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Decode-Forward Transmission for the Two-Way Relay Channels
We propose composite decode-forward (DF) schemes for the two-way relay
channel in both the full- and half-duplex modes by combining coherent relaying,
independent relaying and partial relaying strategies. For the full-duplex mode,
the relay partially decodes each user's information in each block and forwards
this partial information coherently with the source user to the destination
user in the next block as in block Markov coding. In addition, the relay
independently broadcasts a binning index of both users' decoded information
parts in the next block as in independent network coding. Each technique has a
different impact on the relay power usage and the rate region. We further
analyze in detail the independent partial DF scheme and derive in closed-form
link regimes when this scheme achieves a strictly larger rate region than just
time-sharing between its constituent techniques, direct transmission and
independent DF relaying, and when it reduces to a simpler scheme. For the
half-duplex mode, we propose a 6-phase time-division scheme that incorporates
all considered relaying techniques and uses joint decoding simultaneously over
all receiving phases. Numerical results show significant rate gains over
existing DF schemes, obtained by performing link adaptation of the composite
scheme based on the identified link regimes.Comment: This work has been submitted to IEEE Transactions on Communications
for possible publicatio