Improved signal superposition coding for cooperative diversity

This paper proposes an improved scheme for cooperative transmit diversity, which applies the Euclidean superposition of modulated signals. Assuming two sources cooperate in transmitting information to a single destination, each source divides its transmit power between locally generated information and relayed information that originated at the other source. This leads to an encoding scheme in which each source transmits the Euclidean superposition of the local information and the relayed information. The new decoding approach at the destination relies on two decoding iterations: First, each transmitted information is evaluated from two consecutive received sequences (once as local information and once as relayed information); second, decoding is performed assuming that the previous and next information sequences were evaluated correctly. Optimization of this approach is shown to be achieved with significantly higher relay power allocation compared to the known approach. It is shown via simulation that this scheme provides significant coding gain compared to the known approach.