An investigation of multilevel service provision for voice over IP under catastrophic congestion

QoS has been the dominating issue faced in VoIP development today. In this article we investigate and empirically evaluate three DiffServ (Kilkki 1999, Blake et al. 1998) design strategies, WRED Dropper (Cisco Systems), PQ meter, and multiple differentiated meter (MDM), and study how multilevel communication services can be guaranteed for multiple VoIP classes. The novel aspect of our work is that we are trying to provide solutions with the use of features that are not currently available in real routers (Westhead, 2002). By taking advantage of network simulation techniques, a series of experiments have been designed and carried out under different network conditions by using the intersim simulation tool (Westhead, 2002). Our simulation results effectively reflect that: 1) all three designs can provide service differentiation for multiple VoIP classes; 2) the highest-priority VoIP class can always be protected under catastrophic congestion; and 3) each design has some pros and cons in terms of performance stability under varied traffic distribution and changed packet size mix. Based on this investigation, we conclude that MDM is comparatively better at providing even service distribution and staying robust against traffic distribution variation and packet size changes.     

Advanced adaptability and profile management framework for the support of flexible mobile service provision

The long-term vision of beyond 3G wireless communications describes a mobile service provision environment dramatically different from that of today. Users are expected to raise their demands to a significantly higher level, towards the situation-aware provision of ubiquitous personalized multimedia services. From this perspective, the need is emerging to apply, in a systematic way, adaptability and reconfigurability concepts for service delivery in largely diverse contexts. Generic dynamically extensible adaptation mechanisms that can be employed in a wide variety of situations and are independent of the subject and criteria of adaptation is a significant step in this direction. Moreover, effective profile representation and management becomes an increasingly important issue. In the present article we introduce an advanced adaptability and profile management framework aiming to fulfill these requirements. The proposed system has been designed, implemented, and incorporated in a distributed middleware platform for next-generation mobile service provision.     

Enhancing IP service provision over heterogeneous wirelessnetworks: a path toward 4G

Second-generation mobile radio systems have been deployed successfully worldwide and have evolved to higher data rates and services. Third-generation mobile radio systems are currently starting to be developed in different regions of the world. Today, the open question is how the third-generation systems will evolve. It is very likely that fourth-generation systems will not be a single standardized air interface, but a set of different technologies and standards. In particular, wireless LAN/wireless PAN type systems are designed for high/medium-data-rate access, low range, and, in general, low mobility. They are applicable to corporate networks and public access as a complement to cellular mobile radio systems for hot spot applications such as airports, hotels, and campuses. In this specific WLAN/WPAN framework and to guarantee an agreed QoS provision over such infrastructures, we propose a solution based on the wireless adaptation layer approach. In particular, aspects related to wireless link impairments and traffic requirements are approached by the implementation of configurable, modular software that is adapted to the specific conditions and needs of the particular wireless infrastructures     

IMS架构及业务提供

多媒体子系统（IMS）是最初由3GPP制定的,用来提供实时和非实时的IP多媒体业务的通用体系结构,具有分布式、与接入无关、以及标准开放的业务控制接口等特点,被当前业界公认为未来融合的控制平台。文章介绍了IMS的产生背景、业务提供架构,并对基本呼叫流程及presence业务的体系结构进行了分析。     

Performance evaluation of location management in UMTS

The universal mobile telecommunications system utilizes a three-level location-management strategy to reduce the net costs of location update and paging in the packet-switched service domain. Within a communication session, a mobile station (MS) is tracked at the cell level during packet transmission. In the idle period of an ongoing session, the MS is tracked at the UTRAN registration area (URA) level to avoid frequent cell updates while still keeping the radio connection. If the MS is not in any communication session, the MS is tracked at the routing-area (RA) level. The inactivity counter mechanism was proposed in 3GPP 25.331 to determine when to switch between the three location-tracking modes. In this mechanism, two inactivity counters are used to count the numbers of cell and URA updates in an idle period between two packet transmissions. If the number of cell updates reaches a threshold K/sub 1/, the MS is switched from cell tracking to URA tracking. After that, if the number of URA updates reaches a threshold K/sub 2/, the MS is tracked at the RA level. The paper proposes analytical and simulation models to investigate the performance of the inactivity counter mechanism. Our study provides guidelines for K/sub 1/ and K/sub 2/ selection to achieve lower net costs of location update and paging.     

