Modified Coded Frequency/Phase Modulation in the Fading Channel

• Main Authors: Hsiao,Wen-Son, 蕭萬松
• Other Authors: Chang,Yuh-Huu
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/91056602813486973416

碩士 === 中原大學 === 電子工程學系 === 82 === We introduce trellis-coded modulation(TCM),used for data communication with the purpose of gaining noise immunity over uncoded transmision without altering the data rate. TCM is a combined coding and modulation scheme for improving the reliability of a digital transmission system without in increasing the transmitted power or the required bandwith. In a power-limited enviroment,the desired system performance should be achived with the smallest possible power.One solution is the use of error-correcting codes,which increase the power efficiency by adding extra bits to the transmitted symbol sequence. FPM is a scheme which combine FSK and PSK modulation and use of trellis coding and Viterbi decoding to improve error performance over uncoded modulation.The coding gain is a function of the amount of memory introduced by the encoder,i. e., the constrant length,and of signal positioning of the signal point in the signal space,i.e.,the signal constellation. FPM is so enlarge the intra-distrance of signal constellation so as to enhance coding gain. MTCM is implemented by an encoder with b binary input bits ans s binary output bits that are mapped into k M-ary symbols in each transmission interval.The parameter k is reference to as the multiplicity of the code since it represents the number of M-ary symbols allocated to each branch in the trellis diagram. The throughput is r=b/k bits/s/Hz,which,depending on the choice of b and k,may or may not be integer-valued. It is interesting to investigate,the value of trellis multiplicty k which enlarge the distance d2 as to improve coding gain. MTCM/FPM is a new scheme. It is combined two adventages which described for improved performance on the AWGN and Fading channel.