| Summary: | 碩士 === 國立交通大學 === 電子工程系所 === 95 === OFDMA (orthogonal frequency division multiple access) technique has drawn much interest recently in the mobile transmission environment and been successfully applied to a wide variety of digital communications applications over the past several years. One of the main reason to use OFDMA is its robustness against frequency selective fading and narrowband interference. We focus on the OFDMA uplink and downlink channel estimation based on IEEE 802.16e. We also implement these channel estimation schemes on Texas Instruments’ TMS320C6416 digital signal processor (DSP) housed on Sundance board.
The channel estimation schemes can be separated into three steps. First, we use LS estimator on pilot subcarriers because of its low computational complexity. Second, we estimate the channel response on data subcarriers using linear interpolation in the frequency domain. Finally we try time averaging technique to improve the performance in the time domain. We verify our simulation model on AWGN channel and then do the simulation on SUI-2 and SUI-3 multipath channels.
In uplink transmission, we propose the tile linear interpolation and as for downlink, we use the 2-point, 4-point and advanced 4-point cluster linear interpolation. In order to increase the efficiency on DSP, we rewrite the floating-point C program to fixed-point version and further refine our codes by considering the features of the DSP chip.
In this thesis, we first introduce the standard of the IEEE 802.16e OFDMA uplink and downlink and the DSP implementation environment . Then we describe the channel estimation methods we use and discuss the performance and the DSP implementation results in each transmission condition.
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