Bidirctional realy system of powerline communication network based on noma and method thereof

Abstract

The present invention discloses a bidirectional relay system and method for a power line communication network. According to a specific embodiment, by selecting an optimal relay node in which the operating area is determined based on an average channel capacity estimated by a closed-type estimation algorithm for at least one relay node in a power line communication system, a high data transmission rate, high spectral efficiency, better fairness, and low transmission power can be guaranteed, and the system can operate with high spectral efficiency and is robust against signal attenuation and noise.

Description

Technology Field

[0001] The present invention relates to a bidirectional relay system and method for a power line communication network, and more specifically, to a technology that can select an optimal relay node in a power line communication network, wherein the operating area is determined based on the average channel capacity estimated by a closed-type estimation algorithm for the relay node. Background Technology

[0003] Power-line Communication (PLC) systems enable data transmission over power lines. Due to the extensive power grid, PLC is considered a cost-effective communication technology for smart devices, smart homes, smart grids, and smart cities. PLC can be directly applied to real-time smart metering, industrial load switching, smart grid system monitoring, cable diagnostics, and the provision of broadband internet access.

[0004] However, the data transmission performance of power line communication systems is degraded in PLC systems due to signal power loss caused by long cable lengths and the transmission of high-frequency data signals through power cables. Another disadvantage of PLC performance is that PLC noise is primarily non-Gaussian. PLC noise can be broadly classified into narrowband, background, and impulse noise. Impulse noise is the strongest type of noise in PLC networks because it has a high power spectral density (PSD). Impulse noise occurs while turning electronic devices on or off.

[0005] In addition, in accordance with electromagnetic compatibility (EMC) regulations for PLC systems, transmission power limits are imposed on PLC systems to reduce interference with other frequency users. Therefore, bottlenecks must be resolved to improve the reliability and robustness of the PLC network.

[0006] Here, the relay node can operate as a unidirectional relay (OWR) or a bidirectional relay (TWR). Compared to an OWR, a TWR can achieve bidirectional communication in only two time slots, thereby increasing spectrum efficiency. Bidirectional relays can improve PLC performance for smart grid applications.

[0007] Accordingly, the applicant intends to propose a method that can ensure high data transmission rates, high spectral efficiency, better fairness, and low transmission power, and can operate with high spectral efficiency and be robust against signal attenuation and noise by selecting an optimal relay node in which the operating area is determined based on the average channel capacity estimated by a closed-type estimation algorithm for at least one relay node in a power line communication system. The problem to be solved

[0008] The objective of the present invention is to provide a bidirectional relay system and method for a power line communication network that can ensure high data transmission rates, high spectral efficiency, better fairness, and low transmission power, and can operate with high spectral efficiency and is robust against signal attenuation and noise by selecting an optimal relay node whose operating area is determined based on an average channel capacity estimated by a closed-type estimation algorithm for at least one relay node in a power line communication system.

[0009] The purpose of the present invention is not limited to the purposes mentioned above, and other unmentioned purposes will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0010] A bidirectional relay system of a power line communication network according to one embodiment based on one aspect for achieving the above purpose is,

[0011] In a power line communication network in which at least one bidirectional relay node is cooperatively multiple accessed (NOMA) between a source node and at least one target node, the operating area is determined by minimizing the sum of average channel capacities estimated based on a closed-type estimation algorithm for each target node, and the optimal relay node with high spectrum efficiency is further selected and controlled by including a control unit.

[0012] Preferably, the control unit is,

[0013] For the received signal of a relay node derived through the modeling of the channel gain of the power line communication network, signal attenuation according to the distance between the node and the operating frequency, and total noise, respectively,

[0014] For each target node, estimate the average channel capacity based on a closed-form estimation algorithm, and

[0015] The operating region is determined by minimizing the sum of the estimated average channel capacities, and can be configured to select the optimal relay node with high spectral efficiency.

