Physical Layer Network Coding

TLDR

Wireless links broadcast signals that can reach multiple nodes simultaneously, a property that is typically treated as interference rather than an advantage. This work proposes physical‑layer network coding (PNC) to exploit the broadcast property for capacity gains in wireless ad hoc networks. PNC performs coding by leveraging the additive superposition of electromagnetic waves at the receiver, rather than applying arithmetic to decoded bit streams. PNC can double the information‑theoretic capacity and yield up to 100 % throughput improvement over traditional transmission, demonstrating its potential as a first EM‑wave‑based network‑coding approach.

Abstract

A main distinguishing feature of a wireless network compared with a wired network is its broadcast nature, in which the signal transmitted by a node may reach several other nodes, and a node may receive signals from several other nodes simultaneously. Rather than a blessing, this feature is treated more as an interference-inducing nuisance in most wireless networks today (e.g., IEEE 802.11). This paper shows that the concept of network coding can be applied at the physical layer to turn the broadcast property into a capacity-boosting advantage in wireless ad hoc networks. Specifically, we propose a physical-layer network coding (PNC) scheme to coordinate transmissions among nodes. In contrast to straightforward network coding which performs coding arithmetic on digital bit streams after they have been received, PNC makes use of the additive nature of simultaneously arriving electromagnetic (EM) waves for equivalent coding operation. And in doing so, PNC can potentially achieve 100% and 50% throughput increases compared with traditional transmission and straightforward network coding, respectively, in multi-hop networks. More specifically, the information-theoretic capacity of PNC is almost double that of traditional transmission in the SNR region of practical interest (higher than 0dB). We believe this is a first paper that ventures into EM-wave-based network coding at the physical layer and demonstrates its potential for boosting network capacity.