Showing papers presented at "IFIP Wireless Days in 2008"

RFID tags: Positioning principles and localization techniques

Abstract: RFID is an automatic identification technology that enables tracking of people and objects. Both identity and location are generally key information for indoor services. An obvious and interesting method to obtain these two types of data is to localize RFID tags attached to devices or objects or carried by people. However, signals in indoor environments are generally harshly impaired and tags have very limited capabilities which pose many challenges for positioning them. In this work, we propose a classification and survey the current state-of-art of RFID localization by first presenting this technology and positioning principles. Then, we explain and classify RFID localization techniques. Finally, we discuss future trends in this domain.

Implementing the Expected Transmission Time Metric for OLSR Wireless Mesh Networks

Abstract: This paper presents the design of a plug-in for the optimized link state routing (OLSR) protocol with the expected transmission time (ETT) metric and experiments in an indoor testbed. The ETT metric is implemented as a plug-in, keeping portability and facilitating its deployment on operational networks. Our design identifies important implementation issues. Additionally, we run experiments in an indoor testbed to verify the performance of our ETT plug-in. Our results show that the ETT metric has the lowest packet loss rate and the lowest round trip time among the analyzed metrics, because it reproduces link quality conditions and also takes into account physical transmission rates.

On the congestion control within VANET

Abstract: The basic objective of congestion control is to best exploit the available network resources while preventing sustained overloads of network nodes and links. Appropriate congestion control mechanisms are essential to maintain the efficient operation of a network. Ensuring congestion control within vehicular ad hoc networks address special challenges, due to the characteristic and specificities of such environment (High dynamic and mobility of nodes, high rate of topology changes, high variability in nodes density and neighborhood, broadcast/geocast communication nature ...). In this context, we present in this paper a congestion control approach, based on the concept of dynamic priorities-based scheduling, to ensure a reliable and safe communications architecture within VANET. Messages priorities are dynamically evaluated according to their types, the network context and the neighborhood.

Enhanced telemetry system using CP-QPSK Band-Pass modulation technique suitable for smart pill medical application

Abstract: A new approach of continuous phase QPSK Band-Pass modulation technique is being developed as enhancement to the QPSK modulation scheme for inductive data transmission (NFC). The modulation is based on Gaussian filtering of the phase transition from one state to the other rather than discontinuity in phase shift. The carrier is based on low frequency 115 KHz suitable for human body energy penetration due to its large skin-depth and lower inductive power attenuation. The complete signal processing is done digitally, external coil and capacitor is used for transceiver interface. The telemetry assists a smart pill swallowed by human being to trigger an actuator for drug delivery, record temperature, or perform diagnostic task inside the body. The smart pill includes 32bit processor, 16 Kbyte memory, temperature sensor, telemetry unit, and additional external peripheries. The complete system is designed, embedded in one SoC, and realized on ASIC with chip-area less than 14 mm2.

Bit, tone and cyclic prefix allocation in OFDM with application to In-Home PLC

Abstract: We propose to maximize achievable rate in OFDM systems via the adaptation of the cyclic prefix (CP) length jointly with tone and bit loading. We show that significant gains are obtained compared to the case of using a fixed CP with duration equal to the channel. Several metrics for the CP design are described. They tradeoff between performance and complexity. Both single user and multiuser OFDM are considered. Numerical results are reported for typical power line communication indoor channels.

A distributed algorithm for gateway load-balancing in Wireless Mesh Networks

Abstract: Wireless Mesh Networks (WMNs) provide a cost-effective way of deploying a network and providing broadband Internet access. In WMNs a subset of nodes called gateways provide connectivity to the wired infrastructure (typically the Internet). Because traffic volume of WMNs is expected to be high, and due to limited wireless link capacity, gateways are likely to become a potential bottleneck. In this paper, we propose a distributed load-balancing protocol where gateways coordinate to reroute flows from congested gateways to under-utilized gateways. Unlike other approaches, our scheme takes into account the effects of interference. This makes it suitable for implementation in practical scenarios, achieving good results, and improving on shortest path routing. Also, it is load-sensitive and can improve network utilization in both balanced and skewed topologies. Simulation results prove the effectiveness of our approach, which outperforms all schemes tested. We have observed throughput gains of up to 80% over the shortest path algorithm.

Performance evaluation on end-to-end security architecture for mobile banking system

Abstract: The advantage of mobile penetration enables mobile operators to provide value added service such as secured mobile banking, mobile commerce and provide enhanced security for internet banking. Mobile banking is attractive because it is a convenient approach to perform banking from any where any time, but there are security concerns in the implementation, which include problems with GSM, network, SMS, GPRS protocols. In this paper an end-to-end security framework using PKI for mobile banking is proposed. Performance of the proposed model is presented in this paper.

