**4. The mathematical reference model**

Akki and Haber's simulation model for IVC channels with no LOS component gives the complex channel envelope as (Akki & Haber, 1989)

$$Y(t) = \sqrt{\frac{2}{N}} \sum\_{n=1}^{N} \exp\{j[(2\pi f\_1 \cos(\alpha\_n)t + 2\pi f\_2 \cos(\beta\_n)t + \theta\_n)]\}\tag{1}$$

where *f*<sup>1</sup> and *f*<sup>2</sup> are the maximum Doppler frequencies due to the motion of the transmitter and the receiver, respectively. *N* is the number of propagation paths, *αn* and *βn* are the random angle of departure (AOD) and the angle of arrival (AOA) of the *nth* path measured with respect to the transmitter and the receiver velocity vectors, respectively, and *θn* is the random phase uniformly distributed on [−*π*,*π*), independent of *α*� *ns* and *β*� *ns* for all *n*.

Fig. 1. IVC channel with a LOS component in VANETs
