by Arnd Sibila, Technology Marketing Manager, Rohde & Schwarz Mobile Network Testing
3GPP release 15 specifies the initial 5G standardization framework of the radio access network called 5G New Radio (5G NR). The standard contains a high degree of flexibility in radio parameters, which complicates network measurements. However, Rohde & Schwarz has already conducted measurements in pre-commercial 5G NR trial networks with its commercially available 5G NR network measurement solution. We gained interesting insights into the new technology’s performance, capabilities and frequency bands.
The mobile communications industry undertook a paradigm shift in defining the next generation of mobile communications. Before discussing new technologies like in all previous generations, the industry researched and assessed the use cases and needs that 5G should fulfill. After a general agreement about the use cases, requirements were defined, including data rates, carrier bandwidths, latency values, number of devices, etc.
It was only after having reached a consensus on use cases and requirements that the 3GPP identified, discussed and evaluated candidate technologies. 3GPP release 15, issued in March, June and September 2018, specified the initial 5G standardization framework for the radio access network (RAN) called 5G NR.
5G NR is the global standard for providing a unified, more capable 5G wireless air interface. It will deliver significantly faster and more responsive mobile broadband experiences, and it will extend mobile technology to connect and redefine a multitude of new industries.
How Does 5G NR Differ from LTE?
LTE radio access (or, in 3GPP terms, eUTRAN) is an OFMD based technology with a fixed subcarrier spacing of 15 kHz that supports carrier bandwidths from 1.4 MHz up to 20 MHz. LTE has a packet-switched architecture that supports a wide range of data applications. Voice is also supported as voice over LTE (VoLTE) or using fallback mechanisms to 3G and circuit-switched technologies.
The 5G NR specification embraces flexibility. It aims to include different use case families—from enhanced mobile broadband (eMBB) and massive machine type communications (MIoT) to ultra-reliable, low latency communications (URLLC)—that span across industries.
These different use cases require a wide variety of air interface characteristics in terms of frequency range, subcarrier spacing, carrier bandwidths, symbol durations, etc.; the network architecture needs to offer many options. Table 1 shows the flexibility of frequency-specific parameters.
To cope with the different 5G NR use cases and demands per service, 3GPP defines the concept of bandwidth parts (BWP). Each BWP has a fixed numerology (fixed subcarrier spacing, number and location of the resource block, symbol duration, etc.).
User equipment (UE) can be configured with up to four carrier bandwidth parts in downlink/uplink, but at any given time only a single downlink/uplink carrier bandwidth part can be active. The downlink control information (DCI), radio resource control (RRC) or a timer can trigger the switch of the active BWP.
Another significant difference between LTE and 5G NR is the position of the synchronization signals, namely the primary (PSS) and secondary synchronization signals (SSS) within the carrier. Synchronization signals are very important. They are the first information that mobile devices need to identify in order to access the network.
In LTE, the sync signals are always located in the center of the carrier bandwidth; this makes them easy to find. In 5G NR, the sync signals are part of the SS/PBCH block (also called synchronization signal block, SSB) containing the physical broadcast channel (PBCH) information. These SS/PBCH blocks can be located at multiple positions all over the carrier bandwidth and are broadcast periodically as defined symbols in the radio frames and different beams versus time.
Beamforming of Synchronization Signals and Broadcast Channel Information
Beamforming as a technology is not new, but with 5G, beamforming is not only applied to user-specific data streams but also to synchronization signals and broadcast channel information. Beamforming can be implemented with antenna arrays on the base station side, where different groups of antenna elements (dynamically allocated) form beams to different users depending on their phases and amplitudes related to each other.
Using beamforming also for synchronization signals and broadcast channel information provides better overall coverage thanks to the higher antenna gain. The synchronization signal block (SSB) in 5G NR can carry beam-specific information (SSB index). These SSB index “beams” are static and can be considered micro sectors, e.g. eight micro sectors in one macro sector for the 3.7 GHz case.
5G NR Scanner Based Network Measurements in the Field
Understanding 5G NR coverage in real-life environments is just as important as it is for all other technologies. 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 commercial launch.
With pre-commercial 5G NR network trials underway, Rohde & Schwarz mobile network testing (MNT) has already had the opportunity to execute 5G NR field measurements. In collaboration with a tier-1 mobile network operator, measurements in the 3.7 GHz frequency band were conducted in a European country as early as 2018.
