Catálogo de publicaciones - libros

In Wireless mobile ad hoc networks, many unicast and multicast protocols depend on broadcast mechanism to finish control and route establishment functionality. In a straightforward broadcast by flooding, each node will retransmit a message to all it neighbors until the message has been propagated to the entire network. So it will become very inefficient and will be easy to result the broadcast storm problem. Thus an efficient broadcast algorithm should be used to less the broadcast storm caused by broadcast. Due to the dynamic nature of ad hoc networks, global information of the network is difficult to obtain, so the algorithm should be distributed. In this paper, a distributed heuristic-based algorithm is presented. The algorithm is based on joint distance-counter threshold scheme. It runs in a distributed manner by each node in the network without needing any global information. Each node in an ad hoc network hears the message from its neighbors and decides whether to retransmit or not according to the signal strength and the number of the receiving messages. By using the JDCT algorithm, it’s easy to find the nodes that consist of the vertices of the hexagonal lattice to cover the whole networks. The algorithm is very simple and it is easy to operate and has a good performance in mobile wireless communication environments. A comparison among several existing algorithms is conducted. Simulation results show that the new algorithm is efficient and robust.

In hierarchical mobile IPv6 networks, when an inter-domain handover occurs, mobile nodes suffer from excessive signaling traffic and long handover latency. Further, the selection of MAP and its load status critically affect the overall system performance. Therefore, we propose a dynamic MAP selection scheme that seeks to distribute load among MAPs as well as reduces inter-domain handovers. Performance is evaluated from not only an analytic model of average signaling cost but also a simulation. The analytical and simulation results show that our proposed scheme improves load distributedness and reduces inter-domain handovers and signaling cost compared to another existing approach.

Digital fingerprinting is a technology for enforcing digital rights policies where by unique labels, known as digital fingerprints, are inserted into content prior to distribution. As we use it, we can trace illegal users. These fingerprints are typically embedded into the content using watermarking techniques that are designed to be robust to a variety of attacks. Also, it must secure against collusion attack that some colluders remove and alter their fingerprints. In this paper, we propose easily fingerprint generation technique by using of primitive polynomial. The proposed scheme can generate codes more easily and have more buyers than existing schemes. Our scheme is secure against collusion attack with two colluders. And we proposed a new watermarking algorithm that embeds and extracts securely by using MPSK(M-ary Phase Shift Keying) technology. The proposed watermarking algorithm has . Therefore it is effective in conspirator detection.

With the rapid development of wireless multimedia communication and Peer-to-Peer overlay network, it is envisioned that building a content and location addressable overlay network for wireless multimedia communication is promising. In this paper, based on a special structure, Geographically Hierarchical Index (GHI), we propose an efficient algorithm, Content and Location Addressable overlay Network (CLAN) algorithm, which makes p2p multimedia communication over MANETs applicable and efficient, satisfying three goals: efficiency, scalability and adaptability to node movement.

The roles of application program sharing are divided into two main parts; abstraction and sharing of view generation. Application program sharing must take different from each other according to number of replicated application program and an event command. There are two different structures. Those include CACV (Centralized-Abstraction and Centralized-View) and RARV (Replicated-Abstraction and Replicated-View).In this paper, we discuss a hybrid software architecture CARV(Centralized-Abstraction and Replicated-View) which is running on ubiquitous networks for collaborative multimedia distance education services and adopting the advantage of CACV and RARV.

In this paper, we propose an asymmetric link dynamic routing algorithm for ubiquitous multimedia services named DRAMA (Dynamic Routing Algorithm for asymmetric link in Mobile Ad hoc networks). The proposed algorithm allows a first sink node of the unidirectional link to detect the unidirectional link and its reverse route and provide information regarding the reverse route to other sink nodes, thereby minimizing unnecessary flows and effectively using the unidirectional link. DRAMA also incooperates redirection process that actively supports a unidirectional link generated during data transmission to deal with a topology change due to the movement of node. Further, we shows the superiority of DRAMA to the existing algorithms in terms of a delay in data transmission, throughput, and transmission overhead through simulation study.

In this paper, we propose a building detection algorithm for video based navigation system which overlays driving directions on the captured video from in-vehicle camera. We used edge segments of small size blocks within an image frame to remove background objects, trees, etc. Search range determination and edge tracing technique were also developed to determine the building area as the final step. The experiments show 88.9 % detection rate on the average and 95.9% for navigation video without trees and signs. The proposed algorithm can be also applied to point-of-interest (POI) detection for location based services (LBS) in ubiquitous computing environment.

In this paper, we propose local authentication scheme to locally authorize intra-domain mobile nodes (MNs) for efficient authentication in Mobile IPv6 networks, which are based on authentication, authorization, accounting (AAA) architecture. Frequent authentication requests in standard AAA mechanism impose a great burden to deliver the authentication messages between a MN and its AAA server. To solve this problem, we propose this scheme to establish local security associations (SAs) for authentication, so the proposed scheme reduces delay and the risk during MNs roam around a local domain. The performance evaluation results show that the proposed scheme reduces the latency up to 60.7% while maintaining the similar level of security to the previous researches.

IEEE 802.16e standard specifies sleep mode to achieve low power consumption of a mobile station (MS). Since sleep mode is defined only for the current serving base station (BS), a sleeping MS in motion performs handover even if it has no active connection. Accordingly, the power saving efficiency of sleep mode may be severely degraded in a mobile environment. In order to cover the problem, the IEEE 802.16e standard specifies a method that optimizes the sleep mode initiation process specific to handover. With the optimization, a MS that has been in sleep mode and currently performs handover is able to resume sleep mode as soon as it completes the handover process with no additional request. This paper justifies the use of the optimization by showing the simulation results that evaluate the performance gain obtained from the optimization.

This paper develop the complexity reduction schemes of real root method that is mainly used in the CELP (Code Excited Linear Prediction) vocoder. The real root method is that if polynomial equations have the real roots, it is able to find those and transform them into LSP (Line Spectrum Pairs). Proposed algorithm is developed by using Mel scale and is to reduce the LSP complexity That is, the searching interval is arranged by using Mel scale but not it is uniform. In experimental results, complexity of the developed algorithm is reduced about 46% in average, but the transformed LSP parameters of the proposed method were the same as those of real root method. Hence, in case of applying proposed algorithm in G.723.1 (6.3kbps MP-MLQ), the speech quality is no distortion compared to original speech quality.