Christian Kocks

A Spectrum Sensing Prototype for TV White Space in China

TV white space (TVWS) has been considered a favorable spectrum for sharing with other spectrum deficient technologies. There are three popular TV standards in China: the Digital Terrestrial Multimedia Broadcast (DTMB), China Multimedia Mobile Broadcasting (CMMB) and PAL-D/K (Phase Alternating Line -D/K). In this paper we present a prototype platform for experimental spectrum sensing, which is developed in-house to test TVWS spectrum sharing for all the three popular TV standards. We discuss the details on the prototype architecture, the spectrum sensing algorithms and the testing setup in this paper. The performance results show that the developed prototype platform can detect the signals from all the three TV standards robustly and efficiently.

Leadless pacing using induction technology: impact of pulse shape and geometric factors on pacing efficiency

AIMS Leadless pacing can be done by transmitting energy by an alternating magnetic field from a subcutaneous transmitter unit (TU) to an endocardial receiver unit (RU). Safety and energy consumption are key issues that determine the clinical feasibility of this new technique. The aims of the study were (i) to evaluate the stimulation characteristics of the non-rectangular pacing pulses induced by the alternating magnetic field, (ii) to determine the extent and impact of RU movement caused by the beating heart, and (iii) to evaluate the influence of the relative position between TU and RU on pacing efficiency and energy consumption. METHODS AND RESULTS In the first step pacing efficiency and energy consumption for predefined positions were determined by bench testing. Subsequently, in a goat at five different ventricular sites (three in the right ventricle, two in the left ventricle) pacing thresholds using non-rectangular induction pulses were compared with conventional pulses. Relative position, defined by parallel distance, radial distance, and angulation between TU and RU, were determined in vivo by X-ray and an inclination angle measurement system. Bench testing showed that by magnetic induction for every alignment between TU and RU appropriate pulses can be produced up to a distance of 100 mm. In the animal experiment pacing thresholds were similar for non-rectangular pulses as compared with conventional pulse shapes. In all five positions with distances between 62 and 102 mm effective pacing was obtained in vivo. Variations in distance, displacement and angle caused by the beating heart did not cause loss of capture. At pacing threshold energy consumptions between 0.28 and 5.36 mJ were measured. Major determinants of energy consumption were distance and pacing threshold. CONCLUSION For any given RU position up to a distance of 100 mm reliable pacing using induction can be obtained. In anatomically crucial distances, up to 60 mm energy consumption is within a reasonable range.

System implementation study on RSSI based positioning in UWB networks

The Ultra-Wideband Radio Technology (UWB-RT) enables accurate Location and Tracking (LT) applications. However, the required and sophisticated time of arrival (ToA) ranging procedure relies on accurate synchronizations and time measurements. Non-cooperative nodes, not supporting the ToA feature, cannot be localized with this LT approach. Other LT approaches exploit the received signal strength (RSS) or received signal strength difference (RSSD). Simulations of RSS based localization in UWB networks showed promising performance results. In this paper, the authors introduce a RSS based LT demonstrator, build up with conventional Certified Wireless USB (CWUSB) sticks, using multiband UWB-RT. Different LT algorithms are tested. In a small UWB network, measurements of the localization accuracy show a root mean square error (RMSE) of about 0.33 meters.

A DVB-T2 receiver realization based on a software-defined radio concept

When DVB-T (Digital Video Broadcasting - Terrestrial) was introduced in the 1990s, it was impossible to foresee the upcoming demand for HDTV devices. Thus, a revision of this broadcasting standard, namely DVB-T2, was necessary. Recently finalized, this standard is targeting to high-definition television (HDTV). To pave the way to commercialization, an appropriate implementation concept and its corresponding validation are of utmost importance. Without a doubt, the most challenging requirements introduced by the DVB-T2 specification are an FFT (Fast Fourier Transform) size of up to 32k samples, 256-QAM (Quadrature Amplitude Modulation) and LDPC (Low-Density Parity-Check) coding with a block size of 64800 bits. Within this manuscript, the authors present a software-defined radio based realization of a demonstrator platform. This platform employs a combined DSP (Digital Signal Processor) and FPGA (Field-Programmable Gate Array) solution being capable of meeting these requirements.

Positioning in multiband OFDM UWB utilizing received signal strength

Ultra-wideband (UWB) enables accurate Localization and Tracking (LT) applications. However, the required and sophisticated time of arrival (ToA) ranging procedure relies on accurate synchronization and time measurements. Today, only few UWB devices support the required ranging feature. Examples are pulse based low data rate (LDR) UWB devices. Conventional multiband OFDM based high data rate (HDR) UWB devices do not support the ToA ranging feature. But the ultra wide frequency bandwidth of UWB enables not only high resolution of space surrounding UWB transceivers and therefore accurate time measurements, its enormous frequency diversity also minimizes fading effects. This allows reliable distance measurements, based on measurements of the received signal strength (RSS). This paper shows, that RSS based localization can be as accurate as ToA based localization. For this purpose, measurement results of the RSS and a derived path-loss model are used to calibrate a Monte Carlo simulator for RSS based ranging and localization. The RSS measurements are done with conventional wireless USB sticks, using HDR UWB. For a small 2 × 2 meters network, the simulation results show mean localization errors between 0.1 and 0.2 meters.

