How 5G Protocol Testing Ensures Performance and Reliability

How 5G Protocol Testing Ensures Performance and Reliability

Key takeaways:

• The communication between any two components of a 5G network is defined by interfaces with comprehensive and unambiguous specifications.
• Protocols define the structuring of the information exchanged over any interface.
• Network functions, interfaces, and protocols are the logical abstractions that enable information exchange between any two components without requiring direct physical connections.

When a call is made from a 5G phone, the end-to-end call flow involves an incredibly complex mesh of components working seamlessly together across large geographical distances to establish a communication channel and send the speech audio and data packets to the other end.

This incredible marvel of wireless technology is possible only because these components operate with rigorously defined interfaces, procedures, and network protocols.

Ensuring strict adherence to these standards is essential for every 5G device or network element. In this article, find out how 5G protocol testing is the key to standards compliance in the 5G ecosystem.

What is 5G protocol testing?

In 5G protocol testing, various telecommunication stakeholders verify that the subsystems of a 5G network are complying with their respective interface and protocol specifications published by the 3rd Generation Partnership Project (3GPP).

These interfaces and protocols enable critical 5G use cases like:

• high-throughput mobile broadband
• ultra-reliable low latency communication
• beamforming and massive multiple-input-multiple-output (MIMO)
• accurate positioning
• conditional handovers and other mobility scenarios

During 5G protocol testing, the implementation-level interface and protocol details that underlie all these use cases are verified.

Additionally, 5G protocol testing includes different types of verifications like:

• protocol and radio frequency (RF) conformance testing
• radio resource management (RRM) conformance testing
• regulatory compliance testing
• carrier acceptance testing
• performance testing of each interface

Let's first understand 5G interfaces and protocols and then look at key stakeholder businesses and organizations.

The communication between these functions is specified by "interfaces" that describe the semantics for their functionalities, initialization, operational flows, data payload structures, security aspects, mobility aspects, session management, and quality of service (QoS) - among others. These interfaces are defined in various 3GPP technical specifications.

Some key interfaces are shown in the illustration below.

Fig 1. Key 5G interfaces

Protocols and protocol stacks are key components that enable these interface semantics. The protocol and protocol stacks define how to structure the information that's exchanged over an interface. Every interface between any two functions defines a protocol stack and how to structure the information required by those functions using those protocols.

For example, 3GPPTS 24.501 specifies the N1 interface between a UE and the AMF that governs aspects like the registration, authentication, session management, and mobility management of the UE. The non-access-stratum (NAS) is a critical protocol of that interface that specifies the message formats for communication between the UE and the AMF.

We'll explain some key 5G protocol stacks in more detail later in this article.

Which stakeholders conduct 5G protocol testing?

Some of the telecommunication stakeholders that must conduct rigorous 5G protocol testing include:

• mobile device and chipset manufacturers
• mobile network operators
• network equipment manufacturers
• vendors of internet-of-things (IoT) sensors
• automotive manufacturers working on cellular vehicle-to-everything (C-V2X) systems
• research and development organizations
• government regulatory organizations
• 5G-based service providers, like smart city technologies and multimedia content producers

Why is 5G protocol testing important?

Protocol testing is essential to achieve important goals like:

• Interoperability: Every telecom stakeholder must ensure that their products or services can operate seamlessly with those of others. This is particularly critical for hardware manufacturers of mobile devices, 5G chipsets, network equipment, and IoT sensors. Non-compliance with 3GPP specifications can prove costly due to market rejection as well as possible regulatory and contractual penalties.
• Compatibility: Network operators prefer incremental upgrades to their existing infrastructure to optimize expenditure and minimize customer disruption. Protocol testing enables them to ensure that any 5G additions to their 4G networks are operating as expected and also ensures that the 4G equipment is operating as intended after these additions.
• Network reliability: 5G protocol testing enables testers to verify 5G promises like high broadband speeds, high density of devices, and remote connectivity (via non-terrestrial networks). Engineers can configure every interface and protocol layer with custom parameters to test them. This way, edge cases in functionality and performance can be rigorously tested throughout the design, deployment, and operational phases.
• Performance: 5G protocol testing enables hardware manufacturers and service providers to satisfy the performance criteria set by conformance specifications as well as carrier acceptance requirements. Additionally, they can use 5G protocol testing tools to exceed the performance criteria to gain market advantages.
• Security: 5G protocol testing is essential for ensuring network and data security in 5G networks, especially since they're being introduced in potentially hazardous places like automobiles, satellites, unmanned aerial vehicles, and transport systems.
• Regulatory compliance: 5G protocol testing helps operators and manufacturers comply with regulations related to spectrum use, radiation levels, and sustainability (like minimizing power consumption while idling).

