Delivering downlink ACKs to Class A LoRaWAN devices via LEO satellite constellations requires predicting end-to-end propagation delays of 10–500 ms to hit a 1-second receive window, a timing challenge absent from terrestrial schedulers. We present DORSAL, the first Mixed-Integer Linear Programming (MILP) scheduler for downlink delivery in direct-to-satellite LoRaWAN networks. It introduces theDownlink Arrival Receive-window Timing (DART)as the central constraint to jointly optimize gateway selection and packet injection timing across ISL-capable and bent-pipe architectures. Evaluation on a Walker 5×5 polar constellation (25 satellites, 650 km) and a commercial ground station network yields five results: (i) DART infeasibility blocks 73% of bent-pipe deliveries regardless of scheduler quality: DART-unaware approaches collapse from 93% nominal to only 20% real delivery; (ii) ISL routing raises %ACK by +67.4 pp over bent-pipe (91.6% vs. 24.2% atnGS=3 ground stations, ISM band) by eliminating the three-way simultaneous-visibility constraint, with 73% of ACKs delivered via ≥ 2-hop paths; (iii) ISL %ACK is nearly flat acrossnGS∈ {3, 6, 12} ground stations (91.6%–92.7%), showing that a minimal threestation polar network captures the full scheduling benefit of an ISL-equipped constellation; (iv) ISL hardware speed has negligible impact up to 300 ms/hop: %ACK is flat from 0 to 300 ms, then degrades in two discrete steps (−5.3 pp at 500 ms, −2 pp at 700 ms) as successive hop-count tiers lose causal injection feasibility; and (v) the MILP solves to proven optimality within seconds for up to 103devices, confirming that the sparse conflict-graph structure keeps the problem tractable at realistic IoT subscriber counts.

Long-Range (LoRa) is one of the main modulation techniques used for Low Power Wide Area Networks (LPWANs). Recently, it has been extended from the sub-GHz band to the 2.4 GHz Industrial, Scientific, and Medical (ISM) band, enabling the construction of a LPWAN that benefits from global interoperability without duty-cycle limitations. However, the coexistence of LoRa with the other wireless technologies of the 2.4 GHz ISM band is a challenging question. In this article, we make the first performance evaluation of the interference between LoRa and Wireless Fidelity (Wi-Fi) transmissions, by analyzing multiple parameters: LoRa channel occupancy, deployment topology, LoRa physical layer parameters, and the frequency channels used. We also perform simulations to extend our experimental results to other configurations. The performance evaluation is achieved using a generic methodology that can be applied to other wireless technologies. Finally, we provide recommendations for the use and deployment of LoRa that will improve its coexistence with Wi-Fi.

LoRaWAN is a widely used wireless communication standard for the Internet of Things that enables the collection of measurement data from numerous monitoring applications (such as smart metering, pollution, and asset tracking). Most research work has been focused on the performance of LoRaWAN as a function of the uplink traffic, as this is the most common scenario. Nevertheless, downlink traffic is a fundamental building block of the LoRaWAN standard, and a crucial part of applications such as smart healthcare, where reliability is extremely important. In this paper, we study the impact of the downlink traffic and different scheduling policies on the performance of LoRaWAN. We investigate: (i) the impact of an optimal schedule for the downlink traffic, (ii) the choice of the physical layer parameters used to send downlinks to end-devices during the second reception window, and (iii) the choice of the gateway that sends the downlinks. Our results show that even when using an optimal schedule, the presence of downlink traffic reduces the capacity of a LoRaWAN network up to 20%. The most limiting factor is the gateway, due to its duty cycle and half-duplex characteristics.

This work focuses on managing upstream traffic in multigateway Low-Power Wide Area Networks (LPWANs) to support efficient traffic from thousands of nodes. As LP-WANs face challenges such as increased collision probability and network saturation due to node densification, our research introduces a distributed and probabilistic traffic control protocol. This protocol aims to effectively manage network traffic, reduce collisions, and mitigate saturation issues, ensuring better performance and scalability in densely populated IoT environments. The protocol enables nodes to dynamically adapt their traffic to meet application needs, such as transmitting a defined number of measurements (K) within a designated time frame. This adjustment remains unaffected by the node count and network topology, focusing instead on the feedback message's destination to the network nodes, which is crucial for dynamically adapting traffic intensity and reducing collisions. We explore two feedback transmission strategies: a synchronous one, where all gateways transmit feedback simultaneously to all nodes, and a round-robin one, where one gateway at a time sends feedback to nodes within its coverage area. Based on simulation results, our evaluated strategies achieve substantial performance improvements over the Baseline LoRaWAN. Specifically, they demonstrate a network lifetime increase of up to 93.12 %, a success rate increase of up to 96.34 %, and a packet delivery ratio increase of up to 14.97 %. These findings highlight significant enhancements in both efficiency and reliability compared to traditional LoRaWanconfigurations.

