臺灣博碩士論文加值系統

本篇論文提出廣義預編碼用於獨特字離散傅立葉轉換擴展正交分頻多工 (Unique
Word DFT-s-OFDM) 的新波形，我們稱之為「Generalized Unique Word DFT-s-OFDM (G-
UW DFT-s-OFDM)」。它可以對個別使用者制定預編碼，藉此改善偵測可靠度 (detection
reliability) 與降低次頻帶外發射 (out-of-subband emission)，並同時只有增加少量的峰均
功率比 (peak-to-average power ratio) 以及維持相同的頻譜效率 (spectral efficiency)。在下
世代的 5G 無線通訊系統中，要求更高的頻譜效率、更高的能源效率以及更大量的連結數
目。正交多頻分工 (OFDM) 顯然已經不再適合下世代的 5G 無線通訊系統。為了解決這
個問題，相繼有各種候選波形被提出。這些候選波形可以被大致分為三種技術的應用，預
編碼 (precoding)、加窗 (windowing) 與慮波 (filtering)。但是大多的加窗與慮波候選波形
都有符元間干擾的問題，導致了接收端偵測可靠度劣化。因此本篇論文的動機就是基於線
性預編碼的技術，設計出一種偵測可靠且具彈性的候選波形。

在這篇論文中，我們提出了聯合最佳化演算法 (joint optimization algorithm) 去設計
最佳的預編碼架構。我們先針對兩個最佳化問題，分別是降低次頻帶外發射與降低符元
間干擾 (inter-symbol interference)，以部分的條件得出對應的通解。在聯合最佳化過程的
每次迭代中使用，以此降低計算複雜度。此外，由於演算法複雜度較低且靈活性高，我
們能根據不同情況來調整最佳化的條件以符合系統需求。我們相信，所提出的 G-UW
DFT-s-OFDM 能成為下世代 5G 無限通訊系統的候選波形之一。

A new generalized precoding unique word discrete Fourier transform spread orthogonal frequency division multiplexing (GUW DFT-s-OFDM) waveform is proposed in this thesis. It can make the precoder for each user to improve the detection reliability and the out-of-subband emission, and it increases slight PAPR overhead and remain the same spectral efficiency at the same time. In the fifth generation (5G) communication system, higher spectral efficiency (SE), higher energy efficiency (EE) and massive connectivity of users and devices. Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) is apparently not suitable for the fifth generation (5G) communication system, because it has the following issues: (1) Spectral efficiency (SE) (2) Flexible guard interval (3) Out-of-subband emission (OSBE) (4) Peak-to-average ratio (PAPR). To address these issues, there
are various waveform candidates proposed successively. These waveform candidates can be roughly categorized into three techniques, precoding, windowing and filtering. However, most waveform candidates using windowing and filtering suffer form inter-symbol interference. It results in the degradation of detection reliability. Therefore, the motivation of this thesis is to develop a reliable and flexible waveform candidate based on the linear precoding.

In this thesis, we propose a joint optimization algorithm to design the optimal precoding structure. We first focus on two optimization problems, reducing the out-of-subband emission
and reducing inter-symbol interference, to obtain the corresponding general solutions based on part of constraints. In the joint optimization process, we use these general solutions to reduce the computation complexity.

In this thesis, we analysis the precoding structure of OFDM and optimization formulation of precdoer. Our simulation results include the OSBE, PAPR adn BER of GUW
DFT-s-OFDM.

Our achievement is to reduce the OSBE and ISI with similar PAPR compared to DFT-s-OFDM. At the same time, the proposed waveform has the same spectral efficiency as G-DFT-s-OFDM. Additionally, due to the low complexity of algorithm and high flexibility, we are able to adapt the constraints to meet the requirements of system. We believe that the proposed G-UW DFT-s-OFDM will be one of the waveform candidates in the fifth generation communication system.

摘要 i

Abstract ii

Contents iv

1 INTRODUCTION 1

1.1 Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Research Motivation and Objective . . . . . . . . . . . . . . . . . . . . . . . 2

1.3 Related Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.3.1 Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3.2 Windowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.3.3 Transform precoding . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.4 Proposed Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.5 Contribution and Achievement . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.6 Thesis Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2 BACKGROUNDS 8

2.1 Orthogonal Frequency Division Multiple Access (OFDMA) . . . . . . . . . . 8

2.2 Single Carrier Frequency Division Multiple Access (SC-FDMA) . . . . . . . 10

2.3 Generalized DFT-s-OFDM without CP (G-DFT-s-OFDM) . . . . . . . . . . 11

2.4 Improved Unique Word DFT-s-OFDM . . . . . . . . . . . . . . . . . . . . . 14

2.5 Optimal Orthogonal Precoding for Power Leakage Suppression in DFT-Based
Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3 Generalized unique word DFT-s-OFDM 18

3.1 System model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.2 Generalized precoding for Unique Word DFT-s-OFDM . . . . . . . . . . . . 21

3.2.1 Tail Precoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.2.2 Spectral Precoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.3 Joint optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4 SIMULATION RESULTS 33

4.1 Simulation parameters and evaluation requirement . . . . . . . . . . . . . . 33

4.2 Setting of Existing Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.3 Out-of-subband emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.4 PAPR performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

4.5 BER Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.6 Spectral Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5 CONCLUSIONS 40

Bibliography 42

[1] S. Lien, S. Shieh, Y. Huang, B. Su, Y. Hsu, and H. Wei, “5G New Radio: Waveform,
Frame Structure, Multiple Access, and Initial Access,” IEEE Communications Maga-
zine, vol. 55, pp. 64–71, June 2017.

