Optimization and network performance evaluation of beamforming and dynamic DTX techniques in 5G/6G systems

Abstract

In order to support the evolution of cellular communication systems towards the fifth generation (5G) and beyond, the industry and the research community have considered the optimization and development of communication technologies, such as massive multiple-input multiple-output (MIMO) and the exploration of a larger frequency spectrum using millimiter wave (mmWave) and terahertz (THz) bands. However, some challenges emerge during the application of these techniques in these new scenarios. In this context, this dissertation addresses two different scenarios of mobile communication systems, each considering one specific problem regarding 5G and 6G systems. First, it addresses the problem of robust beamforming in multi-user multiple- input single-output (MU-MISO) systems. To this end, it assesses the performance of a deep neural network (DNN)-based beamforming strategy under imperfect channel conditions. A robustness analysis has been provided by adding a controlled independent additive noise term to the channel. The DNN-based beamforming strategy is compared with the classical weighted minimum mean square error (WMMSE) solution in terms of the impact of imperfect channel state information (ICSI) on the average sum rate. Results have shown that the deep neural network (DNN)-based strategy is viable in terms of complexity and is as robust as the weighted minimum mean square error (WMMSE). In the second part, it evaluates the network performance of a cellular system operating at 100 GHz with bandwidth of around 3 GHz under a dynamic transmission and reception point (TRP)-side discontinuous transmission (DTX) regime. The use of THz bands are envisioned as a means to achieve higher data rates in sixth generation (6G) systems. Additionally, to deal with more severe propagation conditions in THz bands, a network with multiple TRPs equipped with large antenna arrays serving multi-panel user equipment (UE) has been adopted. To avoid overheating issues, a TRP-side DTX method has been proposed, which controls downlink transmissions while guaranteeing cell-specific reference signaling. Simulation results considering different DTX settings and traffic loads have been presented and discussed. Results have shown that the considered THz system with the proposed DTX method can provide higher data rates in comparison with a typical, baseline (mmWave) system operating at 28 GHz. It was possible to reach at least 6.84 times higher data rates.