Real-time multimedia over ATM: RMOA

RMOA is a new ATM Forum standard addressing the transport of H.323 VoIP traffic over ATM-based Internet backbones. It defines a new H.323 gateway devised to carry H.323 real-time media streams by taking advantage of the quality of service features of ATM. The approach is extremely efficient in that it reduces the protocol overhead on the ATM transport     

Providing rate guarantees for internet application traffic across ATM networks

The TCP⁄IP protocol suite is the standard requirement for all applications that need to communicate over the Internet. As TCP⁄IP applications are unable to specify the QoS parameters needed for most Asynchronous Transfer Mode (ATM) services, they tend to use the unspecified bit rate (UBR) service category when running across ATM networks. The UBR service utilizes any bandwidth that is left unused by the rest of the ATM services. This has led the ATM Forum's Traffic Management Group to define a new service category called guaranteed frame rate (GFR). GFR is intended to provide minimum cell rate guarantees and fair access to excess bandwidth left over from higher-priority services. This article first presents a tutorial overview of GFR and then presents a survey of the research work that has been carried out toward the design and implementation of associated ATM switch mechanisms.     

Securing multimedia services over satellite ATM networks

In recent years there has been increasing interest in interconnecting satellite and ATM networks, because both share common characteristics of the ability to provide bandwidth-on-demand and flexibility of integrating voice, video and data services. There are several new satellite constellation proposals that support multimedia service and transport ATM traffic. For a successful implementation of such systems it is essential to address the security requirements of users, satellite ATM network operators and multimedia service providers. In order to minimize delay and the cost of implementing security systems for satellite ATM networks, the network operator role (in security services) can be limited to the mutual authentication with satellite users during call set-up periods. In this paper a mutual authentication protocol between the user and the satellite network is presented using digital signature and public key systems. Also, another mutual authentication protocol between the user and the service provider is presented to provide end-to-end authentication and negotiation of security options such as selecting a secret key system and the key length. Finally, a detailed hardware implementation of ATM cell payload encryption is presented using the DES/TripleDES secret key system. © 1998 John Wiley & Sons, Ltd.     

QoS for multimedia applications in satellite systems

We present a policy for handling multimedia traffic over satellite air interfaces. It extends the advantages of ATM to satellite by the statistical multiplexing of variable-rate traffic sources. Effectiveness is assessed within a multimedia satellite platform called EuroSkyWay, based on Ka-band payload and on-board processing     

QoS-aware adaptation for satellite multimedia broadcasting via hierarchical packet scheduling

With the unique broadcast nature and ubiquitous coverage of satellite networks, the synergy between satellite and terrestrial networks provides opportunities for delivering wideband services to a wide range of audiences over extensive geographical areas. This article concerns the optimization techniques pertinent to packet scheduling to facilitate multimedia content delivery over the satellite with a return channel via a terrestrial network. We propose a novel hierarchical packet scheduling scheme that allocates the resources at different parts of the network in response to network dynamics and link variations while under the system power/resource constraints. Simulations prove that the HPS scheme can effectively improve the end-to-end performance and resource utilization with desirable scalability and fairness features.     

Cross-layer quality-driven adaptation for scheduling heterogeneous multimedia over 3G satellite networks

Wireless networks are experiencing a paradigm shift from focusing on the traditional data transfer to accommodating the rapidly increasing multimedia traffic. Hence, their scheduling algorithms have to concern not only network-oriented quality-of-service (QoS) profiles, but also application-oriented QoS targets. This is particularly challenging for satellite multimedia networks that lack fast closed-loop power control and reliable feedbacks. In this paper, we present a cross-layer packet scheduling scheme, namely Hybrid Queuing and Reception Adaptation (HQRA), which performs joint adaptations by considering the traffic information and QoS targets from the applications, the queuing dynamics induced from the network, as well as the end-to-end performance and channel variations from respective users. By jointly optimizing multiple performance criteria at different layers, the scheme enjoys quality-driven, channel-dependant, and network-aware features. HQRA can well accommodate return link diversity and the imperfect feedbacks, whilst ensuring robustness in highly heterogeneous and dynamic satellite environments. We evaluate its performance over diverse network and media configurations in comparison with the state-of-the-art solutions. We observe noticeable performance gains on application-oriented QoS, bandwidth utilization, and objective video quality, together with favorable fairness and scalability measures.     

