Wireless-power line dual-mode communication method based on adaptive channel selection

Abstract

The invention discloses a wireless-power line dual-mode communication method based on adaptive channel selection, which comprises the following steps of: selecting a relay node, forming a system model from a source node to a relay dual-mode node and then to a destination node, and sending a signal to a relay node R by a wireless channel at a source end S; and the relay node R processes the received signal to obtain a relay signal, then adaptively selects a transmission mode with better channel quality in a power line channel or a wireless channel according to dual-mode channel state information and statistical parameter change conditions, and sends the signal to a destination end D. According to the self-adaptive channel selection algorithm, switching between a wireless channel and a power line channel can be carried out according to the channel quality, a transmission mode with better channel quality is selected in dual-mode communication, the probability that a data packet is interrupted due to channel fading and noise influence in the channel transmission process is reduced, and therefore the overall performance of a system is improved. Mobile access and long-distance communication can be realized, and the coverage effect of indoor communication is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid communication, and in particular to a wireless-power line dual-mode communication method based on adaptive channel selection. Background Art

[0002] Wireless communication and power line communication have their own characteristics. In order to improve the coverage and stability of the communication system and flexibly respond to changes in channel statistical parameters caused by sudden abnormal conditions such as environment and equipment, the adaptive channel selection algorithm can switch between wireless channels and power line channels according to channel quality, and select a transmission method with better channel quality in dual-mode communication, thereby reducing the probability of interruption of data packets during channel transmission due to channel fading and noise, thereby improving the overall performance of the system.

[0003] However, the existing dual-mode communication rarely considers adaptive design under relay conditions. Its special feature is that the mode of relay data transmission changes from the original end-to-end direct transmission and reception to two-hop forwarding. The algorithm design needs to consider practical issues such as first-hop access and second-hop link selection. The performance analysis method needs to consider practical issues such as MAC competition during random access of the first hop and the quality of different media channels of the second hop, that is, cross-layer theoretical modeling and analysis are required. However, the existing dual-media communication adaptive technology rarely considers the situation and model of two-hop relay forwarding; the focus of very few dual-mode relay research is the performance analysis of the physical layer, and almost no consideration is given to the problems caused by random access of the first hop. The performance indicators of the physical layer are mainly reliability indicators, and overall performance indicators such as network throughput cannot be obtained.

[0004] Among the prior art, the closest one is the Chinese invention patent with application publication number CN117335906A, application publication date 20240102, and name of a dual-mode communication network channel selection method, which discloses a dual-mode communication network channel selection method for smart grid area communication. The method organically combines power line carrier and micro-power wireless communication to achieve adaptive switching and improve the reliability and real-time performance of data acquisition. First, the nodes of the meter equipment are numbered by modeling the dual-mode network of the area. Secondly, the network inside and between the meter boxes is divided according to the spatial distribution. Then, an adaptive communication mechanism is designed, and the communication link evaluation based on the received signal strength change rate is used to realize the automatic selection of the dual-mode communication mode. In the case of multiple relay nodes, the best relay node is selected by the maximum and minimum signal-to-noise ratio criterion. The method can optimize the communication mode and relay path according to the real-time channel status and network environment, improve the integrity and real-time performance of data transmission, enhance the reliability and anti-interference ability of the communication network, and support smart grid and distributed energy management applications.

[0005] This invention patent proposes to select the optimal relay node using the maximum and minimum signal-to-noise ratio criteria in a multi-relay node scenario. It also proposes to build a link quality assessment mechanism based on the signal strength change rate. The comprehensive channel assessment amount is used to determine the selection of relay nodes, so that the network can select the best relay node to optimize the quality and performance of the communication link. The shortcoming is that it does not take into account the change of data transmission from the original end-to-end direct transmission and reception to two-hop forwarding. The algorithm design needs to consider practical issues such as first-hop access and second-hop link selection. The performance analysis method needs to consider practical issues such as MAC competition during random access of the first hop and the quality of different media channels in the second hop, that is, cross-layer theoretical modeling and analysis are required.

[0006] The Chinese invention patent application with application publication number CN117792439A, application publication date 20240329, and name "A method for dynamic channel selection and information transmission based on dual-mode communication" discloses a method for dynamic channel selection and information transmission based on dual-mode communication, which relates to the field of communication technology and solves the technical problem that local communication efficiency optimization leads to low communication efficiency of the entire network. The key point of its technical solution is to determine the alternative transmission path between sites through the relationship between transmission efficiency and message transmission success rate, effectively avoiding the situation where local communication efficiency optimization leads to low communication efficiency of the entire network, thereby more effectively improving the communication efficiency of the dual-mode entire network; at the same time, under the premise of allowing cross-layer message transmission, the network communication efficiency can be further improved.

[0007] The background technology of this patent document records that the China Intelligent Measurement Alliance, led by the State Grid, has gathered proposals from multiple manufacturers and formulated power line carrier (PLC) communication and wireless (RF) dual-mode communication standards. The physical layer of the power line carrier communication uses the previous State Grid power line carrier communication standard, and the physical layer of the wireless communication proposes a new wireless physical layer solution with its own intellectual property rights, and uses the unlicensed frequency band of 470MHz to 510MHz as the wireless communication frequency band.

