Performance of wideband CDMA systems supporting multimedia traffic

We evaluate the performance of wideband CDMA cellular systems providing different classes of multimedia traffic and supporting user mobility. A Markovian teletraffic model of the user dynamics is developed. Constraints are imposed in the model which account for the multiple access interference among active users. Results are shown in terms of call blocking probabilities and average number of active connections. The methodology proposed is a useful tool for the design and planning of third generation cellular systems     

Computational methods for performance evaluation of a statisticalmultiplexer supporting bursty traffic

A statistical multiplexer supporting a number of bursty sources is modeled as a discrete time, single server queueing system with an infinite buffer. The probability generating function (PGF) method is used to analyze the queueing behavior. The PGF method requires the determination of a large number of boundary values and, hence, the roots of the characteristic equation. An iterative algorithm to evaluate the characteristic roots is proposed. When the arrival process is a superposition of independent processes, a decomposition approach is used to reduce the state space involved in the computational algorithm. Additionally, the computational algorithm is made efficient through the establishment of conditions under which all the roots are either real or nonnegative real numbers. A set of equations to recursively compute the moments of the queue length are established. Sample applications of the computational methods to evaluate the performance of a multiplexer supporting voice and video sources, modeled by two-state Markov and L-state MMPP processes, respectively, demonstrate the viability of the proposed methods     

C-RAN网络中CoMP性能分析与优化

针对无线通信中的能耗巨大和移动用户潮汐现象带来的基站利用率低下问题,C-RAN作为一种基于集中化处理、协作式无线电和实时云计算架构的无线接入网架构,是一种低成本、高性能的解决方案。针对C-RAN网络中的CoMP性能,通过计算无线链路损耗分析了JT下的CoMP的理论增益。针对C-RAN网络规划设计问题,定性分析了CoMP增益与C-RAN网络Cell数的比例关系,最后结合仿真结果给出了合理的网络规划设计建议,且理论证明其能够很好地解决移动运营商所面临的上述挑战。     

Performance evaluation of FDDI under asymmetric traffic conditions

FDDI is a proposed standard for optical fibre LANs. A simulation model is used to examine the performance of the FDDI protocol under asymmetric traffic conditions. The relationship between the average token rotation time and the relative stability of the network is also presented.<>     

Performance evaluation of broadband connections and services undervarying traffic loads

The authors present ongoing work in the RACE R1056 project which is related to the integration and verification part of the RACE programme. The project goal is to establish a basic business integrated broadband communications demonstrator in an evolutionary hybrid network environment. The demonstrator configuration consists of a switching node, a customer access network and a customer premises network; its physical implementation is described. Some key business services which are to be demonstrated together with the supporting user terminals are presented. Test objectives cover verification of the hardware performance, interface compatibility and verification of a new transfer mode technique: ATM (asynchronous transfer mode). Verification activity covers the network performance (verification of end-to-end connections and measurements of key parameters). Evaluation activities cover network performance and its relationship to the quality of service perceived by a user     

Performance evaluation of 10Base-T and 100Base-T Ethernets carryingmultimedia traffic

The performance of 10Base-T and 100Base-T Ethernet segments carrying audio/video traffic is presented. End-to-end delay requirements suitable for a wide range of multimedia applications are considered (ranging from 20-500 ms). Given the specific nature of the network considered and the maximum latency requirement, some data is lost. Data loss at the receiver causes quality degradations in the displayed video in the form of discontinuities, referred to as glitches. We define various quantities characterizing the glitches, namely, the total amount of information lost in glitches, their duration, and the rate at which glitches occur. We study these quantities for various network and traffic scenarios, using a computer simulation model driven by real video traffic generated by encoding video sequences. We also determine the maximum number of video streams that can be supported for given maximum delay requirement and glitch rate. We consider various types of video contents (video conferencing, motion pictures, commercials), two encoding schemes (H.261 and MPEG-1), and two encoder control schemes [constant bit rate (CBR) and constant-quality variable bit rate (CQ-VBR)] and compare their results. Furthermore, we consider scenarios with mixtures of video and data traffic (with various degrees of burstiness), and determine the effect of one traffic type over the other     

