technology proposed for MIMO wireless systems. It aims to increase the spectral efficiency, $(m)$, of single–antenna systems while avoiding ICI [@mhsay0801]. This is attained through the adoption of a new modulation and coding scheme, which foresees: i) the activation, at each time instance, of a single antenna that transmits a given data symbol (*constellation symbol*), and ii) the exploitation of the spatial position (index) of the active antenna as an additional dimension for data transmission (*spatial symbol*) [@rhg1101]. Both the *constellation symbol* and the *spatial symbol* depend on the incoming data bits. An overall increase by the base–two logarithm of the number of transmit–antennas of the spectral efficiency is achieved. This limits the number of transmit antennas to be a power of two unless fractional bit encoding SM (FBE–SM) [@srsmh1001], or generalised SM (GSM) [@ysmh1001] are used. Activating only one antenna at a time means that only one RF chain is needed, which significantly reduces the hardware complexity of the system [@jgsc0901]. Moreover, as only one RF chain is needed, SM offers a reduction in the energy consumption which scales linearly with the number of transmit antennas [@ssrh1201; @ssrhg1201]. Furthermore, the computational complexity of SM–ML is equal to the complexity 