COLAN IV, a local area network for communications and control

Graduation date: 1988This thesis discusses the design and development of a\ud viable local area network (LAN) which supports both\ud communications and control applications. The emphasis was\ud to develop a practical and cost effective system which\ud offered high performance while utilizing low cost\ud components. System cost was kept low by utilizing a\ud twisted-pair cable as the communication medium. Economical\ud and commercially available circuit boards were used to\ud implement the network interface units.\ud The design of COLAN IV involves selection of network\ud topology and media access technique. Bus topology was\ud chosen for its simplicity and its capability to support\ud decentralized control structure. The RS-485 bus standard\ud has been adopted to achieve high performance with the\ud twisted-pair cable. Designed to operate under light loads,\ud COLAN IV uses the CSMA/CD media access method to optimize\ud channel throughput. Requiring no complex software algorithm\ud nor complicated hardware, the CSMA/CD technique offers\ud reliable operation, "fair" bus access, and fully distributed\ud control structure.\ud The current configuration supports 63 network nodes and\ud is expandable to 256 nodes. It employs a message switching\ud technique for data communications among nodes at a data rate\ud of 9600 baud.\ud Its hardware and software were developed to implement\ud both communications and control applications. User\ud applications implemented include distributed control system,\ud data communications, electronic mail, and resource sharing.\ud Designed as a dual purpose LAN, it can support several\ud distributed control systems while operating as a\ud communications network.\ud The features of COLAN IV have been tested with numerous\ud investigative experiments performed with 4 nodes.\ud Satisfactory results from these experiments confirm the\ud viability of COLAN IV as a dual purpose LAN