[2] 3GPP, “User Equipment (UE) radio transmission and reception; Part 1: Range 1 Stan-
dalone,” Technical Specification (TS)38.101, V15.2.0, Sec. 6.5.2, Jul. 2018.

[3] J. Abdoli, M. Jia, and J. Ma, “Filtered OFDM: A new waveform for future wireless
systems,” in 2015 IEEE 16th International Workshop on Signal Processing Advances in
Wireless Communications (SPAWC), pp. 66–70, June 2015.

[4] X. Zhang, M. Jia, L. Chen, J. Ma, and J. Qiu, “Filtered-OFDM - Enabler for Flexible
Waveform in the 5th Generation Cellular Networks,” in 2015 IEEE Global Communi-
cations Conference (GLOBECOM), pp. 1–6, Dec 2015.

[5] F. Schaich, T. Wild, and Y. Chen, “Waveform Contenders for 5G - Suitability for
Short Packet and Low Latency Transmissions,” in 2014 IEEE 79th Vehicular Technology
Conference (VTC Spring), pp. 1–5, May 2014.

[6] T. Wild, F. Schaich, and Y. Chen, “5G air interface design based on Universal Filtered
(UF-)OFDM,” in 2014 19th International Conference on Digital Signal Processing,
pp. 699–704, Aug 2014.

[7] R. Zayani, Y. Medjahdi, H. Shaiek, and D. Roviras, “WOLA-OFDM: A Potential Candi-
date for Asynchronous 5G,” in 2016 IEEE Globecom Workshops (GC Wkshps), pp. 1–5,
Dec 2016.

[8] Y. Medjahdi, R. Zayani, H. Shaïek, and D. Roviras, “WOLA processing: A useful tool
for windowed waveforms in 5G with relaxed synchronicity,” in 2017 IEEE International
Conference on Communications Workshops (ICC Workshops), pp. 393–398, May 2017.

[9] 3GPP, “Physical channels and modulation,” Technicl Specification (TS) 38.211, Sep.
2018.

[10] G. Berardinelli, “Generalized DFT-s-OFDM Waveforms Without Cyclic Prefix,” IEEE
Access, vol. 6, pp. 4677–4689, Dec. 2018.

[11] B. Benammar, N. Thomas, M. Boucheret, C. Poulliat, and M. Dervin, “Analytical
expressions of Power Spectral Density for general spectrally shaped SC-FDMA systems,”
in 21st European Signal Processing Conference (EUSIPCO 2013), pp. 1–5, Sep. 2013.

[12] G. Berardinelli, “Zero-tail DFT-spread-OFDM signals,” IEEE Globecom Workshops
(GC Wkshps), pp. 229–234, Dec. 2013.

[13] A. Sahin, R. Yang, M. Ghosh, and R. L. Olesen, “An Improved Unique Word DFT-
Spread OFDM Scheme for 5G Systems,” in 2015 IEEE Globecom Workshops (GC Wk-
shps), pp. 1–6, Dec 2015.

[14] M. Ma, X. Huang, B. Jiao, and Y. J. Guo, “Optimal Orthogonal Precoding for Power
Leakage Suppression in DFT-Based Systems,” IEEE Transactions on Communications,
vol. 59, pp. 844–853, March 2011.

[15] T. Wu and C. Chung, “Correlatively Precoded OFDM With Reduced PAPR,” IEEE
Transactions on Vehicular Technology, vol. 65, pp. 1409–1419, March 2016.

[16] R. Xu, L. Wang, Z. Geng, H. Deng, L. Peng, and L. Zhang, “A Unitary Precoder for
Optimizing Spectrum and PAPR Characteristic of OFDMA Signal,” IEEE Transactions
on Broadcasting, vol. 64, pp. 293–306, June 2018.

[17] G. Berardinelli, K. I. Pedersen, T. B. Sorensen, and P. Mogensen, “Generalized DFT-
Spread-OFDM as 5G Waveform,” IEEE Communications Magazine, vol. 54, pp. 99–105,
November 2016.

[18] L. Hogben, “Handbook of Linear Algebra,” Chapman Hall/CRC Press, 2007.

[19] G. H. Golub and C. F. V. Loan, “Matrix Computations,” The Johns Hopkins University
Press, 1996.

[20] P. H. Schoenemann, “A Solution of the Orthogonal Procrustes Problem With Applica-
tions to Orthogonal and Oblique Rotation,” University of Illinois at Urbana-Champaign,
1964.