A High Efficient FFT Processor for WiMAX/WLAN Applications

適用於全球互通微波存取與無線區域網路應用的高效率快速傅立葉轉換處理器

鄭嘉寶(Jia-Bao Cheng)

指導教授 ： 張慶元

國立清華大學/電機資訊學院/電機工程學系/碩士(2010年)

摘要

With the lifestyle changes, the wireless communication plays an important role in our life. The orthogonal frequency division multiplexing (OFDM) has excellent bandwidth efficiency and invulnerability to non-ideal channels, so it usually applies in the wireless communication system. And the fast Fourier transform (FFT) is the key module for the hardware implementation of OFDM.
In this thesis, a high efficient FFT processor is proposed. The FFT processor supports two systems, WiMAX and WLAN, and resolves the difference of two wireless communication systems in an efficient way. For an efficient transformation of two systems, the multi-path delay feedback (MDF) is introduced into the memory-based architecture. To lower the power consumption, the interleave cache is proposed. With the employed FFT algorithm, interleave cache reduces not only the power consumption but also the hardware cost of non-trivial multiplication. And the main memory, a more complex memory control is used to gain higher hardware efficient and lower power consumption.
The proposed FFT processor is implemented by TSMC 0.18um process, and the area is 4.177mm2. The power consumption is 37.39mW in the WiMAX application, and 69.39mW in the WLAN application. The WiMAX processes two-stream 2048 point FFTs at 20MHz, and the WLAN processes 4-stream 128 point FFTs at 40MHz.

關鍵字

快速傅立葉轉換 ； 正交分頻多工

並列摘要

隨著時代的演進，無線通訊在人類生活中占有其重要性。正交分頻多工(OFMD)擁有極佳的頻寬使用效率以及對抗非理想通道的能力，因此經常的使用在無線通訊技術當中。而快速傅立葉轉換(FFT)則是使正交分頻多工在硬體實現方面最重要的關鍵。
在本論文中，提出一個高效率的快速傅立葉轉換處理器。此快速傅立葉轉換處理器支援WiMAX以及WLAN兩種不同的無線通訊系統，也有效率的解決兩個無線通訊系統之間的差異。為了有效率的在兩系統之間轉換，一個多路徑延遲回授(multi-path delay feedback)架構引進於一個以記憶體為基礎(memory-based)的快速傅立葉轉換處理器。在降低功率消耗方面，一個分離式快取(interleave cache)記憶體的提出使用，配合所使用的演算法，不僅僅可降低功率消耗，也可以降低複數乘法器的使用。至於主要記憶體部分，利用較複雜的記憶體存取方式來爭取較高的硬體使用效率以及較低的功率消耗。
此快速傅立葉轉換處理器是使用TSMC 0.18um製程，其面積為4.177mm2。在功率消耗方面， WiMAX的應用是處理操作在20MHz兩路徑2048點FFT運算，其為37.39mW，而WLAN應用是處理操作在40MHz四條路徑128點FFT運算，其為69.39mW。

並列關鍵字

FFT ； WiMAX ； WLAN ； MDF ； Cache memory

參考文獻

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