Axel Sikora

Coexistence of IEEE802.15.4 with other Systems in the 2.4 GHz-ISM-Band

Wireless systems continue to rapidly gain popularity. This is extremely true for data networks in the local and personal area, which are called WLAN and WPAN, respectively. However, most of those systems are working in the license-free industrial scientific medical (ISM) frequency bands, where neither resource planning nor bandwidth allocation can be guaranteed. To date, the most widespread systems in the 2.4 GHz ISM band are IEEE802.11 as stated in IEEE Std. 802-11 (1997) and Bluetooth, with ZigBee based in IEEE Std. 802.15.4 (2003) and IEEE802.15.4 as upcoming standards for short range wireless networks. In this paper we examine the mutual effects of these different communication standards. Measurements are performed with real-life equipment, in order to quantify coexistence issues

Free space range measurements with Semtech Lora™ technology

Although short range wireless communication explicitly targets local and very regional applications, range continues to be an extremely important issue. The range directly depends on the so called link budget, which can be increased by the choice of modulation and coding schemes. Especially, the recent transceiver generation comes with extensive and flexible support for Software Defined Radio (SDR). The SX127x family from Semtech Corp. is a member of this device class and promises significant benefits for range, robust performance, and battery lifetime compared to competing technologies. This contribution gives a short overview into the technologies to support Long Range (LoRa ™), describes the outdoor setup at the Laboratory Embedded Systems and Communication Electronics of Offenburg University of Applied Sciences, shows detailed measurement results and discusses the strengths and weaknesses of this technology.

A localization system using inertial measurement units from wireless commercial hand-held devices

This paper describes a newly developed technology for the calculation of trajectories of mobile objects, which is based on commercially available sensors being integrated into modern mobile phones and other gadgets. First, a step counting technique was implemented. Second, a novel step length estimator is proposed. These two algorithms utilize the data from accelerometer sensor only. Third, the heading information was obtained using a gyroscope with complementary filter in quaternion form. The combined algorithm was implemented on a low-power ARM processor to provide the trajectory points relative to an initial point. The proposed technique was tested by 10 subjects, in different shoes with different paces. The dependence of the performance of the technology on the attaching point of the mobile device is weak. The proposed algorithms have better balance and estimation accuracy and depend in less degree on the variety in physical parameters of people in comparison with the existing techniques. In experiments inertial measurement units were mounted in different places, i.e. in the hand, in trousers or in T-shirt pockets. The return position error did not exceed 5% of the total travelled distance for all performed tests.

Fields Tests for Ranging and Localization with Time-of-Flight-Measurements Using Chirp Spread Spectrum RF-devices

Short range wireless networks (SRWN) are an important platform for an increasing number of applications. Apart from the pure communication benefit and other added values, e.g. ease-of-installation, support of mobility, high level of redundancy and reliability, wireless networks can bring in an important additional feature: localization. In many cases, the precision of ranging and localization is based on the measurement of Received Signal Strength (RSS) and is thus quite limited. Systems with time-of-flight measurements promise better performance. However, not many systems are commercially available for applications in Short Range Wireless Networks. One of the first available products uses Chirp Spread Spectrum technology with a symmetric two way ranging. This contribution examines the results, which were achieved with these products for real-life environments. Vehicle-based applications for active safety (eSafety) play a special role in those scenarios.

Wireless protocol design for a cooperative pedestrian protection system

In the research project Ko-TAG, which is part of the research initiative Ko-FAS, cooperative sensor technology is developed and its benefit for traffic safety applications is evaluated. As a result the new sensor concept shall provide essential input data for next generation driver assistant systems. A secondary radar principle based on communication signals enables localization of objects with simultaneous data transmission. It mainly concentrates on pedestrian and other vulnerable road user (VRU) detection. This paper describes the architectural approach of the system design, as well as the main characteristics of the physical and data link layers of the proposed wireless protocol. The protocol is designed in such a way that it can be used as an extension to IEEE802.11p/WAVE protocol. The complete protocol is modeled in OPNET network simulator.