Performance evaluation of random power capture on mobile communications

Power assignment schemes are man‐made methods to enhance the capture effect of radio communications. In a previous study, Wen and Yang investigated the combined capture effect of the fixed power assignment scheme, Rayleigh fading, and near–far effect on the performance of packet radios. The performance analysis was limited to an infinite population environment. This assumption is reasonable for a conventional packet radio system with a vast service area. However, for a cellular mobile system, a finite population model should be used. In this paper, we analyse the combined natural and man‐made capture effect on the performance of a cellular system with finite population in each cell. A random power assignment scheme is adopted to produce the man‐made capture. The system throughput and delay are carried out by a Markov model. Some numerical calculations are used to demonstrate the degree of performance improvement. Copyright © 2001 John Wiley & Sons, Ltd.     

C-RAN无线网络中业务预测的马尔科夫模型

C-RAN架构无线网络由于采用的是云处理模式,从而具有了云处理模式。已有的业务预测方法应用到C-RAN网络中,会存在不能充分利用共享的信息资源从而影响预测效果的问题。针对这个问题,在证明C-RAN架构无线网络中由不同小区业务流量构成的向量随时间变化的过程是一个马尔科夫过程的基础上,提出利用历史数据构建预测矩阵,通过预测矩阵与当前业务流量数据进行预测,并且设计出预测矩阵的构建方法,以及当有新流量数据到来时对预测矩阵的修正方法,从而适应了对网络状态非平稳情况下的预测。仿真结果表明该方法在预测精度上比传统的外延法、回归分析法有所提高。     

Performance evaluation of finite normal mixture model-based image segmentation techniques

Finite normal mixture (FNM) model-based image segmentation techniques adopt the following detection-estimation-classification paradigm: (1) detect the number of image regions by using theoretical information criteria; (2) estimate model parameters by using expectation-maximization (EM)/classification-maximization (CM) algorithms; and (3) classify pixels into regions by using various classifiers. This paper presents a theoretical framework to evaluate the performance of this class of image segmentation techniques. For the detection performance, probabilities of over-detection and under-detection of the number of image regions are defined, and the associated formulae in terms of model parameters and image quality are derived. For the estimation performance, both EM and CM algorithms are showed to produce asymptotically unbiased ML estimates of model parameters in the case of no-overlap. Cramer-Rao bounds of variances of these estimates are derived. For the classification performance, misclassification probability for the Bayesian classifier is defined, and a simple formula based on parameter estimates and classified data is derived to evaluate segmentation errors. This evaluation method provides both theoretically approachable accuracy limits of the techniques and practically achievable performance of the given images. Theoretical and experimental results are in good agreement and indicate that, for images of moderate quality, the detection operation is robust, the parameter estimates are accurate, and the segmentation errors are small.     

Performance evaluation of legacy QCN for multicast and multiple unicast traffic transmission

A multicast congestion control scheme is an interesting feature to control group communication applications such as teleconferencing tools and information dissemination services. This paper addresses a comparison between multiple unicast and multicast traffic congestion control for Carrier Ethernet. In this work, we proposed to study the quantized congestion notification (QCN), which is a layer 2 congestion control scheme, in the case of multicast traffic and multiple unicast traffic. Indeed, the QCN has recently been standardized as the IEEE 802.1Qau Ethernet Congestion Notification standard. This scheme is evaluated through simulation experiments, which are implemented by the OMNeT++ framework. This paper evaluates the reaction point start time congestion detection, feedback rate, loss rate, stability, fairness and scalability performance of the QCN for multicast traffic transmission and multiple unicast traffic transmission. This paper also draws a parallel between QCN for multicast traffic transmission and that for multiple unicast traffic transmission. Despite the benefit of integrating the multicast traffic, results show that performance could degrade when the network scales up. The evaluation results also show that it is probable that the feedback implosion problem caused by the bottlenecks could be solved if we choose to set the queue parameter Qeq threshold value at a high value, 75% of the queue capacity for instance. Copyright © 2016 John Wiley & Sons, Ltd.     

