A PLC self-organizing network method and system based on three-phase line frequency division multiplexing

Abstract

The application discloses a PLC self-networking method and system based on three-phase line frequency division multiplexing, and relates to the technical field of power communication. The method comprises the following steps: a center node simultaneously sends phase line identification signals on three phase lines by using a shared communication frequency band, and then sends networking beacons on corresponding phase lines by using three phase line communication frequency bands; a first layer site receives the phase line identification signals on the shared communication frequency band, identifies the phase lines, switches the frequency band to the corresponding communication frequency band of the phase line to which the first layer site belongs, receives the networking beacons, and initiates a network access application to the center node; in the rest of the layer sites, the last layer site in the network access simultaneously sends phase line identification signals on three phase lines by using the shared communication frequency band, and then sends networking beacons on corresponding phase lines by using three phase line communication frequency bands; the next layer site initiates a network access application to the center node according to the method of the first layer site. The application reduces the communication delay of the PLC network and improves the network throughput.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power communication, in particular to a PLC ad hoc network method and system based on three-phase line frequency division multiplexing. BACKGROUND

[0002] In a general power line communication (PLC) network, there are three physical line branches of A, B and C phase lines. A CCO (Central Control Unit) generally works on the A, B and C phase lines simultaneously and communicates with terminal devices on the A, B and C phase lines. A terminal device, such as a STA (Station), generally works on only one branch of the A, B and C phase lines. When the CCO performs channel access, the phase line factor of the power line needs to be considered. When the STA on different power line phase lines communicates with the CCO, the phase line factor of the power line also needs to be considered.

[0003] At present, under the condition of A, B and C three-phase communication, when the STA needs to communicate with the CCO, the STA needs to use the three-phase line time slot according to the three-phase line time slot planning. The STA on different phase lines can only send messages to the CCO in the time slot of the corresponding phase line. This is actually a three-phase line time division multiplexing mechanism. The communication between the first-level STA and the CCO becomes the bottleneck of the entire network. The STA needs to wait for the arrival of the corresponding time slot before performing the corresponding communication, thereby increasing the communication delay. In addition, the phase line time slot division causes the problem of invalid time fragments, which brings channel competition and conflict and reduces the network throughput. SUMMARY

[0004] The present application aims to provide a PLC ad hoc network method and system based on three-phase line frequency division multiplexing to solve the technical problems of increasing communication delay and reducing network throughput caused by the above-mentioned existing three-phase line time division multiplexing mechanism. The preferred technical solutions in the technical solutions provided by the present application can produce the technical effects described below.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] The PLC ad hoc network method based on three-phase line frequency division multiplexing provided by the present application initiates network formation from the center node to each layer station, including the following steps:

[0007] A corresponding communication frequency band and a common communication frequency band are defined for each of the three phase lines;

[0008] The center node first sends a phase line identification signal on the three phase lines using the common communication frequency band, and then sends a network formation beacon on the corresponding phase line using the communication frequency band of each of the three phase lines.

[0009] The first layer site first receives the phase line identification signal on the common communication frequency band to identify the phase line, and after the phase line identification is completed, switches the frequency band to the communication frequency band corresponding to the phase line to which the site belongs to receive the network group beacon, and initiates the network access application to the center node;

[0010] Among the remaining layer sites, the last layer site that has accessed the network uses the common communication frequency band to send the phase line identification signal on the three phase lines, and then uses the communication frequency band of the three phase lines to send the network group beacon on the corresponding phase line; the next layer site first receives the phase line identification signal on the common communication frequency band to identify the phase line, and after the phase line identification is completed, switches the frequency band to the communication frequency band corresponding to the phase line to which the site belongs to receive the network group beacon, and initiates the network access application to the center node through the last layer site that has accessed the network;

[0011] After the center node receives the network access application, the site in the white list is added to the network.

[0012] In one or more embodiments, the bandwidths of the communication frequency bands of the three phase lines are equal, and the frequencies are higher than the frequency of the common communication frequency band.