[0016] According to another embodiment, a bidirectional relay method for a power line communication network is,

[0017] A control unit of a power line communication network in which at least one bidirectional relay node is connected between at least one power line source node estimates the average channel capacity for each target node based on a closed-type estimation algorithm; and a step of determining an operating area by minimizing the sum of the estimated average channel capacities and selecting an optimal relay node with high spectrum efficiency. Effects of the invention

[0018] According to one embodiment, by selecting an optimal relay node in which the operating area is determined based on the average channel capacity estimated by a closed-type estimation algorithm for at least one relay node in a power line communication system, a high data transmission rate, high spectral efficiency, better fairness, and low transmission power can be guaranteed, and operation with high spectral efficiency can be achieved, and robust effects against signal attenuation and noise are obtained. Brief explanation of the drawing

[0019] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings. Figure 1 is a diagram showing the configuration of a power line communication system of one embodiment. Figures 2 and 3 are comparison graphs showing the average channel capacity by relay node method for each target node of a system of one embodiment. Specific details for implementing the invention

[0020] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings and the following description. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to ensure that the spirit of the present invention is sufficiently conveyed to those skilled in the art. Throughout the specification, the same reference numerals denote the same compositions. Meanwhile, the terms used in this specification are for describing the embodiments and are not intended to limit the present invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. The terms "comprises" and / or "comprising" as used in this specification do not exclude the presence or addition of one or more other compositions, steps, actions, and / or elements to the mentioned compositions, steps, actions, and / or elements.

[0021] Before describing the present specification, we will clarify some terms used in the present specification.

[0022] Hereinafter, a relay selection system based on cooperative multiple access in a power line communication network according to one embodiment will be described in detail with reference to the attached drawings.

[0023] FIG. 1 is a diagram showing the configuration of a power line communication system of one embodiment, and FIG. 2 and FIG. 3 are comparison graphs showing the average channel capacity by relay node method of the system shown in FIG. 1.

[0024] Referring to FIGS. 1 to 3, a power line communication system according to one embodiment includes a user node and , and relay nodes It may include.

[0025] Here, the bidirectional relay node The power line communication system is merely a preferred embodiment, and it goes without saying that some components may be added or removed as needed. In addition, the bidirectional relay node shown in FIG. 1 It should be noted that each component of this power line communication system represents a functionally distinct element, and that multiple components may be implemented in an integrated form in an actual physical environment.

[0026] Here, the source node and A relay node Considering a PLC network communicating with each other through, each node is composed of a PLC system, and the relay node It operates in AF (amplification-forwarding) and DF (decoding-forwarding) modes.

[0027] In other words, the AF relay node is the source node and It amplifies the transmission signal and sends it to the target node, and the DF relay node is the source node and The transmission signal is decoded and re-encrypted before being transmitted to the target node. Due to the decoding process, the DF relay outperforms the AF relay in low SNR scenarios.

[0028] And, relay node It can be supported by unidirectional relays (OWRs) and bidirectional relays (TWRs), and unidirectional relays are source nodes and The transmission signal of the relay node Although it supports unidirectional transmission to target nodes, OWR is very inefficient in smart grids because it requires four time slots for bidirectional communication.

[0029] Accordingly, one embodiment may apply a bidirectional relay TWR in a power line communication network to improve spectrum efficiency. The TWR can support bidirectional communication in just two time slots by utilizing encryption of the transmission signal, and is therefore implemented as a bidirectional relay node TWR in smart applications.

[0030] Source Node and A relay node Considering a bidirectional relay PLC communication network that communicates with each other through [the network], it does not exist in a direct path due to high signal attenuation.

[0031] Source Node and Bidirectional transmission between them is completed in two time slots, namely the Multiple Access (MAC) phase and the Broadcast (BC) phase, during which the transmission power at the source node is, respectively and It is displayed as.

[0032] Source Node and Each transmission signal in the form of a symbol and Each MAC channel and relay node through It is transmitted to, and the relay node Received signal at It includes the channel gain of the PLC network, signal attenuation according to frequency and distance, and total noise.

[0033] Here, channel gain in the PLC network is modeled by log-normal fading, taking into account the irregular effects caused by discontinuous and connected loads. The probability density function (PDF), cumulative distribution function (CDF), and supplementary cumulative distribution function (CCDF) for all PLC channels h can be expressed by the following Equations 1 to 3, respectively.

[0034] [Equation 1]

[0035]

[0036] [Equation 2]

[0037]

[0038] [Equation 3]

[0039]

[0040] Here, and is the average and It is the variance of is a scaling constant and is Gaussian It is a function.

[0041] In addition, the attenuation of the transmission signal of the power line source node with respect to the distance between the relay node, the destination node, and the operating frequency can be determined from the Zimmerman-Dostert model, and this attenuation of the transmission signal of the power line source node can be expressed by the following Equation 4.

[0042] [Equation 4]

[0043]

[0044] Here, , , and ε₀ is the distance (in m), frequency (in MHz), and the exponent of the damping coefficient, respectively. , and These are damping constants obtained from experimental data, respectively.

