Research of Low-Power Long-Range Digital Communication System and SINR Estimation Algorithm

Abstract

This thesis proposes a transmission system for low-power long-range digital communication, achieving distances of over 100 km. The system is designed using one of the optimal modulation techniques, direct sequence spread spectrum, and implemented using LabVIEW, SDR equipment, and RF components. Measurements were conducted in various distances and environments, including Pohang city, Homigot, and the East Sea, validating that the proposed system's structure and specifications are suitable for long-range, low-power communication. For the receiver, this paper introduces an algorithm to estimate SINR (Signal-to-Interference-plus-Noise Ratio) using the received signal based on direct sequence spread spectrum. Ten sequences orthogonal to the m-sequence used for spectrum spreading are generated, and by cross-correlating them, SINR can be estimated. The accuracy of this algorithm is demonstrated through back-to-back measurements in a laboratory setting. Through real-world measurements and analysis based on the link budget, it is expected that this algorithm can be effectively applied to the analysis of wireless communication channel characteristics.