Capacity and performance analysis of signaling networks inmultivendor environments

The load of common channel signaling networks is being increased through the introduction of new services such as supplementary services or mobile communication services. This may lead to a performance degradation of the signaling network, which affects both the quality of the new services and of the services already offered by the network. In the paper, a generic modeling methodology for the signaling load and the signaling network performance as a result of the various communication services is extended in order to include certain implementation-dependent particularities. The models are obtained by considering the protocol functions of Signaling System No. 7 as specified by the CCITT, as well as the information flows through these functions. With this approach, virtual processor models are derived which can be mapped onto particular implementations. This allows the analysis of signaling networks in a multivendor environment. Using these principles, a signaling network planning tool concept has been developed which provides the distinct loading of hardware and software signaling network resources, and on which hierarchical performance analysis and planning procedures are based. This allows to support the planning of signaling networks according to given service, load, and grade-of-service figures. A simple case study outlines the application of the tool concept to a network supporting Freephone, Credit Card, and ISDN voice services     

Design and analysis of cellular mobile communications system basedon DQRAP/CDMA MAC protocol

Future third-generation mobile communication systems will need multi-access control (MAC) protocols suitable for multimedia code division multiple access (CDMA) radio communications. Distributed queueing random access protocol (DQRAP)/CDMA is a general purpose MAC protocol oriented to the CDMA environment. Analytical model expressions and computer simulations have shown its capacity to achieve near-optimum performance under heterogeneous traffic scenarios in a unicellular environment. A cellular environment has been designed to verify that DQPAP/CDMA maintains its near-optimum performance in a packet switched mobile communication system. A new handover technique based on the protocol is proposed to further improve the system performance     

Performability enhancement of fault-tolerant software

Model-based performability evaluation is used to assess and improve the effectiveness of fault-tolerant software. The evaluation employs a measure that combines quantifications of performance and dependability in a synergistic manner, thus capturing the interaction between these two important attributes. The specific systems evaluated are a basic realization of N-version programming (NVP) (N =3) along with variants thereof. For each system, its corresponding stochastic process model is constructed in two layers, with performance and dependability submodels residing in the lower layer. The evaluation results reveal the extent to which performance, dependability, and performability of a variant are improved relative to the basic NVP system. More generally, the investigation demonstrates that such evaluations are indeed feasible and useful with regard to enhancing software performability     

基于RTSP的流媒体传输系统的应用开发

互联网技术在不断发展建设过程中,网络宽带也逐渐完善,流媒体传输技术近几年已经成为科研人员的研究重点,人们在公共场所传输数据过程中经常出现延时性问题,甚至直接造成数据丢失。在这种情况下就需要一个传输性能良好的系统及技术对于现阶段数据传输中所存在的问题针对性解决。     

Performability modelling of wireless communication systems

The high expectations of performance and availability for wireless mobile systems has presented great challenges in the modelling and design of fault tolerant wireless systems. The proper modelling methodology to study the degradation of such systems is so‐called performability modelling. In this paper, we give overview of approaches for the construction and the solution of performability models for wireless cellular networks. First, we start with the Erlang loss model, in which hierarchical and composite Markov chains are constructed to obtain loss formulas for a system with channel failures. Consequently, we develop two level hierarchical models for the wireless cellular system with handoff and channel failures. Then, for a TDMA system consisting of base repeaters and a control channel, we build a hierarchical Markov chain model for automatic protection switching (APS). Finally, we discuss stochastic reward net (SRN) models for performability analysis of wireless systems. Copyright © 2003 John Wiley & Sons, Ltd.     

