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Single-RF Index Shift Keying Aided Differential Space–Time Block Coding

We propose a new single-RF differential space–time block coding using index shift keying (DSTBC-ISK), which is the first differential space–time modulation (DSTM) scheme that can simultaneously achieve the following three imperative objectives: First, forming a finite-cardinality transmit-signals set; second, retaining a single-stream maximum-likelihood (ML) detection complexity; and third, offering a beneficial transmit diversity gain. In order to make a fair comparison, we also conceive a low-complexity single-stream detector for DSM. Furthermore, in order to improve the performance of finite-cardinality DSTM schemes at higher throughputs, we propose to generalize both differential amplitude shift keying (DASK) and amplitude shift keying (ASK), which subsume the existing two-/four-level-ring star quadratic–amplitude modulation (QAM) solutions as special cases. As a result of using star QAM signaling, the power of the DSTM's signal matrix becomes variable. Against this background, we further develop bespoke ML, minimum mean squared error, and least-square detectors for DSTM using DASK/ASK. Our simulation results demonstrate that the proposed DSTBC-ISK is capable of achieving substantial diversity gains over DSM without eroding its low transceiver complexity.