Media-independent handover for seamless service provision in heterogeneous networks

The performance of current Internet applications is based mainly on the capabilities of the underlying network technologies. Modern access systems usually can satisfy delay, loss, or bandwidth requirements; however, design inconsistencies can lead to service degradation as the terminals move across different systems. In this article, the focal point is the satisfaction of service requirements during mobility and more specifically, how the emerging IEEE 802.21 standard enables seamless, inter-technology handover. Based on prior work and a well-known example of seamless mobility, the main seamless mobility principles are identified and used as the basis for further evaluating the potential of the IEEE 802.21 standard to meet the requirements of applications for minimum disruption during an inter-technology handover.     

Mastering quality of service in GPRS/UMTS an overview

Quality of Service (QoS) has become a very important issue in networking, covering many performance aspects and numerous measures. The deployment of next generation wireless system includes 2.5G General Packet Radio Service (Gprs), which is the packet-switched extension of the Global System for Mobile communications (Gsm), and Third-Generation (3G) Universal Mobile Telecommunications System (Umts) to meet the needs of larger capacity and higher bit rates. AnUmts packet core network is an IP-based network. The Internet Engineering Task Force (Ietf) Forum developed several IP QoS related mechanisms available for IP transport networks. Service Quality Management (Sqm), one component of Telecommunication Management Network (Tun), will enable providers to manage QoS against objectives set out in customer Service Level Agreements (Slas) and will enable customers to compare the service offerings of different service providers.     

Universal service creation and provision environment forintelligent network

The evolution of the intelligent network (IN) is summarized, and its service creation requirements and provision environment are clarified. A prototype system called the ISDN development experimental system for advanced services (IDEA), which has been developed to validate the foregoing, is described. The evaluation of the system design and its future evolution are discussed     

Multidimensional PRMA with prioritized Bayesian broadcast-a MACstrategy for multiservice traffic over UMTS

Multidimensional packet reservation multiple access is proposed as a medium-access control (MAC) strategy for the uplink channel of the UTRA (UMTS terrestrial radio access) time-division/code-division multiple-access (TD/CDMA) mode to benefit from efficient statistical multiplexing on the large common pool of available resources (i.e., slots defined both in time and code domain). A prioritized Bayesian broadcast algorithm is derived to stabilize multidimensional packet reservation multiple access (MD PRMA) and to allow for access delay discrimination of four different access classes. Access delay spread can be selected, and trading voice-dropping ratio against data-access delay is possible. To control multiple-access interference, Bayesian broadcast can be combined with load-based access control. The performance of both frequency-division duplex (FDD) and time-division duplex (TDD) mode is evaluated, the latter particularly relevant for TD/CDMA. For mixed voice, Worldwide Web (WWW) browsing, and e-mail traffic, the UMTS WWW model is used, while the e-mail traffic model is derived here     

An improved equation based rate adaptation scheme for video streaming over UMTS

Streaming video has experienced phenomenal growth owing to the extensive research in video transmission over wireless networks. This paper describes an improved equation based rate adaptation (EBRA) scheme for video streaming over universal mobile telecommunications system (UMTS). In our method, transmission rate is determined as a function of packet size (s), round trip time (rtt), loss event rate (p) and two novel control parameters for congestion window adjustment (α and β). Our mechanism is compatible with unpredictable wireless channel conditions and provides smooth and flexible sending rate and slowly responsible congestion control by dynamic modification of mentioned parameters. We have simulated this method in UMTS and our results indicate that EBRA in addition to network stability increases throughput with low variations.     