An emergency communication system is necessary for first responders, who need to enter areas with no network coverage or damaged network infrastructure due to natural or man-made disasters to perform emergency tasks. The first responders usually rely on fixed base stations deployed according to the needs of the mission, to meet the communication needs. However, fixed base stations can pose several limitations, typically for supporting the mobility of groups of users. Thanks to the development of software defined radio and software defined networks, embedding the functions of a base station on a movable platform, such as a vehicle or a drone, is now a possible alternative. The base station carried by the movable platform can react to changes in the network in real time, allowing more flexibility and introducing a new degree of freedom for the emergency communication network. In this work, we present a quantitative network performance comparison between a fixed base station and a movable base station, when a group of first responders is moving in a geographical area for an emergency rescue mission. We show that a movable base station provides up to 4 times the throughput of a fixed base station.

LoRa® and LoRaWAN are one of the most common wireless technologies used today in the Internet of Things. If until now LoRa was strictly used in sub-GHz bands, a new version has been released for the 2.4 GHz band that does not have any duty cycle restrictions and that allows the use of higher datarates, which opens the door to the deployment of new applications (such as asset tracking or indoor localization). In this paper, we present the first extensive evaluation of LoRa 2.4 GHz in a typical indoor environment, both in the presence and lack of human and WiFi activities. We run an exhaustive evaluation of all 128 possible combinations of the different LoRa physical parameters (spreading factor, bandwidth and coding rate) and we show that despite the use of higher frequency, LoRa is capable of maintaining a good connectivity throughout the building, similar to what was observed in sub-GHz bands. Still, some configurations were clearly affected by the daily life activities in the building during the working hours of weekdays.

Long-Range Wide Area Networks (LoRaWAN) enable low-power data collection over long distances, and they are thus widely used for Internet of Things applications, despite their limitations to meet some traffic requirements (e.g., reliability). To achieve the quality of service required by the applications, service differentiation is a promising approach which can be provided by network slicing. In this work, we show that related works are either incompatible with the LoRaWAN specifications, or do not isolate traffic, or assume an a priori known and stable traffic. In this paper, we propose a lightweight approach to achieve slicing in LoRaWAN, compatible with the LoRaWAN specifications. Our approach allows to isolate traffic, to protect confirmed traffic, and to deal with unsolicited traffic.

There is a constant threat of having our computing systems under attack. Information regarding the origins of the traffic we receive can be valuable. Currently, the AS-number and the localization are the most commonly used IP-related information to characterize an attack.In this paper, we propose expanding knowledge about a remote IP’s owner to improve defensive reaction effectiveness and obtain in-depth analyzes of attacker profiles. We introduce the enrichment with socio-organizational information (such as organization type, activity field, etc.) about the entities owning the IP in addition to infrastructural information. This integration is driven by combining RDAP and Wikidata. We demonstrate that this proposal is promising.

LoRaWAN is a major player for IoT data collection in large areas. In such networks, the uplink is mainly used, especially for data transmission, whereas the downlink is used for control purposes, including physical layer configuration, over the air activation and acknowledgments. In most studies of the LoRaWAN capacity, the uplink and the downlink are supposed to be orthogonal. This assumption seems acceptable and correct because the LoRa physical layer uses an inverse modulation for the uplink and the downlink. In this work, we use a real testbed composed of software-defined radio (USRPs, GNU Radio) to show that this assumption is wrong: the frame delivery rate decreases by up to 20% when simultaneous transmissions occur between the uplink and the downlink. As far as we know, it is the first time that this result is shown.

Direct-to-Satellite-IoT (DtS-IoT) is a promising approach for data transfer to/from IoT devices in remote areas where deploying terrestrial infrastructure is not appealing or feasible. In this context, Low-Earth Orbit (LEO) satellites can serve as passing-by IoT gateways to which devices can offload buffered data to. However, transmission distance and orbital dynamics, combined with highly constrained devices on the ground makes DtS-IoT a very challenging problem. In fact, existing IoT medium access control protocols, negotiations schemes, etc. need to be revised and/or extended to scale up to these challenging conditions. The intricate time-dynamic aspects of DtS-IoT networks require of adequate simulation environments to assess the expected performance of enabling technologies. To make up for the lack of such tools, we present a novel event-driven open-source end-to-end simulation tool coined FLoRaSAT. The simulator leverages Omnet++ and includes a benchmarking DtS-IoT scenario comprising 16 cross-linked LEO satellites and 1500 IoT nodes on the surface. Satellites and devices are connected using the standard LoRaWAN Low-Power Wide Area (LPWAN) protocol (Class A and B). FLoRaSAT allows the easy implementation and study of DtS-IoT radio access and core network protocols, and we take advantage of this flexibility to investigate expected network metrics and non-intuitive phenomena emerging from the resulting multi-gateway setup.

