts: One part is used for energy harvesting, the other part for information processing.

In the first time slot, the moving vehicles S→D, S→R simultaneously send a signal x _s , and the signals received by the roadside unit R and the destination vehicle D are respectively:

Where y _RS represents the signal received at the roadside unit R, y _DS represents the signal received at the destination vehicle D; n _i ~CN(0,N ₀ ), i=R, D represents the Additive white Gaussian noise.

Therefore, the signal for information processing at the roadside unit R can be expressed as:

Considering the additional noise generated by the RF to baseband conversion unit sampling at the roadside unit, the above equation (1) is modified as:

Among them, x _s represents the transmitted signal of the source node, and n _R represents the variance of the additive white Gaussian noise of the relay node; Denotes the additive white Gaussian noise generated at the relay node R due to the RF-to-baseband conversion unit.

The signal for harvesting energy at the roadside unit R can be expressed as:

in, The noise energy carried in is negligible, so the energy collected at the roadside unit is expressed as:

Among them, η represents the energy conversion efficiency at the roadside unit, g ₁ =|h ₁ | ² , h ₁ represents the channel fading coefficient from vehicle S→R, and T is the entire time block.

Therefore, the transmission power P _R at the roadside unit R is:

In the second time slot, the roadside unit R→D uses the power P _R to send the signal x _R , so the signal obtained at the vehicle D is:

Among them, n _D2 ～CN(0,N ₀ ) is the additive white Gaussian noise of the target vehicle D, Denotes the additive white Gaussian noise generated at the moving vehicle D due to sampling by the RF-to-baseband conversion unit.

In relatively remote areas, it is a waste of resources to use the power grid to build road-based equipment in the Internet of Vehicles at a high cost. It is a good choice to use renewable energy instead of the power grid. The Internet of Vehicles cooperative communication system provided by the present invention provides services for vehicles by using roadside units collected by RF energy instead of roadbed equipment that requires a large power grid, and realizes a green intelligent transportation system. The development of energy harvesting technology allows road-based equipment to be installed anywhere, regardless of the availability of power sources, and the Internet of Vehicles infrastructure can cover a wider area.

Fig. 2 is a flow chart of a power distribution method for roadside units provided by the present invention. As shown in Figure 2, the power allocation method provided by the present invention includes the following steps:

Step 201: Obtain the channel fading coefficients of each link in the Internet of Vehicles cooperative communication system.

The channel fading coefficients of each link include the channel fading coefficient h ₀ of the link from the source node to the destination node, the channel fading coefficient h 1 of the link from the source node to the relay node, and the channel fading coefficient h ₁ of the link from the relay node to the destination node Coefficient h ₂ .

Step 202: Determine the receiving signal-to-noise ratio of the destination node under the DF protocol or the AF protocol according to the channel fading coefficients of the links.

Step 202, according to the two protocols of DF and AF, analyze the signal reception of each end point in the S→R→D transmission.

(1) DF agreement

Under the Decode-and-Forward (DF) protocol, the roadside unit R decodes the received signal and checks whether the reception is correct or not. If it is correct, the received signal will be forwarded to the destination node, otherwise it will not be forwarded. . Therefore, the signal sent by the relay node R at this time is:

Among them, x _R is the signal sent by the roadside unit R.

According to the signal obtained by the roadside unit R in the first time slot, the signal-to-noise ratio at the roadside unit R is obtained as:

Wherein, g ₁ =|h ₁ | ² , h ₁ represents the channel fading coefficient of S→R, and γ=P _S /N ₀ .

