Multi-resolution multiplexing for 5G wireless spectral efficiency enhancement in strong noise

Abstract

Spectral efficiency enhancement is one of the important objectives of the next generation wireless communication systems. This paper introduces multi-resolution multiplexing (MM), a novel loading mechanism to assign proper rate to each bit of 2n-quadrature amplitude modulation (QAM) code-word so as to enhance its overall spectral efficiency. 2n-QAM with rectangular constellation is decomposed into resolutions where each resolution describes the gain of a unique bit in the code-word. 2n-QAM is modeled as a number of co-existing, independent bipolar binary phase shift keying (BPSK) sub-channels in baseband in-phase and quadrature branches, where it behaves like baseband multiple-input system in each branch. At receiver, successive interference cancellation (SIC) algorithm detects the multiple-output baseband BPSK sub-channels. It is shown that the performance of the SIC algorithm is equivalent to that of maximum likelihood, hard decision decoder. Spectral efficiency of 2n QAM before and after enhancement are compared. It is shown that in the presence of strong noise (low carrier to noise ratio), the proposed approach significantly enhances the modulation's spectral efficiency, against evenly loaded QAM. In this paper, multi-resolution roots in different power level of the modulation code-word's bits of 2n-QAM, where it results in different capacity of the loaded data on each bit.