Wireless communications always strive for higher throughput and higher performance. The Multiple Inputs Multiple Outputs (MIMO)Orthogonal Frequency Division Multiplexing (OFDM) scheme is the key Physical (PHY) layer feature of the next generation wireless local area networks (WLAN) IEEE 802.11ac standards. In this paper, we propose a novel MIMO-OFDM scheme based on modulation diversity for IEEE 802.11ac. This proposed scheme jointly optimizes the MIMO-OFDM and modulation diversity together, which makes full use of time diversity, frequency diversity and space diversity. It exhibits high spectral efficiency and low error rate in fading channels. The simulation results show that the proposed scheme outperforms the current MIMO-OFDM scheme based on BitInterleaved Coded Modulation (BICM) in the 802.11ac standard, which is up to 7dB SNR gain. Keywords-WLAN; 802.11ac; modulation diversity; MIMO; OFDM
—The purpose of this paper is to give an introduction into the new standard base of next-generation Passive Optical Network (NG-PON). Study and analysis of future trends in the development of next-generation fixed broadband optical network is performed. The main intention of this paper is to describe migration from Gigabit-capable Passive Optical Network (GPON) to Ten-Gigabit-Capable Passive Optical Networks (XG-PON). Paper answers the question of what extent active and passive GPON elements need to be replaced and what needs to be added when migrating to XG-PON. Special focus is also pointed on the coexistence of GPON and XG-PON. Keywords-passive optical network; Gigabit PON; XG-PON; fiber to the home; optical access network I. I NTRODUCTION With new services like three-dimensional high-definition television, cloud computing, more and more internet based applications the required bandwidth to the end user is increasing constantly (approx. 50% per year by Nielsen’s law [1]). This gives the infrastructure providers an opportunity to offer new services and consequently increases average revenue per user, and thus they need to make smart decision about the investment into Fiber to the x (FTTx) technology, where x stands for node, cabinet, curb, cell, building, premises or even home as an ultimate and final solution. It is the common fact that running fiber to the end customer (to the home) is the best possible option. After making the decision for FTTH there are two basic architectures possible. One is point-to-point (P2P) [2] and another is point-to-multipoint (P2MP) typically seen on the market as PON (Passive Optical Network) technology. Most of the recent deployment in Europe and America is based on GPON system standardized by ITU-T series G.984 [3]. It offers downstream speed of 2.4 Gbit/s typically for up to 64 users and upstream speed of 1.2 Gbit/s. Since fiber as a media can transport much more, operators are expecting more from FTTH technology. Present Gigabit-capable Passive Optical Network (GPON) as a future safe investment new standard for first generation of Ten-Gigabit-Capable Passive Optical Networks (XG-PON1) has been published in 2010 by ITU-T [4]. This standard will offer 10 Gbit/s downstream and 2.5 Gbit/s upstream speed; but, target distance and split ratio did not increase much. Research in this area continues the job to bring even better P2MP technology. Most of them are today known under the term second generation of next-generation Passive Optical Network (NG-PON2). Incorporating the Wavelength-Division Multiplexing (WDM) technology is mandatory to go beyond XG-PON data rates, splits and reach. The main difference between XG-PON1 and NG-PON2 from operator point of view will be the migration strategy. Since the NG-PON2 will use brand new technology, coexistence of GPON and NG-PON2 will be difficult. This paper presents the migration from GPON to XG-PON. As an enhancement to GPON, XG-PON1 inherits the framing and management from GPON. XG-PON1 provides full-service operations via 4x higher rate and 2x larger split to support a PON network structure. In Section 2 of this paper basic technology and up-to-date standards status are described. Section 3 contains main points in the XG-PONs deployment and development: general description, co-existence with previous standards, physical layer capability, etc. Some information on the RF CATV co-existence inside XG-PON is also described. Section 4 contains information on the examples of products for WDM filters that are planned to use in XG-PON1, possible candidates for OLT filters and also information on the tunable lasers, their possible applications for NG-PONs systems, advantages and disadvantages. Section 5 summarizes the overall conclusions. II. B
Femtocells can be used to improve the indoor coverage and bandwidth of 3G cellular networks in homes and buildings. They are designed to be placed in a fixed location. However, their use would also be interesting in mobile environments such as public transportation systems. This paper studies the mobility limitations at the layer 3 and suggests an approach to support mobility on femtocell networks. This solution employs the protocols already defined in the femtocell architecture, minimizing thus the impact on it. Index Terms—femtocell architecture, mobile femtocell, MOBIKE, IKEv2, IPsec. I. INTRODUCTION Femtocells are small, low-cost and low-power cellular base stations, typically designed for use in a home or small business (e.g., a holiday cottage) to improve indoor coverage and band- width, and also to off-load traffic from the existing macrocell network (1). Nowadays, femtocells are usually deployed by the customers, they have a fixed location (i.e., they do not move), and they always connect to the 3G core network using a ciphered IP tunnel through the Internet connection