Non-Terrestrial Networks
Non-Terrestrial Networks (NTNs) are communication network systems that seamlessly connect IoT devices and mobile devices on land, at sea, and in the sky. 3GPP has defined the fundamental technical specifications for NTNs in Release 17. Enhancements to the NTN specification are underway even after Release 18. They include a proposal to add the Ka-band, beyond the 17 GHz frequency band, to the service link between IoT devices and satellites.
As NTN continues to evolve, users will be able to utilize stable communication services anywhere in the world, without being aware of whether they are connected to a terrestrial base station or a satellite.
NTN Use Cases
NTN using terrestrial base stations and satellites delivers communication services to any location, such as mountainous areas and at sea. There are two types of standards. One is NTN NB-IoT, the other is NTN NR. The broad coverage capability of satellites can provide a stable mobile communications environment for high-speed trains and airborne vehicles. As a result, the range of use cases in mobile communications increases, as described below.
NTN NB-IoT operates based on the NB-IoT standard used in 4G. Due to its low power consumption and low data rates, it is suitable for the following use cases:
- Sending and receiving emergency calls and other short messages as an emergency backup link if terrestrial communications infrastructure becomes unusable.
- Transmitting and receiving non-real-time data from remote locations in agriculture, construction, forestry, shipping, and other industries.
NTN NR is based on 5G and supports higher data rate communications such as voice and video calls and media streaming. It is used in the following use cases:
- Communication for the remote control of heavy machinery and the autonomous driving of vehicles.
- Providing seamless coverage over land, sea, and skies by supplementing the coverage areas of terrestrial base stations.
Challenges in NTN Device Development
Challenge 1: Delay and Frequency Shift
Communications satellites such as Geostationary Earth Orbit (GEO), Geosynchronous Orbit (GSO), Medium Earth Orbit (MEO), and Low Earth Orbit (LEO) satellites incur delays between the satellite and devices due to their distance from the ground. For example, GEO and GSO delays range from 240 to 280 milliseconds, while LEO delays range from 6 to 30 milliseconds. In addition, for non-GEO satellites, the satellite movement causes a Doppler shift in the radio signal frequency. Therefore, NTN-enabled IoT devices and mobile devices must compensate for delay and Doppler shift according to the 3GPP standard.
Challenge 2: Reselection and Roaming
In terrestrial networks (TNs), IoT devices and mobile devices switch their registered base stations by monitoring the difference in signal strength between neighboring base stations. This process is called reselection, which is defined by 3GPP. The reselection for NTN also applies to switching from a TN to an NTN. In addition, the reselection is conducted while monitoring the exact location of the satellites and the devices. This results in a more complex operation than TN reselection. Furthermore, satellite communications, which easily cross borders, cause roaming with different operators, such as switching between a TN operator and an NTN operator. Therefore, when developing NTN-enabled IoT devices and mobile devices, engineers need to ensure that the roaming behavior complies with the 3GPP standard to enable seamless switching between operators.
NTN Device Test Solutions
Anritsu's NTN NB-IoT test solution provides a simulation and quality evaluation environment for NTN device development. This enables NTN devices to be validated without needing a connection to an actual satellite.
- RF TRx Testing
To achieve stable communication in NTN, the RF TRx performance of IoT and mobile devices becomes more crucial. Anritsu's Radio Communication Analyzer MT8821C provides a 3GPP-compliant RF TRx test environment with ease of use and flexible parameter settings.
- Protocol Testing
Evaluating the protocol implementation in the chipsets/modules requires reproducing the connection environment with satellites, including reselection and roaming. Anritsu's Signalling Tester MD8430A supports the rapid creation and evaluation of test cases, enabling efficient protocol development and validation.
- Conformance Testing
Conformance testing to the latest 3GPP standards is essential to ensure the quality of NTN-enabled IoT devices and mobile devices. Anritsu's New Radio RF Conformance Test System ME7873NR and 5G NR Mobile Device Test Platform ME7834NR deliver timely, 3GPP-compliant test cases that fully meet your expectations, accelerating your products' time to market.