What Is 4G? How 4G Networks Work

It replaced the mixed voice-and-data design of 3G with a single, all-IP network built for speed, capacity, and low latency, and it remains, more than a decade after launch, the network most IoT devices in the Nordics actually run on. This guide explains what 4G means technically, how the network architecture behind it works, how it compares to 3G and 5G, and how real Com4 customers use 4G connectivity in production today.

Key takeaways:

• 4G is an all-IP mobile network standard built around the Evolved Packet Core (EPC) and eNodeB radio towers, replacing 3G's separate voice and data paths with a single IP-based architecture.
• LTE is the radio technology that delivers most real-world 4G performance; true 4G, as defined by the ITU, requires LTE Advanced, though "4G" and "LTE" are used interchangeably in practice.
• OFDMA, SC-FDMA, and MIMO are the technologies that give 4G its speed and capacity gains over 3G.
• VoLTE carries voice calls as data over the same 4G network, rather than falling back to an older circuit-switched connection.
• 4G is not being replaced any time soon. It remains the most widely available, cost-effective network standard for the large majority of IoT deployments, and it underpins the LTE-M and NB-IoT variants purpose-built for low-power IoT devices.
• Com4 provisions SIM connectivity across 4G, LTE-M, and NB-IoT, automatically switching between more than 750 networks in over 190 countries so devices stay connected on whichever 4G-based network fits how they are actually used

What does 4G actually mean?

"4G" refers to the fourth generation of cellular network standards, following 2G (which introduced digital voice and basic data) and 3G (which added mobile internet access). Each generation is defined by a new radio technology and a new network architecture, not just faster speeds.

The International Telecommunication Union (ITU) set formal performance targets for what counts as "true" 4G under its IMT-Advanced standard, including peak data rates around 1 Gbps for stationary users and 100 Mbps for mobile users. In practice, the industry settled on LTE and its successor, LTE Advanced, as the commercial technologies marketed as 4G, since LTE Advanced is what actually meets the IMT-Advanced targets. This is why you will sometimes see "4G LTE" and "true 4G" used to distinguish early LTE deployments from later LTE Advanced networks, even though both are sold to consumers simply as "4G."

For IoT deployments, this distinction rarely matters day to day. What matters is that 4G networks, across theirLTE and LTE Advanced generations, deliver mobile broadband performance reliable enough to run everything from digital signage to industrial sensors without the device needing to fall back to a slower, older network.

How does a 4G network work?

A 4G network is built around two main components: the radio access network, which handles the wireless connection to devices, and the core network, which routes traffic and manages the session.

• eNodeB (evolved Node B). This is the 4G radio tower, or base station, that a device connects to directly. Unlike 3G, which routed traffic through an intermediate controller (the RNC), 4G's eNodeB connects straight to the core network, cutting out a hop and reducing latency.
• EPC (Evolved Packet Core). This is the all-IP core network that handles everything the eNodeB does not: routing data, managing mobility as a device moves between towers, authenticating SIMs, and enforcing quality of service. The EPC's Mobility Management Entity (MME) is the control node responsible for tracking devices in idle mode and paging them when data needs to be delivered.
• UE (User Equipment). This is the technical term for any device connecting to the network, whether it is a smartphone, an industrial gateway, or an IoT sensor with an embedded modem.

The key architectural shift from 3G to 4G is that voice, data, and signaling all travel over the same IP-based path instead of separate circuit-switched and packet-switched systems. That simplification is a large part of why 4G networks handle far more simultaneous connections, and far more data-hungry applications, than 3G ever could.

What technologies make 4G fast?

Three technical building blocks account for most of 4G's speed and capacity advantage over 3G:

• OFDMA (Orthogonal Frequency-Division Multiple Access). Used on the downlink, OFDMA splits a radio channel into many narrow subcarriers that can be assigned to different devices simultaneously, packing more data into the same amount of spectrum with less interference than 3G's approach.
• SC-FDMA (Single-Carrier Frequency-Division Multiple Access). Used on the uplink, SC-FDMA achieves similar spectral efficiency to OFDMA while being more power-efficient for the transmitting device, which matters for battery-powered hardware.
• MIMO (Multiple Input, Multiple Output). MIMO uses multiple antennas at both the transmitter and receiver to send and receive more than one data stream at once over the same frequency. More antennas generally means a stronger signal-to-noise ratio, better cell range, and higher throughput, which is why MIMO configurations (such as 2x2 or 4x4 MIMO) are a common spec on 4G routers and modems.

On top of these, carrier aggregation, combining multiple frequency bands into a single, wider effective channel, lets operators push real-world speeds well beyond what any single band could deliver alone. Com4's deep dive on LTE covers carrier aggregation and the specific frequency bands used across the Nordics in more technical detail.

What is the difference between 4G and LTE?

