23.3 5G Basics

A New Generation of Mobile Networks

5G is the fifth generation of mobile network technology. It builds on earlier generations such as 3G and 4G, but introduces new design ideas that aim to support far more devices, much higher speeds, and very low delays. In this chapter you will see what is special about 5G from a networking point of view, without going deep into topics that belong to other chapters such as general wireless theory or advanced enterprise networking.

5G is not a single feature or a single radio. It is a whole ecosystem that affects how radios are built, how networks are designed, how services are delivered, and how applications interact with the network.

How 5G Differs From 4G

4G was designed mainly for mobile broadband, which means giving smartphones decent speeds for web browsing, video streaming, and apps. 5G keeps that goal, but adds two more big ones. These three ideas are often described as three main service types in 5G.

4G networks were largely built with one main data service in mind. 5G is designed from the beginning to carry very different types of traffic over the same infrastructure. This is an important networking idea. The same physical network must support:

High bandwidth flows such as video and virtual reality.

Time critical flows that cannot tolerate long or variable delays.

Short and infrequent messages from very many tiny devices.

This variety of requirements influences many 5G design choices, from the radio layer up to how the core network is structured.

Frequency Ranges and Cells in 5G

A visible change in 5G is how it uses radio spectrum. You will see three broad ranges used in practice, often called low band, mid band, and high band or millimeter wave.

Higher frequencies can carry more data but travel shorter distances and are blocked more easily by obstacles. 5G takes advantage of this by mixing different cell sizes.

Large cells in low or mid band can cover wide areas such as rural zones or whole city blocks. These cells are often called macro cells.

Smaller cells in mid band or high band can cover busy areas such as stadiums, shopping centers, or dense city streets. These are often called small cells.

This mix of many cells of different sizes gives higher capacity where it is needed. It also leads to more complex network planning and more handovers as users move between cells.

Massive MIMO and Beamforming

To reach higher speeds without using unlimited spectrum, 5G base stations use advanced antenna techniques. Two commonly mentioned ideas are massive MIMO and beamforming. Both belong to the broader topic of radio fundamentals, but here you can focus on what they mean for the network.

MIMO stands for Multiple Input Multiple Output. It refers to using multiple antennas at both the transmitter and receiver to send several data streams at once. Massive MIMO uses many more antennas than previous generations, often dozens or more at a single base station.

When there are many antennas, the base station can shape the radio signal more precisely. This is called beamforming. Instead of sending radio energy in all directions, the station directs energy toward a specific user. The result is better signal quality and higher data rates for that user and less interference for others.

From a networking viewpoint, these techniques effectively increase capacity per cell. More users can be served at higher data rates in the same slice of spectrum. The network can also adapt beams over time as users move, which offers more control in crowded environments.

5G Architecture at a High Level

Behind the radio part of 5G there is a core network that handles control, user data, authentication, mobility, and services. The detailed architecture belongs in advanced chapters, but here it is useful to know the simple separation into two main pieces.

The first piece is the radio access network, often abbreviated as RAN. It includes the base stations that talk directly to devices over the air. In 5G these nodes are usually called gNBs. They handle radio related tasks like scheduling, modulation, and access control.

The second piece is the core network, sometimes called the 5G Core or 5GC. It includes functions that route user traffic, enforce policies, manage sessions, and connect to external networks such as the internet or private data centers.

One key design choice in 5G is that many core functions are built as software services that run on general purpose hardware instead of fixed appliances. This is related to concepts like virtualization and cloud networking discussed in other chapters. It makes the 5G core more flexible, easier to update, and easier to integrate with cloud environments.

Standalone and Non Standalone 5G

In real deployments you will often hear two terms: Non Standalone and Standalone. They describe how 5G is integrated with existing 4G networks.

In Non Standalone (NSA) mode, the 5G radio works together with a 4G core. User traffic may run over 5G radio for speed, but control functions still depend on 4G. This mode allowed operators to deploy 5G radios quickly without replacing the entire core network.

In Standalone (SA) mode, the network uses a full 5G core along with the 5G radio. This enables many of the advanced features that are unique to 5G, such as more complete network slicing and improved latency control. SA is what most long term deployments aim for, while NSA was a useful stepping stone.

