臺灣博碩士論文加值系統

在無線通訊系統中，常會使用高階調變技術來增加系統之資料傳輸量(data throughput)，並使用錯誤更正碼(error-correcting codes)技術來提高系統之性能(performance)表現，通常還會伴隨著位元交錯 (bit interleaving)技術來克服無線通道中之連續錯誤(burst errors)，來更有效地增加系統之整體效能，這類之通訊系統被統稱為BICM (Bit Interleaved Coded Modulation)系統。而在寬頻無線行動通訊系統中， 無線通道由於多路徑干擾而造成的選擇性頻率衰落(frequency-selective fading)，會對寬頻傳輸產生嚴重的影響，而使用正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM)技術，即可有效克服無線通道之多路徑干擾問題，並且能節省頻寬與簡化接收端等化器的複雜度，近幾年已被廣泛運用於無線通訊系統之中。雖然在系統中使用交錯技術可改善系統之解碼效能，但也付出了硬體成本(hardware cost)以及時間延遲 (latency delay)的代價。在本論文中，我們提出兩個方法，在不使用交錯技術的情況下，可使系統具有交錯的效果，並節省交錯技術所產生的時間延遲與硬體花費。首先，針對BICM系統，提出一個具有交錯特性的錯誤更正碼新架構。此新架構在傳送端使用N層之現有錯誤更正碼編碼器，如里德-所羅門碼(Reed-Solomon code)、旋積碼(convolutional code)等，在接收端也採用N 層之解碼器來構成。以現有之編解碼技術，新架構便可提高N 倍之編解碼速度，同時，新架構具有交錯之特性，與傳統之BICM 系統相比，將可省去交錯器(interleaver)與解交錯器(deinterleaver)之硬體成本與時間延遲。其次，在使用OFDM 調變的系統中，實現OFDM 調變最簡單的方法，便是以N 點之IFFT 與FFT 運算來完成其硬體實現，當使用N點radix-r 之IFFT 與FFT 來實現OFDM 之調變與解調，藉由省略IFFT 與FFT 硬體架構中第一層運算之排序電路，便能使系統獲得一大小為(N/r)×r 之等效交錯效果，並因此省去交錯技術與排序電路原本所需花費之時間延遲與硬體成本。

In wireless communication systems, the techniques of high-level modulation, error correction coding, and interleaving are often used. The use of high-level modulation can increase the transmission throughput and bandwidth efficiency of the systems. The error correction coding techniques can improve the system performance. And the interleaving techniques can further improve the decoding performance for the wireless channels with burst errors. Besides, the OFDM modulation technique is generally used to overcome the problem of multi-path interference under frequency-selective fading channel without using complex equalizer. Although the techniques of interleaving can deal with burst errors and improve the decoding performance, the advantage is achieved by adding hardware complexity and latency delay to the systems that use interleaving techniques. And longer latency delay will seriously affect the quality of some real-time communication systems. Therefore, this paper proposes two methods. The first is a new error-correcting architecture with the effect of interleaving for high speed wireless communication systems which may provide hundreds of Mbps or several Gbps in the future. In this architecture, N FEC encoders and decoders are used in parallel in the transmitter and receiver respectively. Using the present decoding schemes, the decoding speed can be increased N times. Furthermore, compared with the conventional interleaved code modulation systems, the proposed architecture has the effect of interleaving without the cost of hardware complexity and latency delay of the interleaver and deinterleaver. The second is a new FFT architecture for systems that use OFDM modulation technique. When the system adopts N-points radix-r IFFT and FFT to implement OFDM modulation and demodulation, the system can get an equivalent interleaving affect of (N/r)×r by using this new FFT architecture. Thus, the system can also save the cost of hardware and latency delay of the interleaver and deinterleaver.

中文摘要 ………………………………………………………………………Ⅰ ABSTRACT ………………………………………………………………………Ⅱ 總目錄 ……………………………………………………………………………Ⅲ 圖目錄 ……………………………………………………………………………Ⅳ 表目錄 ……………………………………………………………………………Ⅴ 第一章 序論 ……………………………………………………………………1 1.1 簡介 ………………………………………………………………1 1.2 交錯技術之簡介 ……………………………………………………2 1.3 區塊交錯與迴旋交錯技術 …………………………………………4 第二章 具交錯效果之高速編解碼系統架構 …………………………………11 2.1 傳統BICM 系統概述 ……………………………………………11 2.2 具交錯效果之高速編解碼架構概述 ……………………………12 2.3 具交錯效果之高速編解碼架構使用範例 ………………………15 2.4 系統效能模擬與比較 ……………………………………………19 第三章 適用於OFDM 系統中具交錯效果之FFT 架構 ………………………22 3.1 OFDM 系統與FFT ……………………………………………22 3.2 具交錯效果之FFT 架構 … … … … … … … … … … … … … 2 5 3.3 系統效能模擬與比較 ……………………………………………29 第四章 結論 …………………………………………………………………32 參考文獻 ………………………………………………………………………34 III

[1] IEEE Std 802.11, 1999 Edition, Part 11: Wireless LAN Medium Control (MAC) and Physical Layer (PHY) specifications. LAN/MAN Standards Committee of the IEEE Computer Society, Sep. 1999. [2] IEEE Std 802.11b-1999, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-Speed Physical Layer Extension in the 2.4GHZ Band. LAN/MAN Standards Committee of the IEEE computer society. Sep. 1999. [3] IEEE Std 802.11a-1999, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5 GHZ Band. LAN/MAN Standards Committee of the IEEE computer society. Sep. 1999. [4] IEEE Std 802.11g-2003, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications. Amendment 4: Further Higher Data Rate Extension in the 2.4 GHZ Band. LAN/MAN Standards Committee of the IEEE computer society. June 2003. [5] Bernard Sklar, Digital Communication: Fundamentals and Applications. New Jersey: Prentice-Hall, 2001. [6] S. Lin and D. J. Costello Jr., Error Control Coding: Fundamentals and Applications. New Jersey: Prentice-Hall, 1983. [7] G. Caire, G. Taricco, and E. Biglieri, “Bit-interleaved coded modulation,” IEEE Trans. Inform. Theory, vol. 44, pp. 927~946, May 1998. [8] Xiaodong Li, Aik Chindapol, and James A. Ritcey, “Bit-interleaved coded modulation with iterative decoding and 8PSK signaling,” IEEE Trans. on Communications, Vol. 50, No. 8, pp. 1250-1257, Aug. 2002. [9] J. W Cooley and J. W. Tukey, “An algorithm for the machine calculation of complex Fourier series,” Math. Comput., vol. 19, pp.297–301, 1965. [10] E. E. Swartzlander, W. K. Young, and S. J. Joseph, “A Radix 4 Delay Commutator for Fast Fourier transform processor implementation,” IEEE J. Solid-State Circuits, vol. SC-19, pp. 702~709, No. 5, Oct. 1984. [11] J. García, J. A. Michell, and A. M. Burón, “VLSI Configurable Delay Commutator For A Pipeline Split Radix FFT Architecture,” IEEE Trans. on Signal Processing, vol. 47, No. 11, Nov. 1999.