Analysis and simulation of RedCap for direct- to-satellite connectivity

Abstract

The number of connected internet-of-things (IoT) devices will reach 29 billion by 2030. With the advancement of technology, the demand for wireless communications has been proliferating. The existing terrestrial networks are not able to provide coverage for IoT operations in remote areas. Therefore, non-terrestrial networks (NTNs), specially satellites are a promising solution to combat this existing challenge. In the new space era, massive machine-type communications (mMTC) and satellites integration enable direct-to satellite (DtS) communications, which allows terrestrial low power radio signals to reach low Earth orbit (LEO) satellites. Particularly, radio access technologies (RATs) like narrow-band IoT (NB-IoT), long-range (LoRa), and long-range frequency hopping spread spectrum (LR-FHSS) have been experimentally proven the feasibility of DtS for low data rate use cases. Recently, the satellite IoT industry is focusing on standardized RATs. In this study, first, we present an overview of potential DtS RATs technologies. For link-level analysis, we opted reduced capability (RedCap) technology, which was recently introduced in the fifth generation (5G) by third Generation Partnership Project (3GPP) specifications. RedCap aims to address mid-range IoT applications, ideally suited for applications that require a higher data rate than the capacity of LoRa, LR-FHSS, and NB-IoT. Since RedCap is a new RAT, there remains a need for studies to explore its potential within NTNs. This thesis investigates the performance of direct communications from terrestrial RedCap user equipment (UE) to Earth orbiting LEO satellites. The work follows the 3GPP specifications for RedCap and NTN, particularly, we consider the 16 quadrature amplitude modulation (QAM), orbital height 600 km and 1200 km, NTN frequency spectrum as L-band n255 and S-band n256. The link level analysis accounts for the impact of signal attenuation, interference, and Doppler effect. The obtained results confirm the feasibility of RedCap DtS and pinpoint open challenges and directions for future work.