Mobile terminal roaming access method and system in transformer substation considering WAPI-AP load balancing

Abstract

The invention discloses a mobile terminal roaming access method and system in a transformer substation considering WAPI-AP load balancing. The method comprises the following steps: each mobile terminal in the transformer substation randomly selects a WAPI-AP and establishes a mapping relation; each mobile terminal calculates a communication rate of accessing the WAPI-AP, and calculates an average communication rate according to the communication rates of all the WAPI-APs; if the difference value between the communication rate and the average communication rate does not exceed a tolerable threshold value, the WAPI-AP provides a communication service for the mobile terminal, otherwise, the mobile terminal judges whether the WAPI-AP is reselected for access, if the WAPI-AP is not reselected, the current mapping is kept, and if the WAPI-AP is reselected, the WAPI-AP is randomly selected from a to-be-selected WAPI-AP set for access and a mapping relation is updated; and re-judging whether the difference value between the WAPI-AP communication rate and the average communication rate exceeds a tolerable threshold value or not according to the updated mapping relationship until the WAPI-AP meeting the condition provides communication service for the accessed mobile terminal. Based on the method provided by the invention, the mobile terminal can be guided to dynamically adjust the access selection according to the probability, and the problem of load imbalance is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of roaming access of mobile terminals in a substation, and is a method and system for roaming access of mobile terminals in a substation considering WAPI-AP load balancing. Background Art

[0002] With the rapid development of smart grids and digital substations, power systems are gradually evolving from traditional static architectures to highly automated, intelligent, and mobile ones. As key nodes for grid dispatching, transmission, and distribution, the safety, reliability, and real-time performance of substation operations are crucial to the stable operation of the entire power system. To meet the growing demands for management efficiency and safety control, an increasing number of mobile terminals are being deployed at substations, including handheld terminals, mobile operation terminals, drones, and inspection robots. These devices rely on wireless communication networks for tasks such as remote data transmission, video monitoring, and remote diagnosis. The quality of their communication directly determines the level of intelligence in substation operations and maintenance.

[0003] As critical infrastructure, substations place extremely high demands on the security of wireless communication networks. Traditional Wi-Fi protocols are subject to security vulnerabilities, while WAPI (Wireless LAN Authentication and Privacy Infrastructure) provides a higher level of security. WAPI utilizes a two-way authentication mechanism based on digital certificates, effectively preventing man-in-the-middle attacks and unauthorized access. Its high-strength encryption algorithm ensures the confidentiality and integrity of data transmission. These features make WAPI-APs highly applicable in security-sensitive scenarios such as substations.

[0004] Currently, substations typically deploy numerous WAPI-APs (Wireless LAN Authentication and Privacy Infrastructure Access Points), forming a local wireless communication network that supports access by a large number of mobile terminals. During movement, mobile terminals may need to transfer access from one WAPI-AP to another, enabling roaming between different WAPI-APs. Existing roaming mechanisms primarily rely on mobile terminals to independently determine roaming based on locally perceived static signal strength. For example, under the IEEE 802.11 specification, a mobile terminal determines when to roam based on RSSI thresholds: when a WAPI-AP's signal strength falls below a certain threshold, it scans for nearby WAPI-APs and switches to the one with a stronger signal. Alternatively, mobile terminals can adopt policies based on connection duration (handover timeout) or static priority (assigning fixed priorities to different WAPI-APs or devices). They can even rely on neighbor reports and BSS migration recommendations provided by 802.11k / v, or the fast handoff feature of 802.11r to accelerate roaming.

[0005] However, existing roaming access methods generally suffer from the following shortcomings: First, from the perspective of mobile terminal control, they are primarily based on locally perceived static signal strength, without considering the real-time WAPI-AP load status and the number of connected terminals. Consequently, mobile terminals tend to connect to the WAPI-AP with the strongest signal, regardless of whether it is under high load. This leads to congestion in some hotspot WAPI-APs due to excessive concentration, significantly degrading communication quality, while other WAPI-APs are not selected by mobile terminals and remain idle for long periods of time. Second, from the perspective of WAPI-AP control, the load interaction mechanism between these WAPI-APs relies on communication between access points and coordinated responses from terminals, making deployment complex and computationally complex when mobile terminals dynamically connect at high frequencies. These strategies can easily lead to severe WAPI-AP load imbalance in multi-terminal concurrent scenarios, resulting in reduced communication rates, increased data transmission latency, and task interruptions.