A buffer allocation scheme for ATM networks: complete sharing basedon virtual partition

Buffer allocation to provide an efficient and fair use of the available buffer spaces is critically important for ATM networks. A complete sharing with virtual partition (CSVP) strategy for buffer management at a multiplexer or an output port of an output buffered switch is proposed and analyzed. The total buffer space is partitioned based on the relative traffic loads (measured or estimated). Virtual partition allows a newly arriving cell belonging to an oversubscribed type to occupy the spare space of an undersubscribed type, and to be overwritten when necessary. Using a fluid flow approach, a set of partial differential equations with a triangular stability region is established to characterize the dynamics of a system supporting two traffic flows. Under a buffer full condition, the system behavior is described by a set of non-homogeneous ordinary differential equations. The cell loss probability for each traffic type is obtained by solving the ordinary differential equations. Numerical examples indicate that by appropriately selecting the partitions, the CSVP method may be used to provide differential cell loss rate requirements by the different traffic types     

Common channel signaling networks: past, present, future

The authors wish to provide a unification of this issue's papers by providing a clear context for them. Common channel signaling can be defined as the system that enables stored program control exchanges, network databases, and other nodes of a network to exchange messages related to call setup, supervision, and take down (call and connection control information); information needed for distributed application processing (interprocess query and response or user-to-user data); and network management information     

Performability Evaluation of Fault-Tolerant Satellite Systems

A combined performance and reliability (performability) measure for gracefully degradable fault-tolerant satellite systems is introduced, and a closed-form analytic solution is provided in order to compute the performability for a class of unrepairable systems. An efficient algorithm for the solution of Markovian models which take into account the degradation of more than one type of system components is given. By means of an example on a commercial communication-satellite system we intend to illustrate this novel measure and compare it to more conventional ones.     

Handovers in wireless ATM networks: in-band signaling protocols andperformance analysis

The first part of this paper presents a novel scheme for handover provisioning in wireless asynchronous transfer mode (W-ATM) networks based on in-band signaling. First, the network architecture and principles of in-band signaling are described, discussing advantages and interaction with other procedures and signaling techniques. Then, loss-free protocols for the handover procedures are presented and compared with existing proposals. The second part of the paper is devoted to performance analysis of the handover procedures. A general methodology for evaluating handover delays and required buffer capacity is introduced and exemplified for one of the protocols introduced before. Numerical results give insight into the handover procedure characteristics and are compared with estimates provided by detailed discrete event simulations for validation purposes. Finally, additional simulation results are presented for parallel, concurrent handovers, evaluating the requirements posed to the network by different handover procedures     

LTE信令监测系统建设分析

文章首先对LTE接口进行分析,然后介绍了LTE信令监测系统的采集方式以及组网架构。     

Performability evaluation of multicomponent fault-tolerant systems

A combined performance and reliability (performability) measure for gracefully degradable fault-tolerant systems is introduced and a closed-form, analytic solution is provided for computing the performability of a class of unrepairable systems which can be modeled by general acyclic Markov processes. This allows the study of models which consider the degradation of more than one type of system component, e.g. processors, memories, buses. An efficient evaluation algorithm is provided, with an extensive analysis of its time and space complexity. A numerical example is provided which shows how the combined performance/reliability measure provides for a complete evaluation of the relative merits of different multiprocessor structures     

An autocompensating fiber-optic quantum cryptography system basedon polarization splitting of light

We have developed a system for quantum key distribution (QKD), based on standard telecommunication lasers, detectors, and optical fiber, that passively compensates for time-dependent variations of the fiber-optic path due to stress, temperature changes, or birefringence. This approach allows information encoded in phase shifts imposed on single-photon-level pulses to be accurately read out after transmission over many kilometers of uncontrolled fiber. Cooled InGaAs avalanche photodiodes, pulse-biased using a special noise canceling circuit, are used to detect single 1.31-μm infrared photons with a high efficiency, low dark-count rate, and subnanosecond time resolution. A single optical fiber carries both the quantum information and precise 1.55 μm timing pulses between the two end stations. Overall synchronization of end-station activities, public discussion of basis choices, error correction, and privacy amplification have all been implemented over a local area network (LAN). The system at present generates raw, error-corrected, and privacy-amplified key data at rates of ~1000, 600, and 200 bits/s, respectively, over a 10-km single-mode fiber link     

Investigations on heuristic bandwidth request mechanism with signaling analysis for BWA networks

