Cooperative Stepwise Relaying and Combining for Multihop Vehicular Wireless Communication Vehicular ad hoc networks (VANETs) require cooperation among vehicles in exchanging information, which improves traffic efficiency and safety. Cooperative communication among these vehicles can significantly improve wireless communication performance. This paper proposes a novel cooperative scheme named cooperative stepwise relaying and combining (CSRC) for multihop VANETs, which utilizes low-order demodulations to partially demodulate high-order modulated signals cooperatively at intermediate relay vehicular nodes. Bit error rate (BER) probability is analyzed. The performance comparison among the proposed CSRC and conventional cooperative schemes is conducted through simulation and a software-defined radio testbed. The experiment results show that CSRC significantly improves the multihop VANETs’ performance with cooperative communication.