Catálogo de publicaciones - libros

This thesis intends to suggest how to produce adaptable contents that can be replayed on a device by extracting web contents in order that an existing web page can be replayed by using a device that can replay multimedia technology such as mobile and TV. To perform a service by using MobileGate system and adaptively converting one HTML page existing on web to a device, a page defined as DIDL in MPEG-21 is used. To use numerous amount of web contents in a device having a limited interface, by extracting a contents through DFS method, Circular Doubly-Linked List is established and served. DIDL of average 18 pages to minimize scroll in one web page is generated and all contents on web can be approached and replayed by only up and down button. In this research, web contents service that can be offered by using PC can be offered from mobile and TV device that are under ubiquitous environment.

In the last year, the Internet engineering task force (IETF) adopted the network mobility (NEMO) basic support protocol (NBS) as a request for comments (RFC) to make possible Internet access services on mobile networks. Even though the NBS has opened a new era in NEMO, its long handoff latency should be solved for the support of seamless services. In this paper, we propose a cross-layer scheme using modified reassociation frame to reduce handoff latency in the presence of movements of both the network and the nodes. In addition, the proposed scheme introduces use of a cache to manage the addresses of the mobile nodes (MN) and the mobile routers (MR), and assigns a unique address to each MN or the network based on the information in the cache. We compare the performance of the proposed scheme with those of MIPv6, FMIPv6, and HMIPv6. From the results, the handoff latency of the proposed scheme is lower about 30-80% than those of other algorithms. In addition, the proposed scheme shows 56% higher cost efficiency than others.

In mobile computing system, user location management is one of the most important issues. Conventional IP paging protocols deliver paging request packets without careful consideration of residence pattern of mobile users. In this paper, we propose quick paging IP scheme utilizing the residence pattern of Mobile Node. Paging the whole paging area might incur huger overhead than paging a few subnets. Since the number of frequently visited locations would be small compared to the number of subnets in whole paging area, we deploy xcast in our scheme. For the performance evaluation, we develop an analytical paging cost model to compare the overall cost of our scheme and the cost of Paging Extensions for Mobile IP scheme. The results indicate that the proposed scheme gains about 47% of improvement at its best.

Mobile IPv6 (MIPv6) is protocol to support mobility with no restriction of a mobile node (MN)’s geographical location in the network. However, MIPv6 has weak points, such as handover latency resulting from movement detections, IP address configurations and location updates which is unacceptable in real-time application. To make up for it, IETF considers fast mobile IPv6 (FMIPv6) and hierarchical mobile IPv6 (HMIPv6). FMIPv6 aims to reduce handover latency and data loss. HMIPv6 aims to manage the MN’s mobility and reduce handover latency. Since the FMIPv6 and HMIPv6 provide the fast micro mobility scheme when the MN moves between access routers within same mobility anchor point (MAP), they are not appropriate for the macro mobility when the MN moves between the MAPs. Besides, the macro mobility using these schemes will not provide mobile devices with seamless service, which causes packet losses. To make up for it, the efficient macro mobility scheme supporting fast handover has been proposed However, if the MN does not receive a fast binding acknowledgement (FBACK) message before L3 handover, the packets destined to the MN are lost during L3 handover. In this paper, we propose an efficient macro mobility supporting reactive fast handover mode to reduce packet loss when the MN does not receive the FBACK message before L3 handover. We adopt the fast handover method from FMIPv6 (fast MIPv6) for proposed scheme.

The access scheduling on the control channels in TDMA wireless mesh networks is studied in this paper. The problem is to assign time-slots for each node in the network to access the control channels so that it is guaranteed that each node can broadcast the control packet to any one-hop neighbor in one scheduling cycle. The objective is to minimize the total number of different time-slots in the scheduling cycle. The original contributions of this paper are that it has taken the large interference range problem into consideration for the first time and proposed two algorithms for the scheduling problem, namely, the Speak Once algorithm and the Speak Separately algorithm. We prove that the number of time-slots by the second algorithm is upper-bounded by min(, 2) in some special cases, where is the node numberand is the maximum node degree. The fully distributed versions of these algorithms are given in this paper. Simulation results also show that the performance of the Speak Separately algorithm is rather better than that of the Speak Once algorithm.

