On multilink shadowing effects in measured V2V channels on highway

Shadowing from vehicles can degrade the performance of vehicle-to-vehicle (V2V) communication systems significantly. It is thus important to characterize and model the influence of common shadowing objects like cars properly. For multilink systems it is essential to model the joint effects on the different links. However, the multilink shadowing effects in V2V channels are not yet well understood. In this paper we present a measurement based analysis of multilink shadowing effects in V2V communication systems with cars as blocking objects. In particular we analyze and characterize the joint large scale fading process for multilink communication at 5.9 GHz between four cars in a highway scenario. From our analysis it is found that the coherence time of the large scale fading process for different links can vary from a few seconds to minutes. The results show that it is essential to consider the correlation of the large scale fading processes as the correlation coefficients can have both large negative and large positive values. There is also a clear indication that multihop techniques provide an efficient way to overcome the issue with shadowed cars in V2V systems.