Erik Huizer

A mobility-aware broadcasting infrastructure for a wireless internet with hotspots

In this paper, we consider the problem of adaptively delivering live multimedia broadcasts (e.g., for applications such as TV, radio, or e-cinema) to a potentially large number of mobile hosts that roam about in a wireless internet with hotspots. We take a user-oriented approach based on an application-level delivery infrastructure consisting of and managed by (value-added) service providers. The service providers are mobility-aware and offer broadcasts in configurations that are optimized for wireless links and mobile hosts. In hotspots, mobile hosts may be able to simultaneously reach several localized service providers through different interfaces. Within this context, we present the design of a lightweight application-level protocol that enables mobile hosts to select a service provider from which they want to receive a broadcast. Mobile hosts use the protocol to begin receiving a broadcast and to remain connected to the same logical broadcast as they move across subnets. The protocol is independent of the actual stream control protocol (e.g., RTSP) that service providers might use. We show how our protocol can be realized with the existing protocols SIP and SDP. The realization uses SIP in combination with SDPs offer-answer model in a new way.

Threats and opportunities for new audiovisual cultural heritage archive services: The Dutch case

Purpose: The purpose of this paper is to analyze the business-to-consumer market for digital audiovisual archiving services. In doing so we identify drivers, threats, and opportunities for new services based on audiovisual archives in the cultural heritage domain. By analyzing the market we provide insights into the preconditions for provision of fruitful and viable services that can be build upon these archives. Design/methodology/approach: The research method takes the form of a case study, including literature search and interviews. For this research we adopt the STOF-framework for analyzing purposes. This framework consists of four components: a service component, a technological component, an organizational component, and a financial component (STOF). Findings: The authors argue an imbalance between the different factors of the STOF-model in the Netherlands. First, the service domain in the Dutch audiovisual archive domain shows little knowledge about (potential) users and their needs regarding the archive. The service domain is therefore probably the biggest question mark in this market. Second, the technical component presents few impedances and is therefore least of an issue. Third, the organization component in terms of value network presents issues revolving around the nature of the cultural institution. Non-profit cultural organizations like Sound & Vision in the Netherlands are not naturally inclined towards business modeling around development of services. Fourth and last, the financial domain shows severe bottlenecks for unlocking the content regarding intellectual property. The clearing of copyrights is one of the main tasks of Images for the Future, but engulfs much time in the primary process. In sum, the study shows promising and problematic issues that arise in the field of developing audiovisual archive services. Research limitations/implications: This is a one-case study, so no cross analysis with other cases was possible. Future work includes the investigation of user needs regarding audiovisual cultural heritage and possible services upon the archives. Originality/value: This is one of the first studies that look into the factors in a particular domain that influence the viability of services by using a business model framework. This paper, therefore, extends the utilization of this framework (STOF-model) as it used as a method for the evaluation of a market and provides market insights. Also, the application on the audiovisual cultural heritage domain is quite novel. For practitioners regarding the development of audiovisual archive services the paper presents fresh insights in the configuration of the different business components of the services.

'I Want My HDTV'? Underlying Factors of Perceived Usefulness for High Definition Television

While traditional technology acceptance models concentrate on relationships between usefulness and acceptance, they leave unresolved the questions about why a certain technology is found useful, in which contexts, and by whom. This paper presents an empirical study of some of the factors behind perceived usefulness of HDTV in the Netherlands, where the adoption process has just begun. Results show that HDTV awareness, knowledge about HDTV, daily television viewing habits, household innovativeness and the presence of digital television contribute to perceived usefulness of HDTV characteristics. They also demonstrate that these characteristics accord with Dutch viewer demands for future television.

Measurements of SIP signaling over 802.11b links

The Session Initiation Protocol (SIP) is a popular application-level signaling protocol that is used for a wide variety of applications such as session control and mobility handling. In some of these applications, the exchange of SIP messages is time-critical, for instance when SIP is used to handle mobility for voice over IP sessions. SIP may however introduce significant delays when it runs on top of UDP over lossy (wireless) links. These delays are the result of the exponential back-off retransmission scheme that SIP uses to recover from packet loss, which has a default back-off time of half a second.In this paper, we empirically investigate the delay introduced by SIP when it runs on top of UDP over IEEE 802.11b links. We focus on the operation of SIP at the edge of an 802.11b cell (e.g., to update a mobile hosts IP address after a handoff) as this is where SIPs retransmissions scheme is most likely to come into play. We experiment with a few 802.11 parameters that influence packet loss on the wireless link, specifically with different link-level retransmission thresholds, signal-to-noise-ratios (SNRs), and amounts of background traffic. We conduct these experiments in a controlled environment that is free from interfering 802.11 sources.Our results indicate that (1) SIP usually introduces little delay except for an SNR range of a few dBs at the very edge of an 802.11 cell in which the delay increases sharply, and (2) that a maximum of four 802.11 retransmissions suffices to limit the delay introduced by SIP retransmissions. The first result is of interest to developers of SIP applications who have to decide at which SNR to initiate a handoff to another network. The second result allows network providers to optimize their 802.11b networks for delay sensitive SIP applications.

