The real-time resources sharing in multicast VANETs achieves low bandwidth waste rate because the sender only send a real-time chunk to the group receivers by using a single multicast session. Although the real-time multicasting VANET still exhibits critical issues, the Multicast Ad hoc On-Demand Distance Vector (MAODV) protocol can achieve multicast routing in self-organizing VANET. However, MAODV in VANET suffers from unreliable wireless links and high control message overhead. MAODV thus offers a broadcast-type local repair to repair broken links, but yields a large number of broadcast-type repair messages, increases extensive control overhead, and involves large power consumption. Thus, this paper proposes a cross-layer unicast-type multihop local repair approach to recover broken links in multicasting VANETs. Additionally, the cross-layer mechanism provides mobile nodes to send a cross- layer message to the TCP sender to keep current congestion window (cwnd) and slow start threshold (ssthresh) when downstream links are temporarily broken, and then increases network goodput. Finally, the time complexity of the real-time local repair approach is analyzed. Numerical results demonstrate that the proposed approach outperforms other approaches in successful repair rate, control message overhead, packet delivery ratio, and network goodput.
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