Self-deployable mobile networks represent a new type of cellular networks, that can be rapidly deployed, easily installed, and operated on demand, anywhere, anytime. They can provide network services when a classical cellular network fails, is not suitable, or does not exist. Using network virtualization techniques, core network and base station functions can be co-located together into a single equipment. This brings the network functions closer to the user, but the placement of the local core network has a significant impact on the network performance, mainly in terms of capacity and delay. In this work, we are focused on the delay minimization from BSs to the local core network. We propose a heuristic for the local core network placement, with the objective of reducing the delay. We show that the delay obtained by our solution decreases significantly compared to a strategy that places the local core network in order to maximize the capacity. We also show that considering a capacity-based placement strategy leads to infinite delay in some cases.

In this work, we propose a robust planning tool that allocates power statically in homogeneous and heterogeneous cellular networks with non-regular base station (BTS) placement, to mitigate interference and improve overall performance. Each BTS will use the total available spectrum, but it will divide it into multiple sub-bands, and each BTS will transmit with a specific pre-computed power on each sub-band. We refer to such a power allocation as a power map. Our offline planning tool computes a robust power map for a given topology, by solving a non-convex, non-linear optimization problem, through simple transformations, based on geometric programming. The power map is computed based solely on the network topology, and it is made available to all BTSs that use it throughout the network operation to perform scheduling using a fast quasi-optimal online algorithm that we propose. We evaluate our planning tool for different homogeneous and heterogeneous networks (HetNets), first in a static setting where scheduling is performed optimally and then in a dynamic setting when scheduling is performed with our online scheduler. Results show that our solution significantly outperforms a classical equal power/fixed frequency reuse scheme in terms of sum-rate, by up to 30% in homogeneous networks and by up to 70% in HetNets.

A novel trend in mobile networks is to co-locate the base stations with virtualized core network functions, such as session management and routing. The goal is to lose the long-standing physical dependency between the radio access and the core network, and improve network resiliency. In this work, we focus on the placement of virtualized core functions within a network of multiple base stations interconnected via a potentially limited backhaul. Since all data and signaling traffic are exchanged on the links interconnecting the base stations, the placement of these functions deeply impacts the backhaul load. We compare centralized and distributed placement strategies, with respect to the overall backhaul bandwidth consumption. Results show that distributing instances of the core functions (e.g., routing) in the network is significantly less costly from a backhaul point of view, and can economize backhaul consumption by 86%.

An isolated base station is a base station having no connection to a traditional core network. To provide services to users, an isolated base station is colocated with an entity providing the same functionalities as the traditional core network, referred to as Local EPC. In order to cover wider areas, several base stations are interconnected, forming a network that should be served by a single Local EPC. In this work, we tackle the Local EPC placement problem in the network, to determine with which of the base stations the Local EPC must be co-located. We propose a novel centrality metric, flow centrality, which measures the capacity of a node to receive the total amount of flows in the network. We show that co-locating the Local EPC with the base station having the maximum flow centrality maximizes the total amount of traffic the Local EPC can receive from all base stations, under certain capacity and load distribution constraints. We compare the flow centrality to other state of the art centrality metrics, and emphasize its advantages.

Data aggregation has been developed to take benefits from either spatial or temporal correlation of collected data. In wireless sensor networks, data aggregation is a key mechanism to reduce energy consumption and to increase capacity. Most current aggregation functions are designed for specific network topology or data pattern, with prior assumptions. Concretely, these functions are developed with fixed models or parameters, so they fail to adapt against non-anticipated data variations or dynamic scenarios. In this work, we propose a dynamic forecasting function: Agnostic Aggregation (A2), which can predict values with self-tuned model based on temporal correlation. With A2, sensor nodes are able to adjust model to fit the latest time series better. Compared with previous works, the proposed A2can deliver packets to the sink with higher accuracy, and is more robust to independent and consecutive errors. We also investigate the influence of system parameters on the performance of A2, and highlight the optimal choices. Comparison results verify that A2improves the recovery fidelity and reduces model updates than other aggregation functions.

Energy harvesting capabilities are challenging our understanding of wireless sensor networks by adding recharging capacity to sensor nodes. This has a significant impact on the communication paradigm, as networking mechanisms can benefit from these potentially infinite renewable energy sources. In this work, we study the consequences of implementing photovoltaic energy harvesting on the duty cycle of a wireless sensor node, in both outdoor and indoor scenarios. We show that for the static duty cycle approach in outdoor scenarios, very high duty cycles, in the order of tens of percents, are achieved. This further eliminates the need for additional energy conservation schemes. In the indoor case, our analysis shows that the dynamic duty cycle approach based solely on the battery residual energy does not necessarily achieve better results than the static approach. We identify the main reasons behind this behavior, and test new design considerations by adding information on the battery level variation to the duty cycle computation. We demonstrate that this approach always outperforms static solutions when perfect knowledge of the harvestable energy is assumed, as well as in realistic deployments, where this information is not available.

