311 research outputs found
Enhancing Physical Layer Security in AF Relay Assisted Multi-Carrier Wireless Transmission
In this paper, we study the physical layer security (PLS) problem in the dual
hop orthogonal frequency division multiplexing (OFDM) based wireless
communication system. First, we consider a single user single relay system and
study a joint power optimization problem at the source and relay subject to
individual power constraint at the two nodes. The aim is to maximize the end to
end secrecy rate with optimal power allocation over different sub-carriers.
Later, we consider a more general multi-user multi-relay scenario. Under high
SNR approximation for end to end secrecy rate, an optimization problem is
formulated to jointly optimize power allocation at the BS, the relay selection,
sub-carrier assignment to users and the power loading at each of the relaying
node. The target is to maximize the overall security of the system subject to
independent power budget limits at each transmitting node and the OFDMA based
exclusive sub-carrier allocation constraints. A joint optimization solution is
obtained through duality theory. Dual decomposition allows to exploit convex
optimization techniques to find the power loading at the source and relay
nodes. Further, an optimization for power loading at relaying nodes along with
relay selection and sub carrier assignment for the fixed power allocation at
the BS is also studied. Lastly, a sub-optimal scheme that explores joint power
allocation at all transmitting nodes for the fixed subcarrier allocation and
relay assignment is investigated. Finally, simulation results are presented to
validate the performance of the proposed schemes.Comment: 10 pages, 7 figures, accepted in Transactions on Emerging
Telecommunications Technologies (ETT), formerly known as European
Transactions on Telecommunications (ETT
A Comprehensive Survey of Potential Game Approaches to Wireless Networks
Potential games form a class of non-cooperative games where unilateral
improvement dynamics are guaranteed to converge in many practical cases. The
potential game approach has been applied to a wide range of wireless network
problems, particularly to a variety of channel assignment problems. In this
paper, the properties of potential games are introduced, and games in wireless
networks that have been proven to be potential games are comprehensively
discussed.Comment: 44 pages, 6 figures, to appear in IEICE Transactions on
Communications, vol. E98-B, no. 9, Sept. 201
Underlay Drone Cell for Temporary Events: Impact of Drone Height and Aerial Channel Environments
Providing seamless connection to a large number of devices is one of the
biggest challenges for the Internet of Things (IoT) networks. Using a drone as
an aerial base station (ABS) to provide coverage to devices or users on ground
is envisaged as a promising solution for IoT networks. In this paper, we
consider a communication network with an underlay ABS to provide coverage for a
temporary event, such as a sporting event or a concert in a stadium. Using
stochastic geometry, we propose a general analytical framework to compute the
uplink and downlink coverage probabilities for both the aerial and the
terrestrial cellular system. Our framework is valid for any aerial channel
model for which the probabilistic functions of line-of-sight (LOS) and
non-line-of-sight (NLOS) links are specified. The accuracy of the analytical
results is verified by Monte Carlo simulations considering two commonly adopted
aerial channel models. Our results show the non-trivial impact of the different
aerial channel environments (i.e., suburban, urban, dense urban and high-rise
urban) on the uplink and downlink coverage probabilities and provide design
guidelines for best ABS deployment height.Comment: This work is accepted to appear in IEEE Internet of Things Journal
Special Issue on UAV over IoT. Copyright may be transferred without notice,
after which this version may no longer be accessible. arXiv admin note: text
overlap with arXiv:1801.0594
GSAR: Greedy Stand-Alone Position-Based Routing protocol to avoid hole problem occurance in Mobile Ad Hoc Networks
The routing process in a Mobile Ad Hoc Network (MANET) poses critical challenges because of its features such as frequent topology changes and resource limitations. Hence, designing a reliable and dynamic routing protocol that satisfies MANET requirements is highly demanded. The Greedy Forwarding Strategy (GFS) has been the most used strategy in position-based routing protocols. The GFS algorithm was designed as a high-performance protocol that adopts hop count in soliciting shortest path. However, the GFS does not consider MANET needs and is therefore insufficient in computing reliable routes. Hence, this study aims to improve the existing GFS by transforming it into a dynamic stand-alone routing protocol that responds swiftly to MANET needs, and provides reliable routes among the communicating nodes. To
achieve the aim, two mechanisms were proposed as extensions to the current GFS, namely the Dynamic Beaconing Updates Mechanism (DBUM) and the Dynamic and Reactive Reliability Estimation with Selective Metrics Mechanism (DRESM). The
DBUM algorithm is mainly responsible for providing a node with up-to-date status
information about its neighbours. The DRESM algorithm is responsible for making forwarding decisions based on multiple routing metrics. Both mechanisms were integrated into the conventional GFS to form Greedy Stand-Alone Routing (GSAR) protocol. Evaluations of GSAR were performed using network simulator Ns2 based upon a defined set of performance metrics, scenarios and topologies. The results demonstrate that GSAR eliminates recovery mode mechanism in GFS and consequently improve overall network performance. Under various mobility conditions, GSAR avoids hole problem by about 87% and 79% over Greedy Perimeter Stateless Routing and Position-based Opportunistic Routing Protocol respectively. Therefore, the GSAR protocol is a reasonable alternative to position-based unicast routing protocol in MANET
