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The wireless-powered communication paradigm brings self-sustainability to the on-vehicle sensors by harvesting the energy from radiated radio frequency (RF) signals. This paper proposes a novel transmission and resource allocation strategy for the scenario where multiple wireless powered vehicle area networks (VAN) co-existed with high density. The considered multi-VAN system consists of a remote master access point (MAP), multiple on-vehicle hybrid access points (HAPs) and sensors. Unlike previous works, we consider that the sensors can recycle the radiated radio frequency energy from all the HAPs when HAPs communicate with MAP, so the dedicated signals for energy harvesting (EH) are unnecessary. The proposed strategy can achieve simultaneous wireless information and power transfer (SWIPT) without complex receiver architecture requirements. The extra EH and interference caused by the dense distribution of VANs, which are rarely explored, are fully considered. To maximize the sum throughput of all the sensors while guaranteeing the transmission from HAPs to the MAP, we jointly optimize the time allocation, system energy consumption, power allocation, and receive beamforming. Due to the non-convexity of the formulated problem, we address the sub-problems separately through the Rayleigh quotient, Frobenius norm minimization and convex optimization. Then an efficient iterative algorithm to obtain sub-optimal solutions. The simulation results and discussions illustrate the proposed scheme's effectiveness and advantages. peerReviewed

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Apache Log4j2 is a prevalent logging library for Java-based applications. In December 2021, several critical and high-impact software vulnerabilities, including CVE-2021-44228, were publicly disclosed, enabling remote code execution (RCE) and denial of service (DoS) attacks. To date, these vulnerabilities are considered critical and the consequences of their disclosure far-reaching. The vulnerabilities potentially affect a wide range of internet of things (IoT) devices, embedded devices, critical infrastructure (CI), and cyber-physical systems (CPSs). In this paper, we study the effects and feasibility of exploiting these vulnerabilities in mission-critical aviation and maritime environments using the ACARS, ADS-B, and AIS protocols. We develop a systematic methodology and an experimental setup to study and identify the protocols’ exploitable fields and associated attack payload features. For our experiments, we employ software-defined radios (SDRs), use open-source software, develop novel tools, and develop features to existing software. We evaluate the feasibility of the attacks and demonstrate end-to-end RCE with all three studied protocols. We demonstrate that the aviation and maritime environments are susceptible to the exploitation of the Log4j2 vulnerabilities, and that the attacks are feasible for non-sophisticated attackers. To facilitate further studies related to Log4j2 attacks on aerospace, aviation, and maritime infrastructures, we release relevant artifacts (e.g., software, documentation, and scripts) as open-source, complemented by patches for bugs in open-source software used in this study. peerReviewed

To meet the increasing throughput and reliability demands, satellites may be used to complement the Fifth Gener-ation (5G) Terrestrial Networks (TNs). To increase the efficiency of the satellite communications involved, research on bandwidth-efficient techniques is needed. Multi-Connectivity (MC), where a user can be connected to multiple Next Generation Node Bs (gNBs) simultaneously, is one of such techniques. In this paper, the focus is on MC in NonTerrestrial Networks (NTNs) to improve users' experienced throughputs. First, a study of relevant specifications and algorithms is conducted. Then, the designed load-aware Secondary Node (SN) addition and traffic steering algorithms are presented and evaluated in a realistic two-satellite Low Earth Orbit (LEO) network scenario. The simulation results indicate that usage of MC can be beneficial in 5G NTNs. peerReviewed

Joint localization and communication systems have drawn significant attention due to their high resource utilization. In this paper, we consider a reconfigurable intelligent surface (RIS)-aided simultaneously localization and communication system. We first determine the sum squared position error bound (SPEB) as the localization accuracy metric for the presented localization-communication system. Then, a joint RIS discrete phase shifts design and subcarrier assignment problem is formulated to minimize the SPEB while guaranteeing each user’s achievable data rate requirement. For the presented non-convex mixed-integer problem, we propose an iterative algorithm to obtain a suboptimal solution by utilizing the Lagrange duality as well as penalty-based optimization methods. Simulation results are provided to validate the performance of the proposed algorithm. peerReviewed

Low earth orbit (LEO) satellite-assisted communications have been considered as one of key elements in beyond 5G systems to provide wide coverage and cost-efficient data services. Such dynamic space-terrestrial topologies impose exponential increase in the degrees of freedom in network management. In this paper, we address two practical issues for an over-loaded LEO-terrestrial system. The first challenge is how to efficiently schedule resources to serve the massive number of connected users, such that more data and users can be delivered/served. The second challenge is how to make the algorithmic solution more resilient in adapting to dynamic wireless environments.To address them, we first propose an iterative suboptimal algorithm to provide an offline benchmark. To adapt to unforeseen variations, we propose an enhanced meta-critic learning algorithm (EMCL), where a hybrid neural network for parameterization and the Wolpertinger policy for action mapping are designed in EMCL. The results demonstrate EMCL's effectiveness and fast-response capabilities in over-loaded systems and in adapting to dynamic environments compare to previous actor-critic and meta-learning methods., 12 pages, 9 figures