What are the key 5G protocols?

In this section, we look at some key 5G protocol stacks and how they are tested.

The UE-RAN Uu interface's protocols

The UE-RAN radio interface, known as the Uu interface, includes both user plane and control plane communications. User plane communication is to send user-related data like voice call audio, video call data, internet data packets, short messages, and so on. Control plane communication is to exchange network-related information. The protocol stacks of both planes are quite similar as shown below.

Fig 2. UE-RAN Uu interface's protocol stacks

The protocols that are part of this interface are:

• Physical layer (PHY): This is the layer 1 protocol that specifies low-level radio parameters like frequency and modulation.
• Media access control (MAC): This is the layer 2 protocol responsible for scheduling data packets, multiplexing and demultiplexing, and error corrections.
• Radio link control (RLC): The RLC is responsible for packet segmentation, reassembly, and error correction through retransmissions.
• Packet data convergence protocol (PDCP): This layer is responsible for data compression, data security, delivery of protocol data units in the correct sequence, and bearer management (for separate logical channels based on QoS requirements).
• Service data adaptation protocol (SDAP): This user-plane layer maps QoS flows to data radio bearers and performs QoS flow management and packet marking for QoS handling.
• Radio resource control (RRC): This layer is responsible for managing the radio bearers, controlling the signaling between the UE and the network, and managing the UE's mobility and connection states.

Protocols of the gNodeB-gNodeB Xn interface

The Xn interface that connects two gNBs also uses the same RRC, SDAP, PDCP, and RLC protocol stack.

The UE-AMF and UE-SMF protocol stacks

The UE-AMF and UE-SMF control plane communications involve the following protocols:

• The non-access-stratum (NAS) mobility management (NAS-MM) protocol enables UE registration, connection management, activation, and deactivation.
• The NAS session management (NAS-SM) protocol manages sessions between the UE and the SMF.
• The stream control transmission protocol (SCTP) guarantees the delivery of signaling messages over the internet protocol.

Physically, this NAS information is always exchanged over the UE-RAN radio channels. However, from a logical perspective, it can be considered a direct exchange of information between the UE and the AMF or the SMF.

Core protocol stacks

One of the core protocols is part of the NG interface between the RAN and core network, which actually consists of multiple interfaces like N2 between the RAN and the AMF and N3 between the RAN and the user plane function (UPF). All the other components are also governed by various interfaces.

How does 5G protocol testing ensure compatibility and interoperability?

Compatibility with existing network infrastructure is a key goal of network operators as well as device manufacturers. The following capabilities are enabled by 5G protocol testing:

• Conformance with radio regulations around the world: The testing allows verification of the conformance of devices, chipsets, and network equipment to frequency bands and modulation requirements set by regulators in each region.
• Compatibility with existing infrastructure of network operators: Every operator sets specific acceptance criteria for verifying that new 5G equipment is compatible with all their existing network infrastructure. A key goal of 5G protocol testing is to make these criteria available as test plans that can be run after every network change through automation.
• Assurance for new radio technologies: Beamforming and massive MIMO are new and complicated but also essential for 5G's improved performance and scalability. For verifying all their possible configurations, 5G protocol testing enables configuring the radio interface (the physical layer) with a large number of varying parameters and subjecting the 5G devices and equipment to over-the-air (OTA) testing.

How does 5G protocol testing contribute to network reliability and performance?

