Mobility Management in beyond 3G-Environments

Beyond 3G-environments are typically defined as environments that integrate different wireless and fixed access network technologies. In this paper, we address IP based Mobility Management (MM) in beyond 3G-environments with a focus on wireless access networks, motivated by the current trend of WiFi, GPRS, and UMTS networks. The GPRS and UMTS networks provide countrywide network access, while the WiFi networks provide network access in local areas such as city centres and airports. As a result, mobile end-users can be always on-line and connected to their preferred network(s), these network preferences are typically stored in a user profile. For example, an end-user who wishes to be connected with highest bandwidth could be connected to a WiFi network when available and fall back to GPRS when moving outside the hotspot area.\ud In this paper, we consider a combination of MM for legacy services (like web browsing, telnet, etc.) using Mobile IP and multimedia services using SIP. We assume that the end-user makes use of multi-interface terminals with the capability of selecting one or more types of access networks\ud based on preferences. For multimedia sessions, like VoIP or streaming video, we distinguish between changes in network access when the end-user is in a session or not in a session. If the end-user is not in a session, he or she needs to be able to start new sessions and receive invitations for new sessions. If the end-user is in a session, the session needs to be handed over to the new access network as seamless as possible from the perspective of the end-user. We propose an integrated but flexible solution to these problems that facilitates MM with a customizable transparency to applications and end-users

Using Machine Learning for Handover Optimization in Vehicular Fog Computing

Smart mobility management would be an important prerequisite for future fog computing systems. In this research, we propose a learning-based handover optimization for the Internet of Vehicles that would assist the smooth transition of device connections and offloaded tasks between fog nodes. To accomplish this, we make use of machine learning algorithms to learn from vehicle interactions with fog nodes. Our approach uses a three-layer feed-forward neural network to predict the correct fog node at a given location and time with 99.2 % accuracy on a test set. We also implement a dual stacked recurrent neural network (RNN) with long short-term memory (LSTM) cells capable of learning the latency, or cost, associated with these service requests. We create a simulation in JAMScript using a dataset of real-world vehicle movements to create a dataset to train these networks. We further propose the use of this predictive system in a smarter request routing mechanism to minimize the service interruption during handovers between fog nodes and to anticipate areas of low coverage through a series of experiments and test the models' performance on a test set

WCDMA in Malaysia

Wideband Code Division Multiple Access (WCDMA) A 3G highspeed digital data service provided by cellular carriers that use the time division multiplexing (TDMA) or GSM technology worldwide, including AT&T (formerly Cingular) and T-Mobile in the U.S. WCDMA works on WCDMA cell phones as well as laptops and portable devices with WCDMA modems [1]. Users have typically experienced downstream data rates up to 400 Kbps [1]. WCDMA has been used in the Japanese Freedom of Mobile Multimedia Access (FOMA) system and in the Universal Mobile Telecommunications System (UMTS); a third generation follow-on to the 2G GSM networks deployed worldwide [1]. Although TDMA and GSM carriers both use TDMA modulation, WCDMA stems from CDMA. Part of the 3GPP initiative, the International Telecommunication Union (ITU) refers to WCDMA as the Direct Sequence (DS) interface within the IMT-2000 global 3G standards [1]

Handover management in mobile WiMAX using adaptive cross-layer technique

The protocol type and the base station (BS) technology are the main communication media between the Vehicle to Infrastructure (V2I) communication in vehicular networks. During high speed vehicle movement, the best communication would be with a seamless handover (HO) delay in terms of lower packet loss and throughput. Many studies have focused on how to reduce the HO delay during lower speeds of the vehicle with data link (L2) and network (L3) layers protocol. However, this research studied the Transport Layer (L4) protocol mobile Stream Control Transmission Protocol (mSCTP) used as an optimal protocol in collaboration with the Location Manager (LM) and Domain Name Server (DNS). In addition, the BS technology that performs smooth HO employing an adaptive algorithm in L2 to perform the HO according to current vehicle speed was also included in the research. The methods derived from the combination of L4 and the BS technology methods produced an Adaptive Cross-Layer (ACL) design which is a mobility oriented handover management scheme that adapts the HO procedure among the protocol layers. The optimization has a better performance during HO as it is reduces scanning delay and diversity level as well as support transparent mobility among layers in terms of low packet loss and higher throughput. All of these metrics are capable of offering maximum flexibility and efficiency while allowing applications to refine the behaviour of the HO procedure. Besides that, evaluations were performed in various scenarios including different vehicle speeds and background traffic. The performance evaluation of the proposed ACL had approximately 30% improvement making it better than the other handover solutions

