Abstract
Using advanced Forward Error Correction (FEC) and Adaptive Coding and Modulation (ACM) significant advances have been made to increase the capacity in terms of bits/symbol/Hz for satellite communications. The use of adaptive modems with advanced FEC can increase the capacity for two-way, spot-beam, satellite Internet systems by a factor of three to four over fixed-link based systems using DVB-S on the forward link.
Turbo Product Codes (TPC) and Low Density Parity Check (LPDC) codes permit higher-level modulation (8-ary and above) for providing capacities in the range of 2 to 3 bits/symbol/Hz using power levels that fall within the capability of spot-beam satellite systems. This capacity compares with the typical 1 bit/symbol/Hz for DVB-S using QPSK modulation and a concatenated Reed Solomon outer code with a Convolutional inner code. Gains that can be achieved using TPC and LDPC codes in conjunction with higher level modulations are presented as well as special framing techniques that can be utilized for ACM.
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