Cognitive multicast with partially overlapped channels in vehicular ad hoc networks

Vehicle to many vehicles (V2MV) multicast is an attractive application to provide vehicle safety and traffic control information, urban sensing and multimedia content sharing in vehicular ad hoc networks. Due to the limitation of DSRC channels, Wi-Fi channels can be alternative to realize the multicast in the vehicular networks. However, the deployment using the Wi-Fi in ISM bands is challenging due to the interference from increasing residential Wi-Fi users as well as inter-vehicle interference. In this study, we propose a cognitive multi-channel, multi-radio multicast protocol, CoCast, borrowing concept of recently developed cognitive radio techniques, which can help overcome such interference, with spectrum sensing and multi-channel assignment. Unfortunately, number of orthogonal channels is very limited in the ISM band to avoid interference in urban Wi-Fi cloud. Therefore, we apply two additional features to use partially overlapped channels: parallel frame transmission over OFDM subchannels to exploit spectral diversity, and network coding for the subchannel frames. Our evaluation results show that the reliability of multicast communication among vehicles in a dense urban environment can be significantly improved with these protocol extensions.