Research Reports

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Subject: search.filters.subject.Wireless Sensor Networks

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    Energy-Delay Constrained Minimal Relay Placement in Low Duty-Cycled Sensor Networks Under Anycast Forwarding
    (CERIST, 2016-06) Doudou, Messaoud; M. Barcelo-Ordinas, Jose; Garcia-Vidal, Jorge
    A constrained relay placement problem satisfying application requirements in terms of network lifetime and end-to-end (e2e) delay in Wireless Sensor Networks (WSN) is investigated in this paper. The network and the traffic are adequately modeled considering uniform node deployment and low data rate periodic traffic generation. An optimization problem is defined to obtain the minimum number of relays to be deployed, at each level of the network, in order to fulfil network duty-cycle and e2e delay constraints under anycast forwarding based on the wake-up period parameter of the duty-cycle MAC protocol. Since the optimization problem is non-convex, an alternative and efficient algorithm for relay node placement called EDC-RP (Energy-Delay Constrained Relay Placement) is introduced. The comparison of the proposed node deployment strategy with state-of-the-art relay placement methods demonstrates the gain of the heuristic in terms of deployment cost (number of relays) over other solutions while fulfilling the application constraints.
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    Modified Elastic Routing to support Sink Mobility Characteristics in Wireless Sensor Networks
    (CERIST, 2015-04-12) Benkhelifa, Imane; Belmouloud, Nassim; Moussaoui, Tabia
    This paper presents improvements for the geographic routing protocol Elastic so to support the different sink mobility characteristics. We have proposed a strategy to support multiple mobile sinks; tested Elastic under high speeds of the mobile sink; proposed two strategies in case of the sink temporary absence and finally proposed to predict the sink location by the source node and then by all the nodes. Simulation results show that our propositions improve much the delivery ratio and reduce the delivery delay.
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    Performance Analysis of Sinks Mobility in Geographic Routing for Wireless Sensor Networks
    (CERIST, 2015-04-12) Benkhelifa, Imane; Belmouloud, Nassim; Tabia, Yasmina; Moussaoui, Samira
    This paper presents a performance analysis of sinks mobility in geographic routing based on performance evaluation of two geographic routing protocols namely GPSR with static sinks and Elastic with mobile sinks. Among the scenarios, we observe also the impact of using multi-mobile-sinks, in addition to the effect of mobility model through changing the sink’s trajectory and speed. We analyze the performance results by calculating the delivery ratio of the transmitted packets, as well as the average delay of transmission and the number of hops necessary to transmit successfully a packet from the source to the sink. We show that mobile sinks can play a major role in prolonging the network lifetime and the efficiency of a geographic routing protocol.
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    Disaster Management Projects using Wireless Sensor Networks: An Overview
    (CERIST, 2014-02) Benkhelifa, Imane; Nouali-Taboudjemat, Nadia
    There are numerous projects dealing with disaster management and emergency response that use wireless sensor networks technologies. Indeed, WSNs offer a good alternative compared to traditional ad hoc networks. Air pollution monitoring, forest fire detection, landslide detection, natural disaster prevention, industrial sense and control applications, dangerous gas leakage, water level monitoring, vibration detection to prevent an earthquake, radiation monitoring are examples of the WSN applications related to disaster management. This paper presents an overview of the recent projects using WSN to collect data in disaster areas.
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    Cost Effective Node Deployment Strategy for Energy-Balanced and Delay-Efficient Data Collection in Wireless Sensor Networks
    (CERIST, 2014-01-08) Doudou, Messaoud; Djenouri, Djamel; M. Barcelo-Ordinas, Jose; Badache, Nadjib
    The real-world node deployment aspect is investigated, while considering cost minimization for resolving the energy hole around the sink, which represents a serious problem in typical sensor networks with uniform distribution. A novel strategy is proposed that is based on the use of two sinks and a few extra relay nodes close to the sinks’ areas. The traffic is then alternatively sent to the sinks in every other cycle. As a second contribution, an efficient data collection mechanism has been developed to determine the optimal data rate that meets delay requirements of individual sensor reports and improves the network lifetime. The comparison of the proposed node deployment strategy with uniform, non-uniform geometric and linear increase node distributions demonstrates that the cost of the proposed solution is very close to that of the uniform distribution and much lower than all the others, while achieving a load balancing at the same order of the state-of-the-art solutions perspective.
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    Distributed Receiver/Receiver Synchronization in Wireless Sensor Networks: New Solution and Joint Offset/Skew Estimators for Gaussian Delays
    (CERIST, 2011-06) Djenouri, Djamel
    This paper proposes a synchronization protocol for wireless sensor networks (WSN). The receiver/receiver approach inspired from Reference Broadcast Synchronization (RBS) protocol is chosen for its lower time-critical path compared to the sender/receiver approach. Contrary to RBS upon which rely all current receiver/receiver solutions, the proposed one is totally distributed and does not depend on any fixed reference. The reference’s function is balanced among all sensors, which eliminates the single point of failure shortcomings. RBS needs additional steps for exchanging reception timestamps. On the other hand, the proposed protocol allow these timestamps to be piggybacked to the regular beacons, reducing thus the overhead and energy consumption. The protocol deals with local synchronization and allows neighboring nodes to relatively synchronize with each other by estimating relative skews/offsets. Maximum Likelihood estimators (MLEs) are derived for channels with Gaussian (normal) distributed delays, and for both offset-only and joint offset/skew models. The Cramer- Rao Lower Bounds (CRLBs) are derived for each model and numerically compared with the MLE. Results show quick convergence of the proposed estimators’ precision to CRLB. Like the CRLB, the mean square errors (MSE) of the estimators quadratically decrease toward zero as the number of messages increases. To our knowledge, this is the first distributed receiver/receiver solution that eliminates the need of a fixed reference while taking advantage of the receiver/receiver synchronization’s precision.
