Location update and routing scheme for a mobile computing environment

We present a new hierarchical location update and routing scheme for a wide area mobile computing environment with scalability of network hierarchy. Our scheme provides nearly optimal routing for most communication bypassing the mobile host's home network and home agent. We use simulation to compare our scheme with other schemes in both non‐hierarchical and hierarchical network architectures. Copyright © 2000 John Wiley & Sons, Ltd.     

用于移动计算环境的口令认证协议研究

利用IC（integrated circuit）卡、RSA密码体制以及离散对数，设计了一种适用于移动计算环境的口令认证协议。在服务器侧无需保存验证表，增强了系统的安全性。为了适应移动计算环境中终端计算能力较弱以及无线带宽相对较窄的特点，该协议在无线信道上只需一次认证消息交互。并且，用户在修改密码的时候无需网络侧服务器的参与，在本地终端即可独立完成。利用M／G／1／N排队模型分析协议性能并与TLS（transport layer security）协议比较。     

Just in time multimedia distribution in a mobile computing environment

Poor data rates often hinder the timely dissemination of multimedia content to users in a mobile computing environment. We describe an approach, based on dynamic and proactive precaching, to overcome these limitations. This approach, which we term intelligent precaching, is realized through the innovative deployment of intelligent agents on mobile devices.     

A comparative study and workload distribution model for re‐encryption schemes in a mobile cloud computing environment

The researchers are using the various variations of re‐encryption schemes, which migrate the computational intensive re‐encryption jobs of mobile devices to the trusted entity/cloud. However, the messages are still encrypted and decrypted using the limited computational power of mobile devices. Our contribution in this paper is to propose a workload distribution model for re‐encryption schemes, which offloads the computational intensive operations, such as encryption and decryption on a trusted entity. Moreover, the proposed workload distribution model is compared with existing re‐encryption schemes of resource utilization on trusted entity and mobile device. The experimental results show substantial improvement in performance compared to the existing schemes.     

Channel carrying: a novel handoff scheme for mobile cellularnetworks

We present a new scheme that addresses the call handoff problem in mobile cellular networks. Efficiently solving the handoff problem is important for guaranteeing quality of service to already admitted calls in the network. Our scheme is based on a new approach called channel carrying: when a mobile user moves from one cell to another, render certain mobility conditions, the user is allowed to carry its current channel into the new cell. We propose a new channel assignment scheme to ensure that this movement of channels will not lead to any extra co-channel interference or channel locking. In our scheme, the mobility of channels relies entirely on localized information, and no global coordination is required. Therefore, the scheme is simple and easy to implement. We further develop a hybrid channel carrying scheme that allows us to maximize performance under various constraints     

Downlink queuing model and packet scheduling for providing lossless handoff and QoS in AG mobile networks

Next generation mobile networks are expected to provide seamless personal mobile communication and quality-of-service (QoS) guaranteed IP-based multimedia services. Providing seamless communication in mobile networks means that the networks have to be able to provide not only fast but also lossless handoff. This paper presents a two-layer downlink queuing model and a scheduling mechanism for providing lossless handoff and QoS in mobile networks, which exploit IP as a transport technology for transferring datagrams between base stations and the high-speed downlink packet access (HSDPA) at the radio layer. In order to reduce handoff packet dropping rate at the radio layer and packet forwarding rate at the IP layer and provide high system performance, e.g., downlink throughput, scheduling algorithms are performed at both IP and radio layers, which exploit handoff priority scheduling principles and take into account buffer occupancy and channel conditions. Performance results obtained by computer simulation show that, by exploiting the downlink queuing model and scheduling algorithms, the system is able to provide low handoff packet dropping rate, low packet forwarding rate, and high downlink throughput.     

