FG Verteilte Systeme und Betriebssysteme
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Institute
Today's applications and services become more dependent on fast wireless communication, for the upcoming years data-rate demands of 100Gbit/s can be easily expected. However, fulfilling that demand is a task which cannot simply be solved by upscaling existing technologies. While most of the research tackles the challenges regarding the transmission technology from the physical layer up to base-band processing, we focus on the challenges concerning the handling of that vast amount of data. The overall goal is to bring together the transmission technology with the operating system to create a suitable end-to-end communication solution.
In this paper we argue that communication can be understood as a soft-realtime problem and how that helps introducing parallelism into protocol-processing.
Assessing the Feasibility of Combined BLE and Wi-Fi Communication for High Data Sensing Applications
(2023)
Advanced sensors generate more data than can be transmitted using classic battery-powered wireless sensor networks. While using Wi-Fi would provide plenty of throughput, the receivers are energy hungry and, thus, the radio time needs to be reduced. Previous research suggests to combine Wi-Fi with low-power technologies such as BLE for an energy efficient coordination of the Wi-Fi radios. Existing approaches focus on individual point-to-point routes whereas certain applications require concurrent transmissions. We evaluated the combination of BLE and Wi-Fi on the ESP32-S3 multi-radio microcontroller through detailed energy and throughput measurements. The results show that established BLE connections allow to activateWi-Fi quickly on-demand; the energy efficiency of the data transmission is significantly improved over previous works but the BLE connection setup is prohibitively slow. While the combination of BLE and Wi-Fi provides high throughput with good energy efficiency, careful design of the BLE-based signalling protocol is necessary to also achieve low latency.
In this paper, we present an approach to support
transaction-based spatial-temporal programming of mobile robot
swarms on a systemic level. We introduce a programming model
for swarms of mobile robots. Swarm applications consist of
concurrent, distributed and context-aware actions. We provide
distributed transactions in order to guarantee atomic execution of
a set of dependent actions. We distinguish between schedulability
and executability of a set of actions. In order to guarantee exe-
cutability of a distributed transaction of spatial-temporal actions,
we present the concept of path alternatives and a time-based two-
phase commit protocol in order to assure consistency. We show
the feasibility of our approach by a proof-of-concept.
Experiments have shown that the number of asymmetric and unidirectional links often exceeds the number of bidirectional ones, especially in the transitional area of the communication range of wireless sensor nodes. Still, most of today’s routing protocols ignore their existence or try to remove their implications. Also, links are not stable over time, and routes become unusable often, resulting in a need for new routing protocols that can handle highly dynamic links and use unidirectional links to their advantage. At Sensorcomm 2014, we presented BuckshotDV, a routing protocol which is resilient against link fluctuations and uses the longer reach of unidirectional links to increase its performance. Furthermore, its distance vector nature makes it scalable for large sensor networks. This paper is an extended version which adds some implementation details and the evaluation of BuckshotDV in two more application scenarios.
Experiments with wireless sensor networks have shown that links are often asymmetric or unidirectional. This represents a serious problem for many routing protocols, which often depend on bidirectional links. Routing protocols that can use unidirectional links often induce a high overhead. To overcome this problem we introduced Unidirectional Link Triangle Routing, a routing protocol, which uses neighborhood information, gathered actively or passively, to route around unidirectional links. In this paper, we describe Unidirectional Link Triangle Routing in further detail and present additional evaluation results from different application scenarios.
Experiments with wireless sensor networks have shown that asymmetric and unidirectional links do not only exist, but are indeed quite common. Still, many people argue that the gain in connectivity is not worth the effort of making them usable for routing protocols. In this paper, we follow the opposite approach and introduce Unidirectional Link Triangle Routing, which reduces the overhead and, therefore, makes unidirectional links usable on the routing layer.
Experiments have shown that the number of asym- metric and unidirectional links often exceeds the number of bidirectional ones, especially in the transitional area of the communication range of wireless sensor nodes. Still, most of today’s routing protocols ignore their existence or try to remove their implications. Also, links are not stable over time, and routes become unusable often, resulting in a need for new routing protocols that can handle highly dynamic links and use unidirectional links to their advantage. In this paper, we present BuckshotDV, a routing protocol which is resilient against link fluctuations and uses the longer reach of unidirectional links to increase its performance. Furthermore, its distance vector nature makes it scalable for large sensor networks.
MLMAC-UL and ECTS-MAC - Two MAC Protocols for Wireless Sensor Networks with Unidirectional Links
(2009)
Applying Wireless Sensor Networks to Renaturation Monitoring: From Requirements to Deployment
(2014)
Sensorium - An Active Monitoring System for Neighborhood Relations in Wireless Sensor Networks
(2010)
Embedded systems, e.g. nodes within sensor networks, often have tight bound goals for lifetime while running from a not renewable energy source. Mostly batteries are used, which are vulnerable to temperature and non-linear effects. Additionally, variations within the hardware or induced by the software make the prediction of the available and consumed energy a complicated task. To reach certain lifetime goals under these influences, online energy management is necessary. For a fine-grained management on the level of individual sub-tasks, it is necessary to know where in the system the energy is consumed.
In this work, we extend our online energy accounting approach to enable online energy management. We present ways to control application and device behavior, and, thus, energy using energy budgets. First experiments yield promising results, reaching their lifetime goals while maintaining a high application quality.
Nodes within sensor networks often have tight bound goals for the lifetime while running from a non-renewable energy source. Variations within the hardware or induced by the software complicate the prediction of the energy consumption. Additionally, batteries are vulnerable to temperature and non-linear effects. To reach certain lifetime goals under these influences without sacrificing energy due to pessimistic estimations, online energy management is necessary. At Sensorcomm 2015 we presented policies to control the behavior of applications and devices using energy budgets. This paper is an extended version which adds further details and the evaluation of the proposed dynamic energy management in a real-world scenario.
Nodes within sensor networks often have tight bound goals for the lifetime while running from a non-renewable energy source. Variations within the hardware or induced by the software complicate the prediction of the energy consumption. Additionally, batteries are vulnerable to temperature and non-linear effects. To reach certain lifetime goals under these influences without sacrificing energy due to pessimistic estimations, online energy management is necessary. In this paper, we present policies to control the behavior of applications and devices using energy budgets. First experiments yield promising results, with nodes reaching their lifetime goals while maintaining a high application quality.
Implicit Sleep Mode Determination in Power Management of Event-driven Deeply Embedded Systems
(2008)
Currently, new storage technologies which unite the latency and byte-addressability of DRAM with the persistence of disks are being developed. This non-volatile memory (NVRAM) may start a software revolution. Traditionally, software was developed for two levels of storage and NVRAM reduces the hierarchy to a single-level store. Current research projects are already exploring the potential of NVRAM, but they face a challenge when they want to evaluate the performance: The new hardware is not yet available.
In this paper, we discuss why benchmark results which are gained on existing DRAM are insufficient for a prediction of the performance on NVRAM. Either existing instructions have to be changed or new ones have to be introduced. We further show that the bochs emulator can be used to build systems which resemble NVRAM, to predict the NVRAM's consequences, and it even allows a comparison of algorithms for NVRAM.