During the transmission process, the receiving SNR of vehicle D is:

Among them, γ _D represents the receiving signal-to-noise ratio of the destination node under the DF protocol; g ₀ =|h ₀ | ² obeys the exponential distribution with parameter λ ₀ , h ₀ represents the channel fading coefficient of the source node to the destination node link, c represents a constant related to the environment, τ represents the path loss index, d _SD represents the distance between the source node and the destination node; ρ represents the power distribution ratio of the roadside unit; η represents the energy conversion efficiency of the roadside unit; g ₁ = |h ₁ | ² obeys the exponential distribution with parameter λ ₁ , h ₁ represents the channel fading coefficient of the source node to the relay node link, d _SR represents the distance between the source node and the relay node; g ₂ =|h ₂ | ² obeys the exponential distribution with parameter λ ₂ , h ₂ represents the channel fading coefficient of the link from the relay node to the destination node, d _RD represents the distance between the relay node and the destination node; γ= _{P S} /N ₀ , PS represents the transmit power of the source node, and N ₀ represents the variance of the additive white Gaussian noise at the relay node and the destination node; μ represents the coefficient before the variance of the additive Gaussian white noise generated by the RF-to-baseband conversion unit at the destination node; R correct indicates that the relay node correctly receives the transmitted signal of the source node; R error indicates that the relay node incorrectly receives the transmitted signal of the source node Signal.

(2) AF agreement

Under the Amplify-and-Forward (AF) protocol, the roadside unit R amplifies and forwards the received signal. At this time, the transmitted signal x _R of R is:

Among them, G is the normalization factor before the roadside unit R sends the signal, which can be expressed as:

According to the signal obtained at vehicle D, its received signal-to-noise ratio in the first time slot is:

γ _D1 = g ₀ γ/(1+μ) (12)

Similarly, the received signal-to-noise ratio at the second time slot D is:

Simplified:

Let μ=1, that is, suppose Then the above formula simplifies to:

During the whole communication process, the received signal-to-noise ratio received at the mobile vehicle node D is: γ _D =γ _D1 +γ _D2 .

Step 203: Analyze the interruption probability of the system cooperation link under the DF protocol or the AF protocol according to the receiving signal-to-noise ratio of the destination node. The outage probability is directly related to the power allocation ratio.

In order to find the optimal power allocation ratio ρ∈(0,1) that makes the roadside unit have the optimal power allocation, it is necessary to analyze the outage probability of the system cooperation link under the DF protocol or the AF protocol. The direct transmission link comes from S→D transmission with fixed power, and has nothing to do with the power allocation at the roadside unit, so it is only necessary to study the S→R→D cooperative link to analyze the power allocation at the roadside unit.

All channels are assumed to be stationary random Rayleigh fading channels. The outage probability refers to the probability at vehicle D that the achievable data rate is less than the target data rate because the signal-to-noise ratio is below a given threshold. The expression of the interruption probability of the vehicle S→R→D during the communication transmission process is:

P _SRD =Pr[C _SRD <R] (16)

1) Analyze the interruption probability of the system cooperation link under the DF protocol

When vehicle S→R→D is correctly decoded by R during the communication transmission process, the receiving signal-to-noise ratio at the destination vehicle D is:

Let R _T , R _R , and R _D be the target data rate respectively, the data rate that can be obtained at the roadside unit R in the first time slot, and the data rate that can be obtained by vehicle D when R is correctly decoded in the S→R→D cooperative transmission process . Because the power allocation at the roadside unit only involves the transmission of S→R→D, the interruption probability of the S→R→D link when the DF protocol is adopted can be expressed as:

in, According to Equation (8) and Equation (17), R _R , R _D are:

Substituting the above two equations (19), (20) into equation (18) to get:

in,

Substituting R _R and R _D into equation (4-18), Pr2 can be obtained as:

in, γ = P _S /N ₀ .

g _i ＝|h _i | ² , i∈{1,2} is an exponential distribution with parameters λ _i , i∈{1,2}, h ₁ , h ₂ represent the channels of S→R and R→D respectively Fading coefficient, the above formula is calculated as:

Among them, K1 is the _first -order modified Bessel function of the second kind, γ = P _S /N ₀ .