Improving idle handoff in CDMA mobile systems

In this letter, we have developed an efficient idle handoff technique, starting from field-test results obtained with the method used in present CDMA mobile phones, where the handoff is performed when a new pilot rises over the current one by a predefined constant. Unlike the conventional method, the proposed method decides the handoff based on a variable threshold, the value of which is automatically determined depending on the pilot strength received from the home base. It is shown that the proposed method reduces unnecessary idle handoffs and keeps the mobile tracking the pilot received with sufficient strength     

Design and performance studies of an adaptive cache retrieval scheme in a mobile computing environment

In a mobile computing system, as users move to a new service area, the new server is usually considered to take over the execution of running programs for mobile users from the previous server so as to reduce the communication overhead of a mobile system. This procedure is referred to as service handoff. Note that when service handoff occurs, the new server will lose its advantage for cache access. To remedy this, we explore in this paper several cache retrieval schemes to improve the efficiency of cache retrieval. In particular, we analyze the impact of using a coordinator buffer to improve the overall performance of cache retrieval. Moreover, in light of the properties of transactions (i.e., temporal locality of data access among transactions), we devise a Dynamic and Adaptive cache Retrieval scheme (DAR) that can utilize proper cache methods according to some specific criteria to deal with the service handoff situation in a mobile computing environment. Performance of these cache retrieval schemes is analyzed and a system simulator is developed to validate our results. We devise a systematic procedure for determining the optimal operating points of DAR. Our experimental results show that by adaptively adopting the advantages of different cache retrieval methods, DAR significantly outperforms other schemes and is particularly effective for a mobile computing environment.     

移动计算环境下恶意软件静态检测系统设计

移动终端在互联网中下载到恶意软件的几率非常高,这对用户信息私密性造成了严重的威胁,但科研组织曾研究出的恶意软件检测系统往往误报率过高、实用性不强。为此,设计移动计算环境下恶意软件静态检测系统,其由特性提取与预处理模块和移动计算终端组成。特性提取与预处理模块根据静态检测特性数据库中的恶意软件标志特性,对用户移动终端软件的安装包特性、资源特性和编译特性进行提取,并使用静态检测函数对提取出的特性进行预处理,给出恶意与非恶意软件的特性分类结果。系统通过移动计算终端对特性分类结果中的恶意软件特性进行位置检测,隔离出用户移动终端中的恶意软件,防止恶意软件继续入侵。经实验分析可知,所设计的系统误报率较低、实用性较强。     

Low-latency mobile IP handoff for infrastructure-mode wireless LANs

The increasing popularity of IEEE 802.11-based wireless local area networks (LANs) lends them credibility as a viable alternative to third-generation (3G) wireless technologies. Even though wireless LANs support much higher channel bandwidth than 3G networks, their network-layer handoff latency is still too high to be usable for interactive multimedia applications such as voice over IP or video streaming. Specifically, the peculiarities of commercially available IEEE 802.11b wireless LAN hardware prevent existing mobile Internet protocol (IP) implementations from achieving subsecond Mobile IP handoff latency when the wireless LANs are operating in the infrastructure mode, which is also the prevailing operating mode used in most deployed IEEE 802.11b LANs. In this paper, we propose a low-latency mobile IP handoff scheme that can reduce the handoff latency of infrastructure-mode wireless LANs to less than 100 ms, the fastest known handoff performance for such networks. The proposed scheme overcomes the inability of mobility software to sense the signal strengths of multiple-access points when operating in an infrastructure-mode wireless LAN. It expedites link-layer handoff detection and speeds up network-layer handoff by replaying cached foreign agent advertisements. The proposed scheme strictly adheres to the mobile IP standard specification, and does not require any modifications to existing mobile IP implementations. That is, the proposed mechanism is completely transparent to the existing mobile IP software installed on mobile nodes and wired nodes. As a demonstration of this technology, we show how this low-latency handoff scheme together with a wireless LAN bandwidth guarantee mechanism supports undisrupted playback of remote video streams on mobile stations that are traveling across wireless LAN segments.     

