Polling systems with simultaneous arrivals

The authors analyze polling systems with multiple types of simultaneous arrivals, namely, batches of customers may arrive at the different queues at an arrival epoch. The authors consider cyclic polling systems with N queues, general service time distribution in each queue, and general switchover times. For both the exhaustive and the gated service disciplines the authors derive the necessary equations for computing the N expected waiting time figures. A pseudo conservation law for these system is also derived. The authors compare several special cases of the correlated arrivals polling system, discuss the computational aspects of the numerical method, and examine the applicability of the analysis to other polling systems     

LMDS systems and their application

Local multipoint distribution systems (LMDS) represent a new radio-based access technology with cellular architecture offering flexible high-capacity connections to private users and organizations. The systems employ a point-to-multipoint broadcast downlink with a total capacity of 36-38 Mb/s per transport stream, giving high flexibility for inclusion of any type of data. The interactive channel, being a point-to-point connection, may employ different technologies depending on availability and user demand for capacity. This capacity may basically range from a few kilobits per second up to at least 25.6 Mb/s. LMDS performance relative to other broadband access technologies is discussed. A major remaining development task is the establishment and verification of methods for coverage of normally shielded areas. The availability of cheap repeaters and possibly reflectors for increased coverage is a must, which will significantly improve coverage. The LMDS technology, now in its first stage of implementation, is expected to enhance development of broadband services such as e-commerce and tele-teaching     

Antipodal paraunitary matrices and their application to OFDM systems

Paraunitary (PU) matrices and filterbanks have played an important role in many applications. This paper studies a special class of PU matrices, called antipodal paraunitary (APU) matrices. APU matrices are PU matrices whose coefficient matrices consist of /spl plusmn/1 only. Several new methods will be introduced for the construction of APU matrices. In particular, a new method based on the butterfly structure that has a low cost implementation is proposed. Moreover, one application of APU matrices in precoded orthogonal frequency division multiplexing (OFDM) systems will be considered. By using an APU precoding matrix, the complexity will be very low, and experiments show that the use of APU matrices can greatly enhance the performance.     

Smart antenna techniques and their application to wireless ad hoc networks

In this article the use of smart antennas in mobile ad hoc and mesh networks is discussed. We first give a brief overview of smart antenna techniques and describe the issues that arise when applying these techniques in ad hoc networks. We consider ad hoc/mesh networks with directional antennas, beamforming/adaptive antennas, and/or multiple-input-multiple-output (MIMO) techniques. We then show how the MAC/routing techniques can be modified to get the maximum benefit with smart antennas, while also showing examples of degradation in system performance, rather than improvement, when smart antenna techniques are added to networks with standard MAC/routing techniques.     

Repairable single server systems with multiple breakdown modes

Typically the availability, steady-state queue length distribution, and mean queue length of Markov queueing systems subject to random breakdowns are computed by generating function or matrix geometric numerical methods. In this paper we point out that, for single server systems, a simple partition balance approach is easier. We illustrate this observation by deriving expressions for the availability, steady-state queue length distribution, mean queue length, and server utilization of a single server system subject to multi-mode, bi-level, Poisson distributed breakdowns of exponentially distributed duration. A numerical example illustrating some of the relations between these measures is also given. Our setup provides a simple, computationally tractable, Markov model for systems in which breakdowns of different types occur and are repaired at rates dependent on the type and severity of the breakdown.     

层次模糊系统的全局逼近性质及其与多子波神经网络关系研究

该文首先讨论了B样条基函数的特性,在此基础上证明了基于B样条隶属函数的层次模糊系统(HBFS)是全局逼近器这一重要结论。与此同时,根据基于B样条隶属函数的层次模糊系统与多子波神经网络在逼近问题上的等价性,我们对于多子波神经网络是否为全局逼近器这一问题给出了一种全新的证明方法,以上工作为HBFS的实际应用提供了坚实的的理论基础。     

An evolutive framework for server placement optimization to digital twin networks

