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1.INTRODUCTIONSensor, working as measurement and control terminal, is the bottom of IoT1. But currently there are no unified standards and protocols between the terminals from each company. Terminals from different companies do have different communication protocols and accessing methods2. This paper proposes a set of IoTs connection management and data service platform (hereinafter referred to as IoT platform) which not only has the ability of unified access and management on different measurement and control terminals3, but also can provide unified data service for application systems. 2.CHARACTERISTICS OF THE PLATFORMIoT platform is designed above perception layer and network transport layer, the bottom of the IoT technology system and under the application layer. It works in the middle of the perception layer and the application layer4. The platform can deploy independently and complete the access management of the perception layer devices according to specific application requirements. Application data related to industry applications is handled by the application system in the upper layer5. Due to the different industries and businesses, different application systems should be applied to realize corresponding business logic analysis and processing; and these application systems belong to different measurement and control terminals, which are all required to access IoTs for unified access and device management, so as data analysis and data services6. The main technical characteristics of the IoT platform are
3.RUNNING ENVIRONMENT INDICESThe platform can be deployed in various environments, such as Windows, Linux, clouds that support Docker environment. After performance indices test, the basic requirements of the environment are operation system: Windows Sever 2012, hardware configuration: 32G memory, 8-core CPU, 100G hard disk. 4.THE TECHNICAL IMPLEMENTATION4.1.Global modulesThe IoT platform is comprised of several different global modules, which are connected with each other to provide core services. All lessees are sharing the global setting. The technical framework is shown in Figure 1. 4.1.1.Web application container.The IoT platform is configured as a Web Application Archive (WAR), and it can run in the web containers7. By changing the configuration files, the way how IoT platform deals with device issues and integrates with external service is changed. 4.1.2.Platform server.A server is the central application that control all other modules in IoT platform. It is automatic started in WAR file and uses Spring configuration file in conf/site/site-server.xml to boot. The server is responsible for general system modules management, clients management and REST service. 4.1.3.System management.IoT platform includes HTML5 management application which can be used for managing system functions. Information appeared on the application depends on login credentials and the user authority. In real cases, one administrator with all authorities is in the IoT platform and connects with default clients. Some aspects in this system, such as the clients and lessees, are manages in global scope. The changes in these entities will be reflected in all lessees. Since these users can create new users and lessees, and shut down running lessees, data in the system will be influenced if current users are deleted. Thus, the administrative access in this level should be restricted. The most aspects in this system are lessee oriented. Each user account can be connected with one or more lessees and is permitted to manage several lessee information. While logging into the system, a user connected with several lessees will be asked to select the lessees to be managed before processing. All other system data is managed in lessee level, thus, the majority data in this management interface is depending on the user that logs in and the lessees that user selects8. 4.1.4.REST service.Most core functions that related to IoT platform API can be externally accessed via REST service. By using REST SERVICES, external entities can create, retrieve, update and delete entities that in the system. Also, it can interact with assets management sub-system. Authentication is a necessity for calling REST and Spring Security is adopted to verify if the user has corresponding authority. A formal version Swagger is included in the IoT platform and it adds a user interface around REST service. By using Swagger interface, the running IoT platform server can execute REST API alternatively and check JSON responding. The default Swagger URL of server is http://hostname/servername/, where hostname is for the running IoT platform server. 4.1.5.Global data storage.When store and retrieve data, IoT platform does not deal with database. Conversely, the system defines service provider interface (SPI) for the data manipulation of the third party, and expects that data storage implementations satisfy all interfaces. User management data is stored under global-level configuration and based on following API, IUserManagement: including all cure user management API, CRUD of users and authorities. While configurating a new IoT platform server example, by changing the settings in core Spring configuration file, the specific data storage for storage implementations is defined. Currently, data storage in MongoDB and Apache HBase are supported. 4.1.6.Hazelcast service.Hazelcast is an in-memory data grid (IMDG). Its design involved in high performance. In defaut situation, each Server example can act as Hazelcast example. In default global configuration, Hezelcast is loaded from conf/servername/hazelcast.xml. IoT platform can adopt Hazelcast to interactively broadcast event data to other systems of interest. By adjusting Hazelcast configuration in IoT platform server, the access to Hazelcast client side is controlled, thus, only computers in specific IP range will receive the event data. 4.2.Tenant modulesIoT Platform modules are configured on a per-tenant basis, enabling data and processing logic to be differentiated between different users. This technical approach can realize the access and control of multiple different hardware systems by a unified Internet of Things platform. 4.2.1.Tenant engine.Multi-tenant systems can provide multiple IoT applications for each instance. Each tenant is configured with its own storage space to ensure data independence. Each tenant is configured with an independent processing pipeline, which can be customized without affecting other tenants. When the IoT Platform Server starts, a default tenant user is created in the default tenant folder, and the processing logic can be configured in the corresponding configuration file. Add and create new tenants in the IoT Platform administration application that can be dynamically started and stopped without shutting down the server. 4.2.2.Tenant data stores.Tenant data stores can be implemented by configuring an SPI to provide a persistence service for tenant level information such as device and asset management. The realized service interfaces are IDeviceManagement: Manage and allocate core equipment resources, including sites, specs, devices, events, and so on. IAssetManagement: Manage and allocate core asset resources, including asset classes and ASSET CRUD methods. 