IPv6 based relay gateway protocol in hybrid networks

During the past few years, WMAN (Wireless Metropolitan Area Network) and WLAN (Wireless Local Area Network) provided fast, convenient and reliable solution for all kinds of users. With the development of the communication technology, the future wireless networks will allow mobile users access Internet anywhere, anytime. Therefore, it is a natural trend to combine different wireless networks to provide a seamless roaming for users. It is feasible for mobile terminal which have multiple modes to handoff between different networks. A relay gateway protocol for the WLAN-mode nodes (mono-mode WLAN nodes and dual-mode nodes) in the hybrid network of IEEE 802.16 WMANs and IEEE 802.11 WLANs is proposed to provide wider mobility. Dual-mode mobile nodes with good service can provide WLAN links to nearby WLAN-mode nodes with bad service or out of the WLAN coverage. Simulation results show that the relay gateway scheme can improve network performance of the hybrid networks. Moreover, the relay gateway method can bring additional service coverage and increase the capacity of WMANs and WLANs.     

Enhancing VoIP service for ubiquitous communication in a campus WLAN with partial coverage

The IEEE 802.11 WLAN technology has become the de facto standard for wireless Internet access. The spotty coverage of WLAN access points, however, confines the applicability of many real-time services such as VoIP within the boundary of the WLAN service area. In this paper, we investigate the problem of enhancing VoIP service for ubiquitous communication in a WLAN with spotty service area. We consider a university campus that has an established infrastructure for supporting SIP-based VoIP service through either wired or wireless data networks. The campus WLAN service does not have 100% full coverage, and hence users cannot make untethered VoIP calls anywhere on campus. The goal of this paper is to overcome the limitations of such “dead spots” for motivating the use of campus IP telephony service. To proceed, we start with two approaches called one-hop extension and dual-mode communication. The first approach uses multi-hop relay to extend the WLAN coverage, while the second approach leverages the availability of dual-mode handsets for ubiquitous voice communication. We implement the two approaches, and evaluate their performance in the campus testbed environment. We find that while the two approaches can effectively allow voice communication in WLAN dead spots, they have one common problem as the potential lack of support for voice call continuity that can cause degradation of the speech quality to an active call. We adopt a cross-layer solution based on signal processing algorithms to address the problem, thus achieving seamless voice call continuity while enabling ubiquitous voice communication on campus. Testbed evaluation shows promising results for future research along the proposed direction.     

UMTS: the fusion of fixed and mobile networking

The Universal Mobile Telecommunications System (UMTS) represents the emerging European standard for next generation cellular systems that transmit data as well as voice on a global basis. The UMTS goals involve the integration of evolved versions of today's second generation digital cellular systems, together with new terrestrial and satellite components. They also address a fusion of the mobile and fixed networks with a much greater role for intelligent network services. The integration scenarios take little account of the proliferation of IP based networks, and some system redesign is necessary to correct for this. To build on the strengths of GSM, the core UMTS network will evolve from the existing GSM service. UMTS support for data will probably be based on GPRS developed for GSM. Speeds available will vary from approximately 100 Kbps for a pre UMTS, GSM based system up to 2 Mbps for new UMTS radio access networks. Future mobile broadband systems may extend this up to 155 Mbps in restricted environments. The ETSI timetable for introducing these new systems shows the first equipment going into service in 2002, with full availability of third generation UMTS services by 2005     

异构无线网络中动态优先级接纳控制算法研究

针对在应急情况下的异构网络环境中不同类型业务在群组切换时出现的网络拥塞问题,以及现有研究中较少考虑不同类型用户所进行的业务的重要性和紧急性不同,从而不能合理分配有限的网络资源的情况,提出了一种异构无线网络中动态优先级接纳控制算法。首先,根据用户类型和业务类型对业务设定初始优先级;然后,根据业务的执行紧迫性和业务的剩余价值密度对业务优先级进行动态调整,并提出了一种基于业务优先级的抢占调度算法;最后为避免在业务优先级进行动态调整过程中出现颠簸调度现象,给出了避免颠簸调度的条件。所提算法考虑了实际情况中不同用户类型所进行的业务重要程度的不同,对业务进行了优先级设定,使初始优先级高的业务能够优先得到服务,在此基础上为尽量满足整体用户的用网需求,对业务的优先级进行了动态调整。为验证所提方法的有效性,将基于优先级队列调度算法和基于阻塞率约束的群组切换方法作为对比算法,在MATLAB软件环境下进行仿真分析。结果表明,所提方法相较于对比算法能够在减少业务切换的阻塞率的同时,使总体业务的完成率提高10%左右,证明了该算法在使初始优先级高的业务能够优先得到服务的同时,为初始优先级低的业务提供了网络切换的条件,从而提高了网络资源分配的合理性和公平性。     

