Nadjib Badache

Congestion Control Protocols in Wireless Sensor Networks: A Survey

The performance of wireless sensor networks (WSN) is affected by the lossy communication medium, application diversity, dense deployment, limited processing power and storage capacity, frequent topology change. All these limitations provide significant and unique design challenges to data transport control in wireless sensor networks. An effective transport protocol should consider reliable message delivery, energy-efficiency, quality of service and congestion control. The latter is vital for achieving a high throughput and a long network lifetime. Despite the huge number of protocols proposed in the literature, congestion control in WSN remains challenging. A review and taxonomy of the state-of-the-art protocols from the literature up to 2013 is provided in this paper. First, depending on the control policy, the protocols are divided into resource control vs. traffic control. Traffic control protocols are either reactive or preventive (avoiding). Reactive solutions are classified following the reaction scale, while preventive solutions are split up into buffer limitation vs. interference control. Resource control protocols are classified according to the type of resource to be tuned.

Data replication protocols for mobile ad-hoc networks: a survey and taxonomy

In mobile ad-hoc networks, frequent network partitioning and the failure of mobile nodes due to exhaustion of their battery power can considerably decrease data availability. In addition, the increase in network size and node mobility cause the performance of data access to degrade. To deal with these issues, a number of data replication protocols have been proposed in the recent years. This paper surveys the existing data replication protocols in mobile ad-hoc networks and proposes a classification scheme that categorizes the protocols into various classes, with respect to the issues they address. Network partitioning, energy consumption, and scalability are the three issues that are identified in this paper, and which have not been previously considered in the fixed networks. The paper also provides a comparison of the protocols and investigates opportunities for future research.

A Self-Stabilizing Leader Election Algorithm in Highly Dynamic Ad Hoc Mobile Networks

The classical definition of a self-stabilizing algorithm assumes generally that there are no faults in the system long enough for the algorithm to stabilize. Such an assumption cannot be applied to ad hoc mobile networks characterized by their highly dynamic topology. In this paper, we propose a self-stabilizing leader election algorithm that can tolerate multiple concurrent topological changes. By introducing the time-interval-based computation concept, the algorithm ensures that a network partition can within a finite time converge to a legitimate state even if topological changes occur during the convergence time. Our simulation results show that our algorithm can ensure that each node has a leader over 99 percent of the time. We also give an upper bound on the frequency at which network components merge to guarantee the convergence.

Data Aggregation Scheduling Algorithms in Wireless Sensor Networks: Solutions and Challenges

Energy limitation is the main concern of any wireless sensor network application. The communication between nodes is the greedy factor for the energy consumption. One important mechanism to reduce energy consumption is the in-network data aggregation. In-network data aggregation removes redundancy as well as unnecessary data forwarding, and hence cuts on the energy used in communications. Recently a new kind of applications are proposed which consider, in addition to energy efficiency, data latency and accuracy as important factors. Reducing data latency helps increasing the network throughput and early events detection. Before performing the aggregation process, each node should wait for a predefined time called WT (waiting time) to receive data from other nodes. Data latency (resp., accuracy) is decreased (resp., increased), if network nodes are well scheduled through optimal distribution of WT over the nodes. Many solutions have been proposed to schedule network nodes in order to make the data aggregation process more efficient. In this paper, we propose a taxonomy and classification of existing data aggregation scheduling solutions. We survey main solutions in the literature and illustrate their operations through examples. Furthermore, we discuss each solution and analyze it against performance criteria such as data latency and accuracy, energy consumption and collision avoidance. Finally, we shed some light on future research directions and open issues after deep analysis of existing solutions.

Distributed mutual exclusion algorithms in mobile ad hoc networks: an overview

The problem of mutual exclusion has been extensively studied in distributed systems. The proposed solutions can be mainly classified in consensus based and token based protocols. Some of the proposed solutions consider the physical topology of the networks and try to provide optimal message exchange and minimal synchronisation delays. Others, impose a logical structure on the network like a ring or a tree. Recently, the mutual exclusion problem received an interest for mobile ad hoc networks. These networks are known as a challenging domain. To our knowledge, few algorithms have been proposed in the literature and all of them are token based approach. In this paper, we review the distributed mutual exclusion algorithms developed for mobile environments and principally for ad hoc networks and discuss some issues.

