Embracing Localization Inaccuracy: A Case Study

In recent years, indoor localization has become a hot research topic with some sophisticated solutions reaching accuracy on the order of ten centimeters. While certain classes of applications can justify the corresponding costs that come with these solutions, a wealth of applications have requirements that can be met at much lower cost by accepting lower accuracy. This paper explores one specific application for monitoring patients in a nursing home, showing that sufficient accuracy can be achieved with a carefully designed deployment of low-cost wireless sensor network nodes in combination with a simple RSSI-based localization technique. Notably our solution uses a single radio sample per period, a number that is much lower than similar approaches. This greatly eases the power burden of the nodes, resulting in a significant lifetime increase. This paper evaluates a concrete deployment from summer 2012 composed of fixed anchor motes throughout one floor of a nursing home and mobile units carried by patients. We show how two localization algorithms perform and demonstrate a clear improvement by following a set of simple guidelines to tune the anchor node placement. We show both quantitatively and qualitatively that the results meet the functional and non-functional system requirements

A Rapid Development of Dependable Applications in Ad Hoc Mobility

Advances in wireless communication and network computing technologies make possible new kinds of applications involving transient interactions among physical components that move across a wide range of spaces, from the confines of a room to the airspace across an ocean, and require no fixed networking infrastructure to communicate with one another. Such components may come together to form ad hoc networks for the purpose of exchanging information or in order to engage in cooperative task-oriented behaviors. Ad hoc networks are assembled, reshaped and taken apart as components move in and out of communication range; all interactions are transient; computations become highly decoupled and rely on weak forms of data consistency; disconnections are frequent and unpredictable; and component behavior is sensitive to changes in location, context, quality of service, or administrative domain. Our objective is to develop an environment that will facilitate rapid development of dependable mobile applications executing over ad hoc networks. Our primary focus will be the development of coordination constructs that support transient interactions among components, specifically through the design of global virtual data structures. Operations and their effects on these data structures must be defined with respect to the current connectivity context. We intend to use formal modeling techniques to define these constructs and their operating constraints as well as providing the specification for implementing these structure. Part of this specification will involve the development of algorithms for the ad hoc environment such as leader election, termination detection, and transactions

KRATOS: An Open Source Hardware-Software Platform for Rapid Research in LPWANs

Long-range (LoRa) radio technologies have recently gained momentum in the IoT landscape, allowing low-power communications over distances up to several kilometers. As a result, more and more LoRa networks are being deployed. However, commercially available LoRa devices are expensive and propriety, creating a barrier to entry and possibly slowing down developments and deployments of novel applications. Using open-source hardware and software platforms would allow more developers to test and build intelligent devices resulting in a better overall development ecosystem, lower barriers to entry, and rapid growth in the number of IoT applications. Toward this goal, this paper presents the design, implementation, and evaluation of KRATOS, a low-cost LoRa platform running ContikiOS. Both, our hardware and software designs are released as an open- source to the research community.Comment: Accepted at WiMob 201

Search and Tracking Algorithms for Rapidly Moving Mobiles

With the advent of wireless technology and laptops, mobility is an important area of research. A fundamental problem in this area is the delivery of messages to a moving mobile. Current solutions work correctly only for slowly moving nodes that stay in one location long enough for tracking to stabilize. In this paper we consider the problem of message delivery to rapidly moving mobile units. With these algorithms, we introduce a new method for designing algorithms based on the paradigm of considering a mobile unit as a message, and adapting traditional message passing algorithms to mobility. Our first algorithm is based on tracking and can be efficient when the path of the mobile node exhibits considerable locality. While it uses the Dijkstra-Scholten algorithm for diffusing computations as a point of departure, the final algorithm adds a number of mechanisms. Our second example is a search algorithm based on transforming the classic Chandy-Lamport snapshot algorithm. The algorithm generalizes to multicasting to a set of rapidly moving mobiles. Both our algorithms are based on the assumption that messages and mobiles travel through the same FIFO channels. We show how to enforce this assumption by modifying existing handover protocols

An Algorithm for Message Delivery in a Micromobility Environment

With recent advances in wireless communication and the ubiquity of laptops, mobile computing has become an important research area. An essential problem in mobile computing is the delivery of a message from a source to either a single mobile node, unicast, or to a group of mobile nodes, multicast. Standard solutions proposed for macromobility (Mobile IP) and micromobility (cellular phones) for the unicast problem rely on tracking the mobile node. Tracking solutions scale badly when mobile nodes move frequently, and do not generalize well to multicast delivery. Our paper proposes a new message delivery algorithm for micromobility based on a modification of classical snapshot algorithms. Our algorithm requires no tracking, provides stronger guarantees than existing protocols in micromobility, and generalizes easily to multicasting. Besides a particular solution to the delivery problem, our approach offers a new strategy for transferring established results from distributed computing to mobile computing. The general idea is to treat mobile nodes as messages that roam across the fixed network structure and to leverage off existing distributed algorithms that compute information about messages

Algorithms for Message Delivery in a Micromobility Environment

As computing components get smaller and people become accustomed to having computational power at their disposal at any time, mobile computing is developing as an important research area. One of the fundamental problems in mobility is maintaining connectivity through message passing as the user moves through the network. This is usually accomplished in one of two ways: search or tracking. In search, an algorithm hunts the mobile unit through the network each time a message is to be delivered, while in tracking, a specific home keeps up to date information about the current location of the mobile unit. Our paper proposes two message delivery algorithms based on these two paradigms of mobility. In general, our approach is to adopt existing algorithms from distributed computing to solve the problem of message delivery in the mobile setting, allowing us to leverage off existing knowledge about these algorithms and extensive research from distributed computing. The transformation from distributed to mobile computing is accomplished by treating the mobile units as messages that roam across the fixed network structure. First we show how snapshot algorithms can be adapted to perform message delivery through search, and then how the model of diffusing computations can be altered to track a mobile unit

Tracking Mobile Units for Dependable Message Delivery

As computing components get smaller and people become accustomed to having computational power at their disposal at any time, mobile computing is developing as an important research area. One of the fundamental problems in mobility is maintaining connectivity through message passing as the user moves through the network. An approach to this is to have a single home node constantly track the current location of the mobile unit and forward messages to this location. One problem with this approach is that during the update to the home agent after movement, messages are often dropped, especially in the case of frequent movement. In this paper, we present a new algorithm which uses a home agent, but maintains information regarding a subnet within which the mobile unit must be present. We also present a reliable message delivery algorithm which is superimposed on the region maintenance algorithm. Our strategy is based on ideas from diffusing computations as first proposed by Dijkstra and Scholten. Finally, we present a second algorithm which limits the size of the subnet by keeping only a path from the home node to the mobile unit

An Algorithm for Message Delivery to Mobile Units

With recent advances in wireless communication and the ubiquity of laptops, mobile computing has become an important research area. An essential problem in mobile computing is the delivery of a message from a source to either a single mobile node, unicast, or to a group of mobile nodes, multicast. Standard solutions used in Mobile IP and cellular phones for the unicast problem rely on tracking the mobile unit. Tracking solutions scale badly when mobile nodes move frequently, and do not generalize well to multicast delivery. Our paper proposes a new message delivery algorithm for micromobility based on a modification of classical snapshot algorithms and includes a proof outline using the UNITY logic. Our algorithm requires no tracking, provides stronger guarantees than existing protocols in micromobility, and generalizes easily to multicasting. Besides a particular solution to the delivery problem, our approach offers a new strategy for transferring established results from distributed computing to mobile computing. The general idea is to treat mobile nodes as messages that roam across the fixed network structure and to leverage off existing distributed algorithms that compute information about messages