01 November 2002
Wireless edging into process milieu
By Arturo Herrera
The greatest benefit of wireless networking is the ability to conduct business and stay connected without wires. The three most important features to consider when building or extending a network are scalability, durability, and ease of network management.
A process manager charged with establishing a new network or expanding an existing one needs that network to be able to work for the current application and accommodate future growth and technology.
The rate at which technology is progressing is staggering. A network must be able to support the technology available today, as well as what will be available in 18 months.
Creating a scalable solution that grows with an enterprise is a very important network design objective. Combining wired, wireless, serial, and IP is the challenge.
A network that utilizes open standards architecture and upgradable firmware will ensure the long-term viability of your network. Java, simple network management protocol, IP, and Linux should all be part of the mix.
Another important network design objective is to reuse existing infrastructure and integrate it with more current technology. Because of the significant resources most organizations have invested in existing serial networks, the ability for new, IP-based technology and applications to integrate seamlessly is key.
The idea of combining all of these elements in one solution may seem implausible, but the technology exists now such that IP, Ethernet, and serial work together in one compact, industrial, wireless radio.
This radio allows serial devices to communicate with an IP address, which further allows large-scale network deployment and management.
NO RESIDENTIAL CONSUMER
An important element to consider for a network supporting industrial applications is its ability to perform in an industrial environment. Most wireless components started as office or consumer use products.
Indoor office or residential settings do not resemble the brutal conditions that are typical for process control environments. So the hardware must work in extreme temperature ranges, have low power consumption, and offer network redundancy over a long time period.
Further, today's new network must be easy to use. The problem with many industrial solutions is you have to hire a specially trained individual in order to set up the network and then keep it running.
The bottom line is that, just like with any product, if it is difficult to use it won't see much use. The most cost-effective, efficient solution is one that is easy to install with plug-and-play connectivity (configuration with virtually no setup) and is scalable so adding to your wireless network in the future is easy and cost-effective.
Another aspect to take into account when considering a wireless network is whether to purchase a solution that is a spread spectrum/license-free radio as opposed to one that requires licensing and a permit from the Federal Communications Commission (FCC).
Spread spectrum radios can be either direct sequence or frequency hopping. In a radio using direct sequence spread spectrum (DSSS), a data signal at the sending station is combined with a higher data rate bit sequence, or chipping code, that divides the user data according to a spreading ratio.
In a radio using frequency hopping spread spectrum (FHSS), the data signal modulates with a narrowband carrier signal that moves-hops-in a random sequence from frequency to frequency.
The receiver must set to the same hopping code and listen to the incoming signal at the right time and correct frequency to properly receive the signal.
FHSS is often preferred to DSSS because it is less susceptible to interference. Either solution allows you to bypass the process of filing for a license with the FCC, which can be a time-consuming and costly endeavor.
Today's industrial wireless networks are complex and disparate and consist of hundreds of thousands of elements. They all need management.
Wireless devices/radios have evolved, from pieces of hardware to sophisticated, software-controlled network elements with higher bandwidth, more features, and complex network topologies. Radios must have the ability to perform-and be subject to-remote management, maintenance, and control.
Self-diagnosis and wireless Web alarm reporting allows customers to spot issues/outages quickly and translates into less downtime. IT
Arturo Herrera works for Microwave Data Systems (www.microwavedata.com).