So the outage probability of the S→R→D link is:

in,

2) Analyze the interruption probability of the system cooperation link under the AF protocol

According to the analysis of formulas (15) and (16), using the AF protocol, the interruption probability of the S→R→D link is:

Since γ _D2 = (1-ρ)ρηg ₁ g ₂ γ/[(1-ρ)ρηg ₂ +ρηg ₂ +(1-ρ)], the formula (25) above is calculated as:

Wherein, a=1+1/(1-ρ), γ=P _S /N ₀ . Similarly, the formula (26) above is calculated as:

Wherein, a=1+1/(1-ρ), γ=P _S /N ₀ ,

Step 204: Determine the power allocation ratio when the outage probability reaches the minimum, as the optimal power allocation ratio.

due to seeking and The analytical expression for involves integrals and modified Bessel functions, so use and It is difficult to calculate the closed form expression of the optimal value of ρ. Therefore, according to the system parameters (link distance, vehicle transmission rate, etc.), the optimal value of ρ is numerically analyzed, and the power distribution ratio when the interruption probability reaches the minimum is taken as the optimal power distribution ratio to complete the optimization.

Step 205: Allocate the power of the RF signal received by the roadside unit according to the optimal power allocation ratio.

According to the optimal power allocation ratio, the RF signal y _RS received by the roadside unit R is divided into and section, of which partly for energy harvesting, Some are used for information processing. Therefore, the optimal power allocation at the roadside unit is realized, and the cooperative communication performance of the communication system is improved.

Fig. 3 is a structural diagram of a roadside unit power distribution system provided by the present invention. As shown in Figure 3, the present invention also provides a power distribution system for roadside units, the power distribution system includes:

The channel fading coefficient acquisition module 301 is used to obtain the channel fading coefficient of each link in the vehicle network cooperative communication system; the channel fading coefficient of each link includes the channel fading coefficient of the link from the source node to the destination node, the source node The channel fading coefficient of the link to the relay node and the channel fading coefficient of the link from the relay node to the destination node;

A receiving signal-to-noise ratio determination module 302, configured to determine the receiving signal-to-noise ratio of the destination node under the DF protocol or the AF protocol according to the channel fading coefficients of the links;

The interruption probability analysis module 303 is configured to analyze the interruption probability of the system cooperation link under the DF protocol or the AF protocol according to the receiving signal-to-noise ratio of the destination node; the interruption probability is related to the power allocation ratio;

An optimal power allocation ratio determination module 304, configured to determine the power allocation ratio when the interruption probability reaches the minimum, as the optimal power allocation ratio;

The power allocation module 305 is configured to allocate the power of the RF signal received by the roadside unit according to the optimal power allocation ratio.

Specifically, the receiving signal-to-noise ratio determining module 302 includes:

The receiving signal-to-noise ratio determining unit under the DF protocol is used for formulating Determine the receiving signal-to-noise ratio of the destination node under the DF protocol; where γ _D represents the receiving signal-to-noise ratio of the destination node under the DF protocol; ^g _{0 =} |h _{0 |} The channel fading coefficient of the destination node link, c represents a constant related to the environment, τ represents the path loss index, d _SD represents the distance between the source node and the destination node; ρ represents the power distribution ratio of the roadside unit; η represents the energy conversion efficiency of the roadside unit; g ₁ = |h ₁ | ² obeys the exponential distribution with parameter λ ₁ , h ₁ represents the channel fading coefficient of the source node to the relay node link, d _SR represents the distance between the source node and the relay node; g ₂ =|h ₂ | ² obeys the exponential distribution with parameter λ ₂ , h ₂ represents the channel fading coefficient of the link from the relay node to the destination node, d _RD represents the distance between the relay node and the destination node; γ= _{P S} /N ₀ , PS represents the transmit power of the source node, and N ₀ represents the variance of the additive white Gaussian noise at the relay node and the destination node; μ represents the coefficient before the variance of the additive Gaussian white noise generated by the RF-to-baseband conversion unit at the destination node; R correct indicates that the relay node correctly receives the transmitted signal of the source node; R error indicates that the relay node incorrectly receives the transmitted signal of the source node Signal.