provided by a Digital Subscriber Line (DSL) or cable router. However, femtocells could also be interesting in other scenarios. Trains, buses or trams could provide faster data speeds and better user experience to theirs passengers setting up femto- cells. However, supporting mobility on femtocell networks is a challenge due to their architecture, that was designed to be fixed. Our work is focused on supporting mobility on femtocell networks by suppressing the original fixed interface and setting a pool of heterogeneous wireless interfaces in its place. Toward this end, it will be necessary to provide mechanisms that perform handovers between technologies, ensuring thus conti- nuity of service to the users. It is expected these handovers will be performed between different technologies (inter-handover) or between interfaces of the same technology (intra-handover). Besides, different Internet service providers could be used in different interfaces obtaining redundant links and thus reliable systems. In this paper, we investigate what modifications would be necessary at layer 3 (L3) in the femtocell protocol stack to be able to move femtocells through a heterogeneous wireless network scenario. As far as we know this is the first proposal of a change to the femtocecll architecture to support mobility. The idea is to employ the protocols already defined for femtocells and therefore minimize the impact on the existing architecture. SeGW Internet IPsec tunnel
Digital subscriber line (DSL) technology for copper twisted pair access networks has been evolving to meet the ever-growing demand for higher data rates. This evolution has gone hand in hand with the roll out of fiber deep in the access network. The most recent technology is vectored VDSL2, able to offer an aggregate data rate of 200 Mb/s on a single copper pair. The next step is to reach 500 to 1000 Mb/s over even shorter copper loops up to a few hundred meters. Such a DSL deployment is an enabler for the cost-effective continuation of the fiber roll-out closer to the end-user. In this paper, a reality check is performed on the digital complexity of a next-generation DSL ( Omega DSL) transceiver. By taking into account Moore's law, it is shown that the time is right for this next-generation DSL.
The exponential growth of Internet traffic is generating revenues which are not fairly distributed among all the actors involved in the value chain. In spite of the increasing returns for over-the-top service providers, application developers, and device producers, network operators and content right owners are not taking advantage of Internet evolution. Analysts forecast that in a few years this imbalance will cause the congestion of the network without any motivation for new investments on it, thus ultimately bringing the Internet to collapse. On the other hand, if properly distributed, the value generated by Internet traffic would be sufficient to sustain innovation and growth. This paper analyses the bottlenecks in the value chain induced by the access-based business models currently adopted by operators. Net neutrality and market law are the pillars which sustain an alternative service-based model granting to the network the degrees of freedom necessary to overcome its own bottlenecks without the need for external enforcement.
As part of the development of a general strategy, we present a framework for the establishment of sustainable broadband communication in under-served areas of developing regions often described in terms of low population density, low purchasing power, intermittent power supply, and lack of competent human resources. Due to an increasing political awareness of the importance of ICT for development, not least due to the explosive expansion of the mobile phone networks, such regions are getting more attention also regarding broadband infrastructure. Our research includes experimental validation of a community networking approach based on affordable high-performance, low-effect technologies focusing on pilot projects in Tanzania.
In medical environment, there is a fundamental demand to transfer and store large volumes of image data generated by modern medical devices. Currently the majority of the medical facilities spread around the country have quite limited Internet access. The aim of our work, presented in this article, was to find an optimal solution to transfer large volumes of image date over low-capacity links with regarding to minimum response-times. First we statistically described the traffic generated by the corresponding medical equipment and then evaluated the behaviour of these mathematical models in the OPNET Modeler discrete event simulation environment. The simulation results and their interpretation represent the main contribution of the following text.
A Mobile Station (MS)-controlled fast and simple scheme of handover (HO) in Mobile WiMAX network has been described. An MS can roughly estimate its present distance from any neighbouring Base Stations (BS) using the Received Signal Strength (RSS) and an appropriate pathloss formula. From the Mobile Neighbor Advertisement (MOB_NBR-ADV) broadcasts, the MS periodically monitors the RSS of its Serving BS (SBS), chooses the appropriate times to perform few scanning of selected Neighbouring BSs (NBS) and estimates their changing distances to compute their respective angles of divergence from its own line of motion. The MS selects the NBS having the minimum angle of divergence (AOD), coupled with satisfactory quality of service and bandwidth capability, as its Target BS (TBS) and requests the SBS for executing this HO. Simulation studies show fairly reduced HO latency. MS-controlled HO promises greatly increased scalability for the Mobile WiMAX network.
