Peak Transmission Rate Resilient Crosslayer Broadcast for Body Area Networks

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Protocoles de communication pour les réseaux de capteurs corporels sans fil (WBAN)

The rapid advances in sensors and ultra-low power wireless communication has enabled a new generation of wireless sensor networks: Wireless Body Area Networks (WBAN). WBAN is a recent challenging area. There are several concerns in this area ranging from energy efficient communication to designing delay efficient protocols that support nodes dynamic induced by human body mobility. In WBAN tiny devices are deployed in/on or around a human body, are able to detect and collect the physiological phenomena of the human body (such as: EEG, ECG, SpO2, etc.), and transmit this information to a collector point (i.e Sink) that will process it, take decisions, alert or record. WBAN differs from typical large-scale wireless sensor networks WSN in many aspects: Network size is limited to a dozen of nodes, in-network mobility follows the body movements and the wireless channel has its specificities. Links have a very short range and a quality that varies with the wearer's posture. The transmission power is kept low to improve devices autonomy and reduce wearers electromagnetic exposition. Consequently, the effects of body absorption, reflections and interference cannot be neglected and it is difficult to maintain a direct link (one-hop) between the Sink and all WBAN nodes. Thus, multi-hop communication represents a viable alternative. In this work we investigate energy-efficient multi-hop communication protocols in WBAN. Our work is part of SMART-BAN Self-organizing Mobility Aware, Reliable and Timely Body Area Networks project. In order to evaluate our communication protocols described in the sequel in a specific WBAN scenario, we implemented them under the Omnet++ simulator that we enriched with the Mixim project and a realistic human body mobility and channel model issued from a recent research on biomedical and health informatics. We are interested in WBAN where sensors are placed on the body. We focus on two communication primitives: broadcast and converge-cast. For the broadcasting problem in WBAN, we analyze several broadcast strategies inspired from the area of DTN then we propose two novel broadcast strategies MBP: Mixed Broadcast Protocol and Optimized Flooding: -MBP (Mixed Broadcast Protocol): We proposed this strategy as a mix between the dissemination-based and knowledge-based approaches. -OptFlood (Optimized Flooding): This strategy takes into account the strengths and weaknesses of the basic strategy Flooding. Optimized Flooding is a revised version of Flooding whose purpose is to keep the good end-to-end delay given by Flooding while lowering energy consumption with the simplest way and the minimum cost. Additionally, we performed investigations of independent interest related to the ability of all the studied strategies to ensure the FIFO order consistency property (i.e. packets are received in the order of their sending) when stressed with various transmission rates. These investigations open new and challenging research directions. With no exception, the existing flat broadcast strategies register a dramatic drop of performances when the transmission rate is superior to 11Kb/s. There, we propose the first network-MAC layer broadcast protocol, CLBP, designed for multi-hop communication and resilient to human body postures and mobility. Our protocol is optimized to exploit the human body mobility by carefully choosing the most reliable communication paths in each studied posture. Moreover, our protocol includes a slot assignment mechanism that reduces the energy consumption, collisions, idle listening and overhearing. Additionally, CLBP includes a synchronization scheme that helps nodes to resynchronize with the Sink on the fly. Our protocol outperforms existing flat broadcast strategies in terms of percentage of covered nodes, energy consumption and correct reception of