Capture division packet access: a new cellular access architecturefor future PCNs

The authors describe a new cellular access architecture, known as capture-division packet access, which is a packet-oriented architecture able to support the constant bit rate traffic and variable bandwidth on demand necessary for multimedia traffic. The approach integrates the multiple access and channel reuse issues to achieve a high degree of spectral efficiency, and presents general advantages even if used for delay-constrained circuit-oriented traffic. Unlike CDMA and TDMA, wherein the effective data rate of each connection is typically a small fraction of the total radio channel allocated for PCN, the CDPA approach allows each user to access the entire channel, if necessary, for brief periods of time (packet access). Spectrum sharing is accomplished by exploiting the different path losses suffered by the various signals as they appear at the base stations (the capture effect), with co-channel interference abated through time diversity (colliding users do not successively retry in the same time interval). Results suggest that abating co-channel interference by random retransmission may be more effective than spatial isolation at cells using the same channel, as is usual in FDMA-TDMA systems     

Performance of a Shared Packet Wireless Network with Interactive Data Users

This paper studies the user-perceived performance of a shared packet wireless network for interactive data applications such as Web-browsing. We have defined a new measure: the Equivalent Circuit Rate (ECR) for a user in a shared access network is the dedicated access circuit rate that would be required by the user in order to have an equivalent user experience. The ECR measure is intuitive, useful and robust. We present a simple analytical model based on a closed queueing network with a finite population of interactive data users whose traffic can be modeled as ON/OFF traffic with feedback. The analytical results are consistent with our detailed simulations, where we study TCP-based Web traffic simulations for an EDGE (Enhanced Data Rates for GSM Evolution) TDMA system using realistic workload models. Our study incorporates constant bit-rate channels, variable bit-rate channels, as well as mixed user groups with different channel conditions. We show that a shared wireless network is well characterized by simple parameters that depend only on mean statistics, for a broad range of scenarios. ECR is well approximated by R×(1–U), where U is the utilization and R is the effective shared channel rate; this result holds even if different user groups have different rates or the channel rates are variable. These results will be useful in network dimensioning, admission control, and for defining quality of service targets for different user groups.     

Dimensioning bandwidth for elastic traffic in high-speed datanetworks

Simple and robust engineering rules for dimensioning bandwidth for elastic data traffic are derived for a single bottleneck link via normal approximations for a closed-queueing network (CQN) model in heavy traffic. Elastic data applications adapt to available bandwidth via a feedback control such as the transmission control protocol (TCP) or the available bit rate transfer capability in asynchronous transfer mode. The dimensioning rules satisfy a performance objective based on the mean or tail probability of the per-flow bandwidth. For the mean objective, we obtain a simple expression for the effective bandwidth of an elastic source. We provide a new derivation of the normal approximation in CQNs using more accurate asymptotic expansions and give an explicit estimate of the error in the normal approximation. A CQN model was chosen to obtain the desirable property that the results depend on the distribution of the file sizes only via the mean, and not the heavy-tail characteristics. We view the exogenous “load” in terms of the file sizes and consider the resulting flow of packets as dependent on the presence of other flows and the closed-loop controls. We compare the model with simulations, examine the accuracy of the asymptotic approximations, quantify the increase in bandwidth needed to satisfy the tail-probability performance objective as compared with the mean objective, and show regimes where statistical gain can and cannot be realized     

User’s mobility effect on the performance of wireless cellular networks serving elastic traffic

The objective of the present paper is to give an analytic approximation of the performance of elastic traffic in wireless cellular networks accounting for user’s mobility. To do so we build a Markovian model for users arrivals, departures and mobility in such networks; which we call WET model. We firstly consider intracell mobility where each user is confined to remain within its serving cell. Then we consider the complete mobility where users may either move within each cell or make a handover (i.e. change to another cell). We propose to approximate the WET model by a Whittle one for which the performance is expressed analytically. We validate the approximation by simulating an OFDMA cellular network. We observe that the Whittle approximation underestimates the throughput per user of the WET model. Thus it may be used for a conservative dimensioning of the cellular networks. Moreover, when the traffic demand and the user speed are moderate, the Whittle approximation is good and thus leads to a precise dimensioning.     