[0008] In the State Grid dual-mode communication standard, since RF uses an unlicensed frequency band, the communication bandwidth is subject to certain restrictions, resulting in RF communication rates being significantly lower than PLC communication. Therefore, the dual-mode communication network exists in the form of a power line carrier communication as the backbone network. Therefore, the communication mode of this network is mainly PLC communication and supplemented by wireless communication. In terms of network node routing connection, this principle is also followed: under the condition that both PLC and RF can communicate, PLC is used for communication first; when there may be problems with PLC communication, it is necessary to comprehensively judge which connection method to use based on the communication success rate of PLC and RF, network level, etc.

[0009] Therefore, the patent document determines the alternative transmission paths between sites through the relationship between transmission efficiency and message transmission success rate, which can effectively avoid the situation where the optimization of local communication efficiency leads to low communication efficiency of the entire network, thereby more effectively improving the communication efficiency of the dual-mode entire network; at the same time, under the premise of allowing cross-layer message transmission, it can further improve the network communication efficiency. However, the aforementioned relative shortcomings also exist.

[0010] The present invention is proposed to address the defects of the prior art. Summary of the invention

[0011] In view of the shortcomings of the prior art, the present invention proposes an adaptive algorithm based on the optimal selection of dual-mode communication links for the system model of wireless access and dual-mode relay; and considering the situation where the first hop competes for access and the relay adopts non-competition resource allocation, a cross-layer performance calculation method of the adaptive algorithm is given, which solves the technical problems that the existing cross-layer performance methods rarely consider the above-mentioned system model and the adaptive algorithm evaluation rarely uses cross-layer methods.

[0012] To achieve the above object, the present invention adopts the following technical solution: a wireless-power line dual-mode communication method based on adaptive channel selection, comprising the following steps:

[0013] Step S1, constructing a wireless-power line dual-mode communication system model;

[0014] The selection of relay nodes is based on monitoring data including but not limited to the network environment and regional business traffic, as well as the busyness and data volume of each relay node in the network management system, and the best relay node is selected;

[0015] A system model is formed from the source node to the relay dual-mode node and then to the destination node, where:

[0016] The source node is a source end S, the relay dual-mode node is a DF relay node R with wireless-power line dual-mode communication capability, and the destination node is a destination end D;

[0017] Step S2, first hop processing, source end S to relay node R;

[0018] The source end S has N stations in its listening range and uses a transmission power of P. S Send signal X to relay node R through wireless channel S ;

[0019] Step S20, the source end S station performs competition and backoff according to the MAC layer CSMA algorithm of the IEEE 802.11 standard;

[0020] Step S21, the station that successfully competes sends a data packet to the relay node R through a wireless channel;

[0021] Step S3, second hop processing, relay node R to destination D;

[0022] The relay node R processes the received signal to obtain the relay signal, and then adaptively selects a transmission mode with better channel quality in the power line channel or wireless channel according to the dual-mode channel state information and statistical parameter changes, with the power P R Send signal X R To the destination D; where,

[0023] Step S30, the relay node obtains current channel fading parameter and noise parameter channel information through channel estimation;

[0024] Step S31, calculating the instantaneous signal-to-noise ratio of the wireless channel and the power line channel respectively according to the obtained channel information;

[0025] Step S32, calculating the interruption probability of the wireless channel and the power line channel based on the instantaneous signal-to-noise ratio of different channels;

[0026] Step S33, finally judging the interruption probabilities of the wireless channel and the power line channel, and selecting the channel with the smaller interruption probability as the transmission channel for the second-hop data packet.

[0027] The preferred technical solution provided by the present invention is:

[0028] In the wireless-power line dual-mode communication system model, all channels are affected by multiplicative fading and additive noise, the wireless channel fading satisfies the Nakagami-m distribution, and the power line channel involves LogN distribution fading and Bernoulli-Gaussian impulse noise.

[0029] More preferred:

[0030] In step S3, the method for calculating the probability of wireless channel interruption specifically includes:

[0031] System model SR or RD link instantaneous signal-to-noise ratio calculation:

[0032] The fading of the wireless channel satisfies the Nakagami-m distribution, and the noise is Gaussian white noise. Then the received signal y of R R for:

[0033]

[0034] Among them, H wl,SR =h wl,SR / (d SR ) ν , X S is the transmission signal of S, P S is the transmission power of S, n wIt means that AWGN satisfies the normal distribution N(0,N w );d SR represents the link distance between the source node S and the relay R; ν is the path fading factor of the wireless channel, which ranges from 1.6 to 6;

[0035] Under the DF protocol, the relay node R performs hard decision decoding on the received signal and sends the signal to the destination node D through the wireless interface. The signal at D is:

[0036]

[0037] Among them, H wl,RD =h wl,RD / (d RD ) ν , X R is the transmission signal of relay node R, P R is the transmission power of R, d RD represents the link distance between R and the destination node D, ν is the path loss factor of the wireless channel;

[0038] Among them, the aforementioned h wl,n , n∈(SR,RD) represents the channel fading coefficient of the wireless channel SR link and RD link, which satisfies the Nakagami distribution:

