Multipath propagation

About: Multipath propagation is a research topic. Over the lifetime, 27210 publications have been published within this topic receiving 434603 citations.

Low angle estimation in diffuse multipath environment by time-reversal minimum-norm-like technique

Abstract: This study presents a novel method for low angle estimation in diffuse multipath environment by the time-reversal (TR) minimum-norm-like (MNL) technique. In recent studies, the diffuse multipath is always regarded as the interference which is tried to be eliminated or weakened in low angle estimation for very high-frequency radar. However, it is difficult to establish the accurate model of the multipath environment. The common methods usually ignore the diffuse multipath and use the mirror reflection as the approximate model, but the ideal assumption would cause great errors. The proposed method makes the radar array working in the TR setup and the MNL technique is applied to estimate the low angle. In the proposed method, the exact model of the multipath environment does not need to be established completely but the accuracy performance of low angle estimation can be improved by making use of the multipath. Simulation results are presented to demonstrate the effectiveness of the proposed method. In addition, the performance degradation with respect to target motion is also shown in simulation results.

On the Bit Error Probability of OFDM and FBMC-OQAM Systems in Rayleigh and Rician Multipath Fading Channels

Abstract: Filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) is considered an alternative to conventional orthogonal frequency division multiplexing (OFDM) to meet the various requirements proposed by future communication networks. Among the different perspectives on the merits of FBMC-OQAM and OFDM, a straightforward metric is the bit error probability (BEP). This paper presents a general analytical framework for BEP evaluation that is applicable to FBMCOQAM and OFDM systems in both Rayleigh and Rician multipath fading channels. Explicit BEP expressions are derived for Gray-coded pulse amplitude modulation (PAM) and square quadrature amplitude modulation (QAM) signals with arbitrary constellation sizes. The theoretical analysis results show excellent agreement with the numerical simulation results in different channel scenarios. key words: bit error probability, FBMC-OQAM, OFDM, multipath channel, Gray coding

An ultra wideband positioning system enhanced by a short multipath mitigation technique

Abstract: In this paper an approach for high precision local positioning radar using an ultra wideband technique is presented. The concept is based on the standard FMCW (frequency modulated continuous wave) radar principle combined with short pulses to fulfill the emission limits given by the official regulatory authorities. In this way, a high accuracy in dense multipath indoor environments can be achieved, ideally suited for 1D, 2D and 3D localization. A prototype was built which operates at a center frequency of 7.5 GHz utilizing a bandwidth of 1 GHz. With the setup presented in this paper the distance between two wireless units can be measured achieving a standard deviation down to 6 mm. Additionally, we studied the effects of short multipath propagation and present simulation results for an applicable mitigation technique.

Performance Evaluation of Adaptive Tracking Techniques with Direct-State Kalman Filter

Abstract: This paper evaluates the performance of robust adaptive tracking techniques with the direct-state Kalman filter (DSKF) used in modern digital global navigation satellite system (GNSS) receivers. Under the assumption of a well-known Gaussian distributed model of the states and the measurements, the DSKF adapts its coefficients optimally to achieve the minimum mean square error (MMSE). In time-varying scenarios, the measurements’ distribution changes over time due to noise, signal dynamics, multipath, and non-line-of-sight effects. These kinds of scenarios make difficult the search for a suitable measurement and process noise model, leading to a sub-optimal solution of the DSKF. The loop-bandwidth control algorithm (LBCA) can adapt the DSKF according to the time-varying scenario and improve its performance significantly. This study introduces two methods to adapt the DSKF using the LBCA: The LBCA-based DSKF and the LBCA-based lookup table (LUT)-DSKF. The former method adapts the steady-state process noise variance based on the LBCA’s loop bandwidth update. In contrast, the latter directly relates the loop bandwidth with the steady-state Kalman gains. The presented techniques are compared with the well-known state-of-the-art carrier-to-noise density ratio (C/N0)-based DSKF. These adaptive tracking techniques are implemented in an open software interface GNSS hardware receiver. For each implementation, the receiver’s tracking performance and the system performance are evaluated in simulated scenarios with different dynamics and noise cases. Results confirm that the LBCA can be successfully applied to adapt the DSKF. The LBCA-based LUT-DSKF exhibits superior static and dynamic system performance compared to other adaptive tracking techniques using the DSKF while achieving the lowest complexity.