Adaptive OFDM-IM for Enhancing Physical Layer Security and Spectral Efficiency of Future Wireless Networks

Haji M Furqan,Huseyin Arslan,Jehad M Hamamreh

doi:10.1155/2018/3178303

Abstract

In this paper, we propose algorithms for enhancing physical layer security and spectral efficiency of Orthogonal Frequency Division Multiplexing (OFDM) with Index Modulation (IM) systems. Particularly, different activation ratios and/or Constellation Modulation orders are selected adaptively for each subblock based on the channel quality of the legitimate receiver. More specifically, three approaches named as (1) OFDM with Adaptive Index Modulation and Fixed Constellation Modulation (OFDM-AIM-FCM), (2) OFDM with Adaptive Index Modulation and Adaptive Constellation Modulation (OFDM-AIM-ACM), and (3) OFDM with Variable Index Modulation and Variable Constellation Modulation (OFDM-VIM-VCM) are proposed for enhancing physical layer security and spectral efficiency. Simulation results are presented to investigate the effectiveness of the proposed algorithms.

Highlights

The inherent broadcast characteristic of wireless communication makes it vulnerable to the passive eavesdropping
The authors investigate the randomized mapping rules based on channel reciprocity in Time Division Duplex (TDD) mode in order to secure both data symbol modulation and Index Modulation but in that work spectral efficiency is not taken into account
Due to the channel decorrelation, the Subcarrier Activation Ratio (SAR) values and Constellation Modulation (CM) orders of different subblocks determined by Bob and Eve based on Orthogonal Frequency Division Multiplexing (OFDM)-AIM-ACM are different

Summary

Introduction

The inherent broadcast characteristic of wireless communication makes it vulnerable to the passive eavesdropping. In order to solve this deficiency, the authors in [24] proposed a technique in which the rotation of both the indices of transmit antennas and constellation symbols based on the channel state information of the legitimate receiver are exploited, securing both Index Modulation and data symbol modulation. The authors investigate the randomized mapping rules based on channel reciprocity in TDD mode in order to secure both data symbol modulation and Index Modulation but in that work spectral efficiency is not taken into account. Inspired by the need for joint consideration of security and SE, in this paper, we propose algorithms for the enhancement of PLS of OFDM-IM and for the quality of service (QoS) based communication in order to enhance SE of OFDM-IM. CN(0, σX2 ) represents the distribution of a circularly symmetric complex Gaussian random variable X with variance σX2 . (⋅)H and (⋅)T denote Hermitian transposition and transposition, respectively

System Model and Preliminaries

Adaptive OFDM-IM Model and Proposed Algorithms

Performance Analysis of Adaptive OFDMIM Scheme

Simulation Result

Conclusion