Christian G. Frank

Algorithms for generic role assignment in wireless sensor networks

We consider configuration of wireless sensor networks, where certain functions must be automatically assigned to sensor nodes, such that the properties of a sensor node (e.g., remaining energy, network neighbors) match the requirements of the assigned function. Essentially, sensor nodes take on certain roles in the network as a result of configuration. To help developers with such configuration tasks for a variety of applications, we propose generic role assignment as a programming abstraction, where roles and rules for their assignment can be easily specified using a configuration language. We present such a role specification language and distributed algorithms for role assignment according to such specifications. We evaluate our approach and show that efficient and robust generic role assignment is practically feasible for wireless sensor networks.

Generic role assignment for wireless sensor networks

Wireless ad hoc networks of sensor nodes are envisioned to be deployed in the physical environment to monitor a wide variety of real-world phenomena. Almost any sensor network application requires some form of self-configuration, where sensor nodes take on specific functions or roles in the network without manual intervention. These roles may be based on varying sensor node properties (e.g., available sensors, location, network neighbors) and may be used to support applications requiring heterogeneous node functionality (e.g., clustering, data aggregation). In this paper we argue that the assignment of user-defined roles is a fundamental part of a wide range of sensor network applications. Consequently, a framework for assignment of roles to sensor nodes in an application-specific manner could significantly ease sensor network programming. We outline the general structure of such a framework and present a first approach to its realization. We demonstrate its utility and feasibility using a number of concrete examples.

The sensor internet at work: Locating everyday items using mobile phones

We present a system for monitoring and locating everyday items using mobile phones. The system is based on phones which are enhanced with the capability to detect electronically tagged objects in their vicinity. It supports various functionalities: On the one hand, phones can store the context in which users leave registered items and thus help to locate them later on. On the other hand, object owners can search for their objects using the infrastructure of mobile phones carried by other users. We describe the design of our object location system and provide an algorithm which can be used to search for lost or misplaced items efficiently by selecting the most suitable sensors based on arbitrary domain knowledge. Furthermore, we demonstrate the practicability of such wide-area searching by means of user-held sensors in a series of simulations complemented by a real-world experiment.

Clinical and molecular features of three patients with congenital disorders of glycosylation type Ih (CDG-Ih) (ALG8 deficiency)

Protein glycosylation is an essential post-translational modification of various proteins, affecting their folding, sorting, and function. Inborn defects in the assembly and processing of glycans on glycoproteins are known as congenital disorders of glycosylation (CDG) and can affect both N- and O-glycosylation (for reviews see Marquardt and Denecke,1 Jaeken,2 and Grunewald et al 3). N-glycosylation defects and especially defects in the assembly of the dolichol linked N-glycan precursor in the endoplasmic reticulum (ER) (CDG-I) result in hypoglycosylation of many kinds of (serum) glycoproteins. CDG-I is therefore a group of multisystemic disorders. The assembly of the N-glycan precursor in the ER is a highly ordered process involving at least 30 known gene products. Mutations in 11 of these (PMM2, MPI, ALG6, DPM1, ALG3, MPDU1, ALG12, ALG8, ALG2, DPAGT1, and ALG1) have been shown to cause CDG type I (CDG-Ia to CDG-Ik).2,4–10 Although it remains difficult to define a characteristic clinical phenotype for each type of CDG, mainly because only a limited number of patients have been assigned to most types, they generally share hypotonia and different degrees of mental retardation. Central nervous system defects are absent in CDG-Ib patients (with a deficiency of phosphomannose isomerase, MPI) and in the recently published CDG-Ih patient (with a deficiency of dolichyl-P-Glc: Glc1Man9GlcNAc2-PP-dolichyl α1, 3-glucosyltransferase, ALG8).4 CDG-Ib patients present mainly with hypoglycaemia, coagulopathy, hepatomegaly, protein-losing enteropathy, hepatic fibrosis, cyclic vomiting, and diarrhoea.11–14 It is the only type with an efficient therapy because dietary mannose can be used via an alternative pathway to generate mannose-6-phosphate that is normally produced from fructose-6-phosphate by the action of MPI. The only CDG-Ih patient described so far shares this relatively mild presentation with severe diarrhoea and moderate hepatomegaly.4 Our cohort of unsolved CDG patients included …

