What does gateway mean?
Easy-to-understand explanation: The gateway is our common “router”.In the Internet network we are familiar with, the role of a gateway is an intermediate device that links the internal network with other networks on the Internet.
A more professional explanation: It refers to the “gateway” that connects this network to another network. Everyone knows that to walk from one room to another, you must pass through a door. Similarly, sending information from one network to another must pass through a “gateway”, which is the gateway. As the name suggests, a gateway is a “gateway” that connects one network to another. Gateway is also called Internet connector and protocol converter.
A gateway is also called a protocol converter. The function of the gateway is to realize the interconnection between networks. Gateways not only allow wide area networks to connect to each other, but also allow local area networks to connect to each other. The gateway plays the role of conversion between computers and devices. It is equivalent to a translator, which can convert different protocols, languages, and data between different systems.
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What is an Industrial IoT gateway?
Internet of Things gateway, as a new term, will play a very important role in the future Internet of Things era. It will become the link between the sensing network and the traditional communication network. As a gateway device, the IoT gateway can realize protocol conversion between sensing networks and communication networks, as well as different types of sensing networks. It can realize wide area interconnection. Local area interconnection can also be achieved. In addition, the IoT gateway also needs to have device management functions. Operators can manage the underlying sensing nodes through the IoT gateway device, understand the relevant information of each node, and achieve remote control. Figure 1 schematically shows a typical topology of the Internet of Things built with an Internet of Things gateway.
IoT gateway design
IoT gateway functions:
(1) Extensive access capabilities
There are currently many technical standards for short-range communications. Common WSN technologies include Lonworks, ZigBee, 6LowPAN, RUBEE, etc. Various technologies are mainly developed for a certain application and lack compatibility and system planning. For example, Lonworks is mainly used for building automation, and RUBEE is suitable for malicious environments. How to achieve protocol compatibility, interfaces and system planning? Currently, many organizations at home and abroad are carrying out standardization work on IoT gateways, such as 3GPP and sensor working groups, to achieve interconnection and interoperability of various communication technology standards.
(2) Protocol conversion capability
Protocol conversion from different sensing networks to access networks uniformly encapsulates data in the standard format of the lower layer to ensure that the protocols of different sensing networks can become unified data and signaling; parses data packets sent by the upper layer into sensing signaling and control instructions that can be recognized by layer protocols.
(3) Manageability
Powerful management capabilities are essential for any large network. First, the gateway must be managed, such as registration management, rights management, status supervision, etc. The gateway implements the management of nodes in the subnet, such as obtaining the node’s identity, status, attributes, energy, etc., as well as remote wake-up, control, diagnosis, upgrade and maintenance. Because the technical standards of subnets are different and the complexity of the protocols is different, the management capabilities of the gateways are different. This article proposes a modular IoT gateway approach to manage different sensing networks and different applications, ensuring that unified management interface technology can be used to manage peripheral network nodes. Hierarchy:
1) Business service layer
The business service layer consists of a message receiving module and a message sending module. The message receiving module is responsible for receiving standard messages from the IoT business operation management system and passing the messages to the standard message composition layer. The message sending module is responsible for reliably transmitting the data information collected by the perception extension network to the business operation management system. Messages received and sent by this layer must conform to standard message formats.
(2) Standard message composition layer
The standard message composition layer consists of a message parsing module and a message conversion module. The message parsing module parses the standard messages from the business service layer, and calls the message conversion module to convert the standard messages into a data format that can be understood by the underlying perception extension device and depends on the specific device communication protocol. When the perception extension layer uploads data, the message parsing module of this layer parses the message that depends on the specific device communication protocol, and calls the message conversion module to convert it into a standard format message that the business service layer can receive. The message composition layer is the core of the Internet of Things gateway. It completes the analysis of standard messages and messages that rely on specific perception extension networks, and realizes mutual conversion between the two, achieving unified control and management of the underlying perception extension network, and shielding the underlying network upwards. Purpose of communication protocol heterogeneity.
