Adolf Finger

Comparison of different turbo decoder realizations for IMT-2000

Turbo coding has reached a great interest in the last years. It offers better performance than most of the traditional coding schemes. Turbo coding has been considered for using in the next mobile communications standard (IMT-2000). For decoding of these codes a soft-input-soft-output (SISO) decoder is necessary. Several reduced complexity algorithms suitable for hardware implementation have been introduced. However, a comparison in terms of performance, throughput, complexity and power consumption is not available. In this paper different turbo decoder algorithms and architectures are compared in this aspects with focus on the proposed parameters of IMT-2000.

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.

Simultaneous electro-optical upconversion, remote oscillator generation and air transmission of multiple optical WDM channels for a 60 GHz high capacity indoor system

Bidirectional transmission experiments have been carried out by advantageous use of WDM for simultaneous remote millimeter wave generation in a 60 GHz wireless LAN. Low bit error rates have been obtained under realistic conditions.

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.

Study of coexistence between UWB and narrowband cellular systems

The objective of the reported study is to investigate the impact of cumulative interference from multiple UWB systems to a narrowband victim receiver. The investigations are restricted to cellular victim receivers, in particular to the downlink of GSM-900, GSM-1800, and UMTS voice service. Since indoor environments are considered, a three-dimensional geometry for the spatial distribution of the UWB devices is assumed. To obtain a realistic scenario, a model describing the transmission activity of the UWB devices is taken into account. The outcome of this study is a statistical model, i.e., a probability density function (PDF), describing the cumulative interference from multiple UWB devices. The main question to be answered with this model is what the maximum acceptable UWB-device density is. The question is treated with respect to current FCC and ETSI regulations.

Performance of a multiband impulse radio UWB architecture

In this paper a highly flexible and scaleable multiband impulse radio UWB architecture for high data rates is described and evaluated. The investigations are mainly focused on on-off-keying modulation combined with a low-complexity non-coherent energy detection receiver. Various representative system configurations are defined and examined by simulation, studying effects of pulse generation, filtering, synchronization, demodulation and channel coding.

Radio-Optical System Design and Transmission Experiments for a Mobile Broadband Communications System at 60 GHz

The paper presents the system designconcept for a mobile broadband communications systemat 60 GHz. A dense WDM system is used for the opticalbackbone employing novel add/drop multiplexers. Forsimplicity, there is no signal processing andfrequency generation at the base station and a masteroscillator signal are used for millimetric carriergeneration. The master oscillator signal is modulatedonto the optical carriers by a novel concept ofsimultaneous external modulation, simplifying systemdesign significantly. Transmission experiments over acomplete downlink path using uncoded 2-FSK have beencarried out and a BER of 10-9at 50 MBit/s hasbeen obtained. Furthermore, 512-carrier DQPSK-OFDMtransmission at 45.8 MBit/s using 35 MHz bandwidth at60 GHz has been demonstrated.

A Simple and Fast Detect and Avoid Algorithm for Non-Coherent Multiband Impulse Radio UWB

In this paper we present a simple and fast detect and avoid (DAA) algorithm for non-coherent multiband impulse radio UWB. By independent par- allelized interception of all subbands, this algorithm shows a very robust and reliable behavior in the de- tection of narrowband interference such as the IEEE 802.11a wireless LAN (WLAN) standard (1). Thereby, narrowband interference detection is possible during an initialization mode but also during data transmission. The detection is based on a static threshold which guarantees a maximum bit error rate in each subband. If a narrowband interferer is present the transmission is avoided on the corresponding subband and a receiver known initialization sequence is transmitted. Due to the fact that there is a loss in data rate, this approach retains the possibility of using all subbands when no interferer is present. radio UWB system including its capability for narrowband interference mitigation is necessary. This paper presents a simple and novel narrowband interference mitigation technique for non-coherent multi- band impulse radio UWB. The proposed detect and avoid algorithm is based on an extended initial channel estima- tion as well as a recursive channel estimation which is described in (7). Thereby, the estimated values are used to detect a narrowband interferer within the initialization or the data transmission phase. The detection algorithm is very fast and an active narrowband interferer can be detected in less than 250 ns. The disturbed subband will be deactivated and remains off until a new channel estimation is initialized. The accuracy in the frequency domain of the detect and avoid algorithm depends on several system parameters, especially on the number of subbands. This paper is organized as follows: Section II introduces the system model including the non-coherent energy de- tection scheme. In section III we illustrate the impact of a specific narrowband interference source to a multiband impulse radio UWB system. Section IV shows the appli- cation of a static mitigation approach as well as a simple and robust detect and avoid algorithm. Finally, simulation results as well as conclusions are given.

Multilevel PAM with optimal amplitudes for non-coherent energy detection

This paper analyzes multilevel pulse amplitude modulation (M-PAM) for energy detection receivers. Because of the asymmetric, non Gaussian probability density function (PDF) of the energy detected signal, the optimal signal constellation is not known a priori. In order to achieve optimal symbol error rate performance using M-PAM, the optimal signal constellation will be calculated. Finally the SER performance of the energy detection receiver based multiband impulse radio UWB architecture within the IEEE802.15.3 a channel model using M-PAM will be demonstrated.