A Smooth Handover Scheme for Fast-Moving Users in Mobile IPv6 Networks

As the rapid development of wireless technologies and increasing communication need of people in ubiquitous environment, some handover schemes and improvements were proposed by the IETF in order to support mobility effectively. In addition, mobile Stream Control Transmission Protocol (mSCTP) proposed by the IETF is a new transport protocol supporting mobility and with a built-in feature called Multi-homing has attracted much attention from the research communities. Multi-homing is convenient to introduce IP diversity in mobility management. A seamless handover architecture called SIGMA based on mSCTP has better performance than Mobile IPv6 enhancements. However, the handover performance in SIGMA remains low if the mobile host moves at a fast speed. Aiming at this problem, we propose SHSBM, a Smooth Handover Scheme based-on mSCTP. SHSBM adopts the advantage of SIGMA, and utilize Buffer and Tunnel to better serve fast-moving users. Additionally, we propose two strategies to solve the problem caused by Buffer-scheme—sequence Out of Order. Criteria for performance evaluation including the packets’ loss rate, throughput and handover latency compared with SIGMA and Mobile IPv6 enhancements.     

Searching for Multiple Mobile Users

The problem of searching for mobile users in cellular networks is addressed in this study. Previous studies addressing this issue have focused on the problem of searching for a single user. As it is shown in this study, the problem of maximizing the expected rate of successful searches under delay and bandwidth constraints is NP-hard. {bf When the potential locations of different users overlap, the derivation of an optimal concurrent search for many independent users from a set of optimal single user searches is NP-hard}. In reality, a cellular network has to serve many competing search requests sharing a limited bandwidth. Since the problem of maximizing the expected rate of successful searches under delay and bandwidth constraints is NP-hard, this study proposes a heuristic algorithm, that is optimal for most probable cases, and its worst case running time complexity is $O(n(log{n} + Clog{C}))$, where $n$ is the number of mobile users that must be found, and $C$ is the number of their potential locations. {bf The approximation ratio of the proposed search algorithm is less than 2}.     

Finding Best Matching Community for Common Nodes in Mobile Social Networks

The increase of mobile data users has created traffic congestion in current cellular networks. Due to this, mobile network providers have been facing difficulty in delivering the best services for customers. Since, detecting community in mobile social network is a valuable technique to leverage the downlink traffic congestion by enhancing local communications within the community, it attracts the attention of many researchers. Therefore, developing an algorithm, which detects community, plays a key role in mobile social network. In this paper, first, we proposed external density metrics to detect mobile social network. External density is defined as the ratio of outgoing links to total links of the community. Second, method to find the best group for common node is proposed. Therefore, an external density algorithm, makes a fair partition by grouping common nodes to a community with relatively higher external density. As a result, the overall modularity value of the network has increased. Third, the proposed algorithm is evaluated. Hence, the evaluation results confirm that our proposed approach has demonstrated good performance improvements than traditional methods.

     

Airtime Fairness for IEEE 802.11 Multirate Networks

Under a multirate network scenario, the IEEE 802.11 DCF MAC fails to provide airtime fairness for all competing stations since the protocol is designed for ensuring max-min throughput fairness. As such, the maximum achievable throughput by any station gets bounded by the slowest transmitting peer. In this paper, we present an analytical model to study the delay and throughput characteristics of such networks so that the rate anomaly problem of IEEE DCF multirate networks could be mitigated. We call our proposal time fair CSMA (TFCSMA) which utilizes an interesting baseline property for estimating a target throughput for each competing station so that its minimum contention window could be adjusted in a distributed manner. As opposed to the previous work in this area, TFCSMA is ideally suited for practical scenarios where stations frequently adapt their data rates to changing channel conditions. In addition, TFCSMA also accounts for packet errors due to the time varying properties of the wireless channel. We thoroughly compare the performance of our proposed protocol with IEEE 802.11 and other existing protocols under different network scenarios and traffic conditions. Our comprehensive simulations validate the efficacy of our method toward providing high throughput and time fair channel allocation.     

Community Discovery with Location-Interaction Disparity in Mobile Social Networks

With the fast?growth of mobile social network, people ’s inter?actions are frequently marked with location information, such as longitude and latitude of visited base station. This boom of data has led...     

认知无线网络中小型移动主用户的感知与定位研究

主要对认知无线网络中小型移动主用户的感知与定位技术进行了研究。首先简要介绍认知无线电的概念和研究现状,并对大型主用户和小型主用户的特征进行了对比、归纳及总结;然后描述了小型移动主用户难以感知的特点,并对小型主用户感知与定位的技术进行分类,重点分析和探讨了有关运用不同频谱感知技术来实现定位方法的优缺点;最后给出了认知无线网络中感知小型移动主用户的重点研究方向的建议。     

基于802.11 MAC的移动Ad Hoc网络AODV路由协议改进算法

基于802.11的Ad Hoc网络AODV路由协议会引入通信盲区问题,使路由发现信息建立的路由不能很好地满足高速数据分组的传输,本文在传统通信盲区解决方案的基础上提出一种AODV路由协议改进算法.Opnet仿真表明,改进算法能有效地提高Ad-hoc网络性能.     