Conformance and performance verification are essential stages of 5G protocol testing in the following ways:

• Verify radio frequency and resource management: RF and RRM conformance tests ensure that devices and network equipment operate reliably with each other under any load and environmental condition.
• Ensure lower latency: Ultra-reliable low-latency communication is a key goal of 5G and is tested as part of RedCap (5G-Lite) protocol testing.
• Satisfy QoS requirements: QoS flows and related protocols like SDAP are verified as part of 5G protocol testing.
• Test the core network: Carrier-grade performance, sustained data rates, and seamless mobility are checked as part of testing the interfaces and protocols used by the core network functions.
• Verify non-terrestrial components: For reliable connectivity in remote places and during disasters, 5G protocol testing verifies the non-terrestrial components and their interfaces.

What challenges are commonly encountered in 5G protocol testing?

Some common challenges in 5G protocol testing include:

• Keeping up with the standards: The rapid pace at which 5G technology is advancing requires device and equipment manufacturers as well as network operators to ensure that they are continuously in conformance with the latest 3GPP 5G standards as well as satisfy certification requirements of organizations like the Global Certification Forum.
• Testing OTA behaviors: OTA testing of beamforming and massive MIMO, particularly in the millimeter-wave bands, under varying conditions is a complex process.
• Simulating non-terrestrial networks (NTNs): Simulating satellite and unmanned aerial platforms can be challenging.
• Qualifying for carrier acceptance: Carrier acceptance testing includes supplemental protocol test cases, performance testing, and application testing based on the network operators' specifications.

How are security aspects addressed in 5G protocol testing?

5G protocol testing includes the validation of network and data security aspects. More specifically, it includes the following:

• Authentication tests: To prevent malicious actors, authentication of the UE with the RAN and various functions with core functions are part of 5G protocol tests.
• Security assurance: The 3GPP 5G security assurance specification compliance involves running predefined test suites that cover the security of network functions like the AMF, SMF, and others.
• Cloud security verification: 5G supports many network architectures, like cloud RAN (C-RAN) and open RAN (O-RAN), where functions can be deployed on regular cloud services. So, 5G protocol testing must address cloud security and software-defined networking (SDN) aspects like authentication, access control, data encryption, and virtual networks.

What testing methodologies are employed for evaluating the reliability of 5G protocols?

Fig 3. Configuring a cell in the Keysight Protocol R&D Toolset

The testing methodologies include:

• OTA testing for verifying radio access technologies like beamforming and MIMO
• simulators to emulate the functions of a 5G network
• GUI-based test and scenario planning software for easily creating a large number of real-world situations
• reusable test scripts that can orchestrate various components and functions of the network to test complex scenarios
• test automation, data logging, and log analysis to record the behaviors of network functions during sustained tests

Keysight solutions for 5G protocol testing

Fig 4. Test campaign results in the Keysight S8705A 5G RF/RRM DVT and conformance toolset

Keysight offers powerful solutions for 5G protocol testing and troubleshooting:

• The S8701A protocol R&D toolset provides an easy-to-use environment to develop and execute tests that verify the 5G NR and LTE signaling protocols for chipsets and devices.
• The S8702A RFautomationtoolset provides automated and speed-optimized RF transmitter and receiver tests for 5G NR, LTE, NTN, and C-V2X based on 3GPP-defined test specifications.
• The S8704A 5G protocol conformance toolset provides comprehensive coverage of the 3GPP-defined protocol, IMS, location-based services, and other conformance test cases for 5G, LTE, and C-V2X.
• The S8705A 5G RF/RRM design verification testing and conformance toolset provides comprehensive coverage of RF and RRM 3GPP test specifications. These are essential for the design, conformance, and regulatory testing of 5G and C-V2X features.
• The S8706A protocol carrier acceptance toolset enables comprehensive mobile device evaluation based on the test requirements of major mobile operators.
• The S8707A RF/RRM carrier acceptance toolset provides comprehensive coverage of the 5G RF and RRM test plans of the world's major mobile network operators.

Additionally, solutions for 5G network testing at a higher abstraction level are also available.

Streamline your 5G protocol testing with Keysight

In this article, we covered various aspects, methods, and tools for 5G protocol testing.

Contact us for expert guidance on testing your 5G devices and equipment.

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