Roaming in the Mobile Internet: when coverage sharing agreements call for regulation

Revised: 2006-06We examine competition in Mobile Internet services, when operators bargain over the coverage sharing and their reciprocal roaming charge. Results show that in equilibrium operators cover the overall territory entirely and no-duplication is chosen, no matter how their bargaining power is distributed: operators have aligned incentives to enjoy roaming revenues extra-rents. Only their relative stand-alone coverage and, therefore, their appropriation of these rents, can be affected by how bargaining power is distributed. We finally discuss the scope for regulatory intervention to reduce these rents in the forms of minimum coverage requirements, or control over the level of reciprocal roaming charges

A P2P middleware design for digital access nodes in marginalised rural areas

This thesis addresses software design within the field of Information and Communications Technology for Development (ICTD). Specifically, it makes a case for the design and development of software which is custom-made for the context of marginalised rural areas (MRAs). One of the main aims of any ICTD project is sustainability and such sustainability is particularly difficult in MRAs because of the high costs of projects located there. Most literature on ICTD projects focuses on other factors, such as management, regulations, social and community issues when discussing this issue. Technical matters are often down-played or ignored entirely. This thesis argues that MRAs exhibit unique technical characteristics and that by understanding these characteristics, one can possibly design more cost-effective software. One specific characteristic is described and addressed in this thesis – a characteristic we describe here for the first time and call a network island. Further analysis of the literature generates a picture of a distributed network of access nodes (DANs) within such network islands, which are connected by high speed networks and are able to share resources and stimulate usage of technology by offering a wide range of services. This thesis attempts to design a fitting middleware platform for such a context, which would achieve the following aims: i) allow software developers to create solutions for the context more efficiently (correctly, rapidly); ii) stimulate product managers and business owners to create innovative software products more easily (cost-effectively). A given in the context of this thesis is that the software should use free/libre open source software (FLOSS) – good arguments do also exist for the use of FLOSS. A review of useful FLOSS frameworks is undertaken and several of these are examined in an applied part of the thesis, to see how useful they may be. They form the basis for a walking skeleton implementation of the proposed middleware. The Spring framework is the basis for experiments, along with Spring-Webservices, JMX and PHP 5’s web service capabilities. This thesis builds on three years of work at the Siyakhula Living Lab (SLL), an experimental testbed in a MRA in the Mbashe district of the Eastern Cape of South Africa. Several existing products are deployed at the SLL in the fields of eCommerce, eGovernment and eLearning. Requirements specifications are engineered from a variety of sources, including interviews, mailing lists, the author’s experience as a supervisor at the SLL, and a review of the existing SLL products. Future products are also investigated, as the thesis considers current trends in ICTD. Use cases are also derived and listed. Most of the use cases are concerned with management functions of DANs that can be automated, so that operators of DANs can focus on their core business and not on technology. Using the UML Components methodology, the thesis then proceeds to design a middleware component architecture that is derived from the requirements specification. The process proceeds step-by-step, so that the reader can follow how business rules, operations and interfaces are derived from the use cases. Ultimately, the business rules, interfaces and operations are related to business logic, system interfaces and operations that are situated in specific components. The components in turn are derived from the business information model, that is derived from the business concepts that were initially used to describe the context for the requirements engineering. In this way, a logical method for software design is applied to the problem domain to methodically derive a software design for a middleware solution. The thesis tests the design by considering possible weaknesses in the design. The network aspect is tested by interpolating from formal assumptions about the nature of the context. The data access layer is also identified as a possible bottleneck. We suggest the use of fast indexing methods instead of relational databases to maintain flexibility and efficiency of the data layer. Lessons learned from the exercise are discussed, within the context of the author’s experience in software development teams, as well as in ICTD projects. This synthesis of information leads to warnings about the psychology of middleware development. We note that the ICTD domain is a particularly difficult one with regards to software development as business requirements are not usually clearly formulated and developers do not have the requisite domain knowledge. In conclusion, the core arguments of the thesis are recounted in a bullet form, to lay bare the reasoning behind this work. Novel aspects of the work are also highlighted. They include the description of a network island, and aspects of the DAN middleware requirements engineering and design. Future steps for work based on this thesis are mapped out and open problems relating to this research are touched upon

