Catálogo de publicaciones - libros

Various network technologies have been developed towards ubiquitous computing. Actually, the specific network technology has its own protocol layer, characteristics and objectives. Due to these limitations, though cellular network and WPAN are being used in handset together, the services using both networks are not so popular until now. This paper presents a platform design integrating cellular network and WPAN and its application to the mobile game service. To develop services and applications which utilize cellular network and WPAN, we discuss the WPAN platform for handset. Various aspects are considered on the connection, which can expand the area of mobile services and applications. An illustrative application of this platform is introduced as a mobile game service. In the proposed game service, downloading games or game items, managing players, etc. are provided using cellular network. The actual game traffic between players utilizes WPAN. As shown in the proposed game service design, various applications are being expected through the WPAN platform.

Owing to the inflexibility of the structure, the conventional layered protocols suffer from the inability to distinguish between losses due to route failures and congestion. Recently, in efforts to overcome the challenges of dynamic environment in ad hoc networks, there have been increased interests in protocols that rely on interactions between different layers. In this paper, we propose a cross-layer architecture combining the three layers of data link, network, and transport in order to provide reliable transporting and optimal routing on rate-based, termed as RTOR. In accordance with the rate computed at MAC layer, a path with the optimal rate is selected at network layer. While the flow control and reliability is performed by the determination of transmission rate and SACKs at transport layer, respectively. The transport protocol herein is not a variant of TCP but a rehash. In flow control, the transmission rate is adjusted by rate feedback instead of AIMD congestion windows. In reliability, SACK blocks appended to feedback packet are used rather than implication of packet lost by duplicate ACKs. In addition, choosing a path with the optimal rate can balance the network load in an appropriate degree. The evaluation results clearly indicate the significant performance improvement that RTOR provides over default TCP, TCP-ELFN, and ATP.

While web service technology is becoming a de facto standard for integration of business applications, it is also rapidly emerging as an effective means for achieving inter-operability among the devices in network centric ubiquitous systems. When such a web service enabled device engages in a conversation with a service provider, it becomes necessary to define an interaction logic required between them. For this purpose, one can use a choreography language to specify the rules of engagement between the device and the web service provider. This paper presents a framework for automatically synthesizing conversation protocols from a choreography description defined in WS-CDL. The proposed framework adopts WSCL as a conversation protocol language, and defines a set of rules that can be used to effectively transform a WS-CDL specification into WSCL documents for collaborating peers. It is expected that the work presented in this paper can enhance the interoperability between web service-based processes in ubiquitous systems through automating the process of extracting conversation protocols from a choreography definition.

In this paper, a network-centric subcarrier allocation method is proposed for triple-sectored Orthogonal Frequency Division Multiple Access (OFDMA) systems. The proposed method is based on a network-centric algorithm that is located in a base station (BS) and coordinates the subchannel allocation of each sector. This method controls the resources (subchannels) allocated to each sector, not to waste available bandwidth and avoid inter-sector interference as much as possible. Two methods are suggested for the subchannel allocation method and the detailed algorithms for each method are provided. Simulation results show that the suggested method achieves better throughput than the distributed subchannel and adjacent subchannel configuration methods under a proportional fair algorithm.

Sharing files discovery is a fundamental problem in P2P networking. This paper presents a name-based approach for identifying sharing file correspondences in multilingual P2P systems. The problem is first analyzed through comparing the names of the sharing files in different nodes of a real P2P community, which name those files in different languages. Then based on the relationships of those files names, a computer-aided method is proposed to solve the problem. Furthermore, the framework and identifying procedure of this method have been discussed in the paper.

Gigabit Ethernet has become the main cluster interconnection for its low price and well backward compatibility. But the communication performance through Gigabit Ethernet is quite disappointing due to its performance discre- pancies between the hardware and the communication software. To achieve over two-third physical bandwidth of a gigabit network interface, zero-copy protocol architecture is absolutely necessary. Unfortunately, it is impossible to realize true zero-copy communication over non re-programmable commodity Gigabit Ethernet adapters because the DMA engines cannot separate the protocol headers from the payload data directly. This paper introduces LM (Lightweight Messages), a true zero-copy communication mechanism which combines the application level fragmentation scheme with the driver level defragmentation scheme, for existing non-programmable Gigabit Ethernet adapters. Finally, experimental results show that LM can provide better performance than other lightweight communication approaches over commodity Gigabit Ethernet.

Evaluating the efficiency of unguided search based on random walk in unstructured peer-to-peer networks is important because it provides guidelines in correctly setting the parameters of the search. Most existing work is based on simulations. We evaluate two analytical models – the algebraic model and the combinatorial model – for various search efficiency metrics against simulation results. We use the random graph topology and assume unguided searches. The results show that the two analytical models are accurate and match each other closely. We study the impact of the average node degree, hop count, number of walkers, and replication ratios on node coverage, object recall, and message efficiency, and on the accuracy of the models.

A middleware in ubiquitous computing environment (UbiComp) is required to support seamless on-demand services over diverse resource situations in order to meet various user requirements [11]. Since UbiComp applications need situation-aware middleware services in this environment. In this paper, we propose a semantic middleware architecture to detect errors, analyze causes of errors, and plan semantically meaningful strategies to deal with a problem with associating fault and service ontology in UbiComp environment. We implemented a referenced prototype, Web-service based Application Execution Environment (Wapee), as a proof-of-concept, and showed the efficiency in runtime recovery.

A fundamental feature of Peer-to-Peer (P2P) networks is the honest collaboration among an heterogeneous community of participants. After success –the first P2P file sharing application massively used–, advances in this area have been intense, with the proposal of many new architectures and applications for content and computing sharing, and collaborative working environments. However, the inherent differences between the P2P model and the classic client-server paradigm cause that many security solutions developed for the latter are not applicable or, in the best case, have to be carefully adapted. In this paper, we present a survey on security issues in P2P networks, providing a comparative analysis of existing solutions and identifying directions for future research.

The envisioned realization of ubiquity has resulted into the emergence of new kinds of the hybrid networks. The modern hybrid networks, e.g. combination of wireless mesh and Mobile Ad-hoc Networks (MANETs), help realize ubiquity through spontaneous networking. The network management for these hybrid networks is different from conventional and infrastructure based network management. Heterogeneity, mobility, dynamic topologies, physical security, and survivability make the challenge hard. A new class of management called self-management can effectively be used to cater for the autonomous behavior of hybrid networks We present HYbrid WIreless Network Management ARChitecture (HYWINMARC), a three-tier framework, covering all the management levels, for autonomic network management for hybrid networks. We integrate policy-based network management with mobile-agent technology and design a prototype for a context-aware and self-managing architecture. The context information is collected, from all levels in network hierarchy through monitoring agents, and is used to apply needed self-management operations that include self-optimization, self-healing, self-configuration, and self-growing.