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Djiroun F.Z.,Blida University | Djiroun F.Z.,CERIST Research Center | Djenouri D.,CERIST Research Center
IEEE Communications Surveys and Tutorials | Year: 2017

The use of a low-power wake-up radio in wireless sensor networks is considered in this paper, where relevant medium access control solutions are studied. A variety of asynchronous wake-up MAC protocols have been proposed in the literature, which take advantage of integrating a second radio to the main one for waking it up. However, a complete and a comprehensive survey particularly on these protocols is missing in the literature. This paper aims at filling this gap, proposing a relevant taxonomy, and providing deep analysis and discussions. From both perspectives of energy efficiency and latency reduction, as well as their operation principles, state-of-the-art wake-up MAC protocols are grouped into three main categories: 1) duty cycled wake-up MAC protocols; 2) non-cycled wake-up protocols; and 3) path reservation wake-up protocols. The first category includes two subcategories: 1) static wake-up protocols versus 2) traffic adaptive wake-up protocols. Non-cycled wake-up MAC protocols are again divided into two classes: 1) always-on wake-up protocol and 2) radio-triggered wake-up protocols. The latter is in turn split into two subclasses: 1) passive wake-up MAC protocols versus 2) ultra low power active wake-up MAC protocols. Two schemes could be identified for the last category, 1) broadcast based wake-up versus 2) addressing based wake-up. All these classes are discussed and analyzed in this paper, and canonical protocols are investigated following the proposed taxonomy. © 2016 IEEE.


Djenouri D.,CERIST Research Center | Balasingham I.,University of Oslo
IEEE Transactions on Mobile Computing | Year: 2011

A new localized quality of service (QoS) routing protocol for wireless sensor networks (WSN) is proposed in this paper. The proposed protocol targets WSN's applications having different types of data traffic. It is based on differentiating QoS requirements according to the data type, which enables to provide several and customized QoS metrics for each traffic category. With each packet, the protocol attempts to fulfill the required data-related QoS metric(s) while considering power efficiency. It is modular and uses geographical information, which eliminates the need of propagating routing information. For link quality estimation, the protocol employs distributed, memory and computation efficient mechanisms. It uses a multisink single-path approach to increase reliability. To our knowledge, this protocol is the first that makes use of the diversity in data traffic while considering latency, reliability, residual energy in sensor nodes, and transmission power between nodes to cast QoS metrics as a multiobjective problem. The proposed protocol can operate with any medium access control (MAC) protocol, provided that it employs an acknowledgment (ACK) mechanism. Extensive simulation study with scenarios of 900 nodes shows the proposed protocol outperforms all comparable state-of-the-art QoS and localized routing protocols. Moreover, the protocol has been implemented on sensor motes and tested in a sensor network testbed. © 2011 IEEE.


Khiati M.,University of Science and Technology Houari Boumediene | Djenouri D.,CERIST Research Center
Proceedings - IEEE 11th International Symposium on Network Computing and Applications, NCA 2012 | Year: 2012

This paper proposes a cluster-based broadcast protocol to disseminate delay-sensitive information throughout a wireless sensor network (WSN). The protocol considers the use of duty-cycling at the MAC layer, which is essential to reduce energy dissipation. LEACH's energy-efficiency approach is used for cluster construction. The proposed protocol adds new common static and dynamic broadcast periods to support and accelerate broadcasting. The dynamic periods are scheduled following the past arrivals of messages, and using a Markov-chain model. To our knowledge, this work is the first that proposes the use of clustering to reduce broadcast latency. The clustering mechanism allows for simultaneous local broadcasts at several clusters in the WSN, and it also ensures scalability with the increase of the network size. The protocol has been simulated, numerically analyzed, and compared with LEACH. The results show clear improvement over LEACH with regard to the latency. © 2012 IEEE.


