Hexagonal QAM-Based Two-Way Generalized Code Index Modulation Over Nakagami-m Fading Channels

Cogen F., Özden B. A., Aydin E., Kabaoglu N.

23rd IEEE Consumer Communications and Networking Conference, CCNC 2026, Nevada, United States Of America, 9 - 12 January 2026, (Full Text) identifier identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Doi Number: 10.1109/ccnc65079.2026.11366304
  • City: Nevada
  • Country: United States Of America
  • Keywords: code index modulation, Energy-efficiency, Hexagonal QAM, Nakagami-m fading channels, Two-way communication systems
  • Yıldız Technical University Affiliated: Yes

Abstract

We propose a two-way generalized code index modulation scheme with hexagonal QAM (TW-GCIM-HQAM) over Nakagami-m fading. The design combines GCIM and physical layer network coding with energy-efficient HQAM constellations. Using orthogonal Walsh-Hadamard spreading codes, two users exchange data via a half-duplex relay in two time slots (instead of three in conventional two-way DF). Information is carried by both the HQAM symbols and the indices of the spreading codes on the I/Q branches. We compare the scheme with two-way decode and forward at matched rates and evaluate the average bit error rate via Monte Carlo simulations on Nakagami-m channels for several HQAM constellations. Results show competitive or improved error performance, together with better energy use and time slot efficiency.