LTE (Long-Term Evolution) is the radio technology that carries the vast majority of real-world 4G traffic, and for most practical purposes, "4G" and "LTE" describe the same network. Technically, though, LTE was the first step toward full 4G performance, and LTE Advanced (and later LTE Advanced Pro) is what actually meets the ITU's formal 4G targets. Network operators and device manufacturers market both generations simply as "4G" because the distinction rarely changes how a device or a person experiences the network. When Com4 provisions 4G SIM connectivity, it spans this full range of LTE and LTE Advanced networks, so devices get the strongest available 4G signal regardless of which specific sub-generation a given tower is running.

How does VoLTE work on 4G networks?

Older networks handled voice calls over a separate circuit-switched connection, which is part of why some early 4G phones would drop back to 3G for the duration of a call. VoLTE (Voice over LTE) solves this by carrying voice as just another IP data stream over the same 4G network used for everything else, using the EPC's unified, all-IP architecture. The result is that calls can start faster, hold higher audio quality (often marketed as HD Voice), and run alongside data use without forcing a network handover. For IoT deployments, VoLTE itself is rarely relevant since most devices do not carry voice traffic, but it is a useful illustration of just how much simpler 4G's all-IP design is compared to the patchwork architecture it replaced.

4G vs 3G vs 5G: what's actually different?

The practical takeaway for most IoT deployments: 3G is on its way out across Nordic networks, 5G is still concentrated in specific high-value use cases, and 4G sits in the middle as the mature, dependable default that covers the overwhelming majority of connected devices in production today.

What is 4G's role in IoT connectivity today?

4G is not just the network smartphones use. It is also the foundation for two IoT-specific network variants built on the same underlying LTE standard:

• LTE-M serves devices that need mobility and moderate bandwidth, such as trackers and portable equipment, while consuming less power than standard 4G.
• NB-IoT serves simple, stationary sensors that send small amounts of data infrequently, prioritizing battery life and deep indoor coverage over speed.

Both LTE-M and NB-IoT ride on the same physical 4G network infrastructure operators have already built out, which is exactly why they scale so cost-effectively: there is no separate radio network to deploy.

Com4's guide to LTE covers the technical differences between standard 4G, LTE-M, and NB-IoT, and how to choose between them, in more depth.

Real-world 4G connectivity: Com4 customer examples

ZetaDisplay: always-on 4G for time-critical digital signage. ZetaDisplay's digital signage network, deployed in locations including the Oslo Airport Express Train and Oslo Central Station, runs on industrial 4G modems connected through Com4 SIMs. Because Com4's SIMs automatically switch across multiple mobile networks, the signage stays online even if a single operator's network degrades in a specific location, which matters when the content being displayed includes live train departure times.

Soundsensing: 4G-based sensors deployed at scale. Soundsensing has deployed more than 1,500 noise sensors across roughly 150 buildings, including sites for Statsbygg and properties around Oslo City, using LTE-M connectivity running on Com4's 4G network footprint. At that scale, the deciding factor is not peak speed but consistent, low-maintenance coverage across a large number of physical sites, exactly what a mature 4G network is built to deliver.

Just Eat Norway: 4G connectivity for a distributed kiosk network. Just Eat Norway has run a network of mobile-connected ordering kiosks since 2006, predating most of today's 4G infrastructure and migrating onto it as networks matured. The kiosks depend on dependable mobile connectivity across many retail locations, a use case that plays directly to 4G's combination of broad coverage and manageable cost per connection.

Is 4G being replaced by 5G?

Not any time soon, and for most connected devices, not at all. 5G rollouts remain concentrated in dense urban areas and specific high-bandwidth, low-latency use cases, such as industrial automation or fixed wireless access. For the large majority of IoT deployments, from fleet tracking to smart metering to environmental sensors, 4G already delivers more than enough speed and capacity, at a lower hardware and connectivity cost than 5G. Operators are expected to keep 4G networks running well into the next decade specifically because so much industrial and IoT infrastructure depends on it. Com4's guide to the 5G rollout in the Nordics covers where 5G actually makes sense today if you are weighing the two.

Choosing the right 4G-based connectivity for your devices

Not every device needs the same slice of the 4G standard. Before choosing a SIM and data plan, it helps to work through a short checklist:

1. How much data does the device actually send? A device streaming video needs standard 4G bandwidth; a sensor reporting readings every few minutes may be well served by NB-IoT.
2. Does the device move? Mobile or portable equipment generally needs standard 4G or LTE-M rather than NB-IoT, which is optimized for stationary devices.
3. How constrained is the power budget? Battery-powered devices with multi-year deployment expectations should look at LTE-M or NB-IoT rather than standard 4G modems, which draw meaningfully more power.
4. What does the physical deployment environment look like? Indoor, underground, or otherwise hard-to-reach locations benefit from NB-IoT's deeper penetration characteristics.
5. Does the deployment span multiple countries or networks? If so, look for SIM connectivity that switches automatically across operators rather than locking a device to a single network.
6. Will the device need to be reconfigured remotely after deployment? Confirm the SIM supports over-the-air provisioning so network and profile changes do not require a site visit. Com4's guide to IoT SIM cards, eSIM, and iSIM covers the form factor and provisioning side of that decision.