CDG‐IL: An infant with a novel mutation in the ALG9 gene and additional phenotypic features

We describe the second case of congenital disorder of glycosylation type IL (CDG‐IL) caused by deficiency of the ALG9 a1,2 mannosyltransferase enzyme. The female infants features included psychomotor retardation, seizures, hypotonia, diffuse brain atrophy with delayed myelination, failure to thrive, pericardial effusion, cystic renal disease, hepatosplenomegaly, esotropia, and inverted nipples. Lipodystrophy and dysmorphic facial features were absent. Magnetic resonance imaging of the brain showed volume loss in the cerebral hemispheres and cerebellum and delayed myelination. Laboratory investigations revealed low levels of multiple serum proteins including antithrombin III, factor XI, and cholesterol. Hypoglycosylation was confirmed by the typical CDG type 1 pattern of serum transferrin analyzed by isoelectric focusing. A defect in the ALG9 enzyme was suggested by the accumulation of the DolPP‐GlcNAc2Man6 and DolPP‐GlcNAc2Man8 in the patients fibroblasts and confirmed by mutation analysis: the patient is homozygous for the ALG9 mutation p.Y286C. The causal effect of the mutation was shown by complementation assays in alg9 deficient yeast cells. The child described here further delineates the clinical spectrum of CDG‐IL and confirms the significant clinical overlap amongst CDG subtypes.

Distributed facility location algorithms for flexible configuration of wireless sensor networks

Many self-configuration problems that occur in sensor networks, such as clustering or operator placement for in-network data aggregation, can be modeled as facility location problems. Unfortunately, existing distributed facility location algorithms are hardly applicable to multi-hop sensor networks. Based on an existing centralized algorithm, we therefore devise equivalent distributed versions which, to our knowledge, represent the first distributed approximations of the facility location problem that can be practicably implemented in multihop sensor networks with local communication. Through simulation studies, we demonstrate that, for typical instances derived from sensor-network configuration problems, the algorithms terminate in only few communication rounds, the runtime does not increase with the network size, and, finally, that our implementation requires only local communication confined to small network neighborhoods. In addition, we propose simple extensions to our algorithms to support dynamic networks with varying link qualities and node additions and deletions. Using link quality traces collected from a real sensor network deployment, we demonstrate the effectiveness of our algorithms in realistic multi-hop sensor networks.

Objects calling home: locating objects using mobile phones

Locating physical items is a highly relevant application addressed by numerous systems. Many of these systems share the drawback that costly infrastructure must be installed before a significant physical area can be covered, that is, before these systems may be used in practice. In this paper, we build on the ubiquitous infrastructure provided by the mobile phone network to design a wide-area system for locating objects. Sensor-equipped mobile phones, naturally omnipresent in populated environments, are the main elements of our system. They are used to distribute search queries and to report an objects location. We present the design of our object search system together with a set of simple heuristics which can be used for efficient object search. Moreover, such a system can only be successfully deployed if environment conditions (such as the participant density and their mobility) and system settings (such as number of queried sensors) allow to find an object quickly and efficiently. We therefore demonstrate the practicability of our system and obtain suitable system parameters for its execution in a series of simulations. Further, we use a real-world experiment to validate the obtained simulation results.

Solving generic role assignment exactly

Generic role assignment is a programming abstraction that supports the assignment of user-defined roles to sensor nodes such that certain conditions are met. Many common network configuration problems such as coverage (assign roles ON and OFF to sensor nodes such that ON nodes cover a physical area with their sensors), clustering, or in-network data aggregation can be formulated as role assignment problems. Building on our previous work in this area, we propose an extended role specification language that supports the minimization or maximization of the use of a given role. Moreover, we provide a mapping of this language to integer linear programs and implement this mapping. We show how the resulting tool can be used analyze aspects of role specifications such as feasibility and optimality

Congenital disorder of glycosylation (CDG) Ig: report on a patient and review of the literature.

SummaryWe report a new patient with CDG Ig and review the five other known patients. From the data on this small number of patients, it seems that the association of psychomotor retardation, male hypogenitalism and decreased serum IgG in a patient with a type 1 pattern of serum sialotransferrins might be a clue to the diagnosis of CDG Ig.