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Start with 5G Mobile Networks: A Systems Approach. It is a free, web-based introduction to 5G architecture that explains how the user device, radio access network, mobile core, cloud infrastructure, and applications fit together. The recommendation that popularized it dates from January 31, 2021, so it should be treated as a foundational resource rather than a current deployment manual.
The project now also maintains Private 5G: A Systems Approach, which extends the earlier systems perspective toward private 5G networks and managed cloud services. For most readers, the best route is to learn the architecture from the original book, then use the newer book and current project documentation for practical work.
Where to read the books
Use these links as the starting points:
- Current Private 5G documentation — the project’s reading, source, licensing, and build information.
- Private 5G repository — the public source repository for the newer book.
- Systems Approach GitHub organization — the wider project location.
- Archived earlier-book PDF — a useful copy of 5G Mobile Networks: A Systems Approach.
The project documentation says the earlier 5G book is archived while the newer Private 5G book adds material on implementing and deploying private 5G as a managed cloud service. The archived book remains the more direct match for readers who want a broad introduction to 5G architecture.
What the book actually teaches
This is a systems-oriented book, not primarily a radio-frequency or digital-communications textbook. Its central idea is that 5G is an end-to-end programmable computing and networking system—not simply a faster wireless interface.
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UE → 5G RAN / gNB → 5G Core → Data Network → Cloud or Edge ApplicationThat progression helps explain what happens beyond the antenna:
- User equipment (UE), such as a phone, modem, or test device, connects over the radio interface.
- The radio access network (RAN) provides access, scheduling, radio protocols, and the connection to the core. A 5G base station is commonly called a gNB.
- The 5G Core (5GC) authenticates subscribers, manages mobility and sessions, applies policy, and directs traffic toward external networks.
- Cloud and edge infrastructure can host virtualized or containerized network functions and applications.
- APIs and orchestration make connectivity and network capabilities more programmable.
The contents cover standardization, architecture, radio transmission, RAN design, mobile core networks, software-defined networking, virtualized schedulers, network slicing, Open RAN concepts, managed cloud services, and connectivity APIs. A chapter outline is available in this published table of contents.
The vocabulary you should learn first
A reader with basic IP networking knowledge can use the book to build a practical 5G vocabulary:
- UE: User equipment, including a phone, modem, or laboratory device.
- gNB: The 5G base station.
- RAN: Radio access network.
- 5GC: 5G Core.
- AMF: Access and Mobility Management Function.
- SMF: Session Management Function.
- UPF: User Plane Function, which forwards subscriber traffic.
- NRF: Network Repository Function, used for discovering network functions.
- UDM and UDR: Subscriber and data-management functions.
- NSSF: Network Slice Selection Function.
- CU and DU: Centralized and Distributed Units used in a disaggregated RAN.
- SA: Standalone 5G, using a 5G Core.
- NSA: Non-standalone 5G, where 5G radio works with an LTE-based core architecture.
Commercial “5G” branding does not by itself tell you whether a connection uses Standalone or Non-standalone architecture.
Is it really an open-source book?
It is free to read and its source is publicly available, but “open-source” needs qualification. The current project documentation identifies the book source with a Creative Commons BY-NC-ND 4.0 license.
That generally permits sharing with attribution, subject to the license terms, but it is not the same as an unrestricted software open-source license. In particular, readers should not assume that they may freely modify, remix, commercially republish, or incorporate the book into a derivative product. Check the project’s current license files and the Creative Commons terms before reusing the content.
It is also important to separate three ideas:
- Free to read: You can access the online book without buying a textbook.
- Publicly available source: The project’s source files are available through GitHub.
- Open-source network software: Projects such as OpenAirInterface and srsRAN are separate software projects with their own licenses and capabilities.
Free access to a book or software does not make a complete 5G network free. Compute, cloud infrastructure, SDR hardware, antennas, compatible devices, spectrum compliance, and engineering time may still be required.
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Who should read it?
It is a good fit for
- Network, cloud, and software engineers entering telecom.
- Students and self-learners who understand basic Internet networking.
- Developers evaluating private 5G, Open RAN, or edge computing.
- Engineers who want to understand the relationship between RAN, core, cloud, and applications.
- Readers who prefer an architectural introduction before studying implementation details.
It is not the best first resource for
- Readers with no networking background at all.
- People looking only for a simple explanation of 5G phone coverage or consumer speeds.
- Readers focused mainly on antenna design, RF propagation, modulation, or information theory.
- Teams seeking a current, copy-and-paste private-5G deployment guide.
The book can establish the architecture and vocabulary needed for a lab, but it does not replace a dedicated RF textbook, current software documentation, spectrum guidance, or operational support.
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How to use the book effectively
- Begin with the architecture. Identify the UE, gNB, RAN, core, external data network, cloud, and edge application.
- Separate control and user planes. Understand which functions authenticate users and create sessions, and which function forwards application traffic.