FIFO-ordered packets and maintains its good performances up to 190Kb/s transmission rates. [...]Dans les réseaux WBAN, les capteurs sont utilisés pour surveiller, collecter et transmettre des signes médicaux et d'autres informations sur le corps humain (EEG, ECG, SpO2, température, etc.) à un nœud principal qu’on appelle « Sink ». Il y a plusieurs préoccupations dans les WBAN, allant de la conception de protocoles de communication fiables et efficaces face à la mobilité du corps humain à une communication faible en consommation énergétique. Les WBAN diffèrent des réseaux de capteurs sans fil typiques à grande échelle et se caractérisent par une mobilité dans le réseau qui suit les mouvements du corps humain et une qualité des liens qui varie en fonction de la posture du porteur. Aussi, la puissance d'émission des capteurs est maintenue faible afin d'améliorer leur autonomie et de réduire l’exposition aux ondes électromagnétiques des porteurs. Par conséquent, compte tenu des effets d’absorption du corps, des réflexions et des interférences, il est difficile de maintenir un lien direct (à un saut) entre le « Sink » et les autres nœuds. La communication multi-sauts représente une alternative viable. Nous avons évalué essentiellement deux primitives de communication: broadcast et converge-cast. Nous avons implémenté différentes stratégies de communication avec le simulateur Omnet++ auquel nous avons intégré le projet Mixim et un modèle de canal réaliste pour un scénario représentatif d'un réseau WBAN. Ce modèle est issu d'une recherche récente de l'informatique biomédicale et décrit les liens entre 7 nœuds, qui appartiennent au même WBAN, et qui sont attachés au corps humain sur la tête, la poitrine, le bras, le poignet, le nombril, la cuisse et la cheville. Les atténuations du signal sur ces liens sont calculées pour 7 postures qui varient entre des positions statiques à fortement mobiles et sont présentées, pour chaque couple de nœuds, sous la forme d’une atténuation moyenne et d’écart-type. Ensuite, nous nous sommes intéressés au problème de broadcast dans WBAN. Nous avons analysé plusieurs stratégies de diffusion inspirées des réseaux DTN avec différents niveaux de connaissance du réseau: des stratégies de type flooding, où les nœuds diffusent les paquets à l'aveugle, et des stratégies basées sur la connaissance du voisinage, où la diffusion est plus contraignante. Nos résultats ont montré que les stratégies de diffusion existantes ne résistent pas face à la mobilité du corps humain et ne peuvent pas être transposées sans des modifications significatives dans un contexte WBAN. Ainsi, nous avons proposé deux nouvelles stratégies de diffusion qui surpassent les stratégies existantes en termes de latence, de couverture du réseau et de la consommation d’énergie des capteurs. Nous avons également analysé la capacité de toutes ces stratégies à assurer l’ordre FIFO (c'est-à-dire les paquets sont reçus dans l'ordre de leur envoi) en les stressant avec différents taux de transmission du nœud « Sink ». Sans exception, les stratégies de diffusion à plat existantes enregistrent une baisse drastique de performance lorsque le taux de transmission augmente. Ainsi, nous avons pu proposer le premier protocole de diffusion inter-couches MAC-réseau, CLBP. Notre protocole exploite la mobilité du corps humain en choisissant soigneusement les liens de communication les plus fiables dans chaque posture. De plus, notre protocole a un mécanisme d'attribution de slots qui réduit la consommation d'énergie, les collisions, l'écoute inactive et la sur-écoute des capteurs. Nous nous sommes également concentrés sur le problème de converge-cast dans les réseaux WBAN. Nous avons adapté à partir des réseaux DTN et WSN des stratégies converge-cast représentatives que nous avons classées en trois catégories: basées sur le modèle du canal, basées sur la diffusion et basées sur multi-chemins. Nous avons étudié trois paramètres: la résilience à la mobilité corporelle, le délai de bout en bout et la consommation d'énergie. [...

