Mobile Network Connectivity Research Articles

MUBaaS: mobile ubiquitous brokerage as a service

The use of multiple personalized mobile devices (e.g., smartphones and tablets) is on the increase. As such, users expect to access several network-based services across their n-devices. Previous studies proposed Ubiquitous Cloud Computing (UCC) where a single user or service consumer is facilitated to access multiple services from n-devices. However, seamless synchronization of data between the multiple devices can be hindered by intermittent loss of connectivity in mobile wireless networks due to user mobility. Another source of latency is non-scalable architectures that tend to be overburdened during peak loads. This work proposes a cloud-based application middleware, called Mobile Ubiquitous Brokerage as a Service (MUBaaS), which enables n-devices of a user to access multiple cloud services end-points in soft-real time. This is achieved by proposing distributed brokers that coordinates the transactions of the user while taking load balancing into account. Pilot evaluations of the proposed architecture prove real-time application synchronization with reasonable scalability.

アドホックネットワークを形成する群ロボットの優先度付き分散 Receding Horizon Control

This paper presents a multi-robot control method considering a mobile ad-hoc network connectivity and inter-robot collision avoidance. A method I studied previously was based on a receding horizon control (RHC) method, and was decentralized one by some kind of serialization. However, the previous method remains some disadvantages; especially, no-scalability and huge computations. Because these disadvantages are critical flaws for multi-vehicle systems, I strive to improve the method in this paper. By a distributed priority variable, several vehicles (but not all vehicles) can make their decisions at same time in the proposed method. We show the proposed method in this paper is less computation than the previous method.

모바일 P2P 네트워크에서 피어의 연결성을 고려한 그룹 기반 캐시 공유 기법

모바일 P2P 네트워크에서 사용자 요청을 효과적으로 처리하기 위해 캐시 공유 기법들이 연구되고 있다. 본 논문에서는 모바일 P2P 네트워크에서 피어의 연결성에 기반을 둔 클러스터를 구축하여 캐시를 공유하는 기법을 제안한다. 제안하는 기법은 연결성이 오랫동안 유지될 수 있는 피어들을 하나의 클러스터로 구성하여 캐시를 공유한다. 클러스터 내부에 있는 피어들의 캐시를 하나로 사용함으로써 데이터의 중복을 감소시키고 캐시 공간을 효율적으로 사용한다. 또한, 캐시 공간을 데이터 캐시와 임시 캐시 두 부분으로 분할하여 사용한다. 임시 캐시를 활용하여 클러스터의 토폴로지가 변경되거나 캐시 데이터 교체 시, 지연시간을 감소시킬 수 있다. 일반적인 기법은 협력적 캐시 처리 절차를 통해 질의가 전달되지만 통신비용을 줄이기 위해 1-홉 피어 캐시확인과 클러스터 헤더로 가는 경로에 있는 피어의 캐시를 확인한다. 성능 평가 결과 제안하는 기법이 기존 기법에 비해 캐시 적중률도 높고 지연시간을 감소시키는 것을 확인할 수 있었다. Recently, cache sharing methods have been studied in order to effectively reply to user requests in mobile P2P networks. In this paper, we propose a cache sharing scheme based on a cluster considering the peer connectivity in mobile P2P networks. The proposed scheme shares caches by making a cluster that consists of peers preserving the connectivity among them for a long time. The proposed scheme reduces data duplication to efficiently use the cache space in a cluster. The cache space is divided into two parts with a data cache and a temporary cache for a cache space. It is possible to reduce the delay time when the cluster topology is changed or the cache data is replaced utilizing a temporary cache. The proposed scheme checks the caches of peers in a route to a cluster header and the caches of one-hop peers in order to reduce the communication cost. It is shown through performance evaluation that the proposed scheme outperforms the existing schemes.

