MIMO-enabling PHY layer enhancement for vehicular ad-hoc networks

Depending on traffic density and environmental influences, the radio channel in Vehicular Ad-Hoc Networks (VANETs) can be a limited resource. The Shannon-Hartley theorem gives a theoretical maximum amount of data which can be transmitted per time unit under given channel conditions. This limitation can be exceeded by using multi-antenna approaches commonly known as multiple-input, multiple-output (MIMO) communication systems. While these systems are already common in both infrastructural Wireless LAN (i.e. IEEE 802.11n or IEEE 802.11ac) and in modern cellular mobile networks (i.e. Long Term Evolution), the IEEE 802.11p standard for vehicleto- vehicle communication still comes without any multi-antenna approaches. In this paper we show in a simulation study that compared to plain IEEE 802.11p a MIMO-extended PHY layer based on IEEE 802.11p offers a considerably higher robustness against short-term fading caused by the vehicles´ mobility and other channel-caused adverseness. Therefore we implemented a MIMO-extended PHY model using Orthogonal Space-Time Block Codes (OSTBC) and linked the PHY model to a realistic MIMO radio channel model that is based on a large measurement campaign.