[0039]

[0040] In the formula, m w is the Nakagami distribution parameter, m w ≥0.5; Γ(x) is the gamma function; Ω w Represents the mean value of the fading amplitude, that is, Ω w =E(|h wl,n | 2 ), in order to ensure that fading does not change the average power of the received signal, normalization is performed, and Ω w =1;

[0041] The instantaneous signal-to-noise ratio of the system SR or RD link is:

[0042]

[0043] Known h wl,n Obeying the Nakagami distribution, then |h wl,n | 2 Satisfies Gamma distribution G(α w ,β w ), according to the properties of the Gamma function, |h wl,n | 2 ~G(m w ,Ωw / m w ),Right now

[0044]

[0045] The outage probability is defined as the probability that the signal-to-noise ratio falls below a certain threshold;

[0046] When the channel signal-to-noise ratio γ is less than the minimum threshold R th When , the normal communication of the system will be interrupted. Then the interruption probability of the wireless channel is:

[0047]

[0048] A further preferred technical solution is:

[0049] In the step S3, the method for calculating the probability of power line channel interruption specifically includes:

[0050] The instantaneous signal-to-noise ratio of the power line channel is:

[0051] The power line channel is affected by multiplicative fading and additive noise. The power line channel involves LogN distributed fading and Bernoulli-Gaussian impulse noise; then the received signal y of D D for:

[0052]

[0053] Among them, H pl =h pl / (d RD ) α , X R is the transmission signal of relay node R, P R is the transmission power of R, n pl is the noise term; d RD represents the link distance between R and the destination D; α is the path attenuation factor of the power line channel, which is usually 1.3 to 3.3;

[0054] h pl It represents the channel fading coefficient of the power line channel RD link, which satisfies the log-normal distribution:

[0055]

[0056] In the formula, μ pl and σ pl The variables lnh pl The mean and standard deviation of the channel fading energy are normalized, that is, Available

[0057] The n in the formula plThe power line channel noise is represented by the Bernoulli-Gaussian model, which consists of two parts: background noise and impulse noise. Its probability density function PDF has the following form:

[0058] f(n pl )=(1-p)N(0,N G )+pN(0,N G +N I )

[0059] Among them, N(0,N G ) and N(0,N G +N I ) represent normal distribution, p is the probability of impulse noise, N G and N I Represent the power of background noise and impulse noise respectively, and the average total noise power is N pl =N G +pN I , simplify the model, let k = N G / N I Represents the ratio of background noise to impulse noise.

[0060] The instantaneous signal-to-noise ratio of the power line channel is:

[0061]

[0062] Where k∈{0,1}; N0=N G Represents the noise power of only background noise, N1=N G +N I Indicates the noise power when background noise and impulse noise exist simultaneously;

[0063] h pl satisfies the log-normal distribution, According to the lognormal distribution property, Right now

[0064]

[0065] Where Q(·) is the Gaussian Q function

[0066] Then the interruption probability of the power line channel is:

[0067]

[0068] Where p is the probability of impulse noise occurring; F X (·) represents the cumulative distribution function CDF of X, f X (·) represents the PDF of X. Another preferred technical solution is:

[0069] The system model also includes a cross-layer performance analysis step, specifically:

[0070] For wireless channels, consider the CSMA algorithm based on the IEEE802.11 standard. Let CW min is the minimum contention window value, τ is the sending probability, p is the packet loss rate, m is the number of backoff stages, and N is the number of contention sites;

[0071] Where τ and p form a closed expression, which can be obtained by solving the nonlinear equation system:

[0072]

[0073] The total idle time of the system channel is T e , the total time T for data packets to collide c , the total time T for both hops to successfully transmit s , The total time during which data packets fail to be transmitted due to channel interruption As shown below:

[0074]

[0075]

[0076] Among them, P tr =1-(1-τ) N represents the probability that at least one station transmits, σ ​​is the time slot duration, P s =Nτ(1-τ) N-1 / P tr represents the probability of S successfully sending a data packet, P c =P tr (1-P s ) represents the probability of collision during data packet transmission; T c is the duration of the conflict, T s is the duration of successful transmission, T o1 and T o2 are the duration of the first-hop interruption and the second-hop interruption, respectively;

[0077] Among them, P out represents the system outage probability, which is in represents the interruption probability of the second-hop RD link

[0078]

[0079] The system throughput expression is as follows:

[0080]

[0081] Where D is the frame duration;

[0082] System packet loss rate p sys It consists of two parts: transmission failure due to collision during packet competition and transmission failure due to channel interruption. Its expression is as follows:

[0083] p sys =1-(1-p)(1-P out ).

[0084] Preferably,

[0085] The application scenarios of the wireless-power line dual-mode communication system model include but are not limited to power Internet of Things, smart grid, and smart meter reading.

[0086] Preferably,

[0087] The DF relay node R of the wireless-power line dual-mode communication system model can be regarded as a concentrator of all instruments or sensors in a substation, which is responsible for centrally processing the collected data and transferring the data; the source end S can be regarded as a background management system, which exchanges data with the concentrator and operates the smart meter through the concentrator; the destination end D refers to the smart meter or sensor on the power equipment or independently, which collects equipment information or performs remote operations such as opening and closing the switch.

