The key requirement that NB-IoT User Equipments (UEs) can communicate to satellites with equal or very similar Terrestrial network (TN) solutions in relation to chipsets and protocol implementations has been confirmed during the first phase of the ESA project. This has been done by designing, implementing, and performing link-level simulations in Matlab.

GateHouse now has a NB-IoT NTN simulation environment available for the validation of specific network/satellite configurations (e.g. various parameters like antenna size/type, gain, coverage area) and enabling pre-assessment of expected network capacity. Algorithms that have been evaluated are for example NPSS/NSSS detection, DL BLER as function of SNR.

Additionally, work has been done to create an understanding of what adaptions to TN NB-IoT are necessary to enable the NTN variant of NB-IoT. The distance and speed of the satellite need to be taken into consideration. Carrier and signal frequency are influenced by the Doppler effect and propagation time. Compensation can be done, and it is necessary to reach a network communication efficiency and capacity that enable a commercially deployable NTN service.

The efficiency and link-budget of the communication between UEs and satellites influence the power usage to a very high degree. NB-IoT devices are normally specifically chosen due to their small data, low priority, and very effective power usage which enable IoT devices to operate with long battery lifetime.

Objective of the second phase of the ESA project

In the ongoing second phase of the ESA project, GateHouse SatCom continues to work with design and implementation. The second phase particularly focuses on how the link budget and general communication between the UE and satellite can be optimized, to optimize both the link budget and power usage. We continue to design, implement, and evaluate critical algorithms for NB-IoT NTN. Aspects such as influencing of UE positioning accuracy and quality, power utilization and Random Access (RA) optimizations will continue to be evaluated.

Performance will be both evaluated by simulations, though additionally by field testing of an adopted NB-IoT waveform. Design and implementation work on the physical layer and higher protocol layers is continued, and the performance will be evaluated by an NTN demonstration.

Simulation models for NB-IoT, tailored specifically to NTN, will be extended, for both the Matlab simulation environment and a capacity simulation environment. The first is especially useful for seeing the influence of specific system configuration parameters, like antenna type, gain (power amplification), altitude, footprint influence. The second is seen as very useful to see influence of the overall network capacity by the configuration and scaling of the satellite constellation, and the density and (global and local) placement of UEs.