Two Birds With One Stone: Exploiting Decode-and-Forward Relaying for Opportunistic Ambient Backscattering

Abstract

In this paper, we propose and analyze an opportunistic ambient backscatter (AmBack)-assisted decode-and-forward (DF) (i.e., ODF-AmBack) relaying scheme, where the relay can not only forward the signal from the source as in the traditional DF scheme but also backscatter/transmit the signal of the tag embedded in the relay. Motivated by the fact that the capacity is dominated by the “weak” link in the traditional DF scheme, we are able to split the received power at the relay or the transmit power of the relay to support the AmBack transmission while the DF relaying is not affected, by exploiting the “extra power” due to the power difference between the first-hop link and the second-hop link. For comparison, both the traditional AmBack and the DF schemes are also investigated for performance benchmarks. Since the exact closed-form expressions of the ergodic capacities are difficult to obtain for the proposed ODF-AmBack scheme and the traditional AmBack scheme, their lower bounds are derived to facilitate our analysis. Simulations results show that significant performance gain can be achieved in the proposed ODF-AmBack scheme compared with benchmark schemes, and confirm the tightness of the derived expressions.