[0013] In one or more embodiments, the communication frequency band ranges of the four communication frequency bands are defined as follows:

[0014] The communication frequency band range of the A phase line is [1.953MHz, 5.127MHz];

[0015] The communication frequency band range of the B phase line is [5.371MHz, 8.545MHz];

[0016] The communication frequency band range of the C phase line is [8.789MHz, 11.963MHz];

[0017] The communication frequency band range of the A phase line, the B phase line and the C phase line is [0.708MHz, 1.709MHz].

[0018] In one or more embodiments, the following conditions need to be met at the same time when the phase line identification signal is sent:

[0019] The phase line identification signals sent on the three phase lines are orthogonal; the phase line identification signals sent on the three phase lines have the same power; the phase line identification signals on the three phase lines are sent at the same time.

[0020] In one or more embodiments, the phase line identification signal includes a preamble and a payload, the preambles of the phase line identification signals sent on the three phase lines are the same, the payloads are orthogonal, and contain multiple groups of orthogonal symbols.

[0021] In one or more embodiments, the payload is modulated by OFDM, and the subcarrier modulation mode is BPSK.

[0022] In one or more embodiments, each layer site identifies the phase line to which it belongs by comparing the power of the phase line identification signals from different phase lines at the same time.

[0023] In one or more embodiments, after a certain site receives the mixed signal, three phase line identification signals sent by the three phase lines are obtained through signal decomposition, and the sending phase line corresponding to the maximum power in the three signals is the phase line to which the site belongs.

[0024] In one or more embodiments, each layer site needs to select a target network and a parent node before initiating a network access application.

[0025] According to another aspect of the present application, a PLC ad hoc network system based on three-phase line frequency division multiplexing is also provided, based on the above-described PLC ad hoc network method based on three-phase line frequency division multiplexing, comprising: a center node, a relay node and an end node, the center node works on three phase lines at the same time, the relay node and the end node work on one phase line of the three phase lines.

[0026] The center node comprises a communication frequency band definition module and an ad hoc network module, the communication frequency band definition module is used to define a corresponding communication frequency band for each of the three phase lines and a common communication frequency band; the ad hoc network module is used to realize the networking of the relay node and the end node according to the four communication frequency bands defined by the communication frequency band definition module; the relay node and the end node comprise a phase line identification module, which identifies the phase line to which the relay node and the end node belong by comparing the power of the phase line identification signals from different phase lines at the same time.

[0027] Implementing one of the technical solutions in the above-mentioned technical solutions of the present application has the following advantages or beneficial effects:

[0028] In the present application, the sites of the A-phase line, the B-phase line and the C-phase line use different frequency bands to communicate with the center node at the same time, so there is no need to wait for the time slot corresponding to the phase line, each site can send a message to the center node at any time, which greatly reduces the communication delay of the PLC network and improves the network throughput. At the same time, the A, B and C three-phase line time division multiplexing network is divided into three three-phase line frequency division multiplexing sub-networks, the three sub-networks work in parallel, solving the problem of invalid time fragments caused by phase line time slot division, avoiding channel competition and conflict, and effectively improving the network throughput. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art. In the drawings:

[0030] Figure 1 is a PLC self-networking method flow chart based on three-phase line frequency division multiplexing of an embodiment of the present application;

[0031] Figure 2 is a three-phase line frequency division multiplexing PLC system networking process (n-layer node) schematic diagram of an embodiment of the present application;

[0032] Figure 3 is a PLC self-networking system structure block diagram based on three-phase line frequency division multiplexing of an embodiment of the present application;

[0033] Figure 4 is a three-phase line frequency division multiplexing PLC system protocol stack structure schematic diagram of an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions and advantages of the present application clearer, the various exemplary embodiments to be described below will be described with reference to the corresponding drawings, which constitute a part of the exemplary embodiments, and various exemplary embodiments that can be used to implement the present application are described. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation described in the following exemplary embodiments does not represent all implementations consistent with the present disclosure. It should be understood that they are only examples of processes, methods and devices, etc. consistent with some aspects of the present disclosure as described in the appended claims, and other embodiments can be used, or structural and functional modifications can be made to the embodiments listed herein, without departing from the scope and spirit of the present application.

