Congestion control in cognitive radio networks with event-triggered sliding mode

The increasing demand for assorted services from extensive wireline and wireless users place a significant burden on the band-limited radio spectrum. To settle the demand, smart reuse and management of the spectrum are necessary. In this contribution, Cognitive Radio being an emerging technology provides a platform to share the same spectrum between Primary Users (licensed) and Secondary Users (unlicensed) for significant improvement in the spectrum efficiency. The coexistence of users for data communications in a band-limited channel calls for a robust congestion controller to maximize throughput. This work presents the design of a robust nonlinear congestion controller based on event-triggered sliding mode for Cognitive Radio Networks. The goal is to maintain desired Quality of Service of the network with optimum bandwidth and resource utilization. The controller has been designed on the notions of sliding mode, better known for its inherent robustness and disturbance rejection capabilities. An event-triggering scheme has been incorporated with the sliding mode for optimum utilization of the available resources. The signal is sampled and control is updated only when a predefined condition gets violated while ensuring acceptable closed-loop behavior of the system. The efficiency of the proposed controllers has been validated using simulations.     

Comparison of VBR and CBR service classes for MPEG‐2 video multiplexing—Is statistical multiplexing really useful for bursty video transmission?

It has been believed that a statistical multiplexing technique can bring an effective bandwidth usage. When it is applied to MPEG‐2 video, it has been pointed out that two to several times multiplexing gain can be attained due to the highly bursty nature of video traffic. However, most of the past researches do not take into account the implementation aspects of this technique. In this paper, we thoroughly investigate the actual multiplexing gain by comparing ATM CBR and VBR service classes (deterministic and statistical service classes), and point out that the statistical multiplexing gain is far from what one might expect. Copyright © 2001 John Wiley & Sons, Ltd.     

PoC业务用户群及市场策略分析

文章在研究中国电信市场环境及当前业务特点的基础上,对PoC业务用户群及市场推广策略进行了探讨.文章认为中国PoC业务市场推广不能照搬美国运营商Nextel的发展模式,必须结合中国具体的电信业务环境加以考虑.在中国市场中,行业用户是PoC业务推广应首先关注的目标,而对于已经使用或未使用专网集群服务的用户,应采取差异化的市场策略.在推广PoC业务的过程中,应重点发展能够带来新的业务量的PoC用户群,同时尽量避免与现有移动电话、短信、语音信箱等业务的竞争.     

TD-SCDMA系统终端数据业务研究

TD—SCDMA是目前3G标准中的一个热门话题，与第二代移动通信GSM相比，使用了智能天线、多用户检测、软件无线电等多种新技术，优化了系统设计，无线资源利用率高。其显著特点在于向用户提供各种环境下高速、可靠的数据业务，从而满足人们对未来通信的需求，成为3G的主要发展方向之一。因此，本文首先对TD—SCDMA系统终端的结构及组成进行概述，接着主要阐述了该标准体系中的分组数据业务，分析其业务流程，最后对其发展前景进行了展望。     

A two-station queue with dependent preparation and service times

We discuss a single-server multi-station alternating queue where the preparation times and the service times are auto- and cross-correlated. We examine two cases. In the first case, preparation and service times depend on a common discrete time Markov chain. In the second case, we assume that the service times depend on the previous preparation time through their joint Laplace transform. The waiting time process is directly analysed by solving a Lindley-type equation via transform methods. Numerical examples are included to demonstrate the effect of the auto-correlation of and the cross-correlation between the preparation and service times.     

结算业务集中化架构研究

主要根据结算业务的特点,结合各种软硬件产品特性,采用刀片机、低端磁盘阵列及开源系统软件等搭建一个低成本、全新的系统架构方案,同时通过对软件架构设计的调整及改造,保证在系统安全运行的同时,使系统具有灵活的故障处理和平滑的扩展能力。     

User‐Centric Conflict Management for Media Services Using Personal Companions

In this paper, we propose a user‐centric conflict management method for media services which exploits personal companions for the harmonious detection and resolution of service conflicts. To detect conflicts based on the varying characteristics of individual users, the proposed method exploits the unified context describing all users attempting to access media services. It recommends and mediates users' preferred media contents through a shared screen and personal companions to resolve the detected conflicts. During the recommendation, a list of preferred media contents is displayed on the shared screen, and a personally preferred content list is shown on the user's personal companion comprising the selection of media contents. Mediation assists the selection of a consensual service by gathering the users' selections and highlighting the common media contents. In experiments carried out in a ubiHome, we observed that recommendations and mediation are useful in harmoniously resolving conflicts by encouraging user participation in conflict situations.     

Sensitivity analysis of machine repair problems in manufacturing systems with service interruptions

This paper models a manufacturing system consisting of M operating machines and S spare machines under the supervision of a group of technicians in a repair facility. Machines fail according to a Poisson process, and the repair (service) process of a failed machine may require more than one phase. In each phase, service times are assumed to be exponentially distributed but may be interrupted when the repair facility encounters unpredictable breakdowns. Two models of manufacturing systems are considered. In the first model, technicians repair failed machines at different rates in each phase. In the second model, a two-phase service system with differing numbers of technicians is considered. Profit functions are developed for both models and optimized by a suitable allocation of the number of machines, spares, and technicians in the system. Finally, a sensitivity analysis (see Cao [X.R. Cao, Realization Probabilities: The Dynamics of Queuing Systems, Springer-Verlag: London, 1994; X.R. Cao, The relations among potentials, perturbation analysis, and Markov decision processes, Discrete Event Dynam. Syst.: Theory Applicat. 8 (1998) 71–87]) is performed to provide an approach that quantifies the impact of changes in the parameters on the profit models.     

WCDMA网络规划仿真中混合业务模型的建立及仿真方法研究

介绍了在WCDMA规划仿真工作中建立混合业务模型的方法步骤，及各个关键参数的计算方法。     

CNGI上的一种电信新业务:智能交通

文章介绍了一种基于中国下一代互联网示范工程(CNGI)的城市智能交通系统(ITS).该系统将先进的信息技术、数据通信技术以及自动控制技术有效融合,并运用于交通管理系统,建立起一个大范围全方位发挥作用的实时、准确、高效的综合智能交通管理系统.系统由网络通信平台、地理信息平台、综合指挥平台、信号控制系统、交通视频监控系统等15个子系统组成.文章认为在CNGI基础上建立ITS是电信业务的一种拓展,通过ITS用户可以获得新的移动多媒体集群通信业务,电信运营商也找到了新的业务增长点.