  We continue the study of rateless codes for transmission of information
across channels whose rate of erasure is unknown. In such a code, an infinite
stream of encoding symbols can be generated from the message and sent across
the erasure channel, and the decoder can decode the message after it has
successfully collected a certain number of encoding symbols. A rateless erasure
code is real-time oblivious if rather than collecting encoding symbols as they
are received, the receiver either immediately decodes or discards each symbol
it receives.
  Efficient real-time oblivious erasure correction uses a feedback channel in
order to maximize the probability that a received encoding symbol is decoded
rather than discarded. We construct codes which are real-time oblivious, but
require fewer feedback messages and have faster decoding compared to previous
work. Specifically, for a message of length $k'$, we improve the expected
complexity of the feedback channel from $O(\sqrt{k'})$ to $O(1)$, and the
expected decoding complexity from $O(k'\log(k'))$ to $O(k')$. Our method
involves using an appropriate block erasure code to first encode the $k'$
message symbols, and then using a truncated version of the real-time oblivious
erasure correction of Beimel et al (2007) to transmit the encoded message to
the receiver, which then uses the decoding algorithm for the outer code to
recover the message.
