No abstract

A promising solution for massive Multiple-Input Multiple-Output (m-MIMO) systems is Hybrid digital-analogue (HDA) beamforming as it offers a balanced trade-off between energy efficiency (EE) and spectral efficiency (SE). The lack of practical demonstrations in the open literature is primarily because those most existing works require a large number of phase shifters (PSs), radio frequency (RF) switches, power dividers (PDs), and power combiners which contribute to high hardware complexity and energy consumption (due to insertion loss). In this paper, we introduce a practical dynamic subarray m-MIMO structure that is based on reconfigurable power dividers (RPDs). The extensive system simulation results, considering hardware imperfection extracted from a practical RPD implementation, indicate that the proposed RPD-based dynamic HDA m-MIMO outperforms the fixed subarray counterpart.

Future broadband satellite communication (SatCom) systems require a high throughput of data transmission, which calls for operation at higher frequency bands. Adaptive coding and modulation (ACM) technology has been considered as a means to obtain improved performance further at these frequencies. However, the ACM protocols in current DVB-S2 and DVB-S2(X) standards do not take the effects that arise from the non-linear link with memory into account, which is generated by the cascade of a high-power amplifier (HPA) and digital root raised cosine (RRC) filters. This paper first reveals the non-linear characteristics of the SatCom link, and transfers this into an equivalent full-linear link with an additive noise source thanks to the pre-distortion algorithm. Using this equivalent modeling, an approach of selecting/adapting the optimum coding, modulation scheme and associated system configurations for a given channel fading level is proposed. Both simulations and experimental test-bed performance are presented to validate the proposed method.