464 research outputs found
Reinforcement Learning for Resource Allocation in Steerable Laser-based Optical Wireless Systems
Vertical Cavity Surface Emitting Lasers (VCSELs) have demonstrated
suitability for data transmission in indoor optical wireless communication
(OWC) systems due to the high modulation bandwidth and low manufacturing cost
of these sources. Specifically, resource allocation is one of the major
challenges that can affect the performance of multi-user optical wireless
systems. In this paper, an optimisation problem is formulated to optimally
assign each user to an optical access point (AP) composed of multiple VCSELs
within a VCSEL array at a certain time to maximise the signal to interference
plus noise ratio (SINR). In this context, a mixed-integer linear programming
(MILP) model is introduced to solve this optimisation problem. Despite the
optimality of the MILP model, it is considered impractical due to its high
complexity, high memory and full system information requirements. Therefore,
reinforcement Learning (RL) is considered, which recently has been widely
investigated as a practical solution for various optimization problems in
cellular networks due to its ability to interact with environments with no
previous experience. In particular, a Q-learning (QL) algorithm is investigated
to perform resource management in a steerable VCSEL-based OWC systems. The
results demonstrate the ability of the QL algorithm to achieve optimal
solutions close to the MILP model. Moreover, the adoption of beam steering,
using holograms implemented by exploiting liquid crystal devices, results in
further enhancement in the performance of the network considered
Introduction to indoor networking concepts and challenges in LiFi
LiFi is networked, bidirectional wireless communication with light. It is used to connect fixed and mobile devices at very high data rates by harnessing the visible light and infrared spectrum. Combined, these spectral resources are 2600 times larger than the entire radio frequency (RF) spectrum. This paper provides the motivation behind why LiFi is a very timely technology, especially for 6th generation (6G) cellular communications. It discusses and reviews essential networking technologies, such as interference mitigation and hybrid LiFi/Wi-Fi networking topologies. We also consider the seamless integration of LiFi into existing wireless networks to form heterogeneous networks across the optical and RF domains and discuss implications and solutions in terms of load balancing. Finally, we provide the results of a real-world hybrid LiFi/Wi-Fi network deployment in a software defined networking testbed. In addition, results from a LiFi deployment in a school classroom are provided, which show that Wi-Fi network performance can be improved significantly by offloading traffic to the LiFi
Dynamic mmWave Channel Emulation in a Cost-Effective MPAC with Dominant-Cluster Concept
Millimeter-Wave (mmWave) massive multiple-input multiple-output (MIMO) has
been considered as a key enabler for the fifth-generation (5G) communications.
It is essential to design and test mmWave 5G devices under various realistic
scenarios, since the radio propagation channels pose intrinsic limitations on
the performance. This requires emulating realistic dynamic mmWave channels in a
reproducible manner in laboratories, which is the goal of this paper. In this
contribution, we firstly illustrate the dominant-cluster(s) concept, where the
non-dominant clusters in the mmWave channels are pruned, for mmWave 5G devices
applying massive MIMO beamforming. This demonstrates the importance and
necessity to accurately emulate the mmWave channels at a cluster level rather
than the composite-channel level. Thus, an over-the-air (OTA) emulation
strategy for dynamic mmWave channels is proposed based on the concept of
dominant-cluster(s) in a sectored multiprobe anechoic chamber (SMPAC). The key
design parameters including the probe number and the angular spacing of probes
are investigated through comprehensive simulations. A cost-effective
switchcircuit is also designed for this purpose and validated in the
simulation. Furthermore, a dynamic mmWave channel measured in an indoor
scenario at 28-30 GHz is presented, where the proposed emulation strategy is
also validated by reproducing the measured reality.Comment: Accepted by IEEE Transactions on Antennas and Propagatio
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