Network level cooperation for resource allocation in future wireless networks

Abstract: The increasing number of radio access technologies and the availability of multi-radio devices boost the need for novel resource allocation schemes in cellular networks. This paper uses a cooperative game theoretic approach for resource allocation at the network level, while utilizing simultaneous use of available radio interfaces at the device level. We model resource allocation management using the well known bankruptcy model and apply Kalai-Smorodinsky bargaining solution method to find a distribution rule, based on which we propose resource allocation and call admission control schemes. Performance analysis of our allocation and control schemes demonstrates significant improvements over previous approaches in terms of utilization of the available bandwidth and the number of call drops.

A new generic model for signal propagation in Wi-Fi and WiMAX environments

Abstract: The ability to accurately predict radio propagation behavior for wireless communication systems, such as cellular mobile radio, is becoming crucial to system design. Since site measurements are costly, propagation models have been developed as suitable, low-cost, and convenient alternative. In this paper, we will propose a new generic signal propagation model for Wi-Fi and WiMAX environments. To develop this model we used existing models which are classified as: Free space models and land propagation models. This includes different types of loss: path loss, slow fading (shadowing) and fast fading. Our aim is to have a flexible model to be applicable in indoor and outdoor environments. Experiments carried out for indoor Wi-Fi and outdoor WiMAX cases have shown excellent results for the proposed model.

Frequency-Time Scheduling for streaming services in OFDMA systems

Abstract: This paper proposes a novel Frequency Time scheduler, called Frequency Time Scheduler with Delay Constraints (FTSDC), in order to handle streaming traffic in OFDMA (Orthogonal Frequency Division Multiple Access) system. Streaming technique, widely developed and used in the internet to convey multimedia application (e.g., audio, video clip, etc.), is supposed to occupy a large share of bandwidth in future wireless systems (e.g. WiMAX, LTE ldquoLong Term Evolutionrdquo, etc.). The stringent QoS constraints of these services may be reached at the expense of the system capacity and therefore a trade off between Fairness and capacity should be achieved. The novel opportunistic scheduler proposed in this paper balances this trade off and allows thus OFDMA systems to handle streaming services without losing much cell capacity. Results afforded by this scheduler are promising and show that it outperforms the existing scheduling algorithms.

Optimized MPR-based flooding in wireless ad hoc network using network coding

Abstract: Multipoint relays ldquoMPRrdquo have been introduced in the proactive protocol OLSR in order to optimize the flooding overhead of control traffic. In this paper we propose an algorithm to optimize the MPR-based flooding by using network coding where MPR nodes do not simply forward packets they overhear but may send out information that is coded over the contents of several packets they received. Our interest is to reduce the number of transmissions. We show by simulation that flooding can be efficiently performed by exploiting network coding with multipoint relays, resulting in significant reductions in the number of transmissions in the network. We can get benefits from this approach also in other practical considerations such as restricted complexity and memory capabilities.

Cooperative communication for Wireless Sensors Network : A Mac protocol solution

Abstract: This article proposes a new Mac layer scheme (WSC-MAC) for Wireless Sensor Network (WSN) improving the overall the network reliability by using cooperative communication. We focus our work on a way to define a relay node among the neighborhood of a node, efficiently and with only few signaling messages. We developed a solution based on an automatic forwarder selection and a link state evaluation in order to define the relay node. This automatic selection uses a group identifier uniformly spread in the network and ensures that only few nodes at the time will be chosen as relay. As the sensor nodes switch from active mode to sleep mode, we based our solution on the Long Preamble Emulation (LPE) Mac layer Algorithm which emulates the asynchronous MAC protocol proposed in Polastre et al. (2004). Our Simulations results show that WSC-MAC increases the overall reliability of the sensor network and adjusts to large variety of node density.

Medium access control for a tree-based wireless sensor network: Synchronization management

Abstract: Energy efficiency is a primordial issue in the wireless sensor networks. This is achieved by deactivating nodes when possible. In this paper we describe the MAC protocol MaCARI that synchronizes nodes in order to schedule active and inactive periods. MaCARI divides time into three periods: a synchronization period, a scheduled activities period where communications are constrained by a tree and an unscheduled activities period where nodes can communicate whenever in range. With this synchronization, nodes are able to save energy during specific time intervals. Therefore, we focus on the synchronization period and apply an optimization to reduce its duration. We validate this approach by simulations under different tree topologies.