Digital twin network (DTN) is a foremost enabler for efficient optimization in modern networks, as it owns massive real-time data and requires interaction with the physical network in real-time. When constructing a DTN, it is necessary to deploy many servers in the physical network for digital models' storage, calculation, and communication. Evolutionary algorithms show outstanding global optimization capabilities compared to the constructive heuristic method in such an optimization problem. However, due to the high dimensionality of the problem and the complicated evaluation of the deployment plan, evolutionary algorithms easily fall into the optimum local at a high computational cost, given that the server placement problem is an NP-hard combinatorial optimization problem. In this research, we propose an evolutionary framework for server layout optimization that significantly improves the optimization efficiency of evolutionary algorithms and reduces the algorithm's computational cost. An offline-learning-based approach is used to reduce the search space, and a self-examining guided local search method is proposed to improve the search efficiency. Additionally, a look-up table-based hybrid approach is used for solution evaluation, reducing computational overhead. Experimental results show that the proposed framework and optimization strategy can significantly improve the evolutionary algorithm search efficiency and achieve excellent convergence performance.     

Research advances in cognitive ultra wide band radio and their application to sensor networks

The paper illustrates the novel concept of Cognitive UWB Radio, a wireless system based on UWB transmission able to self-adapt to the characteristics of the surrounding environment. First, salient features of UWB transmission are reviewed, and then, application of UWB characteristics to the problem of cognitive radio systems is discussed. Current ongoing studies and achieved results on a possible physical layer based on Prolate Spheroidal Wave Functions and consistent with the Cognitive UWB Radio paradigm are presented and analyzed, and their application to the sensor network scenario is discussed.     

A conference control model between a web server and a telecom application server

The paper proposes a conference control model between a web server and a telecom application server, referred to as the Conference Directed Graph （CDG）, and describes an asynchronous communication mechanism between them. The Corba Interface Definition Language （IDL） interfaces are defined, and a message sequence chart is illustrated. This web conference control model provides conference users with a new approach to manage and control a conference and the participants. The performance of the system prototype is analyzed and verified in the 863 project named ＂The Multimedia and Mobile Services Enabled Soft-switch System＂.     

Dealing with server corruption in weakly consistent replicated data systems

Providing high availability and the ability to share data despite the weak connectivity of mobile computing raises the problem of trusting replicated data servers that may be corrupt. This is because servers must be run on portable computers, and these machines are less secure and thus less trustworthy than those traditionally used to run servers. We describe the kinds of problems one must be prepared to deal with, noting that even users of secured, nonportable computers are at risk if servers trust all authorized peers. We show that high availability through data replication on portable computers need not be mutually exclusive with various levels of data security one might want. We give three solutions to this trust problem for a simple example architecture, achieving progressively higher levels of security with progressively higher costs. We then show how to solve this trust problem for the more complex architecture of Bayou, a weakly consistent replicated data system we built at Xerox PARC.     

High temperature superconductors and their application in passiveantenna systems

The basic physics of superconductivity is reviewed and related to the high-temperature superconductors. The high-frequency characteristics of the new materials are examined, and the two-fluid model is introduced and used to derive an empirical expression for the conductivity of superconductors. The advantages and disadvantages of using these superconductors in the construction of high-frequency transmission lines and passive microwave and millimeter-wave antenna systems are discussed     

OPC数据访问服务器研究与应用

针对OPC技术在国内的应用现状,以OPC数据的存取规范为依据,利用国产Multi Bus-RTU系列模块基于Modbus TCP协议对OPC数据访问服务器进行开发,设计采用OPCMaster公司的OPC开发工具OM_OPCSvr.dll实现OPC数据传输服务器的开发,通过以太网方式,在Modbus设备和OPC客户端之间提供数据交换通道。通过对OPC数据访问服务器结构和操作流程的设计,构建了服务器的功能框架。基于Modbus TCP OPC服务器和Windows平台,通过对服务器进行初始化,对通信驱动模块和用户界面进行规划,进而对OPC数据访问服务器进行了详细的实现。通过进一步的OPC服务器测试发现,该服务器具有可靠的稳定性,能切实地节约成本,减少通信驱动数量,并缩短开发周期。     

