Catálogo de publicaciones - libros

We considered a network that consists of massively deployed tiny energy constrained sensors with one sink node to communicate with the outer world. The key challenge in design of wireless sensor networks is maximizing its lifetime. We explored this challenge and proposed our algorithm to increase a network lifetime. A node lifetime and numerical analysis show the comparison of the proposed algorithm with existing algorithm to increase a network lifetime. The proposed algorithm increases a critical node lifetime by 38% and hence a network lifetime.

A new wireless packet scheduling scheme is proposed to support differential services to different users over the forward wireless links whose transmission speed changes due to the ever-changing channel conditions. The scheme is intended to maximize the overall system satisfaction level using utility function. Internet applications of elastic, delay adaptive real-time, and rate adaptive real-time types are considered. Obtaining the optimal control scheme is a complicated problem, requiring detailed information on the channel statistics. Even if it were known, the computations would be significantly hampered by the curse of dimensionality. So, a heuristic method, which can run online, is proposed and its performance is evaluated.

The hybrid types of traffic containing traditional data and multimedia streams are delivered in networks. Besides the Best Effort service, Internet has to supply other different services to various types of traffic with multiple priorities. DiffServ architecture is considered to be the promising Internet framework meeting QoS requirements. One of crucial elements in DiffServ is its network node scheme. In this paper, we propose a novel scheme which combines dynamic buffer management with active queue management to assist routers in provisioning loss differentiated services. In order to support several levels of different traffic classes, we extend a dynamic threshold buffer management method in the case of multiple loss priorities. We detail the implementation of the scheme on routers. Simulation results confirmed that our scheme is able to adapt to load changing conditions and offer different guarantees for hybrid traffic flows in terms of their loss priorities.

Numerous research in the literature has convincingly demonstrated the widespread existence of self-similarity in network traffic. Self-similar traffic has infinite variance and long range dependence (LRD) which makes conventional traffic prediction method inappropriate. In this paper, we proposed a traffic prediction method by combining RLS (recursive least square) adaptive filtering with wavelet transform. Wavelet has many advantages when used in traffic analysis. Fundamentally, this is due to the non-trivial fact that the analyzing wavelet family itself possesses a scale invariant feature. It is also proved that wavelet coefficients are largely decorrelated and only has short range dependence (SRD). In this paper, We investigate the computation characteristics of discrete wavelet transform (DWT) and shows that the algorithm is more favorable in time series prediction. The proposed method is applied to real network traffic. Experiment results show that more accurate traffic prediction can be achieved by the proposed method.

Previous works for the AF (Assured Forwarding) service in a Differentiated Service (Diffserv) network have no sufficient consideration on the proportional fairness of bandwidth share based on RTTs, the target rates, and the impact of UDP against TCP. In order to solve these problems, we propose the Fair Differentiated Service Architecture (FDSA), Target rate and RTT Aware Three Color Marking (TRA3CM), and Target Rate Based Dropping (TRBD) mechanisms. These mechanisms provide three color marking and proportional fair bandwidth share among flows by considering RTT, target rate, and UDP flows simultaneously. In the results of comparing the performance among existing and proposed mechanisms, the proposed mechanisms are able to mitigate the RTT and UDP effect better than the existing ones. In addition, the proposed mechanisms are shown to provide the fair bandwidth share proportional to various target rates.

In optical networks, traffic demands often demonstrate periodic nature for which time-overlapping property can be utilized in routing and wavelength assignment (RWA). A RWA problem for scheduled lightpath demands (SLDs) has been solved by combinatorial optimal solution (COS) and graph coloring, or heuristic sequential RWA (sRWA). Such methods are very complex and incurs large computational overhead. In this paper, we propose an efficient RWA algorithm to utilize the time disjoint property as well as space disjoint property through fast grouping of SLDs. The computer simulation shows that our proposed algorithm indeed achieves up to 54% faster computation with similar number of wavelengths than the existing heuristic sRWA algorithm.

This paper investigates the role of nodal degree (meshing degree) in optical burst switching (OBS) mesh networks using signaling protocols with one-way reservation schemes. The analysis is focused on the following topologies: rings, degree-three chordal rings, degree-four chordal rings, degree-five chordal rings, mesh-torus, NSFNET, ARPANET and the European Optical Network. It is shown that when the nodal degree increases from 2 to around 3, the largest gain is observed for degree-three chordal rings (slightly less than three orders of magnitude) and the smallest gain is observed for the ARPANET (less than one order of magnitude). On the other hand, when the nodal degree increases from 2 to around 4, the largest gain is observed for degree-four chordal rings (with a gain between four and five orders of magnitude) and the smallest gain is observed for the European Optical Network (with a gain less than one order of magnitude). Since burst loss probability is a key issue in OBS networks, these results clearly show the importance of the way links are connected in this kind of networks.

Optical Burst Switching (OBS) has intrinsically time-sensitive nature with the separation of the header and the payload. Thus, minute care for offset-time is definitely required, which has not been a highlighted issue in an existing OBS research. In this paper, we focus on the relatively early arrival of the data burst due to the excessive queueing delay of the burst control packet (BCP) under a heavily loaded network. We propose a new scheduling algorithm for the OBS control channel, the Offset-Time Compensation (OTC) algorithm to solve the early arrival problem incurring the data burst drop. In the OTC algorithm, the offset-time is determined by the existing static offset-time scheme and the proposed dynamic offset-time reflecting the offered load of the OBS network. scheme varying with the network condition. By scheduling the BCP, the OTC can reduce the data burst loss rate due to early arrival. With the dynamic offset-time scheme, the data burst loss rate decreases significantly and maintains regular rate regardless of the offered load. We also expend the OTC, QoS-Aware (QA) OTC to provides controllable QoS differentiation in terms of data burst loss rate due to early arrival. The service objective of higher class is satisfied even in a heavily loaded situation.

Previous researches are restricted to scalability or complexity of implementation and are occurred both a high transmission delay and a delay variation resulted from resource reservation over UMTS packet network. Moreover, these techniques are limited to guarantee quality of service over UMTS packet network because these don’t define mapping relation between service classes based on traffic characteristic to maintain consistent QoS characteristic between network elements in accordance with use different protocols and service domains. This paper proposes service architecture of a boundary node for design quality guaranteed network that be able to offer high-speed wireless multimedia service and a mapping algorithms based on traffic characteristic, also evaluates to verify reasonableness of mapping algorithms between service classes and proves excellence of quality guaranteed network.

NEMO basic solution supports network mobility by using a bi-directional tunnel between a mobile router and its home agent. Yet, the multiple levels of bi-directional tunnels in nested mobile networks lead to significant routing overhead (so-called pinball routing). Non-optimal routing increases bandwidth consumption and transmission delays. The current paper proposes Regional Information-based Route Optimization (RIRO) in which mobile routers maintain a Nested Router List (NRL) to obtain next hop information. RIRO supports nested mobility without the nested tunnel overheads. This is accomplished by using a new routing header, called RIRO Routing Header (RIRO-RH). RIRO has the minimum packet overhead that remained constant, irrespective of how deep the mobile network was nested, in comparison with two earlier proposed schemes – Reverse Routing Header (RRH) and Bi-directional tunnel between HA and Top-level mobile router (BHT).