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Distribution of the Fading Coefficients

The following slides show the distribution of the absolute value and phase of the impulse and frequency response. The shape depends mostly on the value of $K$. A greater LoS component will result in a decrease in standard deviation, leading to a more concentrated and higher peak around the mean. Since only the first tap contains a LoS component in this model, it will be the only one affected by changes to $K$. All other taps always follow the distribution for $K=0$. Ideally, the first tap's probability density function (PDF) is given by [3] $$ p_{|a_0|}(\xi) = 2\dfrac{K+1}{P_{\tau_0}}\xi \cdot \exp\left[-\left(K + \dfrac{(K+1)\xi^2}{P_{\tau_0}}\right) \right] \cdot \mathrm{I_0}\left(2\xi\sqrt{\dfrac{K\left( K + 1 \right) }{P_{\tau,0}}}\right) $$ and PDF in the frequency domain is given by $$ p_{|H|}(\xi) = 2(\gamma_{H}K+1)\xi \cdot \exp\left[-\left(\gamma_{H}K + (\gamma_{H}K+1)\xi^2 \right) \right] \cdot \mathrm{I_0}\left(2\xi\sqrt{\gamma_{H}K\left(\gamma_{H}K + 1 \right)}\right). $$ The factor $\gamma_{H}$ is used to convert to a different definition of $K$ and is unimportant for understanding this demo. The function $\mathrm{I_0}(x)$ is the modified Bessel function of the first kind and zeroth order.

The phase is uniformly distributed over $[-\pi, \pi)$ and unaffected by any changes made to the parameters. For the sake of easier visual processing the the phase is normalized to $[-1, 1)$ resulting in a constant PDF with the value $1/2$.

[1] D. Tse and P. Viswanath, Fundamentals of Wireless Communication. Cambridge: Cambridge University Press, 2005.
[3] N. C. Beaulieu, Chengshan Xiao and Yahong Rosa Zheng, “Novel Sum-of-Sinusoids Simulation Models for Rayleigh and Rician fading Channels,” IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, vol. 5, no. 12, pp. 3667–3679, 2006.
[5] S. O. Rice, “Statistical properties of a sine wave plus random noise”, The Bell System Technical Journal, vol. 27, no. 1, pp. 109–157, 1948.