Interactive multimedia communication systems for next-generationeducation using asymmetrical satellite and terrestrial networks

We propose a new concept of a hierarchical network structure for remote education. This system combines broadband satellite networks and simple terrestrial communication networks effectively to meet the demands of point-to-multipoint communications. Remote education experiments have been conducted using the proposed satellite communication networks. The results of network characteristics and degree of satisfaction are discussed. Acceptable communication quality was achieved ensuring an interactive lecture environment     

Real-time implementation of optical OFDM transmitters and receivers for practical end-to-end optical transmission systems

Real-time optical OFDM transceivers are successfully demonstrated for the first time, which support 1.5 Gbit/s transmission over 500 m 62.5/125 μm multimode fibres in an intensity-modulation and direct-detection system involving a directly modulated DFB laser. The implemented transceivers only use standard commercially available components.     

Multilevel trellis-coded modulations for mobile multimedia satellite systems using synchronous CDMA

In this paper the performance of multilevel trellis-coded modulations (MTCMs) for satellite mobile multimedia systems using synchronous CDMA is investigated. A model for the multiple-access interference arising from the non-orthogonality of the spreading waveforms is developed for different modulation and spreading schemes and transmission over the mobile satellite channel. Using this model, the performance of MTCMs for synchronous CDMA is analysed and compared with the Ungerboeck and Schegel–Costello trellis-coded modulation (TCM) designs. The impact on the transmission of synchronization errors between the different users is presented and the power control requirements are derived. © 1998 John Wiley & Sons, Ltd.     

GEO卫星LTE跨层资源调度算法

地球同步轨道(GEO)卫星通信系统具有通信时延长的特点,适用于GEO卫星长期演进(LTE)通信的资源调度算法非常重要。为提升星上资源分配的高效性,基于可变最大加权时延优先(M-LWDF)算法,提出了一种综合考虑媒体接入控制(MAC)层参数和应用层参数的跨层调度算法。该算法在MAC层从数学角度推导,提出权重更大的时延判决因子及在应用层根据业务优先级不同引入Q因子。仿真结果表明,与M-LWDF算法相比,不同业务情况下,跨层资源调度算法减小了通信时延,提高了系统吞吐量,但公平性能略有下降并增加了复杂度。     

Integration of satellite and terrestrial systems in future multimedia communications

In this article we examine the role of satellite communications in future telecommunication networks and service provision. Lessons from the past indicate that satellites are successful as a result of their wide area coverage or speed to market for new services. Niche areas such as coverage of air and sea will persist, but for land masses convergence of fixed, mobile, and broadcasting will dictate that the only way forward for satellites is in an integrated format with terrestrial systems. We outline future ways forward for satellites, and discuss the research challenges and technology advances needed to facilitate this integrated approach.     

OAM MIB: an end-to-end performance management solution for ATM

Current network management needs an end-to-end overview of various connections rather than the information that is purely local to the individual devices. The typical manager-centric polling approach, however, is not adequate to understand network-wide behavior of a large-scale broadband network. We propose a new management information base (MIB) approach, called operation, administration, and maintenance (OAM) MIB. The MIB provides a network manager with dynamic end-to-end management information by utilizing special standard ATM cells. The MIB makes end-to-end management feasible while it reduces management-related traffic and manager-to-manager interactions. In our model, a customer network management system accesses the MIB through M1/M2 reference points of the ATM Forum management architecture with simple network management protocol (SNMP)     

Different queuing policies for handover requests in low Earth orbitmobile satellite systems

In this paper, a mobility model suitable for low Earth orbit mobile satellite systems (LEO-MSS's) has been presented, and its statistical parameters have been derived in order to evaluate the impact of the mobility on the performance of the fixed channel allocation (FCA) strategy. Moreover, we have foreseen that interbeam handover requests, which do not immediately find service, can be queued to reduce the handover failure rate. Two different queuing disciplines have been assumed: (1) the first-input-first-output (FIFO) scheme and (2) an idealized strategy that requires knowledge of the last useful instant (LUI) within which the handover procedure must be completed in order to rank the queued handover requests. An analytical approach has been developed to compare these queuing techniques, and its results have been validated through simulations     