(3) Protocol adaptation layer
The protocol adaptation layer ensures that different perception extension layer protocols can be transformed into data and control signaling in a unified format through this layer. (4) Perceptual extension layer
This layer extends the device to the underlying perception and includes two sub-modules: message sending and message receiving.The message sending module is responsible for sending the message
The message converted by the information composition layer and can be understood by the specific perception extension device is sent to the underlying device.
The message receiving module receives messages from the underlying device and sends them to the standard message composition layer for analysis.
The perception extension network consists of perception devices, including RFID, GPS, video surveillance systems, various types of sensors, etc. A variety of communication protocols are supported between sensing extension devices, which can form Lonworks, Zigbee and other various sensing extension networks.
Information exchange process
(1) The end user generates a message that conforms to the standard data format and sends it to the message receiving module of the gateway business service layer. (2) The business service layer message receiving module sends standard messages to the message parsing module of the standard message composition layer.
(3) The message parsing module calls the corresponding message conversion function to convert standard information into messages that depend on the specific device communication protocol.
(4) The message parsing module converts the message into a message that depends on the specific device communication protocol and transmits it to the message sending module of the perception extension service layer.
(5) The message sending module of the perception extension service layer selects an appropriate transmission method and sends specific messages that depend on the device communication protocol to the specific underlying device.
(6) The underlying device performs information collection operations based on specific messages and returns the results to the message receiving module of the gateway awareness extended service layer.
(7) The message receiving module of the gateway’s perception extension service layer transmits specific messages that depend on the device communication protocol to the message parsing module of the standard message composition layer.
(8) The message parsing module calls the information conversion module to convert specific messages that depend on the device communication protocol into standard messages. As can be seen from Figure 3, the IoT gateway solves the problem of unified control and management of different devices in the IoT network, achieves the purpose of shielding the differences in underlying communications, and eliminates the need for end users to know the specific communication details of the underlying devices to achieve control over different devices. Unified access to awareness extension layer devices.
Key technology
The following key technologies are solved in the design of the IoT gateway system.
Unification of software interaction protocols: The design idea of the IoT gateway system is to implement various parts of software and hardware in a modular manner, making it very easy to replace modules to achieve different perception extension networks and access network interconnections, shielding the underlying layer Communication differences. The hardware modules are connected in the form of UART bus, and the software runs in a modular and loadable manner, and the common parts are abstracted into public modules. Therefore, to support new data aggregation modules and access modules, you only need to develop corresponding hardware modules and drivers. In addition, a unified protocol adaptation layer is added (as shown in Figure 6), the application data is extracted uniformly, organized according to TLV (type, length, value), and then the data packets are encapsulated. So that all standard IP data packets are transmitted in the access network, which encapsulates the collected data in TLV format.
Unified address translation: Different data collection networks use different addressing methods, such as 16-bit short addresses in ZigBee and 64-bit addresses in 6LowPan. In the application, you only need to be able to locate specific nodes. You do not need to care whether the nodes use IP addresses or 16-bit short addresses, nor do you care whether the networking between nodes uses ZigBee or 6LowPan or other methods. Converting these addresses into a unified representation is beneficial to application development. Therefore, an address mapping mechanism is implemented in the gateway to map the IP or 16-bit short address to a unified ID. You only need to pay attention to this during the interaction with the application. Just ID. The specific mapping method can be cumulative from 1. When the gateway receives the first node data, it maps the address of the node to 1, and subsequently adds 1 in sequence, and saves this mapping table in the gateway. At the same time, an aging mechanism is also used. When no data from the node is received within a certain period of time, the mapping relationship is deleted.
Unification of the data interface of the collection module: AT command set is defined between the collection module and the gateway, and the nodes are networked through the ZigBee protocol. The interface with the gateway only focuses on some control instructions and data interaction instructions for the collection module, and does not pay attention to the specific networking protocol to achieve networking protocol independence.
Data mapping relationship management: How to manage the mapping relationship in communication data between devices in two or more systems connected by the gateway, that is, addressing in the usual sense, is a very important step. In this part, the bus devices are also very different depending on the gateway connection.This gateway analyzes the input and output data formats of all possible modules, and then defines the communication interfaces corresponding to each module.