The industrial Internet of Things (IoT) relies on multi-hop radio paths. Synchronized nodes follow a Frequency-Time Division Multiple Access (FTDMA) schedule, but even using channel-hopping to mitigate interference, the radio links suffer packet losses. Resource allocation algorithms must consider the requirements of the applications in terms of delivery and allocate extra resource to compensate for anticipated losses. We propose a hop-by-hop allocation mechanism that extends the Traffic-Aware Scheduling Algorithm (TASA) by enabling retransmissions. We give each flow on the network the possibility to satisfy its applicative end-to-end delivery constraint. We keep the amount of resource allocated for retransmissions low, and balance the allocations on the relay nodes. By means of simulations, we show the gain in terms of reliability, and the cost in terms of number of allocations.

This paper focuses on the resilience of routing protocols against malicious insiders willing to disrupt communications. Previous study showed that introducing randomness and data replication enhances the resilience of routing protocols. It makes them unpredictable for an attacker and provides route diversification. We propose a theoretical framework of the resilience based on biased random walks on a torus lattice. The objective is to evaluate analytically the influence of bias and data replication introduced to random walks. The bias allows to decrease the route length, thus reducing the probability of a data packet to meet a malicious insider along the route; however, it also decreases the degree of randomness (entropy). When combined with data replication, the reliability is improved thanks to route diversity despite an additional overhead in terms of energy consumption. The main goal is to provide a good tradeoff between shortest path and route diversity for a reasonable cost.

Providing high data rates with minimum energy consumption is a crucial challenge for next generation wireless networks. There are few papers in the literature which combine these two issues. This paper focuses on multi-hop wireless mesh networks using a MAC layer based on Spatial Time Division Multiple Access (S-TDMA). We develop an optimization framework based on linear programming to study the relationship between throughput and energy consumption. Our contributions are two-fold. First, we formulate and solve, using column generation, a new MILP to compute offline energy-throughput tradeoff curve. We use a physical interference model where the nodes can perform continuous power control and can use a discrete set of data rates. Second, we highlight network engineering insights. We show, via numerical results, that power control and multi-rate functionalities allow optimal throughput to be reached, with lower energy consumption, using a mix of single hop and multi-hop routes.

The era of the Internet of Things brings complexity and deployment costs in smart cities, particularly in Wireless Sensor Networks (WSNs). Utilities such as gas or water providers are keen on delegating the management of the communications to specialized firms, namely WSN Operators, that will share the WSN resource among their various clients. WSN operators will use a functional architecture to manage the Service Level Agreements (SLAs), i.e. the Quality of Service (QoS) clauses they contract with their clients. WSN operators will need a robust and reliable technology in order to guarantee QoS constraints in a wireless environment, as in the industrial world. IEEE 802.15.4e Time Slotted Channel Hopping (TSCH) [1] is one good candidate. Moreover, the IETF experience in IP networks management is an important input for monitoring and QoS control over WSNs. This article gives formal guidelines for the implementation of a SLA architecture for operated WSNs. It distinguishes the various formal algorithms that are necessary to operate a WSN according to SLAs, and determines which functional entities are necessarily technology-dependent. Detailed examples of such entities are developed in an IPv6 over IEEE 802.15.4e TSCH context, such as advocated in the IETF 6TiSCH Working Group [2].

The operations of smart metering heavily rely on the communication network for efficient data gathering, thus eliminating manual meter reading. Smart electronic devices are deployed in open, unattended and possibly hostile environment such as consumer's home and office areas, making them particularly vulnerable to physical attacks. Resilience is needed to mitigate such inherent vulnerabilities and risks related to security and reliability. In this article, a general overview of the resilience including definition, metric and resilient techniques relevant for smart metering is presented. A quantitative metric, visual and meaningful, based on the graphical representation is adopted to compare routing protocols in the sense of resilience against active insider attacks. Five well-known routing protocols from the main categories have been studied through simulations and their resilience is evaluated according to the given metric. Resilient techniques introduced to these protocols have enhanced significantly the resilience against attacks providing route diversification.

Data aggregation is a key problem in wireless sensor networks due to both energy-constrained and bandwidth-constrained. In this paper, we highlight the aggregation benefits in network layer and MAC layer by modeling the energy consumption for some energy-efficient routing protocols and MAC protocols. Besides, we define two parameters, aggregation ratio w and packet size coefficient λ, to evaluate the efficiency of an aggregation method, and we discuss their trade-off. Additionally, we propose comparison between A-ARMA and compressive sensing, which are on behalf of the state-of-the-art forecasting aggregation and compressing aggregation respectively.

Numerous localization protocols in Wireless Sensor Networks are based on Received Signal Strength Indicator. Because absolute positioning is not always available, localization based on RSSI is popular. More, no extra hardware is needed unlike solutions based on infra-red or ultrasonic. Moreover, the theory gives a RSSI as a function of distance. However, using RSSI as a distance metric involves errors in the measured values, resulting path-loss, fading, and shadowing effects. We present experimentation results from three large WSNs, each with up to 250 nodes. Based on our findings from the 3 systems, the relation between RSSI and distance is investigated according to the topology properties and the radio environment. We underline the intrinsic limitations of RSSI as a distance metric, in terms of accuracy and stability. Contrary to what we assumed, collaborative localization protocol based on Spring-Relaxation algorithm can not smooth the distance-estimation errors obtained with RSSI measurements.