Coverage in 3.7 GHz Frequency Range
Bearing in mind the higher than normal frequency band, it was surprising how the 5G NR beamforming capabilities benefit the achievable coverage. In a suburban environment, the test engineers could measure a reference signal’s received power (RSRP) on the synchronization signals of –125 dBm at a distance of 6.5 km from the base station. They expected that 5G NR UEs could connect to base stations at signal levels down to –120 dBm.
Figure 5 shows the SSB index “beams” or the “micro sectors” very clearly. The outer color layer represents the SSB indices as explained in the color code. For a better overview, the colored micro sectors have been added to the screenshot.
For the trials, the tier-1 mobile network operator trusted the commercially available Rohde & Schwarz 5G NR network measurement solution. It comprises an R&S TSME6 or an R&S TSMA6 network scanner for data collection and the R&S ROMES4 drive test software suite for analysis and visualization. Equipped with an antenna, the 5G NR measurement solution fits into a backpack or shoulder bag for convenient and efficient drive and walk testing.
The described 5G NR network measurement solution can be expanded to a frequency range of up to 30 GHz (FR2) using the downconverter R&S TSME30DC. To avoid an impact of the body of the test engineer on the measurement results, Rohde & Schwarz offers a backpack that allows mounting the 5G NR mmwave receive antenna above head level.
5G NR UE Based Network Measurements
Another important part of 5G NR network testing is using 5G NR devices such as evaluation boards, USB dongles, pre-commercial and commercial smartphones as they become available. This will provide insights into network quality regarding quality of experience (QoE) of applications, the interaction of devices with the real 5G NR networks and the device performance itself.
Such 5G NR UE based measurements include NR serving cell information such as NR DL ARFCN, PCI and SSB index, layer 1 RSRP/RSRQ, layer 2 PDSCH, PDCP, PUSCH information, LTE-NR EN-DC L3 signaling and application layer information.
The R&S ROMES4 software suite for in-field real-time analysis supports the connection of the first-on-the-market Qualcomm X50 based UEs for 5G NR measurements.
Rohde & Schwarz has demonstrated this capability of its network measurement solutions during the introduction of previous mobile communications technologies.
5G NR Data Analytics
Delivering excellent quality of experience to end users is a primary objective for mobile network operators in order to retain subscribers, attract new customers and competitively position themselves.
Network complexity will increase with the emergence of new cellular use cases and more demanding subscriber and machine QoE, enabled by the rollout 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. To measure and analyze pre-commercial 5G NR trials and very early deployments, a real-time analysis tool (such as R&S ROMES4) is sufficient. Network measurements in commercial 5G NR networks require a sophisticated postprocessing 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, easy-to-understand intelligence in a network in order 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.
SmartAnalytics provides 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, network operators can identify strategic areas for investment. As a result, mobile operators can efficiently deliver optimal end-user QoE and move ahead of the competition, which leads to a higher number of subscribers, a lower cost base and access to new revenue streams.
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 OPEX and CAPEX efficiencies in test resources, equipment and execution.
With the 5G NR network rollout clearly on the horizon, network operators worldwide are planning pre-commercial network trials or even starting commercial network rollouts. 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.
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
Rohde & Schwarz fulfills all these requirements from a single source with its end-to-end 5G NR network measurement solution in line with the company’s slogan, “Be ahead in 5G. Turn visions into reality.”
5G NR – 5. Mobile Generation New Radio
BWP – Bandwidth Part
DCI – Downlink Control Information
eMBB – Enhanced Mobile Broadband
EN-DC – E-UTRA – NR Dual Connectivity
E-UTRA – Enhanced UMTS Terrestrial Radio Access (3GPP naming for LTE)
LTE – Long Term Evolution
mMTC – Massive Machine Type Communications
NR DL ARFCN – New Radio Downlink Absolute Radio Frequency Channel Number
OFMD – Orthogonal Frequency-Division Multiplexing
PBCH – Physical Broadcast Channel
PCI – Physical Cell Identity
PDCP – Packet Data Convergence Protocol
PDSCH – Physical Downlink Shared Channel
PSS – Primary Synchronization Signal
PUSCH – Physical Uplink Shared Channel
QoE – Quality of Experience
RAN – Radio Access Network
RRC – Radio Resource Control
RSRP – Reference Signal Received Power
RSRQ – Reference Signal Received Quality
SS – Synchronization Signal
SSB Index – Synchronization Signal Block Index
SSS – Secondary Synchronization Signal
URLLC – Ultra-Reliable Low Latency Communications
UE – User Equipment
VoLTE – Voice over LTE