Digital multimedia broadcasting (DMB), also know as mobile TV, has been developed as a digital radio transmission technology that supports multimedia services such as TV, radio and datacasting. Especially, the terrestrial version of DMB, referred to as T-DMB, has been widely deployed in South Korea to deliver multimedia services to mobile devices ranging from smartphones to laptops, car navigation systems, and telematic devices for automotives. Although T-DMB is claimed to theoretically work without difficulties in vehicles with speeds up to 300 km/h, in practice, occasional skips and other temporal and spatial artifacts have been observed. In this paper, we provide an experimental study of the Quality of Experience (QoE) of T-DMB with focus on TV services. The study is based on a measurement campaign that was conducted in a live T-DMB system in South Korea consisting of TV broadcasters and DMB receivers in vehicles. In particular, a comprehensive subjective test has been conducted on the DMB test material that was obtained in the measurement campaign. A statistical analysis of the user ratings obtained from the subjective tests is reported to quantify the QoE of T-DMB in terms of mean opinion scores (MOSs) and higher order statistics. The obtained results may be used to develop related QoE models for this type of systems and services. In particular, the results may suggest to exploit insights obtained from higher order statistics such as skewness and kurtosis into QoE modeling rather than considering only MOS and variance.

Software organizations face challenges in managing and sustaining their measurement programs over time. The complexity of measurement programs increase with exploding number of goals and metrics to collect. At the same time, organizations usually have limited budget and resources for metrics collection. It has been recognized for quite a while that there is the need for prioritizing goals, which then ought to drive the selection of metrics. On the other hand, the dynamic nature of the organizations requires measurement programs to adapt to the changes in the stakeholders, their goals, information needs and priorities. Therefore, it is crucial for organizations to use structured approaches that provide transparency, traceability and guidance in choosing an optimum set of metrics that would address the highest priority information needs considering limited resources. This paper proposes a decision support framework for metrics selection (DSFMS) which is built upon the widely used Goal Question Metric (GQM) approach. The core of the framework includes an iterative goal-based metrics selection process incorporating decision making mechanisms in metrics selection, a pre-defined Attributes/Metrics Repository, and a Traceability Model among GQM elements. We also discuss alternative prioritization and optimization techniques for organizations to tailor the framework according to their needs. The evaluation of the GQM-DSFMS framework was done through a case study in a CMMI Level 3 software company.

In this paper, we examine the sensitivity of digital multimedia broadcasting (DMB) streams on transmissions errors that are typically induced by a wireless channel. In particular, DMB data is broadcasted using the MPEG-2 transport stream (TS) format. In order to find the sensitivity of different parts of a TS packet on channel errors, each TS packet is divided into 4 parts with equal lengths of 48 bytes, except the last part which is 44 bytes long. Bit errors have been introduced into these different parts of the TS packets. The sensitivity of these DMB videos on the errors and their locations is computed in terms of the following measures: 1) Number of decodable frames which indicates temporal quality; 2) Spatial quality of the resulting videos. The structural similarity (SSIM) index is used as an objective perceptual quality metric to quantify the spatial quality while the well-known fidelity metric mean-squared-error (MSE) is used to quantify the spatial distortions in these erroneous videos. Simulations have been performed on 7 different DMB videos using different bit error rates. The results show that the first part of a TS packet is highly sensitive to bit errors compared to the other 3 parts, both in terms of spatial and temporal video quality. Further, the sensitivity level goes down as we go from Part 1 to Part 4 of the DMB TS packets. The error sensitivity analysis reported in this paper will help designing better transmission systems for future digital multimedia broadcasting and other similar services. Particularly, the insights gained from this study will support designing better error control mechanisms that, among other factors, also take into consideration the sensitivity of different parts of the associated video streams.

This paper proposes a new solution approach for the simultaneous mobility issues in seamless handover. An alternative scheme is designed to minimize handover latency between two different networks with location management support while simultaneous handover occurs. One of the most emerging techniques in recent research projects for mobility management is mobile Stream Transmission Control Protocol (mSCTP). The multi-homing feature of Stream Control Transmission Protocol (SCTP) and dynamic address reconfiguration (DAR) extension of SCTP are applied in the proposed solution to achieve improved seamless performance. We used an additional Location Server (LS) to ensure location management between simultaneously moving mobile nodes (MNs) while simultaneous handover occurs. This research is dedicated to design a new model of simultaneous mobility based on 'Step-length' and the implementation of the model i.e., mSCTP with LS to solve the simultaneous mobility issues. 'Step-length' is defined as the random distance travelled by the simultaneously moving MNs in each step when location changes. The proposed scheme implemented on NS2 and performance evaluations are scrutinized to demonstrate the comparison of proposed simultaneous handover latency with LS and in absence of LS. The results show that our proposed approach has improved performance in reducing handover delay as well as handling simultaneous mobility issues in seamless handover.