The receiving signal-to-noise ratio determining unit of the first time slot under the AF protocol is used to determine the receiving signal-to-noise ratio of the destination node in the first time slot under the AF protocol according to the formula γ _D1 =g ₀ γ/(1+μ);

The receiving signal-to-noise ratio determination unit of the second time slot under the AF protocol is used to determine according to the formula Determine the receiving signal-to-noise ratio of the destination node in the second time slot under the AF protocol;

The receiving signal-to-noise ratio determining unit under the AF protocol is configured to determine the receiving signal-to-noise ratio of the destination node under the AF protocol during the entire communication process according to the formula γ _D =γ _D1 +γ _D2 .

The interruption probability analysis module 303 specifically includes:

The interruption probability analysis unit under the DF protocol is used according to the formula Analyze the interruption probability of the system cooperation link under the DF protocol; the system cooperation link is a cooperation link from the source node to the relay node and then to the destination node; wherein R _T represents the target data rate; K ₁ (x) is the first-order modified Bessel function of the second kind;

The interruption probability analysis unit under the AF protocol is used according to the formula Analyze the interruption probability of the system cooperation link under the AF protocol; where, a=1+1/(1-ρ),

The power distribution module 305 specifically includes:

A power allocation unit, configured to divide the RF signal y _RS received by the roadside unit R into and section, of which partly for energy harvesting, Some are used for information processing.

In a green grid vehicle network, roadside units must efficiently manage their energy usage to serve as many vehicles as possible. The present invention provides a power distribution method and system for roadside units, which proposes a cooperative communication model of the Internet of Vehicles using roadside units as relays, adopts a relay protocol based on power distribution, and derives the network of vehicles system powered by energy collection The outage probability is obtained to obtain the optimal power allocation ratio, and the power allocation of the RF signal received by the roadside unit is realized according to the optimal power allocation ratio, and the cooperative communication performance of the communication system is improved.

Next, through system simulation, analyze the distribution of power at the roadside unit in S→R→D transmission, and the relationship between SNR and outage probability under direct transmission and different values of ρ. Evaluate using equations (24) and (28) respectively and The analysis results of , and using formula (16) to obtain and simulation results.

Figure 4 and Figure 5 respectively depict the relationship between the transmission interruption of the S→R→D link and ρ∈(0,1) when the DF protocol and the AF protocol are adopted. In Figure 4 and Figure 5, the abscissa is the value of the power distribution ratio ρ, and the ordinate is the outage probability. The simulation adopts d _SR =0.2, d _RD =0.8. It is obvious that the analysis and simulation conclusions are consistent with all possible values of ρ∈(0,1). For the power allocation problem at RSUs in S→R→D transmission, _PSRD decreases as ρ increases from 0 to some optimal ρ, but then starts increasing as ρ increases from its optimal value. This is because for values of ρ less than optimal ρ, the power available for energy harvesting is less. Hence, less transmitted power P _R is obtained from the RSU, and a greater probability of outage is observed at the destination vehicle D. For values of ρ larger than optimal ρ, energy harvesting wastes more power and leaves less power for source vehicle S to deliver information transmission. Poor signal strength is observed at the roadside unit and results in a greater probability of outage at the destination when the roadside unit forwards the signal to the destination. Therefore, the present invention uses the power allocation ratio when the probability value of the interruption probability reaches the minimum as the optimal power allocation ratio, which is consistent with the system simulation results.

Figure 6 and Figure 7 respectively plot the relationship between SNR and outage probability under DF direct transmission, AF direct transmission and different values of ρ. In FIG. 6 and FIG. 7 , the abscissa is the signal-to-noise ratio (SIGNAL-NOISERATIO, SNR), and the ordinate is the outage probability. The simulation adopts d _SR ＝0.2, d _RD ＝0.8, d _SRD ＝1, where S→D is the communication between two moving vehicles, so the channel model with double Rayleigh distribution is used to simulate the system interruption with direct transmission link probability. Figure 6 and Figure 7 respectively show the outages of the direct transmission link without roadside units as relays and with roadside units as relays under different values of ρ, which vary with the signal-to-noise ratio using the DF and AF protocols A comparison of probabilities. Obviously, the performance of the direct transmission link is worse than that of any system with the assistance of roadside units; compared with the optimal value of ρ and other values, the performance of the optimal value is the best. Therefore, the overall communication quality can be greatly improved if the communication is assisted by the RSU and the proper power distribution of the signal at the RSU is done before the start.

