In the Internet of Things (IoT), devices and gateways may be equipped with multiple, heterogeneous network interfaces which should be utilized by a large number of services. In this work, we model the problem of assigning services' resource demands to a device's heterogeneous interfaces and give a Mixed Integer Linear Program (MILP) formulation for it. For meaningful instance sizes the MILP model gives optimal solutions to the presented computationally-hard problem. We provide insightful results discussing the properties of the derived solutions with respect to the splitting of services to different interfaces.
In this work, we analyze the probabilistic cooperation of a full-duplex relay in a multiuser random-access network. The relay is equipped with on/off modes for the receiver and the transmitter independently. These modes are modeled as probabilities by which the receiver and the transmitter are activated. We provide analytical expressions for the performance of the relay queue, such as arrival and service rates, stability conditions, and the average queue size. We optimize the relay's operation setup to maximize the network-wide throughput while, simultaneously, we keep the relay's queue stable and minimize the consumed energy. Furthermore, we study the effect of the SINR threshold and the self-interference (SI) coefficient on the per-user and network-wide throughput. For low SINR threshold, we show under which circumstances it is beneficial to switch off the relay completely, or switch off the relay's receiver only.
Internet of ings (IoT) should be able to react with minimal human intervention and contribute to the Arti cial Intelligence (AI) era, requiring real-time and scalable operation under heterogeneous network infrastructures. is thesis investigates how cooperation and allocation of resources can contribute to the evolution of future wireless networks supporting the IoT. First, we examine how to allocate resources to IoT services which run on devices equipped with multiple network interfaces. e resources are heterogeneous and not interchangeable, while their allocation to a service can be split among di erent interfaces. We formulate an optimization model for this allocation problem, prove its complexity, and derive two heuristic algorithms to approximate the solution in large instances of the problem. Our results can act as a guide for designing IoT applications e.g., to simulate the power drain of a ba ery-operated IoT device. e concept of virtualization is promising towards addressing the heterogeneity of IoT resources by providing an abstraction layer between so ware and hardware. Network function virtualization (NFV) decouples traditional network operations such a routing from proprietary hardware platforms and implements them as so ware entities known as virtualized network functions (VNFs). In the second paper, we study how VNF demands can be allocated to Virtual Machines (VMs) by considering the completion-time tolerance of the VNFs. We prove that the problem is NP-complete and, thus, we devise a subgradient optimization algorithm to provide near-optimal solutions. Our numerical results demonstrate the e ectiveness of our algorithm compared to two benchmark algorithms. Furthermore, we explore the potential of using intermediate nodes, the socalled relays, in IoT networks. In the third paper, we study a multiuser random access network with a relay node assisting users in transmi ing their packets to a destination node. We provide analytical expressions for the performance of the relay's queue and the system throughput. We optimize the relay's opiii VWAN very wide area network WAN wide area network WSN Wireless Sensor Networks xiv Contents
Multimedia content streaming from Internet-based sources emerges as one of the most demanded services by wireless users. In order to alleviate excessive traffic due to multimedia content transmission, many architectures (e.g., small cells, femtocells, etc.) have been proposed to offload such traffic to the nearest (or strongest) access point also called “helper”. However, the deployment of more helpers is not necessarily beneficial due to their potential of increasing interference. In this work, we evaluate a wireless system which can serve both cacheable and non-cacheable traffic. More specifically, we consider a general system in which a wireless user with limited cache storage requests cacheable content from a data center that can be directly accessed through a base station. The user can be assisted by a pair of wireless helpers that exchange non-cacheable content as well. Files not available from the helpers are transmitted by the base station. We analyze the system throughput and the delay experienced by the cached user and show how these performance metrics are affected by the packet arrival rate at the source helper, the availability of caching helpers, the caches’ parameters, and the user’s request rate by means of numerical results.
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