[0006] Therefore, for substation scenarios, how to design a mobile terminal roaming access mechanism that does not require negotiation between WAPI-APs to achieve WAPI-AP load balancing has become an urgent problem that needs to be solved. Summary of the Invention

[0007] To address the deficiencies in the prior art, the present invention provides a method for roaming access of mobile terminals in a substation taking into account WAPI-AP load balancing, which can solve the WAPI-AP load imbalance problem that occurs in the prior art method for roaming access of mobile terminals in a substation.

[0008] The present invention adopts the following technical solutions.

[0009] A method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing includes the following steps: Each mobile terminal in the substation randomly selects a WAPI-AP to access and establishes a mapping relationship with the selected WAPI-AP; Each mobile terminal calculates its communication rate for accessing the WAPI-AP, and calculates the average communication rate of all mobile terminals accessing the WAPI-AP based on the communication rate of each mobile terminal accessing the WAPI-AP; Determine whether the difference between the communication rate of each mobile terminal accessing the WAPI-AP and the average communication rate exceeds a tolerance threshold. If not, the WAPI-AP provides communication services to the mobile terminal. If the rate exceeds the tolerance threshold, the mobile terminal that exceeds the tolerance threshold calculates the probability of reselecting the WAPI-AP to which the mobile terminal is connected based on the communication rate of the connected WAPI-AP and the average communication rate. The mobile terminal determines whether to reselect the WAPI-AP based on the calculated probability. If there is no need to reselect a WAPI-AP, the current mapping relationship is maintained; if a WAPI-AP needs to be reselected, the mapping relationship is updated, including constructing a set of candidate WAPI-APs, calculating a handover probability of the mobile terminal accessing each candidate WAPI-AP, and updating the mapping relationship between the mobile terminal and the reselected WAPI-AP based on the calculated handover probability; After all mobile terminals in the substation have been judged and updated, the difference between the mobile terminal communication rate and the average communication rate is re-judged based on the updated mapping relationship to see whether it exceeds the tolerable threshold and the above steps are repeated until a WAPI-AP that meets the conditions provides communication services for the mobile terminal.

[0010] Preferably, the substation includes Mobile terminals and WAPI-APs, each mobile terminal randomly selects a WAPI-AP as the WAPI-AP to be accessed, and a mapping relationship is established between the mobile terminal and the selected WAPI-AP.

[0011] Preferably, each mobile terminal calculates the communication rate of its access to the WAPI-AP as follows:

[0012] Where, For the k The communication rate of each WAPI-AP, For the k WAPI-AP The signal bandwidth, P k For the k WAPI-AP The transmission power, is the channel response coefficient, is the maximum channel response coefficient, is the noise power, To access WAPI-AP The total number of mobile terminals.

[0013] Preferably, the mobile terminal calculates the probability of reselecting the WAPI-AP to be accessed by the mobile terminal based on the communication rate of the selected WAPI-AP and the average communication rate of the WAPI-AP, as follows: For the i mobile terminals , and set the current access to k WAPI-AP , No. k WAPI-AP The communication rate is , the average communication rate of WAPI-AP in the substation is ,but: like , the terminal maintains the current WAPI-AP; like , then calculate the probability that the terminal reselects another WAPI-AP for access .

[0014] Preferably, the probability The calculation formula is as follows: Calculate the average rate of WAPI-AP in the substation Communication rate with the WAPI-AP currently connected to the mobile terminal to be switched and calculate the difference between the difference and the average rate of the WAPI-AP in the substation The ratio of .

[0015] Preferably, the calculating of the handover probability of the mobile terminal accessing each candidate WAPI-AP is specifically as follows: The candidate WAPI-AP is the WAPI-AP whose communication rate is greater than the average communication rate of WAPI-AP in the substation. Candidate WAPI-APs can be obtained by C :

[0016] in, For the j * candidate WAPI-APs, For the j * The transmit power of each WAPI-AP; mobile terminals Select j * Candidate WAPI-APs The switching probability as follows:

[0017] Where, is the mth candidate WAPI-AP, is the communication rate of the mth candidate WAPI-AP.

[0018] Preferably, the mapping relationship between the mobile terminal and the reselected WAPI-AP is updated according to the calculated handover probability, specifically as follows: Candidate WAPI-AP set C The sum of the handover probabilities of the candidate WAPI-APs is 1. The handover probability of each candidate WAPI-AP represents the probability of the mobile terminal handing over to the candidate WAPI-AP. Based on the calculated handover probability, the WAPI-AP reselected by the mobile terminal is obtained, and the mapping relationship between the mobile terminal and the reselected WAPI-AP is updated.

