IEEE 802.11n外部接收機設計

Abstract

IEEE 802.11n使用多輸入多輸出(MIMO)-正交分頻多工(OFDM)系統與位元交錯調變碼(BICM)做為其基頻傳輸技術。在此論文，我們著重在802.11n外部接收機設計。外部接收機主要包括軟性位元產生器與Viterbi解碼器。我們採用兩種方式來獲得軟性位元資訊。第一種方式為最小均方差(MMSE)等化器與多個軟性位元反對映器，第二種方式為名單球解碼(LSD)偵測器與向量軟性位元反對映器。雖然第二種方式有較佳的效能表現，但其運算複雜度較高。為了解決此問題，我們提出一個新的解碼調變方法，稱為頻帶交錯調變碼(TICM)。與BICM不同的地方在於TICM將軟性位元反對映器併入Viterbi解碼器。LSD偵測器也能用來化簡TICM的運算複雜度。在802.11n系統下，模擬證明TICM的解碼運算複雜度低於BICM，且效能優於BICM。

IEEE 802.11n uses the MIMO-OFDM along with bit-interleaved coding modulation (BICM) as its baseband transmission scheme. In this thesis, we will focus on the outer receiver design for the IEEE 802.11n system. The outer receiver mainly consists of a soft-bit computing device and a Viterbi decoder. Two approaches are studied to obtain soft-bit information. The first one uses a minimum mean-square error (MMSE) equalizer followed by multiple scalar soft-bit demappers. The second one involves a list sphere decoding (LSD) detector and a vector demapper. Though the later approach can have excellent performance, its computational complexity is high. To solve the problem, we then propose a new coding-modulation scheme, referred to as tone-interleaved coded modulation (TICM). Different from BICM, TICM merges the soft-bit demapping process into the Viterbi structure. The LSD algorithm can also be applied in TICM resulting in a low-computational algorithm. Simulations with the 802.11n system show that while the computational complexity of the demodulation of TICM is lower than that of BICM, its performance can be much better.