O-RAN an Introduction: Cellular radio technology has been evolving and changing landscape of mobile network architecture from time to time. Traditionally, RAN (Radio Access Network) equipment vendors have optimized performance by combining and tuning the multiple system elements, resulting in locking of mobile operators to one vendor when constructing a RAN. To meet the challenges of 5G, such as wider coverage and lower costs, mobile operators and their ecosystem are organizing open specifications that supplement the 3GPP standards. Many ecosystem contributors started working on an open radio access technology which is now known as O-RAN – Open Radio Access Network. These contributors formed an alliance which is known as O-RAN ALLIANCE. O-RAN ALLIANCE is a global organization with a mission to “re-shape the RAN towards more intelligent, open, virtualized, and fully interoperable mobile networks” by publishing standards and specified authorized interfaces and functions, supporting a more flexible ecosystem of RAN equipment suppliers. In summary O-RAN standards enable a more competitive and vibrant RAN supplier ecosystem with faster innovation. O-RAN-based mobile networks improve the efficiency of RAN deployments and operations.
Benefits of O-RAN: O-RAN offers below core benefits:
Lower Cost – CAPEX is reduced by the multi-vendor ecosystem created by O-RAN. OPEX is less because RAN automation leverages new learning-based technologies to reduce operational actions. Considering the high expenses associated with 5G RAN, economic benefits are main advantage of O-RAN
Improved Efficiency and Performance – O-RAN could enhance network operation and the user experience because it aims to offer efficient and optimized radio resource management via near real-time and non-real-time RAN Intelligent Controllers (RIC).
Seamless Upgrades – Network expansion is simplified through O-RAN, due to its cloud native infrastructures and utilization of continuous integration, test, and deployment methods (CI/CT/CD).
O-RAN architecture (figure 1) utilizes COTS hardware and virtualized software to provide multiple hierarchical cloud deployment options for operators.
The open architecture divides conventional monolithic BTS into the functional splits of an O-CU, O-DU, and O-RU. Engineers must understand the impact of such a split, particularly at the radio unit (RU) and distributed unit (DU) layers.
By breaking the RAN monolithic structure, new vendors have an easier path to enter the network market. Added competition will reduce costs. Such a scenario allows mobile operators to better service more cost-sensitive 5G network use cases, such as rural markets or private commercial 5G networks.
Another benefit of the open environment is that it stimulates innovation, including moving wireless networks to the edge. With the service-based approach of 5G, edge networking is essential for networks to meet KPIs.
O-RAN Testing Aspects
A comprehensive testing strategy must be developed for successful O-RAN implementation. Anritsu has leveraged its vast 3G/4G/5G experience and active membership in the O-RAN ALLIANCE to collaborate with customers to create effective verification processes. Key tests that Anritsu-based solutions conduct are listed in table 1.
Synchronization is a big challenge for O-RAN, because timing information passes across equipment from multiple vendors from the T-GM(Telecom Grandmaster) to the radio with tighter criteria. The O-RAN WG4 is discussing assured interoperability between the O-DU (O-RAN Distributed Unit) and O-RU (ORAN Radio Unit) by defining functional and performance tests. Also, WG9 is discussing a transport network via mobile X-haul, supporting accurate timing distribution to the O-RU.
Need for Test Automation
O-RAN architecture expands across different verticals that require levels of customization. There is also an influx of new companies entering the market, as mentioned previously. Such a scenario places even greater importance on the need to ensure elements work seamlessly. To reduce complexity, as well as control cost-of-test and speed time-to-market, test automation is a necessity.
A successful test process will have automated testing and comprehensive test suites defined and developed in advance and run before any component is released. The same approach is used to validate the deployment of an O-RAN solution, so the testing runs automatically each time a new component is released. Automated tests are particularly beneficial for O-Cloud verification.
Test solutions that are completely integrated with standards and can perform the tests in a few keystrokes provide the accuracy, repeatability, and speed necessary. Flexible platforms that allow for updates as specifications evolve are also beneficial for O-RAN. For production test environments, a software-based solution that automatically updates 3GPP test cases saves time and money.
One way for test companies to develop these test solutions is through collaboration. Anritsu’s membership in the O-RAN ALLIANCE and involvement in the association’s plugfests have forged advantageous relationships. Anritsu is also an active member of the Telecom Infra Project (TIP), a diverse community that includes hundreds of participating companies, from service providers and technology partners to system integrators and other connectivity stakeholders. The result is a unique ability to develop flexible test solutions that meet existing needs and can be easily upgraded as new requirements arise, helping bring O-RAN solutions to market more efficiently and with greater confidence.
Anritsu & O-RAN
The O-RAN ALLIANCE is one global organization with more than 250 members and contributors (at May 2021) and Anritsu is one contributor. Anritsu provides the following test solutions for O-RAN fronthaul (O-RAN FH) equipment configured as an O-DU (O-RAN Distributed Unit) and O-RU (O-RAN Radio Unit) with a lower functional “Split 7-2x”.
- Network Master Pro MT1000A
- Signal Analyzer MS2850A
- Vector Signal Generator MG3710E
The Network Master Pro MT1000A is an all-in-one transport network tester for speeds from 1.5 Mbps to 100 Gbps using various technologies and supports PTP/SyncE tests in the Synchronization plane (S-plane). The Signal Analyzer MS2850A covering 9 kHz to 32 or 44.5 GHz is a high-performance RF signal analyzer supporting an analysis bandwidth up to 1 GHz with excellent flatness and spurious-free dynamic range. The Vector Signal Generator MG3710E is a standard signal source with dual-RF port and dual arbitrary waveform memory options. The MS2850A and MG3710E support the fundamental RF parametric tests for O-RU specified in 3GPP TS38.141 Chapters 6 and 7.
O-RAN Fronthaul Test Cases: Anritsu test instruments are used for O-RAN fronthaul tests. Below figure shown how Network Master MT1000A , Vector Signal Generator MG3710 and Spectrum Analyser/ Signal Analyser MS2850A are used.
Terms to know in O-RAN
O-RAN alliance is growing rapidly, and we hope it will enable a cost-effective network deployment, operation and maintenance along with sustainable growth to telecom ecosystem