Little effort has been made to compare routing protocols according to their resiliency in wireless multi-hop sensor networks in the presence of packet dropping malicious insiders. In this paper, we propose a new taxonomy of routing protocols obtained by applying our resiliency metric. Several resiliency enhancing methods such as introducing a random behavior to the classical routing protocols and a new data replication method based on the distance information have been evaluated as well. Simulation results demonstrate the effectiveness of the proposed approach.

This poster presents the QoS Oriented Opportunistic Routing (QOR) protocol, a novel opportunistic routing protocol for energy constrained Wireless Sensor Networks. QOR builds a joint routing structure and addressing scheme and proposes a cascading forwarding scheme that guarantees reliable, replication-free data transmissions and collision-free acknowledgements even in presence of long-range asymmetric links. QOR makes the opportunistic routing scheme a practical reality and our preliminary simulations show that QOR outperforms the IETF state-of-the-art routing protocol RPL.

For energy constrained wireless sensor networks, lifetime is a critical issue. Several medium access control protocols have been proposed to address this issue, often at the cost of poor network capacity. To address both capacity and energy issues, we propose a novel medium sharing protocol for Wireless Sensor Networks named Cascading Tournament (CT-MAC). CT-MAC is a synchronous, localized, dynamic, joint contention/allocation protocol. Relying on cascading iterations of tournaments, CT-MAC allocates multiple time slots to nodes that compete for accessing the medium. CT-MAC offers an unprecedented trade-off between traffic delay, network capacity and energy efficiency and stands out as a solid candidate for energy constrained sensor networks that must support heterogeneous traffic loads. Our simulations show that CT-MAC significantly outperforms the state-of-the-art SCP-MAC protocol.

This paper proposes a mathematical framework to model and analyze the energy consumption of routing protocols in multihop wireless networks such Mobile Ad Hoc Networks (MANETs) or Sensor Networks (WSNs) by taking into account the protocol parameters, the traffic pattern and the network characteristics defined by the medium channel properties, the dynamic topology behavior, the network diameter and the nodes density. Moreover, our framework allows to classify routing protocols by exploring the relationship between application requirements and wireless network features. To the best of our knowledge, there is no such proposed framework that provides in-depth an analytical investigation of above relationship. We apply this model to a Beacon-less routing protocol Pizza-Forwarding (PF) compared to well known routing protocols such as Optimized Link State Routing, Ad Hoc On Demand Distance Vector Routing, Greedy Perimeter Stateless Routing and a Simple Random Walk Routing in order to underline their behavior according to the network features and application requirements. Finally, we show that Beacon-less routing protocol should be a best candidate to save energy in WSNs.

This paper presents the Self Adapting Receiver Initiated MAC protocol (SARI-MAC), a novel asynchronous MAC protocol for energy constrained Wireless Sensor Networks. SARI-MAC self-adapts to the traffic load to meet specified Quality of Service requirements at the lowest energy cost possible. To do so, SARI-MAC relies on traffic estimation, duty-cycle adaptation and acknowledgement mechanisms. Our performance evaluation assesses that SARI-MAC meets given QoS requirements in a energy efficient manner and outperforms the state of the art protocol RI-MAC in a broad range of traffic scenarios.

Energy-efficient communication protocol is a primary design goal for Wireless Sensor Networks (WSNs). Many efforts have been done to save energy: MAC with duty cycle, energy-aware routing protocols, data aggregation schemes, etc. Recently, beacon-less strategies have emerged as new direction to improve considerably the WSN lifetime. However, the main contributions are not suitable to real radio environments because of hole avoiding strategies based on either planarization or explicit neighbor solicitations. We propose PFMAC (Pizza-Forwarding Medium Access Control), which combines beacon-less geo-routing and energy efficient MAC protocol via a cross-layer design to save more energy with higher reliability. PFMAC supports radio interferences, asymmetric radio links, etc. PFMAC supports a greedy forwarding strategy and, a reactive and optimized neighborhood discovery at 2-hop to deal with holes. Intensive simulations are proposed to highlight the behavior and the performance of PFMAC compared to BOSS over BMAC.

This paper is focused on broadband wireless mesh networks based on OFDMA resource management, considering a realistic SINR model of the physical layer with a fine tuned power control at each node. A linear programming model using column generation leads to compute power efficient schedules with high network capacity. Correlation between capacity and energy consumption is analyzed as well as the impact of physical layer parameters - SINR threshold and path-loss exponent. We highlight that there is no significant tradeoff between capacity and energy when the power consumption of idle nodes is important. We also show that both energy consumption and network capacity are very sensitive to the SINR threshold variation.

