The distinguishing characteristic of LT codes is in employing a particularly simple algorithm based on the exclusive or operation (
[2] LT codes are rateless because the encoding algorithm can in principle produce an infinite number of message packets (i.e., the percentage of packets that must be received to decode the message can be arbitrarily small).
The traditional scheme for transferring data across an erasure channel depends on continuous two-way communication.
The encoding process begins by dividing the uncoded message into n blocks of roughly equal length.
For instance, instead of prefixing each packet with a list of the actual message block indices {i1, i2, ..., id}, the encoder might simply send a short "key" which served as the seed for the pseudorandom number generator (PRNG) or index table used to construct the list of indices.
Since the receiver equipped with the same RNG or index table can reliably recreate the "random" list of indices from this seed, the decoding process can be completed successfully.
[4] Luby himself[1] discussed the "ideal soliton distribution" defined by This degree distribution theoretically minimizes the expected number of redundant code words that will be sent before the decoding process can be completed.