Index Modulation Pattern Design for Non-Orthogonal Multicarrier Signal Waveforms

Abstract

Spectral efficiency improvement is a key focus in most wireless communication systems and achieved by various means such as using large antenna arrays and/or advanced modulation schemes and signal formats. This work proposes to further improve spectral efficiency through combining nonorthogonal spectrally efficient frequency division multiplexing (SEFDM) systems with index modulation (IM), which can efficiently make use of the indices of activated subcarriers as communication information. Recent research has verified that IM may be used with SEFDM to alleviate inter-carrier interference (ICI) and improve error performance. This work proposes new SEFDM signal formats based on novel activation pattern designs, which limit the locations of activated subcarriers and enable a variable number of activated subcarriers in each SEFDM subblock. SEFDM-IM system designs are developed by jointly considering activation patterns, modulation schemes and signal waveform formats, with a set of solutions evaluated under different spectral efficiency scenarios. Detailed modelling of coded systems and simulation studies reveal that the proposed designs not only lead to better bit error rate (BER) but also lower peak-to-average power ratio (PAPR) and reduced computational complexity relative to other reported index-modulated systems.

Design and Optimization of Hierarchical Demodulator and Decoder for Layered Coded OFDM-IM With NR-LDPC

“…The detection accuracy of index bits depends mainly on the Hamming distance for the index bits of different index combinations, while the detection accuracy of modulation bits relies on Euclidean distance of the constellation symbols. There is significant error performance difference between index bits and modulation bits in CS-OFDM-IM [27]. In order to improve the system reliability, we proposed the code rate optimization based on the LC-OFDM-IM-HD system, resulting RO-LC-OFDM-IM-HD.…”

“…Some researchers have evaluated the performance of NR-LDPC-coded OFDM-IM, including OFDM-IM systems and MM-OFDM-IM systems, and indicated that the application of OFDM-IM is limited for LDPC coded scenarios [26]. In recent years, index bits and modulation bits have been separately encoded in [27], which was called coding split [28] OFDM-IM (CS-OFDM-IM) later. A coding split and adjustment (CSA) scheme has been further investigated in [29], which made coded OFDM-IM systems more flexible.…”

Design and Implementation of Spectrally Efficient Frequency Division Multiplexing Receiver

“…W ITH the rapid development of wideband emerging services, such as cloud computing, virtual reality, metaverse, digital twin, etc., next generation wireless communication faces great challenges on the ever-increasing demand of transmission throughput [1]. As a result, an increasing focus has been paid to spectral efficient transmission schemes exemplified by faster-than-Nyquist (FTN) and spectrally efficient frequency division multiplexing (SEFDM) [2]- [4]. In particular, the SEFDM [5], which reduces the spacing between subcarriers compared to orthogonal frequency division multiplexing (OFDM), can enhance the spectral efficiency significantly.…”

Identification and practical validation of spectrally efficient non-orthogonal frequency shaping waveform

“…Detailed studies reported in Mazo’s classic 1975 paper 13 showed that Nyquist criterion may be relaxed; bit rates may be increased by a factor of 25% without compromising the received signal quality, provided Nyquist pulse shapes are used and an optimum detector is used at the receiver. Since then, several groups worldwide worked on non-orthogonal systems such as spectrally efficient frequency division multiplexing (SEFDM) 14 – 16 , faster than Nyquist (FTN) 17 , 18 , Fast-OFDM 19 , generalized frequency division multiplexing (GFDM) 20 and filter bank multicarrier (FBMC) 21 .…”