14 research outputs found
Mobile Edge Computing via a UAV-Mounted Cloudlet: Optimization of Bit Allocation and Path Planning
Unmanned Aerial Vehicles (UAVs) have been recently considered as means to
provide enhanced coverage or relaying services to mobile users (MUs) in
wireless systems with limited or no infrastructure. In this paper, a UAV-based
mobile cloud computing system is studied in which a moving UAV is endowed with
computing capabilities to offer computation offloading opportunities to MUs
with limited local processing capabilities. The system aims at minimizing the
total mobile energy consumption while satisfying quality of service
requirements of the offloaded mobile application. Offloading is enabled by
uplink and downlink communications between the mobile devices and the UAV that
take place by means of frequency division duplex (FDD) via orthogonal or
non-orthogonal multiple access (NOMA) schemes. The problem of jointly
optimizing the bit allocation for uplink and downlink communication as well as
for computing at the UAV, along with the cloudlet's trajectory under latency
and UAV's energy budget constraints is formulated and addressed by leveraging
successive convex approximation (SCA) strategies. Numerical results demonstrate
the significant energy savings that can be accrued by means of the proposed
joint optimization of bit allocation and cloudlet's trajectory as compared to
local mobile execution as well as to partial optimization approaches that
design only the bit allocation or the cloudlet's trajectory.Comment: 14 pages, 5 figures, 2 tables, IEEE Transactions on Vehicular
Technolog
Optimization of Massive Full-Dimensional MIMO for Positioning and Communication
Massive Full-Dimensional multiple-input multiple-output (FD-MIMO) base
stations (BSs) have the potential to bring multiplexing and coverage gains by
means of three-dimensional (3D) beamforming. Key technical challenges for their
deployment include the presence of limited-resolution front ends and the
acquisition of channel state information (CSI) at the BSs. This paper
investigates the use of FD-MIMO BSs to provide simultaneously high-rate data
communication and mobile 3D positioning in the downlink. The analysis
concentrates on the problem of beamforming design by accounting for imperfect
CSI acquisition via Time Division Duplex (TDD)-based training and for the
finite resolution of analog-to-digital converter (ADC) and digital-to-analog
converter (DAC) at the BSs. Both \textit{unstructured beamforming} and a
low-complexity \textit{Kronecker beamforming} solution are considered, where
for the latter the beamforming vectors are decomposed into separate azimuth and
elevation components. The proposed algorithmic solutions are based on Bussgang
theorem, rank-relaxation and successive convex approximation (SCA) methods.
Comprehensive numerical results demonstrate that the proposed schemes can
effectively cater to both data communication and positioning services,
providing only minor performance degradations as compared to the more
conventional cases in which either function is implemented. Moreover, the
proposed low-complexity Kronecker beamforming solutions are seen to guarantee a
limited performance loss in the presence of a large number of BS antennas.Comment: 30 pages, 6 figure
Beamforming Design for Joint Localization and Data Transmission in Distributed Antenna System
A distributed antenna system is studied whose goal is to provide data
communication and positioning functionalities to Mobile Stations (MSs). Each MS
receives data from a number of Base Stations (BSs), and uses the received
signal not only to extract the information but also to determine its location.
This is done based on Time of Arrival (TOA) or Time Difference of Arrival
(TDOA) measurements, depending on the assumed synchronization conditions. The
problem of minimizing the overall power expenditure of the BSs under data
throughput and localization accuracy requirements is formulated with respect to
the beamforming vectors used at the BSs. The analysis covers both
frequency-flat and frequency-selective channels, and accounts also for
robustness constraints in the presence of parameter uncertainty. The proposed
algorithmic solutions are based on rank-relaxation and Difference-of-Convex
(DC) programming.Comment: 15 pages, 9 figures, and 1 table, accepted in IEEE Transactions on
Vehicular Technolog
Collaborative Cloud and Edge Mobile Computing in C-RAN Systems with Minimal End-to-End Latency
Mobile cloud and edge computing protocols make it possible to offer
computationally heavy applications to mobile devices via computational
offloading from devices to nearby edge servers or more powerful, but remote,
cloud servers. Previous work assumed that computational tasks can be
fractionally offloaded at both cloud processor (CP) and at a local edge node
(EN) within a conventional Distributed Radio Access Network (D-RAN) that relies
on non-cooperative ENs equipped with one-way uplink fronthaul connection to the
cloud. In this paper, we propose to integrate collaborative fractional
computing across CP and ENs within a Cloud RAN (C-RAN) architecture with
finite-capacity two-way fronthaul links. Accordingly, tasks offloaded by a
mobile device can be partially carried out at an EN and the CP, with multiple
ENs communicating with a common CP to exchange data and computational outcomes
while allowing for centralized precoding and decoding. Unlike prior work, we
investigate joint optimization of computing and communication resources,
including wireless and fronthaul segments, to minimize the end-to-end latency
by accounting for a two-way uplink and downlink transmission. The problem is
tackled by using fractional programming (FP) and matrix FP. Extensive numerical
results validate the performance gain of the proposed architecture as compared
to the previously studied D-RAN solution.Comment: accepted for publication on IEEE Transactions on Signal and
Information Processing over Network