In this paper, we focus on broadband wireless mesh networks like 3GPP LTE-Advanced. This technology is a key enabler for next generation cellular networks which are about to increase by an order of magnitude the capacity provided to users. Such an objective needs a significative densification of cells which requires an efficient backhauling infrastructure. In many urban areas as well as under-developed countries, wireless mesh networking is the only available solution. Besides, economical and environmental concerns require that the energy expenditure of such infrastructure is optimized. We propose a multi-objective analysis of the correlation between capacity and energy consumption of LTE-like wireless mesh networks. We provide a linear programing modeling using column generation for an efficient computation of the Pareto front between these objectives. Based on this model, we observe that there is actually no significant capacity against energy trade-off.

In this paper, we focus on Wireless Sensor Networks (WSNs) in a more realistic case than classical studies and previous works: we consider wireless sensor nodes having different transmission ranges according to the environment and/or to the wireless chipset. The main consequence of this heterogeneity is the existence of asymmetric links. Such links in a WSN degrade the performance of most protocols which have not been designed to support this heterogeneity and to deal with asymmetric links: so, mainly, these links are pruned. Under this assumption, we propose a routing protocol for data collection from sensors nodes to the sink node in heterogeneous WSNs. Our proposal detects and takes benefit from asymmetric links caused by this heterogeneity. Our proposal, denoted MURA, (1) provides a high delivery ratio, (2) reduces the number of duplicated packets and (3) reduces the number of hop counts by exploiting the asymmetric links.

Wireless Sensor Networks (WSN) need to be organized in order to be more resource-efficient and scalable. Directed Acyclic Graphs (DAG) are of interest for WSN organization because of their route redundancy to the root. A recent routing protocol for WSNs coming from the IETF ROLL Working Group specifies the use of DAGs and proposes to improve the route redundancy even further by routing through sibling nodes as well. In this paper, we investigate the effectiveness of routing through sibling nodes and we propose a new use of siblings which preserves most of the performance but reduces algorithmic complexity and memory requirements.

In Wireless Sensors and Actuators Networks (WSANs), actuator nodes are nodes richer in resources (processing capacity, power transmission and energy storage) and better suited than sensor nodes to process the data, make decisions based on sensed values and perform appropriate actions. In addition, in order to provide timely action, coordination between sensors and actuators is necessary. Thus, in addition to the classical energy constraints of Wireless Sensor Networks (WSNs), WSANs also impose new challenges such as how to support and benefit from the nodes heterogeneity while preserving energy in the self-powered sensor nodes. New communication protocols, specific to WSANs, are needed. In this paper, we propose a hybrid self-organizing data-collection protocol in order to provide energy efficiency, low end-to-end delay and high delivery ratio while taking advantage of the resource available on the actuators nodes in the network. This new self-organization protocol constructs its structure from the actuators and other resource-plentiful nodes. The nature of the structure is different inside and outside of transmission range of these resourceful nodes.

To be efficient, routing protocols in wireless sensor networks suppose to take into account local interactions, noise and collisions. In this work, we propose a routing protocol suitable for noisy environments. Using the qualitative localization algorithm (QLoP) in order to select sensors with a better signal-to-noise ratio, we build a logical topology on which we apply a routing protocol. We show that received signal strength indicator (RSSI) is not a good metric to evaluate proximity. In order to provide a better proximity metric, we introduce the qualitative localization protocol: QLoP. QloP does not use any anchor or dedicated hardware like GPS. Each node builds a qualitative distance according to the 2-hop neighborhood information. Thus, this algorithm allows to determine coarsely the proximity of the neighbors which are classified as very close, close or far. We highlight the routing performances in a noisy environment and compare it to a classical routing protocol on a flat topology. Delivery rate, throughput and average distance reachable in those extremes conditions are appreciably enhanced.

The goal of the self-organization is to structure the wireless sensor networks (WSN) using a connected logical topology (backbone) or a non connected one (clusters) in order to introduce stability and robustness. More, networking protocols based on such virtual structures should lead to better performances than the classical flat approach. A lot of studies deal with performance evaluations of virtual topologies in terms of energy consumption, cardinality, etc. But the network is mainly assumed fully deployed. In our point of view, a more accurate analysis should be done in order to characterize self-organization strategies during the different steps of the WSN life. We propose to study the robustness, the latency and the cardinality of the main self-organization strategies: i) dominant-based strategies which select a subset of nodes as dominants, ii) link-pruning strategies which select all the nodes and a subset of links. We study the evolution of these schemes during the chaotic deployment of the network (birth phase), the working life and the death of nodes.

The self-organization paradigm of wireless sensor networks (WSN) deals with an emergent behavior which can be either a connected logical topology (e.g. virtual backbone) or a non connected one (e.g. clusters): the network is then structured. Based on such logical view of the network, communications protocols should be more efficient than based on a classical flat approach. Numerous studies deal with performance evaluation of these virtual backbones and clusters in terms of energy consumption, complexity, etc. Nevertheless, the network is always assumed fully deployed. In our point of view, a more accurate analysis should be done in order to characterize self- organization strategies during the different steps of the WSN life. We propose to study the key properties like robustness, latency or cardinality of the main self-organization strategies (MPR, MPR-DS, CDS-rule k, CDS-MIS) during the chaotic network deployment (birth phase), the working life dealing with self-healing and the death of nodes.

