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Date 20-22 Oct. 2010

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Displaying Results 1 - 25 of 79
  • [Title page]

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  • Analyzing the potential of cooperative Cognitive Radio technology on inter-vehicle communication

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB) |  | HTML iconHTML  

    Recent studies demonstrate that Cognitive Radio (CR) technology can increase the spectrum efficiency of wireless systems, provided that the activity of primary users (PUs) must be carefully protected. For this reason, several sensing schemes leverage the cooperation among nodes to increase the accuracy of PU detection. In this paper, we propose to employ the CR principles in the vehicular environment in order to increase the spectrum opportunities for inter-vehicle communication (IVC). We propose a cooperative sensing and spectrum allocation scheme through which vehicles can share information about spectrum availability of TV channels on their path, and dynamically decide the channels to use on each road segment. Moreover, we investigate the role of vehicular mobility in the cooperation process, which might allow a vehicle to know in advance the spectrum availability on future locations along its path. Simulation results confirm the ability of our scheme in providing robust PU detection under fading conditions, and analyze the impact of some vehicular networks characteristics into the operations of CR systems. View full abstract»

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  • A multipath traffic balancing proposal to reduce gaming disconnections in MANET

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (100 KB) |  | HTML iconHTML  

    In this work, we aim to improve the gameplay of time-sensitive video games over MANETs. We focus on disconnections problem. Precisely, if the path between a game client and the server breaks, the game on the player side freezes and becomes unplayable until that the network re-establishes the path toward the server. In MANETs, these disconnections occur mainly because of nodes mobility. To overcome this problem, we propose in this paper a multipath approach, which will compute for each source-destination couple two paths. The first path is constructed using end-to-end delay metric. The latter has a well-known impact on the gameplay of time sensitive multiplayers games. The second path is constructed once we have removed from the topology the link in the first path with the lowest ETX value. An adaptive traffic balancing algorithm is also considered. The proportion of traffic carried by each path depends on its robustness. The results for our experiments, which are based on a real implementation of our proposals, show that using multipath and balancing traffic among different paths reduce routes failures and thus improves the gameplay. View full abstract»

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  • Vehicular congestion modeling and estimation for advanced traveler information systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (374 KB) |  | HTML iconHTML  

    It is widely accepted that the steady increase of urban vehicular congestion requires the implementation of adequate countermeasures. Intelligent Transportation Systems (ITSs) represent one of the possible solutions, as they strive to optimize the use of the available road network resources. Within this domain, the Advanced Travel Information Systems (ATISs) specifically address the vehicular congestion problem as they provide travelers, by means of a wireless channel, with updated road information. On receiving such information, travelers use their onboard Personal Navigation Devices (PNDs) to decide the best route to their destination. Clearly, ATISs become increasingly reliable the more they accurately identify the roads that are congested. We here propose a new model for detecting congestion that supports the accurate estimation and short-term forecasting of the state of a road to be used with ATISs. Such model can be generally applied to any type of street, as it does not require any a-priori knowledge, nor an estimate of any street parameter. We present the results of several experiments, performed on different urban roads, which confirm the efficacy of our proposal. View full abstract»

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  • Spectral and energy efficiencies of OFDMA wireless cellular networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (119 KB) |  | HTML iconHTML  

    We study in the present paper the spectral efficiency of OFDMA cellular networks which is a classical indicator of their performance usually calculated by simulations. On the other hand, due to an increasing interest on the environmental impact of these networks, we study also their energy efficiency which may be defined as the ratio of the spectral efficiency and the consumed energy. We give an explicit expression of the signal to interference and noise power ratio (SINR) as function of the user's location. This permits to calculate easily the cell spectral efficiency, and thus to study its variations with respect to the key parameters of the network such as the cell radius, the propagation characteristics and the single link performance. We show that the energy efficiency admits a maximum for some value of the transmitted power which is finite and nonnull. Moreover, we observe that optimizing the transmitted power permits to double the energy efficiency. View full abstract»

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  • BCG Random Expansion: Formulation of scalable topology for ultrafast information dissemination in ad hoc networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (131 KB) |  | HTML iconHTML  