Performance evaluation of an adaptive-rate MPEG encoder matching IntServ traffic constraints

Promoting the evolution of the Internet from a simple data network to a true multiservice network constitutes a challenging task. To this end, the Internet Engineering Task Force (IETF) has set up the Integrated Services (IntServ) and Differentiated Services (DiffServ) Working Groups, with the goal of defining a next-generation Internet, in which traditional best-effort datagram delivery and additional enhanced quality of service delivery classes coexist. The IntServ framework, in particular, is designed to be used in the access network, and requires a traffic source with the capability of matching the traffic characteristics declared to the network, TSpec. We propose to use the rate control facility, usually implemented in current MPEG encoders to provide a constant bit rate, to shape the output traffic according to the declared TSpec while maintaining an acceptable perceived image quality. In order to assess this scenario, we introduce an SBBP/D/N/K queueing system, where the SBBP (switched batch Bernoulli process) emission is varied according to the quantizer scale parameter chosen by the addressed rate control mechanism. The analytical framework allows us: 1) to evaluate system performance in terms of both the marking probability of nonconforming output traffic and the quantization distortion introduced by the encoder; 2) to choose the TSpec parameters to be declared such that given performance parameters are respected.     

Performance analysis of Finite-User slotted aloha in wireless networks with multiple packet reception and random traffic

In this paper, we propose an analytical approach for evaluating the performance of finite-user slotted Aloha in wireless networks with multiple packet reception and random traffic. We derive the exact values of the throughput, the average system size, the packet blocking probability, and the average system delay. Our analysis is based on probability theory. We show that our numerical results are identical to simulation results.     

Semi-supervised internet network traffic classification using a Gaussian mixture model

With a dramatic increase in the number and variety of applications running over the internet, it is very important to be capable of dynamically identifying and classifying flows/traffic according to their network applications. Meanwhile, internet application classification is fundamental to numerous network activities. In this paper, we present a novel methodology for identifying different internet applications. The major contributions are: (1) we propose a Gaussian mixture model (GMM)-based semi-supervised classification system to identify different internet applications; (2) we achieve an optimum configuration for the GMM-based semi-supervised classification system. The effectiveness of these proposed approaches is demonstrated through experimental results.     

Performance evaluation of nonsynchronized initial random access for mobile broadband systems

In this paper, a comparative analysis of the performance of the nonsynchronized initial random access channel in Mobile WiMAX and E-UTRA systems under different conditions (fast fading, multiuser interference) is carried out. The analysis is focused on the correlation properties of the code sequences used in each case. We evaluate their ability to provide low values for false alarm and erroneous detection probabilities (detecting a sequence that has not been transmitted) at the same time as guaranteeing low nondetection probabilities of the effectively transmitted sequences. Results show the promising performance of the E-UTRA scheme, even in high mobility scenarios, where the Doppler effect requires additional considerations to guarantee the correct system operation.     

Performance evaluation of the RQMA-CDMA scheme for multimedia traffic with QoS guarantees

The rapid growth of cellular mobile technology in recent years, coupled with the explosive growth of the Internet, has significantly increased the demand for wireless data services. Traffic on mobile devices is expected to be a mix of real-time traffic such as video, voice, and data, with users requiring diverse quality of service (QoS) guarantees for different types of traffic (video, voice and data). One of the primary challenges of providing QoS is how to prioritize and allocate network resources among contending applications. In order to achieve these goals, a scheduling scheme that can provide equitable and effective packet routing is required. This paper proposes a scheduling scheme called remote queuing multiple access-code division multiple access (RQMA-CDMA), whose purpose is to equitably assign bandwidth resources with QoS guarantees to different mobile devices. RQMA-CDMA is a rate scheduling scheme that can be used to assign bandwidth resources in conjunction with GPS (generalized processor sharing). Additionally, we analyze an admission control that is based on signal to interference plus noise ratio (SINR) for multimedia traffic. Finally, the performance of RQMA-CDMA is evaluated and compared to schemes based on CDMA-GPS according to dropped packets, delay, and throughput.     

