Network coding in convergecast of wireless sensor networks: Friend or foe?

Convergecast is probably the most common communication style in wireless sensor networks (WSNs). And network coding (NC) is a promising concept to improve throughput or reliability of convergecast. Most of the existing works have mainly focused on exploiting these benefits without considering its potential adverse effect. In this paper, we argue that network coding may not always benefit convergecast. This viewpoint is discussed within four scenarios: The network-coding-aided (NC-aided) and the none-network-coding (none-NC) convergecast schemes with or without automatic repeat request (ARQ) mechanisms. The most concerned performance metrics, including packet collection rate, energy consumption and end-to-end delay, are investigated. Theoretical analyses and simulation results show that the way network coding operates, i.e., conscious overhearing and the prerequisite of successfully decoding, could naturally diminish its advantages in convergecast. And NC-aided convergecast schemes may even be inferior to none-NC ones when the wireless link delivery ratio is high enough. The conclusion drawn in this paper casts a new light on how to effectively apply network coding to practical WSNs.