Mobile edge computing (MEC) has been recognized as a promising technique to provide enhanced computation services for low-power wireless devices at the network edge. How to evaluate the timeliness of the task and data delivery is critical for the development of MEC applications. Considering a wireless powered MEC system, in this letter we study the average age of information (AoI), which is a crucial performance metric to measure the freshness of information. Specifically, in the considered system, a sensor node harvests energy from an energy transmitter and transmits computation tasks to the MEC server. The charging time of the sensor node’s capacitor, the waiting time and service time at the MEC server are taken into account when calculating the average AoI. The closed-form expression of the average AoI is obtained accordingly and evaluated through numerical simulations. peerReviewed

The sharing of high-quality traffic information plays a crucial role in enhancing the driving experience and safety performance for vehicular networks, especially in the development of electric vehicles (EVs). The crowdsourcing-based real-time navigation of charging piles is characterized by low delay and high accuracy. However, due to the lack of an effective incentive mechanism and the resource-consuming bottleneck of sharing real-time road conditions, methods to recruit or motivate more EVs to provide high-quality information gathering has attracted considerable interest. In this paper, we first introduce a blockchain platform, where EVs act as the blockchain nodes, and a reputation-based incentive mechanism for vehicular networks. The reputations of blockchain nodes are calculated according to their historical behavior and interactions. Further, we design and implement algorithms for updating honest-behavior-based reputation as well as for screening low-reputation miners, to optimize the profits of miners and address spatial crowdsourcing tasks for sharing information on road conditions. The experimental results show that the proposed reputation-based incentive method can improve the reputation and profits of vehicle users and ensure data timeliness and reliability.

The unmanned aerial vehicle (UAV), which is prominent in its flexibility and low cost, is considered to be fully utilized in the future wireless communication system to provide flexible services and improve connectivities. In this paper, we investigate the resource allocation problem in a wireless powered UAV communication system. In this considered system, The UAV acts as hybrid access point (HAP), which can first perform wireless power transfer in the downlink and charge the Internet of Thing (IoT) user devices (UDs). The UDs can use the harvested energy to deliver the data to the UAV. In the uplink, we explicitly consider short packet communication (SPC) as the transmission feature, which adopts finite block-length codewords and suffers from rate degradation. With the objective to maximize system energy efficiency, we jointly optimize the position and transmit power of the UAV, and transmission time of each UD. To address the formulated non-convex problem, we develop efficient algorithms to find sub-optimal solutions. Extensive simulations are conducted to verify the effectiveness of the proposed scheme. peerReviewed

In vehicular networks, in-vehicle user equipment (UE) with limited battery capacity can achieve opportunistic energy saving by offloading energy-hungry workloads to vehicular edge computing nodes via vehicle-to-infrastructure links. However, how to determine the optimal portion of workload to be offloaded based on the dynamic states of energy consumption and latency in local computing, data transmission, workload execution and handover, is still an open issue. In this paper, we study the energy-efficient workload offloading problem and propose a low-complexity distributed solution based on consensus alternating direction method of multipliers. By incorporating a set of local variables for each UE, the original problem, in which the optimization variables of UEs are coupled together, is transformed into an equivalent general consensus problem with separable objectives and constraints. The consensus problem can be further decomposed into a bunch of subproblems, which are distributed across UEs and solved in parallel simultaneously. Finally, the proposed solution is validated based on a realistic road topology of Beijing, China. Simulation results have demonstrated that significant energy saving gain can be achieved by the proposed algorithm. peerReviewed

Non-orthogonal multiple access (NOMA) holds the promise to be a key enabler of 5G communication. However, the existing design of NOMA systems must be optimized to achieve maximum rate while using minimum transmit power. To do so, this paper provides a novel technique based on multi-objective optimization to efficiently allocate resources in the multi-user NOMA systems supporting downlink transmission. Specifically, our unique optimization technique jointly improves spectrum and energy efficiency while satisfying the constraints on users quality of services (QoS) requirements, transmit power budget and successive interference cancellation. We first formulate a joint problem for spectrum and energy optimization and then employ dual decomposition technique to obtain an efficient solution. For the sake of comparison, a low complexity single-objective NOMA optimization scheme is also provided as a benchmark scheme. The simulation results show that the proposed joint approach not only performs better than the traditional benchmark NOMA scheme but also significantly outperforms its counterpart orthogonal multiple access (OMA) schemes in terms of both energy and spectral efficiency. peerReviewed

Most of the existing literatures on green communications aimed to improve the energy efficiency at the base station or data server. However, in order to fully experience high rate broadband multimedia services, prolonging the battery life of user equipment is also critical for the mobile terminals, especially for the smartphone users. In this work, we investigate the problem of designing a content distribution mobile platform named collaborative mobile clusters (CMC) via user cooperation to reduce the energy consumption at the terminal side. Specifically, given numbers of users interested in downloading a common content from the operator, both centralized and distributed user grouping and scheduling algorithms are proposed in order to find the proper user to join the CMC in different scheduling time with the objective to obtain energy efficiency as well as user fairness. Through simulation studies, it is shown that a significant energy saving can be achieved by the proposed schemes and user fairness can be maintained as well. peerReviewed

