Figure 3
From: Alternative relaying for cooperative multiple-access channels in wireless vehicular networks
The flow chart for the transmission stage. Note that A k denotes the situation that k relays broadcast ACK1 signals, k=0,1,2. The event E denotes that both relays broadcast ACK2 signals, otherwise the system lies in Event . L is used to denote the number of codewords transmitted by each source in the corresponding data frame. α i is power allocation factor at the sources, i=1,2.