An efficient modeling and dimensioning approach for integrated streaming and elastic traffic

Recent studies show that both data traffic and real-time traffic grow very fast in wired and wireless networks. To provide better performance guarantee, these applications need efficient network modeling and planning. In this paper, the problem where the total bandwidth of a link is shared by streaming traffic (real time traffic such as voice or video etc.) and elastic traffic (such as data) is studied. Integrating streaming traffic and elastic traffic presents a unique dimensioning problem. This paper considers dimensioning a link to satisfy both quality of service (QoS) requirements for streaming traffic, such as loss probability, and elastic traffic, such as mean waiting (delay) time. The Erlang loss model is applied to streaming traffic and a bursty traffic model is applied to the elastic traffic. Efficient dimensioning algorithms based on classical Markovian models and time-scale decomposition are then proposed. Numerical results show that the proposed methods have good accuracy.     

ATM Inverse Multiplexing. Fundamentals and Markovian Single-Server Queue Analysis for Performance Evaluation and Validation Purposes

The growing demand of network bandwidth indicates that user access to high speed (i.e. ATM) networks is a key issue. The Inverse Multiplexing for ATM (IMA) is a technology that combines multiple T1/E1 links to support the transparent transmission of ATM cells over one single logical data trunk whose bandwidth is the aggregate of the T1/E1 capacities, minus a small amount due to overhead. That is, it provides high bandwidth by using already deployed WAN infrastructure and at a reasonable cost. Employing this technology, it is possible to dispose of ATM connections with data rates between the T1/E1 (an economical but sometimes too slow option) and T3/E3 ones (with high bandwidth, but expensive for the mass market of users). In this framework, and facing a new technology, it is crucial to have tools (analytical and simulation ones) easy to manipulate that help telecommunication engineers and network planners on the performance evaluation and dimensioning of these systems. In this paper, the fundamentals and major applications of IMA technology are described. Also, the behavior of IMA multiplexers is carefully analyzed and a method to dimension them proposed. An estimate for the Cell Loss Ratio (CLR) and the mean waiting time measured in the IMUX devices are obtained. The analytical study is based on the comparison with a M/D/1 queue system. Even though, we are aware of some weakness of our assumptions, especially concerning the Poisson input traffic, the model is compact, easy to understand and to manipulate, therefore it can be valuable to validate simulation models developed to evaluate IMUX devices under more realistic input traffic patterns.     

Cost models for QoS-differentiated interconnecting and wholesale access services in?future generation networks

Currently, network operators and Internet service providers are offering ??Triple Play?? products integrating services with different Quality of Service (QoS) requirements. It is leading to Internet traffic with strong service integration under an all-IP-based broadband network platform. However, new multimedia service offers require individual QoS guarantees for each type of services. The interconnection between different providers necessitates the reconsideration of the actual cost schemes. Interconnection and wholesale access services (It is an extension of ??wholesale network?? definition, where Telco??s physical network and equipment are ??shared?? to many independent Service Providers. If the incumbent offers broadband access services, the rest of the alternative providers have recourse to the incumbent??s ??wholesale access service??. Bitstream service is the most important service of this type, actually regulated over DSL and cable networks.) appear to be a simple solution, but the consideration of QoS parameters requires an extension of the current network dimensioning methods based mainly on the average bandwidth demand from each user. This paper proposes a cost model which considers QoS parameters and, based on the ??Total Element based Long Run Incremental Cost?? (TELRIC) model, is applied to the wholesale access and interconnection paradigm. Three traffic engineering methods are considered and studied for network dimensioning. Hereby the aim is to guarantee the QoS of the different services: complete traffic segregation under virtual tunnels, complete traffic integration by over-engineering and partial traffic integration using a priority queuing scheme. The proposed method enables the development of a specific cost scheme based on a complete scenario considering different types of users. The variety of used IP applications suppose direct implications over different levels of interconnection, mainly at the low-level Metro access and the high-level edge node.     