    We propose a simple but effective algorithm to formulate growable communication graphs that exhibit (i) fast information dissemination, (ii) high scalability with negligible performance degradation, and (iii) very small diameter and short average path length. In particular, we use Borel Cayley Graphs (BCGs) as base network topologies. Previously, we reported that BCGs are one of the fastest information dissemination topologies. However, practical applications of BCGs to real networks have been challenging because of its lack of size flexibility. The proposed BCG Random Expansion algorithm resolves such size restrictions. Simulation results revealed that the proposed algorithm successfully expands the original BCGs. In fact, even after 25 times of expansion, the expanded BCGs display almost the same or superior topological properties as the original BCGs, such as a small diameter and a short average path length. In the last part of this paper, we discuss the information dissemination performance of communications graphs. Simulation results confirmed that the information dissemination performance of the expanded BCGs remains very close to that of the original BCGs regardless of the amount of expansion. View full abstract»

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  • Measured performance of a memory-efficient segment-based packet-combining scheme

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (221 KB) |  | HTML iconHTML  

    Packet-combining schemes are an attractive improvement to ARQ schemes, since they allow receivers to keep the good parts of an otherwise erroneous packet and use these with good parts from subsequent packets to allow for quicker decoding. In the previous paper a memory-efficient hard-decision packet combining scheme has been described and analysed, which relies on intermediate checksums spread into the user data part of a packet. In this paper we provide experimental data on the performance of the proposed packet-combining scheme, showing that a significant percentage of the wireless links found in a large indoor wireless testbed (the TKN TWIST testbed) indeed benefits from introducing such a packet-combining scheme. View full abstract»

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  • Uplink capacity analysis of OFDMA based cellular networks with reuse-1

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB) |  | HTML iconHTML  

    OFDMA based cellular radio networks aim to operate as close as possible to frequency reuse distance of one, where the whole spectrum would be available in every cell. Modern systems are able to adjust parameters such as transmission power, modulation, and coding separately for each frequency sub-channel on a very short time scale. This way Fractional Frequency Reuse (FFR) can be applied, allowing to operate reuse-1 in the center of cells and reuse greater one at cell edges. This paper presents a novel method to analyze the Carrier to Interference Ratio (CIR) distribution and uplink capacity of a cell, from which spectral efficiency of a cellular radio network using FFR is derived. The results presented apply for OFDMA cellular networks operated in IMT-Advanced evaluation scenarios. View full abstract»

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  • Enhancing FEC application in LTE cellular networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB) |  | HTML iconHTML  

    3rd Generation Partnership Project's (3GPP) Long Term Evolution (LTE) is focused on enhancing the Universal Terrestrial Radio Access (UTRA). Evolved-Multimedia Broadcast and Multicast Service (e-MBMS) uses Multimedia Broadcast over a Single Frequency Network (MBSFN) operation in order to improve its performance. In MBSFN operation, data are transmitted simultaneously over the air from multiple tightly time-synchronized cells. Raptor codes have been standardized as the main application layer Forward Error Correction (FEC) method for e-MBMS due to the advanced error protection they offer and their overall performance. In this study, we investigate the application of FEC in MBSFN-enabled LTE cellular networks and we propose a new scheme that takes into account the properties of MBSFN in order to provide a more efficient operation of FEC during e-MBMS transmissions. The proposed scheme is compared with other file recovery methods and is evaluated against various network parameters in a realistic simulation environment. View full abstract»

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  • A strategy for best access point selection

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    This paper describes a scheme for providing mobile multimedia applications, distributed in a Wireless Local Area Network (WLAN), with seamless communications. Specifically, when multiple WLAN access points are available, the scheme enables a mobile node to select dynamically the access point to connect with, based on a combination of measured parameters such as signal strength, transmission rate, channel load and interference. The proposed scheme has been implemented as part of a cross-layer architecture which offers the possibility of concurrently exploiting multiple networks for the same communication flow generated by some distributed multimedia application. The results which have obtained from an experimental assessment of our scheme demonstrate its adequacy and effectiveness. View full abstract»

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  • Discovery and provision of content in mobile networks with infrastructure support

