Rateless codes for slant path free space optical channels

The application of packet-level rateless codes for slant path free space optical (FSO) links is studied. From the compromise between the code rate and decoding complexity, the raptor codes with moderate block length is considered and the corresponding coding scheme is presented. Two decoding strategies are discussed: maximum-likelihood (ML) decoding and erasure decoding. The decoding performance for these two decoding strategies is compared by calculating their error exponents, and erasure decoding is illustrated to work better in view of reliability. Numerical results indicate that our considered rateless codes with such erasure decoding can always automatically achieve the code rate very close to channel capacity for the slant path FSO links.