MALL: the pedagogical challenges

In this paper the development of mobile-assisted language learning (MALL) over the past 20 years is reviewed with a particular focus on the pedagogical challenges facing its exploitation. Following a consideration of the definition of mobile learning, the paper describes the dominant mobile technologies upon which MALL applications have been based: MP3 players, personal digital assistants, and mobile phones. It then identifies the prevalent methodological approach that has underlain the great majority of MALL implementations: a behaviorist, teacher-centered, transmission model of instruction. However, though rarely implemented, MALL is equally capable of supporting more innovative constructivist, collaborative, learner-centered instruction, examples of which are examined. Besides being restricted by a pedagogical approach very much out of step with methodologies that have guided foreign language teaching for nearly four decades, MALL has also been constrained by access to technology. In part, this problem has been due to the necessity of acquiring mobile devices for student usage and the costs associated with mobile network and Internet connections. Even more so, the exploitation of mobile devices for language learning has been hampered by a lack of hardware standardization and entrenched operating system incompatibilities. The paper concludes that MALL has yet to realize its full potential and that achieving this aim is more a matter of pedagogy than technology. The financial and technological factors that have impeded the effective exploitation of MALL are likely to be resolved as operating system incompatibilities are overcome by market forces and students as well as teachers acquire suitable mobile devices for their own personal use. The future of MALL lies in the exploitation of the communication and multimedia affordances of mobile devices in ways that support collaborative, task-based learning both within and outside of the classroom.

Population Mobility Dynamics Estimated from Mobile Telephony Data

In the last decade, mobile phones and mobile devices using mobile cellular telecommunication network connections have become ubiquitous. In several developed countries, the penetration of such devices has surpassed 100 percent. They facilitate communication and access to large quantities of data without the requirement of a fixed location or connection. Assuming mobile phones usually are in close proximity with the user, their cellular activities and locations are indicative of the user's activities and movements. As such, those cellular devices may be considered as a large scale distributed human activity sensing platform. This paper uses mobile operator telephony data to visualize the regional flows of people across the Republic of Ireland. In addition, the use of modified Markov chains for the ranking of significant regions of interest to mobile subscribers is investigated. Methodology is then presented which demonstrates how the ranking of significant regions of interest may be used to estimate national population, results of which are found to have strong correlation with census data.

Handoff and Route Optimization in Mobile Networks over IEEE 802.16e

To fulfill the need for on-the-move and uninterrupted internet connectivity in Mobile Networks, IETF NEMO working group was created to extend basic end-host mobility support in Mobile IPv6 (MIPv6) protocol. NEMO Basic Support Protocol (NEMO) has been standardized by this group to provide the network mobility support. However, the handover latency in NEMO is high and, the nested tunnels’ problem in the nested NEMO networks is not considered. Many schemes have been proposed to solve these problems by optimizing the handover signaling procedure, and by proposing routing optimization scheme for NEMO. Better optimized signaling procedure is proposed in this paper, and a proposed Routing Optimization scheme as a solution for the lack of the nested tunnels’ problem is proposed as well. Analytical results highlight the importance of the proposed scheme comparing to others are provided, revealing that the proposed scheme has the lowest handover latency and disruption time.

Mobility Increases the Connectivity of Wireless Networks

In this paper, we investigate the connectivity for large-scale clustered wireless sensor and ad hoc networks. We study the effect of mobility on the critical transmission range for asymptotic connectivity in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -hop clustered networks and compare to existing results on nonclustered stationary networks. By introducing <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -hop clustering, any packet from a cluster member can reach a cluster head within <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> hops, and thus the transmission delay is bounded as Θ(1) for any finite <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> . We first characterize the critical transmission range for connectivity in mobile <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -hop clustered networks where all nodes move under either the random walk mobility model with nontrivial velocity or the i.i.d. mobility model. By the term nontrivial velocity, we mean that the velocity of a node <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> is ω( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</i> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> )), where <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</i> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> ) is the transmission range of the node. We then compare with the critical transmission range for stationary <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -hop clustered networks. In addition, the critical number of neighbors is studied in a parallel manner for both stationary and mobile networks. We also study the transmission power versus delay tradeoff and the average energy consumption per flow among different types of networks. We show that random walk mobility with nontrivial velocities increases connectivity in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -hop clustered networks, and thus significantly decreases the energy consumption and improves the power-delay tradeoff. The decrease of energy consumption per flow is shown to be Θ([(log <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> )/( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</i> )]) in clustered networks. These results provide insights on network design and fundamental guidelines on building a large-scale wireless network.