In this paper, a distributed Predictive Bandwidth Reservation scheme based on Road Topology Information (PBR-RTI), and Call Admission Control (CAC) algorithms are proposed. The goal is to reduce the Handoff Call Dropping Probability (HCDP), New Call Blocking Probability (NCBP) and to improve the bandwidth utilization. In the PRB-RTI scheme, we assume that Base Stations (BSs) are equipped with road-topology information and some Mobile Terminals (MTs) have positioning capability, while others MTs do not. The BSs estimate the probability that the MTs will enter the neighboring cells based on their factors (location, direction and speed of the MT) which are estimated by global Positioning System (GPS) and/or Received Signal Strength (RSS) and the road-topology information stored in the BSs. The BSs then compute the amount of bandwidth to be reserved, based on such estimation. Simulation results show that PRB-RTI is capable of keeping low rate for HCDP and NCBP and allocating bandwidth to new/handoff calls efficiently.

The sensors in sensor networks have limited energy and thus energy preserving techniques are important. The low-energy adaptive clustering hierarchy (LEACH) technique improves energy efficiency of the sensor network by selecting a cluster head, and having it aggregate data from other nodes in its cluster and transmit it to the base station. In this paper, we propose three techniques, which we will call collectively Energy Efficient LEACH (EEL), that improve on LEACH to significantly reduce energy consumption and increase the lifetime of the sensor network. Simulation results using the NS-2 network simulator show that EEL improves LEACH by 37% with respect to network lifetime.

In nested mobile networks with NEMO basic support protocol [3], the pinball routing problem occurs because since it is based on bi-directional tunneling between the mobile router (MR) and its home agent (HA). In addition, the nodes in the same mobile networks cannot communicate with each other when the network is disconnected from the Internet. In this paper, we propose a route optimization with additional information to solve these problems. For this we employ a new IPv6 routing header, named the destination-information header instead of routing header type 2 to optimize the route in the nested mobile network. The proposed scheme shows at least 32% better performance than ROTIO [4] and similar performance to DBU [5] in inter-NEMO route optimization. With respect to intra-NEMO route optimization, the proposed scheme always has the optimal routing path.

User requirements have been changed during development progresses, since they are impossible to define all of software requirements. These requirements change leads to mistakes because the developers cannot completely understand the software structure and behavior, or they cannot discover all parts affected by a change. Therefore, requirement changes have to be managed and assessed to ensure that they are feasible, make economic sense, and contribute to the business needs of the customer organization. We propose requirements change management process on feature-oriented requirements tracing. It is based on value analysis and feature-oriented requirement traceability links. Our approach offers two contributions to the study of requirements change: (1)We define a requirements change tree model to make user requirements change request generalize by feature level. (2)We provide overall process such as change request normalization, change impact analysis, change request alternative design, change request implementation, and change request evaluation. In addition, we especially summarize the results of a case study which is carried out in asset management portal system.

Spatio-temporal modeling for urban applications has received special attention lately. Due to the recent advances in computer and geospatial technologies, the temporal aspect of urban applications which was ignored in conventional systems, is under consideration nowadays. This new interest in spatio-temporal modeling, in spite of all its deficiencies, has brought about great advances in spatio-temporal modeling and will enhance the urban systems dramatically. This paper investigates two different viewpoints in spatio-temporal modeling for urban applications. The first category involves CA based modeling, agent based modeling, Artificial Neural Networks modeling and fractal based modeling. These models which have been widely used in simulating complex urban systems are here distinguished as complexity models. The applications of these approaches in modeling complex urban systems are comprehensively reviewed and advantages and weak points of each model are depicted. On the other hand, temporal GIS models as another approach for spatio-temporal modeling are briefly reviewed. Eventually the conceptual differences between these two categories are mentioned to aid modelers to mindfully select the appropriate models for urban applications.