Fig. 8 is a schematic diagram of the comparison of outage probability under the DF and AF protocols, the abscissa is the signal-to-noise ratio, and the ordinate is the outage probability. Figure 8 shows that the interruption performance of the link transmission under the DF protocol is the best, and the direct transmission is the worst. However, the interruption performance of the link transmission under the AF protocol is higher than that of the link transmission under the DF protocol.

The method and system provided by the present invention adopt passive green roadside units with RF energy collection in the vehicle network relay system. The roadside unit adopts a power distribution architecture, and according to the power distribution ratio, the roadside unit can obtain energy from the RF signal transmitted by the source to forward its information. Determine a power-optimal design in the sense of the smallest achievable outage probability for energy harvesting and information processing proportions. Simulation results are used to evaluate the effects of various system parameters. The performance of the optimized design is compared with that of other cases. Energy Harvesting Technology R reuses the energy and broadcast properties of wireless links well, and allows roadside units to be installed anywhere, regardless of the actual power supply situation.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. As for the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and for the related information, please refer to the description of the method part.

In this paper, specific examples are used to illustrate the principle and implementation of the invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. The described embodiments are only part of the embodiments of the present invention. , not all of the embodiments, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work, all belong to the protection scope of the present invention.

Claims (8)

1. A power distribution method of a roadside unit, wherein the roadside unit is applied to a cooperative communication system for a network of vehicles, and the cooperative communication system for a network of vehicles comprises a source node, a relay node and a destination node; Both the source node and the destination node are mobile vehicle nodes with independent physical locations; the relay node is a passive roadside unit; the roadside unit can collect RF energy; the relay node utilizes the collected Energy transmission information; the source node and the destination node perform information exchange through the relay node; the power allocation method includes the following steps: Obtain the channel fading coefficients of each link in the vehicle network cooperative communication system; the channel fading coefficients of each link include the channel fading coefficient of the link from the source node to the destination node, the channel fading coefficient of the link from the source node to the relay node coefficient and the channel fading coefficient of the link from the relay node to the destination node; Determine the receiving signal-to-noise ratio of the destination node under the DF protocol or the AF protocol according to the channel fading coefficients of the links; According to the receiving signal-to-noise ratio of the destination node, analyze the interruption probability of the system cooperation link under the DF protocol or the AF protocol; the interruption probability is related to the power allocation ratio; determining the power allocation ratio when the outage probability reaches the minimum, as the optimal power allocation ratio; Allocating the power of the RF signal received by the roadside unit according to the optimal power allocation ratio. 2. the power allocation method of a kind of roadside unit according to claim 1, it is characterized in that, described according to the channel fading coefficient of each link, determine the receiving SNR of destination node under DF agreement or AF agreement, Specifically include: According to the formula Determine the receiving signal-to-noise ratio of the destination node under the DF protocol; where γ _D represents the receiving signal-to-noise ratio of the destination node under the DF protocol; ^g _{0 =} |h _{0 |} The channel fading coefficient of the destination node link, c represents a constant related to the environment, τ represents the path loss index, d _SD represents the distance between the source node and the destination node; ρ represents the power distribution ratio of the roadside unit; η represents the energy conversion efficiency of the roadside unit; g ₁ = |h ₁ | ² obeys the exponential distribution with parameter λ ₁ , h ₁ represents the channel fading coefficient of the source node to the relay node link, d _SR represents the distance between the source node and the relay node; g ₂ =|h ₂ | ² obeys the exponential distribution with parameter λ ₂ , h ₂ represents the channel fading coefficient of the link from the relay node to the destination node, d _RD represents the distance between the relay node and the destination node; γ= _{P S} /N ₀ , PS represents the transmit power of the source node, and N ₀ represents the variance of the additive white Gaussian noise at the relay node and the destination node; μ represents the coefficient before the variance of the additive Gaussian white noise generated by the RF-to-baseband conversion unit at the destination node; R correct indicates that the relay node correctly receives the transmitted signal of the source node; R error indicates that the relay node incorrectly receives the transmitted signal of the source node Signal. 