Tài liệu Luận án nghiên cứu kỹ thuật điều chế chỉ số lặp lại cho các hệ thống ofdm

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 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 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 thesis 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 ACKNOWLEDGEMENTS It is a pleasure to take this opportunity to send my very great appreciation 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 - Electronics, especially my lecturers and colleagues in Department of Communications 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 studies 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 TABLE OF CONTENTS Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . List of abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv List of figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii List of tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x List of symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Chapter 1. RESEARCH BACKGROUND . . . . . . . . . . . . . . . 8 1.1. Basic principle of IM-OFDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.1.1. IM-OFDM model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.1.2. Sub-carrier mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.1.3. IM-OFDM signal detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.1.4. Advantages and disadvantages of IM-OFDM . . . . . . . . . . . . 16 1.2. Related works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 1.3. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Chapter 2. REPEATED INDEX MODULATION FOR OFDM WITH DIVERSITY RECEPTION . . . . . . . . . . . . . . . . . . . . . . 24 2.1. RIM-OFDM with diversity reception model . . . . . . . . . . . . . . . . 24 2.2. Performance analysis of RIM-OFDM-MRC/SC under perfect CSI 28 2.2.1. Performance analysis for RIM-OFDM-MRC . . . . . . . . . . . . i 29 2.2.2. Performance analysis for RIM-OFDM-SC . . . . . . . . . . . . . . . 34 2.3. Performance analysis of RIM-OFDM-MRC/SC under imperfect CSI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2.3.1. Performance analysis for RIM-OFDM-MRC . . . . . . . . . . . . 35 2.3.2. Performance analysis for RIM-OFDM-SC . . . . . . . . . . . . . . . 40 2.4. Performance evaluation and discussion . . . . . . . . . . . . . . . . . . . . . 41 2.4.1. Performance evaluation under perfect CSI . . . . . . . . . . . . . . 41 2.4.2. SEP performance evaluation under imperfect CSI condition . 48 2.4.3. Comparison of the computational complexity . . . . . . . . . . . 49 2.5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Chapter 3. REPEATED INDEX MODULATION FOR OFDM WITH COORDINATE INTERLEAVING . . . . . . . . . . . . . . . 51 3.1. RIM-OFDM-CI system model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.2. Performance analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.2.1. Symbol error probability derivation . . . . . . . . . . . . . . . . . . . . . 56 3.2.2. Asymptotic analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.2.3. Optimization of rotation angle . . . . . . . . . . . . . . . . . . . . . . . . . . 60 3.3. Low-complexity detectors for RIM-OFDM-CI. . . . . . . . . . . . . . . 62 3.3.1. Low-complexity ML detector . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 3.3.2. LLR detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 3.3.3. GD detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 3.4. Complexity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 3.5. Performance evaluations and discussion. . . . . . . . . . . . . . . . . . . . . 69 ii 3.6. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 CONCLUSIONS AND FUTURE WORK . . . . . . . . . . . . . . . 76 PUBLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 iii 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 Orthogonal 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 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 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 Selection Combining RIM-OFDM-CI Repeated Index Modulation for OFDM with Coordinate 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 LIST OF FIGURES 1.1 Block diagram of an IM-OFDM system. . . . . . . . . . . . 10 2.1 Structure of the RIM-OFDM-MRC/SC transceiver. . . . . . 25 2.2 The SEP comparison between RIM-OFDM-MRC and the conventional IM-OFDM-MRC system when N = 4, K = 2, L = 2, M = {4, 8}. . . . . . . . . . . . . . . . . . . . . . . 42 2.3 The SEP performance of RIM-OFDM-SC in comparison with IM-OFDM-SC for N = 4, K = 2, L = 2, M = {4, 8}. . 43 2.4 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}. . . . . . . . . . . . . . . . . . . . . . . . . 44 2.5 The impact of L on the SEP performance of RIM-OFDMMRC and RIM-OFDM-SC for M = 4, N = 4, K = 2 and L = {1, 2, 4, 6}. . . . . . . . . . . . . . . . . . . . . . . . . . 45 2.6 The SEP performance of RIM-OFDM-MRC under influence of K for M = {2, 4, 8, 16}, N = {5, 8}, K = {2, 3, 4, 5}. 2.7 46 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}. . . 46 2.8 Influence of modulation size on the SEP of RIM-OFDMMRC/SC for N = 5, K = 4, and M = {2, 4, 8, 16, 32}. . . . . 