1.2 The Informatization Wave: The Legacy of Three Network Revolutions
The IoT did not appear out of thin air — it is the next stop in the natural evolution of the networked world. Only by understanding the key characteristics and limits of the first two waves (the PC Internet and the mobile Internet) can we see where the third wave (the Internet of Everything) intersects with industrial software. This section sketches the three waves briefly, with the emphasis on their engineering legacy and the problems they left unsolved.
1.2.1 The Core Differences Among the Three Waves
The industry commonly divides the Internet's evolution into three waves, each of which redefined the subject of "connection." If this history is already familiar to you, jump directly to Section 1.2.4 (the Internet of Everything) or Section 1.3 (the definition of the IoT).
The PC Internet (the 1990s) connected people to information. TCP/IP and the World Wide Web moved content from paper onto the screen, and browsers, portals, and search engines made "people seeking information" an everyday routine, but the devices were fixed and wired, and the sensors and actuators of the physical world lay entirely outside the network's coverage radius.
The mobile Internet (from the early 2000s through the 2010s) shifted the object of connection from information to people. Smartphones and 3G/4G networks made "online anywhere, anytime" possible; social networking, instant messaging, and mobile payment became deeply embedded in daily life, and the user base grew to roughly two billion (per ITU statistics, global mobile-broadband subscriptions reached about 2.3 billion by the end of 2014; note that users and subscriptions are counted differently — one person often holds multiple SIMs or devices, so subscription counts typically exceed user counts). The driving force was "human mobility" — but the participation of things remained limited, and the initiator of every operation was still a person.
The Internet of Everything (from the 2010s to today) pulls sensors, actuators, and embedded systems into the network. The subject of connection expands from several billion people to hundreds of billions of things, and the core driving force shifts from "human mobility" to "the digitalization of things." TCP/IP provides the foundation for heterogeneous devices to interoperate, progress in integrated circuits has driven down the cost of sensors and communication modules, and cloud computing fills in the storage-and-processing base for massive data. The pipes laid down by the first two waves used to carry only letters; now they begin to carry goods of every conceivable shape.
The timeline below summarizes the core characteristics of the three waves.
1.2.2 The PC Internet: Information Comes Online, Things Stay Outside
The communication foundation of the PC Internet was the TCP/IP protocol suite — TCP handles segmenting and reassembling data, IP handles addressing and routing, and devices from different vendors could therefore interoperate. What truly pulled ordinary people into the Internet was the World Wide Web: HTML defines pages, HTTP carries the browser's request-response exchanges, and the URL uniquely identifies every resource. From then on, a user could click a link in the browser and jump from page to page, no longer dependent on the command line.
This stage produced two typical paths for acquiring information: portal sites aggregated content, and users "browsed" rather than "participated"; search engines built full-text keyword indexes, making vast amounts of information efficiently locatable. Fixed location (desktop devices, wired access), static information (fixed once the page loaded), and the exclusion of things (sensors and actuators running on dedicated buses) were its three hard boundaries. The architecture diagram in Figure 1-6 shows this "user — PC — World Wide Web — information" chain, with a dashed box in the lower-right corner marking the device zone not yet networked.
The Application Ecosystem: From Portals to Search
The PC Internet produced two typical paths for acquiring information. The first was the portal site, which aggregated news, email, search, community, and other functions on a single page; users "browsed" rather than "participated." The second was the search engine, where users typed keywords directly and located content through full-text indexes of web pages. Both paths solved the same problem: finding the target efficiently within vast amounts of information. This idea of precise retrieval from massive data matches the logic in today's IoT applications of "searching time-series data for the device awaiting a response" — only the search target has changed, from "web pages" to "IoT data."
The Limits of the Desktop Internet
The PC Internet connected roughly one billion users (ITU data, around 2005), but the desktop model — fixed location, wired access, single center — had hit its ceiling. While one billion people became information-connected through PCs, vast numbers of devices, sensors, and machines around the world were still waiting to be brought into the network.
1.2.3 The Mobile Internet: People Always Online, Things Still Outside the Door
The second wave was driven by two engines: the smartphone, which packed telephone, camera, and GPS into a pocket-sized device; and 3G and 4G networks, which made "connectivity anywhere, anytime" a reality. The mobile Internet connected about two billion users. Social apps such as WeChat, Facebook, and WhatsApp upgraded person-to-person communication from SMS to real-time multimedia interaction, and mobile payment extended social relationships into transaction scenarios.