On eliminating packet droppers in MANET: A modular solution

In this paper we deal with misbehaving nodes in mobile ad hoc networks (MANETs) that drop packets supposed to be relayed, whose purpose may be either saving their resources or launching a DoS attack. We propose a new solution to monitor, detect, and safely isolate such misbehaving nodes, structured around five modules: (i) The monitor, responsible for controlling the forwarding of packets, (ii) the detector, which is in charge of detecting the misbehaving of monitored nodes, (iii) the isolator, basically responsible for isolating misbehaving nodes detected by the detector, (iv) the investigator, which investigates accusations before testifying when the node has not enough experience with the accused, and (v) finally the witness module that responds to witness requests of the isolator. These modules are based on new approaches, aiming at improving the efficiency in detecting and isolating misbehaving nodes with a minimum overhead. We describe these modules in details, and their interactions as well. We also mathematically analyze our solution and assess its performance by simulation, and compare it with the watchdog, which is a monitoring technique employed by almost all the current solutions.

Review: Synchronous contention-based MAC protocols for delay-sensitive wireless sensor networks: A review and taxonomy

Duty-cycling allows obtaining significant energy saving compared to full duty cycle (sleepless) random access MAC protocols. However, it may result in significant latency. 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 receivers active period, which is eliminated with synchronous approach where nodes sleep and wake up all together. Despite the possible increase of contention by grouping active periods, the delay due to packets retransmissions after collisions is less significant compared to the waiting time of asynchronous protocols. Furthermore, contention-based feature makes the protocol conceptually distributed and more dynamic compared to TDMA-based. 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 performance objective considered in the proposed taxonomy is the latency, in the context of energy-limited WSN, where energy is considered as a constraint for the MAC protocol that yields the need of duty-cycling the radio. 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.

A Study of Wireless Sensor Networks for Urban Traffic Monitoring: Applications and Architectures

Abstract With the constant increasing of vehicular traffic around the world, especially in urban areas, existing traffic management solutions become inefficient. This can be clearly seen in our life through persistent traffic jam and rising number of accidents. Wireless sensor networks (WSN) based intelligent transportation systems (ITS) have emerged as a cost effective technology that bear a pivotal potential to overcome these difficulties. This technology enables a new broad range of smart city applications around urban sensing including traffic safety, traffic congestion control, road state monitoring, vehicular warning services, and parking management. This manuscript gives a comprehensive review on WSN based ITS solutions. The main contribution of this paper is to classify current WSNs based ITS projects from the application perspective, with discussions on the fulfillment of the application requirements.

Semi-structured and unstructured data aggregation scheduling in wireless sensor networks

This paper focuses on data aggregation scheduling problem in wireless sensor networks (WSNs), to minimize time latency. Prior works on this problem have adopted a structured approach, in which a tree-based structure is used as an input for the scheduling algorithm. As the scheduling performance mainly depends on the supplied aggregation tree, such an approach cannot guarantee optimal performance. To address this problem, we propose approaches based on Semi-structured Topology (DAS-ST) and Unstructured Topology (DAS-UT). The approaches are based on two key design features, which are: (1) simultaneous execution of aggregation tree construction and scheduling, and (2) parent selection criteria that maximize the choices of parents for each node and maximize time slot reuse. We prove that the latency of DAS-ST is upper-bounded by ([2π/arccos(1/1+ϵ)]+4)R+Δ-4, where R is the network radius, Δ is the maximum node degree, and 0.05 <; ϵ ≤ 1. Simulations results show that DAS-UT outperforms DAS-ST and four competitive state-of-the-art aggregation scheduling algorithms in terms of latency and network lifetime.

A pull‐based service replication protocol in mobile ad hoc networks

The mobility of nodes in ad hoc networks can lead to frequent network partitioning. This partitioning disconnects many nodes from a centralised server. Being aware of a future partitioning can help to provide a continuous service availability for all mobile nodes. In this paper, we propose a service replication protocol consisting of three distributed algorithms. This protocol (i) predicts the occurrence of network partitioning, which allows to create service replicas in the future separate partitions and (ii) constructs a dynamic service replicas deployment scheme. Using linear-time temporal logic, we show that each detection of network partitioning can be predicted before its occurrence. Our simulation results show that the proposed protocol guarantees service availability to all mobile nodes without incurring high cost. Copyright