| Summary: | 碩士 === 國立臺北科技大學 === 電腦與通訊研究所 === 97 === In this paper, We discuss how to decrease TBCC(Tail-Biting Convolutional Codes) memory and maintain optimal error rate in channel coding system of 802.16e OFDMA(Orthogonal Frequency-Division Multiple Access ; OFDMA) standard. We use AWGN (Additive White Gaussian Noise) channel and Rayleigh fading channel as the simulation environment. TBCC decoder adopts soft-decision, the optimal TBCC decoder adopts maximum likelihood decoding algorithm, although it has the optimal error rate, but it needs high complexity and memory demand. To decrease system complexity and memory demand, we combine circular viterbi decoder with sliding window, and it''s suitable for hardware implementation. However, the adding length of sliding window and tail are affected by other factor such as code rate, modulation, encoding block length and channel environment. So we find and suitable length of sliding window and tail in different channel environment. The factor is according to 802.16e OFDMA standard. This result can be referred for har ware implementation.
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