Advance Troubleshooting of 5G NR NTN

Why Is the NTN Important?

The non-terrestrial network (NTN) is a communications network incorporating airborne or spaceborne assets as well as assets on the ground. These hybrid networks apply satellite communication technology to extend existing cellular communications. NTN usually refers to networks connecting the cellular world and satellite links and how to attain direct access to satellite networks for end users.

Today’s new space race primarily focuses on non-terrestrial networks as governments and corporations seek to advance communications, surveillance, sensing, and monitoring capabilities.

Mobile network operators (MNO) strive to provide better and broader coverage to their customers. NTN provides an opportunity especially in terrain where terrestrial coverage is difficult such as in mountain ranges and oceans. Providing reliable wireless communication for users such as hikers and skiers enables real-time posts and improves public safety. Cruise ship and airline customers would be delighted with consistent satellite service during their travels. MNO interest in NTN then drives network equipment manufacturers (NEM) and chipset and device manufacturers to develop NTN solutions.

Governments and their ministries and agencies embrace new technology such as NTN to improve their ability to surveil and protect their constituents. Satellites are an essential part of surveillance today and NTN provides an opportunity to link with existing terrestrial networks for more real-time communication and storage of data.

Many devices connect to wireless networks for monitoring and sensing. Vending machines report their status and request refills of items with low availability. Doorbell cameras report when activity occurs on personal and commercial property. These devices benefit from NTN especially in areas with poor terrestrial wireless communication coverage.

The NTN satellite link uses narrow-band Internet of things (NB IoT) or fifth-generation new radio (5G NR) technology for communication. These two implementations are otherwise known as NB NTN and NR NTN. While NB NTN has been more widely simulated and tested today, NR NTN is expected to be the technology of choice for NTN applications.

NTN ecosystem

MNO, NEM, and chipset and device manufacturers make up the ecosystem of wireless cellular terrestrial networks. They are also part of the NTN ecosystem representing a portion of the ground connection in a satellite system communicating between space and the Earth.

The space connection represents a new part of NTN ecosystems as compared with terrestrial networks. As shown in Figure 1, satellite network operators and satellite manufacturers are new participants in an NTN ecosystem. Also new are launch services to deploy satellites into space and ground systems and terminals to receive and transmit between NTN and existing terrestrial networks.

Space-based components and their development, implementation, and deployment in support of NTN drive this new ecosystem.

New Test Challenges with NR NTN

A non-terrestrial network brings new challenges to testing and verifying signaling and radio frequency (RF) performance.

• GEO are stationary when viewed from Earth, so testing is like terrestrial networks
• GSO is a special case of GEO with inclination different from zero making the satellite appear as a figure eight pattern from the Earth and causing measurable delay and Doppler variation in the ground link, which are important to consider in system and link-level testing
• LEO, MEO, and other NGSO satellites move rapidly when viewed from Earth causing large Doppler and propagation delay shifts and variations, so optimizing beam management requires information about the movement of the satellites (ephemeris)
• Communicating with satellites at high altitudes means longer latency for procedures such as random access channel (RACH), timing advance and UL timing, hybrid automation repeat request (HARQ), and power control, and higher power for successful transmission and reception
• Transmission through the Earth’s atmosphere adds complications such as absorption and reflection
• Troubleshooting is more complex because testing NTN from end to end is practically impossible with separate modem and antenna subsystems

Defining test methods to overcome these challenges while still meeting time-to-market and budget requirements is essential for successful launch of non-terrestrial network elements and devices.

Address NR NTN Challenges with Keysight Solutions

Keysight’s WaveJudge wireless analyzer solutions are key to identifying and resolving issues with NTN. The combination of WaveJudge with Keysight’s PROPSIM, UeSIM, UXM, FieldFox, or non-signaling solutions provides complete emulation and analysis of non-terrestrial network elements and devices. WaveJudge and other Keysight solutions may capture signals over the air using antennas or connect directly to perform conducted analysis.

NTN test capability with Keysight solutions

• Channel and orbit emulation and models
• Base station, gNB, and network emulation
• UE and VSAT emulation including unmodified UE
• Variable delay and Doppler
• Emulation of path loss and multipath
• Import of ephemeris data
• Message capture, decode, and analysis
• RF measurements and charts