We propose a successive relaying decode-and-forward protocol for the half-duplex 2-relay 2-destination multicarrier channel. The proposed protocol performs significantly better than existing protocols and achieves sum rates close to the cutset upper bound. We also prove that the linear program that describes the cutset upper bound for sum capacity is optimized using only 3 of the 4 possible states of the half-duplex network. Of these 3 states, successive relaying uses the two states in which one of the relays is receiving from the source while the other relay is transmitting to the destinations. In simulations under a Rayleigh fading model, the gap between the cutset upper bound and the proposed protocol is observed to be bounded. © 1997-2012 IEEE.