Wideband Video Transmission using Adaptive Modulation in MIMO OFDM System

使用可適性調變多輸入多輸出系統之寬頻視訊傳輸

鄭永霖(Yung-Ling Cheng)

指導教授 ： 黃元豪

國立清華大學/電機資訊學院/電機工程學系/碩士(2009年)

https://doi.org/10.6843/NTHU.2009.00808

摘要

論文摘要
本論文是參考歐規數位電視地面廣播(DVB-T) 標準來改成一套4x4的傳送機架構、並提出基頻等效通道模型與設計一套基頻接收機架構。由於在無線通訊環境中, 有不少的非理想效應存在, 故我們所設計的基頻等效通道模型包含多路徑衰減通道(Multipath Fading Channel)
、加成性白色高斯雜訊(Additive White Gaussian Noise, AWGN) 與載波頻率漂移(Carrier Frequency Offset, CFO) 等效應。對於接收端的架構設計, 主要分為三部份, 擷取, 追蹤補償與資料回復。這三部份總共包含有符元時間偵測、載波頻率漂移之擷取、補償
和追蹤、傅立葉(FFT) 處理器、通道估測與補償、K-BEST 偵測器、映射器、維特比解碼器(Viterbi Decoder) 、和里得所羅門解碼器(Reed-Solomon Decoder) 。本論文也提出一個可適性調變機制, 根據不同通道狀況相對應的LLR 值去做不同的調變機制。可適性調變包
含了六種調變方式, 分別為64QAM , 64HQAM(alpha = 2,beta = 1) , 64HQAM(alpha = 4,beta = 1) ,64HQAM(alpha = 2,beta = 2) , 64HQAM(alpha = 4,beta = 2) , 64HQAM(alpha = 4,beta = 4) 。alpha和beta是兩個在階層調便中所使用的參數。而資料分割可以將影像根據不同的重要性來區分成三部份。
故我們可以使用資料分割搭配階層調變來達到不同保護機制傳輸, 並且可以使用可適性調變方法在不同的通道條件下達到比較好的PSNR 值, 影像也呈現出很好的效果。

關鍵字

可適性調變

並列摘要

Abstract
In the design for a 4×4 transmitter according to DVB-T SPEC, we proposed a baseband
equivalent channel model and designed a baseband receiver. The baseband equivalent
channel model includes multipath fading channel, additive white Gaussian noise(AWGN)
and carrier frequency offset. The receiver consist of symbol timing detection, CFO
estimation, FFT processor, channel estimation, K-BEST detector, demapper, Viterbi
decoder and Reed-Solomon decoder. Besides, we design of adaptive modulation based
on LLR under different channel condition. The adaptive modulation use six modulation
schemes which are 64QAM, 64HQAM(α = 2,β = 1), 64HQAM(α = 4,β = 1),
64HQAM(α = 2,β = 2), 64HQAM(α = 4,β = 2), 64HQAM(α = 4,β = 4), where
and are two parameters in hierarchical modulation. The video data is divided into
three parts according to their importance. Therefore, data partition, hierarchical modulation
and adaptive modulation improve PSNR significantly under different channel
conditions.

參考文獻

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