Long haul wireless communications weren’t always a feasible solution for remote environmental monitoring applications. Slow response times, low bandwidth, the complexity of integrating supervisory or SCADA systems with remote devices, and prohibitive infrastructure / system management / maintenance costs all obstructed the adoption of wireless solutions to automate remote environmental monitoring systems.
But thanks to advancements in cellular packet technology, painless and cost-effective wireless solutions for remote environmental monitoring systems have arrived. Using cellular communication technology in environmental monitoring systems requires no additional infrastructure costs. In addition to expanding your coverage area, your connections will also be less vulnerable to external interferences such as weather and physical obstructions.
Supported by 85% of all cellular networks, GPRS is still the most widely adopted cellular technology in the world. These 2G cellular networks peak at a speed of 115 Kbps and have an average throughput of 30–40 Kbps, so it’s good enough for many remote environmental monitoring applications even today. Although some network issues remain to be addressed, the benefits of GPRS technology have driven many system integrators to adopt GPRS as the communication interface for their remote monitoring systems. (For detailed introduction to GPRS, click here.)
To keep pace with the growing demand for higher data transfer speeds and capacity, cellular technology continues to advance at an astonishing rate. Recently, Australia became the first country in the world to comprehensively upgrade its cellular network from GPRS to 3G HSDPA (High-Speed Downlink Packet Access), marking the beginning of what is sure to be a global trend. The migration from GPRS to HSDPA is also expected to impact the use of cellular technology in remote environmental monitoring systems.
As data packet transmission becomes more efficient and more people subscribe to the data service, operating costs for HSDPA service drops significantly. This also drives down the monthly costs associated with each SIM card.
GPRS has a notoriously slow network latency of 700 ms. On average, network response time falls between 700 ms and 1.5 seconds, with worst case scenarios as slow as 3 seconds. Most remote environmental monitoring systems still rely on polling to acquire remote data. A slow response time means a long polling cycle, rendering real-time monitoring almost impossible. If it takes too long to access your remote devices or to configure them over the air, then you aren’t enjoying much benefit from going wireless.
This problem can be easily avoided by adopting active reporting technology. (For detailed information about active/push technology and its applications, click here). With significantly shorter network latency, active technology lets you achieve 100 ms response times in HSDPA networks. This translates into faster remote data access so you can more easily manage your remote devices.
The most significant improvement from GPRS to HSDPA is increased bandwidth, opening up the possibility of transmitting not only small digital data but large amounts of digital and analog data too. For example, IP cameras can be inexpensively deployed to show real-time images in environmental monitoring systems.
Short network latency and high bandwidth also allow you to take advantage of smart phones for mobile management, effectively transforming your handset into a remote workstation. Thanks to the prevalence of IP-based technology in industrial automation, most devices now transmit their data not only over IP networks but also to IP-based supervisory software. The convergence of IP-based technology in automation and IT makes it feasible and easy to construct a Web-based environmental monitoring and control system that can be managed in the palm of your hand.
3G solutions for environmental monitoring systems
The world’s first wide temperature 3G RTU
As a pioneer in cellular M2M technology, Moxa has released the world’s first wide temperature HSDPA-enabled remote terminal unit. Designed to withstand harsh environments, the ioLogik W5340-HSDPA offers 3G connectivity with an operating temperature range of -20–70°C.
Active technology for real real-time monitoring
The ioLogik W5340-HSDPA also inherited the data report by exception functions from Moxa’s original ioLogik W5340 device. This form of push technology effectively optimizes bandwidth usage and exploits the fast response time in HSDPA for real real-time monitoring. Field data and alarms are actively delivered to remote destinations via at blazing HSDPA speeds.
Popular alarm protocols—such as SNMP Trap, SMTP, TCP, and UDP messaging—also come out of the box. The ioLogik W5340-HSDPA also includes Moxa’s patented Active OPC Server, a freeware that enables the ioLogik to actively push I/O tags from the device to the OPC server tags, and uses standard OPC specifications to connect with commonly-used SCADA systems. (For more information about Active OPC Server, click here).
Free database software to build Web-based monitoring systems
In addition to Active OPC Server, Moxa also offers free OPC Client software, DA-Center, which receives real-time data updates from Active OPC Server. So when the ioLogik pushes I/O tags through 3G networks to Active OPC Server, it simultaneously pushes the data through DA-Center to a database so an application developer can focus on developing an ASP server for remote Web access. Network administrators can then use their 3G mobile phone to access the data from every corner of the globe.
Although GPRS remains the most universal type of cellular network today and is sufficient for many environmental monitoring systems, HSDPA has revolutionized the way we access information and digital data. It has also transformed the way engineers monitor their remote devices and facilities. Advantages such as wider bandwidth, fast response time, and low initial and maintenance costs provide plenty of to consider high performance HSDPA devices for your remote monitoring needs.
Moxa manufactures device networking products for industrial automation. Information about all Moxa products, which include industrial embedded computers, industrial Ethernet switches, serial device servers, multiport serial cards, embedded device servers, and remote I/O servers, is available on Moxa’s corporate website at www.moxa.com.
Edited by Tim(oseam.icn@gmail.com) of Industrial Communication Network, www.icnweb.co.kr.
