ABSTRACT
ISA 100.11a is a network scalable wireless technology based on IEEE 802.15.4. Topologies used are star, mesh, and star-mesh networks. It supports redundancy and interoperability and can blacklists channels that interfere with data transmission. Real-time data transfer is based on time division multiple access (TDMA). A combination of Frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS) is used for the purpose of modulation. Channel hopping takes place on a packet-by-packet basis. It does not have presentation and session layers of the open system interconnection (OSI) model, but its application layer has two sublayers and three data link layers. It checks if a channel is “free,” before sending data—called “clear channel assessment” (CCA). Activities are fully time synchronized. Addressing modes supported are 128-bit long address (IPv6) and 16-bit short address.
System configuration consists of field devices, backbone routers, a backbone network, gateway, system/security manager, control system, and applications. Gateway acts as an interface between the wireless network and control applications like distributed control system (DCS). Backbone router acts as an interface between field network and control network. System security is managed by security manager at every level of the network whereas system manager is responsible for controlling and managing the activities of the whole network.
ISA100.11a supports both symmetric and asymmetric key-based join process. The join process is governed by the administrator of the network.