ViLDAR - Visible Light Sensing Based Speed Estimation using Vehicle's Headlamps
The introduction of light emitting diodes (LED) in automotive exterior
lighting systems provides opportunities to develop viable alternatives to
conventional communication and sensing technologies. Most of the advanced
driver-assist and autonomous vehicle technologies are based on Radio Detection
and Ranging (RADAR) or Light Detection and Ranging (LiDAR) systems that use
radio frequency or laser signals, respectively. While reliable and real-time
information on vehicle speeds is critical for traffic operations management and
autonomous vehicles safety, RADAR or LiDAR systems have some deficiencies
especially in curved road scenarios where the incidence angle is rapidly
varying. In this paper, we propose a novel speed estimation system so-called
the Visible Light Detection and Ranging (ViLDAR) that builds upon sensing
visible light variation of the vehicle's headlamp. We determine the accuracy of
the proposed speed estimator in straight and curved road scenarios. We further
present how the algorithm design parameters and the channel noise level affect
the speed estimation accuracy. For wide incidence angles, the simulation
results show that the ViLDAR outperforms RADAR/LiDAR systems in both straight
and curved road scenarios. A provisional patent (US#62/541,913) has been
obtained for this work
Optimal finite horizon sensing for wirelessly powered devices
We are witnessing a significant advancements in the sensor technologies which has enabled a broad spectrum of applications. Often, the resolution of the produced data by the sensors significantly affects the output quality of an application. We study a sensing resolution optimization problem for a wireless powered device (WPD) that is powered by wireless power transfer (WPT) from an access point (AP). We study a class of harvest-first-transmit-later type of WPT policy, where an access point (AP) first employs RF power to recharge the WPD in the down-link, and then, collects the data from the WPD in the up-link. The WPD optimizes the sensing resolution, WPT duration and dynamic power control in the up-link to maximize an application dependant utility at the AP. The utility of a transmitted packet is only achieved if the data is delivered successfully within a finite time. Thus, we first study a finite horizon throughput maximization problem by jointly optimizing the WPT duration and power control. We prove that the optimal WPT duration obeys a time-dependent threshold form depending on the energy state of the WPD. In the subsequent data transmission stage, the optimal transmit power allocations for the WPD is shown to posses a channel-dependent fractional structure. Then, we optimize the sensing resolution of the WPD by using a Bayesian inference based multi armed bandit problem with fast convergence property to strike a balance between the quality of the sensed data and the probability of successfully delivering it
Energy Efficiency and Sum Rate when Massive MIMO meets Device-to-Device Communication
This paper considers a scenario of short-range communication, known as
device-to-device (D2D) communication, where D2D users reuse the downlink
resources of a cellular network to transmit directly to their corresponding
receivers. In addition, multiple antennas at the base station (BS) are used in
order to simultaneously support multiple cellular users using multiuser or
massive MIMO. The network model considers a fixed number of cellular users and
that D2D users are distributed according to a homogeneous Poisson point process
(PPP). Two metrics are studied, namely, average sum rate (ASR) and energy
efficiency (EE). We derive tractable expressions and study the tradeoffs
between the ASR and EE as functions of the number of BS antennas and density of
D2D users for a given coverage area.Comment: 6 pages, 7 figures, to be presented at the IEEE International
Conference on Communications (ICC) Workshop on Device-to-Device Communication
for Cellular and Wireless Networks, London, UK, June 201
Big Data Meets Telcos: A Proactive Caching Perspective
Mobile cellular networks are becoming increasingly complex to manage while
classical deployment/optimization techniques and current solutions (i.e., cell
densification, acquiring more spectrum, etc.) are cost-ineffective and thus
seen as stopgaps. This calls for development of novel approaches that leverage
recent advances in storage/memory, context-awareness, edge/cloud computing, and
falls into framework of big data. However, the big data by itself is yet
another complex phenomena to handle and comes with its notorious 4V: velocity,
voracity, volume and variety. In this work, we address these issues in
optimization of 5G wireless networks via the notion of proactive caching at the
base stations. In particular, we investigate the gains of proactive caching in
terms of backhaul offloadings and request satisfactions, while tackling the
large-amount of available data for content popularity estimation. In order to
estimate the content popularity, we first collect users' mobile traffic data
from a Turkish telecom operator from several base stations in hours of time
interval. Then, an analysis is carried out locally on a big data platform and
the gains of proactive caching at the base stations are investigated via
numerical simulations. It turns out that several gains are possible depending
on the level of available information and storage size. For instance, with 10%
of content ratings and 15.4 Gbyte of storage size (87% of total catalog size),
proactive caching achieves 100% of request satisfaction and offloads 98% of the
backhaul when considering 16 base stations.Comment: 8 pages, 5 figure
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