Progressive Processing of Continuous Range Queries in Hierarchical Wireless Sensor Networks

In this paper, we study the problem of processing continuous range queries in a hierarchical wireless sensor network. Contrasted with the traditional approach of building networks in a "flat" structure using sensor devices of the same capability, the hierarchical approach deploys devices of higher capability in a higher tier, i.e., a tier closer to the server. While query processing in flat sensor networks has been widely studied, the study on query processing in hierarchical sensor networks has been inadequate. In wireless sensor networks, the main costs that should be considered are the energy for sending data and the storage for storing queries. There is a trade-off between these two costs. Based on this, we first propose a progressive processing method that effectively processes a large number of continuous range queries in hierarchical sensor networks. The proposed method uses the query merging technique proposed by Xiang et al. as the basis and additionally considers the trade-off between the two costs. More specifically, it works toward reducing the storage cost at lower-tier nodes by merging more queries, and toward reducing the energy cost at higher-tier nodes by merging fewer queries (thereby reducing "false alarms"). We then present how to build a hierarchical sensor network that is optimal with respect to the weighted sum of the two costs. It allows for a cost-based systematic control of the trade-off based on the relative importance between the storage and energy in a given network environment and application. Experimental results show that the proposed method achieves a near-optimal control between the storage and energy and reduces the cost by 0.989~84.995 times compared with the cost achieved using the flat (i.e., non-hierarchical) setup as in the work by Xiang et al.Comment: 41 pages, 20 figure

Wireless Sensor Networking in Challenging Environments

Recent years have witnessed growing interest in deploying wireless sensing applications in real-world environments. For example, home automation systems provide fine-grained metering and control of home appliances in residential settings. Similarly, assisted living applications employ wireless sensors to provide continuous health and wellness monitoring in homes. However, real deployments of Wireless Sensor Networks (WSNs) pose significant challenges due to their low-power radios and uncontrolled ambient environments. Our empirical study in over 15 real-world apartments shows that low-power WSNs based on the IEEE 802.15.4 standard are highly susceptible to external interference beyond user control, such as Wi-Fi access points, Bluetooth peripherals, cordless phones, and numerous other devices prevalent in residential environments that share the unlicensed 2.4 GHz ISM band with IEEE 802.15.4 radios. To address these real-world challenges, we developed two practical wireless network protocols including the Adaptive and Robust Channel Hopping (ARCH) protocol and the Adaptive Energy Detection Protocol (AEDP). ARCH enhances network reliability through opportunistically changing radio\u27s frequency to avoid interference and environmental noise and AEDP reduces false wakeups in noisy wireless environments by dynamically adjusting the wakeup threshold of low-power radios. Another major trend in WSNs is the convergence with smart phones. To deal with the dynamic wireless conditions and varying application requirements of mobile users, we developed the Self-Adapting MAC Layer (SAML) to support adaptive communication between smart phones and wireless sensors. SAML dynamically selects and switches Medium Access Control protocols to accommodate changes in ambient conditions and application requirements. Compared with the residential and personal wireless systems, industrial applications pose unique challenges due to their critical demands on reliability and real-time performance. We developed an experimental testbed by realizing key network mechanisms of industrial Wireless Sensor and Actuator Networks (WSANs) and conducted an empirical study that revealed the limitations and potential enhancements of those mechanisms. Our study shows that graph routing is more resilient to interference and its backup routes may be heavily used in noisy environments, which demonstrate the necessity of path diversity for reliable WSANs. Our study also suggests that combining channel diversity with retransmission may effectively reduce the burstiness of transmission failures and judicious allocation of multiple transmissions in a shared slot can effectively improve network capacity without significantly impacting reliability

BIM in the construction industry

En las últimas décadas, el término modelado de información de construcción (BIM) se ha mencionado en una amplia gama de esfuerzos de investigación de la construcción. BIM es una nueva solución para la recesión sin precedentes en la industria de la construcción, es decir, pérdida de productividad, escasez de mano de obra, sobrecostos y competitividad severa. La tecnología BIM proporciona muchos beneficios: detección rápida de conflictos de diseño, regulación automática de diseño algoritmo de verificación, visualización de realidad virtual/aumentada y entorno de trabajo de colaboración. BIM los expertos, así como los profesionales de la industria, enfatizan la importancia de las aplicaciones BIM en el campo de construcción. Dado el rápido desarrollo y adopción de BIM en la arquitectura, ingeniería, y construcción (AEC), están surgiendo nuevas tendencias relevantes para la investigación de BIM, siendo sumamente útil no sólo para los académicos sino también para los profesionales.In recent decades, the term building information modeling (BIM) has been mentioned in a wide range of construction research endeavors. BIM is a new solution for unprecedented recession in the construction industry, i.e., productivity loss, labor shortage, cost overrun, and severe competitiveness. BIM technology provides many benefits: prompt design clash detection, automatic deign regulatory check algorithm, augmented/virtual reality visualization, and collaboration work environment. BIM experts as well as industry practitioners are stressing the importance of BIM applications in the field of construction. Given the rapid development and adoption of BIM in the architecture, engineering, and construction (AEC) industry, new trends relevant to the research of BIM are emerging, being exceedingly helpful not only for academics but also for practitioners

Cross layer network architecture for efficient packet forwarding in wireless networks

With the evolution of 802.11-based wireless networks from hotspots to mesh networks, there has been a tremendous increase in the number of wireless users and density of deployments. Consequently, current wireless network face several problems due to interference, uncoordinated medium access, packet processing overheads at each hop and sub-optimal route selection. While radio technologies continue to improve speeds upto hundred megabits per second, the inadequacies of medium access and routing protocols severely impact the overall network capacity and end-user experience. In this thesis, we focus on improving the scalability and packet forwarding efficiency of multihop wireless networks. We introduce a self-organizing hierarchical ad-hoc network design (SOHAN) based on a three-tier hierarchy with dedicated forwarding nodes to address the scalability of existing multihop networks. We focus on realistic system design considerations and develop a Linux-based system prototype including novel protocols for bootstrapping, discovery and topology control to enable hierarchical self-organization. Experimental and simulation-based evaluations indicate a 2.5 times performance improvement over flat network models. We address packet forwarding inefficiencies of existing techniques over multihop networks due to queuing, contention and reprocessing at each hop and propose an interface contained forwarding architecture (ICF) using a combination of cut-through MAC protocol and label-based forwarding to enable "atomic" channel access for downstream transmissions and reduce self-interference. Next, we design a cross layer enabled cut through architecture (CLEAR) that extends the ICF mechanism with novel airtime metric-based route selection to mitigate the interference between flows. We further outline a time-based coordination scheme using soft reservations during route discovery phase to coordinate multihop "burst" transfers amongst flows. This model can be adapted to support differentiated services and provide a "low-latency socket" for real-time traffic over multiple hops. Our work can be the basis for a switched multihop wireless network design that enables conflict-free transfers resulting in efficient utilization of channel capacity and providing a viable alternative to wired network deployments. A substantial contribution of this thesis also includes the design and development of the ORBIT wireless testbed with focus on cross-layer experimental framework to facilitate rapid prototyping of wireless protocols and experimental evaluations at scale.Ph.D.Includes bibliographical references (p. 152-159)