On the influence of walking people on the Doppler spectral characteristics of indoor channels

When modelling mobile radio channels with moving scatterers, it is generally assumed that the angles of departure (AODs), angles of arrival (AOAs), and the speed of the scatterers are time-invariant. However, this assumption is violated as the AODs and AOAs vary with the positions of the moving scatterers. Also, the speed of the moving scatterers might vary with time due to acceleration/deceleration. In this paper, we model the time-variant Doppler frequencies by taking into account the time-variant AODs, AOAs, and the variations of the speed of the moving scatterers. Furthermore, the complex channel gain of non-stationary single-input-single-output (SISO) fixed-to-fixed (F2F) indoor channels with moving and fixed scatterers is presented. The spectrogram of the complex channel gain using a Gaussian window is provided. The correctness of the analytical solutions is confirmed by simulations. The contribution of this paper paves the way towards the development of a passive in-home activity tracking system.