4.2.3.Communication engine.IoT Platform communication engine handles all functions related to device interaction. Register new or existed equipment. Devices can be manually created by APIs, or they can be registered in batches. Devices provide a unique hardware ID number and specification mark to the system, and each device has a unique ID in the system. At startup, the specification tag indicates the type of hardware the device is using and references device specifications that already exist on the system. A device sends a registration event when it boots or connects to the network. IoT Platform creates a new device record or finds an existing device record and returns a response message to the device indicating the registration status. The event was received from the connected device. Once registered, devices can report any number or type of events to the IoT Platform and store them. Event types include location updates, sensor measurements and other collected data, or alerts in response to special events. Transmits commands to connected devices. Each device registered in the IoT Platform has a device specification that is related to the type of hardware running on the device. The IoT Platform allows you to add any number of commands in a standardized manner, and each command can carry any number of parameters. Commands and parameters can be added through the administrative user interface or through calling REST. 4.3.Object modelIoT Platform provides a comprehensive object model for capturing relationships between concepts in tracking device data. The object model is used to realize unified device access, so that the access tasks of various IoT devices can be configured, and the efficiency of device access and management is improved. 4.3.1.Site and region.Sites are used to organize related devices and view events. An example of a site application is a location-aware device. Each site provides an entity associated with the map. When you create a site in a management application, you can specify the map type and initial location to render the site’s location event on a given map9. IoT Platform sites group devices in the same physical location. IoT Platform management applications allow areas to be defined based on a map associated with a site. Set the boundaries of the region through the region editor. 4.3.2.Device specifications.Specifications are used to capture the characteristics of a given hardware configuration. Device specifications command. Device specifications can be invoked by the IoT Platform from the command list, or they can be added, updated, viewed, and deleted from the admin interface or through REST services. Device command invocation. IoT Platform provides API for invoking commands on a device based on a list in the device specification. Each command invocation is captured as an event associated with the current device association. The admin user interface and REST services allow commands to be invoked and previous calls to be searched. Device command response. After the device processes the command invocation, it may return a response to the IoT Platform. The command invocation message carries an originating event ID and can be sent back through any response to correlate the response events and confirm device events, measurements, or alarm information. Users can list responses to a given command and initiate other actions based on the response. 4.3.3.Devices and device groups.The device refers to connected sensors. Each device can be addressed with a unique hardware ID number. New devices can be registered with this system by using a hardware ID number and device specification token. The IoT Platform can create new device records through APIs (Application Programming Interface) to allow events to be collected for devices. A device group is a logical unit organized by multiple related devices or subgroups. These groups can be used to perform operations collectively rather than individually. Each group can have zero or more roles, allowing arbitrary grouping based on needed application. A device may belong to multiple groups, and zero or more roles may be associated with the groups. 4.3.4.Device association.Events are not directly recorded on devices. Device association is the association between devices, sites, and related assets. Current device status. The device association also acts as a repository for recent device state. When an event is associated with processing, it keeps the numerical record of the recent event. By default, associations store the most recent location metrics, the most recent values for each metric, and the most recent alerts for each alert type. Using this storage state, IoT Platform can infer the current state of the device. The status information contains the stored date, and you can intelligently choose when to request updated data. Associate status indicators. Each device association also preserves the state of the association itself. By default, associations are marked as active immediately after they are created. With REST services or administrative user interfaces, if a device or related asset is missing, the state can be changed to missing state, and the processing logic can be changed to missing association. The association status is updated to release at the end of the association, which indicates that the device is no longer associated and may be re-associated. 4.3.5.Device events.Device events10 are core service data generated by the interaction between connected devices and the IoT Platform. The IoT Platform can capture many types of events, including device measurements, device location, device alert information, command invocation status, and command response return values. 5.DEVELOPMENT KITIoT platform is based on several open-source technologies. The main open-source modules adopted are as follows: Eclipse. IT is chosen as the integrated development environment of the IoT platform. Apache Tomcat 7. It is the core server that support the IoT platform. The platform is configurated as Web Archive (WAR file) which runs when Tomcat server is activated. Spring Structure. It provides the core configuration frame which allows configuration and extension. By using same interface in customize class and inserting with Spring, the third party can extend it without referring to core code. Spring Security. It provides the basic structure for core safety. The platform has its own clients management interface and the Spring Security Interface at the same time, which allows it to authenticate the access to system source with existing security modules. Hazelcast. With the help of Hazelcast, the platform provides access to undergoing events based on subscription. External entities can use Hazelcast app to connect with running IoT platform example, and monitor event source including the location data, measurement, alarm and order execution. MongoDB. It is a NoSQL database to store the platform data, with the advancement of high efficiency and good performance. Apache HBase. In this platform, the customized HBase mode can save the device issues as optimized clusters-crossing time series data, thus realizing quick access to event according to the time of data collection. InfulxDB/Grafana. The platform can store equipment management data in MongoDB and event data in InfluxDB by using mix methods. Thus, the data visualization can be realized using the tools like Grafana. 6.TYPICAL APPLICATION SCENARIOSNowadays, the application of IoT terminals has increased day by day. The development of IoT technology has widely changed our daily like and working style. The proposed IoT platform can be adopted in different industries. Almost all industries can benefit from it for it brings convenience in monitoring, automation, and analysis. Some important application scenarios are listed as follows:
7.CONCLUSIONS AND BENEFITSThere are a variety of sensing terminals and network access devices on the Internet of Things, data models and interface protocols are not unified, and device performance architectures vary greatly. Projects involving multi-system IoT equipment often need to put a lot of effort into equipment access and joint adjustment. By studying the IoT platform for multiple application scenarios, this paper solves the data access problem of highly concurrent IoT sensing devices, and can parse the formatted and encapsulated values in real time and then push them to the business application system, so as to meet the requirements of various typical business scenarios. The IoT Platform can access and parse new device data in a simple and configurable way. It features cross-platform, high concurrency, and high security, and has certain application value. REFERENCESZhao, X.,
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