Research on the Outage Exponent of Superposition Coding Relaying with Only Relay-to-Source Channel State Feedback

Based on the canonical three nodes scheme of cooperative relaying, a 2-level rate Superposition coding relaying (SC-relaying) strategy was investigated as well as the outage performance analysis, in which only the relayto- source Channel state feedback (CSF) and a short term power constraint were considered. For the 2-level SCrelaying, besides the optimizing outage exponent of basic signal obtained, the closed form solution of the optimizing outage exponent was also derived through strict math manipulation. The closed form solution is the exact solution of the optimizing outage exponent when the multiplexing gain of basic signal is more than or equal to 0.5 but it is only the approximate lower bound when it is less than 0.5. The numerical analysis show that as CSF introduced a remarkable performance enhancement of Diversity-andmultiplexing tradeoff (DMT) is obtained, which is also increasing with the link feedback resolution K. However, when K > 6 the DMT performance achieves steady maximal value approximately.