Soft Demodulation of Time Frequency Shift Keying with Index Modulation (TFSK-IM) and Its Performance Analysis

Time-Frequency modulation is a two-dimensional modulation based on FSK and TSK, since it has strong anti-channel fading capability and its performance is far superior to FSK modulation due to its frequency diversity, time diversity and orthogonal coding error detection and error correction capabilities under the same channel conditions. In this paper, we combine time-frequency modulation with index modulation and propose Time Frequency Shift Keying with Index Modulation (TFSK-IM). We theoretically derived the upper bound for closed-form expressions of symbol error rate (SER) performance of TFSK-IM under AWGN channel and Rayleigh fading channel. Moreover the bit log likelihood rate (LLR) calculation method based on maximum likelihood estimation is given. Simulation and comparison results between TFSK-IM and Four Time Four Frequency Shift Keying (4T4FSK) system indicate that combined with index modulation improves the information rate of the system, spectrum efficiency and signal energy utilization. Furthermore bit log likelihood ratio (LLR) information combined with Low Density Parity Check code (LDPC) yields a coding gain by soft demodulation.

[1]  Ihrahim Ghareeb.  Noncoherent MT-MFSK signals with diversity reception over bandwidth constrained and Nakagami fading channels , 2004, 2004 IEEE 15th International Symposium on Personal, Indoor and Mobile Radio Communications (IEEE Cat. No.04TH8754).

[2]  Ahmed Al-Shamma'a,et al.  Underwater wireless communication system , 2009 .

[3]  Miaowen Wen,et al.  Index Modulated OFDM Spread Spectrum , 2018, IEEE Transactions on Wireless Communications.

[4]  Gao Jin-bao.  Simulation of time-frequency modulation and demodulation based on side-correlation algorithm , 2012 .

[5]  Harald Haas,et al.  Index Modulation Techniques for Next-Generation Wireless Networks , 2017, IEEE Access.

[6]  Yong Liang Guan,et al.  Improving the Belief-Propagation Convergence of Irregular LDPC Codes Using Column-Weight Based Scheduling , 2015, IEEE Communications Letters.

[7]  Sheng Chen,et al.  Novel Index Modulation Techniques: A Survey , 2019, IEEE Communications Surveys & Tutorials.

[8]  Miaowen Wen,et al.  OFDM Spread Spectrum with Index Modulation , 2017, 2017 IEEE Globecom Workshops (GC Wkshps).

[9]  Ibrahim Ghareeb.  Noncoherent MT-MFSK signals with diversity reception in arbitrarily correlated and unbalanced Nakagami-m fading channels , 2005, IEEE Journal on Selected Areas in Communications.

[10]  Yue Xiao,et al.  Low Complexity Soft Decision Technique for Gray Mapping Modulation , 2010, Wirel. Pers. Commun..