On the teletraffic capacity of CDMA cellular networks

The aim of this paper is to contribute to the understanding of the teletraffic behavior of code-division multiple-access (CDMA) cellular networks. In particular, we examine a technique to assess the reverse link traffic capacity and its sensitivity to various propagation and system parameters. We begin by discussing methods of characterizing interference from other users in the network. These methods are extremely important in the development of the traffic models. We begin with a review of several existing approaches to the problem of handling other-cell interference before presenting a novel characterization of the interference in the form of an analytic expression for the interference distribution function in the deterministic propagation environment. We then look at extending the capacity analyses that assume a fixed and equal number of users in every cell to handle the random nature of call arrivals and departures. The simplest way to do this is by modeling each cell of the network as an independent M/G/x∞ queue. This allows us to replace the deterministic number of users in each cell by an independent Poisson random variable for each cell. The resulting compound Poisson sums have some very nice properties that allow us to calculate an outage probability by analyzing a single random sum. This leads to a very efficient technique for assessing the reverse link traffic capacity of CDMA cellular networks     

On the analysis of burst-assembly delay in OBS networks and applications in delay-based service differentiation

In Optical Burst Switching (OBS), packets travel through the network core as part of longer-size optical bursts, which do not suffer electronic conversion until they reach an eggress point. Typically, such optical bursts comprise tens or hundreds of packets, which are assembled/deassembled at border nodes. During the burst-formation process, each arriving packet must wait until the final burst is complete, which clearly adds an extra delay on each packet in the burst, especially on those arriving earlier. However, such burst-assembly delay may be excessive for the appropriate performance of certain applications, mainly real-time interactive ones. This work’s findings are twofold: first, it characterises the burst-assembly delay distribution of each packet in a burst arisen by the main assembly algorithms found in the literature; and, second, it introduces a new burst-assembly strategy that takes into account the particular delay constrains of packets in the formation of optical bursts, along with a detailed study of its properties. This work has been funded by the “Ministerio de Educación y Ciencia” of Spain under grant TEC2006-03246.     

On burst-header contention-resolution in OBS networks

Advances in enabling technologies and the explosive growth of Internet traffic has led to the widespread proliferation of network systems in recent years. With their relatively low cost, high throughputs, high-bandwidth utilization, and low-transmission latency, Optical Burst Switching (OBS) networks represent an ideal solution for next-generation Internet applications. However, in OBS networks, Burst Header Packet (BHP) contentions occur when two or more BHPs are switched simultaneously to the same output port of a given core node. These contention events result in significant losses of the corresponding data burst. Accordingly, this study presents a Store-and-forward COntention-REsolution mechanism, designated as SCORE, which utilizes fiber delay line buffers to resolve the BHP collision problem, thereby minimizing the burst loss rate. The results of a series of simulations performed using an OIRC OBS-ns simulator confirm the effectiveness and efficiency of the proposed scheme.

CCITT work in teletraffic engineering

The advantages and drawbacks of standardization in TTE (teletraffic engineering) are examined. It is pointed out that the TTE recommendations of CCITT are intended to be international standards. Unlike signaling systems, interfaces, or protocols, the necessity for standardization in this area is not self-evident. However, standardization of grade of service (GOS) definitions, values, and relevant reference conditions seems to be necessary. Support for engineering methods also offers advantages. TTE-related activities in different CCITT study groups try to satisfy many often contradictory demands. Trends in telecommunications strongly support the view that concentration of TTE studies in CCITT would be desirable     

Change detection in teletraffic models

We propose a likelihood-based ratio test to detect distributional changes in common teletraffic models. These include traditional models like the Markov modulated Poisson process and processes exhibiting long range dependency, in particular, Gaussian fractional ARIMA processes. A practical approach is also developed for the case where the parameter after the change is unknown. It is noticed that the algorithm is robust enough to detect slight perturbations of the parameter value after the change. A comprehensive set of numerical results including results for the mean detection delay is provided     

一种新的突发分配业务模型以及在OBS中的应用

文章提出了一种新的突发分配业务模型,给出了这种业务模型的详细定义,并应用此模型和传统的非突发分配模型对光突发交换(OBS)中的交换机构进行了性能分析和对比.计算结果表明,当交换机构扇出比F=1、突发强度B1=2时,突发分配模式下的丢包率比非突发分配模式下的丢包率增加大约一个数量级.也许该突发业务模型并不能真实地反映现实世界的业务流,但其能提供一种逼近现实世界业务流的分析方法.     