Performance evaluation of multiple input-queued ATM switches withPIM scheduling under bursty traffic

In this letter, we analyze the performance of multiple input-queued asynchronous transfer mode (ATM) switches that use parallel iterative matching (PIM) for scheduling the transmission of head-of-line cells in the input queues. A queueing model of the switch is developed under independently, identically distributed, two-state Markov modulated Bernoulli processes bursty traffic. The underlying Markov chain of the queueing model is a quasi-birth-death (QBD) chain. The QBD chain is solved using an iterative computing method. Interesting performance metrics of the ATM switch such as the throughput, the mean cell delay, and the cell loss probability can be derived from the model. Numerical results from both the analytical model and simulation are presented, and the accuracy of the analysis is briefly discussed     

Performance evaluation of LEO satellite constellations with inter-satellite links under self-similar and Poisson traffic

A real-time simulation study for the evaluation of traffic flow in low earth orbit (LEO) satellite constellations, used for the interconnection of high-speed networks, is presented in this paper. The proposed model simulates the traffic process end to end at the packet level, supporting successfully the implementation of self-similar traffic sources, a modelling approach that has been considered more realistic than the well-known Poisson, for real-time communications. An in-depth study for the establishment of inter-satellite links (ISLs) and the design of the terrestrial and space segments is presented and the performance of the integrated system is evaluated in terms of delay and throughput parameters. Copyright © 1999 John Wiley & Sons, Ltd.     

Congestion probabilities in a batched Poisson multirate loss model supporting elastic and adaptive traffic

The ever increasing demand of elastic and adaptive services, where in-service calls can tolerate bandwidth compression/expansion, together with the bursty nature of traffic, necessitates a proper teletraffic loss model which can contribute to the call-level performance evaluation of modern communication networks. In this paper, we propose a multirate loss model that supports elastic and adaptive traffic, under the assumption that calls arrive in a single link according to a batched Poisson process (a more “bursty” process than the Poisson process, where calls arrive in batches). We assume a general batch size distribution and the partial batch blocking discipline, whereby one or more calls of a new batch are blocked and lost, depending on the available bandwidth of the link. The proposed model does not have a product form solution, and therefore we propose approximate but recursive formulas for the efficient calculation of time and call congestion probabilities, link utilization, average number of calls in the system, and average bandwidth allocated to calls. The consistency and the accuracy of the model are verified through simulation and found to be quite satisfactory.     

Performance of a storage system for supporting different videotypes and qualities

Future video-on-demand (VoD) servers will need to support many existing and emerging video data types. These data types include 15-fps (frames per second) animation, 30-fps National Television Systems Committee (NTSC) quality video, and 60-fps high definition television (HDTV) video. The different display speeds and frame sizes of these various video types impose a major constraint on the design of VoD storage systems. This paper presents the results of an experimental study, conducted on a Silicon Graphics Inc. (SGI) Onyx computer system, that investigated the impact of these video types on the design of a VoD storage system. The key issues involved in supporting these different video types in a VoD environment are as follows: (1) the video allocation method and (2) the proper block size (a “block” is a basic unit of several contiguous video frames that will be accessed from several disks each time a request is made) to use for data striping and retrieval. Two allocation schemes, logical volume striping and application level striping, along with varying frame and block sizes for each of the three different video data types are examined. The focus of our study is to determine the maximum number of concurrent accesses that can be supported with a guaranteed quality-of-service (QoS). The degree of scalability (i.e., striping data over more disk arrays) of the experimental VoD system used is also studied. Based on our experimental results, application level striping demands smaller block sizes for all three video types, and more concurrent accesses can be distributed over the storage devices. The experimental results demonstrate that application level striping has excellent scalability for animation and NTSC videos