USRP-based wireless communication demonstrations for capacity improvement: from coding and waveform design perspectives

• Main Author: Liu, Yile
• Other Authors: Guan Yong Liang
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2025
• Subjects: Computer and Information Science; Engineering; Block fading; Channel coding; Orbital angular momentum; MIMO communication; USRP
• Online Access: https://hdl.handle.net/10356/182060
• Institution: Nanyang Technological University

Today's society is increasingly reliant on mobile communications, especially driven by emerging technologies like the Internet of Things, autonomous driving, and smart cities. The demand for higher transmission rates, low latency, and stable communications has become even more pressing. To make better use of existing resources and technologies, this dissertation proposes two approaches for enhancing the performance of existing communications in extreme scenarios. Orbital Angular Momentum (OAM), a recent technology that utilizes vortex beams, provides a new dimension in mobile communication by enabling high-speed data transmission through superimposing multiple vortex waves. However, the orthogonality during OAM wave transmission can cause inter-channel interference (ICI), leading to signal degradation. Unlike the design of receivers and transmitters, channel conditions influence the performance of a communication system as part of the real physical environment. When examining the traditional coding methods for the AWGN channel, it is also essential to consider another typical form of channel fading in nature—block fading. To address the impact of block fading on the bit error rate, researchers proposed a novel coding method based on the principle of Low Density Parity Check (LDPC) code, referred to as the Root-Protograph LDPC (RP-LDPC) code. However, since replicating block fading in a natural environment is challenging, most existing studies focus on verifying its performance under simulation conditions, with few conducted in real channels. To bridge this gap, a USRP-based prototype was developed to implement a block fading channel in a physical environment, offering a practical solution to this issue. In this dissertation, there will be a brief introduction and experimental verification of the above two techniques. This dissertation proposes and implements 2×2 multi-user communication systems based on OAM and plane-wave antennas. The design and implementation of these systems are based on Universal Software Radio Peripheral (USRP). Additionally, a Single-Input Single-Output (SISO) communication system is also investigated to compare the bit error rate (BER) performance in a block fading channel among no coding, (3,6) Low Density Parity Check (LDPC) code, and Root-Protograph (RP-LDPC) code. These technologies offer assistance for people to better study the coding technology in a complex channel environment and enhance the effect of space division multiplexing of the MIMO system, which will facilitate the future development of wireless communication towards higher capacity and more channel conditions.