How can I use RAN equipment to integrate with existing core systems during a 5G rollout?

To integrate RAN equipment with existing core systems during a 5G rollout, the key is to plan around interoperability, transport, and phased migration. In practice, this usually means introducing 5G radio access while reusing parts of the current 4G/EPC core at first, then moving to a 5G Core later.

Common rollout approach

1. Choose the deployment mode

Most operators start with one of these:

• Non-Standalone (NSA):
  5G RAN works with the existing LTE/EPC core. This is the fastest way to launch 5G service while keeping the current core.
• Standalone (SA):
  5G RAN connects directly to a 5G Core (5GC). This is better for full 5G features, but requires more core modernization.

If you want to integrate with an existing core system during rollout, NSA is usually the first step.

How the RAN integrates with the existing core

2. Connect the new RAN to the current transport network

Your RAN equipment must connect through the backhaul/fronthaul/midhaul network to the core. Focus on:

• sufficient bandwidth
• low latency
• synchronization support
• QoS handling
• resilient IP/MPLS transport

3. Ensure interface compatibility

Depending on architecture, the RAN must support the right interfaces:

• LTE/EPC integration: S1 interface from eNodeB to EPC
• 5G NSA integration: gNB often anchors on LTE via EN-DC
• 5G SA integration: gNB uses NG interfaces to 5GC:
  • NG-C for control plane
  • NG-U for user plane

If your existing core is EPC, you’ll typically need RAN equipment that supports dual connectivity or can operate in NSA mode.

4. Use existing subscriber and mobility systems

Make sure the RAN can interwork with:

• HSS/UDM and subscriber databases
• MME/AMF for mobility management
• PCRF/PCF for policy control
• OSS/BSS systems for provisioning and assurance
• lawful intercept and charging systems

5. Plan for spectrum and cell configuration

Configure the RAN to align with your existing network design:

• band support and carrier aggregation
• PCI planning
• handover parameters
• neighbor relations
• power and coverage optimization
• NSA anchor strategy if using LTE + 5G

6. Test interoperability

Before live deployment, validate:

• attach/register procedures
• handovers between LTE and 5G
• voice service continuity
• QoS and bearer setup
• throughput and latency
• failover and redundancy
• alarms and telemetry integration with OSS/NMS

7. Roll out in phases

A typical migration path is:

1. Add 5G-capable RAN
2. Run 5G NSA using current EPC
3. Expand coverage and capacity
4. Introduce 5G Core functions
5. Transition some or all traffic to SA
6. Retire legacy dependencies where appropriate

Practical integration checklist

• Verify vendor support for your existing core interfaces
• Confirm EPC/5GC compatibility
• Validate timing/synchronization
• Check transport capacity and latency
• Integrate RAN management with OSS/NMS
• Test subscriber provisioning and policy control
• Run interoperability and field trials
• Plan a migration path from NSA to SA

Best practice

If your goal is to reuse current core systems, deploy 5G RAN in NSA mode first, then evolve to SA once the core is ready. This reduces risk and allows a smoother customer transition.

If you want, I can also give you:

1. a reference architecture diagram for RAN + EPC/5GC integration, or
2. a step-by-step migration plan for a specific vendor environment.