OFDM-IDM Space-Time Coding in two-hop relay-systems with error-prone relays

In this paper, the combination of distributed Interleave-Division-Multiplexing-Space-Time Codes (IDM-STCs) with Orthogonal Frequency Division Multiplexing (OFDM) in two-hop relay systems applying Decode-and-Forward (DF) is investigated. In order to cope with erroneous decoding at the relays, a model to capture the decoding reliabilities of the relays is formulated and a method to incorporate these reliabilities in the iterative detection process at the destination is presented. In addition, different approaches to keep the required signaling overhead low are discussed and compared with each other. It is shown, that the proposed scheme achieves significant gains over the common DF detection scheme assuming perfect decoding at the relays. Even with only one bit signaling per frame and relay an improvement of 3.6 dB can be obtained in certain scenarios.