47 vii 2.9 The SEP performance of RIM-OFDM-MRC in comparison with IM-OFDM-MRC under imperfect CSI when N = 4, K = 2, M = {4, 8}, and 2 = {0.01, 0.05}. . . . . . . . . . 48 2.10 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 2 = 0.01. . . . . . . . . . . . . . . . 49 3.1 Block diagram of a typical RIM-OFDM-CI sub-block. . . . . 52 3.2 Rotated signal constellation. . . . . . . . . . . . . . . . . . . 60 3.3 Computational complexity comparison of LLR, GD, ML and lowML detectors when a) N = 8, M = 16, K = {1, 2, . . . , 7} and b) N = 8, K = 4, M = {2, 4, 8, 16, 32, 64}. . 68 3.4 Index error performance comparison of RIM-OFDM-CI, IM-OFDM, IM-OFDM-CI and ReMO systems at the spectral efficiency (SE) of 1 bit/s/Hz, M = {2, 4}, N = 4, K = {2, 3}. . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 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}. . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 3.6 BER comparison between the proposed scheme and the benchmark ones when N = 4, K = {2, 3}, M = {2, 4}. . . . 72 3.7 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 3.8 SEP performance of RIM-OFDM-CI and benchmark systems using different detectors. . . . . . . . . . . . . . . . . . 74 ix LIST OF TABLES 1.1 An example of look-up table when N = 4, K = 2, p1 = 2 . . 13 2.1 Complexity comparison between the proposed schemes and the benchmark. . . . . . . . . . . . . . . . . . . . . . . . 50 3.1 Example of LUT for N = 4, K = 2, pI = 2. . . . . . . . . . . 54 3.2 Complexity comparison between ML, LowML, LLR and GD dectectors. . . . . . . . . . . . . . . . . . . . . . . . . . 68 x 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 indices 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 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  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) = bxc Rounding down to the closest integer log2 (.) The base 2 logarithm E {.} Expectation operation. xii N! K!(N −K)! INTRODUCTION Motivation Wireless communication has been considered to be the fastest developing field of the communication industry. Through more than 30 years of research and development, various generations of wireless communications have been born. The achievable data rate of wireless systems has increased to several thousands of times higher (the fourth generation - 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 antennas and multiple receive antennas to enhance channel capacity without 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 interference (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 sub1 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 system 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 reliability, 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 technologies [2]. Meanwhile, based on OFDM, index modulation for OFDM (IM-OFDM) has been proposed and emerged as a promising multicarrier 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 effi2 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”. Within the scope of the research topic, the thesis aims to conduct a thorough study on the IM-OFDM system, and make its contributions to enhance performances of this attractive system. Research Objectives Motivated by the application potentials of IM-OFDM and the fact that its limitations, such as high computational complexity and limited transmission reliability, which may prevent it from possible implementation, this research aims at proposing enhanced IM-OFDM systems to tackle these problems. Moreover, a mathematical framework for the performance analysis is also developed to evaluate the performance of the proposed systems under various channel conditions. The specific objectives of the thesis research can be summarized as follows: • Upon studying the related IM-OFDM systems in the literature, efficient signal processing techniques such as repetition code and coordinate interleaving are proposed to employ in the considered systems. • Efficient signal detectors for the IM-OFDM system, which can bal3 ance the error performance with computational complexity, are studied and proposed for the considered systems. • Developing mathematical frameworks for performance analysis of the proposed systems, which can give an insight into the system behavior under the impacts of the system parameters. Research areas • Wireless communication systems under the impact of different fading conditions. • Multi-carrier transmission using OFDM and index modulation. • Detection theory and complexity analysis. Research method In this thesis, both the theoretical analysis and the Monte-Carlo simulation are used to evaluate the performance of the considered systems. • The analytical methods are used for calculating the computational complexity of the detection algorithms and to derive the closedform expressions for symbol error and bit error probabilities of the proposed systems. • The Monte-Carlo simulation is applied to validate the analytical results and to make comparison between the performance of the proposed systems and that of the benchmarks. Thesis contribution The major contributions of the thesis can be summarized as follows: 4