514,604 research outputs found
Interference Characterization in Multiple Access Wireless Networks
Contrarily to the point to point wireless link approach adopted in several wireless networks, where
a dedicated channel is usually supporting an exclusive-use wireless link, in the last years several
wireless communication systems have followed a different approach. In the so called “multiple
access wireless networks”, multiple transmitters share the same communication channel in a
simultaneous way, supporting a shared-use of the wireless link. The deployment of multiple access
networks has also originated the emergence of various communication networks operating in the
same geographical area and spectrum space, which is usually referred to as wireless coexistence.
As a consequence of the presence of multiple networks with different technologies that share the
same spectral bands, robust methods of interference management are needed. At the same time,
the adoption of in-band Full-duplex (IBFDX) communication schemes, in which a given node
transmit and receive simultaneously over the same frequency band, is seen as a disruptive topic in
multiple access networks, capable of doubling the network’s capacity.
Motivated by the importance of the interference in multiple access networks, this thesis addresses
new approaches to characterize the interference in multiple access networks. A special
focus is given to the assumption of mobility for the multiple transmitters. The problem of coexistence
interference caused by multiple networks operating in the same band is also considered.
Moreover, given the importance of the residual self-interference (SI) in practical IBFDX multiple
access networks, we study the distribution of the residual SI power in a wireless IBFDX
communication system. In addition, different applications of the proposed interference models
are presented, including the definition of a new sensing capacity metric for cognitive radio networks,
the performance evaluation of wireless-powered coexisting networks, the computation of
an optimal carrier-sensing range in coexisting CSMA networks, and the estimation of residual
self-interference in IBFDX communication systems
Interference Management in Heterogeneous Networks with Blind Transmitters
Future multi-tier communication networks will require enhanced network
capacity and reduced overhead. In the absence of Channel State Information
(CSI) at the transmitters, Blind Interference Alignment (BIA) and Topological
Interference Management (TIM) can achieve optimal Degrees of Freedom (DoF),
minimising network's overhead. In addition, Non-Orthogonal Multiple Access
(NOMA) can increase the sum rate of the network, compared to orthogonal radio
access techniques currently adopted by 4G networks. Our contribution is two
interference management schemes, BIA and a hybrid TIM-NOMA scheme, employed in
heterogeneous networks by applying user-pairing and Kronecker Product
representation. BIA manages inter- and intra-cell interference by antenna
selection and appropriate message scheduling. The hybrid scheme manages
intra-cell interference based on NOMA and inter-cell interference based on TIM.
We show that both schemes achieve at least double the rate of TDMA. The hybrid
scheme always outperforms TDMA and BIA in terms of Degrees of Freedom (DoF).
Comparing the two proposed schemes, BIA achieves more DoF than TDMA under
certain restrictions, and provides better Bit-Error-Rate (BER) and sum rate
performance to macrocell users, whereas the hybrid scheme improves the
performance of femtocell users.Comment: 30 pages, 18 figure
Multiradio Resource Management: Parallel Transmission for Higher Throughput?