Broadcast strategies and performance evaluation of IEEE 802.15.4 in wireless body area networks WBAN

International audienceWireless Body Area Networks (WBANs) can be considered as an evolution of wireless sensor networks towards wearable and implanted technologies. Radio propagation and mobility are particular in this context, as they are influenced by the characteristics and movement of the human body and by the necessity to keep the transmission power at its minimum to save energy and limit interactions with the wearer.In this paper, we investigate the broadcasting problem in which a node, typically the gateway, tries to send a packet to all other nodes in the network at minimal cost. This problem is not as trivial as it looks and we show through simulation that forwarding strategies coming from the Delay Tolerant Networks world cannot be transposed without adaptation. We enriched the Omnet++ simulator with a WBAN-specific channel model from the literature, and use this model to evaluate 9 classes of broadcasting algorithms, including our own proposals, with respect to their ability to cover the whole network, their completion delay, their cost in terms of transmissions volume and their capability to preserve multiple packets order (i.e. total order broadcast).Our study shows that there is a subtle compromise to find between verbose strategies that achieve good performance at the cost of numerous transmissions, ultimately provoking collisions and more cautious solutions that miss transmission opportunities because of mobility

Broadcast strategies in Wireless Body Area Networks

International audienceThe rapid advances in sensors and ultra-low power wireless communication has enabled a new generation of wireless sensor networks: Wireless Body Area Networks (WBAN). To the best of our knowledge the current paper is the first to address broadcast in WBAN. We first analyze several broadcast strategies inspired from the area of Delay Tolerant Networks (DTN). The proposed strategies are evaluated via the OMNET++ simulator that we enriched with realistic human body mobility models and channel models issued from the recent research on biomedical and health informatics. Contrary to the common expectation, our results show that existing research in DTN cannot be transposed without significant modifications in WBANs area. That is, existing broadcast strategies for DTNs do not perform well with human body mobility. However, our extensive simulations give valuable insights and directions for designing efficient broadcast in WBAN. Furthermore, we propose a novel broadcast strategy that outperforms the existing ones in terms of end-to-end delay, network coverage and energy consumption

Broadcast Strategies and Performance Evaluation of IEEE 802.15.4 in Wireless Body Area Networks WBAN

The rapid advances in sensors and ultra-low power wireless communication has enabled a new generation of wireless sensor networks: Wireless Body Area Networks (WBAN). To the best of our knowledge the current paper is the first to address broadcast in WBAN. We first analyze several broadcast strategies inspired from the area of Delay Tolerant Networks (DTN). The proposed strategies are evaluated via the OMNET++ simulator that we enriched with realistic human body mobility models and channel models issued from the recent research on biomedical and health informatics. Contrary to the common expectation, our results show that existing research in DTN cannot be transposed without significant modifications in WBANs area. That is, existing broadcast strategies for DTNs do not perform well with human body mobility. However, our extensive simulations give valuable insights and directions for designing efficient broadcast in WBAN. Furthermore, we propose a novel broadcast strategy that outperforms the existing ones in terms of end-to-end delay, network coverage and energy consumption. Additionally, we performed investigations of independent interest related to the ability of all the studied strategies to ensure the total order delivery property when stressed with various packet rates. These investigations open new and challenging research directions

Convergecast in Wireless Body Area Networks

International audienceWireless Body Area Networks (WBAN) is a recent challenging area in the domain of health monitoring. There are several concerns in this area ranging from energy efficient communication to designing delays efficient protocols that support nodes dynamicity induced by human body mobility. This paper focuses on the convergecast or data gathering protocols in WBAN. Our contribution is twofold. First, we extensively analyze the impact of postural body mobility on various classes of multi-hop convergecast strategies. Our study does not limit itself to the existing state-of-the-art in WBAN, we adapted to WBAN settings strategies from the areas of Delay Tolerant Networks (DTN) and Wireless Sensor Networks (WSN). We evaluate all these strategies via the OMNeT++ simulator that we enriched with realistic human body mobility models and channel models issued from the recent research on biomedical and health informatics. Our simulations show that existing results in DTN and WSN cannot be just extrapolated to WBAN without a deeper investigation. That is, existing convergecast strategies for DTN or WSN do not perform well with postural body movements because of the topological partitioning provoked by important link attenuations due to signal obstructions by clothes or body itself. Our extensive simulations give valuable insights and directions for designing efficient convergecast adaptive strategies in WBAN. Second, we propose and evaluate two novel classes of convergecast strategies. The first class integrates in the routing information the link attenuation while the second one exploits multi (pre-established) paths to the sink node. We stress all the strategies under a realistic channel model and present an extensive analysis in terms of resiliency to mobility, end-to-end delay and energy consumption for seven different mobility patterns. We advocate that, so far, there is no strategy for convergecast in WBAN that optimizes all the above criteria for all possible mobility patterns. However, each considered strategy can be a good candidate for a specific combination of parameters with a specific mobility pattern

