1. Access layer infrastructure: The "last mile" connecting "terminals" and "networks"

The access layer serves as the "entry point" for user devices (such as mobile phones, computers, smart home devices, industrial sensors, etc.) to access the network. Its core objective is to achieve "wide coverage and multi-scenario access". Common devices and technologies include:

Wired access equipment

Broadband Optical Network terminal (ONT) : It converts the optical fiber signals of the operator into Ethernet signals (such as WiFi, network cables) that can be used by homes/enterprises, and is the core entry point of home broadband.

Enterprise-level switches: Used in the internal local area network (LAN) of enterprises, they connect computers, servers, printers and other devices to achieve internal data interaction, support VLAN (Virtual Local Area Network) division, and ensure data security.

Wireless access equipment

Wireless router (Home/enterprise) : Converts wired signals into wireless signals via WiFi (such as WiFi 5, WiFi 6), covering small areas like homes and offices, and supports simultaneous connection of multiple devices.

Base stations (macro base stations, micro base stations) : The core wireless communication equipment deployed by operators, which realizes wide-area wireless coverage (such as in cities and rural areas) through technologies like 4G LTE and 5G NR, and is the key for mobile phones and Internet of Things devices (such as shared bikes and smart meters) to access the mobile network.

Satellite terminal: It is used in remote areas (such as deserts and oceans) or emergency scenarios (such as damage to ground base stations after an earthquake), communicating with the ground gateway through satellites to achieve "no blind spots" access.

2. Aggregation layer infrastructure: "Data Transfer stations" between the "Access layer" and the "backbone Layer"

The core function of the aggregation layer is to "centrally manage access layer devices and optimize data transmission paths", avoiding resource waste caused by a large number of terminals directly connecting to the backbone layer. The main devices include:

Aggregation switch: Deployed in the computer rooms of residential areas, industrial parks, and office buildings, it connects all access layer switches (such as home optical MOdems and enterprise switches) within the area. After "aggregating" the scattered terminal data, it transmits it to the backbone layer through high-speed links (such as optical fibers).

Edge Computing Node (MEC) Some aggregation layers will integrate edge computing capabilities, migrating some computing tasks from the cloud (such as real-time analysis of video surveillance and low-latency decision-making for autonomous driving) to locations "close to the terminal", reducing data transmission latency (from "tens of milliseconds in the cloud" to "1-5 milliseconds at the edge"). It is applicable to scenarios sensitive to latency (such as industrial control, AR/VR).