A new solution for fault-tolerance in wireless sensor and actor networks (WSAN) is proposed. The solution deals with fault-tolerance of actors, contrary to most of the literature that only considers sensors. It considers real-time communication, and ensures the execution of tasks with low latency despite fault occurrence. A simplified MAMS (multiple-actor multiple-sensor) model is used, where sensed events are duplicated only to a limited number of actors. This is different from the basic MAMS model and semi-passive coordination (SPC), which use data dissemination to all actors for every event. Although it provides high level of fault-tolerance, this large dissemination is costly in terms of power consumption and communication overhead. The proposed solution relies on the construction of self-repairing clusters amongst actors, on which the simplified MAMS is applied. This clustering enables actors to rapidly replace one another whenever some actor breaks down, and eliminates the need of consensus protocol execution upon fault detection, as required by the current approaches to decide which actor should replace the faulty node. The extensive simulation study carried out with TOSSIM in different scenarios shows that the proposed protocol reduces the latency of replacing faulty actors compared to current protocols like SPC. The reduction of the overall delay for executing actions reaches 59%, with very close fault-tolerance (action execution success rate). The difference for this metric does not exceed 8% in the worst case. Scenarios of different network sizes confirm the results and demonstrate the protocol's scalability.
Information spreading in self-organized networks is a frequently investigated research topic today; however, investigating the characteristics of application spreading by exploiting the direct connections between the user devices has not been widely studied yet. In this paper, we present our spreading model, in which we use Closed Queuing Networks to model the application spreading process. In this model, we capture the users' behavior, as well. We also give some simulation results to demonstrate the usage of our model.
The optimal base station placement and effective radio resource management are of paramount importance tasks in cellular wireless networks. This paper deals with automatic planning of base station sites on a studied scenario, maintaining coverage requirement and enabling the transmission of traffic demands distributed over the area. A city scenario with different demands is examined and the advantages/disadvantages of this method are discussed. The planner and optimizing tasks are based on an iterative K-Means clustering method. The planning method involves base station positioning and selecting antenna main lobe direction. Results of the output network deployment of this algorithm are shown, with various traffic loads over the studied area.
In this paper we present an insight on the IPv6 features and a few examples of propositions for Extensions to IPv6 protocols, which enable autonomic network set-up and operation. The concept of autonomicity-realized through control-loop structures embedded within node/device architectures and the overall network architecture as a whole is an enabler for advanced self-manageability of network devices and the network as a whole. GANA Model for Autonomic networking introduces autonomic manager components at various levels of abstraction of functionality within device architectures and the overall network architecture, which are capable of performing autonomic management and control of their associated Managed-Entities (MEs) e.g. protocols, as well as cooperating with each other in driving the self-managing features of the Network(s). MEs are started, configured, constantly monitored and dynamically regulated by the autonomic managers towards optimal and reliable network services. This amounts to what we call autonomic setup and operation of the network. We present how to achieve this, and also present the features that IPv6 protocols exhibit, that are fundamental to designing and building self-configuring, self-optimizing and self-healing networks i.e. IPv6 based autonomic networks.
A novel wavelength and bandwidth allocation algorithm in WDM-EPON is proposed to provide subscriber differentiation by ensuring guaranteed bandwidth levels in the upstream direction. Contrary to previous schemes, the new algorithm is designed to save cost at both ends of the network, especially at the users’ side, as it restricts the number of upstream wavelengths which can be used by them. Simulation results show that ShaWaG achieves better performance than other bandwidth allocation algorithms in WDM-EPONs but simultaneously it requires lower number of upstream wavelengths. The novel algorithm makes fairer bandwidth distribution than those methods as it ensures efficiently a minimum guaranteed bandwidth to every subscriber for a larger number of ONUs when compared to existing methods.
The IEEE 802.11 standard is coming from 1999. Since that time lots of research paper were born analyzing WiFi networks. However, until the recent years, WiFi devices and drivers were on closed source, so measurements could rely only on those features that the vendors offered for them. For such reason there could be hardly any research focusing on the bit level internals of WiFi transmissions. Today we already have better tools to access the WiFi devices. This paper presents measurements in real WiFi scenarios and shows what happens with the message bits on their flight. The paper also highlights that the implementation of WiFi devices are very different and using a single parameter set to model them is inappropriate and might be misleading. abstract environment.