Les Stratégies de Diffusion dans les Réseaux Wireless Body Area Networks

International audienceLes progrés rapides des capteurs et de la communication sans fil à ultra-faible puissance ont permis a une nouvelle génération de réseaux de capteurs sans fil de voir le jour : Wireless Body Area Networks (WBAN). Nous commençons d'abord par l'analyse de plusieurs stratégies de diffusion inspirées des réseaux tolérants au délai (DTN : Delay Tolerant Networks). Les stratégies proposées sont ensuite évaluées via le simulateur OMNET++ auquel nous avons intégré un modèle de mobilité réaliste du corps humain issu de la recherche récente dans le domaine de l'informatique biomédicale. Nos résultats de simulation montrent que les stratégies de diffusion DTN ne sont pas adéquates dans le contexte des réseaux WBAN. En revanche, ces simulations nous ont permis de synthétiser une nouvelle stratégie de diffusion efficace dans les réseaux WBAN. La stratégie proposée , Mixed Broadcast Protocol (MBP), montre de meilleures performances comparée aux stratégies existantes en termes de délai de bout-en-bout, de nombre de noeuds couverts et de la consommation énergétique

Isolated lichen planus of the lips: cases reports and literature review

Introduction: Lichen planus is an inflammatory mucocutaneous dermatosis involving skin, appendages and mucosa. Oral mucosa is the most commonly involved in all its sites, rarely the lips especially when isolated. The aim was to conduct a literature review about isolated lichen planus of the lips and reporting two case reports of this lesion in order to highlight epidemiologic, clinical and histological features and therapeutic modalities of this lesion. Observations: Case report 1: a 34-year-old diabetic male patient consulted for an erosive, crusted and hemorrhagic cheilitis of the lower lip. Clinical and histological examination led to the diagnosis of isolated lichen planus of the lips. Case report 2: a 33-year-old female patient was referred from dermatology department for biopsy of chronic cheilitis of the lower lip. Clinical and histological examination confirmed the diagnosis of isolated lichen planus of the lips. Discussion: The review based on 34 case reports of isolated lichen planus of the lips, in addition to literature data confirmed that it is a benign rare lesion affecting mostly male patients having middle age with preponderance of the lower lip, its erosive form is the most frequent and it presents a favorable healing with topical treatment particularly corticosteroids

Pemphigoid gestationis: Report of 44 cases

Introduction: Pemphigoid gestationis (PG) is a rare autoimmune bullous dermatosis occurring during pregnancy and post partum. The aim of our study was to analyse epidemio-clinical, immunopathological, therapeutic and prognostic features of PG through a hospital study of 44 cases. Methods: It is a retrospective study, collecting all cases diagnosed at the dermatological department of Farhat Hached Soussa (Tunisia) from January 1990 to December 2015. Results: The disease began in 40,9% of cases at the second trimester of pregnancy and 48% at the third trimester of pregnancy, one case in post abortum. It was a polymorphic eruption, localized in the chest, the back and limbs in all cases. The face was affected in 18,2% of cases and the mucosa in one case. The skin biopsy showed a subepidermal blister in 25 cases. The direct immunofluoresence found linear C3 deposits along the basement membrane in all cases, associated to IgG deposits in 25% of cases. The treatment was mainly based on local or general corticotherapy with favourable evolution. We noted exacerbation in post partum in 17 cases and relapses during the ulterior pregnancies in 7 cases. Fetal damage was present in PG in 8 cases. Conclusion: Our study is conformed to literature data; nevertheless, it is distinguished by its appearance on the face the less frequency of palmo-plantar manifestations and the exceptional case of PG postabortum