[0045] Also, user nodes of the power line system class The noise is non-Gaussian, modeled using a Bernoulli-Gaussian random process, and is the sum of ambient noise and impulse noise. The total noise of all PLC nodes can be inferred from the following Equation 5.

[0046] [Equation 5]

[0047]

[0048] Here is the impulse noise probability and the variance and These are the power of the ambient noise and the power of the ambient impulse noise, respectively.

[0049] And, relay node is the received signal The DF method is applied to decode it. And after the successful decoding of the symbol, the relay node It applies a network encryption method to the received signal in the form of two symbols Re-encrypt.

[0050] Here, encryption is performed via Physical Layer Network Coding (PNC) or Analog Network Coding (ANC). That is, relay nodes during PNC and ANC. is the source node and Each transmission signal in the form of a symbol and Superimposed signal in symbolic form by performing an exclusive OR (XOR) on it Creates.

[0051] relay node is a superimposed signal in the form of a symbol Encrypt the symbol using PNC and ANC class Generates and each generated symbol class each user node class It transmits as. Here, the difference between PNC and ANC is that it relays transmission power constraints. That is, the PNC method uses each symbol class relay transmission power Transmits as shown, and the ANC method uses symbols class A power allocation factor is applied to transmit. Therefore, the relay node uses PNC and ANC methods. user node class Overlapping signal transmitted to It can be expressed by the following Equations 6 and 7.

[0052] [Equation 6]

[0053]

[0054] [Equation 7]

[0055]

[0056] Here and are the XOR operation and power allocation factor, respectively.

[0057] And relay nodes is a superimposed signal user node and BC Channel and Transmit each via. User node and are each signals and It receives. At this time, the user node and is a transmission signal and Since we already know the MAC and BC channels and have complete knowledge of the channel state information (CSI) to perform SIC, we perform a self-interference cancellation SIC algorithm before decoding.

[0058] And, the PCL system relay nodes based on the average channel capacity estimated according to a closed-loop estimation algorithm It may further include a control unit (100) that determines the operating area of ​​and selects an optimal relay node with high spectrum efficiency.

[0059] The control unit (100) estimates the average total capacity through a closed-type estimation algorithm. That is, the estimated total average channel capacity of the DF bidirectional relay nodes of the PNC and ANC methods is derived according to Equation 8 below, and thus it can be seen that the total average channel capacity of the PLC DF TWR is derived as the sum of the minimum channel capacities of the MAC and BC channels.

[0060] [Equation 8]

[0061]

[0062] Here , and are each relay , and source node and It is the average capacity of, and is, , , the 1 / 2 argument is for half-duplex transmission, and and are each It is the weight and zero of the degree Hermitian polynomial.

[0063] Also, average and variance It can be expressed by the following Equations 9 and 10, respectively.

[0064] [Equation 9]

[0065]

[0066] [Equation 10]

[0067]

[0068] Here Igo am.

[0069] Meanwhile, average channel capacity class It can be expressed as follows.

[0070]

[0071]

[0072] Here , , , and are each and am.

[0073] Regarding PLC TWR using PNC, RVs and are each class It is distributed as. RVs and are each and It is distributed as.

[0074] Meanwhile, to calculate the average capacity of the PLC DF TWR using ANC, RVs and are each and It is distributed as. Also, RVs and are each It is distributed as.

[0075] And the control unit (100) can select an optimal relay node with high spectrum efficiency by determining the operating area with the minimum average channel capacity for the average channel capacity estimated based on a closed-type estimation algorithm.

[0076] Although one embodiment is described using a power line communication network PLC, in a wireless W communication system, an optimal relay node with high spectrum efficiency can be selected by determining the operating area based on the minimum average channel capacity of the average channel capacity estimated through a closed-type performance estimation algorithm for the received signal of the relay node by modeling channel gain and signal attenuation due to normal log fading.

[0077] According to one embodiment, by selecting an optimal relay node in which the operating area is determined based on the average channel capacity estimated by a closed-type estimation algorithm for at least one relay node in a power line communication system, a high data transmission rate, high spectral efficiency, better fairness, and low transmission power can be guaranteed, and it can operate with high spectral efficiency and is robust against signal attenuation and noise.

