Luận án tiến sĩ kỹ thuật điều chế chỉ số lặp lại cho hệ thống OFDM - Học viện Kỹ thuật Mật mã

MINISTRY OF EDUCATION & TRAINING MINISTRY OF NATIONAL DEFENSE MILITARY TECHNICAL ACADEMY LE THI THANH HUYEN REPEATED INDEX MODULATION FOR OFDM SYSTEMS A Thesis for the Degree of Doctor of Philosophy HA NOI - 2020 luan an MINISTRY OF EDUCATION & TRAINING MINISTRY OF NATIONAL DEFENSE MILITARY TECHNICAL ACADEMY LE THI THANH HUYEN REPEATED INDEX MODULATION FOR OFDM SYSTEMS A Thesis for the Degree of Doctor of Philosophy Specialization: Electronic Engineering Specialization code: 9 52 02 03 SUPERVISOR Prof. TRAN XUAN NAM HA NOI - 2020 luan an ASSURANCE I hereby declare that this thesis was carried out by myself under the guidance of my supervisor. The presented results and data in the the- sis are reliable and have not been published anywhere in the form of books, monographs or articles. The references in the thesis are cited in accordance with the university’s regulations.

Hanoi, May 17th, 2019 Author Le Thi Thanh Huyen luan an ACKNOWLEDGEMENTS It is a pleasure to take this opportunity to send my very great appre- ciation to those who made this thesis possible with their supports. First, I would like to express my deep gratitude to my supervisor, Prof. Tran Xuan Nam, for his guidance, encouragement and meaningful critiques during my researching process. This thesis would not have been completed without him.

My special thanks are sent to my lecturers in Faculty of Radio - Elec- tronics, especially my lecturers and colleagues in Department of Com- munications who share a variety of difficulties for me to have more time to concentrate on researching. I also would like to sincerely thank my research group for sharing their knowledge and valuable assistance. Finally, my gratitude is for my family members who support my stud- ies with strong encouragement and sympathy. Especially, my deepest love is for my mother and two little sons who always are my endless inspiration and motivation for me to overcome all obstacles.

Author Le Thi Thanh Huyen luan an TABLE OF CONTENTS Contents. List of abbreviations. iv List of figures. vii List of tables.

x List of symbols. Basic principle of IM-OFDM. IM-OFDM model. Sub-carrier mapping.

IM-OFDM signal detection. Advantages and disadvantages of IM-OFDM. REPEATED INDEX MODULATION FOR OFDM WITH DIVERSITY RECEPTION. RIM-OFDM with diversity reception model.

Performance analysis of RIM-OFDM-MRC/SC under perfect CSI 28 2. Performance analysis for RIM-OFDM-MRC. Performance analysis for RIM-OFDM-SC. Performance analysis of RIM-OFDM-MRC/SC under imperfect CSI.

Performance analysis for RIM-OFDM-MRC. Performance analysis for RIM-OFDM-SC. Performance evaluation and discussion. Performance evaluation under perfect CSI.

SEP performance evaluation under imperfect CSI condition. Comparison of the computational complexity. REPEATED INDEX MODULATION FOR OFDM WITH COORDINATE INTERLEAVING. RIM-OFDM-CI system model.

Symbol error probability derivation. Optimization of rotation angle. Low-complexity detectors for RIM-OFDM-CI. Low-complexity ML detector.