Fuzzy-Q-learning-based autonomic management of macro-diversity algorithm in UMTS networks

Third generationUmts network has come with significant high-quality services that considerably increase the complexity of its management. Autonomic management has been introduced to alleviate these complex lengthy tasks. In this paper, we propose an autonomic management of macro-diversity algorithm inUmts networks. The new approach allows to dynamically adapt macro-diversity parameters to varying network situations. The online adaptation of these parameters is made by an intelligent controller calledfuzzy-Q-Learning. The combination of Fuzzy Inference System (Fis) and Q-learning algorithm allows to determine the best on-line parameterization of base stations and to deal with large number of continuous states and actions. The proposed scheme improves the system capacity up to 30% compared to a classical network with fixed parameters, balances the load between base stations and minimizes human interventions in the network management. However, the reactivity of the controller should be chosen with a special care since it impacts the frequency of active set updates and hence signalling messages in the radio interface as well as in the core network.     

Location management of correlated mobile users in the UMTS

In this paper, we propose concurrently searching for correlated mobile users in mobile communications networks. Previous work either focuses on locating a single mobile user or assumes that the locations of mobile users are statistically independent. We first propose a mobility model in which the movements of mobile users are statistically correlated. Next, we use the theory of Markov chain to derive the joint probability density function of the locations of mobile users. In addition, we propose a novel approach to discover the correlations among the locations of mobile users without explicitly calculating the joint probability density function. Our simulation results indicate that exploring the correlations among the locations of mobile users could significantly reduce the average paging delay and increase the maximum stable throughput.     

Mobility and session management: UMTS vs. cdma2000

This article describes the mobility and session management mechanisms for UMTS and cdma2000 packet-switched (PS) service domains, and compares the design guidelines for these two third-generation technologies. We first introduce the network architectures and protocols for UMTS and cdma2000, and then elaborate on the PS service domain's mobility management, session management, and IP-level mobility mechanisms. Based on the mobility and session management mechanisms of the UMTS and cdma2000 PS service domains, an integrated architecture and intersystem roaming procedures are proposed to show the implementation feasibility of UMTS-cdma2000 IP-level interworking.     

Strong formulations and cutting planes for designing digital data service networks

This paper deals with the problem of designing a least-cost digital data service (DDS) network that connects a given set of locations through digital switching offices with bridging capabilities. We present several alternative mixed 0–1 integer programming formulations and evaluate analytically their relative strengths by comparing their respective linear programming relaxations. By exploiting the structures inherent in a particularly strong formulation, we develop several classes of valid inequalities and cutting planes in order to tighten the initial formulation. For several problems of real-world data, computational results show that the strong formulation with valid inequalities and cutting planes generates a very tight lower bound (over 98% of the optimality) and so finds an optimal solution well within an acceptable time bound.     

UMTS系统和LTE系统的业务流程对比浅析

从业务流程的视角对UMTS系统和LTE系统进行了对比分析,直观地说明了LTE系统比UMTS系统在设计上的合理性和先进性。通过一些关键流程,如RRC连接建立、附着过程、会话过程,简明扼要地解释了LTE系统的时效性高于UMTS系统的原因。     

Performance analysis of multiplexed medical data transmission for mobile emergency care over the UMTS channel

In this paper, a third-generation universal mobile telecommunications system (UMTS) solution for the delivery of biomedical information from an ambulance to a hospital is presented. The joint transmission of voice, real-time video, electrocardiogram signals, and medical scans in a realistic cellular multiuser simulation environment is considered, taking into account the advantages and particularities of UMTS technology for such transmission. The accomplishment of quality of service constraints for different services is investigated and quantitative results are provided in order to demonstrate the feasibility of using UMTS technology for emergency care services on high-speed moving ambulance vehicles.     

UMTS核心网服务质量保证算法研究

UMTS系统——第三代移动通信系统的标准之一．其重要特征是支持多种多样具有不同QoS要求的业务。同时．随着Internet的飞速发展．UMTS已经把IP作为其核心网数据域的协议。然而由于IP尽力而为的特性如何确保对服务质量要求很高的业务性能成为一个急需解决的问题。本文把Differ机制应用于基于IP协议的UMTS核心网数据域，并在此基础上着重研究实现了经典包调度算法虚拟时钟VirtualCLock。此算法根据进入UMTS核心网的不同包的QoS类别进行分类排队．在交换节点上进行拥塞控制。通过仿真与WFQ算法进行比较，可以明显看出VirtualCiock调度算法优越性之所在。