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The 3GPP has standardized the 5G New Radio (NR) sidelink (SL) technology that enables direct device-to-device communications. SL will be key in realizing several high-speed, low-latency vehicle-to-everything (V2X) applications, such as automated driving. To meet these applications’ high data rate requirements, operating SL at mmWave and sub-THz frequencies will be essential. However, the current SL design primarily caters to sub-6 GHz frequencies and does not consider the directionality of transmissions at high frequencies. For Mode 2 of SL, where SL UEs perform sensing-based autonomous resource selection, this results in hidden node interference due to the transmit (Tx) UE’s inability to sense transmissions not aligned with the primary direction of communication. We propose paired transmission and sensing of sidelink control information (SCI), whereby SL Tx UEs transmit and receive SCI in an additional paired direction directly opposite to the primary direction. This helps eliminate hidden node interference while reducing the number of exposed nodes. Simulations in NR V2X highway deployments show that the paired scheme improves the average packet reception ratio (PRR) by 27% over the state-of-the-art at the highest traffic loads. We also propose enhanced transmit power control strategies to minimize interference between concurrent SL transmissions. This enables better resource reuse and further improves performance, with our combined solution achieving at least 95% average PRR in all scenarios. Finally, we present a stochastic geometry-based analytical model for a single-lane highway V2X network and validate it against simulation results. Our model provides insights into the reliability and capacity of high-frequency SL networks.

The high data rates required for next generation applications necessitate the use of millimeter wave and terahertz bands where bandwidth is abundant. Due to high path loss in these bands, antenna arrays (AAs) are needed to focus the signal in highly directional beams in the desired directions. However, highly directional communication links in these bands are vulnerable to misalignment and blockages due to mobility. Thus, both mobile blockers and user equipment (UE) rotations can significantly increase the handover (HO) frequency, while HO delays and HO failures jeopardize system latency and reliability. Furthermore, the scanning angle of each AA is limited by the orientation of the device, the mounting angle of the AA, the element spacing and the grating sidelobes formed during beamforming, which is referred as Field-of-View (FoV). In scenarios with UE rotational mobility, limited FoV may lead to loss of connection with the source next-generation NodeB (gNB). In this paper, we analyze current HO and radio link monitoring protocols in scenarios with UE rotational mobility and mobile blockers. We use a Markov Chain based analytical model as well as MATLAB based system level simulations to show how user rotation can significantly increase the outage duration under various deployment configurations. We propose enhancements to enable faster HO under user rotations and demonstrate significant performance improvements using simulations.

Abstract The recently introduced 5G New Radio is the first wireless standard natively designed to support critical and massive machine type communications (MTC). However, it is already becoming evident that some of the more demanding requirements for MTC cannot be fully supported by 5G networks. Alongside, emerging use cases and applications towards 2030 will give rise to new and more stringent requirements on wireless connectivity in general and MTC in particular. Next generation wireless networks, namely 6G, should therefore be an agile and efficient convergent network designed to meet the diverse and challenging requirements anticipated by 2030. This paper explores the main drivers and requirements of MTC towards 6G, and discusses a wide variety of enabling technologies. More specifically, we first explore the emerging key performance indicators for MTC in 6G. Thereafter, we present a vision for an MTC-optimized holistic end-to-end network architecture. Finally, key enablers towards (1) ultra-low power MTC, (2) massively scalable global connectivity, (3) critical and dependable MTC, and (4) security and privacy preserving schemes for MTC are detailed. Our main objective is to present a set of research directions considering different aspects for an MTC-optimized 6G network in the 2030-era.