Impacts of 5G-TDD Time Slot Configurations on the Downlink and Uplink Data Rates

Diverse and differential service types of 5G trigger the needs of novel technologies in radio resource allocation and management, and it is a challenging problem to enhance flexibility of radio resource allocation while improving radio spectrum efficiency. To tackle this problem, numerology and time division duplex (TDD) have been introduced accordingly. This paper presents analyses of asymmetric performance impacts of flexible 5G-TDD time slot configurations on the downlink (DL) and uplink (UL) data rates, using our lab system design and realization based on the hardware and software reference designs of the OpenAirInterface (OAI) 5G stand-alone (SA) system. For 5G new radio (5G-NR) at frequency range 1 (FR1), aka sub-6 GHz, the adopted numerology scheme is μ = 1, ensuring an enough sub-carrier spacing (SCS) of 30 kHz for supporting higher mobility than 4G, in particular suitable for those bands above 3 GHz in FR1. For this study, the adopted band is n78 (3.3 - 3.8 GHz) due to its dominance among the 5G operators. In addition, six scenarios of TDD time slot configurations are studied for their impacts on the DL and UL data rates, in terms of TCP goodputs. Our measurement results show two effects: (1) asymmetric trend slopes of DL and UL data rates, and (2) symmetric performance degradation at the DL/UL extremes. Analyses of these two effects are proposed with respect to DL/UL traffic orientations, including DL-Heavy, UL-Heavy and Balanced applications, such as internet of humans (IoH), internet of things (IoT) and video conferencing respectively.