Coordinated and uncoordinated PHY/MAC schemes for beaconing

Both advanced schemes significantly outperform the plain Aloha upper bound for the nominal received spectral efficiency n_non.The efficiency of advanced Aloha is not significantly lower than the efficiency of the coordinated approach (Cell-Based SOTDMA). Advanced Aloha needs no common time reference (transmissions are uncoordinated), has no coordination overhead, and needs no guard times.Therefore, Advanced Aloha is probably the better choice for safety-critical aeronautical applications like surveillance beaconing.