Уменьшение PAPR в системах FBMC-OQAM на основе дискретного преобразования скользящей нормы

Полный текст доступен на сайте издания по подписке: http://radio.kpi.ua/article/view/S0021347019020018Работа посвящена преодолению недостатка, связанного с величиной отношения пикового уровня мощности сигнала к среднему PAPR (Peak to Average Power Ratio), возникающего при нескольких несущих в банке фильтров FBMC (Filter-Bank Multi-Carriers) с квадратурной амплитудной модуляцией со сдвигом OQAM (Offset-QAM) в системах FBMC-OQAM, которые являются кандидатом при формировании формы сигнала для беспроводных систем связи пятого поколения. Дискретное преобразование скользящей нормы DSNT (Discrete Sliding Norm Transform) после обратного дискретного преобразования Фурье IDFT (Inverse Discrete Fourier Transform) предлагается на основе L2-метрики и нормы для пяти отсчетов при каждой операции скольжения. В предлагаемом составе L2-на-5 DSNT рассматривается использование перекрывающейся структуры FBMC-OQAM. Это существенно уменьшает величину PAPR в системах FBMC-OQAM, что гарантирует линейность характеристики усилителя большой мощности HPA (High Power Amplifier) и позволяет избежать искажения сигнала. Основные достоинства этой методики состоят в уменьшении вычислительной сложности по сравнению с известными методиками и отсутствии необходимости в какой-либо дополнительной информации SI (Side Information) на стороне приемника. Результаты моделирования показали, что методика L2-на-5 DSNT позволяет достичь 40% уменьшения величины PAPR при CCDF = 10^(–3) по сравнению с исходной системой FBMC-OQAM

Network Virtual Machine (NetVM): A New Architecture for Efficient and Portable Packet Processing Applications

A challenge facing network device designers, besides increasing the speed of network gear, is improving its programmability in order to simplify the implementation of new applications (see for example, active networks, content networking, etc). This paper presents our work on designing and implementing a virtual network processor, called NetVM, which has an instruction set optimized for packet processing applications, i.e., for handling network traffic. Similarly to a Java Virtual Machine that virtualizes a CPU, a NetVM virtualizes a network processor. The NetVM is expected to provide a compatibility layer for networking tasks (e.g., packet filtering, packet counting, string matching) performed by various packet processing applications (firewalls, network monitors, intrusion detectors) so that they can be executed on any network device, ranging from expensive routers to small appliances (e.g. smart phones). Moreover, the NetVM will provide efficient mapping of the elementary functionalities used to realize the above mentioned networking tasks upon specific hardware functional units (e.g., ASICs, FPGAs, and network processing elements) included in special purpose hardware systems possibly deployed to implement network devices

Study on Large-scale Terrestrial Relaying of Satellite Broadcasted Real-time Multimedia Streams

none2The chapter describes an architecture to relay on demand a real-time IP multicast audio-video stream broadcasted by a satellite on a terrestrial link. The stream is received by suitably equipped sites and then relayed to other sites that are not equipped with satellite receiving hardware but are nonetheless willing to receive the stream. By exploiting the properties of satellite transmission and adopting a hybrid satellite/terrestrial, multicast/unicast approach, the described architecture allows to overcome the restrictions suffered by multicast traffic in the global Internet, allowing it to scale easily across autonomous systems. All things considered, the proposed architecture outlines a large-scale interactive audio-video distribution system similar to those based on Content Distribution Networks (CDNs) and it compares favourably with them when performances, costs and scalability are examined.openFranco Tommasi; Catiuscia MelleTommasi, Francesco; Melle, Catiusci

A Tunnel-aware Language for Network Packet Filtering

Abstract—While in computer networks the number of possible protocol encapsulations is growing day after day, network administrators face ever increasing difficulties in selecting accurately the traffic they need to inspect. This is mainly caused by the limited number of encapsulations supported by currently available tools and the difficulty to exactly specify which packets have to be analyzed, especially in presence of tunneled traffic. This paper presents a novel packet processing language that, besides Boolean filtering predicates, introduces special constructs for handling the more complex situations of tunneled and stacked encapsulations, giving the user a finer control over the semantics of a filtering expression. Even though this language is principally focused on packet filters, it is designed to support other advanced packet processing mechanisms such as traffic classification and field extraction. I

On the Novel Network Forensics Perspective of Enhanced E-Business Security

E-business security is crucial to the development of e-business. Due to the complexity and characteristics of e-business security, the current approaches for security focus on preventing the network intrusion or misusing in advanced and seldom concern of the forensics data requiring for the investigation after the network attack or fraud. We discuss the method for resolving the problem of the e-business security from the different side of view - network forensics approaches – from the thinking of the active protection or defense for the e-business security, which can also improve the ability of emergence response and incident investigation for e-business security. It is also for the first time to systematically discuss the network forensics evidence source, network forensics principles, network forensics functions and network forensics techniques

