Facility networking with IP over RS485: Packet control for master-slave cascaded networks

In Smart Grid applications, we need to access end devices for monitoring and control over varieties of communication media (e.g., wireless, wired and power-line communications). The Internet Protocol is useful because it can integrate those heterogeneous media by IP over X architecture. In this paper, we focus on the integration of RS485, an optimal communication media for facility networking in buildings, proposing IP over RS485. We introduce a dynamic priority-based packet-control scheduler (DPPCS) with master-slave and token-passing, and control the transmissions of IP packets on RS485. According to our evaluation with a 20-node and 200-meter scale RS485 testbed, IP over RS485 can perform well for many facility networking applications. It shared the bandwidth among active IP communication nodes. The buffering duration for non-active nodes to transmit the first IP packet were moderate. It had great tolerance for simultaneous packet transmissions.