Mobile communication systems beyond the third generation will see the interconnection of heterogeneous radio access networks (UMTS, WiMax, wireless local area networks, etc.) in order to always provide the best quality of service (QoS) to users with multimode terminals. This scenario poses a number of critical issues, which have to be faced in order to get the best from the integrated access network. In this paper, we will investigate the issue of parallel transmission over multiple radio access technologies (RATs), focusing the attention on the QoS perceived by final users. We will show that the achievement of a real benefit from parallel transmission over multiple RATs is conditioned to the fulfilment of some requirements related to the kind of RATs, the multiradio resource management (MRRM) strategy, and the transport-level protocol behaviour. All these aspects will be carefully considered in our investigation, which will be carried out partly adopting an analytical approach and partly by means of simulations. In this paper, in particular, we will propose a simple but effective MRRM algorithm, whose performance will be investigated in IEEE802.11a-UMTS and IEEE802.11a-IEEE802.16e heterogeneous networks (adopted as case studies)
Optimal Orchestration of Virtual Network Functions
-The emergence of Network Functions Virtualization (NFV) is bringing a set of
novel algorithmic challenges in the operation of communication networks. NFV
introduces volatility in the management of network functions, which can be
dynamically orchestrated, i.e., placed, resized, etc. Virtual Network Functions
(VNFs) can belong to VNF chains, where nodes in a chain can serve multiple
demands coming from the network edges. In this paper, we formally define the
VNF placement and routing (VNF-PR) problem, proposing a versatile linear
programming formulation that is able to accommodate specific features and
constraints of NFV infrastructures, and that is substantially different from
existing virtual network embedding formulations in the state of the art. We
also design a math-heuristic able to scale with multiple objectives and large
instances. By extensive simulations, we draw conclusions on the trade-off
achievable between classical traffic engineering (TE) and NFV infrastructure
efficiency goals, evaluating both Internet access and Virtual Private Network
(VPN) demands. We do also quantitatively compare the performance of our VNF-PR
heuristic with the classical Virtual Network Embedding (VNE) approach proposed
for NFV orchestration, showing the computational differences, and how our
approach can provide a more stable and closer-to-optimum solution
Efficient radio resource management in next generation wireless networks
The current decade has witnessed a phenomenal growth in mobile wireless communication
networks and subscribers. In 2015, mobile wireless devices and connections were reported to have grown to about 7.9 billion, exceeding human
population. The explosive growth in mobile wireless communication network subscribers has created a huge demand for wireless network capacity,
ubiquitous wireless network coverage, and enhanced Quality of Service (QoS). These demands have led to several challenging problems for wireless
communication networks operators and designers. The Next Generation Wireless Networks (NGWNs) will support high mobility communications, such as
communication in high-speed rails. Mobile users in such high mobility environment demand reliable QoS, however, such users are plagued with a
poor signal-tonoise ratio, due to the high vehicular penetration loss, increased transmission outage and handover information overhead, leading
to poor QoS provisioning for the networks' mobile users. Providing a reliable QoS for high mobility users remains one of the unique challenges
for NGWNs. The increased wireless network capacity and coverage of NGWNs means that mobile communication users at the cell-edge should have
enhanced network performance. However, due to path loss (path attenuation), interference, and radio background noise, mobile communication
users at the cell-edge can experience relatively poor transmission channel qualities and subsequently forced to transmit at a low bit transmission
rate, even when the wireless communication networks can support high bit transmission rate. Furthermore, the NGWNs are envisioned to be Heterogeneous
Wireless Networks (HWNs). The NGWNs are going to be the integration platform of diverse homogeneous wireless communication networks for a convergent
wireless communication network. The HWNs support single and multiple calls (group calls), simultaneously. Decision making is an integral core of radio
resource management. One crucial decision making in HWNs is network selection. Network selection addresses the problem of how to select the best
available access network for a given network user connection. For the integrated platform of HWNs to be truly seamless and
efficient, a robust and stable wireless access network selection algorithm is needed. To meet these challenges for the
different mobile wireless communication network users, the NGWNs will have to provide a great leap in wireless network capacity, coverage,
QoS, and radio resource utilization. Moving wireless communication networks (mobile hotspots) have been proposed as a solution to providing
reliable QoS to high mobility users. In this thesis, an Adaptive Thinning Mobility Aware (ATMA) Call Admission Control (CAC) algorithm for
improving the QoS and radio resource utilization of the mobile hotspot networks, which are of critical importance for communicating nodes
in moving wireless networks is proposed. The performance of proposed ATMA CAC scheme is investigated and compare it with the traditional
CAC scheme. The ATMA scheme exploits the mobility events in the highspeed mobility communication environment and the calls (new and
handoff calls) generation pattern to enhance the QoS (new call blocking and
handoff call dropping probabilities) of the mobile users. The numbers of new and
handoff calls in wireless communication networks are dynamic random processes that can be
effectively modeled by the Continuous Furthermore, the NGWNs are envisioned to be Heterogeneous Wireless Networks (HWNs).