Network layer access control for context-aware IPv6 applications

As part of the Lancaster GUIDE II project, we have developed a novel wireless access point protocol designed to support the development of next generation mobile context-aware applications in our local environs. Once deployed, this architecture will allow ordinary citizens secure, accountable and convenient access to a set of tailored applications including location, multimedia and context based services, and the public Internet. Our architecture utilises packet marking and network level packet filtering techniques within a modified Mobile IPv6 protocol stack to perform access control over a range of wireless network technologies. In this paper, we describe the rationale for, and components of, our architecture and contrast our approach with other state-of-the- art systems. The paper also contains details of our current implementation work, including preliminary performance measurements

Delivering Live Multimedia Streams to Mobile Hosts in a Wireless Internet with Multiple Content Aggregators

We consider the distribution of channels of live multimedia content (e.g., radio or TV broadcasts) via multiple content aggregators. In our work, an aggregator receives channels from content sources and redistributes them to a potentially large number of mobile hosts. Each aggregator can offer a channel in various configurations to cater for different wireless links, mobile hosts, and user preferences. As a result, a mobile host can generally choose from different configurations of the same channel offered by multiple alternative aggregators, which may be available through different interfaces (e.g., in a hotspot). A mobile host may need to handoff to another aggregator once it receives a channel. To prevent service disruption, a mobile host may for instance need to handoff to another aggregator when it leaves the subnets that make up its current aggregator�s service area (e.g., a hotspot or a cellular network).\ud In this paper, we present the design of a system that enables (multi-homed) mobile hosts to seamlessly handoff from one aggregator to another so that they can continue to receive a channel wherever they go. We concentrate on handoffs between aggregators as a result of a mobile host crossing a subnet boundary. As part of the system, we discuss a lightweight application-level protocol that enables mobile hosts to select the aggregator that provides the �best� configuration of a channel. The protocol comes into play when a mobile host begins to receive a channel and when it crosses a subnet boundary while receiving the channel. We show how our protocol can be implemented using the standard IETF session control and description protocols SIP and SDP. The implementation combines SIP and SDP�s offer-answer model in a novel way

Governance of Risks in Financing Concentrated Solar Power Investments in North Africa

A low-carbon energy transition on the basis of renewable energy sources (RES) is of crucial importance to solve the interlinked global challenges of climate change and energy security. To transform the global energy system, substantial investments will be needed and private participation will very likely be required to achieve the scale of new investment. Yet, especially developing countries are struggling to foster private RES investments. The literature argues that the economic feasibility and hence the realization of a RES investment project hinges on the availability of affordable project financing, which itself depends on perceived risks by investors. Since financing costs are found to be particularly high for capital-intensive RES projects and in developing countries, we investigate the impacts of a financial de-risking approach on electricity prices from concentrated solar power (CSP) in four North African countries and derive the following three conclusions. (1) By employing a levelized cost of electricity (LCOE) model we find that a comprehensive de-risking approach leads to a 32% reduction in the regional mean of LCOE from CSP. (2) To capture potential macroeconomic feedback effects of a de-risking strategy to CSP investments, we employ a Computable General Equilibrium (CGE) model. By considering a 5% CSP target by 2020, the model results indicate that an ambitious de-risking strategy is still not sufficient to achieve cost competitiveness between CSP and subsidized conventional electricity but has the potential to reduce the required subsidy to stimulate CSP deployment in 2020 by 0.03 USD/kWh which would increase GDP on average by 0.15% or 327 million USD. (3) By conducting expert interviews with RES investors we learn that investors are aware of different investment risks associated with RES projects in North Africa and of private risk transfer measures to mitigate these risks. Our results suggest that given the potential for substantial electricity cost reductions and overall economic benefits, financial de-risking - incorporating both public and private measures - reflects an important strategy to foster the deployment of RES

Sensor Network-Based Localization for Continuous Tracking Applications: Implementation and Performance Evaluation

The increasing interest in systems able to provide users with immersive services (e.g., domotics, context-aware applications, and immersive distance learning tools) has encouraged the development of cheap and effective platforms aimed at tracking objects and people within a certain space. In this context, wireless sensor networks (WSNs) can play a very important role, since specialized sensors can be fruitfully exploited in order to generate/receive signals by means of which the WSN can derive the position of nodes joined to the objects to be tracked. The paper presents an original localization platform that exploits a single-hop WSN, based on a Microchip MCU and a Cypress RF device, to track its moving nodes. Specifically, the nodes of the network are divided into three sets: the first set consists of anchor nodes that, according to the commands from the sink (the central node of the WSN), generate ultrasonic pulses. These pulses are received by the second set of (moving) nodes, which estimate the pulse time trip and communicate it to the sink. Finally, the last set is constituted by general purpose nodes that collect any kind of data from the surrounding field. The sink gathers all the data, computes the position of moving nodes, and transfers information to external users on the Internet. The algorithms adopted to manage the network and to localize moving nodes are discussed. A working prototype based upon the hardware platform, software, and protocol described in this paper has been deployed and tested, and some results are shown. Simulation results of the localization system are presented to show system scalability