In this work, we first assume that the relay node and the destination are connected by the error-free backbond. This scenario is often seen in the situation of handover in the uplink in 3G system, where the signals of a user is combined in either the base station or in the radio network controller . Under this assumption, the decoding metric is derived. Unlike, the decoding metric in this work is based on the joint probability of the received signal at the relay node and the destination rather than the conditional probability of received signal at the destination given the decoding information of the relay node. Based on this decoding metric, the information related to the relay node is calculated and then sent to the destination for fusion according to the derived decoding metric. Thus, the relay node does not need to actually decode the transmitted signal from the source. Therefore, contrast to the HDF protocol, the coding delay can be greatly reduced in this case.