We study the behavior of the belief-propagation (BP) algorithm affected by erroneous data exchange in a wireless sensor network (WSN). The WSN conducts a distributed multidimensional hypothesis test over binary random variables. The joint statistical behavior of the sensor observations is modeled by a Markov random field whose parameters are used to build the BP messages exchanged between the sensing nodes. Through linearization of the BP message-update rule, we analyze the behavior of the resulting erroneous decision variables and derive closed-form relationships that describe the impact of stochastic errors on the performance of the BP algorithm. We then develop a decentralized distributed optimization framework to enhance the system performance by mitigating the impact of errors via a distributed linear data-fusion scheme. Finally, we compare the results of the proposed analysis with the existing works and visualize, via computer simulations, the performance gain obtained by the proposed optimization. peerReviewed

Recent development of wireless communication systems and standards is characterized by constant increase of allocated spectrum resources. Since lower frequency ranges cannot provide sufficient amount of bandwidth, new bands are allocated at higher frequencies, for which operators resort to deploy more base stations to ensure the same coverage and to utilize more efficiently higher frequencies spectrum. Striving for deployment flexibility, mobile operators can consider deploying low power nodes that could be either small cells connected via the wired backhaul or relays that utilize the same spectrum and the wireless access technology. However, even though low power nodes provide a greater flexibility in terms of where they can be deployed, they also create new challenges. In particular, it is often the case that operators need to balance carefully between how many additional low power nodes it is necessary to install versus potential gains of the whole system. Thus, in this study we aim to develop a model that can find optimal network configuration for low power nodes assisting operators network deployment process. The outcome of the analytical model is complemented by extensive dynamic system level simulations, by means of which we analyze overall system performance for the obtained solutions. We also show that deviations from optimal configurations can lead to significantly worse system performance. peerReviewed

In this paper, a bidirectional wireless information and power transmission model with an energy accumulating relay is studied. To implement wireless information and power transmission simultaneously, a time-switching protocol is adopted. In addition, two energy harvesting (EH) protocols are proposed. In the bidirectional continuous-time EH (BI-CT) protocol, the whole transmission block is divided into two parts: EH and information transmission. In the bidirectional discrete-time EH (BI-DT) protocol, the EH time is either 0 or 1. The relay first harvests energy and then forwards information from the user node to the source node. Notably, the relay node stores energy during poor channel conditions, increasing the energy efficiency. Theoretical analyses on the performance of the two proposed protocols are given. It is found that the throughput efficiency depends on various system parameters, such as the transfer power at the relay, distance between the nodes, noise power, and SNR detection threshold. Furthermore, it is observed that BI-DT outperforms BI-CT when the noise power at the relay is high or the distance between the source and the relay is large.

Wireless network virtualization is envisioned as a promising framework to provide efficient and customized services for next-generation wireless networks. In wireless virtualized networks (WVNs), limited radio resources are shared among different services providers for providing services to different users with heterogeneous demands. In this paper, we propose a resource allocation scheme for an orthogonal frequency division multiplexing-based WVN, where one small cell base station equipped with a large number of antennas serves the users with different service requirements. In particular, with the objective to obtain the energy efficiency in the uplink, a joint power, subcarrier, and antenna allocation problem is presented considering availability of both perfect and imperfect channel state information. Subsequently, relaxation and variable transformation are applied to develop the efficient algorithm to solve the formulated non-convex and combinational optimization problem. Extensive simulation studies demonstrate the advantages of our presented system architecture and proposed schemes. peerReviewed

Vehicular ad hoc network (VANET) is able to facilitate data exchange among vehicles and provides diverse data services. Intuitively, end-to-end backlog and delay bounds are considered significant metrics to evaluate the quality of service in VANETs. In order to analyze how the multi-hop transmission impacts the delay performance, we model the multi-hop service process into a virtualized single service in a min-plus convolution form. To obtain multi-hop end-to-end backlog and delay bound, we consider the stochastic network traffic characteristics and the highly dynamic channel environment under the static priority, first in first out, and earliest deadline first scheduling policies by applying the martingale theory. The IEEE 802.11p enhanced distributed channel access mechanism is also adopted to analyze the access performance in the MAC sub-layer. With three kinds of real wireless data traces, i.e., VoIP, gaming, and UDP, we verify our algorithm by considering the double Nakagami- $m$ fading channel model among vehicles. From the simulation results, we can see that the supermartingale end-to-end backlog and delay bound are remarkably tight to the real simulation results when compared with the existing standard bounds. The effect of the number of vehicles on the highway on the end-to-end backlog and delay performance is also investigated.