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (142 KB) |  | HTML iconHTML  

    We consider content discovery and provision in wireless networks with infrastructure, where mobile nodes store, advertise and consume contents while Broker entities running on infrastructure devices let demand and offer meet. We refer to this paradigm as match-making, and study its performance in terms of query success probability, i.e., the probability that a content query is successful. To ensure high success probability, we design a credit-based scheme that entices rational users to provide their contents (thus discouraging free-riding behavior), and that guarantees them a fair treatment. Furthermore, through a feedback and banning mechanism, we effectively counter malicious users whose sole objective is to disrupt the system. The performance of our match-making scheme is shown through ns-3 simulations. View full abstract»

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  • Determine the inter-arrival time in the Non-Uniform Random Waypoint mobility model

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB) |  | HTML iconHTML  

    In the study of the wireless mobile network, Random waypoint mobility model (RWP) and its generalization, nonuniform RWP (NU-RWP) are two of the most widely used mobility models. A useful property in NU-RWP, namely the inter-arrival time (IAT) is studied in this paper. We analytically derive the relationship between waypoint distribution and IAT, and propose two estimation schemes for the evaluation purpose. Simulation shows that our schemes estimate IAT with a higher accuracy than the existing schemes. View full abstract»

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  • A software radio architecture for the baseband level of the multi-standard user terminal: Design methodology and computational assessment

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (521 KB) |  | HTML iconHTML  

    In this paper we present a design methodology and system prototyping for the baseband level of the Software Defined Radio (SDR)-based portable multi-standard terminal. The SDR-based architecture consists of three main layers denoted as: i) Upper Layer to provide communication with an end user and a network; ii) Middle Layer to establish the required protocol configuration; and iii) Bottom Layer to execute the protocol algorithm. Main concern was based on the examination of the SDR-based module behavior in the heterogeneous environment. As a case study we have chosen two different wireless communication standards: data-oriented WiMAX (IEEE 802.16d) and voice-oriented UMTS (release 1999). The simulation of the digital signal processing for both standards was performed in the MATLAB environment. The goal is to achieve and to verify the given system configuration depending on the environment characteristics. For this reason we show that SDR-based module can recognize the required protocol configuration and tune the system accordingly. View full abstract»

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  • A testbed-based study of uni- and multi-path Dynamic Source Routing in a WMN

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (166 KB) |  | HTML iconHTML  

    Dynamic Source Routing (DSR) was one of the first proposed protocols for routing in Mobile Ad-hoc Networks and is among the few that were ratified by the IETF. Despite its source routing overhead, the protocol exhibits particular properties that make it an optimal choice for multi-path routing where multiple paths are discovered for each destination. The alternative paths can either be stored for error recovery situations or used in parallel to improve the throughput. In this paper we present a study of 10 uni- and multi-path DSR variants in a wireless mesh network testbed. A modified ETX metric is proposed for an improved link quality measurement. The experiments are evaluated considering the routing-overhead and packet delivery ratio with focus on the route discovery. View full abstract»

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  • Separable equilibrium distributions for systems with unreliable wireless links

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB) |  | HTML iconHTML  

    Performance evaluation of systems including, among others, components based on wireless links plays an important role both in the software and hardware engineering. In both cases the earlier evaluation of performance characteristics has been proved to be a key-factor for a successful design of new systems. However, most of the quantitative analysis methods suffers the problem of not being scalable with respect to the number of system components, due to the state space explosion problem. In this paper we address the problem of the quantitative modelling of system with some unreliable wireless links (i.e., where packet loss and retransmissions must be considered) using a set of results of product-form theory. Product-form models present separable equilibrium distributions of the state probabilities thus making the derivation of the desired performance indices (e.g., mean number of customers or mean response time) computationally tractable. This work exploits recent advances in this field, e.g., the Reversed Compound Agent Theorem, to efficiently evaluate the performance of systems with unreliable wireless links. View full abstract»

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  • QoE estimation of a location-based mobile game using on-body sensors and QoS-related data

