Effects of 2.4 GHz radiofrequency electromagnetic field (RF-EMF) on glioblastoma cells (U -118 MG).

INTRODUCTION AND OBJECTIVE: Mobile phones and Wi-Fi are the most commonly used forms of telecommunications. Initiated with the first generation, the mobile telephony is currently in its fifth generation without being screened extensively for any biological effects that it may have on humans or on animals. Some studies indicate that high frequency electromagnetic radiation emitted by mobile phone and Wi-Fi connection can have a negative effect upon human health, and can cause cancer, including brain tumour. OBJECTIVE: The aim of the study was to investigate the influence of 2.4 GHz radiofrequency electromagnetic field (RF-EMF) on the proliferation and morphology of normal (human embryonic kidney cell line Hek-293) and cancer cells (glioblastoma cell line U-118 MG). MATERIAL AND METHODS: The cell cultures were incubated in RF-EMF at the frequency of 2.4 GHz, with or without dielectric screen, for 24, 48 and 72h. In order to analyse the influence of the electromagnetic field on cell lines, Cytotoxicity test Cell Counting Kit-8 was performed. To protect cells against emission of the electromagnetic field, a dielectric screen was used. RESULTS: It was found that 2.4 GHz RF electromagnetic field exposure caused a significant decrease in viability of U-118 MG and Hek-293 cells. The impact of the electromagnetic field was strongest in the case of cancer cells, and the decrease in their survival was much greater compared to the healthy (normal) cells of the Hek-293 line. CONCLUSIONS: Results of the study indicate that using a radio frequency electromagnetic field (2.4 GHz) has a clearly negative effect on the metabolic activity of glioblastoma cells. RF-EMF has much less impact on reducing the viability of normal cells (Hek -293) than cancer cells.

Modeling of Downlink Interference in Massive MIMO 5G Macro-Cell.

Multi-beam antenna systems are the basic technology used in developing fifth-generation (5G) mobile communication systems. In practical implementations of 5G networks, different approaches are used to enable a massive multiple-input-multiple-output (mMIMO) technique, including a grid of beams, zero-forcing, or eigen-based beamforming. All of these methods aim to ensure sufficient angular separation between multiple beams that serve different users. Therefore, ensuring the accurate performance evaluation of a realistic 5G network is essential. It is particularly crucial from the perspective of mMIMO implementation feasibility in given radio channel conditions at the stage of network planning and optimization before commercial deployment begins. This paper presents a novel approach to assessing the impact of a multi-beam antenna system on an intra-cell interference level in a downlink, which is important for the accurate modeling and efficient usage of mMIMO in 5G cells. The presented analysis is based on geometric channel models that allow the trajectories of propagation paths to be mapped and, as a result, the angular power distribution of received signals. A multi-elliptical propagation model (MPM) is used and compared with simulation results obtained for a statistical channel model developed by the 3rd Generation Partnership Project (3GPP). Transmission characteristics of propagation environments such as power delay profile and antenna beam patterns define the geometric structure of the MPM. These characteristics were adopted based on the 3GPP standard. The obtained results show the possibility of using the presented novel MPM-based approach to model the required minimum separation angle between co-channel beams under line-of-sight (LOS) and non-LOS conditions, which allows mMIMO performance in 5G cells to be assessed. This statement is justified because for 80% of simulated samples of intra-cell signal-to-interference ratio (SIR), the difference between results obtained by the MPM and commonly used 3GPP channel model was within 2 dB or less for LOS conditions. Additionally, the MPM only needs a single instance of simulation, whereas the 3GPP channel model requires a time-consuming and computational power-consuming Monte Carlo simulation method. Simulation results of intra-cell SIR obtained this way by the MPM approach can be the basis for spectral efficiency maximization in mMIMO cells in 5G systems.

Inter-Beam Co-Channel Downlink and Uplink Interference for 5G New Radio in mm-Wave Bands.

This paper presents a methodology for assessing co-channel interference that arises in multi-beam transmitting and receiving antennas used in fifth-generation (5G) systems. This evaluation is essential for minimizing spectral resources, which allows for using the same frequency bands in angularly separated antenna beams of a 5G-based station (gNodeB). In the developed methodology, a multi-ellipsoidal propagation model (MPM) provides a mapping of the multipath propagation phenomenon and considers the directivity of antenna beams. To demonstrate the designation procedure of interference level we use simulation tests. For exemplary scenarios in downlink and uplink, we showed changes in a signal-to-interference ratio versus a separation angle between the serving (useful) and interfering beams and the distance between the gNodeB and user equipment. This evaluation is the basis for determining the minimum separation angle for which an acceptable interference level is ensured. The analysis was carried out for the lower millimeter-wave band, which is planned to use in 5G micro-cells base stations.