[0035] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse" and the like indicate the orientation or positional relationship based on the drawings shown, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the elements referred to must have a specific orientation, be constructed and operated in a specific orientation. The terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The term "multiple" means two or more. The terms "connected", "connected" should be broadly understood, for example, it can be fixedly connected, detachably connected, integrally connected, mechanically connected, electrically connected, communicatively connected, directly connected, indirectly connected through an intermediate medium, it can be the internal communication or interaction relationship of two elements. The term "and / or" includes any and all combinations of one or more related listed items. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0036] To illustrate the technical solution described in this invention, specific embodiments are described below, showing only the parts related to the embodiments of this invention.

[0037] Example 1:

[0038] like Figure 1 As shown, this invention provides a PLC self-organizing network method based on three-phase line frequency division multiplexing, initiating network formation from the central node to each level of the site, including the following steps:

[0039] S100 defines the corresponding communication frequency bands for the three phase lines and a common communication frequency band;

[0040] S200: The central node first uses the shared communication frequency band to send phase line identification signals on the three phase lines, and then uses the communication frequency bands of the three phase lines to send network beacons on the corresponding phase lines.

[0041] In the S300 architecture, the first-layer stations first receive phase line identification signals on the shared communication frequency band and perform phase line identification. After phase line identification is completed, they switch the frequency band to the communication frequency band corresponding to their respective phase lines to receive network beacons and initiate a network access application to the central node. The first-layer stations only initiate the network access application after completing the selection of the target network and parent node.

[0042] In the S400 network and other layers, the upper-layer station entering the network uses a shared communication frequency band to transmit phase line identification signals on the three phase lines, and then uses the respective communication frequency bands of the three phase lines to transmit network beacons on their corresponding phase lines. The lower-layer station first receives the phase line identification signal on the shared communication frequency band and performs phase line identification. After phase line identification is completed, it switches the frequency band to the communication frequency band corresponding to its own phase line to receive the network beacon, and then initiates a network entry application to the central node through the upper-layer station that has already entered the network. The lower-layer station only initiates the network entry application through the upper-layer station after completing the selection of the target network and parent node.

[0043] After receiving the network access application, the S500 and central node will add the sites in the whitelist to the network.

[0044] This embodiment presents a PLC self-organizing network method supporting three-phase line frequency division multiplexing. Stations (STAs) on phases A, B, and C communicate simultaneously with the central node (CCO) using different frequency bands, eliminating the need to wait for their corresponding phase time slots. This allows them to send messages to the CCO at any time, significantly reducing communication latency and improving network throughput. Furthermore, this embodiment divides a three-phase line time division multiplexing network (A, B, C) into three three-phase line frequency division multiplexing sub-networks. These three sub-networks operate in parallel, resolving the problem of invalid time fragmentation caused by phase time slot allocation, avoiding channel contention and conflicts, and effectively improving network throughput.

[0045] For the convenience of understanding, since there are sometimes multiple central nodes networking at the same time at the work site, the STA will receive beacons from multiple networks at the same time, and needs to select the target network to which it wants to join. If the application to join the first network is rejected, it can select the second network to apply to join, until it joins the network to which it belongs. Therefore, each station needs to select a target network before initiating a network access application, and the selection of the target network can determine the network to which the STA belongs. In addition, each station also needs to select a parent node before initiating a network access application, and a multi-level tree network can be formed through the parent node.

[0046] To support three-phase frequency division multiplexing, four communication frequency bands are defined in the above step S100, including frequency band A, frequency band B, frequency band C and frequency band D. Frequency band A is allocated to phase A, frequency band B is allocated to phase B, frequency band C is allocated to phase C, and frequency band D is a common frequency band for phase A, phase B and phase C.