Performance evaluation of intercarrier interference self-cancellation schemes for space time frequency block codes MIMO-OFDM system

Abstract: Intercarrier interference (ICI) self-cancellation schemes were often employed in many OFDM systems as a simple and effective approach to suppress ICI caused by carrier frequency error. In this paper, we propose a space time frequency block coding technique MIMO-OFDM system with ICI self-cancellation of data conjugate method, which is capable of both error correction and ICI reduction produced by the frequency offsets. Then, the system performance of the data-conjugate method with diversity techniques is compared with those of the conventional data-conversion method. As results, it can be seen that the STFB codes MIMO-OFDM system with data-conjugate method can make remarkable improvement of the BER performance and it is better than data-conversion method and the conventional OFDM system.

Random and realistic mobility models impact on the performance of bypass-AODV routing protocol

Abstract: Due to lack of mass deployment of wireless ad hoc networks, simulation is the main tool to evaluate and compare different routing protocol proposals. Previous studies have shown that a certain routing protocol behaves differently under different presumed mobility patterns. Bypass-AODV is a new optimization of the AODV routing protocol for mobile ad-hoc networks. It is proposed as a local recovery mechanism to enhance the performance of AODV routing protocol. It shows outstanding performance under random waypoint mobility model compared with AODV. However, random waypoint is a simple model that may be applicable to some scenarios but it is not sufficient to capture some important mobility characteristics of scenarios where MANETs deployed. In this work, we would like to investigate the performance of Bypass-AODV under wide range of mobility models including other random mobility models, group mobility models and vehicular mobility models. Ns-2 simulation results show that bypass-AODV is insensitive to the selected random mobility model and it has a clear performance improvement compared to AODV. It shows a comparable performance under group mobility model compared to AODV. But, for vehicular mobility models, bypass-AODV is suffering from performance degradation at high speed conditions.

Codec-based adaptive QoS control for VoWLAN with differentiated services

Abstract: Voice over Wireless LAN (VoWLAN) is becoming more and more helpful in our life and is expected to be among the most important applications in next generation networks. However, the maximum number of VoIP sessions that a WLAN can ensure is very small. Moreover, when the WLAN reaches its capacity the addition of one VoIP session affects the QoS parameters of all VoIP sessions. In this paper, we propose an adaptive technique to ensure the active VoIP sessions of users with high priority (from a provider perspective). Thus, in order to guarantee the quality of high priority sessions, we propose to downgrade the quality (low but acceptable MOS) of user sessions with low priority by changing their used codecs (e.g., ITU G729 instead of ITU G711). This technique and all related monitoring functions are defined into the proposed session-based QoS management architecture. In order to validate our approach a complete test-bed is made up by which we have performed some feasibility and gain tests.

A measurement platform for energy harvesting and software characterization in WSNs

Abstract: Wireless Sensor Network (WSN) nodes are resource- constrained computing devices. Adaptive behavior of autonomously working WSNs tries to maximize the cost efficiency of deployments. This includes maximizing the lifetime through power consumption optimization and recharging energy reservoirs with the use of energy harvesting. The adaptive behavior that leads to efficient resource usage needs information about the WSNs energy balance for decision making. We present a novel platform to measure the harvested, stored and dissipated energy. For being applicable to different environments it allows to attach different energy harvesting devices (EHDs). EHDs do not provide power continuously. Power availability patterns are used to determine how these sources can be used efficiently. Models from harvesting theory try to adapt to it. We implement a model that targets energy neutrality on our platform. It is used to evaluate the model and improve it. Our novel platform can be used to evaluate theories that model different sources. It can utilize and characterize thermoelectric, piezoelectric and magnetic induction generators and solar cells. The measurement platform tracks energy dissipation too. Mote software is implemented to establish communication to the platform. A sample application on top of it shows that the system can be used for software characterization. This paper contributes a novel modular and low-power design for measurement platforms for WSNs. It shows utilization of different energy sources and the ability to supply different mote types. Our work shows how theories for energy harvesting can be evaluated and improved. Our work also contributes to the field of simulation and emulation through online software characterization. The approach improves in accuracy and completeness over the capabilities of offline simulation.

Agent-cooperation based communication architecture for wireless sensor networks

Abstract: The main goal of wireless sensor networks is to gather information from the region of interest through a large number of micro sensor nodes. This gathering is based on a communication architecture such as client/server which consumes a lot of power and doesn't take in consideration the information properties. In this paper, we propose a new communication architecture for wireless sensor networks based on agents' cooperation. This architecture uses techniques from multi-agent systems and networks in order to ensure an optimal information gathering. It benefits from AODV not only for route discovery but also to define the basic list of cooperating agents, using the RREP control message. These agents create cooperatively a simple message summarizing the important information of multiple nodes, where it is widely known that sending a one big message consumes less energy than sending several small messages of the same quantity of information. In order to appreciate our contribution, we discuss its advantages and its limitations by comparing it to client/server and mobile agent architectures.