[0088] The present invention also provides an electronic device, comprising: a memory, a processor, and a program stored in the memory and executable on the processor, wherein when the program is executed by the processor, the program implements the aforementioned wireless-power line dual-mode communication method based on adaptive channel selection.

[0089] The present invention also provides a computer-readable storage medium, on which a program is stored. When the program is executed by a processor, the aforementioned wireless-power line dual-mode communication method based on adaptive channel selection is implemented.

[0090] Beneficial effects:

[0091] Aiming at the system model of wireless access and dual-mode relay, an adaptive algorithm based on the optimal selection of dual-mode communication links is proposed;

[0092] Considering the first-hop contention access and the relay adopting non-contention resource allocation, a cross-layer performance calculation method of the adaptive algorithm is given. However, the existing cross-layer performance methods rarely consider the above system model, and the adaptive algorithm evaluation rarely uses cross-layer methods.

[0093] The above wireless and power line dual-mode communication system model can be applied to power Internet of Things, smart grid, smart meter reading and other scenarios. By adopting the power line-wireless dual-mode communication method, mobile access and long-distance communication can be achieved to ensure the coverage of indoor communication, which has important research value.

[0094] Wireless communication and power line communication each have their own characteristics. In order to improve the coverage and stability of the communication system and flexibly respond to changes in channel statistical parameters caused by sudden abnormal conditions such as the environment and equipment, the adaptive channel selection algorithm of the present invention can switch between wireless channels and power line channels according to channel quality, and select a transmission mode with better channel quality in dual-mode communication, thereby reducing the probability of interruption of data packets during channel transmission due to channel fading and noise, thereby improving the overall performance of the system.

[0095] Terminology explanation:

[0096] PLC, Power Line Carrier Communication, is the abbreviation of power line carrier communication. It is a power communication system that uses the existing power network as a transmission medium. It is widely used in remote meter reading (electricity information collection), automatic billing, home broadband access and other fields;

[0097] RF, Radio Frequency Communication, is the English abbreviation of radio wave communication or radio. It refers to the method of using electromagnetic waves to communicate in wireless channels;

[0098] DF, decode and forward, decode and forward;

[0099] MAC, medium access control, media access control;

[0100] CSMA, carrier sense multiple access, carrier sense multiple access;

[0101] LogN, logarithmic normal distribution, logarithmic normal distribution;

[0102] AWGN, additive white gaussian noise, additive white Gaussian noise;

[0103] CDF, cumulative distribution function, cumulative distribution function;

[0104] PDF, probability density function, probability density function;

[0105] SNR, signal to noise ratio, signal to noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0106] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0107] Figure 1 It is a schematic diagram of the wireless-power line dual-mode communication system model of the present invention;

[0108] Figure 2 A schematic diagram of the adaptive channel selection process of the present invention;

[0109] Figure 3 This is a graph showing the variation of the system outage probability with the average channel signal-to-noise ratio under different channel fading parameters;

[0110] Figure 4 Comparison of normalized throughput performance of different schemes under different signal-to-noise ratio conditions;

[0111] Figure 5 Comparison of normalized packet loss rate performance of different schemes under different signal-to-noise ratio conditions.

[0112] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0113] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0114] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0115] To facilitate understanding of the embodiments of the present invention, two specific embodiments are taken as examples for further explanation below, and these two embodiments do not constitute limitations on the embodiments of the present invention.

[0116] A wireless-power line dual-mode communication method based on adaptive channel selection of the present invention comprises the following steps:

[0117] Step S1, constructing a wireless-power line dual-mode communication system model;

[0118] Figure 1 The wireless-power line dual-mode communication system model diagram of the present invention is combined with Figure 1 illustrate:

[0119] The system consists of a source terminal S, a destination terminal D, and a DF relay node R with wireless and power line dual-mode communication capabilities. The source terminal S has N stations within its listening range. The source terminal S uses a transmission power of P S Send signal X to relay node R through wireless channel S R processes the received signal to obtain the relay signal, and then adaptively selects a transmission mode with better channel quality in the power line channel and the wireless channel according to the dual-mode channel status information, statistical parameter changes, etc. R Send signal X R To the destination node D. All channels are affected by multiplicative fading and additive noise. The fading of wireless channels satisfies the Nakagami-m distribution, and the power line channel involves LogN distribution fading and Bernoulli-Gaussian impulse noise.

[0120] The above wireless and power line dual-mode communication system model can be applied to scenarios such as the power Internet of Things, smart grid, and smart meter reading. R can be regarded as a concentrator of all instruments or sensors in a substation, responsible for centralized processing of collected data and data transfer. S can be regarded as a background management system, which exchanges data with the concentrator R and operates smart meters through the concentrator. The destination D refers to smart meters or sensors on or independently of power equipment, which collect equipment information or perform remote operations such as pulling and closing switches. By adopting the power line-wireless dual-mode communication method, mobile access and long-distance communication can be achieved to ensure the coverage of indoor communications, which has important research value.