Unquestionably, syslog provides the most popular and easily manageable computer system logging environment. In a computer network, syslog messages are used for several purposes such as for optimizing system performance, logging user’s actions and investigating malicious activities. Due to all these essential utilities, a competent transport service for syslog messages becomes important. Most of the current syslog implementations use either the unreliable UDP protocol or the more costly reliable TCP protocol. Neither of these protocols can provide both timeliness and reliability, while transporting inherently prioritized syslog messages in a congested network. In this paper, we both propose and evaluate the use of PR-SCTP, an existing partial reliability extension of the SCTP transport protocol, as a candidate transport service for the next generation syslog standard. In our emulation based experimental results, PR-SCTP shows better performance than TCP in terms of average delay for message transfer. Furthermore, PR-SCTP exhibits less average packet loss than UDP. In both cases, PR-SCTP exploits priority properties of syslog messages during loss recovery.
The domain of Autonomics and Self-Managing networks come with a number of self-* features, such as auto-discovery and auto-configuration to name a few. In this paper, we provide a novel approach to auto-discover and auto/self-configure routers for OSPF routing in an autonomic network. We present the enablers for realizing these self-* functionalities. This includes a framework for describing the network policies, objectives and router configuration, models to be followed by a node/device implementation when self-describing the capabilities of a node and tokens for enforcing security and access control during the auto-discovery and auto-configuration processes of a node. We also present the algorithms that the various entities should employ for realizing these self-* features in their autonomic networks.
BitTorrent as one of the leading P2P file sharing applications has dominant traffic in broadband access networks. In this paper we present the main characteristics of BitTorrent traffic based on actual measurements taken from a commercial network. Analysis results at both application- and flow-levels are presented and discussed.
Autonomic Networking, realized through control loops, is an enabler for advanced self-manageability of network nodes and respectively the network as a whole. Self-healing is one of the desired autonomic features of a system/network that can be facilitated through autonomic behaviors realized by control loop structures. Autonomicity, implemented over existing protocol stacks as managed resources, requires an architectural framework that integrates the diverse aspects and levels of self-healing capabilities of individual protocols, systems and the network as a whole, such that they all should co-operate as required towards achieving reliable network services. This integration should include the traditional resilience capabilities intrinsically embedded within some protocols e.g. some telecommunication protocols, as well as diverse proactive and reactive schemes for incident prevention and resolution, which must be realized by autonomic entities implementing a control loops at a higher-level outside of protocols. In this paper, we present our considerations on how such an architectural framework, integrating the diverse resilience aspects inside an autonomic node, can facilitate collaborative self-healing across end systems, access networks, edge and core network components.
In this paper we discuss the perspectives that should be taken into account by the research community while trying to evolve Fault-Management towards Autonomic Fault-Management. The well known and established FCAPS Management Framework for Fault-management, Configuration-management, Accounting-management, Performance-management and Security-management, assumes the involvement of human technicians in the management of systems and networks as is the practice today. Due to the growing complexity of networks, services and the management of both, it is now widely believed within the academia and the industry that the concept of Self-Managing Networks will address some of the current challenges in the management of networks and services. Emerging Self-Management technologies are promising to reduce OPEX for the network operator. There is still a lot of work to be done before we can see advanced, production level self-manageability aspects of systems and networks, beyond what has been achieved through scripting based automation techniques that have been successfully applied to management and network operation processes. The concept of autonomicity—realized through control-loop structures and feed-back mechanisms and processes, as well as the information/knowledge flow used to drive the control-loops), becomes an enabler for advanced self-manageability of networks and services, beyond what has been achieved through scripting based automation techniques. A control-loop can be introduced to bind the processes involved in each of the FCAPS areas, and the “autonomic manager components” that drive the control loops and are specific for different FCAPS should interwork with each other in order to close the gaps characterized by dependencies among FCAPS functional areas as the FCAPS functional areas go autonomic and realize self-management. The dependencies among FCAPS functional areas need to be studied such that the functions/operations and processes that belong to the different areas can be well interconnected to achieve global system goals, such as integrity, resilience and high degree guarantee of system and service availability.
The diverse characteristics of network anomalies, and the specific recovery approaches that can subsequently be employed to remediate their effects, have generally led to defence mechanisms tuned to respond to specific abnormalities; and they are often suboptimal for providing an overall resilience framework. Emerging future network environments are likely to require always-on, adaptive, and generic mechanisms that can integrate with the core networking infrastructure and provide for a range of self-* capabilities, ranging from self-protection to self-tuning. In this paper we present the design and implementation of an adaptive remediation component built on top of an autonomic network node architecture. A set of pluggable modules that employ diverse algorithms, together with explicit cross-layer interaction, has been engineered to mitigate different classes of anomalous traffic behaviour in response to both legitimate and malicious external stimuli. In collaboration with an always-on measurement-based anomaly detection component, our prototype facilitates the properties of self-optimisation and self-healing.
