Testing regimes for the new frequencies and features of 5G

ROHDE AND SCHWARZ

Measurements taking place in pre-commercial 5G network trials provide new insights and overcome uncertainties before the technology’s formal launch.

The 3rd generation Partnership Project (3GPP) defined fifth generation (5G) cellular technology in Release 15, which updated mission-critical (MC) communications and MC service functions, to meet the International Telecommunication Union’s IMT-2020 performance requirements. IMT-2020 laid out the basic requirements for 5G networks, devices and services. Release 15 also enabled a variety of services associated with usage scenarios such as enhanced mobile broadband (eMBB), ultra-reliable low latency communications (URLLC), and massive machine type communications (mMTC).

Some of the 5G performance requirements spelled out are a 20 Gbps peak data rate, 1 msec radio network latency, 10 Mbps/m 2 area throughput, and 1 million (low-rate) IoT devices per square kilometer. Key building blocks for 5G are the New Radio (NR) air interface, new radio and core network architectures, virtualization and automation technologies, and new types of devices. These building blocks enable 5G to offer targeted 5G services.

Operators worldwide continue to evaluate pre-commercial network trials to ensure a smooth 5G NR network roll-out. The aim is to overcome the challenge of a more demanding and complex air interface and deliver the commercial and technical benefits offered by 5G. While Release 15 provides a solid framework for enhanced network performance and mass offering of amazing services, 3GPP is actively working on further enhancing the framework.

RELEASE 15

3GPP defined the initial ideas for 5G, called 5G Phase 1, in Release 15 (R15). Example features of R15 include the New Radio (NR) air interface, new radio network architecture called next- generation radio access network (NG- RAN), new core network architecture called next generation core (NGC) or 5G core (5GC), service based architecture (SBA), network slicing and edge computing.

3GPP also defined the next phase of 5G, also called 5G Phase 2, in Release 16. Planned features for Release 16 (R16) include NR unlicensed (NR-U), basically a way for devices to share unlicensed spectra by incorporating some kind of coordination mechanism; integrated access and backhaul (IAB), basically an alternative to fiber backhaul that extends NR to support wireless backhaul; enhanced vehicle-to-everything (eV2X), Ultra- Reliable Low-Latency Communication (URLLC) features that provide low latency and ultra-high reliability for mission critical applications such as industrial internet, smart grids, and remote surgery; and industrial IoT (IIoT) enhancements and a service enabler architecture layer (SEAL), basically a way for common services to be used across different vertical industries.

There is also a Release 17. Potential Release 17 (R17) features include non-terrestrial networks (NTN) (i.e. those using satellites), new frequency bands (e.g. 7 GHz to 24 GHz and > 53 GHz), as well as enhancements to NR sidelink (direct communication between devices without going through a base station) and NR light, basically NR extended to simple devices such as low-end wearables or industrial sensor networks.

Some features may initially be introduced in one release, but defined in an elaborated fashion in a future release. The 3GPP work in R16 and R17 is classified into the following categories: (i) service expansions, (ii) NR enhancements, (iii) network architecture enhancements and (iv) miscellaneous enhancements.

Like LTE, NR uses orthogonal frequency division multiplexing but makes it highly flexible. For example, it introduces variable subcarrier spacing, flexible radio frame structure including a self-contained slot, and carrier bandwidth parts. Both sub-7-GHz spectrum (called frequency range 1 or FR1) and millimeter wave spectrum (called frequency range 2 or FR2) are supported. The new high-performance channel coding techniques of low-density parity check coding (a type of linear error-correcting code) and polar coding (a linear block error correcting code) are defined. Spatial multiplexing techniques used in LTE, SU-MIMO and MU-MIMO (single and multi-user MIMO), are enhanced in 5G. NR is a beamformed air interface with fewer beams at low-frequency bands and more beams at high frequency bands. 5G supports hybrid beamforming where both digital beamforming (available in LTE) and analog beamforming are combined. Massive MIMO in 5G enables enhanced combining of beamforming methods with spatial multiplexing.

While NR provides a flexible air interface, it is advantageous in transitioning from 4G to 5G to use dynamic spectrum sharing (DSS) to dynamically allocate 4G and 5G subcarriers in the same channel. Basically, DSS dynamically allocates spectrum resources between 4G LTE and 5G NR based on user demand. With DSS, mobile operators can simultaneously support 4G LTE, 5G NSA and 5G SA devices. DSS was introduced in R15, further refined in R16 and R17 and will probably continue to be refined in future releases, especially to improve the scheduling of resources between and within 4G and 5G subcarriers and across multiple cells. While the transition from one wireless generation to another in a specific band has been a painful experience in the past, it will be much easier with 5G thanks to DSS.