- Trace a registration and data-session flow. Draw the path from device attachment through authentication, session establishment, IP connectivity, and application traffic.
- Compare SA and NSA. This prevents the common mistake of treating every commercial 5G connection as a 5G-Core deployment.
- Read the private-5G material. Consider how local coverage, enterprise applications, edge computing, device provisioning, and operations change the design.
- Move to current project documentation. Installation commands and configuration formats change more quickly than the underlying architecture.
- Attempt a lab only after the concepts are clear. A complete setup may require a RAN, a core, a UE, subscriber configuration, IP routing, timing, and—if using real radio—legal and safe RF arrangements.
What to use after the book
| Goal | Useful next resource |
|---|---|
| Learn end-to-end 5G architecture | 5G Mobile Networks: A Systems Approach |
| Study private-network architecture | Private 5G: A Systems Approach |
| Experiment with an open 5G RAN | srsRAN Project |
| Experiment with RAN and core components | OpenAirInterface |
| Build a radio-based laboratory | Project-specific SDR and hardware documentation |
| Prepare an operational deployment | Versioned official documentation and, where needed, commercial support |
OpenAirInterface
OpenAirInterface describes itself as a nonprofit project developing open-source 4G and 5G RAN and core-network software for research and industry. Its 5G Core page lists functions including AMF, AUSF, UDM, UDR, NRF, NSSF, PCF, SMF, and UPF. It also describes deployment using bare metal, virtual machines, Docker Compose, and Kubernetes/Helm.
According to that project page, its core is aligned with 3GPP Release 16 and evolving toward Releases 17 and 18; this status was checked in August 2026 and may change. Treat project compliance and feature claims as claims tied to the named release and documentation, not as a permanent guarantee.
srsRAN Project
srsRAN Project focuses on an O-RAN-oriented 5G CU/DU with a complete Layer 1/2/3 stack and compatibility goals aligned with 3GPP and O-RAN specifications. The broader srsRAN documentation distinguishes it from the older srsRAN 4G suite, which provides 4G UE, eNodeB, and EPC applications.
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These projects are not interchangeable. srsRAN Project is principally a 5G RAN implementation, while OpenAirInterface provides both RAN and core components. An end-to-end experiment may combine projects, but compatibility, configuration, hardware support, and licensing must be checked for the exact versions involved.
An Ettus reference architecture documents an example that combines srsRAN RAN components with the OpenAirInterface 5G Core. It should be treated as a reference design, not a guarantee that every release or hardware combination will work without adjustment.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Three realistic ways to experiment
1. Software-only lab
Use documentation, emulators, simulators, packet captures, and virtualized network functions. This is the most approachable route for students and software developers learning core procedures and packet flows.
The trade-off is that software-only work abstracts away real over-the-air behavior, RF impairments, timing challenges, and hardware acceleration.
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An SDR lab adds compatible radio hardware, a supported UE or modem, antennas or conducted connections, and a RAN/core stack. It is appropriate for wireless researchers and engineers studying PHY behavior, synchronization, and real network interaction.
Hardware costs can be substantial, and configuration is highly version-sensitive. Use conducted connections, shielding, simulators, or legally authorized frequencies. Do not transmit on spectrum without the required authorization and safeguards.
3. Private-5G evaluation
For an industrial, campus, or edge-computing project, read the newer Private 5G material and compare open-source and commercial RAN/core options. A private network is not automatically cheaper or simpler than Wi-Fi: spectrum, SIM or eSIM provisioning, device support, integration, monitoring, and operations may dominate the cost.
Building the book from source
Ordinary readers should use the rendered web version first. If you need the project source, the current documentation gives this starting sequence:
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mkdir ~/systemsapproach
cd ~/systemsapproach
git clone https://github.com/SystemsApproach/private5g.git
cd private5gThe project says its build process is stored in the repository’s Makefile and requires Python. Build requirements and instructions can change, so consult the repository rather than assuming that this command sequence is a complete installation procedure.
What the book does not provide
- Guaranteed current installation commands for every RAN and core release.
- A turnkey private-5G network.
- Complete antenna, RF, propagation, or signal-processing training.
- Spectrum authorization or regulatory advice for live transmission.
- Commercial support or an enterprise service-level agreement.
- Guaranteed interoperability between unrelated open-source projects.
- A substitute for testing, monitoring, lifecycle management, and operational security.
Bottom line
5G Mobile Networks: A Systems Approach remains one of the more useful free starting points for understanding 5G as an end-to-end system. Use it for durable concepts: RAN and core roles, control and user planes, cloud-native functions, slicing, Open RAN, and programmability. Then move to Private 5G: A Systems Approach for private-network context and to current OpenAirInterface or srsRAN documentation for hands-on work.
Just remember the important qualifications: the original recommendation is from 2021, book licensing is not the same as unrestricted open-source reuse, and reading about 5G is much easier than deploying a reliable and legally compliant network.
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