Out of the box: how bees orient in an ambiguous environment

Dittmar L, Stürzl W, Jetzschke S, Mertes M, Boeddeker N. Out of the box: how bees orient in an ambiguous environment. Animal Behaviour. 2014;89:13-21.How do bees employ multiple visual cues for homing? They could either combine the available cues using a view-based computational mechanism or pick one cue. We tested these strategies by training honeybees, Apis mellifera carnica, and bumblebees, Bombus terrestris, to locate food in one of the four corners of a box-shaped flight arena, providing multiple and also ambiguous cues. In tests, bees confused the diagonally opposite corners, which looked the same from the inside of the box owing to its rectangular shape and because these corners carried the same local colour cues. These 'rotational errors' indicate that the bees did not use compass information inferred from the geomagnetic field under our experimental conditions. When we then swapped cues between corners, bees preferred corners that had local cues similar to the trained corner, even when the geometric relations were incorrect. Apparently, they relied on views, a finding that we corroborated by computer simulations in which we assumed that bees try to match a memorized view of the goal location with the current view when they return to the box. However, when extra visual cues outside the box were provided, bees were able to resolve the ambiguity and locate the correct corner. We show that this performance cannot be explained by view matching from inside the box. Indeed, the bees adapted their behaviour and actively acquired information by leaving the arena and flying towards the cues outside the box. From there they re-entered the arena at the correct corner, now ignoring local cues that previously dominated their choices. All individuals of both species came up with this new behavioural strategy for solving the problem provided by the local ambiguity within the box. Thus both species seemed to be solving the ambiguous task by using their route memory, which is always available during their natural foraging behaviour. (C) 2014 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved

The dominant role of visual motion cues in bumblebee flight control revealed through virtual reality

Flying bees make extensive use of optic flow: the apparent motion in the visual scene generated by their own movement. Much of what is known about bees’ visually-guided flight comes from experiments employing real physical objects, which constrains the types of cues that can be presented. Here we implement a virtual reality system allowing us to create the visual illusion of objects in 3D space. We trained bumblebees, Bombus ignitus, to feed from a static target displayed on the floor of a flight arena, and then observed their responses to various interposing virtual objects. When a virtual floor was presented above the physical floor, bees were reluctant to descend through it, indicating that they perceived the virtual floor as a real surface. To reach a target at ground level, they flew through a hole in a virtual surface above the ground, and around an elevated virtual platform, despite receiving no reward for avoiding the virtual obstacles. These behaviors persisted even when the target was made (unrealistically) visible through the obstructing object. Finally, we challenged the bees with physically impossible ambiguous stimuli, which give conflicting motion and occlusion cues. In such cases, they behaved in accordance with the motion information, seemingly ignoring occlusion

Mechanisms, functions and ecology of colour vision in the honeybee.

notes: PMCID: PMC4035557types: Journal Article© The Author(s) 2014.This is an open access article that is freely available in ORE or from Springerlink.com. Please cite the published version available at: http://link.springer.com/article/10.1007%2Fs00359-014-0915-1Research in the honeybee has laid the foundations for our understanding of insect colour vision. The trichromatic colour vision of honeybees shares fundamental properties with primate and human colour perception, such as colour constancy, colour opponency, segregation of colour and brightness coding. Laborious efforts to reconstruct the colour vision pathway in the honeybee have provided detailed descriptions of neural connectivity and the properties of photoreceptors and interneurons in the optic lobes of the bee brain. The modelling of colour perception advanced with the establishment of colour discrimination models that were based on experimental data, the Colour-Opponent Coding and Receptor Noise-Limited models, which are important tools for the quantitative assessment of bee colour vision and colour-guided behaviours. Major insights into the visual ecology of bees have been gained combining behavioural experiments and quantitative modelling, and asking how bee vision has influenced the evolution of flower colours and patterns. Recently research has focussed on the discrimination and categorisation of coloured patterns, colourful scenes and various other groupings of coloured stimuli, highlighting the bees' behavioural flexibility. The identification of perceptual mechanisms remains of fundamental importance for the interpretation of their learning strategies and performance in diverse experimental tasks.Biotechnology and Biological Sciences Research Council (BBSRC

