Interaction of multiplexing gains and power exponents allocation of two‐level superposition coding relaying
Xiangdong Jia, Longxiang Yang · European Transactions on Telecommunications · 2011
ABSTRACT A two‐level rate superposition coding relaying (SC‐relaying) scheme is discussed, in which only the relay‐to‐source channel state information feedback (CSF) is considered and, at source, a long power constraint is imposed on the basic signalS0and the additional signalS1whose multiplexing gains arer0andr1, respectively. The CSF index is constructed based on the correct decoding of the signalS0at relay. For the SC‐relaying scheme, we propose a multilevel iteration constructing rule for the CSF index. With the proposed CSF constructing rule, the allocation method of the power signal‐to‐noise ratio exponents is first obtained by the investigation of the optimal outage exponent of the signalS0. Secondly, we obtain the value range ofp11,p11 ∈ [1,1∕r0], by studying the outage exponent lower bound of the signalS0, wherep11denotes the minimum of the power signal‐to‐noise ratio exponent of the signalS. Lastly, to observe the interaction between the multiplexing gainsr0andr1, we discuss the closed‐form solution of the lower bound of the optimal outage exponent for the signalS1, through which we find that the multiplexing gain constraint isr1 ≤ 1 −r0p11,p11 ≥ 1. The substantial numerical analyses show that the results in this paper are reasonable. Copyright © 2011 John Wiley & Sons, Ltd.