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    The scope of this paper is the interdisciplinary measurement and modeling methodology of Quality of Experience (QoE) when playing a mobile location-based massively multiplayer online role-playing game (MMORPG) that places the virtual world on top of the real world using the user's location. The paper introduces the implementation of a re-usable mobile QoE measurement framework on the Android platform and illustrates how it was applied in a concrete case-study. In this respect, a multidimensional QoE prediction model consisting of both objective and subjective parameters is presented. In this model, test users' evaluations regarding feelings of amusement, absorption or engagement experienced while playing a popular location based mobile game (Parallel Kingdom) are taken into account and related to a set of objective QoS-related parameters, contextual data, and physiological data obtained from an on-body sensor. The latter evidences the intensity of physical activity of the test users during the gaming session, taking into account Metabolic Equivalent of Task (MET) measurements. Results of this study indicate that the test users' QoE was influenced by their physical effort, the data connection type used, and the playing context (e.g. interaction with other players). Despite of the fact of using a re-usable framework for QoE estimation, the analysis is limited to this particular popular (more than 100000 users) mobile game. View full abstract»

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  • Delay tolerant podcasting with network coding

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    We present a new protocol for information dissemination in intermittently connected networks. The objective of the protocol is to disseminate a piece of information, a podcast episode in our scenario, to a subset of nodes of the network by exploiting the random opportunistic contacts occurring among them. To allow for minimum coordination among nodes we leverage a network coding technique. Our protocol is particularly suitable for Vehicular Ad Hoc Networks (VANETs) where the duration of a contact among two nodes is likely to be short. We present theoretical analysis of the protocol backed up by a comparison against the previously proposed E-NCP protocol using simulations. View full abstract»

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  • CAODV: Routing in mobile ad-hoc cognitive radio networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (249 KB) |  | HTML iconHTML  

    This paper deals with the routing in cognitive mobile ad hoc networks. We propose to modify the widely adopted Ad-hoc On-demand Distance Vector (AODV) protocol in order to assure its functionality in the considered scenario. The resulting protocol, referred to as the Cognitive Ad-hoc On-demand Distance Vector (CAODV) protocol, has been designed according to three guidelines: i) to avoid regions of primary users activity during both route formation and packet discovery without requiring a dedicated common control channel; ii) to perform a joint path and channel selection at each forwarder to minimize the route cost; iii) to take advantage of the availability of multiple channels to improve the overall performances. The performances of CAODV have been evaluated by means of numerical simulations, and the experimental results confirm its effectiveness for cognitive mobile ad hoc networks. View full abstract»

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  • Simple distributed interference source localization for radio environment mapping

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (237 KB) |  | HTML iconHTML  

    In order to construct a radio environmental map that can help navigating secondary communication in TV bands, we present a new method of interference source localization for cognitive radio networks. Our low-cost, high-precision localization method, operates without any prior knowledge of the interference source other than transmitter power. It can be divided into two steps: an estimation step at each sensor based on classical methods to estimate the angle of arrival and the received signal power, followed by an SNR-aided fusion. Simulation results show that tens of sensor nodes each having two antennas in a large-scale area setting are enough to achieve accurate location. The proposed location method is practical, economic and essential for blind interference source localization in cognitive radio networks. View full abstract»

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  • Adaptive CAC with traffic flows classification for IEEE 802.16 networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (549 KB) |  | HTML iconHTML  

    In this paper, we propose an adaptive Call Admission Control for IEEE 802.16 scheduled flows. As the WiMAX defined services aim to adapt the bandwidth grant to the data rate of accepted sessions, a powerful CAC that takes into account flows characteristics and their heterogeneities must be used. Our proposal aims to take advantage of the variability of traffics and to adapt the CAC according to the characteristics of incoming flows. We apply this adaptive CAC to the case of video traffics using measurements done by the BS to guess and classify flows according to the similarities in their behaviours and then adapt the system model parameters that will be used by the CAC. In this purpose we use a Markovian model adapted for each flow instead of a generic one. Performance evaluation is given to demonstrate the interest of our proposal. View full abstract»

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  • Adaptive Random Linear Network Coding with Controlled Forwarding for wireless broadcast