移动用户通话签名业务实现原理简析

通话签名业务是为移动用户提供在通话过程中推送已经设置好的信息内容的增值业务。介绍了该业务的基本功能、业务流程,分析了在智能网和非智能网环境下的业务实现原理,并对该业务和呼转业务的关系进行了探讨。     

MoCA: A Middleware for Developing Collaborative Applications for Mobile Users

The Mobile Collaboration Architecture is a middleware architecture for developing and deploying context-aware collaborative applications for mobile users. MoCA comprises client and server APIs, a set of core services for registering applications, the ability to monitor and infer the execution context of mobile devices, and an object-oriented framework for instantiating and customizing server proxies according to applications’ specific adaptation and context-processing requirements. MoCA facilitates the development of distributed programs that require access to individual and group context to define application-specific and dynamic adaptations. MoCA’s design focuses on simplicity, extensibility, scalability, protocol heterogeneity, and application customization.     

移动Ad Hoc网络研究与发展现状

本文简要介绍移动ad hoc网络发展的历史、理论和技术上的一些热点问题，以及它的一些应用，从而给读者一个概括性的了解，为进一步学习和研究移动ad hoc网络奠定一些基础。为了便于读者跟踪国外先进的研究成果，本文最后介绍了一些在这一领域比较活跃的研究机构以及他们的主要工作。     

发送端自感知的概率粒度的数据包丢失原因甄别机制

We start this paper by answering the questions: What requirements should a good Loss Differentiation Mechanism (LD) for 802.11 networks in IoT meet? Do the existing LDs work well in 802.11 networks when moving towards IoT? Then we present the four properties that a LD used in IoT should own and the two-folded factors that we should consider when designing such a LD. Thereby, a novel LD is proposed utilizing the back-off frozen event to reveal collision probability. Our mechanism works efficiently with standard 802.11; only practical statistics information is needed. In addition, our mechanism can be done solely by the sender without introducing extra signaling overhead. Extensive simulations show that our mechanism can be applicable to different scenarios in 802.11 WLANs.     

Traffic-Aware Link Rate Adaptation for Multi-rate 802.11 Networks

802.11 networks provide multi-rate capability to offer rate adaptability against the time-varying wireless channel. However, how to switch between the available rates has not been standardized. Existing rate adaptation (RA) solutions assume common transmission power and can only passively tune link rate to match the inferred channel condition via different methods. This simple attitude is neither flexible in traffic-aware link rate selection nor effective in energy conservation and spatial reuse since transmission power may be either too low to sustain the link rate or too high that results in unnecessary energy consumption and worse spatial reuse. Different from existing solutions, we think that link rate switch should be driven by traffic load and power control should be considered with rate adaptation together to conserve energy and increase spatial reuse. To this end, we propose a traffic-aware link rate adaptation scheme (TARA) via power control for multi-rate 802.11 networks. Its basic idea consists of a two-step procedure. Firstly, traffic load is sensed in the MAC layer to decide whether link rate should be increased or decreased for the next transmission. Afterwards, power control is carried out in the PHY layer to guarantee that the new link rate can be sustained while minimizing the transmission power. Extensive simulation results show that TARA outperforms typical existing schemes in terms of energy efficiency and throughput.     

Cell Identification Codes for Tracking Mobile Users

The minimization of the wireless cost of tracking mobile users is a crucial issue in wireless networks. Some of the previous strategies addressing this issue leave an open gap, by requiring the use of information that is not generally available to the user (for example, the distance traveled by the user). For this reason, both the implementation of some of these strategies and the performance comparison to existing strategies is not clear. In this work we propose to close this gap by the use of Cell Identification Codes (CIC) for tracking mobile users. Each cell periodically broadcasts a short message which identifies the cell and its orientation relatively to other cells in the network. This information is used by the users to efficiently update their location. We propose several cell identification encoding schemes, which are used to implement different tracking strategies, and analyze the amount of information required by each tracking strategy. One of our major results is that there is no need to transmit a code which is unique for each cell. For example, a 3 bits CIC is sufficient to implement a distance-based tracking strategy in a two-dimensional system. In addition, we propose a combination of timer and movement tracking strategy, based on either a one-bit or a two-bit CIC, depending on system topology and user mobility. An important property of our framework is that the overall performance cost, and hence its comparison to existing methods, is evaluated for each tracking strategy. The CIC-based strategies are shown to outperform the geographic-based method currently used in existing networks, and the timer-based method, over a wide range of parameters. Moreover, this superiority increases as the number of users per cell increases.     

