Sadaqat Jan

Performance analysis of cooperative network over Nakagami and Rician fading channels

This paper presents an analysis on the performance of single-relay and multiple fixed-relay cooperative network. The relay nodes operate in amplify-and-forward AF mode and transmit the signal through orthogonal channels. We consider maximal-ratio combining at the destination to get the spatial diversity by adding the received signals coherently. The closed-form moment-generating function MGF for the total equivalent signal-to-noise ratio SNR is derived. The exact expressions of symbol-error rate, outage capacity, and outage probability are obtained using the closed-form MGF for single-relay and multiple-relay cooperative network with M-ary phase shift keying M-PSK and M-ary quadrature amplitude modulation M-QAM over independent and non-identical Nakagami-m channels and Rician fading channels. The approximated closed-form expression of ergodic capacity is derived for both Nakagami-m and Rician fading channels. The performance of the system is analyzed at various relay locations. The theoretical results are then compared with the simulation results obtained for binary PSK, quadrature PSK, and 16-QAM modulation schemes to verify the analysis. Here, the expressions derived can be easily and more efficiently used to compute the performance parameters than doing Monte Carlo simulations. It is shown that cooperation is significant only for low K values for Rician by plotting cooperation gain versus K. The results show that the cooperative network performs best when the relay is located in the middle of source to destination link, at lower SNR values, and the performance of the system is worst if the relay is located closer to the source than to the destination. Copyright

Semantic file annotation and retrieval on mobile devices

The rapid development of mobile technologies has facilitated users to generate and store files on mobile devices such as mobile phones and PDAs. However, it has become a challenging issue for users to efficiently and effectively search for files of interest in a mobile environment involving a large number of mobile nodes. This paper presents SemFARM framework which facilitates users to publish, annotate and retrieve files which are geographically distributed in a mobile network enabled by Bluetooth. The SemFARM framework is built on semantic web technologies in support of file retrieval on low-end mobile devices. A generic ontology is developed which defines a number of keywords, their possible domains and properties. Based on semantic reasoning, similarity degrees are computed to match user queries with published file descriptions. The SemFARM prototype is implemented using the Java mobile platform (J2ME). The performance of SemFARM is evaluated from a number of aspects in comparison with traditional mobile file systems and enhanced alternatives. Experimental results are encouraging showing the effectiveness of SemFARM in file retrieval. We can conclude that the use of semantic web technologies have facilitated file retrieval in mobile computing environments maximizing user satisfaction in searching for files of interest.

File annotation and sharing on low-end mobile devices

Rapid technological evolutions in mobile industry have revealed new challenges for scientists and researchers by empowering low-end devices in the last decade. Mobile phones with excellent computing power and added features especially with huge storage capacities are very common in the market. As the storage capacity grows on such a device, it becomes very tedious for users to manage and organize different type of files. The file system of such devices itself provide some managing mechanism to store same type of files separately however it proves scarce as the number of files grows. Furthermore, limited user interface on these devices makes file retrieval more difficult. This paper presents detailed analysis of meta-data significance in our proposed framework to annotate and search files on low-end mobile devices. File attributes are extracted from the underlying operating system of the device and used as metadata of the corresponding file. The meta-data is then used for searching the required file. The file search can be performed on the device itself or on other devices when connected in a Personal Area Network (PAN) through Bluetooth. The proposed framework is implemented in Java Micro Edition and a full featured application is developed to demonstrate its validity. The application provides annotation, search options, Bluetooth module, file sharing and transfer options. Results from various performance tests show significant improvement in searching a required file through our proposed framework.

Dealing With Uncertain Entities in Ontology Alignment Using Rough Sets

Ontology alignment facilitates exchange of knowledge among heterogeneous data sources. Many approaches to ontology alignment use multiple similarity measures to map entities between ontologies. However, it remains a key challenge in dealing with uncertain entities for which the employed ontology alignment measures produce conflicting results on similarity of the mapped entities. This paper presents OARS, a rough-set based approach to ontology alignment which achieves a high degree of accuracy in situations where uncertainty arises because of the conflicting results generated by different similarity measures. OARS employs a combinational approach and considers both lexical and structural similarity measures. OARS is extensively evaluated with the benchmark ontologies of the ontology alignment evaluation initiative (OAEI) 2010, and performs best in the aspect of recall in comparison with a number of alignment systems while generating a comparable performance in precision.

