Abstract
WiMAX(Worldwide Interoperability for Microwave Access) and Wi-Fi are based on the IEEE 802.16 standard and the IEEE 802.11 standard, respectively with that the IEEE 802.11n standard supports Multiple-Input Multiple-Output (MIMO) technology. Both the WiMAX/IEEE 802.16 and the Wi-Fi/IEEE 802.11n standards have employed orthogonal frequency division multiplexing (OFDM) technology, that is regarded as a prospective modulation strategy, with great bandwidth efficiency and invulnerability to non-ideal channels.FFT processor is the key module in the all OFDM communication systems. The specifications of WiMAX, scalable channel bandwidths by adjusting FFT size are employed for different applications, and Wi-Fi standard supports MIMO technology. However, it imposes a great challenge on the design of the key component, a dual mode Fast Fourier Transform (FFT) processor with acceptable hardware cost.In this thesis, we propose a configurable and power-efficient FFT processor that is composed of the 4-path-SDF module and the multibutterfly module. The multibutterfly module can operate the radix-2, radix-2^2, radix-2^3, or radix-2^4 butterfly according to different FFT sizes. The 4-path-SDF module can deal with simultaneously the four 128-point FFTs with faster operation speed and higher throughput. Besides, an efficient memory-accessing scheme is proposed and a constant-based multiplier unit is adopted to achieve low complexity, small hardware area, and lower power consumptions. Also, the dynamic scaling method is adopted in the proposed architecture, which can truncate timely the longer word-length such that the word-lengths of data are not increased continuously. The proposed FFT processor, supporting two kinds of wireless communication system standards Wi-Fi (IEEE 802.11n) and WiMAX (802.16e), is implemented by using Faraday 90nm cell library in a UMC 90nm 1P9M CMOS process. The word-length, area in gate level simulation, and power are, respectively, 12 bits, 1,105,584 um^2, and 6.84mW at 20MHz. The SQNR is 33.9247dB when performing the 2048-point FFT. And it only needs 1.325N-word two-port memory, where N is 2048, for continuous flow design. Therefore, the proposed FFT processor is a promising solution to the implementation of OFDM-based WiMAX and Wi-Fi systems in the future.