Feature: Communications Figure 3: Protocol layer for MTSI
equipment, with digital and analogue interfaces. For stress tests, the setup may apply fading on the radio interface and emulate network impairments like IP-packet disordering, delay or discarded packets. In addition to the RAT technologies 5G and LTE, such a setup may also support legacy RAT such as 2G or 3G, and non-cellular technologies like Bluetooth or Wi-Fi, since they offer voice services. An obvious requirement is to emulate
data between 5GC and an external data network, but because of the introduction of voice services, it needs to be extended to provide a connection to another data network – therefore, the IMS.
• If both core networks are applied, EPS and 5GC, the N26 interface may share some signalling information between the EPS mobility management entity and the 5GC access and mobility function. Here, the user equipment uses a single registration procedure as the two core network entities coordinate mobility and registration.
• Te S5 interface exchanges and coordinates user data between the session management and the user plane function, with the serving gateway.
• A typical home subscriber service centre coordinates subscription profiles and access policies.
T&M for voice services in 5G Testing guarantees and verifies the application QoE for the end user and the
proper functioning and implementation of the voice services in 5G. Since voice over 5G operates similarly to voice over LTE, the general test setup does not differ greatly. However, various testing protocols should be considered. Testing voice services in 5G typically
starts with basic verification of proper implementation and functional behaviour; i.e., can a call be established, and is the voice signal audible? Following that, T&M is used to determine the quality of the audio under well-known and reproducible conditions. Besides device-orientated voice testing, mobile network testing and benchmarking of deployed services in a live network guarantee optimal user quality. A voice-quality test setup includes
mobile radio test capability that supports signalling, and functional testing and enhanced protocol procedures, such as interoperability, multi-connectivity and mobility scenarios; see Figure 4. A test setup may also include audio quality test
the IMS network and its signalling protocols SIP, SDP and data provisioning. Audio quality is typically indicated as a mean opinion score value, derived as a result of algorithms like the Perceptual Quality for Voice algorithm published by the ITU. Te advantages of lab-based test setups are that the conditions are reproducible, and the tests repeatable and performed under predefined conditions. To monitor the quality of certain
applications like voice or video, and to fulfil the key performance indicator requirements, field or drive testing is necessary. Here, a passive device like a scanner is connected to a device that can actively set up a connection, so that analysis on application quality can be performed. In addition, network operators may wish to compare their network quality in a benchmarking process against other networks, or monitor the entire network via multiple samples and a statistical analysis, to obtain a summarised view. In summary, test and measurement plays
a pivotal role in successfully supporting voice services in commercial 5G networks.
Figure 4: Example of an audio quality analysis test setup
24 November 2021
www.electronicsworld.co.uk
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