Performance evaluations and discussion. 69 ii luan an 3. 75 CONCLUSIONS AND FUTURE WORK. 81 iii luan an LIST OF ABBREVIATIONS Abbreviation Definition AWGN Additive White Gaussian Noise BEP Bit Error Probability BER Bit Error Rate CI Coordinate Interleaving CS Compressed Sensing CSI Channel State Information D2D Device to Device ESIM-OFDM Enhanced Sub-carrier Index Modulation for Or- thogonal Frequency Division Multiplexing FBMC Filter Bank Multi-Carrier FFT Fast Fourier Transform GD Greedy Detection ICI Inter-Channel Interference IEP Index Error Probability IFFT Inverse Fast Fourier Transform IM Index Modulation IM-OFDM Index Modulation for OFDM iv luan an IM-OFDM-CI Index Modulation for OFDM with Coordinate Interleaving IoT Internet of Things ISI Inter-Symbol Interference ITU International Telecommunications Union LowML Low-complexity Maximum Likelihood LLR Log Likelihood Ratio LUT Look-up Table M2M Machine to Machine Mbps Megabit per second MGF Moment Generating Function MIMO Multiple Input Multiple Output ML Maximum Likelihood MM-IM-OFDM Multi-Mode IM-OFDM MRC Maximal Ratio Combining NOMA Non-Orthogonal Multiple Access OFDM Orthogonal Frequency Division Multiplexing OFDM-GIM OFDM with Generalized IM OFDM-I/Q-IM OFDM with In-phase and Quadrature Index Modulation OFDM-SS OFDM Spread Spectrum PAPR Peak-to-Average Power Ratio PEP Pairwise Error Probability PIEP Pairwise Index Error Probability v luan an PSK Phase Shift Keying QAM Quadrature Amplitude Modulation RIM-OFDM Repeated Index Modulation for OFDM RIM-OFDM-MRC Repeated Index Modulation for OFDM with Maximal Ratio Combining RIM-OFDM-SC Repeated Index Modulation for OFDM with Se- lection Combining RIM-OFDM-CI Repeated Index Modulation for OFDM with Co- ordinate Interleaving SC Selection Combining SEP Symbol Error Probability SIMO Single Input Multiple Output S-IM-OFDM Spread IM-OFDM SNR Signal to Noise Ratio SM Spatial Modulation SS Spread Spectrum UWA Underwater Acoustic V2V Vehicle to Vehicle V2X Vehicle to Everything xG x-th Generation vi luan an LIST OF FIGURES 1.1 Block diagram of an IM-OFDM system.1 Structure of the RIM-OFDM-MRC/SC transceiver.2 The SEP comparison between RIM-OFDM-MRC and the conventional IM-OFDM-MRC system when N = 4, K = 2, L = 2, M = {4, 8}.3 The SEP performance of RIM-OFDM-SC in comparison with IM-OFDM-SC for N = 4, K = 2, L = 2, M = {4, 8}.4 The relationship between the index error probability of RIM-OFDM-MRC/SC and the modulation order M in comparison with IM-OFDM-MRC/SC for N = 4, K = 2, M = {2, 4, 8, 16}.5 The impact of L on the SEP performance of RIM-OFDM- MRC and RIM-OFDM-SC for M = 4, N = 4, K = 2 and L = {1, 2, 4, 6}.6 The SEP performance of RIM-OFDM-MRC under influ- ence of K for M = {2, 4, 8, 16}, N = {5, 8}, K = {2, 3, 4, 5}.7 The SEP performance of RIM-OFDM-SC under influence of K when M = {2, 4, 8, 16}, N = {5, 8}, K = {2, 3, 4, 5}.8 Influence of modulation size on the SEP of RIM-OFDM- MRC/SC for N = 5, K = 4, and M = {2, 4, 8, 16, 32}.

47 vii luan an 2.9 The SEP performance of RIM-OFDM-MRC in compari- son with IM-OFDM-MRC under imperfect CSI when N = 4, K = 2, M = {4, 8}, and ǫ2 = {0.10 The SEP performance of RIM-OFDM-SC in comparison with IM-OFDM-SC under imperfect CSI when N = 4, K = 2, M = {4, 8}, and ǫ2 = 0.1 Block diagram of a typical RIM-OFDM-CI sub-block.2 Rotated signal constellation.3 Computational complexity comparison of LLR, GD, ML and lowML detectors when a) N = 8, M = 16, K = {1, 2, .4 Index error performance comparison of RIM-OFDM-CI, IM-OFDM, IM-OFDM-CI and ReMO systems at the spec- tral efficiency (SE) of 1 bit/s/Hz, M = {2, 4}, N = 4, K = {2, 3}.5 SEP performance comparison between RIM-OFDM-CI, IM-OFDM and CI-IM-OFDM using ML detection at the spectral efficiency of 1 bit/s/Hz when M = {2, 4}, N = 4, K = {2, 3}.6 BER comparison between the proposed scheme and the benchmark ones when N = 4, K = {2, 3}, M = {2, 4}.7 BER comparison between the proposed and benchmark schemes at SE of 1.25 bits/s/Hz when N = {4, 8}, K = {2, 4}, M = {2, 4, 8}. 73 viii luan an 3.8 SEP performance of RIM-OFDM-CI and benchmark sys- tems using different detectors. 74 ix luan an LIST OF TABLES 1.1 An example of look-up table when N = 4, K = 2, p1 = 2 .1 Complexity comparison between the proposed schemes and the benchmark.1 Example of LUT for N = 4, K = 2, pI = 2.2 Complexity comparison between ML, LowML, LLR and GD dectectors. 68 x luan an LIST OF SYMBOLS Symbol Meaning a A complex number aR Real part of a aI Imaginary part of a |a| Modulus of a a A vector A A matrix AH The Hermitian transpose of A AT The transpose of A c Number of possible combinations of active in- dices f (.) Probability density function G Number of sub-blocks K Number of active sub-carriers N Number of sub-carriers in each sub-block NF Number of sub-carriers in IM-OFDM system L Number of receive antennas P (.) The probability of an event PI Index symbol error probability PM M -ary modulated symbol error probability xi luan an Ps Symbol error probability Q (.) The tail probability of the standard Gaussian distribution γ̄ Average SNR at each sub-carrier I Set of possible active sub-carrier indices M (.) The moment generating function.