Efficient utilization of bandwidth is key to providing mobile multimedia services such as wireless imaging. As such, efficient allocation of the available parity budget for error protection of the associated codestreams is essential for ensuring quality of service. Computing the optimal parity allocation to the codestream packets may not be possible in real-time due to the huge number of ways the parity can be assigned to the codestream packets. This is particularly true for systems having limited resources, such as mobile handheld devices. As a result, it is important to provide an error-protection scheme that gives good error-protection performance while imposing low computational and memory demands on the system. We therefore analyze how different parameters such as signal-to-noise ratio and source distortion-rate function affect the optimal unequal error protection (UEP) scheme for embedded codestreams. We also propose to approximate the optimal UEP using suitable mathematical models in order to reduce the complexity that otherwise would occur with computing the optimal UEP. We investigate several models for their fitness in approximating the optimal UEP using different performance metrics. The simulation results show that most of these models provide an excellent trade-off between performance and complexity.

Representation of multimedia requires large amounts of data. Therefore, multimedia source signals are compressed to reduce the data rate that would otherwise be required for its transmission. However, compression renders multimedia data more vulnerable to transmission errors. Therefore, error protection is needed when transmitting multimedia to mobile users over wireless channels. As channel coding adds parity symbols to the data for error protection, which in turn increases transmission data rate, efficient utilization of this added parity budget becomes a key for insuring quality of service for mobile multimedia. Computing the optimal parity allocation among packets of a multimedia stream may not be possible in realtime due to the huge number of ways the parity can be assigned to these packets. Therefore, it is important to design powerful error protection schemes while imposing low computational and memory demands on the system. This is particularly true for systems having limited resources, such as mobile handheld devices. Given that human beings are the final judges on the quality of multimedia services, it will also be beneficial to use perceptual quality metrics that correlate well with human perception when evaluating different error protection schemes. In this work, we have considered the above aspects when designing error protection for mobile multimedia: Providing near optimal performance while keeping complexity low; designing and evaluating of error protection schemes based on perceptual quality metrics. The thesis is divided into five parts. In the first part, region of interest (ROI) identification, coding and advantages of ROI coding are investigated. In addition, a framework is proposed for using ROI coding in wireless imaging. The second part provides a number of unequal error protection (UEP) schemes for wireless imaging ranging from very simple and less efficient equal error protection to very complex yet optimal error protection. The proposed error protection schemes provide an excellent trade-off between performance and omplexity. In the third part, a framework for perception-based error protection of images and video streams is proposed. This framework is based on the fact that the human visual system is more sensitive to quality degradation in the ROI compared to the background. The proposed error protection scheme provides excellent performance. Part four deals with realtime systems and/or systems having limited memory and processing resources. Specifically, an UEP is proposed for wireless imaging systems which provides near optimal performance and puts very low processing/memory demands on the systems. Finally, in the fifth part, optimal UEP is analyzed. Based on the analysis, optimal UEP is modeled using several mathematical models. Each of the considered models is evaluated for its fitness in providing error protection. The simulation results show that most of the investigated models give excellent performance.

In this paper, we propose a number of error protection schemes for wireless imaging ranging from simple but less efficient equal error protection to very complex yet optimal error protection. The main objective is to facilitate tradeoffs between performance and complexity in choosing an error protection scheme. Our technique provides the system designer with a number of solutions from which the application can choose those that best suits the available resources such as processing power and data rate. For this purpose, an image codestream is split into smaller cells each having a certain number of packets while the available parity symbols from the deployed error protection are optimally allocated to these cells. Subsequently, the parity symbols allocated to these cells are distributed among the packets that constitute each of these cell. Finally, the error control codes for every packet are determined based on the number of parity symbols allocated to each packet. Larger cells provide less complex but also less efficient error protection while smaller cells result in a better error protection performance but at the cost of increased complexity. Simulation results validate the effectiveness of the considered technique in providing the desired performances-complexity trade-off. To obtain better correlation with human perception, performance is evaluated in terms of objective perceptual quality metrics.

In this paper, we focus on mobile images given in JPEG2000 format and evaluate their spatio-temporal Quality of Experience (QoE). In particular, the trade-of between spatial QoE supported by progressive source encoding and temporal QoE related to network delay as well as initial transmission delay is examined.