Modified dynamic DF protocol with hybrid-AM for type-2 UE relay in LTE-advanced

To facilitate practical implementation of a dynamic decode-&-forward (DDF) for type-2 user equipment (UE) relay defined in 3GPP which is being considered for next-generation cellular standards (e.g., LTE-Advanced), we propose "Modified Dynamic DF (M-DDF)" to realize fast jump-in relaying and decoding scheme for cooperative transmission. More specifically, subframe based sequential decoding is employed to yield some combinations of energy/information/mixed combining, in conjunction with the random codeset for encoding and reencoding at source and multiple UE relays, depending on their channel conditions. These additional features existing in the M-DDF circumvent the need of directly exchanging control messages between multiple relays and end user, which is not allowed for type-2 UE relays. Further, the early termination of decoding at end user in conjuction with overhearing mechanism as an additional benefit due to the increased data rate is made available for a considerable resource saving. Finally, the hybrid-adaptive modulation (H-AM) mechanism combined with overhearing mechanism can be adopted to further improve the spectral efficiency.