Maximum likelihood localization estimation based on received signal strength

This paper discusses a maximum likelihood (ML) estimator for the localization of mobile nodes in communication networks. The derived estimator is optimized for ranging measurements exploiting the received signal strength (RSS). For this purpose, the bias and uncertainties of the RSS based ranging procedure are analyzed, considering a path loss model of an indoor ultra-wideband (UWB) network under line of sight (LOS) conditions. The nonlinearity of the path loss model is first taken into account before the statistics of the observed RSS are approximated by a Taylor sequence of first order. The so found metrics describe a weighted least squares (WLS) method. The metrics of the estimator are analytically derived in closed-form. The performance of the derived estimator is investigated in Monte-Carlo simulations and compared with a simple least squares (LS) method and another method exploiting RSS fingerprints.

A low-cost protocol and application for UWB localization

Range Radio by Advanced Ultra-Wideband Radio Technology, FP7-ICT-215669, www.euwb.eu) project has been an industry-led initiative of twenty-one major industrial and excellent academic organizations from Europe and Israel who have been targeting innovative improvement, adaptation, integration and application of short-range Ultra-Wideband Radio Technology (UWB-RT). EUWB has effectively leveraged and significantly enhanced the scientific knowledge base in the advanced UWB-RT and has provided sophisticated new applications enabled by UWB and highly demanded in several European key industrial sectors such as home entertainment consumer electronics, automotive, public transportation, and heterogeneous cellular networks. It is anticipated that the efficient exploitation of cross-layer functionalities will fertilize the successful application of UWB technology. Within EUWB, major fields of this emerging challenge have been identified, such as the cognitive radio related Detect-And-Avoid (DAA) technology and the localization and tracking (LT) technology. An important aspect is to design an LT protocol. In this manuscript the authors will first illustrate the technical approach of EUWB, giving a brief overview of the project. Then, the authors will propose a novel LT protocol and application. This application is tailored to operate also with UWB devices that do not fully comply with the previously proposed LT schemes which need specific physical and medium access control layer functionalities.

Wireless Power Transfer H-Bridge design with serial resonance and varying supply voltage

In this manuscript the authors discuss the issues of designing and implementing an H-Bridge circuit with respect to small switching losses, minimal hardware afford and maximal flexibility of excitation and control. The H-Bridge is targeted for a biomedical Wireless Power Transfer (WPT) application, where the receiver (RX) is small compared to the transmitter (TX) and, thus, negligible. Resonance is applied on the TX side, while the input voltage to the H-Bridge is able to vary in the range of 3V to 28V depending on a flexible relation between the TX and RX. This causes effects to the design and the gate drivers of the H-Bridge. An H-Bridge design is proposed, which includes the use of an n-channel and p-channel Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET) for a direct addressing of gates with a microcontroller (μC). In addition, the switching losses are lowered by the introduction of choke inductors and non-overlapping time delayed driving signals. Furthermore, the proposed solution has been verified, since significant advancements compared to state-of-the-art H-Bridge designs can be shown.

On Spectrum Sensing for TV White Space in China

In the field of wireless communications the idea of cognitive radio is of utmost interest. Due to its advantageous propagation properties, the TV white space can be considered to become the first commercial application of cognitive radio. It allows the usage of secondary communication systems at non-occupied frequency bands. Within this paper, spectrum sensing algorithms are introduced for the three predominant Chinese TV standards DTMB, CMMB, and PAL-D/K. A prototype platform is presented and its underlying architecture based on a combination of DSP and FPGA is illustrated including the setup of the cognitive radio application. Furthermore, the performance of the sensing algorithms implemented on the prototype platform is shown in comparison to simulation results.

Java implementation of localization and tracking application based on HDR-UWB platform

In recent years extensive research was carried out in order to develop applications for the Ultra-Wideband (UWB) technology and to resolve the practical challenges in implementing an efficient UWB communication system utilizing the UWB impulse radio for precision localization. ToA (Time of Arrival) or TDoA (Time Difference of Arrival) of ranging frame are widely used because ToA and TDoA provide high accuracy due to the high time resolution with high bandwidth of IR-UWB (Impulse Radio - UWB) signal. HDR-UWB (High Data Rate -UWB) uses MB-OFDM (Multi Band - Orthogonal Frequency Division Multiplexing) to transmit signals, which can reach a data rate of 200 Mbit/s. In this paper a Java implementation of an active LT (Localization and Tracking) method based on a HDR-UWB platform is investigated. The hardware is composed of three UWB anchors, one UWB tag and one UWB location coordinator, which is connected to a PC (Personal Computer) or a PDA (Personal Digital Assistant). The Java program, which is hosted on the PC or PDA, is used to instruct the UWB coordinator to send and receive the UWB ranging frame and localize the tag. ToA is used as a ranging parameter in this work to measure the distance between the used UWB anchors and the UWB tag. The most important aspect is to reduce the jitter of ToA caused by CPU processing and the clock drift between UWB anchors and UWB tag. In this paper a 3-way ranging mechanism to minimize the clock drift is deployed. In addition the use of the JPCAP (Java Package for CAPturing) library in Java reduces the jitter of the ToA.