A Novel Rebroadcast Technique for Reducing Routing Overhead In Mobile Ad Hoc Networks

In mobile ad hoc networks (MANETs), the network topology changes frequently and unpredictably due to the arbitrary mobility of nodes. This feature leads to frequent path failures and route reconstructions, which causes an increase in the routing control overhead. The overhead of a route discovery cannot be neglected. Thus, it is imperative to reduce the overhead of route discovery in the design of routing protocols of MANETs. One of the fundamental challenges of MANETs is the design of dynamic routing protocols with good performance and less overhead. In a route discovery, broadcasting is a fundamental and effective data dissemination mechanism, where a mobile node blindly rebroadcasts the first received route request packets unless it has a route to the destination, and thus it causes the broadcast storm problem. This paper focuses on a probabilistic rebroadcast protocol based on neighbor coverage to reduce the routing overhead in MANETs. Keywords - Mobile Ad Hoc Networks, Neighbor Coverage, and Network Connectivity, Probabilistic Rebroadcast, Routing Overhead, AODV.

Middleware Services with Context Aware Intelligent Decisions for Disconnection Tolerant Mobile Applications

In order to effectively maintain mobile application services in spite of sudden network disruption, middleware services with context aware intelligent decisions are required on the mobile device and the Mobile Intelligent Server (MIS) located between mobile devices and servers. Middleware services provide the management of mobile services, network connection, limited resource and context information. In this paper, we propose middleware services with context aware intelligent decisions for disconnection tolerant mobile application services. Such middleware services manage runtime application and networking contexts for intelligent decision making of the middleware.

Graph-theoretic connectivity control of mobile robot networks

In this paper, we provide a theoretical framework for controlling graph connectivity in mobile robot networks. We discuss proximity-based communication models composed of disk-based or uniformly-fading-signal-strength communication links. A graph-theoretic definition of connectivity is provided, as well as an equivalent definition based on algebraic graph theory, which employs the adjacency and Laplacian matrices of the graph and their spectral properties. Based on these results, we discuss centralized and distributed algorithms to maintain, increase, and control connectivity in mobile robot networks. The various approaches discussed in this paper range from convex optimization and subgradient-descent algorithms, for the maximization of the algebraic connectivity of the network, to potential fields and hybrid systems that maintain communication links or control the network topology in a least restrictive manner. Common to these approaches is the use of mobility to control the topology of the underlying communication network. We discuss applications of connectivity control to multirobot rendezvous, flocking and formation control, where so far, network connectivity has been considered an assumption.

Effect of Transport Models on Connectivity of Interbus Communication Networks

Vehicular Ad-Hoc Networks (VANETs) attract considerable research and commercial interest with promising applications in a number of areas including cooperative vehicle-highways systems, sensor networks, and safety systems. However, as a result of high speed and variable driver behavior, automotive ad-hoc networks behave in fundamentally different ways to the most prevalent models in Mobile Ad-Hoc Network (MANET) research. Previous work in MANETs has mostly assumed that the mobile nodes move randomly with an unconstrained mobility model, and it is clear that a random mobility model is not adequate to represent the major characteristics of real-world vehicle motions and may therefore lead to unreliable results. Recent studies of VANETs have attempted to introduce macro- and micromobility constraints to model vehicle motions, but they have mostly focused on modeling the mobility of generic private vehicles. Given the potential for the coordinated deployment of network nodes on centrally managed fleet vehicles, it has become important to model the characteristics of a VANET featuring vehicles of different types, with systematically different behavior patterns. In this article, the authors study the connectivity of mobile ad-hoc networks that consist of buses moving in urban area and examine the implications for transport-related services. Buses have a unique set of behavior characteristics (e.g., fixed routes, schedules, bus stops, specific priorities), which gives rise to distinct effect on node connectivity in the communication network. Through extensive simulations on the basis of real bus routes in central London, the authors (a) demonstrated the effect of the locations of stops and the prevailing traffic patterns on node connectivity (including the distributions of contact duration and intercontact time between buses) and (b) explored its implication on the design of a dissemination system to capture and disseminate data. Their results give a key message that the mobility of buses has to be modeled explicitly, and such kind of knowledge of connectivity among buses will be significant for the studies of routing algorithms and other networking functions in interbus communication networks.

