PHYVOS: Physical layer voting for secure and fast cooperation

Distributed wireless networks often employ voting to perform critical network functions such as fault-tolerant data fusion, cooperative sensing, and reaching consensus. Voting is implemented by exchanging messages with a fusion center or just between the participants. However, the communication and delay overheads of message-based voting can be prohibitive when voting is frequent. Additional overheads are incurred if voter authentication and vote integrity verification are required. In this paper, we propose a fast PHY-layer voting scheme called PHYVOS, which significantly reduces the voting overhead. In PHYVOS, wireless devices transmit their votes to a fusion center simultaneously, by exploiting the subcarrier orthogonality in OFDM and without explicit messaging. We show that PHYVOS is secure against attackers that attempt to manipulate the voting outcome. Security is achieved without employing cryptography-based authentication and message integrity schemes. We analytically evaluate the voting robustness as a function of PHY-layer parameters. We further discuss practical implementation challenges of PHYVOS related to multi-device frequency and time synchronization. Finally, we present a prototype implementation of PHYVOS on the USRP platform.