The effects of the presence of the user on multiple-input-multiple-output (MIMO) performance for wireless communications systems is investigated through measurements in a reverberation chamber. Measured results have demonstrated that despite a decrement on the envelope correlation coefficient, a degradation of both diversity gain and MIMO capacity are expected when the user is present. While the validity of the correlation coefficients for predicting MIMO performance is limited in the presence of the user, the effects have also been found to be strongly dependent upon frequency, antenna topology, and user characteristics.

Several standards exist for testing the radiated “over the air” (OTA) performance of 5G User Equipment (UE) devices. All these standards are limited to a Single-Input Single-Output (SISO) evaluation of the 5G device. With 5G networks and devices already deployed and in operation, it becomes necessary to develop realistic Multiple-Input Multiple-Output (MIMO) and beamforming performance metrics for 5G UEs. Since the most important feature of 5G is beamforming, this paper reviews the main challenges to realistically evaluate 5G device performance and proposes several novel key performance indicators (KPIs). The results obtained by some measurements show that it is possible to derive figures of merit that address the complexity of beamforming and MIMO-based 5G performance of devices in a much better way compared with the existing SISO KPIs, and that academia should provide advanced future research on these more realistic KPIs for the industry to face the challenges ahead with a better analysis of the problem in hand.

Dual-band handsets are underway to become an industry standard for mobile communication terminals. Integrated antennas have a promising future when dealing with these dual-band mobile handsets, since size and price requirements favour the use of planar antennas, such as the PIFA. In this paper, a novel dual-band antenna is presented, featuring the use of a spur-line filter to obtain the dual-frequency operation. The influence of diverse design parameters, such as the terminal size and the position of the battery, are also investigated.

In this article, we provide concluding evidence that the human head skull acts as a first dynamic barrier to excessive electromagnetic fields (EMFs) and temperature flow at 1800 MHz. This natural barrier is designed to effectively and dynamically protect brain tissue against safety-defined threshold temperature increases due to external EMF induction. A half-wavelength dipole antenna has been employed as the EMF source. The human head is modeled by several coronal planes extracted from the Visible Human Project and combined to the exposure of a 0.45λ-apart dipole and to heat transfer equations to accommodate for the human thermoregulatory response. The results described in this study are of great importance regarding whether thermal effects should be directly used to derive basic restrictions to EM field safety limits for human exposure. Since this study is limited to conditions under vasomotor adjustment, very excessive EMF induction may break this first natural barrier and produce excessive thermal stress, making the barrier incapable of maintaining thermal conditions on the human brain under control. This study is also limited to using a frequency of 1800 MHz.