[0047] In one or more embodiments, the bandwidths of the communication frequency bands of the three phase lines are equal, and the frequencies are higher than the frequency of the common communication frequency band. In a specific embodiment, the bandwidths of frequency band A, frequency band B and frequency band C are about 3.2 MHz, and the bandwidth of frequency band D is about 1.0 MHz. The adjacent frequency bands are separated by about 0.2 MHz.

[0048] In one or more embodiments, the communication frequency band ranges of the four communication frequency bands are defined as shown in Table 1.

[0049] Table 1 Communication frequency band range table

[0050]

[0051] In one or more embodiments, the transmission of the phase line identification signal needs to meet the following conditions at the same time:

[0052] 1) The phase line identification signals transmitted on the three phase lines are orthogonal;

[0053] 2) The phase line identification signals transmitted on the three phase lines have the same power;

[0054] 3) The phase line identification signals on the three phase lines are transmitted at the same time.

[0055] For the convenience of understanding, since the signals among the three phase lines will interfere with each other, i.e. the signals transmitted by phase A can also be received on phase B and phase C, the signals transmitted by phase B can also be received on phase A and phase C, and the signals received by a certain STA are the superimposed mixture of the signals of the three phase lines, therefore the phase line identification signals transmitted on the three phase lines are orthogonal, so as to separate the signal of one phase line from the mixed signal.

[0056] The power of three phase lines is the same, and only the relative size needs to be compared to identify the phase line, without further calculation of channel attenuation, which is simple and reliable to implement.

[0057] Since the power line channel is time-varying, the attenuation of the channel at the previous moment and the next moment is different, and the accuracy of comparing the signal power of three phase lines at the same moment for phase line identification is higher than that at different moments. Therefore, the phase line identification signals on the three phase lines are transmitted at the same time.

[0058] In one or more embodiments, the phase line identification signal includes a preamble and a payload. The preamble is used for automatic gain control adjustment, frame detection and synchronization. The payload is modulated by OFDM, and the subcarrier modulation mode is BPSK. The OFDM symbol is based on a 25MHz sampling rate, and the data is taken after 1024-point IFFT processing. The real part is added to the 512-point cyclic prefix to form the OFDM symbol.

[0059] In specific embodiments, the phase line identification signals transmitted on the three phase lines have the same preamble and orthogonal payloads, and contain multiple groups of orthogonal symbols. Among them, four symbols are a group, the phase relationship between each group of symbols on the A phase line is [+1 -1 +1 +1], the phase relationship between each group of symbols on the B phase line is [+1 +1 -1 +1], and the phase relationship between each group of symbols on the C phase line is [+1 +1 +1 -1].

[0060] In one or more embodiments, each layer site identifies the phase line it belongs to by comparing the power of the phase line identification signals from different phase lines at the same moment. Further, the mixed signal received by a certain site is decomposed into three phase line identification signals transmitted by the three phase lines, and the transmission phase line corresponding to the maximum power in the three signals is the phase line to which the site belongs.

[0061] It should be further noted that considering the transmission function and noise of the channel, the signal received at the frequency domain subcarrier k can be represented as:

[0062] (1) ;

[0063] Where: is the transmitted signal on the A, B, and C three-phase lines, is the received signal on the A, B, and C three-phase lines, is the received noise on the A, B, and C three-phase lines, is the 3x3 channel matrix of subcarrier k.

[0064] (2) ;

[0065] In the channel matrix represents the transfer function of the sub-carrier k from the sending phase line Lt to the receiving phase line Lr. Lt, Lr are substituted by A, B, C respectively, and the transfer functions of the three phases are obtained matrix.

[0066] If a station is on the A phase line, the received signal of the station is obtained by formula (1) and formula (2):

[0067] (3) ;

[0068] It can be seen from formula (3) that the received signal of the station is a mixed signal of the sending signals on the A, B and C phase lines ] after channel transmission and noise superposition. By using the orthogonal characteristics of the signals, the signals sent from the A / B / C phase lines are separated from the received signal by formula (4).

