Catálogo de publicaciones - libros

Data schedule in broadcasting is playing a more importance role due to increasing demand for large client popularity and vast amount of information. For system with multipoint queries, data records which queried by same query are broadcasted contiguously to reduce the average access time. Several techniques have been used in clustering data by defining the affinity between them. The data affinity function defined was mainly aiming at minimizing the linear Query Distance. However, our work showing that in order to minimize the average access time, the objective function shall be in quadratic form. We propose a algorithm() which merge relevant segments base on this new affinity function. Through extensive experiments, the results show not only the query’s access time can be reduced by using this new affinity function, by using a dummy segment to speed our algorithm, the scheme we proposed have significant saving on both time complexity and memory space complexity.

Network mobility (NEMO) basic support protocol maintains the connectivity when mobile router (MR) changes its point of attachment to the Internet by establishing a bidirectional tunnel between MR and Home Agent (HA). However, it results in pin-ball routing and multiple encapsulations especially in the nested NEMO. In order to solve these problems, we propose a simple route optimization scheme for NEMO and nested NEMO. In the proposed scheme, a correspondent node (CN) maintains network prefix binding information of intermediate MRs to obtain optimal path to the mobile network node (MNN). For a CN to receive network prefix bindings, each intermediate MR updates its network prefix binding to the inner source of the encapsulated packet, when it receives an encapsulated packet from its HA. The proposed scheme uses the routing header type 0 (RH0) and the routing header type 2 extension (RH2 extension) to deliver packets to the MNN through the optimal path and to remove multiple encapsulations. In addition, we extend the Router Alert Option (RAO) so that the MR knows the original source address of the packet, when ingress filtering is applied.

Mobile IPv6 is the IETF proposition to support host mobility in the Internet. It provides routing optimization for packets sent to the mobile node at the expense of signaling messages that are periodically sent to the correspondent of the mobile node. We propose using XCAST, a multicast technique best designed for small groups, as a means to decrease this signaling. XCAST records the addresses of all the destinations in the packet itself. We evaluate the performance of our proposition against Mobile IPv6 route optimization. We obtain good results even when a very few routers, well located in the network, are able to process the extension.

Bandpass sampling is a useful digital method for direct downconversion without analog mixer. Therefore, this sampling method is essential for the software-defined radio (SDR) system to be required minimization of RF front-end. Also, the bandpass sampling system can be extended to accommodation of multiple standards for the future wireless communication systems. This paper proposes a novel downconversion scheme for multiple standards based on a complex bandpass sampling method. It includes generalized formulae derivation for the available sampling range, the signal’s intermediate frequency (IF) and the minimum sampling frequency for the multiple RF signals. And we verify from simulation results that the proposed system is more flexible and suitable than a real bandpass sampling system.

In this paper, we propose an enhanced traffic marker (ETM) to amend the inappropriate marking in DiffServ networks. The ETM is based on the Two-Rate-Three-Color-Marker (TRTCM) scheme and introduces the feature of aggressive promotion and fair share marking. Simulation results show that the ETM fairly allocates bandwidth among micro-flows and achieves a higher throughput than TRTCM does.

This paper presents the fuzzy logic-based control structure for incoming traffic from an arbitrary node to provide admission control in a policy-based IP network management structure. The proposed control structure uses a scheme for deciding the network resource allocation depending on the requirement of predefined-policies and network states. The proposed scheme enhances policy adapting methods of existing binary methods, and can use resource of network more effectively to provide adaptive admission control, according to the unpredictable network states for predefined QoS policies. Simulation results show that the proposed controller improves the ratio of packet rejection up to 17%, because it performs the soft adaptation based on the network states instead of accept/reject actions in a conventional CAC(Connection Admission Controller).

Even though several RSVP extensions have been proposed to support QoS guarantee in mobile Internet, they still suffer from issues such as excessive advanced reservations or a nonoptimal path generated by Mobile IP. We propose an algorithm called “Link Layer Assisted Multicast based Mobile RSVP (LM-MRSVP)” to resolve the issues. Our implementation shows practicability of our proposal and the simulation study confirms our claims.

Traffic Engineering aims to optimize the operational performance of a network. This paper focuses on multipath routing for traffic engineering that routes the demand on multiple paths simultaneously for balancing the load in the network. According to the schematic approach of multipath routing that we propose in this paper, a multipath routing algorithm selects candidate paths using multicriteria simultaneously and then distributes the traffic demand among selected paths. Among multipath routing algorithms, we select four algorithms which fit our expectations in terms of architecture: WDP, MATE, multipath-AIMD and LDM. We focused exclusively on technologies designed for MPLS networks. Each algorithm is compared with respect to complexity and stability of two stages: the computation of multiple paths and the traffic splitting among multiple paths.

The current Internet does not offer any quality of service guarantees or support to Internet multimedia applications. There are two requirements of multicast sending rate for Internet DTV: (1) it can adapt well to the change of network congestion; (2) it can meet the requirements of decoding rate. The difficulties of Internet DTV stream multicast are analyzed, then a multicast rate control approach for network DTV stream based on buffer management is given, which can suit for the change of network traffic and satisfy the requirement of DTV decoder by controlling sending rate logically. The test results show the good practical value.

Multi-hop ad hoc wireless networks generally use the IEEE 802.11 Distributed Coordination Function (DCF) MAC protocol, which utilizes the request-to-send/clear-to-send (RTS/CTS) mechanism to prevent the hidden terminal problem. It has been pointed out that the RTS/CTS mechanism cannot completely solve the hidden terminal problem in ad hoc networks because the interference range could exceed the basic rate transmission range. In this paper we provide a worst-case analysis of collision probability induced by the hidden terminal problem in ad hoc networks with multi-rate functionality. We show that the interference caused by the nodes in the area that is not covered by the RTS/CTS is bounded by ′, where ′ is a constant and is the distance between the two transmitting nodes. The analytic result showed that the interference could shorten the data transmission range up to 30 percent. We then propose a simple multi-rate MAC protocol that could prevent the hidden terminal problem when transmit power control (TPC) is employed.