Catálogo de publicaciones - libros

In this paper, we propose a toolkit, wear-UCAM, which can support mobile user interactions in smart environments through utilizing user’s context. With the rapid developments of ubiquitous computing and its relevant technologies, the interest in context-aware applications for mobile/wearable computing also becomes popular in both academic and industrial fields. In such smart environments, furthermore, it is crucial for a user to manage personal information (health, preferences, activities, etc) for the personalized services without his or her explicit inputs. Regarding reflection of user’s context to context-aware applications, however, there are only a few research activities on such frameworks or toolkits for mobile/wearable computers. In the proposed wear-UCAM, therefore, we focus on a software framework for context-aware applications by taking account of how to acquire contextual information relevant to a user from sensors, how to integrate and manage it, and how to control its disclosure in smart environments.

In this paper, we propose a Sensing Resolution-based Energy Efficient (SREE) communication protocol for wireless sensor networks. SREE is intended for meeting the application’s sensing objectives, where sensor nodes are densely deployed and have the determinate accuracy requirement. The primary contribution of this paper is active group head node selection with round-robin procedure, which increases the sensing accuracy and distributes the nodes energy consumption. The second contribution is using energy efficient intermediate node selection by considering both group size and energy consumption. We present the design of SREE and provide simulation results.

Wireless sensor networks is a key technology for new ways of interaction between computers and the physical environment. However, the energy constrained and limited computing resources of the sensor nodes present major challenges in gathering data. Since sensor nodes are densely deployed, redundant data may occur. While cluster-based data gathering is efficient at energy and bandwidth, it’s difficult to cluster network efficiently. In this work, a new distributed clustering algorithm for ubiquitous sensor network is presented. Clustering is based on the distance between nodes and the number in a cluster for wireless sensor networks. Simulation results show that the proposed algorithm balances the energy dissipation over the whole network thus increase the amount of data delivery to the sink.

As the demands for Internet connectivity of ad hoc networks are consistently increasing, the interconnection of Mobile Ad hoc Networks (MANETs) to fixed IP networks is emerging as an issue with considerable attention in the literature [2,3,4]. Here, we focus on connecting MANETs to the Internet by integrating Mobile IPv6. Many previous studies are suffered from some limitations that the dynamic addressing and routing protocol are not suitable in high mobility MANETs. The proposed scheme is based on the prefix delegation method in order to reduce tunneling overhead by ingress filtering and avoid unnecessary address changes. By using this method, MANETs organize a virtual hierarchical architecture for efficient gateway discovery and the optimal routing in high mobility. Comprehensive computer simulation presents that the newly proposed scheme shows up to about 50% better performance in terms of delay and signaling overhead in comparison with existing protocols.

Recently, IETF has standardized Mobile IPv6 (MIPv6) and Hierarchical Mobile IPv6 (HMIPv6) for supporting IPv6 mobility. Even though existing literatures have asserted that HMIPv6 generally improves MIPv6 in terms of handover speed, they do not carefully consider the details of the whole handover procedures. In this paper, based on the current IETF standards of both MIPv6 and HMIPv6, we conduct a comprehensive study of all IP-level handover procedures. We also provide a mathematical analysis on MIPv6 and HMIPv6 performance in terms of handover speed, and reveal that the average HMIPv6 handover latency is not always lower than the average MIPv6 handover latency. A vital finding of our analysis is that some optimization techniques for movement detection and duplicate address detection are essential to increasing the benefit of HMIPv6.

We analyze the performance of MAC-layer Reed-Solomon error-recovery in the cdma2000 1xEV-DO Broadcast and Multicast Services (BCMCS) environment, with respect to the size of the error control block (ECB) and the air-channel condition, and establish the relationship between ECB size, error-recovery capacity and service latency. Real-time traffic, such as voice and video streaming, is very sensitive to delay, but can stand a certain level of packet loss. We therefore propose an adaptive error-recovery scheme which adjusts the size of the ECB to reflect the environment of the mobile nodes so as to meet the required service quality (target bit error-rate), while reducing the latency of real-time applications, decoding complexity, and memory requirement. Extensive simulation results show the effectiveness of our adaptive approach compared to the current static scheme. Our scheme achieves near-optimal service latency while meeting the target service quality criterion, and also reduces energy consumption during error recovery.

White board sharing between PC and PDAs is a typical interactive application between PC and mobile device in ubiquitous environment. Due to the limited size of PDA’ s screen, when a large amount of clients simultaneously use PDAs to share the server’s screen while their viewed areas (or ) are different in size and position, the server must transform the viewports to fit the size of PDA for each client and thus will suffer from heavy burden. A novel approach is proposed in this paper to reduce the burden of the server and provide the clients with real time white board sharing. Instead of zooming the viewport to fit PDA’s screen for every user, it only zooms the screen nine times; then, chunked encoding is adopted to reduce the cost for encoding the overlapped area of different viewports. The experiment results have demonstrated the efficiency and effectiveness of our approach.

Mobility support in the wireless network enables us to be served continuous service. Fast Handover for Mobile IPv6 (FMIPv6) is proposed to support a faster handover than that of Mobile IPv6. Unfortunately, FMIPv6 shows too long handover latency to serve smooth video traffic flows. We proposed semi-soft FMIPv6 handover to minimize the handover latency to serve video traffic efficiently. The proposed scheme clarifies the handover procedure by separating the handover preparation and the actual handover. We also clarify the use of L2 triggering by introducing four triggers and triggering time scheme. With our experimental implementation, the proposed scheme has shortened the handover latency below 50ms and this low handover latency helps to reduce the buffered packet size in access routers.

When Mobile IPv6 is deployed in commercial network, a mobile node needs AAA services for authentication, authorization and accounting. AAA and Mobile IPv6 are operated independently. Hence schemes which merge these protocols have been emerged. These schemes enable the mobile node to establish a security association between the mobile node and a home agent, and to perform a home binding update during AAA authentication procedure. But these schemes introduce lots of signal messages and long handover latency during the handover, since Route Optimization mode for Mobile IPv6 is performed using Return Routability procedure. To solve this problem, we propose an optimized scheme which performs Route Optimization mode via the AAA infrastructure between the home agent and a correspondent node instead of Return Routability procedure. For performance evaluation, we analyze handover latency in three scenarios. We then show that the proposed scheme reduces handover latency like the average of 58% compared with the existing scheme.

The interoperation of home electronic devices and mobile devices has been demonstrated employing a Jini-agent system. The agent system enables a resource-limited mobile device to support a Jini network service by using a web browser of the mobile device without any additional client program installation in it. It provides the lies of services existing on different networks simultaneously, which facilitates the users to utilize various Jini network services in real time and enables the interworking between home and mobile networks.