Research and development of mobile communications systems require a detailed analysis and evaluation of novel technologies to further enhance spectral efficiency, connectivity and reliability. Due to the exponentially increasing demand of mobile broadband data rates and challenging requirements for latency and reliability, mobile communications specifications become increasingly complex to support ever more sophisticated techniques. For this reason, analytic analysis as well as measurement based investigations of link level methods soon encounter feasibility limitations. Therefore, computer aided numeric simulation is an important tool for investigation of wireless communications standards and is indispensable for analysis and developing future technologies. In this contribution, we introduce the Vienna 5G Link Level Simulator, a Matlab-based link level simulation tool to facilitate research and development of 5G and beyond mobile communications. Our simulator enables standard compliant setups according to 4G Long Term Evolution, 5G new radio and even beyond, making it a very flexible simulation tool. Offered under an academic use license to fellow researchers it considerably enhances reproducibility in wireless communications research. We give a brief overview of our simulation platform and introduce unique features of our link level simulator in more detail to outline its versatile functionality.

The Fifth Generation (5G) New Radio (NR) Physical Layer (PHY) is designed to successfully address diverse user and service requirements by providing a highly flexible framework. This flexibility is viable through a scalable numerology. Since 5G NR targets to multiplex various applications with different quality of service requirements within the same band, 3rd Generation Partnership Project has introduced a mixed (multi) numerology approach and a mini-slot approach to enhance the adaptability of the PHY. In this contribution, we compare these two approaches focusing on the achievement of lowlatency communications. We propose optimization problems that enable to maximize the achievable rate of best effort users, while maintaining latency requirements of low-latency users. Exploiting achievable rate performance as one of the fundamental metrics, we show a comparison of mixed numerology and mini-slot approach in different circumstances. In addition to Cyclic Prefix (CP)-Orthogonal Frequency Division Multiplexing (OFDM), we employ Universal Filtered Multicarrier (UFMC) as a potential beyond 5G technology and show that it achieves an improvement over CP-OFDM. The optimization problems for both mixed numerology and the mini-slot approach are initially given by an integer programming solution. In order to reduce computational complexity for large-scale scenarios, we apply the Dantzig-Wolfe decomposition method, showing that it is possible to achieve the optimal solution with significantly reduced complexity by exploiting the structure of the proposed optimization formulation.

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