Innovative Secure Mobile Banking Services

Due to the widespread use of computer technologies in almost all aspects of life, organisations that are connected to the Internet started extending their services to their customers to include new applications and services that satisfy their customersâ?? desires to make better businesses. One of these emerging applications is mobile banking. The term mobile banking (or m-banking) describes the banking services that the user can perform via a mobile device ubiquitously at anytime and from anywhere. In order for users to access their accounts, they need a mobile device and network connectivity. Therefore, sitting in front of a computer is not a requirement anymore; accessing accounts can occur while users are waiting their turn at the dentist clinic or relaxing at the beach!&#x0D; This paper explores the opportunities of using mobile technology in the electronic banking (e-banking) sector to enhance existing banking services by moving toward m-banking using mobile devices and wireless media that can provide opportunities for ubiquitous access to the banking services as mobile technologies can be used at anytime and from anywhere. The technical problems encountered while using the mobile devices presents some technical difficulties and challenges for the m-banking. &#x0D; In this paper we introduce a mobile system that demonstrates the flexibility gained out of this technology and covers the major aspects of such kind of applications. The proposed system covers two parts: the customer services (user interface) and the security aspects. In the user interface part, banking facility is provided to the user through the mobile device to implement banking transactions. The model provides customers with the services: billing payments, transferring of funds, viewing of customerâ??s accounts and transactions, allowing the user to change his/her password and request a cheque book. The application takes into consideration security aspects, it satisfies the following security requirements: Authentication, Confidentiality and Authorisation.&#x0D; This paper introduces the advantages and disadvantages of using mobility in the banking sector. Furthermore, this paper also presents the security, suitability and feasibility aspects of using m-banking in terms of technology and usability.

Network Connection and Perfectly Secure Message Transmission on Wireless Mobile Networks

In this paper we proposed perfectly secure message transmission for reliable and secure communications in order to ensure that an adversary cannot obtain information (in the information theoretic sense) about messages. There are numerous studies about the interplay of network connectivity and perfectly secure message transmission under a Byzantine adversary capable of corrupting up to t players. It is known that perfectly secure communication among any pair of players is possible if and only if the underlying synchronous wired network is (2t+1)-connected. But existing studies deal with traditional wired networks and neglect perfectly secure message transmission on mobile networks. Therefore, we proposed a perfectly secure message transmission protocol and analyzed the interplay of mobile network connectivity and perfectly secure message transmission. We considered that network connection takes priority over other factors for perfectly secure message transmission, and we showed that the number of paths needed to ensure mobile network connection is   n K n N log = in an undirected graph with n nodes. And, we proved that the connectivity (2T+1) on mobile networks with n nodes, where   n K t T log = , must be higher than the connectivity (2t+1) of wired networks.

Island Connections: Icelandic Spatiality in the Wake of Worldly Linkages

The notions and materiality of connections, through electronic networks as well as modes of mobility, play an ever-increasing role in how we define, understand, engage and experience the world we live in and the islands we live on. This article presents an account of Icelandic encounters with technologies of telecommunication and explores how electronic connections have participated in formulating a particularly connected, island spatiality. It is argued that an island can be regarded as a kind of connected laboratory suitable for studying how associations form around technologies of connections, which can be traced through various actors. For this purpose, the historical genealogy of connections and telecommunication in Iceland is analyzed, as well as more contemporary ideas and representations of mobile phone usage and network connectivity. It is maintained that connections have fundamentally altered the spatiality as well as representations of Iceland. While still an island in a geographical sense, and in that manner remote and isolated, the social space of the island now denies such connotations in many respects, valorizing the connectivity of Iceland and its people.

Experimentation and performance analysis of multi-interfaced mobile router scheme

Network mobility (NEMO) aims providing seamless Internet connectivity of the whole mobile network that consists of mobile routers (MRs) and mobile network nodes (MNNs). The network moves around along with vehicles as a whole. According to NEMO basic support protocol (NEMO BSP), only one primary care of address (CoA) of MR can be registered with home agent, which will affect the handover performance. As an extension of NEMO BSP, multiple care of addresses (MCoA) registration scheme was proposed as Internet-draft and has received extensive researches. This paper studies the Internet connectivity of mobile router (MR) on the basis stated above; MR is equipped with WLAN, CDMA and GPRS interfaces simultaneously. Concretely, a smooth handover algorithm is proposed and experimented on our platform successfully; round trip time (RTT) of each link and the handover process between different interfaces are analyzed, respectively. Furthermore, the service disruption time and packet loss ratio performances are also compared between uni-interfaced MR scheme of NEMO BSP and scheme proposed in this paper, and the results indicate that multi-interfaced scheme not only supports large area movement across heterogeneous networks of MR, it also provides a seamless handover with no packet loss and little service disruption time.

