JMM Abstracts 

Vol.7 No.1&2 April, 2011
Mobile Computing Applications and Multimedia Service Quality

Editorial (001-001)
Eric Pardede

Research Articles for the Theme Issues

Personalized Services for Commercial Establishments using PlaSerEs (002-029)
David Marin Diaz, Alejandro Rico Zuluaga, Angela Carrillo-Ramos, María Paula Arias-Báez, and Andrea Barraza-Urbina
This paper presents the application of adaptation aspects defined in IAM (acronym in English of Integrated Adaptation Model) on the platform "PlaSerEs". The main goal of this platform is to provide personalized information about the products and/or services provided by commercial establishments to their clients. This platform is structured in four layers: i) the adaptation layer, composed of four modules: context, access device, user and wireless connection. ii) The general services layer, iii) the personalized services layer and, iv) the application layer. In order to validate and to evaluate how "PlaSerEs" works, we developed a functional prototype for a restaurant. This prototype works on Mobiles Devices (MD).

Pervasive Language Learning on Modern Mobile Devices (030-050)
Bartholomaus Wloka and Werner Winiwarter
In this article, we describe our experience with deploying our previous work on machine translation and language learning on mobile Internet platforms, i.e. smartphones. We present UTROLL – a Ubiquitous Translation and Language Learning Environment, implemented on the Nokia N900 with Maemo5 and KANTEAM – KAnji TEAcher Mobile, implemented on the Samsung Galaxy Tab with Google's operating system Android. In the process of implementation, we have analyzed both platforms as ubiquitous learning devices with special focus on sensor and hardware capabilities as well as usability. This work is combined with our previous efforts and creates a bridge between a server-based machine translation system and an everyday smartphone user. We present a detailed description of both applications, UTROLL and KANTEAM, while comparing their capabilities with respect to their hardware and operating system issues.

A Usability Study of A Mobile Content Sharing System (051-065)
Alton Y.K. Chua, Dion Hoe-lian Goh, Khasfariyati Razikin, and Ee-Peng Lim
We investigate the usability of MobiTOP (Mobile Tagging of Objects and People), a mobile location-based content sharing system. MobiTOP allows users to annotate real world locations with both multimedia and textual content and concurrently, share the annotations among its users. In addition, MobiTOP provides additional functionality such as clustering of annotations and advanced search and filtering options. A usability evaluation of the system was conducted in the context of a travel companion for tourists. The results suggested the potential of the system in terms of functionality for mobile content sharing. Participants agreed that the features in MobiTOP were generally usable as a content sharing tool. Implications and future work are also reported in this paper.

A More Realistic RTP/RTCP-Based Simulation Platform for Video Streaming QoS Evaluation (066-088)
Fernando Boronat, Mario Montagud, and Vigent Vidal
Over the last few years, the demand for real-time multimedia services has been growing progressively so that video streaming applications are expected to be dominant in future communications systems, and most of them using RTP/RTCP protocols. This paper presents an evolved tool-set for video streaming QoS evaluation in simulated environments using such protocols. We have designed a new NS-2 module with a full RTP/RTCP implementation (following strictly the RFC 3550) and we propose to combine it with additional multimedia tools to obtain an advanced simulation framework that allows the measurement of network-level QoS metrics (such as throughput, delay, jitter or loss rate) in simulation time. Besides, as the transmitted video files can be reconstructed and played out at the receiver side, the measurement of the quality of the delivered video streams, by employing the most common objective quality metrics (such as PSNR, SSIM or VQM) or subjective metrics (MOS), is also supported. By using this tool-set, researchers and practitioners can assess their novel designs (such as network protocols, routing strategies or video coding mechanisms) for such applications in heterogeneous scenarios over different network conditions. As RTCP feedback capabilities have been added, source based control techniques (such as rate adaptability or Multiple Description Coding) could be included and tested using this more realistic and powerful simulation platform.

Hash Chain Links Resynchronization Methods in Video Streaming Security: Performance Comparison (089-112)
Emad Abd-Elrahman, Mohamed Boutabia, and Hossam Afifi
Hash chains provide a secure and light way of security to data authentication including two aspects: Data Integrity and Data Origin Authentication. The real challenge of using the hash chains is how it could recover the synchronization state and continue keeping the hash link in case of packet loss? Based on the packet loss tolerance and some accepted delay of video delivery which are representing the permitted tolerance for heavy loaded applications, we propose different mechanisms for such synchronization recovery. Each mechanism is suitable to use according to the video use case and the low capabilities of end devices. This paper proposes comparative results between them based on the status of each one and its overhead. Then, we propose a hybrid technique based Redundancy Code (RC). This hybrid algorithm is simulated and compared analytically against the other techniques (SHHC, TSP, MLHC and TSS). Moreover, a global performance evaluation in terms of delay and overhead is conducted for all techniques.

The Impact of Security on VoIP Call Quality (113-128)
Pedram Radmand, Jaipal Singh, Marc Domingo, Joan Arnedo, and Alex Talevski
Modern multimedia communication tools must have high security, high availability and high quality of service (QoS). Any security implementation will directly impact on QoS. This paper will investigate how end-to-end security impacts on QoS in Voice over Internet Protocol (VoIP). The QoS is measured in terms of lost packet ratio, latency and jitter using different encryption algorithms, no security and just the use of IP firewalls in Local and Wide Area Networks (LAN and WAN) in the lab and in the real world. The results of laboratory tests indicate that the impact on the overall performance of VoIP depends upon the bandwidth availability and encryption algorithm used. The implementation of any encryption algorithm in low bandwidth environments degrades the voice quality due to increased loss packets and packet latency, but as bandwidth increases encrypted VoIP calls provided better service compared to an unsecured environment.

Other Research Articles

Solution For TCP-Unfairness In IEEE802.11-based Ad-Hoc Network by Alleviating Exposed Terminal Problem Using Cross Layer Approach (129-133)
Tutun Juhana
In this paper we proposed an algorithm to improve TCP fairness in IEEE802.11-based ad-hoc network. Proposed algorithm uses cross layer approach which involved the cooperation between MAC layer and network layer. The solution alleviates exposed terminal problem by allowing MAC layer to use the topology information available in network layer.

Differentiated QoS Based on Cross-layer Optimization in Wireless ad hoc Networks (134-150)
Pejman Goudarzi
Generally, real time applications needs different levels of the Quality of Service (QoS) which must be guaranteed by the underlying network infrastructure. Wireless Ad Hoc networks introduce many technological challenges in guaranteeing these stringent QoS requirements which must be addressed. Many optimization theoretic based bandwidth allocation strategies have been developed for guaranteeing some levels of QoS for some classes of competing real-time users in wireless ad hoc networks. The rapid increase in the development of different real-time applications with stringent maximum packet loss requirements in such environments and the existence of difficulties in satisfying the pre-specified QoS limits, is a great motivation for designing some type of differentiated QoS guaranteeing mechanisms that can satisfy the demands of this class of the real-time traffics. In the current work, a cross-layer optimization framework is being developed in which, based on the packet loss information from the lower layers, optimal bandwidths are assigned to the real-time applications which need some levels of the maximum packet loss guaranties. As, each real-time application needs a different level of maximum packet loss guarantee, a weighted aggregate packet loss objective function is being introduced. The weights are proportional with the importance of the packet loss mitigation for a specific application and may be associated with some negotiated Service Level Agreement (SLA). The simulation results verify the claims.

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