Catálogo de publicaciones - libros

Time-Slotted Optical Burst Switching (TS-OBS) is one of the most promising next-generation transport network technologies. This paper proposes a time-slot assignment procedure using centralized control for TS-OBS networks. Our scheme attempts to improve burst contention resolution and optical channel utilization. Analysis and simulation results show that the channel utilization of the TS-OBS network is improved markedly at the expense of ingress buffering delay.

In next-generation wireless networks, OFDM is a potential key technology. Subcarriers in the OFDMA networks are scarce and valuable, operators should manage them efficiently by radio-resource management function. Several OFDMA subcarrier-allocation schemes and performance-evaluation methods have been widely studied, but very few studies focused on managing call blocking probability (CBP) and bandwidth utilization (BU). CBP and BU are two important performance measures, which respectively represent the quality of service for subscribers and the profit of operators. This paper proposes an evaluation model to accurately predict the subcarrier-allocation performance, especially in consideration of the CBP and BU. Theoretical and simulation results indicate that the model works. In addition, the CBP and BU are adopted to solve a subcarrier utilization-optimization problem, which can be applied in network planning and re-planning processes. The optimization problem uses given traffic load and specified maximum CBP constraint to maximize the BU by discovering the optimal number of subcarriers in a base station. Finally, operators may utilize the results to manage their subcarriers flexibly, and to improve their profitability.

The NGN convergence services will play an important role to consolidate the deployment of NGN at the initial phase. At the initial stage, scenario-based approach is expected to act as an efficient way to pre-design before the actual implementation of NGN, the subject for providing the convergence services to the customers. This paper first proposes a deployment model of the NGN convergence services. In this model, NGN-Service Providers (NGN-SP) interact with Service Coordination Function of NGN Service Stratum whereas NGN convergence service terminal equipments (NGN-CTE) provide convergence services to the end users after procedures in End User Service Composition Function. A service composition scenario for the convergence services will be introduced, using the model, to show the usefulness of the proposed deployment model to construct new convergence services on this scenario-based approach.

The Next Generation Network (NGN) has a multilayer logical construction. Network carriers use various tools in complex procedures to operate application servers on the NGN. We try to establish a method for operating application servers in a unified management environment. This method operates between the network layer, which manages applications. First, we select requirements to achieve a unified management environment for application server operation. Then, we select a test function and a monitoring function from operation functions, in an experiment to confirm the achievability of our method. We test the achievability of two application server functions, which supply web services in the experiments. Our method supplies these functions without programming and manual procedures.

This work presents the design and implementation of an optical transparent IP/WDM network testbed. The implemented software allows the characterization of the transport, control and management planes of the network. Furthermore, it was developed a graphic user network interface for the client/management relation in the optical network. We adopted a centralized the control and management planes, obtaining economy of resources and time performance. The transport plane physical model allows the simulation of transponders, amplifiers and OXCs. They are connected with the control and management plane through the use of UDP/IP protocol and using XML for supporting the information base. The control plane provides routing and protection in the event of data plane failures. The management plane has a functional structure based on fail management, on the network configuration program, on performance monitoring, on log of changes and on the access security system.

Recently, quality management of IP networks has become an important issue with the development of real-time applications such as IP-phones, TV-conferencing and video-streaming. Specifically, when voice data is mixed with various application data, there are worries that there will be a critical degradation in voice quality. In current management of voice quality, the general scheme is to monitor the voice quality using a preset threshold for the data. However, it’s not easy to set a proper threshold for data monitoring in each case, because the characteristics of the monitoring data become more diverse as networks become larger in scale and more complex. We propose an automatic change detection scheme that detects changes in the behavior of the monitoring data with changes in the traffic conditions, without any preset threshold. The essential concept of our scheme is the application of a statistical scheme to sequential data monitoring. We also demonstrate the effectiveness of our proposed scheme when applied to voice quality management.

We have previously proposed a diffusion-type flow control mechanism as a solution for severely time-sensitive flow control required for high-speed networks. In this mechanism, each node in a network manages its local traffic flow on the basis of only the local information directly available to it, by using predetermined rules. In addition, the implementation of decision-making at each node can lead to optimal performance for the whole network. Our previous studies show that our flow control mechanism with certain parameter settings works well in high-speed networks. However, to apply this mechanism to actual networks, it is necessary to clarify how to design a parameter in our control mechanism. In this paper, we investigate the range of the parameter and derive its optimal value enabling the diffusion-type flow control to work effectively.

In this work we propose an analytic framework for managing the optimal bandwidth required for a smooth playback of a stored video streaming service. First, we argue that the mean buffering delay in the node is minimized if the video packets are paced to a fixed interval at the beginning of the transfer. Second, we argue that an appropriate level of bandwidth has to be maintained so that neither buffer-underflow nor buffer-overflow occurs, via which a smooth playback of video stream can be maintained. From the numerical evaluation, we found that the paced packet stream experiences smaller delay than the original random packet stream. Next, we computed a range of bandwidth for a video stream so that neither buffer-underflow nor buffer-overflow occurs, and we showed that paced packet stream requires smaller bandwidth than the original random packet stream.

Recently, researchers have explored to provide a queue management scheme with differentiated loss guarantees for the future Internet. The Bounded Random Drop (BRD), known as the best existing scheme, is one of such efforts which guarantees strong loss differentiation to the level of traffic in the different service classes. Even though BRD has several benefits such as low complexities and good functionalities, we identify that it has some shortcomings such as low throughput, long queuing delays, and selection problem of optimal values of parameters. Specifically, the shortcomings stem from calculating drop probabilities based on the arrival rate estimation and dropping incoming packets randomly with calculated drop probabilities without considering the current buffer occupancy. A multiple queue management scheme based on differential drop probability, called MQDDP, is proposed to overcome BRD’s shortcomings as well as support absolute loss differentiation. This scheme extends the original Random Early Detection (RED), recommended by IETF for next generation Internet gateways, into multiple class-based queues by deriving the drop probability equations based on a queueing model. We also compare MQDDP to BRD for high traffic intensity and show that MQDDP has the better performance in terms of packet drop rate.

IP-based IMT Network Platform(IP) is an ubiquitous platform supporting mobility using two step IP address mode converting – IP host address(IPha) and IP routing address(IPra) – in a backbone network. Mobile Node(MN) in IP maintains its state as either active or dormant state, which is transferred to active state through Paging process when communication is required. In this paper, we proposed a Paging method using agent to resolve the problem of the conventional Paging method which transmits the Paging messages to all cells in Location Area(LA) resulting in the excessive use of network resources. Performance evaluation of the proposed method using NS-2 showed that the usage of network resources becomes more efficient by reducing Paging loads, especially under the condition of increased nodes.