Bounds on the Error Probability of Raptor Codes
  In this paper q-ary Raptor codes under ML decoding are considered. An upper bound on the probability of decoding failure is derived using the weight enumerator of the outer code, or its expected weight enumerator if the outer code is drawn randomly from some ensemble of codes. The bound is shown to be tight by means of simulations. This bound provides a new insight into Raptor codes since it shows how Raptor codes can be analyzed similarly to a classical fixed-rate serial concatenation. 
Francisco L\'azaro and Gianluigi Liva and Enrico Paolini and Gerhard   Bauch
cs.IT math.IT