Connectivity of mobile linear networks with dynamic node population and delay constraint

The connectivity properties of a mobile linear network with high speed mobile nodes and strict delay constraint are investigated. A new mobility model is developed to represent the steady state node distribution, and it accurately captures the statistical properties of random node arrival, time-varying node speed, and the distinct behaviors of nodes following different traffic patterns.With the mobility model, the statistical properties of network connectivity are studied and identified. Unlike most previous works that do not consider the impacts of transmission latency, which is critical for real time applications, this paper identifies the quantitative relationship between network connectivity and delay constraint. The results are applicable to both delay constrained networks and delay tolerant networks. The connectivity analysis is performed with a novel geometry-assisted analytical method. Exact connectivity probability expressions are developed by using the volumes of a hypercube intersected by a hyperplane, and a hyperpyramid. The geometry-assisted analytical method significantly simplifies the connectivity analysis.

Autonomic communication services: a new challenge for software agents

The continuous growth in ubiquitous and mobile network connectivity, together with the increasing number of networked devices populating our everyday environments, call for a deep rethinking of traditional communication and service architectures. The emerging area of autonomic communication addresses such challenging issues by trying to identify novel flexible network architectures, and by conceiving novel conceptual and practical tools for the design, development, and execution of "autonomic" (i.e., self-organizing, self-adaptive and context-aware) communication services. In this paper, after having introduced the general concepts behind autonomic communication and autonomic communication services, we analyze the key issue of defining suitable "component" models for autonomic communication services, and discuss the strict relation between such models and agent models. On this basis, we survey and compare different approaches, and eventually try to synthesize the key desirable characteristics that one should expect from a general-purpose component model for autonomic communication services. The key message we will try to deliver is that current research in software agents and multi-agent systems have the potential for playing a major role in inspiring and driving the identification of such a model, and more in general for influencing and advancing the whole area of autonomic communication.

Topology Discovering and Power saving Mechanism for Routing in a Tree of Ad-hoc Wireless Networks

Power management in mobile network is an open challenges where the power level in the network influences the network life time. However, there are a trade off between the power consumption and the connectivity in mobile networks. We present a topology control mechanism and a routing protocol for Ad-Hoc wireless networks that chooses the shortest path given the lower power consumption. The power consumption in forwarding a packet in the proposed topology is depends on only two main factors are the number of hops and the packet size. Our analytical results are confirmed by our simulation results where both has give the same results for power consumption in sending a packet taking in consideration only the power consumed in communication.

Potential Fields for Maintaining Connectivity of Mobile Networks

The control of mobile networks of multiple agents raises fundamental and novel problems in controlling the structure of the resulting dynamic graphs. In this paper, we consider the problem of controlling a network of agents so that the resulting motion always preserves the connectivity property of the network. In particular, the connectivity condition is translated to differentiable constraints on individual agent motion by considering the dynamics of the Laplacian matrix and its spectral properties. Artificial potential fields are then used to drive the agents to configurations away from the undesired space of disconnected networks while avoiding collisions with each other. We conclude by illustrating a class of interesting problems that can be achieved while preserving connectivity constraints.

Confirming Connectivity in Interworked Broadcast and Mobile Networks

Industry reactions to major shifts such as mobile broadcast convergence are typically a mixture of opportunities and threats. Both the mobile and the broadcast industries acknowledge the role that convergence will play in their commercial futures, but both would prefer to achieve convergence "on their own patch." For this reason, the most appealing solution to fulfil the contrasting requirements from the different players is represented by interworking between these networks rather than integration. This approach avoids integration, thereby minimizing the changes required in each network and ensuring each network remains an autonomous, independently managed entity. The Internet protocol (IP) is chosen as the "glue" between these heterogeneous networks, providing the generic interworking platform. The main reason behind this choice is that IP was designed as an "interworking protocol" to connect multiple, physically-different networks in such a way as to remain independent of the underlying transport mechanisms used. This article concentrates on the confirm connectivity architecture definition of the interworking model between WLAN, 3G, and DVB. Broadcast networks are uni-directional in nature. When a user wants to receive a service over a broadcast network, there is no way to know whether the broadcast interface of the terminal is configured correctly. In this article we describe a method to automatically configure and test, without user intervention, that the DVB interface of the terminal can receive datagrams from the broadcast network. Furthermore, an optimization method to reduce the total number of confirm connectivity messages (CCMs) sent by the multimode terminals is introduced with simulation results to validate and prove its effectiveness