Titulo Estágio
Mechanisms for resilient video transmission in wireless networks
Área Tecnológica
Comunicação Telemática
Local do Estágio
DEI
Enquadramento
In the last few years, there has been a rapid proliferation of a wide range of real-time video services and applications. This situation is easily explained by the large amount of new forms of spreading information ranging from education to entertainment that are released everyday by thousands of users. However, real-time video transmission imposes more challenges than non-real-time data transfer. Furthermore, the use of mobile devices with wireless networks introduces additional challenges, such as the fluctuating bandwidth, scarce resources and time-varying error rate. These issues have to be addressed to sustain video quality for the end-users, as a result of a more dynamic and error-prone environment. In order to identify the situations where flaws are more noticeable by the end-user, Quality of Experience (QoE) metrics are commonly used.
Objetivo
The objective of this proposal is to develop a mechanism to overcome the video transmission challenges in wireless networks, providing both good perceived video quality and low network overhead.
This mechanism should make use of at least one Error Correction (EC) technique. Although it is possible to enhance video transmission with packet prioritization, link adaptation, video bitrate adjustment and other means, without using an EC-based scheme, this improvement will only be attainable to a limited degree. Error correction mechanisms are strong candidates to improve the delivery of digital data over unreliable communication channels, because, together with the ability to detect errors, they also allow damaged data to be reconstructed.
Generally speaking, the EC techniques can be carried out with two distinct methods, namely Forward Error Correction (FEC) and Automatic Repeat reQuest (ARQ). ARQ-based schemes use retransmission to correct erroneous data. These schemes should only retransmit lost packets when the delay and other network parameters are considered suitable, to avoid wasting resources by retransmitting information that can no longer be used. Therefore a smart ARQ-based scheme must be employed. This scheme should be able to be turned on or off and even customized to be better adapted to the network status at that moment, as well. An enhanced video quality can be expected since the mechanism is better adapted to the network conditions.
On the other hand, FEC-based schemes send redundant information along with the original data set, which can be used to recover the original data in case of loss. This means that it is not affected by excessive delay and jitter. If FEC-based schemes would be adopted, at least two code types must be implemented, such as Low-density parity-check (LDPC), Convolutional coding, LT, Raptor and Reed-Solomon. The downside of FEC is that the resources in wireless networks might be limited and unevenly distributed. Therefore, to reduce the amount of redundant information, an adaptive FEC-based approach must use Unequal Error Protection (UEP) schemes. Through these UEP-based schemes it is possible to assign different amounts of redundancy to the original data. In doing this, it is possible to set the amount of redundancy so that it corresponds to the importance of the protected data, and allows the protection of the most important video details with lower network overhead.
In the first semester, the applicant should study the main concepts and definitions needed to understand the characteristics of video transmission, wireless networks and error correction techniques. This analysis must take into consideration the current state-of-the-art regarding video optimization techniques. At the end of the semester it is also expected the proposal of a mechanism to optimize video transmission.
During the second semester, the student should design, implement and validate the proposed mechanism, along with the writing of the final report. The proposed mechanism should strengthen video transmission, while increasing user satisfaction and improving the usage of wireless resources. This means that an optimal trade-off between network overhead and video quality must be found. The benefits of the proposed solution need to be measured by using objective QoE metrics. The design and implementation must be in the Network Simulator 3 (NS-3).
Plano de Trabalhos - Semestre 1
• Study of state-of-the-art in video transmission techniques (W1-W4)
• Analysis of error correction techniques and QoE assessment methods (W2-W8)
• Identification of issues in existing mechanisms related to video optimizations and the perceived video quality (QoE) (W4-W10)
• Specification of mechanisms for resilient video transmission in wireless networks (W6-W14)
• Design, implementation and evaluation of a proof-of-concept mechanism in a simulation environment (W8-W15)
• Writing a paper with the state-of-the-art and preliminary results of the proposed mechanism. Results must be assessed with QoE metrics (W11-W15)
• Writing of intermediate report (W1-W15)
Plano de Trabalhos - Semestre 2
• Implementation of proposed mechanism for resilient video transmission in wireless networks (W1-W8)
• Implementation and evaluation of state-of-the-art mechanisms (W2-W13)
• Proposal validation, assessment and comparison with state-of-the-art mechanisms (W4-W13)
• Writing of two papers with the proposed mechanism compared to state-of-the-art mechanisms (W6-W15)
• Writing of final report (W1-W15)
Condições
Research scholarship.
Orientador
Marilia Curado
marilia@dei.uc.pt 📩