Large Antenna Array with Hybrid Beamforming System for 5G Outdoor Mobile Broadband Communication Deployments

Millimeter wave (mmWave) communication requires large antenna arrays to increase the capability of cellular networks of the fifth generation with good beam-forming gains and a substantial reduction in path losses for both transmitting and receiving terminals. As large antenna arrays require one radio frequency chain per antenna element, the fully digital beamforming technique results in high cost and high-power consumption, and it is therefore not feasible. However, in analog solutions, adaptive gain control cannot be used as it reduces the likelihood of advanced processing and contributes to poor efficiency. Hybrid schemes are possible exciting solutions that overcome the deficiencies of pure digital or analog beam forming. The following are the three key contributions of the proposed work: a typical link budget specification for target data rate 3.10 Gbps in downlink and 0.6 Gbps in uplink is provided, micro strip patch antenna with a single element is designed to operate at 28 GHz and then converted into a standard linear array and a Kalman-based hybrid analog/digital precoding is used with a downlink rate of 4.64 Gbps/cell and an uplink rate of 1.84 Gbps/cell in multi-user environments. And the influence of both base station (BS) and 5G User equipment (UEs) beam steering capability is also explored. From the simulation result, it is evident that the proposed work offers a substantial increase in spectral efficiency approximately 9.28 bps/Hz at 20 dB with 10 channel paths.

     

Millimeter Wave Communication for Cellular and Cellular-802.11 Hybrid Networks

The demand for wireless data has been driving network capacity to double about every two years for the past 50 years, if not 100 years, and this has come to be known as Cooper’s Law. In recent years, this trend has accelerated as a greater proportion of the population adopts wireless devices with ever greater capabilities, including tablets that support HD video and other advanced capabilities. Many cellular operators have tried to adapt this trend by throttling data rates, backing away from all-you-can-eat data plans, and offloading to WiFi. Over the next decade, further increases in demand are expected,     

一种基于802.11 DCF Basic Access机制的移动自组网动态速率控制模型

802.11移动自组网由于其固有的动态拓扑、分布式协作等特点,路由协议普遍采用多播方式以提高无线链接的传输效率,由此带来的拥塞使得移动自组网中多播拥塞控制至关重要。针对移动自组网中节点固有的随机特性,基于802.11 DCF协议,该文提出一种精确描述节点数据产生、排队、发送动态过程的拟生灭模型,并通过矩阵几何方法对其进行稳态分析,得出节点速率阈值方程组,并用OPNET进行了仿真实验,仿真结果与理论值拟合较好,为移动自组网中的拥塞控制提供了一个量化的指标。     

基于评分机制的移动用户隐私保护方案研究

开发人员的技术缺陷和用户隐私数据的潜在商业价值,使得用户隐私面临巨大安全威胁,针对恶意应用软件和应用自身缺陷带来的安全危机,结合应用市场的评分评价机制,提出一种方便用户安装和使用移动应用的用户隐私保护方案MURT。此方案提供接口设定终端应用信任阈值,并在应用和隐私数据之间添加强制访问控制模块,该模块会拦截综合评级低于信任阈值的应用的访问请求,并为请求者提供虚假服务,保证应用顺利运行的前提下确保隐私数据的完整性和安全性。方案在Android平台上编码实现,实验表明:MURT在保障用户体验的基础上,有效地扼制了隐私数据泄漏。     

Service Acquisition for Mobile Users in Future Internet

Mobility offers a great deal of advantages. However, mobile users are currently restricted by the network coverage of providers, their access network technologies and the networking capabilities of mobile devices. Moreover, mobile users have to be involved in time consuming and inflexible manual interactions with internet access service providers in order to sign long term contracts. In this paper, a novel framework, which liberates mobile users from predefined, long-term contracts, is presented. This framework enables mobile users to dynamically acquire any kind of Internet Service, irrespectively of their location and the mobile device used. This is based on the automation of the service acquisition process and the collaboration of providers that is required to satisfy end-users’ requests. The flexible communication and negotiation framework that was defined enables automated negotiations between all parties and can be used as basis towards automated service acquisition for mobile users in future internet.     

Distributed Contention Window Control for Selfish Users in IEEE 802.11 Wireless LANs

In this paper, we study non-cooperative user behavior in random-access wireless networks in which users have freedom to choose their back-off contention window size according to network's congestion status. We formulate a non- cooperative game and show the existence and uniqueness of its equilibrium point. We also propose an iterative method leading to the equilibrium point of the game. A discussion of alternative game formulations in the same problem context is also given.