SCADA solutions are mandatory to upgrade the operating reliability of utility installations and industrial by providing remote control. The commercially available GPRS (2.5G level) wireless networks are not optimal for performance critical applications SCADA. However, when Motorola ACE3600 RTUs are operating over GPRS using the MDLC protocol, this combined solution allows establishment of a more reliably versatile and operating SCADA system. This article outlines the technical considerations and main operating and cost benefit achieved with Motorola SCADA solutions operating over GPRS based communication.
When designing SCADA (Supervisory Control and Data Acquisition) system based on wireless communication between field installed RTUs (Remote Terminal Units) and SCADA MCC (Master Control Center, system architect must take into consideration the unique characteristic of the selected network as applicable for the considered system.
Some widely used wireless media for SCADA are: private wireless network, dedicated wireless MAS (Multiple Address Systems), specialized public digital radio networks such as iDEN, TETRA, or ASTRO (APCO-25), broadband networks, and public general cellular services such as the GSM and its GPRS (General Packet Radio Service) providing Internet Protocol service.
The GPRS I a packet data switched technology, using the same infrastructure as the GSM network. The intention for developing the technology of GPRS was to provide broadband access, similar to the wireline internet service which uses circuit switched ADSL, ISDN, or coaxial cables. Network resources are instantly available when data or message actually needs to be transmitted across the wireline media over GPRS. The transmitted data is divided into packets prior to being sent via the wireless modem. Common data applications over GPRS include file transfer video, pictures, Voice over IP, and the ability to remotely access and control industrial installations as described.
The network of GPRS offers data rates up to of 150Kbnps, depending on the network availability, data terminal capability and channel code scheme. This increase in data transmit rates with respect to GSM is achieved by using more than one time slot of the TDMA frame, however each operator can assign one or more time slots.