Complex Channel Transfer Function Research Articles

Modelling, Analysis, and Simulation of the Micro-Doppler Effect in Wideband Indoor Channels with Confirmation Through Pendulum Experiments.

This paper is about designing a 3D no n-stationary wideband indoor channel model for radio-frequency sensing. The proposed channel model allows for simulating the time-variant (TV) characteristics of the received signal of indoor channel in the presence of a moving object. The moving object is modelled by a point scatterer which travels along a trajectory. The trajectory is described by the object’s TV speed, TV horizontal angle of motion, and TV vertical angle of motion. An expression of the TV Doppler frequency caused by the moving scatterer is derived. Furthermore, an expression of the TV complex channel transfer function (CTF) of the received signal is provided, which accounts for the influence of a moving object and fixed objects, such as walls, ceiling, and furniture. An approximate analytical solution of the spectrogram of the CTF is derived. The proposed channel model is confirmed by measurements obtained from a pendulum experiment. In the pendulum experiment, the trajectory of the pendulum has been measured by using an inertial-measurement unit (IMU) and simultaneously collecting CSI data. For validation, we have compared the spectrogram of the proposed channel model fed with IMU data with the spectrogram characteristics of the measured CSI data. The proposed channel model paves the way towards designing simulation-based activity recognition systems.

TIME DOMAIN AND FREQUENCY DOMAIN DETERMINISTIC CHANNEL MODELING FOR TUNNEL/MINING ENVIRONMENTS

Understanding wireless channels in complex mining environments is critical for designing optimized wireless systems operated in these environments. In this paper, we propose two physics-based, deterministic ultra-wideband (UWB) channel models for characterizing wireless channels in mining/tunnel environments - one in the time domain and the other in the frequency domain. For the time domain model, a general Channel Impulse Response (CIR) is derived and the result is expressed in the classic UWB tapped delay line model. The derived time domain channel model takes into account major propagation controlling factors including tunnel or entry dimensions, frequency, polarization, electrical properties of the four tunnel walls, and transmitter and receiver locations. For the frequency domain model, a complex channel transfer function is derived analytically. Based on the proposed physics-based deterministic channel models, channel parameters such as delay spread, multipath component number, and angular spread are analyzed. It is found that, despite the presence of heavy multipath, both channel delay spread and angular spread for tunnel environments are relatively smaller compared to that of typical indoor environments. The results and findings in this paper have application in the design and deployment of wireless systems in underground mining environments.

Verification of the Rician K ‐factor‐based uncertainty model for measurements in reverberation chambers

Measurements in reverberation chamber (RC) produce data that are random, and therefore they need to be processed from the statistical point-of-view for obtaining the desired characteristics and the accuracy. The complex channel transfer function in the RC follows complex Gaussian distribution provided that the RC is well stirred. The authors have recently presented a new uncertainty model based on the presence of an unstirred component of the transfer function, which was modelled by introducing an average Rician K-factor. The model was validated in two RCs with translating mode-stirring plates, being able to correctly describe the improvement in accuracy by rotating the antenna under test, and by blocking the line-of-sight between this and the fixed RC antenna(s). In the present study, they apply this uncertainty model to four RCs with different settings (e.g. RC volumes, number of plates or fixed RC antennas, translating and rotating mode-stirrers etc.). For each RC, they examine the measurement uncertainty under different loading conditions. To repeat (during the different measurements) the actual mode-stirrer positions at which the transfer function is sampled, they conduct all the measurements with stepwise (instead of continuous) mode-stirring. The model is shown to work well for all the cases.