The service curve service discipline for the rate-controlled EDF service discipline in variable-sized packet networks

Guaranteed service will provide high quality services to real-time applications, e.g., audio or video, over packet networks such as the Internet. To support guaranteed service, a service discipline must guarantee a delay bound to each session. In addition, a preferred service discipline should achieve high network utilization and good scalability. The service disciplines studied so far have problems in achieving these two objectives at the same time. Generalized processor sharing (GPS) service disciplines can have low network utilization. Rate-controlled (RC) service disciplines have difficulty in scalability because of regulators. For service curve (SC) service disciplines, both the network utilization and the scalability depend on the adopted SC. To date, there have been no studies on an SC which can make an SC discipline achieve these two objectives. We propose a new service discipline based on SC service disciplines. The proposed discipline achieves these two goals in a variable-sized packet environment. We show that the discipline can achieve the network utilization achievable by the RC service disciplines. We further show that our SC requires O(1) complexity for deadline calculation. Different from the RC service disciplines, the SC service discipline with our SC does not need regulators at all. Thus, it has better scalability than the RC service disciplines and is work-conserving. We also show that the proposed SC makes SC service disciplines have strictly higher network utilization than the GPS service disciplines including the multi-rate service discipline.     

Optimization of QoS parameters using scheduling techniques in heterogeneous network

Multimedia applications in wireless communication have been increased in recent years. A variety of wireless access technologies is introduced for various needs. The abundant increase in mobile computing devices and different networking systems leads to the support of user’s mobility on heterogeneous network. In general, the roaming users migrate between two different wireless technologies and their service must be supported by vertical handover (HO). Since the roaming users expect a rapid handover experience while switching from one wireless network to another, the handover operation must be enhanced by the networks. Various wireless technologies such as wireless LAN, Worldwide Interoperability for Microwave Access (WiMAX), and the 3G Partnership Project (3GPP) are interlaced to support many wireless services in rural, urban, and global scenarios. Moreover, quality of service (QoS) has become more significant in many applications where wireless network resources are utilized. In this paper, a handover management scheme is proposed for QoS enhancement in roaming users between WiMAX and WLAN by subscribers of networks belonging to the 3GPP standards. The proposed algorithms genetic queuing, proportionally fair queuing, and WiMAX aware load balancing are analyzed in the scheduling process during handover. The simulation is implemented using NS–2 and the experimental results are obtained for the proposed algorithms and compared with the standard scheme.     

一种改进的集中式异构无线网络选择算法

对于异构无线网络的无缝移动性实现,在适当的时间内选择目标网络具有重要作用。提出了一种改进的接入路由器发现算法IARD,一种在WLAN网络和UMTS网络构成的异构环境下使用的网络发现和选择技术。在此方法中,核心网络中潜在的网络指定采用一个特殊的加权均值算法[(MW)]实现,并根据不同的任务场景有针对性地改变各项标准的权重,从而确定出最合适于该场景的网络作为目标网络。在不同的业务类型条件下通过仿真测试,结果表明,与其他方法相比该方法给出了更为合适的网络选择。     

User authentication and undeniable billing support for agent-based roaming service in WLAN/cellular integrated mobile networks

In this paper, a framework of authentication and undeniable billing support for an agent-based roaming service in WLAN/cellular networks interworking networks is proposed. This framework circumvents the requirement of peer-to-peer roaming agreements to provide seamless roaming service between WLAN hotspots and cellular networks operated by independent wireless network service providers. Within the framework, an adaptive authentication and an event-tracking scheme have been developed, which allow the application of undeniable billing service to cellular network even when it still uses a traditional authentication scheme. The proposed modified dual directional hash chain (MDDHC) based billing support mechanism features mutual non-repudiation. Security analysis and overhead evaluation demonstrate that the proposed framework is secure and efficient.     

GPRS/UMTS无线数据接入的控制与优化*

提出了一种新的基于代理的协议框架以提高在GPRS/UMTS网络中进行无线数据接入的性能。在此框架下研究了延时阻塞调度策略。该策略利用数据业务对延时不敏感的特性,在不增加带宽的前提下显著改善系统的响应性能,为实现该策略下的无线信道资源管理,设计了最优信道分配和自适应信道分配两种算法。理论分析和仿真表明,新的机制和算法可以显著地提高网络利用率并缩短系统的平均响应时间。     

