Cognitive multicast (CoCast) in vehicular networks using OFDM subchannels and network coding

The deployment of wireless multicast in vehicular networks using the ISM band is challenging due to the interference from residential WiFi users. Recently developed cognitive radio techniques can help overcome such interference, with spectrum sensing and multi-channel assignment. CoCast is a cognitive multi-channel multicast protocol originally designed for the urban environment under the assumption that channels are orthogonal. In fact, Wi-Fi channels in the 2.4-GHz ISM band are partially overlapped. In this paper, we remodel the CoCast protocol to handle the more realistic environment where channels are overlapped in frequency. The main challenge is the adjacent channel interference, the effect of which is mitigated in CoCast by employing two techniques: 1) parallel frame transmission over OFDM subchannels, and 2) network coding. Our evaluation shows that the reliability of multicast communication among vehicles in a dense urban environment can be significantly improved with these protocol extensions.