Dynamic Relay Assignment Scheme for Efficient V2V Content Precaching in Content-Centric Internet of Vehicles

The rapidly growing data demands of autonomous driving and onboard multimedia services pose significant challenges to traditional roadside unit (RSU) based content delivery, particularly under limited cache capacity and coverage gaps. In the content-centric Internet of Vehicles (CIoV), vehicle-to-vehicle (V2V) precaching has emerged as an effective solution to mitigate these limitations. However, existing schemes rely on static precaching roles, leading to inefficiencies when a precaching vehicle initiates its own content request. To address this issue, we propose a dynamic relay assignment scheme (DRAS) that enables seamless role transitions without discarding cached data. Upon detecting such a role-transition event, the RSU assigns two new precaching vehicles to independently serve the original requester vehicle and the newly transitioned requester vehicle, ensuring continuous service. Furthermore, we extend this to an energy-efficient DRAS (EE-DRAS) that incorporates vehicle-to-infrastructure (V2I) and V2V transmission energy costs into the selection process, achieving a balanced trade-off between energy consumption and delivery efficiency. Extensive NS-3 simulations show that DRAS reduces average delay by up to 53% and improves throughput by 8% over existing baselines. EE-DRAS further reduces energy consumption by up to 66% while maintaining service fairness.