服务器的备份及其在视频领域中的应用

讨论了服务器在网络中所起到的作用和地位，阐述了服务器备份在网络中必不可少的意义，介绍了备份服务器工作的模式和具体的实现方法，并针对可能出现的问题及其在视频频域中的应用提出了解决方案。     

探索性软件测试方法及其在嵌入式系统中的应用

探索性软件测试发挥测试人员经验和创造性,强调软件测试各阶段的同时性,并利用测试学习被测系统,已形成应用体系并在工业界成功运用。将探索性测试技术应用于嵌入式系统软件测试,是解决测试时间紧、任务重、软件文档不完备等现实问题的有吸引力的方法。然而,嵌入式系统测试要求严格的软件测试管理流程和文档,并需对测试执行进行有效评价,这些要求在探索性测试中被弱化。调研和综述探索性测试技术,分析探索性测试技术与嵌入式系统软件测试体系的关联和冲突,是将探索性测试在嵌入式软件测试中的恰当运用的关键。以此为基础,对探索性测试在嵌入式系统软件测试中的应用模型提出了建议,并对应用中的问题和后续研究进行了讨论和展望。     

Chaos engineering and its application to parallel distributedprocessing with chaotic neural networks

Chaotic dynamics and its possible applications are considered from the viewpoint of engineering. Various applications, even to consumer products such as household appliances, are developing in the field of chaos engineering. In particular we review parallel distributed processing with spatio-temporal chaos on the basis of a model of chaotic neural networks     

开源视频服务器软件MJPG-streamer的研究和应用

针对嵌入式设备在进行多媒体数据处理时存在的资源限制问题,采用了一种开源视频服务器软件MJPG—streamer完成多媒体数据的处理及存储,基于该软件的特点和体系结构,通过修改MJPG—streamer的源代码,添加新的功能模块,以增强这款软件的功能。并重新交叉编译后,移植到嵌入式系统中,以实现一个可控制前端设备的基于Arm9的嵌入式远程视频监控系统。实验结果表明,该方法很好地增强了视频数据处理的效果,并可流畅地在客户端播放浏览器。     

New adaptive complex IIR filters and their application in OFDM systems

In this article, very low sensitivity variable complex filter (VCF) sections are developed. They have two important advantages: extremely low passband sensitivity and independent tuning of the bandwidth and the central frequency over a wide frequency range. The first advantage provides resistance to quantization effects, while the second one gives a better digital signal processing quality and extends the area of possible applications of the developed filters. Based on the proposed VCF sections an adaptive complex system is designed which demonstrates very fast convergence and low computational complexity. This system is applied for narrowband interference cancellation in multiband orthogonal frequency division multiplexing receivers and wideband noise cancellation in OFDM receivers. It is experimentally verified that a better signal-to-noise ratio and signal-to-interference ratio can be achieved using the proposed adaptive complex filtering scheme.     

Analysis of packet networks having contention-based reservation with application to GPRS

We develop a model to quantify the performance of message transmission systems in which users must reserve transmission resources via a contention mechanism prior to transmission. Our work is motivated by a desire to understand the performance characteristics of systems such as the general packet radio service (GPRS), where the single forward link of the wireless access system is organized as a sequence of frames, each of which has first a contention period and then a service period. There are a fixed number of fixed-length contention slots in each contention period. Each contending customer chooses at random the slot in which to contend, and success is determined by a capture model. A contender who fails waits for the next contention period, then again chooses at random the slot in which to contend; this process is repeated until the contender is successful. Customers who have contended successfully are served during the service period, which has a prescribed number of fixed-length slots, on a first-come-first-served (FCFS) basis, with the required number of service units being drawn independently from a general discrete distribution having finite support. We model the system as a Markov renewal process embedded at service departure times. We solve the model and then compute the equilibrium distributions of the number of customers in the system at arbitrary points in time and at customer arrival times. Finally, we give a numerical example in which we demonstrate the usefulness of our results in understanding the behavior of GPRS.