Generalized Joint Subcarrier-Time Index Modulation Aided Differential Chaos Shift Keying System
Year: 2025
Type: article
Abstract: This paper presents a new dual index modulation system termed the Generalized Joint Subcarrier-Time -Index Modulation DCSK (GJSTIM-DCSK) scheme, intended to enhance spectral efficiency and data-transmitted rate of the recent dual index-DCSK modulation schemes.Efficiently employs two transmitter resource entities presented by subcarrier and time slot, facilitating effective transmission at elevated data rates.Moreover, this system consists of 2 𝑞 +1 subcarriers; one of them is used to carry a chaos reference signal after repeated 𝑀 𝑠 times, and the others are divided equally to 𝑁 𝑠 subcarriers in each group.The k-combinatorial mapping is utilized to choose 𝑁 𝑐 active subcarriers from 𝑁 𝑠 according to 𝑥 s subcarrier index bits, and select 𝑀 𝑐 time slot from 𝑀 𝑠 in each inactive subcarrier according to 𝑥 t time slot index bits.Additional to index bits, there are 𝑁 𝑐 𝑀 𝑠 + (𝑁 𝑆 -𝑁 𝐶 )(𝑀 𝑆 -𝑀 𝐶 ) DCSK modulated bits, first(𝑁 𝑐 𝑀 𝑠 )bits are modulated by 𝑐 𝑥 chaos reference signal carried by 𝑁 𝑐 active subcarriers, and also last (𝑁 𝑆 -𝑁 𝐶 )(𝑀 𝑆 -𝑀 𝐶 )bits are modulated by orthogonal copy of chaos reference generated using Hilbert transform and carried by unselected time slots of inactive subcarriers.Our analysis encompasses the system's transmission bit rate, bandwidth efficiency and complexity, contrasting these functions against to analogous systems.The suggested system improves bandwidth efficiency by approximately 1.33, 1.45 and 5.5 times greater than that of GFTIM-DCSK-II , CTIM-DCSK and GSPIM-DCSK-II, respectively with 𝑁 𝑠 =16, 𝑁 𝑐 =1, 𝑀 𝑠 = 16, 𝑀 𝑐 = 4, and G=2.Furthermore, we devise mathematical BER (Bit Error Rate) theory for the GJSTIM-DCSK scheme with the presence of AWGN (Additive White Gaussian Noise) and multipath fading channels with Rayleigh distribution.The simulation findings not only validate the fidelity of the mathematical BER expression but also demonstrate the system's enhanced BER performance compared to analogous systems under comparable environment.For example, with 𝑀 𝑠 =4 and BER=10 -3 under both additive noise and Rayleigh channels, the GJSTIM-DCSK system exhibits an estimated 2 dB gain over the GFTIM-DCSK-II, while showing gains of 1 dB and 2.5 dB over the GSPIM-DCSK-II in AWGN and Rayleigh fading channels, respectively.
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Funder: Mustansiriyah University
OpenAlex ID: W4407928468