This package implements Raptor and Luby Transform (LT) erasure correction codes in the Julia language. In particular, it implements Raptor10 codes (specified in rfc5053) and RaptorQ codes (specified in rfc6330). The LT code implementation does not follow any particular standard, but can be used with any degree distribution (e.g., the robust Soliton distribution available via Distributions.jl).
Examples on how to use Raptor10, RaptorQ, LT, and LDPC codes with the included decoder are available in examples/examples.jl. After installing Julia, use the following commands to get started.
> julia # start the Julia REPL
julia> ] # enter package management mode
pkg> dev https://github.com/severinson/FountainCodes.jl # download this package
# press ctrl-d to exit julia, and navigate to ~/.julia/dev/FountainCodes
> julia --project # start the Julia REPL with the environment specified for this package
julia> ]
pkg> instantiate
pkg> precompile
# exit package management mode by pressing backspace
julia> include("examples/examples.jl") # load the example code into the REPL
julia> r10_example(10, 20) # run the Raptor10 exampleNote that changes to the source code will not automatically be reflected in the REPL. This can be addressed by using includet, available via Revise.jl, instead of include to load code into the REPL.
This package implements inactivation decoding (specified in rfc6330), which is an efficient algorithm for solving sparse systems of equations of the form Ax=b, with most of the optimizations suggested in rfc6330, such as peeling constraints lazily and using largest-component inactivation. See, e.g., chapter 4 of the PhD thesis of Francisco Lázaro for an easy-to-follow overview of the algorithm.
Note that, although inactivation decoding was proposed as a decoding algorithm for Raptor codes, it is at its core just a version of Gaussian elimination optimized for sparse matrices with a particular set of properties. The decoder assumes there is a unique solution to the system of equations, i.e., it is not a least squares solver in the style of the \ operator.
The Raptor10 and RaptorQ implementations assume that operations are performed over a compatible field (e.g., using the GF256 type implemented in src/GF256.jl), but the LT code implementation and decoder is compatible with any field (including the reals, e.g., using the Float64 type).
The use of Raptor10 and RaptorQ codes, and inactivation decoding, may be protected by patents.