Wahlstrategien bestäubender Hymenopteren als Selektionsfaktor

Title Page and Table of Contents Introduction I. Apis mellifera bees modulate their dance according to perceptual properties of a flower patch. II. Sensory ecology of pollination: The distribution of floral colours and sugar reward in the bee's natural environment. III. Studies on floral colouration and reward properties in Argentinian plant- pollinator communities. IV. Detectability of grouped colour targets for bees is enhanced through edge density. V. A new floral mimicry system between Turneraceae and Malvaceae is Müllerian but not mutualistic. General Conclusions Summary Zusammenfassung Danksagung Curriculum Vitae Cover Page: Appendices Appendix II-1 Appendix II-2 Appendix II-3 Appendix III-1 Appendix III-2 Appendix III-3The present dissertation is an integrated study of plant-pollinator interactions, aiming to understand the colouration of flowers from the perspective of the pollinators. To that purpose and to deepen our understanding of bees visual and cognitive abilities bees foraging behaviour was observed and analysed. Descriptive investigations of flower colour distributions and related rewards in natural plant communities were performed. Behavioural experiments under laboratory conditions were carried out to understand precisely how bees deal with specific colour-reward distributions. During foraging, bees form a reward expectation for a food source. The food source is characterised by its signals. Foraging decisions can therefore be understood as an outcome of interactions between the strength of signal memories and reward estimations. The aim of this work was to evince these kinds of interactions and to characterise the natural conditions under which these abilities of the bees have potentially evolved.Bei der vorliegenden Dissertation handelt es sich um eine integrierte Studie über die Wechselbeziehungen in Pflanzen-Bestäuber-Gemeinschaften, um die Färbung der Blüten aus der Sicht der Bestäuber zu verstehen. Zu diesem Zweck wurde das Sammelverhalten von Honigbienen und Hummeln beobachtet und analysiert, um deren visuelle und kognitive Fähigkeiten zu untersuchen. In natürlichen Pflanzengemeinschaften wurden Verteilungen von Blütenfarben und zugehörige Belohnungsqualitäten gemessen. Verhaltensexperimente unter kontrollierten Bedingungen wurden angewandt, um zu verstehen, wie die Tiere mit solchen Farb-Belohnungs-Verteilungen umgehen. Während des Sammelns bilden Bienen eine Erwartung an die Belohnung an einer Futterquelle, die durch ihr Farbsignal charakterisiert ist. Sammelentscheidungen können daher als ein Ergebnis von Interaktionen zwischen der Erinnerungsstärke an Signale und Belohnungseinschätzungen verstanden werden. Das Ziel dieser Arbeit war, solche Interaktionen aufzuzeigen und die natürlichen Bedingungen zu charakterisieren, unter denen sich diese Fähigkeiten der Bienen möglicherweise entwickelt haben

Roaming in the Mobile Internet: when Competition over Coverage asks for Regulation

We examine competition in Mobile Internet services, when operators bargain over the coverage sharing and their reciprocal roaming charge. Results show that in equilibrium operators cover the overall territory entirely and no-duplication is chosen, no matter how their bargaining power is distributed: operators have aligned incentives to enjoy roaming revenues extra-rents. Only their relative stand-alone coverage and, therefore, their appropriation of these rents, can be a.ected by how bargaining power is distributed. We finally discuss the scope for regulatory intervention to reduce these rents in the forms of minimum coverage requirements, or control over the level of reciprocal roaming charges

Roaming in the Mobile Internet: when coverage sharing agreements call for regulation

Revised: 2006-06We examine competition in Mobile Internet services, when operators bargain over the coverage sharing and their reciprocal roaming charge. Results show that in equilibrium operators cover the overall territory entirely and no-duplication is chosen, no matter how their bargaining power is distributed: operators have aligned incentives to enjoy roaming revenues extra-rents. Only their relative stand-alone coverage and, therefore, their appropriation of these rents, can be affected by how bargaining power is distributed. We finally discuss the scope for regulatory intervention to reduce these rents in the forms of minimum coverage requirements, or control over the level of reciprocal roaming charges

Roaming in the Mobile Internet

With the acquisition of UMTS licenses Mobile Operators (MOs), have often been obliged to deploy 3G network infrastructures covering at least a given percentage of users by a given date. This paper discusses the rationale for imposing these minimum coverage requirements by regulatory bodies. To that end, a model is built, which studies the incentives for MOs to compete for market share and over coverage within an unregulated environment where MOs are assumed to be free to enter sharing agreements and to negotiate a reciprocal roaming charge. Within this framework, it is first shown that MOs would deploy their infrastructure to guarantee the coverage of the entire territory (population), but they would avoid any network duplication in order to maximize rents from roaming revenues. It is then discussed whether a minimum coverage requirement is the best policy to reduce these excess rents, or whether alternative measures could be adopted which could serve other goals as well, such as the avoidance of network duplication.Mobile Internet Coverage Roaming agreements No-duplication Minimum coverage requirement Regulation