Fifth Generation Mobile Networks

5G represents the most ambitious leap in wireless telecommunications history. Unlike previous generational transitions that focused primarily on incremental speed improvements, 5G fundamentally reimagines what wireless networks can accomplish. It's not merely a faster version of 4G—it's an entirely new network paradigm designed to serve as the connectivity foundation for virtually every industry and application imaginable.

The development of 5G standards began in earnest around 2016 under the 3rd Generation Partnership Project (3GPP), with the first commercial deployments launching in 2019. By 2024, 5G networks serve billions of subscribers globally, though the technology's full potential remains unrealized as operators continue deploying advanced features.

Understanding 5G requires grasping three fundamental truths:

1. 5G is not one technology but a constellation — It combines multiple radio technologies, spectrum bands, and network architectures
2. 5G is designed for three distinct use case families — Each requiring radically different network characteristics
3. 5G blurs the line between telecommunications and computing — Integrating network functions with edge computing in unprecedented ways

The International Telecommunication Union (ITU) defined IMT-2020 (the official designation for 5G standards) around three primary usage scenarios, often visualized as a triangle. Each corner represents a fundamentally different set of requirements that 5G must satisfy simultaneously:

The ITU established eight minimum technical performance requirements for 5G that networks must satisfy to be considered compliant with IMT-2020 standards. These KPIs represent order-of-magnitude improvements over 4G LTE:

Understanding These Metrics:

Peak Data Rate represents the theoretical maximum throughput under ideal conditions with all radio resources allocated to a single user. Real-world speeds are significantly lower but still transformative.

User Experienced Data Rate measures what actual users perceive in dense deployments—a more meaningful metric for consumer applications. The 100 Mbps target ensures consistent 4K streaming even in crowded venues.

Latency improvements enable real-time applications. The 1 ms target for URLLC (compared to 4G's 10+ ms) opens entirely new application categories. Note that end-to-end latency involves more than just the air interface—backhaul, core network, and application server contributions matter.

Connection Density addresses IoT scale. Supporting one million devices per square kilometer enables smart city deployments where every streetlight, parking sensor, and environmental monitor connects wirelessly.

Area Traffic Capacity measures total throughput per unit area—critical for venues like stadiums where tens of thousands of users simultaneously stream video.

5G New Radio (NR) is the air interface specification that defines how 5G devices communicate with base stations. Developed by 3GPP and first specified in Release 15 (2018), NR represents a complete reimagining of wireless communication optimized for the diverse requirements of modern applications.

NR introduces fundamental architectural changes compared to LTE:

Understanding Numerology:

The relationship between numerology (μ) and subcarrier spacing follows: Subcarrier Spacing = 15 kHz × 2^μ

Higher numerologies provide:

• Shorter slot durations — Enabling lower latency transmissions
• Wider subcarrier spacing — More robust against Doppler spread at high frequencies
• Faster beam sweeping — Critical for mmWave beam management

However, higher numerologies also require:

• Wider bandwidth — The same number of subcarriers occupies more spectrum
• Shorter cyclic prefix — Reducing tolerance for delay spread in multipath environments

Operators select numerologies based on frequency band, deployment scenario, and dominant use case. A macro cell serving rural areas might use μ=0, while a mmWave small cell in a stadium uses μ=3 or μ=4.

5G operates across an unprecedented range of spectrum, from sub-1 GHz to millimeter wave frequencies above 24 GHz. This multi-band approach isn't a limitation to be worked around—it's a deliberate design enabling different coverage and capacity tradeoffs for different deployment scenarios.

The spectrum is categorized into three ranges:

The 5G Core Network (5GC) represents a fundamental departure from previous cellular architectures. Instead of the monolithic, purpose-built network elements of 3G/4G, 5GC adopts a Service-Based Architecture (SBA) inspired by modern cloud-native software design principles.

In SBA, network functions expose their capabilities as services via standardized APIs. Other functions consume these services as needed. This design enables:

Control and User Plane Separation (CUPS):

5GC strictly separates control plane signaling from user plane data forwarding. The User Plane Function (UPF) handles all user traffic, while control functions (AMF, SMF, etc.) manage signaling. This separation enables:

• Distributed UPF deployment — UPFs can be placed close to users (at edge locations) to minimize latency, while control functions remain centralized for efficiency
• Independent scaling — Control plane capacity scales based on signaling load; user plane scales based on traffic volume
• Traffic localization — Local breakout enables traffic to stay local rather than backhauling to distant data centers

This architecture is essential for URLLC applications. When the UPF resides at the network edge, data doesn't traverse hundreds of kilometers to reach central data centers—enabling single-digit millisecond end-to-end latency.

5G networks can be deployed in multiple configurations, allowing operators to transition gradually from 4G LTE while eventually realizing 5G's full potential. The two primary approaches are Non-Standalone (NSA) and Standalone (SA) deployment:

Non-Standalone (NSA) - Option 3x:

NSA deployment uses 5G New Radio for the user plane while relying on existing 4G LTE infrastructure for control plane signaling. The 4G Evolved Packet Core (EPC) remains in place, and 5G base stations (gNodeBs) connect to it via the eNodeB.

Advantages of NSA:

• Rapid deployment using existing 4G infrastructure
• Lower initial investment
• Faster time-to-market for 5G services
• Leverages proven EPC reliability

Limitations of NSA:

• Cannot deliver URLLC—4G core doesn't support sub-millisecond latency
• No network slicing capability
• Cannot support mMTC optimizations
• Devices must maintain dual connectivity (higher power consumption)
• Limited to eMBB use cases

Standalone (SA) - Option 2:

SA deployment uses the full 5G New Radio air interface connected to a native 5G Core network. This is the 'true' 5G deployment that enables all advanced features.

Advantages of SA:

• Full URLLC capability with sub-millisecond latency
• Network slicing for service isolation
• Native mMTC support
• Improved power efficiency (no dual connectivity requirement)
• Cloud-native, service-based architecture benefits
• Edge computing integration

Limitations of SA:

• Requires new 5G Core infrastructure investment
• More complex initial deployment
• Early devices may not support SA
• Operators must manage parallel 4G and 5G cores during transition

The Industry Trajectory:

Most operators launched with NSA deployments to quickly market 5G speeds. As of 2024, the industry is transitioning to SA, with many operators now offering SA coverage in urban areas. Enterprise and industrial applications increasingly require SA for latency-sensitive use cases.

Beyond the core capabilities, 5G introduces several advanced features that expand what wireless networks can accomplish:

This page established the foundational understanding of 5G technology features. Let's consolidate the key concepts:

What's Next:

With the overall 5G feature landscape established, we'll dive deep into one of its most distinctive technologies: millimeter wave (mmWave) communication. The next page explores how 5G harnesses spectrum above 24 GHz to deliver unprecedented capacity, despite the significant propagation challenges at these frequencies.