3. the power allocation method of a kind of roadside unit according to claim 2, is characterized in that, described according to the channel fading coefficient of described each link determines the receiving signal-to-noise ratio of destination node under DF agreement or AF agreement, Specifically include: According to the formula γ _D1 =g ₀ γ/(1+μ) determine the receiving signal-to-noise ratio of the destination node in the first time slot under the AF protocol; According to the formula Determine the receiving signal-to-noise ratio of the destination node in the second time slot under the AF protocol; According to the formula γ _D =γ _D1 +γ _D2 , determine the receiving signal-to-noise ratio of the destination node in the whole communication process under the AF protocol. 4. The power distribution method of a kind of roadside unit according to claim 3, it is characterized in that, according to the received signal-to-noise ratio of the destination node, analyze the interruption probability of the system cooperation link under the DF protocol or the AF protocol , including: According to the formula Analyze the interruption probability of the system cooperation link under the DF protocol; the system cooperation link is a cooperation link from the source node to the relay node and then to the destination node; wherein R _T represents the target data rate; K ₁ (x) is the first-order modified Bessel function of the second kind; 5. The power distribution method of a kind of roadside unit according to claim 4, it is characterized in that, according to the received signal-to-noise ratio of the destination node, analyze the interruption probability of the system cooperation link under the DF protocol or the AF protocol , including: According to the formula Analyze the interruption probability of the system cooperation link under the AF protocol; where, a=1+1/(1-ρ), 6. The power allocation method of a roadside unit according to claim 5, wherein said allocating the power of the RF signal received by said roadside unit according to said optimal power allocation ratio specifically comprises: According to the optimal power allocation ratio, the RF signal y _RS received by the roadside unit R is divided into and section, of which partly for energy harvesting, Some are used for information processing. 7. A power distribution system of a roadside unit, wherein the roadside unit is applied to a cooperative communication system of the Internet of Vehicles, and the cooperative communication system of the Internet of Vehicles includes a source node, a relay node and a destination node; Both the source node and the destination node are mobile vehicle nodes with independent physical locations; the relay node is a passive roadside unit; the roadside unit can collect RF energy; the relay node utilizes the collected Energy transmission information; the source node and the destination node perform information exchange through the relay node; the power distribution system includes: The channel fading coefficient acquisition module is used to obtain the channel fading coefficient of each link in the Internet of Vehicles cooperative communication system; the channel fading coefficient of each link includes the channel fading coefficient of the source node to the destination node link, the source node to the destination node The channel fading coefficient of the relay node link and the channel fading coefficient of the relay node to the destination node link; The receiving signal-to-noise ratio determination module is used to determine the receiving signal-to-noise ratio of the destination node under the DF protocol or the AF protocol according to the channel fading coefficient of each link; The interruption probability analysis module is used to analyze the interruption probability of the system cooperation link under the DF protocol or the AF protocol according to the receiving signal-to-noise ratio of the destination node; the interruption probability is related to the power allocation ratio; An optimal power allocation ratio determination module, configured to determine the power allocation ratio when the interruption probability reaches the minimum, as the optimal power allocation ratio; A power allocation module, configured to allocate the power of the RF signal received by the roadside unit according to the optimal power allocation ratio. 8. The power distribution system of a roadside unit according to claim 7, wherein the power distribution module specifically comprises: A power allocation unit, configured to divide the RF signal y _RS received by the roadside unit R into and section, of which partly for energy harvesting, Part of it is used for information processing; ρ represents the power allocation ratio of roadside units.