Bandwidth renegotiation for VBR video over ATM networks

A scheme for delivery or variable bit-rate (VBR) video over asynchronous transfer mode (ATM) networks where bandwidth can be renegotiated during the duration of a call between the video source and the network is considered. Renegotiation can be initiated by either the video source or the network. The video bandwidth requirement is characterized by a usage parameter control (UPC) consisting, in general, of peak rate, burst length, and sustained rate. A baseline design is outlined where rate-control adjusts the source's rate while a new UPC is requested from the network. When granted, the new UPC allows the source to maintain its target quantization and delay requirements. Rate control epochs may be extended when the network blocks UPC requests or sets a lower UPC value to temporally deal with congestion. Simulation results are presented for VBR MPEG video. The results show that with a moderate renegotiation rate the scheme tracks the bandwidth requirements of the source. As a result, the video quality and bandwidth efficiency can be maintained     

Performance Analysis of the UPC/NPC Algorithm for Guaranteed QoS in ATM Networks

It is well known that if usage parameter control/network parameter control (UPC/NPC) functions are used together with a cell loss priority control scheme in ATM networks, the measurement phasing problem can occur. This makes it difficult for a network provider to define and commit the cell loss ratio as a QoS parameter. To solve the problem, we propose a new UPC/NPC algorithm. By using the proposed UPC/NPC algorithm, we can define the cell loss ratios for CLP = 0 and CLP = 0+1 cell streams without the measurement phasing problem under any conditions. We analyzed the performance of the proposed UPC/NPC algorithm. Using a discrete time model for the UPC/NPC architecture with a discrete-time semi-Markov process (DSMP) input model, we obtained the cell discarding probabilities of CLP = 0 and CLP = 0+1 cell streams and showed that more CLP = 0 cells are accepted compared to what was proposed in ITU-T.     

ATM网络的使用参数控制

使用参数控制（ＵＰＣ）是ＡＴＭ网络流量控制的一个重要手段。文章从对ＵＰＣ的要求出发,分析了几种ＵＰＣ监测机制,并给出它们的实现方法。另外 ＵＰＣ机制对违 约信元采取的向种警管措施,指出了它们的优缺点,并在此基础上提出了一种新的警管想法。     

A detailed study of a CDMA based approach to enhance ad hoc network performance

Random access schemes operate typically on a contention based common channel, which brings problems with increasing traffic load. These problems are emphasized in a multi-hop wireless ad hoc network environment. Efficient collision avoidance methods are needed, but they also tend to decrease the spatial capacity of the network. With CDMA (Code Division Multiple Access), it is possible to make multiple simultaneous co-located successful transmissions and thus increase network capacity within the limits of multiple access interference (MAI). Bi-code channel access (BCCA) is a method to apply CDMA in ad hoc networking, providing also a common access channel for network connectivity maintenance and self-configuration. With BCCA, collisions are rare, and thus, more straightforward medium access control (MAC) methods can be used. A MAC solution designed especially for BCCA (BC-MAC) and ad hoc networking increases the efficiency of the channel usage. As BCCA is based on receiver code CDMA, the spreading code of the next hop node is needed. A novel network layer spreading code distribution (NSCD) method is proposed for this purpose. The spreading codes are distributed within routing protocol control packets at the route establishment phase.A detailed study on the performance behavior of different methods is provided. Also, interesting aspects considering the ad hoc network operation are discussed. Instead of the widely used unrealistic cut propagation model, a propagation model with realistic MAI calculation is used in this study. It is shown that the use of NSCD increases the network control load only slightly, and that the performance is practically the same as it is with the assumption of known spreading codes. BCCA with its dedicated MAC and NSCD clearly outperforms commonly used methods (like IEEE 802.11) and yet is easy to implement, robust for design parameters under different conditions while maintaining the original idea of ad hoc networking.     