[0019] The present invention also provides a mobile terminal roaming access system in a substation considering WAPI-AP load balancing, which is used to implement the mobile terminal roaming access method in a substation considering WAPI-AP load balancing, including: an access selection module, a rate calculation module, a switching judgment module, an access switching module, and a communication service module; The access selection module is used to enable each mobile terminal in the substation to randomly select a WAPI-AP and establish a mapping relationship with the selected WAPI-AP; The rate calculation module is used to calculate the communication rate of the WAPI-AP to which each mobile terminal is connected, and calculate the average communication rate of the WAPI-AP based on the communication rate of the WAPI-AP; The switching judgment module is used to judge whether the difference between the communication rate of each WAPI-AP and the average rate exceeds a tolerable threshold. If not, the WAPI-AP provides communication services to the mobile terminal; The access switching module is configured to calculate the probability of reselecting a WAPI-AP for access by the mobile terminal based on the communication rate of the selected WAPI-AP and the average communication rate of the WAPI-AP when the difference between the communication rate of each WAPI-AP and the average rate exceeds a tolerable threshold; if reselection is required, construct a set of candidate WAPI-APs, calculate the handover probability of the mobile terminal accessing each candidate WAPI-AP, and update the mapping relationship between the mobile terminal and the reselected WAPI-AP based on the calculated handover probability; if reselection is not required, the mapping relationship is not updated; The communication service module is used to re-judge whether the difference between the mobile terminal communication rate and the average communication rate exceeds the tolerable threshold based on the updated mapping relationship after all mobile terminals in the substation are judged and updated, and repeat the above steps until the WAPI-AP that meets the conditions provides communication services to the mobile terminal.

[0020] The present invention also provides a terminal, comprising a processor and a storage medium; The storage medium is used to store instructions; The processor is configured to operate according to the instruction to execute the steps of the method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing.

[0021] The present invention also provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the steps of the method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing are implemented.

[0022] The beneficial effects of the present invention are that, compared with the prior art, the present invention constructs a dynamic access and iterative switching mechanism on the mobile terminal side, thereby achieving WAPI-AP load balancing; when the communication rate is lower than the average communication rate of the WAPI-AP, an appropriate probability is calculated to determine whether a WAPI-AP needs to be reselected instead of forcibly switching; and when a WAPI-AP needs to be reselected, the probability of each candidate WAPI-AP being selected is calculated, so that the mobile terminal reselects the WAPI-AP to access from the candidate WAPI-APs, thereby avoiding system turbulence caused by collective terminal switching and accelerating convergence; compared with traditional roaming access methods, the method proposed by the present invention guides mobile terminals to adaptively adjust access selection according to the communication rate, without the need for complex communication and multiple calculations on the WAPI-AP side, achieving load balancing of all WAPI-APs, thereby effectively avoiding congestion of a large number of terminals on a certain overloaded WAPI-AP. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of a method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing in the present invention; Figure 2 Schematic diagram of an application scenario of the method of the present invention; Figure 3 Schematic diagram showing how the number of mobile terminals connected to each WAPI-AP changes with the number of iterations in the present invention; Figure 4 Schematic diagram of the change in the communication rate of each WAPI-AP with the number of iterations in the present invention; Figure 5 This is a structural diagram of a mobile terminal roaming access system in a substation taking into account WAPI-AP load balancing in the present invention. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without making creative efforts are all within the scope of protection of the present invention.

[0025] like Figure 1 As shown, the present invention proposes a method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing, which specifically includes the following steps: Step 1: Each mobile terminal in the substation randomly selects a WAPI-AP and establish a mapping relationship with the selected WAPI-AP; like Figure 2 As shown, the substation contains mobile terminals , WAPI-AP ,in, , and obtain The transmit powers of the WAPI-APs are .

[0026] Each mobile terminal randomly selects a WAPI-AP, such as for the i-th mobile terminal Randomly select a WAPI-AP , and establish a mapping relationship with it, that is, (1) Step 2: Each mobile terminal calculates the communication rate of the selected WAPI-AP it accesses, and calculates the average communication rate of the WAPI-AP based on the communication rate of the WAPI-AP; Each mobile terminal Calculate its access to WAPI-AP Communication rate ,Right now (2) Where, WAPI-AP The signal bandwidth, is the channel response coefficient, is the maximum channel response coefficient, P k For the k WAPI-AP The transmission power, is the noise power, To access WAPI-AP The total number of mobile terminals, that is, the set The total number of elements in the , and its dynamic changes directly reflect the WAPI-AP load status.

