of single–input multiple–output (SIMO) systems [@jgs0801], *i.e.* the complexity of SM–ML depends only on the spectral efficiency and the number of receive antennas, and does not depend on the number of transmit antennas. Recently the potential benefits of SM have been validated not only by simulations but also via experiments [@symcrwgbh01; @syh1201]. Moreover, in [@ytrwbhg1301] for the first time the performance of SM is analysed using real–world channel measurements. Accordingly, SM appears to be a good candidate for large scale MIMO [@dh1201a; @dh1301a; @rlgh1201; @rh1102].

In spite of its low–complexity implementation, there is still potential for further reductions, by limiting the number of possible combinations using the SD principle. However, existing SD algorithms in literature do not consider the basic and fundamental principle of SM, that only one antenna is active at any given time instance. Therefore, two modified SD algorithms based on the tree search structure that are tailored to SM are proposed. The first SD will be called receiver–centric SD (SM–Rx), which was first presented in [@ymhg1001]. The algorithm in [@ymhg1001] combines the received signal from the multiple receive antennas, as long as the Euclidean distance from the received point is less than a given radius. This SD–based 