[0121] The selection of relay nodes is based on monitoring data including but not limited to the network environment and regional business traffic, as well as the busyness and data volume of each relay node in the network management system, and the best relay node is selected;

[0122] Figure 2 The adaptive channel selection process diagram of the present invention is shown in FIG. Figure 2 As shown,

[0123] Step S2, first hop processing, source end S to relay node R;

[0124] The source end S has N stations in its listening range and uses a transmission power of P.S Send signal X to relay node R through wireless channel S ;

[0125] Step S20, the source end S station performs competition and backoff according to the MAC layer CSMA algorithm of the IEEE 802.11 standard;

[0126] Step S21, the station that successfully competes sends a data packet to the relay node R through a wireless channel;

[0127] Step S3, second hop processing, relay node R to destination D;

[0128] The relay node R processes the received signal to obtain the relay signal, and then adaptively selects a transmission mode with better channel quality in the power line channel or wireless channel according to the dual-mode channel state information and statistical parameter changes, with the power P R Send signal X R To the destination D; where,

[0129] Step S30, the relay node obtains current channel fading parameter and noise parameter channel information through channel estimation;

[0130] Step S31, calculating the instantaneous signal-to-noise ratio of the wireless channel and the power line channel respectively according to the obtained channel information;

[0131] Step S32, calculating the interruption probability of the wireless channel and the power line channel based on the instantaneous signal-to-noise ratio of different channels;

[0132] The specific instructions are as follows:

[0133] In step S3, the method for calculating the probability of wireless channel interruption specifically includes:

[0134] System model SR or RD link instantaneous signal-to-noise ratio calculation:

[0135] The fading of the wireless channel satisfies the Nakagami-m distribution, and the noise is Gaussian white noise. Then the received signal y of R R for:

[0136]

[0137] Among them, H wl,SR =h wl,SR / (d SR ) ν , X S is the transmission signal of S, P S is the transmission power of S, n w It means that AWGN satisfies the normal distribution N(0,N w );d SRrepresents the link distance between the source node S and the relay R; ν is the path fading factor of the wireless channel, which ranges from 1.6 to 6;

[0138] Under the DF protocol, the relay node R performs hard decision decoding on the received signal and sends the signal to the destination node D through the wireless interface. The signal at D is:

[0139]

[0140] Among them, H wl,RD =h wl,RD / (d RD ) ν ,,X R is the transmission signal of relay node R, P R is the transmission power of R, d RD represents the link distance between R and the destination node D, ν is the path loss factor of the wireless channel;

[0141] Among them, the aforementioned h wl,n , n∈(SR,RD) represents the channel fading coefficient of the wireless channel SR link and RD link, which satisfies the Nakagami distribution:

[0142]

[0143] In the formula, m w is the Nakagami distribution parameter, m w ≥0.5; Γ(x) is the gamma function; Ω w Represents the mean value of the fading amplitude, that is, Ω w =E(|h wl,n | 2 ), in order to ensure that fading does not change the average power of the received signal, normalization is performed, and Ω w =1;

[0144] The instantaneous signal-to-noise ratio of the system SR or RD link is:

[0145]

[0146] Known h wl,n Obeying the Nakagami distribution, then |h wl,n | 2 Satisfies Gamma distribution G(α w ,β w ), according to the properties of the Gamma function, |h wl,n | 2 ~G(m w ,Ω w / m w ),Right now

[0147]

[0148] The outage probability is defined as the probability that the signal-to-noise ratio falls below a certain threshold;

[0149] When the channel signal-to-noise ratio γ is less than the minimum threshold R th When , the normal communication of the system will be interrupted. Then the interruption probability of the wireless channel is:

[0150]

[0151] In the step S3, the method for calculating the probability of power line channel interruption specifically includes:

[0152] The instantaneous signal-to-noise ratio of the power line channel is:

[0153] The power line channel is affected by multiplicative fading and additive noise. The power line channel involves LogN distributed fading and Bernoulli-Gaussian impulse noise; then the received signal y of D D for:

[0154]

[0155] Among them, H pl =h pl / (d RD ) α , X R is the transmission signal of relay node R, P R is the transmission power of R, n pl is the noise term; d RD represents the link distance between R and the destination D; α is the path attenuation factor of the power line channel, which is usually 1.3 to 3.3;

[0156] h pl It represents the channel fading coefficient of the power line channel RD link, which satisfies the log-normal distribution:

[0157]

[0158] In the formula, μ pl ,σ pl The variables lnh pl The mean and standard deviation of the channel fading energy are normalized, that is, Available

[0159] The n in the formula pl The power line channel noise is represented by the Bernoulli-Gaussian model, which consists of two parts: background noise and impulse noise. Its probability density function PDF has the following form:

[0160] f(npl )=(1-p)N(0,N G )+pN(0,N G +N I )

[0161] Among them, N(0,N G ) and N(0,N G +N I ) represent normal distribution, p represents the probability of impulse noise, N G and N I Represent the power of background noise and impulse noise respectively, and the average total noise power is N pl =N G +pN I , simplify the model, let k = N G / N I Represents the ratio of background noise to impulse noise.