[0027] according to Communication rate of each WAPI-AP , calculate the average communication rate This value is used as a criterion for system load balancing and is used to guide terminal access decisions. The average communication rate The calculation formula is as follows: (3) Step 3: Determine whether the difference between the communication rate of each WAPI-AP and the average rate does not exceed the tolerable threshold. If so, proceed to step 7; otherwise, proceed to step 4. If all WAPI-APs Communication rate All conditions are met: (4) Where, Indicates the tolerable threshold.

[0028] Step 4: Each mobile terminal determines whether it needs to reselect the WAPI-AP to which it is connected based on the communication rate of the selected WAPI-AP, the highest communication rate, the lowest communication rate, and the average communication rate of the WAPI-AP in the substation; if the mobile terminal needs to reselect the WAPI-AP to which it is connected, proceed to step 5; otherwise, proceed to step 6.

[0029] Each mobile terminal Determine whether to reselect WAPI-AP access as follows: (1) If , then the terminal Maintain the current WAPI-AP ; (2) If , each mobile terminal calculates the probability according to the communication rate of the selected WAPI-AP, the highest communication rate, the lowest communication rate and the average communication rate of the WAPI-AP in the substation , indicating that the terminal The probability of needing to reselect another WAPI-AP is , probability The greater the difference between the terminal rate and the average rate, the higher the handover tendency, while avoiding oscillation caused by collective handover; Probability The calculation is as follows: (5) Where, is the maximum communication rate of WAPI-AP in the substation, is the minimum communication rate of WAPI-AP in the substation; is the load balancing control coefficient, The larger the value, the more unbalanced the system load is, and the more likely the mobile terminal is to reselect another WAPI-AP.

[0030] Step 5: Based on the communication rates of each WAPI-AP, candidate WAPI-APs are constructed. The handover probability of the mobile terminal accessing each candidate WAPI-AP is calculated based on the communication rates of the candidate WAPI-APs and the average communication rate of the WAPI-APs in the substation. The mapping relationship between the mobile terminal and the newly selected WAPI-AP is updated based on the calculated handover probability. Specifically, first build a candidate WAPI-AP set C , the candidate WAPI-AP is the WAPI-AP whose communication rate is greater than the average communication rate of WAPI-AP in the substation. Candidate WAPI-APs can be obtained by C :

[0031] in, For the j * candidate WAPI-APs, For the j * The transmit power of each WAPI-AP; mobile terminals Select j * Candidate WAPI-APs The switching probability as follows: (6) Where, is the mth candidate WAPI-AP, is the communication rate of the mth candidate WAPI-AP.

[0033] The mobile terminal selects a set of candidate WAPI-APs C The sum of the switching probabilities of the candidate WAPI-APs is 1. The higher the communication rate of the candidate WAPI-AP, the higher the probability of it being selected for switching. The mobile terminal selects a candidate WAPI-AP as the new access WAPI-AP according to the switching probability and updates the mapping relationship. For example, the mobile terminal Switch to If a candidate WAPI-AP accesses, the mapping relationship is updated. .

[0034] Step 6: Wait for all mobile terminals to complete the judgment and update, and return to step 2.

[0035] After all mobile terminals in the substation have completed the judgment and update, the process returns to step 2 and repeats the above steps until the difference between the communication rate of each WAPI-AP and the average rate does not exceed the tolerable threshold, and then proceeds to step 7.

[0036] Based on the probabilistic switching method proposed in the present invention, dynamic adjustment of the WAPI-AP to which the mobile terminal accesses is achieved. Terminals congested with the WAPI-AP are switched with a higher probability, and idle WAPI-APs attract more terminals to access, thereby accelerating smooth convergence and avoiding oscillations caused by simple switching.

[0037] Step 7: According to the mapping relationship between each mobile terminal and WAPI-AP, each WAPI-AP is connected to all mobile terminals. Providing communication services.

[0038] Further, such as Figure 3 As shown, Figure 3 The paper demonstrates the dynamic relationship between the number of mobile terminals connected to each WAPI-AP (i.e., load) and the number of iterations during the application of the method. Initially, the loads on the three WAPI-APs are significantly unbalanced. For example, WAPI-AP1 has far fewer terminals connected than the other WAPI-APs. As the iterations progress, mobile terminals dynamically adjust their access choices based on communication rates, gradually optimizing the load distribution across the APs. After approximately eight iterations, the number of terminals connected to each AP stabilizes and approaches equilibrium, effectively resolving the initial overload issue on some WAPI-APs.