We propose in this paper a low-energy address allocation scheme (LEADS). LEADS is a two-level hierarchical conflict- free address allocation scheme that provides validated address to each node in a wireless sensor network. LEADS provides a quick and energy-efficient self-configuration solution for WSN deployment. It takes the unsolved issues related to random arrival and abrupt departure of sensor nodes into account, both in partitions splitting and merging scenarios. Unlike most of the existing solutions, LEADS does not require any information from neither periodical control packet (HELLO message) (Nesargi and Prakash, 2002), nor routing protocols (Vaidya, 2002). In LEADS, the addresses space is divided into addresses pools which are managed by addresses agents. Every agent uses a stateful function to assign addresses to the nodes in its neighborhood. The uniqueness of assigned addresses is guaranteed by this two-level allocation strategy. Moreover, LEADS is a localized algorithm. Simulation results show that LEADS achieves the dynamic address allocation task with both lower message cost and lower energy consumption comparing to existing solutions. Our results illustrate the need for a dynamic and low-energy address allocation scheme to realize energy efficient sensor network applications and to extend network lifespan.

To enable spontaneous communications in wireless sensors networks, both self-configuration and self-organization appear to be two fundamental mechanisms. However, the majority of prior contributions in ad hoc network suffer from the low processing capability, limited storage space, energy constraint and large number of nodes when being applied in wireless sensor networks. Moreover, self-configuration and self-organization have been always considered as two independent mechanisms. The authors believe that this consideration leads to inefficient network and redundant protocol cost. Hence, in this paper a fully integrated scheme of self-configuration and self-organization was proposed. It can better resolve the distributed address allocation using the structure generated by itself with low message overhead. It also provides significant energy savings comparing to other schemes and low latency.

MANET protocols are often evaluated through simulations, not in a real radio environment. We describe here the implementation and deployment of a complete testbed for hybrid networks, allowing a seamless integration of an ad-hoc network in the Internet. In particular, a self-organization protocol and the mobility management protocol benefiting from this organization were implemented. The performances demonstrate the feasibility and usefulness of this scheme. Besides, this testbed offers a detailed description of the requirements to constitute a wireless testbed and to test any protocol for ad hoc or hybrid networks.

In MANET, the hidden terminals problem is a common situation which leads to poor performances due to collisions and unfairness behavior of nodes. The use of RTS/CTS mechanism is helpful to improve the performances but not sufficient: it is important to design new backoff algorithms. But, before, it is necessary to understand how backoff algorithms deal with long-term and short-term unfairness and also with performances. In this paper, based on a stochastic process algebra, we provide a new study of the hidden terminals problem. The binary exponential backoff and the double increase double decrease backoff algorithms are studied in depth in this case. The state of the medium (idle, occupied by either collision or transmission) is computed and the probability of the different backoff's stage is analysed. The short-term unfairness is clearly shown with a new metric. All results are given in both basic access and RTS/CTS one

Assuming a given network topology and a routing protocol, this work is focused on the capacity evaluation of routing protocols based on either a self-organization scheme or a flat approach. To reach this goal, we propose to use linear-programming formulation to model radio resource sharing as linear constraints. Four models are detailed to evaluate the capacity of any routing scheme in wireless multihops networks. First, two models of fairness are proposed: either each node has a fair access to the channel, or the fairness is among the radio links. Besides, a pessimistic and an optimistic scenarios of spatial re-utilization of the medium are proposed, yielding a lower bound and an upper bound on the network capacity for each fairness case. Finally, using this model, we provide a comparative analysis of some flat and self-organized routing protocols

This paper proposes an automatic base station planning approach. This approach does not only try to assess usual objectives such as radio coverage, but further implements a quality of service (QoS) constraint. This criterion is here defined as the mean available bandwidth per user. Its computation takes the medium access control (MAC) layer behavior, the multiple bit rates of IEEE 802.11b and the coverage area of each access point (AP) into account. A Markov chain is used to evaluate the available bandwidth of each cell independently. This is sensible because a non-overlapping criterion between cells is used during the planning phase to avoid interference between adjacent cells. The planning process estimates an optimal number of APs and their placement minimizing an aggregate criterion using a Tabu meta-heuristic. The AP's coverage is estimated with a powerful multi-resolution radio propagation simulator previously described. This paper presents results for a QoS oriented planning process providing a predefined minimum peruser throughput. The example provided herein applies for 100 users distributed over a 12600 m2building floor

Performance evaluation of wired networks is a well-known problem and many works consider the performance evaluation of wireless networks as the same problem. Compared to wired networks, wireless networks suffer from the shadow effect and Rayleigh fading which makes its performances difficult to predict. Most of the existing performance stochastic models assume that the radio channel is ideal, and as a result, do not consider the radio environment and the interferences. However, we find that deploying a real wireless LAN (especially indoor WLAN) in different environments leads to quite different performance results. We propose in this paper a method integrating radio characterizations in an analytical performance model. Taking advantage of our model, we are able to predict the performance of a wireless network (throughput, global capacity, etc.) of an indoor 802.11b WLAN, whose radio planning chart is known (through radio planning tool WILDE). We also analyze some special scenarios: network with more than one access point and the hidden terminals problem

