於正交分頻多工設計具低峰均功率比、高頻譜緊密度與準確同步性能之前導訊號

Preamble Sequence Design for Low PAPR, High Spectral Compactness and Robust Initial Synchronization in OFDM

林呈臻(Cheng-Chen Lin)

指導教授 ： 鐘嘉德

共同指導教授 ： 陳維昌(Wei-Chang Chen)

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201801116

摘要

在現行的正交分頻多工(OFDM)系統和標準，前導訊號波形多用來作為初步時間和頻率的同步。這些前導訊號波形都來自於設計良好的前導訊號序列，這些序列都具有完全或近乎的零周期自相關函數(ZAC)特性以達到穩定的同步性質，也是由完全或近乎相同振幅(CA)的元素所組成以確保低峰均功率比(PAPR)。不幸的是，由傳統的具有零周期自相關和同振幅性質(CAZAC)序列或具有接近於零周期自相關和同振幅性質(near-CAZAC)序列所組成的前導訊號波形具有很大的旁波，以至於頻譜不緊密。雖然有些具有零周期自相關性質(ZAC)序列和具有接近於零周期自相關性質(near-ZAC)序列已經提出來當作頻譜緊密的前導訊號波形，但是他們的峰均功率比不夠低無法避免非線性放大的發生。在這篇論文中，新的具有接近於零周期自相關和同振幅性質(near-CAZAC)序列被設計出來作為具頻譜緊密、穩定的時間和頻率同步以及非常低的峰均功率比的前導訊號波形，此序列的峰均功率比足以和傳統的具有零周期自相關和同振幅性質(CAZAC)序列堪比。當考慮了非線性放大的情況，由具有接近於零周期自相關和同振幅性質(near-CAZAC)序列所組成的前導訊號波形，展現了比由現有高峰均功率比的具有零周期自相關性質(ZAC)序列或具有接近於零周期自相關性質(near-ZAC)序列所產生的前導訊號波形還好很多的頻譜緊密度。

關鍵字

正交分頻多工 ； 前導訊號 ； 峰均功率比 ； 頻譜緊密度 ； 同步

並列摘要

In practical orthogonal frequency division multiplexing systems and standards, preamble waveforms are adopted to facilitate initial timing and frequency synchronization. These preamble waveforms are constructed from properly designed preamble sequences which possess exact or near zero periodic autocorrelation (ZAC) property to achieve robust synchronization and consist of exact or near constant amplitude (CA) symbols to achieve low waveform peak-to-average power ratio (PAPR). Unfortunately, preamble waveforms carrying conventional CAZAC sequences (which have ZAC property and consist of CA symbols) or near-CAZAC sequences result in large power spectral sidelobes and thus are not spectrally compact. Although several ZAC and near-ZAC sequences are developed to construct spectrally compact preamble waveforms, their PAPR are not low enough to avoid nonlinear distortion. In this paper, new near-CAZAC sequences are designed to construct spectrally compact OFDM preamble waveforms with robust timing and frequency synchronization and very low waveform PAPR comparable to those constructed from the conventional CAZAC sequences. When the nonlinearity is considered, the OFDM preamble waveforms constructed from the proposed near-CAZAC sequences exhibit much better spectral compactness than those constructed from the existing ZAC or near-ZAC sequences with too high PAPR.

並列關鍵字

Orthogonal frequency-division multiplexing ； preamble ； peak-to-average power ratio ； spectral compactness ； synchronization

參考文獻

[1] IEEE 802.11-2012, IEEE standard for information technology– Telecommunications and information exchange between systems– Local and metropolitan area networks– Specific requirements, Part11: Wireless LAN medium access control (MAC) and physical layer (PHY) specifications, Mar.2012

[2] 3GPP TS 36.211 V12.3.0, LTE; Evolved universal terrestrial radio access (E-UTRA): Physical channels and modulation, Oct. 2014.

[3] IEEE 802.16-2009, IEEE standard for local and metropolitan area networks, Part 16: Air interface for broadband wireless access systems, May 2009.

[4] IEEE 802.22-2011, Part 22: Cognitive wireless RAN medium access control (MAC) and physical layer (PHY) specifications: Policies and procedures for operation in the TV bands, Jul. 2011.

[5] IEEE 802.20-2008, IEEE standard for local and metropolitan area networks, Part 20: Air interface for mobile broadband wireless access systems supporting vehicular mobility–Physical and media access control layer specification, Aug. 2008.