《01096103 IEEE High-Level Modulation and Coding for Nonlinear Satellite Channels 》.pdfVIP

616 IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. COM-32, NO. 5, MAY 1984 High-Level Modulationand Codingfor Nonlinear Satellite Channels EZIO BIGLIEN, SENIOR MEMBER, IEEE I Abstract-Currently, 4-PSK is the prevalent modulation formatin use essis provided byincreasing thenumber-of.-codedsymbols for digital satellite communications. To improve bandwidth efficiency, 8- instead of the bandwidth. To justify this, the Shannon capac- PSK could be used instead, but a higher power would be needed; to im- ity argument can be invoked [ 11 to show that, if the size of prove power efficiency, error-correcting codes could be used, but at the the channel alphabet is increased but the information rate is expense of a larger bandwidth. Recently, Ungerboeck111 has proposed a left unchanged, then the power efficiency will increase. Alter- class of codes in which a constellation of 2M signals is used to transmit natively, the same effect can be observed in a computational information at the rate of log, M bits per symbol, and has shown that cutoff rate ( R o )chart [21 ,as shown in Fig. 1, Itis seen that, coding gainsof up to several decibels canbe achieved onthe additive white onthe additivewhite Gaussian noise (AWGN) channel, the Gaussian noise(AWGN) channel withpoincrease in bandwidthoccupancy same information rate of 3 bits per symbol can be achieved and arelatively smalladded complexity. Thus,these co