Isn't Hybrid ARQ Sufficient?
  In practical systems, reliable communication is often accomplished by coding at different network layers. We question the necessity of this approach and examine when it can be beneficial. Through conceptually simple probabilistic models (based on coin tossing), we argue that multicast scenarios and protocol restrictions may make concatenated multi-layer coding preferable to physical layer coding alone, which is mostly not the case in point-to-point communications. 
Michael Heindlmaier and Emina Soljanin
cs.IT math.IT