The transmission of MPEG‐2 VBR video under usage parameter control

This paper studies the transmission of MPEG‐2 VBR video over ATM network under usage parameter control. The idea is to seek a compromise between the network utilization and the quality of video service by applying UPC‐based rate control strategies to the video source. A modified leaky bucket algorithm is proposed to calculate the constraints on the bit‐rate guaranteeing conformance to peak cell rate, sustainable cell rate and burst tolerance usage parameters. Two rate control strategies, one for real‐time generated video coding and the other for pre‐compressed video, are proposed for MPEG‐2 VBR video. The rate control strategies control the video source to generate traffic conforming to the constraints on the bit rate. The experimental results show that both the UPC‐based rate control strategies can provide lossless transmission from the source perspective as well as to reduce the burstiness of the traffic. To keep within the bit‐rate allowed, the control method uses coarser quantization to maintain better picture quality than that by removing the number of AC transformed coefficients. The slight degradation of picture quality caused by the source rate control is preferable than the severe drop of picture quality caused by the cell loss at UPC. Copyright © 2001 John Wiley & Sons, Ltd.     

宽带ISDN与ATM交换技术 第四讲 B－ISDN中的业务量控制

本文介绍了Ｂ－ＩＳＤＮ中业务量控制的原理和方法，讨论了连接／呼叫接纳控制（ＣＡＣ）和用法／网络参数控制（ＵＰＣ／ＮＰＣ）两个最基本的业务量控制功能，并对网络拥塞控制、业务量成形、优先级控制和快速资源管理等附加的控制功能作了简要的叙述。     

Distributed Reservation Protocol and QoS Method in WR-OBS System

1IntroductionOptical Burst Switching (OBS)[1 ~4]provides a feasi-ble paradigm for Internet Protocol (IP) over Wave-length-Division Multiplexing ( WDM) integration[5 ~10],which has been the focus of intense investigation owingtoits flexibilityin utilizingthe terahertz bandwidth of asingle fiber andits capabilitytosupport transparent datatransmissions. However , with the emergence of allkinds of applications such as data ,voice ,the next-gen-eration network must also be designedto provide …     

基于数据流前端检测的快速协议识别

信息战都追求高速反应机动,对网络协议识别提出了高效快速的要求。基于深度包检测DPI的协议识别方法识别准确率高,但是由于要对所有数据包进行检测,计算量很大。基于端口号的协议识别方法速度快,但识别准确率低。提出一种新的基于数据流前端检测的协议识别方法并进行了系统实现,结合了基于端口方法的快速简单和基于DPI的准确性的优点。实验表明,这种综合快速协议识别方法识别准确率高,与基于DPI的方法相比,识别时间减少将近80%。     

A vector controlled current-source PWM rectifier with a novelcurrent damping method

Three-phase current-type pulse width modulation (PWM) rectifiers are becoming increasingly popular as the front-end converter unit in power electronic systems due to tighter electromagnetic compatibility (EMC) regulations. In this paper the control of the current source PWM rectifier in the synchronously rotating reference frame is discussed. A control system is presented in which the active and reactive power are independently controlled with real and imaginary axis components of the supply current vector. A new damping method for supply current oscillations is introduced. The method operates in an open-loop manner and is very suitable for microcontroller implementation since the calculation power demand is low. Furthermore, it is shown that in the synchronously rotating coordinates, where the sinusoidal variables appear as DC quantities, the compensation of the reactive power drawn by the supply filter can be done very easily. The proposed control methods are realized using a single-chip Motorola MC68HC916Y1 microcontroller. The experimental tests show excellent performance in both steady state and transient conditions     

A New Method of Integration Control With Instantaneous Current Monitoring for Class D Series-Resonant Converter

In this paper, the application of the integration control method for class D transistor voltage source series-resonant converters used as dc/dc and dc/ac converters is presented. First, the integration control of the signal as a combination of the resonant frequency and its subharmonics (subharmonic integration control) is discussed. Second, the modulation density of the pulses shorting the bridge diagonal for one current half wave (semi wave integral pulse density modulation) is explained. A detailed control circuit operation, referred to as the four basic algorithms of the resonant current control, is given. The method for the calculation of the value and sequence of the current increments for a dc/dc converter is presented. The results of computer simulations and laboratory experiments demonstrate that the proposed methods allow controlling the converter output quantities fulfilling soft switching conditions (zero-current switching) and provide higher efficiency in comparison to other known methods     