Investigating seamless handover in VANET systems

Wireless communications have been extensively studied for several decades, which has led to various new advancements, including new technologies in the field of Intelligent Transport Systems. Vehicular Ad hoc Networks or VANETs are considered to be a long-term solution, contributing significantly towards Intelligent Transport Systems in providing access to critical life-safety applications and infotainment services. These services will require ubiquitous connectivity and hence there is a need to explore seamless handover mechanisms. Although VANETs are attracting greater commercial interest, current research has not adequately captured the realworld constraints in Vehicular Ad hoc Network handover techniques. Due to the high velocity of the vehicles and smaller coverage distances, there are serious challenges in providing seamless handover from one Road Side Unit (RSU) to another and this comes at the cost of overlapping signals of adjacent RSUs. Therefore, a framework is needed to be able to calculate the regions of overlap in adjacent RSU coverage ranges to guarantee ubiquitous connectivity. This thesis is about providing such a framework by analysing in detail the communication mechanisms in a VANET network, firstly by means of simulations using the VEINs framework via OMNeT++ and then using analytical analysis of the probability of successful packet reception. Some of the concepts of the Y-Comm architecture such as Network Dwell Time, Time Before Handover and Exit Times have been used to provide a framework to investigate handover issues and these parameters are also used in this thesis to explore handover in highly mobile environments such as VANETs. Initial investigation showed that seamless communication was dependant on the beacon frequency, length of the beacon and the velocity of the vehicle. The effects of each of these parameters are explored in detail and results are presented which show the need for a more probabilistic approach to handover based on cumulative probability of successful packet reception. In addition, this work shows how the length of the beacon affects the rate of change of the Signal-to-Noise ratio or SNR as the vehicle approaches the Road-Side Unit. However, the velocity of the vehicle affects both the cumulative probability as well as the Signal-to-Noise ratio as the vehicle approaches the Road-Side Unit. The results of this work will enable systems that can provide ubiquitous connectivity via seamless handover using proactive techniques because traditional models of handover are unable to cope with the high velocity of the vehicles and relatively small area of coverage in these environments. Finally, a testbed has been set-up at the Middlesex University, Hendon campus for the purpose of achieving a better understanding of VANET systems operating in an urban environment. Using the testbed, it was observed that environmental effects have to be taken into considerations in real-time deployment studies to see how these parameters can affect the performance of VANET systems under different scenarios. This work also highlights the fact that in order to build a practical system better propagation models are required in the urban context for highly mobile environments such as VANETs

Advanced mobile network monitoring and automated optimization methods

The operation of mobile networks is a complex task with the networks serving a large amount of subscribers with both voice and data services, containing extensive sets of elements, generating extensive amounts of measurement data and being controlled by a large amount of parameters. The objective of this thesis was to ease the operation of mobile networks by introducing advanced monitoring and automated optimization methods. In the monitoring domain the thesis introduced visualization and anomaly detection methods that were applied to detect intrusions, mal-functioning network elements and cluster network elements to do parameter optimization on network-element-cluster level. A key component in the monitoring methods was the Self-Organizing Map. In the automated optimization domain several rule-based Wideband CDMA radio access parameter optimization methods were introduced. The methods tackled automated optimization in areas such as admission control, handover control and mobile base station cell size setting. The results from test usage of the monitoring methods indicated good performance and simulations indicated that the automated optimization methods enable significant improvements in mobile network performance. The presented methods constitute promising feature candidates for the mobile network management system.reviewe

Propagation model for cellular mobile networks used in UAVcommunications environmentss

