  In wireless communication networks, relays are required when the quality of
the direct link between the source and the destination is not high enough to
support reliable transmission because of long distances or obstacles. Selecting
the proper relay node (RN) to support hybrid automatic repeat request (HARQ) is
of great importance in such a relay-assisted network. Different from previous
works, whether to participate in the transmission is determined by each RN
itself in this work, thus reducing the overhead. As RNs do not need to obtain
channel state information about the whole network, there is no significant
overhead in the system. Using the numbers of transmission attempts required by
both channels calculated from the obtained channel state information, each RN
sets a timer and forwards the packet when time-out occurs. Simulation results
show that our proposed method significantly improves the performance of the
system. When the channels are of relatively high quality, the performance of
our method is close to the optimal relay selection which requires full
information about the network.