Adaptive wireless thin‐client model for mobile computing

The thin‐client computing model has the potential to significantly increase the performance of mobile computing environments. By delivering any application through a single, small‐footprint client (called a thin client) implemented on a mobile device, it is possible to optimize application performance without the need for building wireless application gateways. We thus present two significant contributions in the area of wireless thin‐client computing. Firstly, a mathematical performance model is derived for wireless thin‐client system. This model identifies factors that affect the performance of the system and supports derivation and analysis of adaptation strategies to maintain a user‐specified quality of service (QoS). Secondly, a proxy‐based adaptation framework is developed for wireless thin‐client systems, which dynamically optimizes performance of a wireless thin client via dynamically discovered context. This is implemented with rule‐based fuzzy logic that responds to variations in wireless link bandwidth and client processing power. Our fuzzy inference engine uses contextual data to dynamically optimize tradeoffs among different quality of service parameters offered to the end users. Additionally, our adaptation framework uses highly scalable wavelet‐based image coding to provide scalable QoS that can degrade gracefully. Our thin‐client adaptation framework shields the user from ill effects of highly variable wireless network quality and mobile device resources. This improves performance of active applications, in which the display changes frequently. Further, active application behaviour may produce high transmission latency for screen updates, which can adversely affect user perception of QoS, resulting in poor interactivity. We report measured adaptive performance under realistic mobile device and network conditions for several different clients and servers. Copyright © 2008 John Wiley & Sons, Ltd.     

An efficient handoff management scheme for mobile wireless ATMnetworks

A new handoff management scheme for wireless ATM networks is proposed. In this scheme, all cells are connected to their neighboring cells by permanent virtual circuits (PVCs) and to the access switch (AS) by switched virtual circuits (SVCs) which are only for new calls. Some carefully chosen cells, called rerouting cells, are also connected to the AS by PVCs. In summary, if a mobile roams to an ordinary neighboring cell, its traffic path is simply elongated by a PVC connecting the old and new cells. If a mobile roams to a rerouting cell, its traffic path is rerouted to a PVC between the AS and rerouting cell. By using PVC's for handoff calls, we can guarantee fast and seamless handoff. At the same time, our scheme improves the path efficiency by limiting the maximum number of hops that a path can be extended. Also, allowing path rerouting at a suitable time means the network resources are more efficiently utilized     

云计算环境下网络带宽模型初探

文章以办公型组织为例,从用户体验的角度探讨了云计算环境下网络带宽的需求模型,通过比较计算论证了云计算环境下用户接入带宽达到千兆的必要性,并通过并发系数估算指出不同规模的组织中主干网带宽须达到万兆或十万兆的必要性,从而为云计算环境下网络带宽规划提供了一个最基本的模型或依据。     

云计算环境下的外语移动学习智慧平台研究

随着云计算技术在智慧校园教育教学中的应用,在高校的外语教育教学中也把云计算引入了进来,基于云计算的外语移动学习智慧平台不仅提高了学生外语学习水平,而且外语移动学习智慧平台改变了传统的外语教育教学方法,提高了学生对外语学习的能力.本文对云计算技术的概念及应用进行了分析,对外语移动学习的特点和意义进行了研究,提出了基于云计算的外语移动学习智慧平台体系结构建设,并对基于云计算的环境下外语移动学习智慧平台建设进行了分析和研究.     

Research on intelligent computing offloading model based on reputation value in mobile edge computing

Aiming at the problem of high-latency,high-energy-consumption,and low-reliability mobile caused by computing-intensive and delay-sensitive emerging mobile applications in the explosive growth of IoT smart mobile terminals in the mobile edge computing environment,an offload decision-making model where delay and energy consumption were comprehensively included,and a computing resource game allocation model based on reputation that took into account was proposed,then improved particle swarm algorithm and the method of Lagrange multipliers were used respectively to solve models.Simulation results show that the proposed method can meet the service requirements of emerging intelligent applications for low latency,low energy consumption and high reliability,and effectively implement the overall optimized allocation of computing offload resources.     