Ontology alignment using Rough Sets

Ontology alignment has been one of the most significant research issues to bridge the semantic gap between heterogeneous systems toward Semantic Web. Many proposed systems in recent years, use multiple similarity measures and variety of aggregating algorithms to map entities from two different ontologies. However, the real issue arises when alignment systems turn out to be uncertain about entities which are neither completely similar nor dissimilar. This paper presents an ontology alignment system which uses a combination of various similarity measures in order to map entities from two different ontologies. Rough Sets have been used to deal with uncertainties during the mapping process by defining the similarity measures as the attributes of entities. The proposed alignment system employs the combination of string based, linguistic based and structural matchers. The structural matcher compares the super-classes, sub-classes and properties of two class entities. We use WordNet to compare the linguistic similarity between entities in the mapping process. The performance of proposed system is evaluated in terms of precision and recall and compared with existing state of the art alignment systems. For this purpose, the Ontology Alignment Evaluation Initiative (OAEI) benchmark group-3 test ontologies have been used. Experimental tests show that the performance our proposed alignment system is comparable with existing alignment systems.

Selfish Flow Games in Non-cooperative Multi-radio Multi-channel Wireless Mesh Networks with Imperfect Information

Multi-Radio Multi-Channel capabilities in Wireless Mesh Networks can enormously increase backhaul connectivity, network throughput and fault tolerance as simultaneous transmissions can be achieved through multiple radios tuned to non-overlapping channels with minimum degree of interference. End user flows compete for channel resources along the end to end mesh backhaul path across multiple collision domains, which need high cooperation and trust. On the other hand, realistic mesh topologies span over different collision domains with a minimum degree of cooperation among the network users. This selfish behavior of end users degrades their individual fairness and affects the overall mesh backbone performance too. In this paper, we have proposed a novel multi-radio multi-channel game theoretic model in multiple collision domains, where flows of the network are considered as players of the game. Our analytical results show that Nash Equilibrium exists for such types of games and simulation results show that our distributed algorithm converges to a stable state in finite time with maximum fairness among the players.

Optimal Path Discovery with Mobility Management in Heterogeneous Mesh Networks

Wireless Mesh Networks (WMNs) is a promising technology for backhaul wireless connectivity in user premises due to its multi-hop nature, multi-radio multi-channel capabilities and stable power supplies. With proliferation of new and advanced access technologies, future WMN’s will bean integrated paradigm to provide seamless and ubiquitous connectivity to multi interface end user devices. Co-existence of multiple heterogeneous interfaces on wireless mesh routers increases overall network capacity, resilience and availability in the mesh backhaul as compared to homogenous radios mesh networks. In this paper, we present a novel architecture for heterogeneous WMN’s based on integrated IEEE 802.11/16/15technologies and discuss issues, possible solutions and future insight. We propose an optimal route algorithm along with radio assignment graph which captures the heterogeneity of radios. We also present a handover mechanism for seamless interface switch for mobile and static end user devices.

Performance Analysis of Proactive and Reactive Routing Protocols for Mobile Ad-hoc Grid in e-health Applications

The integration of mobile wireless devices into grids has recently drawn the attention of research community as this integration has resulted in new challenges. Mobile grid enables the mobility of a requesting user to share unused available resources on a network required in different applications in science, health and education. These handheld devices are not capable to cope with the existing demands of networks and applications. Heterogeneous interfaces, computational power, storage and display differences among these devices demands more research. In this paper we present analysis of different routing protocol’s behavior in a mobile ad-hoc grid environment, where best routing is the requirement of a grid application. These analyses were made based on a test scenario of e-health application in a mobile ad-hoc grid environment.

FARM: file annotation and retrieval on mobile devices

As the technology evolves, mobile phones and portable devices are equipped with advanced features like built-in cameras, audio/video recordings, and other applications. When a user starts utilizing such features and applications, usually a large number of files are generated, and as this number grows, it becomes a challenging task to find the requested files with limited user-interface capabilities. This article presents FARM, a framework for file annotation and retrieval on resource-limited mobile devices like mobile phones, PDAs, and other MIDP compliant devices. Once the annotation process is completed, user can easily retrieve the files on the device itself or on in a networked environment where a large number of mobile nodes are involved. The metadata for annotation is gathered from the underlying file system and stored locally, which gives this framework a two-fold gain. Firstly, this framework does not require any common repository and hence, does not require communication medium to store and retrieve metadata. Secondly, searches are performed in a distributed fashion when more than one device is searched. The proposed framework has been implemented with a full featured application, and experimental results show that files can be retrieved efficiently and accurately with annotated data.

Facilitating Mobile Communication with Annotated Messages

The widespread usage of SMS messaging system reflects its importance for the users of mobile phones. However, it is becoming extremely laborious for users to manually write, read and reply every single SMS message due to an increasing high volume of SMS messages received. This paper presents SAMS a semi-automated message annotation system, which facilitates mobile communication with annotated messages. Two scenarios are presented showing that SMS messages can be answered automatically by software agent on behalf of mobile users. As a result, the workload of users in using SMS messages can be significantly reduced.