Robust Wireless Communications for Low Power Short Message Internet-of-Things Applications

The Internet-of-Things (IoT) raises an enormous business in the future because it enables a wide range of novel applications from smart homes to industrial automation. IoT applications possess unique challenges due to device constraints on low power, short message size, and low latency. Low power devices may result in unstable frequency and phase of the transmitted signal and bring difficulties in detection and synchronization. Short messages can no longer rely on capacity-achieving error correction codes, demanding exploration of new reliable transmission schemes to combat noise and interference. Low latency constraint poses additional challenges to system design when packet retransmission is not a viable means to boost reliability.

This dissertation focuses on robust wireless communication system designs for low power short message IoT applications, aiming to enhance the reliability of the transmission by resolving the abovementioned challenges with three works. The first work proposes a gateway receiving algorithm for frequency/phase unstable signal including packet detection, carrier/sampling frequency offset synchronization and demodulation. The second work introduces a novel non-orthogonal modulation scheme suitable for short-message packets in an interference-heavy channel. Lastly, an instantaneous feedback-based variable symbol length transmission scheme that provides ultra-reliability for short packets with low latency is presented in the third work.

The three works presented in this dissertation provide solutions to IoT challenges and enhance the reliability of low power short message wireless communications, broadening the use cases of IoT applications and improving the robustness of IoT connectivity.

Chair: Professor Hun-Seok Kim