應用多重輸入多重輸出－正交分頻多工技術之高速無線區域網路基頻收發機設計

下世代無線區域網路將提供多樣化的多媒體服務，包括高畫質電視（High Definition TV, HDTV）、網路互動式遊戲（interactive gaming）等。欲達成這些目標，我們必須在有限的頻寬內追求更高的傳輸速度( throughput )以及更穩定的傳輸品質( QOS )。在一般無線通訊通道的非平坦衰減下，應用多重輸出多重輸出－正交分頻多工技術( MIMO-OFDM )可以有效提升通道容量，且提供空間多樣性，因此非常具有潛力成為關鍵技術。本篇論文的重點就是提出一個高傳輸速度的2x2 MIMO-OFDM基頻收發機，以適用於未來的高速無線區域網路。我們依據IEEE 802.11 TGn的功能要求，提出了實體層的OFDM參數以及速度參數，並設計一封包格式利於接收機的同步及通道估計運作。接收機的主要架構分為同步、通道估計以及資料回復。其中同步是藉由前置碼與領航碼來達成，執行工作包括有封包偵測、符元邊界的粗調與細調、分數載波頻率偏移的估計與重估計、殘餘分數載波頻率偏移以及殘餘取樣時間偏移的聯合估計並追蹤。而通道估計是利用低複雜度的線性組合來進行最小方差估計，且在低訊噪比的情況可以配合頻域平均來提升估計表現。資料回復會選擇不同的等化演算法，分別因應MIMO傳輸方式為2x2 VBLAST或是2x2 STBC。之後再透過偵測、反交錯、外部解碼以及反攪亂來計算封包錯誤率。另外，在最高速度模式中，系統可以對資料進行空間、時域及頻域上展開，增加多樣性來提升系統表現。最後，我們藉由相關性衰減的MIMO通道，加上各種不完美效應，來模擬系統表現。在兩倍的IEEE 802.11a傳輸速度下，我們提出並比較封包錯誤率0.1所需操作的訊噪比。

關鍵字

通道容量；無線區域網路；時空編碼；多重輸出；高速；多樣性；空間多工傳輸；封包格式；正交分頻多工；收發機架構；多重輸入

並列摘要

Due to increasing demand on new multimedia application, such as HDTV and interactive gaming, next generation wireless LAN will focus on high throughput and QOS within limited bandwidth. Multiple-input multiple-output (MIMO) signal pro- cessing techniques combined with orthogonal frequency division multiplexing (OFDM) can provide a high throughput link as well as an increased diversity gain in frequency selective fading channels, and is therefore regarded as a promising solu- tion in the future IEEE 802.11n standard for high throughput wireless LAN. In the thesis, we propose a MIMO-OFDM baseband transceiver design using two transmit antennas and two receive antennas for high throughput wireless LAN. According to the functional requirement of backward compatibility by IEEE 802.11 TGn, we set the OFDM parameters to be same with the IEEE 802.11a standard. Moreover, we design a packet format suitable for receiver algorithms such as timing synchronization, frequency synchronization, and channel estimation. A MIMO- OFDM receiver is accordingly designed and implemented in cycle-based C code with complete algorithms including initial synchronization, tracking, channel esti- mation, and MIMO equalization. Finally, we use IEEE 802.11 TGn channel model D to simulate the correltated fading channel. Under different kinds of channel impairments such as PA non-linearity, carrier frequency offset, phase noise, I/Q imbalance, timing offset and DC offset, simulation results verify the desired signal to noise ratio for the proposed receiver to attain double transmission rate of the current IEEE 802.11a wireless LAN standard.

並列關鍵字

channel capacity ； OFDM ； MIMO ； LAN ； High Throughput ； Spatial Multiplexing ； Transceiver architecture ； Space-Time code ； Packet format ； 802.11n ； pre802.11n ； diversity ； Wireless

參考文獻

[3.20] L. Schumacher “Matlab program,” contact Laurent Schumacher at lsc@info.fundp.ac.be

[1.3] IEEE 802.11, IEEE Standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, Nov. 1997

[1.6] IEEE 802 11-03/813r9 TGn Functional Requirements

[2.3] David Gesbert, Mansoor Shafi, Da-shan Shiu, Peter J. Smith, and Ayman Naguib, "From Theory to Practice: An Overview of MIMO Space–Time Coded Wireless Systems," JSAC, pp. 281－302, 2003

[2.4] Goldsmith, A., Jafar, S.A., Jindal, N., Vishwanath, S., "Capacity limits of MIMO channels," JSAC, pp.684－702, 2003

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應用多重輸入多重輸出－正交分頻多工技術之高速無線區域網路基頻收發機設計

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