  The wireless blockchain network (WBN) concept, born from the blockchain
deployed in wireless networks, has appealed to many network scenarios.
Blockchain consensus mechanisms (CMs) are key to enabling nodes in a wireless
network to achieve consistency without any trusted entity. However, consensus
reliability will be seriously affected by the instability of communication
links in wireless networks. Meanwhile, it is difficult for nodes in wireless
scenarios to obtain a timely energy supply. Energy-intensive blockchain
functions can quickly drain the power of nodes, thus degrading consensus
performance. Fortunately, a symbiotic radio (SR) system enabled by cognitive
backscatter communications can solve the above problems. In SR, the secondary
transmitter (STx) transmits messages over the radio frequency (RF) signal
emitted from a primary transmitter (PTx) with extremely low energy consumption,
and the STx can provide multipath gain to the PTx in return. Such an approach
is useful for almost all vote-based CMs, such as the Practical Byzantine
Fault-tolerant (PBFT)-like and the RAFT-like CMs. This paper proposes symbiotic
blockchain consensus (SBC) by transforming 6 PBFT-like and 4 RAFT-like
state-of-the-art (SOTA) CMs to demonstrate universality. These new CMs will
benefit from mutualistic transmission relationships in SR, making full use of
the limited spectrum resources in WBN. Simulation results show that SBC can
increase the consensus success rate of PBFT-like and RAFT-like by 54.1% and
5.8%, respectively, and reduce energy consumption by 9.2% and 23.7%,
respectively.