Delivering live multimedia streams to mobile hosts in a wireless internet with multiple content aggregators

We consider the distribution of channels of live multimedia content (e.g., radio or TV broadcasts) via multiple content aggregators. In our work, an aggregator receives channels from content sources and redistributes them to a potentially large number of mobile hosts. Each aggregator can offer a channel in various configurations to cater for different wireless links, mobile hosts, and user preferences. As a result, a mobile host can generally choose from different configurations of the same channel offered by multiple alternative aggregators, which may be available through different interfaces (e.g., in a hotspot). A mobile host may need to handoff to another aggregator once it receives a channel. To prevent service disruption, a mobile host may for instance need to handoff to another aggregator when it leaves the subnets that make up its current aggregator’s service area (e.g., a hotspot or a cellular network).In this paper, we present the design of a system that enables (multi-homed) mobile hosts to seamlessly handoff from one aggregator to another so that they can continue to receive a channel wherever they go. We concentrate on handoffs between aggregators as a result of a mobile host crossing a subnet boundary. As part of the system, we discuss a lightweight application-level protocol that enables mobile hosts to select the aggregator that provides the ‘best’ configuration of a channel. The protocol comes into play when a mobile host begins to receive a channel and when it crosses a subnet boundary while receiving the channel. We show how our protocol can be implemented using the standard IETF session control and description protocols SIP and SDP. The implementation combines SIP and SDP’s offer-answer model in a novel way.

Exploring determinants of early user acceptance for an audio-visual heritage archive service using the vignette method

The purpose of this study is to investigate factors, which explain the behavioural intention of the use of a new audio-visual cultural heritage archive service. An online survey in combination with a factorial survey is utilised to investigate the predictable strength of technological, individual and contextual constructs. The case used to validate this model is that of a not-yet-existing audio-visual archive service. Based on data collected from the survey (N = 1939), it is confirmed that payment and interpersonal influence the intention to adopt a new service thus partially supporting our three-dimensional model (i.e. technology, individual and context). The study contributes to the field of adoption research by studying a new service rather than an existing one. Subsequently, a vignette study is adopted. Moreover, the field of audio-visual archives is introduced in user research, which is considered novel. Pioneering on the unlocking of audio-visual archive this research seeks answers in the user needs and determinants for services upon these archives. Furthermore, the practical and scientific implications are discussed.

Adding policy-based control to mobile hosts switching between streaming proxies

We add a simple policy-based control component to mobile hosts that enables them to control the continuous reception of live multimedia content (e.g. a TV broadcast) while they switch between different distributors of that content. Policy-based control provides a flexible means to automate the switching behavior of mobile hosts. The policies react to changes in the mobile hosts environment (e.g. when a hotspot network appears) and determine when and how to invoke an earlier developed application-level protocol to discover the capabilities (e.g. supported encodings) of the content distributors and to execute the switches. The design of the control component is based on the IETF policy model, but extended and applied at the application-level instead of at the network-level. We implemented the system and deployed it in a small-scale test bed.

Designing online audiovisual heritage services: an empirical study of two comparable online video services

The purpose of this study is to seek input for a new online audiovisual heritage service. In doing so, we assess comparable online video services to gain insights into the motivations and perceptual innovation characteristics of the video services. The research is based on data from a Dutch survey held among 1,939 online video service users. The results show that online video service held overlapping antecedents but does show differences in motivations and in perceived innovation characteristics. Hence, in general, one can state that in comparison, online video services comply with different needs and have differences in perceived innovation characteristics. This implies that one can design online video services for different needs. In addition to scientific implications, the outcomes also provide guidance for practitioners in implementing new online video services.

More Pixels, Less Vision: The Politics of HDTV in the Netherlands

This article studies the policy of the Dutch government regarding the introduction of HDTV in the Netherlands. Utilizing a literature study and interviews with government officials, it shows that government choices are not always in line with the official neo-liberal policy, but are partly based on non-ideological,pragmatic or organizational factors. The findings of this case study challenge the presumption that policy choices made by government officials are based on rational and strategic considerations.

Understanding the diffusion of HDTV through an analysis of risks and uncertainties of supply and demand in the netherlands

This paper analyses the diffusion of HDTV in The Netherlands. The research provides an analysis of the supply side of the broadcast value chain as well as an analysis of consumer acceptance of HDTV in The Netherlands. The research is part of longitudinal research effort and uses both qualitative and quantitative measures. Using risks and uncertainties as a broad theoretical basis, we conclude that the consequence of the reluctant attitude on the supply side leads to a lack of knowledge on the demand side which is a necessary condition for the adoption of HDTV by consumers. This deadlock can be overcome when the supply side starts taking some calculated risks.