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    Fault-Tolerant Implementation of a Distributed MLE-based Time Synchronization Protocol for Wireless Sensor Networks
    (CERIST, 2012) Djenouri, Djamel; Doudou, Messaoud; Merabtine, Nassima; Mekahlia, Fatma Zohra
    This paper describes the implementation and evaluation of R4Syn protocol on MICAz platform and TinyOS operating system. The contribution is two folds. First, the implementation uses thorough maximum-likelihood estimators (MLE) in the joint offset/skew model, while all similar MLE-based estimators are merely evaluated with theoretical and numerical analysis thus far, and empirical solutions use simple computation estimators, such as offset-only models, or linear regression for skew estimation. Difficulties that has been encountered and overcome are reported in this paper. The second contribution is to consider fault-tolerance, an aspect that has been completely abstracted in previous works. The implementation assures correct behavior despite nodes failure or packet loss, as demonstrated by the experiments. Experimental results also demonstrate microsecond-level precision and long-term validity of the estimators in the joint skew/offset model.
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    Survey on Latency Issues of Asynchronous MAC Protocols in Delay-Sensitive Wireless Sensor Networks
    (CERIST, 2012) Doudou, Messaoud; Badache, Nadjib; Djenouri, Djamel
    Energy-efficiency is the main concern in most Wireless Sensor Network (WSN) applications. For this purpose, current WSN MAC (Medium Access Control) protocols use duty-cycling schemes, where they consciously switch a node’s radio between active and sleep modes. However, a node needs to be aware of (or at least use some mechanism to meet) its neighbors’ sleep/active schedules, since messages cannot be exchanged unless both the transmitter and the receiver are awake. Asynchronous duty-cycling schemes have the advantage over synchronous ones to eliminating the need of clock synchronization, and to be conceptually distributed and more dynamic. However, the communicating nodes are prone to spend more time waiting for the active period of each other, which inevitably influences the one-hop delay, and consequently the cumulative end-to-end delay. This paper reviews current asynchronous WSN MAC protocols. Its main contribution is to study these protocols from the delay efficiency perspective, and to investigate on their latency. The asynchronous protocols are divided into six categories: static wakeup preamble, adaptive wake-up preamble, collaborative schedule setting, collisions resolution, receiver-initiated, and anticipation based. Several state-of-the-art protocols are described following the proposed taxonomy, with comprehensive discussions and comparisons with respect to their latency.
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    Slotted Contention-Based Energy-Efficient MAC Protocols in Delay-Sensitive
    (CERIST, 2012) Doudou, Messaoud; Badache, Nadjib; Djenouri, Djamel
    This paper considers slotted duty-cycled medium access control (MAC) protocols, where sensor nodes periodically and synchronously alternate their operations between active and sleep modes to save energy. In order to transmit data from one node to another, both nodes must be in active mode. The synchronous feature makes these protocols more appropriate for delay-sensitive applications compared to asynchronous protocols. With asynchronous protocols, additional delay is needed for the sender to meet the receiver's active period. This is eliminated with synchronous approaches where nodes sleep and wake up all together. Moreover, contention-based feature makes the protocols --considered in this paper-- conceptually distributed and more dynamic compared to TDMA-based protocols. Duty cycling allows obtaining significant energy saving vs. full duty cycle (sleepless) random access MAC protocols. However, it may result in significant latency. Forwarding a packet over multiple hops often requires multiple operational cycles (sleep latency), where nodes have to wait for the next cycle to forward data at each hop. Timeliness issues of slotted contention-based WSN MAC protocols is deal t with in this paper, where a comprehensive review and taxonomy of state-of-the-art synchronous MAC protocols is provided. The main contribution is to study and classify the protocols from the delay-efficiency perspective.
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    Synchronous Contention-Based MAC Protocols for Delay-Sensitive Wireless Sensor Networks: a Review and Taxonomy
    (CERIST, 2012) Doudou, Messaoud
    In slotted duty-cycled medium access control (MAC) protocols, sensor nodes periodically and synchronously alternate their operations between active and sleep modes. The sleep mode allows a sensor node to completely turn off its radio and save energy. In order to transmit data from one node to another, both nodes must be in active mode. The synchronous feature makes the protocols more appropriate for delay-sensitive applications compared to asynchronous protocols. The latter involve additional delay for the sender to meet the receiver’s active period, which is eliminated with synchronous approach where nodes sleep and wake up all together. On the other hand, contention-based feature makes the protocol conceptually distributed and more dynamic compared to TDMA-based. Duty cycling allows obtaining significant energy saving compared to full duty cycle (sleepless) random access MAC protocols. However, it may result in significant latency. Forwarding a packet over multiple hops often requires multiple operational cycles (sleep latency) where nodes have to wait for the next cycle to forward data at each hop. This manuscript deals with timeliness issues of slotted contention-based WSN MAC protocols. It provides a comprehensive review and taxonomy of state-of-the-art synchronous MAC protocols. The main contribution is to study and classify these protocols from the delay efficiency perspective. The protocols are divided into two main categories: static schedule and adaptive schedule. Adaptive schedule are split up into four subclasses: adaptive grouped schedule, adaptive repeated schedule, staggered schedule, and reservation schedule. Several state-of-the-art protocols are described following the proposed classification, with comprehensive discussions and comparisons with respect to their latency.