以FPGA為基礎之WiMAX內接收器設計與實現

FPGA-based Inner Receiver Design and Implementation for WiMAX

陳伯奇(Po-Chi Chen)

指導教授 ： 鐘太郎 ； 丁原梓

國立清華大學/電機資訊學院/電機工程學系/碩士(2006年)

https://doi.org/10.6843/NTHU.2006.00584

摘要

在無線通訊系統中，是利用大氣環境作為媒介來傳遞訊號，因此在傳遞的過程中，會有許多的干擾，如多路徑效應、通道衰減、都卜勒效應、路徑損失、遮蔽效應、高斯雜訊等的通道效應而使訊號失真。除了通道的影響外，電路本身也會產生非理想的效應，如載波頻率的漂移、取樣頻率的偏差等，而使訊號失真。在OFDM系統中，是利用數位電路的方式，在基頻部分進行非理想效應的估測及補償，而使接收端能精確的還原傳送端的訊號。在ODFM系統的同步過程中，首先會在時域做封包偵測來判斷是否接收到訊號，接著進行頻率漂移的估測以及OFDM訊號邊界的估測。經過FFT運算後，在頻域進行通道估測與補償，以及載波頻率追蹤，上述這些工作都是由內接收器(inner receiver)所完成。經過這些運算後，使得非理想效應的影響大幅縮減，再經過Reed Solomon，Viterbi等錯誤更正運算後，可以重建原本的資訊。本論文的目標，是設計用來進行同步運算的內接收器，首先經過理論探討整個內接收器所需之演算法後以MATLAB軟體模擬同步過程所需的演算法，分析同步的效能並加以調整，最後將這些演算法以硬體電路的方式實現，並利用FPGA驗證其設計的正確性，來評估此同步電路設計的可行性，實驗結果證明所設計的內接收器在功能及速度上確實達到Wimax規格的要求。

關鍵字

WiMAX ； 內接收器 ； 同步

並列摘要

In wireless communication system, air is the medium of signal propagation. There are many channel effects in signal propagation that distort transmitted signal, such as multi-path, fading, Doppler effect, path-loss, shadowing, AWGN, and so on. Except channel effects, the hardware circuit itself has some effects in distorting the transmitted signal such as carrier frequency offset, sampling frequency drift, etc. We can recover the transmitted signal from the received distorted signal precisely with some estimation and compensation, which is developed by digital signal processing in base-band, at the receiver. In the synchronization process, the receiver performs packet detection in time domain to judge whether the signal is received or not. Then the receiver precedes the estimation of frequency offset and OFDM symbol boundary. After FFT operations, the receiver estimates and compensates for the channel effect in frequency domain, and tracks the carrier phase. These works described above are completed by the inner receiver. After these operations, the non-ideal channel effects are reduced substantially. Moreover, the original information can be reconstructed by error correcting code, such as Reed Solomon and Viterbi. In this thesis, our goal is to design and implement the inner receiver for signal synchronization. First, we investigate theoretically the algorithms for inner receiver. Then, we simulate the algorithms for synchronization, analyze the performance and adjust the algorithms by using MATLAB. Finally, we implement these algorithms by hardware circuit, verify the design and evaluate the synchronization performance with FPGA. The experimental results verify that our design of inner receiver actually achieves the WiMAX specification in function and speed.

並列關鍵字

WiMAX ； Inner receiver ； Synchronization

參考文獻

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