Ambient backscatter communications is an emerging paradigm and a key enabler for pervasive connectivity of low-powered wireless devices. It is primarily beneficial in the Internet of things (IoT) and the situations where computing and connectivity capabilities expand to sensors and miniature devices that exchange data on a low power budget. The premise of the ambient backscatter communication is to build a network of devices capable of operating in a battery-free manner by means of smart networking, radio frequency (RF) energy harvesting and power management at the granularity of individual bits and instructions. Due to this innovation in communication methods, it is essential to investigate the performance of these devices under practical constraints. To do so, this article formulates a model for wireless-powered ambient backscatter devices and derives a closed-form expression of outage probability under Rayleigh fading. Based on this expression, the article provides the power-splitting factor that balances the tradeoff between energy harvesting and achievable data rate. Our results also shed light on the complex interplay of a power-splitting factor, amount of harvested energy, and the achievable data rates., 11 Pages, 7 Figures

In this paper, we present a joint power allocation and adaptive link selection protocol for an orthogonal frequency division multiplexing (OFDM)-based network consists of one source node i.e., base station (BS), one destination node i.e., (MU) and a buffer aided decode and forward (DF) relay node. Our objective is to maximize the average throughput of the system via power loading over different subcarriers at source and relay nodes. A separate power budget is assumed at each transmitting node to make the system more practical. In order to form our solution more tractable, a decomposition framework is implemented to solve the mixed integer optimization problem. Further, less complex suboptimal approaches have also been presented and simulation results are provided to endorse the efficiency of our designed algorithms.

With the drastic increase of space information network (SIN) traffic and the diversity of network traffic types, the optimal allocation of the scarce network resources is of great significance for optimizing the SIN system capability. In this paper, we propose a multi-resource management method for multi-tier SIN using the cooperative Nash bargaining solution. Since the original problem is a non-convex problem, we firstly make logarithmic transition, and then find a tightest lower bound function to convert the initial problem into a convex one. In order to carry out the optimal bandwidth and power allocation in SIN, we construct a joint bandwidth and power allocation (JBPA) algorithm. Simulation results show the performance improvement of the JBPA scheme and the convergence of JBPA algorithm. peerReviewed

Vehicle collaborative content downloading has become a hotspot in current vehicular ad-hoc network (VANET) research. However, in reality, the highly dynamic nature of VANET makes users lose resources easily, and the transmission of invalid segment data also wastes valuable bandwidth and storage of the users&rsquo, vehicles. In addition, the individual need of each customer vehicle should also be taken into consideration when selecting an agent vehicle for downloading. In this paper, a novel scheme is proposed for vehicle selection in the download of cooperative content from the Internet, by considering the basic evaluation information of the vehicle. To maximize the overall throughput of the system, a collaborative content downloading algorithm is proposed, which is based on fuzzy evaluation and a customer&rsquo, s own expectations, in order to solve the problems of agent vehicle selection. With the premise of ensuring successful downloading and the selection preferences of customer vehicles, linear programming is used to optimize the distribution of agent vehicles and maximize customer&rsquo, s satisfaction. Simulation results show that the proposed scheme works well in terms of average quality of service, average bandwidth efficiency, failure frequency, and average consumption.

Multi-hop device-to-device (D2D) communications play an important role in expanding D2D coverage. In this paper, we study a relay-based and network-coding-assisted (in particular, XOR coding) multi-hop D2D communication system. In the system, toward jointly considering the impact of interference and network traffic conditions on the quality of D2D communications, various channel fading models and traffic models are investigated, and the packet loss probability of D2D links is meticulously computed using these models. With the packet loss probability of D2D links, the general closed-form expressions of end-to-end packet loss probability (E2EPLP) of the system with the presence (or absence) of XOR coding are subsequently derived. Our experiments reveal that both the number of relays and the mechanism of XOR coding can affect the system performance. Specifically, the increase in the number of relays will lower the overall system performance (e.g., an increase in the E2EPLP and end-to-end completion time, and a decrease of the end-to-end rate may follow as a result). On the other hand, although the presence of XOR coding unfortunately raises the system E2EPLP, it can effectively improve the end-to-end completion time and end-to-end rate. It is our belief that the analytical approach proposed in this paper and the results found in our work can be useful to peer studies in the context of applying network coding in multi-hop D2D networks. peerReviewed

Wireless caching systems have been exhaustively investigated in recent years. Due to limited buffer capacity, and unbalanced arrival and service rates, the backlogs may exist in the caching node and even cause buffer overflow. In this paper, we first investigate the relationship among backlogs, buffer capacity, data arrival rate and service rate, utilizing the martingale theory which is flexible in handling any arrival and service processes. Then given a target buffer overflow probability, the minimal required buffer portion is determined. If the devoted buffer capacity can fulfill all serving users' minimal buffer requirements, an optimization problem is constructed with the objective to minimize the overall buffer overflow probability. The optimization solution is obtained by a modified waterfilling scheme. Finally, the numerical results are illustrated to demonstrate the superiority of the proposed scheme. peerReviewed

