The Design of Channel Estimator Using Preamble Signal in Turbo Code under the Rayleigh Fading Channel

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Title:	The Design of Channel Estimator Using Preamble Signal in Turbo Code under the Rayleigh Fading Channel
Authors:	Lee, Yang-Han;Gong, Pei-Min;Leu, Chu-Yang;Lo, Lun-Chieh;Chen, Meng-Hong
Contributors:	淡江大學電機工程學系
Keywords:	通道估測;前奏;渦輪碼;Rayleigh衰減;誤碼率;解碼演算法;信號雜音比;Channel Estimation;Preamble;Turbo Code;Rayleigh Fading;Bit Error Rate;Decoding Algorithm;Signal To Noise Ratio
Date:	1999-12
Issue Date:	2014-02-13 11:35:17 (UTC+8)
Abstract:	Turbo code has been discussed popularly at present because it's near optimal decoding performance. Although the decoding algorithms are proposed such as Soft Output Viterbi Algorithm (SOVA) and Log- Maximum A Posteriori (Log-MAP), they require to estimate the SNR(Eb/NO) of its transmission channel. In [1], the author has demonstrated that the errors of estimating SNR would effect the bit error rate (BER)performance of the turbo code. Therefore, some authors propose their methods to estimate the SNR [2][3], but they are more complicated than our proposal.In the transmission packet, the preamble signals are used for synchronization which were known by the transmitter and receiver. This information would be interfered by noise and channel fading, therefore, after taking off the original preamble signal from the received information, the SNR can be estimated using the remnant information.In this paper, we simulate the BER performance using the preamble signal as the estimator 's input in the AWGN and Rayleigh fading channel, which is modeled using Smith method [5] [6].Besides, the SOVA decoding algorithm was used and each received signals were decoded for 6 iterations which block size = 8192 bits, constraint length K=3, code rate R=l/3 for un-punctured, code rate R=l/2 for punctured, and the preamble length is 144 bits which is referred to the IEEE 802.11 WLAN ( Wireless Local Area Network) system. In Figure 1, we compare two BER performances as the code rate R=l/3: one is using our method to estimate the SNR (which denoted as unknown) and another is that the SNR is known in the ideal case (which denoted as known). From the simulation results we can find that the performance of our method is very closed to the performance which SNR is known. We also simulate the BER performance as the code rate R=l/2 (punctured)in Figure 2. The simulation results are similar as Figure 1 shown. Finally, we will also simulate our estimated method using the Log-MAP algorithm as the decoder.
Relation:	第二屆一九九九無線電科學研討會論文集=Proceedings of the Second (1999) Radio Science Symposium，頁108-109
Appears in Collections:	[Graduate Institute & Department of Electrical Engineering] Proceeding

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