空间信息网络任务智能识别方法

随着星间链路技术的不断发展和星上处理技术的日益成熟,空间信息网络传输的任务类型不断增加并呈现多样化的趋势,这对空间信息网络的多业务协同传输、网络资源全局调度等能力提出了新的挑战。然而,传统的空间信息网络资源调度大多以单一业务为驱动,忽略了任务与业务之间一对多的关系,导致某些低优先级任务抢占高优先级任务的网络资源,致使由多业务构成的空间信息网络任务的服务质量较低。此外,空间信息网络传输环境具有拓扑高动态变化、节点资源有限等特点,将传统的业务识别方法直接迁移到任务识别中存在任务识别效率低和开销大的缺陷。鉴于此,文中设计了部署于空间信息网络边缘的任务服务支持站,该支持站由识别标记模块、路由控制模块和数据通信模块组成,用以完成对任务类型的识别,以及基于任务服务质量需求的路由选择和数据传输。文中通过对流自身特征项的降维处理和基于高斯核函数的特征空间映射,设计了基于支持向量机的业务识别算法,进一步地,在引入网络传输环境相关特征项的基础上,将业务类型、业务数量和环境特征项相结合,设计了基于梯度下降法的任务识别算法。仿真结果表明,设计的任务识别算法具有很好的识别精准率和召回率,且消耗较短的识别时间和较少的识别开销,对空间信息网络任务流量识别的平均准确率达到95%以上,提高了1%以上,相比未经过特征降维的平均训练时间缩短了15%以上。     

异构无线网络中基于效用的呼叫接纳控制及流量均衡策略

目前国内外对于异构无线网络中联合呼叫接纳控制和流量均衡策略的研究大多停留在网络层以上,即认为不同的网络具有不同的覆盖面积和网络容量,而没有考虑不同网络在物理层和链路层的具体特性.本文在对UMTS和WLAN底层特性分析的前提下,结合应用层为用户设定的效用函数,利用跨层信息提出了一种新的联合呼叫接纳控制及流量均衡策略.仿真结果表明该策略可以使异构无线网络中所有呼叫的效用总和最大.     

Interworking of heterogeneous access networks and QoS provisioning via IP multimedia core networks

Moving towards packet networks, where IP will have a prominent role, constitutes nowadays a widely accepted perception of future communications, the first instance of which has begun to materialise with the IP multimedia core network subsystem (IMS). By specification, IMS is the first implementation towards reaching converged communications which allows users to communicate with video, audio and multimedia content, via any fixed, mobile and wireless access network type, with controllable QoS. To enable IMS communications across heterogeneous networks, incorporating UMTS, WLAN and fixed IP access points, 3GPP and ETSI’s TISPAN currently work on schemes for controlling bandwidth allocation at the service level by employing logical interfaces that carry SIP messages. This article analyzes how interconnection between such heterogeneous networks may be performed on real platforms. In this effort, special attention is paid to the way the various interconnection possibilities can affect end-to-end QoS provisioning.     

基于TEASE管道技术的异构网络垂直切换安全认证算法

基于WLAN和UMTS构建的异构网络模型,提出一种适合该模型的垂直切换安全认证算法,用临时管道密钥(TTK)对数据进行加密,在接收端再用TTK进行数据解密。用平均切换次数、传输时延和丢包率三个指标评价所提出算法的性能。与已有垂直切换算法进行性能比较,其结果表明,提出的算法能有效减少切换次数,消除乒乓效应,减少传输时延和丢包率,可为实时业务所需的无缝切换提供有力保障。     

Security enhancements against UMTS–GSM interworking attacks

In this paper we first present three new attacks on Universal Mobile Telecommunication System (UMTS) in access domain. We exploit the interoperation of UMTS network with its predecessor, Global System for Mobile communications (GSMs). Two attacks result in the interception of the entire traffic of the victim UMTS subscriber in the GSM access area of UMTS network. These attacks are applicable, regardless of the strength of the selected GSM encryption algorithm. The third attack is an impersonation attack and allows the attacker to impersonate a genuine UMTS subscriber to a UMTS network and fool the network to provide services at the expense of the victim subscriber. Then, we propose some countermeasures to strengthen the UMTS network against the mentioned attacks with emphasis on the practicality in present networks. The proposed solutions require limited change of the network elements or protocols, insignificant additional computational load on the network elements and negligible additional bandwidth consumption on the network links.     

Automatic planning of 3G UMTS all-IP release 4 networks with realistic traffic

Most Universal Mobile Telecommunications Systems (UMTS) service providers are switching to an all-IP (also called flat-IP) architecture. Using an all-IP architecture within 3G networks provides a cost-effective transport network since the same infrastructure can be used for both voice and data services. However, planning and designing such an architecture is very complex especially if realistic traffic profiles are taken into consideration. As a result, this paper first provides a mathematical formulation (presented in Appendix for readability reasons) for the global planning problem of 3G UMTS all-IP Release 4 networks with realistic traffic profile. Due to the complexity of the problem, heuristics based on local search and tabu search are also proposed. Finally, a comparative study is performed to evaluate how good the heuristics are with respect to a reference model. Results show that the tabu search is able to provide solutions that are close to optimal solutions in a much shorter computation time.     

