7,920 research outputs found
Design of a Cognitive VLC Network with Illumination and Handover Requirements
In this paper, we consider a cognitive indoor visible light communications
(VLC) system, comprised of multiple access points serving primary and secondary
users through the orthogonal frequency division multiple access method. A
cognitive lighting cell is divided into two non-overlapping regions that
distinguish the primary and secondary users based on the region they are
located in. Under the assumption of equal-power allocation among subcarriers,
each region is defined in terms of its physical area and the number of
allocated subcarriers within that region. In this paper, we provide the
lighting cell design with cognitive constraints that guarantee fulfilling
certain illumination, user mobility, and handover requirements in each cell. We
further argue that, under some conditions, a careful assignment of the
subcarriers in each region can mitigate the co-channel interference in the
overlapping areas of adjacent cells. Numerical results depict the influence of
different system parameters, such as user density, on defining both regions.
Finally, a realistic example is implemented to assess the performance of the
proposed scheme via Monte Carlo simulations
Applications of Soft Computing in Mobile and Wireless Communications
Soft computing is a synergistic combination of artificial intelligence methodologies to model and solve real world problems that are either impossible or too difficult to model mathematically. Furthermore, the use of conventional modeling techniques demands rigor, precision and certainty, which carry computational cost. On the other hand, soft computing utilizes computation, reasoning and inference to reduce computational cost by exploiting tolerance for imprecision, uncertainty, partial truth and approximation. In addition to computational cost savings, soft computing is an excellent platform for autonomic computing, owing to its roots in artificial intelligence. Wireless communication networks are associated with much uncertainty and imprecision due to a number of stochastic processes such as escalating number of access points, constantly changing propagation channels, sudden variations in network load and random mobility of users. This reality has fuelled numerous applications of soft computing techniques in mobile and wireless communications. This paper reviews various applications of the core soft computing methodologies in mobile and wireless communications
Optimizing Number, Placement, and Backhaul Connectivity of Multi-UAV Networks
Multi-Unmanned Aerial Vehicle (UAV) Networks is a promising solution to
providing wireless coverage to ground users in challenging rural areas (such as
Internet of Things (IoT) devices in farmlands), where the traditional cellular
networks are sparse or unavailable. A key challenge in such networks is the 3D
placement of all UAV base stations such that the formed Multi-UAV Network (i)
utilizes a minimum number of UAVs while ensuring -- (ii) backhaul connectivity
directly (or via other UAVs) to the nearby terrestrial base station, and (iii)
wireless coverage to all ground users in the area of operation. This joint
Backhaul-and-coverage-aware Drone Deployment (BoaRD) problem is largely
unaddressed in the literature, and, thus, is the focus of the paper. We first
formulate the BoaRD problem as Integer Linear Programming (ILP). However, the
problem is NP-hard, and therefore, we propose a low complexity algorithm with a
provable performance guarantee to solve the problem efficiently. Our simulation
study shows that the Proposed algorithm performs very close to that of the
Optimal algorithm (solved using ILP solver) for smaller scenarios, where the
area size and the number of users are relatively small. For larger scenarios,
where the area size and the number of users are relatively large, the proposed
algorithm greatly outperforms the baseline approaches -- backhaul-aware greedy
and random algorithm, respectively by up to 17% and 95% in utilizing fewer UAVs
while ensuring 100% ground user coverage and backhaul connectivity for all
deployed UAVs across all considered simulation setting.Comment: To appear in IEEE Internet of Things Journa
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