Low Complexity Algorithms for Mission Completion Time Minimization in UAV-Based ISAC Systems

The inherent support of sixth-generation (6G) systems enabling integrated sensing and communications (ISAC) paradigm greatly enhances the application area of intelligent transportation systems (ITS). One of the mission-critical applications enabled by these systems is disaster management, where ISAC functionality may not only provide localization but also provide users with supplementary information such as escape routes, time to rescue, etc. In this paper, by considering a large area with several locations of interest, we formulate and solve the optimization problem of delivering task parameters of the ISAC system by optimizing the UAV speed and the order of visits to the locations of interest such that the mission time is minimized. The formulated problem is a mixed integer non-linear program which is quite challenging to solve. To reduce the complexity of the solution algorithms, we propose two circular trajectory designs. The first algorithm finds the optimal UAV velocity and radius of the circular trajectories. The second algorithm finds the optimal connecting points for joining the individual circular trajectories. Our numerical results reveal that, with practical simulation parameters, the first algorithm provides a time saving of at least $20\%$, while the second algorithm cuts down the total completion time by at least $7$ times.

User Association and Multi-connectivity Strategies in Joint Terahertz and Millimeter Wave 6G Systems

Terahertz (THz) wireless access is considered as a next step towards sixth generation (6G) cellular systems. By utilizing even higher frequency bands than 5G millimeter wave (mmWave) New Radio (NR), they will operate over extreme bandwidth delivering unprecedented rates at the access interface. However, by relying upon pencil-wide beams, these systems will not only inherit mmWave propagation challenges such as blockage phenomenon but introduce their own issues associated with micromobility of user equipment (UE). In this paper, we analyze and compare user association schemes and multi-connectivity strategies for joint 6G THz/mmWave deployments. Differently, from stochastic geometry studies, we develop a unified analytically tractable framework that simultaneously accounts for specifics of THz and mmWave radio part design and traffic service specifics at mmWave and THz base stations (BS). Our results show that (i) for negligible blockers density, $\lambda_B\leq{}0.1$ bl./$m^2$, the operator needs to enlarge the coverage of THz BS by accepting sessions that experience outage in case of blockage (ii) for $\lambda_B>0.1$ bl./$m^2$, only those sessions that does not experience outage in case of blockage need to be accepted at THz BS, (iii) THz/mmWave multi-connectivity improves the ongoing session loss probability by $0.1-0.4$ depending on the system parameters.