Network Coding in Cooperative Communications: Friend or Foe?
A major benefit of employing Network Coding (NC) in Cooperative Communications (CCs) is its ability to reduce time-slot overhead. Such approach is called Network-Coded CC (or NC-CC). Most of the existing works have mainly focused on exploiting this benefit without considering its potential adverse effect. In this paper, the authors show that NC may not always benefit CC. They substantiate this important finding with two important scenarios: employing Analog Network Coding (ANC) in Amplify-and-Forward (AF) CC, and Digital Network Coding (DNC) in Decode-and-Forward (DF) CC. For both scenarios, they introduce the important concept of Network Coding noise (NC noise). They analyze the origin of this noise via a careful study of signal aggregation at a relay node and signal extraction at a destination node.