Data acquisition techniques for next generation wireless sensor networks

The meteoric rise and prevalent usage of wireless networking technologies for mobile communication applications have captured the attention of media and imagination of public in the recent decade. One such proliferation is experienced in Wireless Sensor Networks (WSNs), where multimedia enabled elements are fused with integrated sensors to empower tightly coupled interaction with the physical world. As a promising alternative to antiquated wired systems and traditional WSNs in a multitude of novel application scenarios, the newly renovated WSNs have inspired a wide range of research among which investigation on data acquisition techniques is a fundamental one. In this dissertation, we address the problem of data acquisition in next generation WSNs. As wireless sensors are powered with limited energy resources while they are expected to work in an unattended manner for a long duration, energy conservation stands as the primal concern. Also, to enable in-situ sensing in different rate-constrained applications, routing decisions should care about the medium access feasibility of achievable end-to-end data rates. Driven by the fact, we first design cross-layer medium contention aware routing schemes for rate-constrained traffic in single-channel WSNs that maximize network lifetime. Three sufficient conditions on rate feasibility, referred to as rate-based, degree-based, and mixed constraints, are incorporated into the routing formulations to guarantee the practical viability of the routing solutions. Next, with the aim to mitigate interference and hence to enhance network capacity, we extend our work by proposing energy and cross-layer aware routing schemes for multichannel access WSNs that account for radio, MAC contention, and network constraints. In that context, we first derive three new sets of sufficient conditions that ensure feasibility of data rates in multichannel access WSNs. Then, utilizing these sets, we devise three different MAC-aware routing optimization schemes, each aiming to maximize the network lifetime while meeting data rate requirements of end-to-end flows. Finally, we perform extensive simulation studies to evaluate and compare the performance of the proposed routing approaches under various network conditions. So far works are done in milieu of WSNs with both fixed access node and sensor nodes. In the subsequent part of the dissertation, we present the continuation of our work focusing on reliable data acquisition in Mobile WSNs for a promising application namely free-ranging animal tracking/monitoring. To accomplish that goal, we concentrate on providing sufficient conditions on access-point density that limit the likelihood of buffer overflow. We first derive sufficient access-point density conditions that ensure that the data loss rates are statistically guaranteed to remain below a given threshold. Then, we evaluate and validate the derived theoretical results with both synthetic and real-world data

Rate-Constrained Data Aggregation in Power-Limited Multi-Sink Wireless Sensor Networks

Abstract-We propose a cross-layer data-aggregation approach that maximizes the lifetime of wireless sensor networks with multiple sinks while ensuring the feasibility of the routing solution. The proposed approach accounts for the coupling effects between MAC-and network-layers to ensure the physical feasibility of the obtained solutions, and maximizes the network lifetime by avoiding nodes with critical energy resources. Using simulations, we demonstrate the impact of not including medium access contention constraints in the routing formulation on the physical feasibility of the routing solution. We also study the impact of several network parameters on the network lifetime

Upper Bounds on Expected Hitting Times in Mostly-Covered Delay-Tolerant Networks

Abstract-We derive theoretical bounds on expected hitting times in densely covered delay-tolerant networks (DTNs). We consider a number of fixed (data collector) nodes deployed in the DTN region, and a number of mobile (data generator) nodes that move freely in the region according to Brownian motion. As it moves, each mobile node is assumed to continuously generate and buffer data. When a mobile node comes within the communication coverage range of a data collector node, it downloads its buffered data to it. Otherwise, it keeps generating and buffering its data. In this paper, we derive analytic bounds on the amount of time a mobile node spends without communication coverage. Then, using these derived bounds, we derive sufficient conditions on node density that statistically guarantee that the expected hitting times remain below a given threshold

Translation and validation of MHAQ score in local language Urdu in Patients with rheumatoid arthritis presenting in a tertiary care center of Pakistan

Objective: To translate and validate the Modified Health Assessment Questionnaire from English to Urdu. Method: The validation study was conducted at the Rheumatology outpatient department of Fauji Foundation Hospital, Rawalpindi, Pakistan, from July 1 to September 30, 2019. Two translators were given the modified health assessment questionnaire for translation from English to Urdu. It was then back-translated by two independent translators. The translated version of the tool was applied to rheumatoid arthritis patients to check for reliability, test-retest and internal consistency. It was applied to another group of patients to check for criterion validity. Reliability analysis was checked by applying Cronbach alpha. Criterion validity was checked by assessing disease activity score-28 and its correlation with Modified Health Assessment Questionnaire. Data was analysed using SPSS 23. Results: Of the 30 patients in the initial testing, 28(93%) were females and 2(6.6%) were males, with an overall mean age of 38±13.2 years. Of the 100 patients in the second group, 97(97%) were women and 3(3%) were men, with an overall mean age of 42±12.37 years. The mean disease duration of the cohort was 8.4±4.8 years. The Cronbach alpha value was 0.797 and interclass coefficient was 0.7, reflecting good reliability. A significantly high correlation between Modified Health Assessment Questionnaire and disease activity score-28 was noted along with pain, tenderness, swollen joints, patient global assessment, age and erythrocyte sedimentation rate (p0.05). ---Continu