Igor Danilo Diego Curcio

SIP call setup delay in 3G networks

In this paper, call setup time in Session Initiation Protocol (SIP)-based videotelephony is analyzed. We used a 3G network emulator to measure post-dialing delay, answer-signal delay and call-release delay. The results are compared to local, national, international and overseas intranet LAN calls. Furthermore, we have also studied the effect SIP calls over lossy channels with restricted bandwidth, typical of mobile network signaling bearers.

Movable-multimedia: session mobility in ubiquitous computing ecosystem

IP-based Multimedia creation and consumption is becoming available on an increasing spectrum of devices ranging from low-powered portable devices like cell phones and PDAs to high powered static devices like desktops PCs and IPTVs. High-speed wireless and wire-line network access is becoming widespread. Multimedia services like IPTV, Video-on-demand and Video-conferencing are becoming main stream. These developments have paved the way for creating innovative concepts like session mobility for multimedia applications. Session mobility enables seamless transfer of an on-going multimedia session between different devices based on user preferences. We examine the motivations and use cases for session mobility. In this paper we evaluate architectural design constraints and propose architectural solutions for session mobility. We evaluate current session mobility mechanisms and propose requirements for new mechanisms.

Predictive buffering for streaming video in 3G networks

This paper presents a multimedia streaming service in a mobile (3G) environment that, in addition to in-band congestion signals such as packet losses and delay variations, receives congestion cues from a Network Coverage Map Service (NCMS) to make rate-control decisions. The streaming client routinely queries the NCMS to assess the network conditions at future locations along its expected path. The streaming client may ask the streaming server for short-term transmission bursts to increase pre-buffering when it is approaching areas with bad network performance to maintain media quality. If needed, the client may also switch to a different encoding rate (rate-switching) depending on the severity of expected congestion. These notifications are scheduled as late as possible, so that any changes in network conditions and/or changes in users movements can be taken into account (late scheduling). Using this type of geo-predictive media streaming service we show that the streaming client can provide pause-less playback and better quality of experience to the user.

We want more: human-computer collaboration in mobile social video remixing of music concerts

Recording and publishing mobile video clips from music concerts is popular. There is a high potential to increase the concerts perceived value when producing video remixes from individual video clips and using them socially. A digital production of a video remix is an interactive process between human and computer. However, it is not clear what the collaboration implications between human and computer are. We present a case study where we compare the processes and products of manual and automatic mobile video remixing. We provide results from the first systematic real world study of the subject. We draw our observations from a user trial where fans recorded mobile video clips during a rock concert. The results reveal issues on heterogeneous interests of the stakeholders, unexpected uses of the raw material, the burden of editing, diverse quality requirements, motivations for remixing, the effect of understanding the logic of automation, and the collaborative use of manual and automatic remixing.

Geo-predictive real-time media delivery in mobile environment

Multimedia streaming is one of the most popular services today. When the user is in a mobile scenario, the delivery of multimedia streaming services becomes more challenging. Mobile streaming suffers from discontinuous playback that sometimes impairs user experience. Among other factors, this is also due to the high network bandwidth variation that a user can experience along a path. In some cases, the available bandwidth is close to zero when traversing tunnels or areas where the network capacity goes below what is required for a multimedia session to be pause-less. Typically, media adaptation and rate control are used to fight against variable bandwidth. However, these are usually reactive algorithms, where an event is first detected (e.g., a drop in available bandwidth), and then an action is taken, either by the streaming client or by the server. This action may result just in a mitigation of the problem and not in the complete removal. In this paper we introduce the novel concept of Geo-Predictive mobile streaming. This is a collaborative service that makes use of prediction rather than reaction. Network coverage maps are built with the aid of mobile users; with these maps, the available network bandwidth for each location is recorded in a server, and when a user travels from point A to point B, it is possible to predict well in advance what will be the experienced bandwidth along that route. In case of bandwidth drops, these can be known in advance and media adaptation algorithms can be triggered so that a pause-less media playback experience can be guaranteed to the end users anywhere and all the time.

Rate Adaptation for Conversational 3G Video

Wireless cellular environments, such as UMTS, are often affected by congestion and errors, which are inherent to wireless transmission channels due to fading, interference, resource scarcity, mobility, etc. For a conversational video application to be successful i.e., to provide good viewing quality to the receiver at all times, the sender must be able to quickly adapt its sending/encoding rate (and other related parameters) to that offered by the link. Moreover, for a rate adaptation scheme to be successful, the receiver must provide timely feedback in order to mitigate further losses due to congestion. In this paper, we investigate different rate adaptation mechanisms and redefine them for 3GPP networks, reusing existing RTCP extensions standardized in the IETF and in 3GPP where possible.

Application rate adaptation for mobile streaming

As the adoption of 2.5G and 3G systems grows, multimedia streaming is one of the services that operators will increasingly seek to provide. The multimedia streaming solutions that have successfully been deployed commercially on the Internet in the past are all based on proprietary technologies. However, existing streaming applications need to be considerably rethought to work well over wireless. The 3GPP standardization body has standardized streaming services for Release 4, 5 and 6 specifications. The Release 6 advanced streaming service overcomes the technical challenges posed by wireless and best effort networks. A standard solution for advanced multimedia streaming will ultimately drive adoption by operators and users. The paper describes the solution standardized in 3GPP(2) for adaptive streaming.

Mobile and interactive social television

Services that were traditionally designed for a static environment can now be implemented into mobile devices. At the same time, services with traditionally passive-consumption-oriented paradigms are moving toward participative and interactive services. One such service is mobile and interactive social TV (MIST), which allows geographically dispersed people to meet in a virtual shared space and watch TV while being able to interact with each other. This service allows users to create an experience of watching together by providing its participants a common shared context. We present two novel architectures of a MIST system. In both of the architectures, the interaction is represented by rich audio-visual media, allowing users to hear and see each other. In the first architecture, the mixing of the TV content with the interaction media is performed at the server side. In the second architecture, the mixing is performed in each client device. There are many questions that arise from the consumer perspective regarding a radical change in experience when compared to traditional laid-back TV watching. Mobile and interactive social TV is relatively new when compared to the concept of traditional TV watching in a static context. To develop understanding of the consumer experience with the MIST concept, a focus group study approach was conducted. The study revealed that the feeling of social presence of people of interest when watching content with them was considered to add value to the viewing experience. The key system requirement is the ability for selective enabling/disabling of individual interaction features as per the user preferences and context. The context was considered to be influenced by both the relation with other participants and the content being consumed.

Mobile TV content to home WLAN

The proliferation of mobile broadcast networks and home multimedia networks makes relevant considering a new level of digital convergence. One aspect is the integration of mobile content access to the home network. In this framework, a mobile device serves as a gateway for real time content rebroadcast. This paper investigates the mobile rebroadcasting problem and implementation between the Mobile TV system based on the DVB-H standard and DLNA/UPnP enabled home network based on WLAN.

Evaluation of Error Resilience Mechanisms for 3G Conversational Video

Communication in 3G networks may experience packet losses due to transmission errors on the wireless link(s) which may severely impact the quality of video services, with conversational video being most challenging to repair due to tighter delay constraints. Many error resilience mechanisms have been developed that can be applied at the source (codec) level and transport/application layer to address these challenges. Their respective performance varies depending on the network conditions. This paper analyzes and compares the performance of four error resilience mechanisms under different realistic wireless link conditions: selective retransmissions, slice size adaptation, reference picture selection, and unequal error protection using packet-based forward error correction. We derive suggestions for the applicability of the individual mechanisms.