渦輪等化及渦輪碼在MIMO-OFDM系統上之實現

Abstract

在這篇論文中，我們著重在多輸入多輸出(MIMO)-正交分頻多工(OFDM)系統的外部接收機設計。外部接收機主要包括軟性位元產生器與錯誤更正碼解碼器，一般將這兩部分視為獨立，但依此無法達到最佳效能。在第一部分，我們研究渦輪等化(Turbo Equalization)在多輸入多輸出(MIMO)-正交分頻多工(OFDM)系統中的應用。此方法藉由遞迴的方式來結合軟性位元反對映與錯誤更正碼解碼。然而，位元交錯調變碼(BICM)依舊將錯誤更正碼以及調變視為獨立，並沒有利用到多輸入多輸出(MIMO)架構。而頻帶交錯調變碼(TICM)可用來解決這個問題。在第二部分，我們提出在渦輪碼(Turbo coding)在頻帶交錯調變碼(TICM)上的應用。在802.11n系統下，模擬證明渦輪等化以及渦輪碼結合頻帶交錯調變碼的效能均優於傳統的做法。

In this thesis, we focus on the outer receiver design for multiple-input-multiple output (MIMO) OFDM systems. The outer receiver mainly consists of a soft-bit demapper and an outer code decoder. The conventional approach considers these two devices separately, and cannot achieve true optimum performance. In the first part of the thesis, we study the application of turbo equalization technique in MIMO-OFDM systems. Using this approach, we can combine demapping and decoding in an iterative way. The conventional communication system often uses the bit-interleaved-coding modulation (BICM) scheme. However, the BICM scheme treats coding and modulation separately, and does not exploit the MIMO structure constraint. Tone-interleaved- coding-modulation (TICM) has been proposed to solve the problem. However, only the convolution code was considered. In the second part of the thesis, we propose to use the turbo code in the TICM scheme. Simulations with the IEEE 802.11n systems show that both the turbo equalization and the TICM schemes can significantly outperform conventional approaches.