[0069] (4) ;

[0070] Wherein, N is the number of OFDM symbols, is the signal of the sub-carrier k transmitted from the sending phase line A to the receiving phase line A, is the signal of the sub-carrier k transmitted from the sending phase line B to the receiving phase line A, is the signal of the sub-carrier k transmitted from the sending phase line C to the receiving phase line A.

[0071] Since is the direct channel transfer function, and is the non-direct channel transfer function, the channel attenuation of and is smaller than that of , and the sending power of is the same, the power of the signal is greater than that of . By adding the powers of all the sub-carriers to obtain the whole signal power, the station on the A phase line can be identified by comparing the sizes of the signal powers.

[0072] Similarly, for the stations on the B phase line and the C phase line, the above method can be used to identify the phase lines to which the stations belong.

[0073] As shown in FIG. 1, Figure 2 the end nodes are STAs (stations) in each layer of stations. In the embodiment, only the center node can initiate networking, and the networking process mainly includes that the center node triggers the phase line identification and network access application of the end nodes through the sending phase line identification signal and the beacon, to complete the whole networking. If there are n layers of stations, the specific networking process is as follows:

[0074] After the central node is powered on, it first sends phase line identification signals on the three phase lines A, B and C simultaneously using frequency band D, for the end nodes to identify the phase lines; after the phase line identification signals are sent, it sends beacons on the three phase lines A, B and C using frequency band A, frequency band B and frequency band C respectively; after the beacons are sent, it waits for the network entry application of the end nodes.

[0075] After the end node is powered on, it first receives phase line identification signals on frequency band D to identify the phase line; after the phase line identification is completed, it switches the frequency band to frequency band A, B or C allocated by the phase line to which the node belongs to receive beacons, for example, if the phase line to which the node belongs is phase A, it switches the frequency band to frequency band A to receive network formation beacons; after the target network and the parent node are selected, it initiates the network entry application.

[0076] After the central node receives the network entry application, it checks whether the node applying for network entry is in the white list, if the node is in the white list, it allows the node to join the network, otherwise, it rejects the node to join the network.

[0077] After the first layer nodes complete network entry, the central node arranges the first layer nodes to send phase line identification signals and beacons to trigger the second layer nodes to initiate network entry application; the first layer nodes first send phase line identification signals using frequency band D simultaneously, and after the phase line identification signals are sent, they send beacons using frequency band A, B or C allocated by the phase line to which the node belongs. For example, if the phase line to which the node belongs is phase A, it switches the frequency band to frequency band A to send beacons.

[0078] After the second layer nodes complete network entry, the central node arranges the second layer nodes to send phase line identification signals and beacons to trigger the third layer nodes to initiate network entry application, and the process is repeated until the nth layer nodes complete network formation.

[0079] As an optional implementation, the end node can first apply for network entry using frequency band A, and after all the nodes complete network entry, since all the nodes achieve time synchronization, the phase line identification can be performed by comparing the zero-crossing time, and after the phase line identification is completed, the end node switches to frequency band A, B or C allocated by the phase line to which the node belongs to re-perform network formation. This scheme needs to perform network formation twice, and the network formation time is relatively long.

[0080] Further, the zero-crossing time comparison method for phase line identification: the central node collects the zero-crossing times of the three phase lines A, B and C, and sends them to the end node; the end node collects the zero-crossing time of its own phase line, calculates the difference value with the zero-crossing time of the central node, and identifies the phase line to which it belongs according to the difference value.

[0081] Embodiment two:

[0082] For example, Figure 3As shown, the embodiment also provides a three-phase line frequency division multiplexing based PLC ad hoc network system, based on the three-phase line frequency division multiplexing based PLC ad hoc network method described in Embodiment One, comprising a center node, a relay node and an end node.

[0083] In one or more embodiments, the center node comprises a communication frequency band defining module and an ad hoc network module, the communication frequency band defining module being configured to define a corresponding communication frequency band for each of the three phase lines and a common communication frequency band. The definition of the communication frequency band is consistent with that described in Embodiment One, and is described in detail in Embodiment One.

