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February 6, 2023 Common Basics of LTE Modem

What is an LTE Modem?

The data transmission unit LTE Modem (Data Transfer unit) is a wireless terminal device specially used for converting serial port data into IP data or converting IP data into serial port data for transmission through a wireless communication network.Broadly speaking, during communication, the module unit responsible for sending data information at both ends of the link for transmitting data is called LTE Modem, which performs format conversion and data collation and verification on the transmitted information. In a narrow sense, LTE Modem generally refers to the lower LTE transmitting terminal equipment in wireless communication. The former is a module, while the latter is a device.The following description refers to the latter (lower transmitting terminal equipment) unless otherwise specified.

What are the terms related to LTE Modem?

(1) What are the upper and lower computers?

The upper computer and the lower computer are a relative concept. In communication, there is a pair of devices with master-slave relationship. The terminal device responsible for submitting information is the lower computer, and the device responsible for processing the submitted information is the upper computer.In most cases, the LTE Modem device belongs to the lower computer, and the data center responsible for processing the information returned by the LTE Modem is the upper computer. The typical application mode is that multiple LTE modems correspond to one data center.However, the upper computer and the lower computer do not necessarily correspond to each other. They can be one lower computer corresponding to one or more upper computers, or one upper computer corresponding to one or more lower computers. The specific correspondence depends on the application.

(2) What is a data center?

Data center refers to the upper computer system which collects, summarizes and processes the information returned by the lower computer, and controls and manages the lower computer to a certain extent. It includes complete computer hardware equipment and specific complete software functions.

(3) What is fully transparent transmission?

Transparent transmission is a simple process of sending IP packets without any operation or change.Generally speaking, during fully transparent transmission, the format and content of the data do not change before and after transmission. The data received by the remote data center is the same as the data collected on site. The data does not change during transmission. If there is any operation or change in the IP packet, it is not fully transparent.

Working principle of LTE Modem

The communication between the LTE Modem and the server is initiated by the GPRS LTE Modem side (client side), and the server side responds to the LTE Modem side by sending back feedback or accepting communication. The LTE Modem and the server together form an application system based on GPRS and INTERNET network communication.Compared with the LTE Modem side, the server side is equipped with more complex applications, which can accept any communication request initiated by the LTE Modem side and detect the communication status in the link at all times, so as to realize real-time data acquisition, database services and other applications.

The process of communication and protocol conversion between the LTE Modem and the server is shown in the following diagram:

The four core functions of an LTE Modem?

1. Support automatic heartbeat and keep online forever.

2. Provide bidirectional conversion function of serial port data

3. Internally integrated TCP/IP protocol stack

4. Support parameter configuration and permanent saving

Pusr's LTE Modem solution, covering 2G/4G/NB-IOT, can adapt to the needs of interconnection of various equipment scenarios, with strong compatibility and adaptability, and is widely used in the industry. The company's self-developed LTE Modem has been applied in the field of industrial Internet of Things, automatic water sales in residential areas, power industry, intelligent retail and other fields, pushing forward the application of Internet of Things scenarios.

What do I need to do before the LTE Modem test?

Before testing the LTE Modem, the following conditions are required:

(1) a public IP address or an independent domain name;

In some cases, the computer in the test environment cannot have an independent public network IP address and domain name address because it is in the internal LAN, so it is necessary to obtain an independent public network IP through dial-up Internet access, or set DMZ host mapping or port mapping on the router in the test environment to enable the computer to penetrate the internal network.O that the computer and the LTE Modem can respond normally.

(2) One SIM card with 4G data service (required for testing LTE Modem), or one UIM card with LTE data service (required for testing LTE Modem);

(3) a desktop or laptop computer with a 9Pin RS232 serial port (or USB to TTL);

This computer is used to set and adjust the parameters of the LTE Modem. At the same time, during the test, it can connect the LTE Modem as a virtual data source device, and send and receive data with the host computer data center through the serial debugging tool. Of course, this computer can be both the data center of the upper computer and the lower computer of the virtual data source when the conditions are met.But in the second test purpose, try to avoid doing so, so as not to doubt the test itself.

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