Routing protocols are the main issue of ad hoc networks. Because flat propositions (reactive, proactive) are not sufficient and suffer from a lack of performance, new solutions should he investigated and proposed. On the other hand, virtual topologies propose to structure the network and to give a hierarchy between the strongest and the weakest nodes. We propose a new routing protocol, virtual structure routing (VSR), based on a virtual topology including both a backbone and clusters. The backbone is used to collect control traffic and to reduce overhead for route discovery. VSR uses clusters to define a route as a list of cluster IDs. This cluster topology is more stable than the physical topology. Hence, routes are more robust. VSR combines the assets of both flat approaches; intra-cluster routing is proactive while inter-cluster routing is reactive. Finally, routes are computed dynamically and a mechanism for route repair is proposed.

As mobile networks are growing fast in size and complexity, radio network resource planning needs to be optimized to cope with both increased traffic demand and spectrum scarcity. Although many studies have been reported in the area of mobile network planning in terms of traffic distribution analysis and mobility modeling, relatively few studies have been achieved regarding network planning based on real-world data and measurements. A realistic model has been developed in order to evaluate the performance of a real GSM network providing a voice service in an urban area. In this framework, our contribution addresses an important issue: how to monitor the performance measurements collected in the operations and maintenance centre (OMC) to propose a complete study including a realistic mobility model and a qualitative and quantitative traffic characterization that constitute a generic planning model which can be customized by any operator for mobile network deployment.

Hybrid networks are heterogeneous networks merging both wireless and ad hoc nodes and where the interconnection to the IP world is an important topic through gateways called AP (access point). Indeed, each node can be contacted and can contact another node in the Internet. To reach that, architectures that support mobility management are studied. The solutions inspired by wired networks are not particularly suited to hybrid networks. We propose to use a virtual dynamic infrastructure including both backbone and clusters. A backbone is suited to spare energy, optimize control traffic diffusion and hierarchize participants. The clusters are intended to create service areas and to handle particularly the mobility management. We present algorithms to both construct and maintain such structure. This dynamic topology is robust according to mobility, and is well suited to implement mobility management and localization procedure. Finally, the number of backbone members and clusters are completely parameterizable according to the environment.

The dense multicast zone routing protocol (DMZ) presents a novel approach for robust multicast in mobile ad hoc networks by providing adaptive mesh oriented structures. This paper introduces the notion of dense zone, a high concentration of multicast members in a certain area of the network. Each dense zone owns leader(s) that connect to the multicast source. These leader(s) are the node members located on the upper frontier and thus nearest to the multicast source. This concept provides more robustness and scalability for multicast data transmission in ad hoc networks.

This paper presents a realistic characterization of the channel holding time in an operating GSM network covering an urban area. Our approach is entirely statistical: the data set to be fitted has been provided by the OMC (operations and maintenance center). The Kolmogorov Smirnov goodness of fit test is used in order to test the suitability of the exhibited distribution. From this statistical analysis, it can be concluded that the negative exponential distribution is a good approximation for describing the channel holding time.

This paper presents an incremental computation performance evaluation algorithm for a UMTS (universal mobile telecommunication system) network model. We show that, when solving a set of models for different parameter values, our algorithm has a significant gain over classical methods. We derive performance criteria, such as new call blocking and dropping handover probability, for UMTS networks.

In the third generation of wireless cellular communication systems, cell sizes are expected to become smaller in order to accommodate high user density and multimedia traffic. In such a system, where hierarchical cellular networks are used, microcells may coexist with macrocells. Resource allocation schemes will have to be dynamic and flexible to handle user mobility and traffic variation. In this paper, we propose a new allocation strategy to manage both fast and slow users resources request in such a network. Our contribution uses an enhanced mechanism based on preemption which can be viewed as a reversible strategy on-demand using channel re-allocation. The originality of this work is to take into account the current value of QoS criteria provided to mobile users to perform resource allocation. Our new scheme is simulated and performance is analyzed in terms of new call blocking and dropping handover probabilities and signalling load. Results show that proposed resource management policy reduces significantly call blocking and dropping probabilities compared to other proposals with lower signalling increase.

To provide a service continuation from fixed broadband networks to the wireless part, new frequencies are allocated to increase the system capacity. Whereas the reuse partitioning is not adapted to those new needs, the multi-tier cell concept appears to be a good solution. We propose a new bandwidth allocation policy for a multi-tier cellular network which optimizes bandwidth utilization for customers, denoted MAHCN (multiservice allocation in hierarchical cellular networks). Our new protocol considers the service requirements based on two criteria: the mobile speed (low or high) and the type of request (voice or data).