無線區域網路802.11n內接收機的設計

Abstract

隨著近年來多媒體消費電子產品應用的蓬勃發展，因此也帶來了無線高速的多媒體傳輸需求。為了克服傳統無線系統傳輸容量的限制，多重輸入多重輸出-正交分頻多工(MIMO-OFDM)系統被引入為一個具期待性的技術。多重輸入多重輸出-正交分頻多工系統也已經被下一代高通量(High throughput)無線區域網路(Wireless Local Area Network，WLAN)的標準IEEE 802.11n所採用。藉由使用正交分頻多工技術，通量相較於原有系統WLAN 802.11a/b/g系統可以被大幅的提升，而且基地台的傳輸距離也可以增加。在此論文之中著重在根據EWC (Enhanced Wireless Consortium) HT(High throughput) WLAN 802.11n實體層技術提案設計出具整合性的內接收機演算法。整合的802.11n內接收機模擬效能是利用電腦模擬作為評估依據。而本論文目的為提供WLAN 802.11n接收機演算法一個參考設計依據。

內接收機可以分為幾個部份包含同步(初始同步與追蹤迴路)，IQ 不平衡補償，通道估計，以及資料的偵測。初始同步包含封包偵測、符元邊界粗估與細估、載波頻率的估計與補償；追蹤迴路則涵蓋載波頻率追蹤(相位追蹤)、取樣時脈偏移的追蹤與數位重採樣(Resampling)；IQ 不平衡補償演算法包刮IQ不平衡參數估計與補償的演算法；通道估計則是利用前置符元(Preamble)將不同天線的通道分離出來；資料的偵測除了一般的迫零(Zero-forcing)、最小均方誤差(MMSE)的等化方式外，縱向-貝爾實驗室多層空時(V-BLAST)也被用來解碼接收到的訊號。

In recent years, the booming multi-media consumer electronics applications bring about the demand of high speed media data wireless transmission. To overcome the transmission capacity limit of the traditional wireless systems, MIMO (Multiple Input/Multiple Output) is introduced as the most promising technology. Specially, the MIMO-OFDM technology has been adopted in the next-generation high throughput WLAN (wireless local area network) standard, namely IEEE 802.11n. By using MIMO-OFDM, the data throughput can be dramatically increased compared with the original WLAN 802.11 a/b/g, and the transmission distance to the base station could prolonged. This thesis is focused on the design of the integrated inner receiver algorithms for the proposal of EWC (Enhanced Wireless Consortium) HT (High throughput) WLAN 802.11n PHY layer. The performance of the integrated 802.11n inner receiver is evaluated by using computer simulation. This thesis is purposed to provide a reference design of the WLAN 802.11n receiver algorithms.

The inner receiver includes several parts: synchronization (initial synchronization and tracking loop), IQ imbalance compensation, channel estimation, and data detection. The initial synchronization is a composite of packet detection, coarse/fine timing synchronization, and coarse/fine frequency synchronization. In the synchronization tracking loop, there are the functions of residual frequency tracking (phase tracking), sampling frequency offset tracking, and digital resampling. The IQ imbalance compensation comprises the IQ imbalance parameters estimation and the compensation. The channel estimation is accomplished by using the preamble to extract each antenna-pair response. In the detection of data, in addition to the Zero-forcing and the MMSE equalization methods, the V-BLAST is adopted to decode the received data signal.