On the blocking time distribution of core OBS switches

Given the bufferless nature of Optical Burst- Switched networks, data bursts are either transmitted or dropped; the latter typically occurs when all the wavelengths of a given output port are occupied. Clearly, the amount of time during which a given output port is blocked and cannot schedule incoming data bursts is a key performance measure of OBS networks. This work shows that, under Poissonian burst arrivals, the blocking time distribution of a given output port in an OBS node approaches the exponential distribution as the number of wavelengths increases. It is further shown that this behavior remains regardless of the size distribution of incoming bursts, and therefore, regardless of the burst-assembly algorithms employed at the border nodes. Finally, this result is also applied to the characterization of the amount of overspill traffic, that is, the number of bursts that arrive within a blocked period, and therefore must be either dropped or diverted over alternative routes.     

TELPACK: an advanced teletraffic analysis package

The performance evaluation of computer and communication networks gives rise to teletraffic problems of potentially large dimensionality. We summarize a unifying system theoretic approach to efficient solution of a diversity of such problems, and introduce TELPACK, a publicly available software that implements this approach     

Long-range dependence and heavy-tail modeling for teletraffic data

The analysis and modeling of computer network traffic is a daunting task considering the amount of available data. This is quite obvious when considering the spatial dimension of the problem, since the number of interacting computers, gateways and switches can easily reach several thousands, even in a local area network (LAN) setting. This is also true for the time dimension: Willinger and Paxson (see Ann. Statist., vol.25, no.5, p.1856-66, 1997) cite the figures of 439 million packets and 89 gigabytes of data for a single week record of the activity of a university gateway in 1995. The complexity of the problem further increases when considering wide area network (WAN) data. In light of the above, it is clear that a notion of importance for modern network engineering is that of invariants, i.e., characteristics that are observed with some reproducibility and independently of the precise settings of the network under consideration. In this tutorial article, we focus on two such invariants related to the time dimension of the problem, namely, long-range dependence, or self-similarity, and heavy-tail marginal distributions     

Increasing the efficiency of roulette simulation of teletraffic

A simple modification of the roulette method of teletraffic simulation is presented. At low traffic levels it may result in a reduction, by a factor of ten or more, of the computer time required to simulate a specified number of calls.     

The role of teletraffic modeling in the new communicationsparadigms

Teletraffic engineers provide models allowing communications networks to be planned and systems to be designed to meet the performance needs of users within a reasonable cost. The successful modeler combines analytical or simulation skills with a deep understanding of the technology. In the emerging information networking environment comprising new technologies such as ATM, Internet, wireless, etc., and new services such as video, multimedia, data and personal communications services, the old paradigms of circuit-switched calls and Erlang distributions have been severely challenged. The confluence of the shifts in technologies and services along with the convergence of computing, telecommunications, consumer electronics, and electronic media industries, and the shift from a monopolistic to competitive business paradigm, has created a tremendously rich lode of fundamental problems that need to be addressed by teletraffic engineers. In this article the author describes the historical role of the teletraffic engineer, reviews several of the major paradigm shifts, and discusses some of the challenges facing the teletraffic community with an emphasis on modeling wireless communications systems     

Adaptive algorithm for variable teletraffic demand in highway microcells

An adaptive algorithm is presented which ensures that the probability of a mobile radio call in progress being forced to terminate during handover in highway microcells is always small, even in the presence of high new call request rates.<>     

光突发交换中的路由技术

光突发交换是面向下一代因特网的光交换模式,是光电路交换和光分组交换的有效折衷方案,避免了各自的缺点.它使用的带宽粒度介于光电路交换和光分组交换之间,比光电路交换灵活,带宽利用率高,比光分组交换易于实现,是很有发展前途的光交换技术.路由技术在光突发交换中起重要作用,在很大程度上影响着光突发交换网络的性能.本文首先介绍了光突发交换技术的原理,然后分析了光突发交换技术的现状及存在的问题,最后探讨了光突发交换中的路由技术及其发展.     

