RAN (Radio Access Network) architecture is the blueprint of the part of a mobile network that connects a user's phone to the core network — antennas, radio units, baseband units, and the interfaces between them. In 4G it is built around the eNodeB, and in 5G around the gNodeB. Every modern evolution — centralised RAN, virtualisation, and Open RAN — is essentially a new way of organising these same building blocks, which is why this is the first thing telecom interviewers test.

Traditional RAN is a closed, proprietary system where a single vendor supplies radios, baseband hardware, and software as a locked box. Open RAN architecture disaggregates the base station into O-CU, O-DU, and O-RU connected through open, standardised interfaces, allowing operators to mix vendors, run network functions as software on general-purpose hardware, and add intelligence through the RIC. This brings vendor choice and lower costs, but also new integration and testing challenges — which is exactly why Open RAN skills are in demand.

In the 5G Open RAN architecture, the gNodeB is split into an O-CU (centralised unit), O-DU (distributed unit), and O-RU (radio unit), connected via open fronthaul and F1 interfaces, with software running on a virtualised cloud layer called O-Cloud. A near-real-time RIC sits above the CU/DU to run AI-driven control apps, and the whole setup connects to the 5G core. Most live Open RAN deployments today are 5G networks, making this the most commercially valuable specialisation for RAN engineers right now.

A standard Open RAN architecture diagram shows the O-RU at the bottom (the radio), the O-DU handling lower-layer baseband processing, and the O-CU handling higher-layer functions, linked by Open Fronthaul and F1 interfaces. Above them sits the near-real-time RIC (connected via the E2 interface) and the SMO framework with the non-real-time RIC, while O-Cloud provides the virtualisation layer and O1/O2 interfaces handle management. Reading it layer by layer — radio, baseband, intelligence, management — is the fastest way to genuinely understand O-RAN.

The O-RAN Alliance publishes its official architecture description, technical specifications, and research reports as free downloads on its website, and the underlying 3GPP specifications for 4G and 5G are also freely available. Start with the O-RAN Architecture Description and the use-case and deployment-scenario documents, then move to the specific 3GPP releases relevant to your work. Be careful with random paid PDF bundles circulating online — most are recycled slides rather than actual specifications.

The RIC (RAN Intelligent Controller) is the AI/ML brain of Open RAN, and the Open RAN RIC architecture has two layers: the non-real-time RIC inside the SMO, which runs rApps for policies and optimisation with control loops above one second, and the near-real-time RIC, which runs xApps through the E2 interface for control loops in the 10-millisecond range — traffic steering, energy saving, and QoE optimisation. Because the RIC is where telecom meets AI/ML, it is one of the highest-value skills in the Open RAN ecosystem.

Rakuten Mobile in Japan built the world's first nationwide, fully virtualised, cloud-native mobile network based on Open RAN principles — replacing proprietary baseband hardware with software running on general-purpose commercial servers sourced from multiple vendors. It proved Open RAN could work at national scale, not just in labs, and it is now a standard case study in 5G interviews. With Open RAN adoption growing in India too, including BSNL's indigenous rollout, this architecture is directly relevant for Indian telecom engineers.

5G network architecture has two main parts: the 5G radio access network with gNodeB base stations, and the 5G Core, which uses a service-based architecture where functions like the AMF, SMF, and UPF communicate through standard APIs. Key concepts include separation of control and user planes, network slicing, and edge computing. There are also two deployment modes — NSA, where 5G radio is anchored to the 4G core, and SA, which uses the full 5G core — and the NSA vs SA difference is a classic interview question in India's 5G hiring market.

Yes. LTE still carries a major share of mobile traffic, 5G non-standalone networks use the 4G network architecture as an anchor, and voice calls on many 5G networks still fall back to 4G. Most 5G job interviews expect you to know the 4G baseline — eUTRAN, eNodeB, and the EPC with MME, Serving Gateway, and PDN Gateway. The real career risk is not learning 4G, it is stopping at 4G: pairing it with 5G SA and Open RAN knowledge is what moves engineers from maintenance roles to architect-level roles.

In telecom, network architecture is the overall design of how a network's components and interfaces fit together, broadly divided into the radio access network (RAN), the core network, and the transport/backhaul layer. Within the RAN itself, the main architecture types are traditional D-RAN, centralised C-RAN, virtualised vRAN, and Open RAN — and each generation from 2G to 5G has reshaped how these blocks are designed. Knowing both the big-picture split and the RAN-level types is what interviewers usually mean when they ask about network architecture.

The usual path runs from hands-on RAN or core roles to specialist and then architect: build deep fundamentals across radio, core, and transport, learn to read 3GPP specifications directly, gain exposure to virtualisation, cloud, and automation, and then specialise in a high-demand area such as 5G SA or Open RAN. Architects are hired for design judgment, so lead at least one end-to-end deployment or migration you can discuss in depth. Practising architecture discussions through mock interviews and mentorship from working architects is the fastest way to close the gap — specialist architects typically command far higher salaries than general network engineers.

Prepare in layers: 5G architecture (NSA vs SA and the role of the 5G core), the radio protocol stack from PHY up to NAS, Open RAN concepts like the CU/DU/RU split and the RIC, and real troubleshooting scenarios using KPIs and call traces. Interviewers in India increasingly test Open RAN and AI-in-telecom awareness, not just 4G/5G theory. Rehearse explaining architectures aloud under a timer — a structured telecom mock interview is one of the most effective ways to find weak spots before the actual panel does.

AI-RAN is the industry direction of embedding AI/ML directly into the radio access network — through RIC-based xApps and rApps today, and eventually AI-native air interfaces and self-optimising networks. The AI-RAN Alliance, formed by major global operators and chipset vendors, is driving standardisation in this space, and 6G research assumes AI-native design from day one. For engineers, the combination of RAN fundamentals plus AI/ML skills is the clearest route into next-generation telecom roles instead of getting left behind in legacy network jobs.

Pick a narrow position — 5G RAN, Open RAN, or AI in telecom — and post consistently about real engineering insight: architecture breakdowns, specification explanations, field lessons, and interview learnings rather than generic content. Comment meaningfully on industry discussions, document your certifications and projects, and keep your headline niche-specific so recruiters searching those skills find you. In a fast-shifting market like 5G and 6G, visible expertise consistently pulls inbound opportunities instead of forcing cold applications.