Best effort services in next generation broadband wireless access (BWA) networks would be more interactive and bandwidth demanding. This attracted a substantial amount of researches to focus on contention bandwidth request mechanisms for best effort services. The contention resolution with code division multiple access (CDMA) based mobile assisted truncated binary exponential backoff (C-MAB) suffers low contention efficiency and high access delay due to the nature of accessing mechanism in worldwide interoperability for microwave access (WiMAX) network that confines the mobile station in estimating the optimum contention window. Further, these performances decrease when transmission failure is modeled with unavailability of bandwidth, collision due to contention, transmission code failure, and channel error. To improve the performances, in this paper, we suggest a contention resolution with CDMA based base station assisted backoff (C-BAB) for orthogonal frequency division multiple access (OFDMA) based WiMAX networks. With C-BAB, the base station computes an optimum contention window by accounting average contention window and probability of failure. With a 2.69% additional overhead at the BS, the proposed C-BAB shows a 32.82% increase in contention efficiency and 24.21% decrease in access delay (25% error rate, q = 0.60 and ranging slot = 64) compared to C-MAB.     

基于信令分析的TD-SCDMA速率优化方案及实践

数据业务的网络优化相较于话音业务更加复杂,仅从网管统计和日常路测无法全面分析业务的服务质量与影响业务服务质量的因素,需要进一步考虑引入信令分析系统等手段提升分析和优化能力。通过Gb信令数据和无线侧数据的关联分析,可以从小区中用户上网行为去还原网络中的数据业务速率低的问题,从而制定相应的解决方案,提升数据业务上网速率和用户满意度。     

Performability of the hypercube [reliability]

The authors address the problem of modeling and evaluating the composite performance and reliability measures (performability) of a hypercube architecture running a specific application. A generalized stochastic Petri net (GSPN) is used to model the component failures and repairs in the hypercube. The GSPN model defines the dimension and number of subcubes available for the application. This model generalizes previously proposed models for hypercube reliability and automatically generates the underlying Markov chain needed for performability analysis. A novel performability analysis algorithm is presented that computes both the moments and the distribution of performability in O( N³). The algorithm is conceptually simpler than those previously reported. An example is given to illustrate the modeling process and demonstrate the importance of performability analysis for mission-critical systems     

互连网络接口可靠性性能分析

本文论述了互连网络接口可靠性性能，指出了它是全面、正确评价互连网络综合性能的有效方法，文中马尔可夫故障模式和更新过程故障模式，来表达互连网络中各组成部件内和部件间的故障发生模式，并以互连网络信息分组在该故障模式下的损失，作为性能评价标准对互连网络进行可靠性分析，导出有用的公式。     

7号信令采集卡链路层收发的实现

详细介绍并且分析了7号信令采集卡链路层设计的总体方案和工作原理,并对其接收和发送流程涉及到的重要环节进行了介绍.在已经成功研发的7号信令数据采集卡中,通过实际数据测试,已经成功地对7号信令的信号单元进行了正确的接收重组和组装发送,测试效果良好,符合测试要求.     

基于信令分析的TD速率优化方案及实践

数据业务的网络优化相较与语音业务更加复杂,仅从网管统计和日常路测无法全面分析业务的服务质量与影响业务服务质量的因素,需要进一步考虑引入信令分析系统等手段提升分析和优化能力。通过Gb信令数据和无线侧数据的关联分析,可以从小区中用户上网行为去还原网络中的数据业务速率低的问题 ,从而制定相应的解决方案,提升数据业务上网速率和用户满意度     

Performability of electric-power systems modeled by non-homogeneousMarkov chains

This paper treats a particular type of Markov system: time nonhomogeneous Markov system in discrete time. In order to adapt measures to this kind of system, performability measures are formulated, such as new indicators more dedicated to electrical power systems like `instantaneous mean load curtailed' and `mean energy not supplied on a time interval'. This method considers hazard-rate time variation in order to: 1) obtain more-accurate and more-instructive indicators; and 2) access new performability indicators that cannot be obtained by classical methods. An example from an Electricite De France electrical substation illustrates this