Interoperability testing (IOT) will be needed whenever more than one Network Equipment Vendor (NEV) is supplying components (software modules or hardware equipment) based on standardised interfaces. This testing, between the vendors for shared interfaces, is generally based on test specifications supplied by the standards body but can also be based on an agreement between companies or consortia.

IOT aims to ensure:

• Communication and compatibility between the control plane (CP) signalling messages
• That any user plane (UP) data traffic flows seamlessly across the interfaces
• That the boundaries between modules/equipment is secure and the integrity of messages remain intact
• Handling of abnormal scenarios and failures in a graceful manner without bringing the network down.

The eventual aim is to ensure plug-and-play of the software modules or hardware equipment, meaning parts of the network can be sourced from different suppliers based on performance, price and/or credibility.

There are five types of IOT testing typically required:

Conformance Testing: the most basic level of testing to ensure operation based on the interface specifications. It is conducted in the lab with a simulator and usually serves as a way to perform both regression testing - once new features are introduced in the software - and compatibility testing - once a new version of interface specification is available.

Performance Testing: conducted with all real components or a mix of real and emulated components. The aim is to ensure that the modules/equipment will work in a live setup and meet the expected performance criteria.

End-to-End (E2E) Throughput Testing: all real components are used to check that the user data traffic flows as expected. From a network point of view, this test is based on the assumption that a single device or user equipment (UE) is being served by the network.

Stress Testing: may also be referred to as Capacity Testing or Load Testing. In all cases the assumption is to test the live network setup with a large number of UEs or devices to ensure that it can handle real world traffic for extended periods of time.

Field Testing: While Stress Testing is performed in a lab or a setup with simulated/emulated UEs, Field Testing takes place on a site with real world devices. It typically involves many variations of UEs with different versions of software and hardware. As a result real world issues can often not be identified until this point.

After all this testing, the network equipment is considered ready for deployment and vendors would describe their modules/equipment as GA (General Availability), meaning they can be procured through the usual channels.

To support interoperability testing needs, numerous private sector and government funded labs have been established in the UK, operating within the wider 5G, Open RAN and telecom supplier diversification ecosystem.