Recognizing the growth of the drone market in recent years, it is crucial to evaluate the capacity of the mobile communications technologies as well as their infrastructure to verify if these are capable to support various applications and services that may associate with these type of vehicles, achieving lower costs to the users. The type of application chosen for this thesis is a video streaming that is able to assume different qualities depending on the RF conditions, in order to overcome the limitation of radio communications, in which the user is only able to communicate with the drone when in his line of sight. It was necessary to take into account a propagation model that considered the unique characteristics of an UAV, since the most commonly used models only consider a typical mobile user moving below the level of the BSs and their respective antennas using a short/medium frequency interval that is not able to consider the third and fourth generation technologies at once. In order to choose the ideal model, a theoretical study was carried out, which allowed to conclude that Lisbon University Institute Model is the most accurate since it is able to fulfill the requirements associated to a flying drone, considering a larger frequency spectrum, allowing the use of third and fourth generation technologies that are fundamental to support multimedia services, such as video streaming. To verify the viability of mobile communications, measurements were made in three real scenarios in rural areas using a spectrum analyzer carried by a flying drone, in order to monitor, read and write the data related to the signal’s behavior into a file, during the flight route. Based on this approach, it was possible to analyze the viability of mobile communications for a video streaming service using a drone, in a rural environment and considering UMTS and LTE technologies. In addition, evaluate the signal’s performance when the drone is above the antennas where the “hole phenomenon” occurs, theoretically.Tendo em conta o crescimento que o mercado de drones tem tido nos últimos anos, é importante considerar as tecnologias de comunicações móveis assim como as respectivas infraestruturas e verificar se estas são capazes de suportar diversas aplicações que podem estar associadas a estes veículos, permitindo isto um custo inferior para os utilizadores dos mesmos. O tipo de aplicação escolhida para esta tese foi uma streaming de vídeo, com o objetivo de ultrapassar a limitação das comunicações rádio, em que o utilizador apenas consegue comunicar com o drone caso este se encontre no seu campo de visão. Foi necessário ter em conta um modelo de propagação que considerasse as características únicas de movimentação dum drone, uma vez que os modelos mais utilizados apenas consideram um utilizador móvel comum que se desloque abaixo do nível das estações base e respetivas antenas para um espectro de frequências curto/médio. Para a escolha deste modelo, foi realizado um estudo teórico que permitiu concluir que o Lisbon University Institute Model é o mais acertado, uma vez que é capaz de cumprir os requisitos associados a um drone, considerando um intervalo de frequências maior, permitindo a utilização das tecnologias de terceira e quarta geração, que são fundamentais para suportar aplicações multimedia, como é o caso da streaming de vídeo. Para verificar a viabilidade das comunicações móveis, foram feitas medições em três cenários reais em zona rural recorrendo a um analisador de espectros transportado por um drone, com o objetivo de monitorizar, fazer a leitura e gravação de dados associados ao comportamento do sinal para um ficheiro durante a rota de voo. Com esta abordagem, foi possível analisar a viabilidade das comunicações móveis para a aplicação de streaming de vídeo num drone, em cenário rural, considerando as tecnologias UMTS (3G) e LTE (4G). Para além disso, foi ainda possível avaliar o comportamento do sinal quando o drone se encontra acima do eixo vertical das antenas, onde o “fenómeno do buraco” ocorre

China's United Front Work in Civil Society: the Case of Hong Kong

This article unravels China’s united front work in dealing with civil society, using the case of Hong Kong after the political handover since 1997. While it has been widely analyzed by scholars that state corporatism characterizes the state-society relations in China, including the state’s relations with its autonomous regions, Hong Kong as a special administrative region, however, shows that the ruling strategies of China are very adaptive. Comparing with the rest of China where the united front work is partly characterized by a heavy-handed policy of assimilation, the united front work in the post-handover Hong Kong illustrates a more inclusionary version of state corporatism through five types of measures, namely, integration, cooptation, collaboration, containment, and denunciation. The strategies range from soft to hard tactics, and are adopted depending upon whether the central government regards its targets as friends, valuable potential cooptees or enemies. Nevertheless, the soft and hard tactics used in parallel in Hong Kong have resulted in further politicization and polarization of the civil society, and transformed the tension between the state and the local groups into clashes between different local groups, as seen in other autonomous regions such as Tibet and Xinjiang. Over the years, the agents for state corporatism have been ever expanding in Hong Kong. The ideologies propagated have now gone beyond consensus and harmony to also include patriotism and reinterpre-tation of other political ideas, including universal suffrage, conducive to cultivating obedience.postprin