[0162] The instantaneous signal-to-noise ratio of the power line channel is:

[0163]

[0164] Where k∈{0,1}; N0=N G Represents the noise power of only background noise, N1=N G +N I Indicates the noise power when background noise and impulse noise exist simultaneously;

[0165] h pl satisfies the log-normal distribution, According to the lognormal distribution property, Right now

[0166]

[0167] Where Q(·) is the Gaussian Q function

[0168] Then the interruption probability of the power line channel is:

[0169]

[0170] Where p is the probability of impulse noise occurring; F X (·) represents the cumulative distribution function CDF of X, f X (·) represents the PDF of X.

[0171] Step S33, finally judging the interruption probabilities of the wireless channel and the power line channel, and selecting the channel with the smaller interruption probability as the transmission channel for the second-hop data packet.

[0172] Then the interruption probability of the second-hop RD link is:

[0173]

[0174] The probability of system outage is:

[0175]

[0176] The system model also includes a cross-layer performance analysis step, specifically:

[0177] For wireless channels, consider the CSMA algorithm based on the IEEE802.11 standard. Let CW min is the minimum contention window value, τ is the sending probability, p is the packet loss rate, m is the number of backoff stages, and N is the number of contention sites;

[0178] Where τ and p form a closed expression, which can be obtained by solving the nonlinear equation system:

[0179]

[0180] The total time the system channel is idle The total time that packets collide The total time for both hops to be successfully transmitted The total time during which data packets fail to be transmitted due to channel interruption As shown below:

[0181]

[0182] Among them, P tr =1-(1-τ) N represents the probability that at least one station transmits, σ ​​is the time slot duration, P s =Nτ(1-τ) N-1 / P tr represents the probability of S successfully sending a data packet, P c =P tr (1-P s ) represents the probability of collision during data packet transmission; T c is the duration of the conflict, T s is the duration of successful transmission, T o1 and T o2 are the duration of the first-hop interruption and the second-hop interruption, respectively;

[0183] Among them, P out represents the system outage probability, which is in represents the interruption probability of the second-hop RD link

[0184]

[0185] The system throughput expression is as follows:

[0186]

[0187] Where D is the frame duration;

[0188] System packet loss rate p sys It consists of two parts: transmission failure due to collision during packet competition and transmission failure due to channel interruption. Its expression is as follows:

[0189] p sys =1-(1-p)(1-P out ).

[0190] Simulation and analysis:

[0191] Through extensive Monte Carlo simulation, the model and algorithm performance simulation were carried out. The cross-layer performance of the system under different transmission schemes such as wireless-wireless, wireless-powerline, and adaptive channel selection was compared, and the laws of the physical layer parameters and MAC layer parameters affecting the system performance were analyzed. The simulation results show that the adaptive channel selection algorithm in this paper enables the system to have better performance in terms of normalized throughput, packet loss rate, etc.

[0192] Parameter settings:

[0193] Without loss of generality, unless otherwise specified, the simulation parameters in this section use the following default settings:

[0194] For the physical layer, the distance of each hop link is normalized, and d SR =d RD =1, wireless and power line channel path fading factor ν = 2, α = 1.5; power line channel Bernoulli-Gaussian impulse noise parameters p = 0.1, k = 0.02; channel interruption threshold γ th =0.1;

[0195] For the MAC layer, m = 4; CW = [16, 32, 64, 128]; CW min =16; frame duration T D =5000μs.

[0196] In addition, it is assumed that all packets use the same physical rate, and the slot duration and timing parameters specified by the standard are adopted. The fixed common parameter settings of various overheads introduced by the MAC layer due to priority identification, preamble, acknowledgment and inter-frame space are shown in Table 1.

[0197] Table 1 Main parameters and values ​​of MAC layer protocol

[0198] Table1 Main parameters and values ​​of MAC layer protocol

[0199]

[0200] In the table, the subscript w represents a wireless channel, the subscript pl represents a power line channel; σ represents the time slot duration, PRS represents the priority enhanced time slot, CIFS represents the contention interframe space, RIFS represents the response interframe space, P represents the preamble, ACK represents the acknowledgement frame, D represents the frame duration, EIFS represents the extended interframe space, ACK represents the acknowledgement, RTS and CTS represent request to send / clear to send respectively; SIFS represents the short interframe space, DIFS represents the distributed interframe space, H represents the frame header, RCG represents the receiving end, CMG represents the cooperative multicast group, δ represents the tiny extra time introduced by channel switching, random deviation, etc., and AT represents the access time.

[0201] Assume that all packets use the same physical rate and adopt the time slot duration and timing parameters specified by the standard. Then the duration of successful transmission is T s , the duration of the conflict is T c and the duration of the interruption T o As shown below:

[0202]

[0203] T s =T s1 +T s2

[0204]

[0205] T o =T o1 +T o2

[0206] Simulation results and analysis:

[0207] Figure 3 This is a graph showing the variation of the system outage probability with the average channel signal-to-noise ratio under different channel fading parameters. Figure 3 It can be seen that: as the average signal-to-noise ratio (SNR) of the channel increases, the system outage probability under different channel fading parameters decreases. This is because the larger the value of the average signal-to-noise ratio of the channel, the better the data transmission quality and the better the system performance. For different channel statistical parameters, the channel adaptive algorithm proposed in the paper selects a transmission method with better channel quality between power lines and wireless, so its outage probability is always optimal. Under different channel fading coefficients and signal-to-noise ratios, it has the optimal system outage probability performance.

