VIAVI provides comprehensive testing and assurance from the lab to the field, to assurance and optimization for RAN networks including scalable real-world emulation, end-user experience testing, large scale deployment support and advanced RAN intelligence management platforms.
What is a Radio Access Network (RAN)?
A RAN includes the elements of a telecommunications network that provide radio communication and access between user equipment such as wireless devices and the core network. It typically includes the base station components and antenna arrays providing cell coverage to a specific area. RAN wireless architecture has continually evolved since the inception of cellular technology as more intelligence moves from the core to the edge.
Modern radio access technology has incorporated split architecture, software defined networking (SDN) and massive MIMO antenna arrays to facilitate the high bandwidth, low latency demands of 5G New Radio (NR).
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- Radio Access Network Architecture
Early radio access network deployments employed an “all-in-one” architectural model with digital, analog and power functions centrally located in the base station and coaxial cable scaling the cell tower to provide RF signals to the antenna. Advancements in 3G and LTE networks led to the first split BBU architecture with remote radio head (RHH) functionality moving closer to the antenna and connected to the BBU via fiber.
Further disaggregation of traditional elements and antenna propagation through massive MIMO have been made possible through virtualization and advanced transport technology.
With traditional architecture incapable of meeting the high-performance requirements for new use cases like Massive Machine Type Communication (mMTC), Enhanced Mobile Broadband (eMBB) and Ultra-Reliable Low Latency Communications (uRLLC), 5G has driven a fundamental shift in radio access network infrastructure. Resilience, flexibility and efficiency are the underlying principles that set the new trajectory for RAN mobile network design and deployment.
Incorporating virtualization has enabled the splitting of RAN functions between the user plane (UP) and control plane (CP) in higher layers to establish a more dynamic response to traffic volume and service requirements. Virtual elements of the BBU can be merged with the RRH, allowing more physical separation between RAN elements and tailoring of the deployment to optimize coverage, reliability and latency for each use case.
5G NR will not immediately supplant existing LTE networks. Seamless coordination between new and existing radio access technology provides a foundation for non-standalone (NSA) 5G deployments. Antenna arrays and base stations can operate at the higher frequencies emblematic of 5G NR even while working with existing LTE core networks.
- 5G RAN Lifecycle
The complexity of 5G radio access networks introduces unique challenges that require comprehensive measurement and test solutions throughout the 5G RAN lifecycle. Virtualization, advanced antenna arrays, wideband signals and NR frequencies are some of the RAN advances that call for simulated real-world behavior in both the lab and the field to guarantee successful deployment. These same technological breakthroughs lead to monetization opportunities through the optimization and assurance of the UX.
Emulating 5G RAN
Testing in the lab paints an incomplete picture without an associated core for validation at the system level. A core emulator can bridge this gap while providing the flexibility to continually adapt to evolving 3GPP standards. An emulator allows developers to customize and control the test environment to accelerate development.
Emulation is equally valuable from the users perspective. To validate system performance as experienced by end users, tools to effectively simulate real world behavior such as voice over 5G (vo5G), streaming, user-to-user interaction and mobility across the networks can complement core emulation solutions. This united strategy creates a structured, automated platform for 5G RAN development.
Field deployment of a 5G RAN introduces a host of new variables that require accurate and versatile test solutions. Base station analyzer technology has risen to this challenge by incorporating antenna analysis, spectrum analysis and signal verification capabilities appropriate for the spectrum and interference of millimeter wave 5G signals.
Fiber optic technology is the central nervous system of equipment deployment. Analyzers that incorporate fiber test, inspection and optical power measurement features can assess dense 5G fronthaul and backhaul configurations with PON and WDM technology fully leveraged to ramp up capacity.
Performance monitoring software also becomes an important factor during deployment because it requires high visibility from first activation onward to ensure SLA compliance.
Visibility can be taken to the next level through location intelligence. Capturing, locating and analyzing events is essential for managing wireless infrastructure, planning new coverage areas and optimizing the customer experience. Now, with 5G, Location Intelligence accuracy will be more acute as well as beam-aware and 3D-aware.
Location intelligence using an advanced intelligence platform can enable new B2B verticals in the healthcare, automotive and manufacturing industries. Increased visibility into customer usage trends also becomes a valuable tool for managing SLAs and network slicing. This in turn leads to higher levels of service and satisfaction.
- New Test Challenges
5G RAN has synthesized cutting-edge hardware and software advancements to establish a new model capable of meeting aggressive 5G use case performance standards. This aggregation of new technology and densified enabling infrastructure, including optical fiber and antennas, has also introduced unique test challenges. One fundamental shift behind many of these challenges is the transition to millimeter wave.
