Maximal Spectral Efficiency of OFDM with Index Modulation under Polynomial Space Complexity
Authors
Abstract
In this letter, we demonstrate a mapper that enables all waveforms of OFDM with Index Modulation (OFDM-IM) while preserving polynomial time and space computational complexities. Enabling all OFDM-IM waveforms maximizes the spectral efficiency (SE) gain over the classic OFDM but, as far as we know, the computational overhead of the resulting mapper remains conjectured as prohibitive across the OFDM-IM literature. We show that the largest number of binomial coefficient calculations performed by the original OFDM-IM mapper is polynomial on the number of subcarriers, even under the setup that maximizes the SE gain over OFDM. Also, such coefficients match the entries of the so-called Pascal’s triangle (PT). Thus, by assisting the OFDM-IM mapper with a PT table, we show that the maximum SE gain over OFDM can be achieved under polynomial (rather than exponential) time and space complexities.
Keywords
Computational Complexity, Index Modulation, Look-Up Table, OFDM, Pascal’s Triangle, Spectral Efficiency.
Related Project
5G - Components and Services for 5G Networks (5G - Componentes e Serviços para Redes 5G)
Journal
IEEE Wireless Communications Letters, January 2020
PDF File
DOI