UBC Theses and Dissertations

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UBC Theses and Dissertations

Enhancing low-cost cellular IoT networks on the sidelink and satellite links Rajendran Chandrika, Vishnu


Internet-of-Things (IoT) is one of the fast growing technologies in the current era which holds a large and rapidly increasing global market size. Device-to-device (D2D) communication is a key enabler for connecting devices together to form the IoT, especially when the cellular coverage is limited. Similarly, non-terrestrial networks (NTNs) involving satellites which complement the terrestrial cellular networks to provide global coverage also play a vital role in expanding IoT. Both D2D and satellite links are essential in providing seamless universal cellular IoT (C-IoT) coverage. In this thesis, we propose enhancements for C-IoT devices which address up-to-date problems in D2D communication and NTNs. Leveraging the unlicensed frequency bands for D2D communication reduces the costs, and offloads network traffic from the licensed spectral resources. To this end, we design a new low-cost radio access technology (RAT) protocol called Sidelink Communications on Unlicensed BAnds (SCUBA). SCUBA complements the primary RAT, and functions by reusing the existing hardware on a non-overlapping time-sharing basis. We prove the effectiveness of our protocol with analyses and simulation results of the medium access control layer of SCUBA. One of the most critical problems faced by NTN is the uplink (UL) synchronization failure due to high Doppler offset. While NTN new radio (NR) devices rely on global navigation satellite system (GNSS) to resolve this issue, it is not always feasible for power-critical IoT user equipments (UEs). Therefore, we design Synchronization signal-based Positioning in IoT Non-terrestrial networks (SPIN) which enables the IoT UEs to tackle the UL synchronization problem. Our evaluations show that SPIN positioning accuracy achieves the Cramer-Rao lower bound and meets the target accuracy required for UL synchronization, along with significant battery life savings over GNSS-based solution. Another pertinent problem faced by C-IoT devices in NTN is the extended round-trip time resulting in a degraded network throughput. To this end, we propose smarter hybrid automatic repeat request (HARQ) scheduling methods that can increase the efficiency of resource utilization. We conduct end-to-end link-level simulations of C-IoT traffic over NTNs. Our numerical results of data rate show the improvement in performance achieved using our proposed solutions against legacy scheduling methods.

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