The present invention relates to methods and arrangements in a relaying radio node and/or in a sending/receiving radio node, adapted for use in a relaying communication system. The relaying node is in bidirectional communication with at least a first and a second sending/receiving radio node, and the relaying radio node receives at least a first signal carrying at least first data and a second signal carrying at least second data. The relaying node generates (215) a reduced representation of at least the first and second signal, with a reduced information content as compared to the first and second data, by a joint non-linearly encoding operation, and transmits (220) the reduced representation to at least the first and the second communication node. The first and second sending/receiving node can extract data from the reduced representation by a non-linear decoding operation (225) using stored a priori information.