[0078] Referring to Fig. 2, the average channel capacity of the PLC DF TWR of one embodiment with respect to SNR can be determined, and the performance of the system according to the PNC and ANC methods can be verified. That is, it can be observed that the PNC method has superior system performance compared to the ANC method because the symbol-shaped transmission signal is transmitted at maximum power at the relay node at a low SNR, i.e., 0-15dB. However, the same system performance is achieved at high SNRs in PLC systems using both the PNC and ANC methods.

[0079] In addition, referring to Figure 2, it can be seen that the average channel capacity is improved by the bidirectional relay node for the unidirectional relay node OWR and the bidirectional relay node TWR. For example, at SNR = 30dB, the bidirectional relay node TWR achieves a data transmission rate gain of about 0.8bps / Hz compared to the unidirectional relay node OWR.

[0080] And regarding spectrum efficiency, the bidirectional relay node TWR is further improved compared to the unidirectional relay node.

[0081] Regarding impulse noise, high impulse noise causes a decrease in average channel capacity. For example, the impulse noise probability at It can be seen that when increased to 30dB, the average channel capacity of the TWR decreases by approximately 1.5bps / Hz.

[0082] Meanwhile, referring to Figure 3, it can be seen that the average channel capacity of AF and DF TWR is improved compared to the average channel capacity of PLC AF TWR in the low SNR range (0 - 10 dB), and as the SNR increases, it can be confirmed that the average channel capacity of PLC AF TWR is improved compared to the average channel capacity of PLC DF TWR. The intersection point of these AF relay nodes and DF relay nodes is 12 dB. The operating range of the relay nodes is determined by the different SNR ranges of AF and DF TWR at this intersection point, and based on this, the optimal relay node of the PLC system is selected.

[0083] In another embodiment, a bidirectional relay method for a power line communication network

[0084] The method includes the step of estimating the average channel capacity for each target node based on a closed-type estimation algorithm in a control unit of a power line communication network in which at least one bidirectional relay node is connected between at least one power line source node; and the step of selecting an optimal relay node with high spectrum efficiency by determining an operating area by minimizing the sum of the estimated average channel capacities, wherein each step of the relay method of the power line communication network is a function performed in the aforementioned control unit (100), and detailed description is omitted.

Claims

Claim 1 A bidirectional relay system of a power line communication network, wherein at least one bidirectional relay node is in cooperative multiple access (NOMA) between a source node and at least one target node, and further comprises a control unit for selecting a relay node whose operating area is determined by minimizing the sum of average channel capacities estimated by a closed-type estimation algorithm for each target node, wherein the control unit performs a DF (Decoding Forwarding) mode that decodes and re-encrypts a received signal of the selected relay node and transmits it to the target node, wherein the DF mode is configured to generate an overlapping signal by performing an exclusive OR on the transmission signal of the source node and encrypts the generated overlapping signal using Physical Layer Network Coding (PNC) or Analog Network Coding (ANC) and transmits it to the target node, wherein the encrypted overlapping signal of the PNC transmits the encrypted symbol together with the relay transmission power, and the encrypted overlapping signal of the ANC transmits the encrypted symbol by applying a power allocation factor. Claim 2 A bidirectional relay system of a cooperative multiplexed power line communication network, wherein, in claim 1, the control unit is configured to estimate the average channel capacity for each target node based on a closed-form estimation algorithm for the received signal of a relay node derived through modeling of the channel gain of the power line communication network, signal attenuation according to the distance between the node and the operating frequency, and total noise, and to select a relay node whose operating area is determined by minimizing the sum of the estimated average channel capacities. Claim 3 A bidirectional relay method for a cooperative multiplexed power line communication network performed in a control unit of a power line communication network in which at least one bidirectional relay node is connected between at least one power line source node, comprising: a step of estimating an average channel capacity for each target node based on a closed-form estimation algorithm; and a step of selecting a relay node whose operating area is determined by minimizing the sum of the estimated average channel capacities, wherein a DF (Decoding Forwarding) mode is performed to decode and re-encrypt a received signal of the selected relay node and transmit it to a target node, wherein the method comprises: a step of generating an overlapping signal by performing an exclusive OR on the transmission signal of the source node; and a step of encrypting the generated overlapping signal using Physical Layer Network Coding (PNC) or Analog Network Coding (ANC) and transmitting it to a target node, wherein the encrypted overlapping signal of the PNC transmits the encrypted symbol together with the relay transmission power, and the encrypted overlapping signal of the ANC transmits the encrypted symbol by applying a power allocation factor.

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