[0039] Figure 4The figure also shows the evolution of each WAPI-AP's communication rate over iterations. Initially, due to load imbalance, the communication rate of high-load WAPI-AP3 is significantly lower than that of low-load WAPI-AP1. Through the adaptive terminal access adjustment guided by the present invention, the communication rate differences between the APs gradually narrowed. Ultimately, the rates of all APs converged to a similar level, demonstrating that load balancing directly improves overall communication quality.

[0040] like Figure 5 As shown, the present invention also proposes a roaming access system for mobile terminals in a substation considering WAPI-AP load balancing, which is used to implement the above-mentioned roaming access method for mobile terminals in a substation considering WAPI-AP load balancing. The system includes: an access selection module, a rate calculation module, a switching judgment module, an access switching module, and a communication service module; The access selection module is used to enable each mobile terminal in the substation to randomly select a WAPI-AP and establish a mapping relationship with the selected WAPI-AP; The rate calculation module is used to calculate the communication rate of the WAPI-AP to which each mobile terminal is connected, and calculate the average communication rate of the WAPI-AP based on the communication rate of the WAPI-AP; The switching judgment module is used to judge whether the difference between the communication rate of each WAPI-AP and the average rate exceeds a tolerable threshold. If not, the WAPI-AP provides communication services to the mobile terminal; The access switching module is used to, when the difference between the communication rate of the WAPI-AP and the average rate exceeds a tolerable threshold, enable the mobile terminal to determine whether it is necessary to reselect the WAPI-AP to be accessed by the mobile terminal based on the communication rate of the selected WAPI-AP and the average communication rate of the WAPI-AP; if reselection is required, update the mapping relationship between the mobile terminal and the reselected WAPI-AP; otherwise, do not update the mapping relationship. The communication service module is used to provide communication services to the mobile terminal when the difference between the communication rate of the WAPI-AP and the average rate does not exceed the tolerable threshold or according to the updated mapping relationship of the WAPI-AP.

[0041] The beneficial effect of the present invention is that, compared with the prior art, the present invention can guide the mobile terminal to dynamically adjust access selection, thereby effectively solving the load imbalance problem.

[0042] The present disclosure may be a system, method and / or computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0043] A computer-readable storage medium can be a tangible device that can hold and store instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punched card or raised structure in a groove on which instructions are stored, and any suitable combination thereof. As used herein, a computer-readable storage medium is not to be construed as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse passing through a fiber optic cable), or an electrical signal transmitted through an electrical wire.

[0044] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions to be stored in the computer-readable storage medium in each computing / processing device.

[0045] The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, the state information of the computer-readable program instructions is used to personalize an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), so that the electronic circuit can execute the computer-readable program instructions, thereby implementing various aspects of the present disclosure.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing, characterized in that: The steps include: Each mobile terminal in the substation randomly selects a WAPI-AP to access and establishes a mapping relationship with the selected WAPI-AP; Each mobile terminal calculates its communication rate for accessing the WAPI-AP, and calculates the average communication rate of all mobile terminals accessing the WAPI-AP based on the communication rate of each mobile terminal accessing the WAPI-AP; Determine whether the difference between the communication rate of each mobile terminal accessing the WAPI-AP and the average communication rate exceeds a tolerance threshold. If not, the WAPI-AP provides communication services to the mobile terminal. If the rate exceeds the tolerance threshold, the mobile terminal that exceeds the tolerance threshold calculates the probability of reselecting the WAPI-AP to which the mobile terminal is connected based on the communication rate of the connected WAPI-AP and the average communication rate. The mobile terminal determines whether to reselect the WAPI-AP based on the calculated probability. If there is no need to reselect WAPI-AP to keep the current mapping relationship; If a WAPI-AP needs to be reselected, the mapping relationship is updated, including constructing a set of candidate WAPI-APs, calculating the handover probability of the mobile terminal accessing each candidate WAPI-AP, and updating the mapping relationship between the mobile terminal and the reselected WAPI-AP based on the calculated handover probability; After all mobile terminals in the substation have been judged and updated, the difference between the mobile terminal communication rate and the average communication rate is re-judged based on the updated mapping relationship to see whether it exceeds the tolerable threshold and the above steps are repeated until a WAPI-AP that meets the conditions provides communication services for the mobile terminal.