A demand assignment system for mobile users in a community ofinterest

The paper presents a high performance wireless access and switching system for interconnecting mobile users in a community of interest. Radio channel and time slot assignments are made on user demand, while the switch operations are controlled by a scheduling algorithm designed to maximize utilization of system resources and optimize performance. User requests and assignments are carried over a low-capacity control channel, while user information is transmitted over the traffic channels. The proposed system resolves both the multiple access and the switching problems and allows a direct connection between the mobile end users. The system also provides integration of voice and data traffic in both the access link and the switching equipment. The “movable boundary” approach is used to achieve dynamic sharing of the channel capacity between the voice calls and the data packets. Performance analysis based on a discrete time Markov model, carried out for the case of optimum scheduling yields call blocking probabilities and data packet delays. Performance results indicate that data packets may be routed via the exchange node with limited delays, even with heavy load of voice calls. Also the authors have proposed scheduling algorithms that may be used in implementing this system     

Dimensioning and effective handling of signalling channels in a multimedia GEO Satellite platform

The deployment of highly powerful and sophisticated new-generation satellite broadband systems implies that a large portion of their bandwidth on the radio interface has to be devoted to conveying signalling information. Adequately dimensioning such a signalling bandwidth is an important design objective allowing the effective exploitation of the overall system resources and the cost-effective provision of a target quality of service to multimedia traffic. The performance of two basic techniques for accessing the signalling channels in a reference multimedia geostationary platform is investigated in this paper: random (slotted Aloha) and dedicated access. It is demonstrated here that dedicated access, despite rational appearances, allows 50% saving of signalling bandwidth while satisfying both the system and user constraints in terms of grade and quality of service respectively. This is accomplished by providing a statistical centralized connection admission control on Earth and an intelligent scheduling of the resource requests on board the satellite.     

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.     

On the effect of reservation period on performance of IEEE 802.16 R‐MAC protocol

The IEEE 802.16 standard is gaining broad consideration to serve the expanding demand for broadband access networks. In this standard, the best effort traffic uses the reservation multiple access control (MAC) mechanism, which is widely adopted in recent broadband network technologies. The goal of this paper is to study the performance of the MAC protocol of the best effort traffic in the IEEE 802.16 standard with emphasis on the size of the reservation period. We use a two‐stage Markov chain model to capture all possible events on the reservation and service periods. This allows the computation of the inflow and outflow of bandwidth requests (BWRs) and their associated data packets which leads to the delay and throughput formulas. By means of illustrative examples and numerical results, validated through simulation, we investigate the key importance of the size of reservation period. We highlight potential performance improvement, through opportunistic dynamic control of the size of the reservation period to enhance the performance of reservation MAC protocol. Copyright © 2008 John Wiley & Sons, Ltd.     

WCDMA R4核心网电路域接口分析和带宽计算

本文在研究WCDMA R4核心网网络架构以及接口功能、协议的基础上,对电路域的不同接口从底层数据结构进行了分析,以建立一套适合商用网络建设的规划设计模型.对R4电路域新引入的接口数据流量和带宽需求给出一个规范化的计算方式,并以举例方式进行了实际计算,以便对今后核心网的规划和设计提供有效的帮助.     

Wireless data traffic: a decade of change

This article presents an overview of the most significant changes in wireless data traffic and its main driving forces throughout the past decade (1998?2008). The main axes of change are discussed: wireless technology, user population, and applications. Evolution of wireless technology realized a 200-fold increase in data rate, and facilitated a continuous enrichment of the traffic mix traversing legacy and modern wireless networks. New applications emerged, such as peer-to-peer file sharing, online gaming, and multimedia, establishing a trend of significant increase in traffic volume. User population has also increased and even saturated some markets. However, not all benefits of wireless technologies are equally exploited, with only a few users exercising high mobility or regularly enjoying multimedia services. Future indications include a requirement for either integration or interoperability of two mainstream wireless technologies, WiFi and cellular, as well as continuous user demand for more bandwidth, broader coverage, and better mobility support.     

Analysis and dimensioning of switchless networks for single-layeroptical architecture

The “switchless” all-optical network is an alternative networking approach being developed in the framework of the ACTS project named SONATA, which aims to provide a future single layer, advanced transport architecture on a national scale. The single hop, shared access network employs time and wavelength agility (a WDMA/TDMA scheme), using fast tunable transmitters and receivers, to set up individual customer connections through a single wavelength router (suitably replicated for resilience). The dimensioning of this type of network is one of the main tasks for the design of networks serving a certain number of customers, connected together by means of passive optical networks (PONs). This paper reports an analytical model which allows the network dimensioning according to some relevant design parameters: the number of customers per PON, the number of PONs, the offered traffic per single user (either considering residential or business user), and the required system performance expressed in terms of blocking probability. Furthermore, relevant issues related to the dimensioning of switchless networks are discussed and some results achieved for relevant network scenarios are reported, to assess the feasibility of the system concept     