[0208] Figure 4 and Figure 5 The figure shows the performance comparison of normalized throughput and packet loss rate of different schemes under different signal-to-noise ratio conditions.

[0209] Among them, the normalized throughput and packet loss rate are m w =1,σ pl =2.5, m w =1.5,σ pl =1.2 is the average of the two cases. As can be seen from the figure, as the channel average signal-to-noise ratio (SNR) increases, that is, the wireless and power line channel conditions improve, the system throughput of different schemes increases, the packet loss rate decreases, and the system performance is improved.

[0210] The performance of the wireless-power line transmission scheme is significantly inferior to that of the wireless-wireless transmission scheme under low signal-to-noise ratio conditions, but gradually converges to the same performance as the signal-to-noise ratio increases, and is slightly better than the wireless-wireless transmission scheme under high signal-to-noise ratio conditions. The channel adaptive selection transmission scheme proposed in this paper can select a transmission method with better channel quality under different channel fading and channel noise conditions. Therefore, this scheme has the best performance, can reduce the probability of data packet interruption under different channel conditions, and improve the stability and reliability of communication.

[0211] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0212] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0213] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes a number of instructions for an electronic device (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in each embodiment of the present application.

[0214] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A wireless-power line dual-mode communication method based on adaptive channel selection, characterized in that: The following steps are involved: Step S1, constructing a wireless-power line dual-mode communication system model; The selection of relay nodes is based on monitoring data including but not limited to the network environment and regional business traffic, as well as the busyness and data volume of each relay node in the network management system, and the best relay node is selected; A system model is formed from the source node to the relay dual-mode node and then to the destination node, where: The source node is a source end S, the relay dual-mode node is a DF relay node R with wireless-power line dual-mode communication capability, and the destination node is a destination end D; Step S2, first hop processing, source end S to relay node R; The source end S has N stations in its listening range and uses a transmission power of P. S Send signal X to relay node R through wireless channel S ; Step S20, the source end S station performs competition and backoff according to the MAC layer CSMA algorithm of the IEEE 802.11 standard; Step S21, the station that successfully competes sends a data packet to the relay node R through a wireless channel; Step S3, second hop processing, relay node R to destination D; The relay node R processes the received signal to obtain the relay signal, and then adaptively selects a transmission mode with better channel quality in the power line channel or wireless channel according to the dual-mode channel state information and statistical parameter changes, with the power P R Send signal X R To the destination D; where, Step S30, the relay node obtains current channel fading parameter and noise parameter channel information through channel estimation; Step S31, calculating the instantaneous signal-to-noise ratio of the wireless channel and the power line channel respectively according to the obtained channel information; Step S32, calculating the interruption probability of the wireless channel and the power line channel based on the instantaneous signal-to-noise ratio of different channels; Step S33, finally judging the interruption probabilities of the wireless channel and the power line channel, and selecting the channel with the smaller interruption probability as the transmission channel for the second-hop data packet.

2. According to the wireless-power line dual-mode communication method based on adaptive channel selection as described in claim 1, its characteristics are as follows: In the wireless-power line dual-mode communication system model, all channels are affected by multiplicative fading and additive noise, the wireless channel fading satisfies the Nakagami-m distribution, and the power line channel involves LogN distribution fading and Bernoulli-Gaussian impulse noise.

3. According to the wireless-power line dual-mode communication method based on adaptive channel selection as described in claim 1, its characteristics are as follows: In step S3, the method for calculating the probability of wireless channel interruption specifically includes: System model SR or RD link instantaneous signal-to-noise ratio calculation: The fading of the wireless channel satisfies the Nakagami-m distribution, and the noise is Gaussian white noise. Then the received signal y of R R for: Among them, H wl,SR =h wl,SR / (d SR ) ν , X S is the transmission signal of S, P S is the transmission power of S, n w It means that AWGN satisfies the normal distribution N(0,N w );d SR represents the link distance between the source node S and the relay R; ν is the path fading factor of the wireless channel, which ranges from 1.6 to 6; Under the DF protocol, the relay node R performs hard decision decoding on the received signal and sends the signal to the destination node D through the wireless interface. The signal at D is: Among them, H wl,RD =h wl,RD / (d RD ) ν , X R is the transmission signal of relay node R, P R is the transmission power of R, d RD represents the link distance between R and the destination node D, ν is the path loss factor of the wireless channel; Among them, the aforementioned h wl,n , n∈(SR,RD) represents the channel fading coefficient of the wireless channel SR link and RD link, which satisfies the Nakagami distribution: In the formula, m w is the Nakagami distribution parameter, m w ≥0.5; Γ(x) is the gamma function; Ω w Represents the mean value of the fading amplitude, that is, Ω w =E(|h wl,n | 2 ), in order to ensure that fading does not change the average power of the received signal, normalization is performed, and Ω w =1; The instantaneous signal-to-noise ratio of the system SR or RD link is: Where N w represents the noise power of the wireless channel; Known h wl,n Obeying the Nakagami distribution, then |h wl,n | 2 Satisfies Gamma distribution G(α w ,β w ), according to the properties of the Gamma function, |h wl,n | 2 ~G(m w ,Ω w / m w ),Right now The outage probability is defined as the probability that the signal-to-noise ratio falls below a certain threshold; When the channel signal-to-noise ratio γ is less than the minimum threshold R th When , the normal communication of the system will be interrupted. Then the interruption probability of the wireless channel is:

4. According to the wireless-power line dual-mode communication method based on adaptive channel selection as described in claim 1, its characteristics are as follows: In the step S3, the method for calculating the probability of power line channel interruption specifically includes: The instantaneous signal-to-noise ratio of the power line channel is: The power line channel is affected by multiplicative fading and additive noise. The power line channel involves LogN distributed fading and Bernoulli-Gaussian impulse noise; then the received signal y of D D for: Among them, H pl =h pl / (d RD ) α , X R is the transmission signal of relay node R, P R is the transmission power of R, n pl is the noise term; d RD represents the link distance between R and the destination D; α is the path attenuation factor of the power line channel, which is usually 1.3 to 3.3; h pl It represents the channel fading coefficient of the power line channel RD link, which satisfies the log-normal distribution: In the formula, μ pl ,σ pl The variables lnh pl The mean and standard deviation of the channel fading energy are normalized, that is, Available n in the formula pl The power line channel noise is represented by the Bernoulli-Gaussian model, which consists of two parts: background noise and impulse noise. Its probability density function PDF has the following form: f(n pl )=(1-p)N(0,N G )+pN(0,N G +N I ) Among them, N(0,N G ) and N(0,N G +N I ) represent normal distribution, p represents the probability of impulse noise, N G and N I Represent the power of background noise and impulse noise respectively, and the average total noise power is N pl =N G +pN I , simplify the model, let k = N G / N I Represents the ratio of background noise to impulse noise. The instantaneous signal-to-noise ratio of the power line channel is: Where k∈{0,1}; N0=N G Represents the noise power of only background noise, N1=N G +N I Indicates the noise power when background noise and impulse noise exist simultaneously; h pl satisfies the log-normal distribution, According to the lognormal distribution property, Right now Where Q(·) is the Gaussian Q function Then the interruption probability of the power line channel is: Where p is the probability of impulse noise occurring; F X (·) represents the cumulative distribution function CDF of X, f X (·) represents the PDF of X.

5. According to the wireless-power line dual-mode communication method based on adaptive channel selection as claimed in claim 1, its characteristics are as follows: The system model also includes a cross-layer performance analysis step, specifically: For wireless channels, consider the CSMA algorithm based on the IEEE802.11 standard. Let CW min is the minimum contention window value, τ is the sending probability, p is the packet loss rate, m is the number of backoff stages, and n is the number of contention sites; Where τ and p form a closed expression, which can be obtained by solving the nonlinear equation system: The total time the system channel is idle The total time that packets collide The total time for both hops to be successfully transmitted The total time during which data packets fail to be transmitted due to channel interruption As shown below: Among them, P tr =1-(1-τ) N represents the probability that at least one station transmits, σ ​​is the time slot duration, P s =Nτ(1-τ) N-1 / P tr represents the probability of S successfully sending a data packet, P c =P tr (1-P s ) represents the probability of collision during data packet transmission, T c is the duration of the conflict, T s is the duration of successful transmission, T o1 and T o2 are the duration of the first-hop interruption and the second-hop interruption, respectively; Among them, P out represents the system outage probability, which is in represents the interruption probability of the second-hop RD link The system throughput expression is as follows: Where D is the frame duration; System packet loss rate p sys It consists of two parts: transmission failure due to collision during packet competition and transmission failure due to channel interruption. Its expression is as follows: p sys =1-(1-p)(1-P out )。 6. According to the wireless-power line dual-mode communication method based on adaptive channel selection as claimed in claim 1, its characteristics are as follows: The application scenarios of the wireless-power line dual-mode communication system model include but are not limited to power Internet of Things, smart grid, and smart meter reading.

7. The wireless-power line dual-mode communication method based on adaptive channel selection according to claim 1, wherein: The DF relay node R of the wireless-power line dual-mode communication system model can be regarded as a concentrator of all instruments or sensors in a substation, responsible for centralized processing of collected data and data transfer; the source end S can be regarded as a background management system, which exchanges data with the concentrator and operates the smart meter through the concentrator; The destination D refers to the smart meter or sensor on or off the power equipment, which collects equipment information or performs remote operations such as opening and closing the switch.

8. An electronic device, characterized in that: include: A memory, a processor, and a program stored in the memory and executable on the processor, wherein when the program is executed by the processor, a wireless-power line dual-mode communication method based on adaptive channel selection is implemented as claimed in any one of claims 1 to 7.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a program, and when the program is executed by the processor, the program implements the wireless-power line dual-mode communication method based on adaptive channel selection as claimed in any one of claims 1 to 7.

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