In this thesis, we propose a base-band downlink OFDM processor based on the 3GPP LTE. This processor supports scalable bandwidth for different OFDM modes. A low-cost sampling rate conversion is employed to obtain different sampling rates for different bandwidths. We also integrate a channel-aware low power FFT processor in the system, and the FFT processor can support a variable-length form 128-points to 1024-points. We design a reconfigurable channel interpolator for different channel environments to execute channel estimation. Besides, our system architecture includes symbol timing detection, timing recovery, and carrier recovery. Finally, the circuit architecture is designed and simulated and we use the cell-based design flow to obtain the synthesis result with TSMC 0.18μm cell library.

科技的日新月異，手機也開始追求著高傳輸率，以致影像傳輸的功能，而且還要在高速環境中，能有良好的收訊，而第四代手機系統也正追求著這樣的目標。目前第四代手機規格標準的競爭，非常激烈，最大的兩大競爭對手為Mobile Worldwide Interoperability for Microwave Access技術的標準，簡稱mobile WiMAX標準也就是IEEE 802.16e與3rd Generation Partnership Project Long Tern Evolution所使用的技術規格，簡稱3GPP LTE，這兩大對手的共通點在於其傳輸技術都是利用正交分頻多工存取技術(OFDMA)，而3GPP LTE期望能將傳輸率達到100M bps，並且接收機可以在時速250 km/hr高速移動下，正常接收。著眼於3GPP LTE的優勢，所以在本論文中，乃是根據3GPP LTE所提出的標準，設計了一個可以使用在不同傳輸頻寬下的正交分頻多工系統之基頻下傳接收機。其中包含了低成本的取樣頻率轉換處理器可以操作在不同的頻寬下得到不同的取樣頻率，來實現scalable bandwidth 概念。還有整合可感知通道低功率快速傅立業轉換器，此快速傅立業轉換器與一般常見快速傅立業轉換器相比約可降低36%的功率損耗，並且此傅立業轉換器可以支援FFT的大小從128點到1024點。以及在通道估測部份，我們設計了可重置通道估測內插器，利用polynomial interpolation，不同階數的內插方程式的組合，可以根據不同的通道環境下來使用，而我們主要模擬的環境有三種，一是small cells，二是urban area，以及 hilly terrain。另外還包括了符元時間偵測，取樣頻率同步，載波頻率回復等。最後我們完成其系統電路設計及模擬，然後根據cell-based設計流程，並且使用tsmc0.18μm cell library得到其合成的結果。

[1] http://www.wimaxforum.org/
[2] http://www.3gpp.org/
[3] WiMAX Forum Mobile System Profile, V1.2.0 Sept. 2006.
[4] 3GPP TR 25.814 V1.5.0 3GPP; Technical Specification Group Radio Access Network; Physical layer aspects for evolved Universal Terrestrial Radio Access.
[5] J. Heiskala & J. Terry, OFDM Wireless LANs: A Theoretical and Practical Guide, Sams Publishing, 2002.
[6] K. Pahlavan & A. H. Levesque, Wireless Information Networks, John Wiely & Sons, 1995.
[7] 3GPP TS 45.005 V5.3.0 (2002-04) “Radio Transmission and Reception.”
[8] S. Y. Liu and J. W. Chong, “A Study of joint tracking algorithms of carrier frequency offset and sampling clock offset for OFDM-based WLANs,” in IEEE 2002 International Conference on Communications, Circuits and Systems and West Sino Exposition, Chengdu City, China, Jun. 2002.
[9] T. D. Chiueh and P. Y. Tsai, OFDM Baseband Receiver Design for Wireless Communications, Wiley, September 2007.
[10] Ji-Woong Choi & Yong-Hwan Lee, “Optimum Pilot pattern for Channel Estimation in OFDM Systems,” IEEE Trans. Wireless Commun. vol.4, no.5, Sep. 2005.
[11] G. S. Lin, “Design of a Baseband Receiver for DVB-T Standard,” Master Thesis, Graduate of Institute Electronics Engineering, Nation Taiwan University, Taipei, Taiwan, p.95~p.99.
[12] C. M. Chen, “Channel-Aware Low-Power FFT Processor for 3GPP-LTE OFDMA Transmission,” Master Thesis, Graduate of Institute Electrical Engineering, Nation Tsing Hua University, Hsinchu, Taiwan.
[13] K. H. Chen, “Design and Implementation of an IEEE 802.15.4 Baseband Transceiver,” Master Thesis, Graduate of Institute Electrical Engineering, Nation Tsing Hua University, Hsinchu, Taiwan, p.62~p.63.
[14] F. J. Harris, Multirate Signal Processing for Communication Systems, Prentice Hall, May 2004.