A framework for resource dimensioning in GPON access networks

In gigabit passive optical networks (GPONs), the ports of the optical line terminal (OLT) support passive optical networks (PONs). An optical split ratio supported on an OLT chassis determines the number of optical network units (ONUs) which can share PON link capacity. Generally, network planners tend to do dimensioning for PON link capacity (OLT port) based on the number of subscribers and their type (i.e. residential or business). Although this dimensioning approach is simple, it does not guarantee a selection of optical split ratio which can optimally allocate bandwidth to end‐subscribers. In this paper, we develop an integrated mathematical framework for optimally dimensioning resources in an GPON access network, namely OLT capacity. This framework comprises three resource‐dimensioning approaches which are based on user requirements: GPON link utilization and capacity optimization. Our mathematical framework has been integrated into software for GPON resource dimensioning, which we have developed to evaluate the support and performance of services in GPON access networks. Copyright © 2011 John Wiley & Sons, Ltd.     

Joint source and sending rate modeling in adaptive video streaming

This work addresses the modeling of traffic generated by a video source operating in the context of adaptive streaming services. Traffic modeling is a key in several network design issues, such as dimensioning of core and access network resources, developing pricing procedures, carrying out cost-revenue studies. The actual traffic generated during a video streaming session depends on both the video source and the bandwidth variations imposed by lower communication layers. We propose a new traffic model that jointly encompasses these two effects. Specifically, we consider the modeling of the sequence of frame sizes generated by a video streaming source that dynamically adapts its rate to the available communication channel bandwidth using bitstream switching techniques. In order to represent the source rate adaptation to the random network bandwidth variations on the communication channel, we resort to a framework based on Hidden Markov Processes (HMPs). Our HMP model represents the first joint source and sending rate model in adaptive streaming literature. Thanks to effective modeling assumptions on the frame size probability density function (pdf), the HMP parameters can be estimated by means of the Expectation Maximization algorithm. The traffic model is validated by numerical simulations of a mobile adaptive video streaming scenario. We study the model's ability to predict several traffic statistics, including the traffic load of a video streaming source in different network points. Besides, we evaluate the model accuracy in characterizing aggregate video traffic resulting from multiplexing various video sources. In all experiments, we show that the proposed model is able to accurately capture the traffic characteristics.     

Interleaved Polling with Adaptive Cycle Time (IPACT): A Dynamic Bandwidth Distribution Scheme in an Optical Access Network

While in recent years backbone bandwidth has experienced substantial growth, little has changed in the access network. Last mile still remains the bottleneck between a high capacity LAN or home network and the backbone. Passive optical network (PON) is a technology viewed by many as an attractive solution to this problem.In this study, we discuss and evaluate design issues for PON access networks. Specifically, to drive the cost of an access network down, it is very important to have an efficient, scalable solution. We believe that a PON based on polling, with data encapsulated in Ethernet frames, possesses the best qualities, such as dynamic bandwidth distribution, use of a single downstream and a single upstream wavelength, ability to provision a fractional wavelength capacity to each user, and ease of adding a new user.To support dynamic bandwidth distribution, we propose an interleaved polling algorithm. We then suggest a scheme for in-band signaling that allows using a single wavelength for both downstream data and control message transmission.To obtain realistic simulation results, we generated synthetic traffic that exhibits the properties of self-similarity and long-range dependence. We then analyzed the network performance and its effect on various types of traffic, e.g., best-effort data traffic, VBR video traffic and CBR streams.     

Resource Dimensioning Through Buffer Sampling

Link dimensioning, i.e., selecting a (minimal) link capacity such that the users' performance requirements are met, is a crucial component of network design. It requires insight into the interrelationship among the traffic offered (in terms of the mean offered load M, but also its fluctuation around the mean, i.e., `burstiness'), the envisioned performance level, and the capacity needed. We first derive, for different performance criteria, theoretical dimensioning formulas that estimate the required capacity C as a function of the input traffic and the performance target. For the special case of Gaussian input traffic, these formulas reduce to C=M + alpha V, where alpha directly relates to the performance requirement (as agreed upon in a service level agreement) and V reflects the burstiness (at the timescale of interest). We also observe that Gaussianity applies for virtually all realistic scenarios; notably, already for a relatively low aggregation level, the Gaussianity assumption is justified.