FG Verteilte Systeme und Betriebssysteme
The battery dictates the lifetime of many embedded systems, especially wireless sensor networks.This makes it necessary to deal with battery management.In this paper we present an approach for a battery management which enables a sensor node to reach a defined lifetime.The presented approach gives feedback to an energy manager if the current power consumption must be lowered or can be increased to reach the runtime goal.In contrast to other systems the battery is handled as black box to keep the system independent from the battery type and brand.First experiments yield promising results of this concept to reach a certain lifetime goal 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. 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.
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.
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 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.