Physical layer security (PLS) has been extensively explored as an alternative to conventional cryptographic schemes for securing wireless links. Many studies have shown that the cooperation between the legitimate nodes of a network can significantly enhance their secret communications performance, relative to the noncooperative case. Motivated by the importance of this class of PLS systems, this paper provides a comprehensive survey of the recent works on cooperative relaying and jamming techniques for securing wireless transmissions against eavesdropping nodes, which attempt to intercept the transmissions. First, it provides a in-depth overview of various secure relaying strategies and schemes. Next, a review of recently proposed solutions for cooperative jamming techniques is provided with an emphasis on power allocation and beamforming techniques. Then, the latest developments in hybrid techniques, which use both cooperative relaying and jamming, are elaborated. Finally, several key challenges in the domain of cooperative security are presented along with an extensive discussion on the applications of cooperative security in key enablers for 5G communications, such as nonorthogonal multiple access, device-to-device communications, and massive multiple-input multiple-output systems. peerReviewed

In cognitive radio networks (CRN), secondary users (SUs) are required to detect the presence of the licensed users, known as primary users (PUs), and to find spectrum holes for opportunistic spectrum access without causing harmful interference to PUs. However, due to complicated data processing, non-real-time information exchange and limited memory, SUs often suffer from imperfect sensing and unreliable spectrum access. Cloud computing can solve this problem by allowing the data to be stored and processed in a shared environment. Furthermore, the information from a massive number of SUs allows for more comprehensive information exchanges to assist the resource allocation and interference management at the cloud center while relieving the stringent capacity demands in fronthaul links. Moreover, spectrum resources should be made available to more users, especially when the spectrum is underutilized but occupies a large band. Hence, cloud-based CRN can generate massive sensing samples that will benefit the applications of big data algorithms. The approaches to spectrum sensing and spectrum management can be greatly improved with decision-making capabilities of spectral big data. nonPeerReviewed

Cyber linked with Information Technology, computers and the internet are the most commonly understood potential threats that everybody is aware of nowadays. In the case of National Cyber Strategy most efforts are given to these potential battlefields and threats. But is it enough to stay with these paradigms? Cyber warfare will look for utmost effects for chaos and misalignment of economy and therefore we cannot exclude the facts, that there is a potential threat also possible in the cut volumes between the information technology, the electromagnetic spectrum and its linked infrastructure and processes. We understand the technology for mobile telecommunications and data transfer, as the providers and linked business models are transparent and an open source and therefore a potential threat in the sense of cyber-attacks. All these services are based on the message transfer in the Electromagnetic Spectrum (EMS). It will be more challenging to enter in secured networks and modern data communication protected by encrypted and secured data links, hardened equipment and architecture. But as those systems, like the avionics and communication subsystems in airborne vehicles and commercial aircrafts are highly interlinked and interoperable based on data networks, it will be necessary to understand the architecture and weaknesses in detail. Of course, these principles are not fixed only to the airborne platforms and relevant applications; you may find the same technical pandemics in data transmission and data engineering in the physics of any data transfer chain, like satellite communication, radio transmission links. The paper will discuss the technical background in principle and identify potential weaknesses in aviation electromagnetic spectrum. We propose measures for attention and the implementation of relevant procedures and quality in order to overcome bottlenecks and grey area dull which helps the opponents to weaken society and open a sideshow for conflicts introduced by “simple cyber threat handling”. © 2019, Curran Associates Inc. All rights reserved. peerReviewed

Non-orthogonal multiple access (NOMA) is considered to be one of the best candidates for future networks due to its ability to serve multiple users using the same resource block. Although early studies have focused on transmission reliability and energy efficiency, recent works are considering cooperation among the nodes. The cooperative NOMA techniques allow the user with a better channel (near user) to act as a relay between the source and the user experiencing poor channel (far user). This paper considers the link security aspect of energy harvesting cooperative NOMA users. In particular, the near user applies the decode-and-forward (DF) protocol for relaying the message of the source node to the far user in the presence of an eavesdropper. Moreover, we consider that all the devices use power-splitting architecture for energy harvesting and information decoding. We derive the analytical expression of intercept probability. Next, we employ deep learning based optimization to find the optimal power allocation factor. The results show the robustness and superiority of deep learning optimization over conventional iterative search algorithm., Comment: 6 Pages, Decode-and-forward (DF), Deep learning, Non-orthogonal multiple access (NOMA), Power-splitting

The emerging Device-to-Device (D2D) communications paradigm has received increasing attentions from both research and industry communities. Most of the previous works on D2D communications, however, mainly concentrated on interference management and throughput optimization. Some recent works have observed that by properly caching the data at the device level, the Quality of Experience (QoE) can be enhanced. In this paper, we propose a novel socially-aware data content delivery scheme for D2D underlay wireless networks by taking social ties and common interests among users into consideration. In particular, we jointly consider the features of the D2D transmissions in the physical layer, social characteristics, and interest similarity impact to formulate the D2D content delivery problem. Accordingly, an accurate and efficient three-dimensional matching-based scheme is presented to address the formulated problem. The performance evaluations are conducted to show the potential gain of the proposed approach.

