Asynchronous Media Research Articles

Asynchronous and reliable on-demand media broadcast

We discuss wireless broadcasting of multimedia streams within a framework that allows asynchronous media access. Receivers subscribe at any time to the ongoing broadcast session, but are still able to display the media stream from the beginning. A fully scalable broadcasting scheme is presented where the media stream is appropriately segmented, and segments are protected by fountain codes. Erasure-based decoding as well as soft decoding is discussed. Asynchronous data reception and full reliability are achieved at the same time. Depending on its receiving conditions, the receiver adapts its initial playout delay to guarantee high reliability of successful playout.

Saturation Throughput Analysis of Collision Management Protocol in the HomePNA 3.0 Asynchronous MAC Mode

The Home Phoneline Networking Alliance (HomePNA) 3.0 technology is designed to provide high-speed backbones for home multimedia networks. This technology adopts a collision management protocol in an asynchronous medium access control (MAC) mode to reduce the number of collisions. In this letter, we present a simple analytical model to compute the saturation throughput performance of the collision management protocol, and compare the performance with that of HomePNA 2.0.

The Effect of Electronic Communication Among Franchisees on Franchisee Compliance

The virtual organization has emerged as a result of the availability of information technology. One business model well suited to the virtual form is franchising. Since the success of franchise organizations is highly dependent on communication effectiveness, these organizations are beginning to adopt technologynamely, private corporate networks called intranets and extranetsto support electronic communication. This paper reports the results of an empirical study on the effects of lateral electronic communicationsi.e., the formation of virtual community among franchiseeson a strategic outcome that is important to franchisors, namely, franchisee compliance. The survey results indicate that communication frequency among franchisees increases with the existence of a lateral communication channel. Previous research suggests that electronic communication facilitates lateral communication by providing an asynchronous media choice, making communication on such channels more frequent because they are more convenient. Franchisee compliance, though expected to be higher among franchisees that had electronic communication channels available to them, was actually found to be lower.

Design and performance evaluation of scheduling algorithms for unslotted CSMA/CA with backoff MAC protocol in multiple-access WDM ring networks

The unslotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) with backoff is a fully distributed, asynchronous Media Access Control (MAC) protocol for multiple-access Wavelength Division Multiplexing (WDM) ring networks with simplicity and robustness comparable to those of Ethernet [IEEE J. Select. Areas Commun. 18 (10) (2000) 2004; Proceedings of GLOBECOM’00, vol. 2, 2000, p. 1303]. In this paper, we present the results of performance evaluation of four scheduling algorithms – Random Select (RS), Destination Priority Queueing (DPQ), Longest Queue First (LQF), and Shortest Packet First (SPF) – designed for the unslotted CSMA/CA with backoff MAC protocol to address the issues of fairness and bandwidth efficiency. Through extensive network-level simulations for a multiple-access WDM ring with 10 nodes and 10 wavelengths on a 100 km ring, we have verified that under uniform traffic condition, the LQF with optical buffer size of 13 and 78 octets shows the best performance in terms of fairness, guaranteeing full fairness (fairness index≈1) for arrival rates up to 9.5 Gbps/node, while for throughput and packet delay, the DPQ with the maximum optical buffer size of 1538 octets gives the best results. We have also identified that the optical buffer size greatly affects the performance of nonrandom scheduling algorithms.

Compositionality in Dataflow Synchronous Languages: Specification and Distributed Code Generation

Modularity is advocated as a solution for the design of large systems; the mathematical translation of this concept is often that of compositionality. This paper is devoted to the issues of compositionality for modular code generation, in dataflow synchronous languages. As careless reuse of object code in new or evolving system designs fails to work, we first concentrate on what are the additional features needed to abstract programs for the purpose of code generation: we show that a central notion is that of scheduling specification as resulting from a causality analysis of the given program. Using this notion, we study separate compilation for synchronous programs. An entire section is devoted to the formal study of causality and scheduling specifications. Then we discuss the issue of distributed implementation using an asynchronous medium of communication. Our main results are that it is possible to characterize those synchronous programs which can be distributed on an asynchronous architecture without loosening semantic properties. Two new notions of endochrony and isochrony are introduced for this purpose. As a result, we derive a theory for synthesizing additional schedulers and protocols needed to guarantee the correctness of distributed code generation. Corresponding algorithms are implemented in the framework of the DC+ common format for synchronous languages, and the V4 release of the SIGNAL language.

Mobile asynchronous communication: Exploring the potential for converged applications

Trends in technological development show that devices of personal communication and information management are converging and penetrating to new user segments. Therefore, it is a question of interest how the convergence of applications should be managed. This article explores the current use of email and SMS, focussing on the differences in the ways they are used and understood among their users. It is argued that, since the systems are different and have been in use for some time, established practices in using them as well as systems applied to understanding them are different. Based on analysis of interview data, it is conluded that this is the case, and that the future converged systems should not be considered as replacements of the current ones, but rather that the systems need to supplement each other. For example, the need for a “quick and dirty” instant asynchronous media such as SMS seems to remain, and therefore it cannot be replaced simply by implementing email to mobile phones. The need for email and SMS seems to be different, and thus the development should be towards a better understanding of these needs rather than simple “technological” convergence.

Rapid product development — an overview

The success of innovative engineering processes depend on short and iterative development cycles which offer the possibility of high quality products, cost-efficient on the market and thus to stand up to today's tough competitive pressure. All these new methods are subsumed under the term “Rapid Product Development” (RPD). Research focuses attention not only on the products, but also their development process. By pursuing several variants with modern methods the optimal solution can be found. In order to guarantee the continuity of the whole product development process, organisation structure, process and resources have to be connected ideally. Enhancing the Simultaneous Engineering approach, RPD is an interdisciplinary evolutionary methodology to combine all influences of an engineering process to an iterative product development. To shorten the development process several tools are available: physical and digital prototypes for the early and cost-efficient evaluation of different alternatives, the representation of knowledge for different experts by means of an Active Semantic Network (ASN) for the integration of interdisciplinary teams, technical support of communication and cooperation within the team by adequate synchronous and asynchronous media. The Engineering Solution Center (ESC) demonstrates the realization of these technologies and methods in detail.

Dynamic Resource Allocation for Multimedia Document Retrieval over High Speed LANs

The emergence of gigabit local area networks (G-LANs) has spurred a tremendous interest in supporting networked multimedia applications over a LAN. In this paper, we propose a mechanism for dynamically allocating network resources in asynchronous LANs. Presentation of multimedia objects with required play-out quality requires Quality of Service (QoS) guarantees by the underlying networking infrastructure. Existing asynchronous LANs, such as Ethernet, do not support the notion of QoS due to their asynchronous media access protocol. For such networks, we propose a dynamic bandwidth management scheme that uses the concept of Time Division Multiple Access (TDMA). Significant performance improvement is observed through experimental results. In particular, the transmission rates for multimedia hosts improve significantly with low jitter variations in media streams. We also propose a framework for graceful degradation of play-out quality of multimedia objects in case the LAN‘s total capacity is not sufficient to meet the overall demand.