MIMO-OFDM收發機與V-BLAST之DSP實現

Abstract

OFDM為IEEE 802.11a標準所採用之調變技術，其高傳輸速率、高頻譜效益、及優異的抗多重路徑衰減能力等優點，使其成為現階段無線通訊中最受矚目的傳輸技術之一。在本論文中，吾人使用Aptix® MP3C為系統發展平台，整合DSP、USB與FPGA模組，實現MIMO-OFDM空間分集式與空間多工式收發機架構。DSP具有高速定點、浮點運算功能與彈性修改、即時驗證特性，可提供即時之訊號處理。本論文的重點在以DSP實現MIMO-OFDM通道估計器、相位追蹤器、空時區塊解碼器、V-BLAST及迴旋碼解碼器等。通道估計器與空時區塊解碼器可藉由多根天線產生之分集式增益，提高估計結果之正確性；相位追蹤器可彌補系統之殘餘頻率錯誤；空間多工式系統之V-BLAST可達到干擾消除之效果；迴旋碼解碼器則可修正錯誤位元，強化系統之效能。吾人以DSP為發展核心，引入軟體無線電之概念，透過DSP程式之參數控制，輕易地達成分集與多工模式間之切換。

OFDM is a modulation scheme adopted by the IEEE Std. 802.11a , which provides high data rate, high spectral efficiency, and high resistance to multipath fading. These make it one of most popular transmission technologies. In this thesis, we will use Aptix® MP3C as a system development platform, which integrates DSP, USB, and FPGA modules, to realize the MIMO-OFDM spatial diversity and spatial multiplexing transceiver architecture. DSP provides high speed fixed-point and floating-point operations, flexible modification, and quick verification, which make it suitable for real-time signal processing. This thesis will focus on the DSP realization of channel estimator, phase tracking, space-time block decoder, V-BLAST, and convolutional decoder in the MIMO-OFDM system. In particular, the channel estimator and space-time block decoder can obtain a diversity gain from multiple antennas to improve their accuracy. The phase tracking can compensate for the residual frequency errors. The V-BLAST in the spatial multiplexing mode can achieve interference cancellation. Finally, The convolutional decoder can correct erroneous bits to enhance system performance. With the concept of software-defined radio incorporated, we use DSP as a development core, to easily switch between the diversity and multiplexing modes by parameter control of DSP programs.