NEAR-FIELD MEASUREMENTS FOR SAFETY RELATED SYSTEMS AND JAMMING ATTACK

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UWB and Wideband Channel Models for Working Machine Environment

Abstract—In this paper, we present statistical models for wideband and ultra-wideband (UWB) radio channels for working machine cabin environment. Based on a set of measurements, it was found that such a small and confined space causes mostly diffuse multipath scattering rather than specular paths. The amplitude of the channel impulse responses in the wideband case is mostly Rayleigh distributed small-scale fading signal, with only few paths exhibiting Ricean distributions, whereas the ones in the UWB case tend to be log-normally distributed. For the path amplitude, we suggest an exponential decay profile, which has a constant slope in dB scale, with the corresponding parameters for the UWB case. For the wideband case, a two-fold exponential decay profile provides excellent fits to the measured data. It was also noted that the root-mean-square (RMS) delay spread is independent of line-of-sight (LOS)/obstructed line-of-sight (OLOS) situations of the channel. The multipath components contributing significant energy play a major role in such a small environment if compared to the direct path. In addition, the radio channel gains are attenuated with the presence of a driver inside the cabin. I

CLPDI algorithm in UWB synchronization

Abstract: This paper studies code synchronization in time hopping (TH) ultra wideband (UWB) systems. In TH UWB systems, narrow pulses based on Gaussian pulse are positioned in different locations in consecutive time frames. The location of each frame is defined by a spreading code. The receiver collects the energy of the pulses using the same spreading code. To be able to do that, it has to synchronize itself to the incoming signal. Due to the large bandwidth of the signal, several replicas of the signals arrive into the receiver. Thus, the energy of the signal is spread in time domain causing extra problems to the synchronization procedure. In this paper, earlierly proposed method for direct sequence spread spectrum system is applied for time hopping system. The method is simulated in a multipath environment. The performance measure used is the mean acquisition time. Constant false alarm rate criterion is used for the threshold setting rule for comparator. The energies of the multipath components are combined in the acquisition process. Therefore, diversity combining is obtained in the acquisition process, which also leads to performance improvement. 1

COMPARATIVE STUDIES OF MB-OFDM AND DS-UWB WITH CO-EXISTING SYSTEMS IN AWGN CHANNEL

Multiband orthogonal frequency division multiplexing (MB-OFDM) and direct sequence ultra wideband (DS-UWB) systems’ performances are studied in interfered AWGN channel. Co-existing systems, i.e., interference, are assumed to be based on the forth-coming 4G. The other source is 100 MHz interference locating at IEEE802.11a band. The published studies related to the comparison between MB-OFDM and DS-UWB in interfering environments seems to be unsubstantial in the literature. Therefore, it is crucial to fill this gap. We focus more on MB-OFDM systems, whereas the DS-UWB is applied as a reference. The studied victim systems share the same frequency band and have similar data rates. Simulation results indicate that MB-OFDM system can slightly tolerate interference to achieve reasonable bit error rate level. DS-UWB achieves similar bit error rate level with higher interference-to-signal power ratio than MB-OFDM is able to do. The center frequency of interference has only minor effect on systems ’ performances. Increasing the bandwidth of the interference will reduce the performance in the case of MB-OFDM, whereas DS-UWB seems to be quite resilient to it. I