Technologies and reliability of modern embedded flash cells

Abstract We have examined the various technologies for implementing embedded flash cells. We discuss the technological basics with regard to practical consequences and concentrate on the aspects of reliability of embedded flash cells. The main focus is automotive application because they pose extremely hard requirements in terms of ambient parameters, life-time and programming cycles. Our work is mainly composed of three different parts. The first part gives an insight into the basic technology of embedded flash memory. It specifically concentrates on floating gate devices, which dominate today’s products. This first part is based on a broad analysis of scientific literature and describes the state of the art. The required process steps are presented as well as the test approaches to ensure a high-quality production level. In the second part an overview is given about products actually on the market. Based on this information, the technological characteristics of the different cell architectures are discussed in the third part.

Model based development of a TinyOS-based Wireless M-Bus implementation

In the field of smart metering it can be observed that standardized protocol, like Wireless M-Bus or ZigBee, enjoy a rapidly increasing popularity. For the protocol implementations, however, up to now, mostly legacy engineering processes and technologies are used, and modern approaches such as model driven design processes or open software platform are disregarded. Therefore, within the WiMBex project, it shall be demonstrated that it is possible to develop a commercial class Wireless M-Bus implementation following state-of-the art design process and using TinyOS as an open source platform. This contribution describes the overall approach of the project, as well as the state and the first experiences of the current work in progress.

Extensions to wireless M-Bus protocol for smart metering and smart grid application

Smart metering and smart grid applications are rapidly finding their place in the market in order to improve the provisioning process efficiency of electricity, gas, water and heat. The usage of communication technologies is a major stepping stone for these applications. These applications are commonly structured along a hierarchical four-layer architecture. However, the current technologies, initially developed for the local (primary) communication, leave significant room for improvement in terms of energy efficiency, range and cost. This contribution discusses the state-of-the-art of the wireless metering protocols, identifies the restrictions, and discusses possible solutions to overcome these limitations. This paper further discusses the problems faced when integrating the results from scientific research projects into real-life protocols and products. It is based on research work in progress in two large European research projects in this field, i.e. ME3GAS (Smart Gas Meters & Middleware for Energy Efficient Embedded Services) and WiMBex (Remote wireless water meter reading solution based on the EN 13757 standard, providing high autonomy, interoperability and range).

Simulation & analysis of WirelessHART nodes for real-time actuator application

WirelessHART protocol was specifically designed for real-time communication in the wireless sensor networks domain for industrial process automation requirements. Whereas the major purpose of WirelessHART is the read-out of sensors with moderate real-time requirements, an increasing demand for integration of actuator applications can be observed. Therefore, it must be verified that the WirelessHART protocol gives sufficient support to real-time industry requirements. As a result, the delay of especially burst and command messages from actuator and sensor nodes to the gateway and vice versa must be analyzed. In this paper, we implemented a WirelessHART network scenario in WirelessHART simulator in NS-2 , simulated and analyzed its time characteristics under ideal and noisy conditions. We evaluated the performance of the implementation in order to verify whether the requirements of industrial process and control can be met. This implementation offers an early alternative to expensive test beds for WirelessHART in real-time actuator applications.

The impact of NLOS components in Time-of-Flight networks for indoor positioning systems

Ranging errors are inevitable in all local positioning systems, including those based on Time-of-Flight (ToF) technique. Results of experiments show that the major cause for these errors is a signal degradation from multipath propagation. This effect is especially critical in case of Non-Light-of-Sight (NLOS) conditions. This paper describes causes that affects ranging errors for nanoLOC™-TOF-technology and presents estimations for the probability density functions of such errors under different NLOS conditions. The provided estimations allow the improvement of the accuracy of the localization through the subsequent mitigation of the ranging errors from the measurements. Additionally, it is proposed to increase the number of cases of NLOS-conditions for the improvement of the accuracy.