碩士 / 國立交通大學 / 電子工程系所 / 93 / OFDM (orthogonal frequency division multiplexing) technique has drawn much interest recently for its robustness in the mobile transmission environment and its high transmission data rate. IEEE 802.16a is a wireless local and metropolitan area networks standard which is based on OFDMA (orthogonal frequency division multiple access) technique.
This work considers two main subjects of the downlink channel estimation under the specifications of IEEE 802.16a, the interpolation schemes and the DSP implementation.
We use LS estimator for estimations of pilot carriers because of its low computational complexity. We study the linear, the second-order interpolations in frequency domain and the LMS adaptation algorithm, the two-D interpolation in time domain. We did the simulation on both static and Rayleigh fading channels. Combination of linear interpolation and 2-D interpolation are chosen to be implemented on DSP board for its low computational complexity.
Our implementation is software-based, employing Texas Instruments’ TMS320C6416 digital signal processor (DSP) housed on Innovative Integration’s Quixote cPCI card. For the fixed-point DSP operation environment, floating-point operation is absolutely time-consuming. There are three ways to accelerate the DSP execution speed: changing data type, code style optimization, and using intrinsic functions. Changing data type means we replace the original floating-point operation with 32-bit fixed-point operation and then 16-bit fixed-point operation at last. Code style optimization is to modify the time-wasting parts of code, such as spared if-else instruction. Intrinsic functions are special functions that map directly to C64x instructions, to optimize our C code performance. The execution cycles of each function is improved a lot after optimized although compared with the theoretical execution cycles, the efficiency is 49% at most. At least, we reach the 0.52 multiples of real time needed per symbol in linear interpolation.
| Identifer | oai:union.ndltd.org:TW/093NCTU5428084 |
| Date | January 2005 |
| Creators | Ruu-Ching Chen, 陳汝芩 |
| Contributors | David W. Lin, 林大衛 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 109 |
Page generated in 0.0021 seconds