在OBS网络中改进TCP性能的高效机制

Transmission Control Protocol (TCP) performance over Optical Burst Switching (OBS) is experimentally investigated on an OBS network testbed, concluding that burst losses will lead to a significant drop in the available TCP bandwidth. Two mechanisms are introduced to improve TCP performance. One is concerning the burst assembly optimization and another is based on the novel assembly and scheduling mechanism to reduce the burst losses.     

基于GMPLS的OBS网络技术

GMPLS(通用多协议标签交换)是MPLS技术向光网络发展的产物。描述GMPLS和MPLS控制平台的区别,介绍引用GMPLS协议作为控制平面的OBS网络。提出的网络结构是在OBS的突发控制包中用通用标签代替源节点和目的节点地址,并使用GMPLS协议栈对路由协议、信令功能以及链路管理协议进行增强和扩展以便更好地支持OBS网络。     

Worst-case fraction of CBR teletraffic unpunctual due tostatistical multiplexing

This paper quantitatively analyzes the queueing delay of the constant-bit-rate (CBR) traffic in a multiplexer, where the CBR traffic is mixed with the traffic of another session (interfering traffic) that has throughput and burstiness constraints. This paper focuses as a quality-of-service (QoS) measure on the fraction of the CBR traffic that fails to meet a certain delay requirement. Results include the worst-case QoS of CBR traffic as a function of the throughput and burstiness parameters imposed on the interfering traffic. Results of this paper can be applied to traffic management and call processing of asynchronous transfer mode (ATM) networks     

On the applications of multimedia processing to communications

The challenge of multimedia processing is to provide services that seamlessly integrate text, sound, image, and video information and to do it in a way that preserves the ease of use and interactivity of conventional plain old telephone service (POTS) telephony. To achieve this goal, there are a number of technological problems that must be considered, including: compression and coding of multimedia signals, including algorithmic issues, standards issues, and transmission issues; synthesis and recognition of multimedia signals, including speech, images, handwriting, and text; organization, storage, and retrieval of multimedia signals, including the appropriate method and speed of delivery, resolution, and quality of service; access methods to the multimedia signal, including spoken natural language interfaces, agent interfaces, and media conversion tools; searching by text, speech, and image queries; browsing by accessing the text, by voice, or by indexed images. In each of these areas, a great deal of progress has been made in the past few years, driven in part by the relentless growth in multimedia personal computers and in part by the promise of broad-band access from the home and from wireless connections. Standards have also played a key role in driving new multimedia services, both on the POTS network and on the Internet. It is the purpose of this paper to review the status of the technology in each of the areas listed above and to illustrate current capabilities by describing several multimedia applications that have been implemented at AT&T Labs over the past several years     

一种基于突发分片技术的OBS竞争解决机制

介绍了基于光突发分片技术的竞争解决机制,着重对采用光突发分片技术与数据信道调度算法相结合的竞争解决机制进行了研究.通过建立相应的光突发交换网络仿真模型,对结合后的竞争解决方法与其他方法进行了性能比较.结果表明,将光突发分片技术与数据信道调度算法相结合能够有效地降低网络阻塞率,提高信道利用率,从而改善网络性能.     

On Burst Length Distribution and Preemption Probabilities in OBS Networks with Burst Segmentation

Recently, preemption techniques have attracted considerable attention as a means to provide differentiated quality of service in optical burst switching (OBS) networks. This paper is focused on the analysis of preemption probabilities for bursts within the same priority class. As proposed by Vokkarane and Jue ((2003)* IEEE J Select Areas Commun 21(7): 1198–1209) an incoming burst will preempt the burst in service, within the same priority class, if the residual length of the burst in service is smaller than the incoming burst length. For a general case with wavelength conversion, the preemption probability of contending bursts with a generic service distribution, not necessarily exponential, is analyzed. First, we show that the size distribution for the preempting bursts is shifted to larger values, in comparison to the original burst size distribution. Second, we obtain an upper and lower bound for the preemption probability. Finally, the asymptotic behavior of the OBS switch is analyzed showing that preemption will always occur for a very large number of wavelengths.     

OBS网络中改进的ODBR算法

信道调度算法是提高光突发交换(OBS)网络性能的关键技术之一.结合ODBR重调度算法和FDL的延迟作用,提出来一种Improved-OBDR算法.仿真结果表明改进算法在保证高优先级低丢包率的同时,保证低优先级尽可能低的丢包率,提高了资源利用率.