在電力線通訊PLC(Power Line Communication)的傳輸環境裡，充滿著各式各樣的脈衝雜訊(Impulse Noise)，這些脈衝雜訊與傳統雜訊AWGN(Additive White Gaussian Noise)最大的不同點，在於脈衝雜訊的能量往往是AWGN 雜訊的數十倍或數百倍以上。基於這個原因，現今的處理方式為在對訊號做軟式解碼(Soft Decision)前做個裁減(Clipping)的動作，以減少雜訊的影響。本文著重於對訊號的量測，且在傳輸前端與接收後端分別加上編解碼演算法，以達到降低傳輸錯誤率的目的。
本文所採用的錯誤更正碼是里德-所羅門碼(Reed-Solomon codes，簡稱RS codes)。RS codes 已經廣泛被運用在各項通訊系統，本文所使用的編碼長度分別為31、63、127，針對每一種不同長度的碼長，都採用三種不同的碼率(Code Rate)，分別約為0.25、0.5、0.75。透過使用的德州儀器開發板TMDSPLCKIT-V3 去做實際測試，並且採用電力線標準PRIME(PoweRline Intelligent Metering Evolution)，使這次研究可以更加適切的選擇調變方式、傳輸信號功率與傳輸封包大小，最後就各種實際傳輸情況做比較，比較位元錯誤率(BER)與訊雜比(SNR)的結果。

It is well known that power line communication suffers very severe different
kind of noise such as background noise (Additive White Gaussian Noise) and impulse noise. The difference between impulse noise and Additive White Gaussian Noise(AWGN) is that the power of impulse noise is usually ten times or even hundred times greater than that of AWGN. Accordingly, Clipping method, before executing soft decision decoding, to input signal is employed in order to reduce the influence of impulse noise. In this thesis, we focus on the detection of signal, adding encoding algorithm, and decoding algorithm in the system to reduce the bit error rate (BER) after receiving the signal at the receiver.
In this thesis, we adopt Reed-Solomon (RS) codes to be the error correcting codes implemented in the system. RS codes have been widely implemented in many different communication systems. In our experiment, code word lengths 31, 63 and 127 are implemented. Three different code rates, which are around 0.25, 0.5 and 0.75 for each code word length, are simulated on power line modem developer’s kits (TMDSPLCKIT-V3) from Texas Instrument. According to PoweRline Intelligent Metering Evolution (PRIME), we can easily choose the proper modulation, the signal power level, and the package size to perform our experiments. Finally, we make a comparison of BER for all implemented codes at several signal to noise ratios (SNRs) over real power line transmission.

[1] S. Lin and D. J. Costello, Error Control Coding, Second Edition, Prentice-Hall,2004.
[2] Specification for Power Line Intelligent Metering Evolution, PRIME Alliance Technical Working Group, Oct.2014.
[3] Martin Hoch, “Comparison of PLC G3 and PRIME,” IEEE International
Symposium on Power Line Communications and Its Applications, Erlangen-Nuernberg, Germany, pp. 165-169, 2011.
[4] Il Han Kim., Varadarajan B., & Dabak A., “Performance Analysis and
Enhancements of Narrowband OFDM Powerline Communication Systems,”
Paper presented at the Smart Grid Communications, First IEEE International
Conference, 2010.
[5] MR. Sandesh Y.M and Mr. Kasetty Rambabu, “Implementation of Convolution
Encoder and Viterbi Decoder for Constraint Length 7 and Bit Rate 1/2,” Journal
of Engineering Research and Applications, vol. 3, no. 6, pp. 42-46 Nov-Dec
2013.
[6] Robert H. Morelos-Zaragoza, The Art of Error Correcting Coding., John Wiley & Sons, Inc., 2002.
[7] T.K. Moon, Error Correction Coding: Mathematical Methods and Algorithms.
John Wiley & Sons, Inc., 2005.
[8] TI PLC Development Kit User Guide, Ver 0.7, April 9, 2012
[9] Haykin, Digital Communications, John Wiley and Sons, 1988
[10] Wicker, S. and V. Bhargava. “An Introduction to Reed-Solomon Codes”.
Reed-Solomon Codes and Their Applications, Wiley-IEEE Press: 1-16.
[11] Kazakov, P, “Fast calculation of the number of minimum-weight words of CRC codes,” Information Theory, IEEE Transactions on 47(3), pp. 1190-1195, 2011
[12] Koetter, R. and A. Vardy, “Algebraic soft-decision decoding of Reed-Solomon codes,” Information Theory, IEEE Transactions on 49(11), pp. 2809-2825. 2003
[13] Forney, G. D, “On decoding BCH codes,” Information Theory, IEEE
Transactions on 11(4), pp. 549-557, 1965