Achievable decode and forward rates for the 3-node relay channel considering different energy constraints and synchronization errors

The 3-node relay channel is a well investigated subject in literature combining broadcast channel and Multiple Access (MAC) channel. Due to practical relevance, half-duplex relays are considered. Regarding the MAC, non-orthogonal channel access and orthogonal access, where the source is only active in the broadcast phase, will be distinguished. The emphasis of this paper lies on the achievable Decode and Forward (DF) rates subject to different energy constraints exploiting the degrees of freedom available for power and time allocation. These degrees of freedom are influenced by practical constraints, e.g. , whether source and relay have a local or common power supply. Furthermore, this work takes imperfect synchronization of source and relay into account. It will be shown that orthogonal channel access will approach the maximum achievable DF rate for relay positions close to the destination as well as that distributed Beamforming (dBF) in the presence of phase deviations is still valuable.