A Novel Multi-Mode OFDM with Index Modulation

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Electrical and Computer Engineering


GREEN G, Index modulation, Subcarrier index selector, Wireless communication, Spectral efficiency, Energy efficiency







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Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


Though Orthogonal Frequency Division Multiplexing (OFDM) is the most common modulation scheme, the conventional OFDM cannot meet the requirements of the high demand of throughput, Spectral Efficiency (SE), and lower energy consumption for the Next Generation of Wireless Communication systems. OFDM with Index Modulation (OFDM-IM) introduces additional index bits of Index Modulation with classical OFDM symbols to maximize SE. However, OFDM-IM cannot meet the minimum requirement of throughput and SE as OFDM in higher modulation order.

The objective of this study was to review different OFDM-IM variants to resolve the SE issue. Then, a suitable system, Novel Multi-Mode OFDM with Index Modulation (NMM-OFDM-IM) was developed for improved SE with minimum energy consumption at a given BER performance. The proposed Novel MM-OFDM-IM has similar multiple, distinguishable M-ary modulation constellation as MM-OFDM-IM. The results showed, with the introduction of multiple, different constellations, the challenge with throughput and SE was resolved. However, MM-OFDM-IM lacked energy-saving benefits due to skipping inactive subcarriers through Subcarrier Index Selector (SIS). SIS of OFDM-IM keeps inactive subcarriers to save energy for the target of “GREEN G”.

Based on the results of other IM variant studies, a Novel MM-OFDM-IM with two index selectors consisting of Subcarrier Index Selector (SIS) and Mode Index Selector (MIS) was proposed. SIS helps to maintain lower power consumption. MIS indicates the pattern of active subcarriers of a subblock taking a specific arrangement of mode constellations. Therefore, it can compete with OFDM even in higher modulation order for enhanced SE, whereby it has a higher energy-saving rate than MM-OFDM-IM. This study explains the MIS design and constellation pattern along with the impact of Energy Saving compared with other systems. BER and SER were simulated in MATLAB. The results showed SIS and MIS are less affected by errors than conventional modulated symbols.