A test sequence selection method for protocol testing

A method for automated selection of test sequences from a protocol specification given in Estelle for the purpose of testing both control and data flow aspects of a protocol implementation is discussed. First, a flowgraph modeling the flow of both control and data expressed in the given specification is constructed. In the flowgraph, definitions and uses of each context variable, as well as each input and output interaction parameter employed in the specification, are identified. Based on this information, associations between each output and those inputs that influence the output are established. Test sequences are selected to cover each such association at least once. The resulting test sequences are shown to provide the capability of checking whether a protocol implementation under test establishes the desired flow of both control and data expressed in the protocol specification. The proposed method is illustrated by using the class 0 transport protocol as an example     

vector-controlled PWM current-source-inverter-fed induction motor drive with a new stator current control method

In this paper, the control of the pulsewidth-modulated current-source-inverter-fed induction motor drive is discussed. The vector control system of the induction motor is realized in a rotor-flux-oriented reference frame, where only the measured angular rotor speed and the dc-link current are needed for motor control. A new damping method for stator current oscillations is introduced. The method operates in an open-loop manner and is very suitable for microcontroller implementation, since the calculation power demand is low. Also, the stator current phase error caused by the load filter is compensated without measurement of any electrical variable. With the proposed control methods the motor current sensors can be totally eliminated since the stator current measurements are not needed either for protection in the current-source-inverter-fed drives. The proposed control methods are realized using a single-chip Motorola MC68HC916Y1 microcontroller. The experimental tests show excellent performance in both steady-state and transient conditions.     

Implementation mechanisms for packet switched voice conferencing

A distributed control mechanism for managing a packet-switched voice conference connection is presented. The principal concept introduced is the idea of viewing a conference connection as a logical ring of participants. Alternative methods for implementing voice conferencing on both broadcast and point-to-point networks are introduced, analyzed, and compared. Tradeoffs between the two methods with respect to station workload and maximum number of conference participants are discussed. Experimental implementations on both a carrier-sense multi-access with collision detection (CSMA/CD) Ethernet and a token-ring ProNet are described. The mechanisms presented can be used as part of a packet-switched voice communications protocol that includes conferencing capabilities     

Design principles for communication gateways

The purpose of this study is to define principles that apply to the design of communication gateways between heterogeneous computer systems, and to identify strategies to solve incompatibilities in a systematic manner. The importance of communication service common properties is explored in detail. The modification of the service available for interworking due to subset selection and service concatenation is discussed. Various methods of adaptation are described. Two architectural options for the design of communication gateways are explored, namely, conversion at the service level or at the PDU (protocol data unit) level. While the former is conceptually simpler, various optimizations are possible through the latter approach. A method for deriving the specification of a protocol adapter from the two protocol specifications is given. All these issues are illustrated by a number of simple examples     

ATM基本业务量控制技术

介绍ＡＴＭ基本业务量控制技术，对连接受理控制（ＣＡＣ）、使用量参数控制（ＵＰＣ）、优先控制、拥塞控制等作了全面、系统的说明和分析。     

Energy-Efficient Low Duty Cycle MAC Protocol for Wireless Body Area Networks

This paper presents an energy-efficient medium access control protocol suitable for communication in a wireless body area network for remote monitoring of physiological signals such as EEG and ECG. The protocol takes advantage of the static nature of the body area network to implement the effective time-division multiple access (TDMA) strategy with very little amount of overhead and almost no idle listening (by static, we refer to the fixed topology of the network investigated). The main goal is to develop energy-efficient and reliable communication protocol to support streaming of large amount of data. TDMA synchronization problems are discussed and solutions are presented. Equations for duty cycle calculation are also derived for power consumption and battery life predictions. The power consumption model was also validated through measurements. Our results show that the protocol is energy efficient for streaming communication as well as sending short bursts of data, and thus can be used for different types of physiological signals with different sample rates. The protocol is implemented on the analog devices ADF7020 RF transceivers.      

TETRA数字集群呼叫控制协议适配的设计与实现

提出了一种陆上集群无线电(TETRA)数字集群系统呼叫控制协议适配的设计与实现方案。论述了欧洲通信标准协会(ETSI)TETRA数字集群呼叫控制协议适配(CCSA)在TETRA系统中的位置和功能,提出若干需要解决的核心问题,详细阐述了解决这些问题所用到的关键技术和所采用的设计方法,并部署在TETRA系统设备上进行呼叫测试。通过对设计结果的分析,证明了该设计的可用性和先进性。