NG-RAN, NGC AND SBA

NG-RAN (next-generation radio access network) includes NR-based 5G base stations called next generation node Bs or gNBs. A gNB can be decomposed or disaggregated into a central unit and a distributed unit. Such a gNB architecture reduces infrastructure and transport costs and provides scalability. While LTE uses a limited number of nodes in the evolved packet core (EPC), 5G defines more network functions (NF) that have fewer responsibilities. The overall 5G system is based on SBA (service-based architecture), where NFs communicate with each other using service-based interfaces. SBA facilitates the designs and deployment of the 5G system using virtualization and automation technologies such as network functions virtualization (NFV), software defined networking (SDN), OpenStack (a cloud operating system that manages and controls resources through APIs with common authentication mechanisms) and Orchestration.

R15 fully defines two deployment options for the network architecture: non-standalone (NSA) NR and standalone (SA) NR. Non-standalone NR with the EPC (Evolved Packet Core) uses the LTE eNB (Evolved Node B) as the master node and makes use of a gNB’s additional NR radio resources when possible. Standalone NR with the NGC does not rely on the LTE eNB at all and allows direct communications between the UE and the gNB.

3GPP introduces the concept of network slicing, where different logical networks are created using the same physical network to cater to different services and different customer requirements for a given service. Three standard slices for eMBB (Enhanced mobile broadband, an extension of services first enabled by 4G LTE networks that allows for a high data rate across a wide coverage area), URLLC (Ultra-reliable lowlatency communication) and massive IoT are defined with support for numerous operator defined network slices.

3GPP supports edge computing where the applications reside close to the UE. More specifically, 3GPP allows the selection of a gateway that is close to the gNB. Because user traffic passes through a local gateway instead of a remote gateway located deep inside the core network, both the end-to-end latency and transport requirements are reduced.

5G NR TESTING AND DATA ANALYTICS

Networks are growing more complex with the emergence of new cellular use cases and more demanding subscriber and machine quality of experience (QoE), enabled by the roll out of technologies such as 5G and internet of things (IoT). Therefore, it becomes more critical to understand the current network situation and pinpoint areas for development that will efficiently deliver the required performance. Delivering excellent QoS (quality of service) to end users is a primary objective for mobile network operators to retain subscribers, attract new customers and competitively position themselves. A 5G NR measurement solution should provide accurate and reliable data collection with coverage measurements, application QoE measurements, and verification of the device interaction with a real 5G NR network.

The data analytics of this solution should comprise the entire network testing lifecycle, from network engineering and optimization to benchmarking and monitoring, and have the following objectives:

• To effectively store, process and visualize big data

• To gain deep network insights

• To ultimately build intelligence for investment prioritization based on the most critical factors influencing network performance and QoE

To measure and analyze pre-commercial 5G NR trials and early deployments, a real-time analysis tool, such as R&S ROMES4 from Rohde & Schwarz, is sufficient. Network measurements in commercial 5G NR networks require a sophisticated post-processing tool for data analytics.

For accurate network engineering, benchmarking, monitoring and optimization, it is necessary to process a large quantity of complex data and produce clear, easyto-understand intelligence in a network to make better decisions. Correct decisions can only be made when they are based on reliable and accurate data, processed quickly and appropriately.

By processing data acquired from the end-user perspective, the Rohde & Schwarz data analytics tool SmartAnalytics provides a precise and clear assessment of an operator’s own network quality (QoE from the end-user perspective) and its competitive position in the market.

Analytical tools must provide visibility of the main factors influencing network performance and QoE status, its context, development trends, problems and possible degradation causes. Thanks to the network performance score integrated in SmartAnalytics, a software suite that analyzes and post-processes measurement files collected with R&S Mobile Network Testing solutions, network operators can identify strategic areas for investment. As a result, mobile operators can efficiently deliver optimal end-user QoE.

SmartAnalytics is a flexible tool that encompasses different mobile network testing use cases such as engineering, optimization, monitoring and benchmarking, using the same user interface and platform. It eliminates the need for separate test platforms, removes compatibility issues and provides a seamless interface across each stage of the network testing lifecycle. This provides capital and operating expenditure efficiencies in test resources, equipment and execution.

In a nutshell, the mobile communications industry undertook a paradigm shift in defining the next generation of mobile communications. 5G Phase 1, or R15, provides a strong foundation for enhancements in future releases by defining a high-performance NR air interface and flexible network architecture. R16 and later releases focus on new verticals to significantly expand the applications of wireless communications. The introduction of new frequencies and features, such as 3.7 GHz and beamforming respectively, make testing particularly important and challenging, despite numerous simulations executed by industry players. Conducting measurements in pre-commercial network trials is the only way to gain new insights and to overcome doubts and uncertainties before the technology’s launch.

References: Rohde&Schwarz, https://www.rohde-schwarz.com/us/ products/test-and-measurement/overview/ test-measurement_229579.html