An Improved Long Transmission Protocol for VDL Mode 4

An improved long transmission protocol for very high frequency (VHF) digital link (VDL) mode 4 in aeronautical telecommunications network (ATN) is proposed, which includes a combined transmission scheme and a retransmission mechanism. In the combined transmission scheme, control messages can be piggybacked in conflict-free message transmission, and thus avoids the collision of RTS bursts and saves much more unused slots than original long transmission protocol. In the proposed retransmission mechanism, if destination station does not receive the DATA burst from the source station, it will send a CTS burst instead of a NACK burst in the slot initially reserved for ACK/NACK burst. Simulation results show that the improved long transmission protocol can greatly increase throughput and reduce average message delay