[0084] The ad hoc network module is configured to implement the networking of the relay node and the end node according to the four communication frequency bands defined by the communication frequency band defining module, and the implementation is consistent with the relevant processes in steps S200-S500 in Embodiment One. For details, please refer to the corresponding part in Embodiment One, which will not be described here.

[0085] In one or more embodiments, the relay node and the end node comprise a phase line identification module, which identifies the phase line to which the relay node and the end node belong by comparing the power of the phase line identification signals from different phase lines at the same time. For details, please refer to the corresponding part in Embodiment One, which will not be described here.

[0086] In a specific embodiment, the center node connects all the relay nodes and end nodes through the physical lines of the A, B and C phase lines, forming three multi-level tree networks on the A, B and C phase lines. The center node works on the A, B and C phase lines and can simultaneously transmit and receive signals on the three phase lines; the relay node and the end node work on one of the A, B and C phase lines.

[0087] Further, the center node is the control and management center of the network, responsible for the construction, maintenance and management of the network, and completes the access management and resource allocation of the relay node and the end node. The relay node is a routing node of the network, which completes the data relay forwarding between the center node and the end node and the data transmission of the node itself. The end node accesses the network through the center node or the relay node and completes the data transmission of the end node.

[0088] As shown in Figure 4 The three-phase frequency division multiplexing PLC system protocol stack is divided into five layers: physical layer, data link layer, network layer, transport layer and application layer. In addition to providing services for the network layer, the data link layer can also directly provide transmission services for the application layer.

[0089] Physical layer: realizes the encoding and modulation of the sending end data and the demodulation and decoding of the power line carrier signal at the receiving end.

[0090] Data link layer: divided into MAC sublayer and network management sublayer. The MAC sublayer mainly completes physical channel access and realizes reliable transmission of data; the network management sublayer mainly realizes networking, maintenance, routing management of the link layer network, and aggregation and distribution of network layer data.

[0091] Network layer: provides network services and complies with IPv6 and 6LoWPAN protocols.

[0092] Transport layer: provides transmission services and complies with the UDP protocol.

[0093] Application layer: uses DL / T698.45, DL / T645 and other protocols to realize business data interaction between the center node and the relay node and the end node.

[0094] In summary, the PLC self-organizing network system supporting three-phase line frequency division multiplexing of the embodiment can simultaneously communicate with the center node (CCO) by using different frequency bands by the stations (STAs) of the A-phase line, the B-phase line and the C-phase line, without waiting for the time slot corresponding to the phase line, and can send messages to the CCO at any time, thereby greatly reducing the communication delay of the PLC network and improving the network throughput. In addition, the embodiment divides the A-phase line, the B-phase line and the C-phase line time division multiplexing network into three three-phase line frequency division multiplexing sub-networks, and the three sub-networks work in parallel, thereby solving the invalid time fragment problem caused by phase line time slot division, avoiding channel competition and conflict, and effectively improving the network throughput.

[0095] It should be understood that the above embodiments are only a special case, and do not mean that the present application is in this way.

[0096] It should be understood that although each step in the flowchart involved in the above embodiments is displayed in sequence according to the arrow, these steps are not necessarily executed in the order indicated by the arrow. Unless otherwise stated herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other orders. Moreover, at least part of the steps in the flowchart involved in the above embodiments can include multiple steps or stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but can be executed in rotation or alternation with at least part of other steps or steps or stages in other steps.

[0097] The above description is merely that of the preferred embodiments of the present application, and various changes or modifications can be made to these embodiments without departing from the spirit and scope of the present application. In addition, the features and embodiments described can be modified to adapt them to specific situations and materials without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed herein, but rather covers all embodiments falling within the scope of the claims of the present application.