Adaptive performance management for universal mobile telecommunications system networks

In this paper, we introduce a framework for the adaptive control of universal mobile telecommunications system (UMTS) networks in order to improve bandwidth utilization of the radio channels. The key contribution of the paper constitutes the introduction of a performance management information base for dynamically adjusting the packet scheduler and admission controller. Thus, the adaptive control framework closes the loop between network operation and network control. Furthermore, the adaptive control framework can effectively deal with the different time scales of packet scheduling and admission control. Moreover, we present a traffic model for non-real-time UMTS traffic based on measured trace data. The analysis and scaling process of the measured trace data with respect to different UMTS bandwidth classes constitutes the basic concept of this traffic characterization. Using this traffic model and simulation on the IP level, the gain of employing the adaptive control framework is illustrated by performance curves for various quality of service measures.     

An efficient design and validation technique for secure handover between 3GPP LTE and WLANs systems

Future generations wireless systems, which integrate different wireless access networks together, will support a secured seamless mobility and a wide variety of applications and services with different quality of service (QoS) requirements. Most of the existing re-authentication protocols during vertical handover still have certain limitations such as man in the middle, eavesdropping and session hijacking attacks, and unacceptable delay for real time applications. In this article, we propose two re-authentication schemes to secure handover between 3GPP LTE and WLANs systems: Initial Handover Re-authentication Protocol, and Local Re-authentication Protocol. The second proposed protocol is executed locally in a WLAN network without contacting the authentication server of the home network for credentials verification. In fact, after a successful execution of the Initial Handover Re-authentication Protocol, the local key (LK) is shared between USIM and the authentication server of the WLAN. It is then used for securing handover and traffic in WLAN networks. Performance evaluation results obtained using simulation analysis show that the proposed re-authentication protocol enhances handover parameters such as handover latency, handover blocking rate and packet loss rate. Additionally, the proposed enhanced fast re-authentication protocol has been modeled and verified using the software AVISPA and is found to be safe.     

Distributed information service architecture for overlapping multiaccess networks

Multimedia delivery in mobile multiaccess network environments has emerged as a key area within the future Internet research domain. When network heterogeneity is coupled with the proliferation of multiaccess capabilities in mobile handheld devices, one can expect many new avenues for developing novel services and applications. New mechanisms for audio/video delivery over multiaccess networks will define the next generation of major distribution technologies, but will require significantly more information to operate according to their best potential. In this paper we present and evaluate a distributed information service, which can enhance media delivery over such multiaccess networks. We describe the proposed information service, which is built upon the new distributed control and management framework (DCMF) and the mobility management triggering functionality (TRG). We use a testbed which includes 3G/HSPA, WLAN and WiMAX network accesses to evaluate our proposed architecture and present results that demonstrate its value in enhancing video delivery and minimizing service disruption in an involved scenario.     

An IMS-based network architecture for WiMAX-UMTS and WiMAX-WLAN interworking

The IP Multimedia Subsystem (IMS) seems to be the technology that will prevail in Next Generation Networks (NGNs), since the interworking environment and the service flexibility that this technology offers to the currently deployed wireless broadband technologies makes it appealing to users, service developers and network operators. In this paper we propose a heterogeneous network model based on the IMS that integrates the Worldwide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications System (UMTS) and Wireless Local Area Network (WLAN) technologies and provides guaranteed QoS. We present the complete signalling flow concerning the authorization, registration, session set up and vertical handoff processes, as well as, an analytic model for cost analysis of the proposed architecture.     

LTE系统中提高TCP性能的资源调度算法研究

LTE可以提供真正无处不在基于IP的移动宽带业务,但随着承载网的IP化,网络拥塞、丢包、抖动、延时等质量问题将影响到LTE业务层的QoS质量.作为LTE无线资源管理的核心,研究并设计一个良好的资源调度算法是提高数据业务的性能和终端用户的体验是一个亟待解决的重要任务.本文通过借鉴LTE对VoIP数据分组的半持续调度算法的思想,提出了一种LTE的无线资源调度的改进方案.方案将TCP确认包映射到具有更高优先级的空闲逻辑信道,从而降低了ACK包在无线信道中发生丢弃和拥塞的概率,避免了TCP拥塞控制机制的频繁开启.仿真结果表明,本文提出的TCP确认包映射转换方案在RTT时延、吞吐量等方面均有一定的提升,具有一定的稳定性和性能优势.