Design and Analysis of Grouping Active Subcarrier Frequency-Time Index Modulation for Differential Chaos Shift Keying Communication System

Abstract

In this paper, an innovative system called grouping frequency-time index modulation-based differential chaos shift keying (GFTIM-DCSK-I) is presented to improve the energy efficiency (EE), spectral efficiency, and data rate of the recently proposed grouping subcarrier index modulation in differential chaos shift keying (GSIM-DCSK) system. The proposed system optimally utilizes both frequency and time resources, enabling efficient transmission at high data rates. The data information bits are divided into equal L groups, each containing (p1+p2+1) bits. Within each group, the first set of bits, referred to as p1 bits, are assigned as carrier-indexed bits, whereas the second set of bits, known as p2 bits, are designated as time-indexed bits. Additionally, one bit is assigned for modulation. The p1 bits serve as an index selector for choosing a single active subcarrier from a total of 2p1 subcarriers. p2 bits are utilized to choose a single time slot out of a total of 2p2 available options. The modulated bit undergoes DCSK modulation and is thereafter sent via the active subcarriers. Mathematical expressions are constructed to examine the system performance of energy efficiency, spectral efficiency, and system complexity, then compared with the traditional DCSK modulations. Analytical formulas for the bit error rate (BER) of the proposed system are obtained under the impact of multipath Rayleigh fading channel and additive white Gaussian noise (AWGN). Results from simulations and analysis confirm that the theoretical analysis is accurate. The performance of the suggested approach is also evaluated by comparing it to conventional DCSK techniques, showing an improvement in the performance.

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