Khiati M.,University of Science and Technology Houari Boumediene | Djenouri PhD D.,CERIST Research Center
International Journal of Communication Systems | Year: 2015

Broadcasting delay-sensitive information over a duty-cycled wireless sensor network is considered, and a cluster-based protocol is proposed. The proposed protocol, namely Broadcast over Duty-Cycle and LEACH (BOD-LEACH), takes advantage of the LEACH's energy-efficient clustering. This approach shifts the total burden of energy consumption of a single cluster head by rotating the cluster-head role among all nodes in the network. It also permits the ordinary (member) nodes in a cluster to turn off their radios whenever they enter inactive TDMA slots. However, LEACH does not consider broadcast messages, and the member nodes scheduling is established as a sequence of Time Division Multiple Access (TDMA) without any common active period. A broadcast message should then be postponed to the next TDMA schedule and transmitted in a sequence of unicast messages, which is inefficient in terms of latency, bandwidth occupation, and power consumption. The proposed protocol adds new common static and dynamic broadcast periods to support and accelerate broadcasting. The dynamic periods are scheduled following the past arrivals of messages and using a Markov chain model. To our knowledge, this work is the first that proposes the use of clustering to perform simultaneous local broadcasts at several clusters. This reduces broadcast latency and ensures scalability. The protocol has been simulated, numerically analyzed, and compared with LEACH. The results show clear improvement over LEACH with regard to broadcast latency, at a low energy cost. Copyright © 2013 John Wiley & Sons, Ltd.


Djenouri D.,CERIST Research Center | Merabtine N.,Blida University | Mekahlia F.Z.,Blida University | Doudou M.,CERIST Research Center
Ad Hoc Networks | Year: 2013

The challenging problem of time synchronization in wireless sensor networks is considered in this paper, where a new distributed protocol is proposed for both local and multi-hop synchronization. The receiver-to-receiver paradigm is used, which has the advantage of reducing the time-critical-path and thus improving the accuracy compared to common sender-to-receiver protocols. The protocol is fully distributed and does not rely on any fixed reference. The role of the reference is divided amongst all nodes, while timestamp exchange is integrated with synchronization signals (beacons). This enables fast acquisition of timestamps that are used as samples to estimate relative synchronization parameters. An appropriate model is used to derive maximum likelihood estimators (MLE) and the Cramer-Rao lower bounds (CRLB) for both the offset-only, and the joint offset/skew estimation. The model permits to directly estimating relative parameters without using or referring to a reference' clock. The proposed protocol is extended to multi-hop environment, where local synchronization is performed proactively and the resulted estimates are transferred to the intermediate/end-point nodes on-demand, i.e. as soon as a multi-hop communication that needs synchronization is initiated. On-demand synchronization is targeted for multi-hop synchronization instead of the always-on global synchronization model, which avoids periodic and continuous propagation of synchronization signals beyond a single-hop. Extension of local MLE estimators is proposed to derive relative multi-hop estimators. The protocol is compared by simulation to some state-of-the-art protocols, and results show much faster convergence of the proposed protocol. The difference has been on the order of more than twice compared to CS-MNS, more than ten times compared to RBS, and more than twenty times compared to TPSN. Results also show scalability of the proposed protocol concerning the multi-hop synchronization. The error does not exceed few microseconds for as much as 10 hops in R4Syn, while in CS-MNS, and TPSN, it reaches few tens of microseconds. Implementation and tests of the protocol on real sensor motes confirm microsecond level precision even in multi-hop scenarios, and high stability (long lifetime) of the skew/offset model. © 2013 Elsevier B.V. All rights reserved.


Djenouri D.,CERIST Research Center
IEEE Vehicular Technology Conference | Year: 2014

Receiver-to-receiver time synchronization in wireless networks is considered, and appropriate maximum-likelihood estimators (MLE) for environments with exponential distrusted reception delays are proposed. In the receiver-to-receiver synchronization approach, time at receivers should be directly related to one another without referring to the sender (reference), which permits to eliminate the sender's uncertainty from the variable delays (time critical-path). The models and estimators proposed for the sender-to-receiver approach are thus inappropriate for the receiver-to-receiver one. A model that accurately reflects the relative feature of the considered approach and eliminates the senders's uncertainty is used, where timestamps at the receivers are directly related without referring to the sender's time or timestamps. By directly relating time at two receivers with identical exponential reception delay, Exp(λ), it yields a Laplace(0,1/λ) distribution as the difference between the two delays. By using the log-likelihood function of the latter and the ML method, the offset estimator is analytically derived and a linear program is given for the joint offset/skew model. The accuracy of the proposed estimators has been numerically analyzed by simulation. Results show high precision of the proposed estimators, which can be integrated with any receiver-to-receiver synchronization protocol. © 2014 IEEE.