Non-Orthogonal multiple access (NOMA) holds promise as a spectrally efficient multiple access scheme for 5G communication networks. This work investigates the performance of NOMA in a dual-hop amplify-and-forward (AF) relaying network, which is subject to Nakagami-$m$ fading. Specifically, we obtain a novel closed-form expression of the outage probability for the near and far users when the partial relay selection (PRS) scheme is used for selecting the best among $N$ intermediate relays. The users are considered to employ selection combining technique in order to combine the relayed and the direct transmission signals for an increased reliability of detection. Then, we evaluate the impact of the number of intermediate relays, the NOMA power allocation factor, and the Nakagami-$m$ fading severity parameter on the outage performance of the NOMA users. The analytical results are validated by performing Monte Carlo Simulations.

In this paper, a bidirectional wireless information and power transmission model with an energy accumulating relay is studied. To implement wireless information and power transmission simultaneously, a time-switching (TS) protocol is adopted. In addition, two energy harvesting (EH) protocols are proposed, named bidirectional continuous time EH (BI-CT) protocol and bidirectional discrete time EH (BI-DT) protocol. The relay node stores energy during poor channel conditions, increasing the energy efficiency. Theoretical analyses on the performance of the two proposed protocols are given. It is found that the throughput depends on various system parameters, such as the transfer power at the relay, distance between and so on. Furthermore, it is observed that BI-DT outperforms BI-CT when the noise power at the relay is high or the distance between the source and the relay is large.

In this paper, an energy-efficient vehicular edge computing (VEC) framework is proposed for in-vehicle user equipments (UEs) with limited battery capacity. Firstly, the energy consumption minimization problem is formulated as a joint workload offloading and power control problem, with the explicit consideration of energy consumption and delay models. Queuing theory is applied to derive the stochastic traffic models at UEs and VEC nodes. Then, the original NP-hard problem is transformed to a convex global consensus problem, which can be decomposed into several parallel subproblems and solved subsequently. Next, an alternating direction method of multipliers (ADMM)-based energy-efficient resource allocation algorithm is developed, whose outer loop representing iterations of nonlinear fractional programming, while inner loop representing iterations of primal and dual variable updates. Finally, the relationships between energy consumption and key parameters such as workload offloading portion and transmission power are validated through numerical results.

Recent development of wireless communication systems and standards is characterized by constant increase of allocated spectrum resources. Since lower frequency ranges cannot provide sufficient amount of bandwidth, new bands are allocated at higher frequencies, for which operators might resort to deploy more base stations to ensure the same coverage. Connecting increased number of base stations to the backhaul network with wired connections becomes a non-trivial task and requires more capital investments. To overcome this challenge, it is possible to consider relaying technologies. However, as the operating frequency range increases, so the relay communication range shrinks, which in turn calls for multi-hop relays.