云计算环境下差异化资源的合理调度模型改进

在云计算环境下,需要对链路节点之间差异化资源进行合理调度,以提高云计算中心网络的负载均衡性及进程管理效率。针对当前调度模型的实时性和均衡性不好的问题,提出一种基于时分多址协议的云计算环境下差异化资源合理调度模型。首先构建云计算环境下差异化资源的传输信道模型,进行资源传输的负载均衡设计,采用时分多址协议进行时隙均衡分配,提高差异化资源的调度合理性。仿真结果表明,采用该模型进行云计算环境下差异化资源调度,资源信息的召回性较好,数据传输的保真度较高,具有一定的优越性。     

移动IP在无线局域网下的一种快速切换方法

针对移动IP在无线局域网下的应用,提出了一种新的基于链路层的移动IP快速切换方法,通过在无线局域网的无线接入点间加入特定的MAC网桥来减少移动节点在切换时产生的切换时延,进而减少移动节点上行和下行方向上的数据包的丢失,达到对移动IP切换进行优化的目的。此方法在无线局域网实际环境中进行了性能测试,结果证明优化后的时延较之原来普通移动IP切换时延有明显降低。     

Traffic model and performance analysis for cellular mobile radio telephone systems with prioritized and nonprioritized handoff procedures

A traffic model and analysis for cellular mobile radio telephone systems with handoff are described. Three schemes for call traffic handling are considered. One is nonprioritized and two are priority oriented. Fixed channel assignment is considered. In the nonprioritized scheme the base stations make no distinction between new call attempts and handoff attempts. Attempts which find all channels occupied are cleared. In the first priority scheme considered, a fixed number of channels in each cell are reserved exclusively for handoff calls. The second priority scheme employs a similar channel assignment strategy, but, additionally, the queueing of handoff attempts is allowed. Appropriate analytical models and criteria are developed and used to derive performance characteristics. These show, for example, blocking probability, forced termination probability, and fraction of new calls not completed, as functions of pertinent system parameters. General formulas are given and specific numerical results for nominal system parameters are presented.     

Predictive schemes for handoff prioritization in cellular networksbased on mobile positioning

We propose and evaluate new schemes for channel reservation motivated by the rapidly evolving technology of mobile positioning. The schemes, called predictive channel reservation (PCR), work by sending reservation requests to neighboring cells based on extrapolating the motion of mobile stations (MSs). A number of design enhancements are incorporated to minimize the effect of false reservations and to improve the throughput of the cellular system. These enhancements include: (1) reservation pooling; (2) queuing of reservation requests; (3) hybrid approach for integrating guard channels (GCs); and (4) using a threshold distance (TD) to control the timing of reservation requests. The design enhancements have produced a set of highly efficient schemes that achieve significant reduction in handoff blocking rates while only incurring remarkably small increases in the new call blocking rates. The PCR approach has also been used to solve the MINBLOCK optimization problem and has given significant improvement over the fractional guard channel (FGC) protocol. Detailed performance results of the different variations of the PCR scheme and comparisons with conventional channel reservation schemes are presented. An analytical Markov model for the hybrid predictive version of the scheme is developed and its applicability and numerical results are discussed     

Association control algorithms for handoff frequency minimization in mobile wireless networks

As mobile nodes roam in a wireless network, they continuously associate with different access points and perform handoff operations. Frequent handoffs performed by a mobile device may have undesirable consequences, as they can cause interruptions for interactive applications and increase the energy usage of mobile devices. While existing approaches to this issue focus entirely on improving the latency incurred by individual handoffs, in this paper, we initiate a novel approach to association control of mobile devices with the goal of reducing the frequency of handoffs for mobile devices. We study the handoff minimization problem across multiple dimensions: offline versus online where the complete knowledge of mobility patterns of users is known in advance or unknown respectively; capacity constrained versus unconstrained access points, which imposes limits on the number of mobile devices which could be associated with a given access point at any given point in time; group mobility versus arbitrary mobility of users, which are contrasting ways to model the mobility patterns of the mobile users. We consider various combinations of the above dimensions and present the following: (1) optimal algorithms, (2) provably-good online and offline approximation algorithms, (3) complexity (NP-Completeness) results, and (4) a practical heuristic which is demonstrated to work well on real network traces.