IEEE 802.11b無線區域網路收發機之演算法設計及效能評估

Abstract

在多媒體通訊中，提供高速資料傳輸服務的需求日漸增加。因此，使用操作於2.4 GHz ISM頻段之IEEE 802.11b無線區域網路(Wireless Local Area Network, WLAN)將成為未來之重要趨勢。IEEE 802.11b可同時提供分別為1 Mbps、2 Mbps、5.5 Mbps及11 Mbps的傳輸率。為了滿足多媒體高速傳輸之要求，所使用的調變技術分別為互補碼鍵(Complementary Code Keying, CCK)與封包二元迴旋碼(Packet Binary Convolutional Coding, PBCC)。在本論文中，吾人將介紹互補碼鍵解調器，如相關器(correlator)與快速華許轉換(Fast Walsh Transform, FWT)，並討論兩者之間的差異性。在多重路徑(multipath)環境下，吾人將利用前置訊號與單週期虛擬雜訊序列相關性估測之方法估測出通道脈衝響應(channel impulse response)。接著，吾人以估測出之通道脈衝響應分別作為犁耙接收機與後標記多路徑消除法(Post-Cursor Multipath Cancellation)之權值，以提升整體系統效能。

There is an increasing demand for high data rate services in multimedia communication. To this end, wireless local area networks operated in the 2.4 GHz ISM band such as IEEE 802.11b will be a future trend. IEEE 802.11b provides four kinds of data rate: 1 Mbps, 2 Mbps, 5.5 Mbps and 11 Mbps. In order to satisfy high data rate transmission, it uses the Complementary Code Keying (CCK) and Packet Binary Convolutional Coding (PBCC) as its modulation scheme. In this thesis, we will introduce two kinds of CCK demodulators, correlator and Fast Walsh Transform (FWT), and then investigate their difference. In multipath environments, we will estimate the channel impulse response using the preamble based method and single period correlation of pseudo noise. We then use these estimated channel coefficients as the weights for the RAKE receiver and Post-Cursor Multipath Cancellation to enhance overall system performanc