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (233 KB) |  | HTML iconHTML  

    Multicasting and Broadcasting are important communication techniques in wireless adhoc networks to disseminate control messages and other important information during emergencies, battlefield operations, disaster relief efforts, etc. In this paper we propose an adaptive multi-source broadcasting protocol using Random Linear Network Coding. One key feature of this protocol is its multi-source operation, coding packets from different sources in the same generation. The protocol also efficiently controls the number of re-transmissions based on neighborhood information, limits the size of generations by introducing the concept of Generation Distance (GD) for multi-source operation, supports early decoding, and adaptively calculates the time-out for generations based on the generation size and transmission rate (packets/sec). Simulation results show that inter-mixing of packets from different sources results in improved Packet Delivery Ratio (PDR) as well as lower latency, compared to the already proposed single-source schemes. We also investigated its adaptive performance compared to a baseline flooding protocol and show that our protocol delivers consistently high PDR and low latency in both single-source and multi-source scenarios for a range of network densities and traffic rates. View full abstract»

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  • A distributed link quality based d-clustering protocol for dense ZigBee sensor networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (574 KB) |  | HTML iconHTML  

    The Link Quality Indicator (LQI) is defined in the 802.15.4 standard, but its context of use is not specified in this standard. Some works on the LQI, few of which are field experiments, have shown that the LQI decreases as the distance increases. In WSN, it is not often desirable to use the GPS technology. Indeed, the use of GPS is expensive and may reduce the overall network performance. Moreover, indoor reception of the GPS signal is not possible. However, in cluster formation, it is quite important to sufficiently outspread the clusterheads (or caryommes) in order to improve the network efficiency. Therefore we propose a LQI based d-clustering protocol (LQI-DCP) which produces clusters of which each clusterhead has a better positioning regarding the locations of other clusterheads. Simulation results show that the caryommes resulting from LQI-DCP are sufficiently outspread. LQI-DCP also reduces the density of clusterheads and then improves the WSN energy efficiency, while each sensor remains still at less than d-hops from a caryomme. View full abstract»

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  • PARC: Power aware routing and clustering scheme for wireless sensor networks

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (127 KB) |  | HTML iconHTML  

    In wireless sensor networks constructed from battery driven nodes, it is difficult to supply electric power to the nodes. Because of this, the power consumption must be reduced. To cope with this problem, clustering techniques have been proposed. EACLE is a method that uses a clustering technique. In EACLE, the route selection is executed independently after the CH (Cluster Head) selection. These two phase controls increase overheads and reduce the battery power, which leads to shorten the lifetime of wireless sensor networks. This paper proposes a novel routing and clustering method called PARC for wireless sensor networks that reduces these overheads by integrating the cluster selection phase and the route construction phase into a single phase. However, PARC has a following weak point that the batteries of CHs around the sink node are depleted earlier than the other nodes and the sink node cannot collect sensing data. This phenomenon is called a hot spot problem. In order to cope with this problem of PARC, we propose PARC+, which extends the CH selection method of PARC such as more nodes around the sink can be selected as a CH node. We evaluate our proposed methods by simulation experiments and show its effectiveness. View full abstract»

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  • MCMIPv6: Multicast Configuration-based Mobile IPv6 protocol

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    Mobile IPv6 (MIPv6) and its basic extension for network mobility NEMO were initially designed to manage the mobility of device users and networks respectively while maintaining a permanent IP address. Nevertheless, the different MIPv6's experiments have shown many lacks in case of high mobility of nodes such as in vehicular networks. To overcome these lacks, many solutions have been proposed by the research community. The most famous ones are HMIPv6 and FMIPv6 tackling each a specific issue. On the one hand, FMIPv6 introduces a solution to effectively minimize the L2/L3 latency and avoid the packets losses during the handover procedure. On the other hand, HMIPv6 is especially efficient in case of local mobility and permits in this case to minimize the signaling cost and improve the latency slightly. In this paper, we propose and evaluate a new vehicular mobility management protocol called MCMIPv6 (Multicast Configuration-based Mobile IPv6 protocol). MCMIPv6 is based on two main ideas: (i) definition of a new packet transmission way in visited networks based on a multicast communication and (ii) proposition of an efficient stateful configuration scheme to obtain addresses in visited networks. We used Qualnet simulator to compare the performances of our protocol, MCMIPv6, to those of existing solutions and show the different performance improvements in terms of handover latency and signaling cost. View full abstract»

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