Spectrally-Efficient Wireless Relaying Based on Superposition Coding
Petar Popovski, Elisabeth de Carvalho · 2007
The wireless relay systems represent an important segment in the wireless communication systems. In a simple wireless relay scenario, a source node ASneeds to communicate to a destination AD, with the help of a relay AR. In this paper we introduce a new two-step relaying scheme based on superposition coding, SC-relaying. In step 1, ASbroadcasts a message, created by superposition coding, to ARand AD. After decoding the information from AS, ARrelays a part of this message in step 2, by adapting the transmission rate with respect to the link quality towards AD. The unique point of the proposed scheme is that the signal format in the two steps is chosen in a way that enables a simple combining at AD. The numerical results show that the proposed scheme can bring a notable gain in spectral efficiency over the conventional multi-hop transmission with adaptive modulation, even in the case when the instantaneous SNR about all the links is not fully known at the source. In addition, the proposed scheme performs very closely to the scheme that is optimal in an information-theoretic sense.