“…Three values of k, k = 1, k = 2 and k = 4, are considered, and the applied non-linear mappings are the standard 2:1 and 4:1 space-filling curves in (2) and (3), respectively, plus the circular approximation. By applying the parameter optimization method proposed in [11], ∆ and α are jointly optimized for each channel signalto-noise ratio (CSNR), and optimal energy allocation is performed for each band. In order to reduce the optimization complexity, in all results presented here ML rather than MMSE is considered, which leads to some performance loss.…”