10 research outputs found
Joint User Association and UAV Location Optimization for Two-Tired Visible Light Communication Networks
In this paper, an unmanned aerial vehicle (UAVs)-assisted visible light
communication (VLC) has been considered which has two tiers: UAV-to-centroid
and device-to-device (D2D). In the UAV-to-centroid tier, each UAV can
simultaneously provide communications and illumination for the centroids of the
ground users over VLC links. In the D2D tier, the centroids retransmit received
data from UAV over D2D links to the cluster members. For network, the
optimization problem of joint user association and deployment location of UAVs
is formulated to maximize the received data, satisfy illumination constraint,
and the user cluster size. An iterative algorithm is first proposed to
transform the optimization problem into a series of two interdependent sub
problems. Following the smallest enclosing disk theorem, a random incremental
construction method is designed to find the optimal UAV locations. Then,
inspired by unsupervised learning method, a clustering algorithm to find a
suboptimal user association is proposed. Our simulation results show that the
proposed scheme on average guarantees the users brightness 0.77 lux more than
their threshold requirements. Moreover, the received bitrate plus number of D2D
connected users under our proposed method is 50.69% more than the scenario in
which we have RF Link instead of VLC link and do not optimize UAV location.Comment: 7 pages, 5 figures, conferenc
Energy-Efficient Resource Allocation for Multi-IRS-Aided Indoor 6G Networks
In this paper, we propose a distributed intelligent reflecting surface (IRS)
assisted single-user and multi-user millimeter wave (mmWave) system. Then, we
formulate the resource allocation problem as an optimization to maximize energy
efficiency under individual quality of service (QoS) constraints. We first
propose a centralized algorithm, and further, a low-complexity distributed one
where the access point (AP) and IRSs independently adjust the transmit
beamforming of AP, the phase shifts, and the on-off status of IRSs in an
alternating manner until the convergence is reached. In a multi-user scenario,
in the first stage, the successive convex approximation (SCA) and fractional
programming (FP) approaches are applied to achieve a solution for optimization
subproblems of the phase-shift coefficients and element on-off status of IRSs.
Then, for the beamforming subproblem, a modified nested FP approach is proposed
that finds an optimal solution for the beamforming vectors of AP. Our
performance analysis on a practical scenario shows that the proposed
centralized and distributed approach respectively enhances the energy
efficiency by up to 55%, 42% for single-user, and up to 984% for multi-user
scenarios, in comparison to the case where the on-off status and phase-shift
coefficients of IRS elements are not selected optimally