From a networking perspective, NSA looks like an extension of 4G. SA introduces a genuinely new core with different interfaces and functions.

Network Slicing: One Physical Network, Many Virtual Networks

One of the most important networking ideas in 5G is network slicing. The physical 5G network, including radios, transport, and core, can be logically divided into separate slices. Each slice behaves as if it were its own dedicated network with specific characteristics.

For example, an operator can create:

A slice for consumer mobile broadband with a focus on high throughput.

A slice for industrial automation with strict latency and reliability targets.

A slice for IoT sensors that need low power and can tolerate more delay.

Each slice can have its own policies, quality targets, security rules, and resource allocations. In some cases, even business customers can have their own private slices.

The idea of slicing fits naturally with virtual networks, SDN, and cloud based cores. It allows a single 5G infrastructure to support many different use cases without building separate physical networks.

Latency and Reliability Targets

Another major goal of 5G is lower latency. Latency is the time it takes for data to travel from source to destination, including all processing delays. In older mobile networks, typical latency for everyday use was often tens of milliseconds or more.

5G introduces design features that can reduce this delay. The exact numbers depend on the deployment, but 5G targets are often described as:

A few milliseconds latency for some time critical use cases.

Higher reliability for traffic that cannot tolerate packet loss.

The details of how this is achieved involve radio scheduling, shorter transmission time intervals, and sometimes processing closer to the user, which leads to the concept of edge computing. For this course, it is enough to understand that 5G is designed to support not only high throughput, but also very low and predictable latency for specific services.

This focus on latency allows new types of applications, such as remote robot control or cooperative vehicles, that were difficult to support reliably over earlier mobile networks.

5G and Massive IoT

5G is also built to connect many more devices than people. In a modern city, there can be sensors for traffic, environment, utilities, factories, and buildings, all trying to send data over the network. This is often called massive IoT or massive machine type communication.

The 5G system defines ways to:

Let many devices share radio resources efficiently.

Allow devices to send small bursts of data with minimal power consumption.

Support different traffic patterns, such as infrequent status reports or regular measurements.

From a networking perspective, this means the control plane and data plane must handle high numbers of connections, often with very small payloads, without becoming overloaded. It also means that policies, security, and addressing for IoT devices must scale to large deployments and integrate with existing IP networks.

5G and Edge Computing

5G is often mentioned together with edge computing. The basic idea is to move some compute and storage resources closer to the user, near the edge of the network instead of in a far away data center. For time sensitive applications, shorter physical distance can lower latency.

When 5G base stations and local edge nodes are connected through high speed backhaul, applications such as gaming, augmented reality, or industry control can place some of their logic at the edge. The 5G network can then route traffic in a way that keeps critical paths short.

This does not change IP fundamentals, but it does change where servers may live and how traffic is steered. Concepts like local breakout and traffic offloading become important in advanced designs.

Security Considerations in 5G

5G networks inherit general security topics such as encryption, authentication, and access control. At the same time, they introduce some particular aspects.

More functions are software based and may run in shared cloud infrastructure. This makes configuration, isolation, and monitoring even more critical.

Network slices may have different security requirements. A slice used for public internet access is very different from a slice used for power grid control.

Large numbers of IoT devices may not be physically protected and can be a source of attacks if not managed correctly.

These concerns do not change the basic principles of network security that you will see in other chapters. They do show why 5G operators and designers must combine mobile specific knowledge with general network security best practices.

Relationship to Other Networking Topics

5G uses IP at its core and connects to the public internet and private networks, so all the general networking concepts in this course still apply. Routing, switching, QoS, virtualization, and security are all part of a complete 5G deployment.

5G radio access networks rely on high capacity transport networks that can be built with fiber, Ethernet, and various routing technologies discussed elsewhere. The 5G core itself is often implemented using cloud networking and virtualization platforms that you will encounter in later chapters.

So while 5G introduces new radio techniques and a new architecture, it does not replace traditional networking. Instead it extends it into the mobile domain and gives it new performance characteristics and new possibilities for services.