Analysis of IEEE 802.11p Preamble Insertion in Sidelink C-V2X Signals to Improve Co-Channel Coexistence

The spectrum scarcity is one of the main challenges of future wireless technologies. When looking at vehicle-to-everything (V2X), this magnifies as spectrum sharing might impact on safety and traffic efficiency. It is therefore of increasing interest to focus on the coexistence of the main access layer V2X technologies in the same geographical region and in the same channels, with particular reference to today's main candidates IEEE 802.11p and sidelink LTE-V2X Mode 4. In this work, in addition to investigating the impact of the reciprocal interference, which is shown to heavily impact especially on the former and in congested channel conditions, a mitigation solution is extensively studied, which is based on the insertion of the IEEE 802.11p preamble at the beginning of the sidelink LTE-V2X transmission. The proposal, which is being discussed also within standardization bodies, requires no modifications to the IEEE 802.11p protocol stack and minor modifications to sidelink LTE-V2X. It is also directly applied to upcoming IEEE 802.11bd and extendable to sidelink 5G-V2X. The paper shows, through analysis and simulations in free-flow and dense scenarios, that the proposal allows a significant improvement of co-channel coexistence in lowly loaded channel conditions and that the improvement is granted also in congested cases when combined with additional countermeasures. Regarding the latter aspect, in particular, different approaches are compared, showing that acting on the congestion control mechanisms is a simple but effective solution.