Belazzougui D.,CERIST Research Center
Theoretical Computer Science | Year: 2016

Suppose we have two players A and C, where player A has a string s[0. ..u-1] and player C has a string t[0. ..u-1] and none of the two players knows the other's string.Assume that s and t are both over an integer alphabet [σ]. =[0, σ. -1], where the first string contains n non-zero entries. We would wish to answer the following basic question. Assuming that s and t differ in at most k positions, how many bits does player A need to send to player C so that he can recover s with certainty? Further, how much time does player A need to spend to compute the sent bits and how much time does player C need to recover the string s? This problem has a certain number of applications, for example in databases, where each of the two parties possesses a set of n key-value pairs, where keys are from the universe [. u] and values are from [σ] and usually n≪. u.In this paper, we show a time and message-size optimal Las Vegas reduction from this problem to the problem of systematic error correction of k errors for strings of length Θ(n) over an alphabet of size 2Θ(log σ+log (u/n)).The additional running time incurred by the reduction is linear expected (randomized) for player A and linear worst-case (deterministic) for player C, but the correction works with certainty. When using the popular Reed-Solomon codes, the reduction gives a protocol that transmits O(k(log u+log σ)) bits and runs in time O(n·polylog(n)(log u+log σ)) for all values of k. The time is expected for player A (encoding time) and worst-case for player C (decoding time). The message size is optimal whenever k≤(uσ)1-Ω(1). © 2016.


Doudou M.,CERIST Research Center | Djenouri D.,CERIST Research Center | Badache N.,CERIST Research Center
IEEE Communications Surveys and Tutorials | Year: 2013

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 wake-up 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. © 2013 IEEE.


Djenouri D.,CERIST Research Center
2011 IEEE GLOBECOM Workshops, GC Wkshps 2011 | Year: 2011

A general scenario for using reference broadcast synchronization (RBS) in heterogeneous multi-hop wireless networks is defined, together with an appropriate model allowing to directly derive maximum likelihood estimators (MLE) to the skew and offset between communicating nodes. The model captures nodes heterogeneity that may cause differences in the reception delays. It also eliminates the need for synchronizing to the reference and enables direct relative synchronization. This accurately eliminates sender's delays from the critical path, which faithfully reflects RBS features and the receiver/receiver paradigm. It will be shown that state-of-the-art RBS estimators for the joint skew/offset problem fail to eliminate sender's delay. Appropriate MLEs are accordingly proposed. The Cramer-Rao lower bounds (CRLBs) are calculated, then the proposed estimators are numerically analyzed. Results show the estimators quadratically converge to the CRLB as the sample size rises, and that the precession is uninfluenced by the degree of heterogeneity (increase of delay differences). In a summary, the contribution of this paper is threefold; i) considering usage of RBS in heterogeneous and multi-hop networks, ii) defining an appropriate model and accordingly the maximum likelihood estimators for relative skew/offset between communicating nodes, iii) defining theoretical bounds for the estimators and numerically analyzing their convergence. © 2011 IEEE.


Djenouri D.,CERIST Research Center
IEEE Signal Processing Letters | Year: 2012

A new time synchronization protocol for wireless sensor networks (WSN) is proposed. It uses the receiver-to-receiver principle introduced by the Reference Broadcast Synchronization (RBS), which reduces the time-critical path compared to the sender-to-receiver approach. The proposed protocol has the advantage of distributing the reference's function among all sensors, which eliminates the single point of failure (reference) shortcomings of RBS. It also allows timestamps to be piggybacked to the regular signals (beacons) and thus eliminates the need of separate transmissions for exchanging timestamps. After local synchronization, a multihop extension is proposed using final local estimates, with no forwarding of synchronization signals. Maximum likelihood estimators (MLE) are derived to estimate relative skew/offset for channels with Gaussian distributed delays. The Cramer-Rao lower bounds (CRLB) are accordingly derived and numerically compared with the MLE's mean square error (MSE). Results show convergence of the proposed estimators' precision to their respective CRLB with the increase of the number of signals. © 2006 IEEE.

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