Impulsive noise characterization at source

Abstract: The noise characteristics of an indoor powerline network strongly influence the link capability to achieve high data rates. The appliances shared with PLC modems in the same powerline network generate noises, among them the impulsive ones which are the main source of interference which causes signal distortions leading to bit errors while data transmission. Many models were proposed in the literature. They shared the same impulsive noise definition: "unpredictable noises measured in the receiver side". Authors are, consequently, confronted to model thousands of impulsive noises whose plurality would very likely come from the diversity of paths that the original impulsive noise took. In this paper, an innovative modelisation approach is applied to impulsive noises which are henceforth studied directly at their sources outputs. Noise at receiver would be simply the noise model at source filtered by powerline channel block.

Impact of history on epidemic broadcast in DTNs

Abstract: In this work, we present an analysis of the gain achieved in terms of efficiency with PUSH-based epidemic diffusion of messages, when maintaining and exchanging information about the infection status. Different policies for the exchange of partial status information are compared, with the aim of optimizing bandwidth usage. We analyze the effects of adding a copy-count mechanism to the maintenance of status with respect to the capability of efficiently stopping the diffusion once full coverage is achieved; to this purpose, we adopted an analytical model proposed in the literature to determine the copy-count threshold. We perform initial measures to highlight how the mobility model affects the algorithm performance.

A new channel, power and rate assignment algorithm for multi-radio wireless mesh networks

Abstract: Endowing mesh routers with multiple radios is a recent solution to improve the performance of wireless mesh networks. The consequent problem to assign channels to radios has been recently investigated and its relation to the routing problem has been revealed. The joint channel assignment and routing problem has been shown to be NP-complete and hence mainly heuristics have been proposed. However, such heuristics consider wireless links just like wired links, whereas disregarding their peculiar features. In this paper, we consider the impact of tuning the transmission power and rate of the wireless links on the efficiency of the channel assignment. Then, we present a channel, power and rate assignment heuristic and compare its performance to previously proposed algorithms.

Design, deployment and performance of a complete real-time ZigBee localization system

Abstract: This paper proposes a complete system for nodes localization in a Wireless Sensor Network (WSN) based on the ZigBee standard. The system includes a real-time location engine, which adopts a Received Signal Strength Indicator (RSSI)-based localization algorithm, and three tools, namely an Environment Description Tool (EDT), a Channel Modeling Tool (CMT) and a Network Planning Tool (NPT), which enable efficient deployment and accurate operation. Experimental evaluations show how the system performs in a real environment and how the proposed approach improves localization accuracy.

Energy-aware routing in Mobile Ad-Hoc Networks

Abstract: The next generation communication systems will provide high quality multimedia services in a flexible and efficient manner. As an extension of next generation networks, Mobile Ad Hoc Networks (MANETs) have attracted significant attention amongst researchers. Nodes in a MANET have limited battery power. Hence, ad hoc routing protocols ought to be energy conservative to support real-time multimedia services. In this paper, we propose a proactive routing protocol which gives better performance and satisfies the basic power aware parameters like minimum energy consumption per packet, maximum network lifetime, and minimum variance in the node power levels. We use breadth first search to gather the network topology.. From this global information, a least cost path is generated using Dijkstra's shortest path algorithm. This least cost path has better battery resources and is refreshed after some fixed intervals of data packet delivery to keep the variance in residual battery power to minimum. Our simulation results show that the proposed protocol provides good service to different types of media while conserving energy.

Energy saving in future home environments

Abstract: Already, hundreds of millions of PCs are found in homes, offering high computing capacity without being adequately utilized. This paper reveals the potential for energy saving in future home environments, which can be achieved by sharing resources, and concentrating 24/7 computation on a small number of PCs. We present three evaluation methods for assessing the expected performance. A newly created prototype is able to interconnect an arbitrary number of homes by using the free P2P library FreePastry. The prototype is able to carry out task virtualization by sending virtual machines (VMs) from one home to another, most VMs being of size around 4 MB. We present measurement results from the prototype. We then describe a general model for download sharing, and compare performance results from an analytical model to results obtained from a discrete event simulator. The simulation results demonstrate that it is possible to reach almost optimal energy efficiency for this scenario.

