Enhanced antenna selection techniques for energy-efficient code index modulation aided spatial modulated wireless communication systems.

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Bibliographic Details
Title:	Enhanced antenna selection techniques for energy-efficient code index modulation aided spatial modulated wireless communication systems.
Authors:	ÇÖGEN, Fatih^1,2, ÖZDEN, Burak Ahmet^2,3, AYDIN, Erdoğan² erdogan.aydin@medeniyet.edu.tr
Source:	Turkish Journal of Electrical Engineering & Computer Sciences. 2026, Vol. 34 Issue 2, p264-288. 25p.
Subject Terms:	MIMO systems, Quadrature amplitude modulation, Electronic modulation, Wireless channels, Encoding, Antenna design, Hadamard codes, Energy consumption
Abstract:	This study proposes an integrated multiple-input multiple-output (MIMO) transceiver framework, termed CIM-HQAM-SM, which combines code index modulation (CIM) and spatial modulation (SM) with energy-efficient hexagonal quadrature amplitude modulation (HQAM). In the proposed bit mapping, the information bits jointly select (i) the active transmit-antenna index, (ii) the Walsh–Hadamard spreading-code indices for the in-phase and quadrature branches, and (iii) an HQAM symbol. Hence, the payload is conveyed through the constellation symbol as well as through antenna and code indices. For the considered Rayleigh-fading scenarios and matched spectral-efficiency settings, the proposed framework offers BER improvements over conventional SM and quadrature SM (QSM), while achieving uncoded BER performance comparable to CIM-SM with improved transmission-side energy efficiency due to the lower average energy of HQAM. Euclidean distance-based antenna selection (EDAS) and capacity-optimized antenna selection (COAS) are further incorporated to enhance reliability and capacity. The performance is evaluated under both perfect and imperfect channel state information (CSI), and the throughput, computational complexity, and transmission-side energy-saving characteristics are analyzed. [ABSTRACT FROM AUTHOR]
Database:	Energy & Power Source

Description
Abstract:	This study proposes an integrated multiple-input multiple-output (MIMO) transceiver framework, termed CIM-HQAM-SM, which combines code index modulation (CIM) and spatial modulation (SM) with energy-efficient hexagonal quadrature amplitude modulation (HQAM). In the proposed bit mapping, the information bits jointly select (i) the active transmit-antenna index, (ii) the Walsh–Hadamard spreading-code indices for the in-phase and quadrature branches, and (iii) an HQAM symbol. Hence, the payload is conveyed through the constellation symbol as well as through antenna and code indices. For the considered Rayleigh-fading scenarios and matched spectral-efficiency settings, the proposed framework offers BER improvements over conventional SM and quadrature SM (QSM), while achieving uncoded BER performance comparable to CIM-SM with improved transmission-side energy efficiency due to the lower average energy of HQAM. Euclidean distance-based antenna selection (EDAS) and capacity-optimized antenna selection (COAS) are further incorporated to enhance reliability and capacity. The performance is evaluated under both perfect and imperfect channel state information (CSI), and the throughput, computational complexity, and transmission-side energy-saving characteristics are analyzed. [ABSTRACT FROM AUTHOR]
ISSN:	13000632
DOI:	10.55730/1300-0632.4174