The NGWNs are going to be the integration platform of diverse homogeneous wireless communication networks for a convergent
wireless communication network. The HWNs support single and multiple calls (group calls), simultaneously. Decision making is an
integral core of radio resource management. One crucial decision making in HWNs is network selection. Network selection addresses
the problem of how to select the best available access network for a given network user connection. For the integrated platform of
HWNs to be truly seamless and efficient, a robust and stable wireless access network selection algorithm is needed. To meet these
challenges for the different mobile wireless communication network users, the NGWNs will have to provide a great leap in wireless
network capacity, coverage, QoS, and radio resource utilization. Moving wireless communication networks (mobile hotspots) have been
proposed as a solution to providing reliable QoS to high mobility users. In this thesis, an Adaptive Thinning Mobility Aware (ATMA)
Call Admission Control (CAC) algorithm for improving the QoS and radio resource utilization of the mobile hotspot networks, which are
of critical importance for communicating nodes in moving wireless networks is proposed
Quality-Oriented Mobility Management for Multimedia Content Delivery to Mobile Users
The heterogeneous wireless networking environment determined by the latest developments in wireless access technologies promises a high level of communication resources for mobile
computational devices. Although the communication resources provided, especially referring to bandwidth, enable multimedia streaming to mobile users, maintaining a high user perceived quality is still a challenging task. The main factors which affect quality in multimedia streaming over wireless networks are mainly the error-prone nature of the wireless channels and the user mobility. These factors determine a high level of dynamics of wireless communication resources, namely variations in throughput and packet loss as well as network availability and delays in delivering the data packets. Under these conditions maintaining a high level of quality, as perceived by the user, requires a quality oriented mobility management scheme. Consequently we propose the Smooth Adaptive Soft-Handover Algorithm, a novel quality oriented handover management scheme which unlike other similar solutions, smoothly transfer the data traffic from one network to another using multiple simultaneous connections. To estimate the capacity of each connection the novel Quality of Multimedia Streaming (QMS) metric is proposed. The QMS metric aims at offering maximum flexibility and efficiency allowing the applications to fine tune the behavior of the handover algorithm. The current simulation-based performance evaluation clearly shows the better
performance of the proposed Smooth Adaptive Soft-Handover Algorithm as compared with other handover solutions. The evaluation was performed in various scenarios including
multiple mobile hosts performing handover simultaneously, wireless networks with variable overlapping areas, and various network congestion levels
Network Management, Optimization and Security with Machine Learning Applications in Wireless Networks
Wireless communication networks are emerging fast with a lot of challenges and ambitions. Requirements that are expected to be delivered by modern wireless networks are complex, multi-dimensional, and sometimes contradicting. In this thesis, we investigate several types of emerging wireless networks and tackle some challenges of these various networks. We focus on three main challenges. Those are Resource Optimization, Network Management, and Cyber Security. We present multiple views of these three aspects and propose solutions to probable scenarios. The first challenge (Resource Optimization) is studied in Wireless Powered Communication Networks (WPCNs). WPCNs are considered a very promising approach towards sustainable, self-sufficient wireless sensor networks. We consider a WPCN with Non-Orthogonal Multiple Access (NOMA) and study two decoding schemes aiming for optimizing the performance with and without interference cancellation. This leads to solving convex and non-convex optimization problems. The second challenge (Network Management) is studied for cellular networks and handled using Machine Learning (ML). Two scenarios are considered. First, we target energy conservation. We propose an ML-based approach to turn Multiple Input Multiple Output (MIMO) technology on/off depending on certain criteria. Turning off MIMO can save considerable energy of the total site consumption. To control enabling and disabling MIMO, a Neural Network (NN) based approach is used. It learns some network features and decides whether the site can achieve satisfactory performance with MIMO off or not. In the second scenario, we take a deeper look into the cellular network aiming for more control over the network features. We propose a Reinforcement Learning-based approach to control three features of the network (relative CIOs, transmission power, and MIMO feature). The proposed approach delivers a stable state of the cellular network and enables the network to self-heal after any change or disturbance in the surroundings. In the third challenge (Cyber Security), we propose an NN-based approach with the target of detecting False Data Injection (FDI) in industrial data. FDI attacks corrupt sensor measurements to deceive the industrial platform. The proposed approach uses an Autoencoder (AE) for FDI detection. In addition, a Denoising AE (DAE) is used to clean the corrupted data for further processing
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