Millimeter wave frequencies between 24 and 100 GHz provide a transport medium suitable for high speed, high bandwidth wireless communication. At the same time, higher dynamic range and signal-to-noise ratios (SNR) are required for spectrum analysis in the millimeter wave although the limited range and inability to penetrate solid objects leads to additional deployment challenges.
Beamforming and ultrawide bandwidth have been developed to strategically focus transmissions and deliver short-range signals more effectively, but they add complexity to test solutions with respect to demodulation and coverage, too.
Massive MIMO is another advanced technology that mitigates millimeter wave drawbacks by transmitting data from a large array of antennas in parallel and reconstituting them at the user device. The resulting proliferation of antennas, coupled with split architecture and escalating capacity demands, leads to maximized connection density. This translates to increased fiber inspection, validation and maintenance along with advanced over-the-air (OTA) testing to ensure massive MIMO performance.
5G use cases are elevating and diversifying quality of experience (QoE) expectations. uRLLC applications such as vehicle-to-vehicle communication make stringent latency requirements pivotal for safety compliance. Vo5G will continue to supplant both VoLTE and Wi-Fi.
A lab to field test philosophy is essential for seamless deployment and transition from LTE RAN. While multi-access edge computing (MEC) dramatically improves latency, reliability and efficiency, it also decentralizes hardware and software functions, thereby complicating test, maintenance and monitoring practices.
5G Radio Frequency
Test challenges encountered in the millimeter wave are exacerbated by the repurposing of lower frequency bands for 5G. This includes the low-band (sub 1GHz) occupied by LTE today as well as the mid-band (1- 6 GHz) range. This compilation of frequencies effectively supports widespread coverage and the tailoring of use cases to frequencies. With frequency bands varying by operator, region and application, testing for interference and synchronization require greater functionality and precision.
Open RAN (O-RAN) enhances efficiency and flexibility by standardizing elements and allowing operators to interconnect white-box hardware and RAN elements from different vendors.
The O-RAN Alliance was founded by a conglomeration of operators to define and promote requirements for open RAN architecture with an emphasis on embedded intelligence. This progression has been furthered through Open Virtual RAN (O-vRAN) which extends the concept of open, standardized architecture to the virtual, software based disaggregated elements that separate functions from underlying hardware.
O-RAN architectural models are strategically aligned with the Cloud RAN (C-RAN) precepts of real-time virtualization and multi-technology and multi-vendor ecosystems. As a member of the O-RAN Alliance and a key contributor to the development of O-RAN specifications and test solutions, VIAVI is leading the way with O-RAN compatible emulation, capacity and performance testing over the O-RAN and RF interface.
- Equipment and Test Solutions
A practical approach to lifecycle assurance begins with lab and benchmark automation solutions incorporating load, RF, core and service emulation. The TeraVM 5G Core Emulator is a powerful test solution with the ability to emulate 5G RAN and core elements even when they don’t exist yet. This provides flexibility in the lab by eliminating the need for real world core functionality when testing interoperability of 5G RAN elements. The TeraVM is also the first emulator to fully support 3GPP-compliant 5G standalone specifications.
The variety of 5G use cases and applications makes emulation from the user's perspective an increasingly valuable tool. The TM500 Network Tester is the recognized industry standard for network testing via RF and can validate the user experience across different radio access network technologies. The TM500 can accurately replicate real world behaviors such as file downloads, email and voice communication while supporting high data rates and UE quantities per cell.
Diligence in the lab can bring added confidence when moving to site installation where layer testing, antenna alignment, interference testing and performance verification come together to establish functional integrity. The CellAdvisor 5G is an all-in-one portable test solution that includes real-time spectrum analysis, beam analysis and fiber testing capabilities that are pivotal to installation and site certification. Cloud connectivity through StrataSync makes reporting and data management fast and easy.
Location intelligence is a key enabler for optimized 5G RAN wireless customer experience assurance. The NITRO Mobile platform collects and analyzes data from the RAN to the core and converts it to actionable business intelligence. This includes valuable insight into 5G RAN and 4G/5G handover performance, coverage vs 4G and new site deployment opportunities.
As the radio access network equipment and location intelligence platforms mature along with 5G, NITRO Mobile will help to determine priority sites, assess subscribers’ service levels and manage service issues. Location intelligence is the key to converting mountains of data into unlimited 5G RAN monetization opportunities.