Adaptation techniques for ubiquitous Internet multimedia

Margaritis Margaritidis, George C. Polyzos
2001 Wireless Communications and Mobile Computing  
A major trend in the Internet today is the push for ubiquitous access to rich multimedia content. Achieving this goal requires the incorporation of adaptation techniques, which will transform the media into various formats, suitable for a variety of devices with diverse communication and presentation capabilities. In this survey, we present the categories of adaptation techniques focusing on their characteristics and potential. We analyze various schemes in order to evaluate their
more » ... performance, complexity, and applicability. We then describe the adaptation policies, methods and mechanisms that they use, along with the supporting mechanisms that aim in increasing the efficiency of the adaptation process. Finally, we present several case studies, commercial approaches and current trends in the area of ubiquitous access to Internet multimedia content. Text In the current, rich multimedia content era, text remains significant and has some important applications. One-way time-critical text applications are very popular in today's mobile phones in the form of SMS messaging, and WAP traffic (e.g., for -3news, stock market information, etc.). Such type of traffic usually poses no serious demands for its display or transmission, except for some cases where immediate delivery is critical. More time-critical are some interactive, two-way text applications like chat, telnet and pager messages. However, text applications in general tend to have low demands and are easily displayed in the majority of devices. Rich Web Content As with text, we can categorize rich content based on whether timely delivery is critical or not. E-mail, ftp and off-line browsing are applications with low levels of network interactivity. In most cases, the user is expecting a fair delay during downloading, and accepts the best-effort nature of this type of traffic. Therefore, lower priority and low transmission demands characterize this kind of traffic. On the other hand, rich interactive Web applications also include Web browsing and on-line gaming. These applications are able to operate adequately over slow speed connections, but they can also exploit any available bandwidth in order to achieve better quality presentation or faster response times. Critical parameters are the end-to-end delay, which significantly enhances quality when it is minimal and its variability is low, and the available bandwidth, which should be at least in the order of few tens of Kb/s. Audio Typical streaming audio applications are in use over the Internet for several years. Radio stations and sites that provide pay-per-listen services are very popular. In addition, the domination of the MP3 format [3] revolutionized the distribution methods of music over the Internet. Audio streams have moderate bandwidth requirements that can start from 8 Kb/s (or even lower) for telephone quality audio and rise up to 256 Kb/s for compressed CD quality audio. Timely and reliable delivery are very important, since unrecognizable sounds, due to delayed data, and audible gaps, due to errors and dropped packets (typically due to congestion), severely degrade the listening experience for the user. Recently, interactive audio applications are attracting increased attention, especially in the form of Voice-over-IP (VoIP) [4, 5] . With VoIP, communications companies are able to provide ubiquitous telephony services over any kind of carrier infrastructure. IP is developing into the common layer that will effectively hide the transmission characteristics of the physical and link layers and possibly other underlying switching technologies. Thus, transmission of voice and data is feasible simultaneously through a single "transport" service. VoIP exploits the current Internet infrastructure and abandons the circuit-switching architecture of the telephony network in favor of the packet-switching architecture of the Internet. Consequently, the cost of telephony services is dramatically reduced. However, in the absence of specific Quality-of-Service (QoS) support mechanisms, this is realized at the expense of the
doi:10.1002/wcm.10 fatcat:4zo6bxb2zrg63gjoh4fpps6lbm