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

Abstract

Abstract-We propose a new single-RF Differential Space-Time Block Coding using Index Shift Keying (DSTBC-ISK), which is the first in the family of Differential Space-Time Modulation (DSTM) schemes that can simultaneously achieve the following three imperative objectives of (1) forming a finite-cardinality transmit-signals set under the matrix multiplications of differential encoding; (2) retaining a single-stream ML detection complexity that does not grow with the constellation size; (3) offering a beneficial transmit diversity gain over the recently developed Differential Spatial Modulation (DSM). In order to make a fair comparison, we also conceive a low-complexity single-stream detector for DSM, which does not impose any performance loss in comparison to the existing solutions in open literature. Furthermore, in order to improve the performance of finitecardinality DSTM schemes at higher throughputs, we propose to generalize both Differential Amplitude Shift Keying (DASK) and Amplitude Shift Keying (ASK), which form the generic multilevel-ring star QAM constellation that subsumes the existing two/four-level-ring DASK solutions as special cases. Although the DASK approach has been popularly used in DSTM schemes, we demonstrate that our generalized ASK technique achieves a higher capacity and a better performance in channel coding assisted systems. Moreover, since the employment of star QAM constellations imposes the ring-amplitude dependent signal power problem for detection, we further develop bespoke MaximumLikelihood (ML), Minimum Mean Squared Error (MMSE) and Least Square (LS) detectors for DSTM using DASK/ASK, which exhibit different performance versus complexity tradeoffs. Our simulation results demonstrate that the proposed DSTBC-ISK is capable of achieving substantial diversity gains over DSM without eroding its low transceiver complexity.

Adaptive Coherent/Non-Coherent Spatial Modulation Aided Unmanned Aircraft Systems

“…The schematics of the Index Modulation (IM) schemes of SM [4] and STBC-ISK [5] are portrayed in Figs. 2(a) and 2(b), respectively.…”

“…Secondly, the inter-antenna synchronization is eliminated. Thirdly, in the absence of Inter-Antenna Interference (IAI), the coherent/non-coherent SM and STBC-ISK schemes may [4] and Space-Time Block Code using Index Shift Keying (STBC-ISK) [5] as well as the list of schemes considered in this paper.…”

“…employ single-stream-based signal detection at the receiver [7], which reduces both the signal processing complexity and latency. Moreover, we note that the non-coherent MIMO schemes often suffer from the so-called infinite-cardinality problem discussed in [5], where the transmit signals have an infinite number of arbitrary phases and magnitudes. This imposes extra constraints on the Digital-to-Analog Converter (DAC), which is appropriately matched to the finite number of constellation points to generate the corresponding analog signals.…”

“…Against this background, we propose to invoke the recently developed coherent/non-coherent Spatial Modulation (SM) [4] and Space-Time Block Coding using Index Shift Keying (STBC-ISK) [5]. In a nutshell, firstly, thanks to the employment of multiple Transmit Antennas (TAs), the SM and STBC-ISK schemes achieve a spectral-efficiency gain and a transmit-diversity gain, respectively, which improve the network's QoS.…”

“…Secondly, thanks to the diversity gain, the detrimental airframe shadowing effect is shown to be mitigated by the STBC-ISK arrangement. Thirdly, the noncoherent schemes of Differential SM (DSM) [6] and Differential STBC-ISK (DSTBC-ISK) [5] completely dispense with channel estimation, hence they are more robust to high Doppler frequencies. Lastly, unlike many conventional MIMO schemes such as the V-BLAST and STBC [7], the coherent/non-coherent schemes of SM and STBC-ISK always only activate a single RF chain, which reduces the deployment cost and energy dissipation compared to full-RF MIMO schemes.…”