S Complex signal constellation Sφ Rotated complex signal constellation α Index of an active sub-carrier ǫ Channel estimation error variance Θ Big-Theta notation φ Rotation angle of signal constellation φopt Optimal rotation angle of signal constellation 2 k.kF Frobenius norm of a matrix diag(.) Diagonal matrix ! C (N, K) Binomial coefficient, C (N, K) = K!(NN−K)! ⌊x⌋ Rounding down to the closest integer log2 (.) The base 2 logarithm E {. xii luan an INTRODUCTION Motivation Wireless communication has been considered to be the fastest devel- oping field of the communication industry. Through more than 30 years of research and development, various generations of wireless communi- cations have been born. The achievable data rate of wireless systems has increased to several thousands of times higher (the fourth genera- tion - 4G) than that of the second generation (2G) wireless systems.

Particularly, the 4G wireless communication systems, supported by key technologies such as multiple-input multiple-output (MIMO), orthogonal frequency division multiplexing (OFDM), cooperative communications, have already achieved the data rate of hundreds Mbps [1]. The MIMO technique exploits the diversity of multiple transmit an- tennas and multiple receive antennas to enhance channel capacity with- out either increasing the transmit power or requiring more bandwidth. Meanwhile, OFDM is known as an efficient multi-carrier transmission technique which has high resistance to the multi-path fading. The OFDM system offers a variety of advantages such as inter-symbol in- terference (ISI) resistance, easy implementation by inverse fast Fourier transform/fast Fourier transform (IFFT/FFT).

It can also provide higher spectral efficiency over the single carrier system since its orthogonal sub- 1 luan an carriers overlap in the frequency domain. Due to vast developments of smart terminals, new applications with high-density usage, fast and continuous mobility such as cloud services, machine-to-machine (M2M) communications, autonomous cars, smart home, smart health care, Internet of Things (IoT), etc, the 5G sys- tem has promoted challenging researches in the wireless communication community [2]. It is expected that ubiquitous communications between anybody, anything at anytime with high data rate and transmission re- liability, low latency are soon available [3]. Although there are several 5G trial systems installed worldwide, so far there have not been any official standards released yet.

The International Telecommunications Union (ITU) has set 2020 as the deadline for the IMT-2020 standards. According to a recent report of the ITU [3], 5G can provide data rate significantly higher, about tens to hundreds of times faster than that of 4G. For latency issue, the response time to a request of 5G can reduce to be about 1 millisecond compared to that around 120 milliseconds and between roughly 15-60 milliseconds of 3G and 4G, respectively [3]. In order to achieve the above significant improvement, the 5G system continues employing OFDM as one of the primary modulation technolo- gies [2].

Meanwhile, based on OFDM, index modulation for OFDM (IM-OFDM) has been proposed and emerged as a promising multi- carrier transmission technique. IM-OFDM utilizes the indices of active sub-carriers of OFDM systems to convey additional information bits. There are several advantages over the conventional OFDM proved for IM-OFDM such as the improved transmission reliability, energy effi- 2 luan an ciency and the flexible trade-off between the error performance and the spectral efficiency [4], [5]. However, in order to be accepted for possible inclusion in the 5G standards and have a full understanding about the IM-OFDM capability, more studies should be carried out.

Inspired by the motivation of OFDM in the framework of 5G and the application potentials of IM-OFDM to the future commercial standards, the present thesis has adopted IM-OFDM as the research theme for its study with the title “Repeated index modulation for OFDM systems”.