Thanks to their potentials in providing reliable communications for a large number of devices, 5G non-orthogonal multiple access (NOMA) techniques have recently been the subject of considerable research interest. Accordingly, research of Physical Layer Security approaches in NOMA is essential. A primary purpose and challenge for security at the physical level of NOMA-based systems is to protect the information transmitted against both external and internal eavesdropping attacks. To this end, it is necessary to develop PLS schemes which allow each user to decode the signals transmitted by other users, thus guaranteeing normal operation of the successive interference cancellation, while also providing privacy of the information exchange. In this paper, different types of eavesdropping are studied and a summary of existing approaches to improve security at the physical layer in 5G NOMA networks is provided.

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The 6G communication networks and technologies have to enable the development of wide variety of low latency and ultra-reliable services. Furthermore, the 6G is foreseen to be the era of new devices which integrate our natural human senses in order to create a fully new concept of human-machine interactions. The eXtended Reality (XR) based wearables will surely improve the way we collaborate with modern technologies by merging the real and virtual world in one innovative continuum in order to expand the possibilities of using and interacting with different types of modern or already well-known IT services. In this context, a vital 6G research area is the design of different flexible quality assessment metrics, targets and measures that integrate human perceptions and physical factors from human physiology. This metric design should consider the multisensory nature of XR devices by incorporation of different objective network-related as well as strongly subjective human-related features like sight, touch, smell, taste, body physiology, psychological traits, gestures and even sixth sense. In this paper a conceptual framework incorporating a mixture of new and classical quality assessment constructs like Quality of Service (QoS) and Quality of Experience (QoE) is proposed for 6G networks from human-centric point of view. It considers the development of new types of intelligent XR technologies and give an insight in regard to overall human experience assessment, modelling and prediction.

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