# LwM2M Introduction
LwM2M protocol is Lightweight M2M protocol organized and established by OMA, mainly for IoT applications based on the narrow band cellular Internet of Things (NB-IoT) scenarios, focus on low power and wide coverage (LPWA) Internet of Things (IoT) market, is an emerging technology that can be widely used in the world. It has the features of wide coverage, multiple connections, low speed, low cost, low power consumption and excellent framework and other characteristics.
Functions and characteristics
NB-IoT has 4 major fcharacteristics：
- Wide coverage: At the same frequency band, NB-IoT has a gain of 20dB over the existing network, which equals to 100 times increase in coverage;
- Big connectivity: Easily support a large number of device networking needs, with the ability to support massive connectivity,one sector of NB-IoT can support 100,000 connections;
- Low power consumption: Focus on applications with small data volume and small rate, especially for some devices and occasions where batteries cannot be replaced frequently, the standby time of NB-IoT terminal module theoretically can be as long as 10 years;
- Low cost: The expected cost of one connection module does not exceed $5;
Based on NB-IOT LWM2M protocol and CoAP protocol, the communication between UE and OneNET platform is realized. The transmission layer protocol in data transmission protocol is CoAP, and the application layer protocol is LwM2M protocol.
Coap protocol has the following characteristics:
- Based on lightweight UDP protocol, it has retransmission mechanism
- The protocol supports IP multicasting
- The protocol header is small, only 4 bytes
- Low power consumption，is applicable to low-power IoT scenarios
The LWM2M protocol is applicable to lightweight protocol, a various IoT devices. LWM2M defines three logical entities:
- LWM2M Server;
- LWM2M Client, which is responsible for executing server commands and reporting execution results;
- LWM2M Bootstrap Server, which is responsible for configuring LWM2M Client.
Typical Application Scenarios
LWM2M protocol (NB-IoT) is a lightweight M2M protocol with retransmit mechanism based on UDP protocol. and mainly for IoT applications based on the narrow band cellular Internet of Things (NB-IoT) scenarios, focus on low power and wide coverage (LPWA) Internet of Things (IoT) market, is an emerging technology that can be widely used in the world.
It is widely applicable to the environment where power demand is low, high coverage depth, massive terminal device connection and sensitive device cost. And can be widely used in application scenarios such as intelligent parking, intelligent meter reading, intelligent manhole covers, intelligent streetlights, etc.