Claims

1. A PLC ad hoc network method based on three-phase line frequency division multiplexing, characterized by, The center node initiates network group to each layer site step by step, including the following steps: Three phase lines are defined respectively corresponding communication frequency band and a common communication frequency band; The center node first uses the common communication frequency band to send phase line identification signal on three phase lines, and then uses the communication frequency band of each phase line to send network group beacon on the corresponding phase line; The first layer site first receives the phase line identification signal on the common communication frequency band to identify the phase line, and after the phase line identification is completed, the frequency band is switched to the communication frequency band corresponding to the phase line to which the site belongs to receive the network group beacon, and initiates the network application to the center node; In the remaining layer sites, the last layer site uses the common communication frequency band to send the phase line identification signal on three phase lines, and then uses the communication frequency band of each phase line to send the network group beacon on the corresponding phase line; the next layer site first receives the phase line identification signal on the common communication frequency band to identify the phase line, and after the phase line identification is completed, the frequency band is switched to the communication frequency band corresponding to the phase line to which the site belongs to receive the network group beacon, and initiates the network application to the center node through the last layer site which has entered the network; After the center node receives the network application, each site in the white list is added to the network.

2. The PLC ad hoc network method based on three-phase line frequency division multiplexing according to claim 1, characterized in that, The bandwidth of the communication frequency band of the three phase lines is equal, and the frequency is higher than the frequency of the common communication frequency band.

3. The PLC ad hoc network method based on three-phase line frequency division multiplexing according to claim 1, characterized in that, The communication frequency band range of the four communication frequency bands is defined as follows: The communication frequency band range of the A phase line is [1.953MHz, 5.127MHz]; The communication frequency band range of the B phase line is [5.371MHz, 8.545MHz]; The communication frequency band range of the C phase line is [8.789MHz, 11.963MHz]; The communication frequency band range of the A phase line, the B phase line and the C phase line is [0.708MHz, 1.709MHz].

4. The PLC ad hoc network method based on three-phase line frequency division multiplexing according to claim 1, characterized in that, The following conditions need to be met when sending the phase line identification signal: The phase line identification signals sent on the three phase lines are orthogonal; The phase line identification signals sent on the three phase lines have the same power; The phase line identification signals on the three phase lines are sent at the same time.

5. The PLC ad hoc network method based on three-phase line frequency division multiplexing according to claim 4, characterized in that, The phase line identification signal includes a preamble and a payload, the preambles of the phase line identification signals sent on the three phase lines are the same, the payloads are orthogonal, and contain multiple groups of orthogonal symbols.

6. The PLC ad hoc network method based on three-phase line frequency division multiplexing according to claim 5, characterized in that, The payload is modulated by OFDM, and the subcarrier modulation mode is BPSK.

7. The method according to claim 1, wherein the method is characterized by, Each layer site identifies the phase line to which it belongs by comparing the power of the phase line identification signals from different phase lines at the same time.

8. The PLC ad hoc network method based on three-phase line frequency division multiplexing according to claim 7, characterized in that, After a site receives the mixed signal, three phase line identification signals sent by the three phase lines are obtained through signal decomposition, and the phase line corresponding to the maximum power in the three signals is the phase line to which the site belongs.

9. The method according to any one of claims 2-8, wherein, Each layer site needs to select a target network and a parent node before initiating the network application.

10. A PLC ad hoc network system based on three-phase line frequency division multiplexing, characterized by, The PLC self-networking method based on three-phase line frequency division multiplexing according to any one of claims 1-9, comprising a center node, a relay node and a terminal node, the center node works on three phase lines at the same time, the relay node and the terminal node work on one phase line in the three phase lines; The center node comprises a communication frequency band defining module and an ad hoc network module, the communication frequency band defining module is used for defining a corresponding communication frequency band and a common communication frequency band for three phase lines respectively; the ad hoc network module is used for realizing networking of the relay node and the terminal node according to the four communication frequency bands defined by the communication frequency band defining module; The relay node and the terminal node comprise a phase line identification module, the phase line identification module identifies the phase line to which the relay node and the terminal node belong by comparing the power of the phase line identification signals from different phase lines at the same time.

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