Base-station controlled clustering scheme in wireless sensor networks

Abstract: Wireless Sensor Networks (WSNs) are highly distributed networks of small, light weighted, wireless nodes deployed in large numbers These sensor nodes are immobile, non rechargeable with limited energy The cluster-based protocols make judicious use of this limited energy LEACH-C (Low Energy Adaptive Clustering Hierarchy-Centralized) has a drawback, a lot of energy is consumed by the nodes to send status messages to the base station every round for cluster head selection, LEACH-CE (LEACH Cluster Estimate) protocol overcome this problem We use this property of LEACH-CE, and improve over it We propose LEACH-CCB (LEACH- Completely Controlled by Base-station) which presents two techniques through which energy of the nodes is conserved First, by avoiding frequent communications of the nodes with the base station Second, by making certain percent of nodes sleep every round From simulation, we obtain a greater network lifetime than in LEACH-CE

A new access selection strategy in heterogeneous wireless networks based on traffic distribution

Abstract: Today, we are in a world where several radio networks arise: we speak about mobile networks, wireless networks (IEEE 802.11, .15, .16, .20, .21...), networks of sensors, radio-frequency identification networks (RFID) and more generally networks of ldquoThings connected via radio interfacerdquo. In this heterogeneous environment, a user with a multi-interface terminal can have access to the networks of various technologies with a continuous connectivity; this is the notion of always best connected (ABC). Access selection is the key functional block in ABC networks, that's why the selection decision of a network must be based on several criteria or parameters and must be made in a dynamic way. This paper presents a new algorithm of selection based on the QoS needs of the user, by taking into consideration a better traffic distribution between the various networks of the same operator.

A gradient approach for differentiated wireless sensor network deployment

Abstract: In this paper, we propose a new sensor deployment strategy by considering both a probabilistic sensor detection model and a monitored area with geographical irregularity requirement of the sensed events. In this case, each point in the deployment field needs a specific minimum guarantee in event detection probability. The main objective is to find the minimum number of senors and their positions, in order to guarantee the requirement event detection threshold. Thus, we propose a new scalable deployment strategy based on virtual forces. The fundamental idea of our proposal is to adjust the number and the position of sensors according to virtual forces that must be computed for each sensor. The performance evaluation shows that our proposal obtained the best results compared to several other sensor deployment strategies founded in the literature.

Identity in federated electronic healthcare

Abstract: In electronic healthcare several research and standardization activities are emerging that promote federation. In this scenario, the medical information present at different healthcare providers, such as hospitals, general practitioners, test laboratories, etc., are shared for an improved quality of experience from the patient perspective. However, sharing of medical data on a large scale exposes the patient to several privacy-related threats, such as massive data aggregation or profiling. Therefore, the selection of a privacy-preserving identification scheme is a primary requirement in federated e-health. This paper presents an identity management infrastructure that minimizes the above-mentioned threats.

A mobile-controlled handover management scheme in a loosely-coupled 3G-WLAN interworking architecture

Abstract: In the new area of heterogeneous environments, roaming users, using multi-interface mobile terminals, need to access to services anytime and anywhere. For that, a seamless vertical handover has to be considered. In our paper, we propose a 3G/UMTS-WLAN loosely-coupled interworking architecture with mobile IP as a service continuity solution. We focus on a mobile-controlled vertical handover management scheme. Our solution chooses the best access network according to user preferences and it maintains the ongoing session. It has several advantages to be simple and to generate minor changes at the network side. Moreover, MIP-based handover execution procedure is prepared thanks to a handover decision taken at the mobile side. The scheme proposes an interesting answer to intersystem and inter-domain mobility management issues. Finally, a simulation model is developed to validate the feasibility of the proposed 3G/UMTS-WLAN architecture.

Energy-efficient event detection in 3D wireless sensor networks

Abstract: Event detection techniques are crucial for environmental monitoring and object tracking applications in wireless sensor networks. Event detection requires sensor readings to be collected from multiple sensors, and as sensors have limited resources, their readings should be retrieved efficiently. Existing aggregation-based event detection methods, however, require all sensors in the network to transmit their readings, which results in high energy consumption for the network. We propose an energy-efficient event detection technique for estimating the state of the whole environment based on only some of the sensor readings and use a contour map to represent the outline of the environment. To detect events in 3D environments, we modify an existing 2D contour mapping algorithm, extending it for 3D environments. By simulation, we show how our event detection technique is more energy-efficient than existing solutions that take readings from all sensors. We evaluated our method from the point of energy efficiency and found that it improves the energy efficiency of event detection in 3D wireless sensor networks.