But its limits were just as clear: the initiator of every operation remained a person. To find out how much milk is left in the refrigerator, whether a factory motor is overheating, or which sorting station a parcel has reached, the user had to open an app and check personally. No sensor sensed the state of the physical world automatically on the phone's behalf. At the end of the mobile Internet, the "things" that hold the largest volume of information in the physical world were almost entirely outside this network's connection radius. The star-shaped ecosystem in Figure 1-7 illustrates this pattern, with the user as the single center.
Once the PC had connected information and mobile devices had connected people, the third logical step followed naturally: extend connection to all physical entities.
1.2.4 The Internet of Everything: Thing to Thing, Thing to System
The third wave pulls the "things" of the physical world into the network. These "things" include vibration sensors on industrial machine tools, geomagnetic detectors in parking lots, RFID tags on parcels, and even body-temperature collars around the necks of dairy cows. The subject of connection shifts from "people" to "things" — this is the most essential difference among the three waves.
The Explosive Growth in Device Scale and Diversity
The direct consequence of this shift is an exponential leap in device scale. The first two waves each connected hundreds of millions of users, while the IoT is expected to push the number of connections up another order of magnitude. A user operates only one or two devices, but in industrial settings a single workshop may deploy thousands of sensor nodes. These devices differ wildly in form: some are powered 7×24, others run for years on a coin cell; some report high-precision data every second, others send a single very short message only when their state changes. This diversity completely changes the assumptions behind network and system design — connection is no longer "there are always users online," but "endless heterogeneous devices may come online or go offline at any moment."
The Infrastructure Shift in Communication Technologies
What supports this massive connectivity is not Wi-Fi or 4G cellular networks, but a series of communication technologies designed specifically for the IoT. Low-Power Wide-Area Networks (LPWAN) play the key role among them. Licensed-spectrum technologies such as NB-IoT (Narrowband IoT) and Cat-M, together with unlicensed-spectrum technologies such as LoRa, jointly meet the requirements of low speed, low power, and wide coverage. They do not chase tens of megabits per second of throughput per user; they focus on low power consumption and wide coverage per connection, so that a single battery keeps a sensor running for years. Meanwhile, the mMTC (massive Machine Type Communication) scenario of 5G supports, at the level of standard design, a connection density of one million devices per square kilometer. Release 17 also brought 5G RedCap (Reduced Capability) — a lightweight 5G profile standardized in 2022 and commercially rolling out from 2023 — which fills the gap between NB-IoT and full 5G for mid-rate IoT scenarios such as wearables and video backhaul. LPWAN solved the problems of "is there signal, and is the power budget enough," while 5G opened up "high-density, high-reliability" IoT scenarios.
From Data Collection to System-Level Intelligence: An Example
In the mobile Internet era, the device — the smartphone — had strong computing and interaction capabilities, and data flowed mainly "person to person" or "person to service." In the era of the Internet of Everything, both the producers and the consumers of data are machines and systems. The smart-factory connection topology below illustrates this change:
In this example, the connected objects are the unremarkable sensors and controllers in the workshop; the data transmitted consists of point values flowing machine to machine (M2M); and the system's ultimate value shows up in "intelligence" such as predictive maintenance and efficiency optimization. This is the core of what distinguishes the Internet-of-Everything era from the previous two waves: connection is the means; making the physical world capable of being sensed, controlled, and intelligent is the goal. This evolution from "data collection" to "system intelligence" is reshaping the traditional information-processing architecture, and it lays a key architectural foundation for deploying large AI models in IoT scenarios.
In sum: each of the three waves redefined "who gets connected" and "what the connection is for" — the PC connected information, mobility connected people, and the Internet of Everything connects things and systems. What deserves attention is this: in the first two waves the endpoints were people and value was driven by information consumption; in the third wave the endpoints are things and value is produced by data-driven autonomous coordination among devices. This difference echoes precisely the limits of industrial software discussed in Section 1.1 — strong in deterministic control, weak in adaptive intelligence: the next step for industrial software is not a better SCADA or MES, but letting the connection itself grow the ability to understand and decide. Next we turn to the standard definition and core elements of the IoT.