Tämä pro gradu-tutkielma käsitteli diginatiivien ja digi-immigranttien vaihtokäyttäytymistä, kun tarkastellaan kyseisten henkilöryhmien vaihtoa perinteisen asumisen elinympäristöstä ympäristöön, jossa käytetään hyväksi älyteknologiaa. Vaihtokäyttäytymisestä kartoitettiin olemassaolevan teorian pohjalta tekijöitä, jotka vaikuttavat vaihtoinnokkuuteen ja sitä myötä vaihtokäyttäytymiseen vetävästi, työntävästi tai ankkuroivasti. Näiden kahden ryhmän tuloksia verrattiin toisiinsa, jotta saatiin selville eroavaisuuksia vaihtokäyttäytymisessä. Tutkimuksen tavoitteena oli avata keskustelua ja tuoda julki uutta tietoa eri sukupolvien vaihtokäyttäytymisestä tilanteessa, jossa heidän elämäänsä tuodaan uudenlaista teknologiaa. Tätä tietoa on mahdollista hyväksikäyttää jatkotutkimuksissa sekä apuna vastaavien älyelinympäristöjen suunnittelussa. Lisäksi tarkoituksena oli luoda uutta tietoa diginatiivikeskusteluun, joka on ollut ratkaisemattomana aiheena jo pitkään. Aikaisempia tutkimuksia tarkasteltiin kirjallisuuskatsauksen kautta ja tutkimuksen empiirinen osio toteutettiin laadullisena puolistrukturoiduilla teemahaastatteluilla, joissa haastateltiin 11:tä digi-immigranttia ja 11:tä diginatiivia. Haastateltavat lokeroitiin syntymävuosiensa perusteella. Ennen vuotta 1980 syntyneet laskettiin digi-immigranteiksi, kun vuonna 1980 ja sen jälkeen syntyneet laskettiin digitaalisiksi natiiveiksi. Tutkimuksen tulos oli, että huolimatta sukupolvien välisistä teoreettisista eroavaisuuksista, vaihtokäyttäytyminen erosi vähän ryhmien välillä. Sitoutuneisuus nykyiseen elinympäristöön oli vanhemmilla sukupolvilla merkittävämpi ankkuroiva tekijä, kun nuoremmalla sukupolvella vahvemmaksi työntäväksi tekijäksi osoittautuvat taloudelliset tekijät. Digi-immigranteilla luottamus ja sen vähäisyys nykyiseen elinympäristöön oli merkitsevä työntävä tekijä, kun taas diginatiiveilla kyseinen tekijä ei ollut merkitsevä. Erot johtuivat yksilöiden elämäntilanteista, ei niinkään sukupolven erityisistä ominaisuuksista. Syyksi epäiltiin, että suhtautuminen elinympäristöjä kohtaan pysyy verrattain muuttumattomana sukupolvesta riippumatta. Tulokset eivät tukeneet täysin teoriaa, että diginatiivit ja digi-immigrantit eroaisivat toisistaan merkittävästi teknologiaan asennoitumisen puolesta. Joitakin yhtäläisyyksiä kuitenkin huomattiin. Lisäksi tutkimus laajensi tietämystä tietojärjestelmätutkimuksen saralla. Vaihtoehdon viehätys -tekijän todettiin olevan vaihtoaikomusta ajava tekijä, jota tulisi jatkossa tarkastella sen ala-tekijöiden tasolla. This Master's thesis examined the switching behavior of theoretical digital immigrants' and theoretical digital natives' in the context of switching from a traditional living environment to a smart technology assisted one, in other words a smart home environment. Switching behavior was examined in both groups individually and the determinants were mapped based on former theories and research on push-pull-mooring (PPM) model. The results were compared between the groups in order to generate new information on switching behavior when switching from traditional living environments to smart technology implemented ones. The emerged information is useful in future research with similar contexts and in designing smart living environments for various consumers. A Partial goal was to bring new information to the discussion on digital natives and immigrants which has remained unsolved for some time. Previous research on this topic was examined via a literature review and the empirical part was conducted as qualitative semi-structured thematic interviews. The subjects were categorized by their year of birth. 11 digital immigrants who were born before the year 1980 and 11 digital natives born after the year 1980 were interviewed. Despite of the proposed theoretical differences of these groups only few differences on switching behavior were noticed. Commitment was a strong mooring factor in both groups, but slightly stronger among digital immigrants, whereas economic factors were a more significant push factor for the digital natives. For digital immigrants the lack of trust was a pushing factor when digital natives did not perceive similar effects. The noticed differences were generally due to the individual's personal life situation, not because of the technology orientation differences between the two groups. This might have been because the attitudes towards living environments are relatively static and unchanged regardless of one's year of birth. The results did not entirely support nor object the original claims of theories on digital natives and immigrants and their differences. There were some conflicts and similarities to these theories. The study also continued IS switching behavior research and widened the spectrum of examined environments. Alternatives attractiveness should be examined more accurately via its sub-factors.

In the future mobile networks, a mobile terminal is able to select the best suitable network for each data transmission. The selection of a network connection to be used has been under a lot of study. In this paper, we consider a more extensive case in which we do not select a network connection but use several network connections simultaneously to transfer data. When data is transferred using multiple network connections, a network connection has to be selected for each component of the data. We have modelled this problem as a multiobjective optimization problem and developed a heuristic to solve the problem fast in a static network environment. In this paper, we discuss solving the problem in a dynamic network environment in which the availability as well as the rate and prizing of connections vary. We introduce an improved version of the heuristic that reacts to changing network conditions and improves the solution when possible.

Ari Viinikainen tutki väitöskirjassaan tietoliikenneverkkojen resurssien jakoa hinnoittelun ja palvelun laadun avulla sekä kiinteissä että langattomissa tietoliikenneverkoissa. Aihe on ajankohtainen, sillä vaikka verkkojen tiedonsiirtokapasiteetti kasvaa, ei kaikille sovelluksille voida taata niiden vaatimaa tiedonsiirtopalvelun laatua. Esimerkiksi videoneuvottelujen laadun kannalta olennaisia ovat mahdollisimman pieni viive, vähäinen viiveen vaihtelu ja suuri tiedonsiirtokapasiteetti. Viinikainen esittelee työssään useita viiveen tai tiedonsiirtonopeuden takaavia algoritmeja, joilla reitittimiin saapuvaa dataa voidaan priorisoida. Algoritmien toiminta perustuu siirrettävän tiedon erilaiseen hinnoitteluun sen mukaan, minkälaista laatua tiedonsiirto tarvitsee. Viinikainen esittelee myös uuden menetelmän erityisesti langattomien tietoliikenneverkkojen viiveen pienentämiseksi tukiaseman vaihdon yhteydessä.Tietoliikenneverkon yhtenä solmukohtana ovat reitittimet, jotka siirtävät vastaanottamaansa tietovirtaa oikeisiin suuntiin verkossa. Kun reitittimelle saapuu dataa nopeammin kuin mitä reititin kykenee reaaliaikaisesti käsittelemään, data joutuu jonottamaan käsittelyvuoroaan. Jonotusaika kasvattaa suoraan tiedonsiirrossa koettua viivettä. Nykyään kaikkea dataa käsitellään samalla tavalla riippumatta siirrettävän tiedon luonteesta ja näin ollen esimerkiksi reaaliaikaisen datan vaatimuksia pienelle viiveelle ei voida huomioida.Lähitulevaisuuden visiona on, että kaikki langattomasti siirrettävä tieto, myös puhe, siirretään Internetissä käytettävän protokollan avulla. Tällöin käyttäjä ei huomaa sitä, mikä langaton liityntätapa puhelun aikana on käytössä. Langattomassa tiedonsiirrossa tukiaseman vaihto on yksi suurimmista viiveen aiheuttajista riippumatta käytetystä teknologiasta. Internet-protokollaa käytettäessä viive aiheutuu pääosin langattoman päätelaitteen uuden sijainnin ilmoittamisesta kommunikointikumppanille. Vasta sitten, kun kommunikointikumppani on saanut tiedon liikkuneen päätelaitteen tukiaseman vaihdosta, voidaan tiedonsiirto ohjata uuteen sijaintipaikkaan. Nowadays, the pricing of the Internet is typically based on a flat rate and the users can use the network's resources as much as their connection allows. This leads to congestion of the network: for example, no guarantee can be given for example for real time applications to have the network's resources they need. Pricing that is related to the resource allocation of the network can be used to efficiently control the network's resources and combat congestion. In today's networks the mobile devices must also be taken into consideration, complicating the scheme of providing adequate Quality of Service (QoS) to all customers. Especially, the movement of mobile devices from one networks attachment point to another causes unwanted delays that should be minimized. In this thesis pricing and packet scheduling is combined to maximize the operator's revenue and to guarantee appropriate service for different service classes. Also a new method for minimizing the handover delay in Mobile IPv6 handover situation is proposed. The method uses pricing and service classes to determine the connections that are privileged to make use of the proposed fast handover method.