2. The method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing according to claim 1, characterized in that: The substation includes Mobile terminals and WAPI-APs, each mobile terminal randomly selects a WAPI-AP as the WAPI-AP to be accessed, and a mapping relationship is established between the mobile terminal and the selected WAPI-AP.

3. The method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing according to claim 1, characterized in that: Each mobile terminal calculates the communication rate of its access to the WAPI-AP as follows: Where, For the k The communication rate of each WAPI-AP, For the k WAPI-AP The signal bandwidth, P k For the k WAPI-AP The transmission power, is the channel response coefficient, is the maximum channel response coefficient, is the noise power, To access WAPI-AP The total number of mobile terminals.

4. The method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing according to claim 1, characterized in that: The mobile terminal calculates the probability of reselecting the WAPI-AP to which the mobile terminal accesses based on the communication rate of the selected WAPI-AP and the average communication rate of the WAPI-AP, as follows: For the i mobile terminals , and set the current access to k WAPI-AP , No. k WAPI-AP The communication rate is , the average communication rate of WAPI-AP in the substation is ,but: like , the terminal maintains the current WAPI-AP; like , then calculate the probability that the terminal reselects another WAPI-AP for access .

5. The method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing according to claim 4, characterized in that: The probability The calculation formula is as follows: Calculate the average rate of WAPI-AP in the substation Communication rate with the WAPI-AP currently connected to the mobile terminal to be switched and calculate the difference between the difference and the average rate of the WAPI-AP in the substation The ratio of .

6. The method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing according to claim 1, characterized in that: The calculation of the handover probability of the mobile terminal accessing each candidate WAPI-AP is as follows: The candidate WAPI-AP is the WAPI-AP whose communication rate is greater than the average communication rate of WAPI-AP in the substation. Candidate WAPI-APs can be obtained by C : in, For the j * candidate WAPI-APs, For the j * The transmit power of each WAPI-AP; mobile terminals Select j * Candidate WAPI-APs The switching probability as follows: Where, is the mth candidate WAPI-AP, is the communication rate of the mth candidate WAPI-AP.

7. The method for roaming access of a mobile terminal in a substation considering WAPI-AP load balancing according to claim 6, characterized in that: The mapping relationship between the mobile terminal and the reselected WAPI-AP is updated according to the calculated handover probability as follows: Candidate WAPI-AP set C The sum of the handover probabilities of the candidate WAPI-APs is 1. The handover probability of each candidate WAPI-AP represents the probability of the mobile terminal handing over to the candidate WAPI-AP. Based on the calculated handover probability, the WAPI-AP reselected by the mobile terminal is obtained, and the mapping relationship between the mobile terminal and the reselected WAPI-AP is updated.

8. A mobile terminal roaming access system in a substation considering WAPI-AP load balancing, used to implement the mobile terminal roaming access method in a substation considering WAPI-AP load balancing according to any one of claims 1 to 7, characterized in that: include: Access selection module, rate calculation module, switching judgment module, access switching module, communication service module; The access selection module is used to enable each mobile terminal in the substation to randomly select a WAPI-AP and establish a mapping relationship with the selected WAPI-AP; The rate calculation module is used to calculate the communication rate of the WAPI-AP to which each mobile terminal is connected, and calculate the average communication rate of the WAPI-AP based on the communication rate of the WAPI-AP; The switching judgment module is used to judge whether the difference between the communication rate of each WAPI-AP and the average rate exceeds a tolerable threshold. If not, the WAPI-AP provides communication services to the mobile terminal; The access switching module is used to calculate the probability of reselecting the WAPI-AP to be accessed by the mobile terminal based on the communication rate of the selected WAPI-AP and the average communication rate of the WAPI-AP when the difference between the communication rate of the WAPI-AP and the average rate exceeds a tolerable threshold; If no reselection is required, the current mapping relationship is maintained; If reselection is required, a set of candidate WAPI-APs is constructed, the handover probability of the mobile terminal accessing each candidate WAPI-AP is calculated, and the mapping relationship between the mobile terminal and the reselected WAPI-AP is updated based on the calculated handover probability; The communication service module is used to re-judge whether the difference between the mobile terminal communication rate and the average communication rate exceeds the tolerable threshold based on the updated mapping relationship after all mobile terminals in the substation are judged and updated, and repeat the above steps until the WAPI-AP that meets the conditions provides communication services to the mobile terminal.

9. A terminal comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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