Sven Zeisberg

Simple channel model for 60 GHz indoor wireless LAN design based on complex wideband measurements

Based on practical complex wideband measurements, a simple model for the 60 GHz indoor wireless radio channel is presented in this paper. The multipath channel is modeled by a conventional time invariant FIR filter structure. Two sets of filter coefficients are provided for typical indoor wireless LAN application scenarios with an RF bandwidth of 200 MHz and 62 GHz center frequency. The scenarios represent the line of sight (LOS) and non line of sight (NLOS) cases where omni-directional antennas are used for both transmit and receive sides. The present channel model is used for system design simulations in the European wireless ATM project MEDIAN and can easily be adopted for similar simulation purposes. Thus, a new pragmatic system design tool for the 60 GHz indoor radio environment is given with this paper.

Enabling Mobile Devices for Home Automation Using ZigBee

Home automation systems are collections of interconnected devices for controlling various functions within a house, such as light control, heating, air conditioning, etc. Mobile devices are ideal in providing a user interface in a home automation system, due to their portability and their wide range of capabilities. They can communicate with a home automation network through an Internet gateway, but cannot directly communicate with devices in the network, as these devices usually implement low power communication protocols, such as ZigBee. We investigate several methods to equip an Android device with a dongle capable of ZigBee communication. We propose a scalable architecture, with three abstraction layers, that scales over multiple communication channels, such as the TCP channel, for communication with the gateway, and the USB channel, for direct communication with devices through the dongle. We test the application with two client devices running Android 4.0 and a mock home automation network consisting of a couple of ZigBee devices and a PC as gateway. We estimate the energy consumption of WiFi transfers over several typical use cases and we conclude that using ZigBee can prove beneficial in some cases, both in terms of functionality and performance.

Spreading properties of time hopping codes in ultra wideband systems

We analyse the power spectral density of time hopping (TH) coded impulse trains in ultra-wideband (UWB) systems, where the codes are described by their period and probability distribution. Thereby a number of significant code parameters are derived, which provide appropriate spectral smoothing properties. Furthermore the power spectrum of UWB impulse trains applying three different coders for time hopping are compared.

Coexistence Study between UWB and WiMax at 3.5 GHz Band

The effect of UWB interference on a WiMax system operating in the 3.5 GHz frequency band has been addressed in this paper. The possible impact on WiMax performance is still a topical problem even though the European regulation bodies have paid much attention to the coexistence issue between these two systems. On the other hand WiMax industries claimed that UWB can pose a harmful threat to their users terminals if UWB devices are located in very close proximity less than 1 meter. Hence, UWB may need to scarify their 3.5 GHz channel or implement some suitable mitigation techniques to keep the channel alive. In this paper, the WiMax receiver characteristics have been studied by means of the noise floor, sensitivity level and some interference criteria. Also the possible impacts on their cell coverage and on outage are computed. It is shown that UWB transmit power interference will not have a destructive effect on the performance of a WiMax receiver.

Performance of coherent and non-coherent receivers of UWB communication

Ultra-wideband (UWB) technology is currently investigated as one viable solution for high capacity short range indoor systems, because of its robustness in dense multipath environment, low cost and low power implementation, and the high bit rates achievable. In this paper we present the performance of coherent and non-coherent UWB receivers and especially for LDR-UWB systems with one of the most complicated application scenarios, under a realistic propagation environment, that takes into account also the effect of path-dependent pulse distortion. As far as coherent receivers are concerned, both maximal ratio combining (MRC) and equal gain combining (EGC) techniques are analyzed, considering a limited number of estimated paths.

UWB receiver performance comparison

The BER performance of the imperfect matched filter (IMF) is compared to the BER performance of the transmit reference (TR) receiver. Imperfect channel estimation is taken into account. The resulting BER performance of the IMF receiver is compared to the BER performance of the TR receiver, which has been modified compared to the original concept with regards to: (a) time gating, i.e. integration is just performed in the time interval where significant pulse energy is received; (b) 2PAM/M-PPM modulation; and (c) optional reference pulse averaging. Results show, that both receiver types can reach the uncoiled target BER of 10/sup -2/ in all environments investigated. However the IMF receiver outperforms the TR receiver by about 3 dB in LOS and by about 7 dB in NLOS. For the IMF receiver, the required E/sub b//N/sub 0/ ratio to achieve the target BER strongly depends on the number of filter coefficients. More details can be found in the final D5.3b deliverable of the UWB work package of the European research project whyless.com (Physical layer architecture and performance, 2003).

High resolution approach for phase based TOF ranging using compressive sampling

Phase measurement based time-of-flight ranging techniques are a valid approach for radio-frequency distance measurements using a small relative bandwidth. Step-frequency radar enhances this approach for application on multiple frequencies. In case of presence of narrowband interference, distance calculations are possibly affected depending on the number of frequencies measured and the type of the antennae used. The Inverse Fast Fourier Transform (IFFT) tends to be robust against interferences compared to calculation of a weighted mean. Resolution of IFFT and therefore accuracy of the ranging result depends on the number of measurement taps available. In this paper, the Compressive Sampling (CS) approach is investigated to increase the resolution of IFFT. It is shown that the CS approach is applicable for SFR in such scenario. Field tests have been performed for verification using a commercial ranging system from ZigPos company with different prototype antennae to minimize multipath influence in indoor environment.

An ultra-wideband indoor NLOS radio channel amplitude probability density distribution

The initial results of the development of an ultra-wideband (UWB) radio channel model based on an UWB radio channel measurement campaign carried out at IMST premises are summarised. The derived amplitude statistical model applies for pass band UWB signals under NLOS conditions. From stepped frequency transfer function measurements in the range from 1 to 11 GHz, employing wideband biconical antennas and successive windowed Fourier transform, radio channel responses were obtained in delay windows of approximately 160 ns width. In different locations the radio channel transfer function was measured over a spatial grid of 1500 mm times 300 mm and 10 mm resolution in both horizontal axes. The obtained data were used to verify the statistical model described.

Performance limits of ultra-wideband basic modulation principles

The performance of an ultra-wideband (UWB) communication system applying pulse position modulation (PPM) is investigated. The optimum impulse shift position in the case of binary overlapping PPM (2OPPM) is analytically derived for the AWGN channel. It is shown that the information throughput of a UWB system in the AWGN channel can be optimized by adjusting the time overlap of the pulse shape used according to the actual signal-to-noise ratio (SNR).

Impact of People Movement on Received Signal in Fixed Indoor Radio Communications

The effects of people movement in fixed indoor communications, known as temporal variation, are studied at 900 MHz and 2450 MHz with undertaking experiments in an office/laboratory environment. Intentional and unintentional (natural activities such as meeting, social gathering, etc.) temporal variations were examined with regard to various important parameters (i.e. mean received power, standard deviation, dynamic range of fluctuation, level crossing rate, average fade duration, etc.). In particular, it is found that the amount of dynamic range of fluctuation, mean received power and standard deviation change more likely depending on the level of time invariant received power (in a static environment) rather than on operating frequency. The results presented here could be meaningful for designing a robust fixed digital transceiver; in addition it can lead to model a simulation tool to analyze the temporal variations under diversified sets of conditions