Jani Puttonen tutki väitöskirjassaan liikkuvuuden hallintaa IP-pohjaisissa langattomissa verkoissa. Liikkuvuus monimuotoisessa langattomassa ympäristössä voi aiheuttaa sekä yhden tekniikan sisäisiä että eri tekniikoiden välisiä yhteysvastuun vaihtoja. IETF-standardointiorganisaatiossa on kehitetty Mobile IP -protokolla sekä sen IP versio 6 -versio liikkuvuuden hallinnan ratkaisemiseksi IP-verkoissa. Vaikka Mobile IPv6 hallitsee sovelluksille näkymättömät yhteysvastuun vaihdot, sen laajamittainen käyttöönotto vaatii vielä useiden ongelmien ratkaisua. Puttonen keskittyi lähinnä IP-tason yhteysvastuun vaihdon viiveen minimoimiseen sekä parhaan liitynnän valintaan monimuotoisissa langattomissa ympäristöissä.Puttonen kehitti Mobile IPv6 -yhteysvastuun vaihdon rekisteröintiviiveen pienentämiseen tarkoitetun laajennuksen, jolla pienennetään osoitteiden rekisteröimisviivettä. Täten myös pakettien hävikki yhteysvastuun vaihtotilanteissa pienenee. Menetelmän ansiosta yhteysvastuun vaihtoon kuluva aika ei ole riippuvainen liikennöintikumppanien välisistä etäisyyksistä.Puttonen tutki myös menetelmää, jolla Mobile IPv6 -yhteysvastuun vaihtoja voidaan hallita siten, että käyttäjällä ja sovelluksilla olisi aina käytössään paras langaton yhteys. Käyttäjän ei tarvitse juurikaan puuttua liitynnän valintaan. Liitynnän valinnassa otetaan huomioon liityntöjen reaaliaikainen tila ja laatu sekä käyttäjien vaatimukset. Tutkimusmenetelminä Puttonen käytti sekä simulointeja ns-2-verkkosimulaattorilla että käytännön testejä Linux-käyttöjärjestelmällä oikeassa verkkoympäristössä.Kehitellyillä menetelmillä tarjotaan käyttäjälle aina paras yhteys ja saumattomat yhteysvastuun vaihdot tulevaisuuden monimuotoisissa langattomissa verkkoympäristöissä. Näin ollen tutkimuksen tulokset ovat merkittäviä neljännen sukupolven matkaviestinverkkoja suunniteltaessa. This dissertation discusses mobility management in IP based wireless environments. Mobility management can include both handovers within one technology and selection of access technology in a heterogeneous overlapping environment. IETF has standardized Mobile IP and its IPv6 version for handling mobility management in the IP networks. Even though Mobile IPv6 handles mobility in an application transparent way, several unresolved problems remain. This dissertation focuses on minimizing the Mobile IPv6 handover delays and interface selection in heterogeneous wireless environments.An enhancement called Flow-based Fast Handover for Mobile IPv6 is presented for speeding up the Mobile IPv6 address registration phase. The address registration phase, and thus also packet loss, can be notably decreased. More importantly, the delay is not dependent on the distance of the Corresponding Nodes as is the case with Mobile IPv6. In addition, mechanisms to control Mobile IPv6 handovers to offer the users and applications a best access were researched. Real time information about the link status and quality as well as user preferences are taken into account in the interface selection. The objective is to offer an Always Best Connected access to the user, and seamless handovers.