Interactive channel for multimedia satellite networks

Multimedia, including Internet traffic, can currently be multiplexed within the DVB/MPEG-2 formats and delivered direct to home users. Traditionally a slow terrestrial telephone link between the user and Internet service provider is used to request data. A direct return channel system will facilitate users' high-bit-rate bidirectional communication via satellite. The return link could be used for the fast Internet access or large data exchanges that will be necessary in a multimedia world. The satellite system not only removes the need for wires but also increases transfer speeds. Satellite interactive terminals can establish network connections via satellite and a ground-based hub. The DVB/MPEG-2 format carries up to 45 Mb/s in the forward link, and a multifrequency time-division multiple access scheme allows up to 2 Mbit/s in the return direction. The return channel of the interactive channel for multimedia satellite networks underwent final standardization by ETSI in early 2000. This article reviews the system concept of a typical implementation. The key features of the return channel air interface, from transmission parameter to login procedure, are explained. In general, Internet packets are expected to be carried via DVB/MPEG-2 in the forward direction and via ATM in the return direction. The IP transportation techniques are described     

Adaptive rate-controlled scheduling for multimedia applications

We present a framework for integrated scheduling of continuous media (CM) and other applications. The framework, called ARC scheduling, consists of a rate-controlled on-line CPU scheduler, an admission control interface, a monitoring module, and a rate adaptation interface. ARC scheduling allows threads to reserve CPU time for guaranteed progress. It provides firewall protection between threads such that the progress guarantee to a thread is independent of how other threads actually make scheduling requests. Rate adaptation allows a CM application to adapt its rate to changes in its execution environment. We have implemented the framework as an extension to Solaris 2.3. We present experimental results which show that ARC scheduling is highly effective for integrated scheduling of CM and other applications in a general purpose workstation environment. ARC scheduling is a key component of an end system architecture we have designed and implemented to support networking with quality of service guarantees. In particular, it enables protocol threads to make guaranteed progress     

Switching for IP-based multimedia satellite communications

This paper discusses the structure and performance of an Internet protocol (IP)-based satellite communications system to provide multimedia services. Uplink scheduling and switching to support IP differentiated services (DiffServ) traffic in a multibeam environment are addressed. End-to-end performance of a multibeam satellite communications system using an on-board switch is evaluated using simulation. Aggregate real-time and non-real-time traffic using different DiffServ classes is considered and the effects of their burstiness and long-range dependent behavior on the queueing performance are examined. Multiple-frequency time-division multiple-access is used on the uplink in conjunction with a dynamic capacity allocation scheme. Higher priority is given to voice and video real-time traffic to avoid delay variation. On-board downlink queue for non-real-time traffic is provided to achieve high statistical multiplexing gain.     

Wireless-adaptive fair scheduling for multimedia stream

As packet cellular networks are expected to support multimedia services, the authors incorporate the multimedia QoS requirements into the design of a new scheduling algorithm. The proposed wireless-adaptive fair scheduling tries to allocate time slots for each user with fair share by considering the varying channel condition while reflecting the stream requirements and achieving high throughput.     

Protocol architecture for multimedia applications over ATM networks

At the data-link layer, ATM offers a number of features, such as high-bandwidth and per-session quality-of-service (QoS) guarantees, making it particularly attractive to multimedia applications. Unfortunately, many of these features are not visible to applications because of the inadequacies of existing higher-level protocol architectures. Although there is considerable effort underway to tune these protocols for ATM networks, we believe that a new ATM-specific protocol stack is essential to effectively exploit all the benefits of ATM. We describe the semantics of such a protocol stack, and discuss its advantages over traditional protocol architectures from the perspective of multimedia applications. The performance impact of the new protocol architecture is experimentally demonstrated on a video conferencing testbed built around IBM RS/6000's equipped with prototype hardware for video/audio processing, and connected via ATM links     

Coordinated multihop scheduling: a framework for end-to-end services

In multihop networks, packet schedulers at downstream nodes have an opportunity to make up for excessive latencies due to congestion at upstream nodes. Similarly, when packets incur low delays at upstream nodes, downstream nodes can reduce priority and schedule other packets first. The goal of this paper is to define a framework for design and analysis of coordinated multihop scheduling (CMS) which exploits such internode coordination. We first provide a general CMS definition which enables us to classify a number of schedulers from the literature, including G-EDF, FIFO+, CEDF, and work-conserving CJVC as examples of CMS schedulers. We then develop a distributed theory of traffic envelopes which enables us to derive end-to-end statistical admission control conditions for CMS schedulers. We show that CMS schedulers are able to limit traffic distortion to within a narrow range resulting in improved end-to-end performance and more efficient resource utilization. Consequently, our technique exploits statistical resource sharing among flows, classes, and nodes, and our results provide the first statistical multinode multiclass admission control algorithm for networks of work conserving servers.