基於廣義概度比檢定和領導式通道估測的正交分頻多工單輸入多輸出系統之解調性能分析

Performance Analysis of GLRT-Based OFDM SIMO Demodulation System With Pilot-Aided Channel Estimation

廖芝青(Jy-Chin Liao)

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(2021年)

https://doi.org/10.6342/NTU202101827

摘要

在現行的正交分頻多工(OFDM)系統中做數據解調時，領導信號(pilot symbols)經常穿插到均勻分布的子載波中以促進通道估測(channel estimation)。當分段頻散通道的衰減程度加劇時，基於廣義概度比檢定(GLRT)的原理，由等間隔擺放的領導符號輔助的通道估測能夠實現在同一個正交分頻多工塊中逐個符號的數據解調。為了進一步對抗更加衰減更加劇烈的分段頻散通道，採用單輸入多輸出(SIMO)天線分集系統可以增強基於廣義概度比檢定的解調性能。在本文中，對於所考慮的基於廣義概度比檢定的正交分頻多工單輸入多輸出系統解調，在固定和隨機分段頻散通道上採用各種二維的調變方式，分析推導出位元錯誤率（bit error rate, BEP）的上界和近似值，並通過模擬驗證其緊密性。數值分析顯示，當通道的衰減程度較小或單輸入多輸出系統的接收天線數足夠多時，位元錯誤率的上界表現出良好的緊密性，反之可以採用近似主導界線。透過推導出的界線，針對信號雜訊比、數據與領導信號功率比、天線分集、通道條件和領導信號長度等不同參數，分析且研究所考慮的基於廣義概度比檢定的正交分頻多工單輸入多輸出系統之錯誤性能特徵。

關鍵字

正交分頻多工 ； 領導式通道估測 ； 廣義概度比檢定 ； 單出入多輸出 ； 分段頻散通道

並列摘要

Pilot symbols are commonly inserted into uniformly interleaved subcarriers to facilitate the channel estimation, thereby facilitating the data demodulation in practical orthogonal frequency-division multiplexing (OFDM) systems operating over block dispersive channels. When the block dispersive channel is fast time-varying, the channel estimation aided by the uniformly interleaved pilot symbols can enable symbol-by-symbol data demodulation within the same OFDM block, based on the principle of the generalized likelihood ratio test (GLRT). To further combat strong channel dispersion, a single-input multiple-output (SIMO) antenna diversity system is adopted and can enhance the GLRT-based demodulation performance. In this thesis, upper and approximate bounds to the bit error probability (BEP) are analytically derived for the considered GLRT-based OFDM SIMO demodulation, adopting various two-dimensional component modulation schemes, over both deterministic and random block dispersive channels, and verified by simulation for their tightness. Numerical results show that the BEP upper bounds exhibit tight performance measures when the channel dispersion is less fluctuated or when the SIMO diversity is sufficiently high, and that approximate dominant bounds can be used otherwise. Through the derived bounds, the error performance characteristics of the considered GLRT-based OFDM SIMO system are analytically studied with respect to data-to-noise power ratio, data-to-pilot power ratio, antenna diversity, channel condition, and pilot length.

並列關鍵字

Orthogonal frequency division multiplexing ； pilot-aided channel estimation ； generalized likelihood ratio test ； single-input multiple-output ； block dispersive channel

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